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Publication Date: 2024
Catena (03418162) 244
This study investigated the impacts of two land uses, namely natural oak forests and abandoned rainfed farming, on the long-term redistribution of soil properties in the hilly regions of the semi-arid western part of Iran. We assessed cesium-137 (137Cs) levels in the soil to determine soil erosion and sedimentation rates. We explored the consequences of deforestation and the conversion of an oak forest to rainfed farmland abandoned for over a decade. We measured various soil properties, including magnetic susceptibility, aggregate stability, and soil organic carbon (SOC) levels in different soil fractions. For both forest and abandoned rainfed farming land uses, three slope positions (upper, mid, and lower) were selected. Two soil samples were collected from a depth of 0–20 cm from each slope position. 137Cs analysis revealed that the greatest 137Cs loss occurred at the upper-slope position in both the natural forest (14.5 %) and abandoned rainfed farming (74.1 %) land use. A simplified mass balance model demonstrated average erosion rates of 109 and 706.2 t ha−1 yr−1 in the natural forest and abandoned rainfed farming areas, respectively. The highest erosion rates were recorded at the upper-slope positions of both land-use areas, which was primarily attributed to lower soil organic matter (SOM) and vegetation. Furthermore, we observed lower magnetic susceptibilities in the upper-slope position of both land uses, coinciding with the areas experiencing the highest levels of soil loss. Particulate organic carbon and total nitrogen contents in the sand-sized and larger aggregates in the natural forest land use were significantly higher compared to those in the abandoned rainfed farming land use (p < 0.05). A similar trend was observed for the SOC content associated with various aggregate sizes. In conclusion, the conversion of forest land use to abandoned rainfed farming land use on slopes can lead to soil degradation and redistribution due to accelerated soil erosion and deposition. © 2024 Elsevier B.V.
Publication Date: 2024
Biomedical Physics and Engineering Express (20571976) 10(2)
The inherent biological hazards associated with ionizing radiation necessitate the implementation of effective shielding measures, particularly in medical applications. Interventional radiology, in particular, poses a unique challenge as it often exposes medical personnel to prolonged periods of high x-ray doses. Historically, lead and lead-based compounds have been the primary materials employed for shielding against photons. However, the drawbacks of lead, including its substantial weight causing personnel’s inflexibility and its toxicity, have raised concerns regarding its long-term impact on both human health and the environment. Barium tantalate has emerged as a promising alternative, due to its unique attenuation properties against low-energy x-rays, specifically targeting the weak absorption area of lead. In the present study, we employ the Geant4 Monte Carlo simulation tool to investigate various formulations of barium tantalate doped with rare earth elements. The aim is to identify the optimal composition for shielding x-rays in the context of interventional radiology. To achieve this, we employ a reference x-ray spectrum typical of interventional radiology procedures, with energies extending up to 90 keV, within a carefully designed simulation setup. Our primary performance indicator is the reduction in air kerma transmission. Furthermore, we assess the absorbed doses to critical organs at risk within a standard human body phantom protected by the shield. Our results demonstrate that specific concentrations of the examined rare earth impurities can enhance the shielding performance of barium tantalate. To mitigate x-ray exposure in interventional radiology, our analysis reveals that the most effective shielding performance is achieved when using barium tantalate compositions containing 15% Erbium or 10% Samarium by weight. These findings suggest the possibility of developing lead-free shielding solutions or apron for interventional radiology personnel, offering a remarkable reduction in weight (exceeding 30%) while maintaining shielding performance at levels comparable to traditional lead-based materials. © 2024 The Author(s). Published by IOP Publishing Ltd.
Publication Date: 2023
Scientific Reports (20452322) 13(1)
Runaway electrons are a notable phenomenon occurring during the operation of a tokamak. Proper material selection for the tokamak's first wall structure and plasma facing components, particularly in large sizes tokamaks like ITER and DEMO, is crucial due to the energy deposition of runaway electrons on plasma facing components during collision events, resulting in severe heat transfer and material damage in the form of melting, corrosion, and fracture. These runaway electrons also contribute to the production of photoneutrons through (γ, n) nuclear reactions, lead to material activation and require remote handling. In this study, using a Monte Carlo code and simulating the collision of runaway electrons with a tungsten target exposed to their radiation, the electron transport is investigated, and the energy deposition spectrum resulting from these collisions on the target is analyzed. The influence of incident angle and magnetic field on the energy deposition spectrum and the energy deposition per particle in the target is examined. With an increase in the incident angle of incoming electrons, the amount of energy deposited in the target rises and the energy deposition spectrum broadens. Moreover, applying a magnetic field, results the most significant increase in energy deposition for electrons with energies below 1 MeV in the tangential radiation case. The energy deposition spectrum resulting from each collision event in these interactions is determined. For electrons with energies below 5 MeV, multiple scattering and ionization processes are the primary contributors to energy deposition in the target. However, as the incident electron energy increases, the significance of multiple scattering and ionization diminishes, and the bremsstrahlung process becomes the most effective reaction in energy deposition. The energy deposition profile of electrons in the tungsten target indicates that higher incident electron energies lead to a shift of the maximum energy deposition location towards the inner layers of the target, and the energy deposition peak broadens. Analyzing the electrons transport inside the tungsten target reveals that a substantial portion of electrons with energies of 50–100 MeV passes through the wall and may exit from the back surface, potentially causing damage to equipment behind the tungsten wall. Additionally, secondary products of the reaction, such as photons, secondary electrons, and neutrons and their energy profiles are thoroughly studied. These secondary products can penetrate the target and activate materials in the equipment behind the plasma-facing components. For primary electrons below 1 MeV hitting tungsten, reflection process is significant. Analysis of primary and secondary runaway electrons in the tokamak's tungsten wall shows that electrons with energies of 0.1, 0.2, and 0.5 MeV predominantly interact within a first 0.1 mm layer, without passing through it. The secondary electrons can escape the tungsten target and impact other components, which making them an important consideration in runaway electron collisions with the tokamak wall. Produced photons, as one of the secondary products, also linearly increase with the rising energy of primary electrons. Also, the photoneutrons are produced only when runaway electrons with energies of 10 MeV and above collide with the target. These secondary products can penetrate the target and activate materials in the equipment behind the plasma-facing components. © 2023, The Author(s).
Publication Date: 2022
Agronomy (20734395) 12(2)
This study was executed to explore soil redistribution and soil quality changes induced by land degradation and then rehabilitation by orchard plantation in different slope positions in a semi-arid region in central Iran. A total of 72 surface soil samples (0–30 cm) were collected from three land uses (natural rangelands, dryland farming, and apple orchards) in four slope positions (shoulder, backslope, footslope, and toeslope). The soil physicochemical properties and magnetic parameters were measured, and soil redistribution was determined in the selected soil samples using the137Cs technique. The results showed that rangeland degradation and, subsequently, rainfed cultivation, led to a significant decline in the soil quality indicators, such as soil organic matter (SOM), total nitrogen (TN), available potassium (Kava), and available phosphorous (Pava), thus incurring further soil loss, as determined by the137Cs technique. Conversely, the conversion and rehabilitation of drylands to apple orchards cultivated on the contour terraces improved soil quality significantly and decreased soil loss (p < 0.05) and soil quality grade (p < 0.01). Additionally, the findings indicated that slope positions relative to land use change had a reasonable impact on the variability of soil properties and soil loss and deposition. The results of137Cs analysis showed that the drylands had the highest soil loss (185.3 t ha−1 yr−1) and maximum sedimentation (182. 5 t ha−1 yr−1) in the shoulder and footslope positions, respectively. The random forest model applied between137Cs inventory and soil properties indicated that calcium carbonate equivalent (CCE), TN, Pava, Kava, and bulk density (ρb) could explain 75% of the total variability in137Cs inventory with high R2 (0.94) and low RMSE (111.29). Magnetic measurements have shown great potential as a cost-effective and fast method for assessing soil redistribution in hilly regions, as confirmed by the findings of the137Cs analysis, which agreed well with the magnetic susceptibility at low frequency (χlf). Overall, the results confirmed that restoring abandoned dryland by orchard cultivation may improve soil quality and diminish soil loss in the semi-arid region of Iran. However, further research is required to assess other aspects of the ecosystem affected by this restoration. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
Publication Date: 2021
Applied Radiation and Isotopes (09698043) 176
Nanocrystalline Gd2O2S:Pr powders were successfully synthesized by the co-participation method. The changes of size, shape and luminescence properties of these nanocrystalline powders were studied under different gamma doses (0–50 kGy) during the synthesizing process. Also, the structural, morphology and luminescence properties of these nanocrystalline powders were characterized using the X-ray diffraction, field emission scanning electron microscopy, energy dispersion of X-ray spectroscopy, photoluminescence, and thermoluminescence. The XRD results confirmed that the nanocrystalline Gd2O2S:Pr powders have a pure hexagonal structure with the high crystallinity at a temperature of 900 °C, and the gamma radiation doses have no effect on the structure. The SEM images showed that the nanocrystalline Gd2O2S:Pr powders have a spherical shape and are agglomerated when the irradiation dose increases. These nanopowders, which were prepared at an irradiation dose of 40 kGy, show the lowest crystallite size and hence the highest intensity of emission peaks at the wavelengths of 506, 515 and 671 nm, which are corresponded to the transitions of the 3P1–3H4, 3P0–3H4 and 3P0–3F2 of Pr ions, respectively. The X-ray radiography image was obtained by the screen of Gd2O2S:Pr nanopowders (prepared at 40 kGy gamma dose), coupled with a radiographic film. The TL glow curves of the sample, prepared at 40 kGy gamma dose, were recorded under the X-ray irradiation in the times of 5 and 10 min. The heating rate and preheat temperature were obtained 2 and 50 °C, respectively. The obtained results were investigated in details. © 2021 Elsevier Ltd
Publication Date: 2021
Forest Ecosystems (21975620) 8(1)
Background: As one of the main components of land-use change, deforestation is considered the greatest threat to global environmental diversity with possible irreversible environmental consequences. Specifically, one example could be the impacts of land-use changes from oak forests into agricultural ecosystems, which may have detrimental impacts on soil mobilization across hillslopes. However, to date, scarce studies are assessing these impacts at different slope positions and soil depths, shedding light on key geomorphological processes. Methods: In this research, the Caesium-137 (137Cs) technique was applied to evaluate soil redistribution and soil erosion rates due to the effects of these above-mentioned land-use changes. To achieve this goal, we select a representative area in the Lordegan district, central Iran. 137Cs depth distribution profiles were established in four different hillslope positions after converting natural oak forests to rainfed farming. In each hillslope, soil samples from three depths (0–10, 10–20, and 20–50 cm) and in four different slope positions (summit, shoulder, backslope, and footslope) were taken in three transects of about 20 m away from each other. The activity of 137Cs was determined in all the soil samples (72 soil samples) by a gamma spectrometer. In addition, some physicochemical properties and the magnetic susceptibility (MS) of soil samples were measured. Results: Erosion rates reached 51.1 t·ha− 1·yr− 1 in rainfed farming, whereas in the natural forest, the erosion rate was 9.3 t·ha− 1·yr− 1. Magnetic susceptibility was considerably lower in the cultivated land (χhf = 43.5 × 10− 8 m3·kg− 1) than in the natural forest (χhf = 55.1 × 10− 8 m3·kg− 1). The lower soil erosion rate in the natural forest land indicated significantly higher MS in all landform positions except at the summit one, compared to that in the rainfed farming land. The shoulder and summit positions were the most erodible hillslope positions in the natural forest and rainfed farming, respectively. Conclusions: We concluded that land-use change and hillslope positions played a key role in eroding the surface soils in this area. Moreover, land management can influence soil erosion intensity and may both mitigate and amplify soil loss. © 2021, The Author(s).
Publication Date: 2021
Arabian Journal of Geosciences (discontinued) (18667538) 14(2)
Post-fire erosion is a main concern to society because it has inflicted serious damages in managed ecosystems. In this study, the impacts of fire and time after fire events on soil erosion (as predicted using 137Cs technique) and on some soil chemical and physical properties were investigated in steep rangelands of western Iran. Three sites in rangelands with similar slope gradients and parent materials were selected, and within each site, the burnt (1, 5, and 10 years after the fire events) and the unburnt treatments were studied and soil samples were collected from five depths (0–2.5, 2.5–5, 5–10, 10–20, and 20–40 cm) with three replicates. The results indicated that soil organic matter (SOM), total nitrogen (TN), available phosphorus (Pava), available potassium (Kava), electrical conductivity (EC), and bulk density (BD) were significantly different between burnt and unburnt treatments for two times (1 and 5 years) after fire events. No significant difference by Duncan’s test was obtained for these properties between the 10 and 5 years after fire events. In addition, clay and sand contents and magnetic measures (χlf, χhf) were significantly different between burnt and unburnt treatments for all the three times after fire. The results of soil erosion by the 137Cs technique showed that profile distribution model (PDM) estimated the mean soil erosion rate of 38.9 and 23.02 Mg ha−1 year−1 in the three studied years in the burnt and the unburnt rangelands, respectively. Fire events increased soil erosion rate and altered soil physical, chemical, and magnetic properties in the studied steep rangelands. Overall, the results confirmed that the 137Cs technique could be used as a rapid and efficient model to determine soil degradation in the rangelands. The fire diminished soil organic matter and, subsequently, reduced aggregate stability, and increased soil erosion and degradation in the burnt rangelands. Hence, understanding historical contexts of fire occurrences is paramount to increase our capacity for ecological transformations and management in the face of the critical situation. © 2021, Saudi Society for Geosciences.
Publication Date: 2020
Journal of Luminescence (00222313) 219
In this study, single phase cerium-doped Gd2SiO5 (GSO:Ce) nanopowders were successfully synthesized by a Pechini sol-gel process, and the effect of calcination temperature on the crystallinity and purity of GSO phase was investigated by XRD and FTIR analyses. The suitable temperature for calcination of nanopowders and the formation of single phase GSO is estimated to be about 1250 °C. The morphology of samples, elemental composition, and nanoparticle size distribution of the single phase sample were examined by using FESEM, EDX, and DLS analyses. In addition to crystallite size and crystal lattice strain, the crystal lattice parameters of this sample were obtained using a series of equations, the results of which are very close to those obtained from the Rietveld refinement method. Studies show that unlike undoped GSO single crystal, the optical absorption spectra of synthesized GSO nanopowders are continuous and doping with 2 mol% cerium causes the highest photoluminescence intensity at 435 nm under excitation at 345 nm. The scintillation pulse height spectra of these samples were also investigated under alpha radiation. Finally, the importance of selecting the appropriate calcination temperature and its effect on the size of the nanoparticles, photoluminescence intensity, and scintillation pulse height spectrum has been studied. © 2019 Elsevier B.V.
Publication Date: 2018
Journal of Luminescence (00222313) 194pp. 424-427
This paper studies a new CsI: Eu2+ nanocrystal was synthesized via the sol-gel method. The structural properties of CsI: Eu2+ nanocrystal were characterized by Scanning Electron Microscope (SEM). Optical properties were followed by absorption and emission spectroscopy. Two absorption band peaking at 300 and 370 nm and two emission band with a maximum of 420 and 500 nm were observed. The dominance of 4f65d → 4f7 radiative transitions which were observed for the Eu bands in CsI nanocrystal caused these luminescence bands. Scintillation spectra and decay curve to alpha particles of the sample were monitored and they compared with the results obtained in pure CsI nanocrystal. © 2017 Elsevier B.V.
Publication Date: 2018
Iranian Journal of Physics Research (16826957) 18(3)pp. 369-377
In the present study, the most useful stainless steels in nuclear industry, i.e. 304, 304L and 316L, were provided and laser cut into the 0.5×0.5 cm dimension. Then the effects of radiation on the physical properties of the samples were investigated. Gamma irradiation on the samples was done with a60Co radioisotope to the doses of 100 and 200 kGy. The resistance of the samples was measured through the four-probe technique, also, the special resistance and the electrical conductivity of the samples were measured from resistance. The conductivity of the samples was obtained through Widman-Frantz. The magnetic properties of the samples were also measured by the vibrating sample magnetometer. Changes in the aforementioned properties before and after the irradiation were investigated in terms of thermal and time effects. © 2019, Isfahan University of Technology. All rights reserved.
Publication Date: 2017
Chinese Journal of Chemical Engineering (10049541) 25(6)pp. 782-792
The main purpose of this work was the modification of NaX nanozeolite using copper oxide nanoparticles and various monovalent cations such as K+, Cs+, and Ag+ in order to make the negatively charged zeolite surface accessible for anionic forms of uranium which are the most dominant species of uranium in the contaminated radioactive waters at natural pH. Various methods such as the X-ray fluorescence (XRF), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and atomic absorption spectroscopy (AAS) were used to characterize the final synthesized absorbents. Batch technique was used to study the adsorption behavior of uranium ions from polluted drinking water by NaX nanozeolite and its modified forms. In order to better understand the performance of them, the results were compared with those that were obtained for synthesizing bulk NaX zeolite and Na-form of clinoptilolite natural zeolite. Preliminary results indicated that uranium sorption increased as the loading level of CuO nanoparticles on NaX nanozeolite increased from 2.1 wt% to 11.2 wt%. In addition, from the obtained data, an increase in uranium removal efficiency resulted as charge/ionic radius ratio of exchanged cation decreased. Also, the effect of contact time, solid–liquid ratio, initial concentration and temperature on the adsorption process was studied. It is worth mentioning that, in this study, the sorption of uranium was performed under natural conditions of pH and the presence of competing cations and anions which are available in drinking waters. © 2016 Elsevier B.V.
Publication Date: 2017
Plasma Physics Reports (15626938) 43(3)pp. 280-288
Some experiments for studying the runaway electron (RE) effects have been performed using the poloidal magnetic probes system installed around the plasma column in the Damavand tokamak. In these experiments, the so-called runaway-dominated discharges were considered in which the main part of the plasma current is carried by REs. The induced magnetic effects on the poloidal pickup coils signals are observed simultaneously with the Parail–Pogutse instability moments for REs and hard X-ray bursts. The output signals of all diagnostic systems enter the data acquisition system with 2 Msample/(s channel) sampling rate. The temporal evolution of the diagnostic signals is analyzed by the conditional average sampling (CAS) technique. The CASed profiles indicate RE collisions with the high-field-side plasma facing components at the instability moments. The investigation has been carried out for two discharge modes—low-toroidal-field (LTF) and high-toroidal-field (HTF) ones—related to both up and down limits of the toroidal magnetic field in the Damavand tokamak and their comparison has shown that the RE confinement is better in HTF discharges. © 2017, Pleiades Publishing, Ltd.
Publication Date: 2016
Journal of Materials Science (15734803) 51(22)pp. 9991-10004
In this study, a novel PAN/NaX/ZnO nanocomposite absorbent was introduced and its ability to remove of uranium anionic species, which are the most dominant species of uranium in water at natural pH, from contaminated waters was studied. In this regards, micro and nano sized NaX zeolite and PAN/NaX/ZnO nanocomposite were successfully synthesized and characterized using various methods, including X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), atomic absorption spectroscopy (AAS), and Brunauer–Emmett–Teller (BET) specific surface area analysis. Batch technique was used to study the adsorption behavior of uranium ions from contaminated water as a function of solid–liquid ratio, initial uranium concentration, contact time, and temperature. Results showed that although NaX nanozeolite due to its negative framework charge, showed low sorption capacity for adsorption of uranium anionic species but the composite of it with ZnO nanoparticles and polyacrylonitrile (PAN) effectively improved its uranium adsorption capacity. The novel PAN/NaX/ZnO nanocomposite could selectively remove uranium ions from contaminated water with removal efficiency of more than 98.65 % in the presence of all anions and cations which are available in waters. © 2016, Springer Science+Business Media New York.
Publication Date: 2016
Optical Materials (09253467) 55pp. 22-26
We report on the synthesis of cesium-iodide nanoparticles using sol-gel technique. The structural properties of CsI nanoparticles were characterized by X-ray diffraction and optical properties were followed by optical absorption and UV-vis fluorescence. Intense photoluminescence is also observed, with some spectral tuning possible with ripening time getting a range of emission photon wavelength approximately from 366 to 350 nm. The size effect on CsI luminescence leads to an increase in scintillation light yield, a redshift of the emission bands of the on-center and off-center self-trapped excitons (STEs) and an increase in the contribution of the off-center STEs to the net intrinsic emission yield. The energy transfer from the matrix to CsI nanoparticles is a key characteristic for scintillation detectors. So the scintillation spectra and decay curve to alpha particles of sample were monitored. © 2016 Elsevier B.V. All rights reserved.
Publication Date: 2016
Iranian Journal of Physics Research (16826957) 16(3)pp. 97-101
In this study, some characteristics of a Mather type Plasma Focus (PF) device such as a discharge current, pinch time, ion flux and hard x-ray intensity has been investigated simultaneously in argon and nitrogen gases separately for various operating gas pressures and charging voltages of capacitor bank. It was observed that pinch phenomena was energy and pressure dependent in current sheath as well as ion and hard x-ray emission intensity. Optimum pressure with maximum ion flux and the most intense hard x-ray showed a nearly linear dependence on the charging voltage of the device. Maximum ion flux was estimated in the order of 1018 ions per steradian in both gases. Hard x-ray emission was registered a little after discharge current and Faraday cup (FC) signals. Also, optimum pressure for maximum ion flux was not the same as the pressure for intense hard x-rays. Hard x-ray intensity reached its peak at higher pressures. © 2016, Isfahan University of Technology. All rights reserved.
Publication Date: 2016
Journal of Isfahan Medical School (10277595) 34(371)
Background: The aim of this study was to investigate organ absorbed dose for the patients undergoing routine x-ray imaging procedures in hospitals under the control of Yasuj University of Medical Sciences, Iran, in year 2014 using experimental measurement and Monte Carlo calculations. Methods: Entrance surface dose for three common radiology examinations in five radiology centers was measured. The entrance surface dose was measured in 12 randomly selected patients (male and female) for each x-ray examination. Patients were not exposed to any additional radiation and the radiographs were used for diagnostic purposes. Findings: The entrance surface dose for the chest x-ray examinations were found to be in the range of 0.29 to 1.284 mGy. The ESD values for the skull examinations were in the range of 1.96 to 3.8 mGy. For both chest and skull examinations, females received the maximum imposed radiation dose. Conclusion: The results of the present study indicate a need for quality control (QC) and quality assurance (QA) programs to be undertaken to avert high cost and high patient doses. The recommendations to avoid unnecessary radiation exposure are also needed to decrease the patient’s absorbed dose. © 2016. Isfahan University of Medical Sciences(IUMS). All rights reserved.
Publication Date: 2016
Microporous and Mesoporous Materials (13871811) 234pp. 257-266
A novel PAN/AgX/ZnO nanocomposite was synthesized and used for the removal of uranium ions from contaminated waters. NaX nanozeolite was successfully synthesized using the hydrothermal technique. Ion exchange method was used to modify it by Ag+ cations. Then ZnO nanoparticles were loaded on the AgX nanozeolite by the ion exchange method which was followed by a calcinations process. Various characterization methods such as X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), and atomic absorption spectroscopy (AAS) were utilized to analyze the synthesized absorbents including bulk NaX zeolite, NaX nanozeolite, and PAN/AgX/ZnO nanocomposite. The experiments of uranium adsorption were conducted at different solution temperatures, contact times, initial uranium ion concentration and adsorbent dose by using batch method. Results showed that the novel PAN/AgX/ZnO adsorbent had a better adsorption performance rather than the micro and nano sized NaX zeolite. This demonstrated the immense potential of newly synthesized adsorbent as an alternative adsorbent for heavy metal ion remediation in polluted waters and wastewaters. © 2016 Elsevier Inc.
Publication Date: 2016
Applied Radiation and Isotopes (09698043) 118pp. 43-55
In order to efficiently remove of uranium anionic species (which are the most dominant species of uranium in natural water at neutral pH) from contaminated waters, nano-NaX zeolite was synthesized and then modified using various divalent cations (Mg2+, Ca2+, Mn2+) and ZnO nanoparticles (from 1.7 to 10.3 wt%). Different characterization techniques of XRF, XRD, FE-SEM, TEM, FT-IR, and AAS were used to characterize the final synthesized absorbents. Sorption experiments by batch technique were done to study the effect of solid-liquid ratio, initial uranium concentration, contact time and temperature under neutral condition of pH and presence of all anions and cations which are available in the waters. Results showed that although nano-NaX zeolite due to its negative framework charge had a low sorption capacity for adsorption of uranium anionic species, but modification of parent nano-NaX zeolite with ZnO nanoparticles and various cations effectively improved its uranium adsorption capacity. Also, results showed that under optimum condition of pH=7.56, contact time of 60 min at 27 °C with solid-liquid ratio of 20 g/L a maximum uranium removal efficiency of 99.7% can be obtained in the presence of all anions and cations which are available in the drinking waters by NaX/ZnO nanocomposite. © 2016 Elsevier Ltd
Publication Date: 2016
Physics of Plasmas (1070664X) 23(7)
The time and position behavior of runaway electrons at the Parail-Pogutse instability moments has been investigated using experimental observations in plasma current, loop voltage, the Hard X-ray (HXR) radiations, and 18 poloidal pickup coils signals received by data acquisition system simultaneously. The conditional average sampling (CAS) method was used to analyze the output data. Moreover, a filament current code was modified to study the runaway electrons beam movement in the event of instabilities. The results display a rapid drift of runaway beam toward the inner wall of the vacuum vessel and the collision with the wall components at the instability moments. The existence of the collisions in these experiments is evident in the HXR bursts which are considered as the main trigger for CAS Analysis. Also, the variation of HXR bursts with the toroidal magnetic field shows that the hard X-ray bursts drop with increase in the toroidal magnetic field and runaway electrons confinement quality. © 2016 Author(s).
Publication Date: 2016
Journal of Sol-Gel Science and Technology (15734846) 78(2)pp. 313-321
Thin film of CsI was deposited on glass substrate using the sol–gel technique. The different surface morphology of sol–gel films with respect to evaporated films can be assumed as the main cause of the more QE (quantum efficiency) of sol–gel CsI films. The thin films were characterized by scanning electron microscopy, Atomic force microscopy and X-ray diffraction, and optical properties were followed by optical absorption and UV–vis fluorescence. Also, thin films and bulk samples were studied by fluorescence spectroscopy. The increased contribution of emission spectrum of the nanocrystal in thin film samples in comparison with bulk was observed. In thin films, nanocrystals are more closely in contact with the network and this affects the luminescence features. So the energy transfer from the matrix to nanocrystals, which is a key characteristic for scintillation detectors, was investigated in the two systems. Scintillation tests were performed on the CsI thin film and bulk sample by photo multiplier tube-based material exposed to alpha irradiation. Graphical Abstract: Thin film of CsI was deposited on glass substrate using the sol–gel technique. The increased contribution of emission spectrum of the nanocrystal in thin film samples in comparison with bulk was observed. Also, the energy transfer from the matrix to nanocrystals, which is a key characteristic for scintillation detectors, was investigated in the two systems. Figure 3 shows the SEM image of CsI thin film. SEM studies shows that the particles are distributed uniformly and mostly of homogeneous morphology at high magnification. SEM image of CsI thin film with the molar ratio about 10:1 for EtOH:TEOS and nine times deposited at magnification 100 kx. [Figure not available: see fulltext.] © 2016, Springer Science+Business Media New York.
Publication Date: 2016
Journal of Environmental Radioactivity (18791700) 165pp. 86-92
137Cs technique has been widely used for the evaluation rates and patterns of soil erosion and deposition. This technique requires an accurate estimate of the values of 137Cs inventory at the reference site. This study was conducted to evaluate the variability of the inventory of 137Cs regarding to the sampling program including sample size, distance and sampling method at a reference site located in vicinity of Fereydan district in Isfahan province, west-central Iran. Two 3 × 8 grids were established comprising large grid (35 m length and 8 m width), and small grid (24 m length and 6 m width). At each grid intersection two soil samples were collected from 0 to 15 cm and 15–30 cm depths, totally 96 soil samples from 48 sampling points. Coefficients of variation for 137Cs inventory in the soil samples was relatively low (CV = 15%), and the sampling distance and methods used did not significantly affect the 137Cs inventories across the studied reference site. To obtain a satisfactory estimate of the mean 137Cs activity in the reference sites, particularly those located in the semiarid regions, it is recommended to collect at least four samples along in a grid pattern 3 m apart. © 2016 Elsevier Ltd
Publication Date: 2014
Journal Of Environmental Health Science And Engineering (2052336X) 12(1)
Background: The radiological quality of 226Ra, 232Th and 40K in some samples of water resources collected in Anarak-Khour a desertic area, Iran has been measured by direct gamma ray spectroscopy using high purity germanium detector in this paper. Result: The concentration ranged from ≤0.5 to 9701 mBq/L for 226Ra; =0.2 to 28215 mBq/L for 232Th and < MDA to 10332 mBq/L for 40K. The radium equivalent activity was well below the defined limit of 370Bq/L. The calculated external hazard indices were found to be less than 1 which shows a low dose. Conclusion: These results can be contributed to the database of this area because it may be used as disposal sites of nuclear waste in future. © 2014 Ehsanpour et al.; licensee BioMed Central Ltd.
Publication Date: 2014
Journal of Radioanalytical and Nuclear Chemistry (15882780) 300(3)pp. 1217-1225
For the first time, effects of CuO nanoparticles concentration (from 1 to 24.2 wt%) in CuO/NaX nanocomposite and replacing various cations (Ag +, K+, Ca2+, and Mg2+) with Na + ions in NaX zeolite on removal of uranium ions from drinking water are reported. The removal of uranium was performed under natural conditions of pH, laboratory temperature and the presence of competing cations and anions that are available in tap water of Isfahan city. Characterization of parent NaX zeolite and modified samples were investigated using X-ray fluorescence, X-ray powder diffraction patterns, scanning electron microscopy, and atomic absorption spectroscopy methods. Using Langmuir, Freundlich, and C-models, isotherms of equilibrium adsorption were studied. Results show the removal efficiency and distribution coefficient of NaX zeolite decrease in the presence of other competing anions and cations that exist in drinking water. But, modification of NaX zeolite with various cations and CuO nanoparticles might enhance the ability of X zeolite in removing uranium from drinking water. © 2014 Akadémiai Kiadó.
Publication Date: 2014
Nuclear Technology and Radiation Protection (14513994) 29(1)pp. 34-39
Exposure to radiation is one of the main sources of risk to staff employed in reactor facilities. The staff of a tokamak is exposed to a wide range of neutrons and photons around the tokamak hall. The International Thermonuclear Experimental Reactor (ITER) is a nuclear fusion engineering project and the most advanced experimental tokamak in the world. From the radiobiological point of view, ITER dose rates assessment is particularly important. The aim of this study is the assessment of the amount of radiation in ITER during its normal operation in a radial direction from the plasma chamber to the tokamak hall. To achieve this goal, the ITER system and its components were simulated by the Monte Carlo method using the MCNPX 2.6.0 code. Furthermore, the equivalent dose rates of some radiosensitive organs of the human body were calculated by using the medical internal radiation dose phantom. Our study is based on the deuterium-tritium plasma burning by 14.1 MeV neutron production and also photon radiation due to neutron activation. As our results show, the total equivalent dose rate on the outside of the bioshield wall of the tokamak hall is about 1 mSv per year, which is less than the annual occupational dose rate limit during the normal operation of ITER. Also, equivalent dose rates of radiosensitive organs have shown that the maximum dose rate belongs to the kidney. The data may help calculate how long the staff can stay in such an environment, before the equivalent dose rates reach the whole-body dose limits.
Publication Date: 2014
Journal of Fusion Energy (15729591) 33(4)pp. 351-359
A new 20 kJ Filippov-type plasma focus device has been designed and constructed in Isfahan University. The paper reports on the design and construction of the Iranian Filippov-type plasma focus device (UIPFF1) using modified Lee's model. A Rogowski coil has been used to measure the experimental discharge current. Equivalent electric circuit of the device is RLC circuit; therefore the discharge current has a sinusoidal shape which its amplitude decreases exponentially during the time. The current signal contains a set of data from physical processes in the device as well as discharge current characteristics. In a typical discharge experiment these values were obtained: the discharge current was 181 kA, period of current signal 7.9 μs, the total inductance of the device 132 nH and electrical resistance of the circuit 77 m. By averaging from data obtained with a set of five experiments the calibration factor was obtained 121 kA/V. Temporal changes in plasma focus discharge current, confirmed the occurrence of pinch at a specific pressure of argon, neon and nitrogen gases. UIPFF1 has been tested between 15 and 25 kV and wide range of pressure for various gases. Experiments at various pressures and voltages have also confirmed reproducibility and stability of the plasma focus device. © 2014 Springer Science+Business Media New York.
Publication Date: 2014
Iranian Journal Of Public Health (22516085) 43(2)pp. 252-254
Publication Date: 2014
Journal of Fusion Energy (15729591) 33(3)pp. 286-293
The state space of Lee's model (SSL model) is a model developed for plasma behavior in Filippov-type plasma focus facilities which has been described and used. This model is attractive because it provides a practical approach for analysis of a plasma focus device. In this article, we turn to an alternative method of system analysis using time-domain methods. We will reconsider the differential equations describing the Filippov-type plasma focus device and select a certain form of differential equations. We will use a set of variables that can be used to establish a set of first-order differential equations. Using matrix methods, we will be able to determine the transient response of the Filippov-type plasma focus device and examine the performance of this system. This model is a derivation of modified Lee's model and is based on the so-called slug model. Using the SSL model, the discharged current and its derivative as a function of time, pinch time, and maximum discharge current; as functions of pressure, have been predicted. The experimental data obtained by using the UIPFF1 facility with a maximum energy of 20 kJ is compared with the simulated data obtained through SSL model. This investigation shows that the SSL model is capable of predicting the plasma behavior in the Filippov type plasma focus. © 2014 Springer Science+Business Media New York.
Publication Date: 2014
Journal of Crystal Growth (00220248) 402pp. 161-168
In-doped KClXBr1-X(X=1, 0.75, 0.5, 0.25 and 0) mixed crystal has been grown by the Czochralski method. The segregation coefficient of In was studied by the inductively coupled plasma atomic emission spectrometry (ICP-OES). The crystal structure has been determined using X-ray diffraction (XRD) analysis. The thermoluminescence (TL) characterization of KClXBr1-Xmixed crystals, exposed to gamma radiation has been performed. The results show the introduction of the dopants ions induced changes in the TL glow curve structure. The TL results suggest that doped KClXBr1-Xmixed crystal has good potential active dosimeter applications for gamma ray irradiation. © 2014 Elsevier B.V.
Publication Date: 2013
Journal of Applied Geophysics (09269851) 89pp. 68-75
The objective of this study was to explore the slope position and land use change effects on the variability in magnetic susceptibility and 137Cs inventory as the soil redistribution indicators in a hilly semiarid calcareous area in Iran. The selected study area is located in a hilly region with pasture and cultivation land use of Fereydunshahr, Isfahan Province in west-central Iran. In the two mentioned dominant ecosystems, four slope positions including summit, shoulder, backslope and footslope were identified and in each land use and slope position, three cores were selected to collect 72 soil samples from three depths (0-10, 10-20, 20-30cm) in an area of 15×15cm. Additional 28 soil samples were collected from the reference site for soil loss and deposition calculations by using the Cs-137 measurement. The results of the study with the use of the Cs-137 technique showed that the average soil loss in the pasture land (46.4tha-1yr-1) was significantly (p<0.05) lower than the average soil loss in the cultivated land (80.4tha-1yr-1). The highest soil loss in both land uses was obtained in the shoulder position, 60.1 and 84.4tha-1yr-1, respectively, for the pasture and cultivated lands. Moreover, the highest rates of soil deposition was observed in a footslope position in both land uses and they were 34 and 32.4tha-1yr-1 for the pasture and cultivated lands, respectively. Magnetic susceptibility was significantly (p<0.05) greater in pasture (χlf=41.51×10-8m3/kg) than in the cultivated land (χlf=34.90×10-8m3/kg). The pasture land with a lower soil loss rate, indicated significantly higher magnetic susceptibility in all landform positions as compared to that in the cultivated land. The results of the correlation analysis showed that among the studied soil physico-chemical properties, χlf (r=0.83, p<0.01) in the pasture land had the highest correlation with the Cs-137 inventory. Throughout the non-linear regression analysis, χlf was introduced for relating soil parameters and the cesium inventory explained 68% and 79% of the total variability of 137Cs in the pasture and cultivated lands, respectively. The results implied that the variability in the magnetic susceptibility within the hillslope is consistent with the variation of the Cs-inventory; and the results thus demonstrate the slope and land use effects on soil redistribution. © 2012 Elsevier B.V.
Publication Date: 2013
Radiation Physics and Chemistry (18790895) 91pp. 19-27
A new method, based on reactor prompt gamma radiation detection, for reactor power measurement is introduced and validated. To verify, the ex-core gamma radiation spectrum from the Iranian Heavy Water Zero Power Reactor (HWZPR) were measured by HPGe and NaI detectors each suitably positioned. The collective prompt gamma count rates for all or for a portion of each of 2″×2″ NaI detector spectra were obtained for seven power level readings from calibrated reactor power monitors. A good linear behavior was found between gamma count rate and reactor power. The method of calibrated prompt gamma reactor power determination is a stable and reliable tool, on-line, sensitive to sudden variation of power, working in pulse mode, increasing redundancy and diversity and so improving the reactor safety. The prompt gamma counting system can be adopted and installed in other nuclear reactors to measure power. © 2013 Elsevier Ltd.
Publication Date: 2013
Annals of Nuclear Energy (03064549) 57pp. 368-374
Both gamma rays and neutrons are produced and distributed in different nuclear reactions within the Heavy Water Zero Power Reactor (HWZPR) core. The intensities of distributed gamma rays and neutrons from the reactor core are proportional to the reactor power. The NE213 organic scintillation detector can detect both gamma and neutron simultaneously. In this article, a new method has been used for calibration of the reactor power by measurement of gamma rays and neutrons with the 2″ × 2″ dimensions NE213 detector and suitable nuclear electronic equipments outside of core. The reactor calibrated power by this technique is on-line, prompt, and independent of safety and control rods and fuel configuration of the reactor with a good efficiency. The detector, when used 7-10 m from the core center, has necessary efficiency for full-power range measurement (100 W) and in case of accident occurring and sudden increase of the power up to 170 W. © 2013 Elsevier Ltd. All rights reserved.
Publication Date: 2013
Chinese Physics C (16741137) 37(5)
We investigate the relativistic equation for particles with spin 1/2 in the q-parameter modified Pöschl-Teller potential, including Coulomb-like tensor interaction with spatially-dependent mass for the D-dimension. We present approximate solutions of the Dirac equation with these potentials for any spin-orbit quantum number κ under spin symmetry. The normalized wave functions are expressed in terms of the hyper-geometric series of the scattering states on the k/2π scale. We also give the formula for the phase shifts, and use the Nikiforov-Uvarov method to obtain the energy eigen-values equation. © 2013 Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Sciences and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd. © 2013 Chinese Physical Society.
Publication Date: 2013
Nuclear Engineering and Design (00295493) 256pp. 249-255
In this paper, the effect of perforated plate in horizontal steam generator (SG) has been studied. The injected feed water into the SG is cold and heavy, so it pulls down the fluid around the feed water injection pipeline. The perforated plate has been designed above tube bundles in the SG to relax this asymmetrically void generation. In this work, with consideration of the perforated plate and feed injection effects in tube side, it is illustrated that generated steam will be distributed in the top level of the SG homogeneously. Therefore, the steam collector contains high quality homogeneously distributed dry steam and the perforated plate prevents the water from ascending in the cold side containing cold collector and the steam from descending on the other side. In addition, it can be seen that without the perforated plate, the void fraction distribution becomes heterogeneous in the top level of the SG. In this analysis, the 3D numerical model of a large conventional WWER1000 steam generator in the nuclear industry has been presented. For the computational fluid dynamic (CFD) study of desired steam generator in ANSYS CFX, the SG geometry is prepared with details and interfacial relations of mass, momentum and heat transfer are defined by appropriate functions. In momentum source terms, the interfacial drag forces are defined with Ishii and Zuber model. An Euler-Euler approach is applied to modeling boiling heat transfer and condensation. Porosity model is applied to the primary side in which the tube bundles are not described in detail but they are modeled as sources of enthalpy and pressure loss. The primary side effect is modeled based on a 1D thermal heat source model. Finally, the importance of perforated plate is demonstrated and it shows that the results are in a good agreement with published and experimental data. © 2013 Elsevier B.V.
Publication Date: 2013
Journal of Isfahan Medical School (10277595) 30(220)pp. 2412-2418
Background: Living environment and applied building materials in dwellings contain various amounts of radioactive elements. Knowing about the distribution and the level of radiation in the environment is very important to evaluate the effects of radiation on the human. In this study, the level of radioactive nuclei in the granite was assessed according to the color of the stone. Methods: 13 different types of granite used in city of Isfahan (Iran) dwellings were selected, turned to powder, packaged in Marinli dishes and sealed accordingly. The International Atomic Energy Commission instructions were applied for sampling and all other steps of the survey. The dishes were kept for 5 weeks before spectroscopy, to obtain equivalent amount of uranium and thorium nuclides. Then, the gamma-spectroscopy of each sample was collected by HPGe (high purity germanium detector) for 12 hours and categorized based on its energy level. Finally, the special activity of the radiating nuclides in each sample was obtained. Measuring natural radioactivity, including nucleus radioactivity of 238U232Th40K based on Bq/kg unit, was done. The specific average radioactivity concentration of each radiating nuclei was evaluated, too. Findings: The reported special activities for 238U were less than malondialdehydc (MDA) level for green, 65.72 Bq/Kg for white, 57.26 Bq/kg for red, and 24.31 Bq/kg for black granites. The measured special activities for 232Th were 113.36, 84.31, and 34.28 Bq/kg, and less than MDA level for white, red, black and green granites, respectively. Besides, the measured special activities for 40K were 53.16, 525.82, 897.37, and 1243.28 Bq/kg for green, black, red, and white granites, respectively. Conclusion: White granite sample has the highest special activity for the three nuclides238U232Th, and 40K. Also, the lowest special activity for these nuclides was found in green stones and the red granite had an intermediate activity.
Publication Date: 2013
Journal of Luminescence (00222313) 137pp. 230-236
Nanocrystalline of BaSO4 and BaSO4:Dy,Tb of grain size 45-55 nm has been prepared by the co-precipitation method and its thermoluminescence characteristics have been studied. The formation of the material was confirmed by the X-ray diffraction (XRD) and UV-visible spectroscopy. Shape and size of the prepared nanocrystalline powder was observed by a scanning electron microscope (SEM). The TL glow curve of the nanocrystalline pellets of BaSO4:Dy,Tb shows a prominent single peak at 530 K along with another peak of lesser intensity at around 420 K and 560 K. On the contrary, the nanocrystalline pellets of BaSO4 show a peak of low intensity at 500 K and prominent peak around 460 K. The glow curve structure does not change at the range of 0.1-15 kGy and some new peaks appear at high doses but have low intensities. The 530 K of the nanocrystalline pellets of BaSO4:Dy,Tb shows a linear response with exposure increasing up to very high values (as high as 7 kGy), where the other doped BaSO4 show saturation. © 2013 Elsevier B.V.
Publication Date: 2012
Marine Pollution Bulletin (0025326X) 64(9)pp. 1956-1961
The natural radioactivity levels in sediment samples of the northern coast of Oman Sea, covering the coastal strip from Hormoz canyon to Goatr seaport, as the first time has been determined. The results of measurements will serve as background reference level for Oman Sea coastlines. Sediments from 36 coastal and near shore locations were collected for analysis. Analysis on the collected samples were carried out to determine 235U, 238U, 232Th, 40K and 137Cs using two high purity germanium detectors with 38.5% and 55% relative efficiencies. The concentration of 235U, 238U, 232Th, 40K and 137Cs in sediment samples ranged between 1.01 and 2.87Bq/kg, 11.83 and 22.68Bq/kg, 10.7 and 25.02Bq/kg, 222.89 and 535.07Bq/kg and 0.14 and 2.8Bq/kg, respectively. The radium equivalent activity was well below the defined limit of 370Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. © 2012 Elsevier Ltd.
Publication Date: 2012
World Applied Sciences Journal (discontinued) (18184952) 20(10)pp. 1439-1442
This paper is aimed to investigate the design of an optimized neutron radiography system that utilizes the flux of a reactor. Moderation, collimation aspects are studied. A Monte Carlo code, MCNP4C, was utilized to achieve a maximum and more homogenous neutron flux in the collimator outlet next to the image plane, taking into account geometric characteristics. It was possible to obtain a normalized thermal neutron flux, at the image plane, equals 10-9n cm-2 s-1 by a collimator design set. © IDOSI Publications, 2012.
Publication Date: 2012
Middle East Journal of Scientific Research (discontinued) (19998147) 11(5)pp. 648-651
This paper is aimed to investigate the design of an optimized neutron radiography system that utilizes the flux of a reactor. Moderation, collimation aspects are studied. A Monte Carlo code, MCNP4C, was utilized to achieve a maximum and more homogenous neutron flux in the collimator outlet next to the image plane, taking into account geometric characteristics. It was possible to obtain a normalized thermal neutron flux, at the image plane, equals 10 -9 n cm• 2 s -1 by a collimator design set. © IDOSI Publications, 2012.
Publication Date: 2012
RAD Conference Proceedings (24664626) 2012pp. 59-62
ITER (International Thermonuclear Experimental Reactor) is an international nuclear fusion research and engineering project, which is the largest international science project and most advanced experimental tokamak nuclear fusion reactor. Dose rates assessment and gamma radiation due to the neutron activation of the solid structures in ITER is important from the radiological point of view. Therefore, the gamma dosimetry considered in this case is based on neutron activation due to the Deuterium-Tritium (DT) plasma burning with neutrons production rate at 14.1 MeV. The aim of this study is the assessment of gamma dose rates around ITER by considering neutron activation and delay gammas. To achieve the aim, the ITER system and its components were simulated by Monte Carlo method. Also to increase the accuracy and precision of the absorbed dose assessment the activation of walls around the ITER system were considered in the simulation. The results of this research showed that the total dose rate level near to the outside of bio-shield wall of Tokamak hall is not more than dose limits. © 2012 RAD Conference Proceedings. All rights reserved.
Publication Date: 2012
Journal of Radioanalytical and Nuclear Chemistry (15882780) 291(3)pp. 811-815
The street children phenomenon is an increasing problem in most cities of the world including Isfahan, which is a fast growing town. The number of street children with the growth of the town is increased. It is therefore important to have baseline data on their health problems. Hair element analysis remains an important tool in the nutritional and environmental assessment of them. A measurement of the elemental concentration in recently-grown hair provides an integrated view of the element status in the follicular cells and their blood supply, unaffected by short term fluctuations in the nutrient intake of the subject. This study aimed to assess heavy metals concentrations in the hair of street children in Isfahan using neutron activation analysis method. The concentration of heavy metals (Cu, Cr, Fe, Hg, Mn, and Zn) of 17 Iranian street children (Isfahan) was examined. Data analysis found that different profiles of the concentrations of Cr, Hg, Mn, and Zn were seen in each sample. These results were discussed with reference to show of environmental effects. © 2011 Akadémiai Kiadó, Budapest, Hungary.
Publication Date: 2012
World Applied Sciences Journal (discontinued) (18184952) 18(7)pp. 909-917
In the present study, the fuel bundle in the VVER-440 nuclear reactor is simulated and thermohydraulic parameters such as heat transfer coefficient; pressure drop and temperature of fuel rods are estimated. The most research that has been done is related to split vanes of square fuel bundle; however our objective in this study is to investigate split vanes of triangular fuel bundle. Due to lack of experimental results, the validity of CFD analysis of calculation is performed with three models of turbulence. The results showed that using split vane over the triangular fuel bundle led to decrease heat transfer coefficient while heat transfer coefficient is increased in square array fuel bundle. © IDOSI Publications, 2012.
Publication Date: 2012
Journal of Environmental Radioactivity (18791700) 112pp. 45-51
Erosion is a natural process, but it has been dramatically increased by human activities; and this adversely influences soil productivity and environmental quality. For quantification of soil erosion, several techniques including the use of Cs-137 have been employed. This study was conducted to explore the relationships of Cs-137 inventory with magnetic properties in calcareous soils in western Iran. Ten transects were selected in the hilly region in Chelgerd district of Iran. Soil samples from 0 to 30 and 30-50 cm depths were collected from fifty points to determine Cs-137 inventory, magnetic measures and selected physico-chemical properties (in total there were 100 soil samples). The results showed that simple mass balance model (SMBM) estimated a gross erosion rate of 29.6 t ha -1 yr -1 and a net soil deposition of 21.8 t ha -1 yr -1; hence, a net soil loss of 9.6 t ha -1 yr -1 and a sediment delivery ratio of 31.4%. Simple linear regression and non-linear regression analysis showed that mass magnetic susceptibility (χ lf) explained only 33.64% and 45% of variability in Cs-137 in the transects studied. The results of multiple linear regression analysis of 137Cs with magnetic parameters and physico-chemical properties indicated that extractable potassium and χ lf explained approximately 61% of the total variability in 137Cs in the area studied. Overall, the results suggest that further research is needed for the use of magnetic characteristics as an alternative technique in place Cs-137 methodology for calcareous soils. © 2012 Elsevier Ltd.
Publication Date: 2011
Radiation Protection Dosimetry (17423406) 147(1-2)pp. 296-299
Cardiac disease is one of the most important causes of death in the world. Coronary artery stenosis is a very common cardiac disease. Intravascular brachytherapy (IVBT) is one of the radiotherapy methods which have been used recently in coronary artery radiation therapy for the treatment of restenosis. 90Sr/ 90Y, a beta-emitting source, is a proper option for cardiovascular brachytherapy. In this research, a Monte Carlo simulation was done to calculate dosimetry parameters and effective equivalent doses to the heart and its surrounding tissues during IVBT. The results of this study were compared with the published experimental data and other simulations performed by different programs but with the same source of radiation. A very good agreement was found between results of this work and the published data. An assessment of the risk for cardiac and other sensitive soft tissues surrounding the treated vessel during 90Sr/ 90Y IVBT was also performed in the study. © The Author 2011. Published by Oxford University Press. All rights reserved.
Publication Date: 2011
Environmental Monitoring And Assessment (01676369) 183(1-4)pp. 545-554
The concentrations of arsenic, cadmium, chromium, copper, mercury, nickel, lead and zinc in surface sediments collected from the east coast of peninsular Malaysia, along the South China Sea, were measured by two methods instrumental neutron activation analysis and inductively coupled plasma mass spectroscopy. The obtained results were use to determine the areal distribution of the metals of in the east coast of peninsular Malaysia and potential sources of these metals to this environment. The geochemical data propose that most of the metals found in the east coast of peninsular Malaysia constitute a redistribution of territorial materials within the ecosystem. Then, the metal concentrations can be considered to be present at natural background levels in surface sediments. © 2011 Springer Science+Business Media B.V.
Publication Date: 2011
Journal of Radioanalytical and Nuclear Chemistry (15882780) 287(3)pp. 733-740
In order to complete having data base of elemental assessment of the east coast of Peninsular Malaysia marine sediments along the South China Sea coasts, trace elements are analyzed and their distribution in marine sediments is undertaken. The present study is done parallel with pervious study on elemental assessment of heavy metals, rare earth elements and actinides in the marine sediments of the east coast of Peninsular Malaysia. Thirty surface sediment samples were collected in this area, including regions of Kelantan, Terengganu, Pahang, Rompin and Johor Baharu. Multielemental analysis was carried out by instrumental neutron activation analysis and inductively coupled plasma atomic emission spectroscopy. In both cases methodology validation was performed by certified reference material analyses. For the surface elemental distributions the enrichment factor values, average I geo and mC d values indicate that the trace elements of the surface sediments are uncontaminated in all sampling stations that are consistent with previous studies results of heavy metals, rare earth elements and actinides. © 2011 Akadémiai Kiadó, Budapest, Hungary.
Publication Date: 2011
Applied Radiation and Isotopes (09698043) 69(2)pp. 521-526
The concept of a virtual point detector (VPD) has been developed and validated in the past for Ge(Li) and HPGe detectors. In the present research, a new semi-empirical equation involving photon energy and source-virtual point detector distance for the efficiency of point sources by HPGe detectors is introduced , which is based on the VPD model. The calculated efficiencies for both coaxial and off-axis geometries by this equation are in good agreement with experimental data. The estimated uncertainties are less than 4%. © 2010.
Publication Date: 2011
World Applied Sciences Journal (discontinued) (18184952) 15(4)pp. 532-536
Paramagnetic inelastic neutron scattering measurements have been carried out to investigate the crystal of anomalous rare earth of cerium. The physics of rare earth such as cerium has become very attractive because hybridization of the f electrons with electrons in the conduction band gives rise to a variety of interesting phenomena. In particular, magnetic form factor can use to help in the understanding of the wave functions of localized electrons and inelastic neutron scattering experiments measure energy scales of magnetic fluctuations and characteristic temperatures. At high temperature, the magnetic scattering can be described by two coherent broad peaks. At low temperatures, one narrow inelastic peak indicates dynamic magnetic correlation and paramagnetic effective moment in cerium ions. These results allow us to establish that in Ce+3 ions, at low T, inelastic scattering is contribution of the Kondo effect. © IDOSI Publications, 2011.
Publication Date: 2010
Journal of Radioanalytical and Nuclear Chemistry (15882780) 283(3)pp. 823-829
Results obtained from the analysis of sediments surface samples taken from rivers mouth and polluted marine environment were analyzed for REE contents to determine the concentrations of La, Ce, Sm, Eu, Tb, Dy, Lu and Yb using instrumental neutron activation analysis. Thirty surface samples were collected from ten sites in the coastal marine sediments of the South China Sea along 957 km stretch of the east coast of Peninsular Malaysia. The samples prepared in the powdered form before irradiating them in a neutron flux of ∼4 × 1012 n cm-2 s-1 at 750 kW power using the TRIGA Mark II research reactor at Malaysian Institute for Nuclear Technology (MINT). Results of the total concentration are used to establish baseline data in environmental pollution assessment and to develop the correlations between the Ce/Ce*anomalies and the distribution patterns of some the light rare earth elements (LREEs) and the heavy rare earth elements (HREEs). The Chondrite-normalized REE pattern from each site examined and used to explain the sedimentation patterns by anthropogenic activities and by natural processes such as shoreline erosion, weathering deposits. Shale-normalized (NASC) patterns suggest enrichment of LREEs relative to the HREEs with a positive Ce/Ce*anomaly. Validation of the used method was done using a Soil-7 SRM. © 2009 Akadémiai Kiadó, Budapest, Hungary.
Publication Date: 2010
International Journal Of Environmental Research (17356865) 4(4)pp. 877-886
Forty seven sediment cores recovered from the South China Sea coasts along the east coast of Peninsular Malaysia were analysed for As, Cd, Cr, Cu, Hg, Ni, Pb and Zn using instrumental neutron activation analysis. The results indicate a homogeneous distribution except for As and Pb in all stations. Assessment of heavy metal pollution in marine sediments requires knowledge of pre-anthropogenic metal concentrations to act as a reference against which measured values can be compared. Primitive values for the cored sediments were determined from shale average metal. Various methods for calculating metal enrichment and contamination factors are reviewed in detail and a modified and more robust version of the procedure for calculating the degree of contamination is proposed. The revised procedure allows the incorporation of a flexible range of pollutants, including various organic species, and the degree of contamination is expressed as an average ratio rather than an absolute summation number. Comparative data for normalized enrichment factors and the modified degree of contamination show that the South China Sea sediments are in uncontaminated to moderately contaminated level of heavy metal contamination. Compared to obtained values the Kelantan and Pahang big rivers mouth show higher enrichment averaged across other sites.
Publication Date: 2009
Marine Pollution Bulletin (0025326X) 58(5)pp. 658-662
The determination of activity concentrations of the radioactive elements 238U, 232Th, 40K and 137Cs was performed on grab samples taken from a polluted environment. The samples were sliced into strata from 5 cm depth, dried and ground to sieved through a 170 mesh size prior to the analysis. Activity concentration was quantified using gamma spectroscopy. The results showed that the concentrations of activity in the sediment samples are 177 ± 12.4, 117 ± 11.5, 1085 ± 101.6 and 131 ± 4.8 Bq kg-1 for 238U, 232Th, 40K and 137Cs, respectively. In general, the distribution of activity concentrations along the southern coast of the Caspian Sea area exceeded international limits. The hazard index of the samples was 0.19-0.88, with an average of 0.49. The mean values of radium equivalent activity and dose rate are 176 Bq kg-1 and 63 nGy h-1, respectively. © 2009 Elsevier Ltd. All rights reserved.
Publication Date: 2009
Journal of Rare Earths (10020721) 27(6)pp. 1066-1071
In the east coast Peninsular Malaysia region, sediments are transported by several rivers from the east Malaysia into the South China Sea estuary. In the vicinity of the five river estuaries core sediments were collected in order to investigate rare earth elements (REEs) profile. Core sediments were divided into strata of between 2 to 4 cm intervals and prepared for analyzing by ICP-AES. REE concentrations of 54.3 μg/gr at 24-26 cm in EC4 increased to 114.1 μg/gr at 20-22 cm in EC5. The measured concentration of LREEs and Fe normalized enrichment factors indicated that sediments were not enriched with light rare earth elements derived from effluents of anthropogenic activities. Results of the total concentration were used to establish baseline data in environmental pollution assessment and to develop the correlations between the Ce/Ce* and Eu/Eu* anomalies and the distribution patterns of some light rare earth elements (LREEs) and the heavy rare earth elements (HREEs). The chondrite-normalized ratios of REEs showed LREEs enrichment and flat HREE depletion. © 2009 The Chinese Society of Rare Earths.
Publication Date: 2009
Powder Technology (1873328X) 189(1)pp. 52-56
The zeolite NaA was synthesized from natural clinoptilolite as Si source and aluminum sulfate or sodium aluminate as Al source. The use of aluminum sulfate for the synthesis of zeolite A has not been reported in the literature. This study presents as the first time a synthesis approach in which the low cost and available source is used to prepare zeolite NaA. These nano particles of zeolite were prepared at different conditions in autoclave and a mixer was designed specifically for this purpose. The synthesized zeolites were characterized by instrumental analysis methods, such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscope (SEM), transmission electron microscope (TEM) and wet chemical analysis by atomic absorption spectroscopy (AAS). Cation exchange capacity (CEC) and loss on ignition (LOI) have been also measured on the prepared samples. The influences of different parameters such as reaction time, temperature, initial gel concentration, mechanical stirring and drying conditions on the improvement of the final products were experienced and the procedure for the efficient synthesis of zeolite NaA was optimized with available quality control tests. Solubility of clinoptilolite as the Si source in alkaline solutions was also investigated. © 2008 Elsevier B.V. All rights reserved.
Publication Date: 2006
Journal of Radioanalytical and Nuclear Chemistry (15882780) 270(2)pp. 319-324
A reconnaissance study has been made on the distribution of 238U, 232Th, 40K, 137Cs and geochemical features in soil and sediment samples at various locations in the coast of Persian Gulf. Activity concentration levels due to radionuclides were measured in 50 samples of soils and sediments collected from the coast of Hormozgan. From the measured spectra, activity concentrations were determined for 40K (range from 140 to 1172 Bq·kg-1), 137Cs (from 0 to 15 Bq·kg-1), 238U (from 29 to 385 Bq·kg-1) and 2321Th (from 9 to 156 Bq·kg-1) with the lowest limit of detection (LLD) of 68, 3.2, 4.3 and 4.3 Bq·kg-1, respectively. The dose rate from ambient air at the soil ranges was between 23 to 177 nGy·h-1 with an average of 60±7.86 nGy·h-1. © 2006 Akadémiai Kiadó.
Publication Date: 2006
Iranian Journal of Science and Technology, Transaction A: Science (10286276) 30(3)pp. 259-269
A reconnaissance study has been made on the distribution of 238U, 232Th, 40K, 137Cs and geochemical features in soil and sediment samples at various locations on the coast of Bushehr in the Persian Gulf. In this study a gamma-ray spectrometer based on a High Purity Germanium detector and a PC based MCA and X-ray fluorescence (XRF) method were used. Estimation of the measured radionuclide content have been made for the absorbed dose rate of gamma radiation. The Activity concentration (A), the equivalent radium (Req), and the external hazard index (Hex) which resulted from the natural radionuclides in soil and sediment are also calculated. The base-line data of radionuclides and heavy metals in view of the commissioning of nuclear and non-nuclear industries for the coast of Bushehr, which does not yet exist, was obtained. Activity concentration levels due to radionuclides were measured in 50 soil and sediment samples collected from this region. The measurement was performed with respect to their gamma radioactivity for a counting time of 24 hour intervals. From the accumulated spectra, activity concentration were determined for 40K (range from 108 to 520 Bq Kg-1), 137Cs (from 6 to 40 Bq Kg-1), 238U (from 12 to 75 Bq Kg1) and 232Th (from 8 to 33 Bq Kg-1) with the lowest limit detection (LLD) of, respectively, 68, 3.2, 4.3 and 4.3 Bq Kg-1. The dose rate from ambient air at the soil ranges was between 14 to 44 nGy h-1 with an average of 30.56 ± 7.86 nGy h -1. © Shiraz University.
Publication Date: 2006
Journal of Radioanalytical and Nuclear Chemistry (15882780) 268(3)pp. 539-544
A nonlinear function was applied in combination with the method of mixing activity calibration for fitting the experimental peak efficiency of HPGe spectrometers in the 50-2614 keV energy range. The preparation of Marinelli beaker standards of mixed gamma- and RG-Set at secular equilibrium with its daughter radionucliedes was studied. Self-absorption was measured for the activity calculation of the gamma-ray lines for daughters of 238U series, 232Th series, as well as 137Cs and 40K in soil samples. Self-absorption in the sample depends on a number of factors including sample composition, density, sample size and gamma-ray energy. Seven Marinelli beaker standards were prepared in different degrees of compaction with bulk density (ρ) of 1.000 to 1.600 g·cm-3. The detection efficiency versus density was obtained and the equation of self-absorption correction factors was calculated for soil samples. © 2006 Akadémiai Kiadó.
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