The Exelon (NYSE:EXC) Limerick 1 nuclear unit in Pennsylvania was automatically shut down at approximately 9:40 p.m. ET Feb. 23, after a valve on one of the station’s main steam lines closed.
“Plant equipment responded as designed during the shutdown,” Exelon said in a Feb. 24 news release. “Station operators responded appropriately and technical experts are working to determine the cause of the valve closure.”
An “event notification report” filed with NRC noted that “at 2140 EST on 02/23/2015, Unit 1 reactor automatically scrammed on a valid reactor high pressure signal (1096#). The reactor high pressure signal was caused by the closure of the 1C inboard main steam isolation valve (MSIV), causing reactor pressure to rise, exceeding the reactor protection system (RPS) set point.”
“Limerick Unit 1 will remain in Hot Shutdown until repairs can be made,” according to the NRC report. The licensee notified the NRC Resident Inspector, Pennsylvania Emergency Management Agency, and Berks, Chester and Montgomery counties.
Limerick 2 remained operating at 96% generating capacity, according to Nuclear Regulatory Commission (NRC) data. Units 1 and 2 are both pressurized water reactor (PWRs). Each unit has a generating capacity of roughly 1,100 MW.
Limerick Generating Station is located approximately 21 miles northwest of Philadelphia.
Last fall NRC approved a 20-year license extension for both Limerick units. The new licenses will expire Oct. 26, 2044, for Unit 1 and June 22, 2049, for Unit 2, NRC said.
In 2012 Exelon cancelled a significant generating capacity uprate that had been planned for Limerick.