VOLUME 19 (Supplement)

Monte Carlo evaluation of neutron and gamma shielding in coconut shell ash-based concrete drums with borated moderators

Previous studies have shown that coconut shell ash (CSA)-based concrete outperforms conventional concrete materials used in gamma shielding applications. As CSA is a locally available and abundant aggregate in the Philippines, this study aimed to investigate the neutron and gamma radiation shielding performance of a CSA-based concrete shielding drum paired with borated polyethylene, borated paraffin, and borated water moderators using PHITS. Monte Carlo-based simulations were conducted to calculate ambient dose equivalent rates, Ḣ*(10), at the surface and at 1 m from a shielding drum containing an ²⁴¹Am-Be disused sealed radioactive source. Results indicated that configurations with borated polyethylene yielded total surface and 1 m normalized dose rates of 48.05 ± 0.21 μSv/h/Ci and 1.67 ± 0.02 μSv/h/Ci, respectively. For a 1 Ci source benchmark (Transport Index = 0.17), this places the package strictly into IAEA SSR-6 Category II-YELLOW while complying with IAEA GSR Part 3 occupational dose limits. Although borated polyethylene and borated paraffin demonstrated statistically comparable shielding performance within Monte Carlo uncertainty, borated polyethylene remains the preferred operational choice due to superior structural and thermal stability. The findings highlight the effectiveness of using sustainable CSA-based concrete with various modifiers as radiation-shielding materials.