Calculating the outdoor dose deposited by γ-photons using GEANT4

Abstract

Abstract: The GEANT4 package programs were used to calculate the contribution of external  dose due to natural radioactivity of soils. The method correlates the activity concentrations of 40 K and members of the 238 U and 232 Th radioactive decay chai ns in soil with the  dose absorbed by a water phantom. The obtained results are in agreement with values measured and calculated by other authors. Keywords: soil radioactivity, radionuclides, radioactive series, e quivalent dose, gamma ray transport in matter, GEANT4 simulation. 1. Introduction The knowledge of the distribution and of the behavior of the radionuclides in soil, is important in understanding several aspects of the natural radiation environment, as the exchange of radionuclides betw een the solid soil and surface and ground waters, the uptake of radioactive nuclides by vegetation, the exchange of radionuclides between the upper soil layers and the atmosphere 1 . Furthermore, the knowledge of the soil radioactivity is important in evaluating the average human exposition to the natural radioactivity. The ground radioactivity is generally due to the natural radionuclides present in soil and to artificial radionuclides from accidental releases from nuclear power and industrial plants or from nuclear weapons tests. Also we have to count for the redistribution of natural radioactivity related to agricultural management and the use of fertilizers presenting a high concentration of radioelements. The distribution of the natural occuring uranium and thorium series radionuclides and the