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Nuclear explained U.S. nuclear industry

There are 54 nuclear power plants operating in the United States

Electricity generation from commercial nuclear power plants in the United States began in 1958. As of August 1, 2023, the United States had 93 operating commercial nuclear reactors at 54 nuclear power plants in 28 states. The average age of these nuclear reactors is about 42 years old. The oldest operating reactor, Nine Mile Point Unit 1 in New York, began commercial operation in December 1969. The newest reactor to enter commercial service is Unit 3 at the Alvin W. Vogtle Electric Generating Plant in Georgia, which began commercial operation on July 31, 2023, and is the first reactor to come online since Watts Bar 2 was commissioned in 2016.

The number of operating U.S. nuclear reactors peaked at 112, and their combined net summer electricity generation capacity was 99,624 megawatts. The number of operating reactors declined to 104 in 1998 and remained there through 2013. The number declined to 92 operating reactors in 2022. Total U.S. nuclear net summer electricity generation capacity peaked in 2012 at about 102,000 MW and declined to 94,765 MW in 2022. Although though the number of reactors has declined since 2012, power plant uprates—modifications to increase capacity—at individual nuclear power plants have made it possible for the entire operating nuclear reactor fleet to maintain high capacity-utilization rates (or capacity factors). These relatively high capacity factors helped nuclear power to provide 19%–20% of total annual U.S. electricity generation from 1990 through 2021. Some reactors also increased annual electricity generation by shortening the length of time reactors are offline for refueling.

Nuclear reactors are decommissioned after they are retired from commercial service. According to the U.S. Nuclear Regulatory Commission, 22 commercial nuclear power reactors at 18 sites are in various stages of decommissioning.

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On December 2, 1942, under the bleachers of the football stadium at the University of Chicago, Dr. Enrico Fermi initiated the first controlled nuclear chain reaction. The experiment, conducted as part of the wartime atomic bomb program, also led to peaceful uses of the atom, including construction of the first U.S. commercial nuclear power plant at Shippingport, Pennsylvania, in 1958.

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Twenty-eight states have at least one commercial nuclear reactor

Most U.S. commercial nuclear power reactors are located east of the Mississippi River. Illinois has more reactors than any state (11 reactors at 6 plants), and at the end of 2022, it had the largest total nuclear net summer electricity generation capacity, at about 11,582 megawatts (MW). The Grand Gulf Nuclear Station in Port Gibson, Mississippi, has the largest U.S. nuclear reactor, with a net summer electricity generation capacity of about 1,400 MW. The two smallest operating reactors, each with a net summer generation capacity of about 520 MW, are at the Prairie Island nuclear plant in Red Wing, Minnesota.

Map of United States showing approximate locations of U.S. nuclear power plants as of June 2023

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The Grand Coulee Dam in Washington has the most electricity generation capacity of any electric power plant in the United States—7,079 megawatts (MW) net summer capacity. The Palo Verde nuclear power plant in Arizona, with three reactors, has the second-largest generation capacity—3,937 MW. Nuclear power plants generally use more of their electricity generation capacity on an annual basis than hydropower facilities. In 2022, Grand Coulee generated about 21 million megawatthours of electricity, while Palo Verde generated about 32 million megawatthours.

Many nuclear power plants have more than one reactor

The term power plant refers to an entire facility. A power plant may contain nuclear as well as non-nuclear electricity generating units. Each nuclear reactor located at a commercial nuclear power plant is unique and has its own personnel and equipment. The reactor provides heat to make steam, which drives a turbine that drives the generator that produces electricity.

The number of reactors at U.S. nuclear power plants varies. As of August 2023:

  • 19 U.S. nuclear plants had one reactor
  • 31 had two reactors
  • 4 had three reactors: Alvin W. Vogtle Electric Generation Plant in Georgia, Browns Ferry Nuclear Power Plant in Alabama, Oconee Nuclear Station in South Carolina, and Palo Verde Nuclear Generating Station in Arizona.

Some foreign nuclear power plants have as many as eight reactors.

Nuclear power plants are generally used more intensively than other power plants

For cost and technical reasons, nuclear power plants are generally used more intensively than coal- or natural gas-fired power plants, as measured by electric generation capacity factor. The average annual capacity factor for nuclear power plants in 2022 was 92.7%, which was higher than the capacity factors for other types of power plants.

Recent U.S. nuclear construction activity

The newest nuclear reactor to enter service since 2016 is the Unit 3 at the Alvin W. Vogtle Electric Generating Plant in Georgia as part of a two-unit expansion project. Vogtle Unit 3 began commercial operation on July 31, 2023, with 1,117 MW net summer electricity generation capacity.

In March 2012, the Nuclear Regulatory Commission (NRC) voted to approve South Carolina Electric and Gas Company's application to build and operate two new reactors, Units 2 and 3, at its Virgil C. Summer Nuclear Generating Station in South Carolina. However, construction on these reactors stopped in 2017.

One new reactor is nearing completion in the United States

One new reactor—Unit 4, with a planned net summer electricity generation capacity of about 1,117 MW—is nearing completion at the Vogtle nuclear plant in Georgia and is projected to enter service by early 2024. When Unit 4 is operational, Vogtle will be the largest nuclear power plant in the United States, with four reactors and a total 4,536 MW net summer electricity generation capacity.

The NRC issues license applications for new reactors in various stages of review. The NRC application review process can take up to five years to complete. Under current licensing regulations, a company that seeks to build a new reactor can use reactor designs that the NRC has approved. NRC's design certification is independent of their approval of applications to construct or operate new nuclear power plants. When the applicant uses an NRC-certified reactor design, that means that all safety issues related to the design have been resolved, and the focus of the NRC's review is the quality of construction. Construction of a nuclear power plant may take five years or more.

The U.S. Energy Information Administration (EIA) projects in the Annual Energy Outlook 2023 Reference case that total nuclear net summer electricity generation capacity declines to about 76,000 MW in 2040. Also in the Reference case, nuclear provides about 13% of total U.S. net electricity generation in 2050, a decrease from 18% in 2022.

Last updated: August 24, 2023, with data available at the time of update; data for 2022 are preliminary.