Suitable Shielding Research Articles

Assessment of natural radioactivity levels in polymetallic nodules and potential health risks from deep-sea mining

The activity concentration of U-238, Ra-226, Pb-214, Bi-214, and Pb-210 was measured in samples of polymetallic nodules stored in the repository of the Interoceanmetal Joint Organization (IOM) based in Szczecin, Poland. The nodule samples were collected from the seabed of the Pacific Ocean, within the Clarion-Clipperton Zone, approximately 2,000 kilometres west of Mexico. The activity concentration of U-238 in the studied samples ranged from 9 to 51Bqkg-1. The mean activity concentration of the other radionuclides, Ra-226, Pb-214, Bi-214, and Pb-210, was found to be at comparable levels at 350, 321, 323, and 287Bqkg-1, respectively. Also investigated was the potential radiological hazard to individuals involved in the storing and processing of the nodules, resulting from the radioactive decay of Ra-226 contained in the nodules. It was concluded that the effective dose limit (20mSv) for individuals occupationally exposed to radioactive material can be exceeded in the case of prolonged and close contact with large quantities of nodules. Effective protective measures against the detected radiation include: observing the exposure time, ensuring safe distance from the source of radiation, and selecting suitable shielding where feasible within the operational constraints of the nodule transport or storage system.

Enhanced microwave absorption properties of conducting polymer@graphene composite to counteract electromagnetic radiation pollution: green EMI shielding.

Conducting polymers have been thoroughly investigated and found to have extensive applications in the fields of microwave absorption and electromagnetic (EM) shielding owing to their distinctive characteristics and adaptability. In the present work, conducting polymer (PEDOT and polyaniline) and graphene composites were prepared via an in situ chemical polymerization technique. Further, these composite materials were characterized to determine their potential to address the issue of EM radiation pollution in the microwave frequency (12.4 GHz to 18 GHz). The PEDOT/graphene composites exhibited significant shielding effectiveness of up to 46.53 dB, achieving a green index (gs) of 1.17. Also, absorption was observed to be the dominant shielding mechanism in all the samples owing to significant dielectric losses (ε''/ε' ≈ 1.9-3.1) and microwave conductivity (σs = 19.9-73.6 S m-1) in the samples at 18 GHz. Both dielectric loss and conduction loss occurred because of the strong interactions involving polarization, charge propagation, and the creation of conductive routes through the incorporation of graphene in the polymer matrix. These properties/shielding results indicate the potential of the composites to be used as lightweight EM shielding materials. These materials are suitable shield materials for electronic devices to protect them from harmful electromagnetic radiation, making them vital in various applications.

Characterization of neutronic parameters and radiation shielding design for an aqueous homogeneous reactor

In this research, an aqueous homogeneous reactor is simulated and its neutronic parameters are investigated. Due to the negative reactivity caused by temperature change and void formation, the cold excess reactivity is considered equal to 4 βeff. Also, calculations of radiation shielding and neutronic characterization of the reactor are performed. For different heights of uranyl sulfate fuel, the effective multiplication factor (keff) of the reactor is calculated under cold zero power and hot full power conditions to assess the required excess reactivity. The amount of fuel burnup and changes in the keff are investigated for 500 days, finally 200 operating days are chosen as the working duration of the reactor. The control rods worth (CRW) for different diameters of boron carbid and reactor safety parameters including shot down margin (SDM) and safety reactivity factor (SRF), temperature and void coefficients of reactivity are analyzed. In order to design a suitable radiation shield for this reactor, two different shields are considered. The first shield is a combination of polyethylene thicknesses and barite concrete, and the second shield is made only of barite concrete. The total thickness of the first and second shield was 230 and 180 cm, respectively. Due to the problems of using polyethylene (e.g. problems related to machining, shield dimensions and low melting temperature), the second shield is chosen as the suitable radiation shield for this reactor. Using this radiation shield, the total dose rates of neutron and gamma rays satisfy the ICRP dose limits.

Experimental, analytical, and simulation studies of modified concrete mix for radiation shielding in a mixed radiation field

The current study assessed two concrete mixes prepared using dolomite and barite/limonite aggregates to shield against both energetic photons and neutrons. After that, a designed mix which comprised barite/goethite aggregates plus fine-powdered boron carbide additive, was proposed to improve the overall radiation shielding properties and in the same time, doesn’t compromise or even improve the physic-mechanical properties of the mature concrete. The assessment started first with intensive experimental investigations to investigate the prepared mixes’ shielding capabilities against both γ-rays and fast neutrons. Then, analytical computations were performed via number of reliable software programs such as; Phy-X, NXCom, MRCsC, JANIS-4, and MCNP5, in order to confirm the experimental results and to validate the created Monte-Carlo models. Finally, an intensive radiation shielding assessment for all concrete mixes understudy using, mainly, the validated MCNP models, was performed. The obtained results have revealed the superiority of barite mixes over the dolomite mix concerning attenuating photons moreover, the proposed designed mix has shown superiority over the other two prepared mixes considering shielding against; energetic photons, fast/thermal neutrons, and secondary emitted γ-rays, which nominates this mix to be a suitable universal shield that can be used even in mixed radiation fields.

Design, construction, and characterization of a Prompt Gamma Neutron Activation Analysis (PGNAA) system at Isfahan MNSR

In this research, a prompt gamma neutron activation analysis (PGNAA) system is designed and constructed based on the use of a low power research reactor. For this purpose, despite the fact that this reactor did not include beam tubes, a thermal neutron beam line is installed inside the reactor tank. The extraction of the beam line from inside the tank made it possible to provide the neutron flux from the order of 106 n.cm-2.s-1. Also, because the beam line is installed in a tangential position to the reactor core, its gamma level has been minimized. Also, a suitable radiation shield is considered for the detector to minimize the background radiation and prevent radiation damage to the detector. Calculations and measurements are done in order to characterize this system, as well as spectrometry of several samples. The results of evaluations and experiments show that this system is suitable for performing PGNAA.

Impact of Growth Temperature of Lead-Oxide Nanostructures on the Attenuation of Gamma Radiation.

Chemical bath deposition (CBD) technique is utilized to grow lead-oxide (PbO) nanostructures (NSs) over PbO seed fabricated by physical vapor deposition (PVD) method on glass substrates. The effect of growth temperatures 50 and 70 °C on the surface topography, optical properties, and crystal structure of lead-oxide NSs has been studied. The investigated results suggested that the growth temperature has a huge and very considerable influence on the PbO NS, and the fabricated PbO NS has been indexed as the Pb3O4 polycrystalline tetragonal phase. The crystal size for PbO thin films grown at 50 °C was 85.688 nm and increased to 96.61 nm once the growth temperature reached 70 °C. The fabricated PbO nanofilms show a high rate of transmittance, which are ∼70 and 75% in the visible spectrum for the films deposited at 50 and 70 °C, respectively. The obtained Eg was in the range of 2.099-2.288 eV. Also, the linear attenuation coefficient values of gamma-rays for shielding the Cs-137 radioactive source increased at 50 °C. The transmission factor, mean free path, and half-value layer are reduced at a higher attenuation coefficient of PbO grown at 50 °C. This study evaluates the relationship between synthesized lead-oxide NSs and the radiation energy attenuation of gamma-rays. This study provided a suitable, novel, and flexible protective shield of clothes or an apron made of lead or lead oxide to protect against ionizing radiation that meets safety rules and protects medical workers from ionizing radiation.

Formation of Silver Layer with a Multiporous Structure from Silver Nanoparticles for Highly Efficient Electromagnetic Interference Shielding Materials

In this work, we describe a simple and effective strategy for the fabrication of a thin silver (Ag) layer with a multiporous structure, showing a high electromagnetic interference shielding effectiveness (EMI SE). The Ag layer with a multiporous structure was produced by a simple spray coating of conductive ink containing porous Ag nanoparticles synthesized using a simple chemical reduction method in a wet medium, followed by a low-energy sintering process to develop the Ag layer with an interconnected multiporous structure and average thickness of ∼5.5 μm. The produced Ag layer possessed a remarkable multiporous structure, which was composed of pores in Ag NPs and additional pores generated by coalescence of Ag NPs during the sintering process. Even the thin Ag layer exhibited a high EMI SE (62.3 dB, 99.9% shielding) owing to the multiporous structure, which was comparable to that of Ag foil with much lower Ag loading. This multiporous structure helped to increase the internal multiple reflections of electromagnetic waves. The substantial shielding effectiveness of the obtained multiporous Ag layer was demonstrated by measuring the EMI SE of the Ag layer coated PCB antenna. Our approach is a suitable and alternative EMI shielding method to replace present package-level EMI shielding materials such as Ag foil for a wide range of applications.

The application of graphene/h-BN metamaterial in medical linear accelerators for reducing neutron leakage in the treatment room.

Neutrons can be generated in medical linear accelerators (Linac) due to the interaction of high-energy photons (> 10MeV) with the components of the accelerator head. The generated photoneutrons may penetrate the treatment room if a suitable neutron shield is not used. This causes a biological risk to the patient and occupational workers. The use of appropriate materials in the barriers surrounding the bunker may be effective in preventing the transmission of neutrons from the treatment room to the outside. In addition, neutrons are present in the treatment room due to leakage in the Linac's head. This study aims to reduce the transmission of neutrons from the treatment room by using graphene/hexagonal boron nitride (h-BN) metamaterial as a neutron shielding material. MCNPX code was used to model three layers of graphene/h-BN metamaterial around the target and other components of the linac, and to investigate its effect on the photon spectrum and photoneutrons. Results indicate that the first layer of a graphene/h-BN metamaterial shield around the target improves photon spectrum quality at low energies, whereas the second and third layers have no significant effect. Regarding neutrons, three layers of the metamaterial results in a 50% reduction in the number of neutrons in the air within the treatment room.

Inhaled Lipid Nanoparticles Alleviate Established Pulmonary Fibrosis.

Pulmonary fibrosis, a sequela of lung injury resulting from severe infection such as severe acute respiratory syndrome-like coronavirus (SARS-CoV-2) infection, is a kind of life-threatening lung disease with limited therapeutic options. Herein, inhalable liposomes encapsulating metformin, a first-line antidiabetic drug that has been reported to effectively reverse pulmonary fibrosis by modulating multiple metabolic pathways, and nintedanib, a well-known antifibrotic drug that has been widely used in the clinic, are developed for pulmonary fibrosis treatment. The composition of liposomes made of neutral, cationic or anionic lipids, and poly(ethylene glycol) (PEG) is optimized by evaluating their retention in the lung after inhalation. Neutral liposomes with suitable PEG shielding are found to be ideal delivery carriers for metformin and nintedanib with significantly prolonged retention in the lung. Moreover, repeated noninvasive aerosol inhalation delivery of metformin and nintedanib loaded liposomes can effectively diminish the development of fibrosis and improve pulmonary function in bleomycin-induced pulmonary fibrosis by promoting myofibroblast deactivation and apoptosis, inhibiting transforming growth factor 1 (TGFβ1) action, suppressing collagen formation, and inducing lipogenic differentiation. Therefore, this work presents a versatile platform with promising clinical translation potential for the noninvasive inhalation delivery of drugs for respiratory disease treatment.

Application of Accelerator Beam Dumps for Dark Matter Searches

Light dark matter (LDM) in the mega-electron-volt to giga-electron-volt mass region is an attractive candidate for the all-pervasive and encompassing matter making up the vast bulk of the mass of our universe. Beam dump experiments at high-intensity accelerators are a powerful tool to produce and detect LDM. They can probe an unexplored dark sector that is interacting with the standard model (SM) through one or more portals. At the lowest-beam-energy end, the DarkMESA experiment will run behind the dump of the 150-MeV electron beam of the MESA accelerator, currently under construction at the Institute for Nuclear Physics in Mainz. The concept for detecting direct scattering reactions of LDM comprises an electromagnetic calorimeter surrounded by an active veto system for rejecting backgrounds from SM particles. Suitable shielding will be located between the downstream detectors and the dump. A low-pressure, negative-ion, time-projection chamber could supplement these searches. At much higher beam energies, the Beam Dump eXperiment (BDX) is proposed to run parasitically behind the Jefferson Lab Hall-A beam dump making use of the up to 11-GeV electron beam. BDX employs the same detector concept. Direct LDM scattering reactions can be detected in an electromagnetic calorimeter operated inside hermetic layers of veto counters and a thick lead vault. Both experiments can explore uncovered regions of the parameter space of the LDM interaction strength versus mass, exceeding the discovery potential of existing experiments.

3D프린터와 아두이노를 활용한 교육용 휴머노이드 로봇

Among the types of robots, it is not easy to make a robot that walks on two legs. For this, it is necessary to be able to create software that can control precise servomotor settings and various operations. This process is very difficult for beginners and not easy to make because there is no suitable Arduino shield shape for the robot. Therefore, in this study, a method for manufacturing Arduino and plug-in type shield was proposed. In addition, the process of developing a PC control program that can simplify motion control, manufacturing a robot, and setting servo motor values to easily control motion was introduced. It is expected that this will be of great help to novice developers who are interested in making robots.

Developing a radiation shield and investigating the mechanical properties of polyethylene-polyester/CdO bilayer composite

Radiation attenuation and mechanical properties are two key parameters for shielding in space. This study explored the attenuation parameters of cadmium as a popular filler for the shielding of thermal neutrons in the unsaturated polyester (UPS) polymer matrix. The polyester matrix was used for the first time. The composite behavior against gamma radiation (by applying Cs-137 radioisotope, E gamma = 0.662 MeV) was evaluated using the gamma spectrometer. Also, the sample was exposed to neutron radiation by utilizing a239Pu–Be neutron source. The effect of the composite sample produced with the cadmium filler was also examined when exposed to gamma radiation. Further, the attenuation parameters of the gamma rays were studied. The observations indicated the suitable shielding of this composite for thermal neutrons, such that the half-value layer (HVL) decreased from 7.8 cm in the polyester sample to 0.22 cm in the polyester/10 wt% CdO composite sample. The linear attenuation coefficient of the thermal neutron increased from 0.0888 (cm-1) in the polyester sample to 3.15 (cm-1) in the 10 wt% CdO composite sample, thus indicating more than 35-fold improvement in the neutron attenuation. Composite samples were exposed to gamma radiation; contrary to the expectations, the results showed an almost twofold improvement in the attenuation of gamma radiation, as compared to the polyester sample. This composite specimen was coupled to a 2 mm thick linear low-density polyethylene (LLDPE) layer for the better shielding of thermal neutrons. Finally, the composite sample was mechanically reinforced with a silica glass fiber, which enhanced the ultimate tensile strength (UTS) from 39 to 298 MPa. Also, the elongation rate (% E) was raised from 6% in the polyester sample to 10.5% in the polyester/10 wt% CdO- silica glass fiber sample. Thus, the results indicated the production of a strong composite capable of attenuating neutron and gamma radiation. Accordingly, this composite could be considered a reliable option for use as a shield in space missions.

Influence of Fe3O4 and Carbon Black on the Enhanced Electromagnetic Interference (EMI) Shielding Effectiveness in theEpoxy Resin Matrix.

The present study aims to investigate the shielding properties of the electromagnetic interference of polymer nanocomposites with different weight percentages of magnetite nanoparticles and cost-effective carbon black nanoparticle(CBN) on different thicknesses. X-ray diffractiontest,Raman spectroscopy,thescanning electron microscopy, and the transmission electron microscope analysis were used for investigating the crystallographic structure, morphology and microstructure of the material. The nanocomposites were successfully prepared using a simple mixing and casting. Their shielding efficiency was measured by a vector network analyzer(VNA) in the frequency range of 8.2 ~ 12.4GHz. The maximum total shielding efficiency was 36.6dB at 8.2GHz for a weight percentage of 15% Fe3O4 composite and 50% CBN (0.7mm thickness). The results showed that with an increase of nanocomposite thickness, there is a shift of absorption shielding efficiency peak toward a higher frequency. In addition, nanocomposites had the greatest shielding effectiveness in the low-frequency range. It was found that the proper combination of electrical and magnetic losses causes excellent wave absorption. These findings indicated that epoxy resin with a combination of optimal weight percentage of magnetite and carbon black nanoparticle can be used as a suitable shielding in low thickness.

Shield Design of the First Protective Collimator in the METU-Defocusing Beamline (DBL) Project

The Middle East Technical University Defocusing Beamline (METU-DBL) is being constructed in order to perform single event effects tests for the electronic components in accordance with the European Space Agency (ESA) European Space Components Coordination (ESCC) No. 25100 standard. The aim of this beamline is to provide a suitable test area at the end of the beamline using the beam elements, such as collimators and magnets. Shielding is a crucial precaution for the safety of the radiation workers and the protection of the electronic components from the detrimental effects of radiation. In the METU-DBL, shielding studies have started with the first protective collimator because the proton beam hits the collimator, resulting in secondary particle production that increases the dose level in the research and development (R&D) room. The shielding studies of the first protective collimator used in the pretest setup of the METU-DBL are presented in this study. The whole beamline was defined in the FLUKA simulation program to calculate the absorbed radiation dose and make shielding designs. Various shielding designs were studied in FLUKA and the 15th one was selected as a suitable shielding design for the first protective collimator. This shield was manufactured and mounted on the first protective collimator and used in 20 irradiations during the pretests. At the end of 20 irradiations, it was observed that the shield is effective at decreasing the dose level in the R&D room.

Novel energy efficient window coatings based on In doped CuS nanocrystals with enhanced NIR shielding performance

To achieve good indoor thermal comfortability in the hot summer days, searching for suitable solar shielding materials for buildings is of great importance. In this work, In doped CuS nanocrystals were first synthesized as novel NIR shielding materials for energy efficient windows. The influence of In doping on the microstructure, phase composition, optical performance, and thermal property of CuS were systematically explored. All the products adopted a hexagonal structure. Both of CuS and In doped CuS nanocrystals were composed of nanoplates and nanorods. All samples showed high visible transmittance (63.9–78.4%). Optical tests confirmed that the doping of indium ions was an effective way to improve the NIR shielding performance of the CuS films. The NIR shielding value of the films increased from 47.2% to 68.2% when the doping amount of In increased from 0 to 2%. The reason can be attributed to the enhanced NIR absorption induced by the increased hole concentration after doping of In3+ ions. Moreover, the In doped CuS films lowered the indoor temperature of the heat box by 8.4 °C in the thermal tests, further confirming the superior NIR shielding performance of In doped CuS nanocrystals.

Effect of lead oxide on concrete density for radiation shielding purposes

Selection of suitable shielding materials depends on the type, intensity and energy of radiation source, as well as the shielding properties such as mechanical strength, economic preparation and resistance to radiation damage. When compared to ordinary concrete, the addition of some materials with various fractions in the composition of concrete has provided concrete forms more efficient for gamma ray shielding. Concrete has proven to be an tremendous and adaptable shielding material with a well-established linear attenuation coefficient for gamma rays and neutrons. The objectives of this study is to determine the exact composition of concrete constituents and its density. Concrete samples were prepared by mixing cement, water, aggregate and additive with different composition and densities. Density was increases by decreasing the aggregates percent and increasing the additives such as lead oxide. Sample will be compacting to forming a solid material through pelleting and sintering process. Finally, it will undergo for radiation attenuation test. It was found that, substitution of lead oxide by aggregate causes increasing in the specific density and compressive strength of the concrete.

Radiation attenuation properties of some commercial polymers for advanced shielding applications at low energies

As radiation is an essential tool in various technological applications, searching for a suitable shield is an urgent demand to minimize its damaging effects on human beings. In this research article, we report on the radiation shielding properties of some commercially available polymers namely poly(N‐isopropylacrylamide), polyethylene terephthalate, polystyrene, and polycarbonate (denoted by P1, P2, P3, and P4, respectively). The gamma ray attenuation parameters are calculated using the Geant4 simulation, PHITS code, and XCOM program. Half value layer (HVL), linear attenuation coefficient (LAC), gamma dose rate at different energy levels, mean free path (MFP), specific gamma ray constant, effective atomic number (Zeff) and effective electron density (Neff), removal cross section for fast neutron, and total cross section for thermal neutron are investigated at energies of 0.01, 0.03, 0.05, 0.07, and 0.1 MeV. The results indicate that the highest LAC values were observed for P2 polymer at 0.1 MeV, while the lowest LAC values were noted for P3 polymer at 0.01 MeV among the studied commercial polymers. The total cross sections of thermal neutrons for the investigated polymers change from 24.0717 to 31.8611 cm−1. Moreover, the MFPs and HVLs of the investigated polymers were very close to those of ordinary concrete and RS‐253‐G18 commercial glass, especially at the low energies. This suggests the utility of using the present polymer samples for shielding applications against gamma and/or neutron radiations.

Structural insights into the membrane receptor ShuA in DDM micelles and in a model of gram-negative bacteria outer membrane as seen by SAXS and MD simulations

Successful crystallization of membrane proteins in detergent micelles depends on key factors such as conformational stability of the protein in micellar assemblies, the protein-detergent complex (PDC) monodispersity and favorable protein crystal contacts by suitable shielding of the protein hydrophobic surface by the detergent belt. With the aim of studying the influence of amphiphilic environment on membrane protein structure, stability and crystallizability, we combine molecular dynamics (MD) simulations with SEC-MALLS and SEC-SAXS (Size Exclusion Chromatography in line with Multi Angle Laser Light Scattering or Small Angle X-ray Scattering) experiments to describe the protein-detergent interactions that could help to rationalize PDC crystallization. In this context, we compare the protein-detergent interactions of ShuA from Shigella dysenteriae in n-Dodecyl-β-D-Maltopyranoside (DDM) with ShuA inserted in a realistic model of gram-negative bacteria outer membrane (OM) containing a mixture of bacterial lipopolysaccharide and phospholipids. To evaluate the quality of the PDC models, we compute the corresponding SAXS curves from the MD trajectories and compare with the experimental ones. We show that computed SAXS curves obtained from the MD trajectories reproduce better the SAXS obtained from the SEC-SAXS experiments for ShuA surrounded by 268 DDM molecules. The MD results show that the DDM molecules form around ShuA a closed belt whose the hydrophobic thickness appears slightly smaller (~22 Å) than the hydrophobic transmembrane domain of the protein (24.6 Å) suggested by Orientations of Proteins in Membranes (OPM) database. The simulations also show that ShuA transmembrane domain is remarkably stable in all the systems except for the extracellular and periplasmic loops that exhibit larger movements due to specific molecular interactions with lipopolysaccharides (LPS). We finally point out that this detergent behavior may lead to the occlusion of the periplasmic hydrophilic surface and poor crystal contacts leading to difficulties in crystallization of ShuA in DDM.

A Monte Carlo study on the gamma-ray buildup factors for the linear sources embedded in a cylindrical shield

While the studies on the photon buildup factors for point gamma sources have been widely made, studies for linear gamma sources, for which the spent nuclear fuel rods and/or brachytherapy seeds could be a relatively good approximation, have become extremely scarce. Buildup factors for linear gamma sources are computed here by means of the MCNPX Monte Carlo code. The exposure buildup factors were calculated for isotropic linear gamma sources with different lengths (1, 10, and 100 cm) and also for different energies (0.1, 0.5, 1, 5, and 10 MeV) in a cylindrical concrete shield up to depths of 10 mean free paths. A number of 45 simulations were done to reach the appropriate results for the linear gamma sources and 5 more simulations were performed for point gamma sources to be compared with the linear sources of photons at the same energies. For validation, we calculated the total mass attenuation coefficients, mass energy absorption coefficients, and uncollided photon flux for some photon energy in concrete and we showed that the simulation results have a good agreement with NIST-XCOM database and theory. Finally, comparisons are shown for the exposure buildup factors of the linear source in terms of the gamma-rays energy, of the length of the linear source and of the cylindrical shield, which can be useful in the design of a suitable shield.

Design of Magnetic Shield for Hall-Effect Current Sensor Using Integrated Magnetic Concentrator

This paper proposes a shield shape design for minimizing the integrated magnetic concentrator (IMC) hall current sensor shield. Inside flux density and outside magnetic field error rate aren’t satisfied with performance by reducing an initial U-shaped IMC hall current sensor shield’s width and height for an IMC hall current sensor minimization. In order to solve the problem, first, inside flux density is decreased by adding air gap in the shield. Second, outside magnetic field error rate is decreased by adding top shield. Finally, suitable shield shape for minimization is designed by adding top middle shield. The minimization design work is reduced the number of experiments by using the orthogonal array table and main effect analysis method, which are one of the methods of the experimental design method. The proposed model satisfied the design considerations, and the shield area is reduced by 83.7% from the initial model, proving that it was a suitable shield shape for minimization.