Architecture and management of a geological repository - Andra

6 – Overall underground architecture6.2.7 Capacity to adapt to the possible discontinuity of the geological environmentNo fault was detected during surveys of the Callovo-Oxfordian formation. Geological modelling givesgrounds for considering that this situation can be extrapolated to the whole transposition zoneintroduced in [6] - Tome 1. This is conducive to the description of a regular architecture. However, itis clear that the modular nature of the architecture could be adapted for a scenario (deemed unlikely, asknowledge about the site increases) in which the repository would intercept a secondary fracture witha greater hydraulic transmissivity than that of sound argillite. Such a fracture would, in any event, bedetected at the latest during surveys carried out before or during the construction of connection drifts.The architecture could then be adapted accordingly: an undisturbed argillite thickness over a distanceof a few hundred meters would be maintained between this fault and the nearest repository modules; inaddition to this, connection drifts nearing or passing through the fracture could be sealed when therepository is closed.6.2.8 International comparison factorsIn the United States of America, the Department of Energy has been operating an undergroundradioactive waste repository, the WIPP (Waste Isolation Pilot Plant), situated in a salt bed at a depth of650 m since 1999. It is the only underground long-lived radioactive waste repository facility currentlyoperating in the world. Figure 6.2.4 gives a perspective view of these facilities [77].Figure 6.2.4Perspective view of the WIPP underground repositoryThis architecture and the underlying organisation of the work have several points in common withthose set forth in this chapter:- Modular repository zone, constructed progressively according to disposal needs- Network of a number of dedicated connection drifts facilitating coactivity between nuclear andcivil engineering activities.- Clusters of shafts connecting surface and underground installations.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM263/495