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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Content:
CR-6303 identifies the normal reactor control systems, the RTS, the ESFAS, and the reactor monitoring and indication systems as individual echelons of defense. An overall DI&C system architecture that maintains the integrity of multiple layers of defense is key to ensuring a system’s ability to limit, mitigate, or withstand or cope with the effects of a CCF. Traditional design techniques such as redundancy, independence, and diversity ensure that the architecture provides the basic framework and structure for maintaining defense in depth. Other design features can also contribute to overall defense in depth. Such features include predictable real-time (deterministic) processing, automated self-test provisions, and measures to control access to physical, electronic, and software-based elements that, if tampered with or corrupted, could cause adverse plant consequences. The following documents provide staff guidance for evaluating these features: • SRP Appendix 7.0-A, “Review Process for Digital Instrumentation and Control Systems,” and BTP 7-21, “Guidance on Digital Computer Real-Time Performance,” provide BTP 7-19-4 Revision 8 – January 2021 guidance on real-time deterministic processing. • Item B.3.1 of Table 2 and Item C.7 of Table 3 in SRP Section 13.6.6, “Cyber Security Plan,” provide guidance on control of access. • RG 1.152, “Criteria for Use of Computers in Safety Systems of Nuclear Power Plants,” provides guidance on measures protecting against undesirable acts (e.g., tampering with software code or logic) that can compromise the safety system. • RG 5.71, “Cyber Security Programs for Nuclear Facilities,” provides guidance on protecting digital computers and communication systems and networks against cyberattacks. • BTP 7-17, “Guidance on Self-Test and Surveillance Test Provisions,” provides guidance on self-test features. Over the years, the U.S. Nuclear Regulatory Commission (NRC) staff has approved applications that