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:
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, has functioned properly over its lifetime, and (based on projection of the best available data) is expected to function properly for the lifetime of the nuclear power unit(s). However, compliance with these site characteristics would not remove the need for another source of cooling water if a single failure of the dam could result in losing the cooling capability of this source of water. To ensure that the UHS has sufficient water available for its safety function if a dam or other water-controlling structure is required, the dam or other water-controlling structure and connecting piping systems should be included in the Structures Monitoring Program under the Maintenance Rule at 10 CFR 50.65. Structural components not required to be designed to withstand the SSE or the probable maximum flood should at least be designed and constructed to withstand the effects of the operating-basis DG-1275, Page 7 earthquake, as defined in Appendix A, “Seismic and Geologic Siting Criteria for Nuclear Power Plants,” to 10 CFR Part 100, “Reactor Site Criteria” (Ref. 6), or Appendix S, “Earthquake Engineering Criteria for Nuclear Power Plants,” to 10 CFR Part 50, as applicable. The importance of the UHS to nuclear safety is such that, if during plant operation the capability of the UHS is threatened (e.g., to permit necessary maintenance or as a result of damage), restrictions should be placed on plant operation. The technical specifications should specify a limiting condition for operation and state the actions to be taken if the UHS limiting condition for operation is temporarily unavailable during the operating modes. Harmonization with International and Industry Standards The International Atomic Energy Agency (IAEA) has established a series of safety guides and