Any of several devices that maintain and control a sustained nuclear fission chain reaction, for the production of energy, heat, or artificial elements, or for research purposes. The main fuel sustaining the reaction and consumed by the process is typically uranium or plutonium.
An apparatus in which the nuclear fission chain can be initiated, maintained, and controlled so that energy is released at a specific rate. The reactor apparatus includes fissionable material (fuel) such as uranium or plutonium; fertile material; moderating material (unless it is a fast reactor); a heavy-walled pressure vessel; shielding to protect personnel; provision for heat removal; and control elements and instrumentation. Designs of nuclear reactors currently in use or under development include
A mechanism fueled by fissionable materials in a controlled nuclear chain reaction that releases heat, which can be used for civil purposes to generate electricity. Since reactors also produce fissionable material (e.g. plutonium) in the irradiated fuel, they may be used as a source of fissile material for weapons. Nuclear reactors fall into three general categories: power reactors, production reactors (for weapons), and research reactors.