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no.59RECOMMENDATIONS

Disposal ofLow- and Intermediate-Level Solid Radioactive Wastes in Rock Cavities

A Guidebook

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C A T E G O R IE S O F IA E A S A F E T Y S E R IE S

From Safety Series No. 46 onwards the various publications in the series aredivided into four categories, as follows:

(1 ) IA E A Safety Standards. P ub lications in th is category com prise th e A g en cy ’s sa fety standards as d efin ed in “T he A g en cy ’s Safety Standards and M easures” , approved by th e A g en cy ’s Board o f G overnors on 25 February 1976 and set forth in IA E A d ocu m en t IN F C IR C / 18 /R ev. 1. T h ey are issued under th e au th ority o f th e Board o f G overnors, and are m andatory for th e A g en cy ’s o w n op erations and for A gency-assisted operation s. Such standards com prise th e A g en cy ’s basic sa fe ty standards, th e A g en cy ’s specialized regu lations and the A g en cy ’s co d es o f practice. The covers are distinguished by the wide red band on the lower half.

(2 ) IA E A S afety G uides. A s stated in IA E A d ocu m en t IN F C IR C /18 /R ev . 1, referred to above, IA E A Safety G uides sup p lem ent IA E A S a fety Standards and recom m en d a procedure or procedures th at m ight be fo llo w ed in im p lem en tin g them . T h ey are issued under th e au th ority o f th e D irector G eneral o f th e A gen cy . The covers are distinguished by the wide green band on the lower half.

(3 ) R ecom m en d ation s. P ub lications in th is category , con ta in in g general recom m en d ation s on sa fe ty practices, are issued under th e au thority o f th e D irector G eneral o f th e A gen cy . The covers are distinguished by the wide brown band on the lower half.

(4 ) Procedures and D ata. P u b lications in th is category con ta in in form ation on procedures, tech n iq u es and criteria pertain ing to sa fe ty m atters. T h ey are issued under th e au thority o f th e D irector G eneral o f th e A gen cy . The covers are distinguished by the wide blue band on the lower half.

Note: The covers o f publications brought ou t within the fram ework o f the NUSS (Nuclear Safety Standards) Programme are distinguished by the wide yellow band on the upper half.


DISPOSAL OF LOW- AND INTERMEDIATE-LEVEL SOLID RADIOACTIVE WASTES IN ROCK CAVITIES

A Guidebook


T he following S tates are M embers o f the In ternational A tom ic Energy Agency:

AFGHANISTANALBANIAALGERIAARGENTINAAUSTRALIAAUSTRIABANGLADESHBELGIUMBOLIVIABRAZILBULGARIABURMABYELORUSSIAN SOVIET

SOCIALIST REPUBLIC CANADA CHILE COLOMBIA COSTA RICA CUBA CYPRUSCZECHOSLOVAKIA DEM OCRATIC KAMPUCHEA DEM OCRATIC PEO PLE’S

REPUBLIC O F KOREA DENMARKDOMINICAN REPUBLICECUADOREGYPTEL SALVADORETHIOPIAFINLANDFRANCEGABONGERM AN DEM OCRATIC REPUBLICGERM ANY, FED ER A L REPUBLIC O FGHANAGREECEGUATEM ALAHAITIHOLY SEE

HUNGARYICELANDINDIAINDONESIAIRAN, ISLAMIC REPUBLIC OFIRAQIRELANDISRAELITALYIVORY COASTJAMAICAJAPANJORDANKENYAKOREA, REPUBLIC OF KUWAIT LEBANON LIBERIALIBYAN ARAB JAM AHIRIYALIECHTENSTEINLUXEMBOURGMADAGASCARMALAYSIAMALIM AURITIUSMEXICOMONACOM ONGOLIAMOROCCONAMIBIANETHERLANDSNEW ZEALANDNICARAGUANIGERNIGERIANORWAYPAKISTANPANAMAPARAGUAYPERU

PHILIPPINESPOLANDPORTUGALQATARROMANIASAUDI ARABIASENEGALSIERRA LEONESINGAPORESOUTH AFRICASPAINSRI LANKASUDANSWEDENSW ITZERLANDSYRIAN ARAB REPUBLICTHAILANDTUNISIATURKEYUGANDAUKRAINIAN SOVIET SOCIALIST

REPUBLIC UNION O F SOVIET SOCIALIST

REPUBLICS UNITED ARAB EM IRATES UNITED KINGDOM OF G REAT

BRITAIN AND NORTHERN IRELAND

UNITED REPUBLIC OF CAMEROON

UNITED REPUBLIC OF TANZANIA

UNITED STATES O F AMERICA URUGUAY VENEZUELA VIET NAM YUGOSLAVIA ZAIRE ZAMBIA

The A gency’s S ta tu te was approved on 23 O ctober 1956 by the C onference on the S ta tu te o f the IAEA held a t U nited N ations H eadquarters, New Y ork; it en tered in to force on 29 July 1957. The H eadquarters o f the Agency are s ituated in V ienna. Its principal objective is “ to accelerate and enlarge the con tribu tion o f a tom ic energy to peace, health and prosperity th roughou t the w orld” .

© IAEA, 1983

Permission to reproduce or translate the inform ation con tained in this publication m ay be obtained by w riting to the In ternational A tom ic Energy Agency, W agramerstrasse 5, P.O. Box 100, A -1400 Vienna, Austria.

Prin ted by the IAEA in Austria April 1983


SAFETY SERIES No. 59

DISPOSAL OF LOW- AND INTERMEDIATE-LEVEL

SOLID RADIOACTIVE WASTES IN ROCK CAVITIES

A Guidebook

IN T E R N A T IO N A L ATOMIC E N E R G Y A G E N C Y V IE N N A , 1983


D ISPO SA L O F LOW- A N D IN T ER M E D IA T E-LE V EL SO LID R A D IO A C T IV E W ASTES IN ROCK C AVITIES:

A G U ID EBO O K IA EA, V IE N N A , 1983

S T I/P U B /610 ISBN 9 2 —0 —1 2 3 4 8 3 —X


FOREWORD

This G u id eb ook is in tended for th ose considering or practising disposal o f solid low - and interm ediate-level radioactive w astes in rock cavities. It provides gu idelines to be used by regulatory bod ies and im plem entin g organizations.

The IA E A in itiated its integrated program m e on the underground disposal o f radioactive w astes in 1977 . W ithin th is program m e, a series o f guidance d ocu m ents are being develop ed . T he present report form s part o f th is series.

The G uid eb ook is in tended to serve as a source o f general in form ation . A nother d ocu m en t giving m ore techn ica l and sp ecific in form ation on the principal aspects covered in th is report is currently under preparation.

A w orking paper for the G u id eb ook w as drafted at a C onsu ltan ts’ M eeting held in S tock h o lm , Sw eden , in June 1 9 80 . T he w orking paper was revised and am ended at a T echnical C om m ittee M eeting in V ienna, A ustria, in O ctober 1980 . T he draft report u nderw ent exam ination by th e A gen cy ’s T echnical R eview C om m ittee for U nderground D isposal in N ovem ber 1980 . Further review s and revisions w ere carried ou t in Septem ber 1 9 8 1 , the first at an A dvisory G roup M eeting in M adrid, Spain, and th e second im m ed iate ly thereafter at a C onsu ltan ts’ M eeting in V ienna. F inal exam in ation o f th e report was m ade by the T echnical R eview C om m ittee in N ovem b er 1981 .

A num ber o f relevant p u b lication s have been or are being prepared w ith in the IA E A program m e on the safe underground disposal o f rad ioactive w astes, dealing w ith possib le o p tio n s for the disposal o f high-, in term ediate- and low - level radioactive w astes in deep , con tin en ta l geo log ica l form ation s, in rock cavities at various depths and in shallow ground. T hese are as fo llow s:

S ite S election F actors for R epositories o f So lid H igh-Level and A lpha-Bearing W astes in G eolog ica l F orm ation s, T echnical R eports Series N o . 177 (1 9 7 7 )

D evelop m en t o f R egulatory Procedures for the D isposal o f Solid R adioactive Waste in D eep , C ontinental F orm ations, S a fety Series N o . 51 (1 9 8 0 )

Shallow G round D isposal o f R adioactive Wastes: A G u id eb ook , S a fety Series N o. 53 (1 9 8 1 )

U nderground D isposal o f R adioactive Wastes: B asic G uidance, S a fety Series N o. 5 4 ( 1 9 8 1 )

S afety A ssessm ent for the U nderground D isposal o f R adioactive W astes, Safety Series N o . 56 (1 9 8 1 )


Site Investigations for R ep ositories for Solid R adioactive W astes in D eep C ontinenta l G eologica l F orm ations, T echnical R eports Series N o . 215 (1 9 8 2 )

S ite Investigations for R epositories for Solid R adioactive W astes in Shallow G round, T echnical R eports Series N o. 2 1 6 (1 9 8 2 )

O ther pub lications prepared under the R adiological S afety and N uclear Safety Standards (N U S S ) program m es m ight be con su lted as appropriate.


CONTENTS

1. IN T R O D U C T IO N ................................................................................................................. 1

2. SC O PE ........................................................................................................................................ 2

3. W ASTE A N D DISPO SA L CONCEPT C O N S ID E R A T IO N S ............................ 3

3 .1 . C haracteristics and categories o f w a s te s ......................................................... 33 .2 . A cceptab ility and con d ition in g o f w a s te s ..................................................... 33 .3 . Factors in fluencin g the disposal op tion ......................................................... 63 .4 . T ypes o f h ost r o c k s .................................................................................................. 83 .5 . T ypes o f c a v it ie s ........................................................................................................ 9

4. SA FE T Y A S S E S S M E N T ................................................................................................... 12

4 .1 . Pre-operational sa fety assessm en t....................................................................... 134 .2 . O perational safety a ssessm en t............................................................................. 144 .3 . P ost-operational sa fety a ssessm en t.................................................................... 15

5. R E G U L A TO R Y C O N S ID E R A T IO N S......... :........................................................... 15

5.1 . F unctions o f the regulatory b o d y ..................................................................... 165.2. R egulatory req u irem en ts ....................................................................................... 175.3. L ic e n s in g ....................................................................................................................... 175.4. R egulatory aspects o f operation , shutdow n and se a lin g ........................ 185.5 . P ost-operational su rveillan ce ................................................................................ 19

6. R EPO SITO RY SITE SE LE C TIO N ................................................................................ 19

6 .1 . Planning and general s t u d ie s ................................................................................ 226 .2 . R egional eva lu a tion ...................................................................................................236 .3 . Investigations o f ex istin g m ines and c a v it ie s ................................................236 .4 . Site id e n t if ic a t io n ......................................................................................................246 .5 . Site c o n firm a tio n .......................................................................................................24

7. REPO SITO RY D ESIG N , C O N STR U C TIO N A N D C O M M ISSIO N IN G .... 25

7 .1 . Design co n s id e r a tio n s ..............................................................................................257 .2 . Engineering m eth od s to im prove iso la tion o f the w a ste s ....................... 26


7 .3 . F acilities at the site ....................................................................................................287 .4 . R epository c o n s tr u c t io n .......................................................................................... 297 .5 . C o m m iss io n in g ............................................................................................................. 29

8. O PE R A T IO N O F THE R E P O S IT O R Y ....................................................................... 3 0

8.1 . Waste r e c e p t io n ............................................................................................................3 08 .2 . D isposal operations ....................................................................................................318 .3 . O perational s a f e t y ....................................................................................................... 318 .4 . M onitoring ..................................................................................................................... 328 .5 . A dm inistrative co n sid era tio n s................................................................................32

9. SHUTDOW N A N D S E A L IN G .................................................................. ...................... 33

9 .1 . General and in stitu tion a l aspects .........................................................................339 .2 . C ond itions for s h u td o w n .........................................................................................3 49 .3 . Major step s in shutdow n and se a lin g ..................................................................3 49 .4 . Post-operational s a f e t y ............................................................................................. 3 4

R E F E R E N C E S .................................................................................................................................35

A N N E X I. SY N O PSIS O F N A T IO N A L A CTIV ITIES O N ROCK C AV ITYD ISPO SA L C O N C E P T S ........ .............................................................................37

A N N E X II. D R A F T IN G A N D REVIEW ING BODIES:LIST O F P A R T IC IP A N T S ..................................................................................41


1. INTRODUCTION

D isposal o f radioactive w astes underground after appropriate con d ition in g is generally considered to be a feasible m eth od o f providing the necessary protection for m an and the environm ent. The term ‘underground d isp osa l’ m eans the em placem en t o f radioactive w aste m aterials in the terrestrial subsurface w ithou t in ten tion o f retrieval.

A m ong the d ifferent underground disposal repository system s w hich are in use or under developm ent, on e m eth od involves em placem ent o f solid or solid ified low - or interm ediate-level radioactive w astes in rock cavities — including for exam ple disused m ines, o ther existing m an-m ade cavities, cavities especially excavated for disposal purposes and natural cavities. This rock cavity disposal con cep t is in principle an approach w hich lies som ew here b etw een the op tion s com m on ly called shallow -ground disposal and disposal in deep geological form ations [1 ].

A characteristic feature o f the con cep t is the variety o f d ifferent poten tia l applications, i.e . d ifferent typ es o f cavities located at various depths and in different geological form ations w hich can be used for d ifferent typ es o f waste.The su itab ility and perform ance o f individual disposal system s have to be carefu lly analysed on a case-by-case basis.

The main advantage o f th is approach is that acceptab le operation and long-term safety can be attained by the im p lem en tation o f w ell-established techniques at m oderate costs.

The objective is to d ispose o f the radioactive w astes in such a m anner that the radiological im pact o f released radionuclides con form s to criteria laid dow n by national regulations for radiation p rotection . T hese are norm ally based on the recom m endations o f the International C om m ission on R adiological P rotection (ICRP), w hich are described in other IA E A pub lications [2 , 3].

The geological characteristics o f a site are usually the m ain factors contro lling the m igration o f nuclides. Transport m echanism s o f nuclides related to hydrogeological, geochem ical and b iolog ica l phenom ena and to hum an uptake m ust be taken in to account over the tim e period during w hich they are im portant. Engineering m eth od s m ay be used to im prove the site perform ance in this regard, e.g. b y con d ition in g the w astes or by special engineering o f the repository. A tten tion m ust also be given to the p o ten tia l conseq u en ces o f in trusion by man.

In the safety assessm ent o f w aste disposal, the to ta l system — w hich includes all the com p on en ts retarding the m ovem ent o f radionuclides to the environm ent o f m an — m ust be taken in to consideration . The details o f safety assessm ents are discussed in Chapter 4.

The design, con stru ction and operation o f the facility (C hapters 7 and 8 ) require appropriate licensing and assessm ent o f the sa fety o f the disposal activities.

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These fu n ction s (licensing and sa fety assessm ent) are carried ou t by appropriate national regulatory authorities, w hich should be independent o f those operating th e facility . R egulatory aspects are considered in C hapter 5.

A dditional data concern ing th e h ost rock perform ance, b o th p hysica lly and as a barrier against m igration o f th e radionuclides to th e b iosphere, should con tin u e to be ob tained during the facility operation . T hese data, togeth er w ith in form ation on any changes in th e design an d /or operation o f the facility resulting from actual exp erience , m ust be factored back in to th e sa fety assessm ent and review ed along w ith the proposed shu tdow n and sealing operations. This is done in preparation for the final act o f disposal, i.e . perm anent closure and abandonm ent o f the facility . T hese aspects are discussed in Chapters 8 and 9.

The data on national activ ities con ta ined in A nnex I illustrate th e fact that although rock cavity disposal is being practised in on ly a few countries, the p oten tia l applicab ility o f the con cep t has been w idely recognized.

2. SCOPE

T his G u id eb ook sum m arizes the factors to be considered and the activ ities to be undertaken in the overall p lanning and developm ent o f a disposal system for solid or so lid ified low - and interm ediate-level w astes in rock cavities. A sp ects related to rep ository site se lection , design, con stru ction , operation , sh u tdow n , surveillance, regulation and sa fety assessm ent are discussed here in general term s. T hey will be covered in greater technical detail in a separate d ocu m en t [4].

This report considers th e em placem ent o f w astes in categories II, III, IV and V, as defined in Table 3 .1 , in d ifferent k inds o f cavities located at various depths from just b e lo w th e surface to deep con tin en ta l rock. The ch o ice o f the typ e o f cavity and its depth and o f the d isposal site itse lf is related to the radiological p ro tection requirem ents for the w astes con cerned . The repositories considered include natural caves and abandoned m ines as w ell as specially excavated cavities in various geological form ations. C onsideration is also given to h ydrogeolog ica l, environm ental and societa l factors.

The gu idelines given in the report are m ade su ffic ien tly general to cover a broad variety o f different circum stances. C on seq u en tly , th e practical application o f these guidelines needs a case-by-case consideration w hich takes in to accoun t the local con d ition s, e.g. natural circum stances, the characteristics o f the w astes and national and in ternational regulations and practices.

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3. WASTE AND DISPOSAL CONCEPT CONSIDERATIONS

The overall objective o f radioactive w aste disposal is to d ispose o f th e w astes in such a m anner that there is n o u nacceptab le detrim ent to m an at any tim e.The iso lation o f the w astes from m an’s environm ent by the disposal system should remain effective until the radionuclides have decayed to an accep tab le level.

E ffective p rotection can be achieved by adhering to the basic princip les o f radiation p ro tection [2], by proper planning, and by the ad op tion o f appropriate m ethod s for con d ition in g and disposal. If the w astes con ta in sign ificant am ounts o f radionuclides w ith lon g half-lives, special consideration m ust be given to the long-term behaviour o f the overall system . A safety assessm ent m ust be perform ed to sh ow that e ffective iso lation w ill result from the planned disposal. One basic requirem ent in the disposal strategy is an adequate kn ow ledge o f the w aste characteristics.

3 .1 . C H A RA CTERISTIC S A N D CATEG O R IES OF W ASTES

R adioactive w astes are generated in the d ifferent parts o f the nuclear fuel cycle or arise from various app lications o f radionuclides. O w ing to th e variety both in the origin o f w astes and in disposal con cep ts , m any d ifferent categorization schem es can be used. T he w astes can have d ifferen t physical and chem ical properties and contain varying am ounts o f radionuclides w ith d ifferent half-lives and rad io tox icities . T hey m ay be degradable or non-degradable. Som e o f these characteristics m ay prevent direct disposal o f the w astes in their original form and such w astes m ust therefore be con d ition ed in an appropriate w ay. The desirable w aste properties and the con seq u en t con d ition in g requirem ents w ill very m uch depend on the ty p e o f w astes involved and the characteristics o f th e repository system .

For the purpose o f IA E A pub lication s dealing w ith underground disposal, w astes are grouped in to five categories as show n in Table 3.1 [1]. C ategory I w astes are n o t considered here, b u t are dealt w ith in other IA E A d ocu m en ts [5 —8].

3 .2 . ACCEPTABILITY A N D C O N D IT IO N IN G O F W ASTES

In Table 3 .1 , the w astes are classified for the purpose o f disposal as having either a high, interm ediate, or lo w level o f rad ioactiv ity , and having short or long half-lives. Som e w astes are acceptab le for disposal in rock cavities in the form in w hich th ey are generated. M any w astes, how ever, m ust be con d ition ed to m ake them suitable for disposal. The techn iq ue o f con d ition in g in som e cases determ ines the su itab ility o f the w astes for a particular disposal con cep t. This

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T A B L E 3 .1 . G E N E R A L C H A RA CTERISTIC S OF W ASTE CATEG O R IES WITH R E G A R D TO DISPO SA L

Waste category Important features3

I. High-level, long-lived

High beta/gamma Significant alpha High radiotoxicity High heat output

II. Intermediate-level, long-lived

Intermediate beta/gamma Significant alpha Intermediate radiotoxicity Low heat output

III. Low-level, long-lived

Low beta/gamma Significant alpha Low/intermediate radiotoxicity Insignificant heat output

IV. Intermediate-level, short-lived

Intermediate beta/gamma Insignificant alpha Intermediate radiotoxicity Low heat output

V. Low-level, short-lived

Low beta/gamma Insignificant alpha Low radiotoxicity Insignificant heat output

a The characteristics are qualitative and can vary in some cases; “insignificant” indicates that the characteristic can generally be ignored for disposal purposes. Short-lived wastes are those wastes that decay to acceptable activity levels in time periods during which administrative controls can be expected to last.

applies particularly to w astes w ith relatively h igh activ ity levels, rad io tox ic ities

or radionuclide m ob ilities. An im portant objective o f con d ition in g is to im m obilize the radionuclides so that the con d ition ed w aste form together w ith the repository and its m an-m ade and geological barriers co n stitu te an e ffectiv e barrier system .This barrier then d elays th e entry o f the w aste con stitu en ts in to the environm ent.

D esirable characteristics o f con d ition ed low -level and interm ediate-level w aste are:

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— stab ility against chem ical and b iolog ica l degradation- lo w so lu b ility and leachability in groundw ater— lo w com b u stib ility- lo w sp ecific surface area- m inim al practical vo lu m e— freedom from surface contam in ation and dustiness— ease o f handling and transportation- durability o f packaging.

The con d ition in g o f various typ es o f w aste is d iscussed in other IA EA d ocu m en ts [9, 10]. The fo llow in g is a short sum m ary o f con d ition in g for the typ es o f waste given in Table 3 .1 , based on th e m aterial in R ef. [ 1 ]. It should be em phasized that the accep tab ility o f any given w aste w ill depend on th e o u tcom e o f a safety analysis. C ategory I (high-level, long-lived) w astes are n o t considered su itable for rock cavity disposal.

F uel e lem en t cladding hulls, associated hardware and insoluble dissolver residues, Category II. The con d ition in g op tion s presently available include com p action either m echanically or by m elting, incorporation in a m etal m atrix or cem en t or sim ply placing in m etal containers. The final ch o ice w ill depend on the degree to w hich the hulls can be freed from entrapped fuel m aterials.The e ffic ien cy o f th is separation will determ ine the w aste category o f the hulls and insolub le solvent residues, particularly w ith respect to the levels o f b eta / gam m a radionuclides [5, 11 ]. A lpha radionuclides m ay be reduced to insignificant levels w ith appropriate separation o f the fuel m aterial from the hulls.

In term ediate-level wastes, Categories I I a n d IV . T hese categories com prise a variety o f w astes w hich , because o f their radionuclide co n ten t, require shielding but need little or no provision for heat d issipation during handling and transportation . These w astes are produced in appreciable quantities in the d ifferen t phases o f the nuclear fuel cycle . T ypical exam ples are air filters, spent ion-exchange resins, chem ical sludges, evaporator concentrates, liquid w astes from second and third cyc le processing stages in fuel reprocessing, failed equ ipm ent, etc.

A variety o f m eth od s for con d ition in g these m aterials are available. N ew techn iques are under consideration in m any countries. T h e m eth od s usually used are cem en tation , b itum in ization and incorporation in to polym ers. Each o f these techniques has d ifferen t characteristics and the ch o ice should be m ade in relation to the particular w aste and the sp ecific disposal system under consideration .In som e cases it w ill be su ffic ien t i f the w astes are packaged in to containers after dew atering w ith ou t any con d ition ing . In another techn iqu e, the w astes can be directly d isposed o f w ith ou t packaging in the form o f a se lf-so lid ify in g slurry (obtained b y m ixing w ith an im m obiliz in g m aterial prior to em placem ent).

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L ow -level wastes, Categories I I I and V. L ow -level solid w astes, including general process area trash, m ay be packed in steel drum s, in som e cases w ith com p ression to reduce the volum e. A lternatively , com bustib le w astes m ay be incinerated , w ith the residue being im m obilized by the techniques iden tified above, an d /or p laced in appropriate packaging [6, 10, 12].

A w ide variety o f treatm ent and im m ob iliza tion techn iq ues are in use for liquid w astes from these categories. The im m obiliz ing tech n iq u es are generally the sam e as those discussed previously [6],

A lpha-con tam ina ted wastes w ith low beta/gam m a radioactivity , Category III. C urrently, various techniques are used for the treatm ent and con d ition in g o f this typ e o f w aste and no single technique is y e t dom inant. Processes already ex ist or are under d evelopm ent for ox id iz in g the com b u stib le w astes by incineration or acid d igestion to reduce vo lu m e and flam m ability; th e resulting ash m ay be leached to rem ove any iso top es deem ed to be w orth recovering. The residues cou ld be incorporated in to on e o f the com m on m atrix m aterials [5, 11 ]. They can also be m anaged like C ategory I w astes, a lthough th ey con seq u en tly fall outside th e scop e o f this docum ent.

N on-com bu stib le w astes cou ld be treated by being decontam in ated as far as practicable. The level o f con tam in ation o f m etal com p on en ts can in som e cases be reduced to very lo w levels (e.g. by e lectrop o lish in g) and this cou ld perm it disposal as w astes w ith insignificant levels o f alpha radionuclides (C ategories IV or V).

T ritium -con tam ina ted wastes, Categories I V a n d V. T hese w astes can be disposed o f in rock cavity-typ e repositories i f con d ition ed in an appropriate w ay [13 ], i.e. so lid ified and packaged properly.

D ecom m ission ing wastes and con tam ina ted soil ( Categories II, III, I V and V). A variety o f m eth od s cou ld be used for packaging d ecom m ission ed p lant materials. Incorporation in cem en t or b itum en or p lastic resins, or sealing w ith an adherent coating (all w ith or w ith ou t packaging) m ay be used . H ow ever, som e solid item s with relatively lo w radioactiv ity m ight be packaged w ith ou t prior im m obilization . The large bulk o f m aterial involved suggests that it shou ld be segregated in to appropriate w aste categories according to hazard and hazardous lifetim e as far as possib le before im m ob iliza tion and packaging [12].

3 .3 . FA C T O R S IN FL U E N C IN G THE D ISPO SA L OPTION

D isposal is an in tegrated part o f the w h ole w aste m anagem ent chain and it should be exam ined in that co n tex t . The applicab ility o f a d isposal alternative

6


is strongly in fluenced by th e preceding w aste m anagem ent steps and con d itions, such as quantity and quality o f w astes generated, the degree and m eth od o f con d ition in g and the duration o f interim storage. In turn, the disposal con cep t adopted m ay a ffect th e need for con d ition ing , storage, transport and w aste characterization.

The ch o ice o f w aste m anagem ent strategy is based on the results o f various evaluations carried ou t for d ifferen t purposes (e.g. sa fety analysis, co st analysis, system s analysis) and perform ed for the d ifferen t phases such as treatm ent, transport, storage and disposal.

The circum stances in a country w ill strongly in flu en ce th e d isposal alternative adopted. At the present tim e, disposal o f radioactive w astes in to rock cavities is practised in few countries. The con cep t is, how ever, recognized as p oten tia lly valuable and cavities have also been u tilized for the disposal o f hazardous chem ical wastes [14].

The decision to select a certain disposal op tio n thus depends on a com plex se t o f factors, the m ost im portant o f w hich are listed below :

(a) In itia l conditions

E xisting legislationTim e scale im posed by regulatory bod y Waste characteristics (quantity and ty p e)D ecision to have o n e or m ore repositories Available tech n ology

(b ) S ite availability

Inventory o f geological form ations Inventory o f natural cavities Inventory o f m an-m ade cavities and m ines Inventory o f p ossib ilities for cavity construction

(c) S a fe ty considerations

C onventional sa fety criteria R adiological p ro tection principles

(d ) Societa l considerations

D em ographyFinancial capacityPublic attitudesLand use (present and future)Transport con d ition s Natural resources.

7


The overall ch o ice o f underground disposal op tion s depends upon a num ber o f factors, the m ost im portant o f w hich are: w aste typ es and characteristics; geolog ica l and environm ental con d ition s; and societa l requirem ents. The final se lection depends on a consideration o f th e com p lex interrelationships betw een all o f the factors. Thus, the ch o ice o f a su itable disposal o p tion can be defined o n ly in general term s. H ow ever, the m ost im portant factor in determ ining the disposal op tion is that o f the w aste characteristics.

3 .4 . TYPES O F HO ST ROCKS

The iso lation qualities and m ining properties o f d ifferen t rock typ es vary greatly according to their m ineral co m p osition , their m echanical and geological stab ility and their h ydrogeologica l environm ent. C haracteristics a ffectin g the su itab ility o f the h ost rock for use as a repository are briefly described below .More detailed geological descrip tions o f the h ost rocks can be foun d in C hapter 3 o f IA E A T echnical R eports Series N o. 177 [7]. The fo llow in g sum m ary is based on R efs [1] and [8] and it is n o t exhaustive. T yp es o f h ost rocks o th er than th ose m en tion ed here m ight also be suitable.

Evaporites. T hese are sedim entary rocks that have accum ulated from the evaporation o f large bodies o f saline water, and include halite, anhydrite and gypsum .

R ock salt (h a lite) has received the m ost a tten tion as a poten tia l repository m edium ow ing to its outstanding properties. It is alm ost free o f circulating w ater and thus its sorption characteristics, w hich are in ferior to th ose o f o ther rock typ es, are n o t o f im portance. It is nearly im perm eable and easily m ined even at great depths under h igh lith osta tic pressures.

A nhydrite and gypsum form ations are com posed principally o f calcium sulphate and its hydrate, respectively . T hey are so lub le in water, though less so than halite. T hey are less plastic and in som e cases are prone to fracturing during m ining operations. Their chem ical com p atib ility w ith waste form s and other repository m aterials m ay give them advantages over halite and their sorption characteristics for radionuclides are favourable.

O ther sed im entary deposits. C alcareous form ations are rocks com posed principally o f calcium and calcium -m agnesium carbonates and are typ ified by lim eston e and do lom ite . T hey are m oderately solub le and n o t necessarily dry.T hey m ay conta in pathw ays p erm itting m ovem en t o f water. N evertheless, they can be considered individually on the basis o f actual circum stances even though in general th ey are though t to be hyd ro log ica lly unsu ited to w aste disposal (m any Pre-Cambrian and P alaeozoic lim eston es are qu ite im perm eable, for exam ple).


Sandstones and arenaceous sed im ents are in general porous and perm eable so that w ater can m ove through the bod y o f the rock i f there is no effective geological barrier preventing circulation o f w ater in the form ation . D epending on circum stances th ey can be o f in terest as h ost m edia for certain types o f waste.

A rgillaceous form ations cover a w ide range o f m aterials, including clays and shales. Clay m inerals are in so lub le and exh ib it good sorption characteristics. G enerally, argillaceous form ations have very lo w perm eabilities. These form ations are o f in terest as h ost rocks for w aste repositories o f low - and interm ediate-level w astes. In oth er cases th ey m ay form an effective geo log ica l barrier against w ater m ovem ent in a h ost rock.

Igneous and m etam orph ic rocks. T hese include granites, gneisses, basalts, tu ffs, quartzites and m any others. A ll ex cep t m arble are o f lo w so lu b ility and, w ith the ex cep tio n o f som e C en ozo ic ex ten sive volcan ic rocks, th ey have m oderate to lo w perm eabilities depending prim arily on the degree o f fracturing. Som e im portant advantages are their chem ical and physical stab ility and com m on occurrence in m assive, h om ogen eou s, durable form ations o f little or n o eco n o m ic value.

H ost ro c k su itability. The su itab ility o f the h o st rock w ill depend on individual circum stances related to the sp ecific site rather than th e general properties o f the host rock typ e. For exam ple, rock typ es w hich m ay be satisfactory under certain circum stances, e.g. lim estones and d o lom ites (calcareous form ations), do n ot prevent circulation o f water. H ow ever, dry m ines are foun d in calcareous form ations, particularly w here th ey lie b etw een im perm eable beds. Engineered barriers can serve the sam e purpose as naturally occurring im perm eable beds. These barriers m ay be considered in the sa fety assessm ent and then b ecom e part o f the overall repository design as a m eans o f m itigating the possib le e ffec ts o f a failure m ode, i.e . reducing the failure m od e probability and/or its con seq u en ce severity.This again highlights the fact that a final d ecision regarding the lo ca tio n o f a radioactive w aste rep ository can o n ly be m ade after a very careful, accurate and com prehensive investigation o f a given site and consid eration o f the w aste characteristics.

3 .5 . TYPES O F C A V ITIES

The d ifferent kinds o f rock cavities o f p oten tia l in terest for disposal o f solid low - and interm ediate-level radioactive w astes m ay include:

(a) N atural cavities

so lu tion-form ed lava tubes

9


TABLE 3.2. RELATION BETWEEN CAVITY ENVIRONMENT AND WASTE CATEGORY

Hydrogeological ^~~~~----^_characteristics

Cavity location

Low permeability, e.g. argillaceous, some crystalline rocks, some evaporites (e.g. halite)

Significant permeability, e.g. arenaceous, calcareous, some crystalline rocks

Cavities above the water table which under natural conditions remain relatively dry, but which may transmit significant quantities of water

Possible for II, III, IV and V generally without the need for engineered barriers since groundwater transmission is limited

Generally possible for IV and V only if engineered barriers are considered to retard (limit) movement of water

Cavities below the water table which under natural conditions will fill with water

Possible for II, III, IV and V only if relatively isolated from zone of meteoric water circulation

Not recommended unless the formation is isolated from the zone of meteoric water circulation

Waste categories: II. Intermediate-level, long-livedIII. Low-level, long-livedIV. Intermediate-level, short-lived V. Low-level, short-lived.


mineral and rock extraction ; m echanically excavated or so lu tion-m inedexisting or specially excavated for w aste disposal.

As indicated earlier, d ifferent kinds o f h ost geological form ations and rock typ es are possible.

In relation to groundw ater and th e saturated zon e, the cavity can be located: above the water table; at a shallow depth under or near the w ater table; or deep underneath the w ater table.

In all three situations, the cav ity m ay or m ay n o t be iso lated naturally from the groundw ater circulation . Investigation o f th e individual site w ill determ ine its h ydrological su itab ility , and m ay ind icate the need for engineered barriers.

The m atching o f w aste typ e to d isposal environm ent and site characteristics involves consideration o f m any problem s other than th e ob vious requirem ents for iso lation from th e biosphere. Table 3 .2 show s som e o f the broad general relationships betw een w aste category, cavity location and the h ydrogeological characteristics o f the site. The table should be interpreted w ith care because it on ly gives the ideas in a generalized and sim plified form . T he engineered barriers, the characteristics o f th e w astes and the actual con d ition s in th e geological environm ent can be o f such im portance that a rigorous generalized preclassification o f applicable disposal op tion s is n o t possib le. The decision relies essentia lly on a sa fety assessm ent based on specific local data. The loca tion o f the disposal facility m ay be decided by requirem ents for co -location w ith o ther facilities or by societa l considerations. In these cases tech n o logy m ust supply the necessary sa fety w hich the available form ations or prescribed location do n o t.

On the basis o f present experience, rock salt (h a lite) provides a p oten tia lly suitable disposal m edium for w aste categories II to V (Table 3 .1 ). M ost o ther form ations are su itable in th e absence o f significant groundw ater. Even in these cases grouting, w aste packaging, backfilling and standard m in ing practices for underground w ater m anagem ent m ay m ake a seem ingly unsu itab le site usable. H ow ever, under these con d ition s the necessary engineered barriers m ust be incorporated in to the requirem ents o f the operating licence and m ust be m ade part o f the safety assessm ent, i.e. be included in the consideration o f the release scenarios and con seq u en ce analyses.

A prelim inary evaluation o f the su itab ility o f ex isting cavities such as natural caves and m ines should take place at a relatively early phase in the consideration o f a rock cavity d isposal con cep t. T he ex isting cavities should be evaluated in relation to cavities w hich cou ld be excavated specially for w aste disposal purposes [15 ].

In studying ex istin g m ines and cavities, several aspects should be taken in to consideration . Inform ation concern ing subsurface con d ition s is best obtained from tunnels and excavations and so the subsurface con d ition s are w ell know n

(b) Man-made cavities

11


in the case o f an ex istin g m ine. M ine spaces form a com p lex netw ork o f tunnels and shafts and together w ith test b oreholes m ay be con n ected to the surface at m any points; th is m eans that w ater leakage in to the m ine spaces m ight be significant and cou ld be very d ifficu lt to prevent. For a recen tly disused m ine the loca l infrastructure m ay still be in tact and this cou ld obviate the n ecessity o f develop ing a n ew system and providing a n ew qualified w ork force. On the oth er hand, the industrial and o th er activ ities resulting from the presence o f the m ine m ay ham per the w aste disposal operation. M ines are o ften in geo log ica lly h eterogen eou s form ations that are fractured and thus o f reduced m echanical strength. It is lik ely that further ore m ight still be fou n d in the v icin ity o f existing m ines, and future exp lo ita tion m ight interfere w ith the w aste disposal operation. H ow ever, sim ultaneous operation o f the m ine and disposal site m ay be p ossib le w ith careful planning and m ay indeed have added advantages [16].

4. SAFETY ASSESSMENT

Safety assessm ent is on e o f the m ost im portant processes in the evaluation o f the poten tia l perform ance and im pacts o f a low - and in term ediate-level radioactive w aste disposal facility . T he aim o f such an assessm ent is to com pare the poten tia l con seq u en ces o f events w ith accep tab ility criteria. It should be based on the sa fety analysis o f the relevant factors, including calcu lation o f hazards associated w ith the im p lem entation o f th e disposal operation [17].

Safety assessm ents should be carried ou t for each phase o f the disposal program m e, starting w ith assessm ent o f the disposal con cep t and ending w ith assessm ent o f th e shu tdow n , sealing and post-sealing period. T hese assessm ents at the d ifferen t stages o f the disposal system develop m en t are o f a progressive nature, i.e. the sop h istication o f the m eth od s applied increases in parallel w ith the accuracy o f the site-specific and design-specific in form ation available. Thus the safety analysis perform ed at an early stage o f site se lection /in vestiga tion and o f con cep tu al design can be o f a generic character. Prelim inary sa fety analyses are required w hen the design stud ies are under w ay and site-specific data are available. In the n ex t step , detailed safety analyses are perform ed on the basis o f the results from detailed site investigations and data on final repository design. In all these analyses and sa fety assessm ents the disposal facility and its environm ent should be considered as a system .

Various classification schem es m ay be used for the subdivision o f safety analyses, bu t tw o m ajor com p on en ts should norm ally be included: scenario analysis and con seq u en ce analysis.

12


For the sa fety analysis it is generally necessary to use various m odels w hich q u an tify the relevant factors and the occurrence o f significant phenom ena. The relevant techniques [1 8 ] m ay be divided in to probabilistic analysis, determ in istic analysis, analog analysis, sensitiv ity and uncerta in ty analysis.

T he IA E A program m e on underground disposal o f radioactive w astes includes four d ocu m ents d irectly related to th e sa fety assessm ent. T hese describe the m eth od s available and in use for release and transport scenario analyses and con seq u en ce analyses, and discuss applications through exam ples o f sa fe ty analyses for generic repositories in d ifferen t h ost m edia. T hey consider the sa fety assessm ent for underground disposal in general, and sp ecifica lly for repositories in con tin en ta l geo log ica l form ations, in shallow ground and in rock cavities [4, 18—2 0].

C om parison o f the results o f these analyses and p oten tia l con seq u en ces w ith relevant accep tab ility criteria com p letes the sa fety assessm ent. Safety assessm ent and developm ent o f the repository are c lo se ly interrelated and feedback is necessary at each stage.

4 .1 . P R E -O PE R A T IO N A L SA FE T Y A SSESSM E N T

A prelim inary sa fety assessm ent or con cep t assessm ent should be carried ou t in the early phase o f the disposal program m e to dem onstrate in general term s the sa fety o f the disposal con cep t and ind icate any need for further research and developm ent.

For th is assessm ent a sa fety analysis should be carried o u t covering the fo llow in g topics:

— w aste typ e and form— characteristics o f repository— engineered barriers— effec ts on geosphere and biosphere.

A t th is early stage the relevant factors to be considered in the sa fety analysis are know n on ly in general term s. In m any cases im portant con clu sion s ab out the sa fety o f the proposed disposal con cep t can be drawn from th e prelim inary safety assessm ent, w hich m ay lead to a decision to proceed w ith the d isposal program m e or m ay dem onstrate the need for certain m od ifications.

Em phasis in the analysis should be p laced on the relevant geo log ica l, hydrogeological and geotech n ica l factors w hich w ill generally a ffect the site selection . H ow ever, it should be em phasized again th at in the sa fety analysis o f a selected site th e repository and its geo log ica l environm ent should be considered as one system . C onsequ en tly , it is necessary to have a good kn ow ledge and understanding o f all the com p on en ts and characteristics o f th e system — w aste co m p osition and

13


w aste form , barriers, structural m aterial, site-sp ecific h ydrogeolog ica l characteristics, and th e m echanism for and degree o f the in teraction o f sp ecific radionuclides w ith the site form ation in relation to m igration o f radionuclides to th e biosphere.

The safety analysis should provide su ffic ien t data to the regulatory authorities to enable decisions to be taken w ith respect to the accep tab ility o f a proposed site.It should also provide a basis for selection o f repository design and con struction procedure.

The designs for a repository are developed at the con cep tu al and prelim inary as w ell as as the final stage o f the d isposal planning program m e. The final design should be d eveloped on the basis o f the sa fety assessm ent o f a selected site.

The safety assessm ent o f the final design should be based on the analysis o f geolog ica l, hydrogeological and geotechn ica l factors in addition to all aspects related to the repository perform ance, con stru ction details, w aste characteristics, w aste handling and transport, repository sealing and surveillance after shutdow n.It should perm it a decision to be taken on th e start o f con stru ction o f the repository.

The assessm ent o f the con stru ction safety should be based on an analysis o f the m eth od s and procedures u sed , the p ertinent quality assurance program m es, and the relevant geological characteristics o f the repository h ost rock found as w ork proceeds.

During the construction period , changes in the design m ay have to be in troduced . Such changes m ay have considerable in flu en ce on the behaviour o f the repository. The sa fety o f th e repository should be under con tin u ou s review during developm ent w ork and if m ajor design changes are m ade a re-evaluation o f the previous sa fety assessm ent m ay have to be carried ou t. In princip le, any changes that are m ade m ust at least m aintain th e previous sa fety level.

R elevant observations during the con stru ction should be recorded, as they form im portant background m aterial for further updating o f the sa fety assessm ent.

During developm ent o f the repository, know ledge o f the factors used as input to the previous sa fety analyses is increased. B efore operation o f the repository begins the sa fety analysis should be verified on the basis o f th e actual design and any additional in form ation acquired, includ ing that derived from h o t testing. The sa fety assessm ent resulting from th is analysis w ill serve as a basis for establish ing the requirem ents relating to radioactive w astes to be d isposed o f in the repository.

4 .2 . O PE R A T IO N A L SA FE T Y A SSESSM EN T

A special safety assessm ent should be m ade for the operational phase o f the facility . This assessm ent should include all handling procedures and radiological p rotection requirem ents in th e repository above as w ell as b e lo w ground. It should

14


also consider potential risks for the operational crew and the public in the vicinity of the facility who might be exposed to radiation or radioactive releases.

Unforeseen events or situations can occur during the lifetime of the repository. Such situations might include, for example, unexpected behaviour of waste forms and non-anticipated changes in the geologic environment, the need to use the repository for types of waste other than those for which it was designed, or expansion of the repository in a manner not previously intended. Such situations may require new safety assessments to be performed. A special case is premature closure of the repository.

A repository for low- and intermediate-level wastes will ordinarily operate for a long period of of time. At the end of its industrial life, when emplacement operations have ceased, a new safety assessment has to be made to give guidance as to the extent to which equipment and service facilities should be maintained or operated. Special attention should be given to equipment which will be used later on during the sealing procedure.

4.3. POST-OPERATIONAL SAFETY ASSESSMENT

A final safety assessment has to be made before the rock cavity is sealed.This analysis should include all relevant knowledge accumulated during the operational period; the assessment should be seen as a final check that the assumptions made before starting the disposal operations are still valid. The assessment would also provide the basis for future use of any facilities above ground, storage of the information on the disposal activity, possible surveillance procedures, etc. If post-operational surveillance is carried out, a confirming safety analysis might have to be made before a decision is taken to discontinue it.

5. REGULATORY CONSIDERATIONS

Most countries would regulate waste disposal in rock cavities through licensing actions by a body whose purpose would be to review, certify and ensure the safety of all the stages of waste management. This regulatory body could either be one single national authority or a system of authorities designated by the government.

15


The IAEA has issued a document entitled “Development of Regulatory Procedures for the Disposal of Solid Radioactive Waste in Deep, Continental Formations” [21 ]. The basic principles for regulatory procedures contained in that publication are generally applicable to the disposal of low- and intermediate- level wastes in rock cavities. The present report covers only those aspects which are of direct concern for this latter disposal concept.

5.1. FUNCTIONS OF THE REGULATORY BODY

The functions of the regulatory body may be as follows:

(a) To develop regulations or issue guidance on the criteria to be applied in selecting the sites, in designing, constructing, commissioning, operating and shutting down and sealing the repository, and in determining the types of waste for which it may be used;

(b) To prescribe the information to be supplied at each stage by the implementing organization;

(c) To review the information provided and to assess its implications for: the safety of the public, both immediately and in the future; the safety of the work force; the environment; current and future land resource planning; the transport of waste to the site;

(d) To decide in the light of (c) above on the suitability of the site for radioactive waste disposal; on the types of waste for which it may be used; and on the acceptability of the design, the construction and the operating methods proposed;

(e) To decide on any conditions which may need to be imposed; for example, on operating methods, on the monitoring of surrounding areas and environmental pathways;

(f) To issue the relevant authorizations, licences and directions in conformity with national procedures;

(g) To inspect sites in order to verify compliance with the conditions of the licence, and in the event of any infringement to take the necessary action;

(h) To keep all licences under continuous review and to consider any amendments proposed by the operator which may be shown to be necessary in the light of experience;

(i) To initiate and carry through any action which it considers necessary to supplement the findings of studies conducted by the implementing organization;

G) To maintain contact with regulatory bodies in other countries and international organizations exercising similar responsibilities, and international organizations working in the same area.

16


5.2. REGULATORY REQUIREMENTS

Rock cavities suitable for the disposal of low- and intermediate-level radioactive wastes may already exist in the form of natural cavities or disused mines and civil constructions, or they may be specially excavated for the purpose. They may be located fairly near to the surface. The regulatory requirements for the repository would to a large degree depend on the nature of the cavity and of the wastes concerned.

Aspects to be taken into account in connection with the regulatory requirements of rock cavities include:

— health and safety— effects on the environment— land and resource use planning— repository construction (mining)— waste conditioning and transport documentation— inspection and enforcement— legal and institutional matters and liability.

The procedures established as regulatory requirements should indentify the duties and responsibilities of the implementing organization. The establishment of a repository will have to proceed through a number of defined steps, finally leading to operation and later to the shutdown and sealing of the facility. These steps or stages, e.g. site selection, site confirmation, design, construction and commissioning, may also be used as guidelines for the regulatory body in the designation of procedures which will end in final approval of the repository and issue of the operating licence.

The regulatory body should collect information about the development of the repository and should review the different stages. At the conclusion of certain steps the regulatory body will have to make a decision as to whether the development of the disposal facility should be allowed to proceed or not.

The regulatory body should at an early stage issue general regulatory requirements for the operational as well as the post-operational period of the repository, as such requirements may have important implications for the site selection and for the design and construction of the repository.

5.3. LICENSING

The licensing procedure may vary in different countries and one or several licences may be issued during the period preceding the granting of an operating licence. The stages will cover site selection, site confirmation, design and construction. Commissioning and operation will be covered by a separate licence,

17


which should also include certain requirements relating to the repository shutdown, sealing and surveillance.

' Certain aspects which should be specified by licensing include:

(a) The nature of the permitted wastes (such as chemical and physical properties) and the conditioning involved;

(b) Radioactivity limits, such as the quantities and specific activities of individual radionuclides;

(c) Specifications for the introduction of barrier or structural material if such materials form part of the waste disposal operation;

(d) The site and environmental monitoring and surveillance programme which the implementing organization has to comply with;

(e) Documentation for waste disposal operations including reports to the regulatory authority;

(f) Other conditions such as the power the regulatory bodies would possess to introduce necessary modifications into the terms and conditions of licences or to revoke or suspend licences should either action be judged appropriate.

It may be necessary to emphasize in the licensing documents that no matter how detailed the licensing instructions may be, it is the implementor who has the general responsibility for the safety of the disposal operation although this responsibility has to be taken over by the government at some later stage to be defined.

The necessary documentation should be specified in the operating licence and be based on the safety assessment. Documents required include those to identify each waste package and record its emplacement, a quality assurance plan, quality control and inspection reports, operational safety reports, etc.

5.4. REGULATORY ASPECTS OF OPERATION, SHUTDOWN AND SEALING

During operation, the regulatory authority should carry out inspections to verify that the implementing organization has acted according to the terms and conditions of the licence. The inspectors’ powers should include the right of entry, the right to examine records, and the right to take samples of wastes and environmental materials.

Certain requirements of importance for the shutdown of the repository should be included in the operating licence. Before shutdown the implications of these requirements should be re-evaluated by the regulatory body and additional requirements covering the period when the waste disposal activities cease, as well as the interval between shutdown and sealing of the repository, should be established.

18


5.5. POST-OPERATIONAL SURVEILLANCE

The rock cavity disposal concept does not place ultimate reliance on any continuing services after shutdown and sealing. Post-operational surveillance may occur for a limited time only and may be included in routine environmental surveillance programmes. The regulatory body would then need to establish the rules for such surveillance, bearinjg in mind that the responsibility for the site may be transferred to a new organization during the surveillance period.

After completion of the sealing operation a detailed report should be made describing the sealed facility. The report, together with records, should be kept and stored for the future.

6. REPOSITORY SITE SELECTION

Repository sites should be evaluated on the basis of geological and ecological information as well as societal considerations. This evaluation is performed in several stages, proceeding from generic to specific assessments. Sites found unsuitable for one waste category may be suitable for other categories or waste forms.

The selection of sites for waste disposal in rock cavities requires a knowledge of a number of disciplines. These include many branches of earth sciences, engineering, safety analysis, health physics, ecology, economics and the social sciences. The investigations will follow a detailed programme of theoretical, laboratory and field studies with significant interaction between the disciplines. Among the various factors to be considered in the siting of the repository, emphasis should be placed on the hydrogeological, seismological, geochemical and socio-economic aspects. It is important that information relevant to the investigations is given to officials and the public on local and national levels.

An idealized procedure for site selection is outlined in Table 6.1 together with some of the major activities involved in each stage. The table is a modified form of the schemes presented in Refs [22] and [23],

The investigations start with an identified need for the repository to fulfil safety requirements based on the type and quantities of wastes to be disposed of, and should result in the final selection of a site that has suitable characteristics. The four stages of this process are intended to be of general application but it may not prove feasible or necessary to move sequentially from Stage 1 to Stage 4. This may be the case if potential sites or areas may be selected by means other than a full site investigation programme, for example by administrative decisions or co-location requirements.

19


TABLE 6.1. IDEALIZED SEQUENCE OF ACTIVITIES FOR SITE SELECTION

SITE SELECTION PROCESS

Stages

Activities

1PLANNING AND GENERAL

STUDIES Objective: Develop overall

2REGIONAL EVALUATION

Objective: Select potential

3SITE IDENTIFICATION

Objective: Identify po

4SITE CONFIRMATION

Objective: Confirm acceptplans and criteria and review basic data

repository regions tential sites and existing mines and cavities

ability of identified site(s) and mines/cavities

Waste • Establish plans and • Modify and expand • Modify and expandmanagement timetable, and allocate plan as necessary plan as necessary

resources

• Define waste types, conditioning, quantities

• Establish overallobjectives of the reposi t/5

tory performance c

Host rock • Review site selection fcj • Select and inventory • Select host rocks for • Select specific hostcharacterization factors and identify 3 potential host rock investigation rock(s)

potential host rock CT1) types • Characterize • Characterize site(s) intypes e* • Characterize preliminary sites detail

eo potential areas

Investigation • Review data needs and wBO • Select specific site in • Expand site investi • Expand site investiga

technique site investigation vestigation techniques gation techniques tion techniques asselection techniques c as required required

Sel

ecti

on


Data • Secure access to available T3 • Prepare an inventory of • Perform inspections • Perform detailed QJ

acquisition records on existing C data on suitable existing of suitable cavities inspections in selectedcavities and mines >. cavities and mines and mines cavities and mines » • Licensing, design,

o C construction, operaRepository • Develop repository '55 • Develop conceptual • Develop preliminary • Develop detailed U. tion, shutdown,design concepts o

Q. repository designs repository designs repository designs surveillanceQC for potential host • Perform in situ • Continue site conO

rock types experiments firmation studiesc based on new data

Safety • Review/select safety o • Modify methodology as • Expand and modify • Expand and modifyassessment analysis methods; per r necessary; perform methodology as methodology as neces • Safety analysis on

form generic safety c safety analyses for necessary; perform sary; perform detailed specific site andanalysis and sensitivity Q different systems of safety analyses for safety analyses on on specific designanalysis natural and engineered specific systems of specific site(s) and on

barriers natural and engi specific design(s)neered barriers

Site • Establish guidelines • Identify areas according • Establish criteria forcharacterization, for area selection to guidelines for area site confirmationinvestigation, selectionidentification • Establish factors • Identify potential • Select favourable site(s)

for preliminary site site(s)selection

• Start investigation ofregional geologicalproperties importantfor site selection

Note: At each stage of the site investigations, societal, ecological and national legislative issues are considered and the regulatory body should be involved in accordance with national requirements.


Although the identification of potential sites in the general case will result from a broadly based investigation and screening process, there may be cases, particularly those involving existing mines or cavities, for which sufficient data are available and only detailed characterization and confirmation are required. Furthermore, the depth of the investigation at any one stage may depend on the waste types under consideration.

Precise criteria which would be generally applicable to repositories for low- and intermediate-level wastes cannot be formulated because of the large variation in the characteristics of the geological environment and of the conditioned wastes. Although each site must be considered on its own merits, it is possible to list some of the general factors governing the suitability of a repository:

(a) It should be possible to characterize the properties of the host rock in the vicinity of the repository to such an extent that the performance of the repository can be effectively predicted;

(b) The hydrogeological characteristics of the host rock and the groundwater regime of the surrounding geological environment should favour waste isolation;

(c) It would be an advantage if the host rock and/or the geological barriers can be used to retard the migration of radionuclides;

(d) The repository should be located at sufficient depth in the host rock so that the wastes will not be exposed to the biosphere until the radionuclides have decayed to insignificant levels;

(e) The repository should be constructed so as not to endanger the hydrogeological isolation of the wastes;

(f) The acceptability of a geological formation should also be based on the extent of its occurrence and its economic value.

Wastes containing significant amounts of radionuclides with long half- lives should be placed in formations for which a continuing regional geological stability is predicted.

The site selection should be undertaken in close connection with the work for the repository concept and design, and if necessary the introduction of engineered barriers should be taken into account.

6.1. PLANNING AND GENERAL STUDIES

The first stage (column 1, Table 6.1) is to study the disposal requirements of the national waste management programme. The needs and timing of the repository can then be planned and a site selection programme developed. From

22


a first overview, key decision points are defined, and the programme is subdivided into discrete investigations. Responsibilities for these investigations are defined.

As part of the first stage, the overall objectives of the repository performance are established. Site selection guidelines and procedures, including a methodology for safety analysis, are developed. Earth science factors to be investigated are established. Access to existing records on mines and cavities is secured. Selection of the main techniques for field and laboratory investigations is made. Engineering studies are carried out to produce a conceptual repository design integrating the results of the earth science studies.

6.2. REGIONAL EVALUATION

As the above steps are approaching completion, the regional evaluation stage (column 2, Table 6.1) is started. The objective of this stage is to select areas that have favourable characteristics for a repository and to reduce them to a few preferred areas for further study. This may be done largely with desk and remote sensing studies, supported by laboratory and reconnaissance field work. Activities include, among others, geological mapping, studies of topography and surface water systems, clarification of relevant socio-economic factors and the performance of safety analyses.

6.3. INVESTIGATIONS OF EXISTING MINES AND CAVITIES

In Stage 2 of the site selection process, an inventory of the existing mines and other subsurface excavations should be compiled with information on age, condition, drainage, geometry, access, etc. This information can be extracted from mining records, which in most countries have to be compiled in accordance with mining regulations [4]. If necessary, a supplementary field survey should be carried out at an early stage.

In general the data derived from mining records provide more relevant knowledge of a site than any other general survey, but the quality of the data may vary and a complete picture of the mine will generally not be obtained to the degree of accuracy and completeness that is required for a safety assessment for a radioactive waste repository.

The available data on existing mines, including their geological environments, can be used for identifying potentially suitable repository areas. Existing mines and rock cavities can also be utilized for different kinds of experimental investigations to demonstrate that the geological sites are suitable for repositories.

23


6.4. SITE IDENTIFICATION

The objective of this next stage (column 3, Table 6.1) is to select one or more potential sites for detailed investigations. The earth science studies carried out are generally similar to those in the previous stage but are more detailed and involve laboratory and field work (including drilling). Existing cavities and mines which are of interest are inspected in detail. Data are compiled and assessed on the following:

— earth science aspects (geological, hydrogeological, hydrological and geochemical), radionuclide sorption capacity, geotechnical and climatic features and seismicity and tectonic activity

— mining and technical aspects— capacity of the sites and prospects for extensions of existing cavities and

mines.

The investigations will include the collection of rock samples for laboratory testing of their petrological, mechanical and chemical properties. On the basis of the available earth science data and the concepts for repository design and engineered barriers, radionuclide transport models can be developed. Subsequently, an overall preliminary safety analysis can be applied to the sites under consideration. In addition, ecological and sociological studies are performed at a preliminary level. Site data are evaluated with respect to the waste management requirements.

6.5. SITE CONFIRMATION

As the potential sites are identified, site confirmation studies are conducted (column 4, Table 6.1). The objective of this stage is to check the validity of earlier studies and to confirm the suitability of the site(s). Specific details of the site and its environment are investigated through the use of laboratory, field, drilling and subsurface studies. Additional in situ studies (hydrogeological, geotechnical and geochemical) as well as migration tests on relevant radionuclides are performed at this stage. On the basis of these studies, detailed specifications for the engineering of the repository can be developed and a detailed safety analysis carried out. Site-specific data (in particular on the geological and hydrogeological conditions and on radionuclide migration) will be needed not only for performing a detailed safety analysis but also for completing, expanding or modifying the models or the methodology applied.

Ecological and societal evaluations are carried out in detail and safety analysis models are upgraded for the specific site(s). The results of the study are brought together and summarized and all safety aspects are considered in order

24


to get final confirmation of the site. Such an assessment summarizes all the important data, evaluations and conclusions for design and construction. Appropriate authorities are provided with this information to permit decisions to be made for final site selection and subsequent licensing.

During design, construction, operation, shutdown and perhaps also during sealing of the facility, additional site-specific data will be collected and some confirmation studies may be continued to support the safety analyses.

It must be emphasized that the confirmation studies on existing mines might differ in detail from those performed for specially excavated repository cavities. This type of investigation will be discussed in a related document [4].

7. REPOSITORY DESIGN, CONSTRUCTION AND COMMISSIONING

The design of a rock cavity for the disposal of radioactive wastes is determined by several considerations and must be related to the entire disposal system, including the types of waste, the type of cavity (i.e. specially excavated or disused mine) and the types of geological formation and host rock. The quality of the host rock, for example, will influence not only the design but also the importance of engineered barriers. In the disposal concept as specified, there can exist several design alternatives. These should be analysed in detail.A safety analysis (which takes into account the waste characteristics and the properties of the host rock) is useful as a guide for the design requirements to ensure that sufficient isolation of the wastes will be achieved during the hazardous lifetime.

Various engineering methods are available for limiting the release of radionuclides. The extent to which these should be employed can be finally assessed only when acceptable release rates for the different nuclides are given.

7.1. DESIGN CONSIDERATIONS

Important factors to be considered in connection with existing mines or specially excavated repositories are listed below.

(a) Waste characteristics

Physical, chemical, mechanical and radiological propertiesTotal amountShape, size and weight of individual waste containers

25


(b) Geology

Geological structure and properties of the host rock, such as deformability, strength and failure characteristics, in-situ stress in the rock mass, structure of the rock mass, permeability and sorption properties

Susceptibility of the rock to natural degradation from components in the wastes and engineered barriers

Groundwater pressure, chemistry and general flow pattern

(c) Cavity/repository characteristics

In the case of an existing mine, the stability, hydrology, usable volume andease of accessDepth of the repositoryGeometry and material properties of the engineered barriers Functional requirements of the emplacement, backfilling and sealing operationsCosts of excavation and of transport of rock and wastes

(d) Possible disturbances

Natural events such as earthquakes, erosion or flooding of the rock overburden, major changes in meteorological conditions Events caused by man such as engineering work in the vicinity of the repository (hydroelectric dams, roads, tunnels, etc.).

The form of the repository will be determined by these factors if the rock cavity is specially designed and constructed. Disused cavities built for other purposes (such as, for example, underground storage of other materials) may have to be modified to suit the needs of waste disposal. Disused mines or natural cavities may have to be extensively modified.

7.2. ENGINEERING METHODS TO IMPROVE ISOLATION OF THE WASTES

Isolation of the wastes can be enhanced by improvements to the waste packages (see Section 3.2), by construction of barriers between the wastes and the rock, and by modifications to the surrounding rock.

26


Handling of the wastes at the facility of origin and transport to the repository involve some degree of isolation. Any need to increase this isolation can be met either by improvements in the waste conditioning or by engineered barriers common to all wastes emplaced in a repository. An analysis of safety and costs will indicate which alternative is to be preferred in any particular case.

The main objective of engineered barriers around wastes is to isolate them from contact with groundwater. Secondary objectives may be to stabilize the rock and to provide radiation protection for the personnel during emplacement of the wastes, backfilling, and final sealing of the repository. The need for such engineered barriers depends on the properties of the wastes and the host rock, and also on the operational procedures adopted.

Various materials and combinations of materials can be used in barriers serving to isolate the wastes from groundwater in the surrounding rock. Backfilling of the empty space in a rock cavity also serves the purpose of supporting the walls of the cavity after the repository is sealed. Backfilling (e.g. by the use of sand and gravel) additionally serves to minimize the open space in the cavern. Appropriate selection of the material for backfilling (e.g. clay) may improve the waste isolation by reducing any flow of groundwater, by allowing sorption of radionuclides which may diffuse through the barriers via pore water in the backfill, and by reducing the corrosion of the package materials.

The expertise developed in conventional mining methods of backfilling should be utilized and the capacity of backfilling materials for reducing radionuclide migration must be determined. A combination of materials may serve multiple complementary functions. A concrete barrier stabilizes the disposal cavity and reduces the flow of water through the backfill. A backfill which is plastic and swells in water provides an extra barrier against water flow if cracks should develop in the concrete.

Water-impermeable coatings may be applied to concrete constructions but careful consideration should be given to the longevity of coating materials in connection with the long-term effects of a water- and gas-tight seal around the wastes. In cases where radiolysis and chemical interactions between waste material and water may occur, gases might be produced. The production and characteristics of such gases and their potential long-term accumulation has to be taken into consideration.

Improvement of the isolation properties of the surrounding rock might not be necessary in relatively impermeable strata such as rock salt formations. In rocks with local discontinuities, e.g. crystalline rocks, an improvement may be achieved by injection of cement, clay or other suitable materials.

27


7.3. FACILITIES AT THE SITE

site:

— reception facility with lifting and handling equipment— buffer storage for the wastes— equipment for internal transport of the wastes on the site— equipment for inspection, quality control and monitoring of radioactivity

of the wastes— repackaging facility— the disposal cavity itself— backfilling equipment— office, laboratory and workshop buildings— monitoring equipment for environmental surveillance— equipment for conventional industrial security and for radiological protection— decontamination facilities, if necessary— facilities for continued excavation if these are required in the design.

Reception facilities. The wastes will be carried to the repository on a boat, train or truck with appropriate travel routes into and within the repository site. The transport containers, determined by (suited to) the carrier, provide for safe transport and handling of the wastes. Precautionary measures are, however, required for the unloading of these transport containers. Shielded trucks or remotely controlled lifting cranes may have to be provided for transport outside the containers. The reception facility should have equipment for the measurement and control of radioactivity and the quality assessment of waste packages, decontamination facilities for vehicles and containers and equipment for registration of data on the wastes received. The equipment should be designed for rapid unloading operations so as to decrease the hold-up time of the transport vehicles and minimize personnel exposure. One or more buffer storage facilities may Ije needed, depending on the material flow in the handling and transport scheme at the disposal site.

Facilities fo r handling and conditioning o f wastes. Handling in connection with the receipt of wastes and operation of the facility is discussed above and in Section 7.5. Final conditioning of wastes may be carried out at the place of origin, at a separate conditioning site or at the disposal site. In any case equipment and facilities for repackaging will be needed at the disposal site for the handling of packages received in a damaged condition. The first two alternatives above are generally to be preferred since waste conditioning is a reasonably small effort at most nuclear facilities whereas it is a significant addition to the specialized functions at the disposal site. The selection of the conditioning

T h e fo llo w in g fac ilitie s w ill n o rm a lly have to b e p ro v id ed a t th e re p o s ito ry

28


site will also be influenced by additional considerations, such as the environmental impact of radioactive discharge from the conditioning activities, e.g. incineration of combustible wastes.

Other facilities. A buffer storage for solid wastes is a largely conventional storage facility with conventional requirements. Fire protection, floor drainage, ventilation, radiation shielding and radiation area access protection must, however, be provided to conform with the appropriate national regulations.

Facilities will also be required for ventilation, underground transport and emplacement of the wastes. Supporting services, similar to those for buffer storage, must be provided for the period before the repository is sealed.

7.4. REPOSITORY CONSTRUCTION

The excavation work should be undertaken in such a way that the natural barrier quality of the rock is preserved as far as is practical when the repository is being constructed. The work will provide opportunities for gaining further knowledge of the host rock characteristics and the effect of excavation on them. It is important, therefore, that the site investigator and designer closely follow the development work. Appropriate rock investigation techniques should be employed [4].

It must be ascertained whether the rock characteristics vary beyond the limits assumed in the safety analysis. If the limits are exceeded, further evaluation will be required. The procedure for implementing any necessary changes in the design would probably be covered in the construction licence or might require separate regulatory action.

The technical requirements on both the engineered structures and the surrounding rock that must be met during the subsequent phases have to be determined during the construction phase. Corrective action will be difficult once wastes are emplaced in the disposal cavity. Thus, stringent quality control must be applied throughout to construction materials and procedures.

The construction and operation phases may overlap. A careful evaluation is, however, required before permission is given to start sealing operations in filled parts of the repository while excavation work is continuing in other parts.

7.5. COMMISSIONING

Commissioning as here described includes all tests and verifications that are needed to confirm that the assumptions used in the safety analysis are met in the repository as built, and that the operations and sealing procedures can

29


be executed as specified. Such tests and verifications may have to be made at different stages of the construction because engineered structures might prevent access to vital parts of the repository once they have been installed. The possibility of verification after some wastes have been emplaced, i.e. after a hot-test period, is an option that could be considered.

Commissioning will include functional tests on all the facilities listed in Section 7.3 and include verification by quality assurance documentation that the quality requirements set forth in the construction licence have been met.

8. OPERATION OF THE REPOSITORY

8.1. WASTE RECEPTION

Unloading of the wastes from the transport container requires appropriate radiation protection facilities. In particular, intermediate-level wastes, unless they have proper extra shielding, need to be handled by means of a shielded vehicle or remotely operated cranes.

Checks must be made on waste package identification markings. It is also necessary to check for external contamination as well as for possible damage to the waste packages during transport.

An appropriate scheme for quality assurance has to be established. This implies control of quality in the various stages such as conditioning and in some form also at the disposal Site in order to assure the acceptability of the wastes for disposal. Validation of waste records including monitoring and sampling of wastes may be a necessary part of quality control at the repository. If conditioning is performed at the disposal site, quality control consists of checking the conformity between operating manuals and actual practices.

For the sake of safety and operational convenience, buffer storage should be provided to smooth out the handling of wastes between receipt and disposal.

Conditioning of wastes as a regular operation can be carried out at any preferred site. Some conditioning may, nevertheless, be called for at the disposal facility in the form of repackaging in the event of damage during transport or for the emplacement of conditioned wastes in additional containers. This repackaging may be required as it may not be acceptable either to emplace the wastes in the repository in a damaged condition or to return them to the point of origin. The operator of the disposal facility must therefore have access to the necessary material and personnel resources to cope with such situations.

30


8.2. DISPOSAL OPERATIONS

Disposal operations involve handling of waste packages and their emplacement in the repository. The emplacement of intermediate-level wastes will normally require remote handling equipment or shielded vehicles unless the wastes are contained in disposable shielding. The emplacement sequence should be carefully planned so that the filling of the repository space can proceed in an appropriate manner to allow for any increase in radiation dose rate.

The possibilities of using packages producing low dose rates to shield packages with higher fields and of introducing backfilling as wastes are emplaced should be considered.

Special attention may have to be given to the emplacement pattern of the waste packages if the repository design includes an engineered barrier to be installed after the termination of the waste emplacement operation. This installation work must not be hampered by excessive radiation in the work area.

It might be advisable to backfill or grout the waste pile layer by layer in order to stabilize the pile and reduce radiation. The location of each waste package, identified by its marking, should in any case be recorded in the repository waste register and in the central waste register if such has been established.

Remote inspection equipment must be available in case a waste package is damaged during handling. Instructions should be included in the operations manual on how to deal with this and other types of abnormal event.

8.3. OPERATIONAL SAFETY

Radiation protection. On-site monitoring of radiation dose rates is needed in areas of the repository where wastes are handled or stored. Personnel monitoring should comply with the radiation protection rules and limits should be established by the appropriate regulatory body.

Site contamination can occur only if waste packages are damaged during handling and it could be spread via the ventilation system. The need for on-site monitoring of contamination is thus limited to defined areas and situations.

Conventional safety. Operation of the repository and related facilities should comply with existing industrial and mine safety regulations.

Security aspects. Appropriate security measures should be taken to control access to the disposal site and avoid removal of radioactive and other materials. Access to the repository site should be restricted to authorized persons. Fences and supervised gates should be provided to prevent other persons from entering.

31


Operational limits. Limits on the total amounts of radionuclides disposed of in the repository will normally be specified in the operating licence on the basis of the facility safety assessment.

To ensure operational safety and the integrity of the waste form, limits should also be imposed on non-radioactive components of the wastes. These limits should apply to areas where wastes are handled, stored or disposed of and should relate to materials which are flammable, chemically aggressive or biologically hazardous, etc., or which may cause degradation of the waste packages.

8.4. MONITORING

On-site monitoring. Monitoring of possible radioactive releases from the repository site during operation is needed to assure compliance with release limits specified in the operating licence.

It may be important to monitor conditions in the host rock around and above the repository since if they change, this may lead to a degradation of the isolating and containment function of the barrier.

Examples of such monitoring may be seismographic recordings of rock bursts in the host rock, precision measurement of subsidence of the ground surface above the repository or analysis of the groundwater chemistry upstream and downstream of the repository in or around the host rock.

Such monitoring should be started during the site confirmation period and carried on during the operational phase. It will form a background and a baseline for characterization of the site and should continue as long as prescribed by the relevant authority.

Off-site monitoring. Off-site monitoring should not be necessary, as on-site monitoring should be sufficient to detect and quantify any releases. However, there may be off-site monitoring by other bodies as part of a national environmental monitoring network.

8.5. ADMINISTRATIVE CONSIDERATIONS

Organizations. The previous paragraphs have dealt with the various steps leading to disposal of low- and intermediate-level wastes. Though not a definite requirement, it would be advantageous if all the operations mentioned could be handled by one organization. In such a case the implementing responsibility could lie in a single organization.

32


In any case, during the operation of the facility, there should be a well- defined separation between the implementing organization and the regulatory body. All implementing work should be carried out according to established criteria and under the control of the appropriate regulatory body. However, it is important to realize that the long-term responsibility, extending to many decades or centuries, will always have to be taken over by the government concerned.

Tasks. It has to be established that the disposal of the wastes is being performed according to the operations manual for the repository. In relation to the future shutdown of the repository and the time after shutdown, the following tasks have to be taken into consideration during the operational phase: backfilling as waste is emplaced; allowance for financing the work to be done in later stages; preparation of records of the wastes stored in the repository including nuclide inventory, type of conditioning, characterization of the engineered barriers, drawings of the storage and records of any monitoring.

9. SHUTDOWN AND SEALING

9.1. GENERAL AND INSTITUTIONAL ASPECTS

Generally, an underground disposal site for radioactive wastes will have a limited operating lifetime. It will normally be licensed for the disposal of a limited amount of waste. There may be plans for possible later extension of the cavities, but the possibility of such an extension depends on local circumstances.

The procedures for a future shutdown should be planned for at the design phase of the disposal site, even though it may be difficult to fix an exact date.It is also possible that the site may have to be closed prematurely as a result of unforeseen events.

With shutdown and sealing the repository undergoes a transition from the intermediate stage of controlled emplacement to the final stage of disposal.

Shutdown and sealing of a repository are steps of great importance. With sealing, the possibilities of control and of intervention are greatly reduced. Therefore, a thorough inspection of the repository is necessary before sealing in order to determine any defects or weaknesses which have to be corrected.

The information gathered would be incorporated into a new review and updating of the safety assessment.

33


The authorization to seal has to be taken by an appropriate organization in the regulatory body; in some countries it may be the government itself.There remains the task of controlling future mining operations and, if deemed necessary, of performing limited surveillance of the repository. It may prove appropriate that any remaining tasks and responsibilities are transferred from the implementing organization to a governmental organization, perhaps associated with the regulatory body. In any case, long-term financial arrangements should be established at an early stage.

9.2. CONDITIONS FOR SHUTDOWN

Prior to authorizing sealing of the repository, the regulatory body will normally check that the following conditions are fulfilled:

(a) The waste emplacement operations have been performed in a manner which meets the intent of the operating licence issued to the implementing organization;

(b) The results of the updated safety analysis predict satisfactory behaviour of the sealed repository in both the short and the long term;

(c) Records of the stored wastes and of site monitoring results are available.

9.3. MAJOR STEPS IN SHUTDOWN AND SEALING

Shutdown and sealing are performed in different stages, which may take place either with or without delay. The most important steps are the following:

(a) Sealing of the repository cavity. Before sealing, the space between waste containers and cavity could be backfilled with an appropriate buffer material. This may have been done progressively during operations;

(b) Backfilling and sealing of access tunnels and shafts;(c) Removal of surface buildings and installations and restoration of site if

required.

9.4. POST-OPERATIONAL SAFETY

The post-operational safety in the long term is governed mainly by the geological barriers, complemented by engineered barriers. Governments may carry out radiological surveillance of the site and its surroundings in order to provide assurance that the repository is performing according to the predictions

3 4


of the safety analysis. This surveillance can be done by the organization mentioned in Section 9.1 above.

In order to make the information available in the future, governments must keep all records of the wastes and of the repository itself. This can be done at the site, within the governmental organization or within the framework of international organizations.

Post-sealing interventions. In principle, a sealed repository will not be reopened. Approval for reopening must be given by the appropriate regulatory body and must be preceded by a careful weighing of the advantages and disadvantages of such an action.

Re-use o f the site. After the removal of the buildings, the appropriate authorities may for some time restrict use of the site. In particular, they may restrict subsurface activities. After a certain time, the restrictions will be reduced. On the basis of the repository records, the competent authorities for mining and land planning should control and if necessary assess and/or license all detrimental surface and subsurface activities in the region of the repository such as mining, drilling and excavations.

REFERENCES

[ 1 ] INTERNATIONAL ATOMIC ENERGY AGENCY, Underground Disposal o f Radioactive Wastes, Basic Guidance, Safety Series No. 54, IAEA, Vienna (1981).

[2] INTERNATIONAL ATOMIC ENERGY AGENCY, Basic Safety Standards for Radiation P rotection-1982 Edition, Safety Series No. 9, IAEA, Vienna (1982).

[3] INTERNATIONAL ATOMIC ENERGY AGENCY, Principles for Establishing Limits fo r the Release o f Radioactive Materials in to the Environm ent, Safety Series No. 45,IAEA, Vienna (1978).

[4] INTERNATIONAL ATOMIC ENERGY AGENCY, Site Investigations, Design, C onstruction, O peration, Shutdow n and Surveillance of Repositories fo r Low- and Interm ediate-Level Solid Radioactive Wastes in R ock Cavities, Safety Series, IAEA, Vienna (in preparation).

[5] Management o f A lpha-Contam inated Wastes (Proc. IAEA/CEC Symp. Vienna, 1980),IAEA, Vienna (1981).

[6] Management o f Radioactive Wastes from the Nuclear Fuel Cycle (Proc. IAEA/NEA Symp. Vienna, 1976), IAEA, Vienna (1976).

[7] INTERNATIONAL ATOMIC ENERGY AGENCY, Site Selection Factors fo r R epositories o f Solid High-Level and Alpha-Bearing Wastes in Geological Form ations, Technical R eports Series No. 177, IAEA, Vienna (1977).

35


Underground Disposal o f Radioactive Wastes (Proc. IAEA/NEA Symp. O taniem i, 1979), IAEA, Vienna (1980).INTERNATIONAL ATOMIC ENERGY AGENCY, C onditioning of Low- and Interm ediate- Level Radioactive Wastes, Technical R eports Series No. 222, IAEA, Vienna (1983). INTERNATIONAL ATOMIC ENERGY AGENCY, T reatm ent o f Low- and Interm ediate- Level Solid Radioactive Wastes, Technical Reports Series No. 223, IAEA, Vienna (1983). T reatm ent, C onditioning and Storage o f Solid Alpha-Bearing Waste and Cladding Hulls (Proc. Tech. NEA/IAEA Sem. Paris, 1977), OECD, Paris (1978).On-Site Management o f Power R eactor Wastes (Proc. NEA/IAEA Symp. Zurich, 1979), OECD, Paris (1979).VARASKOVITCH, J.M., W OLTALANDER, W.J., “ Storage o f tritium in m etal hydrides” , Metal-Hydrogen Systems, Proc. Symp. Miami, 1981.BERGMAN, S.M. (Ed.), in Subsurface Space (Proc. Symp. Stockholm , 1980), Pergamon Press, O xford (1980).NIINI, H., HOLPAINEN, P., in Subsurface Space (Proc. Symp. Stockholm , 1980),Pergamon Press, O xford (1980) 949.SCOTESE, T .R ., DAEMEN, J.K ., WRIGHT, S.A., in Waste Management ’81 (Proc. ANS Topical Meeting Tucson, 1981), Arizona Board of Regents (1981).WOOD, D.E., in Waste M anagement ’80 (Proc. ANS Symp. Tucson, 1980), Arizona Board o f Regents (1980).INTERNATIONAL ATOMIC ENERGY AGENCY, Concepts and Exam ples o f Safety Analyses for Radioactive Waste Depositories in Shallow G round, Safety Series, IAEA, Vienna (in preparation).INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Assessment for the Underground Disposal o f Radioactive Wastes, Safety Series No. 56, IAEA, Vienna (1981). INTERNATIONAL ATOMIC ENERGY AGENCY, Concepts and Exam ples o f Safety Analyses fo r Radioactive Waste R epositories in C ontinental Geological Form ations,Safety Series, IAEA, Vienna (in press).INTERNATIONAL ATOMIC ENERGY AGENCY, Developm ent o f Regulatory Procedures for the Disposal o f Solid Radioactive Waste in Deep, C ontinental Form ations, Safety Series No. 51, IAEA, Vienna (1980).INTERNATIONAL ATOMIC ENERGY AGENCY, Site Investigations for Repositories for Solid Radioactive Wastes in Deep C ontinental Geological Form ations, Technical R eports Series No. 215, IAEA, Vienna (1982).INTERNATIONAL ATOMIC ENERGY AGENCY, Site Investigations for R epositories for Solid Radioactive Wastes in Shallow G round, Technical R eports Series No. 216, IAEA, Vienna (1982).


A n n ex I

SYNOPSIS OF NATIONAL ACTIVITIES ON ROCK CAVITY DISPOSAL CONCEPTS

Country Host rock(s) Type of cavity State of the conceptTypes3 and categories of wastes disposed of and their conditioning

Basicreference

CANADA Crystalline rock (e.g. granite)

Mined cavity Conceptual design, research studies

LLW and ILW, solidified and stabilized (II, III, IV, V)

[1]

CZECHOSLOVAKIA (a) Limestone

(b) Limestone

(a) Abandoned mine gallery (a) In operation1959-1963

(b) Abandoned underground (b) In operation 1964- quarry

(a) Solid wastes from isotope users (V)

(b) Solid and solidified wastes from research and isotope users (IV, V)

[2]

FINLAND Crystalline rock granite, gneiss

Specially excavated repository

Preliminary site and concept investigations

Reactor wastes, cementation, bituminization — 200 L steel drums, 1 m3 concrete drums (IV, V)

[3]

GERMANDEMOCRATICREPUBLIC

Rock salt (dome) Abandoned salt mine In operation Solid and solidified LLW and ILW (IV, V)

[4]


A n n ex I (c o n t.)

Country Host rock(s) Type of cavity State of the conceptTypesa and categories of wastes disposed of and their conditioning

Basicreference

GERMANY, FEDERAL REPUBLIC OF

(a) Rock salt (dome) (a) Specially excavated repository

(a) Site investigation (a) Solid and solidified LLW (III, IV) and ILW (II, IV)b

[5, 6]

(b) Rock salt (dome) (b) Disused underground salt mine, mining slopes and chambers

(b) In operation1967—78 as pilot repository, since then licensing under way

(b) Solid and solidified LLW (V) and ILW (II, IV) in steel drums and containers1*

[7 -9 ]

(c) Oolithic limestone (c) Disused iron ore mine, mining galleries

(c) Site investigation (c) Solid and solidified LLW (V) and decommissioning wastes (II, III, IV, V) in steel drums and containers^

[10, 11]

SPAIN (a) Pegmatites

(b) Other igneous rocks, rock salt

(a) Abandoned mine

(b) Rock mass

(a) In operation

(b) Under investigation

(a) Solid wastes in drums (IV, V)

[12]

SWEDEN Hard rock Specially excavated cavity Planning stage, site selected

Reactor wastes (IV, V), conditioned by cementation, bituminization, compaction

[13]


Country Host rock(s) Type of cavity State of the conceptTypes3 and categories of wastes disposed of and their conditioning

Basicreference

SWITZERLAND Anhydrite, clay, marl, crystalline rock, calcareous formations above water table

Civil engineered cavities(a) near surface(b) at least 200 m

overburden

Preliminary projects fOT

facilities finished, screening for detailed site investigations in process

(a) IV, V(b) II, III, IV

Mainly concrete conditioning

[14]

UNITED KINGDOM (a) Sedimentary rocks (a) Specially excavated cavities

(a) Preliminary drilling (a) II [15]

(b) Sedimenary or hard rock

(b) Natural and existing cavities

(b) Site assessment (b) III, IV [16]

UNITED STATES OF AMERICA

All rocks in initial study study

Specially excavated cavities0

Preliminary study All types of low- intermediate level wastes and conditioning are considered in initial study^

[17, 18]

YUGOSLAVIA Sedimentary rocks Natural or artificial General survey Low-intermediate level reactor wastes conditioned by volume reduction (II, III, IV)

3 HLW: High-level wastes.ILW: Intermediate-level wastes.LLW: Low-level wastes.

k The use of the various repositories for the disposal of different waste types is subject to licensing by the regulatory bodies. The use of aspecially excavated repository for HLW-disposal is the subject of an extensive research and development programme.

c An attem pt has been made to utilize an abandoned salt mine for institutional wastes.^ Transuranic content must be less than 10 nCi/g for disposal.


R E F E R E N C E S T O A N N E X I

[1 ] DIXON, D.F., Strategy for the Disposal o f Low- and Interm ediate-Level Radwastes in Canada, Second CNS Conf. O ttaw a, June 1981.

[2] DLOUHY, Z., e t al., “ Disposal o f low- and interm ediate-level waste in Czechoslovakia” , U nderground Disposal o f Radioactive Wastes (Proc. IAEA/NEA Symp. O taniem i, 1979) Vol. 1, IAEA, Vienna (1980) 209.

[3] Management o f Radioactive Waste from Finnish Nuclear Power Plants, R eport Im atran Voima, OY and TVO Power Companies, Helsinki (1980).

[4] CMEA Procedure for Study o f the Sanitary, Hydrological and Radiological Bases for Safety in the Disposal o f Radioactive Waste in Salt Form ations, Berlin (1974).

[5] KUEHN, K„ RANDL, R.P., ROETHEMEYER, H„ “ The Federal Republic o f G erm any’s program m e for the disposal o f radioactive w aste” , Underground Disposal o f Radioactive Wastes (Proc. IAEA/NEA Symp. Otaniem i, 1979) Vol. 1, IAEA, Vienna (1980) 65.

[6] ROETHEMEYER, H., “ Site Investigations and conceptual design fo r the repository in the nuclear ‘Entsorgungszentrum ’ o f the Federal Republic o f G erm any” , Underground Disposal o f Radioactive Wastes (Proc. IAEA/NEA Symp. Otaniem i, 1979) Vol. 1, IAEA/Vienna (1980) 297.

[7 ] ALBRECHT, E., Die Tieflagerung radioaktiver Abfalle in Salzform ationen der Bundes- republik D eutschland, Tatsachen iiber Kernenergie, E. Munich (Hrsg.), Essen, Verlag G irardet E T V (1980).

[8] SALANDER, C., e t al., Interdiscip. Sci. Rev. 5 4 (1980) 292.[9] STIPPLER, R., KLEIMANN, H., Strahlenschutz und Um gebungsiiberwachung bei der

Lagerung von radioaktiven Abfallen in einem Salzbergwerk, 7, IRPA -Regionalkongress/13, FS-Jahrestagung 1979, Bericht FS-79-20-T, 261.

[10] BREWITZ, W., LOESCHHORN, U., “ Geoscientific investigations in the abandoned iron ore mine Konrad for safe disposal o f certain radioactive waste categories” , U nderground Disposal o f Radioactive Wastes (Proc. IAEA/NEA Symp. O taniem i, 1979) Vol. 2, IAEA, Vienna (1980) 89.

[11] BREWITZ, W. (Ed.), F + E Programm zur EignungsprUfung der Schachtanlage Konrad fur die Einlagerung radioaktiver Abfalle - Zusamm enfassender Zwischenbericht,GSF-T 114, Braunschweig (1980).

[12] LOPEZ-PEREZ, B., MARTINEZ, A., “ Experiencia adquirida y tecnologi'a desarTollada en la JE N (Espana) en la gestion de desechos radioactivos” , M anagement o f Radiactive Wastes from the Nuclear Fuel Cycle (Proc. IAEA/NEA Symp. Vienna, 1976) Vol. 1,IAEA, Vienna (1976) 23.

[13] DEVELL, L., e t al., Central Storage for Low- and Medium-Level Wastes - Conceptual Design, Siting and Safety Study, R eport Prav. 1.29, N ational Council for Radioactive Waste, Stockholm (1980).

[14] NAGRA Technical R eports 80 - 01 and 80 - 03, NAGRA, Baden (1980).[15] EEC R eport (to be published).[16] IGS R eport (to be published).[17] KUECK, P.H., WACKS, M.E., “ Alternatives to shallow land burial” , Waste M anagement ’80

(Proc. ANS Symp. Tucson, 1980), Arizona Board o f Regents (1980).[18] A Classification System for Radioactive Waste Disposal — What Waste Goes Where? ,

US Nuclear Regulatory Commission, R eport NUREG 0456 (1978).

4 0


DRAFTING AND REVIEWING BODIES

LIST OF PARTICIPANTS

Annex II

1. Consultants’ Meeting to prepare working draft, Stockholm, Sweden, 16-19 June 1980

SWEDEN

Rydell, N.

Larsson, A.

National Council for Radioactive Waste, Box 5864, S-l 0248 Stockholm

Swedish Nuclear Pow er Inspectorate,PO Box 27106, S-l 0252 Stockholm

SWITZERLAND

Luthi, H.R. Office federal de l’econom ie energetique, Kapellenstrasse 14, CH-3001 Bern

ORGANIZATION

INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)

Heinonen, J.U. (Scientific Secretary)

Division o f Nuclear Safety and Environm ental Protection,

IAEA, PO Box 100, A-1400 Vienna, Austria

2. Technical Committee, Vienna, 13—17 October 1980

CANADA

Dixon, D.F. Chalk River Nuclear Laboratories, A tom ic Energy of Canada Ltd., Chalk River, Ontario K0J 1 JO

CZECHOSLOVAKIA

Malasek, E.(Chairm an)

Czechoslovak A tom ic Energy Commission, Slezska 9, 120 29 Prague 2

41


FINLAND

Peltonen, E.

Gardemeister, R.

Harkonen, H.

Ruokola, E.

Technical Research Centre of Finland, Vuorimiehentie 5, SF-02150 Espoo 15

Imatra Power Company,PL 138, SF-00101 Helsinki 10

TVO Power Company,Kutojantie 8, SF-02630 Espoo 63

Institute o f Radiation Protection,PO Box 268, SF-00101 Helsinki 10

FRANCE

Farges, L. Agence Nationale pour la Gestion des Dechets Radioactifs (ANDRA),

2 9 -3 3 rue de la Federation, F-75015 Paris

GERMAN DEMOCRATIC REPUBLIC

Runge, K. National Board on Nuclear Safety and Radiation Protection,

Waldowallee 117, DDR-1155 Berlin


Brewitz, W. Institut fur Tieflagerung,Gesellschaft fur Strahlen- und Umweltforschung mbH, Berliner Strasse 2, D-3392 Clausthal-Zellerfeld

SPAIN

Sanchez, J. Division de Almacenamiento y Residuos Radioactivos, Junta de Energi'a Nuclear,Ciudad Universitaria, Madrid 3

SWEDEN

Larsson, A. Swedish Nuclear Power Inspectorate, PO Box 27106, S-10252 Stockholm

4 2


S W IT Z E R L A N D

Nold, A. Societe cooperative nationale pour l’entreposage de dechets radioactifs (NAGRA),

Parkstrasse 23, CH-5401 Baden

UNITED KINGDOM

Hudson, J. Building Research Establishment, Building Research Station, Garston, Watford WD2 7JR


Wacks, M.E. Dept, of Nuclear and Energy Engineering, University o f Arizona,Tucson, Arizona 85721

YUGOSLAVIA

Despotovic, R.

Jancovic, O.

Pirs, M.

Rudjer Boskovic Institute,PO Box 1016, 41001 Zagreb

Boris Kidric Institute of Nuclear Sciences, Box 522, 1101 Vinca-Belgrade

Jozef Stefan Institute,PO Box 199, 61001 Ljubljana

ORGANIZATION



Division of Nuclear Fuel Cycle,IAEA, PO Box 100, A-1400 Vienna, Austria

3. Advisory Group, Madrid, Spain, 31 August-4 September 1981

CANADA

Dixon, D.F. Chalk River Nuclear Laboratories, Atomic Energy of Canada Ltd., Chalk River, Ontario K0J 1J0

4 3


C A N A D A (c o n t .)

Poliscuk, V. Atomic Energy Control Board, 270 Albert Street,PO Box 1046, Ottawa KIP 5S9

CZECHOSLOVAKIA

Malasek, E. (Chairm an)

Czechoslovak Atomic Energy Commission, Slezska 9, Prague 2

FINLAND

Vaisanen, S.

Heinonen, O.

Institute o f Radiation Protection,PO Box 268, SF-00101 Helsinki 10

Technical Research Centre o f Finland, Vuorimiehentie 5, SF-021S0 Espoo 15

FRANCE

Farges, L. Agence Nationale pour la Gestion des Dechets Radioactifs (ANDRA),

29—33 rue de la Federation, F -75015 Paris


Runge, K. National Board o f Nuclear Safety and Radiation Protection,



Brewitz, W. Institut fur Tieflagerung,Gesellschaft fur Strahlen- und Umweltforschung mbH, Berliner Strasse 2, D-3392-Clausthal-Zellerfeld

SPAIN

Sanchez, J. Division de Almacenamiento y Residuos Radioactivos, Junta de Energia Nuclear,Ciudad Universitaria, Madrid 3

44


Cabanas, F. Junta de Energi'a Nuclear, Ciudad Universitaria, Madrid 3

SWEDEN

Larsson, A. Swedisch Nuclear Power Inspectorate, PO Box 27106, S-10252 Stockholm

SWITZERLAND

Niederer, U. Division pour la securite des installations nucleaires, Office federal de l ’economie energetique,CH-5303 Wiirenlingen

UNITED KINGDOM

Hudson, J.

Williams, G.M.

Building Research Establishment, Building Research Station, Garston, Watford WD2 7JR

Institute o f Geological Sciences, Exhibition Road,London SW7 2DE


Wacks, M.E. Dept, o f Nuclear and Energy Engineering, University o f Arizona,Tucson, Arizona 85721

YUGOSLAVIA

Despotovic, R. Rudjer Boskovic Institute, PO Box 1016 ,41001 Zagreb

ORGANIZATION



Divison of Nuclear Fuel Cycle,IAEA, PO Box 100, A-1400, Vienna, Austria

45


4. Consultants’ Meeting, Vienna, 7-11 June 1981

CZECHOSLOVAKIA

Malasek, E. Czechoslovak Atomic Energy Commission, Slezska 9, 12029 Prague 2


Wacks, M.E. Dept, o f Nuclear and Energy Engineering, University o f Arizona,Tucson, Arizona 85721

ORGANIZATION



Division of Nuclear Fuel Cycle,IAEA, PO Box 100, A-1400 Vienna, Austria

5. Technical Review Committee on Underground Disposal of Radioactive Wastes, Vienna, 2—6 November 1981

ARGENTINA

de Beninson, A.M. Comision National de Energia Atomica, Avenida Libertador 8250, Buenos Aires 1429

BELGIUM

Heremans, R. Stockage geologique du CEN/SCK, Centre d’etude de l’energie nucleaire, Boeretang 200, B-2400 Mol-Donk

CANADA

Mayman, S.A. Whiteshell Nuclear Research Establishment, Atomic Energy of Canada Ltd.,Pinawa, Manitoba ROE 1L0

CZECHOSLOVAKIA

Malasek, E. Czechoslovak Atomic Energy Commission, Slezska 9, 120 29 Prague 2

4 6


F R A N C E

Sousselier, Y. Institut de protection et de surete nucleaire,CEA, Centre d’etudes nucleaires de Fontenay-aux-Roses, B.P. 6, F-92260 Fontenay-aux-Roses


Runge, K. National Board o f Nuclear Safety andRadiation Protection,



Kuhn, K. Institut fur Tieflagerung,Gesellschaft fur Strahlen- und Umweltforschung mbH, Berliner Strasse 2, D-3392 Clausthal-Zellerfeld

Lieser, K.H. Technical University,Darmstadt

INDIA

Sunder Rajan, N.S. Bhabha Atomic Research Centre, Trombay, Bombay 400 085

JAPAN

Araki, K. Japan Atomic Energy Research Institute, Tokai-mura,Naka-gun, Ibaraki-ken

Yogo, S. Radioactive Waste Management Centre, No. 15 Mori Buildings,2-8-10 Toranomon, Tokyo

Shimada, T. Radioactive Waste Management Centre, No. 15 Mori Buildings,2-9-10 Toranomon, Tokyo

47


N E T H E R L A N D S

Baas, J.

Hamstra, J.

Ministry of Public Health and Environmental Protection,

PO Box 439, NL-2260 AK Leidschendam

Netherlands Energy Research Foundation, PO Box 1, NL-1755 ZG Petten

SPAIN

Lopez-Menchero, E.M. Permanent Mission of Spain to the IAEA, Argentinierstrasse 34, A -1040 Vienna

SWEDEN

Larsson, A. (Chairman)

Boge, R.

Rydell, N.

Swedish Nuclear Power Inspectorate,PO Box 27106, S-10252 Stockholm

National Institute o f Radiation Protection, PO Box 60204, S-10401 Stockholm

Karnbranslenamden,Kungsgatan 35, S-l 1156 Stockholm

SWITZERLAND

Rometsch, R. CEDRA,Parkstrasse 23, CH-5401 Baden

UNION OF SOVIET SOCIALIST REPUBLICS

Savonenkov, V. State Committee for the Utilization o f Atom ic Energy, Moscow

UNITED KINGDOM

Feates, F.S.

Webb, G.

Department o f the Environment,Becket House, Lambeth Palace Road, London SE1 7ER

National Radiological Protection Board,Harwell, Didcot O X 11 0RQ

48


U N IT E D ST A T E S O F A M E R IC A

Vieth, D. United States Department o f Energy,Office o f Nuclear Waste Management,Mail Stop B-107 (GTN), Washington, D.C. 20545

Martin, J. United States Nuclear Regulatory Commission,Washington, D.C. 20555

ORGANIZATIONS

COMMISSION OF THE EUROPEAN COMMUNITIES

Come, B. CEC, Rue de la Loi 200, B-1049 Brussels, BelgiumRue de la Loi 200, B-1049 Brussels, Belgium

NUCLEAR ENERGY AGENCY OF THE OECD

Johnston, P. OECD/NEA,38 Boulevard Suchet, F-75016 Paris, France


Thomas, K.T. Divison o f Nuclear Fuel Cycle(Scientific Secretary)

Richter, D.K. Division of Nuclear Fuel Cycle

Irish, E.R. Division of Nuclear Fuel Cycle

Heinonen, J.U. Division of Nuclear Fuel Cycle

IAEA CONSULTANTS

Gera, F. ISMES,Via T. Taramelli 14, 1-00197 Rome, Italy

Dlouhy, Z. Nuclear Research Institute,Rez, Prague, Czechoslovakia

49


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