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Electricity Generators Among Smallest Users
Electric power generation is among the smallest users of freshwater, accounting for about 3.3 percent of U.S. freshwater consumption, according to the USGS. This is about the same percentage of freshwater consumed by both industry and livestock raising. The largest consumption of freshwater is for irrigation (81.3 percent) and residential use (6.7 percent), the USGS said.

A typical nuclear plant supplies electricity around the clock for 740,000 homes. A nuclear power plant that returns cooling water directly to the source consumes the equivalent of six to 16 gallons of water per day per household. The same plant would consume the equivalent of 20 to 26 gallons of water per day per household if it used cooling tower systems. By comparison, the average U.S. household of three people consumes about 300 gallons of water per day for indoor and outdoor uses, according to the USGS.

Nuclear Plants Perform Well in Severe Weather
All power plants that use water for cooling may reduce electricity generation to moderate discharge temperature to remain in compliance with environmental permit requirements. Depending on the plant’s design and location, there may be environmental permit requirements associated with water levels or flow rates that may prompt power restrictions in drought conditions.

Although extremely high temperatures can reduce the efficiency of electricity production at nuclear power plants, the reactors can continue to operate safely.

Each reactor decreases power production if the cooling water source—lake, river or ocean—exceeds certain temperature or water-level requirements. The maximum allowed temperature for heat removal depends on the individual water source and is specified in each plant’s operating license.

Reduction in power production because of environmental conditions (excessive temperatures or low water levels) has occurred in the United States. However, it often is unnoticed by consumers because the power company is able to compensate for that reduced electricity production through other power production assets on the electricity grid.

Although the southeastern United States recently has suffered from drought conditions, nuclear plants were not affected significantly. In fact, nuclear plants in the region were critical to meeting electricity demand during a two-week heat wave in August 2007.

With the drought and unusually high temperatures last summer, hydropower generation was reduced by as much as 40 percent below annual levels for some companies.  Tennessee Valey Authority cut back on power production at its Browns Ferry Nuclear Plant in Athens, Ala., and at some of its most efficient coal plants last August to keep river temperatures from exceeding state environmental limits.

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