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Les questions du sens de l'École et de l'enseignement–apprentissage ont été posées en France lors de transformations fondamentales du système éducatif (massification et démocratisation scolaires, introduction des technologies de l'information et de la communication pour l'enseignement [TICE]), liées à des changements sociétaux profonds (évolutions socioéconomiques, émergence d'une culture juvénile). Elles concernent tant les élèves que l'ensemble des acteurs de l'éducation dont les repères ont été bousculés. Des problématiques ont pu émerger grâce à l'évolution des recherches sur les théories de l'action. Elles se sont intéressées à l'intentionnalité des acteurs comme à la finalité des actions situées et instrumentées. Nous nous interrogeons sur le rôle de la nouveauté, de l'innovation, comme une mise à l'épreuve du sens pour un sujet en rapport avec la question scolaire. Nous nous appuyons sur une revue de littérature pour aborder cette question en précisant ce que nous entendons par École, à partir du concept de forme scolaire. Nous proposons de l'articuler avec le concept de sens, dans le cadre d'une approche psychosociale en pensant le sens de l'École comme un système de significations (subjective, socio-anthropologique, axiologique, rationnelle). La fonction principale du sens est d'assurer la mobilisation du sujet, son maintien, et les conditions de sa cohérence. L'enjeu de notre recherche est de participer à la construction d'un modèle permettant d'accompagner le sujet vers la prise de conscience des éléments en jeu et des forces à l'œuvre. Il demande l'articulation avec d'autres disciplines permettant de le compléter et de l'affiner. The questions of the meaning of School and teaching–learning have been raised in France during fundamental transformations of the education system [school massification and democratization, introduction of information and communication technologies for education (ICTE)], linked to profound societal changes (socioeconomic changes, emergence of a youth culture). They concern both students and all education actors whose benchmarks have been shaken. Problems have emerged thanks to the evolution of research on action theories. They were interested in the intentionality of the actors as well as in the purpose of situated and instrumented actions. We wonder about the role of novelty, innovation as a test of meaning for a subject related to the school question. We rely on a literature review to address this question by specifying what we mean by School, based on the concept of school form. We propose to articulate it with the concept of meaning, within the framework of a psychosocial approach by thinking of the meaning of the School as a system of meanings (subjective, socio-anthropological, axiological, rational). The main function of meaning is to ensure the mobilization of the subject, its maintenance, and the conditions for its coherence. The challenge of our research is to participate in the construction of a model allowing to accompany the subject towards the awareness of the elements at stake and the forces at work. It requires coordination with other disciplines to complete and refine it. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen content and its distribution in in-core materials of nuclear plants are known to have a strong influence on their behaviour, especially on their mechanical properties but also on their corrosion resistance. This point has to be largely investigated in the case of the nuclear fuel cladding (Zr based alloys) of pressurized water reactors (PWR). Two situations have been considered here, with regards to the hydrogen content and its spatial distribution within the thickness of the tubes: [(1)] Irradiated fuel cladding tubes after a nominal period under working conditions in a PWR core. [(2)] Non-irradiated fuel cladding previously exposed to conditions representative of an hypothetical “loss of coolant accident” scenario (LOCA). As far as micrometric distributions of H were required, μ-ERDA has been performed at the nuclear microprobe of the Pierre Süe Laboratory. This facility is fitted with two beam lines. In the first one, used for non-active sample analysis, the μ-ERDA configuration has been improved to reduce the limits of detection and the reliability of the results. The second one offers the unique feature of being dedicated to radioactive samples. We will present the nuclear microprobe and emphasize on the μ-ERDA configuration of the two beam lines. We will illustrate the performance of the setup by describing the results obtained for Zircaloy-4 cladding both on non-irradiated and irradiated samples. [Copyright &y& Elsevier]

• Different precipitation behaviors were identified between three stainless steel grades using X-ray transmission synchrotron diffraction. • The specimens were heavily carburized in grains and at grain boundaries. • However, equilibrium of precipitation was not reached. • The blocking effect of carbides had to be considered and was observed to evolve with time and microstructure. • Precipitation at grain boundaries could not be simulated with the used model. Three steels were exposed in carburizing sodium at 600 and 650 °C. The kinetics and extent of carburization were characterized. Numerical simulations using the coupled thermodynamic-kinetic modeling software DICTRA were performed. It was proposed that the observed carbon diffusion profiles were induced by the combined diffusion of carbon in the grains and at grain boundaries coupled with the slow formation of carbides. The blocking effect of carbides on the carbon diffusion was observed to evolve as a function of time and microstructure. Acceptable agreement between experimental and simulated intragranular carbon profiles was achieved by optimizing the labyrinth factor and phases. [ABSTRACT FROM AUTHOR]

Abstract: During the last fifteen years, CEA has acquired much experience in the control of the microstructure and the mechanical properties of ODS alloys for nuclear applications. Each major step of the production process has been studied to get the best compromise for the fabrication route of ODS materials. From this scientific background, two new Fe–13/18CrWTi ferritic ODS alloys have been designed to meet the needs of the fusion or GEN-IV programs. These new materials have been investigated at a semi- industrial scale with different industrial partners and consolidated as small plates. The aim of this paper is to present the recent CEA developments on ODS materials, and to show the first results obtained on the Fe–18Cr1WTi new ferritic ODS alloy. The fabrication route for these new materials is presented, along with the measured mechanical properties and the preliminary microstructure characterizations. These new materials look promising for nuclear applications and are considered by CEA as reference materials for the development of new ODS alloys. [Copyright &y& Elsevier]

In-situ time-resolved Synchrotron X-ray diffraction analyses were performed on zirconium alloy (Zircaloy-4) sheet samples, during their heating, isothermal oxidation at 700, 800 and 900 °C under a flowing mixture of He and O 2 and cooling. The oxide growth and the evolution of the oxide structure as a function of time and temperature were studied with suitable time resolution. Oxide layer thicknesses of approximately 10 μm were formed during the experiments. The incident X-rays penetrated the whole oxide thickness. The samples were examined after the experiments by field emission gun scanning electron microscopy, electron backscatter diffraction and electron-probe microanalysis. The results showed that the oxide contains a mixture of monoclinic and tetragonal zirconia evolving during heating, oxidation and cooling. The average volume fraction of tetragonal zirconia decreases during oxidation. This fraction is larger at 900 °C than at 700 and 800 °C. For oxide layers thinner than approximately 5 μm, this fraction is larger at 800 °C than at 700 °C, but it is rather equivalent for both temperatures when the oxide thickness ranges between 5 and 8 μm. Some of the tetragonal zirconia crystals transforms into the monoclinic phase during cooling after oxidation. This fraction of transformed tetragonal zirconia is larger after oxidation at 900 °C than after oxidation at 700 and 800 °C. It is suggested that these evolutions of the oxide crystallographic structure are related to micro-stresses and to temperature dependences of the critical size of zirconia crystals below which tetragonal zirconia is stabilized. [ABSTRACT FROM AUTHOR]