Experimental evaluation of gamma rays shielding parameters for Zn-Cd-Sn-Pb quaternary alloy

Metal Particle Pencil Beam Spray-Coating Method for High-Density Polymer-Resin Composites: Evaluation of Radiation-Shielding Sheet Properties

Medical shielding suits must be lightweight and satisfy the requirements of thin films to guarantee user mobility and safety. The thin film weight is related to the density and thickness, which are associated with the particle dispersion in shielding materials. An even distribution of metal particles in a polymer can maintain the spacing among them. This paper proposes a pencil beam spray-coating method that involves spraying a constant amount of a polyethylene and tungsten mixture in a thin beam onto a nonwoven fabric at a constant speed. This technique yields higher productivity than does the electrospinning method and is expected to produce materials with better shielding performance than that of materials obtained using the calender method. The shielding performance was evaluated by manufacturing shielding sheets (thickness: 0.48-0.54 mm) using the calender and pencil beam spray-coating methods under the same conditions. The densities and performances of the sheets differed significantly. The sheet manufactured using the proposed method had an even particle dispersion and exhibited 2-4% better shielding performance than did that manufactured using the calender method. Therefore, the pencil beam spray-coating method can effectively satisfy the requirements of thin films for medical radiation-shielding materials while increasing the material flexibility.

An alternative method for calculation of half-value layers without the knowledge of attenuation coefficient

Radiation protection is crucial for the safe utilization of ionizing radiation and minimizing the harmful effect upon exposure, hence some standards have been defined by some relevant organizations for the safe uses of radiation. One of the parameters relevant to the calculation of gamma ray shielding is the half-value layer (HVL), which is normally calculated using the knowledge of linear attenuation coefficient (μ). In this research, an attempt has been made to directly calculate HVL without the knowledge of μ via Monte Carlo simulation technique. For this purpose, in the Monte Carlo N-Particle eXtended (MCNPX) code, F1, F5 and Mesh Popul sequences tallies were defined and the optimal structure for the least measurement error was introduced. The MCNPX calculated values showed reasonable agreement with the experimental findings. According to the obtained results, it is suggested that in order to reduce the error of HVL calculations, in exchange for the MCNPX code, the values of the R parameter and the radiation angle of the source should be considered according to the calculations introduced in this plan. Because the results show that by considering the measurement error between 6 and 20%, the code output can be cited in different energy ranges.

Development of ultra-thin radiation-shielding paper through nanofiber modeling of morpho butterfly wing structure

In medical institutions, radiation shielding is an effective strategy to protect medical personnel and patients from exposure. Reducing the weight of the shield worn by medical personnel in the radiation generating area plays a key role in improving their productivity and mobility. In this study, a new lightweight radiation shield was developed by electrospinning a polymer-tungsten composite material to produce nanofibers with a multi-layered thin-film structure similar to that of a morpho butterfly wing. The fabricated shield was in the form of 0.1 mm thick flexible shielding paper. The multi-layer structure of the thin shielding paper was obtained through nanofiber pattern formation via electrospinning a dispersion of tungsten particles. At 0.1 mm thickness, the paper's shielding rate was 64.88% at 60 keV. Furthermore, at 0.3 mm thick and arranged in a laminated structure, the shielding rate was 90.10% and the lead equivalent was 0.296 mmPb. When used as an apron material, the weight can be reduced by 45% compared to existing lead products. In addition, the material is highly processable and can be used to manufacture various flexible products, such as hats, gloves, underwear, and scarves used in medical institutions.

Process Technology for Development and Performance Improvement of Medical Radiation Shield Made of Eco-Friendly Oyster Shell Powder

As radiation-based techniques become increasingly important tools for medical diagnostics, medical professionals face increasing risk from the long-term effects of scattered radiation exposure. Although existing radiation-shielding products used in medicine are traditionally lead-based, recently, the development of more eco-friendly materials such as tungsten, bismuth, and barium sulfate has drawn attention. However, lead continues to be superior to the proposed alternative materials in terms of shielding efficiency and cost effectiveness. This study explores the feasibility of radiation shielding materials based on the shells of bivalve mollusks such as oysters that are discarded from aquaculture, thereby preventing them from going into landfills. In addition, a firing process for enhancing the shielding efficiency of the original material is proposed. Experiments show that shielding sheets comprising 0.3 mm thick layers of oyster shell achieve a shielding efficiency of 37.32% for the low-energy X-rays typically encountered in medical institutions. In addition, the shielding efficiency was improved by increasing the density of the powdered oyster shell via plastic working at 1200 °C. This raises the possibility of developing multi-material radiation shields and highlights a new potential avenue for recycling aquaculture waste.

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.

Experimental measurement of effective atomic numbers and albedo factors for some alloys using the backscattering technique

Alloys of the type Pb₆₀Sn₂₀Zn_xCd_(20-x) where x = 0, 5, 10, 15 or 20 were prepared by a conventional melt quench technique. The intensity distribution of backscattered photons from the radioactive isotopes ²²Na and ¹³⁷Cs (with photon energies of 511 keV and 662 keV, respectively) were recorded for different thicknesses of alloy samples and some metallic samples (Al, Zn, Sn and Pb) with use of a GAMMA-RAD5 spectrometer (76 mm × 76 mm NaI(Tl) scintillation detector). Backscattered photon intensities were plotted as a function of both the atomic number and the target thickness. A best fit curve was drawn between backscattered photon counts and the atomic number of the metallic samples, from which the effective atomic numbers (Z_eff) of the alloys were obtained at a particular photon energy as well as thickness. The experimentally obtained Z_eff values are in good agreement with the theoretical ones (based on mass attenuation coefficients from the WinXCom database). The plot of intensity versus thickness shows that the intensity of backscattered photons increases with sample thickness. The albedo factors (energy albedo, number albedo and dose albedo) were also determined experimentally at these photon energies for the alloys and metallic samples. In the Compton scattering dominant region, the albedo factors decrease with an increase in atomic number as well as with an increase in photon energy.