Teaching Sodium Fast Reactors in CEA

International audienceAmong the Fast Neutron Reactor Systems, the SFR has the most comprehensive technological basis as result of the experience gained from worldwide operation of several experimental, prototype, and commercial size reactors since the 1940s. This experience corresponds to about 402 years of operation by end of 2010. Six reactors are in operation BOR60, BN600 and BN800 in Russia, Joyo in Japan, FBTR in India and CEFR in China. One reactor is being commissioned PFBR (500MWe) in India and several projects are currently developed FBR1 and 2 in India, BN1200 in Russia, JSFR in Japan, PGSFR in Korea, CFR-600 in China and ASTRID in France. In order to support operation of existing reactors, design activities for new projects and decommissioning of old reactors, it is mandatory to develop skills, more particularly among the young generation, who will operate these new reactors. In addition, education and training is also essential to share the knowledge among the teams involved in Research and Development. Several strategies are developed at the national level, or within multilateral framework, like EU or IAEA to support development of Fast Reactors.In France, to answer to this increasing demand of Education and Training, four sessions are proposed, within the frame of INSTN (French National Institute for Nuclear Science and Technology)-SFR History, main options, design and operational feedback-SFR Functional analysis and design-SFR Safety and operation-SFR Sodium structures interactionsThe French Na School (ESML) provides since 1975 also several sessions dedicated to Na facilities design, safe operation, handling, and also decommissioning and sodium treatment. Beside courses, practical exercises are organized during each session. 10 different modules are available, ranging in length from 1 to 5 days. CEA contributes also to the organization of European Sessions dedicated to Sodium Fast Reactors, organized within the frame of the European Commission (CP-ESFR, ESNII+ , ESFR-SMART) This Education and Training strategy is a key element for the future of the development of Sodium Fast Reactors, and more particularly ASTRID project. CEA is ready to share training experience and to collaborate with other foreign Education and Training Entities

Early-life adversity predicts performance and fitness in a wild social carnivore

1. Studies on humans indicate that encountering multiple sources of adversity in childhood increases the risk of poor long-term health and premature death. Far less is known about cumulative effects of adversity during early life in wildlife. 2. Focusing on the spotted hyena Crocuta crocuta, a social mammal with small litters, extensive maternal care, slow development and access to resources determined by social rank, we determined the contribution of ecological, maternal, social and demographic factors during early life on performance and fitness, and tested whether the impact of early-life adversity is cumulative. 3. Using longitudinal data from 666 female hyenas in the Serengeti National Park, we determined the early growth rate, survival to adulthood, age at first reproduction (AFR), lifetime reproductive success (LRS) and longevity. We fitted multivariate models in which we tested the effects of environmental factors on these performance measures. We then constructed a cumulative adversity index and fitted models to test the effect of this index on each performance measure. Finally, the value of cumulative adversity models was tested by comparing them to multivariate and single-effect models in which the effect of each environmental factor was considered separately. 4. High maternal rank decreased the AFR of daughters. Singleton and dominant cubs had higher growth rate than subordinate cubs, and singletons also had a higher survival chance to adulthood than subordinates. Daughters of prime age mothers had a higher growth rate, longevity and LRS. Little and heavy rainfall decreased survival to adulthood. Increasing numbers of lactating female clan members decreased growth rate, survival to adulthood and LRS. Cumulative adversity negatively affected short-term performance and LRS. Multivariate models outperformed cumulative adversity and single-effect models for all measures except for AFR and longevity, for which single-effect models performed better. 5. Our results suggest that in some wildlife populations the combination of specific conditions in early life may matter more than the accumulation of adverse conditions as such

Climate change does not decouple interactions between a central-place-foraging predator and its migratory prey

Little is known about potential cascading effects of climate change on the ability of predators to exploit mobile aggregations of prey with a spatiotemporal distribution largely determined by climatic conditions. If predators employ central-place foraging when rearing offspring, the ability of parents to locate sufficient prey could be reduced by climate change. In the Serengeti National Park, Tanzania, migratory species dominate mammalian herbivore biomass. These migratory herds exploit nutrient-rich vegetation on the southern plains in the rainy season and surface water in the northwest in the dry season. Female spotted hyenas Crocuta crocuta breed throughout the year and use long-distance central-place-foraging “commuting trips” to migratory herds to fuel lactation for ≥12 months. Changes in rainfall patterns that alter prey movements may decrease the ability of mothers to locate profitable foraging areas and thus increase their overall commuting effort, particularly for high-ranking females that have priority of access to food resources within their clan territory and thus less commuting experience. In hyena clan territories, this may be reflected by a decrease in migratory herd presence and a decrease in the presence of lactating females, as maternal den presence represents the opposite of commuting effort. We investigated the strength of the relationship between rainfall volume, migratory herd presence in three hyena clan territories, and the responses of lactating females to this climate/prey relationship in terms of maternal den presence, using an observation-based dataset spanning three decades. The probability of migratory herd presence in hyena clan territories increased with the amount of rainfall 2 months earlier, and maternal den presence increased with migratory herd presence. Rainfall volume substantially increased over 30 years, whereas the presence of migratory herds in hyena clans and the strength of the relationship between rainfall and migratory herd presence decreased. Hyenas thus adjusted well to the climate change-induced decreased the presence of migratory herds in their territories, since maternal den presence did not decrease over 30 years and still matched periods of high prey abundance, irrespective of female social status. These results suggest a high plasticity in the response of this keystone predator to environmental variability

A Thickened-Hole Model for Large Eddy Simulations over Multiperforated Liners

International audienceIn aero-engines, mutiperforation cooling systems are often used to shield the combustor wall and ensure durability of the engine. Fresh air coming from the casing goes through thousands of angled perforations and forms a film which protects the liner. When performing Large Eddy Simulations (LES) of a real engine, the number of sub-millimetric holes is far too large to allow a complete and accurate description of each aperture. Homogeneous models allow to simulate multiperforated plates with a mesh size bigger than the hole but fail in representing the jet penetration and mixing. A heterogeneous approach is proposed in this study, where the apertures are thickened if necessary so that the jet-crossflow interaction is properly represented. Simulations using homogeneous and thickened-hole models are compared to a fully resolved computation for various grid resolutions in order to illustrate the potential of the method

Interactions Between a Condensed Target and a Non-Equilibrium Plasma: Acid-Base Reactions at the Interface

A new approach of plasma processes of industrial use is presented, with emphasis on the chemical properties of the plasma gas. Reactions occurring at the gas/target interface are for the first time interpreted in terms of acid-base reactions and pertinent examples are given of laboratory experiments and of industrial treatments (e. g., etching, plasma polymerization or surface modification processes). Proton exchanges between the plasma phase and an aqueous target gives evidence of Bronsted acid-base phenomena. Illustrations of Lewis acid-base characters are provided by the role of biradicals (e.g., halogenocarbenes, nitrenc) which are the main reacting species in etching or in surface treatment processes

The Composition of Comets

This paper is the result of the International Cometary Workshop, held in Toulouse, France in April 2014, where the participants came together to assess our knowledge of comets prior to the ESA Rosetta Mission. In this paper, we look at the composition of the gas and dust from the comae of comets. With the gas, we cover the various taxonomic studies that have broken comets into groups and compare what is seen at all wavelengths. We also discuss what has been learned from mass spectrometers during flybys. A few caveats for our interpretation are discussed. With dust, much of our information comes from flybys. They include {\it in situ} analyses as well as samples returned to Earth for laboratory measurements. Remote sensing IR observations and polarimetry are also discussed. For both gas and dust, we discuss what instruments the Rosetta spacecraft and Philae lander will bring to bear to improve our understanding of comet 67P/Churyumov-Gerasimenko as "ground-truth" for our previous comprehensive studies. Finally, we summarize some of the initial Rosetta Mission findings.Comment: To appear in Space Science Review

Interactions of Attenuated Mycobacterium tuberculosis phoP Mutant with Human Macrophages

Background: Mycobacterium tuberculosis phoP mutant SO2 derived from a clinical isolate was shown to be attenuated in mouse bone marrow-derived macrophages and in vivo mouse infection model and has demonstrated a high potential as attenuated vaccine candidate against tuberculosis. Methodology/Principal Findings: In this study, we analyze the adhesion and the intracellular growth and trafficking of SO2 in human macrophages. Our results indicate an enhanced adhesion to phagocitic cells and impaired intracellular replication of SO2 in both monocyte-derived macrophages and human cell line THP-1 in comparison with the wild type strain, consistent with murine model. Intracellular trafficking analysis in human THP-1 cells suggest that attenuation of SO2 within macrophages could be due to an impaired ability to block phagosome-lysosome fusion compared with the parental M. tuberculosis strain. No differences were found between SO2 and the wild-type strains in the release and mycobacterial susceptibility to nitric oxide (NO) produced by infected macrophages. Conclusions/Significance: SO2 has enhanced ability to bind human macrophages and differs in intracellular trafficking as to wild-type M. tuberculosis. The altered lipid profile expression of the phoP mutant SO2 and its inability to secrete ESAT-6 i

A mesh adaptation strategy for complex wall-modeled turbomachinery LES

A mesh adaptation methodology for wall-modeled turbomachinery Large Eddy Simulation (LES) is proposed, simultaneously taking into account two quantities of interest: the average kinetic energy dissipation rate and the normalized wall distance y+. This strategy is first tested on a highly loaded transonic blade with separated flow, and is compared to wall-resolved LES results, as well as experimental data. The adaptation methodology allows to predict fairly well the boundary layer transition on the suction side and the recirculation bubble of the pressure side. The method is then tested on a real turbofan stage for which it is shown that the general operating point of the computation converges toward the experimental one. Furthermore, comparison of turbulence predictions with hot-wire anemometry show good agreement as soon as a first adaptation is performed, which confirms the efficiency of the proposed adaptation method

Changes of the phagosomal elemental concentrations by Mycobacterium tuberculosis Mramp

Pathogenic mycobacteria survive within phagosomes which are thought to represent a nutrient-restricted environment. Divalent cation transporters of the Nramp family in phagosomes and mycobacteria (Mramp) may compete for metals that are crucial for bacterial survival. The elemental concentrations in phagosomes of macrophages infected with wild-type Mycobacterium tuberculosis (M. tuberculosis strain H37Rv) and a M. tuberculosis Mramp knockout mutant (Mramp-KO), derived from a clinical isolate isogenic to the strain MT103, were compared. Time points of 1 and 24 h after infection of mouse peritoneal macrophages (bcgS) were compared in both cases. Increased concentrations of P, Ni and Zn and reduced Cl concentration in Mramp-KO after 1 h of infection were observed, compared to M. tuberculosis vacuoles. After 24 h of infection, significant differences in the P, Cl and Zn concentrations were still present. The Mramp-KO phagosome showed a significant increase of P, Ca, Mn, Fe and Zn concentrations between 1 and 24 h after infection, while the concentrations of K and Ni decreased. In the M. tuberculosis vacuole, the Fe concentration showed a similar increase, while the Cl concentration decreased. The fact that the concentration of several divalent cations increased in the Mramp-KO strain suggests that Mramp may have no impact on the import of these divalent cations into the mycobacterium, but may function as a cation efflux pump. The concordant increase of Fe concentrations within M. tuberculosis, as well as within the Mramp-KO vacuoles, implies that Mramp, in contrast to siderophores, might not be important for the attraction of Fe and its retention in phagosomes of unstimulated macrophages