Answer:
Uranium
Nuclear reactors require the use of nuclear fuels, elements that can be readily altered and will release thermal energy. Uranium is the most common element used as a nuclear fuel, although thorium is also possible.
Step-by-step explanation:
All nuclear power plants use nuclear fission, and most nuclear power plants use uranium atoms. During nuclear fission, a neutron collides with a uranium atom and splits it, releasing a large amount of energy in the form of heat and radiation.