ML16308A443

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Generic Letter 2016-01: Monitoring of NEUTRON-Absorbing Materials in Spent Fuel Pools, ML16097A169
ML16308A443
Person / Time
Site: Callaway 
Issue date: 11/03/2016
From: Kovaleski S
Ameren Missouri
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
GL-16-001, ULNRC-06339
Download: ML16308A443 (9)
v • d • e


Text

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'WAmeren MISSOURI Callaway Plant November 3, 2016 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Ladies and Gentlemen:

ULNRC-06339 1 OCFR50.54(f)

DOCKET NUMBER 50-483 CALLAWAY PLANT UNIT 1 UNION ELECTRIC CO.

RENEWED FACILITY OPERATING LICENSE NPF-30 GENERIC LETTER 2016-01: "MONITORING OF NEUTRON-ABSORBING MATERIALS IN SPENT FUEL POOLS" ML16097A169

References:

1. NRC Generic Letter 2016-01, "Monitoring ofNeutron-Absorbing Materials in Spent Fuel Pools," Dated April 7, 2016 NRC Generic Letter (GL) 2016-01, "Monitoring ofNeutron-Absorbing Materials in Spent Fuel Pools," dated April 7, 2016 was issued pursuant to the requirements of 10 CFR Part 50.54(f). The Generic Letter requests that addressees submit information within 21 0 days which demonstrates that credited neutron-absorbing materials in the SFP of power reactors are in compliance with the licensing and design basis, and with applicable regulatory requirements; and that there are measures in place to maintain this compliance.

The Enclosure of this letter contains the requested information for Callaway Plant.

PO Box 620 Fulton, MD 65251 AmerenMissouri.com

. STARS ~

Alliance

ULNRC

November 3, 2016 Page2 This letter does not contain new commitments.

JBL

Enclosure:

Callaway Response to NRC Generic Letter 2016-01 Sincerely, Sarah G. Kovaleski Director, Engineering Design

-06339

ULNRC-06339 November 3, 2016 Page 3 cc:

Mr. Kriss M. Kennedy Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. L. John Klos Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop O8H4 Washington, DC 20555-0001

ULNRC-06339 November 3, 2016 Page 4 Index and send hardcopy to QA File A160.0761 Hardcopy:

Certrec Corporation 6100 Western Place, Suite 1050 Fort Worth, TX 76107 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)

Electronic distribution for the following can be made via Responses and Reports ULNRC Distribution:

F. M. Diya T. E. Herrmann B. L. Cox R. C. Wink T. B. Elwood Corporate Communications NSRB Secretary Mr. Greg Voss, REP Manager (SEMA)

STARS Regulatory Affairs Mr. Jay Silberg (Pillsbury Winthrop Shaw Pittman LLP)

Ms. Leanne Tippett-Mosby (DNR)

Mr. Robert Stout (DNR)

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1. Describetheneutronabsorbingmaterialcreditedinthespentfuelpool(SFP)nuclearcriticalitysafety(NCS)analysisof record(AOR)anditsconfigurationintheSFP,includingthefollowing:

a) manufacturers,datesofmanufacture,anddatesofmaterialinstallationintheSFP;

ThecreditedneutronabsorbingmaterialintheUnionElectricSFPNCSAORisBoral(Ref.1).TheBoralwas manufacturedbyAAR(Ref.1)(also"AARManufacturing","AARBrooks&Perkins",and"AARAdvanced Structures")andinstalledintheSFPbetweenJanuaryandJulyof1999(Ref.2).Afterareasonablesearchof plantrecords,includingdocketedinformation,UnionElectrichasdeterminedthatthedatesofmanufactureof theBoralpanelswerenotpartoftheoriginallicensingbasisorpreviouslyrequestedbytheNRCasapartofthe licensingactionthatapprovedtheinstallationoftheneutronabsorber.

b) neutronabsorbingmaterialspecifications,suchas:

i. materialsofconstruction,includingthecertifiedcontentoftheneutronabsorbingcomponentexpressed asweightpercent;

Boralisacompositematerialmadewith1100seriesaluminumcladenclosinganinnercoreof compacted1100seriesaluminumandboroncarbide(B4C)powders(Ref.3).Itisnotspecifiedona weightpercentbasisoftheneutronabsorbingcomponent;therefore,thissubareaisnotapplicable.

ii. minimumcertified,minimumasbuilt,maximumasbuilt,andnominalasbuiltarealdensityofthe neutronabsorbingcomponent;and

ThenominalB10arealdensityfortheseBoralpanelsis0.0324g/cm2withacertifiedminimumof 0.0300g/cm2(Ref.1).AlthoughnotutilizedintheSFPNCSAOR,theasbuiltmaximumandasbuilt minimumarealdensitiesare0.0414g/cm2and0.0301g/cm2respectively(Ref.4).

iii. materialcharacteristics,includingporosity,density,anddimensions;

ThenominalgeometricdimensionsofeachBoralpanelare145in.length,7.50in.width,and0.101in.

thickness(Ref.1).Thenominaldensityoftheneutronabsorbingcoreis2.639g/cm3(Ref.5).Aftera reasonablesearchofplantrecords,includingdocketedinformation,UnionElectrichasdeterminedthat theporosityoftheBoralpanelswasnotpartoftheoriginallicensingbasisorpreviouslyrequestedby theNRCasapartofthelicensingactionthatapprovedtheinstallationoftheneutronabsorber.

c) qualificationtestingapproachforcompatibilitywiththeSFPenvironmentandresultsfromthetesting;

SamplesofBoralweresubjectedtowatersolubleborontestsandwatersoaktests.Thewatersolubleboron testsusedchemicalanalysisoftheboroncarbidepowdertoensurethecontentofwatersolubleboronwas withinspecificationof0.1wt%to1.0wt%.Thistestingyieldedwatersolubleboroncontentsrangingfrom0.32 wt%to0.56wt%.ThewatersoaktestsusedneutronattenuationtodetermineB10arealdensityofsamples beforeandafterprolongedimmersioninheated,demineralizedandheated,boratedwater.Priortoimmersion, B10arealdensitiesofsamplesrangedfrom0.0333g/cm2to0.0400g/cm2.Afterimmersion,B10areal densitiesofsamplesrangedfrom0.0322g/cm2to0.0361g/cm2(Ref.4).

d) configurationintheSFP,suchas:

i. methodofintegratingneutronabsorbingmaterialintoracks(e.g.,inserts,weldedinplace,spotweldedin place,rodlets);and

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Aventedsheetofstainlesssteelsheathingisskip/spotweldedtoeachstoragecellwall.ABoralpanel isretainedineachsheathingcavity(Ref.1).

ii. sheathinganddegreeofphysicalexposureofneutronabsorbingmaterialstotheSFPenvironment;

StainlesssteelsheathingcompletelyencloseseachBoralpanel.However,thesheathingisvented, allowingtheSFPenvironmenttomakedirectcontactwiththepanel(Ref.1).

e) currentconditionofthecreditedneutronabsorbingmaterialintheSFP,suchas:

i. estimatedcurrentminimumarealdensity;

Thereisnosuperficialindicationofdegradationthatcouldleadtothelossofneutronabsorbing material.Therefore,theestimatedcurrentminimumarealdensityisthesameastheinstalled minimumarealdensity(seeresponsetosubarea1.b.ii).

ii. currentcreditedarealdensityoftheneutronabsorbingmaterialintheNCSAOR;and

ThecurrentcreditedarealdensityoftheneutronabsorbingmaterialintheNCSAORis0.0300g/cm2 (Ref.1).

iii. recordeddegradationanddeformationsoftheneutronabsorbingmaterialintheSFP(e.g.,blisters, swelling,gaps,cracks,lossofmaterial,lossofneutronattenuationcapability).

ThereisnorecordeddegradationordeformationsoftheneutronabsorbingmaterialintheSFP.

2. Describethesurveillanceormonitoringprogramusedtoconfirmthatthecreditedneutronabsorbingmaterialisperforming itssafetyfunction,includingthefrequency,limitations,andaccuracyofthemethodologiesused.

UnionElectricdidnotinstituteaneutronabsorbersurveillanceormonitoringprogramwhentheBoralwasinstalledin theSFP.InJanuary,1999,theNRCissuedAmendmentNo.129toFacilityOperatingLicenseNo.NPF30.Asconcludedin itsSafetyEvaluation(Ref.6):

thestafffindsthatthematerialsinthespentfuelracks,manufacturedbyHoltecInternational,are compatiblewiththeenvironmentintheCallawayPlant,Unit1SFP.ThesenewSFPrackswillnot undergomaterialdegradationwhichcouldaffecttheirabilitytosafelystorespentandnewfuel.A venteddesignoftheBoralsheathingspreventsthecorrosiongeneratedhydrogenfrombuildingup pressureswhichcouldcausedistortionofthefuelcells.Thestaffconcludes,therefore,thatallthe materialsusedinthenewspentfuelracksareacceptable.

ConsistentwiththeUnionElectriclicensingbasisandtheSafetyEvaluationissuedwithAmendmentNo.129,Union Electricdoesnothaveasurveillanceormonitoringprogramtoconfirmthatthecreditedneutronabsorbingmaterialis performingitssafetyfunction.Therefore,theinformationrequestedinArea2isnotapplicable.

AneutronabsorbermonitoringprogramwascreatedandapprovedaspartoftheUnionElectriclicenserenewal application.However,thisprogramwillnotbeactivateduntiljustpriortotheperiodofextendedoperation.

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a) Providethetechnicalbasisforthesurveillanceormonitoringmethod,includingadescriptionofhowthemethod candetectdegradationmechanismsthataffectthematerialsabilitytoperformitssafetyfunction.Also,includea descriptionandtechnicalbasisforthetechnique(s)andmethod(s)usedinthesurveillanceormonitoringprogram, including:

i. approachusedtodeterminefrequency,calculations,andsamplesize; ii. parameterstobeinspectedanddatacollected; iii. acceptancecriteriaoftheprogramandhowtheyensurethatthematerialsstructureandsafetyfunction aremaintainedwithintheassumptionsoftheNCSAOR; iv. monitoringandtrendingofthesurveillanceormonitoringprogramdata;and
v. industrystandardsused.

b) Forthefollowingmonitoringmethods,includetheseadditionaldiscussionitems.

i. Ifthereisvisualinspectionofinservicematerial:
1. describethevisualinspectionperformedoneachsample;and
2. describethescopeoftheinspection(i.e.,numberofpanelsorinspectionpointsperinspection period).

ii. Ifthereisacouponmonitoringprogram:

1. provideadescriptionandtechnicalbasisforhowthecouponsarerepresentativeofthematerial intheracks.Includeinthediscussionthematerialradiationexposurelevels,SFPenvironment conditions,exposuretotheSFPwater,locationofthecoupons,configurationofthecoupons(e.g.,

jacketingorsheathing,ventingboltedon,gluedon,orfreeinthejacket,waterflowpastthe material,bends,shapes,galvanicconsiderations,andstressrelaxationconsiderations),and dimensionsofthecoupons;

2. providethedatesofcouponinstallationforeachsetofcoupons;
3. ifthecouponsarereturnedtotheSFPforfurtherevaluation,providethetechnicaljustificationfor whythereinsertedcouponswouldremainrepresentativeofthematerialsintherack;and
4. providethenumberofcouponsremainingtobetestedandwhetherthereareenoughcouponsfor testingforthelifeoftheSFP.Alsoprovidethescheduleforcouponremovalandtesting.

iii. IfRACKLIFEisused:

1. notetheversionofRACKLIFEbeingused(e.g.,1.10,2.1);
2. notethefrequencyatwhichtheRACKLIFEcodeisrun;
3. describetheconfirmatorytesting(e.g.,insitutesting)beingperformedandhowtheresults confirmthatRACKLIFEisconservativeorrepresentativewithrespecttoneutronattenuation;and
4. providethecurrentminimumRACKLIFEpredictedarealdensityoftheneutronabsorbingmaterial intheSFP.DiscusshowthisarealdensityiscalculatedinRACKLIFE.Includeinthediscussion whetherthearealdensitiescalculatedinRACKLIFEarebasedontheactualasmanufactured arealdensityofeachpanel,thenominalarealdensityofallofthepanels,theminimumcertified arealdensity,theminimumasmanufacturedarealdensity,orthearealdensitycreditedbythe NCSAOR.AlsodiscusstheuseoftheescapecoefficientandthetotalsilicarateofBoraflex degradationintheSFP.

iv. Ifinsitutestingwithaneutronsourceanddetectorisused(e.g.,BADGERtesting,blacknesstesting):

1. describethemethodandcriteriaforchoosingpanelstobetestedandincludewhetherthemost susceptiblepanelsarechosentobetested.Providethestatisticalsamplingplanthataccountsfor bothsamplingandmeasurementerrorandconsiderationofpotentialcorrelationinsample results.Statewhetheritisstatisticallysignificantenoughthattheresultcanbeextrapolatedto thestateoftheentirepool;
2. stateiftheresultsoftheinsitutestingaretrendedandwhetherthereisrepeatpaneltesting fromcampaigntocampaign;

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3. describethesourcesofuncertaintieswhenusingtheinsitutestingdeviceandhowtheyare incorporatedinthetestingresults.Includetheuncertaintiesoutlinedinthetechnicalletterreport titledInitialAssessmentofUncertaintiesAssociatedwithBADGERMethodology,September30, 2012(AgencywideDocumentAccessandManagementSystemAccessionNo.ML12254A064).

Discusstheeffectofrackcelldeformationanddetectororheadmisalignment,suchastilt,twist, offset,orothermisalignmentsoftheheadsandhowtheyaremanagedandaccountedforinthe analysis;and

4. describethecalibrationoftheinsitutestingdevice,includingthefollowing:
a. describehowthematerialsusedinthecalibrationstandardcomparetotheSFPrack materialsandhowanydifferencesareaccountedforinthecalibrationandresults;
b. describehowpotentialmaterialchangesintheSFPrackmaterialscausedby degradationoragingareaccountedforinthecalibrationandresults;and
c.

ifthecalibrationincludestheinsitumeasurementofanSFPrackreferencepanel, explainthefollowing:

i. themethodologyforselectingthereferencepanel(s)andhowthereference panelsareverifiedtomeettherequirements; ii. whetherallsurveillancecampaignsusethesamereferencepanel(s);and iii. ifthesamereferencepanelsarenotusedforeachmeasurementsurveillance, describehowtheuseofdifferentreferencepanelsaffectstheabilitytomake comparisonsfromonecampaigntothenext.
3. ForanyBoraflex,Carborundum,orTetraborbeingcredited,describethetechnicalbasisfordeterminingtheintervalof surveillanceormonitoringforthecreditedneutronabsorbingmaterial.Includeajustificationofwhythematerialproperties oftheneutronabsorbingmaterialwillcontinuetobeconsistentwiththeassumptionsintheSFPNCSAORbetween surveillancesormonitoringintervals.

UnionElectricdoesnotcreditBoraflex,Carborundum,orTetraborintheNCSAOR.Therefore,theinformationrequested inArea3isnotapplicable.

4. ForanyBoraflex,Carborundum,Tetrabor,orBoralbeingcredited,describehowthecreditedneutronabsorbingmaterialis modeledintheSFPNCSAORandhowthemonitoringorsurveillanceprogramensuresthattheactualconditionofthe neutronabsorbingmaterialisboundedbytheNCSAOR.

a) DescribethetechnicalbasisforthemethodofmodelingtheneutronabsorbingmaterialintheNCSAOR.Discuss whetherthemodelingaddressesdegradedneutronabsorbingmaterial,includinglossofmaterial,deformationof material(suchasblisters,gaps,cracks,andshrinkage),andlocalizedeffects,suchasnonuniformdegradation.

ThemodelingthatsupportstheNCSAORutilizesaconservativeassumptionthattheBoralpanelshavethe certifiedminimumarealdensityof0.0300g/cm2(Ref.1).ThereisnoallowanceorreconciliationoftheNCSAOR fortheactualconditionofthepanels.ThisapproachisconsistentwiththeSafetyEvaluationforAmendment No.129toFacilityOperatingLicenseNo.NPF30.

b) Describehowtheresultsofthemonitoringorsurveillanceprogramareusedtoensurethattheactualconditionof theneutronabsorbingmaterialisboundedbytheSFPNCSAOR.Ifacouponmonitoringprogramisused,providea descriptionandtechnicalbasisforthecoupontestsandacceptancecriteriausedtoensurethematerialproperties oftheneutronabsorbingmaterialaremaintainedwithintheassumptionsoftheNCSAOR.Includeadiscussionon themeasureddimensionalchanges,visualinspection,observedsurfacecorrosion,observeddegradationor

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deformationofthematerial(e.g.,blistering,bulging,pitting,orwarping),andneutronattenuationmeasurements ofthecoupons.

AsdiscussedinArea2,UnionElectricdoesnothaveanactivesurveillanceormonitoringprogram.Therefore, theinformationrequestedinsubareas4.b,4.c,&4.disnotapplicable.

c)

DescribehowthebiasanduncertaintyofthemonitoringorsurveillanceprogramareusedintheSFPNCSAOR.

d) DescribehowthedegradationinadjacentpanelsiscorrelatedandaccountedforintheNCSAOR.

5. ForanyBoraflex,Carborundum,orTetraborbeingcredited,describethetechnicalbasisforconcludingthatthesafety functionforthecreditedneutronabsorbingmaterialintheSFPwillbemaintainedduringdesignbasisevents(e.g.,seismic events,lossofSFPcooling,fuelassemblydropaccidents,andanyotherplantspecificdesignbasiseventsthatmayaffect theneutronabsorbingmaterial).

UnionElectricdoesnotcreditBoraflex,Carborundum,orTetraborintheNCSAOR.Therefore,theinformationrequested inArea5isnotapplicable.

a) Foreachdesignbasiseventthatwouldhaveaneffectontheneutronabsorbingmaterial,describethetechnical basisfordeterminingtheeffectsofthedesignbasiseventonthematerialconditionoftheneutronabsorbing materialduringthedesignbasisevent,including:

i. shiftingorsettlingrelativetotheactivefuel; ii. increaseddissolutionorcorrosion;and iii. changesofstateorlossofmaterialpropertiesthathindertheneutronabsorbingmaterialsabilityto performitssafetyfunction.

b) Describehowthemonitoringprogramensuresthatthecurrentmaterialconditionoftheneutronabsorbing materialwillaccommodatethestressorsduringadesignbasiseventandremainwithintheassumptionsoftheNCS AOR,including:

i. monitoringmethodology; ii. parametersmonitored; iii. acceptancecriteria;and iv. intervalsofmonitoring.

REFERENCES:

1. HI971769,LicensingReportforRerackingoftheCallawayandWolfCreekNuclearPlants.
2. NED01006,ClosureInformationAssociatedwithCMP971016A:SpentFuelPoolRerack.
3. "HandbookofNeutronAbsorberMaterialsforSpentNuclearFuelTransportationandStorageApplications,"EPRI,2009.

Report1019110.

4. DOC703843,BoralDocumentationPackage
5. HI971790,CriticalitySafetyAnalysisofSpentFuelStorageRacksforUE.
6. AmendmentNo.129toFacilityOperatingLicenseNo.NPF30(ADAMSaccessionnumberML021640249).
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