Document: NRC Regulatory Guide
Document ID: 239cc7c1-f2cb-46cc-945d-8009db28aa6c
Document Type: regulatory_guide
Title: General Site Suitability Criteria for Nuclear Power Stations + HISTORY - HISTORY 12/2023 – DG-4034 , Proposed Revision 4 12/2011 – DG-4021 , Proposed Revision 3 02/1995 – DG-4004, Second Proposed Revision 2 11/1992 – DG-4003, Proposed Revision 2 (Rev. 4)
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML2312/ML23123A090.pdf
Revision Date: 2023-10
Chapter: 
Section ID: RG-4.7
CFR Part: 
CFR Title: 

Content:
he containment structure. In Figure 1, the two paths represent the two approaches to determining the releases of radionuclides for possible atmospheric dispersion and resultant doses to members of the public. Figure 1: Approaches for estimating radiological releases The following sections outline how these two approaches may be applied to advanced reactor designs to support estimating offsite consequences to inform alternative population-related siting considerations. Acceptable analyses, in general, can be thought of along a continuum of realism and rigor of the analysis, ranging from bounding assumptions and simple modeling to a high level of realism and detail. At the same time, the analysis should balance the degree of conservatism and margin imposed between expected conditions and analytical assumptions to address considerations such as uncertainty or operational flexibility. More conservative analyses often lead to large safety margins on various design features. Such an approach can simplify the analyses while still demonstrating adequate conservatism to address uncertainty. More realistic and rigorous analyses involve more complex modeling of event sequences and contributions from various barriers, but such an approach may justify flexibility in plant design or needed programmatic controls. Therefore, the NRC staff provides the following list of key actions for siting analyses that should be considered regardless of the approach taken: • Perform a comprehensive event assessment to identify all credible events. • Select an event or events that bound the credible events in terms of parameters (e.g., temperatures, stresses) to determine conservative estimates of the radionuclide release(s) from the first barrier (and potentially intermediate barriers) to be used for the siting evaluation. • Consider uncertainties related to the performance of the barriers commensurate with the scope of the analysis performed. • Demonstrate adequate defense in depth for