Abstract
Changes in chemical speciation of uranium oxides following storage under varied conditions of temperature and relative humidity are valuable for characterizing material provenance. In this study, subsamples of high purity α-UO3 were stored under four sets of controlled conditions of temperature and relative humidity over several years, and then measured periodically for chemical speciation. Powder X-ray diffraction (XRD) analysis and extended X-ray absorption fine structure spectroscopy confirm hydration of α-UO3 to a schoepite-like end product following storage under each of the varied storage conditions, but the species formed during exposure to the lower relative humidity and lower temperature condition follows different trends from those formed under the other three storage conditions (high relative humidity with high or low temperatures, and low relative humidity with a high temperature). Thermogravimetry coupled with XRD analysis was carried out to distinguish desorption pathways of water from the hydrated end products. Density functional theory calculations discern changes in the structure of α-UO3 following incorporation of 1, 2 or 3 H2O molecules or 1, 2 or 3 OH groups into the orthorhombic lattice, revealing differences in lattice constants, U-O bond lengths, and U-U distances. The collective results from this analysis are in contrast to analogous studies that report that U3O8 is oxidized and hydrated in air during storage under high relative humidity conditions.
| Original language | English |
|---|---|
| Pages (from-to) | 10452-10462 |
| Number of pages | 11 |
| Journal | Dalton Transactions |
| Volume | 49 |
| Issue number | 30 |
| DOIs | |
| State | Published - Aug 14 2020 |
| Externally published | Yes |
Funding
This work has been supported by the U.S. Department of Homeland Security, Domestic Nuclear Detection Office, under competitively awarded contracts IAA HSHQDC-13-00269 and HDHQDC-08-X-00805. S. C. H. would like to thank the Seaborg Institute at Los Alamos National Laboratory for providing funding to conduct the modelling studies. A. L. T. would like to thank the U.S. Department of Homeland Security under Grant Award Number 2012-DN-130-NF0001-02, the Seaborg Institute, and the University of Missouri for providing funding to perform this work. J. R. W.’s contribution to this material is based upon work supported by the U.S. Department of Homeland Security under Grant Award Number 2012-DN-130-NF-0001-02. The authors would like to thank Drs Corwin Booth, David L. Clark, and Steven D. Conradson for useful discussions. All X-ray absorption data were collected at the Stanford Synchrotron Radiation Lightsource. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract DE-AC02-76SF00515. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Department of Homeland Security or the Government. Los Alamos National Laboratory is operated by Triad National Security, LLC, for the National Nuclear Security Administration for the U.S. Department of Energy (Contract DE-SOL-001206). LA-UR-19-24180.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| U.S. Department of Homeland Security | |
| Office of Science | |
| Basic Energy Sciences | DE-AC02-76SF00515 |
| University of Missouri | |
| Domestic Nuclear Detection Office | 2012-DN-130-NF0001-02, IAA HSHQDC-13-00269, HDHQDC-08-X-00805 |
| Glenn T. Seaborg Institute |