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

The indoor background has significance in determining the minimum detectable level of gamma detection systems. The gamma radiation field in a concrete building was studied by using the Monte Carlo simulations. The parameters of wall thickness, room shape and dimensions were considered in the modeling. A spherical layer model was assumed as the indoor source geometry with the intention of easy and effective calculations. The simulation model was applied to an unshielded germanium detector and the detection system with a more complex shielding configuration. As the results, the indoor radiation field in the concrete building can be predicted well by assuming the source geometry of a spherical concrete layer with a real thickness and the homogeneously distributed source of the natural major three components, the 238U series, 232Th series and 40K. The simulation model is useful for designing and optimizing gamma detection systems or shielding assemblies. (author)