Pyrohydrolysis of Uranium Tetrafluoride and Thorium Tetrafluoride

To meet the needs of the aqueous-reprocessing of used fuel from thorium molten salt reactor, the insoluble fluorides need to be converted into their corresponding oxides form. To realize this, a pyrohydrolysis method was proposed. The pyrohydrolysis behavior of UF₄ and ThF₄ under different temperature and time was studied, and the structural characterization of the pyrohydrolysis products and the dissolution tests of the products were performed. The results show that, UF₄ and ThF₄ are entirely converted into their corresponding oxides UO_2.25 and ThO₂ at 300℃ and 350℃. The results of the dissolution tests show that the pyrohydrolysis products of both UF₄ and ThF₄ can easily dissolved in 3 mol/L HNO₃ and Thorex solution, respectively.