There are 440 nuclear reactors operating around the world, providing about 14 per cent of the world's electricity supply. Most were installed 30–40 years ago, when the relative cost of producing nuclear energy made it an attractive option.

After 1985, lower petroleum costs, combined with concerns over nuclear safety (raised by the nuclear accidents at Three Mile Island, United States, in 1979 and at Chernobyl, Ukraine, in 1986), stagnated worldwide expansion of nuclear-generated electricity.

But more recently,