Limerick nuclear power plant returns one reactor to service, shuts down another

Exelon Corp. took the southeastern Pennsylvania plant's Unit 2 offline today after turning Unit 1 back on, following a notification of an unusual event July 18.

A southeastern Pennsylvania nuclear power plant returned one of its two reactors to service this week, then took the other one offline today.

Limerick Generating Station, in Limerick Township, Pa., outside Pottstown, returned Unit 1 to full power about 5 p.m. Wednesday after an electrical fault July 18 in a transformer that provides electricity to pumps that are part of electricity generation. The reactor went back online following replacement and testing of an electrical transformer, Exelon says in a statement.

The July 18 incident triggered what the U.S. Nuclear Regulatory Commission calls notification of an unusual event. The federal agency says there are about a dozen unusual events declared annually at the nation's 104 operating nuclear plants.

About noon today, operators at the plant took the Unit 2 reactor offline to allow workers to replace a valve on the plant’s steam piping system. Station operators closely monitor performance of plant equipment and made the determination to replace the valve to ensure the continued reliable operation of the plant, according to a statement from Exelon.

Plant personnel will complete the maintenance and test the system before returning Unit 2 to service, Exelon says; the repairs can be performed only with the plant offline.

Operators at the plant today did not declare an unusual event, the lowest of four emergency notifications used by the Nuclear Regulatory Commission.

"This is what we would refer to as a scheduled maintenance outage," Dana Melia, Exelon's spokeswoman for the Limerick plant, said.

At full capacity, the plant's twin, 1,200-megawatt reactors provide electricity for the equivalent of 2 million homes, Exelon says.