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).