Architecture and management of a geological repository - Andra

4 – Waste disposal PackagesFigure 4.2.5Principle for emplacement of C disposal packages into a waste disposal cellThe sliding is achieved by friction between the ceramic sliding runners and the metallic sleeveintrados. The essential function of these sliding runners is to facilitate sliding and limit the thrustrequired. By avoiding direct steel/steel contact between the package and the sleeve, the sliding runnersalso avoid damaging the body during pushing operations.The choice of ceramic is largely inspired by its industrial use in other fields such as aeronautics or theautomobile industry. This material is interesting because of its good friction coefficient, resistance towear and resistance to compression.• Taking into account an eventual retrieval operationWithin the context of an eventual retrieval of the package, we considered a case where generalisedcorrosion of disposal packages and the cell sleeve would have a negative effect on this operation.For dimensioning the groove for gripping packages in this situation, we used the hypothesis thatgeneralised corrosion (2mm) 45 affects all the outer surfaces of the handling groove. Taking thissituation into account when dimensioning consists of making sure that it is possible to grip thepackages and exert a significant tensile force to overcome the friction and sticking engendered bycorrosion. The calculation gives a maximum applicable force, corresponding to the elastic limit, ofabout 40 tonnes. Reaching the breaking strain should theoretically lead to the development of a tensileforce of about 85 tonnes, although with a risk of damaging the handling groove which could destroy it.It should also be noted that the ceramic sliding runners on the container limit the risk of "sticking" dueto corrosion products between the package and the sleeve.452 mm of corrosion engenders an excess thickness of swollen products of 3 mm relative to the initial dimensions (the total thickness ofcorrosion products is therefore 5 mm). The geometric dimensions of the groove take this corrosion thickness into account so that thecentral residual space is enough to allow deployment of the fingers of a specific gripping tool.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM139/495