PNNL

Abstract

This work focuses on progress in gaining a better understanding of the polymorphic nature of the UO3-water system, one of several 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 common throughout the fuel cycle. Powder x-ray diffraction, Raman and fluorescence characterization was performed on polymorphic forms of UO3 and UO3 hydrolysis products for the purpose of developing some predictive capability of estimating process history and utility, e.g. for 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 ß-UO3. Pure phases of UO3, hydrolysis products and starting materials were used to establish optical spectroscopic signatures for these compounds.