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:
, standards or third party guidance documents (“secondary references”). If a secondary reference has itself been incorporated by reference into NRC regulations as a requirement, then licensees and applicants must comply with that standard as set forth in the regulation. If the secondary reference has been endorsed in a regulatory guide as an acceptable approach for meeting an NRC requirement, then the standard constitutes a method acceptable to the NRC staff for meeting that regulatory requirement as described in the specific regulatory guide. If the secondary reference has neither been incorporated by reference into NRC regulations nor endorsed in a regulatory guide, then the secondary reference is neither a legally-binding requirement nor a “generic” NRC approval as an acceptable approach for meeting an NRC requirement. However, licensees and applicants may consider and use the information in the secondary reference, if appropriately justified and consistent with current regulatory practice, consistent with applicable NRC requirements such as 10 CFR 50.59, “Changes, tests and experiments.” DG-1275, Page 8 C. STAFF REGULATORY GUIDANCE 1. System Design Considerations for the Ultimate Heat Sink a. The UHS should be capable of providing sufficient cooling for at least 30 days to: (1) permit simultaneous safe shutdown and cooldown of all nuclear reactor units that it serves and to maintain them in a safe-shutdown condition, and (2) in the event of an accident in one unit, to limit the effects of that accident safely, to permit simultaneous and safe shutdown and cooldown of any remaining units, and to maintain them in a safe-shutdown condition. Procedures should be available for ensuring a continued capability of the UHS to provide sufficient cooling after 30 days. b. Sufficient conservatism should be provided to ensure that a 30-day cooling supply is available and that design-basis temperatures of equipment that is important to safety are not exceeded. For