JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2015 | Volume:- | Issue:70|Papers Count:13

Industrial Radiography is one of the most important methods to detect weld defects such as porosity, slag and crack. The interpretation of radiographic films characterizes the weld defects. The defect detection depends on radiographic film quality and the expert of interpreter. If the provided images of the industrial radiography are not clear, the detection of the defect can be difficult. But the radiographic image is usually noisy and has low quality. Thus, it is requred to use methods that can detect the defect accurately. The use of image processing techniques is available to achieve this aim. It is noticed that human eye is used to see objects in three dimensions and can also detect the depth. Thus, in this research, the shape from the shading (SFS) method is applied for two-dimensional radiographic images to extract three-dimensional ones. For the evaluation, the experts’ opinions in radiography have also been considered. The results of comments indicate that using the SFS method is valuable to improve the defects detection in weld radiography.

In this paper, the effect of the potential barrier and open area of Silicon along the crystallographic direction <100> and <110> on the channeling stopping power and the channeling half- distance for protons are investigated. The channeling stopping power and the channeling half- distance for protons are measured by simulation of the channeling spectra in the energy range of Ep=1800-2200keV. It is assumed that the dechanneling process behaves exponentially. It showed that the channeling stopping power for protons decreases when the potential barrier and open area of channel increase. Furthermore, the channeling half- distance increases by increasing the open area of the channel.

Ion beam analysis (IBA) has been widely used for fast, sensitive, multi-elemental and nondestructive analysis without any sampling, especially for the pigment analysis. External beam PIXE and PIGE techniques are applied simultaneously to large archaeological samples, kept at atmospheric pressure during the irradiation. In this research work, an external beam was used for the analysis of lapis lazuli samples and the azure color of the archaeological tile. By comparing the spectra, we found that cobalt is used to create azure color in archaeological tiles, while in lapis lazuli, no cobalt is observed and sodium is the characteristic element of the azure color in the lapis lazuli samples. It was also shown that lapis lazuli can be identified by the ion beam analysis.

The effect of the host medium viscosity of the superheated drop detector on formation and stability of Freon-12 bubbles produced by neutron irradiation has been investigated. By variation of the acrylamide and methylenbisacrylamide concentrations on monomer solution, different polyacrylamide gels with various viscosities of 1 up to 13 Pa-s were prepared. The gels were utilized to prepare the superheated droplet detector. The irradiation results of the prepared superheated droplet detector using an 241Am-Be neutron source and the 2.89 MeV neutrons obtained from the d-d neutron generator showed that the formed bubbles in the fabricated detector, based on non-crosslinked polyacrylamide gel, with the viscosity of 5-6 Pa-s were stable and could be counted after irradiation with the naked eye. The number of bubbles were found to be proportional to the neutron fluence.

Because of the suitable decay characteristics of terbium-161 (161Tb), it is a promising radioisotope for development of new therapeutic complexes and also a good alternative to 177Lu. In this study, the production routes of 161Tb are evaluated by both theoretical and experimental methods. In the theoretical approach the chain decay equations are solved and the activity of the radionuclide and all of the other products are obtained by imposing constant values in the equations. The main route for the 161Tb production is the 160Gd (n, γ)161Gd (b-)161Tb reaction as an indirect production method. In this method, natural or enriched gadolinium can be used. For the 161Tb production, 1 mg of natural gadolinium is irradiated at the Tehran Research Reactor, using thermal neutron flux of 3×1013 cm-2 s-1 for 34 hours. The activity of each product is evaluated by means of gamma spectrometry. The results show that about 0.11 mCi of 161Tb is produced in this condition. Due to confirmation of the calculations with experiments, it can be concluded that production of about 100 mCi of 161Tb is possible by a long time irradiation of 10 mg of enriched 160Gd.

Nodal is a method for solving the neutron diffusion equation. It is categorized to analytic, semi-analytic and expansion nodal methods. In this research work, a software is developed in order to solve two group neutron diffusion equations in two dimensional Cartesian geometries. There are some approaches to the analytical solution of the neutron diffusion. An interesting approach, that is our recent concern, is the transverse leakage approximation. Based on this approximation, the two-dimensional diffusion equation is split into two one-dimensional equations and is solved analytically for each energy group. In this paper, we used flat and quadratic polynomials in order to approximate the transverse leakage terms. Finally, two reference problems are solved for verifying the proposed method. The results showed that the analytic nodal method with quadratic transverse leakage approximation gives very accurate results for the reactor core calculations.

Over the past decades, the 137Cs approach has been successfully applied in Iran for estimating soil erosion and sedimentation rates. By the progressive reduction in 137Cs activity due to radioactive decay, however, it is essential to investigate the use of an alternative environmental radionuclide with a constant deposition through time, such as Lead-210. In this study, soil samples were collected within seven hectares cultivated field to determine the magnitude and spatial pattern of soil redistribution budgets. The net erosion rates for 137Cs and 210Pbex techniques were estimated to be 4.6 and 12.3t ha-1 yr-1 respectively and the sediment delivery ratio reached 52 and 60 percent respectively using mass balance model 2. Totally, soil erosion and deposition mean estimated from the 210Pbex measurements were much higher than those of 137Cs, since in the case of 137Cs, the results provided an estimate of the mean erosion rate over a period from 1963 to the time of sampling, whereas for the 210Pbex technique, the estimates reflect a longer time period. The changes in the land management and rainfall characteristics that have occurred during the past century in the area under the study have had important influence on the soil redistribution estimates by the 210Pbex. This study has demonstrated the potential of using 210Pbex measurements to estimate soil erosion and deposition in semiarid regions.

The in-situ polyethylene glycol coated superparamagnetic magnetite (Fe3O4) nanoparticles (SPMNPs) were prepared by a co-precipitation method from the acidic solutions of FeCl2.4H2O and FeCl3.6H2O, containing polyethylene glycol (PEG), using aqueous solution of NaOH. The optimum coditions of the precipitation of polymer coated magnetic nanoparticles were determinned. It was found that the concentration of acid, sodium hydroxid, and polyethylene glycol influenced the size and structure of nanoparticles. The sizes and the size distribution, structure, and coating of the nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometry (XRD), Fourier transform infrared spectrometry (FT-IR) and thermogravimetry analysis (TGA) techniques, respectively. The size of the uncoated nanoparticles was varied in the range of 8-28 nm and after the coating it did not change significantly. Finally, the modification of the particles was carried out simply by mixing the modifiere (Cyanex 272) with nanoparticles powder for a time duration of approximately one hour. The nanoparticle that was treated by Cyanex 272/SPMNPs of weight ratio of 7.5:1 possessed better characteristics for Uranium(VI) and Thorium(IV) recovery from aqueous solutions.

Electron microscopy studies (EPMA- WDS and SEM- EDS) provided detailed information about the morphology, source, transport, diffusion, properties, transformation reactions and environmental impacts of aerosol particles in digging tunnels of underground uranium mine in Saghand area. The size, aspect ratio and chemical composition of particles were studied by SEM-EDS but the mineralogical phase compositions of the particles were investigated by EPMA. EPMA analysis indicated that particulate matters (PM) were mainly composed of irregularly shaped mineral particles. Analysis of 46 individual particles showed that all particles were mineral aggregates and some of them contained sulfur. The X-ray diffraction (XRD) analysis showed that the main minerals were clay minerals, iron oxides, amorphous materials, quartz, calcite, pyrite and hornblende. Clay minerals were to the greatest illite/smectite mixed layers and kaolinite and chlorite as secondary elements. The particulate matters collected during the drilling episodes were characterized by high quartz/clay ratio and dominance of illite/smectite mixed layers in clay minerals. The concentration of dusts in different parts of digging tunnels, in poorly ventilated parts of the mine was below the OSHA standard. The existence of aerosols of uranium minerals plus quartz indicated that the personnel of the mine were exposed to serious health hazards unless they were equipped with suitable environmental filters.

In this paper, electron temperature and ion density of laser-produced plasma in the nanosecond time scale at different ambient gas pressures are studied using single Langmuir probe up to distances of the order of centimeter. The plasma is produced due to the interaction of a focused Nd:YAG laser beam of 30 ns pulse duration with a solid target. Stainless steel rods with 0.35mm diameter are used as Langmuir probe. The reduction rate of the electron temperature and plasma density are estimated within a distance of the order of centimeter. The values of the electron temperature at low pressures of 10-5 up to 10×10-5 mbar are in the range of 2-8eV at the probe distances of order of centimeter. The average value of the ion density is in the order of 1011 cm-3 at the distances 4-6 cm from the target.

A perfluorosulfonic acid (PFSA) polymer membrane is an attractive proton-conducting material for polymer electrolyte to be used in fuel cells. In this study the effect of gamma irradiation on the structural changes in perfluorosulfonic acid membrane was investigated. The obtained results showed that the membrane structure changed by increasing the adsorbed dose. The irradiation effects on structural changes were investigated by optical absorption measurement in the wavelength of 190~500 nm, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction. The optical absorption measurement showed an increase in the absorption bands intensity by increasing the adsorbed dose. Moreover, the FT-IR spectra showed a novel absorption band at 1773 cm-1 after the irradiation and the XRD results indicated crystallinity improvement by increasing the absorbed dose. Vickers microhardness test showed that the hardness increased by increasing the absorbed dose.

Tribolium castaneum (Herbst) is a very harmful pest of stored products, which causes qualitative and quantitative damage. Application of gamma radiation is an appropriate strategy to control this pest. In this study, the effect of different doses of gamma radiation on the egg, larvae and adults stages of T. castaneum until all of the pests were amnihilated, is evaluated. The experiment was conducted at 27±1oC, 60±5% R.H. in dark. The egg, larvae and adults were irradiated by 100-500 Gy of gamma radiation. In these experiments, compared with the previous studies, lower doses were used in a long time period. Mortality of different stages of T. castaneum was assessed 24 hours after the irradiation and continued until the death of the last sample. The results showed that the most sensitive stage was egg, with 100% mortality by 50 Gy. The second stage of the sensitivity was the larvae, with the compelete death by 500 Gy after 12 days. Adults, compared with other life stages, showed relative resistance so that only 13.33% mortality was occurred at 100 Gy after 16 days. It was concluded that use of gamma radiation could be an appropriate method to control the population of T. castaneum in the stored products.