Impact of failures of direct current systems on nuclear power generating stations

Reliability of the Class 1E dc power system is important in a nuclear power generating station. The dc power system is designed so that no single failure of a battery, or a battery charger will result in a condition that will prevent the safe shutdown of the plant. A review of various reports from 1989 through September 2001 showed that design errors, component failures in the battery chargers, overloading of dc buses, battery cases cracking, personnel errors, copper contamination, flaking of cell plates and aging caused the failure of batteries, battery chargers and 125 Vdc buses. The licensee should review their equipment, processes, and procedures to ensure these issues would not degrade the performance of their dc electrical system