[Study of radiation dose rate in air at Setagaya in Tokyo].

Abstract

The great earthquake occurred at East Japan on March 11, 2011 and the following tsunami induced the accident which environmentally leaked radioactive materials from the nuclear power plant of the Fukushima Daiichi. We measured radiation dose rate in air by the NaI (Tl) scintillation and GM survey meters from March 15 to May 30 at Setagaya in Tokyo. Three measured points were at the 1m height from the ground on asphalt surfaced road, at the 5cm height from ground with weeds, and at the room of a reinforced concrete building. As a result, a transient increase was observed on March 15, a sustained rise was observed on both days of March 21 and 22. The latter was thought to be due to the radioactive rainfall. These measured values were compared with the radiation dose rate in air of the cities in Kanto area, and it was confirmed that the measured values at Setagaya are not so different from that of those cities.