Nuclear material refers to the metals
uranium,
plutonium, and
thorium, in any form, according to the
IAEA. This is differentiated further into "source material", consisting of natural and depleted uranium, and "special fissionable material", consisting of
enriched uranium (
U-235),
uranium-233, and
plutonium-239. Uranium ore concentrates are considered to be a "source material", although these are not subject to safeguards under the
Nuclear Non-Proliferation Treaty.