Document: NRC Regulatory Guide
Document ID: 50995365-d97f-4101-970a-378af6b5374b
Document Type: regulatory_guide
Title: Qualification of Fiber-Optic Cables, Connections, and Optical Fiber Splices for Use in Safety Systems for Production and Utilization Facilities (Rev. 0)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML2505/ML25052A253.pdf
Revision Date: 2025-08
Chapter: 
Section ID: RG-1.257
CFR Part: 
CFR Title: 

Content:
humidity, radiation, vibration, and if applicable, chemical spray and submergence resulting from a design basis event (DBE) can precipitate common-cause failures of fiber optic cable and/or connection assemblies. For this reason, it is necessary to establish a qualified life (for equipment subject to 10 CFR 50.49) or design life (for electric equipment important to safety not subject to 10 CFR 50.49) for fiber optic cable and/or connection assemblies with significant aging mechanisms. 3. Remove reference to extreme natural events and severe accidents in Section 5.2, “Qualification by type testing,” item b) in IEEE Std. 1682-2023, such that it reads: “The test conditions are at least as severe as the service conditions, plus margin, including DBEs, defined in the qualification plan.” 4. Supplement Section 6.1, “General” of IEEE 1682-2023, regarding the guidance on the use and application of margins, with the following addition: Margins should be applied in addition to any conservatism used during the derivation of local environmental conditions of the equipment unless these conservatisms can be quantified and shown to contain appropriate margins. The margins should account for variations in commercial production of the equipment and the inaccuracies in the test equipment. The design may require some electric equipment to perform its safety function only within the first 10 hours of the event. This equipment should remain functional in the accident environment for a period of at least 1 hour in excess of the time assumed in the accident analysis unless a time margin of less than 1 hour can be justified. This justification for each piece of equipment should include the following: (1) consideration of a spectrum of breaks, RG 1.257, Rev. 0, Page 10 (2) the potential need for the equipment later in an event or during recovery operations, (3) a determination that failure of the equipment after performance of its safety function will not be detrimental to plant