Unexpected reactor trips are not necessarily indicators of degraded safety, and in many cases, they reflect the intended actuation of protection functions. Nevertheless, frequent trips impose substantial economic penalties through lost generation, reduced capacity factor, additional maintenance burden, and restart-related operational costs. While operating experience databases contain detailed descriptions of trip events, prior analyzes often emphasize event counts and qualitative cause summaries, and they less frequently translate event narratives into quantitative timing information that can guide cost-effective trip reduction strategies.
This study analyzes twenty years of operating experience records in Korea to provide a structured and reusable characterization of reactor trip events from three viewpoints. First, event records are reconstructed into a consistent progression from abnormal condition onset to reactor trip, enabling a pathway-level view that connects initiating occurrences to final trip triggers. Second, events are organized using the cause classification, while external influence and other causes are excluded to focus on internal plant-related mechanisms that can be addressed through plant design, maintenance, and operational practices. Third, the time margin from abnormal condition onset to reactor trip is quantified and modelled to support practical use in decision making.
To represent the timing behavior in a form suitable for reuse, time margin is modelled using a two-part form that separates the probability of an immediate trip from the distribution of positive margins, with Akaike information criterion-based selection applied to the continuous component. The proposed framework supports economically motivated trip reduction efforts by linking pathway patterns and timing models to targeted improvement options and by providing defensible inputs for further analysis, simulation, and training scenario design.