Radiation-induced decomposition of U(VI) alteration phases of UO 2

Satoshi Utsunomiya, Rodney C. Ewing

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Citations (Scopus)

Abstract

U6+-phases are common alteration products of spent nuclear fuel under oxidizing conditions, and they may potentially incorporate actinides, such as long-lived 239Pu and 237Np, delaying their transport to the biosphere. In order to evaluate the ballistic effects of α-decay events on the stability of the U6+-phases, we report, for the first time, the results of ion beam irradiations (1.0 MeV Kr 2+) for six different structures of U6+-phases: uranophane, kasolite, boltwoodite, saleeite, carnotite, and liebigite. The target uranyl-minerals were characterized by powder X-ray diffraction and identification confirmed by SAED (selected area electron diffraction) in TEM (transmission electron microscopy). The TEM observation revealed no initial contamination of uraninite in these U6+ phases. All of the samples were irradiated with in situ TEM observation using 1.0 MeV Kr2+ in the IVEM (intermediate-voltage electron microscope) at the IVEM-Tandem Facility of Argonne National Laboratory. The ion flux was 6.3 × 1011 ions/cm2/sec. The specimen temperatures during irradiation were 298 and 673 K, respectively. The Kr2+-irradiation decomposed the U 6+-phases to nanocrystals of UO2 at doses as low as 0.006 dpa. The cumulative doses for the pure U6+-phases, e.g., uranophane, at 0.1 and 1 million years (m.y.) are calculated to be 0.009 and 0.09 dpa using SRIM2003. However, with the incorporation of 1 wt.% 239Pu, the calculated doses reach 0.27 and ∼1.00 dpa in ten thousand and one hundred thousand years, respectively. Under oxidizing conditions, multiple cycles of radiation-induced decomposition to UO2 followed by alteration to U6+-phases should be further investigated to determine the fate of trace elements that may have been incorporated in the U6+-phases.

Original languageEnglish
Title of host publication29th International Symposium on the Scientific Basis for Nuclear Waste Management XXIX
PublisherMaterials Research Society
Pages465-472
Number of pages8
ISBN (Print)1558998896, 9781558998896
DOIs
Publication statusPublished - 2006
Externally publishedYes
Event29th International Symposium on the Scientific Basis for Nuclear Waste Management XXIX - Ghent, Belgium
Duration: Sep 12 2005Sep 16 2005

Publication series

NameMaterials Research Society Symposium Proceedings
Volume932
ISSN (Print)0272-9172

Other

Other29th International Symposium on the Scientific Basis for Nuclear Waste Management XXIX
CountryBelgium
CityGhent
Period9/12/059/16/05

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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