Abstract
Recent accidents resulting in worker injury and radioactive contamination occurred due to pressurization of uranium yellowcake drums produced in the western U.S.A. The drums contained an X-ray amorphous reactive form of uranium oxide that may have contributed to the pressurization. Heating hydrated uranyl peroxides produced during in situ mining can produce an amorphous compound, as shown by X-ray powder diffraction of material from impacted drums. Subsequently, studtite, [(UO2)(O2)(H2O)2](H2O)2, was heated in the laboratory. Its thermal decomposition produced a hygroscopic anhydrous uranyl peroxide that reacts with water to release O2 gas and form metaschoepite, a uranyl-oxide hydrate. Quantum chemical calculations indicate that the most stable U2O7 conformer consists of two bent (UO2)2+ uranyl ions bridged by a peroxide group bidentate and parallel to each uranyl ion, and a μ2-O atom, resulting in charge neutrality. A pair distribution function from neutron total scattering supports this structural model, as do 1H- and 17O-nuclear magnetic resonance spectra. The reactivity of U2O7 in water and with water in air is higher than that of other uranium oxides, and this can be both hazardous and potentially advantageous in the nuclear fuel cycle.
| Original language | English |
|---|---|
| Pages (from-to) | 3541-3546 |
| Number of pages | 6 |
| Journal | Inorganic Chemistry |
| Volume | 55 |
| Issue number | 7 |
| DOIs | |
| State | Published - Apr 18 2016 |
Funding
This research is funded by the Office of Basic Energy Sciences of the U.S. Department of Energy as part of the Materials Science of Actinides Energy Frontier Research Center (DESC0001089). Chemical analyses were conducted at the Center for Environmental Science and Technology at the University of Notre Dame. Spectra and diffraction data were collected at the Materials Characterization Facility of the Center for Sustainable Energy at the University of Notre Dame. A portion of this research at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. The authors thank Dr. Ping Yu of the UC Davis Keck NMR Facility for help with the NMR spectra.