مجله علوم و فنون هسته ای
سال چهل و پنجم شماره 1 (پیاپی 107، بهار 1403)

Due to the importance of removing strontium ions in nuclear wastes, in the present work, while synthesizing hydroxybenzaldehyde propyltriethoxysilane ((EtO)3Si-HL) and pyridylmethylidene propyltriethoxysilane ((EtO)3Si-L) ligands, we investigated the properties of silica nanoparticles modified with these ligands as solid adsorbents in The removal of strontium ion from the aqueous solution was investigated and parameters such as pH, time, the mass of adsorbent, temperature, and interfering ions were tested. The adsorption behavior of the adsorbents showed that by modifying the surface of the nano adsorbent, the ability of the adsorbents to adsorb strontium ion at pH=6 increased from 6.31% to 86% and 22.11% using the (EtO)3Si-HL and (EtO)3Si-L ligands, respectively. The results of isotherms and adsorption kinetics indicate that the adsorption process follows the Longmuir isotherm and the pseudo-second-order model, respectively. Also, thermodynamic parameters show that strontium removal from the aqueous solution is an endothermic process. The positive entropy values are the driving force behind the adsorption process.

This paper explores the vibrational, thermophysical, and structural properties of thorium nitride using density functional theory. An agreement is observed between the calculated and experimental properties of the lattice constant and bulk modulus. In the density functional perturbation theory, diagrams of phonon spectrums and vibrational densities of states along high symmetry paths are calculated. Based on the phonon dispersion diagram, no imaginary frequencies are found, indicating that the crystalline structure is dynamically stable. The compound also exhibits a phonon gap in the range 154-300 cm-1. Under high temperature and pressure, quasi-harmonic Debye models are used to evaluate thermodynamic properties such as Debye temperature, thermal expansion coefficient, entropy isothermal bulk modulus, and vibrational specific heat capacity. As the temperature increases, the volume of the system at a constant pressure decreases, while it increases for all pressures at a constant temperature. As temperature increases at a constant pressure, the coefficient of thermal expansion increases, indicating that the crystalline lattice is transferring more heat.

In nuclear reactor calculations, such as burn-up and fuel management, transient analysis, and pin power reconstruction, methods are being developed that are optimal, and are both cost-efficient and time-efficient. In this paper, the discretization of the neutron diffusion equation with a high-order average current nodal expansion method is shown, which can calculate in optimum time and with acceptable accuracy. The discretization of the Forward and Adjoint neutron diffusion equation is performed for two-dimensional rectangular geometry in two energy groups and then the S3-HACNEM reactor core simulator is developed. To verify, the calculations for the BIBLIS-2D reactor core are performed and compared with valid references. It results that the computational error improves from 9.67% to 0.58% by increasing the flux expansion order from quadratic polynomials to fourth-degree polynomials.

Nuclear fuel clads are among the most important components of a nuclear reactor. These clads are typically made of zirconium alloy; However these alloys do not possess the best thermo-mechanical properties. Therefore, in this study we attempted to achieve a clad with more suitable neutronic and thermo-mechanical properties by changing the clad materials used in the NuScale reactor. The changes in the material used in the reactor core cause a change in the effective multiplication factor as well as the length of the refueling interval. These effective multiplication factors and refueling period were obtained as the most important neutronic results within this research through simulating the NuScale reactor that uses the M5 cladding as a reference reactor and furthermore, the simulation of this reactor accommodating a clad change with three other types of common alloys, two of which are zirconium alloy and one of which is FeCrAl alloy. The results reveal that zirconium alloys in tandem with different thermo-mechanical properties are not much different in the neutronic matter of the core. In addition, FeCrAl alloy however endowed with excellent thermo-mechanical properties has a negative compact on the effective multiplication factor and the duration of the fueling period. Ultimately, in order to compensate for the negative effect of FeCrAl alloy on the neutronic properties, two solutions were used; The solution of using FeCrAl as a coating on a zirconium clad which presented outstanding neutronic results.

X-ray applications in imaging and beyond require efficient and optimal detectors. Energy separation, time loss, and manufacturing cost are among the features that led us to design a semiconductor detector. A low-gain avalanche diode (LGAD) with internal amplification allows, in a sufficient field, the internal propagation process by accelerating the carriers, the energy required for ionization, and the generation of secondary carriers to produce a better gain (higher signal-to-noise ratio) and also provide more time efficiency (in the range of nanoseconds). In this article, we simulate the LGAD silicon detector with Silvaco software by applying reverse bias voltage and radiation in the range of visible light to X-ray. Newton and Gummel's methods were used. In Newton's method, one of the mechanisms of radiation interaction with matter is considered variable and the rest are fixed. However, in Gummel's method, all mechanisms are solved simultaneously. In the X-ray wavelength range, the electron current in this detector is 10-4 amperes, and this current decreases with increasing energy. The dark current is 10-6 amperes. By applying visible light with 0.45-micrometer wavelength and 1 V/cm2 intensity, the detector current was obtained about 6.5×10-4 amperes. For 1.0×10-5 x-ray wavelength and 108 V/cm2 intensity, detector current was obtained about 3.5×10-4 amperes. Considering the quick response time of this detector and the current in the range of microamps, this detector is a suitable option for X-ray detection. Also, this detector shows superior performance in the visible light range.

One of the most significant and common methods for early detection of breast cancer in the world is lymphoscintigraphy. In clinical trials, [99mTc]Tc-phytate has shown remarkable results for the detection of metastatic axillary lymph nodes prior to surgery. It is expected that the introduction and development of an appropriate alternative radiopharmaceutical including 67Ga for lymphoscintigraphy will be an important deal in the clinic as the half-life of 67Ga is longer than that of 99mTc (78.25 hours versus 6 hours). Radiolabeling of phytic acid with 67Ga is conducted in this study. Based on radioactive thin layer chromatography (RTLC), the radiochemical purity (RCP) was estimated at >99%. The final product represented satisfactory stability under human serum conditions, which was calculated to be greater than 89% during 3 days of study. Pre-clinical studies confirmed the urinary system as the main excretion route for radiopharmaceuticals. A human estimation dosimetry study based on preclinical data was also presented.

The purpose of this study was to investigate the effects of human age and gender on the estimation of the death risk due to cancer in head and neck CT scans. The participants were selected from a representative statistical population of different ages and genders who underwent head and neck CT scans. To determine the radiation dose of the patients, Impact-dose calculation software was installed on the computer of the studied device. Using the report of the Biologic Effects of Ionizing Radiation (BEIR) Committee, the risk of death due to cancer has been estimated according to the amount of radiation exposure and dose conversion coefficient, according to the patient's age and gender. The relation between human age and gender in estimating cancer death risk was examined using the obtained data and the SPSS statistical analysis program. A significant relationship was found between the estimation of the radiation-related death risk and gender and age in the studies. In other words, the death risk associated with head and neck CT scans is higher among women than men, at 32 and 27 per million, respectively. Moreover, human age plays a significant role in the estimation of the death risk caused by radiation. So, the younger the patient, the greater the risk of death due to radiation.

A large number of printed board circuits (PCBs) are analyzed by X-ray imaging in reverse engineering for the purpose of identifying their connections, their damage, and how they are linked together. Using this method, an X-ray is passed through single or multi-layer boards in order to determine how they are connected and how the parts are arranged. According to the findings, there is fogging in the radiographs due to X-ray scattering and the thinness of copper connections on the boards as well as the small sizes of electronic components. This research employs the Modified Total Variation method (MTV) with alternating gradient, which is an iterative method based on gradient changes in Total Variation, to increase contrast. Based on the results of the implementation of the MTV algorithm on radiographs of various ranges, the contrast has increased, and besides the copper connections, the internal components of the electronic components have also become clearer. Reconstructed images show a contrast improvement of approximately 20 to 40%, according to experts. Using this information, it is possible to repair or build boards in reverse engineering.

The plasma focus device can be utilized as an X-ray generator in radiographic applications. A few tens of nanoseconds after the pinch moment, the hard X-ray of this device is released in a time interval of 100-150 ns. The pulsed form of X-ray emitted from this device makes the common method of detection and spectrometry useless for characterizing them. In this article, passive spectrometry, using radiographic film with Al attenuation filters, was used to determine the pulsed X-ray spectrum emitted from the UIPF-1. Neural network technology was used to determine the spectrum according to recorded doses. The neural network was trained using MCNPX simulation results. The results showed that the X-ray spectrum extends from 6 keV to 50 keV with a maximum value of 8 keV when the UIPF-1 device is operated with the copper anode, the copper insert, the working voltage of 21 kV, and 0.9 mbar air gas injection. The average spectrum energy was also obtained at 17.5 keV.

Plasma gasification system technology is one of the definitive low-risk disposal methods. The article discusses the design and construction of a plasma gasification system using a plasma torch. In order to dispose of municipal solid waste, a DC plasma arc flame was implemented. The design and construction of the torch electrodes and their arrangement are such that when waste enters the plasma flame through the upper opening, it is permanently exposed to it. In this way, in addition to better mixing of reactants with plasma, stable performance, better control, and erosion will be reduced. In this system, due to the very high processing temperature, it is possible to remove toxic and contaminated waste. To characterize, analyze and identify torch plasma species and radicals, as well as to determine the electron excitation temperature, an optical emission spectrometer was used. Atomic and radical species such as O, N2, N, NO, and OH radicals were detected in the emission spectrum. Using the conditions of thermodynamic equilibrium and the Boltzmann method, the temperature was estimated at 5.38 eV. The gas composition was reported with the gas chromatography method including O2, N2, CO2, CO, and N2O gases.

The use of the initial power density gradient in the plasma makes disorder growth relatively slow and invisible. In fact, the power density reduces the disorder growth rate during the acceleration phase. By choosing a power density greater than 2 for the power density, the density changes decrease rapidly with increasing aspect ratio near the stagnation moment. For n=3 the disturbance amplitude is reduced by five times compared to the uniform state. In this research, the power density gradient along with the effect of static external magnetic field on the growth rate of Rayleigh-Taylor instability in non-uniform incompressible plasma confined between two planes z=0 and z=h has been analyzed analytically. The problem dispersion relation was derived by linearizing the MHD equations and applying appropriate boundary conditions. The results show that the growth rate of instability depends on the horizontal and vertical components of the magnetic field as well as the dimensionless parameter λ* (= -1.5, -0.5, 1), and the maximum instability occurs at λ*= -1.5. In order to manage the growth rate of instability, it is observed that the simultaneous combination of horizontal and vertical magnetic fields provides faster stability for the system. With the increase in the intensity of the static external magnetic field, the square amplitude of the instability growth rate decreases by about 15% and the critical point decreases by 58%. This decreasing process is very slow compared to the results obtained from the apparent density. Therefore, as expected, using the factor of 3 for the initial power density of the plasma causes a slight decrease in the growth rate of the disorder. This confirms the correctness of the calculations and the obtained results.

The purpose of this study was to design and build a tin-113/indium-113m generator with desirable characteristics and reasonable cost. A generator such as this can produce ionic forms of indium-113m that are suitable for labeling applications. The theoretical calculations were conducted using the programs TALYS-1.8, ALICE-91, and SRIM. Tin-113, the mother of indium-113m, the target of natural indium was irradiated in a 30 MeV cyclotron accelerator. The theoretical efficiency of 740 kBq/μAh was calculated for tin-113 production in the cyclotron. Finally, tin-113 was produced with an experimental efficiency of 555 kBq/μAh. Zirconium chloride and 0.05 molar hydrochloride are used as column adsorbents and generator solvents, respectively. The generator's step efficiency in a period of 6 months was 82%. The radionuclide purity of indium-113m from the generator was more than 99.9% and the average amount of parent radionuclide was within the pharmacopeia permissible limits equal to 0.0005%. The amount of interfering metal ions in the solution was less than 0.1 ppm. The results show that the in-house produced tin-113/indium-113m generator has suitable features and reasonable costs and that indium-113m radionuclides can be used in ionic form for labeling purposes.

The common mechanism of proton laser acceleration is Target Normal Sheath acceleration. This study investigates the geometry of the aluminum target used in high-intensity laser pulse interaction with plasma. The target with an exponential profile on the front and back sides and with different scale lengths from 0 to 0.85 μm is used as an input to the two-dimensional particle simulation code. The results of their proton energy distribution have been compared. It was found that proton energy decreased with smooth changes behind the target. This is due to the reduction in the electrostatic field amplitude behind the target. In addition, there is a threshold scale length (here 67/0 μm), after which the proton energy does not change with the increase of this quantity and the energy distribution of the proton beam almost overlaps. The transverse laser field emission and the same electron energy distribution were also observed for two targets with zero and 0.67 μm scale lengths.

Herein, impedimetric determination of uranyl ions (UO22+) by using a modified magnetically carbon paste electrode (MCPE) with hydroxyapatite magnetic nanoparticles (MNP/HAP) was reported for the first time. Firstly, magnetic nanoparticles were synthesized and then hydroxyapatite nanoparticles were precipitated on them via the chemical precipitation method. After that, the MCPE electrode was modified by MNP/HAP to collect UO22+ from an aqueous solution. Modification of the electrode and its interaction with UO22+ ions were studied by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) in the presence of a Fe[(CN)6]3-/4- and PBQ/H2Q, as a redox probe. Electrochemical impedance change against the concentration of UO22+ ions in the presence of electrochemical probes was selected as an analytical signal of this procedure. Optimized response for modified electrode with 100 µg MNP/HAP was observed after preconcentration of UO22+ for 30 min at pH 7, and for 35 min at pH 6 for Fe[(CN)6]3-/4- and PBQ/H2Q as a redox probe, respectively. The applicability of the impedimetric method in the determination of uranyl by using the proposed electrode was shown by drawing a linear calibration curve in the concentration range between 1×10-10 to 4×10-4 M of UO22+ in the presence of both probes. Detection limits as 7.58×10-11 M and 9.12×10-11 M and relative standard deviation (RSD) for n = 5 as %0.82 and % 1.05 were observed for Fe[(CN)6]3-/4- and PBQ/H2Q as a redox probe, respectively.

In this study, graphene oxide (GO) adsorbent was prepared by modified Hummer’s method and functionalized with aminomethylphosphonic acid. Its application to the adsorption of Sr ions from aqueous solutions in a batch sorption process was investigated. Adsorbents were characterized by TEM and FT-IR. The TEM images of functionalized graphene oxide showed that graphene sheets are formed in wavy sheets. The FTIR spectrum revealed that graphene oxide was highly functionalized with aminomethylphosphonic acid and oxygenated functional groups were reduced. Response surface methodology investigates pH, adsorbent dosage, and temperature parameters. The quadratic model corresponds well with the experimental data. The results illustrated that there is no systematic error in the experiments. The verification of the model with random experiments showed a low error in the values predicted by the model. The kinetic data were analyzed by Pseudo-first-order, Pseudo-second-order, and Double- exponential kinetic models, and experimental data were well modeled by the pseudo-second-order kinetic model. The research results showed that graphene oxide functionalized with aminomethylphosphonic acid has a good ability to strontium adsorption from aqueous solutions.

This article presents a simulation of a scoop inside the rotor of a gas centrifuge machine in three dimensions. The scoop inside the centrifuge machine is 3D and curved in shape. Therefore, a 3D simulation is necessary to analyze the proper flow behavior around the scoop. For this purpose, using the results of this simulation, the flow around the product and waste scoops has been investigated in three dimensions. As a result of simulation in the scoop area of the waste and product under operating conditions of pressure and temperature, it was observed that the values of these forces are directly related to the distance between the scoop and the wall, and the drag force values differ between these two areas. According to the investigations, the differences in drag force values between product and waste scoop areas can be explained by the effects of pressure, temperature, and velocity of gas molecules. There is a direct relationship between these effects and the coefficients of adaptation of momentum as well as the difference between the rotational velocity of the fluid around the scoop and the rotational velocity of the scoop per height (duѲ/dz).

In this paper, we first briefly describe the constructed Inductively Coupled Plasma Source device, ICP-13.56, which includes two vacuum and atmospheric pressure torches. Afterward, focusing on the vacuum-torch operation, we discuss the plasma temperature characterization and examine the phenomenon of E to H mode-transition during the variation of experiment parameters including the initial pressure and input RF power. Based on the spectroscopic measurements of argon gas at pressure 4 mbar and input RF power 400 W, the electron excitation temperature of 11636 °K was obtained using the Boltzmann line method. Additionally, we have calculated the absorbed power in terms of plasma density and gas pressure using equations governing electromagnetic fields in ICP plasma. According to these relations, behaviors of load characteristics have been analyzed and E to H mode transition has been identified.

Two phosphorite deposits including Paghela and Gadok, within the Jiroud Formation (Upper Devonian) in the northeast of Firoozkuh in the Central Alborz geotectonic zone have been studied. Microscope studies show that fluorapatite is the main phosphate mineral and the main gangue minerals are calcite and quartz. The P2O5, Uranium and ∑REE contents in the Paghaleh phosphorite range between 35.5-41.2%, 4.8-6.4 and 623-803.2 ppm, and in the Gaduk phosphorite vary from 12.3 to 41.1%, 4.7 to 7.8 and 369.2 to 784.8 ppm, respectively. The REE patterns normalized to Post-Archean Australian shales in Firoozkuh phosphorites are characterized by convex patterns without specific Ce anomaly, which indicates anoxic conditions in the diagenesis environment of the phosphorite formation. Mineralogical and geochemical studies and the positive correlation of REEs with P2O5 and CaO show that the main host mineral of rare earth elements in the phosphorites of Firoozkuh is fluorapatite. Also, minor amount of zircon and trace amount of monazite inclusions in the apatite are other minerals that host rare earth elements in these phosphorites. The lack of uranium enrichment in Firoozkuh phosphorites is probably either due to the lack of favorable source rock with leachable uranium in the continent, or by the initial weak oxidant conditions during phosphatization, which prevented the conversion of U+6 dissolved in seawater to U+4, and uranium could not replace Ca within the apatite lattice.

There are many applications with the CsI:Tl crystal, including spectroscopy, dosimetry, medical imaging, etc. The characteristics of this crystal, such as its atomic number, purity, and high density, have caused more attention to it. However, despite these advantages, the presence of an afterglow phenomenon in its emission spectrum limits CsI: Tl. In order to reduce the afterglow phenomenon, various elements have been used as co-dopants. In this research, Tm2+ and Eu elements were added to the CsI:Tl crystal. The glow curve of the crystal (heating rate of 10 oC/sec) was measured after irradiating the samples for 2 hours with a 90Sr source. The combination of the glow curve with the first and second-order kinetic models showed that the CsI: Tl crystal follows first-order kinetics. The glow curve from the CsI: Tl crystal in the presence of Eu and Tm2+ follows second-order kinetics. Then, with the deconvolution method, glow curves were separated into their individual constituent peaks, and the results showed that adding the co-dopant can reduce the contribution of the Tl element in the formation of the glow curve and shift it to higher temperatures thanks to the increase in the activation energy, as well as the new peak caused by co-dopant at low temperatures. The intensities of the upcoming peaks were lower than the peak caused by thallium. This is due to the high activation energy of the levels created by Eu and Tm2+ in the crystal structure. This phenomenon is due to the fact that electrons cannot be released at low temperatures. It can be concluded from the comparison of the Eu and Tm2+ peaks that Tm2+ elements create deeper traps in the crystal structure than Eu elements. This means that the effect of the element on reducing the afterglow in CsI:Tl crystals is more significant than the effect of the Eu element.

The development of electron beam applications motivates electron gun research. In addition to the beam energy and current, its quality also plays a significant role in the spread of electron guns. Herein, we present the design of an electron gun for use as an electron source in a linear accelerator with high beam current and quality. In this design, starting with the Pierce geometry, a stay-by-stay optimization based on the physics governed by the beam behavior has been carried out to control the emittance growth and get a beam of outstanding quality. In particular, non-linear transverse force, space charge effect, and spherical aberration are considered. This resulted in a threefold improvement in the beam quality as measured by the beam emittance.