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Comportement au feu de réservoirs composites de stockage d’hydrogène sous pression
No full textInternational audienceA type IV composite pressure vessel subjected to fire may burst because of the degradation of the outer layers, but when the inner pressure is less than a critical value, leak is observed instead of burst. This phenomenon is due to the heat transfer through the composite shell which leads to liner melting. In order to characterize this failure mechanisms, engulfing fire tests have been performed in the framework of the FireComp project whose objective is to understand and simulate the fire performance of hydrogen storage. An experimental set-up has been implemented to expose the cylinders to fire by the means of gas injectors. A complete instrumentation of the tank was implemented to follow the behavior of its envelope during and after the fire using thermocouples located inside its composite wall, and pressure measurement inside the vessel. A simple Finite Element model has been developed to simulate the coupled effects of mechanical damage and temperature. This approach accurately predicts the time leading to burst of the composite tank, as well as the transition between burst and leak.L’utilisation de l’hydrogène à grande échelle, et notamment pour les véhicules, nécessite de maîtriser la fiabilité de stockage de ce gaz à très haute pression. Les réservoirs de type IV constitués d’une coque composite enroulée sur un revêtement en polymère, sont aujourd’hui considérés comme une technologie mature. Afin de mieux caractériser les conditions à éviter pour observer une défaillance de ce type de stockage dans des conditions accidentelles, en particulier un incendie, le projet FireComp (projet de recherche pré-normatif de trois ans) vise à caractériser le comportement thermomécanique de ce type de stockag
LA DEMARCHE VIGILANCE COLLECTIVE : PRENDRE DU RECUL SUR LA GESTION DES IMPREVUS ET LA COMPLEXITE DU QUOTIDIEN
No full textInternational audienceThe role of the human and organizations is essential to achieve a high performance level in safety. However, the everyday management of operation always contains a part of complexity (technological, human, organizational, regulatory) and unexpected situations (interruption, change of person, time pressure, conflict of priority, rare or complex tasks, uncertainties and doubts). In spite of existing measures (schedule, prevention plan, procedure, tools...) referring to what is usual to call "rule-based safety", errors remain possible at any time during activities (lack of attention, misrepresentation, lack of communication, inappropriate decision, late action…). Collective mindfullness approach and seminar aim at creating, for managers or workers, conditions of experience sharing, allowing to reconsider serenely, "without taboo", measures taken everyday at all levels of the organization (meetings, briefings, double checks, stop point, …) to manage this complexity and the associated risks (notion of managed safety). The objective is to keep improving from simple solutions thanks to experience of participants, to their creativity and to feedback experience from others hazardous industries (in particular nuclear and aeronautical). So, the objective is to create the conditions of a better collective vigilance.Le rôle des hommes et des organisations est déterminant dans l'atteinte d'un haut niveau de performance en sécurité. Cependant, la gestion au quotidien de l'exploitation comporte toujours une part de complexité (technologique, humaine, organisationnelle, réglementaire...) et des situations non prévues (interruption, changement de personne, pression du temps, conflit de priorité, tache rare ou complexe, incertitudes et doutes…). Malgré les dispositions prises (planning, plan de prévention, procédure, équipements…) référant à ce qu'il est habituel d'appeler la « sécurité réglée », des erreurs restent possibles dans le traitement de ces situations (défaut d'attention, erreur de représentation, communication défaillante, décision inappropriée, action tardive…). La démarche et les ateliers « Vigilance Collective » visent à créer, pour les manageurs ou les opérationnels, les conditions d'un partage d'expérience, permettant de revisiter sereinement, « sans tabou », les dispositions prises au quotidien par les différents niveaux de l'organisation (réunions, briefings, double contrôle, point d'arrêt,…) pour gérer cette complexité et maîtriser les risques associés (notion de sécurité gérée). L'objectif est de continuer à s'améliorer à partir de solutions simples faisant appel à l'expérience des participants, à leur créativité et au retour d'expérience d'autres secteurs industriels à risques (notamment nucléaire et aéronautique). L'objectif est ainsi de créer les conditions d'une plus grande vigilance collective
Transition vers la 5G : que peut-on transposer des études biomédicales antérieures ? Quelles questions spécifiques nouvelles envisager
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Use of stickleback for biomonitoring strategy
No full textInternational audienceThe three-spined stickleback, Gasterosteus aculeatus, is a freshwater fish species commonly used in ecotoxicological studies to assess pollutant effects in laboratory and field conditions. This fish has a wide repartition area and can live in contaminated streams. These advantages make it a good sentinel species, interesting for environmental monitoring studies. Therefore, we propose to develop an active biomonitoring strategy which integrates a multi-biomarker approach and which can be used in various stream conditions. Nevertheless, before monitoring caged sticklebacks, it seems to be important to better understand the effects of caging conditions (confinement, food deprivation, fish density, number of replicates, etc) on fish physiology and metabolism. Moreover, the great advantage of an active biomonitoring strategy is the use of standardized animals. Our statistical analysis of in-house laboratory data obtained with standardized animals aims to reduce data misinterpretation during biomonitoring studies. Finally, the environmental reality does not concern only one pollutant but a cocktail of chemical, biological, and physical contaminants which induce a combination of stresses. For this purpose, we want to determine in which way sticklebacks under chemical stress could respond to a sudden biological stress. The proposed examples, from various fields and laboratory studies, give a global view of our use of sticklebacks in biomonitoring contexts
Influence of Aerosol Sources on Atmospheric Black Carbon Absorption Enhancement in the Region of Paris, France
No full textInternational audienceAtmospheric black carbon (BC) and light absorbing organic aerosol (also referred as brown carbon, BrC) have strong effects on the Earth’s climate by absorbing direct solar radiation. To better characterize and quantify these effects, a better understanding of specific underlying mechanisms is needed such as the influence of primary emissions and secondary processes on absorption properties over long term periods. We report here results of a three year continuous field observations conducted from March 2014 to March 2017 at a suburban background station (SIRTA) in the Paris region (France). Submicron nonrefractory aerosol species were measured in near real time using an aerodyne aerosol chemical speciation monitor and were apportioned using Positive Matrix Factorization (PMF) analysis to identify and quantified major organic aerosol (OA) sources. Light absorption properties of BC and BrC were determined by direct measurements using a 7 wavelength aethalometer equipped with the dual spot technology. Co located 24 h filter based analyses were performed by thermo optical technique to quantify the mass concentration of elemental carbon (EC) in PM2.5. Absorption enhancement (Eabs) of BC containing particles was obtained using mass absorption coefficient (MAC) ratios calculated between observed (= babs / [EC]) and expected values for uncoated BC. Results showed that the observed Eabs significantly increased with the mass ratio of secondary aerosols to EC, suggesting a strong influence of this secondary components on BC absorption enhancement. Important BrC contribution to the total absorption in the near UV could be attributed to residential wood burning activities in winter and led to significant Eabs, independently of internal or external BrC mixing with BC particles. Finally, new findings on summertime aerosol optical properties are also presented and discussed here
Utilisation des données de micro-capteurs pour la modélisation et la cartographie de la qualité de l’air à l’échelle urbaine
No full textInternational audienceL’usage des micro-capteurs en qualité de l’air connaît un essor rapide, comme en témoignent la presse scientifique internationale ainsi que les discussions conduites au niveau européen (AQUILA) et français (GT « Micro-Capteurs pour l’évaluation de la qualité de l’air », lancé en 2017 et animé par le Laboratoire Central de la Surveillance de la Qualité de l’Air, LCSQA). Les expériences réalisées avec des micro-capteurs se multiplient (utilisation fixe ou mobile dans différents types d’environnement urbain, sur des moyens de transport, pour le suivi de l’exposition individuelle, comme outils de sensibilisation…), à l’initiative des acteurs traditionnels de la surveillance, des collectivités locales, ou d’opérateurs privés. L’abondance des informations ainsi collectées pose la question de l’exploitation des données et des possibilités offertes par ces nouvelles technologies pour la surveillance réglementaire de la qualité de l’air ou d’autres applications. La nouveauté avec les micro-capteurs réside dans la possibilité de réaliser des mesures à haute résolution spatiale et temporelle pour différents polluants gazeux et particulaires et avec une densité sans précédent qui ouvre de nouvelles voies de développement, en particulier à l’échelle urbaine..
Prevention of Natech Risks Due to Earthquakes at Seveso Establishments
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Experimental study of the hydromechanical response and liquefaction susceptibility of nickel ore to maritime transportation
No full textInternational audienceWhen transported in ship carriers nickel ore with excessive humidity may exceed its flow moisture point and liquefy under the effect of cyclic ship motion induced by the swell. Liquefaction of solid bulk means that the material loses all internal strength and behaves as a liquid. Once the phenomenon happens in one or several holds, the vessel is potentially unstable and may capsize very fast. The Flow Moisture Point, and then the Transport Moisture Limit, depend on several physical properties of the bulk mineral ore, among which its moisture content, of course, but also the amount of cyclic shear stresses exerting in the mass of ore during its maritime transportation. With the purpose to ascertain this key parameter so-called Cyclic Shear Ratio (CSR) to be considered when calibrating TML tests from triaxial tests in laboratory, a handysize bulk carrier was instrumented inside its nickel ore cargo with a multi-parameter monitoring system aiming to sample dynamic stresses versus ship motion and sea conditions. The authors detail here below this unique experiment based on two sea passages from New Caledonia to Japan and the principal observations and results obtained
