Document: NRC Regulatory Guide
Document ID: b4874b3a-bbf8-4eb6-8b86-db32ecf45ac6
Document Type: regulatory_guide
Title: Guidance for Implementation of 10 CFR 50.59, Changes, Tests, and Experiments (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1904/ML19045A435.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.187
CFR Part: 
CFR Title: 

Content:
lated aspects that could potentially change the screening or evaluation conclusions. For example, the “Note” in example 4-19 of NEI 96-07, Appendix D states, “The acceptability of these new area radiation monitors will be dictated by their reliability, which is assessed as part of Criterion (ii), not Criterion (vi).” The NRC staff’s position is that this note is potentially misleading as it could be read to mean that CCF of a proposed digital I&C modification is solely a reliability issue, applicable to Criterion (ii) and not Criterion (vi), when read within the context of the entirety of example 4-19. d. Software Common Cause Failures The NRC staff’s position is that NEI 01-01, Section 5, as clarified by RIS 2002-22 Supplement 1, is the only guidance the NRC has reviewed or endorsed as providing an acceptable technical basis to determine that the likelihood of software CCF is sufficiently low for the purpose of 10 CFR 50.59 evaluations. There is no consensus method for determining the likelihood of CCF of software (i.e., an industry consensus standard) that has been reviewed or endorsed by the NRC. e. Section 4.3.6 of NEI 96-07, Appendix D The NRC staff takes exception to the application of the term “safety analysis” to the criterion in section 10 CFR 50.59(c)(2)(vi) in lieu of the term “FSAR (as updated)” throughout NEI 96-07, Appendix D, Section 4.3.6. This exception includes the Introduction to Section 4.3.6 of NEI 96-07, Appendix D, which does not itself provide guidance on the application of 10 CFR 50.59(c)(2)(vi) to a DI&C modification. Nonetheless, the NRC staff takes exception to the rationale set forth in the Introduction for DG-1356, Page 9 limiting the matters considered under that criterion to safety analyses. In particular, the NRC staff takes exception to steps 5 and 6 in “Determination of Safety Analysis Result Impact,” Section 4.3.6 of NEI 96- 07, Appendix D, because the determination of the safety analysis result impact is