Document: NUREG-0800
Document ID: ec8e8c49-ea1e-4b46-a508-500ea11caad2
Document Type: srp
Title: ULTIMATE HEAT SINK
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0523/ML052350549.pdf
Revision Date: 2023-06
Chapter: 9
Section ID: 9.2.5
CFR Part: 
CFR Title: 

Content:
for safe shutdown. c. Adequate net positive suction head (NPSH) can be provided to all essen- tial pumps considering variations of water level in the basis. This is verified by performing independent calculations. d. The towers can provide the design cooling water temperature under the worst combination of adverse environmental conditions including freezing, and that the supply of water in the basins can provide a 30-day capability for long-term cooling at the required temperature without makeup unless acceptable makeup capabilities can be demonstrated. This is verified by independent calculations. e. Cooling towers or spray ponds used as a UHS and designed to withstand the effects of tornado missiles need not be designed to seismic Category I if another UHS is also available that is designed to meet the seismic classification guidelines of Regulatory Guide 1.27. 4. Reactor sites that utilize large natural or man-made water sources which for all practical purposes have an infinite supply of water are reviewed as described in items 1 and 2, above, and in addition the reviewer determines: a. By evaluation of the SAR information or independent calculations, that the water source is adequate taking into account the effects of design basis natural phenomena such as tornadoes, hurricane winds, probable maximum floods, tsunamis, seiches, and the SSE. b. By reviewing the SAR preliminary site and plant arrangement sketches (CP) and (OL) site drawings and plant arrangement drawings that the design of the intake and outlet conduits (open or closed type) are properly separated to~prevent recirculation or water temperature stratification. c. That man-made earth dam, dike, or other structure design bases in the SAR include requirements for withstanding the design basis natural phenomena or combinations of such phenomena at historically observed intensities. In the event of failure of a dam, dike, or other struc- ture not designed to withstand the design basis natural phenomena