JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2005 | Volume:- | Issue:2 (34)|Papers Count:8

In this work, during the nuclear reaction of natCd (p, xn)111 In, the irradiated cadmium target was dissolved in 3 M nitric acid. It was passed through a cation exchange column, containing 4 g. of AG 50W-X8, and then was separated from cadmium and copper impurities by using a simple two stage procedure. At the first stage, cadmium was eluted with acetone-water-hydrobromic acid solution. At the second stage, indium was eluted with acetone-water-hydrochloric acid solution. The effluent was evaporated to dry and the residue was dissolved in 0.01 Mhydrochloric acid. The overall yield of the procedure was 95±1 percent and the amount of cadmium and copper contamination were 0.3 and 0.1ppm, respectively.

One of the important goals in chemical agent detection is to construct an instrument with a fast response, to be handled easily, and to be used in various operational conditions. In this paper, based on the phenomenon of "increasing the specific alpha particles ionization rate by decreasing the particles energy" a suggestion has been made for reducing the size of the ionization chamber of an IMS detection system, where a thin layer was placed on the surface of Am-241 ionizing source for decreasing the emitted alpha particles energy. With this method, to some extent, the rate of ionization." loss has been compensated. The effect of layer over the Am-241 source on the ionization rate has been predicted theoretically, as well. For the other two sources with the initial coated layers, a calculation has been performed with the use of the related energy distribution; and the effect of a layer, of the Mylar type, on the ionization rate has also been investigated. The results of both cases have shown that the layer will cause to increase the ionization rate in the ionization chamber, where it subsequently increases the' capability of the instrument, and the system resolution power for detecting various chemical agents.

In an Oscillator-amplifier N2-laser system of the type TE-TE with the amplifier active effective length of 31 cm, both operating with corona-preionizer, the gain coefficient (g0) and saturation energy density (Es) measurements have been carried out for different gas pressures and gas purities. The details of our measurements are tabulated or presented graphically. The obtained values for the cases of I used or cleaned electrodes are also presented for the comparison. At last, our g0 values along with those of our previously reported values for the active length of 94 cm and other reported values for the active I lengths of 45 and 50 cm have been introduced for the comparison, and it was found that the measured values of g0 follow a characteristic curve showing their strong dependency on the length of laser channels, I The present observation indicated that while the length of laser channel has the major contribution to the I go values, the contributions of gas purities and cleaned electrodes are limited to at most 19.4% and 1.9%, I respectively, at the gas pressure of 100 Torr.

As in restoration and conservation of historical objects removing the corrosive salts from historical metal surfaces is important, the application of two types of lasers for removing corrosive salts from several historical copper and bronze species has been investigated. The purpose of this research is to compare the results of Nd:YAG and CO2 lasers application with defined pulses and energies in removing corrosive salts. Two mechanisms including dry laser and steam laser cleaning have been used. Also, the traditional methods (chemical and mechanical) have been used to compare the results of the cleaning. The applications of the applied lasers have been shown that Co2 laser at 10.6mm gives the best results.

Three electrodes spark gap (Trigatron) is widely used in the pulsed high voltage generator circuit in most of the high pressure gas lasers, such as carbon dioxide and nitrogen lasers. In this work switch parameters such as minimum breakdown voltage and switching time of a trigatron under different experimental conditions such as nitrogen gas pressure and discharge gap are investigated. The experimental results are in good agreement with other researcher's results where some of them have not been already demonstrated. The results have shown that the best condition of switching speed will be reached by using hetero-polar triggering configuration. Also, by using the hetero-polar triggering configuration the controllable operation area of switching voltage, i.e. the voltage area where the switch is not operational without triggering, is higher than homo-polar configuration.

In view of the many limitations associated with traditional approaches to documenting soil erosion and sedimentation rates, the potential for using fallout radionuclides as tracers in soil erosion investigations has been increasingly exploited. Most attention has been focused on caesium-137, and the successful use of this bomb-derived radionuclide in soil erosion studies has now been reported for many areas in the world. The main goal of this research was to study the 137Cs 3-D distribution pattern within the key sites and to apply the obtained information for the assessment of soil redistribution. Hence, one transects on a hill slope in Gorgak basin of Chahar Mahal-e- Bakhtiary province was selected and studied. Soils were sampled along the transect and analyzed for cesium-137. The estimated erosion rates was about 200 t/ha/yr for the top of the slope soil profile (the shoulder landform), and about 24.8 t/ha/yr for the middle of the slope soil profile (backslope landform). In the footslope landform no erosion has been observed.

Uranium mineralizaition in Khoshomy prospect, located in central part of Iran, with 300- 15000 (cps) and 14 to 4000 (ppm) released. The main rock types include: gneiss, granite, pegmatite and migmatite, that influenced by pegmatite-albitic vines (quartz-heldespatic). Acidic and basic dykes, granodioritic, units and dolomite and marble have been seen. The alteration associated with the mineralization is potassic, argillic, propylitic, carbonatization, silisificaition and hematitizaition. Uranium mineralization occurred in a hydrothermal phase with Cu, Mo, Ni and Au elements. Uranium primary minerals include pitchblend, coffinite, uraninite; and uranium secondary minerals include uranophan and boltwodite. REE mineralization occurred by the potassic phase in pegmatitization process.

The increasing application of brachytherapy techniques in radiotherapy centers necessitates setting up a calibration system for the relevant radioactive sources. Accordingly, the strength of a low dose rate (LDR) I37Cs source, with specifications common to similar radioactive gamma ray sources used in after loading brachytherapy equipment, is measured free in air in terms of air kerma by a standard spherical ionization chamber. Two different kinds of well type ionization chambers are then calibrated by the aid of the calibrated 137Cs source. The overall uncertainty of the air kerma determination of similar 137Cs sources by the calibrated well type chambers is estimated not to exceed 4%.