Document: NUREG-0800
Document ID: 96afb1d6-6ce9-41e4-b4ec-1fc7747bc0b2
Document Type: srp
Title: Revision 8 – January 2021
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2033/ML20339A647.pdf
Revision Date: 2023-05
Chapter: 7
Section ID: 7
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CFR Title: 

Content:
bilities. If there is integration (e.g., through combined design functions, shared resources, or digital interconnectivity), the system should be assessed using the methods appropriate for the highest safety-significance SSC that is integrated or interconnected. The reviewer should consider whether the applicant included a clear description of the proposed DI&C system or component that identifies (1) shared resources, (2) interconnection with other systems, and (3) whether the modification could reduce the redundancy, diversity, separation, or independence of systems described in the facility’s SAR. Reductions in independence, separation, diversity, or redundancy can adversely affect the defense-in-depth of a plant. The reviewer should also determine whether the assessment of the most safety significant SSCs considers the vulnerability to CCF resulting from failures within the integrated or interconnected system and the consequences of a CCF that could affect the proper operations of the integrated or interconnected systems. For example, a digital protection system may include controllers for performing reactor trip and engineered safety feature (ESF) logic, as well as safety control functions (e.g., auxiliary feedwater level control). If the reactor trip or ESF initiation signal in such a system reaches the final actuation device only through the equipment BTP 7-19-14 Revision 8 – January 2021 that performs safety control functions, then the reviewer should determine whether all the SSCs in that pathway have been assigned to the highest safety significant SSC category. In this example, the reviewer should determine whether the D3 assessment for these interconnected or integrated systems meets the criteria in Sections B.3.1–B.3.3 for D3 assessments of high safety-significant SSCs. Acceptance Criteria for Safety-Significance Determinations: NRC technical reviewers should find an applicant’s safety-significance determination acceptable if it reasonably