Regulatory Effectiveness of the Anticipated Transient Without Scram Rule (NUREG-1780)

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Publication Information

Manuscript Completed: April 2001
Date Published:
September 2003

Prepared by:
W.S. Raughley, G.F. Lanik

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

Availability Notice


The U.S. Nuclear Regulatory Commission's Office of Nuclear Regulatory Research is reviewing selected regulations to determine if the requirements are achieving the desired outcomes. This initiative is part of an evolving program to make NRC activities and decisions more effective, efficient, and realistic. The goal of this evaluation is to determine whether the anticipated transient without scram (ATWS) rule and the recommendations issued with it were effective. The effectiveness of the ATWS rule was determined by comparing regulatory expectations to outcomes. The report concluded that the ATWS rule was effective in reducing ATWS risk and that the cost of implementing the rule was reasonable. However, uncertainties in reactor protection system reliability and mitigative capability may warrant further attention to ensure the expected levels of safety are maintained.

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