Experimental and Monte Carlo investigations of gamma ray transmission and buildup factors for inorganic nanoparticle/epoxy composites

High-density polyethylene (HDPE)-incorporated boron carbide and boric acid nanoparticles as a nanoshield of photoneutrons from medical linear accelerators

PURPOSE

The current study aimed to investigate boron carbide and boric acid nanoparticles (NPs) as absorbents for thermal neutrons and high-density polyethylene (HDPE) as a substrate and neutron moderator for fast neutrons. The goal was to assess the performance of boron carbide and boric acid NPs based on HDPE as a nanoshield of photoneutrons from medical linear accelerators.

MATERIALS AND METHODS

This study was conducted in two parts of simulation and practice. The Monte Carlo (MC) simulation involved modeling and verification of the single-layer, double-layer, and combined nanoshields by selecting nanomaterials and substrates and, finally, calculating the macroscopic cross-sections. The practical part involved manufacturing nanoshields based on the simulation results and evaluating the manufactured nanocomposites via experimental measurements.

RESULTS

MC simulation results with an uncertainty of less than 1% showed that for the monolayer samples, the best result belonged to boron carbide at a concentration of 10% and a macroscopic cross-section of 0.933 cm-1. At a concentration of 20%, the highest value among the double-layer samples was 0.936 cm-1 and for the combined samples, this value was 0.928 cm-1. Boron carbide single-layer nanocomposites at a 10% concentration, as well as the bilayer nanoshield of 10% boron carbide and 20% boric acid performed well; however, the best performance belonged to the nanoshield with a macroscopic cross-section of 0.960 and the combination containing 5% boron carbide and 10% boric acid.

CONCLUSIONS

The research suggests that utilizing boron carbide and boric acid nanoshields in combination with HDPE holds promise as a viable approach to protecting from the photoneutrons. Further exploration of these nanocomposite shields and their practical applications is warranted, with the potential to yield significant advancements in radiation therapy safety and efficacy.

Fe-nanoparticle effect on polypropylene for effective radiation protection: Simulation and theoretical study

An evaluation of the gamma-neutron shielding capabilities of polymer nanocomposite materials based on polypropylene and iron nanoparticles is presented in this study. The chemical composition of the materials is (100-x) PP-Fex, (where x = 0.1, 0.3, 0.5, 1, 2 and 5 wt percent). For the proposed polymer samples with photon energies ranging from 30 to 2000 KeV, the mass attenuation coefficient (MAC), a crucial parameter for studying gamma-ray shielding capability, was calculated using the Geant4 Monte Carlo code. Results were compared with those predicted by EpiXS. The values of the Geant4 code and the EpiXS software were both found to be in excellent agreement. Using the mass attenuation coefficient values, we determined the linear attenuation coefficients, electron density, effective atomic number, and half value layer for all the samples. The shielding properties of the polymer samples were also evaluated by estimating both the fast neutron removal cross-section and the mean free path of the fast neutron at energies between 0.25 and 5.5 keV. The study's findings indicate a positive correlation between the Fe nanoparticle content and the gamma-ray shielding performance of PP-Fe polymer samples. Out of the several glasses that were evaluated, it was found that the PP-Fe5 polymer sample demonstrates the highest efficacy in terms of gamma-ray shielding. Moreover, the polymer sample PP-Fe5, which consists of 5 mol% of iron (Fe), exhibits the highest value of ∑R (1.10650 cm-1) and the lowest value of the mean free path for fast neutrons. This indicates that the PP-Fe5 possesses better gamma-neutron shielding efficiency.

Views on Radiation Shielding Efficiency of Polymeric Composites/Nanocomposites and Multi-Layered Materials: Current State and Advancements

This article highlights advancements in polymeric composite/nanocomposites processes and applications for improved radiation shielding and high-rate attenuation for the spacecraft. Energetic particles, mostly electrons and protons, can annihilate or cause space craft hardware failures. The standard practice in space electronics is the utilization of aluminum as radiation safeguard and structural enclosure. In space, the materials must be lightweight and capable of withstanding extreme temperature/mechanical loads under harsh environments, so the research has focused on advanced multi-functional materials. In this regard, low-Z materials have been found effective in shielding particle radiation, but their structural properties were not sufficient for the desired space applications. As a solution, polymeric composites or nanocomposites have been produced having enhanced material properties and enough radiation shielding (gamma, cosmic, X-rays, protons, neutrons, etc.) properties along with reduced weight. Advantageously, the polymeric composites or nanocomposites can be layered to form multi-layered shields. Hence, polymer composites/nanocomposites offer promising alternatives to developing materials for efficiently attenuating photon or particle radiation. The latest technology developments for micro/nano reinforced polymer composites/nanocomposites have also been surveyed here for the radiation shielding of space crafts and aerospace structures. Moreover, the motive behind this state-of-the-art overview is to put forward recommendations for high performance design/applications of reinforced nanocomposites towards future radiation shielding technology in the spacecraft.

Shielding Properties of Epoxy Matrix Composites Reinforced with MgO Micro- and Nanoparticles

The aim of the current study is to investigate the impact of introducing micro- and nanoparticle MgO as a filler into epoxy resin on the radiation shielding abilities of the prepared samples. To this end, we performed a gamma-radiation spectroscopy experiment with the help of an HPGe detector and Am-241, Cs-137, and Co-60 sources. We evaluated the particle size effect (PSE) and detected the maximum PSE value with the addition of 50 wt% MgO particles, indicating that nanoparticle MgO was more successful in shielding against incoming radiation than microparticle MgO. We compared the half-value layer (HVL) for the samples with 10 wt%, 20 wt%, and 30 wt % micro-MgO and nano-MgO and found that the HVL values were lower for the nanoparticle samples than for the microparticles samples, confirming that smaller particle sizes enhanced the shielding ability of the samples against radiation. The MFP results showed that epoxy matrices containing micro-MgO, for all investigated energies, resulted in higher MFP values that those containing nano-MgO.

Thermal stability, mechanical properties, and gamma radiation shielding performance of polyvinyl chloride/Pb(NO3)2 composites

Radiation shielding composites based on polyvinyl chloride (PVC) reinforced with different weight ratios of Pb(NO3)2 (5, 10, and 20 wt%) were prepared using the solution-casting technique. Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy, and tensile testing method were used to characterize the PVC composite films. FTIR and XRD investigations illustrate the structural change and modification of the as-prepared PVC composites. The morphological analysis of the composite revealed that Pb(NO3)2 was dispersed uniformly within PVC polymer matrix. TGA revealed that the incorporation of Pb(NO3)2 improved the thermal stability of the investigated composites, whereas adding Pb(NO3)2 to the polymer matrix worsened its tensile properties. The as-prepared composite films were investigated for radiation-shielding of gamma-rays radioactive point sources (241Am, 133Ba, 137Cs, and 60Co). Linear attenuation coefficient (μ, cm−1), mass attenuation coefficient (μ/ρ, cm2/g), and half-value layer (HVL, cm) have been estimated from the obtained data using the MicroShield program. Reasonable agreement was attended between theoretical and experimental results. The deviation between the experiment and theoretical values of mass attenuation coefficient is being to be lower than 9%, and this can be correlated to the good distribution of Pb(NO3)2. The results revealed that adding Pb(NO3)2 to PVC polymer composites improved their mass attenuation coefficient.

A Brief Review on the High-Energy Electromagnetic Radiation-Shielding Materials Based on Polymer Nanocomposites

This paper revises the use of polymer nanocomposites to attenuate high-energy electromagnetic radiation (HE-EMR), such as gamma radiation. As known, high-energy radiation produces drastic damage not only in facilities or electronic devices but also to life and the environment. Among the different approaches to attenuate the HE-EMR, we consider the use of compounds with a high atomic number (Z), such as lead, but as known, lead is toxic. Therefore, different works have considered low-toxicity post-transitional metal-based compounds, such as bismuth. Additionally, nanosized particles have shown higher performance to attenuate HE-EMR than those that are micro-sized. On the other hand, materials with π-conjugated systems can also play a role in spreading the energy of electrons ejected as a consequence of the interaction of HE-EMR with matter, preventing the ionization and bond scission of polymers. The different effects produced by the interactions of the matter with HE-EMR are revised. The increase of the shielding properties of lightweight, flexible, and versatile materials such as polymer-based materials can be a contribution for developing technologies to obtain more efficient materials for preventing the damage produced for the HE-EMR in different industries where it is found.

Evaluation of gamma ray and neutron attenuation capability of thermoplastic polymers

The fast neutron and gamma ray attenuation capability of the most common thermoplastic polymers used in nuclear applications has been evaluated theoretically. Monte Carlo simulation has been used to compute the gamma-ray energy absorption buildup factor in the energy range 0.015-15 MeV at penetration depths up to 40 MFP. The results of MCNPX calculations have been validated against the results derived from the Geometric Progression fitting method. To evaluate neutron attenuation performance of the polymers, the fast neutron removal cross-section has been determined using theoretical database. Despite the superior ability of polysulfone and poly (ether sulfone) in gamma ray attenuation, high-density polyethylene has been found to have the best fast neutron removal ability among all. The detailed insights into the fast neutron and gamma ray shielding properties of selected polymers in the present work might have great potential applications in nuclear systems.

Polymeric composite materials for radiation shielding: a review

The rising use of radioactive elements is increasing radioactive pollution and calling for advanced materials to protect individuals. For instance, polymers are promising due to their mechanical, electrical, thermal, and multifunctional properties. Moreover, composites made of polymers and high atomic number fillers should allow to obtain material with low-weight, good flexibility, and good processability. Here we review the synthesis of polymer materials for radiation protection, with focus on the role of the nanofillers. We discuss the effectivness of polymeric materials for the absorption of fast neutrons. We also present the recycling of polymers into composites.