This study evaluates the significance of dynamic interaction within a conventional Probabilistic Safety Assessment (PSA) framework. A small loss-of-coolant accident scenario is considered, in which delayed safety injection and secondary heat removal generate time-dependent success criteria. A conventional PSA model based on binary success criteria is compared with a modified conventional model that explicitly represents the timing interaction between operator actions within the existing event tree and fault tree structure.
The purpose of this comparison is to identify the conditions under which dynamic interaction effects arise and to evaluate their significance at the plant level relative to the conventional model. In particular, the study focuses on how the apparent importance of dynamic sequences depends on the model scope and on assumptions regarding the availability of existing safety functions. By comparing the two modeling approaches and performing sensitivity analysis on key safety-function assumptions, this study provides insight into when dynamic interactions become risk-significant and when their contribution remains limited within a broader plant-level PSA model. The results support a balanced interpretation of conventional and dynamic approaches as complementary modeling strategies rather than competing alternatives.