Application of Photochemical Techniques to Actinide Separation

Apr 16, 1980 - Photochemical techniques offer a potential for selectivity in systems where chemical methods offer little selectivity. Although thermal...
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19 Application of Photochemical Techniques to Actinide Separation Processes G . L . D E P O O R T E R and C . K. R O F E R - D E P O O R T E R

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Los Alamos Scientific Laboratory, University of California, Los Alamos, Ν M 87545

Photochemical techniques offer a potential for selectivity in systems where chemical methods offer l i t t l e selectivity. Although thermal chemical properties of species to be separated may be similar, spectral differences can be exploited in photochemical separations. A further advantage of photochemical methods is the substitution of light energy for quantities of reagents. Both of these characteristics suggest the applicability of photochemical techniques to the actinides, whose separation and purification is often difficult, and whose radioactivity causes problems in the handling of waste reagents from their processing. In this paper, we review the application of photochemical techniques to actinide separations and related photochemical processes. The advent of the laser has brought about renewed interest in this field. Thus, these studies are in research stages and have not been developed to plant-scale processes. The use of photochemistry in separation processes is fairly recent. An attempt was made in 1922 to separate chlorine isotopes by irradiating a mixture of H and Cl with light filtered through Cl enriched in Cl (1), but the first successful attempt was by irradiation of COCl with an aluminum arc in 1932 (2). A l t h o u g h 2

2

35

2

2

the photochemical r e a c t i o n s o f the uranyl i o n ( U 0 ) were known s i n c e 1833 ( 3 ) , t h e y were n o t a p p l i e d t o s e p a r a t i o n s u n t i l t h e e a r l y p a r t o f t h e M a n h a t t a n P r o j e c t , when t h e s p e c t r a a n d p h o t o ­ c h e m i c a l r e a c t i o n s o f u r a n y l compounds a n d U F 6 were i n v e s t i g a t e d f o r t h e i r p o t e n t i a l i n isotope separation (4). No p h o t o c h e m i c a l p r o c e s s was f o u n d t h a t c o u l d c o m p e t e w i t h g a s e o u s d i f f u s i o n i n e f f i c i e n c y and r a p i d development t o l a r g e s c a l e . 2

2

A l l o f the b a s i c requirements f o r photochemical s e p a r a t i o n s were r e c o g n i z e d i n t h i s e a r l y w o r k : 1. T h e a b s o r p t i o n s o f t h e s p e c i e s t o be s e p a r a t e d must b e significantly different. 2.

A p h o t o c h e m i c a l r e a c t i o n must t a k e p l a c e i n one s p e c i e s t o c h a n g e i t s c h e m i c a l f o r m s o t h a t i t c a n be s e p a r a t e d from the m i x t u r e .

0-8412-0527-2/80/47-117-267$05.00/0 © 1980 A m e r i c a n C h e m i c a l Society In Actinide Separations; Navratil, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

ACTINIDE SEPARATIONS

268 3.

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4.

T h e r e must be no o t h e r i n t e r f e r i n g r e a c t i o n s t h a t w i l l cause a l o s s o f the s e l e c t i v i t y . A l i g h t s o u r c e must be a v a i l a b l e w i t h a s u f f i c i e n t l y n a r r o w w a v e l e n g t h d i s t r i b u t i o n t o d i s c r i m i n a t e among s p e c t r a l f e a t u r e s , a n d i t must h a v e s u f f i c i e n t i n t e n s i t y to cause photochemical r e a c t i o n i n a reasonable t i m e .

The f i r s t t h r e e r e q u i r e m e n t s r e l a t e t o t h e i n h e r e n t c h e m i c a l p r o p e r t i e s o f t h e m i x t u r e t o be s e p a r a t e d . The r e q u i r e m e n t s f o r t h e l i g h t s o u r c e d e p e n d on t h e p r o p e r t i e s o f t h e m i x t u r e , b u t i t s availability is a technological variable. Lasers, with their n a r r o w w a v e l e n g t h r a n g e s and h i g h i n t e n s i t i e s , h a v e g e n e r a t e d new i n t e r e s t i n photochemical separations. I n f r a r e d l a s e r s have a l s o made p o s s i b l e t h e c o m p l e t e l y new f i e l d o f i n f r a r e d - i n d u c e d chemi s t r y , i n w h i c h some s i g n i f i c a n t i s o t o p e s e p a r a t i o n s h a v e b e e n reported. The f o u r p r i n c i p l e s o f p h o t o c h e m i c a l s e p a r a t i o n a p p l y t o t h e s e p a r a t i o n o f o t h e r c h e m i c a l e n t i t i e s , e l e m e n t s a n d c o m p o u n d s , as much a s t h e y do t o t h e s e p a r a t i o n o f i s o t o p e s . S i n c e the s p e c t r a o f e l e m e n t s and compounds d i f f e r t o a much g r e a t e r d e g r e e t h a n t h e s p e c t r a o f i s o t o p e s , the problem i s s i m p l e r . Several types of a p p l i c a t i o n of photochemistry to separations c a n be d i s t i n g u i s h e d : separation of a chemical species that underg o e s p h o t o c h e m i c a l r e a c t i o n f r o m s p e c i e s t h a t do n o t ; selective i r r a d i a t i o n and p h o t o c h e m i c a l r e a c t i o n o f one o f s e v e r a l p h o t o c h e m i c a l l y a c t i v e s p e c i e s ; changes i n c o n v e n t i o n a l s e p a r a t i o n s r e s u l t i n g from i r r a d i a t i o n ; and p h o t o c h e m i c a l g e n e r a t i o n o f s e p aration reagents. T h i s l i s t does n o t c o v e r a l l p o s s i b i l i t i e s , but i t serves to c a t e g o r i z e the a v a i l a b l e l i t e r a t u r e . The s o l u t i o n p h o t o c h e m i s t r y o f t h e a c t i n i d e s b e g i n s w i t h u r a n i u m ; none h a s b e e n r e p o r t e d f o r a c t i n i u m , t h o r i u m , and p r o t a c tinium. S p e c t r a h a v e b e e n o b t a i n e d f o r most o f t h e a c t i n i d e i o n s through curium i n s o l u t i o n (5). Most s t u d i e s i n a c t i n i d e p h o t o c h e m i s t r y h a v e b e e n done on u r a n y l c o m p o u n d s , l a r g e l y t o e l u c i d a t e t h e n a t u r e o f t h e e x c i t e d e l e c t r o n i c s t a t e s o f t h e u r a n y l i o n and t h e d e t a i l s o f t h e mechanisms o f i t s p h o t o c h e m i c a l r e a c t i o n s (5a). Some s t u d i e s h a v e a l s o b e e n done on t h e p h o t o c h e m i s t r y o f n e p t u n i u m (6) a n d p l u t o n i u m ( 7 ) . Although not a l l o f these s t u d i e s are d i r e c t e d s p e c i f i c a l l y toward s e p a r a t i o n s , the c h e m i s t r y they d e s c r i b e may be a p p l i c a b l e . The s p e c t r a and c h e m i c a l p r o p e r t i e s o f t h e a c t i n i d e s v a r y greatly. For example, the s p e c t r a o f U 0 and U * a r e shown i n F i g . 1. In t h e p r e s e n c e o f f l u o r i d e , U 0 remains i n s o l u t i o n , b u t UFii p r e c i p i t a t e s . T h u s , c o m b i n a t i o n o f p h o t o c h e m i c a l and t h e r m a l c h e m i c a l p r o p e r t i e s c a n be u s e d i n t h e i r s e p a r a t i o n s . B o t h o x i d a t i o n and r e d u c t i o n h a v e b e e n r e p o r t e d i n t h e l i t e r a t u r e as photochemical reactions of a c t i n i d e s . The r e p o r t e d r e a c t i o n s are s u m m a r i z e d i n F i g . 2. The p r o b l e m o f t h e l i g h t s o u r c e i s s i m p l e s t f o r s e p a r a t i n g a compound t h a t u n d e r g o e s a p h o t o c h e m i c a l r e a c t i o n f r o m compounds t h a t do n o t . In t h i s c a s e , a broadband l i g h t s o u r c e , such as the 2

2

2

+

1

2

In Actinide Separations; Navratil, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

19.

DEPOORTER AND ROFER—DEPOORTER

I

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1

Photochemical

I

I

I

I

Techniques

269

Γ

W A V E L E N G T H (nm)

Figure 1. UV-visible absorption spectra of U (IV) and U (VI) at equal concen­ trations in nitric acid: ( ; 0.042M UO , IN HNO ; ( ; 0.042M U (IV), 4N HNO . U (IV) spectrum from Ref. 28. 2+

t

s

s

Element

O x i d a t i o n State VI

V

IV

III

Uranium

Neptunium

Plutonium

Figure 2. Reported photochemical acti­ nide oxidations and reductions from Ref. 5,6, and 7.

In Actinide Separations; Navratil, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

ACTINIDE SEPARATIONS

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270

s u n , c a n be u s e d . P r o c e s s e s o f t h i s s o r t c a n be b o t h s i m p l e and cheap. T h i s p r i n c i p l e h a s b e e n a p p l i e d t o wet r e f i n i n g o f u r a n i u m o x i d e (8) a n d t o s e p a r a t i o n o f u r a n i u m f r o m some o f i t s f i s s i o n p r o d u c t s , as a p o t e n t i a l s t e p i n n u c l e a r f u e l r e p r o c e s s i n g (.9). Good s e p a r a t i o n s were r e p o r t e d i n t h e s e e x p e r i m e n t s ( T a b l e I ) , b u t no l a r g e - s c a l e a p p l i c a t i o n s h a v e b e e n r e p o r t e d . W i t h a s i n g l e - l i n e s o u r c e , two p h o t o c h e m i c a l l y a c t i v e compo­ n e n t s c a n be s e p a r a t e d i n s o l u t i o n b y i r r a d i a t i o n a n d s u b s e q u e n t r e a c t i o n o f one o f t h e c o m p o n e n t s . T h i s t e c h n i q u e has b e e n a p p l i e d t o t h e s e p a r a t i o n o f t h e t r a n s i t i o n m e t a l s c o b a l t and i r o n (10) a n d o f e u r o p i u m f r o m t h e o t h e r l a n t h a n i d e s ( Π ) . A l t h o u g h no s e p a r a t i o n o f t h i s t y p e has b e e n r e p o r t e d f o r t h e a c t i n i d e s , there i s nothing i n p r i n c i p l e that prevents i t . T h i s method c o u l d prove p a r t i c u l a r l y u s e f u l i n s e p a r a t i n g a c t i n i d e s from l a n t h a n i d e s , where t h e r m a l c h e m i c a l methods a r e p a r t i c u l a r l y d i f f i c u l t . I r r a d i a t i o n a l s o a f f e c t s t h e c o u r s e o f more c o n v e n t i o n a l s e p a ­ ration processes. V i s i b l e and u l t r a v i o l e t l i g h t have been f o u n d to a f f e c t p l u t o n i u m s o l v e n t e x t r a c t i o n by photochemical r e d u c t i o n o f the p l u t o n i u m (12). A l t h o u g h t h e r e s u l t s v a r y somewhat w i t h t h e c o n d i t i o n s , g e n e r a l l y p l u t o n i u m ( V I ) c a n be r e d u c e d t o p l u t o n i u m ( I V ) , and p l u t o n i u m ( I V ) t o p l u t o n i u m ( I I I ) . The r e d u c t i o n a p p e a r s t o t a k e p l a c e more r e a d i l y i f t h e u r a n y l i o n i s a l s o p r e s e n t , p o s s i b l y as a r e s u l t o f p h o t o c h e m i c a l r e d u c t i o n o f t h e u r a n y l i o n and s u b s e q u e n t r e d u c t i o n o f p l u t o n i u m b y u r a n i u m ( I V ) . L i g h t h a s a l s o b e e n f o u n d t o b r e a k up t h e u n e x t r a c t a b l e p l u t o n i u m polymer t h a t forms i n s o l v e n t e x t r a c t i o n systems ( 7 b , c ) . The e f f e c t o f v i b r a t i o n a l e x c i t a t i o n r e s u l t i n g from i n f r a r e d l a s e r i r r a d i a t i o n h a s b e e n s t u d i e d f o r a number o f h e t e r o g e n e o u s proc­ esses, including solvent extraction (13). I n p a r t i c u l a r , when a s o l v e n t e x t r a c t i o n s y s t e m o f u r a n y l n i t r a t e , a q u e o u s n i t r i c a c i d , and t r i - n - b u t y l p h o s p h a t e (TBP) i n a h y d r o c a r b o n d i l u e n t was i r r a d i a t e d w i t h a C 0 l a s e r , a c h a n g e was o b s e r v e d i n t h e e q u i l i b r i u m d i s t r i b u t i o n o f u r a n y l n i t r a t e between the phases (14J. When t h e s o l u t i o n was i r r a d i a t e d a t 944 c m " , c l o s e t o t h e u r a n y l a s y m m e t r i c s t r e t c h i n g f r e q u e n c y , t h e e f f e c t was o b s e r v e d . When a n o n r e s o n a n t f r e q u e n c y was u s e d o r t h e e n e r g y was a b s o r b e d i n t h e s o l v e n t , no e f f e c t was o b s e r v e d . L i t t l e h e a t i n g c o u l d be e x p e c t e d , a n d , i n a n y c a s e , h e a t i n g e f f e c t s s h o u l d have been i n the o p p o s i t e d i r e c t i o n from t h a t o b s e r v e d . 2

1

S i n c e we h a d p r o p o s e d a s i m i l a r e x p e r i m e n t w i t h i r r a d i a t i o n i n the u l t r a v i o l e t - v i s i b l e a b s o r p t i o n band o f the u r a n y l i o n (15), we t r i e d t o r e p r o d u c e t h e s e r e s u l t s , b u t w i t h o u t s u c c e s s (16). C o l l i s i o n s i n t h e l i q u i d p h a s e o c c u r so r a p i d l y ( a b o u t 1 0 s ) t h a t v i b r a t i o n a l e x c i t a t i o n o f t h e u r a n y l i o n s w o u l d be d i s s i p a t e d l o n g b e f o r e any s i g n i f i c a n t f r a c t i o n o f e x c i t e d u r a n y l i o n s c o u l d r e a c h t h e i n t e r f a c e and t h e r e f o r e c h a n g e t h e d i s t r i b u t i o n between t h e two p h a s e s . Rapid loss of v i b r a t i o n a l e x c i t a t i o n i n r e l a t i o n to other processes i s a generic problem f o r i n f r a r e d l a s e r e f f e c t s i n any s y s t e m o f c o n d e n s e d p h a s e s . However, d i f f e r e n c e s between e x p e r i m e n t a l s e t u p s may a c c o u n t f o r t h e d i f f e r e n c e s i n r e s u l t s , 1 2

In Actinide Separations; Navratil, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

1

In Actinide Separations; Navratil, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

in S u l f u r i c Acid.

Spanish Yellow Cake dissolved

2

3

U0 (N0 )

3

Aqueous

2

U0 (N0 )

Aqueous

Starting Solution

2

2

Ethyl Alcohol Hydrazine Sulfate 5

2.5

NH FHF Alcohol

4

4.7

4

pH_

NH FHF Alcohol

Additions

4

U F

F U F

Hydrated Uranous Oxide

4

4

NH F

N H

4

Product

H 2

2

0

H 0

#

f

C d , B P, C u , Cr, Fe, Pb, Mg Z n , Na, Sn

Fe V Be Zr

AI Th, Ce, La

Separated F r o m

Table I. Solar Uranium Separations

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%

88 90 97 97

99 95

Recovery

Purity

99.9 99.9 Not Given Not Given

100 100

%

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although p o s s i b l e reasons are obscure. F u r t h e r e x p e r i m e n t s have shown no o t h e r e x t r a c t a n t s t h a t b e h a v e i n t h i s way u p o n i n f r a r e d irradiation (17). P h o t o c h e m i s t r y c a n a l s o be u s e d i n t h e g e n e r a t i o n o f r e a g e n t s for actinide separations. In t h e f i r s t s t e p o f solvent-extraction r e p r o c e s s i n g methods, u r a n i u m and p l u t o n i u m a r e e x t r a c t e d i n t o the o r g a n i c p h a s e f r o m most o f t h e o t h e r a c t i n i d e s and t h e f i s s i o n p r o d u c t s , w h i c h r e m a i n i n the aqueous p h a s e . In subsequent s t e p s o f r e p r o c e s s i n g , p l u t o n i u m and u r a n i u m a r e s e p a r a t e d and p u r i f i e d . The r e p r o c e s s i n g schemes v a r y i n t h e d e g r e e s o f s e p a r a t i o n achieved i n these steps. F o r e x a m p l e , C i v e x p r o p o s e s t h a t a much h i g h e r c o n c e n t r a t i o n o f f i s s i o n p r o d u c t s be c a r r i e d w i t h t h e u r a n i u m a n d p l u t o n i u m t h a n i n t h e P u r e x p r o c e s s (IS); i n cop r o c e s s i n g , t h e u r a n i u m and p l u t o n i u m a r e t o be i m c o m p l e t e l y s e p a r a t e d from each o t h e r (19). A p l u t o n i u m r e d u c t a n t i s needed f o r t h e c o m p l e t e o r p a r t i a l s e p a r a t i o n o f u r a n i u m and p l u t o n i u m . P l u t o n i u m ( I V ) e x t r a c t s more r e a d i l y i n t o t h e o r g a n i c p h a s e , and p l u t o n i u m ( I I I ) , i n t o t h e aqueous phase o f the t y p i c a l s o l v e n t e x t r a c t i o n system (20). U r a n i u m ( I V ) i s a good r e d u c t a n t for t e t r a v a l e n t p l u t o n i u m (21), and i t can be p r o d u c e d by t h e p h o t o c h e m i c a l r e d u c t i o n o f u r a n y l b y o r g a n i c compounds, i n c l u d i n g s e v e r a l compounds t h a t a r e u s e d i n n o r m a l r e p r o c e s s i n g operations (22). P h o t o c h e m i c a l methods c a n p r o d u c e s o l u t i o n s o f u r a n i u m ( I V ) i n e i t h e r t h e aqueous o r the o r g a n i c phase ( 2 2 , 2 3 ) . TBP i s a good p h o t o c h e m i c a l r e d u c t a n t f o r the u r a n y l i o n , the r e a c t i o n p r o d u c t b e i n g e i t h e r u r a n i u m ( I V ) o r u r a n i u m ( V ) , d e p e n d i n g on t h e experimental conditions (22c,d,e). U r a n i u m ( V ) , by i t s redox p o t e n t i a l , s h o u l d a l s o be a p l u t o n i u m r e d u c t a n t (24). The r e a c t i o n f o r r e d u c t i o n o f p l u t o n i u m ( I V ) by uranium(IV) i s 2 Pu

k+

or,

+ U

4

+

+ 2 H 0 + 2 Pu 2

3 +

+ U0

2

2 +

+ 4 H

+

(1)

f o r r e d u c t i o n by u r a n i u m ( V ) , Pu**

+ U0

2

+

+ Pu

3 +

+ U0

2

2 +

.

(2)

A l t h o u g h t h e r e d o x p o t e n t i a l s f o r aqueous s o l u t i o n i n d i c a t e t h a t u r a n i u m ( I V ) s h o u l d r e d u c e p l u t o n i u m ( I V ) , a n i o n s and o t h e r c o m p l e x i n g a g e n t s can change t h e p o t e n t i a l s s u f f i c i e n t l y t h a t u r a n i u m ( I V ) and p l u t o n i u m ( I V ) can c o e x i s t i n s o l u t i o n (25). Since one o f t h e p r o d u c t s o f p h o t o c h e m i c a l r e d u c t i o n o f u r a n y l b y TBP i s d i b u t y l phosphate (DBP), which complexes p l u t o n i u m ( I V ) s t r o n g l y , e x p e r i m e n t s were done t o t e s t t h e p h o t o c h e m i c a l l y p r o d u c e d u r a n i um(IV) s o l u t i o n s as p l u t o n i u m ( I V ) r e d u c t a n t s (26). Bench-scale s t a t i o n a r y t e s t s showed t h e s e s o l u t i o n s t o be e q u i v a l e n t t o hydroxylamine n i t r a t e s o l u t i o n s s t a b i l i z e d with hydrazine (27). The r e s u l t s o f t h e s e e x p e r i m e n t s a r e shown i n T a b l e I I . For these e x p e r i m e n t s , t h e u r a n i u m ( I V ) was i n t h e o r g a n i c p h a s e a n d t h e p l u t o n i u m ( I V ) was i n t h e a q u e o u s p h a s e . A l t h o u g h l a r g e amounts o f n i t r i t e were p r e s e n t i n t h e a q u e o u s p h a s e , no n i t r i t e suppressors were n e c e s s a r y . I n r e d u c t i o n s i n w h i c h b o t h t h e u r a n i u m ( I V ) and

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DEPOORTER AND ROFER—DEPOORTER

Photochemical

Techniques

Table II. Organic U (IV)-Aqueous Pu (IV) Reductions Experiments

Pu After Reduction Aqueous Organic

U(IV) Pu(IV)

Aqueous

Organic

Pu(o) Pu(a)

Pu(a) Pu(o)

0.73

2.34

1.93 g/8

0.0544

0.0282

35.48

0.29

5.86

1.90

0.0408

0.0215

46.57

0.15

11.72

1.84

0.0245

0.0133

75.10

Initial Solution Concentrations Aqueous: 2.04 g/fi Pu (0.0085 M), 1.5 Ν Η Ν 0 Organic: U(IV) 0.0147 M, U(VI) 0.0187 M, 33 v% Τ BP in CCI, No Nitrite suppressors used in either phase 3

In Actinide Separations; Navratil, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.

ACTINIDE SEPARATIONS

274

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p l u t o n i u m ( I V ) were i n i t i a l l y i n t h e o r g a n i c p h a s e , t h e p h o t o c h e m i c a l l y p r o d u c e d u r a n i u m ( I V ) was a l s o e f f e c t i v e i n r e d u c i n g t h e p l u t o n i u m ( I V ) and a l l o w i n g i t t o be s t r i p p e d i n t o t h e aqueous phase. We c o n c l u d e t h a t t h e amount o f DBP p r o d u c e d i n t h e p h o t o l y s i s was n o t s u f f i c i e n t t o i n t e r f e r e i n t h e s t r i p p i n g o f p l u t o n i u m (III) from the organic phase. F u r t h e r e x p e r i m e n t s s h o u l d b e done t o d e t e r m i n e t h e amounts o f DBP a n d o t h e r p o t e n t i a l l y d e l e t e r i o u s byproducts generated by the various photochemical u r a n y l reductions. The p h o t o c h e m i c a l r e d u c t i o n o f a s o l u t i o n c o n t a i n i n g b o t h uranium(VI) and p l u t o n i u m ( I V ) i s a l s o o f i n t e r e s t f o r r e p r o c e s sing applications. E a r l y experiments (12a) showed a s i g n i f i c a n t reduction o f plutonium(IV) by l i g h t i n Purex-type process s o l u tions. S i n c e t h e quantum y i e l d f o r p l u t o n i u m r e d o x r e a c t i o n s i s a b o u t o n e - t e n t h t h a t f o r u r a n y l r e d u c t i o n ( 7 b , c ) t h e most l i k e l y path o f plutonium(IV) r e d u c t i o n i n these experiments appears to have been by uranium(IV) o r uranium(V) g e n e r a t e d b y p h o t o c h e m i c a l r e d u c t i o n o f u r a n y l b y o t h e r components o f t h e s o l u t i o n s . Further experiments i n t h i s a r e a would be u s e f u l . P h o t o c h e m i c a l s e p a r a t i o n , w i t h t h e new c a p a b i l i t i e s o f l a s e r s as l i g h t s o u r c e s , p r o v i d e s many new a r e a s o f i n v e s t i g a t i o n . Appli c a t i o n of photochemical techniques to a c t i n i d e separations alone h a s an enormous p o t e n t i a l . A s l a s e r s become more r e l i a b l e a n d e c o n o m i c a l , p h o t o c h e m i c a l s e p a r a t i o n s h o u l d become a n a t t r a c t i v e t e c h n i q u e f o r many s y s t e m s . Acknowledgement We t h a n k D . T . V i e r a n d E . L . Z e b r o s k i ( E l e c t r i c Power Research I n s t i t u t e ) f o r h e l p f u l d i s c u s s i o n s o f e a r l y photochemical actinide research. T h e s k i l l o f J . M . F u r n i s h i n l o c a t i n g some o f t h e o l d e r r e f e r e n c e s was i n v a l u a b l e .

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5.

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ACTINIDE SEPARATIONS

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RECEIVED

August 31, 1979.

Work performed under the auspices of U.S. Energy Research and Development Administration under contract number W-7405-eng-36.

In Actinide Separations; Navratil, J., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1980.