مجله علوم و فنون هسته ای
سال:1381 | دوره:- | شماره:25 |تعداد مقالات:15

Thin targets of 209Bi and 197Au were bombarded with 30 MeV protons at the Cyclotron Department of Nuclear Research Center for Agriculture and Medicine (NRCAM). Correlated measurements of kinetic energies of fission fragment pairs, and their time-of-flights were made by using pair spectrometry. The fission cross sections, fragment mass distributions, and total kinetic energy distributions of the fragments were measured in our experiment. The accurate values of cross sections for fission of 209Bi and 197Au nuclei with 30 MeV protons were obtainedto be 1100±100 and 62±5.6 µb, respectively. The cross section of 209Bi fission with its associated error, by using this method, has not been reported previously. The interpretation in terms of liquid-drop model of fissioning nucleus 210Po at the excitation energy of 35 MeV was confirmed by the dispersion of the distribution in fragment mass for bismuth fission.

In this research work, four different growth stages of Glycyrrhiza glabra were studied separately and under green house conditions, and in all of these stages the plants were treated by labelled herbicides 14C-2,4-D and 14C- Glyphosate through the adaxial surface With activity of 0.60µci upto 0.1018µci (in each 10mli of solution). The plants were harvested 72 hours after treatment. They were divided into treated leaf, leaves and stem above the treated leaf and leaves and stem below the treated leaf and root. The amount of radio labelled herbicides in each homogenous solution (Produced from extraction of herbicides from plant samples) was quantified using liquid scintillation counter. The amount of herbicide mobility and transfer to different parts of Glycyrrhiza glabra in each growth stage were determined. This study shows that the best application time of 2,4-D for translocation to the root system of the plant is at 6- leaf stage, and 2,4-D indicates more translocability as compared with Glyphosate.

In this research work the application of the generalized self-filtering unstable resonator (GSFUR) in a longitudinally excited molecular nitrogen laser has been investigated and compared with the plane-parallel resonator. In a typical design of magnification M=-5, the beam divergence of 0.33 mrad, and the brightness of 1.3×109 W/cm2.Sr have been obtained. For a plane-parallel resonator of equivalent length these figures are ~1mrad and 2.3×107 W/cm2.Sr respectively, where it is shown that in the GSFUR design there is a reduction in the beam divergence by a factor of 3 and enhancement in measured brightness by a factor of 56, as compared with the plane-parallel design. Using a field limiting aperture as an output coupler, the beam profile in the far-field and near-field were Gaussian and donut shape, respectively. A mathematical model based on the rate equations for the gain medium and equation for the electric circuit is introduced and the results are consistent with the experimental measurements.

In this research, petrogenetic affiliation between radioactive elements (from Chah-Gas area) and geological phenomena has been discussed. Microscopic examination of thin and polished sections of rocks from Chah-Gas area exhibits more distinguished concentric haloes, surrounding exotic radioactive minerals (i.e.zircon). Haloes with different luminous colours, confirm polygenetic radioactive and radiogenic elements concentrations. This research paper has also discussed the replacement of radioactive elements in Chah-Gas area, Central Iran.

In this research work the chloride and sulfate ions have been decreased in the leach liquors using Hydrofluoric acid 40% and commercial lead nitrate prepared by sea water in sulfuric Acid media. As the result of chloride ion deduction in leach liquor the relative competition of uranium with other elements to transfer to normal TBP structure as solvent extracting of uranium will be also reduced. It is investigated that in nitrated media of leach solution more uranium will transfer to TBP phase. Then reextraction and analysis were done by colorimetric method of developing uranylferrocyanide complex in 540nm as the fixed wavelength. In this study the interfering effect of fluoride ion is also considered and evaluated by the above mentioned complex. Comparing the results of uranium analysis obtained by ICP technique show that the effect of fluoride as an interfering ion is more serious in single stage than multistage of chloride precipitation process. Promising signs of analytical results have led us to be familiar with the high purity yellow cake production Know-How as well. This separation procedure is well organized and well suited to apply on the uranium resources called salted arches shaped. Besides, in this study the successful quantitative Separation of better than 99% of molybdenum from uranium is also considered

Seven different samples of an inorganic ion exchanger, cerium phosphate, suitable for column use have been prepared under varying conditions. The property of these exchangers has been characterized by Inductively Coupled Plasma Spectroscopy. These exchangers are stable in water, dilute mineral acids, ethanol, methanol, acetone and ether. However, in concentrated HCl and HNO3 they decompose. They retain about 50% of their exchange value after drying at 80 C, and can be regenerated twice without any decrease in exchange capacity. The distribution coefficient measurements for alkaline earth metals, tellurium, iodine and molybdenum using these seven ion exchangers were studied. This revealed the relative affinity for each exchanger, where the sorption in general was most effective at pH 6-8. The titration curves of cerium phosphate (disodium) with alkaline earth metals showed that the selectivity sequence Ba2+>Sr2+>Ca2+>Mg2+ is observed. Furthermore, it could be deduced that the adsorption of alkaline earth metal cations greatly depends on the cation. These studies have also shown that cerium phosphates with divalent ions are strongly preferred to monovalent ones. Therefore, as for the cerium phosphates with large monovalent ions, the lack of exchange for Ba2+, Mg2+ or other alkaline earth metal ions should be essentially due to steric hindrance and this could include any one of the following: the large crystalline radius of metal ions or large hydrated ionic radius and high energy of hydration for other divalent ions. Three binary separations of TeIV - MoVI , TeIV - I1 and MoVI - Il has been developed and the recovery ranging from 90 to 100% has been achieved on cerium phosphate (disodium) columns.

In this research we tried to prepare Exploration model and select target areas based on Genetic model of Uranium in Central Iran through integration (GIS) of exploration data including Airborne Geophysical data, Geology, Metallogeny and Remote Sensing.