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| Entered date | Event description | |
|---|---|---|
| ENS 50141 | 25 May 2014 07:30:00 | At 0702 EDT on 5/25/14, Millstone Units 2 and 3 experienced a loss of offsite power and subsequent trip of both units. An Unusual Event was declared by Millstone Units 2 and 3 at 0715 EDT. Power is currently being supplied to all emergency busses by the emergency diesel generators. Offsite power is not available. At this time, it appears that the loss of offsite power is due to a localized issue in the Millstone switchyard. The surrounding areas were not affected. A decision was made to take the NRC to monitoring mode at 0749 EDT with Region 1 in the lead. Notified DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email.
The loss of offsite power was due to one main line coming into the plant shorting to ground. Emergency plan procedures have been implemented, natural circulation has been established, and the plant is stable. Offsite electrical power has been restored to both Unit 2 and Unit 3. Emergency diesel generators have been secured, and plant equipment has been restored to a normal line up. Extended loss of instrument air following the loss of offsite power complicated the recovery actions. The normal reactor coolant system letdown flow path was not able to be established. This resulted in the rupture of the pressurizer relief tank rupture disk inside containment. The relief valve on the volume control tank lifted when restoring normal letdown. This caused the primary drains transfer tank to overflow into the auxiliary building. This overflow path has been isolated. Supplementary leakage collection system radiation monitor HVR-RE19B, and auxiliary building normal ventilation radiation monitor HVR-RE10B, are indicating normal levels. Notified R1DO (Gray), R1DRA (Lew), NRR EO (Kokajko), IRD MOC (Grant).
At 1414 EDT the licensee terminated the Unusual Event. Notified R1DO (Gray), R1DRA (Lew), NRR EO (Kokajko), IRD MOC (Grant), DHS SWO, FEMA Ops Center, NICC Watch Officer, DOE Ops Center, USDA Ops Center, HHS Ops Center, and Nuclear SSA via email. |
| ENS 49377 | 23 September 2013 10:25:00 | Ventilation process radiation monitors for the Turbine Building Stack Discharge (monitors HVR*RE10A and HVR*RE10B) will be out of service for preplanned maintenance. This is reportable in accordance with 10 CFR 50.72(b)(3)(xiii). The licensee stated that this condition is being reported based on the inability to sufficiently identify and classify an Emergency Action Level for radiation releases that utilize input from the affected monitors while they are out of service. The licensee will notify state and local authorities. The licensee will also notify the NRC Resident Inspector. |
| ENS 49190 | 15 July 2013 10:44:00 | Loss of assessment capability due to preplanned maintenance affecting radiation monitors. Terry Turbine Radiation Monitor MSS-RE79 and Supplementary Leak Collection Release System Radiation Monitor HVR-RE19B will be out for preplanned maintenance. This is a reportable condition in accordance with 10 CFR 50.72(b)(3)(xiii). The NRC Resident Inspector has been notified. |