Research on energy loss characteristics during transient process of reactor coolant pump shaft stuck accident

Abstract

After the stuck shaft accident (SSA), the unstable flow in the reactor coolant pump (RCP) will cause huge energy loss. In order to accurately elucidate the mechanism of energy loss in the pump, this paper realizes the total resistance matching and operating condition regulation of the system piping based on the isoflow cross-section method. A full three-dimensional simplified model of HPR1000 reactor coolant system (RCS) of three loops is established. And the transient flow inside the system is reproduced by numerical simulation method. The weak compressibility theory and entropy production theory are introduced to quantitatively analyze the energy loss characteristics of RCP Ⅰ in the accident loop under six typical operating conditions. The results show that: after the SSA, the flow rate and head of RCP I change abruptly in a short time, and then the change slows down gradually. The reverse flow in the accident loop starts to occur around 1 s, and the system reaches dynamic equilibrium again at 3 s. Comparing different operating conditions, the energy loss in the impeller and guide vane flow path is the most drastic. Due to the migration and development of the vortex, the energy losses of two components reach the maximum at TN0 and 0.5TQi, respectively, there is a peak misalignment phenomenon. When the liquid flow is positive, the energy losses are mainly concentrated in the working surface side in the impeller and guide vane passages, and the interference region of the two components. When the liquid flow is reversed, the energy losses are mainly concentrated the middle of the impeller passage and the interference region of the two components. During transient process of the SSA, the impact, vortex, flow separation, wall friction and other unstable flow is the internal cause of energy losses in the pump.