RISK RELATED RELIABILITY REQUIREMENTS FOR BWR SAFETY - IMPORTANT SYSTEMS WITH EMPHASIS ON THE RESIDUAL HEAT REMOVAL SYSTEM

Objective of this study was to identify and evaluate the major safety risk parameters of typical reactor safety systems for use in developing a reliability program. This effort was part of a larger research project aiming to evaluate the feasibility and effectiveness of introducing elements of proven reliability programs from other high technology industries into the nuclear industry. As a reference safety system, the Residual Heat Removal (RHR) system of a Boiling Water Reactor (BWR) was selected. A scoping evaluation was also made for a BWR reactor protection system (RPS). Plant information, existing PRA and other relevant analyses, as well as Licensee Event Reports were used as base material for this study. The results of this evaluation indicate that: (1) recovery of faults can have a very significant impact on the reliability requirements, (2) there exists an obvious need for an adequate reliability data base, (3) reliability analyses must be supported by detailed analyses of the plant's response to accident sequences, and (4) the development of effective emergency operating instructions and proper operator training must be one of the major elements of a Reliability Program.