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:
or taken into account. 3.2 Use of Diverse Means to Mitigate the Impact of a Common-Cause Failure This section addresses applications that credit a diverse means to mitigate the impact of a postulated CCF, either by accomplishing a function that is the same as, or is different from the safety function disabled by the CCF; or by mitigating spurious operations resulting from the CCF. An application that credits any of the diverse means described in sections B.3.2.1–B.3.2.3 of this BTP is considered to have acceptably addressed Point 3 of the NRC position on D3. These diverse means include existing systems, manual operator actions, and new diverse systems. 3.2.1 Crediting Existing Instrumentation and Control Systems An existing reliable I&C system can be used as a diverse means either to accomplish the same or a different function credited in the D3 assessment or to mitigate spurious operations resulting from CCF. The analysis in the LAR of the function performed by this existing I&C system should BTP 7-19-24 Revision 9 — May 2024 show that the consequences of the CCF meet the acceptance criteria defined in the FSAR or the LAR for the limiting events applicable to the proposed DI&C system. If an existing I&C system is credited, then the reviewer should verify that the applicant has performed an analysis demonstrating that the credited system and the proposed DI&C system are not both vulnerable to the same CCF. The reviewer should verify that the applicant has considered how the existing I&C system is credited in the facility’s licensing basis and described in the existing I&C system’s documentation (e.g., the FSAR, detailed design documents). Among other things, the reviewer should consider whether the applicant has appropriately accounted for any unique I&C system design attributes and requirements and for any potential interconnectivities, including resource sharing, with other systems. The reviewer should pay particular attention to whether there may be