Architecture and management of a geological repository - Andra

2 – General DescriptionThe protection and inspection of nuclear materials contained in the installation [23] will be noted inparticular.2.2.3.2 Placing the waste packages in the Callovo-Oxfordian argillitesIn order to place the waste packages in the argillites, underground installations must firstly be madewithin the scope of the gradual development of the repository.This implies surveying the volumes of argillites which will receive the packages by checking that thelocal properties of the argillites are good and, if necessary, by adjusting the data used to design theengineered structures. This survey can be completed in stages as the repository is developed, with eachstage providing additional knowledge specific to each repository zone created. Conventional methodsof geological surveying are used.Next the new repository facilities and the engineered structures serving the repositories are excavated.This involves excavating the argillite, loading it (muck removal) and extracting it to the surface andstockpiling the excavated material, while maintaining the possibility of using the extracted argillitelater to backfill the underground installations.Finally, these repository installations must be equipped by preparing, taking underground andinstalling the equipment required for operation and that contributing to the safety functions.Furthermore, the primary conditioning of the waste (in other words, as carried out by the producers),may have to be supplemented to facilitate operation or perform safety functions after closure. In thetechnical options presented below, it is assumed that the additional packaging is carried out at therepository site.Finally, the packages thus prepared must be transferred to their repository location while it is ensuredthat operating personnel are protected against the risks of external and internal exposure to ionisingradiation.At each stage in the process, the various objects made are characterised by a report of each objectwhich is completed and saved in order to populate and update the repository knowledge base.Among the support functions to all of these activities, two appear particularly important:- ventilating the installations to enable intervention by personnel [24], and control potential riskslinked to the build-up of gases (especially hydrogen generated by radiolysis of the materials incertain B waste packages);- supporting the underground caverns mechanically to provide dimensional stability, ensure safetyand limit argillite deformation.2.2.3.3 Managing the installationsThe installations are managed according to the reversibility paradigm presented earlier. Managementcovers maintenance of the installations, monitoring and the possibility of withdrawing packages fromthe repository, once again while limiting radioactive dissemination.The possibility of closing the underground installations implies preparing the backfilling and sealingmaterials, taking them to the bottom, and then constructing the closing structures.2.2.3.4 Operational nuclear safety functionsThe industrial activities presented above imply the implementation of “operational safety functions”that are comparable to usual nuclear facility practices, whilst taking the underground nature of therepository into consideration.8If spent fuel is received, an inspection will especially be carried out to ensure that there are no ruptured bare rods inside the transfercasks.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM40/495