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:
r technical specifications in determining the inventory of the damaged rods. The licensee should not adjust the fission product inventory for events postulated to occur during power operations at less than full-rated power or those postulated to occur at the beginning of core life. For events postulated to occur while the facility is shut down (e.g., a fuel handling accident), the licensee may model radioactive decay from the time of shutdown. 3.2 Release Fractions10 For the MHA LOCA, Table 1 (for BWRs) and Table 2 (for PWRs) list the core inventory release fractions, by radionuclide groups, for the gap release and early in-vessel damage phases. These fractions are applied to the equilibrium core inventory described in Regulatory Position 3.1. Tables 1 and 2, below, are hybridized accident source terms from SAND-2011-0128 that utilize the maximum release fractions from low- and high burnups results. This approach accounts for different radionuclide quantities at different burnups throughout the operating cycle. “Applicability of Source Term for Accident Tolerant Fuel, High-Burnup and Extended Enrichment,” (Ref. 25) in part, documents the applicability of SAND-2011-0128 for burnups up to 68 gigawatt-days per metric ton of uranium (GWd/MTU) peak rod average and enrichments up to 8 percent for certain near-term ATF designs which include chromium-coated cladding and chromia-doped fuel, but do not include Iron (Fe)-Chromium (Cr)- Aluminum (Al) alloy cladding. The use of these tables is not endorsed for mixed oxide fuels and accident tolerant fuel design concepts not discussed in Ref. 25. U.S. NRC, Internal Memorandum, “Letter Report on Evaluation of the Impact of Fuel Fragmentation, Relocation, and Dispersal for the Radiological Design Basis Accidents in Regulatory Guide 1.183,” (Ref. 26) assessed the impact of fuel fragmentation, relocation, and dispersal (FFRD) behavior on the accident source terms from SAND-2011-0128. Based upon limitations described in Ref.