Repository versus reactors: challenges in site assessment decision-making

The need for rationale decision-making in the regulatory environment leads to some interesting contrasts and common problems between a high-level nuclear waste repository and nuclear reactors. The applicable federal regulations, 10 CFR Part 60, 10 CFR Part 960, and Appendix A to 10 CFR Part 100 along with their supporting regulatory guides set the stage for regulatory decisions. These regulations differ in their emphasis on different facility lifetime, surface and subsurface emphasis, hydrogeology versus earthquake engineering emphasis. The question of what constitutes an appropriate level of reasonable assurance to protect the health and safety of the public will need further resolution. For reactors, the debate still continues. For repositories, the treatment of uncertainty, the extrapolation of short geologic time frame data to long facility lifetime (thousands of years), and the use of bounding versus reasonable conservative estimates will evolve through the complex decision-making process. The use of performance assessment methodologies for repositories as compared to probabilistic safety assessments for reactors presents a unique opportunity to use state-of-the-art techniques to assess uncertainty in all components in both natural processes and engineered components of each facility