Document: NUREG-0800
Document ID: 50ab8154-2a3c-4c0f-8ce4-06ac83096e5c
Document Type: srp
Title: ULTIMATE HEAT SINK
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0705/ML070550048.pdf
Revision Date: 2023-06
Chapter: 9
Section ID: 9.2.5
CFR Part: 
CFR Title: 

Content:
REVIEW RESPONSIBILITIES Primary - Organization responsible for the review of cooling water systems Secondary - None I. AREAS OF REVIEW The ultimate heat sink (UHS) typically consists of an assured supply of water that is credited for dissipating reactor decay heat and essential station heat loads after a normal reactor shutdown or a shutdown following an accident or transient, including a loss-of-coolant accident (LOCA). Many commercial nuclear power plants also rely upon the atmosphere for performing the UHS function to some extent in conjunction with the assured supply of cooling water, such as in the case of spray ponds and cooling towers; and passive reactor plant designs may rely more exclusively on the atmosphere for dissipating reactor decay heat immediately following plant transient and accident conditions. This SRP section provides guidance for evaluating the capability of water sources for performing the UHS function in accordance with the requirements specified by General Design Criteria (GDC) 2, 5, 44, 45, and 46. SRP Section 2.4.11, "Cooling Water Supply," provides guidance for evaluating the effects of atmospheric conditions on the inventory and temperature of the UHS water supply, such as for spray ponds and cooling towers; and the capability of passive containment cooling systems to dissipate accident heat loads is evaluated in accordance with the guidance provided in SRP Section 6.2.2, "Containment Heat Removal Systems." These review considerations are not included within the scope of this SRP section. The water sources that make up the UHS are reviewed to assure that they are capable of performing their safety functions. This review includes the size, type of cooling water supply (e.g., ocean, lake, natural or manmade reservoir, river, or cooling tower), makeup sources to 9.2.5-2 Revision 3 - March 2007 the ultimate heat sink, and the capability of the heat sink to deliver the required flow of cooling water at appropriate temperatures for normal,