L-MT-17-024, Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 3, Focused Evaluation

Response to March 12, 2012, Request for Information Enclosure 2, Recommendation 2.1, Flooding, Required Response 3, Focused Evaluation

ML17093A871
Person / Time
Site:	Monticello
Issue date:	04/03/2017
From:	Gardner P Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CAC MF7712, L-MT-17-024
Download: ML17093A871 (25)

Text

April 3, 2017 L-MT-17-024 10 CFR 50.54(f)

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket No. 50-263 Renewed Facility Operating License No. DPR-22 Monticello Nuclear Generating Plant, Response to March 12, 2012, Request for Information, Recommendation 2.1, Flooding, Required Response 3, Focused Evaluation (CAC No. MF7712)

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. (ADAMS Accession No. ML12056A046)

2) NRC Letter, Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for Beyond-Design-Basis External Events, dated September 1, 2015. (ADAMS Accession No. ML15174A257)

3) NRC COMSECY-15-0019, "Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants," dated June 30, 2015.

(ADAMS Accession No. ML15153A104)

4) NRC SRM COMSECY-15-0019, "Staff Requirements - COMSECY-15-0019

- Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants," dated July 28, 2015. (ADAMS Accession No. ML15209A682)

5) NEI 16-05, "External Flooding Assessment Guidelines," Revision 1, June 2016. (ADAMS Accession No. ML16165A178)

6) NRC JLD-ISG-2016-01, "Guidance for Activities Related to Near-Term Task Force Recommendation 2.1, Flooding Hazard Reevaluation; Focused Evaluation and Integrated Assessment," Revision 0, dated July 11, 2016.

(ADAMS Accession No. ML16162A301) 2807 West County Road 75 Monticello, MN 55362 800.895.4999 xcelenergy.com

Document Control Desk Page 2

7) NSPM Letter to NRC, Monticello Nuclear Generating Plant: Response to Post-Fukushima Near-Term Task Force (NTTF) Recommendation 2.1, Flooding - Flood Hazard Reevaluation Report, L-MT-16-024, dated May 12, 2016. (ADAMS Accession No. ML16145A179)

8) NRC Letter to NSPM, Monticello Nuclear Generating Plant - Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request - Flood-Causing Mechanism Reevaluation (CAC No. MF7712), dated September 16, 2016. (ADAMS Accession No. ML16248A004)

With this letter Northern States Power Company, a Minnesota corporation (NSPM), doing business as Xcel Energy, hereby submits the Monticello Nuclear Generating Plant (MNGP)

Flooding Focused Evaluation (FE).

On March 12, 2012, the NRC issued Reference 1, which included a request for information associated with Near-Term Task Force (NTTF) Recommendation 2.1 for flooding. In of Reference 1, the NRC Staff requested licensees to perform a Flood Hazard Reevaluation (Requested Information Item 1) and submit the Flood Hazard Reevaluation Report (Required Response Item 2). Enclosure 2 of Reference 1 also requested licensees to perform an Integrated Assessment if the design basis flood did not bound the reevaluated hazard for all flood causing mechanisms (Requested Information Item 2). Reference 1 required a written response for the Integrated Assessment (Required Response Item 3).

Subsequent to the Reference 1 requests, discussions within the NRC and industry resulted in a reassessment of the Flooding Impact Assessment Process (Reference 2). On June 30, 2015, the NRC staff issued COMSECY-15-0019 (Reference 3) that described the closure plan for NTTF Recommendation 2.1 regarding the reevaluation of flooding hazards. As discussed in COMSECY-15-0019, the majority of sites with flooding hazards exceeding the design-basis flood screen out from the integrated assessments. The NRC staff concluded that licensees that screened out would provide a focused evaluation (FE) instead of an integrated assessment. The FE would ensure appropriate actions are taken and that these actions are effective and reasonable. The Commission approved the NRC staff's plans to implement a graded approach to the flood hazard reevaluations in Staff Requirements Memorandum (SRM)

COMSECY-15-0019 (Reference 4) on July 28, 2015.

The guidance in Nuclear Energy Institute (NEI) 16-05 (Reference 5) addresses the Reference 1 request for information and describes the methodology for performing FEs and integrated assessments of flood mechanisms that exceed the design basis flood parameters for a facility.

The NRC endorsed NEI 16-05, Revision 1 with clarifications as described in the enclosure to JLD-ISG-2016-01 (Reference 6). The Interim Staff Guidance (ISG) states that licensees may use the methodology of NEI 16-05, with clarifications, upon receipt of the flood hazard parameters for use in the Mitigating Strategies Assessments of NEI 12-06, Appendix G.

In Reference 7 NSPM submitted the flood hazard reevaluation report (FHRR) for MNGP in May 2016. In October 2016, NSPM received the flood hazard parameters from the NRC (Reference 8) needed to begin the FE.

Document Control Desk Page 3 The Enclosure to this letter provides the MNGP Flooding FE. This FE follows Path 2 of NEI 16-05 (Reference 5), and utilizes Appendix B for guidance for evaluating the site protection features. The FE concludes that during local intense precipitation (LIP) events the site has effective flood protection through the determination of available physical margin and the reliability of flood protection features. No human actions are required to protect the MNGP structures, systems and components, therefore, an evaluation of the overall site response was not necessary. Responses to the documentation requirements in Section 9 of NEI16-05 are included in Appendix 1 of the enclosed evaluation. The Appendix 1 responses fulfill Reference 1, Enclosure 2, Requested Information Item 2.

Please contact John Fields, at 763-271-6707, if additional information or clarification is required.

Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on April 3, 2017.

~~

Peter A. Gardner Site Vice President, Monticello Nuclear Generating Plant Northern States Power Company-Minnesota Enclosure cc:

Administrator, Region Ill, USNRC Project Manager, Monticello Nuclear Generating Plant, USNRC Resident Inspector, Monticello Nuclear Generating Plant, USNRC

L-MT-17-024 NSPM 21 pages follow ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT Monticello External Flooding Assessment Focused Evaluation

XcelEnergy ContractNo.00048375

MonticelloExternalFloodingAssessment FocusedEvaluation

CLIENTAPP.: N/A BLACK&VEATCH OverlandPark,KS

0 3/13/2017 IssuedforClientUse (RAR1809990003)

SDT N/A DVR180999 0020 SDT NO.

DATE DESCRIPTION DRN DES CHK APP FILENUMBER50.2000 REVIEWLEVELN/A THISDOCUMENTCONTAINS SAFETYRELATEDITEMS THISDOCUMENTCONTAINS SEISMICCATEGORYIITEMS YES NO YES NO CLIENTDOCUMENTREFERENCENUMBER TOTALSHEETS PROJECTDOCUMENTNUMBER N/A 21 180999.50.230004

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page2of21 TableofContents

1.0 EXECUTIVE

SUMMARY

.....................................................................................................................3

2.0 BACKGROUND

..................................................................................................................................4

3.0 REFERENCES

......................................................................................................................................5 4.0 TERMSANDDEFINITIONS................................................................................................................7 5.0 FLOODHAZARDPARAMETERSFORUNBOUNDEDMECHANISMS.................................................8 5.1 REVISEDLIPANALYSIS.......................................................................................................................9 6.0 OVERALLSITEFLOODINGRESPONSE.............................................................................................11

6.1 DESCRIPTION

OFOVERALLSITEFLOODINGRESPONSE..........................................................................11 6.2

SUMMARY

OFPLANTMODIFICATIONSANDCHANGES..........................................................................11 7.0 FLOODIMPACTASSESSMENT........................................................................................................12 7.1 LOCALINTENSEPRECIPITATION.........................................................................................................12 7.1.1 DescriptionofFloodImpact...............................................................................................12 7.1.2 AdequateAPMJustification...............................................................................................15 7.1.3 ReliabilityofFloodProtection...........................................................................................19 7.1.4 AdequateOverallSiteResponse........................................................................................19

8.0 CONCLUSION

..................................................................................................................................19 APPENDIX1.................................................................................................................................................20

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page3of21 MONTICELLONUCLEARGENERATINGPLANT FLOODINGFOCUSEDEVALUATION

SUMMARY

1.0 EXECUTIVE

SUMMARY

TheMonticelloNuclearGeneratingPlant(MNGP)hasreevaluateditsfloodinghazardinaccordancewith theNRCsMarch12,2012,10CFR50.54(f)requestforinformation(RFI)(Reference1).TheRFIwas issued as part of implementing lessons learned from the Fukushima Daiichi accident; specifically, to address Recommendation 2.1 of the NRCs NearTerm Task Force report. This information was submittedtoNRCinafloodhazardreevaluationreport(FHRR)onMay12,2016,(Reference2)andis providedintheMitigatingStrategiesFloodHazardInformation(MSFHI)documentedinNRCsInterim StaffResponsetoReevaluatedFloodHazardsletterdatedSeptember16,2016(Reference9).Thereis onemechanismthatwasfoundtoexceedthedesignbasisfloodlevelattheMNGP.Thismechanismis listedbelowandaddressedinthisFE:

1. LocalIntensePrecipitation(LIP)

Associatedeffects(AE)andfloodeventduration(FED)parameterswereassessedandsubmitted asapartoftheFHRR.SubsequenttosubmittaloftheFHRR(Reference2),theMNGPperformed additional more refined flooding analysis for the LIP (Reference 10). Reference 10 uses site specificprecipitationinputsinlieuoftheapplicableHMRmethodsfordeterminingprecipitation inputs,andincludesanunsteadyflowapproachtobetterquantifytheimpactsofwateroutside ofvariousplantdoors.ThisrevisedLIPfloodinganalysiswillserveastheinputtothisFocused Evaluation(FE). TheFEaffirmsthatduringLIPeventsthesite haseffectivefloodprotection throughthedeterminationofadequateAvailablePhysicalMargin(APM)andthereliabilityof protectionfeatures.ThesitedoesnotrequireanyhumanactionstoprotectKeySSCssoan evaluationoftheoverallsiteresponsewasnotnecessary.ThisFEfollowsPath2ofNEI1605, Rev. 1 (Reference 7), and utilizes Appendix B for guidance for evaluating the site protection features. This submittal completes the actions related to External Flooding required by the March12,201210CFR50.54(f)letter.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page4of21

2.0 BACKGROUND

OnMarch12,2012,theNRCissuedReference1torequestinformationassociatedwithNearTermTask Force(NTTF)Recommendation2.1forflooding.TheRFI(Reference1)directedlicensees,inpart,to submitaFloodHazardReevaluationReport(FHRR)toreevaluatethefloodhazardsfortheirsitesusing presentdaymethodsandguidanceusedforearlysitepermitsandcombinedoperatinglicenses.Forthe MNGP,Units1and2,theFHRRwassubmittedonMay12,2016(Reference2).

FollowingtheCommissionsdirectivetoNRCStaffinReference6,theNRCissuedalettertoindustry (Reference5)indicatingthatnewguidanceisbeingpreparedtoreplaceinstructionsinReference4and provide for a graded approach to flooding reevaluations and more focused evaluations of local intenseprecipitationandavailablephysicalmargininlieuofproceedingtoanintegratedassessment.

NEIpreparedthenewExternalFloodingAssessmentGuidelinesinNEI1605(Reference7),whichwas endorsed by the NRC in Reference 8. NEI 1605 indicates that each floodcausing mechanism not boundedbythedesignbasisflood(usingonlystillwaterand/orwindwaverunuplevel)shouldfollow oneofthefollowingfiveassessmentpaths:

Path1:DemonstrateFloodMechanismisBoundedThroughImprovedRealism Path2:DemonstrateEffectiveFloodProtection Path3:DemonstrateaFeasibleResponsetoLIP Path4:DemonstrateEffectiveMitigation Path5:ScenarioBasedApproach

NonboundedfloodcausingmechanismsinPaths1,2,or3onlyrequireanFEtocompletetheactions relatedtoexternalfloodingrequiredbytheMarch12,2012,10CFR50.54(f)letter.MechanismsinPaths 4or5requireanIntegratedAssessment.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page5of21

3.0 REFERENCES

1. U.S.NuclearRegulatoryCommissionLetter,RequestforInformationPursuanttoTitle10ofthe CodeofFederalRegulations50.54(f)RegardingRecommendations2.1,2.3,and9.3,oftheNear Term Task Force Review of Insights from the Fukushima Daiichi Accident; dated March 12, 2012.

2. NSPM Letter LM16024 to the U.S. Nuclear Regulatory Commission, Monticello Nuclear GeneratingPlant,Units1and2,ResponsetoMarch12,2012RequestforInformationEnclosure 2,Recommendation2.1,Flooding,RequiredResponse2,FloodingHazardReevaluationReport, datedMay12,2016,(ADAMSAccessionNo.ML16145A233).

3. U.S.NuclearRegulatoryCommissionLetter,SupplementalInformationRelatedtoRequestfor InformationPursuanttoTitle10oftheCodeofFederalRegulations50.54(f)regardingFlooding HazardReevaluationsforRecommendation2.1oftheNearTermTaskForceReviewofInsights fromtheFukushimaDaiichiAccident,datedMarch1,2013.

4. U.S.NuclearRegulatoryCommissionLetter,TriggerConditionsForPerformingAnIntegrated Assessment And Due Date For Response, dated December 3, 2012, (ADAMS Accession No. ML12326A912).

5. U.S. Nuclear Regulatory Commission Letter, Coordination of Requests for Information Regarding Flooding Hazard Reevaluations and Mitigating Strategies for BeyondDesignBasis ExternalEvents,datedSeptember1,2015,(ADAMSAccessionNo.ML15174A257).

6. Commission Staff Requirements Memo (SRM), SRMCOMSECY140037: Integration of MitigatingStrategiesforBeyondDesignBasisExternalEventsandtheReevaluationofFlooding Hazards,"datedMarch30,2015,(ADAMSAccessionNo.ML15089A236).

7. Nuclear Energy Institute (NEI), Report NEI 1605 [Rev 1], External Flooding Assessment Guidelines,datedJune2016.

8. U.S. Nuclear Regulatory Commission, JLDISG201601, Revision 0, Guidance for Activities RelatedtoNearTermTaskForceRecommendation2.1,FloodingHazardReevaluation;Focused EvaluationandIntegratedAssessment,datedJuly11,2016.

9. U.S. Nuclear Regulatory Commission, Letter to Peter A. Gardner, Northern States Power Company-Minnesota,

Subject:

MonticelloNuclearGeneratorPlant-InterimStaffResponse toReevaluatedFloodHazardsSubmittedinResponseto10CFR50.54(f)InformationRequest-FloodCausing Mechanism Reevaluation (CAC Nos. MF7712), Dated September 16, 2016, (ADAMSAccessionNo.ML16248A003).

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page6of21

10. Black&Veatch,"LocalIntensePMP&Hydrology,"Calculation180999.51.1005,Revision4.

11. NSPM,"MonticelloUpdatedSafetyAnalysisReport,"Section2.4,Hydrology,Revision32.

12. NSPM,ProcedureA.6,"ActsofNature,Revision55.

13. NSPM,Procedure830002,ExternalFloodingProtection,ImplementationtoSupportA.6,Acts ofNature,Revision7.

14. NSPM,EC12421-EngineeringEvaluation,EffectofEPUReactorBuildingHELBLiquidBreakson EQSpecifications,PartB.

15. NSPM,Calculation03200,InternalFloodingEvaluationDuetoaPostulatedBreakin2.5Fire Line,Revision0.

16. NSPM,Calculation07035,InternalFloodingAnalysis,Revision0.

17. NSPM,DrawingNF36989,DieselFuelPumpHouse,Revision78.

18. Black & Veatch, "Evaluation of Structural Elements Flood," Calculation 180999.51.1010, Revision1.

19. Black & Veatch, Site Specific PMP and Ancillary Meteorological Analysis, Calculation 180999.51.1008,Revision1.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page7of21 4.0 TERMSANDDEFINITIONS AE-AssociatedEffects AIM-Assumption,Input,Method APM-AvailablePhysicalMargin EDG-EmergencyDieselGenerator FE-FocusedEvaluation FED-FloodEventDuration FFE-FinishedFloorElevation FHRR-FloodHazardReevaluationReport FIAP-FloodingImpactAssessmentProcess FLEX-DiverseandflexiblecopingstrategiescoveredbyNRCorderEA12049 HMR-HydroMeteorologicalReport KeySSC-AsystemStructureorComponentreliedupontofulfillaKeySafetyFunction KSF-KeySafetyFunction,i.e.corecooling,spentfuelpoolcooling,orcontainmentfunction.

LIP-LocalIntensePrecipitation MSA-MitigatingStrategiesAssessment MSFHI-MitigatingStrategiesFloodHazardInformation NTTF-NearTermTaskForcecommissionedbytheNRCtorecommendactionsfollowingthe FukushimaDaiichiaccidents MNGP-MonticelloNuclearGeneratingPlant NB-NotBounded NEI-NuclearEnergyInstitute NGVD29-NationalGeodeticVerticalDatumof1929 PAB-PlantAdministrationBuilding PMF-ProbableMaximumFlood RFI-RequestforInformation USAR-UpdatedSafetyAnalysisReport WSE-WaterSurfaceElevation

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page8of21 5.0 FLOODHAZARDPARAMETERSFORUNBOUNDEDMECHANISMS TheNRChascompletedtheInterimStaffResponsetoReevaluatedFloodHazardstothefloodhazards informationsubmittedintheMNGPFHRR(Reference9);whichstates:

TheNRCstaffhasconcludedthatthelicensee'sreevaluatedfloodhazardinformationissuitable for the assessment of mitigating strategies developed in response to Order EA12049 (i.e.,

defines the mitigating strategies flood hazard information described in guidance documents currentlybeingfinalizedbytheindustryandNRCstaff)forMonticello.Further,theNRCstaff hasconcludedthatthelicensee'sreevaluatedfloodhazardinformationisasuitableinputfor otherassessmentsassociatedwithNearTermTaskForceRecommendation2.1,"Flooding."

Thesummaryofthereevaluatedfloodhazard(i.e.,MSFHI)parameterswasprovidedinReference9.

ThefollowingfloodcausingmechanismswereconsideredaspartoftheFHRR:

LocalIntensePrecipitation StreamsandRivers FailureofDamsandOnsiteWaterControl/StorageStructures StormSurge Seiche Tsunami IceInducedFlooding ChannelMigrations/Diversions Table2intheEnclosuretoReference9identifiesthereevaluatedfloodhazards.PerReference9,this information is suitable input for other assessments associated with Near Term Task Force Recommendation 2.1, Flooding. The Focused Evaluation is considered to be one of the other assessmentsassociatedwithNearTermTaskForceRecommendation2.1.

TheonenonboundingfloodmechanismfortheMNGPisdescribedindetailinReference2,theFHRR submittal.

Table51ReevaluatedFloodHazardsforFloodCausingMechanisms Mechanism StillwaterElevation Waves/Runup ReevaluatedFlood Hazard LocalIntense Precipitation 935.8ftNGVD29 Minimal 935.8ftNGVD29

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page9of21 This is the reevaluated floodcausing mechanism that should be addressed in the external flooding assessment.TheonenonboundingfloodmechanismfortheMNGPisdescribedindetailinReference 2, the FHRR submittal. Table 52 summarizes how the unbounded mechanism is addressed in this externalfloodingassessment:

Table52ApproachforEvaluationofNonBoundedFloodMechanism

FloodMechanism SummaryofAssessment 1

LocalIntensePrecipitation Path2ispursuedfortheMNGPsincepermanentpassive protectionfeaturesaresolelyreliedupontomaintainKSFs(see FIAPPathDeterminationTable,Section6.3.3ofNEI1605).

DuringtheLIP,somewateringressdoesoccuratplant structures;however,KSFsarenotimpacted.FortheMNGP, Path2includesadditionalmorerefinedfloodinganalysisfor theLIP.

5.1 REVISEDLIPANALYSIS Subsequent to submittal of the FHRR (Reference 2), the MNGP performed additional more refined floodinganalysisfortheLIP(Reference10).Thechangestotheassumptions,inputs,andmethods(AIM) aresummarizedinTable5.11.

Table5.11DiscussionofRevisedAIMs

DescriptionofRevisedAIM JustificationofReducedConservatism 1

Reference10usessitespecificprecipitation inputsinlieuoftheapplicableHMR methodsfordeterminingprecipitation inputs Rainfallinputsusedarebasedonasite specificLIPstudyperformedfortheMNGPsite byAppliedWeatherAssociates(AWA)and documentedinReference19.

2 Anunsteadyflowapproachisusedtobetter quantifytheimpactsofwateroutsideof variousplantdoors Thechangeinapproachprovidesamore rigorousdeterminationofthelengthoftime thatthewaterlevelsareabovethedoor thresholds.Basedonthesetimedurations andthewaterlevelstheimpactofthewater intrusioncanbedetermined.

3 Creditistakenfortwoopeningsinthe securitybarrierinthevicinityoftheOffGas Stack Theopeningsarepartofthedesign.The openingsarenotexpectedtobereducedby potentialdebrissourcesbasedonminimal debrissourcesavailable,thelongsectionsof chainlinkfencingthatwillprecludelarger debrissourcesfromreachingtheopening,and therelativelylargeopeningsizewithinthe securitybarrier.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page10of21 TheresultsfromReference10aresummarizedinTable5.12,below.Theprimarydifferencesinthe resultsascomparedtotheFHRRaretheinundationandrecessiontimes.Thesearediscussedinmore detailinSection7.1.1.ElevationsgiveninthisreportareintheNGVD29datum.

Table5.12LocalIntensePrecipitation FloodScenarioParameter CDBFlood Hazard Reevaluated FloodHazard Bounded(B)or NotBounded (NB)

FloodLevelandAssociated Effects

1. MaxStillwaterElevation(ftNGVD29)

LIPwasnotspecificallyaddressedintheUSAR 935.72 NB

2. MaxWaveRunupElevation(ft)

SeeNote2 N/A

3. MaxHydrodynamic/DebrisLoading(psf)

SeeNote3 N/A

4. EffectsofSedimentDeposition/Erosion SeeNote4 N/A

5. ConcurrentSiteConditions SeeNote5 N/A

6. EffectsonGroundwater SeeNote6 N/A FloodEvent Duration

7. WarningTime(hours)

SeeNote7 N/A

8. PeriodofSitePreparation(hours)

SeeNote8 N/A

9. PeriodofInundation(hours)

SeeNote9 NB

10. PeriodofRecession(hours)

SeeNote10 NB Other

11. PlantModeofOperations SeeNote11 N/A

12. OtherFactors SeeNote12 N/A Additionalnotes,N/Ajustifications(whyaparticularparameterisjudgednottoaffectthesite),andexplanationsregardingthe bounded/nonboundeddetermination.

1.

None

2.

ConsiderationofwindgeneratedwaveactionfortheLIPeventisnotexplicitlyrequiredinNUREG/CR7046,ANS2.8orthe 50.54(f)letter.Furthermore,waverunupisconsiderednegligibleduetolimitedflooddepthsandfetch.

3.

Hydrodynamicloadingwasnotconsideredplausibleduetosurfacewaterflowdirectionisnottowardsthebuildings.Debris impactloadingwasnotconsideredplausibleduetolimitedvelocitiesandflooddepths.

4.

Duetolimitedvelocities,andshortdurationofflooding,sedimentdepositionanderosionisnotconsideredtohavean effectontheLIPfloodlevels.

5.

HighwindsandhailcouldcoincidewiththeLIPevent.Ingeneral,nomanualactionsarerequiredtobeperformedoutside.

Personnelmaybe,however,exposedtotheelementswhilemovingbetweenlocations.Environmentalconditionswouldbe consideredpriortopersonnelbeingdirectedtomovebetweenlocations.

6.

DuetorelativelyshortdurationoftheLIPevent,surchargetogroundwaterisnotconsidered.

7.

Warningtimeisnotcreditedinthefloodprotectionstrategy(sinceonlypermanent/passivemeasuresareusedfortheLIP flood)and,therefore,wasnotconsideredaspartoftheanalysis.

8.

SSCsimportanttosafetyareprotectedbymeansofpermanent/passivemeasuresand,therefore,sitepreparationwasnot consideredaspartoftheanalysis.

9.

The period of inundation varies throughout the site; the time that the water surface elevation exceeds the height of openingsforplantaccessdoorsisprovidedinTable7.12.

10. Thetimeforwatertorecedefromthesitevariesbysitelocation.Oncethefloodwatersrecedebelowfinishedfloor elevationitwouldtakeapproximately2to4hoursforfloodwaterstocompletelyrecedefromareasneartheplantaccess doors.

11. Therearenolimitationsonplantmodesofoperationpriorto,orduring,theLIPevent.

12. Therearenootherfactors,includingwaterborneprojectiles,applicabletothisfloodcausingmechanism.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page11of21 6.0 OVERALLSITEFLOODINGRESPONSE

6.1 DESCRIPTION

OFOVERALLSITEFLOODINGRESPONSE TheLIPcalculationfortheMNGPisprovidedinReference10;whichdescribestheinputs,assumptions, methodology,andresults.Permanentprotectionfeaturessuchascharacterizedtopographicandman made features that affected runoff from a LIP were modeled. The timelines for the cumulative precipitationandprecipitationratesduringtheLIPareshowninTable6.11.Theprecipitationrateis determinedbydividingthechangeincumulativeprecipitationbythechangeintimeduration.

Table6.11,PrecipitationCumulativePrecipitationandRates Time Duration Cumulative Precipitation(inches)

PrecipitationRate (inches/hour) 5min 4.5 54.0 15min 7.2 16.2 30min 10.2 12.0 1hr 13.2 6.0 6hr 20.6 1.5

TheperiodofinundationduringtheLIPvariesthroughoutthesite.Table7.12showsthelengthoftime that the water level remains above the door sill/invert height for the various plant doors; column labeledTotalEstimatedInflowTime(min).

TheMNGPislicensedforaPMFfromtheMississippiRiverwithafloodwaterelevationupto939.2ft (USARReference11).Proceduralactionsareimplementedbasedonriverwaterelevationprojections toprovidefloodprotectionforaPMF.FloodpreparationmeasuresforaPMFareimplementedper proceduresA.6and830002(References12and13,respectively).Specificmeasuresaretakenaspartof References12and13forpreparationforafloodfromtheMississippiRiver.Theseprotectivemeasures includeconstructionofaleveeandbinwallextensionsaroundthepowerblockandsealingpenetrations intheIntakeStructureinordertokeepwateroutoftheplant.Implementationofthesepreparation measures can take several days. Based on the time duration of the PMF there is sufficient time to implementtheprotectivemeasures.

For a LIP event the levee and bin wall extensions would not be constructed due to an absence of warningtimeandbecause,ifconstructed,theleveeandbinwallextensionscouldexacerbatetheLIP eventbyprecludingwaterdrainagefromthesite.WiththeexceptionofDoor209,penetrationsinthe Intake Structure will not see water during the LIP. During the LIP flood, the predicted water levels exceedthresholdelevationsofseveralpathwaysasthedoorsarenotprotected.Theevaluationofthe robustnessofplantfloodprotectionfeaturesduringaLIPconsiders(1)theimpactofwaterintrusionat doorsthatwouldnotbeprotected,and(2)thestructuralimpactsofthehydraulicloadstodoorsthat wouldnotbeprotected.

6.2

SUMMARY

OFPLANTMODIFICATIONSANDCHANGES TheMNGPhascompletedthefloodingevaluationsfortheLIP.Therearenoremainingactions(plant modifications,proceduralchanges,orprocurementactivities)necessarytoimplementfloodstrategies described.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page12of21 7.0 FLOODIMPACTASSESSMENT

7.1 LOCALINTENSEPRECIPITATION

7.1.1 DescriptionofFloodImpact AsdescribedinSection6.1,withtheexceptionoftheplantdoors,theplantispassivelyprotectedfor theLIP.ThesedoorsareprotectedfromthePMFthroughinstallationofprotectivefeatures.These sameprotectivefeatureswouldnotbeinplacefortheLIP.

Table7.11belowsummarizesKeySSCsandtheminimumcriticalwaterelevationineachstructurethat couldimpactKeySSCs.TheremaybeotherKeySSCslocatedinthestructureathigherelevations.Tobe conservativeonlythelowestelevationisidentified.

Table71.1,KeySSCsandAssociatedCriticalElevation Structure KeySSC Critical Elevation(ft)

Notes TurbineBuilding DivisionIIElectricalEquipment 931.3 (1)

ReactorBuilding MCCs311and312 896.7 (2)

PlantAdministrationBuilding ACComponentforDivisionIand II125VDCBatteryChargers 928.4 (3)

EmergencyDieselGenerator Building ComponentsInsideofPanels C91andC92 932.3 (4)

IntakeStructure PumpMotorsandAssociated ElectricalComponents 921 (5)

FuelOilPumpHouse FuelOilPumps 927.3 (6)

Notes:

(1) InafloodingscenariointheTurbineBuilding,waterwouldaccumulateinthelowerelevationofthe buildingatelevation911ft.Theavailablevolumeatelevation911fttoacceptinleakageisgreaterthan 140,874ft3;whichcorrespondstoalimitinginternalfloodingscenariointheTurbineBuilding.The minimumelevationof3.75in.abovetheFFEistheminimumwaterheightthatcouldaffectthe4KV switchgear.

(2) Theminimumlevelof8.5in.abovetheFFEistheheightoffthefloortothebottomoftheMCCs (Reference14).ElectricalequipmentinsidetheMCCsisabovethebottomofthecabinet.

(3) Atalevelof4.75in.abovetheFFEinthePABbasement,theDivisionIandII125VDCbatterychargers couldbeaffected(Reference15).

(4) Atalevelof16in.abovetheFFEintheEDGBuilding,thespeedsensingswitchesandotherterminals withinpanelsC91andC92wouldstarttobesubmerged.Thereare9in.curbswhichseparatethetwo EDGroomsfromeachotherandseparatetheEDGBuildingfromtheTurbineBuilding.Atawaterlevelof 9inchesintheEDGBuilding,thewaterwouldovertopthecurbsandflowintotheTurbineBuilding.

Thus,thecurbslimitthemaximumwaterlevelintheEDGroomsto9in.,orbelowthecriticalelevation.

(5) KeySSCspumpmotorsandassociatedelectricalcomponentsareatleast2ftabovetheFFE.Inaddition, leakageintotheIntakeStructurefromtheScreenhousewillflowintotheTurbineBuildingthrougha tunnelconnectingtheIntakeStructurewiththeTurbineBuilding.Thistunnelprecludeswater accumulationintheIntakeStructure(Reference16).WiththeavailablevolumeidentifiedinNote(1),

above,thewaterlevelintheTurbineBuildingcouldbeapproximatelysixinchesabovetheFFEforthe IntakeStructure.

(6) TheFuelOilPumppedestalsare1ft4in.abovetheFFE(Reference17).

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page13of21 Table7.12showsthepredictedmaximumwater surfaceelevations(WSE) attheplantaccessdoors duringtheLIP(Reference10).AsshowninTable7.12,themaximumwatersurfaceelevationsaround theplantstructurescanbeupto1.0ftabovetheopeningforplantaccessdoors.Table7.12includes themaximumwaterdepthateachdoor,thedooropeningwidth,doorgaporifthedoorisassumedto beopen,thepeakwaterinflowrateandtotalinflowvolumeandtimedurationthatthewaterelevation exceedsthedooropening.ThelocationsoftheplantaccessdoorsareshowninFigure7.11.

Table7.12WaterDepthatPlantAccessDoors OpeningLocation Opening Invert/SillLevel (ft)

Estimated Maximum WSE (ft)

Maximum WaterDepthat Opening Door Opening Width (ft)

Gapat Bottomof Door(in)

(Note1)

PeakInflow Total Estimated Inflow Volume (ft3)

Total Estimated Inflow Time (min)

(ft)

(in)

(cfs)

(gpm)

IntakeStructureDoor (Door209)-interior betweenScreenHouse andIntakeStructure 919.50 920.02 0.52 6.24 3

3/4 0.77 346 707 30 1/2 0.51 229 472 30 Open 3.23 1,450 1,520 30 WestRollUpDoor TurbineBldgAddition (Door119) 931.25 931.11 n/a n/a n/a n/a TurbineBuilding Door119Open (Notes2and3) n/a n/a EastRollUpDoor TurbineBldgAddition (Door120) 931.25 931.53 0.28 3.36 n/a n/a TurbineBuilding Door120Open (Notes2and3) n/a n/a TurbineBldgDoor (Door30) 931 931.53 0.53 6.36 3

1 1.04 467 2,242 66 3/4 0.78 350 1,681 66 RailcarEntry-Turbine Bldg(Door24) 935.00 935.72 0.72 8.64 16 1

6.5 2,918 17,700 86 1/4 1.6 719 4,425 86 RailcarEntry-Reactor Bldg(Doors45and46) 935.00 935.23 0.23 2.76 17 1/8 0.48 216 617 36 1/16 0.24 108 309 36 EmergencyDiesel Generator-East (Door8) 931.00 931.11 0.11 1.32 3

1/4 0.12 54 33 7

EmergencyDiesel Generator-West (Door7) 931.00 931.11 0.11 1.32 3

1/4 0.12 54 33 7

PABStairwayDoor (AdjacenttoDoor341) 932.83 933.09 0.26 3.12 4

1/2 0.48 216 177 9

5/16 0.30 135 111 9

13.8KVRoom (Door1) 931.00 931.52 0.52 6.24 6

1/2 1.03 463 2,253 67 1/4 0.51 229 1,127 67 OffGasStack (Door193) 932.50 933.50 1.00 12.00 5

1/4 0.65 292 2,720 101 1/8 0.33 149 1,360 101 FuelOilTransferPump House (Door483) 931.00 931.11 0.11 1.32 2.5 1/4 0.10 45 28 7

1/8 0.05 23 14 7

Open 0.26 117 52 7

Notes:

1.

Wheremorethanonegapforadoorisshown,thesmallergapisbasedonsitemeasurements.Thelargergapisanassumedvaluethatisconservative relativetothemeasuredgap.

2.

Doors119and120canbeopenorclosedandareassumedtobeopenforthisevaluation.AlsoseeNote3.

3.

Doors119and120areexteriordoorsfromtheoutsidetotheTurbineBuildingAddition.Door30isbetweentheTurbineBuildingAdditionandtheTurbine Building.Door30iscreditedwithprecludingwateringressinlieuofDoors119and120.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page14of21 Figure7.11,PlantAccessDoorLocations

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page15of21 7.1.2 AdequateAPMJustification TheAPMforeachoftheKeySSCsisdeterminedbasedonthedifferencebetweenthecriticalwater elevationinTable7.11andthemaximumwatersurfaceelevationinTable7.12.Thisisshownforeach ofthestructuresinTables7.13through7.18.

Table7.13,APMDetermination-IntakeStructure Door Number AffectedStructure MaxWSE(ft)

(Table7.12)

CriticalElevation (Table7.11)

APM(ft)

KeySSC Affected 209 IntakeStructure 920.02 921 0.98 No

TheIntakeStructureFFEis919ft.AsshowninTable7.12thesillforDoor209isat919.5ft,or6in.

abovetheFFE.ThemaximumwaterdepthintheIntakeStructureisbasedontheassumptionthatDoor 209 is open between the Screenhouse and the Intake Structure. As shown in Table 7.12, the WSE exceeds the door sill for30 minutes. Inleakage into the Intake Structure from the Screenhousewill accumulateintheTurbineBuildingthroughatunnelthatconnectstheTurbineBuildingtotheIntake Structure.ThiswillfurtherprecludewateraccumulationintheIntakeStructure.Therefore,giventhe relativelyshortdurationoftheLIP,theAPM,andthesignificantavailablevolumeintheTurbineBuilding toaccommodateinleakage,thereisadequateAPMfortheIntakeStructure.

Table7.14,APMDetermination-TurbineBuilding Door Number AffectedStructure MaxWSE(ft)

(Table7.12)

CriticalElevation (Table7.11)

APM KeySSC Affected 1

TurbineBuilding 931.52 931.3 SeeBelow No 24 TurbineBuilding 935.72 931.3 SeeBelow No 30 TurbineBuilding 931.53 931.3 SeeBelow No 119 TurbineBuilding 931.11 931.3 SeeBelow No 120 TurbineBuilding 931.53 931.3 SeeBelow No 209 TurbineBuilding 920.02 931.3 SeeBelow No

LeakagepastDoors1,24,and30woulddraintothe911ftelevationoftheTurbineBuildingandnot accumulateatthe931ftelevation.Thedrainagetothe911ftelevationprecludeswaterfromaffecting KSFsatthe931ftelevation.Asdiscussed,above,inthesectionassociatedwithTable7.13,leakage pastDoor209canalsoaccumulateintheTurbineBuilding.Doors1,24,and30arenormallyclosed.As showninTable7.12,theWSEexceedsthedoorsillforDoors1,24,30,and209for67,86,66,and30 minutes, respectively. Leakage past Door 1 can accumulate in either the Turbine Building, 911 ft elevation, or the PAB Basement; thus, leakage past Door 1 is included in the determination of total wateraccumulationforbothstructures.TurbineBuildingAdditionDoors119and120caneitherbe openorclosed,thus,Doors119and120arenotcreditedwithprecludingwateringress.Door30is creditedinlieuofcreditingDoors119and120.Asdiscussedabove,leakagepastDoor209fromthe ScreenHousetotheIntakeStructurecouldaccumulateintheTurbineBuilding911ftelevation.Door 209isnormallyclosed,butforthepurposeofthiscalculationisassumedtobeopen.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page16of21 TwogapsizesareprovidedforDoors1,24,and30inTable7.12.Thesmallergapistheactualgapat thebottomofthedoor;thisisreferredtoastherealisticgap.Thelargergapissimplyincreasingthe realistic gap to add margin; this is referred to as the conservative gap. For the purposes of this evaluationDoor209isassumedtobeopen.

UsingrealisticdoorgapsizesforDoors1,24,and30andwithDoor209open,thetotalwatervolume thatcouldaccumulateintheTurbineBuildingis1,127+4,425+1,681+1,520=8,753ft3.Thisisasmall fractionoftheavailablevolumeof140,874ft3toacceptinleakage.Usingconservativedoorgapsizesfor Doors 1, 24, 30, and 209 (Door 209 is assumed to be open) the total water volume that could accumulateintheTurbineBuildingis2,253+17,700+2,242+1,520=23,715ft3.Asexpectedwiththe largerdoorgapsize,thereisagreatertotalinleakagevolume,butthetotalinleakagevolumeisstillwell withintheavailablevolumetoacceptinleakage.

Leakage through a door gap is calculated in Reference 10 using the orifice equation. In the orifice equation,theflowrateis(1)proportionaltothedoorgap,and(2)proportionaltothesquarerootofthe headofwateroutsidethedoorgap.Thus,theeffectontheflowratefromconservativelyincreasingthe gapisequivalenttoanincreaseintheheadofwatermultipliedbythedoorgapratio(conservativeto realistic)squared.

The ratio of the conservative to realistic doors gaps for Doors 1, 24, and 30 are: 2, 4, and 1.33, respectively.Thiscanbetranslatedintothesubstantialmarginofequivalentwaterdepthattherealistic doorgaps.Asdescribedabove,evenattheseconservatisms,theresultingtotalinleakageiswellwithin theavailablevolume.

Therefore,basedonthemarginavailableintheheadofwateroutsidethedoorusedindeterminingthe totalinleakageandthemarginbetweenthetotalinleakageandtheavailablevolume,thereisadequate APMfortheTurbineBuilding.

Table7.15,APMDetermination-ReactorBuilding Door Number AffectedStructure MaxWSE(ft)

(Table7.12)

CriticalElevation (Table7.11)

APM KeySSC Affected 45and46 ReactorBuilding 935.23 896.7 SeeBelow No 193 ReactorBuilding 933.50 896.7 SeeBelow No

Leakage past Doors 45/46 could accumulate in the Reactor Building. Leakage past Door 193 would initiallystarttoaccumulateintheOffGasStack.TherearenokeySSCslocatedintheOffGasStackthat couldbeaffectedbytheLIP.LeakageintotheOffGasStackwouldflowthroughthefloordrainand accumulateintheReactorBuilding.AsshowninTable7.12,theWSEexceedsthedoorsillforDoors 45/46and193for36and101minutes,respectively.

TwogapsizesareprovidedforDoors45/46and193inTable7.12.Thesmallergapistheactualgapat thebottomofthedoor;thisisreferredtoastherealisticgap.Thelargergapissimplyincreasingthe realisticgaptoaddmargin;thisisreferredtoastheconservativegap.

UsingrealisticdoorgapsizesforDoors45/46and193,thetotalwatervolumethataccumulatesinthe ReactorBuildingis309+1,360=1,669ft3.Thecriticalelevationcorrespondstoawatervolumeof6,713 ft3intheReactorBuilding.Thetotalinleakageisapproximately25%oftheavailablecapacity.Usingthe

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page17of21 conservativedoorgapsizeforDoors45/46andDoor193thetotalwatervolumethatcouldaccumulate intheReactorBuildingis617+2,720=3,337ft3.Inthiscasethetotalinleakageisapproximately50%of theavailablecapacity.

Leakage through a door gap is calculated in Reference 10 using the orifice equation. In the orifice equation,theflowrateis(1)proportionaltothedoorgap,and(2)proportionaltothesquarerootofthe headofwateroutsidethedoorgap.Thus,theeffectontheflowratefromconservativelyincreasingthe gapisequivalenttoanincreaseintheheadofwatermultipliedbythedoorgapratio(conservativeto realistic)squared.

TheratiooftheconservativetorealisticdoorsgapsforDoors45/46and193areboth2.Thiscanbe translatedintothesubstantialmarginofequivalentwaterdepthattherealisticdoorgaps.Asdescribed above,evenattheseconservatisms,thereissignificantmargin(approximately50%)betweenthetotal inleakagevolumeandtheavailablevolumetoacceptinleakage.

Therefore,basedonthemarginavailableintheheadofwateroutsidethedoorusedindeterminingthe totalinleakageandthemarginbetweenthetotalinleakageandtheavailablevolume,thereisadequate APMfortheReactorBuilding.

Table7.16,APMDetermination-EmergencyDieselGeneratorBuilding Door Number AffectedStructure MaxWSE(ft)

(Table7.12)

CriticalElevation (Table7.11)

APM(ft)

KeySSC Affected 7

EDGBuilding-West 931.11 932.33 1.2 No 8

EDGBuildingEast 931.11 932.33 1.2 No

AsshowninTable7.12,theWSEexceedstheDoor7and8sillfor7minutes.Thepeakwaterelevation outsidethedoorsis931.11orapproximately1.3inchesabovetheEDGroomfloor;whichislessthanthe waterdepthof16inchesthatcanbeaccommodated.Inaddition,thereare9in.curbswhichseparate thetwoEDGroomsfromeachotherandseparatetheEDGBuildingfromtheTurbineBuilding.Ata waterlevelof9inchesintheEDGBuilding,thewaterwouldflowovertopthecurbsandflowintothe Turbine Building. Thus, the curbs limit the maximum water level in the EDG rooms to 9 in. The maximumwaterdepthisbelow9in.,thus,inleakagewouldbecontainedwithintheEDGrooms.

Given,therelativelyshorttimeperiodthattheWSEexceedsthedoorsill;thatthemaximumwaterlevel thatwouldbereachedintheroomassumingthedrainswereblockedislessthanthecriticalelevation; andthatthemaximumwaterlevelislimitedbythecurbstolessthanthecriticalelevation,thereis adequateAPM.

Table7.17,APMDetermination-PlantAdministrationBuilding DoorNumber Affected Structure MaxWSE(ft)

(Table7.12)

CriticalElevation (Table7.11)

APM(ft)

KeySSC Affected PABStairway Door PAB 933.09 928.4 SeeBelow No 1

PAB 931.52 928.4 SeeBelow No

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page18of21 ThePABStairwayDoorprovidesaccesstothePAB.LeakagepastDoor1couldalsoenterthePAB.Thus, leakagepastthePABStairwayDoorandDoor1couldaccumulateinthePABBasement.Asshownin Table7.12,theWSEexceedsthedoorsillforthePABStairwayDoorandDoor1for9and67minutes, respectively.

TwogapsizesareprovidedforDoors1andthePABStairwayDoorinTable7.12.Thesmallergapisthe realisticgapatthebottomofthedoor;thisisreferredtoastherealisticgap.Thelargergapissimply increasingtheactualgaptoaddmargin;thisisreferredtoastheconservativegap.

Usingrealisticdoorgapsforthetwodoors,thetotalwatervolumethatcouldaccumulateinthePAB Basementis111+1,127=1,238ft3.Thisisequivalenttoawaterdepthof1.6in.Thisisapproximately 33%ofthecriticalelevationof4.75in.UsingtheconservativedoorgapsizesforthePABStairwayDoor andDoor1thetotalwatervolumethatcouldaccumulateinthePABBasementis177+2,253=2,430 ft3.Thisisequivalenttoawaterdepthof3.2in.,orapproximately67%ofthecriticalelevation.

Leakage through a door gap is calculated in Reference 10 using the orifice equation. In the orifice equation,theflowrateis(1)proportionaltothedoorgap,and(2)proportionaltothesquarerootofthe headofwateroutsidethedoorgap.Thus,theeffectontheflowratefromconservativelyincreasingthe gapisequivalenttoanincreaseintheheadofwatermultipliedbythedoorgapratio(conservativeto realistic)squared.

TheratiooftheconservativetorealisticdoorsgapsforDoors1andthePABStairwayDoorare:2and 1.6,respectively.Thiscanbetranslatedintothesubstantialmarginofequivalentwaterdepthatthe realisticdoorgaps.Asshownabove,evenwiththeseincreasesinthewaterelevation,thereismargin (approximately33%)betweenthetotalinleakagevolumeandtheavailablevolumetoacceptinleakage.

Therefore,basedonthemarginavailableintheheadofwateroutsidethedoorusedindeterminingthe totalinleakageandthemarginbetweenthetotalinleakageandtheavailablevolume,thereisadequate APMforthePlantAdministrationBuilding.

Table7.18,APMDetermination-FuelOilPumpHouse DoorNumber Affected Structure MaxWSE(ft)

(Table7.12)

CriticalElevation (Table7.11)

APM(ft)

KeySSC Affected 483 FuelOil PumpHouse 931.11 927.33 SeeBelow No

Door483ismaintainedclosed.AsshowninTable7.12,theWSEexceedsthedoorsillfor7minutes.

ThecriticalwaterelevationintheFuelOilPumpHousecorrespondstoanallowabletotalinleakageof80 ft3.Usingaconservativedoorgapwiththedoorclosedtheinleakageis28ft3;35%oftheavailable volume. The conservative door gap is larger than the actual physical door gap without credit for weatherstripping.Furthermore,ifitisconservativelyassumedthatDoor483isopenthetotalwater volumethatcouldaccumulateintheFuelOilPumpHouseis52ft3;65%oftheavailablevolume.

Giventhatthereismarginbetweenthetotalinleakageandtheavailablevolume,evenwiththenormally closeddoorassumedtobeopen,thereisadequateAPMfortheFuelOilPumpHouse.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page19of21 Summary As described above the limiting flood elevations are below the critical elevations for Key SSCs.

Therefore, the KSFs are protected by the characteristics of the site itself such as plant grading, by locationsoftheKeySSCs,andbythecapabilityofthestructurestoaccommodateinleakage.Therefore, theLIPisnotaconsequentialfloodfortheMNGP.Furthermore,anyflooduptotheLIPflooddescribed abovewouldalsonotbeconsideredaconsequentialfloodfortheMNGP.

7.1.3 ReliabilityofFloodProtection As described above, flood protection for the LIP is provided by the permanently installed plant structures that are designed for a PMF. The WSE for the PMF is much higher than a LIP, thus the permanentlyinstalledplantstructureswillprovidefloodprotectionfortheLIP.Sinceplantdoorswill notbeprotectedfortheLIPbythesameprotectionthatwouldbeinstalledaspartofthePMFflood response,potentialloadsduringtheLIPeventwereevaluatedatthedoors.Thesedoorsandsupporting structureshavebeenevaluated(Reference18)anddeterminedtobecapableofwithstandingtheloads fromtheLIPwaterlevel.TheLIPeventwillnotinclude debrisimpactor appreciable hydrodynamic effectsduetothedirectionofflowbeingawayfromthebuildings.

7.1.4 AdequateOverallSiteResponse ThesitedoesnotrequireanyhumanactionstoprotectKeySSCsduringtheLIP.Thus,anevaluationof theoverallsiteresponsewasnotnecessary.

8.0 CONCLUSION

Associatedeffects(AE)andfloodeventduration(FED)parameterswereassessedandsubmittedasa partoftheFHRR.TheFEaffirmsthatduringLIPeventsthesitehaseffectivefloodprotectionthrough thedeterminationofAvailablePhysicalMargin(APM)andthereliabilityofprotectionfeatures.Thesite doesnotrequireanyhumanactionstoprotectKeySSCssoanevaluationoftheoverallsiteresponse wasnotnecessary.ThisFEfollowsPath2ofNEI1605,Rev.1,andutilizesAppendixBforguidancefor evaluating the site protection features. This submittal completes the actions related to External FloodingrequiredbytheMarch12,2012,10CFR50.54(f)letter.

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page20of21 APPENDIX1 ThisappendixprovidesamatrixoftheitemsidentifiedinSection9.2,Documentation,ofNEI1605, forPath2,withthecorrespondingsection(s)intheMNGPFocusedEvaluationwheretherequested informationisprovided.

CharacterizationofFloodParameters FloodhazardparametersaresummarizedinTable5.12.

EvaluationandDescriptionofFloodImpacts Section6.1providesadescriptionoftheoverallsitefloodingresponseduringaLIP.Section7.1 summarizestheimpactstothesiteduringaLIP.Table7.12identifiesthemaximumwatersurface elevationsateachoftheplantaccessdoorsduringtheLIP.

KeySSCsPotentiallyImpactedbyFloodWaters Table7.11,includingthenotesidentifiestheKeySSCsthatcouldpotentiallybeimpactedbyflood watersduringaLIP.AsdescribedinSection7.1.1,theKeySSCsidentifiedarethosethatwouldbe initiallyimpactedbywaterineachstructure;i.e.,thoseatthelowestelevation.

CriticalElevationsThatCouldImpactKeySSCs Table7.11identifiesthecriticalelevationsfortheKeySSCsforeachofthestructures.Asdescribed inSection7.1.1,tobeconservative,thecriticalelevationcorrespondingtotheKeySSCatthelowest elevationisidentified.

FloodFeaturesReliedOnToProtectKeySSCs DuringaLIPpermanentpassiveprotectionfeaturesarereliedontoprotectKeySSCstomaintain KSFs.Section6.1describesthepermanentpassiveprotectionastheplantstructures.Tobe conservative,gapsatplantaccessdoorswereconsideredinaconservativemannerduringaLIP.The actualgapsaresmallerthanthegapsassumedandwouldfurtherreducetheamountofwater inleakage.AssummarizedinSection7.1.3,plantaccessdoorswereevaluatedtoensurethatthey arecapableofwithstandingtheloadsfromtheLIP.

DemonstrationofEffectiveProtection,Including:

o CalculationofAPMforEachFloodProtectionFeature ThedeterminationofAPMforthefloodprotectionfeaturesforeachoftheplantstructures areprovidedinTables7.13through7.18.

o JustificationthatCalculatedAPMisAdequate AppropriatejustificationthattheAPMforthefloodprotectionfeaturesforeachoftheplant structuresisadequateisprovidedinthediscussionassociatedwithTables7.13through 7.18.

o EvaluationofReliabilityofEachFloodProtectionFeature

MonticelloExternalFloodingAssessmentFocusedEvaluation Rev.0 Page21of21 AsdescribedinSection7.1.3,floodprotectionfortheLIPisprovidedbypermanently installedplantstructures(passiveprotection)thataredesignedforaPMF.TheWSEforthe PMFismuchhigherthanaLIP,thusthepermanentlyinstalledplantstructureswillprovide reliablefloodprotectionfortheLIP.Doorsandtheassociatedsupportingstructureshave beenevaluatedanddeterminedtobecapableofwithstandingtheloadsfromtheLIPwater level.

o EvaluationofHumanActionsandanAdequateSiteResponse AsdescribedinSection7.1.4,thesitedoesnotrequireanyhumanactionstoprotectKey SSCsduringtheLIP.Thus,anevaluationoftheadequacyoftheoverallsiteresponsewas notnecessary.

SummaryofResultsandConclusionsofAssessmentDemonstratingEffectiveProtection AssummarizedinSection8.0,associatedeffectsandfloodeventdurationparameterswere assessedandsubmittedasapartoftheFHRR.TheFEaffirmsthatduringLIPeventsthesitehas effectivefloodprotectionthroughthedeterminationofAvailablePhysicalMarginandthereliability ofprotectionfeatures.ThesitedoesnotrequireanyhumanactionstoprotectKeySSCssoan evaluationoftheoverallsiteresponsewasnotnecessary.ThisFEfollowsPath2ofNEI1605,Rev.

1,andutilizesAppendixBforguidanceforevaluatingthesiteprotectionfeatures.Thissubmittal completestheactionsrelatedtoExternalFloodingrequiredbytheMarch12,2012,10CFR50.54(f) letter.