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By RUSTY DENNEN
For the second time in less than a month, one of North Anna Power Station's two nuclear reactors is offline.
Dominion power early Wednesday morning reported to the Nuclear Regulatory Commission that Unit 2 automatically shut down because of a problem with one of the reactor's steam generators at the Louisa County plant.
Steam generators are heat exchangers that turn water into steam, using heat from the reactor.
Richard Zuercher, spokesman for Dominion's nuclear operations, said Wednesday that the shutdown happened when four valves that govern the flow of steam simultaneously closed. The steam spins the turbine generator, which produces electricity.
"All systems and equipment functioned as designed to shut the unit down safely," Zuercher said.
Meanwhile, workers at the plant "are evaluating what caused the turbine governor valves to close."
There was no impact on Unit 1.
Zuercher said that it is unclear whether the shutdown is related to another one at Unit 2 earlier this month.
"We are still investigating," he said.
In that instance, plant operators shut down the reactor over concerns about degraded reactor coolant pump seals.
Zuercher said at the time that potential problems are addressed and repaired when they are discovered.
Neither problem posed a danger to the public or plant employees.
North Anna generates about 1,863 megawatts with its two reactors, powering about 450,000 homes. The plant is located on Lake Anna near the town of Mineral.
Dominion has an application pending with the NRC to build and operate a third reactor at the plant.
Rusty Dennen: 540/374-5431