Architecture and management of a geological repository - Andra

6 – Overall underground architectureIt is also reiterated within this context that type B2 package (bituminised sludge) repository modulesmust, as far as possible, be maintained at a temperature of under 30°C, in order to preserve theintegrity of the bitumen and its containment capacity. The architecture must therefore protect themagainst a thermal flow coming, in the long term, from other heat generating waste packages.6.1.1.5 Limiting physico-chemical disturbances, independence of the various categories ofwaste packageWe consider the disposal of various categories of package in physically distinct repository zones. Thisseparation prevents having to consider interactions between these various categories, in the study oflong-term behaviour of the repository.In addition to the thermal interactions mentioned above, it also concerns potential physico-chemicalinteractions.Within the type B waste category, this same problem led, in Chapter 5, to considering specificrepository modules according to the chemical content of the waste; in the overall architecture, it istherefore advisable to separate these different modules.6.1.1.6 CompartmentalizationIn order to limit as much as possible the impact of an altered situation to only a fraction of therepository, and thus reduce its potential radiological consequences, the repository can be sub-dividedinto sub-assemblies separated from each other by seals.6.1.2 Taking account of reversibilityReversibility is associated with disposed waste package management flexibility. It refers to thecapability to retrieve waste packages and intervene in the disposal process. As indicated in Chapter 5,the capability to retrieve the waste package has an essential influence on the design of the disposalcells.6.1.2.1 Intervention capabilityThe capability to intervene in the disposal process involves, in particular, the ability to take decisionsconcerning part of the repository without affecting decisions taken or to be taken concerning otherparts of the repository. In other words, in order to be exercised effectively, intervention capabilityrequires a modular repository design. The repository is therefore sub-divided into sub-assemblieswhich can be managed individually with a flexibility similar to that found in a storage facility.Modularity thus defined ties in with the advantage of sub-division for long-term safety reasons.6.1.2.2 Progressive construction of the repositoryThe period of time during which packages are placed in the repository, which may extend over severaldecades, calls for a progressive approach to repository construction. As experience feedback isaccumulated in repository operation, scientific knowledge improves and technology evolves, it ispossible to envisage that disposal procedures will evolve with time.Modular repository design, combined with progressive construction allows these changes to be takeninto account: by constructing these repository sub-assemblies progressively, as they are needed, weretain the ability to alter their design.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM254/495