Document: NUREG-0800
Document ID: 2dffe24e-cd37-4ffc-9c37-16faf25676b1
Document Type: srp
Title: Appendix 7-A
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500579.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
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CFR Title: 

Content:
Appendix 7-A Rev. 4 — June 1997 BTP HICB-21-1 NEW Branch Technical Position HICB-21 Guidance on Digital Computer Real-Time Performance A. Background This branch technical position (BTP) provides guidelines for reviewing digital system real-time performance and system architectures in instrumentation and control (I&C) systems. These guidelines are based on reviews of licensee submittals and the analysis of these issues documented in NUREG/CR-6083, "Reviewing Real-Time Performance of Nuclear Reactor Safety Systems," and NUREG/CR-6082, "Data Communications." 1. Regulatory Basis 10 CFR 50.55a(h), "Protection Systems," requires in part that protection systems satisfy the criteria of IEEE Std 279, "Criteria for Protection Systems for Nuclear Power Generating Stations." Section 3 of the standard requires, in part, specification of the protection system design basis, including system response times. Section 4.1 requires in part that the protection system automatically initiate protective action within the range of performance enumerated in the design basis. 10 CFR 50 Appendix A, General Design Criterion (GDC) 10, "Reactor Design," requires in part that control and protection systems be designed with appropriate margin to ensure that specified acceptable fuel damage limits are not exceeded. This includes timing and performance margins. 10 CFR 50 Appendix A, GDC 12, "Suppression of Reactor Power Oscillations," requires in part that reactor power oscillations are either (1) not possible or (2) detected and suppressed. This requirement places strict real-time constraints on any protection system components that detect and suppress power oscillations. 10 CFR 50 Appendix A, GDC 13, "Instrumentation and Control," requires in part that instrumentation be provided to monitor variables and systems over their anticipated ranges for normal operations, for anticipated operational occurrences, and for accident conditions as appropriate to ensure adequate safety. Digital instrumentation