Sharif Digital Repository

Total air particulate matter of the city of Isfahan has been measured for elemental characterization in four principal directions of the city and during the year 2007-2008. High volume air samplers using whatman 41 filters have been utilized and instrumental neutron activation analysis has been used as the analytical method. Twenty one elements arising from seasonal and geographical distributions of the various elements have been determined. These distribution patterns have been discussed in view of the prevailing wind direction, location of the industrial facilities, and the Pearson correlation coefficients  

Improvement of numerical solutions and application of them is very important section of engineering researches. So, there are several numerical methods and procedures for solution of equations or problems. All of them have advantages and disadvantages for selection best method. The efficiency of a method is a function of Limitation parameter like time, software and hardware. One of the recent numerical methods for engineering problems is Direct Discrete Method (DDM). This method prepares modern theory for balance equations; also this method combines some advantages of the other numerical methods like finite element and finite difference. DDM uses a double set of mesh structures namely primal... 

In a nuclear reaction, particles such as gamma, neutron, alpha beta, etc. May be emitted. Environment and humans could be damaged severely if these radiations are not properly shielded. One of the main goals of this project is manufacture proper shields for neutron and gamma attenuation and absorption in mixed fields, benefiting the particular properties of composites. In preliminary stage of this project, with comprehensive studies, primary materials were selected. These materials are Tungsten, Polyethylene and Lithium Fluoride selected as Gamma absorber, thermalizer and thermalized neutron absorber respectively. In the next step, weight fractions of each material and thicknesses of... 

In operating nuclear reactor core, fluctuations (deviations from normal operating conditions) are usually produced and propagated. These fluctuations can be due to control rod vibrations, inlet coolant temperature fluctuations, inlet coolant velocity fluctuations and so on. The induced neutron noise can be detected by in-core neutron detectors. Noise source identifications (such as the type, location and propagating velocity) as well as the calculation of the dynamical parameters (such as moderator temperature coefficient in PWRs and Decay Ratio in BWRs) are of the main applications of the neutron noise analysis in power reactors.
Investigating the propagation noise in PWRs (specifically... 

There are several methods for identifying unknown elements of an unknown compound. One of the common methods for this purpose, using neutron activation analysis. In conjunction with this method, different computer codes and softwares have been developed and used. One of these methods is K0 method that is a single comparator method. The code that based on this method is K0-IAEA code that is written by the International Atomic Energy Agency and access to it is free. Foremost objective of this study is to determine how to work with this code. In order to evaluate the accuracy of the results of the code, examples have taken into consideration the amount of time previously unknown elements by... 

Analysis of neutronic and thermal-hydraulics fluctuations has various applications in calculation or measurement of the core dynamical parameters (temperature reactivity coefficients) furthermore it is applicable in thermal-hydraulics surveillance and diagnostics. Experience of the Fukushima Dai-ichi plant and the lessons learned from the European stress tests, demonstrated that alternative and various tools and methods are needed for the reactor's condition identification. In this paper the feasibility of development of an alternative accident monitoring via eminent coupling of neutron and thermal-hydraulics noise is proposed. and it is programming a simple simulator for calculating... 

Dust phenomenon is a combination of tiny particle with urban pollution that it is harmful for respiratory disease. But this phenomenon has been prevalent in our country recently. We utilized NASA satellite pictures to observe dust storms in the present project. We have collected images of possible sources of dust on the days when we are faced with the dust storm phenomenon. Then by processing of NASA satellite pictures (recognition of distribution of optical and particle density in the dust particle arising and comparing results through analysis of these images to estimate the main characteristics of the sampling locations). we have find the desired location for taking samples of soil... 

Neutron activation is a nuclear method for determination of elements in each sample. In this method, the samples are exposed to neutron irradiation by neutrons which are usually produced by research reactor, and then the core becomes unstable due to capturing the neutron and emits gamma rays. The emitted gamma rays can be detected by a detector like a HPGe semiconductor which has a high resolution. All nucleuses have a probability of neutron absorption, expressed by the absorption cross section area. The radioactive nuclei value depends on the nuclear half-life and the number of unstable nuclei. The only Windows environment commercial software for neutron activation analysis was K0 for... 

The present M.Sc. thesis consists of two sections including the static calculation and neutron noise calculation in rectangular and hexagonal geometries. The multi-group, two dimensional neutron diffusion equations and corresponding adjoint equations are solved in the static calculation. The spatial discretization of equations is based on Average Current Nodal Expansion Method (ACNEM). Size of nodes is the same size of the fuel assemblies in modeling both of rectangular and hexagonal geometries. The results are benchmarked against the valid results for BIBLIS-2D and IAEA-2D benchmark problems. In the second section, neutron noise calculations are performed for two types of noise sources,... 

Neutron fluctuations in both low and high power reactors provide important information about the system. The origins of these fluctuations are different in both regimes. In low power the branching process is the reason of these fluctuations. But the random nature of technological processes such as boiling in the reactors cooling and mechanical structure vibrating such as control rod and fuel rod created the neutron noise. Mathematical descriptions and applications of neutron noise for each mode are different. In common mode, fluctuations in the neutron detection system, determine some parameters and determin the start abnormality in system. In this study the spatial dependence of the cross... 

Nowadays, the use of numerical methods is very common in solving complex equations, and various methods have been developed in this field. One of the new methods in this field, is the direct discrete method(DDM), Which was initially used to solve the electromagnetic field equations. In the past years, this method has been used to discretization some of the neutronics equations and acceptable results are recorded. So that the convergence order for the neutron diffusion equation in this method is higher than other numerical methods. In this method the geometry of the problem is divided into primary and secondary cell that primary cell platform is fixed but there is the possibility of making... 

The present M.Sc. thesis consists of two sections including static calculation and neutron noise calculations in rectangular and hexagonal geometries. The multi-group, two dimensional neutron diffusion equations and corresponding adjoint equations are solved in the static calculation. The spatial discretization of equation is based on Boundary Element Method (BEM). The result are benchmarked against the valid results for BIBLIS-2D and IAEA -2D benchmark problem. In the second section, neutron noise calculation are performed for two types of noise sources, i.e. absorber of variable strength and Inadvertent Loading and Operation of a Fuel Assembly in an Improper Position (ILOFAIP). The... 

Environmental conditions of various cities of Iran are deteriorating due to various contributing effects of increased traffic, deforestation, industrial pollution etc. Arak is an example in point. It is a city of about 440,000 inhabitants. It is located at the edge of the main central desert (Kavir) of Iran. It lacks any appreciable vegetation or wooded areas and it is the home of a number of major industries. These include aluminum smelting, petrochemical industry, refinery, power plant and various other heavy manufacturing facilities. It was suggested to perform an air sampling of the city for a whole year (2010-2011) to determine the concentration of various elements by instrumental... 

In this thesis, localization of a postulated noise from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The box-scheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. Using the discretised static equations, a 2-D 2-group static simulator (HEXDIF-2) is developed which its results are benchmarked against the well-known CITATION... 

Dealing with natural and handmade radioactive materials and sources is of major aspects of nuclear science and technology. Useful applications of these materials and sources in different fields, such as energy production and health physics, caused the necessity of developing the detection and radiation protection methods. Each of these methods uses different equipment and approaches which are based on different kinds of radiations and radioactive sources. Despite the given ability of radiation detection, in some cases, recognition, distinguish, and estimation of a source radiation level is impossible due to bad effects of these equipment on measured spectrum. Detection of neutron spectrum in... 

Method of Prompt Gamma Neutron Activation Analysis (PGNAA) is useful for controlling some massive production processes such as cement industry and mineral materials. Difficulty of other methods of analysis such as XRF comparing with PGNAA is that mass of sample is small and it doesn’t determine heterogeneity of mixture. On the other hand, need to sampling is also another problem of these analysis methods because sampling is terminated and it doesn’t supervise on production continuously, in fact its quality can’t be revealed simultaneously and there is a long time between sampling and control of process. Usually, analysis methods such as XRF are useful for processes that are controlled... 

Since direct measurement of neutron energy, unlike measuring the energy of ionizing radiation, is difficult, and the use of indirect methods for detecting and measuring neutron energy with high resolution and acceptable efficiency are not possible, the neutron time of flight method is the only direct neutron energy spectroscopy method. This issue is considered and evaluated in two methods: direct and scattering neutron time of flight. For this purpose, we have considered the 241Am-9Be source. In this method, neutron velocity can be determined by measuring time. is the time for the neutron that travels at distance of . The next method is the dispersed neutron time of flight method, in... 

This study consists of two parts: steady state calculations and neutron noise calculations in the frequency domain for two rectangular and hexagonal geometries. In the steady state calculation, the neutron diffusion and its adjoint equations are approximated by two-dimensional coordinates in two-group energy and are solved using the average current nodal expansion method. Then, by considering the node size in the dimensions of a fuel assembly, different orders of flux expansion are investigated. For verification purposes, the calculations have been performed by power iteration method for two test problems of BIBLIS-2D and IAEA-2D. For rectangular geometry with increasing flux expansion order... 

The safety and optimal performance of nuclear reactors require online monitoring in the core. One of the most important requirements of core monitoring is the knowledge at all time of the neutron flux distribution in the core. The present M.Sc thesis describes a method which avoids the solution of time dependent neutron diffusion equation and uses online readings of the fixed in-core neutron detectors to reconstruct the three-dimensional (3D) neutron flux distribution. The essential idea of nodal synthesis method is separation of time and space dependence of the neutron flux distribution. The time dependent section of the flux distribution is determined by neutron detector readings and space... 

In this study, epoxy resin has been modified by nano-clay additives using direct mixing method and epoxy-clay nanocomposites were designed and produced with optimized percentage of clay content. By adding the powder of born carbide and lead oxide in nanocomposites new compounds are obtained. The results are used for protection against neutron and gamma rays, respectively. After preparation of epoxy-clay-born carbide and epoxy- clay-lead oxide nanocomposite the effects of irradiation and carbon fiber on mechanical and thermal properties of nanocomposites were examined. The Nanocomposites were exposed to Electron Beam Irradiation (EBI) in 100 and 500 kGy doses to investigate the effect of...