Enhanced Low-Energy Gamma-Ray Shielding Performance of Nano ZrO2-Reinforced Vinyl Ester Composites: MCNP6.3, XCOM, and Phy-X/PSD Assessment

Vinyl ester (VE) nanocomposites containing 0–20 wt.% ZrO2 relative to the resin were produced to assess the effect of ZrO2 loading on gamma-ray shielding. The crystalline structure and morphology of the ZrO2 nanoparticles were examined by X-ray diffraction and transmission electron microscopy, respectively. Photon transport was simulated using MCNP6.3 at five energies associated with 133Ba, 137Cs, and 60Co, with results benchmarked against XCOM and Phy-X/PSD. The MCNP6.3-derived mass attenuation coefficients (MACs) agreed closely with both methods, with a mean relative deviation of 0.78% in each comparison. ZrO2 incorporation generally increased the effective atomic number (Zeff) and reduced the half-value layer (HVL) and mean free path (MFP), with the strongest effects at low energies. At 81 keV, VE-Zr20 exhibited a 104.1% higher MAC and a 58.1% lower HVL than VE-Zr0, while differences among the composites diminished at higher energies. Peak exposure buildup factor (EBF) and energy absorption buildup factor (EABF) values increased with depth but decreased with ZrO2 content; at 0.5 MFP, the maximum EBF decreased by 51%, from 3.18 (VE-Zr0) to 1.55 (VE-Zr20). VE-Zr20 provided the most favorable low-energy shielding performance, supporting the potential use of ZrO2-reinforced VE composites as lightweight, lead-free shielding materials for applications involving low-energy photons.