Document: NUREG-0800
Document ID: f1629507-6318-4e71-94a6-9d6664ba96a3
Document Type: srp
Title: of the plant safety analysis report (SAR).  Although NRC did not endorse the annexes of
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML0706/ML070660327.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7.6
CFR Part: 
CFR Title: 

Content:
ons. 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 other NRC personnel and/or supervisor for the appropriate review strategy to determine that the communications can not interfere with the safety function. • A communications system which broadcasts data from the safety system to the non-safety system without the use of handshaking and acknowledgment signals would satisfy these requirements. • If the communications system allows two way communications between the safety and non-safety systems, the determination may require more detailed examination of the communications method, including memory allocation methods, communications protocols and message formatting methodology. One possibility may be to determine that the communications method is deterministic, that is, the same information is transmitted in the same way to the safety system, and is then used by the safety system in the same manner. This could be done by having the non- safety system write data to a specific location in shared memory, and the safety system would read that data. The safety system would know what the data means and what to do with the data because the data in that memory location would be the latest written value of the same data. There would have to be appropriate provisions for out-of-date data, garbled data, and communications link failure. This is, of course, one, but not the only possible method of deterministic communications. The objective in the review is to determine that the applicant/licensee has satisfactorily demonstrated that the applicable requirements of 10 CFR 50.55a(h) and GDC-24 are met. Additional guidance on communications independence is provided in SRP Appendix 7.0-A, SRP Appendix 7.1-C, and SRP Section 7.9. 5.7 Capability for Test and Calibration (IEEE Std 7-4.3.2-2003 Clause 5.7) Sub-Clause 5.5.2 of