Key points:

• The present report synthesises the geological information for repository site selection and for the demonstration of post-closure safety.
• Repository safety is ensured by a multi-barrier system including engineered and geological barriers. The geological barrier isolates the waste from humans and the environment, ensures immobilisation, retention and slow release of radionuclides and contributes to the long-term stability of the repository system.
• The site selection process in Switzerland considers 13 criteria addressing long-term safety and construction feasibility. The final stage of the site selection process evaluates three remaining siting regions, all located in Northern Switzerland, an area with an overall low geodynamic activity and tectonic complexity and containing the host rock Opalinus Clay at a suitable depth and tectonic configuration.
• Key geological information provided for the general licence application includes (1) a detailed characterisation of the host rock and low-permeability confining units, (2) independent evidence for the barrier function over long timescales, (3) a detailed tectonic characterisation and (4) an assessment of the future geological evolution (geodynamics, climate, erosion) and its effects on the geological barrier.