Document: NRC Regulatory Guide
Document ID: 26c3e31f-c018-4aee-b926-6db849b72a5a
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:
r power plant. The IEEE revised the consensus national standard for qualification, IEEE Std. 323, in 1983, reaffirmed it in 1991 and 1996, and revised it again in 2003. The 2003 version represents the current national consensus standard. The NRC staff does not currently endorse this version of the standard. The NRC continues to rely on the 1974 version of the standard, two generations old, for licensing actions. Therefore, it is desirable to endorse the 2003 version of the standard. 2. Alternative Approaches The NRC staff considered the following alternative approaches to address the qualification of computer-based I&C systems: (1) Take no action. (2) Enhance current qualification approaches based on the unique features of computer-based I&C systems. (3) Use tailored endorsement of existing environmental qualification standards. DG-1142, Page 11 2.1 Alternative 1: Take No Action The first alternative, taking no action, would impose no additional costs on the NRC, applicants, or licensees compared to current conditions because no change to the process would occur. However, this approach fails to effectively address potential environmental compatibility issues posed by digital systems. Currently, guidance can be inferred from Chapter 7 of the Standard Review Plan, past regulatory practice, or recent SERs (in particular, the SER that the NRC issued by letter dated July 30, 1998, on EPRI 107330, which includes an acceptable mild-environment qualification approach for PLCs), but no comprehensive and explicit guidance for licensees addresses mild-environment qualification for all safety-related computer-based I&C systems. The absence of a well-defined roadmap for mild-environment qualification practices for computer-based technologies could result in inconsistency among the qualification process and its evidence for emerging technologies or commercially dedicated computers. Furthermore, if no action is taken, comprehensive guidance on the acceptable use of current