Tome Architecture and management of a geological repository - Andra

7 - Spent fuel repository zoneevent, it is possible to reverse the process, backtracking to an earlier stage, right back to packageretrieval, even if the deconstruction of more substantial closure structures is required as closureprogresses further.7.7 Functions of the repository components over timeThe previous sections describe the various components of a spent fuel repository. They specify themeans used to construct a reversible disposal system. They expose the principles at the basis of theirdesign and dimensioning for long-term safety.The following table summarises how the various components contribute to the main functions of arepository during the various repository phases (§ 1.1).Table 7.7.1Functions of the repository components over timeCOMPONENTPERIODMAIN REPOSITORYFUNCTIONSPROPERTIES HARNESSEDPart of the graniterock where a disposalcell is installedGranite "block"where the disposalmodule is installedDuringoperationand thereversibilityphaseAfter closureAfter closure1. GEOLOGICAL MEDIUM: GRANITEEmplacing (and being able toretrieve) the packages in thecellsProtecting the disposal cellsfrom water circulationDelaying and reducingradionuclides migration to theenvironmentProtecting the disposal cellsfrom water circulationDelaying and reducingradionuclides migration to theenvironmentMechanical strengthVery low permeabilityChemical properties of the granitewater that tend to delay radionuclidemigration (reducing environment,pH, etc.)Low permeability (at a distance fromthe significant water-conductingfractures)Low underground hydraulic gradientsChemical properties of the granitewater that tend to delay radionuclidemigrationUnderground installation of therepository (500 m taken as reference)Protecting the disposal cellsfrom water circulationLow permeability (at a distance fromthe major faults, the main vectors ofwater in the massif)Low underground hydraulicgradientsThe repository partof the host granitemassifAfter closureDelaying and reducingradionuclides migration to theenvironmentChemical properties of the granitewater that tend to delay radionuclidemigrationGeo-dynamic context that ensuresfavourable repository conditions aremaintained in the long term,particularly in relation to erosionphenomenaIsolating the waste from humanactivitiesDossier 2005 granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY218/228