Phase Analysis of Australian Uranium Ore Concentrates Determined by Variable Temperature Synchrotron Powder X-ray Diffraction

The chemical speciation of uranium oxides is sensitive to the provenance of the samples and their storage conditions. Here, we use diffraction methods to characterize the phases found in three aged (>10 years) uranium ore concentrates of different origins as well as in situ analysis of the thermally induced structural transitions of these materials. The structures of the crystalline phases found in the three samples have been refined, using high-resolution synchrotron X-ray diffraction data. Rietveld analysis of the samples from the Olympic Dam and Ranger uranium mines has revealed the presence of crystalline alpha-UO2(OH)(2), together with metaschoepite (UO2)(4)O(OH)(6)center dot 5H(2)O, in the aged U3O8 samples, and it is speculated that this forms as a consequence of the corrosion of U3O8 in the presence of metaschoepite. The third sample, from the Beverley uranium mine, contains the peroxide [UO2(eta(2)-O-2)(H2O)(2)] (metastudtite) together with alpha-UO2(OH)(2) and metaschoepite. A core-shell model is proposed to account for the broadening of the diffraction peaks of the U3O8 evident in the samples.

Automated summary

The chemical speciation of aged uranium oxides is influenced by the source of the samples and their storage conditions. Diffraction methods were used to analyze the crystalline phases present in three samples, each from a different uranium mine. The study identified specific crystalline structures and proposed a core-shell model to explain certain phenomena observed in the samples.