Oxidation kinetics for conversion of U3O8 to ε-UO3 with NO2

The oxidation kinetics of U3O8 powder to ε-UO3 in an NO2 environment was measured by in situ x-ray diffraction (XRD). Experiments were performed at temperatures of 195, 210, 235, and 250 °C using a custom designed and fabricated sample isolation stage. Data were refined to quantify phase fractions using a newly proposed structure for the ε-UO3 polymorph. The kinetics data were modeled using a shrinking core approach. A proposed two-step reaction process is presented based on the developed models.