Application of a database to manage multilevel area-specific FEP catalogues to identify a site for high-level radioactive waste disposal in Germany

The Federal Company for Radioactive Waste Disposal (BGE) is responsible for identifying the site with the best-possible safety for the disposal of high-level radioactive waste for at least one million years in Germany. The Site Selection Procedure consists of three phases with an increasing level of detail. The first step of the first phase was completed in September 2020. Ninety sub-areas were identified that are expected to have favorable geological conditions for safe disposal. The potentially suitable sub-areas cover approximately 54% of Germany and are located in three different host rocks: rock salt (halite), claystone, and crystalline rock.

The second step of phase one is currently in progress and includes the so-called representative preliminary safety assessments. Within the preliminary safety assessments, the behavior of the disposal system is analyzed in its entirety, across all operational phases of the repository and under consideration of possible future evolutions of the disposal system with regard to the safe containment of the radioactive waste. The actual behavior of the repository system cannot be predicted for the entire assessment period of one million years. Therefore, the evolution of the repository system is derived systematically to ensure that the actual future evolution of the repository is covered.

This contribution presents the methodology and technical implementation for the systematic derivation of a limited number of expected and deviating future evolutions of the potential repository siting areas. Evolutions are derived from the analysis of FEP catalogues (features, events, and processes), which are comprehensive, structured descriptions of a repository system and the existing interactions and dependencies of processes and components within. In order to apply this work-intensive method to the ninety sub-areas under consideration, a basic FEP catalogue is compiled first, from which host rock-specific and area-specific FEP catalogues are created. An analysis of component and process interactions is completed at host-rock level and then transferred and adapted to individual areas, taking site-specific information into account.

To facilitate the documentation and analysis of the disposal system and ensure consistency, a sophisticated in-house database solution has been developed. The properties of the FEP-catalogue components and their relationships are mapped and respectively stored in a relational database. The application is accessible through a user-friendly web application. This approach guarantees data integrity, reproducibility, and usability and accelerates the evaluation process by employing automation where applicable.