Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
eorological data. • Meteorological data sets with missing data are completed by substituting data using interpolation techniques, substitution techniques using data from onsite sources (e.g., from a different tower elevation, nearby onsite locations with similar characteristics), or substitution techniques using data from regional recognized sources (e.g., government weather service stations) where onsite meteorological data are not available. • For PRAs performed prior to selecting a proposed site, postulated meteorological data are provided that are representative of a reasonable number of sites that have been or may be considered. • The uncertainties related to the meteorological data analysis are identified and characterized. RG 1.247, Page 47 The objective of the atmospheric transport and diffusion analysis is to perform an evaluation that provides time-dependent air and ground concentrations resulting from a release of radioisotopes. The characteristics and attributes needed to achieve the objectives of the atmospheric transport and diffusion analysis PRA analysis element are as follows: • An appropriate atmospheric dispersion model is used. • The analysis uses the meteorological data developed in the meteorological data analysis PRA analysis element. • The analysis uses a model that includes uniform hourly wind field data from a single representative meteorological tower. • The analysis includes the selection of dispersion parameters appropriate to the characteristics of the area and distance ranges under consideration. Near-field effects (such as elevated releases of radioactive material, building wake effects such as wake-induced downwash and enhanced diffusion due to near-field wake-induced turbulence, plume meander, and plume rise) are adequately characterized. • The deposition of airborne material on the ground by wet and dry deposition and the resulting depletion of the airborne material with downwind distance are modeled in a manner