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Foreword 

(This foreword is not a part of IEEE Std 649-1991, IEEE Standard for Qualifying Class 1E Motor Control Centers for Nuclear Power Generating Stations.)

The requirements for qualification of Class 1E equipment are included in the Code of Federal Regulations. Among them are the following:

(1) 10CFR Part 50, Appendix B, Quality Assurance Criteria, III - Design Control. This requires that design control measures be established and that such measures provide for verifying or checking the adequacy of design. One of the methods of design verification is the performance of a suitable testing program.

(2) 10CFR Part 50, Appendix B, Quality Assurance Criteria, XI - Test Control. This requires that a test program be established and that testing be performed under suitable environmental conditions. These requirements, at least in part, can be met by suitable qualification.

(3) 10CFR Part 50, Section 50.49, Environmental Qualification of Electric Equipment Important to Safety. This rule codifies the qualification requirements for certain equipment, located in a harsh environment, that is important to safety.

Information pertinent to developing designs and their qualification requirements can be found in the above mentioned documents and in 10CFR Part 50, Appendix A, General Design Criteria 1, 2, 4, and 23.

IEEE Std 323-1983 provides general guidance for demonstrating and documenting the adequacy of electric equipment used in Class 1E systems. This standard has been revised to deal specifically with motor control center equipment, using IEEE Std 323-1983 as the parent document for guidance.

Adherence to this standard may not assure public health and safety because it is the integrated performance of the structures, fluid systems, instrumentation systems, and electrical systems of the station that limits the consequence of accidents. Each user is responsible for assuring that this standard, if used, is pertinent to his or her application.

Class 1E equipment used in nuclear power generating stations must meet its safety functional requirements throughout its installed life. This is accomplished by a thorough program of quality assurance, design, qualification, production, transportation, storage, installation, maintenance, periodic testing, and surveillance. This standard is for the qualification portion of the program.

The user should note that while this standard covers Class 1E equipment qualification, other documents such as IEEE Std 603-1980 also require system integrity. Therefore, attention needs to be given to equipment performance specifications and interfaces to ensure their adequate performance in a system.

The nuclear power generating station safety analysis, in part, considers the station and its safety system design in terms of postulated service conditions.

Inherent to each such analysis are two presumptions that must be evaluated. First, designs must be such that equipment can perform designated safety functions in postulated service environments. Second, in-service aging must not degrade Class 1E equipment to the point where it cannot perform designated safety functions when required.

Production testing, normal service testing, and surveillance may not be able to determine whether the equipment is vulnerable to failure, either as a result of inadequate design or inservice time and environment, because of the special environmental stresses associated with some postulated service conditions included in the station safety analysis. Under these circumstances, common cause failure of redundant Class 1E equipment might occur at the time its safety function(s) is required. It is the fundamental role of qualification to provide reasonable assurance, with due recognition given to the established technology, that common cause failures due to design, manufacture, and age do not exist, and that the design and manufacture are adequate to permit the equipment to perform its safety function(s) during postulated service conditions.

Synergistic effects and ionizing radiation dose-rate effects have become a concern within the industry and remain the subject of continuing research programs. Preliminary results indicate that synergistic effects can be either positive or negative. Such effects should be considered in developing a qualification program but are not, at this time, part of the requirements of this standard.

Motor control centers qualified in accordance with this standard will meet the requirements of IEEE Std 323-1983 or IEEE Std 627-1980, which provide the basic principles for design qualification for all safety systems equipment for use in nuclear power generating stations. This revision to IEEE Std 649-1980 was made to clarify its requirements and to provide greater detailed guidance on both harsh and mild environment qualification. It also incorporates recent research on the use of experience data for seismic qualification.

This standard defines requirements that are adequate to qualify motor control centers and their components located in all areas of the nuclear power generating station, including harsh and mild environmental areas. At this time, it appears that the seismic event is the only design basis event with potential for common cause failure in mild environments; however, other environmental service conditions may also be contributors.

The user of this standard should be aware that other methods of demonstrating qualification may be valid and more cost-effective than those described herein. Methodology should be reviewed at the time the qualification program is established to determine the most effective manner to demonstrate qualification.

Scope

This standard describes the basic principles, requirements, and methods for qualifying Class 1E motor control centers for both harsh and mild environment applications in nuclear power generating stations.