Document: NRC Regulatory Guide
Document ID: 29acb072-d497-44e6-ac1c-a053c0a468a0
Document Type: regulatory_guide
Title: Meteorological Monitoring Programs for Nuclear Power Plants + HISTORY - HISTORY DG-1164 , Third Proposed Revision 1, published 10/2006 Draft ES 926-4 , Second Proposed Revision 1, entitled "Meteorological Measurement Program for Nuclear Power Plants," published 04/1986 Draft SS 926-4 , First Proposed Revision 1, entitled "Meteorological Programs In Support of Nuclear Power Plants," published 09/1980 Revision 0, entitled "Onsite Meteorological Programs," was issued as Safety Guide 23
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0625/ML062540408.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.23
CFR Part: 
CFR Title: 

Content:
same tower. It is defined as the upper level temperature measurement minus the lower level temperature measurement. Water Equivalent: The amount of water, in inches, measured at ground level from rain and/or melted frozen precipitation (e.g., snow, freezing precipitation). 5 The 10-meter (33-foot) level is generally accepted throughout the world as a standard meteorological reference measurement level. The 60-meter (197-foot) level generally coincides with assumptions regarding releases from light- water reactors. A measurement height other than 60 meters (197 feet) may be appropriate for those plants where the most probable atmospheric release height is other than 60 meters (197 feet). 6 Vertical temperature difference is the preferred method for determining Pasquill stability classes at nuclear power plants for licensing purposes because it is an effective indicator for the worst case stability conditions (e.g., Pasquill stability classes E, F, and G), and certain Gaussian plume models endorsed by the NRC (such as the models referenced in Regulatory Guides 1.145 and 1.194) are based on empirically derived plume meander factors from field tracer studies that used ∆T to classify atmospheric stability. Alternative methods may be used to classify atmospheric stability if appropriate justification is provided. However, the use of alternative methods to classify atmospheric stability may require modifications of the models described in Regulatory Guides 1.145 and 1.194. DG-1164, Page 7 Wet-Bulb Temperature: The lowest temperature an air parcel could achieve if cooled by the release of latent heat caused by evaporation of all its available moisture. The bigger the difference between the actual temperature (or dry-bulb temperature) and the wet-bulb temperature, the relatively drier the air. Wind Direction: The direction from which the wind is blowing. Wind direction is reported in degrees azimuth, measured clockwise from true north and ranging from 0E to 360E (e.g.,