Regulatory Guide 1.9

Selection, Design, and Qualification of Diesel-Generator Units Used as Standby (Onsite) Electric Systems at Nuclear Power Plants

ML13038A105
Person / Time
Issue date:	12/31/1979
From:	Office of Nuclear Regulatory Research
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References
RG-1.009, Rev. 2
Download: ML13038A105 (4)

.,UE Revision 2

4-1, U.S.REGUL

NUCLEAR REGULATORY COMMISSION December 1979 REGULATORY GUIDE

1ý *OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 1.9

?SECD C,,AI...ELECTION, DESIGN, AND QUALIFICATION OF DIESEL-GENERATOR UNITS USED AS

• I STANDBY (ONSITE) ELECTRIC POWER SYSTEMS AT NUCLEAR POWER PLANTS

i JA* "; J,* *-'

A. INTRODUCTION

equipment needed to maintain the plant in a safe condition if an extended loss of offsite power occurs.

General Design Criterion 17, "Electric Power Systems,"

of Appendix A, "General Design Criteria for Nuclear Power IEEE Std 387-1977, "IEEE Standard Criteria for Diesel- Plants," to 10 CFR Part 50, "Domestic Licensing of Produc- Generator Units Applied as Standby Power Supplies for Nu- tion and Utilization Facilities," includes a requirement that clear Power Generating Stations,"'I delineates principal the onsite electric power system have sufficient capacity design criteria and qualification testing requirements that, if and capability to ensure that (I) specified acceptable fuel followed, will help ensure that selected diesel-generator design limits and design conditions of the reactor coolant units meet their performance and reliability requirements.

pressure boundary are not exceeded as a result of anticipated IEEE Std 387-1977 was developed by Working-Group 4.2C

operational occurrences and (2) the core is cooled and con- of the Nuclear Power Engineering Committee (NPEC) of tainment integrity and other vital functions are maintained the Institute of Electrical and Electronics Engineers, Inc.

in the event of postulated accidents. (IEEE), approved by NPEC, and subsequently approved by the IEEE Standards Board on September 9, 1976. IEEE Std Criterion III, "Design Control," of Appendix B, "Quality 387-1977 is supplementary to IEEE Std 308-1974, "IEEE

Assurance Criteria for Nuclear Power Plants and Fuel Standard Criteria for Class IE Power Systems and Nuclear Reprocessing Plants," to 10 CFR Part 50 includes a require- Power Generating Stations," I and specifically amplifies ment that measures be provided for verifying or checking paragraph 5.2.4, "Standby Power Supplies," of that docu- the adequacy of design by design reviews, by the use of ment with respect to the application of diesel-generator alternative or simplified calculational methods, or by the units. IEEE Std 308-1974 is endorsed, with certain excep- performance of a suitable testing program. tions, by Regulatory Guide 1.32, "Criteria for Safety-Related Electric Power Systems for Nuclear Power Plants."

Diesel-generator units have been widely used as the power source for the onsite electric power systems. This A knowledge of the characteristics of each load is regulatory guide describes a method acceptable to the NRC essential in establishing the bases for the selection of a staff for complying with the Commission's requirements diesel-generator unit that is able to accept large loads in that diesel-generator units intended for use as onsite power rapid succession. The majority of the emergency loads are sources in nuclear power plants be selected with sufficient large induction motors. This type of motor draws, at full capacity and be qualified for this service. The Advisory voltage, a starting current five to eight times its rated load Committee on Reactor Safeguards has been consulted current. The sudden large increases in current drawn from concerning this guide and has concurred in the regulatory the diesel generator resulting from the startup of induction position. motors can result in substantial voltage reductions. The lower voltage could prevent a motor from starting, i.e.,

B. DISCUSSION

accelerating its load to rated speed in the required time, or cause a running motor to coast down or stall. Other loads A diesel-generator unit selected for use in an onsite might be lost if their contactors drop out. Recovery from electric power system should have the capability to (1) start the transient caused by starting large motors or from the and accelerate a number of large motor loads in rapid loss of a large load could cause diesel engine overspeed succession and be able to sustain the loss of all or any part which, if excessive, might result in a trip of the engine.

of such loads and maintain voltage and frequency within acceptable limits and (2) supply power continuously to the 1 Copies may be obtained from the Institute of Electrical and Electronics Engineers, Inc., United Engineering Center, 345 East Lines indicate substantive changes from Revision 1. 47th Street, New York, New York 10017.

USNRC REGULATORY GUIDES Comments should be sent to the Secretary of the Commission, U.S. Nuclear Regulatory Commission, Regulatory Guides are issued to describe and make available to the Attention: Doclketing and Service Branch. Washington, D.C. 20555, public methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate tech- The guides are issued in the following ten broad divisions:

niques used by the staff in evaluating specific problems or postu- lated accidents, or to provide guidance to applicants. Regulatory 1. Power Reactors 6. Products Guides are not substitutes for regulations, and compliance with 2. Research and Test Reactors 7. Transportation them is not required. Methods and solutions different from those set 3. Fuels and Materials Facilities 8. Occupational Health out in the guides will be acceptable if they provide a basis for the 4. Environmental and Siting 9. Antitrust and Financial Review findings requisite to the issuance or continuance of a permit or 5. Materials and Plant Protection 10. General license by the Commission.

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to accommodate comments and to reflect new information or Information on the subscription service and current GPO prices may experience. This guide was revised as a result of substantive com- be obtained by writing the U.S. Nuclear Regulatory Commission, ments received from the public and additional staff review. Washington, D.C. 20555, Attention: Publications Sales Manager.

These same consequences can also result from the cumu- system should be selected to have a continuous load rating lative effect of a sequence of more moderate transients if (as defined in Section 3.7.1 of IEEE Std 387-1977) equal the system is not permitted to recover sufficiently between to or greater than the sum of the conservatively estimated successive steps in a loading sequence. loads needed to be powered by that unit at any one time.

In the absence of fully substantiated performance character- Generally it has been industry practice to specify a istics for mechanical equipment such as pumps, the electric maximum voltage reduction of 10 to 15 percent when motor drive ratings should be calculated using conservative starting large motors from large-capacity power systems and estimates of these characteristics, e.g., pump runout condi- a voltage reduction of 20 to 30 percent when starting these tions and motor efficiencies of 90 percent or less and motors from limited-capacity power sources such as diesel- power factors of 85 percent or less.

generator units. Large induction motors can achieve rated speed in less than 5 seconds when powered from adequately 2. At the operating license stage of review, the predicted sized diesel-generator units that are capable of restoring the loads should not exceed the short-time rating (as defined in voltage to 90 percent of nominal in about I second. Section 3.7.2 of IEEE Std 387-1977) of the diesel-generator unit.

Protection of the diesel-generator unit from excessive overspeed, which can result from a loss of load, is afforded 3. In Section 5.1.1, "GeneraL" of IEEE Std 387-1977, the by the immediate operation of a diesel-generator unit trip, requirements of IEEE Std 308-1974 should be used subject usually set at 115 percent of nominal speed. In addition, to the regulatory position of Regulatory Guide 1.32.

the generator differential trip must operate immediately in order to prevent substantial damage to the generator. There 4. Section 5.1.2, "Mechanical and Electrical Capabilities,"

are other protective trips provided to protect the diesel- of IEEE Std 387-1977 pertains, in part, to the starting and generator units from possible damage or degradation. load-accepting capabilities of the diesel-generator unit. In However, these trips could interfere with the successful conjunction with Section 5.1.2, each diesel-generator unit functioning of the unit when it is most needed, i.e., during should be capable of starting and accelerating to rated accident conditions. Experience has shown that there have speed, in the required sequence, all the needed engineered been numerous occasions when these trips have needlessly safety feature and emergency shutdown loads. The diesel- shut down diesel-generator units because of spurious generator unit design should be such that at no time during operation of a trip circuit. Consequently, it is important the loading sequence should the frequency and voltage that measures be taken to ensure that spurious actuation of decrease to less than 95 percent of nominal and 75 percent these other protective trips does not prevent the diesel- of nominal, respectively. (A larger decrease in voltage and generator unit from performing its function. frequency may be justified for a diesel-generator unit that carries only one large connected load.) Frequency should The uncertainties inherent in estimates of safety loads at be restored to within 2 percent of nominal, and voltage the construction permit stage of design are sometimes of such should be restored to within 10 percent of nominal within magnitude that it is prudent to provide a substantial margin 60 percent of each load-sequence time interval. (A greater in selecting the load capabilities of the diesel-generator unit. percentage of the time interval may be used if it can be This margin can be provided by estimating the loads conser- justified by analysis. However, the load-sequence time vatively and selecting the continuous rating of the diesel- interval should include sufficient margin to account for the generator unit so that it exceeds the sum of the loads needed accuracy and repeatability of the load-sequence timer.)

at any one time. A more accurate estimate of safety loads is During recovery from transients caused by step load increases possible during the operating license stage of review because or resulting from the disconnection of the largest single detailed .designs have been completed and preoperational load, the speed of the diesel-generator unit should not test data are available. This permits the consideration of a exceed the nominal speed plus 75 percent of the difference somewhat less conservative approach, such as operation between nominal speed and the overspeed trip setpoint with safety loads within the short-time rating of the diesel- or 115 percent of nominal, whichever is lower. Further, the generator unit. transient following the complete loss of load should not cause the speed of the unit to attain the overspeed trip

C. REGULATORY POSITION

setpoint.

Conformance with the requirements of IEEE Std 387-1977, 5. In Section 5.4, "Qualification," of IEEE Std 387-1 977,

"IEEE Standard Criteria for Diesel-Generator Units Applied the qualification testing requirements of IEEE Std 323-1974, as Standby Power Supplies for Nuclear Power Generating "IEEE Standard for Qualifying Class IE Equipment for Stations," dated June 17, 1977, is acceptable for meeting Nuclear Power Generating Stations,"' should be used the requirements of the principal design criteria and qualifica- subject to the regulatory position of Regulatory Guide 1.89, tion testing of diesel-generator units used as onsite electric "Qualification of Class IE Equipment for Nuclear Power power systems for nuclear power plants subject to the Plants."

following:

6. Section 5.5, "Design and Application Considerations,"

I. When the characteristics of loads are not accurately of IEEE Std 387-1977 pertains to design features for con- known, such as during the construction permit stage of sideration in diesel-generator unit design. In conjunction design, each diesel-generator unit of an onsite power supply with Section 5.5, diesel-generator units should be designed I

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to be testable during operation of the nuclear power plant Qualification of Class I E Equipment for Nuclear Power as well as while the plant is shut down. The design should Generating Stations," for seismic analysis or seismic testing

-, include provisions so that the testing of the units will by equipment manufacturers should be used subject to the simulate the parameters of operation (outlined in Regula- regulatory position of Regulatory Guide 1.100, "Seismic tory Guide 1.108, "Periodic Testing of Diesel-Generator Qualification of Electric Equipment for Nuclear Power Units Used as Onsite Electric Power Systems at Nuclear Plants."

Power Plants") that would be expected if actual demand were to be placed on the system. 10. The option indicated by "may" in Section 6.3.2(5)(c)

of IEEE Std 387-1977 should be treated as a requirement.

Testability should be considered in the selection and location of instrumentation sensors and critical components 11. Section 6.5, "Site Acceptance Testing," and Section 6.6, (e.g., governor, starting system components), and the "Periodic Testing," of IEEE Std 387-1977 should be supple- overall design should include status indication and alarm mented by Regulatory Guide 1.108.

features. Instrumentation sensors should be readily accessible and, where practicable, designed so that their inspection 12. Section 4, "Reference Standards," of IEEE Std 387-1977 and calibration can be verified in place. lists additional applicable IEEE standards. The specific appli- cability or acceptability of these referenced standards has

7. Section 5.6.2.2, "Automatic Control," of IEEE Std been or will be covered separately in other regulatory guides,

387-1977 pertains to automatic startup requirements and where appropriate.

their relationship to other operating modes. In conjunction with Section 5.6.2.2, engine-overspeed and generator-differ- 13. Section 6.3.2, "Start and Load Acceptance Qualifi- ential trips may be implemented by a single-channel trip. All cation," pertains to test requirements for diesel-generator other diesel-generator protective trips should be handled in unit qualification. In conjunction with Section 6.3.2, one of two ways: Either, (1) a trip should be implemented fewer successful start-and-load tests and allowed failures with two or more independent measurements for each trip than that specified-300 valid tests with no more than 3 parameter with coincident logic provisions for trip actuation, failures-may be justified for a diesel-generator unit that or (2) a trip may be bypassed under accident conditions, carries only one large connected load tested under actual provided the operator has sufficient time to react appro- conditions, provided an equivalent reliability/confidence priately to an abnormal diesel-generator unit condition. The level is demonstrated.

design of the bypass circuitry should satisfy the requirements of IEEE Std 279-1971 at the diesel-generator system level 14. In Section 6.3.1, "Load Capability Qualification," of

- and should include the capability for (1) testing the status IEEE Std 387-1977, the order of sequence of load tests and operability of the bypass circuits, (2) alarming in the described in parts (1) and (2) should be as follows: Load control room abnormal values of all bypass parameters, and equal to the continuous rating should be applied for the

(3) manually resetting of the trip bypass function. (Capability time required to reach engine temperature equilibrium, at for automatic reset is not acceptable.) which time, the rated short-time load should be applied for a period of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. Immediately following the 2-hour

8. Section 5.6.3.1, "Surveillance Systems," of IEEE Std short-time load test, load equal to the continuous rating

387-1977 pertains to status indication of diesel-generator should be applied for 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />.

unit conditions. In conjunction with Section 5.6.3.1, in order to facilitate trouble diagnosis, the surveillance system

D. IMPLEMENTATION

should indicate which of the diesel-generator protective trips is activated first. Except in those cases in which the applicant proposes an acceptable alternative method for complying with specified

9. In Section 6.3, "Type Qualification Testing Procedures portions of the Commission's regulations, the method de- and Methods," of IEEE Std 387-1977, the requirements of scribed herein will be used in the evaluation of applications IEEE Std 344-1975, "Recommended Practices for Seismic for construction permits docketed after December 1979.

1.9-3

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