Nuclear power refers to the application of nuclear reactions, which discharge nuclear energy to produce heat and is most generally utilized in steam turbines to generate electricity in a nuclear power plant. Nuclear energy can be obtained from nuclear decay, nuclear fission, and nuclear fusion reactions.
The controlled release of nuclear energy in a reactor is attained by controlling the fission without controlling a chain reaction. If a chain reaction occurs, then the amount of energy would increase exponentially, so in order to monitor the release of energy, fission must be controlled without controlling a chain reaction.