Caption: Exelon's Limerick nuclear power plant, located in Pennsylvania.
Workers at the Limerick nuclear power plant in Pennsylvania brought Unit 1 back online after it was shut down.
The reactor automatically shut down Feb. 23 after a valve closed and raised the pressure in the reactor. The closure may have been caused by a loss of primary containment instrument gas pneumatic supply to the valve.
The outage did not impact electrical service to customers.
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