12:30 PM - 12:45 PM
[MAG38-14] Identification of radioactive microparticles in the vicinity of the Fukushima Dai-ichi Nuclear Power Plant
Keywords:FDNPP disaster, Radioactive particle, Consist elements, Isotope ratio
Surface soil samples were collected in the area about 20 km northwest from the FDNPP in June 2013. Spot-type contaminations were detected by IP analysis. Then, the radioactive particles were isolated by repeated sorting process and measured by the γ-spectroscopy with the high purity germanium semiconductor detector. The particles isolated were finally observed by SEM-EDS to determine the elemental composition and the morphology.
So far identified are four particles, and determined radionuclides by γ-spectroscopy were 134Cs and 137Cs. The morphology of the particles exhibited two types; spherical and fragmental. Thus, the spot-type contamination was characterized as due to such specific radioactive particles. The particles consist of Si, O, Zn, Fe, etc. and Cs (of which activity matched with the results by γ-spectroscopy) were also easily detected by SEM-EDS, suggesting glassy molten material. However, other fission products were not found in the particles. Tremendous amount of radioactive particles were collected around the ChNPP, and they were termed hot particle. Dominant components of the hot particle are nuclear fuel and typical fission products such as 90Sr, 153Eu as well as 134Cs and 137Cs. In contrast elemental composition of the present particles were dominated by Si. Uranium was found for only one of the present particles, but its concentration was very low and localized within the particle. In conclusion, characteristics of the present particles are quite different from the Chernobyl hot particles, but very similar to those reported for the particles isolated from HV filter samples in Tsukuba (Adachi et al., 2013, Abe et al., 2014).