<title>Progress toward regulatory acceptance of risk-informed inspection programs for nuclear power plants</title>

Abstract

This paper will describe work within the American Society ofMechanical Engineers (ASME) committee responsible for rules for inservice inspection ofnuclear power plants. Work is progressing with the objective ofproducing proposals for risk-informed inspection programs that will be incorporated by the US Nuclear Regulatory Commission (NRC) into the Federal Regulations governing the construction and inservice inspection ofall domestic commercial power plants. The paper will describe in detail the two primary proposals now under development and review. Both are directed toward enhancing safety while reducing the expense ofperiodic examination ofpiping welds.The first proposal provides a sound technical basis for reducing the number ofClass 1 piping weld examinations as much as 60% while improving or maintaining equivalent safety. This is accomplished by using risk-informed techniques to reestablish the most important areas to examine. The second is a broader approach addressing all piping systems considered to be important under risk-informed assessment techniques.Both proposals are based on recent insights into risk analysis techniques developed within the pressure vessel industry, and both require evaluation oftheoretical analysis and inputs ofpractical experience related to a wide variety of detrimental conditions. These proposals are being supported by pilot programs in a number ofoperating nuclear power plants.The authors will also attempt to explain the institutional constraints inherent in the process ofobtaining regulatory recognition ofproposals developed cooperatively by industry and the regulatory agency.