Application of unavailability analysis method to determining periodic test procedure of emergency core cooling system

The test interval and the test procedure are the main factors that are related to the reliability of the emergency core cooling system in a nuclear power plant. A method is proposed to specify the allowable ranges of the test intervals for the minimal cut sets in the emergency core cooling system; lower and upper limits of test intervals are selected to minimize unavailability and to assure the unavailability goal respectively. A method is also proposed to determine test procedure. All patterns of test procedure for the emergency core cooling system are generated in the allowable ranges of test intervals, and the test procedure is selected to maximize the index (minus log. of (unavailability over unavailability goal), all devided by man-hours) for the purpose of both reliability increase and man-hours decrease. (author)