2022 Volume 32 Pages 73-77
It has been 10 years since the accident at the Fukushima Daiichi Nuclear Power Plant in March 2011. To confirm the radioactivity at the Center for Environmental Science in Saitama, the 1 cm dose equivalent rate (hereafter referred to as air dose rate) and the radioactivity concentration on the ground surface were measured. At sites with soiled area, the air dose rates ranged from 0.04 to 0.05 μSv/h, regardless of the land use type. The air dose rates were close to those derived from natural radionuclides; therefore, it was confirmed that the residual effects of the accident were extremely small. On the other hand, the air dose rates were 0.07 μSv/h at some paved pathway, and were 0.10 μSv/h at sites where the soil accumulated on the pavement near the drainage outlet—these values were higher than the surroundings. The results of the radioactivity concentrations showed that some parts of the pathway contained 40K more than the surroundings. And it is suggested that 137Cs has accumulated near the drainage outlet by rainfall. By removing the soil, the air dose rates decreased to 0.06 μSv/h at the drainage outlet.
