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, Utsunomiya Satoshi
Department of Chemistry, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
National Institute of Polar Research, 10-3 Midori-cho, Tachikawa-shi, Tokyo 190-8518, Japan; Department of Polar Science, The Graduate University for Advanced Studies (SOKENDAI), Shonan, Hayama, Kanagawa 240-0193, Japan.
J Hazard Mater. 2024 May 15;470:134104. doi: 10.1016/j.jhazmat.2024.134104. Epub 2024 Mar 21.
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 CsO) in a zeolite: pollucite. The compositions of three pollucite inclusions are (CsKRbBa)(FeZnX)SiO, (CsKRbBa)(FeZnX)SiO, and (CsKRbBa)(FeZnX)SiO (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 10 - 10 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.
了解放射性铯污染一直是福岛第一核电站及其他核遗留场地的核心问题；然而，环境样品中放射性铯的原子尺度表征从未实现。在此，我们首次报告了使用高分辨率高角度环形暗场扫描透射电子显微镜（HAADF-STEM）对放射性铯原子进行直接成像。在从日本收集的富含铯的微粒中，我们记录到在一种沸石（铯沸石）中含有27 - 36 wt%铯（以CsO形式报告）的包裹体。三个铯沸石包裹体的成分分别为（CsKRbBa）（FeZnX）SiO、（CsKRbBa）（FeZnX）SiO和（CsKRbBa）（FeZnX）SiO（X包括其他阳离子）。沿[111]晶带轴观察的铯沸石的HAADF-STEM成像显示了一系列铯原子，这与使用多层法模拟的图像一致。铯沸石的出现表明，在福岛核事故堆芯熔毁期间，局部富集的铯可能通过挥发和冷凝与硅质物质发生了反应。掺入的铯产生的β辐射剂量估计达到10 - 10 Gy，这比沸石典型的非晶化剂量低三个数量级以上。放射性铯的原子分辨率成像对于更好地理解因熔毁事件受损的核反应堆内外放射性铯的归宿而言是一项重要进展。
