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
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CFR Title: 

Content:
ts set forth in the Institute of Electrical and Electronics Engineers (IEEE) Standard (Std.) 603-1991, “Criteria for Safety Systems for Nuclear Power Generating Stations,” and the correction sheet dated January 30, 1995, or IEEE Std. 279-1971, “Criteria for Protection Systems for Nuclear Power Generating Stations,” contingent on the date that the NRC issued the related construction permit. The design-basis criteria identified by those standards or by similar provisions in the licensing basis for such facilities include the range of transient and steady-state environmental conditions throughout which the equipment shall perform during normal, abnormal, and accident operational events. As reported in NUREG/CR-5904, “Functional Issues and Environmental Qualification of Digital Protection Systems of Advanced Light-Water Reactors,” issued April 1994, safety-related microprocessor-based electric equipment can pose unique functional and qualification issues. Traditional testing and evaluation approaches developed primarily for analog equipment may not fully address these digital issues. The primary focus of IEEE Std. 323, “IEEE Standard for Qualifying Class 1E Equipment for Nuclear Power Generating Stations,” is the reliable operation of safety-related equipment under normal, abnormal, design-basis accident, post-design-basis accident, and containment test conditions. At present, computer-based instrumentation and control (I&C) systems are primarily implemented in nuclear power plant locations that are characterized as mild environments that are not affected by design-basis accident conditions. Thus, the design-basis accident element of type testing for qualification does not apply to computer-based I&C systems in mild environments. In addition, because of ready accessibility for monitoring and maintenance in mild environments, the need to establish a qualified life does not apply. Nonetheless, the qualification criterion of 10 CFR 50.55a(h)(2) shall be