US nuclear power plant regulators approve higher water temperatures for 2nd Millstone unit

Connecticut's nuclear power plant won permission to use warmer water from Long Island Sound for cooling at the second of its two units, federal regulators said Monday.

The approval by the Nuclear Regulatory Commission allows the Millstone 3 unit to use water as warm as 80 degrees Fahrenheit, up from 75 degrees. Millstone first confronted the problem in the summer of 2012, shutting unit 2 for nearly two weeks when water from Long Island Sound averaged 1.7 degrees above the limit following the hottest July on record.

Water is used to cool key components of the plant and is discharged back into the Sound.

The agency approved a similar request for the Millstone 2 unit in April.

Neil Sheehan, a spokesman for the Nuclear Regulatory Commission, said allowing Millstone to use warmer water drew no opposition from the public. The federal agency needed to amend separate licenses and engineering reviews for the two units and the intake for unit 3 is at a greater depth than for unit 2, he said.

"Our review has determined that the plant's safety equipment and systems would continue to function without problems with the new temperature limit in place," the agency said.

Ken Holt, spokesman for the plant, owned by Dominion Resources Inc., said permission was sought for Millstone 3 to ensure that both units can operate with warmer water.

Millstone's shutdown two years ago was the first involving a nuclear power plant on an open body of water, said Dave Lochbaum, director of the Nuclear Safety Project at the Union of Concerned Scientists.

Nuclear power plants that were built in the 1960s and 1970s did not account for rising temperatures. Plant operators have better technology to measure water temperature projections, he said. Millstone's unit 2 began operating in 1975 and unit 3 started in 1986.

"It shows the temperatures are going up," Lochbaum said. "There's still debate over the cause of it."

The Nuclear Regulatory Commission initially issued an emergency license amendment, allowing Millstone to use an average temperature of several readings. It still was not enough to prevent the plant from shutting down.

With permission in hand from the federal government to take in warmer water from Long Island Sound, Millstone may need a change in its state permit that sets rules on water it empties back into the Sound. Spokesman Dennis Schain said the Connecticut Department of Energy and Environmental Protection is considering a request by Millstone to consider whether the nuclear plant's discharge permit must be modified.

Millstone has not had to exceed the temperature limit this year. Water temperature in Long Island Sound is 68 degrees, Holt said.

The plant provides half of Connecticut's power. New England's four nuclear power plants in Connecticut, Massachusetts, New Hampshire and Vermont accounted for one-third of electricity generated in the region last year, according to ISO-New England, the region's power grid operator.


Follow Stephen Singer on Twitter at