A physical tool for severe accident mitigation studies

International audienceWithin the framework of the Generation IV Sodium-cooled Fast Reactors (SFR) R and D program of CEA, the core behavior in case of severe accidents is being assessed. Such transients are usually simulated with mechanistic codes (such as SIMMER-III). As a complement to this code, which gives reference accidental transient, a physico-statistical approach is currently followed; its final objective being to derive the variability of the main results of interest for the safety. This approach involves a fast-running simulation of extended accident sequences coupling low-dimensional physical models to advanced statistical analysis techniques. In this context, this paper presents such a low-dimensional physical tool (models and simulation results) dedicated to molten core materials discharge. This 0D tool handles heat transfers from molten (possibly boiling) pools, fuel crust evolution, phase separation/mixing of fuel/steel pools, radial thermal erosion of mitigation tubes, discharge of core materials and associated axial thermal erosion of mitigation tubes. All modules are coupled with a global neutronic evolution model of the degraded core. This physical tool is used to study and to define mitigation features (function of tubes devoted to mitigation inside the core, impact of absorbers falling into the degraded core…) to avoid energetic core recriticality during a secondary phase of a potential severe accident. In the future, this physical tool, associated to statistical treatments of the effect of uncertainties would enable sensitivity analysis studies. This physical tool is described before presenting its comparison against SIMMER-III code results, including a space-and energy-dependent neutron transport kinetic model, on several test cases. Then some sensitivity studies on design parameters are presented providing preliminary information for this reactor fuel oxide core design

Design and manufacturing of a multi-zone phase-shifting coronagraph mask for extremely large telescopes

Context. High-contrast imaging of exoplanets around nearby stars with future large-segmented apertures requires starlight suppression systems optimized for complex aperture geometries. Future extremely large telescopes (ELTs) equipped with high-contrast instruments operating as close as possible to the diffraction limit will open a bulk of targets in the habitable zone around M-stars. In this context, the phase-induced amplitude apodization complex mask coronagraph (PIAACMC) is a promising concept for high-efficiency coronagraphic imaging at small angular separations with segmented telescopes. Aims. The complex focal plane mask of the PIAACMC is a multi-zone, phase-shifting mask comprised of tiled hexagons that vary in depth. The mask requires micro-fabrication techniques because it is generally made of hundreds micron-scale hexagonal zones with depths ranging over a few microns. We aim to demonstrate that the complex focal plane mask of a PIAACMC with a small inner working angle can be designed and manufactured for segmented apertures. Methods. We report on the numerical design, specifications, manufacturing, and characterization of a PIAACMC complex focal plane mask for the segmented pupil experiment for exoplanet detection facility. Results. Our PIAACMC design offers an inner working angle of 1.3 λ/D and is optimized for a 30% telescope-central-obscuration ratio including six secondary support structures (ESO/ELT design). The fabricated reflective focal plane mask is made of 499 hexagons, and the characteristic size of the mask features is 25 μm, with depths ranging over ±0.4 μm. The mask sag local deviation is measured to an average error of 3 nm and standard deviation of 6 nm rms. The metrological analysis of the mask using interferential microscopy gives access to an in-depth understanding of the component’s optical quality, including a complete mapping of the zone depth distribution zone-depth distribution. The amplitude of the errors in the fabricated mask are within the wavefront control dynamic range. Conclusions. We demonstrate the feasibility of fabricating and characterizing high-quality PIAA complex focal plane masks

La France et les Français en Russie

De Pierre le Grand à la seconde guerre mondiale, les relations de la France et de la Russie, tour à tour alliées ou opposées, ont toujours été importantes pour l’histoire de l’Europe, dans tous les domaines, tant politiques, diplomatiques, militaires, culturels, commerciaux ou industriels. Toutefois, l’historiographie française s’est principalement intéressé aux relations réciproques de ces deux états et des hommes au siècle des Lumières et, à l’opposé, d’autres chercheurs, avec des optiques diverses, ont travaillé sur la Russie depuis la révolution d’Octobre. En revanche, la période qui s’étend entre les révolutions de 1789 et de 1917, mis à part l’épisode napoléonien, était presque une terra incognita, tant du point de vue des sources conservées dans les deux pays que des recherches effectuées. C’est cette lacune que l’ouvrage publié ici comble largement. Un tableau des sources existantes, tant aux Archives nationales qu’au ministère des Affaires étrangère, est présenté en même temps qu’un aperçu sur les ressources des archives bancaires. Comment connaître la communauté française en Russie, conduire une recherche prosopographique ? Quels regards portaient les voyageurs français civils et militaires ? La culture française en Russie à travers l’édition, les bibliothèques et l’enseignement, mais aussi la formation de collections sont explorés, sans oublier le développement des études slaves en France. Les échanges économiques prennent un essor remarquable à partir du milieu du XIXᵉ siècle, l’industrie précède la finance qui précède l’assurance. L’implantation des industriels, leurs réalisations sont remarquables ainsi que le rôle des industriels français dans le développement de l’industrie russe à la veille de la révolution d’Octobre. Dont le regard des assureurs nous donne une vision objective

Career Advancement in a Family-Owned French Construction Firm Under Changing Labor Legislation and Market Demand, 1946-1985

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Photonic beam-combiner for visible interferometry with Subaru coronagraphic extreme adaptive optics/fibered imager for a single telescope: laboratory characterization and design optimization

Integrated optics are used to achieve astronomical interferometry inside robust and compact materials, improving the instrument's stability and sensitivity. To perform differential phase measurements at the Hα line (656.3 nm) with the 600- to 800-nm spectro-interferometer fibered imager for a single telescope (FIRST), a photonic integrated circuit (PIC) is being developed in collaboration with TEEM Photonics. This PIC performs the interferometric combination of the beams coming from subapertures selected in the telescope pupil, thus implementing the pupil remapping technique to restore the diffraction limit of the telescope. In this work, we report on the latest developments carried out within the FIRST project to produce a high-performance visible PIC. The PICs are manufactured by TEEM Photonics, using their technology based on K + : Na + ion exchange in glass. The first part of the study consists in the experimental characterization of the fundamental properties of the waveguides, to build an accurate model, which is the basis for the design of more complex functions. In the second part, theoretical designs and their optimization for three types of combiner architectures are presented: symmetric directional coupler, asymmetric directional couplers, and ABCD cells, including achromatic phase shifters. © 2023 Society of Photo-Optical Instrumentation Engineers (SPIE).Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]