Architecture and management of a geological repository - Andra

6 – Overall underground architectureOn the contrary, a short distance between the shafts eliminates the possibility of a U-shaped flow. Inthe case of an upwards gradient in the shaft zone (Diagram b), no water flow would be trapped in theoverlying formations. In the case of a downwards gradient, the flow trapped by a poorly or un-sealedshaft would be limited by the low permeability of the formation studied and would remain of the sameorder as the flow intercepted in the argillite so there would be no significant impact on the release ofradionuclides by the packages and this flow would not constitute a migration vector of these elements.OxfordianCallovo-OxfordianDoggera) U-shaped flow situation betweendistant shafts under the effect ofhydraulic head gradients within theOxfordian and between the Dogger andOxfordian formationsb) Offset shafts in clustersFigure 6.3.6Shaft layout and flow limitation6.4 Logic governing the overall construction and operation of therepositorySection 6.3 showed that the architecture presented was designed to meet long-term safetyrequirements. This section describes an overall layout that ensures the progressive construction of therepository at the same time as the physical separation of different activities. One point in particularconcerns ventilation which is an essential factor in the dimensioning of the repository infrastructure.6.4.1 Separation of activitiesThe principle of separating construction work and "nuclear" operation has led to certain infrastructuresbeing dedicated to one or other of these activities.The infrastructures dedicated to nuclear operation activities (waste package transfer) comprise thewaste package transfer shafts, waste package transfer drifts which connect the shafts and theoperating units, and access drifts leading to the cells located inside the operating units.The infrastructures dedicated to construction work (and closure) comprise the construction shafts andconstruction drifts.Figure 6.4.1 shows a possible example of work and operation activities being carried outsimultaneously.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM270/495