Technical Basis for Regulatory Guidance on Design-Basis Hurricane-Borne Missile Speeds for Nuclear Power Plants (NUREG/CR-7004)

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Publication Information

Manuscript Completed: February 2011
Date Published: November 2011

Prepared by:
Emil Simiu
Engineering Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899-8611

and

Florian A. Potra
Information Technology Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899-9811

S. Sancaktar, NRC Project Manager

NRC Job Code N6726

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

This report is intended to provide the technical basis for a potential new regulatory guide that would provide licensees and applicants with guidance that the staff of the U.S. Nuclear Regulatory Commission (NRC) considers acceptable for use in selecting the design-basis hurricane-borne missile speeds for the design of nuclear power plants. The design must prevent undue risk to the health and safety of the public in accordance with General Design Criterion 2, “Design Bases for Protection Against Natural Phenomena,” and General Design Criterion 4, “Environmental and Dynamic Effects Design Bases,” of Appendix A, “General Design Criteria for Nuclear Power Plants,” to Title 10, Part 50, of the Code of Federal Regulations, “Domestic Licensing of Production and Utilization Facilities.”

This report documents the approach to and results of the calculation of hurricane-borne missile speeds that may be considered in the design of nuclear power plants. The missile spectrum, the assumptions on which the analyses are based -- which are similar to assumptions used for the development of Revision 1 to Regulatory Guide 1.76, “Design-Basis Tornado and Tornado Missiles for Nuclear Power Plants,”-- and the range of wind speeds being considered, were based on consultations between the authors and NRC staff. In addition, calculated missile speeds based on assumptions on the initial missile height above ground that differ from the assumption used in Revision 1 to Regulatory Guide 1.76 are included in Appendixes. The staff initiated this study because Revision 1 to Regulatory Guide 1.76 was based on the new Enhanced Fujita scale, in which tornado design-basis wind speeds are lower than in the earlier Fujita scale. This reduction in design basis tornado wind speed resulted in a potential for design basis hurricane winds to exceed the wind speeds in Regulatory Guide 1.76, Revision 1. Furthermore, the nature of hurricane winds can result in faster missile speeds than are possible for comparable tornado design basis winds. This report covers missile speeds that, under several hypotheses, could occur in hurricane winds with an exceedance probability of 10^-7 per year. This is consistent with the 10^-7 per year exceedance probability used for tornado winds in Regulatory Guide 1.76, Revision 1.