Analysing the compaction of crushed salt in repositories for high-level waste in salt formations using a dedicated constitutive model

<p>The isolation of radioactive waste in a high-level waste (HLW) repository in salt formations is provided by a multi-barrier system based on a combination of engineered and natural barriers. The natural barrier is provided by salt rock itself, whereas the engineered barrier is comprised of sealing components installed at specific locations in the repository. In this concept, the long-term safety of the mined excavations will be ensured by backfilling with crushed salt. Crushed salt acquires its sealing capacity through compaction due to the convergence of the rock. Convergence increases by the heat produced by the disposed waste and by humidity in the repository and the water content in the rock. After several thousands of years, it is expected that crushed salt will reach the same mechanical and hydraulic properties as the intact salt host rock. In the scope of the R&D project RANGERS aiming at developing a methodology for design and performance assessment of geotechnical barriers in a HLW repository in salt formations, a constitutive model for crushed salt developed by Hein (1991) and modified by Breiderich (1994) has been implemented in the FE-code OpenGeoSys through the code generator MFront. The model has been subsequently applied to model the compaction of crushed salt in disposal drifts in the repository mine and thus helping to determine when the crushed salt will gain its function as long term sealing of the HLW-repository.&#160;</p><p>&#160;</p><p>Hein, H. J.: "Ein Stoffgesetz zur Beschreibung des lhermomechanischen Verhaltens von Steinsolzgranulat", Dissertation RWTH Aachen, 1991.</p><p>Breiderich, H. J.: " Gekoppelte Berechnung der thermomechanischen FeldgroBen in einer Steinsalzformation infolge der Einlagerung radioaktiver warmefreisetzender Abf&#228;lle", Dissertation RWTH Aachen, 1994</p>