ML21243A527

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Attachment 1 - HI-STORE Consolidated Interim Storage Facility Response to Requests for Additional Information Round 2
ML21243A527
Person / Time
Site: HI-STORE
Issue date: 08/31/2021
From:
Holtec
To:
Office of Nuclear Material Safety and Safeguards
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ML21243A525 List:
References
5025069
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HISTOREConsolidatedInterimStorageFacility RequestsforAdditionalInformationRound2 HoltecLetter5025069

Page1of5 CHAPTER2RAIs RAI233S:Justifywhythematerialproperties,asgiveninTable5.3ofReportNo.HI2188143,Revision 1,HISTOREBearingCapacityandSettlementCalculations,areappropriatetorepresentthematerials attheproposedsite.

Clarifywhythevalueassignedtosomegeotechnicalparametersisappropriateforthesite.Forexample:

1)Table5.3oftherevisedreportgivesafrictionanglefortheResidualSoilatthesiteas54o.Thisis anextremelyhighvalueevenformostofthehard,igneousrockandcertainlyforasoil.

AppendixCofReportNo.HI2188143,Revision1,BearingCapacityandSettlement Calculation,hasusedaformulatocalculatethefrictionanglefromEPRI(Kuhlhawayand Main,1990):

=5427.6034[0.0014x(1)60]

AsafunctionofthecorrectedStandardPenetrationTestblowcount(N1)60.AppendixCshows that(N1)valuesvaryfrom58to173;however,thecalculatedvalueofremainsconstant54o irrespectiveof(N1)60values.ProvidetheappropriatefrictionangleoftheResidualSoil.

Additionally,providethecorrectsourceofthisequationifitisnotinthereferencedEPRI document

2)Intherevisedreport,thepreconsolidationstressoftheChinleFormationistakenasthe valueestimatedinsampleSW2,obtainedatdepthof101ftbelowthegroundsurface.Provide therationaleforusingthemeasuredconsolidationpropertiesfromsampleSW2butnotfrom SW1.TheestimatedoverconsolidationratiofromonlySW2sampleseemsveryhigh.Provide therationalefortheestimatedvaluesofthepreconsolidationstressandtheoverconsolidation ratio.

3)ProvidearationaleforwhythemeasuredconsolidationpropertiesinChinlemudstoneata depthof101ftfromthesurface(sampleSW2)wouldbeappropriateforconsolidation settlementinChinleclay(leanclayorCL)formationnearthesurface.

4)PageA9oftherevisedreportstatesthattheChinleFormationmudstonesectionisconsidered bedrock.Also,thefulldepthoftheChinleisconsideredinthecalculation

HoltecResponse:

Thegeotechnicalparametersandtheirassignedvaluesusedtorepresenttheproposedsiteareclarified below.

1)Uponreview,itappearsthattheequationinthecalculationwascitedincorrectly.This equationisnotusedinouranalysesdevelopedforthisRAIresponse.Basedontheboringlog descriptionsoftheResidualsoil,theprevioususeof54degreesforfrictionangleandahigh valueofcohesionareincorrect.

InthelatestrevisiontoHoltecReportHI2188143,thesoilfrictionanglefortheResidualsoilis determinedusingFigure4-12ofKulhawayandMayne(1990).Thecalculationalsonow

HISTOREConsolidatedInterimStorageFacility RequestsforAdditionalInformationRound2 HoltecLetter5025069

Page2of5 includesasmallvalueofdrainedcohesiontoaccountfortheplasticitydescribedwithinthe material.

TheResidualSoilclassifiesasSandyClayorClayeySand.Becauseofthelowwatercontentand unsaturatedinsituconditionoftheResidualSoil,itisappropriatetousedrainedstrength parametersforthismaterial.Africtionangleof44degreescorrespondstotheupperlimitof thecorrelationpresentedinFigure4-12ofKulhawyandMayne,anditisareasonablefriction angleforthismaterial.Duetotheclaycontentofthissoil,asmalldrainedcohesionintercept of200psfisalsoreasonable.Thus,adrainedfrictionangleof44degreesandadrained cohesionof200psfareusedforthebearingcapacityanalysisoftheISFSIandtheCTF.

Thespecifieddensityofthecontrolledlowstrengthmaterial(CLSM)usedtofillbeneaththe ISFSIpadhasalsobeenreducedto120pcftoalignwiththeestablishedvalueforthegeneric HISTORMUMAXlicense,ratherthanusingaconservativevalueof150pcfpertheprevious HI-STOREsubmittal.Thismodificationresultsinareductioninstaticbearingpressureforthe ISFSIPadto3.34ksf.

UsingtheserevisedstrengthparametersfortheResidualSoil,Holteccomputedthefollowing allowablebearingcapacitiesandappliedbearingpressuresontheHI-STOREISFSIpadandthe CTFfoundations.Inallcasesallowablebearingcapacityisgreaterthantheappliedbearing pressure,indicatingbearingcapacityfactorsofsafetyareadequate.

Structure AllowableStaticBearingCapacity(ksf)

BearingPressure(ksf)

Static Seismic Static Seismic ISFSIPad 5.38 8.07 3.34 4.34 CTF 104.02 156.03 4.33 7.05

2) Uponfurtherreview,HoltecagreeswiththeNRCstaffthatitispreferrabletouse consolidationpropertiesfromSW1forsettlementanalysessincetheshapeoftheplot indicatesasoilbehaviormoreinlinewithclassicalsoilmechanicstheorycomparedtoSW2.

TheshapeofthecurveoftestSW2appearstoshowamoresevereimpactfromstressrelief duetosamplinginthefield.Inaddition,SW1hasahigherinitialwatercontentthanSW2 (13.7%inSW1ascomparedwith8.0%inSW2).Ingeotechnicalliterature,compressibility generallyrelatestowatercontent,withahigherwatercontentcorrelatingwithhigher compressibility.Therefore,thecompressibilitypropertiesassociatedwithSW1shouldbe conservativerelativetoSW2.

Tocalculatethemaximumpastpressure(orpreconsolidationstress)fortheChinleFormation, HoltechasperformedaCasagrandeconstructionontheconsolidationplotoftestSW1 followingrecognizedsoilmechanicsliterature.Withthismethod,apreconsolidationstressof approximately3.1tonspersquarefoot(tsf)isobtained.TestSW1wasperformedatadepthof

HISTOREConsolidatedInterimStorageFacility RequestsforAdditionalInformationRound2 HoltecLetter5025069

Page3of5 approximately74.3feet(El.3455.8).Atthatdepth,ourcalculationspredictanexistinginsitu verticalstressofapproximately4.3tsf,whichwouldindicateanunder-consolidatedsoil.Given thegeologyandtheinformationfromthefieldandthelabtests,includingthehighSPT N-valuesandrelativelylowwatercontents,Holtecbelievesthemeasuredpreconsolidation stressislowerthantheactualinsitupreconsolidationstress,likelyduetostressrelieffrom samplinginthefield.Therefore,therevisedcalculationsconservativelyassumethattheChinle Formationisnormallyconsolidated(OCR=1.0),i.e.,themaximumpastpressureatanydepth isequaltotheexistinginsituverticaleffectivestress.

Thespecifieddensityofthecontrolledlowstrengthmaterial(CLSM)usedtofillbeneaththe ISFSIpadhasalsobeenreducedto120pcftoalignwiththeestablishedvalueforthegeneric HISTORMUMAXlicense,ratherthanusingaconservativevalueof150pcfpertheprevious HI-STOREsubmittal.Thismodificationresultsinareductioninstaticbearingpressureforthe ISFSIPadto3.34ksf.

Tomakeaproperanddirectcomparisonwiththe0.2inchsettlementlimitpresentedinTable 2.3.2oftheHISTORMUMAXFSAR,thelongtermsettlementfortheHISTOREISFSIis computedforthesamereferencepadsizeevaluatedinthegenericUMAXlicense,namelya 5x5arrayofVVMs.

AnOCRof1hasbeenusedfortherevisedsettlementcalculationsfortheISFSIpadandforthe CTFfoundation.ThecalculatedlongtermsettlementoftheISFSIpadandCTFfoundationare asfollows:

Structure TotalConsolidationSettlement inChinleFormation Centerofpad(in)

ISFSIPad 0.15 CTF 0.11

3&4) AsnotedintheresponsetoRAI2-32-S,part2above,HoltecagreeswiththeNRCstaffthatitis preferabletouseconsolidationpropertiesfromSW1ratherthanSW2.

BasedonGEIsSiteCharacterizationReport,theChinleFormationisasingleunitwiththetop oftheformationbetweenElevations3499and3502andthebottomoftheformationbetween Elevations3322and332(topofSantaRosaFormation).Thereisnogeologicdistinction betweenChinleFormationclayandChinleFormationmudstone.Intheboringlogs,the distinctionbetweenclayandmudstoneisduetothesamplingmethod,i.e.,mudstoneis calledoutwhenthematerialbecomeshardenoughtocore.

Inaddition,Holteccomparedlaboratoryindextestresultsfromtheshallowersamplesinthe ChinleFormation,whereStandardPenetrationTest(SPT)samplingwasperformed,withthe watercontentfromtestSW1atapproximately74.3feetbelowgrade.Intheliterature,

HISTOREConsolidatedInterimStorageFacility RequestsforAdditionalInformationRound2 HoltecLetter5025069

Page4of5 compressibilityrelatestowatercontentandAtterberglimits.SincetherearenoAtterberg limitstestsperformedontheChinlerockcores,Holtecanalyzedwatercontentresults.

ThewatercontentreportedatshallowerdepthsintheChinlearelowerthanthatreportedfor SW1,whichwouldindicatealowercompressibility.Basedonthenaturalwatercontentvalues reportedinTables3fromGEIsSiteCharacterizationReportfortheChinleFormation,ata depthrangebetween30and56.4feetbelowgrade,Holtecobtainedanaveragewatercontent of11.7%.TheinitialwatercontentfromSW1is13.7%asreportedinTable4ofGEIsSite CharacterizationReport.Thelowerwatercontentwouldcorrelatewithalowercompressibility, andthereforeusingtheSW1consolidationparametersthroughtheentireChinleFormationis conservative.

RAI242S:Justifywhyatwolayersystem,asusedinReportNo.HI-2188143,Revision1,HISTORE BearingCapacityandSettlementCalculations,wouldbeappropriateforestimatingthebearingcapacity andsettlementofthestoragepads.

PageA9ofReportNo.HI-2188143,Revision1,HISTOREBearingCapacityandSettlement Calculations,statesthattheChinleFormationmudstonesectionisconsideredbedrock.Also,thefull depthoftheChinleisconsideredinthecalculationabove(175ft),thisisconservativeasthemudstone willnotsettleasmuchastheclay.TheresponsetoRAI242statesthat[i]nthelatestrevisionof ReportNo.HI2188143,thetopCLsoillayerisconservativelyassumedathroughouttheentire175ft depthoftheChinleFormation.Thesestatementssuggestthatthesettlementcharacteristicsofthe ChinleFormationclaysectionaredifferentthantheChinleFormationmudrock.Providetherationalefor selectingatwolayersystemforestimatingthesettlementunderthestoragepadsandtheCanister TransferFacilityinsteadofamultilayersystem.

Thisinformationisnecessarytodeterminecompliancewith10CFR72.24,72.103,and72.122.

HoltecResponse:

BasedonGEIsSiteCharacterizationReport,theChinleFormationisasingleunitwiththetopofthe formationbetweenElevations3499and3502andthebottomoftheformationbetweenElevations 3322and3321(topofSantaRosaFormation).ThereisnogeologicdistinctionbetweenChinle FormationclayandChinleFormationmudstone.Intheboringlogs,thedistinctionbetweenclay andmudstoneisduetothesamplingmethod,i.e.,mudstoneiscalledoutwhenthematerialbecomes hardenoughtocore.Accordingtotheboringlogs,theChinleFormationmaterialbecomeshardenough tocorebetweenElevations3434.5and3499.6,withanaverageof3469.

InresponsetothequestionsraisedinthisRAI,Holtecperformedadditionalsettlementcalculationsfor boththeISFSIPadandtheCTF.GiventhethicknessandpropertiesoftheChinleFormation(see responsetoRAI2-32-2),thelongtermsettlementundertheISFSIPadandCTFarecalculatedusinga multi-layersysteminaccordancewiththemethodologydescribedinHoltecPositionPaperDS-338.To calculatethetotallongtermconsolidationsettlement,theChinleFormationisdividedintofourlayers betweenElevations3500and3469,andtwolayersbetweenElevations3469and3321.5.

HISTOREConsolidatedInterimStorageFacility RequestsforAdditionalInformationRound2 HoltecLetter5025069

Page5of5 OnlythesettlementintheChinleFormationisconsideredbecausetheResidualSoilisagranular materialwhichhasalowmoisturecontent,isabovethewatertable,andisnotsaturated.Therefore, thesettlementintheResidualSoilwilloccurimmediatelyuponloadingandwillnotcontributetolong termsettlement.Thereboundduetoexcavationandreconsolidationbacktotheinitialexistingstressin theChinleFormationisalsoassumedtooccurrapidly.Therefore,theconsolidationsettlementis calculatedfromtheinitialstress(alsoequaltothemaximumpastpressure)tothefinalstress.The revisedcalculationsinHoltecReportHI2188143conservativelyassumenormallyconsolidated conditionsandusethecompressionindexreportedintestSW1tocalculatetheconsolidation settlement(seediscussioninresponsetoRAI2-32-S).Theloadreductionmethodologyof30-degree angleasdescribedinHoltecsDryStoragePositionPaperDS-338,whichisincorporatedbyreferencein theHISTORMUMAXFSAR,isalsoused.

Thespecifieddensityofthecontrolledlowstrengthmaterial(CLSM)usedtofillbeneaththeISFSIpad hasalsobeenreducedto120pcftoalignwiththeestablishedvalueforthegenericHISTORMUMAX license,ratherthanusingaconservativevalueof150pcfperthepreviousHI-STOREsubmittal.This modificationresultsinareductioninstaticbearingpressurefortheISFSIPadto3.34ksf.

Tomakeaproperanddirectcomparisonwiththe0.2inchsettlementlimitpresentedinTable2.3.2of theHISTORMUMAXFSAR,thelongtermsettlementfortheHISTOREISFSIiscomputedforthesame referencepadsizeevaluatedinthegenericUMAXlicense,namelya5x5arrayofVVMs.

Thefinalresultsaresummarizedinthetablebelow.

Structure TotalLongTermConsolidation SettlementinChinleFormation Centerofpad(in)

ISFSIPad 0.15 CTF 0.11

References AASHTOLRFDBridgeDesignSpecifications,9thEdition,2020.

GEIConsultants,Inc.(GEI).HI-STORECISFPhase1SiteCharacterizationReport,Rev1,LeaCounty,New Mexico,February2018.

J.E.Bowles,FoundationsAnalysisandDesign,5thEdition,McGrawHill,1996.

F.HKulhawy,P.W.Mayne,ManualonEstimatingSoilPropertiesforFoundationDesign,ElectricPower ResearchInstitute,1990.

Holtec,DryStoragePositionPaperDS-338,Revision1,June23,2010.

Holtec,HI-STORMUMAXFSARRev.6

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