ABSTRACT
Following the accident at Three Mile Island, the nuclear power industry recognized the importance of having comprehensive and easy-to-use procedures to handle major plant disturbances. For emergency operations, symptom-based procedures were established that enabled operating crews to restore and maintain the plant’s safety functions without having to diagnose events or the specific causes of process disturbances. While symptom-based procedures reduce the cognitive effort required to identify the disturbances, the human factor community maintains that EOPs still require the operators to engage in higherlevel cognitive activities (Roth, Mumaw, & Lewis, 1994, O’hara, Higgins, & Stubler 2002). Examples are: assessing entry conditions, tracking and evaluating paths, assessing the conditions of applicability of steps, and evaluating the achievements of the overall procedure goals. However, it is common to encounter industry activities where the availability of symptom-based procedures is equated with a much simplified operator role: understanding the meaning of the procedure steps, detecting and monitoring the plant parameter referenced, and controlling the equipment as instructed. In other words, procedure following is seen as a step-by-step, rule-based cognitive activity.
