Annealing tests of in-pile irradiated oxide coated U–Mo/Al–Si dispersed nuclear fuel

Authors do acknowledge the MERARG team for their experimental work (CEA) and F. Charollais, J. Noirot and finally B. Kapusta for their advices and comments. This study was supported by a combined Grant (FRM0911) of the Bundesministerium für Bildung und Forschung (BMBF) and the Bayerisches Staatsministerium für Wissenschaft, Forschung und Kunst (StMWFK).U–Mo/Al based nuclear fuels have been worldwide considered as a promising high density fuel for the conversion of high flux research reactors from highly enriched uranium to lower enrichment. In this paper, we present the annealing test up to 1800°C of in-pile irradiated U–Mo/Al–Si fuel plate samples. More than 70% of the fission gases (FGs) are released during two major FG release peaks around 500°C and 670°C. Additional characterisations of the samples by XRD, EPMA and SEM suggest that up to 500°C FGs are released from IDL/matrix interfaces. The second peak at 670°C representing the main release of FGs originates from the interaction between U–Mo and matrix in the vicinity of the cladding

Analysis of the interaction products in U(Mo,X)/Al and U(Mo,X)/Al(Si) diffusion couples, with X = Cr, Ti, Zr

International audienceIn the framework of the development of a low 235U enriched nuclear fuel for material testing reactors, γ-U(Mo)/Al based materials are considered as the most interesting prospect. In the process to optimize their composition, addition to both γ-U(Mo) and Al have been proposed. In this paper, the crystallographic composition of Interaction Layers (ILs) in γ-U(Mo,X)/Al and γ-U(Mo,X)/AlSi7 diffusion couples, with X = Cr, Ti, Zr, heat-treated at 600 °C for 2 h, were studied by micro-X-ray diffraction (μ-XRD). When compared to the U(Mo)/Al and U(Mo)/Al(Si) reference systems, all investigated systems involving either Al or Al(Si) as counterparts show interaction products composed of similar phases and related sequences of phase formation. Only relative thicknesses of sub-layers and relative fractions of intermediate phases are correlated with the nature of the X element in the γ-U(Mo,X) alloy. More generally this work shows that γ-U(Mo)/Al and γ-U(Mo)/Al(Si) ILs are now robustly described down to the micrometer scale

Influence of the U3O7 domain structure on cracking during the oxidation of UO2

International audienceCracking is observed when a UO2 single crystal is oxidised in air. Previous studies led to the hypothesis that cracking occurs once a critical depth of U3O7 oxidised layer is reached. We present some μ-Laue X-ray diffraction results, which evidence that the U3O7 layer, grown by topotaxy on UO2, is made of domains with different crystalline orientations. This observation was used to perform a modelling of oxidation coupling chemical and mechanical parameters, which showed that the domain patterning induces stress localisation. This result is discussed in comparison with stress localisation observed in thin layer deposited on a substrate and used to propose an interpretation of UO2 oxidation and cracking

Étude par diffraction des rayons X des déformations induites par irradiation/implantation d'ions dans le dioxyde d'uranium

En conditions de stockage définitif, la désintégration a des radionucléides (produits en réacteur) induit desdommages dans le combustible nucléaire usé. Cet endommagement, et les déformations associées, doivent êtreétudiés pour évaluer correctement la tenue et l'évolution à long terme des pastilles de combustible. La démarcheproposée dans cette thèse pour réaliser cette étude consiste :- à simuler la désintégration a par une implantation d'ions hélium dans une couche fine, en surface depolycristaux d'U02 j- à mesurer les déformations qui en résultent par des techniques de diffraction aux rayons X : la macrodiffractionpour une mesure moyenne dans la couche implantée, la microdiffraction, produite par un rayonnementsynchrotron, pour des mesures très localisées, à l'intérieur des grains d'un polycristal d'U02.L'étude des déformations en fonction de la dose implantée permet de d'évaluer les effets des dégâts d'irradiationsur des durées de stockage de plusieurs milliers d'années.De nouvelles méthodes d'analyse ont été mises au point pour interpréter automatiquement les milliers de clichésde microdiffraction et en déduire la mesure des déformations dans la couche implantée. Un modèle mécaniquea été construit pour rendre compte des mesures avec une grande précision, équivalente à la précision expérimentale.Ce modèle permet de mesurer le gonflement induit par les dommages d'irradiation pour des endommagementsallant jusqu'à 0,77 dpa. Les valeurs mesurées sont comparables à des résultats de la littérature, obtenus sur despastilles auto-irradiées. Il a également permis de quantifier l'augmentation avec l'endommagement de l'anisotropieélastique de l'U02.La microdifDuring long term storage of spent nuclear fuel, the a-decays of radionuclides produced by the in-pile irradiationinduces damages in pellets. These damages, and the resulting strains, must be studied in order to assess correctlythe long term evolution of fuel pellets. The approach chosan here is :- to simulate the a-decays by He ion implantation j- to measure the resulting straÏns using X ray diffraction techniques : macrodiffraction for average measurements,and synchrotron radiation based micro diffraction for local measurements inside grains.The study of strains as a function of ion implantation Huency enables to evaluated irradiation damages overthousands of storage yearB.New analytical methods have been developed to automatically interpret thousands of microdiffraction patterns,and to deduce strain into the implanted layer. Mechanical modeling bas been used to accurately predictmeasurements. This model enables to measure the isotropie swelling induced by helium implantation in a lowdamage range (below 0.77 dpa). Measured values are close to results previously reported in literature on selfirradiated pellets. This model also allowed to quantify the increase with damage of U02 elastic aniBOtropy.X ray microdiffraction is a powerful technique to map the strRin fields within grains. This enables to study theinfluence of neighboring grains on the measured straÏns. This influence remains negligible (below the measurementaccuracy) for low depth helium implantation (60 keV). For deeper belium implaotations (500 aod 1500 keV), thisis not anymore the case : strains are very heterogeneous in the vicinity of gYRin boundaries.POITIERS-SCD-Bib. électronique (861949901) / SudocSudocFranceF

2D and 3D X-ray diffraction and Imaging of Nuclear FuelsInitial microstructure and behavior under ion irradiation

International audienc

Le schématisme linguistique chez K.L. Reinhold

abstract : In this paper, I propose to reconsider the philosophy of language of K.L. Reinhold (1757-1823). The matter has not been explored so far, since, usually, Reinhold's work is only considered as a bridge between Kant's philosophy and the nature idealism of Fichte, Schelling and Hegel. However, Reinhold doesn't pave the way for subjectivism and absolute idealism. On the contrary, his theory is based on the perceptive and linguistic systems. According to Reinhold's idea, many cognitive functions that idealism assigns to the absolute Subject are in fact perceptive competences. In this view, oral language is considered as the faculty of the (metaphoric) connection between perception and the mental structure. In this paper, I shall try to show how the role assigned to language is based on a linguistic interpretation of Kant's transcendental schematism.resume : En dépit de son image courante, la philosophie du langage de K.L. Reinhold (1757-1823) — visée par cet article — ne prépare pas le terrain au subjectivisme et à l'idéalisme. Bien au contraire, elle consiste dans un examen de la faculté cognitive humaine tenant compte des dispositifs de médiation perceptive et linguistique. Fondée sur une théorie de la sensibilité d'inspiration empiriste, elle déplace au niveau perceptif plusieurs des fonctions que l'idéalisme va attribuer au sujet absolu. Dans une telle perspective, le langage est conçu en tant que facteur de médiation (métaphorique) entre la sensibilité et le reste de l'articulation cognitive supérieure, l'auteur suggère, à la base de cette fonction, l'existence d'une interprétation linguistique du schématisme transcendantal de Kant.Perconti Pietro, Palancher J.-P. Le schématisme linguistique chez K.L. Reinhold. In: Histoire Épistémologie Langage, tome 18, fascicule 2, 1996. L'esprit et le langage. pp. 29-43

A review about the effect of He on the microstructure of spent nuclear fuel in a repository

International audiencevoir fichier join