LIMERICK, Pa.—Officials at a nuclear power plant near Philadelphia have taken one reactor offline because of a potential valve problem.

The Mercury of Pottstown reports ( http://bit.ly/QnpsNR) Unit 2 at the Limerick Generating Station was shut down on Friday.

Plant spokeswoman Dana Melia says a slight rise in temperatures indicated a possible malfunction in a main steam valve. She says the valve can be replaced only if the reactor is offline.

Exelon Nuclear shut down Limerick's Unit 1 reactor last week for an electrical problem. The "unusual event" on July 18 fell under the lowest of four emergency classifications.

Unit 1 began operating at full power again earlier this week.

The Limerick plant is about 20 miles northwest of Philadelphia.

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Information from: The Mercury, http://www.pottsmerc.com