Document: NRC Regulatory Guide
Document ID: 4d46a966-d280-43da-9b03-8b0abe7b29ce
Document Type: regulatory_guide
Title: Alternative Radiological Source Terms for Evaluating Design Basis Accidents at Nuclear Power Reactors (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2120/ML21204A065.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.183
CFR Part: 
CFR Title: 

Content:
ss each assumption or to propose acceptable alternatives. Such alternatives may be justifiable on the basis of plant-specific considerations, updated technical analyses, or in some cases, a previously approved licensing basis consideration. The assumptions in the appendices are consistent with the AST identified in Regulatory Position 3. Although applicants are free to propose alternatives to these assumptions for consideration by the NRC staff, use of staff positions inconsistent with these assumptions is beyond the scope of this guidance. 5.3 Atmospheric Dispersion Modeling and Meteorology Assumptions Atmospheric dispersion factors (χ/Q values) for the EAB, the LPZ, the control room, and as applicable, the onsite emergency response facility (i.e., TSC)21 that the staff approved during initial 20 Note that for some parameters, the technical specification value may be adjusted for analysis purposes by factors provided in other regulatory guidance. For example, ESF filter efficiencies are based on the guidance in RG 1.52 (Ref. 36), rather than the surveillance test criteria in the technical specifications. Generally, these adjustments address possible changes in the parameter between scheduled surveillance tests. 21 The radiological habitability analysis for an onsite TSC is performed to support the emergency preparedness review of emergency facilities. Reevaluation of TSC habitability as part of a license amendment request may be needed if a radiological analysis of the TSC is included in that plant’s current licensing basis. For an onsite TSC, the atmospheric dispersion modeling is handled similarly to that for the control room. DG-1389, Page 31 facility licensing or in subsequent licensing proceedings may be used in performing the radiological analyses identified by this guide, provided that such values remain relevant to the particular accident, release characteristics that affect plume rise, its release points, and receptor locations. Licensees should ensure