Investigation of the polymorphs and hydrolysis of uranium trioxide

This work focuses on the polymorphic nature of the UO₃ and UO₃-H₂O system, which are important materials associated with the nuclear fuel cycle. The UO₃-water system is complex and has not been fully characterized, even though these species are key fuel cycle materials. Powder X-ray diffraction, and Raman and fluorescence spectroscopies were used to characterize both the several polymorphic forms of UO₃ and the certain UO₃-hydrolysis products for the purpose of developing predictive capabilities and estimating process history; for example, polymorphic phases of unknown origin. Specifically, we have investigated three industrially relevant production pathways of UO₃ and discovered a previously unknown low temperature route to the production of β-UO ₃. Several phases of UO₃, its hydrolysis products, and key starting materials were synthesized and characterized as pure materials to establish optical spectroscopic signatures for these compounds for forensic analysis.