Shielding Attenuation Research Articles

Radiation Attenuation and Stability of ClearView Radiation Shielding TM-A Transparent Liquid High Radiation Shield.

Radiation exposure is a limiting factor to work in sensitive environments seen in nuclear power and test reactors, medical isotope production facilities, spent fuel handling, etc. The established choice for high radiation shielding is lead (Pb), which is toxic, heavy, and abidance by RoHS. Concrete, leaded (Pb) bricks are used as construction materials in nuclear facilities, vaults, and hot cells for radioisotope production. Existing transparent shielding such as leaded glass provides minimal shielding attenuation in radiotherapy procedures, which in some cases is not sufficient. To make working in radioactive environments more practicable while resolving the lead (Pb) issue, a transparent, lightweight, liquid, and lead-free high radiation shield-ClearView Radiation Shielding-(Radium Incorporated, 463 Dinwiddie Ave, Waynesboro, VA). was developed. This paper presents the motivation for developing ClearView, characterization of certain aspects of its use and performance, and its specific attenuation testing. Gamma attenuation testing was done using a 1.11 × 10 Bq Co source and ANSI/HPS-N 13.11 standard. Transparency with increasing thickness, time stability of liquid state, measurements of physical properties, and performance in freezing temperatures are reported. This paper also presents a comparison of ClearView with existing radiation shields. Excerpts from LaSalle nuclear power plant are included, giving additional validation. Results demonstrated and strengthened the expected performance of ClearView as a radiation shield. Due to the proprietary nature of the work, some information is withheld.

Development and Design Mix of Radiation Shielding Concrete for Gamma-ray Shielding

For the first time in the world the development and design mix of radiation shielding concrete using innovative red mud based synthetic shielding aggregates has been reported. The developed shielding aggregates are made up of red mud and are basically ceramic materials consisting of shielding phases namely barium silicate (sanbornite), barium iron titanium silicate (bafertisite), barium aluminum silicate, Iron titanium oxide (pseudorutile), barium titanate, barium iron titanium oxide, barium aluminium oxide and magnetite, which are multi elemental, multi phases, multi layered crystal structures and therefore are excellent shielding materials. The design mix calculations for the development of radiation shielding concrete using developed synthetic shielding aggregates were carried out by adopting IS 10262-2009 for grade designation of M-30 concrete. The reference hematite ore concrete and developed concrete, slabs of size 30 cm × 30 cm × 7.2 cm were casted and sucessfully tested both for radiation shielding attenuation properties for gamma rays of factor using 137Cs (of photon energy 662 keV) and 241Am (of photon energy 60 keV) as well as X-rays of 300 kVp and found to posses highly effective shielding properties. For high energy radiation source i.e. 137Cs, the developed novel design mix concrete achieved attenuation factor of 5.8 as compared to 5.1 attenuation factor for hematite ore concrete. Further, the developed optimized design mix concrete have been tested for durability and the corrosion resistant test using standard 3.5% NaCl solution for optimized design mix were also carried out. The developed design mix of radiation shielding concrete using innovative red mud based synthetic shielding aggregates posses broad application spectrum ranging from construction of nuclear power plants, diagnostic X-ray, CT scanner rooms and storing radioactive waste.

Investigation into dielectric behaviour and electromagnetic interference shielding effectiveness of conducting styrene butadiene rubber composites containing ionic liquid modified MWCNT

Designing new conducting materials with a promise for electromagnetic shielding applications attracted a wide spread interest in recent years. Styrene-butadiene rubber (SBR) is a widely used low cost synthetic rubber for a large number of applications. However, their use in providing an effective barrier for electromagnetic radiations is limited by its poor electrical conductivity. Herein we report a facile synthesis of conducting polymer nanocomposite by incorporating non-covalently functionalized Multiwalled Carbon Nanotube (MWCNT) with ionic liquid into SBR matrix and achieve a shielding efficiency of ca.35.06 dB @ 18 GHz (i.e ∼99.99% shielding attenuation). Importantly, ionic liquid embedded MWCNT makes it dispersible facilitated through cation–π interaction. A synergy between ionic liquid and MWCNT was well understood by analysing the dielectric behaviour and ac conductivity of composites in the frequency range of 100–20 MHz. A 5 mm thick soft rubber shielding material is fabricated and the shielding performance is analysed by vector network analyser for a frequency range of 2 GHz–18 GHz. A significant enhancement in the shielding effectiveness of the polymer nanocomposite with different amounts of f-MWCNT loading is observed. Electron microscopy analysis (TEM and FESEM) clearly illustrate the excellent dispersion state and microstructural development of MWCNTs within the SBR matrix which in turn accounts for the increase in the shielding performance of the polymer nanocomposite. This work opens up new paradigm for EMI shielding applications based on soft elastomer with the aid of a sustainable and simplified methodology.

Radiation shielding and gamma ray attenuation properties of some polymers

In the present work we investigated the gamma radiation parameters as mass attenuation coefficients ?/?, the total atomic scattering cross-sections ??, the electronic scattering cross-sections se, the effective atomic numbers Zeff, and the effective electron densities Neff for some polymers such as polyoxymethylene (CH2O), poly acrylonitrile (C3H3N), natural rubber (C5H8), poly ethyl acrylate (C5H8O2), polyphenyl methacrylate (C10H10O2), and polyethylene tetraphthalate (C10H8O4). The gamma ray photons were detected by NaI(Tl) detector with resolution of 8.2 % at 662 keV, using radioactive gamma ray sources 57Co, 133Ba, 137Cs, 54Mn, 60Co, and 22Na at energies 122, 356, 511, 662, 840, 1170, 1275, and 1330 keV. Values of ?/? for the chosen polymers decrease with increasing energy. The results of investigated data are useful in plastic industry, building materials, agriculture fields radiation shielding, accelerator centers, polymer industry, medical field, etc.

Numerical investigations of electromagnetic processes in a solid cylindrical shield

A mathematical model is suggested to describe the processes in a solid cylindrical shield in protection against an alternating magnetic field. The model is constructed with respect to the complex amplitude of magnetic vector potential. Since magnetic field lines are in a plane perpendicular to the axis of a cylindrical shield, the problem becomes two-dimensional. The electromagnetic parameters of the considered media are constant and isotropic. The plates at which the magnetic potential is set are the source of the magnetic field. A distribution of real and imaginary components of the complex amplitude of magnetic potential is described by four differential equations in the conducting medium and by two equations in the dielectric one. An equality of magnetic potential at both sides of the interface is predetermined at the interfaces. The Robin boundary condition provides equality of the magnetic vector potential to zero at an infinite distance from the shield. The obtained differential equation system supplemented with the boundary conditions can be numerically solved by the finite elements method using the Galerkin method. As a result, distributions of magnetic potential and magnetic field intensity in the absence and presence of a shield are determined; shielding attenuation is then calculated. It is found that, with increasing shield thickness and noise frequency, the efficiency of electromagnetic shielding is increased. The adequacy of the suggested model and technique of determination of the shielding efficiency is corroborated by comparison with the results of an analytical model for a copper cylindrical shield.

Poly(3, 4-ethylene Dioxythiophene) Grafted Multiwalled Carbon Nanotube Decorated Polyurethane Foam For Antistatic And EMI Shielding Applications

The paper reports the designing of PEDOT grafted PU foam by in-situ emulsion polymerization of ethylene dioxy thiophene (EDOT) on polyurethane foam (PU) containing multi-walled carbon nanotube (MWCNT) and by coating PEDOT on PU foam and to study their antistatic and electromagnetic shielding behavior. Static decay time measurements reveal that PEDOT grafted PU foam shows static decay time ranging from 0.17 sec to 0.75 sec on going down from 5000 v to 500 volts. EMI shielding measurement of the foam in Ku-band shows a shielding attenuation of 8-10 dB which indicates that that the foam can find applications as antistatic encapsulation material in electronic packaging of high tech equipments. SEM studies of the foam shows a uniform coating of PEDOT on PU foam leading to better conductivity of the conducting foam which accounts for its better anti-static properties. Copyright © 2016 VBRI Press.

Dual percolation behaviors of electrical and thermal conductivity in metal-ceramic composites

The thermal and electrical properties including the permittivity spectra in radio frequency region were investigated for copper/yttrium iron garnet (Cu/YIG) composites. Interestingly, the percolation behaviors in electrical and thermal conductivity were obtained due to the formation of copper particles' networks. Beyond the electrical percolation threshold, negative permittivity was observed and plasmon frequency was reduced by several orders of magnitude. With the increase in copper content, the thermal conductivity was gradually increased; meanwhile, the phonon scattering effect and thermal resistance get enhanced, so the rate of increase in thermal conductivity gradually slows down. Hopefully, Cu/YIG composites with tunable electrical and thermal properties have great potentials for electromagnetic interference shielding and electromagnetic wave attenuation.

Enhanced electromagnetic shielding behavior of multi-walled carbon nanotube entrenched poly (3,4-ethylenedioxythiophene) nanocomposites

Exceptionally high electromagnetic shielding behavior shown by composites of poly (3,4-ethylenedioxythiophene)/multi-walled carbon nanotube (PCNT) which showed maximum shielding attenuation of 58 dB in the Ku-band. The electron micrographs confirm the wrapping of poly (3,4-ethylenedioxthiophene) (PEDOT) over multiwalled carbon nanotubes (MWCNTs) resulting in strong interfacial, electronic and space charge polarizations. The EMI shielding results showed that shielding by PCNT composites are mainly due to shielding effectiveness by absorption rather than shielding attenuation by reflection. Complex permittivity and permeability of composites have been calculated using scattering parameters (S11 and S21) based on theoretical calculations given in the Nicolson–Ross–Weir method. The composites were further characterized by Raman spectroscopy, TGA, XRD, and FTIR.

Neutron activation analysis of archaeological artifacts using the conventional relative method: a realistic approach for analysis of large samples

A new approach for analysis of entire potsherds of archaeological interest by INAA, using the conventional relative method, is described. The analytical method proposed involves, primarily, the preparation of replicates of the original archaeological pottery, with well known chemical composition (standard), destined to be irradiated simultaneously, in a well thermalized external neutron beam of the RP-10 reactor, with the original object (sample). The basic advantage of this proposal is to avoid the need of performing complicated effect corrections when dealing with large samples, due to neutron self shielding, neutron self-thermalization and gamma ray attenuation. In addition, and in contrast with the other methods, the main advantages are the possibility of evaluating the uncertainty of the results and, fundamentally, validating the overall methodology.

Super-high-frequency shielding properties of excimer-laser-synthesized-single-wall-carbon-nanotubes/polyurethane nanocomposite films

Electromagnetic shielding attenuation (ESA) properties of carbon nanotubes/polymer nanocomposite films, in the super high frequency (SHF) X-band (7–12 GHz) domain are studied. The nanocomposite films consisted of thermoset polyurethane (PU) resin blended with single-walled carbon nanotubes (SWCNTs) mats, and deposited on fused quartz substrates. Two different approaches were used to achieve the nanocomposite films, namely (i) through the on-substrate “all-laser” growth approach of SWCNTs directly onto substrate, followed by their infiltration by the PU resin, and (ii) by appropriately dispersing the chemically-purified SWCNTs (in the soot form) into the PU matrix and their subsequent deposition onto quartz substrates by means of a solvent casting process. Characterizations of the ESA properties of the developed nanocomposite films show that they exhibit systematically a deep shielding band, centered at around 9.5 GHz, with an attenuation as high as |− 30| dB, recorded for SWCNT loads of 2.5 wt. % and above. A direct correlation is established between the electrical conductivity of the nanocomposite films and their electromagnetic shielding capacity. The SWCNTs/PU nanocomposites developed here are highly promising shielding materials as SHF notch filters, as their ESA capacity largely exceeds the target value of |− 20| dB generally requested for commercial applications.

Evaluation of Lithium Gadolinium Borate Capture-Gated Spectrometer Neutron Efficiencies

Accurate determination of neutron dose equivalent requires knowledge of the neutron energy distribution. Existing neutron spectrometers, such as Bonner sphere sets, are typically bulky and require long acquisition times. Hence, a handheld or portable system that could perform area monitoring with acceptable accuracy would be of interest. Such a device will require a detector that is efficient, and possesses gamma-neutron discrimination capabilities. An organic scintillator that contains lithium, gadolinium, and boron, all three of which possess isotopes with large neutron capture cross-sections for highly exothermic reactions, has been recently developed by MSI/Photogenics. This combination of materials provides for the detection of fast neutrons by proton recoil which when used in conjunction with a slow neutron capture gate allows total energy information to be obtained. The system also responds to gamma-rays but n-gamma discrimination techniques allow it to be applied in mixed fields. Photogenics recently completed the full demonstration of a Lithium Gadolinium Borate (LGB) neutron spectrometer's performance under a Department of Homeland Security Domestic Nuclear Detection Office (DNDO) grant. A potential application suggested for this technology is in the identification of shielded fissile materials. A 2" times 2" (50.8 mm times 50.8 mm) sample of composite scintillator, consisting of lithium gadolinium borate crystals in a plastic scintillator matrix, produced by Photogenics has been tested for this purpose. The Tests consist of verifying the n-gamma discrimination and measurements of both capture and capture gated efficiencies using <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">252</sup> Cf and Am-Li neutron sources of various activities under a variety of gamma shielding and neutron attenuation geometries. The results, for this small test sample, showed that in addition to its rudimentary spectroscopic capability, the Photogenics LGB detector has a overall neutron detection efficiency that is attractive for handheld applications.

Body size-dependent patient effective dose for diagnostic radiography

The health-related mean absorbed dose to organs and tissues and the effective dose were usually calculated from the entrance surface dose (ESD) using computational phantoms by the Monte Carlo method. Because these phantoms represented an average adult with simplified organ shape and position within the body, the calculated results were hypothetical doses to the phantom but not to the patient. In order to determine the patient doses, the body size of individual patients should be taken into consideration. In the present work, two approaches were adopted to estimate the radiological thickness of a patient which determined the overlying tissue shielding and photon attenuation in the calculation of organ and effective doses. The first approach involved the determination of this thickness from patient body weight and height. It was found that the body mass index (BMI) was approximately linearly proportional to the body thickness. Therefore, the BMI was used to determine the size-dependent organ and effective doses from patient ESDs measured by the thermoluminescent dosimeters. To verify the applicability of BMI, WinODS software was employed to compute the organ and effective doses using the size- and sex-adjustable anthropomorphic phantom. The second approach involved the estimate of body thickness from the transmission factor, defined as the ratio of exit surface dose to ESD. The transmission factor was measured using polyethylene phantoms of varying thicknesses. Also, a backscatter factor, defined as the ratio of ESDs with and without the presence of patient, was measured using polyethylene phantoms of varying thicknesses.

A reanalysis of the Collaborative Ocular Melanoma Study Medium Tumor Trial eye plaque dosimetry

Purpose To recalculate the radiation doses delivered to structures of interest within the eye, i.e., the lens, tumor apex, 5-mm point, optic disk, and macula for patients treated with eye plaque radiotherapy on the Collaborative Ocular Melanoma Study (COMS) Medium Tumor Trial, using updated dosimetric data. Methods and materials Using the Plaque Simulator planning system, doses were recalculated for a sampling of COMS patients for each plaque size. Dosimetry parameters incorporated into the recalculation were line source approximation, a 90% Silastic transmission factor, and a 0% gold transmission factor. Generic solutions were generated from the dose recalculations for each plaque size and structures of interest combination. Doses for the remainder of the patient population were recalculated using the generic solutions and compared with the originally reported COMS doses. Results Doses to all structures of interest were reduced 7%–21%, depending on the plaque size and structure combination. The reduction in dose for the macula, optic disc, lens, tumor apex, and 5-mm point was on average 10%, 18%, 8%, 11%, and 12%, respectively. The closer the macula and optic disk were to the plaque rim, the greater the dose reduction. Incorporation of the Silastic transmission factor accounted for a large part of the dose reduction. Conclusions Incorporating anisotropy, line source approximation, and Silastic and gold shield attenuation into dose recalculations resulted in a significant and consistent reduction of doses to structures of interest within the eyes.

Electrical and impact properties of the hybrid knitted inlaid fabric reinforced polypropylene composites

A range of conductive knitted fabric reinforced polypropylene composites have been developed and their electromagnetic shielding effectiveness (EMSE), electrostatic discharge (ESD) and impact properties have been investigated. Carbon and aramid fibers are used as the reinforcement phase in the composites, while copper and stainless steel wires are incorporated as conductive fillers to provide the ESD and EMSE properties of the composite materials. The hollow spindle spinning system has been used to make SS/PP, Cu/PP, SS/C/PP, Cu/C/PP and Cu/K/PP uncommingled yarns. The double plain knitted fabric and its inlaid fabrics were fabricated from the yarns using a 5G traverse knitted machine. Changing the yarn composition, fabric knit structure, and stitch density varies the amount of copper and stainless steel conductive fillers in the composites. 4 layer cross-ply laminates were laid-up by hand, then formed into 3-mm thick conductive thermoplastic composites using a compression molding. It was observed that the EMSE and ESD of the composites increase with increasing the incident frequency, especially at higher frequency range. The effects of inlaid ends, materials and yarn constitutions on the EMSE of the conductive thermoplastic composites were investigated. The results indicate that the composites can be used for the purpose of electromagnetic shielding and ESD attenuation, as well as for some microwave applications.

Shielding Design Study of the Demonstration Fast Breeder Reactor (1) -Evaluation of the JASPER Experiment and Its Analytical Results -

The JASPER Experiment had been conducted to obtain useful information on FBR shielding analysis accuracy. Results obtained from the post-experimental analyses are summarized in this paper. Both characteristics for bulk shielding attenuation and streaming of neutron through configurations consisting of several materials including B4C, stainless steel, sodium and etc. were clarified and the analysis accuracy confirmed. The shielding analysis system for fast reactors has been improved and verified. These experimental data and analytical results were reviewed from a viewpoint of the applicability to the shielding design analysis of the DFBR. Useful information to be utilized in the design study of the DFBR is accumulated through those activities.

大型高速炉遮蔽解析手法の開発 ＪＡＳＰＥＲ（日米共同高速炉遮蔽実験）実験解析の成果

All experiments planned in the JASPER, Japanese-American Shielding Program for Experimental Research, had been conducted between 1986 and 1992 under the cooperation between the U.S. Department of Energy and Power Reactor and Nuclear Fuel Development Corporation of Japan to obtain useful information on FBR shielding analysis accuracy. Tower Shielding Facility (TSF) of Oak Ridge National Laboratory was utilized for all the measurements. Results obtained from the post-experimental analyses are summarized in this report. Both characteristics for bulk shielding attenuation and streaming of neutron through configurations consisting of several materials including boron-carbide (B4C), graphite, stainless steel, sodium and etc. were clarified and the analysis accuracy confirmed. Prediction accuracy in both shielding property for configuration containing fissile material and sodium activation characteristics was confirmed. The shielding analysis system for fast reactors using a 2-dimensional discrete ordinates code as a standard has been improved and verified. Through those activities, useful information to be utilized in designing large FBR is accumulated.

Development of a shielded 241Am applicator for continuous low dose rate irradiation of rat rectum

This paper describes the development of sources, applicators, and techniques that can be used to irradiate rat rectums with continuous irradiation at dose rates of interest in brachytherapy, either with the full circumference of the rectum irradiated, or with half of the circumference shielded from the radiation. The system uses encapsulated 241Am sources, to irradiate rat rectum with 60 keV photons continuously at a dose rate of up to 50 cGy/hr. Details of the design and fabrication of the 241Am sources, the rectal applicator, the dosimetry of the system, and the protocols for preparing and irradiating the rats, and for detecting early rectal injury using histological examination of irradiated rectum are presented. Highly effective shielding (attenuation factors as low as 0.04) of half of the circumference of the rat rectum was achievable. Unidirectional 241Am irradiators for intracavitary brachytherapy offer a unique tool for examining the effects of shielding a portion of the circumference of the rat radiation tolerance of the rectum.

Sensitivity/Uncertainty Analysis for Free-in-Air Tissue Kerma Due to Initial Radiation at Hiroshima and Nagasaki

Uncertainty estimates and cross correlations by range/survivor have been calculated for the Hiroshima and Nagasaki free-in-air (FIA) tissue kerma obtained from two-dimensional air/ground transport calculations. The uncertainties due to modeling parameter and basic nuclear transport data uncertainties were calculated for 700-, 1000-, and 1500-m ground ranges. Only the FIA tissue kerma due to initial radiation was treated in the analysis; the uncertainties associated with terrain and building shielding and phantom attenuation were not considered in this study. Uncertainties of --20% were obtained for the prompt neutron and secondary gamma kerma and 30% for the prompt gamma kerma at both cities. The uncertainties on the total prompt kerma at Hiroshima and Nagasaki are --18 and 15%, respectively. The estimated uncertainties vary only slightly by ground range and are fairly highly correlated. The total prompt kerma uncertainties are dominated by the secondary gamma uncertainties, which in turn are dominated by the modeling parameter uncertainties, particularly those associated with the weapon yield and radiation sources.

Shielding of Cylindrical Tubes

Shielding attenuation values at low frequencies have been computed for magnetic and nonmagnetic cylindrical tubes based on formulas developed by King.[2] The attenuation in decibels was computed on a digital computer for a range of ratios of wall thickness to depth of penetration from 0.1 to 10 as a function of a nondimensional parameter as used by Kaden.[4] Two graphs are presented that summarize the computer results.

Design of Minimum Weight and Maximum Effectiveness of Very-Low-Frequency Shielding

Shielding equations developed in a research program were used to generate data for use in the design of an optimum shield for a given set of constraints (a prescribed shielding level, minimum weight shield, etc.). Analysis consisted chiefly of computer processing of the modified equations. To reduce computer time, only symmetrical laminated shielding material was considered. Maximum shielding attenuation with respect to overall shield weight was considered for two cases, using the transmission theory of uniform shielding: 1) the lightest shield for a specified level of attenuation, and 2) the shield providing maximum attenuation within specified constraints of shield weight.