L-14-104, Firstenergy Nuclear Operating Co. Response to NRC Request for Information Pursuant to 10 CFR 50.54 (F) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident: Difference between revisions

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| issue date = 03/11/2014
| issue date = 03/11/2014
| title = Firstenergy Nuclear Operating Co. Response to NRC Request for Information Pursuant to 10 CFR 50.54 (F) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident
| title = Firstenergy Nuclear Operating Co. Response to NRC Request for Information Pursuant to 10 CFR 50.54 (F) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident
| author name = Lieb R A
| author name = Lieb R
| author affiliation = FirstEnergy Nuclear Operating Co
| author affiliation = FirstEnergy Nuclear Operating Co
| addressee name =  
| addressee name =  
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=Text=
=Text=
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..'i-):tk I't,y I:t r. illtii;, I, iC"lll Rty*rutd A. Lieb\riia. i. l.atr,.tri i..f tJ iviri i'i:', t j March 11 , 2A14 L44-144 ATTN: Document Control DeskU.S. Nuclear Regulatory Commission 1 1555 Rockville Pike Rockville, MD ?fr852 10 cFR 50.54(fj
i-):tk I't,y I:t r. illtii;, I, iC"lll Fir stEne        rgy Nt r:l,earr;ratrnq            Ct-trnpany Rty*rutd A. Lieb
\riia. i. l.atr,.tri i..f tJ iviri i'i:', t j March11, 2A14 L44-144                                                                                   10cFR 50.54(fj ATTN: Document                       ControlDesk U.S.NuclearRegulatory                        Commission 11555Rockville                    Pike Rockville,                 MD ?fr852


==SUBJECT:==
==SUBJECT:==
Davis-Besse Nuclear Power StationDocket No.
 
50-346. License No. NPF-3 FirgtEnerqy NucleFI Operatinq Companv (FENOC) Respgnsqt_o NRC Reo.uest fqr tnformation pursuant to tg CFR 50.54{fl Reqardino the F,loodir}o Ag0ects3f Recommendation 2.1 of the Near-Term Task Force
Davis-Besse                   NuclearPowerStation DocketNo.50-346.LicenseNo.NPF-3 FirgtEnerqy                 NucleFIOperatinq      Companv(FENOC)Respgnsqt_o           NRCReo.uest   fqr tnformation                 pursuant     to tg CFR50.54{flReqardino      the F,loodir}oAg0ects3f Recommendation                       2.1of the Near-Term   TaskForce{NTTF}Rqview_of       Insiqhtsffomthe Fukushima                   Dai-ichi Accident On March12,2A12,                         theNuclear  Regulatory Commission   {NRC)issueda lettertitled, "Requestfor Informstion                       Pursuantto Title10of the Codesf FederalRegulatisns 50.54{0Regarding                      Recommendations     2.1,2.3,and9.3of the Near-Term     TaskForce Reviewof lnsights                     fromthe Fukushima     Dai-ichiAccident," to all powerreactorlicensees andholdersof construction                         permitsin activeor deferredstatus.Enclosure   2 of the 10 CFR50.54{0letteraddresses                          NTTFRecommendation        2.1forflooding.Oneof the required                 respon$es     is for licenseesto submita HazardReevaluation      Report(HRR)in accordance                   withthe NRC'sprioritization      plan By letterdatedMay11,2A12,     the NRC placedthe Davis-Besse                       NuclearPowerStation(DBNP$)in Category         2 requiring   a response                 by March12,2414.TheFloodHRRfor DBNPSis enclosed.
{NTTF} Rqview_of Insiqhts ffom the Fukushima Dai-ichi AccidentOn March 12,2A12, the Nuclear Regulatory Commission
As discussed                 in the enclcsedreport,twofloodlevels(localintenseprecipitation          and probable                 maximumstorrnsurge)determined           duringthe hazardreevaluatian  exceedthe currentlicensing                  basis(CLB)floodlevels.Theincreased          levelsarethe resultof newer methodologies                   and notthe resultof errorswithinthe CLBevaluations.         Currentplant procedures                   addressing     floodingat thesiteprovideactionsto be takenin theevent flooding                 is imminent     or hasoccurred  at or nearthe DBNP$site. No additional   actions beyondthosecurrently                        in placearenecessary    at thistime.
{NRC) issued a lettertitled,"Request for Informstion Pursuant to Title 10 of the Code sf Federal Regulatisns50.54{0 Regarding Recommendations 2.1 ,2.3, and 9.3 of the Near-Term Task Force Review of lnsights from the Fukushima Dai-ichi Accident," to all power reactor licensees and holders of construction permits in active or deferred status. Enclosure 2 of the 10 CFR 50.54{0 letter addresses NTTF Recommendation 2.1 forflooding. One of the required respon$es is for licensees to submit a Hazard Reevaluation Report (HRR) in accordance with the NRC's prioritization plan By letter dated May 11,2A12, the NRC placed the Davis-Besse Nuclear Power Station (DBNP$) in Category 2 requiring a response by March 12,2414. The Flood HRR for DBNPS is enclosed.As discussed in the enclcsed report, two flood levels (local intense precipitation and probable maximum storrn surge) determined during the hazard reevaluatian exceed the current licensing basis (CLB) flood levels. The increased levels are the result of newer methodologies and not the result of errors within the CLB evaluations.
 
Current plant procedures addressing flooding at the site provide actions to be taken in the eventflooding is imminent or has occurred at or near the DBNP$ site.
Davis-Besse     NuclearPowerStation L-14-104 Page2 ln accordance   withthe guidanceprovidedby NRCletterdatedDecember3, 2fi12,titled "TriggerConditions      for Performing an IntegratedAssessment    and Due Datefor Respon$,"   an integrated   assessment is requiredif floodlevelsdetermined  duringthe hazardreevaluation      are not boundedby the CLBfloodlevels.The 10 CFR50.54(f) specifiesthatthe integratedassessment        be compfetedand a repartsubmittedwithin twoyearsof submitting       the HRR. Therefore, FENOCintendsto submitan Integrated Assessment               for Report DBNPS         priorto March12,241&.
No additional actions beyond those currently in place are necessary at this time.
Thereare no regulatorycsrnmitments        containedin this letter. lf thereare anyquestions or if additional information             pleasecontactMr.ThomasA. Lentz,Manager-is required, FleetLicensing,   at 330-31   5-6810.
Davis-Besse Nuclear Power Station L-14-104Page 2 ln accordance with the guidance provided by NRC letter dated December 3, 2fi12, titled"Trigger Conditions for Performing an Integrated Assessment and Due Date for Respon$*," an integrated assessment is required if flood levels determined during thehazard reevaluation are not bounded by the CLB flood levels. The 10 CFR 50.54(f) specifies that the integrated assessment be compfeted and a repart submitted within two years of submitting the HRR. Therefore, FENOC intends to submit an Integrated Assessment Report for DBNPS prior to March 12,241&.There are no regulatory csrnmitments contained in this letter.
I declareunderpenaltyof perjurythatthe foregoingis trueandeorrect.Executedon M a r c hf l , 2 A 1 4 .
lf there are any questions or if additional information is required, please contact Mr. Thomas A. Lentz, Manager-Fleet Licensing, at 330-31 5-68 1 0.I declare under penalty of perjury that the foregoing is true and eorrect. Executed on March f l ,2A14.
Respectfully,


==Enclosure:==
==Enclosure:==


Flood Hazard Reevaluation Report cc: Director, Office of Nuclear Reactor Regulation (NRR)NRC Region lll Administrator NRC Resident Inspector NRR Project ManagerUtility Radiological Safety Board Respectfully, Enclosure L-14-104Flood Hazard Reevaluation Report (33 pages follow)
FloodHazardReevaluation          Report cc: Director,Officeof NuclearReactorRegulation          (NRR)
FLOOD HAZARD REEVALUATION REPORT tN RESPONSE TO THE 50.54(f) fNFORMATTON REQUE$T REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2'1: FLOODINGfor the DAVIS-BESSE NUCLEAR POWER STATIOTII5501 North State Route 2 Oak Harbor, OH 43449Flrst Energy Corporation76 South Maln Street Akron, OH 44308Prepared by:
NRCRegionlll Administrator NRCResidentInspector NRRProjectManager UtilityRadiological    SafetyBoard
ET ENERCON ( relhnce - - twty projxl tvay day Enercon Services Inc,12420 Mllestone Cenler Drive, $uite 200 Germantown, MD 20876 Revislon 1Submltted to FENOC; March 06, zAlH Preparer: Verifier: Verifier: Approver: Lead Responslble Engineers:Design Engineering Supervisor Deslgn Englneering Manager Thomas Gulvas Abiot Gemechu EnerconPrlnted Name Anubhav Gaur Affiliatlon Enercon Date"sl*l+rt ollo$lt4_.7--]-.*A i,',1/ 7 t lbla.rr1 s l,.l tLLana Lawrence Ray Sacramo Michael SobotaGregory MichaelJon Hook FENOC NTTF Recommendation 2.1 First Energy Corporation (Hazard Reevaluations):
 
FloodingRevision 1March 06, 2014 2.1,2. Flooding in Streams and Rivers ..........6 2.1.3. Dam Breaches and Failures..  
Enclosure L-14-104 FloodHazardReevaluationReport (33 pagesfollow)
.....,.,.7 2.1.7. Channel Migration or Diversion  
 
.. ........7 2.1.8. Combined Effect Flood (including Wind-Generated Waves) .......7 2.2. Flood-Related Changes to the License Basis
FLOODHAZARDREEVALUATION                            REPORT tN RESPONSE   TO THE50.54(f)fNFORMATTON                     REQUE$TREGARDING NEAR-TERM   TASKFORCERECOMMENDATION                              2'1: FLOODING for the DAVIS-BESSE   NUCLEARPOWERSTATIOTII 5501North State Route 2 Oak Harbor,OH 43449 FlrstEnergyCorporation 76 SouthMalnStreet Akron,OH 44308 Prepared        by:
.................7 2.3. Changes to the Watershed and Local Area since License lssuance .............,..7 2.4. Current Licensing Basis Flood Protection and Pertinent Flood Mitigation Features............8
ET ENERCON
( relhnce - - twty projxl tvay day EnerconServicesInc, 12420Mllestone  CenlerDrive,$uite200 Germantown,         MD 20876 Revislon1 Submlttedto FENOC;March06, zAlH PrlntedName                          Affiliatlon                Date Preparer:                       AnubhavGaur                            Enercon Verifier:                       AbiotGemechu                          Enercon "sl*l+rt ollo$lt4
_.7--]-
Verifier:                      LanaLawrence                                                            i,',1/
                                                                                              .A          7 Approver:                      RaySacramo LeadResponslbleEngineers:      ThomasGulvas MichaelSobota                                                    t lbla.rr1 DesignEngineering Supervisor    GregoryMichael                                                s l,.ltL DeslgnEnglneering Manager        Jon Hook                               FENOC
 
NTTFRecommendation              2.1 (HazardReevaluations):         Flooding                    Revision1 FirstEnergyCorporation                                                                        March06, 2014 2.1,2. Flooding           in Streamsand Rivers                                                   ..........6 2.1.3. DamBreaches                andFailures..                                                   .....,.,.7 2.1.7. Channel           Migration     or Diversion   ..                                         ........7 2.1.8. CombinedEffectFlood(including                       Wind-GeneratedWaves)                     .......7 2.2. Flood-Related           Changesto the LicenseBasis                                      .................7 2.3. Changesto the Watershed                       and LocalAreasinceLicenselssuance          .............,..7 2.4. CurrentLicensing        BasisFloodProtection          and Pertinent             Features............8 FloodMitigation
: 3.  
: 3.  


==SUMMARY==
==SUMMARY==
OF FLOOD HAZARD REEVALUATION
OF FLOODHAZARDREEVALUATION                                                                    ........8 3.1. Floodingin Streamsand Rivers(ReferenceDBNPS2013a,DBNPS2013b,and DBNPS 2013c)                                                                                             ..........9 3 . 1 . 1 . B a s i so f I n p u l s : . . . . . .                                               ........10 3.1.2. Computer             Software       Programs..                                               .....11 3.1.3. Methodology.                                                                                 .....11 3 . 2 . 1 . B a s i so f l n p u t s                                                              ........15 3.2.2. Computer             Software       Programs..                                           .........15 3.2.3. Methodology.                                                                               .......15 3 . 3 . 1 . B a s i so f I n p u t s                                                                  ....16 3.3.2. Computer             Software       Programs..                                             .......16 3.3.3. Methodology..                                                                               .......16 3.4. ChannelMigration              or Diversion       (ReferenceDBNPS2013d)                   .............17 3,4.1. Basisoflnputs                                                                             ........17 DAVIS-BESSE       NUCLEARPOWERSTATION                                                          Page 1 of 32
........83.1. Flooding in Streams and Rivers (Reference DBNPS 2013a, DBNPS 2013b, and DBNPS201 3c) . .... .....93.1.1. Basis of Inpuls:......  
 
........103.1.2. Computer Software Programs..  
NTTFRecommendation    2.1 (HazardReevaluations):
.....113.1.3. Methodology.  
Flooding                     RevisionI FirstEnergyCorporation                                                March06, 2014 3.4.2. Computer SoftwarePrograms.....                               ............17 3.4.3. Methodology..                                                     ,.....,,.17 3.4,4. Results                                                           ........17 3,5. Storm Surge (ReferenceDBNPS20139,DBNPS2013h, DBNPS2013i and DBNFS 2 0 13 m )                                                                     . . . . .1.B 3.5.1. Basisof Inputs                                                         ....18 3.5.2. Computer SoftwarePrograms..                                       .......18 3.5.3. Methodology..
.....113.2.1. Basis of lnputs
3.5.4. Results                                                             ......21 3.6. Tsunami Assessrnent (ReferenceDBNPS2013j)                                 ....21 3.6.1. Basisof lnputs 3.6.2. ModelsUsed                                                      .."........22 3.6.3. Methodology....                                       ,.r...,,.... .....22 3.6.4. Results                                                             ..,...23 3.7. CombinedEffectFlood(including           Waves)(Reference
........15 3.2.2. Computer Software Programs..  
                                      \Mnd-Generated             DBNPS2013n).23 3.7.1. Basisof Inputs                                                 ...,.......24 3.7.2. Computer$oftwarePrograms..                                           .....24 3.7.3. Methodology...                                                   .........24 3.7.4, Results                                                     ..............25 3.8. LocalIntensePrecipitation(Reference DBNPS2013eand DBNPS20130......       .....,..26 3.8.1. Basisoflnputs                                                       ......26 3.8.2. ModelsUsed                                                      ............26 4 , COMPARISON    WITHCURRENTDESIGNBASIS 5.
.........15 3.2.3. Methodology.  
6.
.......153.3.1. Basis of Inputs ....163.3.2. Computer Software Programs..  
DAVIS-BESSE   NUCLEARPOWERSTATION                                      Page2 ol 32
.......163.3.3. Methodology..  
 
.......163.4. Channel Migration or Diversion (Reference DBNPS 2013d)  
NTTFRecommendation      2.1 (HazardReevaluations):   Flooding                          Revision1 FirstEnergyCorporation                                                            March06, 2014
.............173,4.1. Basisoflnputs  
{. PURPOSE 1.1.Background ln responseto the nuclearfueldamageat the FukushimaDai-ichipowerplantdue to the March 11, 2011 earthquakeand subsequenttsunami, the United States Nuclear Regulatory Commission(NRC) establishedthe Near Term Task Force (NTTF)to conducta systematic reviewof NRC processesand regulations,and to make recornmendations           to the NRC for its policydirection.The NTTFreporteda set of recommendations       that were intendedto clarifyand strengthenthe regulatoryframeworkfor protectionagainstnaturalphenomena.
........17 DAVIS-BESSE NUCLEAR POWER STATIONPage 1 of 32 NTTF Recommendation 2.1 (Hazard Reevaluations): Flooding First Energy CorporationRevision I March 06, 2014 3.4.2. Computer Software Programs.....  
On March 12,2012the NRC issuedan informationrequestpursuantto Title 10 of the Code of FederalRegulations,   Section50.54(D(10 CFR50.54(f)or 50.54(f)lette$whichincludedsix (6) enclosures:
............17 3.4.3. Methodology..  
1 . NTTF Recommendation     2.1:Seismic 2 , NTTF Recommendation     2.1:Flooding
,.....,,.17 3.4,4. Results ........17 3,5. Storm Surge (Reference DBNPS 20139, DBNPS 2013h, DBNPS 2013i and DBNFS 201 3m) ...... 1B 3.5.1. Basis of Inputs  
: 3. NTTF Recommendation       2.3:Seismic
....18 3.5.2. Computer Software Programs..  
: 4. NTTF Recommendation       2.3:Flooding 5 . NTTF Recommendation     9.3:EP 6 . Licenseesand Holdersof Construction   Permits fn Enclosure2 of the NRC-issued   information request(ReferenceNRCMarch2A12),the NRC requestedthat licenseesreevaluatethe floodinghazardsat their sites against present-day regulatory guidanceand rnethodologies   beingusedfor earlysite permits(ESP)and combined operatinglicensereviews.
.......18 3.5.3. Methodology..3.5.4. Results  
On behalfof First EnergyCorporation(FENOC)for the Davis-BesseNuclearPower Station (DBNPS),this FloodHazardReevaluation        Report(Report)providesthe informationrequested in the March 12, 2012 50.54(f)letter;specifically, the informationlistedunderthe "Requested
......21 3.6. Tsunami Assessrnent (Reference DBNPS 2013j)  
                                                                'e').The "Reque$ted fnformation"  sectionof Enclosure2, paragraph1 ('a' through                        Information" sectionof Enclosure2, paragraph2 ('a' through     'd'), IntegratedAssessmentReport,will be addressedseparatelyif the currentdesignbasisfloods do not boundthe reevaluatedhazard for all flood-causing mechanisms.
....213.6.1. Basis of lnputs 3.6.2. Models Used .."........223.6.3. Methodology....  
1.2.RequestedActlons Per Enclosure2 of the NRC-issued     informationrequest,50.54(f)Ietter,FENOCis requestedto performa reevaluation   of all appropriateexternal  floodingsourcesfor DBNPS,includingthe effectsfrom localintenseprecipitation  (LlP)on the site,the probablemaximumflood(PMF)on streamsand rivers,lakefloodingfromstormsurges,seichesand tsunamis,and dam failures.lt is requestedthat the reevaluationapply present-dayregulatoryguidanceand methodologies being used for ESPs, and calculationreviewsincludingcurrenttechniques,software,and methodsused in present-daystandardengineeringpracticeto developthe flood hazard.The requestedinformationwill be gatheredin Phase 1 of the NRC staffs two-phaseprocessto irnplementRecornmendation      2,1, and will be used to identifypotential"vulnerabilities"(see definition below).
,.r...,,....  
DAVIS-BESSE     NUCLEARPOWERSTATION                                                  Page3 of 32
.....223.6.4. Results  
 
..,...23 3.7. Combined Effect Flood (including  
NTTFRecommendatisn      2.1 (HazardReevaluations): Flooding                           Revision1 FirstEnergyCorporation                                                              March46,2014 For the siteswherethe reevaluatedfloodexceedsthe designbasis,addresseesare requested to submitan interimactionplan documenting       plannedactionsor measuresimplemented            to addressthe reevaluated   hazards.
\Mnd-Generated Waves) (Reference DBNPS 2013n).23 3.7.1. Basis of Inputs  
Subsequently,   addresseesshall performan integratedassessmentof the plantto fully identify vulnerabilities and detail actionsto addressthem. The scope of the integratedassessment reportwill includefull poweroperationsand otherplantconfigurations      that couldbe susceptible due to the statusof the flood protectionfeatures.The scopealso includesthosefeaturesof the ultimateheat sink (UHS)that could be adverselyaffectedby flood conditions(the loss of UHS from non-floodassociatedcauses is not included).lt is also requestedthat the integrated asses$ment   addressthe entiredurationof the floodconditions.
...,.......243.7.2. Computer $oftware Programs..  
A definition of vulnerability in the context of Enclosure 2 is as follaws: Plant-specific are thosefeaturesimpoftantto safetythat whensubjectta an increaseddemand vulnerabilities due lo the newly calculated hazard evaluation have not been shown to be capable of performingtheirintendadfunctiorts.
.....243.7.3. Methodology...  
1.3.RequestedInformation Per Enclosure2 of the NRC-issuedinformationrequest 50.54(0 letter, the Report should providedocumentedresults,as well as pertinentDBNPSinformationand detailedanalysis,and includethe following:
.........243.7.4, Results  
: 1. Site informationrelaledto the flood hazard.Relevantstructure,systems,and components (SSCs)importantto safetyand the UHS are includedin the scopeof this reevaluation,       and pertinentdata concerningtheseSSCsshouldbe included.Otherrelevantsite data includes the following:
..............253.8. Local Intense Precipitation (Reference DBNPS 2013e and DBNPS 20130...... .....,..26 3.8.1. Basisoflnputs  
: 1. Detailedsite information(both designedand as-built),includingpresent-daysite layout, elevation of pertinentSSCs importantto safety, site topography,and pertinentspatialandtemporaldatasets;
......26 3.8.2. Models Used ............26COMPARISON WITH CURRENT DESIGN BASIS 4, 5.6.DAVIS-BESSE NUCLEAR POWER STATION Page 2 ol 32 NTTF Recommendation 2.1 (Hazard Reevaluations):
: 2. Currentdesignbasisfloodelevations    for all flood-causing mechanism$;
FloodingFirst Energy Corporation{. PURPOSE Revision 1 March 06, 20141.1. Backgroundln response to the nuclear fuel damage at the Fukushima Dai-ichi power plant due to the March 11, 201 1 earthquake and subsequent tsunami, the United States Nuclear Regulatory Commission (NRC) established the Near Term Task Force (NTTF) to conduct a systematic review of NRC processes and regulations, and to make recornmendations to the NRC for its policy direction. The NTTF reported a set of recommendations that were intended to clarify and strengthen the regulatory framework for protection against natural phenomena.On March 12,2012 the NRC issued an information request pursuant to Title 10 of the Code of Federal Regulations, Section 50.54 (D (10 CFR 50.54(f) or 50.54(f) lette$ which included six (6)enclosures:
: 3. Flood-relatedchangesto the licensingbasis and any flood protectionchanges (includingmitigation) sincelicenseissuance;
1.2, 3.NTTF Recommendation 2.1: SeismicNTTF Recommendation 2.1: Flooding NTTF Recommendation 2.3: Seismic NTTF Recommendation 2.3: Flooding NTTF Recommendation 9.3: EP Licensees and Holders of Construction Permits 4.5.6.f n Enclosure 2 of the NRC-issued information request (Reference NRC March 2A12), the NRC requested that licensees reevaluate the flooding hazards at their sites against present-day regulatory guidance and rnethodologies being used for early site permits (ESP) and combinedoperating license reviews.On behalf of First Energy Corporation (FENOC) for the Davis-Besse Nuclear Power Station (DBNPS), this Flood Hazard Reevaluation Report (Report) provides the information requestedin the March 12, 2012 50.54(f) letter; specifically, the information listed under the "Requestedf nformation" section of Enclosure 2, paragraph 1 ('a' through 'e'). The "Reque$ted Information"section of Enclosure 2, paragraph 2 ('a' through 'd'), Integrated Assessment Report, will be addressed separately if the current design basis floods do not bound the reevaluated hazardfor all flood-causing mechanisms.
: 4. Changesto the watershedand localareasincelicenseissuance;
1.2. Requested ActlonsPer Enclosure 2 of the NRC-issued information request, 50.54(f)
: 5. Currentlicensingbasisfloodprotectionand pertinentfloodmitigationfeaturesat the site:and
Ietter, FENOC is requested to perform a reevaluation of all appropriate external flooding sources for DBNPS, including theeffects from local intense precipitation (LlP) on the site, the probable maximum flood (PMF) on streams and rivers, lake flooding from storm surges, seiches and tsunamis, and dam failures.
: 6. Additionalsite details,as necess?ry,to assessthe flood hazard(e.9.,bathymetry andwalkdownresults).
lt is requested that the reevaluation apply present-day regulatory guidance and methodologies being used for ESPs, and calculation reviews including current techniques, software, and methods used in present-day standard engineering practice to develop the flood hazard. The requested information will be gathered in Phase 1 of the NRC staffs two-phase process to irnplement Recornmendation 2,1, and will be used to identify potential "vulnerabilities" (see definition below).DAVIS-BESSE NUCLEAR POWER STATIONPage 3 of 32 NTTF Recommendatisn 2.1 (Hazard Reevaluations):
: 2. Evaluationof the flood hazardfor each flood-causingmechanism,based on present-day methodologiesand regulatoryguidance.Provide an analysis of each flood-causing mechanismthat may impactthe site,includingLIP and site drainage,floodingin streams and rivers, dam breachesand failures,storm surge and seiche, tsunamis,channel migrationor diversion,and combinedeffects.Mechanisms       that are not applicableat the site may be screenedout; however,a     justification shouldbe    provided. A basisfor inputsand assumptions, methodologies and modelsused,includinginputand outputfiles,and other pertinentdatashouldbe provided.
Flooding Revision 1 First Energy Corporation March 46,2014 For the sites where the reevaluated flood exceeds the design basis, addressees are requestedto submit an interim action plan documenting planned actions or measures implemented toaddress the reevaluated hazards.Subsequently, addressees shall perform an integrated assessment of the plant to fully identify vulnerabilities and detail actions to address them. The scope of the integrated assessment report will include full power operations and other plant configurations that could be susceptible due to the status of the flood protection features.
DAVIS-BESSE     NUCLEARPOWERSTATION                                                    Page4 of 32
The scope also includes those features of theultimate heat sink (UHS) that could be adversely affected by flood conditions (the loss of UHS from non-flood associated causes is not included). lt is also requested that the integratedasses$ment address the entire duration of the flood conditions.
 
A definition of vulnerability in the context of Enclosure 2 is as follaws: Plant-specific vulnerabilities are those features impoftant to safety that when subject ta an increased demand due lo the newly calculated hazard evaluation have not been shown to be capable of performing their intendad functiorts.
NTTFRecommendation        2.1 (HazardReevaluations): Flooding                          Revision1 FirstEnergyCorporation                                                            March06, 2014
1.3. Requested InformationPer Enclosure 2 of the NRC-issued information request 50.54(0 letter, the Report should provide documented results, as well as pertinent DBNPS information and detailed analysis, and include the following:
: 3. Cornparisonof currentand reevaluatedflood-causingmechanisrnsat the site. Providean asse$$ment    of the currentdesignbasisfloodelevationto the reevaluated  floodelevationfor each flood-causing    mechanism.Includehow the findingsfrom Enclosure2 of the 50.54(f) letter(i.e., Recommendation                                  supportthis determination.
: 1. Site information relaled to the flood hazard. Relevant structure, systems, and components (SSCs) important to safety and the UHS are included in the scope of this reevaluation, and pertinent data concerning these SSCs should be included. Other relevant site data includes the following:1. Detailed site information (both designed and as-built), including present-day site layout, elevation of pertinent SSCs important to safety, site topography, and pertinent spatial and temporal data sets;2. Current design basis flood elevations for all flood-causing mechanism$;3. Flood-related changes to the licensing basis and any flood protection changes (including mitigation) since license issuance;4. Changes to the watershed and local area since license issuance;5. Current licensing basis flood protection and pertinent flood mitigation features at thesite: and6. Additional site details, as necess?ry, to assess the flood hazard (e.9., bathymetryand walkdown results).
2.1, flood hazardreevaluations)                          lf the current design basis flood bounds the reevaluated       hazard  for  all flood-causing mechanisms,    includehowthisfindingwas determined.
: 2. Evaluation of the flood hazard for each flood-causing mechanism, based on present-day methodologies and regulatory guidance. Provide an analysis of each flood-causing mechanism that may impact the site, including LIP and site drainage, flooding in streamsand rivers, dam breaches and failures, storm surge and seiche, tsunamis, channelmigration or diversion, and combined effects. Mechanisms that are not applicable at the site may be screened out; however, a justification should be provided. A basis for inputs and assumptions, methodologies and models used, including input and output files, and other pertinent data should be provided.DAVIS-BESSE NUCLEAR POWER STATION Page 4 of 32 NTTF Recommendation 2.1 (Hazard Reevaluations):
: 4. Interimevaluationand actionstaken or plannedto addre$sany higherfloodinghazards relativeto the design basis, prior to completionof the integratedassessmentdescribed below,if necessary.
FloodingFirst Energy Corporation
: 5. Additionalactions beyond requestedinformationitem l.d taken or plannedto address floodinghazards,if any.
: 4. Interim evaluation and actions taken or planned relative to the design basis, prior to completion below, if necessary.5. Additional actions beyond requested informationflooding hazards, if any.Revision 1 March 06, 2014to addre$s any higher flooding hazards of the integrated assessment described item l.d taken or planned to address 3. Cornparison of current and reevaluated flood-causing mechanisrns at the site. Provide anasse$$ment of the current design basis flood elevation to the reevaluated flood elevation foreach flood-causing mechanism. Include how the findings from Enclosure 2 of the 50.54(f)letter (i.e., Recommendation 2.1, flood hazard reevaluations) support this determination.
: 2. SITEINFORMATION DBNPSis locatedon the shore of Lake Erie in Oak Harbor,Ohio" The majorhydrological featuresof the terrain are the broad expanseof Lake Erie to the north and east, and the ToussaintRiver,which flows east into the lake along the south side of DBNPS,DBNPS is approximately   3,000 feet (ft) from the Lake Erie shorellne(USAR, Section1.2.1.1)and approximately   2,000ft from the ToussaintRiver.Site areas surroundingthe stationstructures havebeenbuiltup from 6 to 14 feet abovethe existinggradeelevationto an elevationof 584 ft International GreatLakesDatumof 1955(lGLD55)or 15.4ft abovethe LakeErie Low Water Datumof 568.6ft-lGLDs5.Topographyat and aroundDBNPSis relativelyflat,with a mean station elevation of approximately584 ft-lclDss. The site safety-relatedstructuresare protectedagainsthighwaterlevelsup to an elevationof 585 ft-lGLDs5.A LakeEriedike,which is locatedalongthe shoreof Lake Erie,protectsthe site from lakesurges.Additionally,   a wave protectiondike is situatedalongthe northern,eastern,and a small   portionof southernsidesof DBNPS.The elevationat the top of the wave protectiondike is 591 ft-lGLDs5. Present-Day SiteLayoutis shownin Figures2.0.1.
lf the current design basis flood bounds the reevaluated hazard for all flood-causingmechanisms, include how this finding was determined.
DAVIS.BESSE     NUCLEARPOWERSTATION                                                  Page5 of 32
: 2. SITE INFORMATIONDBNPS is located on the shore of Lake Erie in Oak Harbor, Ohio" The major hydrological features of the terrain are the broad expanse of Lake Erie to the north and east, and the Toussaint River, which flows east into the lake along the south side of DBNPS, DBNPS is approximately 3,000 feet (ft) from the Lake Erie shorellne (USAR, Section 1.2.1.1) and approximately 2,000 ft from the Toussaint River.
 
Site areas surrounding the station structureshave been built up from 6 to 14 feet above the existing grade elevation to an elevation of 584 ft International Great Lakes Datum of 1955 (lGLD55) or 15.4 ft above the Lake Erie Low WaterDatum of 568.6 ft-lGLDs5.
NTTFRecommendation        2.1(HazardReevaluations): Flooding                       Revision1 FirstEnergyCorporation                                                        March06,2014 Figure2.0.1- Present-Day Site Layout 2.1,CurrentDesignBasis The currentdesignbasisis definedin the DBNPSUpdatedSafetyAnalysisReport(USAR).
Topography at and around DBNPS is relatively flat, with a meanstation elevation of approximately 584 ft-lclDss. The site safety-related structures are protected against high water levels up to an elevation of 585 ft-lGLDs5.
The followingis a list of flood-causingmechanismsand their associatedwater surface elevations   thatwereconsidered for the DBNPScurrentdesignbasis.
A Lake Erie dike, which is located along the shore of Lake Erie, protects the site from lake surges.
2 . 1 . 1 .L t P The USARindicatesthat the precipitation   valueof 24.l-inchesover a 6 hour periodis utilized for the LIP analysis.As indicatedin the USAR,the averageinvertelevationof rnanholesand catchbasinsis 582ft-lcLD55;with 24.5inchesof estimatedaccumulation,     watercouldbuildup to 584.5ft-lclDss     (USAR, Section2.4.2.3).
Additionally, a wave protection dike is situated along the northern, eastern, and a small portion of southern sides of DBNPS. The elevation at the top of the wave protection dike is 591 ft-lGLDs5.
2.1.2. Floodingin Streamsand Rivers The USAR indicatesthat a flow rate of 78,500cubicfeet per second(cfs) in the Toussaint Riverat DBNPS(USAR,Section2,4.3)wouldresultin a maximumwatersurfaceelevationof 579 ft-lclDss. As indicatedin the USAR,the elevationof 579 ft-lGLDs5was derivedusingthe conservative               that noneof the wateris discharged assumption                                to LakeErie,assumingthat the PMFflowis hypothetically   dammedup atthat   point(USAR,       2.4.3.5).
Present-Day Site Layout is shown in Figures 2.0.1.DAVIS.BESSE NUCLEAR POWER STATION Page 5 of 32 NTTF Recommendation 2.1 First Energy Corporation (Hazard Reevaluations):
Section DAVIS.BESSE       NUCLEARPOWERSTATION                                            Page6 of 32
Flooding Revision 1 March 06, 2014Figure 2.0.1- Present-Day Site Layout2.1, Current Design Basis The current design basis is defined in the DBNPS Updated Safety Analysis Report (USAR).The following is a list of flood-causing mechanisms and their associated water surface elevations that were considered for the DBNPS current design basis.2.1.1. LtP The USAR indicates that the precipitation value of 24.l-inches over a 6 hour period is utilized for the LIP analysis. As indicated in the USAR, the average invert elevation of rnanholes and catch basins is 582 ft-lcLD55; with 24.5 inches of estimated accumulation, water could build upto 584.5 ft-lclDss (USAR, Section 2.4.2.3).
 
2.1.2. Flooding in Streams and RiversThe USAR indicates that a flow rate of 78,500 cubic feet per second (cfs) in the Toussaint River at DBNPS (USAR, Section 2,4.3) would result in a maximum water surface elevation of 579 ft-lclDss. As indicated in the USAR, the elevation of 579 ft-lGLDs5 was derived using the conservative assumption that none of the water is discharged to Lake Erie, assuming that the PMF flow is hypothetically dammed up atthat point (USAR, Section 2.4.3.5).DAVIS.BESSE NUCLEAR POWER STATIONPage 6 of 32 NTTF Recommendation 2.1 (Hazard Reevaluations):
NTTFRecommendation      2.1 (HazardReevaluations): Flooding                       Revision1 FirstEnergyCorporation                                                        March06, 2014 2.1.1. Dam Breachesand Failures The USAR indicatesthat there are no dams or other regulatinghydraulicstructureson the ToussaintRiverwhichwouldaffectthe flowhydrograph      at DBNPS(USAR,Section2.4.31.
Flooding First Energy Corporation Revision 1 March 06, 2014 2.1.1. Dam Breaches and Failures The USAR indicates that there are no dams or other regulating hydraulic structures on the Toussaint River which would affect the flow hydrograph at DBNPS (USAR, Section 2.4.31.2.1.4, Storm Surge & Seiche The probable maximum meteorological event in Lake Erie results in a maximum water surfece elevation of 583.7 ft-lGLD5s.
2.1.4, StormSurge& Seiche The probablemaximummeteorological      eventin LakeErie resultsin a maximumwatersurfece elevationof 583.7 ft-lGLD5s. This meteorologicalevent is caused by a maximumeast-northeast windat any locationof 100 milesper hourfor a 1O-minute duration,anda windspeed of 70 milesper hourduringthe six-hourperiodboth beforeand afterthe maximumwind speed (USAR,Section2.4.5).
This meteorological event is caused by a maximum east-northeast wind at any location of 100 miles per hour for a 1O-minute duration, and a wind speed of 70 miles per hour during the six-hour period both before and after the maximum wind speed (USAR, Section 2.4.5).
2.1.5. Low Water No wateris takenfromthe ToussaintRiverfor plantcoolingwaterrequirements. Therefore,low flows in the Toussaint River will not affect DBNPS operation.The probable maximum meteorological event in Lake Erie resultsin the probableextremelow water level of 556.8ft-lGLD55(USAR,Section2.4.11).
2.1.5. Low Water No water is taken from the Toussaint River for plant cooling water requirements. Therefore, low flows in the Toussaint River will not affect DBNPS operation.
2.1,6. lce-lnduced   Flooding Floodingof the safety-relatedstructuresand equipmentat DBNPS due to ice jams in the ToussaintRiveris not credible.The USARindicatesthat the elevationof the pfantstructuresis abovethe level of normallake ice formations.Category1 wave protectiondikesare designed to withstand the impactof ice (USAR,Section2.4.7).
The probable maximum meteorological event in Lake Erie results in the probable extreme low water level of 556.8 ft-lGLD55 (USAR, Section 2.4.11).2.1,6. lce-lnduced Flooding Flooding of the safety-related structures and equipment at DBNPS due to ice jams in the Toussaint River is not credible.
2.1.7. GhannelMigrationor Diversion As indicatedin the USAR,the mean lake levelis not subjectta variationsdue to diversionsor sourcecutoff(USAR,Section2.4.9).
The USAR indicates that the elevation of the pfant structures is above the level of normal lake ice formations. Category 1 wave protection dikes are designed to withstand the impact of ice (USAR, Section 2.4.7).2.1.7. Ghannel Migration or DiversionAs indicated in the USAR, the mean lake level is not subject ta variations due to diversions orsource cutoff (USAR, Section 2.4.9).
2.1.8. CombinedEffectFlood(lncludingWind-Generated         Waves)
2.1.8. Combined Effect Flood (lncluding Wind-Generated Waves)Wind-wave activity, including runup, was evaluated for its effect on the wave protection dikes on the north, east, and south sides of DBNPS.
Wind-waveactivity,includingrunup,was evaluatedfor its effecton the wave protectiondikes on the north,east,and southsidesof DBNPS.As indicatedin the USAR,the maximumwave run-upon the dike is 6.6 ft abovethe probablemaximumwater surfaceelevationof 583.7ft-lGLD55.The resultingmaximumwave runupelevationis 590.3ft-lGLDs5,whichis belowthe top of the dike(USAR,Section2.4.2.2.1).
As indicated in the USAR, the maximum wave run-up on the dike is 6.6 ft above the probable maximum water surface elevation of 583.7 ft-lGLD55. The resulting maximum wave runup elevation is 590.3 ft-lGLDs5, which is below thetop of the dike (USAR, Section 2.4.2.2.1).
2.2. Flood-Related Changesto the LicenseBasis There were no changesto the licensebasissince the           licenseissuance with regardto I flooding.
2.2. Flood-Related Changes to the License Basis There were no changes to the license basis since the flooding.license issuance with regard to I 2.3. Changes to the Watershed and Local Area since License lssuance The watershed contributory to the Toussaint River upstream of DBNPS is approximately 139.0 square miles (Reference DBNPS 2013c). Based on aerial images of the watershed, the changes to the watershed include commercial development within the watershed area, which isa very small percentage of the overall watershed area.
2.3.Changesto the Watershedand Local Area since Licenselssuance The watershedcontributory  to the ToussaintRiverupstreamof DBNPSis approximately   139.0 square miles (ReferenceDBNPS 2013c).Based on aerial imagesof the watershed,the changesto the watershedincludecommercialdevelopment      withinthe watershedarea,whichis a very small percentageof the overallwatershedarea. The changesto the local area sub-watershedfor DBNPSincludebuifdings,parkingfots,and securitybarrierupgradesthat have beenaddedto the sitesincelicenseissuance.
The changes to the local area sub-watershed for DBNPS include buifdings, parking fots, and security barrier upgrades that havebeen added to the site since license issuance.DAVIS-BESSE NUCLEAR POWER STATIONPage 7 at 32 NTTF Recommendation 2.1 (Hazard Reevaluations):
DAVIS-BESSE     NUCLEARPOWERSTATION                                              Page7 at 32
Flooding First Energy Corporation Revision 1 March 06, 20142.4. Cunent Licensing Basis Flood Protection and Pertinent Flood Mitigation Features The maximum flood level in the design basis is below the site finish floor elevation of 585 ft-lGLD55. Therefore, there were no mitigation actions initiated or taken for flooding at the site.3.  
 
NTTFRecommendation      2.1 (HazardReevaluations):   Flooding                       Revision1 FirstEnergyCorporation                                                          March06, 2014 2.4. Cunent LicensingBasis Flood Protectionand PertinentFlood MitigationFeatures The maximumflood level in the designbasis is belowthe site finishfloor elevationof 585 ft-lGLD55.Therefore,therewere no mitigationactionsinitiatedor takenfor floodingat the site.
: 3.  


==SUMMARY==
==SUMMARY==
OF FLOOD HAZARD REEVALUATIONNUREG/CR-7046, Design-Basis Flood Estimation for Srfe Cfiaracterization at Nuclear Pawer Planfs in the united Sfafes of America (Reference NUREG/CR-7046), by reference to the American Nuclear Society (ANS), states that a single flood-causing event is inadequate as adesign basis for power reactors and recommends that combinations should be evaluated to determine the highest flood water elevation at the site.
OF FLOODHAZARDREEVALUATION NUREG/CR-7046,Design-BasisFlood Estimationfor Srfe Cfiaracterization      at NuclearPawer Planfs in the united Sfafes of America (ReferenceNUREG/CR-7046),by referenceto the AmericanNuclearSociety(ANS),statesthat a singleflood-causing      eventis inadequateas a design basis for power reactorsand recommendsthat combinationsshouldbe evaluatedto determinethe highestflood water elevationat the site. For DBNP$, the combinationthat producesthe highestflood water elevationat the site is the probablemaximumsurge and seicheon Lake Eriewith the effectsof coincidentwind wave activity.
For DBNP$, the combination that produces the highest flood water elevation at the site is the probable maximum surge and seiche on Lake Erie with the effects of coincident wind wave activity.The USAR reports elevations corresponding to lGLDSS vertical datum. The recent site survey, United States Geological Survey (USGS) topographic rnaps, and other reference documents report elevation in North American Vertical Datum of 19BB (NAVDBB). In order to compare the reevaluated flood elevatiens
The USARreportselevationscorresponding        to lGLDSSverticaldatum.The recentsite survey, UnitedStatesGeologicalSurvey      (USGS)  topographicrnaps,and other referencedocuments reportelevationin NorthAmericanVerticalDatumof 19BB(NAVDBB).        In orderto comparethe reevaluatedflood elevatienswith the existingdesign basis    reportedin USAR,final pertinent elevationshave been convertedto lGLD55 datum. The conversionbetween lGLD55 and NAVDBBat DBNPSis represented        as-- ft-lGLDsS= ft-NAVD88* 1.07ft.
Calculation  C-CSS-020.13-017    (Reference  DBNPS2013i)definesthe maximumwatersurface elevationof 585.81ft-lGLDs5at DBNPSadjacentto the powerblock.This elevationis due to a probablemaximumstorm surge (PMSS)during a probablemaximumwind storm (PMWS) event.The revisedmaximumwater surfaceelevationis abovethe site finishfloor elevationof 585 ft-tGLD55.
CalculationC-CSS-020.13-022      (ReferenceDBNPS2013n)definesthe coincidentwind wave runup.The maximumwave runupelevationof the PMSScoincidentwith wind wave activityis determinedby addingthe wind wave runup to the water surfaceflood elevationdue to the PMS$.The maximumrunupon the wave protectiondike is 589.88ft-lcLD55,whichis below the top of the wave protectiondike elevationof 591 ft-lclDss. The maximumwave runup elevationin the vicinityof the powerblockis 585.90feet-lGLD55. The wave runupelevationsin the vicinityof the powerblockare abovethe sitefinishfloorelevationof 585 ft-lGLD55.
Calculation  C-CSS-020.13-014  (Reference  DBNPS20130definesthe maximumwatersurface elevationresultingfrom the LIP event.The watersurfaceelevationdue to the

Latest revision as of 08:06, 4 November 2019

Firstenergy Nuclear Operating Co. Response to NRC Request for Information Pursuant to 10 CFR 50.54 (F) Regarding the Flooding Aspects of Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident
ML14070A108
Person / Time
Site: Davis Besse Cleveland Electric icon.png
Issue date: 03/11/2014
From: Lieb R
FirstEnergy Nuclear Operating Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
L-14-104
Download: ML14070A108 (36)
v • d • e


Text

FENOC," '::ti.j l Ntrtl r sl.t/f l]ilillir ..'

i-):tk I't,y I:t r. illtii;, I, iC"lll Fir stEne rgy Nt r:l,earr;ratrnq Ct-trnpany Rty*rutd A. Lieb

\riia. i. l.atr,.tri i..f tJ iviri i'i:', t j March11, 2A14 L44-144 10cFR 50.54(fj ATTN: Document ControlDesk U.S.NuclearRegulatory Commission 11555Rockville Pike Rockville, MD ?fr852

SUBJECT:

Davis-Besse NuclearPowerStation DocketNo.50-346.LicenseNo.NPF-3 FirgtEnerqy NucleFIOperatinq Companv(FENOC)Respgnsqt_o NRCReo.uest fqr tnformation pursuant to tg CFR50.54{flReqardino the F,loodir}oAg0ects3f Recommendation 2.1of the Near-Term TaskForce{NTTF}Rqview_of Insiqhtsffomthe Fukushima Dai-ichi Accident On March12,2A12, theNuclear Regulatory Commission {NRC)issueda lettertitled, "Requestfor Informstion Pursuantto Title10of the Codesf FederalRegulatisns 50.54{0Regarding Recommendations 2.1,2.3,and9.3of the Near-Term TaskForce Reviewof lnsights fromthe Fukushima Dai-ichiAccident," to all powerreactorlicensees andholdersof construction permitsin activeor deferredstatus.Enclosure 2 of the 10 CFR50.54{0letteraddresses NTTFRecommendation 2.1forflooding.Oneof the required respon$es is for licenseesto submita HazardReevaluation Report(HRR)in accordance withthe NRC'sprioritization plan By letterdatedMay11,2A12, the NRC placedthe Davis-Besse NuclearPowerStation(DBNP$)in Category 2 requiring a response by March12,2414.TheFloodHRRfor DBNPSis enclosed.

As discussed in the enclcsedreport,twofloodlevels(localintenseprecipitation and probable maximumstorrnsurge)determined duringthe hazardreevaluatian exceedthe currentlicensing basis(CLB)floodlevels.Theincreased levelsarethe resultof newer methodologies and notthe resultof errorswithinthe CLBevaluations. Currentplant procedures addressing floodingat thesiteprovideactionsto be takenin theevent flooding is imminent or hasoccurred at or nearthe DBNP$site. No additional actions beyondthosecurrently in placearenecessary at thistime.

Davis-Besse NuclearPowerStation L-14-104 Page2 ln accordance withthe guidanceprovidedby NRCletterdatedDecember3, 2fi12,titled "TriggerConditions for Performing an IntegratedAssessment and Due Datefor Respon$," an integrated assessment is requiredif floodlevelsdetermined duringthe hazardreevaluation are not boundedby the CLBfloodlevels.The 10 CFR50.54(f) specifiesthatthe integratedassessment be compfetedand a repartsubmittedwithin twoyearsof submitting the HRR. Therefore, FENOCintendsto submitan Integrated Assessment for Report DBNPS priorto March12,241&.

Thereare no regulatorycsrnmitments containedin this letter. lf thereare anyquestions or if additional information pleasecontactMr.ThomasA. Lentz,Manager-is required, FleetLicensing, at 330-31 5-6810.

I declareunderpenaltyof perjurythatthe foregoingis trueandeorrect.Executedon M a r c hf l , 2 A 1 4 .

Respectfully,

Enclosure:

FloodHazardReevaluation Report cc: Director,Officeof NuclearReactorRegulation (NRR)

NRCRegionlll Administrator NRCResidentInspector NRRProjectManager UtilityRadiological SafetyBoard

Enclosure L-14-104 FloodHazardReevaluationReport (33 pagesfollow)

FLOODHAZARDREEVALUATION REPORT tN RESPONSE TO THE50.54(f)fNFORMATTON REQUE$TREGARDING NEAR-TERM TASKFORCERECOMMENDATION 2'1: FLOODING for the DAVIS-BESSE NUCLEARPOWERSTATIOTII 5501North State Route 2 Oak Harbor,OH 43449 FlrstEnergyCorporation 76 SouthMalnStreet Akron,OH 44308 Prepared by:

ET ENERCON

( relhnce - - twty projxl tvay day EnerconServicesInc, 12420Mllestone CenlerDrive,$uite200 Germantown, MD 20876 Revislon1 Submlttedto FENOC;March06, zAlH PrlntedName Affiliatlon Date Preparer: AnubhavGaur Enercon Verifier: AbiotGemechu Enercon "sl*l+rt ollo$lt4

_.7--]-

Verifier: LanaLawrence i,',1/

.A 7 Approver: RaySacramo LeadResponslbleEngineers: ThomasGulvas MichaelSobota t lbla.rr1 DesignEngineering Supervisor GregoryMichael s l,.ltL DeslgnEnglneering Manager Jon Hook FENOC

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 2.1,2. Flooding in Streamsand Rivers ..........6 2.1.3. DamBreaches andFailures.. .....,.,.7 2.1.7. Channel Migration or Diversion .. ........7 2.1.8. CombinedEffectFlood(including Wind-GeneratedWaves) .......7 2.2. Flood-Related Changesto the LicenseBasis .................7 2.3. Changesto the Watershed and LocalAreasinceLicenselssuance .............,..7 2.4. CurrentLicensing BasisFloodProtection and Pertinent Features............8 FloodMitigation

3.

SUMMARY

OF FLOODHAZARDREEVALUATION ........8 3.1. Floodingin Streamsand Rivers(ReferenceDBNPS2013a,DBNPS2013b,and DBNPS 2013c) ..........9 3 . 1 . 1 . B a s i so f I n p u l s : . . . . . . ........10 3.1.2. Computer Software Programs.. .....11 3.1.3. Methodology. .....11 3 . 2 . 1 . B a s i so f l n p u t s ........15 3.2.2. Computer Software Programs.. .........15 3.2.3. Methodology. .......15 3 . 3 . 1 . B a s i so f I n p u t s ....16 3.3.2. Computer Software Programs.. .......16 3.3.3. Methodology.. .......16 3.4. ChannelMigration or Diversion (ReferenceDBNPS2013d) .............17 3,4.1. Basisoflnputs ........17 DAVIS-BESSE NUCLEARPOWERSTATION Page 1 of 32

NTTFRecommendation 2.1 (HazardReevaluations):

Flooding RevisionI FirstEnergyCorporation March06, 2014 3.4.2. Computer SoftwarePrograms..... ............17 3.4.3. Methodology.. ,.....,,.17 3.4,4. Results ........17 3,5. Storm Surge (ReferenceDBNPS20139,DBNPS2013h, DBNPS2013i and DBNFS 2 0 13 m ) . . . . .1.B 3.5.1. Basisof Inputs ....18 3.5.2. Computer SoftwarePrograms.. .......18 3.5.3. Methodology..

3.5.4. Results ......21 3.6. Tsunami Assessrnent (ReferenceDBNPS2013j) ....21 3.6.1. Basisof lnputs 3.6.2. ModelsUsed .."........22 3.6.3. Methodology.... ,.r...,,.... .....22 3.6.4. Results ..,...23 3.7. CombinedEffectFlood(including Waves)(Reference

\Mnd-Generated DBNPS2013n).23 3.7.1. Basisof Inputs ...,.......24 3.7.2. Computer$oftwarePrograms.. .....24 3.7.3. Methodology... .........24 3.7.4, Results ..............25 3.8. LocalIntensePrecipitation(Reference DBNPS2013eand DBNPS20130...... .....,..26 3.8.1. Basisoflnputs ......26 3.8.2. ModelsUsed ............26 4 , COMPARISON WITHCURRENTDESIGNBASIS 5.

6.

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NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014

{. PURPOSE 1.1.Background ln responseto the nuclearfueldamageat the FukushimaDai-ichipowerplantdue to the March 11, 2011 earthquakeand subsequenttsunami, the United States Nuclear Regulatory Commission(NRC) establishedthe Near Term Task Force (NTTF)to conducta systematic reviewof NRC processesand regulations,and to make recornmendations to the NRC for its policydirection.The NTTFreporteda set of recommendations that were intendedto clarifyand strengthenthe regulatoryframeworkfor protectionagainstnaturalphenomena.

On March 12,2012the NRC issuedan informationrequestpursuantto Title 10 of the Code of FederalRegulations, Section50.54(D(10 CFR50.54(f)or 50.54(f)lette$whichincludedsix (6) enclosures:

1 . NTTF Recommendation 2.1:Seismic 2 , NTTF Recommendation 2.1:Flooding

3. NTTF Recommendation 2.3:Seismic
4. NTTF Recommendation 2.3:Flooding 5 . NTTF Recommendation 9.3:EP 6 . Licenseesand Holdersof Construction Permits fn Enclosure2 of the NRC-issued information request(ReferenceNRCMarch2A12),the NRC requestedthat licenseesreevaluatethe floodinghazardsat their sites against present-day regulatory guidanceand rnethodologies beingusedfor earlysite permits(ESP)and combined operatinglicensereviews.

On behalfof First EnergyCorporation(FENOC)for the Davis-BesseNuclearPower Station (DBNPS),this FloodHazardReevaluation Report(Report)providesthe informationrequested in the March 12, 2012 50.54(f)letter;specifically, the informationlistedunderthe "Requested

'e').The "Reque$ted fnformation" sectionof Enclosure2, paragraph1 ('a' through Information" sectionof Enclosure2, paragraph2 ('a' through 'd'), IntegratedAssessmentReport,will be addressedseparatelyif the currentdesignbasisfloods do not boundthe reevaluatedhazard for all flood-causing mechanisms.

1.2.RequestedActlons Per Enclosure2 of the NRC-issued informationrequest,50.54(f)Ietter,FENOCis requestedto performa reevaluation of all appropriateexternal floodingsourcesfor DBNPS,includingthe effectsfrom localintenseprecipitation (LlP)on the site,the probablemaximumflood(PMF)on streamsand rivers,lakefloodingfromstormsurges,seichesand tsunamis,and dam failures.lt is requestedthat the reevaluationapply present-dayregulatoryguidanceand methodologies being used for ESPs, and calculationreviewsincludingcurrenttechniques,software,and methodsused in present-daystandardengineeringpracticeto developthe flood hazard.The requestedinformationwill be gatheredin Phase 1 of the NRC staffs two-phaseprocessto irnplementRecornmendation 2,1, and will be used to identifypotential"vulnerabilities"(see definition below).

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NTTFRecommendatisn 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March46,2014 For the siteswherethe reevaluatedfloodexceedsthe designbasis,addresseesare requested to submitan interimactionplan documenting plannedactionsor measuresimplemented to addressthe reevaluated hazards.

Subsequently, addresseesshall performan integratedassessmentof the plantto fully identify vulnerabilities and detail actionsto addressthem. The scope of the integratedassessment reportwill includefull poweroperationsand otherplantconfigurations that couldbe susceptible due to the statusof the flood protectionfeatures.The scopealso includesthosefeaturesof the ultimateheat sink (UHS)that could be adverselyaffectedby flood conditions(the loss of UHS from non-floodassociatedcauses is not included).lt is also requestedthat the integrated asses$ment addressthe entiredurationof the floodconditions.

A definition of vulnerability in the context of Enclosure 2 is as follaws: Plant-specific are thosefeaturesimpoftantto safetythat whensubjectta an increaseddemand vulnerabilities due lo the newly calculated hazard evaluation have not been shown to be capable of performingtheirintendadfunctiorts.

1.3.RequestedInformation Per Enclosure2 of the NRC-issuedinformationrequest 50.54(0 letter, the Report should providedocumentedresults,as well as pertinentDBNPSinformationand detailedanalysis,and includethe following:

1. Site informationrelaledto the flood hazard.Relevantstructure,systems,and components (SSCs)importantto safetyand the UHS are includedin the scopeof this reevaluation, and pertinentdata concerningtheseSSCsshouldbe included.Otherrelevantsite data includes the following:
1. Detailedsite information(both designedand as-built),includingpresent-daysite layout, elevation of pertinentSSCs importantto safety, site topography,and pertinentspatialandtemporaldatasets;
2. Currentdesignbasisfloodelevations for all flood-causing mechanism$;
3. Flood-relatedchangesto the licensingbasis and any flood protectionchanges (includingmitigation) sincelicenseissuance;
4. Changesto the watershedand localareasincelicenseissuance;
5. Currentlicensingbasisfloodprotectionand pertinentfloodmitigationfeaturesat the site:and
6. Additionalsite details,as necess?ry,to assessthe flood hazard(e.9.,bathymetry andwalkdownresults).
2. Evaluationof the flood hazardfor each flood-causingmechanism,based on present-day methodologiesand regulatoryguidance.Provide an analysis of each flood-causing mechanismthat may impactthe site,includingLIP and site drainage,floodingin streams and rivers, dam breachesand failures,storm surge and seiche, tsunamis,channel migrationor diversion,and combinedeffects.Mechanisms that are not applicableat the site may be screenedout; however,a justification shouldbe provided. A basisfor inputsand assumptions, methodologies and modelsused,includinginputand outputfiles,and other pertinentdatashouldbe provided.

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NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014

3. Cornparisonof currentand reevaluatedflood-causingmechanisrnsat the site. Providean asse$$ment of the currentdesignbasisfloodelevationto the reevaluated floodelevationfor each flood-causing mechanism.Includehow the findingsfrom Enclosure2 of the 50.54(f) letter(i.e., Recommendation supportthis determination.

2.1, flood hazardreevaluations) lf the current design basis flood bounds the reevaluated hazard for all flood-causing mechanisms, includehowthisfindingwas determined.

4. Interimevaluationand actionstaken or plannedto addre$sany higherfloodinghazards relativeto the design basis, prior to completionof the integratedassessmentdescribed below,if necessary.
5. Additionalactions beyond requestedinformationitem l.d taken or plannedto address floodinghazards,if any.
2. SITEINFORMATION DBNPSis locatedon the shore of Lake Erie in Oak Harbor,Ohio" The majorhydrological featuresof the terrain are the broad expanseof Lake Erie to the north and east, and the ToussaintRiver,which flows east into the lake along the south side of DBNPS,DBNPS is approximately 3,000 feet (ft) from the Lake Erie shorellne(USAR, Section1.2.1.1)and approximately 2,000ft from the ToussaintRiver.Site areas surroundingthe stationstructures havebeenbuiltup from 6 to 14 feet abovethe existinggradeelevationto an elevationof 584 ft International GreatLakesDatumof 1955(lGLD55)or 15.4ft abovethe LakeErie Low Water Datumof 568.6ft-lGLDs5.Topographyat and aroundDBNPSis relativelyflat,with a mean station elevation of approximately584 ft-lclDss. The site safety-relatedstructuresare protectedagainsthighwaterlevelsup to an elevationof 585 ft-lGLDs5.A LakeEriedike,which is locatedalongthe shoreof Lake Erie,protectsthe site from lakesurges.Additionally, a wave protectiondike is situatedalongthe northern,eastern,and a small portionof southernsidesof DBNPS.The elevationat the top of the wave protectiondike is 591 ft-lGLDs5. Present-Day SiteLayoutis shownin Figures2.0.1.

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NTTFRecommendation 2.1(HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06,2014 Figure2.0.1- Present-Day Site Layout 2.1,CurrentDesignBasis The currentdesignbasisis definedin the DBNPSUpdatedSafetyAnalysisReport(USAR).

The followingis a list of flood-causingmechanismsand their associatedwater surface elevations thatwereconsidered for the DBNPScurrentdesignbasis.

2 . 1 . 1 .L t P The USARindicatesthat the precipitation valueof 24.l-inchesover a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> periodis utilized for the LIP analysis.As indicatedin the USAR,the averageinvertelevationof rnanholesand catchbasinsis 582ft-lcLD55;with 24.5inchesof estimatedaccumulation, watercouldbuildup to 584.5ft-lclDss (USAR, Section2.4.2.3).

2.1.2. Floodingin Streamsand Rivers The USAR indicatesthat a flow rate of 78,500cubicfeet per second(cfs) in the Toussaint Riverat DBNPS(USAR,Section2,4.3)wouldresultin a maximumwatersurfaceelevationof 579 ft-lclDss. As indicatedin the USAR,the elevationof 579 ft-lGLDs5was derivedusingthe conservative that noneof the wateris discharged assumption to LakeErie,assumingthat the PMFflowis hypothetically dammedup atthat point(USAR, 2.4.3.5).

Section DAVIS.BESSE NUCLEARPOWERSTATION Page6 of 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 2.1.1. Dam Breachesand Failures The USAR indicatesthat there are no dams or other regulatinghydraulicstructureson the ToussaintRiverwhichwouldaffectthe flowhydrograph at DBNPS(USAR,Section2.4.31.

2.1.4, StormSurge& Seiche The probablemaximummeteorological eventin LakeErie resultsin a maximumwatersurfece elevationof 583.7 ft-lGLD5s. This meteorologicalevent is caused by a maximumeast-northeast windat any locationof 100 milesper hourfor a 1O-minute duration,anda windspeed of 70 milesper hourduringthe six-hourperiodboth beforeand afterthe maximumwind speed (USAR,Section2.4.5).

2.1.5. Low Water No wateris takenfromthe ToussaintRiverfor plantcoolingwaterrequirements. Therefore,low flows in the Toussaint River will not affect DBNPS operation.The probable maximum meteorological event in Lake Erie resultsin the probableextremelow water level of 556.8ft-lGLD55(USAR,Section2.4.11).

2.1,6. lce-lnduced Flooding Floodingof the safety-relatedstructuresand equipmentat DBNPS due to ice jams in the ToussaintRiveris not credible.The USARindicatesthat the elevationof the pfantstructuresis abovethe level of normallake ice formations.Category1 wave protectiondikesare designed to withstand the impactof ice (USAR,Section2.4.7).

2.1.7. GhannelMigrationor Diversion As indicatedin the USAR,the mean lake levelis not subjectta variationsdue to diversionsor sourcecutoff(USAR,Section2.4.9).

2.1.8. CombinedEffectFlood(lncludingWind-Generated Waves)

Wind-waveactivity,includingrunup,was evaluatedfor its effecton the wave protectiondikes on the north,east,and southsidesof DBNPS.As indicatedin the USAR,the maximumwave run-upon the dike is 6.6 ft abovethe probablemaximumwater surfaceelevationof 583.7ft-lGLD55.The resultingmaximumwave runupelevationis 590.3ft-lGLDs5,whichis belowthe top of the dike(USAR,Section2.4.2.2.1).

2.2. Flood-Related Changesto the LicenseBasis There were no changesto the licensebasissince the licenseissuance with regardto I flooding.

2.3.Changesto the Watershedand Local Area since Licenselssuance The watershedcontributory to the ToussaintRiverupstreamof DBNPSis approximately 139.0 square miles (ReferenceDBNPS 2013c).Based on aerial imagesof the watershed,the changesto the watershedincludecommercialdevelopment withinthe watershedarea,whichis a very small percentageof the overallwatershedarea. The changesto the local area sub-watershedfor DBNPSincludebuifdings,parkingfots,and securitybarrierupgradesthat have beenaddedto the sitesincelicenseissuance.

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NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 2.4. Cunent LicensingBasis Flood Protectionand PertinentFlood MitigationFeatures The maximumflood level in the designbasis is belowthe site finishfloor elevationof 585 ft-lGLD55.Therefore,therewere no mitigationactionsinitiatedor takenfor floodingat the site.

3.

SUMMARY

OF FLOODHAZARDREEVALUATION NUREG/CR-7046,Design-BasisFlood Estimationfor Srfe Cfiaracterization at NuclearPawer Planfs in the united Sfafes of America (ReferenceNUREG/CR-7046),by referenceto the AmericanNuclearSociety(ANS),statesthat a singleflood-causing eventis inadequateas a design basis for power reactorsand recommendsthat combinationsshouldbe evaluatedto determinethe highestflood water elevationat the site. For DBNP$, the combinationthat producesthe highestflood water elevationat the site is the probablemaximumsurge and seicheon Lake Eriewith the effectsof coincidentwind wave activity.

The USARreportselevationscorresponding to lGLDSSverticaldatum.The recentsite survey, UnitedStatesGeologicalSurvey (USGS) topographicrnaps,and other referencedocuments reportelevationin NorthAmericanVerticalDatumof 19BB(NAVDBB). In orderto comparethe reevaluatedflood elevatienswith the existingdesign basis reportedin USAR,final pertinent elevationshave been convertedto lGLD55 datum. The conversionbetween lGLD55 and NAVDBBat DBNPSis represented as-- ft-lGLDsS= ft-NAVD88* 1.07ft.

Calculation C-CSS-020.13-017 (Reference DBNPS2013i)definesthe maximumwatersurface elevationof 585.81ft-lGLDs5at DBNPSadjacentto the powerblock.This elevationis due to a probablemaximumstorm surge (PMSS)during a probablemaximumwind storm (PMWS) event.The revisedmaximumwater surfaceelevationis abovethe site finishfloor elevationof 585 ft-tGLD55.

CalculationC-CSS-020.13-022 (ReferenceDBNPS2013n)definesthe coincidentwind wave runup.The maximumwave runupelevationof the PMSScoincidentwith wind wave activityis determinedby addingthe wind wave runup to the water surfaceflood elevationdue to the PMS$.The maximumrunupon the wave protectiondike is 589.88ft-lcLD55,whichis below the top of the wave protectiondike elevationof 591 ft-lclDss. The maximumwave runup elevationin the vicinityof the powerblockis 585.90feet-lGLD55. The wave runupelevationsin the vicinityof the powerblockare abovethe sitefinishfloorelevationof 585 ft-lGLD55.

Calculation C-CSS-020.13-014 (Reference DBNPS20130definesthe maximumwatersurface elevationresultingfrom the LIP event.The watersurfaceelevationdue to the LIP eventvaries from 585.17ft-lGLDS5to 585.44ft-lGLDsS.The LIP maximumwater surfaceelevationsare abovethe site finishfloorelevationof 585ft-lGLD55 The methodologyused in the floodingreevaluation for DBNPSis consistentwith the following standardsand guidancedocuments:

. NRC StandardReview Plan, NUREG-0800,revised March 2007 (ReferenceNUREG-0800)

. NRC Officeof StandardsDevelopment, RegulatoryGuides,RG 1.102- "FloodProtection for NucfearPowerPfants",Revision1, datedSeptember1976(Reference NRC RG 1.102) and RG 1.59-"Design BasisFloodsfor NuclearPowerPlants",Revision2, datedAugust 1977(Reference NRCRG 1.59)

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NTTFRecomrnendation 2.1 (HazardReevaluations):Flooding Revision1 FirstEnergyCorporation March06, 2014

. NUREGICR-7046, "Design-Basis Flood Estimationfor $ite Characterizationat Nuclear Power Plants in the United States of America," dated November z0fi (Reference NUREG/CR-7046)

. NUREG/CR-6966, "TsunarniHazardAssessmentat NuclearPower Plant Sites in the UnitedStatesof America",datedMarch2009(ReferenceNUREGICR-6966) r "AmericanNationalStandardfor DeterminingDesignBasis Floodingat Power Reactor Site$",datedJuly28, 1992(ReferenceANSI/ANS-2.8-1992)

. NEI Report12-08,"Overviewof ExternalFloodingReevaluations" (ReferenceNEI August 2412)-

r NRC JLD-ISG-2012-06, "Guidancefor Performinga Tsunami,Surgeor SeicheFlooding HazardAssessment", Revision0, datedJanuary4,2A13(Reference JLD-lSG-2012-06)

. NRC JLD-lSG-2013-01, "Guidancefor Assessmentof FloodingHazardsdue to Dam Failure",Revision0, datedJuly29, 2013(Reference JLD-ISG-2O13-01)

The followingprovidesthe flood-causingmechanistnsand their associatedwater surface elevationsthat are consideredin the DBNPSfloodhazardreevaluation study:

3.f . FloodingIn $treamsand Rivers(ReferenceDBNPS2013a,DBNPS20{3b,and DBNPS2013c)

The PMF in rivers and streams adjoiningthe site is determinedby applyingthe probable maximumprecipitation (PMP)to the drainagebasinin whichthe site is located.The PMF is based on a translationof PMP rainfall in the watershedto flood flow. The PMP is a deterministic estimateof the theoreticalmaximumdepthof precipitation that can occurat a time of year for a specifiedarea. A rainfall-to-runoff transforrnation function,as well as runoff characteristics, based on the topographicand drainagesystem networkcharacteristics and watershedproperties,are neededto appropriatelydevelopthe PMF hydrograph.The PMF hydrographis a time historyof the dischargeand serves as the input parameterfor other hydraulicmodelswhichdevelopthe flowcharacteristics, includingfloodflow and elevation.

The PMF is a functionof the combinedeventsdefinedin NUREG/CR-7046 for floodscaused by precipitation events.

Alternative1 - Combinationof:

r Meanmonthlybaseflow

. Mediansoilmoisture

. Antecedentrain:lesserof (1) rainfallequalto 40 percentof the PMP,or (2) a 500-year rainfall

. TheAll-SeasonPMP

, Wavesinducedby 2-yearwindspeedappliedalongthe criticaldirection Afternative 2 - Combination of:

. Meanmonthlybaseflow DAVIS-BESSE NUCLEARPOWERSTATION PageI of 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation MarchA6,2014

. Snowmeltfromthe Probablemaximumsnowpack o fi 10O-year, cool-seasonrainfall

. Wavesinducedby Z-yearwindspeedappliedalongthe criticaldirection Alternative3 - Combination of:

. Meanmonthlybaseflow

. Snowmeltfrom a 100-yearsnowpack

. The cool-seasonPMP

. Wavesinducedby Z-yearwind speedappliedalongthe criticaldirection 3.1,1. Basis of lnputs:

The inputsusedin the PMP,snowmelt,and PMFanalysesare basedon the following:

All-SeasonPMPAnalysisand Cool-SeasonPMPwith $nourmeltAnalysis

. DBNPS and Toussaint River watershed locations, areas, boundaries and configurations; I Historicflow ratedatacollectedby USGSat gage04195820on the PortageRiver; a HMR-52-standardisohyetal patterns, storm orientation,percentage of 6-hour incrementof PMP,and standardisohyetalgeometryinformation; a HMR-s3-seasonal PMPvalues:

I The 100-yearall-seasonpoint rainfallestimatesfrom the NationalOceanic and Atmospheric Administration(NOAA)Precipitation FrequencyData$erver; Medianand extremedaily snow cover by month for Ohio-data is downloadedfrom NOAA;and

' Snowmeltrate (energybudget)equationsand constantsare based on U.S. Army Corpsof Engineers (USACE)Engineering ManualEM-1110-2-1406, PMFanalysis-Hydrologic & HydraulicAnalysis

' Digitalelevationmodel(DEM):The DEM used for the PMF calculation is obtained from the U.$, Departmentof Agriculture(USDA) NationalResourceConservation Services(NRCS),nationalelevation data; r Probablemaximumprecipitation (PMP):72-hourPMP and associated snowmelt,as applicable,for the subjectwatershed area;

. Baseflow:Historicflow rate data collectedby USGS at gage 04195820on the PortageRiver,whichis usedas the baseflowfor the ToussaintRiver;

. Soil Type: The soil types within the projectwatershedare developedusing USDA NRCSsoilinformation;

. Land Use:The land use information for the watershedis obtainedfrom USDANRCS soilsurveygeographic database; DAVIS.BESSE NUCLEARPOWERSTATION Page10 of 32

NTTFRecommendation 2.1 (HazardReevaluations):Flooding Revision1 FirstEnergyCorporation March06, 2014

. Manning'sroughnesscoefficientsare based on a visual assessmentof aerial photographyand selected using standard applicable engineeringguidance references;

. Bridge informationobtainedfrom the Ohio Departmentof Transportation (ODOT);

and

. Supporting Geographic System(GlS)input(Reference Information DBNPS2013k).

3.1.2, ComputerSoftwarePrograms PMPand Snowmeltanalysis r AutoCADCivil3D 2012

. ArcGlSDesktop10.1

. HMR-52software

. MicrosoftExcel PMFanalysis

. ATcGIS Desktop10.1

. HEC-HMS 3.5 r HEC-RAS 4.1

. HEC-GeoRAS 10.1 r lGLD8SHeightConversion OnlineTool

. MicrosoftExcel 3.{.3. Methodology The PMFanalysisincludedthe followingsteps:

' Delineatewatershedand sub-watersheds, then calculatesub-watershed areas for inputintothe USACEHEC-HMSrainfall-runoff hydrologic computermodel.

e Determine rainfall.

' EstimateHEC-HMS rainfall-runoff model initial input parameters:Snyder unit hydrographmethod,peakingand lag coefficient.

. CalculateHEC-HMSmodellossinputparameters: initiallossand constantlossrate.

. CalculateHEC-HMSriverreachroutingmodelinitialinputparameters: Muskingum-Cunge.

. Method:B-pointcross-section, reach slope, and Manning'sroughness coefficient.

. PerformPMFsimufation with PMPinputusingHEC-HMSmodel.

. Estimatewater surfaceelevationusing HEC-RA$unsteady-state model by using runofffromthe HEC-HMSmodelas an input.

WatershedDelineation For the purposesof the hydrologicmodelingeffort,the ToussaintRiverwatershedis subdividedinto three (3) sub-watersheds(PackerCreek,UpperToussaintCreek,and LowerToussaintCreek)basedon the hydrologic unitcode(HUC)boundaries.

DAVIS-BESSE NUCLEARPOWERSTATION P a g e1 1 o f 3 2

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 Rainfall& Snowmelt Eachalternative containsrainfalldefinedeitherby the all-seasonPMP (Alternative 1),

the 1O0-year, cool-season rainfall(Alternative PMP (Alternative 2), or the cool-season 3). Each rainfallevent is consideredto be a 72-hourdurationevent.Note that an antecedentrainfalloccurspriorto the all-seasonPMP.An antesedentstormequivalent to 40 percentof the all-seasonPMP is appliedto the HEC-HMSmodelwith a 72-hour dry periodbetweenthe antecedentstormand the PMPevent.

Snowmeltis includedin the two cool seasonalternatives.For rain-on-snow conditions, the air temperature,dew point temperature,and averagemaximurndaily wind speed are obtained from representativeweather stations. The basin wind coefficientis determinedbasedon the densityof foreststandsin each sub-basin.lt is conservatively assumedthat the ToussaintRiverwatershedis unforestedplainto maximizesnowmelt.

For rain-freeconditions,the snowmeltparametersare selectedbasedon the USACE guidance.

The snowpackis assumedto be at its maximumat the onset of rainfallevents and cover the entire watershed.Soil is assumedto be frozen with no lassesduring the monthsof OctoberthroughApril. For the probablemaximumsnowpack,snowpack depthis assumedto be availablefor the durationof the coincidentrainfallevent.

Alternative{ -All-SeasonPMP The locationof the DBNPSwatershedis withinthe domainof the HMR-51and HMR-52 guidance.The all-seasonPMP is determined by usingthe generalized PMP estimates definedby the HMR-51and HMR-52guidance.Differentstormcentersthroughoutthe watershedare examinedto determinethe criticalstorm centerthat maximizesrunoff.

HMR-52softwareis usedto optimizethe stormand definethe PMP estimatesfor each sub-basin.

HMR-52softwareis based on a standardtemporaldistribution.The HMR guidance indicatesthe greatestprecipitation may occurat othertimesthroughoutthe durationof the storm. The temporaldistributionof the PMP is calculatedin accordancewith recommendationsin HMR-52, wherein individual rainfall incrementsdeerease progres$ivelyto either side of the greatest rainfall increment.Various temporal for each rainfallscenarioare then evaluatedto furthermaximizethe runoff.

distributions Front, one-third, center, two-third, and end-loading temporal distributions are consideredin an effortto capturethe distributionthat maximizesrunoff.

Alternative2 - ProbableMaximumSnowpackand 1O0-Year Cool-SeasonRainfall The probablemaximumsnowpackis assumedto be equalto an unlimitedsnowpack during the entire coincidentrainfall.While the snowpackcan be determineddirectly from the snow depth, there is not adequate data to extrapolateany historical observations up to the magnitudeof the probablemaximumevent.

The 1O0-year,cool-seasonrainfallis determinedfor the watershedlocationusing precipitationfrequencyestimatesdefinedby NOAA Atlas 14 guidanceand applying regionalseasonalguidance.NOAA Atlas 14 providesall-seasonpoint precipitation rainfallestimatesvia the NOAAprecipitation frequencydata server.As NOAAAtlas 14 values are point precipitationvalues,the estimatesare adjustedusing area-depth reductionfactors.NOAAAtlas 14 valuesare also adjustedto reflectcool-season rainfall ratherthanall-season rainfall.

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NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 The 3-day (72-hour)snowmeltduration is assumedin order to correspondto the precipitationevents(PMP and 100-yearrainfall).A 10O-year, cool-sea$onrainfallis equivalentfor all the cool-seasonmonths,However,the snowmeltis expectedto be differentfor each cool-seasonmonth becauseit is highlydependenton ternperature, which variessignificantlyfrom monthto month.Therefore,the monthwith the highest expectedsnowmeltis identifiedand usedfor the calculations of the snowmeltrates Alternative3 - 100-YearSnowpackand Cool-SeasonPMP A 1O0-year snow depth is calculatedby performinga statisticalanalysisbasedon the historicaldata obtainedfrom the NOAA Annual ObservationData website.A Fisher-Tippett Type l (FT-l) distributionfrequencyanalysisis performedto determinethe maximumsnowdepthwith an annualexceedanceprobabilityof 1 percent(i.e. 10O-year snow depth).The FT-l distributionis applicablefor long{erm statisticalanalysesand specificallyfor extremevalue calculations.The cool-seasonPMP is determinedby applyingseasonalHMR-53guidanceto the all-season PMPestimates.

HydrologicModel(HEC-HMS)

The PMF is the floodresultingfrom the PMP.The temporaldistribution of the PMP is calculatedin accordancewith the recommendations in HMR-52,whereinindividual incrementsdecreaseprogressivelyto either side of the greatestincrement.For each sub-watershed, a 9-dayPMP hyetographis constructed usinga rainfallequivalentto 40 percentof the PMP during the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />,followedby a dry 72-hourperiod,and finallyfollowedby the full 72-hourPMPstorm.

USACEHEC-HMShydrologicsoftwareis used to convertrainfallts runoff.A rainfall hyetographis appliedto each sub-watershedand transformedto runoff using unit hydrographmethodology.Generallya unit hydrographis developedusing historical data obtainedfrom various rain and stream gages in the watershed.The DBNPS watershedis ungaged.Thus,there are no historicalobservationsavailableto use as a basisto createa unit hydrograph.Therefore,a syntheticunit hydrographis developed.

The Snyderunithydrographmethodology transformation.

is usedfor rainfall-to-runoff Routing accounts for change in the flow hydrographas a flood wave passes downstreamand accountsfor storageand attenuationduring a floodingevent. The Muskingum-Cunge routingmethodis utilizedin the HEC-HMSmodel,with the streams represented by B-pointcrosssections.

ANSIIANS-2.8-1992 suggeststhat baseflowshouldbe basedon meanmonthlyflow.As mean monthly flow is not available for the Toussaint River, the baseflow is approximatedbased on the mean monthlyflow in an adjacentwatershed.The only gagestationavailablein the samehydrologic unitis on the PortageRivernearElmore, OH. The watershedsof the ToussaintRiverand PortageRiverare locatedin the same HUC and have similar watershed characteristics.Therefore,it is an acceptable approachto use the base flow informationfor the Portage River as the basis for estimationof the baseflow at ToussaintRiver.

lnitiallossesare ignored.Infiltration, or constantlosses,is determinedbasedon the hydrologiccharacteristics of the soilswithineachbasin.Constantlossesare not applied to impervious areas.Additionally, constantlossesare ignoredfor the cool-season PMF alternativesdueto the assumption thatgroundis frozen.

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NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 The unit hydrographs for each sub-watershed are modifiedto accountfor the effectsof nonlinearbasin response in accordance with NUREGICR-7046. The peakof eachunit hydrographis increased by one-fifthand the time-to-peak is reduced by one-third.The remaininghydrographordinates are adjusted to preserve the runoffvolumeto a unit depthoverthe drainagearea.

HydraulicModel(HEC-RAS)

The unsteadyflow modulewithinthe USACEHEC-RASsoftwareis used to transform the resultingflow hydrographsfrom the controllingalternativeinto a water surface elevationhydrographunderunsteadyflow conditions.For referenceand comparison, all threealternatives are evaluatedwith the HEC-RASmodel.

Channeland floodplaingeometryfor the ToussaintRiver is modeledby developing cro$s sectionsof the stream.The cross sectionsare placed at locationsthat define geometriccharacteristics of the river valley and overbanks.Cross sectionsare also placedat representative locationswherechangesoccurin discharge,slope,shape,and roughness,as well as at hydraulicstructures(e.9. bridges). River banks,blocked obstructions,and ineffective flow areasare alsoincorporated intothe HEC-RASmodel.

Two bridgesare modeled(the CR19 Bridgeand the CR2 Bridge)using information receivedfrom ODOT.Thereare two additionalbridgesover the modeledportionof the ToussaintRiver:the N. Benton-Carroll Rd Bridgeand the CR590 Bridge.These two bridgesare locatedfarther away from DBNPS (approximately 7 and 10 river miles respectively).lt is not expectedthat thesetwo bridgeswould havea measurableeffect on the computational resultsbecauseof the distance,Any possibleeffectproducedby the bridgesupstreamof the riverwill be lost due to attenuationin the stream.Therefore, theyare not includedin the model.

The PMF flow hydrographsobtainedfrom the HEC-HMSmodelare enteredinto the HEC-RAS model. The highest observedwater level in Lake Erie is used as a downstreamboundaryconditionin the HEC-RASsoftwareprogram.

The HEC-RASmodel is evaluatedfor both all-seasonPMF (Alternative1) and cool-seasonPMF alternatives (Alternatives 2 and 3).

3.1.4. Results The Alternative1 PMF is the controlling combination and is a resultof the all-season PMP.The maximumwatersurfaceelevationat DBNPSis 575.96fi-lGLDs5(576.93ft-NAVDBB), witha maximumflowof 100,436cfs.

For Alternative 2, the maximumwatersurfaceelevationis 574.15ft-lGLD5s(575.12tt-NAVD88)witha maximumflowof 31,747cfs.

For Alternative3, the maximumwatersurfaceelevationis 575.06ft-lGLDs5(576.03ft-NAVDBB) witha maximumflowof 61,943cfs.

The all-seasonPMF is determinedto be the controllingPMF scenarioand an additionalcombinedeventanalysisis performed in CalculationC-CSS-020.13-022.

DAVIS.BESSE NUCLEARPOWERSTATION Page14 o{ 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 3.2. DamAssessment(ReferenceDBNPS2013d) 3.2.1. Basisof Inputs Inputsusedfor the dam assessment evaluation r HEC-RASmodeldevelopedin the PMFanalysis" r Dam information: The Nationallnventoryof Dams (NlD) is used to identifythe watersheddams.

3,2.2. ComputerSoftwarePrograms n ArcGlSDesktop10.1

. HEC-RAS 4.1 3.2.3. Methodology The criteriafor dam a$sessmentis providedin the hlRC Guidancefor Assessmenfof FloadingHazardsdue to Dam Failure,JLD-lSG-2O13-01. Only two dams reportedby NID are locatedin the DBNPSwatershed - the Genoa UG SewageDisposalLagoons and the GraymontSludgeLagoons.

Effectsof the failureof the two dams are analyzedusing a simplifiedapproachas outlinedin JLD-ISG-2013-01. The peakoutflowwithout attenuation methodis basedon summingestimateddischarges fromsimultaneou$ failuresof upstreamdamsarrivingat the sitewithoutattenuation.

The peakdischargeusingthe simplifiedequation$wa$ calculated to be 4,642cfs and 13,651cfs for GenoaUG SewageDisposalLagoon$and GraymontSludgeLagoons respectively.A cumulativepeakbreachdischargeequalto 18,253cfs from bothdams is included in the HEC-RAS model as additionaftateral inflow at the cros$ section immediatelyupstreamof the DBNPS site. Conservatlvely, the peak breach flow is apptiedto the HEC-RASmodelat the time corre$ponding the PMF peak discharge to determined in the PMFanalysis.

3,2,4, Results The maximumwater surface elevationat the site resultingfrom the PMF event combinedwith the cumulativeupstreamdam failuresis 577.09ft-NAVDBB. Compared to the PMF results,the water surfaceelevationincrease due to the additional dam

- =

breachflowis equalto 0.16ft (577.09ft 576.93ft 0.16ft).The maximum PMF water surfaceelevationat DBNPSis 8.04ft belowthe sitegradeelevationof 584.0ft-lGLD5s.

Consequently, the increasedue to the dam failureresultsin a water surfaceelevation thatis 7.88ft belowsitegrade(8.04ft - 0.16ft = 7.88ft).

The maximumwater surface elevation at the site resultingfrom the PMF event combinedwith the cumulativeupstreamdam failuresis well belowthe plantsite grade elevation,Therefore,the upstreamdams are determinedto be noncriticaldams as referredto in the JLD-lSG-2O13-01 . No furtherdamfailureanalysisis required.

Thereare no damsdownstreamof DBNPSon the ToussaintRiver.

DAVIS.BESSE NUCLEARPOWERSTATION P a g e1 5 o f 3 2

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 3.3. lce-lnducedFlooding(Reference DBNPS2013d)

As identifiedby NUREG/CR-7046, ice jams and ice dams can form in rivers and streams adjacentto a site,and may leadto floodingby two mechanisms:

' Collapseof an ice jam or an ice dam upstreamof the site can result a dam breach-likefloodwave that may propagateto the site;and

. An ice jam or an ice dam downstreamof a site may impoundwater upstreamof itself, thuscausinga floodvia backwatereffects.

3.3.{. Basisof Inputs

. USACEicejam database.

. Bridgegeometry(upstreamand downstreamof DBNPS)- Information relativeto the bridgestructuresprovidedby ODOT.

e DBNPSHEC-RASmodeldeveloped in the PMFanalysis.

3.3.2. ComputerSoftwarePrograms

' HEC-RAS 4.1 3.3.3. Methodology Per NUREG/CR-7046, ice-inducedfloodingis assessedby reviewingthe USACEice jam databaseto determinethe mostseverehistoricaleventsthat haveoccurred.There are no historicalrecordsavailablefor the ToussaintRiver.The nonexistence of ice jam recordsis explainedby the absenceof stream monitoringstationson the Toussaint River.Basedon ice jam occurrencewithinadjacentstreamsin the samehydrologicunit code(HUC),it is determined thaticejam eventsare possiblein the ToussaintRiver.

The maximumice jam is determinedby selectingthe historicevent that producedthe maximumflood stage relativeto the normalwater surfaceelevationat that location.

Regardlessof specificconditionsthat producedthe historicflood stage at a specific location,the full heightis conservatively assumedto representthe icejam.

Historicalice jam data for PortageRiver,RockCreek,BayouDitch,and LacarpeCreek are consideredas they are locatedin the same HUC area. The maximumrecorded stagedue to an icejam is used, The peakwater surfaceelevationat DBNPSas a resultof an upstreamice jam breach

{i.e., failure of ice dam) is estimated.A hypotheticalice jam is incorporatedinto the HEC-RASmodelat the locationof the firstbridgeupstreamof DBNPS,the CR2 Bridge.

lce dam breachparametersare selectedso the entireice jam withinthe main channel wouldbreachwhenthe waterlevelbehindthe icejam is at its maximumelevation.

The recorded ice jams have a maximum reported stage of approximately13 ft; however,thereare no recordsfor the heightof the ice damsthemselves. The clearance between the bottom of the Toussaint River and the low point of the bridge is approximatelyI ft, which is less than the maximum reported stage. Therefore, conservatively, the postulatedlce dam couldcompletelyblockthe bridgeclearance.

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NTTFRecomrnendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 Per NUREG/CR-7046, floodingdue to an ice jam is not requiredto be combinedwith otherextremefloodingevents.However,to representnormalflow in the ToussaintRiver during the cool-seasonmonth, a smaller cool-seasonPMF alternativeis utilized (Alternative2 PMF).The Alternative2 PMF is a combinationof the snowmeltfrom a probable maximum snowpack and a 10O-year,cool-seasonrainfall.The inflow hydrographsrepresenting the Alternative2 PMF eventare usedin the HEC-RASmodel evaluatingthe effectof a postulatedice dam failure.

3.3.4. Results The maximumwater surfaceelevationat DBNPSresultingfrom the upstreamice jam breachingwas calculatedto be 574.05ft-lGLDSs(575.12ft-NAVD88).There are no bridgesor structuresdownstreamof DBNPSon ToussaintRiverthat couldcreatean ice damor icejam.

The watersurfaceelevationat DBNPSdue to the PMF is equalto 575.96ft-lclDss.

Therefore,the ice-inducedfloodingat DBNPSis boundedby the PMF, and no further consideration is required.

3.4. ChannelMigratlonor Diversion(ReferenceDBNPS20f gd)

NUREGICR-7046 indicateshistoricalrecordsand hydrogeomorphological data shouldbe used to determinewhetheran adjacentchannel,stream,or river has exhibitedthe tendencyto meandertowardsthe site.

3.4.1. Basisof lnputs

. USGStopographic maps r Aerialimages 3.4.2. ComputerSoftwarePrograms

. Arc GIS10.1 3.4.3. Methodology Historicand currenttopographicmaps and aerialimagesare reviewedto examinethe conditionand alignment of riversand streamsovertime.

Historicalmapsfor the yearsof 1900,1952,1967,1986,and 2011 were reviewedto assess historic channel migration of the Toussaint River. Toussaint River is approxirnately2,000 ft south of the DBNPS. The locationsof the river and lake shorelinesshown on the historicalmaps are comparedto the present-daylocations

( 2 0 11 ) .

3.4,4. Results Fromthe comparisonof the historicalmaps,the mostsignificantdiscrepancies between the present-dayand historicalstreambank and shorelinelocationsare observedon the USGS map for 1900. More recent USGS maps show both stream and shoreline locationsapproximately the sameas the currentlocation(within+/- 0.1 miledifference).

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NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 Basedon the comparisonbetweenthe currentlocationof the ToussaintRiverand the river locationas shownon the historicalmaps which cover a periodof approximately 110 years,it is determinedthat channeldiversiontowardsthe site is not probable.The same comparisonis performedfor the lake shorelineand similarly,Lake Frie shorefine diversiontowardsthe site is not probable.

3.5. StormSurge(ReferenceDBNPS20139,DBNPS2013h,DBNPS20131and DBNPS 2013m)

Probqhlef.Ulaximum Stofm Surse (PMSSI In accordancewith JLD-ISG-2012-06, all coastalnuclearpowerplantsites and nuclearpower plantsites adjacentto coolingpondsor reservoirssubjectto potentialhurricanes,windstorms and squalllinesmust considerthe potentialfor inundationfrom storm $urgeand waves.JLD-ISG-2012-06 alsosuggeststhatfor the stormsurgehazardas$e$sment, historicalstormevents in the region should be augmentedby a syntheticstorm parameterizedto account for conditionsmoreseverethan thosein the historicalrecordsand consideredreasonablypossible on the basisof technicalreasoning.

3.5.1. Basisof Inputs The inputsusedin PMSSanalysisare basedon the following:

r Historicalwind and pressurefielddatafrom NOAAfor the GreatLakeRegion r Probablemaximumwindstorm(PMWS)

. LakeEriebathymetryfromthe NOAAgeophysical database

. Supporting GISdata (Reference DBNPS 2013o) 3.5.2. Computer$oftware Programs

. ArcMap10.1

. Deft3D sofhnraresuite (Delft3D-FLOWDelft3D-WAVE,Delft3D-RGFGRID, and Delft3D-QUICKIN) 3.5.3. Methodology Several physical processescontributeto the generationof a storm surge. The contributionof wind to a stormsurgeis oftencalledwind setup.Wind blowingover the watercausesa shearstressthat is exertedon the surfaceof the water,pushingwater in the directionof the wind. Atmosphericpressuregradients are another forcing mechanismthat contributesto changesin waterlevel,as wateris forcedfromregionsof highatmospheric pressuretowardregionsof low pre$sure.

The followingdescribesthe methodologies usedin the PMSScalculation:

Developmentof the PMWS The PMWS storm-basedapproachis specificto the characterislicsof the site. Past extremeeventsin a regionare analyzedand consideredtranspositionable. As part of the PMWS, differentstorm types (such as synoptic,squall line, and hybrid) that DAVIS-BESSE NUCLEARPOWERSTATION Page18 of 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 impactedthe GreatLakesregionare consideredin orderto determinethe stormevent that will generatethe maximumsurgeand seiche.Eachstorm'sinputparameter$ are quantifiedand plottedbasedon the locationof lodhigh pressurecenters,concurrent wind/pressure fields,and how they evolvethroughtime and space, Mostof the synopticstormsoccurin associationwith deep areasof low pressurewhich movethroughthe regionfrom southwestto northeast.The generalsynopticpatternis one in which the deep area of low pressureresultsin a very strongpressuregradient force betweenits low pressurecenterand a corresponding regionof higherpressureto the north or west. The larger the gradient betweenthe two systemsover a given distanceis, the strongerthe resulting winds.

Squall line (or derecho)events create a widespreadstraight-linewindstormthat is associatedwith a fast-movingband of severe thunderstorms.These winds have producedsome of the highestinstantaneous gusts on record,but last for only a short time (lessthan 30 minutes)at a given location.The shortdurationof theseevents,as they quicklytraversea given location,mean they will not controlthe PMSS. Further, these events do not occur within deep low pressuresystems or remnanttropical systems.Therefore,theirwind and pressuredata are not combinedwith the olherstorm typesin thisanalysis,as thiswouldresultin a PMWSthatis not physically possible.

Althoughdeep low pressuresystemsoften producethe longestdurationlarge-scale winds,otherstormtypesalso producestrongwindsoverthe region.In rarecases,land-fallingtropicalsystemsalongthe Gulf Coast or AtlanticSeaboardmove inlandacross the Appalachians or up the Mississippi and OhioRivervalleys.By the timethesestorms reach the Great Lakes region,they are no longertropicalsystems,but insteadhave transitioned intoextra-tropical cyclones.Theirgeneralcirculationand centerof deep low pressurepersists.Much like the deep low pressurescenariopreviouslydiscussed, strong and persistentwinds can result.The remnantsof HurricaneHazel (October 1954)and HurricaneSandy (Octoberz}ftl are classicexamplesof this storm type.

This storm scenarioprovidedsome of the strongestwindsfrom the northwestthrough the northeastdirectionsoverLakeErie(withdurationsat 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />sor more).

Delft3DCalibration The Delft3Dhydrodynamicmodel is set up based on the Delft3Dsoftwaresuite.The wave setup contributionto the total storm surge valuesare modeledby couplingthe Delft3D-WAVE and Delft3D-FLOW surgemodels.The generalapproachto stormsurge modelingusing coupled Delft3D-FLOWand Delft3D-\ffAVEmodels consistsof the followingsteps:

I Developing the bathymetric datasetand modelgrid meshfor the lakesystem; a Assemblinginputfilesfor atmospheric forcing(windand pressurefields);

Assembling inputfilesfor initialwaterlevel,boundaryconditions, andthe physical and numericalparameters of the model; Assemblingmeasuredwaterlevelsand wavedatafor modelcalibrationand verification; a Testingand refiningthe initialmodelsetup; t Validatingthe modelfor historicalextremestormevents;and DAVIS-BESSE NUCLEARPOWERSTATION Page19 of 32

NTTFRecommendation 2.1 {HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March00, 2014

. Assessingmodelsensitivityto variousfactorsand adjustableparameterssuchas bottomfrictionand wind drag coefficient.

The Delft3D model is calibrated based on historicaldata obtained from NOAA meteorological and waterlevelrecordingstationslocetedin the LakeErieregion.

Reviewof lristoricaldata shows that variousparts of Lake Erie responddifferentlyto aRyone particularstorm.The stormthat producesextremewater levelsin one part of Lake Erie might not, and probablydoes not, produceextremelevels in other parts.

Thereforethe numberof calibrationand validationstorms selected,to assess model predictionaccuracy,coveredall partsof the lakeshoreline.

Calibrationand verificationof the coupledDelft3D-FLOW and DelflSD-WAVE modelsis performedby a time series comparisonof measuredand predictedlmodeledstorm surge values at differentwater level recordingstationson Lake Erie. A similartime seriescomparisonis also performedfor wave heights.

The Deltt3Dmodelsare calibratedusing extremehistoricwind and pressuredata from multiplemeteorological and waterlevelrecordingstations.Calibrat*on of and verification the coupled Delft3D-FLOWand Delft3D-WAVEmodels demonstratesthat the hydrodynamic modelis capableof computingthe stormsurgeand seichedynamicsfor Lake Erie,as well as the signiticantwave heightsand periodsat DBNPSfrom PMWS events.

PMSS The calibratedDelft3Dmodelis used to determinethe PMSS.The historicwind and pre$surefield data is replacedwith candidatePMWSevents,and the modelis run to determinethe criticalPMWS.

JLD-ISG-2A12-06 and ANSI/ANS2.8-1992requirethe antecedentwater levelequalto the 100-yearmaximumrecordedwater level to be appliedas the initialslorm surge modelstill water level.The 100-yearwater levelof 175.05meters-IGLDBS is used as the initialcondition/antecedent water level in all the Delft3D-FLOW models.$ince the probableminimumlow water level at DBNPScouldoccurat a time when the monthly meanlakelevelis at the long-termmeanlow probablelevel,the anteeedentwaterlevel for low waterevaluationis set to the long-ternrlow probablelevelat Lake Erie,whichis equalto 173.13meters-IGlD 85 Varioustopographicfeaturesmay affectthe storm$urgepropagationtowardsDBNP$.

The elevatedareaaroundDBNPSis protectedalongthe northern,eastern,and alonga smallportionof the southernsidesby an earthfillwaveprotection dikebuiltup to 591.00 ft-lGLD55.The purposeof the wave protectiondike is to protectagainstthe surgeand associatewave run-up.Additionally, the DBNPSarea along the soulhern,western, northern,and easternsidesof the plantis protectedby a vehiclebarriersystem(VBS).

MaximumHistoricaland 26-yearStorm $urge The historicalmaximumstorm surge is the largestof the determinedyearlymaximum storm surge heights.The historicalmaximumstorm surge height will be used in combinedfloodingscenariosin a separatecalculation.

$torm surges are calculatedfrom monthlydata as the differencebetweenmonthfy maximumand monthly mean based on guidanceprovidedby U$ACE. The Log PearsonType lll distributionis the commonlyacceptedfrequencyprocedurefor annual DAVIS.BESSE NUCLEARPOWERSTATION Page20 ot 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 maximumwater levels. A frequencyanalysison the yearly maxlmumstorm surge heightsobtainedfrom the Toledoand Marbleheadstationsis performedusing a Log Pearsonlll statisticalanalysis.The 2S-yearstormsurgeheightwas used in combined floodingscenarios.

3.5.4. Results Simulations of all the candidatePMWSeventsshowedthat the criticalPMWSeventis the October2012 wind stormevent,which is the remnantsof HurricaneSandy.This storm is the most intenseof all the PMWS events with a maximumwind speed of 103.12mileslhourand is alignedalongthe axis of LakeEriewhichis in the northeast direction.The maximumPMSSresultingfrom this PMWSeventproduceda maximum watersurfaceelevationof 585.90ft-lcLD55at the intakeforebaylocation, The Delft3Dmodelingresultsshow that the Lake Erie dike,will be overtoppedfrom the PMSSevent.Overtoppedwaterwill accumulatebehindthe LakeErie dike in the marsh and low elevationareasaroundDBNPS,establishing a highermean water level (i.e.

pondedwater)aroundthe plant.As the surge recedesto Lake Erie,the accumulated wateris forcedto returnto LakeErie (returnflow) alongthe westernand southernVBS.

Eventually, the waterwill overtopthe southernand westernVBS duringthe recessionof surgewaterto LakeErie,and floodDBNPS.

The maximumPMSSwater surfaceefevationin the vicinityof the power blockdue to the criticalPMWSis 585.81ft-lGLD5S.The PMS$ watersurfaceelevationswill remain abovethe site finishfloorelevation(585ft-lGLD55)for approximately 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

$urge, Seiche,and Resonance Resultsfrom CalculationC-CSS-020.13-016 show that the level of the rise due to seicheis significantly lessthan the calculatedsurgeheight.For this rea$on,seichesare not the controlling floodeventat DBNPS.

Resonancegeneratedby wavescan causeproblemsin enclosedwaterbodiessuch as harborsand bayswhen the periodof oscillationof the waterbodyis equalto the period of the incomingwaves. The periodof oscillationof Lake Eriedelerminedin Calculation C-CSS-020.13-016 is in the rangeof 12 to 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br />.This is muchgreaterthan that of the peak spectralperiod of the incidentshallowwater storm waves. Consequently, resonanceis not a detrimentat DBNPSduringthe criticalPMWSevent.

ProbableMinimumLow WaterLevel resultingfrom the PMW$

Simulationsof all the candidatePMWSstormeventsshowthat the criticalPMWSevent that would result in probableminimumlow water level (drawdown)is the transposed January1978stormevent.This stormhad the most intensewest and southwestwinds of the examinedstormevents,with maximumsouthwestwindspeedof 89.0 miles/hour.

The probableminimumlow waterelevation(drawdown)associatedwith the transposed January1978stormproducesa probableminimumlow waterlevelof 547.46ft-lGLD5s at the westernbasinof LakeErie.At this probableminimumlowwaterlevel,the DBNPS intakecanalis completelycut off from LakeEriefor approximately 43 hours4.976852e-4 days <br />0.0119 hours <br />7.109788e-5 weeks <br />1.63615e-5 months <br />.

3.6.TsunamiAssessment(Reference DBNPS2013J)

NUREG/CR-6966 identifies that earthquakes, and volcanoescan initiatetsunamis, landslides, with earthquakesbeing the most frequent cause. Dip-slip earthquakes(due to verlical movement)are more efficientat generatingtsunamisthan strike-slipearthquakes(due to DAVIS-BESSE NUCLEARPOWERSTATION Page21 of 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 horizontalrnovement). To generatea majortsunami,a substantial amountof slip and a large rupturearea is required.Consequently, only largeearthquakes with magnitudes greaterthan 6.5 on the Richterscalegenerateobservable tsunamis.

3,6.1. Basisof Inputs

. NOAAnaturalhazardstsunamidatabase r NOAAnaturalhazardsvolcanodatabase r Historical earthquake hazardsdatabase

. OhioDepartment of NaturalResources(ODNR)database 3.6.2. ModelsUsed

. None 3.6.3. Methodology As identifiedby NUREGICR-7046, tsunamiassessmentis referenced to NUREGICR-6966 and NOAA TechnicalMemorandumOAR PMEL-136.In addition,the more recentlyissuedNRCguidance,JLD-lSG-2012-06, alsoaddresses tsunamiassessment.

However,JLD-lSG-2012-06 providesguidanceon detailedtsunamimodelingand is beyondthe scopeof this assessment. TechnicalMemorandumOAR PMEL-136reflects a similartsunamiscreening assessment describedby NUREGICR-6966.

The NUREGICR-6966 screeningassessmentis basedon a regionalscreeningand a site screening.The regionalscreeningconsistsof researchinghistoricalrecordsfor tsunamirecordsand the potentialfor tsunami-generating sources.The site screening evaluatesthe site based on the horizontaldistancefrom a coast, the longitudinal distancemeasuredalonga river,and the gradeelevationin comparisonto the effectsof a tsunami.This assessmentapproachis basedon a reviewof historicalrecordsand databases.

NUREG/CR-6966identifies that tsunamis are generated by rapid, large-scale disturbances of a bodyof water.The mostfrequentcauseof tsunamisis an earthquake; however,landslidesand volcanoescan also initiatetsunamis.Becauseof the tsunami-generationsequenceassociatedwith earthquakes, dip-slipearthquakes(dueto vertical movement)are rnoreefficientat generating tsunamisthan strike-slipearthquakes(due to horizontalmovement).Furthermore,to generatea major tsunami,a substantial amount of slip and a large rupture area is required.Consequently,only large earthquakes with magnitudes greaterthan6.5 on the Richterscalegenerateobservable tsunamis.

As part of the assessment, the NOAA naturalhazardstsunamidatabasewas used to reviewhistoricaltsunamieventsand associatedrun-upsfor the east coastof the United Statesand Canada.Of the total events,therewere 7 tsunamieventsthat produced14 run-upsoccurringin the GreatLakesregionfrom 1755to 1954"The USGShazardfault databasefindingswere reviewedfor strongearthquakesor the verticaldisplacements necessaryto inducea tsunami.Additionally, the USGSeadhquakehazardsprogramis reviewedfor historicalearthquakesin the region.Lastly,the NOAA naturalhazards volcanodatabaseis reviewedto assessvolcanoesin the LakeErieregion.

An earthquake-generated tsunamiin Lake Erie would requirea very large earthquake on the order of magnitude7.0 or greateralong with significantverticaldisplacement.

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NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 20f 4 Historically,in the Lake Erie region,the largestearthquakes are in the magnitude5.0 range. Preliminaryanalysisof post-glacial sedimentsin the region has not yielded evidence of a large earthquakein the last few thousand years. Furthermore, earthquakesin the region, for which sufficientdata are available,show primarily horizontalrather than vertical movement,which is not as conduciveto tsunami generation.

Tsunamiscan also be generatedby the downslopemovementof a very largevolumeaf rock or sedirnent,eitherfrom a rockfallabovethe water or fiom a submarinelandslide.

Althoughlarge amountsof unconsolidated sedimentsare washedinto Lake Erie each year when shorelinebluffsare undercutby wave action,these masseslack sufficient volumeand rapid collapseto displacea volumeof water that would createa tsunami.

Lake Erie afso has a very gentlebottomprofile,particularlyin the westernand central basins.The easternbasinhas steeperslopes,but not steepenoughfor a largeamount of sedimentto suddenlyflowdownslopein a submarinelandslide.

Lastly, according to the NOAA natural hazards volcano database,there are no volcanoesin the LakeErieregion.

3.S.4. Results The NOAA naturalhazardstsunamidatabaseidentifiesonly two ocsurrencesof non-seiche (or non-wind-induced) tsunami events in the Great Lakes region. The two occurrencesyielded slight or small wave effects. Various earthquakedatabases, includingthe USGS EarthquakeHazardsProgramearthquakedatabase,the National Centerfor EarthquakeEngineeringresearchcatalog,and NaturalResourcesCanada, identifythat the largesteventsin the vicinityare no greaterthan magnitude5.0.

Accordingta the USGS EarthquakeHazards Program,the hazard fault database containsno knownQuaternaryfaults(or currentfaults)in this regionbecausegeologists have not found any faultsat the Earth'ssurface.Consequently, thereis nol a potential for strongearthquakesor the verticaldisplacement necessaryto inducea tsunami.

Therefore,a tsunamiis not expectedto be the controllingfloodeventat DBNP$.

3.7,CombinedEffect Flood (includingWlnd-Generated Waves){ReferenceDBNP$

2013n1 Evafuationof the shoresidelocationis coveredin H.4.1of NUREGICR-7046 and includesone alternative:

Combinationof:

Probablemaximumsurgeand seichewithwind-waveactivity, The lesserof the 1OO-year or the maximumcontrolledwaterlevelin the enclosed bodyof water.

There are three alternativesspecified in H.4.2 af NUREG/CR-7046for streamside locatione.Each of the alternatives consideredhas three componentscontributingto the watersurfaceelevation.

. Alternative1 - Comblnationof:

- The lesserof one-halfof ttrePMFor the 500-yearflood;

- $urge and seiche from the worst regionalhurricaneor windstormwith wind-wave activity;and DAVIS.BES$E NUCLEARPOWERSTATION Page23 af 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06,2A14

- The lesserof the 1O0-year or the maximumcontrolledwater level in the enclosed bodyof water.

. Alternative2 - Combinationof:

- PMF;

- A 25-yearsurgeand seichewithwind-waveactivity;and

- The lesserof the 10O-year or the maximumcontrolledwater level in the enclosed bodyof water.

r Alternative3 - Combinationof:

- A 2S-yearflood;

- Probablemaximumsurgeand seichewith wind-waveactivity;and

- The lesserof the 1O0-year or the maximumcontrolledwater level in the enclosed bodyof water.

3.7.1. Basis of Inputs lnputsincludethe following:

r Toussaint River sub-watershedproperties for rainfall-runotfmodeling from CalculationC-CSS-020.13-011

. ToussaintRiverHEC-RASmodelfromCalculation C-CSS-020.13-011 r PMFdischargehydrographs fromCalculation C-CSS-020.13-01 1

. One-halfPMFdischargehydrographs

. Z5-yeareventrainfallfor inputintoHEC-HMSmodelfromNOAAAtlas 14

. 2S-yeareventdischargehydrographs

. Lake ErieProbablePMSSelevationsfrom CalculationC-CSS-020. rc-417 3.7.2. ComputerSoftwarePrograms

. ArcGlSDesktop10.1 r Delft3D r HEC-HMS 3.5

. HEC-RAS4.1

. MicrosoftExcel 3,7.3. Methodology Eachcombinationincludescoincidentwind-waveactivity.Coincidentwind-waveactivity is determined usingthe USACEguidanceoutlinedin for the criticalfloodingcombination USACECoaslalEngineeingManual.Runupis the maximumelevationof wave uprush abovestillwaterlevel.

H 4.1 Combination Probablemaximumsurgeand seicheis estimatedin CalculationC-CSS-020.13-017.

Wind-waveactivityincludeswave height,wind set-up,and wave runup.Wave height andwindset-upare includedas partof the PMSSdevelopedusingDelft3Dmodel.

DAVIS.BESSE NUCLEARPOWERSTATION Page24 af 32

NTTFRecommendation 2,1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06,2414 H.4.2Alternative1 Alternative 1 requiresusingthe lesserof one-halfof the PMF or the 500-yearevent.In this case,the PMF was alreadydetermined as part of Calculation C-CSS-020.13-011.

Therefore, the one-halfPMF is utilizedas describedin C-CSS-020.13-022. The surge and seiche height from the worst regionalhurricaneor windstormwith wind-wave activityis estimatedusing statisticalanalysisof the historicaldata. Lake Erie has no outletcontrolstructures.Therefore,the 10O-year watersurfaceelevationis usedwithout furtherconsideration of the maximumcontrolledwater elevation.The HEC-RASmodel developedas part of the PMF analysisis revisedto use the one-halfPMF as the inflow boundarycondition and 100-year surge-seicheelevation from the worst regional hurricaneas the downstreamboundarycondition.The HEC-RASmodel providesthe watersurfaceelevationfor this alternative.

H.4,2Alternative2 Alternative 2 requiresusingthe PMFestimatedin Calculation C-CSS-020.13-011. The

$urgeand seiche height from the 25-year event is estirnatedusing analysis statistical of the historicaldata. Similar to Alternative1, the HEC-RAS model was updated to obtain the resuttingwatersurfaceelevation.

H.4.2Alternative3 Afternative3 requiresusingthe 21-yearfloodin the ToussaintRiver.Pointrainfalfdata from NOAAwas used to estimatethe 2S-yearrainfallevent. This rainfallis input into the HEC-HMSmodeldevelopedas part of the PMF analysisto estimaterunoffdue to 25-yearevent.The watersurfaceelevationfor the probablemaximumsurgeand seiche in combinationwith the 100-yearwater level is determinedin CalculationC-CSS-02A13-017.Similarto Alternatives1 and 2, the HEC-RASmodelwas updatedto obtain the resultingwatersurfaceelevation.

3.7.4. Results The predictedwater surfaceelevationat the site for Alternative3 is found to be the maximumfor the alternativesspecifiedin H.4.2.lt is also concludedthat the Toussaint Riverwater surfaceelevationsat the site are completelycontrolledby the backwater conditionsat Lake Erie for that alternative(i.e.,the predictedwatersurfaceelevationin the river is equal to the lake elevation,extendingfor about one mile upstreamof DBNPS).

The watersudaceelevationof 585.93ft-lGLD5Sfor combination H.4.1is equalto the criticalwater surfaceelevationfor combination H.4.2 Alternative3 and representsthe criticalwater sudace elevationat the site resulting from the combined events as specifiedin NUREGCR-7046,AppendixH.4.

DBNPSis protectedagainstfloodingdue to wave runup during a PMWS by wave protectiondikesinstalledalongthe northern,eastern,and alonga smallportionof the southernsidesof the site to an elevationof 591 ft-lclDss. Wave actionat DBNPSis governedby the maximumsupportablewave at the toe of the north dike duringthe PMSS.Waveactionanalysisconcludes thata maximumwaverunupof 3.98ft on top of the PMSSlevelof 585.90ft-lGLDsSmay be generatedat the toe of the northdike,The maximumwave runup elevationduringthe controllingfloodingAlternativeis therefore equalto 589.88ft-lGLD5S.This elevationis less than the top of the wave protection dikes(591ft-lGLD55).Therefore,the wave runupanalysisshowsthat wave protection DAVIS-BESSE NUCLEARPOWERSTATION Page25 of 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March46,2414 dikes are sufficientto protectDBNPSfrom wave runup during the criticaleombined floodingevent.

DBNPS is iloodedduringthe PMWS event along the non-dikedwest and south site boundaries.The maximumPMSSwater surfaceelevationin the vicinityof the power block is 585.81ft-lGLDsS.The maximumwave runup elevationin the vicinityof the powerblockis 585.90feet-lGLD55.

3.8.Local lntensePrecipitation(ReferenceDBNPS2013eand DBNF$2013f1 The LIP is an extremeprecipitation event (high intensity/shortduration)at a given location.

The durationof the event and the coveragearea are needed to quantify an extreme precipitationevent fully. Generally,the amountof precipitationdecreaseswith increasing durationand increasingarea. NUREG/CR-7046 specifiesthat the LIF shouldbe equivalent to the 1-hr, 1-mizprobablemaximumprecipitation (PMP)at the locationof the site.

3.8.{. Basisof Inputs

. Sitetopography

. LIP(cumulative and incremental)

. Manning'sroughnesscoefficients

. Supporting GISdata(Reference DBNPS20131) 3.8.2. ModelsUsed r ArcGlSDesktop10.1

. FLO-ZDPro r MicrosoftExcel 3.8.3. Methodotogy The LIP event was evaluatedto determinethe associatedfloodingelevationand velocitiesassumingthe activeand passivedrainagefeaturesare non-functional. The entire roof drainage is assumed to be contributing to the surface runoff.The LIP evaluationwas performed in accordance with the NUREG/CR-7046.

The runoffcausedby the LIP eventwas estimatedusing the FLO-2Dsoftware. The softwareuses shallowwater equationsto route stormwaterthroughoutthe site. FLO-2D depicts site topography,using a digitalelevationmodel (DEM),to characterize grading,slopes,drainagedivides,and low areasof the site.The DEM is a grid model devetopedfrom compositegroundsurfaceinformation.The methodologyused within the FLO-ZD software included the rainfall function and the levee function (to incorporate site security features which could impact the natural drainage characteristicsof the site).

Per NUREG/CR-7046, the 1-hr,1-mi2PMPeventwas developedusingHMR-52. The total PMP depth per squaremite for the l-hr event was interpolatedfrom the PMP depth contour map providedin HMR-52.The distributionof the 1-hr PMP was developedfor the 5-, 15-, and 3O-minutetime intervals,with the 60-minuteinterval being the 1-hr PMP depth.The depth for each time intervalwas calculatedusingthe DAVIS.BESSE NUCLEARPOWERSTATION Page26 of 32

NTTFRecommendation  ?.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 guidanceprovidedin HMR-52.The 1-hrPMPwas modeledin FLO-2Dto calculatethe subsequent siteflooding.

Active and passivedrainagesystem components(e.9., pumps, gravity storm drain systems,smallculverts,and inlets)were considerednon-functional or cloggedduring the LIP event, per Case 3 in NUREG/CR-7046. The Manning's roughnes$ coefficient valuesare selectedbasedon the land covertype usingthe guidance providedin the FLO-2D manual.Two types of obstructionsare modeled:buildingslstructures that completelyblockthe waterpassage,and securitywalt barriersthat couldbe overtopped if the waterdepthincreasesto abovethe top of the wall.

To determinethe floodingelevationassociatedwith the LlP, the 1-hr,1-mizstormwas appliedevenlyacrossthe site, and the model was allowedto run for 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> to ensurethat only the areas of staticpondingwould remain.Five temporaldistributions similarto the PMFanalysiswereconsidered.

3.8.4. Results The end temporaldistributionof the LIP eventresultedin the highestwaterdepthsand consequentlyin the highestwater surfaceelevations.The water surfaceelevationsat SSCs,are listedin Tabfe1.

criticaldoorlocations,or doorsleadingto safety-related TableI - LIP FloodingElevationand Durationat DBNPS Door MaximumWaterSurface Flood Durationabove Structure Number Elevation(ft-lGLD56) S85ft-lcLD55 (minutes)

AuxiliaryBuilding 300 585.25 6 AuxiliaryBuilding 361 585.20 15 AuxiliaryBuifding 362 585.20 15 AuxiliaryBuilding 315 585.17 15 AuxiliaryBuilding 320A 585.17 15 AuxiliaryBuilding 324 585.1B 18 TurbineBuilding 330 585.1B 18 TurbineBuilding 399A 585.19 1B TurbineBuilding 339 585.20 1B TurbineBuilding 333 585.22 18 TurbineBuilding 334 585.41 57*

IntakeStructure 224 585.44 30

  • The differencein the floodingdurationat Door 333 and Door 334 is causedby the groundsurfaceelevations.The groundat Door 334 is higherthan the groundat Door 333 (585.92vs. 585.67ft NAVDBB). Therefore,minimalfloodingdepthsresultin the water fevel increaseabove the floor elevation.Betweenminute27 and minute54 of floodingeventthewaterdepthabove585.0is 0.01to 0.05ft.

DAVIS.BESSE NUCLEARPOWERSTATION Page27 ol 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 The hydrodynamicloads, or impact loads, on the structuresdue to the LIP are presentedin Table 2. FLO-2Dreportsthe impact pressurea$ a force per unit length (impactpressuretimes flow depth).The maximumimpactforce on the structurewas estimatedby multiplying the impactpressureby the structurelength.

Table2 - MaximumlmpactLoadson Buildings Bulldlng Max lmpact (tblft)

Containment Structure 0.46 AuxiliaryBuilding 1.53 TurbineBuilding 7.14 IntakeStructure 5.27

4. COMPARISON WITHCURRENTDESIGNBASIS The reevaluatedmaximumwater surfaceelevationdue to the riverineflooding(Toussaint River)is belowthe currentlicensingbasis.The reevaluatedmaximumwater surfaceelevation due to the LIP and PMSSeventsexceedthe currentlicensingbasis.

For lake flooding,the currentdesignbasisassumesthe surgeonly in one direction.A site-specificwind and pressurefield is developedas part of the re*analysis. More recentstorms providedthe controllingwind for surgefloodingat DBNP$.

For LIP flooding,the currentdesign basis assumes24.5 inchesof rainfallwill pond evenly acros$ the site. As part of the re-analysis,recent site topographywas used in a two-dimensionalhydraulicmodel(FLO-2DPro)and additionalrainfallestimateswere obtainedfrom the morerecentHMR-52guidance.

ln the interim,it is understoodthat an event of such magnitudeto approachthe postulated accumulationof rainfalfis a low probabilityevent. Such an eventwould likelybe associated with a significanttropicalstorm.Meteorological forecastingwould providesufficientwarning well in advanceof such an event.The InterimActionsdiscussedin Section5 will provide adequateprotectionuntilpermanent are implemented.

solutions The comparisons floodhazardsare providedin Table3, of existingand reevaluated DAVIS-BESSE NUCLEARPOWERSTATION Page28 af 32

NTTFRecommendation 2.1 (HazardReevaluations):Flooding Revision1 FirstEnergyCorporation March06, 2014 Table3 - Gomparisonof Existingand ReevaluatedFlood Hazardsat DBNP$

Flood-Causing Mechanism DesignBasis Comparison Flood HazardReevaluationResults Flooding in PMF Etevation - Bounded All-Season PMF Elevation - 575.96ft-streamsand 579ft-tGLD55 IGLD55, All-Season PMF Flow-rivers 100,436cfs PMFFlow- 78,500 cfs Cool-Season PMF Elevalion- 575.06ft-IGLD55, Cool-$eason PMFFlow-Cool-season PMP 61,943cfs was not evaluated.

Dam breaches No damsor other Bounded Dam as$es$mentindicatedno critical and failures regulatinghydraulic dams.

structures.

Stormsurge Watersurface Not Watersurfaceelevation-585.81 ft-elevation- 583.7 bounded. lGLDSSat powerblock, IGLD55 Exceeds current designbasis.

Seiche Thisflood-causing Thisflood- Not a crediblescenario.Boundedby mechanism is not causing stormsurge.

describedin the mechanism USAR. is not describedin the USAR.

Tsunami Thisflood-causing Thisflood- Tsunamiasses$ment indicatesthereis mechanismis not causing a slightpossibilityof tsunamisin Great describedin the mechanism lakes.However,the seismicityin the USAR. is not regionsuggeststhereis no potentialfor describedin strongearthquakes or the vertical the USAR. displacement necessaryto inducea tsunami.

substantial lce-induced Notplausible Bounded lce-inducedfloodingis boundedby the flooding all-seasonPMFevent.

Channel As indicatedin the Bounded Channeldiversiontowardsthe site is not migration USAR,the mean probable.

diversion lakelevelis not subjectto variationsdue to diversionsor sourcecutoff.

DAVIS-BESSE NUCLEARPOWERSTATION Page29 of 32

NTTFRecommendation 2.1 (HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March08,2014 Table3 - Comparisonof Existingand ReevaluatedFlood Haeardsat DBNPS(Continued)

Flood-Causing Mechanism DesignBasis Comparison Flood HazardReevaluationResults Combinedeffect Waverunupon Bounded Wave runupon wave protectiondike-flood(including wave protection 589.88ft-lclDss.

wind-generated dike-590.3ft-waves) IGLD55.

Maximumwaverunupelevationin the vicinityof the powerblock- 585.90ft-IGLD55.

LIP Maximumwater Not bounded. Maximumwatersurfaceelevaiion-surfaceelevation Exceeds 585.44ft-lGLD55.

- 584.5fr-lGLDs5. currentdesign basis.

DamFailure As indicatedin the Damslocatedin the DBNPgwatershed USAR,thereare are determinedto be noncritical.

no structureson ToussaintRiver that can affectthe flow hydrographat DBNPS.

5. INTERIM AND PLANNEDFUTUREACTIONS The FloodingHazardReevaluation Reportevaluatedapplicablefloodinghazardsfor DBNPS, Two of the postulatedreevaluated floodhazardevents,the PMS$ and the LtP events,resulted in maxirnumflood water elevationshigher than previouslycalculatedfor DBNPS. The assessmentof the buildings,resultingfrom the flood hazardreevaluation, founda numberof doorsfeadingto areascontainingsafetyrelatedequipmentto be susceptibleto the postulated water infiltration.These postulatedflooding events are consideredbeyond design basis events.The reevaluatedflood levels are small increaseswith short durations.These low probabilityeventswould likelybe identifiedin advanceby meteorological Current forecasting.

plant proceduresaddressingfloodingat the site provideactions to be taken in the event floodingis imminentor has occurredat or nearthe DBNPSsite. No additionalactionsbeyond thosecurrentlyin placeare nece$saryat this time. The totalplantresponseto the reevaluated hazardis to be determinedby the Integrated Assessment.

The integratedassessmentwill be performedto addressthe needandlorpotentialdesignsfor temporaryor permanentbarriers(or alternativecountermeasures) to preventpostulatedflood water infiltrationand/ormitigationof the postulatedfloodwater infiltration.This evaluationwill also includea study of emergencyprocedures.The evaluationof the mitigatingstrategyand schedulefor the implementation (as necessary)will be documentedin the of modifications CorrectiveActionProgram.The evaluationwill addressthe followingitems:

DAVIS-BESSE NUCLEARPOWERSTATION Page30 of 32

NTTFRecommendation 2.1(HazardReevaluations): Flooding Revision1 FirstEnergyCorporation March06, 2014 L!E As indicated earlier,the watersurfaceelevation exceedsthe finish ffoor elevationof 585 ft-lGLD55by a maximumvalueof 0.44ft for a totaldurationof approximately 1.0 hrs at one (1) doorand0.5 hrs or lessat the remaining eleven(11)affecteddoors,due to the LIP event.The LIP storm mechanismswill be reviewedin the integratedassessmentto establishtrigger pointswhichsupportimplementation of proceduralized measures.This includesan mitigation evaluationof the forecastinformationavailableto personnelthat would allow for advanced monitoringand warningof meteorological conditionsthat could potentiallyresult in an LIP eventoccurringat the site.Modifications wilf afsobe consideredto affordprotectionfor the site vulnerabilities or to furtherreducethe impactof the LlP, PMSS As indicatedearlier,the water surfaceelevationexceedsthe finish floor elevationof 585 ft-IGLD55by a maximumvalueof 0.81 ft for a totaldurationof approximately 2.5 hrs due to the PMSSevent.The PMSSstorm mechanismswill be reviewedin the integratedassessmentto establishtriggerpointswhich supportimplementation of proceduralizedmitigationmeasures.

This includesan evaluationof the forecastinformationavailableto personnel that wouldallow for advancedmonitoringand warningof meteorological conditionsthat could potentiallyresult in a surgeeventaffectingthe site.Modifications will also be consideredto affordprotectionfor the sitevulnerabilities.

6. REFERENCES (ANSf/ANS-2.8-1992) ANS, American National Standardfor DeterminingDesign Basis Flooding at Power Reactor Sites, Prepared by the American Nuclear Society Standards Committee WorkingGroupANS-2.8,1992.

(JLD-ISG-2A13-01) NRC,Guidancefor Assessmentof FloodingHazardsdue to Dam Failure, Revision0, June2A13.

(JLD-lSG-2012-06) NRC, Guidancefor Performinga Tsunami,Surge and SeicheFlooding SafetyAnalysis,Revision0, June2012 (NElAugust2012,NEl,Report12-08,Overview of External Flooding Reevaluations, August 2012.

(NRCMarch20121NRC,Letterto Licensees, Requestfor Inforrnation Pursuant to Title10 of theCodeof Federal Regulations50.54(0 Regarding Recommendations 2.1 ,2.3,and 9.3of the NearTermTaskForceReviewof Insightsfromthe Fukushima Dai-ichiAccident, March 12, 2012.

(NRC RG 1.59) NRC, DesrgrrBasis Flood for NuclearPower Plants,RegulatoryGuide Revision 2r 1977.

(NRC RG 1.102)NRC, FtoodProtectionfor NuclearPower Plants,RegulatoryGuide 1.1A2, Revision1, 1976.

(NUREG-0800) NRC, NUREG-0800,StandardReviewPlanfor the Reviewof SafetyAnalysis Repods for NuclearPower Plants: LWR Edition - S#e Charccterisftbsand Sr'fe Parameters (Chapter2), M107c400364, March2A07.

(NUREG/CR-7046) NRC, NUREG/CR-7046, PNNL-20091 , Design-8asisFloodEsfttnaffonfor Stle Characterization at NuclearPower Plantsin the UnitedSfafesof America,ML11321,{195, November 2011.

DAVIS-BESSE NUCLEARPOWERSTATION Page31 of 32

NTTFRecommendation 2.1 (HazardReevaluations):

Flooding Revision1 FirstEnergyCorporation March06, 2014 (NUREG/CR-6966) NRC,NUREG/CR-6966, TsunamiHazardAssessment at NuclearPower PlantSitesin theUnitedSfafesof America,NationalTechnicallnformationService,March 2009.

(DBNPS 2013a) FENOC CalculationC-CSS-020.13-009, A//-SeasonPrabableMaximum PrecipitationAnalysisfor Davis-BesseNuclearPowerSfafion,Revision0.

(DBNPS 2013b) FENOC CalculationC-CSS-020.13-010, Coo/-SeasonPrecipitation and SnowmeltAnalysisfor Davis-BesseNuc/earPowerSfaflon,Revision 0.

(DBNPS2013c)FENOCCalculationC-CSS-020.13-01 1, ProbableMaximumFload Analysis for Davis-BesseNuclearPower Station,Revision0.

(DBNPS 2013d) FENOC CalculationC-CSS-02A13-A12, Dam Assessmenli lce Jam, and ChannelMigrationfor Davis-8esseNuclearPawerSfafion,Revision0.

(DBNPS2013e)FENOCCalculationC-CSS-020.13-013, Local lntenseProbableMaximum PrecipitationAnalysrsfor Davis-BesseNuc/earPowerSfafion,Revision0.

(DBNPS20130 FENOC CalculationC-CSS-020.13-014, Effecfsof Local lntenseProbable MaximumPrecipitationAnalysisfor Davis-BesseNuc/earPowerSfaffon,Revision0.

(DBNPS2013g)FENOCCalculationC-CSS-020.13-015, Windand PressureField Sife-specifie Analysisfar Davis-Besse NuclearPowerSfafion,Revision0.

(DBNPS2013h) FENOC CalculationC-CSS-020.13-016, Su4geand Seiche Screeningfor Davis-BesseNuclearPowerSfafion,Revision0.

(DBNPS2013i)FENOCCalculation C-CSS-020.13-017, Surgeand SeicheAnalysisfor Davis-EesseNuclearPowerSfaflon,Revision0.

(DBNPS 2013j) FENOC CalculationC-CSS-020.13-018, Tsunami Screening/Analysis for Davis-BesselVuclearPawerSfafion,Revision0.

(DBNPS 2013k) FENOC CalculationC-CSS-020.13-019, Probable MaximumFlood GIS Analysisfar Davis-BesseNuclearPawerSfafion,Revision0.

(DBNPS 20131)FENOC CalculationC-CSS-020.13-020 Locat lntense PrecipitationGtS Analysisfor Davis-BesseNuclearPowerStafion,Revision0.

(DBNPS2013m) FENOC CalculationC-CSS-020.13-A21, Surge and Seiche Calibrationfar Davis-BesseNuc/earPowerSfafion,Revision0.

(DBNPS 2013n) FENOC CalculationC-CSS-02A13-022,Combined Event includingWind Wave Analysisfor Davis-8esseNuclearPower Statian,Revision0.

(DBNPS2013o)FENOCCalculation C-CSS-020.13-023, Surgeand SeicheGIS Analysis for Davis-BessefVuc/earPawerStafion,Revision0.

(USAR)Davis-Besse NuclearPowerStation,UpdatedFinalSafetyAnalysisReport,Revision 29.

DAVIS-BESSE NUCLEARPOWERSTATION Page32 of 32

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