Identifying and Prioritizing Sources of Uncertainty in External Hazard Probabilistic Risk Assessment: Project Activities and Progress

There are inherently significant sources of uncertainty in external hazard probabilistic risk assessment (PRA) for nuclear power facilities. The state of knowledge and practice associated with these uncertainties varies across hazard groups (e.g., earthquakes, wind, and floods). There is currently a research need to build upon the existing state of knowledge to develop a technically sound, risk-informed strategy for identifying and characterizing drivers of hazard uncertainty in external hazard PRA for multiple classes of hazards. This paper summarizes the ongoing progress of a multi-year research project that seeks to: (1) develop a structured process for identifying, evaluating, categorizing, and communicating the impact of uncertainties on external hazard PRAs, (2) investigate the spectrum of uncertainties associated with parsing the hazard and realistically integrating hazard information into the external hazard PRA, (3) understand how uncertainties in the physical hazard characteristics/timing interfaces with plant response strategies (e.g., plant physics and human reliability), and (4) assess the combined impact of these uncertainties (and uncertainty reduction efforts) on the development of the external hazard PRA. This research will ultimately help to facilitate the prioritization of uncertainty reduction activities based on their risk significance, risk reduction benefit, and value.