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

Determination of single crystal elastic constants in textured polycrystalline materials: inverse approach coupling x-ray diffraction and self consistent model applied to a copper sample

La diffraction des rayons X couplée à l'utilisation d'un modèle polycristallin (modèle auto-cohérent) est utilisée pour déterminer les constantes d'élasticité monocristallines d'un matériau polycristallin texturé. En effet, la connaissance du tenseur de rigidité élastique cijkl d'un solide est fondamentale pour les études s'attachant à la compréhension des propriétés mécaniques de la matière (approches théoriques ou expérimentales). Si, d'autres techniques permettent de déterminer le tenseur d'élasticité d'un matériau (ultrasons par exemple), elles nécessitent souvent l'utilisation d'un monocristal. Ceci n'est pas toujours réalisable, en particulier pour des alliages de concentrations variables. La diffraction des rayons X se révèle alors une alternative intéressante pour l'étude de matériaux polycristallins

A method for the quantification of total xenon concentration in irradiated nuclear fuel with SIMS and EPMA

International audienceA new method for the quantitative determination of the total xenon concentration in irradiated nuclear fuel is presented. The SIMS measurement of xenon enables the detection of the gas filling bubbles which are not detected with EPMA. The quantification is achieved using the EPMA data as reference at position where no or nearly no bubbles are detected. A new approach using the complementary information given by EPMA, SEM and SIMS is proposed, it opens new horizons for the characterisation of fission gases in irradiated nuclear fuel

Behaviour of (U,Am)O2_2 in oxidizing conditions: a high-temperature XRD study

International audienceUranium–americium oxides U$_{1−y}$Am$_y$O$_{2±x}$ are currently investigated as possible transmutation targets for next generation nuclear reactors. In the context of a comprehensive investigation of the thermodynamic and thermal properties of these materials, their behaviour in oxidizing conditions is here investigated for the first time. The results of high-temperature X-ray diffraction measurements in air are here presented. A wide composition domain of the solid solution has been investigated, measuring U$_{1−y}$Am$_y$O$_{2±x}$ oxides with Am/(Am + U) ratios ranging from 0.10 to 0.67. This allowed determining the effect of the americium content on the oxidation kinetics in air. Specifically, it will be shown that americium hinders the formation of the M$_4$O$_9$ and M$_3$O$_8$ phases

Irradiation behavior and post-irradiation examinations of an acoustic sensor using a piezoelectric transducer

International audienc

La diffraction des rayons X : un outil pour l'étude des réactions solides-gaz (avantages et développements)

L'oxydation du zirconium à 850°C sous oxygène (ou air) est un processus pour lequel les analyses aux rayons X présentent un grand intérêt (analyses de phases, textures, contraintes) : en effet, dans cette réaction, des interactions entre processus chimiques (diffusion des espèces, croissance d'une couche d'oxyde) et physiques (microstnicturation de la couche d'oxyde "texture", contraintes mécaniques dans le composite métal-oxide) sont observées. Le produit résultant de l'oxydation contient deux phases , ZrO2 monoclinique majoritaire et ZrO2 quadratique. Les analyses DRX ont établi les résultats suivant : 1) analyse de phases : la DRX en incidence variable révèle la présence d'un gradient de phase au sein de la couche d'oxyde. 2) goniométrie de texture : l'inhomogénéitté de la texture de ZrO2 monoclinique apparaît grâce aux analyses effectuées en incidence variable (fig. 1). 3) goniométrie de contraintes : de nombreuses relaxations des contraintes de compression régnani dans le matériau, inteniennent régulièrement au cours de l'oxydation. Elles ont été corrélées à des accidents morphologiques et cinétiques visualisés par d'autres techniques. L'ensemble de ces résultats permet de proposer un mécanisme d'évolution stnicturae dans la couche d'oxyde au cours de la réaction. Il démontre également l'intérêt de la DRX dans le cadre des recherches en cinétique hétérogène.Zirconium oxidation mechanism can be studied by X-ray diffraction methods : in fact, the interactions between chernical (oxide growth, phases proportion) and physical process (oxide scale texture, mechanical stresses) are observed. The oxide formed is composed of two allotropie structures , monoclinic ZrO2 (highest proportion) and tetragonal ZrO2 (trace). XRD studies show : 1) phases analyses : phases gradient are revealed by XRD variable incidence. 2) textures: Spatial evolution of monoclinic zirconia texture through the oxide scale is shown, and quantifiai. 3) mechanical stresses : several relaxations of the oxide compressive stresses occur at different times of the oxidation. They are correlated to kinetics breakaway, svealed by other methods. A structural mechanism of the oxide formation is then proposefi, which prove the XRD interest in the heterogeneous kinetics researches

On the O-rich domain of the U-Am-O phase diagram

International audienceUranium–Americium oxides U$_{1−y}$Am$_y$O$_{2±x}$ are promising candidates as possible transmutation targets for next generation nuclear reactors. In the context of a comprehensive investigation of their thermodynamic and thermal properties, the behaviour in oxidizing conditions is here studied. In a recent work, the behaviour in air of stoichiometric and sub-stoichiometric U$_{1−y}$Am$_y$O$_{2±x}$ compounds, with various Am content, was investigated by high-temperature X-ray Diffraction. Herein, the hyper-stoichiometric oxides obtained from that study are investigated by X-ray Absorption Spectroscopy. The new data, together with the previous XRD results, allow determining the exact compositions of the samples and hence obtaining phase diagram points in the O-rich domain of the U-Am-O system. Indeed, five phase diagram points at 1473 K are obtained: two tie-lines in the M$_4$O${9-}$M$_3$O$_8$ domain, for Am/(Am + U) = 0.10 and 0.15, one tie line in the MO$_{2+x-}$M$_3$O$_8$ domain, for Am/(Am + U) = 0.28, and two points in the single phase MO$_{2±x}$ domain, for higher americium concentration. From these data, it is also concluded that trivalent americium has a small solubility in the M$_4$O$_9$ and M$_3$O$_8$ phases

Oxydation d'alliages de zirconium : gradients de phase et texture

Ce travail s'inscrit dans la compréhension des phénomènes intervenant lors de l'oxydation d'alliages de zirconium utilisés dans l'industrie nucléaire. L'alliage ici étudié est ZrNb1% oxydé sous oxygène à 470°C. Par une étude qualitative et quantitative de la texture, les orientations majoritairement parallèles à la surface ont pu être caractérisées. De même, l'hypothèse qu'aucun gradient de texture existe, a pu être vérifiée. De plus, une localisation de la phase quadratique a été possible en utilisant la diffraction des Rayons X en incidence variable.This paper deals with phenomenon study linked with zirconium alloys oxidation used in Nuclear Industry. The studied alloy is ZrNb1% oxidized under oxygen at 470°C. The qualitative and quantitative studies of texture lead to characterization of planes which are mainly oriented parallel to surface sample. The hypothesis which is that no texture gradient exist, could be checked. Moreother, by variable incidence X-ray, the tetragonal phase can be localized