SUMMARYTraditional Single-Sensor-Single Indicator (SSSI) displays are poorly matched to the cognitive abilities of operators, especially for large and complex systems. It is difficult for operators to monitor very large arrays of displays and controls, and to integrate the information displayed therein. In addition, standard operating procedures (SOPs) are bulky (running to many hundreds of pages) and difficult to use, and operators may become lost. For these reasons, and also because it is becoming increasingly difficult to find replacements for aging hardware components, there is a trend towards computerized graphical interfaces for nuclear power plants (NPPs). There is, however, little rational theory for display design in this domain.This report describes some recent theoretical developments and shows how to develop displays which will greatly reduce the cognitive load on the operator and allow the use of perceptual rather than cognitive mechanisms while using SOPs and to support state diagnosis and fault management. The report outlines the conceptual framework within which such a new approach could be developed, and provides an example of how the operating procedures for the start-up sequence of a NPP could be realized. A detailed description of a set of displays for a graphical interface for the SOPs of the feedwater system is provided as an example of how the proposed approach could be realized, and a general account of how it would fit into the overall start-up sequence is given.Examples of "direct perception" or "ecological" configural state space displays to support the use of the proposed direct manipulation SOP interface are provided, and also a critical discussion which identifies some difficulties which may be anticipated should the general approach herein advocated be adopted.Full details of the development of the displays, their graphical content, underlying theory, and notes on evaluation are provided in Appendices to the main report. "Information about plant state is always constrained by the design of the human-machine interface, and the quality of such information in turn constrains the ways in which operators can think about problems. For example, some displays may require a painstaking synthesis of data derived from several or many separate gauges and displays, while others provide a direct perception of quite subtle plant states (Rasmussen and Vicente, 1989).Recent work in cognitive psychology suggests that displays of the latter kind should better support decision and diagnosis of plant state by the operator.The traditional control room display is a Single-Sensor-Single-Indicator display. There are almost as many independent displays as there are points at which system variables are measured, and operators must rely on their ability to perform complex cognitive operations to relate information from different sources to each other and thus to build up an understanding of the overall state of the system. This is particularly difficult when the system is in an abnormal state or...