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Center for Nonlinear Studies |
Oxygen isotope ratios of uranium oxides are known to correlate with those of the fluids from which they precipitated. The variety of processing routes utilized in the nuclear fuel cycle, from ore concentration through enrichment, will contribute to a wide variation in δ18O values encountered among uranium oxides. Application of this information for nuclear forensics purposes requires an understanding of the oxygen isotopic fractionation induced through each processing condition. The initial focus of this study is an interrogation of changes in the 18O/16O ratio along each step of commonly employed synthetic routes, with variation in the chemical compositions of starting materials. Beginning with a uranyl nitrate starting material depleted in 18O, uranium oxide intermediate products: α-UO3, am-UO3, and α-U3O8, were synthesized from aqueous solutions enriched in 18O using the uranyl peroxide route. Each of these compounds was then calcined to a final product of uranium dioxide. Identification of each uranium species was confirmed using powder X-ray diffraction, while oxygen isotope ratios of the starting materials, intermediated U-oxides, and the final UO2 were measured using a High Vacuum Fluorination System (HVFS) coupled with Isotope Ratio Mass Spectrometry (IRMS). Scanning electron microscopy (SEM) was used to quantify any morphological differences in the UO2 relative to the intermediate U-oxides. Results of oxygen isotope fractionation arising from variation in processing methods will be discussed, along with their implications for future nuclear forensic investigations.
Host: Enrique Batista/Marianne Wilkerson