ML12332A072

Southern California Edisons Flooding Walkdown Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ich

ML12332A072
Person / Time
Site:	San Onofre
Issue date:	11/26/2012
From:	Bauder D Southern California Edison Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
Download: ML12332A072 (23)

Text

i.i;ilfD RI50RN' An EDISON INTERNATIONAL Company U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555 November 26, 2012 Douglas R. Bauder Site Vice President & Station Manager San Onofre Nuclear Generating Station 10CFR 50.54(f)

Subject:

Docket Nos. 50-361 and 50-362 Southern California Edison's Flooding Walkdown Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident.

References:

1) NRC Letter, Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, dated March 12, 2012.

2) NRC Letter, Endorsement of Nuclear Energy Institute (NEI) 12-07, "Guidelines for Performing Verification Walkdowns of Plant Flood Protection Features", dated May 31,2012.

Dear Sir or Madam:

On March 12,2012, the NRC issued Reference 1 to all power reactor licensees and holders of construction permits in active or deferred status. Enclosure 4 of Reference 1 contains specific Requested Actions, Requested Information,and Required Responses associated with Recommendation 2.3 for Flooding Walkdowns. Specifically, Enclosure 4 of Reference 1 states that within 180 days of the NRC's endorsement of the walkdown process, each addressee will submit its final response, including a list of any areas that are unable to be inspected due to inaccessibility and a schedule for when the walkdown will be completed. to this letter contains Southern California Edison's flooding walkdown response for San Onofre Nuclear Generating Station (SONGS) Units 2 and 3, consistent with the NRC-endorsed guidance (Reference 2).

This letter contains regulatory commitments. The specific regulatory commitments and the scheduled due date for completion are identified in Enclosure 1 of this letter.

Should you have any questions concerning the content of this letter, please contact Licensing Manager, Linda Conklin, at (949) 368-9443.

P.O. Box 128 San Clemente, CA 92672 (949) 368-9275 PAX 89275 Fax: (949) 368-9881 Doug.Bauder@sce.com

Document Control Desk November 26, 2012 I declare under penalty of perjury that the foregoing is true and correct.

Executed on II / ~ CD (;J-()(:L.

BY:~

Douglas R. Bauder Site Vice President and Station Manager cc wI encl :

Director, Office of Nuclear Reactor Regulation E. E. Collins, Regional Administrator, NRC Region IV G. G. Warnick, NRC Senior Resident Inspector, San Onofre Units 2 and 3 R. Hall, NRC Project Manager, San Onofre Units 2 and 3 B. Benney, NRC Project Manager, San Onofre Units 2 and 3

List of Commitments and Schedule for Implementation of Flooding Walkdown Results This table identifies actions discussed in this letter for which Southern California Edison commits to perform. Any other actions discussed in this submittal are described for the NRCs information and are not commitments.

Commitment Action Type Scheduled Due Date One-Time Sustainable Complete inspection of all restricted access features as identified in the SONGS Flood Walkdown Report X

07/01/2013 Resolve deficiencies as identified in the SONGS Flood Walkdown Report X

07/01/2013

San Onofre Nuclear Generating Station Flood Walkdown Report

San Onofre Nuclear Generating Station Flood Walkdown Report Fukushima Near-Term Task Force - Section 2.3, Flooding Walkdowns NN 201899774 November 2012 Pepared By:

Southern California Edison and CH2MHILL

Contents I

SONGSFloodWalkdownReport..........................................................................................................................1 Introduction......................................................................................................................................................1 Purpose.............................................................................................................................................................1 RequestedContent...........................................................................................................................................1 SectionA:DesignBasisFloodHazardLevel(s).....................................................................................1 SectionB:ProtectionMitigationFeaturesConsideredintheLicensingBasis....................................5 SectionC:WarningSystemstoDetectthePresenceofWater...........................................................7 SectionD:EffectivenessofFloodProtectionFeatures.......................................................................8 SectionE:ImplementationoftheWalkdownProcess........................................................................9 SectionF:ResultsoftheFloodFeatureWalkdown...........................................................................10 SectionG:CliffEdgeEffects..............................................................................................................16 SectionH:OtherPlannedand/orNewlyInstalledFloodProtectionFeaturesorMeasures............16 Conclusion.......................................................................................................................................................16 Deficiencies........................................................................................................................................16 RestrictedAccessFloodFeatures......................................................................................................17 InaccessibleFloodFeatures...............................................................................................................17 References......................................................................................................................................................17

Exhibits E1 SONGSFloodFeatureWalkdownTeamComposition....................................................................................10

1 SONGS Flood Walkdown Report Introduction InresponsetothenuclearfueldamageatFukushimaDaiIchipowerfacilityresultingfromanearthquakeand subsequenttsunami,theUnitedStatesNuclearRegulatoryCommission(NRC)requestedinformationpursuantto Title10oftheCodeofFederalRegulations(10CFR),Section50.54(f).Aspartofthisrequest,SouthernCalifornia EdisonsSanOnofreNuclearGeneratingStation(SONGS)wasrequiredtoperformfloodfeaturewalkdownsto fieldverifythatplantfeaturescreditedinthecurrentlicensingbasis(CLB)forprotectionandmitigationfrom externalfloodeventsareavailable,functional,andproperlymaintained[1].

Purpose Thisdocumentprovidesasummaryofthefieldassessmentofexternalfloodprotectionandmitigationcapabilities inaccordancewithNRCRecommendation2.3ofSECY110137[2]andEnclosure4oftheMarch12,2012,Request forInformationPursuanttoTitle10CFR50.54(f)RegardingRecommendations2.1,2.3,and9.3,oftheNearTerm TaskForceReviewofInsightsfromtheFukushimaDaiIchiAccident(50.54(f)letter[3]).

TheSONGSfloodprotectionwalkdownwasdesignedtoverifythatpermanentand/ortemporarystructures, systems,components(SSCs),andproceduresneededduringafloodeventareacceptableandcapableof performingtheirdesignfunctionascreditedintheCLB.Thewalkdownalsoservedasameanstoverifyvisually thatplantmodificationsimplementedsinceoriginalconstruction,suchassecuritybarrierinstallations,donot adverselyaffectplantfloodingprotection[1].

Requested Content AsspecifiedintheNRCendorsedNuclearEnergyInstitute(NEI)1207[Rev.0]GuidelinesforPerforming VerificationWalkdownsofPlantFloodProtectionFeatures(NEI1207[1]),AppendixDprovidesadditional informationonthespecificinformationrequestsinEnclosure4oftheNRCsMarch12,2012,50.54(f)letter.Eight sectionswereidentifiedasrequiringresponse;thesecanbefoundbelowinSectionsAthroughH.

Section A: Design Basis Flood Hazard Level(s)

Requested Information Describethedesignbasisfloodhazardlevel(s)forallfloodcausingmechanisms,includinggroundwateringress.

SONGS Response TheSONGSsiteislocatedonthesouthernCaliforniacoastoftheUnitedStatesonthePacificOceanandissituated onacoastalplainatthebaseofthewesternfoothillsoftheSantaMargaritaMountainRange.Thereareno perennialstreamsinthegeneralvicinityoftheplantsite.Thepowerblockfinishgradeelevationis+30.0feet meanlowerlowwater(mllw),whichisbasedontheplantsbenchmark1977referenceelevation[4].

Themeanannualtemperatureinthecoastalplainregionis61F,withameanminimumtemperatureof42Fin January.Annualrainfallrangesfrom10to16inches,with90percentoftheannualtotaloccurringduringthe monthsofNovemberthroughApril[4].

SONGS FLOOD WALKDOWN REPORT 2

Descriptionsofthedesignbasisfloodhazardlevel(s)forallfloodcausingmechanisms,includinggroundwater ingress,aredetailedintheSanOnofre2&3UpdatedFinalSafetyAnalysisReport(UFSAR)[4],Section2.4.

AdditionalinformationfromotherCLBdocumentsisreferencedasneeded.

ThefollowingsubsectionsprovidetheinformationrequestedbytheNRCforeachfloodcausingmechanismas detailedinthecurrentlicensingbasisdocuments.Inaseparateactivity,SONGSisperforminganexternalflood hazardreevaluationaspartofaresponsetoSECY110137Item2.1ofthe50.54(f)letterrequestforinformation, whichwillevaluatethecurrentlicensingbasis.

LocalIntensePrecipitation(DesignBasisFloodHazard).The6hour,1squaremileprobablemaximum precipitation(PMP)eventcausesthehighestfloodlevelontheSONGSsiteandisthereforeusedasthedesign basisfloodevent[4].ThevolumeofthePMPwas7inchesin1hourand12.25inchesin6hours.

MaximumPostulatedPMPFloodElevation.ThemaximumpostulatedPMPfloodelevationis+31.0feet mllwintheSONGSUnit2andUnit3PowerBlock[4].

KeyAssumptions.Allcatchbasinsforthesubsurfacedrainagesystem,roofdrains,andexposedfloor drainsareassumedpluggedforthepurposeofdeterminingwatersurfaceelevationsarisingduringthe thunderstormPMPevent[4].

MethodologyUsedtoDeveloptheDesignBasisFloodingHazard.U.S.WeatherBureau HydrometeorologicalReport(HMR)36[5]wasusedtocalculatetheorographicandconveyance componentsofthefrontalPMP.EvaluationofthePMPwasalsodeterminedfortheSONGSsitebasedon themethodsoftheU.S.WeatherBureau.Thedistributionofprecipitationinthe6hourthunderstormwas calculated;arrangementoftheincrementalvaluesintothecriticalPMPstormwasbasedonprocedures usedbytheU.S.ArmyCorpsofEngineers.ThedrainageareatributarytotheSONGSUnit2andUnit3 powerblockwasdividedintosubbasins.TheU.S.SoilConservationServicesoilcomplexmethodwasused toconstructthehydrographresultingfromthePMP.Runoffcurvesforthegivensoiltypeswereselected onthebasisofAntecedentMoistureConditionIII.Duetotherelativelyshorttimesofconcentrationand correspondingveryshortlagtimesofthesubbasins,theassumptionwasmadethatallprecipitationexcess withinanyperiodbecamerunoffduringthatperiod.Precipitationintensitiesfordurationslessthan15 minuteswereinterpolatedfromthethunderstormPMPdata[4].

DifferencesorContradictionsinFloodHazardLevels.Nodifferencesorcontradictionsinthefloodhazard levelswereidentifiedindesignorlicensingdocumentation.

ProbableMaximumFlood(PMF)onStreamsandRivers.Ananalysisofthe43squaremileSanOnofreCreekBasin (northofthesite)andthe0.86squaremileFoothillDrainageBasin(eastofthesite)wasconductedtodetermine thePMFandsubsequentcontributiontofloodingattheSONGSsite.RecommendationsofNRCRegulatory Guide1.59wereusedinconductingthePMFanalysis[4].

MaximumPostulatedPMFFloodElevation.

SanOnofreCreekBasin-ThePMFpeakdischargeof71,000cubicfeetpersecond(ft3/s)wasusedin determiningthemaximumfloodstageinSanOnofreCreek.Theresultsoftheanalysisdemonstratedthat theflowwouldbecontainedwithinthelimitsofthefloodplainofSanOnofreCreekandwouldnotpresent anyriskoffloodingatthesite[4].

FoothillDrainageBasin-PMPinducedrunoffisdivertedtotheSanOnofreCreekbyadiversionstructure.

Thediversionstructureconsistsofanearthfilledbermwithanexcavatedchanneldesignedtointercept andconveythepeakdischargeassociatedwiththePMF.Theresultsoftheanalysisshowedthattheflow wouldbecontainedwithinthelimitsofthediversionstructureandwouldnotpresentanyriskofflooding atthesite.[4].

KeyAssumptions.DuringthePMFanalysis,thesoilwasconsideredsaturated.ASnyderpeakingcoefficient of0.7wasusedforunithydrographcomputations.TheMuskingumstoragecoefficientKforeachreach wastakenas50percentofthebasin'slagtime.TheroutingcoefficientXwasassumedas0.3[4].

SONGS FLOOD WALKDOWN REPORT 3

MethodologyUsedtoDeveloptheDesignBasisFloodingHazard.TheSanOnofreareaissusceptibleto frontalstorms,usuallyoccurringduringthemonthsofOctoberthroughApril,andlocalthunderstorms, whicharepredominantduringsummerandearlyfall.ThePMPvaluesassociatedwithbothtypesofstorms werecomparedtodeterminethecriticalevent.HMR36wasusedtocalculatethefrontalstormPMPand theNationalWeatherServiceReportwasusedindeterminingthethunderstormPMP.Itwasconcluded the6hour,1squaremilethunderstormPMP(12.25inches)wasthemorecriticalandconsequentlywas usedasthedesignbasisevent[4].

SanOnofreCreekBasin:TheSanOnofreCreekBasinwassubdividedandhydrologicparametersforeach subbasinwerecalculated.Thesubbasinlagtimeswerecalculatedonthebasisofafigurepublishedbythe U.S.ArmyCorpsofEngineers.Thisbasinlagcurvewasderivedasaresultofastudyofvariousdrainage basinsinsouthernCaliforniaconductedbytheU.S.ArmyCorpsofEngineers.Forpurposesof conservatism,a10percentreductionofallcalculatedlagtimeswasperformedpriortotheirusein calculations.

UsingtheU.S.ArmyCorpsofEngineersHEC1computerprogram,thePMFhydrographforeachsubbasin wasderived.ASnyderpeakingcoefficientof0.7wasusedforunithydrographcomputationsinthe programforeachsubbasin.Thisvaluewasdeterminedasaresultoftheanalysisofthemajorstormsof JanuaryandFebruary1969,asreferencedinSanOnofre2&3UFSARSection2.4.3.2[4].Asnoted,the analysiswasperformedfortheSantaMargaritaRiverBasin,whererecordspermittedavalid reconstructionofthebasinrunoffhydrograph.AfterdeterminingthePMFhydrographforeachindividual subbasin,thehydrographswereroutedandcombinedtoobtainaPMFhydrographatthemouthofSan OnofreCreek.

FloodroutingwasconductedusingtheMuskingumMethod.TheMuskingumstoragecoefficientKforeach reachwastakenas50percentofthebasin'slagtime.Thecoefficientvaluewasdeterminedbyassuming lowflowandhighflowconditionsinsubbasinA5andcalculatingthecorrespondingvelocitiesandaverage flowvelocity.Theaveragevelocitywascombinedwiththereachlengthtoyieldthetraveltimethrough thereach.Fromthisrelationship,aproportionalityconstantwascalculated(i.e.,0.5)andthenusedin calculatingKfortheremainingsubbasins.TheroutingcoefficientXwasassumedas0.3,whichisusedfor mountainousregions[4].

FoothillDrainageBasin:TheanalysisoftheFoothillDrainageBasinwasconductedinamannersimilarto thatofSanOnofreCreekBasindescribedabove.Thedrainageareawassubdividedandsubbasin hydrologicparametersweredefined.

TheHEC1computerprogramwasusedtodeveloptheunithydrographandresultantPMFhydrographfor eachsubbasin.AsexplainedinSanOnofre2&3UFSARSection2.4.3.3.1[4],aSnyderpeakingcoefficient valueof0.7wasusedtoderivetheunithydrographs.ThePMFhydrographsobtainedfromeachsubbasin wereroutedtoSanOnofreCreek.DuetotherelativelyshortdistancebetweentheoutletsofsubbasinsB1 andB2,approximately0.75mile,andnarrowrangeoflagtimesforthesubbasins,itwasdecidedtoignore lagandtraveltimesandcombinetheindividualsubbasinPMFhydrographsdirectly,yieldingaconservative PMFhydrographattheoutletofsubbasinB2[4].

DifferencesorContradictionsinFloodHazardLevels.Nodifferencesorcontradictionsinthefloodhazard levelswereidentifiedindesignorlicensingdocumentation.

PotentialDamFailures.Therearenoexistingdamslocatedwithinthevicinityoftheplantsitewhose seismicallyinducedfailurecouldresultinadversefloodingatthesite[4].

ProbableMaximumSurgeandSeicheFlooding.

MaximumPostulatedSurgeandSeicheFloodElevation.Theworststormgeneratedwaveof54feet wouldbegintobeaffectedbytheoceanflooratadistanceoffshoreofapproximately11,000feetand wouldbecompletelydissipatedbythetimeitreachedthebeachinfrontoftheSanOnofreseawall.The maximumstormsurgeheighthasbeendeterminedtobe+1.98feetabovetheantecedentwaterlevel.It

SONGS FLOOD WALKDOWN REPORT 4

wasconcludedintheSanOnofre2&3UFSARthatlargesurgeswillnotdevelopinthevicinityofSan Onofre.Seichehasbeenfoundtoaffectseasurfaceelevationbyonly0.7centimeter,whichisconsidered negligible.[4].

KeyAssumptions.Themostconservativevalueswereselectedfortheprobablemaximumsurgeand seichefloodingcalculationandaredetailedintheSanOnofre2&3UFSAR,Section2.4.5[4].

MethodologyUsedtoDeveloptheDesignBasisFloodingHazard.

1. ProbableMaximumWindsandAssociatedMeteorologicalParameters-Usingtheclimatologyofthe northeastPacifictropicalcyclonesandthestructureoftypicalhurricanes,thetrackandthesurface windstructureofthehypotheticalmaximumprobablestormfortheSONGSsitewereconstructed.

2. SurgeandSeicheWaterLevels-Waterlevelsantecedenttoprobablesurgeandseichelevelswere established.AcceptedconservativehightidelevelsandsealevelanomaliesfortheSanOnofrearea wereconsideredinestablishingtheantecedentwaterlevels.Themaximumsurgewaterlevel hypotheticallypossibleandapplicabletothesitewouldresultfromthehypotheticalmaximum probablestorm.Indevelopingthehypotheticalmaximumtropicalstorm,particularattentionwas giventotheconfigurationofitsradiusofmaximumwinds,thestorm'sforwardspeed,andthestorm's track.Detailedmeasurementsandanalysesoflongperiodwaves(normalshelfseichingbackground levels)overthecontinentalborderlandwereconductednearOceanside,California,about17miles southeastofSanOnofre,andusedfordeterminationofseichewaterlevels.

3. WaveAction-Severedeepwaterstormwavesdeterminethelowestandhighestinstantaneouswater elevationsinconjunctionwithlongperiodphenomena(e.g.,tideandstormsurge).Asseverewaves areinfrequent,itwasnecessarytodeterminetheircharacteristicsbyhindcasting.Acarefulselectionof paststormsbasedonreportedwavedamageandstrongwindswasconducted.Then,thedeepwater significantwavecharacteristicsforeachstormweredeterminedfromweathermaps.Awaveheight distributionfunctionwasusedtodeterminethehighestindividualshallowwaterwaveheight,Hmax,in thestormfromthehindcastedsignificantwaveheightandperiodtimehistories.MarineAdvisorsand InterseaResearchexaminedatotalofapproximately60stormsthatoccurredbetween1900and1967 andthatoccurrednearenoughtoSanOnofretobeappliedtothisstudy.Twentyfiveofthemost severestormswereselectedforhindcasting.Thedeepwaterwavedatawerecorrectedforrefraction andshoalingattheSONGSsite,andalsoforislandsheltering[4].

DifferencesorContradictionsinFloodHazardLevels.Nodifferencesorcontradictionsinthefloodhazard levelswereidentifiedindesignorlicensingdocumentation.

ProbableMaximumTsunami(PMT)Flooding.Thepotentialfloodingeffectsfrombothlocallygeneratedand distantlygeneratedtsunamiswereanalyzedfortheSONGSsite.Thelocallygeneratedtsunamiwasfoundto produceagreaterwaverunupthanthedistantlygeneratedtsunami.Therefore,thelocallygeneratedtsunami resultsinthedesignbasisfortheSONGSsite.

MaximumPostulatedPMTFloodElevation.Thecontrollingtsunamioccurringduringsimultaneoushigh tideandstormsurgeproducesamaximumrunuptoelevation+15.6feetmllwattheSONGSUnit2and Unit3seawall.Whenstormwavesaresuperimposed,thepredictedmaximumrunupistoelevation+27 feetmllw[4].

KeyAssumptions.Mathematicalmodelingofthehypotheticaltsunamiwasconductedassumingan earthquakewitha7footverticaldisplacementcomponentoftheseafloor5milesoffshorefromSan Onofreasthegeneratingmechanism.NormalfaultingwaspostulatedforthehypothesizedoffshoreZone ofDeformationbecausetheconversionoflargestrikeslipmovementsontheseafloortoatsunamiwave nearSanOnofrewouldbeinefficient[4].

MethodologyUsedtoDeveloptheDesignBasisFloodingHazard.Becauseofthemoderatingeffectof southernCalifornia'soffshoreborderlandondistanttsunamiwaves,localoffshorefaultzonesare consideredtobethemostprobablegeneratorsforlargewavesatSanOnofre.Theclosestsuchzonetothe

SONGS FLOOD WALKDOWN REPORT 5

SONGSsiteisthehypothesizedoffshoreZoneofDeformation,asdiscussedinSanOnofre2&3UFSAR Section2.5.2.4.5[4].Theclosestportionofthiszoneisapproximately5milessouthwestoftheSONGSsite.

TostudytheeffectatSanOnofrecausedbyseafloordisplacementsontheoffshoreZoneofDeformation, detailedspecificanalyseswerecompletedbyDr.BasilW.Wilson[6].

Mathematicalmodelingofthehypotheticaltsunamiwasconductedassuminganearthquakewitha7foot verticaldisplacementcomponentoftheseafloor5milesoffshorefromSanOnofreasthegenerating mechanism.Thisverticaldisplacementismuchlargerthanwouldbeexpectedtooccuronthe hypothesizedoffshoreZoneofDeformation,which,becauseofitsnorthwesttrend,ischaracterizedby predominantlystrikeslipdisplacement.

NormalfaultingwaspostulatedforthehypothesizedoffshoreZoneofDeformationbecausethe conversionoflargestrikeslipmovementsontheseafloortoatsunamiwavenearSanOnofrewouldbe inefficient.Further,therearenolargetopographicfeaturesorientednormaltothedirectionofstrikeslip movementontheoffshoreZoneofDeformation[4].

DifferencesorContradictionsinFloodHazardLevels.Nodifferencesorcontradictionsinthefloodhazard levelswereidentifiedindesignorlicensingdocumentation.

GroundwaterIngress.

MaximumGroundwaterElevation.Theaveragegroundwaterelevationbeneaththesiteis+5feetmllw.

FluctuationswithinthepumpedregionsoftheSanOnofreCreekBasinhavehadlittleimpactonthelevel ofgroundwaterattheSONGSsitebecauseofitsproximitytotheshoreline.Monitoringofgroundwater levelsattheSONGSsitefora10yearperiodbetween1963and1974showedthewatertabletovaryfrom

+2.7feetto+5.7feetmllwinthevicinityofthecontainmentspheres[4].

KeyAssumptions.AsdiscussedintheSanOnofre2&3UFSARSection3.4.1.1.1[4],thefoundation basematsandexteriorwallsofthestructuresthatofferfloodprotectionaredesignedtoresisttheupward andlateralpressurescausedbythehydrostaticgroundwaterleveldesignbasiselevationof+5feetmllw.

DifferencesorContradictionsinFloodHazardLevels.Nodifferencesorcontradictionsinthefloodhazard levelswereidentifiedindesignorlicensingdocumentation.

FloodingHazardsthatScreenedOut.Thefollowingfloodmechanismswerenotconsideredcredibleeventsand werescreenedout:

IceInducedFlooding.Themildclimateandgenerallackoffreezingtemperaturesinthisregionmakeice formationhighlyunlikelyanditis,therefore,notconsideredcredible.

ChannelMigrationandDiversion.Upstreamdiversionsassociatedwithrivers,wherelowflowhasan impactondependablecoolingwatersources,isnotafactorattheSanOnofresite.

DamBreachandFailures.TherearenoupstreamdamsthatcouldimpacttheSanOnofresite.

Section B: Protection Mitigation Features Considered in the Licensing Basis Requested Information Describeprotectionandmitigationfeaturesthatareconsideredinthelicensingbasisevaluationtoprotectagainst externalingressofwaterintoSSCsimportanttosafety.

SONGS Response Thesafetyrelatedsystemsandcomponentsforwhichfloodprotectionisprovidedarethesameasthose identifiedinparagraphC.IofRegulatoryGuide1.29.Externalfloodprotectionofsafetyrelatedsystemsand

SONGS FLOOD WALKDOWN REPORT 6

componentsisprovidedforallpostulatedfloodlevelsandconditionsdescribedinSanOnofre2&3UFSARSection 2.4[4].

Descriptionsoftheprotectionandmitigationfeaturesthatareconsideredinthelicensingbasisevaluationto protectagainstexternalingressofwaterintoSSCsimportanttosafetyaredetailedintheSanOnofre2&3UFSAR Sections2.4and3.4[4].

FloodingLicensingBasis.ThePMFeventisapplicabletoallmodesofoperation(e.g.,fullpoweroperations, reducedpoweroperations,startup,hotshutdown,coldshutdown,andrefueling).The6hour,1squaremilePMP eventwouldcausethehighestfloodlevelontheSONGSsiteandisthereforeusedasthedesignbasisfloodevent.

ThemaximumpostulatedfloodlevelintheSONGSUnit2andUnit3powerblockisbelowelevation+31.0feet mllw[4].

FloodDurationAssumedintheCLB.Thedurationofthedesignbasisfloodeventisdefinedas6hours.The maximumpostulatedfloodlevelisbasedona12.25inch,6hourPMPevent[4].

FloodProtectionFeaturesthatareCreditedintheCLB.

IncorporatedorExteriorPassiveFloodProtectionFeatures.

1. Watercontrolstructuresconsistofthe42inchand72inchdiameterconcreteculvertsunderInterstate5.

TheculvertsaremaintainedbytheCaliforniaStateDepartmentofTransportation.Thecapacityofthese culvertsis180and520ft3/s,respectively.

2. TheSanOnofreCreekdiversionstructurelocatedalongtheeastsideofInterstate5divertsrunofffromthe FoothillDrainageBasintoSanOnofreCreekBasin.Thecapacityofthechannelis1,850ft3/s.

3. Two4footby4footboxculvertsatHighway101remainoperational.Theboxculvertsaresufficiently largeandinanareathatwouldnotsupplymaterialscapableofrestrictingflow.Evenifflowwere restricted,thetopographyalongHighway101issuchthattheresultingdrainageflowswouldnotimpact theplantsite.

4. Theswitchyardhasanupperandlowerbench.Withthenormalcatchbasinsplugged,thepondedwater ontheupperbenchwoulddraintothesouthaccessroad(nearSONGSUnit3).

5. Withthenormalcatchbasinsplugged,theuppersiteareawoulddrainintothebarrancaassociatedwith thesouthaccessroad.

6. AdiversionchannelatthesouthentrancetotheUnit3powerblockonthesouthsideoftheService Buildingdivertsrunofffromtheswitchyardanduppersiteareaovertheseawalloutsideofthepower block.

7. Swalesareprovidedintheasphaltareasaroundthepowerblocktoconveythedrainagetotheseawall, whereitwilldischargetotheocean.

8. Penetrationsintheauxiliarybuildingcontrolareaatelevations30and72feetmllwareprotectedagainst pondingresultingfromroofdrainagebyopeningsintheseismicgap,whichallowthewatertofallto elevation7feetintheturbinebuildingarea.Theroofdrainagecontributingtotheturbinebuildingareais fromthesafetyequipmentbuilding,theauxiliarybuilding,andtheturbineareas.

9. Tunnelsandopeningsbetweenbuildingsaresealedbywaterstops.

10. Surfacewaterwillnotentertheauxiliarybuildingfromthewestbecausethebridgewalkwayoverthe intakestructurehasnumerousparapetopeningsthatallowdrainagetoflowintothecoolingwaterintake structure.

11. Aconcretebermonthewestsideofthebridgewalkwaypreventsthecontrolroomcomplexfromflooding duetoapossiblesurgeinthecirculatingwatersystem.

SONGS FLOOD WALKDOWN REPORT 7

12. StormdrainageintheNorthIndustrialAreawillnotflowtoSONGSUnit2andUnit3becauseofan elevationdifferential;theNorthIndustrialAreaisatanelevationof20feetandSONGSUnit2andUnit3 areatanelevationof30feet.AlthoughtheNorthIndustrialAreaaccessroadconnectstotheaccessroad fortheUnit2andUnit3switchyard,theNorthIndustrialAreaaccessroadisgradedtoprecludedrainage flowsfromenteringtheSONGSsite.

13. Specialstructuresdesignedtoprotectthesiteagainstwaveactionincludetheseawallandthescreenwell perimeterwall.Theonshoreintakestructureisarrangedsothatallpenetrations,exceptinthescreenwell, aresealedagainstleakageofrisingorsurgingseawater.

14. Thefloodprotectionofallpenetrationsofsafetyrelatedstructuresthatarebelowthemaximum postulatedfloodlevel(+31.0feetmllw)aretabulatedinSanOnofre2&3UFSARTable3.41[4].

IncorporatedorExteriorActiveFloodProtectionFeatures.

1. WatertightandNonwatertightDoors-Thefloodprotectionofallexterioropeningsofsafetyrelated structuresbywatertightandnonwatertightdoorsthatarebelowthemaximumpostulatedfloodlevel

(+31.0feetmllw)aretabulatedinSanOnofre2&3UFSARTable3.41[4].

2. FloodSensors-Safetyrelatedareashavefloodlevelalarmsthatindicateinthecontrolroom.

WeatherConditionsorFloodLevelsthatTriggerProceduresandAssociatedActionsforProvidingFlood ProtectionandMitigation.TheSanOnofreAbnormalOperatingInstructionforSevereWeatherprovidesactionsto minimizetheeffectofhurricanes,tornados,flooding,ortsunamisonthesafeoperationofSONGSUnit2andUnit 3.Weatherconditionsconcerningexternalfloodingthattriggerthisprocedureincludethefollowing:flashflood watchorwarningoraheavyrainfallinprogress(rainfallisexpectedtoexceed3inchesina1hourperiodor6 inchesina3hourperiod),andtsunamiwarning.Notificationsourcesareprovidedintheoperatingprocedure.The associatedactionsforprovidingfloodprotectionandmitigationaredetailedintheattachmentstotheAbnormal OperatingInstructionforSevereWeatherforflashfloodwatchorwarningandtsunamiwarning.

ASanOnofreAlarmResponseInstructionprovidesoperatingpersonnelwithavailableoptionsorpossibilitiesfor dealingwithsingleormultiplealarminitiatingeventsincludingexternalfloodingofsafetyrelatedstructures.The associatedactionsforprovidingfloodprotectionandmitigationaredetailedintheprocedure.

AdverseWeatherConditionsthatwereAssumedConcurrentwithFloodProtectionFeaturesandAssociated Actions.Adverseweatherconditionsassumedconcurrentwiththeassociatedactionsforprovidingflood protectionandmitigationinclude,butarenotlimitedto,highwindsandheavyrainwithstandingwater.Noneof theseadverseweatherconditionswillimpedetheexecutionoftheSanOnofreAbnormalOperatingInstruction, SevereWeatherortheSanOnofreAlarmResponseInstruction.

Section C: Warning Systems to Detect the Presence of Water Requested Information Describeanywarningsystemstodetectthepresenceofwaterinroomsimportanttosafety.

SONGS Response WaterLevelWarningSystemsCredited.TheSONGSUnit2andUnit3areequippedwith92mechanicallyactuated floodsensorslocatedthroughoutsafetyrelatedareas,whichprovidethefirstindicationofwaterintrusionfrom internalandexternalsources.Floodsensoralarmsareindicatedoncontrolroomstatuspanels2(3)ZL94801and 94812.ASONGSAlarmResponseInstructionprovidesoperatingpersonnelwithavailableoptionsorpossibilities fordealingwithsingleormultiplealarminitiatingevents,includingexternalfloodingofsafetyrelatedstructures.

ScopeofWaterLevelWarningSystemsEvaluation.AsaresultofaTitle10CFR50.56MaintenanceRule evaluationandresultingcorrectiveactionforfloodsensors(externaltothefloodfeaturewalkdownprogram),a programwasinitiatedtoreplaceall92floodsensorswithina2yearperiodthatstartedinMarch2011.Asaresult

SONGS FLOOD WALKDOWN REPORT 8

ofthisreplacementprogram,credithasbeentakenforfloodsensorsthathavebeenreplacedorarescheduledfor replacementinlieuofavisualinspectionaspartofthefloodfeaturewalkdown.Seventyninefloodsensorswere replacedpriortotheinitiationofthewalkdownsandtheremaining13floodsensorsarescheduledfor replacementpriortotheendofthe2012calendaryear.Eachfloodsensormaintenanceplanwasreviewedto ensurethefloodsensors(1)havebeenorarescheduledtobereplaced,(2)werelastmonitoredortestedwithin periodicity,and(3)werescheduledforcontinuedmonitoringandtestingwithinperiodicityafterreplacement,and toensurethat(4)thescopeofthesurveillancewasadequatetoverifytheabilityofthefeaturetomeetitsCLB floodprotectionrequirement.

Section D: Effectiveness of Flood-Protection Features Requested Information Discusstheeffectivenessoffloodprotectionsystemsandexterior,incorporated,andtemporaryfloodbarriers.

Discusshowthesesystemsandbarrierswereevaluatedusingtheacceptancecriteriadevelopedaspartof RequestedInformationItem1.h.

SONGS Response PurposeoftheWalkdowns.Thepurposeofthefloodfeaturewalkdownwastoverifytheconformanceofexternal floodfeatureswiththeCLB.

Inadditiontothevisualcomponentofthefloodfeaturewalkdown,areviewofthepreventativemaintenanceand surveillanceprogramswasperformed.Thepurposeofthereviewwastovalidatethatthecreditedfeatureswere containedinaprogramthatwouldensuretheircontinuedconformancewiththeCLB.

DevelopmentoftheWalkdownFeatureList.TheCLBwasusedtodeterminewhatfloodfeatureswereincludedin thefloodfeaturewalkdownprogram.Sections2and3oftheSanOnofre2&3UFSARprovidedthebasisfor featurestobeincluded.Basedonthe16typesoffloodprotectionfeaturesdiscussedinSectionBofthisreport, thelistwaspopulatedwithatotalof729features(727physicalfeaturesand2procedures).

AcceptanceCriteriaDevelopment.SONGSadoptedageneralacceptancecriterionfromtheguidanceprovidedby NEI1207Section6andAppendixA[1]foreachtypeoffloodfeaturelistedinSectionB.Thisapproachis consistentwiththeRequestedInformationItem1.hfromEnclosure4ofthe50.54(f)letter[3].

TheacceptancecriteriaforeachfloodfeaturewereannotatedinPartB1ofthewalkdownrecordform,including anyacceptancecriteriafromtheCLBspecifictoagivenfloodprotectionfeature.

EvaluationoftheOverallEffectivenessofthePlantsFloodProtectionFeatures.

Procedures.Asiteprocedure,FukushimaEventResponse-FloodProtectionWalkdownScopingand Evaluation,wascreatedtoprovideguidanceforthescopingandevaluationprocess.Itincludestheflood featurewalkdownprocesstoensureauniformevaluationofthefloodprotectionfeaturesagainsttheCLB.

ThisprocedurewasdevelopedbasedontheguidanceprovidedinNEI1207[1].

Accessibility.Thefloodfeaturesthatcouldbeaccessedwereevaluatedagainstthedefinedacceptance criteriadocumentedonthefloodfeaturewalkdownrecordform.Thosefeaturesthatwererestrictedor inaccessiblewereenteredintothecorrectiveactionprogram(CAP).Floodfeaturesclassifiedas inaccessiblearediscussedinSectionFofthisreport.Floodfeatureswithpartialaccessibilitywere evaluatedagainsttheacceptancecriteria,asapplicable,todetermineifimmediateresponsewas warrantedpriortotheCAPrescheduleddate.

Effectiveness.Atotalof729floodprotectionfeatures(727physicalfeaturesand2procedures)were identifiedandevaluatedattheSONGSsiteanddocumentedonthefloodfeaturewalkdownrecordforms.

Theresultsofthefloodfeaturewalkdownprogramshowthatthefloodprotectionfeaturesare,withthe exceptionoftwoidentifieddeficiencies,effectiveinmeetingtheirintendedcreditedfunctionsbasedupon

SONGS FLOOD WALKDOWN REPORT 9

thedefinedacceptancecriteria.Inthosecaseswhereobservationssuggestedthatacceptancecriteria werenotmetorwerequestionable,thepotentialissuewascapturedintheSONGSCAPtodetermineifit isadeficiencyandwhatactionsaretobetaken.

SectionFofthisreportprovidesadetaileddiscussionoftheresultsfromthefloodfeaturewalkdown program.

OtherExistingPlantEquipment,Structures,andProceduresthatMightMitigatetheEffectsofanExternalFlood underaVarietyofPlantConfigurations.Catchbasinsforthesubsurfacedrainagesystem,roofdrains,andexposed floordrainsareassumedpluggedforthepurposeofdeterminingwatersurfaceelevationsarisingduringthe thunderstormPMPevent.Sumppumpsandfloordrainsinternaltosafetyrelatedbuildingsarenotcreditedto removewaterduringafloodingevent.Thesefeatureswerenotincludedinthescopeofthefloodwalkdowneffort, butmightbeavailabletomitigatetheeffectsofanexternalfloodevent.

AssessmentofMaintenanceandMonitoringProgramsforFloodProtectionFeatures.Areviewofperiodic maintenance(PM),surveillance,periodicmonitoring,andfunctionaltestingrequirementsforeachoftheflood protectionfeatureswasperformed.ResultsweredocumentedontheNEI1207walkdownrecordforms(PartB.2).

ThePM,surveillance,periodicmonitoring,and/orfunctionaltestingwasconsideredacceptableifitwas(1)within thescopeofaprogramorprocedure,(2)waslastmaintained,monitored,ortestedwithinperiodicity,and(3)was scheduledforfuturemaintenance,monitoring,and/ortestingwithinperiodicity;and(4)ifthescopeofthePM, surveillance,ortestwasadequatetoverifytheabilityofthefeaturetomeetitsCLBfloodprotectionrequirement.

AssessmentofMaintenanceActivitiesthatExposeSSCstoFloodHazards.Plantprogramsevaluatetheimpactof plantactivities,includingmaintenanceactivities,ontheabilityofidentifiedfloodprotectionfeaturestoperform theircreditedfunction.Compensatorymeasuresrequiredbysiteprogramsareimplemented,whenrequired,to ensurethatthefloodprotectionfunctionismaintained.

Section E: Implementation of the Walkdown Process Requested Information Presentinformationrelatedtotheimplementationofthewalkdownprocess(e.g.,detailsofselectionofthe walkdownteamandprocedures)usingthedocumentationtemplatediscussedinRequestedInformationItem1.j, includingactionstakeninresponsetothepeerreview.

SONGS Response WalkdownGuidanceandExceptions.

Procedures.ToensureNEI1207guidancewasfollowed,asitespecificprocedure,FukushimaEvent Response-FloodProtectionWalkdownInspectionProcess,forguidingtheinspectionprocesswascreated toensurecompliancewiththefloodfeaturewalkdownexecutionanddocumentationbasedonthecriteria outlinedinNEI1207Sections5.3,7,andAppendixB[1].

WalkdownPackages,PreJobBrief,andPostJobBrief.Thefloodfeaturewalkdownpackageswere developedbaseduponthespecificguidanceprovidedinNEI1207Section5.2,PrepareWalkdown Packages[1],whichincludedthefollowingcomponents:PreJobBrief,WalkdownGuidanceand AcceptanceCriteria,WalkdownRecordForm,DesignDrawings,GeneralArrangementDrawings,andFlood ProtectionStrategyImplementationProcedures.

Eachprejobbriefcontainedthefollowing:IndustrialSafety,RadiologicalSafety,DoseRequirements, AcceptanceCriteria,PlantStatus,IndustryOperatingExperience,ProcedureCompliance,Reporting DegradedConditions,PositiveComponentVerification,InspectionMethodology,andFieldDocumentation Requirements.

SONGS FLOOD WALKDOWN REPORT 10 Atthecompletionofeachdayduringthepostjobbrief,thewalkdownteamwoulddiscusslessonslearned forthatdayandtheinspectionplanforthenextdaysfloodfeatures.

Exceptions.NoexceptionsweretakentotheendorsedguidanceofNEI1207[1].

TeamOrganization.TheSONGSfloodprotectionwalkdownteamwascomposedofqualifiedindividualsofvarious technicaldisciplines,asshowninExhibitE1:SONGSFloodFeatureWalkdownTeamComposition.Assuggestedby NEI1207Section5.3[1],multipleskillsetswereavailabletoparticipateintheevaluationofagivenflood mitigationfeaturedependingontheintendedcreditedfunction.Eachfloodmitigationfeaturewasevaluatedbya minimumoftwoindividualsfromtheteam.

EXHIBITE1 SONGSFloodFeatureWalkdownTeamComposition WalkdownExecutionTeam YearsofExperience SONGSOversight YearsofExperience SeniorNuclearConsultant 40 ProjectManager (SeniorElectricalEngineer) 30 NuclearConsultant 13 TaskTechnicalLead (SeniorCivilEngineer) 15 LicensingandHydrogeologist Consultant 15 CivilEngineer 25 NuclearConsultant 6

ConsultingSeniorMechanical Engineer 36

CivilEngineer 10

CompliancewithSection5.3ofNEI1207.Thefloodfeaturewalkdownteammembersrepresentedfivediscipline areas,asshowninExhibitE1.Theexecutionteamswerepairedtoensurethatcomplementaryskillsetswere activelyengagedineachfeatureevaluation(e.g.,pairinglicensingexpertisewithfield/inspectionexperience).

ThefloodfeaturewalkdownteamwasmadefamiliarwiththeinformationrequiredtorespondtoSECY110137 Items2.1(FloodHazardEvaluation)and2.3(FloodWalkdown)[2],aswellas50.54(f)letterEnclosures2and4[3].

Thefloodfeaturewalkdownteammembers(excludingcraftsupport,healthphysicspersonnel,etc.)werealso currentinNEIdevelopedtrainingprovidedthroughtheNANTeLwebsite(https://nantel.org).Inadditiontothe NANTeLtraining,sitespecifictrainingwasdevelopedanddeliveredtofurtherenhancetheteamsunderstanding oftheimportanceofthefloodfeaturewalkdownprogram.Alltrainingrecordsforfloodfeaturewalkdownteam participantsaredocumentedintheSONGStrainingrecordsdatabase.

Thesiteproceduredevelopedtogoverntheinspectionprocessincludedaqualificationsmatrix,whichcomplies withSection5.3andAppendixCofNEI1207[1].

Section F: Results of the Flood Feature Walkdown Requested Information Resultsofthewalkdownincludingkeyfindingsandidentifieddegraded,nonconforming,orunanalyzed conditions.Includeadetaileddescriptionoftheactionstakenorplannedtoaddresstheseconditionsusingthe guidanceinRegulatoryIssuesSummary200520,Rev1,RevisiontoNRCInspectionManualPart9900Technical Guidance,OperabilityConditionsAdversetoQualityorSafety,includingenteringtheconditioninthecorrective actionprogram.

SONGS FLOOD WALKDOWN REPORT 11 SONGS Response SummaryofFindings.TheplantfloodprotectionfeatureswerefoundtobeasdescribedintheCLB(available, functional,andmaintained),withjustafewexceptionsthatareconsidereddeficiencies.Thesedeficienciesare describedintheDeficienciessectionbelow.Thedeficienciesnotwithstanding,thefloodprotectionfeaturesin aggregatewouldperformtheirdesignfunctionascreditedintheCLB.Detailedobservations,photographs,and qualitativedispositionswereenteredintotheSONGSRecommendation2.3FloodFeaturesDatabaseforeach featureandhavebeentransmittedtocentraldocumentmanagement(CDM).

TwentyfivefloodfeatureswereaddedtotheCAPformaterialordesignevaluationandwereannotatedinthe walkdownrecordforms.Ofthe25itemsaddedtotheCAP,7wereevaluatedfordeficiencydeterminationand2 deficienciesweredeterminedpertheCAP(see"Deficiencies"sectionbelowforfurtherdiscussiononthefeatures identifiedasdeficiencies).

GenericissuesidentifiedduringthewalkdownsandenteredintotheCAP,butnotconsidereddeficiencies,include thefollowing:

Penetrationsealsandfloodfeatureswithincorrectormissingidentificationtags MaterialconditionissuesthatdonotchallengetheabilityofthefeaturetomeettheCLBfloodprotection requirement FeaturesnotlistedintheSanOnofre2&3UFSAR Errorsindrawingsordocuments Operationsprocedurecorrectionsandenhancements(asdiscussedbelow)

Floodfeatureproceduralmonitoringenhancements(asdiscussedbelow)

Ofthe727physicalfloodfeatures,21weredeterminedtohaverestrictedaccessandwereenteredintotheCAP forfutureschedulinganddisposition.Additionally,10floodfeaturesweredeterminedtobeinaccessibledueto eitherametallicbelloworsteelplatestructureobstructingthefeature.SONGSengineeringpersonnelperformed anevaluationofeachinaccessiblefeatureanddeterminedthefeaturesarecapableofperformingtheircredited CLBfunction(see"FeaturesthatareInaccessible"sectionbelowforfurtherdiscussion).

Ofthe727physicalfloodfeatures,allwereincludedinapreventativemaintenanceorsurveillanceprogramwith theexceptionof39features.These39featureswereenteredintotheCAPfordeterminationoftheneedtobe includedinapreventativemaintenanceorsurveillanceprogram.ThelackofinclusionwasdeterminedbytheCAP nottobeadeficiencyofthepreventativemaintenanceorsurveillanceprograms.

Floodsensorscreditedfordetectingexternalandinternalfloodingwerereviewedthoughtherespective maintenanceplansandthereplacementprogram.Thereviewconsistedof(1)evaluatingtoensuretheflood sensorhasbeenreplacedorisscheduledforreplacementperplantschedule,and(2)thefloodsensorisscheduled formaintenanceandtestingontherequiredperiodicityafterthereplacementdate.Noadversefindingswere determined.AdditionalinformationconcerningfloodsensorsisprovidedaboveinSectionC:WarningSystemsto DetectthePresenceofWater.

Twositeproceduresarecreditedforresponsetoexternalfloodresponseandwereevaluatedusingareasonable simulationasdescribedintheNEI1207guidance[1].Thereasonablesimulationconsistedofasimulatedsevere stormreachingthecriteriaofentryrequiringoperatoractiontovalidatetheplantconfiguration.Subsequently,a simulatedsignificantrainfallwasinitiatedresultinginfloodsensoralarmresponsefromsimulatedwateringress perthealarmresponseprocedure.Thisresultedinoperatorresponseinthreelocations,twoinSONGSUnit3and oneinSONGSUnit2.Asaresultoftheproceduresimulation,twononsafetyrelateditemswithintheprocedures wereidentifiedasneedingtobeaddressedandseveralenhancementsweresuggestedtolessenoperatorburden inidentifyingthereferencedfeatures.TheseitemswereenteredintotheCAP.Noneoftheidentifieditemsor suggestionswasdeterminedbytheCAPtobeadeficiencytotheprocedures.Theresultsofthereasonable

SONGS FLOOD WALKDOWN REPORT 12 simulationgoverningsitepreparationandresponseforthelicensingbasisfloodeventwereadequateandcouldbe completedwithinthewarningtime,asspecifiedintheprocedures.

Additionally,trainingfortheprocedureswasdeterminedtobeadequate.Thecriteriafortrainingadequacywere determinedby(1)thesuccessfulperformanceoftheseverestormsimulationinwhichtheprocedureswere implemented,and(2)reviewandvalidationoftrainingrecordsandperiodicity.Alltrainingrecordsareavailablein theSONGStrainingrecordssystem.

DescriptionofAnyObservationsReportedintheCAPthatWereNotDispositioned.Allfloodfeaturewalkdown observationsenteredintotheCAPhavebeenscreenedandassociatedactionshavebeenassigned.

Deficiencies.AsdeterminedbytheCAP,twofeaturesweredeterminedtobedeficienciesmeetingthecriteriaof degraded,nonconforming,orunanalyzed.Thetwodeficienciesarediscussedbelowinthenextsubsection, providingcondition,descriptionoffeature,functionallocation,discussionofthedegradedornonconforming condition,actionstaken,andanticipatedcompletiondateforrepairs.Althoughthesefeaturesaredefinedas deficiencies,theyposelimitedrisktoplantoperationsastheyarepassiveexternalpenetrationsthatprotect againstexternalwateringressanddonotprovidecriticalsafetyfunctionstoensureplantsafetyrelatedequipment canperformtheintendedfunctions.

DescribeActionsthatWereTakenorArePlannedtoAddresstheDeficiencies.Thefollowingactionsweretake orareplannedtoaddressthedeficiencies:

DegradedUnit3RoofDrainPipe(FunctionalLocationS3.PENS.EGT011.502720303).Severecorrosionand widecrackswereidentifiedonthecastirondrainpipeservicingtheroofoftheUnit3Underground ElectricalandPipingGalleriesStructure.ThisconditionrepresentsaleakagepathintotheUnit3 UndergroundElectricalGalleriesTunnelduringapostulatedPMPevent.Thedrainattheroofhasbeen pluggedtopreventwaterfromleakingintotheundergroundtunnelthroughthefaileddrainpipe.Anorder hasbeengeneratedtoreplacethedegradeddrainpipe.TheanticipatedcompletiondatefortherepairJuly 2013.

NonConformingUnit3UndergroundElectricalCableTunnelDuctBankSeal,Conduit1of4(Functional LocationS3.PENS.UCT009.502520143).Waterstaining,corrosion,andmissingfireprotectionsealmaterial wereidentifiedforanelectricalconduitthatispartofaductbankpenetratingtheUnit3Underground CableTunnel.Thisconditionrepresentsaleakagepathfromanoutsideelectricalmanholeintothe UndergroundCableTunnelthroughtheunsealedconduitduringapostulatedexternalfloodingevent.The surfacecoverattheoutsidemanholecoverissealed,significantlyrestrictingtheamountofwaterthat couldtravelintotheundergroundtunnelthroughtheconduit.Asaresultofthewalkdowneffort,awork orderwasgeneratedtoinstallthesealintheconduit.Thesealwasinstalled10/24/2012andthecondition isnolongeradeficiency.

FeaturesAffectedbyRestrictedAccess.DuringthecourseoftheSONGSFloodFeatureWalkdownProgram,21 featureswereaffectedbyrestrictedaccess.

JustificationforDelay.Thebulletedlistbelowprovidesthevariousjustificationsfordelayandrequiredaction togainaccess.

Fireretardantormetallicinsulationobstructingvisualinspection Mitigation:scheduleinspectioninfuturewithmaintenancesupporttoremoveinsulation Featureatanelevationrequiringscaffolderectiontoallowforvisualinspection Mitigation:scheduleinspectioninfuturewithmaintenancesupporttoerectscaffolding Featureobstructedbyinstalledplantsystems,structures,and/orcomponents Mitigation:scheduleinspectioninfuturewithmaintenancesupportfornextscheduledpreventative maintenanceorsurveillance

SONGS FLOOD WALKDOWN REPORT 13 ScheduleforCompletionofInspection.AllrestrictedaccessinspectionswillbecompletedbyJuly2013.

SpecialProceduresRequiredforInspection.Nospecialproceduresarerequiredforinspectionofthe restrictedaccessfeatures.Thefeaturesrequireadditionalplantsupportthatwasnotavailableduetonormal plantoperations.

FeaturesthatareInaccessible.Tenfeaturesweredeterminedtobeinaccessibleandaredescribedbelow.

1. RubberWaterstopsbetweentheContainmentStructure(RecirculatingRooms)andtheSafetyEquipment Building.EachSONGSUnitContainsOneWaterstopatthisLocation.

ReasonInaccessible Thewaterstopsarecoveredbymetalbellowsweldedtothepermanentstructure.Inspectionwouldrequire majordisassembly.

FunctionalRequirement Rubberwaterstopspreventorlimitwaterintrusionattheseismicgapsothatsafetyrelatedequipmentisnot impactedbythefloodlevel.

Location Waterstopsarelocatedintherecirculationrooms(bottomelevation12'9"mllw)intheseismicgapbetween structures.TheroomisaccessedfromtheContainmentTendonGallery.

BasisforReasonableAssurancethatFeatureisAvailableandFunctional Potentialwaterinleakageatwaterstopshasbeenevaluatedinanexistingdesigncalculation.TheSONGS calculationforPlantFloodAnalysisReviewpostulatedtheworstcasescenariobypositioningacrackinthe rubberwaterstopatthelowestelevation,12'9"mllw.Thepredictedleakagerateduetoanexternalsourceis muchlessthanfloodingduetoaninternalcomponentfailureoractuationofthefireprotectionsprinklers.A safetyrelatedfloodsensorislocatedineachrecirculationroomandalarmsintheControlRoom,with operatorresponsespecifiedintheAlarmResponseInstruction.Theseflooddetectorshaverecentlybeen replacedandhaveperiodicfunctionaltesting.Therefore,thefloodeffectsareboundedandthereisnoadverse impacttosafetyrelatedequipment.

AggregateEffects Thereisnocommonfailuremechanismfortherubberwaterstopsduringthecurrentlicensingbasisflood event(PMP).Floodsensorsarelocatedineachrecirculationroom,sooperatorresponsewouldlimitflood effectsandpreventimpactstosafetyrelatedequipmentfromgroundwateringress.

2. WaterstopsbetweentheAuxiliaryControlBuilding(ChilledWaterTunnel)andtheSafetyEquipment Building.SharedWaterstopatNorthandSouthEndoftheTunnel.

ReasonInaccessible Thewaterstopsarecoveredbymetalbellowsweldedtothepermanentstructure.Inspectionwouldrequire majordisassembly.

FunctionalRequirement Rubberwaterstopspreventorlimitwaterintrusionattheseismicgapsothatsafetyrelatedequipmentisnot impactedbythefloodlevel.

Location WaterstopsarelocatedintheChilledWaterPipingtunnel(bottomelevation5'11"mllw)intheseismicgap betweentheSafetyEquipmentBuildingandtheAuxiliaryControlBuilding.

BasisforReasonableAssurancethatFeatureisAvailableandFunctional

SONGS FLOOD WALKDOWN REPORT 14 Potentialwaterinleakageatwaterstopshasbeenevaluatedinanexistingdesigncalculation.TheSONGS calculationforPlantFloodAnalysisReviewpostulatedtheworstcasescenariobypositioningacrackinthe rubberwaterstopatthelowestlevelelevation,12'9"mllw.Thepredictedleakagerateduetoanexternal sourceismuchlessthanfloodingduetoaninternalcomponentfailureoractuationofthefireprotection sprinklers.AsafetyrelatedfloodsensorislocatedineachchilledwaterpipingtunnelandalarmsintheControl Room,withoperatorresponsespecifiedintheAlarmResponseInstruction.Theseflooddetectorshave recentlybeenreplacedandhaveperiodicfunctionaltesting.Therefore,thefloodeffectsareboundedand thereisnoadverseimpacttosafetyrelatedequipment.

AggregateEffects Thereisnocommonfailuremechanismfortherubberwaterstopsduringthecurrentlicensingbasisflood event(PMP).Floodsensorsarelocatedineachchilledwatertunnel,sooperatorresponsewouldlimitflood effectsandpreventimpactstosafetyrelatedequipmentfromgroundwateringress.

3. WaterstopsbetweentheAuxiliaryPenetrationAreaandtheSafetyEquipmentBuilding(ShutdownHeat ExchangerPipingTunnel).EachSONGSUnitContainsOneWaterstopatthisLocation.

ReasonInaccessible Thewaterstopsarecoveredbymetalbellowsweldedtothepermanentstructure.Inspectionwouldrequire majordisassembly.

FunctionalRequirement Rubberwaterstopspreventorlimitwaterintrusionattheseismicgapsothatsafetyrelatedequipmentisnot impactedbythefloodlevel.

Location WaterstopsarelocatedintheShutdownHeatExchangerPipingTunnel(elevation8'6"mllw)intheseismicgap betweentheAuxiliaryPenetrationstructureandSafetyEquipmentBuilding.

BasisforReasonableAssurancethatFeatureisAvailableandFunctional Potentialwaterinleakageatwaterstopshasbeenevaluatedinanexistingdesigncalculation.TheSONGS calculationforPlantFloodAnalysisReviewpostulatedtheworstcasescenariobypositioningacrackinthe rubberwaterstopatthelowestlevelelevation,12'9"mllw.Thepredictedleakagerateduetoanexternal sourceismuchlessthanfloodingduetoaninternalcomponentfailureoractuationofthefireprotection sprinklers.AsafetyrelatedfloodsensorislocatedineachtunnelandalarmsintheControlRoom,with operatorresponsespecifiedintheAlarmResponseInstruction.Theseflooddetectorshaverecentlybeen replacedandhaveperiodicfunctionaltesting.Therefore,thefloodeffectsareboundedandthereisnoadverse impacttosafetyrelatedequipment.

AggregateEffects Thereisnocommonfailuremechanismfortherubberwaterstopsduringthecurrentlicensingbasisflood event(PMP).Floodsensorsarelocatedineachshutdownheatexchangerpipingtunnel,sooperatorresponse wouldlimitfloodeffectsandpreventimpactstosafetyrelatedequipment.

4. WaterstopsbetweentheAuxiliaryPenetrationAreaandtheSafetyEquipmentBuilding (Corridor027).EachSONGSUnitContainsOneWaterstopatthisLocation.

ReasonInaccessible Thewaterstopsarecoveredbysteelplatesfastenedtothepermanentstructure.Inspectionwouldrequire majordisassembly.

FunctionalRequirement

SONGS FLOOD WALKDOWN REPORT 15 Rubberwaterstopspreventorlimitwaterintrusionattheseismicgapsothatsafetyrelatedequipmentisnot impactedbythefloodlevel.

Location WaterstopsarelocatedintheseismicgapbetweentheAuxiliaryPenetrationAreaandtheSafetyEquipment Building(bottomoftheopeningiselevation8'0"mllw).

BasisforReasonableAssurancethatFeatureisAvailableandFunctional Thebottomofthewaterstopislocatedabovethesitegroundwaterlevel.Potentialwaterinleakageat waterstopshasbeenevaluatedinanexistingdesigncalculation.TheSONGScalculationforPlantFloodAnalysis Reviewpostulatedtheworstcasescenariobypositioningacrackintherubberwaterstopatthelowestlevel elevation,12'9"mllw.Thepredictedleakagerateduetoanexternalsourceismuchlessthanfloodingdueto aninternalcomponentfailureoractuationofthefireprotectionsprinklers.Inleakageatthewaterstopatthis locationwouldbecontainedinthecorridorduetoasteelfloodbarrieratthewestendofthecorridorand watertightdoorsattheotheropenings.Thereisnoadverseimpacttosafetyrelatedequipment.

AggregateEffects Waterinleakageiscontainedinthecorridorandthereisnoimpacttosafetyrelatedequipment.

5. WaterstopsforthePipingOpeningbetweentheAuxiliaryPenetrationAreaandtheSafetyEquipment Building(FLOCsS2.PENS.SE00802620012andS3.PENS.00802620033).EachSONGSUnitContainsOne WaterstopatthisLocation.

ReasonInaccessible Thewaterstopsarecoveredbysteelplatesfastenedtothepermanentstructure.Inspectionwouldrequire majordisassembly.

FunctionalRequirement Rubberwaterstopspreventorlimitwaterintrusionattheseismicgapsothatsafetyrelatedequipmentisnot impactedbythefloodlevel.

Location WaterstopsarelocatedintheseismicgapbetweentheAuxiliaryPenetrationAreaandtheSafetyEquipment Building(bottomofopeningiselevation19'6"mllw).

BasisforReasonableAssurancethatFeatureisAvailableandFunctional Thebottomofthewaterstopislocatedabovethesitegroundwaterlevel.Potentialwaterinleakageat waterstopshasbeenevaluatedinanexistingdesigncalculation.TheSONGScalculationforPlantFloodAnalysis Reviewpostulatedtheworstcasescenariobypositioningacrackintherubberwaterstopatthelowestlevel elevation,12'9"mllw.Thepredictedleakagerateduetoanexternalsourceismuchlessthanfloodingdueto aninternalcomponentfailureoractuationofthefireprotectionsprinklers.Inleakageatthewaterstopwould flowthroughflooraccessopeningstoelevation5'6"mllwandbecontainedintheComponentCoolingWater PipingArea.ThereisasafetyrelatedfloodsensorinthisareathatalarmsintheControlRoom,withoperator responsespecifiedintheAlarmResponseInstruction.Theseflooddetectorshaverecentlybeenreplacedand haveperiodicfunctionaltesting.Therefore,thefloodeffectsareboundedandthereisnoadverseimpactto safetyrelatedequipment.

AggregateEffects Thereisnocommonfailuremechanismfortherubberwaterstopsduringthecurrentlicensingbasisflood event(PMP).Waterinleakagewouldcollectinanareawithfloodsensors;operatorresponsewouldlimitflood effectsandpreventimpacttosafetyrelatedequipment.

SONGS FLOOD WALKDOWN REPORT 16 WalkdownRecordForms.Thewalkdownrecordformshavebeencompletedanddetailedobservations, photographs,andqualitativedispositionswereenteredintotheSONGSRecommendation2.3FloodFeatures DatabaseforeachfeatureandhavebeentransmittedtoCDM.

Section G: Cliff-Edge Effects Requested Information Documentanycliffedgeeffectsidentifiedandtheassociatedbasis.Indicatethosethatwereenteredintothe correctiveactionprogram.Alsoincludeadetaileddescriptionoftheactionstakenorplannedtoaddressthese effects.

SONGS Response CliffEdgeEffectsandPhysicalMargins.AsindicatedinSection3.12ofNEI1207[1],theNRCisnolonger expectingtheRecommendation2.3:FloodingWalkdownsofthe50.54(f)letter[3]toincludeanevaluationofcliff edgeeffects.Theavailablephysicalmargin(APM)hasbeenestimatedanddocumented,asapplicable,inthe walkdownrecordforms.TheguidanceprovidedinNEIFAQ006wasalsofollowed.Thisinformationwillbeusedin thefloodhazardreevaluationsperformedinresponsetoItem2.1:Floodinginthe50.54(f)letter[3].

Section H: Other Planned and/or Newly Installed Flood-Protection Features or Measures Requested Information Describeanyotherplannedornewlyinstalledfloodprotectionsystemsorfloodmitigationmeasuresincluding floodbarriersthatfurtherenhancethefloodprotection.Identifyresultsandanysubsequentactionstakenin responsetothepeerreview.

SONGS Response ChangesDeterminedtobeNecessary.FloodprotectionfeatureswithlowAPMhavebeenenteredintotheCAP forfurtherevaluationandconsiderationtoincreasemargin.

Conclusion The727identifiedplantfloodprotectionphysicalfeatures,themajorityofwhichwereincorporatedpassive protectionfeatures,werefoundtobeasdescribedintheCLB(available,functional,andmaintained)withafew exceptionsasdescribedinSectionF:Deficiencies.Thedeficienciesnotwithstanding,thefloodprotectionfeatures inaggregatewouldperformtheirdesignfunctionascreditedintheCLB.Asummaryofthefindingsisbelow.

Additionalfloodprotectionfeatureswereidentifiedduringthefloodwalkdownthatprotectagainstexternal ingressofwaterintoSSCsimportanttosafetybutnotincludedintheSanOnofre2&3UFSAR[4].Thesefeatures wereevaluatedaccordingtoacceptancecriteriadevelopedforsimilarfloodprotectionfeaturesandwerefoundto meettheacceptancecriteria.TheseitemswereaddedtotheCAPandwillbeevaluatedfortheirneedtobe includedintheSanOnofre2&3UFSAR.

Deficiencies Twoobservationsweredeterminedtobedeficiencies(seeSectionF:Deficiencies).Thetwodeficiencieswere enteredintotheCAP.Oneofthedeficiencieswassubsequentlycorrected,andthecorrectiveactionfortheother deficiencyisanticipatedtobecompletebyJuly2013.Thesedeficienciesarepassiveexternalpenetrationsthat protectagainstexternalwateringressandarenotrequiredforplantsafetyrelatedequipmenttofunction.

SONGS FLOOD WALKDOWN REPORT 17 Restricted-Access Flood Features Twentyonefloodfeaturesweredeemedrestrictedaccessandrequirefutureschedulinganddisposition.

RestrictedaccessfeatureshavebeenenteredintotheCAPandaddedtotheworkweekprocesstoalignplant support.Allrestrictedaccessfeatureswillbetrackedbytheirrespectivemaintenanceordersandarecurrently scheduledforvisualinspectionbyJuly2013.

Inaccessible Flood Features TenfloodfeaturesweredeemedinaccessibleandenteredintotheCAPforengineeringevaluation.Thesefeatures wereevaluatedbySONGSengineeringpersonnelanddeterminedtohavereasonableassurancethattheywill performtomeettheirintendedCLBfunction.TheSONGScalculationforPlantFloodAnalysisReviewpostulated theworstcasescenariobypositioningacrackintherubberwaterstopatthelowestlevelelevation,12'9"mllw.

Thepredictedleakagerateduetoanexternalsourceismuchlessthanfloodingduetoaninternalcomponent failureoractuationofthefireprotectionsprinklers.

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