Comparison of Working Fluid Models Used in the Analysis of Main Steam Line Break Accidents of Steam Generators in Nuclear Power Plants

Abstract

The main steam line break (MSLB) in a steam generator is one of the most critical accidents that can occur in a nuclear power plant. When such accidents happen, the steam generator is exposed to high pressure (7.8–0.101 MPa) and temperature differences (273–15 °C) in a short time. In such a case, the selection of the working fluid model is a very important parameter in the numerical analysis because of the steam property changes abruptly. When analyzing compressible fluids, using ideal gas model is one of the simplest ways for calculating the change of the fluid property value (density) according to state variable (temperature and pressure). However, this model becomes more inaccurate at higher pressures and lower temperatures. Therefore, a number of more accurate real gas models have been developed as like IAPWS, Redlich-Kwong, and Peng-Robinson models. In this study, we want to identify the differences in the ideal gas model and real gas models that can be used to carry out the main steam line break accident analysis. In this study, CFD analysis of the main steam line break (MSLB) was performed using the ideal gas equation model and the real gas model, which can be used as the working fluid model. The results show that the real gas models—IAPWS, Redlich-Kwong, and Peng-Robinson are more reliable than the ideal gas model.