Actinide Partitioning Flowsheets - ACS Symposium Series (ACS

27 Actinide Partitioning Flowsheets D. D. TEDDER , B. C. FINNEY, and J. O. BLOMEKE 1

Downloaded by UNIV OF GUELPH LIBRARY on September 6, 2012 | http://pubs.acs.org Publication Date: April 16, 1980 | doi: 10.1021/bk-1980-0117.ch027

Oak Ridge National Laboratory, Oak Ridge, T N 37830

During the past three years, the Department of Energy has funded an R&D program (1,2,3,4,5) to study actinide partitioning for waste management purposes. A large part of this effort has been related to the development of credible, chemical processing flowsheets for removing actinides from fuel reprocessing and refabrication wastes. The result is a concept of waste treatment f a c i l i t i e s (WTFs) that are adjacent to, but not integral with, either conventional or safeguarded reprocessing and refabrication plants. These WTFs treat wastes as they are generated during spent fuel recycle operations, remove residual actinide contamination from the wastes, recycle a mixture of concentrated actinide nitrates to the main processing f a c i l i t i e s , and discharge treated wastes to the on-site waste treatment f a c i l i t i e s for f i n a l packaging and terminal storage. The operation of the WTFs for actinide partitioning does not exclude any particular safeguard strategy, since the concentrated actinides recovered from the wastes are returned to the on-site f a c i l i t y that produced them v i a a shielded, underground pipeline. Moreover, the operation of the WTF is largely independent of the flowsheet operated in the main processing plant insofar as the same generic wastes are produced from a Purex plant regardless of whether or not the actinides are coprocessed or processed separately. Generically, the wastes w i l l have the same compositions, although there may be differences in the quantities of waste. A primary o b j e c t i v e o f the DOE program has been t o develop a c t i n i d e p a r t i t i o n i n g flowsheets t h a t are d e f e n s i b l e from the standpoint o f chemical f e a s i b i l i t y . A f o u r - p o i n t s t r a t e g y was adopted in order t o meet t h i s o b j e c t i v e : 1.

U t i l i z e o n l y demonstrated technology t h a t is r e a d i l y a p p l i c a b l e t o commercial r e c y c l e o p e r a t i o n s .

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Present address: Georgia Institute Institute of Technology, School of Chemical Engineering, Atlanta, GA 30332. 0-8412-0527-2/80/47-117-381$05.00/0

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1980 American Chemical Society

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

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Develop generic c a p a b i l i t i e s t o d e a l w i t h all types of wastes. Choose p r o c e s s i n g systems t h a t complement each other and provide a c t i n i d e recovery o p p o r t u n i t i e s in depth. E x p e r i m e n t a l l y evaluate the proposed treatment concepts.

The first of these p o i n t s g r e a t l y reduced the scope of the study, s i n c e many p o s s i b l e s e p a r a t i o n schemes (e.g., pyrochemical) were excluded on t h i s b a s i s . The second p o i n t tended t o expand the scope of the study, s i n c e work p r i o r t o t h i s program had focused almost e x c l u s i v e l y on removing a c t i n i d e s from the h i g h l e v e l l i q u i d wastes. However, it is w e l l known t h a t s i g n i f i c a n t a c t i n i d e l o s s e s occur t o other wastes as w e l l (e.g., HEPA f i l t e r s , i n c i n e r a t o r ashes, chemical s a l t wastes, d i s s o l v e r s o l i d s , e t c . ) and, as f a r as waste management is concerned, it is e s s e n t i a l l y meaningless t o ignore these wastes. P o i n t three is important w i t h respect t o p r o v i d i n g a d d i t i o n a l assurance t h a t the r e q u i r e d l e v e l s of a c t i n i d e decontamination can be r o u t i n e l y met in a l a r g e - s c a l e o p e r a t i o n . Unfavorable i n t e r a c t i o n s between processes w i t h i n the WTF can make the system unworkable, even i f the separated processes operate w e l l alone. On the other hand, complementary systems provide recovery backup t h a t can be e x p l o i t e d by c o n s i d e r i n g the consequences of v a r i o u s r e c y c l e s t r a t e g i e s w i t h i n the WTF under c o n d i t i o n s of maloperation. The experimental assessments so f a r have y i e l d e d f a v o r a b l e r e s u l t s as f a r as a c h i e v i n g the p a r t i t i o n i n g o b j e c t i v e s . Of course, these t e s t s are not c o n c l u s i v e , s i n c e they have been performed on o n l y a very s m a l l s c a l e and only separate subsystems have been examined. However, there does not appear t o be any fundamental reason t h a t precludes a c h i e v i n g the s t a t e d p a r t i t i o n i n g goals and, in f a c t , it may be p o s s i b l e t o exceed them. Rather, the question appears t o be one of cost and d i m i n i s h i n g r e t u r n s on incremental investment. A c t i n i d e P a r t i t i o n i n g Goals The p a r t i t i o n i n g of a c t i n i d e s from waste has been viewed as a means t o reduce or m i t i g a t e the long-term b i o l o g i c a l hazard of nuclear waste ( a f t e r 1000 years of storage) by a c h i e v i n g higher removal o f all a c t i n i d e s from the waste than has been a t t a i n e d in the past (6_ Ί_ §_ 9_). A f t e r 1000 years in geologic i s o l a t i o n , it is the a c t i n i d e concentrations in the s t o r e d wastes which dominate i t s r a d i o t o x i c i t y . With these elements more completely removed before i s o l a t i o n the waste may be l e s s harmful, even i f r e l e a s e d t o the environment in the d i s t a n t f u t u r e . Therefore, the a c t i n i d e p a r t i t i o n i n g goals were set at l e v e l s such t h a t the r a d i o t o x i c i t y of the r e s u l t i n g waste forms a f t e r 1000 years would be comparable t o t h a t of n a t u r a l bodies of r a d i o a c t i v e ores. 9

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In summmary, these goals would be l a r g e l y achieved i f the a c t i n i d e l o s s e s t o all r e p r o c e s s i n g wastes can be kept below 0.1% of t h e main p l a n t feed and i f t h e l o s s e s t o r e f a b r i c a t i o n wastes can be kept below 0.15% o f t h e a c t i n i d e s r e f a b r i c a t e d .


Waste Treatment Systems The subsystems f o r a WTF supporting a f u e l r e p r o c e s s i n g p l a n t have been subdivided i n t o t h e f o l l o w i n g treatment areas: ( l ) High-Level S o l i d Waste Treatment, (2) High-Level L i q u i d Waste Treatment, (3) S o l i d Alpha Waste Treatment, (k) Cation Exchange Chromatography, (5) S a l t Waste Treatment, (6) A c t i n i d e Recovery, (7) Solvent Cleanup and R e c y c l e , (8) Off-Gas Treatment, (9) Product Concentration, and (10) A c i d and Water Recycle. Each o f these areas has major design problems; t h e WTF supporting a f u e l f a b r i c a t i o n f a c i l i t y is s i m i l a r , but without areas 1 and 2. I n both cases, all subsystems are i n t e g r a t e d so as t o operate together in a s i n g l e , o n - s i t e p r o c e s s i n g b u i l d i n g . High-Level S o l i d Waste Treatment. Cladding h u l l s and d i s s o l v e r s o l i d s are generated as wastes from r e p r o c e s s i n g LWR f u e l s . The alpha a c t i v i t y a s s o c i a t e d w i t h these head-end wastes is norm a l l y low, but as a p r e c a u t i o n a r y measure the WTF provides an area where these wastes may be given an extended t e r t i a r y HN0 /KF/ HC1 l e a c h . Experimental s t u d i e s w i t h mixed-oxide r e a c t o r f u e l s (10,11,12) suggest t h a t a c t i n i d e l o s s e s can be h e l d t o 0.01$ o r l e s s i f f l u o r i d e and c h l o r i d e are present in t h e leachant. 3

High-Level L i q u i d Waste (HLLW) Treatment. The h i g h - l e v e l l i q u i d waste is produced as a raffinâte from t h e HA solvent e x t r a c t i o n c y c l e in Purex. A f t e r g e n e r a t i o n , the HLLW is immedia t e l y t r a n s f e r r e d t o t h e WTF v i a an underground p i p e l i n e without c o n c e n t r a t i o n or i n t e r i m storage. This s t r a t e g y minimizes t h e problems a s s o c i a t e d w i t h s o l i d s p r e c i p i t a t i o n . Upon e n t r y i n t o t h e WTF, t h e HLLW is contacted (see F i g u r e l ) with the bidentate extractant dihexyl-N,N-diethylcarbamylmethylene phosphonate (CMP) which is d i l u t e d t o 30 v o l % w i t h d i - i s o p r o p y l benzene. Under high a c i d c o n d i t i o n s ( l 3 > l M , t h i s e x t r a c t a n t w i l l remove all t r i v a l e n t and t e t r a v a l e n t a c t i n i d e s t o some degree from the HLLW. Of t h e f i s s i o n products, o n l y Z r , Te, Ru, Mo, Kb, Y, and Pd e x t r a c t t o any s i g n i f i c a n t extent. These species can be c o n t r o l l e d e i t h e r by subsequent scrubbing o f t h e organic phase o r by a d j u s t i n g e x t r a c t i o n c o n d i t i o n s so as t o r e j e c t those f i s s i o n products t h a t e x i s t as anions t o t h e r a f f i n a t e . A f t e r scrubbing, t h e c o e x t r a c t e d a c t i n i d e s and l a n t h a n i d e s are removed from t h e organic phase by two separate s t r i p columns (a reductant and d i l u t e n i t r i c a c i d s t r i p , f o l l o w e d by a d i l u t e o x a l i c a c i d s t r i p ) . A f t e r d e s t r u c t i o n o f t h e excess o x a l i c a c i d , the two s t r i p s are combined w i t h other r e c y c l e streams t h a t are



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CMP HLLW TO SOLIDIFICATION

ACTINIDES AND LANTHANIDES TO CEC PURIFICATION

Figure 1. The high-level liquid waste can he adequately partitioned by solvent extraction with 30% CMP.



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produced in t h e WTF, concentrated, p a r t i a l l y d e n i t r a t e d and sent to c a t i o n exchange chromatography f o r l a n t h a n i d e removal. Experimental r e s u l t s t o date ( 1 3 ) , u s i n g a c t u a l HLLW gener ated from d i s s o l v i n g H. B. Robinson r e a c t o r f u e l t h a t had a burnup o f ^27,000 MW days/MT and had been cooled f o r about 2 y e a r s , suggest t h a t g r e a t e r than 99-99$ o f t h e t e t r a v a l e n t a c t i n i d e s and g r e a t e r than 99·9% o f t h e t r i v a l e n t a c t i n i d e s may be removed u s i n g CMP e x t r a c t i o n subsequent t o Purex. A l s o , by adding s m a l l amounts o f f l u o r i d e t o t h e HLLW before CMP e x t r a c t i o n , it may be p o s s i b l e t o convert t h i s stream i n t o a nont r a n s u r a n i c -waste ( i . e . , l 6 ) suggest t h a t they are probably t e c h n i c a l l y f e a s i b l e , although very expen s i v e . The e e r i e n i t r a t e l e a c h i n g has s e v e r a l important f e a t u r e s , r e l a t i v e t o f l u o r i d e , t h a t should be mentioned. F i r s t of all, it is about as e f f e c t i v e as f l u o r i d e in a c c e l e r a t i n g the d i s s o l u t i o n of all t r a n s u r a n i c a c t i n i d e s . Secondly, the e e r i e n i t r a t e s do not d i s s o l v e or g r e a t l y s o f t e n the HEPA f i l t e r waste, whereas f l u o r i d e converts the HEPA f i b e r g l a s s i n t o an i n t r a c t a b l e , gooey mess t h a t cannot be pumped or f i l t e r e d . S i m i l a r l y , f l u o r i d e t o t a l l y d i s s o l v e s i n c i n e r a t o r ashes, whereas t h i s l a t t e r waste is only p a r t l y d i s s o l v e d ( ν ? 0 $ ) by the e e r i e n i t r a t e l e a c h . A l s o , the ash r e s i d u e r e s u l t i n g from cerium treatment is r e a d i l y cent r i f u g e d . A f t e r treatment, the HEPA waste r e t a i n s much of i t s f i b r o u s , pulpy character and can be screw metered i n t o 55-gal drums. In terms of decontamination, the e e r i e l e a c h i n g appears adequate f o r HEPA f i l t e r s . The experimental s t u d i e s (5>15 >l6) have achieved 99-99$ d i s s o l u t i o n of the most r e f r a c t o r y of the t e t r a v a l e n t a c t i n i d e s . However, the l e a c h i n g of the i n c i n e r a t o r ashes ( 5 » l 6 ) has been l e s s s u c c e s s f u l , s i n c e as much as 5$ of the alpha a c t i v i t y i n i t i a l l y in t h i s waste does not d i s s o l v e w i t h e e r i e treatment alone. However, t h i s l a s t 5$ may be recovered by d i s s o l v i n g the ash residuum e n t i r e l y w i t h f l u o r i d e . (This 5$ l o s s would represent about 0.05$ of the a c t i n i d e feed t o the main plant.) For waste management, cerium-promoted d i s s o l u t i o n has another important c h a r a c t e r i s t i c r e l a t i v e t o f l u o r i d e d i s s o l u t i o n . F l u o r i d e d i s s o l v e s these wastes t o t a l l y and is not r e a d i l y r e c y c l e d , since it is consumed by the formation of s i l i c o n f l u o r i d e s . In t h i s case, the f l u o r i d e reagent becomes a waste t h a t must be disposed of at g r e a t e r expense, since t h i s f l u o r i d e a d d i t i o n increases the weight and b u l k of the chemical wastes t h a t must be converted t o immobile s o l i d s ( i . e . , a concrete or g l a s s waste). Cerium, on the other hand, can be r e c y c l e d w i t h i n the WTF by c o e x t r a c t i n g it w i t h the t r i v a l e n t a c t i n i d e s u s i n g the CMP e x t r a c t a n t in the A c t i n i d e Recovery Area. Gadolinium can a l s o be r e c y c l e d w i t h the cerium and used as a neutron poison in the S o l i d Alpha Waste Treatment equipment, thereby e l i m i n a t i n g the need f o r c r i t i c a l l y safe geometry. Although some i n c r e a s e in waste q u a n t i t i e s r e s u l t s from t h i s s t r a t e g y ( p r i m a r i l y from the solvent cleanup scrub wastes), these i n c r e a s e s are modest compared t o the consequences of fluoride-promoted d i s s o l u t i o n . C a t i o n Exchange Chromatography (CEC). i d e n t i c a l t o t h a t d e s c r i b e d elsewhere (l7_), of s m a l l batches must be run in p a r a l l e l in l a r g e q u a n t i t i e s of curium t h a t b u i l d up due

This process is except t h a t a number order t o d e a l w i t h the t o the r e c y c l e of the



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t r a n s u r a n i c s . This problem is d e a l t w i t h by a modular approach in d e s i g n i n g the c a t i o n exchange r a c k s . Each rack (or module) c o n s i s t s o f a s i n g l e feed column and two e l u t i o n columns mounted on a balanced frame t h a t has o v e r a l l dimensions about the s i z e o f an o f f i c e f i l e c a b i n e t . I n t h i s manner, the watts per batch o f r a d i o a c t i v e m a t e r i a l loaded onto the module are kept s m a l l . The experimental work r e l a t i n g t o t h i s p r o c e s s i n g area has focused on i d e n t i f y i n g any i n t e r a c t i o n s between the c a t i o n exchange chromatography (CEC) area o f the WTF and the HLLW Treatment Area t h a t produces the CEC f e e d , and in determining the e l u t i o n sequence f o r the t e t r a v a l e n t a c t i n i d e s . Both s t u d i e s (5,18) gave f a v o r a b l e r e s u l t s . The expected i m p u r i t i e s in t h e feed t o the CEC w i l l not s i g n i f i c a n t l y a f f e c t system performance. No evidence f o r CEC feed adjustment beyond the c o n t r o l o f a c i d i t y l e v e l appears t o be necessary. A l s o , it was v e r i f i e d t h a t the t e t r a v a l e n t a c t i nides w i l l e l u t e ahead o f the b a r r i e r i o n in CEC; t h e r e f o r e , these elements w i l l r e p o r t t o the S a l t Waste Treatment system as desired. S a l t Waste Treatment. A l k a l i n e and a c i d i c s a l t wastes a r e produced from a v a r i e t y o f sources d u r i n g f u e l r e p r o c e s s i n g and r e f a b r i c a t i o n . The most important o f these wastes, w i t h respect to a c t i n i d e l o s s e s , is t h e a l k a l i n e sodium carbonate scrub waste t h a t is generated d u r i n g TBP r e c y c l e and cleanup. This waste may c o n t a i n up t o 0.5% o f the a c t i n i d e f e e d , along w i t h the s o l v e n t degradation products (sodium s a l t s o f monobutyl and d i b u t y l phosphoric a c i d s ) . These a c i d i c degradation products prevent a c t i n i d e s t r i p p i n g from a n e u t r a l e x t r a c t a n t such as TBP and, t h e r e f o r e , they must be removed from the waste before the a c t i nides can be recovered by TBP solvent e x t r a c t i o n . A d d i t i o n a l troublesome s a l t wastes are the a l k a l i n e detergent wastes cont a i n i n g s u r f a c t a n t s t h a t e x t r a c t i n t o TBP and, in the WTF, t h e sodium carbonate scrub wastes r e s u l t i n g from CMP r e c y c l e and cleanup. These p o t e n t i a l l o s s e s are unacceptable d u r i n g a c t i n i d e part i t i o n i n g , but recent developments a t Argonne N a t i o n a l Laboratory have l e d t o an e f f e c t i v e chemical treatment u s i n g 2-ethylhexanol. Detergent wastes may a l s o be t r e a t e d . The Argonne process (5,19)s designated as " a l c o h o l e x t r a c t i o n , " (see F i g u r e 2) c o n s i s t s o f a c i d i f y i n g the a l k a l i n e wastes and then c o n t a c t i n g them w i t h 2-ethylhexanol. T h i s a l c o h o l is a very e f f e c t i v e e x t r a c t a n t f o r those a c i d i c degradation products l i k e d i b u t y l and monobutyl phosphoric a c i d s , but o n l y weakly e x t r a c t s the a c t i n i d e s which remain in the r a f f i n a t e . Consequentl y the r a f f i n a t e may be subsequently t r e a t e d w i t h 30% TBP and CMP f o r a c t i n i d e recovery s i n c e it no longer c o n t a i n s those a c i d i c degradation products t h a t would otherwise e x t r a c t and prevent s t r i p p i n g . The a l c o h o l e x t r a c t a n t which c o n t a i n s the degradation products (and any detergents as w e l l ) is then r e c y c l e d by washing out these a c i d i c species w i t h sodium carbonate.



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Recent t e s t r e s u l t s (19.) appear very f a v o r a b l e f o r t h i s s y s tem. Although it is r e l a t i v e l y r o b u s t , a f u r t h e r improvement has been i d e n t i f i e d through the a d d i t i o n o f s m a l l amounts o f d i e t h y l enetriaminepentaacetic a c i d (DTPA) t o the sodium carbonate scrub before it is contacted w i t h used TBP o r CMP. Under these c o n d i t i o n s , t h e a c t i n i d e l o a d i n g s in t h e carbonate scrub can be i n c r e a s e d s i g n i f i c a n t l y before i n t e r f a c i a l cruds appear. A l s o , when the r e s u l t i n g a l k a l i n e waste is a c i d i f i e d , n e i t h e r i n t e r f a c i a l cruds nor a c t i n i d e polymers a r e formed. A c t i n i d e s are then e a s i l y recovered by TBP solvent e x t r a c t i o n from the a l c o h o l e x t r a c t i o n column r a f f i n a t e , and can be s t r i p p e d from TBP and CMP in the u s u a l f a s h i o n . A c t i n i d e Recovery Area. Both WTFs r e q u i r e an A c t i n i d e Recovery Area where a c t i n i d e s are recovered from the l i q u o r s being produced in t h e above-mentioned treatment areas. The WTF supporting the f u e l r e p r o c e s s i n g p l a n t (see F i g u r e 3) r e q u i r e s both a TBP and CMP e x t r a c t i o n c y c l e , but the WTF s u p p o r t i n g the f u e l r e f a b r i c a t i o n p l a n t can be operated w i t h a CMP e x t r a c t i o n c y c l e alone and by u t i l i z i n g the e x i s t i n g , o n - s i t e TBP scrap recovery system. In both cases, the v a r i o u s a c t i n i d e - b e a r i n g l i q u o r s are concentrated, a c i d i f i e d , and c l a r i f i e d by c e n t r i f u g a t i o n as needed. Subsequently, t h e concentrate is contacted w i t h TBP and then w i t h CMP. The r a f f i n a t e , now e s s e n t i a l l y a c t i n i d e - f r e e , is f u r t h e r concentrated, d e n i t r a t e d w i t h formic a c i d , and t h e r e s u l t i n g s l u r r y converted t o a concrete waste t h a t is packaged in 55-gal drums. The TBP organic is s t r i p p e d in the u s u a l manner, w i t h the recovered a c t i n i d e s being sent back t o the main process i n g f a c i l i t y . The CMP organic is s t r i p p e d in two columns, s i m i l a r t o the o p e r a t i o n o f the HLLW treatment s t r i p columns (see F i g u r e l ) , t o recover the s t a b l e cerium and gadolinium f o r r e c y c l e t o the S o l i d Alpha Waste Treatment Area. Low c o n c e n t r a t i o n s o f t r i v a l e n t a c t i n i d e s are maintained in the cerium r e c y c l e stream by b l e e d i n g a f r a c t i o n o f t h i s stream t o the CEC system. Thus, the major d i f f e r e n c e s between the A c t i n i d e Recovery Area and the HLLW Treatment Area are the a n t i c i p a t e d higher l e v e l s o f r a d i o a c t i v i t y in the l a t t e r system. Solvent Cleanup and Recycle. Both TBP and CMP s o l v e n t s can be cleaned up w i t h simple water and d i l u t e sodium carbonate washes. The conceptual flowsheets a l s o i n c l u d e p r e e q u i l i b r a t i o n o f the s o l v e n t s w i t h a c i d before they are r e c y c l e d t o the e x t r a c t i o n columns. This treatment helps t o m a i n t a i n h i g h a c i d concent r a t i o n s in t h e e x t r a c t i o n column raffinâtes. For the CMP e x t r a c t a n t , e q u i l i b r a t i o n w i t h h i g h a c i d a l s o helps t o s t r i p t h e ruthenate and pertechnetate anions from the s o l v e n t . A c t i v i t y l e v e l s in the A c t i n i d e Recovery Area are f u r t h e r c o n t r o l l e d by b l e e d i n g a f r a c t i o n o f i t s CMP s o l v e n t t o the CMP S o l v e n t Recycle



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SALT WASTE

t

L

L.

RXN

SOLVENT DEGRADATION PRODUCTS

I

EHOH TREATED .SALT WASTE TO ACTINIDE RECOVERY

Figure 2. Actinides may be recovered from acidified salt wastes by TBP extrac tion after the degradation products have been removed using 2-ethylhexanol extraction.

HLLW TREATMENT

I

SALT WASTE TREATMENT

HL SOLID WASTE TREATMENT

MIXED ACTINIDES

CATION EXCHANGE CHROMATOGRAPHY

TETRAVALENTS

ACTINIDE PRODUCT CONCENTRATION

MIXED ACTINIDES

TETRAVALENTS

ACTINIDE RECOVERY AREA

TETRAVALENTS

τ SOLID ALPHA WASTE TREATMENT

CERIUM + ACTINIDES CERIUM RECYCLE

Figure 3. Actinide recycle occurs between the subsystems within the WTF. Wastes enter the subsystemsinthe left column. Actual recovery occursinthe central column subsystems. A mixture of actinide nitratesissent from Actinide Product Concentration to the fuel reprocessing plant for codenitration.


27.

TEDDER E T A L .


391


Area f o r HLLW Treatment. A l s o , a s m a l l f r a c t i o n o f the CMP e x t r a c t a n t from the HLLW Treatment Area is c o n t i n u o u s l y sent t o the o n - s i t e solvent "burner. Off-Gas Treatment. Both WTFs r e q u i r e extensive o f f - g a s treatment. The adequate removal o f n i t r o g e n oxides appears e s p e c i a l l y troublesome f o r the WTF supporting the f u e l reproces s i n g p l a n t , since considerable amounts o f a c i d d e n i t r a t i o n occur in the flowsheets. A l s o , ruthenium v o l a t i l i z a t i o n is problematic in the S o l i d Alpha Waste Treatment Area, so ruthenium a d s o r p t i o n beds are provided t o t r e a t these o f f - g a s e s . The design s t r a t e g y is to a i r - s p a r g e the e l e c t r o l y t i c o x i d i z e r tanks and adsorb any o x i d i z e d ruthenium on s i l i c a g e l beds, r a t h e r than a l l o w i n g it t o r e f l u x in t h e o x i d i z e r s . The f u e l r e p r o c e s s i n g p l a n t WTF w i l l a l s o r e q u i r e i o d i n e r e t e n t i o n systems; both WTFs u t i l i z e extensive HEPA f i l t r a t i o n and c a t a l y t i c Ν 0 d e s t r u c t i o n as a p o l i s h i n g step. χ

A c i d and Water Recycle. A c i d and water r e c y c l e is a s i g n i f i cant problem, e s p e c i a l l y in t h e f u e l r e p r o c e s s i n g WTF. The streams generated i n t e r n a l l y by the WTFs are c h a r a c t e r i s t i c a l l y voluminous, w i t h low l e v e l s o f alpha a c t i v i t y , but c o n t a i n i n g l a r g e amounts o f d i s s o l v e d s o l i d s . This c o n d i t i o n r e s u l t s in a need t o r e c y c l e l a r g e q u a n t i t i e s o f d i l u t e a c i d and water as evaporator overheads. However, the h i g h l e v e l s o f d i s s o l v e d s o l ids in the WTF waste evaporator feeds s e v e r e l y l i m i t the extent t o which solvent e x t r a c t i o n feeds t o the A c t i n i d e Recovery Area can be concentrated without p r e c i p i t a t i n g chemical s o l i d s and t h e r e by running the r i s k o f a d d i t i o n a l a c t i n i d e l o s s e s by c o p r e c i p i t a t i o n . Because o f the d i s s o l v e d s o l i d s c o n s t r a i n t , the pulse columns r e q u i r e d f o r use in the A c t i n i d e Recovery Area o f the WTF are about the same s i z e as those r e q u i r e d in the HLLW Treatment Area, although the a c t i n i d e concentrations in the A c t i n i d e Recovery Area feeds are about an order o f magnitude lower than in the HLLW. Thus, t h e d i s s o l v e d s o l i d s r e s u l t in l e s s e f f i c i e n t o p e r a t i o n in the A c t i n i d e Recovery Area than is p o s s i b l e in t h e HLLW Treatment Area. Conclusions The a c t i n i d e p a r t i t i o n i n g program w i l l show (20) t h a t alphabearing wastes can probably be p a r t i t i o n e d t o a l e v e l t h a t would s i g n i f i c a n t l y reduce the a c t i n i d e concentrations in the r e s u l t i n g wastes. A l s o , the waste q u a n t i t i e s would not be g r e a t l y i n c r e a s e d because o f WTF o p e r a t i o n . No increase in HL g l a s s q u a n t i t i e s is a n t i c i p a t e d . The LL and I L f u e l r e p r o c e s s i n g concrete wastes would i n c r e a s e about 25% in volume w h i l e the f u e l f a b r i c a t i o n waste volumes would increase about l6% w i t h these flowsheets. However, the WTF t h a t p a r t i t i o n s f u e l r e p r o c e s s i n g wastes may a c t u a l l y be l a r g e r in s i z e than the main r e p r o c e s s i n g p l a n t



392


itself. I t appears t e c h n i c a l l y f e a s i b l e t o develop chemical s y s tems f o r d e a l i n g w i t h all types o f alpha wastes, but these t r e a t ment systems a r e themselves h i g h l y complex. A simple Purex p l a n t o n l y uses one solvent ( i . e . TBP); a WTF would u t i l i z e a t l e a s t t h r e e d i f f e r e n t s o l v e n t s ( i . e . TBP, CMP, and 2 - e t h y l h e x a n o l ) . I n a d d i t i o n , the WTF would r e q u i r e complex mechanical hot c e l l s t o t r e a t HEPA f i l t e r wastes and i n c i n e r a t o r ashes, as w e l l as operate a bank o f c a t i o n exchange chromatography columns. Although the CEC system might be r e p l a c e d w i t h an e q u i v a l e n t solvent e x t r a c t i o n c y c l e , t h i s improvement would be s m a l l s i n c e t h e r e s u l t i n g WTF would then be u t i l i z i n g f o u r d i f f e r e n t s o l v e n t s . Acknowledgment s T h i s r e s e a r c h was sponsored by the O f f i c e o f Nuclear Waste Management, U.S. Department o f Energy under c o n t r a c t W-7^05-eng-26 w i t h the Union Carbide C o r p o r a t i o n . Literature Cited 1.

Croff, A. G., Tedder, D. W., Drago, J. P., Blomeke,J.O., and Perona, J. J., "A Preliminary Assessment of Partitioning and Transmutation as a Radioactive Waste Management Concept," ORNL/TM-5808, Oak Ridge National Laboratory, Oak Ridge, TN

2.

Tedder, D. W. and Blomeke, J. O. (ed.), "Actinide Partition ing and Transmutation Program Progress Report for Period October 1, 1976 to March 31, 1977," ORNL/TM-5888, Oak Ridge National Laboratory, Oak Ridge, TN (1977). Tedder, D. W. and Blomeke, J. O. (ed.), "Actinide Partition ing and Transmutation Program Progress Report for Period A p r i l 1 to June 30, 1977," ORNL/TM-6056, Oak Ridge National Laboratory, Oak Ridge, TN (1977). Tedder, D. W. and Blomeke, J. O. (ed.), "Actinide Partition ing and Transmutation Program Progress Report for Period July 1 to September 30, 1977," ORNL/TM-6174, Oak Ridge National Laboratory, Oak Ridge, TN (1978). Tedder, D. W. and Blomeke, J. O. (ed.), "Actinide Partition ing and Transmutation Program Progress Report for Period October 1, 1977 to March 31, 1978," ORNL/TM-6480, Oak Ridge National Laboratory, Oak Ridge, TN (1978). Beaman, S. L., Trans. Am. Nucl. Soc. (1975) 22, 346. Claiborne, H. C., "Effect of Actinide Removal on the LongTerm Hazard of High-Level Waste," ORNL/TM-4724, Oak Ridge National Laboratory, Oak Ridge, TN (1975). Gasteiger, R., "Development of an Irradiation Technology for the Recycling of Am-241 in Nuclear Reactors — A Contribution to the P o s s i b i l i t i e s for the Reduction of the Hazard Poten tial of α-Bearing Wastes," (in German), KFK-2431, Nuclear Re search Center, Karlsruhe, Federal Republic of Germany (1977).

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Haug, H. O., "Production, Disposal, and Relative Toxicity of Long-Lived Fission Products and Actinides in the Radioactive Wastes from Nuclear Fuel Cycles," (in German), KFK-2022, translated as ORNL-tr-4302, Oak Ridge National Laboratory, Oak Ridge, TN (1975). Goode, J. H. and Stacy, R. G., "Head-End Reprocessing Studies with H. B. Robinson-2 Fuel,"ORNL/TM-6037,Oak Ridge National Laboratory, Oak Ridge, TN (1978). Goode, J. H. and Stacy, R. G., "Head-End Processing Studies with Mechanically Blended (U,Pu)O Reactor Fuels," ORNL/TM6266, Oak Ridge National Laboratory, Oak Ridge, TN (1978). Goode, J. H. and Stacy, R. G., "Comparative Studies of HeadEnd Processing Using Irradiated, Mechanically Blended and Coprecipitated (U,Pu)O Reactor Fuels," ORNL/TM-6370, Oak Ridge National Laboratory, Oak Ridge, TN (1978). McIsaac, L. D., Baker, J. D., Krupa, J. F., LaPointe, R. E., Meikrantz, D. Η., and Schroeder, N. C., "Study of Bidentate Compounds for Separation of Actinides from Commercial LWR Reprocessing Wastes," ICP-1180, Idaho National Engineering Laboratory, Idaho F a l l s , ID (in press). McIsaac, L. D., Baker, J. D., Krupa, J. F., Meikrantz, D. Η., and Schroeder, N. C., "Flowsheet Development Work at the Idaho Chemical Processing Plant for the Partitioning of Actinides from Acidic Nuclear Waste," Actinide Separations Symposium, ACS Pacific Chemical Conference, Honolulu, A p r i l 3-5, 1979. Scheitlin, F. M. and Bond, W. D., "Recovery of Plutonium from HEPA F i l t e r Media by Continuously Leaching in a Packed Column with E l e c t r o l y t i c a l l y Produced Ce(IV) Nitrate and Nitric Acid," ORNL/TM-6802, Oak Ridge National Laboratory, Oak Ridge, TN (in press). Thompson, G. H., Childs, E. L., Kochen, R. L., Schmunk, R. Η., and Smith, C. Μ., "Actinide Recovery from Combustible Waste: The Ce(IV)-HNO System," RFP-2907 (in press). Wheelwright, E. J., Bray, L. Α., Van Tuyl, Η. H. and Fullam, Η. Τ., "Flowsheet for Recovery of Curium from Power Reactor Fuel Reprocessing Plant Waste," BNWL-1831, Battelle Pacific Northwest Laboratory, Richland, WA (1974). Forsberg, C. W., personal communication to D. W. Tedder, Oak Ridge National Laboratory (June 1978). Horwitz, E. P., Mason, G. W., Bloomquist, C. Α. Α., Leonard, R. Α., and Bernstein, G. J., "The Extraction of DBP and MBP from Actinides: Applications to the Recovery of Actinides from TBP-Na CO Scrub Solutions," Actinide Separations Symposium, ACS Pacific Chemical Conference, Honolulu, HA A p r i l 3-5, 1979. Tedder, D. W., Finney, B. C., and Blomeke, J. O., "Waste Treatment F a c i l i t i e s for the Partitioning of Actinides from LWR Reprocessing and Refabrication Plant Wastes," ORNL/TM-6881 (in press).


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Actinide Partitioning Flowsheets - ACS Symposium Series (ACS

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