Actinide fluorides are important nuclear fuel cycle materials (e.g., UF4 and PuF4 are common intermediates in the production of uranium and plutonium metal), yet much remains to be learned about the fundamental properties of these materials, including the effects of aging on their chemical and physical properties. Such studies are challenging because standard production techniques involve the manipulation of large quantities of hydrogen fluoride at high temperatures and there are radiological hazards associated with handling actinide materials. In contrast, the synthesis and characterization of lanthanide fluorides via ionic liquids is well established and provides an appealing alternative route to the production of actinide fluorides. This work explores an approach in which the ionic liquid 1-Butyl-3-methylimidzalium hexafluorophosphate ([BMIM][PF6]) is used to fluorinate actinide dioxides (AnO2) and produce anhydrous actinide fluorides (AnF3, AnF4). Powder X-ray diffraction, electron microscopy, thermogravimetric analysis, inductively-coupled plasma optical emission spectroscopy, vibrational spectroscopy, and high temperature oxide melt solution calorimetry were used to characterize the resulting actinide fluorides. The latter technique allows us to determine the heats of formation for each product and can be used to comment on trends across the actinide series. Such baseline thermodynamic information is necessary for future studies directed at understanding the environmental chemistry of these materials.

Synthesis and characterization of anhydrous actinide fluorides

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