Document: NRC Regulatory Guide
Document ID: 82659041-98b0-4721-b25d-c4fb2ea394d0
Document Type: regulatory_guide
Title: An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis (Rev. 3)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1635/ML16358A153.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.174
CFR Part: 
CFR Title: 

Content:
tion or when the failure of the programmatic activity could prevent an engineered safety feature from performing its intended function. The NRC also recognizes that compensatory measures are sometimes associated with temporary conditions. A licensee might propose a risk-informed licensing basis change to permit occasional entry into conditions requiring measures that rely on plant programs to compensate for reduced capability of engineered systems or for one-time to allow completion of corrective action to restore engineered systems to match the design and DG-1285, Page 20 licensing basis. For such situations, the licensee should demonstrate that the plant condition requiring such compensatory measures would occur at a sufficiently low frequency or that the timeframe to implement corrective action is commensurate with the significance of the nonconforming condition. 3. Preserve system redundancy, independence, and diversity commensurate with the expected frequency and consequences of challenges to the system including consideration of uncertainty. The proposed licensing basis change should not significantly reduce the redundancy, independence, or diversity of systems. The evaluation of the proposed licensing basis change should demonstrate that the change does not result in a significant increase in the expected frequency of challenges to the system or consequences of failure of the system functions as a result of a decrease in redundancy, independence, or diversity. To evaluate this factor, the licensee should demonstrate that any reduction in redundancy, independence, or diversity of systems does not result in a significant increase in risk. This evaluation should determine whether the proposed licensing basis change: (1) is consistent with the assumptions in the plant’s safety analysis, if applicable; (2) increases the frequency of challenges to the plant resulting from failure of the system; and (3) decreases the reliability or availability of the system to