Thermo-mechanical analysis of high level nuclear waste in various rocks

The storage of high level nuclear waste in rocks generates an important variation of the existing temperature, which induces displacements and stresses in the rock mass. These quantities must be evaluated for two main reasons: to guarantee the stability of the storage galleries and shafts during construction and handling of the wastes, and to appraise the safety of the whole storage, for long periods (thousands of years) by studying the thermo-hydro- mechanical phenomena due to the heat transfer. The phenomena strongly depend on the type of rock under consideration. The French National Agency for Waste Management: ANDRA is considering the possibility of high level wastes storage in four deep geological formations: salt, clay, granite and shale. This paper presents specific models and tools adapted to a certain number of thermo-mechanical analyses of such media. The authors describe two types of behavior: viscoelastic behavior, which is of primary concern for salt and some clays, and brittle behavior, which is of primary concern for granite and shale