JOURNAL OF NUCLEAR SCIENCE AND TECHNOLOGY
Year:2008 | Volume:- | Issue:3 (45)|Papers Count:10

In this paper, distribution of uranium and other elements with an accuracy of one micron has been investigated, using Scanning Proton Microscope. The correlation between the distribution of uranium and other elements is determined in the samples by the use of elemental distribution. Our results show, that minerals containing uranium are surrounded by minerals containing iron. Also, using Rutherford Backscattering Spectrometry, we were able to find the low-Z elements in the samples. Using this information, we can determine the chemical composition of the samples.

In this study, the method of radiocarbon dating was applied to determine the age of fossil shell samples, obtained from southern shores of Iran. The radiocarbon (14C) dating method has been applied in many fields, including oceanography, geology, and archaeology. In this method the sample is pretreated in physical and chemical procedures, then using a Benzene Synthesis System, benzene (C6H6) is synthesized from the sample. One gram of the synthesized benzene is added into a teflon counting vial containing 12ml scintillator Hisafe3. In order to count and determine the radioactivity concentration of beta particles emitted from radiocarbon, the liquid scintillation counting method is applied. The age determination of fossil samples has been carried out by using count per minute (cpm) values from beta counting of 14C in synthesized samples comparing to the obtained results from Oxalic Acid Modem Standard. For 8 shell samples studied, the determined ages are in the range of 210-3890 years, according to Before Present (BP; before 1950). The efficiency of Liquid Scintillation Counting system for 14C is calculated to be about 92% and the calculation error for the low age samples was ±40 years and for the high age samples was ±100 years, respectively.

Time-dependent behavior of fission reactors is simulated using Monte Carlo method and a code named TDMC is developed for neutron parameters calculations. Parameters such as reactivity, neutron life time, space distribution of flux, and power with several groups of delayed neutrons are calculable by the code. Material composition and system boundaries may be changed as time-dependent in the code. The results which have obtained with the code are in good agreement with the benchmark problems results.

In this research, new physical fission reactor parameters which have very sensitive effects on the qualitative behavior of a reactor, are introduced. Therefore, the two, the nonlinear dynamics of two, three and four dimensional, considering almost the effective parameters are formulated for describing nuclear fission reactor systems. Using both analytical and numerical methods, the stability and instability of the given dynamical equations and the conditions of stability are studied in these systems. We have shown that the two parameters of the mean energy residence time in fuel and coolant and also their ratios have the most qualitative effects on the dynamical behaviour of a typical nuclear fission reactor. Increasing or decreasing of these parameters from a cartain limit can lead to stability or unstability in a given system.

Ferric ions in dilute acidic leach liquor of uranium ore of Saghand were separated by anion exchange resins. In this research, a simulated solution similar to the actual leach liquor of Saghand was prepared. The simulated solution which was containing chloride and ferric ions, rare earth elements, and some other impurities was treated by different types of Dowex anion exchange resins for ferric ions removal. It appeared that hydrochloric acidic concentration, resin types and particle sizes have a great impact on ferric ions adsorption. Dowex IX4 (200-400 mesh) has the best adsorption of 91% in simulated solution and 79% in actual leach liquor of uranium ore of Saghand respectively.

To benefit greatly from 103Rh(p,n) 103Pd cross section curve and to avoid formation of radionuclide 101Pd impurity, the proton incident and exit energy of 18 and 5 MeV, must be considered, using ALICE code and experimental results. According to SRIM code, the Rh thickness must be 480mm for 90°. Beam/target angle geometry. To minimize the thickness of the rhodium layer, and hence to reduce the price of rhodium target, the angle of beam target has been adjusted to 6 degrees so as to decrease the thickness to 48mm.

Concentration of kryptofix 2.2.2 in [18F] FDG solutions and standard solutions of kryptofix 2.2.2 was determined by two methods: Visualization of combination of K2.2.2 with iodine vapor and iodoplatinate reagent. In both methods, concentration difference of K2.2.2 solutions was appeared as difference in color intensity of revealed spots on TLC. The detection limit of K2.2.2 by iodine vapor and iodoplatinate reagent is 25 and 2 ppm, respectively. Both methods can be used to release or reject the quality of [18F] FDG radiopharmaceutical for intravenous injection, but the second method is more suitable because of taking shorter time.

The development of the mathematical model of mass transfer and diffusion process can determine the behavior of dissolved impurities in the flow boiling within viscous sublayer. Application of a new model to calculate the distribution of dissolved impurities concentration within viscous sublayer and estimation of its thickness based on heat conduction layer and evaporation layer (macro-microlayer model) is the major goal of this study.