JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2024 | Volume:44 | Issue:4|Papers Count:20

The total excitation energy, TXE, as a function of fission fragments, is evaluated for neutron-driven fission of 230-236U using the statistical scission point model. In this model, as the systematic model, the total excitation energy includes the deformation and intrinsic energy. TXE values calculated by the systematic model are compared with the available experimental data for the neutron-induced 233U. Then the total excitation energy as a function of fission fragments is evaluated for neutron-induced fission of 230-236U. The total excitation energy distribution is compared for neutron-induced fission and for photofission of 233U and 238U. There is little difference between the TXE distribution of neutron-induced fission and photofission. The prompt neutron distribution is evaluated by using the obtained total excitation energy. The calculated prompt neutron number has a large variation for even uranium isotopes due to the neutron-separated energy of fission fragments. In addition, the prompt neutron number for heavy fission fragments is less than the experimental neutron number which due to the excess neutron of those fragments. It is due to the evaporation of an excess neutron with lower TXE values in heavy fragments.

The nuclear level density parameter is an important quantity in nuclear physics. Nuclear level density parameter has been calculated using different methods. In this work at first, the single particle level density has been calculated by LDA method, then the nuclear level density parameter has been obtained as a function of temperature. Based on Lestone method and using Thomas-Fermi approximation, the level density parameter has been calculated to the order of next to Lestone results (corrected Lestone method). Using calculated nuclear level density parameter and taking into account the pairing energy, the nuclear level density, excitation energy, entropy and heat capacity have been calculated

Hydrogen isotope separation can be achieved by confinement to small mesoporous structures or by strong adsorption sites. MOFs are attractive candidates for isotope separation, considering their tunable pore structures and the potential to introduce adsorption sites. In this research, we investigate the formation of elongated dihydrogen complexes near MOF’s open metal sites as a promising reaction for isotope separation. The electronic structure of all MOFs (M is the first-row transition metal) is studied based on density functional theory. The quantum chemical approach suggests Fe-MOF as a promising candidate for isotope separation by modeling the non-covalent interactions with the active site/H2 cluster.

In this research, the analytical and numerical comparison of the R model cascade with Q and QI model cascades for stable isotope separation has been done. In this regard, the numerical codes for the design of the R and QI model cascade for comparison to the analytical Q model cascade have been written in MATLAB software. The results show that for two components k1 and k2, a few R-cascades are special states of the QI cascade for the k1 component. Also, the findings show that the sum of the partial cut values for two components k1 and k2 in the cascade R is always equal to one (θk1,s+ θk2,s=1). Based on the results, if the parameter M* in the Q model is equal to the mean value of the two components, k1, and k2, in the R model, these two models are the same. Therefore, the R cascade is a special case of QI and Q cascades. The QI cascade encompasses a wide range of cascades, and by choosing the right cut in it, optimal relations can be achieved. For example, the results for isotopes 4 and 9 of Xe show that the total flow rate is optimal for the QI cascade. This is compared to the Q and R models.

The quality of heavy water performance in atomic power plants as a substitute for neutron particles depends on its degree of purity. The concentration of heavy water in the nuclear industry is of significant importance. The Heavy Water Reactor of Isfahan, in the nuclear sector, includes a heavy water purification and condensation system. This was launched at the same time as the reactor was built. For electrolysis of water and its isotopes, such as heavy water, it requires a lot of electrical energy, so it should be economical and workable. Several parameters contribute to the optimization of the operating conditions of the electrically operated apparatus. These parameters can control the number of exhaust gases, energy efficiency, and polarization in electrolysis processes. But the practical study of the role of various parameters on heavy water electrolyzer performance is very costly. Therefore, in this paper, the role of some parameters, such as tube temperature and electrolyte concentration, is modeled on the functional conditions of the electrolyzer by dynamic equations. And by introducing a variety of voltage losses in the electrolyzer system, an equation for the electrolysis voltage is obtained. The electrolyzer voltage equation is selected as the target function. The role of the parameters mentioned in energy efficiency optimization has been investigated. The electrolyzer is alkaline and contains 7% w/w potassium carbonate electrolytes. This electrolyzer has condensed heavy water with a purity of 90% to 99.8%. The results of modeling show that by increasing the concentration of potassium carbonate electrolyte by 10%, the electrolyzer polarization can be reduced (15.4%) and increase the electrical energy efficiency by up to 18.3%. Also, the results of the modeling show that by increasing the temperature to 25 C°, the electrolysis will perform better and reduce the polarization and energy consumption by 4%.

This paper discusses the implementation of an algorithm for solving 2D time-dependent neutron transport equations in heterogeneous media. A novel modular ray tracing algorithm where neutrons are allowed to travel a longer path before being removed from the structure, is adopted for the transient calculation. The time derivative of angular flux is considered as a major source of challenges in implementing the neutron transport equation, in which two cases for the time derivative of angular flux are included, first, the angular dependency of the time derivative is preserved and second mode, isotropic scalar flux approximation is applied to the time derivative. Sensitivity analysis on time step size has been investigated as an effective parameter on both computational accuracy and cost. Investigating the compatibility of the proposed numerical algorithm as well as considering the substantial role of delayed neutrons in transient processes, three multigroup mathematical models for delayed neutrons are evaluated along with the neutron transport equation. For the implementation of the verification algorithm, the well-known TWIGL benchmark is modeled and the results are compared with MPACT and DeCART codes.

Proton computed tomography (pCT) can reduce proton therapy uncertainty by measuring Relative Stopping Power (RSP) directly. The spatial resolution of the pCT images decreases due to the multi colomb scattering (MCS) of protons inside the phantom. This reduction of image quality can be compensated by using the most probable proton path in the reconstruction algorithm. In this study, a pCT system was simulated by particle-to-particle tracking of protons using the Geant4 toolkit. This simulation improves the spatial resolution of images obtained from applying different estimators of the proton path, including straight line path (SLP), cubic spline path (CSP), and most likely path (MLP). The Catphan528 phantom was irradiated with 200MeV protons. The energy, position, and direction of the particle were recorded before and after the phantom. The RSP image matrix was modified by weigthing factors obtaind using SLP, CSP, and MLP path esitimators and image was reconstructed using FBP. Spatial resolution and root mean square errors (RMSE) were compared to phantom image data. According to the results, the MLP method is less error-prone and more accurate than other methods in resolving spatial resolutions. For 100,000 protons, with image resolution ranging from 1 to 0.1 mm, the spatial resolution increased from 3 to 9 line pairs/cm, while the RMSE increased from 8.11% to 14.97%.

Calculating the absorbed dose in the human body is one of the first steps in radiopharmaceutical development. This study estimates the dose absorbed by humans from the novel identified compound of 64Cu-NODAGA-RGD-BBN. For this purpose, 64Cu-NODAGA-RGD-BBN labeled compound was first prepared by changing the labeling decisions in optimal conditions. The stability of labeled heterodimer peptide was evaluated in phosphate-buffered saline (PBS) and human blood serum for 12 hours. After that, the complex's bio-distribution was investigated in tumor-bearing mice for 12 hours after injection. Finally, the dose absorbed by humans after injection of the 64Cu-NODAGA-RGD-BBN labeled compound was calculated based on mouse data using RADAR and mass extrapolation methods. The results showed that the obtained labeled compound could be produced with a high radiochemical purity of more than 99% and is highly stable (higher than 96%). 64Cu-NODAGA-RGD-BBN showed high uptake in gastrin-releasing peptide receptor-expressing tumors compared to other non-target organs. Furthermore, the dose assessment for this compound indicated that the body and other organs did not absorb a significant dose after injection.

In this study, using the MCNP Monte Carlo code, the gamma-ray protection properties of the glass system with the composition of (55-x)Bi2O3-15Pb3O4-20Al2O3-10ZnO-xTiO2 with certain concentrations (35, 30, 25, 20, 15, 10, 5 = mol percent) were examined by calculating the several parameters related to photon attenuation such as half-value layer (HVL), mean free path (MFP), mass attenuation coefficient (𝜇m), effective atomic number (Zeff) and buildup factor (BF) for different energies in the range of 1500-100 keV. To verify the simulation results, a comparison was made with the XCOM database. It was observed that the data extracted from the NIST-XCOM database and the MCNP simulation results are in reasonable agreement with each other. The percentage deviation (PD) between the data extracted from the NIST-XCOM database and the results obtained from the MCNP simulations was less than 0.59% in most cases. The results show that compared to conventional protective materials such as concrete and lead, the new composition shows more effective attenuation parameters in addition to physical properties. The glass with the highest concentration of TiO2 has the most favorable properties in terms of density compared to the investigated protective materials. In this study, one of the variance reduction methods was used in order to reduce the error in MCNP calculations. The agreement between the data extracted from the NIST-XCOM database and the results of the simulations of this study shows that Monte Carlo modeling is an effective method to investigate gamma-ray shielding characteristics.

The LEU miniature plate irradiated in the Tehran Research Reactor, which produces the radioisotope molybdenum-99, is a radioactive source consisting of various radioisotopes. Before any practical application, it is necessary that the dose rate of gamma rays emitted from this source be calculated. This was done for comparison with the recommended dose rates for radioactive materials transport and radiation protection of employees during hot tests. In this paper, the validity of a proposed method for calculating the dose rate of gamma rays emitted from hot targets was investigated, experimentally. The Monte Carlo code MCNPX and multi-step algorithm written in MATLAB were used in the proposed method. The results showed that the calculated dose rate was always lower than the measured dose rate. Therefore, based on a conservative view, it is better to multiply the calculated dose rate values by 2 and then compare them with the allowable limits. This will enable you to determine the appropriate shield thickness.

Electrostatic accelerators use a constant potential difference to create a suitable electric field and accelerate ions and electrons. One of the most widely used electronic accelerators in the industry, the dynamitron accelerator uses a voltage multiplier circuit to generate the voltage required for acceleration. The capacitor elements of the voltage multiplier circuit in the dynamitron accelerator are constituted of semi-cylindrical electrodes located in a columnar array. The design of this column of electrodes, also known as the voltage multiplier column, is a complex process. It requires the study and simulation of electromagnetic fields and circuit models. The conceptual design of this structure is also complicated due to parameter interdependence. In this article, after a brief introduction to different parts of the dynamitron accelerator and details of voltage multiplier columns, a process for the conceptual design of the voltage columns of a dynamitron accelerator is presented.

To perform a neutronic analysis of the reactor core, it is necessary to develop nuclear computing software to produce multi-group constants and numerical solutions to the multi-group neutron diffusion equation. For this purpose, some methods are used in nuclear calculation codes that, in addition to the necessary accuracy of cost and computing time, are optimal. This paper discusses the average current nodal expansion method as well as higher orders of flux expansion. Then, the discretization of the neutron diffusion equation with ACNEM is shown, which has the ability to calculate in optimum time and with good accuracy. The discretization of the Forward and Adjoint neutron diffusion equation is performed for two-dimensional hexagonal geometry in two energy groups and then the SH3-ACNEM reactor core simulator is developed. To verify; the calculations for the IAEA-2D reactor core are performed and compared with valid references. It results that the computational error improves from 11.36% to 3.52% by increasing the flux expansion order from quadratic polynomials to five.

One of the most efficient methods for modifying the surface of polymers for some specific applications such as the production of adsorbents is the grafting of functional monomers onto polymers. In this research, the grafting of acrylonitrile and methacrylic acid on the surface of polypropylene hollow microfibers and its effective parameters such as radiation doses and concentration of functional monomers were investigated using peroxidation and mutual gamma irradiation methods. The highest rate of grafting was 81.2% which was related to the mutual irradiation method with 45 kGy radiation dose, which was carried out in the monomer concentration of 40% and in the presence of ferric chloride inhibiting salt with a concentration of 0.2%. The use of Mohr’s salt in the mutual method had a lesser effect in preventing the side reaction of polymerization due to its low solubility in the organic medium. The highest rate of grafting using 0.2% Mohr’s salt at 40 kGy irradiation dose was 33.62%. Infrared spectroscopy of the grafted samples confirmed the results obtained by calculating the grafting percentages by the gravimetric method. In addition, the results showed that the peroxidation method performed at the Atomic Energy Organization's gamma radiation center was not effective.

In this research, temporal variations in intense TEA CO2 laser pulses passing through SF6 gas-filled cells with a pressure of 10- 150 mbar have been characterized at different energy fluences and gas pressures. It has been shown that for every fluence there is a certain cut-off pressure at which the pulse spike is completely quenched. While the pulse tail escapes, saving appreciable fractions of its initial energy. Experimental evidence along with FTIR spectrometry data have clearly revealed incisive laser-induced multi-photon dissociation of SF6 molecules in these conditions, pronounced as the main responsible for these behaviors.

In this paper, copper-gold and copper-silver bimetallic surface nanospheres were formed using ArF excimer laser irradiation with a wavelength of 193 nm and a duration of 15 ns on thin film samples consisting of two metal layers deposited on BK7 glass. The density and shape of the structures were obtained under different irradiation conditions. The optical properties, morphology, and stability of optimal copper-gold and copper-silver structures were compared. The results show that high-density copper-gold core-shell nanospheres with high optical response and stability are produced at a fluence of 150 mJ/cm2 and 5 laser pulses. Silver-copper nanostructures showed lower density, weaker optical response, and lower stability than other nanostructures. The obtained copper-gold nanostructures are suitable for use in plasmonic applications such as biosensors and surface-enhanced Raman spectroscopy.

In this work, the plasma sputtering technique was used for Cu deposition on the silk fibroin film. Because of the extraordinary properties of silk fibroin such as flexibility, excellent mechanical properties, and biocompatibility, it is considered a promising material for the new generation of flexible electronic devices, implants, and wearable electronic devices. After optimization of magnetron sputtering parameters, silk fibroin film was deposited by Cu as a sputtering target for 6 minutes. The results of conductivity analyses and tests of four probes demonstrated that the deposition of silk fibroin film by plasma sputtering results in conductive film fabrication. Moreover, the surface morphology was examined by SEM analysis which clearly shows the Cu atoms among species on the surface. EDX analyses revealed the elemental composition of the material which shows clear Cu peaks after plasma sputtering. As a result, plasma sputtering is a fast, clean, and efficient technique for the deposition of metal on polymer surfaces including silk fibroin to form a conductive flexible surface.

The conditions of ignition and burn of nuclear fusion fuel in the presence of impurities are one of the critical issues in the fuel pellets design. In this paper, the impurity effect of Au heavy nucleus on all ignition processes in non-equilibrium DT plasma using four temperature models in which the shape of photon energy distribution function effects photon temperature behavior has been investigated. This study investigates the negative effects of fuel impurity during hot spot formation and fuel ignition. The results of numerical calculations obtained from the simulation of all effective processes in ignition show that in the presence of these impurities, effective ion charge and as a result the bremsstrahlung radiation is increased, and eventually the fuel efficiency decreases.

White spot syndrome virus (WSSV) is one of shrimp and other crustaceans' most significant infectious agents. This research isolated WSSV from infected shrimp samples collected from Bushehr’s farms. It was confirmed by PCR and multiplied in Astacus leptodactylus crayfish hemolymph. Titration of WSSV was obtained in postlarvae by the Karber method as 10 5.4 LD50/mL and the virus were inactivated by the electron beam irradiation. The electron beams D10 value and optimum dose was obtained at 1.85 and 13 kGy. Electron beam irradiated WSSV (EBI-WSSV) was used as an electron vaccine to immunize L. vannamei. Gamma-irradiated inactivated Vibrio Parahaemolyticus (GIVP) was used as an immune stimulant. PD50 was calculated 5.62, 6.30 and 2.87 for the injected groups with EBI–WSSV vaccine, EBI-WSSV vaccine+ GIVP and GIVP alone, respectively. The relative percent survival (RPS) values were calculated 64%, 72% and 22% for the EBI-WSSV vaccine, EBI-WSSV+ GIVP and GIVP groups by injection route and 75%, 85% and 12.5% for these three vaccine groups in immersion route, respectively. A significant difference in cumulative mortalities was observed between both vaccination groups (EBI-WSSV and EBI-WSSV+ GIVP), and the GIVP group (P<0.05). Therefore, two vaccine groups 1 and 2 induced productivity responses in shrimp against WSSV infection and GIPV enhanced this response. The conclusion showed the irradiated Vibrio Parahaemolyticus can be used as an immune stimulator and can enhance the protective effect of electron WSSV vaccine. The RPSs in the vaccinated groups by injection and immersion routes are without any significant differences.

Rosemary plant extract as a natural anti-oxidant is 4 times stronger than synthetic anti-oxidant like BHT and BHA. For this reason, it has been under attention not only for its anti-oxidant properties rather for its anti-inflammatory, anti-tumor, anti-bacterial, and anti-virus properties in different studies. This research investigates the effects of temperature, time, pH, and substance concentration in the labeling of irradiated rosmarinic acid by radioisotope gallium-67 as a high-resolution imaging agent for SPECT imaging. In this study, gamma irradiated rosmarinic acid nanoparticles at 20 kGy and 30 kGy levels in two concentrations of 0.5 and 1% were radiolabeled by gallium-67 radioisotope produced in Karaj cyclotron, and their efficiency and radiochemical purity were compared. Labeling conditions (including pH, temperature, time, and compound concentration) were investigated. Quality control was performed by thin-layer chromatography (RTLC). Resulting from the experiments, 30 kGy level and 1% concentration at 45 °C for 30 minutes at pH = 5.5-6 proved to be the best time for labeling rosemary nanoparticles, and the highest radiochemical purity achieved was 95%; radio conjugate also showed good stability after 12 hours.

Determining the magnetic field profile is very important for studying flux surfaces, elongation, plasma boundaries, and real-time control in tokamaks. In this research, a system for calculating and displaying the shape, position, and boundary of plasma for Damavand Tokamak control room has been developed. This system determines the magnetic field profile and flux surfaces in the time interval between two consecutive shots. This software is implemented based on measurements with the probes' sensors and electromagnetic flux loops. It also solves mathematical equations based on the physics of the problem. In order to calculate the magnetic field profile and the plasma shape, after preparing and collecting the data from the data acquisition system, a developed code is used to pre-process the data, such as noise reduction, removing unnecessary data, etc. Then, using another code, the cross-section parameters such as shape, position, and plasma boundary are calculated and displayed in the tokamak control room. All the codes of this system are written in MATLAB software and as a graphical user interface procedure. This is so the tokamak operator has easy access to the results after every shot. This system is currently installed and operated in the Damavand tokamak control room.