Abstract
A simple analysis method for dose rate of gamma ray in the farmlands contaminated by radioactive cesium is proposed. Vertical profiles of radioactive cesium averaged in each farm plot were laid out on GIS. The dose rate was evaluated based on the point-kernel source method, which is a widely applied as a simplified calculation method for radiation field. The proposed method made accurate estimates of dose rate in farm block scale. However the dose rate estimated in plot scale suffered from large variation that is not observed on the site. This discrepancy is probably attributed to the statistical error included in the Cs concentration evaluated from the soil samples having a diameter of no more than 5cm. The estimated dose rate after performing the decontamination by scraping the ground surface tended to be less than the observed value. The underestimation is supposed to be caused by the overestimates of the thickness of the scraped soil and the remains of contaminated soil on the very surface of the ground after the work.
