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# The Effects of Alarm Display, Processing, and Availability on Crew Performance (NUREG/CR-6691)

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## Publication Information

**Manuscript Completed:** October 2000**Date Published:** November 2000

**Prepared by:** J.M. O'Hara, W.S. Brown, BNL B. Hallbert1, G. Skråning, OECD Halden Reactor Project J.J. Persensky, J. Wachtel, NRC

Brookhaven National Laboratory Upton, NY 11973-5000

1Now at Idaho National Engineering and Environmental Laboratory

J. Wachtel, 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 W6546

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## Abstract

The impact of alarm system design characteristics on crew performance was evaluated to contribute to the understanding of potential safety issues and to provide data to support the development of design review guidance. The research served two purposes. First, to provide the information upon which to develop guidance on alarm design review. Second, to confirm that a selected set of previously developed guidelines were acceptable. The characteristics of alarm system design that we investigated were display (a dedicated tile format, a mixed tile and message list format, and a format in which alarm information is integrated into the process displays), processing (degree of alarm reduction), and availability (dynamic prioritization and suppression). These characteristics were combined into eight separate experimental conditions. Six, two-person crews of nuclear power plant operators completed sixteen test trials consisting of two trials in each of the eight experimental conditions (one with a low-complexity scenario and one with a high-complexity scenario). Measures of plant performance, operator task performance, and cognitive performance (situation awareness and workload) were obtained. In addition, operator ratings and evaluations of the alarm characteristics were collected. The results indicated all the crews were able to detect the disturbances and handle them effectively. There were not many significant effects on the plant, task performance, and cognitive measures. The most notable tendency was for the alarm effects to come in the form of interactions with scenario complexity. We concluded that the performance effects were modest because the alarm systems were generally well designed, integrated into an information-rich environment, and the operators were able to shift their information-gathering strategies to compensate for the differences in designs. The operators' ratings and evaluations were more sensitive to differences in alarm design. These data provided many insights on the strengths and weaknesses of the various alarm design features. Confirmatory evidence was found for the alarm guidance evaluated. The results of this study were used to extend and improve human factors guidance for the review of alarm systems.

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