I’ve had many media calls since Millstone Unit 2 had to shut down because temperature of Long Island Sound increased above the maximum design limit of 75 degrees (F).
Many reporters asked about the trend: Are nuclear plants being affected by rising water temperatures more now than in the past?
Even if the number of Millstone-like events is clearly higher now than in the past, it’s harder to single out rising water temperature as the sole cause.
In the past decade, the NRC has approved some 70 increases in nuclear plant maximum power levels.
Many of these were power increases of a few percent, but a number are increases of 15% or more. That’s significantly more waste heat that has to be released to the nearby lake, river, or ocean.
Four years ago, one of the Millstone reactors increased its power by 7%.
Those having uprates of 15% or more in the past decade include Brunswick Units 1 and 2, Clinton, Ginna, Hope Creek, Nine Mile Point 2, and Point Beach 1 and 2.
In July, the New York Times reported a similar concern that nearly shut down the two reactors at the Braidwood nuclear plant in Illinois when the water in its cooling pond got too hot. That was attributed to particularly high air temperatures and low rainfall, which reduced the amount of water in the pool. The situation was compounded by the fact that both Braidwood reactors increased their power by 5% in 2001.
Increasing reactor power levels and increasing water temperatures have collectively begun to increase Millstone-style events—nuclear plants having to reduce power or shut down because of impaired ability to reject waste heat. In some cases, as happened this past summer, plant owners seek waivers to allow them to continue to operate and discharge water hotter than the legal limits, despite the effects on the local ecosystem.
For more information on the energy and water-use connection, click here.