Lead-Free Metal Oxide/PGMA Composites for Gamma-Ray and Fast-Neutron Shielding: A Computational Study with Phy-X/PSD Validated by Geant4

Poly(glycidyl methacrylate) (PGMA) polymer composites loaded with 50 wt% metal oxides (ZnO, MoO₃, Cs₂O, HfO₂, and Bi₂O₃) were investigated computationally as lead-free gamma-ray and fast-neutron shielding over 0.015–15 MeV. Phy-X/PSD was used together with an independent Geant4 model of a narrow-beam transmission experiment to perform the calculations. The two approaches agree to 0.56% on average over 168 material–energy combinations, and the model reproduces the full NaI(Tl) pulse-height response. Above 0.1 MeV, the shielding performance improves in the order ZnO/PGMA < MoO₃/PGMA < Cs₂O/PGMA < HfO₂/PGMA < Bi₂O₃/PGMA, whereas below this energy the ranking is governed by the positions of the K absorption edges of the fillers. Bi₂O₃/PGMA is the most effective composite, with a half-value layer of 3.79 cm at 0.662 MeV and an effective atomic number reaching 72.1; it attenuates as effectively as ordinary concrete while requiring about 19% less mass per unit area, and it outperforms reported polyester composites loaded with WO₃ or HgO. The fast-neutron removal cross-sections ΣR lie between 0.0873 and 0.0977 cm⁻¹, above the value for unloaded PGMA in four of the five composites, and per unit mass, all five exceed ordinary concrete, so the neutron and photon rankings differ and HfO₂/PGMA emerges as the balanced choice for mixed fields. These results identify which oxides merit fabrication and provide a validated model against which future transmission measurements can be compared directly.