Document: NRC Regulatory Guide
Document ID: f0baf50b-5bb7-4783-b2f9-9586e09c97e1
Document Type: regulatory_guide
Title: Preparation of Environmental Reports for Nuclear Power Stations + HISTORY - HISTORY 02/2017 – DG-4026 , Proposed Revision 3 09/2014 – Periodic Review of Revision 2 – Revise (Rev. 3)
Source: NRC Regulatory Guide Division 4
Source URL: https://www.nrc.gov/docs/ML1611/ML16116A068.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-4.2
CFR Part: 
CFR Title: 

Content:
kelihood of occurrence is lower for severe accidents than for DBAs; however the consequences of such accidents may be higher. The risks for specific severe accident types are defined as the product of the probability of that type of accident occurring multiplied by the estimated consequences for that type of accident. Severe accident types (or major release categories), source terms, and associated probabilities (i.e., core damage frequencies) are reactor-specific and determined from the design (i.e., Level 1 and Level 2) probabilistic risk assessment (PRA). DG-4026, Page 108 The Level 1 and Level 2 PRAs should be consistent with the requirements of the NRC staff’s safety review of PRAs (see SRP Chapter 19 of NUREG-0800 (Ref. 57)). The environmental risks of severe accidents (i.e., Level 3 PRA) should consider all severe accident types from the Level 1 PRA, apply all source terms from the Level 2 PRA, and should be generic for DCs and site-specific for all other applications. The Level 2 PRA information for the transition from radioactive material release to Level 3 PRA needs to have clear traceability of the release category quantifications back to the radioactive material release analysis. This would ensure that the necessary event information (e.g. event frequencies, source term release fractions and plume segments) from internally initiated events, fire events, flooding events, low power and shutdown events, and externally initiated events that could affect the Level 3 PRA analysis is provided in a suitable form for the NRC staff environmental review. The risks should be estimated using an acceptable methodology that uses onsite and regional meteorology, population, and land-use data. Relevant environmental pathways that lead to radiation dose should be considered in the consequence assessment, including the air, ground, food, surface water, and groundwater. The applicant should provide the following information to support the NRC staff’s environmental