Micro-Raman spectroscopy of Uranium Oxyfluoride Particulate Material for Nuclear Safeguards

Environmental samples collected by safeguards organizations such as the International Atomic Energy Agency often contain particles of uranium oxyfluoride (UO2F2). UO2F2 is a compound formed from the hydrolysis of uranium hexafluoride (UF6). It is very hygroscopic and is known to lose fluorine over time and from exposure to certain environmental conditions. In order to investigate these changes, uranium oxyfluoride particulate material prepared in a laboratory setting was measured by micro-Raman spectroscopy. The uranyl symmetric stretching frequency of (UO2)2+ at around 865 cm-1 was detected in the majority of the spectra. Depending on the conditions under which the uranium oxyfluoride particles were prepared and stored, additional peaks and features appeared in the spectrum. These features were attributed to changes in hydration of the uranium oxyfluoride and the co-existence of multiple uranium phases in particle aggregates. Experiments were carried out using different incident laser wavelengths at the lowest possible power setting, as the particles appeared to be very heat-sensitive.