Document: NUREG-0800
Document ID: debf22b1-f3aa-4c75-a43c-f162d22de1c8
Document Type: srp
Title: of the plant safety analysis report (SAR).  Although the NRC did not endorse the annexes of
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1515/ML15159A491.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.6
CFR Part: 
CFR Title: 

Content:
ied as safety-related, with all the attendant regulatory requirements for safety software, including communications isolation from other nonsafety software. In some instances, vendors or applicants or licensees may wish to implement systems having some communication between the safety systems and nonsafety systems. General Design Criterion 24, “Separation Of Protection And Control Systems,” requires that the protection system be separated from Appendix 7.1-D-17 Draft Revision 2 – August 2015 control systems to the extent that failure of any single control system component or channel, or failure or removal from service of any single protection system component or channel that is common to the control and protection systems leaves intact a system satisfying all reliability, redundancy, and independence requirements of the protection system, and that interconnection of the protection and control systems be limited so as to ensure that safety is not significantly impaired. In practical terms, this means that for communications between safety and nonsafety systems, the communications must be such that the safety system does not require any nonsafety input to perform its safety function, and that any failure of the nonsafety system, communications system, or data transmitted by the nonsafety system will not prevent or influence that independent safety determination. The portion of the safety software which actually performs the safety function, i.e., determining whether or not to trip based on sensor inputs, should not receive input or influence from any nonsafety system while the safety system is online and performing that safety function. The following provides some of the possible design approaches that a reviewer may encounter for data communications. It is neither exhaustive nor limiting in the possible approaches. If the reviewer is not sufficiently familiar with the communications systems and methods being used, the reviewer should seek the assistance of