Document: NUREG-0800
Document ID: fe8ec6c2-e960-404c-854f-55c77bde1672
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2400/ML24005A077.pdf
Revision Date: 2024-05
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
19-16 Revision 9 — May 2024 SSC “would not adversely affect a safety function or place a plant in a condition that cannot be reasonably mitigated.” Acceptance Criteria for Elimination of Further Consideration of Defense in Depth and Diversity If an SSC meets the following acceptance criteria, the reviewer should conclude that a detailed D3 assessment is not necessary because a failure analysis demonstrates that failure of the specified SSC cannot adversely affect a safety function or place the plant in a condition that cannot reasonably be mitigated: a. The SSC has the characteristics listed in item (c) of section B.2.1 above, or documented risk insights demonstrate that its level of safety significance is similar to that of SSCs with those characteristics. b. The SSC is not interconnected with a more safety-significant SSC. c. The application includes an analysis of a postulated failure of the SSC to perform its design functions and evaluates the effects of that failure, including potential spurious operations. d. The failure does not adversely affect a safety function or place the plant in a condition that cannot reasonably be mitigated. 3. Detailed Defense-in-Depth and Diversity Assessment A D3 assessment is a systematic analysis of a proposed DI&C system for CCFs that can occur concurrently within a redundant design, for example, within two or more independent divisions. These CCFs could cause the DI&C system to fail to perform its intended safety function or could lead to spurious operations. The reviewer should evaluate whether the D3 assessment considers the entire plant performance characteristics in response to CCF. CCFs for DI&C systems of both high and lower safety significance, and SSCs of lowest safety significance that need a detailed D3 assessment, should be evaluated and addressed by considering, as a minimum, the functional partitioning within the DI&C architecture, and whether the CCF could originate in shared resources or could adversely