Numerical analysis on supercritical flow instabilities using APROS

Flow instability investigation is one of the key issues in respect of the design of a nuclear reactor. Considering the possible occurrence of flow instabilities in the supercritical water-cooled reactor (SCWR), numerical analysis has been carried out on the supercritical flow instabilities applying APROS, which is a simulation software product for full-scale modeling and dynamic simulation of industrial processes. Based on the experience in BWR, three cases of density wave oscillations (DWOs) that might occur in the supercritical water-cooled reactor are modeled by APROS, including those in a single channel, two-parallel channels and natural circulation loop. The modeling and analysis of each case of DWO are presented and discussed in detail. Stability boundaries are obtained by APROS, parts of which are compared with previous experimental or numerical studies, showing good coincidence for each DWO case. Several key issues such as the effect of inlet temperature on stability boundary, oscillating period and effect of time step on numerical results are discussed. The discrepancy in oscillating period between the numerical and experimental results is discussed by means of theoretical analysis. Conjecture is raised that some important boundary conditions in experiments are ignored. The work presents an endeavor to establish a common methodology for the stability analysis in SCWR.