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:
348 to Reflect Changes to the 10 CFR 50.59 Rule’” (Ref. 21). RIS 2002-22 endorsed NEI 01-01 as guidance in designing and implementing digital upgrades to nuclear power plant I&C systems. Following the NRC staff’s 2002 endorsement of NEI 01-01 through RIS 2002-22, holders of operating licenses used the guidance in support of digital I&C modifications in conjunction with RG 1.187, Revision 0, which endorses NEI 96-07, Revision 1. The NRC conducted inspection reviews of the documentation of digital I&C plant modifications prepared using the guidance in NEI 01-01 and identified inconsistencies in the performance and documentation of the engineering evaluations by some licensees. In addition, the NRC inspection reviews identified documentation issues with the written evaluations of the 10 CFR 50.59(c)(2) criteria. In May 2018, the NRC issued RIS 2002-22, Supplement 1, “Clarification on Endorsement of Nuclear Energy Institute Guidance in Designing Digital Upgrades in Instrumentation and Control Systems” (Ref. 22), to clarify RIS 2002-22 and provide additional guidance in the areas that were the subject of the NRC inspection findings. The NRC continues to endorse NEI 01-01, as stated in RIS 2002-22, Supplement 1. The guidance in Supplement 1 clarifies the NRC staff’s endorsement of NEI 01-01, Sections 4 and 5, and Appendices A and B. Specifically, Supplement 1 clarifies the guidance that should be more consistently applied for documenting “qualitative assessments.” It also provides a technical basis that the NRC staff considers sufficient for concluding that a proposed digital modification will result in a “sufficiently low” likelihood of failure, including the likelihood of failure due to a common cause (i.e., common-cause failure (CCF)). NRC continues to endorse NEI 01-01 as stated in RIS 2002-22 and RIS 2002-22, Supplement 1, which remain in effect. NEI 96-07, Appendix D, does not replace or supersede NEI 01-01 either in whole or in part. Licensees