Document: NUREG-0800
Document ID: dfad5166-86ba-4d57-a49c-4a918bb0780d
Document Type: srp
Title: and Section 2.4.9, as described in the corresponding SRP sections.
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0701/ML070100647.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.7
CFR Part: 
CFR Title: 

Content:
., elevations measured above a datum, the location of the datum has a significant effect on the difference expressed as a percentage. The staff will use the site grade as the datum for elevation-based site characteristics. The above rule will only be applied to compare final values of site characteristics and will not be used to assess agreement with parameters or results of intermediate calculations. 2.4.2-11 Revision 4 - March 2007 upstream ice dam or backwater effects from a downstream ice jam. Review of ice formation is described in SRP Section 2.4.7 and that of stream blockage from ice dams and ice jams is described in SRP Section 2.4.9. A detailed staff review is carried out in SER Sections 2.4.7 and 2.4.9, respectively. 9. Combined Events Criteria: The staff reviews the combinations of individual flooding mechanisms that are reasonably possible. It is possible that a combination of two or more flooding mechanisms that individually result in floods less severe than their respective worst-case occurrences may combine due to dependence among themselves and result in a more severe flood than the worst case of any one of the mechanisms occurring in isolation. ANSI/ANS-2.8-1992 provides guidance for determination of appropriate combinations of flooding mechanisms along with their relative severity within the combined events. The staff uses the recommendations of ANSI/ANS-2.8-1992, supplemented with best current practices, to review the applicant’s submittal in order to ensure that the most severe flood at the plant site has been determined. The highest flood water surface elevation is reported as a site characteristic in the staff’s SER. The staff accepts the applicant’s estimate of the highest water surface elevation if it is no more than 5% less conservative2 than the corresponding staff's assessment. All safety-related SSC should be protected against flooding by siting them above the highest flood water surface elevation or providing adequate flooding