This diploma thesis deals with the analysis of the drainage pipeline of the Škoda K 220-44 steam turbine. This turbine is operated in Dukovany Nuclear Power Plant. One part of this work is proposal of corrective measures. The aims of this work include the creation of a search for drainage, steam, erosion corrosion and mapping of defects in long-term operated drainage system. Work also includes the evaluation of measured values of the pipe wall thickness measured by ultrasonic analyzer. In addition, the work contains images created from 3D model, on which the location of defects and measurements are displayed.

This Master’s thesis deals with optimization of loading patterns of nuclear reactors VVER. In the thesis is described the process of both types of fuel cycle – the closed and the open one. The middle part of fuel cycle containing the optimization process represents the crucial part of the thesis. The thesis is focused on the fuel cycles of the nuclear power plant Dukovany. The problem of the optimization is solved by using different programs. In the final part of the thesis, the program Athena for the loading patterns optimation is explained by a practical calculation for different versions of Moby-Dick macrocode and the calculated values for the optimization of the third unit of the nuclear power plant Dukovany are compared.

The present Master´s thesis aims at designing an evolutionary scheme of secured power supply at nuclear power plants with VVER 440 reactors during design basis accidents as well as design extension conditions. In the first part of this thesis, concepts relating to the defence in depth of nuclear reactors, operating modes of the blocks as well as types and possibilities of electrical power supply and electric circuits of the block are defined. Although the present thesis deals with PWR 440 in general, special emphasis is put on the Czech NPP in Dukovany, where there are four PWR 440 reactors in operation, and on the possibilities for enhancing the defence in depth in this area. The second part of the thesis deals with the difference in station blackout definitions before and after Fukushima; not only the differences in situation evaluation are dealt with, but a solution is also proposed to make the system of secured power supply system during design basis accidents as well as design extension conditions more robust. This option has been selected out of a number of possibilities based on the evaluation of reliability, availability and cost-effectiveness of the proposal.

This graduation thesis deals with evaluation of power and coolant flow in reactor core. The first part is a description of nuclear power plant VVER 440. It is focused on parts important for transfer and utilize energy in regular operating of generating block. In the second part, the equations for calculation of power and coolant flow in reactor core are deduced. The last part is about designing the program for calculation of published values. There are specified requirements for the program and on the basis of this the source code is written. The parts of code are described. In conclusion of this part, the user's manual is work out. The program is on CD in the annexe.

[ES] La tecnología nuclear para el uso civil genera más preocupación por la seguridad que muchas otras tecnologías que se usan a diario. La Autoridad Nuclear define las bases de cómo debe realizarse la operación segura de una Central Nuclear. De acuerdo a las directrices establecidas por la Autoridad Nuclear, una Central Nuclear debe analizar una envolvente de escenarios hipotéticos y comprobar de manera determinista que los criterios de aceptación para dicho evento se cumplen. El Análisis Determinista de Seguridad utiliza herramientas de simulación que aplican la física conocida sobre el comportamiento de la Central Nuclear para evaluar la evolución de una variable de seguridad y asegurar que los límites no se sobrepasan. El desarrollo de la tecnología informática, de los métodos matemáticos y de la física que envuelve el comportamiento de una Central Nuclear han proporcionado herra-mientas de simulación potentes que son capaces de predecir el comportamiento de las variables de seguridad con una importante precisión. Esto permite analizar escenarios de manera más realista evitando asumir condiciones conservadoras que hasta la fecha compensaban la falta de conocimiento modelado en las herramientas de simulación. Las herramientas conocidas como De Mejor Estimación son capaces de analizar even-tos transitorios en diferentes escalas. Además, emplean modelos analíticos de las dife-rentes físicas más detallados, así como correlaciones experimentales más realistas y actuales. Un paso adelante en el Análisis Determinista de Seguridad pretende combinar las diferentes herramientas de Mejor Estimación que se emplean para analizar las dis-tintas físicas de una Central Nuclear, considerando incluso la interacción entre ellas y el análisis progresivo a diferentes escalas, llegando a analizar fenómenos más locales si es necesario. Para este fin, esta tesis presenta una metodología de análisis multi-físico y multi-escala que emplea diferentes códigos de simulación analizando el escenario propuesto a dife-rentes escalas, es decir, desde un nivel de planta que incluye los distintos componentes, hasta el volumen de control que supone el refrigerante pasando entre las varillas de combustible. Esta metodología permite un flujo de información que va desde el análi-sis a mayor escala hasta el de menor escala. El desarrollo de esta metodología ha sido validado con datos de planta para poder evaluar el alcance de esta metodología y pro-porcionar nuevas líneas de trabajo futuro. Además, se han añadido los resultados de los distintos procesos de validación y verificación que han surgido a lo largo de este trabajo. / [CA] La tecnologia nuclear per a l'ús civil genera més preocupació per la seguretat que moltes altres tecnologies d'ús quotidià. L'Autoritat Nuclear defineix les bases de com ha de realitzar-se l'operació segura d'una Central Nuclear. D'acord amb les directrius establertes per l'Autoritat Nuclear, una Central Nuclear ha d'analitzar una envoltant d'escenaris hipotètics I comprovar de manera determinista que els criteris d'acceptació per a l'esdeveniment seleccionat es compleixen. L'Anàlisi Determinista de Seguretat utilitza eines de simulació que apliquen la física coneguda sobre el comportament de la Central Nuclear per avaluar l'evolució d'una variable de seguretat i assegurar que els límits no es traspassen. El desenvolupament de la tecnologia informàtica, els mètodes matemàtics i de la física que envolta el comportament d'una Central Nuclear han proporcionat eines de simulació potents amb capacitat de predir el comportament de les variables de seguretat amb una precisió significativa. Això permet analitzar escenaris de manera realista evitant assumir condicions conservadores que fins al moment compensaven la mancança de coneixement. Les eines de simulació conegudes com De Millor Estimació son capaces d'analitzar esdeveniment transitoris a diferent escales. A més, utilitzen models analítics per a les diferents físiques amb més detall així com correlacions experimentals més actualitzades i realistes. Un pas més endavant en l'Anàlisi Determinista de Seguretat pretén combinar les diferents eines de Millor Estimació que se utilitzen per analitzar les distintes físiques d'una Central Nuclear, considerant inclús la interacció entre ells i l'anàlisi progressiu a diferents escales, amb la finalitat de poder analitzar fenòmens locals. Per a aquest fi, esta tesi presenta una metodologia d'anàlisi multi-física i multi-escala que utilitza diferents codis de simulació analitzant l'escenari proposat a diferents escales, és a dir, des d'un nivell de planta que inclou els distints components, fins al volum de control que suposa el refrigerant passant entre les varetes de combustible. Esta metodologia permet un flux de informació que va des de l'anàlisi d'una escala major a una menor. El desenvolupament d'aquesta metodologia ha sigut validada i verificada amb dades de planta i els resultats han sigut analitzats a fi d'avaluar la capacitat de la metodologia i les possibles línies de treball futur. A més s'han afegit els principals resultats de verificació i validació que han sorgit en les distintes etapes d'aquest treball. / [EN] The nuclear technology for civil use has generated more concerns for the safety than several other technologies applied to the daily life. The Nuclear Regulators define the basis of how the Safety Operation of Nuclear Power Plants is to be done. According to these guidelines, a Nuclear Power Plant must analyze an envelope of hypothetical events and deterministically define if the acceptance criteria for these events is met. The Deterministic Safety Analysis uses simulation tools that apply the physics known in the behavior of the Nuclear Power Plant to evaluate the evolution of a safety varia-ble and assure that the safety limits will not be exceeded. The development of the computer science, the numerical methods and the physics involved in the behavior of a Nuclear Power Plant have yield powerful simulation tools that are capable to predict the evolution of safety variables which significant accuracy. This allows to consider more realistic simulation scenarios instead of con-servative approaches in order to compensate the lack of knowledge in the applied prediction methods. The so called Best Estimate simulation tools are capable to analyze the transient events in different scales. Furthermore, they account more detailed analytical models and experimental correlations. A step forward in the Deterministic Safety Analysis intends to combine the Best Estimate simulation tools of the different physics considering the interaction among them and analyzing the different scales, considering more local approaches if necessary. For this purpose, this thesis work presents a multi-scale and multi-physics methodology that uses different physics codes and has the aim of modeling postulated scenarios in different scales, i.e. from system models representing the components of the plants to the subchannel models that analyze the behavior of the coolant between the fuel rods. This methodology allows a flow of information where the output of one scale is used as input in a more detailed scale to predict a more local analysis of parameters, such as the Critical Power Ratio, which are of great importance for the estimation of safety margins. The development of this methodology has been validated against plant data with the aim of evaluating the scope of this methodology and in order to provide future lines of development. In addition, different results of the validation and verifi-cation yielded in the development of the parts of this methodology are presented. / Hidalga García-Bermejo, P. (2020). Development and validation of a multi-scale and multi-physics methodology for the safety analysis of fast transients in Light Water Reactors [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/160135 / TESIS

This diploma thesis focuses on the changes in the media image of nuclear power in Ceska Televize, which is the only public television in Czech Republic. The study uses a quantitative research method, content analysis, to find out the changes of nuclear power representation in media and to compare changes of news construction mechanisms in the period of two years - one year before and one year after the Japanese nuclear power plant Fukushima Daiichi disaster. The accident started on 11th March 2011 and there is a short description of the situation in Japan at the beginning of the thesis. The theoretical part of thesis serves as an overview of basic information on principles of the media studies theory and mechanisms of news construction (work with information sources, the news value concept, agenda setting, the framing concept), which is also shown from the environmental point of view. The study also focuses on the nuclear power image in the socio-political field and there are some more information about the nuclear power development and status in Czech Republic. The analytical part of thesis examines the media attention to nuclear power, which was developed in the analysed period. The usage of mechanisms of news construction and the changes in nuclear power image in the news of Ceska Televize...

The current model for electricity generation is based on power plants connected to the transmission network. This provides electricity to the distribution network and after that to the consumers. To ensure the security of the electrical network and prevent a blackout, the performance of every electricity generation unit connected to the network is quantified in grid codes. In the case of the French transmission system, the requirements regarding the performance are written in a document produced by the French Transmission System Operator (TSO). Various events with various configurations of connection to the network have to be simulated and the corresponding performance has to be evaluated. The aim of these simulations is to determine the stability of the generators and key elements, including the response time on the active power after events such as a short circuit.Taking into account the amount of generators connected to the transmission network, the need for optimization appears and is the purpose of this Master Thesis. To perform those simulations in an efficient way on all the generators owned by the main French electricity producer, EDF, this Master Thesis contributes with a tool called AuDySim coded with the softwares MATLAB and EUROSTAG. The implemented tool allows the user to configure an electricity generation unit before realizing all the simulations specified by the TSO and produces a report containing the results by means of curves and data. The simulations and the production of the report are achieved automatically to create a gain of time and resources.In order to validate the performance of the tool, two case studies are performed on different types of power plants. The two case studies analyzed present a hydraulic and a nuclear power plant. In the results the performance of each type of power plant is assessed focusing on the rotor angle stability of the machine and key elements, such as the voltage and the active power. These results lead to the conclusion that AuDySim fulfills its mission, by achieving automatically an analysis of the performance of an electrical generation unit and producing it in a report. / Den nuvarande elproduktionsmodellen baseras på kraftverk som är direktkopplade till stamnätet. Stamnätet i sin tur matar distributionsnätet som därefter levererar el till slutkonsumenterna. För att säkerställa stamnätets integritet samt säkerhet och undvika strömavbrott kvantifieras prestandan hos varje generator som är ansluten till det med hjälp av nätkoder. När det gäller det franska stamnätet skrivs prestandakraven i ett dokument som utfärdas av den franska transmissionssystemoperatören (TSO). Olika händelser med olika anslutningskonfigurationer måste simuleras där dess prestanda ska utvärderats. Syftet med dessa simuleringar är att identifiera stabiliteten vid varje elproduktionsenhet med bl. a. dess reaktionstid för den aktiva effekten efter kortslutningar.Med tanke på antalet generatorer som är anslutna till stamnätet framträder ett behov för överföringsoptimering vilket är syftet med detta examensarbete. För att utföra dessa simuleringar på ett effektivt sätt på alla generatorer som ägs av den ledande franska elproducenten, EDF, bidrar denna avhandling med ett verktyg som heter AuDySim kodat i mjukvarorna MATLAB och EUROSTAG. Verktyget gör det möjligt för användaren att konfigurera en elproduktionsenhet innan man utför alla simuleringar som specificeras av TSO:n och samtidigt producerar en rapport som innehåller grafisk- och data resultat. Både simuleringar och rapporten produceras automatiskt för att optimera en bearbetningstid och resursanvändning.För att validera verktygets prestanda utförs två fallstudier på olika typer av kraftverk. De två fallstudierna fokuserar på ett hydraulisk- respektive ett kärnkraftverk. I resultaten utvärderas prestanda för varje typ av kraftverk, med fokus på maskinens rotorvinkelstabilitet och andra viktiga faktorer, såsom spänning och aktiv effekt. Resultat leder till slutsatsen att AuDySim uppfyller sitt uppdrag genom att automatiskt analysera prestanda hos en elektrisk generationsenhet och presentera analysen i en rapport.

Nuclear power plants are inherently complex systems. While the technology has been used to generate electrical power for many decades, process monitoring continuously evolves. There is always room for improvement in terms of maximizing the availability by reducing the risks of problems and errors. In this context, automated monitoring systems have become important tools – not least with the rapid progress being made in the field of data analytics thanks to ever increasing amounts of processing power. There are many different types of models that can be utilized for identifying anomalies. Some rely on physical properties and theoretical relations, while others rely more on the patterns of historical data. In this thesis, a data-driven approach using a hierarchical autoencoder framework has been developed for the purposes of anomaly detection at the Swedish nuclear power plant Forsmark. The model is first trained to recognize normal operating conditions. The trained model then creates reference values and calculates the deviations in relation to real data in order to identify any issues. This proof-of-concept has been evaluated and benchmarked against a currently used hybrid model with more physical modeling properties in order to identify benefits and drawbacks. Generally speaking, the created model has performed in line with expectations. The currently used tool is more flexible in its understanding of different plant states and is likely better at determining root causes thanks to its physical modeling properties. However, the created autoencoder framework does bring other advantages. For instance, it allows for a higher time resolution thanks to its relatively low calculation intensity. Additionally, thanks to its purely data-driven characteristics, it offers great opportunities for future reconfiguration and adaptation with different signal selections.

Kärnkraft är ett kontroversiellt ämne, som ofta ger upphov till två läger – de som är positivt inställda och de som är negativt inställda till kärnkraft. NIMBY (Not in My Backyard) är ett fenomen som syftar till de som är positiva till kärnkraft generellt, men som inte vill ha den i sin närhet. Utfasningen av fossila bränslen och den kommande ökningen av energibehovet ställer frågan vilken roll kärnkraften ska spela i framtidens energiproduktion. Den svenska regeringen vill satsa mer på kärnkraft och har pekat ut olika platser som möjliga lokaliseringar för kärnkraft. Säffle är en av dessa platser.  Syftet med denna uppsats är att undersöka den lokala uppfattningen i fallet Säffle kring en potentiell kärnkraftsetablering i näromgivningen, samt vilka risker som invånarna ser med kärnkraft, för att se om NIMBY föreligger. Ett vidare syfte är också att undersöka hur invånarna i Säffle anser att energifrågan ska lösas.  Metoden som använts är mixed methods där både en kvantitativ enkät och kvalitativa intervjuer genomförts. Data från 59 enkätrespondenter har analyserats med deskriptiv statistik, och sex djupintervjuer har analyserats med kvalitativ innehållsanalys.  Resultatet pekar på att det finns olika läger hos respondenterna – de som är för och de som är mot kärnkraft. NIMBY föreligger endast i några få fall bland enkätens respondenter, däremot upptäcktes flera fall av omvänd NIMBY, där positiva yttranden om att förlägga ett kärnkraftverk i Säffle uttalades. Det finns olika faktorer som påverkar människors riskperception – de som är positiva till kärnkraft medger även de att det finns risker, samtidigt som de som är negativa också anser att det råder hög säkerhet vid svenska kärnkraftverk. Säkerhet och Rädsla var två således kategorier som identifierades. Både de som är positiva och de som är negativa till kärnkraft pratar om att ta ett miljöansvar, men ur olika utgångspunkter. Alla vill att Sverige satsar på förnyelsebar energi, och vissa vill addera kärnkraft till den mixen. Ingen vill satsa på kol eller olja. Det konstaterades också en brist på kommunikation från beslutsfattare om varför Säffle är utpekat som möjlig plats för kärnkraft i framtiden. / Nuclear power is a controversial subject that often gives rise to two camps – those who are in favor and those who are opposed to nuclear power. NIMBY (Not in My Backyard) is a phenomenon that refers to those who are generally supportive of nuclear power but do not want it in their vicinity. The phasing out of fossil fuels and the upcoming increase in energy demand raise the question of what role nuclear power should play in future energy production. The Swedish government wants to invest more in nuclear power and has identified various locations as possible sites for nuclear power plants, including Säffle.  The purpose of this essay is to examine the local perception in the case of Säffle regarding a potential nuclear power establishment in the vicinity, as well as the risks that residents associate with nuclear power, to determine if NIMBY exists. Another aim is to investigate how the residents of Säffle believe the energy issue should be resolved.  The method used is mixed methods, including both a quantitative survey and qualitative interviews. Data from 59 survey respondents have been analyzed using descriptive statistics, and six in-depth interviews have been analyzed using qualitative content analysis.  The results indicate that there are different camps among the respondents - those who are in favor and those who are against nuclear power. NIMBY exists only in a few cases among the survey respondents; however, several instances of reverse NIMBY were discovered, where positive statements about locating a nuclear power plant in Säffle were expressed. Various factors influence people's risk perception – those who are in favor of nuclear power also acknowledge the existence of risks, while those who are against it believe that Swedish nuclear power plants are highly secure. Safety and Fear were thus identified as two categories. Both those in favor and those against nuclear power discuss taking environmental responsibility, but from different perspectives. Everyone wants Sweden to invest in renewable energy, and some want to add nuclear power to the mix. No one wants to rely on coal or oil. A lack of communication from decision-makers regarding why Säffle has been identified as a potential site for nuclear power in the future was also noted.

<p>The research presented in this dissertation investigates the influence of soil-structure<br> interaction on seismic isolation of nuclear reactor vessels using numerical simulations. This<br> research is motivated by the nuclear industry searching for viable solutions to standardize<br> the design of reactor vessels. Seismic isolation of reactor vessels is a potential solution as it<br> enables deployment of standardized reactor vessels irrespective of site seismic hazard<br> thereby saving time and cost by allowing large-scale factory fabrication of standard<br> modules and by eliminating the need for repeated approval of reactor vessel design. Seismic<br> isolation is also a technology that has matured from successful implementation in buildings<br> and bridges allowing easier transition to nuclear applications. Currently, the<br> implementation of component-level seismic isolation in nuclear industry is challenging due<br> to gaps in research and lack of specific guidelines.</p> <p><br></p> <p><br> In this research, the effectiveness and potential limitations of using conventional friction<br> pendulum bearings for component-level isolation are investigated based on conceptual<br> numerical models of seismically isolated reactor vessels at different nuclear power plant<br> sites subject to a variety of ground motions. The numerical modeling and analysis<br> approach presented in this research are checked using experimental data and results from<br> multiple numerical codes to ensure reliability of the obtained analysis results.</p> <p><br></p> <p><br> Within the scope of this study, it is found that slender vessels are particularly vulnerable<br> to rotational acceleration at the isolation interface. Rotational acceleration at the isolation<br> interface is caused by rotation at the foundation level of the containment building housing<br> the isolated reactor vessel and by excitation of higher horizontal translational modes of the<br> seismically isolated system. Rotation of the building foundation increases with decrease in<br> shear wave velocity of the soil surrounding the building foundation. When the containment<br> building is embedded below the soil surface, the effect of embedment on peak horizontal<br> acceleration of the isolated vessel depends on the amount of increase in shear wave velocity<br> at the foundation level of the building. When embedment does not result in any change in<br> shear wave velocity, it is found to have negligible impact on the acceleration response of the<br> isolated vessel.</p> <p><br></p> <p>  The optimum location to support a vessel for seismic isolation is found to be on a plane<br> passing through its center of mass. It minimizes horizontal acceleration in the isolated<br> vessel as well as the tendency of isolator to uplift. Isolator uplift and exceedence of<br> displacement capacity of the isolator during extreme events are possible drawbacks in using<br> seismic isolation technology since they produce impact forces due to uplift and<br> re-engagement of the isolator or due to collision between the isolated system and the moat<br> wall. If such cases are avoided, seismic isolation of reactor vessel could provide more than<br> 50% reduction in peak acceleration of vessel except for low-intensity motions that do not<br> engage the isolator.<br>  <br>  </p>