Tuesday, August 21, 2007

NPR, the Steam Cycle and Nuclear Energy

This morning on NPR, Morning Edition ran a feature on France's nuclear reactor fleet and how about a third of those reactors had to cut power during the European heat wave of 2003.

While I'm not going to quibble with the basic premise of the piece, there are a number of facts that NPR left out that taken together, fail to show the entire picture.

The situation described in France and occurring right now at Browns Ferry here in the U.S. is not unique to nuclear reactors, it's something that can affect any power plant that uses the steam cycle -- and that's about 80% of our current generating capacity.

For example, three coal plants in Canada had to go off line recently for just the same reason.

We also need to keep in mind that this is not an operating problem, rather, utilities are simply acting as responsible stewards of the environment. As our CEO Skip Bowman put it in a note to us here at NEI this morning:

Commercial reactors typically operate under licenses/agreements that limit the temperature of the water returning to the river that they draw from. As the rivers heat up due to hot weather, they have to cut back on power and/or shutdown to avoid hitting the limit on water temps returning to the river. It is NOT that they "have trouble operating". There is a hit on overall thermal efficiency as inlet water temps go up, but it is lost in the shuffle, and is not why plants must scale back. They are simply being good environmental stewards and meeting their agreed-upon outlet limits.
For more on this, here's a post from my former NEI colleague Lisa Stiles from two Summers ago.

Why are we so concerned about stories like this one? Because anti-nuclear activists like to regularly regurgitate the story as proof that nuclear energy can't possibly contribute to helping constrain the emission of greenhouse gases in the face of climate change.

But as we saw just last week, at the peak of the American Summer, U.S. nuclear plants were running as close to 100% of capacity as practically possible.

As for the European heat wave of 2003, I think the following statement from Dr. Michael Ivanco, Society of Professional Engineers and Associates of Mississauga, Ontario taken from a story in the Hamilton Spectator puts it in the right perspective:
While water shortages have caused some thermo-electric plants to scale back production, it is important to note that they have not been required to shut down.

During the heat wave that hit Europe in the summer of 2003, by contrast, the contribution of wind-generated electricity to the electrical grids was virtually zero, since the wind did not blow.
As was the case during the California heat wave of 2006. By contrast, for the month of July 2006, according to my colleague David Bradish, all of the state's four nuclear reactors were running at above 100% capacity.

Dr. Ivanco continues:
While the overall output of nuclear plants may vary slightly due to other weather conditions, it will not drop to zero as some renewable sources do.

The single largest nuclear facility in North America is in the middle of the desert in Arizona and it does not suffer from any drought-related setbacks, simply because water conservation was built into its design.

There is no technical reason preventing future plants from being built to minimize water usage.
Like building a cooling tower to support possible new reactors at North Anna in Virginia.

To wrap things up, I'll hand it back over to Lisa Stiles, who reminded us that while temperatures might be high now, it won't be long before the mercury drops again:
And consider the other extreme. When the Northeast U.S. gets hit with several blizzards and the trains carrying fuel can't get through (it happened a few years ago) and natural gas prices are through the roof, and all the while the nukes are humming along better than ever, don't try to tell me that solar, wind, corn and biomass are going to save the day. Just like nuclear power, they all have their place in a diverse energy portfolio, they all have their pros and cons, but none alone is the answer to our energy and environmental problems.
Something to keep in mind.

9 comments:

Anonymous said...

I have not understood why the NPDES permits put an absolute cap on discharge temperatures. If the river temperature is, say, 91 degrees, and the discharge also is 91 degrees, how does that create a negative environmental impact? I would think it would make more sense to key the discharge temp to the intake temp. Am I missing something?

Mike said...

...during the California heat wave of 2006...for the month of July 2006, according to my colleague David Bradish, all of the state's four nuclear reactors were running at above 100% capacity.

I don't know exactly how the capacity factor is defined, but if its maximum is not 100% then what is it?

d kosloff said...

Capacity factor is based on a plant's rated capacity . During some weather conditions, or due to equipment improvements, a plant may be able to exceed its rated capacity for some period.

Alex Brown said...

It is a HUGE violation for a nuclear plant to run above its rated capacity, and hte NRC would be all over anyone who was running above rated capacity. The reason why numbers above 100% might be shown is that the plant received an uprate at some point and that whatever source is showing the reactor above 100% is not aware of the uprate and is using the old number to make their calculations on. It is should also be noted that capacity is always given in thermal MW and not electrical MW, so upgrading part of a plant's equipment can casue it to produce more electrical power than before at the same capacity. However it would not be correct to say that the plant is running over 100% because it is thermal MW that the plant is reated for not electrical MW.

KenG said...

Alex,

The licensed power is the core MW thermal. This is the sole factor in determining the maximum decay heat that could be generated after an accident and is the critical factor for licensing.

The capacity factor is calculated based on the electrical rating of the plant. This includes a conservative evaluation of the efficiency of the thermal and mechanical aspects of the electrical generation system. The NRC has no real interest in the electrical rating of the plant from a licensing basis. It is the owner that is vitally interested in the electrical rating because the plant sells megawatts, not heat.

The electrical rating can almost always be exceeded unless some portion of the plant is below design performance.

David Bradish said...

Mike,

The way EIA and NEI calculate capacity factors are by taking its generation divided by the product of the unit's rated summer capacity and number of hours operating. What you are probably thinking of is nameplate capacity. If you would like to check out the data for July to see how a capacity factor can reach over 100%, here is the link to EIA.

Left Atomics said...

Two related items.

"Cooling" is really only half the reason one "Cools" a turbine. The half is vacuum. The sliderule guys a hundred years ago discovered adding 29" of mercury vacuum to the low end of a turbine increases turbine efficiecny by 33%. BIG BUCKS.

Secondly, the plants in France that had to reduce output drew water from rivers. Few had man-made lakes to act as a buffer or reservoir. This was, IMO, a design flaw.

We can turn that around in the US with new builds if we include many acre lakes as part of the construction, turn them into fishing and recreational areas, and generally add Good Thinks to the ecology of the surrounding plant area.

David Walters

Matthew66 said...

Adding a man-mad cooling lake is not a panacea to cooling issues. A case at point: North Anna nuclear plant, where opponents to the plant's ESP application claimed the addition of two more reactors would cause environmental damage by increasing the ambient temperature of Lake Anna. Lake Anna was constructed to cool the originally planned four reactor plant (only two of the original four were built).

Thermal discharge will certainly be a factor in the licensing of any new reactor in the USA (and elsewhere probably). In some circumstances it may be more appropriate to build lakes, in others cooling towers, and others cooling channels. Each plant owner will need to make the best choice taking into account a variety of factors including the local environment.

schreinervideo said...

Thanks for great read! It's important for people who are still skittish about nuclear to know that it's an important piece in the world's energy puzzle.