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:
opriate for satisfying the environmental qualification of safety-related computer-based I&C systems for service in mild environments at nuclear power plants. The standard can be applied subject to the following five enhancements and exceptions: (1) For environmental qualification of safety-related computer-based I&C systems, type testing is the preferred method. Selective use of the service conditions mentioned in Section 6.1.5.1 of IEEE Std. 323-2003 should be based on the actual environmental conditions. The NRC does not consider the age conditioning in Section 6.2.1.2 to be applicable because of the absence of significant aging mechanisms on microprocessor-based modules. (2) With appropriate justification, IEEE Std. 323-2003 allows the omission of elements of the test plan in Section 6.3.1.1 and the test sequence in Section 6.3.1.7 for mild environment qualification. The qualification testing should be performed with the I&C system functioning, with software and diagnostics that are representative of those used in actual operation, while the system is subjected to the specified environmental service conditions, including abnormal operational occurrences. Testing should exercise all portions of the safety-related computer-based I&C systems necessary to accomplish the safety-related function or those portions whose operation or failure could impair the safety-related function. Qualification testing should confirm the response of digital interfaces and verify that the design accommodates the potential impact of environmental effects on the overall response of the system. Although testing of a safety-related computer-based I&C system as a whole is preferred, type testing an entire system as a unit is not always practical. In those cases, confirmation of the dynamic response for a computer-based I&C system is based on type testing of the individual modules and analysis of the cumulative effects of environmental and operational stress on the entire system. (3) Section