Failure modes and effects analysis (FMEA) of the ICS/NNI electric power distribution circuitry at the Oconee 1 Nuclear Plant. [Integrated control system/nonnuclear instrumentation]

The effects of nonnuclear instrumentation (NNI) and integrated control system (ICS) electric power supply failures have been analyzed for the Oconee Unit 1 nuclear plant. The instrument and control system power distribution circuits were analyzed to define a comprehensive set of 19 single-point failure modes. For each power supply failure, the failed and operating control system signal inputs were propagated through the partially energized control system circuits as well as the energized and deenergized output control devices to evaluate the initial plant response. In addition, the effects of the power supply failures on the principal control room parameter displays were combined with the initial plant response to the automatic control circuits to evaluate possible control room operator response. Plant responses to the defined power supply failures are described in detail.