ADVANCED QUANTIFICATION METHODS APPLIED TO SEISMIC RISK ASSESSMENT

摘要

Until recently, one of the key limitations in a Seismic Probabilistic Risk Assessment (PRA) has been quantification of the seismic logic model itself. While the quantification or calculation of the model is similar to the calculations required for an internal-events PRA, the seismic assessments add unique challenges to the calculations of very large models. Over that last several years, enhancements to quantification tools and techniques to address each of these issues have been made. A significant enhancement has been the development of an advanced quantification method and associated tool (Advanced Min Cut Upper Bound Estimator (ACUBE)). Previous to the development of this method, the calculation of the plant risk was subject to conservatisms that could lead a plant to over-state the risk and thus inappropriately determining the significance of various plant systems, structures and components as well as plant configurations and operations. The advancement in the quantification methods allows for the effective removal of over-approximation for the dominant cutsets. The dominant cutsets typically contain the largest magnitude overstatement in the results. In addition, successive model runs can also establish event importance for the seismic model.