The owner of the Millstone Nuclear Power Station has requested license changes to avoid a repeat of the climate-related shutdown that occurred last summer.

In two letters to the Nuclear Regulatory Commission, Millstone’s owner, Dominion, asked that the seawater used to cool its two remaining operating units be allowed to reach a temperature of 80 degrees.

The current license allows it to reach 75 degrees as averaged over a 24-hour period or 77 degrees at any point. [Millstone letters to NRC.pdf]

Last summer, Millstone Unit 2 became the first U.S. nuclear plant to shutdown because the intake water was too warm. The hot, dry summer on top of an unusually warm winter caused the intake water to reach the 75-degree threshold on Aug. 12 and the plant shut down until Aug. 24. In fact the 77-degree level was reached at one point during the shutdown.

Unit 3 never had to shutdown, but Millstone officials said at the time that its intake water temperature, measured a bit differently at a deeper, cooler part of Niantic Bay, was creeping up.

The two Millstone units typically supplies about half Connecticut’s power.  The loss of one unit from the high temperatures forced the Independent System Operator, which manages the electric grid, to rely on a dirtier coal-fired unit In Bridgeport to pick up the slack.

Millstone spokesman Ken Holt said the plant’s engineers did extensive engineering analysis of what the existing equipment could handle in terms of additional water temperature. He said equipment changes were also considered, but were not submitted as part of this license change request. He said both plants will be installing new, more sensitive temperature gauges.

Left unanswered is whether 80 degrees is enough to account for the ongoing temperature increases in Long Island Sound. Since Millstone 2 went online in 1975, its scientists have seen a nearly 3-degree rise in the temperature they monitor.

Scientists who have studied such issues in relation to power plant needs have noted that temperature thresholds are based on past trends, and that might prove troublesome going forward since many of those trends no longer apply in the face of climate change.

Millstone spokesman Holt said plant scientists did look at both temperature and precipitation trends in reaching the 80-degree figure. But NRC spokesman Neil Sheehan said in reviewing the application, the NRC looks at the impact of the water temperature on the equipment, not an overall climate assessment.

That said, he noted that NRC Chairman Allison Macfarlane last year asked NRC staff to evaluate the potential impacts of climate change on the nation’s nuclear power plants, though no time frame was set.

Last summer Department of Energy and Environmental Protection Commissioner Dan Esty expressed multiple concerns over the loss of Millstone power during the high demand summer, the need for dirtier fuel plants in its absence and the environmental impacts of the ongoing climate change on the Sound generally and what that could mean for the plant with such things as additional debris clogs.

Spokesman Dennis Schain said if the NRC determines the temperature increase is safe, DEEP would be inclined to support it. “Such a step would help ensure that the plant could operate on more days in the face of what appears to be a continuing rise in water temperatures,” he said via email.

“It is obviously in Connecticut’s interests for Millstone to operate and provide electricity for our state and this region on as many days as is safely possible. No matter what temperature is set for the intake of water, Millstone will be required to continue complying with permit limits we have set for the volume of water they take in for cooling and the temperature of it when it is discharged into Long Island Sound.”

The review of the Millstone license change request is not expected until sometime in 2014, which begs the question of whether Millstone officials are worried about a repeat situation this summer.

“Right now current temperature trends are lower this year than they were this time last year,” Holt said, noting the cooler, wetter winter and cooler, though drier, spring. “Water temperatures are two or three degrees lower than last year.”

Jan Ellen is CT Mirror's regular freelance Environment and Energy Reporter. As a freelance reporter, her stories have also appeared in The New York Times, The Boston Globe, Yale Climate Connections, and elsewhere. She is a former editor at The Hartford Courant, where she handled national politics including coverage of the controversial 2000 and 2004 presidential elections. She was an editor at the Gazette in Colorado Springs and spent more than 20 years as a TV and radio producer at CBS News and CNN in New York and in the Boston broadcast market. In 2013 she was the recipient of a Knight Journalism Fellowship at MIT on energy and climate. She graduated from the University of Michigan and attended Boston University’s graduate film program.

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