Effect of HfO2 incorporation on the radiation shielding performance of cement mortars under 6 MV photon irradiation.

Improving the radiation shielding performance of cement-based materials is of increasing importance for medical and nuclear facilities exposed to high-energy photon radiation. In this study, the effect of hafnium oxide (HfO2) incorporation on the radiation shielding performance of cement mortars was experimentally and theoretically investigated under clinically relevant 6 MV photon irradiation. Mortar specimens were prepared by partially replacing standard sand with HfO2 at replacement levels of 5 and 10 wt% and irradiated using a medical linear accelerator (LINAC). The linear attenuation coefficient (μ), half-value layer (HVL), tenth-value layer (TVL), and mean free path (mfp) were experimentally determined from photon transmission measurements. In addition, exposure buildup factors (EBF), energy absorption buildup factors (EABF), and fast neutron macroscopic removal cross-sections (ΣR) were theoretically evaluated using the Geometric-Progression (G-P) fitting approach. The incorporation of HfO2 improved photon attenuation, resulting in increased linear attenuation coefficients and reduced HVL, TVL, and mfp values. Although HfO2 incorporation reduced the compressive strength of the mortars and provided limited improvement in neutron shielding performance, it significantly enhanced shielding against 6 MV photon beams. These findings demonstrate that HfO2 is an effective functional additive for improving the radiation shielding performance of cement mortars, highlighting its potential for non-load-bearing shielding components in radiotherapy and other radiation-intensive infrastructures.