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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Analýza provozu uzlu sítě po připojení jaderného bloku velkého výkonu / Grid Node Operation after Large Nuclear Unit Connection to the Grid

Prokop, Ondřej January 2016 (has links)
The thesis deals with the analysis of the grid node operation after the connection the nuclear unit. The aim of the master´s thesis is to describe the influence of network´s faults to a nuclear unit. Thesis is dealing with three fundamental problems. An influence of short circuits and power imbalance on the synchronous generator of nuclear power plant and its operation of the island network. The thesis is focused especially on the nuclear unit. However, in the case of any failure in the network, it´s necessary to check other units and their protections in the test system because unit failure could cause the disintegration of the power network. For the purposes of the simulation a test system of the power network has been developed. The test system was optimized in the LUG software, which is used to calculate the power network. Transient simulations are performed in the MODES software. Single faults are configured with scenarios. Results are generated into output files. Analysis of influence network´s faults on the synchronous generator of nuclear power plants. The ability of the synchronous generator to restore the primary steady state or hold the new steady state during changes in operating parameters of the network is one of the important parts of the safe and reliable operation of the power network. During the short circuit the damped transient actions occur. With the extension of the short circuit duration, the amplitude of the transient action increases. The risk of the stability loss of a synchronous generator increases. Therefore, the critical clearing time of a short circuit is being defined, which is the time when there is not any loss of stability. Critical clearing time of research generator is sufficient to turn off the short circuit with the help of its protection (the worst case is 0,8 s). For example, by comparison with the hydroelectric power plant, the critical clearing time is much longer. Models of other power plants have been designed with high reliability so in the case of these faults, it doesn’t cause the disintegration of the power network. Creation of island grid is characterized by strong current surges. Units must be resistant to these surges. In the island grid fast changes of the electrical parameters often occurs. Therefore, units must respond to these changes as quickly as possible and in the broadest limits. For this purpose an island operation regulator is being used. In the case of surplus island grid in steam power plants a dump condenser can be used. This is an important ability of steam power plants because the units are able to react quickly to changes of electrical parameters in island grid. The main result of this thesis is the behavior of the nuclear power plant during various faults in the power network. Researched generator of the nuclear power plant is highly stable against faults in the power network based on the findings. The results allow to continue in this topic with real network and real unit of nuclear power plant.
62

The feasibility of modern technologies for reinforced concrete containment structures of nuclear power plants

Czerniewski, Sarah January 1900 (has links)
Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / This report explores the requirements for the design and analysis of concrete containment and shows how newer material technologies such as self-consolidating concrete (SCC) and fiber reinforcement could assist in the constructability and durability of new nuclear power plant facilities. SCC for example, enables concrete to flow in the forms around the reinforcement and provides a more uniform adhesion with the reinforcement. Additionally, fiber reinforcement in the concrete mix increases bonding capability, thus making the concrete less likely to fracture. In particular, the ease of constructability benefits offshore floating nuclear power plants and preapproved modular power plants. To differentiate, the offshore plant would employ the assembly line to make all the plants the same while the modular plant, designed to be used anywhere, is not site specific and is typically smaller. Regarding research method, the report starts with the history of the nuclear industry in the United States, including the last nuclear power plant constructed, clarifying that nuclear energy was first harnessed for a submarine propulsion system before being employed to generate electricity. After these early endeavors, two major accidents, Three Mile Island (March 28, 1979) and Chernobyl (April 26, 1986), provided information regarding the lack of safety of nuclear power plant design and operation. Since the containment building is the focus of this report, recognizing the loads and the load combinations for design was the next step in research. Following that, the next step was to determine the design considerations and analyze the containment structure. New material technologies clearly have opened the door to new construction techniques, and the combination of new materials and methods offers structural engineers opportunity to build inherently safer nuclear power plants.
63

Laminar cracking in post-tensioned concrete nuclear containment buildings

Dolphyn, Bradley P. 27 May 2016 (has links)
As a critical public safety-related structure, the long-term integrity of post-tensioned concrete containment buildings (PCCs) is necessary for continued operation of the reactors they house. In 2009, during preparations for a steam generator replacement, extensive subsurface laminar cracking was identified in a portion of the Crystal River 3 (CR3) PCC in Florida, and the plant was permanently shut down in 2013. This study investigates potential contributing factors to the identified cracking with particular focus on the effects of high early-age temperatures on the cracking risk of the concrete, on the development of the concrete properties, and on the late-age structural behavior of the concrete. Two planar, full-scale mock-ups of a portion of the CR3 PCC were constructed and instrumented with temperature and strain gauges to monitor the thermal and mechanical behavior during representative concrete curing and post-tensioning loading. Standard- and match-cured concrete specimens were tested for determination of the time- and temperature-dependent development of thermal and mechanical concrete properties, and hydration parameters were determined for the mock-up cement paste for modeling the heat generation in the concrete. These properties and parameters were utilized in 3D finite element analysis of the mock-ups in COMSOL Multiphysics and compared with experimental results. Non-destructive evaluation via shear wave tomography was conducted on the mock-ups to identify flaws and determine the effectiveness of the methods for identifying delaminations between post-tensioning ducts approximately 10 inches beneath the concrete surface. Though early-age thermal stresses were determined not to have caused cracking in the mock-ups, the high early-age concrete temperatures resulted in decreased late-age mechanical properties that were shown to contribute to greater concrete cracking risk when the mock-up was post-tensioned. Tensile stresses exceeding the tensile strength of the concrete were identified along the post-tensioning ducts when biaxial post-tensioning loads were applied in finite element analysis, but the stresses decreased rapidly with increased distance from the ducts. Through parametric modeling, increasing the tensile strength of the concrete was identified as an effective means of reducing the cracking risk in PCCs. Additionally, relationships between the mechanical properties for the standard- and match-cured specimens were identified that could enable prediction of in-place or match-cured concrete properties based only on the results of tests on fog-cured specimens.
64

台灣海岸地帶土地資源規劃與管理之研究

陳炎基, CHEN, YAN-JI Unknown Date (has links)
海岸地帶係位處陸地與海洋交會之帶狀區域,自然孕育了珍貴且富變化的資源,能提 供高經濟、遊憩、教育、研究、生態保護及國土保安等多樣化使用。惟此等資源甚為 脆弱且不具復原性,一旦遭受破壞,將難以恢復,而遠失去其效用。 台灣土地資源極為有限,近二十年來,因為人口增加,產業結構轉型,對於不同型態 土地的需求日益殷切,而海岸土地具無主資源之特性,遂成為公、私部門競相使用的 對象。由於缺乏一套整體性的規劃與管理制度,致使海岸土地利用所衍生的問題方興 未艾,而這些問題正是以往海岸土地利用不當所累聚的環境惡果。 本研究承續上述問題,首先探討土地資源規劃與管理相關理論及美、日、荷等國海岸 土地資源規劃與管理的理念與精神,以作為本研究的理論基礎。 其次,透過實地訪問調查(使用者、管理者)並選擇彰濱工業區與核能四廠預定廠址 作為實例分析,分析重點為海岸土地資源競用與衝突之根源、政府所扮演的角色以及 規劃與管理之功能。根據分析結果,進一步檢視海岸地帶現行規劃與管理體制之缺失 。 從規劃與管理的角度來看,海岸地帶牽涉到陸域與水域二個方面,所以管轄機關職權 的複雜與重疊,法規的零散以及基於政治層面的考量,都構成規劃與管理的困難,而 海岸地帶規劃與管理的功能在於如何配置資源?建立使用的優先次序、整合法規以及 管理策略等。在這種思想結構下,本研究提出「動態的系統規劃與管理架構」,就政 策、法規、土地使用分派計畫、管理機構等作一詳盡的改革建議。整個架構力求與現 行體制相互配合,俾作為未來台灣地區海岸地帶長期發展規劃與管理之參考。
65

CO<sub>2</sub> Capture With MEA: Integrating the Absorption Process and Steam Cycle of an Existing Coal-Fired Power Plant

Alie, Colin January 2004 (has links)
In Canada, coal-fired power plants are the largest anthropogenic point sources of atmospheric CO<sub>2</sub>. The most promising near-term strategy for mitigating CO<sub>2</sub> emissions from these facilities is the post-combustion capture of CO<sub>2</sub> using MEA (monoethanolamine) with subsequent geologic sequestration. While MEA absorption of CO<sub>2</sub> from coal-derived flue gases on the scale proposed above is technologically feasible, MEA absorption is an energy intensive process and especially requires large quantities of low-pressure steam. It is the magnitude of the cost of providing this supplemental energy that is currently inhibiting the deployment of CO<sub>2</sub> capture with MEA absorption as means of combatting global warming. The steam cycle of a power plant ejects large quantities of low-quality heat to the surroundings. Traditionally, this waste has had no economic value. However, at different times and in different places, it has been recognized that the diversion of lower quality streams could be beneficial, for example, as an energy carrier for district heating systems. In a similar vein, using the waste heat from the power plant steam cycle to satisfy the heat requirements of a proposed CO<sub>2</sub> capture plant would reduce the required outlay for supplemental utilities; the economic barrier to MEA absorption could be removed. In this thesis, state-of-the-art process simulation tools are used to model coal combustion, steam cycle, and MEA absorption processes. These disparate models are then combined to create a model of a coal-fired power plant with integrated CO<sub>2</sub> capture. A sensitivity analysis on the integrated model is performed to ascertain the process variables which most strongly influence the CO<sub>2</sub> energy penalty. From the simulation results with this integrated model, it is clear that there is a substantial thermodynamic advantage to diverting low-pressure steam from the steam cycle for use in the CO<sub>2</sub> capture plant. During the course of the investigation, methodologies for using Aspen Plus?? to predict column pressure profiles and for converging the MEA absorption process flowsheet were developed and are herein presented.
66

Techno-economic study of the calcium looping process for CO2 capture from cement and biomass power plants

Ozcan, Dursun Can January 2014 (has links)
The first detailed systematic investigation of a cement plant with various carbon capture technologies has been performed. The calcium looping (Ca-looping) process has emerged as a leading option for this purpose, since this process applied to a cement plant provides an opportunity to use the CaO purge for clinker production. The Ca-looping process is comprised of two interconnected reactors where the carbonator captures CO2 from flue gases and the calciner regenerates the CaCO3 into CaO by oxy-combustion. Fully integrated process flowsheets have been developed and simulated in UniSim Design Suite from Honeywell. The detailed carbonator model has been implemented using Matlab and incorporated into UniSim to provide a full flowsheet simulation for an exemplary dry-feed cement plant as a user-defined operation. The base cement plant simulation was also modified to integrate three different carbon capture processes: membrane; indirect calcination; and amine-scrubbing. Furthermore, an advanced configuration of Ca-looping process has been investigated where the energy intensive air separation unit was replaced with a chemical looping combustion (CLC) cycle. Each case has been optimised to minimise its energy consumption and compared in terms of levelised cost of cement and its resulting cost of CO2 avoided at the same CO2 avoidance rate. The proposed integration of the Ca-looping process is capable of achieving over 90% CO2 avoidance with additional fuel consumption of 2.5 to 3.0 GJth/ton CO2 avoided. By using an advanced configuration of the Ca-looping process with a CLC cycle, the additional fuel consumption can be reduced to 1.7 GJth/ton CO2 avoided, but the cost of the oxygen carrier is the major concern for this system. Among the other CO2 capture options, the membrane process is a promising alternative for the Ca-looping process since it has a potential of achieving the target CO2 avoidance rate and purity requiring lower energy consumption. The indirect calcination process provides moderate levels of CO2 avoidance (up to 56%) without a need of an external capture process whereas the integration of the amine process in a cement plant is challenging as a result of the requirement of steam for solvent regeneration. Furthermore, considering zero net CO2 emissions associated with biomass combustion systems, a novel concept has been analysed to capture of CO2 in-situ with the Ca-looping process while operating the combustor of a dedicated biomass power plant at sufficiently low temperature. This process is capable of achieving 84% overall CO2 capture rate with an energy penalty of 5.2% when a proper heat exchanger network is designed with the support of a pinch analysis. The techno-economic performance of the biomass power plant with in-situ Ca-looping CO2 capture process was compared with that of the alternative biomass-air-fired and biomass-oxy-fired power plants.
67

Sorpce radionuklidu85Sr na zeminy z areálu jaderné elektrárny Temelín / Sorption of radionuclid 85Sr to soils from area nuclear power plant Temelín

Reidingerová, Markéta January 2012 (has links)
This thesis is focused on the study of sorption of radionuclide 85 Sr in soil collected in the area of a nuclear power plant Temelín. A single-batch method experiment was used when a solution of radionuclide 85 Sr of known activity was added to the soil. The experiments focussed on the influence of pH with the size of the sorption and the influence of the time of the contact of the solution with the sorption. During the experiment with the value of pH closest to the pH of underground water from the nuclear power plant Temelín, the sorption of soil was somewhere between 31 to 44 %. When the time influence on the sorption was examined, radionuclide 85 Sr was sorbed very quickly. For the comparison of the sorption size in connection with the time, for which it was chosen 120 minutes, the sorption was almost constant, reaching 40 to 48 %. Key words Radioactivity, radionuclide 85 Sr, sorption, nuclear power plant Temelín
68

Regionale Unterschiede im Auftreten von Eisablagerungen

Arnold, Klaus, Raabe, Armin, Tetzlaff, Gerd 25 October 2016 (has links) (PDF)
Bei der Errichtung von Windenergieanlagen in Mittelgebirgsregionen ist darauf zu achten, daß an windexponierten Standorten die Gefahr einer Vereisung der Rotorblätter besteht. Es wurden klimatologische Daten im Bereich der Mittelgebirge ausgewertet und daraus eine Karte erarbeitet, in der die jährliche mittlere Häufigkeit der Tage mit Eisablagerungen dargestellt ist. / With the installation of wind turbines in low mountain areas the hazard of ice accretions on rotor blades at windy places must be considered. Interpreting climatological datas of the low mountain areas of S. E. Germany a map has been produced which shows the annual frequencies of days ice accretions on structures occurs.
69

Projekt výstavby fotovoltaickej elektrárne / Project of the construction photovoltaic power plant

Mačugová, Radana January 2010 (has links)
The objective of this thesis is to analyze and evaluate the profitability of photovoltaic power plant construction project. The introductory part deals with general characteristics of solar energy and its utilization, with the Slovakian and the European legislation in connection with use of renewable energy resources. The practical part deals with solar energy from the perspective of private firm. One particular company is considering about the implementation of photovoltaic power plant. This section begins with the presentation of the private company and evaluation of its preconditions for this planned construction. The thesis also describes planned implementation of the project, namely its preparation, possibilities of obtaining funds, necessary communication with the public agencies, selection of technology and the construction itself. At the end is project evaluated from the point of profitability by selected indicators.
70

Método para a análise da composição do custo da eletricidade gerada por usinas termelétricas em ciclo combinado a gás natural / METHOD FOR ANALYSING THE COMPOSITION OF THE ELECTRICITY COST GENERATED IN GAS-FIRED COMBINED CYCLE PLANTS

Borelli, Samuel Jose Sarraf 23 May 2005 (has links)
A proposta do método de análise da composição do custo da eletricidade gerada é baseada nos processos de utilização de energia e destruição da exergia contida no combustível através dos diversos processos termodinâmicos que compõe uma usina termelétrica de ciclo combinado. O método utiliza a termoeconomia para valorar e alocar o custo da degradação da exergia ao longo dos processos, considerando os custos referentes aos insumos e equipamentos utilizados. Embora o conceito possa ser aplicado a qualquer tipo de usina termelétrica em ciclo combinado ou cogeração, é desenvolvida neste trabalho a modelagem matemática para o caso de configurações com três níveis de pressão na caldeira de recuperação e condensação total do vapor produzido. É possível estudar qualquer configuração da forma n x 1 (n conjuntos de turbinas a gás e caldeiras de recuperação, com uma turbina a vapor e condensador) com a modelagem apresentada, desde que todos os conjuntos operem de forma idêntica e em regime permanente. A modelagem apresentada neste trabalho foi concebida a partir de um modelo complexo de usina, sobre o qual podem ser feitas variações para adaptá-lo a uma determinada configuração que se deseja estudar. As variação e adaptações incluem, por exemplo, uso de reaquecimento, queima suplementar e operação em cargas parciais, além de análises de sensibilidade quanto a parâmetros geométricos dos equipamentos. São apresentados e estudados do ponto de vista da termoeconomia, os resultados obtidos para uma termelétrica 2x1 em ciclo combinado operando com gás natural. / The proposal of the method for analyzing the composition of the electricity cost is based on the energy conversion processes and destruction of the exergy contained in the fuel through the several thermodynamic processes that comprise a combined cycle power plant. The method uses thermoeconomics to evaluate and allocate the cost of exergy degradation throughout the processes, considering the costs related to the used inputs and equipment. Although the concept may be applied to any combined cycle power plant or cogeneration one, this work develops only the mathematical modeling for three-pressure heat recovery steam generator configurations and total condensation of the produced steam. It is possible to study any n x 1 plant configuration (n trains of gas turbine and heat recovery steam generators associated to one steam turbine generator and condenser) with the presented model, since every train operates identically and in steady state. The presented model was conceived from a complex configuration of power plant, over which variations may be applied in order to adapt it to a defined configuration under study. The variations and adaptations include, for instance, use of reheat, supplementary firing and partial load operation, besides sensibility analysis of geometrical equipment parameters. The results obtained for a 2x1-combined cycle power plant using natural gas are presented and analyzed from the thermoeconomic point of view.

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