Emergency Diesel Generator Power System Reliability 1987–1993

Abstract

This report documents an analysis of the reliability of emergency diesel generator (EDG) power systems at U.S. commercial nuclear plants during the period 1987-1993. To evaluate EDG power system performance, estimates are given of individual EDG train reliability to supply emergency ac power to the safety-related bus. The estimates are based on EDG train performance data that would be typical of an actual response to a lowvoltage condition on a safety-related bus for averting a station blackout event. A risk-based analysis and an engineering analysis of trends and patterns are performed on data from EDG operational events to provide insights into the reliability performance of EDGs throughout the industry and at a plant-specific level. Comparisons are made to EDG train statistics from Probabilistic Risk Assessments, Individual Plant Examinations, and NUREG reports, representing 40% of the U.S. commercial nuclear power plants. In addition, EDG train reliability estimates and associated uncertainty intervals are compared to station blackout target reliability goals.