Architecture and management of a geological repository - Andra

4 – Waste disposal PackagesThe speed of generalised corrosion observed under these conditions during long-term corrosion tests(several years) falls over time because the protective function of the layers of corrosive products isreinforced. The average speeds observed in samples tend to be very low, between 3 and 5 µm/year fora temperature of 50 to 90°C, with instantaneous speeds lower than one µm/year after a few years.Applying conservative hypotheses, a thickness of 27 millimetres dedicated to corrosion provides for4 000 years of watertightness of the overpack.4.2.3.3 Compatibility with handling methodsDimensions relative to the mechanical strength of the over-pack, subjected to external pressure of12 MPa and its corrosion resistance on a millenium time scale having been established, the packagemust also be compatible with the handling methods used, presented in chapter 9.Three main configurations of the over-pack handling cycle are taken into account for design anddimensioning. The first is the vertical handling of the package during temporary storage operationsprior to its transfer to the package transfer shaft. The second corresponds to emplacing the package inthe disposal cell. Finally, the third one refers to the hypothesis of an eventual retrieval of the packages.• Taking into account vertical handling operations in surface installationsAt the end of production, disposal packages in surface installations are stored vertically. They are thenremoved and inserted into a radiological protection transfer cask for transfer to the undergroundinstallations. During these operations, the height above the ground during handling is about 1.60metres. Within the context of these operations, dimensioning consists of calculating the thickness ofthe handling interface and verifying the package's resistance to falling.The allowable stress (116 MPa) in the material used for the over-pack handling groove is defined bythe calculation rules used for lifting devices, produced by the European Handling Federation (FEM) as2/3 of the elastic limit. The dimensions of this groove give it a robust character with respect to all thestresses induced by handling operations and beyond, during the mechanical loading it will experiencein a disposal situation.Several cases of dropped packages have been simulated, notably an angular fall from a height of1.6 metres, which is the height above ground during handling operations in surface installations. Thesecalculations were used to verify package integrity.• Taking into account operations for placing packages in the waste disposal cellThe principle for transferring C disposal packages to a disposal cell, as illustrated in Figure 4.2.5, iscarried out by sliding the package in the cell sleeve using a pusher robot.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM138/495