Long-term safety studies

The key objective of radioactive waste disposal is the long-term protection of man and the environment against the harmful effects of radioactive substances. Long-term safety analyses are to demonstrate that the proposed disposal and repository concept can meet this target and the respective requirements. The safety assessments require a complete description of the repository system consisting of the mine, the emplaced waste, the geosphere, and the adjacent biosphere (FEP catalogue). The future development of the repository system can be determined from the interactions between the repository system components or features and various relevant processes and events (scenario development).

Especially for geological repositories, it is necessary to carry out structural analyses for the modelling of the long-term development of the repository and its environment. To this end, suitable constitutive models for the host rock and the building materials need to be developed. These have then to be integrated into simulation programs, followed by validation calculations. We usually carry out this work in the course of generic R&D projects. We then use existing and proven models and programmes for existing mine projects, especially for BGE’s mines as discussed below. When applied to different host rocks and repository concepts, specific safety demonstration concepts have to be developed in each case. Important elements of the safety analyses are integrity analyses of the geotechnical and geologic barriers. For this purpose, system analyses with coupled physical processes have to be carried out. The development of the necessary simulation models requires very good knowledge of the calculation programmes and of the basic data; e.g. of the host rock and the repository concept. Furthermore, defined standards, such as comparability of the results and level of detail of the calculations, must be met. We develop models for long-term safety analyses, implement them into corresponding simulation programmes, and apply them to generic and specific cases. The radiological assessment of the expected development of the repository system is based on a radiological consequences analysis. Further numerical tools to evaluate the results of the model calculations are sensitivity and robustness analyses. Due to our participation in national and international waste management and research projects, we have extensive experience in the field of repository safety and are always up-to-date with regard to safety demonstration methodology.