This article is about applications of nuclear reactors as power sources. For the underlying energy itself, see Nuclear energy. For nuclear energy policy, see Nuclear energy policy. For countries which possess nuclear weapons, see List of states with nuclear weapons.

The Ikata Nuclear Power Plant, a pressurized water reactor that has no cooling tower, but cools by direct exchange with the ocean.

The Susquehanna Steam Electric Station, a boiling water reactor. The nuclear reactors are located inside the rectangular containment buildings towards the front of the cooling towers. The towers in the background vent water vapor. Nuclear power is any nuclear technology designed to extract usable energy from atomic nuclei via controlled nuclear reactions. The most common method today is through nuclear fission, though other methods include nuclear fusion and radioactive decay. All current methods involve heating a working fluid such as water, which is then converted into mechanical work for the purpose of generating electricity or propulsion. Today, more than 15% of the world's electricity comes from nuclear power, over 150 nuclear-powered naval vessels have been built, and a few radioisotope rockets have been produced.