Attenuation coefficients and exposure buildup factor of some rocks for gamma ray shielding applications

In the present work, the mass attenuation coefficient mu/rho is investigated experimentally and theoretically for seven rocks (olivine basalt, green marble, jet black granite, telphone black granite, cuddapah limestone, white marble and pink marble). The rock samples were collected from different places of India. The mass attenuation coefficients of the samples were measured experimentally at photon energies of radioisotopes Co-57 (122 keV), Ba-133 (356 keV), Na-22 (511 and 1275 keV), Cs-137 (662 keV), Mn-54 (840 keV), and Co-60 (1330 keV). Theoretically, the simulation results of mu/rho using both XCOM and MCNP5 codes were compared with experimental results and a satisfactory agreement was observed. Total atomic cross sections (sigma(t,a)) electronic cross sections (sigma(t,e)), effective atomic number (Z(eff)), electron density (N-e) and half value layer (HVL) were evaluated using the obtained mu/rho values for investigated rocks. The HVL values for the selected rocks were compared with some common shielding concretes. Moreover, by Geometric Progression method (G-P) exposure buildup factor (EBF) and energy absorption buildup factor (EABF) values were calculated for incident photon energy 0.015-15 MeV up to penetration depths of 40 mean free paths. The results show that among the studied rocks pink marble possesses superior shielding properties for gamma-ray. This work was carried out to explore the advantage of utilizing the selected rocks in engineering structures and building construction to shield gamma-rays.