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:
justification that conservative evaporation, drift loss (if applicable), and heat transfer values have been used. g. A cooling capacity of less than 30 days may be acceptable if it can be demonstrated that replenishment or use of an alternate water supply can be effected to ensure the continuous capability of the UHS to perform its safety functions. The availability of replenishment equipment and limitations that may be imposed on “freedom of movement” following a DBA or the occurrence of severe natural phenomena should be considered. h. Construction materials should be fire resistant. However, buried piping and spray pond piping may be constructed of fiberglass-reinforced thermosetting resin as long as the use of such material is within the limitations of RG 1.72, “Spray Pond Piping Made from Fiberglass- Reinforced Thermosetting Resin” (Ref. 9), and Table 2 of RG 1.84, “Design, Fabrication, and Materials Code Case Acceptability, ASME Section III” (Ref. 10). (Note: At the time of this RG revision, the NRC staff has not approved American Society of Mechanical Engineers (ASME) Code Case N-755-1 (Ref. 11) and the use of high-density polyethylene materials.) i. Heat loads that are important to safety or must be cooled during the 30-day recovery period by the UHS should be included in determining the UHS thermal performance, such as the heat loads from the spent fuel pool and operating pumps. j. UHS active mechanical components, such as pumps, valves, and cooling tower fans, should automatically start and open/close as appropriate to support DBA heat loads. 2. Natural Phenomena and Site Hazards Design for the Ultimate Heat Sink a. The UHS complex, whether supplied by single or multiple water sources, should be capable of withstanding, without loss of the UHS 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