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:
c correction is based on one-half the minimum cross-sectional area of the structure from which the effluent is released. Most accidental releases can be considered as continuous releases (i.e., on the order of several minutes or more). However, some releases such as from steam line breaks or of hazardous chemicals may be considered as instantaneous (puffs). The general Gaussian diffusion model for continuous releases is used to evaluate releases on the order of several minutes or more. For puff releases, instantaneous point-source Gaussian diffusion equations are used with a correction for initial source volume (Ref. 1213 ). 17 Other modifications to the atmospheric dispersion model which should be considered include restrictions to horizontal or vertical plume spread (e.g., by narrow deep valleys, channeling of airflow, and by persistent low-level temperature inversions). Fumigation conditions should be considered for elevated releases. In the absence of site-specific 2.3.4-5 DRAFT Rev. 2 - April 1996 information concerning the frequency, duration, and directional preference of fumigation conditions, deterministic approaches such as those described in Regulatory Guides 1.5, 1.24, 1.25, and 1.145 may be used. 2. Meteorological Data The meteorological data used in atmospheric dispersion analyses are reviewed for compatibility with the models, representativeness with respect 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 data are stated in Regulatory Guide 1.23 and in subsection III.2 of 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