Gamma radiation protection factor of building materials-Validation of wall reflections from measurements

The gamma radiation (INR and fallout radiations using 60 Co and 137 Cs sources, respectively) protection factors for 150 cm of soil (density=1.5 g/cc) followed by 21.5 cm specially prepared concrete (density=2.7 g/cc) have been estimated. Since the measurements are not amenable for such large thickness due to significant contributions from the scattered radiation, experiments are carried out for varying thickness and results are corroborated by Monte Carlo calculations. After ascertaining the calculated accuracy, the protection factors are deduced by Monte Carlo calculations. Simulations could reasonably predict the measurements within a factor of 2 for all the cases measured. It is inferred from the simulations that the dose contributions due to reflected radiations from the wall are significant when the material thickness exceeds 45.5 cm soil plus 21.5 cm concrete. Further, materials have been evaluated against fast neutrons using 252 Cf source.