Document: NUREG-0800
Document ID: dd687b37-3f26-4512-91d8-633ddb655821
Document Type: srp
Title: DATA COMMUNICATION SYSTEMS
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1602/ML16020A097.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.9
CFR Part: 
CFR Title: 

Content:
be reviewed to verify compatibility. • Reliability - The potential hazards to the DCS and from the DCS should be reviewed. Unneeded but included DCS functions should be reviewed to ensure that they cannot be inadvertently activated and thereby prevent operation of the safety functions. The effects of error detection and recovery should be reviewed. Error detection should be at least as good as four byte cyclic redundancy check (CRC). The effects of DCS equipment malfunction or failure that generates erroneous signals, either in content or rate, should be examined. Corrupted messages (missing or corrupted packets), missing messages and duplicate messages should be detected and repaired. The reviewer should determine that the operating history of the DCS in similar applications is known and that it has been satisfactory. The reviewer should verify the existence and quality of maintenance and operator documentation and ensure that appropriate training has been or will be performed. The DCS should be designed to support self- testing and surveillance testing (refer to SRP BTP 7-17, “Guidance on Self-Test and Surveillance Test Provisions”). • Time coherency of data - Methods to ensure the correct sequence of data packets at receiving DCS nodes should be reviewed. • Control of access - The review should confirm that the DCS does not present an electronic path by which unauthorized personnel can change plant software or display erroneous plant status information to the operators. Computers or equipment outside the control of the plant staff may be connected to nonsafety DCS (e.g., connections to remote data displays off site). In such cases, the connections should be through gateways that prevent unauthorized transactions originating from off site. Remote access to safety systems should not be implemented. 7.9-8 Revision 6 - August 2016 Additional major design considerations that should be emphasized in the review of DCS safety systems are identified below: •