Study of the gravity-driven flashing of superheated water in a nuclear Spent- Fuel-Pool : construction of a 2D single phase flow simulation model reproducing the thermal evolution of a SFP mock-up during a loss-of-cooling accident

Following the loss-of-cooling accident at the Fukushima nuclear power plant in 2011, an important but as yet unstudied vaporization mode in a pool configuration has been highlighted in the safety problems encountered, the gravity-driven flashing of superheated water. In order to recreate such accident in laboratory and study it, a mock-up of a spent-fuel-pool has been designed. This master thesis aims to simulate the thermal evolution of the test device built in a loss-of-cooling configuration. To do so, CFD software Code saturne and thermal code Syrthès will be used. First, we learned about the physics of the flow that occurs in the scaled model and thus identify the most adequate turbulence model. A corresponding mesh was then built. Due to the complexity of the overall problem, several geometries were considered with different boundary condition settings. We found that the most accurate solution that best fits the reference data is not the most physically logical. In view of the rough approximation made for some phenomena such as the free surface evaporation, such solution is satisfying. Next, the influence that the flow pattern might have on the nucleation site in the crevices of immersed walls is underlined. Finally, the significant effect that in-plane heat conduction has on the temperature distribution in the walls of the test device is also highlighted.