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:
maintenance of diverse systems for reactivity control). e. The application documents failure analyses (e.g., FMEAs) that demonstrate how failure effects, including spurious operations, are bounded or taken into account. 3.2 Use of Diverse Means to Mitigate Common-Cause Failures If a potential CCF vulnerability has not been eliminated from further consideration using the process in Section B.3.1 of this BTP, the reviewer should verify that the application’s D3 assessment credits a diverse means to accomplish the same or different function than the safety function disabled by the postulated CCF or to mitigate spurious operations resulting from the postulated CCF. Section 2.6 of NUREG/CR-6303 identifies six diversity attributes and 25 related diversity criteria that the reviewer can use to determine whether the diverse means are adequate to mitigate CCF. In addition, NUREG/CR-7007 identifies and develops a baseline set of diversity criteria that may characterize diversity strategies adequate to address CCF vulnerabilities. However, the quantification methodology described in NUREG/CR-7007 should not be used as the sole basis for justifying adequate diversity. 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, or new diverse systems. 3.2.1 Crediting Existing Systems An existing reliable I&C system can be used as a diverse means 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 system should 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 system or component. If an existing system is credited, then the reviewer should