An apparent violation having a preliminary low to moderate safety significance was identified during the licensees review of a similar issue identified at Crystal River Nuclear Plant Unit 3 on January 27, 2005. A design deficiency in a metering circuit for the sites normal 4160 volts-alternating current (Vac) offsite power supply induced a vulnerability whereby a single fault in the metering circuitry, for a given unit, could have resulted in the loss of all Division 1 and Division 2 safety-related 4160 Vac power on a given unit. The finding was determined to be greater than minor because it impacted both the
Initiating Events and
Mitigating Systems Cornerstones. The finding was preliminarily determined to be of low to moderate safety significance following the performance of a case-specific Phase 3
SDP. Corrective actions taken by the licensee included installing
temporary modifications on each unit to remove the metering circuitry in question.
