مجله علوم و فنون هسته ای
سال چهل و چهارم شماره 2 (پیاپی 104، تابستان 1402)

Neutron Computed Tomography (nCT) is one of the modern applications of research reactors. The combination of the Three-dimensional representation capability of tomographic imaging and the unique properties of neutron interaction with materials creates valuable information about the internal structure of materials and components. In this study, the effect of data acquisition geometry and method of image reconstruction on tomographic images of the Tehran Research Reactor Imaging Facility (TRRIF) have been investigated based on contrast and the ratio of contrast to noise parameters. In experimental data acquisition, two radiation geometries have been aligned with angular steps of 1 and 0.5 degrees, respectively. Two samples were turned within the neutron radiation field at a half-screen. Image reconstruction has been performed through FBP and ART, SART, and SIRT algorithms, using Python programming language. The stack of images has been rendered to gain sample volume. Initially, in order to reconstruct the image through a high-quality set of projections, experimental data acquisition parameters have been optimized. Then, pre-processing has been carried out on projections. The results showed that the sample components and some defects could be differentiated from each other. Contrast and CNR were improved in data acquisition geometry with smaller angular steps and through SIRT reconstruction method.

In the present study, the aim is to synthesize and introduce the combination of methoxy amido xanthate MAX and then label it with 99mTc radionuclide as a novel diagnostic agent for single-photon computed tomography (SPECT) imaging. A chelator-designed ligand was synthesized from a blend of chloroacetamide and xanthate in certain proportions. After that MAX ligand labeling process was performed by directly milking 99mTc from the generator (99Mo / 99mTc). Thus, tin chloride was employed as a reducing agent, and the effect of parameters such as additives like ascorbic acid, changing the concentration of the cheating agent, and pH were evaluated to optimize the labeling conditions. The product was then identified by infrared spectroscopy (FTIR) and magnetic resonance imaging (NMR). Labeling of the complex at laboratory temperature was determined to be 93%. The new 99mTc-MAX radiopharmaceutical with a radionuclide and radiochemical purity of over 90% can be used as an encouraging diagnostic agent in clinics and preclinical studies, which will be addressed in future studies.

Neutron radiography (NRG) is a non-destructive imaging technique for image generation using neutron radiation. In this paper, feasibility studies of neutron radiography for IECF were performed by Geant4 Monte Carlo code. The effects of the different thicknesses of lead on the image and the detection possibility of cavities with different sizes inside a thick lead have been investigated to understand the performance of the device for neutron radiography purposes. The quality of the images was evaluated in terms of contrast. The simulation results showed the efficiency and limitations of NRG for IECF devices and the potential areas where NRG can be performed.

In this study, the effect of gamma irradiation and chitosan on the shelf life of minced beef was investigated. A part of the meat sample was treated with a 2% chitosan solution and the other part was irradiated without chitosan at doses of 3, 5, and 7 kGy in the Gamma cell. Non-irradiated samples (controls) and irradiated samples were evaluated for microbial contamination, quality characteristics including color, odor, blood, and customer likelihood (overall acceptability) as well as lipid peroxidation. The results showed that both irradiation and chitosan treatment had a significant effect on reducing the microbial load of the meat, including all living microorganisms, Staphylococcus aureus, Escherichia coli, and Salmonella spp. During the storage period. There were no significant differences in the qualitative characteristics of irradiated and chitosan-treated samples and the non-irradiated control samples. Finally, according to the permissible level of lipid peroxidation, a dose of 3 kGy, was detected as a suitable dose for irradiation of the minced beef to increase its shelf life of it from 2 days to 7 days at 4°C. All meat packing components had good radiation resistance to this dose.

Viruses pass cell walls and enter cells using their spikes, So one of the efficient ways to stop viral infections is to disturb their spikes functionality. In this research, the process of energy absorption and transfer by SARS-COV2, MERS-COV, UK-COV, and SARS-COV spikes was studied. In this research sample viruses exposed to radioactive radiations and results were compared by Geant4-DNA and analyzed. A strategy to reduce the virus life cycle is energy absorption. In this research, the response to viruses spikes to radiation was simulated. Samples were exposed to 10 eV–2 keV electron beams. The level of Energy absorption and its relation to the number of infected patients was studied. It was concluded there is an inverse relationship between absorbed energy level and patient death.

Some different time measurement methods have been presented for similar signals with the same trigger that one can choose by considering signal conditions. Finding the best time measurement method for the output signals from the UFSD (Ultra Fast Silicon Detectors) is our goal because we wanted to use these sensors to detect protons in the proton therapy system to treat cancerous tumors. Some different methods include Constant Fraction Discriminator (CFD), Cross-Correlation (CC), and Time over Threshold (TOT) by different data. These kinds of data include Data from Weightfield2 which is a UFSD signal simulator, Data from simulated signals in practice inside the laboratory, and experiment data, which are real data from the UFSD test in front of a Pico laser beam. Several programs in MATLAB software have been written and run to analyze and compare the different methods. The results are shown that CFD is the best method for time measurement finally

The proton induced prompt gamma spectrum is applied for elemental analysis of irradiation tissues. The main purpose of the analysis in proton therapy is to track oxygen concentration in abnormal tissues. Online monitoring of oxygen concentration over a full course of treatment could provide a direct method for evaluating the response of these tissues to proton therapy and this information on the response of the tumor and healthy tissues to irradiation could then be used by the oncologist to adjust the patient’s treatment plan to ensure proper dose delivery to the tumor. In this study, the prompt gamma spectrum of a human eye phantom is simulated in an HPGe detector using the Geant4 toolkit, and the elemental analysis is accomplished using an artificial neural network (ANN). In the analysis, 33 eye phantoms are considered with different tumors, including different densities and elemental compositions. 21 samples were used as train data in ANN and 6 samples for testing and 6 samples for validation. The results show that there is a good correlation between outputs and targets. They show that the error percent of oxygen, carbon, and nitrogen in test samples are less than 5.8, 12.7, and 25%, respectively. Finally, the potential of quantitative elemental analysis of inhomogeneous targets is confirmed for providing a method to track change in the oxygen level of tumors.

Reactor antineutrino detection is of interest today because it can estimate burnup status and fuel consumption characteristics remotely. Neutrino measurements are usually based on the inverse beta decay reaction of neutrinos with protons (hydrogen atoms) in scintillation materials. In this context, the IRAND scintillator detector has been developed with a segmented design and a scaled sample of it has been developed, which is referred to as a mini-IRAND. Neutrino measurements face challenges; In particular, interfering factors in neutrino measurements need to be well identified and separated from the main signals, of which cosmic muons are one of the most important. This requires an accurate understanding of the detector's response to cosmic muons. In this study, the Geant 4 tool was used to study the muon behavior in the mini-IRAND detector. Also, cosmic muons were measured for 21 days by the mini-IRAND detector and their characteristics were determined. The experiments were carried out with the development of a special digital data collection system and the development of processing algorithms. The results provide estimates of the instantaneous events (Michel spectrum) and the delay events (Landau spectrum). Consistency of results shows the accuracy of the process.

It is shown recently that the thermal neutron field of Isfahan MNSR with stable flux and dose equivalent rate can be used as a calibration field in dosimetry. The fundamental limit of this field is not the feasibility of using phantom for the irradiation of personal dosimeters. This issue leads to underestimating the personal dose-equivalents from the true values. The subject of this work is to correct the calibration curve of TLD-600 dosimeters irradiated without phantom. To do this, Monte Carlo simulations using Geant4 are carried out and absorbed doses in this dosimeter for irradiation with and without phantom are calculated. Then, the ratio of these doses as a correction factor applies to the responses measured without phantom, and then the corrected calibration curve is determined. As an analytical approach, the correction factor is considered as the ratio of the mean number of thermal neutron reflections between air and water (with phantom) and in the air alone (without phantom). Results obtained show that the correction factors determined by the simulation and analytical methods are 1.57 and 1.44, respectively, which agree well with the 8% difference. Finally, the response correction has led to changing the calibration factor of TLD-600 dosimeters from 0.0012 to 0.0008.

To produce the Technetium-99 isotope from Molybdenum-99 radioactive decay and purify the product of small-scale acidic target dissolution, the gaseous Iodine impurity has to be reduced to AN acceptable level. Solid adsorbents are used for this reason. One of the best adsorbents is based on Silver-Exchanged Mordenite. In this research, the synthesis procedure and characteristics of synthesized adsorbent have been discussed. To prepare solid adsorbent, spheric mordenite hallow crystals of about 10 micrometers and the Si/Al ratio of 5.2 were synthesized and granulated using a binding agent, stabilizer, and foaming agent. Prepared granules were silver exchanged. The silver content of the end product was evaluated 8.1 weight percent. Results from gaseous Iodine adsorption showed that 99.2 percent of passing Iodine was adsorbed.

Carbonate solution is used for the alkaline leaching of uranium from solid waste. Time, temperature, stirring speed (independent parameters) and total carbonate concentration, carbonate to bicarbonate ratio, and the ratio of liquid eluent volume to solid waste weight (L/S) (dependent parameters) are effective parameters in the leaching process. Independent parameters were optimized using the one variant at time (OVAT) method and the dependent parameters were evaluated simultaneously with the use of MINITAB software and using the face central composite design (FCCD) method. The solid waste powder was analyzed by EDAX, SEM, and XRD, and elemental analysis of samples was performed by ICP-OES after complete dissolution. Duration time of 0.5 hours, the stirrer rotation speed of 150 rpm, room temperature, concentrations of 0.09, 0.01, and 0.1 M for sodium carbonate, bicarbonate, and total carbonate, respectively, with a ratio of 9.1 and 20 for the ratio of sodium carbonate to sodium bicarbonate and L/S, respectively, were optimal conditions. Reproducibility of solid waste leaching was obtained by performing 4 experiments and the values of 94.2±2 and 4.15±1.6 were obtained for the average percentage of leach and solid residue, respectively. The average uranium grade was 2.09±0.02.

In the current work, the graphene oxide was synthesized through Hummer’s method and modified with nickel hexacyanoferrate nanoparticles. The product was characterized by a Scanning Electron Microscope (SEM) and Fourier Transform Infrared spectroscopy (FTIR). The characterization results confirm the successful synthesis of graphene oxide and the immobilization of nanoparticles on it. The obtained graphene oxide-nickel hexacyanoferrate (GO-NiHCF) was applied for the removal of Sr(II) from the aqueous media in the batch method. The influence of effective factors such as pH, time, and initial concentration of strontium on adsorption was studied. The pH study showed that Sr(II) uptake increases in the pH range of 1-7 and the uptake reduces slightly or remains constant at higher pH values. The adsorption capacity under optimum conditions was obtained at about 140 mg g-1 adsorbent. The kinetic data of Sr(II) sorption by GO-NiHCF were investigated by pseudo-first-order and pseudo-second-order models. The results showed that the kinetic data fitted well to the pseudo-second-order rate model. The equilibrium data suggest the data are relatively fitted well to the Langmuir adsorption isotherm. Therefore, it can be understood that adsorbents’ dispersion on graphene oxide sheets or interlayers is homogenous. The separation factor(RL) value extracted from the Langmuir curve was estimated as 0<RL<1, showing the sorption behavior is favorable.

The resolution of a mass spectrometer is dependent directly on the strength of the output ion and its energy. The number of produced ions depends on the current and the energy of the electron beam. One task of the electronic collision source control circuit is to regulate the current and energy of the electron beam to achieve optimal resolution. Parameters such as the stabilization of the electron beam current and its energy, the precise change of the electrical potential of the lens, and the ion source electrodes are very important in the construction of the electronic collision source control circuit. In this paper, the ion source control circuit was designed and built and stabilize the electron emission current, beam energy, and electrical potential of points. This controller circuit was installed and tested on the Varian MAT 44 mass spectrometer. The stabilization of the current and energy of the electron in this control circuit was measured to be less than 1%.

High-density carbon ablator is one of the promising candidates for thermonuclear ignition in inertial confinement fusion. A double-layer polystyrene-high dense carbon ablator has been used to reduce the hydrodynamic instabilities as well as protect the fuel from the preheating phenomenon. Therefore, in this study, we investigated the optimization of a typical double ablator spherical target with an initial polystyrene ablator layer with a thickness of 37 µm by using MULTI-IFE hydrodynamic code. This target was irradiated with symmetrical laser beams with 22.7 ns pulse duration, 0.25 µm wavelength, and 1.7 MJ total pulse energy. Our calculations show that the optimal thickness of the high-density carbon is about 5.6m. Using a diamond ablator increases the absorbed laser energy at the target surface by approximately 8%. Increasing the absorbed energy leads to an increase of about 5% in the alpha power deposition, and as a result, the fuel burn fraction increases by about 1.5%. Eventually, fuel acquire increases by approximately 12%.

In this study, the current discharge and the power supply system of toroidal field (TF) coils of Damavand tokamak have been designed and simulated to increase the magnetic field time and consequently the plasma duration. Currently, the TF coil current used to form and confine plasma has a sinusoidal half-cycle waveform with a duration of 100ms and a current peak of 12kA which produces a 1.1T magnetic field at the center of the chamber and its flat-top area is about 20ms. With the aim of upgrading Damavand tokamak, in order to increase the plasma duration to 200ms, it is necessary to upgrade the energy supply system and control system of toroidal and poloidal field coil currents. For this purpose, in this paper, the main power supply system has been designed based on super-capacitors with a capacitance of 21F, voltage of 900V, and topology of series-parallel (7*8). Also, to supply and stabilization of TF current, the chopper converter with seven parallel modules with the closed-loop control system with hysteresis controller has been designed and simulated. The general system is capable of supplying and stabilizing the magnetic field from the range of 0.7 to 1.2 Tesla with a ripple of less than 0.2% and a duration of 200ms for the flat area. Also, the charging system of super-capacitors has been designed and simulated using the 12-pulse rectifier converter and the buck converter with the constant current method, which has achieved desirable results.

The electrical method as a geophysical survey can show the geological parameters including fragmentation, rock mass alteration index, saturation percentage and groundwater quality. These parameters play an important role in rock mass engineering classification by affecting the rock mass quality design (RQD) and geological strength index (GSI), mineralization of elements and drilling method. In this paper, using the vertical electrical sounding method in subsurface layers, the determination of these parameters and subsequently two mentioned indicators in anomalous III pyroclastic rock masses of Narigan deposit was investigated. The results showed that the interpreted electrical resistivity (using IPI2win software) has an acceptable correlation betweem the degree of alteration index and GSI in the rock mass. However, accurate determination of GSI and RQD using this geophysical method is not very reliable. In other words, using a mathematical equation, it is not possible to estimate the amount of GSI and the alteration index with the electrical resistivity.

The Dalir phosphate deposit is located 57 km southwest of Chalus city in Mazandaran province, the Central Alborz zone. This deposit is hosted by Soltanieh Formation, one of Iran's important hosts of sedimentary phosphates. The results of X-ray diffraction (XRD) analysis and optical and electron microscopy studies on the phosphate samples indicate that the main minerals include apatite, calcite, quartz, and dolomite accompanied by montmorillonite, pyrite, and barite in minor amounts; siderite, rutile, illite, and goethite in trace amounts. The concentration of P2O5, U, and REEs in the studied samples ranged from 5 to 16.1%, 1.9 to 5.5, and 45.9 to 136.9 ppm, respectively. The studied samples have negative Ce anomaly, indicating an anoxic environment during the Dalir phosphate deposition. Based on the factors controlling uranium concentration in phosphorites, the phosphate horizon of Soltanieh Formation does not have uranium enrichment potential due to warm to semi-warm humid paleoclimate with neutral to acidic pH of the seawater during the Dalir phosphate deposition in lower Cambrian. Finally, considering the results of the chemical analysis of phosphate samples of the Dalir deposit (lack of uranium enrichment) and also the factors controlling uranium concentration in phosphorites, it can be predicted that the other phosphate deposits of Soltanieh Formation probably not be uranium enriched.

Performance of a micropattern gaseous detector of parallel plate type, a Micromega detector, was assessed for X-ray astronomical studies in this research. For this purpose, COMSOL Multiphysics software which solves differential equations based on Finite Element Method was used. Thus, by solving Poisson equation in the detector geometry, electric field in each point was obtained. Gain of the detector was estimated by using the obtained electric field and solving continuity equation. Results show that simulated detector gain was 100 at voltage of 400 V. Obtained results corresponds well with the results of simulation of the detector with Garfield code which verifies the performed simulation. This detector is a proper tool for X-ray polarimetry with respect to its good characteristics such as high resolution, large area and good performance at high flux.

An electric dipole magnet quite similar to that of the IRANCYC10 cyclotron was designed and constructed to conduct the initial tests on the internal Penning ion source to be installed in the cyclotron. This magnet which was designed and constructed in the department of physics, University of Tehran, is capable of producing a magnetic field of 7000 G in the location of the source, a region in the center of the magnet with the radial extent of 15 mm, with no need for cooling. Magnetic fields as high as 1.1 T are also accessible for a few minutes. The ion source in IRANCYC10 is expected to be exposed by a magnetic field of 1100 G. The measurements show that the magnetic field in the location of the source is homogeneous with the maximum deviation value of 1.1% with respect to the magnetic field strength at the center. The magnet is H type with 100 mm pole diameter and 60 mm gap size. Comsol, Ansys Maxwell and SolidWorks codes were employed in the design and construction of the electric dipole magnet.

In this paper, the effect of various parameters on the pulse shape of the CO2 laser has been investigated. For this purpose, various parameters such as gas pressure and the length of the resonator were changed and the laser pulses shapes in each case along with their energy have been recorded. The results show that the output energy increases sharply with increasing gas pressure, so that when the pressure increases by factors of 2 and 3, the output energy increases by factors of 3 and 5 while the pulses duration reaches 0.5 and 0.3 and their buildup time reaches 0.9 and 0.7 of the initial values. In addition, by increasing the oscillator length, the width of the spike and especially of the tail parts of the pulses decease. To perform this series of experiments, a home-made laser with 1-3 atm operational pressure has been used