A direct methodology to establish design requirements for human-system interface (HSI) of automatic systems in nuclear power plants

This paper suggests a systematic approach to establish design requirements for the human-system interface (HSI) between operators and automatic systems. The role of automation in the control of a nuclear power plant (NPP) operation is to support the human operator and act as an efficient team player to help reduce the human operator's workload. Some of the problems related to the interaction between the human operator and automation are out-of-the-loop performance, mode errors, role change to supervisory role and final authority issues. Therefore, the design of HSI is critical to avoiding breakdowns in communication between the human operator and the system. In this paper, the design requirements for human-system interface of automatic systems are constructed with the help of a tool called Itemized Sequence Diagram (ISD). Eight levels of automation (LOA) are initially defined in the function allocation and an ISD is drawn for each of the LOA for task allocation. The ISD is a modified version of sequence diagram, which is widely used in systems engineering as well as software engineering. The ISD elements of arrows, messages, actors and alternative boxes collectively show the interactions between the control agents, which are decomposed into four different roles: information acquiring, plant diagnosing, response selecting and response implementing. Eleven design requirements to optimize the human-automation interaction are suggested by using this method. The design requirements produced from the identified interaction points in the ISD are rationalized and how each requirement addresses the issues related to automation is discussed. We also identify which requirements address which of the stated automation issues and at which operational process stage each requirement applies to. Finally, the strengths of the proposed methodology and its implication on the HSI design are discussed in comparison with the methodology used to produce the existing guidelines or guidance.