Document: NRC Regulatory Guide
Document ID: 8a2332d3-66ca-40af-84e1-507db8b26559
Document Type: regulatory_guide
Title: TRIAL - Acceptability of Probabilistic Risk Assessment Results for Non-Light Water Reactor Risk-Informed Activities
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2123/ML21235A008.pdf
Revision Date: 2023-05
Chapter: 
Section ID: RG-1.247
CFR Part: 
CFR Title: 

Content:
s to the frequency of each risk-significant event sequence and event sequence family. • Uncertainties in the quantification results are characterized and quantified. C.1.3.16 Mechanistic Source Term Analysis Probabilistic Risk Assessment Element This section identifies the objectives and the characteristics and attributes of the mechanistic source term analysis PRA element for an NLWR PRA that addresses all radiological sources, all hazards, all POSs, and all levels of PRA analysis. The objective of the mechanistic source term analysis is to characterize the radiological release to the environment resulting from each event sequence leading to a release. The characterization includes an identification of risk-significant isotopes to be included in the consequence assessment and data needed to characterize release locations, the physical and chemical form of the released radioisotopes, the time- dependent isotopic release rates to the atmosphere, heat content (or energy) of the carrier fluid, and the data needed to estimate plume buoyancy. The mechanistic source term analysis is sufficient to provide mechanistic source terms for radiological consequence analysis. The computer codes used to perform the analyses for developing the mechanistic source terms are validated and verified for both technical integrity and suitability, and they accurately analyze the phenomena of interest. Qualified personnel who are well trained in the use of the codes perform the calculations. The characteristics and attributes needed to achieve the objectives of a mechanistic source term analysis PRA element are as follows: • Radionuclide releases are grouped into smaller subsets of representative source terms or release categories. • Radionuclide releases are assessed for each release category, including consideration of timing, location, amount released, and the radionuclide transport barriers and transport mechanisms. • Radiological source terms are calculated using appropriate