JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2005 | Volume:- | Issue:2 (32)|Papers Count:10

Thallium-201 is one of the medical radioisotopes produced in Nuclear Research Center for Agriculture and Medicine via 203Tl (p, 3n) 201Pb reaction, using protons from cyclotron Cyclone 30. Due to high intensity of the neutrons produced from the thallium target and its copper substrate, protection against this radiation is a necessity. The radiation shield is the concrete walls of the target room accessible from outside through a multi-bend maze. In this work, we have calculated the streaming of neutrons through the maze of the target room using MCNP Monte Carlo radiation transport code. The target has been bombarded with 145 mA of 28.5 MeV protons. Equivalent dose rate of neutrons in various positions in the maze has been calculated and compared with the measured values. The maximum deviation between the calculated and measured values is found to occur at the farthest position from the source, namely at the entrance door of the maze, for which the neutron equivalent dose has been calculated as 93 mmSv/hr and the corrected measured value upon using the energy spectrum weighted correction factor is 136  mSv/hr. These values are in good agreement with each other according to the shielding point of view.

In this research work, single mode operation based on injection of a CW laser beam into a TEA CO2 laser cavity has been demonstrated. The technique has vast applications in research programs for laser spectroscopy and optical pumping. The observed smooth pulse shapes indicated that the system is operating in a single mode of operation, where no additional PZT mounted elements or other cavity stabilizing devices have been used. In addition, it has been observed that the output energy has not been reduced when the laser was operating in a single mode of operation, compared with the case when the laser is operating in the multi-mode regime.

Labeled vitamin B12 with 58 Co is one of the important ingredients of the diagnostic Kits for diagnosis of patients affected by anemia. The insufficient absorption of vitamin B12 is one of the causes of anemia in humans and one of the accurate methods for measurement of the absorbed vitamin B12 is application of labelled vitamin B12 with the cobalt–58 radioisotope. The isolation and purifications of the labelled vitamin B12 from fermentation medium of Streptomyces Olivaceus is an essential process for kit prepration. The first experiment in this research was isolation and purification of B12 using different resins with the solution of cyanocobalamin containing cobalt-59, produced by this bacterium. After investigation and pre-feasibility experiments two non-polar resins XAD-4 and XAD-7 were selected. The results that obtained from different experiments on XAD-4 and XAD-7 showed that XAD-4 is much better than the latter one due to immobilization of cobalamin. The isolation of vitamin B12 on XAD-4 column was achieved by different solvents such as methanol, ethanol and isopropanol in different concentrations ratios. The results of TLC (Thin Layer Chromatography) showed that the best eluant solutions for desorbtion of cobalamin from XAD- 4 column are solvents such as methanol, ethanol and isopropanol with the maximum concentration of vitamin B12 in the concentration ranges of 25 up to 50 percent, 30 up to 40 percent and 10 percent, respectively. Cobalamin was collected in aceton and crystallized in low temperature.

In the last two decades treatment of brain tumors using BNCT has been performed using improved boron compounds and neutron irradiation techniques. Compounds that make use of carborane clusters, which have high inherent boron content, should be more effective, provided, of course, the efficient and selective uptake of the boron-containing carrier molecules by cancer or other target cells. Examples of carborane cluster are the icosahedral C2B10H12carboranes. Many porphyrins and porphyrinoid compounds have demonstrated an ability to selectively accumulate in tumors, and have therefore been considered as the possible candidates for delivery of boron to malignant tissue. The texaphyrins are aromatic pentadentate macro cyclic expanded porphyrins, which have been found to be useful as MRI contrast agents, as radiation sensitizers and in photodynamic therapy (PDT). In this study, a new boronated texaphyrine for potential use in BNCT has been proposed and synthesized.

One of the important herbicide, that can be used for the practical mechanism investigations and studies of metabolism functions of different plants is 2,4 dichlorophenoxy acetic acid compound. In this article, the production method for labeling the titled compound is explained. At the first stage of this research work, barium [14C] carbonate is converted into potassium [14C] cyanide by using potassium azid at a reasonable temperature. Then, after a few synthesis reaction, the compound 2,4 dichlorophenoxy methyl iodide is produced via 2,4 dichlorophenoxy as a starting material. At the next stage, the real material as a herbicide: 2,4 dichlorophenoxy acetic acid [carboxy- 14C] is prepared and produced, by the coupling reaction between 2,4 dichlorophenoxy methyl iodide and potassium [14C] cyanide, and then the resulting nitrile has been hydrolyzed.

DNA in food may sustain damage by gamma irradiation. This damage can be detected by a sensitive technique, called single cell gel electrophoresis. This is a simple and low-cost technique for rapid screening of the cells of irradiated foodstuffs. For this purpose, poultry and shrimp samples were irradiated by the 60Co gamma radiation. The radiation doses for poultry were 2, 5 and 7 kGy and for shrimp were 3 and 7 kGy, respectively. The irradiated samples were compared with those of unirradiated types (control). In addition, the effects of shelf-life and temperature were considered on the poultry samples only. We have found that this technique is easily applicable for identification of irradiated from unirradiated samples and it is found to be irrespective of the applied dose. It is worth mentioning that any DNA change arising from any source, for example temperature fluctuation, may be detected by the SCGE technique.

In this work the design of a target converting high energy electrons to bremsstrahlung x-ray is described. The system has been optimized for different energy of the accelerated electron beam, using the EGS4 Monte-Carlo computer code. For this purpose the thickness of the layers in the target, including the main converter, cooling and lower layer (for the energy spectrum tuning), suitable to the desired and practical conditions have been obtained. In order to evaluate the calculated results, measurements have been carried out for the same geometry using the x-ray converter target, for 2MeV, 5MeV and 10 MeV electron beam. It is shown that the calculated data are in good agreement with the experimental results.

In this article, different types of cyclotron solid targets and their advantages and disadvantages are discussed and a new design is introduced for solid targets of IBA-Cyclone 30 cyclotrons for the first time. In this new targetry, the number and depth of the back grooves for coolant passage were changed. The target material was placed behind an aluminum drawer for bombardment. For this reason the new targetry was named drawer backings. Thus we were able to bombard powders of the target material. These backings have unique capabilities: metallic salts can be bombarded behind the drawer holders and chemical separation may be performed with higher yields and lower costs with respect to other methods. The bombardment may be repeated many times with the same backing. The drawer avoids the presence of contaminant nuclides in the final product.