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The effect of ionizing radiation on uranophane

  • Satoshi Utsunomiya , Lu-Min Wang , Matt Douglas , Susan B. Clark and Rodney C. Ewing EMAIL logo
Published/Copyright: March 31, 2015
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Abstract

The susceptibility of uranophane, a uranyl sheet silicate, ideally Ca(UO2)2(SiO3OH)2(H2O)5. to ionizing irradiation has been evaluated by systematic irradiations with 200 keV elections over the temperature range 94 to 573 K. High-resolution transmission electron microscopy revealed that amorphous domains formed locally, concurrently with a gradual disordering of the entire structure. Amorphization doses at room temperature were 1.1 × 1O10 Gy for uranophane. 1.3 × 1O10 Gy for Sr- substituted uranophane. and 1.9 x 1O10 Gy for Eu-substituted uranophane: thus, there was an in­crease in amorphization dose with increasing average atomic mass. At 573 K. the amorphization dose of uranophane was 2.0 × 1O11 Gy. The temperature dependence of the amorphization dose of uranophane has two stages: ≤413 K and >413 K. Based on a defect accumulation model, the effec­tive activation energies for amorphization at each stage are 0.0440 eV and 0.869 eV, respectively. This suggests that the presence of H2O (and OH-) reduce the energy deposition required to cause amorphization. Above 413 K. the amorphization dose increased due to the absence of H2O and OH- and the absence of radiolytic decomposition of H2O and OH-.

Received: 2002-1-22
Accepted: 2002-9-19
Published Online: 2015-3-31
Published in Print: 2003-1-1

© 2015 by Walter de Gruyter Berlin/Boston

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