Document: NUREG-0800
Document ID: 4e1c316a-99c2-4fd3-9d9b-323791bd85f8
Document Type: srp
Title: SHORT-TERM ATMOSPHERIC DISPERSION ESTIMATES FOR ACCIDENT
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0707/ML070730398.pdf
Revision Date: 2023-06
Chapter: 2
Section ID: 2.3.4
CFR Part: 
CFR Title: 

Content:
espect to airflow characteristics of the site and vicinity, and representation of normal annual distribution of meteorological conditions. If adequate onsite meteorological data are not available, the reviewer must ensure that adequate conservatism is applied. General criteria for onsite meteorological monitoring programs are stated in Regulatory Guide 1.23 and SRP section 2.3.3. Additional sources of meteorological 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 as described in Regulatory Guide 1.23 should be used. Other classification schemes (Refs. 23 and 24) may be used to estimate atmospheric stability but the use of alternative methods to classify atmospheric stability may require modifications to the models described in Regulatory Guides 1.145 and 1.194. 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, σy and σz, as functions of meteorological conditions and topography, are reviewed with respect to the characteristics of the accidental release and distances of interest. For elevated releases or unusual source, meteorological conditions, or topography (e.g., narrow, deep valleys, channeling of airflow), modification of the σy and σz parameters discussed in Regulatory Guide 1.145 may be appropriate (Ref. 18). Modifications based on specific studies under similar conditions may be considered to better represent plume spread over unique terrain features such as deserts (Ref. 22) and large bodies of water (Ref. 26). Such specific