Evaluation of photon shielding properties and exposure buildup factors for various clay using Geant4 simulation and WinXCOM

Radiation shielding is an essential component for any radiation equipment and sites. In this study, Geant4 was used to simulate the mass attenuation coefficients (MACs) of nine clay, pink granite, sandstone and concrete under five gamma radioactive sources ( 22 Na, 54 Mn, 57 Co, 60 Co, and 137 Cs). Key shielding parameters, including the mean free path, half-value layer, radiation protection efficiency (RPE), and effective atomic number were calculated based on MACs. The simulated values were validated against the theoretical values of WinXCOM, with relative deviations ranging from −0.6% to +0.85%, demonstrating the reliability of Geant4 in evaluating the photon shielding ability. The exposure buildup factors were also calculated using the G-P fitting method, revealing a peak around 0.15 MeV and a penetration depth of 40 mfp. It depends on the incident photon energy, the penetration depth, the composition of the material and the photon interaction mechanism. Results of simulations and theoretical calculations show that bentonite and vermiculite have the best photon shielding performance at low and intermediate photon energies, while kaolinite and ball clay have the worst photon shielding properties. All clay with a thickness of 20 cm are sufficient to attenuate more than 99.7% of the incident photons from 57 Co and more than 90% of the incident photons from the other four radioactive sources. Compared to traditional shielding materials (concrete and sandstone), these clay provide comparable or superior shielding effectiveness, with RPE differences within ±6%. This study offers a theoretical basis for using clay as suitable, cost-effective alternatives for radiation shielding, with potential applications in nuclear safety, medical radiation protection, and space radiation shielding.