Document: NRC Regulatory Guide
Document ID: 46049842-54a7-40a0-a0cc-ab115059f05e
Document Type: regulatory_guide
Title: Ultimate Heat Sink for Nuclear Power Plants + HISTORY - HISTORY DG-1275 , Proposed Revision 3, published 09/2013 (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1304/ML13043A624.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.27
CFR Part: 
CFR Title: 

Content:
tendant loads (i.e., water hammer) during normal plant operation as well as upset or accident conditions in accordance with GDC 4. e. Operating experience from other similarly designed and sited power plants should be used as appropriate. For example, if the UHS relies on cooling water from a reservoir, lake, or ocean, etc, the design should accommodate potential clogging of suction flow paths from silt, aquatic fauna such as fish, and biological growth such as seaweed (see Information Notice (IN) 2004-07 “Plugging of Safety Injection Pump Lubrication Oil Cooler with Lakeweed” dated April 7, 2004 (Ref. 12) and IN 2006-17 “Recent Operating Experience of Service Water Systems Due to External Conditions” dated July 31, 2006 (Ref. 13)). 3. Defense-in-Depth Considerations a. The UHS should consist of at least two sources of water, including their retaining structures, each with the capability to perform the safety functions specified in Regulatory Position 1.a, unless it can be demonstrated that there is an extremely low probability of losing the capability of a single source. For closed-loop cooling systems, at least two canals (aqueducts) or piping systems should connect the source(s) with the intake structures of the nuclear power unit(s), and at least two canals (aqueducts) or piping systems should return the cooling water to the source(s), unless it can be demonstrated that there is extremely low probability that a single canal (aqueduct) or piping system can functionally fail entirely as a result of natural or site-related phenomena. For once-through cooling systems, at least two canals (aqueducts) or piping systems should connect the source(s) with the intake structures of the nuclear power units, and at least two canals (aqueducts) or piping systems should discharge the cooling water well away from the nuclear power plant to ensure that there is no potential for plant flooding by the discharged cooling water, unless it can be demonstrated that there is