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PASTELS project - overall progress of the project on experimental and numerical activities on passive safety systems
No full textInternational audienceNuclear accidents such as Fukushima Daiichi have highlighted the potential of passive safety systems to replace or complement active safety systems as part of the overall prevention and/or mitigation strategies. In addition, passive systems are key features of Small Modular Reactors (SMRs), for which they are becoming almost unavoidable and are part of the basic design of many reactors available in today’s nuclear market. Nevertheless, their potential to significantly increase the safety of nuclear power plants still needs to be strengthened, in particular the ability of computer codes to determine their performance and reliability in industrial applications and support the safety demonstration. The PASTELS project (September 2020–February 2024), funded by the European Commission “Euratom H2020” programme, is devoted to the study of passive systems relying on natural circulation. The project focuses on two types, namely the SAfety COndenser (SACO) for the evacuation of the core residual power and the Containment Wall Condenser (CWC) for the reduction of heat and pressure in the containment vessel in case of accident. A specific design for each of these systems is being investigated in the project. Firstly, a straight vertical pool type of SACO has been implemented on the Framatome’s PKL loop at Erlangen. It represents a tube bundle type heat exchanger that transfers heat from the secondary circuit to the water pool in which it is immersed by condensing the vapour generated in the steam generator. Secondly, the project relies on the CWC installed on the PASI test loop at LUT University in Finland. This facility reproduces the thermal-hydraulic behaviour of a Passive Containment Cooling System (PCCS) mainly composed of a CWC, a heat exchanger in the containment vessel connected to a water tank at atmospheric pressure outside the vessel which represents the ultimate heat sink. Several activities are carried out within the framework of the project. Different tests are conducted on these integral test facilities to produce new and relevant experimental data allowing to better characterize the physical behaviours and the performances of these systems for various thermo-hydraulic conditions. These test programmes are simulated by different codes acting at different scales, mainly system and CFD codes. New “system/ CFD” coupling approaches are also considered to evaluate their potential to benefit both from the accuracy of CFD in regions where local 3D effects are dominant and system codes whose computational speed, robustness and general level of physical validation are particularly appreciated in industrial studies. In parallel, the project includes the study of single and two-phase natural circulation loops through a bibliographical study and the simulations of the PERSEO and HERO-2 experimental facilities. After a synthetic presentation of the project and its objectives, this article provides the reader with findings related to the physical analysis of the test results obtained on the PKL and PASI installations as well an overall evaluation of the capability of the different numerical tools to simulate passive systems
Shape and parameter identification by the linear sampling method for a restricted Fourier integral operator
No full textInternational audienceIn this paper we provide a new linear sampling method based on the same data but a different definition of the data operator for two inverse problems: the multi-frequency inverse source problem for a fixed observation direction and the Born inverse scattering problems. We show that the associated regularized linear sampling indicator converges to the average of the unknown in a small neighborhood as the regularization parameter approaches to zero. We develop both a shape identification theory and a parameter identification theory which are stimulated, analyzed, and implemented with the help of the prolate spheroidal wave functions and their generalizations. We further propose a prolate-based implementation of the linear sampling method and provide numerical experiments to demonstrate how this linear sampling method is capable of reconstructing both the shape and the parameter
Support for the “Vancouver call for action to strengthen expertise in radiological protection worldwide”: the position of organisations in formal relations with the International Commission on Radiological Protection (ICRP)
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Dispositif de mesure de l'ancrage de la végétation aquatique : premiers résultats
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Functional approaches of aquatic plant communities along a seasonal cycle in contrasting hydromorphological contexts
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Computation of Green's functions for the acoustic scattering by an elastic structure excited by a turbulent flow in water
No full textInternational audienceTo model the hydrodynamic noise produced by an elastic ship hull or propeller excited by a turbulent boundary layer, we need an efficient method to compute the acoustic scattering by an elastic body surrounded by a fluid. In 3D, Boundary Element Methods (BEM) are used to reduce the computational costs, for both the fluid and the elastic body. A natural way to compute the boundary integral representation (BIR) of the sound pressure is to use formulations based on the free space acoustic and elastic Green's functions. However, since the turbulent flow along the elastic body is known only statistically, the use of these Green's functions would be too expensive. A remedy is to compute a Green's function adapted to the physical problem, thus satisfying the transmission conditions of the fluid-structure problem. This so-called "tailored Green's function" is determined by solving a coupled acoustic-elastic problem with the BEM, and leads to a simplified BIR of the sound pressure compatible with a stochastic source term. We first validate the computation of the tailored Green's function over a classic spherical geometry. Then we compare the scattering of multiple quadrupoles by elastic or rigid NACA0012 profiles
Complementary Finite Element and Monte-Carlo Methods to Solve Industrial Thermal Problems
No full textInternational audienceThis paper presents the integration of a Monte-Carlo solver inside SYRTHES, an open-source thermal code, originally based on finite elements method. Insensitive to both the geometric complexity of the model and the fineness of its discretization, this stochastic method is a good complementary option to simulate large configurations with specific locations of interest. Radiation, conduction and convection can be combined to solve thermal problems in complex geometries. The Monte-Carlo method is described before showing its integration in the code SYRTHES. Comparisons against results obtained thanks to finite elements and Monte-Carlo approaches or analytical solutions are presented. Finally, industrial cases illustrate the advantages of using these two complementary approaches
Influence of clay minerals on pH and major cation concentrations in acid-leached sands: Column experiments and reactive-transport modeling
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salome_meca : A mechanical simulation platform tailored for studies and research
No full textNational audiencesalome_meca is an open source, dedicated platform designed for mechanical simulations. Its primary objective is to provide a comprehensive software environment that enables the entire numerical simulation process, encompassing CAD, meshing, computation, post-processing, result visualisation,and even parametric studies. The platform embedded the code_aster solver developped by EDF R&D . Over the past few years, code_aster has undergone further development with a focus on high-performance computing (HPC) to address intricate and high degrees of freedom (DoF) structures
Régularisation de l'adoucissement par gradient de plasticité dans le potentiel de dissipation
No full textNational audienceOn propose une régularisation de la plasticité avec adoucissement, basée sur le cadre des Matériaux Standard Généralisés à gradients de variables internes. Pour cela, le gradient de la déformation plastique cumulée est introduit dans le potentiel de dissipation, et non pas dans le potentiel d’énergie. Cette stratégie est formulée par une approche variationnelle incrémentale, puis appliquée à un modèle unidimensionnel, et enfin sur la plasticité de von Mises. Des solutions analytiques et numériques démontrenet l’indépendance au maillage et le contrôle des bandes de localisation plastiques