2014 年 3 巻 2 号 p. 43-46
The radioactivity released from the Fukushima Daiichi Nuclear Power Plant (F1NPP) into the environment after an accident clearly decreased. The decrease in radiocesium on the surface of the ground directly results in a decrease in the ambient dose rate. The term “terrestrial halflife” was used to describe the decrease of a radionuclide only from the surface of the ground due to weathering. Terrestrial half-lives of cesium on artificial pavement was determined to be 1.1—2.6 y using official monitoring dose-rate data measured in several areas of the Fukushima region.
