Nuclear reactors refer to a type of power plant that uses nuclear fission reactions to generate heat, which is then converted into electricity. In these facilities, uranium or other radioactive materials are used as fuel and when they undergo fission, they release energy in the form of heat. This heat is transferred to water, turning it into steam, which drives a turbine connected to an electrical generator, producing power. Nuclear reactors have high energy density and produce low greenhouse gas emissions compared to fossil fuel-based power plants, making them an important source of clean energy.