Determination of U₃O₈ in UO₂ by infrared spectroscopy

Abstract

The oxygen-uranium (O-U) system has various oxides, such as UO₂, U₄O₉, U₃O₈, and UO₃. Uranium dioxide is the most important one because it is used as nuclear fuel in nuclear power plants. UO₂ can have a wide stoichiometric variation due to excess or deficiency of oxygen in its crystal lattice, which can cause significant modifications of its proprieties. O/U relation determination by gravimetry cannot differentiate a stoichiometric deviation from contents of other uranium oxides in UO₂. The presence of other oxides in the manufacturing of UO₂ powder or sintered pellets is a critical factor. Fourier Transform Infrared Spectroscopy (FTIR) was used to identify U₃O₈ in samples of UO₂ powder. UO₂ can be identified by bands at 340 cm^-1 and 470 cm^-1, and U₃O₈ and UO₃ by bands at 735 cm^-1, 910 cm^-1, respectively. The methodology for sample preparation for FTIR spectra acquisition is presented, as well as the calibration for quantitative measurement of U₃O₈ in UO₂. The content of U₃O₈ in partially calcined samples of UO₂ powder was measured by FTIR with good agreement with X-rays diffractometry (XRD).

Keywords:
FTIR; uranium dioxide; triuranium octoxide