title: Size distribution of radioactive particles collected at Tokai, Japan 6 days after the nuclear accident.
abstract: Airborne radioactive particles released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 were collected with a cascade low-pressure impactor at the Japan Atomic Energy Agency (JAEA) in Tokai, Japan, 114 km south of the FDNPP. Size-fractionated samples were collected twice, in the periods of March 17-April 1, 2011, and May 9-13, 2011. These size-fractionated samplings were carried out in the earliest days at a short distance from the FDNPP. Radioactivity of short-lived nuclides (several ten days of half-life) was determined as well as (134)Cs and (137)Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of (129m)Te, (140)Ba, (134)Cs, (136)Cs and (137)Cs was 1.5-1.6 μm, while the diameter of (131)I was 0.45 μm. The diameters of (134)Cs and (137)Cs in the second collection were expressed as three peaks at <0.5 μm, 0.94 μm, and 7.8 μm. The (134)Cs/(137)Cs ratio of the first collection was 1.02 in total, but the ratio in the fine fractions was 0.91. A distribution map of (134)Cs/(137)Cs - (136)Cs/(137)Cs ratios was helpful in understanding the change of radioactive Cs composition. The Cs composition of size fractions <0.43 μm and the composition in the 1.1-2.1 μm range (including the AMAD of 1.5-1.6 μm) were similar to the calculated compositions of fuels in the reactors No. 1 and No. 3 at the FDNPP using the ORIGEN-II code. The Cs composition collected in May, 2011 was similar to the calculation results of reactor No. 2 fuel composition. The change of Cs composition implies that the radioactive Cs was released from the three reactors at the FDNPP via different processes.
authors: Research Group for Analytical Chemistry, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan. Electronic address: miyamoto.yutaka@jaea.go.jp.
authors: Yutaka
authors: Y
authors: Miyamoto
authors: Research Group for Analytical Chemistry, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: Kenichiro
authors: K
authors: Yasuda
authors: Research Group for Analytical Chemistry, Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency (JAEA), Tokai, Ibaraki 319-1195, Japan.
authors: Masaaki
authors: M
authors: Magara
mesh_terms: D000336:Aerosols; D000396:Air Pollutants, Radioactive / Q000032:analysis; D001465:Barium Radioisotopes / Q000032:analysis; D002588:Cesium Radioisotopes / Q000032:analysis; D062406:Fukushima Nuclear Accident; D005843:Geography; D007457:Iodine Radioisotopes / Q000032:analysis; D007564:Japan; D009680:Nuclear Fission; D055848:Nuclear Power Plants; D010316:Particle Size; D011834:Radiation Monitoring / Q000379:methods*; D018788:Radioactive Hazard Release; D011868:Radioisotopes / Q000032:analysis; D013691:Tellurium / Q000032:analysis
chemical_list: D000336:Aerosols; D000396:Air Pollutants, Radioactive; D001465:Barium Radioisotopes; D002588:Cesium Radioisotopes; D007457:Iodine Radioisotopes; D011868:Radioisotopes; D013691:Tellurium
keywords: (131)I; (137)Cs; Aerosol; Fission product; Fukushima; Radioactivity ratio