PUREX

Source: Wikipedia, the free encyclopedia.
For other uses, see Purex (disambiguation).
Not to be confused with Pyrex.
reactor grade plutonium (RGPu) for reuse as MOX fuel. It remains controversial, as plutonium can be used to make nuclear weapons.[3][4]
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 (plutonium uranium reduction extraction) is a

ion-exchange.[8]

PUREX is applied to

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

Pu-239
).

Chemical process

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-

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

The term PUREX

nuclear waste
.

Two PUREX raffinates exist. The most highly active

extraction with tributyl phosphate
.

Deep blue is the bulk ions, light blue is the

minor actinides and magenta is the neutron poison
)

Currently PUREX raffinate is stored in

minor actinides
.

Pollution

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

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

See also

  • Nuclear fuel cycle
  • Nuclear breeder reactor
  • Spent nuclear fuel shipping cask
  • Global Nuclear Energy Partnership
    announced February, 2006

References & notes

  1. ^ Greenwood, pp. 1255, 1261
  2. ^ "Reprocessing plants, world-wide". 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. doi:10.1016/S0022-3115(98)00760-0
    .
  6. ^ [1] PUREX and PYRO are not the same, Hannum, Marsh, Stanford.
  7. ISBN 978-0-7506-7463-8
    .
  8. S2CID 94173845
    .
  9. doi:10.1107/S0108270185008125
    .
  10. doi:10.1021/ic00150a006
    .
  11. ISBN 978-0-08-037941-8
    .
  12. 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). "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

  • 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

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