ENS 47476
ENS Event | |
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09:15 Nov 24, 2011 | |
Title | Emergency 4160 Volt Ac Busses Declared Inoperable |
Event Description | On Thursday, November 24, 2011, at 0315 CST, with the reactor at 100% steady state thermal power, Kewaunee Power Station declared both emergency 4160 Volt AC busses inoperable due to voltages being high outside of the procedurally directed voltage band. As a result, in accordance with Technical Specification 3.8.9, Distribution Sources - Operating, Kewaunee entered Technical Specification LCO 3.0.3 to, within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, initiate shutdown of the unit. At 0410 [CST], per management direction, the load tap changers for the supply transformers were adjusted to reduce the emergency bus voltages to within their procedural operating band. At this time, both emergency busses were declared Operable and LCO 3.0.3 was exited. Minimum required accident voltages were met at all times.
The NRC Resident Inspector has been notified.
On November 24, 2011, EN # 47476 provided notification that both emergency 4160 Volt AC busses were inoperable based on voltages being high outside of a procedurally directed voltage band. Subsequent investigation and analysis determined that unnecessary conservatisms were used in the development of the voltage values used in procedure, OSP-MISC-002, Electrical Power System Weekly Surveillance Test. Review of the actual voltages present during the event determined that the voltages did not exceed the required values to support bus operability. Therefore, the busses remained operable and this condition did not meet the reportability criteria identified in 10 CFR 50.72. As a result, the notification made on 11/24/2011 is hereby retracted. The licensee informed the NRC Resident Inspector. |
Where | |
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Kewaunee Wisconsin (NRC Region 3) | |
Reporting | |
10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
Time - Person (Reporting Time:+2.03 h0.0846 days <br />0.0121 weeks <br />0.00278 months <br />) | |
Opened: | Mike Terry 11:17 Nov 24, 2011 |
NRC Officer: | John Knoke |
Last Updated: | Jan 18, 2012 |
47476 - NRC Website | |
Unit 1 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |