Numerical Studies of CO2 Leak Modeling in Sodium-CO2 Heat Exchanger in the SFR coupled with the S-CO2 Brayton Cycle

Abstract

For applying the supercritical CO2 Brayton cycle to the Sodium-cooled Fast Reactor, several technical challenges should be resolved. One of the most significant issues is to comprehend the CO2 leak mechanism initiated from the pressure boundary failure in a sodium-CO2 heat exchanger. Since the chemical reaction between sodium and CO2 is followed, the modeling of CO2 leak process is essential to predict the system dynamics. So far, a few studies have been performed to understand the CO2 leak mechanism but some limitations could be found. Thus, to simulate the transient response of the sodium side and CO2 side during the leak process more realistically, a numerical study was conducted. Prior to fully investigating the CO2 leak and the reaction mechanism, an isentropic critical flow model as a reference model was developed while reflecting sodium-CO2 interaction with several assumptions in this study. A numerical study was performed while varying the nozzle diameter and the cover gas space volume with a conceptually designed simple flow model. Mass flux was calculated by determining the flow state whether the flow is choked or not. Then, the change of system pressure was obtained while calculating the amount of reaction products and generated heat. Even though this model could generally simulate the leak process, it should be modified by adding frictional losses and other assumptions.