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| Entered date | Event description | |
|---|---|---|
| ENS 45951 | 24 May 2010 21:40:00 | The Technical Support Center (TSC) emergency ventilation system was declared inoperable when the acceptance criteria of a periodic surveillance test related to outside air flow was not met. The loss of TSC Emergency Ventilation Function represents a loss of emergency preparedness capability. Actions to restore the TSC Emergency Ventilation system operability are in progress. This event is being reported under I0CFR50.72(b)(3)(xiii). The Senior Resident Inspector has been informed of the event (by the licensee). |
| ENS 44665 | 18 November 2008 17:08:00 | On 11/03/2008, with Unit 3 shut down and all control rods in, an unexpected drift of three control rods out from their full-in position occurred. The immediate cause of this event was high control rod drive (CRD) cooling and exhaust water header pressures as the final group of hydraulic control unit (HCU) valves were being isolated. At the time, Operations personnel were in the process of completing the isolation of the CRD HCUs by closing the (101) Insert Riser Isolation Valve and (102) Withdraw Riser Isolation Valve on each HCU with a CRD pump in operation and the CRD charging water header isolated. A control rod drift alarm was received in the Unit 3 control room, followed by several rod position indication system (RPIS) indications that the associated control rods had drifted from position 00 (full-in) to their 'over travel-in' position. Later, all indications returned to the full-in position, with the exception of three CRDs. These three CRDs settled at final positions 06, 16, and 18, respectively. Immediate corrective actions were taken to re-open the 101 valve for each of the three CRDs, allowing the control rod to re-insert to full-in. The 101 valve was then re-closed. Calculations by nuclear engineering identified that the reactor remained subcritical for the actual plant conditions and that there was no risk of fuel damage. Initial review of the event by Exelon determined that it was not reportable. After additional review and evaluation, the decision was made to conservatively report the event pursuant to 10 CFR 50.72 (b)(3)(v), 'Event or Condition That Could Have Prevented Fulfillment of a Safety Function.' A root cause investigation is underway to determine the cause. The industry has been notified via the operating experience process on November 7, 2008. The licensee notified the NRC Resident Inspector. |
| ENS 43209 | 2 March 2007 22:33:00 | At 1912 hours on 03/02/07, a through wall leak was identified on the U3 High Pressure Coolant Injection (HPCI) Inlet Drain Pot drain piping. This piping is ASME Code class 2 piping and as required by the Technical Requirements Manual the piping was isolated which resulted in isolation of the U3 HPCI System. U3 HPCI was declared inoperable. This event is reportable under 10CFR50.72(b)(3)(v)(D). Piping repair preparations are in progress. The leak was discovered by a licensed operator on rounds. The Technical Specification is a 14 day LCO. The licensee notified the NRC Resident Inspector. |