TY - JOUR

T1 - Investigation of physical and chemical characteristics of radioactive aerosols emitted from reactor unit 1 by fukushima daiichi nuclear power plant accident

AU - Onozaki, Seika

AU - Abe, Yoshinari

AU - Nakai, Izumi

AU - Adachi, Kouji

AU - Igarashi, Yasuhito

AU - Oura, Yasuji

AU - Ebihara, Mitsuru

AU - Miyasaka, Takafumi

AU - Nakamura, Hisashi

AU - Sueki, Keisuke

AU - Tsuruta, Haruo

AU - Moriguchi, Yuichi

PY - 2019/1/1

Y1 - 2019/1/1

N2 - Three radioactive microparticles were separated from particles on filter tape samples collected hourly at a suspended particulate matter (SPM) monitoring site located at ~25 km north of the Fukushima Daiichi Nuclear Power Plant (FDNPP), after the hydrogen explosion of reactor 1 on 12th March 2011. The 134Cs/137Cs radioactivity ratios of the three radioactive aerosol particles showed that they were derived from the FDNPP reactor 1, rather than reactors 2 or 3. The physical characteristics of these particles with < 10 µm in diameter and nonuniform shape are clearly different from those of radioactive particles generated by the hydrogen explosion of the FDNPP reactor 1. A significant amount of Cl was detected by energy dispaersive X-ray spectrometery. Synchrosron radiation microbeam (SR-µ-) X-ray fluoresence (XRF) analysis showed that these particles contain a series of heavy elements related to the nuclear fules and their fission products with a non-homogeneous distribution within the particles. In addition, the SR-µ-XRF identified trace amounts of Br in these particles; the element has firstly been found in radioactive particles derived by the FDNPP accident. In contrast to the hydrogen explosion-generated radioactive particles containing Sr and Ba, both of which are easily volatile under a reduction atmosphere, these elements were not rich in the particles found in this study. By the SR-µ-X-ray absorption near edge structure analysis and SR-µ-X-ray powder diffraction, it was found that these particles consist of an amorphous (or low crystalline) matrix containing metal elements with chemical states in a comparatively high state of oxidation or chloride. Based on these physical and chemical characteristics and a trajectory analysis of air parcels that passed over the SPM monitoring site, we concluded that these radioactive particles were generated and emitted into the atomosphere at the time of seawater injection for cooling the reactor after the hydrogen explosion.

AB - Three radioactive microparticles were separated from particles on filter tape samples collected hourly at a suspended particulate matter (SPM) monitoring site located at ~25 km north of the Fukushima Daiichi Nuclear Power Plant (FDNPP), after the hydrogen explosion of reactor 1 on 12th March 2011. The 134Cs/137Cs radioactivity ratios of the three radioactive aerosol particles showed that they were derived from the FDNPP reactor 1, rather than reactors 2 or 3. The physical characteristics of these particles with < 10 µm in diameter and nonuniform shape are clearly different from those of radioactive particles generated by the hydrogen explosion of the FDNPP reactor 1. A significant amount of Cl was detected by energy dispaersive X-ray spectrometery. Synchrosron radiation microbeam (SR-µ-) X-ray fluoresence (XRF) analysis showed that these particles contain a series of heavy elements related to the nuclear fules and their fission products with a non-homogeneous distribution within the particles. In addition, the SR-µ-XRF identified trace amounts of Br in these particles; the element has firstly been found in radioactive particles derived by the FDNPP accident. In contrast to the hydrogen explosion-generated radioactive particles containing Sr and Ba, both of which are easily volatile under a reduction atmosphere, these elements were not rich in the particles found in this study. By the SR-µ-X-ray absorption near edge structure analysis and SR-µ-X-ray powder diffraction, it was found that these particles consist of an amorphous (or low crystalline) matrix containing metal elements with chemical states in a comparatively high state of oxidation or chloride. Based on these physical and chemical characteristics and a trajectory analysis of air parcels that passed over the SPM monitoring site, we concluded that these radioactive particles were generated and emitted into the atomosphere at the time of seawater injection for cooling the reactor after the hydrogen explosion.

KW - Aerosol particle

KW - Fukushima daiichi nuclear power plant accident

KW - Radioactive material

KW - Synchrotron radiation X-ray analysis

UR - http://www.scopus.com/inward/record.url?scp=85074730554&partnerID=8YFLogxK

U2 - 10.2116/bunsekikagaku.68.757

DO - 10.2116/bunsekikagaku.68.757

M3 - Article

AN - SCOPUS:85074730554

VL - 68

SP - 757

EP - 768

JO - Bunseki Kagaku

JF - Bunseki Kagaku

SN - 0525-1931

IS - 10

ER -