Fissile

In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons (i.e. a thermal system) or fast neutrons. Fissile materials can be used to fuel thermal reactors, with a neutron moderator; fast-neutron reactors, with no moderators; and nuclear explosives.