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PUREX

April 08, 2024

For other uses, see Purex (disambiguation).
Not to be confused with Pyrex.

PUREX (plutonium uranium reduction extraction) is a chemical method used to purify fuel for nuclear reactors or nuclear weapons.[7] PUREX is the de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel (spent nuclear fuel, or irradiated nuclear fuel). It is based on liquid–liquid extraction ion-exchange.[8]

Reprocessing of spent nuclear fuel by the PUREX method, first developed in the 1940s to produce plutonium for nuclear weapons,[1] was demonstrated commercially in Belgium to partially re-fuel a LWR in the 1960s.[2] This aqueous chemical process continues to be used commercially to separate reactor grade plutonium (RGPu) for reuse as MOX fuel. It remains controversial, as plutonium can be used to make nuclear weapons.[3][4]
The most developed, though commercially unfielded, alternative reprocessing method, is Pyroprocessing,[5] suggested as part of the depicted metallic-fueled, Integral fast reactor (IFR) a sodium fast reactor concept of the 1990s. After the spent fuel is dissolved in molten salt, all of the recyclable actinides, consisting largely of plutonium and uranium though with important minor constituents, are extracted using electrorefining/electrowinning. The resulting mixture keeps the plutonium at all times in an unseparated gamma and alpha emitting actinide form, that is also mildly self-protecting in theft scenarios.[6]

PUREX is applied to spent nuclear fuel, which consists primarily of very high atomic-weight (actinoid or "actinide") elements (e.g. uranium, plutonium, americium) along with smaller amounts of material composed of lighter atoms, notably the fission products produced by reactor operation.

A simplified plutonium extraction flow chart.

The actinoid elements in this case consist primarily of the unconsumed remains of the original fuel (typically U-235, U-238, and/or Pu-239).

Chemical process edit

 
Structure of uranyl nitrate complex that is extracted in PUREX.[9]

The fuel is first dissolved in nitric acid at a concentration around 7 M. Solids are removed by filtration to avoid the formation of emulsions, referred to as third phases in the solvent extraction community.

The organic solvent consists of 30% tributyl phosphate (TBP) in a hydrocarbon such as kerosene. Uranyl(VI) UO2+
2 ions are extracted in the organic phase as UO2(NO3)2·2TBP complexes; plutonium is extracted as similar complexes. The heavier actinides, primarily americium and curium, and the fission products remain in the aqueous phase. The nature of uranyl nitrate complexes with trialkyl phosphates has been characterized.[10]

Plutonium is separated from uranium by treating the TBP-kerosene solution with reducing agents to convert the plutonium to its +3 oxidation state, which will pass into the aqueous phase. Typical reducing agents include N,N-diethyl-hydroxylamine, ferrous sulphamate, and hydrazine. Uranium is then stripped from the kerosene solution by back-extraction into nitric acid at a concentration around 0.2 M.[11]

PUREX raffinate edit

The term PUREX raffinate describes the mixture of metals in nitric acid which are left behind when the uranium and plutonium have been removed by the PUREX process from a nuclear fuel dissolution liquor. This mixture is often known as high level nuclear waste.

Two PUREX raffinates exist. The most highly active raffinate from the first cycle is the one which is most commonly known as PUREX raffinate. The other is from the medium-active cycle in which the uranium and plutonium are refined by a second extraction with tributyl phosphate.

 

Deep blue is the bulk ions, light blue is the fission products (group I is Rb/Cs) (group II is Sr/Ba) (group III is Y and the lanthanides), orange is the corrosion products (from stainless steel pipework), green are the major actinides, violet are the minor actinides and magenta is the neutron poison)

Currently PUREX raffinate is stored in stainless steel tanks before being converted into glass. The first cycle PUREX raffinate is very radioactive. It has almost all of the fission products, corrosion products such as iron/nickel, traces of uranium, plutonium and the minor actinides.

Pollution edit

The PUREX plant at the Hanford Site was responsible for producing 'copious volumes of liquid wastes', resulting in the radioactive contamination of groundwater.[12]

Greenpeace measurements in La Hague and Sellafield indicated that radioactive pollutants are steadily released into the sea, and the air. Therefore, people living near these processing plants are exposed to higher radiation levels than the naturally occurring background radiation. According to Greenpeace, this additional radiation is small but not negligible.[13]

History edit

The PUREX process was invented by Herbert H. Anderson and Larned B. Asprey at the Metallurgical Laboratory at the University of Chicago, as part of the Manhattan Project under Glenn T. Seaborg; their patent "Solvent Extraction Process for Plutonium" filed in 1947,[14] mentions tributyl phosphate as the major reactant which accomplishes the bulk of the chemical extraction.[15]

List of nuclear reprocessing sites edit

See also edit

References & notes edit

  1. ^ Greenwood, pp. 1255, 1261
  2. ^ . European Nuclear Society. Archived from the original on 22 June 2015. Retrieved 29 July 2008.
  3. ^ An Evaluation of the Proliferation Resistant Characteristics of Light Water Reactor Fuel with the Potential for Recycle in the United States
  4. ^ Is U.S. Reprocessing Worth The Risk?, Steve Fetter and Frank N. von Hippel, Arms Control Today, September 1, 2005.
  5. ^ L.C. Walters (September 18, 1998). "Thirty years of fuels and materials information from EBR-II". Journal of Nuclear Materials. 270 (1): 39–48. Bibcode:1999JNuM..270...39W. doi:10.1016/S0022-3115(98)00760-0.
  6. ^ [1] PUREX and PYRO are not the same, Hannum, Marsh, Stanford.
  7. ^ Gregory Choppin; Jan-Olov Liljenzin; Jan Rydberg (2002). Radiochemistry and Nuclear Chemistry, Third Edition. p. 610. ISBN 978-0-7506-7463-8.
  8. ^ Paiva, A. P.; Malik, P. (2004). "Recent advances on the chemistry of solvent extraction applied to the reprocessing of spent nuclear fuels and radioactive wastes". Journal of Radioanalytical and Nuclear Chemistry. 261 (2): 485–496. doi:10.1023/B:JRNC.0000034890.23325.b5. S2CID 94173845.
  9. ^ Burns, J. H.; Brown, G. M.; Ryan, R. R. (1985). "Structure of dinitratodioxobis(triisobutyl phosphate)uranium(VI) at 139 K". Acta Crystallographica Section C Crystal Structure Communications. 41 (10): 1446–1448. Bibcode:1985AcCrC..41.1446B. doi:10.1107/S0108270185008125.
  10. ^ J.H. Burns (1983). "Solvent-extraction complexes of the uranyl ion. 2. Crystal and molecular structures of catena-bis(.mu.-di-n-butyl phosphato-O,O')dioxouranium(VI) and bis(.mu.-di-n-butyl phosphato-O,O')bis[(nitrato)(tri-n-butylphosphine oxide)dioxouranium(VI)]". Inorganic Chemistry. 22 (8): 1174–1178. doi:10.1021/ic00150a006.
  11. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1261. ISBN 978-0-08-037941-8.
  12. ^ Gerber, M.S. (February 2001). "History of Hanford Site Defense Production (Brief)" (PDF). Fluor Hanford / US DOE. Retrieved 2009-10-01.
  13. ^ "Greenpeace on La Hague (German version)". Retrieved 2016-04-30.
  14. ^ US patent 2924506, Anderson, Herbert H. and Asprey, Larned B. & Asprey, Larned B., "Solvent extraction process for plutonium", issued 1960-02-09 
  15. ^ P. Gary Eller; Bob Penneman & Bob Ryan (2005). (PDF). The Actinide Research Quarterly. Los Alamos National Laboratory. pp. 13–17. Archived from the original (PDF) on 2014-02-01.

Further reading edit

  • OECD Nuclear Energy Agency, The Economics of the Nuclear Fuel Cycle, Paris, 1994
  • I. Hensing and W Schultz, Economic Comparison of Nuclear Fuel Cycle Options, Energiewirtschaftlichen Instituts, Cologne, 1995.
  • Cogema, Reprocessing-Recycling: the Industrial Stakes, presentation to the Konrad-Adenauer-Stiftung, Bonn, 9 May 1995.
  • OECD Nuclear Energy Agency, Plutonium Fuel: An Assessment, Paris, 1989.
  • National Research Council, "Nuclear Wastes: Technologies for Separation and Transmutation", National Academy Press, Washington D.C. 1996.

External links edit

  • Processing of Used Nuclear Fuel 2007-02-04 at the Wayback Machine, World Nuclear Association
  • , Analytical Center for Non-proliferation
  • Mixed Oxide Fuel (MOX) 2013-03-01 at the Wayback Machine – World Nuclear Association
  • Disposal Options for Surplus Weapons-Usable Plutonium – Congressional Research Service Report for Congress

April 08, 2024
purex, other, uses, purex, disambiguation, confused, with, pyrex, plutonium, uranium, reduction, extraction, chemical, method, used, purify, fuel, nuclear, reactors, nuclear, weapons, facto, standard, aqueous, nuclear, reprocessing, method, recovery, uranium, . For other uses see Purex disambiguation Not to be confused with Pyrex PUREX plutonium uranium reduction extraction is a chemical method used to purify fuel for nuclear reactors or nuclear weapons 7 PUREX is the de facto standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium from used nuclear fuel spent nuclear fuel or irradiated nuclear fuel It is based on liquid liquid extraction ion exchange 8 Reprocessing of spent nuclear fuel by the PUREX method first developed in the 1940s to produce plutonium for nuclear weapons 1 was demonstrated commercially in Belgium to partially re fuel a LWR in the 1960s 2 This aqueous chemical process continues to be used commercially to separate reactor grade plutonium RGPu for reuse as MOX fuel It remains controversial as plutonium can be used to make nuclear weapons 3 4 The most developed though commercially unfielded alternative reprocessing method is Pyroprocessing 5 suggested as part of the depicted metallic fueled Integral fast reactor IFR a sodium fast reactor concept of the 1990s After the spent fuel is dissolved in molten salt all of the recyclable actinides consisting largely of plutonium and uranium though with important minor constituents are extracted using electrorefining electrowinning The resulting mixture keeps the plutonium at all times in an unseparated gamma and alpha emitting actinide form that is also mildly self protecting in theft scenarios 6 PUREX is applied to spent nuclear fuel which consists primarily of very high atomic weight actinoid or actinide elements e g uranium plutonium americium along with smaller amounts of material composed of lighter atoms notably the fission products produced by reactor operation A simplified plutonium extraction flow chart The actinoid elements in this case consist primarily of the unconsumed remains of the original fuel typically U 235 U 238 and or Pu 239 Contents 1 Chemical process 2 PUREX raffinate 3 Pollution 4 History 5 List of nuclear reprocessing sites 6 See also 7 References amp notes 8 Further reading 9 External linksChemical process edit nbsp Structure of uranyl nitrate complex that is extracted in PUREX 9 The fuel is first dissolved in nitric acid at a concentration around 7 M Solids are removed by filtration to avoid the formation of emulsions referred to as third phases in the solvent extraction community The organic solvent consists of 30 tributyl phosphate TBP in a hydrocarbon such as kerosene Uranyl VI UO2 2 ions are extracted in the organic phase as UO2 NO3 2 2TBP complexes plutonium is extracted as similar complexes The heavier actinides primarily americium and curium and the fission products remain in the aqueous phase The nature of uranyl nitrate complexes with trialkyl phosphates has been characterized 10 Plutonium is separated from uranium by treating the TBP kerosene solution with reducing agents to convert the plutonium to its 3 oxidation state which will pass into the aqueous phase Typical reducing agents include N N diethyl hydroxylamine ferrous sulphamate and hydrazine Uranium is then stripped from the kerosene solution by back extraction into nitric acid at a concentration around 0 2 M 11 PUREX raffinate editThe term PUREX raffinate describes the mixture of metals in nitric acid which are left behind when the uranium and plutonium have been removed by the PUREX process from a nuclear fuel dissolution liquor This mixture is often known as high level nuclear waste Two PUREX raffinates exist The most highly active raffinate from the first cycle is the one which is most commonly known as PUREX raffinate The other is from the medium active cycle in which the uranium and plutonium are refined by a second extraction with tributyl phosphate nbsp Deep blue is the bulk ions light blue is the fission products group I is Rb Cs group II is Sr Ba group III is Y and the lanthanides orange is the corrosion products from stainless steel pipework green are the major actinides violet are the minor actinides and magenta is the neutron poison Currently PUREX raffinate is stored in stainless steel tanks before being converted into glass The first cycle PUREX raffinate is very radioactive It has almost all of the fission products corrosion products such as iron nickel traces of uranium plutonium and the minor actinides Pollution editThe PUREX plant at the Hanford Site was responsible for producing copious volumes of liquid wastes resulting in the radioactive contamination of groundwater 12 Greenpeace measurements in La Hague and Sellafield indicated that radioactive pollutants are steadily released into the sea and the air Therefore people living near these processing plants are exposed to higher radiation levels than the naturally occurring background radiation According to Greenpeace this additional radiation is small but not negligible 13 History editThe PUREX process was invented by Herbert H Anderson and Larned B Asprey at the Metallurgical Laboratory at the University of Chicago as part of the Manhattan Project under Glenn T Seaborg their patent Solvent Extraction Process for Plutonium filed in 1947 14 mentions tributyl phosphate as the major reactant which accomplishes the bulk of the chemical extraction 15 List of nuclear reprocessing sites editCOGEMA La Hague site Mayak Thermal Oxide Reprocessing Plant and B205 at Sellafield Tokai Ibaraki West Valley Reprocessing Plant Savannah River Site Hanford Site Idaho Chemical Processing Plant now Idaho National Laboratory Radiochemical Engineering Development Center Oak Ridge National LaboratorySee also editNuclear fuel cycle Nuclear breeder reactor Spent nuclear fuel shipping cask Global Nuclear Energy Partnership announced February 2006References amp notes edit Greenwood pp 1255 1261 Reprocessing plants world wide European Nuclear Society Archived from the original on 22 June 2015 Retrieved 29 July 2008 An Evaluation of the Proliferation Resistant Characteristics of Light Water Reactor Fuel with the Potential for Recycle in the United States Is U S Reprocessing Worth The Risk Steve Fetter and Frank N von Hippel Arms Control Today September 1 2005 L C Walters September 18 1998 Thirty years of fuels and materials information from EBR II Journal of Nuclear Materials 270 1 39 48 Bibcode 1999JNuM 270 39W doi 10 1016 S0022 3115 98 00760 0 1 PUREX and PYRO are not the same Hannum Marsh Stanford Gregory Choppin Jan Olov Liljenzin Jan Rydberg 2002 Radiochemistry and Nuclear Chemistry Third Edition p 610 ISBN 978 0 7506 7463 8 Paiva A P Malik P 2004 Recent advances on the chemistry of solvent extraction applied to the reprocessing of spent nuclear fuels and radioactive wastes Journal of Radioanalytical and Nuclear Chemistry 261 2 485 496 doi 10 1023 B JRNC 0000034890 23325 b5 S2CID 94173845 Burns J H Brown G M Ryan R R 1985 Structure of dinitratodioxobis triisobutyl phosphate uranium VI at 139 K Acta Crystallographica Section C Crystal Structure Communications 41 10 1446 1448 Bibcode 1985AcCrC 41 1446B doi 10 1107 S0108270185008125 J H Burns 1983 Solvent extraction complexes of the uranyl ion 2 Crystal and molecular structures of catena bis mu di n butyl phosphato O O dioxouranium VI and bis mu di n butyl phosphato O O bis nitrato tri n butylphosphine oxide dioxouranium VI Inorganic Chemistry 22 8 1174 1178 doi 10 1021 ic00150a006 Greenwood Norman N Earnshaw Alan 1997 Chemistry of the Elements 2nd ed Butterworth Heinemann p 1261 ISBN 978 0 08 037941 8 Gerber M S February 2001 History of Hanford Site Defense Production Brief PDF Fluor Hanford US DOE Retrieved 2009 10 01 Greenpeace on La Hague German version Retrieved 2016 04 30 US patent 2924506 Anderson Herbert H and Asprey Larned B amp Asprey Larned B Solvent extraction process for plutonium issued 1960 02 09 P Gary Eller Bob Penneman amp Bob Ryan 2005 Pioneer actinide chemist Larned Asprey dies PDF The Actinide Research Quarterly Los Alamos National Laboratory pp 13 17 Archived from the original PDF on 2014 02 01 Further reading editOECD Nuclear Energy Agency The Economics of the Nuclear Fuel Cycle Paris 1994 I Hensing and W Schultz Economic Comparison of Nuclear Fuel Cycle Options Energiewirtschaftlichen Instituts Cologne 1995 Cogema Reprocessing Recycling the Industrial Stakes presentation to the Konrad Adenauer Stiftung Bonn 9 May 1995 OECD Nuclear Energy Agency Plutonium Fuel An Assessment Paris 1989 National Research Council Nuclear Wastes Technologies for Separation and Transmutation National Academy Press Washington D C 1996 External links editProcessing of Used Nuclear Fuel Archived 2007 02 04 at the Wayback Machine World Nuclear Association Reactor Grade Plutonium and Development of Nuclear Weapons Analytical Center for Non proliferation PUREX Process European Nuclear Society Mixed Oxide Fuel MOX Archived 2013 03 01 at the Wayback Machine World Nuclear Association Disposal Options for Surplus Weapons Usable Plutonium Congressional Research Service Report for Congress Brief History of Fuel Reprocessing Retrieved from https en wikipedia org w index php title PUREX amp oldid 1212114067 PUREX raffinate, wikipedia, wiki, book, books, library,

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