U.S. NUCLEAR REGULATORY COMMISSION July 2008

OFFICE OF NUCLEAR REGULATORY RESEARCH Division 1

DRAFT REGULATORY GUIDE

Contact: S. Aggarwal

(301) 415-6005

DRAFT REGULATORY GUIDE DG-1149 

(Proposed New Regulatory Guide) 

QUALIFICATION OF 

SAFETY-RELATED MOTOR CONTROL CENTERS 

FOR NUCLEAR POWER PLANTS 

A. INTRODUCTION 

This regulatory guide describes a method that the staff of the U.S. Nuclear Regulatory 

Commission (NRC) deems acceptable for complying with the Commission’s regulations for qualification 

of safety-related motor control centers for nuclear power plants. 

The Commission’s regulations in Title 10, Part 50, “Domestic Licensing of Production and 

Utilization Facilities,” of the Code of Federal Regulations (10 CFR Part 50) (Ref. 1), require that 

structures, systems, and components in a nuclear power plant that are important to safety be designed to 

accommodate the effects of environmental conditions (i.e., they must remain functional under postulated 

design-basis events (DBEs)). Toward that end, General Design Criteria 1, 2, 4, and 23 of Appendix A, 

“General Design Criteria for Nuclear Power Plants,” to 10 CFR Part 50 contain the general requirements. 

Augmenting those general requirements are the specific requirements pertaining to qualification of certain 

electrical equipment important to safety that appear in 10 CFR 50.49, “Environmental Qualification of 

Electric Equipment Important to Safety for Nuclear Power Plants.” In addition, Criterion III, “Design 

Control,” of Appendix B, “Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing 

Plants,” to 10 CFR Part 50, requires that test programs, when used to verify the adequacy of a specific 

design feature, should include suitable qualification testing of a prototype unit under the most severe 

DBE. 

The NRC issues regulatory guides to describe to the public methods that the staff considers 

acceptable for use in implementing specific parts of the agency’s regulations, to explain techniques that 

This regulatory guide is being issued in draft form to involve the public in the early stages of the development of a regulatory 

position in this area. It has not received final staff review or approval and does not represent an official NRC final staff position. 

Public comments are being solicited on this draft guide (including any implementation schedule) and its associated regulatory 

analysis or value/impact statement. Comments should be accompanied by appropriate supporting data. Written comments may 

be submitted to the Rulemaking, Directives, and Editing Branch, Office of Administration, U.S. Nuclear Regulatory Commission, 

Washington, DC 20555-0001; emailed to NRCREP@nrc.gov; submitted through the NRC’s interactive rulemaking Web page at 

http://www.nrc.gov; faxed to (301) 415-5144; or hand-delivered to Rulemaking, Directives, and Editing Branch, Office of 

Administration, US NRC, 11555 Rockville Pike, Rockville, MD 20852, between 7:30 a.m. and 4:15 p.m. on Federal workdays. 

Copies of comments received may be examined at the NRC’s Public Document Room, 11555 Rockville Pike, Rockville, MD. 

Comments will be most helpful if received by September 19, 2008. 

Electronic copies of this draft regulatory guide are available through the NRC’s interactive rulemaking Web page (see above); the 

NRC’s public Web site under Draft Regulatory Guides in the Regulatory Guides document collection of the NRC’s Electronic 

Reading Room at http://www.nrc.gov/reading-rm/doc-collections/; and the NRC’s Agencywide Documents Access and 

Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML072760149.
DG-1149, Page 2 

the staff uses in evaluating specific problems or postulated accidents, and to provide guidance to 

applicants. Regulatory guides are not substitutes for regulations and compliance with them is not 

required. 

This regulatory guide contains information collections that are covered by 10 CFR Part 50 that 

the Office of Management and Budget (OMB) approved under OMB control number 3150-0011. The 

NRC may neither conduct nor sponsor, and a person is not required to respond to, an information 

collection request or requirement unless the requesting document displays a currently valid OMB control 

number. 

B. DISCUSSION 

The Working Group on Motor Control Centers (Subcommittee (SC 2.14)) of the Nuclear Power 

Engineering Committee of the Institute of Electrical and Electronics Engineers, Inc. (IEEE) developed 

Standard 649-2006, “IEEE Standard for Qualifying Class 1E Motor Control Centers for Nuclear Power 

Generating Stations.” The IEEE Standards Association approved this standard on September 15, 2006, 

and it was published December 29, 2006 (Ref. 2). This standard provides basic principles, requirements, 

and methods for qualifying safety-related motor control centers for applications in both harsh and mild 

environments in nuclear power plants. The demonstration that an installed motor control center will meet 

its design specification requires many steps (a program of quality assurance, design, qualification, 

production quality control, installation, maintenance, periodic testing, and surveillance). The scope of 

IEEE Standard 649-2006 is limited to qualification. 

The purpose of qualification is to provide assurance that the motor control center is capable of 

performing its required safety functions with no failure mechanisms that could lead to common mode 

failures under the postulated conditions stated in the equipment specification. 

Based on the recent operating experience, the NRC staff has concluded that: (1) aluminum buses 

are more prone to oxidation than the copper buses in motor control centers; and (2) the ground fault 

protection for motor control centers is recommended to reduce the damage to the electrical equipment 

caused by fire initiated by a ground fault. The applicants and licensees should give appropriate 

considerations to these findings when designing motor control centers for new nuclear power plants. 

Clause 9.5 of IEEE Standard 649-2006 references IEEE Standard 344-2004, “Recommended 

Practice for Seismic Qualification of Class 1E Equipment for Nuclear Power Generating Stations,” 

published January 1, 2005 (Ref. 3), and provides additional guidance for seismic qualification of motor 

control centers. The vast majority of seismic qualification tests on motor control centers for operating 

plants were performed with input frequencies up to only 33 hertz (Hz). As a result of improved 

understanding gained in the high frequency seismic input motions, the NRC staff does not consider 

attempts to use past testing data for seismic qualification of motor control centers to be adequate for new 

nuclear power plants.1

 Recent studies related to the early site permit applications at certain east coast 

hard-rock-based plants indicate that the site-specific spectra may exceed the certified design spectra of 

new proposed plants in the very high frequency range (from 20 Hz up to 100 Hz). Plants located in the 

central and eastern United States on hard rock should evaluate whether high-frequency earthquake ground 

motion could affect motor control center components (such as digital components). 

 

1 The safety of the operating plants is being addressed through the Generic Issues Program, document 

number GI-199, “Implementations of Updated Probabilistic Seismic Hazard Estimates in Central and 

Eastern United States on Existing Plants.” Additional information is available electronically through the 

Electronic Reading Room on the NRC’s public Web site, at: http://www.nrc.gov/reading-rm/doccollections/generic-issues/open-gis/. 
DG-1149, Page 3 

Applicants and licensees should accomplish these objectives by using qualification methods (type 

testing, operating experience, analysis as a supplement to type testing and operating experience, ongoing 

qualification, or any combination thereof). However, the preferred method of qualification is type testing. 

C. REGULATORY POSITION 

The NRC staff considers conformance with the requirements of IEEE Standard 649-2006 an 

acceptable method for use in satisfying the Commission’s regulations with respect to qualification of 

safety-related motor control centers, subject to the following: 

1. The operational aging of transformers (control power and distribution) should be considered for 

“Test per 5 year aging period” (Table 1 of IEEE Standard 649-2006), if the motor control centers 

are located in “harsh environments.” 

2. In addition to the typical functional tests specified in Table 2 of IEEE Standard 649-2006, the 

alternative criteria a, b, and c should be performed on all motor control center components that do 

not have a specific functional test during and after a harsh environment test. 

3. Typical functional tests for “timing devices” for direct current application in Table 2 of IEEE 

Standard 649-2006 states, “Devices shall not drop out at or above 70% rated coil voltage.” This 

test should be consistent with the plant-specific voltage analysis. 

4. IEEE Standard 649-2006 references several industry codes and standards. If the NRC’s 

regulations separately incorporate a referenced standard, licensees and applicants must comply 

with the standard as set forth in the regulations. By contrast, if the NRC staff has endorsed a 

referenced standard in a regulatory guide, that standard constitutes an acceptable method of 

meeting a regulatory requirement as described in the regulatory guide. 

D. IMPLEMENTATION 

The purpose of this section is to provide information to applicants and licensees regarding the 

NRC’s plans for using this draft regulatory guide. The NRC does not intend or approve any imposition or 

backfit in connection with its issuance. 

The NRC has issued this draft guide to encourage public participation in its development. The 

NRC will consider all public comments received in development of the final guidance document. In 

some cases, applicants or licensees may propose an alternative or use a previously established acceptable 

alternative method for complying with specified portions of the NRC’s regulations. Otherwise, the 

methods described in this guide will be used in evaluating compliance with the applicable regulations for 

license applications, license amendment applications, and amendment requests. 

REGULATORY ANALYSIS 

1. Statement of the Problem 

The nuclear industry has used IEEE Standard 649-1980, “Standard for Qualifying Class 1E Motor 

Control Centers for Nuclear Power Generating Stations” (Ref. 4), for qualification of safety-related motor 

control centers since issuance of the standard in 1980. IEEE revised this standard and issued it with the 

same title in 1991 as IEEE Standard 649-1991. The NRC staff has never endorsed its use. However, over 
DG-1149, Page 4 

the ensuing years, the staff has been working with IEEE to revise this standard, and the revised version, 

IEEE Standard 649-2006, is generally consistent with the NRC’s regulatory requirements. 

Since the issuance in 1980 of IEEE Standard 649-1980, nuclear power plant licensees have used 

either the 1980 standard or IEEE Standard 649-1991 for qualification of safety-related motor control 

centers for nuclear power plants, subject to NRC staff review on a case-by-case basis. This approach is 

time consuming. 

2. Objective 

The objective of this action is to provide clear guidance on qualification of safety-related motor 

control centers. Issuing a regulatory guide is consistent with the NRC policy of evaluating the latest 

versions of consensus safety standards in terms of their suitability for endorsement by regulatory guides. 

This approach would also comply with the NRC’s directive to use standards developed by consensus 

bodies in accordance with Public Law 104-113, “National Technology and Transfer Act of 1995.” 

3. Alternative Approaches 

 The NRC staff considered the following alternative approaches: 

• Do not issue a regulatory guide endorsing IEEE standard 649-2006. 

• Issue a regulatory guide endorsing IEEE standard 649-2006. 

3.1 Alternative 1: Do Not Issue a Regulatory Guide Endorsing IEEE Standard 649-2006

Under this alternative, the NRC would not issue additional guidance, and the current ad hoc 

guidance for qualifying motor control centers would be retained. If NRC does not take action, there 

would not be any changes in costs or benefit to the public, licensees or NRC. However, the “no-action” 

alternative would not address identified concerns with the current lack of guidance. This alternative 

provides a baseline condition from which any other alternatives will be assessed. 

3.2 Alternative 2: Issue a Regulatory Guide Endorsing IEEE Standard 649-2006

Preparing and issuing this regulatory guide will provide the industry with clearer guidance and 

understanding of the methodology the NRC staff will use to establish the basic principles, requirements, 

and methods of qualifying safety-related motor control centers for applications in both harsh and mild 

environments in nuclear power plants. IEEE Standard 649-2006 is an acceptable standard which reflects 

the current state of technology. The technical approach discussed in the revised standard is consistent 

with the NRC’s regulatory requirements. 

The impact to the NRC would be the costs associated with preparing and issuing the regulatory 

guide. The impact to the public would be the voluntary costs associated with reviewing and providing 

comments to NRC during the public comment period. The value to NRC staff and its applicants would be 

the benefits associated with enhanced efficiency and effectiveness in using a common guidance document 

as the technical basis for license applications and other interactions between the NRC and its regulated 

entities. 
DG-1149, Page 5 

4. Conclusion 

The NRC should issue this regulatory guide to enhance the licensing process. The staff has 

concluded that the proposed action will reduce unnecessary burden on both the NRC and its licensees and 

will result in an improved and more uniform process for qualifying safety-related motor control centers. 

Moreover, the staff sees no adverse effects associated with issuing this regulatory guide. 

REFERENCES

1. 10 CFR Part 50, “Domestic Licensing of Production and Utilization Facilities,” U.S. Nuclear 

Regulatory Commission, Washington, DC.2

 

2. IEEE Standard 649-2006, “Qualifying Class 1E Motor Control Centers for Nuclear Power 

Generating Stations,” The Institute of Electrical and Electronics Engineers, Inc., Piscataway, NJ.3

3. IEEE Standard 344-2004, “Recommended Practice for Seismic Qualification of Class 1E 

Equipment for Nuclear Power Generating Stations,” The Institute of Electrical and Electronics 

Engineers, Inc., Piscataway, NJ. 

4. IEEE Standard 649-1980, “Standard for Qualifying Class 1E Motor Control Centers for Nuclear 

Power Generating Stations,” The Institute of Electrical and Electronics Engineers, Inc., 

Piscataway, NJ. 

 

2

 All NRC regulations listed herein are available electronically through the Electronic Reading Room on the NRC’s 

public Web site, at http://www.nrc.gov/reading-rm/doc-collections/. Copies are also available for inspection or 

copying for a fee from the NRC’s Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD; the mailing 

address is USNRC PDR, Washington, DC 20555; telephone (301) 415-4737 or (800) 397-4209; fax (301) 415-3548; 

and email PDR@nrc.gov. 

 

3

 IEEE standards listed herein are available electronically through the IEEE Standards Web site at 

http://www.ieee.org/web/standards/home/find.html. Copies are also available for purchase from the IEEE Operations 

Center, 445 Hoes Lane, Piscataway, NJ 08854-4141, telephone (732) 981-0060.