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Title: Structure and Reactivity of X-ray Amorphous Uranyl Peroxide, U2O7

Recent accidents resulting in worker injury and radioactive contamination occurred due to pressurization of uranium yellowcake drums produced in the western USA. The drums contained an unexpected X-ray amorphous reactive form of uranium oxide, U2O7. Heating hydrated uranyl peroxides produced during in situ mining unintentionally produced U2O7. It is a hygroscopic anhydrous uranyl peroxide that reacts rapidly 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. The reactivity of U2O7 in water and with water in air is much higher than other uranium oxides, and this can be both hazardous and potentially advantageous in the nuclear fuel cycle.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4] ;  [4] ;  [4] ;  [4] ;  [4] ;  [5] ;  [6] ;  [2] ;  [1] ;  [7]
  1. Univ. of Minnesota, Minneapolis, MN (United States). Minnesota Supercomputing Inst., Dept. of Chemistry
  2. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Nuclear Engineering
  3. Univ. of California, Davis, CA (United States). Dept. of Earth and Planetary Sciences, Dept. of Chemistry
  4. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Sciences
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division
  6. Univ. of California, Davis, CA (United States). Dept. of Earth and Planetary Sciences, Dept. of Chemistr
  7. Univ. of Notre Dame, IN (United States). Dept. of Civil and Environmental Engineering and Earth Sciences; Univ. of Notre Dame, IN (United States). Dept. of Chemistry and Biochemistry
Publication Date:
OSTI Identifier:
1241447
Grant/Contract Number:
AC05-00OR22725; SC0001089
Type:
Published Article
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 55; Journal Issue: 7; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY