Jun Su Ha

Development of Human Performance Measures for Human Factors Validation in the Advanced MCR of APR-1400

Main control room (MCR) man-machine interface (MMI) design of advanced nuclear power plants (NPPs) such as APR (advanced power reactor)-1400 can be validated through performance-based tests to determine whether it acceptably supports safe operation of the plant. In this paper, plant performance, personnel task performance, situation awareness, workload, teamwork, and anthropometric/physiological factor are considered for the human performance evaluation. For the development of human performance measures, attention is paid to considerations and constraints such as the changed environment in an advanced MCR, needs for a practical and economic evaluation, and suitability of evaluation criteria. Measures generally used in various industries and empirically proven to be useful are adopted as the main measures with some modifications. In addition, complementary measures are developed to overcome some of the limitations associated with the main measures. The development of the measures is addressed based on theoretical and empirical background. Finally we discuss the way in which the measures can be effectively integrated. The HUPESS (HUman Performance Evaluation Support System) which is in development is also briefly introduced.

A human–machine interface evaluation method: A difficulty evaluation method in information searching (DEMIS)

Abstract A human–machine interface (HMI) evaluation method, which is named “difficulty evaluation method in information searching (DEMIS)”, is proposed and demonstrated with an experimental study. The DEMIS is based on a human performance model and two measures of attentional-resource effectiveness in monitoring and detection tasks in nuclear power plants (NPPs). Operator competence and HMI design are modeled to be most significant factors to human performance. One of the two effectiveness measures is fixation-to-importance ratio (FIR) which represents attentional resource (eye fixations) spent on an information source compared to importance of the information source. The other measure is selective attention effectiveness (SAE) which incorporates FIRs for all information sources. The underlying principle of the measures is that the information source should be selectively attended to according to its informational importance. In this study, poor performance in information searching tasks is modeled to be coupled with difficulties caused by poor mental models of operators or/and poor HMI design. Human performance in information searching tasks is evaluated by analyzing the FIR and the SAE. Operator mental models are evaluated by a questionnaire-based method. Then difficulties caused by a poor HMI design are evaluated by a focused interview based on the FIR evaluation and then root causes leading to poor performance are identified in a systematic way.

HUPESS: Human Performance Evaluation Support System

Research and development for enhancing reliability and safety in NPPs have been mainly focused on areas such as automation of facilities, securing safety margin of safety systems, and improvement of main process systems. Studies of TMI-2, Chernobyl, and other NPP events have revealed that deficiencies in human factors, such as poor control room design, procedure, and training, are significant contributing factors to NPPs incidents and accidents [1–5]. Greater attention has been focused on the human factors study. Modern computer techniques have been gradually introduced into the design of advanced control rooms (ACRs) of NPPs as processing and information presentation capabilities of modern computers are increased [6, 7]. The design of instrumentation and control (I&C) systems for various plant systems is also rapidly moving toward fully digital I&C [8, 9]. For example, CRT- (or LCD-) based displays, large display panels (LDP), soft controls, a CPS, and an advanced alarm system were applied to APR-1400 (Advanced Power Reactor-1400) [10]. The role of operators in advanced NPPs shifts from a manual controller to a supervisor or a decision-maker [11] and the operator tasks have become more cognitive works. As a result, HFE became more important in designing an ACR. The human factors engineering program review model (HFE PRM) was developed with the support of U.S. NRC in order to support advanced reactor design certification reviews [4]. The Integrated System Validation (ISV) is part of this review activity.

Attentional-Resource Effectiveness Measures in Monitoring and Detection Tasks in Nuclear Power Plants

Two measures of attentional-resource effectiveness in monitoring and detection tasks in nuclear power plants are developed based on cost-benefit principle and are validated in experimental studies. The underlying principle of the measures is that information sources should be selectively attended according to their importance. One of the two measures is the fixation to importance ratio (FIR), which represents attentional resource (eye fixations) spent on an information source compared to the importance of the information source. The other measure is selective attention effectiveness (SAE), which incorporates the FIRs of all information sources. The FIR represents the specific effectiveness of an information source, whereas the SAE represents the overall effectiveness of all information sources. Frequency and the duration of eye fixations of an operator on information sources are used as attentional resource. The analytic hierarchy process was used to evaluate the importance of information sources. Experiments were conducted to validate the proposed measure. From the results of the experiments, the FIR and the SAE are concluded to be promising measures of effectiveness in monitoring and detection during complex diagnostic tasks.

A REVIEW OF STUDIES ON OPERATOR'S INFORMATION SEARCHING BEHAVIOR FOR HUMAN FACTORS STUDIES IN NPP MCRS

This paper reviews studies on information searching behavior in process control systems and discusses some implications learned from previous studies for use in human factors studies on nuclear power plants (NPPs) main control rooms (MCRs). Information searching behavior in NPPs depends on expectancy, value, salience, and effort. The first quantitative scanning model developed by Senders for instrument panel monitoring considered bandwidth (change rate) of instruments as a determining factor in scanning behavior. Senders’ model was subsequently elaborated by other researchers to account for value in addition to bandwidth. There is also another type of model based on the operator’s situation awareness (SA) which has been developed for NPP application. In these SA-based models, situation?event relations or rules on system dynamics are considered the most significant factor forming expectancy. From the review of previous studies it is recommended that, for NPP application, (1) a set of symptomatic information sources including both changed and unchanged symptoms should be considered along with bandwidth as determining factors governing information searching (or visual sampling) behavior; (2) both data-driven monitoring and knowledge-driven monitoring should be considered and balanced in a systematic way; (3) sound models describing mechanisms of cognitive activities during information searching tasks should be developed so as to bridge studies on information searching behavior and design improvement in HMI; (4) the attention?situation awareness (A?SA) modeling approach should be recognized as a promising approach to be examined further; and (5) information displays should be expected to have totally different characteristics in advanced control rooms. Hence much attention should be devoted to information searching behavior including human-machine interface (HMI) design and human cognitive processes.

Development of Human Performance Measures for Human Factors Validation in Advanced Nuclear Power Plants

Main control room(MCR) man-machine interface(MMI) design of advanced nuclear power plants(NPPs) such as APR(advanced power reactor)-1400 can be validated through performance-based tests to determine whether it acceptably supports safe operation of the plant. In this work, plant performance, personnel task, situation awareness, workload, teamwork, and anthropometric/physiological factor are considered as factors for the human performance evaluation. For development of measures in each of the factors, techniques generally used in various industries and empirically proven to be useful are adopted as main measures and some helpful techniques are developed in order to complement the main measures. Also the development of the measures is addressed based on the theoretical background. Finally we discuss the way in which the measures can be effectively integrated and then HUPESS(HUman Performance Evaluation Support System) which is in development based on the integrated way is briefly introduced.

How to Evaluate Effectiveness in Monitoring and Detection Tasks in Nuclear Power Plants

Abstract in this study, the monitoring and detection process of operators in NPPs are investigated based on theoretical and empirical background. Then developed are measures of attentional resources effectiveness which represent how well operators monitor and detect the environment. Fixation to Importance Ratio (FIR) which represents the ratio of relative attentional resources spent on an information source to relative importance of the information sources is considered as a measure of the attentional resources effectiveness. Eye fixation number (or duration) is used as the attentional resource. The importance of various information sources is obtained based on the dynamic of the NPP system using the analytic hierarchy process (AHP). FIRs for all information sources are integrated into an overall measure which is called Selective Attention Effectiveness (SAE). Experiment results show that the developed measures can reveal the effectiveness in monitoring and detection tasks and further can be effectively used for finding out drawbacks of man-machine interfaces.

A Quantitative Approach to Risk-Informed Safety Significance Categorization with an Early Expert Participatory

A risk-informed safety significance categorization (RISSC) is to categorize structures, systems, or components (SSCs) of a nuclear power plant (NPP) into two or more groups, according to their safety significance using both probabilistic and deterministic insights [1]. In the conventional methods for the RISSC, SSCs are quantitatively categorized according to their importance measures for the initial categorization [2]. The final categorizations of SSCs, however, are qualitatively made by expert panel through discussions and adjustments of opinions by using the probabilistic insights compiled in the initial categorization process and combining the probabilistic insights with the deterministic insights. Therefore, owing to the qualitative decision-making process, the conventional methods have the demerits that they are very costly in terms of time and labour; and that it is not easy to reach the final decision, when the opinions of the experts are in conflict.