Document: NUREG-0800
Document ID: 1d79b1ad-8e39-4ab1-b2e4-30556b3a5384
Document Type: srp
Title: describes the general procedures to be followed in reviewing any instrumentation and control
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0525/ML052500509.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.1
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Content:
and accidents do not lead to control systems failures that would result in consequences more severe than those described in the analysis in Chapter 15 of the SAR. • Environmental control system — The review should confirm that I&C systems include environmental control as necessary to protect equipment from environmental extremes. This would include, for example, heat tracing of safety instruments and instrument sensing lines as discussed in Reg. Guide 1.151, "Instrument Sensing Lines" and cabinet cooling fans. • Use of digital systems — To minimize the potential for control system failures that could challenge safety systems, control system software should be developed using a structured process similar to that applied to safety system software. Elements of the process may be tailored to account for the lower safety significance of control system software. Refer to Appendix 7.0-A for guidance on digital system review. • Independence — The independence of safety system functions from the control system should be verified. See Appendix 7.1-B item 8 or Appendix 7.1-C item 24. • Defense-in-depth and diversity — Control system elements credited in the Defense-in-Depth and Diversity Analysis (see BTP HICB-19) should be reviewed using the criteria for Diverse I&C systems described in Section 7.8. • Potential for inadvertent actuation — The control systems design should limit the potential for inadvertent actuation and challenges to safety systems. Rev. 4 — June 1997 SRP 7.7-5 • Control of access — Physical and electronic access to digital computer-based control system software and data should be controlled to prevent changes by unauthorized personnel. Control should address access via network connections and via maintenance equipment. In certain instances, it will be the Staff's judgment that, for a specific case under review, emphasis should be placed on specific aspects of the design, while other aspects of the design need not receive the same