Document: NUREG-0800
Document ID: 7f6b0af0-d79e-4704-9eac-aa03109a7731
Document Type: srp
Title: RISK-INFORMED DECISIONMAKING: TECHNICAL SPECIFICATIONS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0425/ML042520260.pdf
Revision Date: 2023-06
Chapter: 16
Section ID: 16.1
CFR Part: 
CFR Title: 

Content:
equency (A CDF), the ICCDP,2 and, where appropriate, the change in large early release frequency (A LERF) and the ICLERP.4 Tier 2 is an evaluation of the process used to address potentially high- risk configurations that could exist if equipment in addition to that associated with the change were to be taken out of service simultaneously, or other risk-significant operational factors such as concurrent system or equipment testing were also involved. The objective of this part of the review is to ensure that appropriate restrictions on dominant risk-significant configurations associated with the change are in place. Tier 3 is an evaluation of the overall configuration risk management program to ensure that adequate programs and procedures are in place to identify and compensate for other potentially lower probability, but nonetheless risk-significant, configurations resulting from maintenance and other operational activities. If the Tier 2 assessment demonstrates, with reasonable assurance, that there are no risk-significant configurations involving the subject equipment, the application of Tier 3 to the proposed AOT may not be necessary. Although defense in depth is protected to some degree by most current TS, the three-tiered approach to the evaluation of risk-informed TS modifications discussed in the following section provides additional assurance that defense in depth will not be significantly impacted by such changes to the licensing basis. a. Tier 1: PRA Capability and Insights The first tier assesses the impact of the proposed TS change on CDF, ICCDP, and where appropriate, on LERF and ICLERP. Two aspects need to be considered: 1) the validity of the PRA, and 2) the PRA insights and findings. The depth of the staff review at this stage will depend on the extent to which the licensee has demonstrated that its PRA is valid for assessing the proposed TS changes and the overall impact of the TS change on plant risk. Rev. 0 - August 1998 SRP 16.1-14 b. Tier 2: