Document: NUREG-0800
Document ID: d52a97d0-a519-4817-9ad6-64d94c9518af
Document Type: srp
Title: DATA COMMUNICATION SYSTEMS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1515/ML15159B177.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.9
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Content:
n 5.4. The review should confirm that data communication media do not present a fault propagation path for environmental effects, such as high-energy electrical faults or lightning, from one redundant portion of a system to another or from another system to a safety system. (Refer to RG 1.180, “Guidelines for Evaluating Electromagnetic and Radio-Frequency Interference in Safety-Related Instrumentation and Control Systems,” for implementation and testing practices to establish electromagnetic compatibility and to RG 1.204, “Guidelines for Lightning Protection of Nuclear Power Plants,” for grounding and surge protection methods to provide lightning protection.) Fiber optics typically offer resistance to such effects but have other attributes that prevent universal acceptability. For example, if the fiber-optic medium may be subject to radiation, fiber that does not become opaque or brittle under irradiation should be specified, or there should be a defined replacement schedule. NUREG/CR-6082, “Data Communications,” compares the qualities of optical and conductive media and provides guidance regarding environmental and performance criteria. • Diversity and Defense-in-depth (D3) analysis - If one or more DCSs are parts of systems (e.g., RTS, ESFAS, anticipated transient without scram [ATWS], diverse I&C) for which a D3 analysis is required, the analysis should be performed by the applicant, and the vulnerabilities to common-cause failure of all similar DCSs should be evaluated. Based on the credibility of postulated failures, potential consequences, availability of diverse preventive or mitigatory responses, and the NRC’s diversity requirements (see the Staff Requirements Memorandum (SRM) on SECY-93-087, “Policy, Technical, and Licensing Issues Pertaining to Evolutionary and Advanced Light-Water Reactor (ALWR) Designs”), the reviewer should determine that the design, including DCSs, has sufficient D3. See SRP BTP 7-19 for guidance on reviewing D3