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National audience; Le projet Agro-éco-Syst’Nvisait à doter les conseillers agricoles, formateurs et enseignants de méthodes, outils et références leur permettant d’identifier et de concevoir des systèmes de culture à faibles pertes azotées vers l’environnement. A cette fin, une méthode de diagnostic des pertes d’azote vers l’eau (par lixiviation) et vers l’air (par volatilisation), utilisant l’outil Syst’N®, a été élaborée et formalisée. Elle a ensuite été utilisée pour évaluer et expliquer les performances azotées de plusieurs systèmes de culture dans des contextes pédoclimatiques variés.Quinze systèmes de culture ont ainsi été évalués et diagnostiqués. Leur analyse transversale a montré comment différentes combinaisons de pratiques dans un contexte donné conduisent à des performances variables en matière de pertes d’azote. Enfin, 21 cas-types ont été mis à disposition pour outiller les enseignants et conseillers sur le diagnostic des pertes d’azote, ressources mobilisables dans un éventail d’objectifs pédagogiques, de l’évaluation des pertes azotées à la reconception de systèmes de culture. Les systèmes simulés avec Syst’N®sont diffusés viala base de données Pertazote, mise à niveau au cours du projet

Among the different agronomic levers mobilised in organic farming (OF), the choice of variety is animportant factor in the design of arable farming systems. The ECoVAB project examined how to describeand evaluate a variety suitable for use in organic farming. The results confirm that the evaluation ofspecific traits is expected. This concerns especially the ability to compete with weeds (or companion cropfor intercropping), useful for all species, of interest beyond OF for agro-ecological transition. The workhas also shown that there is a continuum of varietal assessment between organic and conventionalfarming (CF), which varies according to the species, the criteria considered, the genotypes assessed andthe test conditions (intercropping, level of use of inputs, varied pedoclimates). It is therefore not necessaryto duplicate the networks in OF and CF, but rather to make them work together, with modalities in bothmanagement. Beyond the trials to be fostered, it appears that coordination between actors in the seedand development sectors is essential to optimise the orientation of varietal assessment, the disseminationof references and the production of high-quality seeds.; Parmi les différents leviers agronomiques mobilisés en agriculture biologique (AB), l’entrée variétale est un facteur important dans la conception des systèmes de grandes cultures. Le projet ECoVAB s’est interrogé sur comment décrire et évaluer une variété adaptée à une utilisation en AB. Les résultats confirment que l’évaluation de caractères spécifiques est attendue pour les variétés destinées à l’AB. Il s’agit en particulier de la compétitivité vis-à-vis des adventices (ou d’une plante compagne en cas d’association de cultures), pour toutes les espèces, d’intérêt au-delà de l’AB dans le cadre de la transition agroécologique. Les travaux ont montré par ailleurs qu’il existe un continuum de l’évaluation variétaleentre agricultures biologiques (AB) et agricultures conventionnelles (AC), variable selon les espèces, les critères considérés, les génotypes testés et les conditions d’essais (cultures associées, niveau d’utilisation d’intrants, pédoclimats variés). Aussi, il n’est pas nécessaire de doubler les réseaux en AB et en AC, mais plutôt les faire fonctionner ensemble, avec des modalités en AB et en AC, chacun pouvant mobiliser des résultats issus de l’autre. Au-delà des essais à développer, il apparait que la coordination entre acteurs des filières des semences et du développement est essentielle pour optimiser l’orientation de l’évaluation variétale, la diffusion des références et la production de semences de qualité

Dans sa conférence d’enseignement de la SOFCOT en 2001 sur la spondylolyse (SL) et le spondylolisthésis (SPL) lombosacré de l’enfant et de l’adolescent, Jouve a rappelé les bases historiques, anatomiques et pathogéniques de cette pathologie complexe. En 2015 dans une autre conférence d’enseignement sur ce thème, nous avons actualisé les données récentes de la littérature ayant trait aux rapports entre cette pathologie et l’équilibre sagittal global du rachis et proposer une mise au point sur les controverses encore importantes concernant les indications thérapeutiques des SPL surtout dans leur forme à grand déplacement. Le chapitre sur la SL n’était que très brièvement abordé. C’est donc ici l’occasion de faire le point sur la problématique de la SL dans sa survenue hypothétique post traumatique qui diffère de celle des SPL évolutifs à grand déplacement, souvent de forme dysplasique même s’il existe des formes faisant suite à une SL initiale, SPL appelés « spondylolithiques ».

National audience

International audience; During the irradiation of nuclear fuel in a light water reactor (LWR), fission products (FP) are created and retained in the fuel, modifying its microstructure and properties (thermal conductivity, creep behavior, etc.). In the case of failure of all the three containment barriers, as it could the case during a severe accident, FPs could be released from the fuel to the environment. The chemical nature of FP released from the fuel strongly depends on the scenario and the accident conditions involved (temperature, type of fuel, burn-up, oxygen potential, etc.). Moreover, chemical nature greatly affects FP behavior during their transport in the reactor and hence the source term. FP speciation in the fuel was studied in order to provide experimental data needed to support the speciation mechanisms currently proposed in the literature. Within the framework of the International Source Term Program, the VERDON-3 and-4 tests were devoted to high burn-up MOX fuel behavior and FP releases respectively under oxidizing and reducing conditions at very high temperature (up to 2570 K and 2800 K respectively). Qualitative and quantitative analyses on these fuel samples made it possible to obtain valuable information on fission product behavior in the fuel during the test as a function of the atmosphere. This presentation will provide a series of detailed characterizations including scanning electron microscopy (SEM) and optical microscopic (OM) observations, as well as electron probe microanalyses (EPMA) and Secondary Ion Mass Spectrometry (SIMS) of the VERDON-3 and -4 fuel samples before and after the test.

International audience

International audience; Thanks to its precision, its reproducibility and its stability, Electron Microprobe is a well suited technique for accurately analyzing nearly all chemical elements at concentration levels down to few 10’s ppm with a spatial resolution of about 1 µm, which is relevant to microstructures in a wide variety of materials and mineral specimens. For irradiated samples, EPMA is also one of the technique of choices and can support nuclear fuel development, control, metallurgical or glass analysis. It reveals fine compositional details and the distribution of main and trace elements across the surface of the sample.CAMECA leader in scientific instruments has been manufacturing Electron Microprobe (EPMA) since 1958 and will present its latest CAMECA shielded EPMA model, SKAPHIA released in 2016 for hotlab facilities. One example of the LECA/STAR shielded EPMA in hotlab handling nuclear fuel will be highlighted. In this example, the microstructure and chemical evolution of fuel pellets submitted to two different nuclear severe accident scenarii are shown. EPMA helped to highlight the impact of the atmosphere (i.e the oxygen potential) on the behavior of the fuel and fission products during these tests. These studies are of particular importance to evaluate and better predict the consequences of such an accident in term of contamination.

International audience; The development of realistic models for fission products behavior during a severe accident requires experimental data on fission products speciation into the fuel (as irradiated and during the transient) together with thermodynamic predictions. Due to the limitations in terms of experiments and characterization techniques available to study fission products speciation in nuclear irradiated fuels, simulant materials (SIMFUEL manufactured thanks to conventional process) are often used. However, these materials do not allow the study of volatile fission products because they are totally released during the sintering stage. In the case of SIMFUEL with implanted fission products surrogates, the chemical state and the corresponding evolution of the phases during the thermal sequence are not entirely representative of the real case. An innovative method to study volatile fission products speciation in SIMFUEL samples has thus been developed. Spark plasma sintering was used to synthesize dense SIMFUEL samples containing cesium in collaboration with the JRC-Karlsruhe within the frame of the GENTLE program. Thermodynamic calculations made using the TAF-ID v.6 associated with the FACTSage software enabled to determine the conditions in which to perform thermal treatments. In-temperature XAS experiments in conditions representative of a sevre accident are developed in collaboration with FAME-UHD beamline at the ESRF (Grenoble, France). Additional thermal treatments will also be performed to enable further characterizations (ceramography, SEM-EDX...).

International audience; In order to reduce the uncertainties concerning Source Term assessment under Light Water Reactor(LWR) severe accident conditions, 4 VERDON tests were recently performed. They have been defined in theframework of the International Source Term Program and carried out at CEA Cadarache, in the LECA-STARfacility. Among these 4 VERDON tests, VERDON-1 test was devoted to high burn-up UO$_2$ fuel behavior and FPrelease under H$_2$ reducing conditions at very high temperature.This test was performed with the Release Circuit, which is devoted to the precise characterization of the FP release,in terms of FP release kinetics and fission products (FPs) released fraction. The main components of the circuits area furnace heating the fuel sample, a filter trapping the emitted aerosols and gamma spectrometry detectors for online and post-test measurements. VERDON-1 test was conducted up to about 2600°C without reaching global fuelrelocation, allowing thereby post-test micro-analyses.After a brief description of the fuel sample nature and the experimental set-up, we present the progress of theexperimental sequence and the associated gamma spectrometry measurements. We then focus on the major resultsof the VERDON-1 tests regarding the fuel global behavior. These results are obtained by two complementarytechniques. First, the fuel sight gamma station can be used either on-line to detect fuel relocation or just after thetest, as a longitudinal bench, to get preliminary information on the global shape of the fuel sample inside thefurnace. Secondly, these information are completed by post-test examinations performed on the fuel sample afterextraction from the furnace. Complete qualitative and quantitative characterizations, including EPMA and SEManalysis, were performed for the first time at the CEA Cadarache on a sample that has been submitted to such severeaccident conditions. These results show an advanced state of sample degradation, with locally previously moltenareas, meaning that fuel global relocation was imminent by the end of thermal-hydraulic sequence. The relocationtemperature is compared to that of previous VERCORS tests and discussed regarding the atmosphere of the test andpossible UO$_2$-ZrO$_2$ interaction.