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
CFR Part: 
CFR Title: 

Content:
e DCS satisfies these requirements of GDC 21. Based on the review of software development plans and the inspections of the computer development process and design outputs, the staff concludes that the computer systems conform to the guidance of RG 1.152. Therefore, the special characteristics of computer systems have been adequately addressed, and the staff finds that the DCS satisfies these requirements of GDC 21. The DCS functions were included in the staff’s review of diversity and defense-in-depth analysis for RTS and ESFAS. Based on this review, the staff concludes that the protection systems, including the DCS functions, comply with the criteria for defense against common-cause failure in digital I&C systems. Therefore, the staff finds that adequate diversity and defense against common-cause failure has been provided to satisfy the diversity guidance of GDC 22 and the SRM on SECY-93-087, Item II.Q. The staff has reviewed EMI/RFI susceptibility and seismically exposed portions of the DCS. Based on this review and the finding that the requirements of GDC 2 are satisfied, the staff concludes that the DCS satisfies the requirement for independence from the effects of natural phenomena. The DCS conforms to the guidelines in RG 1.75, “Criteria for Digital Computers in Safety Systems of Nuclear Power Plants,” for protection system independence. Based on the review of system independence and separation, the staff concludes that the DCS satisfies the requirement of (IEEE Std 279-1971 or IEEE Std 603-1991) with regard to systems independence. Therefore, the staff finds that the DCS satisfies the requirements of GDC 22. DCS failure modes were accounted for in the failure modes and effects analysis for the RTS and ESFAS. Based on the staff’s review of these analyses, the staff concludes that the protection systems, including the DCS, are designed to fail into a safe mode if a condition such as disconnection of the system, loss of energy, or postulated adverse