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:
nts. DG-1362, Page 11 C. STAFF REGULATORY GUIDANCE 1. An Acceptable Base PRA This section describes one acceptable approach for defining the acceptability of a base probabilistic risk assessment (PRA) used in regulatory decision-making for commercial light-water reactor (LWR) nuclear power plants. As defined in the Glossary of this RG, an approach is considered to be a PRA when it (1) provides a quantitative assessment of the identified risk in terms of scenarios that result in undesired consequences (e.g., core damage or a large early release) and their frequencies, and (2) is comprised of specific technical elements in performing the quantification. The base PRA is defined as the PRA from which results or insights are derived or that is modified and/or manipulated to support a risk-informed U.S. Nuclear Regulatory Commission (NRC) regulatory activity. The base PRA provides a quantitative assessment of the identified risk of the as-built and as-operated plant in terms of scenarios that result in undesired consequences (e.g., core damage or a large early release) and their frequencies and is comprised of specific technical elements in performing the quantification. The base PRA serves as the foundational representation of the as-built and as-operated plant necessary to support an application. In some cases, such as applications related to 10 CFR 50.69, “Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power Reactors,” the PRA used in the application may be the base PRA. Regulatory position C.1 of this RG and its subsections provide guidance in the following four areas that collectively determine the acceptability of a base PRA: • Scope of a base PRA: The scope of a base PRA is defined in terms of (1) the metrics used to characterize risk, (2) the plant operating states (POSs) for which the risk is to be evaluated, and (3) the causes of initiating events (hazard groups) that can potentially challenge and disrupt the