nuclear fission

https://doi.org/10.1351/goldbook.N04229
The division of a @N04256@ into two or more parts with masses of equal order of magnitude, usually accompanied by the emission of neutrons, gamma radiation and, rarely, small charged nuclear fragments.
Source:
PAC, 1994, 66, 2513. (Nomenclature for radioanalytical chemistry (IUPAC Recommendations 1994)) on page 2519 [Terms] [Paper]