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.

It is a red-brown crystalline solid, and volatile; it melts at 52°C and boils at 62°C. [cite web
url = http://www.webelements.com/webelements/compounds/text/Pu/F6Pu1-13693066.html
title = plutonium (VI) fluoride
publisher = webelements] ; the heat of sublimation is 12.1 Kcal/mol and the heat of vaporization 7.4 Kcal/mol. It is relatively hard to handle, being very corrosive and prone to auto-radiolysis.

It is prepared by fluorination of PuF₄ by powerful fluorinating agents such as elemental fluorine [cite web
url = http://www.fas.org/sgp/othergov/doe/lanl/lib-www/la-pubs/00419717.pdf
title = Report on Plutonium Hexafluoride
publisher = Los Alamos Scientific Laboratory] or chlorine trifluoride; hydrogen fluoride is not sufficient [cite web
url = http://books.nap.edu/openbook.php?record_id=5538&page=42
title = Evaluation of the U.S. Department of Energy's Alternatives for the Removal and Disposition of Molten Salt Reactor Experiment Fluoride Salts] ; it is itself a powerful fluorinating agent.

Under laser irradiation at a wavelength of less than 520nm, it decomposes to plutonium pentafluoride and fluorine [cite web
url = http://www.fas.org/sgp/othergov/doe/lanl/lib-www/aapd.pdf
title = Photochemical Preparation of Plutonium pentafluoride
publisher = Los Alamos Scientific Laboratory] ; after more irradiation it decomposes further to plutonium tetrafluoride.

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