Estimating the Operator’s Performance Time of Emergency Procedural Tasks Based on a Task Complexity Measure
نویسندگان
چکیده
Reliable emergency response by human operators is a prerequisite to secure the safety of a nuclear power plant (NPP). There are some events that require prompt operator response to achieve optimal recovery and to maintain the plant within its design basis. Therefore, it is critical to understand the amount of time required to perform an emergency response when designing a NPP and emergency operating procedures (EOPs) as well as education and training programs[1][2]. For example, it is one of the assumptions used in the design of a NPP that operators should isolate a faulty steam generator (SG) within 30 minutes from initiation of the event, a steam generator tube rupture (SGTR). To validate the safety of the design, designer uses the operator’s performance time (OPT) for isolating a faulty SG as an input to, or a requirement for, the safety analyses. Human reliability analysis (HRA) is another area that requires an OPT as either a direct or an indirect input to estimate human error probability [3]. Despite its significance, there is only a limited set of OPT data related to emergency procedural tasks in the NPPs. Due to the lack of data related to actual events that required an emergency response, a simulator may be used as an alternative to obtain OPT data. Several studies have been performed to collect data from a simulator to secure a technical basis for an HRA or to obtain data related to human performance [4][5]. Recently, a simulated experiment was performed by the Halden Reactor Project, which is an international research program that provides data and technical bases for an HRA [6][7]. A human performance database called OPERA (Operator Performance and Reliability Analysis) was developed by the authors to generate a portion of the input data for an HRA and to support research on human performance in NPPs [8][9]. However, there are difficulties with the broad use of that simulator data for applications in a systematic manner because they are able to support only a partial set of OPT, just for a limited amount of emergency procedural tasks of a few typical accident scenarios. This paper introduces a method for estimating the OPT of a procedural task based on a measure of the task complexity, TACOM (Task Complexity) [10][11]. The method for estimating an OPT is an equation that is expressed by using the TACOM as a variable, and the OPT of a procedural task can be calculated if we know its TACOM score. It is important to understand the amount of time required to execute an emergency procedural task in a high-stress situation for managing human performance under emergencies in a nuclear power plant. However, the time to execute an emergency procedural task is highly dependent upon expert judgment due to the lack of actual data. This paper proposes an analytical method to estimate the operator’s performance time (OPT) of a procedural task, which is based on a measure of the task complexity (TACOM). The proposed method for estimating an OPT is an equation that uses the TACOM as a variable, and the OPT of a procedural task can be calculated if its relevant TACOM score is available. The validity of the proposed equation is demonstrated by comparing the estimated OPTs with the observed OPTs for emergency procedural tasks in a steam generator tube rupture scenario.
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