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-UO3. 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.