The most common fuel for nuclear power plants is uranium.
Processing uranium requires mining, milling, enrichment, and fuel fabrication, all of which use significant quantities of water.
Mining – Uranium mining consumes one to six gallons of water per million Btus of thermal energy output, depending on the mining method.[6] Mining uranium also produces waste that can contaminate local water sources, and which can be especially dangerous given the radioactivity of some of the materials involved.
Processing – Uranium processing consumes seven to eight gallons of water for every million Btus of thermal output.[7],[8]
- Milling – The milling process uses a mix of liquid chemicals to increase the fuel's uranium content ; milling leaves behind uranium-depleted ore that must be placed in settling ponds to evaporate the milling liquids.[9]
- Enrichment – The next step, enriching the gaseous uranium to make it more effective as a fuel accounts for about half of the water consumed in uranium processing. The conventional enrichment method in the United States is gas diffusion, which uses significantly more water than the gas centrifuge approach popular in Europe[10],[11]
- Fuel Fabrication – Fabrication involves bundling the enriched uranium into fuel rods in preparation for the nuclear reactor.
Water-Related Risk Management
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| Enrico Fermi Nuclear Power Plant in Michigan. Photo source: NRC |
In the event of a serious accident, such as an overheated reactor, a nuclear power plant is required by federal regulation to have an emergency supply of water that can continue to cool the plant for at least 30 days. These water sources, called Ultimate Heat Sinks (UHS), are used to cool the reactor, which will continue to produce heat long after it is turned off. During an accident, a UHS may need to supply 10,000 to 30,000 gallons of water per minute for emergency cooling. A UHS can be the same water source used for power plant cooling (lake, river, or ocean) or it can be a separate, dedicated water supply.[14]
When nuclear plants draw water from natural water sources, fish and other wildlife get caught in the cooling system water intake structures. While this is an issue for all power plants with water-cooled systems, a study completed in 2005 in Southern California indicates that the problem is more acute for nuclear facilities. The study investigated impacts from 11 coastal power plants and estimated that in 2003, a single nuclear plant killed close to 3.5 million fish--32 times more than the combined impact of all of the other plants in the study.[15]
Waste Storage
After being removed from the reactor, the nuclear fuel is still very hot and requires storage both to cool down and to control the risks of radiation poisoning. This stage can last as long as 15 years.[16] Water-based storage pools are a common way to cool spent uranium fuel bundles after they are used in nuclear reactors, though air-cooling can also be used. These systems consume limited amounts of water through evaporation.[1] DOE. 2006. Energy Demands on Water Resources: Report to Congress on the Interdependency of Energy and Water. U.S. Department of Energy.
[2] DOE. 2008. Estimating Freshwater Needs to Meet Future Thermoelectric Generation Requirements. National Energy Technology Laboratory.
[3] DOE. 2006.
[4] U.S. Government Accountability Office. 2009. Energy-Water Nexus: Improvements to Federal Water Use Data Would Increase Understanding of Trends in Power Plant Water Use.
[5] UCS. 2007. Got Water? Nuclear Power Plant Cooling Needs.
[6] UCS. 2007.
[7] A Btu or British Thermal Unit is a measure of energy content, usually used to describe the energy content of fuels. Because a Btu is so small, energy is usually measured in millions of Btus. One kilowatt hour is the rough equivalent of 3,400 Btus.
[8] UCS. 2007.
[9] Tester, J. W., and E. M. Drake. 2005. Nuclear Power. In Sustainable Energy: Choosing Among Options, 389-397. Cambridge, MA: MIT Press.
[10] Deutch, J. M., C. W. Forsberg, A. C. Kadak, M. S. Kazimi, E. J. Moniz and J. E. Parsons. 2009. Update of the MIT 2003 Future of Nuclear Power Study.
[11] DOE. 2006.
[12] UCS 2003. How Nuclear Power Works.
[13] UCS. 2007.
[14] UCS. 2007.
[15] Gunter, Linda, Paul Gunter, Scott Cullen and Nancy Burton. 2001. Licensed To Kill: How the nuclear power industry destroys endangered marine wildlife and ocean habitat to save money. Nuclear Information and Resource Service.
[16] Tester et al. 2005.
