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Nuclear Energy

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Electricity from Nuclear Energy

Nuclear energy originates from the splitting of uranium atoms in a process called fission. Fission releases energy that can be used to make steam, which is used in a turbine to generate electricity. Nuclear power accounts for approximately 20 percent of the United States' electricity production. More than 100 nuclear generating units are currently in operation in the United States.1

Uranium is a nonrenewable resource that cannot be replenished on a human time scale. Uranium is extracted from the earth through traditional mining techniques or chemical leaching. Once mined, the uranium ore is sent to a processing plant to be concentrated into enriched fuel (i.e., uranium oxide pellets). Enriched fuel is then transported to the nuclear power plant.

In the plant’s nuclear reactor, neutrons from uranium atoms collide with each other, releasing heat and neutrons in a chain reaction. This heat is used to generate steam, which powers a turbine to generate electricity. Nuclear power generates a number of radioactive by-products, including tritium, cesium, krypton, neptunium and forms of iodine.

Environmental Impacts

Although power plants are regulated by federal and state laws to protect human health and the environment, there is a wide variation of environmental impacts associated with power generation technologies.

The purpose of the following section is to give consumers a better idea of the specific air, water, land, and radioactive waste releases associated with nuclear power electricity generation.

Air Emissions

Nuclear power plants do not emit carbon dioxide, sulfur dioxide, or nitrogen oxides as part of the power generation process. However, fossil fuel emissions are associated with the uranium mining and uranium enrichment process as well as the transport of the uranium fuel to and from the nuclear plant.

Water Resource Use

Nuclear power plants use large quantities of water for steam production and for cooling. Some nuclear power plants remove large quantities of water from a lake or river, which could affect fish and other aquatic life.

Water Discharges

Heavy metals and salts build up in the water used in all power plant systems, including nuclear ones. These water pollutants, as well as the higher temperature of the water discharged from the power plant, can negatively affect water quality and aquatic life. Nuclear power plants sometimes discharge small amounts of tritium and other radioactive elements as allowed by their individual wastewater permits.

Waste generated from uranium mining operations and rainwater runoff can contaminate groundwater and surface water resources with heavy metals and traces of radioactive uranium.

Spent Fuel

Every 18 to 24 months, nuclear power plants must shut down to remove and replace the "spent" uranium fuel.2 This spent fuel has released most of its energy as a result of the fission process and has become radioactive waste.

Currently, the spent fuel is stored at the nuclear plants at which it is generated, either in steel-lined, concrete vaults filled with water or in above-ground steel or steel-reinforced concrete containers with steel inner canisters. In 2012, the President’s Blue Ribbon Commission on America’s Nuclear Future issued a report (PDF) (180 pp., 4.3M, About PDF) recommending the timely development of one or more permanent deep geological facilities for the safe disposal of spent fuel.

Radioactive Waste Generation

Enrichment of uranium ore into fuel and the operation of nuclear power plants generate wastes that contain low-levels of radioactivity. These wastes are shipped to a few specially designed and licensed disposal sites.

When a nuclear power plant is closed, some equipment and structural materials become radioactive wastes. This type of radioactive waste is currently being stored at the closed plants until an appropriate disposal site is opened.

Management, packaging, transport, and disposal of waste are strictly regulated and carefully controlled by the U.S. Nuclear Regulatory Commission and the U.S. Department of Transportation.


In 2008, U.S. uranium ore reserves were estimated at one billion, 227 million pounds. These reserves are located primarily in Wyoming and New Mexico.3

  1. U.S. Department of Energy, Energy Information Administration, Energy in Brief, April 22, 2011.
  2. U.S. Department of Energy, Energy Information Agency, Nuclear Power Generation and Fuel Cycle Report 1997 (PDF) (118 pp., 1M, About PDF).
  3. U.S. Department of Energy, Energy Information Administration, U.S. Uranium Reserves Estimates, July 2010.

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