Lecture on Nuclear Reactions In fusion reactions, two light nuclei are combined to form a heavier, more stable nucleus. In fission reactions, a heavy nucleus is split into two nuclei with smaller mass numbers. In either case, if the new particles contain more stable nuclei, vast quantities of energy are released. Nuclear power plants rely on fission to create vast quantities of energy. U-235 nuclides can be bombarded with neutrons, and the result is lots of energy, three neutrons, and two stable nuclei (Kr-92 and Ba-141). The three neutrons formed can collide with other U-235 atoms, setting off a chain reaction and releasing tons of energy. Is the following process an example of fission or fusion? This is an example of fission. Fission occurs when a large nucleus is bombarded by a small particle, such as a neutron. The result is two smaller nuclei and additional neutrons, and a chain reaction process begins. “Little Boy” bomb was a Uranium Bomb that required nuclear fission. “Fat Man” bomb was a Plutonium Bomb that required nuclear fission.