Integrated Risk-Informed Design (I-RID) methodological framework and computational application for FLEX equipment storage buildings of Nuclear Power Plants

In this research, an Integrated Risk-Informed Design (I-RID) methodological framework is developed for generating and evaluating design options for Nuclear Power Plant (NPP) structures and for providing plant decision makers with a quantitative comparison among design options based on multiple decision criteria, e.g., safety risk and cost. In the I-RID framework, simulations of underlying failure mechanisms are integrated with Probabilistic Risk Assessment (PRA) (consisting of event trees and fault trees) and a cost assessment model in a unified framework. The failure mechanisms are simulated by conducting Finite Element Analysis (FEA), and a probabilistic interface between FEA and the existing plant PRA is generated using structural reliability techniques. A causal model for cost assessment is developed, which allows for the modeling of multi-layer causal relationships among underlying contributing factors and, therefore, creates an explicit connection between cost and safety risk outputs. This paper applies the I-RID framework to the design of a storage building for the Diverse and Flexible Coping Strategies (FLEX) equipment in an NPP subjected to a potential tornado impact. Over two hundred design options are generated and evaluated, and three suggested design options with the lowest values of safety risk and cost are identified.