Document: NUREG-0800
Document ID: fe8ec6c2-e960-404c-854f-55c77bde1672
Document Type: srp
Title: NUREG-0800
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML2400/ML24005A077.pdf
Revision Date: 2024-05
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
pply the methodologies described in this BTP when evaluating spurious operations resulting from CCFs. Spurious Operation and Interconnected Systems As stated in the background section of this BTP, the interconnection of design functions in a DI&C system makes it challenging to identify CCF vulnerabilities and evaluate their potential consequences. System interconnectivities, including shared resources, could reduce a plant’s overall defense in depth (e.g., by reducing independence). When evaluating interconnected systems, the reviewer should focus primarily on SSCs that are not safety related and that are interconnected with safety-related SSCs. This is because safety-related SSCs have particular regulatory requirements (e.g., for independence and quality) that separately address CCF vulnerabilities in interconnected systems. A secondary focus should be on interconnection of SSCs that can directly or indirectly affect reactivity. In some cases, a system may be susceptible to failures not analyzed in the design bases. The reviewer should consider whether a CCF of an interconnected DI&C system or platform (e.g., a single platform controlling multiple system functions) could result in a spurious operation that would have unacceptable consequences. The reviewer should also consider the level of interconnection between a safety system and other systems as a potential vulnerability to be addressed in the application.9 8 Spurious operations addressed “within the design basis” include spurious operations resulting from single failures (including cascading effects) or single malfunctions. Consistent with regulatory requirements such as those of GDC 25 or those incorporated by reference in 10 CFR 50.55a(h) (namely, IEEE Std 279-1971 or IEEE Std 603-1991), spurious operations resulting from single failures and single malfunctions are expected during the lifetime of the plant and are addressed as part of the design basis. 9 See IEEE Std 603-1991. BTP 7-19-19 Revision 9