ENS Event | |
|---|---|
22:07 Apr 11, 2012 | |
| Title | Brief Loss of Rhr Pump Due to Voltage Transient |
| Event Description | On 4/11/12 at 1807 EDT, with the plant shutdown in Mode 5 during Refueling Outage 15, the 'A' Residual Heat Removal pump tripped while operating in the Shutdown Cooling Mode. The pump trip was due to an isolation of the E1150F009 'Division 1 RHR Shutdown Cooling Inboard Isolation Valve.' This resulted in an interruption of primary decay heat removal for approximately 11 minutes. Approximate calculated time to boil was 23.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. This is being reported under 10CFR50.72(b)(3)(v)(B) 'Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat.'
At the time of the pump trip, the station was attempting to restore power to Division 2 Bus 65E from the 64T cross tie bus. A voltage transient occurred due to a fault and caused a Group 4 (Shutdown Cooling/Head Spray) isolation signal. Abnormal Operating Procedure 20.205.01 'Loss of Shutdown Cooling,' was entered, the Group 4 isolation was reset and Shutdown Cooling was restored at 1818 EDT. An investigation is in progress to determine the cause of the bus fault. The licensee has notified the NRC Resident Inspector. |
| Where | |
|---|---|
Fermi  Michigan (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| LER: | 05000341/LER-2012-001 Regarding Loss of Shutdown Cooling Due to a Voltage Transient |
| Time - Person (Reporting Time:+0.52 h0.0217 days <br />0.0031 weeks <br />7.12296e-4 months <br />) | |
| Opened: | Jeff Groff 22:38 Apr 11, 2012 |
| NRC Officer: | Charles Teal |
| Last Updated: | Apr 11, 2012 |
| 47826 - NRC Website
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