TRANSPARENCY AND TRACEABILITY IN PERFORMANCE ASSESSMENT OF HIGH-LEVEL NUCLEAR WASTE REPOSITORIES

Both the pre- and post-closure safety cases for high-level nuclear waste repositories rely to a significant extent on analyses based on mathematical models and use a large amount of data. Such analyses called integrated safety analysis (ISA) and performance assessment (PA), respectively, are usually quite complex. An ISA and a PA contain system descriptions and supporting databases, scenario analyses, consequence analyses, performance measure calculations, sensitivity and uncertainty analyses, and a comparison of estimated performance to regulatory requirements. For a regulator to evaluate compliance with applicable regulatory criteria, the implementor is expected to provide sufficient information in a license application for the regulator to fully understand and evaluate the implementor’s approach and results. Transparency and traceability in the implementor’s ISA and PA are necessary for the regulator to develop confidence in whether or not the regulatory criteria will be complied with. In this paper, we define the terms transparency and traceability as they are applicable to performance assessment of high-level nuclear waste disposal facilities and describe basic attributes (e.g., completeness, clarity, and consistency) of transparent and traceable documents supporting a license application. Although the paper focuses on the regulatory perspectives of transparency and traceability as applicable to high-level nuclear waste repositories, it presents an overview of a framework that may be useful for developing a regulatory framework for any waste disposal facility.