1942, a group of scientists led by Fermi built the world's first "artificial nuclear reactor" in the United States, and realized the controllable self-sustaining chain reaction of uranium nuclear fission for the first time in human history. A nuclear reactor is a device that releases nuclear energy in a controlled way. People build nuclear fission reactors for two purposes: (1) regard them as "neutron sources" and use a large number of neutrons produced by fission to produce military and civilian isotopes. (2) Use it as a "heat source" to provide heat, power generation or power by using the heat released by nuclear reaction. Of course, there are also reactors that combine the above purposes. 1954, under the auspices of kurchatov, the Soviet Union built the world's first nuclear power plant-Obrin Sike nuclear power plant. Since then, nuclear power plants have flourished all over the world.