Developments on ASME code cases to risk-inform repair/replacement activities in support of risk-informed regulation initiatives

摘要

ASME Code Case N-658, "Risk-Informed Safety Classification for Use in Risk-Informed Repair/Replacement Activities" and Code Case N-660, "Alternative Repair/Replacement Requirements For Items Classified In Accordance With Risk-Informed Processes" are being completed to expand the breadth of risk-informed requirements for pressure-retaining items. This initiative, which is built from prior ASME Section XI risk-informed inservice inspection developments over the past decade, has been undertaken in conjunction with U.S. risk-informed regulation efforts. The U.S. Nuclear Regulatory Commission (NRC) is working with the industry on risk informing Title 10 Code of Federal Regulations Part 50 (1OCFR50). The Nuclear Regulatory Commission's basic proposal is to allow modification of some of the special treatment requirements of 1OCFR50. Their effort is proceeding via an Advanced Notice of Public Rulemaking, March 3,2000, and an announcement of Availability of Draft Rule Wording, November 29, 2001, to add 10 CFR 50.69, "Risk-Informed Treatment of Structures, Systems and Components." A parallel task by the Nuclear Energy Institute (NEI) to develop a guideline on how to implement the results of the rulemaking is also well underway via NEI 00-04 (Draft Revision B), "Option 2 Implementation Guideline," May 2001. This paper summarizes the content and status of approval of the proposed ASME Code Cases, including how they relate to the above NRC and NEI efforts. Some initial results from trial application of the Code Cases will also be cited.