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Monitoring and Simulation of ADS Experimental Target Behaviour, Heat Generation, and Neutron Leakage
Svoboda, Josef ; Kliman,, Ján (referee) ; Wagner,, Vladimír (referee) ; Katovský, Karel (advisor)
Urychlovačem řízené podkritické systémy (ADS) se schopností transmutovat dlouhodobě žijící radionuklidy mohou vyřešit problematiku použitého jaderného paliva z aktuálních jaderných reaktorů. Stejně tak i potenciální problém s nedostatkem dnes používaného paliva, U-235, jelikož jsou schopny energeticky využít U-238 nebo i hojný izotop thoria Th-232. Tato disertační práce se v rámci základního ADS výzkumu zabývá spalačními reakcemi a produkcí tepla různých experimentálních terčů. Experimentální měření bylo provedeno ve Spojeném ústavu jaderných výzkumů v Dubně v Ruské federaci. V rámci doktorského studia bylo v průběhu let 2015-2019 provedeno 13 experimentů. Během výzkumu byly na urychlovači Fázotron ozařovány různé terče protony s energií 660 MeV. Nejdříve spalační terč QUINTA složený z 512 kg přírodního uranu, následně pak experimentální terče z olova a uhlíku nebo terč složený z olověných cihel. Byl proveden také speciální experiment zaměřený na detailní výzkum dvou protony ozařovaných uranových válečků, z nichž je složen spalační terč QUINTA. Výzkum byl především zaměřen na monitorování uvolňovaného tepla ze zpomalovaných protonů, spalační reakce a štěpení, způsobeného neutrony produkovanými spalační reakcí. Dále se na uvolňování tepla podílely piony a fotony. Teplota byla experimentálně měřena pomocí přesných termočlánků se speciální kalibrací. Rozdíly teplot byly monitorovány jak na povrchu, tak uvnitř terčů. Další výzkum byl zaměřený na monitorování unikajících neutronů z terče porovnávací metodou mezi dvěma detektory. První obsahoval malé množství štěpného materiálu s teplotním čidlem. Druhý byl složený z neštěpného materiálu (W nebo Ta), avšak s podobnými materiálovými vlastnostmi se stejnými rozměry. Unik neutronů (resp. neutronový tok mimo experimentální terč) byl detekován uvolněnou energií ze štěpné reakce. Tato práce se zabývá přesným měřením změny teploty pomocí termočlánků, s využitím elekroniky od National Instrument a softwaru LabView pro sběr dat. Pro práci s daty, analýzu a vizualizaci dat byl použit skriptovací jazyk Python 3.7. (s využitím několika knihoven). Přenos částic by simulován pomocí MCNPX 2.7.0., a konečně simulace přenosu tepla a určení povrchové teploty simulovaného modelu bylo provedeno v programu ANSYS Fluent (pro jednodušší výpočty ANSYS Transient Thermal).
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Direct digital frequency synthesizer
Svoboda, Josef ; Šebesta, Jiří (referee) ; Kasal, Miroslav (advisor)
Direct Digital Frequency Synthesis (DDFS) is a method of producing an analog waveform, usually a sine wave, by generating a time varying signal in digital form a then performing a digital to analog conversion. Because operations within a DDFS device are primarily digital, it can offer fast switching between output frequencies, fine frequency resolution and operation over a broad spectrum of frequencies.
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The temperature field analysis of the subcritical accelerator-driven reactors
Majer, Šimon ; Šťastný, Ondřej (referee) ; Svoboda, Josef (advisor)
The aim of the bachelor thesis is to discuss the problems of accelerator driven system, to describe the possibilities of temperature measurement, to create model of the spallation target QUINTA target in the program Inventor and to perform the simulation by using the Ansys software. The theoretical part is focused on nuclear energy and its potential for the future and continues smoothly to the issue of accelerator driven system (ADS), where it discusses the possibilities of using mentioned system. The thesis is processed from the point of view of electrical energy, focusing on generation issues and the possibility of heat monitoring. The possibilities of temperature measurement are discussed here for calculation and simulation of heat transfer. The practical part of the bachelor’s thesis is processed with the help of the Joint Institute for Nuclear Research in Dubna, where the ADS research is in process. The input data and the size of the geometry were provided by the JINR research team and were used to simulate heat transfer by using the Ansys program. The results of the simulation are processed graphically in the last chapter of the bachelor thesis.
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Stress and deformation analysis of railway bridge over the Odra River
Svoboda, Josef ; Profant, Tomáš (referee) ; Fuis, Vladimír (advisor)
This bachelor thesis deals with strain, stress and deformation analysis of the planar truss bridge construction. The aim is to determined the size of axial forces for statically determinate system and then making construction changes to reduce axial stresses in the individual beams in the structure. This structural modification becomes statically indeterminate structure. To solve this problem we consider different positions of the train at the bridge. The obtained values we can use to assess stress and deformation of the structure and the analytical results will be compared with the results obtained using the finite element method.
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Possibilities of thorium utilization in current NPPs
Svoboda, Josef ; Praze, Jan Prehradný, ÚE FS ČVUT v (referee) ; Katovský, Karel (advisor)
Nuclear power plants provide about 11 percent of the world's electricity production. For fission process is uranium fuels used with varying percentage of enrichment 235U for most of nuclear reactors. Uranium reserves are reducing and their mining cost increases. Therefore, the thorium fuel is discussed as revolution fuel for current and future nuclear power plants. This diploma thesis deals with possibility of thorium fuel utilization at various types of nuclear reactors with a focus on light water reactors. The practical part of the thesis is focused on simulation and calculations of various uranium dioxide and thorium dioxide layers at the fuel rods. Model of WWER 440 reactor was developed for the calculations with the addition of thorium fuel. The model simulates burning out of fuel for 5 years, with monitoring of fuel behavior and tracking changes of each material. The thesis tries to define the suitable ratio and parameters of layers combination of uranium and thorium fuel. For these ratios and parameters the thesis tries to give sufficient amount of computational analyzes.
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Numerical simulation of crack propagation in ceramic composites in 3D
Svoboda, Josef ; Horníková, Jana (referee) ; Majer, Zdeněk (advisor)
The strength of materials such as glass and ceramics can be influenced by the environment (stress corrosion). Under applied stress defects (cracks) can grow sub-critically below fracture toughness K_Ic. The aim of this work was to develop a three-dimensional finite-element model to analyze the subcritical crack growth behavior of ceramic-based particulate composites. The maximum tangential stress criterion (MTS) was used to predict the direction of the crack propagation in the framework of linear elastic fracture mechanics. The modeled material was a Low Temperature Co-fired Ceramics (LTCC), containing alumina particles embedded in a glass matrix. The main aim of this work was to develop a 3D model describing the crack growth. Conclusions from this work can contribute to a better understanding of subcritical crack propagation in particle composites.
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Comparison of the price shares of individual constructions in the total price stated in the price schedule and detrmined by the item budget
Lorencová, Andrea ; Svoboda, Josef (referee) ; Kosová, Jaroslava (advisor)
The topic of this diploma thesis is a comparasion of the price shares of individual constructions in the total price stated in the price schedule and determined by the item budget. The diploma thesis says and describes cost methods of valuation of building facilities and family houses at the outset. There is contained a procedure for determinating the price shares of construction and equipment and theirs adjustment in the next text. According to the chosen metodology are determined the price shares of constructions and equipments based on the item budget. This way determined the price shares of constructions and equipments are compared with the price shares of construcions and equipments determined by Decree No. 441/2013 Coll. The aim of diploma thesis is to determine if the price shares of constructions and equipments based on the item budget correspond to the price shares of constructions and equipments in the price schedule.
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Heat transfer by thermal radiation
Budovec, Michal ; Svoboda, Josef (referee) ; Foral, Štěpán (advisor)
This bachelor’s thesis deals with heat transfer, specifically with thermal radiation heat transfer by convection. The work is divided into theoretical part and calculations. The theoretical part describes basic thermomechanical notions and all kinds of heat transfer with the emphasis on heat transfer by radiation with convection. Heat conduction chapter describes the basic types of heat conduction. In chapter Heat transfer by convection are given criterion equations and examples for determining dimensionless numbers. Radiation heat transfer chapter focuses on heat transfer between two bodies and the radiation factor. With this equations and dimensionless numbers are quantifying variables in the calculation part. In the theoretical part is wrought calculation for a given case of heat transfer in the air and vacuum. The calculation is experimentally verified, from which is wrought protocol with the measurement and comparison with calculation and measurement in the air and vacuum.
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