Assessing mental workload and situation awareness in the evaluation of computerized procedures in the main control room

Abstract

Computerized procedure (CP) system has been developed in nuclear power plant (NPP) instrumentation and control (I&C) system. The system may include normal operating procedures (OPs), abnormal operating procedures (AOPs), alarm response procedures (ARPs), surveillance test procedures (STPs) and/or emergency operating procedures (EOPs). While there are many ways to evaluate computerized procedures design, the user's mental workload and situation awareness (SA) are particularly important considerations in the supervisory control of safety-critical systems. Users’ mental workload and situation awareness may be influenced by human factor issues relating to computerized procedures, e.g., level of automation, dealing with (partially) unavailable I&C, switching to back-up system (e.g., paper-based procedures). Some of the positive impacts of CPs on operator performance include the following: tasks can be performed more quickly; overall workload can be reduced; cognitive workload can be minimized; fewer errors may be made in transitioning through or between procedures. However, various challenges have also been identified with CP systems. These should be addressed in the design and implementation of CPs where they are applicable. For example, narrower “field of view” provided by CP systems than with paper-based procedures could reduce crew communications and crewmember awareness of the status and progress through the procedure. Based on a human factors experiment in which each participant monitored and controlled multiple simulated reactors, this study applied the NASA-TLX instrument for assessing mental workload. For the assessment of situation awareness (SA), the present research used the situational awareness rating technique (SART). In support of summarizing the results of user interface evaluation along multiple dimensions (e.g., workload, SA), we propose advantages for the CPs compared to the paper-based procedures.