nuclear reprocessing

Nuclear reprocessing separates any usable nuclear fuels (e.g., uranium and plutonium) from fission products and other materials in used nuclear reactor fuels. Spent enriched uranium fuel contains:

3% of the mass consists of products of fission of U-235 (also indirect products in the decay chain), considered radioactive waste or separated further for various industrial and medical uses.
1% of the mass is Pu-239 and PU-240 resulting from conversion of U-238; may either be considered a useful by-product, or as dangerous and inconvenient waste; one of the main concerns regarding nuclear proliferation is to prevent that this plutonium is used by states other than those already established as Nuclear Weapons States, to produce nuclear weapons; if the reactor has been used normally, the plutonium is reactor-grade, not weapon-grade: it contains much Pu-240 and less than 80% Pu-239, which makes it less suitable, but not impossible, to use in a weapon; if the irradiation period has been short then the plutonium is weapon-grade (more than 80%, up to 93%)
96% of the mass is the remaining uranium: most of the original U-238 and a lttle U-235, in a ratio that makes it perhaps, to a small extent, still enriched; it can be enriched again, to be reused

Reprocessing of spent commercial-reactor nuclear fuel is not permitted in the United States due to nonproliferation considerations.

See also