2015 Volume 44 Issue 8 Pages 460-467
We studied radioactivity dispersion caused by the nuclear accident at the Fukushima nuclear plant by analyzing the radioactivity of 33 moss samples belonging to five species. We focused on the fact that the ground coverage area of the moss carpet can be evaluated after sampling the moss so that a deposition rate in Bq/㎡ units is obtained. The moss proves to be much more sensitive to radioactive Cs-137 than the soil. We understand the analysis of the radioactivity in the moss is useful to draw a deposition map around the Fukushima nuclear power plant. Gamma rays from the radioactive Cs are measured using an NaI(Tl) scintillation counter. The influence of meteorological and geographical features is also reviewed using a radioactivity map, so that the local high level of radioactivity in Iitate-mura can be confirmed by an analysis of the mosses. The ratio of the radiation intensities of Cs-134 and Cs-137 in the moss measured with a CdZnTe detector was obtained for several mosses in several areas, finding no significant differences in their ratios.
