Nuclear reprocessing is the chemical separation of fission products and actinides from spent nuclear fuel.Andrews, A. (27 March 2008). Nuclear Fuel Reprocessing: U.S. Policy . CRS Report For Congress. Retrieved 25 March 2011. Originally, reprocessing was used to extract plutonium for producing nuclear weapons. With commercialization of nuclear power, reprocessed plutonium was recycled into MOX nuclear fuel for thermal reactors.MOX fuel can extend the energy extracted by about 12% but slightly reduces plutonium stocks. Information from the World Nuclear Association about MOX . Reprocessed uranium can in principle be re-used as fuel. Nuclear reprocessing may include the reprocessing of other nuclear reactor material, such as Zircaloy cladding.
The high radioactivity of spent fuel means that reprocessing must be controlled and executed in advanced facilities by specialized personnel. Numerous processes exist, dominated by the chemical-based PUREX process. Alternatives include heating to drive off volatile elements, oxidation, and fluoride volatility (which uses reactive fluorine gas). Each process results in some form of refined nuclear product, with radioactive waste as a byproduct. Because this could allow production of weapons grade nuclear material, nuclear reprocessing is a concern for nuclear proliferation.
Spent fuel reprocessing is relatively expensive compared to the once-through fuel cycle, but fuel use can be increased and waste volumes decreased. Reprocessing is performed routinely in Europe, Russia, and Japan. The United States halted commercial reprocessing plans in the 1970s but has continued to pursue reprocessing-related scientific research. Most nuclear fuel does not require reprocessing. Breeder reactors can use recycled plutonium and uranium as well as other actinides, closing the nuclear fuel cycle and potentially multiplying the energy extracted from natural uranium by ~60-fold and dramatically reducing long-lived high-level radioactive waste.
Spent nuclear fuel contains abundant fertile uranium and traces of fissile materials. Methods such as the PUREX process can be used to remove useful actinides for the production of active nuclear fuel.
Another option is to reuse specific isotopes.Milton, R. (January 17, 1978) . heritage.org. Caesium-137, strontium-90 and other isotopes are extracted for food irradiation and radioisotope thermoelectric generators. While re-use does not eliminate the need to manage radioisotopes, it can reduce the quantity of remaining waste.
Separated components and disposition
The potentially useful components dealt with in nuclear reprocessing comprise specific actinides (plutonium, uranium, and some minor actinides). The lighter elements components include fission products, activation products, and cladding.
materialdispositionplutonium, minor actinides, reprocessed uraniumfission in fast, fusion fission hybrid, or subcritical reactor or use as MOX fuelreprocessed uranium, filters less stringent storage as intermediate-level wastelong-lived fission and activation products nuclear transmutation or geological repositorymedium-lived fission products 137Cs and 90Srmedium-term storage as high-level waste; decay heat could be used to drive a Stirling engineuseful radionuclides, rare earths (lanthanides), and noble metals industrial and medical uses cladding, fission product zirconiumre-use for zircalloy cladding or storage as intermediate level waste
History The first large-scale nuclear reactors were built during World War II. These reactors were designed for the production of plutonium for use in nuclear weapons. The only reprocessing required, therefore, was the extraction of the plutonium (free of fission-product contamination) from the spent natural uranium fuel. In 1943, several methods were proposed for separating the relatively small quantity of plutonium from the uranium and fission products. The first method selected, a precipitation process called the bismuth phosphate process, was developed and tested at the Oak Ridge National Laboratory (ORNL) between 1943 and 1945 to produce quantities of plutonium for evaluation and use in the US weapons programs. ORNL produced the first macroscopic quantities (grams) of separated plutonium with these processes.
The bismuth phosphate process was first operated on a large scale at the Hanford Site, in the later part of 1944. It was successful for plutonium separation in the emergency situation existing then, but it had a significant weakness: the inability to recover uranium.
The first successful solvent extraction process for the recovery of pure uranium and plutonium was developed at ORNL in 1949. The PUREX process is the current method of extraction. Separation plants were also constructed at Savannah River Site and a smaller plant at West Valley Reprocessing Plant which closed by 1972 because of its inability to meet new regulatory requirements.
Reprocessing of civilian fuel has long been employed at the COGEMA La Hague site in France, the Sellafield site in the United Kingdom, the Mayak Chemical Combine in Russia, and at sites such as the Tokai plant in Japan, the Tarapur plant in India, and briefly at the West Valley Reprocessing Plant in the United States.
In October 1976,Gerald Ford 28 October 1976 Statement on Nuclear Policy . Retrieved 30 June 2012. concern of nuclear weapons proliferation (especially after India demonstrated nuclear weapons capabilities using reprocessing technology) led President Gerald Ford to issue a Presidential directive to indefinitely suspend the commercial reprocessing and recycling of plutonium in the U.S. On 7 April 1977, President Jimmy Carter banned the reprocessing of commercial reactor spent nuclear fuel. The key issue driving this policy was the risk of nuclear weapons proliferation by diversion of plutonium from the civilian fuel cycle, and to encourage other nations to follow the US lead. After that, only countries that already had large investments in reprocessing infrastructure continued to reprocess spent nuclear fuel. President Reagan lifted the ban in 1981, but did not provide the substantial subsidy that would have been necessary to start up commercial reprocessing.Nuclear Fuel Reprocessing: U.S. Policy Development . (PDF). Retrieved 10 December 2011.
In March 1999, the U.S. Department of Energy (DOE) reversed its policy and signed a contract with a consortium of Duke Energy, COGEMA, and Stone & Webster (DCS) to design and operate a mixed oxide (MOX) fuel fabrication facility. Site preparation at the Savannah River Site (South Carolina) began in October 2005.Duke, Cogema, Stone & Webster (DCS) Reports sent to NRC . Nrc.gov. Retrieved 10 December 2011. In 2011 the New York Times reported "...11 years after the government awarded a construction contract, the cost of the project has soared to nearly $5 billion. The vast concrete and steel structure is a half-finished hulk, and the government has yet to find a single customer, despite offers of lucrative subsidies." TVA (currently the most likely customer) said in April 2011 that it would delay a decision until it could see how MOX fuel performed in the nuclear accident at Fukushima Daiichi.New Doubts About Turning Plutonium Into a Fuel , 10 April 2011.
Separation technologies Water and organic solvents PUREX
PUREX is the standard method as of 2026. It is an acronym standing for Plutonium and Uranium Recovery by EXtraction. The PUREX process is a liquid-liquid extraction method used to separately extract uranium and plutonium.
When used on power reactor fuel, the plutonium extracted typically contains too much to be considered weapons-grade plutonium. Nevertheless, reliable nuclear weapons can be built at all sophistication levels using reactor-grade plutonium.U.S. Program for Disposition of Excess Weapons Plutonium , IAEA-SM-346/102, Matthew Bunn, 2002. Moreover, reactors that are capable of frequent refueling can be used to produce weapons-grade plutonium, which can be recovered using PUREX.
Modifications Many of these concepts, particularly those that separate the minor actinides once U and Pu have been extracted, are extracted via advanced reprocessing.
UREX UREX (URanium EXtraction) process is a modified form of PUREX that can save space inside disposal sites by removing the uranium that makes up the majority of the mass and volume and recycling it.
UREX avoids separating pure plutonium. This can be done by adding a plutonium reductant before the first extraction step. In the UREX process, ~99.9% of the uranium and >95% of technetium are separated. The key is the addition of acetohydroxamic acid (AHA) to the extraction and scrub sections of the process. The addition of AHA diminishes the extractability of plutonium and neptunium, providing somewhat greater proliferation resistance than with PUREX.
TRUEX Adding a second extraction agent, octyl(phenyl)-N, N-dibutyl carbamoylmethyl phosphine oxide (CMPO) in combination with tributylphosphate, (TBP), PUREX can become TRUEX (TRansUranic EXtraction). TRUEX was invented by Argonne National Laboratory and is designed to remove the transuranic metals (Americum/Curium) from waste. The idea is that by lowering alpha activity, the majority can be disposed of more easily. Like PUREX TRUEX operates by solvation.
DIAMEX The DIAMEX (DIAMide EXtraction) process avoids the formation of organic materials that contains elements other than carbon, hydrogen, nitrogen, and oxygen. Such organic waste can be burned without the formation of acidic gases. The French CEA works on DIAMEX. The process is sufficiently mature that an industrial plant could be constructed.DIAMEX operates by a solvation mechanism.
SANEX Selective ActiNide EXtraction. As part of the management of minor actinides it has been proposed that the lanthanides and trivalent minor actinides should be removed from the PUREX raffinate by a process such as DIAMEX or TRUEX. To allow the actinides such as americium to be either reused in industrial sources or used as fuel, the lanthanides must be removed. Several lanthanides have large neutron cross-sections and poison a neutron-driven nuclear reactions. To date the extraction system has not been defined, but research groups are working towards a process. For instance CEA is working on a bis-triazinyl pyridine (BTP) process.C. Hill, D. Guillaneux, X. Hérès, N. Boubals and L. Ramain, SANEX-BTP PROCESS DEVELOPMENT STUDIES. .C. Hill, L. Berthon, P. Bros, J-P. Dancausse and D. Guillaneux, SANEX-BTP PROCESS DEVELOPMENT STUDIES. . Commissariat à l'Énergie Atomique.Béatrice Rat, Xavier Hérès, Modelling and achievement of a SANEX process flowsheet for trivalent actinides/lanthanides separation using BTP extractant (bis-1,2,4-triazinyl-pyridine). . Other systems such as dithiophosphinic acids are under investigation.
UNEX The UNiversal EXtraction process was developed in Russia and the Czech Republic; it is designed to remove the most troublesome radioisotopes (strontium, caesium and minor actinides) from the raffinate remaining after the extraction of uranium and plutonium. The chemistry is based upon Cs and Sr interaction with polyethylene glycol and a cobalt carborane anion (known as chlorinated cobalt dicarbollide). The actinides are extracted by CMPO, with diluents such as a polar aromatic such as nitrobenzene. Other diluents such as meta-nitrobenzotrifluoride and phenyl trifluoromethyl sulfone have been suggested.
Electrochemical and ion exchange methods One exotic method uses electrochemistry and ion exchange in ammonium carbonate. Other ion exchange methods use alkaline carbonate and "fumed" lead oxide.
Obsolete methods Bismuth phosphate