The OECD Nuclear Energy Agency (NEA) hosted an international symposium on “Safety Cases for the Deep Disposal of Radioactive Waste: Where Do We Stand?” in January 2007. The NEA has spearheaded important developments in defining, and in developing methodologies to support, demonstrations of safety for deep disposal, including a similar symposium nearly two decades ago that provided the basis for a 1991 NEA collective opinion that the technical basis and methods exist for undertaking safety assessment of deep geological disposal. The 2007 symposium, co-sponsored by the European Commission and the International Atomic Energy Agency, provided the opportunity to review progress and to identify emerging trends and challenges. It brought together experts in the field of radioactive waste disposal from waste management organisations, regulatory agencies, scientific support organisations, international agencies, private sector consultants, and public interest groups both within and beyond NEA member countries.
The symposium showed that safety cases for radioactive waste disposal have evolved to become important tools both to assess safety and to aid in decision making. There is a good, shared understanding of what a safety case is and what comprises its main components. Importantly, the concept of a safety case today encompasses not only quantitative assessments of potential repository performance but also includes additional (and often more qualitative) lines of evidence and arguments that can contribute to confidence in safety. There has been significant evolution in terms of the analytical tools, lines of evidence, range of performance indicators and communication of the safety case. The value of international co-operation and dialogue in developing the concept and methodology of safety cases was underscored. These proceedings describe the discussions and conclusions of the symposium, and provide copies of the technical papers presented.