Proposal for maintenance optimization scheme based on system based code concept

To develop rationalized maintenance plans for nuclear power plants, the characteristics of each plant must be considered. For sodium-cooled fast reactor (SFR) plants, constraints on inspections exist due to the specialty that equipment retaining sodium must be handled, which is one of the important points that must be considered in maintenance rationalization. In this study, we propose a maintenance optimization scheme, which is a design support tool, using risk information to develop a maintenance strategy based on the system based code (SBC) concept. The SBC concept intends to provide a theoretical procedure to optimize the reliability of structure, system and components (SSCs) by administrating every related engineering requirements throughout the life of the SSCs from design to decommissioning. "The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Code Case, N-875, Alternative In-service Inspection Requirements for Liquid-Metal Reactor Passive Components" was developed based on the SBC concept. The basic procedure of the Code Case has also been implemented in "The ASME Boiler and Pressure Vessel Code, Section XI, Division 2," which provides requirements for Reliability and Integrity Management programs for nuclear power plants, including advanced reactors. The purpose of this study is to establish detailed procedures for the maintenance optimization scheme based on the procedure in Code Case N-875. Furthermore, a quantitative trial evaluation of the core support structure of the next SFR under development in Japan is also performed using the maintenance optimization scheme.