Plutonium hexafluoride

Plutonium hexafluoride is the highest fluoride of plutonium, and is of interest for laser enrichment of plutonium, in particular for the production of pure plutonium-239 from irradiated uranium. This pure plutonium is needed to avoid premature ignition of low-mass nuclear weapon designs by neutrons produced by spontaneous fission of plutonium-240.

Plutonium hexafluoride[1]
Names
IUPAC name
plutonium(VI) fluoride
Identifiers
3D model (JSmol)
ChemSpider
Properties
PuF
6
Appearance Dark red, opaque crystals
Density 5.08 g·cm−3
Melting point 52 °C (126 °F; 325 K)
Boiling point 62 °C (144 °F; 335 K)
Structure
Orthorhombic, oP28
Pnma, No. 62
octahedral (Oh)
0 D
Related compounds
Related fluoroplutoniums
 Plutonium trifluoride

Plutonium tetrafluoride

Hazards
Radiation hazard
T+ C O N
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazard RA: Radioactive. E.g. plutonium
0
4
4
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

It is a red-brown volatile crystalline solid;[1] the heat of sublimation is 12.1 kcal/mol[2] and the heat of vaporization 7.4 kcal/mol.[2] It is relatively hard to handle, being very corrosive and prone to auto-radiolysis.[3][4]

It is prepared by fluorination of plutonium tetrafluoride (PuF4) by powerful fluorinating agents such as elemental fluorine.[2][5][6][7]

PuF
4 + F
2 → PuF
6

It can also be obtained by fluorination of plutonium(III) fluoride or plutonium(IV) oxide.[6]

2 PuF
3 + 3 F
2 → 2 PuF
6
PuO
2 + 3 F
2 → PuF
6 + O
2

In 1984, the synthesis of plutonium hexafluoride was achieved at unprecedented low temperatures through the use of dioxygen difluoride. Previous techniques needed temperatures so high that the plutonium hexafluoride produced would decompose rapidly.[8] Hydrogen fluoride is not sufficient;[9] even though it is a powerful fluorinating agent.

Under laser irradiation at a wavelength of less than 520 nm, it decomposes to plutonium pentafluoride and fluorine;[10] after more irradiation it decomposes further to plutonium tetrafluoride.[11]

References
  1. Lide, David R. (2009). Handbook of Chemistry and Physics (90 ed.). Boca Raton, Florida: CRC Press. pp. 4–81. ISBN 978-1-4200-9084-0. (webelements.com)
  2. Florin, Alan E.; Tannenbaum, Irving R.; Lemons, Joe F. (1956). "Preparation and properties of plutonium hexafluoride and identification of plutonium(VI) oxyfluoride". Journal of Inorganic and Nuclear Chemistry. 2 (5–6): 368–379. doi:10.1016/0022-1902(56)80091-2.
  3. Bibler, Ned E. (23 August 1979). "α and β Radiolysis of Plutonium Hexafluoride Vapor". J. Phys. Chem. 83 (17): 2179–2186. doi:10.1021/j100480a001.
  4. Steindler, M.J.; Steidl, D.V.; Fischer, J. (November 1964). "The decomposition of plutonium hexafluoride by gamma radiation". Journal of Inorganic and Nuclear Chemistry. 26 (11): 1869–1878. doi:10.1016/0022-1902(64)80011-7.
  5. A. E. Florin (9 November 1950). "Plutonium Hexafluoride: Second Report On The Preparation and Properties (LA-1168)" (PDF). Los Alamos Scientific Laboratory.
  6. Mandleberg, C.J.; Rae, H.K.; Hurst, R.; Long, G.; Davies, D.; Francis, K.E. (1956). "Plutonium hexafluoride". Journal of Inorganic and Nuclear Chemistry. 2 (5–6): 358–367. doi:10.1016/0022-1902(56)80090-0.
  7. Weinstock, Bernard; Malm, John G. (July 1956). "The properties of plutonium hexafluoride". Journal of Inorganic and Nuclear Chemistry. 2 (5–6): 380–394. doi:10.1016/0022-1902(56)80092-4.
  8. Malm, J. G.; Eller, P. G.; Asprey, L. B. (1984). "Low temperature synthesis of plutonium hexafluoride using dioxygen difluoride". Journal of the American Chemical Society. 106 (9): 2726–2727. doi:10.1021/ja00321a056.
  9. Evaluation of the U.S. Department of Energy's Alternatives for the Removal and Disposition of Molten Salt Reactor Experiment Fluoride Salts. 1997. p. 42. doi:10.17226/5538. ISBN 978-0-309-05684-7.
  10. US 4670239, Sherman W. Rabideau & George M. Campbell, "Photochemical Preparation of Plutonium Pentafluoride", published June 2, 1987, assigned to The United States of America
  11. Lobikov, E. A.; Prusakov, V. N.; Serik, V. F. (August–September 1992). "Plutonium Hexafluoride Decomposition under the Action of Laser Radiation". Journal of Fluorine Chemistry. 58 (2–3): 277. doi:10.1016/S0022-1139(00)80734-4.

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