On August 23, 2010, at approximately
2210 hours0.0256 days <br />0.614 hours <br />0.00365 weeks <br />8.40905e-4 months <br />, with the Palisades unit at 100% power, the turbine protection relays, 305L and 305R, were identified as being inoperable due to a loss of electrical power from their 125 VDC power supply. On an actual turbine low auto stop oil pressure condition, 305L and 305R energize to generate a loss of load trip signal to all four channels of the
Reactor Protection System (
RPS). 305L provides input to
RPS channels A and C. 305R provides input to
RPS channels B and D. The
RPS generates a
reactor trip upon receipt of two (2) of four (4) loss of load trip signals. The loss of load trip is required by Technical Specification (TS) Limited Condition of Operation (LCO) 3.3.1 and was inoperable until 305L and 305R were reenergized on August 24, 2010, at approximately
0939 hours0.0109 days <br />0.261 hours <br />0.00155 weeks <br />3.572895e-4 months <br />.
The on-shift operations crew entered a TS 3.3.1 LCO, however, TS 3.0.3 LCO should have also been entered. TS 3.0.3 LCO was applicable due to all four (4) loss of load input signals to the RPS being inoperable. The eight (8) hour notification was not reported within the required time frame due to a misinterpretation of the event that has since been re-evaluated and determined to meet the eight hour immediate notification requirement.
The safety significance of this even was minimal. Although required by TS, the loss of load trip function is not credited in the plant safety analysis.
The licensee has informed the NRC Resident Inspector.
