Materials Options and Corrosion-Related Considerations in the Design of Spent Fuel and High-Level Waste Disposal Canisters for a Deep Geological Repository in Opalinus Clay

Opalinus Clay has been selected as a host rock for a future high-level waste deep geological repository in Switzerland, whereas concepts for spent fuel and high-level waste disposal canisters are currently under development. The development of disposal canisters is done with respect to the expected evolution of the near-field conditions in the repository and requirements set by long-term safety, the handling concept, and manufacturing. A wide range of issues such as manufacturing, materials options, corrosion, closing weld, postweld heat treatment, structural performance, and inspection are considered. A detailed design study has shown that a carbon steel concept may be suitable for a geological repository in Opalinus Clay. Additionally, there are good prospects for using carbon steel design concepts as a substrate for copper coatings, which would largely eliminate gas production as an issue in long-term safety and would avoid the need of postweld heat treatment of steel. In parallel, several possible materials and design options are explored and their feasibility is considered through risk-assessment criteria.