Photon Absorption Buildup Factors for Different Concrete Types.

Abstract

Concrete is one of the most widely used materials for structural radiation shielding application. However, the shielding capacity of a concrete has been argued to depend largely on its constituent materials and sometimes its mass density. Hence concretes with different composite materials are expected to perform differently when used for shielding purpose. This research reports the estimation of the equivalent atomic numbers and photon Energy Absorption Buildup Factors (EABF) for eleven different species of concrete. The relationship between equivalent atomic number, density and EABF was also investigated. The concretes considered were categorized into light and heavy concretes based on their mass density. The EABF were calculated using the well-known geometric progression fitting procedure for photon energies from 0.015 MeV to 15 MeV and for penetration depth up to 40 mfp. An appreciable variation in the EABF was observed at different depth, energy and for each concrete type. The EABF were found to be high in the low and high energy regions and maximum in the intermediate energy section. The variation of EABF with energy and depth was attributed to the photoelectric, Compton scattering and pair production interaction modes. Although most high density concretes show lower buildup factor irrespective of depth and energy, an indication of good photon shielding coefficient. However, based on this study, it is the equivalent atomic number that can be best used to accurately compare the buildup factors amongst concrete rather than density.