4. Ukraine – 48 percent
The Ukraine has 15 reactors, generating nearly half of its electricity. Although it was the site of the Chernobyl disaster in 1986, the world’s worst nuclear power-plant accident, the nation has continued to rely on nuclear power. Most of the fuel for its reactors comes from Russia, but last April the Ukraine loaded US nuclear fuel into one of its reactors as part of a joint program to diversify its fuel sources.