Comprehensive Simulation-Based Evaluation of Gamma Radiation Shielding Performance of Bismuth Oxide- and Tungsten Oxide-Reinforced Polymer Composites for Nuclear Medicine Occupational Safety

Abstract

This study employs simulation tools to design and evaluate lightweight, lead-free polymer composites incorporating polytetrafluoroethylene (PTFE), polyethylene (PE), and polyetherimide (PEI) for gamma radiation shielding in nuclear medicine. Targeting clinically relevant photon energies from Tc-99m (140 keV), I-131 (364 keV), and Cs-137 (662 keV), composites' structural and shielding performance with Bi₂O₃ and WO₃ was assessed using XCOM and Phy-X/PSD. PEI emerged as the most suitable polymer for load-bearing and thermally exposed applications, offering superior mechanical stability and dimensional integrity. Bi₂O₃-WO₃ fillers for Tc-99m achieved a ~7000-fold increase in MAC, I-131 ~2063-fold, and Cs-137 ~1370-fold compared to PbO₂. The PEI-75Bi₂O₃-25WO₃ achieved a ~21-fold reduction in half-value layer (HVL) compared to lead for Tc-99m. For higher-energy isotopes of I-131 and Cs-137, HVL reductions of ~0.44-fold and ~0.08-fold, respectively, were achieved. The results demonstrate that high-Z dual filler polymer composites have an equal or enhanced attenuation properties to lead-based shielding, whilst also enhancing the polymer composites' mechanical and thermal characteristics. As the use of ionizing radiation increases, so does the potential risks; high-Z dual filler polymer composites provide a sustainable, lightweight, non-toxic alternative to conventional lead shielding.

Keywords: Monte Carlo simulation; Phy-X/PSD; XCOM simulation; bismuth oxide; gamma shielding; polymer composites; radiation attenuation; radiation protection; shielding materials; tungsten oxide.

Figure 1

Simulated heat transfer profiles of three polymeric materials subjected to their respective melting point temperatures for 30 min: (A) polytetrafluoroethylene (PTFE), (B) polyethylene (PE), and (C) polyetherimide (PEI). The color gradient represents temperature distribution (°C), highlighting the extent of thermal penetration.

Figure 2

ANSYS simulation of material behavior under bending deformation for three polymeric materials: polytetrafluoroethylene (PTFE), polyethylene (PE), and polyetherimide (PEI). The finite element analysis (FEA) was performed under compressive loads of 10 N, 25 N, 50 N, and 100 N. The color contour plots represent the resulting vertical displacement (in mm).

Figure 3

XCOM-based computational analysis of mass attenuation coefficients (cm²/g) for incoherent scattering in bismuth oxide and tungsten oxide-reinforced polymer composites for gamma radiation shielding. (A) Comparison of incoherent scattering cross-sections as a function of photon energy (MeV) for various materials including PbO₂, PTFE, PE, PEI, Bi₂O₃, WO₃, Bi₂O₃-WO₃ composite, and reinforced polymer composites (PTFE-WO₃, PE-WO₃, PEI-WO₃, PTFE-Bi₂O₃, PE-Bi₂O₃, PEI-Bi₂O₃, PTFE-Bi₂O₃-WO₃, PE-Bi₂O₃-WO₃, PEI-Bi₂O₃-WO₃). (B–D) Bar graphs showing mass attenuation coefficients for incoherent scattering at specific photon energies: (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical significance is denoted as ** p < 0.01; results are considered not significant when p > 0.05 (ns).

Figure 4

XCOM-based computational analysis of mass attenuation coefficients (cm²/g) for photoelectric absorption in bismuth oxide and tungsten oxide-reinforced polymer composites for gamma radiation shielding. (A) Comparison of photoelectric absorption cross-sections as a function of photon energy (MeV) for various materials including PbO₂, PTFE, PE, PEI, Bi₂O₃, WO₃, Bi₂O₃-WO₃ composite, and reinforced polymer composites (PTFE-WO₃, PE-WO₃, PEI-WO₃, PTFE-Bi₂O₃, PE-Bi₂O₃, PEI-Bi₂O₃, PTFE-Bi₂O₃-WO₃, PE-Bi₂O₃-WO₃, PEI-Bi₂O₃-WO₃). (B–D) Bar graphs showing mass attenuation coefficients for photoelectric absorption at specific photon energies: (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical significance is denoted as * p < 0.05; results are considered not significant when p > 0.05 (ns).

Figure 5

XCOM-based computational analysis of mass attenuation coefficients (cm²/g) for pair production in the nuclear field in bismuth oxide and tungsten oxide-reinforced polymer composites for gamma radiation shielding. (A) Comparison of pair production in the nuclear field cross-sections as a function of photon energy (MeV) for various materials including PbO₂, PTFE, PE, PEI, Bi₂O₃, WO₃, Bi₂O₃-WO₃ composite, and reinforced polymer composites (PTFE-WO₃, PE-WO₃, PEI-WO₃, PTFE-Bi₂O₃, PE-Bi₂O₃, PEI-Bi₂O₃, PTFE-Bi₂O₃-WO₃, PE-Bi₂O₃-WO₃, PEI-Bi₂O₃-WO₃). (B–D) Bar graphs showing mass attenuation coefficients for pair production in the nuclear field at specific photon energies: (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical significance is denoted as * p < 0.05; results are considered not significant when p > 0.05 (ns).

Figure 6

XCOM-based computational analysis of mass attenuation coefficients (cm²/g) for total attenuation without coherent scattering in bismuth oxide and tungsten oxide-reinforced polymer composites for gamma radiation shielding. (A) Comparison of total attenuation without coherent scattering cross-sections as a function of photon energy (MeV) for various materials including PbO₂, PTFE, PE, PEI, Bi₂O₃, WO₃, Bi₂O₃-WO₃ composite, and reinforced polymer composites (PTFE-WO₃, PE-WO₃, PEI-WO₃, PTFE-Bi₂O₃, PE-Bi₂O₃, PEI-Bi₂O₃, PTFE-Bi₂O₃-WO₃, PE-Bi₂O₃-WO₃, PEI-Bi₂O₃-WO₃). (B–D) Bar graphs showing mass attenuation coefficients for total attenuation without coherent scattering at specific photon energies: (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical significance is denoted as ** p < 0.01; results are considered not significant when p > 0.05 (ns).

Figure 7

Computational analysis of linear attenuation coefficients (LAC, cm−1) in Bi₂O₃- and WO₃-reinforced polymer composites for gamma radiation shielding in nuclear medicine. LAC values were calculated using the Phy-X/PSD software to assess the photon attenuation capabilities of various pure materials, binary oxides, and oxide-loaded polymer composites across a wide energy range and at energies relevant to nuclear medicine. (A) Energy-dependent LAC profiles of PbO₂, Bi₂O₃, WO₃, base polymers (PTFE, PE, PEI), and their oxide-reinforced composites are shown over a photon energy range from 1 keV to 10 MeV. (B–D) Bar charts depict the comparative LAC values at discrete gamma energies of (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical comparisons indicate significant differences (*) between oxide-filled and pure polymer materials (p < 0.05), with “ns” denoting non-significant differences among base materials (p > 0.05).

Figure 8

Computational evaluation of half-value layer (HVL, cm) for Bi₂O₃- and WO₃-reinforced polymer composites as gamma radiation shields in nuclear medicine applications. The HVL, representing the material thickness required to reduce incident gamma radiation intensity by 50%, was calculated using Phy-X/PSD for various oxide-loaded polymer composites and benchmark materials. (A) Energy-dependent HVL values were assessed across a broad photon energy range (1 keV to 20 MeV) for pure compounds (PbO₂, Bi₂O₃, WO₃), base polymers (PTFE, PE, PEI), and their respective composites. (B–D) Bar graphs illustrate HVL values at specific photon energies relevant to nuclear medicine radionuclides: (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical comparisons denote significant differences (*) between high-performance composites and base materials (p < 0.05), while “ns” indicates non-significant differences among certain unreinforced polymers (p > 0.05).

Figure 9

Computational assessment of tenth-value layer (TVL, cm) for Bi₂O₃- and WO₃-reinforced polymer composites for gamma radiation shielding in nuclear medicine applications. The TVL, defined as the material thickness required to attenuate the incident gamma-ray intensity by 90%, was computed using the Phy-X/PSD platform for various pure substances, binary oxides, and polymer-based composites across a wide photon energy spectrum. (A) TVL as a function of photon energy (1 keV to 10 MeV) is shown for unmodified polymers (PTFE, PE, PEI), high-Z oxides (PbO₂, Bi₂O₃, WO₃), and a comprehensive series of Bi₂O₃/WO₃-reinforced polymer composites. (B–D) Bar graphs represent TVL values at key photon energies used in nuclear medicine: (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical comparisons show non-significant differences (ns) among base polymers (p > 0.05).

Figure 10

Computational evaluation of mean free path (MFP, cm) in Bi₂O₃- and WO₃-reinforced polymer composites for gamma radiation shielding in nuclear medicine. (A) Energy-dependent MFP profiles are shown for base polymers (PTFE, PE, PEI), pure high-Z oxides (PbO₂, Bi₂O₃, WO₃), and a comprehensive series of polymer composites reinforced with Bi₂O₃ and/or WO₃. (B–D) Bar plots illustrate MFP values at clinically relevant gamma energies: (B) Tc-99m (140 keV), (C) I-131 (364 keV), and (D) Cs-137 (662 keV). Statistical comparisons reveal non-significant differences (ns) among base polymers, whereas oxide-reinforced composites show marked in MFP (p > 0.05).