Is the Cooling of Power Plants a Constraint on the Future of Nuclear Power?
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While cooling is clearly an essential factor in the siting of individual nuclear plants, this necessary function is a readily manageable aspect of nuclear power operations and constitutes no constraint on the future growth of nuclear power as a large-scale low-cost provider of clean energy with highly stable prices and strong security of supply.
Steam-driven turbines generate most of the world’s electricity. These “thermal” power plants produce the necessary heat using uranium fuel or a fossil fuel - coal, natural gas, or oil.
In the physics of the steam cycle - as water is vaporized and then cooled, condensed and recycled - the production of surplus heat is inherent.
To achieve the requisite heat discharge, power plants normally employ various techniques of “wet” cooling, which use water to transfer heat to the air through evaporation or to a nearby water body with adequate absorptive capacity.
Looking ahead, the question of wet cooling for 21st century power plants will focus mainly on those fuelled by uranium and coal. Oil-fuelled thermal plants are increasingly rare for reasons of cost, and traditional gas-fired plants are giving way to combined-cycle gas plants in which very high efficiency yields less surplus heat and a greatly reduced cooling requirement.
Cooling for coal-fired and nuclear plants is plainly not an issue where the availability of water is unlimited, as when the plant is sited by a large body of water. The wet cooling problem can arise for plants sited on rivers and other locations where water availability is limited in quantity or by regulations on the temperature of returned water.
The amount of cooling required for a steam-cycle plant of any given size is determined by its thermal efficiency. By this measure, coal plants generally have a slight edge over nuclear plants and a correspondingly somewhat lesser need for cooling water.
This distinction does not, however, impede nuclear operations. Unlike coal-fired plants, nuclear plants - which use a fuel that delivers nearly 200,000 times more energy per kilogram - may be sited with no cost or constraint from fuel logistics. For nuclear energy planners, this characteristic offers wide flexibility in site selection as they seek to ensure the availability of reliable cooling while optimizing costs.
Key factors in this calculation are the comparative extra expense of longer electricity transmission and of alternative and supplemental cooling technologies. In those instances where cooling needs might require longer transmission distances or adaptive use of various cooling technologies, the cost increment will usually be relatively minor, particularly when averaged with the costs of a larger nuclear fleet.