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:
not limiting cases are not discussed in the UFSAR. DG-1356, Page 8 An accident of a different type is any new accident, distinct from any previously evaluated in the UFSAR but of similar frequency and significance. A different accident analysis, not simply a revision of an existing analysis, would be needed for this different type of accident. 2. NEI 96-07, Appendix D The NRC staff considers the guidance in NEI 96-07, Appendix D, acceptable for use in complying with the requirements in 10 CFR 50.59, subject to the following exceptions and additions: a. NEI 96-07, Appendix D Use NEI submitted NEI 96-07, Appendix D, to the NRC staff as a means of addressing 10 CFR 50.59 challenges pertaining to digital I&C implementation because of the unique challenges posed (e.g., introduction of software). The NRC staff evaluated NEI 96-07, Appendix D, as applied to digital modifications only, and therefore has not determined Appendix D to be acceptable for other uses. b. Human-System Interface Licensees should not apply the guidance in Appendix D in a way that would be inconsistent with the guidance in NEI 96-07, Rev. 1. However, including Human-System Interface (HSI) changes in the screening process is a change from the guidance contained in NEI 96-07, Revision 1, Section 4.2.1.2. The NRC staff agrees that HSI may be screened as described in Appendix D. Digital interfaces are fundamentally different than analog interfaces. The guidance in Appendix D, Section 4.2.1.2 takes this difference into account, whereas, the guidance in NEI 96-07, Revision 1 does not. c. Examples Illustrate Guidance Examples are meant to illustrate the guidance provided and should not be used to derive guidance. As noted in Appendix D, Section 1.5, examples may deliberately exclude other pertinent or related 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