Document: NUREG-0800
Document ID: dc63e8aa-2a74-4078-9e19-9a26ed1b4d8c
Document Type: srp
Title: Revision 6 – July 2012
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1105/ML110550791.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
parameters as reference bounds for design. Further, the analysis should identify whether coping strategies exist for these postulated spurious actuations and consider the adequacy of such strategies. An applicant or licensee should confirm that a coping strategy has been identified to address the effects from credible spurious actuations caused by a CCF that have the potential to place the plant in a configuration that is not bounded by the plant design basis accident analyses. 3.8 Diversity Types NUREG/CR-6303 provides a method for determining uncompensated CCF in safety system designs. Section 2.6, “Diversity,” of NUREG/CR-6303 defines six diversity attributes and 25 related diversity criteria. When NUREG/CR-6303 was published (December 1994), computer-based digital systems were assumed to comprise the next generation of safety systems. Proposed safety system designs, however, include digital systems that are not computer-based, such as programmable logic devices, field programmable gate arrays, and application-specific integrated circuits. These digital devices and components use software to develop the logic that later resides within the digital component (called “firmware”) and often cannot be changed in an individual component. These all should be considered in the assessment of diversity. NUREG/CR-6303, Section 3.2, describes six types of diversity and describes how instances of different types of diversity might be combined into an overall case for the sufficiency of the diversity provided. Typically, several types of diversity should exist, some of which should exhibit one or more of the stronger attributes listed in NUREG/CR-6303. Functional diversity and signal diversity are considered to be particularly effective. The following cautions should be noted where applicable: ● The justification for equipment diversity, or for the diversity of related system logic such as a real-time operating system, should extend to the equipment’s components to