Optimal Shielding Research Articles

Scalable manufacturing of flexible, durable Ti3C2Tx MXene/Polyvinylidene fluoride film for multifunctional electromagnetic interference shielding and electro/photo-thermal conversion applications

The durability and large-scale production of Ti 3 C 2 T x MXene-based composites are the main obstacles in industrialized application. Herein, a scalable blade coating method is demonstrated for fabricating the flexible and durable polyvinylidene fluoride (PVDF)/Ti 3 C 2 T x MXene layered films with compact hierarchical brick-and-mortar structure. The highly aligned MXene nanosheets make the obtained PVDF/MXene films with high electrical conductivity from 21.1 to 214.6 S cm −1 . In combination to the multiple wave reflection in hierarchical layered structure and the interfacial polarization between dielectric matrix and MXene, PVDF/MXene films reveal excellent electromagnetic interference (EMI) performance with an optimal specific EMI shielding effectiveness (SSE/t) of 19504.8 dB cm 2 g −1 at only 17 μm thickness. More importantly, the PVDF/MXene film can withstand the damages from mechanical deformation , hot/cold attack and chemical corrosion, meanwhile maintain a stable EMI shielding performance within floating of 5%. Besides, arising from the surface plasmon resonance effect and high electrical conductivity, the PVDF/MXene film reveals photo/electro-thermal heating abilities with rapid response time, high stability and controllability, which ensure their reliable EMI shielding performance under extremely cold conditions. • A scalable blade coating method was reported for fabricating PVDF/MXene layered film. • The film with compact brick-and-mortar structure reveals good EMI shielding property. • PVDF/MXene film shows superior durability with stable EMI SE in various environments. • PVDF/MXene film exhibits multifunctional photo/electro-thermal conversion capacities.

Experimental and theoretical investigation of Pb–Sb alloys as a gamma-radiation shielding material

Metal alloys with variable lead and antimony content have been prepared using fusion technique. The prepared alloys formula is (Pb x Sb y Cu 0.15 Al 0.1 ) with [x = 0.5–0.3 - 0.1–0] and [y = 0.25–0.45 - 0.65–0.75] respectively. A comparative study was conducted to find the optimum shielding parameters for the synthesized metal alloys. In terms of total mass attenuation coefficient MAC μ m , linear attenuation coefficient LAC μ l , half-value layer HVL, tenth-value layer TVL, mean free path MFP, effective atomic number Z eff , electron density number N eff , the exposure build-up factor EBF and the energy absorption build-up factor EABF the optimum shielding parameters are provided. Theoretical results were obtained from WinXCom software and interpolated at definite energy values. Simulation of the transmission experiment was conducted using FLUKA-MC software. Experimental results of the prepared metal alloys were compared with the theoretical ones, and a good agreement was found between them. It was found that present work prepared alloys composition can be used effectively as a shielding material for gamma rays with comparable attenuation percentage with high lead content alloys. • Shielding parameters of Pb–Sb alloys. • FLUKA-MC in the simulation of transmission experiments. • Experimental and theoretical calculations of mass and linear attenuation coefficients. • Fusion technique for preparing the metal alloys.

Optimal radiation shielding capacity and thermal properties of poly(methyl methacrylate) films enhanced with different metal complexes

Samples of pure poly(methyl methacrylate) (PMMA) and PMMA enhanced with metal complexes of Zn, Cd, and Hg were synthesized via catalytic chain transfer polymerization. Structural analysis, by means of XRD, showed the amorphous nature of the studied samples which meant high homogenous dissolution of the metals (Zn, Cd and Hg) into the polymer matrix. Density values increased linearly with respect to atomic radius of the incorporated metals. Addition of such elements causes an increase in mass attenuation coefficients and a remarkable decrease in the Half Value Layer (HVL) values, in comparison to existing standard shielding materials. Thermal studies by DSC indicated highly homogenous internal structure of the studied samples, with slight decrease in the Tg value when introducing metals due to heterogeneous nucleation agent role of the Cd, Zn and Hg. All observations and results suggest the studied materials to be used as promising and proper aprons for medical radiation shielding applications.

Optimization of a B[formula omitted]C/graphite composite energy degrader and its shielding for a proton therapy facility

Proton therapy is an advanced cancer treatment modality due to its ability to precisely deliver radiation doses to tumors using the Bragg peak effect. An energy degrader plays a vital role at a cyclotron-based proton therapy facility, as it provides a rapid, reliable, and reproducible method of setting the appropriate beam energy for radiotherapy . However, the protons undergo nuclear interactions with the matter in the degrader, leading to significant secondary particles causing a large ambient radiation dose nearby, creating severe risks for the facility operation. This study investigated the beam loss mechanism and the secondary particle generation in a B 4 C/graphite composite (BGC) energy degrader. Monte Carlo simulations were performed to ensure the shielding design’s reliability. Calculations showed that the BGC degrader had a higher beam transmission efficiency than a pure graphite degrader, while the secondary neutron yield was higher. An optimum shielding configuration can significantly reduce the radiation dose to an acceptable level for sensitive devices and maintenance staff.

Effect of N2 content in shielding gas on formation quality and microstructure of high nitrogen austenitic stainless steel fabricated by wire and arc additive manufacturing

The composition of shielding gas exerts a crucial influence on high nitrogen austenitic stainless steel (HNASS) deposited by gas metal arc additive manufacturing. The proportion of N 2 in shielding gas greatly affected the formation quality and microstructure of deposited parts. As N 2 proportion improved, the formation quality became worse gradually and the nitrogen concentration of deposition metal increased. The maximum nitrogen concentration of deposition metal was more than 1%. However, N 2 porosity in the deposition metal became serious when the N 2 content was over 10 %. The microstructure of the deposition metal changed from two phases of austenite and ferrite in shielding gas of 0∼10 %N 2 to complete austenite with 15 %∼25 %N 2 content in shielding gas. With optimal shielding gas of 5%N 2 +2%O 2 +10%He+83%Ar, the deposited parts of HNASS demonstrated good formation and excellent properties. The average ultimate tensile strength of 920 MPa was achieved and the elongation was 27.7%.

Multiobjective Optimization Shielding Design for Compact Accelerator-Driven Neutron Sources by Application of NSGA-II and MCNP

To find the optimal shielding design for compact accelerator-driven neutron sources (CANS) using multiobjective optimization, we developed a new method called nondominated sorting genetic algorithm-Monte Carlo method (NSGA-MC). NSGA-MC employs NSGA-II to optimize the shielding parameters based on calculations made by the Monte Carlo N-Particle Transport Code (MCNP). A layered shielding configuration with two materials of borated polyethylene (BPE) and lead (Pb) in the order of BPE/Pb/BPE/Pb for RIKEN Accelerator-driven Compact Neutron Source (RANS) was examined using this method, and two objectives were optimized simultaneously: equivalent dose rate and shielding structure weight. As a result, a tradeoff relationship between the objectives was finally obtained in the form of a Pareto front. The optimization results revealed significant improvements compared with the current RANS shielding configurations in terms of both dose and weight. The results indicate that a reduction in shielding weight of about 60% can be obtained by adopting the optimized shielding structure design, without sacrificing shielding performance. The performance of the method was discussed by showing advantages of NSGA-MC over the so-called weight sum method.

Polymethyl methacrylate reinforced with nickel coated multi‐walled carbon nanotubes: Flame, electrical and mechanical properties

AbstractComposites of polymethyl methacrylate (PMMA) as matrix and nickel‐coated multi‐walled carbon nanotubes (Ni‐MWCNT) as nanofillers were prepared using a melt mixing process. In order to improve the dispersion of the nanofillers in the PMMA matrix and thus enhance matrix‐filler interactions, Ni‐MWCNT was treated with amino propyl triethoxy‐silane (APTS). The shielding effectiveness (SE) of the composites improved with increasing Ni‐MWCNT content. In addition, the effects of various combinations of fillers like silver, copper, and nickel nanoparticles on SE have been studied. Among these nanoparticles, copper nanoparticles in combination with MWCNT and Ni‐MWCNT showed optimal shielding effectiveness of 55 dB. The volume and surface resistivity of the composites decreased with increase in nanofiller content. The tensile strength values were increased by 51% at 0.8 wt% loading of Ni‐MWCNT as compared to that of composite without filler. The improvement in tensile strength was further analyzed using micromechanical models. Cone calorimeter studies showed 25.3% reduction in the peak heat release rate for the composite loaded with 1.5 wt% of Ni‐MWCNT as compared to that of neat PMMA. The nanocomposites also showed enhanced thermal stability with the formation of char as the filler content increased.

Evaluations for Determination of Optimum Shields in Nuclear Medicine

Background: 131I source is widely used in the treatment of hyperthyroidism and thyroid cancers. 131I emits both beta and gamma-rays. Radiation protection is considered for gamma rays emitted by 131I. It seems no special shield against 131I source to be designed.Objective: This research aims to evaluate determination of optimum shields in nuclear medicine against 99Tcm and 131I sources by dosimetric method. Additionally, Monte Carlo simulation was used to find the optimum thickness of lead for protection against 131I source.Material and Methods: This is an experimental research in the field of radiation protection. A calibrated model of GraetzX5C Plus dosimeter was used to measure exposure rates passing through the shields. The efficiency of the shields was evaluated against 99Tcm and 131I. Furthermore, Monte Carlo simulation was used to find the optimum thickness of lead for protection against 131I source.Results: The findings of the dosimetric method show that the minimum and maximum efficiencies obtained by the lead apron with lead equivalent thickness of 0.25 mm and the syringe holder shields with thickness of 0.5 mm lead were 50.86% and 99.50%, respectively. The results of the simulations show that the minimum and maximum efficiencies obtained by lead thicknesses of 1 mm and 43 mm were 19.36% and 99.79%, respectively. Conclusion: The optimum shields against 99Tcm are the syringe holder shield, the tungsten syringe shield, and the lead partition, respectively. Furthermore, based on simulations, the thicknesses of 11-28 mm of lead with efficiencies between 90.6% to 99% are suggested as the optimum thicknesses to protect against 131I source.

Optimization of shielding gas composition in high nitrogen stainless steel gas metal arc welding

Abstract High nitrogen stainless steel has extensive applied foreground in industries. But the weldability limits the use of the steel. The weld without nitrogen can become the weakness of the joint in corrosion resistance and strength. In this study, response surface methodology was applied to optimize the Ar-N2-CO2 ternary shielding gas for a nitrogen-containing filler metal in high nitrogen stainless welding. The influence of the proportion of N2 and CO2 on the nitrogen content, the impact energy and the tensile strength were investigated by the statistical regression models. The results show that the tensile strength, nitrogen content and impact energy increase and then decrease with the increasing of CO2, which indicates that CO2 content should not be too high. N2 addition can increase the nitrogen content of the weld obviously. But the impact energy decreases when N2 content exceeds about 7%. Integrating the mathematic models of the three performances, the optimal shielding gas compositions were determined to be 87 %Ar-6.5 %N2-6.5 %CO2. With this optimal shielding gas, the tensile strength and impact energy reached 956.7 MPa and 166.8 J, respectively. The deviation between the experimental value and the predicted value was below 2%.

Neutron Shielding Performance of 3D-Printed Boron Carbide PEEK Composites.

Polyethylene is used as a traditional shielding material in the nuclear industry, but still suffers from low softening point, poor mechanical properties, and difficult machining. In this study, novel boron carbide polyether-ether-ketone (PEEK) composites with different mass ratios were prepared and tested as fast neutron absorbers. Next, shielding test pieces with low porosity were rapidly manufactured through the fused deposition modeling (FDM)-3D printing optimization process. The respective heat resistances, mechanical properties, and neutron shielding characteristics of as-obtained PEEK and boron carbide PEEK composites with different thicknesses were then evaluated. At load of 0.45 MPa, the heat deformation temperature of boron carbide PEEK increased with the boron carbide content. The heat deformation temperature of 30% wt. boron carbide PEEK was recorded as 308.4 °C. After heat treatment, both tensile strength and flexural strength of PEEK and PEEK composites rose by 40%–50% and 65%–78%, respectively. Moreover, the as-prepared composites showed excellent fast neutron shielding performances. For shielding test pieces with thicknesses between 40 mm and 100 mm, the neutron shielding rates exhibited exponential variation as a function of boron carbide content. The addition of 5%–15% boron carbide significantly changed the curvature of the shielding rate curve, suggesting an optimal amount of boron carbide. Meanwhile, the integrated shielding/structure may effectively shield neutron radiation, thereby ensuring optimal shielding performances. In sum, further optimization of the proposed process could achieve lightweight materials with less consumables and small volume.

Multi-objective optimization strategies for radiation shielding design with genetic algorithm

Abstract The radiation shielding design for advanced nuclear facilities is a typical complicated multi-objective and multi-parameter optimization problem in the nuclear engineering. To obtain an optimal solution of the shielding design is of significance in developing high-performance advanced nuclear facilities, especially for compact and mobile devices. The classical method of shielding design is a brute force trial-and-error procedure subjecting to human preferences and expectations, which is of failure to meet the requirements in radiation shielding optimization applications. Two multi-objective optimization strategies were developed to optimize the shielding structures and materials aiming at lightweight, compactness and low radiation dose under a set of constraints. The strategies employed an evolutionary algorithm, genetic algorithm, to perform radiation shielding design optimization efficiently and automatically. The most advantage of the strategies is that multiple optimal shield solutions could be achieved in one single simulation run, which will make the radiation shielding design procedure more efficient and flexible. The strategies were verified fully with a realistic multi-objective radiation shielding design problem. The numerical results showed that the strategies could balance well the shielding quality against the weight and the volume of the shield. It is confirmed that the strategies are applicable and effective for multi-objective and multi-parameter radiation shielding design optimization applications.

Subsurface Radiation Environment of Mars and Its Implication for Shielding Protection of Future Habitats

AbstractIn order to quantify the optimal radiation shielding depth on Mars in preparation for future human habitats on the red planet, it is important to understand the Martian radiation environment and its dependence on the planetary atmospheric and geological properties. With this motivation we calculate the absorbed dose and equivalent dose rates induced by galactic cosmic ray particles at varying heights above and below the Martian surface considering various subsurface compositions (ranging from dry rock to water‐rich regolith). The state‐of‐the‐art Atmospheric Radiation Interaction Simulator based on GEometry And Tracking Monte Carlo method has been employed for simulating particle interaction with the Martian atmosphere as well as subsurface materials. We calculate the absorbed dose in two different phantoms: a thin silicon slab and a water sphere. The former is used to validate our model against the surface measurement by the Radiation Assessment Detector on the Curiosity rover, while the later is used to approximate a human torso, also for evaluation of the biologically weighted equivalent dose. We find that the amount of hydrogen contained in the water‐rich regolith plays an important role in reducing the equivalent dose through modulation of neutron flux (below 10 MeV). This effective shielding by underground water is also present above the surface, providing an indirect shielding for potential human explorations at this region. For long‐term habitats seeking the Martian natural surface material as protection, we also estimate the optimal shielding depth, for different given subsurface compositions, under maximum, average, and minimum heliospheric modulation conditions.

Optimization of shielding to reduce cosmic radiation damage to packaged semiconductors during air transport using Monte Carlo simulation

Cosmic ray-induced particles can lead to failure of semiconductors packaged for export during air transport. This work performed MCNP 6.2 simulations to optimize shielding against neutrons and protons induced by cosmic radiation The energy spectra of protons and neutrons by incident angle at the flight altitude were determined using atmospheric cuboid model. Various candidates for the shielding materials and the geometry of the Unit Load Device Container were evaluated to determine the conditions that allow optimal shielding at all sides of the container. It was found that neutrons and protons, at the flight altitude, generally travel with a downward trajectory especially for the particles with high energy. This indicated that the largest number of particles struck the top of the container. Furthermore, the simulation results showed that, among the materials tested, borated polyethylene and stainless steel were the most optimal shielding materials. The optimal shielding structure was also determined with the weight limit of the container in consideration. Under the determined optimal shielding conditions, a significantly reduced number of neutrons and protons reach the contents inside the container, which ultimately reduces the possibility of semiconductor failure during air transport.

Ionizing radiation shielding properties of metal oxide impregnated conformal coatings

Abstract Conformal coatings provide environmental protection for sensitive military electronics. Preliminary MCNP6® modeling of metal oxide impregnated acrylic conformal coatings indicates a factor of 300 reduction in gammas below 10 keV and up to a 225% reduction in neutron displacement damage to Si-based electronics across the Watt spectrum. This work provides data which can allow an optimal overall shielding worth per total mass to be evaluated.

Persepsi Pegawai Unit Kearsipan SKPD terhadap Aplikasi Sistem Informasi Kearsipan Daerah (SIKEDA) dan Jaringan Informasi Kearsipan Daerah (JIKEDA) di Pemerintahan Kota Bukittinggi

AbstractIn this paper we discuss the SKPD Filing Unit Employee Perception of the Regional Archival Information System Application (SIKEDA) and the Regional Archival Information Network (JIKEDA) in the City Government of Bukittinggi. The purpose of this study is to determine the competence and optimal shield of SKPD employees in inputting files to the SIKEDA application.This type of research is descriptive research with a qualitative approach. The location of this study was carried out in 5 SKPD Institutions in Bukittinggi, namely: (1) the Library and Archives Office of Bukittinggi City, (2) the Education and Culture Office of the City of Bukittinggi, (3) the Youth and Sports Pariwasata Service of the City of Bukittinggi, (4) the Health Service City of Bukittinggi, (5) Social Service of the city of Bukittinggi. The object of the study was SKPD employees in five government agencies in the city of Bukittinggi. Writing this paper aims to describe (1) To describe the optimization of the use of SIKEDA and JIKEDA applications by Admin node SIKEDA in supporting records management in the city administration of the City of Bukittinggi; (2) To describe the competencies possessed by HR in SKPD in utilizing information technology in the application of SIKEDA and JIKEDA applications in the City Government of Bukittinggi.Data was collected by observation and direct interviews with SKPD employees in the Bukittinggi city government and literature studies in the application of electronic records in the government of the City of Bukittinggi.Based on the discussion, it can be concluded that the First Employee in the SKPD in the City Government of Bukittinggi is still not optimal in inputting the archive to the sikeda Second application.iKeywords: optimization, competence, electronic archives.

Optimization Design of Radiation Vault in Jupiter Orbiting Mission

In Jupiter missions, one significant challenge is the harsh environment. The radiation in Jovian orbit is much higher than that in earth bf vicinity in terms of intensity and energy level. In spacecraft (S/C) design, key electronics are packaged in an enclosed vault to help them survive through the mission. The preliminary optimization design methods of a radiation vault based on a genetic algorithm (GA) are introduced, including shield structure optimization and layout pattern of electronics optimization. In shield structure optimization, the method is combined with a total ionizing dose (TID) evaluation tool. The goal is to find the optimal multi-layer shield structure so that the TID, after the shielding, is minimal within the threshold of the total mass of the structure. In a 1-year mission with an orbit of $10\,\,R_{j}\times 25\,\,R_{j} \times 0^{\circ }$ , if the areal density is within 0.5–3 g/cm2, the optimal structure is bilayer or trilayer with high-Z material as an external layer and low-Z material as an internal layer. This structure benefits from the fact that the low-Z material is more effective in shielding energetic protons whereas the high-Z material is more effective in shielding energetic electrons. In the 1-g/cm2 situation, the optimal structure is a 0.829-mm lead layer combined with a 0.158-mm magnesium layer. Comparing with the traditional aluminum shielding structure, about 43.6% of mass can be saved. In layout pattern optimization, this method combines a packing algorithm and a 3-D TID simulation tool. Using this method, an effective design layout of the vault can be found. In this design, all avionics can survive through the mission. In addition, the mass of the vault is low enough that the layout pattern is acceptable in S/C design. As an example, 14 instruments with TID threshold of 50 krad (Si) are packaged in a vault. On the premise that one instrument’s walls are thickened to 3.5-mm aluminum, the total mass of the vault is 68.47 kg. This method is a starting point for the iterative design of the radiation vault and gives principle guidelines for the designers.

Evaluation the gamma, charged particle and fast neutron shielding performances of some important AISI-coded stainless steels: Part II

Abstract This is the second part of a two-part study on the investigation of radiation shielding performances of some important AISI-coded stainless steels (AISI-302, 304, 321 and 430). Part 1 addressed experimental evaluation by means of measured photon-material interaction parameters. In this second part, we focused on the calculation and discussion of other interaction parameters, which are a guide to choice optimum shielding materials in the nuclear processes for the present AISI-coded stainless steels. The present stainless steels have superior mechanical properties, high temperature and corrosion resistances and these properties can make them favorite materials for nuclear applications. For this reason, firstly, the incoherent scattering/total attenuation ratio (Rinc/total) and equivalent atomic number (Zeq) were calculated in the energy region of 0.015–15 MeV. Secondly, the exposure build-up factor (EBF) and energy absorption build-up factor (EABF) were determined to select steels by using Geometric Progression (G-P) fitting method, which have five parameters (a, b, c, d and XK coefficients), up to penetration depth of 40 MFP at energy 0.015–15 MeV. Thirdly, the mass stopping powers (MSPs; d E / ρ d x ; MeVcm2/g) and ranges (Re, Rp and Rα; μm) for electron, proton and alpha particle interactions were calculated at energy 10 keV-20 MeV. Finally, the fast neutron removal cross-sections (FNRCSs; ∑ R ; cm−1) were calculated. To be able to make comparison and a satisfying assessment about radiation shielding capabilities of present AISI-coded steels, all parameters were also computed for ordinary (OC), steel-scrap (SS) and steel-magnetite (SM) concretes (Fe-based steel concretes) that are most commonly used as a shielding material in many nuclear applications. The shielding capabilities of the present stainless steels against both gamma and the fast neutron and charged particle radiation were evaluated in the light of the calculated parameters. As a result of the mutual evaluation of the results obtained for the shielding concretes and the examined stainless steels, it was found that present stainless steels had excellent shielding properties compared to shielding concretes in terms of both photon radiation and particle radiation.

Smart Shielding Techniques for Common Mode Chokes in EMI Filters

This work analyzes the effect of conducting bands placed close to a common mode choke on the attenuation provided by an electromagnetic interference filter where the common mode choke is mounted. The main aim was to determine whether the response of the common mode choke can be modified and to clearly identify and quantify the physical mechanism responsible for the changes found in the attenuation of the common mode choke and the electromagnetic interference filter. The impact of grounded and ungrounded conducting surfaces was studied for the two more typical configurations of common mode chokes: vertically and horizontally mounted. This study has allowed us to devise an optimum shield for a common mode choke that can significantly improve the attenuation to both common mode and differential mode noise of an electromagnetic interference filter at high frequencies, where parasitic effects usually undermine the performance of the filter. Key features of the technique described here are that it can be applied easily and that it does not result in an increase of the weight, volume, or cost of the filter.

Metaheuristic optimization method for compact reactor radiation shielding design based on genetic algorithm

Abstract Obtaining an optimal shielding design is significant in developing of high-performance compact nuclear reactors. The traditional shielding design is a brute force trial-and-error method, which is a manually iterative procedure driven by human experiences. Thus, the shield solution achieved with traditional method is just an empirical one but not an optimal shield solution, which may degrade the overall operational performance of the nuclear-powered systems. To design optimal shields for compact reactors, a metaheuristic optimization method for radiation shielding design based on genetic algorithm was presented. The method is an automated optimization strategy by searching for the parameter space, which will not be subject to the human preferences. The methodology, procedure, implementation and validation were presented. The numerical results showed that the parameters of geometrical structures and material components for the shield could be optimized automatically and efficiently, which demonstrated the applicability and effectiveness of the method in shielding design applications.

Development of the PHITS Code and its Application to the Optimum Shielding Design for Neutron Scattering Instruments

Development of the PHITS Code and its Application to the Optimum Shielding Design for Neutron Scattering Instruments