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:
uidance. Many licensees from among the existing fleet and applicants for new reactors base their annual average (or long-term) X/Q and D/Q analyses of routine releases following the constant mean wind direction modeling approach using the NRC-endorsed XOQDOQ dispersion model. The XOQDOQ model, which implements many of the regulatory positions discussed in Revision 1 to RG 1.111, is over 30 years old and like the PAVAN dispersion model and RG 1.145, “Atmospheric Dispersion Models for Potential Accident Consequence Assessments at Nuclear Power Plants,” relies on dated dispersion algorithms. Integral to developing a draft update to RG 1.111 are three objectives: • revision of the current version of the computer code XOQDOQ; • developing a corresponding technical basis document and/or user’s guidance; and • integrating relevant aspects of the design and method of execution of the revised dispersion model (including endorsement, as appropriate, of the model and its provisions) with other regulatory and procedural guidance into RG 1.111. Issues and items expected to be addressed in the scope of revisions to RG 1.111 and the XOQDOQ dispersion model can be categorized as follows: (1) general technical and administrative; (2) specific to meteorological input data; (3) specific to model provisions and modeling assumptions; (4) requiring input from other internal stakeholders; and (5) items for discussion with the contractor. General technical issues and items include, but are not limited to: a need to provide a Windows-based operating system and graphical user interface to replace the original, main-frame based coding; a need to identify and address potential compatibility issues between the XOQDOQ computer code when revised (or an alternative dispersion model, if chosen) 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