Simulation of LOCA within a German BWR Containment with the Coupled Version of ATHLET-COCOSYS

Abstract

In this paper the effectiveness of the safety system in a generic Boiling Water Reactor (BWR) is investigated by simulating a loss-of-coolant accident (LOCA). To this end, a two-sided large break in a feed water line within the containment is simulated. Since the LOCA is characterized by significant interactions between the reactor cooling circuit and the containment, the simulation is performed using the coupled version of the thermo-hydraulic code ATHLET and the containment code COCOSYS. The analysis focuses on the calculated plant behavior from the accident initiation to the depressurization phase. The results show that the emergency core cooling system with only two operational pumps succeeds in cooling the fuel elements throughout the entire accident sequence. A comparison of the simulation results with a separate ATHLET simulation indicates slight deviations when the pressure in the reactor cooling circuit approaches the drywell pressure.