Document: NRC Regulatory Guide
Document ID: 086612c4-a8a7-4f50-a166-6f1cb05bcdaf
Document Type: regulatory_guide
Title: Guidelines for Environmental Qualification of Safety-Related Computer-Based Instrumentation and Control Systems in Nuclear Power Plants
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML0630/ML063040591.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.209
CFR Part: 
CFR Title: 

Content:
verse effects on the level of staff effort required to conduct reviews and to ensure consistency among reviewers for each I&C system modification. Thus, NRC staff reviews would take longer and require greater effort. From the applicant’s or licensee’s perspective, this flexibility would also entail potential costs because several unknowns are associated with demonstrating compliance with regulations. Thus, although the initial cost would apparently be low, taking no action could result in greater total costs for both the NRC staff and the applicant or licensee, as well as regulatory uncertainty during the safety evaluation process. The staff concludes that this alternative has the following value and impact: • no value beyond the status quo • schedule, budget, and staffing cost to the staff and applicant or licensee, associated with regulatory uncertainty DG-1142, Page 13 3.2 Alternative 2: Enhance Current Qualification Approaches The second alternative, which involves identifying enhancements to current qualification approaches on the basis of unique computer-based I&C system features, could reduce costs to applicants and licensees by removing ambiguities regarding the appropriate set of qualification practices for the range of operating environments for computer-based I&C systems and by establishing the basis for receiving credit for sound engineering practices that minimize environmental susceptibilities. The value in this alternative would be the common understanding among the NRC staff and applicants or licensees of approaches that the expert technical community has accepted as good practices. However, by itself, this approach does not guarantee that the full scope of requirements in 10 CFR 50.55a(h) have been addressed. In addition, this approach does not clearly address the qualification of digital COTS equipment for mild environments. Moreover, this approach might introduce a new de facto standard that differs substantially from existing consensus