Rare-Earth Oxides as Alternative High-Energy Photon Protective Fillers in HDPE Composites: Theoretical Aspects

Abstract

This work theoretically determined the high-energy photon shielding properties of high-density polyethylene (HDPE) composites containing rare-earth oxides, namely samarium oxide (Sm2O3), europium oxide (Eu2O3), and gadolinium oxide (Gd2O3), for potential use as lead-free X-ray-shielding and gamma-shielding materials using the XCOM software package. The considered properties were the mass attenuation coefficient (µm), linear attenuation coefficient (µ), half value layer (HVL), and lead equivalence (Pbeq) that were investigated at varying photon energies (0.001–5 MeV) and filler contents (0–60 wt.%). The results were in good agreement (less than 2% differences) with other available programs (Phy-X/PSD) and Monte Carlo particle transport simulation code, namely PHITS, which showed that the overall high-energy photon shielding abilities of the composites considerably increased with increasing rare-earth oxide contents but reduced with increasing photon energies. In particular, the Gd2O3/HDPE composites had the highest µm values at photon energies of 0.1, 0.5, and 5 MeV, due to having the highest atomic number (Z). Furthermore, the Pbeq determination of the composites within the X-ray energy ranges indicated that the 10 mm thick samples with filler contents of 40 wt.% and 50 wt.% had Pbeq values greater than the minimum requirements for shielding materials used in general diagnostic X-ray rooms and computerized tomography rooms, which required Pbeq values of at least 1.0 and 1.5 mmPb, respectively. In addition, the comparisons of µm, µ, and HVL among the rare-earth oxide/HDPE composites investigated in this work and other lead-free X-ray shielding composites revealed that the materials developed in this work exhibited comparable X-ray shielding properties in comparison with that of the latter, implying great potential to be used as effective X-ray shielding materials in actual applications.

Simulation of Neutron/Self-Emitted Gamma Attenuation and Effects of Silane Surface Treatment on Mechanical and Wear Resistance Properties of Sm2O3/UHMWPE Composites

“…It should be noted that the scattering cross-section (σ s ) and the absorption cross-section (σ a ) for H are 82.02 and 0.3326 barns, respectively, while σ s and σ a for Sm are 39.3 and 5922 barns, respectively [ 31 ], making Sm and Sm-containing compounds more superior neutron attenuators than H and H-containing compounds. The schemes graphically illustrating effects of fillers (Sm 2 O 3 in this work) on neutron attenuations through the mechanism of scattering and absorption are shown in Figure 1 ; with Figure 1 a representing the attenuation mechanisms of a neat UHMWPE through scattering and Figure 1 b representing the attenuation mechanisms of Sm 2 O 3 /UHMWPE composites through both scattering and absorption, making the latter more efficient in reducing the numbers of transmitted neutrons [ 13 ].…”

“…The results from PHITS were independently verified by the comparison with theoretical shielding results, using a web-based program, XCOM. The details of the procedure for using XCOM to find the µ m values of the Sm 2 O 3 /UHMWPE composites can be found elsewhere [ 13 ].…”

“…Furthermore, Sm and Sm 2 O 3 have relatively higher atomic number (Z) and high density ( ρ ) (Z = 62 and ρ = 8.35 g/cm 3 , respectively) than B and B-containing compounds, making the former suitable for self-attenuation of gamma rays emitted after the neutrons have been absorbed by the Sm. This dual-shielding property of Sm 2 O 3 for both neutrons and gamma rays has resulted in a simpler material design and remarkable shielding performance, which are crucially useful and important for workers in proximity to nuclear facilities with a photon-neutron-mixed environment [ 13 ]. Examples of Sm 2 O 3 -containing materials used in neutron protection are Sm 2 O 3 /UHMWPE composites [ 14 ], Sm 2 O 3 /Portland cement pastes [ 15 ], xPbO-(99-x)B 2 O 3 -Sm 2 O 3 glass system [ 16 ], and carbon-fiber reinforced Sm 2 O 3 /polyimide composites [ 17 ], for which their neutron-shielding properties were found to be considerably higher than for borated materials, determined at the same filler content.…”

Gamma Irradiation and the Radiation Shielding Characteristics: For the Lead Oxide Doped the Crosslinked Polystyrene-b-Polyethyleneglycol Block Copolymers and the Polystyrene-b-Polyethyleneglycol-Boron Nitride Nanocomposites

“…Considering the increase in the number of nuclear power plants, the possibilities of using nuclear weapons in wars, the radiation-emitting device, and the increase in the radioisotopes used, it has emerged that more effective measures should be taken to protect from radiation. For this purpose, studies on radiation shielding materials and designs for protection from radiation have also increased [ 1 , 2 , 3 , 4 ].…”

X-ray Shielding, Mechanical, Physical, and Water Absorption Properties of Wood/PVC Composites Containing Bismuth Oxide

“…It is also notable that the values of µ and µ m for a neat PVC, calculated using a web-based software (XCOM) [ 20 , 47 ], were similar to WPVC composites without the addition of Bi 2 O 3 , due to the low σ pe of C, H, and Cl in PVC, leading to low interaction probabilities between the X-rays and the neat PVC.…”