United States Nuclear Regulatory Commission - Protecting People and the Environment

Soft Controls: Technical Basis and Human Factors Review Guidance (NUREG/CR-6635)

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Publication Information

Manuscript Completed: January 2000
Date Published: March 2000

Prepared by:
W. F. Stubler, J. M. O'Hara/BNL
J. Kramer/NRC

Brookhaven National Laboratory
Upton, NY 11973

J. Kramer, NRC Project Manager

Prepared for:
Division of Systems Analysis and Regulatory Effectiveness
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

NRC Job Code J6012

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In conventional control rooms, the predominant means for providing control input is via hard-wired, spatially dedicated control devices that have fixed functions. However, in human-system interfaces featuring computerbased technologies, the operator may interact via "soft" controls – devices having connections with control and display systems that are mediated by software rather than direct physical connections. Soft controls can have functions that are variable and context dependent rather than statically defined. For example, a particular action may produce different results based on the currently active mode of the control device. Also, device locations may be virtual rather than spatially dedicated. That is, personnel may be able to access a particular soft control from multiple locations within a display system. These characteristics provide new opportunities for operator errors and may affect operator response during time-critical tasks. The objective of this study was to develop human factors review guidance for soft control systems. A methodology for developing technically valid guidance was used. To support this objective, we developed a characterization framework for describing key design characteristics of soft control systems including: display devices, input devices, and methods of interaction. Then, we examined research in the following, areas (1) human error in soft control use, (2) general design approaches for error tolerance, and (3) human performance considerations associated with specific control actions. This research provided the technical basis upon which design review guidelines were developed for the following: display devices, input devices, information displays, and interaction methods. There were aspects of soft controls for which the technical basis was insufficient to support development of the guidance. These were identified as issues to be addressed in future research.

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