
U.S. Nuclear Regulatory Commission

Home

Who We Are

What We Do

Nuclear Reactors

Nuclear Materials

Radioactive Waste

Facility Info Finder

Public Involvement

Electronic Reading Room

Fissile material

Although sometimes used as a synonym for fissionable material, this term has acquired a more restricted meaning. Namely, any material fissionable by thermal (slow) neutrons. The three primary fissile materials are uranium-233, uranium-235, and plutonium-239.