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How Climate Change May Affect Nuclear Power Plants

Tom Schueneman's picture

Environmental writer, journalist and web publisher. Founder of

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  • Aug 29, 2012

Many nuclear power plants could be impacted by warming water temperatures making cooling of reactor difficult

Many nuclear power plants rely heavily on access to nearby sources of cold water to keep the system cool. Many of these power plants were built several decades ago and some of them are not well prepared for the warmer weather we are now experiencing.

At a twin-unit nuclear power plant in Illinois, temperatures exceeded what is allowed with current regulations by four degrees Fahrenheit.

Craig Nesbit a spokesman for Exelon, which owns the plant, stated the following about the recent incident:

“I’m not a climatologist. But clearly the calculations when the plant was first operated in 1986 are not what is sufficient today, not all the time.”

The cooling pond consists of a 2,500-acre (10 square kilometer) lake. For a cooling system like this to function properly, the heat dumped into the pond eventually has to move somewhere else.

The warmer the weather the more saturated the air becomes, which means less energy is transferred away from the cooling pond. In a typical situation, cooling ponds loose their heat during the night, but because the temperatures these days have stayed above 90 degrees, the plant`s cooling system has been compromised.

The permitted level that originally was 98 degrees has now been increased to 100 degrees in order keep the power plant up and running.

The safety argument “is likely solid and justified,’’ stated David Lochbaum of the Union of Concerned Scientists, but “it is tough to argue (rationally) that warming water conditions are unforeseen.’’ That is a predictable consequence of global warming, he said.

Drought and water shortages, also caused by the change in weather, could potentially become a problem for nuclear power plants in the near future as well. A nuclear power plant`s cooling could become less efficient by water-shortages in much the same it does with increasing temperatures. Georgia, Alabama and similar states have to be extra careful with this in the coming years.


Energy Engineer Mathias Maehlum regularly writes about wind, solar, geothermal and other sources of energy at Energy Informative.

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James Coleman's picture
James Coleman on Aug 29, 2012

I usually see this argument presented as a nuclear-only problem and a safety risk: "but if the reactors aren't cool enough there'll be a disaster"! I note UCS only says it's "likely" there's a sound safety argument; I can't actually see any problem whatsoever, safety-wise.

I think it's worth mentioning that the reason there are temperature limits for coolant water in *all* thermal-cycle plants, fossil fuels included, is purely environmental. Water discharged above a certain temperature risks harming the local environment, and thus is not permitted; in warm weather the plant has to keep coolant water on site in cooling ponds for longer. Plants, obviously, have limited capacity to do this; so when the ponds are getting too full they need to shut down and stop producing heat - not because it'd be dangerous to do otherwise, but because without the coolant water in the turbine, the electrical output of the plant drops dramatically, and it becomes uneconomical to operate. Basic thermodynamics, the energy that can be extracted from the system is inversely related to the temperature gradient between the hottest and coldest points within it.

Reactors in particular operate at well above the boiling point of water, so you could literally use steam as a coolant if necessary, as long as the coolant pumps are still working (accidents occur only if the coolant pumps fail).


Good article as far as unexpected global warming impacts go; but a little light on some key facts, and sounding rather too much like it's purely a problem for reactors.

Robert Hargraves's picture
Robert Hargraves on Aug 29, 2012

Not just nuclear plants, but all thermal plants require cooling, typically by water. These include coal plants, combined cycle natural gas plants, geothermal plants, and thermal solar plants.

Rather than heating rivers, lakes, or oceans, some thermal plants evaporate water in cooling towers in order to generate electricity from turbine/generators. 

Advanced nuclear power plants that operate at higher temperatures have high efficiency and need less cooling than today's plants. Direct air-cooled power plants are also possible at high temperatures generated by thorium molten salt reactors such as LFTR (liquid fluoride thorium reactor). A new book, THORIUM: energy cheaper than coal covers these topics. It is described at


Nathan Wilson's picture
Nathan Wilson on Aug 30, 2012

"Drought and water shortages, also caused by the change in weather, could potentially become a problem ..."

Let's not forget the critical water dependence of hydro power and biomass/biofuels!  In fact, the problem effects all dispactable power except simple cycle natural gas turbines (which use almost double the fuel of a combined cycle gas plant with the same output).  Without dispatchable power, we simply have no practicle way to use variable renewables: solar PV, wind, & wave (at least for those communities that lack the geography or funding for pumped-hydro storage).

Of the important thing is not what happens at thirty year plants, but rather the choices we make for future plants.  As Robert's comment explains, with nuclear, we can choose dry-cooled plants that need no water.

Bart Blake's picture
Bart Blake on Aug 31, 2012

I find it ironic that environmentalists insinuate that globlal warming is dangerous for nuclear power plants. Envirnmentalists ought to be embracing nuclear power as the best hope for reducing global carbon emmissions,

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