Document: NUREG-0800
Document ID: 757b676a-0f71-4094-8677-ca3a50743281
Document Type: srp
Title: Revision 7 – August 2016
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1601/ML16019A344.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
or software logic based CCF: Diversity or Testability (1) Diversity – If sufficient diversity exists in the protection system, then the potential for CCF within the channels can be considered to be appropriately addressed without further action. Example: An RPS design in which each safety function is implemented in two channels that use one type of digital system and another two channels that use a BTP 7-19-13 Revision 7 – August 2016 diverse digital system. If a D3 analysis performed consistent with the guidance in NUREG/CR-6303 determines that the two diverse digital systems are not subject to a CCF, then, in this case, no additional diversity would be necessary in the safety system. (2) Testability – A system is sufficiently simple such that every possible combination of inputs and every possible sequence of device states are tested and all outputs are verified for every case (100 percent tested). What constitutes “sufficient diversity” should be evaluated on a case-by-case basis, considering diversity attributes and attribute criteria that preclude or limit certain types of CCF. Diversity attributes and associated attribute criteria, and a process for evaluating the application may provide more objective guidance in answering, “What is sufficient diversity?” 2. Information to be Reviewed The information to be reviewed is the D3 assessment conducted by the applicant. If the D3 assessment indicates the need for a diverse means to accomplish a protective safety function, then the diverse means should be evaluated, including any HFE analysis associated with manual operator actions as a diverse means. 3. Acceptance Criteria 3.1 Specific Acceptance Criteria The D3 assessment submitted by the applicant should demonstrate compliance with the NRC position on D3 described above. To reach a conclusion of acceptability, the following conclusions should be reached and supported by summation of the results of the analyses and the diverse means provided. Since