ORNL-3913 by Jon Morrow

ORNC-39 13

UC-4 - Chemistry

TID-4500 (47th

C o n t r a c t No. W-7405-eng-26

REACTOR CHEMISTRY DIVISION ANNUAL PROGRESS REPORT For Period

Ending December 31, 1965

Director

W. R .

Grimes

A s soc j ate Directors

E. G. Bohlmann H. F. McDuffie 6.M. Watson Senior Scientific Advisors

F. F. Blankenship C. H. Secoy

MARCH 1 9 6 6

OAK RIDGE N A T I O N A L LABORATORY Oak Ridge, Tennessee operated by UNION CARBIDE CORPORATION for the U. 5. ATOMIC ENERGY COMMlSSION

e$.)

Contents PART I . MOLTEN-SALT REACTORS 1. Phase Equilibrium and Crystallographic Studies LIQUID-LIQUID IMMISCIBILITY i N T H E SYSTEM L i F - B e F Z - Z r F 4 1-1. A. Friedman and H. E. Thoma .......... .................................................................................................................... Composition-ten;pera(ure limits of liquid-liquid immiscibility in t h e s y s t e m I,iE'-UeF ,-ZrF,

h a v e been partially

e s t a b l i s h e d by a p p l i c a t i o n of high-temperature centrifiigation.

SODIUM FLUORIDE-SCANDIUM FLUORIDE PHASE E Q U l L l B R l A E. H. Karraker and R. E. Thorna .................. ....................................................................................................

Results of a completed i n v e s t i g a t i o n o f t h e high-temperature r e a c t i o n s of N a F and ScF:, show t h a t the s y s t e m

is c h a r a c t e r i z e d by two e u t e c t i c a n d two p e r i t e c t i c r e a c t i o n s which occur i n a s s o c i a t i o n with the i n t e r m e d i a t e

p h a s e s 3 N a F - S c F . and NaF-ScF3. .i

CQMPOSITIONAL V A R l A B I L l T Y IN SODIUM F L U O R I D E - L A N T H A N I D E T R l F L U O R I D E COMPLEX COMPOUNDS R. E. Thonia, H. I n s l e y , and C. M. Hebert ......................................................... ............................................

Monotonic e x p a n s i o n of t h e c o m p o s i t i o n limits of the complex NaF-L.nF3 c r y s t a l l i n e p h a s e s h a s b e e n a s c r i b e d

t o a r e d u c t i o n in t h e p o l a r i z a b i l i t y of t h e l a n t h a n i d e i o n s with i n c r e a s i n g a t o m i c number a c c o m p a n i e d by a corr e s p o n d i n g i n c r e a s e i n f r e e s p a c e within the c r y s t a l l a t t i c e s .

PHASE EQUlLlBRlUM STUDIES I N T H E U 0 2 - Z r Q 2 SYSTEM K. A. RombeIger, H. 1%. Stone, and C. E'. Baes, Jr. .......................................

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

T h e UO 2 -ZrO 2 p h a s e diagram h a s b e e n r e v i s e d in a c c o r d with t h e m e a s u r e d low solubilities o f ZrO 2 in c u b i c IJO, a n d of UO, in t e t r a g o n a l ZrOz a n d monoclinic ZrOZ. These solubi-lities are, r e s p e c t i v e l y , 0.4, 1, a n d 0.15

m o l e 7~ a t tjle e u t e c t i c temperature of IIIO"C.

THE CRYSTAL STRUCTURE OF L i U F 5 G . D . B r u n t o n ..............................................................................................................................................................

An x-ray s t r u c t u r e a n a l y s i s h a s a s c e r t a i n e d t h e formula of t h i s compound, previously d e s j g n a t e d 7LiF-6UF4.

In it a r e found U F 8 polyhedra which a r e q u i t e s i m i l a r t o t h o s e i n c r y s t a l l i n e UF,. TWE C R Y S T A L S T R U C T U R E O F L i 3 A f F 6 ................................................................ J. 1-1. Burns and A. C . T e n n i s s e n ..................................................... +. This compound c r y s t a l l i z e s with A w , ~ - o c t a h e d r a j o i n e d together by Li ~ o n s . R E F I N E M E N T QF THE C R Y S T A L S T R U C T U R E O F ( N H 4 ) p n F 5 D. K. S e a r s ................................................................... ....................................................................................... T h e p r e v i o u s l y determined s t r u c t u r e of (NH4),MnF5 w a s refined by l e a s t s q u a r e s .

H I G H - T E M P E R A T U R E X-RAY S T l l D l E S G. D. Brunton, D. K. S e a r s , and J. â&#x201A;Ź1. Burns .............................................................................................

The f u r n a c e a t t a c h m e n t for t h e x-ray diffractometer h a s b e e n u s e d t o s t u d y phase transformations in rare-earth

trifluorides, t h e 'IJO,-ZrO,

s y s t e m , a n d Li3A1F6.

...

111

C R Y S T A L L O G R A P H I C D A T A ON NEW COMPOUNDS J. H. Burns, D. R. S e a r s , and G. D. Brunton .......................................................................................................... Unit-cell

dimensions a n d s p a c e groups h a v e b e e n determined for N a 3 S c F 6 , P 1 - K L a P 4 , K b P a F 6 , L i 4 U F 8 ,

L i U 4 F 7, a n d NaBiF,.

T H E C R Y S T A L S T R U C T U R E OF N a , Z r 6 F 3 1 J. H. Burns, R. D. E l l i s o n , and H. A. L e v y ....................................................

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

Six formula weights of N a F and s i x of Z r F , comprise a structure which h a s fluorine-bridged zirconium octahedra c o n t a i n i n g a s e v e n t h fluorine atom within; a s e v e n t h sodium atom is a l s o p r e s e n t i n t h e s t r u c t u r e a n d h a s 12 fluorine neighbors.

C h e m i c a l S t u d i e s of M o l t e n

Salts

O X l D E CHEMISTRY O F L i F - B e F 2 - 7 r F 4 M E L TS C. F. B a e s , Jr., and B. F. Hitch ..............................................................................................................................

Measurements of t h e s o l u b i l i t y of Z r 0 2 i n s i m u l a t e d MSRE f u e l s a l t a n d f l u s h s a l t mixtures a r e b e i n g continued by m e a n s of a n improved t e c h n i q u e of oxide a n a l y s i s .

THERMODYNAMICS OF M O L T E N L i F - B e F 2 SOLUTIONS C. F. B a e s , Jr. ...........................................................................................................................................................

E n t h a l p i e s a n d free e n e r g i e s of formations, e l e c t r o d e p o t e n t i a l s , a n d a c t i v i t y c o e f f i c i e n t s a r e e s t i m a t e d for various s o l u t e s in 2 L i F - B e F . from e x i s t i n g c h e m i c a l and thermochemical data. 2

V A P O R PRESSURES O F F L U O R I D E M E L T S S. Cantor, D. S . Hsu, a n d W. T. Ward ......................................................................................................................

Kodebush-Dixon a n d boiling-point t e c h n i q u e s were u s e d t o m e a s u r e vapor p r e s s u r e s of t h e LiF-BeF2 s y s t e m ,

t h e MSRE f u e l solvent, a n d BeF2. A transpiration a p p a r a t u s w a s c o n s t r u c t e d a n d t e s t e d with pure LiF.

V I SCO 51 71ES Q F MQ L T E N F L U O R I D E S S . C a n t o r and W. T. Ward ............................................................................................................................................ S t u d i e s o n t h e LiF-BeF

s y s t e m were extended. T h e compound N a B F 4 w a s found t o b e fluid.

E S T I M A T i N G DENSITIES O F MOL T E N F L U O R I D E MIXTURES

S . C a n t o r ........................................................................................................................................................................

Examination of newer d a t a of molar volumes r e s u l t e d i n r e v i s e d v a l u e s for u s e i n e s t i m a t i n g d e n s i t i e s of molten fluorides.

ESTlMATiNG S P E C l F l C H E A T S AND T H E R M A L C O N D U C T I V I T I E S O F FUSED F L U O R I D E S % C a n t o r ....................................................................................................................................................................... By modifying t h e Dulong-Petit rule t o e q u a l 8 c a l (OK)--' (grani-atom)-', mental d a t a w a s obtained.

r e a s o n a b l e agreement with experi-

A s e m i t h e o r e t i c a l method u s e d t o e s t i m a t e thermal c o n d u c t i v i t i e s a g r e e d with experi-

m e n t a l r e s u l t s ; t h e method d e p e n d s on e s t i m a t i n g s o n i c v e l o c i t y , which i t s e l f c a n be c a l c u l a t e d from thermodynamic parameters.

S O L U B I L I T Y O F DF AND H F I N L i F - B e F 2 ( 6 6 - 3 4 M O L E %) P. E. F i e l d and J. H. Shaffer ...........

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

S o l u b i l i t i e s of D F a n d H F were determined for t h e temperature i n t e r v a l 500-7OO0C

t o provide a b a s i s for

e s t i m a t i n g t h e solubility of tritium fluoride i n t h e b l a n k e t of a thermonuclear b r e e d e r reactor.

C h e m i c a l Separation and Irradiation B e h a v i o r

I N - P I L E MOL T E N - S A L T I R R A D I A T l O N ASSEMBLY H. C. Savage, M. J. Kelly, E. L. Compere, J. M. Raker, a n d E. G. Bohlmann ..................................................

An in-pile molten-salt irradiation experiment is b e i n g c o n s t r u c t e d for operation i n beam h o l e HN-1 of the ORR.

E V A P O R A T I V E - DlSTlL L A T I O N STUDIES ON M O L T E N - S AL T F U E L COMPONENTS M. J. Kelly ................................................................................................................................................................... 35 Mass-rate v a r i a t i o n s w i t h temperature for d i s t i l l a t i o n of 7 L i F and MSRE f u e l s o l v e n t a n d t h e vofatility of N d F , r e l a t i v e t o t h a t of MSRE f u e l s o l v e n t h a v e b e e n determined experimentally. E F F E C T f V E A C T l V I T Y C O E F F I C I E N T S B Y E V A P O R A T I V E D I S T I L L A T I O N O F MOL'TEN S A L T S M. J. Kelly .................................................................................................................................................................... Activity c o e f f i c i e n t s of B e F 2 a n d Z r F ,

h a v e b e e n o b t a i n e d from d a t a on vacuum d i s t i l l a t i o n of t h e s e com-

pounds from molten L.iF s o l v e n t .

R E M O V A L OF i O D I D E FROM L i F - B e F 2 M E L T S B. F . F r e a s i e r , C. 17. B a e s , Ji.. a n d H. H. Stone .

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

Iodide w a s r e a d i l y removed from molten L i F - B e F 2 mixtures by NF-H,

v a l u a b l e means of removing t h e p r e c u r s o r of

s p a r g i n g ; t h i s p r o c e s s s h o u l d prove a

3 5 X e (13sI) from molten-fluoride r e a c t o r fuels.

R E M O V A L O F R A R E E A R T H S FROM M O L T E N F L U O R I D E S BY E X T R A C T I O N l N T O M O L T E N M E T A L S

J. H. Shaffer, F. A. D o s s , W. I(. K. Fitinell, W. P. T e i c h e r t , a n d W. R. Grimes ...............................................

Rare-earth fluorides h a v e b e e n removed from s o l u t i o n i n a fluoride mixture which s i m u l a t e s t h e barren fuel

s o l v e n t for a molten-salt b r e e d e r r e a c t o r by reduction a n d e x t r a c t i o n into molten b j s m u t h .

R E M O V A L O F P R O T A C T I N I U M FROM M O L T E N F L U O R I D E S B Y O X I D E P R E C l P l T A T l O N J. II. Shaffer, F. A. D o s s , W. K. K. F i n n e l l , W. .?I T e i c h e r t , a n d W. R. Grimes ...........................................

P r e v i o u s s t u d i e s were e x t e n d e d to d e m o n s t r a t e thal protactinium c o u l d b e p r e c i p i t a t e d as i t s oxide by t h e

a d d i t i o n of ZrO, t o a fluoride s o l v e n t known to h a v e Z r 0 2 a s a s t a b l e oxide p h a s e .

R E M O V A L O F P R O T A C T I N I U M FROM M O L T E N F L U O R I D E S B Y R E D U C T j O N PROCESSES J. 13. Shaffer, F. A. D o s s , W. I(. R. F i n n e l l , W. P. T e i c h e r t , and W. R. Grimes ............................................. 42 In t h e reference-design MSBR, protactinium c a n be removed from s o l u t i o n i n the proposed fluoride b l a n k e t mixture by reduction with thorium or with a l l o y s o f thorium i n l e a d or bismuth. XOL&IBfLfTY O F THORIUM BN M O L T E N L E A D J. H. Siaffer, F. A. D o s s , W. K. R. F i n n e l l , a n d W, P. T e i c h e r t ..........................................

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

The s o l u b i l i t y of thorium i n l e a d over t h e temperature i n t e r v a l 400--6OO0C w a s determined in order l o support

s t u d i e s of t h e e x t r a c t i o n o f protactinium from molten fluorides.

P R O T A C T l N l 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 7 L A B O R A T O R Y C. J. Barton .................................................................................................................................................................. 44 S e v e n g l o v e h o x e s h a v e b e e n i n t e r c o n n e c t e d arid equipped for s t u d i e s of protactinium recovery from moltenfluoride breeder-blanket mixtures.

SEGREGATION ION F R E E Z f N G LI'CI-KCI E U T E C T l C M E L T S CONTAfNfNG S O L U B L E SOLUTES

Ii. A. Friedman a n d I?. F. B l a n k e n s h i p ....................................................................................................................

T h e f e a s i b i l i t y of purifying s a l t melts by f r e e z i n g with rapid stirring t o f a c i l i t a t e d i f f u s i o n of r e j e c t e d s o l u t e

from the f r e e z i n g front w a s explored.

4. Direct Support

for

MSRE

P R E P A R A T l O N AND LOADlNG O F MSRE F L U O R I D E S J . 11. Shaffer, W. K. R. F i n n e l l , F. A. D o s s , a n d W. P. T e i c h e r t ........................................................................

T h e production of all the component fluoride mixtures for t h e MSRE f u e l w a s completed; t h e s e mixtures were

a d d e d to t h e MSRE a s required during t h e p r e c r i t i c a l and c r i t i c a l t e s t i n g p h a s e s of MSKE operation.

CWEMlCAL BEWAVIOR O F FLUORIDES DURING MSRE O P E R A T l O N K. E. Thoma .................................................................................................................................................................. 48 R e s u l t s of c h e m i c a l l.ests with MSRE f u e l a n d c o o l a n t s a l t s , o b t a i n e d during t h e p r e c r i t i c a l t e s t , the z e r o power t e s t , a n d t h e i n i t i a l period of t h e full-power t e s t , i n d i c a t e d that t h e r e a c t o r s a l t s a r e of e x c e l l e n t purity and that n o a p p r e c i a b l e c o r r o s i o n of t h e interior of t h e r e a c t o r has occurred.

MEASUREMENT O F DENSITIES O F M O L T E N SALTS B. J. Sturm a n d R. E. Thoma .................................................................................................................................... 50 D e n s i t y of t h e MSRE f u e l s a l t w a s determined with molten mixtures u s i n g a n e l e c t r i c a l probe t o m e a s u r e volume of the s a l t . T h e fuel-salt d e n s i t y (in g/cm3) is d e s c r i b e d by t h e e x p r e s s i o n d - 2.848 - 7.693 x l o r 4 t (OC).

PART II. AQUEOUS REACTORS

5. Corrosion

and C h e m i c a l Behavior in R e a c t o r E n v i r o n m e n t s

MECHA NlSM OF ANODlC F I L M GROWTH ON ZIRCONIUM AT E L E V A T E D TEMPERATLlRES A. I,.

B a c a r e l l a and A. L. Sutton ..............................................................................................................................

C o n s i d e r a t i o n s of experimental d a t a for zirconium oxidation a n d of theory provided e v i d e n c e t h a t t h e pre-

e x p o n e n t i a l term in t h e anodic-film-growth e q u a t i o n c a n b e interpreted i n terms of p a r a m e t e r s of fundamental s i g nificance.

MECHANISM OF RADIATION CORROSION O F ZlRCONlUM AND Z I R C A L O Y - 2 R. J. D a v i s a n d G. I-I. J e n k s ......................................................................................................................................

T h e previously reported radiation e f f e c t on t h e postirradiation corrosion w a s confirmed, a n d exploratory work toward n e w methods of e v a l u a t i n g film protective properties is i n progress.

E F F E C T S O F REACTOR O P E R A T I O N ON H F l R C O O L A N T G. H. J e n k s ..................................................................................................................................................................

F i n a l e v a l u a t i o n s were c o m p l e t e d of t h e probable c o n c e n t r a t i o n s of e x c e s s oxidant n e e d e d t o s t a b i l i z e HNO

i n t h e H F I R coolant-moderator a n d of t h e e x p e c t e d s t e a d y - s t a t e concentration of t h e decomposition products of water.

NASA TUNGSTEN 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 , H. C. Savage, a n d E. G. Bohlmann ....................................................................................................

D e s i g n s , equipment, a n d procedures a r e b e i n g d e v e l o p e d for e x p e r i m e n t s t o t e s t t h e e f f e c t s of irradiation on l o s s of cadmium from CdSO, solution under c o n d i t i o n s of i n t e r e s t in t h e NASA T u n g s t e n Water-Moderated Reactor.

CORROSION SUPPORT F O R VA RlOUS PROJECTS

J. C. G r i e s s , J. L. E n g l i s h , L. I.. F a i r c h i l d , a n d P. D. Neumann ......................................................................

Corrosion s t u d i e s were c o n d u c t e d on m a t e r i a l s t o b e u s e d i n t h e High F l u x Isotope, Advanced T e s t , a n d

Argonne Advanced R e s e a r c h reactors; s o m e s t u d i e s of H a s t e l l o y N a n d n i c k e l for u s e i n g a s - p h a s e fluidized-bed fuel-element p r o c e s s equipment were a l s o c a r r i e d out.

5 . Chemistry of

High-Temperature Aqueous Solutions

E L E C T R I C A L CONDUCTANCE MEASUREMENTS O F AQUEOUS SODIUM C H L O R I D E SOLUTIONS T O 80Q째C A N D 4000 BARS A. S. Q u i s t , W. J e n n i n g s , Jr., a n d W. L. Marshall .................................................................................................

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 a q u e o u s sodiuni c h l o r i d e s o l u t i o n s from 0.001 t o 0.1 rn were measured a t tem-

p e r a t u r e s from 100 t o 800OC; sodium c h l o r i d e s o l u t i o n s s t i l l b e h a v e d a s moderately s t r o n g e l e c t r o l y t e s a t high temperatures and densities.

AQUEOUS S O L U B I L I T Y O F M A G N E T I T E A T E L E V A T E D T E M P E R A T U R E S F. N. Sweeton, R. W. R a y , a n d C. F. B a e s , Jr ....................................................................................................... The s o l u b i l i t y of Fe 0 is b e i n g s t u d i e d a s a function of pH a t temperatures b e t w e e n 1 5 0 a n d 26OoC. 3

vii

SOLUBlLlTlES O F C A L C I U M H Y D R O X l D E A N D S A T U R A T I O N B E H A V I O R OF CALCIUM H Y D R O X I D E - C A LClUM C A R B O N A T E M I X T U R E S IN AQUEOUS SODIUM N I T R A T E SOLUTIONS FROM 0.5 TO 350째C L. B. Y e a t t s , Jr., and W. L. Marshall ............................................................................ ................................... The solubilities

of calcium hydroxide and of calcium hydroxide-calcium

carboriate mixtures i n water a n d

a q u e o u s sodium nitrate s o l u t i o n s were determined a n d u s e d both to test further t h e a p p l i c a b i l i t y of a n extended D e b y e - H k k e l equation a n d t o obtain thermodynamic functions.

Interaction of Water with Particulate

Solids

SURFACE CHEMISTRY O F T H O R l A

c. x-'I.

Secoy

Heotr o f

lmmersion and Adsorption H. F. Holmes, E. L. F u l l e r , Jr., and J. E. Stuckey _ . _ . _ _ .........................................

N e t differential h e a t s of adsorption for s e v e r a l high- a n d low-surface-area thoria s a m p l e s h a v e b e e n c a l c u l a t e d from calorimetrically determined h e a t s of immersion.

Adsorption ond Desorption E. L. Fuller, Jr., a n d H. F. Holmes ..........................................................................................................................

Water Vapor

Careful det,ermiriatinn of adsorption a n d desorption isotherms for water vapor on thoria h a s r e v e a l e d t h e complex (letoils of both t h e chemisorption a n d p h y s i c a l adsorption p r o c e s s e s . Irifrored S p e c f r o o f Ads

C . S o Shoup, Jr. .......

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

T h e infrared s p e c t r a of a thin thorium oxide d i s k a s functions of pretreatment c o n d i t i o n s s u b s t a n t i a t e t h e complex nature of t h e c h e m i c a l water-adsorption p r o c e s s ,

E I e c t r o k i n e t i c Phenomeno at t h e Thorium Oxide-Aqueous Solution I n t e r f a c e C. S. Shoup, Jr., and H. F. Holmes .........................................................................................................................

An e l e c t r i c a l s t u d y of t h e i n t e r f a c e b e t w e e n thoria a n d a q u e o u s s o l u t i o n s of s e v e r a l e l e c t r o l y t e s h a s d i s c l o s e d s u r f a c e conductarices two or t h r e e orders of magnitude greater than t h o s e p r e d i c t e d by c l a s s i c a l theory.

G A S E V O L U T I O N FROM S O L - G E L URANIUM-THORIUM O X I D E F U E L S

I). N. H e s s a n d B. A. Soldano ...................................................................................................................................

The %as-adsorption c a p a c i t y of thorium sol-gel is shown to be reduced by e x p o s u r e to b e a r d mixtures of CO

and H,O.

PART 111. GAS-COOLED REACTORS 8. Diffusion Processes ANSPORT P R O P E R T I E S O F GASES Thermal

Transpirotion. Rotational Reloxation Numbers for N i t r o g e n and Carbon Dioxide

A. P. Malinauskas ........................................................................................................................................................

T h e a n a l y s i s of thermal transpiration d a t a in a c c o r d a n c e with the dusty-gas model a p p e a r s t o provide a s i m p l e method f o r the i n v e s t i g a t i o n of i n e l a s t i c c o l l i s i o n s . Coseous Q i f f u s i m in

Noble

Gas S y s t e m s

A. P. Malinauskas ......................................................................

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

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

Preliminary a n a l y s i s of diffusion d a t a of t h e s y s t e m s He-Kr, Ar-Kr, a n d Xe-Kr reaffirms t h e f e a s i b i i i t y of employing v i s c o s i t y measurements t o d e r i v e diffusion c o e f f i c i e n t s a t high temperatures. Guseous

Diffusion i n

Porous

Mediu

A. P. Malinauskas, E. A. Mason, and R. B. E v a n s III ..........................................................................................

T h e additivity of diffusive a n d v i s c o u s f l u x e s h a s b e e n found l o b e t h e o r e t i c a l l y justified; a s a r e s u l t , the

previous treatment of g a s transport in t h e p r e s e n c e of a p r e s s u r e gradient h a s b e e n improved.

viii

S O L I D - S T A T E TRANSPORT PROCESSES I N G R A P H I T I C SYSTEMS Recoil Phenomena R. B. E v a n s 111, J. L. Rutherford, a n d R. B. P e r e z ..............................................................................................

T h e r e c o i l range for light f i s s i o n fragments in G e n e r a l E l e c t r i c pyrolytic carbon is greater t h a n t h e range for t h e h e a v y f r a g m e n t s ( l 3 / l a n d 1 1 p ) , a n d t h e s t r a g g l i n g factor t o r a n g e v a l u e ,

a/R,is 0.126.

Actinide Diffusion R. B. E v a n s 111, J. L. Rutherford, and F. L. C a r l s e n , J r .....................................................................................

A c t i n i d e diffusion a t l o w c o n c e n t r a t i o n s i n G e n e r a l E l e c t r i c pyrocarbon w a s found not t o b e concentrationd e p e n d e n t a s i n experiments with High Temperature Materials pyrocatbon, but preliminary c o n s t a n t - p o t e n t i a l d a t a i n d i c a t e high c o e f f i c i e n t s a n d low a c t i v a t i o n e n e r g i e s .

Self-Diffusion

K. B. E v a n s 111 ............................................................................................................................................................

Equipment a n d t e c h n i q u e s a r e b e i n g d e v e l o p e d t o s t u d y t h e diffusion of 14C i n pyrolytic c a r b o n s a n d various

graphites.

Reactions o f Reactor Components with O x i d i z i n g Gases L. G. Overholser

R E A C T I V I T Y O F A T 1 G R A P H I T E WITH LOW C O N C E N T R A T I O N S OF O X I D I Z I N G AND REDUCING GASES J. P. B l a k e l y ................................................................................................................................................................ Experimental s t u d i e s were made of t h e r e a c t i v i t y of ATJ

graphite with low c o n c e n t r a t i o n s of water vapor,

c a r b o n dioxide, methane, a n d carbon monoxide.

C O M P A T l B I L I T Y O F 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 i C L E S WITH WATER V A P O R ........................................................................................................................................................ ating-failure,

a n d surface-area

d a t a w e r e obtained for s e v e n b a t c h e s of pyrolytic-carbon-

c o a t e d f u e l p a r t i c l e s during and a f t e r e x p o s u r e a t 1000째C t o p a i t i a l p r e s s u r e s of water vapor of 4.5, 45, a n d 570 torrs.

C O M P A T l S l L d T Y O F META 1-5 WITH LOW C O N C E N T R A T I O N S OF C A R B O N MONOXIDE J. E. B a k e r .............

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

T h e e f f e c t of carbon monoxide a t 250 t o 3 0 0 ppm i n H c on molybdenum, gold-plated s t a i n l e s s s t e e l , a n d m i l d s t e e l a t 450 t o 85OoC h a s b e e n e v a l u a t e d .

10.

Irradiation Behavior of High-Temperature

Fuel M a t e r i a l

O s c a r Sisman a n d J. G. Morgan

FISSION-GAS R E L E A S E FROM P Y R O L Y T I C - C A R B O N - C O AP E D F U E L PA R T i C L E S P. E. R e a g a n , J. W. Gooch, J. G. Morgan, T. W. F u l t o n , a n d C. D. Baumann ................................................... F i s s i o n - g a s r e l e a s e r a t e s from pyrolytic-carbon-coated

UO,

f u e l p a r t i c l e s were low e v e n a t e l e v a t e d tem-

p e r a t u r e s a f t e r high burnups.

P O S T I R R A D I A T I O N E X A M l N A T l O N OF C O A T E D F U E L P A R T l C L E S P. E. R e a g a n a n d E. L. Long, Jr. ............................................................................................................................ S e v e r a l pyrolytic-carbon-coated

UO, p a r t i c l e s h a v e shown very l i t t l e radiation damage a t temperatures up t o

16OO0C a n d burnups t o 2 5 a t , 70of t h e h e a v y metal.

POSTIRRAQ!ATION TESTING O F COATED F U E L PARTICLES

M. T. Morgan, R. Id. T o w n s , a n d C. D. Baumann....................................................................................................

Metallic f i s s i o n product r e l e a s e s t u d i e s of pyrolytic-carbon-coated

fuel p a r t i c l e s s h o w p o s s i b l e e f f e c t s of

burnup, c o a t i n g d e n s i t y , a n d f u e l composition on t h e f i s s i o n product r e l e a s e r a t e s .

P O S T l R R A D l A T l O N EXAMlNA T l O N O F F U E L E D G R A P H I T E SPHERES D. K. Cuneo, J. G. Morgan, H. E. Robertson, C . D. Raumann, and E. I,. I,ong, Jr. ........................................

9.5

Postirradiation exaniinat.ion of AVR-type s p h e r e s fueled with c o a t e d p a r t i c l e s led to t h e coriclusion that, a f t e r

10"/,burnup, t h e s p h e r e s h a d retained a c c e p t a b l e s t r u c t u r a l integrity.

P O S T I R R A D l A T l O N E X A M I N A T I O N O F EGCR F U E L E L E M E N T P R O T O T Y P E CAPSULES $1. F. Osborne, E. L. Long, Jr., H. E. Robertson, and .J. G. Morgan .................................................................. 98 An EGCR prototype c a p s u l e t h a t c o n t a i n e d production-run UO p e l l e t s w a s examined after irradiation t o a burnup of 10,000 Mwd/metric ton UO,

a n d w e found no major detrimental c h a n g e s .

11. f i s s i o n - G a s Release During Fissioning of UO, R. M. Carroll, O s c a r Sisman, T. W. F u l t o n , R. E. P e r e z , a n d G. M, Watson E X P E R I M E N T A L................................................................................................................................................................

The modified in-pile a s s e m b l y h a s b e e n u s e d to study fission-gas r e l e a s e r a t e s while t h e f i s s i o n r a t e (at

c o n s t a n t temperature) or the temperature (at c o n s t a n t fissi.tm r a t e ) w a s varied s i n u s o i d a l l y in a carefully controlled way.

M A T H E M A T I C A L MODEL ................................................................................................................................................ 100 The mathematical model of a defect-trapping theory of f i s s i o n - g a s behavior h a s been refined and t e s t e d i n a preliminary way with our experimental data.

iscellaneous Studies for Solid-Fueled Reactors E Q U I L I S R I U M STUDIES IN T H E SYSTEM T h O z - U 0 2 ~ U Q j L, 0. Gilpatrick and C . W. Secoy ... ........................................................................ Altlicugh the general f e a t u r e s cf

p h a s e diagram for t h i s s y s t e m

j n

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

103

eyniliEprium with a i r frvni 700 to 1600')C

had b e e n reported previously, s e v e r a l details h a v e b e e n e i t h e r confirmed or s l i g h t l y r e v i s e d b y additional experi-

ments w i t h improved techniques.

B E H A V 1 8 R O F R E F R A C T O R Y - M E T A L C A R S l D E S U N D E R IRRADIA TlON ......................................................... 6;. W. Keilholtz, K. E. Moore, and M. F, Gsborne ..............................

104

'The e f f e c t s of fast neutrons on monocarbides of Ti,Zr, N b , T a , rind W idre being i n v e s t i g a t e d a t temperatures

Oorrr 100 to 140OoC, i n order to e v a l u a t e their potential u s e in n u c l e a r s y s t e m s r e y u j r i n g extreniely high p o w e i

densities.

EFFECTS O F FAST-NEUTRON ~ ~ R OM A O X I D E~S ~ A ~ ~ ~ ~ ....................................................... 105 6. W. Meilholtz; K, E. Moore, a n d M. F. Osburne .......................... Trradiation e f f e c t s on s i n t e r e d MgO, A 1 2 0 j , and B e 0 were i n v e s t i g a t e d over the temperature i n t e r v a l I(>&1108"(3 a n d the fast-neutron dose range of 0.2 to 5.1 x 10" neutrnns/cm2 in order to determine r e a l i s t i c conditions

f n r u s e of t h e s e oxides in nuclear s y s t e m s a n d i o e s t a b l i s h mecharlistxis of rte?itrun damage.

AhrNEAilNG OF ~

~ T HAE R M~ A L ~C O NO D U C ~T I V I T- Y C~H A NNC E S~O F ~CEWAMlCS ~ ~

B. Bopp .............................................................................................................................................................

109 The a n n e a l i n g of t h e neutron-induced thermal conductivity c h a n g e w a s m e a s u r e d i r i nine ceramic materials

a f t e r a n irradiation dose up t o 2

1019 f a s t neutrons/cm'.

13.

Chemical

Support far

S a l i n e Water P r o g r a m

THERMODYNAMICS OF GYPSUM I N AQUEOUS SODIUM C H L O R I D E SOLUTIONS W. I,. Marshall a n d Ruth S l u s h e r ................................................................................................................................

113

From a n e x t e n s i v e s t u d y of t h e p h a s e behavior of gypsum in a q u e o u s sodium c h l o r i d e a n d of t h o s e s o l u t i o n s c o s a t u r a t e d with sodium c h l o r i d e or a double s a l t , Na SO *5CaSO -3H 0, thermodynamic functions were c a l c u l a t e d 2 4 4 2

both for a s t a n d a r d s t a t e and a t high ionic strengths.

T H E OSMOTIC REWAVIOR O F S I M U L A T E D SEA-SALT SOLUTIONS A T 123OC P. B. B i e n and B. A. Soldano ...................................................................................................................................

115

Varying t h e nature of t h e multivalent i o n i c components of s e a w a t e r g a v e r i s e t o s i g n i f i c a n t c h a n g e s i n t h e o s m o t i c behavior of s a l i n e s o l u t i o n s a t e l e v a t e d temperature.

ALUMINUM- AND T I T A N I U M - A L L O Y CORROSION I N S A L I N E WATERS A T E L E V A T E D T E M P E R A T U R E S E. G. Rohlmann, J. C. G r i e s s , F. A. P o s e y , a n d J. F. Winesette ...................................................................... 117 Continuing s t u d i e s of t h e corrosion of aluminum a n d titanium a l l o y s i n s a l i n e water h a v e demonstrated t h e superiority of 5454 aluminum and s u b s t a n t i a l i n v e r s e temperatuic d e p e n d e n c e of t h e titanium pitting potential.

CHEMISTRY OF S C A L E C O N T R O L E. L. Compere a n d J. E. Savolainen ........................................................................................................................

119

C o n s i d e r a t i o n s of c h e m i c a l f a c t o r s r e l a t e d t o t h e economic control of s c a l e d e p o s i t i o n in s e a w a t e r d i s t i l l a t i o n equipment h a v e included t h e p o s s i b i l i t y of carbon dioxide addition t o prevent a l k a l i n e s c a l e formation, t h e tende n c i e s of c e r t a i n e l e m e n t s t o form ion p a i r s in s e a w a t e r , a n d t h e r a t e f a c t o r s in therinal-precipitation p r o c e s s e s for c a l c i u m sulfate.

14. E f f e c t s of

Radiation

Organic Materials

W. W. P a r k i n s o n and O s c a r S i s n a n

EFFECT

OF R A D l A T I O N O N P O L Y M E R S

W. W. P a r k i n s o n , W. K. Kirkland, a n d R. M. K e y s e r .............................................................................................. T h e t e n s i l e properties of polytetrafluoroethylene a r e r e t a i n e d t o d o s e s i n e x c e s s of 2 x

e l o n g a t i o n a t break s h o w s a maximum a t d o s a g e s n e a r 3

lo7

121

r a d s i n a vacuum;

l o 4 r a d s whether irradiated in a i r or vacuum.

R A D I A T I O N - I N D U C E D R E A C T I O N S OF HYDROCARBONS R. M. K e y s e r a n d W. W. P a r k i n s o n ............................................................................................................................

121

Gamma radiation of s a t u r a t e d s o l u t i o n s of ammonia i n n-hexane a n d i n hexene-1 produced less than t h e det e c t a b l e limit (about 0.2 molecule per 1 0 0 e v a b s o r b e d ) of amities.

ADDITION REACTIONS OF FURAN DERIVATIVES C. D. Bopp, W. D. Burch, and W. W. P a r k i n s o n ......................................................................................................

123

Solutions of dihydrofuran a n d c y c l o h e x e n e i n s a t u r a t e d furan d e r i v a t i v e s were irradiated i n a survey of r e a c t i o n s u t i l i z i n g isotopic-decay radiation, a n d i t w a s found t h a t y i e l d s of a d d u c t s or dimers and trimers approached 10 m o l e c u l e s per 100 ev.

15.

F l u o r i d e S t u d i e s for Other

ORNL

Programs

T H E CHEMISTRY O F CHROMIUM I N T H E F L U O R l D E V O L A T I L I T Y P R O C E S S B. J. Sturm and R. E. Thoma.. ...................................................................................................................................

125

F l u o r i d e s a n d oxyfluorides of chromium i n t h e oxidation s t a t e s Cr(II1) t o Cr(V1) were s y n t h e s i z e d a n d p a r t i a l l y

c h a r a c t e r i z e d ; f r e e energy of formation for s o l i d C r O 2 F 2 w a s found t o b e -189 k c a l / m o l e a t 298OK.

xii FISSION P R O D U C T S FROM HIGH-BURNUP U O g G. W. P a r k e r , W . M. Martin, G. E. Creek, R. A. Lorenz, and C. J. Barton .......................................................... Behavior of f i s s i o n products from UO,

138

previously irradiated t o 1000 Mwd/ton a n d melted i n t h e Containment

Mockup F a c i l i t y w a s similar t o t h a t observed i n similar experiments with s i m u l a t e d high-burnup fuels.

T H E CON T A INM ENT RESEARCH INS T A b L.. A T1ON G. U'. P a r k e r and W. J. Martin ...................................................................................................................................

139

T h e Containment R e s e a r c h I n s t a l l a t i o n , an e n l a r g e d a n d improved v e r s i o n of t h e Containment Mockup F a c i l i t y , is nearly complete, and component t e s t i n g is e x p e c t e d t o b e g i n e a r l y in 1966.

ANALYSIS OF P L A N S F O R SCALE-UP C. E. Miller, Jr.,

N U C L E A R S A F E T Y PROGRAM

and W. E. Browning, J r ................................................................................................................

141

Our a n a l y s i s of experiments planned i n t h e U.S. t o s t u d y t h e behavior of f i s s i o n products following a r e a c t o r

a c c i d e n t s u g e e s t s t h a t a d d i t i o n a l intermediate experiments, 1YG and 1070 of t h e size of t h e L O F T , a r e n e c e s s a r y .

18. Laboratory-Scale Supporting Studies R E P E N T l O N O F R h D l O l O D i N E AND M E T H Y L I O D i D E BY A C T I V A T E D CARSONS Vi. E. Browning, Jr., R. D. Ackley, J. E. Attrill, G. W. P a r k e r , G. E. Creek, F. V. Hensley, R. E. Adams, J. D. Dake, D. C. E v a n s , and A. F e r r e l i ................................................................................................................

142

It h a s b e e n found t h a t a c t i v a t e d carbon impregnated with i n a c t i v e 12712 or K'271 removes iodine a c t i v i t y a s CH31311 from g a s s t r e a m s under a variety of conditions.

I D E N T I T Y O F V A P O R FORMS O F R A D l O l Q D i N E W. E. Brownine, Jr., R. E. Adams, R.

I).

Ackley, J. E. Attrill, J. D. Dake, a n d D. I. F o r d ..........................

144

G a s chromatography with s i m u l t a n e o u s electron-capture a n d radiation d e t e c t i o n h a s b e e n u t i l i z e d in determining t h e identity of various iodine vapor forms encountered and in a s c e r t a i n i n g t h e purity of e l e m e n t a l iodine a n d methyl iodide s o u r c e s employed i n laboratory iodine-behavior s t u d i e s .

D E V E L O P M E N T OF METHODS F O R DlSTlNGUlSHING A N D MEASURING GAS-BORNE F O R M S O F

FISSION P R O D U C T S

W. E. Browning, Jr., R. E. Adams, X. D, Ackley, R. L. B e n n e t t , M. D. Silverman, J. Truitt, W. H. H i n d s , A. F. Roerner, Jr., B. A. Cameron, J. D. Dake, a n d D. I. F o r d ............................................................................

144

C h a r a c t e r i z a t i o n d e v i c e s s u c h a s coinposite diffusion t u b e s , fibrous-filter a n a l y z e r s , g a s chromatographs, a n d May p a c k s a r e b e i n g examined a n d modified for a p p l i c a t i o n in high-humidity experiments d e s i g n e d t o s t u d y t h e behavior of t h e v a r i o u s forms of gas-borne f i s s i o n products under reactor a c c i d e n t conditions.

R E M O V A L O F PARPlCULATE M A T E R I A L S FROM GASES U N B E R A C C I D E N T CONDlTlONS W. E. Browning, Jr., R. E. Adams, J. S. Gill, and G. L. Kochanny ....................................................................

145

Laboratory i n v e s t i g a t i o n s a r e b e i n g continued of t h e filtration efficiency of high-efficiency filter media for p a r t i c u l a t e a e r o s o l s which s i m u l a t e t h o s e e x p e c t e d t o b e generated during r e a c t o r a c c i d e n t s .

IGNITION O F C H A R C O A L ADSORBERS BY FISSION P R O D U C T D E C A Y N E A T W. E. Browning, Jr., C. E. Miller, Jr., B. F. Roberts, a n d R. P. S h i e l d s ..........................................................

146

Preliminary r e s u l t s of a s t u d y t o determine t h e e f f e c t s of iodine-decay h e a t on t h e ignition temperature of c h a r c o a l a d s o r b e r s s h o w t h a t t h e ignition temperature is not greatly a f f e c t e d by a d e c a y - h e a t load greater t h a n t h o s e e x p e c t e d a t various power reactors.

PUBLICATIONS

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

PAPERS PRESENTED AT SCIENTIFIC AND TECHNICAL

MEETINGS ....................................................

147 153

Part

Molten-Salt Reactors

Phase Equilibrium and Crystallogruphis Studies

Ll QU I D-LIQUI D IMMI SCI B1 tiTY

were b a s e d on chemical a n a l y s e s of portions of quenched s a m p l e s obtained after 1-hr periods at elevated temperature i n t h e centrifuge. In preliminary t r i a l s with PbO-E,O,, g l a s s e s , good agrcement was obtained with t h e work of Geller and Bunting.3 Isothermal tie l i n e s at 550, 650, arid 700°C for t h e immiscibility region in EiF-tSeF,ZrF4 are shown in Fig. 1..1. The possibility of stable liquid-liquid imrniscibility in t h e LiF-BeF, system was given s p e c i a l attention. ’Yhis was in part prompted by r e s u l t s on t h e chemical activity of B e F , as a function of composition in the LiF-BeF’, binary, as obtained where there was an from IIIF-H,C) e q ~ i l i b r i a , ~ iridication th;jt immiscibility might occur for 80 mole 76 B e F , at temperatures above 700°C. T e n s a m p l e s representing s i x binary coaiposrtioiis in t h e range from 80 t o 34 m d e % R e F , w e r e centrifuged and examined; n o p h a s e separation w a s found. Further, v i s u a l observations of a n 80 m o l e 74 Be??, melt w e r e made under helium in a glove box and furnace assembly by Cantor and Ward.’ Again t h e liquid was :;ingle phase, a l t h o ~ g h011 t h e i n i t i a l heating to 700°C a lower v i s c o u s layer and a thinner, easily stirred, upper layer persisted; only after heating t o 850°C did the melt become homogeneous. T h e m e l t remained homogeneous through s u b s e q u e n t temperature c y c l e s from mom temperature t o 8SO*C. ‘The conclusion w a s reached that there i s no s t a b l e iiiiniiscibility above the liquidus in t h e L i F - B e F , binary.

IN THE SYSTEM LiF-BeF,-ZrF, 11. A. Friedman

K. E. Thorna

Beryllium fluoride s y s t e m s h a v e been of i n t e r e s t of S i O , b e c a u s e they provide “weakened systems. T h e weakened model contains c a t i o n s and anions of t h e s a m e radius as t h o s e in t h e silicate system, but with half the ionic charge. In MgO-SiO,, a liquid immiscibility region is found; in the weakened model LiF-BeF, t h i s h a s not been found, alf.hough metastable g l a s s e s , mutually ins o l u b l e , are encountered a t 60 t o ‘30 mole % R e F z , where t h e melts are highly viscous. Our recent work on t h e i,iF-BeF2-ZrF, system’ reveals that s t a b l e liquid-liquid regions do e x i s t in t h i s ternary, although they do not extend s t a b l y t o the L i F - H e F , binary, S i l i c a t e and B e F g l a s s e s are structurally analogous and a r e composed of networks of bridging ions, oxide arid fluoride i o n s respectively. Other c a t i o n s , part,ic:ularly t h e low valent ones, if added t o t h e s e glasses, break t h e bridges and a r e referred t o a s modifiers; their effect on v i s c o s i t y is q u i t e prmounced. ’The p o s s i b l e role of ZtF, as a network modifier or network former h a s not previously been examined. Our liquid-liquid immiscibility s t u d i e s w e r e made with a new high4emperature centrifuge that developed a centrifugal force of 530 x g arid gave good layer separation in s e a l e d metal c a p s u l e s . R e s u l t s ‘V.

M. Goldschmidt,

“Ceochumische

3R. F. Geller a n d E. N. B u n t i n g , J . R e s . N a t l . Birr. S t d . 18, 585 (1937).

Verteilungs-

VIII, Untersuchungen uber Bau und Eigenschaftkri von Krystallen” ( G e o c h e m i c a l Distribution L a w s o f the Elements: VIII, R e s e a r c h e s on Structure a n d Properties of Crystals), Skrifter N o r s k e V i d e n s k a p s - A k s d . O s l o , I : Mat.-Noturv. K1. 1926, No. 8, pp. 7-156 (1927); Ceram. Ahstr. 6(7), 308 (1927). 2 R e a c t o r Chcm. Div. Ann. Progr. H e p t . J a n . 31, 1 9 6 5 , ORNL-3789, p. 3. gesetzt. der Elemente:

4A. L. Mathews and C. I?. Baes, O x i d e Chemistry a n d Th emlodynamic s o f M o l tea Li tliiurn Fluori de-h’eryl liizm Fluoride by E quilihrafion wj tti Guseou 8 Wafer-Hydrogen Fluoride Mixtures, ORNL,-TM-1129, p. 104 (May 7,

1965). ’5. Cantor and W. T. Ward, MSRP Semiann. Pro&. Rept. Aup. 3 1 , 1965, O R N 1 ~ 3 8 7 2(in press).

OSNL-OW3

66 - 961

ZrF,

i /'\

Fig. 1.1.

(c)

700째C

L i q u i d - L i q u i d Imniiscibility i n the System L i F - B e F 2 - Z r F q .

isotherm.

SOD1UM F LUORl DE-SCAN DI UM FLUORIDE PHASE EQUlLlBRlA K. H. Karraker6

R. E. Thoma

One of t h e most important f a c t o r s which influence t h e number and t y p e s of intermediate compounds 6 0 R I N S r e s e a r c h participant, Memphis S t a t e University, Memphis, Tenn,

(a) 55OoC isotherm; ( b ) 650째C

isotherm;

formed between pairs of highly ionic compounds s u c h as t h e a l k a l i fluorides and group I11 fluorides is t h e relative s i z e of t h e cation^.^ S i z e effects are of diminishing s i g n i f i c a n c e as bonding becomes less ionic or when unusual ligand effects, s u c h as t h o s e induced by t h e lanthanide and a c t i n i d e contractions, become of importance. In t h e c o u r s e ..................

7R. E. Thoma, lnorg. Chem. 1, 220 (1962).

C)HNI.-DWG

I500

66-962

I300

.-.

.-.u

4100

LLI

Lt.

900

‘-

700

a W

Ill

5 00

300

F i g . 1.2. C o m p a r i s o n of the S y s t e m s (a) NaF-LuF3, ( h ) NaF-ScF3, and ( c ) NaF-AIF3.

of t h e recently completed investigation of t h e sodium fluoride-lanthanide trifluoride s y s t e m s (see 8 1 Compositional Variability i n Sodium Fluoride-i,anthanide Fluoride Complex Compounds,” t h i s report), i t became evident that within t h e s e r i e s cation charge density w a s beginning to obscure t h e effect of size. It. w a s therefore of great i n t e r e s t to obtain information concerning t h e comparative p h a s e behavior among t h e following group of s y s tems, which are ranked below in order o f increasing difference of the tripositive cation to alkali cation radius ratio: NaF-LaF NaF-BiF

0.923

1.054

NaF-LuF

1.156

MaF-IflF

1.210

NaF-Scl”

1.256

KF-LaF

1.254

NaF-A1F3

2.178

‘Investigation of the s y s t e m NaF-ScF,, reported previously in preliminary form, h a s now been completed. ‘Ttie equilibrium phase diagram of the system is a:cjmpared with t h o s e of NaF-LuF, and NaF-AhF, in F i g . 1.2. Equilibrium reactions 01 NaF and ScF, bear closer resemblance to those of PdaF and AI.F, t h a n to NaF and LuF,, d e s p i t e the f a c t t h a t t h e scandium ion r a d i u s (0.78) i s

’

‘ H e a c t o r Chrm. 1965, CRNL-3789.

Div.

Arm.

Pro&.

Rep?. Jan. 31,

nearer t o L u 3 + (0.848) than to A I 3 + (0.45). Similar t.o t h e NaF-ALF, system, molten NaF-ScF’, mixt u r e s Eoriii a cryolite-like phase, 3 N a F ScF’,,, which, l i k e cryolite, i s dimorphic. C r y s t a l s of e a c h form are isomorphous with t h e i r c r y o l i t e analogs. T h e p h a s e 3NaF. ScF, undetgoes a strongly exothermal s o l i d - s t a t e inversion when cooled below 6 8 0 T and inverts to poorly crystallized and highly Single crystal:; OE t h e lowtwinned material. temperature form of 3 N a F . ScF, were obtained by growth from NaF-ScF, mixtures of 70-30 mole % composil.ion. X-ray diffrac:tion a n a l y s i s of t h e s e s i n g l e c r y s t a l s indicated t h a t they are of monoclinic symmetry (see “Crystallographic Data on N e w corn pound^,'^ this report) and are isomorphous with cryolite. A high-temperature form of cryolite is reportedg t o occur a s a face-centered cubic phase. Preliminary r e s u l t s of high-teiiiperatuw x-ray diffracf.ometric experiments with 3NaF . ScF, indicate t h a t the higl~-temperatureforms of 3NaF. ScF and 3 N a F * AI F art? isomorphous. Whereas the intermediate phase in t h e 3NaF AlF,-AlF, subsystem is of 5:3 coinposition, only a 1:l p h a s e is formed in the 3NaF..ScF,-ScF, subsystem. The compound NaF -5cF, melts incongruently to S c F , and liquid at 660°C. X-ray diffraction d a t a obtained froin siagle c r y s t a l s of NaF-ScF, revealed i t t o b e of hexagonal symmetry (see “Crystallographic D a t e on New Compounds, ’’ this report). 1

9E. C. Steward and H. P. Rooksby, Actd Crysf. 6 ,

49 (1953).

6 Table 1 . 1 . -..__

rhe

System

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

Invariant Temperaturc ( O C )

.........

800

Eutectic

885

Congruent melting

point 680

I n v e r s i o n of 3 N a F * S c F perit e c t i c

2,-3NaF . S c F 3 -A

650

Eutectic

660

Peritsrtic

Id t S c F ,

COMPOSITIONAL VAWl ABILITY IN SODIUM FLUOR1DE-LANTH ANI D E TRI F LUORl DE COMPLEX CQMP R. E. Thoma H. Insley G. M. Hebert Investigation of t h e sodium fluoride-lanthanide trifluoride s y s t e m s h a s been completed. A s a l i e n t feature of t h e N a F - L n F , binary systeliis i s t h e unusual behavioral s e q u e n c e produced by t h e cornpositional variability of t h e fluorite-like p h a s e s . T h i s behavior s h o w s t h e remarkable effect of c a t i o n size and polarizability i n lanthanide s y s t e m s . A s shown in T a b l e 1.2, t h e c u b i c p h a s e is not formed a t a l l i n t h e s y s t e m s N a F - L a F , and A. Dietzel, Z . Elektrochern. 48, 9 (1912).

"Reactor Chem. D i v . 1965, ORNL-3789, p. 13.

Ann. Progr. R e p t . Jan. 3 1 ,

...

e NaF i-a-3NaF.ScF3 e a - 3 N a F .ScF,

We b e l i e v e that t h e greater reseniblance of t h e s y s t e m NaF-ScF, t o NaF-AIF, rather than t o NaF-LuF, a r i s e s as a result of t h e lanthanide contraction, producing t h e L u 3 ' ion of extraordinarily high charge density. Quantitative relat i o n s h i p s of t h e combined effects of ion size and c h a r g e d e n s i t y h a v e been developed by Dietzel. T h e y require a c c u r a t e information of interionic d i s t a n c e s , which for t h e s e complex fluorides must await determination of t h e c r y s t a l s t r u c t u r e s . T h e composition and temperatures of invariant equilibrium points i n t h e s y s t e m NaF-ScF, a r e l i s t e d i n T a b l e 1.1.

-.......I______

Phase Reaction a t Specified Temperature

T y p e of Equilibrium

__ ......

.........

NaF-ScF

L r e f e r s to l i q u i d

Composition (mole % ScF,)

lnvoriant Equilibria i n

-+P - 3 N a F *ScF, .

P-3NaF. ScF3 t N a F ScF,

:--

--"

+ N a F .ScF,

N a F - C e F 3 , i s formed by N a F and P r F , , and i s extended t o a n increasingly broad composition range throughout t h e r e s t of t h e s y s t e m s e q u e n c e . A trend also develops toward broadening t h e composition limits and extension of t h e temperature range through which t h e c u b i c and orthorhombic p h a s e s a r e stable. T h e trends toward increasing number, compositional variability, and s t a b i l i t y of t h e N a F - L n F , c r y s t a l p h a s e s appear t o b e d i s tinct, not only with r e s p e c t t o t h e c r y s t a l chemi s t r y of t h e complex compounds, but a l s o in their modes of crystallization. No s a t i s f a c t o r y theory h a s as yet been developed t o explain t h e quantit a t i v e a s p e c t s of compositional variability of N a F - E n F 3 p h a s e s . Qualitatively, t h e trends a r e believed to i n d i c a t e an i n c r e a s e i n t h e l a t t i c e e n e r g i e s of t h e c r y s t a l l i n e p h a s e s resulting from t h e lanthanide contraction and a corresponding d e c r e a s e i n polarizability. T h e d e c r e a s e in polarizability is probably t h e most influential factor in enabling compositional variability of t h e p h a s e s to b e extended with increasing atomic number of t h e lanthanide. A s represented by t h e Lorentz-Lorenz equation, molar refraction approximates t h e volume occupied by t h e constituent i o n s in c i y s t a l l i n e p h a s e s . A measure of t h e c r y s t a l f r e e s p a c e c a n therefore b e estimated from t h e difference between molar volume, a s computed from unit-cell dimens i o n s , and t h e molar refraction. A s t h e atomic number i n c r e a s e s , s m a l l i n c r e a s e s in t h e free s p a c e fraction a r e noted for t h e lanthanide t r i fluorides and for t h e hexagonal N a F L n F , p h a s e s . A more pronounced i n c r e a s e i n free s p a c e fraction is found for t h e fluorite-like NaF-EnF, p h a s e s ,

7 T a b l e 1.2.

O p t i c a l and X - R a y D i f f r a c t i o n D a f a for N a F - L n F 3 C r y s t a l l i n e P h a s e s H e x a g o n a l NaF * LnF3

(A)

O(a,)

c o (A)

"(e,)

6.1.57

0. 006

3.822

0.008

1.486

1.500

CF:

6.131

0.006

3.776

0.004

1.49.3

1.5 14

6.123

0.004

3.743

0.002

1.494

1.516

6.100

0.002

3.711

0.002

1.493

1.515

(6.056)

(1.492)

(1.515 j

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

(3.670)

Slll

6.05 I

0.010

3.640

0.007

1.492

1.516

6.044

0.603

3.613

0.003

1.492

1.516

6.020

0.003

3.601

0.008

1.483

1.507

6.008

0.004

'3.580

0.002

1.486

1.506

5.985

0.004

3.554

0.003

1.486

1.5 10

1-10

5.991

0.001

3.528

0.002

1.486

1.510

Et.

5.959

0.002

3.514

0.002

1.482

1.504

Till

5.953

0.002

1.494

0.002

1.476

1.496

5.929

0.002

3.471

0.002

1.482

5.912

0.003

3.458

0.003

1.484

5.967

0.002

3.523

0.002

1.464

.-__

__I_.

C u b i c NoF-LnF

Phases 3

1.506

.--

5NaF " 9LnF Composition Limit ~

X-Ray D e n s i t y

K.1.

(g/c.)

X-Ray Density

!A)

(dcc) ___..___

..l_l_____l

55.5

1.522

5.710

55.0

1.506

5.670

(54.5)

(1.SOO)

(5.630)

1.486

at Composition L i m i t s

N o F - R i c h Composition Limit

1. 504

4.131

(4.620)

1.526

5.720

1.524

5.635 (S .6 55)

(1.522)

1.520

5.766 5.962 (6.133)

5.1527

6.315

5.616

6.392

1.502

5.594

6.620

5.051

1.504

5.565

6.772

1.504

5.547

1.5 04

6.939

5.490

5.205 5.296

5.52.5

7.093

1.440

5.475

.5.387

1.4513

5.514

7.203

43.5

1.427

5.460

5.466

1.494

5.493

1.415

5.440

5.611

a. 458

7.336

41.5

5.480

7.510

.3!j9.0

1.462

5.425

5.698

1.4232

5.463

7. ,580

53.5

1.495

5.605

4.702

52.5

1.486

4.8OQ

5'2.5

1.470

5.575 5.5so

4 978

50.0

1.472

5.535

45.5

1.462

5,.?05

47.0

1.454

45.0

av 1.519

C. Orthorhombic SNaS ' 9 L n F 3 Ltl

DY is0 Er

Trn

1. 50.1

Refractive Index

Letticc C o n s t a n t s ( A )

Ni.

1.509

___

..... ........_........

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

'''mean

1.514

5.547

21.74

4.804

1.510

5.525

4.784

1.506

5.514

27.63

27.57

4.775

1.501

5.493

27.47

4.7.57

1.482

1.494

1.495

5.480

27.40

4.746

I,ll

1.480

1.496

1.m

5.463

27.32

4.731

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

._......._i___...._._ I

T a b l e 1.2 (continued)

D. H e x a g o n a l and O r t h o r h o m b i c L n F 3 Ln

Symmetry

Lattice Constants (A)

R e f r a c t i v e Index -~

N , or N , .. .

N,or

N y

Density (g/cc)

Ref.

Hexagon a1

1.597

1.603

7.186

7.352

5.936

Hexagonal

1.607

1.613

7.112

7.279

6.157

Hexagonal

1.614

1.618

7.075

7.238

6.14

Hexagonal

1.621

1.628

7.030

7.200

6.506

Orthorhombic

1.577

1.608

6.669

7.059

4.405

6.643

Orthorhombic

1.572

1.600

6.622

7.019

4.396

6.793

Orthorhonibic

1.570

1.600

6.571

6.985

4.393

7.056

Orthorhombic

1.570

1.600

6.513

6.949

4.384

7.236

DY Ho

Orthorhombic

1.570

1.600

6.460

6.906

4.376

7.465

Orthorhombic

1.566

1.598

6.404

6.875

4.379

7.644

Orthorhombic

1.566

1.598

6.354

6.848

4.380

7.814

Orthorhombic

1.564

1.598

6.283

6.811

4.408

7.971

Orthorhombic

1.558

1.568

6.216

6.786

4.434

8.168

Orthorhombic

1.554

1.558

6.181

6.73 1

4.446

8.44

......_ _ . . l . . . . . . ~

~ ________I

- _ - _ _ _ ~ ______..._ _______

_ ~ _........

aE.Staritzky and L. B. Asprey, Anal. Chem. 29, 857 (1957).

bASTM X-Ray Diffraction C a r d No. 8-45.

=ASTiM X-Ray Diffraction C a r d No. 6-0325.

dA. Z a l k i n a n d D. H. Templeton, J . Am. Chem. SOC.75, 2453 (1953).

eASTM X-Kay Diffraction Card No. 12-788.

with a n even greater i n c r e a s e in t h e free s p a c e fraction for t h e equimolar c u b i c p h a s e s than for t h e cubic 5 N a F . 9 h F 3 p h a s e s a s Z i n c r e a s e s . Substitutional s o l i d solution of L n 3 ' into t h e fluorite unit cell gives r i s e to c a t i o n v a c a n c i e s but is partly compensated by filling of interstitial posit i o n s with fluoride i o n s , as described by Roy and Roy. l 2 T h e fact that t h e free s p a c e fraction occupied by t h e i o n s i n t h e cubic structure a t t h e 5 N a F * 9 L n F 3 saturation limit is even greater than a t t h e equimolar composition l e n d s additional e v i d e n c e t o t h e validity of t h e previous interstitial fluorine model for solution mechanism. We conclude that t h e coinbined effect of t h e reduction in polarizability of t h e lanthanide i o n s and t h e i n c r e a s e in free s p a c e within t h e c r y s t a l l a t t i c e i s to reduce t h e specificity of Na t and L n 3 + i o n s with regard to t h e c a t i o n s i t e s they occupy in fluorite-like, orthorhombic, and hexagonal

c r y s t a l s . 'The consequence of t h i s effect is t h e i n c r e a s e observed in compositional variability of t h e c r y s t a l p h a s e s i n t h e N a F - L n F 3 s y s t e m s with increasing atomic number of t h e lanthanide.

"D. M. Roy a n d R. Roy, J . E l e c f r o c h e m . SOC. 1 1 1 , 421 (1964).

1 3 K . A. Komberger et a l . , R e a c t o r Chem. Div. Ann. Progr. l?ept. Jan. 31, 1965, ORNl.,-3789, p. 243.

PHASE EQLJ!LlEiRlUM STUDIES IN THE UO,-ZrQ, SYSTEM K. A . Romberger H. H. Stone C , F. B a e s , Jr. In a previous report, a new p h a s e diagram w a s s u g g e s t e d for t h e UO,-ZrO, s y s t e m in which e s s e n t i a l l y no s o l i d solution formation was indic a t e d below about 1100"C.'3 T h i s conclusion, which i s in variance with previously published

400

99.5

39.0

93.5

100 90 30

M0L.F PERCENT 1.102 70 60 50 40 3 0

4.5

4"0

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

TETRAGONa!.

0.5 S.S.

0 .

3!) 40 5 0

60 70 (30 $10 100

MOLE PERCFNT Z r O ,

98.5

141. Ctihen a n d B. E. Schaner, J . N u c l . Mater. 9 , 18 (1963).

"Go M " Wolten, J. A m . Cheni. S O C . 80, 4772 (1958).

E E v a n s , J. A m . Ceram. Soc. 43, 443 (1960). 17T.R. Wright, D. E. Kizer, a n d D. L. Kellcr, S f u d i e s in the W O -%IO System, BMI-1689 (Aug. 27, 1964). "P.

"N. & Voronov, I. E. A. Voitekhova, and A. S. Damlin, Proc. U . N . Intern. C o n f . Peacefrrl U s e s A t . E n e r g y , 2nd, Genevn, 1958 6, 221 (1958).

"C.

F. B a e s ,

Jt.,

J . 1-1. Shnffrr, a n d H. F. McDuffie,

Triuis. Ani. N u c l . SOC. 6, 393 (1963).

100

ACTI'fAl'IOK A N A L Y S I S I'CR !J

U Q 2 - Z r 0 2 Phase Diagram.

pliase diagrams foi this s y s t e m , 1 4 - " was based primarily on x - r ~ y and petrographic examination of UO 2-Zr0 s o l i d s equilibrated with fluoride m e l t s at temperatures from 500 to 7O0"Ct9 and from 900 to 1 0 2 0 ~ c . ~ ~

99.5

0 " W E T " CI-i f M I CA!. , 5 N A 1 Y 51S X

Fig. 1.3.

9'3 0

Equilibrations of t h e o x i d e s w i t h fluoride melts h a v e s i n c e been completed for temperatures up t o 1150째C. T h e o x i d e s o l i d s lrom t h e s e latter equilibrations were not only examined by x-ray and petrographic techniques as before, but a l s o t h e s e and a11 o f t h e previously equilibrated s o l i d s h a v e been chemically analyzed to determine t h e U-Zr composition of t h e individual p h a s e s . ( T h e s e p a r a t.ion of t h e p h a s e s was performed u s i n g hot nitric acid, a liquid i n which UO, is readily s o l u b l e and ZrO, is virtually insoluble.) Incorporation of t h i s new informai.ion gave t h e more detailed diagram for t h e UO,-ZrO, system shown in Fig. 1.3. T h e monuclinic-tetragonal transformation of t h e Zt02-rich s o l i d s o l u t i o n s At t h i s temperature occxtted at 1111.0 f 5째C.

10 Z r O z i s s o l u b l e i n cubic UO, to about 0.40 m o l e io, while UO, i s s o l u b l e i n monoclinic ZrO, t o about 0.15 mole %, and i n tetragonal ZrO, to about 1 . 0 m o l e %. T h e riionoclinic-tetragorlal transition temperature for pure ZrO, h a s been given by Mumpton and R o y z 0 a s 1170째C. No attempt w a s made to determine t h i s inversion temperature in t h e present work. However, niicioscopic investigation of a saiiiple of pure ZrO, equilibrated a t 1190OC h a s shown that i t definitely had been tetragonal. Hence, t h e Mumpton and Roy value of 1170'C f a l l s within our liiiiits of 1110 to 1190OC. Below the transition temperature of l l l O 째 C , t h e saturating s o l i d s a r e t h e cubic U02-rich and t h e monoclinic Zr0,-rich s o l i d solutioiis. However, even a t l l l O 째 C , t h e s e s o l i d solutions are very dilute. Moreover, i t i s expected that t h e solubili t i e s will d e c r e a s e exponentially a s t h e tempera.ture is reduced. Hence, for all practical purposes, t h e equilibrium s o l i d s a t lower temperatures a r e t h e pure p h a s e materials, that is, piire UO, and pure ZrO,. T h e correlation between t h e data giver1 i n t h e present work and r e s u l t s presented previously by *Or' is . also shown in F i g . 1.3. other authors 4 - 1 For temperatures below 17OO0C, solid l i n e s h a v e been u s e d to represent t h e solubility limits as determined from log X b , o v s 1 / T p l o t s of our d a t a and a l l other pertinezt d a t a presently availa b l e in t h e l i t e r a t ~ r e . ' ~8 ,~2 0' T h e d a s h e d l i n e s a r e t h o s e from t h e recently published diagram of Cohen and Schaner.14 T h e s e l i n e s begin t o deviate from e a c h other a t about 1.600OC. A s t h e temperature i s further reduced, t h e deviations i n c r e a s e rapidly. We believe t h e differences in t h e r e s u l t s reported here and t h o s e reported previously by o t h e r s reflect t h e inability of t h e other investigators to obtain equilibrium products a t temperatures below 1600OC s o l e l y v i a s o l i d - s t a t e reactions. T h e s e temperatures are m o r e than a thousand d e g r e e s below t h e melting points of t h e pure oxides. At s u c h relatively low temperatures, solid-state r e a c t i o n s of t h e o x i d e s should b e very slow. In t h e present investigation t h e u s e of a fused fluoride p h a s e provided a path by which t h e s l o w n e s s of t h e s o l i d - s t a t e reaction could b e overcome and equilibrium could b e achieved.

THE CRYSTAL STRUCTURE OF LiUF,

* I

'OF.

A. Mumpton and R.

43, 2.34 (1960).

Roy, J . A m . Cerani. Soc.

' l W . A. L a n b e r t s o n and M. H. Mueller, J . A m . Ceram. S O C . 36, 365 (1953).

G. D, Hrunton T h e compound L i U F w a s originally described a s Li,;U6F3, ill t h e molten-salt s y s t e m LiFUF,.' T h e c r y s t a l structure w a s determined i n order t o r e s o l v e t h e stoichiometry and b e c a u s e T.,j1JF5 i s t h e uranium s a l t which would b e deposited if fuel should f r e e z e i n t h e Molten-Salt Reactor Experiment. Tetragonal L i U F c r y s t a l l i z e s i n s p a c e group 14,/0 with a = 14.884 1 0.002 A and c - 6.5467 + 0.0003 A. T h e calculated density is 6.23 g / c c with 16 formula weights per unit c e l l . Atomic parameters are l i s t e d i n T a b l e 1.3. Figure 1.4 i s a n illustration of t w o asymmetric u n i t s of l d i U F related by a center of symmetry approximately one-eighth of a unit cell. F i g u r e 1.5 i s a s t e r e o s c o p i c pair showing t h e c o n t e n t s of one unit c e l l . E a c h uranium i s surrounded by nine fluorine ions which form t h e corners of a 1 4 f a c e d polyhedron having t h e form of 3 pristii with triangular b a s e s and with a four-faced pyramid o n e a c h of t h e three prism f a c e s . E a c h lithium ion i s surrounded by s i x fluorine ions at t h e corners of a distorted octahedron. T h e structure of L i U F , c o n s i s t s of 1 6 uraniumcontaining polyhedra and 1 6 lithium-containing octahedra linked together s o that every uranium polyhedron s h a r e s a n end with i t s centrosymmetrical neighbor, s h a r e s corners with f i v e other uranium polyhedra, and s h a r e s a f a c e , an edge, and two corners, respectively, with four lithium octahedra. E a c h lithium octahedron s h a r e s e d g e s with three other lithium octahedra, and s h a r e s an e d g e , a face, and two corners, respectively, with four uranium polyhedra. T h i s linkage gives spiraling cross-connected c h a i n s parallel t o t h e c axis.

"L. A. Harris, T h e Crystal Structures of 7:6 r y p c Compounds of A l k a l i Fluorides with Uranium T e t r a f f u o r i d e , CF-58-3-15 (March 6 , 1958).

2 3 C . J. Barton et a]., J . A m . Ceram. SOC. 41, 63 (1958). 241d. A. Harris, G. D. White, and H. E. Thoma, J . P h y s . C h m . 6 3 , 1974 (1959).

"C. F. Weaver et

(1960).

a]., J . Am. Cer,m. Soc.

43, 213

11 OWL-DWG

65-12543

Fig. 1.4.

Two Centrosymmetricolly R e l a t e d Asymmetric U n i t s of LiUF,.

T a b l e 1.3.

Atomic Parameters f o r L i U F

ORM.

Fig. 1.5.

6 5 - f 25 42

One U n i t Cell of L i U F 5 (Stereographic P a i r ) .

THE CRYSTAL STRUCTURE CoF Li,AIF,

J. 1-1. Burns

- DVJG

A. C. T e n n i s s e n 2 6

A r e c e n t p h a s e diagram study o n t h e ternary s y s t e m s involving A l F , and LiF, N a F , and K F Z 7 '%esearch Participant from Lamar State College of Technology, Seaumont, Tex. 2 7 R . E. Thornd, B. J. Sturm, and E. H, Guinn, MoltenSalt S o l v e n t s for Fluoride V o l a t i l i t y Processing of A turninurn-Matri x Nuclear Fuel E l em en t s, 0RNI.4594 (August 1964).

indicated t h a t Li3A1F6, Na,A1F6, and K3A1F6 are e a c h components of t h e s e s y s t e m s ; and while t h e l a t t e r t w o were known to h a v e t h e cryolite structure, Li,A1F6 had not b e e n s t u d i e d . T h e e x i s t e n c e of sixfold and twelvefold coordination for t h e alkali-metal i o n s i n c r y o l i t e was not expected to hold for Lit, and indeed a new s t r u c t u r e t y p e was found. C r y s t a l s of Li,A1F6 were prepared by melting together under vacuum a 3:l mixture of L i F and

13 AlF,. Some of t h e compound d i s t i l l e d to a cold finger i n t h e v e s s e l , but t h e larger c r y s t a l s were obtained from t h e r e s i d u e i n t h e bottom. Powder x-ray diffraction examination showed both to b e virtually t h e same p h a s e s , with a l i t t l e e x c e s s ALF, on t h e c o l d finger. X-ray p r e c e s s i o n photographs were u s e d to e s t a b l i s h that t h e c r y s t a l s were orthorhombic with unit-cell dimensions: a 9.54, b = 8.23, c = 4.88 (50.02 A). Systematically a b s e n t reflections: h01, h 2n, and Qkl, k -+ I -- 221, indicated t h e probable space groups Pnrna a n d Pna2 which differ by t h e p r e s e n c e of a center of symmet.ry. The density, c a l c u l a t e d with four formula weights i n t h e unit c e l l , is 2.50 g/cm3. T h e d e n s i t y w a s measured to b e between 2.6 and 3.0 by flotation in heavy 1iqui ds. 1ntensit.y d a t a for determination of atomic posit i o n s w a s obtained by photographing Ilk1 zones,

with I - 0, 1, 2, 3 , and 4, tmploying t h e multiplef i l m Weissenberg technique. â&#x20AC;&#x2DC;The i n t e n s i t i e s of t h e r e f l e c t i o n s were estimated by comparison with calibrated film s t r i p s . Some 238 independent reflections were measured and their i n t e n s i t i e s reduced to s t r u c t u r e factors, Fo. T h e P a t t e r s o n vector method w a s applied t o locate t h e A1 and F atoms, and c a l c u l a t i o n of a difference Fourier map then w a s s u c c e s s f u l i n determining t h e Li positions. All atoms of t h e structure occupy fourfold general s i t e s of s p a c e group Pna2 1 . Refinement of atomic p o s i t i o n s arid individual isotropic temperature f a c t o r s w a s carried out by least s q u a r e s . T h e p t e s e n t v a l u e of t h e discrepancy factor,

Fig. 11.6, C r y s r a l Structure of Li3AIF6.

It i s expected that somewhat better agreement will b e achieved with further refinement, but t h e atomic s i t e s given in T a b l e 1.4 a t e not expected t o c h a n g e appreciably. A drawing of t h e Li,A1F6 structure i s shown i n Fig. 1.6 . T h e p r e s e n c e of A1F6 3 - i o n s i s apparent; t h e s e are joined together in s u c h a manner a s to provide octahedral coordination for e a c h of t h e L i t ions. Bond d i s t a n c e s are within t h e normal range, but further refinement of t h e structure will b e awaited before reporting them.

Table 1.4.

-.................... Atom

Atomic Purameters for L i 3 A I F 6

..........

Li (1)

0.357

0.372

0.525

ILi (2)

0.131

0.107

0.499

Li(3)

0.527

0.017

0.349 0.128

0.246

F(1)

0.222

0.086

0.145

F (2)

0.026

0.249

0.299

F(3)

0.238

0.212

0.694

0.022 0.214

0.390

0.856

0.391

0.185

0.020

0.091

0.837

F (4)

F (5)

F (6)

. .

...........

% h o s e n arbitrarily to f i x the origin on 2 1'

'STb REFINEMENT OF THE STRUCTURE OF (NH4),MnF5 D. K. S e a r s T h e manganic ion i s u n s t a b l e with respect to disproportionation, and a s a consequence, simple s a l t s of trivalent manganese a r c rare. Neverthel e s s , i t is d e s i r a b l e to c o l l e c t definitive information o n t h e s t r u c t u r e s of manganic s a l t s when p o s s i b l e , for complex anions containing trivalent manganese c a n b e expected t o exhibit significant c r y s t a l field e f f e c t s . In particular, octahedrally

coordinated Mn3 should b e tetragonally distorted a s a result of t h e Jahn-Teller effect.28 T h e compound (NII,),MnF5 c r y s t a l l i z e s i n t h e centrosymmetric orthorhombic s p a c e group D Pnma, with a = 6.20 t 0.03, b = 7.94 0.01, and c = 10.72 f 0.01 A. E x c e l l e n t photographic and spectrometric zonal x-ray i n t e n s i t y d a t a were collected in 1957 from s p e c i m e n s of (NH,),MnFS prepared by T. S. Piper. T h e d a t a had resulted i n a structure d e t e r m i n a t i ~ n , ~but ' i t had not been p o s s i b l e to perform a s a t i s f a c t o r y refinement with t h e computing f a c i l i t i e s a v a i l a b l e then. The opportunity a r o s e to perform a modern full matrix anisotropic l e a s t - s q u a r e s refinement with t h e

;E-

existing h0l and Okl intensity d a t a , u s i n g a modific a t i o n of t h e Busing-Martin-Levy program ORFLS. Anomalous dispersion e f f e c t s were included in t h e calculations. F i n a l least-squares-adjusted atomic positions and thermal parameters resulted i n an agreement factor,

between observed and c a l c u l a t e d structure factors, 1 F o and I F c a s low a s 0.068 â&#x201A;Źor a l l observable data. T h e c o n t e n t s of o n e unit c e l l and a d j a c e n t atoms are shown in F i g . 1.7. E a c h octahedron h a s t h e composition MnF 6 , with rnaiiganese occupying t h e c e n t e r and fluorines t h e v e r t i c e s . Ammonium groups appear as stippled s p h e r e s and form infinite hexagonal n e t s in mirror p l a n e s a t y = $;, 3%. Infinite kinked c h a i n s of MnF6 octahedra, s h a r i n g opposite v e r t i c e s , p a s s through t h e s e ammonium nets. T h e manganese atoms lie 011 symmetry c e n t e r s , and consequently there are but t h r e e crystallographically distinct fluorines. Bond d i s t a n c e s and a n g l e s are presented i n T a b l e 1.5. In this table, F I i s t h e fluorine atom s h a r e d by adjacent octahedra. Nonbonding c o n t a c t s between adjacent fluorines i n t h e octahedra were i n t h e range 2.59 to 2.81 A. Although nitrogenfluorine d i s t a n c e s a s low a s 2.81 were discovered,

"See.

(1965).

"D. 1958.

f o r example, R. Dingle, Inorg. Chem. 4, 1287

Sears,

Ph.D.

thesis,

Cornel1 University,

30W. K. B u s i n g and K. 0. Martin, O R F L S , a Fortran Crystallographic L e a s t - S q u a r e s Program, ORNL-'lW-305 (1962).

15 ORNL-DWG 65-5847

......._

F i g . 1.7.

Schematic V i e w of U n i t C e l l of

( N H q ) 2 M n F g and Selected Atoms of Adiclcent C e l l s , Mungonese o c c u r s Nitrogeu atoms are s t i p p l e d s p h e r e s .

, ~ the t t e n t e r off e a c h octohedicn, and f l u o r i n e at each v e r t e x .

Table 7"5. Bund Distances" a n d Angles

D i s t a n ces Hot1d Type

Length ( A )

Standard Error {A)

Hond A n g l e

Angle

Standal-d Error

a high coordination number of nitrogen (7 to 9) and the infrared specimm" of (NH,),MnF5 suggesi strongly that. M-$3-F hydrogen burlding is a b s e n t or very weak. The boad distances and angles InmAxing mangmese reveal that t h e r e i:; indeed a proriouriced tetragonal ilisiortiori of t h e octahedral manganese coordinatirm s h e l l , Dou.hl4ess, sharing of the F I atoms between sdjaceni octahedra coritributes to the substani ia! elongation of t h e Mn-F, bonds, but a Jcihn-Tel k r tlisiortlon m u s t coiltribute significantly. XiiweTvtr, qimititative separation of the effects is riot practicable. Dingle2 has di:;c:ui;sed both tile c r y s t a l spectrum of (N144),MiiFs wid the solntion spectrum of trivalent manganese i n conceritrated H F with excess F --, presianied tc contain MnF 6 The nearly perfect correspondence of t h e spectra i n t h e 30,OOC) t.0 28,000 c m region suggests that tetragonally d i s t o r t e d iLrnF63'- octahedra appear i n solution;

'-.

%i:;trrnces

in parentheses d r e c o r r e c t e d or i.hermaI to "ride" o n the t:~iingarrese.

mii!jora, with fluorine a s s u m e d

s u c h a distortion i n aqueous MnF6,- s o l u t i o n s surely cannot result from chain formation. We infer that t h e distortion a r i s e s largely from ligand field e f f e c t s i n solution and, by extension, d o e s so a l s o in t h e crystal.

HIGH-TEMPERATURE X-RAY STUDIES G . U. Brunton I).R. Sears J. 13. S u m s

A Materials R e s e a r c h Corporation high-temperature x-ray diffractometer furnace h a s been employed i n s e v e r a l s t u d i e s of p h a s e change at e l e v a t e d temperatures, with t h e following r e s u l t s . T h e orthorhombic lanthanide trifluoiides SnF, through LuF, and Y F , h a v e b e e n shown to undergo a p h a s e transition below their melting points.' Of t h e s e compounds, SmF, through HoF, invert to t h e hexagonal L a F 3 structure wbile Y F , and ErF, through L u F , invert t o a c r y s t a l l i n e form which i s probably hexagonal but whose unit-cell dimens i o n s s u g g e s t that it is different from the L a F , structure. T h e unit-cell dimensions of t h e hexagonal p h a s e s and t h e approxiinate inversion temperatures a r e summarized in T a b l e 1.6.

T a b l e 1.6.

U n i t - C e l l Puromnters and Approximate Inversion Temperatures

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

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

Transition Temperature ('C)

a~ ( A )

'0 ( A )

7.07

7.24

555

7.04

7.26

700

GdF3

7.06

7.20

900

TbF

7.03

7. I O

950

DYF,

7.01

7.05

1030

IIoF

7.01

7.08

1070

ErF

6.97

8.27

1075

TmF

7.03

8.35

1030

YbF,

6.99

8.32

985

LuF

6.96

8.30

945

7.13

8.45

1052

SmF

EuF

YF3

, ,

P h a s e equilibrium s t u d i e s i n the U0,-ZrO, s y s t e m have been continued, t h e principal o b j e c t s being: (1) t o i n v e s t i g a t e t h e composition-temperature region in which T h o m a 3 ' h a s postulated t h e e x i s t e n c e of a compound of approxiinate composition UO 3 Z r 0 , ; (2) to furnish x-ray diffraction d a t a for t h e continuing fluoride-flux equilibration experiments of Romberger, Stone, and B a e s ; 3 2 and (3) t o develop room-tempeiature l a t t i c e constant-composition relationships for t h e s y s tem UO,(cubic)-ZrO,(cubic). T e n t a t i v e r e s u l t s to d a t e s u g g e s t that t h e s y s tem cubic U0,-cubic ZrO, at room temperature d i s p l a y s a linear relationship between a. and mole fraction ZrO,, at l e a s t t o 50% %IO,. T h e d a t a c a n b e extrapolated t o a. = 5.08 A a t 100% Z r O z , in reasonable agreement with t h e r e s u l t s obtained by extrapolation of t h e Ce0,-Zr0 d a t a (5.11 A) due t o Uuwez and dell.^^ Attempts t o e s t a b l i s h t h e e x i s t e n c e of a compound of composition near UO, * 3Zr0, above 16003C h a v e not been s u c c e s s f u l . We have not obtained pure tetragonal s t a r t i n g material near t h i s mole ratio. X-ray diffraction experiments in t h e temperature range 1400 to 165OOC a t a ZrO,:UO, ratio of 1.36, using a pure tetragonal solid-solution s t a r t i n g material, have resulted i n exsolution, t o form nearly pure c u b i c UO, and tetragonal Zr0,UO, s o l i d solution richer in ZrO,. Our high-tempersture diffractoriieter attachment is being modified extensively t o permit operation a t higher temperatures i n better vacuum and to diminish problems i n window o p a c i t y c a u s e d by filament and s a m p l e volatilization. Some high-temperature x-ray diffraction measurements were made in order to r e l a t e our singlec r y s t a l study of L i 3 A l F 6 to t h e reported34 polymorphism:

. ---A 225'

/3 >-

475'

-46

575'

.-> e ,

705'

T h e pattern for t h e Li,A1Pq6 p h a s e whose s i n g l e c r y s t a l s were analyzed ( s e e Burns and T e n n i s s e n , 3 1 R . E. Thorna, R e a c t o r Chem. Div. Ann, Progr. K e p t .

J a n . 31, 1965, ORNL-3789, p. 245.

,,K3. A. Romberger e t a l . , R e a c t o r Chern. Div. Ann. Progt. Rept. Jan. 31, 1965, ORNL-3789, p. 244.

33P. Duwez and F. Odell, J . Am. Ceram. Soc. 33, 247 (1950).

34P. G r o s s , F u l m e r R e s e a r c h I n s t i t u t e , Stoke Poges, England, unpublished r e s u l t s .

17 Table 1.7. Crystallographic Data Compound

NaScF4

Na3ScF 6

p 1-KLaF4

Li4UIig

XbPaF6

System

H e x agonal

Monochic

Hexagonal

0rt'norhombj.c

Ortho diombic

Unit-cell

az12.97 .kO.O.3

a75.60 cO.02

a z t i . 5 . 3 0 rf-0.002

a-9.%0

k0.001

a ==

8.06 k 0.02

h -= 9.883

?: 0.001

12.00 Ji 0.113

dimensions, A

9.27 f 0 . 0 2

b = 5.81

2 0.02

c = 3.300

0.002

c .= 5 . 8 5

Space group

Pel

Formula weights

or 2'6 / m 3

Calculated density, g/cm

Notes

-.........._._._.. .-

" S e e "Sodium Fluoridt?-Scandiirtu

Pnma or Pnd21

Cmma or Abm2

3/2

2.87

4.51

4.71

5. os

per unit cell

a, b

_I._......._. .

d. 0.02

....

Fluoride Phase Equilibria,'* t h i s report.

bIsostructural with cxyolite, Nn,AlF 6 . 'Previously sludied by W. I-1. Zachariasen, A c t a CP;,,':N~. 1, 255 (1948). 'Prepared

by 0.

I,. K e l l e r , O K N L Chemistry D i v i s i o n .

t h i s report) was c a l c u l a t e d . With i t and t h e knowle d g e of t h e s l u g g i s h n e s s of t h e a -* L3 transition, i t V J ~ concluded S that t h e preparation of t h e c o m pound resulted in a mixture of ,fj and y. T h i s mixture w a s h e a t e d to 7 2 0 T i n t h e diffractometer filmace, where both of the original components disappeared; by slow cooling the component corresponding to the single c r y s t a l s reappeared at about 5QO'C. F r o m these d a t a w e tentatively concluded {.hat the single-crystal study is of y-Li,AYF,. Further a n a l y s i s of t h i s compound will b e c a r t i e d out when t h e diffrsctometer is modified.

determine whe! h e r e a c h compound h a s a known structural type; or, i f it cloes not, they a r e a prerequisite for proceeding with the st.ructure determination. Of t h e s e compounds, Na,ScFI, was found tu be of the cryolite type (Na,A1F6), while the others represent new st.ructure types. T h r e e of these, /?,-KLaF,, L,i4UF39and RbPaF6, a r e b e i n g subjected tu compleie structure analyses.

YSTAQ STRUCTURE

OF IdaXZu6F31 CRYSTALLOGRAPHIC D A T A O N NEW COMPOUNDS

I). R. Sears J. H. B u r n s G. D. Brunton IJnit-cell dimensions and symmetry information f o r five compounds h a v e been obtained by singlec r y s t a l x-ray diffraction and are summarized in T a b l e 1.7. T h e s e d a t a are n e c e s s a r y in older to

K. D. ~ i i i s o ~ ~ j H. A. Levy3'

J. 13. B u r n s

This compound is representcl!ive of a structural t y p e which h a s occurred in numerous molteri-salt s y s t e m s . Among t h o s e which have b e e n observed3' I__.

...__..__..

3 5 0 ~ Qiemistry ~ ~ , Division.

3 E R . E. Thoma, e d . , Phase Dia&aans of N u c l e a r Reactor Mufariais, ORNL-2.548 (Nov. 2, 1959).

T a b l e 1.8.

Structural Paroineters for No 7 r F

7 - 6

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

- .

~~~. ...

a ~

_. . . .

(322

03 3

@I,

0.0793

0.3038

0,4927

0.0033

0.0041

0.0050

0.0020

--0.0006

112

0.0046

0.0054

0.0023

0.1896

0.0515

0.1791

0.0017

0.0013

0.0020

0.0007

0.0002

---0.0001

F (1) F (2)

0.3.556

0.1114

0.0916

0.0020

0.0022

0.0033

0.0010

0.0005

-0.0006

0.1837

0.0554

0.3944

0,0032

0.0023

0.0026

0.0012

---0.0000

-0.0002

E‘(J)

0.2734

0.3706

0.4243

0.0028

0.0017

0.0036

0.0009

-0.0008

---0.0005

F (4)

0.2087

0.1586

0.0020

0.0038

0.0035

0.0028

0.0023

--0.0002

F (5)

0.2433

0.5417

0.4413

0.0030

0.0045

0.0072

0.0028

0.0016

0.0176

0.0947

0.0088

Atom

Na(1) Na(2) Zr

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

F (b)

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

~~~

......__..____~

. .

p23 ....... __...

-0.0001

0.0006

-0.0020 0

..~.

“Hexagonal coordinates for a l l atoms in general p o s i t i o n s , 1 8 ( f ) , of s p a c e group R 3 , except F(6) and Na(2), w h i c h a r e in ?(a) and 3 ( h ) respectively.

and for which t h e x-ray powder diagrams have b e e n reported3’ are t h e 7 : 6 compounds of N a F , K F , and R b F with U F , and T h F , , a s well a s ‘/‘NH,F 6UF,.38 The e x i s t e n c e of t h i s curious stoichiomeiry h a s been s u g g e s t e d as being due t o t h e possibility of an N a Z r F 5 structure with t h e presence of s i t e s where o n e extra NaF per s i x N a Z r F S units could b e a c ~ o m r n o d a t e d . In ~ ~order t o c h e c k t h i s hypothesis and/or a s c e r t a i n t h e structural c a u s e s of t h i s formula, a complete crystal-structure determination w a s carried out. About 900 x-ray intensity d a t a from a small s p h e r i c a l s i n g l e c r y s t a l were c o l l e c t e d with a P i c k e r full-circle goniometer controlled automat-

3 7 G . D. Rriinton et at., Crystallographic D a t a f o r Sonie Metal Fluorides, Chlorides, s n d Oxides, ORNL3761 (February 1965). 3 8 R . A. Penneman et al., Inorg. Chern. 3, 309 (1964). 3 9 P . A. Agron and R. D. E l l i s o n , J. Phys. Chem. 63, 2076 (1959).

i c a l l y by a PUP-5 c o m p ~ t e r . ~ ’T h e structure w a s solved by an a n a l y s i s of t h e P a t t e r s o n function computed with t h e s e d a t a and was refined by ‘The positional and anisotropic l e a s t squares. thermal parameters are given i n T a b l e 1.8. A portion of t h e structure is shown in Fig. 1.8. 1 he atoms arc represented by e l l i p s o i d s showing their thermal motion. T h e very large ellipsoid corresponds to the “extra” fluorine, which is indeed contained i n a polyhedron of s i x Zr atoms bridged by F atoms. T h e large motion of t h i s F atom means that either it is rattling about qujte freely or else t h e i e is a s t a t i s t i c a l disorder i n which t h i s atom is bonded randomly t o o n e of t h e s i x Zr atoms a t a time. T h e “extra” N a atom i s Na(2); it is c l o s e l y coordinated by s i x F neighbois and by s i x additional F neighbors a t a l i t t l e greater d i s t a n c e . E a c h Zr atom h a s eight F atoms about i t and e a c h Na(1) h a s s e v e n E’ atoms.

>.,

W. R. Busing, H. D. E l l i s o n , and H. A. Levy, Chemistry Div. Ann. Progr. Rept. May 1965, OKNL3832, p. 128. 40

ORNL

- DWG

260

Fig. 1.8. A Portion of t h e N a 7 Z r 6 F 3 1 Structure Showing P r o b a b i l i t y E l l i p s o i d s of Thermal Motion of the Atoms.

. e

alas

OXIDE CHEMISTRY OF L.iF-BeF,-ZrF, C. F. B a e s , Jr.

9,:

MELTS

B. F. Witch

In previously reported s t u d i e s of t h e oxide chemistry of L i F - B e F *-ZrF4 melts, equilibrium quotients were determined by t h e transpiration method for t h e following reactions:

However, t h e s e e s t i m a t e s h a v e been of limited accuracy b e c a u s e of the difficulties in dttteimini n g Q by the transpiration inethod. ? During t h e p a s t year, a more direct method for determining oxide solubj l i t i e s h a s b e e n adopted. A measured volume Of s a l t , presaiurated by equilibration with e x c e s s solid oxide, is filtered through a sintered nickel filter into a heated rec e i v i n g v e s s e l . It is then sparged with an I12-HF mixture and t h e total amount of water evolved determined by Karl-Fischer titration. T h u s far, e s s e n t i a l l y complete removal of oxide from t h e filtered s a l t s a m p l e s h a s been accomplislred i n 3 hr or less by u s e of a n influent H F presslire of 0.05 atm. T h e blank h a s been equivalent t o -2 x mole/kg of oxide (32 ppm), t h e s e n s i tivity h a s been -5 x mole/kg (8 ppm), while to t h e experimental v a l u e s ranged from 1-5 x 1.5 x 10 -- mole/kg. T h i s method presently is being u s e d t o redeterniiile t h e s o l u b i l i t i e s of Z r 0 2 in ( 2 L i F - B e F 2 ) + %rF4mixtures, which s i m u l a t e MSRE fuel s a l t and flush s a l t mixtures. T h e r e s u l t s obtained t h u s far a r e compared in Fig. 2.1 with previously reported’ e s t i m a t e s b a s e d on measured v a l u e s of t h e ratio Q,/QZr in s u c h s a l t mixtures. When completed, t h e s e measurernents should permit t h e e s t a b l i s h ment of inore reliable tolerance limits for oxide l e v e l s in t h e MSRE and i n future molten-salt reactors. In addition, t h e more a c c u r a t e soluhility v a l u e s .-. when combined with Q,, v a l u e s [reaction ( 3 ) ] - should yield correspondingly inore reliable T h e s e will b e useful in optimizing v a l u e s of Q,. oxide removal procedures during s a l t purification and s a l t a n a l y s i s .

R e a c t i o n s (1) and (2) were of i n t e r e s t b e c a u s e of their role i n t h e contamination of molten fluorides with oxide, their role in t h e removal of o x i d e s by H F during s a l t purification, and, m a e recently, b e c a u s e of their u s e in oxide a n a l y s i s . 2 Reaction (3) h a s been of i n t e r e s t b e c a u s e i t r e l a t e s t h e therinodynaiiiic properties of t h e d i s s o l v e d fluoride MFZ t o t h e a v a i l a b l e thermodynamic d a t a for MOZ , ( s ) , I120(g), and HI;(&). E s t i m a t e s of t h e solubility product of the oxide MOZ,, h a v e been obtained from t h e equilibrium quotients 9 , and

‘A. L. Mathews, C. F. Baes, Jr., and B. F. Hitch, Reactor Chern. D i v . Ann. Progr. R e p t . J a n . 31, 1965, ORNL-3789, pp. 56-65; a l s o ref. 7, this section.

‘ M S R Program Semiann. Progr. Rept. S e p t . 30, 1965, OKNL-3897 (in press).

2.1. V a r i a t i o n of O x i d e Concentration w i t h ZrFd C o n c e n t r a t i o n B e 0 or ZrO,. Dashed c u r v e s represent previous e s t i m a t e s based on

Fig. with and

Qz,.

in ( 2 e i F - B e F 2 ) -t

ZrF4

M e l t s Saturated

t r a n s p i r a t i o n measurements of

Qo, QBe,

THERMODYNAMICS OF MOLTEN LiF.3eF2 SOLUTIONS3 C. F. Haes, Jr.

Bn connection with t h e p a s t development of t h e I'GKE, a c o n s i d e r a b l e number o f hei erogeneous equilibria h a v e k e n studied which involved a molten fluoride s o l v e n t of t h c approximate composition XiF-BeF 2. T h e s e equilibria h a v e included: (1) reduction by hydrogen of d i s s o l v e d NiI'2, FeF2, C i F , , 4 Bet?,,' and UF,;6 (2) metathetic r e a c t i o n s of g a s e o u s H F with d i s s o l v e d oxide, sulfide,* and iodide;' ( 3 ) metathetic: r e a c t i o n s between t h e solid oxides and d i s s o l v e d fluorides of Be(II), TJ(IV), Zr(IV), l o and Th(IV); and (4) solubility 3

Based upon a p a p e r presented a t t h e IAEA Symposium on Thermodynamics with E m p h a s i s on Nuclear Materials and Atomic T r a n s p o r t i n Solids, Vienna. Austria, .July 22-27, 1965. 4

C,; M. Blond, Solubility and Stability of StructuraI M e t a l Difluorides in Molteri Fluoride Mixtures, O R N L CF-61-5-4 (Sept. 21, 1961). 5C;,

Anti.

76-79,

D i r i a n and K. A. I~omherger,R e a c t o r Chenl. Div. P r o @ . R e p t . J a n . 31, 196.5, OKNL-3789, pp.

6G. Long, Reactor Cheni. Div. Ann. J a n . 31, 1965, ORNL-3789. pp. 65-72.

Pro&.

Rept.

7A. L. Mathews a n d C. F. Baes, Jr.. Oxide Chemistry arid Therrrloclynaniics of Molten L i t h i i i m FluorideBeryllium Fluoride b y Equilibration w i t h G a s e o u s WaterHydrogen F'fuoride Mixtures, OKNL-'I'M-l1%9 (May 7 , 1965); A. L. Mathews, Ph.D. thesisi. The Chemistry arrd 'rhermodynamics of Molten Lithium Flunride---Beryllium Fluoride b y Equilibration with Gaseoua Water-Hydrogen Fluoride Mixtures, University nf Mississippi, Oxford, Miss. (June 1965).

'â&#x201A;Ź1. 11. Stone and C. F. Haes, jr,, R e a c t o r Chem. D i v . Pro&. H p p t , Jan. 31, 1965, OKN1.-3789, pp. 72-76. 'E. F. Freesier, c. F. Baes, Jr., a n d K 15. Stone, in t h i s report, p. 38. 10 5. E. Eorgan et al., Reactor Chsm. Div. Ann. Pro&. Rept. Jan. 31, 1964, ORNL-3591, pp. 45-46. "J. Ha S h a f f e r and G* M. Watson, R e a t o r Chern. D i v . Ann. Pro&. Rept. Jan. 31. 1960, QRNL-29.31, pa 90,

Ann.

"c. F, H a e s , Jr.. anci B, F. Witch, R e a c t o r Chezn. Div. Ann. Pro&. Kept. Jan. 3 1 , 2965, O R N 1 ~ 3 7 8 0 , pp. 6 1--65; "Oxide Chemistry o f LiF-HeF2-%rF4 Melts,?' this report. ""W, T. Ward et al., Solubility R e l a t i o n s Among RareEarth Fluorides iii S e l e c t e d Molten Fluoride Sol v e n t s , OWL-2749 (Oct. 13, 1959); see a l s o W. Ti. G r i m e s et al., Chem. En& Pro&. 55(27), 6 5 - 3 0 (1959).

14C. J. Barton, J. P h y s . Cheni. 64, 306-9 (1960).

22 T a b l e 2.1.

Solu tea

Formation Heats and Free Energies i n 2 L i F - B e F 2 (773 to 1000째K)

-&qf

-:\Cf

(kcal)

Estimated

1 L i + t F-

142.70

124.79

0.8

2 La3++3F-

405.5

351.8

3 Ce3++3F-

400.5

347,O

4 Sm3++3F-

389.5

337.5

5 B ~ ~ + + Z F -

242.75

211.80

424.0

6 Th4+ i4F7 Zr4'+4F-

451.85

386.21

1.7

4F-

444.61

386.48

1.8

9 U3' + 3 F -

336.73

295.19

1,8

IO Cr2+ t 2 ~ -

171.82

150.41

0.9

11 F e 2 + + 2 F -

154.69

132.92

0.8

12 NiZ++2F-

146.57

110.61

0.8

13 R e 2 ' + 0 2 -

131.91

105.10

0.6

14 B e 2 + + 2 0 H -

170.54

159.35

0.7

96.46

63.56

8 U4'1

15 Re2+ t 2 1 16 tIe2++S2-

k Error

(kcal)

< 7 9 (873째K)

a T h e s t a n d a r d s t a t e of the i o n s i s the hypotheticalrnole fraction s o l u t i o n in 2 L i F - B e P 2 , with t h e exception of Li'., Be",

a n d F-, for which t h e s t a n d a r d s t a t e is 2 L i F - B e F

During t h e p a s t year, t h i s information h a s been reviewed and summarized by therrnodynamic methods a s a means of extending i t s usefulness. This seems fitting and proper a t t h i s s t a g e i n t h e development of t h e molten-salt reactor concept. F u t u r e molten-salt reactors may well employ s a l t mixtures similar t o t h o s e of t h e MSRE considered here; hence, a knowledge of t h e thermodynamics of t h e s e s o l u t i o n s could prove generally user'ul. A c o n s i s t e n t s e t of formation h e a t s and free e n e r g i e s h a s been c a l c u l a t e d for t h e s o l v e n t components and for various s o l u t e s a t low concentration in 2 L i F - B e F 2 (Table 2.1). This was

d o n e by combining the observed equilibrium cons t a n t s (a measure of the free energy difference between t h e r e a c t a n t s and t h e products of a given reaction) with e x i s t i n g thermochemical d a t a for t h e s o l i d and g a s e o u s r e a c t a n t s and products,

'- '

1.5

J A N A F (Joint Army-Navy-Air F o r c e ) Interim Thermochemicaf T a b l e s , R e v i s e d Mar. 31, 1965, 'l'herrnal R e s e a r c h Lab.. Dow Chemical Co., Midland, Mich.

161,. Brewer, pp. 76-192 i n T h e Chemistry a n d Metallurgy of M i s c e l l a n e o u s Materials; Themiodynamics, ed. b y L. L. Quill, McGraw-Hill, New York. 1950. I 7 M . 11. R a n d and 0, Kubaschewski, The Thermal P r o p e r t i e s of Uranium Compounds, p. 71, Interscience, New York, 1963.

2 t-

w v W

8 >

t $

0.3

0.6

Fig. 2.2.

V a r i a t i o n of A c t i v i t y C o e f f i c i e n t s i n L i F - B e F 2 a t 600째C.

concentration; r i g h t ,

yZrF

a s a function of and 4 'F4 figure z / r i s t h e r a t i o of c a t i o n c h a r g e t o r a d i u s .

The partial molal free energy of formatiofl, Ljc, of a r,olute, MFZ, at a given m o l e fraction, XhIFz,

/ 2 ~ fTjaluc listed i n may be calculated f r o m Table 2.1 by u s e of the e x p r e s s i o n

y u F4

Left,

function of

XBeF

as a f u n c t i o n of X U F 4 added t o

o t low s o l u t e

ZLiF-BeF?.

In t h i s

lated with the c a t i o n charge (x) t o c a t i o n radius (r) ratio, hut m o r e s u c h data are needed to e s t a b ljsh ( h e generality of the correlatiut1. Table 2.2 lists standard e l e c t r o d e potentials for various half-cell reactions, arbitrarily referred to

wherein

x,,z

-/(nhfF

+- I f I A i F +- n Bel''? )

yMFZ' is defined

'T'nc activity

coefficient,

unity i f X,,

is low and t h e solvent cornposition

is 2LiF-BeF 2.

Variation of yhl

with 2

X ue

and

with s o l u t e concentration is shown for ii few sol~ t e si n Fig. 2.2. These curves were e s t i m a t e d f i o m observed dependence oi heterogeneous equibibria on melt composition. F r o m these it appears that activity coefficient variations m a y be corre-

The manner in which t h e s e potentials ate calcuIated i s niost e a s i l y s e e n by pointing out that any con~binatinn of half-ci:ll reactions which gives a cOnlpl&? TeaCi:i(Xl Of llie fOsIIi MCs)

.I-

.--I?,@) 2

MFZ(d> ~

-!lGf/nF

, (8)

will ijield t h e corresponding A??' value in ~ a b i e 2.1 (n is t h e number of equivalents of charge and b; i s t h e faraday),

T a b l e 2.2.

C a l c u l a t e d E l e c t r o d e P o t e n t i a l s in

2 L i F - B e F 2 a (773 t o 1000째K)

Temperature Half-Cell R e a c t i o n s b

E" /lOOO째K)

Coefficient

(v)

( m v P c)

-2.54 1

0.821

-2.21

0.82 1

-2.14

0.817

-2.01

0.795

-1.721

0.715

.--1.73

-1.316

0.755

-1.319

0.671

--.1.410

0.630

-1.044

0.807

-0.390

0.505

-0.011

0.5 16

f0.473

0.830 0

0.002

-0.343

c . 0 . 10 0.558

0.134

1.734

0.472

2.87 1

0.044

-f

a C a l r u l a t e d from AG v a l u e s i n T a b l e 2.1. bStandard s t a t e s for i o n s a r e defined in footnote a of T a b l e 2.1.

ESSURES OF FLUORIDE MELTS S. Cantor

D. s. I-Isu'8 W. T. Ward

Tat01 P r e s s u r e M e a s u r e m e n t s

T h e vapor p r e s s u r e s of t h e s y s t e m L i F - l e F 2 a r e being investigated t o derive thermodynamic a c t i v i t i e s , to determine t h e significant vapor 18Surnmer employee, California. Berkeley.

1965,

from t h e

University of

s p e c i e s , and to obtain d a t a of importance t o t h e Molten-Salt Reactor Program. Rodebush-Dixon' and boiling point methods were used t o measure t o t a l pressure over 16 melts covering t h e entire composition range. E a c h melt w a s measured over a t l e a s t a 185' temperature range; the p r e s s u r e range usually covered 1 t o 100 riiiii Hg. F o r a l l c a s e s except one, t h e linear expression

"W.

XI.

Rodebush

26, 851 (1925).

and

Dixon,

P h y s . Rev.

25 Table

Me It C o t n p o s i t i n n (mole 7'") ReF -.

LiF

2.3.

Vapor P r e s s u r e i n the CiF-BeF2 System

T e m p e r a t u r e Range b1casured ( <'C)

___

P 00

Equation: log p(rnm) = A -

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

s/T(OK)

____ .... __ ..........________

779-1147

10.491

10, 953

826-1116,s

10.648

11,230

84.99

15.01

75.01

24.99

890-1112 * 5

10.2 5.5

10,756

70.00

30,QO

.443-1150

10.296

10,870

65.00

35.00

857-1 11 2

9.987

10,266

57.54

42-46

866---1 I 21

9.817

10,449

.50,00

50.00

886-1071

9,134

9,788

45. IO4

.54.96

932-1 155

9,096

9,914

30.95

6 0.06

930-1224

8.993

10,058

36.00

54-00

950- 12 14

9.279

IO,639

30.00

70.00

966-1 28 1

8.560

10,138

25.00

75.00

8.336

11,OO

89.00

89 1-1 239

IO,526

6.7'11

8,175

7.00

93.00

978- 1 234

8,702

11,042

3.00

97-00

10.062

13,178

1020-1272

1020-1270

100 "The equation for pure Lib'

See below"

1026-1272 IS

log P

3,619

- 1.5,450/T -- 6,039

provided a d e q u a t e f i t to the d a t a ( A and B a r e coastants). The d a t a are summarized in Table 2.3% T h e c o n s t a n t s f o r e a c h equation w e r e obt a i n e d by t h e method of least s q u a r e s . Isotherm:; at 9000 and 11009C are shown in Fig. 2.3.

To obtain s o m e notion of t h e vapor species, vapor w;is c o l l e c t e d in the t u b e s oE the v e s s e l at t h e c o n c l u s i o n of vapor p r e s s u r e measurements for s e v e r a l compositions. Chemical a n a l y s i s showed only t r a c e s of lithium ion i n c o n d e n s a t e s where t h e composition of t h e melt w a s 75 or greater mole BeF,. For melts with 70 or less mole % BeF,, c o n s i d e r a b l e q u a n t i t i e s of Lithium were found in t h e c o n d e n s a t e s . A l l that may be concluded from t h e s e a n a l y s e s is (1) at greater than 75 mole % B e F , , t.he vapor i s virtually pure BeF,, and ( 2 ) at less than 70 m o l e % hF,, t h e vapor becomes m o r e complicated; the vapor proba b l y c o n t a i n s the compounds I,iBt?F, and

tog '1'-

Li,BeF4. 2 o T h e only activity c o e f f i c i e n t s that may be c a l c u l a t e d from these detta a l o n e are those of BeF2 at melt concentrations of 75 mole % or F o r these concentrations the greater in B e F 2 . activity c o e f f i c i e n t s of BeF, a t temperatures of IOOQ and '110O0C were found to be greater than unity (varying betiveeri 1-02 and 2,114). 'These v a l u e s of the activity c o e f f i c j e n t are it1 reasona b l e accord with r e s u l f s of t h e H,O-WF equilibration studies of t h e LiF-BeF s y s t e m . Manometric vapor p r e s s u r e s were also measured for t h e blSRE fuel s o l v e n t (composition: 64.730.1-5.2 mole 75 L i F - B e F 2 - % r F 4 ) i n t h e f.emperature range 960 to 11.67OC. T h e d a t a fit t h e equation log p(rnm) = 8,803 - 5936/T(OK). Linear ...........

.......

''A. B k h l e r and J. 1,. Stauffer, IAEA Symposium or: Thermodynamics, July 196.5, p a p e r SM-66/26.

'*A. L. Mathews and C. li'. Baes, Jr., 1129 (May 7, IciG5).

ORNL-TM-

26 ORNL DWG 65-10170

200

extrapolation of the d a t a t o 663OC, t h e h i g h e s t temperature of MSRE fuel s a l t a t normal power operation, y i e l d s a vapor pressure of 0.015 rnm. Trans p i ration Studies

io0 50

: io

m m n W

0.5

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

Be F2 F i g . 2.3.

40 mole

Vapor

100

70LiF

P r e s s u r e s in the

Apparatus w a s constructed t o obtain vapor p r e s s u r e s by t h e carrier-gas method in older t o determine (1) vapor composition in t h e L i F - B e F 2 s y s t e m ( t h e s e measurements will complement t h e inanonnetric pressure d a t a already obtained for t h i s s y s t e m ) , and (2) rare-earth vapor concenti-at i o n s i n equilibrium with liquid mixtures of importance t o t h e molten-salt reactor d i s t i l l a t i o n p r o c e s s (from t h e s e concentrations, m o r e a c c u r a t e decontamination factors for the rare-earth f i s s i o n products wiil b e obtained). T h e apparatus, shown schematically in Fig. 2.4, c l o s e l y resembles that of S e n s e et n l . 2 2 To t e s t t h e reliability of the apparatus a t elevated temperatures and t h e procedures for removing condensed vapors, s e v e r a l runs W ~ K Ccarried out with L i F . Satisfactory agreement with the reliable transpirztion d a t a obtained by S e n s e 2 3 was attained if argon flow r a t e s were kept below 50 cm3/min and if t h e c o n d e n s e r s were washed for about 12 hr with t h e s o l v e n t (a d i l u t e solution of disodium Vers e n a t e ) a t about 70' ......

L i f - R e F 2 ยงystem.

.........

"K.

___

Sense. M. J. Snyder, a n d J. P h y s . Chern. 58, 22.7-24 (1954). A.

W. Clegg, 3.

23K. A. Sense and R, W. Stone, J. Phys. Chern. 62,

1411 (1958).

ORNL-DWG 65513115

VOLECULGR SIEVE CRYING COLUMN

,,-PSESSURE

GAGE (0-101n

ti2@)

T!iCRMOCOUT5 NO 3

PIGH TEMPERATURE ALtlr,IirdA 136-1n [LONG)

O DRYING N, THEN ON TO WET TEST METER

TUBE '

MARSHAt.1-

FLIHNACE (16-1n LONG) '--CONDENSER TUBE (CONDENSER H A S O O 3 1 - 1 n OPENIkG I N ABOVECENTEROFSAMPLEBOAT)

END F i g . 2.4.

Transpiration Apporatus.

27 VISCOSITIES OF

MOLTEH FLUORIDES W. T. Ward

S. Cantor

Li F-BeF V i s c o s i t y measurements of t h e LiF-BeF s y s tem w e r e extended to include t.hree more mixtures (36, 40, and 45 mole 470 BeF2). 'The v i s c o s i t y of pure BeF, w a s measured again, t h i s time over a 410째 temperature range. As previously reported, 2 4 all measurements were carried out with t h e Brookfield L V T viscometer. For t h e three mixtures, v i s c o s i t y d e c r e a s e d with T h e degree of d e c r e a s i n g BeF 2 concentration. d e c r e a s e with concentration, however, w a s not V ~ T Ylarge; below SO mole 7G B e F , concentration, melts ate more typically ionic with relatively low v i s c o s i i i e s ; the c l u s t e r s of beryllium-fluorine l i n k a g e s that accounted for t h e very high v i s c o s i t i e s at higher BeF, concentrations a r e greatly diminished when t h e concentration of BeF, is less t h a n SO mole %. T h e v i s c o s i t y of pure BeF, was remeasured t o determine if pronounced deviation from Arrhenius 'behavior occurs. T h e plot of log '7 v s 1/T showed only s l i g h t curvature; hence, BeF, is Arrhenius. Usually t h e p h y s i c a l behavior of BeF is arialogous t o that o f SiO,. Macedo and Litovi&' postulated that t h e Arrhenius behavior of Si(>, is d u e to t h e c o n s t a n c y of d e n s i t y with temperature which, in turn, means that t h e free volume of SiO, does not c h a n g e with temperature. To e s t a b l i s h t h a t dens i t y c o n s t a n c y with temperature is also why E3eF2 i s Arrhenius w i l l b e difficult, b e c a u s e d e n s i t y measurements of B e F , a r e a difficult experimental t a s k ; n e v e r t h e l e s s , w e a r e currently c o n s i d e r i n g methods for measuring t h e d e n s i t y of pure BeF,. T h e d a t a on t h e LiF-BeF, s y s t e m a r e summarized T h e c o n s t a n t s for t h e viscosityi n T a b l e 2.4. temperatuie equations were obtained b y the method of l e a s t s q u a r e s .

NaBF, 'To provide some information for h e a t transfer c a l c u l a t i o n s on t h e MSBR s e c o n d a r y coolant, pre__

S. Cantor and W. T . Ward, Reactor Chenl. Div. A i m . Pro&. R e p t . Jan. 3 1 , 1965, ORNL-3789, p. 81. 24

P. B. Macedo and T. A. L i t n v i t z , J . Chern. Phys.

42, 245 (1965).

liminary measurements were begun to determine t h e v i s c o s i t i e s of fluoroborates. Tie first measurements w e r e made o n NaRF,; t h e r e s u l t s were: 7 'r 2 c e n t i p o i s e s at 4 6 V C and 14 t 3 c e n t i p o i s e s at 436째C. T h e precision is poor b e c a u s e t h e Brookfield viscometer is primarily d e s i g n e d t o measure higher v i s c o s i t i e s . N o mixtures of a l k a l i fluorides with NaHF, w e r e measured b e c a u s e s u c h m e l t s would most l i k e l y h a v e been e v e n less v i s c o u s than pure NaBF,; t h e poor precision i n this lower v i s c o s i t y range discouraged u s from attempting further measurements with t h e instrumentation at hand.

ESTIMATING DENSITIES OF MOLTEN FLUORIDE MIXTURES S. Cantor

Several y e a r s ago,26 t h e author, after examining t h e published d a t a on d e n s i t y of molten fluorides, proposed that t h e s i m p l e rule of additivity of molar volumes w a s very useful for e s t i m a t i n g d e n s i t i e s of fluoride melts. To f a c i l i t a t e calculations, a t a b l e of empirical molar volumes w a s derived from t h e published data. Since t h e earlier report, t h e r e h a v e b e e n s e v e r a l experimental s t u d i e s of d e n s i t i e s of fluoride m e l t s . In t h i s report, we reexamine t h e previous method of e s t i mation taking into account t h e newer measurements. F i r s t , it a p p e a r s that t h e rule of additivity of mol a r volumes held for all binary fluoride s y s t e m s e x c e p t one; t h e one exception was t h e NaF-UF, s y ~ t e m , ~where positive d e v i a t i o n s from additivity were a s great a s 6%; the rule held i n two s t u d i e s of t h e LiF-ThF, ~ y s t e r n ~ ' " ' ~and i n t h e L,iF-UI',,28 NaF-ThF4?' and L,iF-KF " s y s t e m s . It w a s also found that t h e measured densit.ies29 of t h e e u t e c t i c compositions for t h e KF-Nap, 2 6 S . Cantor, Reactor Chern, D i v . Ann. Pro&. R e p . Jan. 3 1 , 1962, ORNL-3262, pp. 38-41. 27 E. A. Brown and B. Porter, U.S, Bur. M i n e s K e p t . I n v e s t , 6500 (1964). "D. G. Hill and S. Cantor, Reactor Cliern. Div. Ann. Progr. Kept. Jan. 3 1 , 1963, OKNL-3417, pp. 47-48. " G . W. Mellors and S. Senderoff, "The Density and Surface Tension of Molten Fluorides,'' p. 578 in P m ceedings uf the First Australian Conference on Electrocheniistry, Pergarnon, N e w York, 1964; a l s o i n IJnion Carbide R e s e a r c h Siimiinary IJRS-70, Union Car-

bide Corp., P a r m a , o'nio.

Table

2,4.

Summary of D a t a and Constants f o r Viscosity-Temperature Equation

log 7 ( c e n t i p o i s e s ) = A / T e K ) .--R for t h e System LiF-BeF Conrposition (mole 75 B e y 2 )

Temperature Range Mzasured

Viscosity at

(OC)

60OCC ( c e n t i p o i s e s )

36.00

462-600

2,000

1.226

11.6

40.00

441-637

2,203

1.367

14.3

45.00

419-638

2.589

1,685

19.1

50.00

376-577

3,066

2.073

27a

55.01

389---584

3,378

2.203

46a

60.00

4 37-584

3,785

2.37b

91a

65.00

451-724

4,198

2.507

200

70.00

480-704

4,695

2.695

480

75.00

490-705

5,362

3.036

1,275

79.99

558-715

5,983

3.223

4,260

85.00

539-747

6,551

3.340

14.600

90.02

594-882

7,528

3.766

71,800

91.02

545-832

7,640

3.702

112.000

93.01

572-842

8,198

3,977

258,000

94.91

557-837

8,604

4.099

569,000

96.01

601-844

8,928

4.218

1 , O 16, OOOa

97.00

601-897

9,587

4.636

2,208. OOOa

98.01

632-917

10,359

5.179

4,840,000a

99.01

692-967

11,358

5.816

100

702.--1112

S e e belowb

12, S60,000a 63,800,000a

aExtrapolated. b T h e equation for pure R e F

is l o g

7 (centipoises)

= 14,148/T

- 18.345 - 3.382 log T .

N a F - L i F , NaF-LiF-CaF2, and KF-NaF-LiF s y s tems were a l l within 1% of d e n s i t i e s estimated by t h e additivity rule (using the molar volumes T w o ternary s y s t e m s , given i n T a b l e 2.5). NaF-LiF-ZrF4 3 0 and KF-LiF-ZrF4, 29 both studied by t h e s a m e investigators and by t h e s a m e method, were e a c h c o n s i s t e n t l y additive in molar volumes. However, t h e molar volume of ZrF4 that f i t s one s y s t e m did not fit the other s y s t e m (e.g., a t 8OO0C, t h e molar volume of ZrF4 in L i F - K F e u t e c t i c was 55 c m 3 ; i n L i F - N a F

e u t e c t i c , t h e molar volume was 45 cm3). For d e n s i t y measurements carried out by Sturm3’ on four fluoride mixtures, t h e additivity e s t i m a t e differed from t h e experimental r e s u l t s by 5 t o 6% for t h r e e mixtures; t h e discrepancy between experimental and estimated density of fluoride mixt u r e s seldom e x c e e d s 3%. Although errors in t h e molar volumes of Z r F 4 and K F may b e responsible, t h e r e a s o n s for t h e s e larger d i s c r e p a n c i e s a r e a s yet unresolved.

30G. W. Mellors and S. Senderoff, J . Electrochem. S O C . 1 1 1, 1355 (1961),

31B. J. Sturn? and R. E. Thoma, “Measurement D e n s i t i e s of Molten Salts,” t h i s report.

29 T h u s , it a p p e a r s that, although t h e r e may b e e x c e p t i o n s , t h e rule of a d d i t i v e molar volumes d e s c r i b e s t h e experimental d a t a on molten fluorides q u i t e w e l l and remains t h e simplest, most a c c u r a t e method for e s t i m a t i n g d e n s i t i e s of fluoride melts. T a b l e 2.5 g i v e s a r e v i s e d and enlarged set of empirical molar volumes. T h e molar volumes of A1F3 were derived from t h e s t u d i e s of Edwards et al. 3 ? on cryolite. Molar volumes of t h e alkalineearth fluorides (other than BeF,), Y F 3 , and t h e rare-earth fluorides a r e b a s e d on measurements of t h e pure components carried out by Kirshenbaum and ~ o - w o r k e t s . ~ ~ T* h~e, v a l u e s for CsF were obtained from Yaffe’s measurements. 3 5 T h e molar volumes of UF, in T a b l e 2.5 a r e b a s e d on measurement of the pure l i q u i d ; j 6 t h e s e volumes, when u s e d additively with t h o s e l i s t e d for LiF and N a F , provided good agreement between c a l c u l a t e d and m e a s u r e d 2 7 d e n s i t i e s i n t h e LiF-UF, and NaFU F , s y s t e m s . T h e previous d u a l v a l u e s for molar volumes of U F , (see ref. 26), b a s e d on nieasurements of r n i ~ t u r e s , ~ ’ * ~were ’ probably in error b e c a u s e much of t h e UF, w a s removed from solution by precipitation of UO,. (To e s t i m a t e a d e n s i t y e x p r e s s i o n of the form

Table 2,*5.

hblar V o l u m e (cm 3 /mole) At 600OC

A t 800OC

LiF

13.46

14.19

NaF

19.08

20.20

(NiMi)

i=l

where N j and M I a r e t h e mole fraction and molecul a r weight of component i , and V j ( f ) is t h e molar volume of component i at temperature t . Substitute molar volumes from T a b l e 2.5 a t t h e t w o different 32

J. D. E d w a r d s et SI., 508 (1953).

J . Electrochem. SOC. 100.

33A. n. Kirshenbaum, J. A. Cahill, and C. S, Stokes, J . Inn&. N r i c l . Chetn. 15, 297 (1960). 3 4 A . D. Kirshenbaum arid J. A. Cahill, J . Chem. En&. D a t a 7, 98 (1962). 35 I. S. Y a f f e , Cheni. Dib. Semiann. Pro&. Rept. June 20, 1956, OKNL-2159, p. 79. 36A. D. Kirshznhaum and J. A. Cahill, J. Inorg. N u c l . mem.19, 6s (1961). 37

B. e. Blanke et al., MLM-1076 (April 1956). 38B. C, PJlanke et af., MLM-1086 (Decemher 1956).

28.1

30.0

KbF

33.9

CsF

40*2

BeF

23.6

22.4

23.3

CaF

27.5

28.3

SrFZ

30.4

31.6

BaF

35.8

37.3

AlF,

26.9

30.7

YF3

34.6

35.5

LaF 3

37.7

38.7

PrF

36.6

CeF3

SmF3

f i r s t s o l v e for two d e n s i t i e s by u s i n g the equation

E m p i r i c a l Molar Volumes of Fluorides

36.3

36.1

43-1 2‘1.4

37.6 37.b

39.0

39.8

ZrF,

ThF4

46.6

47.7

45.5

46.7

UF4

temperatures to obtain t h e two v a l u e s of d,; s i n c e d e n s i t y is 1 inear with temperature, s u b s t i t u t i o n of t h e t w o v a l u e s of d, in Eq. (10) provides t h e solution €or the c o n s t a n t s CI arid b.1

ESTIMATING SPECIFIC MEATS AND THERMAL CQNDUCTIVIT1ES OF FUSED FtUORlDES S. Cantot Specific Heats

T h e s i m p l e s t rule for estimating high-temperature h e a t c a p a c i t i e s in t h e condensed states is that of Dulong and F’etit, i n which the h e a t c a p a c i t y per gram-atom is approximately e q u a l to

6 cal/'K. Accordingly, t h e experimental h e a t c a p a c i t i e s of molten fluorides were examined in order to modify t h e D d o n g - P e t i t v a l u e for molten fluorides. T h e data for pure compounds ( s e e T a b l e 2.6) i n d i c a t e that t h e heat c a p a c i t y per gram-atom is approximately 8 cal/'K. 'The d a t a for fluoride mixtures would seem to i n d i c a t e t h e average v a l u e t o b e somewhat higher than 8. However, t h e h e a t c a p a c i t i e s of t h e mixtures a r e probably uncertain by 10 t o 20%, w h e r e a s t h e experimental uncertainty for riivst of t h e pure compounds i s less than 5%. Hence, 8 cal ( O K ) . . . ' (grameatom)-' i s t h e v a l u e c h o s e n for e s t i m a t i n g s p e c i f i c h e a t s of fluoride melts. T h e temperature variation of C in liquids, when P determined accurately, i s very small; whether t h i s variation is negative or positive h a s not been adequately established. It is, therefore, prudent t o a s s u m e that C i s temperature independent. P [ T h e s p e c i f i c h e a t is estimated from t h e following expression: n

i=l

where c i s t h e s p e c i f i c heat, p i is t h e number of atoms in a molecule of component i, and N j and M I a r e t h e mole fraction and t h e molecular weight, respectively, of component i. Sample calculation: For MSRE coolant, 66-34 mole % LiF-BeF2,

Z ( N i p i ) = 0.66(2)

+ 0.34(3)

Z (NiMi) - 0.66(26) c

-t

8(2.31)

33.1

2.34 ,

0.34(47) = 33.1 ,

0.57 c a l (OK)-

g - - '.I

c i r c u l a t i n g s y s t e m s . Gambil13 has published a n empirical method for e s t i m a t i n g thermal conductivit i e s which a g r e e s with t h e a v a i l a b l e d a t a , T h i s report will d e s c r i b e a new semitheoretical method b a s e d on Bridgman's theory of energy transport in l i q ~ i d s . ~ ' Bridgman proposed that energy is transferred by c o l l i s i o n from one molecular layer to the next at a rate e q u a l to the local s o n i c velocity and t h a t t h e d i s t a n c e traveled between c o l l i s i o n s is e q u a l to s o m e c h a r a c t e r i s t i c molecular distance. Bridgman obtained t h e equation for A, t h e thermal conduct iv ity ,

where k is Boltzmann's c o n s t a n t , p is t h e velocity of sound, and h is c h a r a c t e r i s t i c molecular dist a n c e between c o l l i s i o n s , T o e v a l u a t e A, Ekidgman s u b s t i t u t e d t h e average d i s t a n c e b e t w e e n molecular c e n t e r s , ( v / N )' I 3 (V i s t h e molar volume and N is Avogadro's number), t h u s deriving the expression

Equation (14) i s i n good agreement with t h e experimental d a t a on covalent compounds. However, t h i s equation predicts low thermal conductivities for molten fluorides b e c a u s e the c h a r a c t e r i s t i c c o l l i s i o n d i s t a n c e i s too large, T h e collision d i s t a n c e for molten s a l t s sliould b e less b e c a u s e t h e i o n s (the "molecular" e n t i t i e s in t h e liquid) a r e much less compressible than covalent molec u l e s . Rather than attempt t o e s t i m a t e c o l l i s i o n d i s t a n c e s in fused salts a priori,41 Eq, (14) w a s empirically adjusted t o fit t h e available data, t h e equation obtained being:

h = (4.4)3k(3

2'3

Thermal Canductivities

At present, a c c u r a t e measurement of thermal c o n d u c t i v i t i e s of fused fluorides is very difficult; hence, reliable methods for e s t i m a t i n g thermal c o n d u c t i v i t i e s a r e extremely useful, e s p e c i a l l y if o n e w i s h e s to predict heat transfer r a t e s i n

- ~ ~-- ~

3 9 W . R. Gaiiibill. Chenz. E n g . 66(14), 129 (1959).

40P. W. Bridgman. 162 (1923).

Proc.

A m . A c a d . Arts Sci. 59,

c;olljsion distance may be derived from 4 iDerhaps e i t h e r the molecular free volume or t h e compressibility.

Tnble 2.6.

Heat C a p a c i t i e s of M o l t e n F l u o r i d e s

Pure Compounds

Compound

per Mole

1-i F NaF

per Atom

Reference

15.50 16.40

7.75 8.20

16.00

8.00

18.58 22.70

6.19 7.57

b b

22.60

CaF

23.90

7,53 7.97

a a

93.4

9.34

-1

HeF

8ZsoK

1200° K

UF,

Na3A1F6

Mixtures

C o m p o s i t i o n ( m u l e $4,)

NaF

LiF

BrF,

65 61 57 53 50

50 65 53 56 53.5 76 25 53 11.5

46.5 10.9 11.2

12 60 46

Z r F4

‘I-1llT4

UF4

per Atom

35 39 43 I7

7.82

7.79 7.91

7.50

50 46

8.22 8.15

I 25

25 15

9.16 7.52

8.33

39 40

6.5 12

15 1

a. 12 7.60

9.86 8.86 7.95 9-35

46-5

50 26

44.5 45.3

43.5

1.1

9.85 9-54

2.5

9*26

3EL4

57.6

I8 55

9,24

27.5

48 50, 1

4,8

41.3

3.8 1

53 62

46 37

62 67 71

36,s 18.5 16

Reference

1 14

13 15

0.5 0.5

e Fi

e e

h e e

10,93 9.54 8.36

3.26

7.75 7.99

7*74

7*69

8-89 7.80 8.77

k I k m

32 T a b l e 2.6 (continued)

Composition (mole %j NaF

LiF

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

BeF2

ZTF,

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

ThF4 1

UF4

per Atom

Reference

..........

___I.

8.06

8.32

aK. K. Kelley, "High-'l'emperatuie I-Ieat-Content, Heat-Gapacity, a n d Entropy Data for t h e E l e m e n t s a n d Inorganic Compounds," US. Bur. Mines B u f l . 584 (1960). bA. R. T a y l o r a n d T. E, Gardner. U.S. Bur. Mines R e p t . Invest. 6664 (1965).

CE. G. King a n d A. U. C h r i s t e n s e n , U.S. Bur. Mines Rept. Invest. 5709 (1961). dW.

L).

Powers, A N P Quart. P r o g r . Hept. Mar. 10, 1956, ORNI,-2061. pp. 176-78.

T). P o w e r s and G, C , Blalock. E n t h a l p i e s a n d Efeat C a p a c i t i e s of SoIid and Molten F l u o r i d e M i x f u r e s , ORNL-

1956 (Feb, 1, 1956).

'W. D. Powers, A N P Quart. Progr. Hept. Mar. 31, 1957, ORNL-2277, p. 87. gW. D. P o w e r s , M S R Program Quart. Progr. Rept. Oct, 31, 1958, ORNI,-%h26, pp. 44-45. hS. I. Cohen, W. D, Powers, a n d N. D. Greene, A P h y s i c a l Property Summary for A N P Fluoride Mixtures, ORNL-

2150 (Aug. 23, 1956).

'W. D. P o w e r s , A N P Quart. Progr. R e p i . J u n e 30, 1957, ORNL-2340, p. 103. 'W. D. P o w e r s , !Wl? Program Quart. Progr. R e p t . J u n e 30, 1958, ORNL-2551, p. 31. kh4SR P r o g r n m Quart. Progr. Rept. Apr. 30, 1959, OKNL-2723, p, 38.

'MSH Program Quart. Progr. R e p t . Apz. 30, 1960, ORNL-2973. P. 23

hlSR Program Quart. Progr. Rept. Oct. 31, 1959, OHNL-2890, p. 21.

"MSH Program Quart. Progr. Rept. Feb. 21, 1961, ORNL-3122, p. 139.

OMSR Program Sernionn. f'rogr. Rept. Aug. 31, 1961, ORI'JL-3215, p. 132.

T h e agreement between Eq. (15) and t h e experimental d a t a i s shown in T a b l e 2.7. T h e velocity of sound w a s itself estimated from t h e equation:

T a b l e 2.7.

ThermoI C o n d u c t i v i t i e s i n F l u o r i d e M e l t s

Melt (mole 7%)

X[Btu f t - - l h r - ' .........

eF)-']

Experimentala

Calculated

1.0

0.94

1.2

1,39

2.6

2.10

2.3

2.01

NaF-%rP4-UF 4

1.3

1.24

Nap-ZrF, -UF,

1.2

1.31

2.4

3.20

RbF-ZrF4-iJF,

(48-484) LiF-RbF (43-57)

where G and C v a r e the molar heat c a p a c i t i e s a t P c o n s t a n t p r e s s u r e and volume, respectively, a is t h e expansivity, T is t h e a b s o l u t e temperature, and !If i s t h e molecular weight. T h e ratio C p / C v v a r i e s between 1.2 and 1.3 for most f u s e d s a l t s (1.2 was c h o s e n for making t h e estimation); C a s indicated above, is very close t o 8 cal

(OK)-'

(gram-atom)-T h e expansivity is t h e negative of the temperature coefficient of density divided by t h e d e n s i t y , that i s , a = -(l/p) ( d p / d T ) By using P' t h e additivity riile of molar volume ( s e e "Estimating D e n s i t i e s of Molten Fluoride Mixtures," t h i s report), a i s e a s i l y estimated,

NaF-KF-LiF (1 1 . 5 4 2 4 6 . 5 ) NaF-KF-LiF-UF4 (10.943.5-44.5-1.1)

(50464)

(53.5-40-6.5) NaF-BeF (57-43)

8 0 r i g i n a l l y regarded a s good t o *2570.

OPN-CWG

.................. 7 ~.___

Finally, combining Eqs. (1.5) arid (16) and evaluaiitig c o n s t a n t s , where p o s s i b l e , o n e e n d s up with a simplified e q u a t i o n for thermal conductivity:

55-3120A

....

x 0,

.> ..

........

where c is t h e s p e c i f i c h e a t [cal ( O K ) - ' g-'], T is tempetature P K ) , V i s mo1:ir volume (cm'), and i s expansivity K j -

SOLUBILITY OF

DF AND HF 1N LiF-BeF,

(66-34MOL E X)

P. E. ~ i e l d ~ '

J. H. Shaffer

T h e solubilities of I-IF and D F in the molten iiiixture LiF-BeF (66-34 mole %) *were determined over the temperature range 500 to 700째C and a t gas satutation p r e s s u r e s between 1 and 2 atm. An extrapolation of t h e solubility v a l u e s provides a n approximation of the s o l u b i l i t y of tritium fluoride in the molten fluoride mixture. T h e behavior of tritium fluoride, formed by neutron irradiation of lithium, i n t h e fluoride mixture would b e of i n t e r e s t i n t h e molten-salt reactor c o n c e p t a s well a s i n t h e proposed u s e of a rrmlteti fluoride breeder blanket for a thermonuclear reactor. T h e experimental procedure h a s been previously d e s c r i b e d and employed f o r s y s t e m a t i c s t u d i e s of gas s o l u b i l i t i e s i n molten fluoride mixtures. Anhydrous hydrogen fluoride w a s obtained 'from a commercial s o u r c e and w a s used without furl.tm purificat,ion. Anhydrous deuterium fluoride was prepared by t h e T e c h n i c a l Division, ORGDP, by reaction of elemental deuterium and fluorine. 4 5

42"

bummer OK.DIS R e s e a r c h P a r t i c i p a n t with R e a c t o r C h e m i s t r y D i v i s i o n , 1965. Assistant Professor of Chemistry, Virginia P o l y t e c h n i c Institu ti:.

43D. J. K o s e and M. Clark, Jr.. PJasnzas and Controlled F u s i o n , p. 296, M.I.T. Press, C a r h r i d g e , Mass. 1561.

4 4 J. 11. Shaffer, W. R. Grirnes, and G. &I Watson, . J. Phya. Chem. 63, 1993 (1959).

" S . T. Benton, R. L. Farrar. Jr., arid R. M. McGill, P r e p a r a t i o n o f Anhydrous Deuteririm F l u o r i d e b y D i r e c l Combination of the Elements, K-1585 (Jan. 29, 1964)"

( K H ) TAKEN FHrJM L E A S 1

'5UlJkHF F I T OF li X P E RI MENTAL DATA O F I n K

l-_ _ .........

................. 4

S A T bR AT ION P RE SSU I?E ( 7 1m )

F i g . 2.5.

Henry's &uw Plot of

in LiF-BeF2

(66-34 m o l e 76).

o n d DF S o l u b i l i t i e s

As shown by Fig. 2.5, t h e solubilities of the two g a s e s obeyed Henry's law, within t . 1 ~experimental precision. over the ranges of tempera!.ure and pressure that were studied, V a l u e s obtained for Henry's law constanks e x p r e s s e d as inoles of HF per mole of melt per atmosphere at SOD, GOO, and ~ O V Cwere 3.37 x IO-.", 2.16 x IO-..', and 1.51 x respectively. Corresponding v a l u e s for the solubility of I)F were 2,97 x IO--", l.83 x and 1.25 x at SOO, 600, and xwc respec t.ively Differences in the s o l u b i l i t i e s of D F and H F are o u t s i d e the 95% confidence l e v e l attributed to t h e experimental data. Evaluation of the teniperature dependence of the Henry's law constant.:; by a l e a s t - s q u a r e s fit of !he d a t a indicated t h a t , wit.hin experimental precision, the e n t h a l p i e s of solution of t h e two g a s e s are e q u a l to about -6.0 kcal/mole for I-IFand -6.4 kcal/mole f u r I)F,

aratisn I bd - B \ k E MOL T E W -%AL ‘T 1 R RAD iA T S QN ASSEMBLY

E. L. Compere H. C. Savage M. J . Kelly J . 11. Baker E. (2 Rohlmanti l)evelopmcnt of an in-pile molten-salt irradiation a s s e m b l y t o provide supporting inforination for a n understanding of both short-term and long-term e f f e c t s of irradiation and f i s s i o n i n g on f u e l s and materials for molten-salt reactors h a s contiaued during the p a s t year. The irradiation experim e n t s a r e to b e conducted in beam hole WN-1 of t h e OfiK, and i t i s anticipated that in-pile operation of the first experiment w i l l begin in t h e middle of calendar year 1966. An autoclave-type (capsule) experiment with thermally induced s a l t flow h a s been designed, and s o m e 4500 hr of operation have been accumulated i n mockup t e s t s with two prototype a s s e m b l i e s . T e s t operation h a s b e e n at a nominal salt temperature of 1200OF with a salt mixture whose composition i s LiF-BeF,-ZrF,-UF, (6529-5-1 mole %, liquidus temperature 840°F). Salt circulation rates of ”’ 10 c m 3/min are achieved by maintaining a median temperature gradient of 1 0 0 t o 180°F betweeri t h e autoclave and the cold leg. T h e flow r a t e is monitored by h e a t b a l a n c e measurements around t h e cold leg. R e s u l t s of t h e s e mockup t e s t s i n d i c a t e that the p r e s e n t d e s i g n of t h e a u t o c l a v e i s s u i t a b l e for u s e in a molten-salt irradiation program with t h e irradiation o b j e c t i v e s of (1) 200 w/cm3 fuel f i s s i o n power and (2) up to 50% 2 3 5 U burnup a n d long-term in-pile operation.

‘ R e a c t o r Chem. Div. Ann. Progr. R e p t . J a n . 3 1 , 1 9 6 5 , OKNL-3789, pp. 45-48.

avior Earlier models of t h e autoclave had a horizontal return l i n e c o n n x i i n g t h e cold l e g with the main Test operation with helium cover g a s autoclave. revealed that g a s buildup occurred in t h i s teturn line and c a u s e d a l o s s of s a l t flow after about 16 hr. F l o w recovery after evacuation and re.pressurization w a s invariably successful., but s i n c e continuous s a l t flow in t h e expeiiment i s d e s i r a b l e , t h e autoclave w a s redesigned to e l i m i n a t e the horizontal return l i n e (Fig. 3.1). T h e prototype rnodel w a s modified by reinoving a l l but about 1 in. of the 5-in.-long horizontal line. T h i s modification i n c r e a s e d t h e operating time without loss of flow to s e v e r a l hundred hours. Complete elimination of the horizontal return line in t h e a u t o c l a v e asseiiibly to be operated in-pile i s expected t o correct t h e flow loss from g a s acc~imirlation. Hosvcver, t e s t operation of the first in-pile experirnecit will be carried o u t in the mockup facility to demonstrate s a t i s f a c t o r y performance prior t o in-pile operation. Experiment f a c i l i t i e s a s s o c i a t e d with beam hole HN-1 of t h e QRR a r e bcing modified for t h e molten-salt experiment. Instrument and control p a n e l s , previously u s e d t o operate in-pile corrosion t e s t l o o p s , 3 are being revised for the higher operating temperatures and lower p r e s s u r e requirements of t h e molten-salt experiment. N e c e s s a r y auxiliary equipment now being des i g n e d and constructed includes: (1) a new alnminum liner for beam hole HN-1, (2) a radiations h i e l d plug which is part of the experiment packa g e , and ( 3 ) revisions to a n e x i s t i n g equipment chamber, l o c a t e d a t the face of t h e reactor s h i e l d ing, which will contain tanks and v a l v e s n e c e s s a r y ‘ R e a c t o r Chem. Div. Ann. Progr. K e p t , J a n , 31, 1965, ORNL-3789, Fig. 2.3, p. 46.

3H. C. Savage, G. H. J e n k s , and E. G. Bohlmann, In-Pile Corrosion T e s t L o o p s for A q u e o u s Homogeneous R e a c t o r Solutions, ORWL-2977 (Nov. 10, 1960).

35 O R N L-DWG 66 -- 9 6 5

\NE L.L. :OWE

Fig. 3-1. In-Pile Molten-Salt Convection L o o p .

io remove s a l t sample:; m d add makeup s a l t to the a u t o c l a v e during in-pile operation. After in-pile operation, t h e experiment package, c o n s i s t i n g of the molten-salt a u t o c l a v e a s s e m b l y in i t s container, t h e s h i e l d plug, a n d the interccjnnecting l i n e s , w i l l b e removed from the beam hole into a s h i e l d e d carrier and h i i s p o r t e d to h o t - c e l l f a c i l i t i e s to be c u t up Zind examined.

EYAPORAT IVE-DI ST1LLATION STUD1ES ON MOLTEN-SALT FUEL COMPONENTS

M. J . Kelly Vacuum d i s t i l l a t i o n s e p a r a t i o n of molten-salt fuel or fuel components from t h e rare-earth f i s s i o n

products is a n a t t r a c t i v e method of d e c r e a s i n g 'Po d e s i g n p r o c e s s neutron losses by capture. equipment for t h i s t a s k , both the mas:; rate of d i s t i l l a l i o n and t h e relative volatility of t h e rare e a r t h s must be known for the particular s a l t s y s t e m used. Completed experiments concern t h e planned p r o c e s s demonstration for MSRE fuel but a r e a l s o directly a p p l i c a b l e 1:o any proposed thermal MSBR fuel. F o r MSRE fuel, removal of the uranium by fluorination is proposed. T h e fuel s o l v e n t and remaining f i s s i o n products would then b e fed at the d i s t i l l a t i o n rate to a vacuum still charged with LiF-BeF,-ZrF, a t t h a t composition which will yield t h e fuel s o l v e n t a s d i s t i l l e d product; t h e rare-earth fission products would c o n c e n t r a t e i n t h e s t i l l . T h e r e s i d u e would b e d i s c a r d e d or p r o c e s s e d when n e c e s s i t a t e d by h e a t from t h e f i s s i o n products or by carry over of rare earths.

36 A 10-ml graphite cylinder, containing -17 g of s a l t with a free s u r f a c e (when molten) of 1 c m 2 , w a s used for t h e s t i l l pot. ‘This cylinder fitted in a “I?” s h a p e d INOR-8 tube heated electrically t o a given temperature a s measured by four thermocouples in the graphite cylinder. When the d e s i r e d temperature w a s reached, d i s t i l l a t i o n w a s initiated by e v a c u a t i n g the assembly. Vaporized s a l t then p a s s e d tip and over the top of t h e “fl” with a s m a l l portion (attributed t o thermal reflux) c o l l e c t i n g a t t h e b a s e of the graphite cylinder. ’The product s a l t c o n d e n s e d in a cooler (-45OOC) c o l l e c t i n g c u p i n the opposite leg. Distillation w a s stopped by helium addition after preselected time periods. Mass-rate d a t a for 71,iF were determined first, and then MSRE s o l v e n t w a s added to t h e 7LiF and d i s t i l l e d in aliquot portions from i t . E a c h repetition brought the B e F , and ZrF, concelltrations i n the pot c l o s e r to t h o s e which would yield f u e l s o l v e n t (LiF-I-3eF2-%rF,; 65-30-5 mole %) as product. After t h e equilibrium concentration w a s approached, 2200 ppm of neodymium ( a s NdF,) w a s added to the s t i l l bottom and Then s e v e r a l d i s t i l l a t e s a m p l e s were taken. t h e neodymium concentration w a s raised to 22,000 For both ppm, and the s e q u e n c e w a s repeated,

7LiF and the nominal equilibrium composition, the effect of temperature on inass rate w a s determined. T h e d a t a of Fig. 3.2 show t h e effect of temperature and m a s s rate; s i n g l e experiments are considerably s c a t t e r e d , so i n c l u s i v e bands are shown, T h e s l o p e of t h e bands i s c o n s i s t e n t with t h e h e a t of vaporization of the components and strongly s u g g e s t s that ebullition d o e s not occur. Solvent s u r f a c e heat. flux is < 1 / 1 0 0 of the a v a i l a b l e h e a t to t h e graphite cylinder; i t i s doubtful that the distillation is h e a t limited. ‘The fact that t h e observed rate for ’LiF is only -10% of theoretical is unexplained, but it h a s been observed in many d i s t i l l a t i o n s u s i n g s e v e r a l experimental configurations. T h e s o l v e n t for a n y proposed MSRK s h o u l d d i s t i l l a t r a t e s above that shown for 7LiF with the p o s s i b l e exception of ThF,-bearing s y s t e m s . T h e effect of T h y , is b e i n g studied. E f f e c t i v e n e s s of separation from rare e a r t h s w a s determined by activation a n a l y s i s for ncodymium in the product, the s t i l l bottom, and the refluxed s a l t deposited around the b a s e of t h e graphite. T h e d a t a are shown in ?‘able 3.1. T h e equilibrium composition in t h e s t i l l pot undoubtedly c h a n g e s with temperature due t o the change in activity coefficients of t h e components. ‘l’he composition found a t norninal equilibrium after s e v e r a l s o l v e n t additions of 5 to 7% by weight and after d i s t i l l a t i o n s a t 1030OC was LiF-BeF,-ZrF, (85.4-10.7-3.9) in the p r e s e n c e of 22,000 ppiii of neodymium a s fluoride.

”m

T a b l e 3.1.

N‘

€

.....-_I_

111

Concentration of Neodymiuin i n F r a c t i o n s from V a c u u m D i s t i l l a t i o n s

_ ......................

Nd Concentrationa

‘a r d 3 z

Fraction

k J A c

.---.

(PPm)

2200 ppm Added

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

22,000 ppm Added

1 _ _ 1 . . _ _ . _ _ _ _ _

2570 21

S t i l l bottom Product

Reflux

22,000 600‘ 34

133 . . . . . . . . . . . . . . . . . . I

aMean v a l u e s from s e v e r a l determinations; d a t a s h o w l i t t l e s c a t t e r e x c e p t for reflux s p e c i m e n s .

Fig.

3.2.

O b s e r v e d D i s t i l l a t i o n R a t e v s Temperature.

b T h e s e product s a m p l e s a l s o s h o w e d cerium a n d lanthanum, which undoubtedly r e p r e s e n t contamination during grinding and handling of s p e c i m e n s ; neodymium a n a l y s i s , therefore, may w e l l b e too high.

E F FECTl VE ACT1 VI TY COE F FICl ENTS B Y EVAPORATIVE DISTILLATION OF MOLTEN SALTS M. J. Kelly Evaporation i n t o a vacuum from a q u i e s c e n t molten-salt mixture of low vapor p r e s s u r e should not permit vapor-liquid equilibrium at t h e surface of t h e melt; transport Erom t h e s u r f a c e s h o u l d b e controlled by t h e evaporation r a t e s of t h e The amount vaporized individual components. is a function o f the equilibrium vapor p r e s s u r e , molecular m a s s , temperature, a n d s u r f a c e a r e a ; a c c o r d i n g to Langmuir:

where P, is the vapor p r e s s u r e of component Z , iz/I is molecular weight of component 2, T is a b s o l u t e temperature, and K is a c o n s t a n t which is dependent on u n i t s . In a multicomponent s y s t e m at equilibrium,

grams o f 2

r _ _

c m 2 sec

If w e u s e a fixed rriechanical configuration and, for simplicity, define the a c t i v i t y coefficient of the. major component [in this case LiF) as unity, the activity coefficient for any other constituent may be determined u s i n g t h e ratio

a l t e r e d to

Table 3.2. Vopor P r e s s u r e s f a r Pure F l u o r i d e s Vapor Pressure Compound

(mm

~1000°C

LiF HeF ZrFq

0.47

65 2700

€Id

9 00' C

0.072 12.0 780

LiF-HeF,-ZrF, melts. For comparison purposes, s e l e c t e d d a t a from other s o u r c e s a r e included. 5 - 7 Although internal c o n s i s t e n c y e x i s t s , t h e v a l u e s a r e dependent upon vapor-pressure d a t a for t h e pure components. Calculations were made u s i n g the v a l u e s ( P o ) for the pure components shown in T a b l e 3.2.'-") T h e l e a s t - p r e c i s e measurements are from MSREs o l v e n t distillat.ions; t h e s e a r e included to subs t a n t i a t e t h e s u r m i s e that, when ZrF, is included in t h e m e l t , i t effectively removes LiF from t h e The 1000°C LiF-ReF, l i n e h a s been solvent, extended to 100 mole 76 LiF s i n c e t h e i n i t i a l LiF-I?eF ,-ZrF, experiment contained <Q.35 mole % ZrF,, a quantity so s m a l l that t h e s y s t e m c a n h e assunied to b e LiF-BeF,. On t h e other hand, a s ZrF', builds up in t h e mixed system (to approxiiiiately 3 mole %), enhancement of t h e BeF, activity is noted; t h i s is c o n s i s t e n t with r e s u l t s from MSRE s o l v e n t (LiF-HeF,-ZrF,, 6530-5 mole "/D initially). T n e temperatures reported a r e t h o s e of t h e bulk melt, and it is recognized that the s u r f a c e temperature may be significantly lower, c a u s i n g a n irideterminate (for the present) error. Both s ~ ~ r f a c e - t e m p e r a t u r e e f f e c t s and t h e pure L i F a Z r F , s y s t e m a r e being studied. I t is i n t e r e s t i n g to note t h a t the assumption of unit activity coefficient for LiF d o e s not l e a d to incompatibility with t h e d a t a of others. ' 5 R ~ a c t o rChem. Div. A n n . Progr, R e p r . Jan. 3 1 , 1965, ORNL-3789, pp. 59-62.

'K. A . Sense and R. 311. S t o n e , J . P h y s . Chem. 62, 96 (19.58).

ita

Proceeding with i h i s technique, the d a t a shown Fig. 3.3 h a v e b e e n taken from LiF-BeF, and

'I. Lwngmuir, P h y s . Rev. 2, (Ser. 2 ) , 329 (1913) (and s u b s e q u e n t papers).

'A. Buchler and J. I,. Stauffer, .5ymposicmi on ~ h e r r n o dytiarnics with E m p h a s i s r;n N u c l e a r Materials a n d A t o m i c Trarrsport in Solids, V i e n n a , J u l y 22-27, 196.5, paper SM-66-25, p. 15. 'Haridbook Chernistry arid P h y s i c s , 44th ed., p. 2438, Chemical Rubber P u b l i s h i n g Company.

9 B. P o r t e r arid E. A . Brown, J . Am. Ceram. Scr. 45, 49 (1962). OS. c a n t or, pers -3na1 communication.

O R N L - O W G 66-967

I---

LiF-BeF2+ZrF4, BAES 1 DERIVED FROM MSRE SOLVENT DISTILL ATIONS 900-f050째C 0 I. i F - BeF2, BUCHLER. 600째C LiF. BeF,, iO00"C 0 LiF.BeF2, 9 0 0 째 C A , e LiF.BeF2-7rF4, IOO0"C

-2

.........

____

w -

~...] .........

L i F IN MELT (mole %) Fig.

3.3.

Effective

Activity Coefficients

C a l c u l a t e d from

Evaporavive-Di st i I l o t i o n Bnto

for M5 B R - S o l v e n t

Compositions.

VAL 8 $ IODIDE FROM kiF-BeF, MELTS

C. F. B a e s , J r . B. F. F r e a s i e r ' H. H. Stone T h e removal of t h e 6.7-hr f i s s i o n product 1 3 ' 1 from a molten-salt fuel would reduce t h e amount ....

..................___

"ORINS Summer P a r t i c i p a n t , P o l y t e c h n i c I n s t i t u t e , Ruston.

1965, f r o m L o u i s i a n a

of daughter 13'Xe, a major fission pioduct poison, formed i n the fuel. In measurements not y e t completed," i t h a s been found that iodide (the chemical form of iodine expected to be present) can be readily removed from L i F - B e F , m e l t s

12MSK Program Semiann. Progr. R e p t . A u g . 3 1 , 1 9 6 5 , ORNL-3872, p. 127; iMSR Program Seinzann. Progr. Rept. k e b . 2 8 , 1 9 6 5 , ORNL-3812, p. 137.

39 by s p a r g i n g with mixtures of f i F arid H,, evidently by the reaction

HF(&

I-(d)

;=t

F-(d)

-HI(& i

pHl/pHI<.[I-] kg/mole

(6)

'The experiments were performed i n all-nickel v e s s e l s which did not r e a c t with HI i n the prese n c e of H, a t t h e temperatures s t u d i e d (474 to 635OC). Such reaction w a s avoided a t t h e lower temperatures of t h e g a s e x i t s y s t e m by u s e of gold-lined n i c k e l a n d Teflon tubing. T h e iodine w a s added initially as MaI; tests were made of t h e effluent g a s , and HI, but no e l e m e n t a l iodine, w a s found. T h e HI w a s trapped in a n NaOH scrubbing solution and determined by s t a n d ard iodometric methods. Only about 80% of t h e initially added iodide appeared i n the NaOH scrubber; i t is believed t h a t t h e remaining iodide e s c a p e d as a r e s u l t of adsorption of HI on part i c u l a t e matter which w a s not effectively trapped by the scrubber. When radioactive iodine w a s u s e d i n tracer experiments and a filter w a s plscxd i n t h e effluent gas stream j u s t downstream of t h e reaction v e s s e l , all t h e iodine p a s s i n g t h e f i l t e r was caught in t h e NaOI-I scrubber s o l u t i o n and appeared as iodide ion. T h e discrepancy in n a t e r i a l b a l a n c e will b e i n v e s t i gated further, but it does not s e e m likely that t h e p r e s e n t e s t i m a t e s of Q for the reaction will be s u b s t a n t i a l l y altered. Kesul ts w e r e c o n s i s t e n t with t h e following integrated rate equation which may be derived from reaction ( 6 ) : In

([I'-l/TX-Io> = - Q(riHF/W) .

coefficient of t h e iodide ion did not vary appreciably over the concentration range oE iodide employed. For 2LiF-BeF2 melts (Fig. 3.4) the presently incomplete r e s u l t s give l o g Q = -1.094 t 2.079(103/T)

(8)

with error l i m i t s of pcrhaps t15% in 0. Thus, Q i n c r e a s e s - the ease of iodide removal by H F i n c r e a s e s - with d e c r e a s i n g temperature. With i n c r e a s i n g B e F , content of the s o l v e n t , Q app e a r s to go through a maximum, Mole

7'2

ReF2

49.7 32

41.5

33.3

Q (482째C)

T h e number of moles of IIF n e c e s s a r y to remove half t h e iodide p r e s e n t i n 1 k g of riielt by equilibrium s p a r g i n g i s , by Eg. (7), simply 0.693/(1. F o r a reactor s y s t e m i n which a s i d e stream of t h e fuel is continually treated with HF, t h e minimum amount of HF p a s s e d through t h e fuel per

ORNL-DLVG

TEMPERA-llJRE 1째C) EO0

6550

65-9874

500

5550

(7)

TIE terms [I-']' arid [I-] a r e , respectively, the c:c;ncetitraiions of iodide present initially and of iodide p r e s e n t after n W F moles of HF h a v e been p a s s e d through W kg of m e l t . T h i s relation w a s u s e d to determine t h e equilibrium quotient, (7, f o r reaction (6). T h e value of Q s~ obtained w a s found not to b e significantly dependent on the HF flow rate (0.35 to 1.57 millimoles min-' kg-'), on the partial p r e s s u r e of HF (0.02 to 0.1 a h ) , or on the i n i t i a l iodide concentration (0.004 to 0.04 mnle/kg). This indicated t h a t reaction (6) was indeed the only one of s i g n i f i c a n c e , that equilibrium s p a r g i n g conditions were obtained, and that t h e a c t i v i t y

4.07

F i g . 3.4.

rium

4.45

4.41

4.!9

loco

4.23

4.27

134

4.35

/ r [*xi

V u r i o t i o n w i t h Terriperoture of the E y u i l i b -

Quotient

for

iodide

Removal

from

2LiF-BeF2,

40 hour to give a s p e c i f i e d overall removal halftime ( t l /*) is inoles of HF/hour

> (0.693/t,,,)CVT/Q

T a b l e 3.3.

D i s t r i b u t i o n of R a r e E o r t h s

Between L i F - B e F 2 (66-34 Mole

and Molten Bismuth when Reduced

(9)

where W T is t h e total weight of t h e fuel. Since the half-time for decay of 1 3 ' 1 to ' 3 5 X e is 6.7 hr, iodide-removal half-times of the order of an hour might b e desired. With Q = 40 kg/mole ( 2 L i F - B e F 2 at 500째C), half the iodide p r e s e n t i n a reactor fuel could b e removed in 1 hr by t h e p a s s a g e of a minimum of 0.0173 mole of I-IF (388 s t d c m 3 ) per hour p e r kilogram of fuel.

REMOVAL OF KAWE EARTHS FROM MOLTEN FLUORIDES BY EXTRACTION INTO MOLTEN METALS J . H. Shaffet F. A. Doss

W. K. R. F i n n e l l W. P. T e i c h e r t W. R. Grimes

In a two-region molten-salt breeder reactor, the fuel mixture will require routine r e p r o c e s s i n g t o reduce concentrations of t h o s e f i s s i o n products which h a v e high neutron-capture c r o s s s e c t i o n s . Of the various fission products which form s t a b l e chemical compounds i n t h e fluoride fuel mixture, race e a r t h s will comprise t h e major poison fraction. T h e extiaction of s e l e c t e d rare e a r t h s froin solution in a molten fluoride mixture into immiscible molten metals is b e i n g s t u d i e d a s R possib!e chemical r e p r o c e s s i n g method. Experiments conducted t h u s far h a v e examined t h e extraction of lanthanuiil, cerium, neodymium, and europium from t h e fluoride s o l vent, L i F - B e F , (66-34 mole %), into bismuth metal. T h i s fluoride mixture s i m u l a t e s t h e fuel s o l v e n t proposed for a molten-salt breeder reactor; U F , is here presumed to h a v e been removed from t h e fuel by fluorination. Fluoride mixtures having rare-earth concentiations of about m.f. together with their appropriate radioisotopes (for a n a l y t i c a l purposes) were prepared in n i c k e l v e s s e l s . T h e mixtures were further treated at 600OC with anhydrous H F and H,, according to e s t a b l i s h e d fluoride purification techniques, until the gamma activity i n two or more c o n s e c u t i v e filtrate s a m p l e s of

with Beryllium Metal o t

Rare Earth

Rare E a r t h

60Q째C

Rare Earth

Remaining

Dissolved

i n Salt P h a s e

i n Metal P h a s e

(70)

Lanthanum

Cerium

0.1

Neodymium

Europium

t h e salt mixture became c o n s t a n t and approached anticipated v a l u e s . T h e liquid-metal e x t r a c t a n t s were prepared in s t a i n l e s s s t e e l extraction v e s sels with low-carbon s t e e l liners; pretreatment with hydrogen a t 6QOOC reduced oxide impurities i n t h e liquid metals. An extraction experiment w a s s t a r t e d by transferring a portion of t h e prepared s a l t into the extraction v e s s e l . Each extraction experiment involved about 2 . 3 5 k g of molten bismuth and 1 to 2 kg of s a l t . T h e two p h a s e s were a g i t a t e d by sparging helium through a tube t h a t extended into t h e metal phase. Two t y p e s of extraction experiments h a v e b e e n conducted. In t h c initial experirnerits, beryllium metal w a s added a s machined tuinings to t h e extraction v e s s e l during preparation of t h e molten metal. Following introduction of the s a l t n i x ture, filtered s a m p l e s of e a c h p h a s e were taken a t periodic i n t e r v a l s and analyzed radiochemically for their r e s p e c t i v e rare-earth content. T h e d i s tributions of rare e a r t h s a t the conclusion of e a c h experirnerit a r e summarized i n T a b l e 3.3. T h e s e r e s u l t s demonstrate the e f f e c t i v e removal of rare e a r t h s from the s a l t phase. T h e incomp l e t e d i s s o l u t i o n of rare e a r t h s in the metal p h a s e may i n d i c a t e that a third, solid, p h a s e w a s formed; i t is not unlikely that t h i s insoluble p h a s e is a rare-earth beryllide s u c h a s h a v e been observed by others a t this Laboratory.'3 Spectrographic a n a l y s e s of samples taken from t h e metal p h a s e showed the p r e s e n c e of d i s s o l v e d

'3M. E. Whatley, private communication.

41 lithium in the molten bismuth, sugget,ting that t h e beryllium metal had c a u s e d reduction of part of t h e lithium. in two additional experiments, extractions of cerium and neodymium were accomplished by a d d i n g lithium m e t d l directly to thc molten bismuth, Samples of the salt and m e e d phses were rvithdrawri undei a s s u m e d equiInbiium conditions after t>:tch addition of lithium tilvtal. T h e distribution of cerium and neodymium between the two p h a s e s at t h e c o n c l u s i o n of t h e experiments e s s c n t i a l l y duplicated t h a t found in t h e beryllium-reduction experiments. T h e conct-titration of lithium i n t h e metal p h b s e of e a c h experiment i n c r e a s e d linearly with the quantity of lithium added; however, only P/4 to 1/3 of t h e added lithium appeared i n the metal p h a s e , m d i t mdy be that a reduction of beryllium i o n to i t s elemental form accounted f o r the m i s s i n g Eith~um. Furtherrtiore, as shown i n Fig. 3.5, tht- ccncentration of rare e a r t h s i n the metal p h d s e xn e a c h experiment became independent of f h f lithium c o n c ' e n t r a ~ o tfound ~ in t h e metal p h a s e . Subsequent extraction experiments w i l l be extended to i n c l u d e o t h e r rare e a r t h s and to study tiit3se inferred reaction equilibria.

, a

ORNL-D'dG

66-958

r-i

0.5

1 .o

1.5

2.0

2.5

LiTtiiuiv Fours I N METAL PHASE ( m o l e fraction A 10%)

Fig. 3.5.

E x t r a c t i o n of Cerium and Neodymium from

liF-BeF2 (66-34, Mole X) i n t o

tion of L i f h i u m kletal a t

600째C.

Molten glismuth b y Addi-

J. 51. Shaffer F.A. D o s s

W. R.

W. K. R. Finriell W. P.'Teichett

Grinies

S i n c e a single-region molten-salt breeder reactor would Incorporate the fertile material i n t h e reactor fuel mixture, chemical r e p r o c e s s i n g s c h e m e s for recovering 2 3 3 U could be made m o r e e f f e c t i v e if "3"F'a, its precursor, could be removed without alteration of t h e relatively large uranium concentration i!i t h e fuel inixiure. T h e precipitation of a n oxjde of protactinium by the delibe r a t e addition of oxide i o n may provide the basis for s u c h a r e p r o c e s s i n g method i f the simultaneous ptecipitaticn of UO, c a n be avoided, Previous s t u d i e s h a v e demonstrated t h e chemical f e a s i b i l i t y of oxide precipitatjon f o r removing protactinium from a fluoride mixture, LiF-BeF2ThF, (67-98-15 mole %), proposed as t h e blanket of a two-region molten-salt breeder reactor. In the fluoride fuel mixture of the MSKE, sufficient ZrF, h a s been added to accommodate gross oxide cont.aminat.ion without loss of uranium from s o l u t i o n as UO,. Earlier studies had demonstrated that UO, would not precipitate at 700째C from t h e s o l v e n t , LiF-13eF2 (66-34 mole %) with added U P , and ZrF,, until the concentration ratj.0 o f ZrF, to U F , dropped helow about 1.5.15 Therefore, a preliminary s t u d y was made of t h e precipitation of PaO, from a fluoride mixture known to h a v e Z r 0 2 as t h e s t a b l e oxide phase.'O T h e fluoride mixture c o n s i s t e d of LiF-BeF 2 (66-34 mole 7%) with added ZrF, e q u i v a l e n t to 0.5 m o l e of zirconium per kilogram of salt mixture. About 1 mc of 2 3 3 P a w a s included i n the s a l t preparation as irradiated ThO,. The mixt u r e w a s pretreated with anhydrous H F and W, to convert o x i d e s to fluorides, T h e deliberate introduction of s o l i d - p h a s e oxide to the m e l t w a s made by adding 2510,i n s m a l l increments. F i l t e r e d s a m p l e s of t h e salt mixture were taken a t a s s u m e d equilibrium conditions after e a c h o x i d e addition and were a n a l y z e d

H . Shaffer e t al., N u c l . Sci. Eng. 18, 177 (1961). l S X ~ a c : t v r C h e nDiv. ~ , Arm. Pro&. Hept. J a n . 31, 1961, ORNL-3127, p. 8. 14J.

''Reactor Ghem. Div. A m . Pro@. R e p t . J a n . 3 1 , 1 9 6 5 , O R N L 3 7 8 9 , p. 56.

42 for 2 3 3 P a by gamma spectrometry. T h e r e s u l t s of t h e s e a n a l y s e s showed that approximately 80% of t h e 233Pa activity w a s removed a f t e r the addition of about 67.5 g of ZrO, (equivalent to 0.115 mole per kilogram of s a l t ) to t h c mixture. If protactinium either formed a l a b i l e s o l i d solution with Z r O , or w a s removed from solution in the s a l t mixture by s u r f a c e adsorption on ZrO,, then i t s distribution coefficient s h o u l d have remained constant. T h e fraction of Pa remaining in the liquid p h a s e could thcn b e exp r e s s e d as a linear funrtion of added Z r O , by t h e equation

in F i g . 3.6, i l l u s t r a t e s t h e constancy of t h e distribution coefficient a t a c a l c u l a t e d v a l u e of about 237. T h e d a t a further s u g g e s t that about 7 g of t h e i n i t i a l ZrO, addition partially d i s solved in the s a l t p h a s e or w a s otherwise l o s t from the reaction mixture. Further experiments will include s t u d i e s of the effect of ZrO, surface area on protactinium removal from s a l t mixtures proposed for a single-region molten-salt breeder reactor.

REMQVAL ClF FWCBTACTPNdUha FROM MOLTEN FL&SQRlBES5Y REDUCTION PMOCESSEP

J. H. Shaffei W. K. R. F i n n e l l F. A. D o s s W. P. ’Teicheit where D - [ ~ a l ~ ~ ~ ~F~~ ~ /:[fraction ~ a ]of ~ ~ ~ ~ , 12’. I<. Grimes Pa in s a l t , and Ct’ i s t h e weight of the designated An interpretation of the experimental phase. T h e e f f e c t i v e recovery of 2 3 3 P afrom a inoltend a t a according to t h i s linear function, shown s a l t breeder reactor will provide more economic

2.= FPa

‘

t t D

ORNL-DWG 6 6 - 9 6 9 ..............__

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

(““~‘jJ s

A LT

W H E R E Fpa= F R A C i l O N O F 233Pa iN L I Q U I D

r O2 ___.._. --WEIGHT

RATIO O F P H A S E S

pj’ A LT # = CONC O F Pa IN SOLID _PHASE _ CONC OF Pa IN LIQUID PHASE ~

W E I G H T OF Z r 0 2 A D D E D A S S O L I D P H A S E ( g )

R e m o v a l of 2 3 3 P 0 from Solution in L i F - B e F 2 Mole %) with Added Z r F 4 (0.5 MO!S per K i l o -

F i g . 3.6. (66-34

g r a m of S a l t ) by Addition of

Zr02

production of f i s s i o n a b l e 2 3 3U by s u b s t a n t i a l l y reducing blanket inventory and equipment c o s t s and by improving neutron utilization. Accordingly, chemical developmerit efforts supporting t h e reference-design MSBR a r e concerned with the removal of protactinium from t h e blanket mixture, L i F - B e F , - T h F , (73-2-25 mole %), by methods which c a n be f e a s i b l y adapted a s chemical processes. An experimental program has been initiated to study the reduction of protactinium fluorides froin t h i s salt mixture by molten l e a d or bismuth s a t u r a t e d with thorium metal a t about 4QQOC. I t w a s hoped that protactinium, a s PaF4 i n the salt phase, would b e reduced t o i t s metall i c s t a t e by thorium metal and could he recovered i n the molten lead or bismuth. T h e primary objective of initial experiments with t h i s program h a s been the s t u d y of protactinium removal from the salt p h a s e of the extraction 3Pa system. F o r t h e s e experiments sufficient w a s obtained for radiochemical a n a l y s i s by neutron irradiation of a s m a l l quantity of T h o , . T h e simulated blanket mixture w a s prepared from i t s components, together with t h e irradiated T h o , , i n n i c k e l equipment. T h i s mixture w a s treated a t 60Q°C with a n [IF-H, mixture (1:10 volume ratio) to remove oxide ion and a t 7OOOC with H a l o n e to reduce s t r u c t u r a l m e t a l impuiities. T h e metal-phase extractant, l e a d or bismuth with added thorium metal, w a s prepared in

a t 6OO0C.

43 the extraction v e s s e l (304L s t a i n l e s s s t e e l with a low-caibon s t e e l liner) by treatment with H I at 600'C. T h e extraction experiments were s t a r t e d by transferring a known quantity of t h e prepared s a l t mixture inio t h e extraction v e s s e l containing t h e metal-phase extractant. F i l t e r e d s a m p l e s of the s a l t p h a s e were taken periodically for radiochemical a n a l y s i s of d i s s o l v e d protactinium. In e a c h experiment, 2 3 3 P a w a s rapidly removed from the salt p h a s e and remained a b s e n t h o m t h e solution during the approximately PO0 hr at QDOnQ: w h i l e t e s t s w e r e made. Subsequent hydrofluorination of t h e extraction s y s t e m with an MF-H, mixture (1:20 volume ratio) s h o w e d that 2 3 3 P a could be rapidly and almost quantitatively returned to solution i n thc s a l t phase. 'Typical r e s u l t s of thcw? experiments a r e shown i n Fig- 3.7. In t h i s experiment thorium metal was a d d e d after the sblt mixture w a s m t t o d u c e d into t h e extraction v e s s e l i n order to demonstrate the n e c e s s i t y oi the reduction reaction. T h e o b j e c t i v e of experiments now in p r o g r e s s IS to examine methods for recovering 233Pafrom the extraction s y s t e m . T h e proposed use of macio q u a n t i u e s of 2 3 1 P a may be required to

OHNL.--LMG 66-970

WITHOUT ADDED THOHIUM

'V'

EXTRACTION TIME ( h i ) Fig.

3.7.

E f f e c t of Thorium Metal on the Extraction

af 2 3 3 P a from

head SysPem

tiF-BeFg-fhFq(73-2-25 Mole %) 600째C.

in Salt-

circumvent t h e anticipated adsorption of the m i c r o q u a n t i t i e s of 233Pa,currently used, on the w a l l s of the container, or on other i n s o l u b l e s p e c i e s in t h e system. Additional s t u d i e s of ihe delibe r a t e precipitation m d adsoiption of 3 3 3Pa on solid, stationary b e d s s u c h as s t e e l wool will b e made for comparative evaluation.

BILITY OF ~

J. W, Shaffet F. A. Doss

~ INRMOLTEN I ~ LEAD ~

W. K. R. F i n n e l l W. P. T e i c h e r t

Current s t u d i e s of the removal of protactinium from a molten fluoride mixture, w h i c h s i m u l a t e s t h e blanket of t h e reference d e s i g n I\/ISBR, h a v e been directed toward t h e development of a Iiquidliquid extraction process. The m e t hod proposes that protactinium, as PaF', in a salt phase, c a n b~ reduced to its metallic s t a t e i d e x t r a c t e d i n t o a molten-metal phhse. The possible u s e of a molten mixture o f thorium in l e a d would providc a convenient method for combining t h e reducing a g e n t with t h e metal-phase e x t r a c t a n t a n d for replenishing thorium to t h e fluoride blanket mixture. T h e o b j e c t i v e of t h i s s t u d y h a s b e e n to e s t a b l i s h t h e solubility of thorium i n l e a d over t h e temperature range of i n t e r e s t to t h i s program a n d to provide a lead-thorium s o l u t i o n of known composition for s u b s e q u e n t protactinium-extraction experiments. T h e experimental mixture, contained i n lowcarbon s t e e l , c o n s i s t e d of approximately 3 k g of lead a n d PO0 g of thorium-metal chips. V a l u e s for the s o l u b i l i t y of thorium were obtained by a n a l y s e s of filtered s a m p l e s withdrawn from t h e melt a t s e l e c t e d temperatures over t h e interval 400 to 600째C under a s s u m e d equilibrium conditions. Samples were withdrawn during two heati n g and c o o l i n g c y c l e s a n d submitted for activation a n d spectrographic a n a l y s e s . T h e s e res u l t s , plotted a s t h e logarithm of the s o l u b i l i t y v s the reciprocal of t h e a b s o l u t e temperature in Fig. 3.8, i n d i c a t e that t h e h e a t of solution of thorium in lead 1s approximately 19 kcal/mo?e and t h a t its solubility a t 60O0C i s a b o u t 1.85 x m.f.

ORNL- DWG 65 - 9 7 (

1 EMPEROTURE (“C) 3 .O

600

550

500

450

400 F i g . 3.8.

Temperature Dependence of the S o l u b i l i t y

of Thorium i n Molfen L e a d .

;2.0

0 -; 4.5 c

-2 n

1IJ

z E

I,.

0.8

0.6

& r%

0.4

0 Z

0 <>

0.2

PROTACTlNlUM STUDIES IN THE HI@ MOLTEN-SALT LABORATORY C. J . Barton ‘The Reactor Chemistry Division h a s , for t h e p a s t few y e a r s , l a c k e d f a c i l i t i e s for r e s e a r c h with s i g n i f i c a n t q u a n t i t i e s of alpha-active materials s u c h a s 239Puand 231Pa. I n t e r e s t i n u s i n g t h e l a t t e r i s o t o p e a s a stand-in for t h e more radioactive 233Pa led to construction of the High-Alpha Molten-Salt Laboratory which is shown i n F i g . 3.9. Seven interconnected glove b o x e s a r e presently installed i n t h e laboratory, and o n e e n d of t h e train is connected t o a gloveequipped hood. T h e glove boxes are maintained a t a negative pressure with r e s p e c t to the lahoratory by a n automatic control s y s t e m , and t h e room is a t a negative p r e s s u r e with r e s p e c t to the surrounding a r e a . ’The glove-box e x i t a i r is doubly filtered, and a l l air e x h a u s t e d from the room d i s c h a r g e s through t h e plant c e n t r a l off-gas system. T h e glove boxes a r e equipped for, or are adapta b l e to, a variety of operations, but t h e study

of the removal of protactinium from molten-fluoride breeder-blanket mixtures and supporting b a s i c research a r e the principal u s e s planned for t h i s A Z e i s s polarizing microscope, a laboratory. Mettler b a l a n c e , and a quenching-furnace arrangement a r e mounted i n s e p a r a t e glove boxes. T h e s t a i n l e s s s t e e l box at t h e right s i d e of t h e a n g l e of t h e train in Fig. 3.9 i s fitted with a s t a i n less s t e e l h e a t i n g w e l l that is welded to t h e bottom of the box and is surrounded by a 5-in. tube furnace. Most of t h e high-temperature s t u d i e s other than quenching will b e performed in t h i s box which is also equipped with a manifold to control application of vacuum or admission of helium, hydrogen, or HF to flanged p o t s in t h e h e a t i n g well. An experiment w a s performed i n t h i s box to confirm t h e oxide precipitation of protactinium from molten s a l t s reported earlier. l 4 P r o t a c t i n ium a t tracer concentration (<1 ppb 233F‘a) w a s completely precipitated by addition of thorium oxide to molten L i F - B e F , - T h F , (73-2-2.5 mole %), and treatinent of t h e oxide-contaminated melt with a dry mixture of I W and IlTz r e d i s s o l v e d t h e protactinium, in agreement with the r e s u l t s of t h e previous investigators. An ion exchange method reported by ChethamStrode a n d Keller17 w a s u s e d to purify about 0.1 g of 231Pa,0,. T h e oxide w a s d i s s o l v e d i n 2.5 M H F and loaded on a n anion e x c h a n g e bed. Elution with 17 M IIF gave a purified fraction e s s e n t i a l l y f r e e of alpha-emitting daught e r s and, according to the originator of t h e proce s s , f r e e of niobium which w a s present as a n impurity in t h e oxide received from England. T h e purified 2 3 1 P a fraction will h c u s e d for further s t u d i e s of protactinium recovery from breeder-blanket mixtures. I 7 A . C h e t h a n S t r o d e , Jr., and 0. L. Keller, Jr., “Ion E x c h a n g e of Protactinium(V) i n H F Solutions,” p a p e r p r e s e n t e d at the International Conference on P r o t o c t i n iuin Chemistry, Orsay, F r a n c e , J u l y 2-8, 1965.

Fig. 3.9. V i e w of Glove Boxes in High-Alpha Moiten-Sult Laboratory.

beaker, w a s used as the melt to which impurities Stirring was accomplished with a Pyrex propeller s t i r r i n g rod sevolving at 700 rpm. T h e bealter was lowered from a hot z o n e to a c o l d z 0 n e a t a rate of about 2 cm/hr; this w a s near the Power l i m i t of rates that were deemed oE practical i n t e r e s t and w a s not changed. After some preliminary t r i a l s , the segregations shown i n T a b l e 3.1 were obtained while u s i n g a coiled CaLrod heating element. Beneath the heating element there was a ring zuth holes through which cooling air w a s blown; this helped fix t h e location of t h e freezing front.

were added.

H. A. Friedman

F.F'. Blankenship

?urification by freezing is p o s s i b l e under soiiie circumstances In t h e a b s e n c e of solid-solution formation arid with freezing rates sufficiently !jl<Pw that rejected solute c a n diffuse s w a y from the advancing freezing front, high d e g r e e s of purification c a n be achieved; i n principle, this p r r x e s s might be applicable to reprocessing he1 melts from a molten-salt. reactor. Slowness is o n e cf the Gbvious d i s a d v a n t a g e s of ? h i s method. Stirring, to reduce t h e t h i c k n e s s of tbe fixed f i l m through which diffusion must occur, strongly iniluences the rate at which freezing can be effective. A few experiments were catried out to determine whether the stirring a v a i l a b l e with ordinary laboratory equipment would be a d e q u a t e to give good separation of salts a i freezing rates w f f i c i e n t l y high to h e of potential practical interest. F a r convenience and visibility, tlie LiCl-KCl eutectic, contained in an open 400-ml Pyrex ~

P a r t of each ingot containing PAC1, w a s exposed to moisl: 13,s t o rxwverl. like lead to t h e sulfide, thereby developing the concentration gradient for v i s u a l observation. T h e upper jngot i n Fig. 3.30 is the coiiirol which froze without To the left and right a r e the s e c u n d stirring. Zind fourth ingots l i s t e d in T a b l e 3.4. The s h a r p segregation of the impurity into the last liquid to f r e e z e is clearly evident. T h e experiments were regarded as a demonstration of the s u c c e s s f u l purification of a s a l t mixture by f r e e z i n g w i t h rapid stirring.

46 Table 3.4. Chemical A n a l y s e s af Frozen Ingots Approx irna t e Concentration of Solute Added

Solute

PbC:lZ

(ppm)

Remarks

_ _ _ _ _ I

Bottom

Center

Top

9 00

760

850

1000

H e a t e d with gas-ring burner; n o stirring

1100

(30

140

6700

Started u s i n g method d e s c r i b e d a s t h e f i n a l

(PPm) PbClza

Chemical A n a l y s i s

apparatus; u s e d double-propeller s t i r r e r PbCl PbCl2

1100

<60

960

<60

<12.50

2650

Same method

4940

Same method e x c e p t u s e d sinprle-propeller s timer

790

NIF 2 b Sild?

1000

UF,

1160

391

455

Same method a s d i r e c t l y above

500

1900

Melt remained cloudy; r e s u l t s may have b e e n c o n f u s e d by i n s o l u b l e oxide

3130

Slight clouding of melt

aControl experiment t o show e f f e c t of no stirring.

bRegarded a s failure d u e t o solid-solution formation.

Fig.

moist

3.10.

H2S

Segregation o f PbClp i n F r o z e n I n g o t s of L i C l - K C I E u t e c t i c .

t o d e v e l o p the c o n c e n t r a t i o n p r o f i l e .

segregation w i t h stirring.

Upper s a m p l e :

I n g o t frogrnents were treated w i t h

control, w i t h o u t s t i r r i n g .

L e f t and right: t y p i c a l

4. Direct Support for

j. pi. Shatfeic

vi'.

K. R. F'inncll

out enriched uranium, was then transferred to t h e reactor circuit, was circulated there for some 250 hr i n a precritical t e s t (PC-21, and was returned to f.he MSRE drain tank. 'Ynere, enriched f u e l conceritrate w a s added. Four additions of t h e conc e n t r a t e (with criticality tests of t h e fuel i n t h e reactor core interspersed) brought t h e 2 " 5 U inventory of t h e drain-tank contents to 58.76 kg. T h e s e operations had been accomplished in a routine manner by previously described techniques by late May 8965. Additions of enriched fuel. concentrate to t h e MSRE tank had, a s anticipated, brought t h e 2 3 5 U eoncenitation to more t h a n 95% of that required for ctii:icaIity. The remaining '3siu w a s added to t h e f m l circulating i n MSRE as s o l i d pel Sets of enriched fuel (:oncetiirate i n s m a l l !iicItei capsuIes. 'These capsules, each containing about 85 g of 2 3 5 ~ in about 148 g or the 'L~F-LJF, e u t e c t i c , were Eilled from a s i n g l e l u g e batch 01 enriched iuel concmtrate, Capsules were constructed from b i n . les1gthhs of nickel tubing with ?pi*L ouler ciiameters, Dat335-in, walls, and hemispherical bottoms, 2712 lop plug w a s perie1ral.t.d by T W O 3 ; - i n . - ~ ~x O,O2.Â§in.-wall nicliel fill tubes. Seven c a p s u l e s were conr,t?c:ted it1 seric2.s by their $s-in, iili tubes and cliistererl within 'L1 '%ifla - d i m chamber which w a s externally heated. ';'he inlet and outlet Mi tubes to t h e c l u s t e r were c ~ r i i i e c t dby t u b e fittings to the salt transfer litie and to a n overfl.:,w reservoir, T h e asijembiy was heated to 600Â°C:;helium ptess u r e was applied to the sal!: storage container t o flow the molten fluoride n~iwtureinto t h e cliistered capsiiles. Displaced gases w e r e vented through the top of t h e overflow reservoir. Liquid levels i n $.hec a p s h i e s were visually observed b y radiograpby with a portable x-ray unit atid a 'TVX cartiera.

F a A. Doss VI. P. 'I'eicliert

T h e preparation of all MSRE fluoride mixtures and the loading of these mixtures into the reactor drain t a n k s h a v e been corrrpla:ted by Reactor C n e m itstry B i ~ i s i o n personnel.. Preparation of the secondary-coolant a n d the flush s a l t (t.otaling ~ ~ ; , o oIbo of ' L ~ F BeFz mixture containing 66 mole % 'LiF) was completed arid the mixture w a s loaded into t h e MSRE duting 1 9 6 4 . ' ~ ~ MSKE fuel w a s prepared as t h e following salt. compositions: Fuet s o l v e n t ( 7 L i F - R e F 2-ZrF,, 64.7-30.1-5.2 mole %)# d e p l e t e d fuel concentrate (7LiF-2"TJF4, 73-27 mvle %-I, arid enriched fuel concentrate ( ~ ~ , ~ F . 4'- ~73-27 ~ ~ mole u u F%>. 'The enriched fuel concentrate (six hatches, each cor~taining about 33 I b o f 2 3 5 U ) :~nd m ~ of ~ thet 7.8.6100 Ib of fuel solvent were prepared during 1964.''~ The few remaining batches (each of ahiaut 275 hb) of this material. and the two batches (OS about 600 10) of depleted fuel ccancentrate were prepared during early 4965 I q t h e technique des c r i b e d previously. Loading of the file1 mixtures into t h e MSRE to a c h i e v e final f u e l composition for cziticality and f a r eventual power operatjon w a s completed during t h i s reporting period. Initial Loading consisted i n the t r a d e r of 113,050 Ib of luel solvent to t h e fuel drain tank and the addition of 520 1) of depleted fuel concentrate. 'This rii~xture, quite near to :he ultimate fuel composition but esseiitially with9

3P. N. Ilaubenx~ich,private i.ornmunication (Aug- 16, 1965).

Fig. 4.1.

F i l l i n g of F u e l - E n r i c h i n g C a p s u l e s for MSRE.

T h e c a p s u l e c l u s t e r and salt transfer l i n e were cooled t o near room temperature while back flowing helium through t h e systein. T h e filled c a p s u l e c l u s t e r w a s disconnected from t h e assembly and its e x p o s e d t u b e s w e r e capped. T h e net weight of salt mixture in t h e c l u s t e r w a s determined, and t h e c l u s t e r w a s s e a l e d in a water-tight c a n . A photograph of t h e equipment during a typical filling operation is shown i n F i g . 4.1. T h e lGl c a p s u l e s were filled, a t a rate of about five c l u s t e r s per day, during a fivc.-day period, working two s h i f t s per day. Although t h e accountability of 2 3 5U w a s maintained for e a c h c a p s u l e cluster, e a c h c a p s u l e was photographed by x r a y s before and after filling. T h u s , minor variations i n weight from c a p s u l e to c a p s u l e could be c a l c u l a t e d from measurements on t h e c o n t a c t prints. T h i s examination revealed no

d e f e c t s i n t h e c a p s u l e c l u s t e r s nor any variation i n uranium density in t h e frozen s a l t mixture. F o r u s e i n t h e MSRE, t h e c a p s u l e s wcre d e t a c h e d from t h e c l u s t e r , t h e inlet and outlet t u b e s were s e a l e d , and t h e c a p s u l e s were opened and inserted through an appropriate mechanism into t h e ciicul a t i n g f u e l i n t h e MSRE pump bowl a s needed.3

CHEMICAL BEHAVIOR OF FLUORlDES

DURING MSRE OPERATION R. E. T h o n a

T h e n e c e s s a r y s e r v i c e operations and t h e e v a l uations to determine whether t h e iiiolten fluorides retain their chemical purity during MSRE operation

form a n important, integral part of t h e MSKE sup-

port program. In preparation for t h i s effort, invest i g a t i o n s h a v e b e e n made - and i n some cases a r e continuing - i n s u c h d i v e r s e l i n e s a s c r y s t a l l i z a tion behavior of reactor s a l t s , solubility of p o s s i b l e contaminant o x i d e s as a function of temperature, compatibility of fluorides with their metallic environments, and t h e e f f e c t s Qf irradiation o n molten and frozen s a l t s . ' In a c l o s e l y cooperative effort, t h e OKNL Analytical Chemistry Division h a s developed methods for routine-basis a n a l y s e s for t h e s e v e r a l s p e c i e s w h o s e concentrat i o n s must b e known iE cliemical integrity oâ&#x201A;Ź t h e s y s t e m is to be assured. Initial, precritical operation of t h e MSRE (run PC-1) w a s performed with flush salt (7LiF-BeF,, 66 m o l e 76 7LiF) i n t h e fuel circuit. T h i s flush s a l t , therefore, constituted t h e frozen-salt s e a l i n t h e f r e e z e f l a n g e s and t h e f r e e z e v a l v e s of t h e c o r e circuit. After circulation for a 1000-hr t e s t (and for removal of o x i d e s c a l e , i f any, from t h e reactor circuit), t h e flush s a l t w a s drained to its own s t o r a g e tank. 'fieere it w a s treated with â&#x201A;ŹIF and I i 2 to remove o x i d e before r e u s e ; a reassuringly small quantity, Corresponding to 115 ppm of 0 2 - , w a s recovered as H,O in t h i s s t e p , T h e fuel mixture w a s then constituted - with a n interruption for t h e PC-2 test - in t h e fuel drain tank and t h e reactor circuit as described in the s e c t i o n immediately precediilg. S i n c e t h e reactor circuitry does not drain perfectly, the not unexpected r e s u l t w a s t h e dilution of t h e f u e l mixture by s o m e flush s a l t l e f t i n t h e reactor from PC-1. This dilution resulted in a disparity between nominal and analytical v a l u e s for uranium conc e n t r a t i o n s i n PC-2 and i n differences between 'U enrichment v a l u e s nominal and measured We b e l i e v e during t h e zero-power experiments. that approximately 140 l b ( l e s s t h a n 1.5%)of t h e ' L i F - B e F , flush-salt diluent remained in t h e f u e l circuitry at t h e end of t h e PC-1 t e s t and w a s '

'H. A. Friedman and R. E. Thoma, Redctor Chrm. D t v . Ann. Prugr. Rept. Jan. 31, 1965, ORNL-3789, p. 7. 5MSR Program Sernzann. Pmgr. Xef>t. J a n . 31, 1964, ORNL-3626, p. 117.

6A. L. Mathews, C. F. B a e s , a n d B . F. Hltch, Rrdctor Chwn. DIV.Ant,. Progr. R e p t . J m . 31, 1965, ORNL3789, p. 56.

7W. R. Grimes, MSR Program Semlann. P m g r J u l y 31, 1964, ORNL-3708, p. 238.

Rept.

*F. F. Blankenshlp, MSR Progrum Sumarm. Pro&. Rept. J u l y 31, 1 9 6 4 , ORNL-3708, P. 252.

r e s p o n s i b l e for t h e apparent discrepancy. Careful chemical a n a l y s i s and mass-spectrometric determination of t h e 2JsU/'38U ratio i n d i c a t e t h a t t h e cxiticd concentration i n the MSKE w a s 4.453% by weight of U (1.39% 23sU). T h i s figure i s lower b y P.26'% than t h e book v a l u e of 4.51% U.

A n a l y s i s of s a m p l e s for metallic corrosion products continues t o i n d i c a t e that, a s expected, corrosion of the INOR-8 by t h e fluoride nielts is insignificant. T h e compounds N i F z and FeF2 are u n s t a b l e toward reduct.ion by C r i n INOR-8; t h e s e fluorides would b e corrosion agents, therefore, i f present i n t h e fluids. Neither FeF, nor N i F , is s t a b l e toward reduction by Iiiz a t e l e v a t e d temperatures; t h e pretreatment of fuel, flush, and coolant s a l t s with HF-H, and then H a should, therefore, h a v e removed other fluorides completely. Chemical a n a l y s i s of t h e fluoride mixtures before introduction i n t o t h e reactor showed about 5 ppm of N i and about 125 ppm of F'e. We b e l i e v e that t h e s e materials a r e present largely, i f not entirely, a s colloidally s u s p e n d e d metals. On t h e other hand, C r F z i s riot reduced by H,; t h e analyzed concentration of Cr (about 30 ppm initially) is believed t o be present a s Cr".

During t h e PC-1 t e s t , with 7LiF-BeF2 (66 mole % 7LiF) i n the fuel and coolant c i r c u i t s , chromium

concentrations in t h e melt i n c r e a s e d by about 25 ppm in t h e fuel circuit and by about 10 ppm i n t h e coolant circuit; t h u s , about 100 g of Cr w a s removed from t h e interior w a l l s of t h e reactor circuit. Nickel concentrations remained a t about 5 ppm during t h i s test, while Fe concentrations dropped by about 50 pprn. C)ccurrence of 50 ppm of F e z + i n t h e initial m e l t is ( a s i d e from t h e material-balance difficulty) s c a r c e l y credible. T h e d e c r e a s e i n Fe concentration, therefore, w a s believed to b e due to s e t t l i n g of s o m e 200 g of Fe powder i n t h e drain tank or in t h e circuit. T h e i n c r e a s e in chromium concentration represents, we believe, a real i n c r e a s e i n Cr"; it is probably d u e to dissolving of oxide f i l m s from t h e reactor circuit w a l l s and t h e subsequent reduction by C r of t h e Cr , ' Fe +,and Ni s o obtained. +

A n a l y s e s for F e , Cr, and Ni in t h e reactor fuel of PC-2 and of subsequent c r i t i c a l and zero-power runs (totaling about 1100 hr) show n o appreciable concentration c h a n g e s . T h e failure of Cr" 1.0 i n c r e a s e in concentration is not surprising s i n c e t h e o x i d e s s h o u l d h a v e b e e n well removed i n PC-1 and s i n c e t h e fuel mixture w a s thoroughly treated

50 with Id, (to t h e extent that about 2% of t h e uranium w a s present a s U3') before addition t o t h e reactor. Purity of t h e fuel during PC-2 and t h e zero-power t e s t s w a s a s s u r e d by chemical a n a l y s i s of daily s a m p l e s . V a l u e s for t h e concentration l e v e l s of a l l contaminants except oxide were uniform, credible, and satisfactorily low. Oxide v a l u e s , obtained by t h e KBrF4 m e t h ~ d ,were ~ sporadic and high, presumably a s a result of water adsorbed in s a m p l e s during sample preparation. Verification that oxide concentration did not s e r i o u s l y e x c e e d t h e solubility limits w a s made by regular examination of s a l t s p e c i m e n s ernploying petrographic methods, which under favorable circumstances c a n d e t e c t t h e p r e s e n c e of a few hundred ppm of c r y s t a l l i n e oxide. In recent months, a n improved method for drtermining t h e oxide concentration of MSRE s a l t s h a s been developed. l o T h e method employs t h e reaction

Oxide concentration is regaided a s equivalent t o t h e quantity of water evolved a s a molten-salt specimen is purged with a n I-12-HF g a s mixture. T h e method h a s been applied for a s s a y of t h e flush- and fuel-salt s p e c i m e n s obtained during initial operations of t h e MSRE full-power t e s t s . Oxide concentration w a s found t o b e approximately 100 ppm i n both t h e flush and fuel s a l t s . l 1 F r o m a chemical standpoint, t h e operation of t h e h1SRE during t h e precritical and zero-power experiments w a s a s u c c e s s . T h e r e is every reason t o b e l i e v e t h a t t h e s a l t s were maintained i n a n e x cellent s t a t e of purity during a l l transfer, fill, and circulating operations.

'G. Goldberg, A. S. Meyer, Jr., a n d J. C. White, Anal. Chem. 32, 314 (1960).

'OMSR Program Semiann. Progr. Kept. Aug. 31, 1965, OHNL-3872, p. 140. "A. S. Meyer, Jr., communication.

unpublished work and p e r s o n a l

K. E. 'Thoma

B. J . Sturm

Relatively few measurements of t h e d e n s i t i e s of liquid s a l t mixtures have been made in t h e

development of ORNL molten.-salt technology. V a l u e s h a v e usually been obtained from e s t i m a t e s s u c h a s t h e relatively imprecise method of mixtures employed by Cohen and J o n e s , b a s e d on roomtemperature d e n s i t i e s of t h e components, or t h e more s a t i s f a c t o r y method employed by Cantor, which a s s u m e s additivity of molar volumes. In a n effort to obtain more a c c u r a t e experimental v a l u e s , we have measured directly t h e volumes of molten-salt mixtures 3t various temperatures. Knitial r e s u l t s of t h e s e experiments were reported previously. l 4 By adopting s e v e r a l experimental innovations, w e h a v e improved t h e accuracy of experimental d a t a appreciably. One s u c h measure is t o prevent s a l t mixtures from freezing until a l l volume measurements h a v e been completed. In t h i s way, errors in t h e volume measurcment arising from distortion of t h e container v e s s e l upon freezi n g and remelting t h e s a l t s a r e avoided. V a l u e s obtained by t h i s experimental procedure are c o m pared with previous v a l u e s i n T a b l e 4.1. T h e equation for density, d, a s a function of ternp-,rature is d -a-

bt.

T h e new v a l u e s a r e considered t o b e i n agreement with t h e recent measurements of t h e s a l t s stored in drain t a n k s a t t h e MSRE s i t e . 3 ...................

" S . I. Cohen and T. N. J o n e s , A Summary of D e n s i t y Measurements o n Molten F f u o r i d e Mixtu:es a n d a Correlation f o r P r e d i c t i n g D e n s i t i e s of F l u o r i d e Mixtures, OKNL-1702 (July 19, 1954, decl. NOV. 2, 1961). I3P. B. Bien, S. Cantor, a n d F. F. B l a n k e n s h i p , R e a c t o r Chem. Div. Ann. Progr. Rept. Jan. 31, 1961, ORNL-3127, pp. 24-25; S. Cantor, R e a c t o r Chem. Div. Ann. Progr. Repf. Jan. 31, 1962, ORNL-3262, pp. 38-41.

I4B. J. Sturm a n d R. E. Thoma, R e a c t o r Chem. Div. Ann. Progr. Repf. Jan. 31, 1965, OKNL-3789, pp. 8381.

Table 4.1. D e n s i t i e s of Molten-Salt M i x t u r e s Density Parameters Melt a n d Composition

( s / c m 3,

Method

in Mole %

D e n s i t y (g/crn3) 650째C

600%

Estimate

MSRE Coolant:

66 LiF, 34 FhF,

1.85

Method of mixturesa

2.24

0.0006

Sum of molar volumesb

2.152

0. 000391

1.898

Lindauerctd

2.160

0.00040

1.90

2.158

0.00037

1.921

Measurement Mound Laboratory e P r e s s u r e probed'*

1.954 1.986 2.296

0.000482

1.983

Method of m i x t u r e s U

2.61

0.0007

2.15

sum of m o l a r volumesb

2.670

0.000594

2.384

2.848

0.000769

T h i s vrork Estimate

MSRE Fuel: 65.0 LiF, 29.17 BeF,,

5.00 ZrF,, 0.83 U F 4

Measurement

2.331d

Haubenreich'

T h i s work Volatility Solvent I:

2.348

Estimate

62.5 K F , 20.8 ZrF4,

Method of m i x t u r e s "

2.92

0.0007

2.50

16,7 A1F3

Sum of molar volumesb

3.298

0.000992

2.703

3.178

0.00106

2.54

Method of mixtures"

2.91

0.0007

2.49

Sum of molar volumesb

3.350

0.001038

2.728

T h l s work

3.202

0.00105

2.57

Measurement T h i s work Volatility Solvent 11:

57.7 K F , 19.2 ZrF,, 23.1 A l F ,

Estimate

Measurement

aORNL- 1702. bC)RNL-.3262, pp. 38-41. C P e t e r P a t r i a r c a , private communication (June 1965). 'Originally

reported i n E n g l i s h u n i t s b u t converted t u metric for comparison i n this report.

eMLM-1086 'J. R. E h g e l , private communication (February 1965).

N. I J a u b e n r e i r h , p r i v a t e communication (Aug. 15, 1965).

Part I1

Aqueous Reactors

5. Corrosion and Chemical 8ehavior in Reactor fnvironments t h e activation-energy terms, I t w a s further shown that B could be interpreted in terms of parameters which h a v e fundamental significance:

MECHANISM OF ANODIC FILM GROWTH ON ZIRCONIUM AT ELEVATED TEMPERATURES A. L. Sutton

A. L. B a c a r e l l a

(3)

It w a s shown previously , 2 that t h e anodic-filrngrowth current for zirconium i n oxygenated 0.05 I n H,SQ, at temperatures from 200 to 284째C cat1 be represented by a hyperboljc s i n e function of the field strength,

2iQ s i n h ( B V / X L )

where q is t h e charge oil t h e anion vacancy, a is t h e activation d i s t a n c e , kT is the Boltzrriann energy factor, E is t h e d i e l e c t r i c c o n s t a n t of t h e oxide a t temperature T , and the term [(c i-3 / 3 1 )i ( V / X , ) is t h e local (Lorentz) field effective in the transport of anion v a c a n c i e s . T h e temperature dependence of t h e d i e l e c t r i c c o n s t a n t t was shown to give v a l u e s for ( p ) V which were r e a s o n a b l e and independent of temperature. During t h e p a s t year t h e anodic-film-growth rea c t i o n w a s studied further, and t h e measurements were extended to 174째C. A large number of measurements were performed t o obtain a better s t a t i s t i cal e s t i m a t e of the parameters, particularly those implicit i n io. On t h e b a s i s of t h e model used,

(1)

The f i r s t term in the exponcntial form of t h e equation r e p r e s e n t s t h e current flow a s s i s t e d by the field, and t h e s e c o n d term t h e current flow a g a i n s t A t low temperatures and s m a l l film the field. t h i c k n e s s e s (hxgh field strengths), the s e c o n d term becomes negligible, and t h e "high-field" approximation is valid:

where V / X 1 , is t h e average macroscopic field a c r o s s t h e film t h i c k n e s s XL, 63 is t h e field coefficient, and io c o n t a i n s terms which a r e independe n t of t h e field strength and i n c l u d e s t h e concentration of the mobile i o n s (anion v a c a n c i e s ) and

e x p (-+,/RT)

: i

, (4)

where 10' coulombs per faiaday converts transport of c h a r g e t o u n i t s of amperes, 2a is t h e jump d i s t a n c e , Y (10" to per s e c o n d ) is t h e frequency factor for anion vacancies, C is t h e cone x t r a t i o n of anion v a c a n c i e s (a function of position in t h e oxide), and q5f and ci,, a r e the activation e n e r g i e s for t h e formation and transport of vacnncies.

..___

I,. Bacarella and A. L. Sutton, Reactor Chem. D i v . A n n . Pro&. Rept. J a n . 3 1 , 1965. ORNL-3789.

'A.

pp. 135-38.

'A. L. F3acarella and A. L. Sutton, Elerttochemicaf Technology, in press.

56 T a b l e 5,1.

Parameters in the R a t e Equation for Anodic F i l m Growrh

V = 2.25 v ; q = 1 e

5.02 x

19.3 x

lo-’

6.00 x

24.4 x

lo-’

7.33 x 10-6

447

2.4 x

474

1.15 x

505

8.7 x

525

2.6 x 1 0 - ~

8.54 x

5 57

9.7 x

10.2 x 4.75 x 10-6

2 98

lop6

Earlier h a v e presented a description of t h e electrochemical c e l l and t h e experimental methods. Experimentally, we obtain t h e anodicfilm-growth current i i n amperes per s q u a r e centimeter a s a function of time a t constant potential and temperature. T h e correlative film t h i c k n e s s e s are obtained by integrating t h e anodic current with t i m e and by assuming an i n i t i a l t h i c k n e s s X o = 100 A:

2.88 x l o 5

i dt

3.44

1.53

3.41

1.53

31.8k

3.55

1.58

39.1 x lo-’

3.52

1.56

48.8 x 10K8

(96)

(3.59)

(1.59)

12.2 x l 0 l 8

2.75

1.22

lo...’

through anion-deficient zirconium dioxide films u s i n g t h e “iriterrupted-kinetics” technique6 and h a s reported 4 :31.1 kcal/mole, a value in near agreement with our revised value. ‘This agreement s u g g e s t s further that t h e rate equation used to fit t h e data provides a satisfactory b a s i s for an explanation of t h e film growth. Considerations of the concentration tem C ( X ) in Eq. (4) were made, in which i t w a s assumed that

i- 1 0 0 .

Dielectric c o n s t a n t s previously reported were obtained from but a few measurements and were in error by about 20% b e c a u s e of an unsatisfactory experimental design. T h o s e to be reported here a r e b a s e d on a larger number of measurements and a r e believed to b e more reliable estimates. T a b l e 5.1 contains a more recent compilation of t h e parameters in t h e r a t e equation. F i g u r e 5.1 is a n Arrhenius plot of t h e preexponential current io. ‘The revised value for t h e activation energy, 6 , + qbt, obtained from t h e s e d a t a is 29.5 3 kcal/mole, compared with our previously reported 26 rt 2 kcal/mole. Tennyson Smith5 h a s determined t h e activation energy for diffusion of oxygen

in o n e case and that

C ( X ) = C o exp ( - R X ) i n another case, with C o / C L a c o n s t a n t independe n t of X L . ‘The field w a s taken a s t h e general. function of X , E ( X ) . It w a s found that either distribution of v a c a n c i e s led to an equation i n which t h e vacancy concentration C ( X ) is Co:

3A. L. B a c a r e l l a and A. I.,. Sutton, J . Electrochem. S O C . 112, 546 (1965). 4A. L. Racarella, Reactor Chem. D i v . Ann. Progr. R e p t . J a n . 3 1 , 1962, ORNL-3262. pp. 86-89. 5 Tennyson (1965).

Smith,

J. Electrochem. Soc.

112.

560

‘A.

(1960).

Rosenburg, J . E l e c t r o c h e m , Soc.

107, 795

57 MECHANISM OF RADIATION CORROSION OF ZIRCONIUM AND ZIRCALOY-2 R. J. Davis

G. H. J e n k s

O x i d e Growth a n d F i l m C a p a c i t a n c e o n

Pre i rra di a red S p e c i m e n s

P r e v i o u s work,' which showed that reactor irradiation of Zircaloy-2 c a u s e d a c c e l e r a t e d postirradiation corrosion, was extended t o crystal-bar zirconium. Specimens were: (1) pickled in HFHNO,, (2) vacuum (1 to 3 >i mm Hg) annealed a t 700째C to remove t r a c e s of fluoride, and (3) e x p o s e d to 300OC steam-oxygen for 1 hr and h e a t e d in helium a t 500OC for 16 hr to provide a n oxygenrich layer near t h e surface. The subsequent treatments were t h e s a m e as in previous experiData from two specimens, o n e irradiated ments. and o n e control, s h o w t h a t t h e irradiated specimen corrodes about twice as fast as the control. It is i n d i c a t e d t h a t t h i s radiation effect' is not related to t h e a d d i t i v e s i n Zircaloy-2 nor to fluoride leEt by pickling.

z n W

S e a r c h for

New Methods to Study

Oxide-Film Properties

4.70

1.80

1.90

2.00 'Oo0/T

Fig. 5.1.

Arrhenius

2.10

2.20

2 30

2.40

(OK)

Plot o f the Breexponentiol Cur-

rent io in t h e R a t e E q u a t i o n i = io cxp ( B V / X ) .

where E(X), is t h e field a t X equal to zeto. Comp a r i s o n s between t h e v a l u e s of C ( X ) obtained u s i n g the d a t a i n T a b l e 5.1 and t h o s e e v a l u a t e d by other workers' e 7 u s i n g different approaches show reasonable agreement considering t h e probable uncert a i n t i e s of t h e values. Although t h e form of E ( X ) , is not y e t known, we b e l i e v e t h a t t h e r e s u l t s of t h e considerations i n d i a t e that the empiric-a1 equation (1) c a n be interpreted i n terms of parameters of fundamental significance. 7R. F. nomagala and 2 3 8 (1954).

D. S . McPherson, .J.

Metals

It c a n b e postulated that t h e irradiation damage Alternatingr e s u l t s i n less protective oxide. current impedance d a t a were c o l l e c t e d * in t h e h o p e that they would distinguish, o n an empirical b a s i s , between o x i d e s of varying protective quality. T h e y did not. Some exploratory work h a s theref o r e been d o n e to find a better method to e v a l u a t e film protective properties, The two prevalent t h e o r i e s of oxidation o f zirconium are: (1) diffusion of anion v a c a n c i e s t.hrough a concentration gradient and (2) diffusion of a n oxygen s p e c i e s through pores. Methods of measuring v a c a n c i e s o r p o r e s w e r e therefore sought. The A n i o n - V a c a n c y G r a d i e n t . - Recently an indirect measure of the anion-vacancy concentration gradient in tantalum oxide w a s reported by others. F i l m c a p a c i t a n o e v s temperature was measured; a b o v e a c r i t i c a l temperature a rapid rise in c a p a c i t a n c e occurred from t h e i n c r e a s e d 'R. J. Davis, Reactor Cherr. D i v . Ann. Progr. Rept. Jan. 3 1 , 1965, CRNL-3789, yp. 126 ff.

'D. >I. Smyth e t a l . , J . Electrochem. S o c . ill 1, 1331 (196-4).

electronic conductivity produced by thermal ionization of vacancies. T h e r e s u l t s enabled a c a l c u l a tion of t h e vacancy gradient. T h i s technique works if t h e electronic conductivity c a n b e made high enough. Our c a l c u l a t i o n s u s i n g reported d a t a ' and observations' i n d i c a t e that t h e required conductivity can b e realized in anodic zirconia films after heating i n inert environments. Exploratory experimental work in which s p e c i m e n s were h e a t e d for short times ((1 hr) in helium or oxygen did not show the effect. PIdditional work is planned. Direct-Current Resistance. - T h e possibility w a s explored of determining d c r e s i s t a n c e of anodic films on zirconium u s i n g c o n t a c t s of mercury, evaporated s i l v e r , and gallium. T h e apparent r e s i s t a n c e s with silver, mercury, or unrubbed gallium drifted to higher v a l u e s with time. Accordingly, i t w a s concluded that t h e s e c o n t a c t s a r e not suitable, a t l e a s t without additional work, C o n t a c t s made by rubbing gallium onto t h e s u r f a c e w e r e s t a b l e , they obeyed Ohm's law, they were t h e same a t either polarity, and they were proportional to film thickness; but they were m o r e than four o r d e r s of magnitude lower than c a n b e reconc i l e d with a c impedances measured in electrolytes. T h e ac impedances with t h e rubbed gallium c o n t a c t s a r e c o n s i s t e n t with t h e d c r e s i s t a n c e and f i t a simple parallel r e s i s t a n c e - c a p a c i t a n c e equivalent circuit. T h i s behavior may result from: (1) t h e gallium filling pores (4 x c m 2 pore area/ c m 2 ) or (2) t h e gallium being rubbed through an outer, high-resistance oxide layer to an inner l a y e r of resistivity about 5 x l o 7 ohm-cm. Since t h e s i g n i f i c a n c e of t h e r e s i s t a n c e s is uncertain, work on t h i s will probably not continue. Permeability. - Zirconia membranes made by d i s s o l v i n g t h e metal s u b s t r a t e froiil 100-v-anodized films are permeable t o potassium nitrate in solution. We h a v e confirmed reported' findings, but we c o n s i d e r t h e interpretations uncertain b e c a u s e i t is p o s s i b l e t h a t pores a r e formed during removal of t h e substrate. Zirconia films a r e permeable to hydrogen' under some conditions and the permeation c a n h e

"Tennyson Smith, J . Electrochem. S O C . 1 1 1, 1020 (1964); 1 1 1, 1027 (1964); 112, 5 6 0 (1965).

"M. L. Y o u n g et al., Some E l e c t r i c a l P r o p e r t i e s of Z i 0 2 Film, AERE-R-4957 (.June 1965).

measured with t h e metal s u b s t r a t e i n t a c t b e c a u s e hydrogen d i s s o l v e s rapidly13 in t h e metal. An a p p a r a t u s to measure hydrogen u p t a k e r a t e s under controlled conditions h a s been d e s i g n e d and partially assembled. Specimens will b e exposed to hydrogen a t 100째C, and t h e hydrogen volume will b e periodically measured to about ? l o e 5 c m 3 ( S T P ) / c m2. Correlation of permeability with corrosion r a t e s will i n d i c a t e whether or not corrosion i s a p r o c e s s of permeation through pores.

EFFECTS OF REACTOR OPERATION ON WFlR COOLANT G. H. J e n k s Final e v a l u a t i o n s ' 4 were completed of: (1) the concentration of e x c e s s oxidant required in the HFIK coolant-moderator to provide r e a s o n a b l e a s s u r a n c e that the concentration of hydrogen ions near fuel-element s u r f a c e s will not differ anpreciably from that in t h e bulk of the solution and (2) t h e expected s t e a d y - s t a t e concentrations of t h e decomposition products of water a t particular concentrations of e x c e s s oxidant. I t w a s concluded that t h e excess-oxidant concentration should b e about :VI 0, or t h e equivalent H,O,. T h e expected s t e a d y - s t a t e concentrations of H,, O,, and H,O, with t h i s e x c e s s oxidant are near M. Comparison between t h e predicted and experimental v a l u e s in t h e HFHR a w a i t s power operation of t h e reactor.

NASA TUNGSTEN REACTOR RADIATIQN CHEMISTRY STUDIES 11. C. Savage G. H. J e n k s E. G. Bohlmann

P o i s o n control solutions of CdSO, a r e b e i n g considered for p o s s i b l e u s e i n t h e N A S A Tungsten Water-Moderated Reactor. Information regarding the effects of irradiation on t h e s t a b i l i t y of t h e s e s o l u t i o n s toward loss of cadmium is needed for a complete evaluation of t h i s poison control system.

"A, H. Mitchell and R. E, Salomon, J . Electrochem. S o c . 112, 361 (1965). 13E. A. Gulbransen and K. F. Andrew, J . Electrochern. Soc. 101, 348 (1954); 101, 560 (1954).

14G. H. Jenks, E f f e c t s of R e a c t o r Operation on H F I R Coolant, ORNL-3848 (October 1965).

59 We h a v e planned and a r e developing experiments to t e s t t h e s t a b i l i t y of CdSO, s o l u t i o n s under electron irradiation, with intensity and o t h e r conditions s u c h that they either s i m u l a t e t h o s e i n t h e reactor or provide a s e v e r e t e s t of t h e s t a b i l i t y under irradiation. T e s t s o l u t i o n s i n c o n t a c t with Zircaloy-2 a t temperatures in t h e range 60 to 120째C will be irradiated a t power d e n s i t i e s up t o 150 w/cm3. T h e solution will be s t a t i c in o n e type of experiment. In another type, t h e solution will b e circulated i n ordct to s i m u l a t e fluid-film conditions in t h e reactor. T h e temperatures, power d e n s i t i e s , solution compositions, and container material will b e t h o s e of p o s s i b l e i n t e r e s t i n t h e reactor, T h e u s e oE e l e c t r o n s rather than reactor radiations is exp e c t e d , from theoretical c o n s i d e r a t i o n s , lo inc r e a s e t h e c h a n c e that a n irradiation effect will occur at a given power density. T h e two different t y p e s of experiments are believed n e c e s s a r y to a s s u r e t h a t t h e radiation s t a b i l i t y is t e s t e d under conditions a t l e a s t a s s e v e r e as t h o s e i n the reactor. Theoretical c o n s i d e r a t i o n s did not e n a b l e u s to predict reliably whether agitation would h a v e a n y effect on t h e solution s t a b i l i t y or, in fact, the direction of an e f f e c t i f one occurred. T h e sialic irradiation c e l l is comprised of a s i n g l e loop of small-bore Zircaloy-2 tubing s t i r rounded by a c o o l a n t j a c k e t , as shown in Fig. 5.2. T h e Zircaloy-2 tubing c o n t a i n s a fine filter at o n e end of t h e !oop. In operation, t h e t e s t solution will b e exposed to radiation i n t h e Zircaloy-2 . tube. I t will then be forced through t h e filter, c o l l e c t e d , and analyzed. T h e temperature will b e con trolled by p a s s in g controlled-tempera ture water through t h e j a c k e t sit a rapid rate, T h e rcs u l t s of component t e s t i n g of the s t a t i c :system h a v e provided r e a s o n a b l e a s s u r a n c e of desigp Feasibility a.nd adequacy. The final t e s t s y s t e m is under construction. Dynamic experiments wi! I b e conducted wi!h a s m a l l , high-speed (35,000 centrifugal pump with which solution is circulated ttirough a s m a l l t u b e which fom's a loop in front of t h e cover p l a t e of t h e pump. T h e diameter of t h e pump is about in., a n d the total liquid volume is a b o u t ';4 a n 3 . All t h e solution will be irradiated continuously during an exposure. T h e t u b e is included in order to provide a c h a n n e l i n which t h e flow is well defined arid i n which f i l m coeEficients c a n b e c a l c u l a t e d m d , if n e c e s s a r y , measured. Calculations

Fig. 5 . 2 . X - R o y Photographs of Static-Cell Mockup. Inner d i a m e t e r of the c o o l i n g c o i l = O.d03 in.; inner d i a m e t e r of the i r r o d i o t i o n c o i l

eter of t h e i r r a d i o i i o n c o i l

I: 0.423 i n . > outer diam0.503 in.

s h o w t h a t t h e required niaxirnurii x/elocity i n t h e !ube d e p e n d s upon diameter and is (25 f p s for a diameter of 26 mils. Tests cf t h e performance of a pump design" were made u s i r ~ ga s t a i n l e s s steel model designed by L. V. Wilson o f t h e Reactor Division. 'The resul1.s showed that t h e bend d e m e a s e d with inc r e a s i n g flow, being, at 33,000 tpm, about 77 Et at shutoff and SI it ai. 220 c m 3 / m i n . The r e s u l t s of e t h e r t e s t s h a v e :jho\vtl. that t h e latter head-flow c a p a b i l i t y is sufficieiit to produce t h e required maximum velocity i n a loop of 26-mil tubing. Some 15Thomipsun Ramo %'ooldridy;e, h r o 9 Jet-Centritcigaf Mercury Punip D e s i g n a n d Perlorrnancc. A n a l y s i s , NAA511-6314, TRW R e p o r t No, ER-5420 ( F e b r u a r y 1964) (corifidentiat).

60 problems with t h e s h a f t s e a l and with wear between t h e s h a f t and h o u s i n g were recognized and remain to b e corrected before a final Zircaloy-2 unit is constructed. T h e r e s u l t s of t h e t e s t s with the pump model and of other completed t e s t s of t h e dynamic s y s t e m i n d i c a t e that t h e design is f e a s i b l e and adequate,

CORROSION SUPPORT FOR VARIOUS PROJECTS J. C. C r i e s s J. L. English

L. L. Fairchild P. D. Neumann

8 ery l I i u m Corm si on T h r e e high-flux reactors either b e i n g constructed or d e s i g n e d will u s e metallic beryllium, e x p o s e d directly to t h e coolant, a s moderator. T h e reactors are t h e High F l u x I s o t o p e Reactor (HFW), the Advanced ‘Test Reactor (ATR), and t h e Argonne Advanced Research Reactor (I\ARR). In t h e first two reactors, t h e coolant will b e water adj u s t e d to a p!-I of 5.0 with nitric a c i d a t a maximum temperature of about 100°C; in the AARR, the coolant will b e deionized water a t a slightly lower temperature. showed that, T e s t r e s u l t s reported previously in water adjusted to a pII of 5.0 and flowing a t 12 to 80 fps, beryllium corroded at a c o n s t a n t r a t e of 1.9 m i l s j y e a r over periods that l a s t e d a s long a s 17,600 hr. A few small p i t s were noted on some of t h e specimens. In t h e s e t e s t s , t h e ratio of exposed beryllium s u r f a c e area to volume of water was 10 c m 2 / l i t e r and t h e s y s t e m contained 22.5 l i t e r s of water, which w a s continuously deionized by p a s s i n g a s i d e stream through a cation exchanger (hydrogen foim) a t the rate of 3 liters/hr. In o n e of the specimens in t h e above s e r i e s of t e s t s , two c r a c k s originated from s t e n c i l e d identification marks on one edge of a specimen, T h e s e were first detected after 10,440 hr of exposure. Prior to t h a t time, all s p e c i m e n s had been examined s e v e r a l times and no c r a c k s had been found. T h i s particular specimen was removed from t e s t after 11,980 hr and subjected to metallographic examination. Figure 5.3 s h o w s the larger of t h e two ..........

16 J. C . Griess e t a ] . , Reactor Chem. Div. Ann. Progr. R e p l . J a n . 31, 1965, ORNL-3789. pp. 122-23.

c r a c k s , which penetrated into t h e metal a d i s t a n c e of 7 mils. Examination of t h e polished specimen under polarized light showed t h e c r a c k to b e transgranular i n nature. T h i s appears to b e t h e first incident of stress-corrosion cracking of beryllium ever reported. In recent t e s t s conducted for t h e AARR i n deionized water at 93°C (200°F) a t 44 f p s , t h e effect of t h e ratio of surface a r e a of exposed beryllium to volume o f water was examined. In t e s t s that l a s t e d in e x c e s s of 1000 hr, i t was shown that when t h e exposed beryllium area w a s 0.45 cm2 per l i t e r of water, t h e beryllium corioded a t a c o n s t a n t r a t e of 2.7 mils/year. Under identical conditions with a surfacf-area-to-volume ratio of 4.5 crii2/liter, t h e corrosion r a t e w a s 1.1 m i l s / year. In both of t h e above t e s t s , t h e total volume of w a t e r i n t h e system was 27.6 l i t e r s and a s i d e s t r e a m vias p a s s e d through a mixed-bed deionizer a t a r a t e of 4.9 liters/hr. ‘This is the s a m e relative rate of deionization that will b e used in t h e AARR. T h e ratio of exposed s u r f a c e area of beryllium to volume of water in t h e AARR i s 2.3 cm2/liter, e sse n t i a 11y midway b e t vi een the c Y t iem e s to s t ed Although one i s o l a t e d c a s e of apparent s t r e s s corrosion cracking w a s observed and a few small i s o l a t e d p i t s were found, t h e t e s t r e s u l t s i n d i c a t e that unclad beryllium will h a v e adequate corrosion r e s i s t a n c e i n the three new reactors. Chemical Development for WFlR Operation

G. H. J e n k s h a s concluded from a study of the expected radiation chemistry of t h e IIFIIZ coolant (water adjusted to a pH of 5.0 with nitric a c i d ) that either oxygen or hydrogen peroxide a t some moderate l e v e l must b e p r e s e n t in t h e coolant to assure t h e s t a b i l i t y of t h e nitrate ions.” It i s , therefore, d e s i r a b l e to monitor continuously the e x c e s s oxidizing capacity of the solution, that is, t h e concentration of oxygen and hydrogen peroxide i n e x c e s s of t h e equivalent concentration of hydrogen. During precritical hydraulic t e s t i n g of t h e HFIR system, t h e u s e f u l n e s s of a continuous oxygen analyzer’ s b a s e d on the reaction of d i s s o l v e d oxygen with thallium metal w a s demonstrated. However, t h e hydrogen peroxide 17G. H. J e n k s , Effects of Reactor Operation in H F I R Coolant, ORNL-3848 (October 1965). la:<. S. G r e e l e y e t ai., Checkout of B c t t i s D i s s o l v e d Oxygen Analyzer, ORNJPCF-60-1-57 (Jan. 14, 1960).

F i g . 5.3. t r a c k i n QMV Beryllium Specimen After 11,980 hr in pH 5.0 Water at 100°C Temperature and 23 fps F l o w . A5 p o l i s h e d ; m a g n i f i c a t i o n SOOX.

p r e s e n t i n t h e reactor water r e a c t s with thallium metal relatively slowly and irreproducibly, so i t w a s n e c e s s a r y to includc a c a t a l y t l c chamber containing a l a r g e s u r f a c e area of platinum to decompose t h e peroxide arid permit measurement of t o t a l a v a i l a b l e oxygen. L,aboratory s t u d i e s s h o w e d that t h e platinum effectively recombines d i s s o l v e d hydrogen and oxygen, so that i n t h e MFIR s y s t e m only t h e e x c e s s oxidant will b e measured. T h i s measurement will be u s e d to control t h e addition r a t e of oxidant (either oxygen or hydrogen peroxide) to t h e HFIR primary coolant. With t h e a b o v e analyzer and con€irrnatory c h m i cal a n a l y s e s , t h e decomposltion rate of hydrogen peroxide i n t h e primary c o o l a n t w a s determlned i n the a b s e n c e of radiation. T h e r e s u l t s indicated t h a t t h e decomposition is a homogeneous solution reaction with a halE-life of about 4 hr a t 105 to 110°F. Hydriding of Zircaloy-2 and Tantalum

In t h e Transuranium P r o c e s s i n g F a c i l i t y , t h e aluminum-clad target rods irradiated in t h e WFIK will b e d i s s o l v e d i n hydrochloric acid. Both

Zircaloy-2 and tantalum tihve adequate corrosion r e s i s t a n c e to t h e a c i d solution for equipment u s e , but both c a n suffer hydrogen embrittlement under some conditions. Therefore, a s e r i e s of t e s t s with both m a t e r i a l s was Londucted to determine the amount of hydrogen entering t h e metal from the corrosion p r o c e s s and i t s effect on the ductility of t h e mGteria1. Zircaloy-2 s t r i p s , 1 0 mils thick, and tantalum spec-imens of similar t h i c k n e s s were e x p o s e d to 8 19/1 HCL at s e v e r a l tempcratures for periods of 1000, 2000, and 3000 hr, After exposure, e a c h specimen w a s given a 180'' bend test as a qualitat i v e m e a s u r e of its ductility. Originally, t h e Zircaloy-2 contained 8 ppm hydrogen and the tantalum 1 ppm. The hydrogen c o n t e n t and corrosion r a t e of t h e Zircaloy-2 s p e c i m e n s after various exposure period:; and t h e r e s u l t s of t h e bend tests a r e shown i n T a b l e 5.2. A t e a c h temperature, t h e hydrogen c o n t e n t appeared to b e apptoaching a limitirig v a l u e after 2000 to 3000 hr. Ceneraliy, the corrusion r a t e and t h e corresponding hydrogen content i n c r e a s e d with temperature. For t h e particular geometry involved, t h e hydrogen concentration required t o

Table 5.2.

The Corrosion R u t e nnd Hydrogen P i c k u p of Z i r c o l o y - 2 Exposed C o i r os ion R a t e ( m i l s /year)

Temperature

_._I__

1000 hr

2000 hr

0.4

0.8

0.7

0.5

1.1

0.6

Hydrogen Content (ppm) .... ....

3000 hr

170

220

1.0

1.4

350

380

1.1

2.2

150

730

790

2.3

1.9

3.4

680

820

430

3.2

3.8

2.4

760

15OOa

16OOa

5,o

4.0

3.5

2.5

740

1700a

1900a

4.7

3.1

105

6.0

.---....-_I

2.9

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

1000 h r

8 M HCI

2000 hr

("C)

3000 hr

960

1800a

3400a

4000"

._.__._____

1 gooa

4200a

aRrittle f r a c t u r e of speclmen during 180° bend t e s t .

c a u s e embrittlement w a s between 1000 and 1500 PP". T h e tantalum s p e c i m e n s exposed under t h e s a m e conditions a s t h e Zircaloy-2 s p e c i m e n s were completely r e s i s t a n t to the acid and consequently did not pick up hydrogen. T h e target-rod d i s s o l v e r in t h e Transuranium P r o c e s s i n g F a c i l i t y will b e made of Zircaloy-2 and will operate a t about 4SoC, a temperature where corrosion and emhrittlement should not b e a problem. For evaporators in which a c i d i c solutions will b e concentrated a t the boiling point, tantalum l i n e r s will b e used. Corrosion Testing i n Support of Power- Reactor Fuel- E I e m en t Rep races s i n g

During t h e p a s t year, t h e effort in t h i s program h a s been concerned s o l e l y with t h e bchavior of pure nickel and Hastelloy N i n various gas-phase head-end treatments. In t h e gas-phasc p r o c e s s e s 9 t h e f u e l elements a r e s u s p e n d e d i n a fluidized bed of aluminum oxide, and, depending on t h e s p e c i f i c

p r o c e s s , are s u b j e c t e d c y c l i c a l l y to fluorine, 5040 mixtures of oxygen and hydrogen fluoride, and oxygen a l o n e at temperatures a s high as 8OO0C. In the t e s t s conducted, s p e c i m e n s of both materials were exposed in t h e fluidized bed and in t h e g a s p h a s e above it. Both Hastelloy N and nickel underwent only minor corrosion during 31 c y c l e s of exposure to a 60-40 mixture of 02-BF a t 625°C. Each cycle c o n s i s t e d of a period of 1 hr for heatup, 6 hr a t temperature, and 1 h r for cooling. Both a l l o y s were heavily oxidized on exposure to oxygen a t 800°C. However, only Hastelloy N w a s significantly corroded during eight c y c l e s of a p r o c e s s c o n s i s t i n g of 6 hr in oxygen at 550°C followed by 6 h r i n fluorine a t 550°C. Additional. t e s t i n g in a c y c l e c o n s i s t i n g of 6 hr in a 60-40 mixture of 0 , - H F a t 62S°C followed by 6 h r in fluorine a t 550°C showed that t h e attack on nickel w a s light but t h a t Mastelloy N specimens were heavily a t t a c k e d on t h e edges. T h i s t e s t i n g program i s a n integral p a r t of t h e p r o c e s s development, and t h e r e s u l t s a r e included in various reports by t h e Chemical Technology Division.

Chemistry of High-Temperature Aqueous Solutions plotted as a function of temperature at p r e s s u r e s to 4000 b a r s . The type of behavior shown i n F i g . 6.1 is typical for a strong electrolyte, and is similar to t h e r e s u l t s obtained previously with potassium sulf a t e . 4 * 5 A s the temperature i n c r e a s e s from 0 t o 300”C, i o n i c mobilities i n c r e a s e rapidly d u e t o t h e rapid d e c r e a s e in t h e v i s c o s i t y o i water. Therefore the conductance of 1 he sodium chloride s o l u t i o n s i n c r e a s e s a l s o . However, t h e d i e l e c t r i c c o n s t a n t of w a t e t is also d e c r e a s i n g with i n c r e a s i n g temperature. T h i s lowering of dielectric cons t a n t a l l o w s ion pair formation to begin to occur. Apparently, at approximately 300 to 450OG (depending on t h e pressure) t h e two e f f e c t s (increasi n g mobility of t h c ions; i n c t e a s i n g a s s o c i a t i o n between t h e i o n s ) begin t o o f f s e t one another, and the conductance begins to diminish with i n c r e a s i n g temperature. It should a l s o be noted t h a t when the temperature of an a q u e o u s solution is inc r e a s e d , a t c o n s t a n t p r e s s u r e , t h e d e n s i t y decreases so that t h e r e a r e fewer ions per c u b i c centimeter, and consequently a s m a l l e r conductance. I n another study, measurements h a v e been made on 0.01 denial ( 2 0 . 0 1 m) potassium chloride solutions (this is u s e d a s a s t a n d a r d solution for conductance cell c o n s t a n t determinations a t 25°C) t o 80O0C and 4000 b a r s . It IS thought t h a t t h i s would b e t h e logical s o l u t i o n t o u s e for a reference at e l e v a t e d temperatures and p r e s s u r e s ; t h u s , as more r e s e a r c h e r s make c o n d u c t a n c e measurements a t high temperatures and p r e s s u r e s , the r e s u l t s from t h e dilferent laboratories c a n b e more e a s i l y compared. Figure 6.2 s h o w s a comparison of previously determined c o n d u c t a n c e s of K,SO,,

ELECTRICAL CONDUCTANCE MEASUREMENTS OF AQUEOUS SODIUM CHLORIDE SOLUTIONS TO 800’C AND 4000 SARS

W. J e n n i n g s , J r . W. I,. Marshall

A. S. Q u i s t

The e l e c t r i c a l c o n d u c t a n c e s of sodium chloride solutions, ranging i n concentration from 0.001 to 0.1 rn, h a v e been measured a t temperatures from 100 t o 800’C and at p r e s s u r e s from 1 to 4000 bars. ‘rwo different conductance c e l l s were u s e d for t h i s s e r i e s of measurements. One of t h e c e l l s has b e e n described previously. However, b e c a u s e of experimental difficulties with the k i d g m a n t y p e of p r e s s u r e s e a l in t h e high-temperature region of t h e conductance cell, a new cell w a s constructed which eliminated t h e p r e s s u r e seals in t h c high-temperature region. T h i s new cell w a s constructed from a cylinder of IJdirnet 700, 24 in. long and 1 in. in diameter. A holc 0.250 in. i n diameter w a s drilled t h e length of the bar, and platinum-iridium l i n e r s were inserted to prevent corrosion of t h e Udimet 700 by the high-temperature aqueous solutions. T h e other parts of the r o n d u c t a n c e c e l l a r e of t h e sanic d e s i g n a s d e s c r i b e d earlier. Hoth conductance cells were u s e d for measurements on t h e most d i l u t e (0.001 to 0.02 m) solutions. T h e measurements from t h e two c e l l s were i n agreement to within experimental error (kl to 2%). The r e s u l t s for 0.01 m N a C l s o l u t i o n s are shown In Fig. 6.1, where s p e c i f i c c o n d u c t a n c e s a r e

’

’-’

’E. U. Fraanck et af., Reoc-tor Cherx. Div. Ann. Progr. 3 1 , 1 9 6 1 , OKNL-3127, p[>. 50-52. ’A. S. Quist et [if., Reactor Cherri. D i v . A n n . Progr. R e p t . J a n . 3 1 , 1 9 b 2 , ORNL-3262, pp. 73-75. 3 E. U, E’ranck et a l . , R e v . Sci. Xnslr. 33, 115 (19G2), f?e[Jt. .fan.

‘AA. S. Qnist et al., Reactor (:hem. D i v . A r m . Pro&. Rept. Jan. 3 1 , 1 9 6 3 , ORNL-3417, pp. 77-82. 5 A. S . Quist et a!., J . Phyh. Chem. 67, 24.53 (1903).

64 Oi?NL-DWG

700

-5 -

66-974

600

500

._400 L 0

W u 7

with increasing temperature, and i n c r e a s e with i n c r e a s i n g pressure. T h e difference between thc c o n d u c t a n c e s of NaCl and KC1 is d u e t o the difference in mobility of t h e potassium and sodium ions.

AQUEOUS SObUBlhlTY OF MACNET1TE

300

F. H. Sweeton K. lli. Rag C. F. B a e s , J r . 0

400

200

TEMF'ERATURE

F i g . 6.1.

1째C)

603

800

T h e Specific Conductance of 0.01 m NaCl

Solution f r o m 100 to

800째C

a t Pressures t o 4000 Bars.

700

600

400 300

Lo a

200

'O"

0 0

0 0 2 2 m K2Se4

200

400

600

800

TEMPERATURE I"C)

F i g . 6.2. of

Coniparison

of the Specific Conductances

K2S04, KHS04, H2SQ4, KCI, and N o C l Solutions

Functions of Temperature.

H,SO,, and KHSO, solutioiis with t h e new v a l u e s for NaCl and KC1 a s a function of temperature a t a c o n s t a n t pressure of 4000 bars. T h e different behavior of t h e KHSO, and FI,SO, s o l u t i o n s as compared to t h e other solution^^,^-' is d u e t o c h a n g e s in the first and s e c o n d d i s s o c i a t i o n c o n s t a n t s of sulfuric acid with temperature and pressure. 6,7 Both d i s s o c i a t i o n c o n s t a n t s d e c r e a s e 'A. S. Quist e t at., R e a c t o r Chem. Div. A n n . Pro&. Rept. J a n . 3 1 , 1 9 6 4 , ORNL-3591, pp. 84-88. 7A. S . Q u i s t e t al., J. P f i y s . Chern. 69, 2726 (1965).

T h e solubility of magnetite ( F e , 0 4 ) i n aqueous s o l u t i o n s a t e l e v a t e d temperatures is of s p e c i a l i n t e r e s t i n pressurized-water reactor s y s t e m s , in which Fe,O, i s a main component of t h e corrosion film. I t a l s o i s of i n t e r e s t t o geologists in unders t a n d i n g the origin of Fe,O, deposits.' The flowing s y s t e m for iueasuring t h e solubility that w a s reported e a r l i e r g h a s been modified in s e v e r a l ways to improve the precision of t h e data. One important c h a n g e h a s been t h e substitution of 66 g of nonradioactive Fe30, for 2.7 g of radioactive material, thus making p o s s i b l e a longer c o n t a c t time with t h e solution. T h i s Fe30, w a s prepared by oxidizing a carbonyl iron powder with steam a t 400 to 500째C. I t s final s p e c i f i c s u r f a c e area w a s 0.12 m 2 / g , about t w i c e that of the radioa c t i v e material. Water for the t e s t s vias purified and equilibrated with H , a s before. All b a t c h e s had conductivities of less than 0.08 micromho/cm a t r o o m ternperatures, and concentrations of d i s s o l v e d 0 , below 10 ppb (and usually l e s s than 5 ppb). T h e purified water, sometimes containing added HC1, w a s pumped first through a recombiner in which i t made c o n t a c t with platinum black at 260OC (to c a t a l y z e t h e reaction of the remaining 0, with H,), and on through t h e bed of Fe30, in a column held a t a controlled temperature. T h e solution w a s then cooled and p a s s e d through a Millipore filter with 0.1-p pores. T h e recombiner, column, and filter holder were made of gold-plated stainless steel. Platilium tubing w a s u s e d to c o n n e c t the units. T h e equilibrated solution w a s 'W.

T. Holser and C. J. Schneer, Geol. S O C . A m .

B u l l . 72, 369-86

(1961).

'F. H. Sweeton, C. F. R a e s , Jr., and R. W. K a y , R e a c t o r Cheiii. Div. Ann. Progr. R e p t . Jan. 3 1 , 1965, ORNL-3789, pp. 120-21.

65 ORNI. - 0 W G 56 -~ 975

W e h a v e u s e d t h e upper two groups of d a t a i n Fig. 6.3 to c x k u l a t c t h e s o l u b i l i t y product (in molal and atmospheric u n i t s ) for t h e reaction

T h e resulting v a l u e s of log K at 150 and 200°C a r e 7.00 and 6.08 with s t a n d a r d d e v i a t i o n s of 0.11 and 0.06 respectively. We think the other 150°C: points a r e low due to a s l i g h t l e a k a g e of 0, into t h e pH c e l l to g i v e t h e reaction

Ii ................

15.4

and we a r c now modifying the pH cell to prevent this. T h e solubility product estimated for 200'C predicts that the s o l u b i l i t y of Fe,O, i n pure H,O should b e 1.4 p m ; t h i s is i n good agreement with o u r previously reported9 figure of 1.5 pm. We w i l l continue m e a s u r e m e n t s to cover t h e range of 150 to 260OC with HCl s o l u t i o n s from 0 to 30 pm with the intention of' examining t h e d a t a to see if t h e d i s s o l v e d iron is hydrolyzed.

5.6

......................... 5.8

1 6.0

6.2

SOLUBILITIES OF CALCIUM Y D R Q X l D E AND SATURATION BEHAWOR OF CALCIUM HYDROXI DE-CA LCBUM CARBONATE MIXTURE 5 1N AQUEOUS SODIUM NiTRATE SOLUTIONS FROM 0.5 TO 350% L. B. "eutts, J r .

pa ;sed through flowing conductivity and pM cells and then through beds af cation exchanger t o ro11ect thc d i s s o l v e d iron, wliich wab l a t e r removed ,itid a s s a y e d spectrophotometiically by t h e ophenanthroline method. T h e r e s u l t s a r e shown i n Fig. 6.3. T h e pEI measured at 25°C h a s been converted to pfi at the ~ c j u i l i h r a t i o n temperature, using d i s s o c i a t i o n constants of w a t m a t 25, 150, d 200*C of 0.01, 2.24, and 5.01 (molal u n i t s ) , respectively, and a s s u m i n g 70 hydrolysis of Fez' a t a n y temyeratuic. Sixfold c h a n g e s in t h e flow rate produced no significant c h a n g e i n t h e composition of t h e product solution, indicating t h a t the Fe,O, had reached equilibrtum with t h e flowing solution.

W. L. Marshall

'The s o l u b i l i t i e s of calcium hydroxide and the sat:uratian behavior of c a l c i u m hydroxide-calcium carbonate mixtures were determined a t temperas oSl u t i o n s of t u r e s ftom 0.5 to 350°C in : ~ ~ L I C W U sodium nitrate from 0 to a b o v e 5 m i n concentration. Commercially a v a i l a b l e reagent grade calcium hydroxide and calcium carbonate were d i g e s t e d i n boiling deionized water to remove soluble i m purities. The hot s o l u t i o n s were filtered and t h e recovered product dried a t 100 t o llO°C. T h e dry ca1c:iurn hydroxide wiis ignited at 1150°C: for about. 16 hr to convert c:alcium carbonate impurities to calcium oxide; t h e carbon dioxide content of t h e freshly ignited oxide w a s about 2.58 ppm. E x c e s s

66 T h e dependence of t h e calcium hydroxide solub i l i t y upon the i o n i c strength function, I1"/(1 + a t various temperatures is shown in Fig. 6.4. T h e s e c u r v e s represent t h e b e s t l e a s t - s q u a r e s fit of the experimental d a t a , u s i n g t h e A v a l u e s l i s t e d in the legend. The i n t e r c e p t s for t h e c u r v e s a r e t h e log s o values. The i n v e r s e relationship between solubility and temperature and t h e direct relatioilship between solubility and ionic strength a r e clearly seen. The poorest fit of t h e c u r v e s with the d a t a o c c u r s a t t h e higher temperatures, where the solubility of calcium hydroxide i s sufficiently low to make p r e c i s e a n a l y t i c a l measurements difficult. By u s i n g t h e v a l u e s of K:p determined from t h e d a t a of Fig. 6.4, a s s u m i n g that AC, = 13 + E?'("K), where D and E are cons t a n t s , and then by determining t h e c h a n g e in l o g K:p a s a function of l / T ( O K ) with t h e van't Hoff e x p r e s s i o n , t h e standard thermodynamic quantities were c a l c u l a t e d and a r e presented i n T a b l e 6.1.

s o l i d calcium hydroxide and mixtures of calcium hydroxide and calcium carbonate were equilibrated with aqueous sodium nitrate, prepared with deionized water, using rocking equipment. The containing v e s s e l s for t h e 0.5 and 2S째C experiments were Pyrex stoppered b o t t l e s ; for the 50 to 350OC experiments, they were titanium alloy bombs. T h e s o l u t i o n s were filtered during s a m p l e withdrawal a t the temperature of t h e experiment in order t o remove s u s p e n d e d s o l i d s . A portion of e a c h s a m p l e w a s treated with e x c e s s concentrated nitric a c i d , evaporated to d r y n e s s a t 95 t o 100째C, and weighed a s calcium and sodium nit r a t e s . Another portion of e a c h s a m p l e solution w a s u s e d for t h e determination of calcium ion concentration b y a potentiometric titration with standard EDTA solution. The electrolyte concentration in the solution w a s determined by difference from the results of t h e s e two a n a l y s e s . T h e dissolution of calcium hydroxide was a s sumed to reach t h e following equilibrium: Ca(OH),(s) $ C a 2 ' ( a s ) + 20H-(aq)

T h e thermodynamic solubility product e x p r e s s i o n for t h i s equilibrium is given by:

where ni i s molal concentration, y i s the activity coefficient, and s is the n o l a l solubility of calcium hydroxide. Converting t o logarithms, substituting a n extended Debye-Huckel e x p r e s s i o n for log and rearranging the equation l e a d s to t h e form: ~

log K s p

log KZp

SI1 / 2

+ 3BI+

(1 iAI"')

3C12 ,

where S

I KO

A , B, C

theoretical Debye-Huckel limiting s l o p e for a given temperature,

ionic strength =

t h e solubility product c o n s t a n t a t I

constants.

Since Ksp

4 s 3 and K:p-

log s

log s o

niNaNO 3

SI'

.-- +

(1 + A 1 1 1 2 )

CP .

148 163 114 190 202 2 14

0, 10

SO)^, then

05 25 50

I00 150 200

3mca(011)21 =

T("Cl

I I 2 _

Fig. 6.4.

Solubility

from 0.5 t o 350cC.

0 2

I "2/6+ AI " 2 )

of Co(Okl)2 i n Aqueous ii.(aNO3

67 The s a t u r a t i o n behaTJior of calcium hydroxidecalcium carbonate mixtures was i d e n t i c a l , for all practical purposes, to that of calcium hydroxide

Table 6.1.

Stondord Thcrrnodynomic Properties of the E q u i l i b r i u m :

____

-___

Temperature (OC) ._____._.. ~~

alorie over the same iange of ionic :;trength.

AF'2 (kcal/mole)

Co(OH)2(s) e C a 2 ' ( a q ) ___

ternperaturc and

+ 20H-(aq)

!If1r2

AS"

(kcaI/rnole)

(cal mole-A d r g - l )

___

..........__

...-.

1.32 x 10-5

6.10

-1.26

-26.9

9.61 x lo-"

6.81

-2.47

-32.9

5.81 x

7.74

-4.79

-38.8

100

1.46 x

9.96

-8.74

-.50.1

150

2.60

-13. I

--61*2

12.7

lo-*

200

1.75 x

16.1

-17.9

-71.9

2 50

4.70 x

19.9

-23.2

-82.4

i DO

5.34 x lo-'"

14.3

-28.9

-92.8

ids SURFACE CHEMISTRY OF THORIA

face hydroxyl groups resulting from hydrolysis of s u r f a c e oxide ions. A t larger c o v e r a g e s additional contributions to AH, a r i s e from hydrogen bonding between t h e s u r f a c e hydroxyl groups and t h e subsequently adsorbed layers of water. Samp l e s A and B gave /INa v s coverage c u r v e s which are t y p i c a l of adsorption on a heterogeneous surface.6 T h e corresponding curve for s a m p l e E exhibited three d i s t i n c t regions in which water is adsorbed with a c o n s t a n t AN,. T h e most plausible explanation for t h i s unusual behavior i s t h e formation of s u c c e s s i v e immobile homogeneous monolayers. Such a n idealized adsorption is more likely to occur with s a m p l e E b,- c a u s e of i t s relatively l a r g e c r y s t a l l i t e size (i-2500 A) a s compared t o s a m p l e s A and B (200 A). The dependence of the h e a t of immersion on physical properties s u c h a s s p e c i f i c s u r f a c e a r e a , particle s i z e , and c r y s t a l l i t e size i s a complex and unresolved q ~ e s t i o n . ~ ~ T' h~ e~ h e a t s of immersion of a s e r i e s of low-surface-area T h o , In addition to s a m p l e s a r e shown in Fig. 7.1. s a m p l e E, t h e s e include s a m p l e s D (l2OOcC, 2.20 m2/g); J (12OO0C, 2.96 m2/g); K (140OoC, 1.55 m 2 / g ) ; and 1.. (16OO0C, 0.95 m2/g). Maximum deviation of the experimental points from the c u r v e s i n F i g . 7.1 i s about 2%. From a consideration of the combined uncertainty in the s u r f a c e area and h e a t measurements, one must conclude t h a t s a m p l e s E, J , K , and L h a v e ident i c a l h e a t s of i m m e r s i o n . T h i s i s the f i r s t known case of s u c h behavior. It would t h u s appear that in order to h a v e reproducible i d e a l i z e d s u r f a c e

C. H. Secoy Heats of Immersion and Adsorption

E. I,. Fuller, J r . J . E. Stuckey'

H. F. Holiiies

'The calorimetric investigation of the interaction of water with the s u r f a c e of T h o , i s continuing. T h e apparatus and procedure have beeii described. 2--5 Net differential h e a t s of adsorption ( A H a ) of water on T h o , have been derived froin calorimetrically determined h e a t s of immersion (hi) of T h 0 9 s a m p l e s containing known amounts of presorbed water (adsorbed after o u t g a s s i n g a t 500OC but prior to, t h e immersion experiments). T h e s e s t u d i e s h a v e been completed for three s a m p l e s of T h o , : A (650째C, 14.7 m2/g); M (XOO'C, 11.5 m2/g); and E (16OO0C, 1.24 m 2 / g ) . Data in par e n t h e s e s refer t o the c a l c i n i n g temperature and s p e c i f i c s u r f a c e area respectively. Initial v a l u e s of AHa ranged from -20 to -30 kcal/mole. In n o case did /\Ha d e c r e a s e to zero with completion of the first adsorbed monolayer. 'These large exothermic v a l u e s clearly i n d i c a t e t h a t the water i s in a chemisorbed s t a t e , most probably as s u r ' P r o f e s s o r of Chemistry, Hcndrix C o l l e g e , Conway, Ark. 'C. H. Secoy, H. F. Holmes, and E. I,. F u i i e r , Jr., R e a c t o r Chern. Div. Ann. Progr. Rept. J a n . 3 1 , 1965, OKNL-3789, pp. 164-69, 3 C . H. Secoy a n d 11. b-. Holmes, R e a c t o r Chezn. Uiv. Ann. Progr. R e p t . J a n . 3 1 , 1963, ORNL-3417, PP. 124-29.

6A. C. Zettlemoyer and J. J . C h e s s i c k , Advan. Chern. Ser., No. 43, p. 88, Anlerican Chemical S o c i e t v . Washington, D . C . , i 9 6 4 .

'H. F. Holmes and C. H. Secoy, J . P h y s . Chern. 69, 151 (1965). 'H. F. Holmes, E. I,. F u l l e r , J r . , a n d C. H. S e c o y , t o be published in J. Phps. Chern. (February 1966).

7W. H. Wade and N. Hackerman, Advan: Chem. Set., No. 43, p. 2 2 2 , American Chemical Society, Washington, D.C., 1961.

,......... .

Fig. 7,1. H e a t s Thoria Samples.

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

Immersion

ORNL-DING

........

66--976 ...........

Low-Surface-Area

r e a c t i o n s , o n e m u s t work with s a m p l e s having low specific s u r f a c e s and a relatively l a r g e cryst a l l i t e s i z e (the c r y s t a l l i i e s i z e of t h e s e s a m p l e s ranged from 1500 t o >2500 A). T h i s d o e s not, however, a c c o u n t for t h e r e s u l t s obtained with s a m p l e D. The only p h y s i c a l difference i n S a m p l e D is t h e p a r t i c l e size. Samples E, J J K, and L h a v e a mean particle diameter of about 1.5 p, while t h e corresponding value for s a m p l e D is 3.0 /L. On t h i s b a s i s i t a p p e a r s t h a t the number of c r y s t a l l i t e s per particle i s a n import.ant factor. Conceivably, t h i s could influence t h e number and type of c r y s t a l faces e x p o s e d for s u r f a c e reactions. Further experiments a r e required b.o r e s o l v e t h i s important point, Water Vapor Adsorption and Desorption

E. I.,. F u l l e r , Jr.

11. F. Holmes

T h e complex nature of water adsorptlon on thorium o x i d e h a s b e e n studied by use of a s e n s i t i v e microbaldrice. High-temperature s i n t e r i n g (1200째C) a p p e a r s to produce a material which predominantly p r e s e n t s t h e 100 c u b i c face in t h e s u r f a c e , upon which there arc three d i s t i n c t modes of adsorption. T h e r e is a n initial rapid chemisorption, forming s u r f a c e hydroxyl groups which a r e s l o w l y hydrated. In addition and as a precursor for s u r f a c e hydration, p h y s i c a l adsorption occurs.

Isotherm:; constructed a t 25.0O0C reveal the type II p h y s i c a l adsorption isotherms characteti s t i c of polar a d s o r b a t e s . In addition, the s l o w hydrating p r o c e s s o c c u r s a s a perturbing effect: e a c h s u c c e s s i v e isotherm fails to c l o s e upon the preceding one by a d e c r e a s i n g amount until, after s i x montlis of repetitive adsorption and desorption, a reproducible isotherm is achieved. T h e r a t e of irreversible binding is a complex function of both t h e water vapor pressure and t h e amount nf water previously bound. T h e r a t e i s i n c r e a s e d markedly with t h e first iricreinents of p r e s s u r e , but higher p r e s s u r e increments h a v e less a c c e l e r a t i n g eifec1.s. T h e rate diminishes appreciably a s m o r e water is hound ilnder t h e physically adsorbed water., The final vacuum weight of adsorbed water corresponds e x a c t l y to t h e aforementioned stoichioinetry. T h e 1000째C c a l c i n a t i o n d e c r e a s e s t.he numher of pores but d o e s not a l t e r the distribution (there are s t i l l p o r e s of radii near 10 A); w h e r e a s t h e s m a l l pores a n n e a l out a t t h e 1200OC c a l c i n a t i o n , l e a v i n g a mjnimum radius of 50 A. The fact that thorium oxide must b e heated to 10~lO째C i n vacuo to remove all. water i n d i c a t e s that there a r e two different t y p e s of s i n t e r i n g involved. T h e amount of bound water is stoichiomt.f.tically

equivalent to that required to form t h e s u r f a c e a n a l o g of a hydrated bulk hydroxide. .In addition, t h i s i s t h e amount of water required to build ? ~ p one completed face-centered c u b i c l a t t i c e unit on t h e s u r f a c e a b o v e the 100 T n 0 2 plane, with t h e hydroxide and water oxygen occupying the image p o s i t i o n s of t h e s u b s t r a t e oxide ions. T h u s t h i s bound water may be similar to t h e c u b i c form of ice, where the 0--0 s p a c i n g i s nearly e q u a l to t h a t p r e s e n t i n bulk 'lTh02. T h e s h a p e of t h e nitrogen isotherms a t -195째C c h a n g e s , showing t h a t the partial p r e s s u r e a t which monolayer (BET) coverage o c c u r s i n c r e a s e s from below 0.05 to 0.13 as more water is preadsorbed. T h i s is undoubtedly d u e to t h e fact t h a t t h e water-covered s u r f a c e i s less e n e r g e t i c a n d h a s less affinity for the nitrogen. The extremely low vapor pressure of t h e initially adsorbed water and t h e complex kinet.ics of hydration must b e considered before e v a l u a t i n g thermodynamic properties or s p e c i f i c s u r f a c e areas from water isotherms. One must b e equally c a u t i o u s when attempting t o predict t h e amount of adsorption from t h e s e isotherms.

500"

4000

360C

3200

zRo0 203c

1800

1600 FKUJCNCY

F i g . 7.2.

Infrared Spectra of T h o 2 (Sample

1100

1200

(mi')

1000

800

6C0

A ) in V a c u o A f t e r 24 hr O u t g a s s i n g a + I n d i c a t e d Temperatures.

A m b i e n t spectrum obtained in laboratory environment a t a relative humidity of 30%.

Infrared Spectra of Adsorbed Species on Thoria

C. S. Shoup, Jr. Exploratory infrared s p e c t r a of a thin, s e l f - s u p porting p r e s s e d d i s k ' of thorium oxide (sample A)* were recorded i n vacuo (10W6 torr) a s a function of pretreatment conditions. The disk was held in a nickel s a m p l e holder within a n infrared c e l l and, by means of a n external magnet, could b e raised to a s e c t i o n of t h e c e l l away from the s i l v e r chloride windows and heated a s high a s 5OOOC. After Pretreatment a t a known temperature for a t l e a s t 21 hr, t h e c e l l w a s s e a l e d off under a vacuum, the s a m p l e cooled and lowered t o the optical s e c t i o n , and the c e l l placed in the spectrophotometer. All s p e c t r a were obtained a t about 35OC, and the s a m p l e w a s not e x p o s e d t o the atmosphere between measurements. Several features of i n t e r e s t are shown in t h e T h e most obvious infrared s p e c t r a of Fie;. 7.2. 'C.

H. Secoy a n d C. S. Shoup, Jr., R e a c t o r Chern.

Div. Ann. P r o g r . R e p t . J a n . 31, 1965, ORNL-3789, pp.

172-73. 9Perkin-Elmer model 521 infrared spectrophotometer provided through the c o n r t e s y of the Chemistry D i v i s i o n o f ORNL.

feature i s t h e general d e c r e a s e i n intensity of the various absorption bands with i n c r e a s i n g outg a s s i n g temperatute, particularly between 200 and 500째C. In addition, s e v e r a l of the absorption bands a r e d i s p l a c e d in frequency, and in s o m e cases new b a n d s appear with i n c r e a s i n g outg a s s i n g temperature. T h i s i s indicative of t h e formation of structurally different adsorbed s p e c i e s a s some of the pieviously adsorbed s p e c i e s a r e desorbed. T h e broad bands around 3500 cm-' a n d l e s s , diic to perturbed 0-H s t r e t c h i n g modes of vibration, show t h a t a considerable amount of hydrogenbonded adsorbed water remains on the s u r f a c e after e v a c u a t i n g a t 20OoC. Even after o u t g a s s i n g a t 5OO0C, t h e thoria i s not free of s u r f a c e Q-13 groups, a s shown by t h e rather s h a r p b a n d s a b o v e Spectra obtained with a n improved 3600 c m - l ' . signal-to-noise ratio d i s p l a y three s h a r p b a n d s a t 3715, 3650, and 3520 c m - ' when the quantity of adsorbed water corresponds to approximately one monolayer or l e s s . The relative i n t e n s i t i e s of t h e s e bands and their c h a n g e s under a variety of conditions a r e s u c h a s to i n d i c a t e the p r e s e n c e groups of three different types of s u r f a c e Q--H a t low coverage.

71 Some contamination of t h e s u r f a c e is evident from the b a n d s d u e t o C-1-1 s t r e t c h i n g vibrations i n t h e 2850 t o 2950 c m - ' region. T h i s hydrocarbon-like material is e a s i l y removed by suffic i e n t h e a t or by t r e a t i n g briefly with oxygen a t high temperatures and h a s only minor e f f e c t s on t h e r e s t of t h e spectrum. A prominent absorption band a t 1630 c m - ' w a s revealed in t h e spectrum of the thoria-water vapor interface i n t h e p r e s e n c e of w a t e r vapor a t a partial p r e s s u r e of about 14 torr. Pumping a t room temperature was sufficient t o remove t h i s band, however, confirming i t to b e d u e to t h e H-0-13 bending motion of physically adsorbed hydro gen-bonde d w a 1.er mol e c u I e s . A s e r i e s of i n vaouo infrared s p e c t r a w e r e obtained after t h e 500°C-out-gassed thoria had b e e n e x p o s e d to water vapor for periods of 24 hr t o as long as 11 d a y s e a c h before s u b s e q u e n t evacuation a t room temperature. Each successive spectrum revealed the p r e s e n c e of a greater quantity of adsorbed water than the previous spectrum, thus confirming t h e s l o w "irreversible" adsorption of water that had been originally d e t e c t e d gravimc:trically.

i b(onm

I Q - ~

' cm?)

10'~

F i g . 7.3. Specific Surface C o n d u c t i v i t y o s a F u n c t i o n

of E l e c t r o l y t e Specific C o n d u c t i v i t y .

AII investigation of Tho, plugs from a variety a€ s o u r c e s , however, i n d i c a t e s that the electrokinetic potential is strongly influenced by the method of preparation of t h e thoria. For exatnple,

.l._._ i .I.i_.l._-.~.-.~~~.--.

one b a t c h of thoria c a l c i n e d at 1GOO"C gave no indication of a positive z e t a potential over t h e p1-I range of 5.9 to 12. T h e complex behavior of t h e e l e c t r i c a l double layer h a s been observed in other oxide-aqueous solution s y s t e m s "- l G and a p p e a r s t o b e highly dependent on t h e chemical and thermal history o€ the saniple. Until t h i s d e p e n d e n c e c a n b e put on a concre1.e b a s i s , z e t a potential measurement^ for s u c h s y s t e m s must b e a s s u m e d to h e valid only for the s p e o i f i c samples investigated. Measurements of the e l e c t r i c a l conductance of a q u e o u s s o l u t i o n s flowing through porous plugs of ThO were correlated with measurements u s i n g c e r a m i c c a p i l l a r i e s with known geometries. This made i t p o s s i b l e t o measure the cell c o n s t a n t a s s o c i a t e d with the s u r f a c e conductance and thus to determine the speciEic s u r f a c e conductivity for s e v e r a l e l e c t r o l y t e s . T h e variation of t h e s p e c i f i c s u r f a c e conductivity, As, with the s p e c i f i c conductivity of the bulk solution, A,, is i l l u s t r a t e d i n Fig. 7.3 for a variety of porous p l u g s and c a p i l l a r i e s of thorium oxide.

''(2. 1-1. Secoy, E. L. F u l l e r , Jr., and 1-1. F. H o l m e s , Reactor Chem. Ayiv. Anti. Pro&. Rept. J a n . 31, 1965, ORNL-3789, pp. 169-72.

' I D . J. O'Connor and A. S . Bucbanan, A i ~ ~ ~ r r a l z Jn .r i Chem. 6 , 278 (1953).

Electrokinetic Phenomena a t

Oxide-Aqueous

the

(2. S. SPtoup, Jr.

Fi. .?I

Thorium

Solution Interface'

IIolme:;

Electrokinetic e f f e c t s o f aqueous s o l u t i o n s i n porous plugs of thorium oxide have been investigated from t h e standpoint of irreversible thermoA kinetic electroosmotic technique dynamics. was u s e d t o determine the e l e c t r o k i n e t i c potential. I . ' T h i s method gave r e s u l t s in agreement. with streaming potential d a t a e x c e p t i n t h e prese n c e of a c i d i c s o l u t i o n s . In general, t h e electrokinetic zeta potential w a s observed to d e c r e a s e with i n c r e a s i n g pH, varying from a b o u t -4-25mv t o -55 mv with a n i s o e l e c t r i c point near pIi = 9.4.

' % I . F. Holmes, C. S . S h u u p , Jr., and C . II. Secoy,

j'. P h y s . Chem.

69, 3148 (1965).

125. K. tieGroot, Tlzennodynamics of I r r e v e r s i b l e Proce s s e s , Interscience, New York, 1951.

'jC. 13. Secoy and fi. F. H o l m e s , Chem. Tech. Div. Ann. Pro&. H e p t . A u g . 31, 19.59, ORNL-2788, pp. 85-86.

"D. J. 09Conrior, P. G. Jobansen, and A . S. Buchanan, Trarrs. P a r a d a y SOL. 52, 229 (1956).

Street, Australran J . C h e m 17, 828 (1964). H. ~ e c o yand CY, S. ~ ~ i o u pj r,. , li'eactor Chem. Diva Ann. Pro&. h'ept. Jan. 31, 1 9 6 4 , ORNL-3591, lhN.

l7c-.

pp. 108-9.

An important feature of t h e r e s u l t s shown i n Fig. 7.3 i s the f a c t that they are some two to three orders of magnitude larger than would b e predicted from the c l a s s i c a l theories of s u r f a c e conductance." I n addition, there s e e m s t o b e no obvious relationship between the s u r f a c e conductivity and t h e electrokinetic potential a s predicted by t h e s e theories. C l a s s i c a l l y , t h e exponential dependence of s u r f a c c conductivity on t h e electrokinetic potential is b a s e d on the prese n c e of e x c e s s i o n s in the double layer d u e to the potential difference. In the present s y s t e m , however, i t a p p e a r s that the contribution of the e x c e s s i o n s in t h e double layer is masked by a s e c o n d mechanism which i s much larger in magnitude. I t i s believed that t h i s s e c o n d mechanism is t h e ionization and s u b s e q u e n t conductance of s u r f a c e hydroxyl groups. T h i s mechanism is further indic a t e d by the relatively s l i g h t dependence of t h e s u r f a c e conductivity o n t h e bulk ionic concentration, implying that the concentration of t h e s u r face conducting s p e c i e s is also only slightly If dependent on t h e bulk ionic concentration. the major mechanism for s u r f a c e conduct.ance is ionization of s u r f a c e hydroxyl groups, i t s h o u l d b e dependent on pH, a s shown by the c o n s i s t e n t l y high v a l u e s obtained with NH,OH. In t h e case of b a s i c s o l u t i o n s of Na,CC),, however, the s l i g h t but c o n s i s t e n t reduction in s u r f a c e conductivity may b e due t o s t r o n g s p e c i f i c adsorption of carbonate ions.

GAS EVOLUTION FROM SOL-GEL URANIUM-THORIUM OXIDE FUELS D. N. IIess

E. A. Soldano

Thoria-3% UO, sol-gel material prepared for u s e a s a reactor fuel h a s been found to evolve g a s e s when heated or when in reactor s e r v i c e . Such g a s e s could develop e x c e s s i v e p r e s s u r e within fuel e l e m e n t s or could react with the fuel element c l a d d i n g to weaken i t or t o affect i t s h e a t transfer capability. Previous study of g a s evolution from representative s a m p l e s of t h i s

"5.

Th. G. Overbeek i n Colloid S c i e n c e (ed. by 1-1. K. K r u y t ) , vol. 1, chap. V, E l s e v i e r , N e w York, 1952.

rnaterialIg had shown that particle s i z e , or surf a c e a r e a , w a s an important parameter, with r e s p e c t t o both the amount and composition of t h e g a s evolved, and that CO, w a s reversibly absorbed a t temperatures below 50OOC and e a s i l y desorbed a t higher temperatures. Studies during t h e p a s t year h a v e been directed toward t h e development of treatments which would reduce the s u r f a c e area of the prepared sol-gel and thus reduce the amount of g a s which i t could r e l e a s e in s e r v i c e . Ratch exposures a t tempera t u r e s of 1000째C to Co, or H,O a l o n e did not give any s u b s t a n t i a l c h a n g e in the s u r f a c e area of t h e sol-gel or i n i t s c a p a c i t y for reversible On the other hand, mixtures adsorption of CO,. of t h e two g a s e s , CO, and H,O, a t 1000째C were found to give approximately 50% d e c r e a s e s i n the s u r f a c e a r e a and absorption c a p a c i t y of the sol-gel for e a c h treatment. T h e duration of the treatment did not appear t o b e important. T h u s , two treatments would reduce the s u r f a c e area to 25% of t h e original - three to 12.5% of t h e original. T e s t s in which t h e sol-gel p e l l e t s were ground t o s u c c e s s i v e l y smaller particle sjzes between s u c c e s s i v e batch treatments with mixtures of H,O and CO, a t 1000째C s u g g e s t e d that the effect of the treatment permeated the e n t i r e material and w a s not localized at the s u p e r f i c i a l s u r f a c e exposed by grinding. Table 7.1 illust r a t e s t h e s e r e s u l t s ; a threefold reduction in B E T s u r f a c e a r e a w a s accompanied by a fourfold reduction in CO, adsorption c a p a c i t y , although the particle size reduction would have, i n a n untreated sol-gel, c a u s e d a n eightfold incrcase i n both s u r f a c e a r e a and g a s evolution with a n accompanying i n c r e a s e in CO adsorption capacity. S i n c e batch treatments a r e not convenient for larger-scale c o n c e p t s and s i n c e s i n g l e b a t c h treatments, however extended i n time, did not give more than 50% reduction i n a r e a , t h e effect of treatment in a flowing stream of H,O + CO, a t 1000cC was studied. As shown in F i g . 7 . 4 , t h e flowing-stream technique w a s much more effective; t h e c a p a c i t y of t h e sol-gel for gas adsorption appeared to be a predictable function of treatment time, regardless of whether t h e treatments were continuous or interrupted. A 16-hr treatment appeared appropriate for a 90% reduction in t h e

"D. N. Iless, W . T. R a i n e y , and B. A. Soldano, R e a c t o r Chem. Div. Ann. Progr. R e p t . J a n . 3 1 , 1965, ORNL-3789, p. 177.

original gas-adsorptior? c a p a c i t y of the material. Corresponding reductions in t h e BET s u r f a c e a r e a of t h e material w e r e obtained. T h e linearity of t h e semilogarithmic plot in Fig. 7.4 s u g g e s t s that there may b e a s i m p l e first-order p r o c e s s that is r e s p o n s i b l e for the s u r f a c e area reduction, but t h e d e t a i l e d mechanisms of t h e chemical react i o n s involved h a v e not been elucidated. A new s e r i e s of laboratory s a m p l e s of sol-gel material, prepared with various furnace atmosphetes during heating, calcination, and c o o l i n g and d e s i g n a t e d t h e PI, s e r i e s , was received a n d

Table 7.1.

E f f e c t of T r e a t m e n t w i t h 011

Sol-Gel Properties

Mesh S i z e

S e q u e n c e of

Tests and

Particles

Treattnent

4 0-8 0

H20-CO2

e v a l u a t e d with r e s p e c t to gas evolution and reversible g a s adsorption. All P L s a m p l e s gave much less g a s evolution upon being ground in t h e asreceived condition and h e a t e d to 1000째C in vacuo; a b o u t 0.30 s t d c c / g of gas was evolved, compared with 1.30 for the I-1-11 s a m p l e s previously studied. An even more s t r i k i n g reduct.ion w a s noted in the c a p a c i t y of t h e PL s e r i e s for reversible CO, adsorpt-ion; values of 0.02 s t d c c / g w e r e obtained, compared with 0.27 f o r t h e 1-1-11 material. T h u s the new material, if i t s preparai.ion proves to be reproducible, s h o u l d b e much superior from t h e point of view of gas evolution and might not require a n y treatment to reduce its s u r f a c e area.

BET Surface

Reversible C 0 2

A~~~~~~~~~

Area

Capacity

(m2/g)

( s t d cc/g:)

Original material:

2.57

0.20

degassed a t lOOo0C 110-80

0.10

A f t e i first s u r f a c e a r e a reduction

140

Ground arid s i z e d

1.58

0.10

t o 80-140 mesh (otherwise untreated)

80-140

After second surf a c e a r e a reduction

2 70

Grobnd and s i z e d to 200-270 mesh

0.08

1.67

0.06 0

After third s u r f a c e a r e a reduction

0.78

__ TO

TiiFATMcNT TIME l h r )

(otherwise untreated) 200 -270

0.05

F i g , 7.4. Effect of F l o w i n g C 0 2 a n d H 2 0 Mixture a t 1000째C on the R e v e r s i b l e CO2 C a p a c i t y of Th02-3%

U 0 2 Sol-Gel.

Part 111

Gas-Coole

Reactors

8. Diffusion Processes drodynamic mechanisms compete, were led to reinvestigate t h e thermal transpiration effect a n d uncovered a relation by which i t a p p e a r s p o s s i b l e to obtain information regarding i n e l a s t i c mol e c u l a r c o l l i s i o n s from thermal transpiration data.’ T h e f i r s t real t e s t of t h e theories involved h a v e been completed in t h i s laboratory duting the p a s t year. Thermal transpiration s t u d i e s were conducted with t h e g a s e s Ar, Xe, N,, a n d CO,. T h e phenomenon w a s generated by maintaining temperatures of about 290’K a n d 545rX on t h e opposite e n d s of fourteen 0.1-mrn-ID Pyrex g l a s s c a p i l l a r i e s arranged i n parallel. Although s e v e r a l apparently minor d i s c r e p a n c i e s between theory and experiment w e r e noted, the utility of t h e method for s t u d i e s of i n e l a s t i c coll i s i o n s h a s b e e n dernonstiated to be extremely promising. F u r example, t h e rotational c o l l i s i o n numbers f o r N , a n d CO, which were obtained from the expeiimental data were found t o b e 4.4 and 2.4, respectively, and are in e x c e l l e n t agreement with reported v a l u e s which were determined by t h e morc conventional, and more elaborate, methods.‘

TRANSPORT PROPERTIES’OF GASES T h ermtl I T ran s p ira t ion. Rotat iona I Reiaxat ion Numbers for Nitrogen and Carbon Dioxide A. P. Malinauskas

I t is well known t h a t s e r i o u s errors i n p r e s s u r e measurement c a n result if t h e manometer is maintained at a temperature other t h a n t h a t of the region w h o s e pressure is of interest. T h e phenomenon responsible for t h e discrepancy is known a s thermal 1 ranspiration (or t h e “therinomolecular p r e s s u r e effect”) a n d is defined a s t h e transport of m a s s a s t h e result of a temperature gradient. Unlike thermal diffusion, however, which is simildrly defined, t h e thermal transpiration phenomenon is not restricted to d i s t i n g u i s h a b l c particles. In fact, e v e r s i n c e its discovery in 1873 by Reynolds, investigations of the e f f e c t h a v e b e e n conducted excliisively with pure g a s e s . Unfortunately, t h e utility of t h e phenomenon w a s thCJUght to be s o l e l y that of a p r e s s u r e correction; as a result, t h e s c i e n t i f i c community a p p e a r s l o h a v e b e e n cuiitent with the empirical a n d semiempirical formulatiuns which were proposed and sht>wn experimentally to b e qualitatively correct at b e s t . Recently, however, Mason and cow ~ r k e t s , ~in* a~n attempt to d e s c r i b e g a s transport in t h e region w h e w free-molecule a n d hy-

‘

Caseous Diffusion i n Noble Gas

Systems

A. P. Malinauskas

Unlike related transport properties, g a s e o u s diffusion, the transport of m a s s or idcntity a s t h e resul! of a concentration gradient, is almo:jt totally governed by unlike-molecule interactioiis, t h a t is, like-molecule c o l l i s i o n s affect t h e mechan i s m only d s s m a l l perimbations. However, t h e relative irisensitivity of diffusion to t h e c h o i c e

‘ 0 . Reynolds, Phil. T r a n s . Roy. Soz, London, Ser. R 170, 727 (1880); paper No. 3 3 , S c i e n t i f i c P a p e r s , pi-’.

%.57--390, The University Press, Cambridge.

’R. 8. E v a n s 111, G. PI. Watsot~, atid E. A. Mason, J. Chern. PfiL~s~ 35, 2076 (1961) arid 36, 18Y4 (1962); E. A. ivlasori and A. P. Malinauskas, J . Churn. Phys. 39, 5 2 7 (1963j.

’E. A. Mason, G. M. Watson, and R- B. E v a n s HI# J . Chern. P l i y s . 38, 1808 (1963); E. A. Mason, J . C h e r t i . P h y s . 39, 522 (1963).

4A. P, Malinauskas, t o be publistic-d i n ’/-he Juainsl o f Chemical P h y s i c s .

78 of t h e intermolecular potential c h a r a c t e r i s t i c of t h e interactions n e c e s s i t a t e s measurements either o v e r a wide range of temperature o r of a n accuracy far b e t t e r than t h a t currently possible. Of t h e two alternatives, the former a p p e a r s to b e t h e m o r e f e a s i b l e . Indeed, some diffusion measurements h a v e been reported a t temperatures as high a s llOO°K without a corresponding l o s s in accuracy, but the experimental requirements a r e so stringent and t h e procedure is so elaborate that a more simple approach i s desirable. Such a n approach a p p e a r s to h a v e b e e n provided by theory, in that it is p o s s i b l e t o r e l a t e t h e composition dependence of v i s c o s i t y t o t h e diffusion coefficient c h a r a c t e r i s t i c of a given g a s pair. T h u s , b e c a u s e v i s c o s i t y coefficients a t high (or low) temperatures c a n b e readily determined experimentally, t h e evaluation of diffusion d a t a v i a t h e theoretical relationship is worthy of investigation. Although t h e o b j e c t i v e s of the diffusion program a t t h e L a b o r a t o q are primarily oriented toward a n elucidation of intermolecular interactions, t h e initial s t u d i e s h a v e been concerned with a n affirmation of the viscositydiffusion interrelationship. T h e first s e r i e s of investigations i n t h i s regard were made with t h e s y s t e m s He-Ar, He-Xe, and Ar-Xe and h a v e resolved a previous discrepancy between theory and e ~ p e r i r n e n t . ~ T h e s e c o n d p h a s e of t h e program involves t h e s y s t e m He-Kr, Ar-Kr, a n d Xe-Kr. A n a l y s i s of t h e latter d a t a h a s not yet been completed; however, the preliminary r e s u l t s tend t o further validate t h e theoretical relations h i p between t h e viscosity and diffusion phenomena. Gaseous Diffusion i n Porous Media

A. P. Malinauskas E. A . Mason’ R. B. E v a n s 111 One of t h e major developments regarding t h e migration of g a s e s within a porous medium h a s been t h e formulation of t h e “dusty-gns” model. ’R. E. Walker a n d A. A. Westenberg, J . Chem. P h y s .

31, 519 (1959).

%. Weissman a n d E. A. Mason, J . Chem. P h y s . 37, 1 2 8 9 (1962). 7 A . P. Malinauskas, J . Chem. P h y s . 42, 156 (1955). ‘Consultant, University Molecular P h y s i c s .

Maryland,

I n s t i t u t e for

T h i s model, which i s particularly useful for a description of g a s transport in t h e theoretically difficult transition region where free-molecule and hydrodynamic mechanisms a r e of e q u a l importance, u t i l i z e s t h e somewhat unorthodox view that t h e s o l i d s u r f a c e s of a porous medium or of t h e w a l l s of c a p i l l a r i e s may h e mathematically regarded a s agglomerates of giant g a s molecules (dust). A s a result, a gas-surface interaction i s treated a s a s p e c i a l type of molecular encounter a s would occur between two g a s molecules when one of t h e interacting molecules i s immobile a n d preponderantly larger and heavier than t h e other. U s e of t h e model h a s yielded tile first cons i s t e n t treatments of g a s transport in porous s e p t a for t h e following (1) diffusion due t o a composition gradient; (2) g a s flow as t h e r e s u l t of gradients in composition and press u r e ; (3) thermal transpiration, in which p r e s s u r e and temperature gradients a r e invoived; and (4) migration (and s e p a r a t i o n ) of g a s e s under t h e combined influence of composition and temperature gradients. However, our inability, a t t h e time, t o c o p e with the combination of diffusive and v i s c o u s modes of transpoit in a manner which w a s s a t i s f a c t o r y from a theoretical viewpoint n e c e s s i t a t e d the introduction t o a certain degree of empirical methods in t h o s e cases in which pressure gradients were a t l e a s t partly respons i b l e for t h e particular transport phenomenon. Somewhat erroneously, perhaps, we sought a clarification of t h i s so-called “forced-flow” problem i n higher kinetic theory approximations. T h e approach w a s fruitful in a n indirect manner in t h a t i t led t o the discovery of t h e proper procedure of combining diffusive a n d v i s c o u s flows, and probably t o a complete solution of t h e g a s transport problem. Stated briefly, o n e c a n s e p a r a t e (mentally) motion in a g a s mixture into a diffusive flux and a v i s c o u s flux. What we h a v e learned, however, is that t h e t o t a l flux i s simply t h e sum of t h e s e two fluxes; that is, there i s no direct interaction between v i s c o u s and diffusive flows; t h e only I < cross term” of c o n s e q u e n c e c a n b e absorbed into a c h a n g e in t h e pressure-diffusion coefficient. Although t h i s s i m p l e additivity relation had been u s e d previously by o t h e r s , i t s theoretical 9S. Chapman a n d T. G. C o w l i n g , Proc. R o y . S O C . London, Ser. A 179, 159 (1941); V. Zhdanov, Yu. Kagan, a n d A. Sazykin, S o v i e t Phys. JETP (English

Transl.) 15, 596 (1962).

79 j u s t i f i c a t i o n g a p p e a r s to h a v e b e e n unnoticed. To date, t h e theoretical reinvestigation of diffusion i n t h e p r e s e n c e of a p r e s s u r e gradient h a s b e e n t h e most fruitful a s p e c t of t h i s work; a semiempirical equation which had b e e n derived e a r l i e r h a s now been developed completely from theory, with an e x p l i c t e x p r e s s i o n for what h a d b e e n a n empirical (and a d j u s t a b l e ) coefficient. Moreover, t h e new r e s u l t s l e a d directly t o t h e prediction of t h e Kramers-Kistemakerl or Kirkendall" effect, in which a p r e s s u r e drop is gene r a t e d when t h e n e t flux in a diffusing mixture is zero.

SOLID-STATE TRANSPORT PROCESSES IN GRAPHITIC SYSTEMS Recoil Phenomena

R. B. E v a n s III J. L. Rutherford K. R. P e r e z " Utilization of oxide fuel kernels and multilayer pysocarbon c o a t i n g s e n h a n c e s t h e efficiency of coated fuel paxticles. T e n d e n c i e s for fuel migration, which are greatest during c o a t i n g aperations, ace reduced by t h e u s e of f u e l s . Spearhead propagation is rxiinimized' by applying a parous inner c o a t i n g followed by a n outer c o a t i n g with good retention properties. It is; not unlikely t h a t t h e s u c c e s s of t h e muliilayer concept can b e partially attributed t o sacrificial absorption by t h e inner c o a t i n g of recoiled fissio:i fragments a n d k ~ i ~ c k e d - o nf u e l at<:ms. F o r maximum absorption, ratios of inner-coating fhicliness t o recoil range s h o u l d b e greater than unity. Our objective is the s p e c i f i c a t i o n of t h i s

"11, A. K r a m e r s 699 (1943).

'IC. P. Mceaity 3, 908 (1960). 'Consultant,

and J. K i s t e m a k e r , and E.

Physica 10,

A. Mason, Phys. Fluids

U n i v e r s i t y of Florida.

*'E. B. Evens 111, J. 0. Stieclor, and J . T t u i t t ,

D i f f u s i o n if2 Pyrocarbons ORNL-3711 (December 1944). Pactinide

nrld

Graphite,

I4 R. L. N a m n e r , G C R Program Semiaeirz. Pro&. K e p t . Stipt. 30, 1965 (in. press). ' . 5 ( ~ . simian e t a!.. GCR ~ r o g r a z n Semiatin. progr. Kept. S e p t . 30, I965 (inpress).

ratio for various carbonaceous materials. T h u s w e are engaged i n the determination of t h e d i s tribution of f i s s i o n fragments t h a t h a v e recoiled to a v e r a g e positions within pyrocarbon specimens. From t h e c u r v e s related t o t h e distribution w e c a n e x t r a c t v a l u e s of t h e range R a n d a distribution parameter a s s o c i a t e d with t h e recoil range, c a l l e d t h e straggling factor a. Although s p e c i a l l o w d e n s i t y pyrocarbon s p e c i m e n s h a v e been prepared for experiments to b e conducted in t h e n e a r future, present experiments h a v e b e e n res t r i c t e d t o General E l e c t r i c pyrocarbon s p e c i mens. To i n i t i a t e a s e r i e s of experiments, pyrocarbon s p e c i m e n s a r e bombarded with 2 3 5 U ta t 40 kev T h e source t o form fission-fragment s o u r c e s . specimens, accompanied by a n uncontaminated pyrocarbon target specimen, a r e e x p o s e d t o thermal-neutron fluxes. A l l s p e c i m e n s a r e then incrementally ground and a s s a y e d by gamma counting s o that integral c u r v e s related t o the distribution of various fragments can b e constructed. Applicable transport equations predict t h a t plots of F.R., t h e t o t a l ac1:ivif.y remaining in a specimen a f t e r grinding to a penetration z, v s z can b e approximated by a straight line over most of the interval between zero a n d R. T h e only co.aitribution of (Z is reflected i n the s m a l l t a i l beyond z / K - 0.95. Extrapolations t o the z v a l u e corresponding to F.R. :: 0 w i l l i n d i c a t e t h e true range value. Some tesults a p p e a r in Fig.

8.1.

Several blank experiments

were perlornied using t u e s t a b l i s h the as-deposited condition o f t h e a c t i n i d e CJII source s p e c i m e n s and to provide a z 0 correction for t h e range da1.a. B a s e d on t h e blank d a t a , we <:ondude t h a t t h e :;<)ur<:e l a y e r is very thin (an important requirement for d a t a correlation) and t h a t t h e a v e r a g e layer position is n,0.8 p beneath t h e source-specimen surface. c?s demonstrated hy the recoil d a t a in Fig. 8.1, t h e range v a l u e for the light fragments (13.0 p ) is greater than t h e range v a l u e f o r t h e heavy fragments (I 1.0 p); t h e ratio of the range v a l u e s f o r t h e two groups is 1.13. Similar. experimerits c;onducted in a i r ' G reveal a ratio of 1.32. In order to e s t i m a t e a v a l u e of t h e stragglingfoctnr/range-value ratio, r e s u l t s for t h r e e of our b e s t range experinients h a v e been replotted in 2 3 2 Trr

~.~ ...._......._.__..

I6R. D. Evans, T h e Atomic N u c l e u s , p. 668, McGrawHillv N e w York, 1955,

80 High Temperature Materials pyrocarbon (IITMP y C ) and General E l e c t r i c pyrocarbon (GEPyC). Although superficial examinations s u g g e s t similar structures and properties for t h e s e m a t e r i a l s , ' * we find a distinguishing feature of t h e GE-PyC t o b e continuity of structure across b a s a l planes. T h e integrity of t h i s s t r u c t u r e is retained a t a l l temperatures u p t o 24OOOC without delamination from crystalline rearrangement and Under reasonable conditions of temgrowth. perature and low a c t i n i d e concentrations, acquisition of i e l i a b l e < a > direction r e s u l t s (never obtained with HTM-PyC) i s a s s u r e d . T h i s and t h e f a c t that GE-PyC h a s been s t u d i e d intensely e ~ s e w ~ i e rconstitute e~~ prime reasutrs for our int e r e s t in t h i s material. P r e s e n t r e s u l t s evolved from two d i s t i n c t experiments in which a c t i n i d e invaded pyrocarbon from either a thin layer a t low concentrations or a constant-potential s o u r c e a t t h e maximum concentration C, .- t h e apparent solubility. In e a c h c a s e , determinations of D I a n d D , (coefficients for diffusion in t h e <a? and < c ? directions) were attempted. E s t i m a t e s of C, could b e extracted only from constant-potential r e s u l t s s i n c e s u r f a c e concentrations in thin-layer experiments diiiiinish with time. Some a v e r a g e results ohtained a t comparable diffusion times a r e pres e n t e d in T a b l e 8.1. Clearly, uranium diffuses f a s t e r than thorium - particularly in t h e < a > direction. Additional thorium d a t a reveal a D,< c >/ DI<-c> ratio of 1.5 a t 2065OC. T h i s may b e a valuable c l u e for a n interpretation of t h e wellk n o w n 2 0 * 2 ' nonuniforiii < c ? direction diffusion patterns. F r o m both thorium and uranium diffusion data (not shown), w e found t h e coefficients to b e invariant with time over t h e temperature a n d x/2 ranges investigated. In other words,

'/R F i g . 8.1.

Comparison

Range

Measurements

foi

A v e r a g e Light and Heavy F i s s i o n Fragments from 2 3 5 U i n General E l e c t r i c Pyrogrophite.

experiments a i e a l s o s h o w n .

D a t a for f i v e b l a n k

terms of concentration; that i s , ( 4 a c t i v i t y / A z ) v s z . Correlation of t h e s e plots with a p p l i c a b l e equations s u g g e s t s a n n / R v a l u e of 0,126. We n o t e t h a t t h e Q and H v a l u e s c i t e d a r e automatic a l l y averaged with r e s p e c t t o t h e < a ? and < c > directions by t h e conditions of our experiments, in which fragments e n t e r t h e target a t a l l s o l i d a n g l e s f r o m 0 t o 27 s t e r a d i a n s . T h i s point h a s been verified experimentally u s i n g < a ? and < c > direction specimens. Actinide D i f f u s i o n

R. B. E v a n s I11 J . C . Rutherford F. L. C a r i s e n , J r .

Investigations of uranium and thorium diffusion in graphite matrices h a v e b e e n carried out on 17Formerly with ORNL Metals and C e r a m i c s Division; p r e s e n t a d d r e s s S t e l l i t e Division, Union Carb i d e Corporation, Kokomo, Ind.

"Both G.E. a n d HTM pyrocarbons p o s s e s s turbostratic-columnar (sottretirnes c a l l e d granular) struc-

t u r e s which l e a d t o high matrix d e n s i t i e s (-2,2 g / c m 2 ) and abnormally high a n i s o t r o p i c r a t i o s for many properties. "F. L. C a r l s e n , Jr., "Effects of Pyrolytic-Graphite Stiucture on Diffusion of Thorium," t h e s i s submitted a t t h e University of T e n n e s s e e , i s s u e d a s ORNL-TM1080 (June 1965).

''5. R. Wolfe, D. R. McRenzie, a n d R. J. Rorg, T h e Diffusion of Non-Volatile Metallic E l e m e n t s in Graphite, UCRJ.,-7324 (April 1964). 21R. B. E v a n s 111 e t al., R e a c t o r Chem. Div. Ann. Progr. Rept. Jan. 31, 1965, ORNL-3789, pp. 193-97.

81 Table 8.1. ........... __

D i f f u s i o n C o e f f i c i e n t s a n d R e l a t e d R e s u l t s for A c t i n i d e s a t L o w Concentrations i n General E l e c i r i c Pyrocarbons (Columnar)

...

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

_ . _ _ 1 _ _

D Coefficients (cm2/sec) Thorium

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

Temperature, OC

2065

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

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

n,I

Ill<<+c> __ ................. -

2.1

1.5 x

2.0 x lo-"

1865 1697

1.2 x 6.8 x

1.9 x 1 0 - ' 2

3.0

4.3

lo-"

2.2 x

lO--'O

1.4 x

: i

4.G X

1.6

2.1 x

5.0 x

Related Results

[d", g/cm3

3.1 1.2 *,,

AH", cal/mole /kc, caI/moIe

2.8

lo5

x lo-'&

1.6 x l o s 1.4 X 10'

1.1 :< 1 0 5

1.3 x 10

-in)-';

1.2 x

lo5

........I_____.___.__

....._I__-

aAverage a c t i n i d e concentration, @, ( r D t ) - 1 ' 2 exp

1.2 x 105

1.0

bActivntion energy for p r e s e n t results.

2 pg/cm

'Activation energy reported by J. K. W o l f e et 31.. UCRL-7324 (1964).

ORNL-DWG

55-12433

c o e f f i c i e n t s , obtained a t concentrai i o n s dangerously near the a n t i c i p a t e d C, vijlue, show exc e l l e n t agreement2 with uranium c o e f f i c i e n t s obtained a t practically z e r o a c t i n i d e concentrat i o n s (carrier-free 'u). In opposition to thin-layer r<:sults, preliminary constant-potential d a t a s u g g e s t comparatively high c o e f f i c i e n t s and low a c t i v a t i o n energies, Howe v e r , these r e s u l t s may a g r w with the highconcentration results' for HTM-PyC:. Considerations of combined structural and concentration e f f e c t s might e n a b l e reconciliat ioti of t h e anomalous diffusion behavior a s observed a t high and low concentration leveIs. It is clear, however, that thin-layer data are not indicative of f u e l migration in carbide fuel-particle c o a t i n g s s i n c e t h e a c t i n i d e concentrations a t coatingc a r b i d e i n t e r f a c e s are quite high.

F i g . 8.2. c ients

Comparison

Reported

for

Uranium

General

Diffusion

Electric

Self-Diffusion

Caeffi-

E. B. Evans III

Pyrographite

(Columnar).

t h e c o e f f i c i e n t s a r e true c o n s t a n t s , and structural c h a n g e s induced by high-temperature e x p o s u r e (sometiines c a t a l y z e d by high a c t i n i d e concentrations) do not occur a t the conditions of t h e s e experiments. Dramatic verification ( s e e F i g . 8.2) oE this is evidenced by t h e fact that our uranium

Several dramatic c h a n g e s occur in pyrolytic c a r b o n s when s u b j e c t e d to temperatures above 22

Similar c o m p a r i s o n s i n d i c a t e a less-than-excellent agreement of thorium coefficients. T h e magnitudes of c c e f f i c i e n t s reported by Wolle et a / . , a r e greater than ours by a f a c t o r of 5; however, D /U ratios and A E I I .I. v a l u e s a r e comparable.

t h o s e at which they a r e deposited. At high temperatures the s t r u c t u r e s â&#x20AC;&#x153;improveâ&#x20AC;? in that they tend t o a s s u m e a graphitic structure; v a l u e s of t h e thermal conductivity and impurity-atom diffusivity d e c r e a s e . T h e rote a n d mode of t h i s ann e a l i n g p r o c e s s are diffusion controlled and a r e b e s t interpreted through self-diffusion measurements. In s y s t e m s other than graphite, self-diffusion ineasurements may b e circumvented, s i n c e t h e self-diffusion coefficient h a s been correlated with other properties more amenable t o experimentation. Analogous correlations for graphite a r e undetermined; t h e n e c e s s i t y of conducting t h e formidable self-diffusion experiments s t i l l remains, i f for n o other reason than t o obtain correlations of the type mentioned. We h a v e initiated a s y s t e m a t i c study of t h e role of self-diffusion in t h e annealing phenomena a s s o c i a t e d with graphites and carbons. From t h i s information w e hope to e s t i m a t e diffusion

parameters for perfect graphite c r y s t a l s v i a extrapolation of data for improved s t r u c t u r e s . A s e r i e s of s p e c i a l thorium-pyrocarbon diffusion experiments h a s been completed pursuant to t h e s e l e c t i o n of materials a n d a n n e a l i n g conditions for u s e in t h c present investigation. Observations of a c t i n i d e diffusion patterns a r e q u i t e va!uable in s u r v e y s of t h i s sort, s i n c e a c t i n i d e s migrate preferentially alone; d e f e c t i v e p a t h s in carbons. As a result of t h e s e experiments, s e v eral p o s s i b l e carbon c a n d i d a t e s were chosen for our initial self-diffusion s t u d i e s . Equipment and techniques u s e d t o study diLf u s i o n of a c t i n i d e s and f i s s i o n product s p e c i e s in graphites and carbons are being modified a s required i n order to permit study of 1 4 C diffusion. T h e development of methods for a c c u r a t e placement of t r a c e r on s u r f a c e s and t h e demonstration of certain means of a s s a y for t h e diffused isotope pose t h e most immediate problems.

9. Reactions of Reactor Components

with Oxidizing Gases I,. G. Overholser effect, if a n y , t h e addition of methane might h a v e on t h i s reaction. Data obtained f r o m t h e s e s t u d i e s a r e given i n T a b l e 9.1. Carbon removal c a l c u l a t e d from CO, + CO found i n t h e effluent g a s e s s h o w s t h a t t h e water vapor-graphite reaction w a s retarded by t h e addition of methane, although to a lesser extent than by a n e q u a l concentration of hydrogen. If only weight c h a n g e s are detennined, one might conclude that t h e oxidation of graphite b y water vapor w a s completely s u p p r e s s e d . Data obtained from t h e effluent gases, however, show t h a t both oxidation and deposition occurred. T h e c a l c u l a t e d and observed weight c h a n g e s agreed s a t i s f a c t o r i l y i n t h o s e cases where weight losses o r small weight g a i n s were found. The c a l c u l a t e d weight c h a n g e s were significantly larger than t h e measured weight c h a n g e s i n t h o s e instances where l a r g e weight g a i n s prevailed. T h i s behavior could b e due t o s p a l l i n g of carbon from t h e graphite surface. Both t h e oxidation a n d deposition rates dec r e a s e d with d e c r e a s i n g temperature and were not measurable at temperatures much below 700°C:. Carbon deposition r a t e s from methane-helium mixt u r e s were determined i n t h e a b s e n c e of water vapor to e s t a b l i s h what effect water vapor might h a v e h a d on t h e cracking of methane. A comparison of t h e c a l c u l a t e d deposition r a t e s l i s t e d in T a b l e 9.1. with t h o s e given i n Fig. 9.1 s h o w s that water vapor h a s very little, iE a n y , e f f e c t on the cracking of methane. T h e overall r a t e s are different, however, in t.he hvo cases due to loss o f carbon by oxidation i n t h e p r e s e n c e of water vapor. T h e s l o p e s o f t h e plots given it1 Fig. 9.1 cor50 kcal/rnole respond to activation e n e r g i e s of for all concentrations of methane examined. T h e

EACTIVlTY OF AT9 GRAPHITE WITH LOW CONCENTRATIONS OF OXIDIZING A N D REDUCING GASES

J . P. Blakely R a t e s of reaction of a 1-in,-diam s p h e r e of ATJ graphite with low Concentrations of w a t e r vapor a n d carbon dioxide i n flowing helium (1 atm), obtained from continuously recorded weight c h a n g e s and cornpositionis of t h e effluent g a s e s a s e s t a b l i s h e d by a s e n s i t i v e gas chromatograph, h a v e b e e n reported.‘” T h e s e s t u d i e s h a v e b e e n extended i o g a s mixtures contlaining both water vapor and carbon dioxide in helium.3 Addition of carbon dioxide to t h e water vapor i n c r e a s e d t h e reaction r a t e s above t h o s e observed for water vapor alone, but the r a t e s fourid for t h e mixed o x i d a n t s were less that1 t h e sum of t h e r a t e s for t h e two oxidants. Addition of hydrogen inhibited t h e r e a c t i o n s of both t h e oxidants with graphite. In view of t h e retarding effect of hydrogen on t h e water vapor-graphite reaction noted earlier, s i m i l a r s t u d i e s were perfortned‘ to e s t a b l i s h what

‘

‘L. 12.Ovsrholser a n d J. P. Blakely, GCR Program Scmiann. Progr. R e p t . S e p t . 3 0 , 1 9 6 4 , ORNL-3731, pp. 161-67. 2J. P. B l a k e l y a n d L. G. Overliolser, “Oxida?ion o f A T J Graphite b y Low C3mcentmtlcJns of Water Vapor and Carbon Dioxide in Heliun!,” Carbo17 (in press).

31,. G. Overholser and .J. P. Blakely, GCK Program Seoiiann. Progr, H e p t . /Mar, 3 1 , 1 9 6 5 , ORNL-3807, pp.

150-55. ‘Id. G. Overholser and J. P. U l a k e l y , GCR Program Semiarm. Pro&. K e p t , S e p t . 30, 1 9 6 5 , ORWL-3885 (in

cx,

prrss).

T a b l e 9.1.

Carbon D e p o s i t i o n from Methane-Water

Vapor-Helium

Mixtures

H,O Concentration of 113 ppm L o s s and Gain of Carbon ( m g cm-2 h r - i )

C H 4 Concentranon Temperature (OC)

Flow

Influent

Eifluen:

[cm3 (STP)/minl

Gases

Effluent Concentration (ppm)

Gain

Net

Weight

C a l c u l a t e d from

Calculated from

Gain or

Change

CO,

T o t a l PI,

Corrected H ,

10-3

-8.0

3.2

-2.8

-3.9

6.1

3.9

-2.2

-1.8

6.0

6.7

+o. 7

+O. 8

4.8

8.6

+3.8

f2.0

4.0

9.7

+5.7

+2.8

‘1

4.0

11.1

2.5

+O. 4

132

6.0

270

25.5

‘..l

275

s35

320

800

3 00

560

520

800

300

635

6 10

800

275

680

650

280

‘.. 1

280

800

275

142

800

300

800

750

28.5

290

x -8.1

800

Observed

Loss

8.1

1-7.1

+4.7

1.7

-0.8

-0.6

+1.0

750

285

560

550

2.5

3.5

700

300

260

0.9

1.3

11.2 -3.7

co P

85 ORNL-DWG 65-11486

TEMPERATURE ( ' C ) 800 750

850

700

A'TJ graphite is not a n e f f i c i e n t medium for promoting t h e disproportionation of carbon monoxide under t h e experimental conditions examined.

COMPATIBILITY OF PY ROLYT1C-CARBONCOATED FUEL PARTICLES WITH WATERVAPOR

C. M. Blood

9.5

101

103

'aOOO/r(YK)

Fig. 9.1.

E f f e c t of Temperature on Carbon Deposition

R a t e s a t Various Methane Concentrations.

apparent order of t h e deposition reaction with r e s p e c t to methane falls between 0.5 and 0.8 i n t h e temperature range of 750 to 850°C. S t u d i e s 4 a l s o were made of t h e disproportionation of carbon monoxide on A T J graphite, u s i n g 1.5O-PSQ0 ppm of carbon monoxide in helium a t temperatures of 550 t o 850°C. T h e complete lack of agreement b e t w e e n deposition r a t e s c a l c u l a t e d from t h e carbon dioxide found i n ' t h e e€fluetit g a s e s and t h o s e obtained from measured weight c h a n g e s i s not understood. Using v a l u e s for t h e deposition r a t e s c a l c u l a t e d from t h e carbon dioxide formed, i t w a s found that deposition r a t e s i n c r e a s e d with i n c r e a s i n g carbon monoxide concentrations. T h e deposition rates af. c o n s t a n t carbon monoxide concentration i n c r e a s e d upon raising t h e temperature from 550 to 75O0C and then remained c o n s t a n t or d e c r e a s e d s l i g h t l y when t h e temperature w a s r a i s e d to 850OC. The low r a t e s found s u g g e s t that

Current developments i n d i c a t e that fuel particles c o a t e d with pyrolytic carbon will b e present i n a l l ceramic cores of high-temperature gas-cooled rea c t o r s . Inleakage of water vapor during operation of s u c h a reactor p o s e s h a z a r d s b e c a u s e of t h e high temperatures of the core components. Oxidation o f t h e fuel particle c o a t i n g s could c a u s e coati n g f a i l u r e s and a resultant r e l e a s e of volatile fission products into t h e helium c o o l a n t , T h e compatibility of various b a t c h e s of fuel p a r t i c l e s with water vapor has been examineds in In t h e s e a n attempt t o e v a l u a t e t h e hazards. s t u d i e s , fuel p a r t i c l e s were e x p o s e d a t 1000°C to flowing helium-water vapor mixtures having partial p r e s s u r e s of water vapor of 4.5, 45, a n d 570 torrs. T h e fuel particles had various t y p e s of pyrolytic carbon coat.ings and c o r e s of UC, o r (U,Th)C,. T h e reactivity of t h e fuel c o a t i n g s w a s determined from weight c h a n g e s a n d effluent gas composif.ions. The i n c i d e n c e of failure of t h e c o a t i n g s w a s obtained from t h e quant-ities of uranium and thorium removed by a c i d l e a c h following exposure to water vapor. Microscopic a n d metal lographic examinations were made following exposure to water vapor and also after a c i d leach. Surface a r e a measurements were made on both oxidized and unoxidized fuel particles. Reaction r a t e s for different b a t c h e s o f fuel part i c l e s obtained a t 1000°C u s i n g various partial p r e s s u r e s of water vapor a r e given in Fig. 9.2. T h e s e d a t a show that the apparent order of t h e water vapor-coating reaction i n c r e a s e d with i n c r e a s i n g partial p r e s s u r e of water vapor in virtua l l y all cases. 'fiis could b e due, i n p a d , to diff e r e n c e s i n burnoff a t t h e various partial pressures. ~

C . M. Blood a n d L. G. Overliolser, GCZi Program Sc-niiann, Vrogr. Rept. Mar. 31, 1 9 6 5 , OKNL-3807, pp. 140-42; GCK Program Semiairin. Pro&. R e p t . S e p f . 3 0 , 1 9 6 5 , OKNL-388.5 ( i n p r e s s ) . 5

300

ORU.

DWG 55 11562

-T

200

' I1

100

-L

-m

I L

z 9

graphite body can afford protection for t h e particle c o a t i n g s but that t h e configuration of t h e fuel a s sembly will determine, t o a large degree, t h e extent of protection obtained. T h e s t u d i e s a r e continuing, with e m p h a s i s being placed on t h e effect of higher temperature (1200 to 14OOGC)and of prior irradiation on t h e reactivity with water vapor.

1:'

COMPATlBlLlhY OF METALS WITH LOW CQHCENTRATIONS OF CARBON MONOXIDE

J . E. Baker

ISOTROPIC V

ISOTROPIC \ / I

ISOIt?O'lL

1 1

02 01

2 0

100

H20 PARrlAL PRESSURE

F i g . 9.2.

VI1

NCC-217

200

500

1000

(torr)

E f f e c t of P a r t i a l P r e s s u r e of Waier Vapor

on R e a c t i v i t y of F U ~PI a r t i c l e s a t

IOOO"C.

T h e incidence of failure of t h e c o a t i n g s a l s o may b e responsible for t h i s behavior. In general, only a few particles failed a t a partial pressure of 4.5 torrs, whereas a t 570 torrs appreciable fractions failed in a l l c a s e s . If t h e core r e s i d u e s c a t a l y z e d t h e reaction, t h i s could account for t h e change in apparent order observed. T h i s behavior makes an extrapolation to other partial p r e s s u r e s hazardous. Surface area data obtained for oxidized particles from t h e various h a t c h e s of fuel particles were extremely variable. In general, no correlation of reactivity with s u r f a c e a r e a w a s possible. Also, no c o n s i s t e n t relationship of i n c i d e n c e of failure of c o a t i n g s to reaction rate, s u r f a c e a r e a , or burnoff w a s evident. Photomicrographs of oxidized particles from various b a t c h e s showed that t h e mode of attack varied from b a t c h to batch; t h i s might b e anticipated from the variable reaction rate and s u r f a c e area data. Studies of t h e effect of support media for t h e fuel p a r t i c l e s on t h e reaction rate showed that r a t e s obtained with alumina or platinum were e s s e n t i a l l y the same. U s e of a graphite s l e e v e to support t h e fuel p a r t i c l e s reduced t h e a t t a c k of water vapor on the c o a t i n g s ; the degree of protection i n c r e a s e d with increasing s l e e v e length. T h i s s u g g e s t s that a

In t h e BeO-graphite compatibility t e s t s , metals are u s e d a s h e a t s h i e l d s in an inert-gas atmosphere containing -,200 ppm of carbon monoxide a t temperatures ranging from -,400 to 800cC. P o s s i b l e deposition of carbon on the metal s u r f a c e s and t h e resulting d e c r e a s e in r e f l e c t a n c e prompted a lahoratory study of t h e m e t a l s in an atmosphere a p proximating that prevailing i n t h e engineering t e s t s . Specimens of molybdenum, gold-plated s t a i n l e s s s t e e l , and mild s t e e l were e x p o s e d to flowing helium (1 atm) containing 250 to 300 ppm of carbon 1003C in monoxide a t temperature i n t e r v a l s o f t h e temperature iange of -450 to 85OOC. Expos u r e times averaged -,30 hr at e a c h temperature. Weight c h a n g e s were continuously recorded by a s e n s i t i v e a n a l y t i c a l balance, and t h e influerrt and effluent g a s e s were analyzed by a s e n s i t i v e g a s chromatograph. X-ray s t u d i e s were made of t h e exposed s p e c i m e n s in a n attempt to identify any d e p o s i t s formed. T h e molybdenum specimen gained 1 0 pg/cm2 during an exposure time of 1 5 0 hr. T h e weight c h a n g e s were so small t h a t t h e effect of temperature could not b e measured. T h e e x p o s e d speci.rnen had a very thin dark-gray film and a few s p o t s s u g g e s t i n g localized attack. T h e film is probably a n oxide, which could have been produced by very low concentrations of oxygen and/or water vapor present a s contaminants in t h e helium stream. There w a s no evidence of carbon deposition. T h e gold-plated s t a i n l e s s s t e e l specimen showed an overall weight gain of 1 0 0 pg/cm2 for an ex150 hr. T h e rate of weight gain posure time of %

-i.

' C . A . Brandon and J . A . C o n h n , GCK Program Semianti. P r o g r . K e p t . S e p t . 3 0 , 1 9 6 3 , ORNId-3731, pp.

202 --6.

87 varied by about a factor of 2 over t h e temperature range examined, with no c o n s i s t e n t effect of temperature evident, T h e e x p o s e d specimen h a d a dull green color, s u g g e s t i n g failure of t h e gold plate. X-ray a n a l y s i s showed t h e f i l m t o b e C r L O , with no carbon present. A bright specimen of mild s t e e l l o s t -170 pg/cm2 during 150 ht. T h e r a t e o f weight loss i n c r e a s e d with temperatuie. The s u r f a c e ~7~1s bright a t t h e e n d of t h e t e s t and showed no e v i d c n c c ot carbon dcposition. A rusty specimen of mild s t e e l l o s t ‘ 1500 pg/cm2 during ‘k150 hr, with no c o n s i s t e n t effect of temperature on t h e r a t e of weight loss

evident. T h e s u r f a c e brightened during t h e e x posure, and x-ray a n a l y s i s found only F e O present i n t h e s u r f a c e film. Since t h e original specimen had Fe,O, and Fe,O,-II,O present, carbon rnonoxi d e reduction of t h e o x i d e s s e e m s responsible €or t h e large weight losses. The r e s u l t s i n d i c a t e that carbon is not deposited on t h e s e metal s u r f a c e s i n t h i s temperature range from low concentrations of carbon monoxide i n helium containing e s s e n t i a l l y no hydrogen o r water vapor. T h e situation could be different i n t h e presence of t h e latter.

J . G. Morgan

O s c a r Sisman

FISSION-GAS W EL EAS E F R8M PY WOLYTICCA R BON-COAT E D FU E L PARTICLES

inner l a y e r and a granular outer layer. After a l i t t l e more than 26% bumup a t 14OO0C, a few b u r s t s of f i s s i o n g a s were r e l e a s e d , and t h e fractional r e l e a s e (see ’Table 10.1) i n c r e a s e d by a factor of about 7. Three experiments were conducted u s i n g part i c l e s with a porous carbon buffer l a y e r between t h e uranium oxide core and t h e pyrolytic carbon coating. P a r t i c l e s from h a t c h O R 3 5 4 h a d a relatively thick (82 p ) isotropic coating over t h e porous buffer. T h e fractional fission-gas release, a s shown in T a b l e 10.1, remained very nearly cons t a n t throughout t h e t e s t . Particles from batch OR-348 were similar to t h o s e of OR-354 (porous, isotropic on a n oxide core), but the isotropic c o a t i n g w a s more dense. Initial v a l u e s for fractional r e l e a s e from t h e OR-348 p a r t i c l e s were near t h e v a l u e s increased t o n e a r by t h e e n d of t h e t e s t . N o bursts of f i s s i o n gas were observed. T h e third batch of p a r t i c l e s (batch OR-HB23) with a porous inner layer were made with sol-gel U 0 2 c o r e s ; 4 t h e s e were coated with a n isotropic layer next to t h e porous carbon buffer layer and a granular outer layer. T h e s e p a r t i c l e s operated for 25 at. % ’ heavy metal burnup a t 16OOOC. T h e fission-gas release r a t e s were quite low ( s e e T a b l e 10.1); they i n c r e a s e d by less than a factor of 2 during t h e e n t i r e t e s t . P a r t i c l e s from batch OR-343 were made with a n inner c o a t i n g which would shrink away from t h e uranium oxide core. T h e s e p a r t i c l e s h a d a lowdensity (- 1.5) pyrolytic carbon c o a t i n g applied directly t o the core, followed by a higher-density

P. E. Reagan J. G. Morgan W. Gooch ‘T. W. Fulton C. D. B a u n a n n

In previous experiments’s2 w e showed t h a t radiation damage t o t h e pyrolytic carbon c o a t i n g was d u e priniarily t o fission fragments originating a t t h e core-coating interface. T h i s damage can b e a l l e v i a t e d by providing a gap a t t h e corec o a t i n g interface, by a porous carbon layer, or by a s a c r i f i c i a l pyrolytic carbon layer. Particles of d e n s e U 0 2 h a v e been c o a t e d (in t h e ORNL Metals and Ceramics Division) by techniques which provide one of t h e s e protective measures. We h a v c measured fission-gas r e l e a s e r a t e s from t h e s e three kinds of c o a t e d p a r t i c l e s during irradiations in t h e A9, W9, and C 1 f a c i l i t i e s in T h e irradiation temperature, burnup, t h e ORR. and fission-gas r e l e a s e data a r e given in T a b l e 10.1. Particles. in batch OR-298 had been h e a t treated t o introduce a gap between the uranium oxide core and t h e inner l a y e r of pyrolytic carbon. T h e coating on t h e s e p a r t i c l e s c o n s i s t e d of a n anisotropic ‘P. E. I<eagan, F. L. C a r l s e n , and R. $1. Carroll, “ F i s s i o n - G a s Release from P y r o l y t i c Carbon C o a t e d F u e l Pa;ticIes During Irradiation,” N u c l . S c i . E n & 1 8 ( 3 ) , 301-18 (1361). ‘P. E. sion-Gas Particles Sci. Eng.

Reagan, J. G. Morgan, and 0. Sisman, “FisR e l e a s e from Pyrulptic Carbon Coated F u e l During Irradiation a t 2000 t o 2500°F,*’ N u c l . 23(2), 210-23 (1965).

3P. E. Reagan el al., “ F i s s i o n G a s R e l e a s e from Coated P a r t i c l e s , ” G C R P r o g r a m S e n i a n n . Progr. Kept. S e p t . 30, 1965 (in press).

4J. P. McBride, “Preparation of U O Microspheres b y a Sol-Gel Technique,” ORNL-3874 (in’press).

Fission-Gas Release from Pyrolytic-Carbon=CsatedUranium Oxide Fuel P a r t i c l e s During lrrodiation

Table 10.1.

Capsule

A9-2

OR-298

Barnup

Coating

Batch

Gap

(at.

5% U)

Average Fractior.al Fission*Ges Release, R,’Ba

Temperature (OCj

37.9

anisotropic 4granular

B9-26

OR-354 OR-338

C1-17

OK-343

4.7 x 10-6

4,2 x

Porous carbon i -

9.4

1500

1.6

11.9

i400

1506

14.7

1400”

10-7 1.1 x 10-7

25.2

3 600

6.1‘

Isotropic I t

isotropic

OR-HB23

3.4 x

1350

Porous carbon r 1sot:Oplc

2.8

1.7 x

1.3 x

1.2 x

1.0 k 10-6

0.6 x 10-6

1.1 x

0.8 *: ID-’

0.6 X. IO--?

0.9

1.9

1.4 Y 10-7 0,s >:

1,2 x 10-7

1.7

4.3 s I O e 3

3.9 >: 10-8

aRelease r a t e l b i r t h rate; average for l a s t week of t e s t unless otherwise noted.

’Date not available.

eAfter 2.8% burnup a: 150OoC.

3.7 x

granular

%efore bursm of f i s s i o n gas, ‘After bursts of fission gas.

133

3.5, x 10-6

d e n s e isotropic

C1-16

.jay x

3.9 x

12.1

isotropic

39-27

7.0 x 10-7”

Porous carbon

lSIXe

IO-’

10-6

0.7

IO-?

io-’

7.6

0.4 x 0.7 x d

lo-’

5.4 x lo-*

microscope ( a t OX), and about 100 p a r t i c l e s from e a c h experiment were s e l e c t e d for metallographic T h e p a r t i c l e s made with a n inexamination. tentional g a p a t t h e core-coating interface (batch OR-298) revealed no failed coatings, although their behavior during irradiation s u g g e s t e d t h a t a f e w p a r t i c l e s did fail. Metallographic examination (see Fig. l 0 . 2 j showed that t h e inner pyrolytic carbon c o a t i n g had undergorie s e v e r e dclaniination but that t h e outer c o a t i n g had remained intact. N o reaction product was observed at t h e core-coating interface. T h e uraniarn oxide cores showed s m a l l metallic i n c l u s i o n s i n t h e grain boundaiies and a collection of fission-gas bubbles.

10-8

(3-6

COhTbMINbTlOh, BfiSFC ON ALi'44

Fiy.

10.1.

-...

I 13-5

CCJNT I j r o m s URbNIJlvV

Relationship Between 8 8 K r

R e l e a s e and

Coat in g C o n t a m i 11SI t i on.

(-1.8) pyrolytic carbon outer layer. A s shown in T a b l e 10.1, t h e ftactional fission-gas r e l e a s e nearly doubled when t h e temperature was increased from 1400 t o 150Q째C, hut it returned to about t h e original value when t h e teiapeiature was again d e c r e a s e d to 14OQOC. We observed that a corlelation could b e made between the degree of contamination i n t h e coating and t h e fission-gas r e l e a s e from p a r t i c l e s with unbroken coatings ( s e e Fig. 10.1). T h i s l e a d s to t h e conclusion that (below 1400째C) t h e fission-gas r e l e a s e from unbroken c o a t i n g s is predominantly from contamination in t h e c o a t i n g rather than from t h e fuel core.' We h a v e found t h a t c o a t e d oxide particles h a v e l e s s contamination in the coating than c o a t e d c a r b i d e particles.

POST1~

~ E X MINATION A OF COATED ~ FUEL PARTICLES P. E. Reagan

E. L. Long, J r . '

T h e irradiated uranium oxide p a r t i c l e s described in t h e previous s e c t i o n were examined with a 5~,~,ietals and Ceramics Division.

Postirradiation examination of t h e ura*linm oxide p a r t i c l e s from b a t c h OR-354 revealed that only minor microstructural c h a n g e s had occurred a s a result of t h e irradiation. No failures or e v i d e n c e of potential failures was noted. The only c h a n g e s observed w e r e apparent densification of t h e porous carbon inner c o a t i n g and t h e p r e s e n c e of fission-gas bubbles and sinal1 metal J i c i n c l u s i o n s in t h e grain boundaries of t h e uranium oxide. N o coatiiig f a i l u r e s and only minor microstructural c h a n g e s were noted when irradiated p a r t i c l e s from b a t c h O R 4 4 8 were examined. T h e only c h a n g e i n t h e c o a t i n g w a s a continuous gap t h a t formed a t t h e core-coating interface. T h e third b a t c h of p a r t i c l e s with a porous inner l a y e r (OR-HR23) had been irradiated t o 25 at. % uranium burnup a t 1600OC. An apparent densification of t h e porous carbon layer, a s shown in Fig. 10.3, w a s t h e only microstructural c h a n g e noted in t h e s e c o a t i n g s a f t e r irradiation. T h e p a r t i c l e s of batch OR-343 were c o a t e d in a n experiment to determine whether 3 low-density c o a t i n g applied directly to t h e U 0 2 c o r e would shrink during high-temperature irradiation a n d provide the gap n e c e s s a r y to relieve t h e s t r e s s on t h e coating. T h i s did indeed occur, as i s shown i n Fig. 10.4. Although about 20% of t h e c o a t i n g s showed s h o r t fractures s p i r a l i n g into t h e inner coating, no failed c o a t i n g s were observed. ~ A ~ ~ ~ T h e a d v a n t a g e s of t h e UO, c o r e s over UC c o r e s became more obvious when i t w a s observed t h a t t h e UO, woiild not convert to U C 2 as l o n g a s t h e c o a t i n g w a s intact. From our experience with a variety of coated U 0 2 particles, w e c o n c l u d e that they a r e superior to t h e U(:, p a r t i c l e s for t h e following reasons: (1) the oxide d o e s not flow a t high burnup a n d expand i n t o v o i d s or

91 PHOTO 82346

a 2 x N

...

.-10

Fig. 10.2.

P y r o l y t i c - C a r b o n - C o a t e d Uranium O x i d e P a r t i c l e s from B a t c h

radiated; ( h ) irradiated to

28% burnup

l4OO0C i n c a p s u l e A9-2.

OR-298.

M a g n i f i c a t i o n 200)

(a)v n i r -

92 P H O T O 82347

Fig.

10.3.

Pyrolytic-Carbon-Coated

Uranium O x i d e P a r t i c l e s f r o m Butch

(a) unirradiated;(b) irradiated t o 25% burnup a t 160OoC i n c a p s u l e C1-17.

OR-MB23.

Magnification 2 0 0 ~ :

!348

F i g . 10.4.

Pyrolytic-Carbon-Coated U r a n i u m Oxide P a r t i c l e s from Batch OR-343.

radiated; ( h ) irrad:ated to 12% burnup a t 140OoC and 3% a t 1500째C in capsule C1-16.

Magnification 2 0 0 ~ :

( a ) unir-

94 c r a c k s as t h e carbide d o e s , (2) uranium from t h e oxide will not diffuse into thp pyrolytic carbon coatings even a t high temperatures, ( 3 ) uranium contamination in t h e c o a t i n g c a n b e kept to a much lower l e v e l during fabrication with oxide c o r e s , a n d (4) t h e oxide i s not reactive and is much e a s i e r to handle during fabrication of t h e c o a t e d particle.

ADIAVIOPB TESTING QF COATED FUEL PARTICLES R. E. Towns M. T. Morgan C . I). Baumann Annealing s t u d i e s of irradiated c o a t e d fuel particles were continued t o determine t h e s t a b i l i t y of t h e c o a t i n g s a t temperatures higher t h a n that

T a b l e 10.2.

of t h e irradiation and t o measure their ability t o contain fissiori products. T h e particles tested had fuel c o r e s of UC,, (Th,U)C2, or UO, with duplex or triplex pyrolytic carbon coatings. They were h e a t e d t o temperatures up t o 2000째C in a flowing helium atmosphere; t h e furnace components were periodically removed for a n a l y s i s to measure f i s s i o n product r e l e a s e a s a function of time and temperature. T h e release r a t e s obtained in f i v e annealing experiments a t 1370, 1700, and 2000째C are coil?pared in Table 10.2. T h e v a l u e s shown were averaged over 6 hr of a n n e a l following a n i n i t i a l 1-hr heat.ing period a t each temperature. A graph of t h e cumulative r e l e a s e s v s time for barium and strontium from t h r e e batches. of p a r t i c l e s is shown in Fig. 10.5. ~

%. T. Morgan, R e a c t o r Chem. Dlv. A n n . P r o g r . K e p t . J a n . 31, 1965, ORNL-3789, pp. 212-13.

F i s s i o n Product R e l e a s e R a t e s f r o m Pyrolytic-Carbon-Coated Fuel Part i c les During P o s t i rrad iotion Annea I ing

__... .......

Annealing

Sample*

Temperature

No.

(OC)

__ R9-20

..........

......

....

_____ .........

...___

__......

.......

F i s s i o n Product R e l e a s e R a t e s (%/hr)

--..

..............-..--..-..->

I_____

' ~ r

140Ba .........

144~e

.......

...

2 0.03

0.3

50.003

B9-2 1

0.1

0,2

$0.01

0.01

c1-15

0.1

0.04

0.02

0.8

0.6

50.002

89-2 1

0.6

0.04

0.02

c1-15

0.5

0.4

0.3

0.08

0.3

C1-16

0.0006

0.3

0.02

0.03

B9-21

0.3

c1-15

C1-16

10.

0.005

0.01

R9-20

%9-20

1700

2000

50.1

5 0.2

a n d C1-16 s a m p l e s a r e duplex-coated U 0 2 with uranium b u m u p s of 4.6 and 14.7% respectively.

t h e sample with t h e lower-density outer coating.

9 'Y

137cs

0.1

R9-20

1370

-. . .

C1-16 is

B9-21 and C1-15 a r c from t h e s a m e b a t c h of triplex-coated (Th,U)C,

particles, but with burnups of 0.29 a n d 8.9% respectively.

OHNL-IJWG

6 5 - I2345

POSTIRRADIATION EXAMINATION OF FUELED GRAPHITE SPHERES

CAPSULE B 9 - 2 G , ~ L I T C H O R - ~ O I , U O ~ C O R E - B O

FA-314, (Th,lJlC2 CORE- Ba s Sr u CAPSULE C1-15, BATCH GA--314, ( T h , U ) C 2 C O R E - - E a & Sr A ANNEALING TIME ihr) CAPSULE 8!3-2l, BAT!:il

SQUARE HOOT OF ANNEAL irw TIM^

Fig.

10.5.

Accumulated

(d+)

F i s s i o n Product

Release

D u r i n g P o s t i r r a d i a t i o n Anneal of C o a t e d Fuel P a r t i c l e s at

2000°C.

T h e experiments so f a r h a v e been performed with f u e l materials of current i n t e r c s t . Though n o s y s t e m a t i c and b a s i c study i n fission product r e l e a s e h a s becn made, some t r e n d s a r e evident. The behavior of triplex pyrolytic,-carbon-coatcd (Th,U)C p a r t i c l e s s h o w s some c h a n g e with burnup. P a r t i c l e s irradiated to 8.9% uranium burnup suffered 2% c o a t i n g failures during t h e i n i t i a l hour a t 1700'C or a t 20QO"C, while particles irradiated to 0.29% uranium burnup had no f a i l u r e s during 19 hr at 2000°C. T h e lower release of barium and strontium at t h e higher burnup retnains without explanation. P a r t i c l e s of UO, with a n outer c o a t i n g density o€ 1.8 g/cm3 had higher r e l e a s e r a t e s for barium, strontium, and cesium, but lower r e l e a s e r a t e s for cerium and yttrium than did (Th,U)C2 p a r t i c l e s with o u t e r coating d e n s i t i e s of about 2 g/cm3. The higher r e l e a s e r a t e s of barium, strontium, and cerium may b e d u e to t h e lower-density coating, while t h e lower r e l e a s e r a t e s of cerium a n d yttrium i n t h e U 0 2 p a r t i c l e s may i n d i c a t e b e t t e r retention by t h e fuel core itself.

D. R. Cuneo H. E. Robertson J. G. Morgan C. D. Baumann E. L. Long, Jr. W e h a v e completed t h e evaluation of f i v e irradiation experiments that contained fueled graphite e l e m e n t s i n t h e form of s p h e r e s . T h e s e e l e m e n t s were fueled with pyrolytic-carbon-coated p a r t i c l e s 400 hi in diameter d i s p e r s e d i n a graphite matrix. A summary of t h e irradiations i s shown in T a b l e 10.3. All of t h e s p h e r e s reported in t h e t a b l e were 6 cm in diameter e x c e p t t h o s e in experiment 8B-5, which were in. in diameter. T h e s p h e r e s of i n t e r e s t to t h e German AVR P e b b l e R e d Rea c t o r Program were fabricated with unfueled outer s h e l l s of machined graphite o r s h e l l s molded around t h e cote matrix. Two ol t h e s p h e r e s were completely fueled (no unfueled shell). In addition, w e examined two s p h e r e s of i n t e r e s t to t h e T A R G E T program. T h e s e were s p h e r e s of graphite t h a t contained s e v e r a l drilled h o l e s into which w e r e poured loose c o a t e d p a r t i c l e s . Experiment 8B-5 contained eight 1'/l-in.-diarn s p h e r e s which underwent t h e highest burnups of any s p h e r e s t e s t e d (9.25 at. % o f t h e heavy metal). Metallographic examinations were carried out for four s p h e r e s in t h i s experiment; t h e remaining foul s p h e r e s were duplications of t h o s e examined a n d were u s e d for compresqion t e s t i n g only. W e observed a high percentage of f a i l u r e of t h e laminar-coated p a r t i c l e s i n two s p h e r e s of this experiment. Laminar-coated p a r t i c l e s fabricated by t h e same manufacturer but irradiated l o about '4 the burnup were undamaged. Laminar-coated (LJ,'l'in)C i: p a r t i c l e s made with normal uranium were found to h a v e c o a t i n g fractures a t the fuelc o a t i n g interface and e v i d e n c e of loss of crystall i n e d e t a i l in t h e fuel core. T h i s is the only case of damage w e h a v e observed in p a r t i c l e s containing normal uranium. F i g u r e 90.6 is a photomicrograph of a normal and a n enriched We (U,Th)C, particle from t h i s experiment. found no broken c o a t i n g s in t h e s p h e r e s that cont a i n e d e i t h e r duplex- or triplex-coated fuel part i c l e s . Production-run Carbon P r o d u c t s Division s p h e r e s , experiment Q1A-8, operated s u c c e s s f u l l y . N o damaged particles were found, a n d t h e nonv o l a t i l e f i s s i o n products found in t h e graphite

Fig.

10.6.

Pyrolytic-Carbon-Coated

( T h , U ) C 2 P a r t i c l e s i n Sphere No. 1 froin Experiment 85-5,

p a r t i c l e s were froin b a t c h 3M-120; t h e normal p a r t i c l e s were from b a t c h 3M-119. a

T h e enriched

T h e e n r i c h e d p a r t i c l e ( r i g h t ) reached

burnup o f 25.6% heavy metal, b u t t h e normal p a r t i c l e ( l e f t ) reached a burnup o f approximately 0.2% heavy metal.

powder packed around t h e s p h e r e s s h o w e d a relatively small amount of migration through t h e unfueled s h e l l s of the s p h e r e s . R e l a t i o n s h i p s for compression s t r e n g t h a n d s h r i n k a g e a s related to t y p e s of s p h e r e manuf a c t u r e a r e given in T a b l e 10.4 for s p h e r e s irrad i a t e d t o high burnups in experiment â&#x201A;Ź33-5. All the s p h e r e s had molded fuel c o r e s . T h e two s p h e i e s t h a t were completely fueled (no unfueled s h e l l ) underwent l a r g e s h r i n k a g e s in diameter and a n apparent gain in compression strength. T h e t w o s p h e r e s with molded unfueled s h e l l s wexe found to exhibit t h e same d e g r e e of shrinka g e and, for o n e s p h e r e t e s t e d , a d e c r e a s e in

cornpression strength. The machined unfueled s h e l l s p h e r e s h a d t h e least o u t s i d e diameter shrinkage. However, from t h e l a r g e losses in compression strength (irradiated v s unirradiated spheres), w e conclude that t h e molded c o r e s underwent c o n s i d e r a b l e shrinkage, so t h a t t h e cornpression t e s t s reflect only t h e s t r e n g t h of t h e unfueled s h e l l . Such loss of c o n t a c t between t h e c o r e a n d s h e l l adversely a f f e c t s t h e h e a t transfer from the c o r e as well as t h e mechanical strength of t h e sphere. The s a m e t r e n d s c a n b e shown for 6-cm-diam s p h e r e s , although not to t h i s e x t e n t b e c a u s e of their low burnup.

T a b l e 10.3. ORR Experiment No.

Fueled Graphite Sphere Irradiations

Fuel

Particle

T y p e of Sphere

Composition

Coating

Shell

Estimated Temperaturee

("e)

( % h e a v y metal)

___

-...._......-.____I_....II........

Percent

Hurnup

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

Failed Particles

____l.__----.-----l

AVK-type spheres 8B-5

(U,T h ) C 2 p

Laminar

(upTh)C2,

2 spheres

8R-5

8B-5

(3M)

700-1 000

25.6-27

67-100

Triplex

GA)

Machined

800

26.6

1 sphere

W,Th)C 2,

Duplex

No s h e l l

8 00

27.

Machined

750-1200

9.1-10.8

Machined

700

2.1

Machined

75 0--1200

3.5-4

Molded

900

4.2

Laminar

Molded

(3M)

Y00--1200

7.3-8.6

2 spheres

(U,Th)C2 i r i 18 h o l e s ,

Duplex

Solid s p h e r e

775-1200

2.1

859

2.2

1 sphere 01A-8'

1 molded, 1 machined

uc 2,

(CPD) Duplex

(CPD)

3 spheres 01-8

Uc. 2'

08-8

UC,,

Duplex

1 sphere

(ORNL) Duplex

2 spheres 08-8

U C ,'

05-8

(U,WCy

(ORNL)

Duplex

1 sphere

(3W

TARGET-type spheres

01-8

with 19 h o l e s

UO, i T h o ; , in one hole; 1 sphere

01-8 -.

UC,,

Duplex

1 sphere .-.

(CPD)

Solid s p h e r e with 18 h o l e s

l_ll_-__.ll

__...............I__

RWhere two temperatures a r e given, t h e s e c o n d is c e n t r a l temperature; only one s p h e r e per experiment is e q u i p p e d with c e n t r a l thermocouple.

bBy metallographic examination.

CAVR production-run s p h e r e s .

Table 10.4.

Shrinkages and Cornpression Strengths of Graphite Spheres Irradiated t o Burnups of

Unfueled S h e l l s of S p h e r e s Type

Thickness (in.) ~

25 to 27 at. % in Experiment 8R-5

~ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ~

Aveiage Diameter

Compression L o a d i n g

Unirradiated E q u i v a l e n t Spheres,

Shrinkage e

t o Faillire (lb)

Compression L o a d i n g to F a i l u r e (Ib)

(70) ~-~~~~

Machined

0.2

0.85

Machined

1725 (2)b

0.2

0.77

900

IS00 (?)

Machined

0.2

0.61

22s

1 7 2 5 (2)

Machined

0.2

0.44

275

1500 (2)

No s h e l l

1.49

2650

1740 (4)

No s h e l l

2.32

3050

1740 (4)

Molded

0.2

1.54

1250

2200 (3)

Molded

0.2

1.38

2200 (3)

=Average of r e a d i n g s t a k e n a t pole, equator, a n d temperat-e r e g i o n s of s p h e r e s . bNurnber in p a r e n t h e s e s i n d i c a t e s number of unirradiated s p h e r e s t e s t e d . average.

POST1 RRADlATlQN EXAMINATION OF EGCR FUEL ELEMENT PROTOTYPE CAPSULES

M. F. Osborne E. L. Long, Jr.'

H. E. Robertson J. G. Morgan

E x c e p t for one EGCR prototype c a p s u l e which i s s t i l l being irradiated, a l l t h e e l e m e n t s in t h i s s c r i e s h a v e been examined. Of t h o s e e l e m e n t s irradiated in t h e ETR,' s i x were examined visually and three were e v a l u a t e d in detail. T h e c a p s u l e s contained UO 2 p e l l e t s fabricated at ORNL; t h e s e p e l l e t s w e t e e i t h e r s o l i d , hollow, or hollow with a B e 0 bushing. T h e d e s i g n power rating during irradiation w a s 35,000 M u hr-' ft-', and the s t a i n l e s s s t e e l cladding temperature varied from 1250 to 155O0F. T h e fuel rec e i v e d burnups of from 4500 t o 14,900 Mwd per metric ton of U 0 2 . Only o n c element expeiienced cladding failure. T h c other e l e m e n t s had only minor cladding deformation s u c h a s circumferential ridges a t pellet interfaces and a c o l l a p s e of t h e cladding a g a i n s t t h e fuel. T h e s e e f f e c t s were observed in previous t e s t s . T h e elemcnt with cladding failure contained A longitudinal t e a r in t h e s o l i d U 0 2 pellets.

V a l u e given for l o a d i n g to failure is a n

c l a d d i n g w a s apparently c a u s e d by overpowering of t h e element early i r i t h e irradiation. Grain growth in t h e cladding a t t h e s i t e of failure indic a t e d t h e p r e s e n c r of a hot s p o t . Unlike earlier i n s t a n c e s of cladding failure in t h i s s e r i e s , there was no e v i d e n c e of nitride formation in t h e cladding or columnar grain growth in t h e fuel. We h a v e completed t h e evaluation of a n EGCR prototype c a p s u l e which had been irradiated in t h e ORR. T h i s element w a s of s p e c i a l i n t e r e s t a s i t contained a c t u a l EGCR production-run UO, p e l l e t s and 304H s t a i n l e s s s t e e l cladding. T h e irradiation w a s carried out a t a h e a t rating of 31,000 Btu hr-' f t - ' and a cladding temperature of 1300OC. T h e dished-end hollow fuel p e l l e t s a c h i e v e d a burnup of 10,000 Mwd per metric ton of U 0 2 . Under t h e s e conditions, t h e cladding had c o l l a p s e d around t h e fuel but no circurnferent i a l ridges w e r e formed. Bowing of t h e element w a s nominal, and there w a s no s h i f t i n g of t h e fuel. 'The element had not failed, and i t s performance w a s s a t i s f a c t o r y under EGCK design conditions. 7M. F. O s b o r n e et al., R e a c t o r Chem. D i v . Ann. Progr. Rept. Jan. 31, 1965, ORNL-3789, pp. 218-19. 8C. D. Baumann, Irradiation E f f e c t s in t h e EGCH Fuel. ORNL-3504 (June 1965).

11. Fission-Gas Release During Fissioning of U 0 2 R. M. Carroll T. W. Fulton O s c a r Sisman R. B. P e r e z ' G. M. Watson

EXPERIMENTAL

W e have modified t h e experimental assembly t o permit a s l o w , controlled oscillation of t h e s p e c i men through t h e flux of n e u f r ~ n s . ~ " " T h e s e modif i c a t i o n s pcrmit a controllcd s i n u s o i d a l variation of neutron flux (fission rate) or specimen temperature. The f i s s i o n g a s r e l e a s e d during t h e oscillations is monitored continuously by a gamma-ray spectrometer. Time dependence of t h e temperature (or t h e f i s s i o n rate) and of t h e f i s s i o n - g a s r e l e a s e rate is measured and recorded by punch-tape readA computer program h a s b e e n developed to a n a l y z e the fission-gas r e l e a s e w a v e s i n terms of their Fourier components, t h i s a n a l y s i s y i e l d s amplitude and phase-shift information a s a function of frequency of t h e o s c i l l a t i o n .

From t h e r e s u l t s of in-pile experiments on singlec r y s t a l U O z s p e c i m e n s , w e h a v e concluded t h a t f i s s i o n g a s i s not r e l e a s e d by c l a s s i c a l diffusion p r o c e s s e s . W e conclude that t h e r e l e a s e is controlled by a trapping p r o c e s s . 2 3 3 T h e s e observatioris a r e c o n s i s t e n t with t h o s e b y other experimenters"." and h a v e l e d u s t o a defect-trap theory of f i s s i o n - g a s r e l e a s e . T h i s theory p o s t u l a t e s that a defect in t h e UO, c r y s t a l structure will trap migrating fission gas; t h e r a t e of f i s s i o n - g a s esc a p e , accordingly, is controlled by t h e number of traps present. Gas-trapping d e f e c t s c o n s i s t of inherent flaws, s u c h as grain boundaries and internal pores, in the UO, as w e l l as point d e f e c t s and c l u s t e r s of point d e f e c t s c r e a t e d a s a c o n s e q u e n c e of the f i s s i o n p r o c e s s . Steady-state experiments with s i n g l e c r y s t a l s a n d with polycrystalline UO, (ref. 8) h a v e supported t h i s defect-trap theory.

The e f f e c t of temperature o s c i l l a t i o n s w a s obtained by comparing t h e s t e a d y - s t a l e r e l e a s e (at zero frequency) with t h a t a t different frequencies. l 3 T h e g a s r e l e a s e w a s found to i n c r e a s e as t h e frequency of o s c i l l a t i o n s i n c r e a s e d ; a t very s l o w o s c i l l a t i o n s t h e r e l e a s e rate approached s t e a d y s t a t e l e v e l s . T h i s result is predicted by t h e defecttrap model; that is, as t h e o s c i l l a t i o n frequency

'Consultant from the University of Florida

'R. M. Carroll a n d Oscar S i s m a n , N u c l . Sci. En&. 21, 1.47-58 (1965).

'R. M. Carroll and O s c a r Sisman, F u e l s a n d Materials Dcveloprnent Program Quartetly Progress R e p o r t , Septembet- 1965 (in p r e s s ) .

9R. M. Carroll aitd Oscar Sisman, Trans. A m . N u c l . Soc. 8(1), 22 (June 196S); a c c e p t e d for publication i n Nirc l e a r A p p l i c a t i o n s .

"R. M. Carroll, " T h e

Behavior o f F i s s i o n - G a s i n F u e l s , " AlME Coriference ut1 Hadiatiori Effects, S e p t e m ber 1965 ( t o be p u b l i s h e d by AIME).

OK. M. Carroll a n d O s c a r Sisman, F u e l s a n d Materials D e ve lopnient Program Quarterly Progress Report, Septerriher 196.5 (in press).

'R. M. Carroll, N u c l . S a f e t y 7(1) (in press).

6R. M. Carroll, R. B. P e r e z , and O s c a r Sisrnan, J . Am. Ceram. S O C . 48(2), 55-59 (1965).

7R. M. Carroll and P. E. Reagan, N i i c l ,

1-11-46 (1965).

"u. M. Carroll e t a]., G C I ~Program Semiann. Progr. K e p t . Mar. 31, 1965, p p . 80-87, ORNL-3805.

S z i . En&. 21,

"R. M. Carroll e t a ~ . ,GCK i+ograrri sc-niiiinn. Progr. R e p t . September 1965 (in press).

'R. M. Carroll arid O s c a r Sisman, "In-Pile F i s s i o n G a s R e l e a s e from Fine-Grain UO2," J . NucI. Mater. (in press).

I3R. â&#x201A;Ź3. Perez, T r a n s . Am. N u c l . Soc. 8(1), 22-23 (1965); to be published in N u c l e a r Applications.

100

ORNL-DWG 6 5 - 4 3 0 5

42/ -

0 -

Fig. 11.1.

1-_-

2 3 NEUTRON FLUX (neutrons/crn7

sec)

Knockout R e l e a s e During F i s s i o n R a t e O s c i l l a t i o n s .

i n c r e a s e s , t h e frequency-dependent factors overcome t h e trapping effect; t h e r e l e a s e rate increases and approaches that predicted by models b a s e d upon classical diffusion theory. F i s s i o n - g a s r e l e a s e a t temperatures below 6QO°C o c c u r s primarily by a recoil p r o c e s s wherein f i s s i o n fragments p a s s i n g through t h e s u r f a c e of t h e UO, specimen e j e c t or “knock out” UO, molecules along with a n y f i s s i o n - g a s atoms i n t h e knockout zone. Knockout release during fission-rate o s c i l lations a t a constant temperature of 575°C i s shown i n F i g . 11.1. T h e d a t a points of F i g . 11.1 form a s o r t of h y s t e r e s i s curve; arrows by t h e data points i n d i c a t e whether t h e fission rate w a s i n c r e a s i n g or d e c r e a s i n g when t h e data were obtained. T h e h y s t e r e s i s curve s h o w s the g a s release rate t o b e higher during fission-rate o s c i l l a tions than when t h e f i s s i o n rate w a s constant. We s u g g e s t that t h e d a t a of Fig. 11.1 reflect t h e rhythmically changing concen tration of fission -gas traps created by t h e fission p r o c e s s . ’The c y c l i c destruction and creation of t r a p s allow t h e f i s s i o n gas t o reach t h e specimen s u r f a c e in s u r g e s . T h e s e s u r g e s account for both t h e h y s t e r e s i s and the in-

c r e a s e d amount of g a s a t t h e specimen s u r f a c e available for knockout.

MATH EMAT1CAb MODEL Material b a l a n c e equations for f i s s i o n - g a s re-l e a s e (parent and daughter n u c l i d e s ) from a thin s l a b of f i s s i o n a b l e material a r e b a s e d on production, l o s s , and diffusion-leakage terms. In general: R a t e of change of concentration diffusion-leakage contribution -- l o s s terms

+ production

terns

For t h e diffusion-trapping model t h e l o s s terms involve radioactive d e c a y and trapping by intrinsic flaws and point defects. T h e production terms involve t h e f i s s i o n rate, f i s s i o n yield, and, for t h e daughter, radioactive d e c a y of t h e parent. T h e concentration of point d e f e c t s i s a b a l a n c e between their rate of formation a s a consequence of f i s s i o n and their destruction by annealing a t high temperature.

101 T h r e e material b a l a n c e equations (for which t h e symbols a r e defined in T a b l e 11.1) result; they a r e coupled and nonlinear. Parent: -= D

+ R,)

- hN,r(t) H ( z , t ) i P H F ( t ) + X,M(z,t)

P o i n t defects: dNtr

a,F(t) - v T N f r .

(3t

’4t s t e a d y s t a t e ( d M / d t :: 2 i / d t = (3Ntr/dt = 0) t h e equations become linear and c a n be s o l v e d by conventional methods. T h e s t e a d y - s t a t e s o l u t i o n s for t h e r e l e a s e r a t e s yield e x p r e s s i o n s which a r e similar i n a p p e a r a n c e to t h e e x p r e s s i o n s obtained from t h e old diffusion mode1,l3 except t h a t t h e d e c a y constant, A, i s replaced by an effective d e c a y c o n s t a n t , A’, which i n c l u d e s t h e effect of trapping. An i n c r e a s e i n temperature will i n c r e a s e the r a t e of t r a p annealing arid will d e c r e a s e t h e effective decay c o n s t a n t , A’. An i n c r e a s e i n neutron flux will i n c r e a s e t h e v a l u e of t h e A’, will tend to neutralize t h e i n c r e a s e in production, and will make t h e r e l e a s e rate fairly i n s e n s i t i v e t o flux

T a b l e 11.1.

changes. T h i s behavior a g r e e s qualitatively, at least, with t h e observed phenomena at s t e a d y s t a t e . An approximate solution h a s been obtained for t h e case where t h e flux is varied sinusoidally while t h e temperature remains constant. To c o m pare t h e diffusion-trapping model with t h e simple diffusion model, t h e a n a l y t i c a l e x p r e s s i o n s for t h e total r e l e a s e rate transfer functions for e a c h model were coded for numerical computations. The amplit u d e of t h e r e l e a s e rate transfer function v s frequency is shown in Fig. 11.2a. When t h e diffusion model is u s e d t h i s amplitude d e c r e a s e s with t h e s q u a r e root of t h e frequency; when t h e diffusiontrapping model i s u s e d t h i s amplitude e x h i b i t s an extended plateau in t h e low frequency range. A s t h e frequency i n c r e a s e s , t h e frequency-dependent f a c t o r s overcome t h e trapping e f f e c t s and both

ORNL-DWG 654465

D e f i n i t i o n of Symbols 5

Symbol

10-3

w (radians x

Definition

set'.')

10-2

A t o m i c c o n c e n t r a t i o n of parent and daughter

nuclides, respectively, atoms/cm3

’

D i f f u s i o n c oe fficie t i ts , c tii /s e c, ::. 1)”[ e x p

(-AE /R731

V i s si o n y i e l d s , f i s s i o n fragments j f i s s ion

R a t e c o n s t a n t f o r t.rap a n n e a l i n g

: :

zjJexp

(-!LE t r / ~ 7 ‘ ) ] T r a p s formed per f i s s i o n T r a p p i n g probability, due t o permanent defects, sec-’

Concentration of p o i n t s defects, defects/ctn Second-order r a t e c o n s t a n t , ( c m 3 )/(dt-:fi-ct) (secj

io-4

40-’

10-2

w (rad!ans x sec-‘)

F i g . 11.2. quenc y .

Release

Rate Transfer

Function v s

Fre-

102 models tend to coincide. F o r lower frequencies t h e trapping effect predominates; h e n c e t h e frequency-dependent terms do not significantly affect t h e magnitude of t h e transfer function. Equivalent comparisons were made with t h e p h a s e shift ( F i g . 11.2b) of t h e transfer function. In t h e diffusion model, t h e p h a s e shift quickly r e a c h e s a n asymptotic v a l u e of -45" and is independent of

temperature. T h e p h a s e shift for t h e diffusiontrapping model is a l w a y s smaller, t e n d s inore slowly toward the -45" asymptoie, and i s a function of temperature. Data have been obtained by o s c i l l a t i n g t h e tern perature at c o n s t a n t flux; for t h i s c a s e , t h e equations do not lineniizc readily and t h e solution h a s not been completed.

12. Miscellaneous Studies for Solid-Fueled Reactors EQUILISRIUM STUDIES IN THE SYSTEM

'L. 0. Gi.lpatrick, W. H. Stone, and C. H. Secoy, Reactor Cheni. D i v . A n n . Progr. K e p t . J a n . 3 1 , 1963, ORNL3417, py. 134-39.

Unit cell dimensions were computed from x-ray powder patterns using a least-squares fitting program written by Williams5 i n p l a c e of t h e more t e d i o u s graphical procedure. Test cases showed n o bias due to t h i s change. Comparisons were also made between the Debye-Scherrer camera a n d t h e bench diffractometer methods of measuri n g l a t t i c e parameters by t h e powder technique, Good agreement w a s €ound in t h i s case also. An effort w a s made to better define t h e transition temperature a t which orthorhombic U,O, c o n v e r t s to t h e face-centered c u b i c UO, +x p h a s e in air. T h e transition is sluggish, but the f i r s t s i g n of the fcc p h a s e appeared at 1528°C and progressed fairly rapidly (50% i n 2 hr) at IS40"C. No f c c p h a s e w a s observed a f t e r 2 h r at 1514'C. 'Ternperature calibration w a s f e l t to b e r e l i a b l e to f.5°C: as measured by NO independent methods. During t h e year, Cohen and Berman of t h e Westinghouse B e t t i s 1,aboratory reported on t h i s s y s t e m ' a n d found a lower urania composition (50 mole ?I) for t h e two-phase boundary a t 12OO0C than had been found i n t h i s s t u d y (-.,63 mole %>. In view of t h i s difference, a remeasurement at 1200°C w a s made u s i n g more recent t e c h n i q u e s . No e f f e c t could b e a s c r i b e d to t h e u s e of p e l l e t s at 68 mole "/G uranin. This composition s h o w e d some orihorhoiiibic p h a s e ("2 to §%). Cnmpositions of 56, 53, and 45% urania d i s p l a y e d no d e t e c t a b l e orthorhombic phase. This indicates t h a t t h e p h a s e boundary is between 56 and 60 mole % ncania. Composition of 90% urania showed l i t t l e c h a n g e from the older work. Apparatus and equipment h a v e been d e s i g n e d and built to extend t h i s st.udy to lower p a r t i a l press u r e s of oxygen i n t h e range of atm, where

4L. 0. Gilpatrick and C. H. Secoy, Reactor Chem. D i v . Ann. Pro&. K e p t . Jorz. 31, 2965, ORNL-3789, pp. 239-43.

'D. R. WilliaEs, LRC-2: A Fortran L a t t i c e Constant Refin emtiri f Program, IS -1052 (November 1964). %.C o h e n and R . M. Remian, Am. Cerenl. S O C . Bull. 44(4), 301 (1065j.

T hO 2-U0,-U0

L. 0. Gilpattick

C. H. Secoy

Equilibrium s t u d i e s of t h e s y s t e m T h O ,-UQ,-U0,3 w e r e cont.inued a t partial p r e s s u r e s of 0, e q u a l to t h a t found i n t h e atmosphere a n d a t temperatures ranging from 1200 to 1550°C. P r e v i o u s work h a s e s t a b l i s h e d t h e general features of t h e p h a s e diagram for t h e s y s t e m . l-' A s t u d y w a s made to determine i f the s c a t t e r i n a n a l y t i c a l compositions could be d u e t o experimental techniques. A temperature of 1550'C and a composition of 90 m o l e 7L urania and 1 0 mole % thoria were c h o s e n for t h i s work. Variations i n grinding, s t o r a g e conditions, and l a p s e d time had l i t t l e or no e f f e c t on t h e observed equilibrium Initial oxidation s t a t e a n d degree composition. of i n i t i a l s o l i d solution formation had a very s m a l l e f f e c t on t h e equilibrium composition ( l e s s than 2.576). When quench conditions w e r e varied by s u b s t i t u t i n g liquid N , submersion in p l a c e of rapid a i r cooling, a reduction i n U 0 , 3 c o n t e n t from 29 to a b o u t 2 6 mole "/o was obtained. Compositioiis c a l c u l a t e d from the unit c e l l s i z e 4 derived from x-ray powder patterns also confirmed t h a t t h e f c c p h a s e had a UO, composition near '25 mole %. These findings would i n d i c a t e s o m e s u r f a c e oxidation during t h e quench period by t h e tecilnique.

'w.

l l l _ _

I...___.......

A. i7riedman and R. E. 'rhoma, Reactor Cllem, Ann. Pro&. R e p t . J a n . 3 1 , 1963, ORNL-3417,

Div. pp. 130-34.

"L.0. Gilpattick, H. W. Stone, and C. H. Secuy, R e a c tor Ghem. D i v . Arm. Pro&. l?ept. J a n . 3 1 , 1 9 6 4 , ORNLP 3591, pp. 160-64.

103

104

s h i f t s in t h e oxygen-metal ratio s h o u l d b e large enoiigh to b e e a s i l y measured. A new series of s t a r t i n g compositions h a v e a l s o been prepared by more extreme procedures to a s s u r e a homogeneo u s material in the s o l i d solution form. Mixed oxides have been reduced i n H, a t temperatures in e x c e s s of 1650째C, and reduced mixtures h a v e been fused in helium a t temperatures above 22OOOC.

BEHAVIOR OF R E F RACTQRY -ME TAL CAWBlDES UNDER ~ ~ ~ G.

W. Keilholtz

R. E. Moore M. F. Osborne

Refractory-metal c a r b i d e s of groups IV to VI h a v e potential applications in high-performance nuclear power plants and in reactors for s p e c i a l a p p l i c a t i o n s requiring extremely high power densities. .4 s e r i e s of experiments in progress is aimed a t determining t h e c h a n g e s i n p h y s i c a l and rtiechanical properties of monocarbides of T i , Zr, Nb, T a , and W during fast-neutron irradjation. T h e s p e c i m e n s are being irradiated in

T a b l e 12.1.

t h e form of 15-in. x ?$-in. cylinders over t h e temperature interval 100 to 14OO0C, the neutron flux range 0.5 t o 3.0 x 1 0 1 4 neutrons c m - ' s e c - ' (>1 Mev), a n d t h e neutron d o s e range 0.5 to 5 x l o z 1 neutrons/cm2 ( > 1 Mev). Included i n t h e experimental s e r i e s are s p e c i m e n s of e a c h of t h e monocarbides made by three different methods: (1) hot pressing, (2) s l i p c a s t i n g and sintering, and ( 3 ) explosion pressing. Three low-temperature (100 to 400째C) uninstrumented a s s e m b l i e s and one instrumented high-temperature (1loooC ) assernbly containing t h e s e carbides are undergoing irradiation in t h e ETR. Other experiments a r e planned to ~ a c h i eI v e temperatures A ~ u p ~to 14QOOC. ~ N Examination i s complete for a n a s s e m b l y of one s a m p l e of e a c h of t h e f i v e hot-pressed monocarb i d e s irradiated ( s e e T a b l e 12.1) i n the ORR a t about 100째C.7 Most of t h e s p e c i m e n s s u s t a i n e d very l i t t l e gross damage. Metallographic examinations revealed no e v i d e n c e of grain-boundary s e p a ration i n any of t h e s a m p l e s . T h e volume i n c r e a s e of t h e carbide s p e c i m e n s c a l c u l a t e d from dimens i o n a l measurements and the volume i n c r e a s e calculated from t h e l a t t i c e parameter e x p a n s i o n s are 7G. W. Keilholtz, R. E Moore, a n d M. F. Osborne, OHNL-TM-I 350 (in preparation) ( c l a s s i f i e d ) .

Gross Volume E x p a n s i o n and L a t t i c e Parameter E x p a n s i o n of R e f r a c t o r y - M e t a l C a r b i d e s Irradiated a t

Material

Crystal Structure

Fast-Neutron Dose, nvt

( > 1 MeV)

Hexagonal

TiC

Cubic

Dose, nvt

i > l MeV)

!\a/aoa

(%I

x 1021

1.7 1.7

3.4

0.17 0.58

NbC

Cubic

1.7

3.4

TaC

Cubic

1.4

2.7

ZrC

Cubic

1.4

2.7

(70)

Volume I n c r e a s e

from ~ ~ 1,attice

from Dimensional

Parameters

Measurements

(%I

x 1021

3.4

lOO@C

(%)

0.7

0.3

1.7

2.5

0.16

0.5

(3.6)' 2.7

0.53

1.6

2.6

0.35

L. Y a k e l , O R N L Metals a n d C e r a m i c s Division, p e r s o n a l comiiiunications. T h e v a l u e s for & / a o a n d k / c o i n e a c h c a s e were h a s e d on v a l u c s for a. a n d co obtained from x-ray diffraction p a t t e r n s of nnirradiated s p e c i m e n s from t h e s a m e b a t c h e s . b T h e volume i n c r e a s e s were c a l c u l a t e d from the e q u a t i o n a V / V o from the e q u a t i o n / j v I / V o: 3ha/a0 for c u b i c c r y s t a l s .

2b.a/a0

+ hc/co

for h e x a g o n a l c r y s t a l s a n d

'This v a l u e w a s e x t r a p o l a t e d from d i m e n s i o n a l measurements of the diameter of t h e niobium c a r b i d e s p e c i m e n ; t h e length of the s p e c i m e n could n o t be m e a s u r e d b e c a u s e one end w a s found t o be broken off a f t e r irradiation.

105 given in T a b l e 32.1. T h e l a t t i c e parameters w e r e measured from x-ray patterns obtained from reflectiofis from polished s u r f a c e s . The gross volume expansion of the tungsten carbide specimen, the only one of t h e five c a r b i d e s which d o e s nut h a v e an isotropic c r y s t a l structure, w a s only ahout 0.3%. The gross volume e x p a n s i o n s of t h e c u b i c carbide:; of titanium, tantalum, and zirconium w e r e iilocli greater (* 2.6%); the l a t t i c e expansion a c c o u n t s for a b o u t 60 to 75% of the gross expansiuii of t h e titaniurn and zirconium c a r b i d e s . An. x-ray pattern could not be obtained on tantalum carbide. T h e niobium carbide sample appeared to expand more than the o t h e r s , but I t s lattice parameter expansion w a s very small. T h e s e preliminary r e s u l t s i n d i c a t e that refractory-metal c a r b i d e s are sufficiently r e s i s t a n l to fast neutrons to merit considetation for nuclear a p p l i c a t i o n s involvirig high neutron d o s e s . 'L'ungs t e n carbide, i n particular, is a t t r a c t i v e b e c a u s e of its srna11 l a t t i c e yasameter expansion and s m a l l gross volume expansion. T h e magnitudes o f t h e s e e x p a n s i o n s arc generally reliable indicatioiis of the degree of neutron damage.

3.0 x l o i 4 neutrons C I T I - ~ sec-l (>1 Mev). The results a r e reported elsewhere. Among the three oxides, the g r e a t e s t difference 1

in behavior w a s between MgO, which h a s a c u b i c structure, and Reo, with a hexagonal c r y s t a l structure. P r e v i o u s r e s u l t s h a v e shown t h a t t h e primary mode of damage to Be0 is grainboundary s e p a r a t i o n caused by anisotropic c r y s t a l expansion. The degree of damage, that is, fracturing or powdering, i n c r e a s e s with i n c r e a s i n g dose and d e c r e a s e s ~ d t . hi n c r e a s i n g temperature. The cubic s t r u c t u r e of MgO precludes a n i s o t r o p i c expansion, and the lattice parameter expansion is E u c h s m a l l e r than that of 1-3e0. Accordingly, irradiated MgO e x h i b i t s virtually n o grain-bounda r y separation, no powdering is observed, a a d t h e gross volume e x p a n s i ~ n is srnall relative to that of Beta. Transgranular fracture is s e v e r e in MgO. For example, ;3bout IC% of specimens irradiated at 150°C: over t h e dose range 0.2 to 1.4 x 1OZ1 neutrnns/cm were fractured. Unlike WeO, damsge to MgO s p e c i m e n s w a s not related to t h e neutron d o s e . Approximately 40% of t h e s p e c i m e n s irradiated at 800°C and about 80% of the specim e n s irradiated at I1OO"G c v e r the d o s e range 0.5 to 5.1 x. IO" neutrons/cm' (>I ~ e v were ) fractured ratidomly . The randomness of fracture can I I _

C;. W. Xei!iioltz R. E. Moore M. F. Osbnrne A s y s t e m a t i c investigation of t h e e f f e c t of fastneutron irradiation on sirrtered c o m p a c t s of MgO and A412C33 h a s b e e n completed, and the r e s u l t s h a v e b e e n compared with t h o s e pteviously obtained8'--16 for BeQ. Several hundred cylindrical s p e c i m e n s of e a c h oxide with various grain s i z e s and d e n s i t i e s were irradiated i n the Engineering 'Test R e a c t o r o v e r t h e temperature range 100 t o 1100°C and t h e fast-neutron flux range 0.5 to __

_____

'K. P. Shields, J. E. Lee, Jr., and W. E. Browriing, Jr.

E f f e c t s o f Fsst Necrfron Irradiation a n d €fi&

Teinperbtrtre on BeryIfium Oxide, ORNL-3164 (March 1 6 , 1962). 'R. P. S h i e l d s , J. E. Lee, Jr., a n d W. E. Browning, Jr., Trans. Am. Nucl. S O C . 4(2), 338 (1961).

1°c;. W. Keilholtz et aZ., R a d i a t i o n Damage S o l i d s , Proc. Symp., Venice, 1962, vol. TI (Vienna, IAEA, 1962).

l ? G. U '. Keilholtz, J. E. Lee, Jr., arid R. E. Moore, The Effect of Fast-Neutron Irradiation on Rerylliuni O x i d e Compacts at High Temperatures, ORN1,-TM-741 (Dec. 11, 1963).

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

"Ci. Vi. K e i l h o l t x e t a l , , Behavior tif R e 0 liticier N e w iron Irradiation, 012NL-TM-742 (Dec. 11, L963). 1 3 6 . W , ICeilholtz, J. E. ~ . , e e ,Jr., and R. E;. loor re, J . Nricl. iwatsz. II1(3), 253-64 (1964). I4G. W . Kejlholtz e t a[., J . N u c l , Mater, 1 4 , 87-95 (1 964). 15 6. W. Keillioltz, J. E. Lee, Jr., a i ~ dR. E. Moore, "Irradiatioii Darnage to Sintered R e r y l l i u m oxide a 3 a F u n c l j o n fjf the Fast-Neut-ron D o s e a n d Flu:{ a t 110, 6 S 0 , a n d I I OO"C," submittect to Ntzcfear Scierice i m f ~ n g i 11 eerinfi l ' c x piit>I ic at ion.

"G. W. Keilboltz, J. E. J.,ee, Jr., a n d R. E. Moore, Reactor Chem. Div. Aiin. Progr. R a p t , J a n . 31, 1965, ORNL-3789, pp. 2 3 3 - 4 8 . 1 7 ~ . W . Keilholtz, J. E. Idee, JT., and R. E. ~ o o r e , ORNL-TM-I 050 (Mar. 26, 19653 ( c l a s s i f i e d ) . "6. W. Kicilholtz, J. E. Lee, Js.! a n d R. E. Moore, ORNL-TM-1110 (July 9, 1965) ( c l a s s l f i e d ) .

I9G. W. Keil'noltz, J. E. Lee, Jr., a n d R. E. Moore, UKNL-TM-1300 (in p r e s s ) ( c l a s s i f i e d ) ,

"6. W. Keilholtz, J. E. 'Lee, J r ~ ,and R. E. Moore, P r o p e r t i e s of Magnesium, Alurriinum, and Berylliurrr Oxide Ccmpacts, Irradiated to Fzast-Neutron Doses Greater than 10" N e u t r o n s ern--. a t 150, 800, and 1 100"C," a c c e p t e d for publication i n Proceedings of J o i n t Division Meeting of the Materials S c i e n c e and Technology D i v i s i o n of the American N u c l e a r S o c i e t y a n d the R e f r a c t o r i e s Division of the American Ceramic Society, May 8-11, 19G6, Wushington, D.C. a6

Table 12.2.

L o t t i c e Porurnzter E x p a n s i o n of MgO, i2-Al2O3, and B e 0 l r r a d i o t e d a t L O WTemperatures t o Comparable Fast-Neutron Dqses

Material

Crystal

Iiradia tion

Fast-Neutron

structure

Temperature

D o s e , > 1 hlev

(“C)

____

___ ......~ ~ _ ____.._.. __

....

( n r u t r o n s l c m 2) .....

:2a.’ao

l\c:’c 0

Av’voa

__ ......... _____.______ ....._ _ _ _ _ _ _ ~ x 102’

Me0

Cubic

150

a-A1 0,

Hexagonal

150

BCO

Hexagonal

110

t (,%’c,).

0.0015

0.0023

0.0024

0.0070

0.0013

0.0312

0.0338

jV/V,

The equation AV,’V, - 3 ( 1 a , ’ a o ) n a s u s e d for the c a s e of cubic MgO.

b e explained by postulating that a minimal neutron d o s e c a n weakeri t h e c r y s t a l s eiioilgh to permit t h e propagation of c r a c k s from tandonily d i s tributed s i t e s within MgO compacts. T h e minimal d o s e is probably near the lower limit of o u r e x periments (-2 x I O z 0 neutrons/crn2: >1 Mev), s i n c e i n c r e a s e s i n strength have keen reported for lower d o s e s by other experimenters. 1 , 2 2 Direct e v i d e n c e i s lacking that higher d o s e s produce weakening of MgO c r y s t a l s , bnt electron micrographs of MgO irradiated t o d o s e s greater than 10” neutrons/cm2 ( F i g s . 12.1 and 12.2) show a s e v e r e deterioiation which, i t seems likely, would b e accompanied by a l o s s in strength. In-pile annealing a t high temperatures r e d u c e s t h e volume expansion and l a t t i c e parameter expansion of MgO. Theimal s t r e s s e s within neutrondamaged compacts probably account for t h e markedly greater gross damage observed i n iriadiations at llOO°C. T h e c r y s t a l structure of A 1 2 0 , is anisotropic, but t h e behavior of Al,O, on exposure to fast neutrons resembles that of MgO rather than BeO.

1.o

0.@0@5

fractional voluihe i n c r e a s e , AV‘V,, for R e 0 and A I 2 O 3 w a s c a l c u l a t e d from the equation

aThe

2&1a0)

1.1 1.0

........

“R. A. J. Sambell and H. Bradley, Phil. M a g . 9 ,

1 6 1 (1964).

2 2 J . E l s t o n , “Behavior of Neutron-Irradiated Beryllium Oxide,” Saclay Center of Nuclear S t u d i e s Report DM-1182 (1962).

A comparison of t h c l a t t i c e paraiileicr e x p a n s i o n s of t h e three oxides irradiated at low temperatures t o 3 dose of % l o 2 ’ neutrons/cm2 i s shown i n Table 12.2. ‘The a and c parameters of A120, expanded by about the s a m e amount under t h e s e conditions; t h i s is in s h a r p c o n t r a s t to t h e behavior of BcC, i n which nearly a l l the expansion is i n t h e c parameter. R e c e n t irradiations of transluc-nt 4 1 , 0 , s p e c i m e n s (L,ucalox) to somewhat higher d o s e s (-1.4 x l o 2 ’ neutrons/cm2) produced a greater expansion of c parameter, however, a n d resulted in a n anisotropic expansion of about 3.8. ‘1’Ris ratio, ratio (:\c/c,)/(Aa/a,) however, i s small compared with that for BeO. Therefore, t h e mechanisms through which A1,0, is fractured during fast-neutron irradiation a p p e a r t o b e t h e same a s in MgQ. Neutron damage to all three o x i d e s , as judged from l a t t i c e parameter expansion and gioss volume expansion, d e c r e a s e s with i n c r e a s i n g irradiation temperature. B e c a u s e of in-pile thermal s t r e s s , however, gross fracturing of MgO and A1 ,O, i n c r e a s e d markedly a t high teiuperatures (1100OC). Therefore, to minimize damage to t h e s e o x i d e s in nuclear reactor application, t h e temperature s h o u l d b e maintained a s high as practicable, and t h e s y s t e m should b e designed so a s t o minimize thermal s t r e s s . In t h e case of BeO, therinal cycling, which t e n d s to promote grain-boundary separation, should also be avoided.

107

fig.

ficotion.

12.1.

Electron Micrograph of U n i r r a d i a t e d MgO of Density

Reduced

11%.

3.4 g/cm3 a n d G r a i n S i z e 10 p a t 32,000>;Magni-

108

F i g . 12.2. Dose of

E l e c t r o n Micrograph of MgO of D e n s i t y 3.4 g/crn3 and G r a i n S i z e 10

1.2 x l o 2 â&#x20AC;&#x2122; Neutrons/cm2 (>1 Mew)

Small Crocks.

Reduced 12.5%.

Irradiated t o a F a s t - N e u t r o n

15OoC a t 32,OOOX M a g n i f i c a t i o n Showing General D e t e r i o r a t i o n and

109 ANNEALING OF IRRADIATION-INDUCED THERMAL CONDUCTIVITY CHANGES OF CERAMICS

T a b l e 12.3.

Annealing of Irradiation-Induced Therrna I R e s i s t a n c e

Temperatureb e t Which

C. D. Wopp

the Irradiation-Induced Irradiation

Therm.al R e s i s t a n c e

T h e a n n e a l i n g of t h e neutron-induced thermal conductivity c h a n g e h a s been measured i n s e v e r a l ceramic materials. T h e a n n e a l i n g temperatures a r e A fluxmeter a p p a r a t u s 2 3 l i s t e d in T a b l e 12.3. w a s u s e d with t h e m a t e r i a l s of high conductivity, and a mercury-contact a p p a r a t u s z 4 w a s u s e d with t h e materials of lower conductivity. P r e v i o u s l y , t h e mercury-contact a p p a r a t u s was used for preand postirradiation measurements of t h e s e s a m e materials, but a n n e a l i n g w a s not s t u d i e d . Comparison with the p r e s e n t r e s u l t s s h o w s good agreement e x c e p t in t h e i n s t a n c e of thin s p e c i mens of beryllia, for which i t a p p e a r s t h a t t h e mercury-contact a p p a r a t u s is u n s u i t a b l e b e c a u s e of t h e extremely high conductivity of t h i s msterial. The a n n e a l i n g temperatures for betyllia shown in T a b l e 1 2 . 3 a r e i n good agreement with t h o s e found by other w o r k e r s 2 6 for material given nearly t h e s a m e irradiation dosage.

e T h e d o s a g e u n i t is f a s t neutrons/cm2 ( ? l M e V ) exc e p t i n the i n s t a n c e of z i r c o n , for w h i c h the unit is f i s s i o n s / c m 3 ( s i n c e the p r e s e n c e o f a t r a c e o f uranium impurity dominated t h e radiation e f f e c t i n zircon; see C . D. Wopp et al., Reactor Chem, D i v . Anti. Progr. R e p t . J a n . 3 1 , ,1965, ORNL-3789, p. 231).

23C. D. Bopp and 0 . Sisrnan, Reactor Chrm. Div. A n n . Pro&. Rept. J m .31, 1965, ORNL-3789, p. 232. 2 4 r. D. Bopp, J . Am. Cerarri. SOC. 47, 154 (1964).

bAnnealing w a s conducted isochronally; the s a m p l e w a s h e a t e d for periods of 1 hr a t s u c c e s s i v e l y higher temperatures using 50째C increments, e x c e p t t h a t t h e period o f h e a t i n g at I250"C, t h e highest temperature u s e d , w a s 4 hr.

" 0 . Sisman, C. D. Bopp, and R. L. Towns, Solid S t a t e Di v. h n . Progr. R e p t , Air& 3 1 , 1957, ORNL-2413, p. 80. 26J.

(1 '9 61).

Elstori and C. Labbe, J . N u c l . Mater. 4, 143

Material

Is D e c r e a s e d b y

Dosage"

the Indicated Percentage

Sintered beryllia

Sintered alumina

2 x 10''

Sapphire

4-8 x

1019

lo"

Spinel

2x10'~

Porcelain

2 x1019

Forsterite Zircon Cordierite Steatite

20%

40%

60%

80%

600

650 050

750 c

900

600 600

850

XOOO

1250

550

900 950

550 2x10'' 750 2 x 1014 1000 2 x lo1' 750 2 ~ 1 0 ' ~550

250

1050

1100

1250

1000

1100

1250

800

'This amount o f a n n e a l i n g w a s not a t t a i n e d a f t e r the 1250째C heating.

Part IV Other ORNL Programs

13. Chemical Support for Saline Water Program THERMODYNAMICS OF GYPSUM IN AQUEOUS SODIUM CHLORIDE SOLUTIONS W. L. Marshall

Ruth Slusher

In a n extensive investigation of t h e equilibrium p h a s e relationships of gypsum (CaSO;2H20) in NaCl-II,O s o l u t i o n s continuing from t h e previous work,' s o l u b i l i t i e s were determined a t 12 different temperatures from 0 to 110째C and i n solutions of sodium chloride from very dilute t o t h o s e s a t u r a t e d with sodium chloride or a new s o l i d phase. All r e s u l t s and a v a i l a b l e literature d a t a were e v d u a t e d by an equation, log KslJ - log K:p

+ 8 S f l / ( l + A& - HI

- C12-- 2 log

, (1)

whrrc! SS i s t h e Debye-Hiickel limiting s l o p e for a

2-2 e l e c t r o l y t e corrected for molal units, a1 is t h e activity of water, I is t h e ionic strength, A, B , and C are a d j u s t a b l e parameters, K Z p is the solubility product c o n s t a n t (at I o), and K s i:;t h e

i o n ptoduct [ ( c a 2 +I(SO ,'-)I. Determinecf'values of K:IJ are shown in Fig. 13.1, and the parameters

A, 23, and C arc included in T a b l e 13.1. With t h e obtained parameters, t h e differences between most c a l c u l a t e d a n d experimental v a l u e s of K s l , were betwgen 0.5 and 3% over the e n t i r e rangcs of concrritrati on a n d temperature.

Standard Thermodynamic Values for Gypsum

Assumptions were made that the standard heat of solution, AHo, and t h e standard change in heat 'W. L. ;?/Iarshall, Ruth Slusher, and E. V. Jones, J . C'hem. E n g . Data 9, 187 (1964).

Fig. 13.1.

Logarithm of KO

2H2CD ( G y p s u m ) , 0-1 ~ O ' C .

l/T(OK)

for CaS04.

capacity a t constant presstire, AC$, could be exp r e s s e d by

and

/IC;-. F

+ GT

(31

where E , F , and G are parameters. T h e s e exp r e s s i o n s were substituted into the v m ' t I h f f equation, In K : , / d ( l / ~ )

- AH'/T ,

(4)

which was then integrated over a l l values of K z r , and T("K) to obtain a four-parameter equation. With t h e s e p a r a t e l y determined values of KOp (unsmoothed but obtained u s i n g smoothed v a l u e s

113

114

T a b l e 13.1.

Standard Thermodynamic Q u a n t i t i e s a n d Parameters A , 8, and C U s e d i n Eq. ( 1 )

for the Equilibrium C a 5 Q 4 . 2 H 2 0 ( s ) ~ ~ C o 2 + ( a q )S 0 4 2 - ( a q )

._........

T (OC) -_____

AF"

hi"

(kcal/mole)

(kcal,/mole) ..__._

+ 2H20

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

AS" (tal mole-'

... _.

"c-' )

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

5.58

+2.50

-11.3

1.450

-0.0680

0.0264

5.71

t 1.55

-14.7

1.468

- 0.0274

0.0212

5.87

+0.68

.-"17.7

1.490

--0.0072

0.0178

5.96

+0.27

-19.1

1.500

i0.0006

0.0164

6.06

-0.12

-20.4

1.510

?- 0.0076

0.0160

6.28

-0.85

-22.8

1.530

f0.0178

0.0150

6.52

- 1.50

- 21.8

1.544

i-0.0200

0.0138

6.77

-2.07

,.~ 26.5

1.558

+0.0200

0.0126

7.05

-2.57

-28.0

1.570

i -0.0200

0.0112

7.33

-3.00

-29.2

1.580

+0.0200

0.0094

7.63

-3.35

-30.2

1.588

i -0.0200

0.0072

100

7.91

- 3.62

-31.0

1.594

+0.0200

0.0050

- 3.82

-31.5

1.595

i0.0200

0.0038

110

8.25

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

of A ) from Fig. 13.1, t h e four parameters were SP evaluated by t h e method of l e a s t s q u a r e s to obtain t h e equation log K Z p

Representative c a l c u l a t e d thermodynamic v a l u e s obtained by t h e s e procedures a r e included in T a b l e 13.1.

390.9619 - 152.6246 log T - 12545.62/T : 0.081849287'. (5)

T h e a v e r a g e deviation from t h i s equation of t h e experimentally determined v a l u e s of KO shown in SP Fig. 13.1 w a s +0.6%. V a l u e s of AHo a t e a c h temperatuie were obtained by differentiating Eq. (5) with r e s p e c t to l/T("K) and substituting t h e t h e result into t h e van't IIoff equation, (4), while t h o s e v a l u e s of IC" were obtained by differenP t i a t i n g with r e s p e c t to T t h e resulting e x p r e s s i o n for AHo. While s e p a r a t e v a l u e s of 2C" might P b e expected to b e somewhat inaccurate, t h e a v e r a g e value of IC; from 0 t o llO째C of -57 c a l molr'-' Oca-' is believed to b e significant. Values of AS" a n d IFo were obtained from t h e standard thermodynamic equation,

The Additional Solid Phase At concentrations of NaCl a b o v e 3 to 5 m and at temperatures from 70 to 95"C, a s a t u r a t i n g s o l i d other than CaSO4.2H,O or MaCl w a s found. In s p e c i a l expcriments a t 7OoC, t h i s s e c o n d s a t u r a t i n g s o l i d p h a s e w a s identified by petrographic examination' t o b e Na,S0,-5CaS04.3H20, found previously i n t h e system Ca(312-Na2S04I I , Q . 3 By t h c formation of Na2S0,.5CaS0,.31120 from s o l u t i o n s initially only of NaCl and CaSO,, t h e s y s t e m becomes a four-component s y s t e m , rather than t h r e e , and m u s t b e defined by t h e components CaSO,, NaC'L, CaCI,, a n d H,O. 'Thanks are d u e G. D. Rrunton, R e a c t o r Chemistry Division, for t h e s e examinations. 3A. E. Mill and J. H. Wills, J . A m . Chem. SOC. 60, 1647 (1938).

115

THE OSMOTIC BEHAVIOR OF SIMULATED SEA-SALT SOLUTIONS AT 123’C P. 13. Bien

B. A. Soldano

The i s o p i e s t i c technique previously developed at ORNL4 h a s b e e n u s e d to t e s t t h e behavior of t h r e e simulated sea-salt s o l u t i o n s a t 123°C. T h e t e s t s w e r e made to assess t h e applicability of calculation methods proposed for determining thermodynamic properties, including t h e vapor p r e s s u r e s , of s o l u t i o n s of i n t e r e s t to t h e vacuumd i s t i l l a t i o n p r o c e s s for d e s a l i n a t i o n of seawater. T h e three sea-salt s o l u t i o n s were prepared to s i m u l a t e c l o s e l y t h e “standard s e a w a t e r ” defined by K. S. S ~ i e g l e r . In ~ order to avoid t h e evolution of g a s e s a n d p o s s i b l e corrosion in t h e vapor chamber, t h e troublesome univalent a n i o n s HCO 3 a n d 13r- were replaced by equivalent q u a n t i t i e s of chloride ion, Solution A w a s further modified b y replac i n g t h e c a ICi um w 3th magnesium, t h e reby i n c r e a s i n g t h e magnesium concentration to 0.06451 m; t h e s u l f a t e concentration in solution A w a s kept at 0.02856 m. Solution B w a s modified further b y completely removing t h e calcium together with a n equivalent amount of s u l f a t e ; t h e s u l f a t e concentration in solution B W R S thus reduced to a concentration of 0.01822 m. Saline eS w a s not modified except by t h e replacement of chlaridi? for t h e bicarbonate a n d bromide. T h u s , t h e compositions of the t h r e e s o l u t i o n s were: A (m)

B (m)

CaZi

M2+ K

SO, c71 -

Table 13.2.

0,05417

0.054 I 7

0.01007

0.47564

0.02856

0. 01822

0.02856

0.55761

0.7078

0.6664

0.7078

I _

”B. A. Soldano and G. S. Patterson, J . Chezn. Soc., 1962, 93’7.

R. W. Stoughton and M. Ii. Lietzke, J . C h a m . En&

6 ~ S. . Spiegler, Sea Water P u r i f z c a t i o r i , Wiley, N e w York, 1‘362.

Experimental Values for I o n i c Strength,

2 mi+2

Illarch 9

0.6930

0.8550

0.7965

0.9130

10 11 12

0.6683

0.8228

0,7884

0.8714

0.6734

0.8318

0.8019

0.8580

0.6987

9 8662

0.8087

0.91 34

15 97

0.6993

0.8758

0.8358

0.8911

0.7744

0.9611

0.9278

1.0011

0.8658

1.0229

1.0165

1.1158

1.4601

1.b 58 5

1.5788

1.6892

1.5750

1.7812

1.75 10

123034

1.6342

1.8484

1.7464

2.0445

1.8496

2.1308

2 ” 042 I

2 , Q.568

1.9674

2.2016

2.1102

2.2416

2.0728

2.20138

2.1406

2.3070

2.6290

2.6484

2.5905

2.9369

2.64%

2.7254

2.6530

2.9761

2,7894

2.8‘329

2.8513

2.9808

3.0117

2.9846

3.3 1 08

3,3583

3.3064

3.5966

3.6166

3.5461

3.2420 3 ”435 2

3.6801

3.5466

3,4851

3.8864

4.3018

1.0551

4.0087

4.4950

0 , 0 1 034

Four d i s h e s of e a c h solution, four d i s h e s of NaCl s t a n d a r d solution, a n d four d i s h e s containing s t a n d a r d w e i g h t s for internal calibration of t h e b a l a n c e w e r e loaded into t h e chamber together with a larger d i s h containing NaCl solution which

with t h e concentrations m i deduced from t h e c h a n g e s in t h e solution weights. T a b l e 13.2 p r e s e n t s a v e r a g e v a l u e s of I for t h e NaCl s t a n d a r d

(fll)

0.06451

Data IO, 254 (14ti.5).

s e r v e d as a buffer reservoir. After t h e a i r w a s e v a c u a t e d from t h e s e a l e d chamber, t h e apparatus w a s brought to and h e l d at 123OC. E a c h day, t h e w e i g h t s of every d i s h were recorded as readings on a n e l e c t r i c a l l y operated magnetic balance, after which a s m a l l amount of s t e a m w a s vented from t h e apparatus, t h u s i n c r e a s i n g the concentrations of all t h e test, standard, and buffer s o l u tions. T h e c h a n g e s i n t h e concentrations of t h e t e s t s o l u t i o n s w e r e inferred from t h e c h a n g e s in t h e weights of t h e d i s h e s . The i o n i c s t r e n g t h s of t h e s o l u t i o n s were then c a l c u l a t e d from t h e formula

April

6 7 8 9

3.1081

3.7 ‘2%

4.5016

4.1999

4. 0093

4.4954

6.1244

5.5620

5,2566

6.2986

5,1064

4.5226

4.4029

5.0960

7.9924

6.3590

6.5914

7,6788

7.9248

6.5999

6.2487

6.9631

116

SALINE C-.

-----

0.A

Fig.

4 5 IONIC STRENGTH OF NaCl

13.2.

I s o p i e s t i c R a t i o s of S a l i n e s A,

solution a n d t h e three t e s t solutions at 2 6 diffcicnt l c v e l s of w a t m activity. V a l u e s â&#x201A;Źor t h e i s o p i e s t i c ratios R for e a c h of t h e t c s t s o l u t i o n s were obtained a t e a c h point from the ratio IN a I / Z t e s t s o l n . T h e equations fitted to R a s a function of Z N a C l a r e given a s follows:

0.7701

0.8082 + 0.08891

0.7427

0.001712; crR

0.08791 -

0.005212; crRB

0.0292 ,

0.0270 ,

and

+ 0.07841

0.0055Z2;

Clz = C

0.0344

P l o t s of t h e s e equations, a s shown in F i g . 13.2, s u ~ g e s t e dt h a t solution C w a s clearly different in behavior from s o l u t i o n s A a n d B. T h e cons i d e r a b l e overlap between s o l u t i o n s A and B s u g g e s t e d t h a t a more s e n s i t i v e t e s t could b e made of t h e p o s s i b l e s i g n i f i c a n c e of a n y difference between them. 'l'o t h i s end, t h e hypothesis w a s made that t h e solutions did not differ, and a t t e s t w a s applied t o t h e 26 v a l u e s of 1, - 1 B obtained from t h e data in T a b l e 13.2. An a v e r a g e v a l u e of t h e difference found w a s 0.07'7 unit of ionic strength (not u n i t s of K); t h i s difference

6, and C C o m p a r e d .

w a s found t o b e well a b o v e t h e 0.001 l e v e l of significance. Marshall et 3ZO7 h a v e recently shown that calcium s u l f a t e should begin t o precipitate from s e a w a t e r a t about 117Â°C. Therefore, i t is likely t h a t a l l the t e s t s with solution C w e r e performed in t h e p r e s e n c e of s o l i d CaSO, (anhydrite) 2nd that, consequently, t h e data for solution C s h o u l d not b e s u i t a b l e for a n a l y s i s until a n d u n l e s s a c c u r a t e v a l u e s for t h e solubility of t h e components make it p o s s i b l e to infer t h e true solution composition. It may b e noted, however, that t h e v a l u e s of R c a l c u l a t e d from t h e true solution composition should b e higher than t h o s e plotted in Fig. 13.2, probably bringing t h e d a t a more c l o s e l y in l i n e with t h o s e of s o l u t i o n s A and B. T h e difference between A a n d B w a s observed t o b e quite c o n s i s t e n t over t h e whole concentration range, and t h e a v e r a g e value of t h i s difference, 0.077 ionic strength unit, i s about t w i c e t h e v a l u e c a l c u l a t e d for t h e s o l u t i o n s a s made up at room temperature, 0.0414. T h e s o l u b i l i t i e s of ...................

7~#. L. Marshall, K e a c t o r Chern. D i v . Ann. Progr. R e p t . J a n . 3 1 , 1965, ORNL-3789, p. 294.

117 thi. components of s o l u t i o n s A a n d R h a v e tint y e t b e e n determined as a function of concentration, and it is s t i l l assumed t h a t no precipitation took p l a c e in t h e d i s h e s containing t h e s e solutions. With r e s p e c t t o the original objective, that of t e s t i n g t h e proposed method of c a l c u l a t i n g vapor p r e s s u r e s of s a l i n e w a t e r s , s o l u t i o n s A and B m a y not b e sufficiently different t o permit good evaluation of s u c h a method. Further t e s t s should b e made with solutions known to b e p h a s e s t a b l c at elevated temperatures and probably should begin with simpler s y s t e m s s u c h as t h o s e containing mixtures of NaCl and Na2S0, or mixtures of NaC1 and MgC12.

ALUM1NUM- AND T1T ANIUM-AL LOY CORROSION iN SALINE WATERS AT ELEVATED TEMPERATURES

E. G. Bohlmann J. C. G r i e s s

F. A. Posey' J. F. Winesette

T h e s t u d i e s of t h e corrosion of aluminum and titanium a l l o y s in sodium chloride s o l u t i o n s h a v e continued. They h a v e included investigations in t h c 100-gpm titanium loops, t h e s m a l l titanium electrochemical loop, a n d conventional laboratory equipment. It w a s found n e c e s s a r y to modify t h e electrode assembly in t h e s m a l l titanium loop to reduce troublesotne I R drops; t h i s entailed providing coaxial polarizing e l e c t r o d e s and dual reference e l e c t r o d e s as shown in Fig. 13.3. Galvanostatic polarization s t u d i e s of t h e corrosion of t h e 5454 (27% Mg, 19.8% Mn, 0.1% Cr, c 0.01% Cu) and 6061 (1.0% Mg, 0.6% Si, 0.25% Cu, 0.25% Cr) aluminum a l l o y s in 1 M NaCl at 15O0C h a v e been carried out in t h i s equipment. * The r e s u l t s obtained w e r e generally similar t o t h o s e obtained by other workers a t lower temperatures. Thus, a pronounced minimum e x i s t s in t h e corrosion r a t e of aluminum and i t s a l l o y s i n chloride s o l u t i o n s i n t h e vicinity of neutrality. Changes

'OKNL Chemistry Division. ' S a l i n e Water Conversion Report for 1 9 6 2 , U.S. Dept. Inferior,, pp. 12, 16, 1962. "E. G. Bohlrxiann, F. A. P o s e y , a n d J. F. Winesette, R e a c t o r Chenz. Dlv. Ann. Pro&. R e p t . Jan. 31, 1965, ORNL-3789. p. 296. "E. G. Bohlmann and F. A. P o s e y , "Aluminum and Titanium Corrosion i n S a l i n e Waters a t E l e v a t e d T e m peratures." Proc. F i r s t I n t e r n a t i o n a l Synlposiunl on Water D e s a l i n a t i o n (in press).

with pM i n t h e polarizzitjon curves of anodic and cathodic p r o c e s s e s occurring at the aluminunielectrolyte interface provide a kinetic b a s i s for understanding t h i s and other a s p e c i s of t h e corrosion behavior, A t low potentials, t h e rate of t h e anodic or corrosion reaction is independent of t.he electrode potential, hut it i n c r e a s e s with i n c r e a s i n g pH. 'The rate of t h e anodic process i s controlled by the rate of mass transport o€ hydroxide ions t o the oxide-solution interface. At higher potentials, i n the presence of chloride i o n s , t h e anodic-polarization curve e x h i b i t s a pitting potential which i s independent of the anodic current density. The pitting potential d o e s not vary with pH, but d e c r e a s e s with inc r e a s i n g chloride concentration. T h e cathodic reaction in alkaline solution c o n s i s t s of the reduction of water molecules to form molecular hydrogeti; this process is pI4 independent. With i n c r e a s i n g acidity, reduction of hydrogen ions becomes increasingly important. The rriiriimum corrosion r a t e represents a compromise between t h e d e c r e a s e in the r a t e of the trarisport-controlled anodic reaction with i n c r e a s i n g acidity and t h e i n c r e a s e in t h e rate of t h e cathodic hydrogenevolution reaction. Oxygen in solution may a l s o i n c r e a s e the corrosion rate by providing an additional cathodic process. Comparison of polarization curves of the 54-54 a n d 6061 alloys shows that t h e r a t e of t h e cathodic hydrogen-evolution reaction of the 6061 alloy is considerably greater than that of t h e 5454 alloy. T h e enhanced r a t e of t h e cathodic process on t h e 6061 alloy a c c o u n t s for i t s greater corrosion rate a t any pH and for i t s s u s c e p t i b i l i t y t o pitting a t t a c k . C a t a l y s i s of t h e cathodic process on the 6061 alloy may b e attributable to i t s copper content. It is hypothesized t h a t accumulation of copper a t t h e metal-oxide interface a s corrosion progresses r e s u l t s in pit formation. T h e s e s t u d i e s stemmed from r e s u l t s obtained in t h e 100-gpm titanium loop:;, which showed gross pitting of 6061 alloy specimens after 248-hr exposure to pH 6.0, 1 it! NaCl a t 150°C. Under comparable conditions, t h e 5454 alloy showed uniform a t t a c k after 1620-hr exposure; continuing corrosion r a t e s were ,%,timils/year a t 7 to 25 fps. Similar r e s u l t s are being obtained at 100°C; 6061 specimens s h o w pitting a t t a c k after 500 t o 1500 hr, whereas 5454 specimens s h o w uniform att.ack with continuing corrosion rates of -1 mil/year after 2800-hr exposure.

118

A S B E S T O S WICK FROM CALOMEL ELECTRODE

ORNL-DWG 6 5 - 4 2 2 6 A POLARIZING ELECTRODE ELtCTRODE

UlDFS AND I N S U L P T G R S

Fig.

13.3.

T e s t Assembly for E l e c t r o c h e m i c a l Studies of D y n a m i c Corrosion.

Investigations of t h e s c v e r e corrosion of titanium in s a l i n e waters, reported l a s t year, h a v e a l s o continued. Three racks of s p e c i m e n s a r e being exposed i n t h e water box of t h e No. 1 effect a t t h e Freeport Desalination P l a n t . In t h i s location, t h e s p e c i m e n s a r e exposed t o near-normal concentration, pH -7.5 brine (sulfuric a c i d treated and neutralized f o r scale prevention) a t 129 t o 138째C. R a c k s h a v e b e e n examined a t 12-, 32-, and 82-day intervals a n d h a v e a l l shown negligible t o s e v e r e a t t a c k i n a r e a s of contact with Teflon; no attack w a s observed in metal-to-metal contact a r e a s . T h i s w a s c o n s i s t e n t with t h e previously noted promotion of a t t a c k by c o n t a c t with Teflon. It a p p e a r s likely that t h i s r e s u l t s from the r e l e a s e of small amounts of fluoride ion' by t h e Teflon. Anodic polarization s t u d i e s h a v e shown that a s l i t t l e a s 1 2 ppm fluoride s u b s t a n t i a l l y i n c r e a s e s t h c a c t i v e corrosion rate and t h e rate of activation of titanium. It is a l s o likely that t h e a b s e n c e of more general a t t a c k on t h e rack s p e c i m e n s stemmed from t h e soiriewhat low temperature of exposure - t h e bulk of t h e exposure w a s a t temperatures less than 138OC. T h e previously noted dominant importance "E. G. Bohlmann and J. C. Griess, Reactor Chem. Div. Ann. Progr. R e p t . J a n . 31. 1 9 6 5 , ORNL-3789,

p. 297.

of temperature w a s reemphasized by recent experience with 100-gpm titanium-loop piping. Formation of s e v e r a l large pits w a s observed during operation a t temperature 2 150OC. Subsequently, the loop h a s been operated a t 100째C for -2800 hr with no apparent further a t t a c k . A similar pit initiated in another part of t h e loop penetrated t h e 0.2-in. pipe wall a f t e r approximately 5400 hr a t 150OC a n d after 300 hr at 200OC. A particularly significant point concerning t h e very s h a r p temperature dependence h a s j u s t b e e n discovered. This i s that t h e breakdown or pitting potential for titanium, reported a s -10 v in roomh a s a very sharp temperature chloride solutions, temperature dependence. Studies in t h e s m a l l titanium electrochemical loop showed pitting pot e n t i a l s a t plus 500 IIIV (vs S.C.E.) or l e s s for commercially pure titanium a t temperatures of 15OoC and above. Laboratory and loop electrochemical s t u d i e s h a v e shown t h i s sharp temperature dependence over t h e range 25 to 190OC. T h e actual. potentials measured a n d temperature dependence, however, a r e greatly influenced by alloy composition a n d s u r f a c e condition, s o no quantitative d a t a will b e presented a t t h i s time.

13N. Hackerman and C. D. SOC. 101. 321 (1951).

Hall, Jr., J . Electrochem.

119

CHEMISTRY OF SCALE CONTROL

E. L. Compere

J. E. Savolainen

T h e tendency of s e a w a t e r to d e p o s i t scale in d i s t i l l a t i o n equipment l i m i t s t h e temperature range a n d brine-concentration factor of t h e p r o c e s s and affects t h e efficiency. T h e problem is economic: scale control c o s t s probably should not e x c e e d a few c e n t s per 1000 gal. T h i s elitnin a t e s many technologically f e a s i b l e p r o c e s s e s , u n l e s s s a l a b l e by-products a r e produced. Raw-materials costs a l o n e appear to b e too high for most p r o c e s s e s e x c e p t t h o s e u s i n g compounds of carbon or sulfur. Sulfuric a c i d addition is conventionally u s e d to prevent t h e formation of calcium c a r b o n a t e or magnesium hydroxide scale a n d permits operation up t o temperatures near 250°F. Calcium s u l f a t e may precipitate a b o v e t h i s temperature. T h e prevention of a l k a l i n e scale i n s e a w a t e r h e a t e r s b y m c a n s of carbon dioxide additions h a s b e e n s u g g e s t e d . Ellis14 observed t h e effect of carbon dioxide p r e s s u r e on t h e solubility of calcite in various sodium chloride s o l u t i o n s at e l e v a t e d temperatures. Thermodynamic equilibrium c o n s t a n t s a n d mean activity c o e f f i c i e n t s of calcium a n d bicarbonate ions were reported. We a d a p t e d t h e s e findings to t h e composition and alkalinity of standard s e a w a t e r , a s s u m i n g t h a t t h e s o l u t i o n s a n d a c t i v i t y c o e f f i c i e n t s a r e similar at e q u a l ionic s t r e n g t h s . I t w a s t h u s e s t i m a t e d that t h e addition of 0.9 Ib of CO, per 1000 gal of s e a w a t e r f e c d , corresponding to a CO, partial p r e s s u r e of 0.09 atm a t 2S°C, might prevent In a c a l c i t e precipitation u p t o 125’C (257’F). once-through flash-evaporat o r s y s t e m , a l k a l i n e scale would precipitate i n t h e brine bulk a s carbon dioxide f l a s h e d in the first s t a g e . Heating s u r f a c e s would not b e fouled, a n d C 0 2 might b e recycled without compressors. Data were not a v a i l a b l e permitting consideration of magnesium hydroxide precipitation. T h e assumption t h a t s e a w a t e r resembles sodium chloride s o l u t i o n s of e q u a l ionic strength negl e c t e d consideration of ion-pair formation. T h e chemical model of s e a w a t c r a t 25°C of Garre1sl5 a n d Thompson s h o w e d a s i g n i f i c a n t degree of -

14-4.J. Ellis, Am. J . S a . 261, 259-67 (1963). 1 5 R . M. Garrels a n d Mary E. Thompson, Am. J . SCZ. 260, 57-66 (1962).

a s s o c i a t i o n of s u l f a t e , bicarbonate, and carbonate ions with magnesium a n d sodium arid a l s o with calcium ions. Our preliminary e s t i m a t e s for 100°C h a v e indicated t h a t magnesium s u l f a t e pair formation will b e greater at t h e i n c r e a s e d tempetatute. Calcium s u l f a t e is similarly affected t o a l e s s e r extent. T h e s e phenomena may also affect the application t o s e a w a t e r problems of t h e s t u d i e s of Marshall, Slusher, a n d Joilcs16 on t h e solubility G f calcium s u l f a t e in sodium chloride s o l u tions. T h e economic removal of calcium s u l f a t e s c a l i n g t e n d e n c i e s may b e p o s s i b l e by thermal precipitation techniques in which s e a w a t e r is h e a t e d to a temperature of calcium s u l f a t e supersaturation; precipitation may b e facilitated by contacting with calcium s u l f a t e particles. An understanding of ionic a n d solubility equilibria a n d precipitation k i n e t i c s a r e needed to provide a rational b a s i s f o r a n economic p r o c e s s using t h i s technique. ‘The r a t e of precipitation from a s u p e r s a t u r a t e d solution is affected by m a s s transfer to t h e c r y s t a l surface, reaction with s u r f a c e s i t e s , and nuc l e a t i o n of new p a r t i c l e s , Without nucleation, t h e rate cannot e x c e e d t h a t of mass transfer. Coe f f i c i e n t s for m a s s transfcr t o p a r t i c l e s were related by Harriott” to that for a s i n g l e freely f a l l i n g s p h e r e i n t h e given liquid. T h e coefficient d e c r e a s e s as particle size i n c r e a s e s up to about 1 0 0 p arid c h a n g e s l i t t l e thereafter. F o r anhydrite crystallization from standard s e a w a t e r with about 10°F superheating, w e e s t i m a t e d t h a t t h e masst r a n s f e r limitation would permit growth r a t e s up to s e v e r a l centimeters per hour. Such r a t e s would permit a n effective unit for removing calcium sulf a t e from s e a w a t e r to b e designed. N e i l s e n l Y h a s indicated that, a s supersaturation is d e c r e a s e d and t h e s u r f a c e reaction becomes limiting, crystallization r a t e s d e c r e a s e more than t h e concentration by a s u b s t a n t i a l proportion. On the other hand, if t h e concentration is inc r e a s e d a n d high l e v e l s of supersaturation a r e reached, undesirably rapid nucleation is to b e anticipated. T h u s , t h e supersaturation must b e 16W. L. Marshall, Ruth Slusher, and E. V. J o n e s , J . Chem. Eng. P a & 9, 187-91 (1964). 7Peter Harriott, A.1.Ch.B. (Am. Inst. Chem. E n g r s . ) J . 8(1), 93-102 (1962).

‘*A, E. N e i l s e n , K i n e t i c s millan, New York, 1964.

Precipitation, Mac-

120

maintained in t h e range controlled by m a s s transfer for t h e most effective operation of â&#x20AC;&#x153;contacts tahilizationâ&#x20AC;? equipment. In addition to c a p i t a l and h e a t c o s t s of t h e contact-stabilization p r o c e s s , pumping-energy c o s t s may b e appreciable. At higher temperatures, a higher h e a d is required in order to pressurize t h e

feed to prevent boiling. F o r example, a t 330Â°F t h e vapor pressure of water is 103 psi, and about 1 kwht is required t o pump 1000 gal of feed a g a i n s t t h i s head. The maximum economic temperature is t h u s limited by t h e exponential rise in vapor pressure.

14. Effects of Radiation on Organic Materials W. W. Parkinson

EFFECT O F RADIATION ON

POLYMERS

W. W. Parkinson W. K. Kirkland R . M. Keyser Polytetrafluoroethylene (Teflon) d e g r a d e s at very moderate radiation d o s e s i n air, b u t i t h a s b e e n found to s h o w much less s e n s i t i v i t y when irradia t e d i n a n inert atmosphere or vacuum. l T 2 B e c a u s e of t h e u s e f u l n e s s of Teflon i n d e l e t e r i o u s environments and b e c a u s e t h e f i l m s u s e d i n previous work2 would b e extremely s e n s i t i v e t o atmosphere, and Vl6 in. t h i c k n e s s h a s b e e n s h e e t s t o c k of investigated. T e n s i l e s p e c i m e n s have t e e n irradiated at about 25°C i n a i r and vacuum over a range of d o s e s u p t o 7 x l o 7 rads. T e n s i l e properties were measured i n a i r at room temperat.ure. T h e s p e c i m e n s in vacuum were o u t g a s s e d torr and 140°C and s e a l e d i n g l a s s at 5 x c a p s u l e s . T h e d o s e rate w a s 1.2 x l o 6 rads/hr. ‘The t e n s i l e properties of t h e tG--in. s h e e t irradiated in a i r and i n vacuum a r e plotted v s d o s e in Fig. 14.1. It is s i g n i f i c a n t t h a t i n vacuum t h e t e n s i l e strength d e c r e a s e s to 40-45% of its original v a l u e a t 2 <; l o 6 rads but remains almost c o n s t a n t from t h i s d o s e t o perhaps l o 8 rads or more. Ht i s s e e n that useful mechanical properties a r e retained in an ineri. atmosphere to d o s e s i n excess of 3 x l o 7 rads. In a i r Loth the and ?;,-in. -thick s p e c i m e n s retain 3 3 % of their original t e n s i l e s t r e n g t h a t lo6 r a d s , in c o n t r a s t to t h e f i l m s of t h e earlier work,2 where t h e t e n s i l e

v16-

IC. D. Ropp and G. S i s m a n , Nucleonics 13(7), 2 8

(1 955)”

2 L. A . Wall end R. E. F l o r i n , J . R p p l . Polymer Sci. 2, 251 (1‘259).

O s c a r Sisman

strength d e c r e a s e d t o very low v a l u e s i n t h i s d o s e range. T h e maximum in the elongation a t break, obs e r v e d in t h e t32-in. a s well as t h e 51G-in. s p e c imens, i s interesting in t h e light of “zero s t r e n g t h time” measurcments, demonstrating that s c i s s i o n predominates a t d o s e s above IO4 rads. Probably, radiation-induced d e f e c t s in t h e c r y s t a l structure, indicated b y a minimum in t h e density-dose c u r v e a t IO3 r a d s , 3 i n c r e a s e t h e ductility and a c c o u n t for t h e maximum i n t h e elongation.

RAD! ATION-IN DUCED REACTIONS OF HYDROCARBONS 12. M. Keyser

W. W. Parkinson

’Two p r o c e s s e s are under study a s p o s s i b i l i t i e s for utilizing t h e f i s s i o n energy which a p p e a r s a s k i n e t i c energy of t h e fission fragments. A 6oC:o a s s e m b l y is u s e d c u r r e d l y a s a more convenient s o u r c e of ionizing radiation than a nuclear reactor. O n e of t h e p r o c e s s e s is t h e hydrogenation and alkylation of c o a l in mixtures with a l k a n e s . ‘The other p r o c e s s is the s y n t h e s i s of a m i n e s i n mixt u r e s of ammonia with a l k a n e s and a l k e n e s . T h e radiation-induced reactions of naphthalene in h e x a n e a r e b e i n g i n v e s t i g a t e d initially as a model system for t h e coal p r o c e ~ s . ~A temperature-programmed gas chromatograph is being reconditioned, a n d high-temperature columns s u i t a b l e ‘A. Nishioka et al., J. A p p l . Polymer Scz, 2, 114 (1 959).

4W. W. Parkinson e t al., Reactor Ciztm. D i v . A n n . Pro&. K e p t . J a n . 31, 1965, OKNL-3789, p. 320.

121

122

.$+

7000

6000

I-

A TENSILE STRENGTH, IRRADIATED IN AIR

A ELONGATION, IRRADlA-TED IN AIR 0 TENSILE

a 5000

DWG 6 6 - 979

OW:

S T R E N G T H , IRRADIATED IN VACUUM

ELONGATION, IRRADIATED IN VACUUM -

I I

---.

'a n

4000

cc W

u? k

3000

W I-

2000

I000

lo5

104

406 RADIATION DOSE (rods)

Fig. 14.1.

T e n s i l e Properties of Irradiated Teflon.

for a n a l y s i s of t h e expected products a r e b e i n g procured, T h e e f f e c t of strong b a s e s on reactions involving i o n i c intermediates in irradiated hydrocarbons h a s been demonstrated recently. These results have led u s t o s e a r c h for amines i n the radiolysis products from s o l u t i o n s of ammonia i n n-hexane and in hexene-1. Solutions for irradiation were prepared b y condensing known amounts of anhydrous ammonia into deaerated s a m p l e s of nhexane and hexene-1. Ammonia concent rations in most s o l u t i o n s were of t h e order of 2 t o 3 mole %, which is about t h e limit of ammonia s o l u b i l i t y i n t h e s e hydrocarbons a t room temperature and atmospheric pressure. Irradiations were carried out in a 20.000-curie 6oCo s o u r c e a t a d o s e rate 'W. R. B u s l e r , D. 11. Martin, a n d 'r. F. Williams, LJiscussions F a r a d a y S O C . 36, 102 (1963).

of 8.5 x 10l8 ev g-' m i n ' Total d o s e s w e r e in t h e range 5.0 x 10'' t o 8.6 x l o z 1 ev/g. After irradiation t h e s a m p l e s were opened and s u b j e c t e d to g a s chromatographic a n a l y s i s using a column with a liquid p h a s e c o n s i s t i n g of tetrahydroxyethylenediamine with tetraethylenepentamine added as a tail reducer. T h i s column g i v e s good separation with only s l i g h t peak tailing of calibration mixtures containing e x p e c t e d products s u c h a s t h e 1-, 2-, and 3-aniinohexanes and lowermolecular-weight amines. T h e r e s u l t s obtained so f a r h a v e not been promising. No amines h a v e b e e n detected in t h e irradiated solutions, t h e limit of detection corresponding t o a q a m i n e ) of 0.2 molecule per 100 ev. Mechanistic considerations i n d i c a t e that a p o s s i b l e reaction path leading to amine formation i n irradiated ammonia-hexane s o l u t i o n s may b e formul a t e d a s follows:

123 were recorded of t h e s t a r t i n g materials and t h e product mixtute. T h e telogen w a s p r e s e n t in greater concentration in t h e mixtures s i n c e it w a s d e s i r e d to promote t h e formation o f 1: 1 telomers i n t h e reactions (1)-(3) below and to minimize t h e addition of s e c o n d and third molecules of t h e unsaturated compound.

In view of t h e relatively low concentrations of ammonia p o s s i b l e a t atmospheric pressure, reaction (S) may o x u t before the C GH 3+ carbonium ion encounters an ammonia molecule a s i n ( 3 ) . Experiments with ammonia a t p r e s s u r e s a b o v e atmospheric a r e currently i n progress in an effort 'io i n c r e a s e t h e ammonia concentration i n t h e system,

ADDITION REACTIONS OF FURAN DERIVATIVES

c. D.

W. IP. R u r c h 6 W. W. Patkitison

nopp

Polar organic compounds h a v e been observed t o add t o olefinic groups in c h a i n r e a c t i o n s inif i d e d by chemically produced f r e e r a d i c a l s or ionic intermediates. Such chain r e a c t i o n s offer t h e p o s s i b i l i t y of t h e high y i e l d s required for commercial utilization of the radiation from r i d i o i s o t o p e s . Materials which may be c a n d i d a t e s for upgrading throngh s ~ c hr e a c t i o n s a r e t h e furan derivatives. T h e products, b i c y c l i c and t r i c y c l i c ethers:, would be u s e f u l for s o l v e n t s and for further processing into chelating a g e n t s , surface-active a g e n t s , clc. A survey is being perfonned of t h e mdiationinduced addiLion of s a t u r a t e d furan and similar ethers t o unsaturated ~ K X I d e r i v a t i v e s and alk e n e s . Compounds whj ch h a v e been i n v e s t i g a t e d a r e listed in T a b l e 14.1 mid grouped a s s a t u r a t e d compounds (t elogensj and IJn s a t u r a t e d compounds Solutions containing a telogc:n and an unsaturated compound in concentrahoris of 10 t o 1 by volume were irradiated and partially analyzed by gas chromatography. In many c a s e s , infrared s p e c t r a ~

6 T e m p o r a r y 2 m p l o y r e from K m s a s Stab U n i v e r s i t y , Manhattan.

S o h $ions contai aing 2-meth ylte t tahyd rofuran were studied over a range of concentrations and d o s e s since 1he hydrogen abstraction, step (3), p r o c e e d s with greater ease in t h e case of a tertiary hyd rog en. T h e chromatographic a n a l y s e s s h o w that cons i d e r a b l e quantities of products are formed i n the tnulccular-weight range of dimers a n d s i m p l e teloincrs. 'FIE r e s u l t s for s o l u t i o n s of dihydrofuran in 2-methyltel.rahydro~urall i n d i c a t e that t h e tilajop pmduct c h a n g e s from a dimer or 1:1 adduct to a ttimer or 1 : 2 adduct when t h e d o s e e x c e e d s about 8 x IO7 rads. ~ n c t e a s i n gt h e concentration of dihydrofuran i n t h e solution favors t h e lowermolecular-weight product a t t h e higher d o s e s . Comparison of solutions of tetrahydrofuran and

124 Table 14.1.

Compounds lrrodioted i n a S u r v e y o f Addition R e a c t i o n s

Sattirated Compounds (Telogens)

___

~~~~.~~ ...........

Name ...~

Structure ~

Unsaturated Compounds

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

Name

........ Structure

....

Tetrahydrofuran

Cyclohexeiie

2-Methyltetrahydrofuran

Dihydrofuran

2,5-Dimethyltetrahydrofuran

2,5-Dime thylfuran

C H,

D iis opropy 1 ether

CH,

HC-0-CH

CH3

Furan

CH3

CH3 Is opropy 1 a IC ohol

}-IC- 0 ti I CH3

2-methyltetrahydrofuran in both diliydrofuran and cyclohexene s u g g e s t s t h a t tetrahydrofuran g i v e s higher y i e l d s than t h e 2-methyl compound. Evaporation of t h e irradiated mixtures indicated that over 20% of t h c original materials had b e e n converted to nonvolatile residue a t d o s e s of about 4 x 10' rads. Initial y i e l d s in t e r m s of consumption o f dihydrofuran i n mixtures with methyltetrahydrofuran were estimated a t G v a l u e s (molecules per 100 ev) of about 10.

Infrared s p e c t r a indicated t h e formation of s m a l l q u a n t i t i e s of hydroxy and carbonyl compounds. Mixtures of telogeiis with furan and 2,s-dimethylfuran gave very l i t t l e 1: 1 o r higher telomer, probably b e c a u s e of resonance stabilization of t h e furan ring. Further work will involve identifying t h e products indicated b y g a s chromatography and measurement of y i e l d s a t elevated temperatures.

IS.

Fluoride Studies for Other ORNL

THE CHEMISTRY OF CHROMIUM IN THE FLUORIDE VOLATILITY PROCESS B. J. Sturm

R. E. Thoma

In earlier v e r s i o n s of t h e Fluoride Volatility P r o c e s s , v o l a t i l e UF, w a s obtained by fluorination of fluoride m e l t s in which s o l i d f u e l e l e m e n t s had been d i s s o l v e d by treatment with HF. For zirconium-' or aluminum-based2 fuel e l e m e n t s t h e method worked well b e c a u s e t h e a v a i l a b l e lowmelting s a l t mixtures permitted t h e fluoriliation a t temperatures of 600째C or lower, where corrosion w a s not severe. F u e l e l e m e n t s with m a t r i c e s and claddings of s t a i n l e s s s t e e l proved less t r a c t a b l e ; a p r o c e s s in which UF, is recovered by volatilization from a fluidized bed i n s t e a d of a m e l t " l o o k s promising for these fuels. Uranium hexafluoride from both p r o c e s s e s is purified by adsorptiondesorption c y c l e s on beds of NaF. In t h e fluidized-bed procedure t h e fuel e l e m e n t s a r e supported i n a fluidized alumina powder, which a c t s a s a h e a l transfer rtiedium, and are decomposed by treatment with HF-0, mixtures. Uranium is then recovered as U F 6 by fluorination. When chromium, an important c o n s t i t u e n t of s t a i n l e s s s t e e l , r e a c t s with t h e HF-0, mixture, i t forms nonvolatile o x i d e s and fluorides, On fluorination, chromium is oxidized to higher valence, arid large q u a n t i t i e s of its volatile fluorides and oxyfluorides form. T h e s e compounds might volatilize with and contaminate t h e recovered UF,. L i t t l e is known of t h e s e volatile compounds of chromium. Reactor Chemistry Division r e s e a r c h e s performed 'Chern. Tech. Div. Ann. Progr. R e p t . M a y 3 1 , 1963, ORNL-3452, p. 26. 'Cheni. Tech. D i v . Ann. Pro&. K e p t . May 3 1 , 1963, OHNL-3627, p. 40. J Chem. Tech. Div. Ann. Infonnaticm iMeeting Program, Nov. 10-12, 1965, pp. 5-7.

i n support of the OIiNL Fluoride Volatility P r o c e s s program have, accordingly, been devoted t o the chromium compounds which may affect t h e new method. Synthesis of CrF,

Free-energy action

AgF,

e s t i m a t e s 4 indicated t h a t t h e re-

+ CrF3 $CrF4

-t-

AgF , AF

---

-29 k c a l ,

might b e u s e d for s y n t h e s i z i n g CrF,*. In laboratory t e s t s , we found that d e n s e blue-black CrF, vapors were evolved above 40OoC, t h e boiling point o f the compound, when equimolar amounts of t h e rea c t a n t s were p r e s e n t or when there w a s an e x c e s s of AgF,. Reaction of Chromium Fluorides with

NaF

S i n c e UF, is purified by absorption on Nabbeds, t h e behavior of chromium fluorides with N a F w a s studied. Two compounds, 3 N a F CrF, and 5 N a F XrF,, formed during t h e c r y s t a l l i z a t i o n of molten NaF-CrF, mixtures containing less than SO mole % CrF,. 'The former compound (apparently a structural a n a l o g of cryolite) e x i s t s in two c r y s t a l modifications. T h e high-temperature form melted reproducibly a t 1090째C and exhibited a r a n g e of solid-solution stoichiometry. T h e lowtemperature form is biaxial, with an a v e r a g e tefrnctive index of 1.411. X-ray diffraction p a t t e r n s from 5NaF-3CrF3powder s u g g e s t t h a t t h e cornpound, melting incongruently at 8Q0째C, is isomorphous with c h i o l i t e (5NaF 3AlF',). In the

4A. Glassner, The Therniuclzcmica 1 ProRerties of tho O x i d e s , E'tizorides, a n d Chlorides a t 2500 K, ANI,-5750

(1957).

12.5

126 composition region 0 to 5 0 mole 76 CrF,, t h e s y s tem NaF-CrFJ h a s two invariant points: a e u t e c t i c a t 14 mole 76 CrF, and 873OC and a peritectic n e a r 42 mole % CrF, and 8OO0C, An NaF-CrF, p h a s e w a s s y n t h e s i z e d by exposi n g granulated N a F t o CrF, vapor a t 400 to 50OCC in a controlled-atmosphere glove box. T h i s product had a face-centered c u b i c structure with a l a t t i c e c o n s t a n t of 7.90 A. Since i t i s isostiuctural with t h e high-tcmperature foriii of K2CrF6,' t h e compound is believed to b e Na,CrF6. Behavior of CrO,F,

Chromium oxyfluoride h a s been prepared by reaction of CoF, and CrO, and h a s been exposed in t h e vapor s t a t e for 0.5 hr a t 8OoC to s e v e r a l of t h e materials expected to c o n t a c t t h e Fluoride Volatility Process g a s streams. Sodium fluoride reacted with t h e C r 0 2 F 2 to produce an ( a s yet unidentified) yellow-orange compound. Aluminum fluoride, UF,, and UO, showed no e v i d e n c e of reaction. Equilibrium data7-' for t h e reaction 2 W A 9 + CrQJ4

CrO,F,(g) + H , O W

s u g g e s t that A@ for solid CrO,F, a t 298'K should From t h i s value one b e near - 189 kcal/mole. predicts t h a t CrO,F, should oxidize CrF, to CrF,, UO, t o UO,, and (by 2 k c a l per gram atom of F) UF, to IJF5. No t e s t s of the first two r e a c t i o n s h a v e been made; UF, w a s not oxidized to U F , during t h e relatively mild e x p o s u r e s above.

ON OF LiF SINGLE CRYS MQDlFlED STOCKBARGE METHOD R. G. Ross

R. E. Thoma

A s part of t h e AEC P u r e Materials Program, s u s t a i n e d efforts h a v e been made within t h e Ke5H. C. Clark and Y. N. Sodana, Can. J. Chem. 42, 5 0 (1964). 6G. D. F l e s c h and 13. J. Svec, J. A m . Chem. Soc. 80, 3189 (1958). 7.4. Engelbrecht and A. V. G r o s s e , J. Am. Chem. Soc.

74, 5262 (1952).

'P. A, Munter. 0. T. Sepli, and K. A. K o s s a t z , Ind. E n g . Chem. 39, 427 (1947).

'R. A. Oriani a n d C. P. Smyth, J. Am. Chem. S O C . 70, 1 2 5 (1918).

a c t o r Chemistry Division to develop t e c h n i q u e s and apparatus required for t h e production of very pure, large (350 g) 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 ratios. In a previous report" we indicated t h a t by refinement of standardized techniques for preparing lithium fluoride s i n g l e c r y s t a l s , we could routinely produce s u c h c r y s t a l s in which metallic impurity concentration d o e s not exceed 30 ppb. C r y s t a l s were grown from molten L i F in c a p s u l e s of grade "A" nickel. T h e s i n g l e contaminant d e t e c t e d in t h e LiF product by t h e b e s t analytical methods available i s manganese; i t s s o u r c e is t h e nickel c a p s u l e wall, from which Mno and/or MnZt diffuse into t h e melt. T h e principal application of t h e s e LiF c r y s t a l s h a s been, i n t e s t i n g theoretical models relating t h e variation of t h e thermal conductivity of the c r y s t a l s with their 6Li-iJ.Ai ratio. F o r t h i s purpose, workers a t t h e Cornell Materials S c i e n c e Center" h a v e found that c r y s t a l s must b e sufficiently pure that t h e impurity d o e s not mask t h e i s o t o p i c effect. While a d e q u a t e for m o s t s t u d i e s which require very pure c r y s t a l s of LiF, materia1 which c o n t a i n s a s much a s 1 ppm M n 2 + is insufficiently pure for t e s t i n g theoretical models under consideration, In attempts to improve t h e purity of I,iF c r y s t a l s further, we h a v e modified t h e Stockbarger apparatus to grow LiF c r y s t a l s i n a c a p s u l e lined with laboratory-grade platinum. T h i s innovation h a s proved to b e very effective in improving t h e chemical purity of c r y s t a l l i n e LiF. A 270-e, cryst a l of LiF, designated ORNL-11, and containing 99.99 at, % 7Li, w a s grown in t h e platinum-lined c a p s u l e . A s in previous ORNL preparations, the c r y s t a l w a s vacuum annealed and handled subsequently only in vacuum o r inert atmosphere. T h e c r y s t a l w a s found to contain a lower concentration of heavy-metal contaminants than i s currently d e t e c t a b l e by activation analysis. 'That is to s a y t h a t t h e concentration of manganese, t h e most likely contaminant, i s <1.86 p a r t s per billion, and t h e c r y s t a l i s purer than any of our previous efforts. I

'OC. F. Weaver e t af., T h e Production of L i F Single C r y s t a l s with S e l e c t e d Isotopic R a t i o s of Lithiczm, ORNL-3341 (March 1964).

"R. E. 'l'homa et al., R e a c t o r Chem. Div. Ann. Progr. Rept. Jan. 3 1 , 1965, ORNL-3789. p. 323.

12P. D. Thacher, Thermal Conductivity S t u d i e s of Phonon S c a t t e r i n g by Boundaries a n d I s o t o p e s in Lithium F l u o r i d e C r y s t a l s (thesis). Report 369, Mat e r i a l s S c i e n c e Center, Cornell Univ.. Ithaca, N.Y. (June 1965).

Chemical Support for the Controlled Thermonuclear Research Program I?.

A. Strehlow

Whether controlled thermonuclear d e v i c e s with useful power d e n s i t i e s a r e f e a s i b l e is a q u e s t i o n which c a n b e conveniently divided i n t o two princ i p a l parts. 'The first part a s k s whether a plasma fuel e l e m e n t c a n b e constructed; t h a t i s , whether t h e p h y s i c s of plasma confinement c a n b e s o l v e d in a practical way. T h e s e c o n d part, which is more obscure, a s k s whether there is a n y fundamental bar to construction of a thermonuclear reactor if the Confinement problem is solvable. W e have continued to study c h e m i c a l a s p e c t s of both parts of t h i s question. Our s t u d i e s i n support of t h e confinement problems are directed toward development of techniques to d i a g n o s e t h e quality of t h e plasma environment i n experimental d e v i c e s and to a s s i s t in attempts to improve this quality. Such pursuits h a v e dominated our c h e m i c a l s t u d i e s . In addition, a n e x t e n s i v e literature survey and a n experimental study h a v e been d e v o t e d t o p o s s i b l e probl e m s of tritium inventory and t h e fuel c y c l e of a thermonuclear reactor. Some of our s p e c i a l equipment w a s also u s e d to assist in t h e d e s i g n (by O R N L I s o t o p e s Division personnel) of a n i s o t o p e separator of a new and improved type. E a c h of t h e s e portions of our effort i s described briefly in t h e following.

'-'

' R e a c t o r Chem. D i v . Ann. Progr. R e p t . Ja27. 31, 1965, ORNL-3789. 'Thermonuclear D i v . Semiann. Fro&. R e p t . Apr. 30, 1 9 6 4 , OKNL-3652. pp. 138-4.5. 3Therrr20nric1ear Div. Senliann. Pro&. Rept. Oct. 31, 1964, ORNL-3760, p. 95.

VACUUM ANALYSIS IN AN EXPERIMENTAL PLASMA DEVICE

R. A. Strehlow A simple mass-spectrometric a s s e m b l y h a s been installed and operated routinely t o yield a continui n g record of vacuum conditions during operation of t h e plasma d e v i c e DCX-2. About 2500 m a s s s p e c t r a h a v e b e e n obtained in t h i s study s i n c e installation of t h i s residual-gas analyzer in F e b ruary 1965. Such d a t a h a v e proved helpful in a s s a y i n g various pumping and operating parameters of DCX-2; s u c h s p e c i e s a s a c e t y l e n e , ttichloroethylene, methane, e t h a n e , a l c o h o l s , and vapors of metals (such as Z n ) c a n b e d e t e c t e d unambiguously. T h e mass s p e c t r a alone a r e insufficient to yield a r e a l d i a g n o s i s of the DCX-2 vacuum environments s i n c e , i n many cases, t h e origin of t h e observed s p e c i e s is m o r e important than t h e f a c t of i t s presence. Accordingly, a s t u d y is under way of t h e e f f e c t of p r o c e s s e s within DCX-2 upon t h e m a s s spectrum obtained from pertinent materials. F o r t h i s study a s e c o n d mass-analyzer assembly, similar to that on DCX-2, has b e e n installed on a simple, l a r g e vacuum s y s t e m w h o s e construction materials, assembly methods, pumps, pump o i l s , e t c , , are similar to those of DCX-2. T h i s assembly permits s t u d y of t h e e f f e c t s of v a r i o u s analyzer instrument parameters (electron-acceleratin g volta g e and ion-source assembly procedure, for example) on t h e spectrum observed, More important, however, it permits study of t h e effect of p r o c e s s e s s u c h a s electron and ion bombardment, temperature fluctuations, titanium getter evaporation, and

127

128 others u s e d in DCX-2 on t h e m a s s spectrum observed. With t h i s assembly, mass-spectrometric s t u d i e s h a v e been made of the e f f e c t of warming liquidnitrogen-cooled s u r f a c e s , 0 4 of hot-filament reactions and electron bombardment of contaminated s u r f a c e s , 2 and of r e a c t i o n s of titanium in vacuum s y s t e m s O 3 Recent s t u d i e s h a v e d e a l t with the formation of products from bombardment with hydrogen i o n s during glow d i s c h a r g e s within t h e assembly. T h e s e s t u d i e s s u g g e s t t h a t acetylene is observed, in addition to methane, only when a trisiloxane oil i s present in t h e bombarded materials. Acetylene, previously observed in DCX-2 during ion injection of 11,’ into t h e assembly, i s now believed t o b e e v i d e n c e of contamination by t h i s pump-oil component.

’

INTERACTION aF TRITIUM WITH THERMQNUCLEAR-REACTOR MATERIALS S, S, Kirslis For a thermonuclear reactor to b e feasible, the holdup of tritium in t h e metal of the containment v e s s e l (probably molybdenum or tungsten) and in that of t h e i o n s o u r c e s (alloys of nickel or iron) must not result in e x c e s s i v e tritium inventory and decay l o s s e s . T h e equilibrium solubility of hydrogen i n t h e s e m e t a l s a t low p r e s s u r e s is low. However, t h e m e t a l s c a n b e cathodically “surcharged” with hydrogen to amounts of t h e order of 100 c m 3 (NTP)/g; t h i s is sufficient to c a u s e , in some cases, blistering and cracking of t h e metal. In order to judge m o r e clearly whether t h e metal in a reactor under bombardment by energetic tritium atoms might b e surcharged with tritium, a literature study of t h e various p o s s i b l e s u r f a c e and interior diffusion p r o c e s s e s h a s been made; t h i s survey will b e published separately. T h e 50- to 100-kev tritium atoms may b e expected to penetrate t h e metal to their range depth of 1 to 2 x cm. They presumably diffuse inward (and a l s o back to t h e e n t r a n c e s u r f a c e ) according to normal diffusion laws. If there i s no appreciable bairier to t h e i r e g r e s s a t t h e surface, the concentration of tritium atoms j u s t ins i d e t h e metal will b e low or zero. If all t h i s i s true, t h e s t e a d y - s t a t e concentration of tritium in 4D, M. Richardson and R. A. Strehlow. T r a n s . N a t l . V a c u u m Symp.. loth, 1963, p. 97.

t h e metal will h a v e a peak a t t h e range depth and will fall off to low v a l u e s a t t h e bombarded surface and a t t h e far s u r f a c e of t h e metal. T h e average concentration i n t h e metal would b e half t h e peak concentration. If a barrier to e g r e s s of tritium froin t h e bombarded s u r f a c e e x i s t s , the whole s t e a d y - s t a t e concentration curve would correspondingly rise to higher tritium concentrations. T h e factors determining t h e peak concentration of tritiuiu a r e t h e flux of a t o m s to t h e metal, the diffusion constant of tritium i n t h e metal, and the boundary condition for t h e d e g a s s i n g of t h e bombarded metal surface. Information on hydrogen diffusion i n t h e m e t a l s of i n t e r e s t w a s derived mainly from published permeability and solubility s t u d i e s . For information on t h e d e g a s s i n g boundary condition, the literature w a s s e a r c h e d i n t h e f i e l d s of chernisorption and desoiption, c a t a l y s i s , hydrogen-electrode behavior, and hydrogen-atom recombination. Other peitinent information w a s obtained from published s t u d i e s of ion bombardment, sputtering of metal s u r f a c e s , and saturation of m e t a l s by proton or deuteron bombardment. T h e conclusions of t h e literature s t u d y a r e a s follows:

1. Hydrogen is e a s i l y d e g a s s e d at low pressures

and moderate temperatures, even from metals (such a s tungsten) for which t h e chemisorption h e a t s a r e high. 2. Cathodic surcharging d e p e n d s on t h e poisoning of t h e metal s u r f a c e for hydrogen-atom recombination. In a g a s e o u s environment on c l e a n metals, hydrogen-atom recombination is rapid. 3 . Diffusion r a t e s for hydrogen in molybdenum a t 600 to 8OO0C a r e sufficiently rapid to deliver injected atoms rapidly back to t h e bombarded surface, t h u s maintaining a very low (and from a practical viewpoint, negligible) concentration of hydrogen i n t h e metal. T h e s a m e i s expected to b e true for tritium. If t h e hydrogen concentration will indeed b e a s low a s estimated from t h e s i m p l e diffusion model, i t should c a u s e no hydrogen embrittlement problems. Since the diffusion c o n s t a n t s for nickel and iron a r e much higher than those of molybdenum, high internal. hydrogen concentrations a r e not expected even a t much lower temperatures. 1. Some recent work on deuteron bombardment of m e t a l s i n d i c a t e s higher concentrations of deuterium j u s t i n s i d e t h e metal s u r f a c e than

129 predicted by t h e s i m p l e model. Some e v i d e n c e i n d i c a t e s this may b e the effect of s u r f a c e contamination on t h e metal.

Table 16.1.

Conditions Employed in Experiments

with Glow Discharges

Wire volume, c m 3

HYDROGEN SURCHARGINGOFMOLYBDENUM IN A GLOW DISCHARGE D. $1. Richardson A study of hydrogen occlusion by a molybdenum cathode in a glow d i s c h a r g e h a s been conducted. T h e principal objective of t h i s work w a s to a s s e s s t h e s i g n i f i c a n c e of hydrogen surcharging t o design considerations for thermonuclear reactors. Initial s t u d i e s had indicated a p o s s i b l e hydrogen content of o n e or more atmospheric cubic centimeters per cubic centimeter of metal after bombardment in a discharge. Though t h i s concentration of hydrogen is less than 0.1 at. %, even this low value could, i f i t were typical of the concentration in a large fraction of t h e reactor, p r e s e n t s e r i o u s problems to t h e reactor designer. T h e work described here and the literature s t u d y summarized above, however, h a v e led to the conclusion that, a t elevated temperatures, occlusion of hydrogen is not large. A t lower temperatures i t a p p e a r s that s u r f a c e contamination c a n markedly impede t h e recombination of hydrogen during even low-energy bombardment; very high hydrogen concentrations in the m e t a l are able, therefore, to b e achieved. For t h e s e s t u d i e s , a 45-cm length of molybdenum wire 1 inn1 in diameter w a s u s e d a s a cathode i n a cylindrical tank with a volume of 200 liters. T h e e n d s of the tank were e l e c t r i c a l l y s h i e l d e d with s h e e t Teflon. T h e c e n t e r of t h e tank was connected to a vacuum s y s t e m through a 6-in. isolation gate v a l v e and a g a t e v a l v e with a small orifice which had a s p e e d of 2 x lo-" the s p e e d of t h e vacuum-system manifold. T h i s allowed a s t e a d y introduction of hydrogen g a s through a palladium leak to t h e glow discharge chamber a t a p r e s s u r e of IO-' to 1 torr with continuous m a s s a n a l y s i s of t h e effluent g a s from t h i s chamber. T h e g a s during t h e u s u a l d i s c h a r g e contained not more than I part per thousand of nonhydrogen impurity. T h e conditions for t h e u s u a l low-temperature discharge are summarized i n T a b l e 16.1. T h e total bombardment for t h e conditions shown was 12 amp-sec or about 1 to 3 atm-cm3 of hydrogen gas. After opening the valve and pumping down to a

0.35

Wire a r e a (apparent), anz

P r e s s u r e , torrs

0.25

D i s c h a r g e current, m a

D i s c h a r g e time, min

Applied voltage to cathode, v

500

-I_____

p r e s s u r e of about 1 x IO-' torr, t h e w i r e w a s heated to redness, Mass-spectrometric and iongage observations were m a d e of t h e hydrogen evolved by t h e d e g a s s i n g process. P r e s s u r e rises of a s much a s 6 x torr were observed during the 4-sec d e g a s s i n g procedure. Since the s y s t e m pumping s p e e d for hydrogen w a s about 1000 l i t e r s / s e c , t h i s p r e s s u r e r i s e corresponded to about 2 atm-cm3 of hydrogen. Stringent c l e a n i n g of t h e wire and ion bombardment o f the chamber w a l l s for several hours, followed by repetition of t h e discharge, l e d t o a value of only 0,017 atrn-cm33 Cant-inued repetitions of t h e discharge-degas c y c l e l e d to i n c r e a s i n g amounts of hydrogen being occluded. S i n c e t h e wire w a s not heated p a s t 10OOoC, a gradual i n c r e a s e i n s u r f a c e contaniination could h a v e teen responsible for the very high values. Several attempts w e r e made a t higher current d e n s i t i e s (and consequent high temperatures) to determine t h e amount of hydrogen occluded during a u s u a l discharge. None of t h e s e attempts l e d to an evolution of hydrogen in d e t e c t a b l e amounts. Molybdenum s u r f a c e s which are c l e a n or which are h e a t e d do not s e e m to occlude l a r g e q u a n t i t i e s of hydrogen during low-intensity bombardment with protons.

MEASUREMENT OF GAS LOAD FROM SOURCE OF ELECTROMAGNETIC SEPARATOR R. A. Stehlow S c i e n t i s t s of the OKNL I s o t o p e s Division are designing an improved electromagnetic isotope separator. T h i s separator, a considerably modified calutron, is to h a v e s e p a r a t e differential pumping s y s t e m s for t h e source, collector, and main-vacuumtank regions. For d e s i g n of t h e s e pumping systems,

130 i t was n e c e s s a r y to know t h e g a s load upon e a c h ; that from t h e s o u r c e w a s judged to requite experimental measurement. ORNL electromagnetic s e p a r a t o r s u s e , where p o s s i b l e , vapor of t h e c h l o r i d e of t h e element whose i s o t o p e s a r e t o b e separated. T h i s chloride is generated within t h e s o u r c e assembly by chlorination with CC1, of t h e appropriat, metal or oxide. T h e g a s load from t h e s o u r c e assembly, therefore, c o n s i s t s almost entirely of unreacted CC14. A flow-rate meter with a c o n s t a n t (regulated) p r e s s u r e and variable volume, c a p a b l e of operation with c o n d e n s a b l e g a s e s and a t low p r e s s u r e s , w a s adapted for t h i s study. T h i s d e v i c e , designed to measure flow r a t e s a s low a s io-5 torr-liter/min for t h e thermonuclear support program, w a s i n s t a l l e d near the s o u r c e region of a calutron. T h e CC14 flow rate f r o m t h i s unit w a s monitored during a tun i n which t h e i s o t o p e s of cerium were being s e p arated. T h e measured flow rate, higher by nearly a n order of magnitude than that previously estimated, h a s been u s e d in d e s i g n of t h e differential pumping s y s t e m for t h e s o u r c e of t h e new unit. 0

NC E-POT ENTI AL MEASU R E

F RQM TIM E-QF- F L B CH 16 MASS SP E C T ROMETRY J. 11. Medman Polymeric s p e c i e s are commonly observed in t h e vapor of simple and of mixed metal halides. We hope to a s s i s t in interpreting m a s s s p e c t r a from s u c h halide vapors by determining appearance potentials of t h e various i o n s formed by electron impact with the vapor s p e c i e s evolving from a n effusion cell. A preliminary s t a g e of t h i s work h a s been completed with t h e construction of a retarding-potential circuit and i t s application t o t h e study, with a time-of-flight m a s s spectrometer, of various g a s e s to assess its reliability. T h i s a s s e s s m e n t w a s considered n e c e s s a r y , even though application of retarding-potential-difference methods to t h i s type of spectrometer h a s been demonstrated, to determine whether g a s e s introduced a t t h e low p r e s s u r e s corresponding t o t h e expected flux of salt-vapor s p e c i e s would yield a p p e a r a n c e potent i a l s with satisfactory precision.

ORYL- DWG 66-980

ELECTRON ENE?CY FOR KRYPTON ( e 4

14.3

F i g . 16.1.

44 5

44.7

14.9

15.4

15.3

45.5

45.7

15.9

N o r m a l i z e d 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 for Krypton and for C2H4',

(6.4

16.3

C2H5',

46.5

ond

46.7

C2H6'

46.9

from Ethane.

131 T h e a s s e m b l y w a s standardized by a s e r i e s of cateful appearance-potential (AP) measurements u s i n g krypton. We obtained t h e v a l u e 13.51 10.04 e v from t h e s e measurements; t h i s is less by 0.5 e v than t h e generally a c c e p t e d v a l u e obtained by other i n v e ~ t i g a t o t s . ~l-1 We h a v e ascribed t h i s discrepancy to (reproducible) c o n t a c t p o t e n t i a l s and, perhaps, o t h e r s y s t e m a t i c errors i n our as-. __._

' C , E. Melton and W. 13. Ilamill, J. Cham. Phys. (to be published).

6R E. Fox et al., Ptiys. Rev. 89, 555 (1953). 7D. C. Frost and C. A. M c I h w e l l , Prnc. Roy. SOC. (%CJZldGfl), SeT. A 232, 227 (1955). F. Burns, Nature 192, 651 (1961). 'Yy. Kaneko, J . Phys. S O C . J a p a n 16, 1587 (1961). ' O S . N. Foner and â&#x201A;Ź3. W. Hall, Pliys. R t ~ v . 122, 512 (1961). 'IF. L t F ~ e l dand J. L. Franklin, Election Impact ;3hezmrriena, Academic, N e w Vork, 1957.

sembly. Appearance p o t e n t i a l s for other g a s e s were obtained from ionization-efficiency curves, normalized for t h i s systeinatic deviation at o n s e t , obtained in t h e standardization with krypton. Typical normalized ionization-efficiency plots are shown in Fig. 16.1 for krypton and e t h a n e fragments. Our v a l u e s for o t h e r a p p e a r a n c e p o t e n t i a l s a r e compared in T a b l e 1 6 2 with t h o s e obtained by others. We fail to c h e c k t h e published v a l u e s + and CzHs t fragments from butane, for i h e C,H, but a g r e e q u i t e satisfactorily with published v a l u e s for a l l o t h e r s studied. S i n c e t h e operating source p r e s s u r e w a s maintained at 5 x to 1 x torr in t h e s e s t u d i e s , we b e l i e v e t h a t vapor f l u x e s from effusion c e l l s containing metal h a l i d e s w i l l prove a d e q u a t e for the planned investigation. It i s l i k e l y that tempera t u r e control of t h e effusion-cell s y s t e m will b e of prime importance.

132

I o n i z a t i o n P o t e n t i a l s for Fragment P e a k s of Argon, Nitrogen, Ethane, and B u t a n e

T a b l e 16.2.

N o r m a l i z e d for V a r i o t i a n of Krypton AP from L i t e r a t u r e V a l u e

......... Fragment

Reactant I _

Art Ar

Ionization P o t e n t i a l s (ev) 15.65 4- 0.15

16.00 k 0.10

Reference

....

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

Number of Determinations

16.32

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

k 0.14

T'his work

15.74

Art

15.77

15.65

15.60

'ZH4'

C2H6

12.28

c2E14

C2H6

12.10

'ZH4'

c2116

C2H5

CZH5

C2H6

C2H5 CZH6 CZH6

c XI

'ZH4+

12.70

T h i s work

13.42

0.10

13.20

12.80 ?r 0.2

13.39

12.10

12.55

+ 0.14

13.78

k 0-23

13.40

T h i s work C

C2H6

11.60

12.10

C2H6

11.60 12.26

T h i s work

12.09

k 0.10

12.84 k 0.15 12.6.5

T h i s work C

k 0.24

12.86

0.1

13.52 k 0.3

11,40

10 t

+ 0.20

12.76

11.66 5 0.17

C2H6

C4H10

C2H4

0.08

0.19

12.80

c21?5

16.85

12.10 3

c2%

i 0.18

T h i s work b

0.25

t 0-02

13.77 k 0.09

c4H,0

12.75

C4H,,

12.10

C3H7

C4H10

11.40

11.60

12.10

T h i s work

C3H7

C4H10

11.50

11.80

12.20

C3H7

C4Hlo

11.70

C2H5

1-1

c4x'1

C4Hlo C4H10

C4H 10

10.68 k 0.22

C4H10

10.60

c4E110

10.80

13.27

11.11 k o . 2 0 11.00

......

RC. E. Melton and W. H. Hamill, J . Chem. P h y s . (to be published).

b F . H. F i e l d and J. L. Franklin, E l e c t r o n Impact Phenomena, Academic, New York, 1957. 'C.

'l'his work

E. Melton and W. H. Hamill, j . Cheni. P h y s . 41(7), 546 (1964).

T h i s work C

Part V

Nuclear Safety

17. Nuclear Safety Tests in M a j o r Facilities FISSlOtl PRODUCTS FROM FUELS UNDER REACTOR-TRANS1 ENT CONDITIONS G . W. Parker K. A. Lorenz J. G. Wilhelm' Miniature f u e l elements a r e melted i n a s p e c i a l assembly in t h e T R E A T t o s t u d y t h e r e l e a s e of radioactive material when t h e f u e l cladding and t h e fuel a r e melted o r vaporized rapidly, as i n a nuclear a c c i d e n t resulting from a reactor trans i e n t . The program attempts t o measure and interpret t h e effect upon f i s s i o n product r e l e a s e of f u e l type, cladding, atmosphere during t h e trans i e n t , inventory of f i s s i o n products, and c h a r a c t e r i s t i c s of t h e transient. T h e extent of reaction of t h e cladding and of t h e UO, f u e l with t h e coveri n g atmosphere is a l s o determined.

high-pressure steam provided an effective barrier to f i s s i o n product r e l e a s e . T h e s e c o n d experiment u s e d a s p e c i m e t ~ with Zircaloy-2 cladding on the UO, fuel; after t h e exposure, fuel and cladding w e t e found to h e fragmented and d i s p e r s e d within t h e alumina crucible. Direct comparison of f i s s i o n product release from t h e s t a i n l e s s - s t e e l - arid t h e Zircaloyc l a d s p e c i m e n s cannot be made s i n c e plugged tubing prevented r e l e a s e o f steam from t h e autoc l a v e after t h e transient with t h e Zircaloy-clad specimen. However, t h e distribution of f i s s i o n products within the f u e l a u t o c l a v e showed that t h e r e l e a s e w a s greater for t h e Zircaloy-(:lad specimen; t h i s must b e considered a t present to b e a result of t h e fragmentation. Behavior on Melting

Behuvior on Melting in Steam

T h e first two of a s e r i e s of experiments h a v e been performed with t h e TREAT reactor i n order to s t u d y t h e r e l e a s e of fission products from f u e l melted underwater. T h e experiments u s e d Ttainlesss t e e l - and Zircaloy-2-clad UO f u e l s p e c i m e n s irradiai e d to 18 Mwd/metxic ton. An i n i t i a l s p e c i m e n temperature of 70째C w a s u s e d , and operating and reactor-transient conditions for t h e two experiments were identical. Heat input to t h e fuel during t h e t r a n s i e n t s w a s approximately 500 cal per gram of UO, (50% greater than any previously used); t h e UO, was heated to w e l l above i t s melting point. T h e experiments were d e s i g n e d t o s i m u l a t e trans i e n t a c c i d e n t s with water-cooled reactors i n wluch s t e a m and water &re expelled from t h e c o r e v e s s e l . V a l v e s w e r e opened immediately after t h e transient, and t h e transient-generated s t e a m and a purge of argon gas were permitted to flow through a cond e n s e r , water-collection t r a p s , filters, and a charcoal bed into a gas-collection tank. T h e fuelcontaining autoclave wils then e l e c t r i c a l l y heated

A n a l y s i s of two experiments which u s e d atrnosp h e r e s of 1000 p s i a s t e a m (285OC) has b e e n reported elsewhere.2 One experiment u s e d a s p e c imen of U 0 2 with s t a i n l e s s s t e e l cladding; during exposure i n T R E A T t h e cladding melted, oxidized e x t e n s i v e l y , slumped i n a spongy m a s s , and adhered to t h e unmelted UOz p e l l e t s . F i s s i o n product r e l e a s e from fuel a n d cladding w a s much less than t h a t in a n earlier experiment, which u s e d previously unirradiated s t a i n l e s s - s t e e l - c l a d UO i n 45-psi argon atmosphere, where t h e cladding flowed completely off of t h e unmelted UO, p e l l e t s . Apparently, t h e layer of oxidized cladding formed by t h e

'On a s s i g n m e n t from K a r l s r u h e Center f o r N u c l e a r Research and D e v e l o p m e n t , Karlsruhe, West Gennany.

'G. W. P a r k e r , R. A. Lorenz, and J. G. Wilhelm, Nuc2. S a f e t y Propran, S m i a n r z . Progr. K e p t . June 30, 1965, OKNL-3843, pp. 39-67.

135

136 t o 35OOC maximum for 1 hr t o slowly boil e x c e s s water out of t h e fuel autoclave. ?'he r e l e a s e and distribution of f i s s i o n products were e s s e n t i a l l y t h e s a m e i n t h e two experiments. 'The fuel s p e c i m e n s melted completely ( F i g s . 17.1 and 17.2). F i s s i o n product r e l e a s e to t h e fuel autoclave w a s high, but transport of f i s s i o n products out of t h e autoclave by s t e a m r e l e a s e and argon purge w a s relatively small. T h e lZ9Te, 1 3 7 C s , '1 carried out of t h e fuel autoclave ranged and from 2 to 7%. T h e transported release of nonvolatile materials (95Zr, 141Ce, and UO,) w a s Approximately 0.005% of t h e 1311 only 0.1%. reached t h e filter papers and charcoal bed.

F i g . 17.1.

Puffy-Appearing Cake of Melted F u e l and

C l a d d i n g from Stainless-Steel-Clad UB2 Melted IJnder

Water by T r a n s i e n t Heat Input o f 504 c a l per G r a m of

U 0 2 i n T R E A T Experiment 7 ( F r o n t Half of C r u c i b l e Removed).

P H O T O 81912

Fig.

17.2.

Zircaloy-2-Clad Capsule

End Caps and Melted F u e l and C l a d d i n g i n Sample Holder from T R E A T Experiment 8 i n Which

U 0 2 Was Melted Under Water by T r a n s i e n t H e a t Input of 511 c a l per Gram

in P l a c e on B a c k H a l f of

Crucible).

U 0 2 ( F l u x Monitor

A n unrnelted f u e l specimen i s s h o w n a l o n g s i d e for comparison.

137 Most of t h e transient-generated s t e a m c o n d e n s e d i n t h e fuel a u t o c l a v e , and only a s m a l l amount: w a s immediately discharged through t h e condenser. 'The water i n s i d e t h e Fuel autoclave w a s an e x c e l l e n t trap for t h e f i s s i o n products s i n c e s l o w evaporation of t h e remaining water (simulating a c c i d e n t after-heat) did not transport large amounts of f i s s i o n products. Approximately 1 liter of hydrogen w a s produced in e a c h experiment by reaction between cladding and water; t h i s resulted i n a chemically reducing atmosphere for most f i s s i o n products. Metallographic examination of portions of t h e melted fuel s a m p l e s showed t h e formation of a e u t e c t i c p h a s e i n t h e s p e c i m e n with s t a i n l e s s s t e e l cladding. T h e major p h a s e i n t h e s a m p l e from t h e Zircaloy-2-clad specimen w a s a s o l i d solution of approximately 75% UO, and 25% %to,. T w o additional experitnetits were recently performed with fuel s p e c i m e n s and reactor t r a n s i e n t s simil.ar t o t h o s e described above. The initial temperature w a s i n c r e a s e d a n d t h e argon purge w a s eliminated i n order to h a v e quicker and m o r e comp l e t e r e l e a s e of s t e a m from t h e f u e l autoclave i n t h e first minute following t h e t r a n s i e n t s . Examination of t h e s e experiments is i n progress.

FISSION PRODUCTS FROM SIMULATED LOSS-OF-COOLANT ACCIDENTS IN ORR W. C. W. B.

E. E. [I. F.

Browning, J r . Miller, J r . Montgomery Roberts

R . P. 0. W. A. F. J . G.

Shields Thomas3 Roemer4 Wilhelm'

Kelease of f i s s i o n products and their s u b s e q u e n t behavior under a variety of conditioiis which might occur i n loss-of-coolant a c c i d e n t s to nuclear rea c t o r s is t h e s u b j e c t of a continuing s t u d y . T h e loss-of-coolant a c c i d e n t s are simulated i n a v e r s a t i l e experimental a s s e m b l y i n t h e Oak Ridge R e s e a r c h Reactor. 5 7 6 T h i s a s s e m b l y permits 3General Engineering a n d Construction Division. 4AnaZytical Chemistry Division. 5

W. E. Drowning, Jr., et al., Reactor Chem. Div. Ann. Pro&. R e p t . J a n . 31, 1961, ORNL-3127, pp. 149-52; Reactor Chem. D i v . Ann. Pro&. R e p t . J a n . 31, 1962, ORWL-3262, pp. 172-76.

'W. E. Browning, Jr., et al., R e a c t o r Chem. Div. Ann. Pro&. R e p t . Jan. 31, 1965, ORNL-3789, p. 263.

attainment of controlled temperatures (through nuclear h e a t i n g of t h e small fuel specimen) t o and a b o v e t h e melting point of UO, with a n y of s e v e r a l atmospheres. T h e r e l e a s e and t h e s u b s e q u e n t deposition of eight f i s s i o n products (I, Te, C s , Ru, Sr, Ba, Zr, and Ce) a r e determined i n e a c h of t h e experiments. R e s u l t s of t h e s e investigations a r e published in d e t a i l elsewhere. T h e atmospheres that h a v e heen investigated include helium, moist helium, steam-helium-hydrogen mixtures, dry air, moist air, and steam-air mixtures. Of t h e eight e l e m e n t s measured, only iodine and ruthenium showed significant variations i n behavior with c h a n g e s i n atmosphere. Iodine and ruthenium were both more volatile i n a moist air t h a n i n any other atmosphere s t u d i e d and were transported farther under t h e s e conditions. Iodine p a s s e d through a b s o l u t e filters but w a s retained on charcoal; ruthenium w a s more e a s i l y filtered in t h e v o l a t i l e form (from moist air) than in t h e less v o l a t i l e form. Ruthenium w a s not volatile in a n atmosphere containing appreciable q u a n t i t i e s of s t e a m . T h e r e l e a s e of cesium from t h e 1000째C z o n e w a s lowest in experiments i n which s t e a m w a s H component of t h e atmosphere. Cladding mat.eria1 n e a t t h e heat.ec1 fuel is an abundant, strongly reducing reagent and c a n b e expected t o affect fissioii product behavior. Stainless s t e e l a p p e a r s t o retain ruthenium and, under oxidizing conditions, to lower t h e melting point of UO,. Experiments with Zircaloy cladding ate i n progress. Out-of-pile experiments on t h e eEEects of s t a i n l e s s steel arid Zircaloy cladding h a v e shown t h a t the efficiency of trapping iodine by s t e a m condensation is i n c r e a s e d by t h e p r e s e n c e of t h e s e materials. T h r e e experiments h a v e been performed t o s t u d y t h e effect of high burnup of fuel (>20,000 Mwd/ton) on f i s s i o n product behavior. Such f u e l w a s examined metallographically and w a s found t o b e t y p i c a l of high-burnup fuel u s e d i n power reactors of advanced design. Cesium and ruthenium were t h e only e l e m e n t s affected by burnup; t h e fractional r e l e a s e of ruthenium d e c r e a s e d with i n c r e a s i n g burnup, while that o f c e s i u m i n c r e a s e d . E f f e c t s of maximum temperature of t h e fuel a r e also being investigated. In t h e s e experiments, 7 \ ~ . E. Browning, ~ r . , e t al., ~ t z c l . S a f e t y Progrilni S c m i m n . Pro&. K e p t . J u n e 30, 1965, ORNL-3843, pp. 3-39; and N u c l . S a f e t y Program Semintin. Pro&. R e p t . Dec. 31, 1965, in preparation.

138 v e s s e l is being built into t h e in-pile facility. F u t u r e experiments with t h i s extended facility will treat a e r o s o l aging.

performed under oxidizing conditions i n which t h e maximum fuel temperature w a s maintained a t approximately 2O0O0C, t h e U 0 2 appeared to have melted due to t h e formation of a low-melting e u t e c t i c with s t a i n l e s s s t e e l oxide. T h e r e l e a s e s of t h e eight e l e m e n t s in s u c h intermediate-temp- r a t ure experiments were s i m i l a r t o r e l e a s e s i n experiments i n which complete melting occurred a t approximately 290OOC. F u t u r e experiments are planned a t l e s s than 20OO0C and under reducing conditions. T h e primary purpose of t h e s e in-pile experiments is, of c o u r s e , t o permit prediction of behavior of t h e f i s s i o n products i n p o s s i b l e reactor a c c i d e n t s with reasonably assumed conditions. Accordingly, a s s e s s m e n t of t h e form and t h e physical and chemical c h a r a c t e r i s t i c s of t h e released materials is a n e s s e n t i a l paet of t h e program. Preliminary d a t a with a fibrous filter s u g g e s t that p a r t i c l e s of two size r a n g e s a r e important i n transport of f i s s i o n product activity. A n a l y s i s by composite diffusion t u b e s s h o w s three nonelemental iodine s p e c i e s i n t h e g a s . Studies with composite diffusion t u b e s h a v e a l s o shown t h a t desorption of iodine from t h e apparatus after a simulated a c c i d e n t is small; only about 0.1% of t h e original inventory was desorbed, and t h a t primarily i n a nonelemental form. T h e aging of f i s s i o n product aerosols following release from t h e fuel may s u b s t a n t i a l l y a l t e r t h e form and therefore t h e behavior of t h e f i s s i o n products as a function of t i m e . In order to investig a t e t h i s effect, a simulated reactor containment

T a b l e 17.1.

FISSION PRODUCTS FROM HIGH-BUR G. W. Parker R. A . Lorenz U’. M . Martin C. J . Barton G. E. Creek In t h e first experiment of a series designed piimarily t o t e s t t h e effect of burnup on release and behavior of f i s s i o n products, a re-irradiated specimen of s t a i n l e s s - s t e e l - c l a d UO, previously irradiated t o 1000 Mwd/ton w a s melted i n t h e Containment Mockup F a c i l i t y (CMF). T h e specimen w a s melted by induction heating in a steam-air atmosphere; t h e r e l e a s e d f i s s i o n products were aged i n a s t a i n l e s s s t e e l tank filled with pressurized steam-air mixture. Distributions of r e l e a s e d “real” f i s s i o n products a r e compared in T a b l e 17.1 with t h o s e for simulated f i s s i o n products from previous experiments i n t h e CMF. T h e comparison t e n d s t o validate t h e u s e of simulated high-burnup UO, fuel. Deposition of f i s s i o n products before they reached t h e s t a i n l e s s s t e e l aging tank w a s probably affected by t h e different furnace-tube geometry of t h i s experiment ‘G. W. P a r k e r et a l . , R e a c t o r Chem. Div. Ann. Progr. R e p t . J a n . 31, 1965, ORNL-3789, p. 251.

Distribution o f F i s s i o n P r o d u c t s R e l e a s e d from Siniuloted Fuel (5) and from High-Burnup U 0 2 (HB)

F i s s i o n P r o d u c t s Found (70 of total inventory) -.

Location

Cesium

HB Furnace tube and duct

Ruthenium ~

...........

Tellurium

Strontium

Iodine

IIR

. _ . I -

25.0

3.0

18.1

0.3

0.26

0.07

0.047

0.01

15.0

10.1

8.5

15.1

12.4

6.9

0.054

0.35

0.015

0.04

27.0

33.8

12.6

43.6

0.7

0.8

0.001

0.12

0.005

0.0003

57.6

56.0

2.1

0.8

0.5

0.45

0.002

0.0006

0.0001

0.0004

48.2

62.5

31.7

8.4

0.32

0.54

0.07

0.05

Tank w a l l s and deposition s a m p l e s Condensate Filters l o t a l r e l e a s e from fuel

I .

0.35 -100

0.05 -100

139

from that of earlier experiments. However, few differences i n t h e distribution of f i s s i o n products reaching t h e tank were noted. T h e volatile f i s s i o n products, iodine, cesium, and tellurium, were the only a c t i v i t i e s other than r a r e g a s e s reaching the tank in significant amounts; a large fraction of t h e s e a c t i v i t i e s remained on t h e tank wall or w a s collected i n t h e c o n d e n s a t e after 3 h r aging in t h e tank with gradually d e c r e a s i n g pressure and temperature. Two different t y p e s of samplers were used to study concentrations of gas-borne activity in t h e pressurized tank during t h e aging period. The two samplers g a v e comparable r e s u l t s , and t h e t o t a l airborne gamma activity (mainly from iodine, cesium, and telluriumj indicated by t h e s e samplers agreed w e l l with gross-activity v a l u e s from a collimated ion chamber adjacent t o t h e s i d e of the tank. F i g u r e 17.3 s h o w s t h e variation with time in concentration of t h e various gas-borne activities.

0liNI:-

iJWG 6 6 - 294

O oco31

Measurements were made of deposition r a t e s oE s e v e n f i s s i o n products on four different s u r f a c e s ( s t a i n l e s s s t e e l , carbon s t e e l , aluminum, and vinyl paint) during the experiment. Iodine showed a significant variation i n r a t e of deposition on t h e different s u r f a c e s , but t h e others, with the p o s s i b l e exception of a faster r a t e for molybdenum on carbon steel and vinyl paint, showed no significant variations.

THE CONTAINMENT RESEARCH INSTALLATION G. W. Parker

W. J. Martin

A schematic diagram of the Containment R e s e a r c h Installation (CRI) and a h i e € description of i t s principal features were given i n t h e previous progress report.’ All the major components of t h e CRI h a v e b e e n received, and construction is dpproaching completion. T h e primary simulation v e s s e l , equipped with external r e s i s t a n c e h e a t e r s (21-kw total capacity), has been rriounted in t h e hot cell, and t h e major piping between the furnace and t h e containment v e s s e l h a s been installed {see F i g . 17.4). Installation of t h e containment v e s s e l h a s been delayed by a warpage problem (now solved) t h a t temporatily prevented insertion of one of t h e removable l i n e r s . T h e liners will b e painted with either an epoxy coating that i s of i n t e r e s t to t h e LOFT facility a t t h e NRTS or with a Bakelite coating of t h e type being considered for u s e in t h e Containment Systems Experiment a t I-fanford. Stainless-steel-clad UOz fuel specimens have been s u c c e s s f u l l y melted in t h e Containment Mockup F a c i l i t y using t h e pressurized induction furnace arrangement that will be used in t h e CRI. Modifications of t h e furnace fittings to allow remote loading and unloading of highly irradiated fuel a r e presently being worked out. Wiring and instrumentation of t h e CRI, involving instrument panels on two floor l e v e l s , are about 75% complete. Preliminary t e s t i n g of the CRI is expected to begin early in 1966.

TIME A F T F R M F l T l N G ( m i n )

Fig.

17.3.

Composition of the C o n t a i n m e n t Mockup

F a c i l i t y Tank A h n o s p h e r e a s Determined by G a s S o m p l e s .

’G. W. Parker et a].,Reactor Cheni. Div. Ann. Progr. R e p t . Jan. 31, 1965, ORNL-3789, pp. 259-61.

140

F i g . 17.4.

Primary Simulation V e s s e l of Containment R e s e a r c h I n s t a l l a t i o n Mounted i n Hot C e l l .

141 ANALYSIS OF PLANS FOR SCALE-UP IN NUCLEAR SAFETY PROGRAM C. E. Miller, Jr.

W. E. Browning,

Jt.

T h e Nuclear Safety Program of t h e United S t a t e s i n c l u d e s firm p l a n s for large-scale experiments of which t h e LOFT" is t h e most ambitious - i n which a reactor c o r e would b e destroyed and f i s s i o n product r e l e a s e and behavior would b e measured. Such experiments will b e exceedingly complex and c o s t l y and will, obviously, b e few i n number. It will b e e s s e n t i a l , therefore, to gain from them t h e maximum information p o s s i b l e and to b e a b l e with t h e h e l p of well -designed s m a l l e r - s c a l e sti~dies - to apply t h i s information t o p o s s i b l e a c c i d e n t s under conditions other than t h o s e t e s t e d . A t t h e r e q u e s t of AEC Washington w e h a v e attempted an evaluation of t h e r e s e a r c h and development program a t ORNL and e l s e w h e r e and of t h e various scaled-up experiments for which planning is firm. A s a result of t h i s evaluation, two reports' ' , 1 2 a r e in t h e final s t a g e s of preparation. We conclude that experiments to s t u d y f i s s i o n product behavior in containment arid in gas-cleaning s y s t e m s a r e w e l l s c a l e d over the range between smi3 I1 laboratory experiments and LOFT, but that esperiments t o s t u d y the r e l e a s e and t h e transport of f i s s i o n products from f u e l s a r e not well s c a l e d . We :suggest that intermediate-scale experiments of the order of 1 and 10% of t h e s i z e of L O F T a r e

needed. These intermediate experiments should measure f i s s i o n product r e l e a s e from t h e fuel and s t u d y f i s s i o n product behavior i n t h e primary s y s t e m following release. We would propose for consideration four experiments t o bridge t h e gap between t h o s e described i n t h e previous s e c t i o n s of t h i s chapter arid t h e L O F T assembly. T h e s e arc:

A. T e s t s a t 1%of LOFT power level:

1. Investigation of f i s s i o n product r e l e a s e

and transport i n t h e Containment R e s e a r c h Installation l 3 primary simulator using a dummy core with irradiated fuel elements. T h e s e would b e melted in p l a c e by ceritraltungsten-resistor methods.

2. Investigation of f i s s i o n product r e l e a s e and

transport in an experimental r e s e a r c h reactor using a multiple-pin s u b a s s e m b l y with irradiated fuel pins. T h e s e would b e melted in p l a c e u s i n g nuclear heating induced by the parent reactor.

B. Tests at 10% of LOFT power level: 1. Investigation of fission product r e l e a s e and transport i n t h e Containment Systems Experiment' primary simulator u s i n g a dummy f u e l core with irmdiated fuel elements. These wcxild be melted iri p l a c e by centrattungsten-resistor methods.

2 . Investigal ion

of f i s s i o n product r e l e a s e and transport using a fuel s u b a s s e m b l y of irradiated fi1c.l e l e m e n t s i n the LOFT facilThcsc would b e melted by nuclear ity. self-heating induced by neutrons from t h e LOFT parent core.

T. R. Wilson et al., AZI Engineering T e s t Program t o I r l v c s t i g a t e a L u s s - o f - C o o l a n t Accident, IDO-17049 (Oi;tiJbt?r 1364).

" C . E. Miller, Jr., and W. E. Browning, Jr., An A n a l y s i s o f the Adequacy of Pfanned E x p e r i m e n t s to Teat /lie Effects of S c a l e - U p in R e a c t o r Ac;c:idents, P z r t 1: Scale-Up in Ihs [ J . S . N u c l e a r Safety Program, ORNL-3901, to be published.

and W. E. Browning, Jr., An of the A d e q i i s c y of Planned Experiments to T e s t the E f f e c t s o f Scale-Up ill R e a c t o r A c c i d e n t s , Part 11: Xecurwnended Additional Nucfzirr S a f e t y S c a l e U p E q w r j m e r i t s , in preparation. 12

E. Miller, Jr.,

G. W. Semiam. pp. 92-97. I 4 G . J. periment,

Parker and W. J. Martin, N t i c l . S a f e t y Program Progt. Kept. J u n e 30, 1965, ORiiL-3843, Rogers, P m g r a n f o r C:ox~taizirrim~/ S y s t e m s ExHW-83607 (September 1964).

RETENTICIN OF RADIOIODINE AND METHYL IODlDE B Y ACTIVATED CARBONS W. E. Browning, Jr. R. ID. Ackley J , E. Attrill' G. W. Parker G. E. Creek

F. V. Hensley R. E. Adams J . D. Dake' D. C. E v a n s ' A. E'erreli3

I t s relatively high volatility and i t s great biological hazard combine to make radioiodine a most important f i s s i o n product in nuclear s a f e t y considerations. Elemental I, is relatively e a s y to trap and hold; the great convenience and s a f e t y of ambient-temperature activated-charcoal b e d s h a v e led t o their general adoption for removing iodine from a i r or g a s streams. An i n c r e a s i n g awareness, however, that a significant fraction of t h e iodine liberated i n a nuclear a c c i d e n t might b e p r e s e n t a s organic i o d i d e s (notably methyl iodide) which are poorly retained by common activated c h a r c o a l s h a s c a u s e d concern in t h e field for s e v e r a l years. Careful experiments h a v e s e r v e d only to confirm t h a t methyl iodide is poorly retained by standard c h a r c o a l s under high humidity. Removal of methyl iodide by Pittsburgh type PCB a c t i v a t e d charcoal, 12 x 30 mesh (unimpregnated for CH,I reaction), w a s investigated a t 24OC; g a s chromatography was used t o determine t h e CH,I that p a s s e d t h e bed. T h e i n l e t methyl iodide concentration w a s varied (inversely with a i r velocity) from 8 t o 80 mg of CH,I per c u b i c meter of air to provide a c o n s t a n t introduction rate. T i m e periods over which useful removal efficiencies were ob.___._..... __-

'Analytical Chemistry Division.

4W. E. Browning, Jr., e t al., NucI. Safety Program Seniiann. Progr. R e p t . June 3 0 , 1965, ORNL-3843. pp. 139-43.

5R. E. Adams e t a l . , Nucl. S a f e t y Program Semiann. Progr. Rept. D e c . 31, 1965, to be i s s u e d .

%V. E. Browning, Jr., e t at.. Nucl. S a f e i y Program Semiann. Progr. Rept. June 3 0 , 1965, ORNL-3843. pp. 143-48.

' G . W. P a r k e r and Albert0 F e r r e l i , Nucl. S a f e t y Program Semiann. Pro&. Rept. June 3 0 , 1965, ORNL3843, pp. 19.1-210.

'G. W. P a r k e r e t al., N u c l . S a f e t y Program Semiann. Progr. R e p t . D e c . 31. 1965, to b e i s s u e d .

2Co-op student, University of T e n n e s s e e . 3Noncitizen g u e s t on a s s i g n m e n t froni National Committee for Nuclear Energy.

s e r v e d varied from less than 0.2 h r for a relative humidity near loo%, an air velocity of 100 fpm, and a bed depth of 1 in. to about 100 hr for a relative humidity of less than 3%, a n air velocity of 10 fpm, and a bed depth of 3 in.485 Removal of methyl iodide and of elemental iodine by a variety of c h a r c o a l s w a s i n v e s t i g a t e d with t h e air-charcoal s y s t e m a t around 100째C and with t h e air stream about 80% s a t u r a t e d with steam. In t h e s e t e s t s t h e iodine which p a s s e d t h e bed w a s determined by radioactivity measurements, Elemental iodine was trapped with fairly high efficiency, but methyl iodide w a s not. Both radiation detection and gas chromatography were u s e d to t e s t a method based on dehumidification for improving t h e efficiency of methyl iodide removal from steam-air mixtures. This method w a s observed to b e s u c c e s s f u l but would require a rather complex moisture-iemoval system.' T h e recent o b ~ e r v a t i o n ~ that - - ~ bcds of a cornmercial chaicoal (Mine Safety Appliances Company No. 85851) which is impregnated with several percent by weight of iodine will effectively remove methyl iodide is, therefore, a most important advance. Subsequent t e s t s h a v e shown that other c h a r c o a l s when impregnated with I, or KI a r e equally effective. We confirmed t h e observations

t h e Italian

142

'11. E. Adams e t al., Nucl. S a f e t y Program Semianrr. Progr. i 7 e p t . Dec. 31, 1965, to be issued.

143 GRNL-DWG h5-1!435R 2

"00

g t7

0.1

a t-. 'id z Is LLi

0.01

0.001

0.0001

0.COOOl

0.1

0.2

0.3

RESIDENCE TIME

F i g . 18.1. at

0.4

0.5

0.6

(SPC)

E f f e c t of R e s i d e n c e T i m e on R e t e n t i o n of M e t h y l Iodide by T r e a t e d and Untreated Coconut Charcool

25째C and 70% R e l a t i v e H u m i d i t y w i t h a 20-hr Loading.

reported by British i n v e s t i g a t o r s ' that a c t i v a t e d carbon impregnated with triethylenedlamine IS a l s o a good h a p p i n g m a t e r i a l for methyl iodide. 'Tests conducted with impregnated charcoal under two different s e t s of c o n d i t i o n s postulated for t h e IIFIR and I,OF'T reactor i n s t a l l a t i o n s gave equally good retention values; c h a n g i n g the loading l e v e l (weight of methyl iodide per gram of c h a r c o a l ) over a <.vide range had n o s i g n i f i c a n t effect on retention A comparison of t h e methyl iodide efficiency. retention (actually t h e l 3 'I that w a s originally combined as CH,' 3 1 1 ) of untreated and impregnated activated-carbon m a t e r i a l s is shown i n Fig. 18.1. T h e u s e f u l n e s s of t h e commercially a v a i l a b l e impregnated a c t i v a t e d c h a r c o a l for radioactive 'OR. D. Collms, letter to the edltor, Niic Ieonics 23(9), 7 (1965). See a l s o D. A. Collins, R. Taylor, and L. R. Taylor, CYNF-650407, p. 853 (September 1965).

methyl iodide trapping w a s confirmed a t 24째C and for relative humidities up to 71%, and the mechanism w a s shown to be due to the exchange reaction :

GH31311 i 127[(on c h a r c o a l ) + CI-I,'271 t-

"(on ctiarcoal)

T h e charcoal, a s received, c o n t a i n s a form of iodine, and nonradioactive CH,I is observed emergi n g from the charcoal while it IS trapping radioa c t i v e CH31. T h i s c h a r c o a l w a s a l s o found to trap elemental iodine satisfactorily under the above conditions, a Further tests under mote s e v e r e conditions a r e planned, T h e investigation of t h e possibility of impregnating charcoal with c h e m i c a l s that will r e a c t with methyl iodide to form products retained within

144 t h e charcoal bed w a s d o n e mostly by g a s chromatography. T e s t s were made a t 24 to 25째C with inorganic impregnants for relative humidities around 70% and with organic impregnants for relative humidities ranging up to 100%. A s previously piperidine and piperazine were found observed, to enhance consideiably t h e retention of methyl iodide by charcoal s o impregnated. R e s u l t s obtained with s e v e r a l materials s u g g e s t e d by thermochemical c a l c u l a t i o n s a s impregnants, s u c h as bromine, sodium bromate, and sodium bromide, were rather encouraging. Further work i s under way to e v a l u a t e t h e s e observations.'

IDENTITY OF VAPOR FORMS OF RADlQlOBlNE

W. E. Hrowning, Jr. R. E. Adams K. D. Ackley

iodide method. T h e vapor s a m p l e s showed ten p e a k s by electron capture and eight p e a k s by radioactivity. Three of t h e l a t t e r p e a k s were identified a s methyl, ethyl, and propyl i o d i d e s with methyl. iodide accounting for 62% of t h e A s time permits, p l a n s a r e total radioactivity. to accumulate a compilation of relative retention times for a wide variety of iodine compounds. T h i s chiomatograph w a s u s e d to determine t h e purity of radioactive methyl iodide s o u r c e s u s e d i n related s t u d i e s . T h e s e s o u r c e s , a s far a s their radioactivity w a s concerned, were e s s e n t i a l l y pure methyl iodide. Samples of iodine-containing g a s e s from other nuclear s a f e t y experiments, s u c h a s t h e in-pile meltdown experiments and t h e NSPP, are to b e studied. Additional d e t a i l s of t h i s work appear elsewhere. *

J. E. Attrill' J. D. D a k e 2 D. I. Ford'

G a s chromatography h a s been applicd to and found t o b e very useful in t h e a n a l y s i s of radioiodine-vapor samples. By u s i n g electron-capture d e t e c t o r s , which a r e s e n s i t i v e to organic halogencontaining molecules, methyl iodide concentrations of t h e order of 1 ppb c a n b e measured. In t h e analy s i s of vapor from radioactive-iodine s o u r c e s , a number of unidentified p e a k s were often observed. Since some of t h e s e p e a k s may h a v e been due to s m a l l amounts of extraneous impurities, s u c h a s chloroform and fluorocarbons, and s i n c e there is cons i d e r a b l e variation i n s e n s i t i v i t y between different compounds of iodine, there i s need, on o c c a s i o n , for detection that is more specific. Consequently, a radiation-detector arrangement w a s constructed and i n s t a l l e d s o that i t WRS in s e r i e s with t h e electron-capture detector with r e s p e c t to g a s flow. In t h i s manner, attention w a s focused only on t h o s e compounds containing 1 3 ' 1 , and any interference by extraneous nonradioactive organic s u b s t a n c e s p r e s e n t in t h e sample w a s eliininatcd. T h e g a s chromatograph, equipped with dual detection b a s e d on radiation and electron capture, was t e s t e d with s a m p l e s of t h e vapor over an iodine s o u r c e that was prepared by t h e palladium "R. E. Adams e t al., Nucl. S a f e t y Program Semiann. Progr. Kept. Dec. 3 1 , 1965. to be i s s u e d . '*Temporary summer employee, R i c e University.

DEVELOPMENT OF METHODS FOR BISTINGUISH$NG AND MEASURING RMS 0% FISSION PRODUCTS J. Truitt W. E. [howning, Jr. W. H. Hinds K. E. A d a m A. F. Roemer, Jr.' R. D. Acltley R, A. Cameron' R. L. Bennett J. I). D a k e 2 M. D. Silverman D. I. F o r d '

Characterization d e v i c e s s u c h a s composite diffusion tubes, fibrous-filter analyzers, g a s chromatographs, and May p a c k s a r e needed to measure various forms of gas-borne f i s s i o n products i n order to study and understand their behavior under reactor a c c i d e n t conditions. High humidity reduces t h e e f f e c t i v e n e s s of activated charcoal. for removing various s p e c i e s of radioiodine and consequently interferes with t h e performances of May p a c k s and composite diffusion t u b e s which contain charcoal components. Several techniques h a v e been investigated i n an effort t o reduce t h e moisture e f f e c t in diffusion tubes. Heating t h e tube t o reduce t h e r e l a t i v e humidity and u s i n g ___.

I3W.

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

E. Browning, Jr., R. E. Adams, a n d J. E. Attrill,

Nucl. S a f e t y Program Semiann. Progr. Rept. June 3 0 , 1 9 6 5 , OXNL-3843, pp. 171---73. 14R. E. Adams e t a l . , Nucl. S a f e t y Program Semiann. Progr. R e p t . D e c . 3 1 , 1 9 6 5 , to be i s s u e d . 'Temporary summer employee, Ilanover College.

145 refrigerated c o n d e n s e r s to remove moisture h a v e been only partially successfu1.I Of s e v e r a l d e s i c c a n t s which h a v e been t e s t e d for drying t h e air, Drierite (anhydrous calcium s u l f a t e ) a p p e a r s to be promising b e c a u s e of its minimal adsorption of methyl iodide. An improved deposition pattern f o p methyl iodide a l s o h a s b e e n obtained under moist conditions by substitution of a n iodineimpregnated c h a t c o a l for t h e normal coconutcharcoal lining of t h e diffusion tube. Investigation of i o d i n e behavior i n May p a c k s A test under various conditions w a s continued. of a v o l a t i l e iodine s a m p l e i n a May p a c k of t h e t y p e u s e d in t h e Nuclear Safety P i l o t P l a n t w a s made with a n air-steam atmosphere a t 100째C, 2 atm a b s o l u t e pressure, a n d 90% relative humidity. In general, t h e behavior w a s similar to that of composite diffusion t u b e s at t h e s a m e conditions, but before more p r e c i s e comparisons c a n b e made, further experimentation will b e required. A facility for s t u d y i n g t h e behavior of normal and modified May p a c k s i n moist atmospheres a t e l e v a t e d temperatures is being constructed. C a s chromatography with d u a l d e t e c t i o n (electron c a p t u r e and radiation) has been s u c c e s s f u l l y applied in the a n a l y s i s of various radioactive-iodine and methyl i o d i d e s o u r c e s i n t h e laboratory. l 9 A comparison of t h e deposition of various iodinevapor s p e c i e s i n a c o m p o s i t e diffusion tube of a d e s i g n for u s e in in-pile experiments with t h e deposition i n t h e more u s u a l type of composite diffusion t u b e w a s made.20 Similarities and diff e r e n c e s were observed; however, with t h e a i d of this information a u s e f u l interpretation of t h e inp i l e d a t a c a n b e made. In conjunction with t h i s study, t h e reactivity of i o d i n e vapor with Dacron fiber w a s observed. Deposition on t h e fiber, which is u s e d i n a fibrous-filter characterization d e v i c e for aerosols, w a s g r e a t e r than 90% for elemental iodine a n d negligible for t h e nonelemental s p e c i e s .

16W. E. Browning, Jr., and R. E. Adams, N u c l . Sa&ety Progra117 Semiann. Pro&. H e p t . June 30, 1965. ORNL3843, pp. 223-24.

i7R. E. Adams e t al.. N u c l . S a f e t y Program Seniiann. Pro&. R e p t . D r c . 3 1 , 1.965, to be i s s u e d .

"R. TI. Ackley e t al.. N u c l . S a f e t y Program Semiann. Progr. Rept. Dec. 31, 1965, t u be issued. "R. E. Adams e t al., N u c l . Snfety Program Seniitmn. Pro@. Rept. D e c . 31. 1.965, to be i s s u e d . 'OW. E. Browning. Jr., R. D. Ackley, arid A. F. Roemer, Jr.. N u c I . S a f e t y Program Semiann. Progr. lzept. J u n e 30, 1965, OKNL-3843, PI'. 224-34.

Application of t h e fibrous-filter analyzer, developed previously for s t u d y of filtration p r o c e s s e s , 2 1 a s an a n a l y t i c a l s a m p l e r for particulate material i n moist atmospheres is being evaluated. Two problems a r e currently under study: (1) t h e physical r e s p o n s e of t h e a n a l y z e r to an a e r o s o l under conditions of high humidity and (2) t h e production of a radioactive, monodisperse a e r o s o l of known size with which to c a l i b r a t e t h e r e s p o n s e of t h e analyzer under various combinations of operating parameters. A t low sampling v e l o c i t i e s of 3 to 11 fpm, t h e fibrous-filter analyzer s h o w s promise as a n a n a l y t i c a l s a m p l e r i n a wet atmosphere. T h e fiber configuration and filtration p r o c e s s e s a r e A n o t significantly affected by t h e moisture. s a t i s f a c t o r y monodisperse aerosol of known size h a s been prepared from a Dow polystyrene l a t e x solution; however, efforts to t a g i t radiochemically h a v e not y e t been s u c c e s s f u l .

REMOVAL OF PARTICULATE MATERIALS FROM GASES UNDER ACCIDENT CONDITIONS

J. S. Gill

W. E. Browning, Jr. R. E. Adams

G. L. Kochanny23

Laboratory i n v e s t i g a t i o n s of t h e filtration of particulate a e r o s o l s which s i m u l a t e t h o s e expected to b e generated during reactor a c c i d e n t s a r e continuing. The technique for t h e generation and characterization of t h e t e s t a e r o s o l h a s been reported previously. 2 4 R e s u l t s of t e s t s i n a dry-air (53% relative humidity) s y s t e m i n d i c a t e that t h e arc-generated aerosol c o n s i s t s of two particulate size groups, e a c h of which h a s different t e n d e n c i e s to penet r a t e a commercial ( F l a n d e r s 700) high-efficiency filter medium.25 T h e less penetrating group is trapped with a n efficiency of >99.997% on t h e 2ibL D. Silverman and Vk'.

143, 572 (1964). '*M. D. Silverman

Seniiann.

P r o g r . Kept.

23Present a d d r e s s : Nich.

E. Browning, Jr., S c i e n c e

e t aj., N ~ < - I ,S a f e t y Program D c c . 31, 1965, to be i s s u e d .

Dow Cnemical Company, Midland,

24W. E. Browning .Jr.$ R. E. Addrns, and G. L. Rochanny. Jr., Reactor Clicm. D i v . Ann. Progr. R e p t . Jan. 31, 1965, ORNL-3789, p. 288. 25W. E. Browning. Jr., < A t af., N u c l . S a f e f y Program Seniiann. Pro&. Rept. J u n e 30, 1965, ORNL-3843. PI,. 148-56.

F l a n d e r s filter, while the more penetrating group is trapped a t a slightly lower efficiency of >99.9%. Current experiments u s i n g a e r o s o l s generated from UO, clad with e i t h e r neutron-irradiated s t a i n less s t e e l or Zircaloy h a v e produced r e s u l t s similar to t h e earlier studies. Similar v a l u e s were obtained when a i r velocity ranged from 3.2 to 13 fprn and when dry helium or argon w a s s u b s t i t u t e d for t h e a i r atmosphere. However, i n a recent s e r i e s of experiments26 i n which t h e relative humidity of t h e a i r s w e e p ranged from approximately 46 t o loo%, t h e filter efficiency was noted to drop to a s low a s 93%. Fibrous-filter deposition profiles and photomicrographs of an aerosol produced in 3 46% relative humidity experiment i n d i c a t e that the filtration c h a r a c t e r i s t i c s of t h e p a r t i c l e s of t h e a e r o s o l a r e changed. F u t u r e experiments will attempt to determine t h e role which water vapor p l a y s in t h i s observed reduction in filter efficiency.

IGNITION OF CHARCOAL ADSQRSERS CT DECAY HEAT W. E. Browning, Jr. C. E. Miller, Jr.

B. F. Roberts R. P. Shields

In t h e e v e n t of a nuclear a c c i d e n t in which fiss i o n products a r e r e l e a s e d into t h e containment s y s t e m , the charcoal a d s o r b e r s u s e d for removal of

iodine a r e s u b j e c t to h e a t i n g by decay of iodine adsorbed o n t h e charcoal. T h e h e a t generated in p i e c e s of charcoal containing t h e g r e a t e s t amount of adsorbed iodine may r a i s e their temperature to t h e ignition point. In order to s i m u l a t e s u c h an event, a n in-pile experiment that u t i l i z e s t h e fuelmelting facility in t h e Oak R i d g e R e s e a r c h Reactor h a s been designed. In t h i s experiment the d e c a y of short-lived i o d i n e adsorbed on the charcoal g e n e r a t e s heat. T h e objective of t h i s experiment is to measure and compare the ignition temperature of t h e charcoal with and without fiss i o n product adsorption. A comparison of thc calculated decay-heat load on the front s u r f a c e of t h e charcoal in t h e experimental adsorber with those of a d s o r b e r s a t various reactors i n d i c a t e s that t h e ignition e f f e c t s in t h e reactor adsorbers will b e smaller than t h o s e i n t h e experiment. After t h e mechanical d e s i g n and p l a n s for operati n g t h e experiments w e r e s h o w n to b e adequate by t e s t s in a laboratory mockup,27 a n initial s e r i e s of in-pile experiments w a s performed. In t h e s e experiments t h e ignition temperature w a s studied a s a function of both t h e a i r flow and t h e decayh e a t loading. Preliminary r e s u l t s of t h e s e s t u d i e s i n d i c a t e that t h e c h a r c o a l ignition temperature is n o t greatly affected by t h e d e c a y h e a t of adsorbed fission products. "W.

E. Browning, Jr., e t al., Nucl. S a f e t y Program Progr. K e p t . J u n e 30, 1965, OKNL-3813,

Semiann.

26R. E, Adams. J. S. Gill, and W. E. Browning, Jr., Alricl. S a f e t y Program Semiann. Progr. R e p t . D e c . 3 1 , 1965, to be i s s u e d ,

pp. 156-67.

28W. E. Browning, Jr., et al., Nucl. S a f e t y Program Serniann. Progr. Kept. D e c . 3 1 , 1965, to be issued.

Publications JOURNAL ARTICLES TITLE

AOJTHO R(5) B a c a r e l l a , A. L., a n d A. L. Sutton

E l e c t r o c h e m i c a l Measurements on Zirconium a n d Zircaloy-2 a t E l e v a t e d Temperatures. 2.

Baes. C . F., Jr.

PUBLICATION J . Electrochem. Soc. 1 1 X 6 ) . 546 (1965)

200-3 OO째C

T h e Reduction of Potentiometric Hydrolysis

Inore. Chem. 4, 588 (1965)

Data

U a ~ s ,C. F., Jr..

Ir~org.Chem. 4, 518 (1965)

T h e H y d r o l y s i s of Thorium(1V) a t O-.95째

AT. J. Meyer, a n d C. E. Roberts

Ramberger, C. E. L.,

Purification of Beryllium by Acetylacetone-

13, F. McDuffie, a n d

E D T A Solvent Extraction

C. F. B a e s , JI.

Chemistry

- Procedure

and

N L Z CSci. ~ . En& 22(1). 14 (1965)

F i s s i o n P r o d u c t R e l e a s e and Transport

N u c l . N e w s 8(7), 2 5 (1965)

Browning, W. E., Jr.

Removal of Radioiodine from G a s e s

N u c l . S a f e t y 6 ( 3 ) . ?72 (1965)

Brunton, G. D.

C r y s t a l Structure of Zirconium Tetrafluoride

J . Itlorg. Nucl. Chem. 27, 1173

Rarton. C. J., a n d

W, R.

Cottrell

(1965) Burns, J. H.

C r y s t a l S t r u c t u r e of Hexagonal Sodium

Irrorg. Chem. 4, 881 (1965)

Neodymium F l u o r i d e and R e l a t e d Compounds R u m s , J. H., a n d

W, R. Busing,

Caritor, S.

C r y s t a l Structures of Rubidium Lithium F l u o r i d e and C e s i u m Lithium F l u o r i d e T h e Vapor P r e s s u r e s of Beryllium Fluoride a n d Nickel Fluoride

Inorg. Cheni. 4, 2510 (1965)

J. Chetii. Eng. Data 10(3), 237 (1965)

Carroll, R. M.

F i s s i o n Product R e l e a s e from F u e l s

Nucf, S a f e t y 7(1). 34 (1965)

Carroll,

R e l e a s e of F i s s i o n G a s During F i s s i o n i n g of

J . Am. Cerarn. Soc. 48(2), 55

K. M.,

R. B. Perez, a n d 0. Sisman

(1965)

uo2

Carroll. R. M.,

T e c h n i q u e s for In-Pile Measurements of

Carroll, R. M.,

In-Pile F i s s i o n - G a s R e l e a s e from Single

and P. E. R e a g a n and 0. Sisman

F i s s i o n Gas R e l e a s e

N u c l . Sci. En& 21(2),

(196 5 )

N u c l . Sci. E n g . 21 U ) , 147

(1965)

C r y s t a l UO,

147

141

TITLE

AUTHOR(s) Carroll, R. M., a n d 0. Sisman d e Bruin, H. J., and G. M. Watson

Fuller, E. L., 15. F. Holmes. and

PUBLICATION

In-Pile F i s s i o n - C a s R e l e a s e from F i n e

J . N r i c l . Mater. 17(4), 305

Grain UO,

(1965)

Self-Diffusion of Reryllium i n Uriirradiated

J . Nucl. Mafer. 14, 239 (1964)

Beryllium Oxide Vacutzm Microbalance Tech. 4, 1 0 9

Gravimetric Adsorption Studies of 'I'horiuin Dioxide S u r f a c e s with a Vacuum Microbalance

(1965)

C. H. Secoy Holmes, H. F., C. S. Shoup, Jr.,

J. P h y s . Chern. 69, 3118 (1965)

E l e c t r o k i n e t i c Phenomena a t t h e Thorium Oxide---Aqueous Solution Interface

a n d C. H. S e c o y Johnson, C. I,.,

M. J. Kelly, and

R e a c t i o n s of Aqueous Thorium Nitrate

J . Inore. N u c l . Chern. 27. 1787

Solutions with Hydrogen Peroxide

(1965)

D. R. Cuneo Keilholtz, G. W.,

Behavior of B e 0 Under Neutron Irradiation

J . Nucl. Mater. 14, 8 7 (1964)

J. E. Lee, Jr., R. E. Moore, and

R. I,. Hamner Malinauskas, A. P., and F. L. C a r l s e n , Jr. Marshall, W. L., and Ruth Slusher

G a s Transport C h a r a c t e r i s t i c s of Uranium-

F u e l e d Graphites

Am. Cersm. S O C . €31211. 44, 251 (1965)

Aqueous Systems a t High Temperature.

XV.

Solubility and Hydrolytic I n s t a b i l i t y of

J . Cheni. E n g . D a t a 10, 353 (1965)

Magnesium Sulfate i n Sulfuric Acid-Water and Deuterosulfuric Acid-Deuieriurn Oxide Solutions, 200" to 350°C Miller, C. E., Jr., and W. F'. Hillsmeier Osborne, M. F..

E. L. Long. Jr., and J. G. Morgan Overholser, L. G., and

P. Blakely

Parkinson. W, W., Jr.,

Second AEC Conference on R a d i o a c t i v e F a l l o u t P e r f o r m a n c e of P r o t o t y p e EGCK F u e l Under

Oxidation of Graphite by L o w C o n c e n t r a t i o n s

Carbon 2, 385 (1965)

of Water Vapor and Carbon Dioxide in Helium A Comparison of F a s t Neutron and Gamma Irradiation o f Polystyrene.

and J. E. White

Linking R a t e s

W. I,. Marshall

N u c l . S c i . E n g . 22(4), 420 (1965)

Extreme Conditions

C. D. Bopp. D. Binder,

Quist, A. S , , and

NucJ. S a f e t y 6(3). 283 (1965)

from N u c l e a r Weapons T e s t s

P a r t I.

J. P h y s . Chem. 69, 828 (1965)

Cross-

Assignment of Limiting E q u i v a l e n t Conduct-

J . P h y s . Chem. 69, 2984 (1965)

a n c e s for Single I o n s to 400° J . P h y s . Chem. 69, 3165 (1965)

Estimation of t h e D i e l e c t r i c C o n s t a n t of Water to 800° Quist, A. S., W. L. Marshall, and 1-1. R. Jolley

E l e c t r i c a l C o n d u c t a n c e s of Aqueous Solutions a t High Temperature and P r e s s u r e .

[I.

The

C o n d u c t a n c e s and Ionization C o n s t a n t s of Sulfuric Acid-Water

Solutions from 0-800"C

and a t P r e s s u r e s Up to 4000 B a r s

J . P h y s . Chem. 69, 2726 (1965)

149

TITLE

AUTHOR(s) Reagan, P. E.,

J. G. Morgan, and

0. Sisman Kobbins, G. D.. R E. Thoma, and

PUBLICATION

F i s s i o n - G a s R e l e a s e from Pyrolytic-Carbon-

N I J C ~SCI. . Eng.

Coated F u e l P a r t i c l e s During Irradiation a t

23, 215 (1565)

2000 to 2SOOOF

P h a s e Equilibria in t h e System C s F - Z r F ,

J . Inorg. N u c l . Chem. 27, 559 (1965)

5%- Insley

Singh, A. J.,

J . A p p l . Phhys. 36(4), 13h7

Vacuum D i s t i l l a t i o n of LiF

K. G. Ross, and R. E. Thorna ‘l’homa, R. E.,

H. Insley, H, A. Friedman, and

(1965)

”lie

Condensed System LiF-NaF-ZrF,

- Phase

J . Chern. En& D a t a 10(.3), 219 (1965)

Equilibria and Crystallograpliic Data

G. M. Hebert

REPORTS ISSUED Adams, H. E., and

W. E. Browning, Jr, Adams, R. E., W. E. Browning, Jr.,

Iodine V a p v r Adsorption S t u d i e s for t h e 1Y.S

0 R N L ~ 3 7 2 6(February 15165)

@gSavannah”P r o j e c t The R e l e a s e a n d Adsorption of Methyl Iodide in

OKNL-TM-1291 (October 1965)

the H F I K Maxiinurn Credible A c c i d e n t

Wm. B. Cottrell, and G. W. P a r k e r naumanii, C. I).

Irradiation E f f e c t s in the EGCK F u e l

ORNL-3504 ( J u r ~ t ? 1965)

&owning. W. E., Jr..

A S t a n d a r d S u r f a c e for F i s s i o n Produi:t

OHNIL-TM-1304 (October 1965)

arid M. E. Davis Brunton, G. D.,

13. Insley, T. N, McVay,

and R. E. Thoma

Clark, W. E., L. Rice, and D. N. H e s s

Depositioti E x p e r i m e n t s

ORNL-3761 (February 1965)

Crystallographic D a t a for Some Metal F l u o r i d e s , Chlorides, a n d Oxides

ORNL-3787 (April 1965)

E v a l u a t i o n of Efastelloy F arid Other

Corms ion-Res i s tan t Struc fura 1 Ma t o r i s l s for a Contiiiuous Centrifuge in a Muftipurpose Fuel-Recovery P l a n t

English, J. L,, and J. C. G r i e s s

Ilaynes, V. O.,

I?. H. Sweetun, arid D. E. T i d w e l l

Laboratory Corrosion Studies f o r the Nigh

OKNL-TM-1029 ( J u n e 1965)

F l u x Iso/.olJe Rfiactor

1965)

Irradiation Detci Lor the Army PM Fuel

ORNIPT~LI-983 (1:ebruat-y

Irradiation D a t a for the Ammy P M Fuel

OKNL-’TM-1031 (April 1965)

E x p r i m e n t in the QRR Pressurized-Water L o o p for ORR C y c l e 52 Experinien t in the OKR Pressurized-Water L o o p for ORR C y c l e s 53 a n d 54

Jenks, G. H.

E f f e c t s of R e a c t o r Operatiori

011 H F I R

Coolant

ORNL-3 84 8 (October 1Y 65)

150

TITLE

AUTHOR( s )

PUBLICATION

An E v a l u a t i o n of t h e Chemical Problems

Jenks, G. H.,

E. G. Bohlmann, and J. C. G r i e s s

OlWL-'1'M-978 (March 1965)

A s s o c i a t e d with t h e A q u e o m S y s t e m s in t h e T u n g s t e n Water Moderated Reactor, Addenda 1 a n d 2

Keilholtz, G. W.,

B e h a v i o r o f Iodine in R e a c t o r Containment

ORNL-NSIC-4 (February 1965)

T h e E f f e c t of Accommodation on Thermal

ORNL-3796 (April 1965)

and C. J. Barton Mason, E. A,, and A. P. Malinauskas

Transpiration: Gas"Mode1

L i m i t a t i o n s o f the *'Dusty-

in t h e D e s c r i p t i o n of S u r f a c e

Scattering Mathews, A.

and C. F. B a e s

ORNL-TFrT-1129 (May 1965)

Oxide Chemistry a n d Thermodynamics of Molten Lithium F l u o r i d e - Beryllium F l u o r i d e by E q u i 1i bra t i on wi I h Gas e o u s WaterHydrogen F l u o r i d e Mixtures

Rabin, S, A.,

J. W. Ullmann, E. I,. Long, Jr.,

Irradiation B e h a v i o r of Nigh Burnup T h o -

4.45% U 0 2 F u e l H o d s

ORNL-38.37 (October 19G5)

M. F. Osborne, and A, E. Goldman

Redman, J. D.

A L i t e r a t u r e R e v i e w of Mass Spectrometric-

O K N L - ' ~ M -(June ~ ~ 1965)

Thermochemical 'Technique A p p l i c a b l e to the A n a l y s i s o f Vapor S p e c i e s ovei S o l i d Inorganic Materia 1s Reed, S. A., and

J. C. Moyers

Estiniafion of Annual Operating a n d

ORNL-TM-1057 (April 1965)

M a i n t e n a n c e C o s t s of D u a l P u r p o s e NuclearE l e c t r i c S e a Watcr Conversion S t a t i o n s

Savage, â&#x201A;Ź1. W.,

E. L. Compere,

W. K. Huntley,

SNA P-8 Corrosion Program Quarterly P r o g r e s s

ORNL-3784 (March 1965)

R e p o r t for P e r i o d E n d i n g November 30, 1964

R E. MacPhcrson, and A. T a b o a d a S N A P - 8 Corrosion Program Quarterly P r o g r e s s

ORNL-3823 (June 1965)

R e p d r t f o r P e r i o d E n d i n g F e b r u a r y 28, 19G5 SNAP-S Corrosion Program Quarterly P r o g r e s s

ORNL-3859 (September 1965)

R e p o r t for P e r i o d E n d i n g May 3 1 , 1 9 6 5 Singh, A. J.. K. G.

Z o n e Melting of Inorganic F l u o r i d e s

ORNL-3658 (July 1965)

T h o m a , R. E.

Rare-Earth H a l i d e s

ORNL-3804 (May 1965)

Yeatts. L. B.. Jr.,

Purification of Zirconium Tetrafluoride

ORNL-TM-1292 (November 1965)

R o s s , and R. E. Thoma

and W. 'T. Kainey, Jr.

151

BOOKS AND PROCEEDINGS TITLE

AUTHO R(s) Adams, H. E., a n d W. E. Browning, Jr.

PUBLICATION Proc. Intern. Synip. FissiGn Product R e l e a s e a n d

Removal of Iodine a n d V o l a t i l e Iodine

Compounds from Air S y s t e m s by Activated

Ch arc0 a1

T r a n s p o r t 1Jnder A c c iden t Conditions, Oak Ridge, Tenn., Apr. 5-7,

1965, CONF-650407

(19653 Browning, W. E., Jr.,

K. E. Adams, H.. D.

Identity, Character, and Chemical Behavior of

P r o c . Intern. Syinp. F i s s i o n

Vapor F o r m s of Radioiodine

P r o d u c t Re1z:use a n d

Ackley, M. E. Davis,

T r a n s p o r t Under A cc-iden t

and J. E. Attrill

Conditions, Oak Ridge, Tenn.,

A p r . 5-7,

1965, CONF-650407

(1965) Carroll, R. M., Compere, E.

Uranium(1V) Oxide

I,., and

J. E. S a v o l a i n e n

Davis, & E., I. W. E.

G. E.

(1965)

T r a n s . Am. Nucl. S O C . 8(1), 170

T h e Chemistry of Hydrogen in Liquid Alkali

(1965)

Metal Mixtures U s e f u l a s N u c l e a r R e a c t o r Coolants.

Browning, Jr.,

Trans. Am. Ntrc1. Soc. 8(1), 22

F i s s i o n - G a s R e l e a s e During F i s s i o n i n g i n

and 0. Sisman

I. NaK-78

The Deposition of F i s s i o n - P r o d u c t Iodine

Proc. Intern. S y m p . F i s s i o n

0x1

P r u d u c t Release and

Structural S u r f a c e s

T r a n s p o r t Under A c c i d e n t

Creek, Go W. Parker, a n d L. F. P a r s l y

Condirions, Oak R i d g e , Tenn.,

Apro 5-7, .I 965, CONF-650407 (1965)

Joncich, M. J., a n d â&#x201A;ŹI. F. H o l m e s

P r o c . 1 s t Aiistralian Conf.

H e a t E f f e c t s a t E l e c t r o d e s (work performed a t

Electrochem., S y d n e y and

University of T e n n e s s e e )

Hobart, A ristra lie, February 1963, Pergamon. New York,

1964 Kelly, M. J.

Trans. Am. N u c l . SOC. S(l), 170

Removal of R a r e E a r t h F i s s i o n Products from Molten S a l t R e a c t o r F u e l s by D i s t i l l a t i o n

hliller, C. E., Jr.. W. E. Browning. Jr.,

In-Pile Fission P r o d u c t R e l e a s e Experiments Atmosphere E f f e c t s

R. P. Shields, and B. F. R o b e r t s

(1965)

Proc. Intern. S y m p . F i s s i o n

Product R e l e a s e a n d T r a n s p o r t Under A c c i d e n t C o n d i t i o n s , O a k R i d g e , Tenn., A p r . 5 - 7 , 1965, CONF-650407 (1965)

Parker, G. W.,

R e l e a s e of F i s s i o n P r o d u c t s from R e a c t o r

Proc I n tern Syriip. F i s s i o n a

R. A. Lorenz,

F u e l s During T r a n s i e n t A c c i d e n t s Simulated

Product Release and

and J. C. Wilhelm

in T R E A T

T r a n s p o r t Under A c c i d e n t Conditions. Oak R i d g e , Tain., Apr. 5-7, (1965)

1965, CONF-650407

152 TI TL E

AUTHQR(s) Parker, G. W., W. J. Martin, G. E. Creek,

Behavior of Radioiodine i n t h e Containment Mockup F a c i l i t y

PUBLICATION Proc. Intern. Symp. F i s s i o n Product R e l e a s e a n d T r a n s p o r t Under A c c i d e n t

a n d C. J. Barton

Conditions, Oak Ridge, 'I'enn., A p r . 5-7,

1965, CONE--650107

(1965) P e r e z , R. E.

A Dynamic Method for In-Pile F i s s i o n - G a s

R e l e a s e Studies Roberts. B. F.,

W. E. Browning, Jr., H. P. Shields, and

E f f e c t s of Atmosphere on Behavior of F i s s i o n P r o d u c t s R e l e a s e d by In-Pile Melting of UO,

T r a n s . Am. Nucl. Soc. 8(1), 22 (1965) Trans. Am. Nucl. SOC. 8(1), 139 (1965)

C. E. Miller, Jr.

Mathews, A. L.

Oxide Chemistry a n d Thermodynamics of M o l ten Lithium F l uoride--Beryl lium F l u o r i d e

T h e s i s submitted in partial fulfillment of t h e requirements for

by Equilibration with G a s e o u s Water-Hydrogen

Ph.D. degree, University of

F l u o r i d e Mixtures

M i s s i s s i p p i , May 1965

Papers Presented at Scientific and Technical Meetings TITLE

AUTHO R ( s ) Adarris,

K. E.,

and

W. E. Browning, Jr.

Removal of Iodine and Volatile Iodine

PLACE PRESENTED International Symposium on

Compounds from Air S y s t e m s by Activated

F i s s i o n Product R e l e a s e and

Charcoal

Transport Under Accident

Conditions, Oak Ridge, Tenn., Apr. 5-7,

Bacarella, A. L.

Anodic Film Growth on Zirconium a t Temper-

Electrochemical Society Meeting, Buffalo, N.Y., Oct. 11-14,

a t u r e s from 200-300°C B a e s , C. F., Jr.

1965

The Chemistry arid Thermodynamics of Molten Salt R e a c t o r F l u o r i d e Solutions

1965

‘IAEA Symposium on therm<^dynamics with E m p h a s i s on Nuclear Materials and Atomic Transport in Solids. Vienna, Austria, July 22-27,

Baes, C. F.. Jr.”

N. J. Meyer. and C. E. R o b e r t s Bennett, K. Id.,

Acidity Measurements a t E l e v a t e d Temperatures.

2. Thorium(1V) Hydrolysis. 0-95OC

196.5

American Chemical Society, Detroit, Mich., Apr. 4-9,

1965

Thermal E M F Drift of Refractory Metal

AEC High-Tempera ture Thermom-

1-1. L. Hemphill, and

Thermocouples i n P u r e and Slightly

etry Meeting, Whshington, D. C.,

W. T. Rainey, Jr.

Contaminated Helium Atmospheres

Feb. 24-26,

Beniiett, K. L., 13. L. Hemphill,

Stability of Thermoelectric Materials i n a Helium-Graphite Environment

W. T. Rainey, Jr., a n d

1965

A E C High-Temperature Thermometry Meeting, Washington, D.C., F e b . 24-26,

G. W. K e i l h o l t z

106.5

Conference on Carbon, 7th

Blakely, .J. P., and

Oxidation of A T J Graphite by Low Concentra-

LA. G. Overholser

t i o n s of Water Vapor and Carbon Dioxide i n

Biennial, Cleveland, J u n e 21-25,

H e 1ium

1965

Blankenship, F. F.,

HI. F. McDuffie.

K. E.

Molten F l u o r i d e s a s Nuclear Reactor F u e l s

Electrochemical Society, San F r a n c i s c o , Calif., May 9-13, 1965

Thoma. and

W. R. Grimes

Bohlmnnn, E. G., and F. A. P o s e y

Aluminum and Titanium Corrosion in S a l i n e Waters a t E l e v a t e d Temperatures

1 s t International Symposium on Water Desalination, Washington.

D.C.. Oct. 3-9,

153

1955

154

TITLE

AUTHOR(s) Browning, W. E., Jr.,

R, E. Adams, R. D.

Identity, Character, and Chemical Behavior of Vapor F o r m s of Radioiodine

PLACE PRESENTED International Symposium o n F i s s i o n Product R e l e a s e a n d

Ackley, M. E. D a v i s ,

T r a n s p o r t Under Accident

and J. E. Attrill

Conditions, Oak Ridge, 'Tenn., Apr. 5-7,

Burns, J. H.

C r y s t a l Structure A n a l y s i s Applied to Inorganic F l u o r i d e s

1965

OKINS T r a v e l i n g L e c t u r e Program, University of Arkansas, F a y e t t e v i l l e , Dec.

6, 1965 Bums, J. H.. and

E. R. Gordon

Refinement of t h e Structure of Lithium Tetrafluoroberyllate

American Crystallographic A s s o c i a t i o n , Gatlinburg, 'I'enn., J u n e 27-July

Carroll, R. M.

T h e Behavior of F i s s i o n - G a s i n F u e l s

2, 1965

AIME Conference on Radiation E f f e c t s , Ashville, N.C., Sept. 8-10,

Carroll, K. M., a n d

P. E. R e a g a n

In-Pile Performance of High-Temperature Thermocouples

1965

A E C High-Tempera ture Thermometry Meeting, Washington, D.C.,

Carroll, R. M., and

0. Sisman

F i s s i o n - G a s R e l e a s e During F i s s i o n i n g in Uranium(1V) Oxide

Feh. 24-26,

1965

American Nuclear Society, Gatlinburg. Tenn., June 21-24, 1965

Compere. E. L., and J. E. Savolainen

Dabbs. J. W. T..

F. J. Walter, and

T h e Chemistry of Hydrogen L3 Liquid Alkali

American Nuclear Society,

Metal Mixtures U s e f u l a s Nuclear Coolants.

Gatlinburg, Tenn. June 21-24,

1. NaK-78

1965

Saddle P o i n t R o t a t i o n a l S t a t e s from R e s o n a n c e F i s s i o n of Oriented Nuclei

G. W. P a r k e r

IAEA Symposium o n the P h y s i c s and Chemistry of F i s s i o n , Salzburg, Austria, March 22-26, 1365

Davis, hl. E., W. E. Drowning, Jr., G. E.

' f i e Deposition of F i s s i o n - P r o d u c t Iodine

on Structural Surfaces

International Symposium o n F i s s i o n Product R e l e a s e a n d

Creek, G. W. Parker,

T r a n s p o r t Under Accident

and L. F. P a r s l y

Conditions, Oak Ridge, Tenn., Apr. 5-7,

Davis, R. J.

Oxide Growth and C a p a c i t a n c e on P r e i r r a d i a t e d Zircaloy-2

1965

E l e c t r o c h e m i c a l Society, S a n F r a n c i s c o , Calif., May 9-13, 1965

Grimes. W. K.

Chemistry of Molten F l u o r i d e R e a c t o r Systems

Gordon R e s e a r c h Conference on Molten Salts, Meriden, N.H., Aug. 30-Sept.

Molten F l u o r i d e s a s R e a c t o r Material

3, 1965

Chemistry Seminar a t Argonne N a t i o n a l Laboratory, Nov. 12, 1965

T h e Chemistry of t h e Molten S a l t R e a c t o r

Nuclear E n g i n e ering Colloquium a t Rrookhaven National Laboratory, Dec. 2, 1 3 6 5

155

Grimes, W. R.

PLACE PRESENTED

TITLE

AUTHOR(s)

Molten F l u o r i d e s a s F u e l s , C o o l a n t s , a n d

Chemistty Seminar a t Purdue

B l a n k e t s for N u c l e a r R e a c t o r s

University, Lafayette. Ind., Dec. 9, 1965

Karraker, R. H., and R. E. Thoma

Sodium Fluoride-Scandium

American C h e m i c a l Society, SW-SE

Fluoride P h a s e

Equilibria

R e g i o n a l Meeting, Memphis. Tenn., Dec. 2-4,

Kelly, M. J.

Removal of R a r e E a r t h F i s s i o n P r o d u c t s from

1965

American Nuclear Society.

Molten S a l t R e a c t o r F u e l s by D i s t i l l a t i o n

Gatlinburg, Tenn., June 21-24, 1965

Keyser, R. M.

Experiments i n Chrmonuclear Synthesis a t

Chemonuclear Review Meeting a t

ORNL

Onchiota Conference Center, Tuxedo, N.Y., Oct, 19-20,

Marshall, W. L.

Solubility a n d E l e c t r i c a l C o n d u c t a n c e Meas-

Conference o n K i n e t i c s and

u r e m e n t s of Some A q u r o u s E l e c t r o l y t e s of

Mechanism i n Aqueous Inorganic

I n t e r e s t to Oceanography

Systems, Miami, H a . , Nov.

18-23, Marshall, W. L., and

E. V. J o n e s

1965

196.5

Second D i s s o c i a t i o n C o n s t a n t of Sulfuric Acid

Americati C h e m i c a l Society,

f r o m S o l u b i l i t i e s of Calcium S u l f a t e i n Sul-

Detroit, Mich,, Apr. 4-9,

1965

furic Acid Solutions Mathews, A. I".,

a n d C. F. B a e s , Jr.

American Cherrl i c a 1 Society,

O x i d e Chemistry and Thermodynamics of Molten Lithium Fluoride-Beryllium

SW-SE Regional Meeting,

Fluoride

Memphis, Tenn.. D e r . 2-4, McDuffie, H. F.. and

R. P. Atkinson

1965

T e n n e s s e e Academy of Science,

T h e Development of an Information C e n t e r

O a k Ridge, Tenn., Dec. 10-11,

for Molten S a l t Chemistry

1965 Miller, C. E., Jr., W, E. Browning, Jr.,

In-Pile F i s s i o n P r o d u c t R e l e a s e E x p e r i m e n t s Atmosphere E f f e c t s

International Symposium on F i s s i o n Product R e l e a s e a n d

R. P. Shields, and

T r a n s p o r t Under Accident

B. F. R o b e r t s

Conditions. Oak Ridge, Tenn..

Apr. 5-7, Parker, G. W.,

K. A.

I,orenz, and

J. G. Wilhelm

R e l e a s e of F i s s i o n P r o d u c t s from R e a c t o r

1965

International Symposium on

F u e l s During T r a n s i e n t A c c i d e n t s Simulated

F i s s i o n Product R e l e a s e and

in T R E A T

T r a n s p o r t Under Accident Conditions, Oak Ridge, Tenn., Apr. 5-7. 1965

Parker. G" W..

W. J. Martin, C. E. Creek, a n d

Behavior of Radioiodine i n t h e Containment Mockup F a c i l i t y

F i s s i o n Product R e l e a s e arid T r a n s p o r t Under Accident Conditions. Oak Ridge, Tenn.,

C. J. Barton Parkinson, W. W.

International Symposium on

Apr. 5-7, T h e E f f e c t of R a d i a t i o n on P l a s t i c s and

Rubber

1965

U.S. Army Nuclear S c i e n c e Seminar, O a k Ri.dge, Tenn., July 27, 1965

156 TI TL E

AUTHOR(s) P a r k i n s o n , W. W., and W. D. Burch

S y n t h e s i s of O r g a n i c s Through Isotopic D e c a y Radiation

PLACE P R E S E N T ED Annual Contractors Conference, AEC Division of I s o t o p e s Development, Brookhaven N a t i o n a l Laboratory, Oct. 7-8, 1965

P e r e z , R. R., and

G. M. Watson

A Dynamic Method for In-Pile F i s s i o n - G a s Re1 e a s e S t u d i e s

American N u c l e a r Society, Gatlinbnrg, Tenn.. June 21-24, 1965

Quist, A. S.

E l e c t r i c a l C o n d u c t a n c e s of Aqueous

Karlsruhe T e c h n i s c h e

P o t a s s i u m B i s u l f a t e and Sulfuric Acid

Hochschule, Karlsruhe, Germany,

Solutions to 800OC and 4000 B a r s

Sept. 13-15,

1965

Central Electricity Research Laboratories, L,eatherhead, England, Sept. 2 1 , 1965 R i s d Research Establishment, R i s d (Roskilde). Denmark, Sept. 27, 1965

Quist, A. S . , and

W. L. Marshall

E l e c t r i c a l C o n d u c t a n c e s of Aqueous P o t a s -

C I T C E Symposium on E l e c t r o -

sium B i s u l f a t e a n d Sulfuric Acid Solutions

chemistry a t High Temperatures,

t o 800OC and 4000 B a r s

Budapest, Hungary, Sept. 5-10, 1965

Reed, S . A.

Some Chemical and Materials P r o b l e m s i n S e a Water Conversion P l a n t s

American Chemical Society R e g i o n a l Meeting, Dayton. Ohio, Dec. 14, 1965

Roberts, B. F.,

W. E, Rrowning, Jr., R . P. Shields, and

E f f e c t s of Atmosphere on Rehavior of

American Nuclear Society,

F i s s i o n P r o d u c t s R e l e a s e d by In-Pile

Gatlinhurg, Tenn., June 21-24,

Melting of U 0 2

1965

C. E. Miller, Jr. Rutherford, J. L., J. P. Blakely, and

Oxidation of F u e l e d and Unfueled Graphite S p h e r e s by Steam

Holmes, C. S . Shoup,

T h e Interaction of Water with t h e Surface of Ceramic O x i d e s

1965

International Conference on T r o p i c a l Oceanography, Miami Beach, Fla., Nov. 17-24,

and E. L. F u l l e r Soldano, B. A.

Biennial, Cleveland, June 21-25.

L. G, Overholser Secoy, C. H., H. F.

C o n f e r e n c e on Carbon, 7th

T h e Osmotic Rehavior of Aqueous Solutions a t Elevated Temperatures

1965

ORINS T r a v e l i n g L e c t u r e Program, Furman University, Greenville, S.C., Nov. 1, 1965

Thoma, R. E.

Methods of I n v e s t i g a t i n g High Temperature P h a s e Equilibria

ORINS Traveling L e c t u r e

Program, Furman University, Grcenville, S.C..

R a r e E a r t h Trifluoride Systems

Mar. 1, 1965

Chemistry Seminar a t Argonne N a t i o n a l Laboratory, May 21, 1965

AU THO R( s ) TruiLt, Jack,

Influenced by Actinide a n d Defect

R. B. E v a n s 111

Concentrations

E. L. F u l l e r , Jr.

American Ceramic Society,

Actinide Migration i n Pyrocarbons a s

J. 0. Stiagler, and

Vanderzee, C . E.,l and

P L A C E PRESENTED

TITLE

Philadelphia, May 2 4 , 1965 F i r s t ?didwest Regional Meeting,

Thermochemistry and K i n e t i c s of the Hydrolytic Decomposition of Ammonium

American Chemical Society.

Carbamate a n d Ammonium Dithiocarbamate

K a n s a s City, Mo., Nov. 4-5,

1965 Watson, G. M.

T h e Economics of Nuclear Power

AEC International Exhibit a t San Salvador, E! Salvador, Mar. 19-22,

1965

AEC International Exhibit a t

Chemical A s p e c t s of Nuclear Safety

San Salvador, El Salvador. Mar. 19-22, Physico-Chemical P r o b l e m s of Nuclear R e a c t o r s

1965

ORINS 'Traveling L e c t u r e Program, T a r l e t o n S t a t e College, Stephenville, 'rex.,

Dec. 6, 1965 Yeatts, L. B., Jr., and W. L. Marshall

S o l u b i l i t i e s of Calcium Hydroxide and Saturation Behavior of Calcium Hydroxide Calcium C a r b o n a t e Mixtures in Aqueous

Sodium Nitrate Solutions a t High Temperatures

' R e s e a r c h performed a t University of Nebraska. Lincoln.

American Chemical Society,

SW-SE Regional Meeting, Memphis, Tenn., Dec. 2-4,

1965

ORNL-39 13

159

UC-4 - Chemistry TID-4500 (47th ed.)

INTERNAL DISTRIBUTION

1. Biology Library 2-4. Central Research Library 5. Reactor Division Library 6. Loboratory Shift Supervisor 7-8. QRNL Y-12 Technical Library Document Reference Section 9-58. Laboratory Records Department 59. Laboratory Records, ORNL R.C. 60. C. E. Larson 61. A. M. Weinberg 62. H,G. MacPherson 63-77. G. E. Boyd 78. F. R. Bruce 79. F. L. Culler 80. W. H. Jordan 81. A. H. Snell 82. G. Young 83. A. F. Rupp 84. M. Bender 85. A. L. Boch 86. R. B. Briggs 87. W. B. Cottrell 88. A. F. Fraas 89. K. A. Krous 90. J. A. L a n e 91. A. J. Miller 92. D. B. Trauger 93. G. D.Nhitman 94. S. E. Beall 95. D. S. Billington 96. 5. E. Ferguson 97. J. H Frye, Jr. 98. M. T. Kelley 99. E. W. Taylor 100. M. A. Bredig 101. L. T. Corbin 102. J. E. Cunningham 1103. J. W. Crawford 104. E. hA. King 105. R. N. Lyon 106. R. PI.Porker 107. M. J. Skinner 108. J. C. White 109. G. 6 . W i l l i a m s

110. W. R. Grimes 111. E. G. Bohlmann 112. H. F. McDuffie 113. G. M. Watson 114. F. F. Blankenship 115. C. H. Secoy 116. C. F. Baes, Jr. 117. A. L. Bacareila 118, C. J. Barton 119. C. D. Bopp 120, W. E. Browning, Jr. 121. G. D. Brunton 122. J. H. Burns 123. S. Cantor 124. R. M. Carroll 125. E. L. Compere 126. R. J. Davis 127. J. L. English 128. R. 8. Evans I l l 129. E. L. Fuller, Jr. 130. J. C. Griess 131. H. F. Holmes 132. G. H. Jenks 133. G. W. Keilholtr 134. M. J. Kelly 135. S. S. K i r s l i s 136. R. A. Lorenz 137. A. P. Malinauskas 138, W. L. Marshall 139. C. E. Miller 140. R. E. Moore 141. J. G. Morgan 142. L. 6 . Overholser 143. G. W. Parker 144. W. W. Parkinson 145. A. S . QuiSt 146. S. A. Reed 147. D. M. Richardson 148. K. A. Romberger 149. ti. C. Savage 150. D. R. Sears 151. J. H. Shaffer 152. A, J. Shor 153. M. D. Silverman

160

154. 155. 156. 157. 158. 159-166. 167. 168. 169. 170. 171. 172. 173. 174. 175. 176.

0 . Sisman 8. A. Soldano R. A . Strehlow F. H. Sweeton R. E. Phonia G. C. Warlick C. F. Weuver L. B. Yeatts L. Brewer (consultant) J. W. Cobble (consultant) F. Daniels (consultant) R. W. Dayton (consultant) P. H. Emmett (consultant) H. S. Frank (consultant) N. Hackerman (consultant) D. G. H i l l (consultant)

177. 178. 179. 180. 181. 182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192.

H. H. E. T. G. J.

l n s l e y (consultant) R. Jolley (consultant) V. Jones (consultant) N. McVay (consultant) Mamantov (consultant) L. Margrave (consultant) E. A . Mason (consultant) 8 . F. Newton (consultant) R . B. Perez (consultant) J. E . Ricci (consultant) Howard Reiss (consultant) G. Scatchard (consultant) D. A. Shirley (consultant) H. Steinfink (consultant) R. C. Vogel (consultant) T. F. Young (consultant)

EXTERNAL DlSTRlBUTlON 193. 194. 195. 196. 197. 198. 199. 200. 201. 202. 203. 204. 205-533.

D. F. Bunch, Health Physics Branch, AEC, Washington Paul E. Field, Dept. of Chemistry, Virginia Polytechnic I n s t i t u t e L. R. Zuiiiwalt, General Atomic Division, General Dynamics Corp., Son Diego, C a l i f Research and Development Division, AEC, ORQ Reactor Division, AEC, ORO Assistant General Manager for Research and Development, AEC, Washington Division of Research, AEC, Washington Division of Isotopes Development, AEC, Wushington Assistant General Manager for Reactors, AEC, Washington Division of Reactor Development and Technology, AEC, Washington Space Nuclear Propulsion Office, AEC, Washington J. A. Swartout, 270 Park Ave., New York 17, New York Given distribution as shown i n TID-4500 (47th Ed.) under Chemistry category (75 copies -- CFSTI)