Almost two weeks after shutting down one of its units because seawater was too warm to cool a reactor, Connecticut’s nuclear power plant returned to full service.
Unit 2 returned to 100 percent power Saturday, said Millstone Power Station spokesman Ken Holt. It shuttered Aug. 12 after record heat in July contributed to overheated water from Long Island Sound.
Water cools key components of the Waterford, CT-based plant and then discharges back into the sound. The water’s temperature was averaging 1.7 degrees above the 75-degree limit.
The temperature has since dropped to 72 degrees, Holt said.
“The water temperature cooled sufficiently to support operations and that, combined with the weather forecast, has given us the confidence to restart,” he said.
The U.S. Nuclear Regulatory Commission (NRC) issued an emergency license amendment to Millstone, a subsidiary of Richmond, VA-based Dominion Resources Inc., shortly before it shut down, allowing it to use an average temperature of several readings. Even that amendment wasn’t enough to prevent Unit 2 from closing.
Unit 2 has occasionally shut for maintenance or other issues, but in its 37-year history it has never gone down because of excessively warm water.
As Dominion considers long-term changes in weather and the possibility that excessively warm water will be the rule rather than the exception, it’s looking at doing an engineering analysis allowing the plant to operate at higher Long Island Sound temperatures, Holt said.
A study would take months and must go to the NRC for review, he said.
Millstone provides half of all power in Connecticut and 12 percent in New England.
Some scientists believe the partial Millstone shutdown was the first involving a nuclear plant pulling water from an open body of water. Nuclear plants that draw water from inland sources have powered down because of excessively warm water.