Reprocessing and Recycling
Nuclear reprocessing, sometimes called recycling, is one method of mitigating the eventual peak of uranium production. It is most useful as part of a nuclear fuel cycle utilizing fast-neutron reactors since reprocessed uranium and reactor-grade plutonium both have isotopic compositions not optimal for use in today's thermal-neutron reactors. Although reprocessing of nuclear fuel is done in a few countries (France, United Kingdom, and Japan) the United States President banned reprocessing in the late 1970s due to the high costs and the risk of nuclear proliferation via plutonium. In 2005, U.S. legislators proposed a program to reprocess the spent fuel that has accumulated at power plants. At present prices, such a program is significantly more expensive than disposing spent fuel and mining fresh uranium.
The two large-scale commercial reprocessing plants, in La Hague, France and Sellafield, England, together can reprocess 2,800 tonnes of uranium waste annually. Currently, there are eleven reprocessing plants in the world. Out of those, there are only two large-scale commercially operated plants for the reprocessing of spent fuel elements from light water reactors with throughputs of more than 1 kilotonne (2.2×10 6 lb) of uranium per year. These are La Hague, France with a capacity of 1.6 kilotonnes (3.5×10 6 lb) per year and Sellafield, England at 1.2 kilotonnes (2.6×10 6 lb) uranium per year. The rest are small experimental plants.
Most of the spent fuel components can be recovered and recycled. About two-thirds of the U.S. spent fuel inventory is uranium. This includes residual fissile uranium-235 that can be recycled directly as fuel for heavy water reactors or enriched again for use as fuel in light water reactors.
Plutonium and uranium can be chemically separated from spent fuel. When used nuclear fuel is reprocessed using the de facto standard PUREX method, both plutonium and uranium are recovered separately. The spent fuel contains about 1% plutonium. Reactor-grade plutonium contains Pu-240 which has a high rate of spontaneous fission, making it an undesirable contaminant in producing safe nuclear weapons. Nevertheless, nuclear weapons can be made with reactor grade plutonium.
The spent fuel is primarily composed of uranium, most of which has not been consumed or transmuted in the nuclear reactor. At a typical concentration of around 96% by mass in the used nuclear fuel, uranium is the largest component of used nuclear fuel. The composition of reprocessed uranium depends on the time the fuel has been in the reactor, but it is mostly uranium-238, with about 1% uranium-235, 1% uranium-236 and smaller amounts of other isotopes including uranium-232. However, reprocessed uranium is also a waste product because it is contaminated and undesirable for reuse in reactors. During its irradiation in a reactor, uranium is profoundly modified. The uranium that leaves the reprocessing plant contains all the isotopes of uranium between uranium-232 and uranium-238 except uranium-237, which is rapidly transformed into neptunium-237. The undesirable isotopic contaminants are:
- Uranium-232 (whose decay products emit strong gamma radiation making handling more difficult), and
- Uranium-234 (which is fertile material but can affect reactivity differently than uranium-238).
- Uranium-236 (which affects reactivity and absorbs neutrons without fissioning, becoming neptunium-237 which is one of the most difficult isotopes for long-term disposal in a deep geological repository)
- Daughter products of uranium-232: bismuth-212, thallium-208.
At present, reprocessing and the use of plutonium as reactor fuel is far more expensive than using uranium fuel and disposing of the spent fuel directly—even if the fuel is only reprocessed once. However, nuclear reprocessing becomes more economically attractive, compared to mining more uranium, as uranium prices increase.
The total recovery rate 5 kilotonnes (11×106 lb)/yr from reprocessing currently is only a small fraction compared to the growing gap between the rate demanded 64.615 kilotonnes (142.45×10 6 lb)/yr and the rate at which the primary uranium supply is providing uranium 46.403 kilotonnes (102.30×10 6 lb)/yr.
Energy Returned on Energy Invested (EROEI) on uranium reprocessing is highly positive, though not as positive as the mining and enrichment of uranium, and the process can be repeated. Additional reprocessing plants may bring some economies of scale.
The main problems with uranium reprocessing are the cost of mined uranium compared to the cost of reprocessing, nuclear proliferation risks, the risk of major policy change, the risk of incurring large cleanup costs, stringent regulations for reprocessing plants, and the anti-nuclear movement.
Famous quotes containing the word recycling:
“Both the Moral Majority, who are recycling medieval language to explain AIDS, and those ultra-leftists who attribute AIDS to some sort of conspiracy, have a clearly political analysis of the epidemic. But even if one attributes its cause to a microorganism rather than the wrath of God, or the workings of the CIA, it is clear that the way in which AIDS has been perceived, conceptualized, imagined, researched and financed makes this the most political of diseases.”
—Dennis Altman (b. 1943)