An approach for using risk assessment in risk-informed decisions on plant-specific changes to the licensing basis

This paper discusses an acceptable approach that the US Nuclear Regulatory Commission staff has proposed for using Probabilistic Risk Assessment in ma king decisions on changes to the licensing basis of a nuclear power plant. First, the overall philosophy of risk-informed decision-making, and the pro cess framework are described. The philosophy is encapsulated in five princi ples, one of which states that, if the proposed change leads to an increase in core damage frequency or risk, the increases must be small and consiste nt with the intent of the Nuclear Regulatory Commission's Safety Goal Polic y Statement. The second part of the paper discusses the use of PRA to demon strate that this principle has been met. The discussion focuses on the acce ptance guidelines, and on comparison of the PRA results with those guidelin es. The difficulties that arise because of limitations in scope and analyti cal uncertainties are discussed and approaches to accommodate these difficu lties in the decision-making are described. (C) 1999 Elsevier Science Ltd. All rights reserved.