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Accident Tolerant Fuel simulation loaded in advanced nuclear reactor during severe accident conditions
Hamřík, Lukáš ; Foral, Štěpán (referee) ; Mičian, Peter (advisor)
Tato diplomová práce se zaměřuje na paliva se zvýšenou tolerancí vůči haváriím, jež jsou považována za další krok ke zvyšování bezpečnosti provozu jaderných elektráren. Zpočátku jsou odhaleny slabiny v současnosti provozovaného palivového systému. Jsou popsány možnosti pokročilých paliv a jejich kategorizace, v návaznosti na jejich stav vývoje a problémy, kterým čelí před svým nasazením. Je zmíněna elektrárna APR1400 se svými systémy pro zmírnění následků havárie. Model APR1400 je využit k posouzení vlivu pokročilých materiálů pokrytí při těžké havárii. Stručně jsou představeny možnosti a schopnosti kódu MELCOR, který je schopen simulovat danou problematiku těžkých havárií. Je popsána implementace pokročilých materiálů pokrytí do programu MELCOR, společně se simulovanými scénáři. Na závěr jsou diskutovány výsledky získané ze simulací.
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Spent fuel pool accident simulation
Strieš, Jakub ; Foral, Štěpán (referee) ; Mičian, Peter (advisor)
The aim of the thesis is to provide a theoretical basis for simulating spent fuel pool accidents and to try to build a working model in the Melcor environment. The thesis is divided into four main parts. In the first part a description of the spent fuel pool is given. The processes that take place in nuclear fuel and thus lead to the formation of spent fuel are described. The reasons for the need to cool nuclear fuel after it has been in the reactor are described. For example, the generation of residual heat is described. This is followed by a description of the basic parts and purpose of a spent fuel pool. Structural parts, measuring systems or requirements for the pool itself are shown. Subsequently, an overview of accidents in spent fuel pools that have occurred in the past is also included in this chapter. Their causes and consequences are described, but especially their impact on the further development of nuclear safety, especially in the field of spent fuel pools. For both description and subsequent simulation, the two most studied ones, namely the loss-of-cooling failure and the loss-of-coolant failure, have been selected. The third section introduces the Melcor program which, is the main tool to create the simulation model. The chapter contains a basic description of the program as well as an introduction to the modules that are specifically designed for spent fuel pool simulations. The last part is a description of the model used, its creation, modification, problems in its creation and their solution. Finally, the results obtained are shown and described, together with a commentary to complete their understanding.
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Analysis of the innovated nuclear fuel with FEMAXI code
Čásar, Ondřej ; Novotný, Filip (referee) ; Foral, Štěpán (advisor)
This bachelor thesis deals with modification of source code of program FEMAXI 6 and subsequent analysis of composite nuclear fuel based on SiC admixture. First part introduces the entire open fuel cycle, from the start of the mining to the final disposal of the nuclear waste. The following part describes physical processes in the fuel, especially the processes associated with the low thermal conductivity of classical uranium oxide ceramic pellets, contains the description of the temperature calculations in the pellet and the analysis of the thermal conductivity coefficient including the influences affecting its size. One part of the thesis is an analysis of selected composite fuels increasing the thermal conductivity and introduction of a computational program for FEMAXI 6 nuclear fuel analysis, including its structure, implementation of equations and description of the input file. In the practical part, one can find a description of performed program modifications, comparison with other computational programs and analysis of possible composite nuclear fuel for Dukovany NPP.
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Modern nuclear reactors
Šimík, Michal ; Suk, Ladislav (referee) ; Maar, Tomáš (advisor)
This bachelor’s thesis creates an overview of particular types of nuclear reactors, their history, present and future. Large part focus on the objectives required by modern nuclear reactors provided an international forum GIF. Reactors of fourth generation are characterized also their advantages and disadvantages. In the last section is detail description of selected type of reactor.
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Assessment of the thermomechanical behaviour of perspective nuclear fuel for reactivity insertion accidents
Halabuk, Dávid ; Suk, Ladislav (referee) ; Martinec, Jiří (advisor)
The objective of this master’s thesis is to simulate thermo-mechanical behaviour of nuclear fuel in a pressurized water reactor during a reactivity initiated accident. An important part of this work is focused on examination of processes which occur during such accident and on creation of a detailed overview of material properties of nuclear fuel and fuel cladding which are necessary for simulations that closely reflect reality. Simulations in this thesis examine cases of fresh or irradiated nuclear fuel for two types of fuel cladding, Zircaloy-4, a material that is currently used in nuclear reactors, and ceramic matrix composite material made of SiC. The thesis also presents comparison of results with a corresponding international benchmark and an assessment of the influence of selected input parameters on obtained results.
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Enrichment and reprocessing of nuclear fuel
Janoušek, Petr ; Elbl, Patrik (referee) ; Sitek, Tomáš (advisor)
Nuclear fuel is one form of electricity generation. This bachelor thesis deals with its modification and processing as this fuel has to undergo special processes to ensure its good usability. The aim of the thesis is to list and analyze the main processes involved in the production of nuclear fuel. The thesis is, in particular, focused on the enrichment of nuclear fuel, which is the process of enhancing its properties. The first and second chapter of the paper discusses basic issues of first nuclear energy and then nuclear fuel. The third chapter of the thesis explains in detail the enrichment of nuclear fuel and also describes different methods of enrichment. Another process taking place after nuclear fuel is used is it's reprocessing. This method of converting used fuel into fuel that can be reused is dealt with in the last chapter of the thesis.
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Simulation of Accelerator Driven Nuclear Reactor for Spent Nuclear Fuel Transmutation
Jarchovský, Petr ; Ing. Antonín Krása, Ph.D., SCK.CEN Mol (referee) ; Katovský, Karel (advisor)
This master’s thesis deals with usage of burn-up (spent) nuclear fuel in nuclear power plants of next generation – accelerator driven transmutation plants which is produced in current nuclear power plants. This system could significantly reduce the volume of dangerous long-lived radioisotopes and moreover they would be able to take advantage of its great energy potential due to fast neutron spectrum. In the introduction are listed basic knowledge and aspects of spent nuclear fuel along with its reprocessing and the possibility of further use while minimizing environmental impact. As another point detailed description of accelerator driven systems is described together with its basic components. In addition this search is followed by individual chronological enumeration of projects of global significance concerning their current development. Emphasis is placed on SAD and MYRRHA projects, which are used like base for calculations. This last, computational part, deals with the creation of the geometry of subcritical transmutation reactor driven by accelerator and subsequent evaluation which assembly is the most effective for transmutation and energy purposes along with changing of target, nuclear fuel and coolant/moderator.
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Advanced nuclear reactors’ promising fuels
Kadlec, Miroslav ; Varmuža, Jan (referee) ; Katovský, Karel (advisor)
This bachelor thesis focuses on the development of nuclear reactors and the fuel burned them. Thesis describes the various types of nuclear fuel, including the ways they are treated either before or after use in a nuclear power plant. Also included is a description of the situation of nuclear power plants in the Czech Republic and the Slovak Republic. In conclusion focuses on the state of some upcoming projects of the future.
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Nuclear Fuel and its Behavior during Burn-up
Matocha, Vítězslav ; Foral, Štěpán (referee) ; Katovský, Karel (advisor)
The point of this bachelor’s thesis is to characterize different types of nuclear fuels and their behaviour during the process of burning-up. Futher, basic types of nuclear reactors are mentioned, as well as their history and different kinds of nuclear fuels used in these reactors. Then there are pieces of information about fuel cycles and fuel burning-up. Furthermore, the thesis concentrates on the changes, which happen in the nuclear fuel during the process of burning-up, such as swelling and cracking. In its other parts, this bachelor’s thesis deals with fission products, mainly gas fission products are mentioned here. At the end of this thesis, a simple model of nuclear fuel burning-up is created. This model follows concentration of izotopes of uranium and plutonium during fuel burning-up.
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Safety of the fuel stored in water pool
Mičian, Peter ; Novotný, Filip (referee) ; Foral, Štěpán (advisor)
This diploma thesis deals with storing the spent nuclear fuel and reviewing its safety. The theoretical part analyzes the processes taking place while the fuel is being used, such as fission, isotopic changes, fission gas release, cracking, swelling and densification of fuel pellet. The thesis is also focused on handling the spent fuel and on the way it makes from the reactor, through the spent fuel pool, the transportation, various kinds of storing, till the reprocessing and final deep geological repository. Furthermore, this part of the thesis briefly discusses computing code MCNP, its main characteristics, input files and using. The practical part of the work is focused on creating the model of the spent fuel pool located next to the nuclear reactor WWER 440/V213. This type was chosen, because it is the most used type of nuclear reactor in Czech Republic and Slovakia. With the help of the code MCNP, the multiplication factor of the main configurations of the fuel in the pool was calculated, and then the required safety regulations to ensure sufficient subcriticality, so its safety, were checked. Next, several analysis were performed using this model. These analyses were concerning the temperature of coolant, fuel and the use of various nuclear data libraries. In the future this model can be used to realize new analyses with new kinds of fuels, materials and data libraries.
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