JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2021 | Volume:42 | Issue:1 (95)|Papers Count:15

In the present work, a numerical method is proposed in order to model the subcooled boiling flow in a vertical channel using the Drift Flux Model. The system of nonlinear equations is solved with the fullyimplicit scheme using the Jacobian-free Newton– Krylov (JFNK) method. In order to improve the efficiency of the JFNK method and its numerical stability, a semi-implicit physics based preconditioning (PBP) is implemented. Recently, the JFNK method has been widely used to solve large and sparse system of equations. To validate the proposed method, the results were compared with the experimental data, the results of modeling by using the RELAP5 code, and the available numerical results in the literature. It was found that the results corresponding to the present work have a good agreement with those of the other mentioned methods. Also, it was found that the convergence rate of the JFNK method with the PBP is at least 50% higher than the JFNK method, and the void fraction mean absolute percentage error (MAPE) is less than 7. 34% over a wide range of flow and pressure.

In the present study, the uranium recovery by utilizing the bulk liquid membrane which contains Alamine 336 has been investigated. The effect of uranium and sulfuric acid concentration in the donor phase, carrier concentration in the liquid membrane phase, and ammonium carbonate concentration in the acceptor phase and transport kinetics were studied. The optimum conditions of uranium transport were obtained at 0. 15 mol. L-1 H2SO4 in donor phase, 0. 5 mol. L-1 (NH4)2CO3 in the acceptor phase, 0. 0125 mol. L-1 Alamine 336 in kerosene. The results demonstrated that by increasing the concentration of sulfuric acid up to 0. 15 mol. L-1 and the Alamine 336 concentration to 0. 0125 mol. L-1, the uranium transfer will increase and then decrease. The uranium transfer was decreased with an increment in initial uranium concentration. Studying the effect of time on the uranium transfer showed that the cause of ratecontrolling is the release of uranyl from the liquid membrane phase to the acceptor phase. The kinetics of uranium transport was modeled assuming consecutive irreversible pseudo-first-order reactions. The extraction rate constant of 0. 0061 min-1 and 0. 0107 min-1 and the stripping rate constant of 5. 56×10-4 and 12× 10-4 min-1 were obtained for liquid membrane containing Alamine 336 and sulfated Alamine 336, respectively.

In this paper, the plasma parameters of hydrogen glow discharge were measured using Langmuir probe system. To measure these parameters in Damavand tokamak, different parts of the Langmuir probe were designed and fabricated. The electrode used in this system is a tungsten wire with diameter and length of 0. 1 and 6 mm, respectively. The electrical circuit constructed for this system is capable of supplying voltage and current in the order of 400 V and 1 A, and can produce triangular pulses in the frequency range of 10 Hz to 10 kHz, respectively. Glow discharge hydrogen plasma, which is used for vacuum vessel cleaning and conditioning, is produced by two electrodes located in the lower part of the Damavand tokamak with the voltage of 450 V, current of 1. 5 A and pressure of 10-3 Torr. By applying voltage to the electrode of probe, in the range of 200 to 350 V, the current drawn from the probe was measured. By interpreting the current-voltage characteristic, the plasma parameters were determined. The electron temperature, plasma density, plasma potential, and Debye length of the hydrogen glow discharge measured using this system are 5. 8e V, 1. 17×1015 m-3, 236 V and 523 μ m, respectively.

In designing the fuel rod, having a reliable prediction of fuel performance is of high importance in order to comply with safety principles. Various computer codes have been provided for this purpose. Each of these codes uses different mechanical models, numerical and analytical methods. Accordingly, the purpose of the present work is to develop Fortran computer software for mechanical and thermal analysis of fuel rods using numerical methods, especially applying the principle of virtual work in mechanical analysis of fuel rods in steady-state conditions. The finite element method is used to solve the equations. The mechanical analysis includes phenomena such as swelling and fuel density and clad creep. Through these phenomena and simultaneous performance of mechanical and thermal analysis, fuel-clad interaction, stress and strain rate in fuel and clad, fuel center temperature, oxide layer thickness, fuel, and clad temperature distribution during operation is obtained by the code. The results of the code are compared with the results of the analytical method which are available in other research works. Finally, for the VVER1000 reactor, mechanical and thermal analysis of the fuel rod was performed over a 1600-day interval. According to the simulation, the fuel-clad interaction occurs after 1250 days.

Transverse intensity distribution or laser mode profile is one of the most important characteristics of a laser oscillator. In the present study, mode profile of a LED-pumped Ce: Nd: YAG laser oscillator and its dependency on the geometrical configuration and intensity of optical pump sources have been experimentally and theoretically investigated. Experimental observations show that with a proper pumping geometry and the control of electrical pumping power of the light-emitting diodes, a wide spectrum of stable transverse beam profiles with Ince-Gaussian mode pattern can be generated. In addition, numerical computations based on randomly ray tracing and calculation of the absorbed pump power per unit volume of the active medium, gain profile, and the propagation of optical field inside the optical resonator were confirmed the effect of the pumping configuration and distance between the emitter surface of LEDs and lateral surface of the active medium on the mode profile of the laser oscillator.

The application of gamma irradiation as a factor to graft the synthesized silver nanoparticles to the polypropylene surface and modify the de-ionized (DI) water supply system is a new experimental project. In this study, using the effect of gamma irradiation on the surface of a certain type of filter reduces silver ions and modifies the filter surface, simultaneously. Then, the effect of the modified filter on the performance of DI water supply systems, which are directly and indirectly related to quantum technologies and nuclear science, was investigated by modeling on the surface of indium phosphide (InP) semiconductors. The dose of gamma irradiation and the reduction conditions of silver nanoparticles were determined after passing the optimization stage. So, scanning electron microscopy (SEM), energydispersive X-ray spectroscopy (EDX), ultraviolet-visible absorption spectroscopy (UV-Vis), attenuated total reflection (ATR) and bacterial counting tests by plate count agar (PCA) were used. Then it was found that the desired result of filter surface modification is due to the formation of surface plasmon resonance in the colloidal solution of silver nanoparticles which is produced during gamma irradiation synthesis.

The ability of amino-functionalized hydrothermally synthesized titanosilicate nanoparticles (TiSiNH2) was investigated for the adsorption of Th(IV) from aqueous solutions in batch mode. The effects of four process-independent variables including pH, initial metal concentration, sorbent amount, and temoerature were investigated using response surface methodology (RSM) based on central composite design (CCD). The accuracy of model was verified by coefficient of determination. The results of optimization showed that the sorption capacity of TiSiNH2 for Th(IV) under optimal conditions was 83. 04 mg g-1. The results of modeling showed that, experimental data of adsorption capacity of sorbent for Th(IV) were better fitted with double exponential kinetic model and Langmuir isotherm can describe the equilibrium data well. The maximum adsorption capacity of TiSiNH2 for Th(IV) was estimated to be 87. 71 mg g-1 by Langmuir isotherm.

The aim of this study was to label quercetin as a natural flavonoid compound with technetium-99m and to study its biological distribution in different tissues of C57 mice bearing melanoma B16F10 cells for tumor diagnosis. Quercetin labeling was performed with technetium-99m at 1. 5 mg quercetin and 40 μ g SnCL2 at room temperature and pH about 5. Labeling yield was evaluated using TLC in acetone and water / acetonitrile as solvents. Also, in animal study, the tissue activity of various organs including heart, lung, stomach, intestine, liver, kidney, blood, spleen, muscle, and tumor were measured through gamma counter. Radiochemical purity above 95% and radiochemical stability of 90% at one hour were observed. The results of biological distribution of the labeled compound showed the highest radioactivity uptake in liver, kidney, intestine and tumor (2. 2 ± 0. 17 at 2 h post injection) tissues. Quercetin labeled through direct method with high radiochemical purity can be used as a candidate for diagnostic radiotracer.

One of the important parameters in the square cascade, which has a great influence on its performance in the separation of multicomponent isotopes, is the cascade cut. In this research work, at first, the effect of cascade cut on the separation of xenon middle isotopes in a square cascade with 20 stages was studied. These studies were carried out for two cases in which the separation factor was 1. 2 and 1. 1. Moreover, the minimum length for creating a long cascade by changing the Z/F value and cascade cut has been determined. Based on the calculations, if the separation factor is 1. 2 and 1. 1, the minimum number of cascade stages will be 55 and 110, that's not simply possible. The results showed that the appropriate cascade cut in the long cascade is different from the short cascade. Using the parametric studies of the short cascade, it is possible to determine the most appropriate cascade cut in which the desired isotope concentration reaches its maximum. In order to maximize the amount of Xe-129 in a 20 stages cascade, the suitable cut is 0. 2 in the separation factor of 1. 2 and 0. 15 in the separation factor of 1. 1.

In the present research, mass transfer resistances of various steps of uranium biosorption using Pseudomonas putida @ Chitosan biosorbent in a fixed bed column were calculated. The description process dynamic parameters using dimensionless numbers showed that the Biot number was greater than 30 in all experiments which confirms the high mass transfer rate of the liquid film in comparison with intra-particle diffusion. Increment of the mass transfer driving force across the liquid film via enhancement in the inlet concentration along with a decrease in the liquid film thickness through a reduction in the sorbent particle size caused a decline in the mass transfer resistance of the liquid film. Furthermore, the Peclet number was found to be increased with increment of the bed height and decrement of the sorbent particle size which indicates a shortening in the mass transfer region thickness and reduction in the axial dispersion resistance. The biosorbent structure caused the pore diffusion flux to be negligible in comparison with the surface diffusion flux. The surface diffusion was the dominant intraparticle diffusion mechanism. The obtained results showed that intraparticle diffusion resistances were several times greater than liquid film resistances and axial dispersion resistances in all experiments, and also were the rate-controlling step. Since the change in operational conditions has a small effect on the intraparticle diffusion, the column efficiency was only proportional to the process residence time, varying between 0. 00% to 53. 00%.

Anti-reflective optical elements prepared on ZnSe substrates are the main optical devices in CO2 lasers. These anti-reflective coatings are used in the far-infrared region at the specified wavelength of 10600 nm. For the preparation phase of these anti-reflective coatings, first, the characterization of the used materials in this wavelength was investigated and then YbF3 and ZnS were chosen. However, a lot of research work has been done in the country to make reflection mirrors of gold and silver for a wavelength of 1. 6 microns, but no research has been done on anti-reflective optical window or part of it at this wavelength. Then, antireflective coating at 10600 nm was designed by the Macleod software using these two materials. These thin films were deposited on one side of ZnSe substrates by physical vapor deposition (PVD) method with Balzers-Ba510 coating system. Optical element operation was investigated by a 10 W CO2 laser and the transmission was measured for the standard anti-reflection, the polished substrate, and the deposited antireflective element. The results show that the prepared anti-reflective element has 77. 84% transmission coefficient. By studying the morphology and thickness of the layers by SEM, it was found that the transmission coefficient of ZnSe substrate is optimized by the prepared anti-reflection element.

In this paper, the effects of the pulse rise-time in the performance of the electron heating in the interaction of intense laser pulse with under-dense plasma have been investigated using the particle-incell (PIC) simulation code. In this way, two laser pulses with a length of 200 fs and different pulse risetime of 80 fs and 40 fs have been selected. The laser intensity and the plasma density are I=1018 w/cm2 and n=0. 02 ncr (ncr is the plasma critical density), respectively. To correctly characterize the local plasma temperature in different regions of plasma, the stress tensor elements have been used. Our results show that the electron heating and the temperature of the electrons are strongly dependent on the laser pulse rise-time and increase significantly with decreasing the pulse rise-time. In other words, when the pulse rise-time is initially smooth (80 fs), the scattering fields can provide the necessary condition for stochastic heating. Whereas, in the quickly rising pulses (40 fs), the electron heating is initiated by the wave breaking. In the following, the effect of increasing the laser pulse intensity on the electron heating is investigated for the pulses with different rise-times, hence these effects are more severe for the pulses with the short rise-time.

Distance measuring between two metal plates by γ-ray backscattering is a new method that is applicable for different industries, especially the oil, gas, and petrochemical industry. In the present work, 2, 6, and 10 mm thick steel plates were used as thin, medium, and thick plates to perform the experiments. Also, two sources of 137Cs and 60Co have been used to show the effect of source energy on the accuracy of the measurements. The results showed that the distance measurement depends on the Gamma-ray energy, and for the same measurement accuracy, the Gamma source with higher energy would be more applicable for measuring the distance between two steel plates. Moreover, it was found that increasing the γ-ray energy will increase the accuracy of the measurement. In addition to the energy of the gamma source, the distance measurement depends on the thickness of the two plates, the arrangement of the thicker plate comparing to the thinner ones, and the distance between them. Finally, increasing the distance between the plates leads to reducing the measurement accuracy, which was calculated to be one centimeter.

The purpose of this study is to investigate the possibility of producing iron-55 as an X-ray source for the scientific and industrial applications. There are some advantages for this method: the elimination of the manganese electro-plating, dissolving process in the target production step, and the need for the complex stages of chemical and radio-chemical purification. The calculations of proton energy for the target bombardment was performed using the ALICE/ASH method. The samples were evaluated to produce iron-55 determination by X-ray and gamma spectroscopy. Manganese-54 was produced as a major impurity in the production of iron-55. The Separation and purification phase of iron-55 from manganese was carried out by combining of precipitation and liquid-liquid extraction. The amount of manganese and manganese-54 was significant, but the results showed that the separation of manganese from iron-55 has been performed efficiently. Also, results agreed that the production and purification of iron-55 radioisotope for territorial use in Iran is possible with the proposed method.

This study aimed to produce a personal dosimeter to connect the electronic devices to transfer the dosimetry data online including dose rate data and integral dose. At first, an electronic board was designed. Afterwards, the board was simulated using Altium Designer software. Then, the microcontroller programming was performed using Code Vision software. The performance of the elements was tested using Proteus Design Suite software and the circuit diagnosis and testing were practically implemented. Afterwards, the calibration factor and the count-to-dose conversion coefficient were obtained using an ionization chamber in the Secondary Standard Dosimetry Laboratory of Iran. Furthermore, dose distribution as a function of distance to the source, was obtained using the produced dosimeter and was compared using a calibrated ionization chamber. To this purpose, an unmitigated Cs-137 source, a Cs-137 source with a 22 mm Pb shield, and a Cs-137 source with a 22 mm plus 18 mm shield were used. The results showed a calibration factor of 0. 99 ± 0. 02 for the designed dosimeter. Calibration results showed that the produced dosimeter passed the ISO/IEC 17025: 2005 criteria. Furthermore, the dose distribution results demonstrated negligible differences of less than 0. 01% between the produced dosimeter and the reference ionization chamber. It was concluded that the produced dosimeter could be used as a reference and standard dosimeter in laboratories, for monitoring and dosimetry of ionizing photon radiations.