JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2016 | Volume:- | Issue:75 |Papers Count:11

In this study, modeling and optimization of two in-series UF6 shell and tubes separator condensers were performed to improve the prediction of the amount of the mist output, physical properties of condensing gases and condensed mass of UF6 by computing the mist formation conditions. The main objective of this research was to predict the optimal operating conditions in order to reduce the uranium in the outlet mist from the condenser system. These two shell and tube condensers were modeled via control volumes with finite length in axial direction of input gases. The equations of mass, energy and momentum balance were written for each condenser and then surface temperature of UF6 condensed layer on the condenser tube was determined by the trial and error method. The mass and heat transfer parameters were calculated at each time step during the process. Comparison of the modeling predictions with the Isfahan UCF industrial data in regard to important variables indicated a very good compatibility. The average error between the modeling and industrial data for the first and second condensers were calculated to be 1. 39 and 2. 24%, respectively. Finally, the analysis of the effective variables via the developed modeling computer software revealed that the optimal temperature of cooling brine water and the input gas velocity are 10 ˚ C and 0. 09 m/s, respectively.

In this study, TL signal induced after activation of 6Li present in TlD-100 was applied in order to measure the thermal neutron fluence in the Tehran Research Reactor Core (TRRC). To obtain the TLD thermal neutron responses, the TRRC neutron fluences were set in the range of 1010 to 1016 n/cm2. With this technique, the self-dose as a consequence of 3H activity, which was raised after a relative short storage time of 1 to 3 days, was used to measure the thermal neutron fluence. After a special thermal treatment, aimed to stabilize the dosimeters and subsequent assessment of sensitivity reduction factors, a linear relationship between the neutron fluence and the induced self-dose was found in the TLD-100. The results showed an extended range for the thermal neutron fluence measurement by the TLD-100, an extended upper limit compared to the TLD-600, as well as, extended lower limit in comparison to the TLD-700.

Epoxy resin as a thermoset polymer has a suitable thermal resistance with high mechanical properties. In addition, the resin exhibits good continuum presentation for both neutron and gamma beams. Consequantly, it is the primary concern in the nuclear industry. In a neutron shielding, energetic secondary gamma products are unavoidable. For attenuating these gamma rays, the elements with high atomic number in the polymeric matrix are inevitably used. Because of various problems of lead shield, studies are inclined to the lead free shielding. In this investigation and, by using Monte Carlo method, the ability of secondary gamma attenuating was studied on a polymeric shielding based on reinforced epoxy with different weight percentages of 5, 10 and 20 of tungsten oxide and lead oxide without any neutron poisons. The results show that by the same weight percentage, the reinforced composite shield with tungsten oxide could afford better shielding performance. The more increase in the weight percentage of the reinforced material, in addition to an increase in the weight of the shield, reduce the ability of shielding performance.

The potential use of a biosorbent, Ca-pretreated leaf powder of orientals platanus was investigated for the sorption of Th (IV) ions from aqueous solutions by considering equilibrium, kinetic and thermodynamic aspects by means of the batch method. Th(IV) uptake by the leaf powder of oriental platanus was the pH, biosorbent dosage, contact time, initial adsorbate concentration, and temperature dependence. Biosorption process at the studied initial Th(IV) ion concentrations followed the pseudo-second order kinetic model (R2=0. 9957). The biosorption data could be well described by Langmuir isotherm in comparison to Freundlich and Dubinin-Radushkevich isotherms. The maximum adsorption capacity was estimated to be 200 mg g-1 at 25° C with the pH of 3. 5 by means of the Langmuir model. The thermodynamic parameters indicated that the biosorption of Th(IV) on the biomass was a feasible, spontaneous and endothermic process at the studied temperatures. The reusability of the biomass was also determined after five sorption-desorption cycles and the adsorption capacity decreased only by about 20%.

One of the most important safety problems and challenges of the countries having the nuclear technology is to find the methods for the treatment of the radioactive materials in the nuclear wastes. Thorium ion is one of the elements required to manage in the nuclear wastes. In this study, the modified nano-silica adsorbents with Schiff base ligands salicylaldimine propyl triethoxysilane (L1) and pyridylmethyl idenepropyl triethoxysilane (L2) were used for improvement of the thorium ions adsorption. Besides the influence of the used ligand structure, the effects of different variables such as the pH, contact time and adsorbent were investigated, and the optimum conditions were determined. The results showed that the modified adsorbent with ligand L1 provides better performance in this regard.

Production of bone pain palliation agents is developing increasingly for handling end-stage cancer patients. 153Sm and 175Yb labelled (1-hydroxy-2-imidazol-1-yl-phosphonoethyl) phosphoric acids can be used in bone pain palliation therapy. In this work, 153Sm and 175Yb labelled zoledronates were prepared using the commercial zoledronate ligand and 153SmCl3 and 175YbCl3 at 60º C, respectively. 153Sm Cl3 and 175YbCl3 were obtained by thermal neutron irradiation (4×1013 n. cm-2s-1) of the natural metal oxide samples. The radiochemical purities were checked by the instant thin layer chromatography (ITLC) and high performance liquid chromatography (HPLC) methods. The stability studies of the final preparations in the presence of human serum, as well as, hydroxyapatite (HA) binding test were performed (>97%). The biodistribution of 153Sm and 153Sm-zoledronate performed in 2-48 h and for 175Yb and the 175Yb-zoledronate performed in 2-96 h post injection in the Syrian mice. The maximum bone uptake for 153Sm-zoledronate was 4% (48 h), while for 175Yb-zoledronate it was 10% (48 h). The complexes demonstrated satisfactory stability in the presence of human serum and the final formulations. However, the complexes are not appropriate for human studies due to the high liver uptake, possibly due to release of free metal from the complex and/or colloid formation.

The Grad-Shafranov equation plays an important role in the analysis of the plasma equilibrium in magnetic confinement configurations such as tokamak. In tokamaks which are operating in Ohmic heating regime, the Grad-Shafranov equation can be expanded through the inverse aspect ratio parameter. Consequently, the first order of the poloidal flux function and poloidal/radial components of the magnetic field are obtained. It is possible to estimate the Shafranov equilibrium parameter in a semi-analytical approach just by means of one of the magnetic field components. In this study, the Shafranov equilibrium parameter was estimated by means of the poloidal magnetic field experimental data, measured by the Damavand tokamak magnetic probes.

Shrimp farming industry is of significant importance to the economy, particularly in the south area of Iran. However, this industry faces with various challenges such as viral and bacterial disaeses. The losses due to Vibriosis and white spot syndrome in shrimp are examples of the issues. Therefore, taking into account the control of the diseases outbreaks, this investigation was carried out to study the immunity of Vibrio radio-antigen (inactivated whole-cell bacteria by the gamma irradiation method) against the white spot syndrome virus (WSSV) in Litopeaneus vannamei. The results showed that the treatment with the Vibrio radio-antigen caused an immune response against live WSSV in shrimp via significant decreasing of mortality in the immunized shrimp groups, in comparison with the positive control group after challenge with the live WSSV (P<0. 05). The results of this investigation are potentially useful for future studies in production of radio-vaccine and adjuvant of Vibrio paraheamolyticus.

In this research, the use of tungsten (W) and barium (Ba) in composition with lead (Pb) was investigated to decrease weight and to increase the efficiency of the protective aprons in attenuating of the diagnostic X-rays. First, the X-ray tube of the Radiation Research Center (RCC) of the Shiraz University was simulated by MCNP4C code to obtain the bremsstrahlung and characteristic X-ray spectrum. In order to confirm the simulation, the obtained output of this code was compared with the resultant output of the spectrum simulator software, viz., the spectrum processor (SP). The simulated protective apron samples with the dimension of 10cm×10cm and weight of 86. 5, 81. 5 and 70 g, containing various percentages of Pb, W and Ba, were placed in the path of the simulated spectra, and the attenuation coefficient of radiation was calculated using MCNP4C. The results showed that the composition of Pb, Ba and vinyl, with the percentages of 23, 42 and 35 and also 17, 48 and 35, respectively, improved the attenuation about %46 in comparison with the use of pure Pb.

Nuclear fission of uranium atoms starts when a nuclear pellet is placed into the rod and then inside the nuclear reactor. Thus, the number of the produced atoms would be more than those of fission uranium atoms. No problem exists with solid products, but the gas products following the swelling of the pellets enter the gap between the pellet and rod. This causes destruction of the rod and the reactor safety reduction. It is better to exit the rod from the reactor before the event. Attempts are made to increase the life time and the generated energy with nuclear pellets to achieve higher efficiency. For this purpose, after the identification of the obstacles, the efficiency of the nuclear fuel pellets is increased by some modifications. This work is a review of the world activities to identify the obstacles and solutions provided for modifying the nuclear fuel pellets. The results demonstrate that the most important features of a nuclear fuel influence on the life time and efficiency of UO2 feul pellets are the largeness of grains along with intergranular porosities with controlled size, good creep and thermal conductivity properties.