Integration of DICE and MELCOR for dynamic event tree analysis: Case study for RCS failure phenomena

Dynamic Event Tree Analysis enhances NPP safety assessment by systematically introducing stochastic variability into deterministic simulations and explicitly representing operator actions, system availability, and temporal dependencies. Following the Fukushima accident, the importance of severe accident risk evaluation has grown, and in South Korea, Level 2 PSA is closely tied to safety objectives such as the LERF and Cs-137 release frequency. Physics-based codes such as MELCOR are widely used to support these analyses, yet their efficient integration with dynamic tools remains challenging. This study presents a practical methodology for coupling the DICE platform with MELCOR 2.x using the Analytic Control Function (ACF). Unlike traditional external interfaces, ACF enables direct, bidirectional communication, reducing data-transfer overhead and improving scalability for large simulations. The coupled DICE–MELCOR framework automates scenario generation while capturing operator response times, system availability, and thermal-hydraulic behavior. A station blackout case study in a two-loop PWR demonstrates that the approach explicitly represents uncertainty and yields more realistic insights into accident progression. The results show that ACF-based integration enhances Level 2 PSA fidelity by enabling scenario exploration that better reflects plant dynamics and operator interactions. This methodology provides a robust foundation for reevaluating severe accident management strategies and supporting regulatory safety goals.