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
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CFR Title: 

Content:
lume by wet deposition. 8 For example, trees 15 meters (49 feet) in height should be no closer than 150 meters (492 feet) from the tower or mast. DG-1164, Page 8 Table 1. Classification of Atmospheric Stability Stability Classification Pasquill Stability Category Temperature change with height (EC/100m) Extremely unstable A ∆T # !1.9 Moderately unstable B !1.9 < ∆T # !1.7 Slightly unstable C !1.7 < ∆T # !1.5 Neutral D !1.5 < ∆T # !0.5 Slightly stable E !0.5 < ∆T # 1.5 Moderately stable F 1.5 < ∆T # 4.0 Extremely stable G ∆T > 4.0 Ambient temperature should be monitored at approximately 10 meters (33 feet). Precipitation should be measured at ground level near the base of the mast or tower.7 At sites where there is a potential for fogging or icing from the release of water vapor caused by plant operations (e.g., because of the operation of a cooling tower or cooling pond), instrumentation should be provided for measuring temperature and humidity (e.g., dew point, wet-bulb temperature, or relative humidity) at heights representative of water-vapor release. 3. Siting of Meteorological Instruments To the extent practical, meteorological measurements should be made in locations that can provide data representative of the atmospheric conditions into which material will be released and transported. The tower or mast should be sited at approximately the same elevation as finished plant grade. Factors to be considered in selecting the appropriate measurement locations and installation of the instruments include the prevailing wind direction, the topography, and the location of manmade and vegetation obstructions. Whenever possible, wind measurements should be made at locations and heights that avoid airflow modifications by obstructions such as large structures, trees, or nearby terrain with heights exceeding one-half the height of the wind measurement. The separation between the wind sensor and such obstructions should be 10 times the obstruction height.8 Wind