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

Validation of the French Version of the Child Post-Traumatic Stress Reaction Index: Psychometric Properties in French Speaking School-Aged Children

Background: Although the reliable and valid Child Post-Traumatic Stress Reaction Index (CPTS-RI) is a widely used measure of posttraumatic stress disorder (PTSD) symptoms in children, it has not been validated in French-speaking populations. The present study aims to assess the psychometric properties of the CPTS-RI in three samples of French-speaking school-children. Methods: Data was obtained from three samples. Sample 1 was composed of 106 children (mean (SD) age = 11.7(0.7), 50% females) victims of an industrial disaster. Sample 2 was composed of 50 children (mean (SD) age = 10.8(2.6), 44% females) who had received an orthopaedic surgical procedure after an accident. Sample 3 was composed of 106 children (mean (SD) age = 11.7(2.2), 44% females) admitted to an emergency department after a road traffic accident. We tested internal consistency using Cronbach's alpha. We examined test-retest reliability using intraclass correlation coefficient. In order to assess the convergent validity of the French version of the CPTS-RI and the Clinician Administered PTS Scale-Child and Adolescent (CAPS-CA), spearman-correlation coefficient was computed. To verify the validity of the cut-off scores, a ROC curve was constructed which evaluated the sensitivity and specificity of each score compared to the diagnosis with the CAPS-CA. We also used principal components analysis with varimax rotation to study the structure of the French version of the CPTS-RI. Results: Cronbach's alpha coefficient was 0.87 for the French version of the CPTS-RI. Two-week test-retest intraclass correlation coefficient (n = 30) was 0.67. The French version of the CPTS-RI was well correlated with the CAPS-CA (r = 0.76, p24 for the CPTS-RI, the sensitivity and specificities were 100% and 62.6%, respectively. The French version of the CPTS-RI demonstrated a three-factor structure. Conclusions: The CPTS-RI is reliable and valid in French-speaking children

Contribution à la recherche de solutions remèdes aux interactions U(Mo)/Al (rôle de l ajout de silicium dans l aluminium, étude d effets couplés)

Dans le cadre du développement et de la qualification d'un combustible nucléaire pour les réacteurs de recherche et d'irradiation de matériaux à faible enrichissement en uranium 235, le combustible particulaire U(Mo)/Al est étudié. Différents essais en pile ont montré que, dans certaines conditions, le composé fissile U(Mo) interagit avec la matrice base Al avec pour conséquence le gonflement, voire la ruine de l'élément combustible. Parmi les voies d'amélioration du comportement en pile du combustible U(Mo) dispersé, la solution considérée comme la voie remède de référence est l'addition de silicium dans la matrice aluminium. Dans le but d'apporter des éléments de compréhension et d'optimiser la solution ajout de Si dans la matrice Al sous irradiation neutronique, nous avons choisi d'étudier hors irradiation (i) les mécanismes d'interaction intervenant au sein du système U(Mo)/Al(Si) et (ii) l'impact de l'ajout de Si dans la matrice Al sur les solutions remèdes alternatives aux interactions U(Mo)/Al actuellement développées à savoir: la modification du composé fissile g-U(Mo) par l'ajout d'un élément X et/ou la modification de l'interface composé fissile g-U(Mo)/matrice. Le présent mémoire propose tout d'abord une description mécaniste de l'interaction U(7Mo)/Al(Si) pour une gamme de Si contenu dans l'Al comprise entre 2 et 10 % m, basée sur la caractérisation multi-échelle de couples de diffusion. La localisation du Mo et son rôle dans les mécanismes réactionnels est mise en évidence. L'influence des éléments X = Y, Cu, Zr, Ti, Cr, sur les mécanismes d'interaction U(Mo)/Al et U(Mo)/Al(Si) a ensuite été étudiée. Il est montré que l'ajout d'un élément à l'alliage U(Mo) agit au second ordre sur la cinétique de diffusion et la (micro)structure de la couche d'interaction par rapport à l'ajout de Si dans l'Al. Enfin, un revêtement d'alumine potentiellement intéressant en vue d'améliorer les performances du combustible a été développé et apparaît prometteur.In the project development and qualification program of a nuclear fuel with Low Enriched Uranium for Materials Testing Reactors, the dispersed U(Mo)/Al fuel is being developed due to its excellent stability during irradiation. However, in pile experiments showed that depending on the irradiation conditions (e.g. high burnup or high heat flux), an extensive interaction occurs between the fissile element U(Mo) and the Al based matrix resulting in swelling, which could eventually lead to a fuel plate failure. Among the ways to improve the behavior of the dispersed U(Mo) fuel, the solution now seen as the reference remedy by the entire scientific community is the addition of silicon into the aluminum matrix. In order to provide some understanding and optimizing the solution " Si additions into Al matrix" under neutron irradiation, an out of pile study is performed on (i) the interaction mechanisms involved in the U(Mo)/Al (Si) system and (ii) the impact of the Si additions into the Al matrix on alternative solutions to the U(Mo)/Al interactions, namely the modification of the g-U(Mo) fissile compound by adding a third element and/or modifying the interface between the g-U(Mo) fissile compound and the matrix. This document provides a mechanistic description of the U(7Mo)/Al(Si) interaction for a range of Si content in Al between 2 and 10 wt.%, based on the multi-scale characterization of diffusion couples. The location of the Mo and its role in the reaction mechanisms are demonstrated. The influence of elements X = Y, Cu, Zr, Ti, Cr, on the U (Mo)/Al and U (Mo)/Al (Si) interactions mechanisms was then studied. It is shown that adding a third element to the U(Mo) alloy acts on the second order on diffusion kinetics and (micro)structure of the interaction layer compared to the addition of Si into Al. Finally, an alumina coating which shows a potential interest to improve the performance of the fuel has been developed.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Characterization of fresh EMPIrE and SEMPER FIDELIS U(Mo)/Al fuel plates made with PVD-coated U(Mo) particles

The HERACLES group and the US-DOE work jointly to develop dispersed U(Mo)/Al as LEU fuel for conversion of high performance nuclear research reactors. Within this frame, two irradiation programs are in progress. In the first, EMPIrE, mini-plates are tested in the ATR reactor (USA) and in the second, SEMPER FIDELIS, full-size plates are irradiated in BR2 (Belgium). In both experiments, U(Mo)/Al plates with optimized microstructure are tested under high duty conditions. This paper focuses on analyses made at CEA Cadarache on seven fresh plates made of atomized particles, with or without Mo homogenization, and with ZrN coating. Five EMPIrE mini-plates and two SEMPER FIDELIS full-size plates were examined by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). A particular attention is paid to the integrity of the ZrN coating (thickness, cracks…) and to the U(Mo) particles microstructure

Morphological characterization of the fresh ZrN coated UMo powders used in EMPIrE irradiation experiment: A practical approach

The European Mini-Plate Irradiation Experiment (EMPIrE) aims to test the in-pile behavior of various ZrN coated UMo powder batches, produced using different technological processes. UMo(ZrN) particles are typical core-shell systems taking advantages of a dense fissile material, UMo, with a coated ZrN layer acting as a diffusion barrier. The U-7Mo kernels were produced by centrifugal or rotating electrode atomization processes and the ZrN coating was performed by physical vapor deposition or atomic layer deposition processes. A total of ten batches of UMo(ZrN) powders were examined in the as-obtained state, i.e prior to fuel-plate fabrication and before in-pile irradiation. The present investigation gives a characterization of each powder batch mainly in terms of morphological and microstructural features carried out by means of SEM-EDS, LOM, EPMA, AFM and TEM analyses. Digital image processing using ImageJ software was employed to determine several particle size (major axis, minor axis, Feret’s diameters, and equivalent diameter) and shape (aspect ratio, circularity, convexity and concavity) parameters as well as the ZrN deposited layer thickness. The quality of the ZrN layer was examined in terms of surface roughness, grain structure and aggregated habits. Our characterization results draw a detailed portrait of the UMo(ZrN) powders selected for the EMPIrE experiment and allow a classification of the powder batches which is presented as radar chart (Kiviat diagram)

Morphological and microstructural characterizations of the fresh fuel plates for the SEMPER FIDELIS in-pile test

International audienceThe UMo/Al dispersion fuel in plate form is considered for the conversion of high-performance research reactors in Europe. In the framework of the UMo fuel qualification program, the adequate margin of safety performance by considering several technological solutions associated with the fabrication parameters, such as heat-treatment of the UMo particles, coating with a diffusion barrier material and powder size distribution as some examples. All these parameters, along with the effect of the hot-rolling process were evaluated by means of image processing and detailed microstructural characterizations for fresh samples i.e. prior to irradiation tests. Principle macroscopic features of powder batches include the size and shape distributions and coating surface examinations. Microscale investigations explored both the coating and kernel microstructures as well as the interface layer between them. Finally, nanoscale analyses examined the UMo–coating interface. The extensive stresses associated with the hot-rolling process have a significant impact on the deformation of the UMo kernels and the degradation of the coated film. The UMo kernels mostly lost their spherical shape for faceted and elongated shapes whereas three types of film degradations were identified including cracks, chippings and delamination

ROC (receiver operating characteristics) curve.

<p>ROC (receiver operating characteristics) curve.</p

Principal components analysis (PCA) of three factors and of one factor. Matrix of items.

<p>Principal components analysis (PCA) of three factors and of one factor. Matrix of items.</p

ROC (receiver operating characteristics) curve coordinates.

<p>ROC (receiver operating characteristics) curve coordinates.</p