Monte Carlo Study of Gamma-Ray Attenuation in Structures with Basements

摘要

A theoretical investigation of the radiation reaching the basement of cylindrical concrete structures surrounded by a 60Co simulated fallout field has been carried out using Monte Carlo techniques to determine the effects of wall height, wall thickness, floor thickness, and detector location. Also, reduction and attenuation factors obtained from Monte Carlo and other calculational methods were compared. The structures considered were ten feet in radius, with wall heights between four feet and ten feet and with a 40-psf roof. Wall thicknesses of 20 psf, 40 psf and 80 psf, and basement ceiling thicknesses of 0 psf, 20 psf and 40 psf were considered. The wall thickness was found to have relatively little effect upon the shape of the reduction factor or the magnitude of the floor attenuation factor as functions of detector location and floor thickness. Increasing the wall height resulted in an increase in both the reduction factor and the attenuation factor. The Monte Carlo results were compared with those of the original and various proposed improved versions of the engineering method. For the case analyzed, the extended engineering and Batter-Starbird results tended to overpredict the reduction factor, while the engineering method gave fairly good agreement for solid angle fractions in the neighborhood of 0.7. The extended engineering and Eisenhauer attenuation factors agreed to within 15% of the Monte Carlo data for the 20-psf basement ceiling case, and to approximately within 40% when the basement ceiling thickness was increased to 40 psf. (Author)