Simple analysis of the effect of farmland decontamination on the dose rate reduction by 360-degree photos

Abstract

The effect of decontamination of radiocesium on the air dose rate reduction in farmlands depends on the landscape around the observing point. This study aimed to develop a simple method to estimate the reduction of dose rate from the change in the field of view, or solid angle of the contaminated landscape by decontamination around the observing points. To validate the methods, the ratios of the measured air dose rates after the decontamination work to those before the work were calculated for the data provided by Iitate Village, Fukushima Pref. The change in the fields of view of the contaminated landscape were analyzed by taking a 360-degree photo at the observing points by the village. In the analyses, main grounds of paddies were regarded as being subject to the decontamination, while the bunds and slopes around the paddies and forests were not. The virtual contaminated slopes and horizontal ground, in which the dose rates had been simulated by 3-dimensional particle transport code, were also used to test the applicability of the methods. The proposed method could predict the reduction rate of air dose by the decontamination of the virtual slope and horizontal ground. However, the application to the real landscapes only partially succeeded. This is possibly because the horizontal and vertical distribution of radiocesium was not so uniform that the particular hotspot in the view could affect the measured air dose rate although the method assumes uniform distribution over the landscape in the 360-degree photos.