Nuclear power is power (generally electrical) produced from controlled (i.e., non-explosive) nuclear reactions. Commercial plants in use to date use nuclear fission reactions. Electric utility reactors heat water to produce steam, which is then used to generate electricity. In 2007, 14% of the world's electricity came from nuclear power, despite concerns about safety and radioactive waste management. More than 150 naval vessels using nuclear propulsion have been built.
Nuclear fusion reactions are widely believed to be safer than fission and appear potentially viable, though technically quite difficult. Fusion power has been under intense theoretical and experimental investigation for many years.
Both fission and fusion appear promising for some space propulsion applications in the mid- to distant-future, using low thrust for long durations to achieve high mission velocities. Radioactive decay has been used on a relatively small (few kW) scale, mostly to power space missions and experiments.
The nuclear power debate concerns the desirability of using nuclear fission reactors to generate electricity from nuclear fuel for civilian purposes.
Proponents of nuclear energy contend that nuclear power is a sustainable energy source that reduces carbon emissions and increases energy security by decreasing dependence on foreign oil. Proponents also emphasize that the risks of storing waste are small and can be further reduced by using the latest technology in newer reactors, and the operational safety record in the Western world is excellent when compared to the other major kinds of power plants.
Critics believe that nuclear power is a potentially dangerous energy source, with decreasing proportion of nuclear energy in power production, and dispute whether the risks can be reduced through new technology. Proponents advance the notion that nuclear power produces virtually no air pollution, in contrast to the chief viable alternative of fossil fuel. Proponents also point out that nuclear power is the only viable course to achieve energy independence for most Western countries. Critics point to the issue of storing radioactive waste, the history of and continuing potential for radioactive contamination by accident or sabotage, the history of and continuing possibility of nuclear proliferation and the disadvantages of centralized electricity production.
Arguments of economics and safety are used by both sides of the debate.