Architecture and management of a geological repository - Andra

Figure 10.2.4Diagrammatic representation of the principal phenomena within a type B wastedisposal cell after closing.• Evolution of the access drift and sealIn the access drift, stopping the ventilation, as in the cell, causes very slow re-saturation of the rock.Over several centuries, the wall rock and liner concrete are again significantly de-saturated, as is thesealing clay [8], [66]. The swelling of the sealing clay caused by re-saturation thus remains verylimited, or even non-existent, during the operation of the repository.In the access drifts to cells containing only slightly exothermic waste, sealing considerably slowsdown heat propagation; the temperature at the downstream end of the seal in the accessible zoneincreases by only a few degrees. Furthermore, as with the cell liner concrete, the concrete either sideof the clay seal remain intact for several centuries or much longer.The small change to the seal over a period of several centuries [85] facilitates its eventual dismantlingin the event of reversing the disposal process in order to retrieve the packages or simply to return tooperating conditions close to those of a storage facility.• Possibilities available for taking action and possible duration of the stageAt this stage, it remains technically possible to retrieve the packages using means similar to those usedwhen inserting the packages, thanks to having maintained the functional clearances in the cell, as longas the latter is mechanically stable, i.e. for several centuries after its construction. It would howeverrequire preparatory work whose technical content, as described in section 10.4, could be adaptedaccording to the condition of the cell, established by analysing the results of observation.The observation of the liner and the terrain thrust on the liner, associated with temperaturemeasurements within the cell, can be carried out for as long as possible in order to establish soundknowledge of the effective condition of the cell.Monitoring of the quantities of gas actually emitted in the cell and evacuated by ventilation during theprevious stage, make it possible to detail the precise gas production kinetics and, thus, more accuratelypredict the quantities of gas trapped in the cell after closing.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM374/495