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Nuclear explained Nuclear power plants

Nuclear power comes from nuclear fission

Nuclear power reactors use heat produced during atomic fission to boil water and produce pressurized steam. The steam is routed through the reactor steam system to spin large turbines blades that drive magnetic generators to produce electricity.

Nuclear fission occurs when a neutron slams into a larger atom, forcing it to excite and split into two smaller atoms—also known as fission products. Additional neutrons are also released that can initiate a chain reaction. When each atom splits, a tremendous amount of energy is released.

At the center of a nuclear reactor is the core, which contains fuel fabricated from uranium ore. Uranium ore is mined and processed to be eventually formed into ceramic pellets. Each ceramic pellet produces about the same amount of energy as 150 gallons of oil. These energy-rich pellets are stacked end-to-end in 12-foot fuel rods that are loaded into the reactor fuel assembly for plant operation.

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Nuclear reactors in the United States may have large concrete domes covering the reactors, which are required to contain accidental releases of radiation. Not all nuclear power plants have cooling towers. Some nuclear power plants use water from lakes, rivers, or the ocean for cooling.

Photo of a containment dome on a U.S. nuclear power reactor

Containment dome of a nuclear reactor

Source: Stock photography (copyrighted)

Nuclear power plants have generated about 20% of U.S. electricity since 1990

As of August 1, 2023, 93 nuclear reactors were operating at 54 nuclear power plants in 28 states. Of the 54 operating nuclear power plants, 19 have one reactor, 31 have two reactors, and 4 have three reactors. The U.S. nuclear energy industry has supplied about 20% of total annual U.S. electricity since 1990.

The United States generates more nuclear power than any other country

In 2021, 33 countries had commercial nuclear power plants, and in 15 of those countries, nuclear energy supplied at least 20% of their total annual electricity generation. The United States had the most nuclear electricity generation capacity and generated more nuclear electricity than any other country. France had the second-largest nuclear electricity generation capacity and third-highest nuclear electricity generation. In addition, France had the world's highest nuclear share—about 68%—of total national annual electricity generation.

Top five nuclear electric generation capacity countries, 2021

Country Nuclear electricity generation capacity (million kilowatts) Nuclear electricity generation (billion kilowatthours) Nuclear share of country's total electricity generation
United States 95.49 778.15 19%
France 61.37 360.70 68%
China 53.26 407.52 5%
Russia 27.73 222.44 20%
South Korea 24.43 150.52 26%
Source: U.S. Energy Information Administration, International Energy Statistics, as of August 7, 2023

Last updated: August 21, 2023, with data available as of August 7, 2023.