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:
and system flow requirements of the service water system are compatible with the heat rejection capability of the UHS. b. The UHS has the capability to dissipate the maximum possible total heat load, including LOCA under the worst combination of adverse environmental conditions including freezing and has provisions for cooling the unit (or units, including LOCA for one unit for a multiunit station with one heat sink) for a minimum of 30 days without makeup unless acceptable makeup capabilities can be demon- strated. This capability is verified by independent check calculations. c. The connecting channels, structures, man-made embankments and dams, and conduits to and from the UHS are capable of withstanding design basis natural phenomena in combination with other site-related events 9.2.5-4 Rev. 2 - July 1981 and that a single failure of any man-made feature resulting from such phenomena or events cannot prevent adequate cooling water flow or adversely effect the temperature of the water from the sink. 3. Plants utilizing cooling towers as the ultimate heat sink are reviewed as described above and in addition the reviewer determines that: a. The tower structure and basin design bases in the SAR include require- ments for withstanding design basis natural phenomena or combinations of such phenomena at historically observed intensities. The natural phenomena to be considered include tornadoes, tornado missiles, hurri- cane winds, floods, and the SSE. b. The results of failure modes and effects analyses show that the mecha- nical systems (fans, pumps, and controls) can withstand a single active failure in any of these systems, including failure of any auxiliary electric power source, and not prevent delivery of water in the quanti- ties and at temperatures required 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