ORNL-4076 by Jon Morrow

QRNL-4076

Contract No.

W-7405-eng-26

REACTOR CHEMISTRY DIVISION ANNUAL PROGRESS For Period Ending December 31, 1966

REPORT

Director

W. R.

Grimes

As socia te Di rectors

E. G.

Bohlmann

G. M.

Watson

F. McDuffie

Senior S c i e n t i f i c Advisors

F. F.

Blankenship

C. H. Secoy

MARCH 1 9 6 7

OAK RIDGE NATlONAL L A B O R A T O R Y Oak Ridge, Tennessee oaeroted bv

3 Y456 0134074 I

Reports previously issued in t h i s series are a s follows:

0 R NL- 29 3 1

P e r i o d Ending January

31, 1960

ORNL-3127

P e r i o d E n d i n g January

31, 1961

0 RNL-3262

P e r i o d Ending January

31, 1962

0 RNL-3417

Period Ending January

31, 1963

ORNL-359 1

P e r i o d Ending January

31, 1964

0 RNL-3789

P e r i o d Ending January

31, 1965

ORNL-3913

P e r i o d E n d i n g December

31, 1965

Contents PART 1. MOLTEN-SALT REACTORS 1. Phase Equilibrium and Crystallographic Studies T H E EQUlLlBRlUM PHASE DIAGRAM F O R THE SYSTEM L i F - 6 e F 2 - Z r F 4 R. E. Thoma, R. A. Friedman, and H. I n s l e y ....................................................

......................

.........

Investigatioris o f the equilibrium p h a s e diagrams of t h e s y s t e m s LiF-ReF -ZrF, and F3eF2-ZrF4 were

completed.

Hoth s y s t e m s e x h i b i t liquid-liquid irnniiscibility, behavior which h a s heretofore been con-

s i d e r e d t o b e very unusual in molten fluoride systems.

P R E L I M I N A R Y STUDY O F T H E SYSTEM L i F - T h F 4 - P a F 4 C. J. Barton, H. H. Stone, and G. D. Brunton ....................................................

O p t i c a l examinaLion of two slowly cool-ed m i x t u r e s o f LiF. T h F 4 , and P a F

e x i s t e n c e of the compounds LiPaF, and Li Pap 3

..................

......... 4

i n d i c a t e s the probable

8‘

A P P A R A T U S F O R D I F F E R E N T l A L T H E R M A L ANALYSIS C . 0. Gilpatrick, R. E. Thotiia. a n d S. Cantor

...............

............

Automatic DTA a p p a r a t u s w a s developed, t e s t e d , nnd found t o b e s u i t a b l e for the s t u d y of p h a s e t r a n s i t i o n s i n mixtures of fluoroborate s a l t s .

SOLID-PHASE E Q U l L l B R l A IN THE SYSTEM SmF2-SmF3-UF3 R. B. ‘L’liorna a n d H. A. Friedman ......................................................................... E x t e n s i v e mutual s o l i d - s t a t e solubility of components and intermediate phas SmF2-SmF3-UF

...........................

system.

PHASE R E L A T I O N S IN T H E SYSTEM K F * C e F 3 C. J. Harton. G. z). Brunton, D. 1-Isu, a n d H. I n s l e y ....... and two incongruerilly melting cxjmpounds, 3KF. Cel’

................................................................ n c e of one e u t e c t i c composition

An incomplete i n v e s t i g a t i o n of t h e s y s t e m KF-CeF

and KITeCeF

3’

T H E CRYSTAL STRUCTURE OF Li4UF8 G. D. Brunton ............................................................................................. T h e U4’ ion i n t h i s s t r u c t u r e is surrounded by

12..

........

...................................

i o n s a t t h e c o r n e r s of a 14-faced polyhedron.

T h e Li-F

coordinations a r e irregular o c t a h e d r a , two of w h i r h s h a r e f a c e s with the W 4 + pnlyhedruti.

T H E C R Y S T A L S T R U C T U R E S O F N o F - L o F 3 S O l l D SOLUTIONS D. R. S e a r s and G. D. Brunton _ . _ .

....................................................................

C r y s t a l structure a n a l y s e s of two s p e c i m e n s n e a r the 50:50 composition 3re d e s c r i b e d . A model

s t r u c t u r e b a s e d on t h a t of

CaFz with c a t i o n v a c a n c i e s and anion i n t e r s t i t i a l s a p p e a r s t o f i t t h e i n t e n s i t y

d a t a b e s t , b u t t h e r e are anomalies in the thermal motion.

T H E C R Y S T A L S T R U C T U R E OF y-CsBeF3 H. Steinfink and G. D. Bnrnton ......................................................................... T h i s s t r u c t u r e is s i m i l a r t o t h a t o f the high-temperature form of RaGeO 3’

iii

.................................

iv THE C R Y S T A L STRUCTURE O F P , - K L a F 4 D. R. S e a r s ...................................................................................................................................................................... .This compound forms merohedral t w i n s which a r e almost isostructiiral with NaNdF

C E N T R A L C A T i O N DISPLACEMENTS IN THE "TRIPYRAMJDAL"

COORDINA T l O N

D. R. S e a r s ......................................................................................................................................................................

Interatomic potential c a l c u l a t i o n s s u g g e s t which anion configurations favor displacements of t h e c a t i o n from t h e medial plane and a r e correlated with t h e s t r u c t u r e s of P l - K L a F 4 and NaNdF4.

P R E P A R A T l O N O F F L U O R I D E SINGLE CRYSTALS FOR RESEARCH PURPOSES R. E. 'Thoma, R. G. R o s s , and H. A . Friedman ........................................

P u r e s i n g l e c r y s t a l s of t h e fluorides 7LiF, L i 2 R e F 4 , Na,Zr6F31, 7 L i 2 N a T h 2 F 11, P - C s B e F 3 , and

Li U F were grown from the melt and furnished for u s e i n r e s e a r c h programs a t ORNL and elsewhere. 4 8

2, C h e m i c a l Studies

of Molten S a l t s

A POLYMER MODEL F O R LiF-BeF2 MIXTURES

................................................................................................................................

C. F. B a e s , Jr.

BeaFb(b"2a)-a n i o n s containing BeF 2- tetrahedra, bridging F--, a n d A model which terminal F- i o n s is found t o b e c o n s i s t e n t wi'h measured a c t i v i t i e s of R e F 2'

PHASE E Q U l L l S R l U M STUDIES i N T H E W 2 - Z r 0 2 SYSTEM K. A . Romberger, C. F. B a e s , Jr., a n d IT. H. Stone ......................................................................................

New r e s u l t s from equilibration of t h e o x i d e s i n t h e presence of molten fluorides, while confirming t h e nearly complete exsolution of t h e o x i d e s from o n e another below t h e e u t e c t o i d a t l l l O ° C , show evidence of nonideal behavior i n t h e dilute s o l i d s o l u t i o n s j u s t above t h i s temperature.

T H E O X I D E CHEMISTRY O F T h F 4 - U F 4 M E L T S R , F. H i t c h , C. E. L. Barnberger, and C. F. B a e s , Jr.

._._

.........................................

T h e o x i d e phase a t equilibrium with 2 L i F - B e F + U F +ThF is a (U-Th)O s o l i d s o l u t i o n into which 2 4 4 2 t h e uranium is strongly extracted.

T H E O X I D E CHEMISTRY O F LiF-BeF2-ZrF4 M I X T U R E S €3. F. Hitch a n d C.

F. B a e s , Jr. ..................................................................................................................................

Measurements of the solubility of B e 0 and Zn02 i n d i c a t e the oxide t o l e r a n c e of MSRE f l u s h s a l t a n d fuel salt.

CONSTANT-VOLUME H E A T C A P A C I T I E S OF M O L T E N S A L T S Stanley Cantor ................................................................................................................................................................ Values of C y were obtained by combining published C

.... 20

values, s o n i c v e l o c i t i e s , and density-tempera-

ture d a t a ; i n almost every case experimental C v e x c e e d e d t h a t c a l c u l a t e d on the b a s i s of simple c l a s s i c a l and/or quantum contributions.

T E M P E R A T U R E C Q E F F l C l E N T O f Cv

FOR M O L T E N S A L T S

.........................................................................................................

Stanley Cantor

By u s i n g a n empirical e q u a t i o n i n which compressibility is a l i n e a r function of p r e s s u r e , t h e ternpgrature dependence of C v for 34 s a l t s w a s c a l c u l a t e d ; where compression w a s n e c e s s a r y to s u s t a i n a fixed volume,

C v increased with temperature. T E M P E R A T U R E C O E F F I C I E N T OF COMPRESSIBILITY F O R M O L T E N S A L T S Stanley Cantor

...............................................................................................................................................................

A simple empirical equation, p: A e b T , w a s found to hold for a l l molten s a l t s . compressibility a t 1 atm, A4 and b a r e c o n s t a n t s , and T is t h e a b s o l u t e temperature.)

(P:

is t h e isothermal

VISCOSITY AND DENSITY IN T H E L i F - B e F 2 SYSTEM C. T. Moynihan a n d Stanley Cantor ..............................................................................................................................

Viscosity a n d d e n s i t y measuretnents show t h a t t h e temperature c o e f f i c i e n t of v i s c o s i t y d e c r e a s e s when the volume expansion coefficient i n c r e a s e s ; t h e volume expansion c o e f f i c i e n t is d i r e c t l y c o r r e l a t e d to t h e temperature dependence of “free”

volume i n t h e s e melts.

V A P O R PRESSURES OF M O L T E N F L U O R l D E M I X T U R E S S t a n l e y Cantor, W. T. Ward, a n d C. E. Roberts ..................................................

Vapor e q u i l i b r i a t h a t a r e involved in the reprocessing by d i s t i l l a t i o n h a v e b e e n measured. Decontarnination f a c t o r s of t h e order of 1000 for rare e a r t h s were evidenced.

The vapor p r e s s u r e of t h e composition of

h1SKE f u e l c o n c e n t r a t e w a s a l s o tneasured. PO T E N T I O M E T R ! C MEASUREMENTS IN MOL T E N F L UORl DES A. R. N i c h o l s , Jr., K. A. Romberger, and C . F. R a e s , Jr. ..................................................... Preliminary r e s u l t s for niobium i n 2 L i F - B e F 2 i n d i c a t e t h e formaticn of s t a b l e , i n s o l u b l e N b F

.......... 2‘

A P P E A R A N C E P O T E N T I A L S O F L I T H / U M F L U O R I D E AND L I T H I U M B E R Y L L I U M F L U O R I D E IONS R. A. Strehlow a n d J. D. Redman .......................................................................................................... A s t u d y w a s made of appearance p o t e n t i a l s of i o n s formed by e l e c t r o n impact from JLiF and Li ReF 2 4 vapor, and a s u r p r i s i n g atnount of s t r u c t u r e w a s found i n the i o n i z a t i o n e f f i c i e n c y c u r v e s .

Separations Chemistry and Irradiation Behavior

R E M O V A L OF l O D l D E FROM L i F - B e F 2 M E L T S C . E. L. Batnherger and C. F. R a e s , Jr.

..............

T h e e f f i c i e n c y of HF u t i l i z a t i o n during s p a r g h g

..........................................................................

se rvith d e c r e a s i n g pressure c a u s e d

e i t h e r by a s y e t unidentified s i d e r e a c t i o n s or by a r a t e effect.

REMOVAL OF RARE EARTHS FROM M O L T E N F L U O R I D E S B Y SIMULTANEOUS P R E C I P I T A T I O N U F ~ F. A. D o s s , N. F. McDuffie, a n d J. H. Shaffer ........................................................................................... mole fraction CeF 3 or N d F t o e x c e s s s o l i d Exposure of L i F - B e F 2 (66-34 mole 7“) c o n t a i n i n g about IJF, c a u s e d removal of the rare e a r t h s from t h e motten solution.

wirn

E X T R A C T l O N OF RARE E A R T H S FROM M O L T E N F L U O R l D E S l N T O M O L T E N M E T A L S J. H . Shaffer, W . P. T e i c h e r t , D. M. Moulton, F. F. Blartkenship, W. K. R . F i n n e l l , W. R. Grimes ............... The distribution of rare e a r t h s (lanthanum, cerium, neodymium, saniariuni, and europium) between molten

T.,iF-BeFZ (66-34 mole ”/) and molten bismuth w a s s t u d i e d a t 600OC: a s a function of t h e concentration of lithium tuetal added a s a reducing agent.

R E M O V A L O F P R O T A C T l N f U M FROM M O L T E N F L U O R I D E S BY R E D U C T l O N PROCESSES J . H. Shaffer, D, M. Moulton, W. K . R. F i n n e l l , W. 1’. T e i c h e r t , F. F. Blankenship, a n d W. R. Grimes ..........

T h e removal o f protactinium from a simulated molten-salt breeder r e a c t o r b l a n k e t w a s demonstrated in a

six-week experiment in which liquid bismuth w a s r e c i r c u l a t e d through t h e b l a n k e t s a l t , a bed of s t e e l wool, and a bed of thorium metal chips. T h e e v i d e n c e s u g g e s t e d that the protactinium w a s transported as a S U S petloion, perhaps associated

with high-melting m e t a l l i c compounds of iron, chromium, and thorium.

R E M O V A L O F P R O T A C T l N l U M FROM M O L T E N F L U O R I D E S B Y O X l D E P R E C l P l T A T l O N J. H. Shaffer, W. P. T e i c h e r t , W. K. R . F i n n e l l , F. F. Blankenship, a n d W. R. Grimes .................................... The removal of protactinium from s o l u t i o n i n molten LiF-BeF2 (66-34 m o l e yo) by o x i d e precipitation upon

the a d d i t i o n of ZrO 2 a t 600°C w a s s t u d i e d with a variety of ZrO,2 powders of differing s u r f a c e a r e a s (from 1.3 t o 80 m2/g). ‘The r e s u l t s were not c o n s i s t e n t w i t h s i m p l e t h e o r i e s of e i t h e r complete s o l i d s o l u t i o n for-

mation o r p r e c i p i t a t i o n on the s u r f a r e of the ZrO

2‘

P R O T A C T I N I U M STUDIES I N T H E H I G H - A L P H A M O L T E N - S A L T L A B O R A T O R Y C. J. Barton and H. H. Stone ........................................................................................................................................ Reduction of protactinium d i s s o l v e d i n a molten L i F - T h F

breeder b l a n k e t mixture by exposure t o s o l i d

thorium, followed by adsorption of t h e reduction product on an iron s u r f a c e , is the most promising of t h e s e v e r a l recovery methods s t u d i e d t o date.

G R A P H I T E - M O L T E N - S A L T I R R A Q l A T l O N 18 HlGH FISSION DOSE H. C. Savage, J. M. Baker, E. L. Conipere, M. J. K e l l y , and E. G. Bohlmann

....................................................

Irradiation of the f i r s t molten-salt thermal convection loop experiment in t h e ORR w a s terminated August 8 , 1966, b e c a u s e of a l e a k through a broken t r a n s f e r l i n e a f t e r achieyJing power d e n s i t i e s of 1 0 5 w/cm3 i n t h e f u e l c h a n n e l s of t h e graphite core. A s e c o n d loop, modified t o eliminate c a u s e s of failure encountered in t h e first, begins long-term irradiation i n January 1967.

4. Direct Support

for

MSRE

E X T E N T QF U F 4 R E D U C T I O N D U R l N C M S R E F U E L P R E P A R A T I O N R . F. Hitch and C. F. B a e s , Jr. ..

.....................................................

I t is estimated t h a t 0.16% of t h e uranium introduced into t h e MSRE h a d b e e n reduced to U F purification.

during s a l t

C H E M I C A L B E H A V I O R OF FLUORIWES DURING M ยง R E O P E R A T l O N R. E. 'rhoma .....................................................................................................................................

a n a l y s e s of MSRE fuel, flush, and c o o l a n t s a l t s show that a f t e r approximately 20 months in t h e MSRE, t h e molten s a l t s h a v e retained their o r i g i n a l chemical composition and h a v e n o t induced perceptible corrosion in t h e reactor.

FISSION P R O D U C T S IN M S R E FUEL. S. S . K i r s l i s and F. F. Blankenship ........................................................................................................

Radiochemical a n a l y s e s for f i s s i o n products i n MSRE f u e l s a l t s a m p l e s i n d i c a t e d t h a t a p p r e c i a b l e fractions of t h e "Mo,

132Tc, l o 3 R u , and '06Ru produced by f i s s i o n h a d left t h e fuel p h a s e .

F ~ S S ~ OPNR o D u C r s I N MRE E X I T G A S Equilibrium Pressures o f Noble-Metal Fluorides U n d e r MSRE Conditions C. F. B a e s , Jr.

....................................................................................................................................

Theimochemical d a t a i n d i c a t e t h a t , with i n c r e a s i n g oxidizing power, t h e order of appearance of volatile fluorides should b e NbF5, MoF,, RuF,, TeF,.

Analysis f o i F i s s i o n Piwducrs in MSRE E x i f G a s S . S . K i r s l i s and F. F. Blankenship .................................

...............

..................................

Small metal s a m p l e s exposed t o t h e g a s p h a s e of t h e MSRE putlip bowl demonstrated q u a l i t a t i v e l y a n appreciable volatility of 9 9 ~ 1 0 ,I 3 * T e , '03Ru, and l o 6 R u presumably a s high-valent fluorides.

FlSSlON P R O D U C T S ON M E S A L AND GRAPHITE F R O M MSRE C O R E S. S. K i r s l i s and F. F. Blankenship ......

..................................................................................................................

Samples of MSRE graphite removed from t h e r e a c t o r c o r e after 7800 Mwhr of operation showed no radiation damage e f f e c t s but were found t o b e significantly peimeated o r p l a t e d by noble-metal f i s s i o n products a n d t h o s e with noble-gas precursors. Adjacent Hastelloy N samples were a l s o undamaged a n d were more h e a v i l y plated with noble-metal f i s s i o n products.

XENON D I F F U S I O N AND FORMATION OF CESlUM C A R B I D E IN AN MSBR C. F. B a e s , Jr., and K. U. E v a n s XI1 ............................................................................................................... Carbide formation in t h e moderator graphite should occur, b u t n o t i n s i g n i f i c a n t amounts;

35Xe poisoning

could b e reduced effectively either by i o d i n e removal or by some means which r e d u c e s the salt-graphite film coefficient.

vii

P A R T I I . AQUEOUS REACTORS 5 . Corrosion and Chemical Behavior i n R e a c t o r

Environments

NASA T U N G S T E N R E A C T O R R A D I A T I O N CHEMISTRY STUDIES G . H. J e n k s , II. C. Savage, a n d E. G. Bohlruann ...................................................................................................... Experimental r e s u l t s showed tinat e l e c t r o n irradiation produces a s m a l l l o s s of cadmium from C d W 4 solu-

t i o n s under c o n d i t i o n s of i n t e r e s t i n the NASA T u n g s t e n Water-Moderated Reactor.

Equipment w a s d e s i g n e d

for a d d i t i o n a l s t u d i e s of the e f f e c t s of a g i t a t i o n on the radiation s t a b i l i t y of the solution.

CORROSION OF Z I R C A L O Y - 2 BY D I L U T E HYDROGEN P E R O X I D E AT 280°C R. J. D a v i s , T. H. Mauney, a n d R. J. H a r t .................... ...................................................................................... T h e corrosion of Zircaloy-2 in oxygenated water a t 280

w a s shown to be unaffected by the p r e s e n c e of

lo-' M H 2 0 2 , and i t w a s concluded that the radiation e f f e c t on zirconium-alloy corrosion in t h e s e s o l u t i o n s not a d i r e c t r e s u l t of the peroxide formed during irradiation.

ANODIC F I L M GROWTH ON ZIRCONBUM A T E L E V A T E D T E M P E R A T U R E S A. L. B a c a r e l l a , €1. S. Gadiyat, and A. L. Sutton ......................................................................................................

A new e x p r e s s i o n for the anodic filii1 growth current on zirconium w a s derived u s i n g t.he triple-harrier

model with a field-dependent a c t i v a t i o n d i s t a n c e in the oxide phase, a n d ouI experimental d a t a were t ' i t k d with t h i s e x p r e s s i o n ,

AC I M P E D A N C E OF O X l D E FILMS

AQUEOUS SOLUTIONS A T E L E V A T E D T E M P E R A T U R E S ............

G. 1-1. Jenks, A. L. B a c a r e l l a , R. J. Davis, a n d H. S. Gadiyar ._._

..I h e immediate o h j e r t i v e of

Equipment., methods, a n d t e c h n i q u e s a r e being developed and t e s t e d for measuring a c impt.dance of corrosion fjlrns on zirconium a l l o y s in a q u e o u s s o l u t i o n s a t e l e v a t e d temperatures.

...

s u c h m e a s u r e m e n t s is the d e t e c t i o n of f i l r r i porosity.

CORROSION SUPPORT FOR R E A C T O R P R O J E C T S J. C . G r i e s s , Jr., J. L. E n g l i s h , and P. D. Neumann

..__

..............

Corrosion i n v e s t i g a t i o n s conducted for s e l e c t i n g s t r u c t u r a l m a t e r i a l s for use in t h e High F l u x Isotope Rea c t o r and the Aigonne Advanced R e s e a r c h R e a c t o r were completed.

Generally, both r e a c t o r s should o p e r a t e

many y e a r s without major corrosion problems providing t h e them-istry of the coolant is properly maintained.

6. C h e m i s t r y of High-Temperature Aqueous Solutions E L E C T R l C A L C O N D U C T A N C E S OF AQUEOUS E L E C T R O L Y T E SOLUTIONS FROM 0 TO 800°C AND TO

4000 BARS

A. S . Q u i s t , W. Jennings, Jr., and W. L. Marshall

..................................................................................................

Continuing, e x t e n s i v e conductance s t u d i e s on a q u e o u s e l e c t r o l y ? e s to 800OC and 4000 bars have provided

limit-ing e q u i v a l e n t c o n d u c t a n c e s a n d d i s s o c i a t i o n c o n s t a n t s of sodium chloride, differing sharply from liehavior a t 25"C, a n d measurements o n 16 other 0.01 m 1-1 e l e c t r o l y t e s .

DISSOCIATION CONSTANT OF MAGMESIUM S U L F A J E TO 2OO0C FROM SOLUBILITY MEASUREMENTS W. L. Marshall _ _ .................................................................................................................................................

F r o m the d i f f e r e n c e s in s o l u b i l i t y of calcium s u l f a t e i n sodium chloride and in s e a - s a l t solutions, d k s o c j a t i o n q u o t i e n t s , c o n s t a n t s , a n d other thermodynamic q u a n t i t i e s h a v e b e e n c a l c u l a l e d .

DlSSOC!AT/ON CONSTANT OF CALCIUM S U L F A T E TO 350°C O B T A l N E D F R O M S O L U B I L I T Y BEHAVIOR IN MIXED E L E C T R O L Y T E S I,. B. Y e a l t s and W. L. Marshall .......................................................................................................... I n p e r h a p s t h e f i r s t e x t e n s i v e study of a four-component, [nixed e l e c t r o l y t e s y s t e m l o high terrrperntures, s o l u b i l i t i e s of calcium s u l f a t e were determined from 25 to 350°C from which d i s s o c i a t i o n quotients. solubility products, their r e s p e c t i v e c o n s t a n t s , a n d thermodynamic q u a n t i t i e s were c a l c n l a t e d .

...

Vlll

S O L U B I L I T Y OF F e 3 0 4 AT E L E V A T E D T E M P E R A T U R E F. H. Sweeton, R. W. Ray, and C. F. B a e s , Jr. ...................................................................... T h e solubility of F e 0 in d i l u t e HC1 s o l u t i o n s containing dissolved H, h a s been meas 3

....

and 3OO0C, and solubility products for formation of Fez' a n d FeOH- h a v e b e e n calculated.

HYDROLYSIS OF B E R Y L L I U M ION IN 1.0 M C H L O R I D E A T 25OC R. E. hlesmer and C . F. B a e s , Jr. .........................................................................................................................

T h e previously reported h y d r o l y s i s s c h e m e s for beryllium a r e n o t fully supported by t h e p r e s e n t d a t a a t 25OC. T h e u n i q u e n e s s of other p o s s i b l e s c h e m e s is being t e s t e d .

interaction of Water w i t h P a r t i c u l a t e Solids

S U R F A C E CHEMISTRY OF T H O R I A C. H. Secoy ........................................................ Meats o f I m m e r s i o n

.............................................

and Adsorption

E. L. F u l l e r , Jr., H. F. Holmes, and S. A. Taylor ....................

Thoria powders composed of c r y s t a l l i t e s with a n average s i z e greater than about 1400 A y i e l d a c o n s t a n t amount of h e a t per unit s u r f a c e a r e a upon immersion in water after o u t g a s s i n g a t a given temperature.

Powders

composed of s m a l l e r c r y s t a l l i t e s r e a c t more e n e r g e t i c a l l y and r e l e a s e a portion of t h e h e a t by k i n e t i c a l l y s l o w processes.

Adsorption of Water and Nitrogen on P o r o u s and Nonporous Thoria H . F. Holmes and E. L. F u l l e r , Jr. ............................................................................................................................

T h e concept t h a t chemisorbed water d e c r e a s e s t h e pore volume is n o t a d e q u a t e to e x p l a i n t h e observed d e c r e a s e s i n nitrogen and water s u r f a c e a r e a s of nonporous thoria, nor is t h e s m a l l e r size of t h e water molecule compared with nitrogen c o n s i s t e n t wj.th t h e observation of water a r e a s much s m a l l e r than nitrogen areas.

Infrared S p e c t r a o f Adsorbed Species on Thoria C. S. Shoup, Jr.

____

......................................................................................

Infrared s p e c t r a of t h e T h o -H 0 i n t e r f a c e obtained by both adsorption and desorption h a v e confirmed t h e 2

nonequilibrium nature of t h e s u r f a c e i n t e r a c t i o n s of thoriutii oxide and water.

BEHAVIOR O F GASES WITH SOL-GEL URANIUM-THORIUM O X I D E F U E L S D. N. H e s s , H. F. McDuffie, B. A. Soldano, and C. F. Weaver .............................................................................. T h e g a s e s r e l e a s e d when sol-gel microspheres of T h o

or UO

were h e a t e d i n vacuum were identified,

and t h e temperatures of maximum g a s evolution were e s t a b l i s h e d . A conditioning procedure w a s developed which, when applied to wet, unfired microspheres, converted them i n t o s a t i s f a c t o r y reactor-fuel-element products of high density, low carbon content, and low 0 : U ratio.

PART Ill. GAS-COCILED

Diffusion Processes

TRANSPORT P R O P E R T I E S O F GASES Gaseous Diffusion Studies i n Noble-Gns Systems

A. P. hfalinauskas

....................................................

.........................................................................................

Diffusion d a t a a r e reported for t h e s y s t e m s He-Kr, Ar-Kr, and Kr-Xe over t h e temperature range 0 to 12OoC. T h e r m a l Tronzpiration

B. A. Cameron and A. P. Malinauskas ........................................................................................................................ Thermal transpiration measurements u s i n g a porous septum h a v e b e e n attempted. Although s t e a d y - s t a t e c o n d i t i o n s a r e a t t a i n e d very rapidly, t h e thermal conductivity of t h e g a s now e n t e r s i n a pronounced manner and c a u s e s t h e a n a l y s i s of the d a t a to b e extremely difficult.

Gaseous Diffusion in Porous Media A. P. Malinauskas, R. B. E v a n s 111, a n d E. A. Mason ......................................................................................

A g e n e r a l i z e d treatment of g a s transport i n porous media h a s b e e n developed on t h e b a s i s of the “dusty-

gas” model.

Gas T r a n s p o r t Studies Related to Vented F u e l Elements for Fast Gas-Cooled Reactors R. E3. E v a n s 111 and D. E. B r u i n s ......................................................................................................

An i n v e s t i g a t i o n of the p o s s i b i l i t y of u s i n g d i r e c t venting d e v i c e s on f u e l e l e m e n t s i n f a s t gas-cooled rea c t o r s h a s b e e n initiated.

R E C O I L P H E N O M E N A IN G R A P H I T E S R. R. E v a n s 1x1, J. L. Rutherford, a n d €3. B. P e r e z ................................................................................................. T h e e f f e c t s of d e n s i t y and porosity of graphitic s t r u c t u r e s on the range of “light” and ‘bheavyp’f i s s i o n

fragtiients have been determined.

Behavior of G r a p h i t e with R e a c t i v e Gases L. 6. O v e r h o l s e r

OXlDATlON O F GRAPHlTE SLEEVES C . M. Blood and G. M. Hebert .

STEAM

.....

.............................................................................

Oxidation r a t e s of virgin, impregnated, and irradiated ATJ graphite s l e e v e s were measured a i 1000°C u s i n g a p a r t i a l p r e s s u r e of water vapor a t *-,250 torrs.

T R A N S P O R T O F FISSION P R O D U C T S C. M. Blood ....................................................................................................................................................................

D e p o s i t i o n profiles for (1) 133J3a transported from barium-impregnated graphite by wet or dry h e l i u m a n d (2) *Io&

1 3 7 C s 9and 13‘Cs transported from previously irradiated graphite by wet helium were e s t a b l i s h e d by

s e c t i o n i n g and counting techniques.

FUEL PARTICLES B Y WATER VAPOR .................................................................................................................

OXIDATION O F COATED

R a t e s of oxidation and i n c i d e n c e o f c o a t i n g f a i l u r e s were determined for various b a t c h e s of c o a t e d fuel p a r t i c l e s a t 1100 to 140O0C u s i n g helium-water-vapor

10. Irradiation Behavior

mixtures c o n t a i n i n g 500 o r 1000 ppm of water vapor.

o f High-Temperature F u e l M a t e r i a l s

0. Sisman and J. G. Morgan

I R R A D I A T I O N E F F E C T S ON P Y R O L Y T I C - C A R B O N - C O A T E D F U E L P A R T f C L E S P . E. Reagan, J. G. Morgan, J. W. Gooch, M. 7’. Morgan, and ILI. F. Osborne .....................................................

Pyrolytic-carbon-coated thorium-uranium c a r b i d e p a r t i c l e s prepared commercially for the C,erman AVR re-

a c t o r withstood irradiation to 10 at. % heavy-metal burnup a t 130OnC,a n d a barrier layer of s i l i c o n carbide added to a pyrolytic carbon c o a t i n g greatly reduced the r e l e a s e of f i s s i o n s o l i d s .

IN-PILE TESTS O F A MODEL TO PREDICT T H E PERFORMANCE OF COATED F U E L PARTICLES P. E. Reagan, E. L. Long, Jr., J. G. Morgan, and J. W. Gooch ..............................................................................

100

A mathematical model d e v e l o p e d to predict t h e b u m u p n e c e s s a r y to c a u s e pyrolytic-carbon-coating

failure w a s found t o b e a c c u r a t e for the w e a k e s t c o a t i n g s in the b a t c h , a n d a thick carbon buffer Layer c a u s e d uranium oxide p a r t i c l e s to o v e r h e a t and a t t a c k t h e coating.

P O S T I R R A D I A T I O N T E S T I N G OF C O A T E D F U E L P A R T f C L E S M. T. Morgan, C. D. Baumann, a n d K. L. Towns .................................................................................................... Various t y p e s o f pyrolytic carbon c o a t i n g s a p p l i e d t o fuel p a r t i c l e s of UO a n d U C 2

h a v e been a n n e a l e d

a t high temperatures after neutron irradiation to t e s t for c o a t i n g s t a b i l i t y , retention o f f i s s i o n products, a n d fuel migration.

101

I R R A D l A T I O N E F F E C T S O N C O M P A T l B l L l T Y OF F U E L O X l D E S A N D B E R Y L L I U M O X I D E WITH

GRAPH! T E D. R. Cuneo, C. A. Brandon, H. E. Robertson, and E. L. Long, Jr. ...................................................................... Graphite is chemically compatible with both (U,’Ih)O

105

and 3 c 0 ; t h e concentration of 61,i found in R e 0

diminishes in s m a l l e r p i e c e s in a direction c o n s i s t e n t with a surface-to-volume relationship.

FAST GAS-COOLED REACTOR D E V E L O P M E N T D. R. Cuneo, H. 53. f2obertson, E. J... Long, Jr., and J. A. Conlin ............ In low-burnup irradiations no indication of fuel element failures h a v e been found with U O s t a i n l e s s s t e e l or Hastelloy X.

................ 2

FISSION-GAS RELEASE DURING FISSIONING OF e602 R. M. Carroll, R. L3. P e r e z , 0. Sisman, G. M. Watson, and T. W. F u l t o n .............................................................. Refinements h a v e been made in t h e defect-trap model, and c l u s t e r i n g of d e f e c t s at about 1000°C i n s i n g l e crystal U O

107

in e i t h e r

109

w a s observed a s predicted.

T H E R M A L C O N D U C T I V I T Y OF U 0 2 D U R l N G I R R A D I A T I O N C. D. Baumann, R. M. Carroll, J. G. Morgan, M. F. Osborne, and R. B. P e r e z ....................................................

111

T h e thermal conductivity of a U O fuel specimen is being n e a s u r e d a s a function of flux and temperature during irradiation.

11. Behavior

of High-Temperature Materials Under Irradiation

E F F E C T S OF FAST-NEUTRON I R R A D I A T I O N ON O X l D E S

G. W. K e i l h o l t z and R. E. Moore .................................................................................................................................. , \ l r a n s l u c e n t alurnirium oxide of high d e n s i t y h a s b e e n found to be iiiorc r e s i s t a n t to irradiation damage than

s i n t e r e d A1 0 2

113

a t irradiation temperatures of 300 to 600°C u p to 3 x l o z 1 m u t r o n s / c m 2 ( > 1 Mev).

B E H A Y l O R O F R E F R A C T O R Y METAL. C A R B I D E S U N D E R BRRADbATIQN ................................................................... G. W. Keilholtz, R. E. Moore, and M. F. Osborne .......... Irradiation e f f e c t s on specimens of monocarbides of Ti, Zr. Nb, T a , and W made by h o t pressing, s l i p

114

c a s t i n g , and explosion p r e s s i n g were i n v e s t i g a t e d a t low temperatures (300 to 70OoC) over t h e fast-neutron dose range 0.7 to 5.4 x 10” tion under t h e s e conditions.

neutrons/cm* (> 1 Mev); W and Ti monocarbides were q u i t e r e s i s t a n t to irradia-

P A R T I V . OTHE 12. Chemical Suppart for the Saline

ORHL PROGRAMS

Water Program

S O L U B S L I T Y OF CALCIUM S U L F A T E IN SEA SALT SOLUTIONS TO 200°C; T E M P E R A T U R E S O L U B I L I T Y L I M I T S F O R ZALlME W A T E R S W. L. Marshall and Ruth Slusher ..........................................................................................................................

S o l u b i l i t i e s of calcium s u l f a t e were determined i n s e a s a l t s o l u t i o n s f r o m 30 t o 2OO0C, and t h e d a t a were

used to c a l c u l a t e r e v i s e d temperature-solubility

limits for s a l i n e waters i n general.

CORROSlON OF TITANIUM I N S A L I N E WATER E. G. Rohlmann, J. F. Winesette, J. C. G r i e s s , Jr.,

and F. A. P o s e y ..................................................................

121

Continuing elcctrochernical s t u d i e s of titanium corrosion a t e l e v a t e d temperatures h a v e supported t h e a c i d s o l u t i o n c r e v i c e corrosion mechanism and s u g g e s t e d that the complex i n v e r s e temperature dependence of t h e p i t t i n g potential is related to e f f e c t s of alloy c o n s t i t u e n t s on t h e p a s s i v e oxide film.

13.

Effects of R a d i a t i o n on Organic M a t e r i a l s W. W. P a r k i n s o n a n d 0. Sisman

E F F E C T S O F R A D I A T I O N ON P O L Y M E R S W. W. P a r k i n s o n mid W. K. Kirkland ........ T h e olefin groups of a l l isomeric fortns o

..................

125

.......... is-

a p p e a r a n c e of s i d e vinyl groups showing a h i g h enough r a t e to s u g g e s t a c h a i n reaction.

R A D I A T I O N - I N D U C E D REACTIONS OF HYDROCARBONS R. M. K e y s e r and W. K. Kirkland ................................................................................................................................. T h e nonvolatile products from the irtadjation of t h e model s y s t e m n a p h t h a l e n e i n h e x a n e were found by chromatographic and s p e c t r a l a n a l y s i s to be chiefly a- and p - a l k y l - s u b s t i t u t e d n a p h t h a l e n e s ( a s s u m i n g nci

127

decomposition on t h e chromatographic column).

A D D l T l O N R E A C T l O N S OF F U R A N D E R I V A T I V E S C . D. Bopp and W. W. P a r k i n s o n _.

......

..........

........

......

123

T h e major radiation proclucts from s o l u t i o n s of cyclohexene in tetrahydrofuran h a v e b e e n tentatively

iderit-ified a s 1:1 a d d u c t s and dimers, with y i e l d s ranging from G

0.5 to 2 a t room temperature.

D E V E L O P M E N T O F R A D I A T I O N - R E S I S T A N T INSULATORS W. W. P a r k i n s o n , I3. J . Sturm, and E. J. Kennedy ....................................................................................................

Many s a m p l e s of s t y r e n e - b a s e polymers and s a m p l e s of s e v e r a l other chemically simple p l a s t i c s have been

130

obtained and a n a l y z e d for common impurities, and a n e l e c t r i c a l m e a s u r i n g a p p a r a t u s h a s b e e n t e s t e d f o r sensitivity.

14. Chemical Support

for the Controlled Thermonuclear Program

R. A. Strehlaw a n d D. $1. Richardson

I N T E R P R E T A T I O N O F DCX-2 MASS S P E C T R A ........................ The composition of r e s i d u a l g a s in t h e DCX-2 vacuum s y s t e m was a n a l y z e d in d e t a i l from m a s s s p e c t r a obt a i n e d during operation. Several low-molecular-weight hydrocarbons were found to b e g e n e r a t e d during b e a m injection.

MASS S P E C T R O M E T E R C A L I B R A T I O N STUDIES ....................................................................................... Improvement w a s made in q u a n t i t a t i v e i n t e r p r e t a t i o n s of r e s i d u a l g a s s p e c t r a by s t u d i k s of m a s s discrimination in t h e spectrometer; t h e o b s e r v e d t r a n s m i s s i o n fraction of carbo11 dioxide i o n s w a s one-fourth t h a t o f water ions.

WATER V A P O R CHEMISORPTION ON STAINLESS S T E E L ....

..........................................

T h e desorption of water from s t a i n l e s s s t e e l a f t e r s h o r t e x

w a s s t u d i e d in a n oil-

134

free system; t h e r e s u l t s followed chemisorption k i n e t i c s .

DECOMPOSITION O F DC-705 D l F F U S I O N PUMP F L U I D .........................................................................

A white s o l i d accumulation found in t h e i n l e t of a diffusion pump w a s identified a s the decomposition

138

product of t h e s i l i c o n e o i l pump fluid.

PART

V. NUCLEAR SAFETY

15. A c t i v i t i e s of Nuclear Safety T e c h n i c a l Staff W. L?. Browning, Jr., M. â&#x201A;Ź1. F o n t a n a , and U. A . Soldano .......................................................................................... T n e N u c l e a r Safety T e c h n i c a l Staff, comprised of three persons, w a s formed early t h i s year to a i d in

planning, coordinating, and directing t h e r e s e a r c h and development a c t i v i t i e s within t h e N u c l e a r S a f e t y Pro gram.

143

xi i

16. Correlotions

of F i s s i o n Product Behavior

T H E L l G l l P B U L B MODEL F O R R E L E A S E O F FISSION PRODUCTS C. E. Miller, J r . .............................................. ...................................................................................

145

A modcl, b a s e d on boundary layer diffusion p r o c e s s e s , s a t i s f a c t o r i l y d e s c r i b e s t h e dependence of the fraction of f i s s i o n product r e l e a s e d from reactor f u e l s on (1) t h e composition and p r e s s u r e of the surrounding atmosphere, (2) t h e temperature, ( 3 ) t h e h e a t i n g time, and (4) t h e chemical form of the f i s s i o n product s p e c i e s .

EFFECT'

O F CONTAiNMEMT SYSTEM S I Z E ON FISSION P R O D U C T B E H A V I O R

G. M. Watson, R. B. P e r e z , and M. H . Fontana

.................................................................................

T h e behavior of iodine i n containment s y s t e m s

z e by two orders of magnitude h a s b e e n cor-

147

related with inoderate s u c c e s s u s i n g simple mathematical relationships.

C H E M I C A L E Q U I L I B R l U M STUDIES OF ORGANIC-lODlWE FORMATION UNDER N U C L E A R R E A C T O R

ACCIDENT CO NDi T i O N S I?. H. B a r n e s , J. F. Kircher, and C. W. Townley

.....................................................

149

n d i t i o n s under which CH I

Computerized thermodynainic c a l c u l a t i o n s indica could b e generated in reactor a c c i d e n t s .

T H E ADEQUACY OF SCAiLEUP IN E X P E R I M E N T S O N FISSION PRODUCT B E H A V I O R I N R E A C T O R A CClD EN TS C. E. Miller, Jr.. and W. E. Browning, Jr. .................................................... A repoit h a s b e e n written which d e s c r i b e s two p o s s i b l e intermediate-scale experiments a t 1 and 10% t h e

150

size of LOFT which a i e needed to extend t h e s c a l i n g range of experiments on f i s s i o n product behavior over

t h e five orders of magnitude betwsen s m a l l experiments and LOFT.

FISSION P R O D U C T S FROM FUELS UNDER REACTOR-TRANSIENT C0NDdTEON.S G. W. Parker, R. A. Lorenz, and J. G. Wilhelm .......................................................................................................... S t u d i e s of f i s s i o n product r e l e a s e and transport from metal-clad UO

c l u d e t h e e f f e c t of and p r e s s u r e r a t e of s t e a m r e l e a s e .

152

f u e l transient-melted under water in-

S I M U L A T E D LOSS-OF-COOLANT E X P E R I M E N T S i N T H E OAK R l O G E RESEARCH R E A C T O R C. E. Miller, Jr., R. P. S h i e l d s , R. F. Roberts, and R. J. Davis ............................................................................ 'The interpretation of d a t a from previous experiments on f i s s i o n product r e l e a s e a n d a literature review of

153

iodine d e p o s i t i o n have been t h e main a c t i v i t i e s during a period when major c o n s t r u c t i o n work h a s been under way on t h e reactor facility.

I G N I T I O N OF CHARCOAL. A D S O R B E R S C . E. Miller, Jr., and R. P. S h i e l d s ............................................................................................................................

155

R e s u l t s of both in-pile a n d out-of-pile experiments on ignition t e m p e i a t u i e s of c h a r c o a l used i n contain-

ment v e s s e l a i r c l e a n i n g s y s t e m s show t h a t t h e temperature can b e a f f e c t e d significantly by long-term exposure, s l i g h t l y by moisture, and very little by adsorption of e x c e s s i v e l y large q u a n t i t i e s of iodine.

FISSION PRODUCTS FROM Z I R C A L O Y - C L A D HIGH-RURNUP UQ2 G. E. Creek, R. A. Lorenz, W. J. Martin, and G. W. Parker .................................................................................... Zircaloy-clad U O irradiated to a buriiup of 7000 Mwd/ton w a s melted in t h e Containment Mockup 2 F a c i l i t y (CMF), and t h e behavior of r e l e a s e d f i s s i o n products jn t h e s t a i n l e s s s t e e l CMF tank w a s compared with t h a t r e l e a s e d from a s t a i n l e s s - s t e e l - c l a d specimen irradiated to 1000 h.lwd/ton.

157

BEHAVIOR OF l2 AND HI IN THE C O N T A l N M E N T RESEARCH I N S T A L L A T ~ O NT A N K G. W . Parker, W. J. Martin, G. E. C r e e k , a n d N. H. IIorton ....................................................................... T h e r e l a t i v e d e p o s i t i o n behavior of molecular i o d i n e and hydrogen iodide h a s been observed in t h e 1200-gal CRI s t a i n l e s s s t e e l containment v e s s e l .

158

xiii

18,

Laboratory- Sca le Suppo tting Studies

D E V E L O P M E N T DF F I L T R A T I O N AND ADSORPTION TECHNOLOGY R. E. Adams, J a c k Trui tt, J. S. Gill, a n d W. D. Y u i l l e .............................. ............................................... The e f f e c t of a c c i d e n t environments o n t h e behavior of t e s t a e r o s o l s a n d o n the performance of fi!ter

160

media is being s t u d i e d i n the laboratory.

E X A M I N A T I O N O F P A R T I C U L A T E AEROSOLS WITH T H E F I B R O U S - F I L T E R A N A L Y Z E R M. D. Silverman, J a c k Truitt, W. E. Browning, Jr., and R. E. Adams .................................................................... The Fibrous-filter a n a l y z e r is b e i n g developed a s a device f o r examining t h e c h a r a c t e r i s t i c s of r a d i o a c t i v e aerosols

terms of particle r e s p o n s e to t h e major p r o c e s s e s of filtration:

162

diffusion, iiitercaption, and

inei-iial impaction.

DISTINGUISHING l O D l N E F O R M S A T HfGH T E M P E R A T U R E S AND HUMIDITIES R. E. Adarns, Z e l l Comhs, R. L. B e n n e t t , W. 13. Hinds ...........................................................................................

E x t e n s i v e tests of May p a c k s , which are d e s i g n e d t o d i s t i n g u i s h i o d i n e f o r m s , h a v e been conducted under

163

elevated-temperature and high-hnmidity c o n d i t i o n s s u c h a s t h o s e e x p e c t e d in water r e a c t o r a c c i d e n t s .

R E A C T I O N S O F IODlNE VAPOR W I T H ORGANIC M A T E R I A L S R. E. Adams, Ruth Slusber, R. L, Bennett, arid Z e l l Combs

.................................

........

165

ie production of

Laboratory i n v e s t i g a t i o n s a r e being made to detertnine t h e r e a c t j o n s r c s p o n s l

methyl iodj.de, which h a s betm observed i n containment experiments involving elemental iodine.

BEPilAVlOR OF FISSION PRODUCTS I N GAS-LIQUID SYSTEMS R. E. Adams, B. A. Soldatlo, and W . T. Ward ............................................. A s t u d y of t h e behavior

.................................................

f i s s i o n products at the gas-liquid interface 11

165

undertaken.

H l G H - T E M P E R A T U R E B E H A V I O R OF GAS-BORNE FISSION PRODUCTS. T E L L U R I U M D l O X l D E M. D. :iilvermnn and A. P. Malinauskas ................................................................ ........................................

167

An experimental i n v e s t i g a t i o n of the enhanced volatility of metal oxides i n the p r e s e n c e of water vapor h a s been i n i t i a t e d .

T H E CASCADE IMPACTOR AS A T O O L FOR T H E STUDY A ERQSDLS G. W. P a r k e r and H. Buchholz

O F S I Z E D I S T R I B U T I O N O F FISSSION P R O D U C T

..................................................................................

C a l c u l a t i o n s :jhow that operation of the Andersen c a s c a d e impactor a t p r e s s u r H g permits e x t e n s i o n of i t s useful range t o particle-s with a diameter l e s s than 0.1

.......................................

267

h e range 1.0 tu 40 mm

p, and

apparatus h a s been

d e v i s e d , a n d is presently being t e s t e d , for this mode of operatiorr.

R E A C T I O N OF M O L E C U L A R l O D I N E AND OF M E T H Y L IODIDE WITH SODIUM T H I O S U L F A T E SPRAYS ....................................... G. W. P a r k e r , W. J. Martin. G. E. Creek, a n d N. R . Fiorton .................................... Mockup F a c i l i t y W e h a v e performed t e s t s in t h e s m a l l (180-liter) s t a i n l e s s steel tank of the C o

169

(CMF) u s i n g m i s t i n g s p r a y s containirlg 0.1 M sodium thiosulfate to remove niolecular iodine and met-hyl iodide.

STUDIES OF C S E - T Y P E FlSSlON P R O D U C T SIhlULATION 6. W . P a r k e r , R. A. Lorenz, a n d N. J - Iiorton ................

Design, construction, a n d preliminary test.ing of equip11

......................................................................................

170

for performing CSE-type s i m u l a n t esperimerits

in the CMP a n d CRI h a v e b e e n completed.

R E T E N T I O N OF R A D I O A C T I V E M E T H Y L IODIDE B Y I M P R E G N A T E D C H A R C O A L S R. E. Adams, R. D. Ackley, J. D. Dake, J. &I. Gimbel, and F. V. I l e n s l e y ..........................

......................

172

C e r t a i n s p e c i a l l y impregnated (iodjzed) CharciJalS have t h e c a p a b i h t y of e f f e c t i v e l y trapping r a d i o a c t i v e methyl iodide, by a n i s o t o p i c exchange mechanism, from â&#x201A;Źlowing a i r a n d steam-air over a wide range of

COW

ditioris iricluding 70 to 300"F, 1 4 to 60 p s i a , a n d 0 to 90% r e l a t i v e humidity.

PUBLICATIONS ........................ ....................

....................

..&I..

..*

.......

........................*...,..-*........

PAPERS PRESENTED AT SCIENTIFIC AND TECHNICAL MEETINGS ..................................................

175

180

Part 1

Molten-Sa

Phase Equilibrium and Crystallographic Studies

THE EQUILIBRIUM PHASE DIAGRAM FOR THE SYSTEM LiF-BeF2-ZrF,

Invariant equilibria i n t h e s e s y s t e m s were found to occur a t t h e composition-temperature l o c a t i o n s l i s t e d i n T a b l e 1.1. As Fig. 1.1 i n d i c a t e s , t h e binary system BeF,ZrF, exhibits relatively simple p h a s e behavior. A s i n g l e e u t e c t i c o c c u r s at a relatively low ZrF, concentration, and the system is free from binary compounds. Two immiscible liquids occur in mixtures containing 1 4 t o 25 m o l e % ZrF,; the upper consolute temperature is near 740% T h e LiF-BeF,-ZrF, system (Fig. 1.2) is, so far as w e a r e aware, t h e only ternary fluoride system yet shown to include immiscible liquids. A s the temperature is i n c r e a s e d above t h e liquidus, t h e composition interval showing two liquid p h a s e s steadily diminishes; i t d i s a p p e a r s at an upper consolute point at 25 mole % LiF' and 55 mole % H e F , a t 955째C. T h i s occurrence of two liquid p h a s e s in t h e system a t high concentratjons of Belli, d o e s not prejudice u s e of materials i n the composition region near 65 mole % LiF and 30 mole % B e F , a s fuel s o l v e n t s for molten-salt reactors.

H. A. Friedman K. E, 'I'homa H. I n s l e y ' Mixtures of 7 L i F , B e F , , and ZrF, are of e s p e c i a l i n t e r e s t in t h i s Laboratory b e c a u s e s u c h mixtures s a v e a s t h e solvent for 2 3 5 U F , i n t h e MoltenSalt Keactor Experiment. P h a s e behavior of t h i s ternary system and of its constituent binary subs y s t e m s h a s , accordingly, been examined i n some detail. T h e binary s y s t e m s L i F - B e F Z z r 3and LiFZrF, h a v e been carefully inv-estigated h e r e and elsewhere and have been described in available literature. Study of t h e ReF,-ZrF, and the LIFWeF,-ZrF, s y s t e m s w a s completed during the p a s t year. Most of t h e d a t a for t h e s e s y s t e m s w e r e obtained by t h e technique of thermal gradient quenching followed by careful examination of t h e products by o p b c a l niicroscopy, though t h e older technique of thermal a n a l y s i s w a s of v a l u e in s o m e regions. T h e regions of liquid-liquid immiscibility in t h e s e s y s t e m s w e r e defined with t h e help of high-temperature centrifugationG and careful examtnation of t h e s e p a r a t e d products. T h e combined d a t a were used in construction of t h e p h a s e diagrams shown as F i g s . 1.1 and 1.2.

OHlll

_ I

D W G 6 6 7875

700

'Consultant.

'D. M. Roy, R. Roy, and E. F. Osborn, J. Am. Ceraui. 37, 300 (1954). 3 A. V. Novoselova, Yu. P. Slmanov, and E. I. Yarembaqh, J. Phys. Chem. (U.S.S.R.) 26, 1244 (1952). SOC.

400

'13. I n s l e y et al., Bull. ~ o c .Franc. Cersm., NO. 48, July-Sept. 1960. 'K. E. 'Ihoma et al., J . Chem. En& Data 10(3), 219

300 EleF,

( 195 5).

'RRenLtor Chem. Div. Anti. Pro&. K e p t . D e r . 31, 196.5, OHNL-3913, p. 3

Fig. 1.1.

50 60 Z r G (mole'%)

The S y s t e m BeF 2 -ZrF 4 '

ZrF,

4 ZrF,

903 TEMPERATURES IN ' C

COMPOSITION IN mole %

F i g . 1.2.

Table 1.1. ~

..........__.-

Composition (mole

__I

LiF .......

.......

..........

Bel",

92.5

The S y s t e m L i F - H e F 2 - Z r F 4 .

Invariant E q u i l i b r i u m P o i n t s i n the S y s t e m s B e F 2 - Z r f 4 and L i F - B e F 2 - Z r F 4 .....____._-. ___ ............

70)

1emperature

, ?

ZrF,

(OC)

7.5

525

..........___

Type of Equilibrium -.

Eutectic

Solid P h a s e s P r e s e n t .......... 13eF2, ZrF,

645

ZrF,

645

ZrF,

480

Peritectic

L i F , 3 L i F * ZrF,, 2 L i F

470

P eri tec ti c

L i F , 6 L i F * B e F Z ZrF,, 2 L i F * ZrF,

29.5

445

Peritectic

LiF, 6 L i F . BeF,

64.5

3.5

2L.j.F

30.5

428

Peritectic

ReF,

- ZrF,,

6 L i F R e F z * ZrF,,

2 L i F ZrF,,

2LiF BeF

ZrF,

355

Eutectic

2 L i F ZrF,,

2 L i F * B e F 2 , BeF2

47.5

42.5

466

P e ii t e c tic

2 L i F * ZrF,,

3 L i F 4ZrF4, ZrF,

460

Eute r)t i c

2LiF

532

10 ..........

B e F 2 , ZrF,

BeF2, ZrFj

532 ..........

ZrF,,

....

ReF2, ZrF,

.........

PRELIMINARY STUDY OF THE SYSTEM Li F- Th F ,-Pa F

H. H. Stone C. J. Barton G. D. Brunton In t h e protactinium recovery s t u d i e s described i n Chap. 3 of t h i s report i t h a s been generally assumed that protactinium is p r e s e n t i n t h e L i F T h F , (73 mole 74 LiF) m e l t s as PaF,. 'This assumption h a s seemed p l a u s i b l e s i n c e t h e m e l t s have, i n every c a s e , received a treatment with I-I, at temperatures near 6SO'C, and s i n c e H, is knozvn to r e d u c e pure PaF, to PaF, at much lower temperatures. ( T h e Pa4' s t a t e seems to b e t h e l o w e s t known i n fluoride systems.) W e have, however, conducted a few preliminary experiments to t e s t t h i s assumption and t o see if t h e p h a s e behavior of PaF, is similar to that of T h F , i n mixtures with L i F . A h u t 100 mg of 23'PaF, w a s prepared by evaporating a measured portion of purified stock solution (9 M in H F j t o d r y n e s s i n platinum and h e a t i n g t h e r e s i d u e to 6OO0C i n flowing HF-11, mixture. Conversion to PaF, w a s confirmed by weight and by t h e brown color of t h e material. A portion of t h i s material w a s mixed with L i F - T h F , (73 mole % L i F j to y i e l d a mix with 68 m o l e "/o LiF and 32 mole 76 (Th,Pa)F,. Another portion w a s mixed with LiF and the L i F - T h F , mixture to y i e l d a mix with 73 mole 74 LiF and 27 mole X (Th,Pa)F,. Both mixtures were admixed with ammonium bifluoride (whose decomposition products on heating h e l p to minimize p o s s i b l e hydrolysis), h e a t e d to 6SO째C, and cooled slowly. Examination of t h e slowly cooled m e l t s showed that segregation of PaF,-rich p h a s e s from t h e bulk of the LiF-ThF, material occurred i n both cases. Material from t h e mixture with 68 mole % ' I,iF is believed to b e a s o l i d solution of LiPaF, i n LiThF,. O n e of t h e p h a s e s from t h e s a m p l e with 73 mole % LiF is believed, b e c a u s e of i t s similarity to t h e analogous uranium compound, to be Li,PaF,. 'The PaF, d o e s not appear isomorphous with ThF,; t h e LiF-PaF, system may, i n fact, b e more l i k e t h e LiF-UF, than t h e LiFThF, system. I t i s o b v i o u s that study of t h e binary L i F - P a F , s y s t e m is n e e d e d before attempting further d e d u c t i o n s concerning p h a s e relations i n the ternary s y s t e m LiF-ThF,-PaF,. A portion of t h e LiF-'l'hF,-PaF, mixture with 73 mole 76 LiF w a s transferred to a small thorium

c r u c i b l e and h e a t e d to 650'C in a helium atmosphere. Examination of t h e material with t h e polarbut a i z i n g microscope revealed s o m e I,i,ThF,, l a r g e p a r t of t h e mixture w a s in t h e form of opaque angular fragments, which a r e probably protactinium metal. X-ray examination will b e required to confirm t h i s conclusion.

APPARATUS FOR AUTOMATIC DIFFERENTIAL THERMAL ANALYSIS L. 0. Gilpatrick R, E. Thoma S. Cantor Fluoborate mixtures containing high concentrat i o n s of NaBF, appear useful as secondary coola n t s i n molten-salt breeder reactors. Since s u c h systetns show significant H F , p r e s s u r e s at ternperatures a b o v e t h e liquidus, our standard techn i q u e s of thermal a n a l y s i s and thermal gradient quenching are a p p l i c a b l e only with difficulty to t h e s e materials. W e h a v e , accordingly, developed (with help from t h e O R N L Instrumentation and Controls Division) a s e n s i t i v e automatic differential thermal a n a l y s i s apparatus for study of t h e fluoborates. T h i s equipment, similar to that u s e d by Holm,' c o r i s i s t s of a s e r i e s of components a s s e m b l e d as illustrated i n Fig. 1.3, Specimens are contained i n s e a l e d thin-walled nickel tubing, having outer x 2.5 in. Temperatures a r e monitored dimensions by armored 40-mil thermocouples which are positioned from below i n reentrant chambers. Specimen c o n t a i n e r s and thermocouple a s s e m b l i e s were des i g n e d for minimal h e a t capacity. T h e specimen thermocouple s u p p l i e s a signal in opposition to that from a matched cell containing fired A1,0, as a comparison standard. Both c e l l s are mounted i n a m a s s i v e nickel block and out of direct thermal c o n t a c t with t h e block by m e a n s of ceramic supports. An independent thermocouple embedded i n t h e block provides a s i g n a l which programs t h e temperature and h e a t i n g r a t e of t h e system a s a whole. Differential temperatures are recorded as a function of time on a model 7002AMR Moseley x-y recorder after amplification of from SO0 to 'R. E. Thoma aid G. M. I-Isbert, "Coolant Salt for a Molten Salt Breeder Reactor," P a t e n t Application CNID-2100, Nov. 16, 1966.

'5.

L. Holm,

A c t a Chern. Scand. 19, 261 (1965).

6 ORNL-DWG 67- 768

FURNACE HEATER

.................

........

.......... .......

c..

N I C K E LBLOCK

"LABAC"

SOI.10 - S T A T E

.........

SIGNAL TEMPERATURE CONTROLLER

CONTROL T.C.

ICE B A T H . . .

.......A

......... Fig.

1.3. Block Diagram for

20,000 a s desired, v i a a L e e d s and Northrup microvolt amplifier, model No. 9835B. T h e recordi n g system is calibrated daily by a potentiometric circuit and a standard c e l l used to produce a known input signal. T h e apparatus temperature w a s calibrated by measuring t h e melting points of l e a d and bisinuth metal s t a n d a r d s from t h e National Bureau of Standards. T h e temperature programming unit w a s designed to control linear temperature c h a n g e s over variable time periods from 30 to 300 min. Output from t h e programmer, c o n s i s t i n g of a 0- to 10-mv s i g n a l , is fed to a solid-state power unit which c o n t r o l s t h e h e a t input. T h i s d e v i c e automatically programs repeated h e a t i n g and cooling of s p e c i m e n s within p r e s e t l i m i t s and thereby e n a b l e s automatic collection of p h a s e transition d a t a for periods of 50 hr or more. T h e equipment is b e i n g applied to definition of liquid-solid and solid-solid f-ransitions in t h e NaFBF, system. Initial r e s u l t s show that t h e melting point of NaRF, i s 383.1OC; t h i s material, which c o n t a i n s less than 200 ppm of o x i d e ion, a p p e a r s

Autotnatic D T A Apparatus.

to melt some 153C higher than t h e (probably l e s s pure) material described by Selivanov and Stander.'

SOLID-PHASE EQUlLlBWBA IH THE SYSTEM saw F ,-Srn F,-U F R. E. T'homa

H. 4. Friedman

T h e fact that reduction p o t e n t i a l s for t h e reaction L n 3 + L n 2 + a r e l o w e s t for t h e l a n t h a n i d e s europium and samarium (approximately 0.4 v) implies that t h e interactions of SrnF,, Sin!?,, and

UF, possibly are significant in t h e development of molten-salt fuel reprocessing iiiethods which would employ U F , a s an ion exchanger for s e l e c t i v e removal of rare-earth fission product fluorides. P r o d u c t s of t h e reactions of Sm0 or Uo with SmF2, Sin%,, UF,, and mixtures of t h e s e fluorides, which t a k e p l a c e a t 1300 t o 14OO0C, were analyzed. ~.

.........

............

'V. G. Selivanov and V. V. Stander, R u s s . J. Inorg. Chem. 4, 9341,1959).

7 'The c r y s t a l p h a s e s were characterized with micros c o p i c , x-ray diffraction, and electron r e s o n a n c e methods and were chemically analyzed, Samarium trifluoride w a s found to b e stoichiometrically reducible wit.h Smo to SmF,, a c u b i c blue p h a s e with refractive index 1.534 and a(, :--5.866 A. P a r t i a l reduction of SmF, with SmO produces a birefringent red intermediate p h a s e of unknown structure, inferred t e n t a t i v e l y to b e t h e compound T h e limited d a t a which a r e curS m F 2 - SmF,. rently a v a i l a b l e i n d i c a t e t h a t within t h e system SmF2-SmF3-lJF, e x t e n s i v e mutual solubility of t.he various components and intermediate p h a s e s p r e v a i l s except between SmF,, and t h e intermediate p h a s e SmF, SmF,. If t h i s conclusion is borne out i n future experiments, t h e reduction p o t e n t i a l s of s a l t s which p a s s through U F , ion exchange b e d s will p o s s i b l y b e significant parameters iri p r o c e s s control. 1

ASE RELATIONS IN T H E SYSTEM KF-CeF, C . J. Barton G. 1). l-3runton

IJ. Hsril' H. InsIey'

ture well a b o v e t h e e s t i m a t e d l i q u i d u s temperature w a s reached, Gradient q u e n c h e s were performed with portions of t h e slowly cooled melts, and the resufting s a m p l e s were examined by u s e of a polarizing microscope. T h e principal findings of t h e incomplete investigation a r e a s follows: There i s o n e e u t e c t i c cmmposition at about 19 mole 76 CeF3, melting at 625 ..t 5"C, and two incongruently melting compounds, 3 K F C e F , and K F = CeF,. The former m e l t s at 67.5 i- 5°C to g i v e R F CeF, and liquid and i t aIso decomposes o n cooling a t 595°C 5" giving K F and K F CeF,. The latter compound m e l t s at 755 i 5°C giving liquid and a c u b i c p h a s e of unknown composition. 'l'bermal a n a l y s i s did not i n d i c a t e t h e upper and lower stability l i m i t s o f 3 K F C e F , , n o r did i t provide reli-. a b l e l i q u i d u s v a l u e s for mixtures containing inore than 20 mole % CeF,. It w a s i n t e r e s t i n g to compare t h e d a t a obtained for t h i s system with t h e proposed diagram for t h e system KF-NdF, recently reported by Schmutz. l 3 H e reported a e u t e c t i c containing about 20 iiiole % NdF,, melting a t 625'C: 1 0 9 and three compounds, 3 K F NdF,, K F NdF,, and K F 2NdF',, melting incongruently at 695, 750, and 1.B15°(: respectively, H i s p h a s e diagram w a s b a s e d on differential thermal a n a l y s i s d a t a and examination of t h e slowly cooled m e l t s by m e a n s of x-ray diffraction. On i.he b a s i s of our s t u d i e s of quenched m e l t s it seems probable that. t h e system i s inore complex than shown by Schmutz' diagram. W e plan lo perform further thermal ana1ys.k and quenching s t u d i e s to better d e f i n e t h e composition of t h e high-temperature c u b i c p h a s e mentioned above. It is q u i t e p o s s i b l e t h a t it i s more closely rel a t e d to t h e 5NaF. 9YF, compound'" than to t h e s i m p l e 1 to 2 compound p o s t u l a t e d by Schmutz.

h a v e shown that p h a s e r e l a t i o n s h i p s i n t h e LiF-CeF, and NaF-CeF, :;y!;tems a r e very similar to t h o s e €or t h e i r LiFP u F , and NaF-PuF, counterparts. A btief examination of t h e KF-CeF, s y s t e m h a s , accordingly, been conducted to show probable behavior for KF-PuF,. Work will begin on K F - P u F , as soon a s di f ferenti a1 therm d mal y si s equipment btxome s available to provide a d e q u a t e s e n s i t i v i t y with s m a l l amounts of materials. We obtained thermal a n a l y s i s d a t a from cooling c u r v e s obtained with a h a r e platirium-platinumrhodium thermocouple immersed i n t h e melt contained i n a small (5 ml) platinum crucible, 'The c a l c u l a t e d weights of K F and CeF, (to g i v e 3 to 4 g total) were p l a c e d i n a c r u c i b l e along with several grams of ammonium bifluoride, and t h e mixture w a s h e a t e d i n a flowing stream of helium, slowly a t first until t h e arrirnonium hifluoride decomposed, and then more rapidly until a tempera20 Summer Berkeley. 11

employee

from

TJniversity

C. J. Barton and R. A. Strchlow, Chem. 18, 143-47 (1961).

Califorma,

1. Iriurg.

Nucl.

" C . J. Barton, J. D. Redman, atid R. A. Strehlow, J . Inorg. Nucl. Cherri. 20, 45 (1961).

THE CRYSTAL STRUCTURE OF Li,UF, G. D. Brunton ?'he compound Li,UE crystallizes in space 9.960, h, - 9.883, and co group Pnmd with a0 5.986. T h e x-ray d e n s i t y I S 4.71 g/c.c, and 2 - 4. 13

H. Schmiutz (thesis), Investigations in the A l k a l i ct A ctiriide Flunride Systerns. Fln..~rirfa---LiltitZi~nide K e r n r e a k t u r B a u - und Hetriebs---Gesellschaft rn.h.H., K u r l s r u h e , G e r m a n y , KFK-431 ( J u l y 1966). 14

R. E. Thoma e t ol., Inorg. c'lzern. 2, 1005 (1963).

.......L

YiT:-

.-U

a a u

2 L

F(2)

0.023(2)

0.121(2)

0.608(2)

0.00 45(6)

F(3)

0.241(2)

0.03 I( 2)

0 57 S( 3 )

O.O0S8(7)

by4)

0.309(3)

0.250

0.117(‘1)

0.0059( 10)

F(5)

0.292(2)

0.250

0.633(4)

O.OO45(9)

Li( 1)

0.376(9)

0.1155 ( 9 )

0.099 ( 15)

0.0 106(39)

0. 395( 13)

0.060(10)

0.649(2%)

0.0174(73)

J,l(Zj

Twenty-lour position $11 parameters, four anisotropic u r n n i u m temperature factors, and s e v e n isotropic temperature f a c t o r s ( T a b l e 1.2) were determined from 634 independent r e f l e c t i o n s measured by t h e The 2fi-scan technique with a scintillometer. parameters were refined by l e a s t s q u a r e s to an H factor of 0.082, Absorption corrections were made for Cu K n radiation on a n o b l a t e spheroid with a short 36-p a x i s , [OOll, and a 61-[r diameter for t h e circular section. “he U4’ ion h a s eight neare s t neighbors with bond d i s t a n c e s of 2.21 to 2.39 A, Fig. 1.4. T h e next three n e a r e s t neighbors are two L i. + and another F- at 3.27 and 3.39 A respectively. T h e n i n e F- ions a r e at t h e corners of a 14-faced polyhedron which h a s t h e form of a triangular prism with pyramids on e a c h of t h e three prism faces, and t h e t w o L i t i o n s are at t h e c e n t e r s of irregular F- o c t a h e d r a which s h a r e f a c e s with t h e uranium polyhedron. T h e Li ‘-F- d i s t a n c e s arc: 1..82 to 2.28 A.

THE CRYSTAL STRUCTURES OF NoF-LuF, SOLID SOLUTIQNS I). R. S e a r s

G. 1). Brunton

A remarkable f e a t u r e of t h e sodium fluoride-raietlarth ttifluoride binary s y s t e m s is t h e occurrence of a c u b i c p h a s e w h o s e lanthanide-rich composttion limit corresponds to a formula 5 N a F Yl,nF,.” The 5 . 3 stoichiometry is bizarre, but i t s independ-

_ _ _i...._..-

~...

”R. E. ‘lkoma, 1-1. I n s t e y , arid G, M. Hebert, R e a c t o r

Chem. Div. Arm. Progr. R e p f . Dei:. 3913, pp. 6 ff.

3 1 , 1965, ORNL-

I so tropi c 1eniprrature f acturs: b*

P L 2--+-jll

d X

e n c e of c h o i c e of l e n t h a n i d e $.e.> of c a t i o n i c radius) is even more surprising. Seeking a crystalchemical explanation of this behavior, w e h a v e begun to determine c r y s t a l s t r u c t u r e s of c u b i c NaF-LnF:, m a t e r i a l s of s e l e c t e d coriipositions, Complete three-dimensional x-ray intensity d a t a h a v e been collected for two c u b i c sodium lutetium fluorides, whose compositions a r e 51.2 arid 56.6% LuF,. R e f l e c t i o n s w e r e measured with a spectrogoniometer and sing1 e-crysial orienter, using t h e 20-scan technique. U s i n g full-matrix l e a s t - s q u a r e s and difference-synihesis methods, a variety of c a t i o n vacancy and anion i n t e r s t i t i a l models were t e s t e d and refined. B a s i c a l l y , all models were derived from t h e c l a s s i c a l fluorite (CaF,) s t r u c h r e . Best goodness of fit ( a s judged by R f a c t o r s and difference s y n t h e s e s ) w a s obtained for e a c h c r y s t a l u s i n g a model c o n s i s t i n g of a mixed cation s i t e at t h e origin, a fractionally occupied fluorine s i t e at (0.275, 0.275, 0.27.5), and a second fractionally occupied fluorine s i t e at ( k 2 , x, x>. For 51.2% L u F J , x = 0.114, and for 55.6% LuF,,, x .: 0.061. T h e corresponding K factors are 4.6 and 3,Y% respectively. Fluorine-fluorine d i s t a n c e s a r e itripossihly short and would s e e m to b e u n a c c e p t a b l e even if x = 0. T h e model i s u n r e a l i s t i c also i n t h e c o n s t r a i n t s n e c e s s a r i l y imposed upon thermal parameters i n order to a s s u r e convergence: t h e isotropic thermal motion parameters of t h e two l-ypes of fluorine were constrained to b e equal. W e c o n c l u d e that t.he anion interstit.ia1 model is t e n a b l e only i f t h e s t a t i c fluorine d i s p l a c e m e n t s 1%) ;md ($z, 0, 0) a r e fictitious and from t h a t anharmonic thermal m o t i o n o c c u r s along

( i ,t ,

OR N L-D WG 6 5 - 13 040

-.._I_ -_._--

Fig. 1.5.

Stereoscopic D r a w i n g s of t h e Structure of

CsBeFj.

11 Table

Atom

cs Be

F( 1) F(Z)

1.3.

Atomic Parameters for C s B e F

0.265

0.250

0.107

0.0234

0.0143

0.0058

0.0

0.0007

0.0

0.705

0.250

0.679

0.0216

0.0319

0.0063

0.0

0.0003

0.0

0.244

0.042

0.783

0.0245

0.0211

0.0106

0.0031

0.0006

0.0069

0.884

0.250

0.079

0.0 169

0.0282

0.0033

0.0

0.0007

0.0

B1l

tetrahedral directions from t h e s e s i t e s . T h i s kind of motion has been p o s t u l a t e d i n the case of UO,, ‘Tho,, and and t h e conclusion is at l e a s t c o n s i s t e n t with t h e appearance of h f f e r e n c e s y n t h e s e s of t h e two NaF-LuF:, c r y s t a l s hitherto examined. W e will attempt to c o l l e c t intensity d a t a from N a F - L u F , c r y s t a l s near t h e compLsition limits (39 and 64.29% LuF,) in order to reduce t h e calculational ambiguities and to attack directly the problems imposed by the puzzling 5 : 9 ratio.

THE CRYSTAL STRUCTURE OF y-CsBeF, 1-1. Steinfink’

G. I). Brunton

T h e gamma (low-temperature) form of t h e cornpound CsHeF, c r y s t a l l i z e s in s p a c e group Prima with a. :-4.828 A, bo = 6.004 A, and co -- 12.794 A. ?’tie x-ray density is 3.56 g/cc, and 2 = 4. Nine positional parameters and 16 anisotropic ternperature f a c t o r s (Table 1.3) w e r e determined from ref l e c t i o n s measured on a Norelco PAILRED automatic crystal d:da collector. ‘The parameters w e r e refined by least s q u a r e s to an I? of 0.11. E a c h C:s+ ion is surrounded by eight F- n e a r e s t neighbors with bond d i s t a n c e s o f 3.02 to 3.92 A (Fig. 1.5). T h e B e 2 ’ i o n s h a v e four n e a r e s t neighbor F’- i o n s a t t h e corners of a tetrahedron. ’The Be2t-FI- d i s t a n c e s a r e 1.47 to 1 - 6 2 A, T h e structure of t h i s compound is similar t o that of The ret h e high-temperature form of BaGeO . I 8 pulsion of the doubly charged B e 2 cons i n c r e a s e s t h e Be-F d i s t a n c e s where t h e F--ions a r e shared between two tetrahedra. This a c c o u n t s for t h e unusually long (1.62 A) B e 2 + -E--- d i s t a n c e s .

’

..__...__...... __ 16B. T.

M. W i l l i s , A c t a Cryst. 18, 75f (1965).

7Consultant from the I J n i v e r s i t y of Texas.

“Von Waltrud Elilmer, A c t a C r y s t . 15, 1101 (1962).

THE CRYSTAL STRUCTURE OF /?,-KLoF, I).

R. S e a r s

Hexagonal P , - K L a F , solidified as merohedrally twinned c r y s t a l s of s p a c e group P6, almost isostructural with NaNdF,, and not with /3,-K,UF, a s previously reported. Seven coordinates, fourteen nnisot-ropic thermal parameters, and one occupancy fraction (vide infra) were determined from 258 independent reflections measured with a spectrogoniometer and s i n g l e c r y s t a l orienter, T h e sf ructural u s i n g t h e 20-scan technj que. parameters were refined to an K factor of 5.8% using full-matrix l e a s t - s q u a r e s methods and appear in T a b l e 1.4. T h e unit cell and s o m e adjacent atoms a r e illustrated in Fig. 1-6. T h i s c e l l , with a. = 6.530 i 0.002 A, co = 3.800 t 0.002 A, c o n t a i n s T2 formula weights o f K L a F , and is disordered with r e s p e c t to fluorine occupancy of a pair of unrelated sites o n either s i d e of t h e twinning p l a n e s arid potassium occupancy of a p a i r of half-occupied, crystallographically equivalent s i t e s above and below the horizontal mirror planes. Furthermore, there e x i s t s a cation s i t e filled randomly by both latithanurn and patasOrdered 1;mthanum and disordered sium ions. potassium, as well a s t h e mixed c:af.ion s i t e s , are all nine-coordinated by fluorines, each of w h i c h is shared with five additional (but not identical) coordination polyhedra. These polyhedra, comprisi n g t h e “tripyramidal” coordination, are constructed by erecting right. pyramids upon each rectangular f a c e of a trigonal p r i s m . In P,-KI,aF4, individual polyhedra l a c k a 6 figure a x i s b e c a u s e both fluorine and potassium a r e disordered. T h e La-F d i s t a n c e s range from 2.36 to 2.51 A, and t h e K - F d i s t a n c e s from 2.46 to 3.05 A. 19W. €1. Zachariasen, A c t s C r y s t , 1, 265 (1948).

Table.

I(&

1.4.

Sites, Symmetry, a n d Leust-Squares Adiusted Parametersa o f P 1 - K L a F 4

4.4(0.2)

6.3(0.4)

3.4(0.3)

8( 1)

13( 1)

31(9)

22(4)

4(1)

1(~r)6

2 /3

2(i)3

213

0.455(4)

F(1)

j(ic)m

0.255( 2)

0.247(2)

9(2)

K2)

F(2)

3(j)m

0.57 TO.G2

0.380(9)

0.040(7)

24( 12)

53(23)

F(3)

3G)m

0.358(18)

(K + L a )

- 0.035(16)

5 2( 20) d

2@(16)

?Zoordinates were calculaIed i n :he l a s : c y c l e of a “coordinates-only” refinement, thermal parameters and fluorine occupancy fraction i n an e a r l i e r c y c l e when only they were adjusted. Ali s t a n d a r d errors, however, were c a l c u l a t e d i n a one-cycle l e a s t - s q u a r e s adjustment i n which a l l d i s p o s a b l e paremeters were allowed t o vary. F o r t h e atom coordinates, t h e s e standard errors average 46% higher than t h e errors c a l c u l a t e d i n a coordinaEes-only calcdation. ‘These parameters are fixed by syrnrnetry relations:

9, 679 (1956),

p,,

PI], p,,

‘Constrained to equal 1 minus t h e occupancy fraction of F(2).

5. @,,.Ir. addicion, for a l l atoms Pl3- p,,

parameters were artificially c c n s t r a i n e d t c equal t h e corresponding parameters of atom F(2).

0. Cf. H. A. Levy, A c t a C r y s t .

13 ORNL - DWG 6 6 -6926

F i g . 1.6. S c h e i n a t i c P e r s p e c t i v e of the @ , - K L a F 4 U n i t Cell and Its Environs.

CENTRAL CATION DlSPLACEMENTS IN THE “TRI PY RAMI DAL” COORDINATION D. R. S e a r s

All c a t i o n s in N a N d F 4 ” and KLaF, (preceding section) a r e l o c a t e d i n “tripyramidal’3 coordination environments. Both sodium and potassium exhibit large d i s p l a c e m e n t s from their ideal p o s i t i o n s , although it h a s been a s s u m e d ” generally that t h e cation s h o u l d lie o n the polyhedron mediai plane. Seeking ;m explanation of t h e s e data, we have calc u l a t e d potential energy s u m s 2 2 of t h e “exponentials i x ” form:

m d of t h e Lennard-Jones form:

a s well as t h e Coulombic sum

2j : ( l / r . .) for 1)

various

anion configurations i n t h e tripyramidal coordination. W e u s e d v a l u e s of o and s from 7 through 12 and incremented t h e central cation position along t h e polyhedron figure axis from the medial p l a n e l o t h e basal plane. I n t e r a c t i o n s beyond t h e polyhedron w e r e ignored, t h e anion framework w a s assumed t o b e rigid, and ro w a s taken to be t h e sum of P a u l i n g radii. For t h e examples s t u d i e d so far (Na, Nd, and mixed N a i- Nd i n NaNdF,, and K, La, and mixed K t La in I_I,-KLaF,) t h e Coulombic term varied less than 0.1 to 1%for a 1 - A displacement. By contrast, relatively larger variations in the exponential-six arid Lennard-Jones functions were found. R e s u l t s were nearly independent of c h o i c e of function and c h o i c e of s or 0; insofar its t h e qualitative c o n c l u s i o n s a r e concerned, and accordingly t h e r e s u l t s a r e p r e s e n t e d here only for (T -:12 in t h e exponent.ial-six case. In T a b l e 1.5,

hzohs is t h e experimental cation displacernent,

___I.__ 20

.J. H. Burns, Innrg. Chctii. 4, 8 8 1 ff. (1965).

21See, for example, D. I,. Kepert, J. Cherri. SOC. 7, 348 ff. (1952). 2 2 S e e , for example, T. Kihera and S. Koha, J. P h y s . SOL-.J a p a n 7, 348 ff. (1952).

Japan

Azcalc is t h e location of t h e tial function, iSz(l%) is t h e minimum Corresponding to a tial, and /E--. uobs is t h e rms

minimum in t h e potendisplacement from t h e 1%i n c r e a s e in potenthermal displacement

derived from t h e experimental thermal pararneters P s 3 corresponding to vibration along the polyhedron figure a x i s (Le., t h e hexagonal z axis).

14 Table 1.5,

_--

Results o f Potential C a l c u l a t i o n s in N a N d f 4 and P , - K L a F 4

N a in NaNdF,

0.58

0.71

0.19

0.15

K in KLaF,

0.17

0.15

0.17

L a i n KLaF,

0.07

0.06

Nd in NaNdF,

0.05

0.12

..._..

We conclude that t h e c a t i o n d i s p l a c e m e n t s c a n b e rationalized i n terms of t h e relative insensitivity of t h e Coulombic i n t e r a c t i o n s to cation location i n t h e s e s t r u c t u r e s and that d i s p l a c e d potential minima, or very shallow minima, in the remaining potential contributions will s u g g e s t which anion configurations will favor o r permit cation displacements. Calculations are being extended to include other framework structures containing tripyramidal coordination polyhedra.

O F FLUORIDE SINGLE RESEARCH PURPOSES R. E. Thoma R. G. Ross H. A. Friedman

Our efforts to develop t e c h n i q u e s for t h e production of l a r g e (350 g), p u r e s i n g l e c r y s t a l s of LiF with s e l e c t e d i s o t o p i c r a t i o s 2 3 h a v e s u c c e e d e d i n t h e production by Stockbarger-Bridgman methods of c r y s t a l s of a s high chemical purity as c a n b e obtained with Czochral s k i techniques. Conc ent ration of heavy-metal impurities i n c r y s t a l s produced t h i s year w a s found to b e l e s s than 2 ppb from activation a n a l y s i s and thermal conductivity data. ‘Thermal conductivity of t h e s e c r y s t a l s , a s m e a s ured by investigators a t Cornel1 University, w a s found to b e virtually identical through t h e temperature range 2 to 50°K with t h e b e s t 7Li(.‘ c r y s t a l s grown from o u r starting materials by t h e Czochralski method. Since purity control h a s been developed t o t h e extent that further improvement i s limited by t h e

..._

c a p a b i l i t i e s of t h e analytical methods (spectrochemical, infrared absorption, and activation analysis), most recent efforts h a v e sought to reduce t h e population of c r y s t a l dislocations. By programming t h e reduction of annealing temperat u r e s at a slow s t e a d y rate after cxystal growth, in one experiment a t 2.5OC/hr i n t h e temperature range from 840°C to room temperature, t h e population of c r y s t a l d i s l o c a t i o n s iil L i F c r y s t a l s h a s been reduced significantly. Preliminary indication of t h e e f f e c t i v e n e s s of such programmed annealing w a s obtained by neutron diffraction examination of ORNL-14,’, a 550-g crystal of lithium fluoride of 99.993 at. % 7 L i , which showed a major volume of t h e crystal to b e e s s e n t i a l l y free of disorder. P a r t of t h e effort to s y n t h e s i z e fluoride s i n g l e c r y s t a l s w a s devoted to t h e preparation of c r y s t a l s for I J S ~i n x-ray and neutron diffraction experiments. For such purposes, neither size nor purity standa r d s a r e a s demanding a s t h o s e imposed for L i F preparation. Single c r y s t a l s (approximately 1 c m maximum dimension) of e a c h of t h e three compounds L i 2 B e F , , N a , Z r 6 F 3 and 71di2NaTh2F11 were grown by t h e Stockbarger-Bridgman method. For other structural investigations2’ which employ even smaller c r y s t a l s , s u i t a b l e s i n g l e c r y s t a l s of P-CsBeF, and Li,UF, were grown by hightemperature anneal-quench experiments.

2 3 R e a c t o r Chem. Div. Ann. Progr. R e p t . U e c . 31, 1965, OHNL-3913, p. 126. 2 4 P e r f o n n e d by H. G. Smith, ORNL Solid S t a t e Division. “G. D. Brunton, preceding s e c t i o n s , t h i s chapter.

2. Chemical Studies of Molten Salts A POLYMER MODEL FOR LiF-BeF, MIXTURES @. F. B a e s , J r .

T h e s a l t s LiF and BeF, a r e q u i t e dissimilar in character; LiF i s a normal i o n i c s a l t , while BeF, q u i t e evidently is more c o v a l e n t s i n c e i t forms a very v i s c o u s liquid’ which i s obviously polym e r i c . Solid R e F , h a s a st.ructure analogous to S i 0 2; B e 2 + i o n s a r e surrounded tetrahedrally by four fluoride ions, and e a c h F-- ion is bonded to two Be” ions, t h a t is, BeF, tetrahedra s h a r e corners to f o r m a three-dimensional network. The Ii.qn.id would be e x p e c t e d to h a v e a similar pol~yrneric structure. A s LiF is added to molten BeF2, t h e viscosity drops sharply, presumably b e c a u s e bridging fluoride l i n k a g e s are broken,

’-

t h e number of bridging F- i o n s i n c r e a s e s by 4a - b while t w i c e t h a t number of terminal F- i o n s d i s appear. It seems reasonable, therefore, to write a s an a.pproximation for t h e free energy of reaction the equ:ition

i n which ( a t a given temperature) A is ;I constant representing t h e free energy i n c r e a s e a s s o c i a t e d with t h e formations of 1 mole of hridging F” bonds from 2 moles of terminal F- bunds. T h e development of t h e model from t h i s approximation is summarized iti Table 2.1, a n d equation numbers given below are from t h a t table. In t h e equilibrium cons t a n t e x p r e s s i o n ( E q ~41, the anion a c t i v i t i e s iire represented by a d a p t a t i o n s (Eqs. 5-71 of Flory’s e q u a t i o n 2 for polymer solutions, in which t h e volume fraction (vsa, b) o f B ~ ~ F ) , ( ~ - ’ is ~ )c-a l c u l a t e d i n terms of the number of F... ions the s p e c i e s c o n t a i n s (Eq. 8). T h e s e modified Flory e q u a t i o n s also contain a h e a t of mixing parameter ( B j and an a v e r a g e value o f b (6> ~ q 7.) i n the mixture. F r o m E q s . 4-9, t h e volume fraction of a given polymeric ion may b e c a l c u l a t e d (Eq. 10) in terms of a, h, the volume fraction of BeF,2(QI , 4 ) , t h e volume fract.ion of F.-- (<$,,, and t h e two a d j u s t a b l e parameters A and B . Introducing t h i s e x p r e s s i o n for $ha, into two material b a l a n c e e q u a t i o n s (11 and 12) o n e o b t a i n s two equations which may b e s o l v e d for the unknowns and

a n d t h e degree of polymerization d e c r e a s e s . T h e stoichiometric end point for this p r o c e s s OCCXTS a t the composition 2LiF-ReF,. Thereafter, the principal beryllium s p e c i e s in t h e melt presumiiibly is This p l a u s i b l e q u a l i t a t i v e picture of L i F - B e F melts h a s been treated more quantitatively i n t h e following fashjon. It w a s as.sumed that a l l of Ilie marly 1 k - F complexes formed would retain the same t h r e e e l e m e n t s of structure: - X3eF42 - - 1:etra1,4 hedra, bridging F- i o n s , and terminal F- i o n s . +,,,IT h e s e , i n turn, were u s e d to c a l c u l a t e t h e os a given complex anion 1 3 e ( , ~ ~ ( ~ -i t- -c a~n~ ) -activity of R e F , by a relationship (Eq. 13) d e then b e shown that there are 40 - b bridging F.-’ rived from t h e proportionality i o m and 2 b - 4.3 terminal F- i o n s . H e n c e , for t h e formation reaction,

My--.

a n d Eqs. 6 and 7 1.

2 ~ J.. Flory, Principles of Polymer Chemistry, p. 513, Cornel1 Univ. Press, Iihaca, N.U., 19.53.

S. Cantor a n d W. T. Ward, Reactor Chem, D i v Ann. P r o g r . Rept D e c . 3 1 , 196.5, ORN1.-39113, p. 27.

Table 2.1. D e r i v a t i o n of BeF,

c t i v i t y in biR from Polymer

T h e formation c o n s t a n t for BeaFb(b--2â&#x20AC;?).-IS given by

T h i s i s introduced into the material. b a l a n c e e x p r e s s i o n s

to obtain

Q 1,

and Q , ,

,, which a r c introduced into

to give t h e activity of BeF,.

Model

17 T h e c a l c u l a t i o n of n R e F 2 by t h i s model t h u s inv o l v e s three double summations,

These were extended to include all v a l u e s of a and, for e a c h v a l u e of 3 , v a l u e s of h beginning a t b 2a 1- 2, until e a c h s e r i e s converged. Ustng t h e CDC 1604 computer, t h e a d j u s t a b l e parameters A a n d €3 were varied by a l e a s t - s q u a r e s procedure until the c a l c u l a t r d v a l u e s of a B e F awere t h e most c o n s i s t e n t with v a l u e s 3 * 4 c a l c u l d e d from meastirem e n i s of t h e equilibrium

P2HF

PN,O

(If;>

aElt'F,

While t h e p r e s e n t c a l c u l a t i o n s of a R e were lengthy, t h e model at its p r e s e n t s t a g e i s a s i m p l e o n e which fits t h e d a t a well enough to s u g g e s t t h a t it offers a reasonable representations of t h e s t m c t u r e of X,iF'-BelF, mixtures. In t h i s repret sentat.ion, t h e mixtures contain L i a s the only c a t i o n ; t h e a n i o n s a r e F , R~F,'?-, and numerous p o ~ y m e r i c a n i o n s B ~ ~ F , ( ~ - - - which i n c l u d e c h a i n s of varying length and cross-linked s t r u c t u r e s containing rings in various numbers, and

' , ,/F.-..

in s i z e s down to ,,3e.,p.,,Be,

T h e difjtti-

bution of B e z t and F- among all t h e s e p o s s i b l e structures d e p e n d s primarily upon tlie F - / B ~2'. ratio i n a given mixture and upon the relative I I s t a b i l i t y of - B e - F - R e plus F- compared to I I I two - Be - F groups. I

PHASE ~ Q STUDIES ~ IN THE 110,-Zr02 SYSTEM I(. A. Komberger

r-r.

C. F'. Waes, J r . Stone

The previously d e s c r i b e d s t u d y ' of t h e I7O,-ZrO, s y s t e m i t 1 which a m o l t e n - s a l t flux was used Lo a c h i e v e equilibrium between t h e o x i d e p h a s e s h a s b e e n completed during the p a s t year. T h e c o m position a s s i g n e d to t h e tetragonal s o l i d s o l u t i o n s at the eutectoid temperature (1110OC) h a s been

i n c r e a s e d from the value 1 mole 70 UO, reported previously to 2.7 molt: 70 on the b a s i s of recent measurements which i n d i c a t e t h a t t h e previous result had not corresponded t o equilibrium. In addition, a n a l y s e s h a v e been obtained on a mixture of c u b i c UO, and monoclinic ZrO, which had b e e n equilibrated with a molten s a l t a t -,60O"C for 60 d a y s 6 giving -,0,3 mole % ZrO, in UO, and -20.07 mole 76 L J 0 2 in Z r 0 2 . T h e s e r e s u l t s i n d i c a t e a lower rate of exsolution of t h e two p h a s e s with d e c r e a s i n g temperature than previously estimated. The revised p h a s e boundaries in Fig. 2.1 reflect t h e s e c h a n g e s . In addition, t h e boundaries below 1150°C: reflect the distribution behavior e x p e c t e d for d i l u t e s o l i d s o l u t i o n s in the t h r e e two-phase regions C F? M, M F: T, and C a T. In particular, it w a s a s s u m e d t h a t the distribution coeffic i e n t ( D , a ratio of mole fractions) for one component between two s o l i d s o l u t i o n s a t equilibrium would obey t h e relationship

log

: R

i-b/2'

(17)

In t h e case of t h e M e 'I' equilibrium, t h e e s t i mated dependence of X z r o 2(T)/Xzro ,(M) 011 temT transiperature i n d i c a t e s t h e enthalpy o f the M tion i n pure ZrO, (1170°C) to b e 1.7 L: X kcal/mole. T h i s compares favorably with a measured value of -,1.4 k ~ a l . Just ~ above 1150°C (the upper limit of t h e p r e s e n t measurements) it is c l e a r t h a t v a l u e s of La m u s t d e v i a t e markedly from those predicted by Ey. (97) (cotresponditig to tlie sharply bending d a s h e d c u r v e s in F i g . 2.1) i f the C ==t T p h a s e 'boundaries a r e to be c o n s i s t e n t with tlie published higher temperature d a t a . Such pronounced d e v i a t i o n s from i d e a l behavior i n solid solutions that are still q u i t e d i l u t e seem unusual. Consequently, additional measurements between 1150 and 1500°C 'by t h e methods used h e r e would b e of c o n s i d e r a b l e i n t e r e s t . -1

~ 3A.

Id. Mathews

(May 196.5).

~ and C .

F. Baes, Jr., ORNL-TICI-1129

4A. I,. Mathews, Ph.D. t h r s i s , "Oxide C h e m i s t r y and Thermodynamics of Molten Lithium ~ I u o r i d e - l ' l e r y l l i u m F l u o r i d e b y E q u i l i b r a t i o n w i t h Gast.ous Water-Hydrogen Fluoride Mixtures, '' U n i v e r s i t y o f M i s s i s s i p p i , Oxford,

19h5. A . Komherger et a t . , R e a c t o r Ctiern. D i v . Ann. Pro&. R e p t . D e c . 3 1 , 196.5, ORNL-3913, 11. 8 . 'J. E. Eorgan et al., Keaclior Chem. Wiv. Anrr. Pro&. R e p t . Ja21- 31, 1964, O K N L - 3 S 9 1 , P. 45. Julie

'K.

75. P, C o u g h l i n and E . C;. K i n g , J . Am. Chem. SO(:. 72, 2262 ( I 9.50).

18 ORNL-DWG 66-+1779 ..............

3000

solution of UO, and T h o , and (2) to determine t h e distribution behavior of T h 4 + and U 4 + between t h e nxide and t h e fluoride s o l u t i o n s ,

U 4 + ( f ) t Th4+(o)

2500

2000

ILI

(500

E (

io00

500

0 2

u02

0.4 06 mole f r a c t i o n

Zr02

2.1. R e v i s e d U 0 2 - Z r 0 2 Phase Diagram. L, C , face-centered cubic; T, face-centered tetragM, monoclinic.

Fig.

(18)

(here f and o denote t h e fluoride and t h e oxide phases). 'The experimental technique is similar to that u s e d in t h e UO,-ZrO, p h a s e s t u d y ( s e e preceding section); Tho, and UO, were c o n t a c t e d with 2 L i F B e F , containing IJF, and T h F , within nickel c a p s u l e s under a hydrogen atmosphere in a rocking furnace. T h e equilibrated oxide s o l i d s were a l lowed to s e t t l e before t h e s a m p l e s were frozen. Good p h a s e separation w a s obtained provided sufficient quantity of t h e fluoride p h a s e had been added originally. A (U-Th)O, solid solution h a s been found in every s a m p l e examined t h u s far; t h e l a t t i c e parame t e r determined by x-ray diffraction w a s cons i s t e n t with the composition c a l c u l a t e d for s u c h an oxide p h a s e . T h e equilibrium quotient for t h e m e t a t h e s i s reaction shown above w a s determined by a n a l y s i s of t h e fluoiide p h a s e for the s m a l l amount of uranium which i t contained. T h e r e s u l t s obtained t h u s far give

liquid; onal;

.+ U 4 + ( 0 ) + T h 4 + ( f )

x!w X

TWf) =

1000 to 2000

(19)

G ( f ) XTh(0)

THE OXiDE CHE ISTRY OF ThF,-UF, MELTS B. F. Hitch

,.1h e

C. E. L . Hamberger C. F . B a e s , Jr.

precipitation of protactinium and uranium from LiF-HeF,-ThF, mixtures by addition either of B e 0 or T h o , was demonstrated s e v e r a l y e a r s a s a p o s s i b l e method a g o by Shaffer et for p r o c e s s i n g an MSBR blanket s a l t . T h e purpose of the present investigation is (1) to verify that t h e oxide s o l i d p h a s e formed a t equilibrium with UF,-?'hi?,-containing melts is the expected s o l i d

a t 6OOOC. T h e mole fraction of uranium in t h e oxide phase, w a s varied from 0.2 to 0.9 while t h e mole fraction of thorium in t h e fluoride p h a s e w a s varied from 0.01 t o 0.07. I t t h u s a p p e a r s that t h e U 4 + present i s strongly extracted from the fluoride p h a s e by t h e oxide s o l i d solution formed a t equilibrium. T h i s confirms t h e effective precipitation of U 4 + by oxide In addition, t h e first reported by Shaffer et formation of a s i n g l e oxide solution p h a s e offers a much more flexible and effective oxide separation method for breeder b l a n k e t s than would b e t h e case if only t h e s e p a r a t e o x i d e s T h o , and UO, were formed. -.

J . H. Shaffer et a l . , N u c l . Sci. E n g . 18(2), 177 (1964).

J. H. Shaffer, G. M. Watson, and W. R. Grimes, Rea c t o r Chem. D i v . A n n . P r o g r . R e p t . J a n . 3 1 , 1960, ORNL-2931, pp. 84-90. 'OJ. H. Shaffer e t a l . , R e a c t o r Chern. D i v . A n n . Pro&. R e p t . J a n . 31, 1961, ORNL-3127, pp. 8-11.

.........

"These x-ray examinations were performed b y G. D. Brnnton and D. K. S e a r s of Reactor Chemistry Division. T h e mole f r a c t i o n of Tho, i n t h e oxide s o l i d s o l u t i o n s was c a l c u l a t e d from t h e l a t t i c e parameter using the e q u a t i o n given by L. 0. Gilpatrick and C. H. S e c o y , R e a c t o r Chem. D i v . A n n . Pro&. R e p t . J a n . 31, 1965, ORNL-3789, P. 211.

19 We plan t o continue t h e s e measurements in order t o extend the range of oxide composition and T h F , concentration i n the melts and to determine the temperature coefficient of the distribution quotient.

THE OXIDE CHEMISTRY OF LiF-BeF,-ZrF, MIXTURES C. F. B a e s , Jr.

B. F . Hitch

where log b =

T h e r e s u l t s ate reasonably c o n s i s t e n t with previous, less direct e s t i m a t e s l 4 b a s e d upon measutements of t h e following equilibria: H,O(g)

Measurements of t h e solubility of B e 0 in L i F B e F , m e l t s and of ZrO, in 2 L i F - B e F 2 -t Z t F , melts (simulating mixtures of MSRE flush salt and fuel s a l t ) h a v e been completed. As described previously, 1 2 ’ 1 t h e procedure c o n s i s t e d i n withdrawing from an oxide-saturated melt a filtered sample which w a s then sparged with an € I F - € 1 , mixture l o remove t h e d i s s o l v e d oxide a s water. T h e totaI amount of water liberated w a s determined by Karl F i s c h e t titration. T h e principal difficulty encountered with t h e method w a s in filtering t h e s a m p l e s . Particularly in t h e case of BeO-saturated melts, t h e oxide c r y s t a l s evidently were sometimes small enough t o p a s s through or t o plug the filter. T h e BeQ solubility measurements w e r e found t o be reproducible only after s e v e f a l d a y s of equilibration at temperatures above 600°C. Considerably less difficulty w a s encountered with melts s a t u rated with ZrO,. T h e r e s u l t s of t h e s e measurements are repre-120%) by t h e following e x s e n t e d adequately pressions; t h e concentration unit employed i s t h e mole fraction:

- 2970/T , 1.195 - 2055/T .

log ;2 := -1.530

2F-(d)

H,O(g) t B e F 2 ( d ) 2t1,0(g) i %rF,(d)

+ 0 2 - ( d ) i-2 H F ( g ) , BeO(s)

* ZrO,(s)

i-2I-IF(g)

(23)

, (24)

4HF(&). (25)

T h e tolerance of MSRE flush salt For oxide should be determined by the solubility of B e 0 (Fig. 2.2). When t h e flush s a l t becomes contaminated with enough fuel s a l t (,1,1.6% by weight) t o produce a Z r F , concentration of ‘-0.0008 mole fraction, ZrO, should appear as t h e least s o l u b l e oxide. T h e oxide tolerance should then d e c r e a s e with i n c r e a s i n g fuel s a l t content b e c a u s e of t h e m a s s action effect of t h e increasing concentration of ZrF,. T h i s oxide tolerance should pass through a minimum a t X Z r F q h . 0.01 ( F i g . 2.2), and then i t should i n c r e a s e b e c a u s e of the effect of t h e medium upon ZrO, solubility. ‘The oxide tolerance of s u c h fuelsalt-flush-salt mixtures is given by

(-2

T h e solubility of B e 0 in LiF-HeF,, with X B e F 2 0 3 t o 0.5 a n d T - 7 5 0 t o 1000°M, is given by

log X o

= -0.901 i 1 . 5 4 7 X B e F 2- 2 6 2 5 / T

. (21)

T h e solubility product of Z r O , in 2 t i F - B e F 2 iZrF,, with X Z r F 4= 0.001 to 0.05 and i n t h e same temperature range, is given by

_____

and I3. F. Hitch, Reactor Chem. D i v . Ann. Pro&. R e p t . D e c 31, 1965, OKNL-3913, p. 20.

T h e solubility of Z r O , w a s a l s o measured in a salt mixture w h o s e composition (65.5% LiF-29.4% 13eF2-S.1% Z t F , ) simulated more c l o s e l y the MSRE fuel composition than did the 2 L i F - B e F 2 t Z r F , mixtures. T h e r e s u l t s ( F i g . 2.2) differ little from the v a l u e s given by t h e equation immediately a b o v e for t h e case where X Z r 4 t - 0.05. T h e effect of s a l t composition on the ZrO, solubility product may be c a u s e d , at l e a s t in part, by s p e c i f i c chemical e f f e c t s , t h a t is, complex formation. F o r example, the form of t h e expression for t h e variation in t h e ZrO, solubility product is c o n s i s t e n t with - though it d o e s not prove the e x i s t e n c e of - the following complex-forming reaction,

2 a 4 ++ 0 2 - e

zr,06+.

(27)

I2C. F. R a e s , Jr.,

3MSRP Semiann. Pro&. 3936, p. 133.

l i e p t . Fcb. 28, 1966, ORNL-

14MSRIJ Sernionn. Pro& Rept. F r b . 28, 1965, ORNIL3812, p. 129.

,20 ORNL-DWG

f(T1 700

67-769

500

600

to i o n i c motions. I n t h i s s t u d y , C y w a s ealcul a t e d from t h e relationship

500

where C is t h e h e a t c a p a c i t y a t c o n s t a n t pressure P of 1 gram-formula weight, a i s t h e volume expans i v i t y , 11 i s t h e velocity of sound in the molten s a l t , M is t h e gram-formula weight, and T is t h e a b s o l u t e temperature. T h e volume expansivity is obtained from density-temperature d a t a by

200

100 W

4 Y

Mixtures.

Fig. 2.2.

E s t i m a t e d Oxide T o l e r a n c e in MSRE Salt (1) F l u s h s a l t saturated w i t h B e O , (2) flush

salt-fuel

salt mixture of minimum oxide tolerance, and

( 3 ) fuel

salt.

T h e activity coefficient of Z r 4 + , 02.-, and any oxide complex of Z r 4 + will vary with the melt composition, however, and no quantitative interpretation of the present r e s u l t s i n terms of c o m plex formation is warranted until more c a n b e learned about s u c h activity coefficient variations. l 5

STANT-VOLUME HEAT CAP OF MOLTEN SALTS Stanley Cantor From the magnitude of the constant-volume h e a t c a p a c i t y (Cv)of molten s a l t s one c a n infer what kinds of inotion a r e e x e c u t e d by the ions. An attempt h a s been made, therefore, to derive acc u r a t e v a l u e s of C v and to relate t h e s e v a l u e s 15C. F. Baes, J r . , Reactor Chem. Div. Ann. Pro.&. R e p t . D e c . 3 1 , 1965, ORNL-3913, p. 2 3 .

where p i s density and p i s pressure. F o r s y s t e m a t i c s t u d y , i t is n e c e s s a r y to compare C y of t h e s a l t s a t corresponding temperatures. An obvious corresponding temperature is t h e inelti n g point. Other corresponding temperatures were defined empirically by the equation

where T , and T , a r e t h e normal melting and boiling points respectively, and 0 is a c o n s t a n t t h a t may vary between 0 and 1. Values of C v a t Tr4 and a t s o m e other corresponding temperature a r e given in T a b l e s 2.2 and 2.3. An obvious limitation of t h i s treatment is that, s i n c e virtually all a v a i l a b l e d a t a were obtained a t atmospheric pressure, t h e v a l u e s c a l culated for a s i n g l e s a l t at t h e various temperatures ( a s in ‘Table 2.2) do not refer to precisely t h e same volume. A method for calculating t h e effect of temperature on a truly constant-volume h e a t c a p a c i t y is described briefly in t h e following section. T h e “expeeimental” Cv’s l i s t e d i n T a b l e s 2.2 and 2.3 e x c e e d in almost all cases t h o s e calculated on the b a s i s of contributions due to (1) harmonic oscillation, (2) molecular rotation, (3) intraionic vibrations. FOPthe h a l i d e s , i t may be showri t h a t for contributions 1 through 3, the h i g h e s t calculated C v would b e b a s e d on t h e assumption that e a c h ion e x e c u t e s harmonic o s c i l lations in three coordinates. For i n s t a n c e , for a n alkaline-earth halide, i f we a s s u m e only harmonic oscillation, then C v for 1 gram-formula weight would b e 9R cal/deg. If we a s s u m e a model for

Table

Halide

2.2.

References

Constant-Volume Heat C a p a c i t i e s of Molten H a l i d e s

c y (cal/degj TIM(melting point)

____

8-0.1"

LiF

c , d, e

12.5,

12.45

LAC1

1, h

12.7j

12.j9

LiRr

f, g, h

12.q9

12.8,

NaF

2 , d,

12.3,

NaC?

f, & h

12.79

12.6,

NaBr

g, h

12.65

12.51

Nal

c , g, h

12.5,

12.3,

GR( :11.92)

ll.j

11.

Calculated C," (cal/deg)

1 2 . 4q

1159

12.0, 13. l 3

CsDr

f, A 11

13.25,

13.1b

MP=*

c, k, h

21.z3

21. l 5

9 R ( -1'7.88)

19.32 24. 4o 20.85

21.46 22.77

21.5 19.7,

18.56 20.3 CdClz

rn, R, h

24.

2 3 . , (at

0 :. 0.5)

CdRrZ

m, k, h

18.

18. (at 0

I). 5 )

Cdlz

m, k, 11

22.

21.~ (at

70.5)

%GI,

c , k, h

17., (at Tbr i-8)

H@rz

c, k, h

17.

16.7 (at T n )

c, k, h

17.,

17. (at TB)

Table

2.3. Constant-Volume H e a t C a p a c i t i e s of N i t r a t e s and Sulfates a t the M e l t i n g Temperature

Compound

References

C v (cal/deg)

....................

Experimental

Calculateda

I,iN03

b, c , d

24.

21.47

NaN03

e, c, d

26.

22.12

KN03

b, c, f

23.

22.44

&NO3

g> c,

25.

21.37

Li 2S0,

h, i , f

42.

37.21

Na2S0,

b, i , f

39.

37.27

%armonic o s c i l l a t i o n s (6R, n i t r a t e s ; 9R, s u l f a t e s ) plus rotation of the nitrate or s u l f a t e ion (1.5R) p l u s vibrational contribution of n i t r a t e or sulfate.

bK. K . Kelley, U . S . Bur. Mines B u l l . 584 (1960).

'R. Higgs and T. A. L i t o v i t z , J . A c o u s t . S o c . A m . 32, 1108 (1960). *G. P. Smith et ai., J . Chem. E n g . D a t a 6, 493 (1961). eG.J . J a n z et a t . , J . Chern. E n g . D a t a 9, 133 (1961). fG.1. Tanz e t a t . (eds.). . .. Molten S a l t D a t a . T e c h . Bull. I

Series, K e n s s e l a e r , P o l y t e c h n i c I n s t i t u t e , Troy, N.Y., J u l y 1964. g G . J . J a n z e t al., J . P h y s . Chem. 67, 2848 (1963).

contribution for t h e s e complex i o n s may b e s a f e l y a s s u m e d as ?,,I?. Contributions due to harmonic oscillation for t h e n i t r a t e s were assumed e q u a l to 6R, and for t h e s u l f a t e s , 9R. Note in T a b l e 2.3 that t h e experimental C v for t h e s e s a l t s a l w a y s e x c e e d e d t h e v a l u e calculated b a s e d on t h e contributions j u s t noted. Two general patteins are c l e a r from t h i s study: (1) experimental C y e x c e e d s that c a l c u l a t e d on t h e b a s i s of simple classical and/or quantum contributions; (2) C v d e c r e a s e s with i n c r e a s i n g volumes. P a t t e r n 1 may b e partly explained by correcting t h e notion that t h e s e i o n s e x e c u t e harmonic o s c i l l a t i o n s ; almost certainly t h e s e i o n s may b e better represented a s anharmonic o s c i l l a t o r s w h o s e potential energy Contribution e x c e e d s the 3/kT per ion that is a s s o c i a t e d with harmonic motion ( s e e following section); t h i s e x c e s s cannot presently b e c a l c u l a t e d with very much accuracy. P a t t e i n 2 probably reflects t h e d e c r e a s e in average potential energy per ion that o c c u r s when t h e volume of t h e liquid i n c r e a s e s . In other words, the liquid exh i b i t s moie g a s l i k e behavior a s volume i n c r e a s e s ; t h e k i n e t i c energy contribution per ion probably remains a t 3/kT, but ihe potential energy contribution slowly d e c r e a s e s with volume.

hN. K. V o s k r e s e n s k a y a e t at., l z v . Sektora Fiz.-Khim. A n a l i z a . Inst. Obshch. Neorgan. Khim., Akad. Nauk S S S R 25, 150 (1954).

'M. B l a n c et af., Compt. R e n d . 254, 2532 and 255, 3131 (1962); 258, 491 (1964).

TEMPERATURE COEFFICIENT QF C y MOLTEN SALTS Stanley Cantor

a liquid alkaline-earth h a l i d e in which the c a t i o n s a r e a s s o c i a t e d , for example, [MXI' and X-, then C v would b e less than 9R; for t h e example c h o s e n , a s s u m i n g that t h e vibration of t h e ion [MX]' i s fully excited, C v e q u a l s 8R. Since experimental C v ' s for mercuric s a l t s are less than 9 R , i t is q u i t e probable the same a s s o c i a t e d s p e c i e s e x i s t in these salts. Experimental Cv's of n i t r a t e s and s u l f a t e s are e s p e c i a l l y interesting b e c a u s e t h e s e s a l t s contain bona-fide complex ions, that i s , nitrate o r sulfate ions. Furthermore, the measured vibiational s p e c t r a l 6 provide t h e m e a n s for c a l c u l a t i n g vibrational contributions of nitrate or s u l f a t e to the heat capacity of e a c h s a l t . 'The rotational

As noted in t h e previous s e c t i o n , experimental v a l u e s of C v for molten s a l t s exceeded v a l u e s c a l c u l a t e d from t h e expected contributions (i.e., d e g r e e s of freedom). To determine how t h e inter.n a l energy is changing with temperature alone, it i s n e c e s s a r y to e v a l u a t e C v maintaining the volume c o n s t a n t with changing temperature. T h e method of evaluation u s e d here is similar to that published by Harrison and Moelwyn-Hughes. l 7 ?'he variation of C v with volume a t c o n s t a n t temperature i s given by -

6K.

Nakamoto, Infrared Spectra of Inorganic a n d Coordination Compounds, pp. 92, 107, Wiley, New York, 1963.

----

.........

D. Harrison and E. A. Moelwyn-Hughes, R o c . R o y . SOC.239A, 230 (1957).

23 Integrating between t h e molar volume at a reference p r e s s u r e ( V o >and a n y volume, V , o n e o b t a i n s

C v -= C

(---------)

v d2P

d T 2'

dV ,

P To

(31)

DR-'" - 3R-"

where A and b a r e c o n s t a n t s , which h o l d s remarkwell for all molten salts and which is disc u s s e d more fully in t h e next s e c t i o n . Diff(?rentiating po, with respect to temperature and substituting in Eq. ( 3 yields ~

(32)

(where D a n d E? a r e c o n s t a n t s , I I I and n a r e integeers, a n d R is t h e interatomic d i s t a n c e ) , the cons t a n t c in a 'I'ait equation of t h e form

Cy =

(33'1 ,-

is given b y c

: :

(m t n

-t

(34)

(63,

is t h e isothermal compressibility). Owens' 2 o d a t a on n i t r a t e s afford t h e only experimental t e s t s of whether t h e s e e q u a t i o n s ate valid for molten s a l t s . His wotk s u g g e s t s that t h e form u l a s a r e obeyed a t c o n s l a n t temperature but t h a t c v a r i e s somewhat with temperature. For NaNO,, for example, c - 4.5 a t 400째C and 5.0 a t 500째C. Integration o f t h e Tait equation between a s t a n d ard reference p r e s s u r e ( P o ) arid p r e s s u r e P y i e l d s

where t h e s u p e r s c r i p t s refer to the reference condition:;. S u c c e s s i v e differentiation of t h i s with r e s p e c t to T at c o n s t a n t volume and s u b s t i t u t i o n in Eq. (31) y i e l d s

_____I__

_ I

where C v o is w h a t o n e a c t u a l l y o b t a i n s from t h e equations of t h e preceding s e c t i o n . bloelwyn-Hughes h a s shown that, for liquids which obey a s i m p l e potential function of the form -=

Fortunately, t h i s complicated e x p r e s s i o n c a n be simplified by u s e of t h e relation

____..

"111. A . Moelwyn-Hughes, 1. P h y S . Ch63ln. 55, 1246 (1951). "Handbook of Cirernislty arid Physics, 44th cd., p. 2212, Chem. Rubber P u b l i s h i n g C o . , Cleveland, Ohio,

1 902 -6.3. 'OB. B. Owens, J. Chem. P h y s . 44, 3918 (1966).

T ( V O- Y ) b 2 CP

;

TV'

.-_I__

- 1.>po,

T h i s equation w a s then u s e d to generate (with the a i d of a computer) many v a l u e s of C v for 34 s a l t s . F o r t h e cases of t h e n i t r a t e s , experimental v a l u e s of c were u s e d . For all other s a l t s , v a l u e s of c were e s t i m a t e d from Eqs. (32) and (35) by s e t t i n g m 1 a n d allowing n to vary between 5 and 14. F o r all salts, C v i n c r e a s e d with temperature when compression w a s n e c e s s a r y to maintain c o n s t a n t volume. When pressure w a s d e c r e a s e d , C v d e c r e a s e d with temperature. Some t y p i c a l r e s u l t s a r e shown in T a b l e s 2.4 and 2.5. T h e s e i n c r e a s e s of C v may b e coirelated with a d e c r e a s e in t h e e l a s t i c forces holding the i o n s together. Such a d e c r e a s e in e l a s t i c forces for t h e c r y s t a l l i n e s t a t e u s u n l l y m e a n s t h a t t h e avera g e potential e n e r g y e x c e e d s t h e average k i n e t i c energy. I B e c a u s e t h e temperature range examined w a s in t h e vicinity of the melting point rather

than the c r i t i c a l point, the liquid is probably more solid-like in it would then follow that t h e s e molten salts similarly possess an a v e r a g e ...

*E.F e r m i , Molecules, Crysfnl a n d Quantirrri S t a t i s t i c s , p. 156, W. A . Benjamin, I n c , , New York, 1966.

Table

C y of L i F u t 14.662

2.4.

Eq. (39) a e t h e same a s t h o s e for c a l c u l a t i n g C y ( s e e T a b l e s 2.2 and 2.3). The magnitudes of t h e c o n s t a n t s A .md b a r e given in T a b l e 2.6. Moth c o n s t a n t s are roughly c 0 i i d r ; t e d with t h e position of t h e i o n s in t h e periodic table. The snomalous v a l u e s for MgC1, reflect the observation that s o n i c velocity i n t h i s medium d o e s not vary with teiilpeiaturc; t h i s observation i s most likely erroneous. Since t h e c o n s t a n t s A and b a r e rather restricted in magnittide, i t i s an easy matter to empirically e s t i m a t e [j; for s a l t s a s yet unmeasured. For i n s t a n c e j me might predict, by a rough interpolation between KCI and C s C l , that for Rbblli, A and b 1.77 x 5.5 x l h e r e a s o n s t h a t simple Eq. (37) s u c c e s s f u l l y correlates /jF with T are not a s yet known. The

( V o a t 1204째K) '1' ( OK)

u-4

C=6

cvQ

1121 (mp)

12.23

12.36

12.54

1204

12.45

1287

12.68

12.53

12.38

1370

12.89

12.59

12.32

Toble

c y of

2.5.

NaHCd3 a t 44.61 crn

( V o a t 580'K)

T ( OK)

4.5

5.0

cvo ~

580 (mp)

26.53

650

26.84

76.71

2G.22

723

27.19

26.90

25.94

T o b l c 3 . 6 . Constants for Equation of Isothermal

800

27.54

27.07

75.71

C o m p r e s s i b i l i t y a t 1 atm vs T e m p e i n t v r e

3:(cm2

potential rncrgy greater than t h e avcrage k i n e t i c encrgy. A s s u m i n g that t h e k i n e t i c energy coniponent of C v is "/k per ion (for simple ions), then it is understandablc why t h e total C v per ion cxceeds 3k.

PERATURE @OEFF%CIEHT OF. COMPRESSIBILITY FOR MOLTEN SALTS Stanley Cantor

The temperature variation of isotheim2- compressibility a t 1 atm w a s found t o follow t h e s i m p l e equation (see previous s e c t i o n )

/3:

AebT.

(37)

Individual v a l u e s of [j; a t temperature T were obtained from t h e expression

(39) (all s y m b o l s wer- defined i n t h e previous two sec tions). T h e s o u r c e s of d a t a for substitution in

Salt

dyrie) b

bf(Ok)

Salt

X I O - ~ x ~

~ o - ~

LiF

2.31

1.35

CdCi

11.6

1.07

LlCi

5.96

1.38

CdBrZ

13.5

1.49

LiBr

6.81

1.33

Cd12

17.9

1.32

NaF

2.29

1.51

HgBrZ

21.1

1.78

NaCI

4.92

1.61

10.9

3.34 1.43

NaEr

6.64

1.54

NaI

8.63

1.59

LiN03

8.99

3.83

1.53

NaN03

6.20

1.89

KC 1

5.88

1.74

KNO,

6.49

2.08

&NO3

5.23

1.53

KRr

7.20

1.72

8.13

1.82

CsCl

6.92

1.82

Li,SO,

3.36

1.00

CsBr

7.39

1.34

Na2S0,

4.16

1.02

0.239

MgCIZ

44.41

CaClz

4.42

1.07

CaBr2

6.06

0.969

Ca12

8.30

1.13

SrC12

4.14

1.00

SrBrl

4.80

1.06

SrIZ

7.51

1.03

DaC12

3.70

1.08

BaBrz

3.91

1.22

Ba12

5.88

1.13 ..........

..........

25 narrow ranges for A and b are perhaps more understandable. Compressibility at low p r e s s u r e most likely r e p r e s e n t s s q u e e z i n g a g a i n s t t h e volume not occupied by t h e ions, that i s , t h e "free" volume. Since t h e f o r c e s exerted by t h e i o n s on this f r e e volume should b e virtually independent of the kind of i o n s , i t follows that i n c r e a s e s in free volume which occur with temperature should b e roughly t h e s a m e for all ionic l i q u i d s ; h e n c e the temperaturt. dependence of squeezing a g a i n s t t h e f r e e volume would ;dso b e e s s e n t i a l l y independent of the ions involved.

VISCOSITY AND DENSITY IN THE LiF-BeF, SYSTEM C. T. MoynihanZ2

(poises)

: :

-8.119

D e n s i t i e s , Molar Volumes, a n d

Mole Fractiori

LiF-BeF2 M e l t s

800°C

Density

Molar Volume

(g/cm3)

3 (rn1 )

Exponsivity

0.000

X.8.3Ia

14.1Ta

2.6 x

0.502

1.894

19.28

2.3

0,749

1.902

21.93

1.3

0.892

1.916

23.35

0.8

1.000

1.921

24.47b

O.,lb

BeF

sExtrapolated below f r e e z i n g point of s a t l . b

Extrapolated from composition-volume or c o m p o s i t i o n expansivity c u r v e s .

Stanley Cantor

D e n s i t i e s and v i s c o s i t i e s of s e l e c t e d oompositions i n t h e LiF-Bel?,, system were measured to determine if temperature coefficients of v i s c o s i t y are correlated with c o e f f i c i e n t s of volume expansion. 'The viscosity of pure R e F , w a s measured over the temperature range 573 t o 98S"C, u s i n g Brookfield L V T and H B F SX viscometers. In t h i s range t h e v i s c o s i t y , 7 , varied from 10 to 106 p o i s e s a n d was about 10% greater than previously reported. 2 3 The plot of log '7 v s l/T("K) s h o w e d only s l i g h t curvature. A l e a s t - s q u a r e s fit of I.he d a t a to an equation quadratic in 1 / T yielded log

Table 2.7.

E x p o n s i v i t i e s of

io4

1.1494 ?'(OK)

lo5

6.39

(4 0 )

(standard error in log p 0.013). This equation y i e l d s a n activation energy for v i s c o u s flow of 57.3 kcal/mole a t 985°C and S9 6 kcal/mole a t 575°C. T h e s e are relatively small activation energy changes; thus t h e temperature dependence of viscosity for BeF i s b a s i c a l l y Arrhenius over the range covered i n t h i s investigation (10 to l o 6 poisesj. For L i F - B e F mixtures, v i s c o s i t y measurements confinned earlier r e s u l t s 2 3 which showed marked -7

2 2 c h e m i s t r y Department, California State C o l l e g e a t

Los A n g e l u s ; surnrncr participant, 1966. ' " S . Cantor acd W. T. Ward, Reactor Chem. l l i v . A n n . Pro&. X e p f . nec. 31, 1965, O R N L - 3 9 1 3 , pp. 27-28,

d e c r e a s e s of v i s c o s i t y and its temperature coefficient with LiF concentration. T h e d e n s i t i e s of three B e F , - L i F mixtures ( s e e T a b l e 2.7) were determined by t h e A r c h i m e d e a n method by measuring t h e apparent. weight loss of a platinum sinker upon immersion i n t h e melt. Volume expansion coefficients (i.e., expansivities) derived from t h e density d a t a d e c r e a s e d with dec r e a s i n g LiF concentration. Molar volumes, also derived from t h e s e d a t a , appeared to be additive at 800OC. Density measurements of pure BeF, were attempted by adapting the Archimedean method t o the technique of zero velocity extrapolation. 2 4 In n o n e of the four attempts t o measure t h e B e F 2 d e n s i t y was i t p o s s i b l e to eliminate t h e f e w small bubbles that adhered to t h e sinker. T h e buoyant effect of t h e bubbles l e a d s to low v a l u e s of t h e apparent weight of t h e sinker and h e n c e t h e high v a l u e s of t h e density. If a s u r f a c e tension of 200 dynes/cm is assumed for H t ? F z , the b e s t of O U K density r e s u l t s yielded a value of 1 . 9 6 i 0 . 0 1 g/cm3 for BeF, a t 850°C. T h i s result must b e considered only a s a n upper limit t o t h e real 13eF2 density, but i t may b e compared to 1.95 i 0.01 g/cm3 a t 800°C reported by MacKenzie2' and t o 1.968 g/cm" measured for t h e BeF, glass a t rooin temperature. T h e s e r e s u l t s s u g g e s t that t h e expansivity of liquid €3eF2 is quite small.

24L. Stiartsis and S . Spinner, J . Res. N a t l . Bur. Std.

46, 176 (1951). 25

J . D. M a c K e n z i c , J. Chem. P h y s . 32, 1150 (1960).

26 'The r e s u l t s t h u s f a r obtained i n d i c a t e that t h e temperature coefficient of v i s c o s i t y d e c r e a s e s with i n c r e a s i n g volume expansion coefficient and in particular (1) t h e Arrhenius behavior of pure BeF2, l i k e t h a t of S i 0 2 , i s a s s o c i a t e d with t h e temperature-independence of "free" volume ( i . e . , volume imoccupied by t h e i o n s ) , 2 6 and (2) L i F , when dissolved in BeF2, not only breaks up t h e network of l i n k a g e s between beryllium and fluorine. but a l s o i n c r e a s e s t h e temperature dependence of t h e free volume, thereby d e c r e a s i n g t h e activation energy of v i s c o u s flow.

VAPOR PRESSURES OF MOLTEN FLUORIDE MIXTURES Stanley Cantor W. T. Ward C. E. Roberts Transpiration Studies i n Support of the V c c u v m Di s t i I I a t inn Proce 5 %

'1'0 determine t h e equilibrium vapor separation of rare-earth fission pioducts from MSR carrier s a l t s , a s e r i e s of vapor p r e s s u r e s h a v e been inensured by t h e transpiration (i.e., gas-entrainment) method. T h e m e l t s were composed of 87.5-11.9-0.6 mole 76 LiF-BeF 2 - L a F3 . T h e concentrations of C i F and BeF2 a r e approximately t h o s e expected i n t h e s t i l l pot of t h e vacuum d i s t i l l a t i o n p r o c e s s . 'The lanthanum concentration is many t i m e s greater than what would b e permitted a s tutal rare-eearthc o n c e n tration i n t h e still; t h i s high concentration of lanthanum in t h e melt w a s required in order t o g i v e lanthanum concentrations in t h e vapor that were high enough to analyze. Measurements were carried out in t h e temperature interval 1000 to 1062OC; dry argon, t h e entraining g a s , flowed over e a c h m e l t at t h e r a t e of about 30 cm3/min. S a l t vapor, c o n d e n s i n g i n a nickel tube, ?rms analyzed by spectrochemical and neutron activation methods. T h e latter method gave higher, more consistent, and probably more reliable lanthanum a n a l y s e s . The most c o n s i s t e n t r e s u l t s have been obtained a t t h e two temperatures shown below. 26

P. B. Macedo and T. 4 . Litovita, J . Chem. E'hys. 42, 1 (1965).

Decontaniiiintion F a c t o r e

Teinpesature ..............

f o r Lanthanum .........

...

l0OO0C

91 0

1028OC

1150

.... ..... aDefined a s (mole f r a c t i o n of lanthanum uid)/(mole fractj on of lanthanum in vapor).

......

i n liq-

A t s i x other temperatures, transpiratiari p r e s s u r e measurements hdve yielded much higher (up to '7300) decontamination factors; however, t h e s e determiilations either were b a s e d on insufficient s a m p l e or else duplicate ana!yses gave vridely different r e s u l t s . It did appear that t h e higher t h e temperature t h c higher t h e decontamination f a c t o r s Although much inore study is required before t h c vacuum distillation p r o c e s s i s shown to be practical, i t seems that decontamination f a c t o r s c l o s e to 1000 can probably b e demonstrated.

Vapor Pressures of

73-27Mole % LiF-UF,

T h e manoinetric p r e s s u r e of t h i s mixture, which i s t h e composition of t h e MSRE fuel concentrate, w a s measured by t h e Rodebush-Dixon m e t h o d 2 7 i n t h e temperature r a n g e 1090 to 1291째C. 'I'he r e s u l t s fit t h e equation l o g p ( m m ) - 7.944

10,04O/T(OK).

(41)

Transpilation s t u d i e s h a v e a l s o been carried out to determine t h e composition of t h e vapor. T h e r e s u l t s to d a t e i n d i c a t e t h a t a t 1050째C, t h e mole ratio of L i F to U F , i n the vapoi e q u a l s 3 3.

POT ENYlOMET R9C M E AS MOLTEN FRUORlDES A.

R. Nichols, J r .

K. A.

C. F. B a e s , Jr.

Romberger

Continuing t h e program of potentiometric m e a surements i n molten fluorides, i t is planned to 27W. I<. Rodebush and A. 1,. Dixon, F'hys. Rev. 26, 851 (1925). "Visiting

P a r k , Calif.

s c i e n t i s t , Sonoiria S t a t e C o l l e g c , Kohneit

27 explore t h e chemistry and thermodynamics of a variety of s u b s t a n c e s which c a n occur i n a moltensalt reactor, either i n container m a t e r i a l s or a s f i s s i o n products. P r e v i o u s l y , t h e development of an H,,,HF/Fe l e c t r o d e and a Be"/Be2+ e l e c t r o d e a s &itable reference electrode h a l f - c e l l s for u s e in 2 L i F - B e F 2 m e l t s h a s been described. 2 9 P r e s e n t l y i n v e s t i g a t i o n s a r e being made of niobium in molten 2LiF*€3eF2. Several attempts to m e a s u r e t h e voltage of t h e cell B e o ) B e F, , L i F l R e F 2 , L i F , N b F , lNbo

(42)

(in which t h e e l e c t r o d e compartments were of graphite and, later, copper) h a v e b e e n only part i a l l y s u c c e s s f u l b e c a u s e t h e v o l t a g e of t h i s c e l l invariably d e c r e a s e d with time. I t is inferred, but h a s not yet been proved, that t h e c e l l v o l t a g e d e c r e a s e d b e c a u s e a small amount of beryllium metal d i s s o l v e d in t h e 2 L i F * 1 3 e F 2 s o l v e n t and internally shorted t h e cell. However, before t h e s e d e c r e a s e s became marked, reasonably s t a b l e v o l t a g e s were observed, i n one case for a s long a s three d a y s . Measurements of t h e cell v o l t a g e were made as a function of i n c r e a s i n g NbF, concentration. (NbF, w a s added to t h e melt by anodic dissolution o f niobium metal.) T h e voltage first i n c r e a s e d and then remained constant, a n indication t h a t t h e m e l t h a d become s a t u r a t e d with NbF,. B a s e d upon t h e number of f a r a d a y s which were required to l e a c h saturation and t h e amount of melt within t h e niobium compartment, i t is e s t i m a t e d t h a t at 597°C t h e solubility w a s "3 x lo-" equivalent of t h e niobium s a l t per kilogram of solvent. T h e cell voltage ai saturation w a s 0 . 9 6 + 0 04 v. This v a l u e c a n b e combined with t h e f r e e energy of foniiation of d i s s o l v e d BeF, (-214.6 k ~ a l / m o l e ) to ~ ~yield t h e f r e e energy of formation of NbF,,

(F is t h e F a r a d a y constant, 23 06 k c a l per equivalent). T h i s preliminary r e s u l t s u g g e s t s a s u r p r i s i n g s t a b i l i t y of t h e lower fluoride. Compared to the H ,,HF/Freference couple, t h e NbF,/Nbo c o u p l e would h a v e t h e potential 1 -hy NbF x

+ e;;L-Nb" X

F- , E o (597°C)

-85.1

0.9 k c a l

(43)

(44)

T h i s i n d i c a t e s t h a t N b o should b e more electrop o s i t i v e than chromium i n 22,iF7-f3eF,. T h i s r e s u l l is difficult to reconcile with t h e evident corrosion r e s i s t a n c e of Nb toward N a F - Z r F 4 - U F , m e l t s observed in early loop t e s t s , but i t is reasonably c o n s i s t e n t with p o t e n t i a l s reported recently by Senderoff and Metlors. 3 1 T h e beryllium e l e c t r o d e h a s now b e e n replaced by an €12,11F/F- half-cell. T h e l a t t e r , while less convenient to u s e than the B e 0 / B e 2 ' half-cell, is expected to yield v o l t a g e s which are more s t a b l e and reproducible. No r e s u l t s a r e yet a v a i l a b l e from t h i s new cell. T h e v a l u e of X , that is, t h e oxidation s t a t e of the niobium i n t h e p r e s e n c e of t h e metal and t h e fluoride s a l t , a p p e a r s to b e +2. T h i s is a t e n t a t i v e conclusion b a s e d upon t h e r e s u l t s of a transpiration experiment in which a known amount of gaseous H F w a s u s e d to partially o x i d i z e niobium metal in c o n t a c t with t h e melt. T h e value of t h e oxidation number w a s then determined from t h e amount of metal which w a s consumed. No apparent evolution of N b F , occurred, which is c o n s i s t e n t with a s t a b l e lower v a l e n c e s t a t e .

APPEARANCE POTENTIALS OF LITHIUM FLUORIDE AND LiTHtUM BERYLLiUM FLUORIDE IONS R. A. Strehlow

-0.85 v

J . D. Redman

A study w a s m a d e o f a p p e a r a n c e p o t e n t i a l s of i o n s fonned by electron impact from LiF and L i z B e F I vapor. This work w a s undertaken i n order __ .........

29G. D i r i a n , K. A . Romberger, and C . F. Baes, JK., Reactor Chem. O i v . Ann. Pro&. Kept. Jan. 31, 1965, ORNL-3789, pp. 76-79. 30A. L. Mathews and C . F. B a e s , Jr., ORXI,-TM-1129, pp. 74-7.5 (May 7, 1965).

31E;.

A. Kovachevich, E. I,. Long, and D. 17. Stonaburner, Results of Niobiwn Thermal Coz~vection Loop 'I'es fs, ORNI.,-CF-57-1-161. 32S. Senderoff and G . W. Mellors, J . Electrochem. Soc.

113(1), 66 (1966).

28 to a s s i s t in t h e interpretation of sublimation h e a t s determined m a s s spectrometrically. A surprising amount of structure was found in t h e ionization efficiency curves, and i t is t h i s a s p e c t of t h e work which i s emphasized here. The study of sublimation h e a t s with a m a s s spectrometer requires either a knowledge of fragmeiitation p a t t e r n s of polymeric vapoi molecules or t h e assumption that a given ion, for example, L i t or L i 3 F 2 * , h a s only o n e neutral precursor. This assumption, called t h e s p e c i f i c i t y rule, h a s been found not to apply to lithium h a l i d e s . 3 3 T h e fragmentation p a t t e r n s of ( L i F ) 2 h a v e been t h e s u b j e c t of study. 3 3 , 3 4 In addition, for lithiurnberyllium fluoride s p e c i e s , t h e need to p o s t u l a t e s t r u c t u r e s s u c h a s (1) to a c c o u n t for t h e m a s s spectrometric o b s e r v a t i o n s l e d to t h e expectation that a detailed study of a p p e a r a n c e p o t e n t i a l s might help t o clarify t h e phenomena which h a v e been observed.

Be’ r

(I)

-Ihe

ioni zatio efficiency ( l . E j c u r v e s obtai ed in t h i s study p o s s e s s structure t o an unexpected degree (considering that t h e vapor d e n s i t y for some of t h e s p e c i e s corresponded t o l e s s t h m 1 V 8 tori). Selected LE. c u r v e s are show^ i n Fig. 2.3. i n e d a t a were o b t a i n e l u s i n g t h e retarding potential dilference method and a Mendix time-offlight m a s s spectrometer. Siinultaneous determinations were made for a reference g a s with appiopriate appearance p o t e n t i a l s and for two s a l t ions. T h e reference g a s w a s admitted (at a pressure of 1 x l o p 7 torr) to permit voltage calibration a s well a s to d e t e c t p o s s i b l e instrumental vagaries. The simultaneous monitoring of two s a l t vapoi p e a k s

33J. Berkowiiz, II. A . Tasman, and V I . A. Chupka, J . Chern. P h y s . 36, 2170-79 (1962).

34P. A . Akishin, I,. N. Gorokhov, and I,. N. Siderov, K u s s . J. P h y s . Chem. 33, 648-49 (1959). 3 5 A . Buchler and J . L. S t a u f f e r , Syrnp. on T h e r m o dynamics with E m p h a s i s on Nuclear Materials and A t o m i c Transport i n S o l i d s , Vienna, 22---27 J u l y 1965.

eliminated temperature c h a n g e s of t h e furnace a s a s e r i o u s s o u r c e of error. A s h a s often been observed for other g a s e s , a current of singly charged i o n s a p p e a r s a t some o n s e t potential and then i n c r e a s e s linearly witti electron energy until a s u b s e q u e n t a p p e a r a n c e potential (AP) d u e to an added p r o c e s s of ion generation. T h e s e AF’s for fragment i o n s may a r i s e i n s e v e r a l ways: ion pair formation, ionneutral reaction, rearrangement, fragmentation of t h e neutral moiety, formation of excited s t a t e s i n the neutral or ion, and o t h e r s . Unambiguous assigilment of a process to a n A P other than o n s e t is not often p o s s i b l e . For t h e s p e c i e s studied h e r e most of t h e s e p o s s i b i l i t i e s , howcvei-, may b e eliminated. T a b l e 2 . 8 l i s t s t h e AP’s found for various of t h e i o n s from LiF and Li2BeF4. T h e range of v a l u e s and t h e number of determinations a r e shown to give a n indication of precision. T h e e x i s t e n c e of APII(Li’-) a p p e a r s to b e slight, but r d . ‘There seems to be l i t t l e question of th? exi s t n n c e of structure for t h e other s p e c i e s . . 1h e observed o n s e t a p p e a r a n c e potential for Li’ of 1 1 . 2 1 v with t h e ionization potentia! ( L i + > of 5.36 v l e a d s t o a value of II(LiF) = 5 . 8 4 0.10 e v , which i s iil agreement with t h e literatur? v a l u e of 5.95 T h e oilset is therefore probably c h a r a c t e r i z e d b y formation of L i ” and F c in ground s t a t e s from LiF in i t s ground state. T h e xmall diff e r e n c e s betsvcen t h e o n s e t s for Li’, L i p t . and L i , F , + are believed t o b e d u e principally t o t h e s u c c e s s i v e l y greater v a l u e s of the bond s t r e n g t h s , D(I.,i2F - Y ) and D ( T . i 3 F - Y ) . T h i s belief is corroborated by a consideration of t h e appearance p o t e n t i a l s €or n e g a t i v e ions. 3 7 Using t h e v a l a r of 2.90 for t h e e!ectron affiility of F Q and considering the p r o c e s s 9

Li 2F2

+ J-,i 2

.......

y’.-

3.55 v ,

(45)

one o b t a i n s D&i 2F - F j = 6.45 ev. T h i s v a l u e is about 0.5 e v greater than jI(l.,iF) and d o e s not conflict with t h e v a l u e of

[ A P J L i 2 F t ) .. API(Lit)l - Q.14 e v , s i n c e t h e ionization potential of t h e neutral L i L F may b e less thar. t h a t for J i . Similar reasoning 361,. Brewer and E. B r a c k e t t , Chom. Rev. 61, 425 (1951).

37:1.

Ebinzliaus, Z . N a t u r f o r s c h , 19a, 727- -32 (1964).

UKNL-LJWb b / - / (

*.*-

.i/T

................. ..

~~~~

14.0

11.5

12.0

(2.5

13.0

43.5

F i g . 2.3.

14.0

14.5

._.......

15.0

15.5

I o n i z a t i o n E f f i c i e n c y Curves.

16.0

16.5

17.0

17.5

Table

2.8.

Appeoronce P o t e n t i a l s of Ions from L i F orid L i

T Sample

LiF

Ion

Quantitya

lit

11.21

11.73

fO.10

+0.24

5 11.35

11.84

f0.16

'0.40

11.61

12.12

fO.10

+0.30

. ....~ ... ~

111

0.13

'0.24

0.23

13.51

f0.42

f0.17

0.40

t0.23

(12.2)

(14.1)

+0.22 3

+0.19

0.14

12.79

13.46

14.52

f0.02

f 0.02

10.29

15.38

(16.31)

-t 0.02

i0.07

0.19

r0.15

13.72

12.44 0.12

13.69

(11.7)

55'

0.36

12.78

11.90

......... IV

13.59 -

BcF 2 '

Vapor

..-

LiBe F

Appearance P o t e n t i a l

-.-.

BeF

800 t o 920째C

Li2BeF

(14.9)

17.22 fO.10 - 0.08 3

Reference g a s e s L

11.60 (Li-F ions j

Kr+

14.00 (LiBcr *')

Art

C,H,

CP6'

Kr Ar

aAP

15.75 ( I ~ c F ~ ~ ) ..........

....................

s _

appearance potential i n volts; w = r a n g e ; n

number of d-terminations.

..........

..........__

31 a p p l i e s to D(Li,F,-F). From o t h e r d a t a , 3 6 est i m a t e s of some other bond s t r e n g t h s and electron a f f i n i t i e s for s o m e of t h e pertinent s p e c i e s may b e made. T h e s e include: D(WF - Li)

3.0 ev

D(LiF - Li)

8.0

U(1,iF -Is)

1.6

E,(LiF

3.35

LiF)

EA(L1)

0.29

EA(Li2F)

-0.25

T h e v a l u e for EA(Li,F) i n d i c a t e s t h e general deg r e e of uncertainty in t h e s e v a l u e s . With the derived v a l u e of D ( L i F 2 -Li) =: 8.00 ev, o n e would a n t i c i p a t e t h e p o s s i b i l i t y of producing I,i+ from the dimer a t an AP of 8.00 t- 5.36 = 13.36 v. Our v a l u e of AP,,,(Li+) = 13.6 k O . 3 indicates that t h i s p r o c e s s is r e s p o n s i b l e for APIII(Li+). The s e c o n d a p p e a r a n c e potential, A P ,,(Li+), i s , i f real, not readily e x p l a i n a b l e s i n c e t h e l o w e s t excitation l e v e l for F' is 14.4 e v and for Li', m u c h more. Invoking p o s s i b l e precursor excitation is not a happy explanation in view of t h e 0.5-v difference between AP,(Li') and APJLi') and t h e agreement of our v a l u e of D ( L i F ) with t h e literature. + T h e o n s e t potential for the mixed s p e c i e s LiBeF c a n b e u s e d t o e s t i m a t e a D ( L i B e F - F ) =: 7.9 v, which is n e a r DCBeF) = 8.02. 3 6 T h i s i n d i c a t e s t h a t t h e fluoride atoms a r e a l l a s s o c i a t e d with the beryllium i n t h e vapor s p e c i e s L i B e F 3 . Consideration of t h e e n e r g i e s a n d bond s t r e n g t h s and t h e n e a t agreement between AP,(Li 2F+)from LiF w i t h

that from L i 2 B e F 4 m a k e it s e e m unlikely that Li,BeF, is a precursor of L i 2 F s . F o r BeF,' a n additional s e t of p o s s i b i l i t i e s musi. b e considered a s c a u s e s of structure i n t h e I.E. curve. T h e s e i n c l u d e autoionization and metas t a b l e i o n formation. S i n c e all of t h e i o n s except p o s s i b l y Li+ p r e s e n t marked similarity of structure, i t s e e m s most p l a u s i b l e that e v e n for t h e s p e c i e s from L,i 2BeF4t h e s t r u c t u r e observed is attributable t o i o n i c excitation, either vibrational or electronic. T h e e n e r g i e s determined c a n b e u s e d to predict p o s s i b l e a p p e a r a n c e p o t e n t i a l s beyond t h e limited range u s e d i n t h e s e s t u d i e s . F o r examples,

(LiF),

a 67.4

Ions from

(46)

20.6 v ,

(47)

23 v

(4 9)

LiF

65.7

* 0.7

F+

64.1

LiF'

62.3 *0.6

64.8 i 2

66.5

Li 2Ft

67.7 -t 1.3

68.3 f 2

71.6 f 2

70.4

73.9 1 3

14.6 v ,

T h e i o n Li,â&#x201A;Ź3eF3+ w a s a l s o observed but in too small amounts For A P determinations. During t h e melting of o n e s a m p l e of L i z B e F , many b u r s t s of CO, were observed; t h e s e b u r s t s total about 2 x 10 - 4 atm cc g--', but w e b e l i e v e t h i s did not c a u s e a n y irregularity i n t h e Knudsen c e l l operation. Some i n i t i a l determinations were made of s l o p e s of l o g (I'T) v s 1/T for LIF s p e c i e s i n order t o provide some comparison with t h e literature v a l u e s before undertaking t h e more difficult t a s k of studyi n g t h e LiF-BeF s y s t e m vaporization. T h e r e s u l t s of numerous determinations a r e shown in T a b l e 2.9 without further d i s c u s s i o n of d e t a i l s .

L,i+

Li,F,+

+F,

+Lie + F+ ,

Average

+ LiF ,

------3L i F + -t

Table 2.9. Second L a w Apparent A H ' S for

T h i s Work

LiF'

1.3

0.7

__.-.___

62.4 f 1 . 5

(62.7)

65.3

(70.4)

* 1.7

74.9 5 1 . 0 ....................

____

aA. Buchler, CPIA Publ. No. 44 (Fehruary 1964).

bD. L. Hildenbrand et a l . , J . Chem. P h y s . 40, 2882-90 (1961). 'P. A. Akishin, 1,. N. Gorokhov, and L. N. Siderov, K u s s . J. Phys. Chem. 33, 648-49 (1959). dA. C . P. Pugh and R. F. I3arrov1, Trans. Faraday S O C . 54, 671 (1958). Note: Values are torsion-effusion !\If's (sublimation heats for monomer and dimer).

REMOVAL 0%:IODiDE FR0M LiF-BeF, MELTS C. E. L. Eamberger

With t h e assumption that reaction (1) w a s t h e only reaction involved, t h e negative s l o p e ( @ / 2 . 3 ) of a plot of l o g ([I---l/[I-Io) vs fl H F /w was equated to t h e equilibrium quotient Q , of reaction (1),

C. I?. B a e s , Jr.

T h e removal of iodide from L i F - B e F ’ mixtures by I-IF sparging, presumably by the reaction

D r

Q,= w a s previously described’,’ a s a promising method for removing 6.’7-hr I 3 ’ I from a n MSRR fuel a t a rate greater than t h e rate of d e c a y of t h i s nuclide to 3 5 ~ e . One difficulty with t h e r e s u l t s reported previously w a s that poor recoveries (typically 80%) of iodide were obtained by H F sparging. In continued s t u d i e s the c a u s e of t h i s h a s been traced to s m a l l particles of s a l t entrained in the g a s e o u s mixture of H F , HI, and €3, emerging from t h e r e a c t i o n v e s s e l . Evidently t h e s e particles c a u s e d condensation of the H F and HI with water vapor in the NaOH bubbler u s e d to trap the HI. T h e condensed droplets of a c i d i c solution, readily visible as a fog in the g a s p h a s e of t h e trap, evidently did not react completely with the NaOH solution, thus c a u s i n g low recoveries. Introduction of a filter of s i n t e r e d Teflon or gold in t h e effluent g a s stream a h e a d of the trap h a s resulted in iodide recoveries greater than 95%. It w a s found previously t h a t t h e fraction of iodide remaining in t h e melt ([I-]/[I-~l0) dec r e a s e d logarithmically with the n u m b e r of iiioles of H F p a s s e d per kilogram of melt (nHP./w),

HI ~

PHF[I

!:g/mole

(3)

T h i s interpretation o f the previous data w a s supported by the observation that, wit.hin t h e s c a t t e r of the measurements, Q w a s indepcndent of t h e flow rate and the partial pressure of HF. In the s u b s e q u e n t measurements, however, a fuller study of the e f f e c t of t h e H F pressure a t different teiiiperatures and a s a function of melt composition b a s shown a pronounced effect. It h a s been found (Fig. 3.1) that @ v a r i e s approximately inversely with P H Fa s follows:

‘ 8 . F. Freasier, C . F. R a e s , Jr., and H. H. Stone, M S K Prograiii Semiann. P r o g r . R e p t . A u g . 31, 1 9 6 5 , ORNL-3872, p. 127.

‘R. F. Freasier, C . F. Baps. Jr., and H. H. Stone, R e a c t o r Chem. D i v . A n n . P r o g r . R e p t . D e c . 3 1 , 1965, OKWL-3913, p. 28.

0C5

bPHF

oio

PARTIAI PRESSURF OF Iir (atm)

Fig. 3,1. with the

045

0 20

V o r i o t i o n of Q for iodide Remcvnl (Eq.

Sporging Pressure i n

L i F - B e F , Malts.

33 While t h e c a u s e of t h i s e f f e c t is still being inv e s t i g a t e d , i t may b e noted t h a t if, in addition to reaction (I), there is a n a p p r e c i a b l e s o l u bility of HI in the melt,

the a b o v e e x p r e s s i o n c a n b e a c c o u n t e d for with

a :. 1/Q, a n d 5 Q , . Sparging with HI a s w e l l a s HF is presently b e i n g u s e d to determine

whether or not equilibrium conditions a r e b e i n g a t t a i n e d during t h e measurements and t o determine t h e solubility or other p o s s i b l e reactions of HI i n t h e s e melts. Whether t h e d e p e n d e n c e of Q on P,, is d u e to a rate effect OK to t h e occurrence of other equilibria i n addition to reaction (I), i t s e e m s e v i d e n t that, i n t h e a p p l i c a t i o n of t h i s treatment to t h e p r o c e s s i n g of a n MSBR fuel, better HF utilization (higher Q values) w i l l be obtained a t lower â&#x201A;Ź-IF partial p r e s s u r e s , T h e limiting (maximum) v a l u e of Q obtained as P I * , a p p r o a c h e s z e r o is plotted v s the mole fraction of BeF, in F i g . 3.2.

ORNL-DWG 67-772

~. ........

...... ....

!..

REMOVALOF RARE EARTHSFROMMOLTEN FLUORIDES BY SIMULTANEOUS PRECIPITATION WITH UF,

Fig.

3.2.

T h e Dependence of the L i m i t i n g Value af

LiF-BeF 2 M e l t s .

J . H.Shaffer

McDuffie

T h e relatively low solubility of U F , i n fluoride mixtures of i n t e r e s t to the MSR program3 and t h e known s i m i l a r i t i e s of the c r y s t a l structure of rareearth trifluorldes with U F 3 4 provide a b a s i s for s t u d i e s of t h e precipitation of s o l i d s o l u t i o n s of these compounds from fluoride melts. Since fission product rare e a r t h s represent a major portion of t h e poison fraction in the fuel of a molten-salt nuclear reactor, this s t u d y may b e a p p l i c a b l e toward t h e development of s u i t a b l e r e p r o c e s s i n g methods for rare-earth removal. Initial experiments conducted in t h i s program cons i d e r e d the reduction of U F , contained in a rea c t o r fuel mixture to U F , a n d the simultaneous precipitation of rare-earth trifluorides with U F a s t h e temperature of t h e fuel mixture w a s reA s e c o n d s e r i e s of experiments 1s in duced. progress t o examine t h e precipitation of rare e a r t h s from a simulated fuel s o l v e n t upon addition of s o l i d U F , . If all U F , contained in t h e current MSRE fuel mixture, LiF-BeF ,-ZrF ,-UF4 (65.0-29.1-5.0-0.9 m o l e % respectively), were reduced t o UF,, t h e solution would b e s a t u r a t e d with U F , a t approximately 725'C. By lowering t h e melt temperature t o 55OUC, approximately 83.5% of t h e uranium would b e precipitated from solution. R e s u l t s of preliminary experiments designed to investigate this r e p r o c e s s l n g method demonstrated t h a t LaF J , C e F , , and N d F , c o u l d b e precipitated with UF,. Europium and samarium w e r e probably reduced t o their d i v a l e n t s t a t e s by t h e i n s i t u reduction of uranium with added zirconium metal and showed l i t t l e or no loss from solution during t h e precipitation of UF,. Subsequent experiments with e x c e s s reducing a g e n t s h o w e d that cerium removal could b e related to t h e U 3 + concentration in s o l u tion by the equation In

upon the B e F 2 C o n c e n t r a t i o n i n

H. F.

F. A. Doss

N,,

k In N

u3+

const,

3 R e a c t o r Chem. D I V . Ann. 1 9 6 4 , ORNI~--3591,p. 50,

Pro&.

Rept. J a n . 3 1 ,

4Reactor Chem D I V . Ann. 196.5, ORNL-3789, p. 16.

Pro&.

R e p t . Jail. 31,

34 ORNL-DWG 6 6 - 1 1 4 6 0 , .-, ~ R A N G E : 850; 550 "C EX'PT C e - 2 ,

-5

n .-z

-/*~

--~

/:-

' P-

-/p

-4

p/--,

'-.-

-4

INITIAL U CONCENTRATION

11 w t % 5 wi %

5 6

20 25

URANIUM FOUND IN SOLUTION ( m o l e fraction x 103)

Fig.

UF3

3.3.

Simultaneous

from Siniulatad

where N R E and

Precipitation of

CeF3

and

MSRE Fuel Mixture.

"3+

a r e r e s p e c t i v e iiiole frac-

tions of rare earth and trivalent uranium. As illustrated by F i g . 3.3, a value of about 0.55 w a s obtained for k in Eq. (5) for the simultaneous precipitation of CeF,. Further investigation would 3e needed t o verify t h i s experimental relationship for other rare e a r t h s of i n t e r e s t t o t h e pro gra m . A m o i e recent experimental program h a s been concerned with t h e retention of rare-earth trifluorides on a bed of s o l i d U F , a s an a l t e r n a t e reprocessing technique. In t h e first experiment U F , w a s added in 30-g increments to approximately 2.2 k g of L i F - B e F 2 (66-34 mole %) that initially contained m o l e fraction of C e F , with about 1 m c of ' 4 4 C e a s a radiotracer. F i l tered s a m p l e s of t h e s a l t mixture were taken approximately 48 hr after e a c h addition of U F , and analyzed radiochemically for cerium. The r e s u l t s illustrated a soinewhat linear d e c r e a s e i n cerium concentration a s U F , w a s added and corresponded to a. s o l i d p h a s e which contained Similar r e s u l t s were obabout 1 mole % C e F , . tained in a s e p a r a t e experiment with NdF,, e x c e p t t h a t t h e s o l i d p h a s e corresponded t o about 0.2 mole % NdF, in U F , .

EXlfRACTlON OF R A R E EARTHS FROM MOLTEN FB_UORIDES INTO MOLTEN MET F. F. Blankenship J . H. Shaffer W. K. R. F i n n e l l W. P. T e i c h e r t

D. M. Moulton W. K. Grimes This experimental program h a s been oriented

toward t h e development of a liquid-liquid ex-

traction p r o c e s s for removing rare-earth f i s s i o n products from the fuel of a two-region molten-salt breeder reactor. In p r o c e s s i n g s c h e m e s proposed for t h e reference d e s i g n MSBR, uranium will b e removed by fluorination. T h u s , for purposes of t h i s investigation, t h e barren f u s l s o l v e n t h a s been simulated by d i s s o l v i n g s e l e c t e d rare-earth fluorides into a mixture containing 66 mole % LiF and 31 mole % BeF,. When t h i s mixture is contacted with a molten bismuth-lithium mixture, rare e a r t h s a r e reduced t o the metallic s t a t e a n d d i s s o l v e d in t h e molten metal p h a s e . T h e program further e n v i s i o n s a similar back-extraction p r o c e s s for concentrati.ng rare-earth f i s s i o n products i n a s e c o n d s a l t mixture for d i s p o s a l or further utilization. Experiments conducted t h u s far h a v e examined the distribution of rare e a r t h s between the two liquid p h a s e s a s functions of the lithium concentration in the metal phase. Studies of t h e equilibrium 21,i'

+ BeF,

F::

2 1 . i ~t ~ e '

(6)

in the extraction s y s t e m a r e currently i n progress to a s c e r t a i n activity coefficients of lithium and rare e a r t h s in bismuth and to s t u d y effects of s a l t composition on iare-earth distribution coefficients. Fluoride s t a r t i n g materials were prepared in nickel equipment by treatment with WF-H, rnixtures a t 6OOOC to remove oxide impurities and a t 70OOC with H, a l o n e t o reduce concentrations of structural metal difluorides in t h e fluoride melts. Selected rnre-earth fluorides were added prior to t h i s treatment in q u a n t i t i e s sufficient t o attain concentrations of about mole fraction in t h e s a l t mixture. Bismuth w a s further purified by treatment with II, at 6OOOC in t h e 304L s t a i n l e s s s t e e l , low-carbon-steel-lined extraction v e s s e l . Following t h i s treatment t h e prepared s a l t mixture was transferred a s a liquid t o t h e extraction vessel. E a c h experiment typically contained 2 . 3 5 k g of bismuth and about 2 kg of t h e s a l t mixture. Lithium, for incremental additions t o the experiment, was freshly c u t and tared under mineral oil, affixed t o a small-diameter s t e e l rod, rinsed in benzene, and dried i n t h e flowing inert atmosphere of the loading port prior t o i t s insertion into t h e molten bismuth. T h i s loading port extended near the bottom of the extraction v e s s e l t o avoid contact of lithium with t h e s a l t p h a s e prior to its dissolution into the molten metal phase. F i l t e r e d s a m p l e s of e a c h p h a s e were taken under a s s u m e d equilibrium conditions a f t e r e a c h

35 addition of lithium. Radiochemical a n a l y s e s of e a c h p h a s e for rare-earth gamma activity a n d spectrographic a n a l y s e s of t h e metal p h a s e for rare-earth and lithium concentrations provided d a t a for c a l c u l a t i n g t h e distribution of rare earth in t h e s y s t e m dnd its dependence on t h e lithium concentration of t h e metal p h a s e . A summary of t h e s e r e s u l t s , illustrated in Fig. 3.4, s h o w s that a mixture containing 0.02 mole fraction of lithium metal sufficed for removing e s s e n t i a l l y a l l cerium, lanthanum, and neodymiurn and s u b s t a n t i a l quant i t i e s of samarium and europium from t h e barren f u e l s o l v e n t under s e p a r a t e but comparative conditions. In a l l experiments rare e a r t h s that were reduced from s o l u t i o n i n t h e salt p h a s e were found a s d i s s o l v e d components of t h e metal phase. T h e reductio11 of rare-earth fluorides by lithium is e x p e c t e d to proceed by the reaction

where rn is t h e e f f e c t i v e valence of t h e rare-earth c a t i o n . If unit a c t i v i t i e s prevail for all metal s p e c i e s in t h e salt p h a s e a n d for all ionic s p e c i e s in t h e metal phase, then t h e activity of lithium d i s s o l v e d in t h e metal p h a s e c a n b e e x p r e s s e d

0 R N L -- DWG 6 6.- 4

a s a function of other a c t i v i t i e s in t h e s y s t e m a s

By a s s u m i n g that the activity of LiF and the activity c o e f f i c i e n t s of Li', RE', and RE"' remain c o n s t a n t , t h e dependence of rare-earth d i s tribution on t h e lithium concentration c a n b e e x p r e s s e d as

D-K

N"' Q

(9)

[-io'

where D is t h e ratio of t h e mole fraction of rare earth in t h e metal p h a s e to t h e mole fraction of rare earth in t h e s a l t p h a s e a n d

K a . ( r 1. i O ) ~ e t a l ~ ( ~ K p ! ) s a l t

I__..__I

(yK E o )m e t a l . ( A

iFlm

(10)

A plot of t h e experimental d a t a a c c o r d i n g to t h e logarithmic form of Eq. (9) i s shown a s Fig. 3.5. Values for m and K c a l c u l a t e d from the s l o p e s Q and intercepts of t h i s plot a r e a s follows: R a r e Earth

Lanthanum

2.7

2.5 x

Cerium

2.3

3.8

Neodymium

2.5

Samarium

1.6

1.8 x

Europium

1.9

io7 x lo6 x loG lo4

9l o 3.

Although the apparent fractional exponents for t h e reductions a r e a s y e t unexplained, t h e r e s u l t s 10

0.1

0.04 1 2 3 4 5 t ITHIUM FOUND IN M E T A L P H A S E (mole f r o c t i o n 6 10')

Extraction of Rare Earths from L i F - B e F 2 Fig. 3.4. (66-34 Mole %) into Bismuth by the Addition of Lithium Metal a t 60OoC.

0.01

0.1

.YOLE ..._. ...FRACTION ....... ..OF ...... RlHE

duo

1000

E A W H IN LdklAi.

MOLC FRACTION OF RARE LAHTII IN SA1 I

Fig. 3.5. Effect of Lithium Concentration in Metal Phase on the Distribution of Rare Earths Between L i F -

B e F 2 (66-34 Mole %) and Bismuth

600째C

36 are in rough agreement with t h e occurrence of lanthanum, cerium, and neodyriiium as trivalent ions i n t h e s a l t mixture; samarium and europium are probably reduced t o their divalent s t a t e s prior t o their extraction into the metal p h a s e . In earlier experiments the extraction of rare e a r t h s from a s a l t p h a s e into iiiolttn bismuth w a s achieved by the addition of beryllium metal t o the s y s t e m . ' T h i s reduction p r o c e s s a l s o res u l t e d in a measurable i n c r e a s e of t h e lithium concentration of the molten metal p h a s e . Accordingly, further s t u d y of t h e Yeaction

2LiF

+ Be0 e 2X.i'

BeF,

In t h e beryllium-addition experiments a t 60OoC a limiting mole fraction of lithium in bismuth w a s reached. A s t h i s w a s w e l l below the solubility, it w a s a s s u m e d that t h e lithium w a s i n equilibrium with metallic beryllium. From t h i s i t w a s p o s s i b l e t o calcul-ate a n activity coefficient for lithium of 9.8 x lo-' t o 1.3 x l o p 4 (two experiments) for t h e mole fraction of lithiuiii referred t o a s t a n d a r d s t a t e of unit activity (i.e., pure lithium). A sirnilar a n a l y s i s gave the activity coefficient of lithium in l e a d a s 1.5 x lo-'.

REMOVAL OF PROTACTINIUM FROM MORTEN FLUORIDES BY REDUCTION PROCESSES

i n the two-phase extraction s y s t e m w a s initiated by experimental procedures s i m i l a r t o t h o s e employed for t h e rare-eaith extractions. The intention of t h e s e experiments was t o measure t h e activity coefficient of lithium i n bismuth by bringing it t o equilibrium with metallic beryllium. It w a s found, however, t h a t t h e stoichiometric amount of lithium did not appear in the metal phase. In experiments where lithium metal w a s added t o t h e s y s t e m , t h e lithium loss W ~ proS portional t o t h e s q u a r e of the mole fraction of lithium in bismuth. Such behavior suggests the presence of a reduced divalent s p e c i e s a t l e s s than unit activity, for which t h e most obvious c h o i c e i s Be' d i s s o l v e d in the melt. W k n B e o was added to t h e melt, t h e lithium l o s s w a s proportional t o t h e first power of X r A i ( B i l , which is c o n s i s t e n t with the formation of neither BeO(d) nor Ret(Cj). F o r a third s e t of experiments: where s a l t w a s added to bismuth containing lithium, the loss w a s independent of t h e lithium concentration, indicating the p r e s e n c e of s o m e e a s i l y reduced impurity in t h e melt. N o simple mechanism h a s been devised t o explain a l l three of t h e s e reactions. It i s known that certain properties of t h i s melt [e.g., h e a t s of solution of H F and s o l u b i l i t i e s of PuF, and ( R E ) F 3 ] show extreme v a l u e s at the ratio 21,i:Be. T h e s a l t composition u s e d in t h e described experiments s t a r t e d a t about t h i s concentration and went t o opposite s i d e s of it. One c a n conceive, therefore, that further experimentation may reveal s o l v e n t e f f e c t s which a r e a s yet unexplained.

T h e removal of protactinium from solution in LiF-BeF,-ThF, (73-2-25 mole X ) h a s been demonstrated by addin-g thoriuin metal that w a s either put directly i n t h e s a l t mixture or initially d i s s o l v e d in molten lead or bismuth that w a s in c o n t a c t with the s a l t . 6 hlore recent s t u d i e s h a v e examined methods by which t h i s reduction reaction might h e u s e d for r e p r o c e s s i n g t h e fertile blanket of a two-region molten-salt breeder reactor. T h e r e s u l t s of s e v e r a l batch-type laboratory experiments led to t h e design and operation of a s m a l l pump-loop experiment which h a s demons t r a t e d , in principle, the iemoval of protactinium f r o m the fluoride iilixture by a liquid-liquid extraction technique. In s t a t i c batch-type experiments, only minor fractions of 2 3 3 P a removed from t h e s a l t p h a s e , on adding thorium metal, were found a s s o l u b l e components of t h e metal phase. Subsequent examinations of t h e low-carbon-steel containers used in t h e s e experiments indicated that most of the precipitated protactinium had deposited on t h e v e s s e l walls t h a t were i n c o n t a c t with the s a l t phase. Although t h i s behavior may have resulted from nonwetting c h a r a c t e r i s t i c s of the two liquid p h a s e s , a n experiment w a s conducted t o examine the absorption of 2 3 3 P a on iron s u r f a c e s in t h e a b s e n c e of a molten metal p h a s e . A s a i e s u l t of adding thorium metal, 2 3 3 P a w a s found uniformly

' K e a c t o r Chem. Dzv. A n n . 1965, ORNL-3913, p . 40.

6 K e a c t o r Chem. D i v . A n n . 1 9 6 5 , OWNk-3913, p. 42.

Progr.

R e p t . Dec. 31,

J . W. Shaffer D. M. Motilton W. K. 12. F i n n e l l

W. P. Teichert E'. F. Elankenship W. K. Grimes

Progr. A e p t . D e c . 31,

37 distributed on s t e e l wool that had been immersed in a blanket salt mixture, When t h i s s a l t mixture w a s drained from t h e v e s s e l and filtered through s i n t e r e d nickel, e s s e n t i a l l y no 3 3 P a activity could b e found i n t h e s a l t mixture or on t h e filter. In other experiments in which no s a l t p h a s e w a s used, s o l u t i o n s of 233Pa i n molten l e a d or bismuth, obtained by t h e addition of irradiated thorium metal, w e r e not s t a b l e i n e i t h e r metal solvent. However, a much larger fraction of 233Pa a c t i v i t y w a s retained i n bismuth than in l e a d during 48-hr c o n t a c t periods. Subsequent examination of t h e low-carbon-steel v e s s e l s u s e d in t h e s e experiments showed a distribution of 233Pa on t h e container w a l l s which resembled sedimentary d e p o s i t i o n of insoluble materials rather than s u r f a c e absorption. In view of e a r l i e r 3Pa r e s u l t s , t e n t a t i v e concIusions a s s u m e d t h a t was preferentially absorbed on insoluble part i c l e s that were initially p r e s e n t in the molten metals or formed by r e a c t i o n s with added thorium. S i n c e t h e a n t i c i p a t e d function of t h e molten metal p h a s e i n the extraction p r o c e s s is t h a t of a n intermediate carrier for protactinium, t h e rate at which '33Pa c a n b e e x t r a c t e d from t h e blanket s a l t and concentrated in a s e c o n d s a l t mixture by b a c k extraction with H F need only depend on t h e m a s s transfer rate of protactinium d i s s o l v e d in a recirculating molten metal s t r e a m T h u s a pumploop experiment, s h o w n s c h e m a t i c a l l y in Fig. 3.6, w a s tried in a n endeavor to a c h i e v e t h e transport of "'Pa in bismuth w h i l e maintaining its concentration or that of its carrier at relatively low v a l u e s . Thorium w a s introduced into t h e s y s t e m by contacting t h e liquid metal with thorium c h i p s j u s t prior to its reentry i n t o t h e extraction v e s s e l . At low bismuth flow r a t e s protactinium could b e reduced a t t h e s u r f a c e s of free-falling droplets. For simplicity t h e recirculating molten metal stream w a s pumped through a b e d of s t e e l wool t o provide for t h e collection of protactinium, presumably by absorption, a n d to provide coarse filtration of the bismuth in t h e event t h a t z 3 3 P a w a s being carried by s u s p e n d e d s o l i d particles. Surface a r e a s of steel wool columns u s e d i n the experiment were at l e a s t tenfold greater than t h o s e of other iron s u r f a c e s e x p o s e d to the molten metal e l s e w h e r e in t h e loop. T h e extraction v e s s e l w a s also provided with a niobium s l e e v e t o i s o l a t e the s a l t p h a s e from t h e iron s u r f a c e s of t h e loop.

T h e pump-loop experiment w a s operated d i s continuously for approximately 60 hr over a period of about s i x w e e k s and w a s terminated b e c a u s e of pump failure. Material b a l a n c e c a l c u l a t i o n s on t h e s y s t e m a t t h e c o n c l u s i o n of t h e experiment showed t h a t approximately 96% of the 233Pa had been removed from t h e s a l t mixture. At least 43% of t h e 2 3 3 P a originally in the s y s t e m h a d been pumped a s a solution or a s u s p e n s i o n with molten bismuth and deposited on rather s m a l l volumes of steel wool, Since only 4% of t h e 33Pa remained i n solution i n the bismuth, approximately 49% of t h e 233Paw a s l o s t as s o l i d s in the s y s t e m . T h e collection of 2 3 3 P a o n t h e columns w a s , in f a c t , better identified with a filtration p r o c e s s e v e n though some s u r f a c e absorption was apparent. Spectrographic a n a l y s e s of high-melting metallic plugs t a k e n from t h e s y s t e m a s s o c i a t e d relatively high concentrations ol thorium with iron and chromium. T h e s e obs e r v a t i o n s s u g g e s t that a more inert containment material will b e needed before a s a t i s f a c t o r y

ORNL -DWG 66 -11464

HELIUM SIJPPI.Y I

Fig.

3.6.

Pump Loop.

Schematic

Diagram of

EXIHAUST

2 3 3 P ~E x t r a c t i o n

38 s o l u t i o n s or a s s u r f a c e absorption of 233Paon t h e Further s t u d i e s of this oxide pie.s o l i d ZrO,. cipitat.ion method were conducted i n the same fluoride s o l v e n t with ZrO, powders having varied surface areas. Zirconium dioxide u s e d in t h e original experiment w a s purchased commercially and had a s u r face area of about 19.6 m2/g. Material having higher s u r f a c e areas w a s prepared from Zr(Ol-9)4 by dehydration.8 Sufficient ZrO, for this e x perimental s e r i e s was fired at 600, 700, and 1000°C in s e p a r a t e b a t c h e s that yielded average s u r f a c e a r e a s of 80, 50, and 1 . 3 2 m 2 / g respectively. About 3.55 kg of a s a l t mixture having a nominal composition of LiF-BeF,-ZrF, (64.833.5-1.6 mole %) with about 1 m c of 2 3 3 P aa s irradiated ThO, w a s p r e p a d i n n i c k e l by conventional HF-€I, treatment a t 6OOOC and H, sparging at 70OoC for further purification and d i s solution of protactinium a s i t s fluoride s a l t . Selected ZrD2 w a s added to t h e s a l t mixture in 10-g increments; t h e mixture w a s then s p a r g e d

demonstration of t h e liquid-liquid extraction p r o c e s s c a n be achieved.

J . H. Shaffer U'. K. I?. Finnell W. P. 'feichert F. %. Blankenship W. R. Grimes

In a previous experiment protactinium was removed from solution in a s o l v e n t mixture of L i F BcF, (66-34 mole %) which also contained ZrF4 (0.5 mole per k g of s a l t ) by t h e addition of ZiO, a t 6OOOC. An interpretation of the experirriental data according to the equation

where D (Pn)oxide/(Pa)salt, F p a fraction of protactinium in t h e s a l t , and W = weight of the designated phase, showed t h a t t h e distribution of protactinium between the two p h a s e s remained c o n s i a n i over t h e protactinium concentration range of the experiment. T h e s e results could b e explained a s t h e forination of l a b i l e oxide s o l i d :

_-. ~.

.. ....

7 R e a c t o r Cheni. D i v . Ann. Progr. R e p t . D e c . 31, 1 9 6 5 , ORNI,-3913, p. 31. 8 L r O w a s piepared b y H. I I . Stone, R e a c t o r Ch-rn,,

istry D h i s i o n .

I -

B 0

SURFACF AREA Z r 0 2 - a 0 m2/g S U R F A C E A R E A Zr0,=50n7-/g

SURFACE A R E A Z r O 2 - i

32 m2/g

W H E R E Fpa= F R K I ION OF 233Pa IN LIQUID

8 z

O i DESIGNATL I P ' I A S E CONC OF Pa IN SOLID PHASE CONC OF Pa IN LIQUID 3 i4SE

W= WCIGH

2 cc

I 30

l--

---A 40 50 60

7r02 ADDED ( g )

Fig. 3.7.

600°C.

E f f e c t o f S u r f d c e Area Qf Z r 0 2 o n the R e m o v a l of 2 3 3 P a froin L i F - 5 e F 2 - Z r F 4 (64.8-33.6-1.6

Mole %)

39 with helium a t a r a t e of a b o u t 1 liter/min during 24-hr equilibration periods. F i l t e r e d s a m p l e s of t h e s a l t mixture were taken a f t e r e a c h equilibration period a n d a n a l y z e d radiochemically for 2 3 3 P a by counting i t s 310-kv photopeak on a single-channel gamma spectrometer. At t h e conc l u s i o n of t h e experiment t h e mixture w a s hydtofluorinated to convert added ZrQ, to i t s fluoride salt and t o restore 233Paactivity in the tnoltensalt p h a s e . T h i s experimental procedure w a s repeated with t h e s a m e salt mixture for a l l thrce lots of ZrO,. In e a c h experiment t h e addition of ZrO, t o the fluoride mixture r e s u l t e d in t h e loss of protactinium from solution. However, a s shown by F i g . 3 7, a plot of t h e reciprocal fraction of 2 3 3 P a in solution v s ZrO, added, yielded, according to Eq. (12), distribution c o e f f i c i e n t s for 1 3 3Pa between t h e t w o p h a s e s which varied continuously as t h e precipitation reaction approached complrtion. Although t h e s e experimental r e s u l t s a r e contrary t o t h o s e obtained previously, with res p c c t t o t h e c o n s t a n c y of t h e 2 3 3 P a distribution 3Pa removal coefficients, they i n d i c a t e that from the sa!t mixture i s probably not singularly dependent on the s u r f a c e a r e a of t h e added oxide particles nor on s o l i d s o l u t i o n formation.

PROTACTINIUM STUDIES IN THE HIGH-ALPHA MOLT EN-SALT LABORATQR Y C. 'J. Barton

H . H . Stone

T h e High-Alpha Molten-Salt Laboratory w a s briefly d e s c r i b e d in t h e previous report,g and r e s u l t s of the f i r s t experiments performed in t h i s facility were given. Attention h a s b e e n f o c u s e d on developnient of methods of removing protactinium a t r e a l i s t i c concentrations (25 ppm) from breeder b l a n k e t s , but a few experiments h a v e b e e n performed in a n effort to obtain a better unders t a n d i n g of the chemistry of protactinium in molten fluoride s y s t e m s . B e c a u s e of t h e variety of experimental methods t h a t h a v e been applied to t h e protactinium removal problem, only a brief summary is presented h e r e , with e m p h a s i s on t h e experiments t h a t g a v e t h e most promising r e s u l t s . Some information from t h e s e experiments h a s been previously reported. lo-' ' C . J. Barton, R e a c t o r Chem. D i v . U e p t . D O C .31, 1965, OKNL-3913, p . 41.

Ann. Pro&.

Protactinium Recovery Experiments

W e found t h a t protactinium d i s s o l v e d t o t h e e x tent of 2 0 t o 3 0 ppm in molten L i F - T h F , (73-27 mole %) could b e readily reduced by solid thorium or by thorium d i s s o l v e d in l e a d . In t h e l a t t e r c a s e , only a s m a l l fraction of the reduced protactinium w a s found in t h e molten m e t a l phase. Keduction experiments with s o l i d thorium in three different container materials (nickel, copper, and graphite) showed t h a t m o r e than half t h e reduced protactinium remained s u s p e n d e d in t h e molten fluoride mixture. We b e l i e v e that t h e reduced protactinium is a t t a c h e d t o small p a r t i c l e s of a s t r u c tural metal s u c h a s iron or nickel which a r e large enough t o b e removed by the s i n t e r e d copper filter material through which t h e s a m p l e s are drawn but s m a l l enough to remain s u s p e n d e d for a reasonable length of time in t h e high-density molten s a l t . P a r t i a l reduction of protactinium w a s effected by e l e c t r o l y s i s with various e l e c t r o d e arrangements, but very l i t t l e protactinium w a s found in thie bismuth layer t h a t underlay t h e molten-salt mixture i n most of t h e e l e c t r o l y s i s experiments. T h e aim of t h e s e experiments, to transfer protactinium from t h e fluoride mixture to bismuth or to some other e l e c t r o d e material that could b e readily s e p a r a t e d from t h e s a l t mixture, w a s not realized. Efforts to c o l l e c t tracer q u a n t i t i e s of reduced 233Pa on s t e e l wool h a v e been reported.13 A s e r i e s of three experiments of t h i s type were re-. c e n t l y performed with 2 3 1 P a concentrations in a n LiF-ThF, (73-27 mole %) mixture i n the range 24 to 81 ppm. T h e principal variable w a s the ratio of milligrams of 2 3 1 ~ tao grams of steel wool. T h e s e r a t i o s were 1.1, 3.1, and 6.5 For t h e t h r e e experiments. Detailed r e s u l t s are given only for one experiment ( 2 3 1 P a to Fe ratio G.3, but c o n c l u s i o n s a r e b a s e d on findings of all three experiments, which g a v e s i m i l a r r e s u l t s . A weighed quantity of L i F - T h F , , previously purified, w a s placed in a welded n i c k e l reaction "C. J. Barton and I I . ET. Stone, R i m o v a l of Protactinium from Molten F l i t o r i r k Breeder B l a n k e t Mixtures, ORNL-TM-1543 (June 1, 1966).

'c. J. Barton, MSR P m g r a m ~ e n i i a r m .Progr. Izept. Fish. 28, 1966, O R N I r 3 9 3 6 . pp. 148-52.

12C. J. Barton, M S R Program Serniariri. Progr. R e p t . A @ . 31, 1966, OHNL-4037, pp. 156-58. 13J. H. Shaffer e t a]., M S R Program Serniann. Progr. R e p t . A u g . 31, 1966, ORNL-4037, p p . 148-46.

v e s s e l , irradiated T h F , containing a known amount of 2 3 3 P a and 231Pa w a s added t o t h e mixture, and it w a s treated first with a mixture of H F and I:, and then with I I , alone. Four grams of s t e e l wool (grade 00, 0.068 m 2 / g surf a c e area) w a s placed in a low-caibon-steel liner i n s i d e another nickel v e s s e l . 'The contents of t h e v e s s e l w e r e then treated with purified hydrogen a t 8OOOC for s e v e r a l hours to remove a s much a s p o s s i b l e of t h e oxide s u r f a c e contamination of t h e steel wool and liner. T h e two v e s s e l s were then connected together a t room temperature and h e a t e d to about 650째C, and t h e s a l t w a s transferred t o the steel-lined v e s s e l . After two s e p a r a t e e x p o s u r e s of t h e s a l t t o a s o l i d thorium s u r f a c e , a s indicated in T a b l e 3.1, the s a l t w a s transferred back t o i t s original container and allowed to cool in helium. The steel-lined v e s s e l w a s c u t up, and s a m p l e s were submitted for a n a l y s i s .

Tohla 3.1.

_____~

T h e data i n 'Table 3.1 show that 99% of t h e protactinium w a s precipitated i n a form that would not p a s s through a s i n t e r e d copper filter after a fairly short exposure t o s o l i d thorium, but nearly 7% w a s in the unfiltered s a l t t h a t w a s transferred back to t h e nickel v e s s e l a f t e r exposure t o thorium. About 69 g of s a l t w a s a s s o c i a t e d with t h e s t e e l wool in t h e s t e e l liner in t h e form of a hard ball. P a r t i a l s e p a r a t i o n of t h e s a l t from s t e e l wool was effected by u s e of a magnet a f t e r crushing t h e ball, and t h e iron-rich fraction had the higher protactinium concentration. The s m a l l amount of protactiniiim found on the v e s s e l wall is e s p e c i a l l y notable. T h e Inst column in 'Table 3.1 s h o w s t h a t a reduction in the iron concentration occurred concurrently with t h e reduction in protactinium concentration. It may b e signific a n t that t h e ratio of precipitated iron t o peecipitated protactinium w a s milch smaller in t h i s experiment than i n t h e other two experiments,

Pcecipitotion of Protactinium f r s m M o l t e n d-iF.ThF4

.......

........

(73-27 Mole

a)by

Thorium Reduction

i n t h e Presence of S t e e l Wool .........

I _ -

.......

..........

___

231~a Sample

Concentration (n1e/d

S a l t a f t e r HF-H, treatment

0.0634

20.3

(1.5

S a l t j u s t before transfer

0.081

26.1

116

S a l t 3 5 m i n a f t e r transfer

0.079

24,9

S a l t after 50 snin thorium exposure

0.0026

S a l t a f t e r 45 min thorium exposure

0.0009

Nonmagnetic fraction of material

0.20

11.5

994

0.628

10.2

2750

0.69

0.27

i n s t e e l liner Magnetic fraction of material in s t e e l liner Unfiltered s a l t a f t e r transfer to

0.0076

1.75

nickel v e s s e l S t e e l liner w a l l

0.0006

S t a i n l e s s s t e e l dip l e g

0.53

F i l i n g s from thorium r o d

0.29

.4ll s a l t s a m p l e s

1.35

T o t a l protactinium recovered

25.5

(15

where t h e retention of protactinium by t h e s t c e l wool w a s more efficient. Coprecipitation of metallic protactinium and iron (and possibly nickel) would h e l p to a c c o u n t for t h e manner in which protactinium s e t t l e d o u t on, and adhered to, t h e s t e e l wool s u r f a c e . On t h e b a s i s of presently a v a i l a b l e information, thorium rcduction of protactinium From molten breeder blanket mixtures in t h e p r e s e n c e of s t e e l wool is believed to be a promising recovery method warranting further investigation.

GRAPHlTE-MOLTEN-SALT IRRADIATION T O HIGH FiSSION DOSE E. L. Compere 11. C. S a v a g e J . M. Baker M. J. Kelly E. G. Bohlmann. Irradiation of t h e f i r s t molten-salt convection loop experiment in ORK beam h o l e HN-1 was tetminated on August 8, 1966, after development of 1.1 x f i s s i o n s / c m 3 (0.27% 2 3 s U burnup) in t h e 'LiF-HeF,-ZrF,-UF, (65.16-28.57-4.901.36 mole "/o) fuel. Average f u e l power d e n s i t i e s u p to 10.5 w per c u b i c centimeter of s a l t were a t t a i n e d i n t h e fuel c h a n n e l s of t h e c o r e of MSREgrade graphite. S u c c e s s f u l operation of the major heating, cooling, temperature-control, and sampling s y s tems w a s demonstrated; however, l e a k s developed i n two of t h e four cooling s y s t e m s . T h e experiment w a s terminated after radioactivity, r e s u l t i n g from fuel l e a k a g e from a break in t h e s a m p l e l i n e near the loop, w a s d e t e c t e d i n t h e secondary containment. Irradiation of a s e c o n d loop, modified t o elimin a t e c a u s e s of failures encountered in the f i r s t , Operation a t a n will begin in January 1967. average c o r e f u e l power density of 200 w/cm3 for a period of t h e order of a y e a r will b e s o u g h t .

s t u d y t h e interaction of f i s s i o n products with graphite, metal, fuel, a n d g a s p h a s e s and t h e s t a b i l i t y of t h e fuel s a l t at high l e v e l s of burnUP.

T h e c o r e of t h e first loop c o n s i s t e d of a 2-in.diam by 6-in.-long cylinder of graphite obtained from MSKE s t o c k . Through t h e core, eight vertical holes for s a l t flow w e r e bored, arranged ' in. from the graphite octagonally with c e n t e r s 6 center line. A horizontal g a s s e p a r a t i o n tank connected t h e top of t h e c o r e t o a return line t o t h e core bottom, completing t.he loop. T h e tank, l i n e s , and t h e c o r e s h e l l were fabricated of Hastelloy N. The h e a t e r s and t h e coolirig tubes in the c o r e and return l i n e were embedded in sprayed-on nickel, as w a s t h e 12-ft s a m p l e tube leading from t h e loop t o the s a m p l e s t a t i o n in the external equipment chamber. Operations. - T h e loop w a s operated with MSRE s o l v e n t s a l t for 187 h r a t Y-12, and s e v e r a l s a l t s a m p l e s w e r e taken. It w a s inserted in beam h o l e HN-1 of t h e ORR on June 9, 1966, a n d operated 1100 hr with s o l v e n t s a l t ; during t h i s period calibration and t e s t i n g of equipment arid performance were conducted. T h e b o p w a s ins e r t e d to t h e position n e a r e s t t.he reactor l a t t i c e on July 21, and water injection into ihe air s t r e a m s t o t h e tubular c o r e coolers and t h e j a c k e t around t h e g a s separation tank w a s t e s t e d . One of t h e two core coolers leaked and w a s plugged off. Water injection was discontinued until after uranium addition. On July 27, after sampling, e u t e c t i c 7LiF-UF, (93% enriched) fuel s a l t w a s added to develop a uranium inventory concentration of 1 . 3 6 mole %. At t h i s time a capillary tube in t h e s a m p l e removal s y s t e m broke, precluding further sampling. An a s s o c i a t e d i n l e a k a g e of a i r impelled s o l v e n t s a l t to a c o l d s p o t in t h e g a s s a m p l e line, thereby plugging it. During s u b s e q u e n t operation f i s s i o n h e a t w a s determined. During t h i s period water w a s rel e a s e d into t h e loop container from what proved

Objectives and Description

T h e loop is d e s i g n e d to irradiate a representat i v e molten-salt fuel c i r c u l a t i n g at typical temperature differences in c o n t a c t with graphite a n d Hastelloy N a t d e s i r e d core power d e n s i t i e s of 200 w/cm3, with provisions for gas removal a n d salt sampling. In particular, it is d e s i r e d to

14blSK Program Semiann. Pro&. R e p t . Rug. ORNL-3872, pp. 106-10. sM.Si? Prograni Semianrr. P t o g r . R e p t . F e b . ORNId-393G, pp. 152-54. 1 6 R e n c t o r them. Div. ~ n n .Progr. R c p t . 196.5, ORNL-391.3, pp. 34-35. 17Rc.3ctor Chen7. n i v . Ami. Progr. Rept. 1965, ORNL-3784, pp. 4S.18, Fig. 2 . 4 .

3 1 , 1965, 28, 1966, ~ e c 31, .

J a n . 31,

42 t o b e a l e a k in the cooling j a c k e t around t h e g a s separation tank. After R short reactor shutdown. on August 8 to permit removal of the water accumulated a s a result of t h e l e a k , t h e irradiation w a s resumed. 'That evening, r e l e a s e of subs t a n t i a l radioactivity into t h e loop container indicated fuel leakage. T h e loop temperature w a s lowered to freeze the s a l t , and t h e loop w a s retracted t o 2% flux. It w a s removed to t h e hot c e l l s for d i s a s s e m b l y and examination on August 11, 1966. C h e m i c a l A n a l y s i s O B Salt. - Samples of s o l v e n t salt taken prior to irradiation and after 1100 hr in pile and of irradiated fuel s a l t obtained after dismantling were analyzed chemically and radiochemically. A s a m p l e of s a l t found between t h e metal core s h e l l and t h e graphite w a s a l s o analyzed. R e s u l t s a r e given in T a b l e 3.2 and are d i s c u s s e d below. Carrasion. - T h e l e v e l of corrosion products, particularly chromium and nickel, in the s a l t increased in t h e s u c c e s s i v e saniplen. T h i s was possibly due to uptake of moisture by the s o l v e n t s a l t prior t o loading, with consequent corrosion of t h e Hastelloy N. T h i s a p p e a r s t o h a v e occurred in t h e addition tank, s i n c e a sample taken directly from the addition tank without entering t h e loop showed similar l e v e l s of corrosion products. Fission Products. F i s s i o n products w e r s counted in a fuel s a m p l e after 1 1 0 d a y s ' cooling; concentrations a r c given below a s a percentage of t h e amount produced, c a l c u l a t e d on t h e b a s i s of observed f i s s i o n h e a t (4.8 x 1 0 ' f i s s i o n s / g ) . Cerium-144 and -141 (77, 64%) and zirconium-89 (65%) were somewhat below t h e c a l c u l a t e d production. Cesium-137 (41%) and s t r o n t i u m 8 9 (42%), with noble-gas precursors of -3 min half-life, could h a v e thereby been l o s t to t h e g a s s p a c e or graphite voids. Tellurium-127 (10%) w a s largely removed from t h e s a l t . Ruthenium-103 and -106, which were expected to d e p o s i t on Hastelloy N s u r f a c e s , were not detected (<0.03%) in t h e s a l t . Nuclear Heat and Neutron F l u x . - Nuclear h e a t w a s measured at various loop insertion positions by comparing e l e c t r i c a l h e a t requirements under s i m i l a r conditions with t h e reactor a t z e r o and full power. Reactor gamma h e a t fully inserted w a s 2900 w (with unfueled s a l t ) . With fuel containing 1.36 mole % uranium (93% enriched), fission h e a t in the fully inserted position w a s 5800 w. The corresponding overall a v e r a g e fis-

s i o n h e a t density w a s 80 w per c u b i c centimeter of s a l t a t 65OCC, and in the graphite core t h e average f i s s i o n h e a t density was 1 0 5 w per c u b i c centimeter of fuel s a l t . T h e overall e f f e c t i v e thermal-neutron flux in the s a l t w a s estimated independently from nuclear h e a t , from activation of s o l v e n t s a l t zirconium, from cobalt inonitors in t h e loop exterior, and by neutron transport calculation. T h e r e s u l t s agreed well, ranging between 0.9 and 1.2 x 1 0 l 3 neutrons c i r s~e c~- I .~ Wot-Cel! Examination of: Components. -- Aftei separation froin other p a r t s of the package, the loop proper was kept for about three months in a furnace a t 300째C t o prevent fluorine evolution by fission product radiolysis of t h e s a l t . At t h i s time i t was removed for detailed examination. 'The type 304 s t a i n l e s s s t e e l tubular c o r e cooler w a s found t o h a v e broken cntiiely l o o s e without ductility a t i t s outlet end a s i t left t h e core near a tack weld t o t h e core s h e l l . Intergranular c r a c k s originated on t h e outer circumference of the coiled tube. 'l'he cooling j a c k e t on t h e g a s separation tank leaked a t a weld. 'The fuel l e a k resulted from a nonductile break in the IPastelloy N sample l i n e tubing n e a r the attachment t o t h e c o r e bottom. T h e sprayed nickel w a s also cracked in t h i s region. F u e l s a l t in t h e form of a s c a l e a few mils thick w a s found on the interior of t h e core s h e l l , between i t and the c l o s e l y fitting graphite core. T h e anadysis shown in T a b l e 3.2 a p p e a r s t o b e a mixture of fuel s a l t and Hastelloy N (probably metal d e b r i s froin c u t u p operation). Hot-cell metallurgical examination of the interior s u r f a c e s of the Hastelloy N comprising t h e core bottom and core s h e l l w a l l showed n o evid e n c e of any interaction with s a l t or carbon, or other change. Evaluation of System Performance H e a t e r s . - T h e molten-salt loop package u s e d 2 1 continuous or intermittent h e a t e r s , all '4-in.OD, Inconel-sheathed, MgO-insulated, with Nichrome V e l e m e n t s designed for 870째 continuous operation. No failures occurred. 6eaolers. -- The h e a t removal rate of t h e loop coolers w a s entirely a d e q u a t e t o remove t h e 8.8 kw of f i s s i o n and gamma h e a t , e v e n after

k i, 24

,-+

z 0 N

x z

0 0

N. W 01

0 0

a 0 0

0 N

?rn

,--. W

" W k

-1

14 t h e l o s s described earlier of one of the two cooling c o i l s around t h e loop c o r e s e c t i o n . T h e a i r plus water-injection technique a p p e a r s adeq u a t e and responsive. T h e u s e of water injection w a s not n e c e s s a r i l y t h e c a u s e of failure of t h e two c o o l i n g units, but only made t h e failures evident. Temperature Cantral. - T h e r e s p o n s e of t h e h e a t i n g and c o o l i n g s y s t e m s t o rapid c h a n g e s in t h e nnclear h e a t could only b e t e s t e d under full f i s s i o n conditions in pile. S i n c e t h i s w a s regarded as import-ant, reactor s e t b a c k t e s t s were conducted. Temperature-control s y s t e m r e s p o n s e was a d e q u a t e to maintain t h e s a l t molten during a reactor s e t b a c k with resultant l o s s of 8.8 kw of nuclear h e a t , and to return t h e loop to normal operating condition during a rapid (11-min) return t o full power. Sampling a n d Adbinion. -.-Sampling and addition s y s t e m s a n d procedures were a d e q u a t e to permit addition and removal of molten s a l t while operating t h e loop in pile and to transport s h i e l d e d s a m p l e s under a n inert-gas atmosphere t o t h e analytical laboratory. A broken capillary connecting tube prevented additional sampling. Salt C i r C U l Q t i O n . .-Convective s a l t circulation, a t r a t e s of 5 t o 1 0 cm3/min, w a s achieved by c a u s i n g t h e return line to operate a t temperatures below t h e core temperature. Flow s t o p p a g e s occurred from time to time. T h e s e were attributed to bubble formation resulting f r o m different s o l u bility of argon cover gas a t t h e varied temperatures around t h e loop. Salt flow w a s reestablished by evacuation and readdition of cover g a s . Loss of flow had no a d v e r s e e f f e c t on loop operation. Second I n - F i l s I r r a d i a t i o n A s s e m b l y . - A s e c o n d in-pile molten-salt convection loop, e s s e n t i a l l y identical t o t h e first convection loop experim e n t , I 6 h a s been constructed, and it i s anticipated that in-pile irradiation will begin early in 1967. Problems encountered in t h e first convection loop experiment and s u b s e q u e n t postirradiation hot-cell examination, described above, h a v e led t o modifications t o t h e s e c o n d loop which a r e designed to eliminate t h e s e problems. l'he coolant tubes, embedded in nickel spray around t h e core s e c t i o n , a r e now of '<-in.-OT) x 0.035-in.-wall Inconel tubing i n s t e a d of t h e '$-in.OD x 0.035-in.-wall 304 s t a i n l e s s s t e e l u s e d on

t h e f i r s t loop. T h e s t a i n l e s s s t e e l tubing should h a v e been entirely adequate for t h e s e r v i c e , but Inconel is t h e preferred material for exposure to t h e high-temperature s t e a m (- 400"C) generated when air-water mixtures a r e u s e d as coolant. S i n c e the rupture of one of t h e core coolant t u b e s occurrcd a d j a c e n t t o a point where t h e tube w a s tack welded to t h e c o r e wall, t h e t a c k weld w a s eliminated in favor of a mechanical s t r a p attachment. An expansion loop to relieve s t r e s s e s h a s b e e n included in e a c h of t h e coolant outlet l i n e s . A mockup of t h e modified cooling c o i l w a s operated a t teinperature with air-water mixtures for more than 400 hr, including 120 thermal shock c y c l e s (600 + 35O0C), with no s i g n of difficulty. Thermal c y c l i n g o c c u r s during a reactor s e t b a c k and startup, and i t i s estimated t h a t no more than about 20 s u c h thermal c y c l e s will occur during a y e a r of operation. T h e two failures which occurred in t h e capillaiy tubing (0.100 in. OD x 0.050 in. ID> u s e d in t h e s a l t transfer s y s t e m appear t o h a v e r e s u l t e d from e x c e s s i v e mechanical s t r e s s . Consequently, t h e wall t h i c k n e s s of t h i s line h a s been i n c r e a s e d to 0.050 in., and additional mechanical support h a s been added s u c h t h a t there i s now no part of t h e s a l t s a m p l e l i n e which i s unsuppoited - a s w a s t h e case in the f i r s t loop assembly. T h e '4 6-in.-thick s t a i n l e s s s t e e l cooling j a c k e t surrounding t h e reservoir tank h a s b e e n replaced by a n Incone! tube wrapped around t h e o u t s i d e of the tank and a t t a c h e d by means of sprayed-on nickel metal, a s i s done o n t h e core s e c t i o n and cold leg. Also, provisions for u s e of a n air-water mixture as coolant h a v e been added, s i n c e i t w a x found that a i r a l o n e did not provide s u f f i c i e n t cooling in t h e f i r s t experiment. Continuous s a l t circulation by thermal convection w a s not maintained in t h e f i r s t experiment. It w a s concluded that loss of circulation w a s c a u s e d by gas accumulation in t h e top of t h e c o r e section. Accordingly, t h e s a l t flow c h a n n e l s a t t h e t o p and bottom of t h e e i g h t '$-in. h o l e s for s a l t flow in t h e graphite c o r e were redesigned t o provide better flow conditions l 7 a t the i n l e t s a n d exits of t h e vertical h o l e s . Further, t h e top and bottom of t h e core s e c t i o n , horizontally oriented on t h e f i r s t loop, w e r e inclined a t 5" t o minimize trapping of g a s .

4. Direct Support for MSRE EXTENT OF UF, REDUCTION DURING MSRE FUEL PREPARATION B. F. Hitch

and to determine t h e e x t e n t of U F , reduction in t h e LiF-UF, mixture. For s m a l l amounts of reduction, the U F , / U F , ratio may be related t o Q and t h e volume, V , of 13, p a s s e d per mole of UF4(nu) b y 4

C. F. B a e s , Jr.

Uranium w a s added to t h e barren fuel s a l t of the MSRE a s a binary mixture of 27 mole % U F , in 'LiF. T h i s f u e l c o n c e n t r a t e had first been purified by t h e usual s p a r g i n g with a n IIF-H, mixture to remove oxide, followed by sparging with hydrogen a l o n e t o complete t h e reduction of structural metal fluorides s u c h a s N i F , a n d FeF,. During t h i s final reduction s t e p , a small portion of the U F , should also h a v e b e e n reduced, the amount depending upon t h e duration of the treatment and the equilibrium c o n s t a n t for the reaction

(2) provided equilibrium conditions a t e maintained during sparging. T h e l a s t t e r m on t h e right is the initial n u F 3/nU ratio. Replacing nrrF 3 / n U

UF,(d)

-1

?2H2(g)

* UF,(d)

by Q P A Y / P n ,?,

+ €IF(&). In accord with this equation, plots of l / P i F v s V , b a s e d on d a t a c o l l e c t e d at 700°C during the purification of t h e various b a t c h e s of fuel conc e n t r a t e , were found t o b e linear. All plots could b e fitted reasonably well with lines of slopes corresponding to Q 0.9 j c atm'". By measuring V from t h e intercept of e a c h plot a t

T h c e x a c t amount of U F , t h u s introduced into the MSRE fuel has become a matter of s p e c i a l i n t e r e s t with continued operation of the MSRE, owing t o e v i d e n c e t h a t s i g n i f i c a n t amounts of s o m e f i s s i o n products a r e far more oxidized ( s e e following s e c t i o n ) than would s e e m compatible with t h e presence of s i g n i f i c a n t amounts of U F , in the MSRE fuel. Consequently, t h e d a t a c o l l e c t e d by Shaffer et 3 2 . during t h e purification of the fuel s a l t concentrate at t h e production facility recently h a v e been examined i n d e t a i l in a n attempt t o determine the equilibrium quotient for the above reaction,

4Combinalion of

and

t o e l i m i n a t e PHF,followed by jntegratiori g i v e s

' 7 . €1. Shaffer e t a l . , Reactor Chem. D i v . Ann. Progr. Rept, J a n . 3 1 , 1965, ORNL-3789, pp. 99-109. 2 J . H. Shaffer, MSR Program Semiann. Progr. K e p t . J u l y 3 1 , 1964, ORNL-3708, pp. 288-303. 3 U n p u b l i s l ~ e dd a t a , s u p p l i e d by J. €1. Shaffer.

where

r = nUF3/nU.

For s m a l l values of r this s i m -

plified to Eq. (2) of this repoi t.

46 l/’F’;lF = 0, the a v e r a g e amount of uranium r e duction a t t h e e n d of t h e hydrogen treatinent w a s estimated t o b e 0.15%. In a n attempt to confirm t h i s e s t i m a t e of Q and the amount of reduced uranium present initially in t h e MSRE fuel, a n 11.4-kg portion of unused fuel concentrate w a s studied further in the laboratory. Hydrogen s p a r g i n g w a s initiated a t 51OOC. At t h i s relatively low temperature, no significant reduction of U4’ t o U 3 + should occur; however, H F evolution was d e t e c t e d immediately and continued a t a s i g n i f i c a n t leve! until 250 l i t e r s of 13, had been p a s s e d and 0.0019 mole of I W per mole of uranium had been evolved. T h i s iridicated that inadvertent exposure of t h e s a l t t o oxidizing impurities s u c h as water or oxygen had occurred during prior s t o r a g e , during transfer of the Sample t o the reaction v e s s e l , or i n l a t e r handling. Since the I-PF a t t h i s temperature in t h e amounts seen should have quickly oxidized t h e UF, prese n t , i t w a s not p o s s i b l e t o confirm t h e amount of U F , initially present in t h e fuel concentrate. In two s u b s e q u e n t H , s p a r g i n g runs a t 700°C, however, data were obtained which permitted improved e s t i m a t e s of Q from plots of l/I’iF v s V :

(“a

H 2 Flow

Temperature

Run 1 Run 2

(ml rnin-’

kg-’)

0 (a+m’”)

707

1 . 7 1 ~

705

1 . 8 5 X 10-6

‘The resulting v a l u e s of Q are about twice t h o s e estimated from t h e s a l t production d a t a . It i s not reasonable t o a t t r i b u t e t h i s discrepancy e n tirely t o t h e differences in temperature, s i n c e , judging f r o m Long’s measurements of t h e temperatuie dependence of Q in L i F - B e F , melts,’ more than a 30OC difference would be required. Kt seems m o r e likely t h a t t h e d i s c r e p a n c y i s due partly t o nonequilibrium s p a r g i n g conditions in the production treatment. T h e present v a l u e of Q = 1.8x atm determined for t h e fuel concentrate is somewhat lowei than the value “-4 x l o p 6 a t m ’ ” which may b e estiinated for t h e MSRE fuel s a l t a t 700°C from Long’s ineasurements. T h i s ind i c a t e s t h a t U F , is riot a s e a s i l y reduccd i n t h e fuel concentrate a s in t h e fuel s a l t . Even though equilibrium conditions might not have prevailed during purification of the fuel con-

’”

__ 5G. Long, R e a c t o r Chem. Div. Ann. J a n . 31, 1965, ORNL-3789, pp. 68--72.

Progr. R s p t .

centrate, 0.15% reduction of IJF, remains a valid e s t i m a t e , s i n c e , in e f f e c t , i t is b a s e d upon t h e integrated amount of H F evolved by reduction, which, in turn, i s related by material b a l a n c e t o t h e amount of U F , formed.

H . E. Thoma ‘The Molten-Salt Reactor Experiinent operated during s i x s e p a r a t e periods in 1966; virtually all. of t h e operating tiine accumulated after mid-May was a t t h e maximum p o s s i b l e power of about 7.5 MY?. T h e reactor accumulated approximately 11,200 Mwhr during t h e year. During periods of reactor operation, s a m p l e s of t h e reactor s a l t s were removed routinely and were a n a l y z e d for major c o n s t i t u e n t s , corrosion products, and ( l e s s frequently) oxide contamination. Stanbaid s a m p l e s of fuel are drawri three times per week; the LiF-Hel? c o o l a n t salt i s sampled every two weeks. Current chemical a n a l y s e s s u g g e s t no perceptible composition c h a n g e s for the s a l t s s i n c e they WCFC f i r s t introduced into t h e reactor some 20 months ago. While a n a l y s e s for Z r F a n d for U F agrec quite well with the material b a l a n c e on quantities charged to t h e reactor tanks;, the v a l u e s for ’LiF and 3eF2 have never done s o ; a a a l y s e s for L,iF have shown higher and for BeF, have shown lower v a l u e s than t h e book value s i n c e startup. T a b l e 4.1 s h o w s a comparison of current a n a l y s i s with t h e original inventory v a l u e . While t h e discrepancy in LiF and B e F , concentration remains a puzzle, there is nothing in t h e a n a l y s i s (or in t h e behavior of t h e reactor) t o s u g g e s t t h a t a n y c h a n g e s h a v e occurred. T h e burnup of uranium totaling some 0.3 k g out of 230 k g i n t h e s y s t e m should b e perceptible (and d o e s not s e e m t o b e ) within t h e expciimental s c a t t e r . A chronological summary of a l l MSRE fuel s a l t a n a l y s e s i s shown i n F i g . 4.1; periods of reactor operation a r c indicated by t h e s h a d e d a r e a s of t h e figure. T h e chromium concentiation in MSRE fuel is 64 ppm a t present; t h e e n t i r e operation s e e m t o

%. E. Thoma, MSR Program Semiann. Progr. Rept. A u g . 31, 1966, ORNL-4037, PP. 131-39.

47 h a v e i n c r e a s e d t h e chromium concent ration only 26 ppm. T h i s i n c r e a s e corresponds to removal of a b o u t 130 g of chromium from t h e metal of t h e f u e l circuit. If t h i s were removed uniformly i t would r e p r e s e n t removal of chromium t o a depth of a b o u t 0 1 mil. A n a l y s e s for iron and n i c k e l in t h e s y s t e m are relatively high (120 and SO ppm respectively) a n d d o not s e e m to represent d i s s o l v e d F e z + a n d Ni2+. While there is consider-

Table 4.1. Current a n d Original Composition o f MSRE Fuel Mixture

Cons tiluent

Original Valuea

Current Analysis

(mole %)

(mole X)

‘LiF

63.40 t 0.49

64.88

Bel?

30.63 - t O . S S

29.26

5.14 50.12

5. Oil

0.821 kO.008

0.82

Z S F ,

UF4

aFroni amounts of m a t e r i a l s charged t o s y s t e m .

a b l e s c a t t e r in t h e s e a n a l y s e s , there seems t o b e no indication oE corrosion of t h e Hastelloy N by t h e s a l t . ’The f u e l mixture in the MSRE contained (see preceding s e c t i o n ) considerably l e s s UF than t h e quantity intended; 1.5%of the added uraniuni w a s t o b e a s U”. Furthermore, the f i s s i o n process should prove oxidizing to U F , in t h e melt7 (or t o chromium in t h e H a s t e l l o y N). T h e extent to which t h e f i s s i o n p r o c e s s should prove oxid i z i n g d e p e n d s on s e v e r a l variables including (1) the e x t e n t to which Kr and X e a r e s w e p t from the reactor, (2) t h e redox potential of t h e fuel-metal s y s t e m , and (3) t h e e x t e n t to which evolution of et u n s t a b l e ” s p e c i e s (such a s MnF, or lZuF,) occurs through nonequilibrium behavior. It seems very likely, however, that fission of about 0.3 kg of uranium (perhaps a i d e d by a stnall amount of inadvertent oxidation within t h e MSRE) c a n have u s e d u p tnost of t h e UF, a d d e d . An attempt to determine UF concentration i n the MSRE after a b o u t 11,000 Mwhr of operation (by I-I,-HF e q u i librium, a method similar to that employed i n t h e preceding s e c t i o n ) s h o w e d less than O,lD% of the uranium t o b e in t h e trivalent s t a t e . * Accordingly, t h e l a c k of corrosion i n the MSRE s e e m s to be somewhat surprising. It c a n b e rationalized by t h e assumptiori (I) t h a t the H a s t e l l o y N has been d e p l e t e d in Cr (and F’e) a t t h e s u r f a c e s o that Mo a n d Ni only a r e under a t t a c k , with Cr (and Fe) r e a c t i n g only a t i.he slosv rate at which it is furnished to t h e s u r f a c e by diffusion, o r (2) t h a t t h e n o b l e m e t a l f i s s i o n products (see s e c t i o n on F i s s i o n P r o d u c t s on Metal and Graphite from MSRE Core) a r e forming an adherent and protective p l a t e on t h e reactor m e t a l . Though neither of t h e a n a l y s e s nor t h e reactor behavior s u g g e s t s a p p r e c i a b l e corrosion, p l a n s a r e under way, a n d t e c h n i q u e s a r e b e i n g s t u d i e d , for reducing ahout 1%of the MSKE UF, to U F , within t h e reactor. Such a reduction (which would s u r e l y t a k e t h e &ISRE f u e l to near i t s intended UF, c o n centration) should remove all apprehension about p o s s i b l e corrosion a n d s h o u l d , we b e l i e v e , a l l e v i a t e some of t h e problems of volatile fission product fluorides (see s u b s e q u e n t s e c t i o n s ) . ..-

7W. R . Grimes, i n t e r n a l memorandum.

Fig. 4.1.

Summary of

MSRE Fuel S a l t A n a l y s e s .

‘“Hydroyeri Reduction of MSKE F u e l , ” intralaboratory correspondence from A. S. Mryer to W. R. Grimes, Jan. 3 , 1967.

48 Routine determinations of oxide (by study of salt-H ,O-HF equilibria) continue t o s h o w low v a l u e s (about 50 ppm) for 0 2 . - . T h e r e i s no i e a s o n t o b e l i e v e that contamination of t h e fuel h a s been significant in operations t o t h e present. MSRE maintenance operations h a v e n e c e s s i t a t e d flushing t h e interior of t h e drained reactor c i r c u i t on four o c c a s i o n s . T h e s a l t used for t h i s oper-ation c o n s i s t e d originally of a n ' L i p - B e F (66.03 4 . 0 mole %) mixture. A n a l y s i s of t h i s s a l t before and after e a c h u s e s h o w s t h a t 215 ppni of uranium is added to t h e flush s a l t in e a c h flushing operation, corresponding t o t h e removal of 22.7 kg of fuel-salt residue (about 0.5% of t h e charge) from t h e reactor circuit. T h e MSRE coolant s a l t h a s circulated within t h e reactor for approximately 6400 hr. Current a n a l y s i s of t h i s s a l t i n d i c a t e s no coirosion or leakage in t h e coolant s a l t circuit. On one o c c a s i o n , coolant s a l t w a s inadverteiitly partially

frozen in t h e radiator. No damage w a s s u s t a i n e d by t h e radiator either as the s a l t froze or thawed. It is believed that t h e remarkably low volume c h a n g e which t h e coolant s a l t undergoes i n freezethaw c y c l e s (less than 5%) is a consequeiicc of the large free s p a c e found i n t h e Li,BeF4 c r y s t a l structure.

' f a b l e 4.2.

F i s s i o n Products in

FlSSBOH PRODUCTS IN MSWE FUEL F . F. Blankenship

S . S. K i r s l i s

It h a s b e e n p o s s i b l e t o a n a l y z e s a m p l e s of t h e

MSRE fuel for t h e 12 f i s s i o n product i s o t o p e s

s h o w n in T a b l e 4.2 and for 239Np and the 2.44 x lo4 year 239Pu produced in t h e reactor fuel. 'J. H. Burns a n d E. K . Gordon, R e a c t o r Chem U I V . A n n . Progr. R e p t . Jan. 31, 1955, OKNL-3789, p. 30.

MSRf F u e l

Samples During Full Power O p e r a i i s n

Sample No.

I'P6

FP7-7

FP7-12

Sample dat?

5-26

6-27

7-13

A c c u ~ n u l ated Mwhi

2800

5100

7200

Operating time, d a y s a

2.5

13.3

11.9

Isotope

Half-Life

- 19

F i s s i o n Yield

Disintegrations per Minute p e r Gramb

(%)

(x 10")

( x 10")

' ~ r

9.67 hr

5.81

1.20

1.16

1.32

2Sr

2.6 hr

5.3

1.19

0.97

1.49

0.223

0.296

0.396

0.61

0.688

89%

51 days

4.79

l41Ce

33 days

6.0

143ce

3 3 hr

5.7

1.45

1.5

1.32

66 hr

6.06

3.51

0.951

0.315

lo3Ru

39.7 d a y s

3.0

0.070

0.024

0.071

105RU

0.35

0.376

4 . 4 5 hr

0.9

132,

77 hr

4.7

0.421

0.51 5

0.381

13 l I

8 . 0 5 days

3.1

0.42

0.50

0.536

1331

20.8 hr

6.9

1.31

1.35

1.45

13SI

6.7 hr

6.1

1.50

1.17

1.11

239Np

2.33 days

.. ...............-.

5.35 ..........

~~~.

10.8 .......

eContinuous operating t i m e s i n c e shutdown of more than 12 hr or s i n c e a p p r e c i a b l e c h a n g e i n power. b C a l c u l a t e d a s of sampling time.

49 T y p i c a l r e s u l t s obtained for t h e s e materials are shown in the t a b l e . T h e strontium and cerium i s o t o p e s are of s p e c i a l i n t e r e s t a s f i s s i o n monitors s i n c e they h a v e convenient half-lives and s t a b l e , nonvolatile fluorides which would b e expected t o remain almost completely i n t h e circulating fuel. T h e concentration of t h e s e monitors, however, is in only fair a g r e e ment with c a l c u l a t i o n s b a s e d on power l e v e l of the reactor from h e a t b a l a n c e ; f i s s i o n power b a s e d on "Sr is 75% of nominal power, while that b a s e d on 1 4 3 C e s h o w s 88'76 of normal reactor power. Molybdenum and ruthenium a r e t y p i c a l of a class of metals e x p e c t e d to d e p o s i t , at least in part, a s elements. T h e s e a n a l y s e s of the salt s h o w that: t h e s e materials a r e p r e s e n t in less than t h e e x p e c t e d concentration; if c a l c u l a t i o n s of total yield a r e b a s e d on "Sr, about 60% of the "Mo and about 30% of t h e '' Ru a r e accounted for in t h e s a l t . It is not p o s s i b l e to decide whether t h e s e i s o t o p e s are p r e s e n t a s c o l l o i d a l particles or are s o l u b l e chemical s p e c i e s . Isotopes of tellurium a n d iodine are of interest a s xenon precursors and a s e l e m e n t s which might shovr appreciable volatility f r o m the melt. Only about 30% of t h e 13'Te a p p e a r s in the s a l t , but the expected q u a n t i t i e s (90 to 100%) of the iodine i s o t o p e s were found in t h e s a l t s a m p l e s . A n a l y s e s of the MSRE: f u e l s a m p l e s d o not, therefore, s e e m surprising e x c e p t for t h e low concentration of 132Te. Examination of graphite and metal s a m p l e s and, e s p e c i a l l y , of s p e c i m e n s from the vapor phase as d e s c r i b e d in s u b s e q u e n t sections d o s h o w s e v e r a l s u r p r i s e s .

FISSION PRODUCTS IN MSRE E X I T GAS Equilibrium Pressures of Nobie-Metol Fluorides Under MSRE Conditions

C . F. B a e s , Jr.

A s t h e following s e c t i o n s of this document des c r i b e in brief, volatile s p e c i e s of Mo, T e , Ru, and (probably) Nb h a v e b e e n found in the helium cover g a s of the DIISRE. In addition, s i z a b l e Eractions of t h e s e e l e m e n t s appear (presumably a s m e t a l ) on t h e metallic s u r f a c e s of the reactor. Their unexpected behavior prompted a review of t h e thermodynamic d a t a on t h e volatile fluorides of t h e s e elements and a n a s s e s s m e n t of their

equilibrium p r e s s u r e s under some hypothetical MSKE conditions T h e formation free e n e r g i e s for NhF,, MoF,, a n d U F , may b e c a l c u l a t e d with relatively good a c c u r a c y b e c a u s e of recent measurements a t .4rgonne of the h e a t s of formation of t h e s e compounds by fluotine bomb calorimetry. "-The entropies and heat c a p a c i t y d a t a a l s o are a v a i l a b l e . '.$ While t h e people a t Argonne have measured RuF,,'' no entropy or h e a t c a p a c i t y d a t a seem t o b e a v a i l a b l e :

MoF6(g)

-3'72.35

i0.22

-72.13

UF&)

--510.77

-67.01

NbF5(s)

-433.5

t0.45

:L 0.15

-91.56

RuF5(.3)

-213.41

P0.3.5

From t h e s e values and t h e a v a i l a b l e h e a t capacity d a t a t h e following e x p r e s s i o n s for A Gf w e r e derived. In the case of RuF,, C l a ~ s n e r ' sear~~ lier e s t i m a t e w a s corrected t o be c o n s i s t e n t with t h e above A H f measurement:

AGf (NbF,, 9) =- -416.70 + 54.4h)(7'/1000), RGf (RuP,, 8) z -200

25 (T/1000) ,

AGf (MoF6, g)

--370.99 + 69.7(T/l000) ,

/ICf (UF,, g)

-509.94

+ 65.15(T/1000) .

' r h e following values of AGf have been reported previously for U F , and UF, in 2Z,iF-f3e[.',:'6

Acf (UF,, d )

AGf (UF,,

-336.73 + 10.54(T/1000) ,

I f ) = -444

58 1 3 ( T / 1 0 5 0 ) .

From t h e s e free-energy v a l u e s t h e following equilibrium c o n s t a n t s have been calculated for the "E. Greenberg, C. A. Natke, and W. N . Hubbard, J. P h y a . Cham. 6 9 , 2089 (196.5). "J. L. S e t t l e , H. M. Feder, and W. N. Hubbard, J , Phys. Chern. 65, 1337 (19hIj. "J. L. S e t t l e , H . M. Feder, arid W. N. Hubbard, J . Phys. Chern. 67, 1892 (1963).

K. K . K e l l y , U . S . B u r . Mines B u t f . 584, 1960.

141X. A. Porte, E. Greenberg, and W. N. Hubbard, J .

P h y s . Chem. 6 9 , 2308 (1965). 1s A . Glassnet, The ?'laerrnochemical Properties of O x i d e s , Fluorides, a n d Chlorides t o ZSOO'iK, ANIr57.50

(1958).

16C. 17. Baes, Jr., Reactor Chern. D i v . Ann. Pro&. Rcpt. Dec. 3 1 , 1965, ORNL-3913, p. 22.

50 formation of t h e volatile fluorides by ieaction with UF,(d) in t h e MSKE from the equation

Tellurium hexafluoride h a s not b e e n included in t h i s l i s t i n g , but t h i s compound s e e m s certaairi to b e less s t a b l e than a n y shown here. No data

log K = a t b ( 1 0 3 / T ):

Reaction

+SUF~(~)

Nb(s)

5UF4(d)

:<U(S)

5UF4(d)

+ i<uF,(g) + 5 U F 3 ( d )

Mo(s)

6UF,(d)

3UF,(d)

bIbF,(g)

MoF,(g)

UF,(g)

7.33

-26.82

13.76

-74.17

PWoF6 x:F3ixEF4

7.83

-60.38

2 P U F 6 xUF3'x$F,

6.15

-32.88

P N b F 5 xeF3'x:F, D

+ 6UF3(d)

+ 2UF3(d)

R U E 5 X:F3/X:F4

In F i g . 4.2, c a l c u l a t e d equilibrium partial press u r e s of t h e g a s e s a r e plotted v s the U F , / U F 4 ratio in the melt. A s t h e oxidizing power of the melt is i n c r e a s e d , N b F , is expected t o a p p e a i first, followed by MoF,, a n d then RuF,. Uranium hexafluoride h a s a lower dependence on oxidizing power b e c a u s e i t s reduction product is U F , rather than the metal. It w a s a s s u m e d i n t h e case of NbF,, MoF,, and R u F , that t h e reduction product w a s the metal. T h e U F , should not b e formed in significant amounts until t h e melt is oxidizing enough t o produce R u F , . If any s t a b l e intermediate fluorides of Nb, Mo, and K u a r c formed in t h e melt, t h e result would b e correspondingly lowered equilibrium g a s p r e s s u r e s and lowered power d e p e n d e n c e s on t h e U F ,/UF ratio.

OR N L- DWG 67-773

io 10

-5

-+o

9 10 W

01 v) 3

,0'-'5 Q LT

10-~~

4 0 '

F i y . 4.2.

10'

104

406

40'

10"

X U F ~ / ~ U F ~

40"

(0''

Equilibrium P r e s s u r e s of Volotile Fluorides

a s Function of UF4/UF3 Ratio in

MSRE Fuel.

which would permit inclusion of t h e fluorides of technetium seem tcj b e a v a i l a b l e . A n a l y s i s for F i s s i a n Products i n

S. S. K i r s l i s

MSRF E x i t G a s

F. F . Blankenship

T h e only gas-liquid interface in the MSRE (EX. c e p t for t h e c o n t a c t between liquid and t h e g a s filled. pores of t h e moderator graphite) e x i s t s in the pump bowl. There a s a l t flow of about 69 gpm (5% of t h e t o t a l s y s t e m flow) c o n t a c t s a helium cover g a s which flows through the bowl a t 4 liters/min. P r o v i s i o n s â&#x201A;Źor d i r e c t sampliiig of t h i s e x i t gas a r e planned but h a v e not yet been ins t a l l e d in t h e MSRE. Samples of t h e liquid fuel a r e obtained by lowe r i n g a sampler, on a s t a i n l e s s s t e e l c a b l e , through t h i s cover g a s a n d into the liquid. It h a s b e e n p o s s i b l e , accordingly, t o d e t e c t chemically a c t i v e f i s s i o n product s p e c i e s in t h i s cover g a s by radiochemical a n a l y s i s of t h e s t a i n l e s s s t e e l c a b l e a n d its a c c e s s o r i e s which c o n t a c t only t h e g a s p h a s e and by a n a l y s i s of s p e c i a l getter materials which ace a t t a c h e d t o t h e c a b l e . Coils of s i l v e r wire and specimeiis of Hastelloy N h a v e generally been u s e d a s getters for t h i s puipose. N o quantitative measure of t h e i s o t o p e s p r e s e n t in t h e gas p h a s e i s p o s s i b l e , s i n c e no good estimate c a n b e made of t h e g a s volume sampled. T h e quantity of material d e p o s i t e d on t h e wise specimen d o e s not correlate ' well with c o n t a c t time (in t h e range 1 t o 10 min) or with t h e getter materia 1s s t u d i e d . T h e quantity of material. deposited, however, is relatively large. T a b l e 4 . 3 indicates relative

51 Table

4.3.

Qualitative Indication in

MSRE

F i s s i o n Product

E x i t Gas

Amounta Isotope

On N i

’1110

On A g

Io6Ru

1351

132Te Io5Ru

1331

131

On H a s t e l l o y

From Liquidb

1.5

0.9

0.5

0.8

Ihe unit of quantity is t h a t amount of the i s o t o p e

B, *

i n 1 g of salt.

“On s t a i n l e s s s t e e l c a b l e .

amounts found in t y p i c a l tests. Volatile s p e c i e s of Mo, T e , and R u must c e r t a i n l y b e presumed to e x i s t i n t h e g a s p h a s e . T h e iodine i s o t o p e s s h o w perceptibly different behavior. Iodine-135, w h o s e tellurium precursor h a s a s h o r t half-life, does not appear, while 13’1 and 1331, both of which have tellurium precursors of appreciable half-life, a r e found. T h e s e findings - a l o n g with t h e f a c t t h a t t h e s e iodine i s o t o p e s a r e p r e s e n t in t h e s a l t a t n e a r their e x p e c t e d concentration s u g g e s t t h a t any iodine i n t h e vapor p h a s e c o m e s a s a r e s u l t of volatilization of t h e tellurium precursors Attempts t o d e t e c t deposition of uranium (from evolution of UF,) on the wires h a v e so far been u n s u c c e s s f u l . T h i s f a c t - a l o n g with t h e failure to find many of t h e f i s s i o n products which h a v e no volatile compounds - rules out the possibility t h a t s a l t s p r a y is r e s p o n s i b l e for t h e s e observations. It s e e m s most unlikely t h a t t h e s e d a t a c a n b e reconciled as equilibrium behavior of t h e volatile fluorides. It is p o s s i b l e t h a t t h e MSRE metal is plated with a noble-metal alloy whose t h i c k n e s s is s e v e r a l hundred angstroms, a n d it i s conceiva b l e that t h e U F , / U F 3 r a t i o is near IO4. T h e compound N b F , (not t e s t e d for in t h e g a s phase) could s h o w a n a p p r e c i a b l e pressure under t h e s e c i r c u m s t a n c e s , T h e other p o s s i b i l i t i e s s u c h a s MoF,, T e F , , a n d R u F , would require much higher

U F , / U F , r a t i o s , a n d it seems most unlikely t h a t a n y s i n g l e redox potential c a n yield t h e relative a b u n d a n c e observed for t h e s e i s o t o p e s . T h e following s p e c u l a t i o n may b e relevant: As t h e f i s s i o n products, which originate i n highly electron-deficient s t a t e s , thermalize and acquire e l e c t r o n s i n t h e m e l t , they p a s s through t h e s e :8 u n s t a b l e ” but volatile v a l e n c e conditions. If t h e plated reactor metal is sufficiently unreactive and if (as i t s e e m s t o b e a t present) the MSRE fuel is quite deficient in UF,, it is conceivable that some fraction of t h e s e materials might a p pear i n t h e g a s p h a s e a n d e n t e r t h e MSRE graphite or l e a v e t h e s y s t e m in t h e e x i t gas. If t h i s is true, then a c o n s i d e r a b l e i n c r e a s e in UF3 concentration i n MSRE fuel might well markedly dec r e a s e t h e fraction in t h e vapoi p h a s e . It i s c l e a r that additional s t u d y will b e required before t h e s i t u a t i o n becomes c l e a r . FISSION PRODUCTS ON METAL AND GRAPHITE FROM MSRE CORE S . S. K i r s l i s

F F. Blankenship

An a s s e m b l y of MSRE graphite and ttastelloy N s p e c i m e n s w a s e x p o s e d on t h e c e n t r a l s t r i n g e r within t h e MSRE c o r e during its initial operation. This a s s e m b l y w a s removed during t h e July 17 shutdown a f t e r 7800 Mwhr of reactor operation, and many s p e c i m e n s h a v e b e e n carefully examined. N o e v i d e n c e of a l t e r a t i o n of t h e graphlte w a s found under examination by visual, x-radiographic, a n d metallographic examination Autoradiographs showed that penetration of radioactive materials into the graphite w a s not uniform and d i s c l o s e d a thin (perhaps I- t o 2-mil) l a y e r of highly radioa c t i v e materials on or near t h e e x p o s e d graphite surfaces. Examination of t h e metal s p e c i m e n s h o w e d no e v i d e n c e of corrosion or other danger Rectangular b a r s of graphite from t h e top (outlet), middle, a n d bottom (inlet) region of t h i s c e n t r a l stringer were milled i n t h e hot cell to retnove s i x s u c c e s s i v e l a y e r s from e a c h surface. T h e removed l a y e r s were t h e n analyzed for s e v eral fission product i s o t o p e s . l 7 T h e r e s u l t s of a n a l y s i s of t h e outer layer from t h e graphite s p e c i m e n a r e shown in T a b l e 4 4 . ”The i n i t i a l sampling w a s carried out by J. G. Morgan, M. F. Osbome, and H. E. Robertson. T h e i r h e l p and that of t h e Hot-Cell Operation Group is gratefully a c knowledged.

52 Table 4.4.

_.. .....

F i s s i o n Product Deposition on Surfacea o f MSRE t m p h i t e

....__..

~. .......

Graphite 1,ocation Middle

TOP

___I___....._...I

Isotope

Pelcent

dpm /cnn

dpm,'cin

of T o t a l b

Bottoili

Percent of T o t a l b

- -. dpin /,cm

Percent of T o t a l b

___

9Mo

13'Te 1

5Nb

io9)

10')

lo9)

39.7

13.4

51.4

17.2

34.2

11.5

32.2

13.8

32.6

13.6

27.8

12.0

8.3

11.4

7.5

10.3

4.8

6.3

4.6

22.8

59.2

21.0

62.4

13II

0.21

9 5Zr

144~e

0.16

0.42

0.33

0.25

0.38

0.33

0.31

0.2)

0.17

0.15

0.03 6

0.052

0.083

0.27

0.044

0.14

' ~ r

3.52

3.24

3.58

3.30

2.90

2.71

14'Ba

3.56

1.38

4.76

1.85

2.33

1.14

14lCe

0.32

0.19

1.03

0.63

0.5M

0.36

6 . 6 ~

0.07

0.25

2 . 0 ~

137cs -

2.3

0.212

~~~~~

aAverage of v a l t e s i n 7- to 10-mll c u t s from e a c h of three e x p o s e d graphite f a c e s . b P e r c e n t of t o t a l in reactor d e p o s i t e d o n grapiiiie i f e a c h cin' of the 2 centration a s t l e specimen.

It i s c l e a r that, with t h e sssuiilption of uniform deposition on or i n all t h e moderator graphite, appreciable fractions of Mo, Te, and R u and a large fraction of t h e N b a r e a s s o c i a t e d with t h e graphite. No a n a l y s e s for 'rc h a v e b e e n obtained. T h e concentrations of t h e s e noble metals would b e sufficient t o exert significant poisoning in a breeder reactor. The behavior of I4'Ba, SgSr, l 4 'C e , 1 4 4 ~ eand , 1 3 7 C s , a l l of which h a v e xenon or krypton precurs o r s , c a n b e accounted for in terms of l a w s of diffusion and half-lives of t h e precursors. F i g u r e 4.3 shows t h e c h a n g e i n Concentration of t h e f i s s i o n prodiict isotope with depth in t h e graphite. T h o s e i s o t o p e s (such a s 14'Ba) which penetrated t h e graphite a s noble g a s e s s h o w straight l i n e s on t h e logarithmic plot; they s e e m to h a v e remained a t t h e point where t h e noblc g a s decayed. As ex'Ra with a 1 6 - s e c 'Xe pected, t h e gradient for precursor i s much s t e e p e r than that for "Sr, which h a s a 3.2-min "Kr precursor. All t h e others shown

10, cui2 of riioderator h a d the s a m e c o n -

show a much s t e e p e r Concentration dependence. Generally t h e concentration drops a factor of 100 from t h e top 6 t o 10 mils t o t h e second layer. It is p o s s i b l e t h a t carbide formation i s respons i b l e for t h e deposition of Nb and possibly for that af Mo, but i t seems q u i t e unlikely for Ru and 're; t h e iodine probably got in a s i t s tellurium y e - c i m o r . Since t h e s e materials have been s h o w n to appear in t h e e x i t g a s a s volatile s p e c i e s , i t seern.~ likely t h a t they entered the graphite by T h e possibility that t h e t h e same mechanism. strongly oxidizing fluorides s u c h a s MoF, w e r e present raised t h e q u e s t i o n a s t o whether U F , was accumulating in t h e graphite. An average of 0 . 2 3 pg/cm' was found in t h e s u r f a c e of t h e graphite; much l e a s w a s p r e s e n t i n interior s a m p l e s . T h i s amount of uranium, equivalent t o less than 1 g in t h e core, w a s considered to b e negligible. Table 4.5 s h o w s the e x t e n t to which various f i s s i o n product i s o t o p e s are deposited on t h e

53 Hastelloy N s p e c i m e n s in t h e core A large fraction of t h e molybdenum and tellurium and a s u b s t a n t i a l fraction of t h e ruthenium s e e m to b e s o d e p o s i t e d . It s e e m s p o s s i b l e that t h e I 3 l I w a s carried into t h e s p e c i m e n a s its tellurium precursor. T h e v a l u e s for 95Zr s e e m surprisingly high, s i n c e t h o s e for t h e " ' C e and ' 4 4 C e with noble-gas precursors probably reflect t h e amount expected by d i r e c t recoil a t t h e moment of f i s s i o n . If t h e Nb a n d Tc a r e a s s u m e d t o behave l i k e the Mo, Te, and Ru, it may b e noted t h a t the MSRE could h a v e b e e n uniformly plated during its opera t i o n with s e v e r a l hundred angstrorils of relatively noble metals.

XENON DIFFUSION AND FORMATION O F CESIUM CARBIDE IN AN MSBR K. â&#x201A;Ź3. E v a n s 111

C . F. Baes, J r .

L 0

Fig. in

I.........!..-.............1..1........... 1.......J 30

DISTANCE FROM SURFACE OF GRCPI-IITE (mils1

4.3.

MSRE

Compared to t h e MSRE, a full-scale molten-salt breeder reactor is e x p e c t e d to h a v e approximately 50-fold greater neutron flux and 25-fold greater flow velocity through t h e c o r e . C a l c u l a t i o n s have been made" in order t o c o n s i d e r t h e e x t e n t of 18C. F. B a e s , Jr., and R. R. E v a n s TIT, MSR Program Semianri. Progr. R e p t . Arrg, 31, 1 3 6 6 , ORNL-4037, pp.

Concentration P r o f i l e of F i s s i o n Products

158--6.5.

Core Graphite A f t e r 8000 Mwhr.

Table .___I.

4.5. D e p o s i t i o n of F i s s i o n Products on H a s t e l l o y N i n M S R E Core I _

Wastelloy L o c a t i o n _ i i

I___

Isotope dpm/cm

99M0 1 3 2 ,le .

Middle

TOP 2

(x 1 0 3 212

508

Percent

of Total"

Percent ctprn/cm2 (X

42.5

131

lo9)

341

42 7

8.2

3.5

4.0

1.8

1.0

141ce

0.05

144ce

0.01

Percent

of Totala

lo9)

2 04

25.5

' ~ r

dpin /cm

55.6

29.3

1311

of Total"

276

35.5

3Ru

Bottom

41.2

110

23.2

19.1

1.8

5.2

2.4

1.8

1.0

2.6

1.3

0.02

0.22

0.07

0.15

0.06

0.02

0.09

0.18

0.35

0.07

" P e r c e n t of t o t a l p r e s e n t in r e a c t o r which w o u l d d e p o s i t o n the 1.2 x surfaces w a s the s a m e as on the specimen.

lo6

c m z of H a s t e l l o y N if d e p o s i t i o n o n 011

54 xenon diffusion and t h e behavior of daughter cesium born i n t h e moderator graphite of a n MSBW operating under s u c h conditions. A one-dimens i o n a l s t e a d y - s t a t e diffusion model w a s a s s u m e d in which t h e moderator w a s reprtseiited as a s l a b of graphite infinite i n two dimensions, with a t h i c k n e s s of 1 em, immersed in t h e fuel s a l t . It was further assumed that a l l c e s i u m born in t h e graphite w a s in t h e e l e m e n t a l ( g a s e o u s ) form. (1) t h e diffusion T h e parameters varied were: coefficients 0 of xenon and c e s i u m in t h e graphite (assumed t o b e equal), (2) t h e f i l m coefficient H a s s o c i a t e d with t h e salt-graphite interface, and (3) t h e rate a t which g a s is stripped from t h e fuel, A,, Over the range c h o s e n for t h e s e parameters, t h e rate s t e p in t h e diffusion of xenon into t h e graphite w a s found t o b e a t t h e salt-graphite interface and w a s depeiident on t h e value of H ( F i g . 4.4). A s a c o n s e q u e n c e , a d e c r e a s e i n D did not materially d e c r e a s e the inward diffusion of xenon; however, i t did d e c r e a s e the rate a t which g a s e o u s c e s i u m diffused t o the graphite s u r f a c e , where i t was a s s u m e d t o react instantaneously with the fuel s a l t :

ORNL-

IO”

DWG 66-41469

G1 0

V LL 4

g 2

a 0

10.’

T h u s , somewhat paradoxically, t h e maximum part i a l pressuro of Cs’ (at thP c e n t e r of the s l a b ) was found t o i n c t e a s e a s D w a s d e c r e a s e d Under all Combinations of If, D, and h S T v a l u e s c h o s e n . the c a l c u l a t e d cesium partial p r e s s u r e a t s t e a d y s t a t e was high enough to c a u s e t h e formation of lamellar cesium carloides ( F i g 4 4):

However, t h e c a l c u l a t e d accumulation rate of Cs w a s s o low t h a t the amounts of CsC, which could b e formed did not a p p e a r t o b e s i g n i f i c a n t . F i n a l l y , t h e s e ca!culations indicate that in the a b s e n c e of iodine removal (i.e., 6.7-hr 13’1), X e poisoning in a full-scale MSBW will be controlled primarily by t h e filin coefficient N ( F i g . 4.4) and will b e difficult t o reduce to a n a c c e p t a b l e value by g a s stripping a l o n e . It could be reduced more effectively either by iodine removal or by S O I i i e means which effectively r e d u c e s t h e film coefficient.

E S T I M A T E D PRESSURE AT WHICti CsC

-......_..........- __ 0.I

.. .....

0.001

C a l c u l a t e d Steady-State ? r e s s i ~ r e s of C e -

C a n t e r of a

P o i s o n i n g cis

(AsI).

0.01

Fig. 4.4 sium

IS FORMED

- L __ p z I.<’ I I

1 c m Graphite Slab and 1 3 5 X e

uriction of

the

Gas

Stripping

Rate

the D i f f u s i o n C o e f f i c i e n t ( D ) , and ?he Film Co-

efficient

(TI).

T h e 13’Xe

poisoning i s represented n s

the fraction o f the inaximum p o s s i b l e value (a poison

The flux i s 7 x 1014 neutrons c m s 2 fraction of 0 05). -1 sec and ?he graphite porosity i s 0 95.

Part II

Aqueous Reactors

5. Corrosion and Chemical

Reactor Enwironme

NASA TUNGSTEN REACTOR RADIATION CHEM1STRV STUD1 ES H. C. Savage G. 1-1. Jettks E. G. Rohlmann P o i s o n control solutions of CdSO, are being considered by NASA L e w i s R e s e a r c h Center fop. p o s s i b l e u s e in t h e NASA 'Tungsten Water-Moderated R e a c t o r (TWMK). Information regarding t h e effects of irradiation 0.2 the stability of t h e s e s o l u t i o n s toward loss of Cd w a s needed in e v a l u a t i o n s of t h i s poison control system. We h a v e conducted experimental i n v e s t i g a t i o n s 3 of the stability of CdSO, solution under electron irradiation u s i n g the following experimental conditions: Solution composition, 0.02 and 0.067 M CdSO, i n water Temperature, 60 t o 120°C

Radiation j n t e n s i t y , 7 3 and 145 w p e r c m

of so!ution

Container, Zircaloy-2 with titanium f i l t e r

Agitation, s t a t i c solution Su~face-area-to-volllmc ratio, 61 c r n ' / ~ n ! ~

. .

The c o n t a i n e r w a s i n the form of a loop of 26tnil-ID tubing with t h e titanium filter (3 p ) at o n e end. T h e s o l u t i o n w a s e x p o s e 6 within the tubing for a period of time and then expelled though t h e falter; t h e e x p e l l e d solution w a s anslyzed for Cd. 'G. H. J e n k s , H. C . Savage, mind E. G. Bohlmann, R e a c t o r Cher;r, C Z Y . Ann. Progr, H e p l . Ilec. 31, 1965, OENLA-3913, p. 58. 2

G. SI. J e n k s , E. G. Bohlmanri, and J. C. G r i e s s , Arz Evalnatiorr of the Chemical Problems A s s o c i a t e d with the Aqueous S y s t e m s in the Timg.stt?ri Watar Moderated R e a c t o r , Addenda, 1 and 2 , ORNL-TILT- 978, NASA-CR-54214 (March 1965).

Small amounts of Cd were lost from t h e solution during 30-min irradiations at e a c h t e s t e d combination o f (.he a b o v e set of condiiions. With 0.02 rW CdSO, solutions, t h e loss at 120°C and 145 w / c m 3 w a s 5.0 f 3,476 error at 80% confidence. T h e loss at 77OC w a s 3.3 f 2.8% and that at 77°C and 7 3 w / c m 3 was 2.0 -t 2.7%. One experiment with 0.02 M CdSO, and FI,SQ,, pH 2, indicated negligible loss. With 0.06 M CdSO,, t h e loss at 60°C and 145 w/cm3 w a s 1.5 .i: 1.0%. At 12O"C, the b e s t iridication w a s about 4% l o s s . The re:;ults of experiments with 5- and 50-min irradiations of 0.067 111 CdSO, at 60°C and 145 w / c m 3 indicated that t h e amount of Cd lost w a s g r e a t e s t at t h e longer time. Experimental information o n recovery of t h e seTparated Cd after irradiation indicated that t h e r a t e s of redissolution are slow. C o n s i d e r a t i o n s of t h e s e resul!s and of thwory s u g g e s t that Gd metal is formed under irradiation and that t h i s :separates as relatively i n s o l u b l e material by agglornexation or by p l a t i n g on s o l i d surfaces. Addj t i o n d experimental i n v e s t i g a t i o n of effects of agitation and of surface-area-tovolume ratios would b e required to predict t h e eff e c t s of radiation on stability i n a reactor i n which t h e s e parameters differ from those in our experiments. Design and development work w a s done on a system which could b e used to study effects of electron irradiation on stability in a dynamic system. he planned dyriainic experiment w a s to b e conducted with a s m a l l , high-speed (35,000 qmi) centrifugal pump with which solution w a s to be c i r c u l a t e d through a 2 6 - m i l -lD t u b e forming ~~~~

,6. H. Jenks, W. C. Savage, and E. G. Holiltiiann, N A S A Turrgstori Reactor Radialion Chemistry S f d i e s , Phase I , E x p e r i m e n t Design, ORNL-1M- 11.03, NASACK-51.887 (March 1966).

3G. 1%. Jenks, H. C. Savage, arid E" G. Rohlmann, N A S A T u n g s t en K e a (3 tor R a d i atiorr Gh enii s t r y St ildi e s , Final Report, ORNL-TM-1630,NASA-CH-72070 (October

1966).

58 a loop in fiorrt of t h e cover plat:,

of t h e pump. T h e entire solution inventory w a s to b e irradiated continuously. T h e purpose of t h e tube was to provide a channel in which film conditions could b e made comparable to t h o s e in t h e TWMR. 'The r e s u l t s of component t e s t s showed that t h e proposed design wa.s f e a s i b l e . Detailed design drawings of t h e equipment were reported, 5 Work on t h i s prograrn w a s discontinued prior to construction of t h e dynamic system b e c a u s e of a lack of funds.

S . J. D a v i s

'r. H.

H. J. Hart

Mauney

Heavy -p articl e bombardment a c c e l e r a t e s t h e corrosion of Zircaloy-2 in oxygenated aqueous media6p but probably d o e s not a c c e l e r a t e corrosion i n hydrogenated a q u e o u s media.' Ionizing radiations ( b e t a or gamma) do not a c c e l e r a t e Zircaloy-2 corrosion i n aqiueous T h e a b o v e observations, along with intrrpretation" of recent corrosion d a t a ' * and recent calc u l a t i o n s of t h e concentration of radiolytically formed s p e c i e s in aqueous solutions, l e d to t h e following hypothesis. Hydrogen peroxide is res p o n s i b l e for t h e acceleration of corrosion by heavy-particle irradiation. Beta-gamma irradiation produces peroxide concentrations too low for not ab1e corrosion acceleration. Heavy-p article bombardment also r e s u l t s in low peroxide concen-

'G. H. J e n k s , 13. C. Savage, and E. G. Rohlmann, internal memorandum, 1966.

trations i n a q u e o u s s o l u t i o n s with e x c e s s hydrogen, but re1ativel.y high coneenirations a r e formed with e x c e s s oxygen. A peroxide concentration of M w a s e s i i i n a t d " for a fast-neutron ( e n e r E above 1 MeV) fiux of 1013 neutrons c n - ' sec---1 .

An e x p ~ r i m e n t ' ~w a s mil i n which Zircaloy-2 s p e c i m e n s were e x p o s e d to lo-' M H z O , a t 28OOC for 297 hr. T h e peroxide concentration w a s main~ ~peroxide. 2 tained by a continuous feed of 1 0 ~ M Control s p e c i m e n s were exposed to oxygenated water in t h e same experimental setup. T h e s p e c i m e n s and controls a l l gained weight at a v e r a g e r a t e s of 7 to 8 (rg ern--' day-'. There w a s no significant effect due to peroxide. T h i s r a t e of i n c r e a s e in weight is about a factor of 10 less than that known to occur a s a r e s ~ l tof a fast-rleutron flux of IO neutrons cinseco n a s y s t e m of Zircaloy-2 in oxygenated water a t 280OC. It follows that t h e acceleration of corrosion of Zircaloy-2 in oxygenated aqueous media by heavyparticle bombardment is not due, s o l e l y at l e a s t , to t h e hydrogen peroxide generated irr t h e aqueous environment

ANODIC: FILM GROWTH 0 ZIRCONIUM AT E L E V A T E D TEMPERATURES 1-1. S. Gadiyar" A. I,. Uacarella A. L. Sutton

In our previous report16 w e postulated that t h e current (i) for anodic film growth on zirconium in oxygenated, dilute II,SQ4 a t temperatuies from 174 to 284OC: is an exponential function of t h e field strength, V , / X , a c r o s s t h e o x i d e film. T h i s relation is given b y

6G. H. J e n k s , pp. 232-45 i n Fluid Fuel R e a c t o r s , ed. by J. A. L a n e , 11. 6. MacPherson, and Frank Maslan, Addison-Wesley, Reading, Mass., 1958. 'G. W. J e n k s , pp. 41-57 i n AS?;%Âś S p e c . T e c h . Pub. N o . 368, ASTM, P h i l a d e l p h i a , 1963.

'G. H. .Jenks, H. J. D a v i s et al., H R P Quart. Progr. R e p t . J u l y 31, 1958, ORNL-2561, pp. 231.--36; J u l y 31, 1957, ORNL-2379, pp. 115-21. 'B. 0. H e s t o n and M, D. Silverman, OKNL-CF-56-2-2 (February 1956). 'OD. J. Harrop, N. J. M. Wilkins, and J. N. Wanklyn, AEKE-K-4779 (1964). "13. c o x , p r i v a t e communication.

"W. 13

A. Burns, UNWL-88, p. 2 3 (August 1965).

G EI. J e n k s , E f f e c t s of R e a c t o r Operation on H F i R

Coolan 1, ORNL-3818 (October 1965).

where i is t h e anodic current (amp), io is t h e current a t zero field strength (amp), (sa)* i s t h e produ c t of t h e c h a r g e of t h e mobile ion ( e ) and t h e

14R. J. D a v i s , T. H. Mauney, and J. K. Electrochem. SOC.113, 1222 (1966).

Hart, J .

"Alien G u e s t from t h e Indian Atomic Energy E s t a b lishment, Bombay, India. 1 6 ~ e L. Racarella and A. L. Sutton, lieactor Chem. Drv. Ann. P r o g r . R e p t . Jan. 31, 1965, ORNL-3789, pp. 135-38.

59 activation d i s t a n c e (cm), V , is t h e potential difference a c r o s s t h e o x i d e l a y e r (v), X is t h e f i l m t h i c k n e s s (cm), and k’l’ is t h e thermal energy equivalent (ev). Calculaiion o f the magnitutk o f t h e “activation dipole,” (qa)*, showed that t h e activation d i s t a n c e ( a ) i n c r e a s e d from 13.5 A a t 25°C to 37 A at 284OC. T h e s e l a r g e values were explained1 ‘-19 according to a model which cons i d e r s d i e l e c t r i c polarization of the o x i d e and p r e d i c t s that t h e effective field c a u s i n g ion migrntion is greater than the average applied field. Using t h e Mossotti-Lorentz field, t.he apparent activation dipole is

where E i s t h e dielectric: c o n s t a n t of t h e o x i d e (dimensionless) and ( q a ) is t h e “true” activation r Bpo 1e. We showed further that at l a r g e film t h i c k n e s s (small field sf.rength), current flow of riiobile c h a r g e c a r r i e r s a g a i n s t the field becomes significant and that the net f i l m growth current m a y be exp r e s s e d by a hyperbolic s i n e fuactiotl of thc field strength:

that t h e Tafel s l o p e is given by Eq. (3), where B t- (qa)*ikT:

’The experimental r e s u l t s from Eqs. (2) and ( 3 ) were found to b e greatly improved i f a c o n s t a n t 150 A were added to all f i l m t h i c k n e s s e s (X). Furthermore, with t h e u s e of t h i s correction, deviations o b s e r v e d at very small film thicknesses16’17were &so accounted for. U s e of an additional c o n s t a n t i n Eqs. (2) and ( 3 ) can h e justified by a more general derivation of t h e relation for anodic film growth, Equation (2) w ~ derived s o n the assumption that t h e fraction of the total potential difference, from m e t d to solution, which a f f e c t s i o n transport is that portion which exists a c r o s s t h e oxide film. The potential differences at the met.d-oxide and oxidesolution i n t e r f a c e s were considered to b e constant arid independent of i. 1x1 a inore general treatment, w e t a k e into a c m u n t t h e possibility that c h a r g e transport acroijs e a c h interface m a y also a f f e c t the poterltial distribution. We h a v e therefore extended t h e formalism of t h e so-called dual-barrier model”to a triple-barrier problem and derived t h e rate e x p r e s s i o n of Eq. (4):

’

More recent nieasiirements in dilute K,SQ, solution, particularry nieasurements af t h e Tafel s l o p e at c o n s t a n t film, t h i c k n e s s , (rl log i / ( ? V 2 ) x , showed the n e e d for two additional modifications to t h e moilel, In I<,SO, solution, i t w a s found that t h e deviations from e x p e c t e d behavior a t large Film t h i c k n e s s were greater than could be accounted for by the current flow of mobile charge c a r r i e r s a g a i n s t t h e field. AI so, llleaSuiemerltS of polarization m r v e s and Tafel s l o p e s at constant f i l m t h i c k n e s s were not i n satisfactory agreement Differentiation of Eq, (2) s h o w s with Eq. (2).

In Eq. (41,V =- V I + V , i V , is the total potential difference L:etweeri metah arid solution p h a s e s ; i t e q u a l s t h e sum of V, (poiential difference between metal and o x i d e p h a s e s ) , V i (potential difference iicross o x i d e Iayer), and V , (potential difference between oxide and solution phases). ?%e parurne t e r s k , , it2, arid k, a r e i h e corresponding rate c o n s t s n t s of t h e charge transfer p r o c e s s e s at ea.& barrier. T h e fractional exponents are obtained f r o m t h e assumptions that t h e electrochemical transfer co el fici en t a t t lie metal-oxi de barrier ’‘A. I-,. Bacarella and A L. Sutton, J . Electroctiem. 11 2, 546 (1965)“ 21K. E. M e y e r , j . Elecrrucheni. Soc, 1110, 167 (1963).

SUC.

1 7 ~ .L. Dacarella and A. I,. Sutton, J . ~ l e c r s u c ~ i e r n . Techrrol. 4, 117 (196Gj. 18

M. J. Dignam, J .

Electmchorn. Soc. 112, 722-29

(1965)” 19 K. J. Illaurer, j ” chonl. P17y.s. 9, 579 (1941).

22F. A. P o s e y , G. PI. Cartledge, and j . EZectrodieni S O C . 106, 5 8 2 (1959). 23

J. &lacDonald and

Soc.’ 8 2 6 9 . 419 11962).

R. P . Jafftte,

B. E. Conway,

Proc, R o y .

60 is given by ya, (2) (0.5) = 1, while that for t h e o x i d e harrier i s qa, = 2a/X and that for t h e oxidesolution barrier i s qa3 = 0.5. Differentiation of Eq. (4) s h o w s that t h e 'Tafel s l o p e is given by Eq. (5): 7

where B = 2 a / k T . Equations ( 4 ) and (5) w e r e found to b e very satisfactory in accounting for t h e d a t a i n both H,SO, and K,SO, media, where to a first approximation t h e activation d i s t a n c e a = 2 ( t + 2)/3. In a great majority of t h e experiments performed, t h e potential o f t h e zirconium electrode w a s maintained c o n s t a n t a t 10.0 v v s a P t reference electrode. T h i s potential is about +1.0 v more noble than t h e open-circuit corrosion potential, E , (cf, Fig. 51). The Tnfel s l o p e s were determined over a range of about 0.3 to 0.4 v from t h i s potential. Over t h i s potential range t h e Tafel slopes,

(6' log i/dV),,

were apparently linear, and Eqs. Res u l t s of a much inore e x t e n s i v e anodic polarization measurement (covering a 9-v range) are pres e n t e d in Fig. 5.1. We find that t h e 'Tafel s l o p e is not c o n s t a n t but d e c r e a s e s somewhat with increasing V . T h e foregoing observation may b e rationalized on t h e b a s i s of D1gr1arn's'8-24 theory, which po still a t e s a f i el d-dependent transfer coefficient in t h e o x i d e phase. Incorporation of t h i s theory in our triple-barrier model l e a d s to Eq. (6), exp r e s s e d in logarithmic form:

(4) and (5) described t h e data satisfactorily.

In i

2al'l

X + 5.311

(2aV,/cdX)l

...................-

- (2aV2/cdX)]

(6)

7.0

8.0

+ I n k, __ .........

.........____

24M. J. Dignazn, Can. J. Chem. 42, 1155 (1964).

5 ~ 1 0 - ~ 2

5 2 10-~

5 2

m7 5 2

to-@ -1.a

-1.2

-1.0 -0.8

-0.6 -0.n -0.2

0.2

0.4

0.6

0.8

1.0

2.0

3.0

4.0

5.0

6.0

POTENTIAL [volts v s P t ( r e f ) ]

Fig. 5.1.

Polurizutian

T h i c k n e s s 700 A.

Curve for Z i r c o n i u m in Oxygenated 0.05 m

Solution u t

203OC

and Canstan?

Film

In Eq. (6) t h e potential V 2 (the potential difference a c r o s s t h e o x i d e layer) a p p e a r s implicitly in t h e r a t e e x p r e s s i o n , and q5 is t h e activation energy of t h e anodic reaction. T h e parameter c is not an independent constant in Dignam's theory;24 i t is il function of t h e quantity 2 a V 2 / 4 X . V a l u e s of c may b e computed on t h e assumption t h a t t h e interaction potential between t h e mobile ion and i t s immediate surroundings can b e represented by a Morse function for s m a l l displacements. The validity of Eq. (6), which w a s applied to d a t a shown in Fig. 5.1, is indicated by t h e r e s u l t s shown i n F i g . 5.2. Here t h e activation e n e r a $ -:: 1.35 e v w a s determined by u s in previous experiments, and V , =- 2.3 v w a s assumed to b e a good f i r s t a p p r o x i ~ n a t i o n . ~We find that a v a l u e of a 26.5 A may be estimated f r o m p l o t s of l o g i v s 1/(X i- 6.3) for l a r g e X . T h i s v a l u e of t h e activation d i s t a n c e s e e m s to b e q u i t e reasonable. We conclude t h a t t h i s model is c a p a b l e of describing t h e anodic film growth p r o c e s s i n zirconium over a wide range o f e l e c t r o d e p o t e n t i a l s and film thicknesses with satisfactory accuracy by u s e of reasonab1 e v a l u e s of physical parameters. ~:-

AC IMPEDANCE OF OXIDE FiLMS I N AQUEOUS SOLUTIONS AT ELEVATED TEMPERATURES R. j. Davis H. S. Gadiyar"

G . H. J e n k s A. I.. B a c a r e l l a

W e are i n t h e p r o c e s s of developing equipment, methods, and techniques which w i l l permit u s to measure t h e ac impedance of corrosion films o n zirconium and i t s a l l o y s it1 aqueous solutions at e l e v a t e d temperatures. The immediate object i v e of t h e s e measurements is to determine whether pores or f i s s u r e s which admit aqueous s o l u t i o n s occur i n t h e s e f i l m s during corrosion at temperat u r e s up to about 300째C. If t h e s e determinations c a n b e m a d e satisfactorily, w e will then attempt to conduct similar experiments in-pile. It is expected t h a t valuable information on t h e electrical properties of t h e high-temperature corrosion f i l m s will b e obtained a l s o during t h e c o u r s e of t h e measurements. In t h e method employed, the specimen is irnmersed in an electrolyte which, together with t h e metal container, comprises o n e electrode for imp e d a n c e measurements of t h e oxide film on the specimen. T h e met.al of th.e specimen is the second electrode. Measurements are made of the capacit a n c e and r e s i s t a n c e of the oxide over a range of frequencies and a t two o r more electrolyte concentrations. T h e r e s u l t s a r e examined for behavior e x p e c t e d to result from penetration of the electrol y t e into f i s s u r e s within t h e oxide. T h e p r i n c i p l e s upon which t h i s method of port? detection is b a s e d w e r e d i s c u s s e d by Young. Wanklyn and co-workersZ6.2 7 h a v e u s e d a c imp e d a n c e measurements at room temperature i n s t u d i e s of t h e protective arid electrical properties of o x i d e films formed on zirmnium alloys during high-t ernp e r a!x e cor ro sion Our measurements to d a t e h a v e covered a temperature range of 2.5 to 20OU'c a d h a v e been made on a s i n g l e zirconium specimen bearing a 1500-A film formed anodically (0.0 v v s Pt at 5S"C) in oxygenated 0.05 rn H,SO a t 220 to 230째C i n t h e Ti electrochemical cdle4" T h e electrolyte for

"I,. Young, Anodic Oxide F i l m s , pp. 150-70, demic, N e w Yolk, 1961. 26J.

(1966).

N. Wanklyn, E l e c t t o t h e m . T c c I u i o l . 4 3 - 4 ) ,

275. N.

F i g . 5.2.

P o l a r i z a t i o n Data of Fig. 5.1 Plotted A c .

cording to Eq.

SOC.

28A. T.,.

Wanklyn and D. R. S t l v e s t e r , J . E l e r t r u c i i m i .

105, 647 (1958)

(1961).

(6).

Aca-

Bacarella, J . &lecrror;tiern. S O C . 108, 3.31

62 o n e seiies (25, 50, 100, and 198OC) of impedance measurements w a s oxygenated 0.05 m H,SO,. For a subsequent s e r i e s (25, 50, 100, and lSOOCj, t h e e l e c t r o l y t e w a s oxygenated 0.05 m K,SO,. T h e impedance cell was made up of a small Zircaloy-2 autoclave containing an insulated gold in. i n i n s i d e diameter x in. long, which cup held t h e electrolyte. T h e 0.2-cm rod-shaped s p e c i men was positioned along the a x i s of t h e clip and protruded into t h e gas-steam phase. T h e bottom end of t h e specimen w a s covered and s e a l e d with 'Teflon, so that only t h e axial s u r f a c e s were in contact with t h e electrolyte. Electrical l e a d s from the specimen, gold cup, and from a small platinum reference electrode which dipped into t h e electrolyte were p a s s e d through the gas-steam p h a s e and out of t h e autoclave through a Teflon seal. In operation, g a s (02-He) pressurization w a s u s e d ta prevent gas-bubble formation within T h i s was act h e electrolyte of t h e gold cup. complished by adjusting t h e p r e s s u r e upward a s t h e temperature w a s raised, s o that t h e p r e s s u r e of d i s s o l v e d g a s never exceeded t h e overpressure. A General Radio 1515-A bridge with three terminal connections was e n p l o y e d i n impedance measurements. T h e r e s u l t s of s e r i e s c a p a c i t a n c e measurements on t h e s i n g l e specimen over a range of tem,perat u r e s and f r e q u e n c i e s are illustrated i n Fig. 5.3. The s l o p e s o f t h e s e straight l i n e s are l i s t e d in T h e r e s u l t s of the corresponding T a b l e 5.1. series r e s i s t a n c e measurements for t h e filitl fell near straight l i n e s in p l o t s of R s vs l / f . T h e s e l i n e s p a s s e d through t h e origin after correction for t h e electrolyte r e s i s t a n c e . 'The s l o p e s of t h e l i n e s in t h e s e d a t a p l o t s are also l i s t e d in T a b l e 5.1. T e n t a t i v e e v a l u a t i o n s of t h e s e d a t a with regard to overall c o n s i s t e n c y and with regard to e v i d e n c e of penetration of e l e c t r o l y t e were b a s e d on t h e theoretical e x p r e s s i o n s for R r and C,- d i s c u s s e d by Young,25

'/z

'/4

Young deiived t h e s e equations by employing a model in which t h e resistivity, p, v a r i e s exponentially with d i s t a n c e through t h e oxide, T h e res i s t i v i t i e s at t h e o p p o s i t e s u r f a c e s of t h e o x i d e of t h i c k n e s s d are p(0) and p ( 4 respectively; E is t h e dielectric constant and A is t h e area. T h e s e equations reproduced Young's experiniental re.. sults for anodic films on Nb with respect to straightl i n e formation i n p l o t s of l/Cs v s l o g / and of X , v s l / f and with r e s p e c t t o t h e relationship between t h e s l o p e s of t h e l / C s and R , plots.*' T h e frequency d e p e n d e n c i e s of Cs and Rs observed by o t h e r s for a n o d i c and corrosion films o n %r h a v e been a s c r i b e d to conductivity gradients through t h e oxide. Values of p(6/ and p(0) determined from our c a p a c i t a n c e d a t a employing Eq. ( 7 ) are l i s t e d in T a b l e 5.1. P l o t s of the p(d) v a l u e s are shown in Fig. 5.4. T h e r a t i o s of t h e slopes of t h e l/Cs and

O R N L ~ D W G67-71?

II 2

IO 8

104

100

5 84

56 L

FREOIJFNCY I k c )

fig.

5.3.

Temperature.

Variation of

l/Cs

with

F r e q u e n c y and

Table

5.1.

KzSo,

50 100

lo5

, cycles) --

(ohms, cm 2

(cm2, f-') H2S04

M,h A

MI a A

Tempe ratu rc

("0

II,SO,

K,SO,

io4

lo5 4.9

5.02

5.94

4.1

5.7

4.98

6.42

5.1

7.3

5.78

7.52

8.7

7.8

fl0)

P(d)

(0hm- c m )

(ohm-cm)

H P ,

K, SO,

H SO,

K20,

lo4

4.3

150 198

198째C

E l e c t r i c a l P r o p e r t i e s o f Z i r c o n i u m O x i d e Corrosion F i l m at T e m p e r a t u r e s U p to

2.3 x

5.2 x 10l6

9.15 8.70

lo2'

2.2 x 1 0 '

2.9 s

lo1,

2.0

10"

3.7

x 10'

2.7 x 1 0 l 6

4.5 x

3.8 ?; 6.1 x 10"

6.5 x

los

2.9 x lo6

3.1

x lo6

2.7 x I O 6

2.7 x loG

2.4 x 10'

a s l o p e of l i n e in p l o t of l / C s vs l o g l o f.

'Slope of l i n e in p l o t of t o t a l series resistance vs l / f . 'Dielectric

c o n s t a n t at 20 kc employed in c a l c u l a t i o n s .

ORNI.-

DWG 67-778

A value of

Our tcntative conclusions a r e that the observed frequency, temperature, and electrolyte dependence of the impedance components can b e reasonably ascribed to resistivity gradients through the oxide and to changes, with tempeiature and with electrolyte, of the resistivity of the l a y e r s of oxide in contact with t h e electrolyte. 'There is no evidence for f i s s u r e s which admit e l e c t r o l y t e into t h e oxide. Additional work is needed to confirm t h e s e conclusions and to permit more complete explanations of t h e impedance behavior. W e expect to continue t h e s e s t u d i e s . Some modihcations of t h e cell will probably b e n e c e s sary to permit measurements with smaller speci men areas. Also, it may b e n e c e s s a r y ' t o modify t h e method of prcssurizatlon to permit better control of p r e s s u r e on t h e elcctrolytca.

46 34 42

38 >_-. 9

& c

Rs p l o t s varied between 8.3 and 9.7. 9.2 is predicted by Eqs. (7) and (8).

34 32

CORROSION SUPPORT FOR REACTOR

PRQJ ECTS

J. L. English J. C. Griess, Jr, P. D, Neumann '2.4

Fig.

5.4,

2.3

2.5

2.7 1000,

Variation

2.9

3.4

3.3

3.5

P K)

with T e m p e r a t u r e of R e s i s t i v i t y

of O u t e r Surface of Z i r c o n i u m F i l m .

Expeiimental programs conducted for t h e purpose of s e l e c t i n g and estimating t h e corrosion damage to engineering materials in t h e High Flux Isotope Reactor (HFIK) and the Argonne Advanced Research

64 Reactor (AARR) were completed during t h e p a s t year, and t h e r e s u l t s w e ~ epresented i n two re.. ports. 2 9 , 3 0 Summaries of t h e pertinent r e s u l t s a r e given below. R e s u l t s concerning t h e corrosion of t h e aluminum-clad MFIK fuel e l e m e n t s h a v e been reported previously3' and a r e not included here. T h e H F I R , which is presently operating a t t h e design power of 100 M w , uses water adjusted to a pI3 of 5.0 with nitric a c i d a s coolant; all t e s t s w e r e conducted i n t h i s enviroiiment a t 100째C. Aluminum a l l o y s (6061, 1100, and X-8001) corroded at r a t e s of 0.2 mil/year or less at a l l flow r a t e s up to 81 fps. Contacting aluminum with al.uminum, beiyl.lium, nickel, o r s t a i n l e s s s t e e l resulted in pitting of t h e aluminum i n c o n t a c t a r e a s only. T h e p i t s were of appreciable depth, but they w e r e randomly spread and should not b e of major c o n s e q u e n c e in the H F I R system. At v e l o c i t i e s of 13 to 81 fps, beryllium corroded a t a constant rate of 2 m i l d y e a r and showed only a slight tendency t o pit. Corrosion damage to t h e beryllium reflector in t h e MFIR should b e negligibly small. Both nickel and e l e c t r o l e s s nickel dep o s i t s corroded e x c e s s i v e l y i n t h e acidified water and a r e not u s a b l e in t h e HFIR. Electrolyzed cos-tings ( a proprietary p r o c e s s for coating mat e r i a l s with chromium) on s t a i n l e s s s t e e l exhibited excellent corrosion i e s i s t a n c e and good a d h e r e n c e to s t a i n l e s s s t e e l . Similar d e p o s i t s flaked and peeled from aluminum surfaces. Hardened t y p e s 416 and 420 s t a i n l e s s s t e e l were shown to b e unsuitable; t h e former alloy blisteied, arid the l a t t e r underwent stress-corrosion cracking. T h e r e s u l t s of t h i s t e s t i n g program and t h e experience gained during operation of other water-

"5. L. English and J. C . G r i e s s , Dynamic Corrosion S t u d i e s for the High Flux Isotopc Reactor, ORNL-TM1030 (September 1966). 30

J. C. G r i e s s and J. L. English, Materials Comp a / i h i l i t y and Corrusion Studies for / h e Argonnc A d vanced R e s e a r c h Reactor, ORNL-4034 (November 1966). 31

J. C. Criess, II. C. Savage, a n d J. L. English, E f f e c t of Heat F l u x on the Corrosion of Aluminum by Water, P a r ? IV, ORNL-3541 (February 1964).

cooled production and research r e a c t o r s were fully u s e d in t h e d e s i g n of the HFHR. Assuming a d e q u a t e control of t h e water chemistry, t h e H F I R should b e free of major corrosion problems. T h e primaiy a r m s of concern in t h e AARR were t h e beryllium reflector, t h e 5061-T'b al!mninum beam t u b e s , and t h e s t a i n l e s s s t e e l fuel element cladding. All t e s t s were conducted in deionized water a t 93OC (200째F). T h e r e s u l t s indicated that t h e corrosion rate of t h e beryllium reflector in t h e AARR will b e between 1 and 3 mils/year with a minimum of localized a.ttack. T h e cori-osion of 5051-?6 aluminum i n water resill-ts i n t h e formation of an insulating l a y e r of corrosion products on t h e surfacc. Since h e a t generated in t h e beam t u b e s must b e transferred a c r o s s t h i s insulating layer, t h e corrosion rate of aluminum m u s i b e minimized to prevent e x c e s The s i v e temperatures in t h e beam-tube walls. AARM beam-tube cooling system in i t s initial design would allow s u r f a c e temperatures up to 260째F; under t h e s e conditions e x c e s s i v e filiil formation would occur and would c a u s e i n c r e a s e s i n temperature of a s much as 66OC (150OF) duriilg r 15 d a y s of operation. T e s t s showed that t h e cooling system lyould h a v e to b e c a p a b l e of keeping t h e temperature at t h e aluriii num-wat e r i n t e r f a c e a t 200째F o r l e s s if frequent replacement of beam t u b e s w a s to b e avoided. T y p e 304 s t a i n l e s s s t e e l did not develop appreciable d e p o s i t s on water--cooled s u r f a c e s when exposed under thermal conditions similar to and even more s e v e r e than t h o s e anticipated in the AARR fuel elements. Hoiwever, after a 1000-hr exposure a t a heat flux of 3.8 x lo6 Btu hr-' ft'--2, numerous shzllo7.v c r a c k s were present on t h e cooled surface. In a comparable t e s t in wliicli t h e h e a t flux w a s 2 x l o 6 Btu hr-' W 2 (hot-spot h e a t flux for 100 M w operation of t h e AARR) and t h e exposure time w a s 2000 hr, no c r a c k s were found. T h e c a u s e of t h e o b s e x e d c r a c k s was not determined, but i t i s p o s s i b l e that they were related to high thermal s t r e s s e s existing in t h e specirn

Chemistry of High-Temperature A q w e ~

ELECTRICAL CONDUCTANCES OF AQUEOUS ELECTROLYTE SQLUTIONS FROM 0 TO 80OOC AND TO 4000 BARS

r. ?I-

............ ..-

cw; F B - T R 7 ..................

OR,,.

..,................,

.-.

W. Jennings, Jr. W. L. Marshall

A. S. Q u i s t

T h e r e i s relatively l i t t l e information a v a i l a b l e on t h e properties of a q u e o u s e l e c t r o l y t e s o l u t i o n s a t supercritical temperatures and p r e s s u r e s . T h e s i m p l e s t and most direct method for obtaining information about t h e e x i s t e n c e and behavior of ic~rrsi n t h e s e s o l u t i o n s is to m e a s u r e their electric a l conductances, By u s i n g t h i s method, w e h a v e stuc'lied aqueous s o l u t i o n s of K,SO,, KIJSO,, and H,SO, to 800°C and to 4000 bars; from t h e s e measurements we h a v e c a l c u l a t e d first and s e c o n d Aft.er ionization c o n s t a n t s of sulfuric acid. t h e s e s t u d i e s , e x t e n s i v e conductruice measurements were made o n NaCl solutions (0.001. to 0.1 m) in order to o b s e r v e t h e behavior of a strong uni-univalent e l e c t r o l y t e under t h e s a m e contlitions. T h e experimental data TJlere evaluated w.ith t h e u s u a l theoretical e q u a t i o n s that d e s c r i b e equivalent c o n d u c t a n c e a s a function of conceniration. By using a digital computer to €it t h e d a t a to t h e e q u a t i o n s by nonlinear l e a s t - s q u a r e s methods, limiting equivalent c o n d u c t a n c e s were c a l c u l a t e d at integral temperatures (0 to 80O0C)and d e n s i t i e s (0.4 to 1.0 g/cm3). T h e s e v a l u e s are shown graphically i n Fig. 6.1, w h e r e limiting equivalent

-_. I

T*L,

800"

. - _ 1

ll(i

WPSITY 9 6 r 3 )

Fig. 6-1,

L i m i t i n g Equivalent Conductance of NaCi

a s a Function of D e n s i t y a t TernperaPures to 800°C.

c o n d u c t a n c e s a r e plotted a s a Gurnction of density. T h i s graph i n d i c a t e s that t h e limiting equivalent conductance of NaCl is a l i n e a r function of solution density (at constaint terripetaturct). Figure 6.1 a l s o r e v e a l s that at temperatures of 400°C and above, t h e limiting equivalent conductance of NaCl a p p e a r s to he independent o f temperature z41though t h e v a l u e s a t (at c o n s t m i density). 800°C are slightly below t h e ,400 to 700OC values, t h i s difference is mostly a c o n s e q u e n c e of inc r e a s i n g ion-pair formation at higher temperatures. As NaCl b e c o m e s a weaker electrolyte, t h e extrapo l a t e d limiting equivalent c o n d u c t a n c e s become n id tend to fall below their somewhat uncertain m true values. T h e s e solutions showed t h i s behavior a!. d e n s i t i e s below 0.4 g/cm3 cmd at temperatures above 70OoC, D i s s o c i a t i o n c o n s t a n t s for ion-pair formation i n NaCl s o l u t i o n s were c a l c u l a t e d from t h e Shedlovsky equation4 at densities f n x n 0.3 to O X g/cm3 and temperatures from 400 to SOOOC.

'A. S. Q u i s t et a l . , Reactor Chenz..niv. Ann. ProQr. Kept. J a n . 31, 1962, ORNL-3262, pp. 73-75; Reacfoi Chem. D i v . Ann. Pro&. R e p t J a n . 31, 1903, O R N L 3417, pp. 77-82; Reactor Chem. Div. A n n . Pro&. l i e p t . J a n . 31, 1964, OKNL-3.591, pp. 84-58; R e a c t o r Chem. D i v . Ann. Progr. R e p t . J a n . 31, 1965, ORNL-3789, pp. 139-43.

2 A . S. Qiiist et a l . , J . P h y s . Chem. 67, 245.3 (196.3); 69, 2726 (1965); 70, 3714 (1566). 3 A . S. Quist e t a l . , Reactor Cham. Div. Ann. Pro&, R e p t . D e c . 3 6 , 1965, OKNL-3913; pp. 63-.M.

4T. Sbedlovsky, J . Franklin Inst. 225, 7 3 9 (1938).

66 F i g u r e 6.2 s h o w s t h e dependence of t h e logarithm of t h e s e dissociation c o n s t a n t s on the logarithm 3f t h e density of t h e solution a t t h e several temperatures. An e x t e n s i v e s e r i e s of measurements were made usiiig 0.01 dernal (0.01 mole per 1000 g of solution) KCI solutions. A s w a s mentioned previously,3 a KC1 solution of t h i s concentration a p p e a r s to be t h e logical c h o i c e a s a reference for conductance measurements a t elevated temperatures and p i e s s u r e s , s i n c e i t i s used a s a standard solution for c e l l constant determinations a t 2S0C. Accordingly, many measurements h a v e been made in t h i s Lahoratory over a period of s e v e r a l y e a r s on 0.01 demal KC1 solutions. Some of t h e r e s u l t s a r e shown i n Fig. 6.3, where t h e s p e c i f i c c o n d u c t a n c e s a r e plotted a s a function of temperature a t a cons t a n t pressure of 4000 bars. T h i s graph r e p r e s e n t s t h e r e s u l t s of 50 s e p a r a t e runs, using three cond u c t a n c e cells and s e v e n different inner electrode assemblies. A comprehensive investigation of t h e e l e c t r i c a l c o n d u c t a n c e s of alkali metal h a l i d e s o l u t i o n s and s o l u t i o n s of related compounds w a s initiated and i s presently nearing completion. Measurements h a v e been completed from 0 t o 800째C and t o 4000 bars on 0 . 0 1 rn s o l u t i o n s of t h e followiilg e l e c t r m l y l e s : NaCi, NaBr, NaI, KC1, KBr, KI, RbF, RbC1, KbHr, RbI, CsCI, CsBr, C s I , N H 4 B r , (CHJ4NBr7 HBr, and N H 4 0 H . Some preliminary r e s u l t s a r e

ORNL-DWG 67-530

- 800 - - i ro

-- 700 'E 600

500 w

9 a

A00

2 300 2

iz %

m a

200

Fig. 6 . 3 .

ORNLCVVG 66-8096R

040

030

050

060

070 080 090 1.

400

8oo

600

800

TEMPFHAlURE ("C)

S p e c i f i c Conductance of 0.01-denial

a Function of Temperature.

--I

100

Pressure,

KCI as

4000 b a r s .

ORNI. OWC 67 534

--1

0 700 x _.

' E 600

-v - 500

> LI

2 400

7 u 2

300

u 200 0 LL

400

DENSITY(oJccn13)

1 -

T-

Fig.

6.4.

ZOO

600

A00

TFMf'tRAiU9E

800

(%)

f o m p o r i s o n of the Specific Conductance C(

0.01 m Solutions of RbF, RbCI, R b B r , and Rbl a s a Function of Temperature.

Pressure,

4000 bars.

shown i n F i g . 6.4, where s p e c i f i c c o n d u c t a n c e s of t h e rubidium h a l i d e s o l u t i o n s are plotted a g a i n s t temperature a t a p r e s s u r e of 4000 bars. .-5/

W. L. Marshall log DENSrIY

Fig.

6.2.

L o g K(NuCI

Na'

of L o g DensiTy a t Temperatures f r o m

m o l a r units.

CI-) as o Function 400 to 80OoC. K in

There a r e relatively few experiiuentally determined v a l u e s for d i s s o c i a t i o n c o n s t a n t s a t high 'Jointly sponsored by t h e Office of S a l i n e Water, U.S. Dept. of t h e Interior, and t h e USAEC.

67 temperatures, a s contrasted to t h e very large number at 25°C. In t h i s Division, v a l u e s above 100°C h a v e been obtained from conductance' and solubility measurrinents. Any contribution to t h e equilibrium behavior of e l e c t r o l y t e s a t high temperature, e s p e c i a l l y the behavior of 2-2 electrol y t e s , is of very much fundamental and applied i n t e r e s t . T h e equilibrium of c o n s i d e r a b l e i n t e r e s t to t h e high-temperature behavior of s e a w a t e r arid of h e r s a l i n e w a l e r s is the d i s s o c i a t i o n equilibrium of magnesium s u l f a t e represented b y

where Qd is the d i s s o c i a t i o n quotient a t a n ionic: :;tr<?ngI.h 1. From t h e i n c r e a s e i n solubility of calcium s u l f a t e (or its h y d r a t e s ) i n s e a w a t e r conceritrates compared to i t s behavior in a q u e o u s sodium chloride solutions, and with t h e assumption that t h i s i n c r e a s e is d u e predomirlalltly to t h e formation of the magnesium sulfate complex, dis-. s o c i a t i o n quotients could b e c a l c u l a t e d a t many ioiiic strengths. 'The equilibrium o f Kq. (1) and t h e f o B lowi ng s ol II bil it y product e q u i l i bri 11m,

given e l s e w h e r e i n t h i s report. T h e v a l u e s for K s , a s a function of i o n i c strength w e r e c a l c u l a t e d from the solubility behavior in sodium chloride solutions. 9 ,l o an iterative p r o c e s s , where I' i s initially assumed to e q u a l I (formal), Eqs. (3-6) were s o l v e d io o b t a i n values of Q, and 'I at t h e many different ionic s t r e n g t h s . These v a l u e s were extmpolated at e a c h temperature by m e a n s of an extended Debye-Hiickcl equation,

where 5 is the Debye-Huckel limiting s l o p e for ii 1-1 electrolyt.e, to obtain t h e d i s s o c i a t i o n cons t a n t K ; (at I = 0). V a l u e s of t h e constant to 200°i[", tititairled by this method a r e plotted a s t h e logarithm of K : v s 1/T("K) i n F i g . 6.5. Jncluded in F i g . 63.5 a r e many published v a l u e s for t h i s c o n s t a n t obtained by s e v e r a l different methods ai temperatures up to 40*C, t h e highest temperature of previously pilbl i s h e d work. T h e p r e s e n t results appear to k in good agreement a t d extend t h e v a l u e s for the c o n s t a n t to 20VC. BYPeast-squares fitting t h e values of Nancollas, J o n e s and Monk, others at O°C, and t h o s e to 200°C from t h i s p r e s e n t study to t h e van't Huff isochore, I

where K eqiials the solubility product a t I and SP jncludes a n y contribution from a izeutral s p e c i e s , c ~ s o ~ 'were , lis4 to obtain t h e tollowing equat ion s :

w i t h AN" e x p r e s s e d a s i t function of AC" (23 conP stant) and T(''IQ thermodynamic q u a n t i t i e s were c a l c u l a t e d ; t h e resuLt::; are given i n T a b l e 6.1.

'$4'. Marshall and R. Slusher, "Solubility of Calciuiii Sulfate i n sea Salt S o l u t i o n s t o :?oo"c; TemperatureSolubiliky L i m i t s €or Saline Waters, e ' include4 in this Annual Report in another s e c t i o n : C:lii-mical Support for Saline Water Program. L .

Values for K i p , [Ca2'1, total magnesium, arid t o t a l sulfate w e r e obtained from t h e experimental r e s u l t s 6

of Electro!ytes to 80d'o~ and 4090 wars," contained i n anot1ier Dart of t h i s s e c t i o n ; J . P h y s . Chein. 67, 2453 (1963); 2726 (196.5); 7Q, 37 14 (1%6). A . S . Q u i s t et a ! . , "CConductanc;e

&??

'W. L. Marahall ami E. V. Jones, 9 . P h y s . Cheni. 70, 4028 (19fjfj); Raacror Chern. D i v . Ann. Pro&. K e p t . i a 1 i . 3 1 , 1965, ~ ~ ~ ~ ~ -p.3 14s. 7 8 9 ,

9 W. L. Marshall, R . Slusher, arid E. V. jones,J. Chem. En$. D a t a 9 , 187 (1964).

l%. I,. Marslialt a n d R. Slustirr, J. ~ h y s . hem. 70, 4015 (lr)6G); X e e c r o r Chern. D i v . Anti. Pro&. RepL. U c c . 31, 196.5, ORNL3cJ13, 41. 113.

"G. H , N a n c o l l a s , Discub3sions F a r a d a y ~ o c 24, . 108 (14573. 1 2 ~ W. ~ . Jories anrl C. E. ~ u t t k , 'rriins. F a r a d a y soz. 48, 929 (1952). 13J.

Kenntarnaa, .%omen Kenlistilehli 298, 59 (1956).

G . M. Urown and J . F:. P r u e , Proc. ROY. (London) 232A, 326 (1955).

SOC.

68 ORNL-CVJG G6-7797R

TEMPERATURE ("C) 200

150

,i-.--.-i

4.5

100

1: PRESENT WORK (MARSHALL-1966) SOLY

b D

-rip

----

ATKINSON PETRUCCI ( 1 9 6 6 ) , ULTtiAWNlCS EIGEN,TAMM (19G21,UI TRASOb ICs NAhCOLLAS (t9571,COPID .oH,SOLY K E N i i d M A A (D56),COND RROWN,PRUE (49551, MIDVALUE,bH PT DUNSMC'RE, JAMFS - R'rVAL UATEU BY JONES, MCNK 1'7521 ,COND JONES,MONK (1952) E M F DUNSMORE, JAMFS (19511,COND DEUBNER. HEiSE ( 1 9 5 1 ) , C O ~ D MASON,sHIJTT (49401, Dlci LONST ~

D m x s ( i y z e i , COPID T MONCY.DAVIE7 (19321 COND DAVIFS ('7211, LUND 0

~~~

I I

20.

'00%

F i g , 6.5.

D i s s o c i a t i o n Constont of Magnesium Sulfate from

O t o 200°C

L. B. Y e a t t s Table 6.1.

Thermodynornic Quontities for the

D i s s o c i a t i o n of M a g n e s i u m Sulfate i n Aqueous Solution,

Found

o to 200'~;

(kcal/mole) ~.

.........

Average

25 rai m o l c - '

.... ____-.__

Ac:

de¶-'

(kcal/mole) ....

deg-l) ..........

____

-24.7

2.129

2.66

-4.

2.399

3.27

-4.01

---24.4

2.631

3.89

-- 4.22

-25.1

100

3.057

5.22

-5.41

-28.5

150

3.501

6.78

-7.67

-34.1

200

4.002

8.66

.......

........

-41.5

-11,o .........

W. L. Marshall

T h e d i s s o c i a t i o n quotients, Q,, for CaSO,' were determined from e x t e n s i v e solubility measurements of calcium sulfate (or t h e dihydrate at 25") in a n a q u e o u s s y s t e m of mixed e l e c t r o l y t e s , varying from pure N a N 0 3 to pure Na,SO, when p o s s i b l e . Measurements were made a t s e v e r a l constant ionic s t r e n g t h s from 0.25 to 6 m at 25, 150, 250, and 35OoC. When solid calcium s u l f a t e d i s s o l v e s in a q u e o u s s o l u t i o n s , i t may b e assumed t h a t a n equilibrium is reached with u n d i s s o c i a t e d molecules:

which at sataration c a n b e e x p r e s s e d by

69 T h e neutral s p e c i e s c a n b e considered also to undergo partial d i s s o c i a t i o n :

~ a ~ ~ , ' ( a q ) + ~ a ~ ' ( a qt) SO,"(aq)

67 532

ORNL-DWG

, (11)

in which case t h e equilibrium quotient e x p r e s s i o n is

T h e solubility product quotient in t h i s study w a s then defined a s

Q,,

[Ca2'llS042-l

- Q,Q,

(13)

With t h e s e a s s u m p t i o n s , t h e molal solubility of calcium s u l f a t e , s, at various ionic s t r e n g t h s and temperatures c a n b e e x p r e s s e d by s

Ic~so,']

Since [Ca2+I

[ea2+] .

- Q,,/[so,~-I

(IS)

V ~ S O , ~ -(Im ) Fig.

(14)

6.6.

Solubility a t

25OC

of C a l c i u m Sulfate

hydrate i n Sodium Sulfate-Sodium

total s u l f a t e

Di-

N i t r u t e Solutions a t

Several Ionic Strengths.

3.0

................

....................

ORNL-DWG 6 7 - 5 3 3 ~

.........................

E IN PURE NoNO? (NO NopS04 PRESENTi

and

SO,^-]

- [C~SO,']

=[so-11(f) - rCaSO,'I, then

~CaSO4'1+ QS,/([SO,l,,,

- rcaso,0l) .

A plot of v a l u e s of s v s I/([so,I(~~ - [ c ~ s o , ~ ~ ) , with t h e assumption of c o n s t a n c y (or near cons t a n c y ) of activity c o e f f i c i e n t s a t constant. ionic strength, should y i e l d a straight l i n e of s l o p e Qsp arid intercept [CaSO,']. 'The r e s u l t s obtained at 25OC at c o n s t a n t i o n i c s t r e n g t h s of 0.25, 0.5, 1, 2, and 6 m, a t lSO째C a t 0.25, 0.5, 1, and 6 m , at 250째C at 0.25, 0.5, 1, and 6 nz, and a t 350')C at 1 and 6 m were t r e a t e d by a method of l e a s t squares to yield v a l u e s for Q,, Qsp, and [.CaSO,'I for e a c h set of measurements. A s examples, d a t a a t 25"C:, and a representative series at I = 1 from 150 to 3.'iO"C, s o t r e a t e d are shown i n F i gs . 6.6 and 6.?; the solubilities are observed to be a linear function of I / ( [ S O ~ ] ( ~) [caso,'I) within the p r e c i s i o n of t h e measurements.

F i g . 6.7.

Solubility of C a l c i u m Sulfate a t H i g h T e m -

peratures i n Sodium Sulfate-Sodium

a Constunt I o n i c Strength of

N i t r a t e Solutions a t

1 ( R e p r e s e n t a t i v e a l s o of

R e s u l t s a t Other Ionic S9rengths Stated in Text).

‘70 In order to determine whether t h e above linear relationships were an artifact of Marned’s rille, v a l u e s of t h e logaiithm of t h e a n a l y t i c a l solubility prodiuct, m(tota1 calcium) .m(total sulfate), were plotted a g a i n s t t h e molality of added s u l f a t e a t constant ionic strength. H a ~ n e d ’ s rule would b e expected to yield a linear relationship if t h e plot W F ~ C made a t c o n s t a n t molality (which for 1-1 electrolyte mixtures would. b e constant ionic strength). T h e p l o t s were not linear nor w e r e they linear by estimating t h e nature of t h e p l o t s a t constant molality. =ne v a l u e s of Q d , Qsp, and Q , obtained a t t h e s e v e r a l constant ionic s t r e n g t h s a n 3 temperatures were ext-apolated t o zero i o n i c s t r e n g t h s to yie!d d i s s o c i a t i o n c o n s t a n t s for CaSO,’, v a l u e s for solubility product c o n s t a n t s , and K Z . When the previously obtained l 5 v a l u e s of KO were corrected SP for neutral CaSO,’, t h e r e w a s relatively good agreement (within -10%) between the two s e t s of v a l u e s . \Crith the solubility behavior in the mixed electrolyte system, t h e mean a c t i v i t y coefficients of calcium s u l f a t e were o b t a i n a b l e over e s s e n t i a l l y t h e entire four-component systein by the d a t i o n ship

, I 0 n

Table 5.2.

0) of C a l c i i m Sulfnte, 2 5 to 350°C (the DihydrLiie ut 25°C)

4.70

2.0

2.68

150

6.0

2.7

3.55

250

8.05

4.46

4.68

8.8

7.0

350

11.0

e d l y with ris~i15 temperature, reflecting t h e predominating effect of t h e decreasing dielectric constant of w.+ter over that of increasing kinetic energy.

F. s.Swectnn

R. W. Ray

C F. Bacs, J r .

sulfate

where t h e m’s in t h i s expression r e f e r to t h e t o t a l molality of calcium and sulfate, respectively, and KZp is defined a s the thennodynamic solubility product c o n s t a n t defined by Eq. (13) a t I 0. V a l u e s for t h e c o n s t a n t s of C a S O , a r e tabulated i n ‘Table 6.2, from which thermodynamic q u a n t i t i e s were calculated. No v a l u e s for dissociation cons t a n t s for CaSC),’ h a v e been published a t temperatures higher than 40OC. l 6 Our own pK: value a t 25°C of 2.00 compares with a literature value of 2.31. l 7 C h a r a c t e r i s t i c of t h e behavior of s e v eral other 1-1, 1-2, and 2-2 e l e c t r o l y t e s studied the a t elevated temperatures in our Laboratory, dissociation c o n s t a n t of CaSO,’ d e c r e a s e d mark-

rrue”)

(KO ), D i s s o c i a t i o n SP 0 Coiistant (K ), and K o (rnolality of CaSO at

---, (18)

.-.............. SP

T h e N e g a t i v e Logarithms of t h e (‘

S o l u b i l i t y Product Constant

This study of t h e solubility of Fe,O, i n HCI solutions i s being carried out b e c a u s e Fe,O, i s a corrosion product of t h e steel-water s y s t e m s u s e d in pressurized-water reactors. Measurements previously reported * O have been extended i.n temperature and in IIC! concentration. T h e method u s e d was e s s e n t i a l l y t h e s a m e a s before. ,%ti I K l solution in a reservoir of Pyrex g l a s s w a s equilibrated a t room temperature with H , a t a pressure of 1.0 atm. T h e n i t w a s pumped

“A. S. Q u i s t e t af., J . P f i y s . Chem. 70, 3714 (1966); 69, 2726 (1965); 67, 2453 (1963); J . Chem. E n g . Data 9, 187 (19G4); J . P h y s . Chem. 70, 4028 (1966). 19

E s s e n t i a l l y t h e s a m e material w a s included i n a

paper e n t i t l c d “The ”W. 1,. Marshall, K . S l u s h e r , a n 3 E. J . Chcm. En& D a t a 9, 187 (1964).

V. J o n e s ,

J . Bjerrum, 6. Scirwarzenbach, a n d L. G. Sill& (Compilers), “Stability C o n s t a n t s , ” P a r t 11, Inorganic L i g a n d s , T h e C h e m i c a l Society, Burlington H o u s e , London. 1958. 17

R. P. S e l l and J. H. R. George, T r a n s . b’araday S O C .

49, 619 (1953).

Solubility of F e - 0 ,

Solutiuns a t E l e v a t e d Temperatures,

”

i n Aqueous

p r e s e n t e d a t the

1 8 t h Southeastern Regional Meeting of t h e American Chemical Society held i n L o u i s v i l l e , K y . , Oct. 27-29, 1966.

* O F . 13. Sweeton, R. W . R a y , a n d C . P. Facs, J r . , R e a c t o r Chem. Div. Arm. Progr. R e p t . D e c . 3 1 , 196.5, ORNL-3913, PP. 64-65.

71 through a pressurized h e a t e d column of t h e s p e c i a l l y prepared Fe jO,. T h e equilibrated solution was cooled and then p a s s e d through a cation exchanger t o strip o u t t h e d i s s o l v e d iron. T h e iron w a s l a t e r e l u t e d a n d a n a l y z e d spec:trochemically b y m e a n s of o-phenanthroline. After obtaining most of t h e d a t a reported h e r e , w e modified t h e s y s t e m for eventual u s e of a l k a l i n e s o l u t i o n s . A copper reservoir w a s substituted for t h e g l a s s one, and provision w a s made for i n j e c t i n g an HC1 solution i n t o t h e stream of hot equilibrated solution t o prevent precipitation of d i s s o l v e d iron o n cooling. The d a t a are shown i n F i g . 6.8, where t h e logarithm of t h e iron concentration is plotted a g a i n s t t h e C1- concentration obtained from t h e electrolytic conductivity of t h e makeup solution. T h e l i n e s on t h e graph h a v e b e e n c a l c u l a t e d o n t h e b a s i s of i r o n being i n solution a s t h e two i o n s , Fez’ and FeOII’, formed in t h e s e equilibria:

with t h e corresponding solubility products:

and

Using trial v a l u e s of t h e s e products a t e a c h t e m perature, t h e known C1- concentration for e a c h point, a n d t h e known ionization c o n s t a n t of H,O, 2 1 w e c a l c u l a t e d t h e Ht concentration that g a v e a c h a r g e neutrality for t h e ionic s p e c i e s at t h e e x periment temperature. T h e logarithm of t h e corresponding concentration of iron w a s i b e n compared with t h e experimental value. After treating a l l the d a t a t h i s way, a l e a s t - s q u a r e s procedure w a s u s e d to a d j u s t t h e solubility products to v a l u e s that minimized t h e differences between c a l c u l a t e d and observed iron concentrations. T h e s e c o n s t a n t s , which i n c l u d e t h e effective H Z p r e s s u r e as c a l c u l a t e d from t h e solubility d a t a of Gilpatrick and Stone, 2 2 a r e given below: (OC)

Tern pero tu re

1.79 (fo.10)

200 ORNL-DWG

............

67--534

KFcOtl

__ ......-.

IO6

Q.2 6

2 60

0.0037 (*0.0045) X 10

3 00

0.0109 (kO.0015) X

lo6

0.53 (k0.05) 0.072 ( k 0 . 0 2 6 )

T h e s e c a l c u l a t e d solubility products i n d i c a t e t h a t t h e fraction of iron in t h e F e 2 + form w a s 100%a t 200°, 15% or less ai 2605: and 55 to 85% at 3OOG. T h e apparent c h a n g e in t h e s i g n s of t h e temperat u r e c o e f f i c i e n t s of t h e solubility products over t h i s temperature range is of i n t e r e s t , as t h i s i s i n the s a m e temperature range where t h e d i s s o c i a tion c o n s t a n t of water goes through a maximum. In future work WE will extend t h e H+ concentration r a n g e by u s i n g a l k a l i n e s o l u t i o n s , for which 21The v a l u e s used w e r e 5.01

atid 6.45 x 10-l’

(m’)

lo-”,

6.76

at 200, 260, and 3 0 0 respec~ ~

t i v e l y ; these v a l u e s a r e based on the d a t a of A. A.

CONCENTRATION Cl-(pm)

Fig. 6.8.

M e a s u r e d S o l u b i l i t y of Fe304 i n H C I S o l u -

t i o n s S a t u r a t e d at

25OC w i t h 1 otm

H2.

N o y e s , Yogoro Kato, and R. H. Sosman i n J . A m . Chem.

SOC. 32, 159 (1910).

221A. 0. Gilpatrick and 1-1. 11. Stone, Reactor Chem. Div. Ann. Pro&. R e p t . J a n . 31, 1961, OKNL-3127, pp. 60--.61 and Reactor Cliem. Div. A n n . Pro&. R e p t . J a n . 3 1 , 1962, ORNL-3262, pp. 64-65.

72 t h e present system i s adapted. Such d s t a should i n c r e a s e t h e precision of t h e c a l c u l a t e d solubility products and their temperature coefficients, and perhaps i n d i c a t e the p r e s e n c e of other complexes of iron. We will a l s o go to lower temperatures i f w e are a b l e to a c h i e v e equilibrium a t practical flow rates.

HYDRBLYSIS OF BERYLLIUM !OH IN 1.0 M CHLORIDE AT 25Â°C R. E. Mesmer

C. F. B a e s , Jr.

T h e a q u e o u s chemistry of Ue(1I) s o l u t i o n s i s not yet s a t i s f a c t o d l y defined. T h e r e have b e e n a great number of s t u d i e s on t h e hydrolysis of beryllium beginning with t h e work of P r y t ~ *in~ 1929. Probably t h e most authorative s t u d i e s a r e t h o s e coming from Sill6n's s c h o o l i n Stockholm s i n c e 1956. 2 4 - - 2 7 T h e s e workers favor a s c h e m e of t h r e e s p e c i e s to explain potentiometric d a t a below 1 M berylliuin concentration i n a c i d i c perchlorate media, that is, Be,(QH),', Be,(OH),3+, and Be(OIl)*. Over t h e years a great many other s c h e m e s have b e e n proposed which were not supported b y t h e work of Sill& and h i s co-workers. The neutral s p e c i e s Be(QH), is the least a c c e p t a b l e of t h o s e in the above scheme. T h e e x i s t e n c e of s u c h a s p e c i e s implies a lower limit for the solubility of beryllium hydioxide. 'This limit would b e l o p 4 M b a s e d upon hydrolysis e q u i l i b r i a z 4 and t h e solubility product. 2 8 However, t h e work of Gilbert and Garrett * h a s indicated solubilitiks l e s s than t h i s and even a s low a s l o p 7 iM. A cursory examination of t h e d a t a in ref. 24 i n d i c a t e s that comparable or better f i t s to t h e d a t a are obBe3(01-I)33', tained with t h e scheme Be3(OtI),4t-, and &e3(OH)42t a s well a s other s c h e m e s containing Be3(OH),3t. T h e logarithm â&#x201A;Źor the s t a bility constant for t h e s p e c i e s He O OH),^' i s -8.94 t 0.01, compared with t h e v a l u e of -8.65 i 0.01 reported by S i l l d n Z 4in 3 M perchlorate. A s part of a program to r e i n v e s t i g a t e t h e hydroly s i s behavior of beryllium ion, potentiometric mea-

surements h a v e been completed a t 25OC i n the pH region 2 to 7 and a t beryllium concentrations between 0.001 and 0.05 rn u s i n g quinhydrone and calomel electrodes. T h e f a c t o r s limiting t h e pII or hydroxide-to-metal concentration r a t i o s which can b e attained are t h c equilibration rate and t h e solubility. Generally, equilibrium ratios up to about 1.1 wehe achieved without precipitation within 1 hr. A n a l y s i s of our d a t a at 25" i n d i c a t e s that no pair of s p e c i e s with up to f i v e meta! i o n s or hydroxide i o n s per s p e c i e s i s sufficient t o explain t h e d a t a within experimcntal error. L,east-squares c a l c u l a t i o n s for 33 p a i r s led t o t h i s conclusion. T h e s c h e m e s involving three or m o r e s p e c i e s h a v e not yet been examined i n d e t a i l . However, preliminary r e s u l t s i n d i c a t e t h a t a polynuclear s p e c i e s i s m o r e s u i t a b l e than Be(QH) 2 . A s Kakihana and S i l l k n Z 4 h a v e pointed out, t h e p r e s e n c e of t h e s p e c i e s F3c(OH), l e a d s to an inter-. s e c t i o n of a l l E \is pH c u r v e s a t fi of 1.0 and pH ca. 5.5. Clearly s u c h an i n t e r s e c t i o n is a b s e n t i n t h e d a t a showri in Fig. 5.9. T h i s observation is c o n s i s t e n t with d a t a reported in 1355 by Hertin ci a!., 2 9 although t h e s e i n v e s t i g a t o r s a l s o c h o s e t o interpret their d a t a in terms of Be(OM), a s s u g g e s t e d earlier by Sillkn. In order t o better define the !nost representative hydrolysis scheme, similar s t u d i e s are being conducted a t higher temperatures.

23hI. P r y t z , Z . Anorg. Allgem. Chem. 180, 3 5 5 (1929). 24X-i.

Kakihana and I,. G. Sillgn, A c t a Chem. Scand.

10, 985 (1956).

2513. C a r e l l and A. Olin, A c t a Chem. Scand. 15, 1875 (1961).

2 6 B . C a r e l l and A. Olin, A c t a Chem. Scand. 16, 2357 (1962). 2 7 S . Mietanen and L. G. S i d n , .4cta Chem. Scand. 18, 1015 (1964).

"R. A . Gilbert and A . B. Garrett, J . A m . Chem. S O C . 78, 5501 (1956). "F. Bertin, G . Thomas, and J. Merlin, Cornpi. R e n d . 260, 1670 (1 965).

.........

...........

rorAt

., 1

............. ~

(n)

( A 1 STA9T AND

n ~l

...............

ORNL- DWF 6 7 - 535

C D N C F N IRATION END Or T l r R A T l O N l

(0.0464 -- 0.0.323) rn

(0.0224 -- 0 0176Y)m (0 00732 - 0.00514)m (0.00270 1).001931m

A .,. .-

...

45x467

F i g . 6.9.

to-6

L 2

40-4

-log

(0-3

A v e r a g e Number of H y d r o x i d e I o n s per B e r y l l i u m C o m p l e x e d a5 a F u n c t i o n of -log

b y Potentiometric Titration with N Q O H .

10-2

h as Determined

SURFACE CHEMISTRY OF THORIA

(OKNL lot No. DT 102W) to produce thoria with a s p e c i f i c s u r f a c e a r e a of 35.5 m2/g. P o r t i o n s of t h i s material were calcined for 4 hr a t higher temperatures t o s u c c e s s i v e l y d e c r e a s e t h e s p e c i f i c s u r f a c e a r e a . T h e s p e c i f i c s u r f a c e areas (2) and c r y s t a l l i t e dimensions (from x-ray line-broadening d a t a ) are given a s a function of c a l c i n i n g temperature i n Fig. 7.1. T h i s graph also s h o w s t h e varia t i o n s of t h e h e a t s of immersion with r e s p e c t to

C. H. Secoy Heats of Immersion and Adsorption

E. L . Fuller, J r . I I . F. Holmes S. A . T a y l o r ' H e a t s of immersion of s a m p l e s of thoria in water a t 25.OoC Rave been iiieasiired for various pretreatments. T h e b a s e material for t h i s s e r i e s w a s obtained by a 65OOC calcination of thorium o x a l a t e

' P r o f e s s o r of Chemistry, Centenaiy College, Shreveport, L a .

DRNL-DWG 67-536

'i ( r n 2 / g 1 35.5

14.5

6.6

3.0

98.5

235

655

1485

1.6

2542

0.95

>> 2500

CRYSTALLITE SIZE ( A )

L _

800

1000

1200

1400

CAI C I N I N G T E M P E R A T U R E ( " C )

F i g . 7.1. H e a t s of Immersion of T h o r i o i n Water.

___i

1600

75 t h e s e parameters for o u t g a s s i n g temperatures rangi n g from 25 to 500°C. T h e s a m p l e s were maint a i n e d at a p r e s s u r e less than torr for 24 h r a t e a c h temperature, prior to s e a l i n g under vacuum. E a c h point r e p r e s e n t s t h e mean of a t l e a s t t.wo experimental determinations. T h e calorimetric and a s s o c i a t e d t e c h n i q u e s h a v e been d e s c r i b e d previously. As observed earlier, t h e m a t e r i a l s from the lower-temperature calcination liberated a portion of t h e h e a t slowly after an i n i t i a l i n s t a n t a n e o u s b u r s t of heat. The slow h e a t eEfects for t h e 650 and, 800°C c a l c i n e d thoria a r e b e s t characteri z e d a s two concurrent first-order p r o c e s s e s : a s l o w heat e f f e c t with a half-life of ca. 4 min and a very s l o w h e a t with a half-life of C R . 40 min. ‘The 1000°C c a l c i n e d thoria exhibited only one s l o w p r o c e s s (halE-life of ca. 12 min) in addition to the instantaneous process. T h e higher calcination temperatures (1200 to 160Q°C) produce materials which r e l e a s e all t h e immersional h e a t i n s t a n t a n e o u s l y , with no d e t e c t a b l e s l o w p r o c e s s e s present , The heat of immersion at a n y given o u t g a s s i n g temperature s h o w s a n i n c r e a s e with i n c r e a s i n g c r y s t a l l i t e s i z e ( d e c r e a s i n g s p e c i f i c s u r f a c e area) for t h e lowest-fired materials, followed by a dec r e a s e to a n e s s e n t i a l l y c o n s t a n t value for t h e larger c r y s t a l l i t e s . T h e variation of t h e h e a t s of immersion with r e s p e c t to c r y s t a l l i t e size is not w e l l understood and h a s been t h e o b j e c t of i n v e s t i g a t i o n s with other o x i d e s , as reviewed recently by Z e t t l e m ~ y e r . ~T h e invariance of t h e immers i o n a l h e a t per unit a r e a for our larger c r y s t a l l i t e s s u g g e s t s that t h e s e v a l u e s may b e truly repres e n t a t i v e of an “ideal” thoria surface, with some s o r t of perturbations present for t h e s m a l l e r crys-. t a l l i t e s . Such a conclusion must r e c e i v e justific a t i o n from other t e c h n i q u e s that will allow construction of a creditable model, T h e inversion of t h e d a t a for t h e 300°C-outgassed, 1000°Cc a l c i n e d material is probably due to experimental error, with t h e h e a t of immersion being 850 $: 20 e r g s / c m 2 for 300 to 500°C o u t g a s s i n g of t h i s material. In a n attempt to see if t h e aforementioned behavior is t h e result of t h e o x a l a t e preparatioll of H. F. Holmes and C . 11. S e c o y , J . P h y s . Cherr~.69, 151 (1965). 3A. C. Zettlemoyer, R. D. Igenyar, and Peter Scheidt, J . Colloid h t e r f n c e S c i . 22, 172 (1966). 2

thoria, a similar series w a s c h e c k e d for a thoria prepared by t h e steam denitration of thorium nitrate. T h e low-fired, high-surface-area m a t e r i a l s also showed slow h e a t e f f e c t s , with none present for t h e higher-fired materials.

Adsorption of Water and Nitrogen on Porous and N O ~ ~ Q R X Thoria JS

1-1. F. Holmes

E. L. Fuller, Jr.

P r e v i o u s calorimetric 2 - and gravimetric’ i n v e s t i g a t i o n s of t h e interaction of water with t h e s u r f a c e of thoria h a v e revealed t h e very complex nature of t h i s p r o c e s s . Material u s e d in t h e previous work c o n s i s t e d entirely of porous thoria derived from t h e o x a l a t e . Two s a m p l e s of comperable s u r f a c e a r e a were used in t h e present work. Sample C is a typical o x a l a t e material, while s a m p l e S w& prepared i n an attempt io minimize t h e internal surface, t h a t is, d e c r e a s e t h e POrosity. 6 , 7 T h e porous and nonporous character of s a m p l e s C and S, respectively, a r e clearly revealed from t h e typical adsorption isotherms shown in F i g s . 7.2 and 7.3. Inflections in t h e desorption branch for s a m p l e C at a relative pressure of about 0.35 i n d i c a t e pore sizes ranging down to about 10 A i n radius. The nonporous character of s a m p l e S is further confirmed by the f a c t that t h e x-ray cryst a l l i t e size is compatible with the nitrogen s u r f a c e a r e a . However, both s a m p l e s exhibited t h e low-pressure h y s t e r e s i s and irreversible retention of water d i s c u s s e d previously. T h e quantities of irreversibly adsorbed water l i s t e d i n T a b l e 7.1 a r e much greater than would b e required to form a s i n g l e l a y e r of s u r f a c e hydroxyl groups. On t h e b a s i s of t h e present results, it is concluded t h a t t h e irreversible retention of water in s u c h large q u a n t i t i e s is not a unique property of porous material. T h e phenomenon has b e e n d e s c r i b e d 5 as a n immobile a s s o c i a t i o n adsorption to g i v e t h e s u r f a c e a n a l o g of a hydrated bulk hydroxide.

’

411. F. Holmes, E. I,. F u l l e r , Jr., and C . 11. Secoy, J . P h y s . Chem. 70, 436 (1966). 5 E. L. Fuller, Jr., H , F. Holmes, a n d C . H. S e c o y , J . P h y s . Chem. 70, 1633 (1966). ‘Sample S w a s kindly supplied b y .’1

€I. Sweeton.

7F. €I. Sweeton, Reactor Chem. Div. Ann. Propr. R e p t . J a n . 31, 1961, ORNL-3127, p. 71.

76 ..........

ORNL-OWG 67-53' .........

T a b l e 7.1.

Summary o f Nitrogen

Adsorption Measurements .... . ................-

........-

Micrograms Sample

I1 A F T E R P R E V I O U S HO , ISOTiiERMS S A M P L E bvE1Gti.T: 501.134 r n g ,

0.2

0.3

0.4

0.5

0.6

0.7

P/P"

F i g . 7.2.

(xne)

Meter

Surface Area'

of S u r f a c e b

(1x1

RET

Constant

2/g)

499.810

5.52

1050

500.276

174

4,78

152

501.264

533

4.40

499.803

5.48

1270

199.81 5

5.96

490

200.012

222

5.46

200.108

302

5.50

200.170

354

5.25

200.338

496

5.29

199.8 1 3

5.96

39 0

bChemisorhed H 2 0 i n e x c e s s of sample weight i n vacuum a t 50OoC. Computed u s i n g N 2 s u r f a c e a r e a measured a f t e r o u t g a s s i n g a t 500째C.

END I1

0.1

per Square

eSarnple weight i n vacuum a t s t a r t of experiment.

of H,O

Weightn

Sample

'Assumes t h a t a n adsorbed nitrogen molecule o c c u p i e s 16.2 A 2 .

Adsorption of Water on Sample C a t 25.00'.

ORNL-DWG 67-538

Application of the BET theoiy to t h e water iso-

therms y i e l d s interesting information concerning 7

t h e apparent s u r f a c e a r e a s . T h e d a t a for s a m p l e C i n d i c a t e t h a t t h e effective s u r f a c e a r e a d e c r e a s e s with increasing amounts of irreversibly adsorbed water. Ultimately the effective s u r f a c e a r e a d e c r e a s e d to about '75% of t h e a r e a determined by nitrogen after o u t g a s s i n g at 5OOOC. T h i s i s not unexpected, s i n c e chemisorbed water s h o u l d deHowever, i n t h e c r e a s e t h e t o t a l pore volume. case of t h e nonporous sample S, t h e effective s u r f a c e a r e a d e c r e a s e d to about 40% of t h e original nitrogen value. In opposition to t h i s , t h e amount of water adsorbed a t t h e higher relative p r e s s u r e s indicated a n effective s u r f a c e area roughly equal to t h e original nitrogen s u r f a c e area. Surfac a r e a s were c a l c u l a t e d frorri the water d a t a on the assumption of a liquid-like monolayer, that i s , e a c h molecule o c c u p i e s 10.6 A '. Tentatively, t h e anomaly with sample S c a n b e explained by assuming that e a c h water molecule i n the first physically adsorbed layer i s hydrogen bonded to t w o underlying chemisorbed water molecules. Calc u l a t i o n s b a s e d o n t h i s assumption give s u r f a c e 1

0 2

0 4

0.5

0 6

P/PO

Ftg.

7.3. Adsorption

of Water o n Sample 5 a t 25.009

77 a r e a s which a r e much more compatible with t h e nitrogen s u r f a c e a r e a s . R e s u l t s from the nitrogen adsorption experiments a r e summarized i n T a b l e 7.1, which gives t h e RET parameters obtained from t h e isotherms. I t is evident t h a t i n c r e a s i n g amounts of irreversibly adsorbed water d e c r e a s e both t h e measured nitrogen s u r f a c e area and t h e BET C constant. A d e c r e a s i n g value of C implies a smaller average h e a t of adsorption in t h e first monolayer, a less s h a r p "knee" of the isotherm, and that higher p r e s s u r e s a r e required t o fill t h e first s t a t i s t i c a l monolayer. D e c r e a s i n g nitrogen surface a r e a s for sample C, l i k e t h o s e obtained from the water, c a n perhaps b e explained on t h e b a s i s of t h e chemisorbed water d e c r e a s i n g t h e pore volume. T h i s c o n c e p t cannot, however, explain t h e d e c r e a s i n g nitrogen s u r f a c e a r e a s observed with sample S. Explanations for t h e e f f e c t of chemisorbed water on t h e nitrogen s u r f a c e a r e a s of s a m p l e S are, at best, tentative. T h e effect of the magnitude of t h e BET C constant and of t h e s u b s t r a t e lattice on t h e a r e a occupied by a nitsogen molecule i s currently b e i n g investigated. Infrared Spectra of Adsorbed Species on T h o r i a

C . S. Shoup, Jr. Infrared s p e c t r a l s t u d i e s of adsorbed s p e c i e s on thorium oxide h a v e continued with higher otitgass i n g temperaturcs than were previously attainable. h i i ial room-tenpetbture o u t g a s s i n g of a p r e s s e d disk of T h o , which had been calcined tn air at 650" (see F i g . 7.1) produced a prominent absorption band at 3740 cm-', attributed t o unperturbcd s u r f a c e hydroxyl groups, and a band a t 3660 cm-'. In addition, a dramatic reduction in the intensity ~ n idn c r e a s e i n the frequency at maximum absorba n c e of a broad band due t o the s t r e t c h i n g mode of hydrogen-bonded OH groups occurred. I n COLIt r a s t t o most other o x i d e s , however, i n c r e a s i n g t h e o u t g a s s i n g temperature above 100° reduced the intensity of t h e band at 3740 c n 1 - l . After o u t g a s s i n g at SOO", t h i s band had virtually dis-

',''

'C. H. Secoy and

c. S. Shoup,

Jr., Reactor Chem. D i v .

Ann. Pro&. R e p t . D e s . 3 1 , 1965, ORNL-3913, pp. 70-71.

'M. R. Bastla, J . Phy:s. Chem. 66, 2223 (1962). 'OK. E. L e w i s and 6. D. Parfitt, T r a n s . Faraday S o c .

62, 204 (1966).

appeared, leaving a doublet at 3645 to 3660 cm-' and a weaker band at 3520 CRI-' superimposed on a weak, broad contour, indicating s o m e residual polymeric hydrogen bonding. Although t h i s thoria had previously been c a l c i n e d in air at only 650°, t h e sample w a s n e v e r t h e l e s s o u t g a s s e d a t increasingly higher temperatures, t h u s producing some sintering action. l 1 Outgass i n g a t 650' left only weak bands i n the 01-1stretchi n g region at 3656 and 3503 C ~ I - No ~ ~ surface hydroxyl groups were spectroscopically evident after o u t g a s s i n g a t SOOO, but other bands in t h e 1200 t o 1700 cm-' region were present. T h e s e latter bands disappeared after o u t g a s s i n g at 950°. However, b a n d s a t 1040 and about 730 c m - l were very l i t t l e affected by the o u t g a s s i n g treatment, and their i n t e n s i t i e s were hardly reduced after in vacuo s i n t e r i n g at 950°. Examination of other s a m p l e s of T h o , indicated that t h e s e bands w e r e properties of t h e total m a s s , either a s thorium oxide o r bulk impurities. T h e discoloration of T h o , , which h a s been obs e r v e d often after o u t g a s s i n g at SOUo, h a s been s h o w n to b e due to t h e presence of a s m a l l amount of carbon residue from organic contamination d e posited ducing the initial o u t g a s s i n g s t e p s (indic a t e d by the p r e s e n c e of carbon-hydrogen s t r e t c h i n g bands in the 2850 to 3000 region). T h i s carbon residue c a n b e removed by oxidation at 400°, with an accompanying weight toss, or by volatilization a t 900 to 1000".s 111 t h e a b s e n c e of prior organic contamination, heating to 500° i n vacuo produced no discoloration. T h e fact t h a t t h e infrared s p e c t r a and t h e energetics of water adsorption were independent of color and oxygen i n d i c a t e s that treatment (in contrast to rutile oxygen d e f e c t s , a s proposed elsewhere, l 2 do not play an important role i n the discoloration of thoria. In the presence of pure water vapor a t a relative humidity of 6076, the H-0-H deformation mode of physically adsorbed H,O at I630 an.-.' w a s t h e only absorption band to appear (except in t h e OH s t r e t c h i n g region) that w a s not present after outAfter room-temperature evacu-g a s s i n g a t 950". ation, a brief exposure of the thoria to the laboratory atmosphere a t 40% relative humidity produced

"After 24 hr each a t 650, 800, and 0SO0 i n vacuo, the s p e c i f i c s u r f a c e a r e a w a s reduced t o 1 2 . 3 m 2 / g and the average c r y s t a l l i t e size w a s increased t o 319 A.

"M. E. Wadsworth et o l . , "The Surface Chemistry of Thoria, '' Progress Report, University o f IJtah, Salt L a k e City, TJtah (Jan. 31. 1'959).

78 s e v e r a l absorption bands. Even a f t e r e v a c u a t i n g the c e l l for 24 hr, s t r o n g and fairly s h a r p b a n d s remained at 861, 1020, 1303, 1416, and 1583 c m in addition t o t h o s e present before the T h O , w a s e x p o s e d to t h e atmosphere. It i s apparent from t h i s that atmospheric carbon dioxide i s rapidly and strongly adsorbed on thoriap a t l e a s t i n t h e prese n c e of water vapor. When water vapor w a s adsorbed on T h o , which had been o u t g a s s e d a t 950", s h a r p bands a t 3940, 3695, and 3668 CIII-' appeared with c o n s t a n t rela t i v e i n t e n s i t i e s up to approximately one monolayer coverage (10 to 12 d o s e s of H20),a s shown in F i g . 7.4. With i n c r e a s i n g coverage, t h e 3668-

O R N L - D V f G 66-12569

c m - I band continued to i n c r e a s e in intensity, but

t h e i n t e n s i t i e s af t h e 3740- and 3695-crn--l b a n d s In addition, a broad band at 1630 decreased. c m - * began to appear, proving t h e adsorption of molecular mater. Nevertheless, the growth of t h e broad band in t h e OH stretching region showed that polymeric hydrogen bonding was present at significantly l e s s than o n e monolayer coverage. T h e nonequilibrium nature of water adsorption w a s further demonstrated by s u c c e s s i v e adsorptiondesorption c y c l e s between 4.58 torrs (for 1 to 150 hr) and < l o p 5 torr (for 24 hr). E a c h s u c c e s s i v e in vacuo spectrum showed a d e c r e a s e in t h e i n t e n s i t y of the 3740-cm-' band and an i n c r e a s e in t h e intensity of t h e broad band around 3440 cm-'. In addition, b a n d s a t 1564.5 (strong), 1430, 1375 (sharp), and 1362 c m - (sharp) appeared. T h e s e bands i n c r e a s e d in intensity with each s u c c e s s i v e adsorption-desorption c y c l e , al thaugh their relative i n t e n s i t i e s remained unchanged. These bands appear to b e due t o the adsorbed water rather than t o a n y contaiiiination, but a firm interpretation of their nature a w a i t s further experimental d a t a .

D. N. IIess H. F. McDuffie

4000

3800

3600

3400

3200

5000

B. A . Soldano C. F. Weaver

Sol-gel microspheres of ThO, or UO, h a v e b e e n found to evolve g a s e s when heated, as did t h e thoria-3% IJO I sol-gel materials previously re ported. ' Efforts h a v e been made to reiilove t h e s e g a s e s , a s well a s the carbon, which a r e generated by interaction and pyrolysis of t h e water, n i t i a t e s , organic s o l v e n t s , and s u r f a c t a n t s included in the sol-gel m a t e r i a l s during their preparation. Such removal is considered d e s i r a b l e becarisc e x cess gas p r e s s u r e or reactions between t h e g a s and metal might occur in s e a l e d fuel e l e m e n t s , c a u s i n g rupture during reactor operation. T h e air-dried ThO microspheres yielded CO 2 , CO, H,, NO, N,, and organics upon h e a t i n g in vacuum. 'The first three were dominant. 'T'he

FREQUENCY ( c , n - ' )

Fig.

7.4.

Infrared Spectra of the OH Strctching Region

After Adsorption of the lndiroted Number o f E q u a l V o l u m e D o s e s of M2h9 Vapor on Tho*. Ordinates disp l a c e d s l i g h t l y for c l a r i t y .

I). N. H e s s , W. T. R a i n e y , and R. A. Soldano, R e a c f o r Chern. D I V . Ann. P r o g r . R e p t . J a n . 31, 1965, ORNL3789, p. 177.

14D. N. H e s s a n d B. A . Soldano, R e a c t o r Chem. Div.

A n n . P r o g r . R e p l . D r c . 31, 1965, ORNL-3913, p. 7 2 .

79 l a r g e s t amount of g a s evolution occurred a t t h e following centigrade temperature intervals: 240 to 260, 400 to 460, and 700 to 760. Above 76OoC, only a negligible amount of g a s remained. T h e wet UO, microspheres yielded CO,, CO, €I2, N,, O,, NO, and organics when heated with s t e a m and evacuated. T h e temperature i n t e r v a l s of maximum gas evolution appear t o b e 150 to 250°C and 400 to 650'C. T h e principal g a s evolved (primarily in t h e 300 to 350° range) w a s CH,. T h i s is in d i r e c t c o n t r a s t with t h e production of higher-molecular-weight organic products previously noted in t h e case of the T h o , microspheres. A p o s s i b l e explanation for the difference is t h a t i n dry T h o , c a t a l y t i c cracking of t h e included organics o c c u r s , while i n the wet UO, matrix thermal cracking i s dominant. T h e l a t t e r rase is expeutcd t o produce lower-molecular-weight products. A conditioning scheme, s u c c e s s f u l with r e s p e c t to producing a low carbon content, a low O : U ratio, and high density, is shown in d e t a i l in T a b l e 7.2. T h e flow of water vapor w a s n e c e s s a r y for the removal of carbonaceous material and, thus, for production of a low final concentration of carbon i n t h e UO, microspheres. T h e water vapor a l s o s e e m s to prevent fragmentation of the s p h e r e s . T h e mixture of CO, and H,O was superior to e i t h e r compound s e p a r a t e l y for i n c r e a s i n g t h e rate of sintering. I t w a s of prime importance that the carbon removal b e complete before t h e mixture of CO, and H,O w a s added, s i n c e t h e densification s t e p trapped any remaining carbonaceous material. T h e final u s e of pure €4, to counter t h e oxidizing effect of the mixture of CO, and H,O produced the low O:IT ratios. I t is e x p e c t e d that t h e s a m e p r o c e s s i n g s c h e m e would be applicable to microspheres c o n s i s t i n g of a n y member of the ThO,-UO, solid-solution s y s tem, although no experimerital information is avail1s

P. W. Emmett, p e r s o n a l communication.

a b l e for s u c h materials. F o r pure T h o , , the H , gas in t h e p r o c e s s i n g s c h e m e i s both u n n e c e s s a r y and h a r m l e s s . Table 7.2.

Successful G a s

Flow Conditioning Scheme

for Sol-Gel U 0 2 Microspheres

Batch p-9-12-1153; weight: 9.976 g Treatment Schedule

16 hr

170nC

Ar-H20

25 0

A r 4 % H 2 -H,O

350

3.---4% I3 2 ---I12 0

450

Ar-4% H 2 - H 2 0

Cool

Ar---l% 1%.--H20

Store

He1i urn

16 h r 25

Ar-47~ €12--H20

550

Ar-4"lo H2-H

650

Ar--4% H -I3 0

750

Ar-4% H2-H20

Cool

Ar-4% €I -13

Store

Heliurii

850

Ar-4%

---I3 0 2

850

Ar-4% H 2 - H , 0

850

C02-1-1,0

850

1000

Physical and A n a l y t i c a l Data

15%

2.001

0.008

10.82

Shiny black; n o fines;

nonuniform size

Part 111

Gas-Cooled Reactors

8. Diffusion Processes TRANSPORT PROPERTIES OF GASES

worsen as the m a s s difference of t h e g a s pair increases. Unfortunately, i t is not p o s s i b l e to pursue t h i s a s p e c t further, s i n c e experimental thermal conductivity d a t a are neither plentiful

Gaseous D i f f u s i o n Studies i n Noble-Gas Systems A. P. Malinauskas G a s e o u s diffusion experiments h a v e b e e n conducted with t h e gas p a i r s We-Kr, Ar-Kt, and Kr-Xe over t h e temperature range 0 to 120째C to provide additional d a t a for u s e i n a n investigation of t h e interaction c h a r a c t e r i s t i c s of noble-gas molecules. T h i s work r e p r e s e n t s t h e s e c o n d p h a s e of a s y s tematic s t u d y of t h e binary diffusion p r o c e s s in s y s t e m s involving all p o s s i b l e combinations of t h e noble g a s e s . T h e third part of t h i s r e s e a r c h , involving t h e s y s t e m s He-Ne, Ne-Ar, Ne-.Kr, and Ne-Xe, is i n progress. All t h e diffusion d a t a a v a i l a b l e concerning the s y s t e m He-Kr, Ar-Kr, and Kr-Xe a r e graphically summarized in Figs. 8.1 to 8.3, where t h e diffusion c o e f f i c i e n t D,,, a t 1 a t m p r e s s u r e , i s platted as a function of t h e a b s o l u t e temperature T. T h e s o l i d l i n e s i n t h e f i g u r e s h a v e been coils t r u c t e d using t h e u s u a l Chapman-Enskog expression for t h e diffusion coefEicient, i n which the Lennard- J o n e s (12-6) potential energy parameters presented i n T a b l e 8.1 h a v e b e e n e m ployed. T h e s e parameters yield t h e b e s t represelltation of t h e experimental d a t a ; they l i k e w i s e give favorable agreement with diffusion coefficient v a l u e s deduced from measurements of t h e composition dependence of t h e v i s c o s i t i e s of t h e COPresponding g a s mixtures. On t h e other hand, a siniilar comparison with v a l u e s obtained from t h e measured thermal c o n d u c t i v i t i e s of t h e mixtures i s not as good, and t h e d e v i a t i o n s appear to

ORNL-DWG 66-4100

'A. P. M a l i n a u s k a s ,

0.9

0.8

-. -5 N

0.7

..........

-.I ... ...

0.6

0.5 250

300

T Fig,

8.1.

350

("K)

400

E x p e r i m e n t a l Values of the D i f f u s i o n

dicient of the S y s t e m

He-Kr a t 1 atm Pressure.

CoefSolid

M. Watts, T r a n s . F a r a d a y Soc. 6 0 , 1745 (1964). A B. N. Srivastavo a n d R. Paul, P h y s i c a 28, 646 (1962). L. D u r b i n and R. K o b a y a s h i , J. Chem. P h y s . 37, 1643 (1962). K. P. S r i v a s t a v u und A. K . Barua, Ind. J. P h y s . 33, 229 (1959). l i n e : L e n n a r d - J o n e s (12-6) potential.

J. Chem. Phys. 45, 4074 (1966).

2A. P. M a l i n a u s k a s , J . Chem. Pplys. 42, 156 (1965).

'J. 0. H i r s c h f e l d e r , C. F. Curti.ss, and R. B. Bird, Molecular Theory of G a s e s and L i q u i d s , c h a p . 8, Wiley,

N e w York. 1954.

t h i s work.

ORNL O W G 6 6 - 4 8 9 9

Table

8.1.

Lcnnord-Jones

( 1 2 - 6 ) P o t e n t i a l Energy

I T Parameters Obtained ~ G O W the D i f f u s i o n Studies ~~

He-Kr

3.071

AI-Kr

3.609

121

Kr-Xe

3.923

170

58.8

nor sufficiently a c c u r a t e for other than a superficial 3nalysis. Thermal T r a n s p i r a t i o n E;.

zoo Fig. 8.2.

r ("Kl

500

Experimental V a l u e s of the Diffusion C o e f -

f i c i e n t of the S y s t e m Ar-Kr ot line:

400

300

1 o t n Pressure. Solid 1-4. Watts, Trnns.

Lennard-Jones ( 1 2 - 6 ) potential. 8LE

F a r a d a y Soc. 60, 1745 (1964).

A R. P a u l , Ind. J. P h y s . 36, 464 (1962). cI$ L. Durbin and R . Kobayashi, J. Chem. P h y s . 37, 1643 (1962). 3 K. Schafer and K. Schuhmann. Z . Elektrochem. 61, 246 (1957). Lj B. N. Srivastava and K. P . Srivastava, J . Chem. Phys. 30, 984 (1959). (1 this work.

004L 250

Fig.

8.3.

300

350

400

(OK)

Experimental V a l u e s of the Diffusion C n e f

1 atm P i e s s u r s . Solid l i n e : Lennord-Jones ( 1 2 - 6 ) potential. S H Wutt;, Trans. this work. Faraday SOC. 60, 1745 (1964). f i c i e n t of the System K r - X e a i

A . P. Malinauskas

A . Cameron4

We had demonstrated e a r l i e r that therinal transpiration d a t a may b e employed t o obtain information regardirig t h e interchange of energy a s s o c i a t e d with t r a n s l a t i o n a l and internal molecular motion by c o l l i s i o n . Expeririieiltally, t h i s e n t a i l s t h e careful measurement of s m a l l pressure drops, under s t e a d y - s t a t e conditions, which r e s d t by imposing a temperature gradient a c r o s s 3 g a s confined in a c a p i l l a r y . In t h e previous work, fourteen 0.1-nm-ID c a p i l l a r i e s had been einployed, arid the method u s e d w a s s a t i s f a c t o r y from a l l a s p e c t s e x c e p t one: 5 hr were required to obtain a single datum point. In a n attempt t o remove t h i s shoitcoming, we s o u g h t t o replace t h e c a p i l l a r i e s with a fritted glass disk. Experiments were conducted with t h e porous d i s k arrangement; although t h e time interval for a given experiment w a s reduced to 5 min, it w a s no longer p o s s i b l e e i t h e r to measure or t o control t h e temperature gradient accurately, s i n c e the u s e of t h c porotis p l a t e permitted t h e thermal conductivity of the g a s to markedly affect t h e temperature conditions. Consequently, t h e reproducibility of t h e d a t a obtained w a s q u i t e poor, and t h e method w a s therefore abandoned. In t h e meantime, a more s e n s i t i v e pressures e n s i n g d e v i c e than t h a t employed in the earlier work h a s been procured. Since t h e instrument will permit us t o employ c a p i l l a r i e s of a larger s i z e , thereby i n c r e a s i n g t h e r a t e of attainment of s t e a d y - s t a t e conditions, we are currently cons t r u c t i n g a modified version of the original c a p illary d e s i g n . ~

____

4Surnrner participant, Hanover 5 A . P. M a l i n a u s k a s ,

College.

J. Chem. P h y s . 44, 1196 (1966).

85 Gaseous D i f f u s i o n in Porous Media

R . B. E v a n s 111 A . P. Malinauskas E. A. Mason6 A generalized treatment of gas transport i n porous media h a s b e e n realized; as a r e s u l t , .it i s now p o s s i b l e to a c c o u n t for a variety of phenomena involving gas transport from a s i n g l e viewpoint h a v i n g a s o u n d t h e o r e t i c a l foundation. ‘Tle treatment h a s b e e n developed on the b a s i s of t h e “dusty-gas” model, a model in which a porous septum is d e s c r i b e d a s c o n s i s t i n g of uniformly distributed giant molecules (dust) h e l d s t a t i o n a r y in s p a c e , Although t h i s description is not a s p a l a t a b l e a s t h e more common “bundle of c a p i l l a r i e s ” c o n c e p t , i t d o e s p o s s e s s t w o d i s t i n c t a d v a n t a g e s from a mathematical standpoirlt. First, the geometrical past of the problem n e a t l y s e p a m t e s from thal part which d e a l s with t h e dynamics of t h e g a s transport. Second, the importance of gas-surface c o l l i s i o n s relative t.o g a s - g a s interactions is readily a s s e s s e d ; one merely v a r i e s tbe “mole fraction2’ of t h e d u s t . TKI other words, i t is u n n e c e s s a r y to p o s t u l a t e one mechanism for free-molecule conditions and another for hytllmdynamie transport and then a t k m p t t o reconcile t h e two in t.he transitiorl region; the validity of the dusty-gas modcl a p p l i e s throughout. Moreover, t h e r e s u l t s are l i k e w i s e a p p l i c a b l e to d e s c r i b e gas transport through c a p i l l a r i e s simply by n s u i t a b l e s u b s t i t u t i o n for geometric parameters. T h e following brief summary i n d i c a t e s t h e riumher of phenomena which h a v e b e e n d e s c r i b e d as s p e c i a l forms of t h e general case (some of t h e s e h a v e b e e n p r e s e n t e d previously). Binary Gaseous D i f f u s i o n at Uniform TemperT h i s pheriornenon is treated ature and Pressure.

a s three-component diffusion in terms of the d u s t y g a s rnod,el; t h e most notable r e s u l t is a theoretical formulation for t h e observation that t h e r a t i o of t h e fluxes of the two diffusing g a s e s is approximately inversely proportional t o t h e s q u a r e roots of their molecular w e i g h t s , not only under c o n ditions of free-molecule transport but in t h e region 6Consultant, U n i v e r s i t y o f Maryland, I n s t i t u t e for Molecular P h y s i c s . 7,-.o. A. Mason, A. P. Malinauskas, a n d R.. B. Evans TKI, a c c e p t e d for publication i n J . Chc-m. Ptiy?“

%<, B. E v a n s 111, G. M. Watson, and E. A. Mason, J. Clzern. P h y s . 35, 2076 (1961); 36, 1894 (1962); E. A. Macon, R. B. E v a n s 111, and G. M. Watson, J . Chefll. b h y s . 38, 1808 (1963); E. A . Mason and A. P. Malinausk a s , J . Chem. Pfiys. 41, 3815 (1961).

of hydrodynamic transport as well. Parenthetically, t h i s observation a p p e a r s to h a v e b e e n made first by Graham i n 1833, but h a s either become forgotton or confused with h i s work on effusion (transport into a vacuum), which w a s done about 13 y e a r s l a t e r . Isothermal Transport i n the Presence of a Prss-

s u r e Gradienb. - When only a s i n g l e gas i.s cons i d e r e d , t h e mathematical e x p r e s s i o n which r e s u l t s from a n application of t h e model r e p r e s e n t s a n analogous form of P o i s e u i l l e ’ s flow equation with v i s c o u s s l i p . However, t h v i s c o u s part a r i s e s from Stokes’ l a w , w h e r e a s t h e s l i p term is d e veloped from a c o n s i d e r a t i o n of pure g a s diffusion Moreover, t h e in a s t a t i c d u s t environment. Knudsen minimum, which h a s y e t to h e rigorously d e s c r i b e d utilizing the c a p i l l a r y c o n c e p t , is s a t isfactorily taken i n t o a c c o u n t b y considering the next-higher approximation to the diffusion coelficien t. Whether a pure g a s ox a binary gns mixture is considered, i t turns out t h a t it is p o s s i b l e to s e p a r a t e (mentally) t h e v i s c o u s flow contribution from t h a t d u e 1.0 diffusive transport; but i n the latter case the e q u a t i o n s remain coupled through t h e composition dependetice of the c h a r a c t e r i s t i c transport c o e f f i c i e n t s . Chnseyueratly, few situations c a n b e conveniently handled without r e c o u r s ~ to ~ numerical methods. ( h c of t h e s e is known as t h e Krarner-Kisterrlaker e f f e c t , wherein B p r e s s u r e gradient develops i n a c l o s e d s y s t e m b e c a u s e of d i f f u s i o n . In t h i s instarice the equation derived from t h e dusty-gas c o n c e p t a p p e a r s to be t h e f i r s t description of rlre phenomenon t h a t is a p p l i c a b l e at a l l p r e s s u r e s . nder the Combined InfluPure G a s Transport ence of Gradients o f P r e s s u r e and Temperature. T h i s phenomenon is known as thermal transpiration or t h e thermomolecular p r e s s u r e difEerence. Prior t o t h e application of the dusty-gas model, t h e e f f e c t w a s primarily investigated only b e c a u s e of i t s influence on a c c u r a t e pressure lfieasurement. As s t a t e d in the s e c t i o n “Thermal Transpiration, ’’ t h e phenomenon iiow a p p e a r s to provide a particularly s i m p l e approach to an i n tigation of i n e l a s t i c c inary G a s Transport perature and Pressure Conditions.

A l l the PKOvious items represent s p e c i a l cases of ttiis rather coiiiplex s i t u a t i o n , arid only two a s p e c t s of t h e The problem h a v e b e e n c o n s i d e r e d in d e t a i l . first of t h e s e i s the p r e s s u r e difference, a t s t e a d y s t a t e conditions, w h i c h is produced in a binary

86 g a s mixture under t h e influence of a temperature gradient, without regard for variations in composition; the resultant e x p r e s s i o n d e s c r i b e s thermal transpiration in a binary g a s mixture. The second case a l s o concerns a steady-state solution; t h e problem considered i s the relative separation produced in a binary g a s mixture a s t h e result of a temperature gradient, without regard for pressure variations. The e x p r e s s i o n derived for t h i s c a s e d e s c r i b e s t h e variation of the thermal diffusion factor with p i e s s u r e , a s one proceeds from t h e free-molecule region to t h e region of hydrodynamic transport. It i s interesting t o note t h a t i n neither of t h e s e l a s t two cases d o e s there appear t o b e a n y e x perimental d a t a with which t h e theoretical relationships may b e verified. Gas Transport Studies Related to Vented Fuel E l e m e n t s for F a s t Gas-Cooled Reactors

R . B. E v a n s I11

D. E . E r u i n s g

Tentative reference d e s i g n s for a 2500-Mw (thermal) fast-flux helium-cooled reactor c a l l for utilization of fuel pins comprising (U, Pu)O, bushings s t a c k e d i n free-standing s t a i n l e s s s t e e l cladding. Requirements for high power d e n s i t i e s demand very high fuel temperatures, close pin s p a c i n g , and minimum c l a d d i n g w a l l t h i c k n e s s . One might envision 0.38-in.-OD claddings (0.010-in. w a l l s ) containing 6-ft s e c t i o n s of 80% effective d e n s i t y fuel. Cladding temperature will be 815OC a t s t e a d y - s t a t e conditions; helium coolant pressure will b e about 1000 p s i . If, for any reason, the c o o l a n t pressure e x c e e d s t h e internal pin pressure by 200 psi a t 815OC, t h e claddings might c o l l a p s e . A means for press u r e equalization i s c l e a r l y needed. In t h e present investigation t h e possibility of using direct venting devices l o t o e n s u r e p r e s s u r e equalization is being examined under t h e realization that direct v e n t s pose s p e c i a l problems regarding f i s s i o n product release and coolant contamination.

We h a v e e l e c t e d t o i n i t i a t e our work by giving first consideration t o the r e l e a s e problenis and means for their mitigation. This approach w a s adopted to take advantage of t h e only established criterion a v a i l a b l e for s t u d i e s of t h i s type, namely, t h e maximum allowable release-to-birth ratio, R / B , of f i s s i o n products a s l e g i s l a t e d in the P B R E ” fuel s p e c i f i c a t i o n s , modified t o account for z e r o retention by f u e l a t f a s t flux reactor temperaThe reference criterion turns out t o b e tures. a c o n s t a n t S / B of 1.8 x lo-’ for a l l f i s s i o n products. Venting e f f i c i e n c i e s h a v e been left a s somewhat of a dependent variable b e c a u s e , once a s u i t a b l e venting d e v i c e h a s b e e n contrived, dimensioned, and evaluated, venting c a p a b i l i t i e s a s w e l l a s inherent limitations c a n b e determined. Under t h i s approach we need not b e concerned (for t h e time being) with rather nebulous considerations that might govern venting c r i t e r i a in t h e future, for example, “inaximum c r e d i b l e ” coolant p r e s s u r e and /or fuel-temperature e x c u r s i o n s . In summary, we s e e k s e l e c t i v e venting d e v i c e s , materials, or configurations t h a t c a n discriminate gradients in t o t a l p r e s s u r e and partial p r e s s u r e s ; thus forced-coolant flow admittances will be high when h p 4 0 , and diffusive-flow admittances will b e low when hp = 0 . Both laboratory and d e s k s t u d i e s h a v e b e e n initiated t o obtain t h e obj e c t i v e s c i t e d above.

’’

R . B. E v a n s III J . I... Rutherford R . W. PerezI3

Pyrolytic-carbon-coated (Th,U)C and (Th,lJ)O, microspheres h a v e demonstrated a d e q u a t e irradi.........

“ A . P. F r a a s et a l . , Preliminary D e s i g n of a 10 Mw(t)

Pebble Bed R e a c t o r 63(Rev.) (May 1961).

Experiment,

ORNL-CF-60-10-

“The

PBRE criterion for R I B w a s 1 x 10’-6(tl/z)1’‘,

where tl,,,,

sec, is the f i s s i o n product h a l f - l i v e s .

fuel which is 5.5 x 1 0 - 5 ( t l , 2 ) ” z .

For fair c o m p a r i s o n s

the PBRE value must therefore b e promoted to 1.8 x ’Summer participant, Carnegie I n s t i t u t e of Technology, Pittsburgh, Pa. “Alternate methods for p r e s s u r e equalization of f a s t reactor fuel e l e m e n t s a r e reviewed by F. R. McQuilkin e t a l . , G C R P S e m i a n n . Progr. R e p t . Mar. 31, 1965, p. 169, ORNL-3951. Additional d e s c r i p t i o n s and v i e w s of coll a p s e d fuel p i n s a r e p r e s e n t e d by D. R. Cuneo e t of., Ibid., pp. 179-90.

But

t h i s v a l u e t a k e s full advantage of the l o w R / R of the

(then

f1/’

lo-’

terms c a n c e l ) to a c c o u n t for a fuel R I B of

unity a s a n t i c i p a t e d for f a s t g a s r e a c t o r s .

The R I B

v a l u e s c i t e d were reported by P. E. Reagan e t al., R e a c t o r Chem. Div. Ann. Progr. R e p t . Jan. 31, 1963, O R N L 3417, p. 213. 13Consultant, t h e University of Florida, Department of Nuclear Engineering S c i e n c e s , Gainesville.

87 ation s t a b i l i t y l 4 under d e s i g n conditions of e x i s t i n g high-temperature gas-cooled reactors. However, extension of current technology t o include performance e s t i m a t e s for advanced c o n c e p t s and has required optimization of c o a t i n g d e s i g n s additional arid supporting s t u d i e s of phenomena related t o c o a t i n g failure. One mode of failure concerns s p e a r h e a d s , gaps, and fractures t h a t a r e initiated in recoil damage arid fragment-densified regions a t coating layer interfaces. R e c e n t irradiation t e s t s have ind i c a t e d , for example, t h a t premature failure o c c u r s when inner-buffet l a y e r s a r e too thin t o provide sufficient recoil-damage protection for outer containinent layers. Accordingly, our present objective is t o determine what fraction of t h e total c o a t i n g t h i c k n e s s c o n s t i t u t e s effective s t o p ping regions for recoiled f i s s i o n fragments. Studies of t h i s kind should provide supporting information fox one a s p e c t of t h e optimization a n a l y s i s m e n t iotied a b o v e , R e s u l t s obtained in t h i s investigation s t e m directly from the experiiiienta 1 determination of the penetration d i s t a n c e s of f i s s i o n fragments that have recoiled into target s p e c i m e n s from tliinlayer s o u r c e regions. These regions are formed hy placing 2 3 5 U on one surfac;e oE d e n s e pyrocarbon coupons using an electromagnstic-separator technique. l 7 T a r g e t s p e c i m e n s are placed a g a i n s t this surface, and source-target p a i r s a r e s u b j e c t e d to a thermal-neutron flux t o induce fissiori and subsequent fragment recoil. Under this configuration, fragments e n t e r the target (and source) a s nearly monoetiergetic but randomly directed beams. T h e t a r g e t s are then ground," and grinding increments are a s s a y e d by gamma counting S O t h a t integral forms of t h e distribution curves can b e constructed. Activity v a l u e s f i x s e v e r a l fragments a r e e x t r a c t e d from t h e overall count d a t a with the a i d of computer program A L P H A . The

1,. Scott, J. G. Morgan, end V. A. DeCarlo, Trans. Am. N u c I . SOC. 8 426-27 (1965). 14J.

"5. W. Prados and J . L. Scott, T r a n s . A m , N u c l . Soi. 8, 387-88 (1965); a l s o issued a s OKNL-TM-1405 (March 1965).

1 6 ~ . K. 01sen e t al., GCRP .yemiarm. Progr. li'ept. M a r . 3 1 , 1 9 6 6 , ORNL-3951, pp. 41-53. "5. Truitt, G . D. Alton, a n d C . M . Blood, A p p l . P h y s . Letters 3(9), 150-52 (1963).

"R. B. E v a n s 111, J. L. Rutherford, a n d R. B. Perez, GCRP Semiann. P r o g r . R e p t . S e p t . 3 0 , 1 9 6 5 . O R N L 3885, pp. 141-46.

"E, Schonfeld, N I I C ~Instr. . Mefhods 42, 213-18 (19tj6).

integral curves yield information concerning rec o i l d i s t a n c e s along z normal to the s o u r c e plane. They a l s o give informatibn concerning the fragment distributions f(z) a s they occur in coatings and t h e distributions f ( r ) a s they occur either in CL r s p a c e " or along z in collimated beam experirnents. T h e b a s i c range c o n c e p t is given in mjcros c o p i c terms by simple relationships between n t , t h e d e n s i t y of s c a t t e r i n g c e n t e r s i n the target; T , t h e s p e c i f i c energy loss t o target e l e c t r o n s and atoms; a i d d a , the differential c r o s s s e c t i o n for s u c h loss. T h e macroscopic range-energy [II(E) .--E ] relationship is derived from

where

is the stopping c r o s s section per s c a t t e r i n g center, and

dE/dbi = -n,

- S( E )

(3)

i s the average energy loss per unit path length. One a s s u m e s that this average loss i s B contin-

uous function and finds t h a t for electronic contributions is similar t o energy losses in c o n s t a n t deceleration p r o c e s s e s in eleineiitary mechunics. T h e theoretical problem reduces to derivatioii of relationships between atomic properties arid S ( E ) , T , and C ~ C In most treatments the range-density product is taken t o b e c o n s t a n t , as in Eq. (I.). Thus, in principle, range values for a l l target d e n s i t i e s a r e known if this product is determined for any one given target density. Implied restrictions a t e : materials in question must be homogeneous t o s a t i s f y t h e condition dn,/d'R = 8, and [it imst be the same for a l l heams. Along t h e s e li11es we note t h a t current l o c a l trends favor the u s e of very-low-density carbons ( d ".. 0.8 to 1 . 2 g/cm3) for inner coatings of fuel particles. T h e s e are in many i n s t a n c e s q u i t e porous. T h e implied restrictions on n t will obviously be violated, and t h i s feature of t h e macroscopic theory provides t h e major justification for our work.

88 A solution t o Eqs. (1 t o 3 ) , a s given by Lindhard e t aZ.,‘O is simply T ( E ) = Fe(t) - h(k,e

) = (?c”’)/(k)

which form t h e b a s i s for a recent generalized range-energy correlation reported by F r a n k . Some predicted and experimental range v a l u e s a r e presented in t h e top s e c t i o n of T a b l e 8.2. S u c c e s s f u l correlation of penetration d a t a depends heavily upon a proper s e l e c t i o n of a n r-space distribution function a s d i c t a t e d by t h e s t r u c t u r e of t h e target material under investigation. F o r uniform s t r u c t u r e s we have a s s u m e d validity of t h e normal-Laplace distribution given in F i g . 8.4. S i n c e r-space distributions ate not measured d i rectly in o u r e x p e r i n e n t s , the f(r) function must b e converted t o f ( z ) t o derive a p p l i c a b l e e q u a t i o n s . T h e connection between t h e s e functions is obtained by pretending that a l l s o u r c e points c a n

’

- A ( k , E ) . (4a)

Here t h e reduced q u a n t i t i e s E , T ( E ) , and t correspond t o t h e original v a r i a b l e s E , R ( E ) , and T. Contributions of nuclear s t o p p i n g are given a s a correction term h ( k , ~t )o be applied t o t h e electronic range .,(E). T h e k i s sort of a n integration constant involving the masses and c h a n g e s of fragment and target a t o m s . Lindhard p r e s e n t s v a l u e s of h ( k , t ) in graphical....... form .as well as theoretical fluctuation v a l u e s A [ p (E)]’ which re-l a t e t o the straggling f a c t o r s a . T h e s e f a c t o r s a i e negligibly s m a l l compared with those introduced by instrumentation. A t f i s s i o n recoil energ i e s , 2 1 A ( k , E ) v a l u e s a r e s u c h that p ( t > * C t 2 I 3and K ( E ) * C ’ E 2 I 3 ,

‘‘5. Lindhard, M. Scharff, a n d H. E. Schiott, K g l . D a n s k e Videnskab. S e l s k a b , Mat.-Phys. Medd. 33(14), 1 (1963).

(4b)

”5. M. Alexander a n d M. F. G a z d i k , P h y s . Rev. 120, 874-86 (1960). ‘=P. W. F r a n k , B e t t l s T e c h n i c a l Review, WAPD-BT-30 (April 1964), pp. 47-53.

where C and C’are arbitrary c o n s t a n t s . T h i s is merely Rutherford’s equation, modified f o r m s of

Table

8.2. Comparison of E x p e r i m e n t a l a n d P r e d i c t e d R e c o i l Ranger; A p p l i c a b l e to l d e o l and Porous Carbon M a t r i c e s ,-

Target Material

Iargei Density

K ‘ d , Range-Density Product (mg/cm‘) .................. .I4’xe(cea) 1 4 0 ~ e ( ~ a a ) lo3~Ua ”~(zr”)

:g/c*n3)

Number of Experiments

Ideal T a r g e t M a t e r i a l s Predictedb for carbons D e n s e pyrolytic carbon

2.19,

2.21

2.24

2.91

2.93

2.54

2.50

2.94

3.01

2.63

2.70

3.54

3.59

(massive d e p o s i t ) Predicted‘ for carbons

Parous T a r g e t M a t e r i a l s

Isotropic pyrolytic

1.49

2.47

2.42

2.89

2.96

1.865

2.52

3.09

3.16

2.94

3.33

3.41

carbon (disk c o a t i n g ) Impregnated graphite (C GR3

Very porous graphite (C-18) .

1.63, ........

%Species counted.

bBased on Frank’s correlation and t a b u l a t e d e n e r g i e s (ref. 22). ‘Based on Lindhard’s correlation (ref. 20) u s i n g e n c r g i e s a s plotted by Alexander and G a s d i k (ref. 21).

89 b e c o l l e c t e d at a s i n g l e point corresponding to t h e origin of a s p h e r i c a l coordinate s y s t e m , where B is t h e polar a n g l e measured from z, r = is the radius vector, &) is a n element of s o l i d a n g l e , and p - 2 n r s i n 8. T h u s

4 7 -

An a d d i t i o n a l integration of f(z) over z is required t o obtain the result sought, namely,

F.R.

J/gf(z) dz = 1

zâ&#x20AC;&#x2122;/R

-t

f,(z, u / R )

. (6)

This approximate r e l a t i o n s h i p g i v e s F.R., the fraction of activity remaining after grinding to a pene t r a t i o n z, a s a function of z in homogeneous

(uniform) targets. T h e c u r v e is e s s e n t i a l l y a straight line with a small t a i l accounted for by the fc t e r m that reflects effects of straggling. T h e s e a r e greatly a t t e n u a t e d by the integration and c a n , in theory, b e s a f e l y neglected. Most of the s t r a g g l i n g shown in our r e s u l t s i s the result of experimental imperfections. Experimental data that follow the normal-distribution correlations appear on t h e left s i d e of F i g . 8.5. An equation giving a c l o s e approximation to f(z) in uniform particle c o a t i n g s d e v e l o p s when the point s o u r c e pertaining to Eq. (5) is extended as a n infinite line s o u r c e positioned along t h e negative z a x i s . T h i s g i v e s rise t o a n a d d i t i o n a l integration and e q u a t i o n s that a r c one degree higher with r e s p e c t to z / R than Eqs. (5) and (6). It turns out t h a t the f(z) for the line s o u r c e is identical to t h e right s i d e of the integral function OR NL- DWG EE-12373R

Fig. 8.4.

0.4

0.8

4.2

r/H

4.6

2.0

2.4

P l o t s of the Norrnolized D i s t r i b u t i o n F u n c t i o n s U s e d to Correlate R e c o i l D a t a .

2.8

T h e s e â&#x20AC;&#x153;r-spaceâ&#x20AC;?

tributions correspond t o concentration vs penetration curves for p e r f e c t l y c o l l i m a t e d beam experiments.

dis-

I n the pres-

ent i n v e s t i g a t i o n beams a r e not collimated, but the observed stopping behavior does r e l a t e t o the curves shownobove.

90 ORNL-DVG

F. R.

66-42374R

0.9

, E N

4 +

0.8

$ 0.7

(I)

w n

0.6

z L-

5 0.5 4

lL E J

2 LL

0.4

0.3 0.2

0.4

Fig. 8.5. a r e referred to

0.4

z/R

4.4

4.2

P e n e t r o t i o n D a t a for “ L i g h t

and Heavy”

F.R.

10 /R

Fraginentr in D e n s e and Porous Pyrocorbons.

R v a l u e s peculiar t o g i v e n experiments and s p e c i e s .

carbon d a t a w a s p l o t t e d on the b a s i s of

Penetrations

The curve t h a t passes through t h e porous pyro-

z/R values a s g i v e n b y Eq. (7).

for a point s o u r c e [Eq. (5)] multiplied by a factor slightly l e s s than 2. T h i s factor is required t o normalize the new distribution curve. Therefore the experimental plot of Fig. 8.4 is a l s o a plot of t h e distribution a s it would occur in a c o a t i n g , diffusion and densification neglected. For the c a s e of porous carbons and graphites, w e find that Eq. (6) d o e s not give a good fit of experimental d a t a plots. Obviously, the normal r-space distribution d o e s not hold, b e c a u s e wcllcollimated beams would “see” density variations in porous t a r g e t s . T h e probability for stopping f(r) dr about a mean R would not b e symmetrical, a s it i s for a normal distribution. In terms of bulk volume most of the matrices of our porous t a r g e t s are composed of s o l i d s (open porosities range from 10 t o 20 vol 76)) and the most probable range rm should correspond t o a “low” value which might b e predicted using a “high” porositycorrected d e n s i t y . T h u s , on t h e r-space distribution, rm should r e s i d e t o t h e left of t h e average ( r ) or K , while portions of the curve t o the right of R should “ t a i l o u t ” s l o w l y to a c c o u n t for fragments that encountered nonstopping eegions (pores).

Several s k e w e d distribution functions were t e s t e d for applicability t o t h i s problem; t h e most s u c c e s s f u l candidate a p p e a r s t o b e that shown in Fig. 8.4 for poroiis t a r g e t s . T h i s function is simply Maxwell’s s p e e d distribution for g a s e s with v/v, replaced by r/ruz. When t h e Maxwellian distribution i s s u b j e c t e d t o the same manipiilations employed to d e v e l o p Eq. (6), one finds that

e x a c t l y . As before, the F . H . function a l s o repr e s e n t s the f ( z ) distribution in c o a t i n g s . T y p i c a l porous target data are shown on t h e right s i d e of Fig. 8.5. T h e s o l i d l i n e represents a plot of Eq. (7), and the dotted line r e p r e s e n t s a plot of Eq. (6), which clearly d o e s not apply. Average range v a l u e s for porous targets appear in T a b l e 8 . 2 . Values for two of t h e porous mat e r i a l s show good agreement with ideal v a l u e s . Range v a l u e s for the very porous graphite a r e somewhat high; however, a large fraction of t h e pores in t h i s material were several. times gieater

91 than K. Our original intentions were t o u s e t h e s e data t o e s t a b l i s h a n upper l i m i t on pore sizes, and in this r e s p e c t t h e experiments failed b e c a u s e Eq. (7) w a s followed (except a t large z / R ) and the ranges were only s l i g h t l y greater than the ideal values. In summary, we h a v e found t h a t e f f e c t s of porosity and variations i n nr c a n b e taken into a c count through a proper s e l e c t i o n of t h e primitive r-space distribution function. When this is a c -

complished, t h e mean range for porous targets should be approximately t h e s a m e a s t h o s e observed or predicted for homogeneous (ideal) materials. Specific d e t a i l s concerning porosity chara c t e r i s t i c s a r e of little importance, if the pores a r e not too l a r g e or well connected, b e c a u s e the range correlation d e p e n d s only on the bulk dens i t y and/or total porosity. F i n a l l y , w e note that s t r a g g l i n g factors, a s given by the theory, are of l i t t l e c o n s e q u e n c e with r e s p e c t to t h e present investigation.

hit

ctiv

I,. G. Ovcrholser in.-ID) were machined from A T J graphite s t o c k and various l e n g t h s u s e d i n t h e oxidation s t u d i e s . 'These dimensions approximated t h o s e of graphite s p e c i m e n s a v a i l a b l e froin irradiation s t u d i e s . Graphite s l e e v e s (2 in. long) were impregnated with barium using '33BaCI and Ba(OH), solution; drying t h e impregnated specimen a t %125"C, and finally heat-treating i n dry helium a t 800 or 1000째C for various periods of time. Sectioning and counti n g of impregnated s p e c i m e n s a r e incomplete, but preliminary measurements s u g g e s t that t h e treated s p e c i m e n s contained - 0 . 1 wt % of barium and that t h e barium w a s not uniformly distributed through the graphite. One specimen of graphite previously irradiated in loop 1, experiment 14 (ref. 2) w a s oxidized and examined for transport of f i s s i o n proaucts. Reaction r a t e s measured for various graphite s p e c i m e n s a r e given in T a b l e 9.1. Average r a t e s determined from weight c h a n g e s are e s p i e s s e d on a weight b a s i s , but e s s e n t i a l l y t h e s a m e relative r a t e s would b e obtained if geometric s u r f a c e a r e a s \iieie employed i n s t e a d of weights b e c a u s e of the geometry of the specimensr,. A superficial comparison of t h e r a t e s obtained for t h e untreated s p e c i m e n s of various lengths suggests t h a t t h e r a t e s i n c r e a s e d with d e c r e a s i n g s l e e v e lengths. T h e reaction r a t e s i n c r e a s e d with increasing burnoff, and any c r i t i c a l comparison of reaction r a t e s must take t h i s effect into account. T h e length effect a p p e a r s to b e sirla11 in t h o s e cases where burnoffs are comparable. Reaction r a t e s given for the s p e c i m e n s impregnated with barium show that t h e steam-graphite reaction w a s d e f initely c a t a l y z c d . D a t a are too fragmentary to i n d i c a t e whether or not length of t h e specimen had a n y effect on reaction r a t e s . Data given for the one previously irradiated graphite speeiliien

QXlDATION OF GRAPHITE SLEEVES BY S T E M C. M. Blood

G. M. Hebert

L e a k a g e of steam into t h e coolant circuit of an HTGK having coated fuel p a r t i c l e s and graphite structural elements i n t h e c o r e could result in damage to t h e fuel c o a t i n g s and graphite components due to e x t e n s i v e oxidation if appreciable partial p r e s s u r e s of steam were present during t h e period in which t h e c o r e components were a t high temperatures. At t h i s time, s u c h parameters a s partial pressure of s t e a m and temperature of t h e various core components under a c c i d e n t conditions cannot be p r e c i s e l y defined. Consequently the steam-graphite reaction must b e examined experiinentally using fairly wide r a n g e s of tern.peratures and partial p r e s s u r e s of steam i n an attempt t o cover t h e abnormal conditions which may prevail. Some fission products c a t a l y z e t h e oxidation of graphite, and if s u c h products have moved from the fuel p a r t i c l e to t h e a d j a c e n t graphite abnormal reaction r a t e s may b e e x p e c t e d . T h e reaction a l s o may b e mass transport controlled a t very high reaction r a t e s resulting from e x c e s s i v e l y high temperatures or strong c a t a l y s i s a t lower temperatures. T h e oxidation of ATJ graphite s p h e r e s by s t e a m w a s studied previously. More recently, A"I'Q graphite s l e e v e s have b e e n oxidized a t 1000째C using a helium-steam mixture having a partial p r e s s u r e of "250 torrs and a total pressure of 1 atm. Mullite reaction t u b e s and quartz deposition t u b e s used in t h e s e s t u d i e s have b e e n replaced recently with alumina tubes, and s t u d i e s now are being performed i n t h e temperature range of 1100 to 1500째C. Graphite s l e e v e s ( 15,16-in.-OD, 1' 6 -

'J. L. Rutherford, J . P. R l a k e l e y , and L. G. Overh o l s e r , Oxidation of U n f u e l e d and Fueled Graphite Spheres b y Steam. ORNL-3947 (May 1966).

'A. W. L o n g e s t e t a ] . , GCH Program Semiann. Progr. K e p t . M a r . 31, 1 9 6 6 , ORNi-3951, pp. 56-64.

93 T a b l e 9.1. R e a c t i v i t y of A T J Graphite S l e e v e s with Steam a t 1OOO'C

( P I I , o = 250 torrs) Length

Specimen Designation

(in.)

Flow

Rates

Reaction

Initial

Time

Weight

!hr)

(R)

( c m 3 / m i n , STPj

Burnoff

(wt

Reaction

Surface Area' (m"d

Kateb (mi: g - - l hr-l)

Original

Final

11-H

0.5

900

3.3

3.931

27.4

0.16

8.2

18 -I3

0.5

900

3.4

3.952

33.4

116

0.15

9.9

0.5

900

3.4

4.140

50.6

2 00

0.09

0.5

900

1.1

3.798

32.9

365

18-A

900

3.2

7.888

19.6

0.15

7.8

11-A

900

3.3

7.791

21.6

0.16

7.2

U N L - I - E X P 14-Ad

900

3.3

8.427

24.8

0.09

13.5

A TJ-3-CY L -3.4

900

1.1

8.290

3.1

0.14

2.6

ATJ-3-CYL-2-4

900

2.1

8.530

8.2

0.13

5.2

ATJ-2-CYL-GA'

900

1.2

7.412

40.9

420

0.17

8.5

400

3.4

14.912

14.1

400

2.7

15.608

9.2

900

3.7

15.2 1 1

13.0

0.15

7.3

IR-GI-2R

1.6

900

3.3

12.424

13.4

0.18

1.4

ATJ-2-CYL-8'

900

2.1

15.330

39.8

240

0.16

U N L - 1- E X P 14-Ed ATJ-2-CYLr9B

a F l o w rate given for h e l i u m . 'Average r e a c t i o n r a t e b a s e d on average burnoff.

'BET s u r f a c e a r e a obtained with nitrogen. dSleeve from ATJ g r a p h i t e s t o c k used i n l o o p 1, experiment 14.

@ N o t determined. 'Impregnated with b a r i u m .

'ATJ g r a p h i t e s l e e v e from loop 1, experiment 14 following irradiation.

from loop 1, experiment 14 (ref. 2) i n d i c a t e that neither t h e prior irradiation nor t h e p r e s e n c e of s m a l l amounts of f i s s i o n products h a d any significant effect on t h e reaction rate. Surface a r e a d a t a included i n T a b l e 9.1 indicate, as would be expected, that t h e reaction rates of t h e unimpregnated s l e e v e s i n c r e a s e d , i n general, with i n c r e a s i n g s u r f a c e a r e a although no quaritit a t i v e relationship is evident. Limited d a t a availa b l e for t h e impregnated s l e e v e s s u g g e s t t h a t a different relationship between reaction rate and s u r f a c e area development prevailed in t h e p r e s e n c e of barium. T h e low v a l u e found for t h e s u r f a c e a r e a of t h e o n e irradiated graphite specimen after

oxidation may or may not b e significant; additional d a t a from other irradiated s p e c i m c n s a r e needed t o r e s o l v e t h i s question. T h e s t u d i e s are continuing with e m p h a s i s b e i n g placed on the e f f e c t of higher temperatures (1100 to 1500째C) o n t h e steam-graphite s y s l e m .

TRANSPORT

OF FlSSlON PRODUCTS

c. M. Blood

Quartz d e p o s i t i o n t u b e s w e r e u s e d i n t h e runs in which t h e barium-impregnated and t h e previously irradiated graphite s l e e v e s were oxidized by

94 steam, a s well a s during t h e p i i o i heat treatment of t h e impregnated s l e e v e s i n dry helium. T h e s e t u b e s were utilized to determine any movement of barium downstream from t h e impregnated s p e c imens i n wet or dry helium and (in t h e case of previously irradiated graphite specimens) t o capture a n y fission products transported by wet helium. A number of t h e deposition t u b e s have been s e c t i o n e d by c u t t i n g into 1.5-cm lengths, and t h e gamma activity due t o '3313a h a s been measured in e a c h s e c t i o n . Studies using graphite s l e e v e s impregnated with 133Ba and subsequently heat-treated a t 800 or 1000째C employing a flow of 330 cm3/min (STP) of dry helium showed that very small quantities

of '3313a deposited o n t h e deposition l u b e s . Even smaller q u a n t i t i e s of transported 33Ba were found o n t h e deposition t u b e s froin runs i n which heattreated impregnated graphite s p e c i m e n s were oxidized b y steam-helium mixtures 1900 c m 3/1~1in (STP) of helium] a t 1000째C. T h e d a t a s u g g e s t that barium i s less readily transported by wet helium than by dry helium. T h e fact t h a t a l l t h e impregnated graphite Specimens had received a heat treatment in dry helium prior to oxidation complic a t e s t h e comparison, however, because there i s evidence that barium i s fixed in graphite t o s o m e extent by t h e prior h e a t treatment. T h e flow r a t e of t h e dry helium during t h e h e a t treatment a t 1000째C appears to have had an important effect

O R N L - D W G 67-539

DIS r A N C E (cm) Fig.

9.1.

Distribution of 1 3 3 B a A c t i v i t y as a F u n c t i o n of D i s t a n c e (Temperature) Along the Deposition T u b a .

95 o n t h e movement of barium. T h e o n e run made a t 975OC using a flow rate of 930 cm3/min (STP) of dry helium showed a much larger transport of l3'[-3a than t h o s e runs made a t t h e lower flow r a t e Counting d a t a obtained of 330 cm3/min (STP). from t h e s e c t i o n e d d e p o s i t i o n t u b e u s e d i n the run a t t h e higher flow r a t e of dry helium a r e given i n Fig. 9.1. T h e marked temperature dependence of t h e ''%a deposition s u g g e s t s t h a t condensation oE some s p e c i e s occurred over a relatively short length of t h e deposition tube. At t h i s s t a g e , however, t h e transported s p e c i e s h a s not b e e n identified, and t h e a v a i l a b l e d a t a d o not permit an a c c u r a t e determination of t h e c o n d e n s a t i o n temperature or h e a t of sublimation. A gamma s c a n of t h e t u b e did not provide a better profile than that obtained by sectioning. A smaller temperature gradient and improved s e c t i o n i n g or s c a n n i n g t e c h n i q u e s a r e required to provide t h e m o r 6 p r e c i s e d a t a needed for further s t u d y of t h e transported mat erial. Sectioning and counting of t h e deposition tube u s e d in t h e tun i n which irradiated graphite from

loop 1, experiment 14 w a s oxidized b y s t e a m (Table 9.1) revealed that appreciable a c t i v i t y had b e e n transported downstream by t h e wet helium. T h e deposition profile is given i n Fig. 9.2, in which t h e total gamma activity is shown as a function of d i s t a n c e (temperature) along t h e deposition tube. T h e t w o maxima i n d i c a t e that a t l e a s t two radioactive s p e c i e s had b e e n transported b y t h e wet helium. Further examination of the s e c t i o n s by m e a n s of a gamma spectrometer gave t h e d a t a included i n F i g . 9.3. It was p o s s i b l e t o 1 3 4 C s , and s e p a r a t e t h e a c t i v i t i e s d u e to "'Ag, 137c s. Silver-110 w a s produced from structural m a t e r i a l s which were u s e d in t h e irradiation experiment and which subsequently migrated to t h e graphite. L o w l e v e l s of a c t i v i t y from other nuc l i d e s a r e probably masked by s i l v e r and c e s i u m . Experimental difficulties similar t o t h o s e indicated for 133Batransport preclude a n y rigorous a n a l y s e s 134 of d a t a obtained for ""Ag, Cs, and '."Cs transport a t t h i s time.

ORNL-DWG 67-540

-x

" 4

C E m 3 c c 3

- 2 >

t z

i = 1 u 4

F i g . 9.2.

30 35 40 DISTANCE (cm)

D i s t r i b u t i o n of Gamma R a d i o a c t i v i t y a s a F u n c t i o n of D i s t a n c e (Ternperoture) Along the D e p o s i t i o n T u b e .

96 ORNL-DWG

-7

67-541

TOTAL ACTIVITY

'37cs

"OAg

0 '34cs

DISTANCE ( c n ) Fig.

9.3.

Spectra of Specific Gamlnu R a d i o a c t i v i t i e s as n Function of D i s t a n c e Along the D e p o s i t i o n Tube.

OXIDATl6N OF COATED FUEL PAWTlCLES BY WATER VAPOR J. E. Baker T h e pyrolytic-carbon coating on thc f u e l particle is expected t o retain g a s e o n s f i s s i o n products until t h e c o a t i n g f a i l s ; nonvolatile f i s s i o n products may diffuse slowly into t h e c o a t i n g during pro-

longed u s e a t high temperatures. If l e a k a g e of water vapor into t h e reactor o c c u r s , subsequent oxidation of t h e c o a t i n g on t h e fuel particle may c a u s e failure of t h e c o a t i n g and r e l e a s e of g a s e o u s f i s s i o n products. The nonvolatile fission products may b e transported by the coolant and deposited on various s u r f a c e s within t h e reactor following failure of t h e coating.

97 E k l i e r s t u d i e s 3 , 4 of t h e oxidation of pyrolyticcarbon-coated fuel p a r t i c l e s by water vapor were perEormed a t temperatures of 1000째C or less and utilized partial p r e s s u r e s of water vapor ranging from 4 5 t o 560 torrs. T h e e f f e c t s of higher t e m peratures and lower concentrations of water vapor h a v e been examined in more recent s t u d i e s . R a t e s of reaction of pyrolytic-carbon c o a t i n g s present on unirradiated fuel p a r t i c l e s were determined a t temperatures of 1100 to 1400째C. Heliumwaler-vapor mixtures containing 500 to 1000 ppm (parts per million by volume) of water vapor aid Toble

Cuatod Fuel

having a total p r e s s u r e of 1 atm were used in a single-pass system. Reaction r a t e s were obtained from weight c h a n g e s given by a continuously re-

3 C . M. Blood and L. Ci. Overholscr, G C R ProQram Semiann. Progr. K e p t . Sept. 30, 1965, ORNL,-3885, pp. 12.5-3OS 4C. M. Blood and I,. G. (heuholser, C o m p a t i b i l i t y of Pyrolytic-Carbon Coated F u e l P a r t i c l e s with Water Vapor, ORNL-4014 (November 1966). 5

J,. E. Baker and L. G. Overholser, G C R Program S m r a n n . Progr. R e p t . S e p t 30, 1966, ORNL-4036 (in press j.

9 . 2 . R a t e s o f R e n c t i o n of P y r o l y t i c - C a r b o n - C o a t e d Fuel P a r t i c l e s witk

Temperature

ParticlesB

Water Vapor Concentration (ppm)

Water Vopor

Exposure

Percent of

Reaction

Coating

'low Rate (cm3/min, STP)

Time

Coating

Rateh

Failure"

(hr)

Oxidized

(mg g-'

lir'.')

(%)

1100

1000

2 00

1200

1000

2 00

1300

1000

2 00

1400

1000

200

1100

1000

200

1.7

0.5

0.2

1200

1000

200

3.6

1.5

0.2

1300

zoo0

200

5.6

0.1

1300

1000

400

7.4

0.1

1300

500

400

4.2

0.1

1400

I000

200

Psutropic VI1

1300

1000

400

8.7

1200

1000

200

4.7

1300

1000

400

1200

1000

2 00

500

200

1000

2 00

19 38

Isotropic V'

Isotropic VI

Granular IV

OK .f,88' OR-689'

1200 1200

8.3

5.0

8.1

32 1.6

51 72

6.7

4.4

8.4

1200

1000

200

YZ--135

1200

1000

200

YZ-ISd

1200

1000

200

YZ-134' f

~ ~ ~ . . . . . ~ ~ ~ ~ ~ ~ ~

a l ~ O - m gsample used in a l l c a s e s . bReac:tion r a t e b a s e d on weight of pyrolytic-carbon coating; r a t e s given for less than 5% burnuff. "Calculated from quantity of uranium (thorium) in a c i d leach s o l u t i o n and total quantity of uranium (thorilurn) originally present i n 100 m g of c o a t e d f u e l p a r t i c l e s . 'Supplied

b y General Atomic Division, General Dynamics Corp.

eNot available. %upplied b y Metals and Ceramics Division, Oak Ridge N a t i o n a l Laboratory.

98 cording semimicro b a l a n c e and from a n a l y s e s of effluent g a s e s performed by a s e n s i t i v e gas chromatograph. T h e extent of c o a t i n g failures w a s determined by microscopic examination and acid l e a c h of t h e oxidized c o a t e d fuel particles. Experiments performed in mullite reaction tubes during t h e early part of t h e s e s t u d i e s gave r e s u l t s which were so erratic that i t w a s impossible t o determine t h e effect of temperature and water vapor concentration o n t h e reaction r a t e s . In virtually a l l c a s e s , t h e observed reaction r a t e s d e c r e a s e d with time, and i n s o m e i n s t a n c e s the final r a t e s were a n order of magnitude lower than the i n i t i a l rates. C o n s i s t e n t d a t a obtained after replacing t h e mullite t u b e with an alumina t u b e i n d i c a t e that mullite w a s responsible for t h e e r r a t i c r e s u l t s . Gearey and Littlewood a l s o observed a d e c r e a s e i n reaction r a t e with time and attributed i t to c a t a l y s i s of t h e steam-graphite reaction by s i l i c a from t h e mullite tube. Reaction r a t e s obtained for various b a t c h e s of coated fuel p a r t i c l e s using a n alumina reaction tube are given in T a b l e 9.2. The most interesting feature of t h e s e d a t a i s the l a r g e variation in reaction r a t e s found for t h e different b a t c h e s .

%. G e a r e y a n d

K. Littlewood, N a t u r e 206, 395 (1965).

Isotropic VI and VI1 p a r t i c l e s , for example, were l e s s reactive than Isotropic V p a r t i c l e s . The lower c o a t i n g d e n s i t y (1.55 compared to 2.00 g/cm3 for Isotropic VI> of Isotropic v p a r t i c l e s may be responsible for t h e higher reaction r a t e s . Some of t h e YZ and OR b a t c h e s of particles, however, have properties (including d e n s i t y ) very similar t o those of Isotropic VI p a r t i c l e s but were considerably inore reactive. T h e long exposure t i m e s combined with relatively high reaction r a t e s resulted i n oxidation of a large portion of t h e c o a t i n g s present on a number of b a t c h e s of particles. In view of t h i s , it i s not surprising t h a t s e v e r e darnago and high percentages of failures occurred. Microscopic examination suggests t h a t a pitting attack followed by cracking of t h e c o a t i n g s occurred a t a l l temperatures. Conditions were more favorable for Isotropic vi p a r t i c l e s b e c a u s e of lower reaction r a t e s and l e s s burnoff of t h e c o a t i n g s . T h e s e and other d a t a i n d i c a t e that --lo wt % of t h e c o a t i n g s may b e removed before failure o c c u r s with Isotropic V1 particles. Subsequent s t u d i e s , i n which failures will b e d e t e c t e d by bursts of activity from irradiated materials, will u t i l i z e higher partial p r e s s u r e s of water vapor t o reduce failure time, particularly when oxidizing t h e iiiore resistant t y p e s of c o a t i n g s .

10- Irradiation Sehavior of High-Temperature Fuel Materials

J . G. Morgan

0. Sisman

IRRADIATION EFFECTS ON PYROLYTICCAR BON-COATE D FUEL PARTIC L ES P. E. Reagax J . 6.Morgan J . W. Gooch M. F. Osborne M. T. Morgan We are studying t h e irradiation effects on c o a t e d fuel p a r t i c l e s by measuring the fission-gas release r a t e s during irradiation at high temperatures, and by postirradiation exaniination to determine what damage w a s done. T h e s e s t u d i e s a r e b e i n g performed in cooperation with t h e groups who a r e developing the c o a t i n g s for fuel p a r t i c l e s at ORNL, General Atomic, arid the Carbon Products Ilivision of IJnion Carbide Corporation. T h e integrity of production-run coated p a r t i c l e s for the AVR reactor w a s studied during a long-term t e s t . The e f f e c t i v e n e s s of s i l i c o n carbide barrier to s o l i d f i s s i o n product release is being s t u d i e d , and the e f f e c t i v e n e s s of a g a s gap in retarding s o l i d f i s s i o n product r e l e a s e is also being inv e s t i ga ted . Pyrolytic-carbon-coated thorium-uranium (4.59 to 1) carbide particles, prepared commercially for fuel elements for the pebble-bed gas-cooled German AVR reactor, were irradiated t o 10 a t . % heavy-metal burnup a t 1300°C.’ T h e s e w e r e a blend of s e v e r a l b a t c h e s of duplex-coated part i c l e s t h a t were representative of t h e productionrun c o a t e d particles. T h e fractional fission-gas release for 88Kr w a s 5 x 10-” a t the beginning of the t e s t and i n c r e a s e d with burnup t o 4 A lo-’. N o bursts of f i s s i o n g a s were r e l e a s e d during t h e t e s t , and no broken coatings w e r e found on postirradiation examination. Metallographic examination revealed s o m e damage t o the inner coating, but nothing t h a t indicated potential failure of the c o a t e d particles.

’

Pyrolytic carbon coatings on fuel particles will contain e s s e n t i a l l y a l l of the f i s s i o n g a s e s , but a t e l e v a t e d temperatures some of the s o l i d f i s s i o n products (notably Sr, Ba, and C s ) will diffuse through the coating. To reduce the migration of fission s o l i d s , a s i l i c o n carbide barrier layer may be deposited between layers of pyrolytic carbon. One experiment (capsule AS)-7) contairii n g thorium-uranium carbide--coated particles of this type (batch GA-327) w a s irradiated a t 1300’G for 1800 hr. T h e fission-gas r e l e a s e w a s low (the R / R for *%r was in the IO--* range), and postirradiation examination a t 30x showed no damaged coatings. Postirradiation metallography and f i s s i o n s o l i d a n a l y s i s a r e not complete, but preliminary r e s u l t s on postirradiation h e a t i n g experiments have indicated very low r e l e a s e of t h e s o l i d f i s s i o n products a t temperatures up to

2 000°C.

One irradiation c a p s u l e assembly ( A M ) , after being irradiated for 1100 hr a t 1500°C, w a s examined for t h e location of the principal s o l i d f i s s i o n products. In t h i s experiment the graphite fuel particle holder w a s i s o l a t e d from a graphite s h e l l by an annular g a s gap as shown in Fig. 10.1. Seven components of the assembly, including the fuel particles, were e i t h e r a c i d leached or d i s s o l v e d for recovery of ‘%r, ”Zr, ls7Cs, 1

M . N. Burkett, W. P. Eatherly, and W. 0. Harms, “Fueled-Graphite E l e m e n t s for the German Pebble-Red R e a c t o r (AVR),” paper presented at the 196b AIME Nuclear Metallurgy Symposium on Nigh Temperature 1966 (to bc Nuclear Fuels, Delarati, Wis., O r t . 3-5, published).

‘R. A. Reuther, N u c l . Scz. Eng. 20(2), 219 (1964). 3P. E. Reagan, “ F i s s i o n - G a s R e l e a s e and Irradiation Damage to AVR P y r o l y t i c Carbon Coated ThoriumUranium Carbide P a r t i c l e s ” (in press).

100 and 1 4 4 C e . Some data were obtained for 14'E3a, but t h e d e c a y time w a s too long for c o n c l u s i v e of t h e r e s u l t s . No appreciable fractions zirconium and cerium were found o u t s i d e the fuel. About 5% of t h e cesium had e s c a p e d from the fuel and graphite holder and had c o n d e n s e d on t h e relatively c o l d metal s u r f a c e s of the c a p s u l e . Strontium appeared t o b e considerably more mobile; more than 50% of the 89Sr had e s c a p e d the fuel and w a s found in significant fractions (>1%) in the graphite holder and s h e l l and on t h e metal c a p s u l e . With t h e exception of some 2% of the 1 3 7 C s found in the lead tube, n o significant fractions of any of t h e fission products were found o u t s i d e the irradiation c a p s u l e . T h i s is t h e first of a series of experiments t o study the r e l e a s e of s o l i d fission products during irradiation. Future

ORNL-DWG 66-4CGO

FILTER HOUSING = i L r b K THIMBLE 2S AI UMINlJM DERS AIRPORE

COOLING COIL, 12 TURNS STAINLESS STEEL TUBE 32rnmOD

ERMOCOUPLE HOUSING AND H e I N L E T

CAPSULE CA

THEYMOCOUPLE SHEATH RHEhlUM FOIL/

I r J c o v r i CAPSU E

s t u d i e s in t h i s series will include a n improved filter design and a n a l y s i s for other f i s s i o n products, e s p e c i a l l y 4 0 B a .

IN-PILE TESTS OF A ha D E L fQ PREDICT THE P E R F O R M A N C E O F C O A T E D F U E L PARTICLES

I-'. E. Reagan

E. I,. Long, J r .

J . G. Morgan J. W. Gooch

A mathematical model that will predict t h e conditions under which a pyrolytic-carbon-coatcd particle will fail h a s been formulated by P r a d o s and S ~ o t t . T~ h i s model t a k e s into consideration the combined e f f e c t s of fuel s w e l l i n g and fissiong a s p r e s s u r e from fuel buinup, and f a s t neutron damage t o t h e coating. T o t e s t t h e model, w e irradiated a c a p s u l e containing about 4000 coated p a r t i c l e s with structural c h a r a c t e r i s t i c s for which t h e model w a s readily applicable. T h e s e were sol-gel UO particles, coated with a high-density 2 laminar pyrolytic carbon inner c o a t i n g and a high-density isotropic carbon outer coating. T h e a v e r a g e f u e l particle diameter w a s 202 p, and t h e a v e r a g e c o a t i n g t h i c k n e s s w a s 1 2 3 p" T h e s e pat-t i c l e s (designated OR-YZ66) w e r e irradiated at 14OOOC in t h e B9 facility. After 1209 hr (15 a t . % uranium burnup), the particles began t o r e l e a s e b u r s t s of f i s s i o n g a s a t irregular intervals. T h e b u r s t s continued, and a t the end of the t e s t (23% burnup) we had observed 197 b u r s t s . Postirradiation examination of the c o a t e d p a r t i c l e s showed t h a t about 5 t o 10% of t h e c o a t i n g s had indeed broken and in many cases w e r e completely s e p arated from t h e uranium oxide p a r t i c l e s , a s shown in Fig. 10.2. Metallographic examinations a r e in progress and postirradiation burnup determinations a r e being made t o check t h e values obtained by argon activation during irradiation. T h e mathematical iilodel bad predicted c o a t i n g failure a t 14.2 a t . % burnup.' Since t h e f i r s t failure occurred a t 15% burnup and a rather small fraction of t h e coated particles had failed even a t 23% burnup, i t appears that t h e calculation gave ~

HOLDER CAP

OXIDE WOOL COATED PARTICLES

3C"OSITION PLATE THERMOCOUPLES ( 2 )

THERM0COU"LES ( 3 1

- %ELL THERMOCOUPLES ( 4 ) DEPOSITION PLATES 2 HA1 VES HOLDER PIN

4 J . W. P r a d o s and J . L. Scott, Nuc2. A p p l . 2 ( 8 ) , 402-14 (1966).

DEPOSITION E N D P L A TOP A N D BOTTOM P AND B O T T O M

F i g . 10.1.

Gas-Gap F i s s i o n Solid Capsule.

5D. M. EIewette e t a t . , Preparafion a n d Preirwdiation

D a t a for P y r o l y t i c Carbon C o a t e d Sol-Gel Uranium Oxide

P a r t i c l e s for E T K X-Basket 2 Irradiation Experiment, ORNL-TM report (in preparation).

1.0I a 1ow value. If the postirradiation burnup v a l u e proves t h i s to b e true, the c o n s t a n t s in t h e eqtlatiot.ls c a n b e changed t o i n c r e a s e t h e a c c u r a c y of the calculation To study t h e effect of t h e r a t i o of t h i c k n e s s of porous carbon to d e n s e pyrolytic carbon i n the particle c o a t i n g , uranium oxide p a r t i c l e s were c o a t e d with t h r e e different r a t i o s of dense t o porous c o a t i n g but with t h e s a m e t o t a l c o a t i n g I

Fig. 10.2.

U r a n i u m Burnup a t

‘Table 10.1.

Uranium Oxide BR-YZliS, Irradiated to 23 a t . %

Pyrolytic-Carban-Coatgd

Paxtieles f r o m Ra+ch

8400°C

nn C a p s u l e

89-31. 3 0 ~ .

Pyrolytic-Corbon-Zontud U 0 2 P a r t i c l e s

lrrodiated to Study Optimum Coating-Thickness R o t i o

OR-491

OR493

OR-494

Avcrage particle

‘

thickness. T h e coated-particle dimensions are given in T a b l e 10.1. These coated p a r t i c l e s were irradiated in c a p s u l e B9-00 at 1400°C for 159 hr (1.9 a t . % uranium burnup). A t the beginning of t h e t e s t , t h e fractional r e l e a s e of 8 H K r w a s in the range, but it increased :suddenly to the IOu4 range n e a r t h e end of the t e s t when p a r t i c l e s from batch C)K-494 (which h a d t h e l a r g e s t ratio of porous c o a t i n g t o pyrolytic cuating) began t o rupture. Nom of the 15 low- and intermediateratio particles (batches OH-491 and -4933) failed; in both cases aboul. half of the thickness of t h e porous carbon coating had been consumed during; irradiation; but there w a s no e v i d e n c e of uranium c a r b i d e formation. Motst of t h e kiigh-rstio p a r t i c l e s (batch OR-494) either failed or were clamaged almost t o the poitit of failure. F a i l u r e was by unilateral movement o f the ZJ02 Ihrough bcth l a y e r s of the coating. The fuel. in t h e s e p a r t i c l e s appears to have operated at a higher temperature than p a r t i c l e s with the thinner p o r o u s carburl coating. Crystals of UC2 were found a t the fuel surface of t h e roi.ally f a i l e d partrcles. When the experiment was designed, i t was a s s u m e d illat the fi.ve c o a t e d particles with t h e t h i n n e s t porous carbon layer would fail f i r s t , b e c a u s e t h e r e is l i t t l e room for e x p a n s i o n of t h e f u e l and accumulation of fission g a s . The coated p a r t i c l e s with thick l a y e r s of porous carbon were not s u p p o s e d tu fail. T h e bumup w a s too low t o c a u s e f a i l u r e in m y of t h e s e particles. W e h a v e observed, however, that a very thick buffer layer of poro’us carbon will i n s u l a t e the fuel particle and may c a u s e failure b e c a u s e of exc e s s i v e l y high temperature i n the fuel.

POSTIRRADIATION TESTING OF COATED FUEL PARTICLES M. T. Morgari C , D. Baumann R. I-,. Towns

diincnsions Q) T o t a l diameter

7 13

703

704

Fuel particle

429

41 9

412

ti1

114

142

146

P o r o u s carbon c o a t i n g thickness P y r o l y t i c carbon c o a t i n g thickiiess T o t a l coating t h i c k n e s s P o r o u s coating to

0.25

0.70

1.47

pyrolytic c o a t i n g r a t i o Number of p a r t i c l e s

570

irradiated I._..._

To a i d i n t h e development of b e t t e r c o a t i n g s for c o a t e d fuel p a r t i c l e s , a s e r i e s of postirradiation a n n e a l s h a v e b e e n made on four t y p e s of pyro1yt.ic carbon c o a t i n g s applied to UC, and UQ, fuel particles. F u e l migration s t u d i e s by metallography

E. Reagan, E. L. B e a t t y , and E. I,. Long, Jr.. “Performance of P y r o l y t i c Carbon C o a t e d Uranium Oxide P a r t i c l e s During Irradiation at High Temperatures” (in prrss).

102 and microradiography h a v e been made, and f i s s i o n products released during a n n e a l s a r e being analyzed. Anisotropy, d e n s i t y , and c r y s t a l l i t e s i z e were t h e variables in t h e four types of outer c o a t i n g s , t h e d e t a i l s of which a r e given in F i g s . 10.3 and 10.4. These coatings were applied over i d e n t i c a l inner coatings. The coated particles were a l l irradiated in t h e same c a p s u l e a t t h e same temperature (14QOOC) and t o t h e same burnup (14.5% of t h e heavy metal). Samples of ten c o a t e d particles from e a c h batch were annealed a t 1700°C, a n d duplicate s a m p l e s were annealed a t 2000OC for a t o t a l of 19l4 hr for e a c h s a m p l e in s t e p s of 6 % hr.

Evealuatian of Fuel Migration by MatnIlography and Microradiography

Microradiographs and metallographic photomicrogiaphs were made on e a c h of t h e eight b a t c h e s of c o a t e d particles as c o a t e d , on the irradiated c o a t e d particles before heating, a n d on t h e irradiated c o a t e d particles after t h e 1700 and 2000°C a n n e a l s . T h e photomicrogiaphs a r e shown in F i g s . 10.3 and 10.4. T h e microradiographs a r e not shown, but the outer d i a n e t z r of t h e d e n s e a r e a s in t h e radiographs corresponds t o that of t h e s h a d e d or s p o t t e d a r e a s of the c o a t i n g s i n t h e photomicrographs, indicating uranium diffusion into these areas. Reaction a r e a s in t h e c o a t e d UO, p a r t i c l e s were restricted t o the inner coating. Spearheadtype a t t a c k occurred during irradiation in c o a t e d p a r t i c l e s with low-temperature outer c o a t i n g s , and the UO, seemed t o expand t o fill t h e void a r e a s . In t h e c o a t e d UO, particles with outer c o a t i n g s d e p o s i t e d a t 2000°C, spearhead a t t a c k i s not evident, and penetration of the inner c o a t i n g is s l i g h t ; t h i s i s probably a result of t h e 2000°C h e a t treatment received during’ t h e deposition of t h e outer coatings. T h e UO, p a r t i c l e s l o s t ’M. T. Morgan, D. C. E v a n s , and R. M. Martin, “Fission-Gas K e l e a s e from I-Iigh-Burnup UO ,” GCR Program Semiann. Progr. Hept. Mar. 3 1 , 1 9 6 3 , 20&NL-3445, pp. 103---6. 8

M. T. Morgan et a l . , “ F i s s i o n - G a s R e l e a s e from I-Iigh-Burnup Coated Particles.” G C R Program Senziann. Progr. R e p t . Sept. 30, 1963, ORNL-3523, pp. 149-52.

c r y s t a l l i n e detail during irradiation, and void a r e a s were redistributed a s s m a l l e r voids. No carbide formation w a s evident. T h e UC, fuel showed no apparent fine porosity after irradiation. H e a t treatment a t 2000°C seemed to h a v e consolidated t h e fine porosity into larger pores or voids. Some graphite f l a k e s were s e e n around t h e periphery of t h e fuel particles. The particle-coating reaction areas i n t h e c o a t e d carbide p a r t i c l e s were not a s l o c a l a s t h e spearh e a d a t t a c k in t h e coated oxide p a r t i c l e s and were a s s o c i a t e d with a progressive, more ext e n s i v e diffusion of fuel into t h e coating. T h e microradiographs of t h e uniriadiated carbide part i c l e s indicated that fuel diffusion into the inner c o a t i n g s s t a r t e d during t h e manufacture of t h e p a r t i c l e s . Penetration of t h e inner c o a t i n g s was complete in a l l coated carbide p a r t i c l e s a f t e r irradiation, a s indicated by t h e s p o t t e d a r e a s in the micrographs. Diffusion of fucl d e e p into the low-density outer coating was evideint in the irradiated YZ-13 c o a t e d p a r t i c l e s . L a r g e voids and s e p a r a t i o n of the inner coating from the outer c o a t i n g w e r e apparent in the XZ-15 and YZ-19 c o a t e d p a r t i c l e s after h e a t treatment a t 1700 and 200O0C.

Con ting Stebi I i t y

N o c o a t i n g failures were observed in t h e e i g h t groups during irradiation a t 1400’C. Coatings of the UC p a r t i c l e s failed during the postirradiation t e s t s a t both 1700 and 20OO0C, but no failures occurred with t h e UO, particles. B a s e d on 8 5 K r r e l e a s e , approximately 30% of t h e Y Z - 4 s a m p l e and 25% of t h e YZ-13 s a m p l e failed a t 170OOC. At 20OO0C, 80% of the YZ-4, 70% of t h e YZ-13, and 45% of t h e YZ-19 s a m p l e s failed. F a i l u r e s all occurred during heatup or within a few minutes after t h e annealing temperature w a s reached. ’The two s a m p l e s of c o a t e d IJC, p a r t i c l e s which did not fail a t 170OOC (one of which a l s o survived t h e 20QO°C a n n e a l ) had undergone t h e h e a t treatment during fabrication. We think t h a t t h e migration of fuel into t h e c o a t i n g s of UC, p a r t i c l e s weakened t h e c o a t i n g and c a u s e d the high perc e n t a g e of failures.

103

PHOTO a4909

OIJTER COATING DEPOSIlION CONDITIONS BATCH NUMBER

YZ--2

CORE MATERIAL

IJ02 1300 2.0 94 4.99

DEP0SiTION TEMPERATURE. 'C CH+ supP!-.< RATE. cmYrnin.cm2 OUTER COATING THICKNESS, p OIJTER COATING DENSITY, g/ctn3 CUTER CCATING CRYS1ALL.ITF SIZE,L,,

CUTER COA.r\NG ANISWROPY FACTOR, ooz / o ; , ~

YZ-4

YZ-14

"CZ

4300

"02 1600

20 83

20 4

2.0 76

4 44

4 43 50

31)

1.5

YZ-43 "C,

$600 20 71

AFTER iRRADlATlON

IRRAUlA1W:U AND ANNEALED w V 2 hr A I t7OO"C

IRRADIATED ANI3 ANNEALED 43?2 hr AT 2000째C

iNNER COATING DEPOSITION CONDITIONS

DEPOSII ION

UO,

FUEL I'Af?TI(:I.ES

TEMPERbTUHE, " C : i 6 0 0

FUEL PARTICLES

CH4 SUPPLY RATE, crn3/n;in. m2.4 .O INNER COATING THICKNESS. p,,26

CH* SUPPLY RATE, cm3/m/m;n.crn': t INNER COATING TH1CKNESS.p- 31

INNER COATING DENSITY, q / c m 3 . i . 5 6 INNER COA7:NG CRYSTALLITE SIZE, L C , a:50

INNER COATING I:ENSI'fY, q/crn3. 4.63

INNER COATING ANISOTROPY FACTOR, u o z / ~ o Io x : A L L BATCHES OF UO.( PARTICLES HAD THE SAME INNER COATING

F i g . 10.3.

IJC,

DEPOSITION TEMPERATURE. " C . i600

A L L GPTCHES OF UCz PARTICLES HAD THE SAME lNNEH COATING

!J02and UC2 P a r t i c l e s 3 e f o r e and After Irradiation and 1700 and 2000째C R e s p e c t i v e l y . Groups YZ-2, Y Z - 4 , YZ-14, a n d YZ-13.

Photomicrcgrophs of P y r o l y t i c - C a r b o n - C o a t e d

After Postirradiation H e a t Treatment at

INNER COaTiNG CRYSTaLLiTE SIZE, Lc,a:50 INNER COATING AEilSOTROPY FACTOR, ~ O L / u o x ' i

104

PHOTO 84908

OUTER COATING DEPOSITION CONDITIONS BATCH NUMBER

YZ-$1

YZ-15

yz-48

YZ-49

CORE M A T F R I A L

uo2 2000

UCZ

"02 2000 10 82 1 94 i;5

UCZ 2000

1-1 2

4-4

DEPOSITION TEMPERATURE, 'C C H SUPPLY ~ RATE, cm3/m,n cm2

2000 0 2 78

02 78 2 00

OUTER COATING THICKNESS, p OUTER COAi ING DENSITY, g/cm3

2 05

120-430 45

120-130

OUTER COATING CRYSTALLITE SIZF, Lc,H

OUTER COATING ANISOTROPY FACTOR, uooz/oox

76 1 94 119

BEFORE IRRADIATION

AFTER IRRADIATION

IRRADIATED AND ANFIEALED i9vz hr 4T t 7 0 0 " C

IRRADIATED A N D ANNEALED 19vz hr AT 2 0 0 0 째 C

INNER C O T I N G DEPOSITION CONDITIONS UOz FUEL PARTICLES

UCz

DEPOSITION TEMPFRATURE >L 1600

C H ~SUPPLY R A T E , cm3//rnii c m 2 4

C H SUPPLY ~ RATE, cm3/, In cmz 1

INNER C04TING THICKNESS, p 1 6 INNER C O A T I N G DENSITY, g / c m 3

4 515

INNER COATING CRYSTALLITE SIZE, L,,h 5 0 INNER COATING ANISOTROPY FACTOR, ~ o z / o - o ' o x1

INNER COATING THICKNESS,:c

INNER COATING O t N S I T Y , g/cm3 1 63

INNER COATING CRYSTAL1 I T F SIZE, L c , A 50 INNER COATING 4NISOTROPY FACTOR, 'J,,~/'J~~ 1

A L L BATCHES OF UO, PARTICLES HAD T H E SAMF INNER COATING

F i g . 10.4.

F U E L PARTICLES

DEPOSITION TEMPERATURF, "C 1600

A L L BATC!iES OF UC, PARTICLES HAD THE SclME INNER COATING

Photomicrographs of Pyrolytic-Ca;rbon-Coated l l Q Z and UCz Particles Before and After l r r u d i o t i o n and

After P o s t i r r a d i a t i o n H e a t Treatment at

1700 and 2000째C R e s p e c t i v e l y .

Groups

YZ-11, Y Z - I S , YZ-18, and YP-'19.

105

IRRADIATION EFFECTS ON COMPATIBILITY OF FUEL OXIDES A N D BERYLLIUM OXIDE WITH GRAPHITE D. K. C u n e o C. A . Brandon"

H. E. Robertson E. I,. Long, Jr."

T h e Compatibility of (U,Th)O, with graphite and t h e compatibility of beryllium oxide witti graphite were s t u d i e d in s e p a r a t e experiments in t h e ORR.

(U,Th)O 2-Gra ph ite Experiment T h e o b j e c t i v e s of t h i s experiment w e r e to s t u d y , at a fuel center temperature of 1650째C and a s u r face temperature of 1370"G, irradiation e f f e c t s on chemical compatibility of (U,Th)O, with graphite and f i s s ion-gas release, ,md to determine p o s s i b l e fuel s w e l l i n g and its e f f e c t s on the graphite. l'he dssembly w a s s w e p t with hellurn containing 250 ppm of CC? t o s u p p r e s s the reaction of t h e fuel oxides with graphite. T h e fuel loading m d operating conditions a r e given in T a b l e 10.2. During the last s i x w e e k s of irradiation, the 13'Xe release rate i n c i e a s e d tiom 1 5 to 1875, t h e temperature drop from fuel c e n t e r to s u r f a c e

Table 10.2.

( N t %)

Position

Ur3

90RNI, Reactor Division. "ORNI, Metals and Ceramics Division.

Fuel L o a d i n g and Operating Conditions for (U,Th)02-Graphite Compatibility T e s t

Composition

Fuel Pellet

i n c r e a s e d from 315 t o 390째C. The gamma s c a n of the c a p s u l e after irradiation and before disassembly s h o w e d about 1 2 individual p e a k s of activity for the s p a c e occupied by eight liollow p e l l e t s in t h e upper fuel region. T h i s indicated that the p e l l e t s were broken and p i e c e s had s e p a r a t e d ; this w a s verified upon disassembly. The seven solid p e l l e t s in the upper region s h o w e d general deterioration of their outer s u r f a c e s . T h e 1 2 p e l l e t s in the lower region appeared intact; however, attetnpts t o determine dimensions c a u s e d one of them t o powder. Metallography revealed that b e c a u s e of d e n s i fication there w a s much less porosity i n the irradiated s a m p l e (compared t o a n unirradiated control), and shrinkage c r a c k s w e r e apparent. In s p i t e of this shrinkage, the diameters of two pell e t s which we were a b l e to measure did not change. Weight and dimerisional changes of the graphite d i s k s and s p a c e r s were negligible. We conclude that no carbide formation occurred from the following:

Tho

Density

Power

Density (w/,3,~)

o f theoretical)

Integrated Fluxa

ID (in.)

.................

(in.)

'Ieight

(in.)

(nwtrons/crn2)

(st. 74; LJ

Thermal > 4 Mev

fissioned)

____..I_-

Upper Region

90.8 90.8

600

2400

220a

9.2

9-15 (solid)

9.2

(% t o t a l heavy

1.3

3.5

8.9

0.3

1.3

3.5

9.3

2.4

0.125

0.140

0.258

0.070

0.200

0.069

0.200

0.061

0.15fi 0.100

~ o w e Regionb r

16, 18, 20,

-..-

___I_

1---8 (hollow)

Burnup

22, 24, 26

(hollow)

17, 19, 21,

23, 2 5 , 2'7

(solid)

.___

.....

l i

a'F,xperirnent operated f o r 8 3 d a y s at e q u i v a l e n t f u l l power of 30 Mw in t h e ORR; i t w a s at design temperature of 16SOOC f o r 54 d a y s .

bThc p e l l e t s in the lower fuel region were individually inserted i n graphite d i s k s a n d sandwiched between fueled gtaphi te spacers.

un-

106

F i g . 10.5. ity Test.

Comparison of ( a ) U n i r r a d i a t e d

Etched;

1OOx.

B e 0 w i t h ( b ) an I r r a d i a t e d Specimen from the B a O - G r a p h i t e C o m p o t i b i l -

107 No reaction w a s obtained with powdered fuel HCI a t 80°C p e l l e t s in a q u e o u s media (2 for 8 hr). T h e x-ray diffraction pattern of a graphite s p a c e r which had b e e n i n c o n t a c t with a fuel p e l l e t showed n o carbides. Metallographic s t u d i e s s h o w e d no e v i d e n c e of any reaction products on t h e s u r f a c e s of five p e l l e t s or on matching graphite p i e c e s . BeO-Graphite Experiment

The BeO-graphite t e s t w a s d e s i g n e d to s t u d y irradiation e f f e c t s at 1500°C on the chemical compatibility of graphite with ReO, to i n v e s t i g a t e t h e distribution. of 61-i formed in t h e BeO, and to determine weight, dimensional, arid structural c h a n g e s in t h e graphite and BeO. A Be0 ring a n d a graphite ring were i n close c o n t a c t o n flat sucfaces and were n e s t e d over a s o l i d H e 0 core within ii graphite s l e e v e . T h e experiment w a s not fueled. T h e d e s i r e d temperature w a s a c h i e v e d for about four months by gainma heating. Duririg the last f i v e months of irradiation, t h e temperature gradually fell to a b o u t 1280°C, probably b e c a u s e of formation of soot (ea -3 GO, -t C), r e s u l t i n g i n loss i n cffectiveness of reflective insulation i n t h e c a p s u l e . The t o t a l irradiation d o s e w a s 1.0 <; l o z 1 negtruns/cm2 ( E > 0.18 MeV). T h e r e w a s n o p h y s i c a l damage to t h e 13e0 or graphite during irradiation. Metallographic examination of t;elt><:ted s u r f a c e s s h o w e d n o reaction products, a n d x-ray diffraction of t h e Be0 ring s h o w e d no Be,G. T h e r e w a s a d e p o s i t of Mo,C on the graphite s l e e v e a d j a c e n t to s e v e r a l large h o l e s which appeared in a molybdenum h e a t shield. Examination of the irradiated graphite showed no rriicrostructural ohi3nges. Examinatioii of t h e irradiated B e 0 showed t h a t the grain s i z e doubled, and e a c h grain was outlined hy g a s bubbles, a s s e e n i n F i g . 10.5. A n a l y s e s of experimental cotnponents for ‘Li concentrations s h o w e d that t h e major portion of the ki s t a y e d in t h e B e 0 core where it w a s formed. A surface-to-volume relationship for 6Li retention w a s found by comparing This is in t h e B e 0 ring with t h e B e 0 core. agreement with work by Stieglitz and Zurnwalt. Weight and dimensional c h a n g e s for the B e 0 arid graphite s h o w e d about 1% s h r i n k a g e for the graphite and 0.5% expansion for t h e BeO.

FAST GAS-COOLED REACTOR DEVELOPMENT D. R. Cuneo [I. E. Robertson

E. L. Long, J r . ” J. A. Conling

Iluring t h e p a s t year w e h a v e begun postirradiation e v a l u a t i o n s of experimental a s s e m b l i e s related to fuel elements for f a s t gas-cooled reactors. T h i s is a cooperative program with General Atomic Division (GA) of General Dynamics Corporation. D e t a i l s of t e s t conditions and procedures were determined by t h e OHNL Reactor Division i n cooperation with GA, and t h e fuel specitnens were s u p p l i e d by GA. T h e present s e r i e s of t e s t s is designed to i n v e s t i g a t e t h e effects of irradiation, thermal cycling, external pressure, a n d f u e l - c l a d d h g interactions 011 the integrity and behavior of metrPl-clad 110, fuel e l e m e n t s having design feahres t h a t approximate t h o s e for t h e General Atomic f a s t gas-cooled rea c t o r d e s i g n . Design and operation of t h e s e e x perimental a s s e m b l i e s and d e t a i l s of postirradiation findings h a v e been reported elsewhere. Two t y p e s of elements a r e b e i n g s t u d i e d in t h e f i r s t group of t e s t s ; t h e fuel-supported type, in which t h e c l a d d i n g is designed to c o l l a p s e onto t h e fuel p e l l e t s a t the o u t s e t of p r e s s u r e a n d temperature application, and t h e f r e e - s t a n d i n g fuel or “flexcan” type. T h e latter has a deformed s e c t i o n of c l a d d i n g a b o v e t h e fueled region t h a t is c a p a b l e of flexing with p r e s s u r e c h a n g e s , and t h e internal void is filled with sodium. W e h a v e completed examinations of four a s s e m b l i e s (lacking metallography for t h e fourth) which contained s i x of t h e fuel-supported elements and two of the sodium-filled flexcan types. All e l e m e n t s were fueled with UO, p e l l e t s . Operating d a t a and metallographic findings a r e given i n T a b l e 10..3, while the a p p e a r a n c e of two of t h e t e s t elements is shown in Fig. 10.6. “ I d . J. Stieglitz and 1,. R. Zumwalt, N n c l . Appf. 2(5),

394-401 (1965).

“P. R. McQuilkin et ul., “Fuel Irradiation Tests i n Facility,” C C R Prog~arzi Semianri. Pro&. K e p t . Sepl. 30, 196.5, QKNL-3885, pp. 244---50. 1317. R. McQuilkin et a l . , “ F u e l Irradiation Tests in the ORR Poolside F a c i j i t y , ” G C R Program Serniann. Pro&. H e p f . Mar. 31, 1966, ORNL-3951,, pp. 169-79. the CIRR Pnolside

1 4 ~ K. . Cuneo et a]., “E;xarnination of Trracliated Capsules,” GCH Program S e m i a n t i . Pro&. Kept. Mar. 31, 1 9 6 6 , ORNLA951, pp. 179-230.

I’D. R. Cuneo et af., “Examination of Irradiated Capsules,” G C R Progrerrr Semiaim. Progr. Rept. SspC, 30, 1966, ORNL-4036.

Table iC.3.

Experiment

Fuel

No.

Element NO.

P4B1

Operatiny Candifions and Metailogrcph;c O b s e r v a t i o n s for F G S ?G a s - C o o l e d Renciur Fuel Elements Maximum

Burnup

Thermal Flux

(a heavy

Dose

( n e u t r o n s / c a ') 4 x 1019

GAI

1.6

0.35

Cladding

Material

Temperature

Hastelloy X

7601

Metallographic Observations

< OC)

Capsule badly flattened ( s e e Fig. 1G.6). lenticular voids.

General s u b s u r f a c e voids i n inner s u r f a c e

region of cladding t o depth of 1 mil. layer (" 2

CA2

1.6

0.35

Hastelloy X

Coiumnar grain

growth observed i n t h e fuel. N o evidence of h e 1 melting o r

750+

u)and

Formation of thin oxide

thin metallic l a y e r found on I D s u r f a c e .

N o evidence of fuel me1tir.g.

P a r t i a l c o l i a p s e of UO, r e s u l t e d i n

slight wrinklina of cladding. Pelle: i n t e r f a c e s had sinrered together. L a r g e radial c r a c k s found a t pellet midlengths.

evidence of a t t a c k on cladding. GA3 (unfueled,

unconnected

flexcm)

P4B2

GA4.

5.2 x i 0 1 9

GA 5

5.2

10"

1.4

3.46

Has;elloy X

650

Fuel element not sampied for metallog-aphic examination.

1.4

0.46

Wastelloy X

650

No evidence of fuel melting. Columnar grai:i growth noted. Central h o l e i n fnel pellet moved 44 m i l s off center. Reshaping of central h o l e w a s observed a s s e e n i n F i g . 10.6. N o microstmctural c h a c g e s observed in c l a d d i n g .

P4B3

GA6

5.2 x 1019

2.4

0.58

304 S S

650

N o evidence of microsTructural c h a n g e s i n cladding. Neithe: high- nor low-density fue: p e l l e t showed evidence of columnar

(fueled flexcan)

grain growth or central voids.

No d e i e t e r i o u s e f f e c t s from

sodium i n c a p s u l e . GA7

T4B4

. .

5.2

1019

2.4

0.59

Hastelloy X

650

N o evidence of microstructural c h a n g e s in cladding. N o evidence of cen:ral voids

GA8

1.3 x :OZo

4.0

0.86

304 SS

650

Examinatiox coctinuing.

GA9

1.3 x 10"

3. 0

3.90

Zastelloy X

680

Examination continuing.

o r columnar grain growth in fuci p e l l e t s .

109

Fig, 10.6.

(a) T r a n s v e r s e Section of Element GA1, Showing Columnar G r a i n Growth i n Central R e g i o n of UB2

Weli a s Severe FlrPtteniiig of C l a d d i n g ; ( b )L o n g i t u d i n a l Section of E l e m e n t GAS, Showing ?hat U 0 2 Moved Out A g a i n s t

C l a d d i n g in Gtooved Portion of Pellet, Accounting for

Increase in S i r e of C e n t r a l Hole in Pellet.

To summarize t h e postirradiation findings:

1. In a l l cases the cladding showed n o indica-

tions of failure, d e s p i t e t h e fact t h a t element G A 1 was badly deformed a n d GA2 w a s deformed to a lesser e x t e n t . (Some more recent e l e m e n t s have been prepressurized to avoid large press u r e diiferer!ces across the cladding.)

2. T h e r e

no e v i d e n c e of incompa(.ibility between t h e daddirig and .the fuel in the elemerits t e s t e d , except f o r s u b s u r f a c e voids (to a depth of about 10% of the w a l l t h i c k n e s s ) noted jn t h e inner s u r f a c e regions of (;AI WBS

(Hastelloy XI.

3 . There w a s no e v i d e n c e of fuel melting i n any element. 4. The flexcan elements which contained sodium in the ftee volume did not r e v e a l any delet e r i o u s e f f e c t s from the sodium.

In all reactor s y s t e m s the f i s s i o n gas which e s c a p e s from the fuel m u s t b e cotitrolled by containment within the f u r l e l e m e n t or by removal from t h e fuel coolant. In high-tetnperature reactors this problem i s e s p e c i a l l y important. Some empirical formulas have beer1 developed for e s t i m a t i n g t h e fission-gas r e l e a s e tinder certain conditions," b u t rnost v a l u e s a r e obtained by

' U m v e r s i t y of Florida, Consultapt to Reactor Chemi s t r y Division. I 7 R . M. Carroll, N ~ i c l Safety . 7(1), 3 4 - 4 3 (1965).

W. D. Lewis, N u c l . App1. 2(%), 171-81 (1966).

110 experiments simulating s p e c i f i c reactor operating conditions. We a r e s e e k i n g a general solution t o t h i s problem by studying t h e behavior of fission-gas r e l e a s e under well-controlled condit i o n s in a n attempt to understand t h e b a s i c mecha n i s m s of fission-gas r e l e a s e . 9--21 Defect-Trap Model

'4s a result of t h e s e s t u d i e s , w e b e l i e v e that t h e f i s s i o n g a s i s released by a combination trapping and diffusion p r o c e s s , where t h e trapping i s t h e dominant factor determining t h e time for the We h a v e formed a defect-trap g a s to e s c a p e . theory which p o s t u l a t e s that d e f e c t s in t h e IJO, c r y s t a l structure will trap migrating xenon and krypton a t o m s . 2 2 Some d e f e c t s , s u c h as grain boundaries and c l o s e d pores, a r e naturally present in the IJO,, and others c a n b e formed by irradiation. T h e iriadiation-formed d e f e c t s s t a r t a s point d e f e c t s which may be destroyed by a n n e a l i n g but may c l u s t e r to form larger d e f e c t s t h a t will require longer times t o anneal. Experiiiieiits h a v e shown that t h e model h a s the correct general characteristics and that grain boundaries will trap f i s s i o n g a s . 2 4 T h i s model predicts that higher f i s s i o n i a t e s , which will produce m o r e f i s s i o n g a s , will a l s o produce more traps; therefore, the fission-gas ielease rate will not c h a n g e much with a change in fission rate. Fission-gas r e l e a s e measurements h a v e been made during fission-rate and temperature o s c i l l a t i o n s . T h e s e d a t a a r e being fitted into a computer c o d e to determine t h e parameters of t h e defect-trap model. One complication w a s c a u s e d by the mixing of the fission g a s with t h e flowing helium s w e e p g a s . We developed a n a p p a r a t u s to measure t h e amount of mixing, u s i n g argon to s i m u l a t e the f i s s i o n g a s and a thermal conductivity c e l l to measure argon concentration in t h e s w e e p gas. The mixing transfer function h a s now ~.

..........-

been determined and will b e u s e d to correct the fission-gas r e l e a s e transfer function for t h e inpile experiment. F i s s i o n fragments which recoil free of t h e s p e c i men s u r f a c e will knock out UO, molecules a l o n g with any fission g a s i n t h e immediate vicinity. T h e knockout r e l e a s e depends on t h e f i s s i o n rate, t h e t o t a l s u r f a c e a r e a of the specimen, and poss i b l y t h e condition of t h e surface. In order to s t u d y t h e e f f e c t s of s u r f a c e condition on fissiong a s r e l e a s e , t h e g a s r e l e a s e r a t e s from UO, singlec r y s t a l s p e c i m e n s with highly polished s u r f a c e s were compared w i t h t h o s e from unpolished s p e c i mens. 2 5 T h e fission-gas r e l e a s e from unpolished s p e c i m e n s d e c r e a s e d with time in t h e early s t a g e s of irradiation, while the fission-gas r e l e a s e from t h e polished single c r y s t a l s showed XIO change with t i m e . We f e e l t h i s confirms our theory that t h e s u r f a c e is smoothed by iriadiation, c a u s i n g a reduction in a r e a . Measurement of krypton r e l e a s e from a polished s i n g l e c r y s t a l specimen is compared with that from a polycrystalline specimen in Fig. 10.7. At 25R.bl. Carroll and 0. Sisman, ORNL-TM-1400 ( D e c .

31, 1965).

......-

"R.

M. Carroll and P. E. Reagan, N u c l . Sci. Eng. 21, 141-46 (1965).

'OR. M. Carroll and 0. Sisman, N u c l . A p p l . 2(2), 142-50 (1966).

'lK. El. P e r e z , N u c l . A p p l . 2(2), 151-57 (1966). 22R. M. Carroll and 0. Sisman, N u c l . Sci. Eng. 21,

147-58 (1965)

23R. M. Carroll, R. B. Perez, and 0. Sisman, J . A m . Cerarn. S o c . 48(2), 55-59 (1965). 24

R . M. Carroll and 0. Sisman, J . N u c l . Mater. 17(4), 305-12 (1965).

500

600

700

800

900

1000

1400

(200

TEMPFRATURE ("C)

Fig.

10.7.

R e l e a s e Watt? of

Single-Crystul

U02.

**Kr

from Fine-Grain and

111 !emperatures u p to about 60OoC, knockoui r e l e a s e predominates, and the g a s r e l e a s e s h o w s l i t t l e temperature dependence. T h e rougher s u r f a c e d polycrystalline specimen s h o w s greater knockout r e l e a s e (both s p e c i m e n s a r e t h e same size). At temperatures a b o v e 700°C t h e gas r e l e a s e is from point-defect t r a p s for both specimens. Ai 950 to 1050°C t h e point d e f e c t s ate mobile enough to form c l u s t e r s , s l o w down t h e gas r e l e a s e , and t h u s c a u s e t h e s t e p i n t h e curve for the singlec r y s t a l specimen. T h e point d e f e c t s a r e trapped by grain boundaries i n t h e polycrystalline s p e c i men before they c a n c l u s t e r , and therefore the At higher temperatures, t h e s t e p is a b s e n t . c l u s i e r s in t h e s i n g l e - c r y s t a l s p e c i m e n may ailmal. and migrate, and o n c e again t h e r e l e a s e r a t e h a s an exponential temperature dependence, but the dependence differs from thai. where r e l e a s e is primarily from point d e f e c t s . T h e temperature dependerice of gas release f r o m the polycrystalline specimen, where t h e gas r e l e a s e is a l w a y s from All of point d e f e c t s , is c o n s t a n t to 1200'C. t h e s e observations were predictable by t h e derectt r a p model.

THERMAE ~~~~~~~~V~~~ C , I). Btaurnann R. M. Carroll

J . G. Morgan M . F. Oshorne R. B. P e r e z "

Studies of t h e effect of inadiat.ion on t h e thermal conductivity of (40, have, f o r t h e m a s t part, been limited to postirradiation t e s t s . Annealing t e s t s s h o w that irradiation at a low ( < 100°C) tempwat u r e c a u s e s a d e c r e a s e in thermal conductivity which cai b e recovered i n stages near 150 and 400°C" 2 6 E f f e c t s of d e n s i t y , grain size, a n d burnup h a v e also been studied after irradiation, 2 7 Data are lacking, however, on t h e a c t u a l t - h e m a l conductivity during irradiation a s i t is affected by f i s s i o n rate a i d temperature. We h a v e tiegun O U T in-pile t e s t i n g with a s i n g l e c r y s t a l of UO, to eliminate i.he parameter of grain-boundary e f f e c t s .

W e a r e evaluating dat-a obtained while the s p e c i men w a s at three different neut.ron flux l e v e l s a n d three temperatures a t e a c h neutron flux. T h e evaluation i s not complete, but w e can >jees o m e rather definite trends: (1) t h e thermal conductivity i s lowered by i n c r e a s i n g t h e f i s s i o n rate at a given temperature, and (2) t h e thermal conductivity increases with temperature up to about 900°C and then d e c t e a s e s with further i n c r e a s e in temperature. T h e s e c h a n g e s of thermal conductivity with temperature, while fissioning, a r e consistent with t h e c o n c e p t that disorder lowers t h e thermal conductivity. When the temperature of the specimen is changed (for example from 600 to 700°C) while a t a c o n s t a n t fission rate, two different p r o c e s s e s a r e i n competition which affect t h e thermal conductivity: (1) t h e conductivity of the undamaged matrix t e n d s to d e c r e a s e as the temperat.ure is i n c r e a s e d , and (2) the i n c r e a s e d temperature would i n c r e a s e the conductivity by annealing t h e ac:cumulafed radiation darnage. When t h e temperature i s i n c r e a s e d from 600 to 700°C, t h e thermal conductivity i n c r e a s e s b e c a u s e annealing t h e iadiation damage i s t h e dominant process. At temperatures higher than about 900"C, t h e equilibrium amourit of damage is small enough so that tlx: c h a n g e in conductivity c:aused by the i n c r e a s e i n temperature will r e s u l t in a n e t lowering of t h e conduc tivity . T h e s p e c i m e n i s moved sinusoidally in t h e reactor neutron flux. The fission r a t e and, thus, t h e h e a t production wit-hin the speciinen respond instantarieuusly to t h e change in neLitron flux, but the temperature d o e s not. I f the o s c i l l a t i o n s are s o rapid that the tcmpsrature does not have a

j. L. Daniel et af,, Thermal Cotiductivity of U O :2 ' HW-69945 (Septeh'Jber 196%). '"M. A r a y o n e s and li. Guerrero, The E f f e c t of D e n s i t y arid C m i r i Size m i the Thermal Conrfiiclivity of L I 0 2 During Irradiation, AECL-2564 (April 1966). 2K

"R. M. Carroll. 2nd J . G. Morgan, F\rels a n d M a t e r i a l s Developnetzt Program Quart. Progr. Rept. J u n e 30, 1 9 6 6 , O R N L,-TM-I 57 (It pp 8 5 -95 I

Fig. 10.8.

Uraniwrn D i o x i d e Single C r y s t a l Tempera-

ture Respanse to O s c i l l a t i n g Fission Rote.

112 c h a n c e to reach i t s maximum value, then the amplitude of t h e temperature o s c i l l a t i o n s will d e crease a s t h e oscillation frequency i n c r e a s e s ( s e e Fig. 10.8). T h e time delay or p h a s e s h i f t between t h e neutron flux o s c i l l a t i o n s and t h e resultant temperature o s c i l l a t i o n s will also change with frequency. 'The p h a s e s h i f t and amplitude relation of t h e temperature o s c i l l a t i o n s in comparison with t h e neutron flux o s c i l l a t i o n s over a range of frequencies will yield d a t a to deterrniile t h e therm a l conductivity of t h e specimen.

The a n a l y s i s of t h e temperature response of t h e sample to s m a l l o s c i l l a t i n g c h a n g e s in neutron flux (heat generation) h a s been completed, and t h e n e c e s s a r y mathematical relations to obtain t h e thnrinal conductivity have been derived. 29 Measurements of t h e thermal. conductivity of s i n g l e c r y s t a l UO, a t t h r e e neutron flux l e v e l s and three temperatures a t each neutron flux a r e in progress.

......... "R. M. Carroll, J. G. Morgan, and 0. Sismdn, F u e l s and Materials Development Program @tiart. Progr. R e p t . , OKNL-TM--1500 (June and September 1966). ......

11. Behavior of High-Temperature Materials Under Irradiation EFFECTS OF FAST-NEUTRON 1RRADIATION ON OXIDES C.

W. Keilholtz

to 5.2 x 1021 nt?utrons/cm2 (> 1 Mev) a r e given below.

0.6

R. E. Moore

Gross Damage

A comparison of t h e e f f e c t s of fast-neutron irradiation o n sintered compacts of BeO, MgO, and i t - A 1 2 0 3 has been reported previously.1m-3 During t h e p a s t y e a r we h a v e initiated an inv e s t i g a t i o n of t h e irradiation behavior of a corrriiiercially a v a i l a b l e translucent aluminum o x i d e of high d e n s i t y 4 which i s of interest- a s a p o s s i b l e insulator i n thermionic emitters. The o h j e c t i v e s were (1) to e s t a b l i s h its l i m i t s of s t a b i l i t y toward f a s t neutrons and (2) to determine whether grain boundary separation would o c c u r a t ~ e r yhigh d o s e s , a s i t does in Be0 a t d o s e s w e l l below 1 x IO2’ neutrons/cm2. T h e experimental t e c h n i q u e s used in t h e irradiations, which a r e carried out i n the Engineering T e s t R e a c t o r (Idaho), are described elsewhere. The results of postirradiation exaniinations and measurements of translucent a - A l ?1 0 3 s p e c i m e n s irradiated at 3100 t o 600°C over the d o s e range

At low irradiation doses, translucent A l z O is much m o r e r e s i s t a n t to fracturing than s i n t e r e d A 1 2 0 3 . Below 3 x 10‘l ntwtrons/cni2 (> 1 Mev), there w a s virtually no fracturirig of t r a n s l u c e n t A120J,but s e v e r e fracturing along intergranular p a t h s occuricd a t higher d o s e s . Metallographic Examinations

Grain boundmy separation begins to appear at a d o s e of 2 ” 3 x l o 2 * neutrorrs/cm2 >:( 1 Mev). This s e p a r a t i o n is very e x t e n s i v e at a dose o f 4.7 x IO2’ ( i 1 Mev). T h e s a m e degree o f grain boundary separation occurs i n Re0 a t doses smaller by a factor of 5 to 10. Grain boundary separation in 1.ranslucent A 1 2 0 , is probably the p r e d e c e s s o r of g r o s s fracturing. D i m e n sicno I Measurements

‘G. W . Keilholtz, R. E. Moore, and M. F. Osbomr, Cfiem. D i v . Arm. Progi. R e p t . Dee. 31, 196.5, URNL-3913, p. 105. ’C;. W. Kcilholtz, J. E. Lee, Jr., and R. E. Moore, “Properties uf Magnesium, Aluminum, and B e r y l l i u m Oxide Cotupacts Irradiated to Fast-Neutron Doses

T h e t r a n s l u c e n t A 1 2 0 3 expanded i n volume by about 1.3% o v e r t h e d o s e range 0.6 to 1.4 i 1Q21 neutrons/cm2 [>, 1 Mev); this i s approximately t h e s a m e expansiori observed in the col d-presseds i n t e r e d A1 0 irradiated previously. Above 2 x 1 3 1021 neutrons/cm2 ( > I M e V ) , t h e volume e x p a n s i o n

Kedi,tor

...2

than 1021 Neutrons c m a t 150, 800, and 1 100‘’C,a8 Proceedings of Joint Division Meeting o f the Materials Science and Technology Division of the American N u c l e a r Society and t h e Refractories Division Greater

of the A m e r i c a n Ceramic Society h e l d in conjunction w i t b the 68th Annual Meeting of t h e A m e r i c a n CeramicSociety, May 8-11, 1966, Washington, D.C., pp. 233-48.

3 G. W. Keiltioltz, J. E. Lee, Jr., N u c l . Sci. En&. 24, 329-38 (19%).

5 G., W. Krilholtz, R. E. Moore, M. F. Osbome, B. W. Wieland, and A. I?. Zulliger, “Techiiicpes f o r h a d i a t i n g Hi& Temperature Materials i n a Steep Flux Gradient,”

and R. E. Moore,

Irradistiori Capsule Expetinients, Proc. o f USAEC C o n f . on D e v e l o p m e n t s in Irradiation Capsule Technolo g y , Pleasanton, Calif., M a y 3-5, 1966, TID-7697 ( 2 6 ed.).

4 ~ u c a 1 0 x , trade name o f a proprietary pruciuct o f G c n s m l E l e c t r i c eo., Cleveland, Ohio.

113

114

of t r a n s l u c e n t A 1 2 0 3 increases. nearly linearly with neutron d o s e t o about 5% a t a d o s e of 5 x l o 2 ' ileutrons/cm2 (>1Mev). %-Ray Diffraction Examinations

T h e volume i n c r e a s e calculated from t h e l a t t i c e parameter expansion w a s less than 1.5% over t h e d o s e range 1.3 to 4.7 x l o z 1 neutrons/cm*. T h e anisotropic exparrsion ratio ( A c / c , ) / ( h a / a , ) was about 2 t o 3 , a s compared with that of BeO, which is about 20 for d o s e s less than 1 x l o 2 ' neutrons/cm2 (>1 Mev). Grain boundary separation in Be0 c o m p a c t s irradiated a t low temperatures i s generally believed to result from anisotropic l a t t i c e parameter expansion. In t h e case of A 1 2 0 3 , however, t h e l a t t i c e parameter expansion i n i t s e l f probably d o e s not produce t h e grain boundary s e p a r a t i o n , which i s observed in i n c r e a s i n g d e g r e e a s t h e neutron d o s e is i n c r e a s e d from 2.3 to 4.7 x l o 2 ' neutrons/cm2 ( > 1 Mev). T h e l a t t i c e parameter expansion i n A1 0 i s small and d o e s not i n c r e a s e 2 3 with i n c r e a s i n g neutron d o s e over t h i s range. I t i s p o s s i b l e , however, that defect agglomerates t o o large to affect t h e l a t t i c e parameters c a u s e a n additional anisotropic crystal expansion l a r g e enoiugh a t high d o s e s t o produce s e p a r a t i o n of grains. T h e grain boundary separation a p p e a r s tc limit t h e u s e f u l n e s s of translucent A120, t o fastneutron e x p o s u r e s of less than ?. to 3 x 1 0 2 1 neutrons/cm2 ( > 1 M e V ) at temperatiires below 6 O O O C . T h e neutron d o s e limit a t higher temperat u r e s will b e e s t a b l i s h e d when speciiiiens now b e i n g irradiated i n high-temperature a s s e m b l i e s are examined.

form of '/2 x 32 in. cylinders made by (1) hot p r e s s i n g , (2) s l i p c a s t i n g and sintering, and ( 3 ) explosion p r e s s i n g and sintering were s e l e c t e d for t h e s e s t u d i e s . L o w t e m p e r a t u r e (300 to 700OC) irradiations a r e now complete, a high-temperature (-lOOO째C) irradiation i s i n progress, and ass e m b l i e s for higher-temperature irradiations are being designed. T h e experimental t e c h n i q u e s u s e d in t h e irradiations are described elsewhere. Hot-pressed s p e c i m e n s and slip-cast-sintered speciinens of e a c h of t h e five monocarbides behaved very similarly in low-temperature irradiations (300 t o 700cC) over t h e neutron d o s e range 0.7 to 5.4 x 1 0 2 1 neutrons/cm2 (>1Mev). T h e r e s u l t s are summarized below. Grass Damage

T u n g s t e n carbide and titaniuin c a r b i d e were generally undamaged ovet t h e e n t i r e d o s e range of t h e irradiations. F i g u r e 11.1 is a bar graph showing t h e approximate neutron d o s e r a n g e s where fracturiiig occurred in e a c h of t h e five carbides. ..~...

........ ..

6G. W. Keilholtz, M. F. Osbome, and R. E, Moore, f?eactor Chern. Div. Arm. Progr. H e p t . B e c . 3 1 , 1965, ORNL-3913, p. 104.

a SEVERE

ORUL-DWG 66 10268

FRACTURING

MINOR F R A C T L R I N G

U N O DAMAGE OR ONLY VERY MINOR DAMAGE -~ ~

a R. E. Moore G. W. Keilholtz M. F. Osborne Refractory metal carbides h a v e potential uses in nuclear rpactors designed to o p e r a t e a t very high temperatures. We are investigating t h e c h a n g e s in t h e physical and mechanical properties of t h e s e m a t e r i a l s during exposure to fast-neutron d o s e s a s high a s 5 . 4 1021 ~ neutrons/cin2 (>1M e V ) a t temperatures ranging upward t o 1400째C.6 T h e monocarbides of Ti, Zr, Nb, Ta, and W i n t h e

TIC

F i g . 11.1.

ZrC

Ta C N bC T Y P E OF CARBIDE

Gross Damage t o Specimens o f H o t - P r e s s e d

a n d Slip-Cost-Sintered Refractory M e t a l Monocorbides in

the Form o f

Tempeiotures

Neutron Dose,

in. S o l i d C y l i n d e r s I r r a d i a t e d o t L o w

(300 t o 70OoC)

a s a F u n c t i o n of the F a s t -

115 M e t a 1 Iog ra ph i c Exam i no ti on s

N o grain boundary separation could b e s e e n i n photomicrographs of any of t h e carbide s p e c i m e n s . Dimensional Measurements

A s shown i n Fig. 11.2, i n which t h e volume exp a n s i o n d a t a are summarized, the c a r b i d e s expanded on exposure to a d o s e of 1 x I O z 1 neutrons/cm2 (21 Me\; and theti shrank a t different r a t e s as t h e neutron d o s e i n c r e a s e d t o 5.4 x 10" neutrons/cm2 ( > I M e V ) .

2. A c o l l a p s e o f t h e large agglomerates as t h e neutron d o s e is i n c r e a s e d from 1 to 5 x l o * ' neutrons/cm2 ( > I Mev) is t h e principal c a u s e of t h e s h r i n k a g e in gross volume o v e r this d o s e range.

3. T h e l e v e l i n g effect on g r o s s damage to t h e

f i v e c a r b i d e s when explosion-pressed s a m p l e s were irradiated i n d i c a t e s that t h e n i c k e l a d d i t i v e is primarily responsible for t h e inc r e a s e d fracturing observed.

4. Hot-pressed

and slip-cast-sintered tungsten c a r b i d e and titanium carbide prepared without a d d i t i v e s a r e more resistant to fast-neutron irradiation a t low temperatures ( i700°C) than any of t h e other types CJf carbide s p e c i m e n s investigated.

X-Ray Diffraction Exominations

T h e volume i n c r e a s e s c a l c u l a t e d from t h e l a t t i c e parameter c h a n g e s account €or only 30 to 50% of t h e gross volume expansions. F r a c t u r i n g of explosion-pressed s p e c i m e n s with 1%n i c k e l additive generally occurred a t l o w e r neutron d o s e s than with the corresporiding hotp r e s s e d and s l i p - c a s t carbide s p e c i m e n s with no additive. T h i s w a s part.icularly true for explosion-pressed titanium and tungsten c a r b i d e s , which were damaged on exposure to d o s e s a b o v e "2 x 10" neutrons/cm2 ( > I Mev). T h e volume expansion of explosion-pressed s a m p l e s w a s approximately t h e same as t h a t of t h e corresponding c a r b i d e s fabricated by the other methods, T h e following c o n c l u s i o n s were drawn from t h e r e s u l t s of t h e low-temperature (300 to 700°C) i r radi at i on s

1. 'The gross volume expansion is t h e sum of

t h e lattice parameter expansion and agglomera t e s of d e f e c t s too l a r g e to affect measured v a l u e s of the l a t t i c e parameters.

-I .i$, , 2

111

C i> Y

L W

.......

................

F i g . 11.2. fa,

....

!.................

.....

Zr, (300 to

V o l u m e I n c r e a s e of Monocarbides of Ti,

Nb, and W i r r a d i a t e d

700°C)

at L o w Temperatures

Function o f F a s t - N e u t r o n Dose.

Part IV

Other ORNL Programs

emical Support for the Saline Water Program SOLUBILATY OF CALCIUM SULFATE IN SEA SALT SOLUTIONS TO 200째C; TEMP ERATURE-SOLUBI LI TY LlMl TS FOR SAUNE WATERS' W. L. Marshall

is shown by t h e undashcd l i n e s , t h e experimental d a t a for which are given elsewhere.',' Our evaluations of s o m e published s o l u b i l i t i e s in sea s a l t s o l u t i o n s 5 a r e a l s o included in t h i s figure; t h e comparative r e s u l t s appear to b e in good agreement. In t h e temperature interval 30 to 90째C t h e only significant difference i n solubility in t h e two s y s t e m s i s observed a t very high ionic strengths. The s o l u b i l i t i e s for temperatures from 100 to 200OC a r e greater i n sea salt s o l u t i o n s , but t h e v a l u e s do not s h o w a cont.inuous (tiionotorlic) i n c r e a s e i n t h e difference with increasing temperature. T h i s behavior (:an be explained by the formation of ai1 MgSO,' neutral s p e c i e s that allows the molal solubility of calcium s u l f a t e to i n c r e a s e until t h e limiting v a l u e of t h e solubility product, I< obtained from the comparative solubi1it.y in s z f i u m chloride solutions, is reached. T h e c h a n g e with i n c r e a s i n g temperature in solubility between that in sea s a l t (containing approximat.eIy 2 moles o f magnesium per m o l e o f s u l f a t e ) and i n sodium chloride s o l u t i o n s i s then explained by an iriterrelated function of an i n c r e a s i n g a s s o c i a t i o n cons t a n t of magnesiuni s u l f a t e and t h e d e c r e a s i n g solubility product c o n s t a n t of calcium sulfate. W i t h t h e d i s s o c i a t i o n quotients (at ioriic strengths, I> and c o n s t a n t s (at I : 0) for magnesium s u l f a t e , c a l c u l a t e d from t h e solubility behavior shown i n Fig. 12.1 and presented e l s e w h e r e in t h i s report,6

Ruth Slusher

In a previous s t u d y 2 t h e e x t e n s i v e solubility measurernents of calcium s u l f a t e and its hydrates in sodium chloride s o l u t i o n s " were u s e d to e s t i m a t e solubility limits for t h e s e s p e c i e s i n s a l i n e w a t e r s i n general, s i n c e s u c h e s t i m a t e s a r e of great. value to t h o s e concerned with distillation of s a l i n e waters. The e f f e c t of divalent i o n s (magnesium in particxlar), which c a n partially complex t h e s u l f a t e ion and thereby i n c r e a s e t h e solubility of calcium s u l f a t e over t h a t 'fnormally" expected, could not b e taken into account i n t h e s e e s t i m a t e s . We h a v e , therefore, meusured t h e s o l u b i l i t y of c a l c i u m s u l f a t e (or of t h e dihydrate at temperatures below 100째C) in s e a s a l t s o l u t i o n s (aqueous solut-ions containing t h e s a l t composition o f s e a w a t e r but with varying d e g r e e s o f conceritratiori or dilution) a t temperatures from 30 to 200째C and a t i o n i c s t r e n g t h s to 6 m , and h a v e compared t h e r e s u l t s with those obtained in sodium chloride solutions. F i g u r e 12.1 s h o w s all solubilily v a l u e s obtained experimentally; i n t h i s figure t h e logarithm of t.he sol.ubility product, K ; , , is plotted a g a i n s t a functiori of t h e formal i o n i c strength, I. 'The term K $ [ , is defined a s the molal solubility of calcium s u l f a t e times t h e molality of t o t a l s u l f a t e . T h e analogous, comparative behavior i n sodium chloride s o l u t i o n s

L. Marshall aiid 12. S l u s h e r , J . F h y s . Chem. 70, 'W. 4015 (1966). 5R.Hnra, Y , T a n a k a , a r r d K. N a k a m u r a , Sendai T o h u h Imp. Univ. 11, 199 (1934); R. H a r a , K. Nakamura, and K. Higashi, i b i d . , lo, 4.33 (1932). W. F. Larlgelier, D. W. Caldwell, md W. 13. Lnwrence, Ind. E n & Chem. 42, 12fi (195Oj; An invvesti&?tion of the Solubz!tty of Calcium S u l f a t e iri S e a w a t e r Concentrnfse a t Ta.i;ipcrofuresfrom ..fmbierif to 65'C, Office of S a l i n e Water R e s e a r c h and Development Report No. 191, U.3. Dept. of I n t e r i o r (May 1966); E. P o s n j a k , Am. J . Sci. 238, S59 (1940). 'W. L. Marshall, *"Tine Dissociation C o n s t a n t of hfagricsium Sulfate t.2 200"C," Chap. 6, t h i s report.

'Jointly sponsored by the Office of S a l i n e Water, W.S. D e p a r t m e n t of the Interior, and the U.S. Atornic E n e r g y Commission. 'W. &. Marshall, Reactor Chem. Div. Ann. P r o g r . Rept. Jar). 3 I , 196.5, ORNIr3789, p. 294. 3 W. L, Marshall, R. Slusher, and E. V. J o n e s , J. Chem. E r @ . D a t a , 9, 187 (1964).

119

120 a previously developed computer method’ was revised to obtain refined temperature-solubility l i m i t s for s a l i n e w a t e r s in general within which precipitation of calcium s u l f a t e or its h y d r a t e s c a n be avoided. T h e v a l u e s needed for t h e c a l c u l a t i o n s are t h e molalities of calcium, magnesium, and s u l f a t e , and t h e (rnolal) i o n i c strength of t h e

s a l i n e water. A representation of t h e r e v i s e d solubility limits for s e a w a t e r i s shown in F i g . 12.2; i n t h i s figure C F e q u a l s t h e concentration factor on a molal, molar (at 2S°C), or weight fraction b a s i s . If calcium and magnesium a r e removed initially from a s a l i n e water, other sets of concentration limits c a n h e obtained with ease.

F/ ( 1 F i g . 12.1.

AS P I P )

Solubility Products, K’

Compared w i t h Their Behavior i n

0 2

0 3

0 4

0.5

dI/(1+dS,Dfi)

fi/(l

t ASPfi),

o f CoS04’2H2(a ond C o S 0 4 i n Seawoter Concentrates

N o C I - H ~ OSolutions, 30-200°C.

121 GRNL.-DWG 68-7799

SEA WAlER (molol uniis)

UNSAl URAI EO I7EI;IONS

F i g . 12.2.

125

150

C a l c u l a t e d l i m i t s of Solution S t a b i l i t y to A v o i d P r e c i p i t a t i o n of Gypsum (CaSB,

o r i g i n a l molalities o f Ca a n d Mg;

R :=

from Seawater C o n c e n t r a t e s . m o l a l ratio,

CORROSION OF TITANIUM IN SALINE WATER

E. G. Bohlmann J. F. Winesette

J . C. G r i e s s , Jr. F. A. P o s e y '

Titanium h a s e x c e l l e n t r e s i s t a n c e to s a l i n e waters, but at temperatures of 150OC and higher it is s u b j e c t to s e v e r e corrosion damage in c r e v i c e s . Studies to determine t h e c a u s e and t o find w a y s to mitigate s u c h attack are i n progress. Electrochemical polarization s t u d i e s a t temperat u r e s up t o 150째C s h o w e d that i t w a s not p o s s i b l e to produce corrosion of t h e s a m e magnitude as observed in c r e v i c e s when t h e pW of 1 (13 N a C l s o l u t i o n s w a s 3 or higher; t h i s s u g g e s t s that t h e

Division.

'E. C . Bohlinnnn and J. C . Griess, Reactor Cbem. Div. Ann. Pro&. R e p t . Jan. 3 1 , 1965, ORNL-3789, pp. 297-305.

'2H20), H e m i -

1 , = molal i o n i c strength o f seawater;

504/Ca.

s111al1 volume of solution in the c r e v i c e becomes appreciably acid (mote than 10" M ) before c r e v i c e corrosion c a n occur. * To determine t h e approximate pM of t h e solution in a corroding crevice, specimens w e r e prepared in which t h e t i p of a fine itanium capillary extended into t h e crevice. 'The capillary tubing p a s s e d through t h e head of an autoclave, and with appropriate valving a s m a l l volume of the solution from t h e c r e v i c e region could b e sampled while t h e specimen was at 150째C. T h e ptt of s i n g l e small drops of solution w a s about 1 in those cases where c r e v i c e corrosion w a s observed and 4 t o 5 when significant corrosion w a s absent. T h e pE-1 of t h e bulk solution was 6 t o 7. Figure 12.3 s h o w s a series of paitial anodic: polarization c u r v e s obtained potentiostatically i n a solution containing 0.1 M HCI and 0.9 M NaCl. T h e c u r v e s originate at t h e corrosion potential, and t h e potential was changed i n a noble direction at 3-min intervals. In the a c t i v e region t h e current density achieved a s t e a d y - s t a t e v a l u e in less than 3 min, whereas in t h e p a s s i v e region t h e current d e n s i t y d e c r e a s e d slowly for long periods. Although

Crevice Attack

'Chemistry

100

TC:MPEHATURE ("C)

hydrate ( C o S 0 4 ' '$W20), a n d A n h y d r i t e (CaSO,) Ca, Mg

122 not shown, t h e p a s s i v e region e x t e n d s u p to t h e pitting potential, which i s ‘nigher t h e lower t h e temperature ( s e e s e c t i o n on “Pitting”). The c r i t i c a l current for passivation i n c r e a s e d with temperature, corresponding t o a n activation energy of about 11 kcal/mole. T h e a c t u a l niaximum current density a t 15OoC corresponds t o a corrosion rate of 360 mils/year, which is close t o , but less than, t h e maximum corrosion rate observed i n t h e c r e v i c e regions (as high a s 500 mils/year) at the same temperature. T h e corrosion of titanium in c r e v i c e s is not confined to chloride s y s t e m s . Titanium c r e v i c e s p e c i m e n s exposed t o neutral aerated 1 M NaBr, Nal, or Na,SO, a t 150°C underwent corrosion i n t h e c r e v i c e s t o about t h e same extent as observed in chloride solutions. Anodic polarization c u r v e s obtained in boiling acidified s o l u t i o n s of t h e s e s a l t s were e s s e n t i a l l y t h e s a m e a s t h o s e obtained i n chloride s y s t e m s (though t h e pitting potential is different). T h e s e r e s u l t s show that c r e v i c e corrosion of titanium is not peculiar to chloride solutions, but that i t is a s s o c i a t e d with t h e development of an acid environment within t h e crevice.

T h e preceding r e s u l t s imply t h a t a titanium alloy r e s i s t a n t t o d i l u t e acid s o l u t i o n s at 100°C may b e immune t o c r e v i c e corrosion a t higher temperatures; conversely, an alloy showing a c t i v e corrosion i n d i l u t e acid s o l u t i o n s a t lower temperatures probably will b e s u s c e p t i b l e t o c r e v i c e attack at high t e m peratures. It w a s of interest, therefore, t o determine t h e anodic polarization c h a r a c t e r i s t i c s of a number of commercially a v a i l a b l e titanium a l l o y s and of a l l o y s prepared i n s m a l l quantities by t h e Metals and Ceramics Division. T h e nominal cornpositions of t h e commercial a l l o y s t e s t e d were: 0.15% P d ; 4% Mn-4% AI; 5% Cr-3% Al; 4% V-6% Al; 14% V-11% Cr-4% ‘41; 2.5% Sn---5% ‘41; 2% Nb-l% Ta-8% AI; and 8% Zr---I% (Nb + ‘l’a)-8% Al. Alloys produced locally contained individually 1 , 5, 1 0 , 20, and 30% Mo; 0.5% Nb; 0.5% T a ; 0.5% Cu; 1% Sn; 1% Al; 2% Ni; and 1% Ni-1% Mo. P o t e n t i o s t a t i c anodic polarization c u r v e s were obtained for e a c h alloy in a solution containing 0.1 1l.I HC1 and 0.9 M NaCl. a t t h e atmospheric boiling temperature. Of all t h e a l l o y s t e s t e d , only t h e 0.15% P d alloy, t h o s e containing 5% or more Mo, and both a l l o y s containing n i c k e l showed

ORNL-CWG 6 6 - 6 2 3 2

- 0.150

-0.250

-4 -0.350 3 2 Y)

--0.450

r! cI

LU L

-0.550

-0.650

-0.750 2

Fig. 12.3.

2 5 IO0 CURRENT DENSITY (microomps/cm2)

E f f e c t of Temperature on the Anodic P o l a r i r o t i a n of T i t a r i i u m in a

0.9 ,VI NcnCI-0.1 M HCI

5 Solution.

1000

123 no a c t i v e region. Open-circuit potentials of freshly abraded or pickled s u r f a c e s for t h e l a t t e r group of a l l o y s were greater than t h e a c t i v e potential (more than -0.4 v v s S.C.E.), w h e r e a s all t h e other a l l o y s had polarization c u r v e s similar to t h a t observed with commercial purity titanium. The c r i t i c a l current density for p a s s i v a t i o n , however, varied somewhat from alloy to alloy. Additional anodic polarization c u r v e s were obtained i n boiling 1 M HC1 with t h o s e a l l o y s exhibiting p a s s i v i t y i n t h e 0.1 M HCl-0.9 M NaCl In t h i s environment only t h e a l l o y s solution. containing 20 and 30% Mo and t h e 0.15% P d alloy d i d not develop a potential c h a r a c t e r i s t i c of actively corroding titanium. T h e 2% Ni alloy w a s p a s s i v e initially, but after exposure to t h e 1 M HC1 for s e v e r a l d a y s or after c a t h o d i c polarization, the alloy developed an a c t i v e potential and corroded at about t h e s a m e r a t e as pure titanium. T h e 1% Ni-I.% M Q alloy exhibited borderline passivity. Most of t h e time the pot-entia1 o f t h e alloy w a s about -0.3 v v s S.C.E., but periodically i t dec r e a s e d to -0.47, at which potential t h e alloy corroded with. evolution of hydrogen. After a few minutes a t the l a t t e r value, t h e potential returned t o -0.30 v v s S.C.E. T h e time between periods of a c t i v e corrosion was 20 to 30 min. On t h e b a s i s that c r e v i c e corrosion o c c u r s bec a u s e of t h e production and maintenance of a n a c i d solution in the c r e v i c e , t h e a l l o y s which would tend to resist s u c h a t t a c k a r e 2%N i , 5% Mo, 1% Ni - t ~1%Mo, 10%Mo, 0.15% P d , 20% hlo, and 30% W, with t h e last b e i n g t h e most r e s i s t a n t . Observations on a large number of s p e c i m e n s e x p o s e d in high-temperature (150 to 200Â°C) loop experiments a r e qualitatively c o n s i s t e n t with t h i s xariking, but a s a t i s f a c t o r y quantitative m e a n s of a s s e s s i n g and demonstrating s u s c e p t i b i l i t y h a s not been devised.

range. However, in s o l u t i o n s containing a sufficient concentration of chloride ions (also bromide or iodide ions), l o c a l i z e d breakdown of t h e p a s s i v e l a y e r occurs, arid titanium e x h i b i t s a pitting pot-ent i a l similar to t h a t observed for aluminum, iron, s t a i n l e s s s t e e l , and other metals and a l l o y s which are c a p a b l e of existing i n both a c t i v e and p a s s i v e states. Electrochemical s t u d i e s of titanium a l l o y s i n s a l i n e w a t e r s h a v e shown a s h a r p i n v e r s e dependence of t h e pitting potential on temperature. T h u s , w h e r e a s most s u c h a l l o y s require anodic potentials of t h e order of 10 v or higher to i n i t i a t e breakdown of t h e protective o x i d e and c o n s e q u e n t p i t t i n g attack a t approximately 2 5 T , we h a v e found that t h e potential requited is only 0.5 to 2.0 v at e l e v a t e d temperatures. D e t a i l s of t h e variation of t h e pitting potential with temperature a r e dependent o n alloy arid solution composition but h a v e b e e n shown to b e quite reproducible under a given set of conditions. T h e e f f e c t of temperature on t h e pitting potentials of a number of titanium a l l o y s is s h o w n in Fig. 12.4. T h e s e d a t a were obtained by variation of t h e temperature of t h e 1 M NaCl solution while t h e titanium e l e c t r o d e s were polarized to their pitting

TEMPERATURE ("Fj

125

I75

225

275

OFINL- DJVG 66 -35558

575

3225

425

Pitting

Titanium, in common with many other metallic materials of construction, o w e s its immunity to corrosion to t h e e x i s t e n c e of a p a s s i v e o x i d e layer a t t h e metal-solution interface. E x c e p t in strongly acidic s o l u t i o n s under reducing condit i o n s , titanium normally corrodes spont.aneously a t a very low r a t e i n t h e p a s s i v e s t a t e , a n d t h e current d e n s i t y of t h e anodic p r o c e s s (formation of a TiO, p a s s i v e layer) is independent oâ&#x201A;Ź t h e v a l u e of t h e e l e c t r o d e potential over ii wide p o t e n t i a l

Fig. 12.4.

400 125 150 TEMPEf?ATL!HE ("C)

175

200

225

250

Efifect of Temperature on Pitting Poten-

tiuls af Tituniurn A l l a y s i n 1 iM NaCI.

124 potentials by p a s s a g e of a c o n s t a n t high anodic current. Commercially pure Ti a l l o y s and t h e 0.15% P d alloy, with s m a l l ainounts of added elements, show high pitting potentials (9 t o 11 v) i n t h e vicinity of room temperature. With i n c r e a s i n g temperature t h e pitting potentials of t h e s e materials d e c r e a s e more or less ui~iformlyt o v a l u e s of t h e order of + l to 2 v a t 175 t o 200OC. A relatively s u d d e n change (-2 v) i n t h e pitting potential o f t h e 0.15% P d alloy o c c u r s i n t h e vicinity of 125'C. T h e type 150 A alloy (28% Cr, 0.3% E'e) s h o w s a similar sharp drop in t h e v a l u e of i t s pitting potent i a l i n t h e vicinity of 70째C; t h e pitting potential c h a n g e s about 2.5 v over a temperature range of only a few degrees. P i t t i n g potentials of t h e t y p e 110-AT alloy (5.5% Al, 2.5% Sn) a r e generally low and attain v a l u e s of only about + 0.4 v at 190째C. Qualitatively, t h e c u r v e s of F i g . 12.4 show t h a t i n general t h e addition of alloying elements dec r e a s e s t h e value of t h e pitting potential of titanium. T h i s is c o n s i s t e n t with observations of F i s c h e r g on e f f e c t s of various s u r f a c e treatments and of intentionally added impurities on t h e initiation of titanium pitting corrosion. One way to rationalize t h e s e differences in pitting potentials of titanium a l l o y s is t o s u p p o s e that t h e pr-., n-ence of alloying elements a f f e c t s t h e ionic a s well as t h e electronic conductivity of t h e protective o x i d e layer. It is known that t h e p r e s e n c e of certain impurities or l a t t i c e d e f e c t s considerably e n h a n c e s t h e electronic conductivity of rutile ('!?io 2 ) crystals. Analogous e f f e c t s on t h e k i n e t i c s of

t h e anodic p r o c e s s h a v e been observed as a result of incorporation of alloying elements into t h e T102 l a t t i ~ e . ' ~ ~ In ' ~ addition to direct e f f e c t s on anodic reaction mechanisms, t h e p r e s e n c e of additional electronic energy l e v e l s in a s e m i conductor of t h e type in question and t h e resulting enhanced electronic conductivity imply a simult a n e o u s i n c r e a s e in hole concentration i n t h e v a l e n c e band (weakened bonds), so that a further i n c r e a s e in t h e mobility of ionic charge carriers c a n b e expected. An a n a l y s i s b a s e d on a simple r e s i s t a n c e analogy s u g g e s t s that differences in t h e mobility of ionic charge carriers, which affect t h e k i n e t i c s of t h e anodic p r o c e s s e s occurring i n t h e p a s s i v e o x i d e film, c a n account f o r observed variation in v a l u e s of pitting potentials a s a function of alloy composition.

9W. R. F i s c h e r , Tech. M i t t . Knrpp, Forsch. Ber. 22(3), 65-82 (1964). 'OK. IIauffe, H. Grunewald, and R. T r a n c k l e r - G e e s e , Z . Efeklrochcrn. 56(10), 937-44 (1952). "R. G. Breckenridge and W. R. Ilosler, P h y s . Rev.

91(4), 793-802 (1953). "W. Kleber, 1-1. P e i b s t , and W . Schroder, 2 . P h y s i k . Chern. ( L e i p z i g ) 215, 63-76 (1960). 13L. E. Hollander, Jr., and P. L. Castro, P h y s . Rev. 119(6), 1882-85 (1960). 14F. A. Grant,

Rev. Mod. P h y s . 31(3), 646-74

(1959).

Maserjian, Conduction Through Thin Titanium Dioxide F i l m s , J e t Propulsion Laboratory T e c h n i c a l Report No. 32-976, October 1966. 15J.

13. Effects of Radiation on Organic Materials W. W. Parkinson

EFFECTS

W. W.

OF RADlAPlON ON POLYMERS

s t u d i e d w e r e high cis Cr)%%j, high trans (95%), and two mixed polymc?rs, o n e 73% t r a n s and t h e other 71% s i d e vinyl. To derive a c t u a l concentratians of t h e olefin groups from t h e spectral measurements, it proved n e c e s s a r y to use t h e unirradiated s p e c i m e n s t h e m s e l v e s as calibration standards. Calibration c u r v e s developed from liquid olefins proved inapplicable. However, they w e r e adequal e to determine t h e small content of cis groups in t h e two mixed polymers. Since t h e total unsaturation was known, t h i s permitted f.he solution of simultaneous e q u a t i o n s relating t h e concentration of trans and s i d e vinyl groups to the o p t i c a l d e n s i t i e s at 967 and 910 cm-“’. T h e a b s o r p t i v i t i e s t h u s c a l c u l a t e d , coupled with t h e a c c e p t e d v a l u e for the t o t a l unsaturation in high-cis polybutadiene, enabled u s to deterrriiiie t h e cis concentration in t h e polymer of t h i s type from i t s spectrum. T h e integrated band area a t 740 c m - I , c a l c u l a t e d from theoretical band s h a p e s , 3 a 4 w a s required for t h e calibration and concentration determination of t h e cis group b e c a u s e of t h e dependence of the siinple absorptivity on groups adjacent to t h e c i s s p e c i e s in the molecule. F r o m t h i s treatment o f t h e infrared s p e c t r a , the concentrations of olefin groups were obtained for specimens irradiated under various conditions. T h e c h a n g e s in t h e s e groups for high-cis polybutadiene are plotted v s d o s e in F i g . 13.1. T h e d e c r e a s e i n cis groups at. t h e lower d o s e s appears to b e independent of their coiicent ration (zeroorder), whereas t h e d e c r e a s e in trans and s i d e vinyl groups i n t h e other t y p e s of potybutadiene followed first-order k i n e t i c s , In addition, t h e high-

W. K. Kirkland

Parkinson

Radiation-induced p r o c e s s e s in polybutadiene are significant b e c a u s e t h e polymer h a s a simple hydrocarbon structure related to natural and many of t h e s y n t h e t i c rubbers and b e c a u s e t h e olefin groups of t h i s polymer undergo rapid c h a n g e s upon irradiation. Furthermore, t y p e s of polybutadiene ate obtainable having a high fraction of t h e olefin groups in any one o f t h e t h r e e p o s s i b l e isomeric forms. T h e s e forms are CIS, t r a n s , and s i d e vinyl, a s shown:

CIS

TRANS

SIDE VINYL

C h a n g e s i n t h e s e groups may be s t u d i e d by infrared s p e c t r a , s i n c e e a c h has a t least o n e absorption band a t a characteristic frequency: cis a t 740 cm-’, trans at 967, and s i d e vinyl a t 910. P r e v i o u s reports described infrared s p e c t r a l rrieasurem erits on polybutadiene s p e c i m e n s of various t y p e s jrradiated in 6 o C gamma ~ sources and in a nuclear reactor.1s2 T h e four t y p e s ‘W. W. P a r k i n s o n e t a l - , N e a c f o r Cherrl. Uiv. .4rui. Progr. R e p t . J a n . 31, 1964, ORNL-3591, p. 226. ‘W. W. Parkinson and W. Radiation on the Olefinic p r e s e n t e d a t the American Mar. 29, 1966, Pittsburgh, Chemistzy S e r i e s (1F67).

0. Sisman

C. Sears, “The Effects of Groups i n Polybutadiene,’@ Chemical Society Meeting, Pa.; in press, A d v a n c e s in

3D. A. Ramsay, J .

~ J I Chern. .

S o c . 76, 7 2 (1952).

‘S. A. F r a n c i s , J. Chenz. P h y s . 17, 942 (1951).

125

126 cis polymer w a s t h e only type showing an inc r e a s e in concentration of o n e of t h e olefin isomeric forms. In t h i s polymer there w a s a convers i o n of cis groups t o t h e t r a n s form, t h e more s t a b l e isomer thermodynamically. T h e radiation

Fig.

13.1.

SIDE V I N Y L

Concentration of O l e f i n Sraups

in I r r o -

d i a t e d C i s Polybutadiene.

Table

13.1.

y i e l d s , r a t e c o n s t a n t s , and activation e n e r g i e s c a l c u l a t e d for a l l t h e polymers from t h e s e c h a n g e s in concentration a r e l i s t e d in T a b l e 5.3.1. T h e activation Energies were c a l c u l a t e d from radiation y i e l d s a t room temperature and a t 110OC. 'They a r e similar to activation e n e r g i e s in other radiation-induced reactions and i n d i c a t e that lowenergy p r o c e s s e s s u c h a s t h e addition of r a d i c a l s and t h e diffusion of relatively s m a l l s p e c i e s are t h e rate-controlling s t e p s . T h e high y i e l d s and high r a t e c o n s t a n t s indicate efficient transfer of radiation energy from t h e points of absorption t o reactive s i t e s , either through charge or excitation transfer. It is also p o s s i b l e that t h e high rate c o n s t a n t s observed for t h e s i d e vinyl groups result from s h o r t c h a i n reactions. T h e products resulting from t h e s e r e a c t i o n s a r e unidentified a s yet. B e c a u s e t h e cross-link y i e l d s a r e f a r too low t o account for t h e loss i n olefin groups, i t h a s heen s p e c u l a t e d that intramolecular

Radiation Y i e l d s and R e a c t i o n R a t a Constants ....

T y p e of Poly bu t a d i e n e

High Cis-1,4

High T r a n s 1,4

.4morphous Trans

S i d e Vinyl (Sodium)

(Emulsion)

t i s Groups

Initial yield, GO, groups per 100 e v Activation energy, E , kcal/rnole

-15.2

0.8

3.7

Reactor yield, Go, g o u p s per 100 e v

<4-1.0

<+0.5

- 12

T r a n s Groups

R a t e c o n s t a n t , k, g/ev

(1.4-3.3)

Initial yield, Go, groups per 100 e v

+6.8

1.5 t 0.3

Activation energy, E , kcal/iiiole

-11 to -22

Reactor rate constant, k , g/ev

2.4

.-19

-7

3.4

t 1.1

Reactor y i e l d , Go, groups per 100 e v

2.2 x

4.0

0.9 Side V i n y l Groups

R a t e c o n s t a n t , k , g/ev

0 ... 1.4

Initial yield, Go, groups per 100 e v

4.3 x

0.5

- 12

-0.2

lorz3

5.4 -40

Activation energy, 17, kcal/mole

3.8

3.9

Reactor rate constant, k , g / e v

1.6

-1

-3 1

- 47

N e t Change,

Initial yield, Go, groups p e r 100 e v

-8.4

A l l Groups (Gamma R a d i a t i o n ) -11

-22

127 ring l i n k s are formed, but t h e s e h a v e not been identified definitely in irradiated polybutadiene b e c a u s e of difficulties in both s p e c t r a l and chemi r a l observations of s u c h c y c l i c s t r u c t u r e s .

RAD1ATION-INDUCED REACTlON 5 OF HYDROCARBONS R. M. Keyser

W. K. Kirklaiid

T h e irradiation of c o a l together with a condensedp h a s e s o u r c e 'of hydrogen atoms and alkyl free radicals offers t h e possibility of t h e s y n t h e s i s of useful hydrocarbon chemicals from jnexpensive raw materials in a chernonuclear reactor, Initial irradiations h a v e been confined t o a model s y s t e m for experimental convenience: n-hexane (simulating liquefied petroleum g a s e s j t h e condensed s o u r c e of hydrogen and r a d i c a l s , with naphthalene simulating coal. It is expected that t h e overall c o u r s e of t h e reaction, t h e addition of radiation-generated hydrogen atoms and alkyl free r a d i c a l s t o aromatic rings,6 will b e s i m i l a r i n both t h e model and c o a l systems.

Samples irradiated with 'Co gamma radiation h a v e been analyzed by gas chromatography on a 5-m column containing Apiezon L a s t h e s e p a r a t i n g medium. T h e r e s u l t s of a typical run are shown in Fig. 13.2, Erom which it is apparent that irradiation of naphthalene-hexane solutions y i e l d s a quite complex array of products. Efforts to d a t e h a v e b e e n directed toward identification of t h e compounds responsible for t h e peaks in Fig. 13.2. T h e s i x dimers of hexane, t h e peaks labeled 4,s-diethyloctane through r2-dodecaiie in Fig. 13.2, h a v e b e e n identified by using chromatographic retention t i m e s to obtain e s t i m a t e s ot t h e boiling points of the compounds in question and comparing t h e s e with literature values. Apiezon L, a nonpolar liquid, s e p a r a t e s saturated hydrocarbons ess e n t i a l l y on t h e b a s i s of their boiling points. It

%I. A. Golub, J. Phys. Chem. 59, 2639 (1965).

'W. W. Parkinson e t H I . , Kesctor CZiern. U i v . A r m . Progr. R u p t . J a n . 31, 1965, OHNL-3789, p. 320.

. .

..............................

OHNL-DWi;

61- 542

............ .................

RETENTION T l f ~ l E (min )

I 125

-1 ............................ 1 SC

I ........... I........I ...........1 ........

175

200

2.25

235

TEMPE IIAl-UIX ("C)

F i g . 13.2.

C a s Chromatogram on a

J IS0TIiEflPMAL PT

235 ---

5-171 A p i a r o n L Column of a Sample C o n s i s t i n g of 0.10 M o l e F r a c t i o n o f

N a p h t h a l e n e i n n - H e x a n e l r r a d i a f e d t o a Dose o f 1 .O

x 1 022 e v . g-

128 c a n b e shown, from thermodynamics, that t h e following relation should hold: log t r

= :

K + (4.5/T) I", ,

(13.1)

where t r is retention time, T is g a s chromatograph column temperature, T , is boiling point, and K c a n b e regarded a s a c o n s t a n t piovided t h e operati n g parameters of t h e chromatograph are c l o s e l y duplicated from run to run. V a l u e s of log t r for standard s a m p l e s of nheptane, n-decane, and n-dodecane were plotted against their r e s p e c t i v e boiling points, and t h e relationship predicted by Eq. (13.1) w a s found to hold. Boiling points of t h e compounds correspondi n g to t h e p e a k s indicated i n F i g . 13.2 were then 7 S e e , f o r example, J. H. Knox, G a s Chrornafography, chap. 2, 'Niley, N e w York, 1962.

obtained from their respective retention times and t h e l o g t r v s T , plot. T h e boiling points obtained i n t h i s way agreed within 1 t o 2' of t h e literature v a l u e s for t h e hexane dimers, T h e identification of o n e of t h e radiation products a s n-dodecane w a s further confirmed by t h e coinc i d e n c e of i t s retention time with that of a standard s a m p l e of n-dodecane. T h i s same technique w a s a l s o u s e d to tentatively identify the peak preceding naphthalene a s 1,2-dihydronaphthalene. Compounds corresponding to peaks 1 t o 8 i n t h e chromatogram of F i g . 13.2 h a v e b e e n individually trapped in g l a s s c a p i l l a r i e s at liquid-nitrogen t e m perature upon elution from t h e chromatograph. T h e s e collected fractions were u s e d to obtain ultraviolet absorption s p e c t r a i n cyclohexane solution of compounds 1 through 8. Some typical r e s u l t s a r e shown in F i g . 13.3 for t h e 240-to330m p region. Differences i n overall i n t e n s i t i e s are ORNL-DWG

2.0

57-543

1.5

t v) z W

a 9 + a

1.0

0.5

240 F i g . 13.3. of Fig.

13.2.

250

260

270

280

290

310

300

.......~.~

--- -----_.

320

330

WAVELENGTH ( m p ) U l t r a v i o l e t Absorption Spectra of Compounds Corresponding to P e a k s 2,

3, ond 8 in the Chromatogram

Solvent i s cyclohexane and concentrations a r e d i f f e r e n t for e a c h compound.

129 ture, and s o l u t i o n s of 1 : 3 concentration were irradiated at 150 and 300째C. T h e irradiated mixt u r e s were s u b j e c t e d to chromatographic a n a l y s i s on a butanediol s u c c i n a t e polar column and on a s i l i c o n e rubber nonpolar column. At room temperature there were four products in t h e range of dimers and 1 : l adducts, plus t h e nonvolatile residue. At t h e higher temperatures o n e of t h e products disappeared. To identify t h e radiation products observed b y chromatographic a n a l y s i s , cornpounds which were probable products were s y n t h e s i z e d by conventional chemical methods. T h e chromatographic retention times of t h e s y n t h e s i z e d cornpourids were then matched with those of t h e radiation products o n columns o i a t l e a s t two types. T h e methods u s e d for pteparation of t h e dimeric compounds were Wurtz-type c o n d e n s a t i o n s of organic h a l i d e s with a c t i v e zinc-copper and cond e n s a t i o n s with CH3MgI. For a d d u c t s the s y n t h e t i c method w a s t h e Grignard reaction, c o n d e n s i n g ~ ~ REACTIONS ~ ~ ~ t h e c y c lI o h e s e n y l~or furanylNmagnesium h a l i d e with OF FURAN DERIVATIVES t h e proper halide. T h e h a l i d e s in a l l t h e s e rea(:t i o n s were prepared by a c c e p t e d methods. For c. I>. F3opp W, \V. Parkinson example, 2-chlorotetrahydroiuran w a s obtaiiied by direct chlorination of tetrahydrofuran at - .50째C; 'l'he cadiat-ion-induced additiotn of s a t u r a t e d furan allyl-type bromides, s u c h a s 3-bromocyclohexetie derivatives to olefinic groups is being s t u d i e d to 2-bromo-2,5-dihydrofuran, were obtained by and develop high-yield reactions which could u t i l i z e bromination with a s u s p e n s i o n of N-bromosucradioisotopes i n chemical s y n t h e s i s . An earlier cinimide i n carbon tetrachloride. By t h e s e Inethods susveyR covered c h i e f l y monoolefinic and s a t u r a t e d t h e t e n p o s s i b l e allyl-type or a l p h a isomers of t.he furan d e r i v a t i v e s and cyclohexene. T h e r e s u l t s dimers arid 1 :1 a d d u c t s of cyclohexane, cyclowere promising in that t h e array of products w a s hexene , tetrahydrofuran, arid dihydrofuran were limited; there were only three or four major products, prepared. c o n s i s t i n g of dimers, 1: 1 a d d u c t s , and a nonBy comparing retention t i m e s of t h e s e s y n t h e t i c v o l a t i l e residue: probably comprising trimers and products with t h o s e of t h e irradiated mixture, t h e higher adducts. Furthertnore, t h e yield of major compounds l i s t e d in T a b l e 13.2 were tentatively products w a s enhanced by irradiation at higher as t h e major radiation products. T h e identified temperatures, while t h e yield of minor products identification remains tentative b e c a u s e of the was reduced. On t h e other hand, none of t h e p r e s e n c e of t h e products of s i d e reactions in t h e mixtures containing s a t u r a t e d furan compounds s y n t h e s i z e d compounds. T h e s y n t h e s i z e d comg a v e t h e high y i e l d s c h a r a c t e r i s t i c of c h a i n reacpounds a r e now b e i n g i s o l a t e d , by d i s t i l l a t i o n tions. and extraction, for infrared s p e c t r a to eliminate The s y s k m cyclohexene-tetrahydrofuran h a s uncertainties. Chromatographic fractions a r e also b e e n investigated i n d e t a i l , s i n c e t h e radiationb e i n g c o l l e c t e d from t h e radiation products for induced r e a c t i o n s of cyclohexene a r e better known similar examination to confirm our identifications. Solutions of than t h o s e of t h e other reagents. T h e tabulated product y i e l d s were obtained from cyclohexerie in tetrahydrofuran i n concentrations chromatographic peak a r e a s utilizing d o d e c a n e as of 1:3 and 1 : 7 were irradiated at room temperaa n internal standard. Evaporation of t h e irradiated mixture indicated that t h e yield of polymeric nonv o l a t i l e r e s i d u e w a s greater than G := 6, probabiy 'C. D. U o p p e t a l , , Reactor Chem. U i v . Ann. Pro&. e x c e e d i n g t h e combined y i e l d s of dimers and 1 : 1 H e p t . D e e . 3 1 , 196.5, ORNL-3913, p. 123. not significant, s i n c e t h e s p e c t r a w e r e obtained a t diEfe rent concentrations. T h e uv spectrum of a-methylnaphthalene, included in F i g . 13.3 for comparison, e x h i b i t s absorpt i o n b a n d s in t h e s e same regions a l s o , and t h e comparison strongly s u g g e s t s t h a t compounds 1, 2 , 3 , 4 , 6 , and 8 a r e u-substituted alkylnaphthalenes. S i n c e t h e chromatographic retention time of rxmethylnaphthalene is l e s s than t h a t of compound 1, t h e a l k y l s u b s t i t u e n t s must b e larger than methyl. r . Lhe uv s p e c t r a of compounds 5 and 7 i n d i c a t e t h a t t h e s e coraipounds a r e j?-substituted alkylnaphthalenes. Additional iamount:; of t h e s e compounds a r e being !rapped from t h e chromatograph effluent, arid i t is planned to u s e t h e s e to obtain mass, infrared, and nuclear magnetic resonarace s p e c t r a , which, i n conjunction wi1.h t h e uv d a t a , should e n a b l e u s to make 2. positive identification of t h e unknowns.

130 T a b l e 13.2.

R a d i a t i o n P r o d u c t s from C y c l o h e x e n c Tetrahydrofuran S o l u t i o n s

Producl

Y i e l d ( m o l e c u l .e ~. s per 100ev) ~~

25째C

!50"C

t:30

!:70

-4

Z(Cyc1ohcxene- 3.~1)lelrahydrofuron

2,2'-Di(tetrohydrofuran)

3,3'-Dicyclohexenyl

-0.5

0~0

t.5

300째C 1:30

-8

-6 -2

nConcelntrol\on of cyclohexene In t e t r a h y d r o f u r a n by v o l u m e

adducts. Additional derivatives of furan and furfural are being irradiated tu explore t h e nature of t h e reactions and t o look for t h e high y i e l d s of c h a i n reactions.

DEV EkQPM EN T OF RADIATION- R ESI STAN T INSULATORS

B. j . Sturm W. W. Parkinson E. J. Kennedy' A program h a s been initiated under t h e sponsors h i p of t h e Office of Civil Defense t o develop radiation-resistant insulators for personnel dosime t e r s . Since t h e dosimeters a r e s m a l l fiber electrometers, the e l e c t r i c a l r e s i s t a n c e of t h e construction materials must b e very high, both before and after irradiation. A copolymer of s t y r e n e and a-methylstyrene with a moderate impurity c o n t e n t h a s been found t o h a v e high r e s i s t a n c e before irradiation and extremely low postirradiation conductivity. Objectives of t h e program, then, a r e to correlate t h e e l e c t r i c a l c o n ductivity of p l a s t i c s with t h e molecular striactrire 'In s t r u m e n tation and Controls D i v i s i o n .

of t h e b a s e polymers and a l s o with t h e chemical nature of t h e impurities, siiice t h e s e a r e known to affect t h e conductivity prior t o irradiation and appear t o play a part in reducing t h e postirradiation conduction. T h e correlations should permit t h e s e l e c t i o n of ii~aterinlsand t h e development of fabrication methods s u i t a b l e for both t h e bulk insulators and t h e c a p a c itor dielectric in t h e dosimeters. We a l s o hope to identify t h e mechanism of t h e impurity e f f e c t s ; i t could b e a s u r f a c e p r o c e s s or a p r o c e s s i n t h e bulk of t h e polymer involving supplying and trapping charge carriers. Analytical work on s t y r e n e - b a s e p l a s t i c s h a s indicated that t h e content of unpolymerized s t y r e n e v a r i e s widely in t h e s e materials. T h e copolymer of low conductivity showed a monomer content of -0.1%. T h e solvent-cast fillii ( t h e form for c a p a c itor d i e l e c t r i c and specimen material for r e s i s t a n c e measurement) showed less than 0.01% monoriier. Since t h e unsaturated nature of s t y r e n e monomer makes i t chemically different from t h e polymer, t h e role of t h e monomer i n e l e c t r i c a l p r o c e s s e s in t h e p l a s t i c will b e investigated early i n t h e program. A vibrating-reed electrometer h a s b e e n modified slightly t o permit e l e c t r i c a l measurements i n t h e required low-current range. T e s t s h a v e indicated that i t s minimum s e n s i t i v i t y is of t h e order of 10amp. T h i s will b e s u i t a b l e for postirradiation measurements and a t l e a s t some of t h e preirradiation measurements. T h e procurement of saiuple materials h a s b e e n confined t o s i m p l e polymers, either hydrocarbons or polyiiiers of carbon, hydrogen, and either oxygeri or nitrogen, and to materials of relatively high purity, with t h e e m p h a s i s on t h e g l a s s y , amorphous p l a s t i c s . Common commercial additives, for e x ample, ultiaviolet s t a b i l i z e r s and antioxidants, h a v e a l s o been obtained. Measurements and irradiations will b e made f i r s t on polymers of s i m p l e chemical and physical structure i n t h e hope of obtaining d a t a amenable to interpretation i n terms of t h e b a s i c composition of t h e material.

14. Chemical Support for the Contaalle Thermonuclear

D. $1. Richardson

R. A. Strehlow lNTERPRETATlON OF DCX-2 MASS SPECTRA

n a n t change, e x c e p t during a period of probe adjustment a t noon, i n d i c a t e s that the water offg a s s i n g rate i n c r e a s e d during the morning and presiurnably w a s a thermal effect. B e c a u s e oE t h e dominance of water vapor and its s l o w removal from unbaked vacuum s y s t e m s , s o m e of the parameters a f f e c t i n g water behavior (in unbaked s t a i n l e s s s t e e l s y s t e m s ) h a v e been s e p a t a k l y s t u d i e d . T h e partial pressure of carbon dioxide h a s been generally observed t o follow that of water vapor. T h e average carbon dioxide partial p r e s s u r e app e a r e d to be about 15% of the water vapor p r e s s u r e during t h e day. Methane (present during t h e titanium evaporation) w a s about 5% of the water partial p r e s s u r e , Other organic spe~iesand carbon monoxide comprised t h e b a l a n c e af t h e b a s e - p r e s s u r e g a s e s , hut were not studied. Of t h e g a s e s which a r e introduced d o n g wid1 intentionally admitted g a s , water vapor and a i r h a v e been observed. Air from l e a k s i n the gas manifold is present in amounts which depend upon t h e length of time s u b s e q u e n t to manifold e v a c u ation, a s w e l l a s t h e l e a k rate. Water vapor is u s u a l l y t h e dominant manifold impurity and w a s so for t h i s study. The water partial pressure variation with ion-gage reading for a hydrogen l e a k is shown i n Fig. 14.2. T h e linearity of t h e d a t a points a n d t h e times involved in t h e exposure ind i c a t e d that t h i s i n c r e a s e w a s not an artifact of t h e spectrometer but w a s d n e t iricrease of water partial p r e s s u r e admitted with or d u e t o admission of t h e hydrogen. T h e water p r e s s u r e w a s o b s e r v e d to vary only s l i g h t l y during beam injection. It w a s therefore concluded not to b e a g a s of t h e fourth type ( g a s e s produced during beam injection).

Twenty DCX-2 m a s s s p e c t r a obtained during a s i n g l e day w e r e s u b j e c t e d to d e t a i l e d examination. F o u r t y p e s of impurity g a s e s (viz., not hydrogen) were distinguished by peak height comparisotls. ’These four t y p e s were:

’

1. t h o s e s p e c i e s generated or evolved n e a r the spectrometer,

2. the s o - c a l l e d b a s e p r e s s u r e g a s e s ,

3, impurity gases introduced with intentionally admitted gas,,

4. impurity g a s e s generated during beam injection. As noted earlier, the spectrometer s p e c i e s dec a y e d rapidly for 30 to 50 min after t h e spectromThose s p e c i e s , e t e r filament was turned on. primarily organic, apparently h a v e no significant relation to g a s e s impinging on t h e DCX-2 plasma. Quantitative interpretation of t h e m a s s s p e c t r a is complicated by their presence. Of fer more s i g n i f i c a n c e is t h e behavior of t h e b a s e - p r e s s u r e s p e c i e s other than hydrogen. Air l e a k s h a v e been only o c c a s i o n a l l y responsible for a s i g n i f i c a n t part of the background gases. Water vapor, carbon dioxide, and methane were t h e principal identifiable s p e c i e s in t h e background gas a n t h e day of the s t u d y (August 11, 1966). Water vapor c o n s t i t u t e d about thtee-quarters of tlie irnpurity background g a s e s . Although t h e water partial p r e s s u r e i n c r e a s e d during admission of hydro gen, i t was p o s s i b l e to n o t i c e the variation of t h i s component of t h e background during t h e day. T h i s variation i s shown i n F i g . 14.1. T h i s domi-

’See s u b s e c t i o n ‘‘Water Vapor Chemisorption on Stainless Steel,” this section.

‘~12emzonuc1ear ~ i v Senziann. . P r o g r . Refit. A p r . 30, 1966, ORNL-3989, pp. 128-32.

131

132 ORNL-DWG

67-779

- <

J l

PROBE ADJUSTMENT-

-1 F i y . 14.1.

3 4 5 6 T I M E (hours after R A N i , 8 - 1 1 - 6 6 )

H20

DCX-2 (8-11-66) as a F u n c t i o n o f

T i m e (5ockground Impuiity).

Figure 1 4 . 3 s h o w s t h e variation of identifiable s p e c i e s with ion-gage w a d i n g during beam i n j e c tion. T h e fractional contribution of t h e s e s p e c i e s is shown i n parentheses. Water, though not produced by t h e injection p r o c e s s , i s shown for comparison. T h e variation of m a s s 28 (primarily from ethane, ethylcnc, carbon dioxide, carbon inonoxide, and nitrogen) after adjusting for CO, and e t h a n e appeared, from consideration of fragmentation patterns, t o b e primarily carbon monoxide and e t h y l e n e in about e q u a l amounts. T h e variation of m a s s 28 so adjusted contributed s l i g h t l y less to t h e A fractional t o t a l pressure than did methane. abundance of 0.003 to 0.004 for e a c h of t h e s e g a s e s relative to hydrogen w a s indicated. T h i s behavior appeared to b e typical for the mode of DCX-2 operation a t the time t h i s work w a s done. T h e principal organic s p e c i e s identified a s being produced during beam injection a r e methane, ethyle n e , acetylene, and ethane. T h e partial p i n s s u r e of t h e s e g a s e s w a s found for one day to b e about 2.5% of t h e indicated p r e s s u r e . F o r many plasma experiments in DCX-2, i t h a s not been a s n e c e s s a r y t o maintain a high-purity environment a s to have some knowledge of t h e purity l e v e l . A purity index c a n b e defined a s

F i g , 14.2. Impurity).

APH$ (xt07torri

l n c r e a z e of p

w i ? h H2 B l e e d ( M a n i f o l d

H20

10 2 8

0.5

p(impurityi i x ~ ~ ~ t o r r i

Fig.

14.3.

P a r t i a l Prs355ures of

@MA,

C 0 2 , C2W2 and

C2H6 (Produced I m p u r i t i e s ) in DCX-2 (8-1 1-66) D u r i n g Injectior! a t D i f f e r e n t

112 P a r t i a l Pressures.

F i g 1 4 . 2 ) i s shown f o i comparison.

p H l o (see

pft2/(ptotal - pw2). mately given by

T h i s index (P.1.) is approxi-

ORNL-OWG 57-782

..............

----~-T--

where .

2.2 is t h e ion-gage factor for H , , [jlnd

is the indicated ion gage pressure,

p B j is t h e partial pressure of "base" contaminants other than H 2 , Y

- .....

pressure

is t h e fraction of t h e ion-gage reading (p,,,d) due to contaminants produced by t h e injection, introduced with bleed g a s , or generated by t h e s e s p e c i e s (a gage factor of unity i s a s sumed).

For t h e d a t a described here, u s i n g the values d

p,,

...

-'torr and 9 x

3.5 x 10-

torr,

0 057 (based on the m a s s s p e c t r a l analysis),

o n e obtains, for the two indicated p r e s s u r e s , v a l u e s of the purity index of 7.0 and 20.8, respect.iw?ly, for t h e two pressure l e v e l s . The data obtained on August 11 yielded the purity index variations shown i n Fig. 14.4. T h e s e d a t a were obtained over a period of s e v e r a l hours in t h e rtiorning when the water partial p r e s s u r e w a s i n c r e a s i n g as d i s c u s s e d above. T h e points a t indicated p r e s s u r e s of 1.0 and 1.3 x torr, which were obtained later, were, accordingly, s o m e what lower than t h e v a l u e s interpolated from t h e e a r l i e r detenninat-ions. T h e agreement of t h e c:ald a t e d values of P.I. with t h o s e shown i n Fig. 14.4 i n d i c a t e s that unidentified s p e c i e s a r e not present i n significant amounts. R e s i d u a l gas a n a l y s i s strongly depends 011 t h e useful m a s s range of the spectrometer, the existe n c e of identifiable parent m a s s peaks, and a knowledge of fragnieritation patterns. We have l i t t l e knowledge of s p e c i e s with molecular weights higher than 44 u for the DCX-2 spectrometer, or higher than about 92 u for t h e instrument u s e d i n t h e calibration and chemistry s t u d i e s . A spectrome t e r d e s i g n study h a s begun with t h e goal of improving t h e analytical capability in the ORNL mirror machines.

.I .......

F i g . 14.4.

......

............

.............

..........

P u r i t y lridex V a r i a t i o n (DCX-2, 8-11-66) v s

U n c o r r e c t e d !on G a g e R e a d i n g .

MASS SPECTROMETER ~

~ STUDlES B ~ ~

Dispersion of mass spectronieter i o n beams aff e c t s both t h e c r a c k i n g pattern:; and the relative partial pressure s e n s i t i v i t i e s far different g a s e s . Calibration s t u d i e s carried out using the type of mass spectrometer u s e d on DCX-2 (Veeco model No. RGA-3) s h o w e d that the instrument h a s a s i g nificant degree of m a s s dispersion. ']This clispersion is attributable t o space-charge effects and to thermal velocities in t h e direction parallel t o t h e magnetic field during t h e ion's life.

131 Space-charge e f f e c t s a t higher p r e s s u r e s were observed a s a diminution of ion i n t e n s i t i e s upon increasing t h e hydrogen pressure. As e x p e c t e d , t h i s effect i s most pronounced for g a s e s of higher molecular weight ( e .g., argon and krypton). Hydrotorr gen p r e s s u r e s of a s much as 2 to 3 x were needed before a significant d e c r e a s e of t h e 28 and 18 m a s s p e a k s occurred. At lower p r e s s u r e s t h e m a s s discrimination c a n b e attributed principally to thermal drift in the direction of t h e magnetic field during t h e flight time of i o n s to t h e collector. Estimation of t h i s e f f e c t for t h e a n a l y z e r region only, u s i n g a s parameters t h e flight path (23 cm), t h e ion velocity derived from t h e ion energy meter, t h e average thermal velocity ( a t 100째C), and relative spectrome t e r s l i t lengths, l e a d s to the estimated transmiss i o n s l i s t e d in T a b l e 1 4 . 1 along with the transmission a s determined from experimental d a t a d e s c r i b e d below. T h e observed transmission fractions were uniformly lower than t h o s e estimated. T h i s i s presumably due t o m a s s discrimination in t h e s o u r c e . F o r t h i s 60' spectrometer (supplied with almost e q u a l s o u r c e and collector s l i t lengths), i t should be p o s s i b l e to d e c r e a s e the m a s s d i s crimination of t h e analyzer region by perhaps 60%,

T a b l e 14.1.

R e l a t i v e T r a n s m i s s i o n s for the RGA-3 Spectrometer

Estimated Fiaction

Species

Transmitted,

Ex peritue nta 1 Fraction

Transmitted, Entire ~ l

Analyzer Region Only

Path

1.0

H20

0.9

0.8

0.7

~ 0 . 4 t o 0.5

co,

0.5

0.2

C61-16

0.2

Low m a s s

0.98

18 ......,..

range, 1-1,~

0.1

J,nw mass

range, H 2 0 ...

=0.1 .......

=Low m a s s e s are obtained by s h u n t i n g t h e magnet, which reduces the f i e l d by a factor of about 0.55.

but probably with l i t t l e overall improvement of t h i s parameter b e c a u s e of t h e s o u r c e contribution. T h e method u s e d t o experimentally determine t h e e x t e n t of m a s s discrimination was simply to m e a s ure the peak height ratios for argon ( + l , +2, and + 3) and compare t h e s e with t h e literature values. ( T h e electron energy for the RGA-3 i s 1 4 5 I 4 v.) T h e same technique applied t o t h e spectrometer on DCX-2 yielded similar results. T h e d a t a shown in T a b l e 1 4 . 1 were estimated u s i n g a smooth curve drawn through t h e points a t M/e = 13.3, 20, and 40. R e l a t i v e calibration of t h e spectrometer to an ion gage for nitrogen and water vapor yielded additional points within 15 and 5%, respectively, of t h e derived argon transmission curve. T h e iong a g e s e n s i t i v i t y factor for water vapor w a s incidentally determined froin measured flow r a t e s , a s s u m i n g t h e pumping s p e e d for water vapor t o b e ~ % 3 / 1 8 that of nitrogen (with water cooling of t h e trap). T h i s value of t h e gage s e n s i t i v i t y of water vapor w a s found to b e 0.9 I 0.03 that of nitrogen . T h e s e d a t a were u s e d in t h e measurement of contaminant l e v e l s in the DCX-2 work described above. T h e s e r e s u l t s should not be indiscriminately applied to other similar a n a l y z e r s , b e c a u s e t h e e x t e n t of mass discrimination i s strongly affected by operating parameters s u c h as repeller potential. In order to avoid overly h a r s h evaluation two things should be noted. T h e first is that residual g a s a n a l y z e r s are designed primarily for qualitative a s s e s s m e n t of vacuum conditions and that their application to quantitative work i s usually res t r i c t e d to individual mass p e a k s or simple ratios. T h e s e c o n d i s that t h e a n a l y t i c a l capability is restricted to masses less than 44 11. i ~ ~generally ~ T h e spectrometer model u s e d in our s t u d i e s perf o r m s t h e s e t a s k s well. The need for more quantit a t i v e d a t a , however, d o e s markedly s t r a i n the instrument's capability.

T h e dominance of water vapor impurity in DCX-2 and t h e lack of information about i t s sorption k i n e t i c s prompted a study of water sorption at low partial p r e s s u r e s . T h e results of the study .....

3H. S. W. Massey and E. H. S . Burhop, Electronic and I o n i c Impact Phenomena, p. 38, Oxford, 1956.

135 s h o w e d distinctly that chemisorption occurred in the experimental vacuum s y s t e m . T h e experiments were conducted in a manner to give a s s u r a n c e that t h e observed chemisorption occurred primarily on s t t i n l e s s s t e e l s u r f a c e s . T h u s , s i n c e a large body of information on chemisorption e x i s t s , t h e description of water vapor behavior in vacuum s y s t e m s c a n be greatly simplified. Specifically, ii s e l e c t i o n from empirical relations between the extent of sorption and time, exposure, pressure, or temperature which a r e observed tor other chemisorption reactions may be applied t o s t u d i e s of water vapor. Chemisorption may be distinguished from physic ~ adsorptian 1 u s i n g s e v e r a l criteria, including the f01lowing:

1. Chemisorption requires an appreciable (> 0.1 ev) h e a t of activation.

2. It usually involves sorption h e a t values greater than about 0.5 to 1 a) ev, whereas physical. adsorption is u s u a l l y a s s o c i a t e d with s m a l l e r values.

3 . Chemisorption or cliemidesorption is ( a s a cons e q u e n c e of criterion 1) a slow p r o c e s s .

4. T h e quantity of s u b s t a n c e chemisorbed often is related to time by t h e t-mpiiical relation:

(1) where y is the amount sorbed a t time t and where a and 0 are c o n s t a n t during any single experiment or at the very least h a v e discontiriuous derivatives with r e s p e c t to time during a s i n g l e experiment. Water Chemisorption s t u d i e s h a v e been made for TR0,,5,6A1,0,,5,7 l ' i 0 , , R r 9 and s i l i c a " SOTbents, principally calorimetrically. (Infrared, gravimetric, and pressure-change techniques h a v e also

b e e n used.) N o report has been found in the literature on water sorption k i n e t i c s a t low ptcssures torr) or on metals. T h e technique u s e d i n this study w a s to o b s e r v e t h e pressure fall after water vapor exposures at different p r e s s u r e s and durations iii a dynamical ty pumped vacuum s y s t e m (Fig. 14.5)~ T h e apparatus w a s designed t o h a v e two regions ( A and Is) which could b e s e p a r a t e l y heated. T o minimize temperature nonuniformity, region A, a steel tube with 1.1 x IO4 cm2 a r e a , was baked by r e s i s t a n c e h e a t e r s strapped to t h e outside of an aluminunr pipe which fitted concentrically around the s t e e l tube with a uniform ?2-in. gap. Insulat.ion material and aluminum foil w e r e applied around the alurninum pipe, A copper tubing cooling circuit w a s strapped to the s t e e l t u b e in order t o a c h i e v e a rapid cooling capability. Region B , down to below the conductance-limiting baffle, w a s h e a t e d u s i n g strapped-on and serpentine h e a t e r s , and a hot air assembly to h e a t the trap. The m a s s spectrometer (Veeco RGA-3) w a s heated with tape h e a t e r s . Glass ion g a g e s (used only for early experiments) w e r e heated by h e a t l a m p s . Only metal seals were u s e d . T h e water w a s admitted through a valve from a regulated pressure of 1 o r 2 torrs, T h e gas line w a s periodically haked and operated with cold water cooling t o minimize organic contamination. Water vapor with less than 0.03% total organic ORNI. --DWG 67-783

EA K A R I.. E

---...

"J.

W. Whalen, J . P h y s . Chern. 6 5 , 1876 (1961).

C 0 N 0 U C TA NC E LIMITING BAFF1-F -.......... LlO!.JiD

Fig. 14.5.

I I

.......

N2 TR4P

DIFFUSION PUMP ----

*C. M. Hollabaugh and J . J . Chessick, J . P h y s . Chern.

919 (1944).

; I I I

..........

&in.

I I

4The review a r t i c l e by En. J . D. L.ow with 342 references is e s p e c i a l l y recommended; Chern. R e v . 6 0 , 26731%(1960),

65, 109 (1961). 'W. D. Ilaskins and G. Jura, J . Am. Chem. SOC.6 6 ,

......

-- -

. .

'M. E. Winfield, Australiari J . Chem. 6 , 2 2 1 (1953). 6 ~ F. ~ I+olrnes, . L. L. F U I I ~ ~ and , C . H. ~ e c o y ,J. Phys. Chem. 70, 436 (1966). 7R. L. Yenable, W. â&#x201A;Ź1. Wade, and N. Hackerman, J. P h y s . Cheni. 6 9 , 317 (19G5).

REG IONS

Vacuum S y s t e m U s e d

Water Vapor Chemisorption.

I D for t h e Studies o f

136 Contamination could b e admitted to t h e system. 'Two temperatiire conditions were s t u d i e d . T h e e l e v a t e d temperature condition w a s 180 + 2OoC ( a s monitored by s e v e r a l thermocouples) for a l l regions of t h e apparatus. T h e lower temperature condition w a s reached following a rapid cooling of region A to 28OC. T h e temperature of region B w a s not changed. At the e l e v a t e d temperature, typical partial p r e s s u r e s in torrs were 3 x 112, 4 to 8 x lo-'' H,O, 1 t o 2 x l o - ' CO (produced almost entirely by gage and spectrometer filaments). N o effort w a s made to reduce the hy-

drogen pressure by higher-temperature baking s i n c e t h e g a s under study w a s water. Water w a s admitted for periods of time ranging from about 0.5 sec to a s long as 30 min, after which t h e valve w a s c l o s e d and t h e e x h a u s t c u r v e was obtained. 'The partial p r e s s u r e of water w a s followed by monitoring m a s s 18 with t h e spectrome t e r . A s w a s expected, agreement with g l a s s ion g a g e s w a s good only when t h e g a g e s were heated. For m o s t of t h e determinations, however, to minimize the possibility t h a t the glass might b e affecti n g t h e r e s u l t s , they were replaced by n u d e gages.

0.5

TIME ( s e d

Fig. 14.6.

Typical L a g p

H20

100

200

500

vs L o g t ( s e c ) P l o t s for Four E x p o s u r e Conditions.

137 F o r the hot-system, short-exposu re c a s e s , the slope of log p ~ vs ,t (the ~ u s u a l e x h a u s t relation) initially corresponded to a value of 540 l i t e r s / s e c -t 10% e x c e p t when the i n i t i a l p r e s s u r e exceeded 1 x lo-' significantly, for which cases the mass 18 spectrometer peak w a s not e x a c t l y proportional to pressure. Four typical log p E I Z Ovs log i plots a r e shown in Fig. 1 4 . 6 for the cases of hot and cold region A and for O.S-sec and 10-min exposures. T h e expos u r e pressures, pexp, were a l l within 20% e x c e p t for case X I , where pexp w a s about a factor of 5 lower. Exponential exhaust, indicated for watei by curve V, w a s observed for N, over almost â&#x201A;Źour orders af magnitude of pressure. W e observed that the log P , ~ ,v s~ log t plot of oiir d a t a c l o s e l y approximated straight l i n e s of reproducible s l o p e s , which, of course, varied with exposure conditions. Integtatiorl of e a c h curve from the extrapolated limit of 0.1 sec to 1000 sec and multiplying t h e r e s u l t by our measured H Z O pumping s p e e d (590 l i t e r s / s e c r! 3%) yielded the quantity desorbed isothermally following t h e expos u r e . T h e value of q (quantity absorbed) is believed io be within 20% oE the measured quantity aesoebed. The Elor/ick plots [Eq. (I)] from our d a t a for two temperatures and normalized t o the s a m e exposure pressure (assuming variation of q with the first power of pexp) a r e shown i n Fig. 14.7. T h e exposure p r e s s u r e s w e r e from 0.7 to 4.0 x IO-5 torr. Determination of q â&#x201A;Źor exposure p r e s s u r e s as low as 4x torr led t o the relation of q and P ( , , ~ ) ;

w a s e x e r c i s e d to b e a b l e t o attribute the observed chemisorption t o the s t e e l s u r f a c e , Some e f f e c t on water chemisorption k i n e t i c s by ion or electron bombardment i s to be anticipated by analogy t o other chemisorption phenomena. Neither l.he magnitnde not the direction of change seems to be presently predictable. Water sorption by unbaked and baked s t a i n l e s s s t e e l during a pressure excursion t o atmosphere of different humidities h a s been observed and is reported in the literature but with inadequate reported d a t a to permit s c a l i n g the parameters s t u d i e d here over t h e required five t o s i x orders of magnitude, Samples with different s p e c i f i c s u r f a c e a r e a s [nay b e expected to s h o w different sorption capabilities. T h e conclusion t h a t chemisorption phenomena e x i s t l e a d s to p o s s i b l e practical application in

T h e only study found in t h e literature of the press u r e dependence of p is t h a t of Winfield,5 who reported a n exponent of 1.2 with thoria a t , of course, higher water vapor p r e s s u r e s . T h e v a l u e of 1 . 2 introduces an error hand of somewhat less than 15% to our d a t a . T h e q u a n t i t i e s observed correspond to about 0.1 monolayer a t room temperature following a 10-min exposure and about 0.15 monolayer after 30 min. Dust or other impurities could be r e s p o n s i b l e for s o m e or even a l l of t h e observed sorption. W e believe, however, that t h e method is reliable and that sufficient c a r e 0.02

John Howard and H. S. Taylor, J. A m . Chem. "See: Soc. 56, 2259 (1934) and other references in Low, O P . e i t . , pp. 301-7.

Fig. 14.7.

0.04 006 008 q (Iorr-lIlPrs of ti20 desorbed)

0.10

012

E l o v i c h P l o t s for Water Chemisorption on

Stainless Steel.

138 Table

14.2.

Proton

Signal

Height

Position

of Integral (mm)

NMR Spectra of DC-705 Diffusion Pump O i l and Height x 0.1344 Structure

Decomposition Product

Assignment

Protons per Signal

I , 34 protons

(CH3)4Si, reference

2.96

6.18

3 6

43 5

185

24.86

---Me

2 equivalent Mc 5 equivalent

253 mm 0.1344 protons/mrrr Unknown

Signal

Height

Position

of Integral (mm)

Assumed Group

Solid €Ie i g h t ....

Assignment

P r o t o n s per Group

Me4Si, reference

436

196

operating nonbakeable vacuum s y s t e m s . First, s i n c e chemisorption occiirs at even very low press u r e s and is a s t r o n g function of exposure time, maintenance of very low partial p r e s s u r e s of water by liquid-nitrogen cooling of appreciable a r e a s in t h e s y s t e m , followed by intermittent warming of the cooled a r e a s , desorption, and rapid e x h a u s t , s h o u l d result in a lower water impurity l e v e l than t h e same period of pumping would produce. Another c o n s e q u e n c e of the observations reported here is that even s m a l l water impurity l e v e l s introduced from g a s manifolds are expected t o result in significant impairment of the “ b a s e ” pressure of water vapor.

DECQMPOSlTlON OF DC-705 DlFFUSlQN PUMP FLUID A white s o l i d w a s found c o n d e n s e d on t h e c o l d c a p s and w a l l of o n e 10-in. diffusion pump on t h e DCX-2 vacuum system. It w a s found to melt sharply a t 47OC. T h e infrared spectrum l 2 w a s

2 equivalent methyl groups per 39.6

4 equivalent phenyl groups

not distinguishable froin that of t h e diffusion pump fluid, a pentaphenyl tritnethyl trisiloxane, structure I.

cp = C 6 i i 5 Me = C k i 3 J

T h e rnariufacturer indicated t h a t decomposition to t h e dimer might occur if t h e operating temperature is too high, in a radiation field, or i f t h e fluid is h e a t e d i n t h e p r e s e n c e of a l k a l i impurities i n ..........

G. Goldberg a n d H. I,. I-Iolsopple, Jr., Analytical Chemistry Division.

139 t h e pump. Proton nuclear magnetic resonance (60 Mc) s p e c t r a were o b t a i n e d ' 3 for t h e s o l i d and for a sample of the pump fluid with the r e s u l t s s u m miirized in T a b l e 14.2. The dimer structure I1 may therefore be a s s i g n e d to the s o l i d material. It would appear that for the pump in question s o m e period of excessive-temperattire operation probably o c c a s i o n e d the decompos i t i o n . The observed lowered pumping s p e e d of this pump w a s presumably c a u s e d by the d e p o s i t .

I I Me

--sl---o--sl-+

13J.

R. Lund, Analytical Chemistry Dlvlsion.

Part V

Nuclear Safety

15. Activities of Nuc ear Safety fechnica W. E. Browning, Jr.

M. CI. Fontana

T h e Nuclear Safety 'I'echnica.1 Staff, comprised of three persons, w a s formed e a r l y t h i s y e a r to a i d in planning, coordinating, a n d directing t h e r e s e a r c h and development a c t i v i t i e s within t h e Nuclear Safety Program. One of the first a c t i v i t i e s of the t e c h n i c a l s t a f f was t o s u r v e y work b e i n g done in the Nuclear Safety Program on the development of a n a l y t i c a l models for f i s s i o n product behavior in various s t a g e s of reactor a c c i d e n t s and to recommend t h e initiation of additional theoretical and experimerita1 a c t i v i t i e s which were needed, preferably in e x i s t i n g g r o q s o u t s i d e the technical s t a f i . En a new activity, theoretical treatment of t h e chemical behavior of gas-borne fission products a t high temperatures is combined with a Iahoratory investigation. There are separate studies of dynamic transport phenomena (continuing) and o f s u r f a c e phenomena (new) of fission product Models a r e deposition at high temperatures. b e i n g developed for t h e transport a n d deposition of f i s s i o n products in containment v e s s e l s and for t h e convective circulation of gases. Other theoretical work c o v e r s t h e behavior of a e r o s o l s . A new program on behavior of fission products in gas-liquid s y s t e m s w a s s t a r t e d with s t u d i e s on t h e f i s s i o n product reinoval by s p r a y s at ORNL arid by s u p p r e s s i o n pools at General E l e c t r i c , San J o s e , under s u b c o n t r a c t . Another subcontract, with B a t t e l l e Memorial Institute, supports work on t h e theoretical c h e m i c a l yield of methyl iodide. A continuing program h a s b e e n maintained for computing thermochemical equilibria of f i s s i o n product fuel mixtures a t high temperatures and for predicting vapor p r e s s u r e s in the g a s p h a s e a b o v e a condensed-phase solution. A multicomponent equilibrium program h a s been obtained and debugged, and thermochemical d a t a t a p e s h a v e been made for U, Sr, SrO, UO, UO,, and

143

B. A . Soldano

UO:I in addition to 140 compounds from the JANAF Tables. Computer programs h a v e been written to generate therrriocheniical t a b l e s in the J A N A F format for compounds of i n t e r e s t , given some spect.roscopic or experimental d a t a . An experimental program to c h e c k theoretical calculations by mass spectrometric measurements has been initiated, and preliminary shakedown r u n s h a v e b e e n made. One member h a s a s s i s t e d i n the development of a t h e o r e t i c a l model d e s c r i b i n g fission product behavior in containment v e s s e l s and in planning a n experimental program of s c a l i n g , flow visualization, and pilot-plant experiments to test the model. A t the invitation of ihe AEC, the staff h a s participated in t h e management of an AEC contract with P r o f e s s o r N. C. Ozisik a t North Caroliria S t a t e University, who i s working on the theory of diffusional transport as it a p p l i e s t o containment v e s s e l s . One member h a s been a s s i g n e d full-time t o t h e program on s p r a y e f f e c t i v e n e s s (Sect. 18) during i t s formative s t a g e s . A s t u d y undertaken by the Chemical 'Technology Division a t the instigation of t h e t e c h n i c a l staff h a s led to a report. on the theory of f o a m decontamination a s it might b e applied to (3 reactor containment v e s s e l . Recently, one man h a s s p e n t half lime 011 t h e s p e c i a l core melt-through problem a s s i s t i n g t h e t a s k f o r c e d i r e c t e d by W. K.. Ergen. T h e work involved e s t i m a t i n g amounts of f i s s i o n products r e l e a s e d from masses of molten c o r e materials in l a i g e water-cooled reactors. E s t i m a t e s were made on r e l e a s e by diffusion from t h e melt in various configurations, a n d tough approximations

IS. 11. J u r y , F o a m Decoritomination of A i r Corzttiinirig Radioactive Indine and Particulates Following a N u clear Incident, ORNL-TM-158Ci (Oct. 3 , 1366).

were made for t h e c a s e where natural convection within t h e melt e x i s t s . T h e T e c h n i c a l Staff participated in s e v e r a l information dissemination a c t i v i t i e s . A s s i s t a n c e is given at the Nuclear Safety Information Center in a b s t r a c t i n g literature on a c c i d e n t a n a l y s i s , h e a t transfer, thermodynamics, and fluid mechanics, and providing consultation s e r v i c e s . Information on filter and adsorber efficiency and pool decontamination in reactor safeguards w a s prepared

for the United S t a t e s represcntative a t a meeting held in November 1966 by t h e Committee on Rea c t o r Safety Technology of t h e European Nuclear Energy Agency. T h e technical staff a s s i s t e d t h e A E C in the production of a document describing t h e Water Reactor Safety Program, i t s b a s e s , t h e interrelationships of t h e various projects, a delineation of t h e problems that a r e t o h e solved, t h e relationship of the program s t a n d a r d s and c o d e s , and other factors.

16. Correlations of Fission Pro THE LIGHT BULB MODEL FOR RELEASE OF FISSION PRODUCTS

where

C. E. Millet, Jr.

molar diffusion flux (moles c r n p 2 sec--.’), binary diffusion coefficient i n which subscripts A ~ n dR d e n o t e the f.wo diffusing s p e c i e s (cm 2/sec), concentration (moIes/cm ’), d i s t a n c e (cm).

: -

Experiments in various laboratories and i n rea c t o r s h a v e accumulated much d a t a on r e l e a s e of fission products under conditions which s i m u l a t e reactor accidents, The e f f e c t s of important vatiables on fission product behavior h a v e generally b e e n recognized, but: interpretations of t h e d a t a have b e e n at best empirical. The ‘“light bulb” rnodel of fission product r e l e a s e p r e s e n t e d below seems to explain i n a s i m p l e fashion most, i f r;ot all, of t h e a v a i l a b l e release data. Fondti, in s t u d i e s of the i n c a n d e s c e n t lamp, observtxl that tungsten filurnerits lost weight (at a given temperature) more rapidly i n a vacuum than i n the p r e s e n c e of a nonreactive gas. Ile related t h i s to Langmuir’s‘ theory that h e a t loss fraiu i n c a n d e s c e n t w i r e s i n gases is controlled by conduction of h e a t through a stationary gas film around the wire, F’onda proposed that evaporation of material from t h e filament i n a norirei3ctive gas is controlled by diffusion through a similar stationary g a s layer. I f i t is assunied t h a t a h e a t e d specimen of reactor fuel h a s such a nonreactive g a s e o u s boundary layer and that diffusion (by Fick’s law) through t h i s l a y e r controls t h e rate of r e l e a s e of fissiori products, then t h e t h e o r i e s of 1.,angmuir atid of Fonda may b e applied i t ? a straightforward manner. If t h e r a t e of evaporation of s p e c i e s A is controlled by F i c k ’ s l a w diffusion o f A through a boundary l a y e r of s p e c i e s B ,

z =

The concentratioti of fission products at the surface of the m e l t is given by 1Tet1ry’s law,

where

1’ =: partial p r e s s u r e of fission product (atmj, k = Henry’s l a w constarlt, X .= mole fraction !,E fission product in reactor k‘ PO

fuel, femperature.~independent portion o f Henry’s l a w constant, -:: vapor p r e s s u r e of p u r e Fission product temper atur e-t-tlependent pu rtiori of Henry ’ s law constant (attnj. =

where

fraction. r e l e a s e d , nioleculat weight f o r fission product W m o l e), /VIl3- molecular weight o f inert gas (g/mole),

_I__..__..____.__._._ __

3C. E. Miller, Jr., The Lighht Bulb M o d p l of F i s s i o n Product R e l e a s e from i ? e d L f V r Fuels, ORN1,-40W, in prep arutioti.

145

' $

;

';u

io,

147 s u r f a c e a r e a of melt (cm’), temperature of melt ( O K ) , f time during which t h e specimen is molten (sec), p , , = p r e s s u r e of g a s (atm), II = moles of melt, mA = collision diameter of fission product rnolecule (A), o.* : c o l l i s i o n diameter of inert gas molecule (A), 6 :--boundary l a y e r t.hickness (cm).

A T

,.,

I h e f i s s i o n products are, of course, t h e d i l u t e s o l u t e in a solute-solvent mixture. Equation ( 3 ) d e s c r i b e s t h e behavior of t h e solute. During long h e a t i n g p e r i o d s t h e reactor fuel may vaporize appreciably. If t h i s phenomenon i s to be accounted for, Lhe u term i n Eq. ( 3 ) must b e e x p r e s s e d as a function of time. A similar r e l e a s e expression h a s also been derived for t h e solvent, i n which case Raoult’s law, 1’

rJnU ,

(4)

w a s used rather than Henry’s law. T h e corresporrding equation for t h e fraction of f u e l vaporized i s given by

LI*

.- u

2.264

where t h e s u b s c r i p t 3. r e f e r s to t h e f u e l material. T h e model h a s been t e s t e d with datu. from s e v e r a l s o u r c e s and satisfactorily e x p l a i n s t h e observed behavior of f i s s i o n products arid fuel. One s u c h s e t w a s p r e s e n t e d by n a v i e s , Long, and Stanaway4 on t h e e m i s s i o n of f i s s i o n products on postirradiation h e a t i n g of UO,. T h e r e s u l t s of t h e comparison of t h e c a l c u l a t e d and measured v a l u e s for UO, and s e v e r a l f i s s i o n products a r e given i n T a b l e 16.1. A d e t a i l e d description of this application of t h e model is given e l ~ e w h e r e . ~T h e model d e s c r i b e s t h e dependence of t h e fraction r e l e a s e d on t h e atmosphere, that i s , i t s composition and pressure; t h e solvent, that is, its s u r f a c e a r e a arid amount; and t h e chemical forin of t h e fission products, the temperature; and time a t temperature. 4

D. Davies, G. Long, and W. F. Stannway, The Ernission of Volatile Fission Prodircts from Uranium D i o x i d e , AEKE-K-4342 (1953).

EFFECT OF CONTAINMENT SYSTEM SIZE ON FISSION PRODUCT BEHAVIOR G. M. Watson

R. B. P e r e z M. € I . F o n t a n a

Simple mathematical models ta a i d i n t h e determination of effect of containment s i z e o n r a t e and e x t e n t of deposition oE iodine from t h e g a s e o u s p h a s e h a v e been postulated. ‘rwo general c l a s s e s of s y s t e m s ( t h o s e with and without condensing steam) h a v e b e e n considered. [n t h e a b s e n c e of steam t h e principal assumptioris made were: (1) homogeneous mixing within t h e g a s , (2) boundary g a s l a y e r enveloping all s u r f a c e s , ( 3 ) diffusion through t h i s boundary l a y e r a s t h e rate-limiting process, and (4) iodine p r e s e n t i n t h e molecular form with combined forms s u c h as methyl i o d i d e absent. Mathematical relations i n terms of m a s s transfer coefficients, sutface-tovolume r a t i o s of containers, and surface-characteri zation parameters were developed f o r cases with and without de.mrption from partially covered surf aces. In t h e presetice of condensing s t e a m , there is hulk flow of steam toward t h e walls. In s u c h cases, i t h a s been a s s u m e d that t h e iodine flux, which c o n s i s t s of d i f f u s i v e and hulk flow components, ma:y h e approximated by t h e bulk flow component alone. Furthermore, i t h a s been assumed that t h e solubility of iodine In s t e m cond e n s a t e is high enough to permit t h e iodine and t h e s t e a m to c o n d e n s e together with t h e s a m e As a result of composition a s t h e g a s phase. t h e s e assumptions, mathematical relations h a v e been derived for t h e concentration of iodine a s a function of time in t e r m s of the surfece-to-volume ratios, condensing s t e m fluxes, and steam concent ratio t i s. T h e case of molecular iodine-methyl iodidecondensing stem h a s been considered. It w a s assumed that t h e deposition of methyl iodide is limited by i t s smaller solubility i n steam condensate. Development of t h e model for predicting m a s s transfer c o e f f i c i e n t s u s i n g film theory and boundary l a y e r a n a l y s i s f o r cases in which no steam was p r e s e n t w a s b a s e d on rough approximations concerning t h e flow velocity structure within t h e containment shell; f l o w s were a s s u m e d to be induced by natural convection. T h e model shows that o b s e r v a b l e m a s s transfer c o e f f i c i e n t s can be

148 predicted if t h e temperature differences c a u s i n g t h e flow are very small (0.001'K). Both t h e v e l o c i t i e s and t h e temperature differences are too small to b e observed u s i n g currently a v a i l a b l e instrumentation. 'The model a l s o p r e d i c t s s i z e - and pressure-scaling e f f e c t s which appear to b e subs t a n t i a t e d by liniited available data. Some correlations of t h e mathematical express i o n s with experiruental d a t a h a v e been performed. R e s u l t s of iodine-air experiments i n the CMF, CRI, and N S P P h a v e been compared with t h e simple theoretical e x p r e s s i o n s with moderate s u c c e s s . T h e r e s u l t s of t h e correlations of experiments with dty atmospheres are shown e l s e v ~ h e r e . ~T h e v a l u e s of t h e m a s s transfer coefficient and of t h e asymptotic concentration were obtain e d e m pi ric ally f o r t h e Nuclear Safety P i l o t P l a n t (NSPP) from r e s u l t s of experiments with iodine in dry air. 'G. M. Watson, R. H. Perez, and M. 13. Fontana, Effects of Containment S y s t e m Size on Fission Product Behavior, ORNJ.,-4033 (in press).

Corresponding v a l u e s for t h e Containment Mockup F a c i l i t y (CMF) and for t h e Containment R e s e a r c h Installation (CKB) were obtained by s c a l i n g with s i z e and p r e s s u r e t h e NSPP parameters i n a manner prescribed by relationships obtained from t h e model. F o r t h e asymptotic concentrations, t h e surface-chernistry e f f e c t s were assumed equal i n all three s y s t e m . An example of t h e correlation of d a t a obtained i n t h e a b s e n c e of steam i n t h e NSPP and i n the CMF is shown in Fig. 16.1. We c a n conclude from t h e r e s u l t s 5 that t h e model p r e d i c t s t h e general behavior of t h e concentration-time curve in t h e a b s e n c e of steam. It a p p e a r s quite s u c c e s s f u l i n t h e extrapolation of m a s s transfer c o e f f i c i e n t s a s indicated by t h e agreement between t h e predicted and experimental initial slopes. T h e n e c e s sity for additional research on t h e s u r f a c e chemi s t r y of containment materials is apparent from t h e relatively poor agreement of t h e asymptotic concentrations using t h e simple assumption of equal s u r f a c e behavior in all three facilities. R

100 1

90 80

0.5

0 W

w u

.J .J

0.2

bo ~

p b

..1

2 0 b-

0.1

5w V

0.05

111

30 20

0.02

40 0.01

Fig.

>I0 0

16.1.

CMF E x p e r i m e n t a l I o d i n e Concentration NSPP BQtn.

and V a l u e s P r e d i c t e d f r o m

Fig. 16.2.

TIME I h r ) Accuinulation o f Condensate a n d

sion Products i n Condensate vs T i m e ,

NSPP

of F i s 8,

Run

149 T h e simple assumptions of t h e condensing steam model h a v e been t e s t e d u s i n g t h e experimental d a t a on an NSP'P experiment which provides information on both iodine and water c o n d e n s a t e collection as w e l l a s system p r e s s u r e and temperature a s a function of time, Figure 16.2 shows a comparison of the calculated and experimental values of t h e iodine collected. T h e agreement a p p e a r s t a b e q u i t e satisfactory. B a s e d o n a very limited number of test.s, i t a p p e a r s that. t h e behavior of iodine i n containment s y s t e m s differing in s i z e by two orders of magnitude may b e correlated with moderate s u c c e s s utilizing simple mathematical re1 ationships.

-7

-9

-I! 1

* -

* -13

.-.

: 0

z Q

+-4

-1" d

-17

W 0

-19

CHEMICAL EQUILIBRIUM STUDIES OF ORGANIC-IODIDE FORMATION UNDER NUCLEAR REACTOR ACCIDENT CONDITIONS

R. N. Barnesfi

J. F. Kircher6

C. W. Townley6

Tfie p r e s e n c e of CH,I in nuclear reactor environments p o s e s a potential hazard b e c a u s e of t h e diff i c u l t i e s involved in removing t h i s compound from g a s e s u s i n g conventional trapping techniques. To gain i n s i g h t into t h e chemical p r o c e s s e s leading to CH,I formation, a study w a s performed of cal d a t e d equilibrium concentrations of CM,I and other important s p e c i e s for a range of condit i o n s typical of reactor-accident systems. A report of t h i s work h a s been issued.' T h e r e s u l t s of t h i s study indicated that chemic a l s y s t e m s containing iodine and simple compounds s u c h a s CO,, H,O, C,H,, and CH, would b e expected t o generate CH,I. Such matertals a r e found a s trace pollutants i n t h e atmosphere, even i f s o m e of them a r e thermodynamically unstable','

6Battelle nilemurial Institute; work performed under subcontract. T h i s summary, prepared by W. E. Mowning, Jr., is based on r e p o r t s by the l i s t e d authors.

H. Barnes, J. F. Kircher, and C. W. Townley, Ch emi cat-Equili briurn S t u d i e s o f Orgari i c-Iodi de Furmation Under Niicfaor R e a c t o r Accident Conditions, BMI1781 (Aug. 15, 1966). ' C . E. .Junge, A i r Chemistry and Radioactivity, p. 355, Academic, N e w York, 1963.

'A. P. Attshuller and T. A, Bellar, .I, A i r Pollution Coritrol A s e o c . 13, 81 (1963).

0 -J

-21

- 23

-25

300

Fig.

16.3.

700

1300

900 1100 TEMPEf?OTURE ( " K )

500

Species Concentrations

CIS a

1500

Function of

Temperature for the C h e m i c a l E q u i l i b r i u m Systems Containing

C2H4, H2,

HI, i2,

and

concentrations e q u i v a l e n t t o

of H2, 1 x

CH31. 10-8

g-mole p e r l i t e r of

g-mole per l i t e r of

Based on t o t a l g-mole per l i t e r

C2H4, and 1 x 1Q-l'

and may e x i s t only in transient conditions. Accordingly, equilibrium c a l c u l a t i o n s w e r e made postulating t h e p r e s e n c e of several possibly significant pollutants. T h e calculated equilibrium composition i n the p r e s e n c e of ethylene is shown in Fig. 16.3, which shows that a t 300 to 500째K a major fraction of the iodine a p p e a r s a s CH,L T h e s e chemical equilibrium c a l c u l a t i o n s i n d i c a t e that t h e r e a r e realistic conditions under which CH,I could b e generated if sufficient reaction time w e r e available. Chemical kinetic c a l c u l a t i o n s a r e riow being made for promising reactions and conditions identified in the equilibrium s t u d i e s in order to assess r a t e s of formation of methyl iodide.

150 ACY OF SCALEUP IN

I:. E. Miller, Jr.

W. E. Browning, Jr.

We concluded in a previous report" that s c d i n g of experiments o n f i s s i o n product r e l e a s e and transport i n the 1J.S. Nuclear Safety Program d o e s not seem adequate; a very l a r g e extrapolation w i l l Le n e c e s s a r y to compare presently a v a i l a b l e d a t a t o t h a t obtained from t h e projected Loss-ofIn a s u b s e q u e n t report" F l u i d T e s t (LOFT)." w e p r o p o s e experiments at 1 and 10% of t h e s i z e of LOFT (based on t h e m a s s of fuel) i n order to fill t h e gap in scaling. Intermediate- scal e experiments t o study f i s s i o n product r e l e a s e and transport should b e designed sn t h a t they (1) generate f i s s i o n products with maximum practical realism as a function of various simulated loss-of-coolant a c c i d e n t environments and heatup r a t e s and (2) simulate core geometry sufficiently to achieve proper temperature profiles and heatup r a t e s , to allow natural movement of c o r e components during the heatup c y c l e , and to provide R r e a l i s t i c e s c a p e path for fission products through remaining core materials. T h e following gene ra1 c h a r a c t e r i s t i c s and c a p a b i l i t i e s should b e incorporated into t h e experiments:

P a r a m e t e r s of i n t e r e s t in t h e experiments a r e

(1) maximum operating temperature ( t h e experi-

ment should b e c a p a b l e of operating a t initial conditions similar to t h o s e of real reactor operation), (2) c o r e environment (steam, steamhydrogen, steam-air), ( 3 ) cladding and core materials, arid (4) burnup. Measurements of i n t e r e s t are: (1) temperatures of fuel and cladding, (2) observation of geometrical changes, ( 3 ) permanent and temporary fission product plateout (on fuel materials, cladding, and oxidized cladding i n t h e unmelted part of t h e fuel subassembly, and on t h e w a l l s of t h e primary, etc.) a s a function of time and temperature in t h e primary system, (4) exTent of fuel oxidation, fuel melting, a n d fuel melting point lowering v i a e u t e c t i c formation, (5) extent and rate of metal-water reaction, (6) p a r t i c l e s i z e , (7) fission product transport a s a function of flow (diffusion or forced), and (8) p h y s i c a l and chemical form of radioactive a e r o s o l s which remain i n t h e g a s p h a s e ;3s a function of time. ORNL-DWG

- -*

56-70493

1. The experiments s h o u l d b e performed in-pile

o n rnultipin fuel s u b a s s e m b l i e s to give maxirnum realism to the time-temperatureposition prcfiles. 2" Where p o s s i b l e the experiments should b e des i g n e d to accommodate watei, liquid metall and gas-cooled fuel s y s t e m s . 3 . T h e r e l e a s e d fission products should b e transported through a representative primary s y s t e m in which the transport r a t e s result from renlist i c thermal gradients and natural steam flow.

(PROPOSED!

ORNL TREAT

'OC. E, Miller, Jr., and W . E. Browning, j r . , T h e A d e q u a c y o f S c a l e - u p in Experiments on F i s s i o n An Product Behavior in Reactor A c c i d e n t s , Part I. A n a l y s i s o f Scaleup ifz the U.S. Nuclear S a f e t y Program, ORNL-3901 ( J u l y 1966). "T. K. Wilson et al., A n Engineering T e s t Program to I n v e s t i g a t e a Loss-of-Coolant A c c i d e n t , IDO-97049 (October 1964).

"'2. E. Miller, Jr., and W. E. Browning, Jr., T h e A d e q u a c y o f S c a l e - u p in Experiments on F i s s i o n Product Behavior in Reactor A c c i d e n t s , Part I I . Hecommended Additional Nuclear S a f e t y S c a l e - u p Experimen t s , ORNL-40 2 1 (December 1966).

RELEASE

FROM r u E L

TRANSFORT

IN P R I M A R Y

SYSTEM

BEHAVIOR I N CONTAINMENT SYSTEM

BEHAVIOR IN GAS CLEANING SY ST E F4

AREAS Oc INVESTIGATION

Fig. Safety

16.4,

Comparison of S i z e of

Planned Nuclea:

Experiments with Regard to V a r i o u s Stages of

F i s s i o n Product 5 ~ h a v i o r(Including the Proposed pe F iilia n t s ) .

Er-

151 T h e proposed experiments on t h e r e l e a s e and transport of f i s s i o n products from UO, a r e described i n s o n e detail elsewhere.’2 They are s c a l e d a t 1 and 10% of t h e size of t h e L O F T experiment b a s e d upon the m a s s of fuel in t h e L O F T core. T h e fuel in t h e s e experiments i s to b e melted by nuclear self-heating i n a reactor facility using a driver core. T h e s u g g e s t e d f a c i l i t i e s a r e t h e P o w e r Burst F a c i l i t y 1 3 for t h e 1%s c a l e experiment using approximately one L O F T h e 1 element, and t h e L O F T i t s e l f for t h e 10% s c a I e experiment u s i n g approximately five LOFT fuel el em ent s. Alternative experiments at the same scale u s i n g a nonnuclear mef.hod of heating are proposed to fill t h e gap i n s c a l i n g i f for r e a s o n s of e x p e n s e o r scheduling t h e nuclear experiments cannot b e performed. T h e 1%scale experiment i s proposed for t h e Containment Research Installation, and t h e 10% scale experimerit is proposed for t h e Containment Systems Experiment. l 5 An electrical method of heating t h e fuel is proposed, which is presently under development in a n AEC-sponsored pro gram. 1 2 T h e capability’of performing any of t h e proposed experiments a p p e a r s to b e near at hand. All four Eacilities are under construction, and t h e capability

of e l e c t r i c a l heating is being developed. However, three of t h e four p o s s i b l e experiments involve f a c i l i t i e s which a r e already scheduled for experimental programs. T h e s e a r e t h e L,OFT, CSE, and CRI facilities. T h e addition of t h e s e proposed experiments would c a u s e d e l a y s in programs which a r e very much needed i n other p h a s e s of nuclear safety work. T h e remaining facility, t h e P o w e r Burst Facility, which is still to b e constructed, seems t h e most promising. With t h e addition of t h e s e experiments to t h e AEC Nuclear Safety Program, t h e comparison of s i z e o f planned nuclear safety experiments w i l l b e a s shown i n Fig. 16.4. T h e accomplishment of t h e s e experiments w i l l produce a s c a l i n g range which should cover all p o s s i b l e mechanisms of f i s s i o n product behavior and make extrapolation of d a t a from o n e experiment to the other more reliable. 1 3 E . F e i n a u e r and R. S . Kern (eds.), Preliminary Safcly A n a l y s i s Hcporf, Power Bnrst Faczlity, IDO17060 (revised June 1965).

“G. W. Parker and W. J. Martin, “The Containment Research Installation,’’ NtzcJ. S a f e t y Program Semianrl. Progr. RefJt. J u n e 30, 196.5, ORNL-3843, pp. 92-97.

”s. J. Rogers, Program for Corltsinment S y s t e m s Experiment, WW-83607 (September 1964).

17.

R . A. Lorenz G . W. P a r k e r J. G. W h e l m ' OKNE f i s s i o n product release experiments a r e performed i n t h e T R E A T reactor to study t h e r e l e a s e and transport of fission products from fuel during reactor t r a n s i e n t s in which fuel i s h e a t e d and m e l t s rapidly. In t h e current s e r i e s of experiments, vario u s components of t h e equipment a r e designed t o simulate t h e core, p r e s s u r e v e s s e l , containment vess e l , and t h e filter a n d charcoal cleanup system of a typical l a r g e pressurized- o r boiling-water power reactor. Experiments 9, IOZ, 1 1 Z , and 1 2 % were recently completed and reported i n d e t a i l elsewhere, making a total of s i x experiments i n which s t a i n l e s s - s t e e l - or Zircaloy-2-clad UO, fuel specimens were melted underwater by transient heating. T h e l e t t e r Z i n d i c a t e s experiments in which Zircaloy-2 cladding w a s used. E a c h of t h e s e experiments u s e d 32 g of 10.7% enriched UO, sintered into p e l l e t s 0.400 in. i n diameter, with 0.020in.-thick cladding. Heat input to t h e fuel by internal f i s s i o n i n g during t h e transient w a s approxj m a t e l y 5 2 0 c a l o r i e s per gram of UO,; t h i s treatment h e a t e d t h e U O , well a b o v e i t s melting point. In e a c h experiment a reactor a c c i d e n t w a s simulated by first preheating t h e fuel autoclave to ahout 12OoC, executing t h e t r a n s i e n t which melted t h e fuel specimen, a n d allowing t h e transientgenerated steam aerosol to l e a v e t h e hiel autoclave. Steam w a s c o n d e n s e d and c o l l e c t e d in water t r a p s , and noncondensahle g a s e s p a s s e d through a s e r i e s of filter p a p e r s and charcoal-

loaded papers into a g a s collection tank. In simulation o f accident after-heat, t h e fuel autoclave w a s then h e a t e d electrically to about 300째C for 1 hr to boil out any remaining water. We wished to determine t h e maximum fission product release; s o in addition t o u s i n g t h e two different cladding materials, t h e r a t e of s t e a m r e l e a s e from t h e melting region w a s varied. In experiments 7 and 8 2 , only aboiit 5% of t h e water surrounding t h e fuel specimen boiled out of t h e fuel a u t o c l a v e s i n t h e first minute following t h e transient. In experiments 9 a n d IOZ, approximately 75% of t h e water boiled out in t h e first minute, and e s s e n t i a l l y a l l of t h e water boiled out of t h e l l Z and 1 2 % fuel a u t o c l a v e s in 1 min. T h e s e two l a t e s t experiments a l s o explored t h e effect of p r e s s u r e during melting by e n c l o s i n g t h e fuel and water in s e a l e d primary v e s s e l s . Experiment l l Z u s e d a 300-psi nipture d i s k to r e l e a s e t h e s t e a m , and experiment 1 2 2 u s e d a 2500-psi rupture disk along with SO0 p s i of helium a s preliminary p r e s surization. Examination of t h e s e two experiments is in progress. T h e fuel a n d cladding melted completely in experiments 7, 8 2 , 9, and l O Z , except for portions of t h e metal end c a p s . The melted residue froin experiments '7 and 9, which u s e d s t a i n l e s s steel cladding, appeared t o b e foamy and more porous than t h e r e s i d u e from experiments 8 2 and 1OZ. In Fig. 1 7 . 1 t h e front half of t h e crucible i n experiment 10%: h a s b e e n removed t o reveal some of t h e nonporous solidified fuel and cladding around t h e s a m p l e holder p e d e s t a l and some material splattered onto t h e c r u c i b l e and flux monitor capsule. Approximately 24 and 15% of t h e s t a i n l e s s s t e e l cladding reacted with steam to form hydrogen in

'On assignment from Karlsruhe Center for Nuclear R e s e a r c h and Development, K a r k r u h e , West Germany.

...._______ ___

2G. Vi. Parker, R. A . T,orenz, and J. G. W i l h e h , N u c l . S a f e t y Program Semiann. Progr. K e p t . n e c . 3 1 , 1366 (in preparation).

3G. V I . Porker, R. A. Lorenz, and J. G. Wilhelm, N u c l .

S a f e t y Program Semiann. Progr. R e p t . J u n e 30, 1965, ORNL-3843, pp. 39-67.

152

153 experiments 7 and 9. Forty-one a n d forty-nine percent of t h e Zircaloy-2 cladding reacted in experiments 82 and 1OZ. T h e s e r e s u l t s a l l a g r e e well with t h o s e found by workers a t Argonne National Laboratory in metal-water reaction s t u d i e s in TREAT. F i s s i o n product r e l e a s e and transport w a s simi l a r i n all four experiments e x c e p t that transport of t h e volatile e l e m e n t s tellurium, cesium, and iodine out of t h e fuel a u t o c l a v e i n experiments 9 and 1OZ (6 to 190%)w a s about t w i c e that in experiments 7 and 8 2 (2 t o 7%). T h e larger r e l e a s e

in 9 a n d 1OZ is attributed to t h e f a s t e r s t e a m r e l e a s e . About 1%of the barium and strontium, 0.3% of t h e ruthenium, and less t h a n 0.1% of t h e cerium, zirconium, and UO, were carried out of t h e f u e l autoclave with the r e l e a s e d steam in each of t h e four experiments. T h e condensation p r o c e s s w a s highly efficient i n trapping f i s s i o n products and UO, i n t h e s e experiments; a decontamination factor of about IO3 for nonvolatile materials w a s observed. No significant effect of cladding material w a s evident. In experiments 9 and 102, distilled-water r i n s e s of t h e fuel autoclave w a l l s contained 33 to 44% of t h e t o t a l cesium and iodine; t h i s behavior sugg e s t e d rapid formation of nonvolatile water-soluble compounds, p o s s i b l y cesium hydroxide and v a r i o u s metal iodides. T h e amount of u n r e a c t i v e or penetrating iodine w a s only a s m a l l fraction of t h e total i n all four experiments. Sixty t o eighty percent of t h e total 13’1 w a s r e l e a s e d from t h e melted fuel specimens, but only 0,0006 t o 0.005% w a s found on t h e charcoal-loaded p a p e r s and i n t h e g a s collection tank. T h i s i o d i n e w a s characterized as unreactive or penetrating, b a s e d o n its pool sorbability in t h e b e d of 2 7 charcoal-loaded papers.

SIMULATED LOSS-OF-COOLANT EXPERIMENTS IN THE OAK RIDGE RESEARCH REACTOR C. E. Miller, Jr. R. P. S h i e l d s

B. F. Roberts R. J. D a v i s

T h e simulated loss-of-coolant experiments, conducted i n previously described f a c i l i t i e s ’ at the QRR, a r e designed to provide information on release and transport of f i s s i o n products in reactor a c c i d e n t s . I t is intended that t h e information obtained c a n b e u s e d t o predict f i s s i o n product behavior under conditions beyond t h o s e t e s t e d so that hypothetical a c c i d e n t s c a n b e more realist i c a l l y evaluated. The interpretation of d a t a from previous experiments on f i s s i o n product r e l e a s e and behavior h a s been t h e main activity during a period when major

Fig.

lot,

17.1.

Opened C r u c i b l e from

Showing Upper

End Cap,

TREAT

Experiment

F l u x Monitor C o p s u l e ,

and P a r t of Nonporous F u e l - C l a d d i n g R e s i d u e Around Sample Holder and on C r u c i b l e Wall.

4R. C. L i i m a t e i m e n and F. J. Testa, Chem. Eng. Div. Semiann. Progr. R e p t . July-Dec. 1965, A4NL-7125, pp. 170-78.

’W. E. Browning, Jr., e t nl., N u c l . Safety Program Semiann. Pro&. R e p t June 30, 1965, ORNL-3843, p. 156.

154 constiuction work h a s been under way on t h e reactor facility. A major construction program h a s been carried on during t h e p a s t y e a r involving t h e reactor facility in which t h e in-pile f i s s i o n product r e l e a s e experiments a r e performed. T h e ~iiodificationsa r e in l i n e with t h e e m p h a s i s on fission product transport. They i n c l u d e t h e construction and i n s t a l lation of a simulated reactor containment v e s s e l , t h e installation of on-line a n a l y z e r s for the d e termination of water, hydrogen, oxygen, and carbon o x i d e s in t h e s w e e p g a s , and of i n c r e a s e d capability for temperature measurement and control in t h e experiment s y s t e m . A s c h e m a t i c diagram of t h e new system i s shown i n Fig. 17.2. The availability of t h i s modified facility will allow t h e complete study of r e a l i s t i c f i s s i o n product r e l e a s e , transport, and behavior in a v e s s e l . T h e considerable literature h a s been examined in a study of t h e extent and t h e rate of sorption of iodine o n a variety of s u r f a c e s and p o s s i b l e components of reactor s y s t e m s . T h e practical re-

s u l t s of t h i s study, from n u c l e a r s a f e t y considerations, a r e as follows: 1. Sorption of iodine on several materials (notably c l e a n s t e e l , c l e a n s t a i n l e s s s t e e l , and s o i l e d s t e e l with oxide coatings) can b e interpreted very well by mechanisms involvin g monolayer adsorption with dissociation. 2. Absorption of iodine i n water or in aqueous solutions c a n b e treated by u s e of models involving, diffusion through boundary l a y e r s . Such me&a n i s m s for iodine deposition will b e important when s u r f a c e s arc covered with water f i l m s during steam condensation within a containment v e s s e l . 3. Sorption of i o d i n e on s t a i n l e s s s t e e l and some other m e t a l s covered with an o x i d e layer (e.g., as-received s t a i n l e s s s t e e l ) seems to involve complicated mechanisiiis and to follow relatively complex k i n e t i c s . S i n c e s t a i n l e s s s t e e l is l i k e l y to h e an abundant material i n containment s y s t e m s , it will b e n e c e s s a r y to study t h e sorption-desorption p r o c e s s as a function of o x i d e t h i c k n e s s and temperature. CRN1.-LR-DWG 56274R HV-808 (METERING VALVE).;

>''

p s ~ e o CONTAINMENT i

VESSEL,

/o"pE~~~L

PS-802 COXTAINMENT SECON OARY

"",,

,HV-80? /H~-~oG

' OISCCNN'CT QIJICK

FERRULE SEAL-,

/, I/

GAS I N L E T

SPRAY NOZZLE FOR

_I A

RADIATION DCTEZTORS

0 .J

r-(

..........+ -J .

I I I I

OUTSIDE eOTTLE RACK

Fig.

LlQlJlD

NITROGFNCOOLED CHARCOAL iKAP

OFF-GPS HOOD

FURNACE ir

8 '

Cr:RE

SECONDARY

PS PRESSURE SWITCH DP DIFFERENTIAL PRESSURE GAGE F l FLOW INDICATOR

17.2. ORNL In-Pile F u e l Destruction Experiment:

OFF-GAS

CONTAINMFNT VESSEL

'CONTAINMENT

RMAL

_________

,HV-807 HV-E03

F l c w Diagram.

155 IGN1TION OF CHARCOAL ADSORBERS C. E. Miller, Jr.

R. P. Shields

Charcoal adsorbers a r e used i n many present and proposed reactor s a f e t y s y s t e m s t o remove iodine from t h e containment system atmosphere. T h e High F l u x Isotope R e a c t o r u s e s s u c h a s a f e t y system. Such charcoal a d s o r b e r s will i g n i t e and burn if temperatures and air f l o w s a r e sufficiently high. Reactor a c c i d e n t s would discharge large quant i t i e s of f i s s i o n products w h o s e radioactive decay could produce s e r i o u s overheating (especially in local hot s p o t s ) of t h e adsorber beds. Such acc i d e n t s might a l s o permit air to enter t h e containment system and t h e adsorber bed. Accordingly, w e h a v e i n i t i a t e d a program of t e s t s both in t h e laboratory and in-pile to e s t a b l i s h t h e effect of f i s s i o n products and of irradiation on t h e ignition temperature of charcoal adsorbers. Laboratory s t u d i e s h a v e b e e n conducted primari l y with Barnebey-Cheney type KE (BC-KE) and Mine Safety Appliances (MSA) No. 85851 charc o a l s , both of which h a v e been widely used in adsorbers. T h e d a t a from small-scale investigat i o n s o f t h e s e materials s h o w t h a t ignition temperatures vary somewhat for various l o t s of t h e s a m e charcoal; initial ignition temperatures diff e r e d by 30°C for two l o t s of MSA charcoal, while s u b s e q u e n t ignition temperatures differed by 15 t o 2OoC. Ignition temperatures seem independent of a p p a r a t u s material ( g l a s s or m e t a l s s u c h as s t a i n l e s s s t e e l ) and of tubing s i z e over t h e s m a l l range (0.5 and 0.7 i n . in diameter) studied. Initial ignition temperature w a s unafiected b y change in air flow rate from 20 t o 40 fpm, but subsequent ignition occurred a t temperatures 10 t o 15OC lower at t h e higher flow rates. Ignition temperatures were lowered measurably (about 6OC) when m o i s t air w a s s u b s t i t u t e d for dry a i r a t t h e s a m e velocity. T h e ignition temperatures for t h e BC-KE c h a r c o a l s were i n c r e a s e d by addition of iodine. A most important finding in t h i s study is that c h a r c o a l from adsorbers which had been i n s e r v i c e for one year on t h e NS “Savannah” showed ignition temperatures 150 to 2OO0C lower than unexposed s a m p l e s o f t h e s a m e charcoal. T h e reason for t h i s difference is not yet known.

In-pile t e s t s h a v e b e e n conducted in an experimental unit (see F i g . 17.3) designed for u s e in t h e fuel melting f a c i l i t y in the QRR. T h i s f a c i l i t y and t h e f i r s t in-pile ignition t e s t of t h i s series w e r e described in a prevjous report.’ A t o t a l of 100 ignitions h a v e been performed with t e n ignition c y c l e s per position. Control o i t h e position of the UO, cylinder (from which f i s s i o n products were emitted t o t h e charcoal adsorber) permitted study a t three l e v e l s of f i s s i o n product concentration in t h e charcoal; iodine concentrations corresponded to 4.3, 5.0, and 7.0 w per s q u a r e i n c h of chatcoal surface. T h e s e energy release r a t e s a r e greater by a factor of 8 than t h o s e expected in HFIR, LOFT, or N P R adsorbers. Ignition temperatures for t h e in-pile experiments differed i n s e v e r a l regards from t h o s e observed in the laboratory experiments, Typical experiments with a BC-KE charcoal s h o w e d that i n i t i a l ignition, which took p l a c e after t h e iodines were at equilibrium, occurred a t 336OC; t h i s value is not significantly different from the value 341OC which is the average of ten f a s t ignitions in t h e s a m e a p p a r a t u s out-of-pile. However, subsequent ignit i o n s in t h e in-pile assembly occurred a t temperat u r e s up to 40°C higher. This i n c r e a s e in ignition temperature (which is quite unlike the laboratory behavior) p e r s i s t e d e v e n after the unit w a s ret r a c t e d t o s t o p f i s s i o n product (and iodine) generation. When a n in-pile ignition experiment w a s resumed (in t h e retracted position) after a &day l a p s e following a n equipment malfunction, the ignition temperature remained a t some 20°C a b o v e i t s laboratory value, even though virtually all iodine a c t i v i t y had decayed. Some factor in addition t o iodine and t h e short-lived f i s s i o n products seems r e s p c n s i b l e for a part of this temperature increase. F u t u r e in-pile experiments will b e performed to study t h e ignition temperature behavior of highignition c h a r c o a l s and impregnated c h a r c o a l s . In t h e s e experiments a controller will be used to reproducibly control t h e heating rate of t h e adsorber. Future out-of-pile experiments will include t h e further development of a standard ignition app a r a t u s and t h e study of ignition c h a r a c t e r i s t i c s of various c h a r c o a l s .

156

ORNL-UWG E G - B O ~ ~ ~

SAS E X I T SOLEhOID VDLVt

BYPDSS TO GAS EXIT CHARCOAL TRAP GAS INLET TO I G h I i l O h

TUBE

CPARCOAL TRDP (GAS E X I T )

GLASS WCOL BLFFER SOLENOID VALVt

ELECTRIC HEATER

C b ARCOAI.

THERMOCOUPLE (21 ‘As-in STAINLESS

CHARCOAL IGNITION UNIT

STAlhLESS STEEI SCREEN FILTER HEATER

AdFfllNUM COOLER

FISSION CHAMBER (GAS EXIT1 ~~

T h o E PLUG T W O UO,

CYLINDERS

FISSION CHAMBER (8EACTOR FURNACF)

-?O, HOLDE‘I

Fig.

17.3.

E x p e r i m e n t a l Equipment for

I n - P i l c C h a r c o a l I g n i t i o n E x p e r i m e n t IGR-2.

157

lSSfON PRODUCTS FROM ZIRCALQY-CLAD HIGH-BURNUP UQ,

G. E. Creek R. A . Lorenz

Table 17.1.

D i s t r i b u t i o n (76) of Iodine Released from High-Burnup

W. J. Martin G. W. Parker

T h e previous report6 g a v e r e s u l t s of a n experiment performed in t h e Containment Mockup F a c i l i t y (CMF) with s t a i n l e s s - s t e e l - c l a d UO, irradiated to a burnup of 1000 Mwd/ton. Data obtained i n a similar experiment (run 4 11) with Zircaloy-clad UO, irradiated t o a burnup of 7000 Mwd/ton are reported below. T h e conditions u s e d in t h i s experiment were q u i t e close to t h o s e prevailing in the previous high-burnup experiment. T h e t o t a l p r e s s u r e in t h r CMF, fuinished by a mixtuie of a i r and s t e a m , was a b o u t 29 p s i g before heating t h e f u e l . Heating of t h e fuel w a s s t a r t e d with a mixture of s t e a m a n d air flowing through t h e pressurized furnace tube, but s t e a m flow w a s discontinued before t h e fuel temperature reached a n estimated 2200OC bcc a u s e af steam condensation i n t h e furnace lube. Dry air flow coritiiiued during t h e b a l a n c e of t h e b a t i n g period (10 min total) and for 20 m i n thereafter. During most of t h e 20-min cooling period, burning of t h e s p e c i m e n w a s observed a t irregular i n t e r v a l s ; s u c h behavior h a s b e e n observed wlth previous Zircaloy-clad UO s p e c i m e n s t h a t had b e e n melted and then c o o l e d i n air. T h e distribution of i o d i n e observed in t h i s experiment is compared i n T a b l e 17 1 with t h e d a t a obtained with t h e 1000 Mwd/ton burnup f u e l 6 (run 10-29). T h e distribution of four other important f i s s i o n products is similarly conipared i n T a b l e 17 2. I n both t a b l e s t h e observed differences a r e not l a r g e enough to b e considered significant without further, confirmatory, d a t a . The high transport of i o d i n e observed i n t h e 7000 Mwd/ton experiment (21.6% as compared with 9% for the 1000 Mwd/ton experiment and 6 to 10% i n simulant experiments) w a s a n unexpectedly l a r g e difference. â&#x20AC;&#x2DC;rhe difference i n i o d i n e collection o n plateout s a m p l e s is due, at least i n part, to a lclrger number of painted c a i b o n - s t e e l s a m p l e s i n run 4-11 as compared with iun 10-29 T h e r e a p p e a r s to b e no obvious explanation for t h e smaller fraction of iodine i n t h e c o n d e n s a t e i n t h e 7000 Mwd/ton experiment. 6G, W. Parker e t S I . , Reactor Chem. D i v . Ann. f r o g r . 12ept. D C C . 31, 1965, ORNL-3913, p. 138.

Bumup 1000

M w d / t on

7000 Mwd /Io n .........

Iodine r e l e a s e d

-100

90.8

19.8

20.3

7.2

23.7

Iodine h e l d i n containment tank R e t a i n e d on t a n k w a l l s C o l l e c t e d on plateout s a m p l e s Collected in condensate

57.6

19.2

T o t a l iodine retained

84.6

63.2

Todine removed from t a n k a f t e r aging by Pressure release

2.9

7.7

Argon d i s p l a c e m e n t

4.8

11.5

Air sweep T o t a l iodine transported

1.2

2.6

8.9

21.8

from t a n k Retention of airborne iodine from tank On f i l t e r s On s i l v e r or copper s c r e e n s In c h a r c o a l c a r t r i d g e s

Iodine i n penetrating form

13.35

2.1

5.5

5.0

2.2

11.7

0.6

0.6F1

?%sed on the r a t i o of a c t i v i t y o n the s i l v e r s e c t i o n of the diffusion tube to t h a t o n t h e c h a r c o a l - l i n e d s e c t i o n .

Data o n airborne f i s s i o n products iri t h e contain ment tank a s a function of time were also obtained from a n a l y s i s Qf g a s s a m p l e s taken a t various intervals. Comparison of t h e d a t a with t h o s e for t h e 1000 Mwd/ton experiment6 s h o w s l i t t l e diff e r e n c e i n airborne I, Cs, Mo, and Ru. T h e airborne tellurium v a l u e s are lower for t h e 7000 Mwd/ton experiment, reflecting t h e alloying effect of t h e zirconium cladding, while t h e barium and sttontiurn v a l u e s a r e higher a s t h e result of the reducing effect of the zirconium. Both phenomena h a v e been observed earlier. F i s s i o n products r e l e a s e d from Zircaloy-clad 7000 Mwd/ton burnup f u e l i n t h e CMF differed from t h o s e r e l e a s e d from s t a i n l e s s - s t e e l - c l a d 1000

â&#x20AC;&#x2122;

7G. W. Parker e t af., N u c l . Safety Progtam Semiann. Progr. K e p t . D e c 3 1 , 1962, ORNL-3401, p. 5.

158 Tnblr

17.2. D i s t r i b u t i o n of F i s s i o n Products R e l e a s e d from High-Burriup U02 (Runs 10-29 and 4-11) .. . ....

F i s s i o n Product Element

__-____

Rurnup L e v e l (Mwdlton)

...... .......... .......... Amount of F i s s i o n Product Found (% of t o t a l inventory)

..........

Furnace T u b e and Duct

Aerosol

t o Tank

Walls

Tank

.. .

Total

Condensate

Filters

Release from F u e l

1000

3.0

15.1

43.6

0.8

62.5

7000

8.6

13.8

6.2

1.5

30.0

Tellurium

1000

0.3

6.9

0.8

8.4

7000

0.7

1.4

0.04

0.45 0.112

Ruthenium

1000

0.Oi

0.35

0.12

0.0006

0.54

7000

0.16

0.0s

0.002

0.004

0.22

1000

0.01

0.04

a. a003

0.0004

0.05

7000

0.05

0.11

0.015

0.0026

0.18

Ceslum

Strontium

Mwd/ton ftiel in a way that could h a v e b e e n p r e dicted from t h e difference in cladding materials. N o variations werc o b s e i v e d that could b e a t tributed t o t h e difference i n bnrnup l e v e l of t h e fuel speciriiens.

ESEE-GAVIOR OF: 3 , AND HB IN THE CQHTAIHMEHY RESEARCH INSTALL4'TIIQH TANK G. W. Parker G. E. Creek N. K . Eorton8 W . J . Martin The Containment R e s e a r c h Installation (CKI) h a s been const.ructed a t Oak Ridge National L a b oratory- for t h e investigation of f i s s i o n product r e l e a s e , transport, and plateout a s a function of burnup, fuel and containment temperature, time at temperature, and atmospheric and containment s u r f a c e composition. 'The primary o b j e c t i v e of t h e initial experiments i n t h e CW! was to coinparc the deposition behavior of molecular iodine (run 100) and HI (run 101) i n a s t a i n l e s s s t e e l system under ambient conditions of temperature and humidity and an internal air pressure of 30 p s i g . ~n run 100 a n initial concentration of 2 m g / i n 3 of elemental iodine tagged with 1 3 0 1 was introduced into t h e CRI containment v e s s e l b y cornp r e s s i n g a thin-wall s t a i n l e s s s t e e l lube which contained a n iodine-filled g l a s s ampule. An eir stream p a s s e d through the heated tube for 12 rnin to t-ansport iodine t o t h e containinent v e s s e l . 8 P h i l l i p s Petroleum C o . , o n assignment t o Oak Ridge Nation a 1 Ldahora t ory.

2.3

Over a peiiod of 22 hr, approximaicly 98% of t h e airborne iodine w a s d e p e s i t e d on t h e tank w a l l s . Depletion of t h e iodiric ocrurri.d very iapidly during t h e first 1 2 min and then more slowly for t h e remainder of t h c experiirimt. T h e r e s u l t s are summarized in T a b l e 1 7 . 3 . T h e fraction of iodine retained b y t h e a b s o l u t e filter media increased with time, while t h e f r a c t i o n s which p a s s e d s u c h filters did not. It a p p e a r s that t h e filterable fraction of t h e iodine h a s a rate of deposition on t h e t a n k which differs from that of t h e other forms of iodine p r e s e n t . Tn run 101, Iiy-drogeil iodide w a s formed by p a s s i n g a hydrogen g a s stream over a crushed c a p s u l e containing I, tagged with 1 3 0 1 and combining t h e s e components on a platinum c a t a l y s t a t 40OoC. T h e product w a s formed and injected into the CKI tank during a period of about 35 m i n . T h e t o t a l weight of iodine u s e d was again sufficient to give an i n i t i a l concentration of about 2 m g / m 3 . In t h i s run, a s well a s in run 100, approximately 98% of t h e activity w a s d e p o s i t e d on the containment v e s s e l s u r f a c e s during t h e c o u r s e of t h e experiment. Ta.ble 1'7.4 surainarizes t h e sampling d a t a , which show that the ( a t e of d e p o s i tion of HI over t h e first 3 hr was f a s t e r than that of I, in run 100. T h e slowee deposition r a t e after 3 hr p o s s i b l y i n d i c a t e s that t h e HI h a s changed t h e adsorption c h a r a c t e r i s t i c s of t h e s t a i i i l e s s s t e e l s u r f a c e s , rendering them more inactive, or that i t reacted to give a n unidentified form of iodine which w a s only s l i g h t l y r e a c t i v e with t h e s t a i n l e s s s t e e l containment v e s s e l .

159 Distribution of Iodine A m o n g C R I Gas Sampler Components in M o l e c u l a r l2 Experiment ( R u n 100)

T a b l e 17.3.

Time After

Percent of

Completing

T o t a l Iodine

I Injection

Invent ur y

into T a n k

Airborne in

(min)

Tank

F r a c t i o n of Sample Iodine Activity Collected by Absolute

Silver Membranes h

FiIters e

32.4

0.093

0.898

0.009

26.3

0.083

0.911

0.006

22.7

0.074

0.922

0.004

161

10.5

0.073

0.922

0.004

285

6.9

0.089

0.904

0.007

4 00

3.2

0.128

0.860

0.012

710

1.0

0.417

0.539

0.044

832

0.77

0.506

0.434

0.060

1020

0.47

0.594

0.328

0.078

1155

0.42

0.59

0.328

0.080

1255

0.41

0.588

0.329

0.083 ~

Note:

. . . . . . . . . . . . . . . . . . . .

S e e T a b l e 17.4 f o r eaplanation of footnotes. Distribution of Iodine Among CRI G a s Sampler Components in HI Experiment (CRI Run 101)

T a b l e 17.4. _

~~~~

Time After

Percent of

Cotnple tint:

Total Iodine

HI Injection

Inventory

into 'Tank

Airborne in

Tank

(min) _

Charcoal Cartridges

Absolute

F r a c t i o n of Sample Iodine Collected by

FiltersR

Silver Membranes

Charcoal Cartridges"

_..._ 0.16

0.83

0.01

8.5

0.07

0.84

0.09

6.1

0.05

0.4gd

0.47

151

4.2

0.04

0.91

0.05

477

2.8

0.04

0.94

0.02

604

2.5

0.03

0.9G

0.01

728

2.3

0.04

0.95

0.01

842

2.0

0.04

0.90

0.06

918

1.9

0.05

0.93

0.02

996

1.7

0.04

0.34

0.02

1093

0.9

0.05

0.93

0.02

12.0

aAhsolute filter media

- Flanders

filter 71170A.

'Silver membrane filter - Flowtronics silver membrane, 5 "Charcoal cartridge

- 52

in. of unimpregnated charcoal and

pore s i z e , four or eight filters were u s e d . $2

in. of impregnated charcoal.

'Faulty mounting of s i l v e r membranes apparently c a u s e d low HI retention on s i l v e r membranes and high charcoal collect ion value.

R . E. Adams J a c k Truitt

J . S. Gill W. D . YuiHe

T h i s program is intended t o a d v a n c e t h e technology of removal of f i s s i o n product g a s e s and colloidal d i s p e r s i o n s b y adsorption and filtrat-ion techniques in order t o i n c r e a s e the confidence in t h e reliability of t h e e f f e c t i v e n e s s of various a i r cleaning s y s t e m s iinder a c c i d e n t conditions. A s t h i s confidence i s a c h i e v e d , a wider a c c e p t a n c e of air c l e a n i n g s y s i e n s a s engineered safeguards will b e accomplished. R e s u l t s of t h e s e s t u d i e s a r e reported in d e t a i l e l s e w h e r e . * Prior r e s u l t s a n d experimental techBriefly, niques h a v e been reported p w v i o u s l y . a reproducible a e r o s o l containing s t a i n l e s s s t e e l a n d oxides of uranium is u s e d for t h e s e t e s t s . T h e t e s t a e r o s o l is prepared by s t r i k i n g a n e l e c tric a r c betweeri e l e c t r o d e s c o n s i s t i n g of UO, (with thoriated tungsten) and a s t a i n l e s s s t e e l tube packed with UO,. Urider dry conditions the t e s t a e r o s o l (median s i z e of primary particles 0.018 p ) is e a s i l y filtered o u t of air s t r e a m s by a n y of t h e so-called “high-efficiency (absolute)” filters with e f f i c i e n c i e s of rcmoval in e x c e s s of s 4

99.9%. 1

. . .

V i s i t i n g s c i e n t i s t f r o m Great Britain.

2 R . E. Adams et a l . , N u c l . S a f e t y Program A n n . Progr. Me@. D e c . 3 1 , 1966 (to b e i s s u e d ) .

%Y. E. Browning, Jr., e t a l . , “Removal of P a r t i c u l a t e Materials from G a s e s Under Reactor Accident Cond i t i o n s , ” Nucl. S a f e t y Program Semiann. Progr. R e p t . June 3 0 , 1465, OHPIX,-3843, pp. 148-56.

4 R . E. Adarns, J. S. Gill, and W. 6.Drowning, Jr., Removal of P a r t i c u l a t e Materials from G a s e s Under R e a c t o r Accident Conditions,” N u c I . S a f e t y Program Semiann. Pro&. R e p t . D n c . 3 1 , 1965, OXNL-3915, pp. 80-81. ‘8

Prior experiments a t room temperature have shown that a moist atmosphere may reduce t h e efficiency of t h e same filter medium toward t h e same t e s t a e r o s o l t o a s low a s 93% under -95% relative humidity. T h e effect of moisture had not b e e n anticipated by reactor d e s i g n e r s , a n d , b e c a u s e of i t s i m p l i c a t i o n s in case of reactor a c c i d e n t s , recent r e s e a r c h efforts h a v e b e e n directed toward defining t h e mechanism of ixoisture i n reducing filtration efficiency. T h e e f f e c t of moisture m a y be d u e t o c h a n g e s in t h e properties of t h e a e r o s o l , c h a n g e s i n t h e filter media, or both. A difference h a s b e e n noted in t h e physical characte:istics of a e r o s o l s produced under humid and under dry conditions. E l e c t r o n photomicrographs of a n a e r o s o l produced under high relative humidity reveal that t h e p a r t i c l e s a i e covered with a thin f i l m of unknowii composition and that a g glomerates a r e in t h e form of c h a i n s (Fig. 1 8 . 1 ) rather than c l u s t e r s a s observed under dry conditioils. Evidently t h e s t a b i l i t y and filtration c h a r a c t e r i s t i c s of t h e s e two t y p e s of a e r o s o l s differ in some rzspects. l e s t s h a v e e s t a b l i s h e d that activity profiles obtained by filtration of moist and dry a e r o s o l s throi.ip,h fibrous-filter a n a l y z e r s a r e quit? different. In a dry atmosphere a s much a s 90% of t h e aerosol p a s s e d through t h e fibrous-filter analyzer is retained on t h e f i r s t fiber mat, whereas under high humidity conditions a f l a t a c t i v i t y profile is o h tained a s a r e s u l t of more e v e n distribution of p a r t i c l e s on t h e s u c c e s s i v e fiber mats. Interpretation of r e s u l t s under wet conditions c a n b e t a k e n t o mean that t h e fibrous filter inat efficienc i e s a r e being r e d w e d , or moisture i s affecting t h e a e r o s o l in some w a y , making it more difficult t o filter, or both. In a n y c a s e , a f l a t distribution of particles through t h e filter pa.ck would result. --. I O resolve t h e anomalous filtration behavior in the p r e s e n c e of moisture, a series of experi-

160

161

Fig. 18.1.

Appearance of Aerosol Formed i n a H i g h - H u m i d i t y Atmosphere.

1 6 5 , 0 0 0 ~ . R e d u c e d 6.5%.

Note thin

f i l m c o v e r i n g the p a r t i c l e s .

162 ments w a s made in which a n a e r o s o l generated in a high-humidity a i r atmosphere w a s sampled by two filter p a c k s . One p a c k was held a t room temperature, and t h e f i b e r s were s a t u r a t e d with water vapor from t h e high-humidity carrier g a s . To reduce the moisture content of t h e fibers, t h e other pack w a s h e a t e d t o 100°C under similar In another s e t of experiments the conditions. aerosol w a s generated in a dry a i r atmosphere and once more sampled with t w o p a c k s . One pack w a s dry, and t h e other w a s wetted by pretreating it with 90% relative hiimidity a i r immediately prior t o i t s u s e i n a n experiment. T h e conclusion drawn f r o m t h e s e experiments w a s that inoisture d o e s not affect t h e efficiency of a fibrous filter but that it influences t h e physical properties of the a e r o s o l , making it m o r e difficult t o filter. However, not a l l t h e r e s u l t s from t h e s e experimerits were equally unaiihiguous. At a e r o s o l concentrations e s t i m a t e d t o b e a t t h e l e v e l of l o 9 nuclei/cm the activity profile obtained in t h e presence of a w e t atmosphere V J ~ Snot characteri s t i c a l l y flat. It i s probable that a t t h e s e higher concentrations, agglomeration will occur r e g a r d l e s s of the presence of moisture. Study of t h e e f f e c t s of moisture i s continuing. Construction of a recirculating a e r o s o l facility for laboratory a e r o s o l s t u d i e s h a s b e e n proceeding parallel t o t h e moisture e f f e c t s s t u d y j u s t des c r i b e d . T h i s recircula t ing facility c o n s i s t s of a 100-liter s t a i n l e s s s t e e l v e s s e l w it11 a s s o c i a t e d piping which will allow t h e behavior of a n a e r o s o l , or a scaled-down a i r c l e a n i n g s y s t e m , t o b e studied under a variety of a c c i d e n t conditions ranging froin temperatures of 25 t o 12OOC and humidities from -0 t o Tu 100%. T h e recirculating aerosol facility h a s b e e n i n s t a l l e d , and s h a k e down t e s t s a r e i n t h e final p h a s e .

’,

EXAMINATION O F PARTICULATE AEROSOLS WSBH T H E FIBROUS-FILTER ANABXZEW

M. D.Silveiinan J a c k Truitt

b“ E. Browning, J r .

R . E. Adanis

T h e fibrous-filter analyzer ( F F A ) is being d e veloped for measuririg t h e c h a r a c t e r i s t i c s of radioactive a e r o s o l s in terms of their response t o filtration p r o c e s s e s by determining their distribution v s depth in a filter under carefully controlled conditions. Moisture d o e s not significantly

a f f e c t t h e peiformance of t h e FFA, although t h e t e s t a e r o s o l itself w a s a f f e c t e d . T h e filtration efficiency d a t a agreed well with t h e theoretical treatment of filtration developed by Torgeson. T h e analyzer w a s calibrated a g a i n s t p a r t i c l e s 150 to 1500 A in diameter, measured by e l e c t r o n microsCOPY. A summary report on t h i s project h a s been completed:’ and only a brief review of t h e s u b j e c t material will b e presented here. The FFA i s a n “in s i t u ” a n a l y t i c a l device which c h a r a c t e r i z e s radioactive aerosols dynamically by particle respoiise to t h e major p r o c e s s e s of filtration: diffusion, i n t e ice ptioii , and inertial impaction. T h e c o n c e p t of t h e FFA originated from a note by S i s e f s k y , 6 who determined t h e penetration of “fallout” material in a commercial filter by r a d i o a s s a y by peeling off l a y e r s of t h e filters with p r e s s u r e - s e n s i t i v e cellophane t a p e . B y c o n t r a s t , t h e fibrous-filter analyzer i s made froin uniform-diameter Dacron fiber (which is formed into a uniform wet by a cardirrg machine) into a layered s t r u c t u i e to f a c i l i t a t e s e p a r a t i o n of t h e fiber bed into d i s c r e t e l a y e r s for r a d i o a s s a y . T h e t e s t a e r o s o l containing 6 5 % n w a s produced by u s i n g a T e s l a c o i l t o generate a s p a r k between two preirradiated z i n c e l e c t r o d e s . A stream of air p a s s i n g over t h e e l e c t r o d e s carried the a e r o s o l through t h e s y s t e m containing t h e filters. E l e c tron micrographs of s a m p l e s of t h e a e r o s o l collected on carbon-covered Millipore membrane filters yielded information regarding t h e size of the part i c l e s . Depending on t h e experimental conditions, a e r o s o l s have been prepared over t h e size range SO t o 10,000 A (0.05 t o 1 p>. The d a t a were a n a l y z e d giaphically by means of t h e Chen equation’ to e s t i m a t e single-fiber efficiencies. T h e s e were compared with theoretical fiber e f f i c i e n c i e s c a l c u l a t e d according to Torgeson,’ who u s e d a n adaptation of D a ~ i e s ’inter~ ception and impaction theory combined with a new 5 ~ l B. . Silverman e t a l . . C h a r a c t e r i z a t i o n of Radioa c t i v i P a r t i c u l a t e Aerosols b y the Fibroris-Filter A n a l y z e r , ORNL-4047 (in p r e s s ) . 6J. S i s e f s k y , Nature 182: 1438 (1958).

7C. Chen, Chern. R e v . 55, 595 (1955). ‘W. L. Torgeson, “The T h e o r e t i c a l C o l l e c t i o n E f -

ficiency of Fibrous F i l t e r s D u e t o t h e Combined E f f e c t s of I n e r t i a , Diffiision, and Interception,” paper No. 5-1057, Applied Science Division, L i t t o n Systems, Inc., St. Paul, Minn., 1963.

’c. pi. n a v i e s , Proc. l i l j t . Mech. E n g r s . (London) 1 B, 185 (1952).

163 c

interception and diffusion theory. T h e Torgeson theory was s e l e c t e d by Whitby a s that which agreed most c l o s e l y with experimental d a t a a c cumulated in numerous r e s e a r c h e s . A computer program developed s p e c i f i c a l l y for t h e s e FFA c a l c u l a t i o n s is given in Appendix I1 of t h e summary report. Calibration of t h e FFA w a s performed by comparing particle sizes e s t i m a t e d from electron photomicrographs of t h e inlet and outlet a e r o s o l s with t h o s e c a l c u l a t e d according t o the Torgeson treatment. T h e b e s t correlations were observed in dry experiments and a t low v e l o c i t i e s Additional calibrations will b e performed a t t h e University of Minnesota under a subcontract.

’

DiSTlNGUlSHiNG IODINE FORMS A T HIGH TEMPERATURES AND HUMIDITIES

R . E. Adams Zell Combs

R . L. Bennett W.H. Hinds

In the e v e n t of a nuclear a c c i d e n t , radioiodine

i s the most hazardous f i s s i o n product which may

bc r e l e a s e d . Iodine may e x i s t in elemental or in chemically combined s p e c i e s in molecular form or as a e r o s o l s d i s p e r s e d on particulate material from t h e fuel or structural members of the reactor core. T h e various s p e c i e s exhibit diffetent behavior toward removal, and information is needed on their behavior in order t o d e s i g n adequate gas cleaning systems A program is in progress t o develop tools for d i s t i n g u i s h i n g the various vapor forms of iodine which occur in the laboratory and i n larger-scale experiments T h e identifying dev i c e s should b e c a p a b l e of remote operation and prefer:hly should keep their e f f e c t i v e n e s s under extreme conditions of temperature and humidity that may cccur in a reactor a c c i d e n t . T h e a n a l y t i c a l d e v i c e s most commonly used for radioiodine s t u d i e s a r e composite diffusion t u b e s and May p a c k s . T h e a d v e r s e effects of high humidity on t h e r e s p o n s e of diffusion t u b e s and t h e application of s e l e c t i v e d e s i c c a n t s and impregnated c h a r c o a l linings in improving their performance have b e e n reported. 1 1 , 1 2 Extensive t e s t s of May p a c k s under e l e v a t e d temperatures and high-humidity c o n d i i i o n s , s u c h as t h o s e e x pected in t h e LOFT experiments, are in progress

l a K . T. Whitby, ASHRAE J . 7(9), 56-65 (1965).

T h e May pack is a n a s s e m b l y of filter materials and adsorbent b e d s intended to s e p a r a t e iodine forms of different reactivity or adsorption tende n c y . Since high s p e c i f i c i t y is difficult to obt a i n for wide ranges of temperature and humidity, considerable t e s t i n g is needed t o e s t a b l i s h t h e range of reliability of t h e optimum components of t h e pack. Initial e m p h a s i s h a s been placed on a configuration s u g g e s t e d for t h e L O F T program. T h i s arrangement c o n s i s t s of a s e q u e n c e of three high-efficiency fitters, eight s i l v e r s c r e e n s , f i v e charcoal-impregnatetl filters, two %--in. charc o a l b e d s , and finally one more high-efficiency filter s e c t i o n . T h e i n i t i a l filter s e c t i o n is intended t o remove particulate forms of iodine, the s i l v e r s c r e e n s remove elemental iodine, and t h e charcoal filters retain the iodine s p e c i e s which a r e not removed by t h e s i l v e r s c r e e n s but which are e a s i l y adsorbed by charcoal-impregnated filter papers. T h e more penetrating Eorms, s u c h a s met.hy1 iodide, a r e adsorbed in the charcoal beds. T h e l a s t high-efficiency filter s e c t i o n is designed t o trap any c h a r c o a l p a r t i c l e s which might b e dislodged from the b e d s . Duplicate May packs were usually t e s t e d with two a s s o c i a t e d diffusion tube a s s e m b l i e s , one at room temperature under dry conditions and the other a t the s a m e conditions a s the May p a c k s . T h e tests were made a t 90°C with a superficial face velocity of 10 fpm. Dry or 90% relativehutnidity a i r streanis were used in t e s t s with elemental iodine and methyl iodide. R e s u l t s and d i s c u s s i o n of a large number of t h e s e t e s t s h a v e b e e n reported. l 3 Briefly, the effect of moisture on penetration of methyl iodide into the pack is illustrated i n F i g . 18.2. Under dry conditions the CH,I w a s about evenly distributed betweer, t h e charcoalloaded f i l t e r s and t h e first c h a r c o a l bed, while a t 90% relative humidity most of t h e f.’H31 was s w e p t i n t o t h e b e d s . The s h a r p separation of a “R. E. Adams e t al., “Characterization and Behavior of Various F o r m s of Radioiodine,” NucI. S a f e t y Program Semiann. Progr. Nept. D e c . 3 1 , 196.5, ORNI,-3915, pp. 101-11.

”R. E. Adams, R. L. Bennett, and W. E. Browning, Jr., Characterization of Volatile Forms of Iodine a t N i g h R e f a t i v e Humidity by Composite D i f f u s i o n T u b e s , O R N L 3 9 8 5 (August 1966). I 3 R . E. Adams e t a f . , “Characterization, Control, and Simulation of F i s s i o n P r o d u c t s R e l e a s e d Under LOFT Conditions,” N u c l . S a f e t y Frogram Ann. Pro&. R e p t . D e c . 3 1 , 1966 (to b e issued).

164 mixture of 16% with elemental. iodine is shown in Fig. 18.3. T h e e l e m e n t a l iodine d e posited on t h e f i r s t two s e c t i o n s , and the CH,I d e p o s i t e d on t h e charcoal b e d s . T h e penetration of t h e CH,I into t h e s e c o n d bed c a n be greatly reduced by use of iodine-impregnated charcoal. Several t e s t s have revealed that t h e elemental iodine deposition on the first high-efficiency filter

s e c t i o n is erratic and often large. F i l t e r materials investigated include Hollingsworth-Vose IIV-70, Millipore AP-20, F l a n d e r s F-700, Cambridge l G , R e e v e s Angel 934AI-I, and Z i t e x 5- t o 10-11 pore membranes. It a p p e a r s that s e p a r a t i o n of part i c u l a t e iodine from elemental iodine by u s e of a high-efficiency filter in t h e first s e c t i o n of t h e May pack is not reliable under the conditions

__ SAMPI E

-10

ORNk-DWG _ _

65-8204

RF L 4T IVE HUMID IT Y 90°C

_ _

fpm

_ _ _ _ _

1.-

CHjI

TEMPERA1 URC FLOW

V [L W

_I.

J E E P

nlG1-lEFFICIENCY FILTER

SILVER SCREENS

(31

(8)

CHARCOAL FII TFR PAP€?

CHARCOAL BED

(51

( 0 7 5 in 1 PCB

tlV 70 F i g . 18.2.

ACG/B

CH4RCOAL HIGH Et 0 EFFICIENCY FILTER

( 0 7 5 in ) PCB

(3) HV - i O

Retention of M e t h y l Iodide by May-Puck Components i n D r y a n d High-Humidity A i r Streams.

'0°

ORNL-DWG S.6 8 2 0 6

20 0

H IGH EFFICIENCY FILTER

SILVER SCREENS

(31

(81

F-700

F i g . 18.3.

Retention of M i x e d M e t h y l

H u m i d i t y A i r Stream.

CHARCO.4L FlUER PAPER

(5) ACG/R

CHARCOAL RED (0.75 in.] PC8

CHARCOAL BED

(0.75 in.] PC R

HIGHEFFICIENCY FILTER

(3) F-700

Iodide and E l e m e n t a l Iodine by M a y - B o c k Components

in a High-Rziative-

165 t e s t e d . Alternate p a c k configurations without t h e initial s e c t i o n of f i l t e r s are being s t u d i e d . Both s i l v e r s c r e e n s and s i l v e r membrane filters were found to be effective for removal of elemental iodine from s t r e a m s of 90% relative humidity. T h e c h a r c o a l b e d s should b e of t h e iodine-impregnated type for maximum retention of methyl iodide under moist conditions.

REACTIONS OF BOD1NE VAPOR WITH ORGANIC MATERIALS

R . L. Bennett Zell Combs

R . E. Adams

Ruth Slusher

When radioiodine is r e l e a s e d i n t o a closed environment, s u c h a s in a contairiment t e s t f a c i l i t y , i t Lias been noted that a generally s m a l l , but poss i b l y significant, fraction may appear i n the form In of methyl iodide and other a l k y l iodides. an a c c i d e n t s i t u a t i o n , methyl iodide may h e formed in t h e containlment atmosphere by gas-phase rea c t i o n s with organic contaminants, or on t h e varioiis t y p e s of s u r f a c e s within the containment ver,sel with s u b s e q u e n t desorption into the g a s phase. This investigation, which is a n e x t e n s i o n of some earlier e f f o r t s , i s concerned with the methods of formation of methyl iodides to avoid, if p o s s i b l e , conditions or materials conducive to its formation in a reactor system. P o s s i b l e reactioiis between painted s u r f a c e s and elemental iodine t o produce rr;ethyP iodide have been investigated. Preliminary work h a s b e e n dorie u s i n g g a s chrromatography, with e l e c t r o n c a p t u r e d e t e c t o r s fa arialysis of t h e reaction products. Calibration of methyl iodide r e s p o n s e h a s been made with s a m p l e s in the g a s and in t h e liquid phase (cyc lijliexane). T h e first experiments were performed using a reaction v e s s e l painted with two coats of Amercoat 64 primer and t w o c o a t s of Amercoat 66 s e a l coat

and heated at 10QOC. Periodic sampling gave chromatograms with about s i x major peaks, none of which f e l l near t h e methyl iodide peak. About 1 mg of elemental iodine was placed in another painted v e s s e l and heated a t 100째C. Chroniatographic a n a l y s i s indicated t h e p r e s e n c e of methyl iodide, with a total mass in f.he vapor p h a s e of about l o v 5 mg. Additional s t u d i e s will b e made with coating formulations of i n t e r e s t in t h e LOFT program. When a d u a l detection chromatograph which is on order becomes a v a i l a b l e , i t will b e used to examine t h e paint and reaction product vapors in more def-ail. T h e s e techniques will a l s o be employed to i n v e s t i g a t e the reaction of iodine with t r a c e organic components in the g a s phase.

FISSION PRODUCTS 1QU113 SYSTEMS

R. E.

Adams B. A. Soldano W . T. Ward

IZernovnl of f i s s i o n product d i s p e r s i o n s from containment atmospheres by application of 1iquid s y s t e m s has b e e n proposed a s a n engineered s a f e guard. Examples of t h e s e s y s t e n i s a r e pressure s u p p r e s s i o n pools and containment s p r a y s . An experimental program h a s been initiated to study both the c h e m i c a l and p h y s i c a l a s p e c t s of such gas-liquid s y s t e m s . A s t u d y of t h e adsorption of g a s e s , or p a r t i c l e s in g a s e s , by a liquid in a spray s y s t e m involves a situatioti wherein there e x i s t s a large amount of gas and a relatively s m a l l amount of liquid under highly dynmnic conditions. On t h e other hand, a s t u d y of f i s s i o n product trapping in a pressure s u p p r e s s i o n pool represents a situation in which there i s a very large amount of water under relatively s t a t i c conditions iri cont a c t with a s m a l l amount of gas. Since t h e t w o s y s t e m s involve t h e two extremes of the gasliquid spectrum, t h e study h a s b e e n divided irito two parts. T h i s d u a l i s t i c approach will hopefully "R. E. A d s m s et a l . , The ReleaGe and Adsorption permit extrapolation of inforniation t o intermediate of Methyl Iodide .in the H F R Maxiniturn Credible A c conditions and w i l l allow one to fix experimental cidorit, ORNL-TIM-I291 (Oct. E, 1965). 15 conditions s u c h t h a t a chemical-physical descrip1. E. Browning, Jr., et a l . , " K e a c t ~ o n of R a d i o iodine Vapors with Organic T7apnrs," PJui.1. S a f e t y P ~ c J - tinri of our experiments becomes fea:;ihle. gram S e m i a m . Frogr. R e p t . June 30, .I 965, ORNL-3843, An experimental s t u d y of the efficacy of water pp. 187-91. s p r a y s in t h e removal of r e l e a s e d f i s s i o n products '%. E. Browning, ~ r e.t ~el., "l"peactiun of Radioiodine Vapors with o r g a n i c Vapors," Nucl. S a f e t y Proin reactor containment v e s s e l s requires a knowl&am Semiann. pro&. Rept. D e c . 3 1 , 1965, ORNL-3915, e d g e of t h e hydrodynamics of t h e s e s y s t e m s a s pp. 39--100. I

166 well a s a n understanding of their kinematic b e havior. Since s i n g l e liquid drops under highly dynamic conditions c o n s t i t u t e a primary element of t h e spray i t s e l f , w e propose t o study t h e behavior of liquid drops s u s p e n d e d in a low-velocity wind t u n n e l . 1 7 Such a t u n n e l cat1 be u s e d t o simulate t h e gas-liquid environment accompanying a f i s s i o n r e l e a s e a c c i d e n t . Some of the pertinent variables are drop s i z e , height of fall, time of c o n t a c t , composition of both g a s and liquid p h a s e s , pressure, temperature, and t h e volume of tunnel gases. The a d v a n t a g e s of a wind tunnel in s u c h dynamic s t u d i e s a r e , i n part7 3 s follows:

1. The time of c o n t a c t of e a c h drop with t h e g a s stream c a n b e widely varied.

2. Drops s u s p e n d e d b y t h e g a s stream i n the tun-

nel c a n b e directly observed and photographed s o that s h a p e and o s c i l l a t i o n f a c t o r s c a n b e properly accounted for.

s i s t s i n bubbling air containing methyl iodide vapor through a I !;-in.-diain g l a s s column containing 800 m l of the s o l u t i o n a t approximately 2S°C (depth of solution = 28 in.) for approximately 2 hr, followed by a “ c l e a n ” a i r s p a r g e of from 16 t o 20 h r . T h e a i r entering the bottom of the column i s d i s p e r s e d through a porous g l a s s d i s k . The air leaving t h e column is p a s s e d through two or three beds of iodine-impregnated a c t i v a t e d c h a r c o a l t o remove t h e methyl iodide that is not captured by the solution. Iodine-131 tracer is used; t h e radioactivity of t h e c h a r c o a l and solution indicates t h e iodine distribntion. A l l t h e activity on t h e charcoal w a s found to b e in t h e first bed.

A cornparison of the e f f i c i e n c i e s of t h e various solutions t e s t e d to d a t e i s given i n T a b l e 18.1. Tests of other s o l u t i o n s a r e planned, a s well a s t e s t s to determine t h e effect of increasing t h e teiiipera ture.

3 . Random convection e f f e c t s a r e eliminated. 4. C l o s e temperature control c a n b e achieved in the workin, a r e a .

5. Homogeneity of t h e g a s mixtures and therefore

reproducibility of r e s u l t s is, in principle, a t tainable with s u c h a probe.

T h e second part of t h i s program involves a study of t h e behavior of f i s s i o n products in a pre-d S U l “ C s u p p r e s s i o n pool. General E l e c t r i c Company is incorporating s u c h pools in t h e i i d e s i g n of commercial power reactors a n d , for t h i s reason, is conducting research into t h e behavior of supprens i o n pools during and s u b s e q u e n t t o a reactor accident. Negotiations are under way with Geneial E l e c t r i c , San J o s e , for a subcoiitract under which they would perforiil t h e o r e t i c a l and laboratory investigations of the e f f e c t i v e n e s s of pressure supp r e s s i o n pools for f i s s i o n product trapping. At present, engineering d e s i g n s h a v e b e e n c n m pleted on both t h e wind tunnel and t h e supporting drop collection equipment. It i s estimated that approximately 75% of t h e p a r t s h a v e b e e n fabricated. Prior t o initiation of t h e wind tunnel investigation, studies. were undertaken t o determine t h e efficiency of various s o l u t i o n s in removing methyl iodide from air. T h e experimental procedure r o n -

Table

18.1. E f f i c i e n c y of Scrubbing Solutions

for Methyl Iodide Wernnvol from A i r

Amount

Solution

Concentration

of Activity Retained by

Solution (70) .. -.

... 0

D i s t i l l e d water Sodium hydroxide

0.01 M

Hydrogen peroxide

15 Wt 70

Iodic a c i d

0.1 M

Sodium a c e t a t e

4.2 M

Ammonium hydroxide

0.5 M

Potassium i o d i d e

0.1 M

Sodiuii? t h i o s u l f a t e

0.01 M

59.9

0.05 M

87.3

0.10 M

93.5

0.25 M

96.8

Hydrazine

27 wt

99.8

Solution A a

0.1 w t

84.7

99.6

57 0

99.92

12%

99.99t

..___.

”F. H. Garner and R. Kendrick, Trans. Znst. Chern. E n g r s . ( L o n d o n ) 37, 155-61 (1959).

aThe i d e n t i t y of s o l u t i o n A is being withheld pending p a t e n t e v a l u a t i o n b y t h e USAEC.

167 HIGH-TEMPERATURE BEHAVIOR OF GAS-BORNE FISSION PRODUCTS. TELLURIUM DIOXIDE

M.D. Silverman

Table 18.2. of

’

+ H,O($

- hydroxide(,d) ,

(Preliminary Results)

(OC)

653

Duration of‘ experiment (hr)

Oxygen carrier gas flow r a t e (moks/min)

7 . 0 0 ~

H,O transported ( g )

’reo2 transported

(g)

Apparent vapor pressure o f T e O , (torrs)

19.92

0.0245

661

7.55~

0 0.0016

8.72 x 10---2 0.61 x 1 0 - 2

(1)

in which t h e hydroxide s o fotmed is s t a b l e only at high temperatures. T h e present investigations are directed toward a s t u d y of t h i s reaction. T h e research h a s b e e n initiated iising tellurium dioxide, TeO 2 , as the compound under investigation. Although reaction (1) b a s y e t to b e unequivocally established in this case, t h e i n c r e a s e i n t h e apparent vapor p r e s s u r e , due to water vapor, h a s been experimentally demonstrated o v e r the temperature range bOO to 7 0 0 ” ~ . Our immediate objective is to verify t h e s e d a t a and to extend the temperature range. T h e transport method (also called t h e ” t m n s f e r ” or ““transpiration ’’ method) has been c h o s e n for u s e in the current research. In brief, the procedure involves s a t u r a t i n g a suilable carrier g a s with t h e material under s t u d y in one s e c t i o n of the apparatus and allowing t h i s s u b s t a n c e to be transported and collected i n m o t h e r region. A det.ailedl description of the experiniet~talaiid theoretical aspects can be found e l s e w h e r e , I 8 - ’ O Since the prc>ggrarn h a s only receni.ly been i n i tiated, much of the work h a s been concerned t h u s f a r with the d e s i g n , construction, and t e s t i n g of the a p p a r a t u s i t s e l f . Data obtained from two o f the preliminary r u n s , however, rather drarnatically demonstrate t h e effect of water vapor on t h e vola t i l i t y QE TeO,. These data ate presented iri T a b l e 18.2.

I d a . Glernser and 13. 6. Wendlamit, A d v a n . Inor. dzochem. 5, 215--$8 (1963).

TeOZ

Sample t e m p e r a t u r e

A . P Malinauskas

Recent experimental s t u d i e s indicate a n enhanced volatility of a rather broad c l a s s of metal oxides in t h e p r e s e n c e of water vapor. T h i s enhancement is believed t o be t h e r e s u l t of the generalized reaction

oxide(s)

E f f e c t of Water V a p o r on the V o l a t i l i t y

Ra-

” 0 . Giemser and R. v. Haaselcr, ~ r tui.r,,rssenschaften r 47, 467 (1960); 0. Glemser, X. v. I-Iaeseler, and A Muller, Z. A n o r g . A1IQern. Chem. 3 2 9 , 51 (1964); 0. Glemser, A. Muller, and If. Schwarzkopf, Narurwissenschaften 52, 129 (1965). ” 0 . Glemsee a n d K . v. Haeseler, Z . Ariorg. AUger~t. Chern. 316, 158 (1962).

THE CASCADE i ~ P A AS ~ A~ TOOL ~ R FOR THE STUDY OF S Z E ~ I S ~ ~ ~ B ~ T ~ O OF FISSION PRODUCT AEROSOLS 6. W. Parker

1-1. Buchholz

C a s c a d e impactors a r e instruments used to s e p a r a t e aerosok int9 fractions o f a d i s c r e t e range of pi3tticle sjze. T h e y are lrequelltly used for analyzing radioactive a e r o s o l s to c o l l e c t a range of s i z e groups which may later be examined for their radioactivity. Several theoretical arid experimental s t u d i e s of c a s c a d e impactors have been reported. 2 3 - ‘ 2 7 Impactors are limited to relatively large p a r t i c l e s , usually above 0.5 p9 and, in order t o make t h i s instrument genuinely useful in nuclear safety r e s e a r c h , i t is n e c e s s a r y t o extetld their range to particles below ’3.1 p . T h e b a s i c theory QE t h e s e d e v i c e s is quite simple. \The11 a gas jet carrying particles is directed toward a surface, all particles having sufficient inertia i n the f i r s t stage w i l l l e a v e t h e i r s t r e a m lines and s e t t l e on the s u r f a c e . Smaller particles will r e main within the jet stream. In the next s t a g e the ‘visiting scientist m i assignment. froin Hahn-Meitner Institute, Nuclear Research, Berlin. 2 2 K . R. May, J . Sci. 1n:itr. 22, 187-93 (1945).

2 3 ~ . C. ~ o u c ~ i r n a n~, e e of cascade Impactors for Analyzing Airborne f>aaurticles sf H i g h S p e c i f i c Gravity, CONF-650407, pp. I1 63-1203 (1 965).

I. Mitchell and .J. M. P i l c h e r , Design and C a l i Br;iltioti of a11 Improved C a s c a d e Impactor f o r S i z e A n a lysis~of Aerosofs, TTD-7.551, pp. 67-84 (April 1958).

2 5*r . T. Mercer, M. I. Tillery, end C. W. Ballew, A C a s c a d e Impactor Operating a t L o w Volumetric Flow R a t e s , LF-5 (December 196%).

2 5 ~ .J. C s h e n and D. N. bIortan, Theoretical considerations, Design, and EvaIriation of a Ce*.cade Impactor, UCKL-14440, R e v . 1 (June L966). 2 7 A . R . McE’arlatici a n d 1%. W. Zerllur, Study of a LargeVolume Impactor for H i g h - A l t i f i i d e Aerosol Collection, TTD -18624 (April 1963).

168 g a s p a s s e s through smaller h o l e s , and t h e j e t is accelerated t o a higher velocity. T h e probability of smaller p a r t i c l e s s e t t l i n g i s t h u s increased. If t h e pressure within t h e c a s c a d e impactor is lowered until t h e particle diameter is comparable t o t h e mean f r e e path of t h e gas molecules, there arc fewer c o l l i s i o n s between p a r t i c l e s and g a s molecules. P a r t i c l e s having s m a l l inertia a r e a b l e

under rediiced pressure t o l e a v e t h e jet. By t h i s s l i p e f f e c t , d e s m i b e d by t h e Cunningham correction, t h e c a s c a d e impactor becomes more efficient for s e p a r a t i n g smaller p a r t i c l e s . Using a n equation we c a l c u l a t e d t h e s i z e b a s e d on Mayâ&#x20AC;&#x2122;s theory, of p a r t i c l e s that have a 50% probability of d e positing on e a c h s t a g e of t h e Andersen sampler. T h e results for t h e case where t h e i n l e t g a s flow OSNL-DWG 67-708

0.4

0.2

I,.

0..

+ W

a 0.w 0

0.02

0.0

F i g . 18.4.

3 STAGE NO.

C a l c u l a t e d P a r t i c l e Distribution i n the Andeasen S a m p l e r cas a Function o f Internal Pressure and

Particle Density.

169 r a t e is 100 cm3/sec and t h e d e n s i t y is 1 or 6 g/cm3 a r e displayed i n F i g . 18.4. It is clear from t h i s graph that p r e s s u r e s less than 40 mm tig will allow t h e c a s c a d e impactor range t o b e extended t o particles s m a l l e r than 0.1 p. T h e original Andersen sampler w a s modified for subatmospheric operation. E a c h s t a g e of the s a m pler is connected t o a s e p a r a t e manometer to allow measurement of differences in internal pressure. T h e modified apparatus will b e calibrated by coll e c t i n g particles directly on electron m i c r o s c o p grids a t e a c h s t a g e .

REACTION OF MOLECULAR IODINE AND OF METHYL IODIDE WITH SODIUM THiOSULFATE SPRAYS G. W. Parker W. J . Martin

G. E. Creek N . R. Horton

Addition of c h e m i c a l s t o water used in reactor containment misting s p r a y s t o a i d in the rapid scavenging of radioiodine from steam-filled reactor containment s h e l l s h a s been proposed in many recent applications for power reactor construction permits presented t o t h e Atomic Energy Commission Pure water s p r a y s d o . n o t provide the des i r e d iodine removal rate. 'The removal of h e a t in most large reactor d e s i g n s is e f f e c t e d prim:lrily by ait-recirculation cooling units, and t h e removal of inorganic vapor forms of iodine (I, and MI) is t h e major requirement of the s p r a y s Griffiths described a method for predicting t h e r a t e of iodine removal from g a s e s by s p r a y s and presented most of t h e parameters for making s u c h c a l c u l a t i o n s in a comprehensive report which w a s summarized i n Nuclear Safety. 2 9 T h e most useful experimental examination of Grifflths' theory w a s performed by Taylor,30 using g l a s s columns i n which h e varied both t h e liquid flow r a t e and t h e g a s velocity. From t h e s e experiments t h e m a s s transfer process through t h e liquid f i l m w a s confirmed, It i s c l e a r that elementai iodine, a s i t is absorbed by a

28V. Grifflths, T h e Removal of Iodzne from the A t mosphere b y S p r a y s , Britlsh Repott AHSB(S)R-45 (December 1962). "V. G r i f f l t h s , N u c l . S a f e t y 6 ( 2 ) , 186-94 1964-65).

"OR. F. Taylor, Chem. E n g . Sci. 10(1/2),

(1 959).

(Wlnter 68-80

liquid drop containing reducing material, is chemic a l l y altered t o t h e form of iodide by t h e reducing agent. 'rhus, there is a s h a r p reduction in the vapor pressure of iodine near t h e liquid surface, and, s i n c e t h e total quantity of iodine available from a reactor is almost negligible (by comparison with t h e quantity of reducing agent in t h e spray), there is e s s e n t i a l l y n o change in efficiency as t h e drop c o n t i n u e s to fall. T h e iodine present a s HI is e v e n more s o l u b l e in t h e droplet, and it should b e removed at a f a s t e r rate than I , . In order to t e s t the s p r a y removal concept under conditions u s e d in f i s s i o n product transport s t u d i e s and in order to b e a b l e to assess t h e limitations of t h e process for t h e nonreactive forms of iodine, we decided t o carry out spray experiments in the Containment Mockup F a c i l i t y (CMF) with charact e r i s t i c forms of radioiodine. T h e d e s i g n of t h e spray s y s t e m allowed very s m a l l quantities of liquid to b e u s e d , and therefore the liquid-to-gas ratio could b e a d j u s t e d t o reactor containment proportions. T h e s p r a y s y s t e m c h o s e n for test contained s i x atomizing n o z z l e s , e a c h of which delivered 0.1 liter/min at 80 psig. Since t h e test containment w a s small (180 liters), t h e s p r a y s were generally operated for only 15 to 30 sec. Operation for 30 sec produced a liquid volume of 0.3 liter or 1/600 of t h e containment t a n k volume. A concentration of N a 2 S 2 0 3 of 0.1 mole/liter (1.6%) w a s used in t h e s e t e s t s .

Test with Molecular lodine (I,) T h e conditions s e l e c t e d for !he molecular iodine test were typical of t h o s e used in previous CMF steam-air runs. T h e i n i t i a l pressure was about 35 p s i g , of which about 20 p s i g was d u e to steam. T h e tank atmosphere temperature w a s about 130OC a t t h e injection time, and t h e cooling rate without s p r a y s w a s about 3O0/hr Since t h e natural removal rate for molecular iodine i n t h e CMF ( t 1 , 2 = 3 0 min) w a s fairly well known, t h e e f f e c t of thiosulfate s p r a y s on the removal r a t e could b e readily c a l c u l a t e d . W e found that addition of sodium thiosulfate spray a t a r a t e of 1/300 of t h e containment tank volume per minute d e c r e a s e d the half-life of d i s a p p e a r a n c e of I , from t h e tank atmosphere t o 3 9 sec. T h i s value agreed quite well witti t h e c a l c u l a t e d value of 2.6 sec for t h e half-time of removal of I , by 200-p droplets of 0.1 rn Na,S,O,.

170 T e s t s with Methyl Iodide

(CH,I)

In two experiments conducted in a similar manner t o t h e moleciilar iodine expeiirnent described above, methyl iodide injected a t similar concent i a t i o n s (2 tng/m3) w a s f i r s t exposed t o s t e a m and t o t h e condensation p r o c e s s and then t o sodium thiosulfate s p r a y . T h e r e s u l t s were e n couraging, but t h e rate of removal of CH,I i s only a fraction of t h e corresponding iodine rate. Ifowever, t h e CH,I removal r a t e i s of sufficient magnitude t o warrant i t s consideration in s a f e t y a n a l y s i s c a l c u l a t i o n s . T h e c a l c u l a t e d half-times for depletion of CH,I weIe approximately 2 hr in one ~ U I Iand 4 hr i n t h e other. Coiic I u s ion s

A model for removing r e a c t i v e iodine b y thios u l f a t e s p r a y s w a s t e s t e d in t h e s t a i n l e s s s t e e l CIvIF tank. E x c e l l e n t agreement between t h e c a l culated and t h e experimental iodine removal r a t e s w a s found. T e s t s of methyl iodide removal with N a , S 2 0 , s p r a y s gave encouraging r e s u l t s but showed much slower removal r a t e s t h a n t h e corresponding iodine r a t e s . More efficient s c a v e n g i n g a g e n t s will b e required for methyl iodide removal.

S T U D ~ E SO F C S E - T Y P E m s PRODUCT SIMULATION

G . W. Parker R . A . Lorenz N . J . Horton F i s s i o n product a e r o s o l s w i l l b e simulated in experiments t o b e performed in the Containment Systems Experiment (CSE) a t Elanford u s i n g a different t e c h ~ i i q u efrom that used at O R N L . Rogers pointed out that, in t h e 30,000-ft3 CSE containment tank, u s e of irradiated f u e l t o furnish reali s t i c f i s s i o n pi-oduct l e v e l s is impractical. Neither is it f e a s i b l e t o USE simulated high-burnup fuel p e l l e t s of t h e type u s e d in t h e CMF32 and i n

3 1 J .~ R o~g e r s , Program f o r Containment System periment, MW-53607 (September 1964).

EX-

3 2 G . W . Parker e t a l . , “Simulation of High-Buinup W o 2 Fuel i n t h e Containment Mockup F a c i l i t y , ” N u c l . S a f e t y Program Semlann. Pro&. R e p t . D e c . 3 1 , 1 9 6 4 . ORNL-3776, pp. 70--74.

thz NSPP. 3 3 T h e sirriulation technique devised for t h e CSE experinleiits, d e s c r i b e d by Hilliard and McCormack, 3 4 involves vaporization of suita b l e q u a n t i t i e s of f i s s i o n product e l e m e n t s containing radioactive t r a c e r s and p a s s i n g t h e vapor over molten uniiiadiated UO, before it e n t e r s t h e containment v e s s e l . In order t o determine how well t h e a e r o s o l s produced by t h i s teclriiiqur imit a t e t h o s e produced by overheated high-burnup fuel, it will b c n e c e s s a r y t o make direct comWe plan to parisons under similar conditions. d o t h i s in t h e CMF, where experiments with high-burnup fuel have already b e e n performed., and perhaps later i n t h e c o n t a i n m e n t Kesearch Installation (CRI). W e have completed t h e d e s i g n , construction, and preliminary t e s t i n g of equipment for performing CSE-type simulation experiments either i n the CMF or t h e CRI (the fuel-melting c a n s of t h e s e s y s tems ate interchangeable). It wa.s n e c e s s a r y t o mod-ify the expe1imen:al arrangement described by Hilliard a n d M c C o r ~ i i a c k rather ~~ extensively in order t o a d a p t it t o the CMF-CRI fuel meltdown arrangement, but t h e d i f f e r e n c e s r c l a t e mainly t o methods of getting t h e vaporized materials into the pressurized mcltdowri furnace. In addition, we c h o s e t o provide a steam-air environment in t h e vicinity of t h e molten UO, and in t h e containment tank, both at 30 l b t o t a l p i e s s u r e , rather than air, b e c a u s e our r e c e n t experimcnts with high-burnup fuel were a l l carried out u s i n g a s t e a n a i r atmosphere. A s shown by F i g . 18.5, two ribbon h e a t i n g units a r e insertzd through t h e g l a s s envelope, which i s fitted t o t h e end of t h e quartz meltdown tube by means of a tapered joint. A platinum ribbon which c a n b e operated a t a temperature between 1400 and 1600°C in t h e furnace tube atmosphere will b e u s e d t o vaporize tellurium (in t h e form of TeQ,), c e s i u m (introduced a s Cs,CO,), and ruthenium metal. Cesium will probably b e vaporized a s t h e mEtal but will quickly b e reoxidized in t h e furnace atmosphere. Ruthenium metal will undoubtedly b e converted t o a volatile oxide, RuO, 33L. F. P a r s l y e t a l . , “Transport Behavior of F i s s i o n Products in t h e Nuclear Safety P i l o t P l a n t , ” N u c l . Safety- Progcam Semiann. Pro&. R e p t . D e c . 3 1 , 1 9 6 5 , ORNL-3915, pp. 44-51. ,‘R. K . Hilliard and J . D. McCoimack, “Simulation i n t h e Containment Systems Experiment,” pp. 588-602 i n I n t e r n a t i o n a l Symposium on F i s s i o n Product R e l e a s e a n d Transport Under Accident C o n d i t i o n s , O a k Ridge, T e n n e s s e e , A p r i l 5-7, 1 9 6 5 . CONF-650407.

17 1

Pti-1070 84154

Fig.

18.5.

G l a s s Envelope Used in

CSE

Fission

T u n g s t e n (Upper) R i b b o n F i l a m e n t H e a t i n g E l e m e n t s .

Product Simulation T e s t s , Showing P l a t i n u m ( L o w e r ) and

172 or RuO,. T h e other h e a t e r , which h a s a tantalum i n . long, V shaped), i n . wide and ribbon operates i n a helium atmosphere i n a s m a l l g l a s s envelope having a ,-in.-diam hole through which helium carrying t h e v a p o r i ~ e dmaterial flows into the furnace tube. A inixture of 13aC0, and finely divided zirconium metal is placed on the tantalum ribbon t o i n c r e a s e t h e volatility of barium by re-d u c i n g t h e oxide t o t h e more volatile metal. Iodine iil t h e form of I , is introduced through a s i d e a r m a t t a c h e d t o the o u t s i d e pressurized t u b e e x t e n s i o n . A g l a s s c a p s u l e containing t h e I, is inserted in a Teflon-lined s i d e a i m , and it i s crushed while a s t r e a m of a i r flows through t h e tube t o carry t h e iodine i n t o t h e inner (furnace) tube. F i n a l l y , st-am i s introduced through a b a l l joint a t t h e end of t h e g l a s s e n v e l o p e . \Yater supplied under pressure a t a carefully controlled rate i s converted t o s t e a m by a miniature water vaporizer located in t h e outer pressurized s h e l l , quite c l o s e t o t h e ball-joint e n t r a n c e to t h e furnace tube. Preliminary t e s t i n g h a s centered on achieving satisfactory volatilization of barium, t h e l e a s t volatile s p e c i e s expected t o b e used in t h e s e e x periinents. We found that a temperature of 18OOOC was needed to volatize half t h e barium activity froiii a RaCO,-Zr mixture in a flowing helium a t m os p h e w .

(v8

R E T E N T I O N OF RADlOACTiVE METHYL I0D:DE

BY IMPREGNATED CHARCOALS

R . E . Adailis R . D . Acltley

J. U. ~ a k e , ~ J . M. G i ~ n b e l ~ ~ F. V. Hensley

Methyl iodide, which is more difficult t o t r a p than elemental iodine, may b e generated i n re actor accidents. It readily p e n e t r a t e s b e d s of t h e common t y p e s of a c t i v a t e d c h a r c o a l a t ambient temperatures e x c e p t when t h e relative humidity is low. However, certain s p e c i a l l y irnpiegnated (iodized) c h a r c o a l s h a v e bcen observed t o h a v e t h e capability of effectively trapping radioactive methyl iodide from a i r s t r e a m s of fairly high relative humidity a t temperatures a s high a s 1 1 5 째 F . 3 7 , 3 8 T h e s e c h a r c o a l s , which a r e impregnated with one 35Co-op s t u d e n t , University of T e n n e s s e e .

36Co-0p s t u d e n t , Drexel I n s t i t u t e of Technology.

or more iodine-containing s u b s t a n c e s , appear t o p o s s e s s t h i s unusual c a p a b i l i t y a s t h e result of a n isotopic exchange mechanism. '1'0 obtain information pertaining to t h e applicability of i m pregnated c h a r c o a l s under various reactor a c c i d e n t s i t u a t i o n s is t h e objective of t h i s work, which h a s been reported in more d e t a i l elsewhere. 3 9 , 4 0 A rather large number of s c r e e n i n g t e s t s on various laboratory-impregnated c h a r c o a l s and on various types of commercially impregnated charc o a l were performed. T h e maimer of conducting t h e s e t e s t s i s illustrated in F i g . 18.6. T h e t e s t s are made a t ambient temperature and pressure and usually a t around 70% r e l a t i v e humidity. Four commercial products were observed t o b e effective for CH3 'I trapping. 'They are BC-727 (from Uarnebey--Cheney), MSA-85551 and MSA-24207 [from Mine Safety Appliances Company), and G601 (from North Americaii Carbon, Inc.). R e s u l t s f r o m t h e s e room-temperature t e s t s for t h e four cominercial c h a r c o a l s a r e given in T a b l e 18.3. A number of laboratory-impregnated c h a r c o a l s a l s o gave promi s i n g i-e.sults, although a t p r e s e n t none of them are regarded t o h a v e a n y s p e c i a l advantage over t h e commercial c h a r c o a l s mentioned. 'The conditions coriesponding t o the earlier t e s t s 3 8 and t h o s e d i s c u s s e d a b o v e are less Severe than t h e conditions which h a v e b e e n postulated for t h e atmosphere i n a reactor containment v e s sel in which s t e a m is r e l e a s e d , cai-ising consider-a b l e elevation of temperature, pressure, and humidity. Consequently, t e s t s have a l s o been made under t h e m o r e s e v e r e conditions c h a r a c t e r i s t i c of steam-air s y s t e m s . Methyl iodide labeled with CH, 'I i s employed. T y p i c a l r e s u l t s a r e shown i n F i g . 18.7, where t h e d e l e t e r i o u s effect of very high relative humidity is displayed. T h e u s e of charcoal laboratory impregnated with triethylenediamine w a s prompted by r e s u l t s of United Kingdom r e s e a r c h e r s . 4 1 T o t h e e x t e n t they h a v e been t e s t e d , t h e other commercial c h a r c o a l s identified

37R. E. A d a m s c t a l . , T h e R e l e a s e a n d Adsorption of Methyl Iodide in the H F l H Maximum Credible A c c i d e n t , OHNL-TM-1291, pp. 21-26, 40 (Oct. 1 , 1965). 3 8 K . I). A c k l e y et a l . , N u c f . S a f e t y Program Semiarm. Progr. R e p t . D e c . 3 1 , 1965, ORNL-3915, pp. 61-80.

39R. E. Adams e t a l . , N u c f . S a f e t y Program Anti. Progr. R e p t . D e c . 3 1 . 1 9 6 6 (to be i s s u e d ) .

40R.E. A d a m s , K. 13. Ackley, and $11. E. Browning, Jr., R e m o v a l of Radioactive Methyl Iodide from Steam-Air S y s t e m s , ORNI.-4040 (in p r e s s ) .

D. C o l l i n s (letter), N u c l e o n i c s 23(9), 7 (1965).

173

DIFFERENTIAL

PRESSURE TRANSMITTER

ORNL-DW 66-7C5B

IVATED CHARCOAL S BEING T E S T E D

S1 E A M

AIR

HOOD

EXHAUST

ACTIVATED CHARCOAL BACKUP BEDS

FLOWMETER

1.& 1

CONTROL VALVE

AIR- CH31

Fig.

18.6.

Simplified D r a w i n g of S e t u p for I n v e s t i g a t i o n of Removal of R a d i o a c t i v e Methyl Iodide f r o m F l o w i n g

Steam-Air by Impregnated Charcoals.

Table

18.3.

R a d i o a c t i v e M e t h y l I o d i d e Removal T e s t s on C o m m e r c i a l l y Impregnated C h a r c o a l s a t 25OC

C h a r c o a l bed diameter: 1 in. C h a r c o a l bed depths: 0.5, 0.5, and 1 in. in s e r i e s or 1 and 1 in.

Air velocity (superficial):

40 fpm

Duration of air f l o w measured from s t a r t of CH31 injection:

6 hr

Duration of CH31 injection: 2 hr ( 1 s t 2 of above 6 hr)

__ cII 1 3 1I K e m o v a l

.I-

Relative Charcoal. Mesh S i z e

Humidity [Yo)

Amount of CH31

Unimpregnated activated charcoal, 6 X 1 6

MSA-85851 lot No. 5 3 , 8-14

MSA-85851 No. 93066, 8-14 (3)

MSA-24207h (2)

BC-727, 8-14 (6)

G-601, 12 x 16 ( 2 )

1.4 1.4

1.4 1.0 1.2 1.4 0.8

aNumber in parentheses denotes r e s u l t s are a v e r a g e s for that number of t e s t s . bNo mesh size furnished (appears to be 8-14),

' T e s t b e d s were 1 and 1 i n . rather than 0.5, 0.5, a n d 1 in.

Red Depth of:

to Amount

of C h a r c o a l (mg:/g)

MSA-85851 lot No. 2 3 , 8-14 (11)'

Efficiency (%) f o r

Injected R e l a t i v e

0.5 in. 4.6

1 in. 8.9

2 in, 17.3

56.3

82.3

97.1

52.0

79.2

88.0

52.8

81.2

97.5

64.8

88.7

98.9

85.9

98.1

97.0 98.7

174 a b o v e behave similarly under t h e s e condiiions to t h e c h a r c o a l s for which r e s u l t s a r e shown. In addition t o t h e t e s t s a t room temperature and a t approximately 28OoF, a s e r i e s w a s a l s o conducted a t -212OF. According t o t h e varioiis r e s u l t s obtained and s u b j e c t to certain qualifications, a number of commercially a v a i l a b l e impregnated c h a r c o a l s a r e highly effective for trapping tadioactive methyl

iodide from flowing a i r and steam-air over a wide range of conditions including 7 0 to 300째F and 14 to 50 p s i a . The qualifications a r e (1) that t h e s a m p l e s te.sted a r e representative of t h e cornrner.c i a 1 material; (2) that t h e c h a r c o a l h a s not been damaged, for example, by s e v e r e weathering or by poisoning from adsorbed foreign s u b s t a n c e s s u c h a s oil vapor; and ( 3 ) t h a t the prevailing relative hnmidity in t h e c h a r c o a l d o e s not greatly e x c e e d 90%.

ORNL--DUG 66-7637

100

.8 >

P 60

IMPREGNATFD CHARCOAI MSA 85851 0 BC-727

ILL

W Lc

a >

Fig.

moval and

CONDITIONS STEAM-BIR A T SUPERFICIPL VELOCITY

OF 27 10 45 fom

S T F A M - A I R FLOW C O N I I M U E D FOR AT LEAST 3 h r AFTER COMPLETION OF CH3I INJECTION ARCJUND 3 5 mg CH31 I N I HODUCED PER g OF CHARCOAI

RELATIVE HUMIDITY

(%I

18.7. of

E f f e c t of R e l a t i v e Humidity on the R e -

Radioactive

Methyl

Iodide

by Impregnated

C h a r c o a l s a t Temperatures and Pressures Around

5 " / o T R I E i H Y L E N E D l A M I N E ON PCB,

I-

i n DEPTH

6 x 16 mesh

e m

100

60 psia.

250째 6

Publications JOURNAL ARTICLES F' U B L ICAT IO N

AUTHOR( s)

TITLE

B a c a r e l l a , A. L., a n d A. L.

Anodic Fjlm Growth on Zirconium at Tem-

Barton, C . J., and

F i s s i o n P r o d u c t R e l e a s e a n d Transport

Sutton

W. B. C o t t r e l l

p e r a t u r e s from 200'

Electrochem. Technol. 4 , 117 (1966)

to 300°C Ntrcl. Safety 7(2), 203 (1966)

Under A c c i d e n t Conditions

Brunton, G. D.

T h e C r y s t a l Structure of L i U F 5

A c t a Cryst. 21(5), 814 (1966)

B u m s , J. H., a n d

Refinement of t h e C r y s t a l Structure of

Acta Cryst. 20, 135 (1566)

E. K. Gordon Cantor, S., D. G. Hill, a n d W. T. Ward Carroll, R. M., and

0. Sisman Davis, R. J., T. € I . Mauney, arid J. R. Hart De Bruin, H. J., G. M.

Watson, and C. JM. Blood

LiaBeFq D e n s i t y of Molten T h F 4 ; I n c r e a s e of

Inorg. N u c l . Chem. Letters 2, I S

F i s s i o n - G a s K e l e a s e During F i s s i o n i n g in

Nucl. A p p l . 2, 142 (1966)

D e n s i t y on Melting

(1566)

uo2

Corrosion of Z i r c a l o y 2 by Hydrogen P e r -

J . Electrachern. S o c , 113, 1222 (1966)

oxide a t E l e v a t e d Temperature Cation Self-Diffusion and E l e c t r i c a l Conductivity i n P o l y c r y s t a l l i n e Beryllium

J . A p p l . Phys. 37, 4543 (1966)

Oxide Fuller, E. L., Jr.. 1-1. F. Holmes, a n d

c. € I .

Gravimetric Adsorption S t u d i e s of Thorium Oxide.

11. Water Adsorption a t 25.00OC

J . Phys. Chern. 70, 1633 (1966)

Secoy

Holmes, II. F., E. I,.

Fuller, Jr., a n d C. S.

Secoy

J e n k s , C. H.

H e a t s of Immersion i n t h e Thoriutii OxideWater System. 11. N e t Differential H e a t s o f Adsorption

P r e d i c t i o n of Radiation E f f e c t s on Reactor Water a n d Solutions

Keilholtz. 6. W.

J . Phys. Chem. 70, 436 (1966)

Trans. Am. Nucl. S O C . 9(2), 382 (1966)

R e l e a s e and T r a n s p o r t of F i s s i o n - P r o d u c t Iodine and I t s Removal from Reactor-

Nucl. Safety

7(1), 72

(1965)

Containment S y s t e m s KeilholLz, G. W., J. E.

Irradiation Damage to Sintered Beryllium

Lee, Jr., a n d R. E.

Oxide a s a F u n c t i o n of Fast-Neutron

Moore

Dose and F l u x a t 110, 650, and llOO°C

Malinauskas, A. P.

Thermal Transpiration.

R o t a t i o n a l Relaxa-

tion Numbers for Nitrogen a n d Carbon Dioxide

175

N u c l . Sei. E n g . 26, 329 (1966)

J . Chem. Phys. 44(3), 1196 (1966)

176

TITI..E

A UTrl0 R ( s) Malinnuskas, A . P.

PlJBklCAKBON

G a s e o u s Diffusion - t h e S y s t e m s He-Kr, Ar-Kr, and Kr-Xe

Marshall, W. I,.,

and

E. V. J o n e s

Second D i s s o c i a t i o n C o n s t a n t o f Sulfuric

J . Chem. F h y s . 45, 4704 (1966)

J . P h y s . Chem. 76, 4028 (1966)

Acid from 25 to 350OEvaluated f r o m Solubilities of Calcium Sulfate in Sulfuric Acid Solutions

Marshall, SV. L., and Ruth S l u s h e r

J . P h y s . Chem. 70, 4015 (1966)

P'heimodynamics of Calcium Sulfate Dihydrate in Aqueous Sodium Chloride Solutions. 0--1 10'

P e r e z , R.. R.

A Dynamic Method for In-Pile F i s s i o n - G a s

Quist, A. S., and VI. L.

E l e c t r i c a l C o n d u c t a n c e s of Aqueous Solu-

Marshall

Nucl. A p p l . 2, 151 (1966)

Release Studies t i o n s a t High Temperatures a n d P r e s -

J . P h y s . Chem. 70, 3714 (1966)

surzs. 111. The C o n d u c t a n c e s of P o tassium B i s u l f a t e Solutions from 0 t o 700째 and a t P r e s s u r e s to 4000 B a r s

Reagan, P. E., J. G. Morgan, and 0. Sisman

Performance of Pyrolytic Carbon C o a t e d Uranium Oxide P a r t i c l e s During Iriadia-

Trans. A n . Nucl. Soc. 9(1), 2829 (1966)

tion a t High Temperatures

- Fission-Gas

Sisman, 0.

Preface

Soldano, H. A., a n d P. R,

Osmotic Behaviour of Aqueous S a l t Solu-

Thoma, H. E., H. A.

Isomorphous Complex F l u o r i d e s of Tri-,

Bien

Friedman. a n d K. A.

R e l e a s e Symposium

tions a t E l e v a t e d Tempcratures.

Nucl. Appl. 2, 116 (1966) J - Chem. SOC.(A) 1965, 1825

P a r i TY

Tetra-, a n d P e n t a v a l e n t Wianium

J . Am. Chern. Soc. 88, 2046

(1966)

Penneman

Thoma, R. E.

S e l e c t e d T o p i c s i n High Temperature Chemistry (book review)

Thoma, R. E., 13. I n s l e y , and G. M. Hebert 'Thoma, H. E., and R. H. Karrakcr Thoma, R. E., and G. D. Rrunton

T h e Sodium Fluoride..-Lzanthanide Tri-

J . Am. Cernm. SOC.49, 292 (1966)

Inorg. Chem. 5, 1222 (1956)

fluoride S y s t e m s T h e Sodium Fluoride---Scandium T r i -

Inorg. Chem. 5(11), 1933 (1966)

fluoride System Equilibrium Dimorphism of L a n t h a n i d e

Inorg. Chem. 5(11), 1937 (1966)

Trifluoride s

REPORTS ISSUED Friedman, H . A., a n d K. E.

Chemical S t a b i l i t y of liefiactozy Ceramics

Griess, J. C., and J. I,.

Materials C o n p a ti bili ty a n d Corrasion

Thoma

English

ORNL-TM- 1406 (January 1956)

in MSRE F u e l ORNI,-4034 (November 1966)

S t f i r l i e s for the Argonne A d v a n c e d R e -

search Reactor Hitch, B. F., 17. G. R o s s , and H. F. McDuffLe

Tests of Various P a r t i c l e F i l t e r s for

RemovBl of Oil M i s t s and Hyilrocarbon Vapor

ORNI,-TM-l623

(September 1966)

177

J e n k s , G. H., H. C .

Savage, and E. G.

PUBLICATION

TlTLE

AUTHOR(s)

N A S A T u n g s t e n R e a c t o r Radiation Chemistry S t u d i e s

- Final

ORNL-TM-1630 (October 1965)

Report

Bohlmann J e n k s , G. H . , H . Z.

N A S A T u n g s t e n R e a c t o r Radiation

Savage, and E. 6.

Chemistry S t u d i e s . I. Experiment

Rohlmann

Design

ORNL-TM-1403 (March 1966)

Keilholtz, G . W.

Filters, Sorbents, and Air-Cleaning S y s -

Kelly, M . J

An Analytical Approach to Waterlogging Fa i l u re

ORNL-3867 (December 1966)

McQuilkin, F. R., D. R.

A n Irradiation T e s t o f A V R Production

ORNL-TM-1512 ( J u a e 1966)

ORNL-NSIC-13 (October 1966)

t e m s a s Engineered Safeguards in Nuclear Installations

Cuneo, J . W. Prsdos,

F u e l Spheres in the O a k R i d g e R e s e a r c h

E. L. Long, Jr., and

Rcactor

J. H. Coobs

Miller, C. E., Jr., and

W. E. Browning, Jr.

T h e A d e q u a c y of Scale-Up in Experiments

ORNL-3901 ( J u ~ Y 1966)

on F i s s i o n Product Behavior in Reactor Accidents.

Part I. A n A n a l y s i s of

Scale-Up in the U . S . Nuclear S a f e t y PrfJ&tam

T h e A d e q u a c y of S c a l e - u p in Experiments

ORNL-1021 (December 1966)

on F i s s i o n Product Behavior i n Reactor

A c c i d e n t s . Part II. Recommended Additional Nriclear S a f e t y Scale-Up Experiments Morgan, J. G., M . F. Osborne, and E , L.

Postirradiation Bxaminatiori o f EGCR

ORNL-TM-1378 (February 1966)

Prototype C a p s u l e 03A-6

Long. Jr. Morgan, J . G . ,

P. E.

Reagan, and E. I,. Long,

JC.

N i c e l y , V. A., and R. J.

Davis

Evaluation and Irradiation E f f e c t s S t u d i e s OR

Particles Some Electrical Measurements on A n o d i c

Films

ORNL-TM-143.5 (December 1965)

011 Zirconium

Osborne, M. F., E.

Postirradiation Examination of Hi& Burntip

Redman, J. D.

A Literature R e v i e w of M a s s Spectrometric

R e e d , S . A.

Corrosion o f Carbon and A l l o y S t e e l s in

Long, Jr., and J. C . Morgan

ORNL-3923 (March 1966)

Pyrolytic Carbon Coated F u e l

ORNL-TM-1.511 ( J u n e 1966)

EGCK Prototype Fuel C a p s u l e s OKNL-TM-989 ( J u l y 1966)

Themioclieniical T e c h n i q u e - Supplement T ORNL-Tbl-1612 (October 1966)

Water and Seawaler Rutherford, J . L., J . P. R l a k e l y , and La. G .

Oxidation of U n f u e l e d and F u e l e d Graphite

ORN1,-3947 (May 1966)

Spheres by Steam

Overholser

Savage, H. W., E. L. Compere, W. R. Huntley, B. F l e i s c h e r , R. E. MacPherson, and A . Taboada

SNAP-8 Corrosion Profirem Summary Report

ORNL-3898 (December 1965)

178

T ITbE

AUTHOR( s) Ackley, R. D., K. E. P-dams, and W. E. Browning,

Reinoval of R a d i o a c t i v e Methyl Iodide from Steam-Air S y s t e m s

W, D. Yuille, L. F.

Proc. 9th A E C A i r Cleaning Conf., Boston, Mass., Sept. 14-16,

1966,

CONF-660904 (1966)

Ji.

Adams, R. E., J. S . Gill,

PUBLlCAHIQM

Performance of F i l t e r System Under Accident Conditions

Proc. 9th A E C Air Cleaning Conf., Boston, M a s s . , Sept. 14-16,

1966,

CONF-660904 (1966)

P a r s l y , W. E. Browning,

Jr., and C. E. Guthrie

Bae5, C. F., Jr.

T h e Chemistry and Thermodynamics of Molten S a l t Reactor Fluoride Solutions

Bennett, H. L., R. E.

Characterization of Volatile Iodine Forms

SM-66/60 in Thermodynamics, vul. 1, IABA, Vienna, 1966 P r o c . 9th A E C A i r Cleaning Conf.,

Adams, and W. E.

Boston, M a s s . , Sept. 14-16, 1966,

Browning, Jr.

CONF-660901 (1966)

Carroll, R. M., and

0. Sisman

In-Pile P r o p e r t i e s of R e a c t o r F u e l s by Oscillating Techniques

P r o c . Intern. Symp. C a p s u l e Irradiation Experiments, P i e a s a n t o n , Calif., May 3-5,

1966, TID-7697

(September 1966) Keilholtz, G. W., J. E. L e e , Jr., and R. E. Moore

P r o p e t t i e s of Magnesium, Aluminum, and

P r o c . Conf. N u c l e a r Applications o f

to Fast-Neutron D o s e s Grcater than 10”

Non-Fissionable Ceramics, Washington, D . C., May 9-11,

neutrons/cm2 a t 150, 800, and llOO°C

ed. by Alvin Roltax and J. II.

Beryllium Oxide Compacts Irradiated

1966,

Handwerk, I n t e r s t a t e , Danville, Ill. (1966) Bla!cely, J. P., and L. G. Overholser

Oxidation of ATJ Graphite by L o w Concen-

Carbon 3, 269-75 (1966)

trations of Water Vapor and Carbon Dioxide in Helium

Keilholtz, G. W., R. E.

Moore, M. F. Osborne,

T e c h n i q u e s f o r Irradiating High Temperature Materials in a S t e e p F l u x Gradient

P r o c . Inteni. Symp. C a p s u l e Iliadiation Experiments, p l e a s a n t o n , Calif.,

B. W. Wieland, a n d A . F.

May 3 - 5 , 1966, TID-7697 (September

Zulliger

1966)

Park, ,’, G. W., G. E. Creek, and A. F e r r e l i

Retention of Methyl Iodide by Impregnated Carbons Under Ambient Conditions

P r o c . 9th A E C A i r Cleaning Coiif., Boston, Mass., Sept. 14--16, 1966, CONF-660901 (1966)

S a v - g e , H . C., J . M. Baker,

M. J. Kelly, a n d E. 1,. Compere

An Asseiirbly for Irradiation of Molten

Proc. Intern. Syrnp. C a p s u l e l r r a d i a -

Fluoride F u e l to High Burnups in the

tion Experiments, P l e a s a n t o n , Calif.,

Oak Ridge R e s e a r c h R e a c t o r

May 3-5,

1966, TID-7697 (September

1966) Silverman, hi. D., J. T r u i t t ,

Characterization of R a d i o a c t i v e Particu-

P r o c . 9th ABC A i r Cleaning Conf.,

W. E. Rrowning, Jr., L. F.

l a t e Aerosols by t h e Fibrous F i l t e r

Boston, Mass., Sept. 14-16,

F r a n z e n , and R. E. Adams

Analyzer

C O N F a 6 0 9 0 4 (1966)

Watson, G. M., R. U. P e r e z , and M. H. F o n t a n a

E f f e c t s of Containment System S i z e on F i s s i o n Product Behavior

1966,

Proc. 9th A E C Air Cieaning Conf., Boston, Mass., S e p t . 14-16, CONF-660904 (1966)

1966,

179 AUTHORls) Thoma, R. E.

TlfLE T h e R a r e Earth H a l i d e s

PUBLICATION Progress in the Science and Technolo g y of the Rare Earths, vol. 11,

pp. 90-122,

Pergamon, New York,

1966 Complex Compounds in t h e Sodium Fluoride-Rare

Rare Earth Res. III, 561-70 (1966)

E a r t h Trifluoride S y s t e m s

THESIS Weaver, Clayton F.

Icinetics of Formation of Xenon F l u o r i d e s

T h e s i s submitted in p a r t i a l fulfillment

of t h e requirements for t h e P h . D. degree, University of California, Berkeley, 1966

PATENTS Compere, E. L., a n d E. G. Rohlmann Keilholtz, G. W., a n d

C. C. Wehster Thoma, R. E., M, K. Bennett, and J. W. U1lniann

Method of Removing Hydrogen from Liquid

U. S. P a t . 3,243,280, Mar. 29, 1966

Alkali Metals Method for A n a l y z i n g I n e r t G a s for

U. S. P a t . 3,262,756, July 26, 1966

P r e s e n c e of Oxygeri or Water Vapor Method for P r o c e s s i n g Aluminum-Containing N u c l e a r F u e l s

U. S. P a t . 3,273,993, Sept. 20, 1966

AUTHOR( s) Ackley, R. D., R. E. Adarns, a n d W. E.

tin

ntific

P L A C E PRESENTED

TITLE Removal of Radioactive Methyl Iodide from

9 t h A E C Air Cleaning Conference, Boston, Mass., Sept. 13-16,

Steam-Air Systems

1966

Browning, Jr. Adams, W. E., J. S . Gill, W. D. Yuille, W. E.

Perforiiiance of F i l t e r Systems Under Ac-

9th AEC Air Cleaning Conference, Boston, Mass., Sept. 13-16,

c i d e n t Conditions

1966

Browning, Jr., L. F. P a r s l y , and C. E. Guthrie Apple, R. F., J. M. D a l e ,

F. L. Whiting, A. S.

Determination of Oxide in I-Iighly Radioactive F u s e d Fluoride Salts

A n a l y t i c a l Chemical Society, Phoenix, Ariz., Jan. 16-21,

1966

Meyer, and C. F. B a e s , Jr. Bennett, R. L., R. E.

C h a r a c t e i i z u t i o n of V o l a t i l e Iodine Foriiis

9th AEC Air C l e a n i n g Conference, Boston, Mass., Sept. 13-16,

Adsms, and W. E. Browning,

1966

Jr. Bennett, H. i.,R. E. Adams, and W. E. Browning, Jr.

C h a r a c t e r i z a t i o n of V o l a t i l e Forms of Radioiodine Under High Hiimidity

American Chemical Society, N e w Y o i k , Sept. 11-16,

1966

Conditions Bien. P. B.

T h e Corresponding S t a t e s of Aqueous S a l t Solutions

Blankenship, F. F.

American Chemical Society, New York, Sept. 11-16,

Chemical S e p a r a t i o n s i n Molten F l u o r i d e s

2nd Intel-n. l'horium F u e l Cycle Symposium, Gatlinburg, Tenn., May 3-6,

Blood, C. M., a n d

L. G. Overholser

Compatibility of Pyrolytic-Carbon Coated F u e l P a r t i c l e s with Water Vapor

P a r k i n s o n , Jr.

Kadiation-Induced Codimerization of Ether-Unsaturate Mixtures

1966

Libby-Gockcroft Graphite Chem. Meeting, Haizvell, England, Apr. 25-27,

Bopp, C. D., and iV. VI.

1966

6 t h Annual Contractors Meeting, P r o c e s s Radiation Development Program, Washington, D. C., Sept. 26-27,

Brunton, G. D.

'The C r y s t d l Structure of LiUh'5

1966

American Crystallographic Assoc., Austin, Tex., Feb. 28-Mar.

Cantor, S.

P r e d i c t i n g D e n s i t y , S p e c i f i c H e a t and Thermal Conductivity of F l u o r i d e Melts Constant Volume H e a t C a p a c i t i e s of Molten S a l t s

2 , 1966

American Chemical Society, New Y o r k , Sept. 11-16,

1966

American Chemical Society, SU'

Regional Meeting, Albuquerquc,

N. Mex., Nov. 30.-Dec. 2, 1966

180

181 TITLE

AUTHOR( s) Carroll, I?. M., and

P L A C E PRESENTED

I n - P i l e Prvperties of R e a c t o r F u e l s by

0.Sisiiiari

Oscillating Techniques

Intetnatiorial Symposiurn Calif., May 3-5,

Coobs, J. H., and

Coated P a r t i c l e Fuels Development a t

Oak Ridge National Laboratory

J. G, Tvlorgan

T h e S o l u b i l i t i e s of Hydrogen F l u o r i d e and

Druteriurn F l u o r i d e in Molten F l u o r i d e s

J. â&#x201A;ŹI. Shaffer Gritiies.

W. R.

Capsule

1966

1 1 t h AEC C o a t e d - P a r t i c l e Working Group Meeting, Los Alamos, N. Mcx., June 1-2,

Field, P. E., and

011

Irradiation Experiments, P l e a s a n t o n ,

Molten F l u o r i d e s a s Nuclear R e a c t h t

1966

American Chemical Society, New

York, Sept. 11-16, 1966

EUCHEM Conference on Molten Salt Chemistry, Ulvik, Norway, M a y

Fuels

10-13, 1966 Molten F l u o r i d e s a s Fuels and Coolants

i n t h e Molten Salt Reactor Exptxirnent Jenks, G. N.

Predicti.on of Radiation E f f e c t s on Reactor

Keilholtz, G. W., R. E. M ~ o c M. J ~F~a, Oshorne,

T e c h n i q u e s for I r r a d i a t i n g High Tempera-

ture Materials i n a S t e e p k l u x Gradient

Zu1ligi.r

Keilholtz, 6. W., j. E. Lee, J r . # a n d R , E. Moore

K r j l h o l t a , 6.

w., I?.

P r o p e r t i e s of Magnesium, Aluminurn, arid Beryllium Osirle Compacts Irradiated to

'Fast-Neutron D o s e s G r e a t e r thaii 1021

neutrons/cm2 a t I 5 0 , 800, and 1100"~

Moore, and M. F. Osborne

York, Sept. 11-16, 1966 American Nuclear Society, Pittsburgh,

Pa., Oct. 31-Nov.

Water a n d S o l u t i o n s

R. W. Wieland, and A. F.

American Chemical Society, New

P r o p e r t i e s o f t.he Refractory Metal Carbides of Titanium, Zirconium, Tantalum, Niobium, a n d T u n g s t e n Irradiated t o F a s t Neutron D o s e s Greater

4, 1966

Int ernwt i o n a l Syrnpos iiirri r m C a p s u l e Irradiati on Experiments, P l e a santon, Calif., May 3-5, 1956

Joint American Nuclear Society a n d American Ceramic Society Meeting,

Washington, 1). C., May 9-11, 1966 American Ceramic Society, P a c i f i c

Coast Regional Meetmp, P o r t l a n d , Ore., October 1956

than IO2 neutrons/cm2 ( G r e a t e r than 1

MeV)

Marshail, W. L.

Aqueous S o l u t i o n s a t Nigh Ternperatures

Princeton University, C h e m i s t r y Serninar, Feb, 10, 1966

and Pressiirfs

New York University, Chemistry Seminar, F e b . 11, 1966 Northwestern University, Chemistry

Seminar, Feh. 24, 1966 Marshall, W. I,.* a n d Ruth

Slusher

Thermodynnrnics of Gypsum i n Aqueous

American C h e m i c a l Society,

Sodium Chloride Solutions, 0-11 O('C

P l l t s b u r g h , Pa., Mar. 28-31,

S o l u b i l i t i e s of Calcium S u l f a t e i n Sea

American Chemical Society, SW

- *l.emperuture

S a l t Sotlitions 4 0 2 0 0 " ~

Concentration L i m i t s for Saline Water i n

I966

Regjonal Meeting, Albuquerque, N. %lex., Nov. 30-Dec.

2 , 1966

General Parker, G. W.,

R. A. Lorenz,

a n d J. 6. Wilhelrn

Chemical F a c t o r s Affecting t h e histriburion of F i s s i o n Products from UO,. File1 L

Melted Under Water During Transient Accidents

American Chemical Society, New

liork, Sept. 11-16, 1966

182 AUTHORS( 5 ) Parker, G. W.

TITLE Chemical F a c t o r s i n t h e Removal of Radioiodine by R e a c t o r F i l t e r Systems

Parker, G. W., G. E. Creeb, and A . F e r r e l i Parkinson, W. W., Jr., and 'A'. C. S e a r s

Q u i s t , A . S., and W. I>. Marshall

g e t e n t i o n of Methyl Iodide by Impregnated Carbons Under Ambient Conditions T h e E f f e c t of Radiation on t h e Olefinic Groups i n Polyhutadiene E l e c t r i c a l c o n d u c t a n c e s of Aqueous Sodium Chloride Solutions to 8OOoC and

PLACE PRESENTED American Chemical Society, New York, Sept. 11-16, 1966 9th A E C A i r Cleaning Conference, Boston, Mass., Sept. 14-16,

1966

American Chemical Society, P i t t s b u r g h , Pa., Mar. 22-31,

1966

American Chemical Society, New Y o r k , Sept. 11-16,

1966

4000 B a r s Quist, A. S.

E l e c t r i c a l Conductances of Aqueous Solut i o n s t o 800°C a n d 4000 Atmospheres

University of Nebraska, Dept. of Chemistry Seminar, Lincoln, Neb., Dec. 14, 1966

Reagan, P. E., J. G. Morgan, and 0. Sisman

Performance of Pyrolytic Carbon Coated Uranium Oxide P a r t i c l e s During Irradia-

American Nuclear Society, Denver, Colo., J u n e 20,--23, 1966

tion a t IIigh Temperatures Romberger, K. A., C. F. B a e s , a n d €1. H. Stone Rutherford, J . L., J. P. Rlakely, and L. G.

P h a s e Equilibrium S t u d i e s i n t h e U O z ZrO, System Oxidation of Unfueled and F u e l e d Graphite Spheres by Steam

Overholser Savage, 1%. C., J. M. B a k e r ,

American Chemical Society, P i t t s b u r g h , F a . , Mar. 22-31,

Libby-Cockcroft Graphite Chemistry Meeting, Hanvell, England, Apr. 25---27, 1966

An Assembly for Iiradiation of Molten

hl. J . Kelly, and E. L.

Fiuoride F u e l t o High llurnups i n t h e

Compere

Oak Ridge R e s e a r c h Reactor

I n t e r n a t i o n a l Symposiuni on C a p s u l e Irradiation Experiments, Castlewood Country Club, P l e a s a n t o n , Calif., May 3-5,

S e a r s , D. K., and J. H.

T h e C r y s t a l Structure of Beta-1 K L a F 4

1965

American Crystallographic A s s o c i a tion, Austin, T e x . , F e b . 28-Mar.

Bums Secoy, C. H.

1966

Electro-Kinetic Transport a t P h a s e Boundaries Adsorption of Water on Refractory Oxides

2, 1966

ORAU Traveling Lecture Program, University of Toledo, Mar. 9, 1966 ORAU Traveling Lecture Program, Ilendrix C o l l e g e , Conway, Ark., Apr. 1 5 , 1966

Silverman, hl. D.,

Characterization of Radioactive P a r t i c u -

J. Truitt, R. E, Adams,

l a t e Aerosols by t h e Fibrous F i l t e r

and L. F. F i a n z e n

Analyzer

Strehlow, R. A.

Lithium F l u o r i d e H e a t s of Sublimation

9 t h AEC Air Cleaning Conference, Boston, Mass., Sept. 14-16,

1966

Bendix Time-of-Flight Symposium, C i n c i n n a t i , Ohio, October 1966

Sweeton, F. H . , C. F. R a e s , and R. W. Hay 'l'homa, R . E.

T h e Solubility of F e r r o s o f e r r i c Oxide i n

American Chemical Society, SE

Aqueous S o l u t i o n s a t EIevated Tempera-

Regional Meeting, L o u i s v i l l e , Xy.,

tures

Oct. 27-29,

Corrosion Behavior of t h e MSRE i n Zeroand Low-Power T e s t s

1966

15th A E C Corrosion Symposium, Oak R i d g e , Tenn., May 23-25,

1966

183

T h o m a , R. E.

P L A C E PRESENTED

TITLE

AUTHOR( s)

Molten S a l t R e a c t o r Technology

ORAU T r a v e l i n g L.,ecture Program, University of T e x a s , Nov. 7, 1966 ORAU T r a v e l i n g L e c t u r e Program, North Texzs State College, Nov. 0, 1966 ORAU T r a v e l i n g L e c t u r e Program, T e x a s T e c h n o l o g i c a l University, Nov. 10, 1966

Thoma, R. E., R. G. R o s s , a n d C . F. Weaver

Production of Lithium F l u o r i d e C r y s t a l s with S e l e c t e d I s o t o p i c R a t i o s of Lithium

Thoma, R. E., 11. I n s l e y ,

â&#x201A;Ź I . A. Friedman, a n d

I n t e r n a t i o n a l Conference on C r y s t a l Growth, Boston, Mass., J u n e 20-24, 1966

T h e I,it~iiuin--Beryllium--Zirconium Fluoride

American Chemical Society,

E f f e c t s of Containment System S i z e on

9th AEC Air C l e a n i n g Conference,

System in Molten S a l t R e a c t o r Technology

New York, Sept. 11-16,

1966

G. M. Hebert Watson, G . M., R. R. P e r e z , and M. H. F o n t a n a Watson, 6. M.

F i s s i o n P r o d u c t Behavior Defect-Trap Theory of F i s s i o n Cfas

Re l e a s e

Boston, Mass., Sept. 13-16,

R e a c t o r Chemistry Information Exc h a n g e Meeting, General Atomic, San Djego, Calif., Nov. 8-9,

Recoil Range of Fission F r a g m e n t s i n Graphitic S y s t e m s

1966

R e a c t o r Chemistry Information Exc h a n g e Meeting, General Atomic,

San Diego, Calif., Nov. 8-9, Gas-Graphite R e a c tioris

1966

R e a c t o r Chemistry Information Exc h a n g e Meeting, General Atomic, San Diego, Calif., Nov. 8-9,

Carbon Deposition S t u d i e s

1966

R e a c t o r Chemistry Informa tion Exc h a n g e Meeting, General Atomic,

San Diego, Calif., NGV.8-9, Migration of A c t i n i d e s in Graphite and Pyrocnrbons

1966

R e a c t o r Chemistry Information Exc h a n g e Meeting, General Atomic, San Diego, Calif., Nov. 8--9, 1966

Effects of Containment S i z e on F i s s i o n Product Behavior

R e a c t o r Chemistry Information Exc h a n g e Meeting, General Atomic, San Diego, Calif., Nov. 8-9, 1966

185

ORN L-4076 UC-4 - Chemistry INTERNAL Dl S TRI B U TlOM

1. 2-4. 5. 6-7. 8-58. 59â&#x20AC;? 60. 61. 62. 63-77. 78. 79. 80. 81. 82. 83. 84. 85. 86. a7 88. 89. 90. 91. 92. 93. 94. 95. 94. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111-112. 113. =

Biology Library Centra I Research Library Laboratory Shift Supervisor ORNL Y-12 Technical Library (Document Reference Section) Laboratory Records Department Laboratory Records, ORNL R.C C. E. L a r s o n A. M. Weinberg H. G, MacPherson G. E. Boyd F. R. Bruce F. L. Culler W. H . Jordon A. H. Snell G. Young A. F. Rupp M. Bender A. L. Boch R. B. Briggs W. 6. CottreII A. P. F r a a s K. A. Kraus J. A. L a n e A. J. Miller M. W. Rosenthal D. B. Trouger G. D. Whitman S . E. Beall D. S. Billington D. E. Ferguson J. H Frye, Jr. M. T. Kelley E. H. Taylor E. S. Bettis M. A. Bredig L. T. Corbin J. E. Cunningham J. H. Crawford P. N. Haubenreich P. R. Kasten M. A. Kastenbaum E. M. King R. N. Lyon R. B. Parker M. J. Skinner

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J. C. White G. C. Williams W. R. Grimes E. G. Bohlmann H. F. McDuffie G. M. Watson F. F. Blankenship C. H. Secoy R. D. Ackley R. E. Adams A . L. Bacarella C. F. Baes J. E. Baker J. M. Baker C. E. Bamberger C. J. Barton C. D. Bauinann R. L. Bennett P. 8. Bien C. M. Blood C. D. Bopp J. Braunstein W. E. Browning, Jr. G. D. Brunton H. Buchholz S . Cantor R . M. Carroll Zell Combs E. L. Compere G. E. Creek D. R. Cuneo R. J. Davis F. A. Doss J. L. English R. B. Evans, Ill C. L. Fairchild M. H. Fontana S. H. Fried H. A . Friedman E. L. Fuller, Jr. H. S. Gadiyar J. S. G i l l L. 0. Gilpatrick J. C. Griess, Jr. G. M. Hebert D. N. Hess

186

160. M. F. Holmes 161. G. H. Jenks 162. G. W. Keilholtz 163. M. J. Kelly 164. R. M. Keyser 165. S. S. Kirslis 166. R. A. Lorenz 167. A . P. Malinauskas 168. W. k. Marshall, Jr. 169. \rY. J. Martin 170. T. H. Mauney 171. R. E. Mesmer 172. C. E. Miller, Jr. 173. R. E. Moore 174. J. G. Morgan 175. B. M. Moulton 176. M. T. Morgan 177. J. J. Myron 178. P. D. Neumann 179. M. F. Osborne 180. L. G. Overholser 181. G. W. Parker 182. W. W. Parkinson, Jr. 183. A. S . Quist 184. P. E. Reagan 185. J. D. Redrnan 186, S. A. Reed 187. 13. M. Richardson 188. B. F. Roberts 189. ti. E. Robertson 190. K. A. Romberger 191. 14. C . Savage 192. J. E. Savolainen 193. D. R. Sears 194. J. H. Shnffer 195. R. P. Shields 196. A. J. Shor 197. M. D. Silverman

4 J

198. 199. 200. 201. 202. 203. 204. 205. 206. 207. 208. 209. 210. 211. 212. 213. 214. 215. 216. 217. 218. 219. 220. 221. 222. 223. 224. 225. 226. 227. 228. 229. 230. 231. 232. 233. 234,

0. Sisman Ruth Slusher F3. A . Soldano 1.1. H. Stone R. A. Strehlow

B. J. Sfurm F. 14. Sweeton R . E. Thoina, Jr.

J. W. G. C.

Truitt T. Ward C. Warlick

F. Weaver J . F. Wincsette L. B. Yeatts

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D. F. Bunch, Health Physics Branch, AEC, Washington Paul E. Field, Dpt, of Chernistty, Virginia Polytechnic Institute Research and Development Div., AEC, OW0 Reactor Div., AEC, ORQ Asst. Generol Manager for Research and Development, AEC, Washington Division o f Research, AEC, Washington Di v i s ion of I sotopes Development, Washington Asst. General Manager for Reactors, AEC, Washington

157

; i;

243, 244.

245.

246. 247.

248-510.

Division of Reactor Development and Technology, AEC, Washington Nuclear Propulsion Office, AEC, washington J. A. Swartout, 270 Park Ave., New York, N. Y . Milton Shaw, AEC, Washington W. W. Grigorieff, Assistant to the Executive Director, Oak Ridge Associated Idni vers i t i e s Given distribution o s shown in TID-4500 under Chemistry category (25 copies - CFSTI) Space