I-PRA Uncertainty Importance Ranking to Enhance Fire PRA Realism for Nuclear Power Plants

摘要

State-of-the-art methodologies, tools, and data for Fire PRA of Nuclear Power Plants (NPPs) are documented in NUREG/CR-6850, hereinafter the "current methodology." Despite recent advances in Fire PRA research and implementation, the current methodology can still lead to risk overestimation due to use of excessively conservative input parameters and assumptions [1]. Lack of realism in Fire PRA may mask identification of critical risk-contributing factors and result in unnecessary and costly plant modifications. To better facilitate risk-informed decision-making, the degree of realism in Fire PRA should be improved.There have been studies that utilized dynamic PRA approaches for improving the realism of the current Fire PRA methodology. These studies, however, have had challenges in areas such as (i) completeness in exploration of the solution space, (ⅱ) aggregation, interpretation, and communication of the large volume of outputs, and (ⅲ) validation of dynamic accident scenarios and underlying physical models. Furthermore, due to the widespread use of classical PRA by the nuclear industry and regulatory agency, the transition to a fully dynamic PRA would require a significant investment of resources. As a more feasible alternative, the Integrated PRA (I-PRA) methodology [1] has been developed by some of the authors of this paper.