Document: NRC Regulatory Guide
Document ID: c406a126-ec51-4b8a-aafa-6fd4c7a7e7b9
Document Type: regulatory_guide
Title: Methods for Estimating Atmospheric Transport and Dispersion of Gaseous Effluents in Routine Releases from Light-Water-Cooled Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1411/ML14114A674.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.111
CFR Part: 
CFR Title: 

Content:
hosen) and a commercially available version included as part of the NRCDose© suite of codes used to implement RG 1.109, “Calculation of Annual Doses to Man from Routine Release of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, Appendix I,” (not known if the XOQDOQ code is checked by NRC when that part of the NRCDose© package is updated by the vendor); and a need to evaluate the extent to which revisions to XOQDOQ and RG 1.111 will take into consideration the modeling criteria specified in the recently issued standard ANSI/ANS-2.15-2013, “Criteria for Modeling and Calculating Atmospheric Dispersion of Routine Radiological Releases from Nuclear Facilities.” Lessons-learned from the update of the PAVAN dispersion model (in process) need to be considered as well. Administrative issues and items to be addressed in the revision of RG 1.111 include, but are not limited to: updating references (some of which may no longer be applicable) and regulatory citations (some of which are no longer valid); defining terminology; considering the need to address the scope of NRC approval or acceptance of non-NRC endorsed dispersion models; and recognizing the need to update other related guidance documents and, if necessary, developing related interim staff guidance. Issues and items specific to meteorological input data include, but are not limited to: using hourly data instead of joint frequency distribution summaries; clarifying acceptable period(s) of record; and discussing potential implications of using non-sequential data sets. The current guidance mentions situations where it is appropriate to account for wet deposition effects although the current dispersion model has no such provisions. In that regard, the revised guidance should clearly address related terminology (e.g., a well- defined rainy season, grazing and growing seasons), the possible use of seasonal as opposed to, or in addition to, annual data sets, whether and how to