At
1331 hours0.0154 days <br />0.37 hours <br />0.0022 weeks <br />5.064455e-4 months <br /> [EDT] on August 18, 2015 with the plant in mode 1, IP2 entered TS [Technical Specification] 3.0.3 upon determination by the Shift Manager that MOV-746 and 747 at the outlet of the
Residual Heat Removal (
RHR) Heat Exchangers may not (fully) open on an Sl [Safety Injection] signal if there was a degraded grid voltage (where the voltage at the 480V Safeguards Buses is below the minimum drop-out value of 415V and above the loss-of-voltage value of 206.6V). The
MOV 746 and 747 valves are normally closed so the Sl signal with degraded voltage present could cause the fuses to fail. The time when the fuses would fail and the extent to which the
MOVs open has not yet been analyzed. Immediate corrective actions was taken to replace the fuses with fuses that would not fail. The
RHR trains were restored to an operable condition at 1419 and
1431 hours0.0166 days <br />0.398 hours <br />0.00237 weeks <br />5.444955e-4 months <br />. This event is potentially reportable under
10 CFR 50. 72(b)(3)(ii) and
10 CFR 50.72(b)(3)(v) since the condition has not yet been fully analyzed but has been corrected.
The plant remained at 100% power during the time of this event. All technical specification requirements were followed.
The licensee will notify the NRC Resident Inspector and the State.
