A computerized operator support system (COSS) is proposed for use in nuclear power plants to assist control room operators in addressing time-critical plant upsets. A COSS is a collection of technologies to assist operators in monitoring overall plant performance and making timely, informed decisions on appropriate control actions for the projected plant condition. A prototype COSS was developed in order to demonstrate the concept and provide a test bed for further research. The prototype is based on four underlying elements consisting of a digital alarm system, computer-based procedures, piping and instrumentation diagram system representations, and a recommender module for mitigation actions. The initial version of the prototype is now operational at the Idaho National Laboratory using the Human System Simulation Laboratory.
INTRODUCTIONNuclear power plants (NPPs) face a trade-off in control philosophy between automatic systems versus operator control. Some automatic systems are used when there is insufficient time for operators to diagnose and respond to fast-moving events. The plant operates in an envelope of conditions that are supervised by the plant protection system, in the form of setpoints for protective actions that will be automatically invoked if the thresholds are exceeded. These automatic actions are designed to put the plant to a safe and known condition, such as a reactor trip. Other automatic actions are part of the plant control system (PCS), which maintains important plant parameters at the desired operating points by adjusting plant components, such as valve positions and pump speeds. The PCS relieves the operators from the burden of continuous, tedious manual control of these components.A previous report by Quinn et al. described the benefits of automating operator actions for plant transients (2012). The report identified situations in which alternate configurations and actions can mitigate the need for extreme measures, such a safety actuation, if there is time to do so. These situations are sometimes limited by the ability of the operator to accurately diagnose the cause of the upset and take the needed actions in the short available time. Any delays in procedure-based manual control actions can possibly result in the protection setpoints being reached, leading to an automatic reactor trip or other safety system actuation. Even when the operator is successful in arresting a plant transient and averting the need for safety actions, the time required may negatively impact plant operations.A computerized operator support system (COSS) is a collection of capabilities to assist operators in monitoring overall plant performance and making timely, informed decisions on appropriate control actions for the projected plant condition. They generally have the following features: (i) Monitoring a process to detect off-normal conditions; (ii) Diagnosis of plant faults; (iii) Prediction of future plant states; (iv) Recommendation of mitigation alternatives; and (v) Decision support in selecting mitigati...
