مجله علوم و فنون هسته ای
سال چهلم شماره 1 (پیاپی 87، بهار 1398)

In this paper, adaptive thresholding at the wavelet transform is utilized for improving the industrial radiography images. The quality of radiographic images is a very effective parameter in the defect determining by the experts. Therefore, the defect detection capabilities can be improved by the image processing algorithms. In this research, two-stage adaptive thresholding method has been used to improve the contrast of the inspected areas. The radiographic image is decomposed to several sub-bands using the wavelet function and the obtained coefficients are corrected by the threshold function. Then, the inverse wavelet transform is applied for obtaining the corrected image. Unlike the usual methods, in the threshold function of this method, the coefficient of under the threshold level is not zero and weakened by the multi-polyminal function. The advantages of this method are the continuity and derivability at threshold level. The proposed algorithm is implemented to the several radiographs of standard welded objects with known defects. The results have been evaluated by industrial radiography experts and show that the defect regions are clearer in reconstructed images than the original radiograph according to the operator perception analysis. Mean while, the dimensions and style of defects can be evaluated more precisely by this method.

Photo-transferred thermoluminescence (PTTL) response of α-Al2O3:C (TLD-500) was fitted to the theoretical PTTL model. It was found that, the area under the PTTL glow curve depends only on the population of charge carriers in the active traps and the numbers of active traps does not affect the PTTL glow curve area. Further more, the deep trapping states in this phosphor depopulate at high temperatures and it is not possible to obtain their kinetic parameters directly, as by increasing the temperature, the peaks in the glow curve are affected by the thermal quenching effect (decrease in TL glow curve at increased temperature due to non-radiative transitions). In this work, the experimental PTTL responses obtained for different absorbed doses were fitted to the theoretical PTTL ones. Thus, the kinetic parameters of deep traps were obtained by comparing the responses generated by the model with the experimental results. The PTTL glow curve of TLD-500 is of importance since it can be used to re-estimate the absorbed dose, UV dosimetry and dating.

Nowadays, high temperature superconductors have been proposed for high current density at high magnetic field applications such as tokamak and MRI machines. In this paper, dependency of critical current on magnetic field, temperature and different curvature radius for specific sample of Bi-2223/AgMg composite tape are obtained. By using this superconducting tape, a D-shaped pancake coil is designed and built. The coil characteristics in the liquid nitrogen temperature are reported and compared with the results of the tape. Furthermore, we have obtained the portion effects of the bending and self-field in the critical current drop. Hysteresis behavior as a function of current rate during ramp up and ramp down cases on the voltage current curve at liquid nitrogen temperature has been investigated. Then by considering equivalent circuit for high temperature superconducting magnet, the behavior of the voltage in terms of current is analyzed. Maximum field generated in this magnet is obtained and quench minimum energy is measured for working current of 37 A at nitrogen vapor.

Performance of parallel-hole collimators may be evaluated by determining their response to a point radioactive source which for instance, the amount of collimator resolution is calculated by measuring the full width at half maximum (FWHM) of point spread function (PSF). The conventional method in calculating the response of the collimator to a point source by using Monte Carlo simulations is to map the signal values in each detector cell to the center of cell on the x or y axis. In this paper, a new computing algorithm has been proposed which optimally maps the signal values on these axes. The responses of LEUHR, LEHR, LEGP and LEHS collimators are simulated based on the conventional method and the optimized computing one by the MCNP5 code. The results have been indicated that the response based on the optimized method has a higher accuracy compared to that of the conventional one. The average relative differences between the amounts of resolution based on the optimized method and experimental data have been found to be considerably fewer than those of the conventional one. Therefore, one may obtain parallel hole collimators’ response with a higher accuracy by using the optimized computing method.

Medium power electron accelerators have many applications in industrial irradiations. In order to meet the industry needs of Iran, several investigations for design and construction of the medium power linear electron accelerator in the VHF band frequency with the energy range of 1 MeV - 5 MeV have been started. The acceleration cavity is one of the important components of this design. In this article the design and construction of the cavity are reported and the results of the simulations and measurements are compered. Mean while the essential parameters, including resonance frequency, quality factor, shunt impedance, figure of merit and transit time factor are evaluated for several configuration of cylindrical cavity using (CST), (HFSS) and (SUPERFISH) codes in order to design an efficient cavity for electron beam with the maximum energy up to 5 MeV and 50 kW power with the lowest power loss. After repeating the simulations and reliability of the results, the designed cavity was constructed and its parameters were measured. The results showed that the measured parameters are in good agreement with simulation results.

In this research work, different terbium doped lutetium aluminium garnet nano crystalline powders were prepared by the co-precipitation method in different sizes at different annealing temperatures. The structural properties and size of the different nano crystalline powders prepared at different temperatures were investigated by the X-ray diffraction pattern and TEM. Also, the atomic structure of different nano crystals in garnet forming was studied by Fourier Trans from Infrared (FTIR) method. The impact of different crystallite sizes on the absorption energy was investigated by the UV-visible spectroscopy. The emission and excitation spectra of terbium doped lutetium aluminium garnet nano-structure powders were measured at room temperature. The decay time of different nano crystalline with different sizes was examined at room temperature. The change of nanocrystalline size affects the decay time. Also, the investigation of terbium doped garnet emission spectra showed that this material can be used as an appropriate scintillator for detection systems such as medical diagnostic and therapeutic.

The paper deals with the optimization of uranium back extraction from the Alamine-336 loaded by synthetic solution (synthetic LOS) and Bandarabbas leach liquor (real LOS) by means of stripping process method. In this regard, the impact of two essential parameters including the reagent concentration and phase ratio (O:A) for stripping of alkaline agent containing sodium hydroxide (NaOH) and sodium carbonate (Na2CO3) togather with the pH for sodium chloride (NaCl) were investigated. To study these effects, a central composite design (CCD) under the response surface methodology (RSM) was employed. Based on the design of the experiments, the second-order regression model has been constructed to evaluate the optimzation of the stripping efficiency of uranium from Alamine-336. The optimum conditions for these stripping agents have been determined as NaCl (0.6 molL-1) with the ratios of O:A (1.41) and pH (3.1) NaOH (1.33 mol  L-1) with the ratio of O:A (1.26) and Na2O3 (0.72 mol  L-1) with the ratio of O:A (1.16). Under these optimal conditions, the stripping efficiency values up to %31, %45 and %54 were obtained for NaCl, NaOH, and Na2CO3 cases, respectively.

In this work, the ability of the modified Cystoseira indica algae by the Xanthation method has been investigated for the biosorption of Th (IV) ions from aqueous solution in the batch mode. The effects of the three process independent variables including pH(2–6), biomass dosage (0.5 g L-1 – 2.5 g L-1) and initial metal concentration(50 mg L-1 – 250 mg L-1) were investigated using the response surface methodology (RSM) based on the central composite design (CCD). The accuracy of the model was confirmed by ANOVA such as low p-value, high F-value and Regression. The results of the optimization showed that the biosorption capacity of Th(IV) under the optimal conditions (pH=3.31, initial concentration 250 mg L-1, and biosorbent concentration 0.5 g L-1) will be 230.628 mg g-1. The results of the modeling showed that the experimental data of biosorption rate of thorium were better fitted by the pseudo second-order kinetic model, and also the Langmuir isotherm describes the experimental data of biosorption quite well. The maximum biosorption capacity of thorium was estimated to be 329.90 mg g-1 by the Langmuir isotherm. In addition, the specifications surface of algae and mechanism of biosorption were investigated using the Fourier transform infrared (FTIR) analysis.

Dual purpose cask system is one of the most important developing systems of dry interim storage of nuclear spent fuels. Thermal evaluation of a dual purpose cask designed for transport and interim storage of spent fuels of Bushehr Nuclear Power Plant is carried out as appears in this paper. SolidWorks and ANSYS Workbench 15 are utilized for the modeling and thermal simulation of the cask under normal condition of transport, as well as, normal condition of interim storage, respectively. According to the results, the maximum temperature of the fuel cladding will not exceed the allowed limits and the fuel integrity will be maintainel. Furthermore, the temperatures of the other components are predicted in the range of allowed limits, demonstrating the safety of the cask under the normal conditions based on the IAEA safety standards.

Uranium playa type is limited reserves which are formed in special conditions. The Dagh-e-Sorkh playa is located at 30 km north-norgh east of Ardestan which is located in the Central part of Iran. The two main facies type of basin, including pediment and playa type were determined, and by drilling 77 pit, sampling and analysis with the Induced Coupled Plasma - Mass Spectroscopy (CP-MS), the uranium anomaly was identified in a layer with the thickness of 10 cm - 15 cm, where the maximum activity and uranium grade were 250 cps and 15 mg kg-1, respectively. The results showed the uranium mineralization potential of the basin is low.

Induced mutation is an appropriate method for increasing genetic diversity. In this study, some morphological traits of 33 mutant lines of M3 generation in medicinal plant Lallemantia royleana, derived from gamma irradiation of seeds at doses of 50, 100, 150, 250, 350, 450 and 700 Gy and control, were investigated through a completely randomized design with 5 repetition. Traits under the study included: the number of days to maturity, plant height, number of branches, inflorescence height, number of flower cycle per plant, number of flower cycle in the main branch and side branch, number of nut in flower cycle and plant, number of grains per nut, seed yield, biological yield, 100 seed weight and harvest index. The differences among mutant lines were statistically significant for all traits with exception of the number of nut in the flower cycle. Mutant line No. 11 that derived from dose 700 Gy, had the highest amount in traits such as inflorescence length, number of flowers per plant cycle, nut number per plant, seed yield per plant and biological yield. The cluster analysis based on the square Euclidean distance and Ward method divided the mutant lines into four clusters where the mutant line No. 11 alone was in a single group.

Heavy water has two heavy hydrogen atoms or deuterium. Chemical properties of heavy water are similar to light water, but their physical, thermodynamic, and nuclear properties are different. On the other hand, the Equation of State (EOS) is an important and suitable tool for studying the thermophysical behavior of materials and predicting them in different conditions in terms of pressure, temperature and amount. At present, there are different equations of state that can be categorized as theoreticall, empericall and semi-emperical. Regarding to the importance of heavy water and its role in various researches, in particular nuclear researches, and the application of this material in medicine and industry, the thermodynamic regularities of this material have been studied in this research using different semi-experimental equations of state based on van der Waals and Dieterici models. The comparison between calculations with the experimental data showed that the equations of state predicted the thermodynamic regularities of heavy water well qualitatively, but their quantitative behavior is different.