Regulatory Guide 1.9

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

ML13350A381
Person / Time
Issue date:	11/30/1978
From:	NRC/OSD
To:
References
RG-1.009, Rev. 1
Download: ML13350A381 (3)

Revision 1November 1978U.S. NUCLEAR REGULATORY COMMISSIONk REGULATORY GUIDEOFFICE OF STANDARDS DEVELOPMENTREGULATORY GUIDE 1.9SELECTION, DESIGN, AND QUALIFICATION OF DIESEL-GENERATORUNITS USED AS ONSITE ELECTRIC POWER SYSTEMSAT NUCLEAR POWER PLANTS

B. DISCUSSION

General Design Criterion 17, "Electric Power A diesel-generator unit selected for use in anSystems," of Appendix A, "General Design onsite electric power system should have theCriteria for Nuclear Power Plants," to 10 CFR capability to (1) start and acceate a numberPart 50, "Domestic Licensing of Production and of large motor loads in rapid ar sion and beUtilization Facilities," includes a requirement able to sustain the loss ok an o%1._y part ofthat the onsite electric power system have such loads and maintain an, Irequencysufficient capacity and capability to ensure within acceptable limit " supply powerthat (1) specified acceptable fuel design limits continuously to the i V~eded to main-and design conditions of the reactor coolant tain the plant in a .*2e c 4itioA if an extendedpressure boundary are not exceeded as a loss of offsite po A~r o urý b'result of anticipated operational occurrences A*and (2) the core is cooled and containment in- IEEE Std -197 ;,,; E Standard Criteriategrity and other vital functions are maintained for Diesel-G k*tor mits Applied as Standbyin the event of postulated accidents. Power " K Nuclear Power GeneratingStations 4ceea'kes principal design criteriaCriterion III, "Design Control," of Appen- an a testing requirements that, ifdix B, "Quality Assurance Criteria for Nuclear foI , help ensure that selected diesel-Power Plants and Fuel Reprocessing Plants," to .genrhrat" Units meet their performance and10 CFR Part 50 includes a requirement that ' a IEEE Std 387-1977 wasmeasures be provided for verifying or checking 'f; ed by Working Group 4.2C of thethe adequacy of design by design reviews, J%$. cl r Power Engineering Committee (NPEC)the use of alternative or simplified calculati al 0 ot .he Institute of Electrical and Electronicsmethods, or by the performance of a suit".e Engineers, Inc. (IEEE), approved by NPEC,testing program. , and subsequently approved by the -IEEE Stan--" dards Board on September 9, 1976. IEEE StdDiesel-generator units have been wiely ud 387-1977 is supplementary to IEEE Std 308-as the power source for the onsi V le ic 1974, "IEEE Standard. Criteria for Class IEpower systems. This regulatory gfiae -Power Systems and Nuclear Power Generatingscribes a method acceptable to the NRC staff Stations,"' and specifically amplifies paragraphfor complying with the a mission's require- 5.2.4, "Standby Power Supplies," of that doc-ments that diesel-gene units intended for ument with respect to'the application of diesel-use as onsite power r j nuclear power generator units. IEEE Std 308-1974 is en-plants be selected with ic capacity and dorsed, with certain exceptions, by Regulatorybe qualified for v Guide 1.32, "Criteria for Safety-RelatedElectric Power Systems for Nuclear PowerwThe substantial her of ges in this revision has made Plants. "it impractical to the c ges es in the margin.'Copies e the Institute of Electrical andElectronics In .. n ited Engineering Center, 345 East47th Street, ork, New York 10017.A knowledge of the characteristics of eachload is essential in establishing the bases forUSNRC REGULATORY GUIDESRegulatney Guides re Issued to descrbe and rnake available to the publicmethods acceptable to the NRC staff of specific parts of thecommlssiora's regultionts, to delinestedvt sdb the staff In avalu-atg spec probles or postulated accidents. or to provide guidance toapplicants. Regulatory Guides ae not sutbstitutes for regulations, and corn-plence with them Is not requked. Methods end solutions different from thoseset out In the guides wil b acceptable If they provide a b"si for the findingsre=ui to the issgirce or continuance of a pewrh or Bse e by theComments and suggestions for Imroernemeis In tees gudes are encouragedat Imes, end guides wil e rwl sd, be aspramopas, to accommodate corn-mene= and to reflect new rmt or Howeve. corment t,this gtuld. If eeed wlfhn about two mond afte Its Issuance, wil bewfttleft useful In awluating the need for an eauly r .evilon.Comments should be sMnt to the Secrety of the Conmi;slon, U.S. NudcerRegulatory Commurorn , Wastington, D.C. 26. Attention: Dockasth andSevice Branch.The guides are Issued In the following ten broad divisioin:1. Power React"2. Reseerch end Teat Reactors3. Fuels and Materiab Factites4. Environmental and SitngrL Matmerilsand Plant protectionB. Products7. Transportation& Occupational Health9. Antitrust and Financial Review10. GeneralRequests for single copies of Isued guides Iwit-h may be reproducedl or forplacerment on en autonlatic: distribution list for single copies of fuaum guldesIn s divslons should be ,de In wrtltng to the US. NudIsr ReguatoryCornenssion, Washingion, D.C. I, Attentio: Okector, D,4lon ofTechnical Informaiwon and Document Control.

the selection of a diesel-generator unit that isable to accept large loads in rapid succession.The majority of the emergency loads are largeinduction motors. This type of motor draws, atfull voltage, a starting current five to tentimes its rated load current. The sudden largeincreases in current drawn from the dieselgenerator resulting from the startup of induc-tion motors can result in substantial voltagereductions. The lower voltage could prevent amotor from starting, i.e. , accelerating its loadto rated speed in the required time, or cause arunning motor to coast down or stall. Otherloads might be lost if their contactors dropout. Recovery from the transient caused bystarting large motors or from the loss of alarge load could cause diesel engine overspeedwhich, if excessive, might result in a trip ofthe engine. These same consequences can alsoresult from the cumulative effect of a sequenceof more moderate transients if the system is notpermitted to recover sufficiently between suc-cessive steps in a loading sequence.Generally it has been industry practice tospecify a maximum voltage reduction of 10 to 15percent when starting large motors from large-capacity power systems and a voltage reductionof 20 to 30 percent when starting these motorsfrom limited-capacity power sources such asdiesel-generator units. Large induction motorscan achieve rated speed in less than 5 secondswhen powered from adequately sized diesel-generator units that are capable of restoringthe voltage to 90 percent of nominal in about 1second.Protection of the diesel-generator unit fromexcessive overspeed, which can result from aloss of load, is afforded by the immediate oper-ation of a diesel-generator unit trip, usuallyset at 115 percent of nominal speed. In addi-tion, the generator differential trip must oper-ate immediately in order to prevent substantialdamage to the generator. There are other pro-tective trips provided to protect the diesel-generator units from possible damage or degra-dation. However, these trips could interferewith the successful functioning of the unitwhen it is most needed, i.e. , during accidentconditions. Experience has shown that therehave been numerous occasions when these tripshave needlessly shut down diesel-generatorunits because of spurious operation of a tripcircuit. Consequently, it is important thatmeasures be taken to ensure that spurious ac-tuation of these other protective trips does notprevent the diesel-generator unit fromperforming its function.The uncertainties inherent in estimates ofsafety loads at the construction permit stage ofdesign are sometimes of such magnitude that itis prudent to provide a substantial margin inselecting the load capabilities of the diesel-generator unit. This margin can be providedby estimating the loads conservatively andselecting the continuous rating of the diesel-generator unit so that it exceeds the sum ofthe loads needed at any one time. A more accu-rate estimate of safety loads is possihle duringlthe operating license stage of review becausedetailed designs have been completed andpreoperational test data are available. Thispermits the consideration of a somewhat lessconservative approach, such as operation withsafety loads within the short-time rating of thediesel-generator unit.

C. REGULATORY POSITION

Conformance with the requirements of IEEEStd 387-1977, "IEEE Standard Criteria forDiesel-Generator Units Applied as StandbyPower Supplies for Nuclear Power GeneratingStations," dated June 17, 1977, is acceptablefor meeting the requirements of the principaldesign criteria and qualification testing ofdiesel-generator units used as onsite electric.power systems for nuclear power plants subjectto the following:1. When the characteristics of loads are notaccurately known, such as during the con-struction permit stage of design, each diesel-generator unit of an onsite power supplysystem should be selected to have a continuousload rating (as defined in Section 3.7.1 of IEEEStd 387-1977) equal to or greater than the sumof the conservatively estimated loads needed tobe powered by that unit at any one time. Inthe absence of fully substantiated performancecharacteristics for mechanical equipment suchas pumps, the electric motor drive ratingsshould be calculated using conservative esti-mates of these characteristics, e.g., pumprunout conditions and motor efficiencies of 90%or less.2. At the operating license stage of review,the predicted loads should not exceed theshort-time rating (as defined in Section 3.7.2of IEEE Std 387-1977) of the diesel-generatorunit.3. During preoperational testing, the pre-dicted loads should be verified by tests.4. In Section 5.1.1, "General," of IEEE Std387-1977, the requirements of IEEE Std 308-1974 should be used subject to the regulatoryposition of Regulatory Guide 1.32.5. Section 5.1.2, "Mechanical and ElectricalCapabilities," of IEEE Std 387-1977 should besupplemented with the following:"Each diesel-generator unit should be capa-ble of starting and 'accelerating to ratedspeed, in the required sequence, all theneeded engineered safety feature and emer-gency shutdown loads. At no time during theloading sequence should the frequency andvoltage decrease to less than 95 percent ofnominal and 75 percent of nominal, respec-tively"b Frequency should be restored to1.9-2

• within 2 percent of nominal, and voltageshould be restored to within 10 percent ofnominal within 60 percent of each load-sequence time interval. (A greater percent-age of the time interval may be used if it canbe justified by analysis. However, the load-sequence time interval should include suffi-cient margin to account for the accuracy andrepeatability of the load-sequence timer.)During recovery from transients caused bystep load increases or resulting from thedisconnection of the largest single load, thespeed of the diesel-generator unit should notexceed the nominal speed plus 75 percent ofthe difference between nominal speed and theoverspeed trip setpoint or 115 *percent ofnominal, whichever is lowei. Further, thetransient following the complete loss of loadshould not cause the speed of the unit toattain the overspeed trip setpoint."6. In Section 5.4, "Qualification," of IEEEStd 387-1977, the qualification testing require-ments of IEEE Std 323-1974, "IEEE Standard forQualifying Class IE Equipment for NuclearPower Generating Stations,"' should be usedsubject to the regulatory of RegulatoryGuide 1.89, "Qualification of C!ass IE Equip-ment for Nuclear Power Plants."7. Section 5.5, "Design and Application Con-siderations," of IEEE Std 387-1977 should besupplemented with the following:"Diesel-generator units should be designed tobe testable during operation of the nuclearpower plant as well as while the plant is shutdown. The design should include provisionsso that the testing of the units will simulatethe parameters of operation (outlined inRegulatory Guide 1.108, "Periodic Testing ofDiesel-Generator Units Used as OnsiteElectric Power Systems at Nuclear PowerPlants") that would be expected if actualdemand were to be placed on the system."Testability should be considered in theselection and location of instrumentation sen-sors and critical components (e.g., gover-nor, starting system components), and theoverall design should include status indica-tion and alarm features. Instrumentationsensors should be readily accessible anddesigned so that their inspection and calibra-tion can be verified in place."8. Section 5.6.2.2, "Automatic Control," ofIEEE Std 387-1977 should be supplemented with,the following:(3) "With the exception of the engine over-speed trip and the generator differentialtrip, all diesel-generator protective tripsshould be either (1) implemented withtwo or more independent measurementsfor each trip parameter with coincidentlogic provisions for trip actuation or (2)automatically bypassed during accidentconditions. The design of the bypasscircuitry should satisfy the requirementsof IEEE Std 279-1971 at the diesel-generator system level and shouldinclude the capability for (I) testing thestatus and operability of the bypasscircuits, (2) alarming in the control roomabnormal values of all bypass param-eters, and (3) manually resetting of thetrip bypass function. (Capability forautomatic reset is not acceptable.)"9. Section 5.6.3. 1, "Surveillance Systems," orIEEE Std 387-1977 should be supplemented withthe following:"In order to facilitate trouble diagnosis, thesurveillance system should indicate which ofthe diesel-generator protective trips is acti-vated first."10. In Section 6.3, "Type Qualification Test-ing Procedures and Methods," of IEEE Std 387-1977, the requirements of IEEE Std 344-1975,"Recommended Practices for Seismic Qualifica-tion of Class 1E Equipment for Nuclear PowerGenerating Stations," for seismic analysis orseismic testing by equipment manufacturersshould be used subject to the regulatory posi-tion of Regulatory Guide 1.100, "Seismic Quali-fication of Electric Equipment for NuclearPower Plants."11. The option indicated by "may" in Sec-tion 6.3.2(5)(c) of IEEE Std 387-1977 shouldbe treated as a requirement.12. Section 6.5, "Site Acceptance Testing,"and Section 6.6, "Periodic Testing," of IEEEStd 387-1977 should be supplemented by Regu-latory Guide 1.108.13. Section 4, "Reference Standards," ofIEEE Std 387-1977 lists additional applicableIEEE standards. The specific applicability oracceptability of these referenced standards hasbeen or will be covered separately in otherregulatory guides, where appropriate.

D. IMPLEMENTATION

This proposed guide has been released toencourage public participation in its develop-ment. Except in those cases in which an appli-cant proposes an acceptable alternative methodfor complying with specified portions of theCommission's regulations, the method to bedescribed in the active guide reflecting publiccomments will be used in the evaluation ofapplications for construction permits docketedafter the implementation date to be specified inthe active guide. This implementation date willin no case be earlier than July 1979.If an .applicant wishes to use this draft guidein an application docketed prior to the imple-mentation date, the pertinent portions of theapplication will be evaluated on the basis ofthis draft guide.1.9-3