Peter Beattie, the Queensland, Australia Premier, does not like nuclear power. As he said back in March, 2006:
“If power is being generated by uranium we don’t need enough coal. I mean this is … black and white – I am a strong supporter of the coal industry, I’m a strong supporter of clean coal technology and I do not support the uranium industry because it will be a competing energy source,” he said.
He remains firm in his conviction that it is better to burn coal than to use uranium. The ABC (Australian Broadcasting Corporation) published a story this morning in which Mr. Beattie points to a study indicating that a typical nuclear power plant uses more cooling water than a typical coal fired plant of the same power output.
However, Mr. Beattie then confused me by claiming that meant that a “clean coal” plant would be a better fit for his arid area than a nuclear plant in terms of reducing greenhouse gas emissions. (Be careful, the next few paragraphs may cause a few glazed eyes, but the details are important here.)
The technical reason that a typical nuclear steam plant uses more cooling water than a typical coal fired plant is that light water reactors run at a lower temperature than modern coal boilers, allowing the coal plants to achieve somewhat higher thermal efficiency. The quantity of cooling water needed per unit power is directly related to the plant thermal efficiency.
That statement assumes that both plants use water fed condensers to cool the steam that comes out of the turbines and that the cooling water system uses an evaporative cooling tower that takes advantage of the latent heat of vaporization to reject the heat to the surrounding environment. Casual observers of nuclear plants will recall seeing the billowing clouds of steam that come out of the cooling towers – that is the water that is consumed during the process.
A higher efficiency steam plant still needs water and still uses cooling towers; it just uses a bit less water. In the study that Mr. Beattie pointed to, a modern coal fired steam power plant would use about 25% less water than a nuclear heated steam power plant if both used evaporative cooling systems.
(Of course, if the plants are located on the coast, neither one needs to consume fresh water in order to cool the condenser; direct cooling with sea water is a great alternative that cannot heat up the ocean. It is also possible to use a dry cooling system that uses less water, but it is also more costly in terms of additional equipment and requires continuing operating cost considerations.)
What Mr. Beattie (a politician, not an engineer or scientist) fails to understand is that a “clean” coal plant would use at least 30-40% more water than today’s typical coal stations because they would need to expend considerable quantities of power to capture, compress and transport CO2. Mr. Beattie’s comment also does not take into account the other parts of the coal cycle that consume water, including coal washing to remove contaminants and water used to suppress coal dust in transportation systems.
I also cannot neglect the opportunity to mention that it is possible to design effective coolers for nuclear plants that do not use water at all. If the plant is a nuclear gas turbine, direct cooling with atmospheric air provides sufficient efficiency while eliminating the need to consume water to move the heat out of the system and into the surrounding environment. I just happen to know of a company (Adams Atomic Engines, Inc.) that anticipates using such coolers in atomic engines destined for arid areas.
