Neutron emission

Neutron emission is a type of radioactive decay of atoms containing excess neutrons, in which a neutron is simply ejected from the nucleus. Two examples of isotopes which emit neutrons are helium-5 and beryllium-13. However, the decay of helium-5 is also (by definition) a case of alpha-decay.

Many heavy isotopes, most notably californium-252, emit neutrons among the products of a different radioactive decay process, spontaneous fission.

Neutrons are absorbed and emitted in the process of nuclear fission, a nuclear chain reaction propagated by neutrons. Delayed neutrons emitted by neutron-rich fission products aid control of nuclear reactors by making reactivity change much slower than it would be for prompt neutrons alone.