Influence of non-uniform inflow on performance of reactor coolant pump and improved design

Abstract

In Chinese Advanced Passive (CAP) series reactors, the two canned Reactor Coolant Pumps (RCP) are directly connected to the bottom of the steam generator (SG) rather than a longer pipe for the full development of inflow, which leads to a decrease in head and efficiency of RCP. However, the head of the RCP determines whether the reactor coolant system can circulate normally. The efficiency determines the power of cannedmotorstator. Overload power under limited size conditions will bring failure risk to the canned motor stator. With such a large impact, we first employed numerical simulation to investigate the influence mechanism of the non-uniform inflow and improve the RCP design, and then verified by experiment. It is found that the flow separation due to the SG asymmetrical structure and the abrupt change of cross section when linking to the inlet pipe is the main cause of non-uniform inflow. Accordingly, we proposed an improved RCP design which can effectively improve the head and efficiency of RCP by more than 1% under non-uniform inflow condition. This research reveals the formation mechanism of the non-uniform inflow of RCP and proposes the improved design scheme to improve the performance of RCP under the non-uniform inflow conditions for the first time, which provides guidance for the design of the RCP.