Document: NRC Regulatory Guide
Document ID: 82021804-a487-471b-a76c-095315525b53
Document Type: regulatory_guide
Title: Guidelines for Evaluating Electromagnetic and Radio-Frequency Interference in Safety-Related Instrumentation and Control Systems (Rev. 2)
Source: NRC Regulatory Guide Division 1
Source URL: https://www.nrc.gov/docs/ML1628/ML16281A531.pdf
Revision Date: 2023-06
Chapter: 
Section ID: RG-1.180
CFR Part: 
CFR Title: 

Content:
f safety-related I&C equipment and the location of portable EMI/RFI emitters. The size of the exclusion zones should be site-specific and depend on the effective radiated power and antenna gain of the portable EMI/RFI emitters used within a particular nuclear power plant. The size of exclusion zones should also depend on the allowable electric field emission levels designated for the area in the vicinity of the installed safety-related I&C system. To establish the size of an exclusion zone, an 8 dB difference between the susceptibility operating envelope and the allowed 1 If the NRC staff does not endorse part of standard, it denotes that matter as an “exception” to the NRC staff endorsement of the standard. DG-1333, Page 10 emissions level should be maintained. For the radiated electric field operating envelope of 10 V/m (140 dB/m), the size of the exclusion zones should be set such that the radiated electric fields emanating from the portable EMI/RFI emitters are limited to 4 V/m (132 dB /m) in the vicinity of safety-related I&C systems. The minimum distance of an exclusion zone (d) in meters should be calculated by the following equation derived from the free space propagation model: 𝑑𝑑= ඥ30𝑃𝑃𝑡𝑡𝐺𝐺𝑡𝑡 𝐸𝐸 (𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚𝑚) where: Pt = the effective radiated power of the EMI/RFI emitter (in Watts); Gt = the gain of the EMI/RFI emitter (dimensionless); and E = the allowable radiated electric field strength of the EMI/RFI emitter (in Volts/meter) at the point of installation. Note that unintentional transmitters (welders, motors, etc.) will typically have a gain that is less than or equal to 1 (the gain of an isotropic emitter), and the gain for intentional transmitters (two-way radios, cell phones, etc.) will typically be greater than 1. Typical values for the gain of intentional transmitters might vary from 1.5 for a short dipole antenna to 3 for a monopole antenna, and to 6 for a horn