ORNL-TM-2335 by Jon Morrow

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O A K RIDGE N A T I O N A L LABORATORY 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. It i s subject to revision or correction and therefore does not represent o final report.

LEGAL NOTICE T h i s 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:

Makos any warranty or ropnsontation, o x p o s s o d complotonoss, any

implied, w i t h respoct t o the accuracy,

ar usofulnoss of the information containod i n this roport, or that the use of

information,

apparatus, mothod, or procosr disclosed i n this roport may not infringo

privately ownod rights; or

Asrumos any l i a b i l i t i o s w i t h r e s w c t t o tho

any information, apparatus, mothod,

US.

of, or for damages resulting from the use of

procosr disclosed i n this report.

As "sod in tho above, "porson acting o n behalf of the Commission'' contract^^

of the Commission, or employ..

contractw of the Commission,

of such comtroctoi, t o the

includes any employee or extont

that such e m p l o y e e

or employoo of such contractor propares, diiseminatos, or

providos access to, any information pursuant t o h i s employment w contract w i t h the Commission, ar h i s employment w i t h 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 . Cloud S t a t e C o l l e g e ,

S t . Cloud, Minnesota

OAK RIDGE NATIONAL LABORATORY Oak Ridge , Tennessee operated by UNION CARBIDE CORPORATION f o r the U.S. ATOMIC ENERGY COMMISSION ~~

LEGAL

NOTICE

This report %-asPrepared 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 accuracy, 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 employee 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

. . . Introduction . Equipment . . . Materials . . . Procedure . . . Abstract

. . . . .

1 1 2

4 5

. . . . . . . . .

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

R e s u l t s and D i s c u s s i o n References

. . . . .

SOLUBILITY OF CERIUM TRIFLUORIDE I N MOLTEN MIXTURES OF

L i F , 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 . B a r t o n ABSTRACT The s o l u b i l i t y of CeF, was d e t e r m i n e d a t v a r i o u s t e m p e r a t u r e s i n s i x m i x t u r e s of L i F , BeF,,

ThF,

t h e t y p e t h a t may be used t o f u e l a molten s a l t b r e e d e r reactor.

Comparison of e a r l i e r d a t a on t h e s o l u -

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 compositions a t r e a c t o r o p e r a t i n g t e m p e r a t u r e s w i l l be more t h a n a d e q u a t e . 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 compos 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 b e complexed a s t h e BeFQZ' i o n and ThF, t h e ThF,''

ion.

INTRODUCTION

S t u d i e s performed e a r l i e r a t t h e Oak Ridge N a t i o n a l L a b o r a t o r y d e m o n s t r a t e d 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 , ' s o l u b i l i t y of PuF,

b u t no d a t a a r e a v a i l a b l e on t h e

i n single-fluid reactor f u e l containing a

h i g h c o n c e n t r a t i o n of ThF,.

Previous data indicated t h a t t h e

s o l u b i l i t y would p r o b a b l y be a d e q u a t e a t p r o p o s e d 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 C o l l e g e , S t Cloud, Minnesota.

operating temperatures.

To v e r i f y t h i s b e l i e f , t h e most

o b v i o u s a p p r o a c h would b e d i r e c t measurement of PuF,

solu-

b i l i t y i n m o l t e n 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 h a v e c h o s e n

t o s t u d y 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,, b e c a u s e of i t s s i m i l a r b e h a v i o r and s i m p l e r h a n d l i n g .

i s e v i d e n c e i n d i c a t i n g t h a t PuF,

There

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 â&#x20AC;&#x2122; 3

A thorough

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 L i F , BeF, and ThF, t h e p r o b a b l e s o l u b i l i t y of PuF,

i n m e l t s w i l l indicate

i n such m e l t s .

This investi-

g a t i o n may b e f o l l o w e d by l i m i t e d d e t e r m i n a t i o n s of PuF, b i l i t y t o c o n f i r m p r e d i c t i o n s based on t h e CeF,

solu-

investigation.

The c h e m i c a l f e a s i b i l i t y of f u e l i n g m o l t e n s a l t r e a c t o r s w i t h PuF,

h a s been c o n s i d e r e d i n a n o t h e r r e p o r t .

This report gives t h e r e s u l t s obtained t o d a t e i n an 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, ThF,

i n mixed L i F , BeF,

and

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 t h i c k n e s s of 1 / 8 i n .

i n . , a d e p t h of 6 i i n . ,

and a w a l l

A s e v e n - i n c h s e c t i o n of * - i n .

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 with a s t a i n l e s s s t e e l b a l l valve having an i n t e r n a l clearance of

in.

a 1/4-in.

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 e q u i p p e d w i t h

g a s d i s c h a r g e p o r t welded n e a r i t s u p p e r e n d .

a d d i t i o n a l o p e n i n g i n t h e l i d accommodated a thermocouple w e l l of 1 / 4 - i n .

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 l o s e d a t t h e lower

e n d , which e x t e n d e d t o w i t h i n 1 / 8 i n . of t h e bottom. remaining l i d opening h e l d a 1/4-in.

The

n i c k e l d i p l e g of heavy

w a l l ( 3 5 m i l ) n i c k e l t u b i n g e x t e n d i n g 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 g a s e s b e n e a t h 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 l e c t r i c t u b e f u r n a c e whose t e m p e r a t u r e was r e g u l a t e d by means of a chromel-alumel thermocouple p l a c e d 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 controller.

M e l t t e m p e r a t u r e s w e r e d e t e r m i n e d by a second chromela l u m e l thermocouple l o c a t e d i n t h e thermocouple w e l l s u r r o u n d e d 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

N o r t h r u p t y p e K-2

p o t e n t i o m e t e r were u s e d t o measure t h e E.M.F.

i n t h i s measuring c i r c u i t .

T e m p e r a t u r e s 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 - i n . s i n t e r e d d i s k f r i t t s 1/8-in. 0.0004 i n .

t h i c k w i t h a nominal p o r e s i z e of

T h e s e were welded i n t o s e c t i o n s of 3 / 8 - i n .

tubing 1/2-in.

long.

l e n g t h of 1 / 8 - i n .

O.D.

These t u b e s were s l i p p e d t h r o u g h a T e f l o n g l a n d made

t o f i t a 1/2-in. W

O.D.

A t t h e o p p o s i t e e n d , t h i s t u b e was r e d u c e d

i n d i a m e t e r and welded t o a 20-in. tubing.

diameter

Swagelok t u b i n g c o n n e c t o r and compressed by a

s t a n d a r d connector c o l l a r .

T h i s g l a n d formed a vacuum t i g h t

s e a l around t h e 1 / 8 - i n .

f i l t e r t u b e b u t i t a l l o w e d movement

of t h e f i l t e r t h r o u g h t h e g l a n d 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 s p a c e was p r o v i d e d 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 g l a n d t o accommodate t h e

f i l t e r u n i t f o r e v a c u a t i o n and f l u s h i n g w i t h h e l i u m p r i o r t o admitting i t t o t h e clean (oxide free) m e l t .

A p i e c e of s o f t

r u b b e r t u b i n g w h i c h f i t t e d o v e r t h e f r e e end of t h e f i l t e r s t i c k c o u l d be c o n n e c t e d t o e i t h e r a vacuum pump or a h e l i u m source.

A m a n i f o l d 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

g a g e s , and f l o w meters c o n t r o l l e d a d m i s s i o n of h e l i u m , 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 a n a l y z e d u s i n g a 256-channel or 400-channel a n a l y z e r a t f i x e d geometry w i t h a 3 x 3 i n . NaI,

thallium activated crystal.

Sample p r e p a r a t i o n

and weighing was done i n a hood e q u i p p e d w i t h a d u s t c o n t a i n ment g l o v e box. MATERIALS Some of t h e c o m p o s i t i o n s u s e d 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. and ThF4 ( 7 2 - 1 6 - 1 2

and 68-20-12

mole

Mixtures of L i F , BeF,,

TO) were u s e d a s r e c e i v e d

a s was a m i x t u r e of LiF and ThF4 (73-27 m o l e 4.8-22.5)

'$0).

The ( 7 2 . 7 -

m i x t u r e was p r e p a r e d by a d d i n g 53 g of (72-16-12)

198 g of t h e 7 3 - 2 7 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 r e v i o u s s o l u b i l i t y determinations.

Likewise a mixture c a l c u l a t e d t o

have t h e c o m p o s i t i o n (72-3-11.0-16.7)

1 9 5 . 5 g of (72-16-12)

was p r e p a r e d by a d d i n g

t o 2 2 5 . 1 g of (73.1-4.8-22.4)

remaining

a t t h e end of a s e r i e s of measurements. composition (67.8-25.2-7.0)

A mixture having t h e

was p r e p a r e d by m i x i n g 94.7 g of

66 L i F - 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 a n a q u e o u s H C 1 s o l u t i o n was s e c u r e d from t h e I s o t o p e s D i v i s i o n a t ORNL.

This

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 h e a t e d t o 9OoC and d i g e s t e d w i t h 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 w a t e r 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 째 C

f o r 24 h o u r s .

Commercial hydrogen was p u r i f i e d by p a s s a g e t h r o u g h 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,

trap.

Anhydrous HF ( 9 9 . 9 % ) , was u s e d from t h e c y l i n d e r a s

received without purification.

Commercial h e l i u m was p u r i f i e d

by p a s s a g e t h r o u g h a n 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 , a n d a c h a r c o a l t r a p a t l i q u i d N,

temperature.

PROCEDURE Helium l e a k t e s t i n g was done a t room t e m p e r a t u r e 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 m i c r o n s was secured.

A weighed amount of f u e l s a l t , u s u a l l y a b o u t 250

grams, and more t h a n t h e amount of CeF,

expected t o d i s s o l v e

a t t h e maximum t e m p e r a t u r e were added t o t h e v e s s e l t h r o u g h

* V

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

** Baker

and Adamson, t e c h n i c a l g r a d e .

6 t h e o p e n b a l l v a l v e by means o f a l o n g - n e c k e d

funnel.

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 .

The A

h e a t e d s o d i u m 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 h o o d .

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 e l i u m ( 1 0 0 ml/min)

(100 ml/min),

f o r a t least t h r e e hours.

and

Hydrogen

f l u o r i d e e l i m i n a t e d a n y 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 o n 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 them to fluorides.

The h y d r o g e n h e l p e d 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 N i F z p r o d u c e d t o N i w h i l e t h e helium served a s a carrier gas.

N e x t , t h e m e l t was

s u b j e c t e d t o t w o h o u r s of h y d r o g e n ( 1 0 0 ml/min) ( 1 0 0 ml/min)

formed

helium

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 a n y NiF,

H y d r o g e n 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 "Bubble-0-Meter."

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 v o l u m e 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 watch 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 for neutralization. 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 hour s t a r t i n g a t t h e h i g h e s t sampling 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

per minute.

Each m e l t , w i t h a n e x c e s s of CeF,,

formed a

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 t e m p e r a t u r e which was t h e n sampled t o d e t e r m i n e 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

melt.

Sampling was performed by a s s e m b l i n g 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 w i t h s t e e l wool t o remove t h e o x i d e c o a t i n g , and t h e g l a n d above t h e c l o s e d b a l l v a l v e .

T h i s 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 t h r e a d e d c o l l a r around t h e T e f l o n g l a n d , and a vacuum was a p p l i e d f o l l o w e d by f l u s h i n g w i t h h e l i u m t o remove a i r .

T h i s f l u s h was r e p e a t e d b e f o r e 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 s m a l l f l o w of h e l i u m was m a i n t a i n e d

t h r o u g h t h e f i l t e r s t i c k w h i l e i t was b e i n g i n s e r t e d and submerged.

F i v e or t e n m i n u t e s was a l l o w e d f o r t h e f i l t e r t o

r e a c h t h e m e l t t e m p e r a t u r e b e f o r e t h e h e l i u m f l o w was s t o p p e d and a vacuum was a p p l i e d t o t h e s t e m . 1/8-in.

The s a l t f r o z e i n t h e

d i a m e t e r 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 s l o w l y t o p r o t e c t t h e T e f l o n g l a n d from o v e r 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 i s a s s e m b l i n g t h e g l a n d and compression c o l l a r .

I t was t h e n

c u t open and emptied i n t h e g l o v e box where t h e m e l t s a m p l e s

were ground and 5 0 mg k 3 mg was weighed from each f i l t e r for c o u n t i n g and one gram f o r w e t c h e m i c a l a n a l y s i s . The 5 0 mg p o r t i o n s of ground s a l t were weighed and p l a c e d i n p l a s t i c v i a l s 1-in.

i n d i a m e t e r and 2 - i n .

high,

S i x samples

were drawn a t 4OoC i n t e r v a l s e n d i n g a t a b o u t 2OoC above t h e m e l t i n g p o i n t of t h e s a l t c o m p o s i t i o n s . W

Seven c h a n n e l s

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 c o u n t i n g which was

done m o s t l y f o r one m i n u t e i n t e r v a l s . Analyzing t h e samples radiochemically involved p r e p a r i n g s t a n d a r d s a m p l e s made f o r e a c h m o l t e n s a l t m i x t u r e c o n s i s t i n g of 5 0 mg of s o l v e n t (i 5%) p l u s v a r y i n g amounts of a c c u r a t e l y weighed CeF,

tracer salt.

A b l a n k was a l s o p r e p a r e d which

c o n t a i n e d o n l y t h e s o l v e n t which was u s e d t o d e t e r m i n e 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 c o u n t 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 t h o r i u m d a u g h t e r p r o d u c t s .

The n e t

c o u n t i n g r a t e o b t a i n e d f o r e a c h 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 m i l l i g r a m s of l a b e l e d c e r i u m 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 m i l l i g r a m s of CeF, p r e s e n t i n e a c h sample from t h e count r a t e .

From t h e s e 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 c e r i u m f l u o r i d e p r e s e n t i n each m o l t e n s a l t m i x t u r e a t t h e various temperatures.

N o a d j u s t m e n t 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 d a y s and a l l c o u n t i n g f o r a g i v e n s e t of s a m p l e s , 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 s e q u e n c e on a s i n g l e d a y . RESULTS AND DISCUSSION The d a t a o b t a i n e d a r e p l o t t e d i n F i g s .

1-6,

inclusive.

Both r a d i o c h e m i c a l and w e t c h e m i c a l a n a l y s i s a r e shown i n t h e s e plots.

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 considered 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 r e c h e c k i n g t h e w e t c h e m i c a l a n a l y s e s and, i n o t h e r s , re-examination

of t h e r a d i o c h e m i c a l

ORNL-DWG

700

TEMPERATURE ("C) 600

I 0

68- 12064

RADIOCHEMICAL ANALYSIS WET CHEMICAL ANALYSIS

I-

0.0

0.6

0.4

0.2

0.1

1 .o

I .I

1.2

'OOO/T(oK)

F i g . 1.

S o l u b i l i t y of CeF,

i n LiF-BeF2-ThF,

(72-16-12

mole yo).

10 v ORNL-DWG

68-42063

TEMPERATURE (“C)

800

600

700

8 7

4 1

s-” a, -

L! 0,

o RADIOCHEMICAL ANALYSIS 0 WET CHEMICAL A N A L Y S I S

\ \ \

0.9

1 .o

i.1

‘OOO/T

Fig. 2.

i.2

(OK)

Solubility of CeF, i n LiF-ThF4

( 7 3 - 2 7 mole

yo).

ORNL-DWG 68-{2065

TEMPERATURE ("C) 700

800

600

10 9 8

\ \O

E+ a

-E L!

3 0 0

RADIOCHEMICAL ANALYSIS WET CHEMICAL A N A L Y S I S

0.9

4.0

1.4

'OOO/,

Fig. 3 .

S o l u b i l i t y of CeF, mole %).

4.2

(OK,

i n LiF-BeF2 -ThF4

(72.7-4.8-22.5

ORNL-DWG 68- 12066

TEMPERATURE ("C) 70 0

800 1

600

8 7 o 0

RADIOCHEMICAL ANALYSIS WET CHEMICAL ANALYSIS

\ \o \

1 ,

0) 0

\ \ \

0.9

f.1

1.2

'Oo0/)T ( O K )

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 7 0 ) .

ORNL-DWG 68-42067

TEMPERATURE ("C)

800

700

600

L \

'\\ 0

o RADIOCHEM . A L ANALYSIS 0

WET CHEMICAL ANALYSIS

1.2

0.9

Fig. 5.

Solubility of CeF, in LiF-BeF2 -ThF4 mole 7 0 )

(72.3-11.0-16.7

ORNL- DWG 68 - f2068

TEMPERATURE

800

("C)

700 1

600

8 7

- !

RADIOCHEMICAL ANALYSIS e WET CHEMICAL ANALYSIS 0

$ al -

a13

i 0.9

Fig. 6 .

4 .O

S o l u b i l i t y of CeF, mole 70)

'O OO/r

1.1

1.2

( 0K1

i n LiF-BeF2 -ThF,

(67.8-25.2-7.0

15 v

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 temperature 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.

comparison of PuF, solubility data1 with similar values reported'

for CeF, i n F i g .

7 indicates that the solubility

of PuF, at 600째 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. 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 W

LiF - 2(BeFZ) - 3(ThF,)

This relation is based on the assumption that LiF is complexed

Table 1. Solubility and Heat of Solution of CeF3 in Mixtures of LiF, BeF2, and ThF4

Salt Composition (mole $ ) LiF -

CeF3 Solubility (mole $)

Heat of Solution (ea1 per mole)

1.6

800째C 5.5

11,500

ThF4 12

6OO0C

2.6

9.0

11,560

72.7

4.8

22.5

2.4

7.9

11,100

1.35

6.0

13,890

72.3

11.0

16.7

2.1

6.3

10,230

67.8

25.2

7.0

1.05

5.0

14,530

17 V

ORNL-DWG 68-5997

1.8

1.6

1.4

1.2

I-

1.0

/ r

PuF3- 650"

z k '

0.8

a LT

0 LL'

0.6

0.4

0.2

0 10

Fig. 7 .

30 40 50 BeF2 IN SOLVENT (mole %)

Comparison of CeF, Solvents.

a n d PuF,

S o l u b i l i t y i n LiF-BeF2

a s Li,BeF4

and Li,ThF,

i n the liquid state.

I t is i n t e r e s t i n g

t o t e s t t h i s c o n c e p t 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 here.

The r e s u l t i n g g r a p h ( F i g . 8) shows a r a t h e r p o o r

c o r r e l a t i o n b a s e d 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 f r o m t h e a s s u m p t i o n t h a t BeF, ThF,

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

a s LiThF,.

The l a t t e r a s s u m p t i o n h a s a r a t h e r s h a k y

b a s i s s i n c e t h e p u b l i s h e d p h a s e diagram6 for t h e s y s t e m 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 7) m e l t s i n c o n g r u e n t l y .

The o n l y d e f e n s e for t h i s

a s s u m p t i o n i s t h a t f i v e of t h e s i x c o m p o s i t i o n s 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 . REFERENCES 1.

C . J . B a r t o n , J . Phys. Chem. 6 4 , 306 ( 1 9 6 0 ) .

T. Ward, R . A . S t r e h l o w , W .

R . G r i m e s , and

Watson, J . Chem. Eng. D a t a 5, 2 (1960).

C. J . B a r t o n , M e m o t o P. R . K a s t e n , J u n e 4 , 1 9 6 8 , 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,

J u n e 2 0 , 1968

M. A . Bredig, 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 . P h y s . Chem. 6 3 , 1267 4.1959).

G . B r u n t o n , Acta C r y s t . 2 1 ( 5 ) , 814 ( 1 9 6 6 ) .

ORNL-DWG 68-12069

io.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 7 2 LiF-16 BeF2-12 ThF4 0

9.0

8.0 \

7.0 h

72.7 LLF-4.8 BeF2-22.5ThF4

800째C

6.0

I I

- 5.0 rc)

4.0

3.0 600째C

2.0

1.0

0 -8 F i g . 8.

-6

-4

-2 0 2 FREE LiF (mole '3")

Solubility of CeF, As A F u n c t i o n of F r e e L i F Assuming Li,BeF4 and Li,ThF, I n L i q u i d .

ORNL-DWG 68-42070

5 Fig. 9 .

20 25 30 FREE LiF (mole %)

S o l u b i l i t y of CeF, Li,BeF4 a n d LiThF,

A s A F u n c t i o n of F r e e L i F Assuming i n Liquid.

REFERENCES

C. J . B a r t o n , J . P h y s . Chem. 6 4 , 306 ( 1 9 6 0 ) .

W . T. Ward, R . A . S t r e h l o w , W . R . G r i m e s , and G . W . Watson, J . Chem. Eng. Data 5 , 2 (1960).

C. J . B a r t o n , M e m o t o P . R. K a s t e n , J u n e 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, J u n e 20, 1 9 6 8 .

M . A . B r e d i g , Memo t o W. MSR 68-75.

R . E . Thoma e t a l , J . Phys. Chem. 63, 1267 (1959).

G . D . B r u n t o n , Acta C r y s t . 2 1 ( 5 ) , 814 ( 1 9 6 6 ) .

R. G r i m e s , A p r i l 2 6 , 1 9 6 8 ,

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