Document: NUREG-0800
Document ID: dc7fdaed-8abd-4b49-b5df-dcf64a9b93b0
Document Type: srp
Title: SHORT-TERM DISPERSION ESTIMATES FOR ACCIDENTAL ATMOSPHERIC
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0520/ML052070235.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.3.4
CFR Part: 
CFR Title: 

Content:
logical data for consideration in the description of airflow trajectories from the site may include National Weather Service stations or other meteorological programs that are well maintained and well exposed (e.g., other nuclear facilities, university and private meteorological programs). 3. Atmospheric Diffusion Parameters To define atmospheric stability, measurement of vertical temperature gradient (Ref. 45 ) 18 should be used, particularly during stable conditions accompanied by low wind speeds (i.e., less than 1.5 m/s). Other classification schemes (Refs. 14 and 1515 and 16 ) may 19 be used to estimate atmospheric stability class or to determine plume spread parameters directly for unstable and neutral conditions, or for wind speeds greater than 1.5 m/s. Methods for the classification of atmospheric stability, or for direct determination of plume spread parameters, should be adequately described and substantiated for applicability to the site. Lateral and vertical plume spread parameters, and , as functions of meteorological y z conditions and topography, are reviewed with respect to the characteristics of the accidental release and distances of interest. For stability typing schemes, the curves of y and as functions of downwind distance and atmospheric stability as presented in z reference 16Ref. 17 are acceptable for most sites with the addition of an extremely 20 stable (Type G) class. For elevated releases (Ref. 1718 ) or unusual source, 21 meteorological conditions, or topography (e.g., narrow, deep valleys, channeling of airflow), modification of the and curves may be appropriate (Ref. 1819 ). y z 22 Modifications to these curves which reflect recent atmospheric tracer tests primarily during stable, light wind conditions may be used with the atmospheric dispersion model described in Regulatory Guide 1.145. Modifications based on specific studies under similar conditions may also be considered to better represent plume spread over unique terrain features