Open Failure Analysis of Parallel Slide Gate Valves in Steam Entrance of Steam Pump for PWR Auxiliary Water Supply System

In view of the failure of ASG steam pump steam inlet isolation valve which cannot be opened as required in many domestic PWR nuclear power plants, the fault tree analysis method is used to analyze the root cause of the failure. It is determined that the root cause of the failure is too much friction of the packing or too little spring force. The failure is completely solved by replacing the graphite packing of the valve with Teflon packing.