Nuclear power now makes up about 25% of the generation of Georgia Power, the largest unit of Atlanta-based Southern Co.
First U.S. nuclear reactor built from scratch in decades enters commercial operation in Georgia::ATLANTA — A new reactor at a nuclear power plant in Georgia has entered commercial operation, becoming the first new American reactor built from scratch in decades.
Looks like the only completed Gen 3 nuclear reactors are in Asia, at Kashiwazaki (Japan), Kori (South Korea), Yangjiang, Fangchenggang, Tianwan (China), and Kudankulam (India).
Edit: I missed the Gen III+ part of that Wikipedia page. The other currently operation or under construction Gen 3+ reactors are in Sanmen, Shidao Bay, Taishan (China), Novovoronezh II, Leningrad II, Kursk (Russia), Akkuyu (Turkey), Rooppur (Bangladesh).
Not sure, this isn't super easy to research, but an identical reactor is being built along side this one, so if it is our only 3+ it hopefully won't be for long