32 巻 (2017) 4 号 p. 255-260
Insoluble radioactive particles emitted from the Fukushima nuclear accident have been found from the samples collected in various environments. This manuscript summarizes the studies that characterized such particles using electron microscopy and synchrotron radiation analyses. The shapes and compositions of 33 radioactive particles from aerosol particles, soil, plant tissues, non-woven fabric cloth, and masks have been identified. These radioactive particles contained radioactive Cs ranging from 0.5 to 109 becquerel per particle. Diameters of spherical particles ranged from 0.8 to 4 μm, and those of non-spherical particles were from 1.4 to 250 μm. They consisted of silicate glass with Cs, Zn, and Fe as well as many minor elements (in total, 33 elements were detected). These particles tended to have more Cs on their surface than the core and contained nano-crystals consisting of, for example, Cu-Zn-Mo, Ag-Te, CaSO4, FeCr2O4, Sn-Te, Ag-Sb, and iron oxides. Such crystalline structures will be important to understand the formation and degradation processes.