Nuclear reactors are systems that utilize the process of nuclear fission to generate heat, which is then used to produce electricity. These reactors use controlled nuclear chain reactions to create high amounts of thermal energy, which can be converted into electrical power through steam turbines. Nuclear reactors are used as a source of clean and reliable energy in many countries around the world. They are also used in research for medical purposes, production of isotopes, and military applications. There are several types of nuclear reactors, including pressurized water reactors (PWR), boiling water reactors (BWR), fast neutron reactors, and molten salt reactors. Each type has its own unique design, fuel type, and safety features. Research in the area of nuclear reactors focuses on improving reactor safety, efficiency, waste management, and proliferation resistance. This research is crucial for ensuring the continued safe and sustainable use of nuclear energy in the future.