56 A Process for Risk-Informed Decision-Making (PSAM-0088)

The use of PRA results in decision-making has been addressed in Regulatory Guide 1.174, which describes an integrated risk-informed decision-making process that was specifically developed to provide guidance to licensees on how to use risk information in a licensing submittal to change the licensing basis of a plant. While the guidance in that document was at a fairly high level, it has proved to be a useful and successful guide, and the principles of risk-informed decision-making described in RG 1.174 have been adopted for more general use in regulatory activities.

This paper describes a process developed to enable the United States Nuclear Regulatory Commission (NRC) to improve its use of probabilistic risk assessment estimates in decision-making. Recognizing that the various inputs to a decision are very different in nature, some being qualitative, and others, in particular the risk assessment, being quantitative, the guidance focuses on documenting each analysis so that its value and relevance to the decision can be clearly understood and suitably qualified to address uncertainties, and on documenting the decision so that the driving factors for the decision are identified. The process requires the use of templates to ensure that the risk estimates, uncertainties, and assumptions made in developing the estimates are fully defined, documented, and communicated to NRC decision-makers, and provides guidance to decision-makers on how to consider the relative importance, validity, and reliability of quantitative risk estimates in conjunction with other, qualitative, safety related factors.