Document: NRC Regulatory Guide
Document ID: c6321e39-3d1b-40a6-ace3-8c6a0c54e2cd
Document Type: regulatory_guide
Title: Developing Software Life Cycle Processes for Digital Computer Software Used in Safety Systems of Nuclear Power Plants + HISTORY - HISTORY 08/2012 – DG-1210 , Proposed Revision 1 08/1996 – DG-1059 , Proposed Revision 0 (Rev. 1)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1031/ML103120727.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.173
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CFR Title: 

Content:
performed only when all functions affected by the software have been declared inoperable in accordance with the plant technical specifications. When software is involved, particularly for distributed software architectures, the determination of affected functions can depend on extremely subtle considerations. For example, two programs related to each other only through the use of a single data item might not be evident from the examination of architecture diagrams. As a minimum, all functions performed, in part, by a given software executable should be declared inoperable if the software executable, its configuration, or its operating platform is to be altered; interconnections of all types with other software, hardware, or human elements should also be examined. A disposition plan, rework procedures that conform to configuration control and verification and validation procedures agreed to under the licensing basis, and a resolution schedule should accompany any work-arounds used during installation (Section A.4.1.2 of IEEE Std. 1074-2006). Before affected functions may be declared operable (Section A.4.1.3 of IEEE Std 1074-2006), the currently approved software, under the control of configuration management, should be installed according to the procedures specified in the installation process. This ensures that the intended software is installed and that any work-arounds employed during the installation activities are removed. An interfacing / interconnected system must also be taken out of service and declared inoperable. c. Operation. Section A.4.2.1, “Operate the System,” of Annex A to IEEE Std. 1074-2006 requires the identification and reporting of anomalies, the conduct of reviews, and the performance of configuration control. Section A.4.3, “Maintenance Activity Group,” requires the software life cycle to be “remapped and executed, thereby treating the Maintenance Activity Group as iterations of development.” This process will produce revisions