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Advanced courses; International audience

International audience; Oxide glasses have many advantageous properties, including optical transparency, low thermal expansion coefficients, thermally insulating, etc. As such, they have a number of applications in the world today (windows in buildings, dishes, protection panels for plasma screens and solar panels, etc.). Optimizing a wide range of physical, thermodynamic and mechanical properties is necessary to ensure their best performance in each use. However, literature focuses on a select number of compositions; making optimization of the glass as a whole unreachable. This is in part due to sample lost between different tests, multiple batches, expense of sample fabrication, etc.Recently, the development of complex interatomic empirical potentials modeling simultaneously multiple oxides makes way for capturing various physical, thermodynamic and mechanical properties. Hence, a systematic approach to capture a large numbers of different chemical compositions is feasible. This work concerns molecular dynamics simulations based on two simple and reliable empirical potentials. This presentation will focus on select physical, thermodynamic and mechanical properties presented in [1].[1] M. B. Mama Toulou, P. C. M. Fossati, C. L. Rountree, “Systematic approach to thermophysical and mechanical properties of SiO2–B2O3–Na2O glasses using molecular dynamics simulations,” Journal of Non-Crystalline Solids, 603(2023):122099.

International audience; Evaluation of the mobility behaviour of radionuclides under highly saline and alkaline conditions is a major concern for the performance assessment of radioactive waste disposal. The aim of this study was to determine the effect of up to 2.8 mol/kgsolution content of NaNO3, on the solubility and the retention of U(VI) at 22 °C onto a hardened cement paste (HCP) prepared from ordinary Portland cement (CEM I). To avoid the interference of the high salt concentration and ionic strength,and because of the expected low solubility of uranium under such alkaline conditions, time-resolved laser fluorescence spectroscopy (TRLFS) was selected to accurately measure U(VI) concentration in solution using the standard addition method in 85% H3PO4. This allows both limiting the dilution and matrix effects and determining the resulting [U(VI)] in solution with acceptable precision for the distribution factor (Rd) in both sorption and desorption experiments. The operational solubilitylimit measured at high ionic strength lowered by a factor of three compared to the reference cementitious condition, and its Rd values decreased by a factor ca. four. The sorption of U(VI) appears to be reversible under these conditions.

International audience; The formation of alkaline earth(II)triscarbonatouranyl(VI) (AenUO2(CO3)3(4-2n)-) species that have been evidenced both in laboratory and in-field studies, is important from slightly acidic pH up to near degraded cementitious in carbonated waters. They are also showing distinctive luminescence properties with a hypsochromic shift relative to UO22+. The conditions of pH, activities of alkaline earth(II) free ions (mostly Mg2+ and Ca2+) and carbonate ions (HCO3−) can be predicted from the thermodynamic functions and constants. The predictive validity of the activity of major alkaline ions (mostly Na+) is determined from the models used to describe the ionic strength comportment of these species, particularly using coefficients from the specific ion interaction theory (SIT). The stability domains of these species are better defined as a function of the activity of the constituents, and applied to natural waters. In this work, using recently obtained complete thermodynamic data and SIT coefficients, we will draw the stability domains of the AenUO2(CO3)3(4-2n)- species in combinations of activities of H+, HCO3−, Mg2+, Ca2+, and Na+ for a wide selection of water compositions from the literature. Water samples were collected near a French mining legacy-site (Site du Bosc, Lodève, France). After determining the major ion compositions, we will verify that the luminescence signal of uranium is in agreement with the predicted speciation in the stability domains.

International audience; Understanding and limiting the impact of uranium (U) on man requires the characterization of the interactions of UO₂²⁺, the chemical form of U in vivo, with target biomolecules that are unknown until now1. In this context, biomimetic peptides, designed specifically to mimic the coordination sites of UO₂²⁺ in proteins, are very useful chemical tools to determine the parameters responsible for UO₂²⁺ affinity towards its target proteins and further develop selective decorporating agents2.The aim of this work is to develop a dedicated analytical method to determine in a single step and at physiological pH, the affinity and selectivity of multi-phosphorylated biomimetic peptides for UO₂²⁺. The strategy was based on the simultaneous coupling of hydrophilic interaction liquid chromatography (HILIC) to electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS)3. Firstly, different sets of UO₂(peptide) complexes were successfully separated using different polar stationary phases, being the first HILIC separations of UO₂²⁺ complexes reported in the literature. A dedicated method had been developed for identifying the separated peptide complexes online by ESI-MS and simultaneously quantifying them by ICP-MS, based on U quantification using external calibration. The effect of several structural parameters of the peptides, such as the number and position of phosphoserine (pSer) residues but also their cyclic/linear structure, on UO₂²⁺ affinity were determined. Results showed that the tetra-phosphorylated cyclic peptide (pS1368) exhibited the highest affinity for UO₂²⁺ in comparison with its linear homologue and with cyclic peptides containing lower number of pSer, while the position of pSer had very little influence on this affinity. Following the same approach, the selectivity of pS1368 was determined in the presence of endogenous cations as potential competitors in biological media. pS1368 was the most selective towards UO₂²⁺, underlying its potential as a promising decorporating agent of this element in vivo

It is generally considered that the elementary building blocks of defects in face-centred cubic (fcc) metals, e.g., interstitial dumbbells, coalesce directly into ever larger 2D dislocation loops, implying a continuous coarsening process. Here, we reveal that, prior to the formation of dislocation loops, interstitial atoms in fcc metals cluster into compact 3D inclusions of A15 Frank-Kasper phase. After reaching the critical size, A15 nano-phase inclusions act as a source of prismatic or faulted dislocation loops, dependent on the energy landscape of the host material. Using cutting-edge atomistic simulations we demonstrate this scenario in Al, Cu, and Ni. Our results explain the enigmatic 3D cluster structures observed in experiments combining diffuse X-ray scattering and resistivity recovery. Formation of compact nano-phase inclusions in fcc structure, along with previous observations in bcc structure, suggests that the fundamental mechanisms of interstitial defect formation are more complex than historically assumed and require a general revision. Interstitial-mediated formation of compact 3D precipitates can be a generic phenomenon, which should be further explored in systems with different crystallographic lattices.

International audience; We describe the recent developments in using machine learning techniques to compute Hodge numbers of complete intersection Calabi-Yau (CICY) 3- and 4-folds. The main motivation is to understand how to study data from algebraic geometry and solve problems relevant for string theory with machine learning. We describe the state-of-the art methods which reach near-perfect accuracy for several Hodge numbers, and discuss extrapolating from low to high Hodge numbers, and conversely.

The reactive transfer of Ni-rich corrosion products into the water circuits of PWR has a major impact on the dose rate absorbed by nuclear power plant staff. Physical modeling of the behavior of the Metal-Oxide-Electrolyte (MOE) system makes it possible to predict long-term mass release. The simplified system Ni-NiO-Electrolyte, encountered in the reactor core has been chosen as a preliminary model to represent the real systems formed by Metal-Oxide-Electrolyte (MOE) phases. The main aim of this study is then to develop a continuous model, capable of describing the process of diffusion and mass transfer within the oxide film and at both interfaces. In addition, the goal is to propose a model that can provide a generalized description (extrapolated according to physicochemical conditions and time).; Dans les réacteurs à eau pressurisée (REP), les tubes des générateurs de vapeurs (GV) sont fabriqués à partir des alliages à base de nickel de type "Inconels". Dans les conditions physicochimiques de fonctionnement nominal, ces matériaux s’oxydent et forment des couches d’oxydes protectrices vis-à-vis de la corrosion. Néanmoins, les variations thermochimiques du réacteur, n’empêchent pas les échanges de matière entre ces oxydes riches en nickel et le fluide en mouvement. Transportée par le fluide primaire, une partie de ces produits de corrosion passe ou séjourne dans le cœur pour s’activer sous l’effet du flux neutronique. Ainsi des radionucléides 58Co et 60Co sont générés amenant à la contamination radioactive du circuit primaire. En effet, dans les réacteurs électrogènes, environ 80 % de la dosimétrie individuelle est due aux radiocobalts. Dans le domaine du nucléaire, la maîtrise de la dosimétrie individuelle du personnel constitue un enjeu majeur. Il apparaît donc nécessaire de prévoir et d’anticiper le degré de contamination radioactive de l’installation. Dans ce contexte, l’objectif principal de cette étude est de prévoir la quantité de matière relâchée et transférée dans le fluide primaire, en se fondant sur la modélisation physique du comportement des différents systèmes rencontrés dans le circuit primaire des REP, c’est-à-dire la description du transport réactif de matière dans les systèmes impliquant le métal (M), l’oxyde (O) et l’électrolyte (E). L’enjeu est de développer un modèle continu dérivable, qui couple les trois approches cinétique, électrochimique et thermodynamique dans le but de décrire les différents phénomènes impliqués (corrosion du métal, dissolution/précipitation de l'oxyde). Dans une première approche, le modèle généralisé M/O/E, est testé avec un seul élément chimique et ainsi le système Ni/NiO/Eau est choisi comme modèle préliminaire simplifié.

During a severe accident involving the meltdown of the core of a pressurized water nuclear reactor, the nuclear fuel will react with the zircalloy cladding around it and the structural materials of the core to make a high temperature magma called corium. Depending on its composition and its temperature, the corium can stratify because of two non-miscible metallic and oxidic liquids. For some stratification configurations, the heat flow can focus on the vessel’s wall, threatening its integrity with a corium flowing outside of it. The aim of this thesis is to collect thermodynamic and thermophysic data on a prototypical corium, the U-Zr-Fe-O system. The thermodynamic data collected in this thesis are related to the definition of the liquid miscibility gap and the compositions of the liquids in the U-Zr-Fe-O system and its sub-systems, depending on the composition and the temperature. Compositions of interest were selected after performing thermodynamic calculation by the CALPHAD method with the TAF-ID V13 database. The corresponding samples underwent heat treatments and post-treatment analyses to measure the compositions of the liquids and to compare them to thermodynamic calculations. An iron rich liquid miscibility gap and a zirconium rich one were highlighted in the Fe-Zr-O system. Although calculations were in agreement with data from the first miscibility gap at 1990 °C, measurements in the zirconium rich miscibility gap at 2420 °C and 2650 °C reveal an underestimation of the zirconium quantity in the metallic liquid and its overestimation in the oxidic liquid by the model. Studies on the UO2-Zr-Fe system at 2423 °C show that the liquid miscibility gap definition and the compositions of the liquids depend on the quantity of iron in the system, the U/Zr ratio and corium oxidation degree. Furthermore, the zirconium molar fraction is underestimated by the model in the metallic liquid to the benefit of iron, and is overestimated in the oxidic liquid. Finally, the oxygen solubility in the metallic liquid is underestimated by the model. Thermophysic data were collected thanks to the improvement of the ATTILHA experimental setup, allowing the study of oxygen sensitive or radioactive liquids at high temperature by using a laser heating. Experimental values on liquidus and eutectic transformation temperatures of the oxygen-rich domain of the Zr-O system were acquired with this setup. Furthermore, the development of the aerodynamic levitation allows us the investigation liquids’densities for the Zr-Fe2O3 and the Zr-UO2 systems between 1884 °C and 2268 °C for different zirconium molar fractions. Densities of liquids from the Zr-Fe2O3 system were used to refine surface tension values acquired on the VITI-MBP setup at CEA Cadarache. These values confirmed the surfacting properties of the oxygen on these liquids. The experimental data collected during this thesis will be used to feed the databases and to improve the forecast of the corium’s behavior during a severe accident.; Lors d’un accident grave impliquant la fusion du cœur d’un réacteur nucléaire à eau pressurisée, le combustible nucléaire va réagir avec la gaine en zircalloy qui l’enrobe et les matériaux de structure présents dans le cœur pour former un magma à haute température appelé corium. Suivant sa composition et sa température, le corium peut se stratifier dû à la présence d’un liquide métallique et d’un liquide oxyde non-miscibles. Selon la configuration de cette stratification, une concentration du flux de chaleur peut avoir lieu sur la paroi de la cuve, menaçant son intégrité et risquant un écoulement du corium hors de celle-ci. L’objectif de cette thèse est d’obtenir des données thermodynamiques et thermophysiques sur un corium prototypique, le système U-Zr-Fe-O. Les données thermodynamiques recueillies dans cette thèse sont liées à la définition de la lacune de miscibilité liquide et à la composition des liquides dans le système U-Zr-Fe-O et de ses sous-systèmes, en fonction de la composition et de la température. Des compositions d’intérêt sont sélectionnées suite à des calculs thermodynamiques réalisés par la méthode CALPHAD grâce à la base de données TAF-ID V13. Les échantillons relatifs à ces compositions ont subi des traitements thermiques et des analyses post-opératoires afin de mesurer les compositions des liquides et de les comparer aux calculs thermodynamiques. Une lacune de miscibilité liquide riche en fer et une autre riche en zirconium ont été mises en évidence dans le système Fe-Zr-O. Alors que les données obtenues sur la première lacune à 1990 °C et 2614 °C montrent un bon accord entre le calcul et l’expérience, les mesures sur la lacune riche en zirconium à 2420 °C et 2650 °C indiquent que le modèle sous-estime la quantité de zirconium dans le liquide métallique et, à l’inverse, la surestime dans le liquide oxyde. Les études réalisées sur le système UO2-Zr-Fe à 2423 °C montrent que la présence de la lacune de miscibilité liquide et la composition des liquides dépendent grandement de la quantité de fer dans le système, du rapport U/Zr et du degré d’oxydation du corium. De plus, le modèle tend à sous-estimer la fraction molaire de zirconium dans le liquide métallique au profit du fer, et à la surestimer dans le liquide oxyde. Enfin, le modèle sous-estime grandement la solubilité de l’oxygène dans le liquide métallique. L’obtention de données thermophysiques a pu être réalisée grâce à l’amélioration du banc expérimental ATTILHA, rendant possible l’étude de liquides sensibles à l’oxygène ou radioactifs à hautes températures via un chauffage laser. Ce banc a permis de mesurer des valeurs expérimentales de température de liquidus et de transition eutectique sur le système Zr-O dans le domaine riche en oxygène. De plus, le développement de la lévitation aérodynamique sur ce banc permit l’étude de la masse volumique de liquides Zr-Fe2O3 et Zr-UO2 entre 1884 °C et 2268 °C pour différentes fractions molaires de zirconium. Les résultats de masse volumique des liquides Zr-Fe2O3 ont permis d’affiner des mesures de tension de surface réalisées sur le banc VITI-MBP au CEA Cadarache. Ces mesures confirmèrent les propriétés surfactantes de l’oxygène sur ces liquides. Les données expérimentales recueillies durant cette thèse pourront servir à alimenter les codes de calcul afin de mieux prédire le comportement du corium et le déroulement des accidents graves.

International audience; Le cobalt constitue une grande partie des déchets radioactifs du circuit primaire des réacteurs nucléaires. Le remplacement des revêtements durs à base de cobalt fait l'objet de recherches depuis des années dans les applications nucléaires. A ce jour, il n'existe pas d'alliage capable de résister à l'abrasion et à la corrosion à 350°C et 150bar de pression pendant des cycles longs. Les alliages complexes concentrés constitués de Cr-Fe-Mo-Ni-Ti ont montré des propriétés prometteuses pour ces applications [1].La méthode CALPHAD (CALculation of PHAse Diagram) a été choisie pour déterminer les compositions les plus intéressantes de ce système. Pour cela, une évaluation critique de tous les sous-systèmes constitutifs a été réalisée. Comme ce système présente plusieurs phases de Frank-Kasper (σ, µ, χ, R, Laves), les modèles ont été discutés et choisis en fonction de la structure cristalline. La stabilité du réseau (lattice stability) et l'enthalpie de formation des composés stables et métastables ont été calculées par DFT (Density Functional Theory). Il a également été constaté que certains systèmes manquent de données fiables ou que des contradictions existent parmi différentes études. Par conséquent, la détermination expérimentale des équilibres de phase dans ces systèmes a été effectuée. Des échantillons du système Cr-Mo-Ti ont été synthétisés pour déterminer les limites de phase des phases de Laves et l'extension de la lacune de miscibilité Cr-Mo au système ternaire. Le système binaire Cr-Ti a été réoptimisé, et les systèmes ternaires où il est présent seront réévalués.

International audience

International audience

International audience; Corrosion of titanium alloys in pressurized water at 300 °C, 15 MPa, pH300 °C = 7.2 follows a flow acceleration corrosion mechanism between 0 m.s-1 and 8 m.s-1. At low water velocity (0 m.s-1 or 10-3 m.s-1), the evacuation rate of titanium hydroxides away from the samples is low, the concentration of titanium hydroxides in the vicinity of the TiO2 layer is high, which limits the dissolution rate. The increase in the water velocity up to 8 m.s-1 increases both the corrosion rate (from ~1 µm/yr to ~10 µm/yr) and the fraction of oxidized titanium that is moved away from the samples (from ~0.3 to ~0.8). When titanium alloys are used in association with stainless steel, the increase of water velocity also accelerates the coverage of the TiO2 layer by FeTiO3 ilmenite crystallites, which protect the titanium alloys from further corrosion as long as the corresponding product of solubility is maintained in the water.

International audience; Les alliages de titane sont largement utilisés dans les domaines aéronautique, biomédical et l'industrie chimique car ils possèdent une bonne résistance à la corrosion dans de nombreux milieux. Leur utilisation dans l'industrie nucléaire est envisagée ; une étude de leur durabilité dans l'eau sous pression à 300 °C a donc été engagée au CEA (commissariat à l'énergie atomique et aux énergies alternatives) en collaboration avec l'Université Grenoble Alpes.Trois matériaux ont été étudiés : du titane commercialement pur, du Ti-6Al-4V et du Ti-10V-2Fe-3Al. Ils ont été exposés à un milieu représentatif du milieu primaire des réacteurs nucléaires à eau sous pression (REP) : de l'eau désaérée, hydrogénée, contenant de la lithine, à 300 °C entre 110 et 150 bars, jusqu'à 15 mois, dans des dispositifs en acier inoxydable.Cette exposition conduit à la croissance et à la dissolution simultanées d'une couche nanométrique continue de TiO2 en surface des échantillons ainsi qu'à son recouvrement progressif par des cristallites micrométriques de TiO2 anatase et de FeTiO3 ilménite formées par la précipitation des hydroxydes de fer et de titane en solution issus de la corrosion des échantillons et du dispositif expérimental. Après un premier stade transitoire, la couche continue atteint une épaisseur stationnaire. La vitesse de corrosion est alors constante (quelques µm/an) et augmente avec la vitesse du fluide. Lorsque l'on conserve une teneur suffisante en hydroxydes dans le milieu, la totalité de la surface des échantillons finit par être recouverte d'ilménite, ce qui ralentit très fortement la corrosion et l'absorption d'hydrogène associée.

International audience; This work presents the experimental study of the behavior of copper and copper oxides in presence of pollutants in steam generator flow-restricted areas. The experiments were conducted under secondary circuit thermochemical conditions. Two redox conditions were performed, reducing ones to reproduce operating conditions, with or without presence of magnetite, and a weakly oxidizing one to simulate an oxygen inlet. High concentrations of sodium and phosphates were used to simulate a heavily polluted environment that can be encountered in flow-restricted areas during hideout process.In a steam generator (SG) of a Pressurized Water Reactor (PWR), the hideout process can occur in flow-restricted areas. Non-volatile polluting species tend to accumulate in these regions due to boiling. Their concentrations can reach up to several orders of magnitude [1] above those encountered in the chemical conditioning yielding extreme pH values. Such pollutants include various metallic elements like iron, nickel, sodium, aluminum or copper, and other ions like sulfates, chlorides or phosphates. Some authors have already discussed the behavior of solid copper species in presence of phosphate under secondary circuit thermochemical conditions. Turner et al. [2] showed how sodium phosphate lead to aconsolidation of a magnetite-copper sludge already formed with few information on which phases were observed, and Ziemniak et al. [3] and Palmer [4] had a major focus on the dissolved species rather than the solids. This study is a step towards a more complete description of the flow-restricted areas, including the interaction of copper and copper oxides with other species present in the secondary circuit. The objective was to identify the stable solid copper-containing species under the thermochemical conditions encountered in SG flow-restricted areas

International audience; A French R&D program (CEA, CNRS, Orano) has been launched on molten salts cooled reactors which aims at assessing the feasibility of fast MSRs and confirm their potential assets. Chloride salts have been selected and in the French context (closed cycle, transmutation, Pu multirecycling), we focus on chlorides fast MSR with a focus on actinides conversion (reducing ultimate wastes). One of the major constraints on the use of molten chlorides is the corrosion behaviour of structural materials. To overcome this constraint, different approaches are performed with different time scales:- Evaluation of already available and /or qualified materials such as nickel base alloys but also high entropy alloys or ceramics.- Evaluation of different corrosion protection strategies: protective coatings, electrochemical potential control, chemistry control…- Evaluation of more innovative solutions: advanced manufacturing processes, smart materials, architectured materials…In the same time a large French research program has been launched together with CEA and CNRS to work on the global acceleration of materials discovery, the DIADEM (DIscovery Acceleration for the Deployment of Emerging Materials) project. In the frame of this large project which will be launched in 2022 for 8 years, shorter targeted projects have been already selected (duration of 3 years), as the A-DREAM project which is dedicated to the acceleration of the development of corrosion resistant materials in molten chlorides. For this, the A-DREAM project proposes an integrated approach implementing: (i) the digital design of materials/coatings, (ii) the high throughput synthesis of these materials and (iii) the implementation of an accelerated corrosion methodology. In this presentation, the French corrosion strategy for MSR will be presented together with results obtained.

The radiological characterization of radioactive waste and effluents requires the measurement of many radionuclides, including 90Sr. The usual methods for 90Sr analysis are efficient but they are relatively long and require the use of toxic products such as fuming nitric acid and scintillation cocktails. This thesis work consisted in developing new analytical procedures for 90Sr analysis, in particular new separation methods. A first method based on successive selective precipitations was optimized using design of experiments methodology and speciation modelling. Fuming nitric acid was replaced by concentrated nitric acid at 69 % while preserving the separation selectivity between Sr and Ca, and an understanding of the mechanisms involved in this precipitation was provided. A second method using the Sr® chromatographic extraction resin was developed by including a new pre-treatment based on the TRU® resin, allowing the elimination of problematic interferents for liquid scintillation measurements, such as 241Pu. Finally, a method was developed with a scintillating resin called PS-Sr resin, which enables to isolate Sr, to perform a nuclear measurement by plastic scintillation and thus to be compatible with REACH regulation. The performances of the methods were validated by participation in inter-laboratory comparisons.; La caractérisation radiologique des déchets et des effluents radioactifs nécessite la mesure de nombreux radionucléides dont le 90Sr. Les méthodes usuelles d’analyse du 90Sr sont performantes mais elles sont relativement longues et nécessitent l’utilisation de produits toxiques tels que l’acide nitrique fumant et les liquides scintillants. Ce travail de thèse a consisté à développer de nouvelles procédures d’analyse du 90Sr, en particulier de nouvelles méthodes de séparation. Une première méthode basée sur des précipitations sélectives successives a été optimisée à partir de la méthodologie des plans d’expériences et de la modélisation de la spéciation. A l’issue de ces travaux, l’acide nitrique fumant a été remplacé par de l’acide nitrique concentré à 69 % tout en préservant la sélectivité de la séparation entre le Sr et le Ca et une compréhension des mécanismes mis en jeu lors de cette précipitation a été apportée. Une seconde méthode utilisant la résine d’extraction chromatographique Sr® a été développée en intégrant un nouveau prétraitement basé sur la résine TRU®, permettant d’éliminer les interférents problématiques pour la mesure par scintillation liquide, comme le 241Pu. Enfin, une dernière méthode a été mise au point avec la résine dite scintillante appelée résine PS-Sr qui permet d’isoler le Sr, d’effectuer une mesure nucléaire par scintillation plastique et ainsi d’être conforme à la directive REACH. Les performances des méthodes ont été validées par la participation à des comparaisons inter-laboratoires.

International audience; Over the past decade, additive manufacturing has made a tremendous progress. More ever, additive manufacturing get a great interest to the development of mechanical parts with complex geometries and compositions. This design freedom allows the additive manufacturing process to be used to integrate optical sensors during the printing process, making it possible to produce instrumented components for SHM (structural health monitoring). The latter required a particular process with adapted printing strategy and an interruption of the procedure in order to place the sensor. The impact of these modifications on the parts mechanical properties needs to be investigated in order to determine the influence of the sensor insertion on the mechanical parts behaviors. In this work, we perform several experiments on different 3D Printed parts with and without sensor insertion. The focus is to identify the best procedure that minimize the impact of the sensor insertion on the mechanical properties.

Mechanical or geometrical interlock between steel bars and concrete directly affects the bond strength in reinforced concrete structures. This aspect is usually neglected, or at least indirectly considered, when modelling and simulating reinforced concrete structures using macroscopic models, due to the difficulty and complexity it adds to such structural simulations on large structures. However, modelling of the steel-concrete bond at the mesoscale is capable of showing the effect of varying the geometry of the ribs. In this contribution, the effect of the geometry of the ribs at the mesoscale is numerically modelled in 3D. Mazars’ damage model is assigned for concrete and a frictional cohesive zone model is used for the steel-concrete interface. Pull-out test simulations are performed on steel bars having rectangular ribs and compared to experimental results to prove the ability of the models to reproduce the overall behavior. Samples having only one rib are then considered in order to understand the general effect of varying each rib dimension at a time. A simulation is performed on a bar having a herringbone shape and the corresponding results are compared to those of a spiral bar. Using the simulated results, a simple function is proposed to predict the variation in the mean bond stress with the geometry of the ribs shape. It depends on two main geometrical parameters, which are detailed in the contribution. It is verified using experimental and numerical data to show its efficiency to reproduce macroscopic quantities.

International audience; It is essential to model the behavior of the interfaces between steel reinforcement and concrete in order to understand the stress transfer between these two components in reinforced concrete structures. The interface models commonly used include several parameters whose identification is based on pull-out tests, for which sensitivity to a number of parameters is not fully explained. In this contribution, the steel-concrete interface is studied at the mesoscopic scale through the simulation of pull-out tests. The three dimensional numerical reinforced concrete samples are first generated by applying a procedure, in which each sample is made up of concrete surrounding a ribbed or smooth bar embedded in the center of a cubic sample. The detailed geometry of the ribs of the steel bar is modelled with different possible shapes. Then, the finite element code Cast3M is used to perform the pull-out numerical simulations on the generated samples, using Mazar’s damage approach with regularization to describe cracking in concrete. The steel-concrete interface is modelled by combining a modified cohesive zone model (CZM) based on Tvergaard’s approach and a frictional model accounting for the frictional behavior in the damaged part of the interface. This is done by modifying an initial approach, by replacing the Crisfield’s damage model by the more adapted Tvergaard’s model and modifying the corresponding stresses to account for its exponential behavior. The interface is divided into an undamaged part where the CZM model applies and a damaged part where the frictional model dominates. The total stress is then the addition of the two corresponding stresses, and is equivalent to the CZM stress when the interface is initially undamaged, and fully equivalent to frictional model’s stress when the joint element is finally fully damaged. The overall response is studied in terms of the damage near the steel bar, the applied force versus displacement curves, and free end displacements. The results of mean bond stress versus the free end displacement are compared to available experimental data.

International audience; Hierarchical porosity sol-gel monoliths (HPMs) are of increasing interest for a wide variety of applications due to their outstanding microstructural (homogenous) and textural properties (high porosity and specific surface area) [1]. The high flow rate and low-pressure resultant compared to conventional materials, makes them suited for extraction and enrichment of analytes of interest in analytical techniques (HPLC, SPE, etc.) [2–4]. However, pure inorganic materials have rarely been considered for relevant applications in various omics fields such as metabolomics or proteomics [5].In the context, we report on: (i) a pure silica HPM based on a finely tuned bimodal porosity thoroughly controlled, (ii) coupled to a new way to a miniaturize shaping (iii) and its use as an innovative tool for sample preparation prior to glycan analysis by mass spectrometry, as a new source of disease biomarkers (glycomics analysis). The monolith synthesis will be presented with a special emphasize on its robustness and on the modulations of the bimodal porosity obtained ([0.1–5] μm and [1-25] nm). Beside microstructural and textural properties measurements (SEM, Hg porosimetry, etc.), the transport of small molecules through mesoporous network were evaluated by TEM tomography. Finally, the material was processed in different shapes and size (50 μm – 4 mm in diameter) demonstrating a high flexibility of our approach to produce devices dedicated to a biological analysis. The use of HPM for the analysis of both free and protein-bound oligosaccharides present in precious samples (human blood and milk) and their detection by MALDI-TOF mass spectrometry will be presented as a proof of concept. Optimized experimental conditions, as well as material textures and shapes, enabled straightforward and time-efficient purification and MS- based glycomics analysis using minute quantities (few μl) of solvents but above all of complex human biofluids, thus outperforming common laboratory protocols.

Multi-metal additive manufacturing by laser projection offers new opportunities for the creation of high performance components combining metals with different properties. However, several obstacles limit the freedom of manufacturing, such as the existence of incompatibilities between certain metal pairs, like the formation of brittle intermetallic phases or the overheating of less refractory metals. The control of the process is moreover made complex in view of the numerous phenomena involved and the variations of the composition during the manufacturing process. In this work, coatings combining incompatible metals have been produced by laser projection, thanks to the use of intermediate metals chosen with the help of equilibrium phase thermodynamics. The analysis of early fabrications revealed the importance of the remelting ratio of the melt pool with the underlayer, which allows to generate a composition gradient and avoid the occurrence of defects at the interface between two dissimilar metals. A coating of W on Cu, of interest for the realization of heat sinks in extreme environments, has been achieved through the integration of a succession of miscible metals between the two, as well as composition gradients across the layers. These gradients allowed the progressive increase of the melt pool temperatures from Cu to W. Theoretical tools have been developed and used to better understand the impact of parameters and the evolution of key phenomena during these complex multi-material fabrications. In particular, a numerical simulation model at the melt pool scale has been built, taking into account conduction, deformation and dynamics of the liquid, vaporization, as well as mixing of the elements. The experimental and theoretical analyses of the different deposits highlighted the importance of the melt pool temperature and power on the presence of unmelted refractory particles, the influence of the scanning speed on the dissolution of the particles, and the evolution of the vaporization of less refractory elements when mixing dissimilar metals. Overall, this work contributes to the development of a general methodology for the design, implementation and analysis of multi-material additive manufacturing combining dissimilar metals.; La fabrication additive multi-métallique par projection laser offre de nouvelles opportunités pour la création de composants de haute performance combinant des métaux aux propriétés différentes. Des obstacles limitent cependant la liberté de fabrication, comme l'existence d'incompatibilités entre certains couples de métaux, telles que l'apparition de phases intermétalliques fragiles ou encore la surchauffe des métaux moins réfractaires. Le contrôle du procédé est de plus rendu complexe en raison des nombreux phénomènes en jeu et des variations de la composition au cours de la fabrication. Dans ce travail, des revêtements combinant des métaux incompatibles ont été réalisés par projection laser, grâce à l'utilisation de métaux intermédiaires choisis à l'aide de la thermodynamique des phases à l'équilibre. L'analyse de premières fabrications a permis de révéler l'importance du taux de refusion du bain avec la sous-couche, qui permet de générer un gradient de composition et d'éviter l'apparition de défauts à l'interface entre deux métaux dissimilaires. Un revêtement de W sur Cu, d'intérêt pour la réalisation de dissipateurs thermiques en environnement extrême, a finalement pu être obtenu grâce à l'insertion d'une succession de métaux miscibles entre les deux, ainsi que de gradients de composition à travers les couches. Ces gradients ont notamment permis l'augmentation progressive des températures des bains de fusion du Cu jusqu'au W. Des outils théoriques ont été développés et utilisés pour mieux comprendre l'impact des paramètres et l'évolution de phénomènes clés durant ces fabrications multi-matériaux complexes. Un modèle de simulation numérique à l'échelle du bain de fusion a notamment été construit, prenant en compte les phénomènes de conduction, de déformation et de dynamique du liquide, de vaporisation, ainsi que de mélange des éléments. Les analyses expérimentales et théoriques des différents dépôts ont permis de mettre en lumière l'importance de la température de fusion du bain et de la puissance sur la présence de particules réfractaires infondues, l'influence de la vitesse de balayage sur la dissolution des particules, et l'évolution de la vaporisation préférentielle d'éléments peu réfractaires pour des mélanges entre métaux dissimilaires. Ce travail contribue globalement à la construction d'une méthodologie générale pour la conception, la réalisation et l'analyse de fabrication additive multi-matériaux combinant des métaux dissimilaires.

International audience; The precipitation of strontium in highly concentrated nitric acid is often used in standard radiochemical methods for $^90$ Sr separation. In this work, the description of Sr behavior in such conditions was studied in the point of speciation simulation. Standard speciation method based on Phreeqc software was considered but two problems underlined the limits of this approach to study this process: inappropriate ionic strength correction model (for I>10 M) and the particular dissociation of nitric acid. To overcome these issues, a multipurpose-fitting routine, Minuit, was used to fit chemical model parameters. A polynomial expression was also added to the model in order to take into account nitric acid dissociation. This alternative was proved successful to calculate the Sr precipitate in highly concentrated nitric acid. Comparison was made with the results obtained with Design of Experiment methodology.

This document presents the thermochemical data, i.e. constants and functions, that areincluded in the database PRODATA, which is developed to answer the needs of ORANOMining in terms of exploration, exploitation, and remediation of uranium mining facilities. Thereactions for complexation, dissolution-precipitation and gas solubility can be exported in threedatabase files that can be used by either software packages PHREEQC, CHESS, andGeochemist’s WorkBench (GWB). The PRODATA database includes data for uranium andradium, and all elements that are necessary to model their comportment in the different contextsfor a total of 38 elements. The data selection is based on CODATA and NEA-OECD selections.The coherency and traceability are checked whenever possible. The ionic strength correction isdone through either the Davies equation or the specific ion interaction theory (SIT). Applicationof the database files is proposed for a solution that is containing the 38 elements included inPRODATA. Pourbaix diagrams at varying O2(g) fugacity, and speciations at atmospheric O2(g)and 1 atm H2(g), are proposed to exemplify the performance of the database.; Ce document présente les données thermochimiques, constants et fonctions, inclusesdans la base de données PRODATA, développée pour répondre aux besoins d’ORANO Miningen terme d’exploration, d’exploitation et de remédiation des activités minières pour l’uranium.Les réactions de complexation, dissolution-précipitation de phases solides et de gaz peuvent êtreexportées sous forme de fichiers qui peuvent être utilisés par chacun des trois logicielsPHREEQC, CHESS, et Geochemist’s WorkBench (GWB). La base PRODATA inclut lesdonnées pour l’uranium et le radium, ainsi que pour les éléments nécessaires à la simulation deleur comportement dans différents contextes pour un total de 38 éléments. La sélection desdonnées est fondée sur celles de CODATA et de la base de l’OCDE-AEN. La cohérence et latraçabilité sont vérifiées autant que possible. La correction de force ionique est faite soit parl’équation de Davies, soit par la théorie de l’interaction spécifique (SIT). Des applications desfichiers d’extraction sont proposées pour des solutions contenant les 38 éléments inclus dansPRODATA. Des diagrammes de Pourbaix en fonction de la pression partielle d’O2(g), et desdiagrammes de spéciations à pression atmosphérique d’O2(g) et à 1 atm d’H2(g) sont proposésafin de tester les performances de la base de données.

Ecole d'été; International audience

The formation constants and specific ion interaction coefficients of MgUO2(CO3)32− complex were determined in 0.1 to 1.0 mol kgw−1 NaCl and 0.10 to 2.21 mol kgw−1 NaClO4 media in the framework of the specific ion interaction theory (SIT), by time-resolved laser-induced luminescence spectroscopy. The upper limits of ionic strength were chosen in order to limit luminescence quenching effects generated by high concentrations of Cl− and ClO4− already observed during our earlier studies on CanUO2(CO3)3(4−2n)− complexes (Shang & Reiller, Dalton Trans., 49, 466; Shang et al., Dalton Trans., 49, 15443). The cumulative formation constant determined is , and the specific ion interaction coefficients are e(MgUO2(CO3)32−, Na+) = 0.19 ± 0.11 kgw mol−1 in NaClO4 and e(MgUO2(CO3)32−, Na+) = 0.09 ± 0.16 kgw mol−1 in NaCl. Two gratings of 300 and 1800 lines per mm were used to acquire MgUO2(CO3)32− luminescence spectra, where the high-resolution 1800 lines per mm grating detected slight spectral shifts for the principal luminescent bands relative to CanUO2(CO3)3(4−2n)−. The applications of the consistent set of thermodynamic constants and e values for MnUO2(CO3)3(4−2n)− (M = Mg and Ca) were examined in different geochemical contexts, where Mg over Ca concentration ratio varies to help defining the relative importance of these species.

International audience; The impact of the contamination of living organisms by actinide elements has been a constant subject of attention since the 1950s. But to date still little is understood. Ferritin is the major storage and regulation protein of iron in many organisms, it consists of a protein ring and a ferrihydric core at the center. This work sheds light on the interactions of early actinides (Th, Pu) at oxidation state +IV with ferritin and its ability to store those elements at physiological pH compared to Fe. The Ferritin - thorium load curve suggests that Th(IV) saturates the protein (2840 Th atoms per ferritin) in a similar way that Fe does on the protein ring. Complementary spectroscopic techniques (Spectrophotometry, Infrared Spectroscopy and X-ray Absorption Spectroscopy) were combined with Molecular Dynamics to provide a structural model of the interaction of Th(IV) and Pu(IV) with ferritin. Comparison of spectroscopic data together with MD calculations suggests that Th(IV) and Pu(IV) are complexed mainly on the protein ring and not on the ferrihydric core. Indeed from XAS data, there is no evidence of Fe neighbors in the Th and Pu environments. On the other hand, carboxylates from amino acids of the protein ring and a possible additional carbonate anion are shaping the cation coordination spheres. This thorough description from a molecular view point of Th(IV) and Pu(IV) interaction with ferritin, an essential iron storage protein, is a cornerstone in comprehensive nuclear toxicology.

International audience

International audience; Le Laboratoire de développement Analytique Nucléaire Isotopique et Elémentaire (LANIE) du Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA) Paris-Saclay est spécialisé dans l'analyse de haute précision d'échantillons de combustibles nucléaires. La caractérisation des radionucléides présents après irradiation est d'une importance majeure pour la validation des codes de neutronique ou l'accès aux données nucléaires de base. Ce travail porte sur l'analyse d'échantillons irradiés dans un réacteur expérimental constitués de pastilles d'oxydes d'uranium dopées en 236U. Un des challenges analytiques sur ces échantillons précieux était la détermination du rapport $^{237}$Np/$^{238}$U dans une gamme comprise entre 10 et 100 µmol/mol. La méthode usuellement employée au laboratoire pour cette détermination est composée de plusieurs étapes : une mesure en ICPMS quadripolaire de la concentration du neptunium en utilisant la méthode d'étalonnage externe, une mesure de l'isotopie de l'uranium et une détermination de la concentration en uranium total par la méthode de dilution isotopique combinée à la spectrométrie de masse à thermo-ionisation. Cette méthode, longue à mettre en œuvre en raison notamment des étapes de séparations chimiques qu'elle implique, permet d'obtenir des incertitudes de l'ordre du pourcent. Cependant, pour certains échantillons, son désavantage majeur provient du phénomène de sensibilité en abondance relativement élevée en ICPMS Q, aux alentours de 2 ppm, qui empêche la détermination précise des rapports proches de 10 µmol/mol. Afin de pouvoir mesurer ces échantillons, une méthode innovante a donc été développée au LANIE pour permettre la mesure directe de ce rapport élémentaire sur un ICPMS multi-collecteur. Celle-ci utilise la large gamme dynamique de l'instrument en mesurant les isotopes de l'uranium sur cages de Faraday et le neptunium sur un compteur d'ions équipé en amont d'un filtre à retard de potentiel (RPQ) qui permet d'améliorer la sensibilité en abondance d'un facteur 100 et donc d'améliorer la précision des mesures sur les plus faibles rapports $^{237}$Np/$^{238}$U. Après une présentation détaillée de la méthode et des corrections associées, les résultats et leurs incertitudes obtenus seront présentés et seront comparés à la méthode usuelle à des fins de validation pour des rapports $^{237}$Np/$^{238}$U variant de 30 à 100 µmol/mol. Pour ces ordres de grandeur, les incertitudes sont de l'ordre du pourcent, ce qui est comparable à la méthode par ICPMS quadripolaire combiné à l'IDMS. En revanche, pour les rapports plus faibles, le rapport $^{237}$Np/$^{238}$U a été également déterminé avec des incertitudes de l'ordre du pourcent, ce qui n'aurait pas été possible par la méthode classique, élargissant la gamme de rapports $^{237}$Np/$^{238}$U mesurables. Il est important de noter que cette méthode innovante a aussi permis de réduire considérablement le temps de manipulation et par conséquence le temps d'exposition aux irradiations des expérimentateurs.

International audience; La carbonatation correspond à la réaction entre le Ca présent dans les matériaux cimentaires et le CO2 de l'atmosphère. Il s'agit d'un phénomène connu de longue date. Cependant, des études récentes montrent qu'au delà de la baisse du pH et la corrosion des armatures, elle entraine une micro-fissuration. Cette keynote détailles les mécanismes à l'origine de cette micro-fissuration ainsi que les conséquences sur les propriétés de transport dans les matériaux cimentaires.

International audience; During 2022, the global market for flat glass is estimated to exceed 100 billion metric tons. Moreover, the glass industry concerns many sectors of our daily lives (buildings, cars, dishes…) along with being integral parts of heat resistant technologies, protection panels (smart phones, plasma screens…), low-carbon energies (protection for solar panels) and satellites in outer space to name a few. Making them less reactive to Stress Corrosion Cracking (SCC), tougher (increasing their fracture toughness, K_c) and lighter, while maintaining other properties, is a fundamental issue plaguing glass scientists and researchers. This presentation will take a closer look on how the chemical composition of SiO2-B2O3-Na2O ternary glass systems alters the physical, mechanical and fracture properties of these systems. These changes lead to mesoscale changes as revealed by a novel parameter coined the depolymerization index. This parameter reveals surprising trends with the stress corrosion cracking behavior in Region I. The presentation will focus on stress corrosion cracking and how it varies with chemical composition and the depolymerization index.

International audience; As a caracteristic fission product with a half-life of 28.8 years, Sr-90 must be quantified in nuclear waste. Prior to its nuclear measurement, it is necessary to separate it from its matrix and interferents with radiochemical method. The extraction chromatographic resin, Sr-resin®, developed by Eichrom in the 1990s is widely applied. Its efficiency has been demonstrated for a wide range of samples even if pre-treatments are necessary depending on the nature of the sample. For nuclear waste, difficulties can be encountered especially with samples with high Pu content. A precipitation with ammonia can be used but this can lead to a Sr loss depending on the experimental conditions (ex: digestion step with HF acid or not) and interferents present. In this presentation, the robustness of an alternative pre-treatment using TRU-resin® will be highlighted. It has been proven to be efficient on all the nuclear waste samples investigated in the study, such as effluent, sludge, resin and concrete, even if they contain high Pu amount. Moreover, in this method, a plastic scintillation resin for Sr-90, PS-resin, developed by Bàgan et al., has been tested for nuclear waste samples. The advantages of this new resin is to reduce time of separation by eliminating elution step but mainly to avoid the use of scintillation cocktails. Due to their high toxicity, they are concerned by the REACH regulation and their implementation will become complicated in a near future. The PS-resin could be a suitable alternative for Sr-90 measurement by scintillation counting.

International audience; The irradiation-induced defects in stainless steel internal components of pressurized water reactors com- bined with hydrogen uptake during the oxidation process could be a key parameter in the mechanism for Irradiation-Assisted Stress Corrosion Cracking (IASCC). A heat-treated 316 L SS containing a low amount of defects was Fe 3 + ions-implanted; irradiation-induced defects types and depth distributions were charac- terized by Transmission electron microscopy (TEM). Deuterium was then inserted in the specimens either by cathodic charging or by sample exposure to deuterated primary water. Secondary Ions Mass Spectrom- etry –SIMS –permitted to access the deuterium distribution at the implanted stainless steel surface. A finite difference numerical solver accounting for hydrogen diffusion/trapping coupling was used to simu- late the hydrogen transport in the implanted material, taken into consideration the specific heterogeneous character of the irradiation-induced defects distribution in matter. Taking as input data the experimen- tal defects distribution associated with Frank loops or voids, the main trapping sites for hydrogen were assigned to voids, not Frank loops. Such numerical approach was able to deal accurately with the prob- lem of hydrogen transport in a heterogeneous material as well as to differentiate two potential trap sites contributions to the experimental deuterium distribution. In addition, according to results obtained after primary water exposure, trapping at voids was still effective at 320 °C, signature of a high binding energy of hydrogen in voids.

International audience; A new method has been developed to image surface contamination on-site by short range radiation emitters (such as alpha or beta particle emitters). The measurement is performed in direct contact with the contaminated surface and uses a solid scintillator coupled with Silicon Photomultiplier (SiPM) arrays. The signal readout is processed using a dedicated electronic. The experimental setup used to acquire the data, as well as the analysis procedure, are described and the results are discussed with regard to dismantling requirements. Image reconstruction is investigated using various algorithms. A proof of principle is performed in laboratory using a simple prototype and multiple alpha and beta sources. All the common beta and alpha emitters are detected (including tritium) and tests on gamma radiation are also performed. The minimum detectable activity is estimated to be 0.4 Bq/cm² for beta radiations (14C) and 0.3 Bq/cm² for alpha radiations (239Pu). Finally, promising discrimination capability of the prototype is highlighted.

The aim of this work was to develop an analytical method in order to determine at physiological pH the affinity scale of biomimetic peptides for uranyl (UO22+), and their selectivity towards this element in the presence of endogenous cations (Ca2+, Cu2+, Zn2+), in a single step. This approach is essential to better understand the mechanisms of toxicity of UO22+ at the molecular level and to develop selective decorporating agents by chelation. The analytical strategy was based on the implementation of the simultaneous coupling of hydrophilic interaction chromatography (HILIC) with molecular (ESI-MS) and elemental (ICP-MS) mass spectrometry. An essential step has been devoted to the development of the separation of multiphosphorylated peptides including their positional isomers, UO22+ complexes formed with peptides of different structure and degrees of phosphorylation, and metal complexes formed with the tetraphosphorylated peptide. It is the first separations ever described using HILIC. Dedicated methods have been developed online for the structural characterization by ESI-MS of peptide complexes resulting from the separation and simultaneous quantification by ICP-MS of the elements in these complexes. Thus, the affinity scale of the peptides for UO22+ was determined and made it possible to demonstrate the effect of the position of phosphorylated residues in the peptide backbone and of the structure of the peptides on their affinity for UO22+. Following the same approach, the selectivity of the tetraphosphorylated peptide towards UO22+ has been demonstrated in the presence of endogenous cations, potential competitors in biological media., L'objectif de ce travail a consisté à développer une méthode analytique pour déterminer à pH physiologique l'échelle d'affinité de peptides biomimétiques pour l'uranyle (UO22+), et leur sélectivité envers cet élément en présence de cations endogènes (Ca2+, Cu2+, Zn2+) en une étape unique. Cette approche est essentielle pour mieux comprendre les mécanismes de toxicité de l’UO22+ au niveau moléculaire et pour développer des agents décorporants sélectifs par chélation. La stratégie analytique a reposé sur la mise en œuvre du couplage simultané de la chromatographie d’interaction hydrophile (HILIC) avec les spectrométries de masse moléculaire (ESI-MS) et élémentaire (ICP-MS). Une étape essentielle a été consacrée à la mise au point de la séparation des peptides multiphosphorylés incluant leurs isomères de position, des complexes d‘UO22+ formés avec les peptides de différente structure et degrés de phosphorylation, et des complexes des métaux avec le peptide tétraphosphorylé. Il s’agit des premières séparations jamais décrites par HILIC. Des méthodes dédiées ont été développées en ligne pour la caractérisation structurale par ESI-MS des complexes peptidiques issus de la séparation et la quantification simultanée par ICP-MS des éléments dans ces complexes. Ainsi, une échelle d'affinité des peptides pour l’UO22+ a été déterminée et a permis de mettre en évidence l'effet de la position des résidus phosphorylés dans le squelette peptidique et de la structure des peptides sur leur affinité pour l’UO22+. Suivant la même approche, la sélectivité du peptide tétraphosphorylé envers l'UO22+ a été démontrée en présence de cations endogènes, compétiteurs potentiels dans les milieux biologiques.

International audience; La matrice d'un échantillon est définie par l'IUPAC (International Union of Pure and Applied Chemistry) comme les composants de l'échantillon autres que l'analyte. Et l'effet de matrice d'une technique analytique désignent alors l'effet combiné de tous les composants autres que l'analyte sur la mesure de sa quantité. Chose que l'on peut visualiser, par exemple, sur des droites d'étalonnage de pente différente pour différentes matrices. En LIBS, ces effets se traduisent physiquement par une interaction laser-surface et laser-plasma dépendant de la nature du matériau analysé, et induisant des variations de masse ablatée, de température et de densité électroniques d'un échantillon à un autre. Sous l'hypothèse de l'équilibre thermodynamique local, la caractérisation de ces trois paramètres permet donc en principe de s'affranchir de ces effets, et cette approche est à la base des méthodes de quantification sans étalonnage .Contrairement à la masse ablatée qui peut être mesurée en observant les cratères, la température et la densité électroniques sont généralement déterminées par des méthodes spectroscopiques. Les plus répandues sont, pour Te, le graphe de Boltzmann, pour Ne, l'équation de Saha-Boltzmann ou l'élargissement Stark. Ces méthodes reposent sur la mesure de certaines raies bien choisies. Les critères de choix sont connus (énergie d'excitation, absence d'interférence, d'auto-absorption…) mais pas toujours simples à mettre en pratique. Cependant, les négliger peut conduire à des biais significatifs sur le plan analytique. De plus, le choix qui en résulte dépend justement de la matrice. C'est pourquoi, alors que les effets de matrice sont très souvent cités dans la littérature sur la LIBS, il est très difficile de trouver des données comparables de température et densité électronique d'une matrice à l'autre.Cette présentation abordera trois questions, illustrées dans le cas des métaux. 1. Pourquoi s'attacher à caractériser précisément le plasma d'ablation laser ? 2. Quels sont les écueils à éviter ? 3. Quelle est l'étendue réelle des effets de matrice ? Pour y répondre, nous introduirons la méthode standardisée de caractérisation du plasma que nous avons mise au point, méthode basée sur un dépôt d'électrolyte en surface de l'échantillon

International audience; The ternary Cr-Mo-Ti system is a constitutive alloying system for steels and titanium alloys. Ferritic alloys with Cr, Mo and Ti contents have been studied, achieving good mechanical properties, corrosion resistance and microstructural stability to 550°C. Beta titanium alloys are nowadays largely employed in biomedical applications, and aviation and aerospace industries. The system is also interesting for the development of new high-entropy alloys with a body-centered cubic structure. The Calphad method is a useful tool to explore and study all these alloy systems.Nevertheless, the experimental data about this ternary system remains scarce and no recent data was published. Thermodynamical assessments were carried out by Lee et al.[1] and recently by Hu et al. [2]. The first assessment was based on the solid phase boundaries in the Ti-rich region published by Elliot et al. [3]. In the respective re-assessment, they added with a low weight data from Grum-Grizhimailo and Gromova [4].Therefore, we will study the Laves phase extension in the ternary Cr-Mo-Ti system. DFT calculation will be used in order to obtain the enthalpy of formation of the metastable end-members. Cumulate data will be evaluated and used to re-assess the ternary system.References[1] J. Y. Lee, J. H. Kim, et H. M. Lee, « Effect of Mo and Nb on the phase equilibrium of the Ti-Cr-V ternary system in the non-burning β-Ti alloy region », J. Alloys Compd., vol. 297, n 1, p. 231-239, févr. 2000, doi: 10.1016/S0925-8388(99)00557-5.[2] B. Hu, J. Wang, C. Wang, Y. Du, et J. Zhu, « CALPHAD-type thermodynamic assessment of the Ti-Mo-Cr-V quaternary system », Calphad, vol. 55, p. 103-112, déc. 2016, doi: 10.1016/j.calphad.2016.08.003.[3] R. Elliott, B. Levinger, et W. Rostoker, « System Titanium-Chromium-Molybdenum », Trans. Am. Inst. Min. Metall. Eng., vol. 197, n 11, p. 1544-1548, 1953.[4] N. B. Grum-Grzhimaylo et V. G. Gromova, « Phase diagram of the Ti-Cr-Mo-system at 1200, 900 and 600°C », Akad Nauk SSSR, vol. 7, p. 35-42, 1962.

Slow strain rate tensile tests (SSRT) and oxidation tests were performed on a 316L stainless steel in Pressurized Water Reactors (PWR) primary water. The tests were performed under transient conditions (hydrogenated-oxygenated water cycling). The present results indicate stress corrosion cracking (SCC) susceptibility dependence of SSRT samples on cumulated time exposure to hydrogenated water. After short-time exposure under hydrogenated conditions, most of the crack-like defects are shorter than 2 µm and crack mean depth is around 5 µm. In contrast, after long-time exposure, most SCC crack-like defects are longer than 2 µm and the crack mean depth increases linearly with the cumulated time spent under hydrogenated conditions.

International audience; L’analyse isotopique de solide est utilisée dans différents domaines tels que la géochimie,l’archéologie, la biochimie et les énergies. Les approches classiques généralement mises en œuvrecomprennent des étapes préalables de préparation et de conditionnement des échantillons. Cesétapes peuvent induire des incertitudes sur le résultat obtenu et rallongent les délais d’analyse. C’estpourquoi, les méthodes d’analyse directe sont développées avec parmi elles l’ablation laser. Cettetechnique permet la détermination de la composition d’un échantillon solide grâce à la création d’unplasma et peut aisément être couplée à d’autres méthodes de caractérisation.Cette présentation met l’accent sur les méthodes spectroscopiques couplées à l’ablation laser pourl’analyse isotopique de solides. Un intérêt particulier est porté aux techniques permettant l’analyse àpression atmosphérique donc potentiellement employables en ligne ou utilisables sur le terrain tellesque la LIBS (Laser Induced Breakdown Spectroscopy), la LAMIS (Laser Ablation Molecular IsotopicSpectrometry) et la LIBRIS (Laser-Induced Breakdown self-Reversal Isotopic Spectrometry).Cependant, sous pression ambiante le décalage spectral entre les raies de deux isotopes estgénéralement faible par rapport à l’élargissement spectral induit par le plasma. Les techniques LAMISet LIBRIS visent à contourner cette limitation, en mesurant respectivement l’émission moléculaireplutôt que l’émission atomique, ou la longueur d’onde du creux d’absorption d’une raie renversée.La faisabilité de la technique LIBRIS a été montrée dans le cas de l’analyse isotopique du lithium. Undes axes de recherche actuel sur la technique réside dans son développement pour l’analyse et lacompréhension à différentes échelles des mécanismes de déplacement du lithium dans lesélectrolytes solides, entrant dans la composition des batteries de quatrième génération. L’une des méthodes employées pour cela est le traçage isotopique du lithium. Pour ce faire, un développement instrumental et paramétrique est mis en œuvre afin de quantifier le rapport isotopique du lithium dans des matériaux de batteries à l’échelle micrométrique par la technique LIBRIS, en complément des techniques utilisées aujourd’hui telles que la RMN ou la TOF-SIMS. L’objectif à terme est dedévelopper un système d’analyse isotopique du lithium à pression atmosphérique, rapide et à hauterésolution spatiale utilisant la technologie LIBRIS.

International audience; Sr-90 is, with Cs-137, one of the main radioactive fission product occurring in nuclear power plants in terms of abundance proportion. This radionuclide can thus be present in significant amount in spent nuclear fuel or in radioactive waste from nuclear reactors. In the context of the increase of the number of decommissioning and dismantling operations in nuclear facilities, a reliable and rapid determination of Sr-90 is of prime interest for the characterization of all types of radioactive waste (effluents, ion exchange resins, concretes, sludges…). Sr-90 has a half-life of 28.8 years and emits beta particles of relatively high energy (maximum energy of 546 keV). It disintegrates into Y-90 which is also a pure β-emitter (maximum energy of 2280 keV) with a half-life of 2.67 days. Sr-90 needs to be purified from interfering analytes through selective radiochemical separations before any reliable detection. It can be directly measured or indirectly evaluated from Y-90 growth. Both radionuclides are often measured by gas flow proportional counting and liquid scintillation counting (LSC). The separation yield is determined from stable strontium carrier by inductively coupled plasma (ICP) techniques or gravimetry. Two main radiochemical methods for Sr-90 determination are generally implemented1: Sr precipitation in highly concentrated nitric acid or extraction chromatography on Sr-resin®. Both procedures are robust and selective to provide accurate measurement of Sr-90 in radioactive samples. However, they involve the use of harmful chemical substances, respectively fuming nitric acid and liquid scintillation cocktails for LSC detection. Both reagents are in the scope of European REACH regulation and have to be removed from use as much as possible. The purpose of this presentation is to demonstrate the feasibility of accurate Sr-90 measurement in radioactive waste without the use of toxic chemical reagents. The presentation will first focus on the optimization of a precipitation method by applying a design of experiments methodology2. The implemented strategy induces the replacement of fuming nitric acid (above 82 % concentration) by concentrated nitric acid (69 % concentration) while maintaining high separation yield and improving the selectivity towards calcium which is the main interfering analyte of this method. Secondly, the presentation will deal with the implementation of plastic scintillation resin3 (noted PS resin) to avoid the use of liquid scintillation cocktails. A method based on a PS resin selective towards Sr was optimized so as to achieve high decontamination factors towards interfering radionuclides, in particular Pu-241 β-emitter. For both developed purification methods, the validation step is performed by comparing the results obtained on different types of radioactive waste (effluents, concretes and sludges) with the ones obtained with the reference method of the laboratory based on fuming nitric acid. The selectivity of both methods is also evaluated by checking Y-90 growth (see Figure 1).

International audience; Molten corium is considered to form in a severe accident at the Fukushima Daiichi Nuclear Power Station (FDNPS). Investigation of the primary containment vessel (PCV) inside at the FDNPS showed that a significant amount of the molten corium reached the bottom of the pedestal region. The molten corium and concrete likely caused a complex interaction called Molten Corium Concrete Interaction (MCCI). Then, ex-vessel debris was formed after the solidification of the MCCI products and accumulated in the pedestal region. The solidification hysteresis of ex-vessel debris significantly influences its properties. Although many studies on the MCCI behavior were previously carried out, the solidification path analysis was hardly attempted. We performed a thermodynamic analysis using the TAF-ID database to infer the solidification path of U-Zr-Al-Ca-Si-O molten corium, which was chosen for a prototypic system of ex-vessel debris. The solidification path for the CaO-rich sim-corium showed the following sequence: (i) melting as a single liquid phase at temperatures higher than 2430 K, (ii) selective solidification of the oxide-rich corium mainly consisted of fuel materials, and (iii) solidification of the remaining materials as a silicate matrix. In contrast, the solidification path for the SiO2-rich corium indicated that (i) formation of liquid miscibility gap above 2200 K, (ii) individual precipitation of solid phases in each liquid phase. Identified features of these solidification paths were in good agreement with the experimental data for the solidified sim-corium.

Under irradiation, the formation of fission products in the (U,Pu)O2 fuel with time has a substantial effect on its chemistry. In particular, migration of the most volatile fission products (Cs, Te, I, Mo) from the center to the periphery of the fuel pellet is induced by the large radial thermal gradient. To predict the thermodynamic properties of the irradiated fuel, thermodynamic modeling of the complex multi-component (Cs-I-Te-Mo)–(U-Pu)–O system is performed using the CALPHAD method. In this work, the thermodynamic assessment of the U–Te sub-system is performed. The literature review reveals a lack of experimental data as well as scattering and inconsistency of some of the data. In particular, no thermodynamic data exist on the liquid. From this review, input thermodynamic and phase diagram data are carefully selected. The Gibbs energy functions are then adjusted by fitting these data. An overall good agreement is obtained with all the selected data except for the enthalpy of formation for UTe which is underestimated by 13% by our model. This could be due to an inconsistency between the enthalpy of formation and vapor pressure data. In a second step, the uncertainties on the thermodynamic parameters and their propagation on the calculated thermodynamic and phase diagram data are estimated using a Bayesian approach. The analysis shows that there are too many parameters (22) for too few data points (120 points). The uncertainties are thus large on some of the calculated data. Moreover the inconsistency of some of the data and the lack of thermodynamic data for the liquid makes the model uncertain. New experimental data such as heat capacity, enthalpy of formation for the compounds, and chemical potentials or activities for the liquid phase would improve the reliability of our model. Measurements of phase diagram data in the U–UTe2 region are also required. However this work provides the first detailed uncertainty analysis of the U–Te CALPHAD model. Moreover our approach, contrary to other Bayesian methods, provides an analytical posterior probability distribution and analytical credible intervals for the calculated thermodynamic quantities. It also speeds up the simulation of the uncertainty estimations on the phase diagram.

International audience; In Laser Powder Bed Fusion (L-PBF) of metallic materials, costs and material yield strongly depend on the ability to reuse powder efficiently, as a significant amount is not solidified as part by the laser beam. However, some of the powder is nevertheless exposed to high temperatures during the manufacturing process resulting in an alteration of the feedstock properties if reused. Therefore, there is a need to study and understand powder degradation during the L-PBF process and its direct effects on the printed parts. In this study, gas-atomized 316L stainless steel powder was used, recovered, sieved and reused up to 15 times in order to produce successive L-PBF prints without adding any virgin powder. Both recycled powders and elaborated parts were fully characterized at each iteration to investigate changes in particles (morphology, rheology, microstructure and chemical composition) as well as printed parts (porosity, microstructure, microhardness and tensile properties). Recycled powder exhibited larger particle size and an improved flowability. A gradual increase in oxygen content was observed, along with the presence of colored and oxidized particles, as well as magnetic particles. Parts density slightly decreased with powder reuse and their microstructure featured more numerous and finer grains along reuse cycles. On the other hand, no significant difference was found on the microhardness and the tensile properties of the L-PBF components.

International audience; Molecular dynamics simulations of microstructural evolution under irradiation of (U,Pu)O2 solid solutions have been carried out with the Frenkel pair accumulation method with two empirical potentials. Simulated X-Ray diffraction patterns have been systematically generated along the irradiation pathway from the computed atomistic configurations. Description of the X-Ray diffraction patterns with increasing irradiation dose is discussed. Attempt to correlate the features of the X-Ray diffraction peaks with the microstructural evolution is also provided. Special attention is dedicated to the swelling effect.

International audience; Precipitation of radial hydrides in zirconium-based cladding concomitant with the cooling of spent nuclear fuel can potentially compromise cladding integrity during its subsequent handling and transportation. Complementary experimental programs on unirradiated and irradiated cladding were performed to assess the conditions leading to the precipitation of radial hydrides and their detrimental effects on mechanical properties. This sequel paper to a previous publication [1] presents results for cold-worked, stress-relieved Zircaloy-4 and ZirloTM cladding used in pressurized water reactors. Cold-worked, stress-relieved Zircaloy-4 and ZirloTM behave very similarly, although irradiated ZirloTM was found to be slightly more prone to hydride reorientation (HRO) than irradiated Zircaloy-4. No distinct irradiation-induced effect on the HRO critical stress was detected. Depending on the initial high temperature that varied from 350 to 450 °C, HRO may cause a ductile-to-brittle transition when the cladding hoop stress, created by internal pressurization of the specimen, ranges from 70 MPa to 120 MPa. Cracking of the oxide layer caused local preferential radial hydride precipitation. The impact of the decreasing temperature and internal pressure during cool-down was also investigated: it has been found that samples undergoing decreasing temperature and pressure cycles are less prone to hydride reorientation.

International audience; Water radiolysis is a major concern for the conditioning of radioactive waste in cement materials. Synthetic calcium silicate hydrate (CSH), the main hydrates of concrete, were synthesized with different C/S ratios and relative humidities. The samples were irradiated under γ- and electron beam irradiation. The radiolytic hydrogen production has been quantified and the radiation induced defect produced at low temperature characterized by electron paramagnetic resonance. The results show that the H production and defect production are only marginally sensitive to the relative humidity

Costs and resource efficiency of laser powder bed fusion (L-PBF) are highly dependent on the ability to produce high quality parts with recycled powders. There is a need to control the quality of the material, which has a direct influence on the performance of the printed parts. Particles oxidation is known to increase with repeated powder recycling and can be a good indicator of powder degradation. The characterization of powders oxygen content is time-consuming, expensive, and usually carried out ex-situ on non-reusable quantities that are not necessarily representative of the entire feedstock. In this work, a new methodology was developed to measure the oxygen content of powders by in-line scanning of powder bed layers. The method takes advantage of stainless steel particles coloration related to their oxidation level in order to assess their oxygen concentration as a function of Red, Green and Blue channel values of image scans. The calibration procedure once carried out, several recycled powder samples were scanned and analyzed, and the determined powder beds oxygen contents were demonstrated to be in accordance with ex-situ measurements. The results highlight a new opportunity to monitor and evaluate powder degradation in-situ on powder bed layers by image analysis.

International audience; Several proteins have been identified in the past decades as targets of uranyl (UO$_2$$^{2+}$) in vivo. However, the molecular interactions responsible for this affinity are still poorly known which requires the identification of the UO$_2$$^{2+}$ coordination sites in these proteins. Biomimetic peptides are efficient chemical tools to characterize the nature of these sites. The aim of this work is to develop a dedicated analytical method to determine the affinity of biomimetic synthetic multi-phosphorylated peptides for UO$_2$$^{2+}$ and to evaluate the effect of several structural parameters of these peptides on this affinity at physiological pH. The analytical strategy was based on the implementation of the simultaneous coupling of hydrophilic interaction chromatography (HILIC) with electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS). An essential step had been devoted to the definition of the best separation conditions of UO$_2$$^{2+}$ complexes formed with di-phosphorylated peptide isomers and also with peptides of different structure and degrees of phosphorylation. We developed in this work the first separations of several sets of UO$_2$$^{2+}$ complexes by HILIC ever reported in the literature. A dedicated method had then been developed for identifying the separated peptide complexes online by ESI-MS and simultaneously quantifying them by ICP-MS, based on uranium quantification using external calibration. Thus, the affinity of the peptides for UO$_2$$^{2+}$ was determined and made it possible to demonstrate that (i) the increasing number of pSer promotes the affinity of the peptides for UO22+, (ii) the position of phosphorylated residues (pSer) in the peptide backbone has very low impact on this affinity (iii) and finally the cyclic structure of the peptide favors the UO$_2$$^{2+}$ complexation in comparison with the linear structure. The results obtained using this approach are essential to better understand the mechanisms of toxicity of UO$_2$$^{2+}$ at the molecular level and to further develop selective decorporating agents by chelation

International audience; It is essential to model the behavior of the interfaces between steel reinforcement and concrete in order to understand the stress transfer between these two components in reinforced concrete structures, which strongly affects the initiation and propagation of cracks. The macroscopic interface models commonly used in structure simulations are functions of various parameters whose physical significance is sometimes not very clear and identification is difficult. That is why the mesoscopic scale is investigated here to improve the understanding of the behavior of the interface when considering both ribbed and smooth bars. A 3D interface model is proposed and implemented to this aim. It takes into account friction and damage by combining a modified cohesive zone model (CZM) based on Tvergaard's approach, and a frictional model in the damaged part of the interface. In this contribution, three dimensional numerical reinforced concrete samples, representing pullout tests, are generated with a detailed geometry of the steel bar. Then, pull-out numerical simulations are performed on the generated samples using an isotropic damage approach with regularization in tension and in compression in order to describe cracking in concrete. The interface model is described and its functionality is verified on a pullout test with smooth bar. The overall response is studied in terms of damage and distribution of the principle stresses near the steel bar, and the applied force versus free end displacements curves which are compared to available experimental data. Finally, a good agreement between simulations and experimental results when using smooth and ribbed bars is obtained.

Euratom Research and Training in 2022: the Awards collection; International audience; CHICADE (CHimie CAractérisation DEchets – Chemistry CAracterization Wastes) is one of the nuclear facilities of the Energy Division of the French Alternative Energies and Atomic Energy Commission (CEA/DES). The CEA/DES is responsible for structuring and piloting the research programmes on energy at CEA. It involves its own institutes of research and those of other divisions. CHICADE is part of the Directorate for Nuclear Dismantling, Services and Waste Management. The Laboratory of Expertise and Destructive characterization is set up in the Basic Nuclear Facility – N° 156 called “CHICADE” where heavy equipment is used. The laboratory brings together both skills and means of characterization, using destructive methods on nuclear waste packages. It also carries out measurements on the whole waste package (gas release measurements, leaching tests). After a short presentation of the CEA and the Cadarache Centre, this publication aims to present the CHICADE facility and present the types of expertise on nuclear waste that are conducted there, i.e., measurement of the diffusion coefficient, inventories, leaching test, permeability measurement, gas measurements, radiochemistry, imaging. In conclusion, CHICADE is a nuclear facility with unique equipment, allowing exhaustive expertise to be carried out in a single location, benefiting from cross and complementary methods.