SAMG-based human reliability analysis method in support of level 2 PSA. Part II: Methodology and application

The second part of this series provides the methodological framework of the developed SAM-L2HRA method for evaluating severe accident management (SAM) strategies utilizing portable equipment for preventing and mitigating severe accidents. SAM-L2HRA uses two fundamental approaches for the evaluation of SAM strategies: a time-based approach and a task-based approach. In the time-based approach, a time uncertainty analysis is performed based on the convolution of two distributions of time available and time required for detailed quantification. Time elements in the time uncertainty analysis include the distribution of time available with consideration of phenomenological uncertainty, the time elapsed (or required), and its distribution for an individual SAM strategy. In the task-based analysis, the human error potential or decision-making likelihood associated with a SAM strategy is assessed. The task-based approach deals with the availability of essential information, evaluation of potential negative impacts associated with the strategy and their effects on decision-making likelihood, and the reliability of implementation activities between distributed organizations. The SAM-L2HRA method can be used to identify the major task characteristics and vulnerabilities associated with a SAM strategy that impede high reliability of strategy implementation, as well as to quantify the probability of failure to perform and complete the strategy.