Radiation Measurement in Paddy Soil Layer That Was Buried Contaminated Topsoil in Fukushima.

We have developed a new soil radiation measuring instrument with 10 pieces of GM tube arranged at 10cm intervals in order to measure the soil radiation of paddy soil layer, in which contaminated topsoil is buried at the depth of 50-80cm layer in Iitate, Fukushima. In addition, a PVC pipe in inner diameter 10cm and 200cm long is installed at the depth of 150cm to the height of 50cm over the ground. We measured the soil radiation of each depth pulling the instrument by 20 cm each from the bottom of the PCV pipe. As a result, Gaussian distribution of the soil radiation was observed with a peak at around the depth of 70cm. The distribution shape was reproduced in a model that takes into account the attenuation of the radiation by the soil. It is found from this experiment that radioactive cesium does not move.