NRC: News Release - Region I - 2003-055 - NRC Sends Augmented Inspection Team to Peach Bottom Plant

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NRC NEWS
U.S. NUCLEAR REGULATORY COMMISSION

Office of Public Affairs, Region I
475 Allendale Road, King of Prussia, Pa. 19406
www.nrc.gov

No. I-03-055		September 24, 2003
CONTACT:	Diane Screnci (610) 337-5330 Neil A. Sheehan (610) 337-5331	E-mail: opa1@nrc.gov
NRC SENDS AUGMENTED INSPECTION TEAM TO PEACH BOTTOM PLANT Printable Version
The Nuclear Regulatory Commission has dispatched a six-member team from its Region I Office in King of Prussia, Pa., to the Peach Bottom nuclear power plant to look into the causes of, and the plant response to, the shutdown of the twin reactors at the site on September 15th. An electrical grid disturbance has been identified as the initiating cause of the shutdowns. Known as an Augmented Inspection Team (AIT), it will be charged with learning the facts surrounding the event at Peach Bottom, which is located near Delta, Pa., and operated by Exelon. The AIT members will arrive at the facility today. The team’s findings will be made public in an inspection report to be issued within about 30 days after the completion of its on-site reviews. At about 1:32 a.m. on Sept. 15th, at a location far from the plant site, breakers on the grid apparently did not function properly to isolate the effects of a lightning strike, resulting in a low-voltage condition on both of the off-site power lines that feed Peach Bottom. Like other nuclear power plants, Peach Bottom not only sends power to the grid, it also receives energy back for operational purposes. If those power sources are significantly reduced or interrupted, an affected plant will shut down. That is what automatically occurred at Peach Bottom immediately after its off-site power sources were impacted. As they are designed to do, the plant’s four emergency diesel generators started upon the interruption of off-site power. Those generators are used to provide power to key safety systems and assist with the safe shutdown of the reactors. At 2:30 a.m., one of the emergency generators tripped, or switched off, because of a problem with its diesel engine coolant system. The plant continued to have sufficient power to safely shut down the reactors. However, following the generator trip, Exelon declared an Unusual Event, based on the shift manager’s discretion, because of what were perceived to be degrading plant conditions. An Unusual Event is the lowest of four levels of emergency classification used by the NRC. Exelon restored the normal configuration of its power supplies at approximately 7:40 a.m. The Unusual Event was declared over at 10:46 a.m.