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| Entered date | Event description | |
|---|---|---|
| ENS 43910 | 17 January 2008 10:10:00 | This 60-day report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Units 2 and 3 Primary Containment Isolation Systems (PCIS). On 12/11/07, at approximately 1645 hours, the 13 Kv non-safety related AS4 feeder breaker tripped as a result of an electrical fault downstream of the breaker. The electrical fault resulted in a momentary voltage dip on the offsite power source (3SU). The momentary voltage dip resulted in PCIS Group II and III isolations on Units 2 and 3. Unit 2 experienced inboard PCIS isolations, while Unit 3 experienced outboard PCIS isolations. The isolations involved various process lines including Reactor Water Cleanup (RWCU), Containment Atmospheric Control (CAC) / Containment Atmospheric Dilution (CAD), Drywell Sumps, and Containment Instrument Nitrogen. The Units 2 and 3 PCIS isolations were reset by approximately 1715 hours in accordance with procedures. All required isolation valves operated as designed. The AS4 breaker trip has been preliminarily determined to be an electrical fault of a fuse clip associated with a non-safety related transformer (00X029). This transformer provides power to equipment at the discharge canal control structure. This issue has been entered into the site Corrective Action Program (CRs 710316, 711652, 710769) for evaluation and implementation of further corrective actions. The NRC resident has been informed of this notification. |
| ENS 41193 | 12 November 2004 10:58:00 | |
| ENS 41192 | 12 November 2004 10:58:00 | This 60-day optional report, as allowed by 10 CFR 50.73(a)(1), is being made under the reporting requirement in 10CFR50.73(a)(2)(iv)(A) to describe an unplanned, invalid actuation of specified systems, specifically the Units 2 and 3 Primary Containment Isolation Systems (PCIS). On 9/18/04, at approximately 0357 hours (EDT), the 343SU offsite-power source tripped resulting in a fast transfer of expected 4 kV emergency busses to the alternate offsite power source. The fast transfer resulted in system isolations on both units due to the affect on the PCIS instrumentation logic. The system isolations are an expected occurrence for a fast transfer. The isolations involved various process lines such as Reactor Water Cleanup (RWCU) and Containment Atmospheric Control (CAC) / Containment Atmospheric Dilution (CAD). The Units 2 and 3 PCIS isolations were reset by approximately 0420 hours in accordance with procedures. All required isolation valves operated as designed. The offsite power source (343SU) was lost as a result of a momentary deenergization of the 220-34 Newlinville Transmission Line to clear a ground fault. The fault was approximately 29 miles from the PBAPS site and was caused by a lightning strike to a transmission tower near the Newlinville substation. Field inspections of the 220-34 Transmission Lines and Towers were performed and it was identified that there was a flash mark on the tower insulator confirming the lightning strike. It was determined that the protective relaying for the 220-34 Newlinville Transmission Line operated as designed. The 343SU offsite power source was returned to service by approximately 2115 hours on 9/18/04. This issue has been entered into the site Corrective Action Program (CR 254392) for evaluation and implementation of further corrective actions. The NRC Resident Inspector has been informed of this notification. |