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, Ph.D. Dissertation Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
The present ph.D. thesis consists of three sections including the static calculation, neutron noise calculation and neutron noise source unfolding in VVER-1000 reactor core. 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 Galerkin Finite Element Method (GFEM) using unstructured triangle elements generated by Gambit software. The static calculation is performed for both linear and quadratic approximations of shape function; baesd on which results are compared. Using power iteration method for the static calculation, the neutron and adjoint fluxes with the...
Determination of Reactor Dynamic Parameters Using Correlation Equation
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor)
Abstract
Effective delayed neutrons fraction is one of important reactor dynamic parameters. Prompt neutrons decay constant is one of another reactor dynamic parameters that for its relation with effective delayed neutrons fraction is important. The Feynman- alpha method is one of famous methods in noise analysis. In this method, prompt neutrons decay constant can be obtained by obtaining variance to mean ratio of a detector counts in different time windows and fitting a specific formula to these ratios. In previous applied works, required data of Feynman- alpha method were obtaining mainly by experimental data or Monte Carlo simulations. In experimental way, detectors with high efficiency are needed...
On an improved Direct Discrete Method and its application in two dimensional multi-group neutron diffusion equation
, Article Annals of Nuclear Energy ; Volume 44 , June , 2012 , Pages 1-7 ; 03064549 (ISSN) ; Vosoughi, N ; Ayyoubzadeh, S. M ; Sharif University of Technology
2012
Abstract
An improvement to the Direct Discrete Method (DDM), also known as the Cell Method, has been discussed. The improvement is based on a duality theorem between the primal and dual complexes. Also, the analog counterpart of the Integral operator has been derived in this paper. The multi-group neutron diffusion is then derived, directly in a discrete algebraic form, according to this procedure. A numerical example has shown that this method would yield a high order of convergence (approximately 4.6) if its parameters are adjusted suitably. Finally, the method is applied to the 2D IAEA benchmark problem, and has shown to yield accurate solutions with a reasonably low number of unknowns
Development of MCNPX-ESUT computer code for simulation of neutron/gamma pulse height distribution
, Article Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment ; Volume 782 , May , 2015 , Pages 112-119 ; 01689002 (ISSN) ; Vosoughi, N ; Zangian, M ; Sharif University of Technology
Elsevier
2015
Abstract
In this paper, the development of the MCNPX-ESUT (MCNPX-Energy Engineering of Sharif University of Technology) computer code for simulation of neutron/gamma pulse height distribution is reported. Since liquid organic scintillators like NE-213 are well suited and routinely used for spectrometry in mixed neutron/gamma fields, this type of detectors is selected for simulation in the present study. The proposed algorithm for simulation includes four main steps. The first step is the modeling of the neutron/gamma particle transport and their interactions with the materials in the environment and detector volume. In the second step, the number of scintillation photons due to charged particles such...
SN transport method for neutronic noise calculation in nuclear reactor systems: comparative study between transport theory and diffusion theory
, Article Annals of Nuclear Energy ; Volume 114 , 2018 , Pages 236-244 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In this paper, the neutron noise based on transport theory and diffusion noise theory using Green's function technique is calculated. As the neutron noise is used for core diagnostic, surveillance and monitoring, calculation of neutron noise precisely can play an important role in monitoring and safety. We compare the accuracy of Green's function based on transport and diffusion theory in order to survey the differences between these theories. In this study some deviation between results obtained two theories are observed, and the impact of dimensions, cross sections and frequency on the results investigated. © 2017
Neutron noise simulation using ACNEM in the hexagonal geometry
, Article Annals of Nuclear Energy ; Volume 113 , 2018 , Pages 246-255 ; 03064549 (ISSN) ; Vosoughi, N ; Vosoughi, J ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In the present study, the development of a neutron noise simulator, DYN-ACNEM, using the Average Current Nodal Expansion Method (ACNEM) in 2-G, 2-D hexagonal geometries is reported. In first stage, the static neutron calculation is performed. The neutron/adjoint flux distribution and corresponding eigen-values are calculated using the algorithm developed based on power iteration method by considering the coarse meshes. The results of the static calculation are validated against the well-known IAEA-2D benchmark problem. In the second stage, the dynamic calculation is performed in the frequency domain in which the dimension of the variable space of the noise equations is lower than the time...
Neutron noise simulator based on the boundary element method (BEM)
, Article Annals of Nuclear Energy ; Volume 159 , 2021 ; 03064549 (ISSN) ; Mohamadbeygi, S ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The purpose of the present study is to develop the neutron diffusion solver and neutron noise simulator based on the Boundary Element Method (BEM). The 2-D, 2-G neutron/adjoint diffusion equation and corresponding neutron/adjoint noise equation were solved using the mentioned method. The developed neutron static and noise simulator based on the finite element method gives accurate results when the more number of the elements is used. The motivation of the present research is to use the boundary element method to reduce the computational cost. The boundary element method attempts to use the given boundary conditions to fit boundary values into the integral equation, rather than values...
Rapid quantitative elemental analysis using artificial neural network for case study of Isfahan Miniature Neutron Source Reactor
, Article Journal of Radioanalytical and Nuclear Chemistry ; Volume 331, Issue 11 , 2022 , Pages 4479-4487 ; 02365731 (ISSN) ; Hosseini, S. A ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
In this study, new method for NAA purposes at 30 kW Isfahan MNSR is suggested. An algorithm based on ANN is proposed to quantitatively predict the unknown elements with no need standard sample. A three-layer feed-forward ANN with back-propagation algorithm has been used to determine concentration of selenium and fluorine in Multiple Sclerosis patients and healthy people blood samples. Predicted concentration of elements show good agreement between new method and experiment results. The correlation coefficient between the experimentally determined and predicted values are 0.99104 and 0.99364, respectively. This method is a rapid and precise approach for elemental analysis. © 2022, Akadémiai...
Neutron Noise Calculation using Nodal Expansion Method
, M.Sc. Thesis Sharif University of Technology ; Vosoughi, Naser (Supervisor) ; Hosseini, Abolfazl (Co-Advisor)
Abstract
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,...
Development of Neutron Noise Simulator Based on the Boundary Element Method
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Aboulfazl (Supervisor)
Abstract
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...
Simulation and Optimization of the Neutron Velocity Selector
, M.Sc. Thesis Sharif University of Technology ; Hosseini, Abolfazl (Supervisor)
Abstract
To study the structure of materials, among materials containing hydrogen, an instrument called the "small-angle neutron scattering instrument" is used. Having a monochromatic neutron beam is the most basic component of this instrument. This beam is often produced using a device called the "neutron velocity selector". The neutron velocity selector is a rotating mechanical piece that allows for passage of neutrons at a certain speed, according to its rotational speed. In fact, this device produces a monochromatic neutron beam with continuous flux. Until now, it has been designed and manufactured in a variety of models, which are generally divided into two groups of multi-disc and multi-blade...
Technical note Variable moderation high performance light water reactor (VMHWR)
, Article Annals of Nuclear Energy ; Volume 58 , 2013 , Pages 1-5 ; 03064549 (ISSN) ; Tashakor, S ; Salehi, A. A ; Abbaspour Tehrani Fard, A ; Sharif University of Technology
2013
Abstract
A new flow model of high performance light water reactor (HPLWR) is discussed in the present study. HPLWR involves a negative density reactivity coefficient with high time delay. This factor decreases the stability of such reactors when transient and abnormal accidents happen. A new design for enhancing safety and efficiency in such reactors is presented. In the new design, the fluid passing through the moderator channels and the assembly gaps (known as a moderator) flows in channels detached from coolants. It is possible to control the moderator mass flux. Increasing or decreasing the moderator mass flux will modify the moderation capacity, which results in a change in the reactor power....
Axial enrichment profile in advance nuclear energy power plant at supercritical-pressures
, Article Kerntechnik ; Volume 80, Issue 6 , 2015 , Pages 541-544 ; 09323902 (ISSN) ; Zarifi, E ; Salehi, A. A ; Sharif University of Technology
Carl Hanser Verlag
2015
Abstract
The High-Performance Light Water Reactor (HPLWR) is the European version of the advance nuclear energy power plant at Supercritical-pressure. A light water reactor at supercritical pressure, being currently under design, is the new generation of nuclear reactors. The aim of this study is to predict the HPLWR neutronic behavior of the axial enrichment profile with an average enrichment of 5 w/o U-235. Neutronic calculations are performed using WIMS and CITATION codes. Changes in neutronic parameter, such as Power Peaking Factor (PPF) are discussed in this paper
Investigating the propagation noise in PWRs via closed-loop neutron-kinetic/thermal-hydraulic noise calculations
, Article Annals of Nuclear Energy ; Volume 80 , 2015 , Pages 101-113 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Neutron noise induced by propagating thermal-hydraulic disturbances (propagation noise for short) in pressurized water reactors is investigated in this paper. A closed-loop neutron-kinetic/thermal-hydraulic noise simulator (named NOISIM) has been developed, with the capability of modeling the propagation noise in both Western-type and VVER-type pressurized water reactors. The neutron-kinetic/thermal-hydraulic noise equations are on the basis of the first-order perturbation theory. The spatial discretization among the neutron-kinetic noise equations is based on the box-scheme finite difference method (BSFDM) for rectangular-z, triangular-z and hexagonal-z geometries. Furthermore, the finite...
Development of 3D neutron noise simulator based on GFEM with unstructured tetrahedron elements
, Article Annals of Nuclear Energy ; Volume 97 , 2016 , Pages 132-141 ; 03064549 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Elsevier Ltd
Abstract
In the present study, the neutron noise, i.e. the stationary fluctuation of the neutron flux around its mean value is calculated based on the 2G, 3D neutron diffusion theory. To this end, the static neutron calculation is performed at the first stage. The spatial discretization of the neutron diffusion equation is performed based on linear approximation of Galerkin Finite Element Method (GFEM) using unstructured tetrahedron elements. Using power iteration method, neutron flux and corresponding eigen-value are obtained. The results are then benchmarked against the valid results for VVER-1000 (3D) benchmark problem. In the second stage, the neutron noise equation is solved using GFEM and...
Theory of neutron scattering for gapless neutral spin-1 collective mode in graphite
, Article European Physical Journal B ; Volume 43, Issue 2 , 2005 , Pages 175-185 ; 14346028 (ISSN) ; Baskaran, G ; Sharif University of Technology
2005
Abstract
Using tight binding band picture for 2D graphite, and the Hubbard interaction, recently we obtained a gapless, neutral spin-1 collective mode branch in graphite [Phys. Rev. Lett. 89, 016402], In this paper we present a detailed RPA analysis of the Neutron Scattering cross section for this collective mode. Near K-point and very close to Γ-point, the intensity of neutron scattering peaks vanishes as q3. This is shown using a simple Dirac cone model for the graphite band structure, which captures the small-q behavior of the system. As we move away from the Γ- and Κ-points in the Brillouin zone of the collective mode momenta, we can identify our collective mode quanta with spin triplet excitons...
Influence of ridge filter material on the beam efficiency and secondary neutron production in a proton therapy system
, Article Zeitschrift fur Medizinische Physik ; Volume 22, Issue 3 , September , 2012 , Pages 231-240 ; 09393889 (ISSN) ; Afarideh, H ; Sadighi-Bonabi, R ; Sharif University of Technology
Elsevier
2012
Abstract
In this work, the 3D proton dose profile is calculated in a homogenous water phantom using a Monte Carlo application developed with the Geant4 toolkit. The effect of the ridge filter material (for SOBP widths of 6, 9 and 12 cm) on the homogeneity of the dose distribution, secondary neutron production and beam efficiency are investigated in a single ring wobbling irradiation system. The energy spectrum of secondary neutrons per primary proton at various locations around the phantom surface is calculated. The simulation revealed that most of the produced neutrons are released at slight angles which enable them to reach the patient and consequently to be hazardous. Also, the homogeneity of the...
Uncertainty evaluation of calculated and measured kinetics parameters of Tehran Research Reactor
, Article Nuclear Engineering and Design ; Volume 240, Issue 10 , 2010 , Pages 2761-2767 ; 00295493 (ISSN) ; Vosoughi, N ; Sharif University of Technology
Abstract
Effective delayed neutron fraction βeff and neutron generation time Λ are important factors in reactor physics calculation and transient analysis. In the first stage of this research, these kinetics parameters have been calculated for two states of Tehran Research Reactor (TRR), i.e. cold (fuel, clad and coolant temperature 20 °C) and hot (fuel, clad and coolant temperature 65, 49 and 44 °C, respectively) states using MTR-PC computer code. The ratio of (βeff) i/(βeff)core plays an important role in reactivity accident analysis codes. This parameter and its contribution to effective delayed neutron fraction from each nucleus have been calculated in cold and hot reactor states. Uncertainty of...
Enhanced finite difference scheme for the neutron diffusion equation using the importance function
, Article Annals of Nuclear Energy ; Volume 96 , 2016 , Pages 412-421 ; 03064549 (ISSN) ; Vosoughi, N ; Gharib, M ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
Mesh point positions in Finite Difference Method (FDM) of discretization for the neutron diffusion equation can remarkably affect the averaged neutron fluxes as well as the effective multiplication factor. In this study, by aid of improving the mesh point positions, an enhanced finite difference scheme for the neutron diffusion equation is proposed based on the neutron importance function. In order to determine the neutron importance function, the adjoint (backward) neutron diffusion calculations are performed in the same procedure as for the forward calculations. Considering the neutron importance function, the mesh points can be improved through the entire reactor core. Accordingly, in...
Conduction mechanism in Pr-doped GdBa2Cu3O 7
, Article Physica Status Solidi C: Conferences ; Volume 1, Issue 7 , 2004 , Pages 1851-1854 ; 16101634 (ISSN) ; Akhavan, M ; Sharif University of Technology
2004
Abstract
The normal state resistivity of single phase polycrystalline Gd(Ba 2-xPrx)Cu3O7+δ samples with 0.0 ≤ x ≤ 0.50 have been investigated. The two-dimensional variable range hopping is dominant in the normal state resistivity of the samples. The conduction shows that Pr-doping strongly localizes the carriers in normal state, and finally causes the suppression of superconductivity. Based on the resistivity measurements, the effect of Pr substitution in 123 structure of HTSC at Gd or Ba site is to increase the pseudogap temperature Ts, although, Pr at Ba site has a stronger effect on the suppression of T s and superconductivity. Pr-doping not only reduces the carrier density and induces pseudogap,...