The integration of the safety arguments presented above further reinforces the findings from Project Entsorgungsnachweis (Nagra 2002) and subsequent investigations. The geological barrier is of primary importance due to the excellent properties and long-term geological stability of the Opalinus Clay host rock and the wider containment-providing rock zone (CRZ). The extensive research over the last 20 years conducted by Nagra and other organisations further underlines the suitability of the Opalinus Clay as an outstanding host rock for the disposal of radioactive waste.

A key role of the engineered barriers is the minimisation and mitigation of disturbances to the CRZ. The current safety and repository concept at the chosen site has been shown to be well chosen, with the site itself providing highly favourable and stable properties, as well as significant flexibility for the placement of the repository. The remaining uncertainties have been assessed as insignificant to post-closure safety and are expected to be further reduced when additional underground information becomes available.

Post-closure safety is demonstrated based on the current mature and robust, but still provisional concept and design. In future stages of the waste management programme, up until construction and finally operation, further optimisation of the current safety and repository concept and design will be carried out as discussed in the next chapter.