Distinction of radioactive particles derived from the Fukushima nuclear accident based on different heating characteristics

Okumura, Taiga*; Kogure, Toshihiro*; Yamaguchi, Noriko*; Dohi, Terumi   ; Fujiwara, Kenso ; Iijima, Kazuki  

Most of the radiocesium released by the Fukushima nuclear accident was sorbed to clay minerals such as weathered biotite (WB), whereas radiocesium-bearing microparticles (CsMPs) were also emitted from the damaged reactors. In this study, we report CsMPs with smaller size and lower radioactivity and suggest the way to distinguish CsMPs from other radioactive particles. Radioactive particles were collected from non-woven fabric cloth and contaminated soil and identified by SEM-EDS, and their radioactivity was measured by IP autoradiography. As a result, five CsMPs of less than 0.05 Bq and two WB particles of more than 0.05 Bq were identified, indicating the presence of CsMPs with lower radioactivity than WB. Next, the contaminated soil was uniformly scattered on the substrate to which a heat-resistant adhesive was applied, and IP autoradiography was performed before and after heating at 800 C. It was suggested that CsMPs could be distinguished by the heating treatment.