Depth distributions of radionuclides in soils from the Fukushima nuclear accident

We have measured depth distributions of radionuclides in characteristic soils from Fukushima No. 1 nuclear plant accidents. Some researchers already reported depth deposit and profiling in soils for long half life radionuclides environmentally released from previous nuclear accidents or nuclear bomb tests. However short half-life radionuclides have not been really investigated, because they disappear relatively quickly. In this study, we collected four characteristic soils at Fukushima Pref. Soil core samples were frozen at -20 degree Celsius and sliced them into pieces 1 cm layer. The separated samples were inspected by γ-ray spectrometry (¹³¹I, ^129mTe, ¹³⁷Cs and ¹³⁴Cs) with an HP-Ge detector. ¹³¹I, ¹³⁷Cs and ¹³⁴Cs show the same tendency with respect to density deposit. The behavior of radionuclides in soils depends on particle size distribution of soil. (author)