Īn alternative definition defines fissile nuclides as those nuclides that can be made to undergo nuclear fission (i.e., are fissionable) and also produce neutrons from such fission that can sustain a nuclear chain reaction in the correct setting. Consequently, uranium-238 is fissionable but not fissile. By contrast, the binding energy released by uranium-238 absorbing a thermal neutron is less than the critical energy, so the neutron must possess additional energy for fission to be possible. Uranium-235 fissions with low-energy thermal neutrons because the binding energy resulting from the absorption of a neutron is greater than the critical energy required for fission therefore uranium-235 is fissile.

As a result, fissile materials (such as uranium-235) are a subset of fissionable materials. Fissionable materials include also those (such as uranium-238) for which fission can be induced only by high-energy neutrons. A fissionable nuclide that can be induced to fission with low-energy thermal neutrons with a high probability is referred to as fissile. A nuclide capable of undergoing fission (even with a low probability) after capturing a neutron of high or low energy is referred to as fissionable. The term fissile is distinct from fissionable. Only nuclides with a half-life of at least one year are shown on this table. Region of relative stability: radium-226 to einsteinium-252

Fissile material can be used to fuel thermal-neutron reactors, fast-neutron reactors and nuclear explosives.Īccording to the Ronen Fissile rule, for a heavy element with 90 ≤ Z ≤ 100, its isotopes with 2 × Z − N = 43 ± 2, with few exceptions, are fissile (where N = number of neutrons and Z = number of protons). The predominant neutron energy may be typified by either slow neutrons (i.e., a thermal system) or fast neutrons. By definition, fissile material can sustain a chain reaction with neutrons of thermal energy. In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction. For the topic in geology, see Fissility (geology).

Fission fission meaning