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Evaluate the Contribution of the Fuel Cladding Oxidation Process on The Evaluate the contribution of the fuel cladding oxidation process on the hydrogen production from the reflooding during a potential severe accident in a nuclear reactor Florian Haurais To cite this version: Florian Haurais. Evaluate the contribution of the fuel cladding oxidation process on the hydrogen production from the reflooding during a potential severe accident in a nuclear reactor. Materials. Université Paris-Saclay, 2016. English. NNT : 2016SACLS375. tel-01519349 HAL Id: tel-01519349 https://tel.archives-ouvertes.fr/tel-01519349 Submitted on 6 May 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. NNT : 2016SACLS375 THÈSE DE DOCTORAT DE L’UNIVERSITÉ PARIS-SACLAY PRÉPARÉE À L’UNIVERSITÉ PARIS-SUD ÉCOLE DOCTORALE N°576 Particules Hadrons Énergie et Noyau : Instrumentation, Image, Cosmos et Simulation Spécialité de doctorat : Énergie Nucléaire Par M. Florian Haurais Evaluate the contribution of the fuel cladding oxidation process on the hydrogen production from the reflooding during a potential severe accident in a nuclear reactor Thèse présentée et soutenue à Palaiseau, le Lundi 14 Novembre 2016. Composition du Jury : M. Frédérico Garrido, Professeur des universités, Université Paris-Sud, Président du jury M. Arthur Motta, Professeur, Pennsylvania State University, Rapporteur M. Daniel Monceau, Directeur de recherche, CNRS, Rapporteur M. Christian Duriez, Docteur - Chargé de recherche, IRSN, Examinateur M. Jean-Christophe Brachet, Docteur - Chargé de Recherche, CEA, Examinateur M. Éric Simoni, Professeur des universités, Université Paris-Sud, Directeur de thèse Mme Émilie Beuzet, Docteur - Chargée de Recherche, EDF, Encadrante de thèse M. Martin Steinbrück, Docteur - Chargé de Recherche, KIT, Invité 1 Remerciements Les trois années d’une thèse de doctorat sont très paradoxales. À la fois extrêmement courtes au regard des nombreuses et passionnantes questions qui émergent au fur et à mesure et qui ne peuvent pas toutes être traitées. Et en même temps suffisamment longues pour requérir une certaine endurance mentale… Mais aussi et surtout de bonnes conditions de vie et de travail ! Je souhaite donc naturellement remercier les nombreuses personnes qui y ont contribué. J’adresse mes premiers remerciements aux membres de mon jury de thèse. Merci à Éric Simoni qui m’a fait confiance en acceptant d’être mon directeur de thèse et qui m’a guidé avec sérieux et bienveillance pendant trois ans. Je remercie Daniel Monceau et Arthur Motta d’avoir accepté d’être rapporteurs de ce travail de doctorat et d’avoir pleinement rempli cette importante mission à travers leurs lectures attentives et leurs remarques constructives. Similairement, merci aux examinateurs de ma thèse qui ont parfaitement joué leur rôle, notamment avec les nombreuses questions pertinentes posées lors de la soutenance : Christian Duriez, Jean-Christophe Brachet, ainsi que Frederico Garrido qui a également été président de ce jury de thèse. Je tiens également à remercier Martin Steinbrück qui, en plus d’avoir été notre correspondant privilégié au KIT, s’est investi à 100 % dans la progression de ma thèse. Enfin, je remercie très sincèrement Émilie Beuzet, mon encadrante de thèse chez EDF, dont la clarté des explications, le suivi idéalement dosé, et les conseils très avisés, m’ont permis d’être rapidement autonome et d’avancer sereinement pendant trois ans. Merci également pour ton humour qui a été très bénéfique, notamment les dernières semaines ! J’en profite pour remercier mon second encadrant chez EDF : Antoine Ambard, dont l’expérience et l’expertise m’ont beaucoup aidé et m’ont indéniablement fait progresser. Cette thèse s’est déroulée chez EDF R&D, au sein du département SINETICS, groupe I28, dans le cadre du projet MAGESTIC. Je remercie donc Stéphane Bugat, chef du département, Jean-Sylvestre Lamy et Franck Lavaud, successivement chefs du groupe, ainsi qu’Andreas Schumm et Mohamed Torkhani, chefs de projet successifs, tous deux très impliqués dans le suivi de ma thèse. Plus globalement, merci aux agents des groupes I28 et I27 pour leur accueil, leur sympathie, leur humour, et leurs (très diverses) personnalités ! Je retiendrai notamment les (très diverses) discussions aux pauses café, les concours de pronostics, les QUENCH workshops, les voyages de département et les sorties footing pour celles et ceux qui en avaient le courage (et qui n’oubliaient pas leurs chaussures) ! J’adresse également une dédicace aux agents I28 impliqués sur MAGESTIC (Mohamed Torkhani, David Lemasson, Martin Boissavit, Jérémy Bittan, Léna Gosmain et Nikolaï Bakouta) et en particulier aux membres du B4 de Palaiseau (Émilie Beuzet, Alix Le Belguet et Virginie Lombard) qui m’ont parfaitement bien intégré, humainement et scientifiquement ! Ce sujet de thèse s’inscrivait par ailleurs dans le cadre d’une collaboration européenne de recherche scientifique sur la compréhension et la modélisation des phénomènes d’accidents graves en réacteurs nucléaires. À ce titre, je souhaite remercier nos collègues français du CEA, de l’IRSN et d’AREVA, ainsi que nos homologues allemands du KIT et de GRS, suisses de PSI, hongrois de MTA EK, et russes d’IBRAE. Les échanges avec vous, et en particulier avec le KIT, ont conféré à ce travail de thèse une dimension partenariale et européenne passionnante. Enfin, je remercie très chaleureusement ma famille qui m’a toujours soutenu, et ce dans tous les domaines : mes parents, mon frère, ma sœur, et bien entendu ma Pauline. Merci infiniment pour ta patience, ton soutien, tes conseils et pour ta présence inconditionnelle pendant ces trois ans de thèse, et même ces huit longues années d’études ! Tu mérites cette thèse autant que moi. Et plus généralement merci pour tout ce que l’on a déjà partagé en bientôt 9 ans… 2 Abstract In nuclear power plants, a severe accident is a very unlikely sequence of events during which components of the reactor core get significantly damaged, through chemical interactions and/or melting, because of very high temperatures. This may potentially lead to radiotoxic releases in the containment building and to air ingress in the reactor core. In that context, this thesis led at EDF R&D aimed at modeling the deterioration of the nuclear fuel cladding, made of zirconium alloys, in accidental conditions: high temperature and either pure steam or air-steam mixture. The final objective was to improve the simulation by the MAAP code of the cladding oxidation and of the hydrogen production, in particular during a core reflooding with water. Due to the progressive thickening of a dense and protective ZrO2 layer, the oxidation kinetics of Zr in steam at high temperatures is generally (sub-)parabolic. However, at certain temperatures, this oxide layer may crack, becoming porous and not protective anymore. By this “breakaway” process, the oxidation kinetics becomes rather linear. Additionally, the temperature increase can lead core materials to melt and to relocate down to the vessel lower head whose failure may induce air ingress into the reactor core. In this event, oxygen and nitrogen both react with the pre-oxidized claddings, successively through oxidation of Zr (thickening the ZrO2 layer), nitriding of Zr (forming ZrN particles) and oxidation of ZrN (creating oxide and releasing nitrogen). These self-sustained reactions enhance the cracking of the cladding and of its ZrO2 layer, inducing a rise of its open porosity. In order to quantify this cladding porosity, an innovative two-step experimental protocol was defined and applied: it consisted in submitting ZIRLO® cladding samples first to various accidental conditions during several time periods and then to measurements of the open porosity through porosimetry by mercury intrusion. The tested corrosion conditions included numerous temperatures ranging from 1100 up to 1500 K as well as both pure steam and a 50-50 mol% air-steam mixture. For the ZIRLO® samples oxidized in pure steam, except at 1200 and 1250 K, the “breakaway” kinetic transitions do not occur and the open porosity remains negligible along the oxidation process. However, for all other samples, corroded in air-steam or oxidized in pure steam at 1200 or 1250 K, “breakaway” transitions are observed and the porosimetries show that the open porosity increases along the corrosion process, proportionally to the mass gain. Moreover, it was evidenced that the pore size distribution of ZIRLO® samples significantly extends during corrosion, especially after “breakaway” transitions. Indeed, the detected pore sizes ranged from 60 μm down to around: 2 μm before the transition, 50 nm just after and 2 nm longer after. Finally, a two-step numerical model was developed in the MAAP code to improve its simulation of the cladding oxidation. First, thanks to the proportionality between open porosity and mass gain of cladding samples, porosity correlations were implemented for each tested corrosion condition. Second, the calculated porosity values are used to proportionally enhance the cladding oxidation rate. This improved model thus simulates not only chemical
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