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Les alliages de zirconium sont utilisés comme matériaux de gainage des combustibles nucléaires dans les réacteurs à eau pressurisée. Ces gaines sont utilisées dans un milieu extrêmement radiatif et corrosif, elles peuvent dans certains cas être le siège de fortes variations de température et doivent répondre à des sollicitations mécaniques importantes, que ce soit en conditions de service ou accidentelles. Dans un tel contexte, il est intéressant de pouvoir prédire les transformations de phases ayant lieu au sein de la gaine en fonction des variations de température et de composition chimique, la précipitation de phases fragiles induites par la présence des éléments d’alliages, mais aussi de tester de nouvelles compositions d’alliages afin de l’optimiser.La méthode la plus adaptée pour la modélisation thermodynamique de systèmes multiconstitués est la méthode Calphad (CALculation of PHAse Diagrams). Il s’agit d’une méthode semi-empirique, consistant à modéliser les enthalpies libres des différentes phases constitutives d’un système par ajustement de certains paramètres, dans le but de reproduire les données expérimentales.Ce mémoire détaille la construction d’une base de données thermodynamiques du système quinaire Cr-Fe-Nb-Sn-Zr selon la méthode Calphad. L’originalité de notre démarche est liée à l’utilisation des calculs DFT de manière systématique et massive. Il s’agit en particulier de calculer par DFT les enthalpies de formation de tous les end-members des phases intermétalliques constitutives du système quinaire. De plus, des calculs sur des mailles « quasi aléatoires » (SQS) sont également effectués de manière systématique afin de déterminer les enthalpies de mélange des solutions solides binaires en structure fcc, bcc et hcp. En outre, une étape importante de ce travail consiste à compléter les données expérimentales de la littérature par de nouvelles mesures sur des systèmes choisis. En particulier, nous nous sommes employés à décrire quelques équilibres de phases des systèmes ternaires Cr-Nb-Sn, Cr-Fe-Sn, Cr-Sn-Zr et Fe-Nb-Sn qui n’avaient jamais été déterminés expérimentalement. Nous avons ensuite utilisé ces calculs et ces nouvelles données expérimentales en complément de données de la littérature comme données d’entrée pour la modélisation thermodynamique des vingt sous-systèmes binaires et ternaires du système quinaire considéré. Enfin, le pouvoir prédictif de notre base de données a pu être vérifié en confrontant ces prédictions à des données expérimentales relatives à des alliages quinaires industriels ou à de nouveaux concepts de gaines Currently, zirconium alloys are used as fuel cladding materials in PWR (Pressurized Water Reactors). The claddings stand in a very corrosive and radiative environnement, and can be submitted to temperature variations. In addition, the claddings will be subjected to mechanical stresses in reactor or accidental conditions. Thus, it appears useful to have a better understanding of phase transformations occurring in these alloys, as a function of temperature and chemical composition variations, but also to forecast the precipitation of fragile phases induced by the addition of alloying elements. At last, the ability to test new alloy compositions may allow to optimize it.The most suitable method for the thermodynamic modeling of multicomponent systems is the Calphad method (CALculation of PHAse Diagrams). The Calphad method is a widely used technique of semi-empirical modelling of phase diagrams. It consists in the description of the Gibbs energies of the different phases by fitting parameters allowing to describe the experimental data.This report details the design of a thermodynamic database considering the five following elements Zr, Cr, Fe, Nb, and Sn. The originality of this database lies in a systematic use of DFT calculations. Indeed, DFT calculations are performed to predict the formation enthalpy of the intermetallic phases appearing in these systems. Moreover, the SQS method (Special Quasirandom Structure) is used to predict the mixing enthalpy of the fcc, bcc and hcp binary solid solutions. Besides, experimental investigations are an important step of this thesis. Since no experimental data were available for the Cr-Fe-Sn, Cr-Nb-Sn, Cr-Sn-Zr and Fe-Nb-Sn ternary systems, new experimental data are provided, within this study, on the isothermal sections of these systems at different temperatures. All these calculated data in addition to the experimental data and the data from literature are used as input data for the Calphad modelling of the twenty binary and ternary systems which are then combined in the new database. A last part is dedicated to comparisons between predictions obtained with our new database and experimental results on industrial quinary alloys and a new concept of claddings

LES DISCOURS INSTITUTIONNELS DU NUCLEAIRE: STRATEGIES DISCURSIVES D'EUPHORISATION Quelle est l'image que les responsables de la production nucléaire souhaitent voir s'imposer aujourd'hui ? Dans une perspective d'analyse de discours, l'examen des brochures informatives, qui émanent des grandes entreprises du nucléaire en direction du public, révèle une démarche tout entière tournée vers l'euphorisation. LOS DISCURSOS INSTITUCIONALES DEL NUCLEAR: ESTRATEGIAS DISCURSIVAS DE EUFORIZACION ¿ Cuál es la imagen que los responsables de la producción nuclear desean ver imponerse hoy en dia ? En una perspectiva de analisis del discurso, el examen de folletos informativos que emanan de grandes empresas nucleares en dirección del público, revela una demarcha toda inclinada hacia la euforización. Delavigne Valérie. Les discours institutionnels du nucléaire. Stratégies discursives d'euphorisation. In: Mots, n°39, juin 1994. Environnement, Écologie, Verts, sous la direction de Lamria Chetouani et Maurice Tournier. pp. 53-68.

AbstractAt first sight, French nuclear energy policy offers a textbook example of how technical, constitutional and economic restrictions, powerful interest groups and path dependence constrain democratic responsiveness. This paper uses what might seem to be an unlikely case in order to question explanations of policy choices in terms of technocracy, path dependence and interest groups against the background of an under-estimated factor: party and coalition strategies. The original data collected on public attitudes towards nuclear energy and the attention dedicated to this issue in the media, as well as in the parliamentary and electoral arenas, show that the effect of public opinion is conditioned by party incentives to politicise the issue at stake. In other words, parties and coalition-making constraints act as a mediating variable between citizens’ preferences and policy choices. These findings point to the need to integrate this conditional variable into analyses of responsiveness and models of policymaking.

This chapter examines the profound changes that have taken place in Environmental and Energy Policy (EEP) study in and about France. It explains why and how they constitute a challenge from a substantive and an analytic perspective, as well as it accounts for its ambivalent position in comparative political research. In the French context, it argues that EEP still holds an ambivalent position as a case study in comparison with other Western democracies and as a field of study in French policy studies. This chapter develops two main arguments in order to account for this. First, the emergence of EEP study in the French context is closely related to this policy’s origins and long-held strong relationships with the ecologist movement. Second, EEP in France long constituted a challenge for both comparative political research and for classic models about the functioning of the State and policy-making in France. This chapter concludes by challenging the idea that EEP in France is sufficiently specific, as a policy domain and as a political context, to justify excluding it any further from comparative political research agendas.

International audience; This contribution relies on a prospective study of the French power sector up to 2050 conducted by the TIMES model, combined with a reliability condition for operation. To consider short-term power grid transient conditions, a reliability indicator related to the reserves of kinetic energy has been defined and endogenized in the model to guarantee the power system reliability under the implementation of a high share of variable renewable energy source (VRES). For a declining share of nuclear inducing a high share of VRES, the pace of investments, additional backup and flexible options to guarantee the grid's stability anytime have been studied.

Le parc électrique français, caractérisé par une part élevée d’électricité nucléaire, est à l’aube d’une période de transition qui s’étendra au-delà de 2050. Cette transition est caractérisée par une augmentation de la part de l’éolien et du solaire et, en parallèle, une réduction de la part du nucléaire dans le mix électrique, laquelle devrait rester toutefois significative. L’intégration de l’éolien et du solaire dans un mix nécessite de mobiliser des moyens de flexibilité supplémentaires pour maintenir le niveau de fiabilité objectif du système, tant dans le court terme que dans le long terme. L’ensemble des leviers du côté de l’offre et de la demande électrique devra être mis en oeuvre pour répondre à ces nouveaux besoins de flexibilité. Le parc nucléaire aura son rôle à jouer.Dans ce contexte, comment la France peut-elle adapter son parc électrique vers plus de flexibilité, tout en conservant un mix bas carbone et en maîtrisant les coûts associés ? L’objectif de la thèse est d’apporter des éclairages à cette question, par l’intermédiaire d’analyses technico-économiques.Les interactions entre énergie nucléaire et énergies renouvelables variables sont analysées grâce à deux approches complémentaires : l’une, essentiellement technique, confronte les sollicitations futures du parc nucléaire à ses possibilités théoriques ; l’autre, technico-économique, évalue le coût pour le système électrique de voir assurée une partie de la flexibilité par le nucléaire et examine des leviers pour réduire ce coût et rendre compétitif un parc nucléaire fonctionnant en mode flexible. Ces deux approches sont basées sur la construction de scénarios aux horizons 2030 et 2050.Nous montrons que les sollicitations en suivi de charge du parc nucléaire croîtront fortement avec l’augmentation de l’éolien et du solaire. Même si le parc possède des marges de manoeuvre pour réaliser plus d’opérations de suivi de charge, celles demandées au parc nucléaire en présence de solaire et d’éolien à des taux supérieurs à 30% de la demande électrique paraissent difficilement soutenables techniquement par lui seul. Du point de vue de la gestion opérationnelle du parc nucléaire, nous remarquons qu’il est souhaitable de favoriser le développement de l’éolien par rapport à celui du solaire, puisque c’est ce dernier qui induit les sollicitations extrêmes en puissance.Le coût de production du nucléaire pourrait augmenter significativement avec la réduction de l’utilisation du parc. Il apparaît alors essentiel de promouvoir un remplacement progressif du parc pour réduire l’impact économique d’une participation à la flexibilité dans la période de transition. Dans le cas de nouveaux investissements nucléaires, une augmentation du prix de la tonne de CO2 pourrait rendre le back-up nucléaire compétitif face aux centrales à gaz à cycle combiné. Par ailleurs, anticiper le développement de nouveaux débouchés devient crucial pour éclairer les choix d’investissements électriques bas-carbone.Pour contourner la difficulté posée par la réduction du taux d’utilisation du nucléaire, nous examinons la flexibilité du nucléaire comme un levier d’offre de service énergétique plus vaste, tout en contribuant à la fiabilité du système électrique. La production d’hydrogène permet des synergies entre renouvelables et nucléaire pour valoriser ses surplus de production. Cette solution paraît intéressante dès 2030 si les capacités du parc nucléaire sont conservées et que l’opérateur choisit une stratégie économique adaptée pour s’ouvrir à de nouveaux débouchés. Le développement des exportations ou des usages de la chaleur sont aussi des options envisageables pour l’utilisation des surplus.Au global, nous recommandons, afin d’encourager les synergies possibles entre énergies bas-carbone, d’appréhender la part du nucléaire en France dans une dynamique adaptée à la pénétration des renouvelables, et au déploiement des marchés des coproduits nucléaires, dont l’hydrogène. The French power system is transitioning towards a more diversified low carbon mix. The power mix is characterised by a high nuclear share which is to remain significant and the target to increase variable renewables (wind and solar) by 2050. When introduced massively, wind and solar trigger new needs for back-up power, both in the short and long term, to answer the flexibility required in order to maintain the reliability target level of the power system. All flexibility options should be complementarily developed, given their characteristics, and nuclear will have a role to play in this context.How could the French power mix be adapted towards more flexibility while maintaining a low-carbon level and mastering associated costs? The purpose of this PhD thesis is to shed light on this issue thanks to a techno-economic analysisAt first, interactions between nuclear and variable renewables are analysed thanks to two complementary approaches. On the one hand, a technical perspective is adopted by confronting prospective nuclear load-following requirements to the fleet theoretical capabilities. On the other hand, thanks to a techno-economic approach, we evaluate the additional cost of ensuring part of the flexibility requirements with the nuclear fleet and examine options to reduce this cost to make nuclear back-up competitive. These two approaches are based on the construction of realistic scenarios by 2030 and 2050.The French nuclear fleet will be asked for a strong increase of the load following operations with growing wind and solar shares. Even if the nuclear fleet can enable higher power ramps and amplitude variations, when wind and solar account for more than 30% in the total demand, compensating for the power variations induced would require complementary means. From a fleet management perspective, it would be beneficial to favour wind compared to solar in the power mix. The latter induces extreme power ramps and amplitudes for the nuclear fleet.The nuclear production cost could be significantly increased with the decrease of the nuclear utilisation rate. In the transition phase, it would be of great importance to promote a progressive replacement of the nuclear fleet to compensate for the production cost increase. In the case of new nuclear investments, a carbon price increase could make nuclear back-up able to compete with combined-cycle gas turbine plants as the alternative back-up option. Anticipating the development of new outlets becomes crucial to guide future investments in low-carbon power plants.To bypass the issue of the nuclear utilisation rate reduction, it would be worth considering taking advantage of the available excess energy to produce valuable products while providing flexibility services to the grid. Hydrogen production, as a flexible power demand, could enhance synergies between nuclear and variable renewables through new markets to valorise the excess nuclear energy. When wind and solar shares increase, along with the hydrogen market expected growth driven by mobility uses, opportunities are created for the nuclear operator. If the French nuclear capacities are maintained and if an adapted business model is developed, nuclear-hydrogen coproduction could answer the hydrogen demand by 2030. Other options could be considered to find outlets to the excess power such as the development of power exportations or the coproduction of heat and electricity.Overall, in order to foster synergies between low-carbon power plants, the change of the nuclear share in the French power mix should be apprehended through dynamics adapted to the penetration of renewables as well as to the deployment of hydrogen markets, and new markets in general.

International audience; Risk perception is socially constructed. Socialization influences at individual, group and societal levels can thus play a significant role in shaping how a person views his/her surrounding /environment, and lead to the development of different “cultures” in risk perception. While the term “two cultures” was originally used by Snow in 1956 to describe the gap between the natural/physical sciences and the humanities, a cultural divide has also been observed in risk analysis and assessment approaches by experts from different professional backgrounds (e.g. technical vs. social sciences).There is some evidence that the two cultures phenomenon has considerable relevance in the energy context. An education-induced cultural difference in energy perception has been demonstrated for nuclear energy between experts from different disciplines. Previous research furthermore suggests that a cultural divide in energy perception extends beyond education boundaries – a gender difference has been consistently observed in nuclear perception. Studies have also reported international differences in the perception and acceptance of nuclear energyIt appears that gender (individual-level), education discipline (group-level) and culture-specific (societal-level) socialization play a significant role in shaping nuclear perception and contributing to divergence in how this energy source is being evaluated – and, in definitive, accepted. However, progress has been slow in explaining how such socialization influences could interact and plant the seeds for an eventual cultural divide in nuclear perception. Nor could previous studies provide insight into whether this three level / layer divergence (gender-education-cultural) is unique to nuclear perception or applies more generally across a range of energy sources.In the present research, our objective is an assessment of the two cultures phenomenon in energy perception. We examined the interaction of gender, education discipline and culture in influencing the perception of nuclear, coal and wind energy sources. 729 young adults (university students from engineering and business disciplines) from France, Germany and Russia took part in the survey study between February 2012 and January 2013.Findings indicated that gender, education discipline and culture-specific socialization contribute to the development of a “two cultures” in nuclear perception which is already detectable in young adults at the beginning of their higher education path. In contrast, this new cross-national and cultural approach, showed that societal norms appear to play a considerable role in shaping how young adults (irrespective of gender and education discipline) view coal and wind. Implications of findings for energy policy and industry decision-makers, educators as well as future research will be discussed.

Although nuclear accidents are often presented as inherently global issues, the Fukushima Daiichi accident in 2011 developed above all into a problem for France in the French news media. This seems surprising when compared to the coverage of Chernobyl in 1986, which rendered international debates visible. Based on a comparative analysis of the newspaper Le Monde and the TV channel France 2, this chapter shows how these changes of frames can be related to the creation, since Chernobyl, of transnational organizations for nuclear safety. These bodies reframed the ways in which the international effects of nuclear energy appear in the news media, reducing the visibility of international stakes in this controversial policy field. Government agencies play a key role in “renationalizing” nuclear accidents by adapting international stakes and information to national contexts.

This paper attempts to introduce factors which are linked to the sources of CO2 emissions using a standard scale, technique and composition approach. In their early work, Grossman & Krueger (1991) suggest that the impact of economic factors such as growth and trade on the environment can be decomposed into scale, technique and composition effects. Later work of Antweiler et al. (1998) provides a well-completed theoretical guideline that allows researchers to estimate separately these 3 effects. However, studies of Cole & Elliott (2003) and Managi et al. (2009), while providing partial support for Antweiler et al., show that the relationship between economic factors and pollution vary by pollutant given the differences between many common pollutants, "particularly with regards to their sources" (Cole & Elliott (2003)). Thus, this study contributes to this literature and pay attention to variables which are linked to the sources of CO2 emissions. Since electricity production and the conversion of land use into agricultural land are two main single sources of carbon dioxide emissions, I examine these impact on per capita CO2 emissions. The results of estimation for a panel of 99 countries spanning the period 1971-2010 indicate that :(1) increasing the share in electricity production from nuclear and renewable sources can decrease CO2 emissions whereas (2) the conversion of land use into agriculture land raises the amount of carbon emitted.