Millstone coming back online after shutdown
Waterford — Dominion has discovered the reason that a pump shut off on Sunday,which led to a shutdown of the Unit 2 reactor at Millstone Power Station.
The reactor was powering back up this morning, said spokesman Ken Holt, and was at 76 percent power, according to the Nuclear Regulatory Commission's daily status report.
Operators were cleaning a condenser in the cooling system Sunday and shut off one pump, but failed to wait until it was completely shut off before proceeding with the maintenance work, Holt said. A computer shut down a second pump, leading to a shutdown of the reactor.
The reason operators needed to wait is that new variable frequency drives, one per pump, were recently installed, giving Dominion a way to use less water, particularly during the winter flounder spawning season. With the new drives in place, the pumps operate differently than they did before, Holt said.
"The procedure wasn't explicit ... ensuring the pump is stopped before moving to the next step," Holt said. "Now, we've changed our procedures so they explicitly say to verify the pump is completely off before moving onto the next step."
The NRC and its onsite inspectors reviewed and were satisfied with Dominion’s analysis of the cause of the unplanned shutdown, and as a result allowed Unit 2 to reconnect to the grid, said spokeswoman Diane Screnci.
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