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August 09, 2006


Eric McErlain

At our blog, my colleague Lisa Shell answered these charges in detail:



This is not a nuclear issue. All power plants that use a steam cycle (this includes nuclear, coal, gas, oil and most large solar plants) require a cooling source. This can be a river, a lake or the ocean or can be a cooling tower. Direct cooling with a body of water rejects the most heat to the water. A "wet" cooling tower reduces the heat rejected to a small fraction of that but costs more. A "dry" cooling tower is even more expensive but does not reject heat to the body of water.

Again, this problem has nothing to do nuclear power but is only related to the use of a condensing steam cycle (which the vast majority of electrical generating stations do.)

Jim Hopf

As Ken points out, all thermal cycle power plants, including nuclear and fossil plants as well as many types of renewable energy such as solar thermal, geothermal and biomass are vulnerable to the same problem. Only two specific sources, wind and photovoltaic solar, do not have this problem.

The difference between nuclear (and renewable) plants and fossil plants is that they do not actually CAUSE global warming. Thus, over the long term, fossil plants will actually make the hot water problem worse, along with a host of other GW-related problems.

There are many ways in which nuclear can largely handle this issue. Cooling towers can dramatically reduce the required water usage (I'm guessing that most of the plants having problems don't have cooling towers). Also, the new HTGR (or pebble bed) reactors have thermal efficiencies over 50% (vs. ~33%) which cuts the heat rejection per kW-hr generated in half.

Finally, the magnitude of the issue is being overplayed. These occassional power output reductions during hot spells is only reducing the annual generation of these plants by a few percent at most. As only a fraction of the nuclear plants are affected, the overall effect is only ~1%. The other 99% of the time, the nuclear plants are cranking out massive amounts of power w/o emitting any CO2.

Nuclear constitutes the great majority of emissions free power, in Europe and elsewhere. Saying that it is not a solution to global warming, over this hot water issue or any other, defies logic.


If this is not a nuclear issue, then why are we only hearing reports about nuclear plant shut-downs/curtailments?

Are all the other steam cycle plants being shut down, but not reported?

The main thing that I take away is that Nuclear is not as reliable as we (the public) have been led to assume. Moreover it seems to cut out on the highest demand days of the year, leading to significant (and costly) additional power requirements that could add stress to an already creaky energy system.

David Bradish


Nuclear plants operate at about a 90% capacity factor. Coal plants operate at about 70%. It is much more noticable when a nuclear plant dips a few percents than a coal plant. Coal plants are able to change their output much easier. And since it is more common for coal it is not news.

The Palo Verde nuclear station outside Phoenix, Arizona operates through the summer when temperatures are for several weeks at a time over 110 degrees. They have been doing this since the 1980s and have been having no problems.

You're reaching if you believe that a handful of plants dipping a few percentage points due to elevated temperatures constitutes nuclear is unreliable. There are 442 operating reactors in the world right now and that dip of generation for the few we're talking about lasted for a day or two.


This is news only because "nuclear" catches eyes in the headlines. Coal plants power down due to water temperature, emissions limit exceedance, all sorts of things and never are reported in the news. In fact, when a coal silo blows up or a steam line at a fossil plant bursts and workers are killed, it is generally only local news. Think how that would be reported for a nuclear unit.



If you study the articles carefully (at least some of them, anyway) you'll find a single sentence or so, deeply buried, that quitly/sheepishly acknowledges that some fossil units are being throttled back or shut down as well. But that gets hardly any play. Politics is very definitely playing a role here. Either that, or the fact that hyping nuclear problems sells more newspapers.

One other under-reported (and therefore forgotten) fact is that during the height of the deadly heat wave that struck Europe a year or so ago, the winds in the region were virtually still. Apparently, winds are often less during heat waves, which occur when a still, high-pressure dome lies over the region. Thus, just when it was needed most, Europe's wind power production was almost zero.

A drop to zero, compared with a drop of only a few percent for nuclear. So which, again, is a better option for a warmer-climate future? Don't get me wrong. I fully support both wind and nuclear, as neither of them actually CAUSES global warming. It's just that using lack of reliability as an argument against nuclear is a bit tough to take, especially when it comes from people (not you, necessarily) who advocate using renewables (only) instead, when the fact is that renewables are far less reliable and more intermittant. This is renewables' #1 problem.

Again, to the people raising this "issue", if nuclear is "not the answer" to GW, due to issues like this, then what is? Surely you don't advocate using fossil fuels instead! They are the actual cause of the GW problem, and they still have the hot water issue. What; all renewables? They have an even bigger reliability problem!

Gee, how about a combination of nuclear and renewables? That and some gas plants for occassional use (to cover gaps in generation). That along with, perhaps, some IGCC coal w/ sequestration. The result is a generation portfolio that is reliable and has negligible emissions.

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