noun
spontaneous fission
Technical term in nuclear physics for fission that occurs without external neutron bombardment.
ウラン238は自発核分裂を起こすことがある。
Uranium-238 can undergo spontaneous fission.
General term for nuclear fission; 自発核分裂 specifies fission that occurs spontaneously, without external trigger.
Compound of 自発 (spontaneous) + 核分裂 (nuclear fission).