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:
hod for Calculating the Fractional Release of Volatile Fission Products from Oxide Fuel” (Ref. 6), (4) adding information to acknowledge the proposed RG may provide useful information for satisfying the radiological dose analysis requirements in 10 CFR Part 50 and 10 CFR Part 52 for advanced LWR design and siting, (5) providing additional guidance for modeling boiling-water reactor (BWR) main steam isolation valve (MSIV) leakage, (6) adding guidance for accident tolerant fuel (ATF), high-burnup fuel, and increased enrichment source term analyses, (7) revising transport and decontamination models for the fuel handling DBA, (8) adding guidance for crediting holdup and retention of MSIV leakage within the main steamlines and condenser for BWRs, and (9) providing additional meteorological assumption guidance. Background An accident source term is intended to represent a major accident involving significant core damage not exceeded by that from any other credible accident. NRC staff experience in reviewing license applications has indicated the need to consider other accident sequences of lesser consequence but higher probability of occurrence. Facility-analyzed DBAs are not intended to be actual event sequences; rather, they are intended to be surrogates to enable deterministic evaluation of the response of engineered safety features (ESFs). These accident analyses are intentionally conservative to compensate for known uncertainties in accident progression, fission product transport, and atmospheric dispersion. Probabilistic risk assessments (PRAs) can provide useful insights into system performance and suggest changes in how the desired defense in depth is achieved. The NRC’s policy statement on the use of PRA methods (Ref. 7) calls for the use of PRA technology in all regulatory matters in a manner that complements the NRC’s deterministic approach and supports the traditional defense in depth philosophy, which continues to be an effective way to account for