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:
Heat Sink Spray Ponds” (Ref. 4), and a technical report titled “Method for Analysis of Ultimate Heat Sink Cooling Tower Performance” (Ref. 5), respectively. Design inputs for wind functions and wind gradients and UHS modeling are unique to each facility and should be justified for cooling ponds and spray ponds. In addition, UHS cooling towers should be designed for the potential effects of recirculation (defined as some portion of the saturated air leaving a tower being induced back into the same tower’s air inlets) and interference (defined as a portion of the saturated effluent of an upwind tower contaminating the ambient intake air of a downwind tower). The design, location, and orientation of the towers can influence the entering wet-bulb temperature, which can require additional wet-bulb temperature margins ranging from 0.5 °F to 4 °F. These additional wet-bulb temperature margins should be determined on a case-by-case basis. The meteorological conditions considered in the design of the UHS to ensure sufficient cooling for at least 30 days should be selected with respect to the controlling parameter(s) and critical time periods unique to the specific design of the UHS. One critical time period is associated with ensuring that the design basis temperatures of equipment that is important to safety are not exceeded. This critical time period would be the time interval after a DBA to when the intake water to the plant from the UHS reaches its maximum value. The meteorological conditions resulting in the maximum intake water temperature to the plant from the UHS should be the worst combination of controlling parameters, including diurnal variations, where appropriate, for the critical time period unique to the specific design of the UHS. For example, if a wet cooling tower is used as the UHS, the controlling parameter would be a wet-bulb temperature, and the critical time period may be on the order of several hours. Therefore, an acceptable design basis