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:
HS safety functions, all of the following events: (1) the most severe natural phenomena expected at the site in accordance with GDC 2, (2) the site-related events (e.g., transportation accident, river diversion) that historically have occurred or that may reasonably be expected to occur during the plant lifetime, (3) reasonably probable combinations of less severe natural phenomena or site-related events, and (4) failure of reservoirs, dams, and other manmade water retaining structures both upstream and downstream of the site including the potential for resultant debris to block water flow. DG-1275, Page 10 b. UHS features constructed specifically for normal operation and shutdown of the nuclear power unit(s) that do not provide a post-accident safety function and are not required to be designed to withstand the SSE, tornadoes, or the probable maximum flood, should at least be designed and constructed to withstand the effects of the operating-basis earthquake as defined in Appendix A to 10 CFR Part 100 or Appendix S to 10 CFR Part 50, as applicable. c. The potential for adverse environmental conditions, such as icing, should be considered in determining UHS performance. If applicable, the potential for water freezing in the UHS water storage facility should also be analyzed. The maximum accumulated degree-days below freezing recorded in the site region during the winter (or during the worst-case freezing spell in warmer climates) may be a reasonably conservative site characteristic for evaluating this potential. d. The UHS complex should be designed to accommodate the effects of missiles inside and outside of containment, effects of pipe whip, jets, environmental conditions from high and moderate energy line breaks, and dynamic effects of flow instabilities and attendant 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