Behavior of Emergency Core Cooling System (ECCS) during the early stage of Loss of Coolant Accident (LOCA) for APR 1400 with Flownex software

The behavior of Emergency Core Cooling System (ECCS) in an Advanced Pressurized Reactor 1400 (APR) during the early stage of Loss of Coolant Accident (LOCA), was analyzed by using Flownex software. The LOCA has been considered in the primary loop in one of the cold legs of APR1400. Through evaluation of the varying break sizes, sensitivity analysis as well as an uncertainty analysis was performed on the Safety Injection System (SIS) where its performance was tested to observe its capability to mitigate a LOCA. The sensitivity analysis was performed on five out puts including core mass flow rate, break mass flow rate, pressure, temperature, and SIS mass flow rate. Ten different break sizes were considered, and sensitivity coefficients were obtained and used to calculate the uncertainty of all outputs. It was observed that all five output responses were sensitive to changes in the input parameter, and both high levels of uncertainty as well as low were observed.