The United States currently has 700,000 metric tons of depleted uranium hexafluoride (DUF6) in cylinders. There is a need to develop methods for reducing the amount of DUF6 and the corresponding risk of corrosion and release of the volatile substance into the atmosphere. Current methods utilize vaporized DUF6 that reacts with steam, H2, and N2 gases to produce uranium oxides and HF gas that must also be captured. In the current studies solid DUF6 at depressed temperature was introduced to the room temperature ionic liquid, 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide ([MPPi][TFSI]) by simple addition. The addition DUF6 to the IL results in the spontaneous dissolution to form a green solution through the oxidation of TFSI and reduction of UF6 to UF62-. At concentrations below 1 M the solution is stable and the dissolved UF6 remains soluble in the IL. However, above 1 M a green precipitate is formed which can then be filtered directly from the IL. This precipitate is air stable once removed from the [MPPi][TFSI]. TGA analysis indicates that 58% of the mass is lost at temperatures exceeding 1148 oC. PXRD shows that a bulk of the product after TGA-DSC is UO2 after exposure to air. The TGA/DSC analysis suggests the decomposition of [MPPi]2[UF6] to UO2 through the loss of cation species and F. Additional studies are being conducted to evaluate pathways to uranium reduction from the decomposition of [MPPi]2[UF6] to form metal. The electrochemical reduction of UF6 to U metal is also targeted using the UF6 dissolved in IL.

Reduction of uranium hexafluoride with a room temperature ionic liquid (1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide)

2019 Spring National Meeting

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