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:
ocumented in a scrutable form that facilitates public review and discourse. e. The AST is peer-reviewed by appropriately qualified subject matter experts. The peer-review comments and their resolution should be part of the documentation supporting the AST. Regulatory Position 3 of this guide also identifies steady-state fission product release fractions residing in the fuel rod void volume (plenum and pellet-to-cladding gap) that are acceptable to the NRC staff for use in new power reactor applications and operating power reactors. As an alternative to these bounding release fractions, Appendix J to this guide provides an acceptable analytical procedure for calculating plant-specific or fuel rod design-specific fission product release fractions. U.S. NRC, Internal Memorandum, “Technical Bases for Draft RG 1.183 Revision 1 (2021) Non-LOCA Fission Product Release Fractions,” (Ref. 24) provides an example calculation illustrating the application of this analytical procedure. 3. Accident Source Term This regulatory position provides an AST that is acceptable to the NRC staff. It offers guidance on the fission product inventory, release fractions, timing of the release phases, radionuclide composition, chemical form, and fuel damage for LOCA and non-LOCA DBAs. The data in Regulatory Positions 3.1 through 3.5 are fundamental to the definition of an AST. Once approved, the AST assumptions or parameters specified in these positions become part of the facility’s design basis. The NRC will evaluate deviations from this guidance against Regulatory Position 2. After the NRC staff has approved an implementation of an AST, subsequent changes to the AST will also require NRC staff review under 10 CFR 50.67. 3.1 Fission Product Inventory The inventory of fission products in the reactor core and available for release to the containment should be based on the maximum full-power operation of the core with, as a minimum, current licensed values for fuel enrichment, fuel burnup,