CEMENTATXON OF RESIDUE ION EXCHANGE RESINS AT ROCKY FLATS

Donald F. Dustin, Safe S i t e s of Colorado, L . L . C . Thomas d. Beckman, Safe S i t e s o f Colorado, L . L . C . Catherine M. Madore, Safe S i t e s of Colorado, L . L . C .

ABSTRACT

Ion exchange r e s i n s have been used t o pur i fy n i t r i c acid solutions of plutonium a t Rocky Flats s ince the 1950s. r e t a i n e d for eventual recovery of res idual plutonium, t y p i c a l l y by i n c i n e r a t i o n followed by the aqueous ex t r ac t ion of plutonium from the resultant ash. The el iminat ion of inc inera t ion as a recovery process in the l a t e 1980s and the absence of a s u i t a b l e a l t e r n a t i v e process for plutonium recovery from r e s i n s led t o a s i t u a t i o n where spent ion exchange resins were simply placed i n t o temporary s torage .

By t h e mid-l990s, temporary s torage had extended f o r a minimum of e i g h t y e a r s . wrapped in p l a s t i c , and placed in 55-gallon drums. Depending on the extent of washing t h a t took place just p r i o r t o taking t h e spent r e s in out of s e rv i ce , varying amounts of res idual n i t r i c acid remained absorbed in the r e s i n matr ix . The in t ima te mixture of n i t r i c ac id , a s t rong oxid izer , and the resin matr ix , *

a f u e l , represented a p o t e n t i a l f i r e hazard and led t h e Defense Nuclear F a c i l i t i e s Safe ty Board t o consider ion exchange r e s ins as one of the highest hazard res idue mater ia l s s tored a t the S i t e .

Spent ion exchange resins were

The s torage conta iners were t y p i c a l l y l a rge diameter cardboard tubes ,

In 1996, Rocky F la t s began processing p o t e n t i a l l y unstable ion exchange r e s i n s by combining small amounts o f r e s in i n t o a drum of cement used t o s t a b i l i z e aqueous waste l i q u i d s . any i g n i t a b i l i t y hazard associated with the r e s in and met a l l in te r im s torage and waste disposal c r i t e r i a . An addi t ional advantage was t h a t , by cementing the r e s i n in conjunction with the cementation of l i q u i d wastes, the r e s i n was e f f e c t i v e l y cemented a t a wattage l i m i t t h a t was ten times higher t h a n t h e wat tage l i m i t assigned t o a cemented product where ion exchange resins alone were immobilized.

The r e s u l t i n g product e f f e c t i v e l y el iminated

The e f f o r t t o prepare s tored r e s in f o r s t a b i l i z a t i o n v i a cementation with aqueous waste l i q u i d s began in April 1996. To da te , 100% of the inventory of r e s i d u e ion exchange r e s ins has been neut ra l ized and repackaged in preparat ion f o r t h e cementation opera t ion , and approximately 35% of t h e r e s in has been cemented. Work continues t o assay recent ly repackaged r e s in and t o cement t h e repackaged product. one more yea r a t which time a l l res idue i o n exchange r e s ins wil l have been e l imina ted as a d i s c r e t e res idue form from the S i t e .

The cementation e f f o r t i s expected t o continue f o r about

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DISCLAIMER

This report was prepared as an acwunt of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liabiiity or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, process, or service by trade name, trademark, manufac- turer, or otherwise does not necessarily constitute or imply its endorsement, m m - mendktion. or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

t

INTRODUCTION

The Rocky F1 a t s Environmental Techno1 ogy S i t e near Denver, Colorado i s c u r r e n t l y s t o r i n g a backlog of approximately 100 metric tons of plutonium- bear ing r e s idues . high concent ra t ions of plutonium t h a t the recovery of t h a t plutonium was, a t one t ime, considered t o be economically more favorable than the production o f new plutonium in a r e a c t o r f a c i l i t y . F l a t s from weapons production t o environmental r e s t o r a t i o n and waste management, plutonium recovery opera t ions will not be requi red f o r the fo reseeab le f u t u r e . The problem remains, however, a s t o t h e u l t ima te d i s p o s i t i o n of the res idue backlog.

Residues comprise a category of ma te r i a l s with s u f f i c i e n t l y

With the change i n mission for-Rocky

Residues c o n s i s t of a v a r i e t y of ma te r i a l s t h a t are by-products of nea r ly f o r t y yea r s of weapons production. Typical res idues a r e i n c i n e r a t o r ash, pyrochemical s a l t s , combustibles (paper , c l o t h , and p l a s t i c ) , metal , g l a s s , s ludges , c a s t i n g ma te r i a l s , i n s u l a t i o n , f i r e b r i c k , f i l t e r s , and ion exchange r e s i n s . w t % . A t Rocky F l a t s , res idues and wastes a r e given a unique i d e n t i f i e r known a s an Item Descript ion Code (IDC). There a r e cu r ren t ly 99 res idues IDCs await ing d i s p o s i t i o n . determined t o be hazardous a s def ined by t h e Resource Conservation and Recovery Act (RCRA) and, a s such, a r e sub jec t t o regula t ion a s mixed waste.

The average plutonium concentrat ion i n these ma te r i a l s i s about 3

Approximately 45% of these res idues have been

This r e p o r t descr ibes the method t h a t Rocky F l a t s i s c u r r e n t l y using t o s t a b i l i z e r e s idue ion exchange r e s i n s . s t a b i l i z a t i o n program i s : 1 ) t o ensure t h e i r s a f e t y during in te r im s to rage a t the s i t e , and 2 ) t o prepare them f o r u l t imate shipment t o t h e Waste I s o l a t i o n P i l o t Plant (WIPP) in New Mexico. Included in t h e d iscuss ion i s a d e s c r i p t i o n of t h e s a f e t y concerns assoc ia ted with ion exchange r e s i n s , a l t e r n a t i v e s considered f o r t h e i r s t a b i l i z a t i o n , the s e l e c t i o n of the prefer red t rea tment method, the means of implementing t h e prefer red opt ion , and t h e progress t o d a t e .

The ob jec t ive of t he resin

BACKGROUND

Ion exchange r e s i n s a r e f i n e beads of polymeric ( p l a s t i c ) mater ia l c o n s i s t i n g of s tyrene and divinyl benzene monomer u n i t s . va r i ed with use, t he typ ica l p a r t i c l e s i z e was in the range of 20 t o 100 mesh. Plutonium p u r i f i c a t i o n was accomplished by t h e s e l e c t i v e adsorpt ion of plutonium ions ( e i t h e r P u + ~ ions on ca t ion exchange r e s i n s o r P ~ ( N 0 3 ) 6 ; ~ ions on anion exchange r e s i n s ) . Resins were loaded in to an ion exchange column where the adsorpt ion process took p lace . even tua l ly e lu t ed from t h e column using 0.351 n i t r i c ac id f o r anion exchange r e s i n s o r , in t h e case of ca t ion exchange r e s i n s , 7 .01 n i t r i c ac id .

Although bead s i z e

The adsorbed plutonium was

Resins in ion exchange columns were pe r iod ica l ly replaced and t h e spent r e s i n s to red f o r eventual plutonium recovery. During t h e replacement ope ra t ion , some of t he r e s i n s were e i t h e r washed with water (producing leached ion exchange r e s i n s , I D C 431) o r packaged d i r e c t l y (producing unleached ion exchange r e s i n s , IDC 430). I n 1996, Rocky F l a t s was s t o r i n g approximately 267 kilograms o f res idue ion exchange r e s i n s containing over a kilogram o f plutonium.

Resins were drained o f a l l f r e e l i qu id before being packaged i n t o r e s idue drums, so they a re not considered t o have the R C R A c h a r a c t e r i s t i c of

02 J a n 98 Page 2

c o r r o s i v i t y . Furthermore, samples o f r e s i n s have been s u b j e c t t o T o x i c C h a r a c t e r i s t i c Leaching Procedure analyses, and none of t h e samples y i e l d e d r e s u l t s above r e g u l a t o r y t h r e s h o l d s f o r t o x i c meta ls . Therefore, i o n exchange r e s i n s a r e n o t r e g u l a t e d as RCRA hazardous wastes.

A l though t h e spent r e s i n s a r e n o t cons idered a hazardous waste, t h e r e i s concern t h a t t h e i n t i m a t e c o n t a c t o f an ox idan t ( n i t r i c a c i d ) and an o rgan ic s u b s t r a t e ( t h e po lymer i c beads) may, ove r t ime, r e s u l t i n t h e g e n e r a t i o n o f p roduc ts which c o u l d have a reduced i g n i t i o n temperature thus p r e s e n t i n g a p o t e n t i a l f i r e hazard. I n 1993, t h e Defense Nuclear F a c i l i t i e s S a f e t y Board (DNFSB) began i n v e s t i g a t i n g t h e s a f e t y o f res idues be ing s t o r e d a t Rocky F l a t s . T h e i r conc lus ions , p u b l i s h e d i n DNFSB Recommendation 94-1 i n May 1994, s t a t e d t h a t p o s s i b l y uns tab le res idues should be s t a b i l i z e d t o e l i m i n a t e p o t e n t i a l f l a m m a b i l i t y , p y r o p h o r i c i t y , and r e a c t i v i t y concerns and packaged t o ensure s a f e s to rage u n t i l such t i m e as they c o u l d be sh ipped o f f s i t e (Reference I ) . Residues b e l i e v e d t o p resent h i g h r i s k s t o o p e r a t i n g personnel were t o be s t a b i l i z e d w i t h i n t h r e e yea rs w h i l e t h e s t a b i l i z a t i o n and/or repackaging o f l ower hazard m a t e r i a l s was t o be completed i n seven years .

I o n exchange r e s i n s were cons idered by t h e DNFSB t o be enough o f a f l a m m a b i l i t y hazard t h a t t h e i r con t i nued s to rage a t t h e s i t e represented a s i g n i f i c a n t r i s k t o p l a n t workers. types o f res idues t h a t should be cons idered f o r exped i ted t rea tmen t , w e l l i n advance o f any o t h e r t rea tmen t ope ra t i ons t h a t would r e q u i r e e x t e n s i v e upgrades t o c a p i t a l f a c i l i t i e s t o implement. I n 1994, Rocky F l a t s embarked on *

a program t o i n v e s t i g a t e cand ida te processes t o e l i m i n a t e any p o t e n t i a l f o r an adverse o x i d i z e r / f u e l r e a c t i o n l e a d i n g t o t h e genera t i on o f r e a d i l y i g n i t a b l e m a t e r i a1 s .

Thus, t hey were des ignated as one o f a few

The s a f e t y concern w i t h i o n exchange r e s i n s i s based on t h e knowledge t h a t spent r e s i n s c o n t a i n s i g n i f i c a n t q u a n t i t i e s of n i t r a t e s which may r e a c t e x o t h e r m i c a l l y w i t h t h e o r g a n i c m a t r i x o f t h e r e s i n . r e s i n m a t r i x c o u l d be present i n one o r more o f t h r e e chemical forms. n i t r o groups (-NO2) c o u l d be c o v a l e n t l y bonded t o t h e o rgan ic m a t r i x fo rming n i t r o - o r g a n i c compounds. T h i s s i t u a t i o n i s n o t l i k e l y s i n c e t h e c o n d i t i o n s necessary t o e f f e c t t h e n i t r a t i o n r e a c t i o n never e x i s t e d . Such a r e a c t i o n r e q u i r e s t h e presence o f a m i x t u r e o f concent ra ted n i t r i c and s u l f u r i c ac ids .

N i t r a t e s w i t h i n t h e F i r s t ,

The second PO s i b l e form o f n i t r a t e s w i t h i n t h e r e s i n m a t r i x i s i n o r g a n i c n i t r a t e i o n s (NO3 - 2 ) bound t o exchange s i t e s . I n an ion exchange r e s i n s , p o s i t i v e l y charged exchange s i t e s a re i o n i c a l l y bound t o an ions such - a s n i t r a t e i ons . The exchange process s u b s t i t u t e s n e g a t i v e l y charged p lu ton ium complex anions f o r n i t r a t e i ons . The regenera t i on of r e s i n columns reverses t h e process l e a v i n g n i t r a t e i o n s bound t o t h e r e s i n . Washing t h e r e s i n w i t h water a f t e r use w i l l l eave some i f n o t most o f t h e n i t r a t e i o n s i n p lace ; t h e r e f o r e , t h e r e i s a h i g h p r o b a b i l i t y t h a t i o n i c a l l y bound n i t r a t e i o n s are p resen t i n t h e r e s i n .

The t h i r d form o f n i t r a t e w i t h i n t h e r e s i n m a t r i x i s as i n t e r s t i t i a l n i t r i c a c i d (HN03). Resins a re very porous by des ign, s ince e f f e c t i v e i o n exchange r e q u i r e s h i g h su r face area and i n t i m a t e con tac t between d i s s o l v e d species and t h e r e s i n exchange s i t e s . h i g h l y l i k e l y t o c o n t a i n i n t e r s t i t i a l d i l u t e n i t r i c a c i d even though t h e r e s i n i t s e l f may n o t c o n t a i n obv ious f r e e l i q u i d . which have been washed w i t h water p r i o r t o removal from t h e column, w i l l have a l ower , b u t n o t zero, p r o b a b i l i t y o f c o n t a i n i n g i n t e r s t i t i a l n i t r i c a c i d .

Unleached i o n exchange r e s i n s a r e

Leached i o n exchange r e s i n s ,

02 Jan 98 S a g e 3

,

TREATMENT AND DISPOSAL OPTIONS

The development o f p o t e n t i a l t r e a t m e n t o p t i o n s t o s t a b i l i z e i o n exchange r e s i n s was focused on two s e t s o f requi rements. was embodied i n t h e WIPP Waste Acceptance C r i t e r i a (WIPP/WAC) which d e f i n e d t h e m a t e r i a l f o rm and packaging requ i remen ts f o r a l l t r a n s u r a n i c (TRU) waste t o be d i sposed o f i n WIPP (Reference 2). u l t i m a t e r e p o s i t o r y f o r a l l Rocky F l a t s res idues , any t r e a t m e n t process -

under taken shou ld produce W I P P - c e r t i f i a b l e wastes w i t h o u t t h e need f o r a d d i t i o n a l p r o c e s s i n g a t some 1 a t e r d a t e .

The f i r s t s e t o f requ i remen ts

Since WIPP i s e n v i s i o n e d as t h e

The second s e t o f requ i remen ts was p u b l i s h e d as t h e I n t e r i m Safe Storage C r i t e r i a ( I S S C ) which was developed by DOE i n response t o t h e DNFSB Recommendation 94-1 (Reference 3). The I S S C d e f i n e d m a t e r i a l f o r m and packaging requ i remen ts f o r p l u t o n i m - b e a r i n g m a t e r i a l s t h a t would be s t o r e d a t t h e v a r i o u s DOE s i t e s u n t i l such t i m e as WIPP opened.

An i n i t i a l d r a f t o f t h e I S S C d i r e c t e d t h a t hydrogenous m a t e r i a l s such as i o n exchange r e s i n s d i d n o t c o n s t i t u t e an acceptable waste form f o r s a f e i n t e r i m s t o r a g e a t DOE s i t e s . f o r s t a b i l i z i n g such r e s i d u e s i n c l u d e d v a r i o u s m a t r i x d e s t r u c t i o n techn iques . Candidate processes such as i n c i n e r a t i o n , p y r o l y s i s , a v a r i e t y o f nove l thermal o x i d a t i o n techniques, c a t a l y z e d e lec t rochemica l o x i d a t i o n , c a t a l y z e d chemical o x i d a t i o n , and a c i d d i g e s t i o n were i d e n t i f i e d and eva lua ted . The f i n a l v e r s i o n o f t h e ISSC, however, a l l owed t h a t hydrogenous m a t r i c e s c o u l d b e ' s t o r e d s a f e l y i f a l l o t h e r hazards were e l i m i n a t e d and p r o v i s i o n s were made t o p reven t t h e accumulat ion o f f lammable gases f rom r a d i o l y s i s .

Consequent ly, t h e process o p t i o n s cons ide red

The e l i m i n a t i o n o f m a t r i x d e s t r u c t i o n as a requi rement f o r t h e s t a b i l i z a t i o n o f hydrogenous m a t e r i a l s meant t h a t s imp le r , cheaper, s a f e r , and more e x p e d i t i o u s p rocess ing techn iques c o u l d be employed t o meet DNFSB e x p e c t a t i o n s . For i o n exchange r e s i n s , t h r e e cand ida te processes were i d e n t i f i e d by t h e Residue S t a b i l i z a t i o n o r g a n i z a t i o n a t Rocky F l a t s : r e s i n d e n i t r a t i o n , d i r e c t cementat ion, and cementat ion i n c o n j u n c t i o n w i t h an e x i s t i n g l i q u i d s t a b i l i z a t i o n o p e r a t i o n . i n t h e f o l 1 owing paragraphs.

These t h r e e processes a r e d e s c r i b e d

Resin D e n i t r a t i o n

The r e s i n d e n i t r a t i o n process t a k e s advantage o f one o f t h e chemical p r o p e r t i e s o f r e s i n s , i .e., t h e a b i l i t y t o undergo an exchange o f one i o n f o r ano the r depending on c o n c e n t r a t i o n and t h e r e l a t i v e a f f i n i t y o f t h e two i o n s t o be bound t o t h e i o n exchange s i t e s w i t h i n t h e r e s i n m a t r i x . Exper imenta l work s u p p o r t i n g t h e development o f t h i s process was performed by t h e Los A1 amos N a t i o n a l Labora to ry (Reference 4 ) .

To beg in t h e d e n i t r a t i o n process, t h e r e s i n i s f i r s t s l u r r i e d i n an aqueous s o l u t i o n o f 2p1 sodium s a l i c y l a t e [Na+C6H (OH)(COO)-]and 1p1 sodium h y d r o x i d e (NaOH). The r e s u l t i n g s l u r r y i s t r a n s 4. e r r e d t o an i o n exchange column 5 inches i n d iamete r and 2 f e e t i n l e n g t h . (washed) w i t h app rox ima te l y two bed volumes o f a d d i t i o n a l sodium s a l i c y l a t e f o l l o w e d by two bed volumes o f d e i o n i z e d water . The washed r e s i n i s t h e n removed f rom t h e column, d r i e d t o e l i m i n a t e a l l t r a c e s o f f r e e l i q u i d s , and repackaged f o r s to rage o r d i s p o s a l .

The column i s e l u t e d

02 J a n 98 Page 4

,

The liquids generated from the process are collected, and the pH is adjusted to a value less than 2 by the addition of 61 nitric acid. The . -

neutralization of the a1 kal ine wash solution will result in the precipitation of salicylic acid which is then removed from the resulting slurry by filtration. The salicylic acid is then redissolved in 2M sodium hydroxide to be used for denitration of the next batch of resin. The filtrate from the salicylic acid precipitation (which contains nitric acid, other impurities originating in the resin, and approximately 0.01fl salicylic acid) is disposed o f as plutonium-contaminated 1 iquid waste.

Direct Cementation

Direct cementation- is accomplished by mixing resin, dry portland cement, and water in the appropriate proportions to generate a grout which will subsequently cure into an acceptable mono1 i th. the development of the process control parameters for the cementation operation was a1 so performed by the Los A1 amos National Laboratory (Reference

Resin is first removed from its current packaging, and approximately 750

Experimental work supporting

5) -

grams are placed in a mixing bowl for a standard industrial-sized electric mixer. Water is added to the resin, and the pH of the resulting slurry is determined with a pH meter. Sodium hydroxide is added to the slurry to adjust the pH to a value between 9.0 and 10.5. approximately 2 liters) and approximately 5 kilograms of dry portland cement are added to the mixing bowl. The resulting mixture is stirred until a homogeneous grout containing about 10 wt% resin i s obtained. The grout is then poured into a metal can for curing, packaging, storage, and disposal. The only liquid waste generated from this operation is that due to spills and clean-up activities.

Additional water (up to a total of *

Cementation in Conjunction with Liquid Stabilization

A modification to the direct cementation process is achieved by incorporating the resin material into an existing cementation operation being used to stabilize plutonium-contaminated liquids. possible by a provision of the TRAMPAC Waste Codes which allows for the addition of up to 1 wt% of ion exchange resins as an impurity to drums of cemented aqueous waste (Reference 6). an approved procedure for the cementation of aqueous waste in the Building 774 Bottle Box.

This modification is made

The process described here is based on

Bottle Box operations are initiated by the preparation of a drum of a mixture of dry portland cement and dry Ramcote 1200 cement. The drum is then affixed to a port in the floor of a glove box in Building 774. In parallel, approximately 60 liters- of aqueous waste (containing a maximum of 70 grams of plutonium) are batched for treatment. The batched liquids are transported to Building 774 in 4-liter plastic bottles where they are bagged into the glove box, transferred via vacuum to a feed tank, neutralized (if acidic), and then added to the drum of dry cement. produces a grout which is then left to cure producing a cemented waste form containing no free liquids and no respirable fines.

Manual stirring of the liquid-cement mixture

The existing Bottle Box operation would be modified by including, .in the batching process, a bottle of neutralized ion exchange resin weighing u p to 2

02 Jan 98 Page 5

kilograms and containing a nominal 10 grams of plutonium. content of the batched liquids would then have to be decremented by 10 grams to ensure that the total plutonium in the final waste product does not exceed 70 grams. Both the liquid waste and the resin would be mixed into the cement at the same time. The cured drum of cement would then be stored and eventually disposed of as TRU waste.

EVALUAT I ON OF ALTERNAT I V E PROC ESS ES

The plutonium :

The three alternative processes described above were assessed using a qualitative, relative comparison o f the merits of each process. To complete this analysis, fourteen evaluation criteria were identified. These criteria were, in turn, grouped into five categories: safety, cost, schedule, waste generation, and state of technical development.

.

The assessment of the relative safety considerations included, first, the effectiveness of a particular process in eliminating the known hazards associated with nitrated ion exchange resins. Also considered was the relative safety of the stabilization operation with respect to the degree of risk to be assumed by the operating staff. exposure and reagent hand1 i ng.

Considerations included radiation

The re1 at i ve costs of the three candidate processes i ncl uded preparat i on costs, equipment costs, labor costs, and material costs. Preparation costs included those necessary to write procedures, train operators, and obtain the - necessary authorization basis to conduct operations. Equipment costs included design, procurement, and installation costs. Labor costs related to the operating and support staff necessary to perform the stabilization operations. Material costs included reagents, supplies, and other expendable materials.

Schedule considerations included preparation time and operating time. Preparation time was concerned with the time necessary to put all systems in place to initiate stabilization operations. Considered in this criterion are the times required for the design and installation of equipment, the development of procedures, the training of operators, the completion o f the appropriate level of NEPA documentation, and the establishment o f an authorization basis for operations. inversely proportional to the expected throughput of a particular process.

Operating time was determined to be

Waste generation was concerned primarily with the volume of waste into which the resin would be transformed by the stabilization operation. limiting factor in determining final waste volume was the wattage limit associated with a drum o f stabilized resin. Secondary waste volume; consisting o f discarded packaging materials, expended equipment, and supplies; comprised the secondary solid waste stream. Liquid waste generation was a criterion as well as the relative amounts of gaseous emissions of environmental concern.

The

The degree to which the particular stabilization technique had been developed and demonstrated was a criterion. Also considered was the applicability o f the process to residue materials other than ion exchange resins.

02 Jan 98 Page 6

EVALUATION RESULTS

The cementation of ion exchange resins in conjunction with the cementation o f aqueous wastes was determined to be the stabilization process of choice. were costs (all types), the preparation time required to initiate operations, and the volume of both liquid and solid waste generated. decision matrix that was used to assess the evaluation criteria and arrive at the recommended course of action. cementation in conjunction with liquid cementation was assumed to be the baseline and was given a rating of 2 for each criterion. denitration and direct cementation processes were given a rating of either 1, 2, or 3 depending on whether they were evaluated as being worse than, the same as, or better than the baseline, respectively. equally. the preferred course o f action.

The criteria that were instrumental in arriving at this conclusion

Figure 1 is the

For purposes o f this evaluation, resin

The resin

All criteria were weighted The results o f this assessment showed that liquid cementation was

[PLACE FIGURE 1 HERE]

The preparations required for the adaptation of the Bottle Box operation to incorporate ion exchange resins included the revision of existing procedures, incremental training of operators, and the modification of the existing authorization basis. activities for a new nuclear operation were significantly greater. Liquid cementation equipment had already been purchased, and no new process equipment *

was needed. program, and only incremental costs to prepare resins for cementation were required. Very little in the way of additional material costs were identified.

Costs associated with initiating these

Labor costs were to be shared with the Liquid Stabilization

The time required for the revision of existing procedures, incremental training of operators, and the modification of the existing authorization basis was estimated to be completed three months sooner than the time estimated for accomplishing the same objectives for a new process. Hence, stabilization of a residue considered to be a high-risk material by the DNFSB could begin that much sooner.

Cementation of resins along with aqueous wastes would generate no additional liquid wastes, a key factor at a plant where liquid waste treatment capability was diminishing. selection of this process over direct cementation and denitration was the volume of solid waste to be generated. denitration or direct cementation would have to be packaged in a manner where the decay heat was limited to about 0.02 watts per drum. established as part of the WIPP/WAC to ensure that the radiolytic generation of hydrogen or other flammable gases would not represent a fire or explosion hazard. repackaged into approximately 200 WIPP-certifiable 55-gallon drums.

But a primary consideration that led to the

The products of either resin

This limit was

Hence, the 267 kilograms of stabilized resin would eventually be

The wattage limit for cemented aqueous waste, which allowed the presence of resin as an impurity, was established by W I P P requirements as 0 . 2 rather than 0.02 watts per drum. Therefore, the cemented resin would effectively be packaged at the higher wattage limit, and only an additional 20 drums o f cemented product, above what would have been generated by the Bottle Box anyway, would be generated. Thus, there were distinct advantages in terms o f

02 Jan 98 Page 7

waste genera t i on , s torage, c e r t i f i c a t i o n , and d i sposa l t h a t c o u l d be r e a l i z e d by i n c o r p o r a t i n g i o n exchange r e s i n s i n t o t h e e x i s t i n g B o t t l e Box o p e r a t i o n .

IMPLEMENTATION OF PREFERRED TREATMENT PROCESS

Once t h e e v a l u a t i o n o f a l t e r n a t i v e s was completed and t h e p r e f e r r e d method o f t r e a t m e n t i d e n t i f i e d , imp lementa t ion of t h a t t r e a t m e n t p rocess was i n i t i a t e d . Severa l i n d i v i d u a l o p e r a t i o n s -had t o be f u n c t i o n a l be fo re any cementa t ion c o u l d begin. a c e n t r a l repackag ing f a c i l i t y , n e u t r a l i z i n g and repackag ing r e s i n s i n p r e p a r a t i o n f o r cementation, movement o f repackaged drums o f r e s i n t o t h e B o t t l e Box, and f i n a l l y , . t h e cementat ion o p e r a t i o n i t s e l f .

t h e c u r r e n t packaging c o n f i g u r a t i o n was n o t amenable t o t h e B o t t l e Box o p e r a t i o n , r e s i n drums were sh ipped t o an e x i s t i n g g l o v e box l i n e i n B u i l d i n g 707 where t h e y were repackaged. I n i t i a l l y , 20 o u t o f 22 drums o f r e s i n s were repackaged i n t h i s manner. c o n f i g u r a t i o n th rough FY1997 s i n c e t h e y were s t o r e d i n areas t h a t were i n f r a c t e d due t o c r i t i c a l i t y s a f e t y concerns. i n November 1997.

These opera t i ons i n c l u d e d movement o f r e s i n drums t o

I n 1996, r e s i n s were s t o r e d i n severa l b u i l d i n g s a t Rocky F l a t s . Because

Two drums remained i n t h e i r c u r r e n t packag ing

Those two drums were repackaged

The repackag ing o p e r a t i o n e n t a i l e d removing t h e cardboard r e s i n c o n t a i n e r s f rom t h e i r drum, i n t r o d u c i n g t h e c o n t a i n e r s i n t o t h e g l o v e box l i n e , and empty ing t h e c o n t a i n e r s i n t o a s u i t a b l e m i x i n g pan f o r i n s p e c t i o n and sampl ing. A l though t h e r e was r a r e l y any d e t e c t a b l e f r e e l i q u i d i n t h e r e s i n package, s u f f i c i e n t mo is tu re was present t o p e r m i t t h e d e t e r m i n a t i o n o f t h e r e s i n pH. A 50 w t % s o l u t i o n o f sodium hydrox ide was added t o t h e r e s i n t o ensure t h a t t h e pH was a minimum o f 7.0. repackaged i n t o 4 - l i t e r p l a s t i c b o t t l e s t h a t con ta ined a maximum o f 2 k i l og rams o f r e s i n o r 12 grams o f p lu ton ium. The repackaged r e s i n was removed f rom t h e g l o v e box l i n e , assayed t o determine t h e exac t p l u t o n i u m con ten t , and p l a c e d back i n t o a 55 -ga l l on drum a w a i t i n g shipment t o t h e B o t t l e Box.

B u i l d i n g 774, which housed t h e B o t t l e Box, had a compara t i ve l y l o w l i m i t on t h e amount o f p lu ton ium t h a t c o u l d be s t o r e d i n t h e b u i l d i n g a t any g i v e n t i m e . There fo re , t h e shipment o f drums o f repackaged r e s i n was accompl ished on a j u s t - i n - t i m e b a s i s ensur ing an u n i n t e r r u p t e d f l o w o f r e s i n t o t h e B o t t l e Box w h i l e n o t exceeding b u i l d i n g p lu ton ium l i m i t s .

*

The n e u t r a l i z e d r e s i n was t h e n

The a c t u a l cementat ion o p e r a t i o n i s t a k i n g p lace as p r e v i o u s l y d e s c r i b e d .

The l i q u i d s a re then d r a i n e d f rom t h e feed t a n k

The cement i s t h e n mixed by

One b o t t l e o f repackaged r e s i n and up t o s i x t e e n b o t t l e s o f aqueous l i q u i d waste a re i n t r o d u c e d t o t h e B o t t l e Box. t ank , mixed, and n e u t r a l i z e d . i n t o t h e drum o f d r y cement t h a t was p r e v i o u s l y prepared. s i n g l e b o t t l e o f r e s i n i s a l s o added t o t h e drum. hand and a l l owed t o cure . s to rage and u l t i m a t e d i s p o s a l . o p e r a t i o n i s t w o batches pe r week.

The l i q u i d s a re c o l l e c t e d i n a f e e d

A t t h i s p o i n t , a

The drum i s then disengaged f rom t h e g l o v e box f o r The maximum throughput o f t h e B o t t l e Box

A f l o w c h a r t o f t h e combined r e s i n repackaging and B o t t l e Box o p e r a t i o n i s shown i n F i g u r e 2 . residue ion exchange resins has been stabilized in this manner. B o t t l e Box runs have been completed each o f which has i n c l u d e d between 1 - a n d 2 k i l og rams o f r e s i n .

As o f October 1997, approx imate ly o n e - t h i r d o f t h e Over 60

The o p e r a t i o n w i l l con t i nue i n t h i s manner f o r a t l e a s t

02 J a n 98 Page 8

one more y e a r a f t e r which a l l o f t h e r e s i d u e i o n exchange r e s i n s w i l l have been i n c o r p o r a t e d i n t o a cement mono l i t h . Completion o f t h i s a c t i v i t y w i l l r e s u l t n o t o n l y i n t h e s t a b i l i z a t i o n o f a p o s s i b l y u n s t a b l e r e s i d u e o f p a r t i c u l a r concern t o t h e DNFSB, b u t a l s o t h e complete e l i m i n a t i o n o f an e n t i r e i n v e n t o r y o f one t y p e o f r e s i d u e a t Rocky F l a t s .

[PLACE FIGURE 2 HERE]

CONCLUSIONS

Rocky F l a t s has under taken a program t o s t a b i l i z e r e s i d u e i o n exchange r e s i n s by cement ing t h e - r e s i n s i n c o n j u n c t i o n w i t h t h e cementat ion o f aqueous l i q u i d wastes. e x p e d i t i o u s and c o s t - e f f e c t i v e means t o address a s a f e t y concern r a i s e d by t h e DNFSB. c o o p e r a t i v e t r e a t m e n t o f two waste streams w i l l r e s u l t i n a r e d u c t i o n i n t h e t o t a l number of drums o f TRU waste by approx imate ly 180. program i s about o n e - t h i r d complete. The r e d u c t i o n i n t h e amount o f e f f o r t t o commission a new waste t rea tmen t f a c i l i t y ; t h e avoidance o f hav ing t o s t a f f and o p e r a t e a separa te t rea tmen t process; t h e e l i m i n a t i o n o f secondary l i q u i d wastes; and t h e r e d u c t i o n i n t h e number of TRU waste drums r e q u i r i n g s torage, c e r t i f i c a t i o n , and d i s p o s a l w i l l r e s u l t i n an eventual c o s t savings t o t h e S i t e of n e a r l y 1 m i l l i o n d o l l a r s .

REFERENCES

T h i s method o f t rea tmen t was determined t o be t h e most

By v i r t u e o f a p r o v i s i o n i n t h e WIPP waste form requirements, t h e

C u r r e n t l y , t h e

1.

2.

3.

4.

J . T. CONWAY, l e t t e r t o H. R . O'Leary, DNFSB Recommendation 94-1 t o t h e S e c r e t a r y o f Energy (May 26, 1994). "Waste Acceptance C r i t e r i a f o r t h e Waste I s o l a t i o n P i l o t P lan t , DOE/WIPP- 069, Change 1 t o R e v i s i o n 5 (January 15, 1997). " C r i t e r i a f o r I n t e r i m Safe Storage of P luton ium-Bear ing Sol i d M a t e r i a l s , " Addendum t o t h e Department o f Energy Implementat ion Plan f o r DNFSB Recommendation 94 -1 (November 1995). M. E. BARR and R. L. AMES, " D e n i t r a t i o n of Rocky F l a t s I o n Exchange Resins F i n a l Report--Recommendation o f D e n i t r a t i o n Process," NMRT/RF:95-520, Los A1 amos N a t i o n a l Labora to ry (September 29, 1995).

5. G . W . VEAZY and R. L . AMES, " F i n a l Report f o r RFETS Resin Cementation P r o j e c t , " LANL/RF:95-517, Los A1 amos Na t iona l Labora to ry (September 29, 1995).

6. "TRUPACT-I1 Au tho r i zed Methods f o r Payload Con t ro l (TRAMPAC) , I t Appendix 1.3.7 t o t h e NuPac TRUPACT-I1 S a f e t y Ana lys i s Report , Sec t i on 5.2.4, October 1994.

.

.

02 J a n 98 Page 9

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