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:
priate. Since the AST and the TEDE criteria are part of the approved design basis for the facility, use of the AST and TEDE criteria in new applications at the facility does not constitute a change in analysis methodology that would require NRC approval.7 This guidance also applies to selective implementations to the extent that the affected analyses are within the scope of the approved implementation as described in the facility design basis. In these cases, the updated analyses should consider the characteristics of the AST and TEDE criteria identified in the facility design basis. Use of other characteristics of the AST or TEDE criteria that are not part of the approved design basis and changes to previously approved AST characteristics require prior NRC staff approval under 10 CFR 50.67. 1.3.5 Equipment Environmental Qualification A proposed plant modification associated with the AST implementation may affect current EQ analyses. The licensee should update EQ analyses that have assumptions or inputs affected by the plant modification to address these impacts. New facilities proposing to implement an AST should continue to use the guidance in Appendix I to RG 1.183, Revision 0, until RG 1.89 incorporates guidance on an AST. 1.4 Risk Implications This guide provides regulatory assumptions that licensees should use in their calculation of the radiological consequences of DBAs. These assumptions have no direct influence on the probability of the design basis initiator. These analysis assumptions cannot increase the core damage frequency or the large early release frequency. However, facility modifications made possible by the AST could have an impact on risk. If the proposed implementation of the AST involves changes to the facility design that would invalidate assumptions made in the facility’s PRA, the licensee should evaluate the impact on the existing PRAs. 7 In performing screenings and evaluations pursuant to 10 CFR 50.59, it may be necessary to compare dose