ENS 46535
ENS Event | |
|---|---|
16:20 Jan 12, 2011 | |
| Title | Loss of Unit 2 Essential Service 480V Bus |
| Event Description | On January 12, 2011, at 1020 hours0.0118 days <br />0.283 hours <br />0.00169 weeks <br />3.8811e-4 months <br />, Unit 2 480V Essential Service Bus 29 was inadvertently deenergized. The cause of the bus trip was inadvertent contact with a bus feed breaker by a station employee during unrelated work activities. Normal power to Bus 29 was restored at 1026 hours0.0119 days <br />0.285 hours <br />0.0017 weeks <br />3.90393e-4 months <br />. While Bus 29 was deenergized Division II core and containment cooling systems were unavailable and inoperable.
The plant responded normally to the loss of Bus 29 with the exception of Bus 28/29-5 which should have automatically transferred from Bus 29 to the reserve feed from Bus 28. This condition renders both divisions of the Low Pressure Cooling Injection (LPCI) mode of the Residual Heat Removal (RHR) system inoperable. Technical Specifications 3.5.1.E has been entered, requiring restoration of LPCI in 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Bus 28/29-5 was manually energized from Bus 28 at 1213 hours0.014 days <br />0.337 hours <br />0.00201 weeks <br />4.615465e-4 months <br />; however, LPCI remains inoperable pending investigation and restoration of Bus 28/29-5 auto-transfer function. This event is reportable under 10 CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented fulfillment of a safety function. LPCI mode of the RHR system is inoperable because the auto-transfer function for Bus 28/29-5 provides a back-up power supply to the LPCI injection motor operated valves from Bus 28. A swing diesel test was in progress during this bus loss, however the diesel was not loaded and had no impact on the bus failure. The diesel was subsequently secured. The licensee notified the NRC Resident Inspector. |
| Where | |
|---|---|
Quad Cities  Illinois (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| LER: | 05000265/LER-2011-001 |
| Time - Person (Reporting Time:+-1.07 h-0.0446 days <br />-0.00637 weeks <br />-0.00147 months <br />) | |
| Opened: | Ken Hill 15:16 Jan 12, 2011 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Jan 12, 2011 |
| 46535 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |