Document: NRC Regulatory Guide
Document ID: c7b1689b-ff17-4083-9fb1-f91b6965ea1a
Document Type: regulatory_guide
Title: Design Basis Floods for Nuclear Power Plants + HISTORY - HISTORY 02/2022 – DG-1290 , Proposed Revision 3 09/2014 – Periodic Review of Revision 2 – Revise 07/1980 – Errata to Revision 2 07/2024 – DG-1290 Revision 1 (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0037/ML003740388.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.59
CFR Part: 
CFR Title: 

Content:
ries, and large lakes, techniques are presented in Appendices A and C of this guide. Analyses of only the most severe flood conditions may not indicate potential threats to safety-related systems that might result from combinations of flood conditions thought to be less severe. Therefore, reasonable combinations of less-severe flood condi tions should also be considered to the extent needed for a consistent level of conservatism. Such combina tions should be evaluated in cases where the probability of their existing at the same time and hav ing significant consequences is at least comparable to that associated with the most severe hydro meteorological or seismically induced flood. For ex ample, a failure of relatively high levees adjacent to a plant could occur during floods less severe than the worst site-related flood, but would produce condi tions more severe than would result during a greater flood (where a levee failure elsewhere would produce less severe conditions at the plant site). Wind-generated wave activity may produce severe flood-induced static and dynamic conditions either independent of or coincident with severe hydrometeorological or seismic flood-producing mechanisms. For example, along a lake, reservoir, river, or seashore, reasonably severe wave action should be considered coincident with the probable maximum water level conditions.' The coincidence of wave activity with probable maximum water level conditions should take into account the fact that suf ficient time can elapse between the occurrence of the assumed meteorological mechanism and the max imum water level to allow subsequent meteorological activity to produce substantial wind-generated waves coincident with the high water level. In addition, the most severe wave activity at the site that can be generated by distant hydrometeorological activity should be considered' For instance, coastal locations may be subjected to severe wave action caused by a distant storm that, although not as