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
CFR Part: 
CFR Title: 

Content:
er Consideration Diversity within an I&C system or component constitutes the use of different techniques, schemes, features, or additions to eliminate a CCF from further consideration. If diversity is used, each portion of the system or component has different potential latent design defects, so that a failure in one portion will not result in a failure in other portions. Diversity can be implemented in various ways, such as the use of different technologies, algorithms, or logics; sensing devices; or actuation devices. However, diversity needs to be paired with independence from any SSC performing the same function within the digital control system; otherwise the diverse means could be susceptible to the same CCF. The reviewer should determine whether the proposed system contains sufficient diversity to perform the safety function, including diversity within each safety division or among redundant safety divisions of a system. If so, then the potential CCF can be eliminated from further 13 See IEEE Std 603-1991. BTP 7-19-20 Revision 8 – January 2021 consideration. 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 system includes adequate diversity. Also, NUREG/CR-7007 identifies and develops a baseline set of diversity criteria that may characterize appropriate diversity strategies for mitigating CCF vulnerabilities. However, the quantification methodology described in NUREG/CR-7007 should not be used as the sole basis for justifying adequate diversity. For example, a proposed digital protection system could implement each credited safety function in two or more independent divisions of the system, each using a different type of digital technology. In this case, the reviewer should determine whether the application includes an analysis reflecting the guidance of NUREG/CR-6303 and NUREG/CR-7007 to demonstrate that the diversity of these independent divisions is