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#REDIRECT [[RS-12-168, Co., Llc'S 180-day Response to NRC Request for Information Pursuant to 10CFR50.54(f) Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident]]
| number = ML12332A305
| issue date = 11/27/2012
| title = Exelon Generation Co., Llc'S 180-day Response to NRC Request for Information Pursuant to 10CFR50.54(f) Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident
| author name = Kaegi G T
| author affiliation = Exelon Generation Co, LLC
| addressee name =
| addressee affiliation = NRC/NRR, NRC/Document Control Desk
| docket = 05000237, 05000249
| license number = DPR-019, DPR-025
| contact person =
| case reference number = RS-12-168
| document type = Letter
| page count = 53
| project =
| stage = Response to RAI
}}
 
=Text=
{{#Wiki_filter:10 CFR 50.54(f)
 
RS-12-168
 
November 27, 2012
 
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk
 
11555 Rockville Pike
 
Rockville, MD  20852 Dresden Nuclear Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-19 and DPR-25 NRC Docket Nos. 50-237 and 50-249
 
==Subject:==
Exelon Generation Company, LLC's 180-day 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
: 3. Exelon Generation Company, LLC's 90-day Response to NRC Request for Information Pursuant to 10 CFR 50.54(f)  Regarding Recommendations 2.1 and 2.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident (Flooding), dated June 11, 2012 On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued Reference 1 to all power reactor licensees. Enclosure 4 of Reference 1 contains specific Requested Actions, Requested Information, and Required Responses associated with Recommendation 2.3 for Flooding. On June 11, 2012, Exelon Generation Company, LLC (EGC) submitted the 90-day response  requested in Enclosure 4 of Reference 1, confirming that EGC would use the NRC-endorsed
 
flooding walkdown procedure (Reference 3).
U.S. Nuclear Regulatory Commission 180-Day Response to 50.54(f) Letter NTTF Recommendation 2.3: Flooding November 27, 2012 Page 2 For flooding Recommendation 2.3 (walkdowns), Enclosure 4 of Reference 1 states that within 180 days of the NRC's endorsement of the walkdown process (Reference 2), each addressee will submit a 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. This letter provides the Dresden Station, Units 2 and 3 180-day response to Reference 1 for Flooding Recommendation 2.3.Conditions identified during the walkdowns were documented and entered into the corrective action program. Performance of the walkdowns provided confirmation, with two exceptions, that flood protection features are in place, are in good condition and will perform as credited in the current licensing basis. The two deficiencies will be restored to their original design for resolution of the issues. to this letter provides the requested information for Dresden Station Units 2 and 3.
This letter contains no new regulatory commitments.
Should you have any questions concerning the content of this letter, please contact Ron Gaston at (630) 657-3359.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 27th day of November 2012.
Respectfully, 0 Glen T. Kaegi Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC
 
==Enclosures:==
 
1.Flooding Walkdown Report In Response To The 50.54(f)Information Request Regarding Near-Term Task Force Recommendation 2.3: Flooding for the Dresden Nuclear Power Station, Units 2 and 3 cc:Director, Office of Nuclear Reactor Regulation Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Units 2 and 3 NRC Project Manager, NRR - Dresden Units 2 and 3 Illinois Emergency Management Agency - Division of Nuclear Safety U.S. Nuclear Regulatory Commission 180-Day Response to 50.54(f) Letter NTTF Recommendation 2.3: Flooding November 27,2012 Page 2 For flooding Recommendation 2.3 (walkdowns), Enclosure 4 of Reference 1 states that within 180 days of the NRC's endorsement of the walkdown process (Reference 2), each addressee will submit a 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.
This letter provides the Dresden Station, Units 2 and 3 180-day response to Reference 1 for Flooding Recommendation
 
===2.3. Conditions===
 
identified during the walkdowns were documented and entered into the corrective action program. Performance of the walkdowns provided confirmation, with two exceptions, that flood protection features are in place, are in good condition and will perform as credited in the current licensing basis. The two deficiencies will be restored to their original design for resolution of the issues. Enclosure 1 to this letter provides the requested information for Dresden Station Units 2 and 3. This letter contains no new regulatory commitments.
Should you have any questions concerning the content of this letter, please contact Ron Gaston at (630) 657-3359.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 27th day of November 2012. Respectfully, Glen T. Kaegi Director -Licensing
& Regulatory Affairs Exelon Generation Company, LLC
 
==Enclosures:==
: 1. Flooding Walkdown Report In Response To The 50.54(f) Information Request Regarding Near-Term Task Force Recommendation 2.3: Flooding for the Dresden Nuclear Power Station, Units 2 and 3 cc: Director, Office of Nuclear Reactor Regulation Regional Administrator
-NRC Region III NRC Senior Resident Inspector
-Dresden Units 2 and 3 NRC Project Manager, NRR -Dresden Units 2 and 3 Illinois Emergency Management Agency -Division of Nuclear Safety U.S. Nuclear Regulatory Commission 180-Day Response to 50.54(f) Letter NTTF Recommendation 2.3: Flooding November 27, 2012
 
Page 3
 
Enclosure 1
 
Flooding Walkdown Report In Response To The 50.54(f) Information Request Regarding Near-Term Task Force Recommendation 2.3: Flooding for the Dresden Station, Units 2 and 3 (50 pages)
 
Joseph V. Bellini AMEC/Exelon 11/20/12 FLOODING WALKDOWN REPORT IN RESPONSE TO THE 50.54(f) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.3: FLOODING for the DRESDEN NUCLEAR POWER STATION (UNIT 2 & UNIT 3) 6500 North Dresden Road, Morris, IL 60450 Renewed Facility Operating License Nos. DPR-19 & DPR-25 NRC Docket Nos. 50-237 & 50-249 Exelon Generation Company, LLC 300 Exelon Way, Kennett Square, PA 19348 Prepared by: AMEC Environment
& Infrastructure, Inc. 502 West Germantown Pike, Suite 850, Plymouth Meeting, PA 19462 November 20, 2012 Printed Name Affiliation Signature Preparer:
PETR MASOPUST AMEC Reviewer:
MATIHEW LEHRER AMEC Approver:
JEFFREY WRIGHT AMEC Lead Responsible Engineer: " /!) '7."7 . Branch Manager: , Jose b Re:bk Senior Manager F Design Engineering:
tAut.. WO"S" n<.\Ew\c<..
Corporate Acceptance:
11/20/2012 11/20/2012 11/20/2012 1//2-D lUll "2-Ii 12.0)2013-.. , ,
NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Contents1.EXECUTIVE
 
==SUMMARY==
...............................................................................................................................22.PURPOSE....................................................................................................................................................3a.Background............................................................................................................................................3b.SiteDescription......................................................................................................................................4c.RequestedActions.................................................................................................................................6d.RequestedInformation..........................................................................................................................63.METHODOLOGY.........................................................................................................................................7a.OverviewofNEI12 07(WalkdownGuidance)......................................................................................7b.ApplicationofNEI12 07........................................................................................................................8c.ReasonableSimulations.........................................................................................................................9d.WalkdownInspectionGuidance..........................................................................................................124.RESULTS...................................................................................................................................................12a.RequestedInformationItem2(a)-DesignBasisFloodHazards.........................................................12b.RequestedInformationItem2(b)-CLBProtectionandMitigationFeatures.....................................17c.RequestedInformationItem2(c)-FloodWarningSystems...............................................................18d.RequestedInformationItem2(d)-FloodProtectionSystem/BarrierEffectiveness..........................19e.RequestedInformationItem2(e)-ImplementationofWalkdownProcess.......................................36f.RequestedInformationItem2(f)-FindingsandCorrectiveActionsTaken/Planned.........................38g.RequestedInformationItem2(g)-Cliff-EdgeEffectsandAvailablePhysicalMargin.......................41h.RequestedInformationItem2(h)-Planned/Newly InstalledFloodProtectionEnhancements........415.CONCLUSIONS..........................................................................................................................................426.REFERENCES.............................................................................................................................................48Page1 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision01. EXECUTIVE
 
==SUMMARY==
PerNRC'srequest,afloodingprotectionwalkdownwasconductedatDresdenNuclearPowerStation(DresdenStation)toidentifyandaddressplantspecificdegraded,nonconforming,orunanalyzedconditionsofplant'sfloodprotectionfeatures,includingfloodmitigationprocedures.ThefloodingwalkdownwasconductedbetweenAugust8andAugust16,2012andincludedvisualinspectionsandreasonablesimulations.Thescopeofthefloodingwalkdownwasdevelopedfollowingadetailedreviewofallrelevantlicensingdocuments.SincethesiteisinundatedduringthedesignbasisPMFevent,DresdenStationislicensedtomitigateagainsttheaffectsofafloodbyimplementingprocedurestopreventdamagetothereactorcore.Themainfloodemergencyprocedure(DOA001004)invokesseveralstandardoperatingprocedurestoprovideforsafeshutdownandcool downofbothreactors.Therefore,thefloodemergencyproceduresalongwithassociatedstandardoperatingprocedureswerethemainfocusofthewalkdown.DresdenStationdoesnothaveincorporated/exteriorortemporaryfeaturesthatarecreditedinthecurrentlicensingbasis(CLB)documentswithprovidingfloodprotection.However,belowgradestructures(i.e.,basementwallsandbasementslabs)ofUnit2and3ReactorandTurbineBuildingsweredesignedtowithstandhydrostaticloadsassociatedwithextremegroundwaterconditionsandwerevisuallyinspectedaspartofthefloodingwalkdown.ThemethodologyandacceptancecriteriafortheevaluationoffloodprotectionfeatureswasdevelopedbasedonNEIreport12 07(Rev0A),GuidelinesforPerformingVerificationWalkdownsofPlantProtectionFeatures.Theverificationprocessforallimplementingproceduresincludedareasonablesimulation(i.e.,adetailedprocedurewalk throughwiththestaffresponsibleforimplementationoftheprocedure).Forproceduresorproceduralstepsthathavenotbeenperformedinthepast,adrillorexercisewasperformedaspartofthereasonablesimulationtoverifythattheprocedurecanbeperformedasspecified.SincestandardoperatingshutdownproceduresareanintegralpartoftheofthefloodmitigationstrategyatDresdenStation,theseprocedureswerealsoreviewedtoverifythattheycanbeimplementedduringafloodemergencyandwillnotbechallengedbyfloodingconditions.Visualinspectionsofbelow gradewallsofUnit2and3ReactorandTurbineBuildingswereconductedtoverifytherearenopotentialobservablestructuraldeficienciesthatmayimpactthestructure'sabilitytowithstandhydrostaticloads.Inaddition,penetrationsealswerealsovisuallyinspectedanddocumentedasacomponentofthewallfeatures.Therewerefifteen(15)areaswithbelowgradewallsandslabs,whichwerevisuallyinspectedduringthewalkdown.Allofthewallsandslabswereaccessible;however,threepenetrationswereconsideredinaccessible,duetoapipeconfigurationorapullboxpreventingaccesstothepenetration.SincethepenetrationsarenotcreditedasindividualfloodprotectionfeaturesintheCLB,reviewofavailabledrawingsandengineeringjudgmentwereusedtoassesswhethertheycouldpotentiallyimpacttheabilityofbelow gradewallstofunctionasafloodbarrier.Therewasnoevidenceofleakagebelowtheseinaccessiblepenetrations.Electricalconduitsenteringthereactorbuildingwereevaluatedtodeterminewhethertheycanprovideapathwayforgroundwaterintosafety relatedbuildings.Ingeneral,electricalconduitsroutedtosafety relatedbuildingsareequippedwithcouplingsandplugsonbothendstopreventgroundwaterintrusion.Atoneinstance,twoelectricalconduitswereroutedthroughapenetrationsleevewithaninternalseal,whichwasinaccessibleforvisualinspectionduringthewalkdown;however,areasonableassurancethattheconditionoftheconduitisacceptablewasprovided.Noneoftheelectricalconduitsenteringthesafety relatedareasoftheplantareroutedthroughelectricalmanholes.Page2 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Thefloodemergencyprocedureandtheassociatedprocedures(includingstandardshutdownprocedures)werereasonablysimulatedtoensurethattheycanbeperformedasspecifiedandprotectthereactorfromcoredamageduringfloodingconditions.Overall,nineteen(19)reasonablesimulationsrelatedtotheimplementationofthefloodemergencyprocedurewereperformed.Basedontheresultsoftheevaluationandthereviewofoperatorlogs,thecriticalpathitemsofthefloodemergencyprocedurecanbeimplementedaswrittenifsufficientfloodwarningavailable.DuringtheevaluationitwasdeterminedthatresourcesarenotavailabletoaccuratelypredictriverlevelsattheDresdenintakeinadvance.However,itisreasonabletoassumethatalimitedfloodwarningwouldbeobtainedfromDresdenLockMasterorusingriverforecastingtoolsfortheIllinoisRiverwatershed.Inaddition,thefloodemergencyprocedureisalsoenteredfollowinganotificationfromTransmissionSystemOperatorpredictingrainfallof2inchesin6hours.Thisallowsthesitetoinitiatefloodprotectionmeasuresbasedonarainfallforecastand/orlimitedfloodwarning.Assumingthatonlyashortfloodwarningisavailable,theconstructionoftheIsolationCondenserMakeupPumphousesandbagmaynotbeimplementedintimeusingtheavailableresources.However,initiationofsandbaggingpreparationsatanearlierpointinthefloodemergencyprocedureduetoweatherforecastwillaidtheStationintimelyconstructionofthesandbagbermandprovideadditionalmarginofsafety.2. PURPOSEa. BackgroundInresponsetothenuclearfueldamageattheFukushimaDaiichipowerplantduetotheMarch11,2011earthquakeandsubsequenttsunami,theUnitedStatesNuclearRegulatoryCommission(NRC)establishedtheNearTermTaskForce(NTTF)toconductasystematicreviewofNRCprocessesandregulations,andtomakerecommendationstotheCommissionforitspolicydirection.TheNTTFreportedasetofrecommendationsthatwereintendedtoclarifyandstrengthentheregulatoryframeworkforprotectionagainstnaturalphenomena.OnMarch12,2012,theNRCissuedaninformationrequestpursuanttoTitle10oftheCodeofFederalRegulations,Section50.54(f)(10CFR50.54(f)or50.54(f))(Reference3)whichincludedsix(6)enclosures: [NTTF]Recommendation2.1:Seismic [NTTF]Recommendation2.1:Flooding [NTTF]Recommendation2.3:Seismic [NTTF]Recommendation2.3:Flooding [NTTF]Recommendation9.3:EP LicenseesandHoldersofConstructionPermitsInEnclosure4ofReference3 ,theNRCrequestedthatlicensees"performfloodprotectionwalkdownstoidentifyandaddressplantspecificdegraded,nonconforming,orunanalyzedconditionsandcliff edgeeffects(throughthecorrectiveactionprogram)andverifytheadequacyofmonitoringandmaintenanceprocedures"(seenoteregarding"cliff edgeeffects").Structures,systems,andcomponents(SSCs)importanttosafetyatnuclearpowerplantsmustbedesignedtowithstandtheeffectsofnaturalphenomena,includingfloods,withoutlossofcapabilitytoperformtheirPage3 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0intendedsafetyfunctions.Forfloodingwalkdowns,identifying/addressingplantspecificdegraded,nonconforming,orunanalyzedconditions(throughthecorrectiveactionprogram)andverifyingtheadequacyofmonitoringandmaintenanceproceduresisassociatedwithfloodprotectionandmitigationfeaturescreditedinthecurrentdesign/licensingbasis.NewfloodhazardinformationwillbeconsideredinresponsetoEnclosure2ofReference3.OnbehalfofExelonGenerationCompany,LLC(Exelon),thisreportprovidestheinformationrequestedintheMarch12,201250.54(f)letter;specifically,theinformationlistedunderthe"RequestedInformation"sectionofEnclosure4,paragraph2("a"through"h").The"RequestedInformation"sectionofEnclosure4,paragraph1("a"through"j"),regardingfloodingwalkdownprocedures,wasaddressedviaExelon'sJune11,2012,acceptance(Reference1)oftheindustrywalkdownguidance(Reference2).NoteRegardingCliff EdgeEffectsCliff edgeeffectsweredefinedbytheNTTFReport(Reference5),whichnotedthat'thesafetyconsequencesofafloodingeventmayincreasesharplywithasmallincreaseinthefloodinglevel'.WhiletheNRCusedthesametermastheNTTFReportintheMarch1250.54(f)informationrequest(Reference3),theinformationtheNRCexpectsutilitiestoobtainduringtheRecommendation2.3:FloodingWalkdownsisdifferent.Toclarify,theNRCisnowdifferentiatingbetweencliff edgeeffects(whicharedealtwithunderEnclosure2ofReference3)andanewterm,AvailablePhysicalMargin(APM).APMinformationwillbecollectedduringthewalkdowns,butwillnotbereportedintheresponsetoEnclosure4ofReference3.ThecollectedAPMinformationwillbeavailableforuseindevelopingtheresponsetoEnclosure2ofReference3.b. SiteDescriptionDresdenStationislocatedapproximately8mileseastofMorris,Illinois.TheplantislocatedattheconfluenceoftheKankakee,DesPlaines,andIllinoisrivers,whicharethemajorfloodingsourcesconsideredintheCLB.ThecontributingdrainageareatotheKankakeeRiverupstreamoftheintakeisapproximately5,165squaremiles,andthecontributingdrainageareatotheDesPlainesRiverupstreamoftheconfluenceisapproximately2,111squaremiles.Page4 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0DresdenNuclearPowerStationFigure1:SiteLocationTheplantissituateddirectlyadjacenttotheriver,withadesignplantgradeelevationof517.0feetMeanSeaLevel(MSL).AlloftheelevationsreferencedintheDresdenLicensingdocumentsarebasedonaMSLDatum.Thelowestsubgradefloorcontainingequipmentimportanttosafetyareservicewaterpumpsmotorsintheintakestructure,whicharesetonafloorelevation509.0ftMSLandareunprotectedfromfloodingabovethiselevation(Reference10).Nonwatertightopeningsinwallsofsafety relatedstructuresarelocatedatelevation517.5ftMSL.Therearenoexteriorfloodprotectionbarriers(i.e.,levees,dikes,gates)thatwillpreventfloodingatthesite.TheDresdenStation'sexternalfloodmitigationstrategyistopreventlossofsafeplantcontrolthatcouldbecausedbytheProbableMaximumFlood(PMF)oftheIllinoisandKankakeeriversthroughtheimplementationofafloodemergencyprocedure.Thefloodemergencyprocedureentailsthesafeshutdownoftheplant.ThePMFisestimatedtoreachapeakStillwaterElevationof524.5ftMSL.WindgeneratedwavesontheKankakeeRiverwouldbe2.6feethighandwaverun upwouldreach3feetabovestillwaterlevel,increasingthemaximumwatersurfaceelevationtoapproximately528ftMSL(Reference10).Asaresult,predictedmaximumwatersurfaceelevationsaresignificantlyaboveboththeplantgradeelevationandthelowestopeningleadingtosafetyrelatedequipment.Itisalsoestimatedthattheplantwouldexperienceflooding(waterelevationsgreaterthanthedesignplantgradeof517.0ftMSL)for57hours,andwillrequiretheemergencydieselmake uppumptoprovidemake upwatertotheisolationcondensersforatleast78hoursbeforethefloodwaterrecededtoelevation509ftMSLandadditional12hourstoallowforservicewaterpumpmotorstobere installed.TheCLBalsoconsideredtheaffectsofalocalintenseprecipitation(LIP)onsitedrainage.Page5 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0c. RequestedActionsPerEnclosure4ofReference3 ,theNRCrequeststhateachlicenseeconfirmuseoftheindustry developed,NRC endorsed,floodwalkdownproceduresorprovideadescriptionofplant specificwalkdownprocedures.InaletterdatedJune11,2012(Reference1),Exelonconfirmedthatthefloodingwalkdownprocedure(Reference2),endorsedbytheNRConMay31,2012,willbeusedasthebasisforthefloodingwalkdowns.OtherNRCrequestedactionsinclude:(1) PerformfloodprotectionwalkdownsusinganNRC endorsedwalkdownmethodology;(2) Identifyandaddressplant specificdegraded,nonconforming,orunanalyzedconditions,aswellascliff edgeeffects,throughthecorrectiveactionprogram,andconsiderthesefindingsintheRecommendation2.1hazardevaluations,asappropriate;(3) Identifyanyotheractionstakenorplannedtofurtherenhancethesitefloodprotection;(4) Verifytheadequacyofprograms,monitoringandmaintenanceforprotectionfeatures;and(5) ReporttotheNRCtheresultsofthewalkdownsandcorrectiveactionstakenorplanned.Enclosure4ofReference3alsostates,"ifanyconditionidentifiedduringthewalkdownactivitiesrepresentsadegraded,nonconforming,orunanalyzedcondition(i.e.,noncompliancewiththecurrentlicensingbasis)foranSSC,describeactionsthatweretakenorareplannedtoaddresstheconditionusingtheguidanceinReference6 ,includingenteringtheconditioninthecorrectiveactionprogram.Reportingrequirementspursuantto10CFR50.72shouldalsobeconsidered."d. RequestedInformationPerEnclosure4ofReference3 ,1. TheNRCrequeststhateachlicenseeconfirmthatitwillusetheindustrydeveloped,NRCendorsed,floodingwalkdownproceduresorprovideadescriptionofplant specificwalkdownprocedures.Exelon'sletterdatedJune11,2012(Reference1),confirmedthatthefloodingwalkdownprocedure(Reference2),endorsedbytheNRConMay31,2012,willbeusedasthebasisforthefloodingwalkdowns.2. TheNRCrequeststhateachlicenseeconductthewalkdownandsubmitafinalreportwhichincludesthefollowing:a. Describethedesignbasisfloodhazardlevel(s)forallfloodcausingmechanisms,includinggroundwateringress.b. DescribeprotectionandmitigationfeaturesthatareconsideredinthelicensingbasisevaluationtoprotectagainstexternalingressofwaterintoSSCsimportanttosafety.c. Describeanywarningsystemstodetectthepresenceofwaterinroomsimportanttosafety.d. Discusstheeffectivenessoffloodprotectionsystemsandexterior,incorporated,andtemporaryfloodbarriers.DiscusshowthesesystemsandbarrierswereevaluatedusingtheacceptancecriteriadevelopedaspartofRequestedInformationitem1.h.Page6 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0e. Presentinformationrelatedtotheimplementationofthewalkdownprocess(e.g.,detailsofselectionofthewalkdownteamandprocedures,)usingthedocumentationtemplatediscussedinRequestedInformationitem1.j,includingactionstakeninresponsetothepeerreview.f. Resultsofthewalkdownincludingkeyfindingsandidentifieddegraded,nonconforming,orunanalyzedconditions.IncludeadetaileddescriptionoftheactionstakenorplannedtoaddresstheseconditionsusingtheguidanceinRegulatoryIssuesSummary2005 20,Revision1,RevisiontoNRCInspectionManualPart9900TechnicalGuidance,"OperabilityConditionsAdversetoQualityorSafety,"includingenteringtheconditioninthecorrectiveactionprogram.g. Documentanycliff edgeeffectsidentifiedandtheassociatedbasis.Indicatethosethatwereenteredintothecorrectiveactionprogram.Alsoincludeadetaileddescriptionoftheactionstakenorplannedtoaddresstheseeffects.SeenoteinSection1 aregardingtheNRC'schangeinpositiononcliff edgeeffects.h. Describeanyotherplannedornewlyinstalledfloodprotectionsystemsorfloodmitigationmeasuresincludingfloodbarriersthatfurtherenhancethefloodprotection.Identifyresultsandanysubsequentactionstakeninresponsetothepeerreview.3. METHODOLOGYa. OverviewofNEI1207(WalkdownGuidance)InacollaborativeeffortwithNRCstaff,NEIdevelopedandissuedreport12 07(Rev0 A),GuidelinesforPerformingVerificationWalkdownsofPlantProtectionFeatures ,datedMay2012(Reference2).TheNRCendorsedNEI12 07onMay31,2012withamendments.NEI12 07wasupdatedtoincorporatetheamendmentsandre issuedonJune18,2012.OnJune11,2012,ExelonissuedalettertotheNRC(Reference1)statingthattheendorsedfloodingwalkdownprocedure(Reference2)willbeusedasthebasisforthefloodingwalkdowns.NEI12 07providesguidanceonthefollowingitems: D efinitionso I ncorporatedBarrier/Featureo T emporaryBarrier/Featureo ExteriorBarrier/Featureo CurrentLicensingBasis(CLB)o DesignBaseso Inaccessibleo RestrictedAccesso Deficiencyo FloodProtectionFeatureso ReasonableSimulationo VisualInspectiono Cliff EdgeEffectso AvailablePhysicalMargino VarietyofSiteConditionso FloodDurationPage7 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Scopeo BasisforEstablishingWalkdownScopeo IdentifyFloodProtectionFeatures(WalkdownList) Methodologyo DevelopWalkdownScopeo PrepareWalkdownPackageso WalkdownTeamSelectionandTrainingo PerformPre JobBriefso InspectionofFloodProtectionAndMitigationFeatures General IncorporatedorExteriorPassiveFloodProtectionFeatures IncorporatedorExteriorActiveFloodProtectionFeatures TemporaryPassiveFloodProtectionFeatures TemporaryActiveFloodProtectionFeatures ProcedureWalkthroughandReasonableSimulationo ReviewoftheMaintenanceandMonitoringofFloodProtectionFeatureso ReviewofOperatingProcedureso DocumentationofAvailablePhysicalMarginso DocumentingPossibleDeficiencieso RestrictedAccess,orInaccessible AcceptanceCriteria EvaluationandReportingResultsofTheWalkdown RelatedInformationSources Examples WalkdownRecordForm SampleTrainingContent WalkdownReportb. ApplicationofNEI1207Exelon'sapproachtothefloodingwalkdownsincludedthreephases:Phase1-Preparation,Training,DataGathering,andScopingPhase2-InspectionsandReasonableSimulationsPhase3-FinalReportingThepurposeofPhase1wastoobtainaclearunderstandingofthesite'sfloodmitigationstrategy;developscope,methodology,andacceptancecriteriaforthewalkdowns;andlogisticalplanning.ThefollowingactivitieswereperformedduringPhase1: Datagathering(CLBdocuments,procedures,andO&Mproceduresanddocumentation); Sitevisittopreviewfeaturesandplantconditions; DesktopreviewofCLBdocumentstoidentifyanddescribetheCLBfloodhazard; D esktopreviewofCLBdocumentstoidentifyanddescribefloodprotection/mitigationstrategy; DevelopmentofWalkdownList;Page8 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 DevelopmentofWalkdownmethodologyandacceptancecriteria; Logisticsandstrategyplanning;and PreparationofWalkdownPackages.ThepurposeofPhase2wastoexecutetheFloodingWalkdownforDresden,whichincluded: VisualInspection; ReasonableSimulation; Evaluationofmaintenance/monitoringprocedures;and Documentationofobservationsandpossibledeficiencies.ThepurposeofPhase3istodeveloptheWalkdownReporttodocumentthemethodologyandfindingsoftheFloodingWalkdownsandprovidearesponseto"RequestedInformation"sectionofthe"Recommendation2.3:Flooding"enclosurefromthe10CFR50.54(f)letter.TheWalkdownReportwasdevelopedperthetemplateprovidedinNEI12 07[Rev.0 A],AppendixD.c. ReasonableSimulationsAprocedurewalkthrough,or"ReasonableSimulation",wasconductedfortemporaryand/oractivefeaturesthatrequiremanual/operatoractionstoperformtheirintendedfloodprotectionfunction.Thepurposeofthereasonablesimulationswastoverifytheprocedureoractivitycanbeexecutedasspecified/written.PerNEI12 07(Reference2),reasonablesimulationincludedthefollowing: Verifythatanycreditedtimedependentactivitiescanbecompletedinthetimerequired.Timedependentactivitiesincludedetection(somesignalthattheeventwilloccur,hasoccurred,orisoccurring),recognition(bysomeonewhowillnotifytheplant),communication(tothecontrolroom),andaction(byplantstaff). Verifythatspecifiedequipment/toolsareproperlystagedandingoodworkingcondition. Verifythatconnection/installationpointsareaccessible. V erifythattheexecutionoftheactivitywillnotbeimpededbytheeventitisintendedtomitigateorprevent.Forexample,movementofequipmentacrossunpavedareasonthesitecouldbeimpededbysoftsoilconditionscreatedbyexcessivewater. Reviewtherelianceonthestationstafftoexecuterequiredfloodprotectionfeatures.Ifduringthereviewseveralactivitiesareidentifiedtorelyonstationstaff,thenperformanddocumentanevaluationoftheaggregateeffectonthestationstafftodemonstrateallactionscanbecompletedasrequired. Verifythatallresourcesneededtocompletetheactionswillbeavailable.(Notethatstaffingassumptionsmustbeconsistentwithsiteaccessassumptionsinemergencyplanningprocedures.) Showthattheexecutionoftheactivitywillnotbeimpededbyotheradverseconditionsthatcouldreasonablybeexpectedtosimultaneouslyoccur(forexample,winds,lightning,andextremeairtemperatures).Page9 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Personnel/departmentsthathaveresponsibilityforsupportingorimplementingtheprocedureshouldparticipateinthesimulationeffort. Thesimulationshoulddemonstratethatthepersonnelassignedtotheproceduredonothaveotherdutiesthatcouldkeepthemfromcompletingtheirfloodprotectionactivitiesduringanactualevent.Actionsthatwouldbeperformedinparallelduringaneventshouldbesimulatedinparallel;notcheckedindividuallyandtheresultscombined. Reasonablesimulationneednotrequiretheactualperformanceofthenecessaryactivitiesiftheyhavebeenpreviouslyperformedanddocumentedorithasbeenperiodicallydemonstratedanddocumentedthattheactivitiescanbecompletedinthecreditedtime.TheFloodingWalkdownactivitiesforDresdenpredominantlyinvolvedreasonablesimulationssincethefloodmitigationstrategyistoexecutethefloodemergencyprocedure,whichpreparestheplantforsafeshutdownpriortotheadventoftheCLBfloodevent.Thefollowingcategoriesofreasonablesimulationswereperformed: SimpleSimulations-simulations/walk throughswithshortperformancetimesthathavebeenpreviouslyperformed,andforwhichrecordsareavailabletodocumentthesuccessfulimplementationoftheprocedureinthecreditedtime. ComplexSimulationssimulations/walkthroughswithlongperformancetimesthathavebeenpreviouslyperformed,andforwhichrecordsareavailabletodocumentthesuccessfulimplementationoftheprocedureinthecreditedtime. DrillsorExercises-activitiesthathavenotbeenperformedbeforerequiretheactualperformanceoftheactivitytodemonstratethattheycanbecompletedinthecreditedtime. Records/DesktopEvaluationforproceduresthatareconsideredstandardoperatingprocedures,suchasplantshutdownprocedures.Onlytheportionsoftheseproceduresthatareapplicabletothefloodresponseshouldbevalidated.Thevalidation/evaluationshouldincludereviewofpastperformancerecordstoverifythattheprocedurecanbeexecutedinthecreditedtime.Theevaluationshouldalsoincludethepossibleeffectfloodingconditionsonexecutionoftheprocedureandwhethertheavailablewarningtimeissufficienttoexecutetheprocedure.Aspartofthereasonablesimulations,visualinspectionswereperformedtoverifythattools,materials,andcomponentsrequiredtoexecutetheprocedureswereinworkingorder,stored,andaccessiblepertherequirementsoftheprocedures.TheReasonableSimulationWorksheetsandWalkdownRecordFormswereusedtodocumenttheresultsofthereasonablesimulations.Overall,nineteen(19)reasonablesimulationsofproceduralstepsorstandardshutdownprocedureswereperformedtodemonstratecompliancewiththeCLBrequirements.Table1providesasummaryofreasonablesimulationsperformedduringthewalkdown.AdetaileddescriptionofeachreasonablesimulationisprovidedinSection4.dofthisreport.Page10 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Table1:ListofReasonableSimulationsSimulation#SimulationName1FloodWarning&FloodWatch2Diesel drivenEmergencyMake upPump(movingandstaging)3ConstructionofSandbagBermaroundtheIsolationCondenserMake upPumpsBuilding4DeenergizeMotorControlCenters(MCCs)5ManualOperationoftheIsolationCondensers6PreparefortheRemovalofSWPMotorsandSecure2 3SWPs7RaiseWaterStorageTankLevel&Check/FillBelowgroundWaterStorageTanks8RestoreReactorVesseltoNormalWaterLevel9SealDieselOilStorageTankVents10SecureIsolationCondenserPumps11Unit1-DFPControlSwitchOffSecureEquipment,SecurePowertoPC 512Unit1PostIncidentPump13Close/OpenFireProtectionSystemValves14OpenPlantDoors15PlaceLocalIsolationCondenserSightglassintoService16LossofSpentFuelPoolCooling17ReactorScram18ReactorVesselSlowFill19UnitShutdownPage11 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0d. WalkdownInspectionGuidanceA"WalkdownInspectionGuidance"wasdevelopedbyExelontosupplementNEI12 07(Reference2),basedlargelyonAppendixAofNEI12 07(Examples).Theguidancewasintendedtosupplement,notsupersede,NEI12 07andprovideinspectionguidanceforspecificfeatures,listedbelow. IncorporatedorExteriorPassiveFeatures:o SiteElevationsandTopographyo EarthenFeatures(i.e.,FloodProtectionBerm,Dike,Levee)o C oncreteandSteelStructureso Wall,Ceiling,andFloorSeals(e.g.PenetrationSeals,CorkSeals)o PassiveFloodBarriersorWaterDiversionStructureso DrainsandCatchBasinso PlugsandManholeCoverso DrainagePathways(Swales,SubsurfaceDrainageSystem,etc.)o PipingandCableVaultsandTunnels,ElectricalCableConduito FloorHatcheso FlapGate/BackwaterValve/DuckbillValveo FloodWall IncorporatedorExteriorActiveFeatures:o CreditedWatertightDoorso CreditedNon WatertightDoorso Pumpso WaterLevelIndicationo GateValves TemporaryPassiveFeatures:o PortableFloodBarriersandInflatableRubberSealso FloodGate TemporaryActiveFeatureo Pumps4. RESULTSTheinformationrequestedinReference3 ,Enclosure4,underparagraph2ofthe'RequestedInformation'section,isprovidedbelow.ThecontentsofeachitemweredevelopedinaccordancewithReference2 ,AppendixD.a. RequestedInformationItem2(a)-DesignBasisFloodHazardsDescribethedesignbasisfloodhazardlevel(s)forallflood causingmechanisms,includinggroundwateringress.ThedesignbasisfloodhazardlevelfortheDresdensitehasbeenevaluatedbytheNRCaspartoftheSystematicEvaluationProgram(SEP)TopicsII 3.A,II 3.B,II 3.B.1andII 3.C,whichwascompletedin1982.TheresultsoftheSEPstudywerepresentedintheSafetyEvaluationReport(Enclosure1)andTechnicalPage12 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0EvaluationReport(Enclosure2).BasedontheinformationprovidedintheSEPreport,thedesignbasisfloodhazardlevelisassociatedwiththePMF,whichresultsinapeakstillwaterelevationof524.5ftMSL.Coincidental2 yearwindgeneratedwavesandwaverun upwouldincreasethemaximumwatersurfaceelevationtoapproximately528ftMSL.Bothfloodelevationsaresignificantlyabovethegradeelevation(517.0ftMSL),theelevationofnon watertightopeningsinwallsofsafety relatedstructures(517.5ftMSL),andthelowestsubgradefloorcontainingequipmentimportanttosafety(CribHouse)(509.0ftMSL).ThepeakflowrateforthePMFwasdeterminedbyestimatingthewatershed'sresponsetotheProbableMaximumPrecipitation(PMP),followingtheproceduredescribedinEM1110 02 1411.ThePMPusedintheanalysiswasbasedona23.25inch,24 hourindexstormdistributedover72hours.UsingtheUSACEHEC 1software,thepeakdischargeintheIllinoisRiverwasestimatedtobe490,000cfs.ThePMFpeakdischargefortheIllinoisRiverwasusedintheUSACEHEC 2computerprogramtocomputethecorrespondingfloodstageatthesite.TheHEC 2modelwascalibratedtorecordedhighwatermarksfromthe1947and1957floods.ThePMFhydrograph,presentedinEnclosure2oftheSEPreport,indicatesthattheplantwouldexperiencefloodingconditions(elevationsgreaterthan517.0ftMSL)forapproximately57hours.FloodingofSSCswouldbeginatriverflowsbetween240,000cfsand290,000cfs(Reference10).ThePMFhydrographisprovidedinFigure2andisannotatedwiththecorrespondingfloodelevationsandtiming.InadditiontoestimatingfloodhazardlevelsassociatedwiththePMF,theSEPreportevaluatedthefloodhazardforLIP(i.e.,sitedrainageflooding)anddeterminedthatthe29 acrestudyareacanproduceanestimatedpeakdischargeof1,230cfsfromtheLIP.Twositedrainagescenarioswereevaluatedtoestimatethedepthoffloodingadjacenttothebuildings.ThefirstassumedthatfloodingfromaLIPwithinthethreedrainageareasoccurredsimultaneouslyandwascombinedandroutedthroughasingledrainagechannel.AnevaluationofthedrainagechanneldeterminedthatthechannelcouldconveythepeakflowrateassociatedwiththeLIPevent.Thesecondanalysesevaluatedthedrainagecharacteristicsofthesiteandbetweenthebuildings.Theresultsoftheanalysisshowedapeakflooddepthof0.45ft.Sincethedifferenceinelevationbetweenthelandsurfaceandthefinishedfloorofthebuildings0.5ft,thereisapproximately0.05ftoffreeboardduringtheLIPeventbeforesafety relatedequipmentisaffected.TheaffectsoftheLIPeventonroofstructureswasalsoevaluated.Noneoftheroofsofsafety relatedstructuresweredesignedtosustainLIPloadingwiththedrainsclogged.Assuch,theNRCrecommendedthatstructuralmodificationsbecompleted(Reference10).Scuppersintheroofparapetsoftheturbinebuilding,reactorbuilding,andthecribhousewereinstalledtocomplywiththerecommendation.TheSEPreportindicatesthatnormalgroundwaterlevelsatthesitearebetweenelevations505and508ftMSLandthedesignbasisgroundwaterelevationis514ftMSL.However,supportingdocumentationforthedeterminationofthedesignbasisgroundwaterelevationwasnotprovided.TheNRCacknowledgedthatthegroundwaterlevelsintheplantareaarecontrolledbythewaterlevelsintheadjacentwaterbodiesandthatthegroundwaterelevationof514ftMSLmaybeareasonableestimate.Regardless,theNRCrecommendedthatadesignbasisof517ftMSLbeusedincombinationwithseismiceventstoevaluatestructuralstabilityandintegrityofthebuildings.AccordingtotheUFSAR(Section3.4.1.1),thestructuresforUnits2and3weredesignedtowithstandhydrostaticloads,includingthoseassociatedwithextremegroundwaterelevations,uptotheplantgradeelevation.Oncefloodingreachesabovetheplantelevation,thenfloodingoftheinteriorofthestructures,whichwilloccurpertheCLB,ispostulated.ThishasbeenpreviouslyreviewedandassessedbytheNRC(SEPreport,TopicIII 3.A),whichstatesthatfloodsorhighwaterlevelwillnotjeopardizethestructuralintegrityoftheplant'sseismicCategoryIstructuresandthatthesestructuresareadequatelyprotected.ForthePage13 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0purposeofthefloodingwalkdowns,groundwateringresswasnotidentifiedasaplausibleflood causingeventsincetherearenopenetrationsorfloodprotectionfeaturescreditedwithprovidingabarriertopreventagainstgroundwateringresswereidentifiedintheCLBdocuments.However,sincetheCLBdididentifytheplantbasementwallsasbeingdesignedtowithstandhydrostaticloading,thefloodingwalkdownincludedvisualinspectionofthebelowgradestructures(i.e.basementwallsandfloorslabs)toverifytherearenopotentialobservablephysicaldeficiencies(i.e.cracking,spalling,ordegradedconcrete)thatmayimpactthestructure'sabilitytowithstandhydrostaticloads.Thepurposeofthevisualinspectionissolelytoverifythestructuralintegrityofthewallsandfloorslabs,includinganyassociatedpenetrationsandseals.TheCLBdoesnotidentifythewallasabarriercreditedtopreventgroundwateringressand,therefore,potentialpenetrationsthroughthewallbelowgradewerenotincludedasindividualfeaturesontheWalkdownList.Penetrationsandassociatedsealswereinspectedasacomponentofthewalltoidentifyifthereareanyobserveddegradedconditions.AnydegradedconditionsrelatedtopenetrationswererecordedontheFieldObservationReportandattachedtotheWalkdownRecordFormfortheassociatedwallfeature.Ice inducedfloodingwasnotidentifiedasaconcernforsafety relatedequipment.Alogboomislocatedattheentranceoftheintakecanalstopreventfloatingicechunksfromreachingtheintakestructures.ThereachoftheKankakeeRiverupstreamfromtheconfluenceoftheDesPlainesRiveriskeptfreefromicetomaintainclearshippinglanes.Inaddition,nofloodingproblemshavebeenrecordedinthepast.Noadditionalflood causingevents,whichcouldresultinafloodhazardforthesafety relatedequipment,wereidentifiedintheCLBdocuments.SinceDresdenStationisnotconsidereda"flooddry"site(i.e.,thesitewillbeinundatedduringthedesignbasisPMFevent),thefloodingstrategyprimarilyinvolvesimplementationoffloodemergencyprocedurestomitigatetheeffectsofthefloodandpreventdamagetothereactorcore.Sufficientfloodwarningiscriticalforasuccessfulexecutionofthefloodemergencyprocedure,includingthesafeshutdownofbothreactors,removalofdecayheat,andstagingofemergencyequipmentforalternatereactorcooling.TwotypesoffloodhydrographsarepresentedintheSEPreport,whichcanbeusedtoestimatetheminimumrequiredfloodwarning:thePMFhydrograph(Figure2)andthecritical timehydrograph(Figure3).ThePMFhydrographandstagedischargecurveindicatesthatthetimebetweentheonsetofrainfallandthetimewhenthefloodlevelsreachplantgradeelevationis51hours.Theplantwouldthencontinuetobeinundatedfor57hoursanditwouldtakeanother23hoursforfloodelevationtorecedebelowelevation509ftMSL.Thecriticaltimefloodhydrographdepictstherelationshipoffloodelevationtotimesincethebeginningofthelimitingrainfallevent.Thecritical timefloodisdefinedasthefloodduringwhichwaterlevelrisestoelevation509ftMSLandsubsequentlyto517.5ftMSL.Inaddition,thereportstatesthatthetimeframeinwhichsafeshutdownmustbeachievedisdeterminedbythecriticalflood.Basedonthecriticaltimehydrograph,33hourswillbeavailablefromtheonsetofthelimitingrainfalleventuntiltheIllinoisRiverreacheselevation517.5ftMSLandbeginsfloodingthesafety relatedequipmentinthemainreactorbuilding.Forthepurposeofthewalkdown,theshortesttimeperiod,asrepresentedonthecritical timehydrograph,shouldbeusedtoevaluatewhethertheprocedurecanbeexecutedasspecified.ThedurationofthefloodwasevaluatedbasedonthetimeperiodasdeterminedbythePMFhydrograph.However,additionalconsiderationsweregiventoproceduralstepscompletedbetweenwatersurfaceelevations509ftMSLand517ftMSL.ThePMFhydrographshowsthatonly7hourswillbeavailabletocompletetherequiredactivitiesbeforefloodwatersrisefrom509ftMSLto517ftMSL.Thistimeframeisshorterthaninthecritical timehydrograph,whichshows11hoursforfloodwaterstorisefrom509ftMSLto517.5ftMSL.Becausethecritical timeandPMFhydrographsappeartocontrolproceduresandPage14 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0resourcesatdifferentfloodelevations,thetimeperiodtoimplementthesetaskswereevaluatedagainstbothhydrographstoestablishtheshortesttimeavailabletoachievesafeshutdownofthereactor.TheCLBdoesnotaddressspecificplantconfigurationsduringvariousmodesofoperation.However,afullpoweroperationmodewasconsideredduringtheevaluation,asthisrepresentsthemostcriticalplantfailuremode.Figure2:PMFHydrographfromtheSEPreport(annotatedwiththecorrespondingfloodelevationsandtiming).Page15 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Figure3:Critical TimeHydrographfromtheSEPreport.Page16! I I. I Difference in Time (hours) I ,17 I ** 310,000 cfs W.S. &#xa3;Jev. 518 (Ffunup to Efev. 520A) m.oo, ill'\ 2130.000 1 'I r I \, 280,000 cfs i ! I I I \\ W.S. &#xa3;Jev. 517.5 , ! j (All Gate Conditions)
I I / 1 \ 240,000 t 11.1 I i \ \ I \, 200,000 -;-\ /Ilinois River At Dresden Power Plant , , I i I 160,00e I f i \\ I; \. I , ___
125,000 cts I 120,0001 i \ '" --I -090 , ___ +1.1../..,.'1
___ -+ ___________
I I 1/ [' \ W,S, :/ev. 506 It I 30,000 -J. I -\ Recorded Hignest ,I \ F/ood of Record (1957) ! i r ',. I i ---+-'-----+---------------"'----50,000 cfs i 40.000 1 1 i "" artess i I! WS, &#xa3;lev. 509.0 I r i (Possibie Gate I I Closures Due I J 1'-i f to OcerationaJ O ' r 'If' 'If' Failure) . -I 1 30. 50 90 120 I I HYDROGRAPH i I FOR THE ILUNOIS RIVER i ELEVATIONS ASSOCIATED WITH ST".
______________________________ -L ______________________ T!ME SINCE BEGINNING OF RAINFALL (Hours)
NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0b. RequestedInformationItem2(b)-CLBProtectionandMitigationFeaturesDescribeprotectionandmitigationfeaturesthatareconsideredinthelicensingbasisevaluationtoprotectagainstexternalingressofwaterintoSSCsimportanttosafety.TheDresdenStationisinundatedduringthePMFeventandexternalfloodmitigationeffortsaredirectedtowardthepreventionofdamagetothereactorcoreduringfloodingconditions.Inaddition,thestructuresforUnits2and3aredesignedtowithstandhydrostaticloads,combinedwithotherapplicableloads,uptogradeelevationof517ftMSL.TheexternalfloodprotectionprocedureforDresdenmakesuseofonsiteequipmenttoachieveasafeshutdownofthereactorandrequirestheopeningofalldoorstopermitfreeflowofwaterthroughtheplant.Alongwiththis,theprocedureutilizesthereactorcoolingsystemstodischargedecayheatthroughoutthetermofthePMF.Thefloodemergencyprocedure(DOA0010 04)iscreditedintheCLBdocumentsastheprotectionmeasureavailabletominimizetheimpactofanexternalfloodevent.Theprocedurerequiresthatactionsorotherproceduresareinitiatedwhenthefloodwatersreachcertainelevationstosuccessfullymaintainthereactorcoreinasafeandstablecondition.Thefollowingparagraphsprovideasummaryofthefloodemergencyprocedureandthemainactionsthatareinitiatedwhenfloodwatersreachacertainelevation.TheprocedureisinitiatedbyafloodforecastbytheU.S.WeatherService,notificationofpredictedrainfallexceeding2inchesin6hoursorforactualwaterlevelsexceedingelevation506ftMSLintheUnit2/3CribHouse.Consequently,floodmonitoringisconductedatleastonceevery2hours.Sincethelowestopeningtoequipmentimportanttosafetyisatelevation509ftMSL,proceduresforUnitShutdown(DGP02 01)andVesselSlowFill(DGP02 02)areinvokedwhenriverlevelsarepredictedtoexceedelevation509ftMSLwithinthreedays.ReactorScram(DGP02 03)andVesselSlowFill(DGP02 02)areinitiatedshouldthefloodlevelsreachelevation509ftMSLandasufficientfloodwarningwasnotissuedtoallownormalunitshutdown.In,addition,afloodprotectionsandbagbermisconstructedaroundtheisolationcondensermake uppumpsbuilding.Whenfloodlevelsreachelevation509ftMSLadditionalstepsareinitiated,including: RemovaloftwoUnit2servicewaterpumpmotorstorelocateabove530ftMSLtoallowthemtobeavailableforserviceoncethefloodrecedes. S tagingofthedieseldrivenemergencymake uppumpinthecenterofUnit2ReactorBuildingequipmenthatchonelevation517.5ftMSLandsettingupthepumpforoperation,includingliftingofthepumpusingacraneandbuildingofscaffolding. C onfiguringofvalvesinthefireprotectionsystemtoallowforconnectionofpumptothesystem.Oncefloodwaterlevelsreachanelevationof513ftMSL,additionalproceduresareinitiatedtosecureservicewaterpumps(DOP3900 01),transferreactorcoolingtoisolationcondenser(DOP1300 03),andtoinitiateplanstoaddresslossoffuelpoolcooling(DOA1900 01)andAttachmentCofthefloodprotectionprocedure(DOA0010 04).Oncefloodwaterlevelsreachanelevationof517ftMSL,alltransformersandelectricalequipmentwillbedeenergizedandreactordoorswillbeopenedtopermituninhibitedwaterflowthroughtheplant.Severalotheractionsareperformedpriortothiswhentheriverlevelsarepredictedtoexceed517ftMSL,includingPage17 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0sealingofventsonbelowgrounddieseloilstoragetanks,fillingofbelow groundwaterstoragetankswithdemineralizedwater,andsecuringofmotorboatsfortransportation.Thedieseldrivenemergencymake uppumpwouldbestartedprovidingmake upwatertotheisolationcondenserusedforcoolingofthereactorswhenthefloodlevelreacheselevation518ftMSL.Thepumpwillcontinuetooperateuntilwaterrecedesbelowanelevation509ftMSLandtwoservicewaterpumpsareinstalledandmadeoperational.Thepumpwillbeattachedtoacraneandraisedandloweredasthefloodlevelrisesandrecedes.Basedonthecriticaltimehydrograph,approximately33hoursaftertheonsetofthelimitingrainfalleventwaterlevelswillreachanelevationof517.5ftMSLandbeginfloodingsafety relatedequipmentlocatedinthemainreactorbuilding.Assuch,itiscriticalthatavailableinstrumentationandforecastingdatapertainingtoregionalprecipitationandwaterlevelrisearemonitoredtoensureadvancedwarningintheeventofthePMForthecriticalflood.WhilenotspecificallymentionedintheCLB,below gradewallsandslabsofthereactorandturbinebuildingswereconsideredtobefloodprotectionfeaturesatDresdenStation.Thesestructuresandtheassociatedpenetrationsareintendedtopreventgroundwateringressintothespacecreditedasdrybeforefloodwatersreachelevation517.5andbeforeexteriordoorsareopenedtoallowfreeflowofwaterintothebuilding.Itiscritical,however,thatthebelowgradestructuresprovideprotectionagainstgroundwateringresssincesafetyrelatedSSCsarelocatedinbasementareasofreactorandturbinebuildings.TheseSSCsarecreditedwithmaintainingreactorcoolinguntiltheemergencypumpisusedtoprovidemake upwaterfortheisolationcondensersandgroundwateringresspriortotheshutdownofbothunitscouldaffectplant'simplementationofthefloodemergencyprocedure.TheCLBdocumentsdonotindicatethatStationsumppumpswereinstalledtocontrolgroundwateringress.Furthermore,thesumppumpsdonotpenetratethroughbasementfloorslabsand,therefore,theywerenotincludedinthescopeofthefloodingwalkdown.c. RequestedInformationItem2(c)-FloodWarningSystemsDescribeanywarningsystemstodetectthepresenceofwaterinroomsimportanttosafety.Sincethesiteisallowedtobeflooded,warningsystemsinroomsimportanttosafetyarenotcreditedintheplant'sexternalfloodinglicensingbasisandwerenotidentifiedaspartofthewalkdown.Accordingtothefloodemergencyprocedure,risingfloodlevelswouldbemonitoredatleastonceeverytwohoursoncetheintakecanallevelexceeds506ftMSL.Frequentmonitoringoffloodlevelsiscriticalforinitiationofcertainfloodemergencyactionsandthesuccessfulimplementationofthefloodemergencyprocedure.Inadditiontofrequentmonitoringoffloodlevelsattheintakebay,plantstaffwouldcommunicatewiththeDresdenLockMasteronaregularbasistodetermineactualfloodlevelsonsite.ItisexpectedthatoncetheUnit2/3CribHouseisflooded,thesitewouldhavetorelyontheDresdenLockMastertoreportactualfloodlevelsonsite.Page18 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0d. RequestedInformationItem2(d)-FloodProtectionSystem/BarrierEffectivenessDiscusstheeffectivenessoffloodprotectionsystemsandexterior,incorporated,andtemporaryfloodbarriers.DiscusshowthesesystemsandbarrierswereevaluatedusingtheacceptancecriteriadevelopedaspartofRequestedInformationItem1.h[inEnclosure4oftheMarch12,2012,50.54(f)letter]Section6ofNEI12 07defines"acceptance"as:"Floodprotectionfeaturesareconsideredacceptableifnoconditionsadversetoqualitywereidentifiedduringwalkdowns,verificationactivities,orprogramreviewsasdeterminedbythelicensee'sCorrectiveActionProgram.Conditionsadversetoqualityarethosethatpreventthefloodprotectionfeaturefromperformingitscreditedfunctionduringadesignbasisexternalfloodingeventandare'deficiencies'.DeficienciesmustbereportedtotheNRCintheresponsetothe50.54(f)letter."AsindicatedinSection3d,inspectionguidancewasdeveloped,supplementingNEI12 07,toprovidemorespecificcriteriaforjudgingacceptance.Allobservationsthatwerenotimmediatelyjudgedasacceptablewereenteredintothesite'sCorrectiveActionProgram(CAP)whereanevaluationoftheobservationcanbemade.AsdescribedinSection4b,DresdenStation'sfloodprotectionstrategyagainstexternalfloodingisgovernedbyafloodemergencyprocedure.Thefloodemergencyprocedureinvokesotherproceduresandactionsintendedtosafelyshutdownthereactor,protectthereactorcoreandprovidemake upcoolingduringthedesign basisfloodwhenothercoolingsystemsarenotoperational.TheevaluationofthefloodemergencyprocedurewasperformedinaccordancewithNEI12 07guidelinesusingtheacceptancecriteriadevelopedpriortotheexecutionofthewalkdown.Duetothecomplexityofthefloodemergencyprocedure,theevaluationofitseffectivenesswasperformedbyfirstevaluatingindividualproceduralstepsandactionsduringthewalkdown,followedbyadesktopevaluationoftheprocedureasawhole.Theindividualproceduralstepsandactionsweredrilledorsimulatedduringthewalkdowntoverifythattheactionscanbecompletedinthecreditedtimeandtoestimatethemanpowerresourcesrequiredtocompletethetask.Thedesktopevaluationofthefloodemergencyprocedureincludedevaluationofavailableresourcesbasedonpaststaffinglogsandestimatesofstaffavailabletorespondtoemergency.Thissectionisdividedintothefollowingsub sections:1. FieldevaluationofFloodEmergencyProcedure-evaluationofeffectivenessofproceduralstepsandactionsbasedonreasonablesimulations.Timesstatedforperformingeachprocedureorproceduralstepwerebasedontheactualperformanceofthedrill/exerciseor,incaseofsimulationsthatwereperformedinthepast,onanestimateprovidedbythestaffresponsibleforexecutionoftheprocedure.2. DesktopevaluationofFloodEmergencyProcedure-evaluationofoveralleffectivenessoftheentirefloodemergencyprocedure.3. EvaluationofIncorporatedPassiveBarriers-evaluationofbelow gradewallsandslabsagainstgroundwateringress.4. SiteTopography-evaluationofsitetopography(i.e.contours,slopes,grades,imperviousness,structures,fences,etc.)againstthatassumedintheCLBsitedrainageevaluation.Page19 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0FIELDEVALUATIONOFFLOODEMERGENCYPROCEDUREFloodWarningandFloodWatch F loodwarningandfloodwatcharetwocriticalcomponentsofthefloodemergencyprocedure.ThefloodemergencyprocedurerequiresthatOperationsSupervisormonitorsweatherandfloodforecastusingavailablesourcessuchastheNationalWeatherService(NWS)ChicagoOffice,USACE,andExelon'sownweathermonitoringsystem.Inaddition,Exelon'sTransmissionSystemOperatorwouldalertDresdenStationofanysevereweatherconditionstooccurinthearea.Thefloodemergencyprocedurespecifieswhatactionsneedtobetakenifadverseweatherconditionsorfloodconditionsareforecastwithinacertaintimeperiod.PlantOperatorsalsomonitorriverlevelsattheUnit2/3CribHouseevery24hours.Themonitoringfrequencyincreaseswhenriverlevelsexceedcertainelevationtoensurethatthereissufficientfloodwarningandtimeforimplementationoffloodemergencyactions. M anpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)EquipmentOperator1Continuousmonitoringoffloodlevels2)OperationsSupervisor1Continuousmonitoringofflood&weatherforecast T hewalkdownteaminterviewedtheOperationsSupportManagertoevaluatewhetherplantstaffisknowledgeableofproceduralstepsrelatedtofloodwarningandfloodwatchandwhethertheplantcanreceivesufficientfloodwarningtoallowforsuccessfulimplementationofthefloodemergencyprocedure.BasedonAMEC'sevaluation,thesitehasresourcesandabilitytomonitorweatherconditionsandfloodinginrealtime;however,theabilitytopredictfloodlevelsatthesiteappearstobelimited.ThisisdueinparttovariablesthataffecttheabilitytopredictriverlevelsattheDresdenIntake,suchasoperationofthelockanddamsbothupstreamanddownstreamofthesite.ThefloodemergencyprocedurestatesthatUnit2andUnit3reactorsshouldbeshutdownusingtheUnitShutdown(DGP02 01)standardoperatingprocedureandsubsequenttasksareinitiatedwhentheriverlevelsarepredictedtoexceedelevation509ftMSLwithin72hours.However,currentriverforecastingtoolsarenotabletoreliablypredictexactlywhen509ftMSLwillbeexceededattheDresdenintake.Whenreviewingavailableinformation,ifStationpersonnelanticipatewaterlevelsexceeding509ftMSLanytimewithinthenext72hoursaplantshutdownisinitiated. T heFloodWarningandFloodWatchproceduralstepcanbeimplementedsuccessfullybyplantstaff.TheOperationsSupportManagerinterviewedduringthewalkdownwasknowledgeableoftheprocedureandwasabletoperformtherequiredactionsasspecified.WhileresourcesarenotavailabletoaccuratelypredictriverlevelsattheDresdenintake,itisreasonabletoassumethatalimitedfloodwarningcanbeobtainedfromDresdenLockMasterorusingriverforecastingtoolsfortheIllinoisRiverwatershed.Inaddition,theFloodEmergencyProcedureisenteredfollowinganotificationfromTransmissionSystemOperatorpredictingrainfallof2inchesin6hours.Thisallowsthesitetoinitiatefloodprotectionmeasuresbasedonarainfallforecastand/orlimitedfloodwarning.Page20 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Diesel drivenEmergencyMake upPump(movingandstaging) Thedieseldrivenemergencymake uppump(GodwinModelHL80)isusedtoprovidemake upcoolingfortheisolationcondensersoncefloodwatersexceedelevation518ftMSLperstep14.c.Themake uppumpisconnectedtoplant'sfiresuppressionsystemandusesriverwaterassourceofmake upwater.ThepumpislocatedintheEmergencyResponseOrganizationbarnandhosesandfittings,whicharerequiredtoconnectthepumptothefiresuppressionsystem,arelocatedintheSea Vansstoragecontainer.Oncethefloodwatersarepredictedtoreachorexceedelevation509ftMSL,thepump,hoses,andfittingaremovedtothecenteroftheUnit2ReactorBuildingequipmenthatch.Thehosesarethenconnectedtothepumpandthefiresuppressionsystemisdisengagedtoallowforconnectionofthehosestothefiresuppressionsystem.Finally,thepumpisriggedtothereactorbuildingcrane(orthejibcrane)withachainfalltoensurethatitcanbemanuallymovedupanddownasthefloodwatersriseandrecede.Scaffoldingisbuiltuptoa15 ftheighttoallowforoperationofpumpcontrolsandthechainfall.Sincethepumpisexpectedtooperateforextendedperiodoftime,additionaldieselfuelsupplyisstagedontheflooratelevation545ftMSL.Thedieselfuelwouldbethentransferredtotheemergencymake uppumptankusingahandpump,hose,andafunnel. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)MechanicalMaintenanceStaff43.6hours2)MechanicalMaintenanceSupervisor13)EquipmentOperators44)OperationsSupervisor1 Thewalkdownteamobservedadrillofthisproceduralstep,whichincludedmovingthemake uppumpandhosesinsidetheprotectedarea,connectingthehoses,andhoistingthepumponacraneandraising/loweringthepumpusingthechainfall.AnalternativelocationintheMaintenanceShopwasselectedtoperformthedrillforhoistingthepumpsoplantoperationswerenotimpacted.Connectionofthepumpandvalvemanipulationwasreasonablysimulatedsincethefiresuppressionsystemcannotbedisengagedunderfullreactoroperation.Duringthereasonablesimulation,theMaintenancestaffwalkedAMECevaluatorsthroughtheprocedure,gatheredthenecessarytools,andwalkedtothelocationwherethemake uppumpwouldbeconnectedtothefiresuppressionsystem.Thetimeforcompletionofthetaskwasestimatedbasedonpreviousperformancecompletedaspartofstation'smaintenanceprogram.TheOperationsstaffidentifiedthevalvesthatneedtobeclosedpriortoconnectingtothefiresuppressionsystemandopenedoncethemake upisconnected.TheOperationsstaffalsodemonstratedhowthevalveswouldbeopenedandclosedmanually.Theplanthassufficientsupplyofdieselfuelforthemake uppump.Dieselfuelisstoredina4,000 gallonabovegroundstoragetankfromwhichitwouldbetransferredintoempty55 gallonbarrels.Thefloodemergencyprocedureassumesthat,basedonthefull loadfuelassumption,four55 gallonbarrelswouldconservativelyprovideatwo daysupplyofdieselfuel.However,thePMFhydrographindicatesthatthemake uppumpwouldhavetooperateatminimumofapproximately78hours(durationoffloodfromelevation519.5ftMSLuntilPage21 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0theriverrecedestoelevation509ftMSL)andadditional12hoursuntilservicewaterpumpsareinstalled.Therefore,thesupplyofdieselfuelstagedinthereactorbuildingatelevation545ftMSLmaynotbesufficienttoprovidecontinuousoperationofthemake uppumpforatleast90hoursbeforethefloodwatersrecedebelowelevation509ftMSLandservicewaterpumpmotorsarere installed. Theobserveddrills/exercisesandreasonablesimulationsindicatethattheDiesel drivenEmergencyMake upPumpproceduralstepcanbeperformedwithinthespecifiedtimeframe.TheOperationsandMaintenanceStaffperformeddrills/exercisesorprocedurewalkthroughsanddemonstratedthattheyhaveagoodunderstandingoftheprocedureandcanperformthetasksasspecified.Theminimumresourcesavailabletoperformtheprocedureareadequate;however,itwasnotedthattheflangedelbowfittingusedasanalternateconnectiontothefiresuppressionsystemwasmissinganidentificationtag.ThefittingwasavailableintheSea Vanstorageandthemissingtagdidnotimpactthestagingofthemakeup uppump.Basedonthesimulationitisanticipatedthatifneeded,thisproceduralstepcouldbeperformedinashorterperiodoftimebyutilizingadditionalstaffthatwouldrespondtoanemergencywithin4hours.ConstructionofSandbagBermaroundtheIsolationCondenserMake upPumpsBuilding Thesandbagbermisconstructedaroundtheisolationcondensermake uppumpsbuildingtopreventfloodinguptoelevation519.5ftMSLwhenfloodwatersarehighenoughtobeusedasasourceofmake upwaterfortheisolationcondensers.Thefloodemergencyprocedurestatesthatsuppliesforconstructionoftheberm(i.e.,sandandsandbags)wouldbeobtainedfromtheGrundyCountyEmergencyOperationsCenter;however,approximately3,000bagswereobtainedpriortoconductingthedrillandwillbestoredonsiteforfutureuse.Supplyofsandisstoredadjacenttothecontractorparkinglotanditismixedwithsaltforuseduringthewintermonths.Whilenotspecifiedinthefloodemergencyprocedure,therequiredlengthofthesandbagbermtoprotectthenonwatertightdoorstobuildingis50linearfeet. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)MechanicalMaintenanceStaff58.5hours2)MechanicalMaintenanceSupervisor1 TheMechanicalMaintenancestaffconstructedarepresentativesampleofthesandbagberminthecontractorparkinglot.Thewalkdownteamusedtherepresentativesampletoestimatethetimetoconstructthe50 ftlongbermduringthefloodemergency.TheMechanicalMaintenancestaffwereabletofollowtheinstructionsinthefloodemergencyprocedureandconstructthebermasspecified. Basedontheobserveddrill/exercise,thesandbagbermcanbeconstructedasspecified.However,conditionsduringamajorfloodareexpectedtobesignificantlymorechallengingandstaffmayexperiencefatigueandexhaustion,whichmightresultinutilizationofagreaternumberofresources.HighwindsanticipatedduringamajorfloodcouldpotentiallydispersesandbagmaterialsPage22 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0throughoutthesiteandrainwilllikelymakesandheavierandmoredifficulttohandle.Inaddition,achain linkgateinfrontofthemake uppumpbuildingwouldhavetoberemovedpriortoconstructingthesandbagberm.Theseadditionalconstraintsandadverseconditionsmayincreaseresourcerequirements;however,thedurationofthetaskshouldnotbeaffectedsignificantly.Inaddition,constructionofthesandbagbermdoesnotrequireanyspecificskillsorknowledgeandanyavailablestaffcouldbedeployedtoperformthistasksuccessfully.DeenergizeMotorControlCenters(MCCs) SectionD.14.arequiresthatalltransformersandMCCsonelevation517ftMSLbedeenergizedwhentheriverlevelreacheselevation517ftMSL.ThispartoftheprocedureiscompletedintheControlRoom. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)ReactorOperators220minutes TheOperationsstaffdemonstratedtheknowledgeoftheproceduralstepandtheabilitytosuccessfullyperformtheproceduralstepaswritten;however,thisproceduralstepdoesnotclearlystatewhichBusshouldbedeenergizednordoesitexplicitlystatewhichtransformersandMCCsonelevation517ftMSLareimpacted. Basedonthereasonablesimulation,theevaluatedproceduralstepcanbeperformedsuccessfullyperSectionD.14.aandtheOperationstaffshowedsufficientknowledgeoftheactionneededtobeperformed.ManualOperationoftheIsolationCondensers SectionD.12.b.(1)requiresthetransferofUnit2(3)coolingtotheIsolationCondensersandtomonitorandcontroloperationoftheIsolationCondenserswhenriverlevelreacheselevation513ftMSL.Thisstepwasevaluatedforaworstcasescenarioinwhichthesitehaslossofoffsiteandbackupbatterypower. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)EquipmentOperators245minutes TheOperationsstaffwasabletosuccessfullysimulateproceduralstepsaswrittenandnoconflicts/issueswerefound.Theprocessoftransferringcoolingwatertotheisolationcondensersisanindependentprocessforeachunit,whichcanbedoneinparallel,ifneeded.The45-minuteestimatetoperformthetaskisthetimedurationforcompletingthetaskinparallelusingoneoperatorforeachUnit.Page23 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionD.12.b.(1)andtheOperationstaffshowedsufficientknowledgeoftheactionneededtobeperformed.PreparefortheRemovalofSWPMotorsandSecure2 3SWPs SectionD.9.crequiresthepreparationandremovaloftwoUnit2ServiceWaterPump(SWP)Motorstoberelocatedtoanareaaboveelevation530ftMSL.Thisstepisinitiatedwhentheriverlevelreachesorispredictedtoreachelevation509ftMSL.AnElectricalMaintenanceSupervisorandaSeniorElectricianwalkedAMECevaluatorsthroughtheprocessstep by step,showinghowcomponentswouldbesecured,disconnected,andtransportedtoanareaaboveelevation530ftMSL.Sincethemotorshavebeenpreviouslyremoved,adrillwasnotrequired.However,theelectricianandthesupervisorprovidedreasonableestimatesoftimedurationsforcompletionofeachstep.Pastmaintenancerecordswerealsoreviewedtoverifytheestimatedtimesandaconsiderationwasgiventothefactthatcertainactionsmaybeperformedfasterduringafloodemergencythanduringascheduledmaintenanceoutage. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)MechanicalMaintenance111.17hours2)ElectricalMaintenance9 TheElectricalMaintenancestaffwasabletosuccessfullysimulatecompletionoftheproceduralstepperSectionD.9.c.Itshouldbepointedout,however,thatthefloorofUnit2/3Cribhouseisatelevation509.5ftMSLandtheprocedurecanbeinitiatedaslateaswhenriverlevelsreachelevation509ftMSL.Underthisscenario,itislikelythattherewouldnotbeenoughtimetomovethemotorstotheupperlevelbeforethefloodwatersinundatethelowerlevelsofthecribhouse.Forinstance,thePMFhydrographestimatesthatthefloodlevelswouldrisefromelevation509ftMSLtoelevation513ftMSLinaslittleas3hoursandtheestimatedrequiredtimetomovethemotorstotheupperlevelisapproximately8hours(9hoursand11hours,respectively,tomovebothmotorstotheTurbineBuilding).ThistaskisNOTcriticalforensuringthatthereactorissafelyshutdownandcoolingofthereactorismaintained. Basedonthereasonablesimulation,theElectricalMaintenancestaffshowedsufficientknowledgeandskillstosuccessfullyexecutethetask.However,assumingthethatfloodwatersarerisingaccordingtothePMFhydrographandtheStationcannotrelyonthefloodwarning,theElectricalMaintenancestaffmaynothavesufficienttimetomovethemotorstotheupperlevelbeforetheCribHouseisinundated.Inaddition,thistaskcouldonlybeinitiatedafterthesufficientElectricalMaintenancestaffhasrespondedtothefloodemergency(between1and4hoursaftertheissuanceoffloodemergency).RaiseWaterStorageTankLevel&Check/FillBelow groundWaterStorageTanks SectionsD.13.aandD.13.bstatethelevelinabove groundwaterstoragetankswillberaisedtoalevelatleast10feetabovethegroundandthelevelinbelowgroundwaterstoragetankswillbecheckedandthestoragetankswillbefilledwithwater,ifneeded,whenriverlevelsarepredictedtoexceedelevation517ftMSL.Page24 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)ReactorOperator12hours TheOperationsstaffwasabletosuccessfullysimulatetheproceduralstepaswritten;however,theproceduredoesnotspecificallystatewhichtankstheactionsshouldbeperformedon.Theabove groundwaterstoragetanksaremaintainedabove50%capacityand,therefore,theywillalreadybefilledtotherequired10feet. Basedonthereasonablesimulation,theevaluatedproceduralstepcanbeperformedsuccessfullyperSectionsD.13.a,bandtheOperationsstaffshowedsufficientknowledgeandskillandwouldbeabletosuccessfullyexecutethetask.RestoreReactorVesseltoNormalWaterLevel SectionD.12.brequiresthesitetorestorereactorvesselstonormalwaterlevelwhenriverlevelsreachelevation513ftMSLandbeforereactorcoolingistransferredtotheisolationcondensers.TheReactorWaterCleanup(RWCU)Blowdownmethodwouldbeusedtolowerthereactorwaterlevelfrom140inchesto30inches.However,reactorcoolingcouldbetransferredtoisolationcondenserswhenreactorwaterlevelisbelowtheisolationcondensersteamline(at66inches). Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)ReactorOperator274minutes2)SeniorReactorOperator1 TheOperationsstaffwereabletosuccessfullysimulatetheproceduralstepaswrittenwithnoconflictsorissues.Thedurationofthistaskwasbasedonanestimatedmaximumblowdownof200gpm(perDOP1200 02)andreactorvolumeof200gal/in. Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionD.12.b.TheShiftUnitSupervisorshowedsufficientknowledgeandabilitytoperformthisstepintheprocedure.SealDieselOilStorageTankVents SectionD.13.cstateswhenriverlevelsarepredictedtoexceedelevation517ftMSL,thesitewillsealtheventsonthebelow grounddieseloilstoragetanks. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)MechanicalMaintenance130minutes TheMechanicalMaintenancestaffwereabletosuccessfullysimulatetheproceduralstepaswrittenwithnoconflictsorissues.Page25 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionD.13.c.TheMechanicalMaintenancestaffshowedsufficientknowledgeoftheactionbeingperformed.SecureIsolationCondenserPumps SectionD.14.hstatesthatifthediesel drivenemergencymake uppumpisprovidingmake uptotheisolationcondensers,thentheisolationcondensermake uppumpsshouldbesecured.Thisactionwouldoccurtheearliestwhenriverlevelsareaboveelevation519ftMSL.Theisolationcondenserpumpsaresecuredfromthecontrolroom.Ifthecontrolroomdoesnothavepower,thepumpscanbesecuredmanually.Thisstepwasevaluatedfortheworstcasescenariobyhavingthesitesecurethepumpsmanually. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)EquipmentOperator125minutes TheOperationsstaffwereabletosuccessfullysimulatetheproceduralstepaswrittenwithnoconflictsorissues.Thepossibleconcernisthatduringfloodingconditionstheaccesstotheisolationcondensersmake uppumpbuildingwouldlikelyrequireaboat,whichcoulddelaytheexecutionofthetask.Securingoftheisolationcondenserpumpsis,however,NOTacriticalitemforsuccessfulimplementationoftheprocedure. Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionD.14.h.TheOperationsstaffshowedsufficientknowledgeoftheactionbeingperformed.Unit1-DFPControlSwitchOffSecureEquipment,SecurePowertoPC 5 SectionD.10.a cstatesthatiftheriverlevelreacheselevation508ftMSL,thenthesitewillplacetheUnit1DFPcontrolswitchintheoffpositiontopreventautomaticstartonlossofpower,securealloftheUnit1equipmentfromPC 5intheUnit1Cribhousebasement,andverifytwobreakersareopentosecurepowertoPC 5. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)EquipmentOperator120minutes TheOperationsstaffwasabletosuccessfullysimulatetheproceduralstepaswritten.However,therewerefouradditionalcubiclesthatneededsecuringintheUnit1Cribhousebutwerenotlistedintheprocedure.Also,somebreakers'nomenclaturevariedfromwhatwasspecifiedintheprocedure.Thebreakerswerestilllabeledsufficientlyenoughtoensurethatthecorrectbreakersaresecured.Page26 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionsD.10.a. c.TheOperationsstaffshowedsufficientknowledgeoftheactionbeingperformed.Unit1PostIncidentPump SectionD.13.estatesthatmechanicalmaintenanceistobedirectedtoremoveoneUnit1postincidentpumpoutofitswelltoprovideflowpathintotheUnit1sphereandtoequalizepressuresonspherewalls.Thisproceduralstepistobeinitiatedwhenriverlevelsarepredictedtoexceedelevation517ftMSL. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)MechanicalMaintenance23.08hours TheseactionsareperformedtoprotectDresdenUnit1equipment.TheyarenotrequiredtosupportDresdenUnit2andUnit3andarenotrequiredtobeaddressedinthe10CFR50.54(f)informationrequest.TheMechanicalMaintenancestaffwereabletosuccessfullysimulatetheremovalofthepostincidentpump;however,thereisnosetprocedureforremovalofthepump.TheMechanicalMaintenancepersonnelshowedsufficientknowledgetoperformthistaskbuttheremaybeminordifficultiessettingupriggingsincethetaskhasnotbeenperformedinthepast.TheestimatedtimetoremovethepumpisbasedoninputprovidedbytheMechanicalMaintenancesupervisor.Thetimeallocatedforthisproceduralstepensuresadetailedandthoroughremovalofthepump. Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionsD.13.e.TheMechanicalMaintenancestaffshowedsufficientknowledgeoftheactionbeingperformed.Close/OpenFireProtectionSystemValves SectionD.9.fstatessix(6)fireprotectionvalveswillbeclosedandtwo(2)openedonceothertasksarecompleted.Thisstepwillbeinitiatedwhentheriverlevelisatelevation509ftMSL.Avisualinspectionofthesevalveswasdonetoevaluatephysicalappearanceofthevalvesandaccessibilityofthevalves. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)EquipmentOperator240minutes TheOperationsstaffwereabletosuccessfullysimulatetheproceduralstepaswrittenandnoconflictsorissueswerefound.Page27 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionD.9.f.TheOperationsstaffshowedsufficientknowledgeoftheactionbeingperformed.OpenPlantDoors StepD.14.bcallsfortheopeningofdoorsasnecessarytopermitthefreeflowofwaterthroughtheplant.Thisactionisintendedtoallowforthefloodwaterstoevenlyfilltheplantandequalizethepressureonbuildingwalls. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)RadiationProtectionbutcouldincludeanyavailableonsitepersonnelAllavailablestaffminimum2teamsof2(4staff)*1.5hours*OncetheOperationsControlCenterisstaffedall14RadiationProtectionStaffaremobilizedtotheplant.Thereisaminimumof2RadiationProtectionstaffonsiteatalltimes. AsimplesimulationofopeningthedoorsinvolvedavisualinspectionofthereactorandturbinebuildingsledbyanOperationsSupervisorpointingoutthedoorsinUnits2and3thatwouldbeopenedinafloodingevent.Inaddition,aRadiationProtection(RadPro)Supervisorwasinterviewed.OncenotifiedbytheOperationSupervisor,theRadProdepartmentwouldleadthiseffortwithassistancefromanyavailableonsitestaff.TheRadProsupervisorinterviewedduringthereasonablesimulationestimatedthatitwouldtake1.5hourstoopenandsecurealldoorsintheplant.Theestimatewasbasedonpreviousperformanceofthetaskduringtheannualoutage.
Alldoorsappearedingoodconditionanddidnotshowsignsthattheycouldmalfunctioninafloodevent.However,theproceduredoesnotspecifyhowthedoorswouldbesecuredtoremainopened.Ifthedoorsarenotsecuredcorrectly,theincomingfloodwatercouldforcethedoorstocloseandpreventthefreeflowofwaterbetweenrooms.Therewerenopotentialobstructionsobservedthatwouldpreventthedoorsfrombeingopenedandsecured,RadProandOperationsstaffwereknowledgeabletoproperlysecurethedoors,andtherearesufficientquantitiesofropetosecurethedoors.BasedontheexistingPMFhydrograph,theriverlevelswillrisefromelevation517ftMSLtoelevation518ftMSLinapproximately1.5hoursandtherisingfloodwaterscouldmakeopeningdoorsmoredifficult. Basedonthereasonablesimulation,theplantdoorsareinaconditionthatwouldallowthemtobeopenedandsecuredasspecified.Openingofthedoorscould,however,beimpededduetotherisingwatersifitisinitiatedwhenriverlevelsreachelevation517ftMSL.PlaceLocalIsolationCondenserSightglassintoService StepD.13.gcallsforplacingtheisolationcondensersightglassintoserviceandusingittomonitorthereactortemperaturetoestimatethecooldown/heatuprate.Page28 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)EquipmentOperator125minforbothunits TheOperationsstaffwalkedthroughthestepstoplacetheisolationcondensersightglassintoserviceanddemonstratedhowtheprocedurewouldbeexecuted.Theequipmentwasvisuallyinspectedandtherewerenosignsofmaterialdegradationornonconformance. Basedonthereasonablesimulation,theevaluatedproceduralstepcanperformedsuccessfullyperSectionsD.13.g.TheOperationsstaffshowedsufficientknowledgeoftheactionbeingperformed.LossofSpentFuelPoolCooling StepD.14.icallsforaddingofmake upwatertothespentfuelpoolusingthefiresystemwaterviahosestationslocatedadjacenttothespentfuelpool. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)EquipmentOperator220minforbothunits TheOperationsstaffwalkedthroughthestepsrequiredtofillthespentfuelpoolandidentifiedthehosestationthatwouldbeusedtoaddwatertothespentfuelpool.Theinitialtimetosetupthehoseandinitiateaddingwaterwouldrequireapproximately20minutesforbothunits.However,theOperationsstaffwouldthenberequiredtocontinuetomonitorspentfuelpoollevelsandaddwaterasneeded.ThistaskwouldNOTrequirecontinuousstaffingbyOperations. Basedonthereasonablesimulation,theevaluatedproceduralstepcanbeperformedsuccessfullyperSectionsD.14.i.TheOperationsstaffshowedsufficientknowledgeoftheactionbeingperformed.ReactorScram DGP02 03,ReactorScramisaprocedurethatisinitiatedwhenthewaterlevelsreachelevation509ftMSL 1.ThisprocedureisaStandardOperatingProcedurethathasbeenperformedinthepastand,therefore,adesktopreviewoftheprocedurewasperformedtoevaluatethetimingandresourcesneededfortheexecutionoftheprocedure.DGP02 03istypicallyperformedinresponsetoanautomaticreactorscramorwhenamanualscramisdesiredpriortoreachinganautomatictripsetpoint.
1Theversionoftheprocedureevaluatedduringthewalkdown(rev.32)incorrectlystatedthatUnitShutdown(DGP0201)ratherthanReactorScram(DGP0203)wouldbeusedtoshutdownbothunits.Theissuewasidentifiedpriortothewalkdown(AR01393890)andtheprocedurehasbeenrevisedaccordingly(rev.34).Page29 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)ReactorOperator25minutes TheOperationstaffpresentedoperatorlogs,outageschedulesanddatatrendgraphstosupportthedeterminationwhetherReactorScram(DGP02 03)canbeperformedinthecreditedtime.Theprocedurewillnotbechallengedbyfloodingconditionssinceitisperformedfromthecontrolroombeforefloodwatersinundatethesite. Basedontheprovidedoperatorlogs,outageschedules,anddatatrendgraphs,ReactorScramcanbeperformedinthecreditedtime.ReactorVesselSlowFill DGP02 02,ReactorVesselSlowFillisaprocedurethatisinitiatedfollowingaReactorScramorUnitShutdown.ThisprocedureisaStandardOperatingProcedurethathasbeenperformedinthepastand,therefore,adesktopreviewoftheprocedurewasperformedtoevaluatethetimingandresourcesneededfortheexecutionoftheprocedure.ReactorVesselSlowFillisaprocedureimplementedtoprovidecooldowntothereactorbyfloodingthereactorvessel. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)ReactorOperator245minutes2)MechanicalMaintenance1 TheOperationstaffpresentedoperatorlogs,outageschedulesanddatatrendgraphstosupportthedeterminationofwhetherReactorVesselSlowFill(DGP02 02)canbeperformedinthecreditedtime.Theprocedurewillnotbechallengedbyfloodingconditionssinceitisperformedfromthecontrolroombeforefloodwatersinundatethesite. Basedontheprovidedoperatorlogs,outageschedules,anddatatrendgraphs,ReactorVesselSlowFillcanbeperformedinthecreditedtime.UnitShutdown DGP02 01,UnitShutdown,isaprocedurethatisinitiatedwhenriverlevelispredictedtoreachelevation509ftMSLwithin72hours(i.e.,theprocedurewouldbeinitiatedwhenStationpersonnelanticipatewaterlevelexceedingelevation509ftMSLanytimewithinthenext72hours).ThisprocedureisaStandardOperatingProcedurethathasbeenperformedinthepastand,therefore,adesktopreviewoftheprocedurewasperformedtoevaluatethetimingandresourcesneededfortheexecutionoftheprocedure. Manpowerresourcesrequiredforimplementationofthistaskareasfollowing:TypeofResourcesRequiredQuantityofResourcesDurationofResourcesRequiredtoPerformTask1)ReactorOperator211.75hoursPage30 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0 TheOperationstaffpresentedoperatorlogs,outageschedulesanddatatrendgraphstosupportthedeterminationwhetherUnitShutdown(DGP02 01)canbeperformedinthecreditedtime.Theprocedurewillnotbechallengedbyfloodingconditionssinceitisperformedfromthecontrolroombeforefloodwatersinundatethesite. Basedontheprovidedoperatorlogs,outageschedules,anddatatrendgraphs,UnitShutdowncanbeperformedinthecreditedtime.DESKTOPEVALUATIONOFFLOODEMERGENCYPROCEDUREFollowingthecompletionofreasonablesimulationsandevaluationofindividualproceduralstepsandactions,AMECperformedadesktopevaluationofthefloodemergencyprocedure.Duringthedesktopevaluation,timingandresourcedataobtainedduringthewalkdownwereanalyzedandcompiledtogether.Themajoremphasisofthedesktopevaluationfocusedonansweringthefollowingquestions:1. Arerequiredresourcesavailableduringoverlappingtasks?2. Isthereasufficientfloodwarningavailabletoallowforsafereactorshutdownandstagingofthediesel drivenemergencymake uppumpandtheassociatedcomponentsandconsumables?3. Areconsumablesavailablefortheentiredurationsofthedesignbasisflood?4. Canthefloodemergencyprocedurebeperformedundersimultaneousadverseweatherconditionsorifthereisalossofoff sitepower?AvailabilityofResourcesActualstaffinglogs,EPDialogicsDatabase,andinterviewswithOperationsstaffwereusedtodeterminewhethersufficientresourcesareavailabletoimplementtheentirefloodprocedure.Basedonthestaffinglogs,thestaffingattheStationisatitsminimumlevelsduringtheweekendshiftsandtypicallyonlyOperationsstaffwouldbeavailabletoimmediatelyrespondtoanemergency.TheremainingstaffwouldreporttotheplantbasedontheEmergencyClassificationLevelandfollowingtheprocedureforemergencyresponse.ThelogsprovidedbytheStationindicatethat191staff,whichincludesMechanicalMaintenance,ElectricalMaintenance,InstrumentMaintenance,andRadiationProtectionstaff,isavailabletorespondtoanemergencyandanadditional59off shiftOperationspersonnelareavailableforshortnoticecall out.Toquantifythenumberofstaffavailableforimplementationoftheprocedure,thefollowingassumptionswereused(basedoninterviewswithStationstaff):1. Responsetimelessthanonehour-10%ofallavailablepersonnel.2. Responsetimelessthanfourhours-additional70%(80%total)ofallavailablepersonnel.3. Unabletorespondtoanemergencyduetoadverseweatherconditionsorduetootherreasons-20%ofallavailablepersonnel.AsummaryofavailablestaffbasedontheabovementionedassumptionsandthestaffinglogsispresentedinTable2below.Page31 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Table2:SummaryofStaffAvailabilityIngeneral,allpersonnelrespondingtoafloodemergencywouldbeavailabletoassistwithimplementationofthefloodemergencyprocedurewithoutbeingrequiredtoperformtasksrelatedtotheirusualjobduties.Basedontheresultsofreasonablesimulations,alloverlappingtaskscouldbestaffedasneededusingtheavailableresourcesorinitiatedafteradditionalstaffreportstothesite.Theonlytaskthatappearstohavelimitedresourceavailabilitywithinthefirsthourofdeclaredfloodemergencyistheremovalofservicewaterpumps.ThistaskisNOTrequiredfortheStationtorespondtorisingwaterleveland,therefore,NOTconsideredacriticalpathitem.Table3providesasummaryofresourcesneededforimplementationoftheprocedure,whichwerecross referencedwithavailableresources.Page32 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Table3:ResourceUtilizationbasedonAvailability77047182910171648-424915110615505514422440936945Response Time<1hr<4 hrAvailableSenior Reactor OperatorsReactor OperatorsEquipment OperatorsUtilizedDeltaMechanical Maintenance (craft)Mechanical Maintenance (supervisors)Electrical Maintenance (craft)Electrical Maintenance (supervisors)UtilizedDeltaAvailable ThefloodemergencyprocedurewouldbeinitiatedbytheShiftManager,whowouldcoordinatewithUnitSupervisorsanddeterminetheactionsneededtobeperformedimmediately.TheShiftManagerwouldalsodeterminewhetherconditionsofanEmergencyActionLevelaremetanddeclareEmergencyClassificationLevel,asappropriate.DependingontheEmergencyClassificationLevel,anEmergencyResponseOrganizationwouldlikelybeactivatedtocoordinateemergencyactivitiesonsite.FloodWarningAsdescribedpreviously,thefloodwarningandthefloodwatcharetwocriticalcomponentsofthefloodemergencyprocedure.Thefloodemergencyprocedurereliesonanassumptionthatfloodwarningofriverlevelsexceedingelevation509ftMSLwouldbeavailabletoprovidesufficienttimetoshutdownbothreactorsusingstandardoperatingprocedureandimplementdependentactivities.However,itcouldnotbereadilyconcludedthatcurrentfloodwarning/watchproceduresprovideadequatefloodpredictionsfortherequiredmitigatingactions.Furthermore,currentriverforecastingtoolsarenotabletoaccuratelypredictexactlywhenelevation509ftMSLwillbeexceededattheDresdenintake.Theproceduredoestakeintoconsiderationthepossibilitythatsufficientfloodwarningwillnotbeavailableandthatthefloodlevelscouldreachelevation509ftMSLwithoutsuchwarning.Underthisscenario,bothunitswouldbeshutdownusingaReactorScramstandardoperatingprocedure,whichwouldallowthereactorsystemstobecooledtothelowestpracticaltemperatureinamuchshorterperiodoftime.Sincetheprocedureacknowledgesthatasufficientfloodwarningmaynotavailable,itwasassumedthatthesubsequentproceduralstepswouldalsobeinitiatedonceriverlevelsreachelevation509ftMSL.ThecriticaltimedurationtocompletethesetasksisbasedonthePMFhydrograph,whichpredictsthatriverlevelswouldrisefromelevation509ftMSLto517ftMSLin7hours.Themajorityoftheactionscouldbeaccomplishedduringthistime;however,theconstructionofthesandbagbermwouldrequirelongerdurationandcouldpotentiallyaffecttheimplementationoftheprocedure.Notethattheconstructionofthesandbagbermisnotrequiredtoensureplantsafety.TheintentistoextendtheavailabilityoftheIsolationCondensermakeuppumps.Thebermdoesnotneedtobecompletedupto519.5ftMSL.Page33 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0AvailabilityofConsumablesTheplanthassufficientsupplyofdieselfuelforoperationofthemake uppumpduringthefloodemergency.Thedieselfuelisstoredina4,000 gallonabove groundstoragetankandthetankisrefueledwhenthefuellevelisbelowapproximately1,000gallons.Thefuelfromthestoragetankwouldbetransferredinto55 gallonbarrelsduringtheearlystagesofthefloodemergency.Oncethebarrelsarefilledwithdieselfuel,theywouldbetransportedintothereactorbuildingandstagedatanelevationabovethedesign basisfloodtoensurethatdieselfuelisavailablefortheentiredurationofthestorm.Thefloodemergencyprocedurestatesthatfour(4)55gallonbarrelswouldbestagedinthereactorbuilding;however,full loadfuelconsumptionestimatesof3.82gallonsperhour,suggestthat344gallons(6.25barrels)ofdieselfuelwouldberequiredforacontinuousoperationofthepump.Fillingthebarrelswithdieselfuelbeforethesiteisinundatedand/orlosesoff sitepowerwouldalsoensurethatthefuelcanbetransferredfromtheabove groundstoragetank.EvaluationofOverallEffectivenessoftheFloodEmergencyProcedureTheoveralleffectivenessofthefloodemergencyprocedureisdependentonaccuratefloodwarningandfloodpredictionattheintakebay.Asdemonstratedduringthereasonablesimulation,theStationfloodpredictioncapabilitiesarecurrentlylimited.Therefore,itcouldnotbereadilyconcludedthatafloodwarning,onwhichthefloodprocedurerelies,wouldbeadequatetoallowforasafeshutdownofbothrectorsusingtheUnitShutdownstandardoperatingprocedure.ThemorelikelyscenarioisthatbothreactorswouldhavetobeshutdownusingtheReactorScramstandardoperatingprocedureonceriverlevelsreachelevation509ftMSL.Asaresult,thetimeneededforimplementationoftheprocedurewouldbereduced.Giventheavailableresources,theinstallationofthesandbagbermcouldlikelybeaccomplishedinashorterperiodoftimetoensurethattheisolationcondensermake uppumpsareprotectedwhenfloodlevelsrisetoplantgrade.Modificationstothesandbagbermconfigurationcouldalsobeconsidered.Thesubsequentproceduralstepscanbeaccomplishedefficiently(asdescribedearlierinthissection)andwouldsupporttheoverallimplementationofthefloodemergencyprocedure.Thesequenceoftheproceduralstepsallowsforproperstaffingwithavailableresources.GiventhatthesubsequentproceduralstepsareinitiatedatcertainfloodstagesandtheStationdoesnothaveaproperrivergage,theShiftmanagerortheEROwouldhavetocommunicatewiththeDresdenLockMasteronaregularbasistodeterminewhencertaintasksneedtobeinitiated.Alternatively,riverlevelscouldbedeterminedusingcomputerpointE354,DischargeCanalWaterLeveland/orbymeasuringfloodwatersintheCribHouseusingatapemeasureandreferencedrawingB 320CribHouseElevations.Oncetheriverlevelsreachplantgrade,risingfloodlevelscouldbedeterminedusingtheplantgradeareferencepoint.Adverseweatherconditions(e.g.,highwinds,localizedflooding,andfreezingtemperatures)canbeexpectedduringtheexecutionofthefloodemergencyprocedure.However,themajorityoftheproceduralstepswouldlikelynotbeaffectedbytheseconditions,sincetheyareperformedfromthecontrolroomorinside.Forproceduralstepsperformedoutside,siteconditionswereevaluatedtodeterminewhetheradverseweatherconditionscoulddelaythecompletionofthetask.Thetaskmostlikelytobeaffectedbyadverseweatherconditionsistheconstructionofthesandbagberm.Asdescribedabove,thistaskisacriticalpathitemthatshouldbeinitiatedearlyenoughduringresponsetoafloodtoensurethatitcanbecompletedinthespecifiedtime.Earlyinitiationofthistaskwouldalsoprovideadditionalmarginofsafety,withrespecttoadverseweatherconditions.AllproceduralstepsweresimulatedassumingalossofoffsitePage34 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0power.EmergencyDieselGeneratorswouldbeusedtopowertheequipmentandsystemsrequiredfortheexecutionoftheprocedureuptoafloodlevelof517ftMSL.EVALUATIONOFINCORPORATEDPASSIVEBARRIERSTheexteriorbelow gradestructuresofreactorandturbinebuildingswereincludedonthewalkdownlistasincorporatedpassivebarriers.Thestructureswereevaluatedfortheireffectivenesstopreventgroundwateringressandwithstandhydrostaticloadsassociatedwithextremegroundwaterconditions.Thepenetrationsthroughtheexteriorwallswerealsoinspectedaspartofthevisualinspectionofthewallsandbasementslabs.AnydegradedandnonconformingconditionswereenteredintotheCAPfordisposition.Thepenetrationsandtheassociatedsealswere,however,nottreatedasseparatefeaturesandwererecordedasobservationsassociatedwiththeWalkdownRecordFormforthewallorslabfeature.Thefollowingacceptancecriteriawereusedforvisualinspectionsofbelow gradewallsandpenetrationsseals:Below-GradeWalls/BasementFloorSlabs N osignsofdegradationofstructuralmembers. N osignificantsurfacecracks. N osignsofsignificantdegradation. N osignificantspalling,scaling,orcrackingofconcretesurfacesPenetrations/Seals: Noindicationofdegradationthatwouldallowfloodwaterstopenetrateintothefloodprotectedarea.Conditionsthatshouldberecordedinclude(butarenotlimitedto)damage,undocumentedopeningsorholes(suchasthoseduetoabandonedequipment),etc. Visiblepenetrationsaresealedwithnovisiblegaps. Penetrationsleeves,linkseals,piping,andconduitshouldhaveanabsenceofcorrosionontheexposedsteelsurface. Conduitsealmaterialshouldhaveanabsenceofwaterstainsbelowthepenetrations. Materialshouldappeartobeasindicatedinplantdocumentsandingenerallygoodcondition.Basedonthevisualinspection,theconditionofbelow gradewallsUnit2/3ReactorBuildingsandUnit2/3TurbineBuildingswereconsideredtobeacceptable.Overall,AMECdeterminedthattheincorporatedpassivebarrierswouldbeabletoperformtheirintendedfloodprotectionfunctionandwithstandthehydrostaticloadsassociatedwithextremegroundwaterconditionspertheCLB.However,duringthevisualinspection,AMECobservedwallsegmentswithevidenceofspalling,mineraldeposition,andconcretedegradationpossiblycausedbygroundwaterseepage.Inaddition,severalpenetrationsealsintheUnit2/3EmergencyDieselGenerationRoomweredegradedandcouldnotbereadilyjudgedasacceptable.TheseconditionswereidentifiedontheFieldObservationReportsandreportedtoExelon.AMECdoesnotbelievethatthesenonconformingconditionswouldcompromisethewalls'abilitytowithstandhydrostaticloadsandkeepthebelow gradeareasdry.Aspartoftheevaluationofincorporatedpassivebarriers,AMECperformedadesktopevaluationofstructuralandflooddrawingstoprovideareasonableassurancethatconduitsenteringthebuildingbelowPage35 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0gradewouldnotbecomeapathwayforgroundwater.AMEChasidentifiedtwoelectricalconduitsina20 inchsleevelocatedinthesoutheastcornerroomofUnitReactorBuilding.Thesetwoconduitswereinaccessibleforvisualinspectionduringthewalkdownduetoapullboxontheinsideofthebasementwall.Thefacilitydrawingsindicatethatasealringwasinstalledinthecenterofthesleevetopreventpotentialgroundwateringressandtheconduitsweresealedaswell.Inaddition,therewasnoindicationofpastgroundwateringressbelowthepenetration.Nootherbelowgradeelectricalconduitswereidentifiedduringthewalkdowns.Thefloodemergencyproceduredoesnotspecificallystatemodesofoperationforwhichtheprocedureisapplicable.Forthisevaluationfullpowermodeoperationwasconsideredthemostcriticalplantfailuremode,whichwouldrequirethehighestnumberofresourcesandthelongestduration.Duringothermodesofoperation,e.g.refuelingoutage,additionalresourceswouldbeavailabletoassistwithimplementationoftheprocedure.SITETOPOGRAPHYDetaileddescriptionofsitetopographyusedfortheLIPanalysiswasnotprovidedintheSEPreportorotherCLBdocuments.TheSEPreportonlydescribedthesizeofdrainageareas,averageManning"n"values,andanaverageslopebetweenthebuildingsandthedrainagechannel.Dimensionsofthechannelorotherdetailedmeasurementswerenotprovided.TheavailablefreeboardaroundthebuildingswasbasedonthedifferencebetweenthePMFdischargedepthandelevationsofnonwatertightopeningsinwallsofsafety relatedstructures(517.5ftMSL),whichhavenotchangedsincethecompletionoftheLIPanalysis.Theplantgradeelevation(517ftMSL)usedintheanalysisisconsistentwithexistinggradeelevation.e. RequestedInformationItem2(e)-ImplementationofWalkdownProcessPresentinformationrelatedtotheimplementationofthewalkdownprocess(e.g.,detailsofselectionofthewalkdownteamandprocedures)usingthedocumentationtemplatediscussedinRequestedInformationItem1.j[inEnclosure4oftheMarch12,2012,50.54(f)letter],includingactionstakeninresponsetothepeerreview.Themembersofthewalkdownteamwerecarefullyselectedtoensurethattheteamincludesindividualswhoareexperiencedinconductingvisualinspectionsofplantstructures,systemsandcomponentsandfloodprotectionfeatures.TheteamforDresdenStationincludedtwoWaterResourcesEngineers,anElectricalEngineer,andaStructuralEngineer.Bothwaterresourcesengineersarefloodingspecialistsandhavesignificantexperiencewithinspectionsandevaluationsoffloodprotectionfeatures.TheremainingtwoengineersareemployeesofAMEC'sNuclearServicesdivisionandareexperiencedinconductingvisualinspectionofplantSSCs.
EachmemberoftheteamcompletedExelon'sWalkdownTraining,NuclearGenerationEmployeeTraining(NGET),andNANTeL'sgenericverificationwalkdownsofplantfloodprotectionfeaturescourse,includingpassingtheNANTeLexam.Inpreparationforthewalkdown,theteammembersbecameknowledgeableofthesite'scurrentlicensingbasisandoperatingproceduresbythoroughlyreviewingthemduringthefirstphaseoftheproject.Wherespecificknowledgewasnecessarytoinspectafloodprotectionfeature/procedure,atleastonememberofthewalkdownteamhadtheabilitytodetermineiftheconditionofthefeature/procedureneededtobeenteredintotheCAP.Page36 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Theapproachusedforimplementationofthewalkdownprocesswastobreakdowntheevaluationoftheproceduresandfeaturesbasedonstaff'sindividualexperienceandexpertise.Allteammembershadathoroughunderstandingoftheproceduresandtheactionsrequiredtobeaccomplishedtomitigatethedesignbasisflood;however,AMEC'sstaffwithrelevantnuclearinspectionexperiencefocusedpredominatelyonnuclearspecifictasks(e.g.,StandardOperatingProcedures)andonassessingmajorityofcontrolroomactions.Thefloodingspecialistsfocusedpredominatelyonevaluationoffloodpredictionwarningsandonvisualinspectionofpenetrationsandbelowgradewalls/slabs.Theremainingreasonablesimulationsweredividedbyindividualswithspecificknowledgeoftheevaluatedtask/action.
Apre jobbriefwasperformedatthebeginningofeachworkday.Thesubjectsdiscussedinthepre jobbriefsincludedbutwerenotlimitedtopositivecomponentverification,inspectionmethodology,acceptancecriteria,fielddocumentationrequirements,reportingdegradedconditionsandpreviouswalkdownlessonslearned.Ahighradiationpre jobbriefwasperformedwiththewalkdownteamandradiationprotectionpersonnel,asnecessary.Subjectsdiscussedinhighradiationpre jobbriefsincludedbutwerenotlimitedtotasksrequiredtocompletethejob,timerequiredtocompletethetasks,doseratesurveys,maximumdoseratesandtotalallowabledose.Aladderanda"cameraonastick"wereusedtoperformvisualinspectionoffloodprotectionfeaturesthatwerenotaccessiblefromtheplantfloor.ObservationscapturedduringthewalkdownsweredocumentedusingtheWalkdownInspectionToolSmartphoneapplicationandusingthepapercopiesoftheFieldObservationReports.Twomembersofthewalkdownteamcompletedthevisualinspectionstocomplywiththepeerreviewrequirements.WalkdownRecordFormsprovidedinAppendixBofNEI12 07(Rev0 A)werecompletedbasedontheobservationsmadeduringthevisualinspection.Degradedornonconformingconditionsweredocumentedusingacamera.CompletedWalkdownRecordFormswerepeerreviewedandsignedasrequired.Adailyprojectreportwasgeneratedattheendofeachworkdaydocumentingthefollowing: IndustrialSafety/FirstAid RadiologicalInformation ALARAInformation P roductionPerformance DeficienciesIdentified OperabilityIssuesIdentified GeneralProblems IRs ItemsRequiringFurtherReview LessonsLearnedObservationsnotimmediatelyjudgedasacceptablewerereportedtoExelonpersonnelimmediatelyandenteredintheCAP,asnecessary.Page37 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0f. RequestedInformationItem2(f)-FindingsandCorrectiveActionsTaken/PlannedResultsofthewalkdownincludingkeyfindingsandidentifieddegraded,non conforming,orunanalyzedconditions.IncludeadetaileddescriptionoftheactionstakenorplannedtoaddresstheseconditionsusingtheguidanceinRegulatoryIssuesSummary2005 20,Rev1,RevisiontoNRCInspectionManualPart9900TechnicalGuidance,"OperabilityConditionsAdversetoQualityorSafety,"includingenteringtheconditioninthecorrectiveactionprogram.ObservationsnotImmediatelyJudgedasAcceptableBelowGradeWallsandBasementSlabsDuringthefloodingwalkdown,AMECdidnotidentifydegradedornon conformingconditionsofbelow gradebasementwallsthatwouldpreventthewallsfromperformingtheirfloodprotectionfunction.Assuch,theoverallconditionofthebasementwallswasconsideredacceptable;however,severalwallsegmentswithevidenceofspallingandconcretedegradation,possiblyresultingfromgroundwaterseepage,wereobservedduringthewalkdown(asnotedonFieldObservationReports).TheseconditionswerepreviouslyidentifiedandenteredintheCAP(ARnumbers1290630,1054344,1068074,1070652,1108699,1249329,1249834,and1376704).Inaddition,twopenetrationsealsinthe2/3EmergencyDieselGenerator(EDG)Roomcouldnotbereadilyjudgedasacceptable.However,theseconditionswerepreviouslyidentifiedduringaStructuresMonitoringWalkdownperER MW450anddispositionedthroughtheCAPasacceptable(AR01131053).Noneoftheindividualfloodprotectionfeatures(below gradewallsorbasementslabs)wereconsideredinaccessible.However,threepenetrations/sealswerenotvisuallyinspectedduringthewalkdownandareconsideredinaccessible.Onepenetrationisa20 inchsleevewithtwoelectricalconduits.Basedonthereviewoffacilitydrawings,asealringwasinstalledinthecenterofthesleevetopreventpotentialgroundwateringressandbothconduitsdaylightatabovegroundjunctionboxesatthecontaminatedcondensatestoragetanks.Inaddition,therewasnoevidenceofleakagebelowthepenetrationsleeve.Therefore,itisreasonabletoconcludethattheconditionofthepenetrationsealisacceptableandwouldnotcompromisethebelow gradewall'sabilitytofunctionasafloodprotectionbarrier.Inaddition,conduitsthemselveswouldnotbecomepathwayforgroundwatersincetheydonotleadtoanymanholesanddaylightabovetheground.TwoadditionalinaccessiblepenetrationsarelocatedintheUnit2CCSWPumpArea(Vault)andUnit3CCSWPumpArea(Vault),respectively.Thepenetrationscouldnotbevisuallyinspectedwithoutbreakingtheplaneduetotheconfigurationofthepipe.Therewasnoindicationofgroundwateringressbelowthepenetrationsleeve.Adesktopevaluationwasconductedtodeterminewhetherapenetrationsealispresent.However,theinformationprovidedinthedrawingsiscontradictory.Forinstance,theFloodBarrierDrawings(FL 8andFL 24)indicatethatbothpenetrationsleeveshaveasealandrefertoM 151andM476drawingsforsealtypebutthelatterdrawingsindicatethatthepenetrationsleeveswerenotequippedwithseals.ThisdiscrepancywasresolvedthroughAR00127680.Inaddition,theabsenceofpastandcurrentevidenceofgroundwaterseepagebelowthepenetrationindicatesthatthesleeveswouldnotbecomepathwayforgroundwater.ThepenetrationsarealsoinspectedonaregularbasisduringtheStructuresMonitoringWalkdown.Theoveralleffectivenessofthebasementwalltoprovidefloodprotectionagainstgroundwateringressshouldnotbeaffected.Page38 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0FloodEmergencyProcedureBasedonthereasonablesimulationsanddesktopevaluationofthefloodemergencyprocedureandtheassociatedoperatingprocedures,thewalkdownteamdeterminedthattheStationhastherequiredresourcestoeffectivelyimplementtheminimumcriticalpathactionsrequiredtosafelyshutdownthereactorusingaReactorScramstandardoperatingprocedureandprovidealternativecoolingofthereactorcoreduringafloodemergency.AMEChas,however,identifiedseveralproceduralstepsthatrelyonknowledge basedactionsandlacksufficientspecificity,relyonfloodwarningthatmaynotbeavailable,orcannotbeimplementedaswrittenduetotheinsufficientfloodwarning.Asummaryoftheseitemsisprovidedbelow.1. ResourcesarenotavailabletoaccuratelypredictriverlevelsattheDresdenintake.However,thefloodemergencyprocedureisenteredfollowingfloodforecastbyNWS,notificationfromTransmissionSystemOperatorpredictingrainfallof2inchesin6hours,orriverlevel506.5ftMSLattheCribHouse.Furthermore,itisreasonabletoassumethatarainfallofthedesign basismagnitudewouldbepredictedinadvance,whichwouldallowthesitetoinitiatefloodprotectionmeasuresbasedonarainfallforecast.ButitispossiblethatthenormalshutdownperUnitShutdown(DGP02 01)maynotbecompletedpriortothefloodwaterselevation509ftMSL.ShutdownperReactorScram(DGP02 03)wouldthenhavetobeinitiatedoncefloodwatersreachelevation509ftMSLtoreducedecayheattothelowestpossiblelevelandallowfortheuseofisolationcondensersmake uppumpsandthediesel drivenemergencymake uppumpforreactorcooling.Inaddition,theversionoftheprocedureevaluatedduringthewalkdown(rev.32)didnotstatethatReactorScramwouldbeusedtoshutdownbothunits.TheissuewasaddressedbyAR01393890andtheprocedurehasbeenrevisedaccordingly(rev.34).2. Thefloodemergencyprocedureaddressesremovaloftwo(2)ServiceWaterPump(SWP)Motorstoaidinrecoveryafterthefloodwatersrecede.However,motorremovalisNOTrequiredfortheStationtorespondtorisingwaterlevel,safelyshutdownbothreactors,andmaintainalternatecoolingduringthedurationoftheflood.GiventheindefinitefloodwarningandtheimportanceofmaintainingequipmentredundancyontheServiceWaterSystem,itispossiblethattheremovaloftwoSWPMotorswouldbeinitiatedonlyonceriverlevelsreachelevation509ftMSL.Underthisscenario,theElectricalMaintenancestaffwouldnothavesufficienttimetomovethemotorstotheupperlevelbeforefloodwatersinundatethelowerlevelsofthecribhouse.ThePMFhydrographestimatesthatthefloodlevelswouldrisefromelevation509toelevation513in3hoursandtheestimatedtimetomovethemotorstotheupperlevelisapproximately8hours(9hoursand11hours,respectively,tomovebothmotorstotheTurbineBuilding).Inaddition,thistaskappearstohavelimitedresourceavailabilitywithinthefirsthourofdeclaredfloodemergency.RemovaloftwoSWPmotorsrequires9ElectricalMaintenancestaffwhileonly5staffwouldbeavailabletoreporttodutywithinthefirsthour.WhilethistaskisNOTcriticalforensuringthatthereactorissafelyshutdownandcoolingofthereactorismaintained,theinabilitytoperformthetaskmayaffecttherecoverystageandrequireadditionalresourcestobeemployed(e.g.,continuouscoolingusingthemake uppump).TheissuewasaddressedbyAR01393890andprocedurerevisionisinprocess.3. Constructionofthesandbagbermisinitiatedwhentheriverlevelsarepredictedtoexceedelevation509ftMSL.Asstatedabove,resourcesarenotavailabletoaccuratelypredictriverlevelsattheDresdenintakeinadvance.However,thefloodemergencyprocedureisenteredfollowingfloodforecastbyNWS,notificationfromBulkPowerOperationspredictingrainfallof2inchesin6hours,orriverlevel506.5ftMSLattheCribHouse.Furthermore,itisreasonabletoassumethataPage39 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0rainfallofthedesign basismagnitudewouldbepredictedinadvance,whichwouldallowthesitetoinitiatefloodprotectionmeasuresbasedonarainfallforecast.Sincetheminimumtimetoconstructthesandbagbermis8.5hours,thereisapossibilitythatthebermwouldbenotbeconstructedintimebeforefloodwatersreachtheplantgradeifconstructiondoesnotbeginbeforeriverlevelsreachelevation509ftMSL.Risingfloodwaterscouldthenimpacttheoperationoftheisolationcondensermake uppumps.However,initiationofsandbaggingpreparationswhenthefloodemergencyprocedureisenteredduetoweatherforecastwillaidtheStationintimelyconstructionofthesandbagberm.TheissuewasaddressedbyAR01393890andprocedurerevisionisinprocess.4. Theprocedurestatesthatfour(4)55 gallonbarrelsofdieselfuelstagedinthereactorbuildingwillconservativelyprovidea2 daysupplyofdieselfuelfortheemergencymake uppump.However,basedonthePMFhydrographtheemergencymake uppumpwouldhavetobeusedforaminimumof78hoursbeforefloodlevelsrecedetoelevation509ftMSLandadditional12hoursbeforeservicewaterpumpsareallowedtobereinstalled.Basedonthefullloadfuelconsumptionof3.82gallonsperhour,344gallons(6.25barrels)ofdieselfuelwouldberequiredforacontinuousoperationofthepump.TheStationhasadditionaldieselfuelbarrelsavailableforuseduringfloodemergency.TheissuewasaddressedbyAR01422791andprocedurerevisionisinprocess.5. Theopeningofplantdoorsisinitiatedwhenfloodwaterreachelevation517ftMSL.However,basedontheexistingPMFhydrographfloodwaterscouldreachelevation518ftMSLinapproximately1.5hours.Asaresult,risingfloodwaterscouldmakeopeningdoorsmoredifficult.TheissuewasaddressedbyAR01422791andprocedurerevisionisinprocess.6. TheprocedurerequiresthatalltransformersandMCCsonelevation517ftMSLbedeenergizedwhentheriverlevelreacheselevation517ftMSL.WhiletheOperationsstaffdemonstratedtheknowledgeoftheproceduralstepandtheabilitytosuccessfullyperformtheproceduralstepaswritten,theproceduralstepdoesnotclearlystatewhichBusshouldbedeenergizeddownordoesnotexplicitlystatewhichtransformersandMCCsonelevation517ftMSLareimpacted.TheissuewasaddressedbyAR01422791andprocedurerevisionisinprocess.7. Theprocedurestates(D.13.a,D.13.b)thatthelevelinabove groundwaterstoragetankswillberaisedtoalevelatleast10feetabovethegroundandthelevelinbelowgroundwaterstoragetankswillbecheckedandthestoragetankswillbefilledwithwater,ifneeded,whenriverlevelsarepredictedtoexceedelevation517ftMSL.WhiletheOperationsstaffwasabletosuccessfullysimulatetheproceduralstepaswritten,theproceduredoesnotspecificallystatewhichtankstheactionsshouldbeperformedon.TheissuewasaddressedbyAR01422791andprocedurerevisionisinprocess.ObservationsDesignatedthroughCAPasDeficientNoneObservationsAwaitingFinalDispositioninCAPAllobservationsnotreadilyjudgedasacceptablearecurrentlyawaitingfinaldispositionintheCAP.FeaturesinRestrictedAccessAreasNonePage40 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0FeaturesinInaccessibleAreasThree(3)penetrationswereconsideredinaccessibleforvisualinspection.Reasonableassurancethatthecomponentscanprovidetheirintendedfunctionwasprovidedbyabsenceofpastandcurrentevidenceofgroundwaterseepagebelowthepenetrationandbyreviewofavailabledrawings.ActionsTakenorPlannedtoAddressDeficienciesNoneg. RequestedInformationItem2(g)-Cliff-EdgeEffectsandAvailablePhysicalMarginDocumentanycliffedgeeffectsidentifiedandtheassociatedbasis.Indicatethosethatwereenteredintothecorrectiveactionprogram.Alsoincludeadetaileddescriptionoftheactionstakenorplannedtoaddresstheseeffects.Cliff edgeeffectsweredefinedintheNTTFReport(Reference5)as"thesafetyconsequencesofafloodingeventmayincreasesharplywithasmallincreaseinthefloodinglevel."AsindicatedinSections3.12ofNEI12 07(Reference2),theNRCisnolongerexpectingtheRecommendation2.3:FloodingWalkdownstoincludeanevaluationofcliff edgeeffects.TheNRCisnowdifferentiatingbetweencliffedgeeffects,whichareaddressedinEnclosure2ofReference3 ,andAvailablePhysicalMargin(APM).AsindicatedinSections3.13ofNEI12 07(Reference2),APMdescribesthefloodmarginavailableforapplicablefloodprotectionfeaturesatasite(notallfloodprotectionfeatureshaveAPMs).TheAPMforeachapplicablefloodprotectionfeatureisthedifferencebetweenlicensingbasisfloodheightandthefloodheightatwhichwatercouldaffectanSSCimportanttosafety.APMinformationwascollectedduringthewalkdownstoprimarilysupporttheresponsetoEnclosure2ofReference3and,assuch,isnotincludedinthisreport.APMdeterminationsdidnotinvolvecalculatingcliff edgeeffects(i.e.thesafetyconsequences).DuringtheIntegratedAssessment(seeEnclosure2ofReference3),thecliff edgeeffectsandtheassociatedsafetyriskswillbeevaluatedusingtheAPMsandotherinformation,suchasthespecificSSCsthataresubjectedtofloodingandthepotentialavailabilityofothersystemstomitigatetherisk.Furthermore,observationsof"smallmarginandsignificantconsequences"wereenteredintotheCAPforfurtherevaluation.SincethewalkdownswerecompletedpriortothefinalresolutionofFAQ 006(September13,2012),APMinformationwascollectedanddocumentedontheWalkdownRecordFormusingthe"oldapproach";thatis,asimplemeasurementofthedifferencebetweenthelicensingbasisfloodheightandthefloodheightatwhichwatercouldaffectanSSCimportanttosafety.h. RequestedInformationItem2(h)-Planned/NewlyInstalledFloodProtectionEnhancementsDescribeanyotherplannedornewlyinstalledfloodprotectionsystemsorfloodmitigationmeasuresincludingfloodbarriersthatfurtherenhancethefloodprotection.Identifyresultsandanysubsequentactionstakeninresponsetothepeerreview.TheStationiscurrentlyconsideringchangesthatwouldstreamlinetheexistingfloodemergencyprocedure,reducetheneedformanpowerresourcestoimplementtheprocedure,andenhancefloodprotection.Thefollowingitemsarebeingconsidered:Page41 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision01. Obtainingafloatingdockthatwouldbeusedforstagingoftheemergencydieselmake uppump,reducingtheneedforraisingandloweringofthepumpduringaflood.Duringaflood,thefloatingdockwouldbestagedandsecuredatthecenteroftheUnit2ReactorBuildingequipmenthatch.ThisdockhasbeenprocuredbytheStationandaprocedurerevisionisinprocess.2. Floodproofingofisolationcondensermake uppumpsbuildingaccessdoorstoeliminatetheneedforconstructionofthesandbagberm.3. Floodproofingofadditionalbuildingaccessdoorstomaintainequipmentavailabilityandpersonnelsafetyaslongaspossibleinotherlocationssuchasthereactorbuildings.4. InitiationofsandbagberminstallationbasedonacombinationofactualriverlevelsattheDresdenintakeandfloodpredictionsfromthetwoclosestrivergaugeswithfloodforecastingcapabilities(KankakeeRiveratWilmingtonandIllinoisRiveratMorris).5. Developmentofamethodtoprovideadditionalwaterintothebelow gradeareasbeingusedbythedieseldrivenemergencymake uppumponcefloodwatersrecedebelowelevation518ftMSL.BasedonaninterviewwiththeOperationsSupportManager,theStationcouldutilizeFLEXpumpstodivertwaterfromcoolingcanalsintothereactorbuildingbasementorthefireheadercouldbereconfiguredtodivertwaterfromthecanaltothefiresuppressionsystemtobeusedformake upcoolingwater.Thiswouldallowforflexibilityduringrecoveryeffortsbymaintainingthecontinuedavailabilityofthedieseldrivenemergencymake uppump.5. CONCLUSIONSThefloodingwalkdownatDresdenStationwasconductedbetweenAugust8andAugust16,2012andincludedavisualinspectionofbelow gradewallsandtheassociatedpenetrations,avisualinspectionofbasementslabs,andreasonablesimulationsofthefloodemergencyprocedureandtheassociatedtasksandprocedures.AsummaryofthefloodingwalkdownresultsisprovidedinTable4throughTable9.Thebelowgrade wallsandslabswereinspectedandarrangedbyareasorroomsforatotaloffifteen(15)features.Associatedpenetrations/sealswerevisuallyinspectedduringthewalkdown;however,theywerenotconsideredindividualfloodprotectionfeaturesandonlypenetrations/sealsnotreadilyjudgedasacceptableorinaccessiblepenetrations/sealswerelistedinTable7andTable9 ,respectively.Nineteen(19)reasonablesimulationsofthefloodemergencyprocedureandtheassociatedprocedures(includingstandardshutdownprocedures)wereperformedtoensurethattheycanbeperformedasspecifiedandprotectthereactorfromcoredamageduringfloodingconditions.Basedontheevaluationofreasonablesimulationsandreviewofoperatorlogs,thecriticalpathitemsoffloodemergencyprocedurecanbeimplementedtoensurethatbothunitsaresafelyshutdownandreactorcoolingisprovidedtoremovedecayheat.DuringtheevaluationitwasdeterminedthatresourcesarenotavailabletoaccuratelypredictriverlevelsattheDresdenintakeinadvance.Assumingonlyashortfloodwarningisavailable,theconstructionofthesandbagmaynotbeimplementedintimeorusingtheavailableresources.However,initiationofsandbaggingpreparationsatanearlierpointintheFloodEmergencyProcedureduetoweatherforecastwillaidtheStationintimelyconstructionofthesandbagbermandprovideanadditionalmarginofsafety.Page42 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Table4:Summary-FeaturesIncludedintheWalkdownScopeFeatureTypeTotalNumber Passive-Incorporated15Passive-Temporary0Active-Incorporated0Active-Temporary0Table5:ReasonableSimulations#DescriptionPurpose 1FloodWarning&FloodWatchProvidesufficientfloodwarningtosafelyshutdownbothreactorsandimplementsdependentfloodemergencyactions.2Diesel drivenEmergencyMake upPump(movingandstaging)Providemake upcoolingwaterfortheisolationcondenserswhenpermanentlyinstalledequipmentisinoperable.3ConstructionofSandbagBermaroundtheIsolationCondenserMake upPumpsBuildingDesignedtoprotecttheisolationcondensersmake uppumpbuildinguntilfloodwatersreachhighenoughtoprovidesuctionfortheemergencydiesel drivenmake uppump.4DeenergizeMCCsDisconnectallelectricalequipmentpriortofloodwaterreachingplantgradeelevation.5ManualOperationoftheIsolationCondensersProvidecoolingofthereactorsystemswhenothersystemsareinoperableandisolationcondensershavetomanuallyoperated(e.g.,duringlossofoffsiteandbackupbatterypower).6PreparefortheRemovalofSWPMotorsandSecure2 3SWPsProtectSWPmotorsforrecoveryphasewhenSWPwillbeusedforcoolingofreactorsystems.7RaiseWaterStorageTankLevel&Check/FillBelow groundWaterStorageTanksPreventthetanksfrombecomingbuoyant.Page43 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0#DescriptionPurpose8RestoreReactorVesseltoNormalWaterLevelRestorenormalwaterlevelsbeforereactorcoolingistransferredtotheisolationcondensers.9SealDieselOilStorageTankVentsPreventintroductionofriverwaterintodieseloilstoragetanks.10SecureIsolationCondenserPumpsTakespumpmotorsofflineoncethedieseldrivenemergencypumpisusedtoprovidemake uptotheisolationcondensers.11Unit1-DFPControlSwitchOffSecureEquipment,SecurePowertoPC 5Preventautomaticstartonlossofpower.12Unit1PostIncidentPumpProvideflowpathintotheUnit1spheretoequalizepressuresonspherewalls.13Close/OpenFireProtectionSystemValvesAllowtheconnectionoftheemergencydiesel drivenmake uppumptothefireprotectionsystemandtheuseofriverwaterasmake upwatersource.14OpenPlantDoorsAllowfreeflowofwaterthroughplanttoequalizehydrostaticpressureandpreventcollapseofexteriorwalls.15PlaceLocalIsolationCondenserSightglassintoServiceMonitorIsolationCondenserleveltomaintainaheatsink.16LossofSpentFuelPoolCoolingProvidemake upwaterforspentfuelpoolswhensafety relatedequipmentisinoperable.17ReactorScramFastshutdownofthereactorwhensufficientfloodwarningisnotavailable.18ReactorVesselSlowFillCoolreactorsystemstolowestpracticaltemperatureasquicklyaspossible.19UnitShutdownNormalshutdownprocedureincaseofafloodemergencywhensufficientfloodwarningisavailable.Page44 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Table6:ListofFeaturesImmediatelyJudgedasAcceptable#FeatureID#DescriptionPassive/ActiveIncorporated/Temporary1D02 RB 476 W001 FWDO2 RB 476 W002 FWEastandsouthbelowgradewallsofU2southeastcornerroomIncorporatedPassive2RB2TORUSEastandsouthbelowgradewallsofU2torusIncorporatedPassive3D02 RB 476 W005 FWSouthbelow gradewallofU2southwestcornerroomIncorporatedPassive4D23 RB 476 W006 FWD23 RB 476 W007 FWD23 RB 476 W008 FWEast,south,andwestbelow gradewallsofU2/3HPCIRoomIncorporatedPassive5RB3TORUSWestandsouthbelowgradewallsofU3torusIncorporatedPassive6D03 RB 476 W002 FWDO3 RB 476 W001 FWWestandsouthbelowgradewallsofU3southwestcornerroomIncorporatedPassive7D02 TB 469 W001 FWD02 TB 469 W002 FWD02 TB 469 W003 FWD02 TB 469 W004 FWD02 TB 469 W005 FWD02 TB 469 W006 FWBelowgradewallsofU2CondensateBoosterPumpAreaIncorporatedPassive8D02 TB 495 W007 FWD02 TB 495 W008 FWD02 TB 495 W009 FWD02 TB 495 W010 FWD02 TB 495 W014 FWD02 TB 495 W015 FWD02 TB 495 W016 FWD02 TB 495 W017 FWD02 TB 495 W018 FWBelow gradewallsofU2CCSWPumpAreaIncorporatedPassivePage45 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0#FeatureID#DescriptionPassive/ActiveIncorporated/Temporary9D03 TB 469 W001 FWD03 TB 469 W002 FWD03 TB 469 W003 FWD03 TB 469 W004 FWD03 TB 469 W005 FWD03 TB 469 W006 FWBelow gradewallsofU3CondensateBoosterPumpAreaIncorporatedPassive10D03 TB 495 W007 FWD03 TB 495 W008 FWD03 TB 495 W009 FWD03 TB 495 W010 FWD03 TB 495 W014 FWD03 TB 495 W015 FWD03 TB 495 W016 FWD03 TB 495 W017 FWD03 TB 495 W018 FWBelow gradewallsofU3CCSWPumpAreaIncorporatedPassive11D23 EDGBelow gradewallsofU2/3EmergencyDieselGeneratorRoomIncorporatedPassive12D02 RB SLABFloorslabsofU2ReactorBuildingIncorporatedPassive13D03 RB SLABFloorslabsofU3ReactorBuildingIncorporatedPassive14D02 TB SLABFloorslabsofU2TurbineBuildingIncorporatedPassive15D03 TB SLABFloorslabsofU3TurbineBuildingIncorporatedPassivePage46 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Table7:ListofFeaturesNotImmediatelyJudgedasAcceptable#FeatureID#DescriptionObservationComponentOperabilityResolution115 PEN(Penetration#2,drawingFL 34)20 insleevew/16 incappedpipePenetrationsealshowedsignsofwaterseepage,bacterialgrowth,andmaterialdegradation.Yes-previouslydocumentedinAR01131053BasedonthewalkdownassociatedwithAR1131053,plantpersonneldeterminedthatthefloodsealsareacceptableandcapableofperformingtheirintendedfunction.217 PEN(Penetration#4,drawingFL 34)20 insleevew/16 incappedpipePenetrationsealshowedsignsofwaterseepage,bacterialgrowth,andmaterialdegradation.Yes-previouslydocumentedinAR01131053BasedonthewalkdownassociatedwithAR1131053,plantpersonneldeterminedthatthefloodsealsareacceptableandcapableofperformingtheirintendedfunction.3DOA0010 04,Floods(W 4)Rev.33FloodEmergencyProcedureSeveralproceduralsteps,asdescribedinSection4fN/A-documentedinAR01422791andAR01422880ProcedurerevisioninprogresstoenhancestationresponsetoissuesidentifiedinthisreportTable8:ListofFeaturesinRestrictedAccessAreas#FeatureID#DescriptionReasonResolutionN/AN/AN/AN/AN/APage47 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Table9:ListofFeaturesinInaccessibleAreas#FeatureID#DescriptionReasonResolution13 PEN(Penetration#1,drawingFL 8)12 insleeveSealnotvisibleduetopipeconnection.Wouldrequireintrusivemethodstoinspect.Reasonableassurancethatthecomponentcanprovideitsintendedfunctionwasprovidedbyabsenceofpastandcurrentevidenceofgroundwaterseepagebelowthepenetration.26 PEN(Penetration#1,drawingFL24)16 insleevew/6 inhypochloritepipe.Sealnotvisibleduetopipeconfigurationandelbowconnection.Wouldrequireintrusivemethodstoinspect.Reasonableassurancethatthecomponentcanprovideitsintendedfunctionwasprovidedbyabsenceofpastandcurrentevidenceofgroundwaterseepagebelowthepenetration.318 PEN(Penetration#1,drawingFL 39)20 insleevew/2electricalconduitsCoveredwithpullbox.Reasonableassurancethatthecomponentcanprovideitsintendedfunctionwasprovidedbyabsenceofpastandcurrentevidenceofgroundwaterseepagebelowthepenetrationandbyreviewofdrawings.6. REFERENCES1. ExelonLettertoU.S.NuclearRegulatoryCommission.ExelonGenerationCompany,LLC's90 DayResponsetoMarch12,2012RequestforInformationPursuanttoTitle10oftheCodeofFederalRegulations50.54(f)RegardingRecommendations2.1and2.3,oftheNearTermTaskForceReviewofInsightsfromtheFukushimaDai ichiAccident(Flooding).June11,2012.2. NuclearEnergyInstitute(NEI),Report12 07(Rev0 A).GuidelinesforPerformingVerificationWalkdownsofPlantProtectionFeatures.May2012[NRCendorsedMay31,2012;updatedandre issuedJune18,2012].Page48 NTTFRecommendation2.3(Walkdowns):FloodingExelonCorporationNovember20,2012Revision0Page493. U.S.NuclearRegulatoryCommission.LettertoLicensees.RequestforInformationPursuanttoTitle10oftheCodeofFederalRegulations50.54(f)RegardingRecommendations2.1,2.3,and9.3oftheNearTermTaskForceReviewofInsightsfromtheFukushimaDaiichiAccident.March12,2012.4. U.S.NuclearRegulatoryCommission.DemonstratingtheFeasibilityandReliabilityofOperatorManualActionsinResponsetoFire.NUREG 1852.October2007.5. U.S.NuclearRegulatoryCommission.RecommendationsforEnhancingReactorSafetyinthe21 stCentury,TheNearTermTaskForceReviewofInsightsfromtheFukushimaDai ichiAccident.July12,2011.6. U.S.NuclearRegulatoryCommission.OperabilityDeterminations&FunctionalityAssessmentsforResolutionofDegradedorNonconformingConditionsAdversetoQualityorSafety.NRCInspectionManual.Part9900:TechnicalGuidance.RegulatoryIssuesSummary2005 20,Revisions1.September26,2005.7. U.S.NuclearRegulatoryCommission.Follow uptotheFukushimaDai ichiNuclearStationFuelDamageEvent.InspectionManual.TemporaryInstruction2515/183.ML113220407.November2011.8. U.S.NuclearRegulatoryCommission.EvaluateReadinesstoCopewithExternalFlooding.InspectionProcedures.Attachment71111.01.AdverseWeatherProtection
.Section02.04.9. UpdatedFinalSafetyAnalysisReportforDresdenGeneratingStation,Rev.7,June2007,Sections2.3,2.4,and3.4.10. U.S.NuclearRegulatoryCommission.Dresden2NuclearGeneratingStation,SafetyEvaluationofHydrologySEPTopicsII3.A,II 3.B,II 3.B.1andII 3.C,Enclosure1-SafetyEvaluationReport,Enclosure2-TechnicalEvaluationReport.June21,1982.11. AMECEnvironment&Infrastructure.IndependentFloodRiskAssessmentfollowingtheFukushimaDaiichiNuclearPowerStationEvents.August23,2011.12. DOA0010 04,Floods(W4),Rev.32,Rev.33,andRev.3413. DGP02 01,NormalUnitShutdown14. DGP02 02,VesselSlowFill15. DGP02 03,ReactorScram16. DOP1300 03,ManualOperationofIsolationCondenser17. DOS1300 04,OperationoftheIsolationCondenserExternalFloodEmergencyMake upPump18. DOP1300 05IsolationCondenserLevelMonitoringUsingtheLocalSightGlass19. ER AA 450,StructuresMonitoring,Rev.1}}

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