Study of Gamma-Ray Spectrum at Height of 1 m from Radionuclide Widely Distributed on Soil Surface Using EGS5 Monte Carlo Code

Abstract

  Gamma-ray pulse-height distributions from widely distributed Cs-134 and Cs-137 calculated using the EGS5 Monte Carlo code with the transformation of a system consisting of a plane isotropic source and a unit sphere detector into a system consisting of a point isotropic source and a plane detector were compared with measured ones. Results agree well in terms of both spectrum shape and absolute value. Spectra at a height of 1 m from widely distributed I-131, Cs-134 and Cs-137 were studied by EGS5 calculation. It was clarified that the contribution of scattered gamma rays is dominant within the total gamma-ray flux. The contributions of the scattered gamma rays to ambient dose equivalents and effective dose were also studied.