Document: NRC Regulatory Guide
Document ID: 6828ed7d-219b-4105-acf2-37d8a69c3f72
Document Type: regulatory_guide
Title: Use of ARCON Methodology For Calculation Of Accident-Related Offsite Atmospheric Dispersion Factors + HISTORY - HISTORY 08/2021 – DG-4030 , Proposed Revision 0
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML2116/ML21165A005.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-4.28
CFR Part: 
CFR Title: 

Content:
with the application. Wind direction should be expressed as the direction from which the wind is blowing (i.e., the upwind direction from the center of the site) referenced to true north. Atmospheric stability should be determined by the vertical temperature difference (ΔT) measured over the difference in height appropriate for the projected release height, including plume rise as applicable. RG 1.23 gives a table of ΔT values in units of degrees Celsius per 100 meters (°C/100m) versus stability class. If other well-documented methodologies are used to estimate atmospheric stability with appropriate justification, the ARCON model referred to in this RG may require modification. A well-documented methodology is one that is substantiated by diffusion data for conditions similar to those at the nuclear power plant site or design involved. 2.1.2 Alternative Meteorological Data This section of the RG presents examples of plausible alternate meteorological monitoring approaches for use with ARCON that have not been previously provided in recent NRC guidance. Offsite (in lieu of, or in addition to, onsite) meteorological data may be acquired by an applicant from one or more measurement locations. These may include data obtained from National Weather Service (NWS) stations, Federal Aviation Administration stations, U.S. Environmental Protection Agency (EPA)-endorsed measurement programs, other sources such as at U.S. Department of Defense or U.S. Department of Energy facilities, or from other non-NWS or non-EPA-endorsed measurement programs. If these data are not able to be directly input to ARCON, then additional processing, and additional justification, by an applicant will be necessary before the data can be used. Some technical issues that might be associated with a given data source are listed below. These are not intended to be an all-inclusive list. Additional issues may be identified by an applicant or the NRC staff during pre-application meetings, subsequent