Document: NRC Regulatory Guide
Document ID: 687c884d-2807-4ca3-ac21-69b87c59f4ab
Document Type: regulatory_guide
Title: Use of ARCON Methodology For Calculation Of Accident-Related Offsite Atmospheric Dispersion Factors
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2116/ML21165A005.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.249
CFR Part: 
CFR Title: 

Content:
for doing so and the relevant requirements in the applicable regulations are met). DG-4030, Page 8 2.1.1. Onsite Meteorological Data The meteorological data needed for χ/Q calculations using ARCON or PAVAN include wind speed, wind direction, and a measure of atmospheric stability. For construction permit, operating license, early site permit, and combined license applications, these data should be obtained from an onsite meteorological measurement program based on the guidance of RG 1.23. The meteorological data set used in these assessments should represent hourly averages as defined in RG 1.23. Data should be representative of the overall site conditions and be free from local effects such as building and cooling tower wakes, brush and vegetation, or terrain. Collected data should be reviewed on a regular basis to identify instrumentation problems and missing or anomalous observations, and the data should meet the 90-percent recovery criterion for individual and composite parameters. The size of the data set used in the χ/Q assessments should be sufficiently large such that it is representative of long-term meteorological trends at the site. The minimum amount of onsite meteorological data to be provided at the time of application (1) for a construction permit is a representative consecutive 12-month period, (2) for an operating license is a representative consecutive 24-month period, including the most recent 1-year period, and (3) for an early site permit or a combined license that does not reference an early site permit is a consecutive 24-month period of data that is defendable, representative, and complete, but not older than 10 years from the date of the application. However, three or more years of data are preferable and, if available, should be submitted 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