Mostafa Heydari; Hamid Jafari; Zohreh Gholamzadeh
Abstract
The neutron transmutation doping method is widely used in various fields, such as solar cells, hybrid cars, etc. The Silicon doping process can provide direct commercial income for nuclear research reactors. In this study, we aim to find the optimal location for silicon doping in the thermal column ...
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The neutron transmutation doping method is widely used in various fields, such as solar cells, hybrid cars, etc. The Silicon doping process can provide direct commercial income for nuclear research reactors. In this study, we aim to find the optimal location for silicon doping in the thermal column nose of the Tehran research reactor. For this purpose, computational MCNPX and ORIGEN2 codes were used to calculate the neutronic and radioactivity parameters of the silicon ingot. The important parameters such as the thermal to fast neutron ratio, heat deposition by gamma and neutron, and the radioactivity level of the silicon ingot and the produced radioisotopes have been determined to obtain the optimal irradiation channel. The results showed that the irradiation channel placed in the thermal column at a distance of 90 cm from the center of the TRR core has optimal conditions for the implementation of silicon doping. The channel provides a thermal neutron flux in order of 1.721012 n.cm-2.s-1 which is the least acceptable value to achieve a proposed neutron fluence during the operation cycles of TRR reactor. Also, the channel has the least possible heat deposition inside the silicon ingot of about 191 W. In addition, the thermal to fast neutron flux ratio of about 311 is enough higher than the determined IAEA limit for NTD.
Kambiz Valavi; Ali Pazirandeh; Gholamreza Jahanfarnia
Abstract
In the present work, a time-dependent neutron diffusion simulator is developed utilizing the second order of average current nodal expansion method. Generally, nodal methods can accurately simulate the reactor core with coarse meshes as long as the sizes of a fuel assembly. In this case, an adopted iterative ...
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In the present work, a time-dependent neutron diffusion simulator is developed utilizing the second order of average current nodal expansion method. Generally, nodal methods can accurately simulate the reactor core with coarse meshes as long as the sizes of a fuel assembly. In this case, an adopted iterative approach is used for resolving the time-dependent three-dimensional multi-group neutron balance equations coupled with six-group precursor equations. In order to evaluate the implemented methodology, two popular transient problems are used including TWIGL two-dimensional seed-blanket reactor and three-dimensional LMW LWR. For indicating the precision of the method, the numerical results of high (second) order approach also have been compared with the basic methodology i.e. the zeroth order solution. From the comparison of obtained results with references, the suitable and precise simulating of transient schemes can be comprehended using the time-dependent second order average current nodal expansion method. Moreover, the results confirm that the second order solution can treat the coarse mesh dynamic problems with more accuracy relative to the basic approach.
Maryam Azizi; Ali Biganeh; Omidreza Kakuee; Behjat Ghasemi; Yashar Vosoughi
Abstract
Primary standardization of radioactivity is related to the direct measurement of activity in radioactive decay. A large variety of primary standardization techniques have been developed in the past years. The photon-photon coincidence counting is one of the methods for activity determination. This method ...
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Primary standardization of radioactivity is related to the direct measurement of activity in radioactive decay. A large variety of primary standardization techniques have been developed in the past years. The photon-photon coincidence counting is one of the methods for activity determination. This method is particularly applied for the standardization of I-125 using the detection of X-ray and gamma-ray coincident counting. In this paper, a 2D photon-photon coincidence digital system with two similar 2'' × 2'' NaI(Tl) detectors for absolute activity measurement is developed. The system is established based on a 100 MHz CAEN waveform digitizer (DT5724) which directly records the pre-amplifier output signals of the two NaI(Tl) detectors. The sampled signals was transformed to trapezoidal signals using pulse height analyzer firmware and coincidence events were recorded in a list file. The list file was analyzed offline using a Matlab code to realize correlated gama lines of Co-60 source. The Volkovitsky formulas were used for the activity calculation and the details of the experimental setup were also discussed. Standardization of the two Co-60 standard sources was performed using this system. Results are in good agreement with the reference activity of Co-60 sources. The presented formula can be modified for absolute calibration of the other medical radioisotopes. The technique can be generalized for absolute activity measurement of I-125 which uses for ophthalmic plaque radiation therapy.
Mahdi Eshghi; Sasan Soudi; Sameer M. Khadir
Abstract
The scattering problems, in the presence of an external potential field, have become highly interesting topics in relativistic and non-relativistic quantum mechanics. It is well known that the scattering of a relativistic particle in the field of a potential can be treated exactly by finding the continuum ...
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The scattering problems, in the presence of an external potential field, have become highly interesting topics in relativistic and non-relativistic quantum mechanics. It is well known that the scattering of a relativistic particle in the field of a potential can be treated exactly by finding the continuum solutions of the Dirac equation. In this research, we obtain the exact solution to the Dirac equation with the Pöschl-Teller double ring-shaped Coulomb (PTDRSC) potential for any spin-orbit quantum number k. The relativistic scattering amplitude for spin 1/2 particles in the field of this potential has been studied. The wave functions are being expressed in terms of the hyper-geometric series of the continuous states on the k/2π scale. In addition, a formula for the phase shifts has also been found. In the nonrelativistic limits, our solution to the Dirac particle converges to that of the Schrödinger one. At the high temperature, the partition function is being calculated in order to study the behavior of some thermodynamic properties.
Shahryar Malekie; Sedigheh Kashian; Seyed Musa Safdari; Morteza Akbari; Arjang Shahvar
Abstract
In this experimental work, Polycarbonate/Bismuth Oxide (PC-Bi2O3) nanocomposites were prepared in various concentrations of 0, 10, 30, and 50 wt% with thicknesses of 1 mm and irradiated by a pure beta-emitter source of Sr-90. To fabricate the electrodes, copper sheets with thickness of 100 µm were ...
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In this experimental work, Polycarbonate/Bismuth Oxide (PC-Bi2O3) nanocomposites were prepared in various concentrations of 0, 10, 30, and 50 wt% with thicknesses of 1 mm and irradiated by a pure beta-emitter source of Sr-90. To fabricate the electrodes, copper sheets with thickness of 100 µm were attached to the top and bottom surfaces of the samples using the silver paste. Then, electric current as the dosimetry response, was measured at various dose rates ranging from 30-102 mSv.h-1 at a fixed voltage of 400 V using an electrometer. Results showed that increasing the Bi2O3 wt% led to improvement in the dosimetry response linearly at various dose rates. Also, the amounts of sensitivities for the samples of 0, 10, 30, and 50 wt% were measured as 20.3, 19.8, 28.6, and 36.7 nC.mSv-1.cm-3, respectively. Regarding the mechanism of beta interaction with a polymer-heavy metal oxide nanocomposite, the Bremsstrahlung radiation can be considered as a dominant effect.
Majid Zamani; Mohsen Shayesteh
Abstract
Using the experimental data in nuclear computing to verify the calculation methods and tools based on numerical and statistical methods has many benefits such as illustrating the quality, ensuring the capabilities, and computer codes validating. Simulation by computer tools is also applicable in the ...
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Using the experimental data in nuclear computing to verify the calculation methods and tools based on numerical and statistical methods has many benefits such as illustrating the quality, ensuring the capabilities, and computer codes validating. Simulation by computer tools is also applicable in the safety analysis of research reactors. In this research, the computer tool (MCNPX 2.7.0: 2011) was verified against the experimental data of neutron flux and spectrum on the sample position of the Tehran Research Reactor (TRR) neutron imaging system by the neutron activation method. To determine the benchmark specifications, the simulation of the system was done at the first step by considering a well-defined facility geometric, material specification and reactor core configuration, fuel elements, and radiation facility (beam tubes and collimator, reactor core, and neutron imaging components). Then the flux and neutron spectrum at the sample position were calculated. In the second step, a set of In (bare and covered by cd) and Au foils and a set of Au, Ni, Ti, and Zr, were placed and exposed almost in front of the reactor E beam tube. The neutron energy spectrum was unfolded by calculating the saturation activity of each foil by SAND-II code, and the neutron flux was calculated. A comparison of the results obtained in two steps shows a relatively good and acceptable agreement (Max. 30% deviation) between the flux and the shape of the flux profile obtained from calculations and experimental data.
Ali Zahian; Mahdi Aghaie
Abstract
In this analysis, nanofluid properties are evaluated by interaction correlations between particles using molecular dynamics (MD) method, and thermal-hydraulics characteristics of nanofluids in a WWER-1000 reactor is investigated by Computational Fluid Dynamics (CFD). This study conceptualizes power increase ...
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In this analysis, nanofluid properties are evaluated by interaction correlations between particles using molecular dynamics (MD) method, and thermal-hydraulics characteristics of nanofluids in a WWER-1000 reactor is investigated by Computational Fluid Dynamics (CFD). This study conceptualizes power increase by changing the cooling from pure water to nanofluid without changing the safety parameters. The Copper nanoparticles are used in primary loop cooling system, to evaluate the heat removal from the core. Thermophysical properties such as thermal conductivity and shear viscosity of Cu-Water nanofluids are obtained by MD in operating pressure and temperature of the Bushehr reactor core. These properties have been used in thermal-hydraulics analysis and nanofluids are considered as a homogeneous fluid. Thermal hydraulic properties of coolant have been calculated for different volume fractions of nanofluids. Thermal hydraulic simulation illustrated enhancement of the thermal characteristics of the core, due to the increment in heat transfer coefficient and thermal diffusivity. The thermal-hydraulic analysis of the reactor core has been performed in steady state at different powers. The requirements for changing the reactor power are not to change the fuel center temperature and Outer Cladding Surface temperature compared to the current state.
Sajjad Shahmaleki; Faezeh Rahmani
Abstract
In this research, the Tm content as codopant in CsI(Tl) was optimized for reducing the afterglow. As an experimental reference, CsI(Tl) and CsI(Tl-0.05%Eu) single crystals were grown by Bridgman method. The grown crystals were characterized through photoluminescence analysis, and the measurements of ...
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In this research, the Tm content as codopant in CsI(Tl) was optimized for reducing the afterglow. As an experimental reference, CsI(Tl) and CsI(Tl-0.05%Eu) single crystals were grown by Bridgman method. The grown crystals were characterized through photoluminescence analysis, and the measurements of charge collection time, energy resolution, photon light yield as well as the amount of afterglow were performed. It was observed that the change in codopant shifted the emission curve of Tl+. For CsI(Tl) codoped with Tm in the range of 0.02 to 0.1 mol%, the afterglow of 0.05 mol% Tm reduced in comparison with Tm-free CsI(Tl). The results showed that the Tm codopant resulted in a decrease of 32 to 42% in afterglow depending on the Tl concentration. The addition of various contents of Tm also decreased the light yield, up to 23%, and as well as the resolution about 2 to 33%. The light yield exhibited insignificant changes, whilst the measured energy resolution was about 8.8% at 662 keV. Overall, the improvement in the afterglow, as well as the insignificant reduction in both the energy resolution and light yield of CsI(Tl-Tm), may motivate some researchers to consider it as a good candidate for fast spectroscopy and high-frequency imaging applications.
Farrokh Khoshahval
Abstract
Selecting a genuine objective function in the fuel management optimization (FMO) of newly developed reactors is fundamentally important. The FMO problem becomes harder when a multi-objective fitness (cost) function (MOCF) is in use. Usually, when undertaking a MOCF fuel management optimization problem, ...
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Selecting a genuine objective function in the fuel management optimization (FMO) of newly developed reactors is fundamentally important. The FMO problem becomes harder when a multi-objective fitness (cost) function (MOCF) is in use. Usually, when undertaking a MOCF fuel management optimization problem, it is transformed into the summation of objective functions, which are related to weighting factors. Different parameters can be chosen as the main fitness function in an optimization problem. In the case of a nuclear reactor, the cycle length, the multiplication factor and power peaking factor are the most significant. The value of the weighting factors and/or the method with which the cost function has been formulated may affect the final result of optimization. In this paper, the effect of the selection of the cost function has been analyzed in order to reach an optimum in core fuel management of a typical pressurized water reactor, PWR. It is understood from the results that finding a loading pattern that results in a better power peaking factor (lower PPF) is stricter than that of a longer cycle length. Indeed, the obtained loading pattern strongly depends on the selected fitness function. Finally, the flattening function is proposed instead of minimizing the PPF to attain better loading patterns.
Ali Adeli Ahmadabadi; Zahra Shahbazi rad; Fereidon Abbasi Davani; Behjat Ghasemi
Abstract
In this research, the effect of ions produced in deuterium plasma on Tungsten (W) and Aluminum (Al) plates has been investigated using a plasma focus device with the specifications of (C=10.4 μF, V=23 kV, E=2.75 kJ). The W samples used because it is one of the key elements in the Tokamak device. Because ...
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In this research, the effect of ions produced in deuterium plasma on Tungsten (W) and Aluminum (Al) plates has been investigated using a plasma focus device with the specifications of (C=10.4 μF, V=23 kV, E=2.75 kJ). The W samples used because it is one of the key elements in the Tokamak device. Because we wanted to put the W samples at the distance from the anode top with maximum plasma produced ions, we should find the optimum place. Due to the high cost of W samples, we used Al samples to find the optimal conditions. The samples were irradiated at 8 cm distance from the anode top with deuterium ions produced by a plasma focus device. The sample analyses were done by the SEM and EDX methods. The sample irradiation by deuterium plasma ions caused a lot of damages and bubble formation on the sample surfaces. The analyses showed the extent of surface damage and the number of ions deposited on the surface. The number of damages on the Al surface was much higher than W. Bubbles were formed on the surface were due to the impact of deuterium ions on the W and Al samples. Also, the deuterium ion energy was measured with a Faraday cup as about 50 keV.
Mohammad Hadi Najarzadeh; Mohammad Reza Rezaie; Ali Negarestani; Ahmad Akhound
Abstract
Neutron detection techniques are widely studied in many articles. Most of this research requires a lot of electronic equipment. In this study, using the Thick Gas electron multiplier (THGEM) detector, a new method for neutron detection is proposed to reduce electronic equipment. In the neutron detection ...
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Neutron detection techniques are widely studied in many articles. Most of this research requires a lot of electronic equipment. In this study, using the Thick Gas electron multiplier (THGEM) detector, a new method for neutron detection is proposed to reduce electronic equipment. In the neutron detection system, the converter material is used for converting neutrons to protons that are directed to the THGEM detector. By filling the detector space with noble gas and applying special voltage, THGEM enters to Self-Quenched Streamer (SQS) mode for protons detection. All these steps are examined by simulation, then the detection system is made and is examined in the laboratory. Finally, the simulation results and laboratory results are compared. The results show that the 1 mm Plexiglas layer is suitable for converting neutrons to protons. The suitable distance between the converter layer and the THGEM detector is 3 cm. Also, the SQS mode happens in the most number of THGEM holes when the THGEM voltage is 980 volt. Investigating an approach to neutron detection by placing THGEM in SQS mode can be useful because, firstly, placing the THGEM detector in SQS mode simplifies electrical circuits and secondly, with this proposed detection system; it is possible to design detectors with different dimensions for neutrons.
Ali Nouraddini-Shahabadi; Mohammad Reza Rezaie; Saeed Mohammadi
Abstract
High-energy heavy ions produced by accelerators are used in industrial and medical applications. Recently carbon ions have been used in the treatment of cancerous tumors. Heavy ions by the spallation process will activate the soft tissue components before tumors. In this research by GEANT4 toolkit and ...
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High-energy heavy ions produced by accelerators are used in industrial and medical applications. Recently carbon ions have been used in the treatment of cancerous tumors. Heavy ions by the spallation process will activate the soft tissue components before tumors. In this research by GEANT4 toolkit and MCNPX code simulation were tried to calculate the secondary particles and radioactive elements produced in the soft tissue around tumors by the carbon ions spallation process. In the MCNPX code, the F8 tally card with the FT8 command was used to extract the activation and spallation information of secondary particles in the Z1=1 to Z2=25 atomic numbers range. It was shown that a wide range of radioactive elements was produced in healthy tissues in carbon therapy. addition to produced secondary particles, the Be-10 and C-14 radioactive elements were produced in high-energy carbon ions in soft tissue. Also, the GEANT4 toolkit result of produced secondary particles dosimetry was shown that the secondary particles dose per carbon ion is between 1.66 to 33.54 nGy for carbon ion energy between 1140 to 5160 MeV. The tail for 3480, 4080, and 5160 MeV of carbon ion energy are 0.12,1.01 and 11 cm respectively. The carbon ion beam divergence increases with beam energy and achieve to 33 mm for 5160 MeV carbon ion.
Saeideh Koohestani; Morteza Habibi; Azimeh NV Dehkordi
Abstract
For configuring plasma focus device (PFD), the gap between electrodes is filled out with a gas at low pressure. When discharge is starting at the surface of the insulator, the gas breaks down, leading to the flow of the plasma current sheath toward the anode end. A homogeneous and symmetric current sheath ...
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For configuring plasma focus device (PFD), the gap between electrodes is filled out with a gas at low pressure. When discharge is starting at the surface of the insulator, the gas breaks down, leading to the flow of the plasma current sheath toward the anode end. A homogeneous and symmetric current sheath which is essential for ion emission and a proper plasma pinching can be obtained when there is an electrical breakdown along the insulator. Therefore, one of the most important parts of the plasma focus is the insulator. In the present research, the effect of different insulator sleeves on the intensity of ions emitted from a 4 kJ PFD filled with Neon has been studied. Pyrex and Quartz are considered for the insulator materials and the length is varied from 3 to 6 cm for Pyrex and from 3.5 to 5.5 for Quartz. Numerous gas pressures were experimented with voltages of 11, 12 and 13 kV. The results show that both the length and the material of the insulator sleeve can affect the intensity of ions emitted from the device. The length of 4.5 cm seems optimal to yield maximum ion emission for Pyrex insulator. For the Quartz insulator, on the other hand, length of 3.5 cm results in higher ion emission. In addition, in some cases, utilizing Quartz insulator causes more ion emission compared to the Pyrex insulator.
Oveis Hasanpour; Fereydoun Abbasi Davani; Farshad Ghasemi; Mahdi Aghayan; Mohammad Nazari; Shahin Sanaye Hajari
Abstract
Two main insulating gases of SF₆ and N₂/CO₂ mixture are employed to increase voltage capability of electrostatic accelerators. SF₆ offers more insulating capability, but environmental and technical disadvantages of SF₆ makes usage of N₂/CO₂ mixture a desirable option. This paper aims to ...
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Two main insulating gases of SF₆ and N₂/CO₂ mixture are employed to increase voltage capability of electrostatic accelerators. SF₆ offers more insulating capability, but environmental and technical disadvantages of SF₆ makes usage of N₂/CO₂ mixture a desirable option. This paper aims to replace SF₆ with N₂/CO₂ in design of a 500 kV/30 mA parallel-fed voltage multiplier. High-voltage section of the accelerator is a capacitive structure which in combination with rectifying elements, generates the accelerating high-voltage. The structure which is called Voltage Multiplier Capacitive Structure (VMCS) is designed and analyzed in this paper. The first structure is designed to employ SF₆ as insulating gas (VMCS500). Then, the structure is modified to be capable of using N₂/CO₂ as insulating gas with lower breakdown voltage (VMCS500-m). The modified structure requires more complex mechanical manufacturing process, but offers the simplicity of using N₂/CO₂ mixture, the option of using the modified structure with superior SF₆ gas, increasing the output voltage and beam energy. CST EM STUDIO was used for capacitance calculation and electric field analysis. LTSPICE was used for equivalent circuit analysis of the high voltage generating section.
Hafez Taghipour Aslani; Alireza Jokar; Aliakbar Mehmandoost-Khajeh-Dad; Hossien Rafi-kheiri
Abstract
To measure excitation functions of particle-induced prompt gamma-ray production reactions on Li, a thin LiF target was fabricated by thermal evaporation technique onto self-supporting Ag film. The thickness and the stochiometric ratio of the thin LiF target was measured using Elastic Backscattering Spectroscopy ...
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To measure excitation functions of particle-induced prompt gamma-ray production reactions on Li, a thin LiF target was fabricated by thermal evaporation technique onto self-supporting Ag film. The thickness and the stochiometric ratio of the thin LiF target was measured using Elastic Backscattering Spectroscopy (EBS), Particle Induced Gamma-ray Emission (PIGE) and Nuclear Reaction Analysis (NRA) techniques. The target was characterized to check uniformity and its stability under beam bombardment. Carbon and Molybdenium contaminations in the target also were examinated. The values of the thickness of the target obtained by EBS, PIGE and NRA techniques are in good agreement with each other , within the estimated uncertainties. Measurements were conducted using the proton/deuteron beams of the 3 MV Van de Graaff electrostatic accelerator of Nuclear Science and Technology Research Institute (NSTRI). All results are presented in an absolute approach by using the experimental cross-section values available through the Ion Beam Nuclear Data Library (IBANDL).
Ali Biganeh; Banin Shakeri Jooybari
Abstract
Compton scattering events are the main source of error on the peak counting during the Neutron Activation Analysis (NAA). The Compton suppressor system in instrumental NAA reduces the detection limit of the technique and leads to a data with a higher degree of precision. In this paper, a two-dimensional ...
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Compton scattering events are the main source of error on the peak counting during the Neutron Activation Analysis (NAA). The Compton suppressor system in instrumental NAA reduces the detection limit of the technique and leads to a data with a higher degree of precision. In this paper, a two-dimensional pseudo coincidence Compton suppressor system is presented for the NAA technique. The system is established based on a CAEN digitizer which directly records the pre-amplifier output signals of the two HPGe detectors. The recorded events in the list mode file are analyzed offline by a Matlab code and the correlated photopeak events are realized. The performance of the system for Compton suppression is tested by measuring the gamma lines of Ba-133 and Cs-137 standard sources. The results show that the presented technique provides the peak to Compton ratio up to 104 and can be an alternative for conventional Compton suppressor systems.
Mahdi Eshghi
Abstract
The buildup factor is becoming a required parameter for exposure and energy absorption in the area of radiation physics for shielding, dosimetry, health physics and medical physics. In this research, photon buildup for dysprosium doped lithium magnesium borate glasses system has been investigated. Photon ...
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The buildup factor is becoming a required parameter for exposure and energy absorption in the area of radiation physics for shielding, dosimetry, health physics and medical physics. In this research, photon buildup for dysprosium doped lithium magnesium borate glasses system has been investigated. Photon energy absorption buildup factors and photon exposure buildup factors were computed for the chosen glasses using the five-parameter geometric progression fitting method in energy range of 0.015 MeV to 15 MeV. Also, effective and equivalent atomic numbers were calculated for these compositions and discussed for possible implementation in radiation dosimetry.
Danial Salehi; Gholamreza Jahanfarnia; Ehsan Zarifi
Abstract
Canadian GEN IV Super Critical Water Reactor (Canadian-SCWR) is a combination version of conventional CANDU reactor with the using super critical water as coolant. Thermal-hydraulic analysis of a nuclear reactor is done to ensure that reactor will work in its safety margins. In this study, thermal hydraulic ...
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Canadian GEN IV Super Critical Water Reactor (Canadian-SCWR) is a combination version of conventional CANDU reactor with the using super critical water as coolant. Thermal-hydraulic analysis of a nuclear reactor is done to ensure that reactor will work in its safety margins. In this study, thermal hydraulic analysis of Canadian-SCWR is conducted by numerically solving of conservation equations by a porous media approach. The latest concept of Canadian-SCWR core was used for this purpose. In this concept, in each fuel bundles, super critical water flows in two pass and low pressure and low temperature heavy water moderator flows around fuel channel in the Calandria vessel, separately. Average axial temperature, density, heat capacity, pressure and velocity of supercritical water was estimated in two regions of fuel channels (two pass) i.e centeral flow tubes and the fuel rods channel. Compared to the literature, there is a good agreement between our results and the reported results.
Vahidreza Babaei; Peiman Rezaeian; Sedigheh Kashian; Reza Pourimani; Azam Akhavan
Abstract
In this paper, the spectrophotometric properties of a colored Nickel-based solution complex (Nickel nitrate hexahydrate and Methyl Orange (MO)) were investigated as a stable chemical dosimeter for using in radiation processing of agricultural products. Its simple synthesis method as well as low cost ...
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In this paper, the spectrophotometric properties of a colored Nickel-based solution complex (Nickel nitrate hexahydrate and Methyl Orange (MO)) were investigated as a stable chemical dosimeter for using in radiation processing of agricultural products. Its simple synthesis method as well as low cost made it a suitable dosimeter for use in radiation processing. The variation of absorbed dose was applied to measure the absorbed dose. The maximum absorbance for the solution was observed at 460 nm. This solution was irradiated at three different concentrations of Ni(No3)2.6H2O and MO by Co-60 gamma-ray. Also the variation of the absorbance as a function of PH of the solution was investigated. The results showed the solution absorbance decreases with an increase in doses, and this solution can be used as a routine dosimeter and has a linear response in the 50 to 1500 Gy range with acceptable stability in environmental conditions up to 40 days before and after irradiation.
Saeed Kakaei; Elham Sattarzadeh Khameneh; Akbar Monji Boveiri
Abstract
For the first time, sorption characteristics and mechanisms of group-4 elements were investigated and compared in extremely acidic solutions (4 M HCl) by rice bran (RB) biomass. Numerous instrumental strategies and hard-soft acid-base (HSAB) theory were applied to investigate the sorption features and ...
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For the first time, sorption characteristics and mechanisms of group-4 elements were investigated and compared in extremely acidic solutions (4 M HCl) by rice bran (RB) biomass. Numerous instrumental strategies and hard-soft acid-base (HSAB) theory were applied to investigate the sorption features and mechanisms of Ti(IV), Zr(IV), and Hf(IV). The specific surface area of the raw biomass was 4.79 m2.g−1 as determined by Barrett-Emmet-Taller analyzer (BET). Deposition of planned metal ions on the biomass was determined through a scanning electron microscope (SEM) with energy-dispersive X-ray spectroscopy (EDS). The linkage of C=O, O-H, and N-H functional groups of biomass with metal ions became clear with Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectrum analysis. The role of C=O functional group of ammonium oxalate/ammonium carbonate in metal ions desorption was confirmed by elution experiment. The experiments showed that the high-affinity of rubidium to sorption of zirconium and hafnium (>99%) was owing to their lower hydrated ionic radius. From all the results obtained, exhausting-hard interactions and electrostatic complexation mechanism were diagnosed between hard-functional groups of RB biomass and hard cations of Ti(IV), Zr(IV), and Hf(IV).
Saeed Alamdar Milani; Ali Yadollahi; Mohammad Faryadi
Abstract
An immobilized hybrid biosorbent (IHB) was prepared by hybridizing two biosorbents and evaluated for its ability to remove thorium ions from aqueous solution. The combined effect of the initial pH of solution (2 to 6), initial Th(IV) ion solution concentration (50-300 mg.L-1), IHB dose (0.5-5 g.L-1), ...
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An immobilized hybrid biosorbent (IHB) was prepared by hybridizing two biosorbents and evaluated for its ability to remove thorium ions from aqueous solution. The combined effect of the initial pH of solution (2 to 6), initial Th(IV) ion solution concentration (50-300 mg.L-1), IHB dose (0.5-5 g.L-1), and sorption duration (10 to 180 min) was investigated using central composite design (CCD). Experimental data were analyzed using Design Expert 8.0.6 software and fitted to a second order polynomial model with logarithm transform function. The adequacy of the model was verified using three indices, model analysis, coefficient of determination (R2) and the lack-of-fit test. The initial pH of solution was determined as the most effectual factor on Th(IV) ions biosorption removal by using the analysis of variance (ANOVA). According to the obtained results, pH value of 4.5, initial metal ion concentration of 210 mg.L-1, IHB dose of 5 g.L-1, and sorption duration of 95 minutes were proven to be the optimum conditions, for maximum biosorption removal of Th(IV) ions from aqueous solutions. Thermodynamic parameters have been evaluated, and it has been determined that the sorption process is feasible in going forward with more products than reactants, exothermic in nature and the reaction is entropy-driven. The equilibrium data were analyzed by the Langmuir, Freundlich, and Temkin sorption isotherms. Maximum monolayer sorption capacity of the IHB was found to be 142.86 mg.g-1. Pseudo-second-order kinetics model provided the better fit for all the biosorption processes which let suppose a physical rate-limiting step for the process.
Afshin Hedayat
Abstract
Nowadays, a very particular type of nuclear reactors has become fascinating not only for most nuclear communities but also for the prominent energy suppliers to fix the global warming effects worldwide. They are Small Modular Reactors called SMRs. Usually, SMRs can are classified according to the seven ...
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Nowadays, a very particular type of nuclear reactors has become fascinating not only for most nuclear communities but also for the prominent energy suppliers to fix the global warming effects worldwide. They are Small Modular Reactors called SMRs. Usually, SMRs can are classified according to the seven different categories. They include PWRs (especially iPWRs), BWRs, PHWRs, GCR, LMFBR, MSR, and MMRs. Although many different plans have been proposed worldwide, only a few well-established or successive developing action plans are among many innovative conceptual designs. This paper briefly presents a comparison study reviewing the last advances and challenges. The proposed roadmap is strongly correlated and depends on the technology readiness and documentation, technology availability, safety and reliability, design, and construction feasibility for different countries. A new graded approach Phenomenological Identification Ranking Table (PIRT) has been developed and proposed to choose the most profitable and compatible action plan dependent on the situation. Finally, the best feasible designs are compared and proposed against the lack of First-of-A-Kind (FOAK). Furthermore, different options are proposed for different priorities and preferences based on the available nuclear infrastructures. Studies are very profitable to save money and time and develop a strategic action plan for newcomers and developing countries. On the other hand, some exceptional designs have extraordinary advantages for industrial countries and even more for the future of nuclear energy worldwide. Therefore, the proposed roadmap covers short-term, mid-term, and long-term strategies for developing countries and newcomers in the nuclear reactor industry.
Ali Biganeh; Hosein Rafi-Kheiri; Omidreza Kakuee
Abstract
A two-dimensional coincidence technique is carried out to suppress the background for exploring the contribution of positron annihilation with core electrons. The spectrometer is composed of two face-to-face HPGe detectors. To test the performance of the system, the Coincidence Doppler Broadening (CDB) ...
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A two-dimensional coincidence technique is carried out to suppress the background for exploring the contribution of positron annihilation with core electrons. The spectrometer is composed of two face-to-face HPGe detectors. To test the performance of the system, the Coincidence Doppler Broadening (CDB) ratio curve of pure well-annealed Copper is investigated. The quality of the annealing process is measured using Positron Annihilation Lifetime Spectroscopy (PALS). For comparison of the ratio curve of different laboratories, an Aluminum sample is considered as a reference due to its simple electronic structure. The element-specific CDBS signature of Copper shows the two peaks around 12.8×10-3 m0c and 19×10-3 m0c at the ratio curve which is dependent on the momentum of Fermi electrons. The presented ratio curve is compared with the reference measurement and simulation. Differences and the similarities in the reported ratio curves are discussed. The comparison shows that our result is more compatible with the theoretical calculations and can be considered as a new reference for future studies on the chemical environment of defects in alloys that include Copper in their contents.
Abolfazl Shoghi; Seyed Ali Hosseini; Amir Saeed Shirani; Mehdi Zangian
Abstract
The pressurizer is a key equipment to ensure the safe operation of pressurized water reactor by maintaining the reactor coolant system pressure within allowed tolerances. Various pressure control systems (Pressurizer) are adopted in industrial applications to satisfy their characteristics. In accordance ...
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The pressurizer is a key equipment to ensure the safe operation of pressurized water reactor by maintaining the reactor coolant system pressure within allowed tolerances. Various pressure control systems (Pressurizer) are adopted in industrial applications to satisfy their characteristics. In accordance with the purpose of using nuclear facilities, Steam, Gas-Steam, and Gas Pressurizer (PRZ) have been used. In nuclear industry, the dynamic behavior of each PRZ is different. Peak pressure is one of the important parameters in choosing the type of PRZ. This study has been evaluated for the University of Wisconsin High-Pressure Critical Heat Flux (WHPCHF) facility as the base loop. Three PRZs are connected to the WHPCHF loop to evaluate their performance during the in-surge scenario. The Peak pressure of the three PRZs is evaluated during transients. The results showed that the use of the Non-condensable Gas (NCG) increases the peak pressure due to the lack of NCG condensation during transient conditions. The use of gas PRZ makes it possible to change the pressure quickly. Also, the pure gas PRZ has the highest peak pressure but has straightforward control logic. The gas PRZ is the best choice for small reactors and high-pressure test facilities.
Sepideh Shafiei; Mohammad Lamehi-Rachti
Abstract
In the present paper, the dechanneling and the energy loss of protons at the energy interval of 1400 to 2200 keV along the {100} and the {110} planar directions of Si were studied by the simulation of the measured channeling Rutherford back-scattering spectra based on the exponential dechanneling function ...
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In the present paper, the dechanneling and the energy loss of protons at the energy interval of 1400 to 2200 keV along the {100} and the {110} planar directions of Si were studied by the simulation of the measured channeling Rutherford back-scattering spectra based on the exponential dechanneling function with a parameter λ. This parameter is proportional to the dechanneling rate and represents the mean distance that ions travel along the channel before escaping from the channel. The Levenberg-Marquardt algorithm was used to set the best values of the channeling to random energy loss ratio, and the mean channeling distance. The experimental results are well reproduced by this simulation. The data analyzed in this energy range did not show any particular trend with regard to energy dependence of the parameters. The differences between both the planar channels in the Si crystal and their influence on the energy loss ratio and dechanneling of proton ions are described.
