The nuclear power industry and reactor technology have constantly been developing for more than five decades now. Nuclear reactors can be classified based on their nuclear reaction, the moderator material used, generation of the reactor, fuel phase, fuel type, coolant used, etc. The fusion nuclear reactors are mainly dealt with because the fusion reactors are still in the developing stages, and the fission reactors are already being used for the past six decades. Based on nuclear reaction This type refers to the thermal (slow) reactors and the fast reactors based on neutrons’ speed. Thermal reactors are the most affordable and ordinary as they use natural and raw uranium. The neutrons are decelerated from their natural rate when emitted from the broken atomic nuclei and moderated material in the process. Fast reactors are costly that require more enriched fuel.