Geomechanical Stability and Integrity of Radioactive Waste Repositories in Salt Rock

摘要

To prove the suitability and safety of underground structures for the disposal of radioactive wastes, an extensive safety analysis has to be carried out. Basic steps of the analysis are the geological modelling of the entire structure including the host rock, the overburden and the repository geometry, the idealization of the geology as well as the geomechanical modelling taking into account the modelling of the underground structure and the appropriate material models with respect to creep and dilatancy of rock salt. For the geomechanical analysis the ANSALT finite-element code was compared to the JIFE code which allows the consideration of large three-dimensional structures with complex inelastic material behaviour. To establish the finite-element models needed for stability and integrity calculations, the geological models are simplified with respect to homogenous rock layers with uniform creep behaviour. The modelling results are basic values for the evaluation of the stability of the repository and the long-term integrity of the geological barrier. Concerning the barrier integrity, two geomechanical criteria are considered, the dilatancy criterion and the frac criterion. As an example of application, the analysis of the central part of the Morsleben site, used for the disposal of low and medium radioactive waste, is described.