L’uranium hexafluoré (UF6), seul composé d’uranium volatil à basse température, est utilisé industriellement pour enrichir isotopiquement l’uranium afin de produire du combustible nucléaire. Cette thèse s’intéresse à trois problématiques rencontrées industriellement lors de la production d’UF6 : Celui-ci est synthétisé par l’action de fluor gazeux sur du tétrafluorure d’uranium (UF4) à haute température. Selon les conditions, cette réaction peut s’accompagner de la formation de fluorures dont la composition se situe entre UF4 et UF6, appelés fluorures d’uranium intermédiaires tels que UF5, U2F9 et U4F17 et qui viennent polluer les installations industrielles. Cette thèse permet de compléter le diagramme d’Agron qui définit les zones de stabilité des fluorures intermédiaires en fonction de la température et de la pression en UF6. Elle montre l’importance de la morphologie du solide utilisé et confirme la formation d’un nouveau fluorure intermédiaire de formule U4F19. Les fluorures d’uranium peuvent aussi former des composés en présence de polluants tels que les métaux alcalins. Les composés formés de fluorures de métaux alcalins (NaF et KF) et de tétrafluorure d’uranium ont été synthétisés. Leur fluoration par le fluor gazeux (F2) et l’UF6 a montré une oxydation de l’uranium jusqu’au degré d’oxydation V ou VI. Dans ce dernier cas de l’UF6 gazeux est produit ; mais la dissociation totale de l’uranium et de son fluorure alcalin n’a pas été observée. Enfin l’hexafluorure d’uranium est un puissant agent de corrosion notamment parce qu’il peut se dismuter et libérer du fluor. Une étude de fluoration par le fluor gazeux (F2) sur des nuances d’aciers inoxydables enrichis ou non en nickel et monel (70% Ni, 30% Cu) permet de mettre en évidence la faible résistance de ces aciers. Seul le monel présente une résistance accrue, confirmée par des essais de corrosion par UF6 qui mettent en évidence l’importance de la couche de passivation NiF2, formée par F2 avant l’attaque par UF6. Pour terminer, des études structurales réalisées à partir de diffraction des rayons X sur monocristal de composés uranifères utilisés au cours de ces études (UF4, UF5, Na7U6F31, Na7U2F15) permettent d’affiner la connaissance de ces composés. / Uranium hexafluoride (UF6), the only uranium compound volatile at low temperature, is used industrially for isotopical enrichment of uranium to produce nuclear fuel. This dissertation addresses three problems encountered industrially in the production of UF6 : It is synthesized by the action of fluorine gas (F2) on uranium tetrafluoride (UF4) at high temperature. Depending on conditions, this reaction may be accompanied by the formation of fluorides whose composition is between UF4 and UF6, called intermediate uranium fluorides such as UF5, U2F9 and U4F17 which pollute industrial facilities. This dissertation will complete Agron’s diagram which defines the stability zones of intermediate fluorides as a function of temperature and pressure of UF6. It shows the importance of the morphology of the solid used and confirms the formation of a new fluoride intermediate which formula is U4F19. The uranium fluorides can also form compounds in the presence of contaminants such as alkali metals. The compounds formed of alkali metal fluorides (NaF and KF) and uranium tetrafluoride were synthesized. Their fluorination with fluorine gas (F2) and UF6 showed an oxidation of uranium to the oxidation state V or VI. In the latter case, the UF6 gas is produced, but the total dissociation of uranium from its alkali fluoride was not observed. Finally uranium hexafluoride is a powerful agent of corrosion in particular because it can dismute and release fluoride. A study of fluorination by fluorine gas (F2) on stainless steel grades enriched or not in nickel and Monel (70% Ni, 30% Cu) is used to highlight the low resistance of steels. Only monel has a high resistance, confirmed by corrosion tests by UF6 that highlight the importance of the passivation layer NiF2, formed by F2 before the attack by UF6. Finally, structural studies carried out using X-ray diffraction on single crystal of uranium compounds used in these studies (UF4, UF5 Na7U6F31, Na7U2F15) enhance the knowledge of these compounds.

A Agência - International Atomic Energy Agency (IAEA), seguindo a tendência de mercado de integração de sistemas de gestão, decidiu rever as normas de Garantia da Qualidade - IAEA 50-C/SG-Q publicando, em 2006, a norma sobre Sistema de Gestão (SG) - IAEA GS-R-3 e sua guia IAEA GS-G-3.1 e está em vias de publicar uma guia suplementar - IAEA DS349, que consideram a integração das várias funções envolvidas na gestão de instalações nucleares, tais como: segurança, saúde, meio ambiente e qualidade, assegurando que a segurança nuclear não seja comprometida. As plantas de conversão de Yellowcake em UF6 utilizam e processam materiais radioativos, bem como outras substâncias normalmente encontradas na indústria química convencional, se inserindo no perfil de organizações que requerem um elevado padrão de definição, implementação e melhoria contínua de seus SG, e que, portanto, devem considerar uma abordagem de sistema integrado de gestão (SIG). Tendo como foco uma planta de conversão de UF6, foi estudada a correlação entre as normas sobre SG da Agência com aquelas de mercado - ISO 9001, ISO 14001 e OHSAS 18001, e com os projetos de normas da Agência - DS316 e DS344, sobre segurança; concluindo-se que, ao se estruturar um SIG de acordo com as normas de SG da Agência, salvo alguns ajustes, estarão sendo atendidas as ISO 9001, ISO 14001 e OHSAS 18001. Por sua vez, a estruturação do SIG deve identificar outros requisitos sobre segurança, saúde e meio ambiente que considerem, também, as características químicas e industriais convencionais da planta, que estão fora do escopo (radiação ionizante) das normas de segurança da Agência. A pesquisa propõe um procedimento documental para um SIG para a planta em questão, fornecendo subsídios para racionalização e conteúdo da documentação identificada, para promoção da integração das funções de SG consideradas. / The Agency - International Atomic Energy Agency (IAEA), following the market trend of the management system integration, has decided to revise the quality assurance standards - IAEA 50-C/SG-Q publishing, in 2006, the standard on Management System (MS) IAEA GS-R-3 and its IAEA GS-G-3.1 guide. Also, the IAEA is about to publish a supplementary guide - IAEA DS349, which consider the integration of several functions involved in management of nuclear facilities, such as: safety, health, environmental and quality, ensuring that nuclear safety is not compromised. Conversion plants of Yellowcake in UF6 use and process radioactive materials, as well as other substances normally found in the chemical conventional industry, inserting themselves in the organization profile that require a high pattern of definition, implementation and continuous improvement of their MS and, therefore, should consider an approach of management integrated system (MIS). Taking a UF6 conversion plant as focus, the correlation was performed among the Agency MS standards and those of the market - ISO 9001, ISO 14001 and OHSAS 18001, as well as with the Agency drafts standards on safety (DS316 and DS344), concluding that, in structuring an MIS, in compliance with the Agency MS standards, except for some adjustments, the ISO 9001, ISO 14001, and OHSAS 18001 are going to be met. On the other hand, the structuring of MIS should identify other requirements on safety, health and environmental, which also consider the conventional chemical and industrial characteristics that are out of the scope (ionizing radiation) of the safety standards of the Agency. The research proposes a documental procedure for a MIS applicable to this plant, providing elements for rationalization and contents of the identified documentation, for the promotion of the integration of the considered MS functions.

L’hexafluorure d’uranium (UF6), est le seul composé utilisé à l’état gazeux dans les procédés d’enrichissement pour la production du combustible nucléaire. Pour le bon déroulement de l’étape d’enrichissement, la qualité de UF6  est primordiale. Cette étude s’est intéressée principalement aux impuretés volatiles sous forme de fluorures et oxyfluorures et leur réactivité avec des matériaux en présence ou non de l’UF6. La nature des produits adsorbés et de réactions a été identifiée. Les mécanismes physico-chimiques mis en jeux lors de la sorption ont été investigués. Les performances (capacité de sorption, sélectivité et régénération) de ces matériaux absorbants et adsorbants ont été évaluées en vue de leur utilisation comme filtre UF6 dans les usines de conversion. / Uranium hexafluoride (UF6), is the only compound used in the gaseous state in the process of enrichment to produce nuclear fuel. For the success of the enrichment step, the UF6 quality is paramount. This study is mainly concerned with volatile impurities in form of fluorides and oxyfluorides and their reactivity with the materials in presence or not of UF6. The nature of the adsorbed compounds and reactions products was identified. The physico-chemical mechanisms of sorption were investigated. The performances (sorption capacity, selectivity and regeneration) of the absorbent and adsorbent materials have been evaluated to be used as UF6 filters in conversion plants.

A Agência - International Atomic Energy Agency (IAEA), seguindo a tendência de mercado de integração de sistemas de gestão, decidiu rever as normas de Garantia da Qualidade - IAEA 50-C/SG-Q publicando, em 2006, a norma sobre Sistema de Gestão (SG) - IAEA GS-R-3 e sua guia IAEA GS-G-3.1 e está em vias de publicar uma guia suplementar - IAEA DS349, que consideram a integração das várias funções envolvidas na gestão de instalações nucleares, tais como: segurança, saúde, meio ambiente e qualidade, assegurando que a segurança nuclear não seja comprometida. As plantas de conversão de Yellowcake em UF6 utilizam e processam materiais radioativos, bem como outras substâncias normalmente encontradas na indústria química convencional, se inserindo no perfil de organizações que requerem um elevado padrão de definição, implementação e melhoria contínua de seus SG, e que, portanto, devem considerar uma abordagem de sistema integrado de gestão (SIG). Tendo como foco uma planta de conversão de UF6, foi estudada a correlação entre as normas sobre SG da Agência com aquelas de mercado - ISO 9001, ISO 14001 e OHSAS 18001, e com os projetos de normas da Agência - DS316 e DS344, sobre segurança; concluindo-se que, ao se estruturar um SIG de acordo com as normas de SG da Agência, salvo alguns ajustes, estarão sendo atendidas as ISO 9001, ISO 14001 e OHSAS 18001. Por sua vez, a estruturação do SIG deve identificar outros requisitos sobre segurança, saúde e meio ambiente que considerem, também, as características químicas e industriais convencionais da planta, que estão fora do escopo (radiação ionizante) das normas de segurança da Agência. A pesquisa propõe um procedimento documental para um SIG para a planta em questão, fornecendo subsídios para racionalização e conteúdo da documentação identificada, para promoção da integração das funções de SG consideradas. / The Agency - International Atomic Energy Agency (IAEA), following the market trend of the management system integration, has decided to revise the quality assurance standards - IAEA 50-C/SG-Q publishing, in 2006, the standard on Management System (MS) IAEA GS-R-3 and its IAEA GS-G-3.1 guide. Also, the IAEA is about to publish a supplementary guide - IAEA DS349, which consider the integration of several functions involved in management of nuclear facilities, such as: safety, health, environmental and quality, ensuring that nuclear safety is not compromised. Conversion plants of Yellowcake in UF6 use and process radioactive materials, as well as other substances normally found in the chemical conventional industry, inserting themselves in the organization profile that require a high pattern of definition, implementation and continuous improvement of their MS and, therefore, should consider an approach of management integrated system (MIS). Taking a UF6 conversion plant as focus, the correlation was performed among the Agency MS standards and those of the market - ISO 9001, ISO 14001 and OHSAS 18001, as well as with the Agency drafts standards on safety (DS316 and DS344), concluding that, in structuring an MIS, in compliance with the Agency MS standards, except for some adjustments, the ISO 9001, ISO 14001, and OHSAS 18001 are going to be met. On the other hand, the structuring of MIS should identify other requirements on safety, health and environmental, which also consider the conventional chemical and industrial characteristics that are out of the scope (ionizing radiation) of the safety standards of the Agency. The research proposes a documental procedure for a MIS applicable to this plant, providing elements for rationalization and contents of the identified documentation, for the promotion of the integration of the considered MS functions.