05000362/LER-2009-001

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LER-2009-001, Component Declared Inoperable After LCO Time Limit
San Onofre Nuclear Generating Station Unit 3
Event date: 09-14-2009
Report date: 11-16-2009
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
3622009001R00 - NRC Website

On 9/15/09 (Event Date) at 0030 PDT, with Unit 3 at 100 percent power, operators determined Limiting Condition of Operation (LCO) 3.8.1 B.2 for the Emergency Diesel Generators (EDG) was not met. Post- Accident Monitoring Instrumentation (PAMI) is required by TS 3.3.11 and is supported by the EDGs because the mission time exceeds the battery capacity. Some of the PAMI indications are displayed to the operators by the Qualified Safety Parameter Display System (QSPDS).

LCO 3.8.1 B.2 requires declaring EDG supported features inoperable within four hours. On 9/14/09 at 1200 EDG Train B failed a surveillance test; however, it was not identified that QSPDS Train A had been previously removed from service to repair a display monitor. Both trains of QSPDS were returned to service at 1728. At 0030 on 9/15 it was discovered QSPDS Train B had not been declared inoperable by 1600 as required, and a late log entry was made.

The apparent causes were an inadequate procedure, a failure to adequately assess the emergent equipment failure for cross-train impact, and failure to recognize QSPDS as integral to PAM I.

Corrective actions revised the EDG surveillance procedure to emphasize QSPDS is part of PAMI, and issued a required reading on preventing an inadvertent loss of safety function. There was no safety significance as components were restored to service within the allowable time limits.