مجله علوم و فنون هسته ای
سال بیست و نهم شماره 4 (پیاپی 46، زمستان 1387)

Yttrium-90 radioisotope as a daughter of Strontium-90 is one of the nuclear fission products and plays an important role in the treatment of malignant tumors in nuclear medicine. There are at least five methods for the separation of Y-90 from Sr-90 including: Liquid membrane separation, Precipitation solvent extraction ion exchange and solvent extraction combined with ion exchange method. In this work ion exchange chromatography was used by Dowex50Wx8 resin as a stationary phase and ammonium oxalate, EDTA and sodium Acetate solutions as mobile phases. Separation of yttrium and strontium was performed in the various simulation conditions and for determining the elements, ICP-AES technique was used. The activities of real samples were estimated with β-liquid scintillation counter. The various shielding parameters for designing different parts of generator were also considered in this work.

Nowadays, anti-CD20 antibodies are being used in the therapy of lymphomas in free or radiolabeled form. Conjugation process was performed using native antibody and DOTA-NHS compound, synthesized in our laboratory. Thin layer chromatography and gel filtration were used to control the reaction progress as well as purification of the final antibody conjugate. 67GaCl3 produced at AMIRS was used to label the immunoconjugate and the reaction conditions were optimized for time, temperature and reactant concentrations. Quality control of the radioimmunoconjugate was performed using RTLC and gel filtration. The radiochemical purity was shown to be over 95%. The radioimmunoconjugate was used in the biodistribution studies up to 28 h and it was shown that after 24h most of the activity was accumulated in reticuloendothelial system consisting liver and spleen.

In this study, the stability constant of dioxouranium with asparagine complexes and protonation constant of asparagine at different ionic strength was investigated. Measurements have been performed at 25°C, pH<3.5 and at ionic strengths ranging from 0.1 to 1.0 mol dm-3 sodium perchlorate, using combination of potentiometric and spectrophotometric techniques. The composition of the formed complexes and their stability constants were determined by cruve fitting method and it was shown that dioxouranium forms two mononuclear 1:1 and 1:2 species in the form of UO2(HL)2+ and UO2(HL)22+. The overall analysis of the present and the previous data dealing with the determination of stability constant at different ionic strength allowed us to obtain a general equation by which the formation constant determined at a fixed ionic strength can be calculated with a good approximation.

Because of the importance of safety in a nuclear system, nuclear data which are used in neutronic reactors design must be in a good accuracy. So examination and enhancement of nuclear data are of great importance. The aim of this work is to investigate the neutron cross section with carbon and lead and consequently improving them. In a research program conducted at the Isfahan Production and Research Center, blocks of lead and graphite were used. In the core of lead and carbon blocks, we placed an Am-Be source and then measured the flux of neutron outside of the assembly. The flux distribution was also calculated theoretically by MCNP code and the results were compared with the experiment. Comparison of the computation and the experimental results showed that the carbon sensitivity coefficients in the range of energies lower than 1MeV are negligible, while for the higher energies, especially between 5 to 6 MeV, these coefficients are nearly 5 percent. Also, lead sensitivity coefficients was varied from 0.2 to 0.67 for different energies. Finally, with the help of defining sensitivity coefficients, the values of cross section were varied. By using more advanced equipment for fast neutron detection, we are able to find better results in the other range of energy groups.

Uranium deposits of Iran occur mainly in the Central Iran zone. Several uranium deposits have been discovered in this zone. The Narigan area is one of the most important uranium mineralized area in this zone. The uranium bearing sequences in this area are contained in the plutonic to volcanic rocks of Narigan which intruded to the Pre-Cambrian pyroclastics rocks. Plutonic and volcanic rocks are granite, ryolite and volcanoclastic. Diabasic dykes have been intruded to these igneous rocks. The plutonic and volcanic rocks have been covered by Cretaceous limestons which seem to be youngest the rocks in this area. The aim of our project is to develop a regional exploration strategy for uranium in these igneous rocks. A grid-based sampling was planned following the results of the previous geochemical mapping at a scale of 1:100,000, integrated with geophysical data and alteration zones and outcrop of intrusive rocks. The following results are based on geological, and stream geochemical explorations in 1:20000 scale of this area. During this study 121 samples were collected from the stream sediments of <80 mesh for final sampling. Ten percent of the samples were used for checking laboratories errors. The samples were collected according to conventional methods from 30-40 cm depth of stream sediments. Finally, geochemical and radiometric data were combined and the results introduced 3 anomalies in the Narigan area.

In this project, production of radioactive rhenium for medical application by the Tehran Research Reactor, using natural rhenium along with labeling Rhenium by hydroxy ethiliden diphosphonate(HEDP) was investigated. After the production of Re-HEDP, its biodistribution in rats was also evaluated. To obtain the radioactive isotopes, natural rhenium with %99.9 purity, manufactured by Merck, was irradiated by the Tehran Research Reactor. Natural rhenium consists of two isotopes, Re-185 and Re-187, so irradiation the target with neutron in the reactor eventuates in two radioisotopes,186Re and 188Re. This research was performed in three phases. At the first phase, rhenium was irradiated in various irradiation boxes. The best result was 470mCi/mg after 5 days of irradiation. The chemical process includes oxidation of Re which in the presence of water results in formation of perhenic acid. Afterward, labeling of HEDP by means of Re is performed. All the process was performed in Lead Cell. Gamma spectroscopy and Thin Layer Chromatography were used for radionuclide and radiochemical purity, respectively. Re-HEDP was injected in rats and the biodistribution in different organs were studied by means of gamma spectroscopy. The results of the gamma spectroscopy approved the radionuclide purity. Labeling via HEDP resulted in %97.57 radiochemical purity. Biodistribution in rats showed (1.007 %ID/g 4h P.I), (0.89%ID/g 24h P.I) and (0.58 %ID/g 48h P.I) for bone and was the maximum percent of the absorbed dose rate.

In nuclear facility, the enrichment operation usually is carreid out under the medium and high vacuum conditions. Measurement of UF6 gas flow rate in the form of feed or product and tail is one of the principal parameters in operation and production. In this facility, several orifices were used to measure UF6 gas flow rate in the range of 10-80 gr/hr. Due to low pressure and mass flow range, measurement of flow rate should be made accurately. In this research, the method of flow rate measurement in tubes by using orifice and needle valve, and also effective parameters on it, has been studied. For the study of the gas flow rates, several orifices with different diameters were used. We observed that for a defined orifice diameter, an increase in the input pressure causes an increase in the flow rate and at a constant flow rate an increase in the input pressure causes a decrease in the orifice diameter. As the pressure difference between the upside and downside of the orifice increases, the flow rate will rise up to a certain limit. Since in all experiments of the needle valve, the ratio of outlet to the inlet pressure is less than 0.5926, the linearity of the mass flow change versus the inlet pressure at a constant cross sectional area shown to be consistant with the chock current equation. Also, the investigation of mass flow rates, when the valve is open, indicates that variations of the mass flow rate will increase against the inlet pressure and the pressure difference, intensively.

The fresh fuel for BNPP-1 is due to be transported inside special containers which are supposed to be designed to stand against vibrations and impacts in order to protect the fuel from any possible damage. In order to perform the structural dynamic analysis of the containers, while being subjected to impact of dynamic forces, it is necessary to perform the vibration analysis which will lead to the vibrational modes and their natural frequencies for the structure of the containers. The vibration opposition of the containers must be far beyond the critical resonance. The resonance frequencies about the natural frequency of the structure will cause the enhancement of the oscillation range and may be ended with its disintegration. Determination of the natural frequencies and their mode shapes can be achieved by vibration-analyzing-methods. The amount of the natural frequency of any structure depends strongly on its shape, material and its lean points, as well as the amount and the type of the loads which the structure will be subjected to. In the presente research, the container of the fresh fuel of BNPP-1 is simulated by ANSYS®10.0 and their ten natural frequency modes have been calculated.

The safflower or Carthamus tinctorius belongs to Asteraceae family. As a forage and oil crop, it is commonly used in dry or non dry farms. In this research, the seeds of Zarghan 279 as a winter variety was radiated by Gamma ray in 80, 100, 150 and 200 Grey doses and they were sown in farm. The mutants after the second generation, were under dry stress and non stress conditions and they were grown and selected up to the 5 th generation, M5. Their traits were measured in the final generation of mutants. The results shows that in two conditions yield, days to buding, days to start of flowering, days to 50% flowering, days to maturity and difference of days to maturity and days to buding were significant between mutants at 1% level. The difference in the oil percentage in two conditions were not significant.

An attempt was made to isolate bacterial strains capable of removing strontium biologically. In this study ten different water samples collected from Neydasht spring in the north of Iran and then the bacterial species were isolated from the water samples. the initial screening of a total of 50 bacterial isolates resulted in selection of one strain. The isolated strain showed a maximum adsorption capacity with 55mg strontium/g dry wt. It was tentatively identified as Bacillus sp. according to the morphological and biochemical properties, and called strain GT-83. Our studies indicated that Bacillus sp. GT-83 is able to grow aerobically in the presence of 50mM SrCl2, but its growth was inhibited at high levels of strontium concentrations. The biosorption capacity of Bacillus sp. GT-83 depends strongly on the pH solution. Hence the maximum strontium sorption capacity of Bacillus sp. GT-83 was obtained at pH 10, independent of absence or presence of MgCl2 of different concentrations. Strontium-salt biosorption studies were also performed at this pH values. The equilibrium biosorption of strontium was elevated by increasing the strontium concentration, up to 250mg/l for Bacillus sp. GT-83. The maximum biosorption of strontium was obtained at temperatures in the range of 30-35˚C. The bacillus sp. GT-83 biosorbed 97mg strontium/g dry wt at 100mg/l initial strontium concentration without MgCl2. When MgCl2 concentration increased to 15%(w/v), these values dropped to 23.6mg strontium/g dry wt at the same conditions. Uptake of strontium within 5 min of incubation was relatively rapid and the absorption continued slowly thereafter.