Architecture and management of a geological repository - Andra

5 – Repository ModulesThe carrying capacity of a 380 mm diameter air cushion is around 2 500 kg. Each cushion is inflatedto 0.3 MPa and slightly raises the ring to be moved by lifting it.The procedure for putting heavy loads with large diameters in place is the subject of technologicaltesting in the framework of the ESDRED project.Figure 5.3.18Fitting buffer rings using an air cushionInserting concrete rings at the head of the cell and connecting to the access drift lining.The concrete rings forming the future swelling clay plug bearing support are inserted after the swellingclay buffer rings. They contribute to the protection of the swelling clay against hygrometric variationsduring the construction and operating phases.A mechanical stop is then made with the drift lining in order to absorb any clay swelling thrust.Inserting the sleeveThe sleeve is inserted after the last concrete ring. The preferred method of tube assembly, as for thetype C cell, is welding and for the same reasons.As far as fitting out the cell is concerned, special provisions are envisaged to make it easier to handlethe packages, given their size : a cradle with shims, if necessary ceramic coated, is a possiblesolution.(see figure 5.3.11). The shims can be fitted to the elements of the cradle in the workshop, inorder to facilitate their installation inside the sleeve.5.3.3.4 Closing the disposal cellThe spent fuel disposal cell closing process begins as for that of the type C cell, with the fitting themetal radiological protection plug.Once the choice has been made, there follows the fitting of the swelling clay core, in addition to therings already installed. There are at least two possible processes:- one consists of inserting pre-fabricated cylinders in the central space, probably at the same time asthe temporary sleeve is withdrawn; this process, however, leads to the creation of an initial roundspace between the prefabricated cylinders and the rings already in place (thickness of thetemporary sleeve increased by the handling clearance), a space which will in time close up as theclay swells;DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM248/495