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:
s assurance that offsite radiation doses from postulated accidents will not exceed the guideline radiation doses specified in 10 CFR Part 100.14 III. REVIEW PROCEDURES 1. Atmospheric Dispersion Models The reviewer verifies that adequately conservative atmospheric dispersion models, with adequate onsite meteorological data as input to the models, have been used to calculate relative concentrations at appropriate distances and directions from postulated release points during accidental airborne releases of potentially hazardous materials. If adequate onsite meteorological data are not available for the CP review, the reviewer must ensure that adequate conservatism has been applied to the calculated relative concentrations for accidental airborne effluent releases based on available data.15 The applicant's dispersion models are compared to the general Gaussian models which are contained in Regulatory Guide 1.145 for design basis accidental releases. The models are reviewed for suitability to release characteristics, plant configuration, and site topography. The accidents and release characteristics to be considered are obtained from the reviews of SAR safety analysis report (SAR) Chapter 15. When the Gaussian 16 assumptions are not applicable (e.g., buoyant gases and close-in estimates made for points among or near buildings), other models and techniques used to make estimates are identified and evaluated. Each release should be characterized as either an elevated point source or a ground-level point source. Generally the release is considered to be elevated if the release point is at least two-and-one-half times as high as nearby solid structures. Turbulent mixing of the effluent into the wake of plant structures is usually allowed for ground-level releases. The volumetric 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