Mac Cune-Albright syndrome. Answer to the e-quid “Painful lameness in a child”

International audienc

CoreSOAR Core Degradation State-of-the Art Report Update: Conclusions [in press]

In 1991 the CSNI published the first State-of-the-Art Report on In-Vessel Core Degradation, which was updated to 1995 under the EC 3rd Framework programme. These covered phenomena, experimental programmes, material data, main modelling codes, code assessments, identification of modelling needs, and conclusions including the needs for further research. This knowledge was fundamental to such safety issues as in-vessel melt retention of the core, recovery of the core by water reflood, hydrogen generation and fission product release. In the last 20 years, there has been much progress in understanding, with major experimental series finished, e.g. the integral in-reactor Phébus FP tests, while others have many tests completed, e.g. the electrically-heated QUENCH series on reflooding degraded rod bundles, and one test using a debris bed. The small-scale PRELUDE/PEARL experiments study debris bed quench, while LIVE examines melt pool behaviour in the lower head using simulant materials. The integral severe accident modelling codes, such as MELCOR and MAAP (USA) and ASTEC (Europe), encapsulate current knowledge in a quantitative way. After two EC-funded projects on the SARNET network of excellence, continued in NUGENIA, it is timely to take stock of the vast range of knowledge and technical improvements gained in the experimental and modelling areas. The CoreSOAR project, in NUGENIA/SARNET, drew together the experience of 11 European partners to update the state of the art in core degradation, finishing at the end of 2018. The review covered knowledge of phenomena, available integral experiments, separate-effects data, modelling codes and code validation, then drawing overall conclusions and identifying needs for further research. The final report serves as a reference for current and future research programmes concerning core degradation in NUGENIA, in other EC research projects such as in Horizon2020 and for projects under the auspices of OECD/NEA/CSNI

Needs for large mass prototypic corium experiments the PLINIUS-2 platform

International audienceCorium is the molten material formed after meltdown of a nuclear reactor core during a severe accident. In order to improve the understanding and modelling of corium behavior, experiments are needed both for LWRs and GenIV fast reactors. Experiments using low temperature simulant materials, thanks to lower costs and constraints, allow the testing of a larger number of configurations and the determination of correlations. But some crucial corium phenomena cannot be reproduced at low temperatures such as the importance of radiation heat transfer or the presence of a large (up to 1000 K) liquidus-solidus interval. Consequently, some experiments are performed with high temperature simulant materials alumina thermite as well as refractory oxides. However, it is not feasible to simulate all the aspects of corium phenomenology, especially its high temperature physico-chemistry. Therefore, even though the use of depleted uranium implies a series of protective and regulatory measures, the need for prototypic corium experimented is supported through several examples Another important aspect of experiment design deals with scaling. Small or medium scale corium experiments are easier to operate and only a few large scale (>100 kg) facilities have been built. Several effects are only visible with significant masses, as for instance, the formation of a corium cake during FCI or all the phenomena controlled by crust strength, such as underwater spreading or corium jet ablation. CEA is currently designing a new large prototypic corium platform PLINIUS-2 for both LWR and SFR corium experimental research. Its main characteristics will be presented

Detection, classification, and location of seismovolcanic signals with multi-component seismic data, example from the Piton de la Fournaise volcano (La Réunion, France)

International audienceWe apply three different methods based on the analysis of the multi-component seismic data to detect seismovolcanic tremors and other seismovolcanic signals, to propose an approach to classify them and to locate their sources. We use continuous seismograms recorded during one year by 21 stations at the Piton de la Fournaise volcano (La R ́eunion, France). The first method allows to detect seismovolcanic signals based on stability in time of the inter-components cross-correlations function. Two other methods based on the simultaneous analysis of the whole network can be used to detect seismovolcanic signals and to locate their sources. In the first network-based method, the seismic wave-field is analyzed by calculating the width of the network covariance matrix eigenvalue distribution. The second network-based method consists in performing the 3D back-projection of the inter-stations cross-correlations in order to calculate the network response function. Simultaneous analysis of the parameters measured by the three different methodscan be used to classify different types of seismovolcanic tremors. Our results demonstrate that all three methods efficiently detect seismovolcanic tremors accompanying the 2010 eruptions and the preceding pre-eruptive seismic swarms. Furthermore, methods 2 and 3 based on simultaneous analysis of the whole network detect a large number of volcanic earthquakes. Our location results show that each seismovolcanic tremor is located in a distinct region of the volcano, close to the eruptive site at a shallow depth and the pre- ceding seismic crisis is located deeper at about the sea level under the summit crater

Plinius-2 a new corium facility and programs to support the safety demonstration of the astrid mitigation provisions under severe accident conditions

International audienceThe ASTRID reactor (Advanced Sodium Technological Reactor for Industrial Demonstration) is a technological demonstrator of sodium-cooled fast reactor (SFR) designed by the CEA with its industrial partners, with very high levels of requirements. Innovative options have been integrated to enhance the safety, to reduce the capital cost and improve the efficiency, reliability and operability, making the Generation IV SFR an attractive option for electricity production. In the ASTRID project, the safety objectives are first to prevent the core melting, in particular by the development of an innovative core (named CFV core) with heterogeneous pins and complementary safety prevention devices, and second, to enhance the reactor resistance to severe accident by design. In order to mitigate the consequences of hypothetical core melting situations, specific dispositions or mitigation devices are added to the core and to the reactor some corium Transfer Tubes are implemented, allowing molten corium discharge outside the core region toward a core catcher which insures sub-criticality, cooling and confinement of the relocated materials.For a robust safety demonstration, CEA with its partners is improving or developing codes (SIMMER, SCONE and EUROPLEXUS) to simulate de Severe Accidents progression. These codes must be assessed, and the mitigation devices qualified against experiments. Since no facility is worldwide available allowing tests with Sodium and large masses of prototypic corium (about 500kg) to study corium discharge through full-scale Corium Transfer Tube, Fuel-Sodium-Interactions and subsequent Sodium vapor explosion, and Corium Interactions with the sacrificial material which protects the Core-Catcher tray, CEA has decided to build a new versatile facility, called PLINIUS-2; this new experimental platform will extend the PLINIUS capabilities where the handled corium mass was limited to 50kg of UO2, and only Fuel-Water-Interaction where studied. After describing the ASTRID design options related to Severe Accidents and the main features of the PLINIUS-2, the paper will describe the analytical and global experimental programs planned in PLINIUS-2, supporting the ASTRID development; the used molten mass of UO2 will range from few grams to 500kg. The programs will be devoted to the study of Fuel-Sodium Interactions (Droplet fragmentation, Corium Jet Fragmentation, Sodium Vapor Explosion), of Corium-Sacrificial Material Interactions (corium jet impingement, long term sacrificial material ablation by the corium), and to the qualification of the corium Transfer Tubes

Fabrication et découpe laser de simulants des débris de corium de l'accident de Fukushima Dai-ichi

National audienceUn consortium français (COMEX Nucleaire/ONET Technologies + CEA et IRSN) a été sélectionné dans le cadre d'appels d'offre japonais relatif au démantèlement de Fukushima Daiichi afin d’étudier la faisabilité d'une découpe laser du corium.On a pour ce faire, selectionné des blocs de simulants de corium, issus des etudes passées du CEA pour la sûreté des réacteurs a eau pressurisée a l'aide du four a arc plasma VULCANO, et fabrique de nouveaux échantillons simulants grace a un chauffage par induction, avec une composition issue de calculs des accidents graves de Fukushima Daiichi. Les temperatures de liquidus de ces melanges varient entre 1700 et 3000 K selon les compositions, principalement en fonction de la fraction de produits de decomposition du béton. Le CEA a aussi developpé et validé une tête de découpe laser pour la découpe d'acier lors du démantèlement des installations nucléaires. Des essais ont montre la faisabilité de la découpe laser tant sur des échantillons simulants que sur de la zircone electro-fondue. Ces résultats encourageants ont été obtenus, non seulement sur des debris céramique denses ou poreux mais aussi sur des échantillons contenant des inclusions métalliques (acier, zirconium) qui sont généralement difficile a couper avec les outils traditionnels

Ant behavioral maturation is mediated by a stochastic transition between two fundamental states.

The remarkable ecological success of social insects is often attributed to their advanced division of labor, which is closely associated with temporal polyethism in which workers transition between different tasks as they age. Young nurses are typically found deep within the nest where they tend to the queen and the brood, whereas older foragers are found near the entrance and outside the nest. <sup>1-3</sup> However, the individual-level maturation dynamics remain poorly understood because following individuals over relevant timescales is difficult; hence, previous experimental studies used same-age cohort designs. <sup>4-15</sup> To address this, we used an automated tracking system to follow >500 individuals over >100 days and constructed networks of physical contacts to provide a continuous measure of worker social maturity. These analyses revealed that most workers occupied one of two steady states, namely a low-maturity nurse state and a high-maturity forager state, with the remaining workers rapidly transitioning between these states. There was considerable variation in the age at transition, and, surprisingly, the transition probability was age independent. This suggests that the transition is largely stochastic rather than a hard-wired age-dependent physiological change. Despite the variation in timing, the transition dynamics were highly stereotyped. Transitioning workers moved from the nurse to the forager state according to an S-shaped trajectory, and only began foraging after completing the transition. Stochastic switching, which occurs in many other biological systems, may provide ant colonies with robustness to extrinsic perturbations by allowing the colony to decouple its division of labor from its demography