Radioactive Waste in Geologic Storage - ACS Publications

1 The Department of Energy Program for Long-Term Isolation of Radioactive Waste C O L I N A.

HEATH

Radioactive Waste in Geologic Storage Downloaded from pubs.acs.org by 185.101.71.38 on 11/30/16. For personal use only.

Division of Waste Isolation, B-107, U.S. Department of Energy, Washington, DC 20545

I wish to thank the American Chemical Society and its members f o r the opportunity to d i s c u s s with you today the Department of Energy (DOE) program i n r a d i o a c t i v e waste management. This program, which is of vital concern to our country's energy and defense programs, has r e c e n t l y become the t o p i c of newspaper articles, TV shows and much p u b l i c d i s c u s s i o n . I welcome t h i s chance to describe to you some of the activities underway to move the program forward and perhaps answer questions that may have been r a i s e d during all t h i s p u b l i c d i s c u s s i o n . The Department of Energy is charged by the Congress with the r e s p o n s i b i l i t y f o r accepting h i g h - l e v e l r a d i o a c t i v e waste from commercial uses of nuclear power and p r o v i d i n g f o r t h e i r management l e a d i n g to final d i s p o s a l . This final d i s p o s a l must provide i s o l a t i o n of these wastes from the human environment f o r as long as they remain hazardous. At the present time, there is some u n c e r t a i n t y as to what form the r a d i o a c t i v e wastes from the commercial nuclear f u e l c y c l e will take. E a r l y development of the f u e l c y c l e and the power r e a c t o r s now p r o v i d i n g electricity i n s e v e r a l regions of the count r y was undertaken w i t h the assumption that f u e l elements would be p e r i o d i c a l l y removed from operating r e a c t o r s and subjected to r e processing and r e c y c l e whereby unburned uranium and generated plutonium would be recovered from the f u e l elements f o r r e f a b r i c a t i o n and r e c y c l e d back i n t o operating r e a c t o r s . The e f f l u e n t byproducts stream from t h i s chemical processing was then to become a h i g h - l e v e l waste which must be processed f o r permanent d i s p o s a l . Within the l a s t two years, major concerns over the p r o l i f e r a t i o n problems a s s o c i a t e d with the r e c y c l e of uranium and plutonium have l e a d the President of the United States to call f o r an indefinite delay i n f u t u r e plans f o r reprocessing pending an e v a l u a t i o n Paper presented at the American Chemical Society Meeting i n Miami Beach, F l o r i d a on September 13, 1978.

This chapter not subject to U.S. copyright. Published 1979 American Chemical Society


2

RADIOACTIVE WASTE IN GEOLOGIC

STORAGE

of a l t e r n a t i v e s to provide p r o l i f e r a t i o n r e s i s t a n t f u e l c y c l e s . The waste management program i s t h e r e f o r e faced with the p o t e n t i a l that the r a d i o a c t i v e waste from the commercial f u e l c y c l e could be i n the form of spent f u e l elements which have been d e c l a r e d to be waste or i n the form of s o l i d i f i e d h i g h - l e v e l waste produced from the byproducts stream of the r e p r o c e s s i n g p l a n t . The issues surrounding the use or nonuse of r e c y c l e d r e a c t o r f u e l and plutonium are exceedingly complex and w i l l r e q u i r e a cons i d e r a b l e amount of time b e f o r e our s o c i e t y and the i n t e r n a t i o n a l community can reach a d e c i s i o n as to whether or not the r i s k s of p r o l i f e r a t i o n are appropriate to the b e n e f i t s that might be r e ceived from the r e c y c l e of these m a t e r i a l s . In the meantime, the Department of Energy's waste management program needs to get on with the long-neglected job of i d e n t i f y i n g the technology, systems, and f a c i l i t i e s f o r p r o v i d i n g f o r the permanent i s o l a t i o n of these wastes from the human environment. In order not to get bogged down i n the dispute over p r o l i f e r a t i o n , t h e r e f o r e , the program i s proceeding on the b a s i s that the waste could take e i t h e r form. P r e l i m i n a r y e v a l u a t i o n i n d i c a t e s that, even though d i s p o s a l of spent f u e l w i l l r e s u l t i n l a r g e r q u a n t i t i e s of plutonium being placed i n permanent i s o l a t i o n , there i s no o v e r r i d i n g s a f e t y r e a son which suggests that d i s p o s a l of spent f u e l w i l l not be able to be accomplished with any more d i f f i c u l t y than d i s p o s a l of s o l i d i f i e d r a d i o a c t i v e waste i n which the plutonium content has been reduced by r e p r o c e s s i n g . Over the l a s t twenty years, s i g n i f i c a n t research and development has been performed concerning the u l t i m a t e d i s p o s a l mechanism for r a d i o a c t i v e waste. In 1957, the N a t i o n a l Academy of Sciences recommended that deep beds of bedded s a l t be considered as potent i a l l o c a t i o n s f o r the d i s p o s a l of r a d i o a c t i v e waste m a t e r i a l s . Following t h i s recommendation a program of research and development was undertaken by the Atomic Energy Commission (AEC) to exp l o r e t h i s approach. The high point of t h i s program was the opera t i o n of P r o j e c t S a l t Vault i n an abandoned s a l t mine i n Lyons, Kansas. T h i s p r o j e c t placed encapsulated spent f u e l elements from an experimental AEC r e a c t o r i n t o storage holes d r i l l e d i n t o the f l o o r of the mine l o c a t e d i n a s a l t bed. Valuable experimental informat i o n was obtained about the i n t e r a c t i o n between the waste form and the s a l t i n which the waste was emplaced. I t was i n f a c t t h i s experiment, conducted i n 1968, which revealed that i n c l u s i o n s of moisture, or b r i n e , i n the s a l t beds have a tendency to migrate up a thermal gradient towards a heat source placed i n the s a l t . Q u a n t i t i e s of b r i n e were measured as migrating to the deposited waste c a n i s t e r s and the i n t e r a c t i o n of t h i s b r i n e with the c a n i s tered m a t e r i a l was observed. The i n i t i a l experiments conducted i n P r o j e c t S a l t Vault were not extended to provide more d e t a i l e d work. I f i t had been poss i b l e f o r t h i s experiment to have continued to operate s i n c e 1970, we would d e f i n i t e l y have a c o n s i d e r a b l y greater amount of informa-


1.

HEATH

DOE Isolation

of Radioactive

Waste

3

t i o n concerning the a c t u a l i n t e r a c t i o n s between waste and the bedded s a l t than we p r e s e n t l y have today. U n f o r t u n a t e l y , a dispute between the AEC and the State of Kansas over p o t e n t i a l use of t h i s s i t e as a permanent r e p o s i t o r y l e d the AEC to withdraw from f u r ther operations i n Kansas. In r e t r o s p e c t , one can only r e g r e t that an arrangement was not made whereby the experimental f a c i l i t y would have been permitted to remain i n o p e r a t i o n with a c l e a r understanding that the F e d e r a l Government would make no f u r t h e r a t tempt to q u a l i f y the s i t e as a permanent r e p o s i t o r y . F o l l o w i n g the abandonment of P r o j e c t S a l t V a u l t , a t t e n t i o n of the AEC turned towards the p o s s i b i l i t y o f using a r e t r i e v a b l e surface storage concept f o r temporary storage o f r a d i o a c t i v e waste u n t i l such time as a permanent i s o l a t i o n f a c i l i t y could be d e v e l oped. At the time, t h i s seemed to provide a reasonable and perf e c t l y adequate plan to handle the waste from the commercial i n dustry p a r t i c u l a r l y s i n c e the l a r g e - s c a l e r e p r o c e s s i n g o f commerc i a l nuclear f u e l hadn't s t a r t e d e i t h e r . Since t e n years was env i s i o n e d between s e p a r a t i o n of waste i n a r e p r o c e s s i n g p l a n t and d e l i v e r y f o r u l t i m a t e d i s p o s a l to the F e d e r a l Government, there appeared to be p l e n t y of time. The r e j e c t i o n by the C o u n c i l of Environmental Q u a l i t y and the Environmental P r o t e c t i o n Agency of the impact statement concerning the proposed R e t r i e v a b l e Surface Storage F a c i l i t y (RSSF) made everybody r e a l i z e that a s s e r t i n g the t e c h n i c a l f e a s i b i l i t y of u l timate g e o l o g i c d i s p o s a l was i n s u f f i c i e n t . These agencies took the p o s i t i o n that the RSSF merely put o f f p r o v i d i n g f a c i l i t i e s f o r permanent d i s p o s a l and d i v e r t e d the e f f o r t to another i n t e r i m measure. Dr. Seamans i n one of h i s f i r s t a c t s as the new a d m i n i s t r a tor o f the Energy Research and Development A d m i n i s t r a t i o n (ERDA) decided to withdraw the Environmental Impact Statement (EIS) assoc i a t e d with the RSSF and that establishment of a permanent waste r e p o s i t o r y should be given much greater budget p r i o r i t y . A new l a r g e - s c a l e program was i n i t i a t e d by ERDA i n 1976 with an announcement that each o f 36 s t a t e s contained g e o l o g i c format i o n s which might be s u i t a b l e f o r establishment of permanent waste repositories. ERDA e s t a b l i s h e d an O f f i c e of Waste I s o l a t i o n managed by Union Carbide Corporation i n Oak Ridge, Tennessee, to d i r e c t the program t o e s t a b l i s h the s u i t a b i l i t y of l o c a t i o n s f o r r e p o s i t o r y s i t e s and to develop the necessary technology to design, b u i l d and o b t a i n l i c e n s i n g approval of these permanent geologic f a c i l i t i e s . Two years a f t e r the i n i t i a t i o n of t h i s f u l l s c a l e program, a number of changes have taken place both i n the s i t e s e l e c t i o n and t e c h n i c a l areas, and a t t h i s p o i n t approximatel y two years l a t e r , i t i s a p p r o p r i a t e to provide a s t a t u s r e p o r t of where things stand today. 1

Organization o f DOE s Waste Management Program In May 1978 Secretary S c h l e s i n g e r approved a r e o r g a n i z a t i o n w i t h i n the Department of Energy which e s t a b l i s h e d an O f f i c e of


4

RADIOACTIVE WASTE IN GEOLOGIC STORAGE

Nuclear Waste Management r e p o r t i n g d i r e c t l y t o the A s s i s t a n t Secr e t a r y f o r Energy Technology. Within the waste i s o l a t i o n program, the major t e c h n i c a l a c t i v i t i e s are c a r r i e d on a t three f i e l d o f f i c e l o c a t i o n s . These l o c a t i o n s and the supporting c o n t r a c t o r s are summarized i n Table I . A c t u a l d i r e c t i o n o f the t e c h n i c a l a c t i v i t i e s w i t h i n the program i s the r e s p o n s i b i l i t y o f f i e l d o f f i c e s . The primary f i e l d o f f i c e i n the waste i s o l a t i o n program i s l o c a t e d i n Columbus, Ohio as a s a t e l l i t e t o the Richland Operations O f f i c e . Co-located with t h i s o f f i c e i s the O f f i c e of Nuclear Waste I s o l a t i o n (ONWI) r e c e n t l y e s t a b l i s h e d by B a t t e l l e Memorial I n s t i t u t e . T h i s o f f i c e d i r e c t s geologic e x p l o r a t i o n outside those areas occupied by e x i s t i n g Department o f Energy r e s e r v a t i o n s . Current ONWI i n v e s t i g a t i o n s are c o n c e n t r a t i n g on v a r i o u s s a l t formations around the country. ONWI w i l l a l s o develop the supporting data base and technology and coordinate the development of waste i s o l a t i o n technology as i t a p p l i e s to a number of p o t e n t i a l l y p o s s i b l e geologic media. The other three major a c t i v i t i e s w i t h i n the waste i s o l a t i o n program are s p e c i f i c t o p a r t i c u l a r s i t e s . We are c u r r e n t l y e v a l u a t i n g the p o t e n t i a l o f deep b a s a l t flows below the Hanford r e s e r v a t i o n i n the State o f Washington. T h i s work i s managed by the Richland Operations O f f i c e and i s being conducted by the Rockwell Hanford Company. An e v a l u a t i o n of a p o t e n t i a l s i t e i s underway i n southeast New Mexico f o r the l o c a t i o n of the Waste I s o l a t i o n P i l o t Plant (WIPP) which i s p r i m a r i l y a f a c i l i t y f o r the placement of transuranium contaminated wastes (TRU) from the defense program. F i n a l l y , a study i s underway to determine the s u i t a b i l i t y o f the Nevada Test S i t e i n southern Nevada which has been used i n the past f o r both surface and underground t e s t i n g o f nuclear weapons, to see i f i t may p o s s i b l y be s u i t a b l e as a p o t e n t i a l permanent r a d i o a c t i v e waste r e p o s i t o r y s i t e . T e c h n i c a l Issues and the DOE T e c h n i c a l Program T e c h n i c a l i s s u e s concerning the placement and d i s p o s a l o f r a d i o a c t i v e waste can be broken i n t o two c a t e g o r i e s . The f i r s t i s sue i s whether o r not we have a v a i l a b l e t o us the technology to provide f o r the safe encapsulation, t r a n s p o r t a t i o n , handling and placement o f r a d i o a c t i v e m a t e r i a l s i n an o p e r a t i n g g e o l o g i c f a c i l ity. The second i s s u e i s , when the f a c i l i t y has been f i l l e d with these m a t e r i a l s and subsequently decommissioned, w i l l the p l a c e ment of these m a t e r i a l s i n geologic formations provide the permanent i s o l a t i o n from the human environment that i s sought. There has been a past p e r c e p t i o n , p a r t i c u l a r l y i n the nuclear community, that the i s s u e s of waste i s o l a t i o n l i e p r i m a r i l y i n the p o l i t i c a l and socio-economic arena and that no r e a l t e c h n i c a l problems remain. I b e l i e v e that t h i s i s c o r r e c t with respect t o the f i r s t category o f i s s u e s , namely, there i s no question that we understand how t o encapsulate, t r a n s p o r t and s a f e l y handle r a d i o -


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a c t i v e m a t e r i a l s and the placement of those i n an operating mine i s a technology a v a i l a b l e today. However, I must disagree somewhat with t h i s view of the status of technology when i t comes to the second category, namely, to prove that we can provide f o r permanent i s o l a t i o n of these m a t e r i a l s from the human environment to the s a t i s f a c t i o n of an independent l i c e n s i n g a u t h o r i t y , and the general p u b l i c . We must understand a l l of the processes i n v o l v e d to be a b l e to guarantee to a reasonable degree that these wastes w i l l indeed be permanently i s o l a t e d . Over the l a s t year or so, s e v e r a l papers have been published which have been concerned with the adequacy of the technology f o r p r o v i d i n g f o r permanent i s o l a t i o n of r a d i o a c t i v e wastes. In a l l cases the concerns that have been r a i s e d have focused on the second set of i s s u e s , r a t h e r than the f i r s t , so that the apparent d i s p u t e between those who say that there are no t e c h n i c a l problems and those who say that there are s t i l l some to be solved i s perhaps more a dispute as to what p a r t i c u l a r set of problems are being d e s c r i b e d . These papers have provided a v a l u a b l e mechanism f o r independent peer review from t e c h n i c a l experts not n e c e s s a r i l y a s s o c i a t e d with the waste management program. These review papers have i n c l u d e d the c i r c u l a r by the U.S. G e o l o g i c a l Survey, C i r c u l a r 779, "Geologic D i s p o s a l of High-Level Radioactive Wastes - Earth-Science P e r s p e c t i v e s " ; the review by the Ad-Hoc Committee of Earth S c i e n t i s t s f o r the EPA; reviews by the O f f i c e of Science and Technology P o l i c y and f i n a l l y a review prepared by an Interagency Committee chaired by the O f f i c e of Science and Technology P o l i c y whose paper was r e l e a s e d f o r p u b l i c comment on J u l y 3, 1978. Without going i n t o great d e t a i l about the i s s u e s described i n these papers, I would l i k e to make the p o i n t that the response of the waste i s o l a t i o n program to these papers w i l l be to use them to help us to design a t e c h n i c a l program p l a n to ensure that these i s s u e s are adequately addressed, as indeed they must be, before we can commit r a d i o a c t i v e waste to i r r e t r i e v a b l e permanent d i s p o s a l . I would l i k e , however, to spend a few minutes b r i e f l y summarizing the questions that have been r a i s e d and d e s c r i b e the v a r i o u s p a r t s of the DOE program which are addressing them. In the c o n s t r u c t i o n of a f a c i l i t y c o n t a i n i n g hazardous mat e r i a l s , m u l t i p l e b a r r i e r s are provided between the m a t e r i a l and the human environment. F i g u r e 1 i l l u s t r a t e s s c h e m a t i c a l l y what these b a r r i e r s might be. T h i s f i g u r e i l l u s t r a t e s that by supplying a number of m u l t i p l e and redundant b a r r i e r s , one gains a d d i t i o n a l assurance that true i s o l a t i o n can be maintained f o r very long periods of time. Although i t i s impossible to guarantee abs o l u t e l y f u t u r e events, one does not need absolute c e r t a i n t y that any s i n g l e b a r r i e r w i l l provide r e q u i r e d i s o l a t i o n . The redundancy of b a r r i e r s provides greater assurance that the r e q u i r e d permanent i s o l a t i o n can be achieved. The f i n a l design of a geologic r e p o s i t o r y w i l l employ m u l t i -

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Table I ELEMENTS OF DOE'S WASTE ISOLATION


Lead Contractor

Corresponding Projects

Field Office

PROGRAM

Richland

B a s a l t Program

Rockwell Hanford

Richland-Columbus

ONWI

B a t t e l l e Mem. I n s t . ONWI

Albuquerque

WIPP

Sandia/Westinghouse

Nevada

NTS I n v e s t i g a t i o n s

Sandia/LASL/LLL/USGS

WASTE FORM (P„J

Figure 1.

CONTAINER (P > P

OVERPACK (P ) ft

BUFFER

ROCK

(p )

(ρ*)

n

ISOLATION (p > T

Barriers between waste and biosphere. Protection of biosphere = PWF + ρ + ρ + ρ + ρ + Ρj. ο

0

Β

η

1.

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Isolation

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Waste

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pie b a r r i e r s but the exact form that each might take w i l l depend on the s p e c i f i c c o n d i t i o n s i n the g e o l o g i c a l system that i s f i n a l l y chosen f o r the s i t e . Let me now t u r n to some of the s p e c i f i c areas of concern i d e n t i f i e d i n the v a r i o u s reviews r e f e r r e d to and t r y to i n d i c a t e e x a c t l y how we are addressing these i s s u e s . Waste Form and I n t e r a c t i o n s . Several reviewers have expressed concern over the waste form and the p o t e n t i a l f o r i n t e r a c t i o n s between waste and surrounding m i n e r a l s . Chemical and r a d i o l o g i c a l i n t e r a c t i o n s between the host rock with i t s contained water and e i t h e r the waste form or the c o n t a i n e r might lead to d i s i n t e g r a t i o n of the packaging and p a r t i a l d i s s o l u t i o n i n g of the waste. E a r l y experiments with some of the proposed waste forms have i n d i cated a high r e s i s t a n c e to l e a c h i n g by groundwaters, however, the environment to which these waste forms w i l l be exposed w i l l i n clude a number of f a c t o r s . F i r s t of a l l , the pressure which e x i s t s at the depths at which we are c o n s i d e r i n g p l a c i n g t h i s mat e r i a l w i l l change the p h y s i c a l behavior of l i q u i d s which may e x i s t at those depths. Secondly, concern with the phenomena of b r i n e m i g r a t i o n has r e s u l t e d i n research which i n d i c a t e s that the s o l u t i o n s which might be formed i n the presence of m u l t i p l e ions may l e a d to a much higher degree of c o r r o s i o n than had p r e v i o u s l y been considered. T h e o r e t i c a l i n v e s t i g a t i o n s of these phenomena are c o n t i n u i n g i n a d d i t i o n to which a number of s p e c i f i c i n s i t u experiments are planned. We have over the l a s t s e v e r a l years been planning and conducting e l e c t r i c a l l y heated t e s t s i n both near-surface and deep f a c i l i t i e s i n order to simulate the r a d i o a c t i v e h e a t i n g that w i l l come from deposited waste forms and to l e a r n more about the e f f e c t s of t h i s heat upon the g e o l o g i c media. As more i n f o r m a t i o n i s being obtained about the p o t e n t i a l geochemical i n t e r a c t i o n s between the b r i n e s and these complex s o l u t i o n s , e f f o r t s w i l l be made to d u p l i c a t e s o l u t i o n s i n s i t u to see i f the mechanisms that are being p o s t u l a t e d f o r p o s s i b l e d i s s o l u t i o n and f a i l u r e of c o n t a i n ers w i l l indeed occur. At the present time we are conducting t e s t s with e l e c t r i c a l heaters i n a s a l e mine i n L o u i s i a n a , i n a g r a n i t e formation i n Sweden, i n a g r a n i t e formation i n Nevada and i n shale formations both i n Tennessee and Nevada. E a r l y information developing from these heater t e s t s w i l l be used i n the design of f u r t h e r , more s o p h i s t i c a t e d t e s t s i n which some of these geochemical i n t e r a c t i o n s w i l l be simulated. We are p r e s e n t l y c o n s t r u c t i n g a near-surface t e s t f a c i l i t y at the Hanford r e s e r v a t i o n which w i l l be l o c a t e d i n a b a s a l t i c flow i n the s i d e of a mountain t h e r e . T h i s f a c i l i t y w i l l have e l e c t r i c a l heaters emplaced i n i t i n 1979 and by 1980 we expect to emplace encapsulated c y l i n d e r s c o n t a i n i n g spent f u e l elements there. A second p r o j e c t under development w i l l provide placement of spent f u e l i n s i m i l a r c o n t a i n e r s i n a deep g r a n i t e f a c i l i t y at the

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RADIOACTIVE WASTE IN GEOLOGIC

STORAGE


Nevada Test S i t e , h o p e f u l l y as e a r l y as 1979. Both of these experiments are s t r i c t l y to e s t a b l i s h a b e t t e r understanding of the i n t e r a c t i o n s between the waste form and the media. In n e i t h e r case i s the experimental l o c a t i o n considered as a permanent d i s posal l o c a t i o n . P r o p e r t i e s of the Host Rock and Rock Mechanics. Considerable information w i l l be needed about the p r o p e r t i e s of the host rock i n t o which m a t e r i a l w i l l be placed. The host rock provides the f i r s t n a t u r a l b a r r i e r to waste migration and s t r o n g l y i n f l u e n c e s the d e t a i l e d design of the engineered r e p o s i t o r y . Some media that e x h i b i t creep or p l a s t i c flow might be capable of s e a l i n g r e p o s i t o r y workings by flow without f r a c t u r e propagation or might s e l f heal i n the event of f a u l t - i n d u c e d f r a c t u r i n g . Creep i s observed i n rock s a l t and to a l e s s e r extent i n some s h a l e s . The creep p r o p e r t i e s of these m a t e r i a l s can be measured i n the l a b o r a t o r y but g e n e r a l l y these observations are not completely accurate because of the l a c k of the r e s t a i n i n g l i t h o s t a t i c pressure. The recent report by the N a t i o n a l Research C o u n c i l of the N a t i o n a l Academy of Sciences e n t i t l e d " L i m i t a t i o n s of Rock Mecha n i c s i n Energy Resource Recovery and Development", h i g h l i g h t e d some of the problems which must be addressed. The rock strength and other mechanical p r o p e r t i e s of the media must be understood both under the impact of the thermal pulse represented by the r e l e a s e of heat from decaying r a d i o a c t i v e waste m a t e r i a l s and the p e r t u r b a t i o n represented by c o n s t r u c t i o n of the mine. The r e s u l t ing thermal s t r e s s e s must be understood i n developing the layout and the allowable r a t e of heat generation from the i n d i v i d u a l canisters. C a l c u l a t i o n a l models are being developed to b e t t e r understand the p r o p e r t i e s and behavior of rock i n response to these s t i m u l i . Measurement of p r o p e r t i e s at depth w i l l probably be r e q u i r e d i n order to get a b e t t e r understanding of the behavior of these rocks. These i s s u e s are important because rock motion or f r a c t u r ing could r e s u l t i n changes to the o v e r l y i n g s t r a t a which might a f f e c t the flow of ground water i n a q u i f e r s o v e r l y i n g the r e p o s i tory. In order to understand t h i s p r o p e r l y , t h e r e f o r e , an extens i v e program of rock mechanics w i l l be conducted. Hydrogeologic Transport. A f t e r a r e p o s i t o r y i s f u l l y loaded and sealed, the most l i k e l y mechanism f o r the r e l e a s e of r a d i o n u c l i d e s to the biosphere would be by t h e i r d i s s o l u t i o n and t r a n s port i n ground water. R e p o s i t o r i e s l o c a t e d below the water t a b l e are expected to f i l l with ground water at some time a f t e r t h e i r s e a l i n g . The r a t e of ground water i n f l o w w i l l depend on the host rock p e r m e a b i l i t y , the depth of the r e p o s i t o r y beneath the water t a b l e , the design of the s h a f t s and bore holes, and the e f f e c t i v e ness of techniques f o r s e a l i n g the shaft and bore h o l e s . After the r e p o s i t o r y has been sealed and l a t e r has become saturated, ground water flow through the r e p o s i t o r y w i l l be i n f l u e n c e d by the


1.

HEATH

DOE

Isohtion

of

Radioactive

Waste

9

mechanical response of the host rock to the r e p o s i t o r y construct i o n and to the thermal pulse and by n a t u r a l h y d r a u l i c g r a d i e n t s . The c h a r a c t e r i z a t i o n of the hydrology of p o t e n t i a l s i t e s i s as the present time a major item i n our program. In most areas the capab i l i t y of the United Stated G e o l o g i c a l Survey i s being employed to assess the e x i s t i n g h y d r a u l i c gradients i n the areas being considered. The a b i l i t y of the ground water to d i s s o l v e wastes and t r a n s port them from the r e p o s i t o r y depends on the s o l u b i l i t y of the waste forms at the temperatures that the r e p o s i t o r y w i l l reach and the ion-exchange p r o p e r t i e s of the host rock and of a l l media between the r e p o s i t o r y and the p o t e n t i a l r e l e a s e point to the b i o sphere. Consequently, measurements are p r e s e n t l y being made on absorption c o e f f i c i e n t s of v a r i o u s r a d i o i s o t o p e s with the minerals that are expected to be encountered i n the g e o l o g i c a l environment. Measurements are being taken not only f o r s i n g l e species but a l s o f o r combinations of species with the range of pH values of the ground water that may be expected to be found. A number of models have been developed to estimate the p o t e n t i a l transport of r a d i o n u c l i d e s by ground water. By v a r y i n g boundary c o n d i t i o n s and generic input data such as p e r m e a b i l i t y , p o r o s i t y and a b s o r p t i o n c a p a c i t y of geologic media these models y i e l d the measure of r e l a t i v e importance of the flow path l i f e , the flow v e l o c i t y and a q u i f e r absorption c h a r a c t e r i s t i c s as b a r r i e r s to r a d i o n u c l i d e t r a n s p o r t . Results from c a l c u l a t i o n s with the model suggest that i f a r e p o s i t o r y i s s i t e d w i t h a flow path s u f f i c i e n t l y long, such as may be found i n r e g i o n a l a q u i f e r systems, the r e t e n t i o n of r a d i o n u c l i d e s i n the geology f o r periods of thousands of years w i l l be achieved. A major i s s u e that needs more work i n the area of hydrogeol o g i c t r a n s f e r has to do with flow of ground water through f r a c tured rock systems. There are a number of models that have been developed to date to t r y to o b t a i n a b e t t e r understanding of ground water flow through geologic media. But most of these assume the p r o p e r t i e s of porous or semi-porous media. Should the ground water flow be p r i m a r i l y through f r a c t u r e s , which of course i s v e r y s i t e s p e c i f i c , models are not yet a v a i l a b l e to represent t h i s flow a c c u r a t e l y . I t may very w e l l be that s i t e s p e c i f i c experiments w i l l be r e q u i r e d i n order to c h a r a c t e r i z e the flow through f r a c t u r e d media. A d d i t i o n a l work i n t h i s area w i l l be r e q u i r e d before we w i l l be i n a p o s i t i o n to i d e n t i f y the c h a r a c t e r i s t i c s of flow paths where considerable q u a n t i t i e s of f r a c t u r e d rock e x i s t . Risk Assessment. The o v e r a l l compilation and assessment of the f a c t o r s that must be considered i n designing and s i t i n g geol o g i c r e p o s i t o r i e s i s p u l l e d together i n a general d i s c i p l i n e of r i s k assessment. Risk assessment c a l c u l a t i o n s develop both generi c and site s p e c i f i c models and c a l c u l a t e the p o t e n t i a l t r a n s p o r t times as a r e s u l t of v a r i o u s phenomena. C a l c u l a t i o n s are being


10


performed f o r those s i t u a t i o n s i n which the r e p o s i t o r y environment remains e s s e n t i a l l y unchanged and a l s o f o r those c o n d i t i o n s where s i g n i f i c a n t unplanned events such as earthquakes, climate change or other phenomena take p l a c e . As each of these s i t u a t i o n s are analyzed, an understanding i s gained of the importance of the v a r ious f a c t o r s and the m u l t i p l e b a r r i e r s which might be provided between the r a d i o a c t i v e m a t e r i a l s and the environment. An important element of r i s k a n a l y s i s i s a s s e s s i n g the importance of the u n c e r t a i n t i e s i n the data now being used to e v a l uate v a r i o u s s c e n a r i o s . By v a r y i n g the value of the parameters that are used i n the a n a l y s i s , one can understand the importance of present u n c e r t a i n t i e s i n s i g n i f i c a n t v a r i a b l e s by t h e i r impact on the c a l c u l a t e d r i s k from the r e p o s i t o r y . These r e s u l t s w i l l be used to d i r e c t the research program toward those elements which are most s i g n i f i c a n t . The o v e r a l l design of the program by e v a l u a t i n g f a c t o r s which could l e a d to r i s k of r e l e a s e to the environment i n v o l v e s the type of a n a l y s i s that w i l l be r e q u i r e d during a l i c e n s i n g process. A d e t a i l e d l i c e n s i n g plan i s being prepared and w i l l be published when a v a i l a b l e to d e s c r i b e those areas which w i l l be of concern to the l i c e n s i n g a u t h o r i t i e s , the methods a v a i l a b l e to us to analyze those areas and the data that w i l l be used i n performing the a n a l yses. The s e n s i t i v i t y a n a l y s i s j u s t described w i l l i n d i c a t e where a d d i t i o n a l data are r e q u i r e d i n order to gain more assurance i n p r e d i c t i n g p o t e n t i a l r i s k s that might occur from the placement of the r e p o s i t o r i e s . Conclusion I have t r i e d to present to you some of the c o n s i d e r a t i o n s that go i n t o designing the research and development programs which are and w i l l be undertaken under the sponsorship of the Department of Energy. The new O f f i c e of Nuclear Waste I s o l a t i o n has been charged with the task of compiling a l l of these v a r i o u s thoughts and c o n s i d e r a t i o n s i n t o a s i n g l e program plan document. T h i s document w i l l i n c o r p o r a t e the input of the l i c e n s i n g plan, the r i s k assessment and s e n s i t i v i t y analyses which have been performed and a l s o the independent review that has been s u p p l i e d by such groups as the USGS, the N a t i o n a l Academy of Sciences, EPA and others. T h i s program plan w i l l be published w i t h i n the next few months and w i l l be c i r c u l a t e d f o r p u b l i c review and comment. We hope that both the American Chemical Society and i t s i n d i v i d u a l members w i l l provide us feedback on t h i s p l a n . H o p e f u l l y , i n t h i s way a greater understanding of the t e c h n i c a l components of the program w i l l be achieved and we w i l l be able to demonstrate that we are addressing the concerns that have been r a i s e d i n a respons i b l e manner. I f I can supply an o v e r a l l assessment of where we stand i n the program today, I b e l i e v e that there i s a consensus i n the


1.

HEATH

DOE

Isolation

of Radioactive

11

Waste

s c i e n t i f i c community that a p p r o p r i a t e i s o l a t i o n of r a d i o a c t i v e wastes can be obtained by p l a c i n g them i n g e o l o g i c formations. There are s e v e r a l f a c t o r s that have to be considered before speci f i c s i t e s can be i d e n t i f i e d and many of the gaps i n our knowledge are indeed very s p e c i f i c to the s i t e s i n q u e s t i o n . P r i m a r i l y because of t h i s s i t e s p e c i f i c c h a r a c t e r i s t i c I b e l i e v e one can say that the concept of r a d i o a c t i v e waste i s o l a t i o n w i l l not be proven u n t i l we are i n a p o s i t i o n of being able to i d e n t i f y a s p e c i f i c s i t e with a l l of these m u l t i p l e c h a r a c t e r i s t i c s adequately chara c t e r i z e d so that we can o b t a i n a c l e a r e r understanding and app r o v a l by both the r e g u l a t o r y a u t h o r i t i e s and the general p u b l i c . The proposed f a c i l i t y i n southeast New Mexico i s the c l o s e s t to being completely c a t e g o r i z e d i n t h i s way. I t i s i n t h i s context that the Department of Energy has proposed that t h i s p r o j e c t be subjected to the l i c e n s i n g process by NRC even i f the m a t e r i a l to be placed there i s only defense r a d i o a c t i v e waste. Unfortuna t e l y , the sponsoring committees of the Congress who are concerned p r i m a r i l y with the i s s u e s of defense have taken the p o s i t i o n that f a c i l i t i e s r e l a t e d to the defense program should remain completely exempt from the l i c e n s i n g process. Opposition to work l e a d i n g to i d e n t i f i c a t i o n of s p e c i f i c s i t e s i s the g r e a t e s t problem f a c i n g the program today. It i s agreed i n the s c i e n t i f i c community that one cannot reach a f i n a l c o n c l u s i o n of the s u i t a b i l i t y of g e o l o g i c i s o l a t i o n without looking at s p e c i f i c s i t e s i n d e t a i l . This of course i s the one area to which there has been s i g n i f i c a n t o p p o s i t i o n . Members of the p u b l i c and s t a t e and l o c a l l e a d e r s have stated that more s p e c i f i c information i s needed as to the s a f e t y and p o t e n t i a l s u i t a b i l i t y of r a d i o a c t i v e waste d i s p o s a l before one can allow even the exami n a t i o n or d i s c u s s i o n of s p e c i f i c s i t e s . On the other hand, s c i e n t i f i c consensus i s that u n t i l one does evaluate s p e c i f i c s i t e s one i s not going to be a b l e to o b t a i n the r e q u i r e d information. In order to r e s o l v e t h i s dilemma, we are seeking to cons t r u c t a j o i n t c o n s u l t a t i o n process with s t a t e and l o c a l authori t i e s to allow the examination of s p e c i f i c s i t e s i n order that we can answer the s c i e n t i f i c questions that we must. The ongoing a c t i v i t i e s of the Interagency Review Group on Waste Management and i t s i n t e r a c t i o n w i t h s t a t e and l o c a l o f f i c i a l s and the p u b l i c i s the f i r s t step i n o b t a i n i n g the necessary consensus before proceeding . We have reached a c r i t i c a l t u r n i n g p o i n t i n the DOE s waste management program. The program i s now adequately funded, and with the a s s i s t a n c e of many q u a l i f i e d and experienced s c i e n t i s t s and engineers a comprehensive t e c h n i c a l program i s underway. A r e s o l u t i o n must now be reached to a l l o w us to extend our i n v e s t i gations i n t o s p e c i f i c s i t e l o c a t i o n s . With input and feedback from groups such as t h i s , and with cooperation at a l l l e v e l s of government, I am c o n f i d e n t that we can proceed to r e s o l v e t h i s very important n a t i o n a l problem. 1

RECEIVED January 16,

1979.

Radioactive Waste in Geologic Storage - ACS Publications

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