This report focuses on the different functions of a repository within its life cycle and describes the processes relevant to the containment of long lived radioactive waste and other criteria influencing the long term integrity of the repository. It emphasizes the central role of safety and the importance of safety/performance assessments in the decision making process during repository development. Contents: 1. Introduction; 2. The geological disposal concept; 3. Near field components and processes; 4. Far field barriers and processes; 5. Confidence in adequate isolation; 6. Summary and conclusions.