Document: NUREG-0800
Document ID: dc63e8aa-2a74-4078-9e19-9a26ed1b4d8c
Document Type: srp
Title: Revision 6 – July 2012
Source: NUREG-0800
Source URL: https://www.nrc.gov/docs/ML1105/ML110550791.pdf
Revision Date: 2023-06
Chapter: 7
Section ID: 7
CFR Part: 
CFR Title: 

Content:
MCR using the Point 4 displays and controls has been completed, controls outside the MCR for long-term management of these (plant) critical safety functions may be used when supported by suitable HFE analysis and site-specific procedures or instructions. The above four-point position is based on the NRC concern that software based or software logic based digital system development errors are a credible source of CCF. In this guidance, common software includes software, firmware,1 and logic developed from software-based development systems. Generally, digital systems cannot be proven to be error-free and, therefore, are considered susceptible to CCF because identical copies of the software based logic and architecture are present in redundant divisions of safety-related systems. Also, some errors labeled as “software errors” (for example) actually result from errors in the higher level requirements specifications used to direct the system development that fail in some way to 1 IEEE 100, “The Authoritative Dictionary of IEEE Standards Terms,” defines firmware as the combination of a hardware device and computer instructions and data that reside as read-only software on that device. Revision 6 – July 2012 BTP 7-19-9 represent the actual process. Such errors place further emphasis on the need for diversity to avoid or mitigate CCF. 1.5 Manual Initiation of Automatically Initiated Protective Actions Subject to CCF Two types of manual initiation of automatically initiated protective actions may be necessary. To satisfy IEEE Std. 603-1991 Clauses 6.2 and 7.2, a safety-related means shall be provided in the control room to implement manual initiation of the automatically initiated protective actions at the division level. System level actuation of all divisions also may be used to meet the requirements of IEEE Std. 603-1991. If a D3 analysis indicates that the safety-related manual initiation would be subject to the same potential CCF affecting the automatically