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

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

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

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Short communication: Spark plasma sintering as an innovative process for nuclear fuel plate manufacturing

International audienceIn this paper, we propose an alternative process based on spark plasma sintering for the manufacture of nuclear fuel plates for research reactors. This process presents significant flexibility to control manufacturing parameters such as fuel meat geometry and porosity according to the designer specifications. Furthermore, it allows to increase uranium loading up to 7.3 gU cm−3, exceeding the current requirements for high performance MTRs. With this process neither dogbone, fishtail nor sharp particles penetrating the cladding are observed. The potentialities of this approach are illustrated with the manufacturing of a high loaded (5.6 gU cm−3) U3Si2/Al mini-plate. © 202

Dislocation densities and crystallite size distributions in nanocrystalline ball-milled fluorides, M F 2 ( M = Ca, Sr, Ba and Cd), determined by X-ray diffraction line-profile analysis

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Towards Operando Characterisation by Powder Diffraction Techniques of Molecular Sieves

Working molecular sieves imply numerous and various atoms and for their characterisation we need chemical selective probes. Thus they can be studied either by neutron powder diffraction or by anomalous X-ray powder diffraction techniques to extract structural information. We will illustrate the complementarities of these methods in the analysis of two different chemical processes on X-type zeolite. In the first case, a fully exchanged barium X-type zeolite was, firstly, characterised by neutron powder diffraction after an ex situ preparation step. During the preparation step, the sample was saturated with a mixture of heavy water and deuterated para-xylene. The selectivity of neutron diffraction for light elements allows the precise location of both water and xylene molecules. In the second example, an X-type zeolite exchanged by both strontium and rubidium cations was studied during the dehydration process. The in situ structural characterisation was performed by recording, for each state of the zeolite (hydrated, dehydrated), three X-ray powder patterns. Two of them were measured at an energy close to the absorption edge of each compensating cation (Sr2+ and Rb+) and one far from both absorption edges. The chemical selectivity of resonant diffraction allows an accurate determination of the distribution of compensating cations (location, distribution and mobility) during the dehydration process. Finally a comparison of some specificities and limitations of both methods are summarized

X-ray resonant powder diffraction

X-ray resonant diffraction can be applied in structural chemistry studies on powder samples. It enables an important limitation of powder diffraction to be overcome. This limitation is related to the low ability of powder diffraction to differentiate elements with close atomic numbers when they occupy the same or close crystallographic sites (mixed occupancy case) and also to discriminate cations with different valence states in different sites. However the resonant effect usually has a second order influence on the measured intensity. As a consequence, the efficiency of this method directly implies the need for excellent quality data collection and has generally been better assessed on elements present in single phase powder samples. In recent years, instrumental developments have been made in synchrotron radiation facilities which allow easier use of resonant powder diffraction for site-specific contrast and valence i.e. oxidation state analyses. Moreover, resonant contrast diffraction tools also have been proposed for better visualization of the anomalous effect both in direct and reciprocal space by using differences between electron density maps or diffraction patterns. Finally the potentialities of this technique for de novo structure solution on macromolecular systems are mentioned

As-fabricated Nitride and Silicide Coated U-Mo Atomized Particles Complementary Microstructural Analyses

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Full characterization of dislocations in ion-irradiated polycrystalline UO2_2

International audienceIn order to fully characterize the dislocation loops and lines features (Burgers vectors, habit/slip planes, interstitial or vacancy type) induced by irradiation in UO2, polycrystalline thin foils were irradiated with 4 MeV Au or 390 keV Xe ions at different temperatures (25, 600 and 800 °C) and fluences (0.5 and 1 × 1015 ions/cm2), and further analyzed using TEM. In all the cases, this study, performed on a large number of dislocation loops (diameter ranging from 10 to 80 nm) and for the first time on several dislocation lines, reveals unfaulted prismatic dislocation loops with an interstitial nature and Burgers vectors only along the -type directions. Almost 60% of the studied loops are purely prismatic type and lie on {110} habit planes perpendicular to the Burgers vector directions. The others lie on the {110} or {111} planes, which are neither perpendicular to the Burgers vectors, nor contain them. About 87% of the dislocation lines, formed by loop overlapping as fluence increases, are edge or mixed type in the {100} slip systems, as those induced under mechanical load