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:
uide 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. 26, for the purposes of assessing the radiological consequences of the MHA LOCA, the impact of FFRD does not need to be considered for the range of applicability of burnups and enrichments in SAND-2011-0128. For non-LOCA DBAs, Table 3 (for BWRs) and Table 4 (for PWRs) list the maximum steady-state fission product release fractions residing in the fuel rod void volume (plenum and pellet-to-cladding gap), by radionuclide groups, available for release upon cladding breach. The licensing basis of some facilities may include non-LOCA events that assume the release of the gap activity from the entire core (e.g., heavy load drop accident). For events involving the entire core, the core-average gap fractions of Tables 1 and 2 may be used, and the radial peaking factor may be omitted. The applicability of Tables 3 and 4 steady-state fission product release fractions is limited to currently approved full-length uranium dioxide (UO2) fuel rod designs operating up to 68 GWd/MTU rod average burnup at power levels below the burnup-dependent power envelope depicted in Figure 1. If it can be demonstrated that local power level, rate of fission gas release, and cumulative fission gas release remain less than the limiting co-resident UO2 fuel rod, then Table 3 and 4 steady-state fission product release fractions apply to fuel rod designs containing integral burnable absorbers (e.g., Gadolinia). If BWR part-length fuel rods are treated as full-length fuel rods with respect to overall quantity of fission products, then Table 3 steady-state fission product release fractions apply to these part-length fuel rod designs. Applicability to future fuel rod designs, including chromium (Cr)-coated zirconium (Zr) cladding, non-Zr claddings, doped UO2 fuel, high-density fuel, and mixed-oxide fuel,