Regulatory Guide 1.108

Periodic Testing of Diesel Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants

ML12216A011
Person / Time
Issue date:	08/31/1977
From:	NRC/OSD, Office of Nuclear Regulatory Research
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References
RG-1.108, Rev.1
Download: ML12216A011 (4)

Revision IAugust 1977U.S. NUCLEAR REGULATORY COMMISSIONREGULATORY GUIDEOFFICE OF STANDARDS DEVELOPMENTREGULATORY GUIDE 1.108PERIODIC TESTING OF DIESEL GENERATOR UNITSUSED AS ONSITE ELECTRIC POWER SYSTEMSAT NUCLEAR POWER PLANTS

A. INTRODUCTION

Criterion XI, "Test Control," of Appendix B,"Quality Assurance Criteria for Nuclear PowerPlants and Fuel Reprocessing Plants," to 10 CFRPart 50, "Licensing of Production and UtilizationFacilities," requires that a test program be es-tablished to ensure that systems and components per-form satisfactorily and that the test program includeoperational tests during nuclear power plant opera-tion.Criterion 17, "Electric Power Systems," of Appen-dix A, "General Design Criteria for Nuclear PowerPlants," to 10 CFR Part 50 requires that onsiteelectric power systems have sufficient independence,capacity, redundancy, and testability to perform theirsafety functions, assuming a single failure.Criterion 18, "Inspection and Testing of ElectricPower Systems," of Appendix A to 10 CFR Part 50requires that electric power systems important tosafety be designed to permit appropriate periodic in-spection and testing to assess the continuity of the.systems and the coindition. of their components.This regulatory guide describes a method accep-table to the NRC staff for complying with the Com-mission's regulations with regard to periodic testingof diesel electric power units to ensure that the dieselelectric power systems will meet their availability re-quirements. The Advisory Committee on ReactorSafeguards has been consulted concerning this guideand has concurred in the regulatory position.features if a loss of offsite power and an accident oc-cur during the same time period and (2) to providepower to equipment needed to maintain the plant in asafe condition if an extended loss of offsite power oc-curs. Diesel generator units are the most commonsource of onsite electric power.High reliability must be designed into the dieselgenerator units and maintained throughout their ser-vice lifetime by appropriate testing, maintenance, andoperating programs. Branch Technical PositionEICSB 2, "Diesel-Generator Reliability Qualifica-tion Testing," dated 11/24/75, of the StandardReview Plan (Appendix 7-A of NUREG-75/0871) es-tablishes a reliability goal of 0.99 (at a nominal 50%confidence level) and an acceptable qualificationtesting program for diesel generator units of a type orsize not previously used as standby emergency powersources in nuclear power plants. The preoperationaland periodic testing provisions set forth in this guidehave been designed to provide a basis for taking thosecorrective actions needed to maintain high inservicereliability of installed diesel generator units. In addi-tion, the data developed will provide an ongoingdemonstration of performance and reliability for alldiesel generator, units after installation and in service.Reliability objectives concerning the entire onsiteelectric power system's probability of failure dependon the interconnections among the system's compo-nents and are not within the scope of this guide."Failure" is taken here to mean the failure to start,accelerate, and assume the design-rated load withinand for the time prescribed during an emergency or avalid test.I NUREG-75/087, "Standard Review Plan for the Review ofSafety Analysis Reports for Nuclear Power Plants," U.S. NuclearRegulatory Commission. Copies may be purchased from theNational Technical Information Service, Springfield, Virginia22161.*-

B. DISCUSSION

The purposes of onsite electric power systems are(1) to provide power promptly to engineered safety*Lines indicate substantive changes from previous issue.USNRC REGULATORY GUIDESRegulatory Guides are issued to describe and make.available to the public methodsacceptable to the NRC staff of implementing specific parts of the Commission'sregulations, to delineate techniques used by the staff in evaluating specific problemsor postulated accidents, or to proyide guidance to applicants. Regulatory Guidesare not substitutes for regulations, and compliance with them is not required.Methods and solutions different from those set out in the guides will be accept-able if they provide a basis for the findings requisite to the issuance or continuanceof a permit or license by the Commission.Comments and suggestions for improvements in these guides are encouraged at alltimes, and guides will be revised, as appropriate, to accommodate comments andto reflect new information or experience. This guide was revised as a result ofsubstantive comments received from the public and additional staff review.Comments should be sent to the Secretary of the Commission, US. Nuclear Regu-latory Commission, Washington, D.C 20555, Attention: Docketing and ServiceBranch.The guides are issued in the following ten broad divisions:1. Power Reactors2. Research and Test Reactors3. Fuelsand Materials Facilities4. Environmental and Siting5. Materials and Plant Protection6. Products7. Transportation8. Occupational Health9. Antitrust Review10. GeneralRequests for single copies of issued guides (which may be reproducedl or for place-ment on an automatic distribution list for single copies of future guides in specificdivisions should be made in writing to the US. Nuclear Regulatory Commission,Washington, D.C. 20555, Attention: Director, Division of Document Contro The testing of the diesel generator unit shouldsimulate, where practicable, the parameters of opera-tion (automatic start, load sequencing, load shed-ding, operation time, etc.) and environments(temperature, humidity, etc.) that would be expectedif actual demand were to be placed on the system.This guide provides design and operational provi-sions for the performance of periodic testing of dieselgenerator units used for onsite electric power fornuclear power plants. A "diesel generator unit" con-sists of the engine, generator, combustion air system,cooling water system up to the supply, fuel supplysystem, lubricating oil system, starting energysources, autostart controls, manual controls, anddiesel generator breaker.

C. REGULATORY POSITION

1. Generala. The design of a diesel generator unit should besuch that it can accommodate diesel generator testingas defined in Regulatory Position C.2.b. Diesel generator units should be designed to betestable during operation of the nuclear power plant,as well as while the plant is shut down. The designshould include provisions so that the testing of theunits will simulate the parameters of operation(outlined in Regulatory Position C.2) that would beexpected if actual demand were to be placed on thesystem.(1) Capability should be provided to test eachdiesel generator unit independently of redundant un-its. Test equipment should not cause a loss of in-dependence between redundant diesel generator unitsor between diesel generator load groups.(2) Testability should be considered in the selec-tion and location of instrumentation sensors andcritical components (e.g., governor, starting systemcomponents). Instrumentation sensors should bereadily accessible and designed so that their inspec-tion and calibration can be verified in place.Testability should be considered in selecting criticalcomponents, and the overall design should includestatus indication and alarm features.(3) Periodic testing of diesel generator unitsshould not impair the capability of the unit to supplyemergency power within the required time. Wherenecessary, diesel generator unit design should includean emergency override of the test mode to permitresponse to bona fide signals.(4) A surveillance system should be providedwith remote indication in the control room as todiesel generator unit status, i.e., under test, ready-standby, lockout. A means of communication shouldalso be provided between diesel generator unit testinglocations and the main control room to ensure thatthe operators are cognizant of the status of the unitunder test.(5) The surveillance system should indicatewhich of the diesel generator protective trips is ac-tivated first in order to facilitate trouble diagnosis.(6) All diesel generator protective trips shouldbe in force during diesel generator unit testing.c. Detailed step-by-step procedures should beprovided for each test under Regulatory Position C.2.The procedures should identify those special arrange-ments or changes in normal system configurationthat must be made to put the diesel generator unit un-der test. Jumpers and other nonstandard configura-tions or arrangements should not be used subsequentto initial equipment startup testing.d. Subsequent to any failure, the cause should bedetermined and corrective action taken in a timelymanner, with emphasis on preventing reoccurrence ofthe failure.2. Testinga. Testing of diesel generator units during theplant preoperational test program and at least onceevery 18 months should:(1) Demonstrate proper startup operation bysimulating loss of all a.c. voltage and demonstratethat the diesel generator unit can start automaticallyand attain the required voltage and frequency withinacceptable limits and time.(2) Demonstrate proper operation for design-accident-loading-sequence to design-load require-ments and verify that voltage and frequency aremaintained within required limits.(3) Demonstrate full-load-carrying capabilityfor an interval of not less than 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, of which 22hours should be at a load equivalent to the con-tinuous rating of the diesel generator and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> at aload equivalent to the 2-hour rating of the dieselgenerator. Verify that voltage and frequency require-ments are maintained. The test should also verify thatthe cooling system functions within design limits.(4) Demonstrate proper operation during dieselgenerator load shedding, including a test of the lossof the largest single load and of complete loss of load,and verify that the voltage requirements are met andthat the overspeed limits are not exceeded.(5) Demonstrate functional capability at full-load temperature conditions by rerunning the testphase outlined in Regulatory Positions C.2.a.(l) and(2) above immediately following (3) above.I1.108-2 (6) Demonstrate the ability to (a) synchronizethe diesel generator unit with offsite power while theunit is connected to the emergency load, (b) transferthis load to the offsite power, (c) isolate the dieselgenerator unit, and (d) restore it to standby status.(7) Demonstrate that the engine will performproperly if switching from one fuel oil supply systemto another is a part of the normal operatingprocedure to satisfy the 7-day storage requirement.(8) Demonstrate that the capability of the dieselgenerator unit to supply emergency power within therequired time is not impaired during periodic testingunder Regulatory Position C.2.c..(9) Demonstrate the required reliability bymeans of any 69 consecutive valid tests2 (per plant)with no failures, with a minimum of 23 or 69/n tests,whichever is the larger, per diesel generator unit(where n is equal to the number of diesel generatorunits of the same design and size).b. Testing of redundant diesel generator unitsduring normal plant operation should be performedindependently (nonconcurrently) to minimize com-mon failure modes resulting from undetected in-terdependences among diesel generator units.However, during reliability demonstration of dieselgenerator units during plant preoperational testingand testing subsequent to any plant modificationwhere diesel generator unit interdependence mayhave been affected or every 10 years (during a plantshutdown), whichever is the shorter, a test should beconducted in which redundant units are startedsimultaneously to help identify certain commonfailure modes undetected in single diesel generatorunit tests.c. Periodic testing of diesel generator units duringnormal plant operation should:(1) Demonstrate proper startup and verify thatthe required voltage and frequency are automaticallyattained within acceptable limits and time. This testshould also verify that the components of the dieselgenerator unit required for automatic startup areoperable.(2) Demonstrate full-load-carrying capability(continuous rating) for an interval of not less thanone hour. The test should also verify that the coolingsystem functions within design limits. This test couldbe accomplished by synchronizing the generator withthe offsite power and assuming a load at the max-imum practical rate.d. After completion of the diesel generator unitreliability demonstration under Regulatory Postition2 Valid test as defined in Regulatory Position C.2.e.C.2.a.(9), the interval for periodic testing underRegulatory Position C.2.c (on a per diesel generatorunit basis) should be no more than 31 days andshould depend on demonstrated performance. Ifmore than one failure has occurred in the last 100tests (on a per nuclear unit basis), the test intervalshould be shortened in accordance with the followingschedule.:(I) If the number of failures in the last 100 validtests is one or zero, the test interval should be notmore than 31 days.(2) If the number of failures in the last 100 validtests is two, the test interval should be not more than14 days.(3) If the number of failures in the last 100 validtests is three, the test interval should be not morethan 7 days.(4) If the number of failures in the last 100 validtests is four or more, the test interval should be notmore than 3 days.e. Valid tests and failures (under RegulatoryPositions C.2.a.(9) and C.2.d) should be based on thefollowing criteria:(1) All start attempts (automatic, includingthose from bona tide signals, or manual) that result ina failure to start, except as noted in (2) below, shouldbe considered valid tests and failures.(2) Unsuccessful start and load attempts thatcan definitely be attributed to operating error, tospurious operation of a trip that is bypassed in theemergency operating mode, to malfunction of equip-ment that is not operative in the emergency operatingmode (e.g., synchronizing circuitry) or is not part ofthe defined diesel generator unit design should not beconsidered valid tests or failures.(3) Successful starts, including those initiated bybona fide signals, followed by successful loading (se-quential or manual) to at least 50% of continuousrating and continued operation for at least one hourshould be considered valid successful tests.(4) Successful starts that are terminated inten-tionally without loading, as defined in (3) above,should not be considered valid tests or failures.(5) Successful starts followed by an unsuccessfulloading attempt should be considered valid tests andfailures, except as noted in (2) above.(6) Tests that are terminated intentionallybefore completion as defined in (3) above because ofan alarmed abnormal condition that would ultimate-ly have resulted in diesel generator damage or failureshould be considered valid tests and failures.I1.108-3 (7) Tests performed in the process oftroubleshooting should not be considered valid tests.Tests that are performed to verify correction of theproblem should be considered valid tests and succes-ses or failures, as appropriate.(8) Cranking and venting procedures that leadto the discovery of conditions (e.g., excessive water oroil in a cylinder) that would have resulted in thefailure of the diesel generator unit during test or dur-ing response to a bona fide signal should be con-sidered a valid test and failure.3. Records and Reportsa. All start attempts, including those from bonafide signals, should be logged. The log shoulddescribe each occurrence in sufficient detail to permitindependent determination of statistical validity inaccordance with Regulatory Position C.2.e.Maintenance, repair, and out-of-service-timehistories, as well as cumulative maintenance andoperating data, should also be logged. Cumulativestatistical analyses of diesel generator unit testresults, together with results of operation of the dieselgenerator unit when required by actual demand,should be maintained. These analyses should includeexamination of the trend of critical failuremechanisms, human errors, and common modefailures.b. All diesel generator unit failures, valid or in-valid, should be reported3 consistent with thelicensee's reporting requirements. This report should(1) identify the diesel generator unit involved, (2)identify the failure as being the nth f'ailure in the last100 valid tests, (3) describe the cause of failure, (4)describe the corrective measures taken, (5) indicatethe length of time the diesel generator unit was un-available, (6) define the current surveillance test inter-val, and (7) verify that the test interval is in confor-mance with the schedule of Regulatory PositionC.2.d. If the number of failures in the last 100 validtests is seven or more, the reliability of the diesel' See Regulatory Guide 1.16, "Reporting of Operating Infor-mation."generator units requires special evaluation, and theinformation provided on the report form should besupplemented, as needed, by additional narrativematerial that:(1) Identifies the reported failure as the 7th orgreater failure in the last 100 valid tests,(2) Describes corrective measures, taken orplanned, to increase the reliability of the generatorunits,(3) Provides an assessment of the existingreliability of electric power to engineered-safety-ieature equipment,(4) Provides the licensee's basis for continuedplant operation if that is planned, and(5) Provides a summary of all tests (valid and in-valid) that occurred within the time period overwhich the last 100 valid tests were performed, andverifies that surveillance testing during this periodwas in conformance with the schedule of RegulatoryPosition C.2.d.Invalid failures experienced during trouble-shooting should be included in the report of thefailure (valid or invalid) that made thetroubleshooting necessary.

D. IMPLEMENTATION

The purpose of this section is to provide informa-tion to applicants regarding the NRC staffs plans forusing this regulatory guide.This guide reflects current NRC staff practice.Therefore, except in those cases in which the appli-cant proposes an acceptable alternative method forcomplying with the specified portions of the Commis-sion's regulations, the method described herein is be-ing and will continue to be used in the evaluation ofsubmittals for construction permit applications untilthis guide is revised as a result of suggestions from thepublic or additional staff review.001.108-4