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:
is should also be made. In cases where canals (aqueducts) or piping systems are required as part of the UHS, at least two should be provided, even if only one source of water can be demonstrated to be adequate. However, a single canal (aqueduct) may be acceptable if it satisfies the four conditions above. In the event the UHS includes more than one source of water, the individual water sources may have different design requirements. Multiple water sources, including their associated retaining structures and required canals (aqueducts) and piping systems, should be separated and protected so that failure of either one will not induce failure in any other that would preclude accomplishing the safety functions of the UHS. The UHS complex (whether it comprises an acceptable single source or multiple sources of water), but not necessarily its individual features, must be capable of withstanding each of the most severe natural phenomena expected, other site-related events, reasonable combinations of natural phenomena or site- related events, and a single failure of manmade structural features without loss of capability of the UHS to accomplish its safety functions. The most severe phenomena may be considered to occur independently and not simultaneously (e.g., a tornado and an earthquake). In addition, the single failure of manmade structural features need not be considered to occur simultaneously with severe natural phenomena or site-related events unless the severe natural phenomena can cause failure of a manmade structural feature. The UHS complex should be shown to be highly reliable by demonstrating that certain site characteristics are satisfied. Such site characteristics might include: (1) the river cannot be diverted or blocked sufficiently to affect the availability of water at the connecting piping systems, (2) no serious transportation accidents have occurred or can be reasonably expected, and (3) the dam was designed to appropriately conservative requirements,