Document: NRC Regulatory Guide
Document ID: 22ccfd5e-c5d8-4615-a02c-32369aa9f533
Document Type: regulatory_guide
Title: Acceptability of Probabilistic Risk Assessment Results for Risk-Informed Activities (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1930/ML19308B636.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.200
CFR Part: 
CFR Title: 

Content:
e of information (e.g., assumptions) that provides high confidence that the assessed outcome is as conservative as it is portrayed to be. DG-1362, Page 55 key assumption An assumption is considered to be key to a risk-informed decision when it could affect the PRA results that are being used in a decision and, consequently, may influence the decision being made. An assumption may be a key assumption relative to the base PRA or relative to an application. With respect to a base PRA, an assumption would be considered key if it affects the insights gained from the PRA results. key source of uncertainty A key source of uncertainty relates to an issue in which there is no consensus approach or model and where the choice of approach or model is known to have an impact on the risk profile (e.g., total CDF and total LERF), the set of initiating events and accident sequences that contribute most to CDF and to LERF such that it influences a decision being made using the PRA. Such an impact might occur, for example, by introducing a new functional accident sequence or a change to the overall CDF or LERF estimates significant enough to affect insights gained from the PRA. level of detail Relates to the degree to which (i.e., amount of) information is discretized and included in the model or analysis. model4 A qualitative and/or quantitative representation that is constructed to portray the inherent characteristics and properties of what is being represented (e.g., a system, component or human performance, theory or phenomenon). A model may be in the form, for example, of a structure, schematic or equation. Method(s) are used to construct the model under consideration. newly developed method4 A PRA method that has either been developed separately from a state-of- practice method or is one that involves a fundamental change to a state-of- practice method. An NDM is not a state-of practice or a consensus method. PRA An approach is considered to be a PRA when it (1) provides a