Document: NUREG-0800
Document ID: 96b2f110-400e-48b7-847b-b1b258cef99e
Document Type: srp
Title: TECHNICAL SPECIFICATIONS AND EMERGENCY OPERATION
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070264.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.4.14
CFR Part: 
CFR Title: 

Content:
l allow preparation steps and some damage, but will withhold major economic damage until Stage II warning assures ensures a flood above plant grade. 2.4.14-5 DRAFT Rev. 3 - April 1996 Reservoir levels for large rainfall floods can be predicted well in advance by the applicant. The applicant estimates that a minimum of 27 hours, divided into the two warning stages, will be available between the time a pre-flood preparation order is issued and the time the flood water could exceed plant grade. A minimum 10-hour Stage I will begin upon prediction that flood-producing conditions might develop. A minimum 17-hour Stage II will be based on a confirmed estimate that conditions will produce a flood above plant grade. Seismically induced failure of upstream dams can result in flood surges that exceed plant grade. However, such surges do not have a water level potential as great as the rainfall-induced probable maximum flood water level. A minimum of 27 hours, divided into the warning stages, is estimated by the applicant to be available to prepare the plant for such flooding. The applicant defines "flood mode" operation as the means by which the plant will be safely maintained during the time when flood waters exceed plant grade, elevation 215 meters (705 feet) above mean sea level, and are allowed ingress into plant structures, 23 and during the succeeding time period until recovery is accomplished. Plant cooling requirements during flood mode operation will be met by the essential raw cooling water system, unless flood mode operation is necessary prior to operation of the permanent essential raw cooling water pumping station. If the latter is necessary, the auxiliary essential raw cooling water system will provide closed-cycle water circulation to meet plant cooling requirements. Water supplied by both these systems is discussed in greater detail above in Sections 2.4.1 and 2.4.11. The applicant proposes one kind of warning scheme for rainfall floods and another type of