A national mission

The high-level long-lived radioactivewaste (HLLL) resulting fromnuclear power plants, spent fuel

reprocessing, research and defenceactivities is currently stored safely andtemporarily in industrial facilities.The French Waste Act dated 30th

December 1991 initiated a researchprogramme to define methods for thelong-term management of this waste.It has entrusted Andra, the French NationalRadioactive Waste Management Agency,with the task of assessing the feasibilityof deep geological disposal of this waste,a solution also considered by variousother countries (Finland, Sweden,Belgium, Switzerland, United States) anddeemed particularly robust with regardto safety by international authorities suchas the IAEA1. The results of this researchare regularly assessed by the French

National Review Board, an independentauthority created by the December 30th

1991 Waste Act, and constitute the basisof the parliamentary debate scheduledfor 2006.

Picture

of an R7T7 vitrified C

waste primary

package

1.34

m

0.43 m

Andra researchon the geological disposalof high-level long-livedradioactive waste

1 International Atomic Energy Agency

> Detailed knowledgeof the waste to bemanaged

Andra has compiled an inventory ofthe waste and assessed its futureproduction by current facilitiesbased on four scenarios definedwith waste producers (EDF,AREVA, CEA) and representative ofpossible strategies for spent fuelreprocessing (from continuation tocomplete interruption).

There are two types of waste:

> C waste: high-level waste (1%of the total volume and 96% ofthe radioactivity) resulting fromspent fuel reprocessing, confinedin a glass matrix and poured intostainless steel drums. This typeof waste gives off large amountsof heat.

> B waste: long-lived intermediate-level waste (the most abundantin terms of volume) compactedor conditioned in bitumen orconcrete matrixes and then pla-ced in concrete or steel drums.

The radioactivity of the wastedecreases over time.

The studies have encompassed thepossibility of the disposal of non-reprocessed spent fuel, althoughspent fuel is not today consideredas waste and is planned for repro-cessing in the next years.

> A repository system consists of a seriesof elementary cavities (disposal cells) excavated in the rock (hostformation). These disposal cells are grouped into large sets (modules)and receive the waste packages. The modules are connectedby drifts, themselves serviced by access paths connected to thesurface via shafts.

Experimental drift (-445 m) of the Meuse/Haute-Marne underground research laboratory

Clay and granite:Two researchprogrammes

Meuse/Haute-Marne site

referred to as the Callovo-Oxfordian for-mation. Since 1994, Andra has drilled 27deep boreholes meaning over 15 km ofdrilled formations, cored 2.3 km ofargillite from these boreholes, andtaken over 30 000 samples. Direct sur-vey of the Callovo-Oxfordian and in situexperiments are pursued since 2004 inthe shafts and in nearly 100 metres ofdrifts. The Mont Terri laboratory inSwitzerland is also an essential resour-ce, with clay similar to that of the Buresite.

Andra has studied the feasibility of anHLLL waste repository in French clayand granite formations. The results ofthis research are presented in theDossier "2005 Argile" (clay) and Dossier"2005 Granite".The studies covered four complementaryaspects:> Acquisition of data concerning the

waste packages, material behaviourand clay and granite mediums.

> Repository design: waste conditioning,repository architecture and integrationin a geological site, operating modesand reversibility.

> Analysis of the long-term behaviour ofthe repository and modelling of itsthermal, mechanical, chemical andhydraulic evolution.

> Long-term safety analyses.

> Clay mediumAndra has conducted studies inits Meuse/Haute-Marne undergroundresearch laboratory, created by thedecree of August 1999 and located at adepth of 490 m in a stiff argillaceousrock (argillite) 155 million years old,

> International cooperationand review

Andra has conducted these tworesearch programmes in collaborationwith foreign counterparts (Nagra inSwitzerland, Enresa in Spain, BGR inGermany, Ondraf in Belgium, etc.) and

with the scientific community in France(French Geological Survey BRGM,Atomic Energy Commission CEA,French National Centre for ScientificResearch CNRS, French PetroleumInstitute IFP, National Institute forIndustrial Environment & Risks INERIS,National Polytechnic Institute ofLorraine INPL, School of Mines, etc.)

and abroad. Over 100 laboratoriesthroughout the world have participated.In addition, Andra submits its researchfor international review. In 2003, agroup of international experts under theaegis of the OECD/NEA examined thesynthesis report on clay produced in 2001and considered the results obtained aspositive.

Vertical exaggeration : 4x

Research laboratory

Gondrecourt le Château

Joinville

Gondrecourt graben

Ligny-en-Barrois

Marne graben

Marne river

Ornain river

Saulx river

Savonnières-en-Perthois syncline

Poissonsfault

Cal

lovo

-Oxf

ord

ian

0 5 km Scale :

SURFACE GEOLOGY

LITHOLOGICAL CROSS SECTION

Lower CretaceousTithonianKimmeridgianOxfordianlimestone

Sandstone and evaporites (Trias)Sandstone and clays (Permian)Undifferentiated basement

LimestoneMarls and clays

Alluviums orPlio-Quaternary

> An argillaceousformation favourablefor waste disposal

After 10 years of research, Andra hasacquired sufficient data to consider thatthe Callovo-Oxfordian formation of theMeuse/Haute-Marne site has favourableproperties for an HLLL waste repository.This argillaceous formation with verylow permeability and homogeneousover a large area, located at an averagedepth of 500 metres, is unaffected byfaults and presents very low seismicrisk. Since deep enough, future climaticchanges (erosion) will not impact it.

Other characteristics are: very lowwater flow, little deformation, goodresponse to the perturbations dueto mining excavation work and to thethermal and chemical impact of thewaste and repository materials (thuspreserving its confinement propertiesover very long periods of time), stablegeological environment.As well, surrounding formations presentslow permeability and slow water flow. These favourable characteristics arefound throughout a 200 km2 area northand west of the laboratory.

Callovo-Oxfordian

formation and its

surrounding layers

Meuse/Haute-Marne research laboratory

> Granite mediumSince Andra does not have available anunderground laboratory in a French graniteformation, its research teams have partici-pated in experiments conducted in Sweden(Äspö), Switzerland (Grimsel), Canada (Lacdu Bonnet) and Finland (Olkiluoto). Thesestudies were not intended to assess thefeasibility of a repository designed accor-ding to the specific characteristics of a parti-cular site. Their purpose was to assess theinterest of the granite medium and to pro-pose generic concepts capable of meetingthe long-term safety objectives within theFrench geological context. In the samemanner, the safety analysis is not intendedto produce specific conclusions regardingthe performance of the system consideredwith respect to quantified radiologicalprotection objectives. Its purpose is toidentify and handle essential issues andto verify that none of the problem areasexamined rules out feasibility.

Repository architecturesin an argillaceous formation

placed in concrete containers (B waste)or steel containers (C waste and spentfuel). The repository is located on a sin-gle level in the middle of the Callovo-Oxfordian and organised into distinctzones (according to package type)separated by 250 metres of argillite andsubdivided into modules. The generally circular profile of the engi-neered structures, their dimensioning,their dead-end arrangement, their closurewith low-permeability seals, the back-filling of the drifts at the end of the ope-rating phase and the choice of materials(concrete, steel, clay) all contribute atfirst to reducing perturbations and mini-mising water flow in the geological

formation, then later to limiting anddelaying the release and migration ofradioactive elements.

Integrated as of the repository designphase, the reversibility requirementleads to privileging durable materialsand to the implementation of systemsfor package retrieval. Waste packageretrieval is possible through simpleinversion of the emplacement processover various centuries.

The B waste disposal cell

has a useful lenght of 250 m,

an excavated diameter of

12 m, and is equipped with

concrete lining.The waste

disposal packages, wich

contain primary packages,

are manufactured in concrete

and stacked in several layers

in the disposal cell.

> Robust options andmodular systemspecialized accordingto waste type

In order to dispose of and manage thevarious types of waste packages (B, C,and possibly spent fuel) in a safe andreversible manner, Andra has adoptedsimple and robust options, proposing amodular and flexible architectureconsisting of elementary components(repository modules).In order to simplify operation and increaseits robustness, the waste packagesmanufactured by waste producers are

> Reversibilityguaranteed for atleast three centuries

These functions are ensured by barriersand various redundant components.The approach to reversibility proposedby Andra consists of allowing the flexibleand step-wise management of therepository. The objective is to leavefuture generations the freedom to makedecisions concerning repository mana-gement. The modular repository designis intended to offer the widest possiblerange of choices. Reversibility meansthe possibility to retrieve emplaced

packages and as well to intervene inthe disposal process and to modify therepository design. An observationprogramme has been developed toensure the technical feasibility of thebackward process. The studies haveshown that reversibility could be ensuredfor a minimum period of two to threecenturies, with no intervention otherthan standard maintenance and monito-ring operations.

Long-term safety and reversibilityare the guiding principles for repo-sitory design

The purpose of a geological repositoryis to protect man and environment fromthe possible impact of radioactivewaste by interposing various barrierscapable of confining the radioactivity forseveral hundreds of thousands of years(packages containing the waste, reposi-tory installations, geological medium).The safety approach adopted thereforetakes into account very long periods oftime and privileges the most robustsolutions so as to ensure the threemajor functions of the repository:

> Limiting the release of radioactiveelements and immobilising them inthe repository

> Delaying and reducing the migra-tion of radioactive elements beyondthe repository

> Preventing water circulation (whichcan degrade the waste packages andfavour the migration of the radionu-clides contained therein)

Two basic guidelinesThree major functions

Surface installations

Shafts

500 m

Zone B

Zone C0

Zone C

Underground installations

Disposal cells

Basic layout of the

geological repository

> Demonstration of therobustness of the repo-sitory concept in anargillaceous formation

To verify the robustness of the solutionsproposed, Andra has simulated therepository evolution in the very longterm through a phenomenological ana-lysis of repository situations (PARS) andthen tested the limits of validity of thisrepresentation via a safety analysis. Thissafety analysis defines the simplifiedhistory of repository evolution (normalevolution scenario). It covers the fullrange of possible situations throughvery cautious choices. Andra has alsoexamined scenarios entailing highly unlikely events (intrusion, failure of safetyfunctions).

According to the methodological guidepublished by the Nuclear Safety Authority(Basic Safety Rule RFS.III.2.f), the impactof the repository on man and the envi-ronment must amount to less than 0.25

millisievert in normal situations (i.e., 1/4the dose due to non-natural exposure cur-rently admitted for the public and approxi-mately 1/10 the annual dose due to natu-ral radioactivity). This impact has beensubsequently calculated based onmodels. Andra has extended its calcula-tions to one million years, in accordancewith international practice. The analysis shows that for all the situa-tions considered, normal or altered, theproposed system ensures the three mainsafety functions without excessivelydepending on any of its components (eachcomponent contributes to the overall safe-ty of the system in a significant but non-preponderant manner). The Callovo-Oxfordian formation plays a major role inimmobilising the radionuclides and indelaying and limiting their migration intothe environment in all situations. The repository performance meets thedose objectives recommended by Basicsafety rule III.2.f in all the scenariosconsidered, whether accidental oraltered, and with significant margins.The repository represents therefore arobust disposal concept, including inrather unlikely situations with concurrentpenalizing circumstances.

© Andra 264 VA - March 2006 - Graphic design: Mediagérance - Photo credits: Graphix Images - CEA - SKB

Agence nationale pour la gestion des déchets radioactifs

Parc de la Croix Blanche - 1/7, rue Jean Monnet - 92298 Châtenay-Malabry Cedex - Tél. : 01 46 11 80 00www.andra.fr

Safety assessment

> Calculations projectedover a period of1 million years

> Granite medium:Interesting properties

In the absence of a specifically site, thedesign principles adopted by Andra arebased on research conducted in foreignlaboratories and on a typological analy-sis of 78 granitic zones of over 20 km2

located in the Massif Central andMassif Armoricain formations, quiteapart from large faults.

The architectures proposed are adap-ted to granite fracturing and rely on thevery low permeability and highresistance of the non-fractured rock.Various options have been transposedfrom the repository studies concerningthe clay medium: overpacking, separa-tion of packages into specialized zonesand modules, modular operation andclosure, sealing and backfilling ofengineered structures, measuresfavouring reversibility.

In the absence of a specific site,the safety analysis has not estimatedthe impact of the repository in terms ofthe dose to which the public may beexposed. It has been used to determinethe role and performance of the reposi-tory components with regard to thesafety functions, and to identify andhandle uncertainties. It stresses therelevance of the architecture adopted(adapted to granite fracturing) and theefficiency of the engineered compo-nents. A strong uncertainty remainsregarding the possibility of finding siteswith sound granite blocks of sufficientsize outside the fracture network.

> ConclusionBased on the research completed,the basic feasibility of geologicaldisposal in an argillaceousformation appears to be achieved.

Äspö laboratory (Sweden)