TRACE/PARCS Modelling of Feedwater Pump Trip Transients for Lungmen ABWR

The Feedwater Pump Trip transient in the Lungmen startup test has been analyzed by the TRACE/PARCS model of Lungmen ABWR. The purpose of this test is to show the capability of the feedwater pump to support continuing operation following the trip of one operating feedwater pump plus the Motor Driven Reactor Feedwater Pump (MDRFP) initiated automatically. The sensitivity studies of this transient include MDRFP Start Time, RIP runback rate and RIP final speed. The MDRFP Start Time shows that the main variation is in the feedwater flow rate. The variation of the Power and RPV water level, however, is insignificant due to small time steps. In addition, the different RIP runback rates have a noteworthy effect on power. The water level would fluctuate between L3 and L8, having reliable safety margins to avoid either low or high water level scram trip setpoint. The RIP final speed seriously affects the power and water level. Higher RIP runback final speed may cause a smaller power reduction and more vessel steam flow could be produced accordingly. In order to keep the water level between L3 and L8, the highest final speed cannot exceed 55%. Otherwise, the low water level would trigger the scram trip setpoint.