Comparative X-ray shielding properties of bismuth oxide/natural rubber composites using a Monte Carlo code of PHITS

Abstract

Natural rubber (NR) is a material for potential development as a flexible X-ray shielding material, subject to improvement in its attenuation ability as one of the necessary measures to ensure safety for radiation-related workers and the general public. Consequently, this work used Monte Carlo coding and the Particle and Heavy Ion Transport System (PHITS) to simulate the X-ray shielding properties of NR composites that were added with Bi2O3 particles at different Bi2O3 contents (0-50 wt% in 10-wt% increments) and different material thicknesses (2, 4, and 6 cm). The X-ray source used for the simulation was a point source with energy ranges of 0.05, 0.1, 0.5, 5.0, and 15.0 MeV, respectively, and the detector was assumed to have 100% detection efficiency. The simulated results showed that at lower energies of X-rays (0.05 and 0.1 MeV), the values of X-ray transmission substantially decreased with increasing filler contents and material thicknesses. However, at higher energies of X-rays (0.5, 5.0, and 15.0 MeV), changes in the X-ray transmission ratios for different filler contents and material thicknesses were not as pronounced as for the lower-energy X-rays due to the high penetration ability of the high-energy X-rays. In particular, the highest attenuation ability of the materials obtained in this work was in the NR composites with 50 wt% Bi2O3, which had the values of half value layer (HVL; the thickness required to attenuate the incoming X-ray intensity by 50%) of 0.002, 0.004, 0.324, 0.990 and 1.540 m for X-ray energies of 0.05, 0.1, 0.5, 5.0, and 15.0 MeV, respectively. Other parameters including the linear attenuation coefficients (μ) and HVL of all filler contents were also reported and thoroughly discussed in this work.