Definition of spontaneous fission
Spontaneous fission, the fission of an atomic nucleus without particle bombardment or the addition of energy. The process of splitting a heavy nucleus into two or more medium-mass fragments that emit neutrons and energy at the same time is called spontaneous fission of the nucleus. Spontaneous fission is a nuclear fission that occurs spontaneously without the bombardment of foreign particles. It can also use the half-life to measure the difficulty of fission. Spontaneous fission of natural elements is found only in isotopes of uranium and plutonium. Compared to alpha decay, the spontaneous fission branch ratio of uranium and plutonium is small and can be almost ignored.