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:
le for some requirements. There may be other situations where the state-of-practice is not acceptable for a specific application. For example, it is not state-of-practice to include pipe failures in a base PRA model; however, for changes to inservice inspection and pressure boundary repair and replacement requirements, inclusion of pipe failures is needed. Therefore, it cannot be assumed that the state-of-practice is acceptable for every risk-informed application. The requirements in an ASME/ANS PRA standard are either process-related or are technical in nature. The process-related requirements address the process for application, development, maintenance and upgrade, and peer review. The technical requirements address the technical elements of the PRA and what is necessary to acceptably perform that element. For process requirements, the intent is generally straightforward and the requirement is either met or not met. For the technical requirements, it is not always as straightforward. Many of the technical requirements in an ASME/ANS PRA standard are applied more than once in developing the PRA model. For example, the requirements for systems analysis in a Level 1, internal events, at-power PRA apply to all systems modeled, and certain data requirements apply to all parameters for which estimates are provided. If among these systems or parameter estimates there are instances where a specific requirement has not been met, it is not necessarily indicative that this requirement has not been met. If the requirement has been met for the majority of the systems or parameter estimates, and the identified instances are understood to be isolated mistakes or oversights, the requirement would be considered to be met. If, however, there is a systematic failure to address the requirement (e.g., component boundaries have not been defined anywhere), then the requirement has not been met. In either case, the instances of noncompliance with the PRA standard requirements are to be