A new reactor at Georgia’s Vogtle nuclear power plant is now in commercial operation, according to an announcement from Georgia Power, one of the plant’s owners. It is the first new nuclear reactor to start up in the United States since the Tennessee Valley Authority’s Watts Bar 2 was commissioned in 2016.

The new 1,114 megawatt (MW) Unit 3 reactor joins two existing reactors at Plant Vogtle, which is jointly owned by Georgia Power and three other electric utility companies. The plant’s first two reactors, with a combined 2,430 MW of nameplate capacity, came online in the late 1980s. Georgia Power expects another similar-sized fourth reactor, Vogtle Unit 4, to begin operation sometime between November 2023 and March 2024. The two new reactors will make Plant Vogtle the largest nuclear power plant in the country, surpassing the 4,210 MW Palo Verde plant in Arizona.

Construction at the two new reactor sites began in 2009. Originally expected to cost $14 billion and begin commercial operation in 2016 (Vogtle 3) and 2017 (Vogtle 4), the project ran into significant construction delays and cost overruns. The total cost of the project is now estimated at more than $30 billion.

Both Vogtle Units 3 and 4 use a new reactor design, the Westinghouse AP1000. This next generation advanced reactor has a smaller footprint and simpler design than previous generation reactor technologies. It also features robust passive safety systems that can shut down the reactor without any operator action or external power source. Units 3 and 4 are the first U.S. deployment of the AP1000 Generation III+ reactor. Two other Westinghouse AP1000 reactors were planned for a nuclear power plant in South Carolina, but construction was halted in 2017.

The first commercial nuclear power reactor in the United States came online in December 1957 in Shippingport, Pennsylvania. Most U.S. nuclear reactors were built in the 20-year period from 1970 to 1990. Prior to Vogtle Unit 3, the last nuclear reactor to start in the United States was Watts Bar Unit 2 in Tennessee. Construction on Watts Bar 2 began in 1973 but was suspended in 1985. Work resumed in 2007, and the reactor came online in 2016.

With 95,881 MW of nuclear power capacity at 93 operating commercial reactors, the United States has more nuclear capacity than any other country. Nuclear power plants produce nearly 20% of the country’s electricity.

Although a number of nuclear reactors have retired in recent years, there has been interest in nuclear power as an energy resource to help reduce the carbon footprint of the U.S. electric power sector. Generation from nuclear reactors doesn’t produce CO2 emissions and can provide essential baseload power that would otherwise largely come from coal- and natural gas-fired plants.

Recent legislation, such as the Bipartisan Infrastructure Law and the Inflation Reduction Act, supports U.S. nuclear energy as part of a clean energy, zero-carbon generating portfolio.