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:
ments. 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 warning scheme for seismically induced dam failure floods. For rainfall floods, the first stage (Stage I) of shutdown will begin when sufficient rainfall occurs to yield a projected plant site water level of 212.4 meters (697.0 feet) above mean sea level in the 24 winter months (October 1 through April 15) and 214 meters (703 feet) above mean sea 25 level in the summer months (April 16 through September 30). These water levels assure ensure that any additional rain will not produce water levels in excess of 214 meters26 (703 feet) mean sea level in less than 27 hours. This level provides a 0.6-meter (2-foot) 27 margin (requested by us) so that waves resulting from high winds cannot disrupt flood protection preparation, i.e., cannot exceed plant grade of 215 meters (705 feet) above 28 mean sea level. Stage I will be maintained until either Stage II begins, or until the applicant determines that floodwaters will not exceed elevation 214 meters (703 feet) above mean sea level 29 at the plant. Stage II shutdown will begin only when enough additional rain has fallen to yield water levels in excess of 214.3 meters (703.0 feet) above mean sea level. The 30 applicant estimates that required shutdown procedures will take no longer than 24 hours, which allows a 3-hour contingency margin. As stated in Section 2.4.4 above, the failure of nine upstream dams either singly or in varying combinations can produce floods over plant grade. Stage I shutdown will be DRAFT Rev. 3 - April 1996 2.4.14-6 started upon notification that any one of these dams has failed, and will continue until it has been determined that critical combinations do not exist. At our request, the applicant committed to initiating Stage II shutdown if communications are lost, or if there is no certainty that critical