MELCOR 1.8.4 sensitivity analysis of severe accident progressions for LOCA scenarios in APR 1400

This paper provides the results and insights gained from plant-specific MELCOR 1.8.4 analysis of severe accident progressions for a large-to-medium break loss-of-coolant accident (LOCA) in the APR 1400 (Advanced Power Reactor 1400), a Korean PWR with a large dry containment. Unlike most other systems in which the emergency core cooling water is injected into the cold legs, the APR 1400 is designed with an advanced engineering feature for the direct vessel injection (DVI) that takes a suction of water from an in-containment refueling storage tank (IRWST) as the safety injection system. Results include timings of key events, thermal-hydraulic responses of the primary coolant system, core degradation and evolution of core materials, and thermal-hydraulic responses of the containment. The paper also explores the impacts of different break location and sizes, and operation of containment spray systems on the timings of key events predicted during severe accident progressions. No significant strategy for sever accident management has been taken into account in the present analysis. Thus, the present results should be taken as the important basis for assessing the effectiveness of potential severe accident management. (author)