Human Reliability and the Current Dilemma in Human-Machine Interface Design Strategies

Since human error dominates the probability of failures of still-existing human-requiring systems (as the Monju reactor), the human-machine interface needs to be improved. Several rationales may lead to the conclusion that “humans” should limit themselves to monitor the “machine”. For example, this is the trend in the aviation industry: newest aircrafts are designed to be able to return to a safe state by the use of control systems, which do not need human intervention. Thus, the dilemma whether we really need operators (for example in the nuclear industry) might arise. However, social-technical approaches in recent human error analyses are pointing out the so-called “organizational errors” and the importance of a human-machine interface harmonization. Typically plant’s operators are a “redundant” safety system with a much lower reliability (than the machine): organizational factors and harmonization requirements suggest designing the human-machine interface in a way that allows improvement of operator’s reliability. In addition, taxonomy studies of accident databases have also proved that operators’ training should promote processes of decision-making. This is accomplished in the latest trends of PSA technology by introducing the concept of a “Safety Monitor” that is a computer-based tool that uses a level 1 PSA model of the plant. Operators and maintenance schedulers of the Monju FBR will be able to perform real-time estimations of the plant risk level. The main benefits are risk awareness and improvements in decision-making by operators. Also scheduled maintenance can be approached in a more rational (safe and economic) way.