In nuclear engineering, a fissile material's one that's capable of sustaining a chain reaction of nuclear fission. All known fissile materials are capable of sustaining a chain reaction in which either thermal or slow neutrons or fast neutrons predominate. That's, they can all be used to fuel: A thermal reactor, with a neutron moderator A fast reactor, with no moderator A nuclear explosive Fissile vs fissionable "Fissile"'s distinguished from "fissionable". "Fissionable" are any materials… (More on Fissile)