On the influence of a DC magnetic field upon a bubble

International audienceMolten Salt Fast Reactor (MSFR) is a new fast nuclear reactor, which is at present under memoranda and understanding (MOU) from Generation IV International Forum (GIF). In the MSFR concept, fissile material dissolved in molten fluoride salts serves as a liquid fuel in a primary loop. One of the issues that need to be addressed is the development of an extraction technique of fission products from the fuel [1]. The technique addressed here is based on the injection of helium bubbles in the molten salt in order to absorb fission products by liquid/gas mass transfer. Solid particles are expected to adsorb at bubble surfaces as well. Taking into account that molten salts, as a continuous phase, are electrically conductive, an externally applied magnetic field offers opportunities for a contactless flow control. In addition, the jump in electrical conductivities between molten salts and contaminated bubbles is expected to enhance electromagnetic separation of gaseous phase after ad/absorption processes. To address this online extraction, it is important to simulate the dynamics of bubbles flowing in a molten salt, taking into account magnetohydrodynamics of the liquid phase. Numerical simulations of the process are performed with a CFD code based on finite volume method (ANSYS FLUENT). Bubble surfaces are captured by Volume of Fluid (VOF) strategy while the electric current densities are calculated in the carrier phase by making use of the Magnetic Induction Method. In this way, we are able to describe bubble deformation due to the hydrodynamic forces and the Lorentz force, which makes the fluid to circulate mainly in planes perpendicular to the magnetic field. We investigate the transient regime required to get the terminal bubble velocity. The way the magnetic field is able to change the streamlines around a bubble is particularly investigated while varying the Hartmann number

Developement of thermal hydraulics models for Molten Salt Coolant

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Progress in modeling solidification in molten salt coolants

International audienceMolten salts have been proposed as heat carrier media in the nuclear and concentrating solar power plants. Due to their high melting temperature, solidification of the salts is expected to occur during routine and accidental scenarios. Furthermore, passive safety systems based on the solidification of these salts are being studied. The following article presents new developments in the modeling of eutectic molten salts by means of a multiphase, multicomponent, phase-field model. Besides, an application of this methodology for the eutectic solidification process of the ternary system LiF–KF–NaF is presented. The model predictions are compared with a newly developed semi-analytical solution for directional eutectic solidification at stable growth rate. A good qualitative agreement is obtained between the two approaches. The results obtained with the phase-field model are then used for calculating the homogenized properties of the solid phase distribution. These properties can then be included in a mixture macroscale model, more suitable for industrial applications

Development of Data-Driven Turbulence Models in OpenFOAM ® : Application to Liquid Fuel Nuclear Reactors

International audienceThe following chapter presents a new approach for the development of turbulent models, with potential application to the design of liquid fuel nuclear reactors. To begin the chapter, the work being carried out at LPSC (Grenoble) for validating the modeling of molten salt coolants is presented, alongside a Backward-Facing Step (BFS) geometry, which will be studied throughout this work. In the subsequent section, various turbulence models are evaluated in the BFS and their advantages and limitations are analyzed, with the conclusion that some improvements in the turbulence modeling are necessary. Therefore, the next section introduces a methodology for developing a nonlinear closure for turbulence models by means of Symbolic Regression via Genetic Evolutionary Programming (GEATFOAM). Then, this new methodology is implemented for direct numerical simulation data of the BFS, obtaining a new nonlinear closure for the standard k– ε model. Finally, the new model is compared against classical turbulence models for the BFS, and, then, the extrapolability of this model is analyzed for available experimental data of an axial expansion in a pipe. Encouraging results are obtained in both cases

Progress in modeling solidification in molten salt coolants

International audienceMolten salts have been proposed as heat carrier media in the nuclear and concentrating solar power plants. Due to their high melting temperature, solidification of the salts is expected to occur during routine and accidental scenarios. Furthermore, passive safety systems based on the solidification of these salts are being studied. The following article presents new developments in the modeling of eutectic molten salts by means of a multiphase, multicomponent, phase-field model. Besides, an application of this methodology for the eutectic solidification process of the ternary system LiF–KF–NaF is presented. The model predictions are compared with a newly developed semi-analytical solution for directional eutectic solidification at stable growth rate. A good qualitative agreement is obtained between the two approaches. The results obtained with the phase-field model are then used for calculating the homogenized properties of the solid phase distribution. These properties can then be included in a mixture macroscale model, more suitable for industrial applications

Relevance of Low-Rm MHD for Surface Viscosimetry of Liquid Metals

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A novel accelerated corrosion test for exhaust system by mean of power ultrasound

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A novel accelerated corrosion test for exhaust system by mean of power ultrasound

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Design of close and open channels experiments to study molten salt flows

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