Analysis of Flow Instability for Advanced Secondary Passive Residual Heat Removal System

The advanced secondary passive residual heat removal (ASP) system is one of the most important improvement measures to cope with station blackout accident in the pressurized water reator nuclear power plant. In order to obtain the operation characteristics of ASP system, the ASP system test facility (ASPTF) was constructed. The effects of different influence factors on flow instability of ASP system and theoretical analysis were obtained based on ASPTF. The experimental and theoretical results show that the flow instability of ASP system occurs in ASPTF with low system pressure and low heating power. By increasing the drag coefficient of steam pipeline or the drag coefficient of backwater pipeline, the flow instability of ASP system can be avoided. The flow instability of ASP system occurs under lower heating power conditions. The operation state of main pump influences the total inputting power of ASP system, which can further lead to the flow instability of ASP system.