ML20293A289
| ML20293A289 | |
| Person / Time | |
|---|---|
| Issue date: | 10/20/2020 |
| From: | Office of Nuclear Material Safety and Safeguards |
| To: | |
| Terry T | |
| References | |
| Download: ML20293A289 (21) | |
Text
NRC&NAC10CFRPart72Inspection PreDecisionalEnforcementConference KentCole President&CEO,NACInternational GeorgeCarver VicePresidentEngineering&SupportServices WrenFowler DirectorofLicensing MarcGriswold SeniorProjectEngineer RyanBailey SeniorProjectManager October20,2020 TheSkillsandExperiencetoDeliverNuclearExcellence
DemonstrateNACusedtheexistingFSARdesigncontrolmeasuresfor incorporatingCC5intotheMAGNASTORFSAR,relativetothetipover evaluation.
Demonstratethatthemethodofevaluation(MOE)usedbyNACto incorporateCC5intotheFSARwasnotadepartureperthe regulations,relativetothetipoverevaluation.
2 PURPOSE
Part1ofthepresentationwillbeconductedasfollows:
ApparentViolations(AVs)
NonMechanisticTipOverEvent FSARNonMechanisticTipOverLicensingBasis FSARDesignControlMeasures 10CFR72.48DesignControlProcess 10CFR72.48DeterminationforCC5 Summary 3
OUTLINE - PART 1
Part2ofthepresentationwillbeconductedasfollows:
MAGNASTORAmendment9 NACCommentsontheNRCInspectionReport PaloVerdeNRCInspectionvs.NACNRCInspection NACCorrectiveActionsFollowingthePaloVerdeInspection NACActionsFollowingAVs PresentationConclusion 4
OUTLINE - PART 2
10CFR72.146(c)- Designcontrol NRCsPosition (
Reference:
AVA,Enclosure1,NRCChoiceLetter)
NACimplementedadesignchangefortheMAGNASTORspentfuelcask withoutensuringthatdesigncontrolmeasureswerecommensuratewith thoseappliedtotheoriginaldesign.
Specifically,NACfailedtousethenonlinearLSDYNAcomputermodel (identifiedintheMAGNASTORFSARSections3.7.3.7and3.10.4.4asthe methodofevaluationforconcretecasktipoveranalysisappliedtothe originaldesign)fortheassessmentofaccelerationvaluesforadesignbasis tipoveraccidentoftheMAGNASTORCC5spentfuelcask.
5 APPARENT VIOLATIONS
10CFR72.48(c)(2)(viii)- Changes,tests,andexperimentsdeparture fromamethodofevaluation NRCsPosition(
Reference:
AVB,Enclosure1,NRCChoiceLetter)
NACfailedtoobtainaCoC amendmentfromtheNRCpursuantto10 CFR72.244priortoimplementingadesignchangefortheMAGNASTOR CC5spentfuelcaskthatresultedinadeparturefromamethodof evaluationdescribedintheMAGNASTORFSAR.
Specifically,NACfailedtoutilizeLSDYNA,anonlinearanalysis methodologythatwasdescribedintheMAGASTORFSARSection3.7.3.7, whenimplementingadesignchangefortheMAGNASTORCC5spentfuel storagecask.
6 APPARENT VIOLATIONS (CONTD)
Thefollowingisadetaileddiscussionaboutthenonmechanistictipoverevent andsubsequentevaluations:
Thetipovereventisahypotheticalaccidentconditioninwhichtheconcretecasktipsover ontoanISFSIpad.
Intheabsenceofacrediblehazardthatinducestipover,itisevaluatedasanonmechanistic event(i.e.,aneventwithnoidentifiablecause).
Duringanonmechanistictipover,thecaskispostulatedtorotatefromapositionwithits centerofgravity(CG)overitslowestcornertoahorizontalorientation,whichresultsinan impactwiththeISFSIpad.
Whenthecaskimpactsthepad,kineticenergyistransferredtothepadandthecask experiencesarapiddeceleration(measuredingloads).
Thecasksconfinementboundary(canister)andinternalbasketstructureareevaluatedforthe inertialloadsexperiencedduringthisdecelerationtoconfirmstresslevelsarebelowlimits.
7 NONMECHANISTIC TIPOVER EVENT
PositionA VerticalOrientation NormalStorageCondition PositionB CGOverCorner ZeroVelocity PositionC HorizontalOrientation PriortoImpact PositionD HorizontalOrientation Impact/Deceleration
H
CG
h R
R 8
NonMechanisticTipOverEvent(Contd)
Caskatrest CaskCGatitshighestpoint (maximumpotentialenergy)
Caskiscompletelytippedover,justpriorto contactwiththepad.Thevalueh correspondstoachangeinpotentialenergy(PE) whichisassumedtobecompletelytransformed intorotationalkineticenergy(KE).Usingthe lawofconservationofenergy,thisrelationship isexpressedas:
CaskhasimpactedtheISFSIPad andisdecelerating.Cask decelerationsaregovernedby thestructuralcharacteristicsof thecask,ISFSIpad,and underlyingsoil.
CG-centerofgravity R-caskradius LCG - CGheightfromcaskbottomH-caskheight dCG - CGheightatPositionB h-changeinCGheight
m-caskmass g-accelerationofgravity I-massmomentofinertia-angularvelocity mgh=
(EQ1)
TheFSAR(Section3.7.3.7)usesacomputercodeknownasLSDYNAintheoriginallicensingof MAGNASTORtocalculatethecaskcontentgloads(i.e.,decelerationsatthetopofthecanisterlid andtopofthefuelbasket).
ThetipoverissimulatedinLSDYNAbyapplyinganinitialangularvelocitytotheentirecaskas describedintheFSAR(Section3.10.4.4).
NotethatthesimulationstartswiththecaskonitssideonthegenericISFSIpad.
Themethodofevaluation(MOE)usedintheFSAR(Section3.10.4.4)fordeterminingtheangular velocityinputforLSDYNA(andcheckingtheLSDYNAoutputkineticenergy)isthefollowing classicalmechanicsequationwhichrelatesthecaskspotentialenergyatCGovercornertothe kineticenergy(angularvelocity)atimpactonthestoragepad.
Wheremisthemassofthesystem;gistheaccelerationduetogravity;histheCGheightchange;Iis thecasksmomentofinertia;andistheresultingangularvelocityatimpact.
ThepotentialenergyneedstomatchthekineticenergyandviceversatoensuretheLSDYNAresultsforgload accelerationsareaccurate.
Thekeyvariableistheangularvelocity,whichistheenergybeingimpartedtothecaskduringimpact.
9 FSARNonMechanisticTipOverLicensingBasis
ThegloadsfromLSDYNAareusedtojustifytheacceptanceofthe valuesusedinthesubsequentstructuralevaluationsintheFSAR, whichareperformedusingANSYS.
LSDYNAisnotthelicensingbasisprogramusedtostructurallyevaluatethe casksystem.Itisasimplisticmodelusedtovalidatethatthegloads(usedin ANSYS)boundtheloadsseenduringtheevent.
TheANSYSevaluationscanbefoundinFSARSections3.7.1,3.7.2,and 12.2.12.4.
10 FSARNonMechanisticTipOverLicensingBasis(Contd)
11 CC1/CC2 DesignAttributes LSDYNA ConservationofEnergy BoundingTipOverAnalysis
InitialKE
>PE 26.6g 29.6g TSC Basket ANSYS DetailedBasketAnalysis 35g Stress ASMEIIING, App.F DetailedCanisterAnalysis ANSYS 40g Stress ASMEIIINB AccelerationTimeHistory Basket&TSC accelerations withdynamic amplification arebounded bythoseused inthestatic structural analysisfor tipover Verification FSARNonMechanisticTipOverLicensingBasis(Contd)
Thecaskissimplisticallymodeled astwoconcentric rightcircularcylinders Aninnersteellinersurrounded byconcrete.
Discretevolumesofthecaskmodelareassigned appropriatedensitiestorepresentthemassand relativedistribution(i.e.,CG)ofallcaskcomponents.
Finedesigndetailssuchastherebar,vents,pedestal, lid,canister,etc.arenotexplicitlymodeled.
Thelinerismodeledasarigidbody.
Theloadedcanisterisrepresentedbyincludingits massinastripofelementsattheIDofthecask.
Caskisinthehorizontalorientationabovethepadand soil.
Aninitialangularvelocityisappliedtotheentire caskaboutthepointofrotation.
12 CC1/CC2LSDYNACask&PadModel FSARNonMechanisticTipOverLicensingBasis(Contd)
Forthetipoverevaluation,thefollowingarethedesigncontrol measures:
SimplisticLSDYNAmodelofacaskandagenericpad&soil.
Applicationofaninitialangularvelocityonthecask.
AnevaluationthatensurestheconservationofenergyispreservedinLSDYNA.
VerificationthattheresultingLSDYNAgloadsareboundedbythegloads usedinthesubsequentANSYSstructuralevaluations.
13 FSARDESIGN CONTROL MEASURES
10CFR72.48allowsthecaskdesignertomakechangestotheir licensingbasisdesign,providedcertainconditionsaremet.
Pertheregulation(72.48(c)(2)(viii))acertificateholdershallobtainaCoC amendmentforaproposedchangethatwould(viii)Resultinadeparture fromamethodofevaluationdescribedintheFSAR(asupdated)usedin establishingthedesignbasesorinthesafetyanalyses.
AdeparturefromanMOEisdefinedin72.48(a)(2),andacaskdesignercan changeanyoftheelementsofanMOE(72.48(a)(2)(i))orchangetoanother MOE(72.48(a)(2)(ii)) providedcertainconditionsaremet.
14 10CFR72.48CHANGE CONTROL PROCESS
Themostrecentlypublished(September22,2020)NRCguidanceis RegulatoryGuide3.72,Revision1,GuidanceforImplementationof10CFR 72.48,Changes,Tests,AndExperiments. Page3ofRG3.72Rev.1states that:
Thestatementofconsiderations(SOC)forthefinalrulestatesthatadeparturefrom anMOEasdescribedintheFSAR(asupdated)usedinestablishingthedesignbasesor inthesafetyanalysesmeans(1)changinganyoftheelementsofthemethod describedintheFSAR(asupdated)unlesstheresultsoftheanalysisareconservative oressentiallythesameor(2)changingfromamethoddescribedintheFSARto anothermethodunlessthatmethodhasbeenapprovedbytheNRCfortheintended application.
RegulatoryGuide3.72,Rev.1formallyendorsesNEI1204,Rev.2.
15 10CFR72.48CHANGE CONTROL PROCESS (CONTD)
ToincorporateCC5intotheFSAR,NACevaluatedthenewcaskviathe 72.48processtodetermineifpriorNRCapprovalwasneeded.
NACconfirmedthat:
TheFSARcontainsalicensingbasisMOE(asimplisticLSDYNAcaskmodel) usedtojustifyANSYSgloads.
TheFSARalsocontainsalicensingbasisMOEfordeterminingtheangular velocityinputforLSDYNA(andcheckingtheLSDYNAoutputkineticenergy).
16 10CFR72.48DETERMINATION FOR CC5
NACusedthelicensingbasisMOEfordeterminingtheangularvelocity inputforLSDYNA.
Aspreviouslydiscussed,thiscanbefoundintheFSAR(Section 3.10.4.4)andisshownbelow:
Wheremisthemassofthesystem;gistheaccelerationduetogravity;h istheCGheightchange;Iisthecasksmomentofinertia;andisthe resultingangularvelocityatimpact.
17 10CFR72.48DETERMINATION FOR CC5(CONTD)
BytakingthelicensingbasisMOEequationfordeterminingthe angularvelocityinputforLSDYNA(andcheckingtheLSDYNAoutput kineticenergy),thetermscanberearrangedtosolvefortheangular velocity.
TheangularvelocityforCC5canthenbecomparedtoCC1bysolving fortheirratiotodeterminetheextentthattheyaredifferent.
18 10CFR72.48DETERMINATION FOR CC5(CONTD)
Thus,therelativedifferenceinangularvelocitybetweenCC5andCC1 wasdetermined.
ThedifferenceinangularvelocitybetweenCC5andCC1islessthan 1%.
Inthiscase,thelicensingbasisLSDYNAmodelangularvelocityinput wasverifiedtobeapplicabletoCC5.
19 10CFR72.48DETERMINATION FOR CC5(CONTD)
BeforebuildinganynewLSDYNAmodel,NACdeterminedwhetherthe previousmodelwasrelevanttoCC5.
SincethegenericFSARpadandsoilremainedunchangedandthecasksare similarindesignandmaterials,thelicensingbasisLSDYNAmodelforCC1is applicabletoCC5afterconfirmingthattheangularvelocitiesareessentially thesame.
Asubstantialdifferenceinangularvelocitywouldprecludetheabilitytouse thepreviousLSDYNAresultsforCC5.Inthatcase,aCC5specificLSDYNA modelwouldneedtobebuiltandruntoensurethesubsequentANSYS structuralevaluationswerebounding.
Thisisthelicensingbasisdesigncontrolprocess.
20 10CFR72.48DETERMINATION FOR CC5(CONTD)
TheFSARlicensingbasisMOEfordeterminingtheangularvelocityinputforLS DYNAcontainsbothinputparametersandelements.
IndustryguidanceonthesekeytermsisprovidedinNEI1204,whichisendorsed byReg.Guide3.72,Rev.1asfollows:
Theinputparametersarethephysicaldimensionsofthesystemandconstantsofnature (i.e.,themass,gravity,andcenterofgravityforthesystem).
Theelementsarethemomentofinertiaandtheangularvelocity.
InordertoverifythelicensingbasisLSDYNAmodelwasapplicabletoCC5,NAC followedthelicensingbasisdesigncontrolprocessanddeterminedtherelative differenceinangularvelocitybetweenCC5andCC1.
Forthemomentofinertia,NACelectedtoderivethemomentofinertiaviaahand calculationinsteadofusingLSDYNA,whichisthemethoddescribedintheFSAR.
21 10CFR72.48DETERMINATION FOR CC5(CONTD)
NACrecognizesthatcalculatingthemomentofinertiabyhandratherthanusing LSDYNAisanewmethod.
However,NACcandothisprovideditisnotadeparture.
TheregulationallowsNACtochangetoanothermethodprovidedthemethodhas beenpreviouslyapprovedbytheNRCfortheintendedapplication.
NACpreviouslyreceivedNRCacceptancetousehandcalculationsforderivingthe momentofinertiaforacaskinthetipoverevaluation.
TheNACMPC(721025 FSARSection11.2.12.2.1)andNACUMS(721015-FSARSection 11.2.12.3.1)systemsarelicensedbytheNRCthisway.
ThisisconsistentwiththeregulationandtheNRCsguidance(Reg.Guide3.72,Rev.1),which endorsedNEI1204,Rev.2.
Therefore,adeparturehasnotoccurred,andNACisallowedtousehand calculationsinlieuofLSDYNA.
22 10CFR72.48DETERMINATION FOR CC5(CONTD)
NACusedthelicensingbasisdesigncontrolmeasuresintheFSAR.
NACusedthelicensingbasismethodsofevaluationintheFSARexcept forthemomentofinertiaforCC5.
NACdidchangethewaythemomentofinertiawasderivedbutitdidnot constituteadeparturebecausethemethodhadbeenpreviouslyapproved bytheNRCfortheintendedapplication.
23
SUMMARY
Part2ofthepresentationwillbeconductedasfollows:
MAGNASTORAmendment9 NACCommentsontheNRCInspectionReport PaloVerdeNRCInspectionvs.NACNRCInspection NACCorrectiveActionsFollowingthePaloVerdeInspection NACActionsFollowingAVs PresentationConclusion 24 OUTLINE - PART 2
ContrarytotheIR,theNRCstaffhassubstantiatedandapprovedtheadequacyof the72.48tipoverapproachtaken.
TheNRCIRstatesthatNACs72.48approachwouldlikelynotbeapprovedby thetechnicalstaff(seeChoiceLetterEnclosure2Page#15,3rd paragraph).
However,theNRCthroughtheMAGNASTORAmd.9SafetyEvaluationReport(SER) concludestheapproachisacceptabletotheNRC(seeSERPages7and8)
Amd.9includedanalternativecaskknownasCC6.
NACcouldhaveincorporateditviathe72.48process,butelectedtoincludeallcaskdesign changesinacomprehensiveamendmentforaspecificproject.
ThiscaskwasevaluatedbyNACfortipoverinthesamemannerasCC5.
TheAmd.9SERhasalreadybeenapprovedbytheNRCStaff.
25 MAGNASTORAMENDMENT 9
ThefollowingisfromtheSER(Page8,lastparagraph;emphasisadded)
However,despitehavingnotperformedamoreindepthtipoveranalysis,thestaffhas concludedthatnoadditionalnonmechanistictipoveranalysisoftheCC6isneeded,inthis instance,becausethereisreasonableassurancethattheCC6willperformitsintendedsafety functionsunderanonmechanistictipoverevent.Thisisduetoconservatismandsimilarityof theCC6tootherapplicantsconcretecasksasshowninTable3.3ofthisSERbelow.Specifically:
(i)CC1wasdesignedwithanadditional50%marginwiththegloadscalculatedbyLSDYNAtip overanalysis(i.e.,designbasisof35.0gand40.0gatthetopofthefuelbasketandcask, respectively,comparedtocalculatedgloads);(ii)boththeCC1andCC6areevaluatedonthe samepad;(iii)theCC1andCC6areofsimilarconstruction;(iv)theCC6isshorterandhasa slightlyshortercenterofgravityascomparedtotheCC1,thereforeitismorestable;and(v)the initialangularvelocityofCC6iswithin2%oftheCC1.
26 MAGNASTORAMENDMENT 9(CONTD)
Cask Type Method Fuel Basket (Design Basis = 35g)
Cask Design Basis = 40g CC1 LS-DYNA 26.4g 29.5g Table 3.3 - g-load at Top of the Fuel Basket and Cask
ThereareseveralimportanttakeawaysfromthisSER:
ALSDYNAmodelforCC6wasnotbuiltandrun.
TheNACcasktipoverapproachforCC3,CC4,CC5andCC6arethesame.
TheNRCSERconcludesCC6issimilartotheapplicantsotherconcretecask,CC1.
TheNRCSERparagraphonthepreviousslidepresentsthebasisoftheNRCsacceptanceofCC6; thefollowingpresentshowCC5comparestothesameNRCscriteria:
i.
Significantdesignmarginexistsinthelicensingbasis(CC1).
ii.
SameISFSIpadandsoil.
iii.
Similarconstructionandmaterials.
iv.
CC5isnotshorterthanCC1(likeCC6)butisessentiallythesame(<0.3%)
v.
TheangularvelocityrelativetoCC1isacceptable(<2%difference)
Note,CC5is<1%differentthanCC1 NRCstaffapprovedtheapproachNACusedforCC5whenitapprovedAmendment9 demonstratingitasanacceptabletechnicalbasiswithouttheneedtoreperformLSDYNA 27 MAGNASTORAMENDMENT 9(CONTD)
TheNRCstaffrepresentsintheIRthatLSDYNAisthe MOEfortipoverevaluation.
However,theMOEfortipoveralsoincludes:
Thepredecessorcalculationofpotentialenergyandangularvelocitypriortoimpact.TheseareinputstotheLSDYNAmodel thatcanbedevelopedfromclassicalformulasthroughapplicationoftheconservationofenergyequationandbasiccask physicalparametersandareelementsoftheMOEinNACslicensingbasis.
LSDYNAisusedtoperformdynamicanalysisofstructures,butitdoesnotcalculateinitialpotentialenergy,orangular velocitiesresultingfromatipover.
TheNRCIRdidnotacknowledgesignificantconservatismingloadinputsintothesubsequentANSYSstress evaluationsfordeterminingwhetherthecanisterandbasketstressesresultingfromthetipovergloadsare withinapplicablestresslimits.
GLoadsresultingfromatipovercalculatedbyLSDYNAareNOTsubjecttospecifiedregulatorylimitsorcriteria.
NACutilizedboundingaccelerationvaluesof35g(basket)and40g(canister)initsdownstreamANSYSstructuralevaluations.
NRCstaffassertsthatNACchangeditsMOEfortipoverfromLSDYNAtolinearscaling,butitisclearfrom NACs72.48evaluationandsupportingcalculationsthatNACdidnotestimateanygloadsforCC5.
AnyMOEthatreplacesLSDYNAfordynamicanalysisoftipovereventswould,likeLSDYNA,needtoproducegloadoutputs.
28 NACCOMMENTS ON THE NRCINSPECTION REPORT
TheNRCIRi haspresentedconcernsoverthenonlinearbehaviorofthetipover modelparametersandinputs,specificallywithrespecttothestoragepadand underlyingsoil.
NACusedidenticalpad&soil(thesehavenotchangedintheFSARsinceCC1/CC2)properties inthe72.48evaluation.
TheNRCIRindicatedascalingmethodresultedinerrantdeterminationthateach caskhadauniformdensitycylinder.
Theuseofanapproximationofthecasksmomentofinertiausingahandcalculationfora uniformdensitycylinderisappropriatefortheevaluationofthecasksrelativeangularvelocity.
TheNRCIRindicatedmanydifferencesincaskdesigns.
TherearenosignificantdifferencesinCC1/CC2andCC5caskdesigns.
Generalgeometry,materialsanddesignofbothcasksareverysimilar.Weightisslightlyhigher,butthegeneral effectonthetipoverisareductionofdecelerationswithasimilarangularvelocity.
29 NACCOMMENTS ON THE NRCINSPECTION REPORT (CONTD) i.
TheNRCsChoiceLetterconsidersthepadandsoilpropertieshavechangedwiththeincorporationofCC5(seeChoiceLetterEnclosure2Page#15)
SimilaritiesofCC5toCC1/2 Therearesubstantialsimilaritiesthatwillcontrolthecasksbehaviorina tipoverevent.*
AllMaterialsofcaskconstructionarethesame.
ConcreteCaskoutsideandinsidediameterarethesame.
Caskheightisessentiallythesame- 0.6 0.3%.
Caskcenterofgravityisessentiallythesame-2.1 <2%.
Shieldingenhancements Loadedcaskweightincreasedby~17,500 lbs.,thisislessthan6%andislargelycomprisedofdistributedmasses withlittleimpactontheCGofthesystemincluding:
Rebarspacingoftheoutercageisslightlydenserbutdistributed(~900 lbs.- 0.3%).
Casklineris1.25thickerand,althoughamoresignificantcontributor tothesystemweightincrease(14,900lbs ~4%),isdistributed.
Casklidthickness(1,630lbs)andinletventsteelbars(580lbs.),are morelocalmassesbutcontributeaverysmallpercentage(0.7%)tothe systemweight.
30 NACCOMMENTS ON THE NRCINSPECTION REPORT (CONTD)
- TheNRCChoiceLetterstatesmanycharacteristicsaredifferent(seeChoiceLetter Page#12,2nd Paragraph)
UniformDensityCylinderApproximation Themassmomentofinertiacalculationisonlyusedin calculatingtherelativedifference ofthecasksystems responsetomotioninthedeterminationofrelative angular velocities.
Theapproximationformassmomentofinertiaforthe uniformdensityrepresentationresultsinaCC5toCC1ratio of1.073.
Todemonstratethesuitabilityofsimplifieduniformdensity representation,whichtheIRdescribedaserrant,NAC subsequentlydevelopedhighlydetailed3Ddesignmodels oftheCC5andCC1caskstoobtaininertialpropertiestoa highlevelofaccuracy. The3DmodelsresultinaCC5toCC1 ratioof1.062.
Thesmalldifferenceinthesetworatiosdemonstratesthe suitabilityoftheuniformdensitycylinderrepresentationof amomentofinertia.
31 Detailed3DModelofCC5 Detailed3DModelofCC1 NACCOMMENTS ON THE NRCINSPECTION REPORT (CONTD)
PaloVerde(PVGS)TransitionfromNACUMStoMAGNASTOR FirstcustomertoutilizetheCC5ConcreteCaskDesign TheNRCInspectionatPaloVerdewasongoingduringthescheduledtriennialNACFebruary2020inspection.
InSeptember2019,RegionIVInspectorshadconcernsrelatedtothelinearscalingofgloadsforthesitespecific condition.
PriortotheloadingofthefirstMAGNASTORsystematPaloVerde,NACperformedasitespecificLSDYNA evaluation(300322010)whichresolvedtheInspectionTeamsquestions.
Resultswereinlinewithourpreviouscalculationalresults.
WhyisthePVGSInspectionrelevanttotodaysconference?BecausetheIRcomminglesfactsbetweentheNAC InspectionandthePVGSInspection.Forexample:
IRstatesthatNACcomparedhandcalculatedaccelerationresults tothepreviousnonlinearLSDYNAaccelerationresults"i IRstatesthatlinearscalingorratioingwouldlikelynotbeapprovedbythetechnicalstaffbecausesomanyvariablessuch as the concreteandsoilmaterialproperties,padandsoilconfigurations(e.g.,compressivestrength)canchangeii ThesePVGS72.212supportactivitieswerecompletelyseparatefrom,andlongafterNACslicensingeffortswhich incorporatedCC5intoourFSAR.
32 PALO VERDE NRCINSPECTION VS.NACNRCINSPECTION i.
NRCChoiceLetterEnclosure2Page#13,3rd Paragraph ii.
NRCChoiceLetterEnclosure2Page#15,3rd Paragraph
TimelineofSignificantEvents 33 PALO VERDE NRCINSPECTION VS.NACNRCINSPECTION (CONTD) 2016 May14-NACissues Memorandum ED20190048to documentthePalo VerdeSiteSpecificISFSI PadTipOver(Supports PVGS72.212Evaluation) 2017 2018 2019 2020 December30 NAC incorporatesCC5 intoMAGNASTOR FSARvia72.48 NAC16MAG018 February27-NRC TriennialInspection ofNACComplete (NoExitMeeting pendingongoing RegionIV inspectionatPVGS September12-NRC RegionIVInspector submitsquestionsto PVGSregardingthe sitespecificTipOver Evaluation November7-PVGS/NAC RespondtoNRCsquestionsby revisingED20190048and providingwrittenresponsesto theinspectorsquestions NACInspection remainsopen July22-NRCholds ExitMeetingwith NAC.FirsttimeNAC isinformedof2AVs andforthcoming ChoiceLetter February27-NAC completesPVGSSite SpecificLSDYNATip Over(300322010)
March2PVGS beginsMAGNASTOR CaskLoading September4 NAC ReceivesChoice LetterandAVsfrom NRC July6-PVGS receivesChoice Letterandnoticeof 2AVsfromNRC December26-NAC contractstoprovide PaloVerde11 MAGNASTORSystem
- 1st CC5Order NACInspectionRelatedEvents PaloVerdeInspectionRelatedEvents
CC5IncorporationintoFSARvia72.48(2016)
NACinitiatesthe72.48processtodetermineifincorporationofCC5intotheFSARrequirespriorNRCapproval.
NACperformedascreeningandsubsequentevaluation,pertheregulation.
NACdeterminedthatCC5wasacceptablewithoutobtainingpriorNRCapproval.
NACdidnotuselinearscaling.
CC5AcceptanceonthePaloVerdeISFSIPadvia72.212(2019-2020) 10CFR72.212requiresPaloVerdetoreviewtheFSARgenericISFSIpadandidentify/justifydifferences.
PaloVerdeprovidedtheseISFSIpaddifferencestoNACviaaspecification.
NACprovidedareport(ED20190048)whichratioedpriorLSDYNAtipoverevaluationresultstoestimategloadsthatwouldbe expectedwithCC5onthePaloVerdeISFSIpad.
PaloVerdethenperformeda72.48determination,referencingtheNACreporttojustifythepadwasacceptableforCC5tipover.
NRCRegionIVraisedquestionsontheMOEusedintheevaluation.
NACpromptlydevelopedasitespecificLSDYNAmodelandcalculation(300322010)tosupportthePVGSMAGNASTORCC5tip overandresolvetheRegionIVconcerns.
APSrevisedtheir72.212reportpriortocaskloadingtoinclude300322010.
ThroughsubsequentdialogwithPaloVerdeandRegionIV,NACunderstandstheNRCsposition.NACacknowledgesthisratioing (orlinearscaling)approachwhenappliedtomultipleparameterdifferenceswithnonlinearbehavior(i.e.thosebetweenthe genericFSARpadandthePVGSpad)wasanoverrelianceonratioing.ThesitespecificLSDYNAmodelandcalculationwasthe appropriatechoiceofanalysis.
34 PALO VERDE NRCINSPECTION VS.NACNRCINSPECTION (CONTD)
FollowingtheAPSInspection,NACissuedCAR2001withrespecttoNACsdecisionnottoinitially performasitespecificLSDYNArun.
CAR2001CorrectiveActions:
Evaluationoftheabilityofthecomponentstoperformintendedsafetyfunction(reportability).
Extentofconditionreview:
DesignControlMethods OtherCustomerssitespecifictipoveranalyses RootCauseAnalysis.
ReviewNACcalculationprocessandprocedureforweaknessrelatedtothespecificissue.
ReviewNACprojectmanagementplanningprocedureforweaknessrelatedtodesigndeliverables.
Employeetraining-includingemphasisoncompliancewithlicensingbasisMOE.
ParticipatedinthePaloVerdecorrectiveactionprocess.
NACisintheprocessofupdatingour72.48trainingprogramtoincludeRegGuide3.72Rev.1and NEI1204nowthatithasbeenendorsedbytheNRC.
35 NACCORRECTIVE ACTIONS FOLLOWING PALO VERDE INSPECTION
NAChasissuedaSelfIdentificationReport(SIR)todocumenttheAVsforpotential escalationintoNACsCorrectiveActionProgram(CAP)includingextentofcondition reviewpendingoutcomeofthePEC.
NAChasperformedLSDYNAanalysesexplicitlyforCC3,CC4,CC5andCC6viaNAC calculation711602024 ResultingaccelerationsareessentiallythesameasFSARCC1/CC2 NACverifiedLSDYNAwasusedforallsubcontractedsitespecificMAGNASTOR implementations.
NAChasreviewedearliercasksystemdesigns(i.e.,NACMPCandNACUMS)andfound FSARtipoveranalysestobeconsistentwiththecurrentMAGNASTORlicensingbasis.
NAChasperformedaninspectionofour72.48activitieswithrespecttolinearscalingor ratioingdispositions.
36 NACACTIONS FOLLOWING AVS
InpreparationforthisPEC,NAChasusedLSDYNAtoexplicitlyevaluatethe CC5caskforthenonmechanistictipoverimpactontotheFSARpad&soil.
TheCC5caskwasmodeledinLSDYNAusinganapproachconsistentwiththe licensingbasisanalysisdescribedpreviously.
ThecaskmodelreflectstheminorphysicaldifferencesintheCC5caskdesign (taller,thickerlid,thickerliner,inletbars,andoutercagerebarspacing).
TheISFSIpadandunderlyingsoilarerepresentedwiththesamematerialmodels consideredinthelicensingbasisanalysis.
ResultsshowthattheLSDYNAproducedaccelerationsforCC5arelower thanthelicensingbasisanalysisaccelerations.
TherelativedifferenceinIfortheseCC5andCC1caskmodelsis1.064 whichisconsistentwiththeuniformdensitycylinderapproximation presentedearlier.
TheseresultsfurthersupporttheconclusionNACmadeintheCC572.48 determination,thatnoadditionaltipoveranalysiswasrequiredasthe existinglicensingbasisanalysisisapplicabletotheCC5caskdesign.
37 NACACTIONS FOLLOWING AVS (CONTD)
CC1/CC2(1)
CC5(2)
Basketpeakacceleration,g 26.6 25.8 TSCpeakacceleration,g 29.6 28.9 1)
NACCalculation711602005,Rev.0,NewgenVCCTipOverAnalysis,2004 2)
NACCalculation711602034,Rev.0,LSDYNATipOverAnalysisforCC1andCC5ConcreteCasks,2020 CC5LSDYNACask&PadModel
The72.48evaluationperformedforCC5FSARnonmechanistictipoverdidnotresultina departurefromtheexistingMOEinthelicensingbasis.
TheCC1/CC2FSARLSDYNAlicensingbasiswasreasonablydeterminedtobeapplicableto CC5.
CC5meetsthesamecriteriaNRCusedtoapproveCC6intheAmendment9SER.
ThereislowregulatorysignificanceandlowsafetysignificanceassociatedwiththeAVs, sincenoFSARlimitsorcriteriaarebasedontheLSDYNAresults.
NACssupplementalLSDYNAcalculationconfirmedtheadequacyofthedesign.
NACbelievesneithera72.48noradesigncontrolviolationhasoccurred.
NACtakesnuclearsafetyandregulatorycomplianceseriouslyandhopesthispresentation helpsclarifyanymisunderstandingstheNRCmayhavewithregardstotheunderlying facts.
38 PRESENTATION CONCLUSION
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