T \” O A K RIDGE NATIONAL LABORATORY

k

operated by

UNION CARBIDE CORPORATION NUCLEAR DIVISION

for the US. ATOMIC ENERGY COMMISSION

ORNL - TM- 2335

SOLUBILITY OF CERIUM TRIFLUORIDE IN MOLTEN MIXTURES OF

LiF, BeF2‘ AND ThF4

NOTICE This document contoins information of o preliminory nature and was prepared primarily for internal use ot the Oak Ridge Notional Loborotory. I t is subject to revision or correction and therefore does not represent o final report.

LEGAL NOTICE

This report was proparod as an account o f Govornmont sponsored work. Noither the Unitod States,

nor the Commission, nor any porson acting on bohalf of tho Commission:

A. Makos any warranty or ropnsontation, oxpossod 01 implied, wi th respoct to the accuracy,

complotonoss, ar usofulnoss of the information containod in this roport, or that the use of any information, apparatus, mothod, or procosr disclosed in this roport may not infringo

privately ownod rights; or

B. Asrumos any l iabi l i t ios wi th r e s w c t t o tho US. of, or for damages resulting from the use of

any information, apparatus, mothod, OT procosr disclosed i n this report.

As "sod in tho above, "porson acting on behalf of the Commission'' includes any employee or contract^^ of the Commission, or employ.. of such comtroctoi, t o the extont that such e m p l o y e e

or contractw of the Commission, or employoo of such contractor propares, diiseminatos, or

providos access to, any information pursuant to his employment w contract wi th the Commission,

ar his employment wi th such contractor.

ORNL-TM-2335

Contract No. W-7405-eng-26

REACTOR CHEMISTRY DIVISION

SOLUBILITY OF CERIUM TRIFLUORIDE IN MOLTEN MIXTURES OF LiF, BeF, , AND ThF4

Judy A. Fredricksen: L. 0. Gilpatrick, C. J. Barton

JANUARY 1969

* Summer ORAU P a r t i c i p a n t from S t . S t . Cloud, Minnesota

Cloud S t a t e Co l l ege ,

OAK RIDGE NATIONAL LABORATORY Oak Ridge , Tennessee

operated by UNION CARBIDE CORPORATION

f o r the U.S. ATOMIC ENERGY COMMISSION

~~

L E G A L N O T I C E This report %-as Prepared a s an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behaif of the Commission:

A. Makes any warranty or representation. expressed or Implied, with respect to the accu- racy, completeness. or usefulness of the information contained in this report, or that the use of any information, apparatus, method, o r Process disrlascd in this report may not infringe privately owned rights; or

B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in ibis report.

As used in the above, “person acting on behalf of the Commission” includes m y em- ployee or contractor of the Commission. or employee of such contractor, to the extent that such employee or contractor of the Comrmasion, o r employee of such contractor prepares, disseminates, or provides access to, any Information pursuant to his employment or contract with the Commission, o r his employment with such contractor.

iii

CONTENTS

Page

A b s t r a c t . . . . . . . . . . . . . . . . I n t r o d u c t i o n . . . . . . . . . . . . . . Equipment . . . . . . . . . . . . . . . . M a t e r i a l s . . . . . . . . . . . . . . . . Procedure . . . . . . . . . . . . . . . . R e s u l t s and Discuss ion . . . . . . . . . References . . . . . . . . . . . . . . .

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V SOLUBILITY OF CERIUM TRIFLUORIDE I N MOLTEN MIXTURES OF

LiF , BeF, AND ThF,

Judy A . F r e d r i c k s e n , * L. 0. G i l p a t r i c k ,

C. J . Barton

ABSTRACT

The s o l u b i l i t y of CeF, was determined a t v a r i o u s t empera tu res i n s i x mixtures of LiF, BeF,, ThF, of

t h e type t h a t may be used t o f u e l a molten s a l t b reede r

r e a c t o r . Comparison of e a r l i e r d a t a on t h e so lu -

b i l i t y of PuF, and CeF, i n f l u o r i d e s o l v e n t s makes

i t p o s s i b l e t o p r e d i c t t h a t t h e s o l u b i l i t y of PuF,

i n s i n g l e - r e g i o n f u e l composi t ions a t r e a c t o r

o p e r a t i n g tempera tures w i l l be more t h a n adequate .

The s o l u b i l i t y d a t a a s a f u n c t i o n of s o l v e n t compo-

s i t i o n were b e s t c o r r e l a t e d by a model t h a t assumes

BeFz t o be complexed a s t h e BeFQZ' i o n and ThF, a s

t h e ThF,'' i o n .

INTRODUCTION

S t u d i e s performed e a r l i e r a t t h e Oak Ridge Na t iona l

Laboratory demonstrated t h e s o l u b i l i t y of PuF, i n c e r t a i n

molten f l u o r i d e s o l v e n t s , ' but no d a t a a r e a v a i l a b l e on t h e

s o l u b i l i t y of PuF, i n s i n g l e - f l u i d r e a c t o r f u e l c o n t a i n i n g a

h igh c o n c e n t r a t i o n of ThF,. P rev ious d a t a i n d i c a t e d t h a t t h e

s o l u b i l i t y would probably be adequate a t proposed r e a c t o r

* Summer ORAU P a r t i c i p a n t from St. Cloud S t a t e Col lege , S t Cloud, Minnesota.

2

o p e r a t i n g t empera tu res . To v e r i f y t h i s b e l i e f , t h e most

obvious approach would be direct measurement of PuF, s o l u -

b i l i t y i n molten f l u o r i d e s a l t s of i n t e r e s t , b u t w e have chosen

t o s tudy t h e s o l u b i l i t y of a n o t h e r t r i v a l e n t f l u o r i d e , CeF,,

because of i t s s i m i l a r behavior and s i m p l e r hand l ing . There

is evidence i n d i c a t i n g t h a t PuF, and CeF, a r e q u i t e s i m i l a r i n

t h e i r s o l u b i l i t y behavior i n f l u o r i d e m e l t s . 2 ’ 3

s t u d y of t h e e f f e c t on t h e s o l u b i l i t y of CeF, of v a r y i n g t h e

c o n c e n t r a t i o n s of LiF , BeF, and ThF, i n m e l t s w i l l i n d i c a t e

t h e p robab le s o l u b i l i t y of PuF, i n such m e l t s . T h i s i n v e s t i -

g a t i o n may be fo l lowed by l i m i t e d d e t e r m i n a t i o n s of PuF, s o l u -

b i l i t y t o conf i rm p r e d i c t i o n s based on t h e CeF, i n v e s t i g a t i o n .

The chemical f e a s i b i l i t y of f u e l i n g molten s a l t r e a c t o r s w i t h

PuF, h a s been cons ide red i n a n o t h e r r e p o r t .

A thorough

4

T h i s r e p o r t g i v e s t h e r e s u l t s o b t a i n e d t o d a t e i n a n

i n v e s t i g a t i o n on t h e s o l u b i l i t y of CeF, i n mixed LiF , BeF, and

ThF, molten f l u o r i d e s o l v e n t s .

EQUIPMENT

The r e a c t i o n v e s s e l i n which t h e s o l u b i l i t y measurements

were made was a welded c y l i n d r i c a l n i c k e l c o n t a i n e r w i t h a n

i n t e r n a l d i a m e t e r of 12 i n . , a d e p t h of 6 i i n . , and a w a l l

t h i c k n e s s of 1/8 i n . A seven-inch s e c t i o n of *- in . I . D .

n i c k e l p i p e was welded t o t h e l i d and w a s c l o s e d a t t h e t o p

wi th a s t a i n l e s s s t e e l b a l l v a l v e having a n i n t e r n a l c l e a r a n c e

of i n . T h i s c o o l i n g and l o a d i n g s t e m was a l s o equipped w i t h

a 1 /4- in . g a s d i s c h a r g e p o r t welded n e a r i t s upper end. An

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Y

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W

a d d i t i o n a l opening i n t h e l i d accommodated a thermocouple w e l l

of 1/4- in . t h i n w a l l (10 m i l ) n i c k e l t u b i n g c losed a t t h e lower

end, which extended t o w i t h i n 1/8 i n . of t h e bottom. The

remaining l i d opening he ld a 1 /4- in . n i c k e l d i p l e g of heavy

w a l l ( 3 5 mil) n i c k e l t ub ing ex tending t o w i t h i n 1 /4 i n . of t h e

v e s s e l bottom t o f a c i l i t a t e a g i t a t i o n and p u r i f i c a t i o n of t h e

m e l t by a d m i t t i n g gases beneath t h e m e l t s u r f a c e .

The v e s s e l was mounted v e r t i c a l l y i n a 3 - i n . , 1400-watt

e lec t r ic t u b e f u r n a c e whose tempera ture was r e g u l a t e d by means

of a chromel-alumel thermocouple p laced between t h e f u r n a c e

w a l l and t h e v e s s e l and a h i g h - s e n s i t i v i t y bucking c i r c u i t

c o n t r o l l e r .

M e l t t empera tures w e r e determined by a second chromel-

a lumel thermocouple l o c a t e d i n t h e thermocouple w e l l surrounded

by t h e m e l t . An i c e b a t h , a s t a n d a r d c e l l , and a Leeds and

Northrup type K-2 po ten t iome te r were used t o measure t h e E.M.F.

i n t h i s measuring c i r c u i t . Temperatures were deduced from

standard tables of temperature versus E.M.F.

Copper f i l t e r s t i c k s were c o n s t r u c t e d from 3/8-in. d iameter

s i n t e r e d d i s k f r i t t s 1/8- in . t h i c k wi th a nominal pore s i ze of

0.0004 i n . These were welded i n t o s e c t i o n s of 3/8-in. O . D .

t u b i n g 1 / 2 - i n . long. A t t h e o p p o s i t e end, t h i s t ube was reduced

i n d iameter and welded t o a 20-in. l e n g t h of 1/8- in . O . D .

t ub ing . These tubes were s l i p p e d through a Tef lon gland made

t o f i t a 1/2- in . Swagelok t u b i n g connec tor and compressed by a

s t a n d a r d connector c o l l a r . Th i s gland formed a vacuum t i g h t

4

s e a l around t h e 1 /8- in . f i l t e r t ube bu t i t al lowed movement

of t h e f i l t e r through t h e gland which was f i t t e d t o t h e t o p

end of t h e b a l l v a l v e . S u f f i c i e n t space was provided between

t h e c l o s e d b a l l of t h e v a l v e and t h e gland t o accommodate t h e

f i l t e r u n i t f o r evacuat ion and f l u s h i n g wi th helium p r i o r t o

admi t t i ng i t t o t h e c l e a n (ox ide f r e e ) m e l t . A p i e c e of s o f t

rubber tub ing which f i t t e d over t h e f r e e end of t h e f i l t e r

s t i c k could be connected t o e i t h e r a vacuum pump or a helium

source . A manifold s y s t e m c o n s i s t i n g of v a l v e s , p r e s s u r e

gages , and flow meters c o n t r o l l e d admission of helium, hydrogen,

H F or a p p l i c a t i o n of vacuum t o t h e a p p a r a t u s .

Samples c o n t a i n i n g 1 4 b C e t r a c e r w e r e ana lyzed u s i n g a

256-channel or 400-channel ana lyze r a t f i x e d geometry wi th a

3 x 3 i n . NaI, t h a l l i u m a c t i v a t e d c r y s t a l . Sample p r e p a r a t i o n

and weighing was done i n a hood equipped wi th a d u s t con ta in -

ment g love box.

MATERIALS

Some of t h e composi t ions used i n t h e s e s t u d i e s were s u p p l i e d

by J. H. S h a f f e r and F. A . D o s s of ORNL. Mixtures of LiF, BeF,,

and ThF4 (72-16-12 and 68-20-12 mole TO) were used a s r e c e i v e d

a s was a mix tu re of LiF and ThF4 (73-27 m o l e '$0). The ( 7 2 . 7 -

4.8-22.5) mixture was prepared by adding 53 g of (72-16-12) t o

198 g of t h e 73-27 r e s i d u e l e f t i n t h e v e s s e l a f t e r p rev ious

s o l u b i l i t y d e t e r m i n a t i o n s . Likewise a mixture c a l c u l a t e d t o

have t h e composi t ion (72-3-11.0-16.7) was prepared by adding

1 9 5 . 5 g of (72-16-12) t o 2 2 5 . 1 g of (73.1-4.8-22.4) remaining

W

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5

a t t h e end of a ser ies of measurements. A mix tu re having t h e

composi t ion (67.8-25.2-7.0) was p repa red by mixing 94.7 g of

66 LiF - 34 BeF, w i t h 1 0 2 . 1 g of t h e 73-27 p r e p a r a t i o n .

Ten m i l l i c u r i e s of l c 4 C e i n t h e form of an aqueous HC1

s o l u t i o n was secu red from t h e I s o t o p e s D i v i s i o n a t ORNL. T h i s

was mixed w i t h a s o l u t i o n c o n t a i n i n g 308 g of CeC1, x H 2 0 . *

The r e s u l t i n g s o l u t i o n was hea ted t o 9OoC and d i g e s t e d wi th

214 g of NH,F.HF** d i s s o l v e d i n 1000 m l of H,O, which y i e l d e d

a homogeneous p r e c i p i t a t e of CeF, c o n t a i n i n g t h e r a d i o i s o t o p e .

T h i s p r e c i p i t a t e was washed w i t h d i s t i l l e d water f o u r t i m e s

and c e n t r i f u g e d b e f o r e d r y i n g a t l l O ° C f o r 24 hours .

Commercial hydrogen was p u r i f i e d by passage through a

Deoxo u n i t , a magnesium p e r c h l o r a t e d r y i n g t u b e , and a l i q u i d

N, t r a p . Anhydrous HF (99.9%), was used from t h e c y l i n d e r a s

r e c e i v e d wi thou t p u r i f i c a t i o n . Commercial hel ium was p u r i f i e d

by passage through an A s c a r i t e t r a p , a magnesium p e r c h l o r a t e

t r a p , and a c h a r c o a l t r a p a t l i q u i d N, t empera ture .

PROCEDURE

Helium l e a k t e s t i n g was done a t room t empera tu re p r i o r t o

l o a d i n g t h e u n i t u n t i l a vacuum of a t l e a s t 74 microns was

secu red . A weighed amount of f u e l s a l t , u s u a l l y about 250

grams, and more than t h e amount of CeF, expec ted t o d i s s o l v e

a t t h e maximum tempera tu re were added t o t h e v e s s e l through

V

* A. D o MacKay, I n c . , C O P . grade.

Baker and Adamson, t e c h n i c a l grade . **

6

t h e o p e n b a l l v a l v e by means of a l o n g - n e c k e d f u n n e l . The

a p p a r a t u s was t h e n c o n n e c t e d t o t h e m a n i f o l d s y s t e m . A

h e a t e d sod ium f l u o r i d e t r a p was p l a c e d a t t h e o u t l e t t o

p r e v e i i t HF f r o m e s c a p i n g i n t o t h e hood . T h i s was f o l l o w e d by

a b u b b l e r t o i n d i c a t e when g a s was f l o w i n g t h r o u g h t h e s y s t e m .

P u r i f i c a t i o n was c a r r i e d o u t a t a b o u t 6 2 5 O C by t r e a t i n g

t h e m e l t w i t h g a s e o u s HF ( 2 0 m l / m i n ) , H, ( 1 0 0 m l / m i n ) , a n d

h e l i u m ( 1 0 0 ml/min) f o r a t l eas t t h r e e h o u r s . Hydrogen

f l u o r i d e e l i m i n a t e d any p r o d u c t s of h y d r o l y s i s r e s u l t i n g f r o m

a d s o r b e d w a t e r on t h e s u r f a c e o f t h e f u e l s a l t by c o n v e r t i n g

t h e m t o f l u o r i d e s . The h y d r o g e n he lped t o m i n i m i z e t h e cor-

r o s i v e n e s s of t h e HF by r e d u c i n g a n y NiFz p r o d u c e d t o N i w h i l e

t h e h e l i u m s e r v e d a s a c a r r i e r g a s . N e x t , t h e m e l t was

s u b j e c t e d t o two h o u r s of hydrogen ( 1 0 0 ml/min) -- h e l i u m

( 1 0 0 ml/min) t r e a t m e n t t o c o m p l e t e t h e r e d u c t i o n o f any NiF,

formed . Hydrogen a n d h e l i u m f l o w r a t e s were m e a s u r e d by r o t a m e t e r s

c a l i b r a t e d w i t h a "Bubb le -0 -Mete r . " The h y d r o g e n f l u o r i d e f l o w

r a t e was m e a s u r e d by p a s s i n g t h e g a s m i x t u r e t h r o u g h a m e a s u r e d

volume o f 0 . 1 M KOH s o l u t i o n u s i n g p h e n o l p h t h a l e i n a s a n

i n d i c a t o r and a s t o p wa tch t o d e t e r m i n e t h e t i m e n e c e s s a r y

f o r n e u t r a l i z a t i o n .

The m i x t u r e i n t h e a p p a r a t u s was a l l o w e d t o e q u i l i b r a t e

f o r one h o u r s t a r t i n g a t t h e h i g h e s t s a m p l i n g t e m p e r a t u r e

w h i l e a g i t a t i o n was m a i n t a i n e d by a s l o w h e l i u m f l o w of 3 0 m l

p e r m i n u t e . Each m e l t , w i t h a n e x c e s s o f CeF , , fo rmed a Y

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s a t u r a t e d s o l u t i o n a t t h e s e l e c t e d tempera ture which was then

sampled t o de termine t h e c o n c e n t r a t i o n of CeF, i n t h e f i l t e r e d

m e l t . Sampling was performed by assembling t h e f i l t e r s t i c k ,

a f t e r p o l i s h i n g wi th s teel wool t o remove t h e oxide c o a t i n g ,

and t h e gland above t h e c l o s e d b a l l va lve . This a r e a was

s e a l e d by t i g h t e n i n g t h e threaded c o l l a r around t h e Teflon

g land , and a vacuum was a p p l i e d fol lowed by f l u s h i n g w i t h

helium t o remove a i r . T h i s f l u s h was r epea ted be fo re t h e b a l l

v a l v e was opened and t h e f i l t e r was i n s e r t e d t o w i t h i n 1 / 2 - i n .

of t h e v e s s e l bottom. A smal l f low of helium was maintained

through t h e f i l t e r s t i c k w h i l e i t was be ing i n s e r t e d and

submerged. F ive or t e n minutes was al lowed f o r t h e f i l t e r t o

r each t h e m e l t t empera ture b e f o r e t h e helium f low was s topped

and a vacuum was a p p l i e d t o t h e s t e m . The s a l t f r o z e i n t h e

1/8- in . d iameter c o l d s t e m of t h e f i l t e r s t i c k . Samples were

withdrawn slowly t o p r o t e c t t h e Tef lon gland from over h e a t i n g .

A f t e r c l o s i n g t h e b a l l v a l v e , t h e f i l t e r s t i c k was removed by

d isassembl ing t h e gland and compression c o l l a r . I t was then

c u t open and emptied i n t h e g love box where t h e m e l t samples

were ground and 50 mg k 3 mg was weighed from each f i l t e r for

coun t ing and one gram f o r w e t chemical a n a l y s i s .

The 50 mg p o r t i o n s of ground s a l t were weighed and p l aced

i n p l a s t i c v i a l s 1 - i n . i n d iameter and 2- in . h igh , S i x samples

were drawn a t 4OoC i n t e r v a l s ending a t about 2OoC above t h e

me l t ing p o i n t of t h e s a l t composi t ions. Seven channels

c e n t e r i n g around t h e most e n e r g e t i c y d i s i n t e g r a t i o n a t

8

0.124 M . E . V . were i n t e g r a t e d d u r i n g t h e coun t ing which was

done mostly f o r one minute i n t e r v a l s .

Analyzing t h e samples rad iochemica l ly involved p repa r ing

s t a n d a r d samples made f o r each molten s a l t mix ture c o n s i s t i n g

of 50 mg of s o l v e n t (i 5%) p l u s va ry ing amounts of a c c u r a t e l y

weighed CeF, t r a c e r s a l t . A blank was a l s o prepared which

con ta ined only t h e s o l v e n t which was used t o de te rmine t h e

v a l u e t o be s u b t r a c t e d from t h e t o t a l count t o c o r r e c t f o r

t h e gamma a c t i v i t y of thorium daughter p roduc t s . The n e t

count ing r a t e ob ta ined f o r each s t a n d a r d was p l o t t e d on a

l i n e a r s c a l e a g a i n s t mi l l i g rams of l a b e l e d cerium f l u o r i d e .

T h e s e c a l i b r a t i o n d a t a made i t p o s s i b l e t o d e t e r m i n e t h e

number of mi l l i g rams of CeF, p r e s e n t i n each sample from t h e

count r a t e . From these v a l u e s w e c a l c u l a t e d t h e mole p e r c e n t

of cerium f l u o r i d e p r e s e n t i n each molten s a l t mix ture a t

t h e v a r i o u s tempera tures . N o adjustment was made f o r r a d i o -

a c t i v e decay s i n c e t h e h a l f l i f e of 1 4 4 C e i s 285 days and

a l l count ing f o r a g iven set of samples , i n c l u d i n g c a l i b r a -

t i o n s , was performed i n sequence on a s i n g l e day.

RESULTS AND DISCUSSION

The d a t a ob ta ined a r e p l o t t e d i n F i g s . 1 - 6 , i n c l u s i v e .

Both rad iochemica l and w e t chemical a n a l y s i s a r e shown i n t h e s e

p l o t s . I n g e n e r a l , t h e agreement between t h e two methods of

a n a l y s i s is cons idered q u i t e s a t i s f a c t o r y . I n some c a s e s ,

comparison of t h e d a t a r e q u i r e d rechecking t h e w e t chemical

a n a l y s e s and, i n o t h e r s , re-examinat ion of t h e rad iochemica l

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10

8

6

4

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ro LL

0 Q, 0.0

0.6

0.4

0.2

0.1 1 .o

700

ORNL-DWG 68- 12064 TEMPERATURE ("C)

600

I I 0 RADIOCHEMICAL ANALYSIS -. 0 WET CHEMICAL ANALYSIS

~

I- -

I

I .I

' O O O / T ( o K )

1.2

Fig . 1. S o l u b i l i t y of CeF, i n LiF-BeF2-ThF, ( 7 2 - 1 6 - 1 2 mole yo).

10

9

8

7

6

5

4

1

s-” a, - E - 3 L! 0, 0

2

i

10

ORNL-DWG 68-42063 TEMPERATURE (“C)

800 700

l o RADIOCHEMICAL ANALYSIS 0 WET CHEMICAL ANALYSIS

600

I

\ \ \

0.9 1 .o i . 1 i.2

‘OOO/T ( O K )

Fig. 2. Solubility of CeF, i n LiF-ThF4 (73-27 mole yo).

v

11

ORNL-DWG 68-{2065

10

9

8

7

6

5

c

E+ - a 4

L!

E - a 0

3

2

I

TEMPERATURE ("C) 800 700

\ \ O I

0 RADIOCHEMICAL ANALYSIS 0 WET CHEMICAL ANALYSIS

600

\ \

0.9 4.0 1 . 4 4.2

'OOO/, ( O K ,

F i g . 3 . S o l u b i l i t y of CeF, i n LiF-BeF2 -ThF4 ( 7 2 . 7 - 4 . 8 - 2 2 . 5 mole %).

1 2

ORNL-DWG 68- 12066

10

9

8

7

6

5

4

- $ 0) 0 - E

n 3 Y

L L

0 0,

2

1

800 1

\ \

\ o \

1,

TEMPERATURE ("C) 70 0 600

0.9

I

i o RADIOCHEMICAL ANALYSIS 0 WET CHEMICAL ANALYSIS

'r \O

0 \ 0

\ \ \

1 .o f . 1

'Oo0/)T ( O K )

1.2

F i g . 4. S o l u b i l i t y of CeF, i n LiF-BeF,-ThF4 (68-20-12 mole 70) .

1 3

ORNL-DWG 68-42067

0.9

800

\ L

\ \ \

\ '\

0

e 0

o RADIOCHEM

TEMPERATURE ("C)

700

.AL ANALYSIS 0 WET CHEMICAL ANALYSIS

600

I

1.2

Fig. 5. Solubility of CeF, in LiF-BeF2 -ThF4 (72.3-11.0-16.7 mole 7 0 ) .

14

ORNL- DWG 68 - f2068

TEMPERATURE ("C) 800 700 600

I I

1 i o

9

8

7

6

5

4 - $ al - E

a 1 3

Y

m LL

0

2

i

- -+ - !

I 0 RADIOCHEMICAL ANALYSIS e WET CHEMICAL ANALYSIS

\ \

0.9 4 .O 1 . 1 1.2

' O OO/r ( 0 K 1

F i g . 6 . S o l u b i l i t y of CeF, i n LiF-BeF2 -ThF, ( 6 7 . 8 - 2 5 . 2 - 7 . 0 mole 70) .

V

..

15

v

W

calibration values. It is apparent in Figs. 3, 5, and 6 that

insufficient CeF, was present in the system to saturate the

melts at the highest temperatures. The data are summarized

in Table 1 together with heats of solution calculated from

the relation

where S z is the solubility (in mole 70) at the higher tempera-

ture and S1 is the corresponding value at the lower temperature.

The heats of solution are in approximately the same range as

those reported' for solutions of PuF, in various fluoride

solvents (12,000 to 16,800 cal per mole).

The solubility data obtained in this investigation are

very reassuring in respect to the potential use of PuF, as

the fissionable species in single-region fuel compositions.

The lowest solubility observed at 6OO0C was 1.05 mole yo. A 1 comparison of PuF, solubility data with similar values

reported ' for CeF, i n Fig.

of PuF, at 600° may be less than 1.0 mole 70 but will almost

certainly exceed the few tenths mole 70 value required to fuel

a single region breeder reactor.

7 i n d i c a t e s t h a t t h e s o l u b i l i t y

Bredig has suggested5 that the "free fluoride" content of

liquid mixtures of LiF, BeF2, and ThF, can be calculated from

the following relation in terms of mole 70:

Free fluoride = LiF - 2(BeFZ) - 3(ThF,)

This relation is based on the assumption that LiF is complexed

16

Table 1. Solubility and Heat of Solution of CeF3

in Mixtures of LiF, BeF2, and ThF4

Salt Composition (mole $)

LiF ThF4 72 16 12 -

73 0 27

72.7 4.8 22.5

68 20 12

72.3 11.0 16.7

67.8 25.2 7.0

CeF3 Solubility (mole $)

6OO0C 800°C 1.6 5.5

2.6 9.0

2.4 7.9

1.35 6.0

2.1 6.3

1.05 5.0

Heat of Solution (ea1 per mole)

11,500

11,560

11,100

13,890

10,230

14,530

1 7

V

1.8

1.6

1.4

8 u 1.2 e 2 1.0 5 -

v

v, W I-

LL

z k' 0.8 53 a

LT 0

LL' 0" 0.6

0.4

0.2

0

ORNL-DWG 68-5997

I / r

PuF3- 650" /

10 20 30 40 50 60 BeF2 IN SOLVENT (mole %)

F i g . 7 . Comparison of CeF, and PuF, S o l u b i l i t y i n LiF-BeF2 S o l v e n t s .

18

Y a s Li,BeF4 and Li,ThF, i n t h e l i q u i d s t a t e . I t is i n t e r e s t i n g

t o t es t t h i s concept w i t h t h e CeF, s o l u b i l i t y d a t a r e p o r t e d

h e r e . The r e s u l t i n g graph (F ig . 8) shows a r a t h e r poor

c o r r e l a t i o n based on t h i s r e l a t i o n s h i p . A somewhat b e t t e r

c o r r e l a t i o n , shown i n F i g . 9 , r e s u l t s from t h e assumption

t h a t BeF, is complexed i n t h e l i q u i d s t a t e a s Li,BeF4 and

ThF, a s LiThF,. The l a t t e r assumption h a s a r a t h e r shaky

b a s i s s i n c e t h e pub l i shed phase diagram6 for t h e system

LiF-ThF4 i n d i c a t e s t h a t t h e 1:l compound ( a s i t is now known

t o be ) m e l t s i ncongruen t ly . The on ly d e f e n s e for t h i s

assumption is t h a t f i v e of t h e s i x composi t ions t e s t e d t o

d a t e show s o l u b i l i t y d a t a t h a t c o r r e l a t e on t h i s b a s i s .

7

1.

2 .

3 .

4.

5.

6 .

7 .

REFERENCES C . J . Bar ton , J . Phys. Chem. - 6 4 , 306 (1960) .

W . T. Ward, R . A . St reh low, W . R . G r i m e s , and

G . M. Watson, J . Chem. Eng. Data - 5 , 2 (1960) .

C. J . Bar ton , M e m o t o P. R . Kas ten , June 4 , 1968,

MSR 68-88.

R . E . Thoma, Chemical F e a s i b i l i t y of F u e l i n g Molten

S a l t R e a c t o r s w i t h PuF,, ORNL-TM-2256, June 2 0 , 1968

M . A . B red ig , M e m o t o W . R. G r i m e s , A p r i l 26, 1968,

MSR 68-75.

R . E . Thoma e t a l , J . Phys. Chem. 6 3 , 1267 4.1959).

G . Brunton, Acta C r y s t . - 2 1 ( 5 ) , 814 (1966) .

Y

1 9

io. 0

9.0

8.0

7.0

h

6.0 Q, -

- rc) 5.0 LL a 0

4.0

3.0

2.0

1.0

0

ORNL-DWG 68-12069

0 73 LiF-27 ThF4 + 68 LiF- 20 BeF2-12ThF4

67.8 LiF-25.2 BeF2- 7.0 ThG a 72.3 LiF-11.0 BeF2-46.7 ThF4 0 72 LiF-16 BeF2-12 ThF4

\ I A 72.7 LLF-4.8 BeF2-22.5ThF4

I I 800°C I

600°C

-8 -6 -4 -2 0 2 4 6 8 FREE LiF (mole '3")

Fig . 8. Solubility of CeF, As A Funct ion of F ree LiF Assuming Li,BeF4 and Li,ThF, I n Liquid .

2 0

ORNL-DWG 68-42070

5 40 15 20 25 30 35 40 45 FREE LiF (mole %)

Fig. 9 . S o l u b i l i t y of CeF, A s A F u n c t i o n of F r e e L i F Assuming Li,BeF4 and LiThF, i n L i q u i d .

2 1

REFERENCES

1. C. J . B a r t o n , J . Phys. Chem. - 64, 306 (1960) .

2 . W . T. Ward, R . A . Streh low, W . R . G r i m e s , and G . W . Watson, J . Chem. Eng. Data - 5 , 2 (1960).

3. C. J. Bar ton , M e m o t o P. R. Kas ten , June 4, 1968, MSR 68-88.

4 . R. E . Thoma, Chemical F e a s i b i l i t y of F u e l i n g Molten S a l t Reac to r s w i t h PuF,, ORNL-TM-2256, June 20, 1968.

5. M . A . Bred ig , Memo t o W . R. G r i m e s , A p r i l 2 6 , 1968, MSR 68-75.

6 . R . E . Thoma e t a l , J. Phys. Chem. - 63, 1 2 6 7 (1959) .

7. G . D . Brunton, Acta C r y s t . - 2 1 ( 5 ) , 814 (1966) .

-.

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