مجله علوم و فنون هسته ای
سال سی و هشتم شماره 2 (پیاپی 80، تابستان 1396)

The first prototype Iranian undulator is under design and fabrication. The undulator makes a periodic magnetic field which forces the electrons travelling through it to move along the undulator with a sinusoidal motion and radiate synchrotron radiation with specific properties. In this paper, two classes of errors, which are important to consider in the design and fabrication of undulators, so to speak, the period error and field error are introduced. Additionally, their effects on the radiation harmonics were studied. For this purpose, MATLAB software was used to generate pseudo-random errors for the undulator periods and peak fields. Then, the fields were applied to a pure sinusoidal magnetic field, used for calculation of the final harmonics by the B2E code. It was found that with the increase of the number of harmonics, the effects of errors are enhamced. Also, it was found that the effect of the field error is higher than that of the phase error. Finally, it could be concluded that in order to reach %90 of the ideal intensity at the first and third harmonics, the desired errors at the peak field and the period must be less than %0.1 and 3 degree, respectively. Also, the tolerance for the gap value must be no more than 15±0.2 mm.

In this paper, the effect of the anode electrode geometry with different insulator sleeve lengths and materials on the ion beam emitted from a 3 kJ plasma focus device is studied. Two Pyrex and Quartz insulators with different lengths and two anode tip geometries, i.e. cylindrical and conic, are used. Ion beam intensity in 12 kV charging voltage and conic anode with the 50 mm Pyrex insulator was increased by a factor of 1.11. Optimum length of the Pyrex insulator related to the maximum ion beam intensity varied with the anode geometry and increased from 45 mm to 50 mm, when we replaced the cylindrical anode with the conic one in 12 kV applied voltage. Under the same working condition, the conic anode tip tended to have more ion beam intensity in comparison with the conventional cylindrical flat geometry.

Rossi-α method is one of the useful techniques for diagnosis of subcritical nuclear reactors. In the present work, Rossi- α method was used to measure the prompt neutron decay constant of the reactor core of the Esfahan Light Water Subcritical Reactor (ELWSCR), and to drive the neutron chain reactions, a 252Cf neutron source was used. The experimental data in the form of the arrival time of the stochastic pulses were collected by a dedicated data acquisition system, and the required data were stored in a PC. Offline processing of the data was performed by the MATLAB software engineering tool, and Rossi distribution was extracted. Finally, by the curve fitting of Rossi distribution function to the processed data, the prompt neutron decay constant of the core was determined. Based on MCNPX code simulation, the reactor core was also studied. A comparison of the results obtained by the two methods shows a fairly good agreement.

111In pentetreotide (OctreoScanTM) radiopharmaceutical is used extensively for the detection of a variety of cancers in medicine. Octerotide is a pharmaceutical with a structure similar to somatostatin which is administrated via intravenous injection in an 111In labeled form. This radiopharmaceutical acts as a theranostic agent with binding to somatostatin receptors. Over the last decade, 111In pentetreotide has remained the most widely used radiopharmaceutical for the scintigraphic detection and staging of primary and metastatic neuroendocrine tumors. In this study, application of this radiopharmaceutical as well as the production and quality control strategies was investigated precisely. Briefly, the labeling yield of 111In pentetreotide was determined before the administration to the rodents. The incorporation of the radionuclide was measured by RTLC and the radiochemical purity was measured by HPLC. Due to the high thermodynamic stability constants for DTPA and In3+, the formation yield of 111In pentetreotide under the terms applied in this study was found to be high.

In this study, phenol and furfural removals from the standard solutions and petroleum refineries wastewater by electron beams have been investigated. The standard solutions of phenol and furfural were irradiated in the range of 1-10kGy and their concentrations were determined before and after irradiation by UV-VIS spectrophotometer. The effects of the experimental parameters including the amounts of the absorbed doses, pH variation, initial concentration of the organic compound and the salt effect were studied. The results of pH in the range of 3-11 showed that the removal of phenol and furfural was remarkably facilitated in the acidic condition. Studies showed that, at the dose of 6kGy, the removal percentages of phenol and furfural in the lower concentration of 20 and 100 mg/l respectively were more than 99%. However, by increasing the concentration, the amount of the removal gradually decreased. Also, investigation of the salt effect on the removal of these compounds within the range of 0.5-30% w/v concentration showed that at the dose of 6kGy, the presence of salt has no significant effect on the removal of phenol and furfural. Finally, the results of petroleum refinery wastewater irradiation in the optimum condition, obtained from the experiments, indicated that the removal percentages of phenol and furfural were more than 95%.

This research is dedicated to modeling  the wiikit uranium ore for HLW radioactive waste storing. At first, during X-ray Crystallography it was determined that wiikit has metamict structure. Then SEM revealed the U phase and different mineral phases that could be regarded as a reason for being amorphous. EMP was used to determine the chemical composition of the sample showing that wiikit contains 4% of uranium. The radioactive elements U and Th were separated by ion exchange chromatography using Dowex АВ-17-8 anion exchanger. During the next stage, the U and Th sources were prepared by molecular plating. Alpha-spectroscopy of the U and Th sources revealed high deficit in 234U/238U activity ratios, which violates secular equilibrium in the series of 238U decay. Finally, according to the results obtained by the behavior analysis of the U and Th atoms in this wiikit, modeling of the wiikit as 237Np, 239Pu, 241Am, 242Cm, 244Cm radioactive waste matrices and other heavy radioisotopes was performed when neutral oxides such as Al2O3,SiO2, Fe2O3 were added.  

The aim of this research work is the investigation of process parameters and breakthrough modeling of thorium biosorption on orange peel in a fixed-bed column. For this purpose, a number of  experiments have been performed on the surbents with diameters (0.4–2 mm), flow rates (1.5-6 mL/min), bed heights (4-8 cm) and feed inlet concentration (30-90 mg/L) at 25˚C and optimized pH of 3.8. The highest sorption capacity of 87.7 mg/g, occurred for the sorbents with 0.4-0.8 mm in diameter. The breakthrough point decreased with decreasing the bed height, increasing feed inlet concentration and increasing flow rate. Meanwhile, the sorption capacity increased with decreasing the bed height and flow rate. The experimental results were fitted by Thomas, Yan and Modified Dose-Response (MDR) models. Based on the experimental outcomes, the Yan and MDR models showed better results in comparison with the Thomas model. The XRF analysis results and calcium and potassium concentrations in the outlet stream of the bed showed that the ion exchange mechanism of the thorium biosorption by the orange peel sorbent is superior.

Immobilized Cystoseira indica algae and Saccharomyces Cerevisiae on the silica gel were used for the biosorption of Th (IV) from aqueous solutions. Ability and capacity of bi-functionalized algae- yeast biosorbent for adsorption of thorium (IV) from aqueous solutions were investigated in a batch method. The response surface methodology (RSM) based on the central composite design (CCD) was used to investigate the effect of pH (2-6), time (10-180 min), initial thorium(IV) concentration (50-300 mg/l) and adsorbent dosage (0.5-5 g/l) on the sorption of thorium (IV) from aqueous solutions, and to optimize the biosorption of Th (IV). Variance analysis showed that the adsorbent dosage, initial Th(IV) concentration, time and pH were respectively, the most effective factors in the biosorption of thorium(IV). Under optimal conditions (pH 5, contact time 137.5 min, initial Th(IV) concentration 237.5 mg/l, and adsorbent dosage 1.63 g/l ) the capacity of the biosorbent for Th(IV) was estimated to be 128.82 mg/g. The kinetic data were fitted well the pseudo-second-order rate equation. The biosorption data could be well described by Langmuir isotherm in comparison to Freundlich and Temkin isotherms. The maximum sorption capacity of the biosorbent for Th (IV), by Langmuir isotherm was estimated to be 142.86 mg/g. The thermodynamic parameters indicated that the biosorption of Th(IV) on the biomass was a spontaneous, and endothermic process, at the studied temperatures and would occur via physical adsorption.  

In order to achieve high quality crystals, it is necessary to purify the raw material. In the present experimental study, the zone melting method was used to purify Lithium Flouride powder. A small amount of melt moves slowly from the solid area in order to remove impurities in the frozen solid. In this case, the number, size and length of the zone melting affect the final result, and cause the optimal distribution of solutes. At the beginning, the regional purification system was equipped. The mechanism of work was moving furnace on a graphic crucible with full of LiF powder by 20 mm/h-1. This procedure was followed in a vacuum for 7, 9 and 14 times. At last the amounts of impurities such as Fe, Ba were measured by ICP (Inductively Coupled Plasma) analysis before and after purification.

White spot syndrome virus is a major pathogen in cultured penaeid shrimp industries. The virus not only is present in shrimp but also occurs in marine crustaceans. The infected shrimp samples were collected from south of Iran and the infection was confirmed by Nested PCR. WSSV was isolated from the infected samples by centrifugation and filtration and multiplied in crayfish by intramuscular inoculation. WSSV was purified from the infected crayfish haemolymph by sucrose gradient and ultracentrifuge, and then confirmed under electron Microscopy. In vivo virus titration was made in Penaeus semiculcatus in a period of 8-10 days, and calculated as LD50. WSSV was inactivated by the 10-MeV electron accelerator and formalin treatment. The LD50 of the live virus and the irradiated virus samples were calculated by the Karber method. The dose survival curve for the irradiated and non-irradiated virus samples was drawn by Origin 6.1 software and D10 Value factor was calculated according to the curve. In vivo titration of the live virus stock obtained was 10 5.4 LD50/ ml and the optimum dose of the electron beam for inactivation of WSSV was obtained as 13 kGy. The inactivated, irradiated WSSV antigen can be used for the evaluation of shrimp immune response in the near future.