Compaction of Crushed Salt for Safe Containment - Overview of Phase 2 of the KOMPASS Project Article Swipe
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· 2023
· Open Access
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· DOI: https://doi.org/10.56952/arma-2023-0340
· OA: W4386525031
Crushed salt may be used as backfill material and sealing measures of open cavities, drifts and shafts in nuclear waste repositories located in rock salt formations. The host rock salt will gradually compact the crushed over time due to salt creep. A comprehensive understanding of the crushed salt compaction process is essential, yet crushed salt compaction involves several thermal-hydraulic-mechanical (THM) coupled processes and is influenced by internal, as well as external conditions. The current understanding has some important knowledge gaps. For example, the porosity/permeability evolution, especially for the low porosity range is not known in its entireness and the calibration of numerical models is not finished yet. The KOMPASS projects were initiated with the aim to reduce these knowledge gaps and improve predictions of crushed salt behavior. This paper gives an insight in the KOMPASS projects with focus on the outcomings of the second phase. The experimental program for a detailed investigation of crushed salt compaction is presented. In the microstructural investigations, microscale indicators were found that can clearly be related to pre-compaction treatment. The numerical work showed that deficits still exists in the simulation of crushed salt compaction with the available constitutive models. INTRODUCTION Rock salt is considered as a possible host rock formation for the underground disposal of high-level nuclear waste in several countries. The safety concept for a salt repository in Germany is based on a multi-barrier system including the rock salt as geological barrier, geotechnical seals ensuring the safe containment and the waste canisters (Bertrams et al., 2020). For backfilling and sealing measures of open cavities crushed salt will be used due to its favorable properties as mined-off material, its easy availability and its lithological characteristics which guarantee a maximum compatibility with the host rock. The use of crushed salt for barriers and seals represent an important paradigm shift in repository design in Germany, since crushed salt previously served only as stabilizing backfill.
