// Long-term Safety Studies, Repository Design

GEIST

Comparison of repository concepts in salt and claystone

The aim of this project was to compare a generic repository concept for high-level radioactive waste in salt with one in claystone. The comparison focused on the areas of technology, safety, and costs, highlighting the characteristic differences and identifying open questions. Initially, publications on international repository concepts in claystone from countries such as Belgium, Switzerland, France, and Spain were evaluated. Subsequently, a concept for a repository in claystone in Germany was developed and compared with the current repository concept for salt in terms of mining experience, repository container concepts, emplacement concepts, required repository areas, backfilling and sealing concepts, and a relative cost analysis. Regarding safety during the operational phase, operational radiation protection, criticality concerns in the claystone repository concept, and safeguards measures during the operational phase were examined. Additionally, an initial shielding calculation for a bentonite-encased HAW cask was performed. Concerning safety in the post-closure phase, it was found that safety strategies for both host rocks rely on a long-term effective geological barrier. Criticality safety, safeguards aspects, and the geochemistry of the host rocks were also evaluated. Finally, a comparison of potential repository regions in clay/claystone and rock salt in the depositional basins of the North German Basin and the South German Molasse Basin was conducted.