Regulatory guides are issued to describe and make available to the public such information as methods acceptable to the NRC staff for implementing specific parts of the NRC’s  regulations, techniques used by the staff in evaluating specific problems or postulated accidents, and data needed by the NRC staff in its review of applications for permits and licenses.  Regulatory guides are not substitutes for regulations, and compliance with them is not required.  Methods and solutions different from those set out in the guides will be acceptable if they provide a basis for the findings requisite to the issuance or continuance of a permit or license by the Commission.
This guide was issued after consideration of comments received from the public.  Comments and suggestions for improvements in these guides are encouraged at all times, and guides will be revised, as appropriate, to accommodate comments and to reflect new information or experience.  Written comments may be submitted to the Rules and Directives Branch, ADM, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.
Regulatory guides are issued in ten broad divisions:  1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities; 4, Environmental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Health; 9, Antitrust and Financial Review; and 10, General.
Single copies of regulatory guides (which may be reproduced) may be obtained free of charge by writing the Distribution Services Section, U.S. Nuclear
U.S. NUCLEAR REGULATORY COMMISSION                Revision 1
October 2003
REGULATORY GUIDE
OFFICE OF NUCLEAR REGULATORY RESEARCH
REGULATORY GUIDE 1.180
(Draft was issued as DG-1119)
GUIDELINES FOR EVALUATING ELECTROMAGNETIC AND
RADIO-FREQUENCY INTERFERENCE
IN SAFETY-RELATED INSTRUMENTATION
AND CONTROL SYSTEMS
A.  INTRODUCTION
This regulatory guide has been revised to provide guidance to licensees and applicants on
additional methods acceptable to the NRC staff for complying with the NRC’s regulations on design,ins
tallation, and testing practices for addressing the effects of electromagnetic and radio-frequency interference (EMI/RFI) and power surges on safety-related instrumentation and control (I&C) systems. The changes in this revision include endorsing Military Standard MIL-STD-461E and the International Electrotechnical Commission (IEC) 61000 series of EMI/RFI test methods, extending the guidance to cover signal line testing, incorporating frequency ranges where portable communications devices are experiencing increasing use, and relaxing the operating envelopes (test levels) when experience and
confirmatory research warrants.  Exemptions from specific test criteria are also offered based on technical considerations such as plant conditions and the intended location of the safety-related I&C equipment.
The NRC’s regulations in Part 50, “Domestic Licensing of Production and Utilization Facilities,”of Title 10 of the Code of Federal Regulations (10 CFR Part 50) state that structures, systems, and
components important to safety in a nuclear power plant are to be designed to accommodate the effects of environmental conditions (i.e., remain functional under all postulated service conditions) and that design control measures such as testing are to be used to check the adequacy of design.  Section 50.55a(h) of 10
CFR Part 50 states that protection systems must meet the requirements of the Institute of Electrical and Electronics Engineers (IEEE) standard (Std) 603-1991, “Criteria for Safety Systems for Nuclear Power Generating Stations,”1 or IEEE Std 279-1971, “Criteria for Protection Systems for Nuclear Power Generating Stations,”1 contingent on the date of construction permit issuance.  The design basis criteria identified in those standards, or by similar provisions in the licensing basis for such facilities, include the range of transient and steady state environmental conditions during normal, abnormal, and accident circumstances throughout which the equipment must perform. Criterion III, “Design Control,” Criterion XI, “Test Control,” and Criterion XVII, “Quality Assurance Records,” of Appendix B, “Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants,” to 10 CFR Part 50 establish practices to confirm that a design fulfills its technical requirements.  Furthermore, 10 CFR 50.49 and 50.55a address validation measures such as testing that can be used to check the adequacy of design.  Related requirements are contained in General Design Criteria 1, 2, 4, 13, 21, 22, and 23 of Appendix A, “General Design Criteria for Nuclear Power Plants,” to 10 CFR Part 50.  Additionally, Subpart B, “Standard Design Certifications,” of 10 CFR Part 52, “Early Site Permits; Standard Design Certifications; and Combined Licenses for Nuclear Power Plants,” addresses verification requirements for advanced reactor designs.  Specifically, 10 CFR 52.47(a)(vi) requires that an application for design certification must state the tests, inspections, analyses, and acc
eptance criteria that are necessary and sufficient to provide reasonable assurance that a plant will operate within the design certification.  Methods for addressing electromagnetic compatibility (EMC) constitute Tier 2* information under the 10 CFR Part 52 requirements.2
Electromagnetic interference (EMI), radio-frequency interference (RFI), and power surges have been identified as environmental conditions that can affect the performance of safety-related electrical equipment.  Confirmatory research findings to support this observation can be found in NUREG/CR-5700, “Aging Assessment of Reactor Instrumentation and Protection System Components”3 (July 1992); NUREG/CR-5904, “Functional Issues and Environmental Qualification of Digital Protection Systems of Advanced Light-Water Nuclear Reactors”3 (April 1994); NUREG/CR-6406, “Environmental Testing of an Experimental Digital Safety Channel”3 (September 1996); and NUREG/CR-6579, “Digital I&C Systems in Nuclear Power Plants: Risk-Screening of Environmental Stressors and a Comparison of Hardware Unavailability With an Existing Analog System”3 (January 1998).  Therefore, controlling electrical noise and the susceptibility of I&C systems to EMI/RFI and power surges is an important step in meeting the aforementioned requirements.
This regulatory guide endorses design, installation, and testing practices acceptable to the NRC staff for addressing the effects of EMI/RFI and power surges on safety-related I&C systems
1 IEEE publications may be purchased from the IEEE Service Center, 445 Hoes Lane, Piscataway, NJ 08855-1331.
2 An applicant who references an advanced reactor certification is not allowed to depart from the Tier 2* commitments without NRC approval.  Thus, changes cannot be made under a process such as that in 10 CFR 50.59.
3  Copies are available at current rates from the U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20402-9328 (telephone (202)512-1800); or from the National Technical Information Service by writing NTIS at 5285 Port Royal Road, Springfield, VA 22161; <v/ordernow> (telephone (703)487-4650;.  Copies are available for inspection or copying for a fee from the NRC Public Document Room at 11555 Rockville Pike, Rockville, MD; the PDR’s mailing address is USNRC PDR, Washington, DC 20555; telephone (301)415-4737 or (800)397-4209; fax (301)415-3548; email is
PDR@NRC.GOV.
in a nuclear power plant environment.  The design and installation practices described in IEEE Std 1050-1996, “IEEE Guide for Instrumentation and Control Equipment Grounding in Generating Stations,
”1 are endorsed for limiting EMI/RFI subject to the conditions stated in the Regulatory Position.  EMC testing practices from military and commercial standards are endorsed to address electromagnetic emissions, EMI/RFI susceptibility, and power surge withstand capability (SWC). Selected EMI/RFI test methods from MIL-STD-461E, “Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment,”4 and the IEC 61000 Series are endorsed to evaluate conducted and radiated EMI/RFI phenomena for safety-related
I&C systems.  The IEC standards include IEC 61000-3, “Electromagnetic Compatibility (EMC) -Part 3: Limits,”5 IEC 61000-4, “Electromagnetic Compatibility (EMC) - Part 4: Testing and Measurement Techniques,”5 and IEC 61000-6, Electromagnetic Compatibility (EMC) - Part 6: Generic Standards.”5  This regulatory guide provides acceptable suites of EMI/RFI emissions and susceptibility methods from the most recent versions of the military standard and international commercial standards.  These suites of test methods can be applied as alternative sets (guidance is provided in the Regulatory Position).  This regulatory guide also endorses electromagnetic operating envelopes corresponding to the MIL-STD-461E test methods.  These operating envelopes were tailored from the MIL-STD-461E test limits to represent the characteristic electromagnetic environment in key locations at nuclear power plants.  Comparable operating envelopes for the IEC 61000 test methods are also endorsed.  T
he operating envelopes are presented within the Regulatory Position, along with descriptions of the endorsed MIL-STD-461E and IEC 61000 test methods.
The SWC practices described in IEEE Std C62.41-1991 (reaffirmed in 1995), “IEEE Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits,”1 and IEEE Std
C62.45-1992 (reaffirmed in 1997), “IEEE Guide on Surge Testing for Equipment Connected to Low-Voltage AC Power Circuits,”1 are acceptable to the NRC staff regarding the effect of power surges on safety-related I&C systems in nuclear power plants.  A specific set of surge test waveforms are endorsed from IEEE Std C62.41-19911 as acceptable SWC test criteria.  The associated test methods in IEEE Std C62.45-19921 are endorsed to describe the approach to be employed when assessing SWC.  General withstand levels are endorsed for use with the SWC test criteria and are presented within the Regulatory Position, along with the description of the endorsed surge waveforms.  Alternative SWC practices from IEC 61000-45 are acceptable to the NRC staff and are also presented within the Regulatory Position.
The practices endorsed in this regulatory guide apply to both safety-related I&C systems and non-safety-related I&C systems whose failures can affect safety functions.  The rationale for the selection o
f the practices depicted in this guide is that they provide a well established, systematic approach for ensuring EMC and the capability to withstand power surges in I&C equipment within the environment in which it operates.  The technical basis for selecting these particular practices is given in NUREG/CR-5941, “Technical Basis for Evaluating Electromagnetic and Radio-Frequency Interference in Safety-Related I&C Systems”3 (April 1994), 4 Military Standards are available from the Department of Defense, Standardization Documents Order Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.
5  IEC publications may be purchased from the International Electrotechnical Commission, 3 rue de Varembé, Geneva, Switzerland.  Telefax: +41 22 919 0300.
NUREG/CR-6431, “Recommended Electromagnetic Operating Envelopes for Safety-Related I&C Systems in Nuclear Power Plants”3 (April 1999), NUREG/CR-5609, “Electromagnetic Compatibility Testing for Conducted Susceptibility Along Interconnecting Signal Lines”3 (May 2003), and NUREG/CR-6782, “Comparison of U.S. Military and International Electromagnetic Compatibility Guidance”3 (May 2003).
In general, information provided by regulatory guides is reflected in the Standard Review Plan (NURE
G-0800, “Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants”).3  NRC’s Office of Nuclear Reactor Regulation uses the Standard Review Plan to review applications to construct and operate nuclear power plants.  This regulatory guide conforms to the revised Chapter 7, “Instrumentation and Controls,” of the Standard Review Plan.
editor evaluating revision
The information collections contained in this regulatory guide are covered by the requirements of 10 CFR Part 50, which were approved by the Office of Management and Budget (OMB), approval number 3150-0011.  The NRC may not conduct or sponsor, and a person is not required to respond to, a request for information or an information collection requirement unless the requesting document displays a currently valid OMB control number.
B.  DISCUSSION
Existing I&C equipment in nuclear power plants is currently being replaced with computer-based digital I&C systems or advanced analog systems.  However, these technologies may exhibit greater vulnerability to the nuclear power plant EMI/RFI environment than existing I&C systems. This regulatory guide provides an acceptable method for qualifying digital and advanced analog systems for the projected electromagnetic environment in nuclear power plants.
The typical environment in a nuclear power plant includes many sources of electrical noise, for example, hand-held two-way radios, arc welders, switching of large inductive loads, high fault currents, and high-energy fast transients associated with switching at the generator or transmission voltage levels.  The increasing use of advanced analog- and microprocessor-based I&C systems in reactor protection and other safety-related plant systems has introduced concerns with respect to the creation of additional noise sources and the susceptibility of this equipment to the electrical noise already present in the nuclear power plant environment.
Digital technology is constantly evolving, and manufacturers of digital systems are incorporating increasingly higher clock frequencies and lower logic level voltages into their designs.  However, these performance advancements may have an adverse impact on the operation of digital systems with respect to EMI/RFI and power surges because of the increased likelihood of extraneous noise being misinterpreted as legitimate logic signals.  With recent advances in analog electronics, many of the functions presently being performed by several analog circuit boards could be combined into a single analog circuit board operating at reduced voltage levels, thereby making analog circuitry more susceptible to EMI/RFI and power surges as well.  Hence, opera-tional and functional issues related to safety in the nuclear power plant environment must address the possibility of upsets and malfunctions in I&C systems caused by EMI/RFI and power surges.
The NRC staff accepted the Electric Power Research Institute (EPRI) topical report
TR-102323, "Guidelines for Electromagnetic Interference Testing in Nuclear Power Plants," in a Safety Evaluation Report (SER) by letter dated April 17, 1996, as one method of addressing issues of EMC for safety-related digital I&C systems in nuclear power plants.  The original Regulatory Guide 1.180 (January 2000) and this revision complement the position set forth in the SER.  The guidance in these documents constitutes acceptable methods for addressing EMC considerations for qualifying safety-related I&C systems for the expected electromagnetic environment in nuclear power plants.  This guide provides additional acceptable methods and includes guidance on testing to address signal line susceptibility and very high frequency (> 1 Ghz) phenomena.
The EMI/RFI practices, SWC practices, and operating envelopes endorsed in this guide are only elements of the total package that is needed to ensure EMC within nuclear power plants.  In addition to assessing the electromagnetic environment, plants should apply sound engineering practices for non-safety-related upgrades and I&C maintenance as part of an overall EMC program.  While non-safety-related systems are not part of the regulatory guidance being developed, control of EMI/RFI from these systems is necessary to ensure that safety-related I&C systems can continue to perform properly in the nuclear power plant environment.  When feasible, the emissions from non-safety-relate
d systems should be held to the same levels as safety-related systems.
As with the original Regulatory Guide 1.180, this revision endorses IEEE Std 1050-1996 with one exception as stated in Regulatory Position 2.  The exception was cited in NUREG/CR-5941.  IEEE Std 1050-1996 provides guidance on the engineering practices needed to control upsets and malfunctions in safety-related I&C systems when exposed to EMI/RFI and power surges.  IEEE Std 1050-1996 was developed to provide guidance on the design and installation of grounding systems for I&C equipment specific to power generating stations.  Further purposes of the standard are to achieve both a suitable level of protection for personnel and equipment and suitable electrical noise immunity for signal ground references in power generating stations.
IEEE Std 1050-1996 addresses grounding and noise-minimization techniques for I&C systems in a generating station environment.  This standard recommends practices for the treatment of both analog and digital systems that address the grounding and shielding of electronic circuits on the basis of minimizing emissions and their susceptibility to EMI/RFI and power surges.  The standard is comprehensive in that it covers both the theoretical and practical aspects of grounding and electromagnetic compatibility.
Design verification measures for EMI/RFI testing (emissions and susceptibility) are beyond the scope of IEEE Std 1050-1996.  To determine the adequacy of safety-related I&C system designs, the NRC staff has endorsed the applicable EMI/RFI test methods in MIL-STD-461E and the IEC 61000 Series (i.e., the most recently issued military and international commercial guidance), along with custom operating envelopes developed to represent the characteristic electromagnetic environment for nuclear power plants. The test methods and operating envelopes are cited in Regulatory Positions 3, 4, and 6 of this guide.  MIL-STD-461E is included in this revision because it replaced MIL-STD-461D and MIL-STD-462D.  The associated changes are discussed in NUREG/CR-6782.  The original Regulatory Guide 1.180 cited EMI/RFI test guidance

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