scope:

This standard establishes guidelines to estimate the frequency of occurrence and the magnitude of parameters associated with tornadoes, hurricanes, and other extreme winds at nuclear power reactor sites. It treats data and methods to determine wind speed, characteristics of the wind field, atmospheric pressure change, rate of pressure change, and missile characteristics. It does not treat the forces on structures that result from these physical phenomena.

For a site within the contiguous United States, the standard presents the design basis tornado and tornado-generated missile characteristics and a recommended methodology for determining non-tornadic extreme winds that a nuclear power plant be designed to withstand in order to assure that public health and safety will be maintained as required in the Code of Federal Regulations, Title 10 "Energy," Part 50, "Domestic Licensing of Production and Utilization Facilities," Appendix A, Criteria 2 and 4 [1].¹ Tornadoes have occurred in all states covered by this standard. The standard does not address the determination of the design basis tornado, other extreme windspeeds for sites located in Alaska, Hawaii, and Puerto Rico or over the oceans. Such determinations should be evaluated on a case-by-case basis. Additionally, the standard does not identify the structures, systems, and components that should be designed to withstand the effects of the design basis windspeeds and remain functional; nor does it treat the structural design requirements for protection from these winds.²

¹Numbers in brackets refer to corresponding numbers in Section 5, References.

²U.S. NRC Regulatory Guide 1.76, "Design Basis Tornado for Nuclear Power Plants" and its supporting document WASH-1300 were issued in 1974. The analyses and conclusions contained in ANSI/ANS-2.3-1983 are felt to represent the current state of knowledge on tornado and extreme wind characteristics.