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O A K RIDGE N A T I O N A L LABORATORY operated by U N I O N CARBIDE CORPORATION for the U.S. A T O M I C ENERGY C O M M I S S I O N

ORNL- TM- 1051 COPY NO.

DATE

- d.2

- March 11, 1965

-_-

RECONSTITUTION OF MSR FUEL BY REDUCING UF6 GAS T O UF4 I N A MOLTEN SALT

L. E . McNeese C . D e Scott

HSTRIBUTIONOF THISDOCUMENI UNLIMITED c

LEGAL NOTICE T h i s report was prepared as an account of Government sponsored work.

Neither the United Stotes,

nor the Commission, nor any person a c t i n g on behalf of the Commission:

Makes any warranty or representation, completeness,

any

information,

apparatus,

p r i v a t e l y owned rights;

expressed or implied, w i t h respect t o the accuracy,

or usefulness of the information contained in t h i s report, or t h a t the use of method,

or process disclosed

i n t h i s report m a y not infringe

Assumes any l i a b i l i t i e s w i t h respect t o the use of, or for damages r e s u l t i n g from the use of any information, apparatus, method, or process disclosed i n t h i s report.

used i n the above,

Contractor or

"person

a c t i n g o n behalf of the Commission"

includes ony employee or

of the Commission, or employee of such contractor, t o the extent that such employee

contractor

of the Commission,

or employee of such contractor

prepares,

disseminates,

provides access to, any information pursuant t o h i s employment or contract w i t h the Commission, or h i s employment w i t h such contractor.

RECONSTDUTION OF MSR FUEL BY REDUCING

UF6 GAS TO UFb I N A MODEN SAXT

L. E. McrJeese C. D. S c o t t

NOTICE

This report was prepared as an account of work sponsored by the United States Government. NeitheI the United States nor the United States 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 01 responsibility for the accuracy, completeness of usefulness of any informtion, apparatus, product or Process disclosed, or represents that its use would not infringe privately owned rights.

OAK RIDGE NATIONAL M30RAToRY Oak R i d g e , T e n n e s s e e operated by UNION CAHBIDE CORPORATION f o r the U.S. ATOMIC ENERGY COMMISSION

COJ!KCENTS Abstract..

Introduction.

............... ......... ... ...... a

. of Experimental R e s u l t s . . and Recommendations . . . . .... ........

Discussion Conclusion References

.. .. .. ..

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

Proposed Process and A p p l i c a t i o n t o K R Processing Experimental Equipment and Procedure

Page 1 1 2

4 10

1 RECONSTITUTION OF MSR FUEL BY REDUCING

UF6 GAS TO UF4 I N A MOLTEN SALT L. E . McNeese C . D. Scott ABSTRACT The d i r e c t r e d u c t i o n of U F t o UF i n a molten s a l t i s proposed a s a s t e p i n t e p u r i i c a t i o n of f u e l s a l t from a molten s a l t r e a c t o r . This s t e p would r e p l a c e t h e c o n v e n t i o n a l method of r e d u c t i o n F, i n which UF' i s reduced t o UF powder i n a H 6 flame. Reduction of t h e UTc, kn a molten sal? w i l f r e s u l t i n a s h o r t e r and more d i r e c t p r o c e s s f o r f u e l s a l t p u r i f i c a t i o n . The r e d u c t i o n i s t o b e e f f e c t e d i n two s t e p s which c o n s i s t of a b s o r p t i o n of UF6 i n t o a molten s a l t c o n t a i n i n g UF and of r e d u c t i o n of t h e 4 r e s u l t i n g i n t e r m e d i a t e f l u o r i d e s t o UF w i t h hydro4 gen. Experimental d a t a on t h e a b s o r p t i o n s t e p a r e p r e s e n t e d and information concerning t h e r e d u c t i o n of i n t e r m e d i a t e f l u o r i d e s i s c o n s i d e r e d .

. INTR ODUC T I O N One proposed p r o c e s s i n g s t e p f o r Molten S a l t Reactor (MSR) f u e l

i s t h e r e d u c t ion of p u r i f fed UF6 t o UF14. \ S O t h a t t h e UF 4 can be r e t u r n e d t o b a r r e n , p u r i f i e d f u e l s a l t . 'I

The u s u a l method f o r r e -

ducing UF6 t o UF4 i s b y use of H 2 i n a H2-F2 flame :

T h i s r e d u c t i o n i s c a r r i e d o u t i n a t a l l column where t h e UF6 and H2

-F flame and d r y U F ~powder ( f i n e l y d i v i d e d ) 2 2 It i s a r o u t i n e p r o d u c t i o n o p e r a t i o n and t h e r e i s much

are introduced i n t o a H

is collected.

available operating d e s i r a b l e f o r remote o p e r a t i o n .

Such a p r o c e s s would n o t be It i n v o l v e s a s o l i d s h a n d l i n g problem

which r o u t i n e l y r e q u i r e s equipment a c c e s s and p r o c e s s c o n t r o l is sometimes d i f f i c u l t

It would b e d e s i r a b l e t o reduce t h e UF6 t o UF 4 i n a molten s a l t environment, and t h u s circumvent t h e problems of s o l i d s handling and f u e l make-up.

P a s t experience of o t h e r workers has i n d i c a t e d t h e

2 f e a s i b i l i t y of absorbing UF6 i n t o molten s a l t which c o n t a i n s UF

and

(ft)

reducing t h e absorbed UFc t o U F 4 by sparging w i t h H

Kirslis 2' found t h a t c o r r o s i o n w a s n o t severe i n a b s o r p t i o n of F2 by molten s a l t c o n t a i n i n g U u n t i l t h e intermediate f l u o r i d e of uranium had a f l u o r i d e c o n t e n t g r e a t e r t h a n UF,. ),

i n a molten s a l t and

found t h a t H would reduce UF4 t o 2 reduced v a r i o u s metal f l u o r i d e s

B l o o d (61 has

i n molten s a l t s by use of H

2' This r e p o r t p r e s e n t s a proposed continuous processing method f o r

t h e r e d u c t i o n of UFh to UF4 i n a molten s a l t environment b y a b s o r p t i o n of UF6 i n t h e s a l t and r e d u c t i o n w i t h H

The r e s u l t s from a s c o u t i n g 2' t e s t are analyzed t o i n d i c a t e process f e a s i b i l i t y . PROPOSED PROCESS AND APPLICATION TO MSR PREESSING The c u r r e n t scheme f o r processing Molten S a l t Reactor ( K R ) f u e l c o n s i s t s of removal of ;Iranium as UF,

and v o l a t i l e f i s s i o n products

(FP) from the s a l t by f l u o r i n a t i o n , s e p a r a t i o n of r e f r a c t o r y FP from t h e s a l t by d i s t i l l a t i o n , and recomb i n a t ion of t h e v o l a t i l i z e d uranium and p u r i f i e d b a r r e n s a l t f o r r e t u r n t o t h e MSR ( F i g . 1)'l). During t h e f l u o r i n a t i o n s t e p , b o t h i x - a n i m and v o l a t i l e f i s s i o n products are r e moved from t8he s a l t 'cy t h e r e a c t i o n s :

F P ( i n molten s a l t )

-volatile

FP f l u o r i d e s .

The UF6 and v o l a t i l e FP f l u o r i d e s w i l l be s e p a r a t e d b y s o r p t i o n t e c h niques and t h e urani-xn w i l l t h e n b e b a r r e n s a l t t o form t h e M3R f.iel.

1 - s i n t r d u c e d as UF4 t o t h e p u r i f i e d Thus, t h e r e must be a method f o r re-

ducing UF6 t o UF4.

Since t h e end r e s u l t of t h e UF

r e d u c t i o n w i l l be a s o l u t i o n of UF

i n molten s a l t r a t h e r t h a n UT4 as a d r y powder, it i s a t t r a c t i v e t o c a r r y on t h e r e d u c t i o n i n a molten s a l t environment and p r e f e r a b l y i n the purified barren salt.

To achieve t h i s requirement, UF

can be con-

t a c t e d w i t h a molten f l u o r i d e s a l t c o n t a i n i n g some uranium as UF4 where

it w i l l be absorbed by r e a c t i o n w i t h t h e UF mediate f l u o r i d e of uranium, such as UF

4 t o form an e q u i v a l e n t i n t e r -

i n the salt:

ORNL VOLATILE

DWG

65-1790

4 SORPTION

StPARATlON

UF6

FP + UF6 I

SORBED

FLUORINATION

BARREN

F2 I

SALT

I“LL I.., ...-. *

b DISTILLATION

‘i

MSR REACTOR

CERAMIC

cl 11~1 UAKF-I

FUEL

SALT

4 L FILTER

Fig.

MSR Fuel

Processing

with

Hz -+- HF

PURIFIED

Conventional

UF.6 Reduction.

T h i s i n t e r m e d i a t e f l u o r i d e w i l l t h e n b e reduced to -UF4 i n t h e s a l t b y means of H2:

Such a p r o c e s s could b e c a r r i e d out c o n t i n u o u s l y i n a c3lumn in

6 a r e introduced a t t h e bottom of t h e column

which t h e b a r r e n s a l t and UF

a l o n g w i t h s a l t c o n t a i n i n g UF4 which is r e c y c l e d from t h e t o p of t h e colurr, (Fig. 2 ) .

A s t h e s a l t and UF

6 progress

up t h e column, t h e TJF6

w i l l b e absorbed i n t h e s a l t and subsequently reduced t o UF4 a s it p a s s e s b t o t h e H2 r e d u c t i o n sect,ion.

The column o f f - g a s w i l l b e a m i x -

t u r e of H and HF and a s i d e strearr, of t h e overhead molten s a l t w i l l b e 2 ready f o r r e t u r n t o t h e n u c l e a r r e a c t o r core a f t e r f i l t r a t i o n s i n c e the

HF and H2 sparge u s u a l l y given make-up salt w i l l have been achieved in t h e r e d u c t i o n column.

\Then t h i s r e d u c t i o n s t e p i s incorporatea into t h e

flowsheet, t h e r e s u l t h g p r o c e s s is m a r e d i r e c t and s h o r t e r ( F i g . 3). i n i t i a l t e s t s ( n e x t stzt) i t x i i c a t e t k a t t h e a b s o r p t i o n s t e p i s very r a p i d , however, it w i l l b e d e s i r a b l e t o keep t h e f l u o r i d e c o n t e n t of t h e i n t e r z e d i a t e f l u o r i d e below t h a t eqJiva1en-L to W minimize c o r r o s i o n .

h oder t o

The rate of t h e hjrdrogen r e d u c t i o n r e a c t i o n i s z.9t

know-, although t h e l i m i t e d d a t a a v a i l a b l e looks f a v o r a k l e .

st-dybg

3 ir molten s a l t b y H2 b y t h e r e a c t i o r , :

t h e r e d u c t i o n of UF4 to UF

uF4 ( s a l t Longi5

l/2H2-uF

3blt)

+xi?,

observed t h a t e q u i l i b r i u m was e s t a b l i s h e d between a

Hp-HF s t r e a m

and molten s a l t c o n t a i n i n g u r m i u m f i u o r i d e s a f t e r t h e g a s b a b b l e s had r i s e n a f e w inches through t h e s a l t . t o UF

r e d u c t i o n of UF

H i s d a t a a l s o i r d i c a t e only 1%

b y a gas s t r e a m c o c t a i n i n g 1% 83' i n H, a t a c

3 0

p r e s s u r e of 1 atm a t 600 C .

The e x p e r i m e n t a l equipment was assezibled from e x i s t i n g equipment a v a i l a b l e as a r e s u l t of work b- support of t h e Moltes S a l t F l c o r i d e V o l a t i l i t y Process.

Means were p r m i d e d for c o n t a c t k g UP

dissolved

i n molten s a l t , w i t h 'fl6 i n t h e f i r s t s t e p of t h e r e d u c t i o n p r m e s a a:id

ORNL DWG 65-1791

SALT + UFA

-FUEL

SALT

f Fig. 2.

Continuous Reduction of UFb by H2 in a Molten Salt.

ORNL VOLATILE A

111

SORPTION

DWG

HF + H2 4

SEPARATION

UF6

FP + 9F6 + 1

/ I

FLUQRINA

I-

SORBED

2v,

JION

REDUCTION H2-l

FP + SALT

CERAMIC

PURIFIED

FUEL

l-l-

SALT

Fl LTER Fig.

MSR Fuel

Processing

with

Continuous

UF6 Reduction

in Molten

Salt.

65-1792

7 f o r c o n t a c t i n g t h e r e s u l t i n g uranium f l u o r i d e w i t h hydrogen i n t h e second step.

Details of t h e experimental equipment and of t h e procedure f o r

t e s t i n g t h e r e d u c t i o n process a r e d i s c u s s e d i n t h e f o l l m i n g s e c t i o n s . EQUIPI$Em AN3 M4TERIALS

The r e d u c t i o n t e s t was c a r r i e d out i n t h e v e s s e l shown schematic-

a l l y in Fig*

The v e s s e l was c o n s t r u c t e d from b i n . - d i a m

A 3/8-in.

n i c k e l p i p e and w a s 26 inches i n l e n g t h .

Sch

nickel inlet line

was l o c a t e d i n t h e c e n t e r of t h e v e s s e l and termkated 1/4-in. bottom of t h e v e s s e l .

A 3/4-in.

i n s e r t i o n of a cold, 3/8-in. salt.

from t h e

f i t t i n g on the t o p f l a n g e allowed t h e

n i c k e l rod which was used f o r sampling t h e

The v e s s e l was heated b y two n i c h r o m w i r e r e s i s t a n c e f u r n a c e s . A flow diagram f o r t h e equiprnernt used in t h e t e s t i s s h m i n F i g .

The equipment included a

m t e r i n g system, a hydrogen metering sys-

t e m , means f o r purging b o t h t h e

UF6

system and H2 system w i t h N2, t h e

r e d u c t i o n v e s s e l , and a NaF t r a p d a m s t r e a m from t h e v e s s e l f o r absorbing UF6 o r HF from t h e off-gas of t h e r e d u c t i o n v e s s e l . The s a l t charge w a s prepared by mixing LiF, Z r F 4 and UF4.

w a s r e a g e n t grade and c o n t a i n e d < 0 . 2 3 w t

i m p u r i t i e s (mostly NaF).

The zirconium c o n t e n t of t h e Z r F 4 w a s found b y a n a l y s i s t o b e which compares f a v o r a b l y w i t h t h e s t o i c h i o m t r i c a l value of uranium c o n t e n t of t h e UF

4 w a s found t o

f a v o r a b l y w i t h t h e s t o i c h i o m e t r i c a l value

The L i F

76.5% which a l s o of 75.q; and t h e

h e x a f l u o r i d e contained l e s s t h a n 200 ppm i m p u r i t i e s .

54.7%

54.6%; t h e compares uranium

Hydrogen t h a t was

used contained l e s s t h a n 0.005 v o l f r a c t i o n i m p u r i t i e s .

A s a l t charge c o n s i s t i n g of 5320 g Z r F 4 ,

(0.197 gmole

863 g LiF, and 61.8 g UF4

UF ) was placed in t h e r e d u c t i o n v e s s e l and h e a t e d t o 600째C.

A t t h i s temperature t h e d e p t h of molten s a l t w a s 12 inches. mixture had a UF4 c o n c e n t r a t i o n of 1 w t

The s a l t

'$ and a m e l t i n g p o i n t of approx-

A salt sample (UR-1) was t a k e n b y i n s e r t i o n of a c o l d 3/8-in.-diam n i c k e l rod i n t o t h e molten s a l t . A w6 f l a w of 1.5 g / m h w a s t h e n f e d through t h e by-pass around t h e r e d u c t i o n v e s s e l f o r 16 imately 51OoC.

ORNL DWG 65-1793

3/8" NICKEL G A S INLET

3/8"-diam. OFFGAS LINE

COPPER GASKET

. 4-in. SCHEDULE 40 NICKEL PIPE

Fig. 4.

Vessel Used for Reduction of UF6 to UF4 in a Molten Salt:

ORNL

DWG

65-1794

SUPPLY-,

CALIBRATED CAPILLARY

SUPPLY

NaF TRAP

11I

UF6 SUPPLY

OFFGAS

REDUCTION VESSEL

Fig.

Flow

Diagram

for Equipment

Used in Reduction

of UF6 to UF4 in a Molten

Salt.

10 The UF6 f l o w w a s t h e n d i v e r t 2' ed i n t o t h e d i p l i n e of t h e r e d u c t i o n v e s s e l and w a s continued f o r 25

minutes i n o r d e r t o f r e e t h e system of N

A t t h i s time, t h e UF6 flow w a s stopped and t h e system was

minutes.

purged w i t h N, f o r 5 minutes a f t e r which a s a l t sample (UR-2) w a s t a k e n .

38.2 g r a t e O f 95 s t .

The q u a n t i t y of UF,: f e d t o t h e system d u r i n g t h i s s t e p w a s L

(0.108 gmoles). The s a l t w a s t h e n purged w i t h H2 a t t h e cm3/min f o r 25 minutes. A t o t a l of 0.107 gmoles H2 was added t h i s step. sample

A f t e r t h e system was purged w i t h N2 f o r 10 min, a s a l t

(UR-3) w a s

The system w a s t h e n allowed t o c o o l down over-

taken.

night.

The f o l l o w i n g day t h e system w a s heated t o 600 C and a s a l t Sam-

p l e was t a k e n st.

during

cm3/min

The s a l t w a s t h e n sparged w i t h H2 a t a rate of

f o r 20 min d u r i n g which a t o t a l of 0.076 gmoles H2 w a s fed

t o t h e system. sample

(UR-4).

The system w a s t h e n purged w i t h N2 f o r 1 0 min and a s a l t

(UR-5)w a s

The system w a s t h e n cooled and t h e t e s t con-

taken.

cluded.

DISCUSSION OF EXPERIMENTAL RESULTS Two q u e s t i o n s r e l a t e d t o t h e experimental work are of primary i n t e r est.

These are (1)t h e f r a c t i o n of UF/ which w a s absorbed b y t h e molten '3

s a l t and ( 2 ) t h e valence of t h e uranium i n t h e r e s u l t i n g mixture.

Also,

of i n t e r e s t are t h e c o n c e n t r a t i o n l e v e l of t r a c e i m p u r i t i e s such as Ni and 02. The composition of t h e various s a l t samples i s given i n Table 1. The uranium c o n c e n t r a t i o n i n t h e i n i t i a l s a l t (UR-1) w a s found by analys i s t o be 0.66; w t $ which i s ll.& c o n c e n t r a t i o n of 0.75 wt

lower t h a n t h e c a l c u l a t e d uranium

The c a l c u l a t e d uranium c o n c e n t r a t i o n f o r

complete a b s o r p t i o n of t h e UF, bubbled through t h e s a l t d u r i n g t h e 25 v

rnin a d d i t i o n p e r i o d was 1 . 1 5 w t

';"ne average uranium c o n c e n t r a t i o n

a f t e r t h e TJFc a d d i t i o n was found b y a n a l y s i s t o be @J

lower t h a n t h e c a l c u l a t e d value.

1.07 wt $

which i s

It w a s concluded t h a t , w i t h i n t h e

accuracy of t h e experimental d a t a , complete a b s o r p t i o n of t h e UF6 had occurred

It is b e l i e v e d t h a t t h e a d d i t i o n of UF,: t o a s a l t c o n t a i n i n g UF'

r e s u l t s i n t h e formation of d i s s o l v e d f l u o r i d e s of uranium w i t h a val e n c e i n t e r m e d i a t e between

+4 and t6.

This b e h a v i o r i s i n d i c a t e d by

Table

Composition Uranium

Sample

U h%

Ud d%

of Salt Reduction

Samples

Taken

During

Experiment

Zr ti%

Li e%

Ni PPm

O2 mm

46.65

3.64

874

4045

Initial

933

4695

After

UF6 addition

Remarks

UR-1

0.666

UR-2

1.05

m-3

1.01

1.074

< .Ol

1002

4940

After

1st

UR-4

1-97

o-990

< .Ol

1007

3060

After night

cooling overard remelting

m-5

1.14

0.922

< .Ol

852

3245

After

2nd H2 sparge

.954

< .Ol

salt

melt

H2 addition

12 t h e f a c t t h a t q u a n t i t i e s of F2 s u f f i c i e n t f o r t h e formation of UF

b e absorbed b y molten s a l t c o n t a i n i n g UF

can

4 without t h e e v o l u t i o n of UF6.

6 in

A s i m i l a r b e h a v i o r is a l s o noted in r e a c t i o n s between UF4 and UF

the

absence of molten s a l t t o y i e l d i n t e r m e d i a t e f l u o r i d e s such a s U4F17.

It is assumed t h a t uranium p r e s e n t i n a molten s a l t as an i n t e r m e d i a t e f l u o r i d e w i l l appear as U+4 and U in

afâ&#x20AC;&#x2122;ter d i s s o l u t i o n i n phosphoric a c i d

p r e p a r a t i o n f o r a n a l y s i s . (7)

The c o n c e n t r a t i o n of U

i n t h e sample after

t h e l i m i t of d e t e c t i o n of 0.01 wt wt

UF6

a d d i t i o n w a s below

and t h e U+4 c o n c e n t r a t i o n was 0.95

(Table 1). A f t e r t h e f i r s t and second hydrogen s p a r g e s , t h e U

c o n c e n t r a t i o n w a s found to be 1.07 Wt

and 0.922 w t

$, r e s p e c t i v e l y .

Although d i f f e r e n c e s i n U+4 c o n c e n t r a t i o n were observed, it is f e l t t h a t t h e s e a r e w i t h i n t h e limits of a n a l y t i c a l e r r o r and are not meaningful. Reduction of t h e

to U+4 probably occurred d u r i n g t h e a d d i t i o n of UF6

b y r e a c t i o n of t h e i n t e r m e d i a t e f l u o r i d e w i t h n i c k e l from t h e v e s s e l w a l l

or w i t h reduced f l u o r i d e s of n i c k e l , chromium, or iron i n i t i a l l y p r e s e n t i n t h e salt.

The n i c k e l c o n c e n t r a t i o n increased from

t o approximately 1000 ppm d u r i n g t h e gen t r e a t m e n t .

874 ppm i n i t i a l l y

a d d i t i o n and t h e i n i t i a l hydro-

T h i s i n c r e a s e i n N i c o n c e n t r a t i o n of approximately 130

ppm i s s u f f i c i e n t f o r t h e r e d u c t i o n of approximately

15% of t h e UF6 added.

The c o n c e n t r a t i o n of oxide i n t h e salt d u r i n g t h e t e s t w a s approximately 4000 ppm.

In t h e absence of c o n c l u s i v e information on t h e r e d u c t i o n of uranium f l u o r i d e s i n t e r m e d i a t e between UF and UF 4 6â&#x20AC;&#x2122; r e f e r e n c e can be made to d a t a on m a t e r i a l s having s i m i l a r c h a r a c t e r i s t i c s .

The e q u i l i b r i u m between UF

(5 1 3 i n molten mixtures of L i F and BeF,2 has been s t u d i e d b y Long b y observing t h e c o n c e n t r a t i o n of HF i n H in e q u i l i b r i u m w i t h t h e salt. 2 E q u i l i b r i u m was observed t o have been e s t a b l i s h e d d u r i n g t h e rise of H2

and UF

bubbles through a few inches of molten salt. r e d u c t i o n of UF cord it ions

t o UF

The d a t a i n d i c a t e d t h a t

could b e achieved over a wide range of o p e r a t i n g

The r e d u c t i o n of N i F 2 ,

CrF2, FeF2 t o t h e m e t a l s b y hydrogen is u t i l a

ized f o r removal of t h e s e contaminants from molten s a l t .

It was also

rjbserved t h a t molten salts c o n t a i n i n g uranium f l u o r i d e w i t h a v a l e n c e >

13 "k

a r e q u i t e c o r r o s i v e toward n i c k e l m e t a l . ( 4 )

NiF2

H2-Ni

Since t h e r e a c t i o n s :

2HF

a r e known t o occur i n molten s a l t s , it is f e l t t h a t t h e r e a c t i o n : UF

l/2H2-UF

+ HF

w i l l a l s o occur. CONCLUSIONS AND REC OMMENDAT IONS The f o l l o w i n g c o n c l u s i o n s have been made on t h e b a s i s of t h e materi a l p r e s e n t e d i n t h e preceding s e c t i o n s . 1. Uranium h e x a f l u o r i d e i s absorbed r a p i d l y b y molten f l u o r i d e

s a l t c o n t a i n i n g approx. 1 w t $ UF4 a t 60OoC.

It i s b e l i e v e d

t h a t t h e a b s o r p t i o n r e s u l t s i n t h e f o r m a t i o n of an i n t e r m e d i -

a t e f l u o r i d e of uranium.

2. It i s l i k e l y t h a t r e d u c t i o n of t h e i n t e r m e d i a t e f l u o r i d e t o *

3. I

4 can b e accomplished b y c o n t a c t w i t h hydrogen.

I n c o r p o r a t i o n of t h e proposed r e d u c t i o n s t e p i n t o t h e f l o w s h e e t f o r WR p r o c e s s i n g r e s u l t s iia a s h o r t e r and more d i r e c t p r o c e s s .

It i s recommended t h a t e x p e r i m e n t a l work on t h e r e d u c t i o n of UF6 t o UF

i n a molten s a l t environment b e continued w i t h emphasis i n t h e f o l l o w -

ing a r e a s : 1.

rate of r e d u c t i o n of i n t e r m e d i a t e uranium f l u o r i d e t o UF

4 by

hydrogen. 2.

c o r r o s i v i t y of molten f l u o r i d e m e l t s c o n t a i n i n g i n t e r m e d i a t e uranium f l u o r i d e s .

a d a p t a t i o n of t h e r e d u c t i o n p r o c e s s t o continuous o p e r a t i o n .

REFERENCES 1. W . L. C a r t e r and C . D.

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S c o t t , I%BR F u e l and F e r t i l e Stream Pro-

P r e l i m i n a r y Design and E v a l u a t i o n of a Reactor I n t e g r a t e d

P l a n t , ORNL-3791 ( i n p r e s s ) . 2. H . C . Francke, Y - 1 2 P l a n t , Union Carbide Corp.., Oak Ridge, Tenn., P e r s o n a l communications (1965 )

34 S . H. Smiley, D . C . B r a t e r and R . H. Nemo, Development of t h e Continuous Method f o r t h e Reduction of Uranium Hexafluoride w i t h Hydrogen

Process Development

Cold W a l l Reactor, K-l248(Del)

(1959)

4. S. S. K i r s l i s , p e r s o n a l communications (1965). 5. G . Long, S t a b i l i t y of UF

3â&#x20AC;&#x2122;

( i n preparation).

M. Blood, S o l u b i l i t y and S t a b i l i t y of S t r u c t u r a l Metal D i f l u o r i d e s i n Molten F l u o r i d e Mixtures, ORNL CF 61-5-4 (1961).

7 . W.

R . k i n g , p e r s o n a l communication

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