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:
es on which the plant design was based are not compromised. Design basis accidents (DBAs) play a central role in nuclear power plant design. DBAs are a combination of postulated challenges and failure events against which plants are designed and design features that ensure adequate and safe plant response. During the design process, plant response and associated safety margins are evaluated using assumptions which are intended to be conservative. National standards and other considerations such as defense-in-depth attributes and the single failure criterion constitute additional engineering considerations that influence plant design and operation. Margins and defenses associated with these considerations may be affected by the licensee's proposed TS change and, theRefore, should be reevaluated to support a requested TS change. As part of this SRP 16.1-13 Rev. 0 - August 1998 evaluation, the impact of the proposed TS change on affected equipment functionality, reliability, and availability will be determined. The engineering evaluation conducted should evaluate whether the proposed TS change is consistent with the defense-in-depth philosophy. In addition, the engineering evaluation conducted should assess whether the proposed TS change maintains sufficient safety margins. The reviewers should confirm that the acceptance guidelines in Section II.A of this SRP are met with respect to the principles regarding defense-in-depth and safety margins. 2. Probabilistic Engineering Evaluation Risk Evaluation for AOTs The staff has identified a three-tiered approach for licensees and the staff to evaluate the risk associated with proposed TS AOT changes. Tier I is an evaluation of the impact on plant risk of the proposed TS change as expressed by the change in core damage frequency (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