The effect of ionizing radiation on uranophane
Journal
American Mineralogist
Journal Volume
88
Journal Issue
1
Start Page
159
End Page
166
ISSN
0003-004X
Date Issued
2003-01
Author(s)
Abstract
The susceptibility of uranophane, a uranyl sheet silicate, ideally Ca(UO2)2(SiO3OH)2(H2 (H2O)5, to ionizing irradiation has been evaluated by systematic irradations with 200 ke V electrons 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 × 1010 Gy for uranophane, 1.3 × 1010 Gy for Sr-substituted uranophane, and 1.9 × 1010 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 × 1011 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-.
Subjects
Activation energy
Amorphization
Ionizing radiation
Oxide minerals
Radiolysis
Silicates
Temperature distribution
Uranium dioxide
Atomic mass
Defect accumulation
Effective activation energy
Energy depositions
Ionizing irradiation
Radiolytic decompositions
Temperature dependence
Temperature range
crystal structure
mineral alteration
radiation exposure
radioactivity
uranophane
High resolution transmission electron microscopy
Publisher
Mineralogical Society of America
Type
journal article