Peach Bottom Dual Reactor Scram, September 15, 2003

Event Number: 40158
Region: 1
State: PA
Unit: [2] [3] [ ]
RX Type: [2] GE-4,[3] GE-4
Notification Date: 09/15/2003
Notification Time: 03:06 [EST]
Event Date: 09/15/2003
Event Time: 02:39 [EDT]
Last Update Date: 09/15/2003
Emergency Class: UNUSUAL EVENT
10 CFR Section: 50.72(a) (1) (i) - EMERGENCY DECLARED
Person (Organization):
Unit 2, 3
Initial PWR 100, 91
Initial RX Mode Power Operation
Current PWR 0
Current RX Mode Hot Shutdown


"A discretionary UE has been declared for PB (Peach Bottom) U/2 (Unit 2) and U/3 (Unit 3) due to a dual unit transient that has resulted in both unit's scramming with a Group 1 (Main Steam Isolation Valve closure) PCLS isolation.

"An electrical transient caused all 4KV emergency buses to be powered by the diesel generators. One diesel generator (E2) subsequently tripped leaving 6 of 8 (3 per unit) buses energized.

"Off-site power is available. Preparations for transfer back to off-site power is in progress. The U/3 (Unit 3) "D" SRV (Safety relief valve) opened and did not close until electrically deenergized. The SRV is closed at this this time.'

Both reactors scrammed at 0132 EDT.

NRC Resident Inspectors, State and Local were notified by the licensee.

--PEACH BOTTOM-2 AND -3 TRIPPED EARLY THIS MORNING FOLLOWING "an electrical disturbance on the grid," Exelon said. The company said that the units shut down as designed, but one of the four emergency backup diesel generators tripped about an hour after the generators all came on line. Exelon spokesman Ted Caddell said the company is still investigating the cause of the diesel generator trip. He declined to give an estimate as to when the two units would return to service.

NEPA News: Two units at nuke plant shut down; grid disturbance cited

September 15, 2003

An electrical disturbance on the power grid cut off incoming electricity at the Peach Bottom nuclear power plant and caused both reactors to shut down automatically early Monday, Exelon Nuclear officials said.

Plant officials declared an "unusual event" just after 2:30 a.m.

The plant's four emergency backup diesel generators provided emergency power for about an hour, said Exelon spokesman David Simon. One of the generators malfunctioned, and then another backup source of power was used to power vital equipment, such as lights and emergency feedwater pumps, until power was restored later in the morning, Simon said.

No radiation was released and there were no injuries to workers, Simon said.

An unusual event is the lowest of four emergency classifications set by the Nuclear Regulatory Commission.

Both reactors remained shut down at 11 a.m., and plant officials were preparing to restart the reactors. Simon declined to say how soon they would be back on line.

"No utility gives out that information," he said.

PJM Interconnection, the company that operates the power grid in the Mid-Atlantic, said it was investigating the grid disturbance. PJM spokesman Ray Dodter said the company couldn't yet say what caused the disruption.

©NEPA News 2003

NRC Sends Augmented Inspection Team to Peach Bottom Plant

News Release - Region I - 2003-05
Office of Public Affairs, Region I
No. I-03-055 September 24, 2003

Diane Screnci (610) 337-5330
Neil A. Sheehan (610) 337-5331

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 teams 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 plants 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 managers 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.

Peach Bottom to get more oversight

The NRC will increase its inspections after four unplanned shutdowns of the nuclear plantís unit 2 reactor.

Daily Record staff
Saturday, November 15, 2003

For the next year, the U.S. Nuclear Regulatory Commission will increase the frequency of its inspections at Peach Bottom Atomic Power Stationís unit 2.

Since October 2002, unit 2 has experienced four unplanned reactor shutdowns, said Neil Sheehan, commission spokesman. An NRC rule permits a utility to have three unscheduled reactor shutdowns within 7,000 critical hours of operation or about one year, he said.

If a reactor has more than three unplanned shutdowns, the NRC bumps its level of oversight of the reactor.

Dave Simon, spokesman for Exelon Nuclear, said the issue of the shutdowns will be addressed at a public meeting slated for next week. Exelon Nuclear declared an unusual event Sept. 15 when electrical breakers on the PJM Interconnection power grid failed to isolate a lightning strike in Chester County.

The strike generated a power surge on two electrical lines that feed into the plant, forcing the unit 2 and unit 3 reactors into automatic shutdown.

Exelon co-owns and operates Peach Bottom Atomic Power Station and Three Mile Island unit 1 in Dauphin County.

On July 22, a fault in the main generator system caused an automatic shutdown of Peach Bottomís unit 2. The unitís computerized reactor protection system received an over-current signal from the generator, which caused a trip of the main turbine and shut down the unit.

On April 12, the power stationís unit 2 reactor shut down after an air line failure. The malfunction resulted in the closure of a main steam line isolation valve, which tripped the automatic shutdown.

An equipment failure that caused multiple bypass valves to open Dec. 21 of last year also led to an unplanned shutdown of Peach Bottom Atomic Power Stationís unit 2 reactor.

In response to those four unscheduled reactor shutdowns, the NRC has labeled unit 2 with a white performance indicator. A green indicator is awarded to reactors that require the basic level of inspection. The next level up, a white performance indicator, is assigned to a reactor that requires extra monitoring.

As part of the additional inspections, NRC officials will examine the unit 2 reactor for equipment reliability and operator performance, Sheehan said.

ďThese shutdowns pose no danger to the public,Ē he said.

Reach Sean Adkins at 771-2047 or


U.S. Nuclear Regulatory Commission officials and members of Exelon Nuclear staff will meet at 6 p.m. Tuesday at Peach Bottom Inn in Peach Bottom Township.

The public meeting will focus on the results of an inspection conducted by an NRC Augmented Inspection Team that investigated the Sept. 15 shutdown of Peach Bottom Atomic Power Stationís unit 2 and unit 3 reactors.

A report detailing the teamís findings will be issued next month.