Information Notice 1991-13, Inadequate Testing of Emergency Diesel Generators (EDGs)

Inadequate Testing of Emergency Diesel Generators (EDGs)

ML031190586
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	03/04/1991
Revision:	0
From:	Rossi C E Office of Nuclear Reactor Regulation
To:
References
IN-91-013, NUDOCS 9102260165
Download: ML031190586 (10)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON, D.C. 20555March 4, 1991NRC INFORMATION NOTICE NO. 91-13: INADEQUATE TESTING OF EMERGENCYDIESEL GENERATORS (EDGs)

Addressees

All holders of operating licenses or construction permits for nuclear powerreactors.

Purpose

This information notice is intended to alert addressees to inadequacies in thetestingof emergency diesel generators at'nuclear power plants. Specifically,some EDG testing has not adequately verified the capability of the-EDG to carryits maximum expected loads and other tests have failed to properly verify theoperation of the load shedding logic for the EDG. These testing deficienciesindicate that other licensees may have similar deficiencies that have not yetbeen detected. It is expected that recipients will review the information forapplicability to their facilities and consider actions, as appropriate, toavoid similar problems. However, suggestions contained in this informationnotice-do-not constitute NRC requirements; therefore no specific action orwritten response is required.

Description of Circumstances

Yankee Atomic Electric Company, the licensee'for the Yankee Nuclear PowerStation (Yankee Rowe), recently identified that the EDGs at the Yankee'Roweplant were undersized for their maximum accident electrical load demand. TheEDGs failed to reach their technical specification (TS) required loading of400 kilowatts (kW) while connected in parallel to the electrical grid.' Thelicensee then retested the EDGs using a resistor bank in place of the grid.Using this test configuration, Yankee Atomic determined that the frequency ofthe generator dropped to 58 hertz with a maximum electrical output of 385 kW.The licensee attributed the reduction in power output, in part, to high ambientair temperatures that reduced engine power and cooling. The licensee had notconsidered the effect of ambient air temperature during previous testing. Theexisting air temperature was within design basis limits. Although highambient air temperature was the immediate cause of the failure to attain400 kW, the root cause was the fact that the engines were undersized. Themanufacturer's rating of 400 kW also failed to consider the effects of ambientair temperature. The licensee calculated that the dependable capacity of theseEDGs was between 359 kW and 399kW. Yankee Atomic eventually replaced all3 EDGs with models capable of producing 600 kW (450 kW continuous) because theQ9102260165Z4&

IN 91-13 -March 4, 1991 estimated electrical load on the EDGs is very close to 400 kW and modificationsto the original EDGs failed to raise their output capabilities. The OmahaPublic Power District, the licensee for Fort Calhoun Station, Unit 1, reporteda similar problem with their EDGs. At Fort Calhoun, the EDGs could temporarilyachieve their design rating at high ambient temperatures, but they could notmaintain this power level for an extended period of time.At the Vermont Yankee Generating Station, during a safety system functionalinspection, the U.S. Nuclear Regulatory Commission (NRC) staff determined thatthe surveillance testing of the station EDGs was inadequate. The staff foundthat there was insufficient electrical loading during testing as well asinsufficient compensation for the expected electrical power factor (pf).Specifically, the plant surveillance test for the EDGs required that the EDGsmaintain a load of 2500 to 2750 kW, which is equivalent to 2500 to 2750kilovolt-amperes (kMA) at pf-1.0. The licensee considered this limit suffi-cient to meet the maximum load of 2471 kW specified in the final safety analy-sis report (FSAR). However, during subsequent analysis-, the licenseedetermined that the worst-case EDG loading could actually reach 2751 kW. Inaddition, the EDG would realistically experience an electrical power factor of0.85 lagging, causing the actual generator output current to be significantlyhigher (i.e., assuming generator output voltage is maintained roughly constant,generator output current and kYA at pf=0.85 are approximately 1.18 times thegenerator output current and kVA at pf- 1.0.) Therefore, the existing surveil-lance did not adequately demonstrate the capability of the EDG to carry itsaccident-kW-and-current loading-.-- As a-result-,-the -licensee-is-modffying -tts--EDG testing requirements to ensure that both the engine and the generator willbe appropriately tested to demonstrate their capability to produce the accidentelectrical load.At Millstone Nuclear Power Station, Unit 3, the Northeast Nuclear EnergyCompany (the licensee) determined that its testing of the EDG load sheddingcircuitry was inadequate. In particular, the surveillance tests did not verifythe load shedding of five nonsafety-related loads and two safety-related loads.This condition was a violation of TS requirements and had existed from initialplant operation in April 1986 until January 1990. Subsequent testing verifiedthat the load shedding circuits operated properly.Discussion:The events at Yankee Rowe, Fort Calhoun, and Vermont Yankee illustrate thefailure of EDG testing to demonstrate properly the capability of the EDGs toassume the design-basis electrical loading during an accident. The intent ofthe required surveillance testing is to assure that the EDG can dependablycarry its accident loads. It is important that the worst-case conditions(frequency, voltage, electrical power factor, and environment) be consideredwhen the EDG is tested. In particular, the effects of the electrical powerfactor and the environment may have been overlooked. It is important thatprocedures give personnel performing the test sufficient information to allowthem to load the EDG to simulate worst-case conditions. Since the simulationof environmental conditions is generally impractical, it may be necessary touse analysis to correct for environmental conditions or to show that the effect IN 91-13March 4, 1991 of such conditions Is negligible for the EDG. Information from the vendor mayhelp in determining what changes, if any, may be necessary. It is alsoimportant for procedures to give adequate guidance to ensure that the EDG isnot inadvertently overloaded during the 'test.The last event illustrates the failure of EDG testing to verify adequately theproper operation of all of the logic necessary to support the EDG in an acci-dent.' Millstone Unit 3 was given as an example, but other similar cases havebeen reported.Generic Letter 88-15, OElectric Power Systems -Inadequate Control Over DesignProcesses,' discussed problems similar to those in this information notice.This information notice requires no specific-action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.es iDirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: C. H. Woodard, Region I(215) 337-5261A. J. Kugler, NRR(301) 492-0834

Attachment:

List of Recently Issued NRC Information NoticesI amW EIOnla -LoIn (Amn2CCnMI=2Attachment IIN 91-13March 4, 1991Page 1 of ILIST OF RECENTLY ISSUEDKRC INFORMATION NOTICESInformationNotice No.91-1291-11Date of86-99,Supp. 189-32,Sapp. 191-1091-0991-0890-77,S"u. 191-07SubjectPotential Loss of Net PositiveSuctio Head (MPSH) of StandbyLiquid Control System PumpsInadequate Physical Separationad Electrical Isolation ofNon-safety-related Circuitsfrom Reactor Protection SystemCircuitsDeyradation of Steel Con-t.7_m tsSurveillance Testing of Low-Temperature Overpressure-Protection SystemwSumary of Semlaniwal ProgramPerformance Reports on Fitness-for-Duty (FFD) In the NuclearIndustryCounterfeiting of Crane ValvesMedical Examinations forLicensed OperatorsInadvertent Reaoval of FuelAss clies from the Reactor CoreMaintenance Deficiency Assoc-iated with General ElectricHorizontal Custom 8000Induction MotorsIssuance Issued to02/15/91 All holders of OLsor CPs for boilingwater reactors (BWRs).02/20/91 All holders of OLsor CPs for W-designednuclear power reactors.02/14/91 All holders of OLs orCPs for nuclear powerreactors.02/12/91 All holders of OLs orCPs for nuclear powerreactors.02/12/91 All holders of OLs orCps for nuclear powerreactors.02/05/91 All holders of OLs or 4Cps for nuclear powerreactors.02/05/91 All holders of OLs orCPs for nuclear power,test and researchreactors.02/04/91 All holders of OLs orCPs for pressurized-water reactors (PiRs).02/04/91 All holders of OLs orCps for nuclear powerreactors.Kr"(X :11 OaOL : Operating LicenseCU Connstruction Permit IN 91-13March 4, 1991 of such conditions is negligible for the EDG. Information from the vendor mayhelp in determining what changes, if any, may be necessary. It is alsoimportant for procedures to give adequate guidance to ensure that the EDG isnot inadvertently overloaded during the test.The last event illustrates the failure of EVG testing to verify adequately theproper operation of all of the logic necessary to support the EDG in an acci-dent. Millstone Unit 3 was given as an example, but other similar cases havebeen reported.Generic Letter 88-15, OElectric Power Systems -Inadequate Control Over DesignProcesses," discussed problems similar to those in this information notice.This Information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Original Signed byCharles E RossiCharles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:C. H. Woodard, Region I(215) 337-5261A. J.(301)Kugler, NRR492-0834

Attachment:

List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCESBDLPEiAgPt'7>C/OGCB:DOEA:NRR*RPB:ADMCHBerlinger TechEdlk&/91 Q/21/91 12/27/90*OGCB:DOEA:NRR*OTSB:DOEA:NRR *SPLB:DST:NRRAJKugler EBTomlinson REArchitzel12/20/90 01/29/91 01/29/91*RI *RICWoodard TKoshy01/14/91 12/21/90*C/SPLB:DST:NRR*C/SELB:DST:NRRCEMcCracken FRosa01/30/91 01/31/91DOCUMENT NAME: IN 91-13 IN 91-XXFebruary xx, 1991 what changes, if any, may be necessary. Procedures should also give adequateguidance to ensure that the EDG is not inadvertently overloaded during thetest.The last event illustrates the failure of EDG testing to verify adequately theproper operation of all of the logic necessary to support the EDG in an acci-dent. Millstone Unit 3, was given as an example, but other similar cases havebeen reported. The TS surveillance tests should verify that logic, such as theload shedding logic, which supports the accident response of the EDGs, willperform its intended function.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:C. H. Woodard, Region I(215) 337-5261A. J.(301)Kugler, NRR492-0834

Attachment:

List of Recently Issued NRC Information NoticesDocument Name: EDGIN*SEE PREVIOUS CONCURREIqQOD/DOEA:NRR C/QJ; tA :NRR*RPB:ADMCERossi CH i ger TechEd02/ /91 020t /91 12/27/90*OGCB:DOEA:NRR*OT DOEA:NRR *SPLB:DST:NRRAJKugler EBTomlinson REArchitzel12/20/90 01/29/91 01/29/91*RI *RICWoodard TKoshy01/14/91 12/21/90*C/SPLB:DST:NRR*C/SELB:DST:NRRCEMcCracken FRosa01/30/91 01/31/91 IN 91-XXJanuary xx, 1991 The last event illustrates the failure of EDG testing to verify adequately theproper operation of all of the logic necessary to support the EDG in an acci-dent. Millstone Unit 3, was given as an example, but other similar cases havebeen reported. The TS surveillance tests must verify that the logic associatedwith the various sequences (loss of offsite power, loss of coolant accident,load shedding and sequencing, etc.) will perform its intended function.This information notice requires no specific action or written response. Ifyou have any questions about the Information in this notice, please contact oneof the technical contacts listed below or the appropriate NRR project manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts:C. H. Woodard, Region I(215) 337-5261A. J.(301)Kugler, NRR492-0834

Attachment:

List of Recently Issued NRC Information NoticesDocument Name:EDGIN*SEE PREVIOUSD/DOEA:NRRCERossi01/ /91*OGCB:DOEA:NRf.AJKugler12/20/90CONCURRENCESC/OGCB:DOEA:NRR*RPB:ADM ICHBerlinger TechEd01/ /91 12/27/90t OTSB:DOEA:NRR SPLB:DST:NRREBTomlinsoil" REArchitzAl .01Z/191 01/25/91 W*RICWoodard01/14/91C/SPLB:DST:NRFCEMcCra01/36/9LYJII*RI.TKoshy (Zi12/21 "t'tC/SEL K:DSINRRFRosa,01 bL/9 1 IN 90-XXD i .,errXX 1990~Page 4 ofthird event illustrates the failure of EDG testing to)erify th proper operation of edtof the logic necessary to support Atthe ES[) in an accident. Millstone, Uhit 3, was given as an example,but other similar cases have been reported. The TS surveillance testsmust verify that the logic associated with the various sequences (lossof offsite power, loss-of-coolant accident, load shedding andsequencing, etc.) will perform its intended function.This information notice requires no specific action or writtenresponse. If you have any questions about this matter, please contactone of the technical contacts listed below or the appropriate NRRproject manager.Charles E. Rossi, DirectorDivision of Operational Events AssessmentOffice of Nuclear Reactor RegulationTechnical Contacts: C. H. Wbodard, Region I(215) =7-5261T. Koshy, Senior Resident Inspector, Yankee Rowe(413) 424-5242

Attachment:

1. List of Recently Issued NRC Information NbticesOGCB:DOE4:RR RI RI RPB: ADM C/OGCB:DOEU:ERR D/DOEA:NRRAMugler m CWoodard TKoshy TechEd ClBerlinger CERossi12/20/90 12/ /90 12/ /90 12/vV/90 12/ /90 12/ /90 G NRC '~.AKEE ROWE P02IN 90-XXDecember XX, 1990P&W 4ocfThe thir event illustrates~ the failure of EDG tes-ting to adequatzlYverily the- proper oporsatior of all of the logic rowt*sHryY to wUoort,thp ED( in an accident. Milletcrot Wkit 3, was qivenl as an Qxamplpe,but other similar easm have, bmen reported. Thm TS Eurei~lfleci testsrImit veri+/-fy that the logic asswiated with the various coqueasC9(lossof of fritc pavpr-, 105; of coolant accident, loaid shedding andfWqLanrirx;, ec~t.) will por-forml its intended funiction.a'This~ informatkio rotice requidres no specific action or wr-ittenrep-n If yct have any queirtion about this niattar, please contactone of the technicial centacto listed below or the appropriata NRproject m".ager.Charles E. Rossi, DirectorDivisicn' of Operatimal E>.nts AssesirentOff ice of Uclak)Nr IL-=tor RegulationTechnical Cnter-teg C. H. tWkiodard, Regian!I(215) qq7u-MU'T. mfsthy, Sonior Resident. Inspectors YVnkm, Rc~(413) 424-5242I.. List of Rec-ently Issued NC Iinformationi W~ticesOGCMiD0EA1R RI ~ J RMADH ClO=C2DOEAaUMl DV/OEAIMiAKtUS1sr Mo~dard TKashy TectilE Cill g, Mse121 /90 II/ 190 121z/90 121 /90 it/ /90It 9

-a -IN 9-XXDecembe XX, '9ot AWe 4 elthird event i11uStrates thie tailure oC EG twst.M +aO adequatelyty the prowr operatib of &11 of tho logic nrlpsoty to uPportthe EX In an Oident. fistC2W Uit Zs was given as an example,but other i- milar eMS have WM reportgd The TS irul 11 1ff twStsm.st verify that the logic asuC4AtW with the variculs Wu3!n tlos%of aftsite por, loss zT cmlnt accidonts load shucddinM andaaquenwti atc.) will Farform its Intanded fLrlctiu.This information notice requires no speci'C action or writtenrespcn3e. If yu have any qu-st3uns atcut this matter, pleas cotatane of tte tectnAcal cantacts lsted tolow or the appropriate Wf(projet m&oer.Charles E.

• zzi, DirwctorDtiSion flpf Operationl Evwte AreswrmntOffice of tL=lear Reetoir ftgulationTchnilcal Cmt.eti Co He 1nerds flgiIn I(215) XW7-WT. IaPhys Einaor Residaft Inapmtor, Yan&Mea FovO4M5) 4.4-=42Attarhmmts1. List of FRecntly IEszud NKC Informaticn NbticezOGCB:D0EAtRR RI RI RPB3AM C/OGCB:DOEA:UIIRR WDOEsNRRMugler CMoodard TKashy Techtd CHSerlintger C$.OS12/ /90 A11.44. 12/ /90 12J /90 121 /90 12/ /90