ML16365A194

Mitigating Strategies Assessment (MSA) for Flooding Submittal

ML16365A194
Person / Time
Site:	Grand Gulf
Issue date:	12/30/2016
From:	Fallacara V Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CAC MF1102, EA-12-049, GNRO-2016/00053
Download: ML16365A194 (16)

Text

GNRO-2016/00053 December 30,2016U.S.NuclearRegulatoryCommissionAttn:DocumentControlDeskWashington,DC20555-0001 Entergy Operations, Inc.P.o.Box 756PortGibson,MS39150 Vincent FallacaraVicePresident,OperationsGrandGulfNuclearStationTel.(601)437-7500

SUBJECT:

Mitigating Strategies Assessment(MSA)forFloodingSubmittalGrandGulfNuclearStation,Unit1DocketNo.50-416LicenseNo.NPF-29

REFERENCES:

1.NRClettertoEntergy, RFI PursuanttoTitle 10 oftheCode of Federal Regulations 50.54(f)Regarding Recommendations2.1,2.3, and 9.3 of the NTTF Review of Insightsfromthe Fukushima Dai-ichi Accident, datedMarch12,2012 (GNRI-2012/00059)(ML12053A340)2.EntergylettertoNRC, ResponsetoMarch 12, 2012, Request for Information, Enclosure 2, Recommendation 2.1, Flooding, Required Response 1, Integrated Assessment Approach,datedJanuary29,2013 (GNRO-2013/00002)(ML13029A627).3.EntergylettertoNRC, Required Response 2forNear-TermTaskForce Recommendation 2.1: Flooding-Hazard Reevaluation Report, datedMarch11,2013 (GNRO-2013/00020)(ML13071A457)4.EntergylettertoNRC, Grand Gulf Nuclear Station Request for Additional Information Regarding Flooding Hazard, dated December 11, 2013,datedJanuary9,2014 (GNRO-2014/00005)(ML14014A277) 5.NRC Staff Requirements Memoranda to COMSECY-14-0037,"Integration of Mitigating Strategies for Beyond-Design-Basis ExternalEventsandthe Reevaluation of Flooding Hazards",datedMarch30,2015(ML15089A236)6.NRCLetter, Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events, dated September1,2015(ML15174A257)7.NuclearEnergyInstitute(NEI), Report NE112-06[Rev 2J,DiverseandFlexibleCoping Strategies (FLEX)Implementation Guide, dated December2015(ML15348A015)8.NRCLettertoEntergy,GrandGulfNuclearStation,Unit1, Supplement to Staff Assessment of Response to 10CFR50.54(f)

Information Request-Flood-Causing Mechanism Reevaluation,datedDecember4,2015(CACNO.MF1102)

GNRO-2016/00053Page2of39.U.S.NuclearRegulatoryCommission, JLD-ISG-2012-01,Revision1, Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigating Strategies for Basis External Events,datedJanuary22,2016(ML1537A163)

DearSirorMadam:

OnMarch12,2012,theUSNuclearRegulatoryCommission(NRC)issuedarequestforinformationpursuanttoTitle10oftheCodeofFederalRegulations,Section50.54(f)(Reference1).TherequestwasissuedaspartofimplementinglessonslearnedfromtheaccidentattheFukushimaDai-ichinuclearpowerplant.Enclosure2tothe50.54(f)letterrequestedlicenseestoreevaluateflood-causingmechanismsusingpresent-daymethodologiesandguidance.GrandGulfNuclearStation(GGNS)respondedtothe50.54(f)letterbyReferences2and3.SupplementalinformationwasprovidedinReference4.Concurrenttothefloodhazardreevaluation,GGNSdevelopedandimplementedmitigatingstrategiesinaccordancewithNRCOrderEA-12-049,"OrderModifyingLicenseswithRegardtoRequirementsforMitigationStrategiesforBeyondDesign-BasisExternalEvents".InReference5,theNRCaffirmedthatlicenseesneedtoaddressthereevaluatedfloodinghazardswithintheirmitigatingstrategiesassessment(MSA)forbeyond-designbasis(BDB)externalevents,includingthereevaluatedfloodhazards.ThisrequirementwasconfirmedbytheNRCinReference6.GuidanceforperformingMSAforFloodingiscontainedinAppendixGofReference6,endorsedbytheNRCinReference9.ForthepurposeoftheMSAforFloodingandinReference6,theNRCtermedthereevaluatedfloodhazard,summarizedinReference8,asthe"MitigatingStrategiesFloodHazardInformation"(MSFHI).Reference6,AppendixG,describestheMSAforFlooding.InReference8,theNRCconcludedthatthe"reevaluatedfloodhazardsinformation,assummarizedinthe Attachmenttothisletter,issuitablefortheassessmentofmitigatingstrategiesdevelopedinresponsetoOrderEA-12-049"forPlantandUnit.TheuseofthesandbagsasdiscussonpagefiveandtenoftheattachmenthasbeenidentifiedasanonconformingconditionfortheuseofmanualoperatoractionsinplaceofapermanentplantmodificationandisbeingaddressedthroughtheGrandGulfCorrectiveActionProgram.TheAttachmenttothisletterprovidestheMitigatingStrategies AssessmentforFloodingReportforGrandGulfNuclearStation,Unit1.The assessmentconcludedthattheexistingFLEXstrategycanbesuccessfullyimplementedanddeployedasdesignedforallapplicable-floodcausingmechanisms.ThislettercontainsnonewRegulatoryCommitments.Ifyouhaveanyquestionsorrequireadditionalinformation,pleasecontactJamesNadeauat 601-437-2103.Ideclareunderpenaltyofperjurythattheforegoingistrueandcorrect.ExecutedonDecember 30,2016.VF/sas

Attachment:

2016MitigatingStrategies AssessmentforFloodingDocumentationRequirementsatGrandGulfNuclearStation GNRO-2016/00053Page3of3cc:U.S.Nuclear Regulatory CommissionATTN:Mr.JimKim, NRR/DORL (w/2)MailStopOWFN8 B1Rockville,MD 20852-2738U.S.Nuclear Regulatory CommissionATTN:Mr.KrissM.Kennedy(w/2)

Regional Administrator,RegionIV1600EastLamarBoulevardArlington,TX76011-4511Mr.B.J.Smith(w/2)Director,DivisionofRadiologicalHealthMississippiState DepartmentofHealthDivisionofRadiologicalHealth3150LawsonStreetJackson,MS39213NRCSeniorResident InspectorGrandGulfNuclearStationPortGibson,MS39150 Attachment to GNRO-2016/000532016Mitigating Strategies AssessmentforFlooding Documentation Requirements atGrandGulf Nuclear Station r------------------------------.-------.--------,EngineeringReport No.GGNS-SA-16-0000tRev0 Page of U ENTERGY NUCLEAR Engineering Report Cover Sheet Engineering Report Title: 2016lVUTIGATING STRATEGIES ASSESSlVlENT FOR FLOODING DOCUMENl'ATION REQUIRE1\'1ENTS AT GRAND GULF NUCLEAR STATION New k8J Engineering Report Type: Revision 0 Cancelled 0 Superseded 0 Superseded by: Applicable Site(s)IPI D ANOl D IP2 0 AN02 D IP3 0 ECH 0.IAF 0 GGNSPNPS D RBS D vv D WF3 0 WPO D I'Ll'DECNo.64741 Report Origin: 0 EntergyVendor Vendor Document No.: ENTCORP038-REPT-002 Quality-Related: DYesNo Datc: Date: Date: 8/1//6

.'Date::;1 It fa Design Verified:

ENERCON PROJECTREPORTCOVERSHEETPAGE1OF11 6::'1 Title: REPORT NO.: ENTCORP038-REPT

-002 2016 MITIGATING STRATEGIES ASSESSMENTFORFLOODING DOCUMENTATIONREVISION:0 REQUIREMENTS AT GRAND GULF NUCLEAR Client: Entergy STATION Project Identifier:

ENTCORP038 Item Cover Sheet Items Yes No 1DoesthisProjectReportcontainanyopenassumptions,including preliminaryinformationthatrequire confirmation?(IfYES,identifythe assumptions.)

0[gJ 2DoesthisProjectReport supersedeanexistingProjectReport?(IfYES, identifythesupersededProjectReport.)

Superseded Project Report No.0 IZI Scope of Revision:InitialIssue Revision Impact on Results: N/A Safety-Related 0 Non-Safety-Related IZI Originator:

Jessica Maddocks..;.,Ay;...."', Reviewer: Jeffrey Head Approver: Jared Monroe I Date: 7/xJZOI G,/'\I (,

it ENERCON REVISION STATUS SHEETPAGE2OF11£:xcc;;'(:ncp*****F.\*fry doy 2016 MITIGATING STRATEGIES ASSESSMENT FOR REPORT NO.: ENTCORP038-REPT

-002 FLOODING DOCUMENTATION REQUIREMENTS AT GRAND GULF NUCLEAR STATION REVISION: 0 PROJECT REPORT REVISION STATUS REVISION DATE DESCRIPTION 0 7/8/2016InitialIssue ATTACHMENT REVISION STATUS ATTACHMENTNO.OF REVISION ATTACHMENTNO.OF REVISION NO.PAGES NO.PAGES N/A ENERCON TABLEOFCONTENTS PAGE3OF11 t);(e![;?o(p***..F.v(-.".i.'

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do, 2016 MITIGATING STRATEGIES ASSESSMENT FOR REPORT NO.ENTCORP038-REPT

-002 FLOODING DOCUMENTATION REQUIREMENTS AT GRAND GULF NUCLEAR STATION REVISION 0 Section 1.Summary 2.Documentation2.1NEI12-06,Rev.2, SectionG.2-Characterizationofthe MSFHI2.2NEI12-06,Rev.2, SectionG.3-Comparisonofthe MSFHI and FLEXDBFlood2.3NEI12-06,Rev.2, SectionG.4-Evaluation of Mitigating Strategiesforthe MSFHI 2.4 References Page No.4 5 5 7 10 11 ENTCORP038-REPT-002Rev.0 2016 Mitigating Strategies Assessment Flooding Documentation Requirements Grand Gulf Nuclear Station Acronyms:*COB-CurrentDesignBasis*ELAP-ExtendedLossofAC Power*FHRR-FloodHazardReevaluationReport*FLEXDB-FLEXDesignBasis(floodhazard)*FSG-FLEX Support Guideline*GGNS-GrandGulf Nuclear Station*LIP-LocalIntensePrecipitation

• MSFHI-MitigatingStrategiesFloodHazardInformation(fromtheFHRRand MSFHlietter)*MSL-MeanSeaLevel*PA-ProtectedArea*PMF-ProbableMaximumFlood

• PMP-ProbableMaximumPrecipitation*PMWE-ProbableMaximum Water Elevation*SSC-Structures,Systemsand Components Definitions:

FLEX Design Basis:ThefloodhazardforwhichFLEXwasdesigned.

FLEX DesignBasisFlood Hazard:Thecontrollingflood parametersusedtodeveloptheFLEXflood strategies.

1.SummaryTheGGNSFHRR(Ref.7)hasconcludedthatthePMFontheMississippiRiverandStreamAarenotboundedbytheCOBPMFbutareboundedbytheFLEXDBforstoragebuildingdesignand equipmentstaging.PMFonStreamAleadstothelossofthe deploymentpathfromthenorthFLEXstoragebuilding(Site1).The deploymentpathfromthesouthstoragebuilding(Site4)remainsavailable,sotheoverallstrategyforthestorageand deploymentofFLEX equipment canstillbeimplementedasdesigned.TheGGNSFHRR(Ref.7)hasconcludedthatthePMFonStreamBisboundedbytheCOBandtheFLEXDB.TheFHRR,asupdatedbyReference9, determinedLIPexceedstheCOBforfloodingattheplantsitebutisboundedbytheFLEXdesignbasis.LIPistheonlyfloodmechanismthatresultsininundationofthe outdoorareasinthevicinityofSSCs importanttosafety,andduetotheexistingmitigatingstrategyofsandbagdeployment,doorsealsoninactivedoors,andtherelativelyfastrecessiontimes,theoverallstrategyforthestorageand deploymentofFLEX equipmentfromthesouthstoragebuilding(Site4)canbe implementedasdesigned.Otherreevaluatedfloodhazard mechanisms(e.g.,tsunami,channel migrations/diversions, etc.)areboundedbytheFLEXdesignbasisandCOB,andthereforehavenoimpactonthesite.DetailsoftheFLEXstrategiesalongwiththeboundingfloodwillbediscussedlaterinthisdocument.Page4of11 ENTCORP038-REPT-002Rev.0 2.Documentation2.1.NEI12-06,Rev.2,SectionG.2-CharacterizationoftheMSFHI.TheFHRR(Ref.7)identifiedthatLIPandPMFoftheMississippiRiverandStreamAarenot boundedbytheCOBfloodelevation.StreamBPMFisboundedbytheCOBfloodelevation.TheFHRRalsoanalyzedthewatershedassociatedwiththeBayouPierreand determinedthatthereisnoimpactontheGGNSplantsite.Other reevaluatedfloodhazard mechanisms(e.g.,tsunami, channel migrations/diversions,etc.)areboundedbytheCOBandhavenoimpactonthesite.

Mississippi River PMFTheMississippiRiverPMFmaximumfloodheightof106.2 ft.MSLis3.2 ft.higherthantheCOBfloodheightof103 ft.MSL.ThePMWEonthe MississippiRiveratGGNSis122.5 ft.Thisisthecombinationof stillwaterelevationandwavesetupandwaverunupinducedbythe 2-year windspeed.Plantgradeisat132.5 ft.andany safety-related equipmentorFLEX equipment isprotectedfromthisevent.Therefore,thiseventdoesnotchallengetheFLEXstrategies.

Stream A PMFStreamAPMFmaximumfloodheightof132.1 ft.MSLis3.2 ft.higherthantheCOBfloodheightof128.9 ft.MSL.ThePMWEonLocalStreamAis132.5 ft.Thisisthecombinationof stillwaterelevationandwavesetupandwaverunupinducedbythe2-yearwindspeed.Thisfloodlevelleadstolossofcertainpartsofoneofthetwo deploymentpaths(i.e.lossofthepathfromthenorthFLEXstoragebuilding[Site1 D.StreamBPMFStreamBPMFmaximumfloodheight determinedbytheMSFHIof131.7 ft.MSLis1.1 ft.lowerthantheCOBfloodheightof132.8 ft.MSL.WindwaveheightwasnotcalculatedbecauseStreamBisboundedbyStreamA.Plantgradeisat132.5 ft.Therefore,thiseventdoesnotchallengetheFLEXstrategies.BayouPierreTheBayouPierrewasnotevaluatedaspartoftheCOBbutwasevaluatedbytheFHRR.TheFHRRconcludedthatthemaximumfloodleveloftheBayouPierreis130.7 ft.,whichiswellbelowtheelevationoftheBayouPierrewatersheddivideelevationofabout175 ft.Therefore,thiseventdoesnotchallengetheFLEXstrategies.

Flood HeightThemaximumwatersurfaceelevationduetotheLIPatGGNSresultsfromatotalrainfalldepthof19.3incheswithinanhourand31.4incheswithin6hours.IntheimmediatevicinityofGGNSUnit1,predictedmaximumwaterdepthsatsafetyrelatedbuildingentrancesresultingfromtheLIPrangefrom approximately 0.3 ftto1.0 ft(Ref.9)atdoorsprotectingsafetyrelatedequipment.Theseflowdepthscorrespondtowatersurface elevationsrangingfrom133.3 ft.to133.7 ft.(Ref.7and9).ThisisabovetheCOBfloodheightof133.25 ft.,andisboundedbytheFLEXDBheightof133.7 ftforthesouthFLEXstoragebuilding(Site4).Sandbagsuptoaheightof1.5 ft.anddoorsealsatinactivedoors10301andOCT05areusedtoprotectthese exteriordoorsfromflooding.Therefore,floodingthroughdoorwaysisnotaconcern(Ref.7).Page5of11 ENTCORP038-REPT-002Rev.0Flowvelocitiesarounddoorsrangesfrom0.4fpsto2.1fps(Ref.9).Significantdebris loading/transportationisnotasafetyhazardduetotherelativelylowvelocityanddepthofLIPfloodwatersinthevicinityof safety-relatedSSCsatGGNS,inadditiontothelackofnaturaldebrissourcesonsite(Ref.7).FloodEventDurationFlooddurationswereevaluatedatvariouslocationsaroundthepowerblocknearexternaldoorsprotectivesafetyrelatedequipment.Flood durationsvaryateachlocation,buttheanalyzed locations typicallyreachthepeakfloodelevationabout30minutesafterthebeginningoftheLIPevent,droppingrapidlytobelowhalfofthepeakflooddepth approximately2hoursaftertheonsetoftheLIPevent,whichisbeforePhase2 equipmentisdeployed(Ref.7).Flooddepths almost completelyrecedeby8hourswhichis2hoursbeforeanyPhase2portable equipment iscredited.Thisgeneraltrendoffloodrecessionisdeemed appropriatefortheSouthStorageBuildingatSite4andtheprimary deploymentpath(s)fromSite4duetotheproximitytothepowerblockandbecausetheterrainisverysimilar.However,theserecessiontimesmaynotapplytoareasfloodedbyStreamA (specificallytheareaoftheNorthAccessRoadthatisunder approximately6ftofwater,preventing deployment of equipmentfromtheNorthStorageBuildingatSite1)becausewateris intentionallydivertedtoStreamAfordrainage,thusincreasingtherecessiontime.ItshouldbenotedReference9reanalyzestheLIPflooddepthsbyconsideringroofrunoff,butthisdoesnotchangetheflooddurationsbya significantamountsuchthattheFLEXstrategywouldbeaffected.

Relevant Associated EffectsOnlythesouthstoragebuildingatSite4iswithinthescopeoftheLIPreanalysisduetoitslocationrelativelyclosetothepowerblock.Duetoitsremotelocationandgradeelevation,Site1isnotincludedintheLIPreanalysis.TheLIPreanalysissupportsamaximumexpecteddepthof0.1ft.to0.2ft.atSite1baseduponthe adjacentmodeledareas.ThenorthFLEXstoragebuildingatSite1islocatedsuchthatthe top-of-slabelevationisat163ft.,andSite4hasaof-slabelevationof133.2ft.Thefoundation(slab)designsofbothstoragebuildingsincludeaninternalspill containmentcurbextending0.5ft.abovethe top-of-slab.Thisresultsinan"effective"top-of-slabelevationof163.5ft.forSite1and133.7ft.forSite4.Thefloodheightsattheselocationsare163.2ft.and133.5ft.respectively.Therefore,giventheconcreteslab,curbheight,grading,anddrainage,thebuilding elevations are sufficienttopreclude challenges/impacttothestoredequipment.Theprimary deploymentpathbetweenthenorthstoragebuildingatSite1andthePArunsalongtheNorthAccessRoadformostofitslength.Inonelocationtheroaddips approximately6feetbelowtheLIPfloodelevation(Ref.10).Therefore,itwouldrequire deploymentofthe FLEX*equipmentfromthesouthstoragebuildingatSite4.Site4islocated approximately500ftwestofthePA.Theprimary deploymentrouteforSite4isnorthalongthePlantAccessRoadgainingaccesstothePAthroughtheSallyPortlocated justsouthofthe AdministrationBuilding.ThealternatepathsforSite1andSite4bothrunalongthenorthaccessroad,behindtheUnit2warehouse,andenterthesiteneartheISFSIpadatthenortheasternedgeoftheprotectedarea.Portionsofthispathare unanalyzedforallfloodingscenariossoitisassumedthatthealternatepathsareunavailable.BasedonFigure12ofReference9,themaximumLIPdepthalongtheprimary deployment pathfromSite4tothestaginglocationsis1.5feet.BecauseofSite4'sproximitytothepowerblock,itisexpectedthattherecessiontimesforthe deploymentpathfromSite4wouldbesimilartotherecessiontimesforthesafetyrelateddoorsstatedinthe"FloodEventDuration"sectionabove.Therefore,the1.5ft.depthwouldbedecreasedto approximately0.75ft.orlessafter2hoursandwouldbealmost completelyrecededby8hours.Thelimitingpieceofphase2 equipment withPage6of11 ENTCORP038-REPT-002Rev.0respecttoheightoffthegroundistheChevy3500truckwhichhasaclearanceof approximately16"fromthegroundtothecenterofthe exhaustpipepertheRBSFLEX Equipment Walkdown Report, Attachment10.002toEC64548(Ref.11).GGNSandRBSbothutilizetheChevy3500truckforFLEX equipment deployment.Sinceno equipmentisrequiredtobedeployedpriorto2hours,atwhichtimethe maximumflooddepthwouldbe approximately0.75ft(9inches),thereisnoimpacton deploymentofFLEX equipmentfromthesouthstoragebuildingatSite4duetotheLIP.ItshouldalsobenotedthattheFLEXelectrical equipmentisprotectedfromtherainbydesignandwillnotbe submersedinfloodwaterssincethetrailerheightsare sufficiently abovethefloodlevelsatthetime equipmentisdeployed(atleast7inchesofclearance).Thiswouldalsoprecludeany significantrunupdueto traversingthefloodwaterssincethe trailerfloorsareabovethefloodlevelatthetimeofdeployment.ForPhase3,the NSRC'sabilityto transport equipmenttoStagingAreaB(sitelocationwhere equipmentwillbepre-staged,parked,orplacedpriorto movementintothefinallocation)isdiscussedintheGGNSSAFERResponsePlan(Ref.2)whichincludesmultiplemeansandpathwaysof transporting NSRC equipmenttothesite.Therefore, transportationofNSRC equipmenttothesiteisdeemedfeasibleandisnotdiscussedfurtherinthisdocument.Since deploymentofNSRC equipmentoccurslaterintheevent(after24hours),nofurtheranalysisisnecessary.Notethat deploymentofPhase3 equipmentisnotimpactedbyanyflood mechanismsidentifiedintheFHRR.WarningTimeAfloodwarningtimeof24hoursisusedforpredictionofover12inches(30.5cm)ofrainfromtheNational WeatherService(Ref.3),andsitepreparationisgovernedbythe Off-Normal Event Procedure 05-1-02-VI-2,"Off-NormalEventProcedure-Hurricanes,Tornadoes,andSevereWeather-SafetyRelated"(Ref.5).2.2.NEI12-06,Rev.2,SectionG.3-ComparisonoftheMSFHIandFLEXDBFloodTable1reflectsdatafromtheFHRRfortheLIPcomparedtothesite'sCOBandFLEXdesignbasisflood.AtableisnotincludedforthePMFfromtheMississippiRiver,StreamA,StreamB,andBayouPierrebecause,asstatedinSection2.1,plantgrade, safety-related equipment,thesouthstoragebuildingatSite4,andtheSite4 deploymentpathrequiredfortheFLEXstrategyarewellaboveany wind-wavewaterlevelsuchthatthisdoesnotneedtobeevaluated.

Any parameterswheretheFLEXDBflooddoesnotboundtheMSFHIareevaluatedinSection2.3.Page7of11 ENTCORP038-REPT-002Rev.0 Table1*Flood Causing Mechanism (LIP)or Bounding Set of Parameters Flood Scenario Parameter Plant FLEX Design MSFHI Bounded (B)CurrentBasisFlood or Not DesignHazardLIP Bounded Basis Flood(NB)byFLEX Hazard DB1.Max Stillwater Elevation(ft.MSL)133.25 133.7 (See 133.7 B Cf)Note1)t52.Max Wave Run-up Elevation(ft.Not Identified Not IdentifiedSeeNote2BMSL)inCOBinFLEX w"0 (1)3.Max Hydrodynamic/Debris Not identifiedSeeNote3SeeNote3 N/A 10'(3Loading(psf)intheCOB 0 Cf)Cf)-cEffectsof Sediment Not identifiedSeeNote4SeeNote4N/A "0 Deposition/ErosionintheCOB c co Q5>5.Other Associatedeffects(identify N/A N/A N/A N/A (1)-l each effect)"0 0 0 6.Concurrent Site Conditions u::: Not identifiedSeeNote6SeeNote6BintheCOB 7.Effectson Groundwater Not identifiedSeeNote7SeeNote7BintheCOB 8.Warning Time (hours)Not identified 24 24 BintheCOB.e 9.PeriodofSite Preparation (hours)Not identified 6 24 NB (1)>cintheCOB w 0"0:;::;10.Periodof Inundation (hours)6 6>15 NB o co o'-_:::J u.O11.Periodof Recession (hours)7 8>14 NB12.PlantModeof Operations Normal Normal Normal B Other Operations Operations Operations 13.Other Factors N/A N/A N/A N/A N/A=Not Applicable Additional notes,'N/A'justifications (why a particular parameter is judgednotto affectthesite),and explanations regarding the bounded/non-bounded determination.Thenote numbers below correspondtothe parameter numberinthetable.

1.The GGNSFIP(Ref.1) addressed the maximum flood height elevationof133.7ft.MSLfrom the GGNS FHRR.2.Consideration of wind-waveactionfortheLIP eventisnot explicitly required by NUREG/CR-7046andis judgedtobe negligible because of limited fetch lengthsandflow depths.3.Debris loadingisnot considered a hazardduetothe relatively low velocityanddepthofLIP flood watersinthe vicinity of safety-relatedSSCs,in additiontothelackof natural debris sourcesonthesite.

4.Erosionand sedimentationarenot applicabletothissite,and therefore,donotneedtobe evaluated.(Ref.6)Page8of11 ENTCORP038-REPT-002Rev.05.None6.TheGumbelDistributionwasappliedtothe2-minutewindspeeddatafromNCDCstationatTallulahVicksburgRegionalAirport,todeterminethe2-yearreturnperiodwindspeed,whichwascalculatedtobe45.2mph.7.ThePMPeventimpactonthegroundwaterlevelwasdiscountedasamajorityoftheprecipitationresultingfromaPMPeventdoesnotinfiltratetothelocalgroundwatertablebutinsteadresultsinsurfacewaterrunofftostreamsandrivers.8.None9.None10.LocalIntensePrecipitationandAssociatedDrainagefor6hourprecipitationevent.Thisisbasedonthehydrographatthedoor"OCT5"presentedbyFigure3.1-16intheFHRR.11.LocalIntensePrecipitationandAssociatedDrainagefor6hourprecipitationevent.Thisisbasedonthehydrographatthedoor"OCT5"presentedbyFigure3.1-16intheFHRR.12.None 13.NonePage9of11 ENTCORP038-REPT-002Rev.02.3.NEI12-06,Rev.2,SectionG.4-EvaluationofMitigatingStrategiesfortheMSFHI2.3.1.NEI12-06,Rev.2,SectionG.4.1-AssessmentofCurrentFLEXStrategies2.3.1.1.StreamAPMFPMFonStreamAwith coincident wind generatedwavesresultsininundationoftheprimaryaccessroad,butdoesnotresultininundationofSSCs importanttosafety.Inundationofthe primaryaccessroadwould potentially restrict deploymentofFLEX equipmentfromthenorthFLEXstoragebuilding(Site1)locatednorthofStreamA.However,asFigure2oftheFinalIntegrationPlanshows(Ref.1),thereisasecond redundantFLEXstoragefacilitylocatedsouthofStreamA,suchthatinundationoftheaccessroadwillnotrestrict deployment.

Therefore,theFLEXstrategiesarenotimpactedbythisevent.(Ref.7)2.3.1.2.LIPThreefloodingscenario parametersfortheLIParenotboundedbytheFLEXstrategy:PeriodofSitePreparation(hours),PeriodofInundation(hours),andPeriodofRecession(hours).Toaddressthis,protectionofFLEX equipmentagainstexternalfloodingeventswasevaluatedin accordancewithSection 6.2.3.1.1.aofNEI12-06(Ref.8)whichstatesthattheFLEX equipmentisprotectedfromfloodsifitisstoredabovethefloodelevationdeterminedinthemostrecentsitefloodanalysis.FloodingduetoLIPisthecontrollingfloodeventforthenewfloodevaluation.Nootherflood mechanism generates waterelevationswiththepotentialtoimpactsafetyrelatedSSCsor equipmentrelieduponforFLEX.ThemaximumwatersurfaceelevationduetotheLIPatGGNSresultsfromatotalrainfallof19.3incheswithinanhourand31.4incheswithin6hours.IntheimmediatevicinityofGGNSUnit1,predictedmaximumwaterdepthsatsafetyrelatedstructuredoorwaysresultingfromtheLIPrangefrom approximately 0.3 ftto1.0 ft(Ref.9).Table4.3-1intheFHRR(Ref.7)asrevisedbySection6.4.7ofReference9showstheheightofmodeledLIPfloodwaterateach doorwaytoasafetyrelatedstructurethatcan be potentiallyimpactedbythisevent.

Sandbagsareuseduptoaheightof1.5 ft.toprotectentrancestothediesel generator building, standbyservicewaterbuildingsandcontrolbuilding;anddoorsealsatinactivedoors10301andOCT05alsoprotectthese exteriordoorsfromflooding.Noneofthe protectionsinplaceforidentified safety-relatedSSCorPMPsealeddoorsareexceededbyLIPfloodwaterheights.Therefore, equipmentintheseareasareprotectedandtheareasremain accessibleforuseduringaFLEXevent.

2.3.2.ConclusionsTheplantresponse strategiestoanELAPandlossofultimateheatsinkeventusingthecurrentFLEX strategyandassociatedECshavebeen developed in accordancewiththeGGNSfloodingreanalysis.Inundationofthe primaryaccessroadwouldrequiremobilizationofFLEX equipmentfromthesouthFLEXstoragefacilitylocatedsouthofStreamAsinceinundation potentiallyrestrictsmobilizationofthe equipmentfromthenorthFLEXstoragefacilitylocatednorthofStreamA.Therefore,theflooding assessmentwillhavenoimpactontheGGNSFLEXstrategy.

EquipmentandpersonnelwillbeavailablesuchthattheGGNSFLEX StrategiescanbeimplementedasdescribedintheFinalIntegratedPlan(Ref.1).Page10of11 ENTCORP038-REPT-002Rev.02.4.References 1.GNRO-2016-00006,FinalIntegratedPlanDocumentGrandGulfNuclearStation,April2016 2.GNRO-SA-15-00001,Rev.001,SAFERResponsePlanforGrandGulfNuclear Station, September 8,20153.NEI15-05,Rev.6,WarningTimeforLocalIntensePrecipitationEvents,April20154.EC50275,Rev.2,FLEXBasisEC5.05-1-02-VI-2,Rev.129,Off-NormalEventProcedure-Hurricanes,Tornados,andSevereWeather, December 4,20146.GrandGulfNuclearStation,Unit1-SupplementtoStaffAssessmentofResponseto10CFR50.54(f)InformationRequest-Flood-causingMechanismReevaluation(CACNo.MF1102), December4,2015 7.51-9195288-000,EntergyFleetFukushimaProgramFloodHazardReevaluationReportforGrandGulfNuclearStation,ML13071A457,March20138.NEI12-06,Rev.2,DiverseandFlexibleCopingStrategies(FLEX)Implementation Guide, December 20159.32-9195573-000,Rev.1,FloodHazardRe-evaluation-LocalIntensePrecipitationGeneratedFloodFlowandElevationsatGrandGulfNuclearStations,September24, 201410.EC50287,Rev.0,GGNSFLEXStorageBuilding11.EC64548,Rev.0,AdminECtoIssueFLEXFloodMitigatingStrategiesAssessment(MSA)ReportPage11of11