Spontaneous Fission Definition

Spontaneous fission is the splitting of an atomic nucleus from natural radioactive decay.
Spontaneous fission is the splitting of an atomic nucleus from natural radioactive decay. Ian Cuming / Getty Images

Spontaneous Fission Definition

Spontaneous fission is a form of radioactive decay where an atom's nucleus splits into two smaller nuclei and generally one or more neutrons.

Spontaneous fission generally in atoms with atomic numbers above 90.

Spontaneous fission is a relatively slow process except for the heaviest isotopes. For example, uranium-238 decays by alpha decay with a half-life on the order of 109 years, but also decays by spontaneous fission on the order of 1016 years.

Examples: Cf-252 undergoes spontaneous fission to produce Xe-140, Ru-108 and 4 neutrons.