Architecture and management of a geological repository - Andra

10.2.2.2 “Post cell-sealing” stageClosing the cell consists of extracting the temporary sleeve and fitting a clay plug confined by aconcrete plug. The ventilation in the access drifts is maintained and the sealed cell ends are stillaccessible under the same conditions as in the previous stage (see section 10.2.2.1).Figure 10.2.8Accessibility of type C cell ends after fitting the sealAs in the case of type B cells, fitting the seal makes cell monitoring more difficult. However,techniques exist (notably wireless transmission technology) making it possible to continue to monitortheir evolution (see section 10.3). The access and connecting drifts are monitored and, if necessary, arethe subject of maintenance (see §10.3.). Moreover, it remains technically possible to dismantle the sealand retrieve the packages. (see §10.4.).• Evolution of the cellThe fitting of a cell’s seal requires the cell to be left open throughout the operations (a few days).However, the quantity of oxygen provided by the partial or total renewal of the air in the cell issufficiently small not to induce notable corrosion inside the sleeve.As far as air renewal is concerned, after the cell has been sealed, the plug plays the same role as theoperational shielded trap door or leaktight cover. The core of the cell and the packages it contains thuscontinue to evolve to the next stage, without significant variations due to the presence of the clay plug.The durability of the sleeve and the corrosion-limiting conditions inside the cell continue to provideflexibility in the management of the packages in the cell. Furthermore, the thickness of the over-packsensures that the radioactive nuclides are confined for at least four thousand years in the case of type Cwaste and for over ten thousand years in the case of spent fuel (see chapter 4).At the top of the cell, extracting the temporary sleeve allows the argilites to deform and graduallyclose the clearances left at the time of fitting the cell seal. Then, as soon as the seal has been fitted, it issubjected to heating by the waste: its internal face quickly comes into thermal equilibrium with thenearest package, whilst the external face is in thermal equilibrium with the rock of the access driftwall, which is ventilated [10], [13].DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM379/495