PHITS computational investigation of the gamma attenuation properties of metal oxide-doped Philippine natural bentonite

Abstract

The gamma attenuation properties of Philippine natural bentonite (PNB) were investigated for its potential use as a shielding material. The enhancement of its attenuation properties was also investigated using two metal oxides: cadmium oxide (CdO) and lead monoxide (PbO). The attenuation abilities were evaluated based on the values of mass attenuation coefficient (μ/ρ), half-value layer (HVL), effective atomic number (Z_eff), and effective electron density (N_eff) from 81 to 1332 keV. Photon Cross Sections Database (XCOM) and Particle and Heavy Ion Transport code System (PHITS) simulation were used to obtain the theoretical and simulated μ/ρ, respectively. Results showed that for CdO-doped PNB, μ/ρ, Z_eff, and N_eff generally decreased with increasing photon energy while HVL increased. On the other hand, doping with PbO resulted in similar trends except at low energies, where peaks occurred at 113 keV due to an increase in photoelectric absorption above the K-edge of Pb atom. The accuracy of the simulation, as determined by the obtained percent error, highlighted the improved shielding capacity of PNB through the inclusion of metal oxides. Notably, the addition of 8.5% wt of PbO demonstrated the most promising shielding material that offered the highest density and attenuation ability at most energies, notably at the intermediate range.