Rising seawater temperatures forced an unprecedented shutdown last month of a nuclear reactor on the Connecticut coast.
Dominion Resources Inc. was forced to shutter Unit 2 of its Millstone nuclear plant in Waterford on Aug. 12 because water being drawn from Long Island Sound was too hot to cool emergency diesel generators and other safety-related equipment.
Dominion has recorded a steady rise in water temperatures at the plant since 1975, but the warmth recorded last month topped all, utility spokesman Ken Holt said. The plant's operating license requires that the 37-year-old reactor be shut down if cooling water tops 75 degrees Fahrenheit (Greenwire, Aug. 14).
"This is the first year that it's been a real challenge for us, the temperatures being that high," Holt said. "In previous summers, you get a week where it approaches the limit, but this summer it's been closer to the limit longer than any other summer on record."
This summer -- which the National Weather Service says is the third warmest on record since 1895 -- has caused the most trouble for reactors in the Northeast and Midwest, a challenging situation compounded by a record drought across the Great Plains. Jake Crouch, a scientist at NOAA's National Climatic Data Center, said the warming trend makes it likely that the United States will see more summers just like this.
"It's like this will be the new normal, as opposed to what we've seen in the past," Crouch said.
Some are treating the Millstone shutdown as a wakeup call. Nuclear Regulatory Commission Chairwoman Allison Macfarlane has asked her staff to examine the effects of climate change on reactors. And House Energy and Commerce Committee ranking member Henry Waxman (D-Calif.) and Rep. Rush Holt (D-N.J.) urged the panel's Republican leadership to hold a hearing on the matter.
Nuclear reactors are "canaries in the coal mine" because they are more sensitive to warming temperatures than other generators, said Mihaela Carstei, associate director of the nonpartisan Atlantic Council's Energy and Environment Program. She added that it's an issue she has flagged for years.
"The trend is that we're going to experience higher and more frequent peak temperatures, and with increased temperature brings warmer water or warmer air, and you may have to switch to dry cooling," Carstei said. "We're going to be in a very tight situation because it's harder to put in a lot of investment all at the same time, instead of planning and adapting."
But industry officials say the problem is manageable. This summer's heat waves did not disrupt electricity production at the country's 104 reactors, they say, and Millstone's license is "conservative" and possibly outdated.
Steve Kerekes, a spokesman for the Nuclear Energy Institute, said 85 to 90 percent of nuclear facilities operated at full capacity this summer, which is consistent with previous years.
"If there was any kind of substantial impact related to summer temperature, there's no way we could maintain that number," Kerekes said. "If that trend existed, there's no way we could post those numbers."
But David Lochbaum, director of the Union of Concerned Scientists' Nuclear Safety Project, said plants have been forced to power down more frequently during the past two decades at a rate that may not yet be detected in NEI's power production analyses.
"If plants had to shut down for months, [the statistics] would pick it up," Lochbaum said. "But if only for a matter of days, then that wouldn't show up."
'Time will tell'
Some federal scientists are warning that power plants will face challenges from hotter air temperatures, reduced rainfall and increased competition for water in the coming years.
Michael Hightower, lead researcher for Sandia National Laboratories' Water for Energy project, said warming is exacerbated in shallow water bodies, such as Long Island Sound, where the Millstone plant is located. Nuclear plants adjacent to large open bodies of water, he said, are less likely to feel the effect of rising temperatures because water there is traditionally cold, he said.
Millstone's closure suggests the warming trend is speeding up and spreading, Hightower said.
"It's suggesting that the trends are accelerating, so we're seeing it in more and more areas and more and more parts of the country," he said. "I wouldn't say that every coastal power plant is going to have a problem, but power plants that are in shallower regions -- bays, estuaries -- that are in places that have traditionally warmer water temperatures will see this as a bigger issue."
Issues arise because nuclear plants rely on water from rivers, lakes and oceans to cool the plants' safety systems like the control room and other machinery. If the water is too hot, it is incapable of taking heat away from those processes and critical cooling safety equipment.
Nuclear plants also face temperature limits on water they discharge. If the water's considered too warm for aquatic life, reactor operators must power down or close.
Hightower said accelerating warming trends were expected to begin affecting cooling water for the nuclear fleet this decade by 2015, but it is happening sooner than expected.
"These temperatures are going to continue to increase," Hightower said. "We're looking at this becoming more the norm than a drought."
Other Midwest power plants also felt the heat this summer.
In Illinois, the twin-unit Braidwood plant was on alert after its 2,500-acre cooling pond warmed to more than 100 degrees Fahrenheit (Greenwire, July 18).
But sources say it's not yet understood how the rising temperatures will affect each reactor site.
Research on how reactors and other power plants cope with changing water temperatures and availability is lagging, said Vince Tidwell, a nuclear expert at Sandia National Laboratories. "No one has looked at it, on a power-plant-by-power-plant level," he said.
William Skaff, NEI's director of policy analysis, said that if conditions worsen, plants can be upgraded to handle hotter water. Time will tell, he said, whether computer models on water temperature and quantity are correct.
"You have uncertainty in the models that deal with water temperatures and availability, then you have studies that try to calculate effects on power plants and they're uncertain because each plant is different," Skaff said.
"What we have to do is look at the situation right now and there are things that can be done in terms of intake temperatures if, say, 20 to 30 years from now, temperatures become a problem."
If scorching summers are the new normal, plant operators could be forced to spend millions of dollars to study whether their plants can safely operate using warmer water and possibly install new equipment to safeguard the plants, said Lake Barrett, the former head of the Energy Department's Office of Civilian Radioactive Waste Management.
Millstone, for example, may have to install bigger "heat exchangers," large structures filled with hundreds of metal tubes that extract the heat from water as it moves through the plant.
Operators could also see financial loss when plants are closed, even for a matter of days. Dominion's Holt would not say how much the company lost when the Millstone plant was shuttered for more than a week, but he did say the utility didn't address the issue sooner because the needed study was a costly, long-term project.
But Barrett said warming waters would not halt the construction of new plants.
"Nuclear power plants are more difficult and are more challenged, assuming there's global heating of significance," Barrett said. "But to me, it's not a major determining factor on running existing plants or building new plants."
The Union of Concerned Scientists' Lochbaum also said the licensing regime that deals with temperatures should be revamped.
Many temperature limits are based on data on water temperature trends over past decades, he said, but those limits are changing and companies need to use forecasting data to look at possible impending climate trends.
"When plants go for relicensing, that's an opportunity to look forward," Lochbaum said. "It's a chance to look at the margins that are available to look at adjustments to revise them."
Scientists are also exploring ways to reduce power plants' reliance on water -- particularly relevant for the nuclear industry, which uses more water than any other electricity generator.
Search for alternatives
The Electric Power Research Institute is researching the use of chemically engineered nanoparticles to cool water. The particles would allow the water to soak up more heat and reduce the amount of water the generators need.
The technology, EPRI said, could cut water usage at some power plants by as much as 20 percent. It is one of four research projects the institute hopes will be "out of the box" game-changers for the industry.
EPRI is also studying whether refrigerants can be used to chill water and thereby reduce the need for energy-intensive cooling towers.
That technology, which could slash some plants' water usage by 75 percent, is slated to be tested next year in a pilot project at Georgia Power's Plant Bowen, about 50 miles northwest of Atlanta.
Even so, Kent Zammit, senior program manager with EPRI's water and ecosystems group, said the nuclear industry may be slow to implement the developing technologies because regulations are so strict.
"In general, nuclear plants would be among the last ... due to high safety requirements," Zammit said. "It would be a risk to the capital."