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A Study of Tritium Removal from Fusion Reactor Blankets of Molten Salt and Lith ium-AIuminum Jan B. Talbot

O b.

Printed in the United States of America. Available from National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road, Springfield, Virginia 22161 Price: Printed Copy $5.00; Microfiche $2.25 This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the Energy Research and Development Administration, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately owned rights.

. f

. d

Contract No. W-7405-eng-26

CHEMICAL TECHNOLOGY DIVISION

A STUDY OF TRITIUM RENOVAL FROM FUSION REACTOR BLANKETS OF MOLTEN SALT AND LI-ALUMINUM

Jan B. Talbot

A thesis presented to the Graduate Council of the Pennsylvania State University in partial f'ulfillment of the requirements for the degree of Master of Science

MARCH 1976

OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee 37830 operat ed by UNION CARBIDE CORPORATION for the ENERGY RESEARCH AND DEVELOPMENT ADMINISTRATION

DISTRIBUTION OF THIS DOCUMENT IS UNLIMIT~D

iii

ACKNOWLEDGMENTS This study w a s c a r r i e d out as p a r t of t h e Laboratory Graduate P a r t i -

c i p a t i o n Program, which i s conducted by O a k Ridge Associated U n i v e r s i t i e s , i n cooperation with Oak Ridge National Laboratory, which i s operated by Union Carbide Corporation f o r t h e Energy Research and Development Administration.

The w r i t e r wishes t o thank G. C. Kyker, Head of t h e University

Programs Office, and D. E. Ferguson, Director, and C. D. S c o t t , Experimental Engineering Section Chief, of t h e ORNL Chemical Technology Division, whose support made t h i s work possible. The author wishes t o acknowledge t h e advice and suggestions of P. Barton, J. S. Watson, and F. J . Smith, who served as advisors f o r t h i s study. The lithium-aluminum samples were prepared by t h e Metals and Ceramics Division under t h e supervision of J. H. DeVan.

Chemical analyses w e r e

performed by t h e Analytical Chemistry Division under t h e supervision of W. R. Laing.

The mass spectrometer experiment was conducted by J: D.

Redman o f t h e C h e m i s t r y Division.

Special thanks a r e due J. F. Land,

who assisted with t h e operation of t h e experiments.

Much appreciation

i s expressed t o Y. H. Callahan and M. G. Stewart, who e d i t e d t h e manu-

s c r i p t , and t o Janice Shannon, who ty-ped t h e f i n a l e d i t i o n . were prepared under t h e supervision of A. J. Farmer.

The drawings

ABSTRACT

. c

The sorption of tritium by molten lithium-bismuth

(Li-Bi,

15 a t .

.rl

% l i t h i u m ) and s o l i d equiatomic lithium-aluminum ( L i - A l ) w a s investigated experimentally t o evaluate t h e p o t e n t i a l applications of both materials i n a controlled thermonuclear r e a c t o r .

The Li-Bi a l l o y w a s proposed t o

countercurrently e x t r a c t tritium from a molten s a l t ( L i BeF ) blanket. 2 4 However, because of t h e low s o l u b i l i t y (< 1 0 ppb) a t temperatures ranging from 500 t o 7OO0C, t h e extraction process i s not a t t r a c t i v e . Powell of Brookhaven National Laboratory has proposed using s o l i d Li-A1 a s a minimum inventory blanket material.

I n t h e present study,

t h e tritium sorption w a s determined t o range from t i o n , which i s i n agreement with Powellâ&#x20AC;&#x2122;s estimates.

at. frac-

The q u a n t i t i e s of

tritium sorbed seemed t o be controlled by surface reaction and/or slow

i n t e r n a l diffusion. The f e a s i b i l i t y of t h e tritium recovery scheme suggested by Johnson f o r t h e Princeton Reference Design Tokamak w a s analyzed.

The spray

disengager process t o recover tritium from molten s a l t seems discouraging due t o t h e l a r g e j e t v e l o c i t y , t h e number of nozzles, and t h e droplet s i z e needed f o r mass t r a n s f e r of tritium f l u o r i d e from s a l t .

v ii TABLE OF CONTENTS '

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . iii ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v ix LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . x CHAPTER I . INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . 1 CHAPTER I1. REVIEW OF LITERATURE . . . . . . . . . . . . . . . . . . 3 CHAPTER111 . THEORY . . . . . . . . . . . . . . . . . . . . . . . . 10 CHAPTER I V . EXPERIMENTAL APPARATUS AND PROCEDURE . . . . . . . . . . 1 4 Reagents . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Apparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Li-Bi Sorption System . . . . . . . . . . . . . . . . . . . 15 L i - U Sorption System . . . . . . . . . . . . . . . . . . . 18 Operational Procedures . . . . . . . . . . . . . . . . . . . . . 23 Li-Bi Sorption System . . . . . . . . . . . . . . . . . . . 23 23 Sampling Procedure . . . . . . . . . . . . . . . . . . . . L i - U Sorption System . . . . . . . . . . . . . . . . . . . 24

ACKNOWLEDGMENTS

Analytical Procedure

.................... Li-Bi Sorption System . . . . . . . . . . . . . . . . . . . . . Li-A1 Sorption System . . . . . . . . . . . . . . . . . . . . . CHAPTER V I . DISCUSSION OF RESULTS . . . . . . . . . . . . . . . . . Li-Bi Sorption System . . . . . . . . . . . . . . . . . . . . . L i - M Sorption System . . . . . . . . . . . . . . . . . . . . . CHAPTER V I 1 . ANALYSIS OF THE TRITIUM RECOVERY SYSTEM FOR THE PRINCETON REFERENCE DESIGN . . . . . . . . . . . . . . Description of t h e Process . . . . . . . . . . . . . . . . . . . Disengager Analysis . . . . . . . . . . . . . . . . . . . . . . CHAPTERV

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

MPERIMENTALDATA

28 28

37 38 42 42

viii TABLE OF CONTENTS (Continued)

................... Other Design Considerations. . . . . . . . . . . . . . . . . . . CHAPTER VIII. CONCLUSIONS AND RECOMMENDATIONS. . . . . . . . . . . . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . Recommendations. . . . . . . . . . . . . . . . . . . . . . . . . BIBLIOGRAPHY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . APPENDIX A. THE COMPATIBILITY OF Li-Bi WITH Li2BeF4. . . . . . . . . Cyclic Condenser Analysis,

56 56

57 58

APPENDIX B.

SAMPLF: CALCULATIONS FOR Li-Bi--TRITIUM SORPTION DATA FOR SAMPLF: NO. 2.7 AT 600Oc.

APPENDIX C.

CALCULATION OF RESIDENCE TIME FOR MASS TRANSFER OF TRITIUM FLUORIDE FROM A SALT DROPLET

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

..........

APPENDIX D. CALCULATION OF SPRAY DISENGAGER HEIGHT FOR SALT DROPLETS OF VARIOUS SIZES (25)

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

APPENDIX E.

CALCULATION OF THE FREQUENCIES OF MOLECULAR COLLISIONS (10)

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

APPENDIX F. CALCULATION OF MXECULAR COLLISIONS WITH CONDENSER

WALLS..

APPENDIX G. APPENDIX H.

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

CALCULATION OF MEAN FREE PATHS OF TF AND HELIUM COLLISIONS

....................... CALCULATION OF CYCLIC CONDENSER HEAT LOAD. . . . . . . .

71 76 78 81

ix L I S T OF TABLES i

Page

Table

I. 11.

111. IV

V. VI.

VII.

VI11

........ RESULTS OF L i - B i METAL PHASE ANALYSES FOR TRITIUM. . . . . RESULTS OF GAS-PHASE ANALYSES FOR TRITIUM CONCENTRATION. . RESULTS OF Li-A1 ANALYSES FOR TRITIUM AT 40OoC . . . . . . TIME-INDEPENDENT RESULTS OF L i - m ANALYSES FOR TRITIUM . . HYDROGEN REACTIONS WITH THE ELEMENTS ( 4 0 ) .

13 29 30

FLOW RATES AND CONCENTFLATIONS FOR THE TRITIUM RECOVERY SYSTEM FOR THE PRINCETON REFERENCE REACTOR

........

CHARACTERISTICS, ADVANTAGES, AND DISADVANTAGES OF PRESSURE NOZZLES AND S P I N N I N G D I S K ATOMIZERS (25)

MOLECULAR AND WALL COLLISION FREQUENCIES AND MEAN FREE PATHS O F H e and TF I N THE CYCLIC CONDENSERS.

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

LIST OF FIGURES Figure 1

Simplified Schematic of a Controlled Thermonuclear Reactor System..

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

Apparatus f o r Study of Sorption of T r i t i u m i n Li-Bi Alloy

Reaction Vessel f o r Studying t h e Sorption of T r i t i u m i n Li-BiAlloy..

I n i t i a l Equipment Design f o r Studying Sorption of T r i t i u m i n Li-Al Alloy.

Revised Apparatus f o r Studying Sorption of T r i t i u m i n Li-AlAlloy..

Photograph of t h e Equipment Used t o Measure T r i t i u m Sorpt i o n i n Li-Al Alloy

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

................... Sample Dissolution Apparatus f o r T r i t i u m Analysis . . . .

T r i t i u m Concentration i n Li-Bi Samples a t t h e Corresponding T r i t i u m P a r t i a l Pressure. 31

T r i t i u m Concentration as a Function of Percent Li-Al Sample Dissolved.

A Comparison of S i e v e r t s ' Constants f o r Aluminum, Lithium, and Li-Al Alloy

Princeton's Reference Design S a l t Blanket Processing System..

14 15

PagSe

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

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

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

........................ Schematic o f t h e S a l t Disengager and S a l t Trap. . . . . .

Residence Time vs Drop Diameter f o r Molten S a l t Mass Transfer.

........................ Schematic of t h e Cyclic Condensers. . . . . . . . . . . . Numerical Solution of Liquid Diffusion i n a Sphere. . . .

Ohnesorge's Chart (25) Showing Jet Breakup as a Function of Reynolds Number and Liquid Properties.

........

48 52

kd CHAPTER I i

INTRODUCTION

The f e a s i b i l i t y o f commercial fusion power r e a c t o r s depends upon t h e development of e f f e c t i v e methods f o r containing and recovering tritium. D i f f i c u l t problems are expected t o be encountered i n t h e handling, recovery, and containment of t h e f u e l inventory of a controlled thermonuclear r e a c t o r (CTR) fueled with tritium and deuterium.

Deuterium can

be obtained from n a t u r a l waters; however, tritium, which does not e x i s t

i n u s e f u l concentrations i n nature, must be generated by neutron bombardment of lithium-containing material i n a blanket surrounding t h e r e a c t o r plasma.

It i s necessary t o recycle tritium and deuterium from t h e exhaust

plasma and t o recover bred tritium from i t s blanket system f o r subsequent i

use as f u e l .

concentrations i n t h e system because of t h e d i r e c t e f f e c t upon t h e tritium

Stringent l i m i t a t i o n s must be imposed on t h e use of tritium

inventory, t h e tritium r e l e a s e rate t o t h e environment, and t h e embrittlement of s t r u c t u r a l materials by helium r e s u l t i n g f r o m t r i t i u m decay. Lithium-containing materials have been proposed f o r a v a r i e t y of applications i n CTRs.

It i s suggested i n t h i s study t h a t molten lithium-

bismuth ( L i - B i ) a l l o y could be useful f o r e x t r a c t i n g tritium from a CTR breeding blanket consisting of a molten m i x t u r e of l i t h i u m and beryllium fluorides.

O f course, t h e a p p l i c a b i l i t y of such a recovery system depends

upon t h e equilibrium uptake of tritium by t h e Li-Bi a l l o y . i

has suggested using a s o l i d lithium-aluminum ( L i - A l ) breeding blanket.

Power (30)

a l l o y i n t h e tritium

The a l l o y plus i t s aluminum s t r u c t u r e would produce a

minimum neutron a c t i v a t i o n and a low tritium inventory.

However, t h e

I , usefulness of t h e material i s contingept upon i t s sorption of tritium and i t s a b i l i t y t o rapidly exchange tritium with a f l u s h gas such as helium.

The objectives of t h i s study were t o evaluate experimentally t h e p o t e n t i a l application of Li-Bi and Li-A1 i n a CTR.

Thus, t h e tritium

s o l u b i l i t y and thermochemical behavior of t h e l i t h i u m a l l o y s were invest

1 I

tigated.

The Pennsylvania S t a t e University i s not l i c e n s e d t o work rou-

t i n e l y with amounts of tritium g r e a t e r than 100 p C i .

Since samples of

more than t e n times t h a t amount were needed t o a t t a i n meaningful experimental results, t h i s study w a s conducted a t t h e Oak Ridge National Laboratory (ORNL) as p a r t of t h e Oak Ridge Associated U n i v e r s i t i e s ' Program. Another objective of t h e research w a s t o analyze t h e blanket recovery system proposed f o r t h e Princeton Reference Design CTR (21).

I n t h i s con-

ceptual design, tritium i s generated from a molten f l u o r i d e salt blanket. The p r a c t i c a l i t y o f t h e blanket processing system w a s reviewed i n t h i s report by studying each of t h e required process s t e p s and estimating t h e f e a s i b i l i t y and equipment s i z e involved.

t/ CHAPTER I1 i

REVIEW OF LITERATURE

Many conceptual and engineering designs have been made for a CTR Most of t h e CTR concepts resemble t h e system shown i n

(13,14,26,30,32).

Fig. 1. The thermonuclear reactions t h a t r e l e a s e energy are:

4He + n,

17.6 MeV

eq. 1

D + D

T+H,

4.03 MeV

eq. 2

-t

3He + n ,

3.27 MeV

eq. 3

+ D D + 3He

+ 6L i

-+ -+

4H e + H, 3He + â&#x20AC;&#x2DC;He.

18.3

MeV

eq. 4

4.0

MeV

eq. 5

For t h e f i r s t generation of thermonuclear r e a c t o r s , t h e deuterium-tritium (D-T)

r e a c t i o n i s favored because it r e l e a s e s one of t h e l a r g e s t quanti-

t i e s of energy and i t s p r o b a b i l i t y of occurrence (cross s e c t i o n ) i s t h e highest o f t h e above reactions (19).

I n a D-T r e a c t o r , a small percen- .

t a g e of t h e D-T mixture fises during i t s residence i n t h e plasma region. This fusion generates high-energy neutrons which deposit heat i n t h e surrounding blanket f l u i d .

The energy i s then t r a n s f e r r e d t o a secondary

coolant f l u i d connected t o a conventional steam cycle. T r i t i u m must be bred t o f u e l t h e r e a c t o r at a r a t e equal t o , or

g r e a t e r than, t h e rate at which it i s consumed i n t h e plasma.

The neu-

t r o n bombardment of l i t h i u m produces tritium by t h e following reactions: 6,i

7Li

n -+

4H e + T ,

eq. 6

4H e + n1 + T.

eq* 7

Lithium must be included i n t h e blanket material for breeding purposes. Subsequently, tritium handling systems are needed t o recover tritium

ORNL DWG. 75-8303

STEAM lo* TURBINE

L-

. 1'

8 A

T Figure 1. Simplified Schematic of a Controlled Thermonuclear Reactor System.

from t h e blanket f o r recycling t o t h e plasma. '

Although tritium breeding

i s not necessary f o r t h e deuterium-deuterium (D-D) and deuterium-helium P

3 5 (D- H e ) f u e l cycles, tritium w i l l be produced by D-D

reactions (Equa-

t i o n 2 ) and handling systems w i l l s t i l l be required, although t h e probl e m s w i l l probably be l e s s severe. Low tritium concentrations must be maintained i n t h e blanket m a t e -

r i a l by a tritium recovery system.

T r i t i u m has a h a l f - l i f e of 12.3 years

and undergoes radioactive decay according t o t h e reaction T

-t

3He + e- + 5.6 keV.

eq. 8

The current Energy Research and Development Administration (ERDA) guidelines on r a d i o a c t i v i t y i n e f f l u e n t s from light-water-cooled

fission

f i s s i o n r e a c t o r s require ( a ) t h a t t h e dose r a t e a t t h e s i t e boundary not exceed 5 millirems/year and ( b ) t h a t t h e annual average concentration of

tritium prior t o d i l u t i o n i n a n a t u r a l body of water not exceed 5 x pCi/liter (39).

When considering a

1000-MW(e) fusion r e a c t o r , t h e s e

guidelines imply ( a ) t h a t t h e r e l e a s e of tritium i n t o coolant w a t e r should be limited t o

1 0 Ci/day and ( b ) t h a t t h e amount discharged

through a stack ( Q 30 m high) should be l i m i t e d t o

1 0 t o 100 Ci/day

(37,38). However, current designs o f fusion r e a c t o r s attempt t o l i m i t tritium r e l e a s e rates t o a range of

1 t o 1 0 Ci/day.

This l i m i t a t i o n

constrains t h e concentration of tritium i n t h e blanket material.

Trit-

ium, which i s extremely mobile, will diffuse through a l l metal s t r u c t u r e s and heat t r a n s f e r surfaces.

Large concentrations of tritium i n t h e

blanket would lead t o high r e l e a s e r a t e s ; t h e r e f o r e , t h e blanket must be processed t o achieve t h e lowest possible concentration of tritium.

6 The thermonuclear power systems will process t h e blanket material within t h e blanket loop, as shown i n Fig. 1; however, t h e choice of blanket and coolant f l u i d s w i l l have an important e f f e c t i n t h e tritium recovery scheme.

The two r e a c t o r designs of i n t e r e s t i n t h e present

study are those proposed by t h e Princeton Plasma Physics Laboratory (26) and t h e Brookhaven National Laboratory (30). Tokamak produces 2030 MW of e l e c t r i c power.

Princeton's Reference The blanket material chosen

t o generate tritium i s a mixture of l i t h i u m and beryllium f l u o r i d e s (Li2BeF4).

H e l i u m w a s chosen as a coolant t o carry heat from t h e Li2BeF4

blanket t o t h e steam system.

a s o l i d Li-A1 a l l o y as a blanket material i n which tritium i s bred and a

helium coolant stream.

The Brookhaven conceptual design suggests

This concept i s advantageous because s t r u c t u r a l

materials with very l i t t l e long-lived a c t i v a t i o n (e.@;. aluminum), which are not compatible with L i BeF4, can be used. 2 Recovery of tritium from molten L i BeF4 i s d i f f i c u l t because t h e 2

tritium concentration i n t h e s a l t must be maintained at less than 1 ppm

t o prevent tritium leakage.

Watson (41) has drawn s e v e r a l conclusions

from an evaluation of t h e tritium recovery process f o r t h e Li2BeF4 blanket.

Cold trapping and s o l i d sorbents are not a t t r a c t i v e due t o t h e

l i m i t e d operating temperature range imposed by t h e salt and possible

tritium permeation through regenerator surfaces.

Diffusion c e l l s a r e not

p r a c t i c a l because of s a l t c o r r o s i v i t y and l i q u i d film r e s i s t a n c e .

Counter-

current gas sparging with e i t h e r helium o r argon may be possible i f a

suitable compromise between t h e sparge rate and corrosion can be made.

-8

This n e c e s s i t a t e s t h a t tritium pressures i n t h e range of 1 0

-4

a t m and tritium f l u o r i d e (TF) pressures i n t h e range of

t o 10

atm

be maintained. I n t h i s study, t h e proposal examined i s one i n which L i BeF would 2 4 be contacted with an immiscible diffusion sink i n a countercurrent l i q u i d extractor.

tritium g e t t e r , added t o t h e molten m e t a l , would form a

hydride t o reduce t h e equilibrium a c t i v i t y of tritium and t o obtain low tritium concentrations i n t h e s a l t phase.

gated w a s L i - B i ,

The contacting medium i n v e s t i -

with lithium being t h e tritium g e t t e r .

then recovered from t h e molten Li-Bi

The tritium i s

e i t h e r by a p r e c i p i t a t i o n process or

i n diffusion cells. The experimental apparatus used t o determine t h e equilibrium d i s t r i bution of t r i t i u m a t low concentration l e v e l s i n molten Li-Bi was a modif i c a t i o n of t h a t u t i l i z e d previously a t ORNL f o r phase equilibrium s t u d i e s of molten salt and molten metal systems (12).

The concentration of Li-Bi

compatible with Li2BeF4 was determined by using available thermodynamic data (Appendix A ) .

Lithium w i l l reduce beryllium from t h e L i BeF at 2 4

l a r g e concentrations and w i l l subsequently form another immiscible phase. A maximum concentration o f 15 a t .

% l i t h i u m i n bismuth w a s chosen f o r t h e

tritium s o l u b i l i t y experiment; t h i s molten a l l o y i s compatible with L i BeF at t h e temperatures observed. 2 4 a l e s s e r concentration of about 1 a t .

The proposed e x t r a c t o r would use

% lithium and operate a t 900째K.

The process suggested by Johnson (21) i n t h e Princeton Reference Tokamak study o f f e r s another method for recovering tritium from L i BeF4. 2 The molten s a l t i s sprayed continuously i n t o e i g h t towers which are main-

-4 a t m and l o c a t e d around t h e r e a c t o r system.

t a i n e d below 10

TF and

helium gases vaporize from t h e t i n y droplets and a r e drawn through cold

/-'

W t r a p s , where all t h e TF i s frozen out.

The s a l t i s c o l l e c t e d at t h e

bottom of each discharger and r e c i r c u l a t e d through t h e blanket.

Period-

i c a l l y , t h e nitrogen-cooled t r a p s are thawed, and l i q u i d TF flows i n t o e l e c t r o l y t i c c e l l s , where it i s electrolyzed t o T2 and F 2'

The tritium

i s recycled t o t h e primary f u e l loop. The tritium recovery scheme f o r t h e solid-lithium-containing

blanket

proposed by Brookhaven (30) seems less complex i n comparison t o t h e L i BeF recovery systems. 2 4

The tritium bred i n t h e Li-A1 a l l o y d i f f u s e s

out of t h e s o l i d , e i t h e r i n t o t h e vacuum region between t h e plasma and t h e f i r s t w a l l or i n t o t h e helium coolant stream.

By l e t t i n g t h e tritium

d i f f u s e d i r e c t l y i n t o t h e vacuum region, t h e tritium concentration i n the Li-A1 w i l l eventually reach a steady-state value as it i s released a t

t h e same rate t h a t it i s bred.

If t h e r e s i s t a n c e t o tritium release i s 1

s u f f i c i e n t l y s m a l l , t h e steady-state concentration w i l l d i f f e r l i t t l e from equilibrium conditions.

-6

If t h e vacuum region i s maintained at 1 0

t o r r tritium pressure (1t o r r equals 1 mm Hg of pressure) and t h e r e s i d u a l gas i s assumed t o be 100%tritium, t h e equilibrium atom f r a c t i o n of trit-

-6 i u m i n Li-A1 i s about 2 x 1 0 (30). This corresponds t o a tritium blan6 k e t inventory of about 160 g ( 2 x 1 0 C i ) .

-6

be burned d a i l y i n t h e plasma, 2 x 1 0

a day's inventory.

Since

300 g of tritium w i l l

atom f r a c t i o n represents less than

If t h e tritium inventory i n t h e blanket i s too l a r g e ,

protium (normal hydrogen) could be used t o scavenge t h e tritium.

Finally,

t h e tritium i s recovered, combined with p u r i f i e d D-T f u e l from t h e plasma, and recycled t o t h e plasma. 9

Alternatively, t h e tritium could d i f f u s e out t h e Li-AI.

into the

helium coolant stream, where it i s removed by absorption i n a m e t a l

hydride bed from which it i s l a t e r recovered.

i u m i n Li-A1 i s estimated t o be

which i s an order of magnitude

g r e a t e r than t h e previous case (30).

The atom f r a c t i o n of trit-

The tritium concentration i n t h e

helium depends on t h e flow r a t e of helium coolant and t h e tritium diffu-

sion rate.

Again, additions of protium could lower t h e tritium concen-

tration. However, t h e d i f f i c u l t y of removing tritium from Li-Al depends upon both t h e equilibrium tritium concentration i n Li-A1 and t h e tritium d i f f u s i o n rate i n Li-Al.

An experimental study by W i s w a l l and Wirsing

( 4 3 ) t e s t e d t h e removal of tritium from granular forms of Li-Al, LiAlO and L i S i 0 2

The procedure w a s t o f l u s h helium through a bed of irra-

diated compounds at a controlled temperature i n t h e range 400 t o 600Oc.

T r i t i u m , generated by exposure t o thermal neutrons, diffused out of a

sample and w a s c a r r i e d t o a tritium monitor. i ' i :

The d a t a c o l l e c t e d were

not successfully analyzed i n terms of a physical model.

Removal r a t e s

were increased both by an increase i n t h e helium flow rate and by addit i o n s o f 1000 ppm of hydrogen t o t h e helium; t h i s shows t h a t surface sorption i s important.

Yet, t h e escaping rate increased with a decrease

i n p a r t i c l e s i z e , which i n d i c a t e s a slow d i f f u s i o n within t h e a l l o y . This would a l s o result from surface sorption, f o r t h e same loading, and surface r e s i s t a n c e .

CHAPTER I11

THEORY

The recovery of tritium from CTR materials depends on i t s d i s t r i b u -

These f a c t o r s are de4ermined by tritium

t i o n and leakage c h a r a c t e r i s t i c s .

s o l u b i l i t y i n t h e contacted materials, tritium d i f f u s i o n rates through r e a c t o r f l u i d s and s t r u c t u r a l components, and t h e formation o f stable compounds. The r e a c t i o n f o r s o l u t i o n s of tritium i n a metal can be w r i t t e n as

follows :

where X ( d ) = dissolved i n m e t a l phase,

T2(d

= tritium gas.

The equilibrium constant f o r t h e r e a c t i o n i s :

eq. 10

where K = equilibrium constant,

a = a c t i v i t y of substance,

= tritium p a r t i a l pressures, pT2 y = a c t i v i t y coefficient,

N = concentration.

jfd i !

approaches zero, 'X( d ) and 'XT(d) become constant. I n d i l u t e XT(d) solutions of tritium i n metals, t h e r e l a t i o n s h i p between s o l u b i l i t y and

As N 6

j t

pressures i s given by S i e v e r t s ' l a w (27,33,36):

where

= tritium concentration i n t h e metal phase,

= tritium p a r t i a l pressure,

p T2 k

= S i e v e r t s ' constant.

S i e v e r t s ' constant i s exponentially dependent on temperature, as follows:

where 0

= material-related constant

Qs = a c t i v a t i o n energy f o r t h e solution of tritium i n t h e m e t a l , k = Boltzmann's constant,

T = absolute temperature,

OK.

According t o Cantor and Grimes (61, t h e s o l u b i l i t y of tritium i n molten

salt i s related by Henry's l a w , which i s expressed as follows:

NT = P

eq. 13

where

j i

% = Henry's

l a w constant.

The permeation of tritium through bulk m a t e r i a l i s given by t h e

equation

eq.

where Q = f l u x of tritium through t h e i n t e r f a c e , A = a r e a of t h e i n t e r f a c e , X = thickness of t h e i n t e r f a c e ,

p = tritium pressure on a s i d e of t h e i n t e r f a c e (pi > Po), B = material-related parameter, â&#x201A;Ź$ = material-related parameter.

T r i t i d e s a r e r e a d i l y formed s i n c e hydrogen and i t s isotopes r e a c t w i t h nearly every element.

Table I i l l u s t r a t e s t h e behavior of hydrogen

w i t h groups of t h e periodic t a b l e .

TABLE I

HYDROGEN REACTIONS WITH THE ELEMENTS ( 4 0 ) __

Elements

Period

S, Se, Te, Po P, A s , Sb, B i S i , G e , Sn, Pb A l , Ga, In, T i

Type of Hydrogen Bond Covalent

Hydride Character Decomposable gases of l i q u i d s (except s o l i d A1H )

VIA VA IVA IIIA

0, N, C, B,

VIIA

F , C 1 , B r , I, A t

Ionic with t h e hydrogen e l e c t r o positive

Corrosive gases or liquids

IIA IA

Be, Mg, C a , Se, Ba, Ra L i , N a , K, Rb, C s , Fr

Ionic with t h e hydrogen e l e c t r o negative

S a l t l i k e (except noncrystalline BeH2)

IIB IB VIIIB VIIB VIB

Zn, Cu, Co, Mn,

Cd, Hg Ag, Au, N i , Pd, P t R h , Ir, Fe, Ru, Os Tc, R e C r , Mo, W

Endothermic hydrogen occluder; no compound formation (except exothermic palladium)

Metallic; usually ductile

VB IVB IIIB

Y , Nb, T a Ti, Zr, H f s c , Y, La,&

Exothermic hydrogen occluder ; m e t a l l i c or i n t e r s t i t i a l compound formation

Metallic; usually brittle

All lanthanides

b A l l actinides

A C ~

CHAPTER IV I

EXPERIMEXTAL APPARATUS AND PROCEDURE Reagents The bismuth w a s obtained f r o m t h e Cominco American Company (99.9999% purity).

The l i t h i u m metal w a s supplied by Fischer S c i e n t i f i c Company.

J u s t p r i o r t o loading under an argon atmosphere, t h e pure l i t h i u m w a s cut and cleaned of oxide film.

The Li-A1 a l l o y w a s prepared by t h e Metals

and Ceramics Division of ORNL.

The procedure consisted of wrapping known

amounts of l i t h i u m i n aluminum f o i l , submerging t h e packets i n t o a known quantity o f molten aluminum (99.999% p u r i t y ) contained i n a molybdenum crucible, and continually mixing t h e alloy with a molybdenum s t i r r e r . 50-50 a t .

% mixture w a s then c a s t i n t o l/b-in.-OD

w a s approximately

rods ( 9 ) .

1 / 4 t o 1 / 2 i n . long and weighed about 0.5

rods were t h i n l y coated with a b l u i s h oxide film.

Each sample g.

The a l l o y

The i n t e r m e t a l l i c com-

pound Li-A1 i s a s o l i d s o l u t i o n between 45 and 56 a t .

% l i t h i u m (18).

Li-A1 displays a g l a s s l i k e b r i t t l e n e s s , and i t s density has been determined as 1.725 g/ml a t room temperature ( 2 ) .

The equiatomic composition

m e l t s a t 718Oc. A l l gases were of t h e highest p u r i t y commercially available.

Argon,

which w a s used as t h e i n e r t cover gas, w a s f u r t h e r p u r i f i e d by passage through a titanium sponge t r a p ; t h e lower s e c t i o n was held a t 600Oc f o r t h e removal of oxygen and water, and t h e upper portion w a s held a t about t

T r i t i u m , obtained from t h e ORNL Isotopes

2OO0C f o r t h e removal of hydrogen. Division, w a s supplied i n 3/8-in.

glass ampules, each containing 1 C i i n

a volume o f 1 m l (pressure equal t o

324 t o r r ) .

Apparatus L i - B i Sorption System.

Equilibration and tritium sorption w e r e con-

ducted i n a v e s s e l of t h e type shown i n Fig. 2.

The apparatus has been

used previously at ORNL f o r phase e q u i l i b r i a s t u d i e s of molten s a l t s and molten metal systems (12). detail.

Figure 3 i l l u s t r a t e s t h e reaction v e s s e l i n

The v e s s e l w a s f a b r i c a t e d from a 22-in.

s t a i n l e s s s t e e l pipe.

l e n g t h of 2-in.-OD

Cooling f i n s welded t o t h e e x t e r i o r of t h e upper

s e c t i o n o f t h e v e s s e l served both t o cool and t o support t h e v e s s e l when it w a s positioned i n a well-type furnace, which heated 6 i n . of t h e container.

A gas o u t l e t tube w a s welded i n t o t h e pipe between t h e furnace

support and t h e flange.

The upper flange s e c t i o n w a s f i t t e d with a 1/2-

i n . b a l l valve, a thermocouple p o r t , and a 1/4-in.-diam tube

1 0 t o 20-mil w a l l thickness).

molybdenum sparge

A Cajon O-ring f i t t i n g at t h e t o p

of t h e sparge tube allowed r a i s i n g and lowering.

A Teflon plug, through

which t h e samplers were i n s e r t e d , w a s held i n place by another O-ring, which was connected t o t h e top of t h e b a l l valve.

The Li-Bi a l l o y was

contained i n a molybdenum crucible 6 in. long, 1-1/2 in. I D , and 1-3/4

i n . OD.

The molybdenum c r u c i b l e f i t t e d l o o s e l y i n t h e reaction vessel

as shown i n Fig. 3 .

The apparatus was operated i n a radiochemical hood,

which a l s o provided secondary containment of tritium. The temperature of t h e system w a s measured by a c a l i b r a t e d ChromelAlumel thermocouple and recorded by a Brown potentiometric recorder. temperature o f t h e system w a s c o n t r o l l e d with

The

2 2OC by a Wheelco propor-

t i o n a l c o n t r o l l e r operating from a c o n t r o l thermocouple, which w a s placed against t h e e x t e r i o r w a l l of t h e r e a c t o r vessel.

O W L DWG. 75-5342R1

LIQUID SA MPLE PORT

G A S SAMPLE (VOL.rn4.5 c c )

THERMOCOUPLE

II STAINLESS STEEL VESSEL (vOL.-80Oc~)

! !

Mo CRUCIBLE

L i - B i ALLOY I

Figure 2.

Apparatus for Study of T r i t i u m i n Li-Bi Alloy.

I I

I ~

l i i

ORNL DWG. 75-8304R1

ARGON OR VACUUM EFLON PLUG

STAINLESS STEEL FILTER-SAM PLER MOLYBDENU SPARGE TUBE

CAJON O-RING F'ITTING

/BALL

VALVE

-THERMOCOUPLE

TEFLON O-RING

GAS SAMPLE PORT-

MOLYBDENUM

CRUClB LE

-Li-E3i ALLO'

Figure 3. Reaction Vessel f o r Studying t h e Sorption of T r i t i u m in Li-Bi Alloy.

18 i I

The samplers were constructed as follows: "The f i l t e r - t y p e samplers were f a b r i c a t e d of s t a i n l e s s s t e e l . The 1-in.-long body w a s d r i l l e d from heavy-walled, 1/4-in.OD tubing, leaving a 1/8-in.-thick shoulder on one end; t h e w a l l thickness a r t e r d r i l l i n g w a s about 30 m i l s . A 20-in. length of 1/16-in.-OD c a p i l l a r y tubing w a s welded i n t o t h e shoulder t o provide t h e s t e m f o r t h e sampler. The sampler w a s completed by welding a disk of FELTMETAL f i b e r m e t a l (Huyck Metal Co., product No. FM 225), having a median pore s i z e of 20 1-1, i n t o t h e open end of t h e body." (12) Li-A1 Sorption System.

The preliminary sorption apparatus w a s con-

s t r u c t e d of Pyrex t o minimize tritium permeation from t h e system.

4 shows

a schematic of t h e equipment.

Figure

Four Pyrex sample tubes were

attached by ground-glass j o i n t s t o a 4-ft-long

by 1/2-in.-OD

manifold;

a mechanical vacuum pump w a s connected t o one end of t h e manifold.

Dow-

Corning high-vacuum grease (No. 970V), a nonmelting s i l i c o n e l u b r i c a n t ,

w a s sparingly applied t o t h e ground-glass and stopcock j o i n t s . vacuum stopcocks were used throughout t h e system.

High-

The pressure of t h e

system w a s measured by a V i r t i s McCloud mercury manometer (0.005 t o 5.00 t o r r ) and a Hastings vacuum gauge

t o 1t o r r ) .

Each sample tube w a s positioned i n a l-l/b-in.-ID

clamshell furnace.

The temperature of each sample w a s measured by a c a l i b r a t e d ChromelA l u m e l thermocouple and indicated on a Doric D i g i t a l Thermocouple I n d i c a t o r

(No. DS-300) (-50 t o +135OoC).

+ 2OC by

The temperatures were controlled within

a Wheelco proportional c o n t r o l l e r operating from a c o n t r o l

thermocouple placed against a copper s h i e l d i n s i d e each furnace. The tritium leakage from t h e ground-glass j o i n t s and vacuum stopcocks w a s excessive at t h e 1 - t o r r tritium p a r t i a l pressure involved. Although g l a s s j o i n t s proved t o be adequate f o r previous ORNL s t u d i e s o f

tritium sorption i n lithium, t h e r e s u l t i n g e r r o r s became s i g n i f i c a n t when

I I

O W L DWG. 75-8300R1

V2"O.D.

TO MCCLOUD PRESSURE GAUGE

--1/8"0.D. THERMOCOUPLE WELL

I"O.D. cu ~ I N G 6"LONG

Figure 4. I n i t i a l Equipment Design f o r Studying Sorption of T r i t i u m i n Li-Al Alloy.

20 materials with low tritium uptake were used.

Thus, a more r e l i a b l e s t a i n -

less s t e e l system w a s b u i l t . Figure 5 shows a schematic of t h e revised tritium sorption system used i n t h i s study.

The pumping system had been used previously at ORNL

as p a r t of a S i e v e r t s ' apparatus f o r obtaining measurements of equilibrium i

hydrogen isotope s o l u b i l i t i e s i n lithium (35).

This pumping system con-

s i s t e d of a mechanical pump coupled t o a Consolidated Vacuum Corporation o i l diffusion pump.

The pressure measurement instruments included two

Wallace and Tiernan precision pressure gauges, Model ~ ~ 1 (60 0t o 20 t o r r ) and Model 62A-4D-0800 t o 1t o r r ) .

-3

( 0 t o 800 t o r r ) , and a Hastings vacuum gauge (10

The sorption system consisted o f four 1/2-in.-OD

long quartz sample tubes connected t o a 3-ft-long w a s constructed of 1/4-in. l i n e d w i t h a 10-in.-long less s t e e l tube.

s t a i n l e s s s t e e l tubing.

by 3/8-in.-OD

manifold.

by 14-in.The manifold

Each quartz tube w a s

thin-walled (about 1 0 m i l ) s t a i n -

A Cajon O-ring f i t t i n g connected each quartz tube t o a

Hoke vacuum valve, which w a s attached t o t h e sorption manifold by another O-ring j o i n t .

Hoke vacuum valves were used throughout t h e system.

Figure

6 shows a photograph of t h e equipment. Each sample tube w a s positioned i n a l-l/h-in.-ID

clamshell furnace

by r a i s i n g a lab-jack which had been placed underneath each furnace.

The

temperature of each sample tube w a s measured by a c a l i b r a t e d ChromelAlumel thermocouple and recorded by a Brown potentiometric.recorder.

Wheelco proportional c o n t r o l l e r regulated temperatures within

2OC.

c o n t r o l thermocouple w a s placed against a copper s h i e l d i n s i d e each furnace.

Figure 5 . Li-Al Alloy.

Revised Apparatus for Studying Sorption o f T r i t i u m i n

Figure

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

. .

........

.......

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

Photograph of t h e Equipment Used t o Measure T r i t i u m Sorption i n Li-A1 Alloy.

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

LJ Operational Procedures Li-Bi c

Sorption System.

About 600 g of bismuth and 3.47 g of l i t h i u m

( Q 15 a t . %) were loaded under an argon atmosphere i n t o a molybdenum cru-

c i b l e , which w a s placed i n s i d e t h e reaction vessel. s e c t i o n was b o l t e d i n t o place. surized with argon.

The upper flange

To t e s t f o r leaks, t h e v e s s e l was pres-

After ensuring t h a t no leaks w e r e present, t h e sys-

tem was heated t o 600Oc t o m e l t t h e Li-Bi for sample analysis. Sampling Procedure s e c t i o n . )

(See

The molybdenum sparge tube w a s lowered i n t o

t h e molten m e t a l , and argon was bubbled through t h e L i - B i .

The tritium

ampule was attached t o t h e sparge tube; t h e system w a s evacuated t o about I

0 . 1 t o r r ; and t h e s e a l within t h e ampule w a s broken.

To break t h e g l a s s

s e a l , a small m e t a l bar w a s placed i n s i d e t h e ampule before attaching it r^

t o t h e sparge tube.

Then a magnet w a s used t o p u l l t h e b a r through t h e

s e a l , r e l e a s i n g t h e tritium.

Argon w a s subsequently passed through t h e

sparge tube t o sweep t h e r e s i d u a l tritium i n t o t h e Li-Bi a l l o y ; t h e t o t a l system pressure w a s thereby increased t o about 3 p s i .

Throughout t h e

experiment (except during sampling), t h e system w a s kept under a 1- t o >-psi s t a t i c argon pressure.

A period of a t 'least 24 hr w a s allowed t o

a t t a i n equilibrium at each temperature (500, 600, or 7 O O O C ) .

P a i r s of

l i q u i d and gas samples w e r e removed f o r analysis. Sampling Procedure. before use.

Each sampler w a s polished with emery paper

The stem of t h e sampler was then forced through a hole i n

t h e Teflon plug and connected t o a f l e x i b l e tube which leads t o a manir

f o l d supplying both argon and vacuum.

The sampler w a s placed i n t h e upper

chamber of t h e b a l l valve, and argon w a s flushed through t h e sampler and chamber f o r s e v e r a l minutes.

Subsequently, t h e Teflon plug was i n s e r t e d

i n t o t h e O-ring f i t t i n g and tightened.

The b a l l valve w a s then opened

and t h e sampler, with argon flowing through it, w a s lowered and positioned

i n the l i q u i d alloy.

The flow of argon w a s continued for 2 t o 5 min while

t h e sampler was heated t o t h e temperature of t h e a l l o y .

w a s stopped, and a vacuum w a s applied t o t h e sampler.

The argon flow Li-Bi r a p i d l y

f i l l e d ( < 1 0 s e c ) t h e sampler and s o l i d i f i e d i n t h e cool p a r t of t h e c a p i l l a r y s t e m , thus s e a l i n g t h e sampler.

The sampler w a s then drawn i n t o

t h e upper chamber, and t h e b a l l valve w a s closed.

The outside of t h e

f i l l e d sampler w a s c a r e f u l l y polished with emery c l o t h , and t h e stem and f i l t e r ends were removed with tubing c u t t e r s . t h e sampler contained about 2 g of Li-Bi.

The remaining p a r t of

The m e t a l sample w a s dissolved

i n n i t r i c acid, and t h e solution w a s analyzed f o r tritium. Gas-phase sampling involved f i r s t inducing a vacuum on t h e 4.5-mlvolume gas sample tubing.

The sampler w a s f i l l e d by opening a valve t o

t h e v e s s e l and r e l e a s i n g t h e gas.

The valve t o t h e r e a c t i o n v e s s e l w a s

then closed, and t h e gas sample w a s slowly flushed t o t h e analysis system by using argon containing a t r a c e of hydrogen as a c a r r i e r gas.

For trit-

i u m concentrations below 5 x 1 03 r \ C i / m 3 , t h e vapor phase w a s analyzed by a Triton monitor (Johnston Laboratory, Inc.

, Model

10.55 B )

For higher

tritium concentrations, t h e tritium was oxidized a t 600Oc on CuO and trapped i n water bubblers.

Samples of t h e bubbler f l u i d s w e r e analyzed

by l i q u i d s c i n t i l l a t i o n . Li-AI. Sorption System. as described below.

The preliminary g l a s s apparatus w a s operated

One rod-shaped Li-A1 sample w a s loaded under an i n e r t

atmosphere i n t o each Pyrex tube.

A vacuum stopcock w a s attached t o each

sample tube and closed a l s o under an i n e r t atmosphere.

The sorption

manifold w a s evacuated and checked f o r leaks.

The sample tubes were

fastened t o t h e manifold, and t h e t o t a l system w a s pumped down t o about t o r r t o remove any r e s i d u a l gas.

A f t e r ensuring t h a t t h e r e were no leaks, t h e sample tubes were posi-

tioned i n t h e furnaces, heated t o about 4OO0C,

and continually evacu-

a t e d , as t h e Li-A1 outgassed, u n t i l t h e system pressure remained steady. I

T r i t i u m w a s added as described i n t h e Li-Bi sorption experiment.

Usu-

a l l y , a t least 24 h r w a s allowed f o r t h e L i - a samples and tritium t o equilibrate.

F i n a l l y , t h e sample tubes were quickly cooled with a flow

of a i r t o ambient temperature and t h e samples were removed f o r analysis. The procedure f o r operating t h e s t a i n l e s s s t e e l system w a s similar

t o t h a t used f o r t h e Pyrex equipment. stainless-steel-lined

A sample w a s loaded i n t o each

quartz tube under an i n e r t atmosphere.

The sample

w a s e i t h e r used i n rod form or w a s crushed i n t o a powder (< 20 mesh). f

The vacuum valve w a s attached t o t h e tube and t i g h t l y closed under an i n e r t atmosphere. ated.

The pumping system and sorption manifold were evacu-

A f t e r ensuring t h a t no leaks were present, t h e sample tubes w e r e

fastened t o t h e evacuated manifold. -2

down t o approximately 1 0

Then t h e e n t i r e system w a s pumped

t o r r t o remove any r e s i d u a l gas.

Again, t h e

system w a s t e s t e d f o r leaks, and t h e sample tubes were positioned i n t h e furnaces and heated.

The system w a s continually evacuated u n t i l t h e

pressure remained steady. i

a g l a s s ampule.

T r i t i u m w a s added t o t h e sorption system from

The amounts of tritium used ranged from 1 t o

Ci.

The

Li-A1 samples and tritium were allowed t o e q u i l i b r a t e f o r at least 24 h r

at temperatures ranging from 400 t o 600Oc.

A f t e r t h e samples had cooled

t o ambient temperature, they were removed f o r analysis.

Analytical Procedure (.

The Li-Bi and Li-A1 samples were analyzed by dissolving them i n n i t r i c a c i d and counting a d i l u t e portion of t h e r e s u l t i n g s o l u t i o n s by liquid scintillation. t i o n process.

Figure 7 shows t h e apparatus used i n t h e dissolu-

A sample w a s placed i n a 300-ml r e a c t i o n flask.

After an

argon sweep gas had been established, a quantity of warm 75% n i t r i c a c i d i n excess of t h e amount necessary t o r e a c t w i t h t h e sample w a s poured i n t o the flask.

A s t h e sample dissolved, t h e released tritium w a s oxidized by

hot CuO (600Oc) and captured i n water bubblers.

A trace of hydrogen w a s

added t o t h e argon t o continuously f l u s h tritium from t h e CuO bed and tubing w a l l s .

Since t h e granular Li-A1 samples reacted v i o l e n t l y when

n i t r i c a c i d w a s added, a modified technique w a s used t o dissolve t h e crushed samples.

A sample was placed i n t o t h e r e a c t i o n f l a s k , and water

w a s slowly sprayed from a syringe t o s t a r t t h e d i s s o l u t i o n .

Once t h e

r e a c t i o n was controlled, n i t r i c a c i d w a s added and t h e a l i q u o t s w e r e analyzed.

The gas-phase samples were a l s o swept through t h e CuO bed,

and t h e tritium w a s trapped i n t h e water bubblers.

About 90% of t h e oxi-

dized tritium w a s captured i n t h e first bubbler; t h u s , e s s e n t i a l l y all t h e tritium was trapped by two bubblers i n series.

The tritium monitor

d i d not r e g i s t e r above background tritium i n t h e gas e x i t i n g t h e second

water bubbler. Diluted a l i q u o t s from t h e reaction v e s s e l and t h e w a t e r bubblers were analyzed by conventional l i q u i d s c i n t i l l a t i o n techniques.

The scin-

t i l l a t i o n s o l u t i o n recipe was: 12 g PPO ( 2,5-diphenyloxazole ) 0.3 g POPOP (1,4-b&-2( 5-phenyloxazoly1)benzene) 2010 m l of toluene 990 ml of Triton X-100 (an emulsifier product of R o b and Haas)

One milliliter of the sample solution was mixed with 10 m l of the scintils

lation counting solution. The tritium in each solution was detected by a Packard Model 574 Tri-carb scintillation spectrometer, which had an efficiency of about 20%. Samples were a l s o analyzed by a similar method by the ORNL Analytical Chemistry Division.

ORNL DWG. 75-5344

- VENT 600 OC

R E ACTION I

FLASK

:..

& 5

.. < .+.. I .I

WATER BUBBLERS

Figure 7. Sample Dissolution Apparatus for Tritium Analysis.

28 CHAPTER V

EXPERIMENTAL DATA

Li-Bi Sorption System

The a n a l y t i c a l results i n Table I1 and Table I11 show t h a t t h e quan-

t i t i e s of tritium sorbed by molten L i - B i were very low.

Because o f t h e

d i f f u s i o n of tritium through t h e stainless s t e e l r e a c t o r and t h e leakage during sampling, t h e t o t a l amounts of tritium continuously decreased from

-4

t h e i n i t i a l 1 C i addition t o about.10

Ci.

Therefore, t h e s o l u b i l i t y of

tritium i n Li-Bi ranged from about 0 . 1 . t o 0.01 ppb, respectively. ' M u l t i p l e metal-phase samples were taken t o check t h e r e p r o d u c i b i l i t y of t h e sampling and analysis techniques.

However, samples 2 . 1 t o 2.7 were

exceptions, and t h e values i n Table I1 represent only one concentration value r a t h e r than an average of s e v e r a l values as do t h e remainder of samples.

Since t h e tritium concentration i n t h e gas w a s s u b s t a n t i a l l y

g r e a t e r than t h a t i n t h e L i - B i ,

cross-contamination w a s found from using

one CuO bed and contaminated bubblers.

Consequently, t h e lowest concen-

t r a t i o n value w a s used f o r t h e f i r s t seven samples.

For t h e r C s t of t h e

samples, a separate c a t a l y s t bed w a s used f o r each phase a n a l y s i s and all glassware w a s c a r e f u l l y cleaned between runs.

Reproducibility o f

t h e gas-phase analyses i n Table I11 w a s checked by a tritium monitor at

l e v e l s of l e s s than 5 x 1 0

pCi/m

The i d e a l gas l a w w a s applied t o determine tritium p a r t i a l pressures above t h e Li-Bi phase.

Data were taken at 500, 600, and 7OO0C.

How-

ever, most of t h e simultaneous gas and metal sampling was done a t 600Oc. Figure 8 shows a l l t h e d a t a points and a least-squares f i t of t h e d a t a

at 600Oc.

The equation represented by t h e s t r a i g h t l i n e is:

TABLE I1

RESULTS OF Li-Bi METAL PHASE ANALYSES FOR TRITIvM& Sample No.

Temp

Sample Wt

("C)

(€3 1

2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8A 2.8B

600 600 500 600 700 500 600

2.1573 1.go43 0.8304 1.8375

700

1.8659

2.9~ 2.9~ 2.9~

500

210A 210B 210c

600

21u 211B 211c

700

3.lA 3.1B

500

3.2A 3.2B

700

3.3A

600

3.3B

dpm/d x

1.9409

105

78.03 32.9 267

1.7661 1 9991

107 32.7 11.og 12.89

Tritium Concentration in Li-Bi Ci Q PPb

1.645 x 7.409 x 6.013 x 2.409 x 7.365 x 2.498 x 2.903 x

1.704 x

loW6

7.676 x 6.229 x 2.496 x 7.630 x 2.588 x 3.008 x

0.0878 0.0435 1 0 ' ~ ~0.3129 0.1157 0.0401 0.0312 0.0164

at. %

6.057 x

10'~

3.001 x 2.159 x 7.982 x 2.766 x 10'~ 2.152 x 1.131 x

2.98 2.16

6.712 x 10'~ 4.865 x

6.954 x

2.1041

5.040 x

0.00239 0-00373)

2.0251 2.3340 2.3196

2.99 2.92 2.19

6.734 x low8 6.577 x

6.976 x 6.814 x

0.00345

4.932 x

5.106 x

0.00220

1.80 x 10-7 1.113 x 1.054 x

1.865 x 1.153 x 1.092 x

0.00886

2.236 x 10-7 8.806 x 8 ' 0 1 2.189 x

2.316 x 10-11 9.123 x lO'l2 2.268 x 10-11

0.01063

2.407

8.288 x 10-8 5.421 x 10-8

8.586 x 10-12 5.616 x 10-12

0.00270 0*00564} 2.877 x

21.44 9.593

4.828 x 10-7 2.161 x 10-7

5.002 x 10-11 2.239 x 10'11

0.0109 0*02453

1.122

5.73

1.291 x 10-7 1.171 x

1.337 x 10-11 1.213 x 10'11

0.00591 0.00552)

3.943 x 10'8

2.1038

8.00

1,9041

4.94

1.6492

4.68 9.93

2.1793 2.2471

1.5147 1.5229 2 0795 2.0424 2.0452 2.4211 2.0520

3.91 '

9-72

3.68

5.20

&Sample calculations of values appear in Appendix B.

2.111 x 10-8

1.971 x

10-8

4.953 x

10'~

0.00662 6.821 x 10-8 0.01497

10-7

TABLE I11 RESULTSOF GAS-WE

IWAIYSES FOR TRITIUM CONCE~BTRATION~

Tritium Concentration in Gas Phase Sample No.

Temp ("C)

By Liquid Scintillation

By Tritium

Monitor

(~~i/m3)b

(dpm/ml)

T2 Partial Pressure (torr)

600

1.131 x 10'

4.528 x

4.691 x

1.059 x''01

2.2

600

6 1.941 x 10

7.772 x

8.052 x

2.3 2.4

500 600

1.802 x lo7 3.574 x lo6

7.215 x 1.431 x

7.475

1.819 x 1.495 x 10-1

2.5 2.6

700

9.730 x lo5

2.1

2.7

500 600

2.8

700

1.480 x 10

500

2.629 x lo5

2.10

600

1.726 x lo5

3.1 3.2 3.3

700 500

700 600

4.036 x

1.016 x l d 2

2.074 x

.4.148 x

1.913 10-3 1.306 x 10-3

1.982

4.9 x 103

5.926 x

6.139 x

1.545 x

1.091 x

2.182 x

3.9 x 103

1.053 x 10-3 1.037 x 10-3

1.680 x lo5

10-7

4.477

6.911 x

7.243 x

1.636 x

2.5 x 103

6.665 3.946

4.088 x

1.029 x

8.0 x 103

2.128 x 2.613 x 2.594 10-4

2.707 x

5.414 x

3.702 x

3.835 x

9.654

3.724 10-4 6.727 x 5.466 10-4

6.969 x lo-'

1.574 x

6.525 x 104

3.349 x

9.854 x 104

9.246 x 10

1.483 x

2.002 x

6 5.011 x io 4.778 lo5

2.9

2.11

3.896

9.75 x lo2 1.4

103

2.05 x 103

x 10-4 x

a Sample calculations of values appear in Appendix B. bTritium monitor is useful for tritium concentrations of < 5.0 x lo3 vCi/m 3 (< 1.33 X

Ci).

31 O W L DWG. 75-8301Rl

I L

b w

a I) v)

w IO"

a a

-I

a ta a a

10-3

I 0-7 10-6 I TRITIUM CONCENTRATION ( at. % T I IN Li-Bi

Figure 8. T r i t i u m Concentration i n L i - B i Samples at t h e Corresponding T r i t i u m P a r t i a l Pressure.

.32

bj eq, 1 5

where

= tritium p a r t i a l pressure above' t h e L i - B i ,

torr,

pT2 NT = f r a c t i o n of tritium i n t h e L i - B i ,

at.

From s t a t i s t i c a l a n a l y s i s , t h e data a t 60ooc f a l l within t h e 95% confidence i n t e r v a l which i s 1.288

2 0.535 (1.823 t o 0.753) f o r t h e slope of

the line. Li-AI. Sorption System

The tritium sorption data f o r Li-A1 are shown i n Tables I V and V. The time-dependent data of Table V I a t 40OoC were measured when t h e system pressure w a s not remaining steady.

The leakage problem w a s resolved, f

and constant-pressure measurements were' taken ( s e e Table V ) most reliable data points are presented i n Table V.

Also, t h e

P a r t i a l dissolution

o f Li-AI. samples shows t h a t t h e concentration of tritium decreases as a function of dissolved Li-AI. (Table I V ) .

Figure 9 shows t h e data graphi-

ca l l y . The l i m i t e d d a t a have noticeable discrepancies; however, t h e tritium concentration i n t h e rod samples range from 0.01 t o pressures of 0.14 t o 5.42 t o r r , respectively.

w t ppm f o r tritium

The concentration of

tritium w a s generally higher i n most of t h e powdered samples. The chemical properties of Li-A1 were more complex than w a s i n i t i a l l y anticipated.

According t o t h e phase diagram (18), Li-A1 forms an equic

atomic homogeneous s o l i d solution. some material v o l a t i l i z e d .

Yet, during heating of t h e samples,

A r i n g of a shiny, m e t a l l i c s i l v e r substance

TABLE IV RESULTS OF Li-A1 ANALYSES FOR TRITIUM AT 4 0 0 O C

Sample No.

All A1 2 A1 3

2A11 2A12 2A1

Time ( days

1.76 2.75 5 -78 0.95 3.75 0.89

Pressure (torr) Initial Final

0.66 0.66 0.66 1.36 1.36 1.36

Sample

(g>

0.545 0 455 0.450 0.78 0.79 0.58

1.17 2.18

2.37 1.06 3.40 1.02

T r i t i u m Concentration i n L i - A l dpm/ml wt PPm at.

6.60 1.25 7.64 1.14 4.22 2.37

lo9

0.565

x 1 010

1.282

109

792 0.682 2.661 1 9 -07

x 10” x 10”

x 1 011

4.305 x 9.765 x 10-4 6.035 x 10-4 5.195 x 2.027 x 10” 1.453 x

Li-A1 P a r t i a l Dissolution Results Percent Sample Dissolved A 1 2.1

Al 3.2 A1 1

Al 3.1 Al 2.2 aPowder.

5-92 5*92 5-92 5.92 5.92

1.20

1.20. 1.20

1.20 1.20

5.42 5.42 5.42 5.42 5.42

0.8036 0.8968 1.7018 0.6110

0.5050

13.2

15.7 49.8 68.8 100.0

3.96 3.53 1-39 3.22

1.07

3.04 2.70 1.06 x 2.64 8.18 x

TABLE V TIME-INDEPENDENT RESULTS OF Li-A1 ANALYSES FOR TRITIUM

Sample W t

Sample No.

Temperature

4Al2

500

0.46

0.52

4.11

4 A1 3

500

0.48

0.52

2.08

3Al1 3 Al 3& 4Al1

550

0.458

0.14

0.013

550

0.413

0.14

0.067

-6 9.96 x 10 5.14 10-5

550

0.39

0.53

0.136

1.04

4 Al 4&

550 * 600

0.50

0.53

0.534

0.13

("C

3Al2

cg 1

Pressure [torr 1

T r i t i u m Concentration i n Li-A1 w t PPm at. %

33.29

3.14 1.59

2.36 x lo-*

0.158

1.21

Most Reliable Data

5Al1

400

5 A1 2 5 A1 3 5 A1 4

C,! ,

0.032

0.343

2.62

450

0.35 0.37

0.0325

0.467

3.58

500

0.29

0.029

0.513

3.92 x 10

550

0.29

0.028

1.086

8.32

-4

lom4

ORNL DWG. 75-8294R1 1 -

\ \

---.

----O----

LEAST-SQUAFES

\ \

20 O/O

40 60 80 Li-AI SAMPLE DISSOLVED

100

Figure 9. Tritium Concentration as a Function of Percent Li-A1 Sample Dissolved.

36 condensed on t h e cooled portion of t h e quartz sample tube.

Initially,

s t a i n l e s s , s t e e l l i n e r s were not i n s e r t e d i n t h e sample tubes t o contain t h e Li-Al;

t h e quartz tubes were attacked and cracked by t h e substance.

S i l i c a compounds, such as quartz, are rapidly attacked by molten l i t h i u m

(1.5); t h e r e f o r e , it was suspected t h a t excess l i t h i u m was present.

analyze t h e constituents o f t h e v o l a t i l i z e d material, a time-of-flight mass spectrometer experiment w a s conducted by John Redman of t h e ORNL

Chemistry Division.

Several Li-A1 samples were analyzed both under

vacuum and with a pure hydrogen flow.

The temperature of t h e sample

ranged from 400 t o 650Oc; however, no lithium-containing vapor species were observed.

This behavior needs t o be v e r i f i e d before Li-A1 i s

s e l e c t e d for a CTR blanket material.

37 CHAPTER V I DISCUSSION OF RESULTS L i - B i Sorption System

The s o l u b i l i t y of tritium i n molten L i - B i

15 a t .

% lithium) was

determined t o be l e s s than 1 0 ppb a t temperatures ranging from 500 t o 70OoC.

Therefore, an e x t r a c t i o n process based on t h i s a l l o y would not

be f e a s i b l e . The pressure-concentration r e l a t i o n s h i p of Equation 1 5 does not correspond t o S i e v e r t s ' l a w (Equation 11) o r Henry's l a w , which states t h a t t h e tritium p a r t i a l pressure would be d i r e c t l y proportional t o i t s concentration i n t h e s o l u t i o n .

If data followed Henry's l a w , t h e e r r o r

of t h e slope could be due t o impurities i n t h e m e t a l . of i n t e r m e t a l l i c L i - B i

However, formation

compounds could cause a slope between 1 and 2.

temperature dependence cannot be determined from t h e s c a t t e r of d a t a from Fig. 8. tions.

Further experiments would be needed t o provide t h e s e correlaSince t h e data c l e a r l y show t h a t t h e proposed process i s not

p r a c t i c a l , no f u r t h e r experiments were made i n t h i s area. With appropriate equipment a l t e r a t i o n s , t h e leakage rate of tritium could be reduced and t h e sampling technique could be improved.

Neverthe-

l e s s , a t such low s o l u b i l i t y l e v e l s , t h e s e n s i t i v i t y of t h e l i q u i d scint i l l a t i o n counting of samples could not be increased t o enhance t h e accuracy o f t h e data.

Thus it was concluded t h a t , due t o t h e low sorp-

t i o n of tritium i n L i - B i ,

t h e proposed e x t r a c t i o n process would not

s u f f i c e as a tritium recovery method f o r a CTR molten salt blanket. Further experiments are not l i k e l y t o a l t e r t h e s e conclusions.

One reason f o r t h e low s o l u b i l i t y of tritium i n L i - B i i s that t h e l i t h i u m present i s bonded s o strongly with bismuth (18) t h a t lithium t r i t i d e i s not e a s i l y formed.

It has been suggested t h a t Li-Pb, which

i s chemically s i m i l a r t o t h e Li-Bi a l l o y , be used f o r neutron s h i e l d s , and collimators (15).

Previous s t u d i e s suggest t h a t t h i s material i s

p o t e n t i a l l y u s e f u l because it i s r e l a t i v e l y inexpensive, e a s i l y handled and fabricated, and stable i n a i r at temperatures over 2OO0C and neutron

fluxes of t h e order of 10l2 neutrons/cm

sec.

But, it was a l s o consid-

ered useful because it w a s assumed t h a t t h e tritium produced would be bound chemically, as lithium t r i t i d e , within t h e Li-Fâ&#x20AC;&#x2122;b.

This i s doubt-

f u l due t o t h e low s o l u b i l i t y of t r i t i u m i n Li-Bi which w a s determined

i n t h i s investigation.

This study could a l s o be relevant t o some pro-

posed uses of Li-Fâ&#x20AC;&#x2122;b i n fusion r e a c t o r s . Li-A1 Sorption System The tritium sorption data i n Tables I V and V, although not conclu-

sive, do provide some i n s i g h t i n t o t h e r e l a t i v e l y complex nature of Li-A1. The l i m i t e d amount of data and t h e apparent inconsistencies make corre-

l a t i o n s of temperature, pressure, concentration, and sorption r a t e impossible.

T r i t i u m sorption rates were low, and e q u i l i b r i m probably

w a s not achieved i n many of t h e experiments. The p a r t i a l d i s s o l u t i o n experiment does i n d i c a t e t h a t t h e loading

w a s determined by sorption r a t e r a t h e r than equilibrium, but it does not explain t h e manner i n which t h e sorption occurred.

The tritium concen-

t r a t i o n decreased as more of t h e t o t a l sample was dissolved, t h e concent r a t i o n being higher a t t h e surface.

Sorption may be c o n t r o l l e d by

e i t h e r surface r e a c t i o n o r slow d i f f u s i o n , o r both.

Surface adsorption

could be very important i f t h e s o l i d blanket material were t o "powder" r

under i r r a d i a t i o n ; also, d i f f u s i o n by grain boundaries could be s i g n i f i The sorption time does seem t o be s e v e r a l days.

cant.

This i n d i c a t e s

t h a t a desorption t i m e would be a l s o s e v e r a l days, thus increasing t h e

tritium inventory s i g n i f i c a n t l y

The tritium s o l u b i l i t i e s observed i n t h i s study were low and i n t h e

-8

range of 10

atom f r a c t i o n i n Li-A1 suggested by Powell ( 3 0 ) .

Powell assumed t h a t t h e tritium equilibrium s o l u b i l i t y i n Li-A1 alloy 2 followed S i e v e r t s ' l a w ; S i e v e r t s ' constant was chosen t o be 4.47 x 1 0 (atom fraction)-' applicable t o Li-Al,

at 50OoC.

Assuming t h a t S i e v e r t s ' l a w i s

S i e v e r t s ' constants were determined f o r t h e most

r e l i a b l e data (most l i k e l y t o be equilibrium s o l u b i l i t y d a t a ) i n Table I

Figure 10 i s a p l o t of S i e v e r t s ' constants f o r t h i s d a t a s e t , l i q u i d

l i t h i u m (35),and aluminum (11)as a function of inverse temperature. o

S i e v e r t s ' constants f o r Li-A1 a r e between t h e l i t h i u m and aluminum data; t h e slope of t h e l i n e i s i n t h e same d i r e c t i o n as t h a t of t h e aluminum data l i n e . fraction)-'.

The value from Fig. 1 0 a t 5OO0C i s 3.4 x 1 0 torr1j2

(atom

W i s w a l l and Wirsing (43) found a t y p i c a l value of 1.22 x

4 a t 50OoC; t h e r e f o r e , Powell's estimate of a S i e v e r t s ' constant i s t o o

small. Some of t h e data suggest t h a t tritium inventories may not follow a simple S i e v e r t s ' r e l a t i o n s h i p , but t h i s cannot be determined conclusively The tritium p a r t i a l pressure readings were

from t h e present study.

a f f e c t e d by t h e presence of t h e s t a i n l e s s steel tube l i n e r s , which absorb

tritium throughout t h e experimental temperature range.

T r i t i u m solubil-

i t y i n stainless s t e e l follows t h e S i e v e r t s ' r e l a t i o n s h i p (28):

ORNL DWG. 75-8290R1

lo,

IO'

IO*

1000 900800 700 600 I

500

400

-E b E

5 u)

8 10'I-

6 > It!

I .8

I 1.0

1.4

1.6

1000 T(OK)

Figure 10. A Comparison of Sieverts' Constants for Aluminum, Lithium, and Li-A1 Alloy.

LJ c

eq. 16 where NT = mole f r a c t i o n of tritium i n 304 s t a i n l e s s steel,

= tritium p a r t i a l pressure, t o r r ,

T2 T = temperature, OK.

The s t a i n l e s s s t e e l l i n e r s were necessary t o prevent an a t t a c k of t h e quartz containers.

It has been reported (1)t h a t Li-A1 a l l o y s with

a l i t h i u m content g r e a t e r than 4 w t % (Q 1 2 a t . % l i t h i u m ) form a separ a t e m e t a l l i c l i t h i u m phase; however, t h e mass spectrometer experiments d i d not v e r i f y t h i s .

t h e Li-A1 samples.

The a t t a c k was probably due t o excess lithium i n Further thermochemical study of Li-A1 i s needed.

CHAPTER V I 1 c

ANALYSIS OF THE TRITIUM RECOVERY SYSTEM FOR THE PRINCETON REFERFNCE DESIGN A Tokamak fusion r e a c t o r consumes deuterium and tritium which are

i n j e c t e d continuously i n t o t h e t o r o i d a l r e a c t o r .

I n t h e Princeton

Reference Design, about 10% of t h e fuel ions f'use and t h e r e s u l t i n g f a s t neutrons are captured i n t h e molten Li2BeF

blanket.

generated f r o m t h e l i t h i u m i n t h e s a l t blanket.

Tritium fuel is

The p r i n c i p a l coolant

f o r t h e fusion p l a n t i s helium gas, which cools t h e r e a c t o r and d i v e r t o r w a l l s , as w e l l as t h e blanket.

Conventional water b o i l e r s then cool

t h e helium and produce steam which i s used t o d r i v e e l e c t r i c power generators. T r i t i u m must be recovered from t h e blanket and recycled t o replace

t h a t consumed i n t h e plasma.

Johnson ( 2 1 ) has proposed t h e t r i t i u m

recovery scheme considered i n t h i s section. Description of t h e Process Figure 11 shows t h e tritium recovery system f o r t h e molten f l u o r i d e loop.

The flow rates and concentrations are l i s t e d i n Table V I . The breeder s a l t r e c i r c u l a t e s constantly through e i g h t disengagers

arranged i n p a r a l l e l about t h e periphery o f t h e r e a c t o r .

The salt i s

sprayed i n t o t h e disengagers as s m a l l droplets t o provide an extended surface a r e a for t h e dissolved helium and TF t o d i f f u s e from t h e l i q u i d salt.

S a l t c o l l e c t s i n t h e bottom of t h e disengager and flows back t o

t h e r e a c t o r blanket.

An unspecified doctor system removes impurities

f r o m t h e L i BeF and adds makeup agents t o maintain t h e desired s a l t 2 4 composition t o a s m a l l drag stream of s a l t .

tci

ORNL DWG. 75-8288

I I

*I t

CYCLIC CONDENSERS USENGAGER

I I

______

+-----J

i i .

RECEIVER

TRAPS

A,, r-I I

T >

KF ~LEcTRocvncCELL

Figure 11. Princeton's Reference Design S a l t B l a n k e t Processing System.

T A B U VI FLOW RATES AND CONCENTRATIONS FOR TKE TRITIUM RECOVERY SYSTEM FOR THE PRINCETON REFERENCE REACTOR

L i BeF salt flow through disengagers 2 4

4.0 x 1 0 kg/hr

TF Concentration i n s a l t Entering disengagers Exiting disengagers

2.09 x

mole f r a c t i o n mole f r a c t i o n

1.29 x

Exhaust gas composition

1.0 x 10- a t m 1.53 x 1044 a t m 1.3 x 10- a t m

TF He Salt T r i t i u m recovery

548 d d a y

H e l i u m ash discharge

1120 glday

The gas e f f l u e n t i s drawn successively through a water-cooled s a l t t r a p and l i q u i d nitrogen-cooled c y c l i c condensers. charged t o a storage system for f i n a l control.

The helium i s dis-

S o l i d TF i s melted out

of t h e offstream c y c l i c condenser and c o l l e c t e d i n a s m a l l r e c e i v e r .

The

salt flows i n t e r m i t t e n t l y through a p u r i f i c a t i o n system and i n t o an e l e c t r o l y s i s c e l l , where a s o l u t i o n of KF i n TF i s electrolyzed t o F2 and T 2'

The gases emerging from t h e electrodes are s a t u r a t e d with TF

and must pass through t h e l i q u i d nitrogen-cooled t r a p s t o remove t h e TF. The pure tritium gas i s recycled t o t h e primary f u e l loop. 1

The main components of t h e processing scheme, t h e spray disengagers, and c y c l i c condensers were investigated i n d e t a i l t o evaluate t h e i r assoc i a t e d problems.

The areas t h a t may cause problems f o r t h e usage of

disengagers are:

( a ) t h e diameter and residence t i m e of t h e droplets

needed f o r adequate mass t r a n s f e r of t h e dissolved TF and He i n t h e s a l t ,

i ?-

( b ) t h e a b i l i t y t o spray a molten s a l t i n an evacuated v e s s e l , and ( c )

t h e c h a r a c t e r i s t i c s of spray nozzles t o disengage t h e s a l t .

The possible

d i f f i c u l t i e s of t h e c y c l i c condensers involve ( a ) t h e e f f e c t of a noncondensable gas on t h e surface a r e a needed f o r condensation, and ( b ) t h e type of TF flow i n t h e condenser.

These considerations were examined

t o evaluate t h e s a l t processing system. Disengager Analysis Figure 1 2 shows a d e t a i l e d schematic of t h e proposed disengagers. Each of t h e eight disengagers i s equipped with spray nozzles near t h e t o p and a salt discharge l i n e at t h e bottom.

Baffles near t h e top of t h e ves-

s e l prevent s a l t entrainment i n t o t h e vapors which are vented a t t h e top.

I i s

To avoid w a l l embrittlement , t h e m a x i m u m t o l e r a b l e t r i t i u u i pressure i n t h e s a l t w a s estimated by Maroni (24) as

t o r r o r 1.32 x

atm.

The corresponding TF concentration i n t h e entering s a l t was c a l c u l a t e d - t o be 2.09 x lo-? mole f r a c t i o n . TF pressure of

The e x i t concentration corresponding t o a

a t m i s 1.29 x

mole f r a c t i o n .

A s i m p l i f i e d p i c t u r e o f t h e mass t r a n s f e r mechanism i n an i n d i v i d u a l i

salt droplet i s as follows:

( a ) TF d i f f u s e s from within t h e drop t o t h e

surface of t h e drop, and ( b ) TF d i f f u s e s from t h e ' d r o p surface i n t o t h e gas phase.

For t h e first s t e p involving l i q u i d d i f f u s i o n i n a s p h e r i c a l

drop, with n e g l i g i b l e drag e f f e c t s , t h e r a t e equation i s (29): i

-C- - -6 co

2 -' Dt/r

+ 1/4

e-4n2Dt/r

2 +

l/g e-gn2Dt/r2 +

. . .), eq. 17

ORNL DWG. 75-8292

COOLED GASES e IOOOC, 0.204m~/sec/disengager 7.57 g mole / hr TF 11.6 gmole /hr He

lr SALT TRAP _+ 9.84 gmole /hr SALT

COOLER "20

EXHAUST GAS Q 660' C, 0.201m3/sec/disengager 1.0x IG4a tm TF

1.08x 108gmole/hr MOLTEN Li2Be F4 @ 660' C b 3 2.09~10mole fract TF DISENGAGER (8 UNITS)

f MOLTEN Li2Be F4

1.29~ Idernole fract TF Figure 1 2 .

Schematic of t h e S a l t Disengaf3er and S a l t Trap.

where .I

= i n i t i a l TF concentration, mole f r a c t i o n ,

C = f i n a l average TF concentration, mole f r a c t i o n , 2 D = l i q u i d d i f f u s i v i t y o f TF i n molten s a l t , cm /sec,

r = radius o f t h e droplet, cm,

t = t i m e , sec. Using t h e values f o r t h e i n i t i a l and f i n a l average TF concentrations i n t h e salt, C/Co i s calculated t o be 6.17 x value i s 0.232 (Appendix C ) . suggested by Cantor ( 5 ) i s

The corresponding Dt/r

The l i q u i d d i f f u s i v i t y of TF i p molten s a l t 2 2 cm /sec; therefore, t / r equals 2.32 x

4 sec/cm 2 . Figure 13 i s a graph of time vs diameter f o r t h i s equation.

For t h e second s t e p involving l i q u i d d i f f u s i o n i n a s p h e r i c d drop, t h e d i f f u s i o n r a t e equation for TF removal through t h e gas f i l m r e s i s t a n c e

is:

eq. 18 where

N = m o l e s of TF,

K = m a s s t r a n s f e r c o e f f i c i e n t , moles/cm sec t o r r , g

2 a = surface area o f drop, cm , pi = vapor pressure of TF, t o r r , p = p a r t i a l pressure of TF i n gas phase, t o r r .

This s t e p i s n e g l i g i b l e since t h e s a l t i s sprayed i n t o a vacuum and t h e gas f i l m r e s i s t a n c e i s e s s e n t i a l l y zero.

Atomization o f a f l u i d usually involves t h e application of an extern a l force, such as a gas r e s i s t a n c e .

However, d i s i n t e g r a t i o n w i l l occur

i n a vacuum i f t h e l i q u i d j e t i s turbulent throughout and i t s surface

48 ORNL DWG. 75-8293R1

io3

IO'

!ii b

e l

I0-

IO4

io3

IO2

IO Y

DROP DIAMETER, d(microns) /

Figure 1 3 . Transfer

Residence Time v s Drop Diameter for Molten Salt Mass

49 tension i s overcome (25).

The e f f e c t s of l i q u i d p r o p e r t i e s and j e t

v e l o c i t y on t h e j e t breakup have been studied f o r t h e case of atomizat i o n without t h e influence of a surrounding medium.

The mechanism can

be predicted t o be dependent on j e t diameter, j e t v e l o c i t y , l i q u i d den-

s i t y , surface tension, and v i s c o s i t y (Appendix D ) .

From t h i s correla-

t i o n , t h e j e t v e l o c i t y needed t o achieve atomization must be g r e a t e r than

488 fps t o obtain a droplet s i z e of 150

From Fig. 13, t h e residence

t i m e f o r m a s s t r a n s f e r f o r a 150-v drop i s found t o be 1.31 sec; theref o r e , a column height of over 637 f t i s necessary.

A smaller :droplet

s i z e would decrease t h e height of a disengager. The s e l e c t i o n of t h e type of spray nozzle has a considerable bearing on t h e dimension of t h e spray tower.

The c h a r a c t e r i s t i c s , operating

ranges, advantages, and disadvantages f o r hydraulic-pressure nozzles and spinning-disk atomizers are l i s t e d i n Table VII.

The m a x i m u m capacity

through a s i n g l e nozzle o r t h e feed rate from a spinning d i s k i s about 10,000 l b / h r .

The s a l t flow r a t e through each disengager i s 5.0 x 1 05

kg/hr o r 1.1 x 1 0 l b / h r ; therefore, t h e minimum number of nozzles per disengager would be about 110.

A preliminary study of a dropwise liquid-gas contacting system w a s

made by Gabor e t a l . (16).

Fused NaF-ZrF

containing dissolved u r h i u m .,

t e t r a f l u o r i d e w a s sprayed i n t o a f l u o r i n e atmosphere t o recover uranium hexafluoride.

Experimental. equipment w a s developed t o t e s t heat and mass

t r a n s f e r rates. i

A Spraying Systems Company full-cone spray nozzle

(1/8 G3001.4) constructed of Monelwas used f o r t h e heat t r a n s f e r t e s t s .

i i

This nozzle had a 0.026-in.

sprayed i n t o a i r at 2OoC. mined t o be 164

orifice.

The s a l t was heated t o 650Oc and

The average diameter f o r a droplet was deter-

TABLE V I 1 CHARACTERISTICS, ADVANTAGES, AND DISADVANTAGES OF PRESSURE NOZZLES AND SPINNINEDISK ATOMIZERS (25) Hydraulic-Pressure Nozzles

Spinning-Disk Atomizers Characteristics

1. Pressure:

2. 3.

up t o 10,000 lb/in. up t o 10,000 l b of feed per hour

1. Disk speed: 500-30,000 rpm 2. Disk diameter: 2-10 i n .

Capacity: per nozzle 3. Feed rate: Feed viscosity: up t o several hundred centipoises depending on pressures, capacity, and orifice size Advantages

1. Suited for multiple atomizers

0.05-15,000 l b per hour per disk

1. More flexible than nozzles; handle changes i n

2. 3.

Used f o r countercurrent spray drying Nozzles generally inexpensive

4. 5.

Flexibility i n designs and types Better for viscous fluids than are spinning disks, since feed can be preheated under pressure

2. 3.

feed rate since disk speed and feed rate vary independently Multiple fluids can be easily handled and mixed Liquid feed i s under low pressure No small clearances or openings which may plug or erode

Disadvantages 1. Inflexible due t o pressure, capacity, and

orifice s i z e variables being independent 2.

4. 5.

Nozzle susceptible t o erosion and plugging High-pressure pumps are expensive

1. Counterflow i s d i f f i c u l t

2. 3.

L i m i t t o the fineness of atomization

Variations i n feed rate not always feasible

Disks as well as the drive mechanisms are expensive Not readily adapted t o horizontal spray dryers Not well suited t o very viscous liquids

51 Several problems were encountered i n spraying t h e f l u o r i d e s a l t . D i f f i c u l t i e s associated w i t h plugging of t h e spray nozzle were solved by heating the nozzle f o r f u l l y controlled operation.

I n other fused-

s a l t process s t u d i e s , a u t o r e s i s t i v e l y heated s a l t t r a n s f e r l i n e s have proved successful. 20 batch sprayings.

The nozzles use& were removed and inspected a f t e r Examination revealed t h a t t h e o r i f i c e had enlarged

from 26 t o 32 m i l s , increasing t h e area about 50% and i n d i c a t i n g frequent nozzle replacement. The prospect of a spray process f o r t h e recovery of tritium from

molten f l u o r i d e s a l t appears discouraging.

The v e l o c i t y of t h e j e t must

be high t o overcome t h e surface t e n d o n of t h e s a l t f o r atomization t o occur w i t h n e g l i g i b l e gas film r e s i s t a n c e or drag e f f e c t s of a vacuum of torr.

The droplet diameter and residence t i m e i n t h e disengager

needed f o r mass t r a n s f e r , coupled w i t h t h e acceleration of t h e drops as they f a l l , lead t o a design of a tower of considerable height.

If t h e

minimum number of nozzles i f 110, t h e column diameter must a l s o be l a r g e t o decrease coalescence of t h e droplets.

The corrosion within t h e spray 3

nozzles would m a k e frequent replacement necessary f o r full operation. Cyclic Condenser k a l y s i s A schematic of t h e c y c l i c condensers i s shown 2n Fig. 14.

The

cooled helium and TF leave t h e s a l t t r a p and are drawn through an on-

stream c y c l i c condenser. temperature of

The gas i s cooled f u r t h e r t o t h e l i q u i d nitrogen

77.boK, and t h e TF i s condensed out.

I d e a l l y , t h e condenser w a l l s must be kept cold enough t o freeze out nearly a l l t h e TF t o a negligibly low equilibrium pressure.

This would

expose t h e condenser surface t o gas bombardment, so t h a t t h e pumping speed

td ORNL DWG. 75-8295

CO 0 L E D G A S a t loooC, 0.204 rn3/sec 7.57 gmolelhr TF 11.6 gmole/hr He

CONDENSERS CYCLIC

7.57grnole/hr TF

11.6 qmole/hr He

TF Figure 1 4 .

Schematic of t h e Cyclic Condensers.

53 would be l i m i t e d only by surface a r e a and t h e s t i c k i n g p r o b a b i l i t y of t h e impinging molecules ( 3 1 ) .

Noncondensables o f t e n influence t h e pumping

speed and t h e condenser surface area.

The condensing gas i s l i k e l y t o

sweep t h e noncondensable gas against t h e condenser surface, creating a blanket through which t h e condensing gas must d i f f u s e t o reach t h e cold wall.

However, gas blankets a r e not formed when t h e mean f r e e paths are

long or when t h e proportion of uncondensable gas i s s u f f i c i e n t l y low (31).

Since an appreciable amount of helium, a noncondensable gas, i s drawn through t h e condenser, t h e mean free paths were calculated t o determine whether a gaseous d i f f u s i o n b a r r i e r would form.

The mean f r e e path

i s t h e average distance t r a v e l e d by a molecule between c o l l i s i o n s .

Mean

f r e e paths can be determined from t h e c o l l i s i o n frequencies of t h e i n t e r a c t i n g molecules.

The frequencies of c o l l i s i o n of t h e possible p a i r s of

impacting molecules, t h e subsequent mean free paths, and t h e frequencies of c o l l i s i o n with t h e condenser w a l l s are l i s t e d i n Table V I I I . When c o l l i s i o n s of molecules with each o t h e r are n e g l i g i b l e i n comparison w i t h t h e i r impacts on t h e w a l l s of t h e surrounding enclosure, t h e gas i s i n Knudsen or "free molecular" flow.

Knudsen flow usually assumes

very d i l u t e gases with pressures i n t h e region of very narrow c a p i l l a r y tube.

t o lo-'

a t m or a

Also, t h e mean free path i s g r e a t e r than

t h e tube diameter f o r Knudsen flow of a gas (23). A s s t a t e d i n Johnson's process design, t h e duct diameter must not be

less than 0.5 m t o avoid l a r g e pressure l o s s e s . from about

cm t o about 107 cm.

The mean free paths vary

The impacts of molecules with t h e

w a l l s are i n t h e same range as t h e intermolecular c o l l i s i o n s ; t h e r e f o r e ,

it i s d i f f i c u l t t o determine whether t h e gas flowing through t h e

54 TABLE V I 1 1 t

MOLECULAR AND WALL COLLISION FPEQUENCIES AND MEAN m E PATHS OF He and TF I N THE CYCLIC CONDENSERS

(1) Molecular Collision Frequencies , molecules cm-3

He-TF

7.142 x 1 021 2.013 x 1 01 4

TF-TF

6.782 x

He-He

(2)

SeC-'

(Appendix E )

lo5

W a l l Impact Frequencies, molecules cm-2 sec -1 (Appendix F)

1.516 x 10 2.430 x 1 0 l 2

(3) Mean Free Paths ( A ) , cm (Appendix G ) AHe-He

8.49

ATF-He

4.82

x 1 06 1.43 x 1 07

AHe-TF

3.01

ATF-TF

condenser i s i n Knudsen flow. with t h e condensation of TF.

Consequently, t h e helium may i n t e r f e r e An a l t e r n a t e condenser design, such as

using multiple tubes with smaller-diameter ducts i n s t e a d of one 0.5-m duct, may be a possible solution. A s s t a t e d i n t h e proposed design, t h e heat load of each condenser

c o n s i s t s b a s i c a l l y of t h e periodic heating and cooling of t h e mass of

metal (equivalent t o 500 kg of s t e e l ) c o n s t i t u t i n g t h e condenser.

The

heat flux t o cool t h e TF gas from 373OK t o 77.4OK can be approximated L

by summing t h e l a t e n t and sensible heat changes (Appendix H ) . enthalpy change w a s calculated t o be

The t o t a l

132 kcal/hr; however, assuming

55 t h a t t h e energy l o s s equals t h e decrease of t h e condenser temperature i t s e l f from t h e melting point of TF (2OoC) t o 77.kÂ°K, t h e t o t a l heat exchange duty per condenser i s 1075 kcal/hr (Appendix H ) .

Thus, t h e

freezing out of TF i s a minor p a r t of t h e heat load. The c y c l i c condensers seem t o be feasible as an i n t e g r a l p a r t of t h e tritium recovery system.

H e l i u m may increase t h e surface area

required t o freeze out t h e TF; thus t h e condenser design w i l l have t o take t h i s i n t o account.

Since t h e cooling of t h e condenser i t s e l f ,

r a t h e r than t h e heat f l u x of condensing t h e TF gas, i s t h e main component of t h e heat exchange duty, t h e t o t a l power requirement i s not increased unless t h e r e i s an increase i n t h e condenser a r e a i t s e l f . Other Design Considerations The s a l t t r a p s above each spray tower and t h e vacuum pump system may be areas of a d d i t i o n a l design consideration.

The molten salt e n t e r i n g

t h e spray disengagers at 660Oc may be b o i l i n g , inasmuch as t h e uncert a i n t y i s a f a c t o r of 1 0 f o r t h e reported values of vapor pressure f o r molten Li2BeF4 ( 4 ) .

The vapor pressure at 660Oc of t h e molten s a l t i s

-4 a t m , and t h e t o t a l pressure of t h e v e s s e l

determined t o be 1.3 x 1 0

i s 3.83 x

atm.

An increase i n t h e quantity of vaporized s a l t i n t h e

gas effluent would increase t h e s a l t t r a p s i z e needed.

The salt captured

i n t h e cold t r a p s may have t o be reprocessed due t o r e d i s s o l u t i o n of TF i n t o the salt. T r i t i u m l o s s from t h e vacuum pump system w i l l be inherent; there-

fore, a trapping system should be a requirement t o prevent t h e escape of TF.

,In choosing t h e vacuum pumps, t h e compatibility of TF withâ&#x20AC;&#x2122;the

components must be reviewed.

pump

56 CHAPTER VI11

CONCLUSIONS AND RECOMMENDATIONS Conclusions From t h i s study, t h e following conclusions can be drawn:

1. The s o l u b i l i t y of tritium i n molten Li-Bi

( % 15 a t .

lithium) i s

l e s s than 0 . 1 ppb at temperatures ranging from 500 t o 700째C. 2.

Because of t h e l o w s o l u b i l i t y of tritium i n L i - B i ,

the extraction

process proposed t o recover tritium from a L i BeF4 blanket i s not 2

attractive.

-6

t o 10

T r i t i u m sorption i n s o l i d equiatomic Li-A1 ranges from

atom f r a c t i o n tritium, which i s i n agreement with estimates f o r t h e blanket recovery system proposed by Powell (30).

The S i e v e r t s ' constants determined f o r t h e s o l u b i l i t y of tritium i n Li-A1 are smaller than those f o r aluminum, but l a r g e r than those f o r

l i t h i u m a t 400 t o 600Oc.

The sorption of tritium i n Li-A1 appears t o be c o n t r o l l e d by surface

r e a c t i o n , slow i n t e r n a l d i f f u s i o n , o r both.

The spray disengager process f o r t h e recovery of tritium from molten L i BeF4 does not look a t t r a c t i v e f o r t h e following reasons: 2

( a ) The v e l o c i t y of t h e s a l t j e t must be high f o r atomization

-4

in a 10 (b)

a t m vacuum ( > 488 f p s f o r 150-LId r o p l e t s ) .

The drop diameter and residence time needed i n t h e disengager a

f o r t h e m a s s t r a n s f e r of TF leads t o a tower of considerable height ( > 637 f t f o r 150-LId r o p l e t s ) . (c)

The minimum number of nozzles needed t o atomize t h e amount o f L i BeF4 t o be processed per disengager i s 110. 2

Corrosion

within t h e nozzles would make frequent replacement necessary.

L, Recommendations c

. )

For f'urther study, the following recommendations are made: 1. Appropriate equipment design and sampling technique improve-

ments are necessary to collect more accurate data for determining the physical chemistry of the Li-Bi--tritium system. 2.

Removal of tritium from irradiated Li-Al of low lithium content should be investigated to determine tritium solubility and release rates.

Alternative flowsheets for recovering tritium from Li BeF 2 4 blankets should be investigated.

BIBLIOGRAPHY c

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10.

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TM-3096 (19731

59 14.

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24.

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28.

Metal

Nelson, Howard G., and S t e i n , James E., Gas-Phase Hydrogen Permeation T h r o u a Alpha I r o n , 4130 S t e e l , and 304 S t a i n l e s s S t e e l from Less Than 100째C t o Near 6oo0c, NASA-TN-DT265, Ames Research Center, Iowa, A p r i l 1973.

Newman, A. B.

, Trans.

Am. I n s t . Chem. Engrs.

(1931). I

Powell, J. R., e t al., Studies of Fusion Reactor Blankets with Minimum Radioactive Inventory and with T r i t i u m Breeding i n S o l i d Lithium Compounds: A Preliminary Report , BNL-18236 (June 1973).

31.

Power, B. D., High Vacuum Pumping Equipment, Reinhold Publishing Co., New York, 1966.

32.

Rose, D. J., On t h e F e a s i b i l i t y of Power by Nuclear Fusion, ORNGTM2204 (May 1968).

33.

S i e v e r t s , A., 37-46 (1929

34. Simons, J. H.,

"Absorption of Gases by Metals," Z. Metalkunde

21,

ed., Fluorine Chemistry, p. 233, Academic P r e s s , New

York, 1950.

Smith, F. J., and Land, J. F., "Hydrogen Isotope-Lithium System," Trans. Am. Nucl. SOC. 2l, 167 (1975).

36.

Sokol'skaya, L. I., Gases i n Light Metals, Pergamon P r e s s , New York, 1961.

S t e i n e r , D . , "Fusion Reactor Design Problems," I n t e r n a t i o n a l Atomic Energy Agency, Vienna, 1974.

38. S t e i n e r , D., and Fraas, A. P., "Preliminary Observation on t h e Radiological Implications of Fusion Power," Nucl. Safety (1972)

13,353

U , S. Energy Research and Development Administration, (formerly USAEC), Proposed R u l e Making, 1 0 CFR 50, Federal Register 36, No. 111 (June 1971).

40.

Vetrano, J. B., "Hydrides as Neutron Moderator and Reflector Materials," Nuclear Engr. and Design &, 390-412 (1970).

41. Watson, J. S., A Summary of T r i t i u m Handling Problems i n Fusion Reactors. ORNL-TM-4022 (November 1972). _. ,

42.

Weast, R. C . , ed., Handbook of Chemistry and Physics, 50th ed., p. F-44, The Chemical Rubber Co. , Cleveland, Ohio (1970).

43. W i s w a l l , R. H., and Wirsing, E., The Removal of T r i t i u m from S o l i d CTR Blanket Materials: 1975)

A Progress Report , BNL-19766 (February

61 APPENDIX A THE COMPATIBILITY OF L i - B i WITH Li2BeFh

The equilibrium d i s t r i b u t i o n studied can be represented by t h e reaction:

BeF2( s a l t ) + 2Li(Bi) = Be (Bi)

+ 2LiF ( s a l t )

eq* 1 9

The equilibrium constant f o r r e a c t i o n 19 can be w r i t t e n as:

K =

'Be

2 LiF

%eF2 'BeF2

2 ' LiF 2 2 L i 'L i

eq. 20

where K = equilibrium constant, Y = mole f r a c t i o n of component i n t h e Li-Bi phase, X = mole f r a c t i o n of component i n t h e salt phase, y = a c t i v i t y c o e f f i c i e n t referred t o t h e appropriate pure s o l i d or liquid.

The change o f standard f r e e energy f o r r e a c t i o n 1 9 i s : AG

= -RT I n K =

AGfLiF

- AGf BeF2

where 0

= change of standard free energy, kcal/mole,

AGf = standard f r e e energy of formation, kcal/mole, R = gas constant, 1.987 cal/g-mole OK,

T = temperature,

OK.

From Equations 20 and 21, t h e following r e l a t i o n i s obtained:

eq. 21

AG' BeF2

In K =

i d

2AGLLiF

2 'Be

= In

2 LiF LiF 2 2 Li Li

eq. 22

kcal/mole, (Reference 3) ,

eq. 23

'Be

%eF2 'BeF2

The experimental conditions are: T

600Oc = 873OK,

siF =

0.667,

'BeF2

0.333,

yLi

0.15.

The thermodynamic d a t a needed are: f

BeF2

= -243.86 + 30.01

[l-&] -

or f

AG BeF2 f

LiF

= -217.66 kcal/mole at

= -141.79 + 16.58

6oo0c,

[%] kcal/mole,

(Reference 31,

eq. 24

or f LiF

= -127.32 kcal/mole at 6oo0c,

I n yLi = 0.4509

- 8705 T(OK)

(Reference 1 2 ) ,

eq. 25

or 1 x 1YLi

= -9.5205 at

6oo0c, 7

In 'LiF

= -0.8913 at 600Oc. (Reference 20)

From Equation 22, we obtain:

eq. 26

63 n

AG' BeF2 In K =

- 2AGLLiF = 21.318

l o g (ppm B e ) = 6.85

eq. 27

-6140 , (Reference 11) T(OK)

ppm Be = -0.1832 at

eq. 28

6oo0c,

or 'Be

= 1.5207 x

The a c t i v i t y , a, of a pure substance i s unity. \

By d e f i n i t i o n ,

Therefore, 'Bi

?Eli = 'Be

%e = 1 ,

eq. 30

Assuming y BeF2

1, from Equations 22 and 27,

I n YBe = 21.318

- 32.436

= -11.110,

or 'Be

= 1.4846 x

This value of YBe = 1.4846 x 1.5207 x

i s less than t h e s o l u b i l i t y value of

at 6OOOC from Equation 28; thus Li-Bi

compatible with Li2BeF4 at 600Oc.

at 980OKand YLi = 0.01.

( Q 15 at. $ L i ) i s

The proposed e x t r a c t o r w i l l operate

A t t h e s e conditions, YBe = 2.779 x:'01

i s less than t h e s o l u b i l i t y value of 8.912 x

which

hsi

APPENDIX B SAMPLE CALCULATIONS FOR Li-Bi--TRITIUM SORPTION DATA FOR SAMPLE NO. 2.7 AT 600Oc

(I) For t h e Li-Bi metal-phase a n a l y s i s , t h e L i - B i sample weight = 1.8375 g,

and

l i q u i d s c i n t i l l a t i o n result = 1.289 x 10

(1.289 x 10

dpm/ml;

12 2.22 x 1 0 dpm

= 2.903 x

C i T.

The s p e c i f i c a c t i v i t y of tritium i s calculated from t h e following equation: 1 3

s p e c i f i c a c t i v i t y = ’*I3 IOL’>

(MI(ti

g 9

(Reference 7 ) ,

where M = molecular weight of T, 3.016 g/g-mole,

= h a l f - l i f e o f T2, 12.3 years or 3.8815 x 108 sec; therefore, t h e 7 -

3 L 8 = 9.653 x 10 g T (3.016)(3.8815 x 10 ) 1.13 x loL5

specific activity =

Thus, (2.903 x 10-7 Ci)

(1.036 Cxi

-11 g T) = 2.996 x 10 g T,

eq. 31

Lid c

2.996 x

1.8375 g Li-Bi + 2.996 x 1T 0-11 g T = 0.0163 ppb

T 3.016 E/g-mole

= [3.016

g T sample wt (6.899 x

1.125 x

lo3)

208.1 g/g-mole

= 2*996 x

1.8375 g

(6.899 x lo3)

(11) For the gas-phase analysis for tritium,

4.778 x 1 05 dpm/ml, and tritium monitor result = 4.9 x 1 03 pCi/m 3

the liquid scintillation result

(a) For the liquid scintillation result:

(4.778 x l o 5

s ) ( b .5-ml 50-ml solution )(8OO-ml gas sample

= 1.913 x

gas volume '(2.22

x 1OI2 dpm

(1.913 x lom3 Ci) (1.036 Ci

) = 1.982

g T.

Using the ideal gas law,

eq. 32

where t

= tritium partial pressure, torr,

= moles of tritium, g-moles,

T = temperature,

OK,

= gas volume, 800 cm

62,400 torr cm3/ O K g-mole.

By substitution,

1.982 x g P = ( 3.016 g/g-mole T

p = 4.499 x

(62,400 torr cm O K g-mole

(873.loK)( 800 cm3

torr.

(b) For the tritium monitor result: liters gas volume in monitor

m = 1.307 x

Ci.

APPENDIX C I

CALCULATION O F RESIDENCE TIME FOR MASS TRANSFER OF TRITIUM FLUORIDE FROM A SATJT DROPLET

A numerical s o l u t i o n of l i q u i d d i f f u s i o n i n a sphere i s expressed i n

Fig. 15, which relates C/Co,

t h e r a t i o of t h e f i n a l average concentra-

t i o n t o t h e i n i t i a l concentration, t o Dt/r2, where D i s t h e l i q u i d d i f f u s i v i t y , t i s t h e residence t i m e , and r i s t h e radius of t h e sphere (29).

ORNL DWG. 75-8289Rl

Figure 1 5 .

Numerical Solution of Liquid Diffusion i n a Sphere.

68 APPENDIX D CALCULATION OF SPRAY DISENGAGER HEIGHT FOR SALT DROPLETS OF VARIOUS SIZES (25)

For Tyler's mathematical predictions, drop diameter and wavelength can be c o r r e l a t e d by t h e equation

-x - -

(-$)3

= 4.69

eq. 33

where

1 = wavelength, cm, do = j e t diameter, cm,

x = drop diameter, cm; therefore ,

x = 1.92 d

If x = 150 p or

1.5 x

cm, do = 7.8 x

. cm.

The breakup mechanism of a j e t as predicted by dimensional a n a l y s i s

i s a function of t h e j e t Reynolds number, vdo p L / p , and a dimensionless group, p/&pLdo,

r e f e r r e d t o as t h e Z-number, where v i s t h e j e t v e l o c i t y

(cm/sec), u i s t h e surface tension (dynes/cm), pL i s t h e l i q u i d density

(g/cm ), and p i s t h e l i q u i d v i s c o s i t y (g/cm s e c ) . are correlated

Experimental d a t a

i n Fig. 16 t o show t h i s r e l a t i o n s h i p .

From t h e physical p r o p e r t i e s o f Li2BeFk s a l t , t

From Fig. 16, N > XI3 for atomization of t h e j e t . Re

That i s ,

ORNL DWG. 8296Rl I

Io-

Rayleigh Breakup Zone

9 d

\Transitional

\Zone

Atomization Zone

IO J

I I 10s IO' Reynolds Number, NRe = vdopr

\ 104

IO'

Figure 16. Ohnesorge's Chart (25) Showing Jet Breakup as a Function of Reynolds Number and Liquid Properties.

I IO'

or NRe

v =

6.696 x

= 5.21 x 10-j cm,

z= NRe

0.168,

> g

.x 102 ,

t = 0.58 sec, and h >

382 ft. -2

If x = 200 p or 2 x 1 0 = 1.04 x

z =

cm,

0.119,

NRf2 > 10

v > 367 ft sec â&#x20AC;&#x2122; t = 2.32 sec, and h >

851 f t .

cm, t h e n

4cm

1.49 x 10 -sec =

488 sec

APPENDIX E CALCULATION OF THE FREQUENCIES OF MOLECULAR C O L L I S I O N S (10)

The total collision number for N’ molecules of Ty-pe A per unit volume is: ‘2

F A A = NA

2 ‘A

(

IT kT

)

1/2

eq. 34

where N i = number of Ty-pe A molecules per unit volume, molecules/cm 3 ,

u = molecular diameter, cm,

k = Boltzmann’s constant, 1.38 x

g cm /sec OK,

= reduced mass, g/molecule,

m = molecular mass, g/molecule, T = temperature, OK,

P = pressure, g/cm sec2

For collisions between unlike molecules,

Fm = 2 where

N;]

[am2]

(Yfl2 ,

eq- 35

72 If A = TF and B = helium,

where

- 3.809 x

cm sec

â&#x20AC;&#x2122;A

Nd, = E -

-(3.809

sec2

cm sec ()g 1.38 x

g cm

a-mole

6.02 x

1.83 x

g/molecule.

molecules

The molecular diameter of hydrogen fluoride (HF) is 9.4 x

cm (34).

Assuming the molecular diameter of TF to be approximately the same as for

uA = 9.4 x 10-9 cm. Then,

8 2 FAA = (3.56 x 10 ~m-~)~(9.4 x lo-â&#x20AC;&#x2122; cm)

73 or

5 molecules

FAA = 6.782 x 1 0

cm3 sec

where

-4 atm

= 10

cm sec

- B' -

'; 'IB

= 101.3

= -

101.3 sec =(cm ~ e c ~ k . 3x 8

g cm2

-mole

(4*003 g-mole") (6.02

x :023 molecules

77.4OK

)

= 3.32 x

g/molecule

The molecular diameter i s r e l a t e d t o gas v i s c o s i t y by t h e following equation: I.r

-2 16

['- t:c'2]

(Reference 8 )

eq* 36

where p = gas v i s c o s i t y , g/cm sec.

For helium a t 77.hoK,

~.r equals

c a l c u l a t e d from Equation 36:

8.4 x

g/cm sec ( 4 2 ) and uB i s

-16

B Q

= 5.592 x 10

-8

F~~

= 2.365 x 10

, or

cm.

= (9.48 x 1015 ~m-~?(2.365x

1.38 x

a cm2)

cm)

(77.4OK)

(

mo1ec%4 3.32 x 10

)],

21 molecules FBB = 7.142 x 10 cm3 sec

where

4.003) (22.02)

g/molecule, or

(4.003(+ 22.02)(6.02 x

= 5.627 x

g/molecule,

cm + 9.4 x lo" 2

2 Q

OAB

Then,

r.365 x

2 = 2.731 x

cm2

cm]

W FAB = 2(9.48 x

(3.56 x lo8

(2.731 x

m2)

FAB = 1.843 x 109 cm-4 [2n(l.38

x 10-I6 sec2

14 molecules

FAB = 2.013 x 10

cm3 sec

CIII-~)

'-")

(77.40K)

( 5.627

112

76 APPENDIX F CALCULATION OF MOLECULAR COLLISIONS W I T H CONDENSER WALLS

2 The mass of gas striking 1 cm of wall surface per second is given by :

M = N'

m/4, (Reference 17)

eq. 37

where 2

M = mass of gas colliding with the w a l l , g/cm sec,

N = number of molecules per unit volume, molecules/cm 3 , I

= average velocity of a molecule, cm/sec,

m = mass of a single molecule, g/molecule. If A = TF and B = He, then, M = NA A

FAmA/4 ,

where

3.56 x

10 molecdes/cm

CA = 2.727 x 10 cm/sec, mA = 3.66 x

g/molecule,

MA = 8.88 x 10-11

cm2Osec

2.43 x 1012 molecules cm2 sec

and

where

Ni = 9.48 x

d5molecules/cm3 ,

W r

= 6.395 x 10 cm/sec, = 6.649 x

g/molecule,

1.008 x lom3 cm

The ratio,

MS, MA

,u !

sec

is calculated,

20 molecules 1.516 x 10 2 cm sec

W I

APPENDIX G P

CALCULATION OF MEAN FREE PATHS OF TF AND HELIUM COLLISIONS SP

The mean free path is the average distance traveled by a molecule A in a straight line before it collides with a molecule B.

This value is

related to the frequency of collisions between molecules A and B as follows :

= A,B

NA FAB

, (Reference 17),

eq. 38

where

A,B

= mean free path of molecule A colliding with molecule B, cm,

CA = mean velocity of molecule A, cm/sec,

Ni = number of molecules of A in unit volume,

molecules cm3

The mean velocity may be expressed by

CA = (8 kT/am)1'2

, (Reference 17) ,

where k = Boltzmann's constant, 1.38 x

T = temperature,

OK,

m = mass of a single molecule, g/molecule. Therefore, if A = TF and B = He,

where I

NA = 3.56 x 10 molecules/cm

g cm /sec

OK,

eq* 39

79 =

A '

6.782 x 105 molecules/cm3 sec,

['8(

2.727 x 104 cm/sec;

substituting

1.38 xsec2

O Kg

cm2)

(77.4OK)

22.02 g

molecule$]

. 4 cm/sec)(3.56 x 108 cm-3 (6.782 x l o 5 sec-l)

= I2.727 x 10

(,.,,

1/2

A,A

Âś

where

i c

molecules/cm-3

Ni = 9.48 x F~~

7.142 x 1021 molecules/cm3 sec, 1/2

-cB

[,(l.38

g cm2)

sec2

(77.40K) (6.02 x 4.003 molecules g

substituting, 'B,B

8.49 x

cm.

where

Fm = thus

2.013 x 1014 molecules/cm3 sec;

80 I

'A,B

xB,A

= 4.82 x

cm.

6 cm.

= 3.01 x 1 0

APPENDIX H L

CALCULATION OF CYCLIC CONDENSER HEAT LOAD !

I i

The heat exchange duty of t h e c y c l i c condenser, as expressed i n t h e Princeton Reference Design (211, i s t h e cooling duty of decreasing t h e condenser temperature from t h e melting point of TF (2OoC) t o 78OK.

Thus,

t h e t o t a l duty p e r condenser i s calculated t o be:

where 60 0~ kc& equals t h e t o t a l thermal capacity equivalent t o 500 kg of s t e e l . To estimate t h e heat change required t o cool TF from 100째C t o :78OK,

t h e s e n s i b l e and l a t e n t heats are summed as shown below.

The heat 'capa-

c i t i e s and enthalpy changes are HF physical p r o p e r t i e s (22,34). ( a ) Sensible h e a t , 100째C t o 2OoC (melting point of TF) I

4, = mCp ( g ) ATT1 = (7.57

k) -mole ( g - ~ ~ ~ (el oco ~- ~20Oc) ) = 8.66 x i o 4 cal hr

(b)

Latent heat of vaporization

(c)

Sensible heat, 2OoC t o -83OC ( f r e e z i n g point of TF)

(a)

L a t e n t heat of f u s i o n

-mole

Q4 = d H f

(7.57

22.02 g ( g-mole ) (46.93

*)t3

3* = 7.823 x 10 hr

( e ) Sensible heat, -83Oc t o 78OK

= 1.506 x i o4 * I

The t o t a l heat load i s

i=l

83 ORNL/TM-51&

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