Modeling and program development of supercritical CO2 sub-channel based on Modelica language

Abstract

The application of supercritical carbon dioxide (S-CO2) in small nuclear reactors is a new research direction with promising prospects. Most of the research on S-CO2 cooled reactors focuses on the design and optimization of core parameters, but few on detailed thermal and hydraulic analysis of the reactor interior using the sub-channel method. To supplement the lack of research in S-CO2 small nuclear reactors, this paper developed an S-CO2 cooled reactor two-dimensional sub-channel analysis model based on Modelica language. To verify the correctness of the model and program, the calculated results of the sub-channel program are compared with the results of KAIST MMR in Korea, the power deviation is less than 4%, the coolant temperature deviation is less than 7%, and the fuel rod temperature deviation is less than 10%. Based on the developed sub-channel model, the transient analysis is carried out, including reactor power increase, reactivity insertion, and coolant flow loss accidents, and then the safety performance of the reactor is evaluated. The transient response of the reactor under accident conditions is obtained, and the self-stability and self-adjustment characteristics are proved. This paper relies on theoretical modeling and program development methods, studying the sub-channel thermal-hydraulic characteristics of steady-state and transient conditions, which provides theoretical reference and program support for the study of the S-CO2 small nuclear reactor.