Thermomechanical Model and Bursting Tests to Evaluate the Risk of Swelling and Bursting of Modified 9Cr-1Mo Steel Steam Generator Tubes during a Sodium-Water Reaction Accident

The MECTUB code was developed to evaluate the risk of swelling and bursting of Steam Generator (SG) tubes. This code deals with the physic of intermediate steam-water leaks into sodium which induce a Sodium-Water Reaction (SWR). It is based on a one-dimensional calculation to describe the thermomechanical behavior of tubes under a high internal pressure and a fast external overheating. The mechanical model of MECTUB is strongly correlated with the kind of the material of the SG tubes. It has been developed and validated by using experiments performed on the alloy 800. A change to tubes made of Modified 9Cr-1Mo steel requires more knowledge of Modified 9Cr-1Mo steel behavior which influences the bursting time at high temperatures (up to 1200°C). Studies have been initiated to adapt the mechanical model and to qualify it for this material. The first part of this paper focuses on the mechanical law modelling (elasticity, plasticity, and creep) for Modified 9Cr-1Mo steel and on overheating thermal data. In a second part, the results of bursting tests performed on Modified 9Cr-1Mo tubes in the SQUAT facility of CEA are used to validate the mechanical model of MECTUB for the Modified 9Cr-1Mo material

French developments for improving In Service Inspection of SFRs

International audienceIn Service Inspection (ISI) is a major issue to be taken into account for future Sodium Fast Reactors safety, thus, a large R&D work is performed since 2010 in France for the future SFRs. ISI requirements have been taken into account since the early pre-conceptual design phase (specific rules for design have been merged into RCC-MRx design rules until 2012), then consolidated through the basic design phase with more detailed specifications leading to increase the ISI tools ability for immersed sodium structures of SFRs, at about 200°C (shut down conditions). Inspection within the main vessel are planned with transducers immersed in sodium and also with transducers located out of sodium medium. Finally, the qualification of ISI ultrasonic transducers (for Non Destructive Examination, Telemetry and Imaging) is being performed with experimental water and sodium testing, to be compared to simulation with CIVA software platform results. A pluri-annual R&D program mainly deals with the reactor block structures, the primary components and circuit, and the Power Conversion System. Specific developments have been performed for NDE of thick austenitic steel welds, NDE using guided Lamb waves, telemetry from the outside of reactor vessel, imaging of immersed structures and components within the large primary vessel (in a pool type reactor concept) and associated in sodium robotics (with in-sodium tightness). Some results of testing and simulation are given for some ASTRID project applications

Non destructive examination of immersed structures within liquid sodium

International audienceThe In Service Inspection of internal structures of future liquid sodium cooled fast reactors implies, among different options, the use of ultrasounds from the outside of sodium circuit. In these conditions, ultrasounds have to propagate through the metallic envelope of main vessel, then other immersed plates. Thus the study aims at mastering ultrasonic propagation in these multilayered structures in order to determine the best conditions allowing NDT of a plate behind some screens. The necessity of propagating a maximum of energy through bounded media orientated the study towards Lamb waves. Those are often employed for singles plates or solid layers but they are less usual for liquid/solid alternations. Theoretical results are obtained using transfer matrix method. They are compared to in water experimental measurements. Cases with one, two and three parallel plates without then with an artificial defect are presented for identical and different thicknesses of plates. Results show that an artificial crack defect is obviously detected in a plate located behind one and two screens. Measured attenuation is compatible with industrial NDT conditions. Thus a promising potential is shown for this inspection technique

Modelling of ultrasound transmission through a solid-liquid interface comprising a network of gas pockets

International audienceUltrasonic inspection of sodium-cooled fast reactor requires a good acoustic coupling between the transducer and the liquid sodium. Ultrasonic transmission through a solid surface in contact with liquid sodium can be complex due to the presence of microscopic gas pockets entrapped by the surface roughness. Experiments are run using substrates with controlled roughness consisting of a network of holes and a modeling approach is then developed. In this model, a gas pocket stiffness at a partially solid-liquid interface is defined. This stiffness is then used to calculate the transmission coefficient of ultrasound at the entire interface. The gas pocket stiffness has a static, as well as an inertial component, which depends on the ultrasonic frequency and the radiative mass

Potentiel du contrôle ultrasonore d’une plaque masquée par des écrans parallèles

National audienceThe in-service inspection of internal structures of future liquid sodium-cooled fast reactors isan important issue of the CEA. The ultrasonic methods can overcome the sodium opacity,are insensitive to radiation and are adapted to high temperatures. Moreover, they allow tocontrol from outside the circuit sodium; this communication regards this point. Thepropagation of ultrasounds is studied in a plate masked by n plates immersed in liquidsodium to control it. The need to obtain a maximum of propagating energy directed the studytowards Lamb waves in layered solid-fluid structures. The model developed is based on themethod of transfer matrix and leads to the optimization of the pair (angle, frequency). Anexperimental study validates the model on a set of stainless steel plates immersed in water.The possibilities for the control of a plate behind n screens are then analyzed and discussed.L'inspection en service de structures internes des réacteurs à neutrons rapides refroidis ausodium liquide constitue une problématique importante au CEA. Les méthodes ultrasonorespermettent de s’affranchir du caractère opaque du sodium, sont insensibles au rayonnementet sont adaptées aux hautes températures. De plus, elles permettent des contrôles depuisl’extérieur du circuit sodium ; c’est dans ce cadre que s’insère cette communication. Il s’agitd’étudier la propagation des ultrasons dans une plaque masquée par n plaques immergéesen sodium afin de la contrôler. La nécessité de propager le maximum d'énergie a orientél'étude vers les ondes de Lamb dans des structures multicouches solide-fluide. Lamodélisation repose sur la méthode des matrices de transfert et conduit à l’optimisation ducouple (angle, fréquence). Une étude expérimentale valide ce modèle sur un ensemble deplaques d’acier inoxydable immergées dans l’eau. Les possibilités de contrôle d’une plaquederrière n écrans sont analysées et discutées

Recommandations de Conception issues du Contrôle Non Destructif (RCC-MRx)

National audienceUne réflexion a été initiée en 2008 par les concepteurs de centrales nucléaires RNRrefroidies au sodium, avec l’aide de spécialistes du LCND (Université Aix-Marseille).L’objectif était d’insuffler une culture CND, un réflexe pour les besoinsd’inspectabilité/réparabilité. Le constat qui a motivé cette réflexion était que toutes les règlesrelatives aux CND présentes dans le code RCC-MR (édition 2007) étaient spécifiquementdévolues aux contrôles de fabrication. Un Groupe de Travail Thématique (GTT) a produit fin2012 une révision de l’Annexe A20 «Dispositions constructives associées aux visites desurveillance en exploitation» du code RCC-MRx, résultant de la fusion des codes RCC-MRet RCC-MX dédié aux réacteurs expérimentaux. Cette révision est volontairement peuprescriptive car le GTT a montré que, vis-à-vis de la complexité des problèmes posés, ledialogue entre concepteur, fabricant et contrôleur semble être le meilleur moyen pour trouverun compromis entre conception, fabrication et besoin d’inspection en service. Le GTT aconsidéré indispensable d’accompagner cette Annexe d’un document qui fournisse lesfondements des recommandations (criteria), et qui permette de comprendre et justifier lessolutions apportées avec les moyens techniques de contrôles actuels. Certaines mises enperspective sont également indiquées. La présente communication montre le principe de larévision retenue, et présente quelques exemples extraits des criteria

Funcionament dels esfigmomanòmetres en l'assistència primària

Es revisa el funcionament de 102 esfigmomanòmetres localitzats en diferents zones d'assistència primària de Barcelona i comarques circumdants. 44 dels aparells eren de mercuri i 58 aneroides. Un 13,63% dels esfigmomanòmetres de mercuri i un 67,24% dels aparells aneroides funcionaven incorrectament considerant funcionament incorrecte un error igual o superior a 4 mm Hg en la lectura respecte un esfigmomanòmetre control, per excés o per defecte. Únicament en una petita fracció dels aparells l'error es podia justificar pel mal estat de les gomes

Is there such a thing as a biosignature?

The concept of a biosignature is widely used in astrobiology to suggest a link between some observation and a biological cause, given some context. The term itself has been defined and used in several ways in different parts of the scientific community involved in the search for past or present life on Earth and beyond. With the ongoing acceleration in the search for life in distant time and/or deep space, there is a need for clarity and accuracy in the formulation and reporting of claims. Here, we critically review the biosignature concept(s) and the associated nomenclature in light of several problems and ambiguities emphasized by recent works. One worry is that these terms and concepts may imply greater certainty than is usually justified by a rational interpretation of the data. A related worry is that terms such as “biosignature” may be inherently misleading, for example, because the divide between life and non-life—and their observable effects—is fuzzy. Another worry is that different parts of the multidisciplinary community may use non-equivalent or conflicting definitions and conceptions, leading to avoidable confusion. This review leads us to identify a number of pitfalls and to suggest how they can be circumvented. In general, we conclude that astrobiologists should exercise particular caution in deciding whether and how to use the concept of biosignature when thinking and communicating about habitability or life. Concepts and terms should be selected carefully and defined explicitly where appropriate. This would improve clarity and accuracy in the formulation of claims and subsequent technical and public communication about some of the most profound and important questions in science and society. With this objective in mind, we provide a checklist of questions that scientists and other interested parties should ask when assessing any reported detection of a “biosignature” to better understand exactly what is being claimed

Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports—among others—the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit