Pennsylvania nuclear power plant in ‘Hot Shutdown’ over valve closure via lehigh valley live

A southeastern Pennsylvania nuclear power reactor unexpectedly shut down Monday night, and the owner was trying to find out why.

Unit 1 at Exelon Corp.’s Limerick Generating Station in Montgomery County automatically shut down about 9:40 p.m. after a valve on a main steam line closed, Exelon said Tuesday.

“Plant equipment responded as designed during the shutdown,” the company said in a statement. “Station operators responded appropriately and technical experts are working to determine the cause of the valve closure.”

An Exelon spokeswoman could not say Tuesday night how long the repairs were expected to last.


The Limerick plant about 30 miles south of Allentown and 21 miles northwest of Philadelphia has a second reactor that was unaffected and continued Tuesday to generate electricity, according to a U.S. Nuclear Regulatory Commission “event notification report.”

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

The Norristown, Pennsylvania-based Times Herald reports the valve closed due to a leak in the nitrogen supply line, which is the gas used in the hydraulic system to operate the valve, citing U.S. Nuclear Regulatory Commission spokesman Neil Sheehan.

“During an accident, the (main steam isolation valves) would be closed to prevent the release of radioactivity from the containment building, which houses the reactor,” Sheehan told The Times Herald in an email.

The valve closure caused “reactor pressure to rise, exceeding the reactor protection system (RPS) setpoint …,” the NRC says in its report.

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