| 11-29-2004 | On October 1, 2004, at 7:17 a.m., with the plant operating at 100% power, a loss of power to the Division 1 standby switchgear caused the automatic start of the Division 1 diesel generator.
Some non-safety switchgear were also deenergized by this event. At 7:30 a.m., an automatic reactor scram was initiated by a main turbine trip. Both of these events were caused by the flashover of high-voltage insulator strings in the station transformer yard. During the event, all main reactor feedwater pumps shut down, main condenser vacuum was lost, and the standby service water system initiated. The reactor core isolation cooling (RCIC) turbine steam supply valve isolated during the pressure transient associated with the main turbine trip. Operators manually started the high pressure core spray (HPCS) system to provide water to the reactor. A momentary low reactor water level caused a primary containment isolation signal. This is being reported in accordance with 10CFR50.73(a)(2)(iv)(A) as an event that resulted in the automatic actuation of the reactor protection system, Division 1 diesel generator, and standby service water system; an automatic isolation of primary containment; and the manual actuation of the RCIC and HPCS systems. There were no safety systems out of service at the time of the first event. Mitigating safety systems responded as designed. This event is bounded by the River Bend safety analysis, and was thus of minimal safety significance. |
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| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 10-01-2004 |
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| Report date: | 11-29-2004 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 4582004002R00 - NRC Website | |