None of these affects the use of handling of the reprocessed uranium significantly. It is then stripped from the organic solvent with dilute nitric acid. The GANEX (grouped extraction of actinides) process co-precipitates some uranium with the plutonium (as with COEX), but then separates minor actinides and some lanthanides from the short-lived fission products. In 2014, H Canyon completed reprocessing the long-stored uranium-thorium metal fuel from the 20 MWt Sodium Reactor Experiment (SRE), which had a high proportion of U-233. There has been particular emphasis on fast reactor fuels, since all actinides with uranium can be burned together. Achieving effective full separation for any transmutation program is likely to mean electrolytic processing of residuals from the PUREX or similar aqueous processes. GE Hitachi Nuclear Energy (GEH) is developing this concept by combining electrometallurgical separation (see section on Electrometallurgical 'pyroprocessing' below) and burning the final product in one or more of its PRISM fast reactors on the same site. Separating all actinides together for recycle gives a very radioactive fuel which is thus self-protecting.
Areva and CEA have developed three processes on the basis of extensive French experience with PUREX: Initial work was at ATALANTEgat Marcoule, which started operation in 1992 to consolidate reprocessing and recycling research from three other sites. However, the specific separation achieved is not as great as with PUREX. In France a 400 t/yr reprocessing plant operated for metal fuel from gas-cooled reactors at Marcoule until 1997. Uranium, plutonium, fission products and minor actinides are kept together in the fuel powder and bound together again in the DUPIC fuel bundles. (The longer-lived fission products may also be separated from the waste and transmuted in some other way.) It is largely formed through alpha decay of Pu-236, and the concentration of it peaks after about 10 years of storage. Originally in the 1960s it was developed to separate actinides, notably Am & Cm from lanthanides. It could also recover Np-237 and Pu-238 from irradiated targets. The metal now as anode can then be electro-refined in molten LiCl salt to deposit uranium and actinides (including Pu) together onto a liquid cadmium cathode, leaving fission products behind. Several European countries, Russia, China and Japan have policies to reprocess used nuclear fuel, although government policies in many other countries have not yet come round to seeing used fuel as a resource rather than a waste. The U-232, though only in trace amounts, has daughter nuclides which are strong gamma-emitters, making the material difficult to handle. The partly-built 3000 t/yr RT-2 plant at Zheleznogorsk in Siberia has been redesigned and first stage completion of 700 t/yr is expected about 2025. In either case, the remaining liquid after Pu and U are removed is high-level waste, containing about 3% of the used fuel in the form of fission products and minor actinides (notably Np, Am, Cm). Cost estimates for direct disposal at Yucca Mountain had risen sharply and capacity was limited (even if doubled), Increased US nuclear generation, potentially from 103 to 160 GWe, The economics of reprocessing and associated waste disposal have improved. In addition, the level of radioactivity in the waste from reprocessing is much smaller and after about 100 years falls much more rapidly than in used fuel itself. Accelerator Transmutation of Waste System, NEA/OECD Workshop on Pyrochemical Separations, Avignon, France (14-15 March 2000) The highly-enriched uranium recovered from the EBR-II driver fuel is down-blended to less than 20% enrichment and stored for possible future use. * However, there are chemical safety problems with the Pu-Np recovery in the aqueous phase, and the process has been abandoned since 2008. Alternatively, some small amount of recovered uranium can be left with the plutonium which is sent to the MOX plant, so that the plutonium is never separated on its own. A full commercial-scale ARC would comprise an electrometallurgical plant and three power blocks of 622 MWe each (six 311 MWe reactor modules), but a 'full-scale building block' of ARC is a 50 t/yr electrometallurgical plant coupled to one 311 MWe reactor module, with breeding ratio of 0.8. In all, the USA has over 250 plant-years of reprocessing operational experience, the vast majority being at government-operated defence plants since the 1940s. US research in recent years has focused on the TALSPEAK process which would come after a modified PUREX or COEX process to separate trivalent lanthanides from trivalent actinides, but this has only reached bench scale. Nuclear Energy Data 2019, OECD Nuclear Energy Agency [Back] James Laidler, Pyrochemical Separations Technologies Envisioned for the U.S. (NUE would be more radioactive than natural U, due to U-232 in the RU.). The residual is put through a Purex circuit which separates fission products and minor actinides, leaving the unseparated U-Pu mix (about 4:1) to be made into MOX fuel. Allowing for impurities affecting both its treatment and use, RepU value has been assessed as about half that of natural uranium. P.Netter, Areva, in Nuclear Fuel Science and Engineering, Woodhead Publishing, 2012 Uranium mining will become much less significant. In 1991-92 2.1 tonnes of MOX was reprocessed at Marcoule and 4.7 tonnes was reprocessed La Hague. There is now a lot of experience with civil reprocessing. It would contain all the actinides and most of the fission products from irradiation in LWR. Reprocessing of spent oxide fuel from nuclear power reactors. Also for fast reactors, depleted uranium is plentiful and cheap. An underground military reprocessing plant there is decommissioned. Used fuel from PHWRs such as CANDU is not attractive for reprocessing as it has a very low proportion of U-235 and Pu typically 0.2% and 0.4% respectively. It is then converted to UO2 product by reduction in hydrogen. COEX may have from 20 to 80% uranium in the oxide product (apart from U stream), the baseline is 50%. This is apparently Purex though that is not confirmed. Canada, which developed the CANDU reactor, and South Korea, which hosts four CANDU units as well as many PWRs, initiated a bilateral joint research programme to develop DUPIC. A new reprocessing technology is part of the reduced-moderation water reactor (RMWR) concept. The nitrates in the residual raffinate acid solution are converted to oxides, which are then reduced electrochemically in a LiCl-Li2Omolten salt bath. This may be directly using RepU, or by blending RepU with depleted uranium to give natural uranium equivalent (NUE), or by direct use of used PWR fuel in CANDU reactors (DUPIC).
A modified version of the PUREX that does not involve the isolation of a plutonium stream is the suite of UREX (uranium extraction) processes. AECL says that it is also possible to use the RepU directly in CANDUs, without blending it down,and Qinshan III envisages this possibility with recycled uranium (RU) having 0.9% U-235. This led to KAERIs Pyro-process Integrated Inactive Demonstration Facility (PRIDE), which began testing operations in 2014. Management of Reprocessed Uranium Current Status and Future Prospects, IAEA TECDOC 1529 (2007), International Atomic Energy Agency (ISBN: 920114606X) 3. Most of it about 96% is uranium, of which less than 1% is the fissile U-235 (often 0.4-0.8%); and up to 1% is plutonium. In this, 90-92% of the uranium in the used fuel is volatalised as UF6,then purified for enrichment or storage. Another 800 t/yr is planned for 2028. Russia has an old 400 t/yr RT-1 oxide fuel reprocessing plant at Ozersk (near Chelyabinsk, Siberia), the main feed for which has been VVER-440 fuel, including that from Ukraine and Hungary. KAERI believes that although it is too early to commercialise the DUPIC fuel cycle, the key technologies are in place for a practical demonstration of the technique. A BNFL-Cogema study in 2001 reported that 99% removal of actinides, Tc-99 & I-129 would be necessary to justify the effort in reducing the radiological load in a waste repository. [Back], h. Spallation is the process where nucleons are ejected from a heavy nucleus being hit by a high energy particle. RIAR has substantial experience in reprocessing used fuel from BOR-60 and BN-350 fast reactors and has developed a pilot scale pyroprocessing demonstration facility for fast reactor fuel. Reuse of World Nuclear Association Content, Sustainable Development Goals and Nuclear, Background, Status, and Issues Related to the Regulation of Advanced Spent Nuclear Fuel Recycle Facilities, Recycled LWR uranium and used fuel in PHWRs, Economic Assessment of Used Nuclear Fuel Management in the United States, Chinese Candu reactor trials uranium reuse, Japanese Waste and MOX Shipments From Europe, Pyrometallurgy using heat to initiate separation of the metals from their mineral concentrate (, Electrometallurgy using electric current to separate the metals (, Hydrometallurgy using aqueous solutions that dissolve the metal, with sometimes also electrolytic cells to separate them (. Two significant new elements in the strategy were new reprocessing technologies at advanced recycling centres, which separate all transuranic elements together (and not plutonium on its own) starting with the UREX+ process (see section on Developments of PUREX below), and 'advanced burner reactors' to consume the result of this while generating power. Until the mid 1990s some 60% of all AGR fuel was made from MDU and it amounted to about 1650 tonnes of low enriched uranium. After removal of the cladding, a thermal-mechanical process is used to reduce the used LWR fuel pellet to a powder. This included the reactor physics of DUPIC fuel and the impacts on safety systems. Registered office: Tower House, 10 Southampton Street, London, WC2E 7HA, United Kingdom. In Japan, platinum group metals are also targeted, for commercial recovery. With US assistance through the International Nuclear Energy Research Initiative (I-NERI) programme, KAERI built the Advanced Spent Fuel Conditioning Process Facility (ACPF). In 2007 the US Nuclear Regulatory Commissions Advisory Committee on Nuclear Waste and Materials published a report on Background, Status, and Issues Related to the Regulation of Advanced Spent Nuclear Fuel Recycle Facilities, which canvassed the advantages of reprocessing US civil spent fuel. With it, all actinide anions (notably uranium and plutonium) are recovered together.
However, its future is uncertain. In the last decade interest has grown in recovering all long-lived actinides* together (i.e. The term 'electrometallurgical' is also increasingly used to refer to this in the USA.
A great deal of hydrometallurgical reprocessing has been going on since the 1940s, originally for military purposes, to recover plutonium for weapons (from low burn-up used fuel, which has been in a reactor for only a few months). This also raises issues for licensing. From 1969 to 1973 oxide fuels were also reprocessed, using part of the plant modified for the purpose, and the 900 t/yr Thermal Oxide Reprocessing Plant (THORP) at Sellafield was commissioned in 1994. The PYRO-A process, being developed at Argonne to follow the UREX process, is a pyrochemical process for the separation of transuranic elements and fission products contained in the oxide powder resulting from denitration of the UREX raffinate. Energy Solutions holds the rights to PUREX in the USA and has developed NUEX, which separates uranium and then all transuranics (including plutonium) together, with fission products separately.
In the latter, a high-energy proton beam hitting a heavy metal target produces a shower of neutrons by spallationh. The smaller black building to the rear is the vitrification plant. There are three broad kinds of metallurgical treatment at metal smelters and refineries: The main historic and current process is Purex (see below), a hydrometallurgical process. The uranium can be re-enriched or used as fuel for Candu reactors. Nuclear Technology Review 2020, International Atomic Energy Agency [Back] with plutonium) so as to recycle them in fast reactors so that they end up as short-lived fission products. Reprocessing options include: In today's reactors, reprocessed uranium (RepU) needs to be enriched, whereas plutonium goes straight to mixed oxide (MOX) fuel fabrication. The cathode deposit of transuranic elements is then processed to remove any adhering salt and is formed into ingots for subsequent fabrication of transmutation targets or fast reactor fuel. GNEP goals included reducing US dependence on imported fossil fuels, and building a new generation of nuclear power plants in the USA. The MDU was converted to UF6, enriched to 0.7% at BNFL's Capenhurst diffusion plant and then to 2.6% to 3.4% at Urenco's centrifuge plant. Remote fuel fabrication facilities would therefore be required, leading to high fuel fabrication costs and requiring significant technological development. Separate U, Pu+actinides, certain fission products. The second was a 300 t/yr plant built at Morris, Illinois, incorporating new technology based on the volatility of UF6 which, although proven on a pilot-scale, failed to work successfully in the production plant. If plutonium is stored for some years the level of americium-241, the isotope used in household smoke detectors, will accumulate and make it difficult to handle through a MOX plant due to the elevated levels of gamma radioactivity.
This is sent to the Russian Institute of Atomic Reactors (RIAR) at Dimitrovgrad for vibropacking and producing fuel assemblies for the BN-800 fast reactor. A key, nearly unique, characteristic of nuclear energy is that used fuel may be reprocessed to recover fissile and fertile materials in order to provide fresh fuel for existing and future nuclear power plants. Processing it is thus inherently complex chemically, and made more difficult because many of those nuclides are also radioactive. Electrometallurgical processing techniques ('pyroprocessing') to separate nuclides from a radioactive waste stream have been under development in the US Department of Energy laboratories, notably Argonne, as well as by the Korea Atomic Energy Research Institute (KAERI) in conjunction with work on DUPIC (see section on Recycled LWR uranium and used fuel in PHWRs below). The U-236 isotope is a neutron absorber present in much larger amounts, typically 0.4% to 0.6% more with higher burn-up which means that if reprocessed uranium is used for fresh fuel in a conventional reactor it must be enriched significantly more (e.g. This is the fluoride volatility process, developed in the 1980s, which is coupled with solvent extraction for plutonium to give Hitachi's Fluorex process. Plutonium is then transferred to the aqueous phase while the mixture of U4+ and U6+ remains in the organic phase. If transmutation targets are not of high purity then the results of transmutation will be uncertain. The PYRO-B process, has been developed for the processing and recycle of used fuel from a transmuter reactor a fast reactor designed to burn all transuranics. All but one of the six Generation IV reactors being developed have closed fuel cycles which recycle all the actinides. Used fuel from light water reactors (at normal US burn-up levels) contains approximately: b. Chinese Candu reactor trials uranium reuse, World Nuclear News (24 March 2010) [Back], Charles Madic, Overview of the Hydrometallurgical and Pyro-metallurgical Processes Studied Worldwide for the Partitioning of High Active Nuclear Wastes, NEA/OECD 6th Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation, Madrid, Spain (11-13 December 2000) Another approach to used nuclear fuel recycling is directing recycled uranium (referred to as RepU, reprocessed uranium), or actual used light water reactor (LWR) fuel, into pressurized heavy water reactors (PHWRs). Some figures for the Oskarshamn 3 nuclear unit: with 30 GWd/t burn-up, 69% Pu is fissile; 40 GWd/t, 61% fissile; 50 GWd/t, 55% fissile; and 60 GWD/t, 50% fissile. However, KAERI successfully manufactured DUPIC small fuel elements for irradiation tests inside the HANARO research reactor in April 2000 and fabricated full-size DUPIC elements in February 2001. For the future, the focus is on removing the minor actinides along with uranium and plutonium from the final waste and burning them all together in fast neutron reactors. Alternatively, a "dry reprocessing" technology has been developed which removes only the volatile fission products from the used LWR fuel mix. Electrometallurgical 'pyroprocessing' can readily be applied to high burn-up fuel and fuel which has had little cooling time, since the operating temperatures are high already.
Boston Consulting Group gave four reasons for reconsidering US used fuel strategy which has applied since 1977: Soon after this the US Department of Energy said that it might start the GNEP (now IFNEC) program using reprocessing technologies that "do not require further development of any substantial nature" such as COEX while others were further developed. The third was a 1500 t/yr Purex plant at Barnwell, South Carolina, which was aborted due to a 1977 change in government policy which ruled out all US civilian reprocessing as one facet of US non-proliferation policy. The DIAMEX-SANEX processes involving selective separation of long-lived radionuclides (with a focus on Am and Cm separation) from short-lived fission products. H Canyon also reprocessed a variety of materials for recovery of uranium and plutonium both for military purposes and later high-enriched uranium for blending down into civil reactor fuel. It also flagged detailed siting studies on the feasibility of this accelerated "development and deployment of advanced recycling technologies by proceeding with commercial-scale demonstration facilities.". (Sellafield Ltd.). The report states: The DOEs current program for implementing SNF recycle contemplates building three facilities: an integrated nuclear fuel recycle facility, an advanced reactor for irradiating Np, Pu, Am, and Cm, and an advanced fuel cycle research facility to develop recycle technology. It recycles over 96% of the used fuel. up to one-tenth more) than is required for natural uraniumb. Management of Recyclable Fissile and Fertile Materials, NEA #6107 (April 2007), Nuclear Energy Agency (ISBN: 9789264032552) The reprocessing output in France is co-ordinated with MOX plant input, to avoid building up stocks of plutonium. In this case, a high-energy proton beam directed at a heavy target expels a number of spallation particles, including neutrons. The fact that uranium, plutonium and minor actinides are recovered together is seen as great advantage from a non-proliferation perspective. The central feature of this system was to increase proliferation resistance by keeping the plutonium with other transuranics all of which are then destroyed by recycling in fast reactors.