Digital Repository for Department of Nuclear Engineering

In this paper, a new concept of the Reactivity Trace Curve (RTC) for reactor power control is presented. The concept is demonstrated for a reactor model with one group of delayed neutrons, where the reactivity trace curve is simply a closed form exponential solution of the RTC-differential equation identifier. An extended reactor model of multigroup (six groups) of delayed neutrons is discussed for power control using the RTC-method which is based on numerical solution of the governing equation for the RTC-differential equation identifier. In this numerical solution, an impeded analytical solution for the RTC-identifier in every sampling time step is used. Finally, the concept is applied to a more rigorous reactor model, namely; a model of multigroup of delayed neutrons with temperature feedback. The simulation studies for all of the above mentioned cases demonstrate the validity of the concept for reactor power control with absolute elimination of power shootings.
Wajdi Mohamed Ratemi (1-1998)

In this paper, a nuclear reactor kinetics model based on Guelph expansion coefficients calculation ( Coefficients Based Model, CBM), for n groups of delayed neutrons is developed. The accompanying characteristic equation is a polynomial form of the Inhour equation with the same coefficients of the CBM- kinetics model. Those coefficients depend on Universal abc- values which are dependent on the type of the fuel fueling a nuclear reactor. Furthermore, such coefficients are linearly dependent on the inserted reactivity. In this paper, the Universal abc- values have been presented symbolically, for the first time, as well as with their numerical values for U-235 fueled reactors for one, two, three, and six groups of delayed neutrons. Simulation studies for constant and variable reactivity insertions are made for the CBM kinetics model, and a comparison of results, with numerical solutions of classical kinetics models for one, two, three, and six groups of delayed neutrons are presented. The results show good agreements, especially for single step insertion of reactivity, with the advantage of the CBM- solution of not encountering the stiffness problem accompanying the numerical solutions of the classical kinetics model. (author)
Wajdi Mohamed Ratemi(1-2011)

In previous studies for nuclear reactor kinetics0, the author developed a mathematical formulation for special form of binomial expansion which introduced a new mathematical representation of nuclear reactor kinetics. Further research by the author introduced a generalization of the developed expansion which is named the Embedded Pascal Triangles (EPTs) expansion which has applications in different disciplines. It is the objective of this paper to extend the applications of the introduced expansion from neutronics to genomics applications. Hence, the paper explores the attempt to reduce the representation complexity of the DNA sequencing of genomes which then minimizes computer storage. Also the paper presents an attempt for providing a generating function of the DNA sequencing of genomes via the use of the EPTs expansion. The result of the attempt established a generating function which is capable of providing the number of A, T, C, and G nucleotides in the genome, along with a number representing all the possible sequences of those nucleotides, of which only one corresponds to the complete nucleotides sequence of the genome in concern. Four numbers which are called the four genomic numbers (n, k, k', k")  are used in the generating function to represent the number of nucleotides presented in the genome, and are used, as well, to represent the number of sequences (T) of those nucleotides, one of which corresponds to the complete sequence of the genome in consideration. Such T-number which is generated from the four genomic numbers, and the four genomic numbers themselves can be used for tagging of the genome in concern. Simple example was used to demonstrate the concept, and a tagging of the complete DNA sequence of the Hepatitis B Virus genome, using the tagger: T(n, k, k', k")   is presented in this paper.
Wajdi Mohamed Ratemi(4-2014)

The subject of modeling and simulation is considered to be as one of the effective scientific tools for understanding system behaviors as well as testing and verifying of new control methods. In this paper. We modeled a nuclear power plant with sodium cooled fast reactor. The physical modeling considers; reactor core, heat exchangers, steam drums, preheaters, piping, pums, and valves. We simulated the plant through the control rod movements, as well as, cases of flow changes through valves opening and closure, and pumps being on and off. Most of the industrial complexes base their control methods on the well known PID - controllers. However, many of them are developing high interest in using modern control approaches. The nuclear industry, on the other hand, still cautious even with the availability of large theoretical studies which are performed by researchers that try to convince atomic authorities to transfer such studies which are performed by researchers that try to convince atomic authorities to transfer such studies to practical applications. In this work, we made study on the control of a nuclear reactor using neural network control. Such method has the advantage of not requiring a knowledge concise model of plant under investigation, it is the same advantage that is making PID- controllers quite famous and very suited for many control applications. Our complete work is developed in a computer package written in C-language. The package is developed with user friendly interface both in arabic and in english helps the user to browse freely through three phases, namely, preprocessor, simulation and control, and postprocessor for cross graphing analysis. Such package can be used as a tool for either a computer aide training CAT, or for computer aide learning CAL.  
Wajdi Mohamed Ratemi, Othman A. Awin, O.A.Ohaib(12-1996)

The neutron transport equation represents the description of the neutron flux in nuclear reactors as a function of seven independent variables. Three of these are spatial (X, Y, Z), one for the neutron energy (E), and two for the neutron direction (theta,phi),and one for the time (t). This complicated dependence makes the analytical solution of the neutron transport equation a quite tedious job, and almost impossible even with the use of highly sophisticated computers. This resulted in many simplification for the purpose of its solution. In this study, the neural network concept has been adopted for tackling such problem in stages. In Neural network there is no need to know the physical principles of the system, neither it necessitates the linearity of the system to be analyzed, and furthermore, the network has the capability of generalization. Special forms of the neutron transport equation have been used as reference models to train the different neural network architectures.Such reference model are; the time independent one group diffusion equation in one dimensional, and three dimensional cases, and multi-energy two dimensional diffusion equation, and finally the second order even parity form of the neutron transport equation. After the appropriate training of the designed networks, such networks were able to predict the flux behavior at neutron fluxes without the use of complicated computer codes, and this can be a valuable tool for decision support systems used by nuclear reactor operators.  
Wajdi Mohamed Ratemi, Essam S. AL- Sagear(12-2002)

In this work, the conventional nth group inhour equation is represented in a polynomial form with a degree of n + 1. A general formula for the coefficients of such polynomial is derived. Those coefficients have linear dependence on the inserted reactivity. The related constants of this linear dependence (the abc-values) are calculated and have universal values for different types of nuclear reactors. A qualitative graph representing the new form of the inhour equation is presented for positive and negative insertions of reactivity.
Wajdi Mohamed Ratemi, A.E.Eshabo(4-1998)

Computed tomography (CT) is a powerful imaging technique widely used. In Libya, the performed CT examinations are increasing, and the high doses associated with those CT examinations must be controlled. The aim of this study is to investigate the performance of several CT scanners image quality used in different medical clinics in Tripoli.Philips CT phantom (Serial Number: 4535-671-35962) was used to acquire images, under the same imaging parameters (120 kVp, 200 mAs, image size of (512 x 512) by implementing the IAEA standards for image quality control (QC). Images were obtained in the DICOM format from each CT.Results showed that there was no major difference in uniformity between the selected regions of interest ROIs in X and Y- directions within all obtained scans, with the coefficient of variation %CV varying between 0.330 and 0.528. The linearity test of all scans exhibited the same trend as it was provided by the phantom manual; the lowest mean pixel intensity value was 956.678 for polyethylene and the highest mean pixel intensity value was for Teflon 1945.347. The contrast C and CNR, between the water layer and Teflon was the highest value varied between 172.913 and 262.199, and the lowest value, varied between 0.844 to 19.015.
Karima Mohamed Ali Elmasri(7-2022)

The very well-known stacked sets of numbers referred to as Pascal’s triangle present the coefficients of the binomial expansion of the form (x+y)n. This paper presents an approach (the Staircase Horizontal Vertical, SHV-method) to the generalization of planar Pascal’s triangle for polynomial expansion of the form (x+y+z+w+r+⋯)n. The presented generalization of Pascal’s triangle is different from other generalizations of Pascal’s triangles given in the literature. The coefficients of the generalized Pascal’s triangles, presented in this work, are generated by inspection, using embedded Pascal’s triangles. The coefficients of I-variables expansion are generated by horizontally laying out the Pascal’s elements of (I-1) variables expansion, in a staircase manner, and multiplying them with the relevant columns of vertically laid out classical Pascal’s elements, hence avoiding factorial calculations for generating the coefficients of the polynomial expansion. Furthermore, the classical Pascal’s triangle has some pattern built into it regarding its odd and even numbers. Such pattern is known as the Sierpinski’s triangle. In this study, a presentation of Sierpinski-like patterns of the generalized Pascal’s triangles is given. Applications related to those coefficients of the binomial expansion (Pascal’s triangle), or polynomial expansion (generalized Pascal’s triangles) can be in areas of combinatorics, and probabilities.
Wajdi Mohamed Ratemi(1-2016)