JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2013 | Volume:- | Issue:1 (63)|Papers Count:13

These days, application of mesh free methods in the areas of numerical analysis and computational sciences has been the subject of many researches. In this paper, the mesh free method based on the point interpolation scheme is used to solve the one-group neutron diffusion equation in a two- dimensional Cartesian coordinate system. The Wendland type radial basis functions were applied to perform the interpolations. The Galerkin method was employed to discretise the weak form of the neutron diffusion equation. In order to calculate the integrations of the weak form of the equations, Gauss-Legendre scheme was applied. The efficiency and accuracy of the method was evaluated through a number of case studies. The results were compared with the analytical solutions. For the cases where the numerical solutions did not exist, the problem was simulated through the Citation code and the results were compared, accordingly. The Reed test problem was solved to show the performance of the developed code. A PWR reactor core was also simulated through the introduced method. The effect of combination of different Wendland functions with polynomial functions on the accuracy of the results was also assessed. There is a good agreement between the numerical and the analytical solutions, and also the result from the Citation code revealed the accuracy of the method, and the good performance of the applied method was also confirmed in this study. At last, the developed method introduced in this work was found to be applicable to implement the desired nuclear computational codes.

Poly (vinyl alcohol) / tetraethyl orthosilicate (PVA/TEOS) hybrid adsorbent modified with 3-mercaptopropyltrimethoxysilane (TMPTMS) was prepared by the sol-gel method, and its application for the adsorption of uranium ions from aqueous solutions in a batch sorption process was studied. The functional groups of the hybrid adsorbents were characterized by the FTIR analysis. The batch adsorption studies such as TEOS content, TMPTMS content, pH, adsorbent dosage, contact time, initial concentration and temperature were investigated. The maximum adsorption capacity of uranium ions was found to be 39.08 mg g-1 at pH of 4.5 and temperature of 25oC. The kinetic data were analyzed by Pseudo-first-order, Pseudo-second-order and Double-exponential kinetic models. The Freundlich, Langmuir and Dubinin-Radushkevich isotherm models were applied to describe the equilibrium data. Thermodynamic parameters indicated that the uranium sorption onto the adsorbent was an endothermic and spontaneous process. The PVA/TEOS/TMPTMS hybrid adsorbent was regenerated by 0.5 M HNO3/0.1 M HCl in an equal ratio solution and the adpsorption capacity did not change remarkably after five sorption-desorption cycles.

The extractive separation of thorium, uranium, iron, titanium and lanthanides, represented by lanthanum, yttrium and cerium, has been investigated by Cyanex272 into the synthetic nitrate solutions. The concentration of each studied element in the synthetic solution was 10-4 M. It was found that the extraction increases in the order of La (III)<Ce (III)<Y (III)<Fe (III)<Th (IV)<U (VI)<Ti (IV). Thorium was optimally separated utilizing 0.5 M nitric acid solution. The slope analysis method showed that thorium was extracted as Th (OH)2 (NO3)A.HA. Also, the effects of complexing agent, acid type and acid concentration on the stripping of thorium, uranium, lanthanum and iron from the loaded organic phase were studied by Taguchi method. The optimum conditions for the selective stripping of thorium were observed when 0.5 M sulfuric acid and 2.7x10-4 M EDTA were used. The thermodynamic functions have been calculated.

Oxidation-reduction potential (ORP) in uranium bioleaching from a low grade ore by Acidithiobacillus ferrooxidans is measured experimentally under different conditions. The experimental results are fitted to the mixed potential model, obtained from Butler-Volmer equation. The results from this fitting showed that the model predictes the ORP in uranium bioleaching from 1th anomaly of Saghand ore with very high accuracy the relative error of the present applied model in the process of the used ore is less than 4%. The average values of the electrochemical rates constants km/ka, kc/ka and b related to the experiments with the pulp density of 5% and 10% (w/v) were obtained to be 260, 30606 and 0.01 respectively. The experimental results were also compared with the Nernst equation prediction for two cases of yi=1, yi≠1. The results showed that the relative error of this model is less than 45% with activity coefficients equal to one and less than 35% with real activity coefficients.

A three-dimensional reactor static code for calculation of flux, power, multiplication factor and also power peaking factor in rectangular, triangular and cylindrical geometry core has been developed and benchmarked. For solution of the time independent neuron diffusion equation a finite difference method was used. To solve the equation with finite difference method, the speed of the applied numerical calculation is a major subject of interest, especially when the number of nodes increases. For this reason using an appropriate method to make the calculation faster is considered as the main priority. The aim of this paper is to present this three-dimensional nuclear reactor code with an emphasis made on the comparison between the advanced iterative algorithms in this code.

By means of interaction between neutron magnetic moment and magnetic sextupole that leads to a specific path equation for neutrons, the neutron motion in a sextupole magnetic field has been obtained. By utilizing the result, the conditions for focusing the cold neutron beam on the end of the magnet have been investigated. Also, using the simulated results, the focused wavelength has been obtained for different conditions depending on the dimensions of the sextupole magnet and its strength. The effect of the dimensions of the neutron source is also investigated on the focusing process.

The antibacterial activity of essential oil extracted from gamma irradiated caraway seeds was studied by using of disk diffusion method and Minimal inhibitory concentration and Minimal bactericidal concentration. Caraway seeds were irradiated at the dosages of 0, 10 and 25 kilogray by a 60Co source of Gammacell system 220. The essential oil samples were extracted using Clevenger method and their antibacterial activities were studied by the use of disk diffusion method on four species of bacteria, namely: Escherichia coli (ATCC 25922), Pseudomonas aeroginosa (ATCC 27853), Bacillus subtilis (ATCC 6633) and Staphylococcus aureus (ATCC 29213) on the PCA and MHA culture media. Afterward, the diameters of the inhibition zones were studied. In addition, the antibacterial activity of the essential oil was compared with antibiotics such as ciprofloxacin, chloramphenicol and gentamicin on these bacteria in similar conditions. Minimal inhibitory concentration and Minimal bactericidal concentration of essential oil were also determined on these bacterial suspensions. The results showed that the antibacterial activity of the extracted essential oil from the irradiated caraway seeds. In addition, the Gram positive bacteria of Bacillus subtilis and Staphylococcus aureus were found to have more sensitivity with respect to the Gram negative Escherichia coli and Pseudomonas aeroginosa. The results also showed that the antibacterial activity of essential oil extracted from the gamma irradiated with 25 kilogry caraway seeds decreased slightly.

Eigenvalues and eigenvectors of the excited states of three body molecular systems contacting under the coulomb potential are calculated parametrically by the direct solution of Schrodinger equation without using any approximation or variation parameters. This has done by expressing the coordinates of system in Jacobi and then in hyperspherical coordinates and consequently by the expansion of the angular part of wave function in hyperspherical harmonics and the spherical part of the wave function in extended Laguerre functions. Thus, the Schrodinger equation for three body molecular system becomes a non-differential matrix equation for eigenvalues and eigenvectors (expansion coefficients). After computing the expansion coefficients (wave function) the expectation value of various parameters of the system such as separation between particles can be determined.

Alkali metals have a unique combination of physicochemical properties, such as extremely high electrical and thermal conductivities, law densities and viscosities, wide temperature ranges of a liquid state, great heat of evaporation, etc. Therefore, they are widely used in modern science and technology, especially liquid alkali metals act as a coolant in nuclear power plants. In this work, we developed an equation of state (EoS) based on statistical-mechanical perturbation theory for alkaline and alkaline earth metals. The theoretical EoS undertaken is Ihm-Song-Mason (ISM), and there are three temperature-dependent quantities that are required to use the EoS: the second virial coefficients B2 (T), an effective van der Waals covolume, b (T) and a correction factor, a (T). Those are calculated from a two-parameter corresponding states correlation, which is constructed with two constants as scaling parameters, i.e., the temperature, Tc and molar density pc at critical points. This new correlation has been applied to the ISM EoS to predict the volumetric behavior of alkali and alkali earth metals. We have tested the predicted EoS against the experimental data. The results show that in comparison to previous works, the present correlation is more accurate and covers a much wider range of temperature and pressure.

Following the successful design and construction of a 150keV accelerator tube, the construction of a 200keV electrostatic accelerator system at the Physics Department of the Nuclear Science Research School has been completed. This accelerator includes a 200keV accelerator tube, a high voltage power supply capable of supplying 200kV at 10mA current and a 200kV isolating transformer. An RF type ion source with a system for the control of ion beam could provide ions to the accelerator system. The vacuum system employed is a turbo molecular pumping system coupled with a mechanical rotary pump, where they can provide clean vacuum in the order of 7-10 Torr. In this paper the design criteria and some technical details of the construction of the accelerator system are presented. The construction of this accelerator provides a useful tool for research in various fields and gives an opportunity for the Iranian industry to develop and build accelerator components such as RF, vacuum and accelerator control systems.