ABSTRACT
The Nuclear Regulatory Commission (NRC) investigative report on the Three Mile Island accident included several descriptions of poor human-factors design at the man-machine interface in the control room. This chapter examines the degree to which poor design of instruments may have contributed to the Three Mile Island accident. The NRC report described how lamps that indicated the open or closed state of an emergency feedwater valve were obscured by a caution tag attached to another valve controller. The NRC report hinted at many human-factor limitations to instrumentation that could easily have caused an operator to misread or misunderstand a state of the reactor system. The relationship of human-factors engineering at the macro and micro levels of detail to the overall design and organization of a system as complex as a nuclear-powered generating plant must be seen in the context of the time scales and organizational problems in fabricating such a plant.
