Due to the long half-lives of the radionuclides contained in waste, a repository for high-level radioactive waste must safely contain them for long timescales, which include geological and climatic changes. For this reason, numerical groundwater models are developed in this work considering various climate processes and influences in relation to repository safety. Glaciers, permafrost, erosion, and sea level fluctuations will be considered and related to the geological situation in Germany.

Crystalline rock is a potential candidate for storing nuclear waste in the deep geological underground in Germany. However, fractures within these rocks pose a challenge, as they can create pathways for fluids that might corrode barriers and release radioactive materials into the environment. The exact configuration of these fracture networks is often unknown. Our study aims to better understand and predict these networks by combining existing data with advanced modelling techniques.

Based on the German site selection process for a deep geological repository for high-level radioactive waste, we propose a site-prioritization method based on a multi-criteria decision-making approach and risk estimates for each sub-region. The method takes into account the geological factors as well as the uncertainty associated with the heterogeneous nature of subsurface data quality and quantity, in order to enable stakeholders to make informed decisions during the site selection process.

Since the requirement of the proof of safety to up to 100 years arises, integrity of the spent fuel elements in prolonged interim storage and long-term repository is getting more critical issue. In response to this safety matter, we developed and applied a multiscale simulation methodology to assess the impact of the radiation induced microstructures on mechanical properties of the spent fuel elements to provide reliable structural performance limits and safety margin respectively.