title: Structure and Reactivity of X-ray Amorphous Uranyl Peroxide, U2O7.
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 (1)H- and (17)O-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.
authors.affiliation: University of Minnesota , Department of Chemistry, Minnesota Supercomputing Institute, Minneapolis, Minnesota 55455, United States.
authors.forename: Samuel O
authors.initials: SO
authors.lastname: Odoh
authors.affiliation: Department of Nuclear Engineering, University of Tennessee , Knoxville, Tennesee 37996, United States.
authors.forename: Jacob
authors.initials: J
authors.lastname: Shamblin
authors.affiliation: Department of Earth and Planetary Sciences, Department of Chemistry; University of California , Davis, California 95616, United States.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Colla
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Sarah
authors.initials: S
authors.lastname: Hickam
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Haylie L
authors.initials: HL
authors.lastname: Lobeck
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Rachel A K
authors.initials: RA
authors.lastname: Lopez
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Travis
authors.initials: T
authors.lastname: Olds
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Jennifer E S
authors.initials: JE
authors.lastname: Szymanowski
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Ginger E
authors.initials: GE
authors.lastname: Sigmon
authors.affiliation: Chemical and Engineering Materials Division, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Joerg
authors.initials: J
authors.lastname: Neuefeind
authors.affiliation: Department of Earth and Planetary Sciences, Department of Chemistry; University of California , Davis, California 95616, United States.
authors.forename: William H
authors.initials: WH
authors.lastname: Casey
authors.affiliation: Department of Nuclear Engineering, University of Tennessee , Knoxville, Tennesee 37996, United States.
authors.forename: Maik
authors.initials: M
authors.lastname: Lang
authors.affiliation: University of Minnesota , Department of Chemistry, Minnesota Supercomputing Institute, Minneapolis, Minnesota 55455, United States.
authors.forename: Laura
authors.initials: L
authors.lastname: Gagliardi
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame , Notre Dame, Indiana 46556, United States.|Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Burns