Studies of the Uranium Pyrochlore Mineral Betafite [(Ca,U)₂(Nb,Ti,Ta)₂O₇]

Refractory uranium minerals are gaining increased attention as future sources of nuclear fuel to keep up with the world's growing demand for energy. One such mineral is the uranium pyrochlore betafite. Two betafite containing samples were characterised using XPS, XRD and multi acid digestion / ICP-MS. XPS results showed the U oxidation state of the surficial uranium in both samples was predominantly U⁶⁺, although some U⁵⁺ was detected. XRD analysis showed the betafite in the samples was amorphous, although after heating at 1100°C for 2 hours strong matches for both betafite and rutile were obtained for both samples. Dissolution studies showed similar trends for both samples, although the extent of dissolution for the betafite from the Ambatofotsky region in Madagascar was significantly greater in each experiment than that from Silver Crater Mine, Bancroft, Canada. This was most likely due to a higher amount of U⁶⁺ present in this sample. Heat-treating showed a higher rate of dissolution over the initial 100 min. of the dissolution test in both samples before the rate slowed over the remainder of the experiment. Unheated samples showed relatively consistent rates of dissolution over the duration of the experiments. (author)