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Nuclear power plant control rooms contain large numbers of identical or similar control and display components. The discrimination cues available for selecting a single component are frequently minimal. This situation can lead to substitution errors in which the wrong display is read or the wrong control is operated. An example of such an error is discussed in relation to a generic procedure sequence and remedial approaches are presented with respect to both original design and modification of existing control panels.

As part of an effort to develop human engineerging guidelines and a methodology for the evaluation of nuclear power plant control room operability, the Essex Corporation conducted T & E (test and evaluation) reviews of a wide sample of nuclear power plant control rooms. The objectives of these design reviews were: 1) selection, application, and development of human engineering evaluation guidelines applicable to the nuclear power industry; 2) selection and development of data collection and analysis procedures; and 3) identification of recurrent human engineering design problems in the control rooms of currently operating nuclear power plants. The present paper discusses the approach taken and the findings in item three above. Thirteen control rooms were visited, and guidelines and data collection methods under various degrees of development were applied. Following control room visits, data were analyzed according to usability, number of incidences of similar or identical operability design problems, criticality of problems with respect to both public and plant safety, and subjective assessment of operational affects due to human engineering problems in design. Results to date show that the following areas have recurrent operability design problems: layout of controls and displays according to either operational or functional use; coding of information for visual and auditory presentation; job performance aid and procedures design; communications; environmental factors such as ambient noise; violations in control and display conventions employed; use of conventions which violate population stereotypes; and failure to design within anthropometric constraints. Further work is being conducted by Essex Corporation to identify critical human engineering deficiencies in control room design and to select adequate yet cost-effective and corrective backfits.