Tome Architecture and management of a geological repository - Andra

8 - Conclusions8.3 Architecture taking in account the reversibility rationaleThe request for reversibility has been incorporated into the proposed generic architecture.The considerable mechanical stability of excavations in the granite medium is generally conducive topackage retrieval capability and management flexibility of the repository process over very longperiods. Thus, structures, with very long service life (at least several centuries long) and without theneed for human intervention, can be constructed.Similarly reversibility is particularly enhanced by adopting long-lasting repository containers.In a first disposal process phase, the disposal packages may be managed as flexibly as if they were in awarehouse. They can be retrieved using the same facilities as for their emplacement with nodeterioration to the installations or the packages themselves.At this preliminary stage of design, it appears that this phase will last at least a few centuries (typically200-300 years), with no heavy maintenance.Repository observation would provide an re-assessment of (i) the alteration and durability of thecomponents (swelling of swelling clay, service life of cell sleeve) and (ii) the impact on the granite ofoperating the structures. However it must be noted that operations in ventilated drifts or structures (Bwaste tunnels, access drifts to various disposal cells, connecting drifts) entails hydro-geological andhydro-geochemical impacts on the granite. However these site-dependent disturbances appear to bereversible.In contrast to storage, a repository may also be closed by passive means to ensure the confinement ofthe waste and long-term protection of man and the environment. The proposed options are consistentwith a flexible management of the repository process by providing the possibility of progressiveclosure. As this closure progresses, the reversibility level gradually diminishes to the lowest level thatcoincides with total closure of the installation. However, after this closure, it remains technicallypossible to access the repository structures and retrieve the emplaced waste.To conclude, it appears that for two to three centuries it is technically possible to manage therepository process with a reversibility rationale and without involving heavy operations. During thisperiod, whatever the repository closure level, once access to the packages has been re-established,package retrieval from a disposal cell can be carried out using comparable handling equipment as thatused for its emplacement.Dossier 2005 granite - ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL REPOSITORY224/228