(A) computational model for evaluating the effects of cognitive factors on situation assessment of nuclear power plant operators

Abstract

Operators in nuclear power plants have to acquire information from human system interfaces (HSIs) and the environment in order to create, update, and confirm their understanding of a plant state, as failures of situation assessment may cause wrong decisions for process control and finally errors of commission in nuclear power plants. A few computational models that can be used to predict and quantify the situation awareness of operators have been suggested. However, these models do not sufficiently consider human characteristics for nuclear power plant operators. In this thesis, a computational model for situation assessment of nuclear power plant operators using a Bayesian network is proposed. This model incorporates human factors significantly affecting operators’ situation assessment, such as attention, working memory decay, and mental model. It is assumed that both the salience level and the information value of information sources are the most significant factors that decide which information sources operators heed. The perception index (PI) is defined as the geometric mean of the salience level and the information value of information sources in this study. The attention allocation rule in the proposed model is defined to direct the operator’s attention to the information source with the largest PI value at that moment. There are two approaches for incorporating a mental model of nuclear power plant operators into a Bayesian network: the deterministic rules and the probabilistic rules. The proposed model adopted the probabilistic rules because the deterministic rules are a special case of the probabilistic rules and the probabilistic rules can describe various skill levels of operators. Two working memory decay mechanisms have been suggested: a power law and an exponential law. The proposed model assumes that the situation awareness stored in the working memory decays exponentially because the exponential decay formulas are more popular and require jus...