ICONE19-43754 RETRAN Analysis of Feedwater Controller Failure Transient for Lungmen ABWR

This study used RETRAN-3D program to analyze the FWCFWB transient at 100% rated power/111% rated core flow and under EOC operating condition where the ΔCPR response was worst. Important system operational actions included (1) the turbine and the feedwater pumps tripped on high water level (L8), (2) fast bypass valves opening which inhibited reactor scram and RIPs trip on turbine trip, (3) reactor scram and the four RIPs which are not connected to the Motor Generator (M-G) sets tripped on low water level (L3), (4) low-low water level (L2) initiation of the Reactor Core Isolation Cooling System (RCIC). The ΔCPR of this event was 0.05 and the results were compared with those from FSAR. It showed that there was a significant difference in the change rate of vessel water level, but other transient trends were in good agreement with FSAR. A test of all bypass valves failed to open was also covered in this study. In this situation, the reactor scram occurred on high water level turbine trip, and the ΔCPR would rise to 0.17.