A type of nuclear reactor fuel (often called "MOX" that contains plutonium oxide mixed with either natural or depleted uranium oxide, in ceramic pellet form. (This differs from conventional nuclear fuel, which is made of pure uranium oxide. ) Using plutonium reduces the amount of highly enriched uranium needed to produce a controlled reaction in commercial light-water reactors. However, plutonium exists only in trace amounts in nature and, therefore, must be produced by neutron irradiation of uranium-238 or obtained from other manufactured sources. As directed by Congress, the NRC regulates the fabrication of MOX fuel by DOE, a programme that is intended to dispose of plutonium from international nuclear disarmament agreements. For further detail, see the Fact Sheet on Mixed Oxide Fuel and Frequently Asked Questions About Mixed Oxide Fuel.