“Invisible” radioactive cesium atoms revealed: Pollucite inclusion in cesium-rich microparticles (CsMPs) from the Fukushima Daiichi Nuclear Power Plant
Journal
Journal of Hazardous Materials
Journal Volume
470
Start Page
134104
ISSN
0304-3894
Date Issued
2024-05
Author(s)
Miyazaki, Kanako
Takehara, Masato
Minomo, Kenta
Horie, Kenji
Takehara, Mami
Yamasaki, Shinya
Saito, Takumi
Ohnuki, Toshihiko
Takano, Masahide
Shiotsu, Hiroyuki
Iwata, Hajime
Vettese, Gianni F.
Sarparanta, Mirkka P.
Law, Gareth T.W.
Grambow, Bernd
Ewing, Rodney C.
Abstract
Understanding radioactive Cs contamination has been a central issue at Fukushima Daiichi and other nuclear legacy sites; however, atomic-scale characterization of radioactive Cs in environmental samples has never been achieved. Here we report, for the first time, the direct imaging of radioactive Cs atoms using high-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). In Cs-rich microparticles collected from Japan, we document inclusions that contain 27 – 36 wt% of Cs (reported as Cs2O) in a zeolite: pollucite. The compositions of three pollucite inclusions are (Cs1.86K0.11Rb0.19Ba0.22)2.4(Fe0.85Zn0.84X0.31)2.0Si4.1O12, (Cs1.19K0.05Rb0.19Ba0.22)1.7(Fe0.66Zn0.32X0.41)1.4Si4.6O12, and (Cs1.27K0.21Rb0.29Ba0.15)1.9(Fe0.60Zn0.32X0.69)1.6Si4.4O12 (X includes other cations). HAADF-STEM imaging of pollucite, viewed along the [111] zone axis, revealed an array of Cs atoms, which is consistent with a simulated image using the multi-slice method. The occurrence of pollucite indicates that locally enriched Cs reacted with siliceous substances during the Fukushima meltdowns, presumably through volatilization and condensation. Beta radiation doses from the incorporated Cs are estimated to reach 106 – 107 Gy, which is more than three orders of magnitude less than typical amorphization dose of zeolite. The atomic-resolution imaging of radioactive Cs is an important advance for better understanding the fate of radioactive Cs inside and outside of nuclear reactors damaged by meltdown events.
Subjects
Cesium radioisotope
Cesium-rich microparticles
Fukushima Daiichi Nuclear Power Plant
High-angle annular dark-field scanning transmission electron microscopy
Pollucite
Publisher
Elsevier BV
Type
journal article