Size distribution of radioactive particles collected at Tokai, Japan 6 days after the nuclear accident

Miyamoto, Yutaka   ; Yasuda, Kenichiro   ; Magara, Masaaki  

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. 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 FDNPPs. Radioactivity of short-lived nuclides (several ten days of half-life) were determined as well as Cs and Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of Te, Cs, Cs and Cs was 1.5-1.6m, while the diameter of I was 0.45m.