Cabon, M. Arthur (2024) Modeling core melt flow in the event of a major nuclear accident PRE - Research Project, ENSTA.
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Abstract
Understanding the behavior of a nuclear reactor core in an accident scenario is crucial to preventing a malfunction from turning into a tragedy. The complexity and multiplicity of concomitant physical phenomena mean that researchers constantly need to develop more accurate and effective models in order to prepare the best response strategies. The Lattice Boltzmann Method (LBM) is one of the most promising advances in the field of flow simulation, and IRSN wishes to integrate it into its numerical arsenal in order to finely simulate molten core behavior. To this end, an initial thesis was carried out to select the numerical methods to be employed : a hybrid LBM-MVF algorithm taking into account liquid-solid phase changes on a local scale, as well as a free surface ([Sar22]). This work consists of validating the implementation of the algorithm in the PELICANS C++ library. To achieve this, we reproduce well-known flows and compare the data acquired with experience or, where appropriate, analytical formulas. These test cases are of increasing complexity in order to progressively validate more advanced aspects of the code : plane Poiseuille flow, lid-driven cavity, drag of a 2D cylinder, DamBreak and finally a 2D drop in suspension. This approach revealed a few errors in the code, themost notable of which was the erroneous external force term. All components of the algorithm were validated, with the exception of one : surface tension. Surface tension seems to destabilize the simulation and lead to unphysical results. A few clues as to the origin of this anomaly have been suggested. Furthermore, additions to the code were proposed in the course of this work, notably the implementation of a new boundary condition, the addition of the possibility of injecting variable boundary conditions, and a global optimization of the algorithmresulting in a performance gain of the order of 80%. We have thus identified very specific elements of the code that need to be revised to ensure the validity of the simulations. As the model is not yet complete, it cannot simulate corium flow through the degraded core. However, this work has ensured the solidity of the model’s foundations, enabling the project’s future development to proceed with confidence.
Item Type: | Thesis (PRE - Research Project) |
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Uncontrolled Keywords: | nuclear safety, corium, severe accident, Lattice Boltzmann method, validation, optimization |
Subjects: | Fluid Mechanics and Energy |
ID Code: | 10064 |
Deposited By: | Yves CABON |
Deposited On: | 02 sept. 2024 16:43 |
Dernière modification: | 02 sept. 2024 16:43 |
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