ENS 46874
ENS Event | |
|---|---|
18:44 May 22, 2011 | |
| Title | Safe Shutdown Operability Concern Associated with Offsite Power Circuits |
| Event Description | On May 22, 2011, at 1444 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.49442e-4 months <br />, the Fermi 2 Control Room was notified by the Central System Supervisor that the switchyard voltage for both the 345kV (Division II) and 120kV (Division I) offsite power circuits following a generator trip would not be sufficient to sustain operability of the safety-related loads. Technical Specification (TS) 3.8.1 'AC-Sources Operating,' Condition E was entered at 1444 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.49442e-4 months <br />. At 1535, both offsite power circuit voltages were at acceptable levels and the offsite circuits were declared operable. Technical Specification (TS) 3.8.1, Condition E was exited at 1535 hours0.0178 days <br />0.426 hours <br />0.00254 weeks <br />5.840675e-4 months <br />. Abnormal Operating Procedure (AOP) 20.300 GRID was entered. The Emergency Diesel Generators (EDG) remained operable during the degraded voltage condition. The ability of the EDGs to fulfill their design function was not affected by this condition.
The event is being reported per 50.72(b)(3)(V)(A), as any event or condition that at the time of discovery could have prevented fulfillment of the safety function of structures or systems that are needed to shutdown the reactor and maintain it in a safe shutdown condition. The NRC Resident Inspector was notified.
This event is retracted. The original report was based on calculated unit trip voltage drop results reported to Detroit Edison by ITC Transmission Company that exceeded acceptance criteria. ITC has subsequently informed Fermi 2 that this notification was in error due to a software feature of their real time contingency analyzer that resulted in inappropriately high results. Based on the results of other similar real time contingency analyzers employed at that time, without the problematic software feature, none of the acceptance criteria were exceeded and both divisions of offsite power were capable of supporting operability of safety-related loads. Additionally, Fermi 2 has determined that even at the inappropriately high voltage drop originally reported, the Division II system could have performed its safety related functions. Therefore, there was no loss of safety function. The licensee has notified the NRC Resident Inspector. Notified R3DO (Lara). |
| Where | |
|---|---|
Fermi  Michigan (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | |
| Time - Person (Reporting Time:+22.32 h0.93 days <br />0.133 weeks <br />0.0306 months <br />) | |
| Opened: | Jim Konrad 17:03 May 23, 2011 |
| NRC Officer: | Joe O'Hara |
| Last Updated: | Jun 7, 2011 |
| 46874 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |