Cette thèse étudie le rôle de l'innovation et des structures industrielles dans l'industrie nucléaire. L'analyse de l'innovation est basée sur l'utilisation de données de brevets comme mesure de l'effort d'innovation. Nous étudions d'une part les déterminants de l'innovation et, d'autre part, son impact sur la performance économique et de sureté des réacteurs nucléaires existants et sur les coûts de construction. Nous montrons que la régulation de sureté nucléaire peut promouvoir l'innovation et permet d'améliorer la performance de sureté, mais dans le même temps contribue à l'augmentation des coûts de construction. L'analyse du rôle des structures industrielles permet d'étudier l'effet des opportunités d'effets d'apprentissage, à la fois pour la construction et l'exploitation des réacteurs, ainsi que l'effet de la libéralisation des marchés de l'électricité sur la performance d'exploitation. En particulier, nous montrons que la séparation entre les activités de production et de distribution d'électricité induit une importante amélioration de la disponibilité des réacteurs nucléaires. / This thesis studies the role of innovation and industrial structures in the nuclear power sector. The analysis of innovation is based on the use of patent data as a measure of innovation effort. On the one hand, we study the determinants of innovation and, on the other hand, its impact on operating and safety performance of existing nuclear reactors and on construction costs. We show that nuclear safety regulation can induce innovation and improve safety performance, but at the same time contributes to increases in construction costs. The analysis of the role of industrial structures allows us to study the impact of learning by doing opportunities both for construction and operation of reactors, as well as the effect of electricity market liberalization on operating performance. In particular, we show that the divestiture of electricity production and distribution activities induces a substantial improvement in the availability of nuclear reactors.

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RASTEP (RApid Source TErm Prediction) is a computerized tool for use in the fast diagnosis of accidents in nuclear power plants and analysis of the subsequent radiological source term. The tool is based on a Bayesian Belief Network that is used to determine the most likely plant state which in turn is associated with a pre-calculated source term from level 2 PSA. In its current design the source term predicting abilities of RASTEP are not flexible enough. Therefore, the purpose of this thesis is to identify and evaluate different approaches of enhancing the source term module of RASTEP and provide the foundation for future implementations. Literature studies along with interviews and analysis have been carried out in order to identify possible methods and also to rank them according to feasibility. 4 main methods have been identified of which 2 are considered the most feasible in the short term. The other 2 might prove useful when their maturity level is strengthened. It is concluded from the study that the identified methods can be used in order to enhance RASTEP.

Open pool research reactors play a crucial role in industry, medicine, scientific research and training. Ensuring its safety involves the use of widely accepted computer codes, such as RELAP5, that can predict the progression of accidents and evaluate reactor performance during transient events. These codes need a continuous validation process against various accident scenarios to ensure the reliability of the results. Two Loss of Heat Sink events (LOHS) took place previously in the McMaster Nuclear Reactor. One is the Loss of Forced Circulation in the Secondary Side event that happened in the year 2020, and the second is the Pool Temperature Experiment conducted at the McMaster Nuclear Reactor (MNR) in March 2023. These two events became a perfect opportunity to validate the safety analysis tools used by the NOF (Nuclear Operations and Facilities) staff. The focus was on validating the MNR RELAP5 model, particularly on the simulation of a loss of heat sink (LOHS) accident caused by the loss of the secondary pump. This study elucidates the validation results of the RELAP5 code for these two events and also under steady state conditions. A particular finding of this research was that reactor pool cooling transients prior to the start of a loss of heat sink accident (LOHS) can have an impact on the pool heating rate due to the pool thermal stratification. In these cases, the common assumption of an initial homogeneous temperature profile in the pool might not be accurate and could lead to underestimating the core temperature. With the help of CFD simulations it was possible to adjust the RELAP5 model, by providing a stratified temperature profile of the pool to be used as initial condition for the simulations. This led to more accurate estimations of the pool heating rate during the LOHS. Moreover, a sensitivity analysis on the pool nodalization showed that a minimum of two vertical pipes interconnected laterally by cross flow junctions is needed for the accurate analysis of this kind of transients. / Thesis / Master of Applied Science (MASc)

Les accidents graves de centrales nucléaires ont une probabilité d’occurrence très faible, mais compte tenu des risques encourus, il est nécessaire de savoir prédire l’évolution de l’accident. Dans le scénario le plus critique, le dégagement de chaleur induit par la désintégration des produits de fission entraînerait la fusion du cœur et la formation d’un magma (« corium ») qui tomberait sur le radier en béton du bâtiment réacteur, provoquant sa fusion. L’objectif des études est d’évaluer la vitesse de fusion du béton. Dans ce contexte, le travail effectué dans cette thèse se situe dans la continuité du modèle de ségrégation de phases développé par Seiler et Froment, et s’appuie sur les résultats expérimentaux des essais ARTEMIS. D’une part, nous avons développé un nouveau modèle de transferts à travers le milieu interfacial. Ce modèle fait intervenir trois mécanismes de transfert : la conduction, la convection et un dégagement de chaleur latente. D’autre part, nous avons revu la modélisation couplée du bain et du milieu interfacial, ce qui a conduit au développement de deux nouveaux modèles : « le modèle liquidus », pour lequel on suppose qu’il n’y a pas de résistance au transfert de soluté, et le « modèle à épaisseur de milieu interfacial constante », pour lequel on suppose qu’il n’y a pas de dissolution du milieu interfacial. Le modèle à épaisseur de milieu interfacial constante permet de prédire correctement les valeurs expérimentales de la vitesse de fusion du béton et de la température du bain, dans les essais 3 et 4 tandis que le modèle liquidus, appliqué aux essais 2 et 6, prédit correctement l’évolution de la vitesse de fusion et de la température du bain / Severe accidents of nuclear power plants are very unlikely to occur, yet it is necessary to be able to predict the evolution of the accident. In some situations, heat generation due to the disintegration of fission products could lead to the melting of the core. If the molten core falls on the floor of the building, it would provoke the melting of the concrete floor. The objective of the studies is to calculate the melting rate of the concrete floor. The work presented in this report is in the continuity of the segregation phase model of Seiler and Froment. It is based on the results of the ARTEMIS experiments. Firstly, we have developed a new model to simulate the transfers within the interfacial area. The new model explains how heat is transmitted to concrete: by conduction, convection and latent heat generation. Secondly, we have modified the coupled modelling of the pool and the interfacial area. We have developed two new models: the first one is the “liquidus model”, whose main hypothesis is that there is no resistance to solute transfer between the pool and the interfacial area. The second one is “the thermal resistance model”, whose main hypothesis is that there is no solute transfer and no dissolution of the interfacial area. The second model is able to predict the evolution of the pool temperature and the melting rate in the tests 3 and 4, with the condition that the obstruction time of the interfacial area is about 105 s. The model is not able to explain precisely the origin of this value. The liquidus model is able to predict correctly the evolution of the pool temperature and the melting rate in the tests 2 and 6

This master thesis called ''Nuclear devices in the view of law'', deals with the current legal arrangement of civil nuclear facilities (devices) in the Czech Republic. Due to the fact that the Czech Republic is bound by the international commitments and its membership in the EU, the master thesis also covers the international and European regulations. The master thesis is composed of four parts, which are subdivided into chapters and subchapters. The first part is devoted to the concept of the nuclear facilities, its kinds, position in the legal system and the relevant legal instruments. The second part deals with a particular legal framework of the nuclear law, which governs the issue, including the international, European and Czech regulations. A separate chapter discusses the principles, which are common to the all relevant branch of law. The third part is concerned with the life cycle of the operation of the nuclear facility and the conditions for execution of its particular stages. The final part deals with the safety and security of nuclear facility and its realization as the key issue of the nuclear facility legal regulation.

Les quatre chapitres de cette thèse s’attachent à répondre à deux questions de recherche.Dans un premier temps, je développe des outils théoriques et statistiques visant à mesurer la sûreté nucléaire malgré la rareté des accidents nucléaires majeurs. En particulier, j’applique des résultats de théorie de la décision afin de déterminer le coût social espéré d’un accident nucléaire majeur, en prenant en compte les attitudes individuelles envers les incertitudes qui le caractérisent. Ensuite, j’utilise des données récentes concernant des incidents de sûreté déclarés dans les réacteurs Français afin de mener une analyse statistique de l’évolution de la sûreté nucléaire au cours des 20 dernières années.Dans la seconde partie de cette thèse, j’aborde la question de l’implémentation de réglementations de la sûreté nucléaire et des politiques post-accidentelles face à des risques rares et catastrophiques. En particulier, j’évalue empiriquement l’effet d’une politique publique française encadrant la surveillance des opérateurs nucléaires par des commissions locales sur le comportement déclaratif des opérateurs et sur leur conformité avec les réglementations existantes. Je propose ensuite une analyse par la théorie des jeux des problèmes de coordination qui existent entre les stratégies de communications de crises et les politiques publiques de prévention et de compensation post-accidentelles. / The four chapters of this Ph.D. thesis follow two research axes.First, I develop theoretical and statistical tools for the measurement of nuclear safety, when rare occurrences of accidents preclude the measurement of objective probabilities of incurring harm. In particular, using recent results from decision theory, I develop a framework for the assessment of the expected social cost of major nuclear accidents that accounts for the attitude of individuals towards the uncertainties that characterize their likelihood of occurrence. Next, I provide an empirical analysis of the French nuclear safety based on a novel dataset containing all the significant safety events reported in the currently-operated French reactors. Despite their minor consequences, I show how valuable information regarding safety can be drawn from this data.In the second part of the thesis, I tackle the question of the implementation of safety regulations and disaster management strategies when risks are rare and catastrophic. I first focus on identifying the causal impact of an information-based incentive mechanism implemented in France on the levels of safety care and compliance exerted by nuclear plant managers. I then develop a cheap-talk model to analyse the coordination of disaster communication strategies with several preparedness and disaster response policies.

Tecnologia nuclear, ter o seu domínio é, considerado nos dias de hoje, um diferencial para um país frente aos demais, podendo representar uma ameaça internacional a ser contida ou um aspecto de valorização tecnológica e política para aqueles cuja credibilidade internacional é reconhecida. Diante do uso crescente de novas tecnologias no setor e a necessidade de uma regulamentação, de acordo com os padrões de segurança internacionais, para assegurar a sua utilização, o objetivo desse estudo foi demonstrar se a radioproteção ocupacional e ambiental praticada em nosso país está de acordo com os padrões internacionais de segurança radiológica e nuclear. Para tanto, foi atualizada e revisada a legislação brasileira na área da energia nuclear comparando-a com as da União Europeia, contextualizados os pontos fortes e os pontos fracos da legislação nacional, apontadas críticas e sugestões para que reformas sejam realizadas visando a sua adequação aos padrões internacionais. A hipótese considerada demonstrou que mudanças na estrutura de regulação do setor nuclear brasileiro são necessárias, visando a criação de uma agência reguladora de atividades nucleares, com o intuito de assegurar que o estado da arte e da tecnologia, em termos de segurança nuclear, seja a base do exercício de suas atividades normativas de fiscalização e de avaliação de segurança na preservação do meio ambiente, da saúde do público e dos trabalhadores, frente às aplicações da energia nuclear. / Nuclear technology: to keep its domain is actually considered a differential for a country in relation to other ones, being able to represent an international threat to be contained or an aspect on technological and political valorization for those ones with recognized international credibility. Face to a raising use of new technologies in the field and the requirement asking for regulation in accordance with international safety standards, in order to assure its employment, the objective of this study was to demonstrate whether occupational and environmental radioprotection performed in our country is within radiological and nuclear safety international standards, and so it was updated and revised the Brazilian law in nuclear energy area, by comparing it with European Union, contextualized strong and weak points from national law, indicating criticisms and suggestions, in order that modifications will be able to be accomplished, aiming to its adequacy to international standards. The considered hypothesis showed that are required changes in the regulation structure in Brazilian nuclear area, aiming to the creation of a regulator agency of nuclear activities, with the purpose of assuring that the state of art and of technology, in terms of nuclear safety, to be the basis of the exercise related to their normative, control and safety assessment activities, on environment preservation, public and workers health, face to nuclear energy applications.

Tecnologia nuclear, ter o seu domínio é, considerado nos dias de hoje, um diferencial para um país frente aos demais, podendo representar uma ameaça internacional a ser contida ou um aspecto de valorização tecnológica e política para aqueles cuja credibilidade internacional é reconhecida. Diante do uso crescente de novas tecnologias no setor e a necessidade de uma regulamentação, de acordo com os padrões de segurança internacionais, para assegurar a sua utilização, o objetivo desse estudo foi demonstrar se a radioproteção ocupacional e ambiental praticada em nosso país está de acordo com os padrões internacionais de segurança radiológica e nuclear. Para tanto, foi atualizada e revisada a legislação brasileira na área da energia nuclear comparando-a com as da União Europeia, contextualizados os pontos fortes e os pontos fracos da legislação nacional, apontadas críticas e sugestões para que reformas sejam realizadas visando a sua adequação aos padrões internacionais. A hipótese considerada demonstrou que mudanças na estrutura de regulação do setor nuclear brasileiro são necessárias, visando a criação de uma agência reguladora de atividades nucleares, com o intuito de assegurar que o estado da arte e da tecnologia, em termos de segurança nuclear, seja a base do exercício de suas atividades normativas de fiscalização e de avaliação de segurança na preservação do meio ambiente, da saúde do público e dos trabalhadores, frente às aplicações da energia nuclear. / Nuclear technology: to keep its domain is actually considered a differential for a country in relation to other ones, being able to represent an international threat to be contained or an aspect on technological and political valorization for those ones with recognized international credibility. Face to a raising use of new technologies in the field and the requirement asking for regulation in accordance with international safety standards, in order to assure its employment, the objective of this study was to demonstrate whether occupational and environmental radioprotection performed in our country is within radiological and nuclear safety international standards, and so it was updated and revised the Brazilian law in nuclear energy area, by comparing it with European Union, contextualized strong and weak points from national law, indicating criticisms and suggestions, in order that modifications will be able to be accomplished, aiming to its adequacy to international standards. The considered hypothesis showed that are required changes in the regulation structure in Brazilian nuclear area, aiming to the creation of a regulator agency of nuclear activities, with the purpose of assuring that the state of art and of technology, in terms of nuclear safety, to be the basis of the exercise related to their normative, control and safety assessment activities, on environment preservation, public and workers health, face to nuclear energy applications.