Chemical treatment of used reactor fuel to separate uranium and plutonium, and possibly the very heavy transuranic elements (mostly plutonium and curium) from the fission nuclear waste.
By reprocessing spent fuel one can:
turn nuclear waste into nuclear fuel for use in another nuclear power plant;
hugely reduce the quantity of high-level waste which today includes the transuranic elements;
Reprocessing is at the heart of the so-called closed fuel cycle. The latter is considered a more promising nuclear plant alternative than the predominant open fuel cycle in which uranium is burned once in the reactor, leaving large amounts of high-level waste.
However, the option presents two shortcomings:
It is a much costlier process than the once-through cycle;
Reprocessing is intrinsically hazardous and complex.
In 2008, France was the number one adopter, but only recycling 28% by mass of yearly spent fuel.
Depleted uranium is left as a by-product of uranium enrichment in the fuel cycle, and it generally has 0.25% to 0.30% U-235, the rest being U-238. Depleted uranium can be blended with highly-enriched uranium (e.g. from weapons) to make reactor fuel or, given its high density, it may be used in products such as special ammunition and shielding for military purposes.