Getting back to the original subject -
Nuclear, while it has its problems, is one of the carbon-free sources of energy that may help with reducing our carbon production. Unfortunately the very problems being caused by that carbon may make it more difficult to site and operate nuclear reactors. Many reactors need cool water to carry away the waste heat, and they need a certain starting temperature (i.e. the water has to be cool enough when it enters) and cannot exceed a maximum exhaust temperature (i.e. they can't return water to a river at fish-killing temperatures.) Other reactors use cooling towers, and this requires evaporating water to provide cooling. And nuclear power uses a lot more water than natural gas plants, due to its single-cycle design. As droughts intensify due to a warmer climate, there will be less water for such plants to use.
The one place where nuclear power plants won't see as much change is on the coast, since the amount of water they can pull from the sea is effectively unlimited, and sea temperatures will change far more slowly than land temperatures. However, fears of another Fukushima may limit the sites where coastal reactors can be permitted.
These problems have already resulted in nuclear power plants having to shut down to avoid exceeding thermal limits. From a Quartz article from Aug 8:
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Europe’s heatwave—which led to wildfires in Greece and Sweden, droughts in central and northern parts, and made the normally green UK look brown from space—is forcing nuclear plants to shut down or curtail the amount of power they produce. French utility EDF shut four reactors at three power plants on Saturday, Swedish utility Vattenfall shut one of two reactors at a power plant earlier last week, and nuclear plants in Finland, Germany, and Switzerland have cut back the amount of power they produce.
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From Huffpo earlier today:
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. .The second installment of the Fourth National Climate Assessment, a congressionally mandated update on the causes and effects of anthropogenic warming from 13 federal agencies, devoted its entire third chapter to water contamination and depletion. Aging, deteriorating infrastructure means “water systems face considerable risk even without anticipated future climate changes,” the report states. But warming-linked droughts and drastic changes in seasonal precipitation “will add to the stress on water supplies and adversely impact water supply.”
Nearly every sector of the economy is susceptible to water system changes. And utilities are particularly at risk. In the fourth chapter, the report’s roughly 300 authors conclude, “Most U.S. power plants … rely on a steady supply of water for cooling, and operations are expected to be affected by changes in water availability and temperature increases.”
For nuclear plants, that warning is particularly grave. Reactors require 720 gallons of water per megawatt-hour of electricity they produce, according to data from the National Energy Technology Laboratory in West Virginia cited in 2012 by the magazine New Scientist. That compares with the roughly 500 gallons coal requires and 190 gallons natural gas needs to produce the same amount of electricity. Solar plants, by contrast, use approximately 20 gallons per megawatt-hour, mostly for cleaning equipment, according to the Solar Energy Industries Association, a trade group.
Nuclear plants are already vulnerable to drought. Federal regulations require plants to shut down if water in the river or lake that feeds its cooling drops below a certain level. By the end of the 2012 North American heat wave, nuclear generation fell to its lowest point in a decade, with plants operating at only 93 percent of capacity.
The availability of water is one problem, particularly for the majority of U.S. nuclear plants located far from the coasts and dependent on freshwater. Another is the temperature of the water that’s available.
Nearly half the nuclear plants in the U.S. use once-through cooling systems, meaning they draw water from a local source, cool their reactors, then discharge the warmed water into another part of the river, lake, aquifer or ocean. Environmental regulations bar plants from releasing used water back into nature above certain temperatures. In recent years, regulators in states like New York and California rejected plant operators’ requests to pull more water from local rivers, essentially mandating the installation of costly closed-loop systems that cool and reuse cooling water.
In 2012, Connecticut’s lone nuclear power plant shut down one of its two units because the seawater used to cool the plant was too warm. The heat wave that struck Europe this summer forced utilities to scale back electricity production at nuclear plants in Finland, Germany, Sweden and Switzerland. In France the utility EDF shut down four reactors in one day.
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