What goes on inside a nuclear reactor? It’s kind of like one big dodgeball game 👇 The main job of a reactor is to house and control nuclear fission – a physical process where atoms split and release energy. Neutrons are introduced to the uranium particles inside the fuel pellets. When the uranium is hit by a neutron, it splits apart, releasing energy and more neutrons. The neutrons hit other uranium particles and eventually start a chain reaction. You can learn more about how a nuclear reactor