Simulation of coolant boiling phenomenon in sodium cooled fast reactor based on porous medium approach

As the first stage of severe accidents in sodium cooled fast reactors, accurate prediction of the occurrence time and location of coolant boiling is of great significance for the safety assessment of Sodium Cooled Fast Reactors (SFR). Based on a two fluid six equation model, conservation equations are constructed for the gas-liquid two-phase flow of sodium. The evaporation-condensation model is used to characterize the interphase mass exchange, and explicit and implicit methods are used to calculate evaporation-condensation model. Constitutive relationships such as Sobolev resistance model, two phase flow heat transfer model, and phase momentum exchange are considered. A porous medium analysis approach which is suitable for simulating SFR coolant boiling was developed, and comparative verification was conducted using KNS-37 L22 loss of flow experiment data. L29 flow data is used to verify the applicability of the model. The results indicate that the established sodium boiling porous medium analysis approach can effectively simulate the boiling phenomenon. It predicts that the boiling time will be around 6.3 seconds, which is 0.2 seconds different from the experiment. The overall trend of temperature and flow rate changes are in good agreement with experimental data.