Results of the environmental radiation monitoring following the accident at the Fukushima Daiichi Nuclear Power Plant; Interim report (Ambient radiation dose rate, radioactivity concentration in the air and radioactivity concentration in the fallout)

Furuta, Sadaaki; Sumiya, Shuichi ; Watanabe, Hitoshi; Nakano, Masanao ; Imaizumi, Kenji; Takeyasu, Masanori ; Nakada, Akira ; Fujita, Hiroki; Mizutani, Tomoko ; Morisawa, Masato; Kokubun, Yuji ; Kono, Takahiko  ; Nagaoka, Mika  ; Yokoyama, Hiroya; Hokama, Tomonori ; Isozaki, Tokuju; Nemoto, Masashi; Hiyama, Yoshinori; Onuma, Toshimitsu; Kato, Chiaki; Kurachi, Tamotsu

As a correspondence to the accident at the Fukushima Daiichi Nuclear Power Plant, the environmental radiation monitoring was performed at the Nuclear Fuel Cycle Engineering Laboratories, JAEA. This report presented the measurement results of ambient radiation dose rate, radioactivity concentration in the air and radioactivity concentration in fallout and meteorological observation result until May 31, 2011. The ambient radiation dose rate increased, with the peak dose rate of several thousand nGy/h at 7 o'clock in March 15, at 5 o'clock in March 16, and at 4 o'clock in March 21. The variation on the radioactivity concentration in the air and in fallout showed the almost same tendency as that of the dose rate. The concentration ratio of I-131/Cs-137 in the air increased to about 100. The dose was estimated resulting from internal exposure due to inhalation.