Thesis: Two-phase flow modeling for the simulation of loss-of-coolant accidents in nuclear reactors

PhD defense: Anil Kemal GUN

Team: MecaFlu

Date & time: November 15th, 2024 at 2:30 PM in the amphitheater Eau (Manufacture des Tabacs, Strasbourg)

Title: Two-phase flow modeling for the simulation of loss-of-coolant accidents in nuclear reactors

Abstract: This thesis investigates the dynamics of gas-liquid flows, focusing specifically on Loss of Coolant Accidents (LOCAs) in Pressurized Water Reactors (PWRs). LOCAs present significant safety challenges, as they lead to rapid coolant loss, potentially causing severe reactor accidents. The study emphasizes the critical role of metastable states, which occur when water, typically maintained at high pressure to remain in liquid form, experiences rapid depressurization. To address these complex phenomena, this research implements and validates different two-phase flow models within a custom-built numerical solver. Two specific models are examined: a six-equation model incorporating a relaxed velocity equilibrium and a four-equation model based on kinetic, mechanical, and thermal equilibrium assumptions. Additionally, the six-equation model with an arbitrary-rate relaxation method is investigated to emphasize the non-instantaneous mass transfer, which is critical for accurately predicting the metastable state during phase transitions. The models are validated using a range of test cases, including both standard cases and specific test cases related to loss-of-coolant accidents.

The jury will be composed of:

• Examiner: Pr. Philippe Helluy, Université de Strasbourg, IRMA
• Reporter : Pr. Hélène Mathis, Université de Montpellier, IMAG
• Reporter : Pr. Christophe Corre, École Centrale de Lyon, LMFA
• Supervisor : Pr. Yannick Hoarau, Université de Strasbourg, ICube
• Co-Supervisor : Pr. Eric Goncalves, ENSMA, Institut Pprime