Simulation of the background for detection system in the indoor environments of concrete buildings

Tsutsumi, Masahiro; Oishi, Tetsuya ; Kinouchi, Nobuyuki ; Sakamoto, Ryuichi; Yoshida, Makoto

In order to predict the indoor background spectra to gamma detection systems, the gamma radiation field in a concrete building is studied by the Monte Carlo simulations. The parameters of wall thickness, room shape and dimensions were considered in the modeling. The indoor source geometry was simulated by a spherical layer model with the intention of easy and effective calculations. The model was applied to an unshielded germanium detector and the detection system with a more complex shielding configuration. As the results, we found that the indoor radiation field in concrete buildings can be predicted well with the source geometry of a spherical concrete layer of 25cm thickness and with the source of the natural major three components of the U series, Th series and K that are homogeneously distributed. The simulation model is useful for designing and optimizing gamma detection systems or shielding assemblies.