L-16-337, Mitigating Strategies Assessment (MSA) for Flooding
| ML16348A010 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/12/2016 |
| From: | Boles B FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of New Reactors |
| References | |
| L-16-337, TAC MF3721 | |
| Download: ML16348A010 (18) | |
Text
FENOC' FirstEnergy Nuclear Operating Company Brian D. Boles Vice President, Nuclear December 12, 2016 L-16-337 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852
SUBJECT:
Davis-Besse Nuclear Power Station Docket No. 50-346, License No. NPF-3 5501 North State Route 2 Oak Harbor, Ohio 43449 419-321-7676 Fax: 419-321-7582 10 CFR 50.54(f)
Mitigating Strategies Assessment (MSA) for Flooding CT AC No. MF3721)
On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued a letter titled, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," to all power reactor licensees and holders of construction permits in active or deferred status. Enclosure 2 of the 10 CFR 50.54(f) letter addresses Near-Term Task Force (NTTF) Recommendation 2.1 for flooding. One of the required responses is for licensees to submit a hazard reevaluation report (HRR) in accordance with the NRC's prioritization plan. By letter dated March 11, 2014, FirstEnergy Nuclear Operating Company (FENOC) submitted the flood HRR for Davis-Besse Nuclear Power Station (DBNPS). Additional information was provided by FENOC letters dated August 25, 2014, December 10, 2014, February 25, 2015, and August 11, 2015. As indicated in NRC letter dated March 1, 2013, the NRC staff considers the reevaluated flood hazard to be "beyond the current design/licensing basis of operating plants."
Concurrent to the flood hazard reevaluation, FENOC developed and implemented mitigating strategies in accordance with NRC Order EA-12-049, "Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events." By letter dated September 1, 2015, the NRC staff confirmed that licensees need to address the reevaluated flooding hazards within their mitigating strategies for beyond-design-basis (BDB) external events. Guidance for performing mitigating strategies assessments (MSAs) for reevaluated flooding hazards is contained in Appendix G of Nuclear Energy Institute 12-06, Revision 2, which was endorsed by
Davis-Besse Nuclear Power Station L-16-337 Page 2 the NRC in JLD-ISG-2012-01, Revision 1. In the NRC interim staff assessment for DBNPS, dated September 3, 2015, the NRC concluded that the "reevaluated flood hazards information, as summarized in the Enclosure [Summary Tables of Reevaluated Flood Hazard Levels], is suitable for the assessment of mitigating strategies developed in response to Order EA-12-049" for DBNPS.
The enclosure to this letter provides the MSA for flooding for DBNPS. This assessment indicated that the FLEX strategy design basis did not bound the reevaluated flood hazard (that is, mitigating strategies flood hazard information) for the local intense precipitation (LIP) flood and the probable maximum storm surge (PMSS) flooding, which could challenge the successfully implementation of the FLEX strategy as designed. As a result, use of alternate staging areas and trigger points for pre-deployment of FLEX N+1 equipment are being developed. This will remove the challenges to the FLEX mitigating strategies from LIP and PMSS.
There are no new regulatory commitments contained in this letter. If there are any questions or if additional information is required, please contact Mr. Thomas A. Lentz, Manager - Fleet Licensing, at 330-315-6810.
I declare under penalty of perjury that the foregoing is true and correct. Executed on December~, 2016.
Sincerely,
~J~
Brian D. Boles
Enclosure:
Mitigating Strategies Assessment for Flooding cc:
Director, Office of Nuclear Reactor Regulation (NRR)
NRC Region Ill Administrator NRC Resident Inspector NRR Project Manager Utility Radiological Safety Board
Page1of16 MitigatingStrategiesAssessmentforFlooding
BDBEEBeyondDesignBasisExternalEvent DBDavisBesseNuclearPowerStation EFWFEmergencyFeedwaterFacility FHRRFloodHazardReevaluationReport FIPFinalIntegratedPlan LIPLocalIntensePrecipitation MSFHIMitigatingStrategiesFloodHazardInformation(fromtheFHRRandMSFHIletter)
NORMNuclearOperatingReferenceMaterial NSRCNationalSAFERResponseCenter PMSSProbableMaximumStormSurge PMWEProbableMaximumWindEvent RAIRequestforAdditionalInformation USAR-UpdatedSafetyAnalysisReport
Definitions:
FLEXDesignBasisFloodHazardThecontrollingfloodparametersusedtodeveloptheFLEX flood strategies.
FLEXDiverse&FlexibleCopingStrategies Phase1Initiallycopebyrelyingoninstalledplantequipment.
Phase2TransitionfrominstalledplantequipmenttotheonsiteFLEXequipment.
Phase3Obtainadditionalcapabilityandredundancyfromoffsiteequipmentuntilpower, water,andcoolantinjectionsystemsarerestoredorcommissioned.
FLEXNEquipmentEquipmentusedisprotectedfromallBDBEEhazardsandistheprimaryFLEX responseequipment.
FLEXN+1EquipmentEquipmentusedisNOTprotectedfromallBDBEEhazardsandisusedasan alternatetoFLEXNequipment.
FLEXNSRCEquipmentEquipmentprovidedbytheNSRCtosupportFLEXPhase3strategy.
Unitabbreviations:
ft-feet
in-inches
psf-poundspersquarefoot
fps-feetpersecond
Page2of16
- 1. Summary
TheMitigatingStrategyFloodHazardInformation(MSFHI)providedintheDavisBesseFlood HazardReevaluationReport(FHRR)(Ref.1)hasconcludedthattheLocalIntensePrecipitation (LIP)andProbableMaximumStormSurge(PMSS)canchallengeimplementationoftheFLEX strategies.TheexistingFLEXstrategiesfortheseeventscanbemodifiedtoaddressthe impactsoftheMSFHI.Otherreevaluatedfloodhazardmechanisms(i.e.tsunami,channel migrations/diversions,etc.),areboundedbytheplantdesignbasisandhavenoimpactonthe site.
TheMSFHILIPfloodinglevelsdevelopadepthabovecriticaldoorsillsforalimitedperiodof time.Doorsareclosedininclementweatherbasedonexistingplantprocedures.Asstated inreferences1,2and3nointernalfloodingwillbeexperiencedthatcouldjeopardizeeither safetyrelatedorFLEXequipment.SufficientmarginexistsintheFLEXstrategiestoallowfor waterrecessionaroundthepowerblocktherebypreventingachallengetoPhase1and Phase2FLEXstrategies.FLEXN+1andNSRCequipmentareaffectedbytheLIPstandingwater inthedeploymentroutes.Phase3strategiesrelyonNSRCequipment.Alternatestagingareas havebeenconfirmedtobeavailableduringandafteraLIPevent,whichwillallow implementationofallphasesoftheFLEXstrategies.Triggerpointswillbedevelopedtoallow forpredeploymentofN+1equipment.Useofalternatestagingareasandpredeploymentof N+1equipmentwillremovechallengestotheFLEXmitigationstrategyfromtheLIP.
SimilartotheLIPtheMSFHIPMSSaffectscriticalstationdoorsforashortperiodoftime.
Theseimpactsandtheirmitigationarethesameasdescribedabove.ThePMSSfloodduration above585ft.inthepowerblockareais2.5hours.SufficientmarginexistintheFLEXstrategy todelayimplementationuntilfloodlevelsdropbelow585ft.Thetotalabovegradeflood durationissixhours,butthedepthandvelocitiesallowforFLEXactionsanddeploymentto becompletedduringthisminorflooding.ThePMSSalsoimpactsNSRCsitestagingareaand N+1equipmentdeploymentduetostandingwater.Thedepthanddurationofthestanding waterisgreaterthantheLIPeffects.Alternatestagingareashavebeenconfirmedtobe available,whichwillallowimplementationofallphasesoftheFLEXstrategies(Ref.5).Trigger pointswillbedevelopedtoallowforpredeploymentofN+1equipment.Useofalternate stagingareasandpredeploymentofN+1equipmentwillremovechallengestotheFLEX mitigationstrategyfromthePMSSevent.
TheFLEXresponsetimelinehasbeenreviewedandverifiedtoensureFLEXstrategiescanbe implementedtoaddresstheLIPandPMSSimpactsthroughtheuseofalternatestaging areasandpredeploymentofN+1equipment(Ref.5).
DevelopmentoftriggerpointsforLIPandPMSSpredeploymentofN+1equipmentand documentationofthealternatestagingareasarebeingtrackedintheFENOCcorrective actionprogram.
TheEFWFandauxiliarybuildingwhichhousetheFLEXNequipmentarenotaffectedbythe LIPorPMSS.
Page3of16
- 2. Documentation
2.1NEI1206,Rev.2,SectionG.2-CharacterizationoftheMSFHI
LocalIntensePrecipitation(LIP)
FloodHeight ThereevaluatedLIPanalysis,documentedintheDBFHRR(Ref.1),isashortdurationlow velocityevent.Themaximumfloodingdepthofaccumulatedwaterinthepowerblockareais 0.5ft.
FloodEventDuration AsdescribedinSection5oftheFHRR(Ref.1)andpage2oftheRAIresponse(Ref.3)theLIP doesnotaffectsafetyrelatedequipment.Totaleventdurationis2.5hoursinthepowerblock areawithwaterlevelabovecriticaldoorsills(11doors)fornotmorethan33minutes.One turbinebuildingdoorhaswaterabovethesillfor54minutes,butthepotentialtoaffect safetyrelatedequipmentisprecludedbyacurblocatedintheturbinebuilding.Residual waterinlowlyingnonpowerblockareaswillexistforanextendedperiodoftime.
RelevantAssociatedEffects TheimpactoftheLIPontheFLEXstrategieswasevaluatedinNORMLP7221(Ref.5).This evaluationdeterminedthatthereissufficientmarginintheFLEXstrategytodelayPhase1 andPhase2FLEXexternalactions,ifneeded,untilthewaterlevelrecededbelowcritical doorsilllevels.Italsodeterminedthatduetotheshallowdepthsofthefloodandthelow velocitiesofthefloodwater,Phase1andPhase2externalactivitiescouldbecompletedif necessary.TheevaluationidentifiedthattheN+1equipmentdeploymentpathandPhase3 NSRCstagingareawereaffectedbytheLIP.BoththestagingareaandtheN+1deployment patharesubjecttoLIPfloodingandresidualwaterinlowlyingareasforanextendedperiod oftime.
Additionalengineeringevaluationswereperformedtodeterminetheflooddurationand identifyalternateviablestagingareas(Ref.5).Twoviablestagingareaswereidentified.A triggerpointforaLIPeventwillbedevelopedtoallowpredeploymentofN+1equipment.
ThesechangeswillallowsuccessfulimplementationoftheFLEXstrategiesasdesigned.
WarningTime ALIPeventresultingfromasynopticstorm(i.e.largefrontalsystem)provideslimitedwarning time.BasedonexistingDBsiteproceduresandtheMSFHIevaluationperformedinNORMLP 7221(Ref.5),thesitehasapproximatelyonehourofpreparationtime.Thetriggerpointto bedevelopedwillallowforenoughtimetopredeploytheN+1equipment.Theamountof N+1equipmentrequiringpredeploymentislimitedtoa480voltgenerator,cablecart,and twopumps(Ref.5).Intheeventpredeploymentwasunsuccessful,theFLEXNequipment remainsavailabletosupportFLEXimplementation.
Page4of16 ProbableMaximumStormSurge(PMSS)
FloodHeight ThereevaluatedPMSSanalysis,documentedintheDBFHRR(Ref.1),isashortdurationlow velocityeventinthepowerblockarea.PMSSwithwaverunupwasalsoanalyzedresulting ina.1ftwaverunup.Themaximumfloodingdepthofaccumulatedwater,includingwave runup,inthepowerblockareais10.8inches(in)abovethepowerblockflooranddoorsill elevationsof585ft.
FloodEventDuration AsdescribedinSection5oftheFHRR(Ref.1)andtheRAIresponse(Ref.3)thePMSSdoes notaffectsafetyrelatedequipment.Totaleventdurationissixhoursinthepowerblock areawithwaterlevelabove585ftdoorsillelevationfor2.5hours.
RelevantAssociatedEffects TheimpactofthePMSSontheFLEXstrategieswasevaluatedinNORMLP7221(Ref.5).
ThisevaluationdeterminedthatthereissufficientmarginintheFLEXstrategytodelay Phase1andPhase2FLEXexternalactions,ifneeded,untilthewaterlevelrecededbelow criticaldoorsilllevels.Italsodeterminedthatduetotheshallowdepthsofthefloodand thelowvelocitiesofthefloodwaterPhase1andPhase2externalactivitiescouldbe completedifnecessary.TheevaluationidentifiedthattheN+1equipmentdeploymentpath andPhase3NSRCstagingareawereaffectedbythePMSS.Boththestagingareaandthe N+1deploymentpatharesubjecttoPMSSfloodingandresidualwaterinlowlyingareasfor anextendedperiodoftime.
Additionalengineeringevaluationswereperformedtodeterminetheflooddurationand identifyalternateviablestagingareas(Ref.5).Twoviablestagingareaswereidentified.A triggerpointforthePMSSeventwillbedevelopedtoallowpredeploymentofN+1 equipment.ThesechangeswillallowsuccessfulimplementationoftheFLEXstrategiesas designed
WarningTime ThePMSSeventtakesseveralhourstodevelop.Oncetheprobablemaximumwindevent (PMWE)developsittakesapproximatelythreehoursforfloodinginlowlyingareastodevelop andsixhourstocausefloodingabovethesitegradeelevation(584ft)inthepowerblockarea.
ThisallowsampletimeforsitepreparationsaswellasN+1equipmentpredeployment.
Page5of16 2.2NEI1206,Rev.2,SectionG.3-ComparisonoftheMSFHIandFLEXDBFlood Table1a-FloodCausingMechanismA(LIP)orBoundingSetofParameters
FloodScenarioParameterLIP PlantDesign BasisFlood FLEX Design BasisFlood Hazard MSFHI MSFHI Bounded (B)or Not Bounded (NB)
FloodLevelandAssociatedEffects 1.MaxStillwaterElevation 584.5ft 584.5ft 585.5ft NB 2.MaxWaveRunupElevation N/A N/A N/A N/A 3.MaxHydrodynamic/Debris Loading(psf)
Not discussedin USAR Not discussed inUSAR SeeNote 3
NB 4.EffectsofSediment Deposition/Erosion Not discussedin USAR Not discussed inUSAR SeeNote 4
NB 5.Otherassociatedeffects (identifyeacheffect)
N/A N/A
N/A N/A 6.ConcurrentSiteConditions N/A N/A
N/A N/A 7.EffectsonGroundwater 250psf 250psf See Notes3
&7 B
FloodEvent Duration 8.WarningTime(hours)
Varies Varies Varies SeeNote 8
NB 9.PeriodofSitePreparation(hours)
Not discussedin USAR Not discussed inUSAR 1
NB 10.PeriodofInundation(hours)
Not discussedin USAR Not discussed inUSAR 0.5 NB 11.PeriodofRecession(hours)
Not discussedin USAR Not discussed inUSAR 1
NB Other 12.PlantModeofOperations Not discussedin USAR Not discussed inUSAR Mode1 6
NB 13.OtherFactors N/A N/A N/A N/A
Page6of16 Additionalnotes,N/Ajustifications(whyaparticularparameterisjudgednottoaffectthe site),andexplanationsregardingthebounded/nonboundeddetermination.
1.
AllelevationvalueswillbeintheSiteDatum,IGLD55,unlessnotedotherwiseastheMSFHIvalueis abovedesignbasisitisconsiderednotbounded(NB).
References:
CCSS020.13014Rev1,FHRRSection3.8&FHRRTable1,FHRRSection2.1.1,USAR Section2.4.2.3 2.
ThereisnowaverunupassociatedwiththeLIP.Theeventhasashortdurationandthestanding waterrecedesquickly.TheUSARdidnotaddressfloodingfromtheLIP,specificallywithregardto standingwater,sonowaverunupdiscussionexists.SinceneitherthedesignbasisnortheMSFHI identifiedthisasanissue,thesevaluesaremarkedN/A.
References:
USARChapter2,FHRR 3.
DebriswasaccountedforintheLIPmodelbyassuming55%blockageofthespacesbetweenthe vehiclebarriersystem(VBS)concreteblocks.Thisblockagehastheeffectofincreasingthewater retentiontimearoundthepowerblock.ThehydrodynamiceffectsontheVBSareminimalsince therestillaresufficientflowpathstopreventexcessivehydrodynamicandhydrostaticloading.The VBSisasecurityfeature,notafloodbarrier.Basedonthelackoffreedebrisinthesurroundingarea thereisnoloadingexpectedfromdebris.BuildingloadsidentifiedincalculationCCSS020.013014 Rev.1areasfollows:
- Themaximumfloodvelocityandwaterdeptharoundeachbuildingisusedforloadcomputation.
Basedontheshortdurationandsmalllocalizedloadsthereisnoeffectonthestructuresasaresultof aLIPevent.ThesestructuresareeitherCategory1orCategory2andareevaluatedformore significantloadsthanthosepresentedbytheLIP.PertheDesignCriteriaManual,allwallsfor Category1seismicstructuresandCategory2nonseismicstructuresaredesignedwithhydrostatic andhydrodynamicloadsuptothe584ftlevel.Theseloadsincludesoilandwaterloads.Seismic Category1structuresareevaluatedwithloadsappliedinconjunctionwiththeseismicloads.These Table5.0.2MaximumLoadsonBuildings
Building
Max Velocity*
(fps)
Max Depth*
(ft)
Max Hydrostatic Load(psf)
Max Hydrodynamic Load(psf)
ContainmentStructure 3.87 1.30 81 29
AuxiliaryBuilding 2.46 1.23 77 12
TurbineBuilding 2.31 1.02 64 10
PersonnelShop 2.04 0.90 56 8
LLRadwasteStorage 1.47 0.76 47 4
ContainmentAccess 1.84 0.53 33 7
WaterTreatmentBuilding 6.14 1.30 81 73
IntakeStructure 5.48 0.39 24 58
DieselGeneratorBuilding 2.82 1.55 97 15
Page7of16 loadsaresignificantlygreaterthantheloadsfromtheLIPevent;thereforenoadverseconsequences resultfromtheLIP.
SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded (NB).
References:
CCSS020.13014Rev1,DesignCriteriaManualSectionII.G.2,USARChapter2&3.4 4.
DavisBesseislocatedonflatterrain.TheaveragevelocityofthefloodwatersatthepeakoftheLIPis 4.3fpsinthevicinityofthepowerblock.Verylittledebrisorsedimentwillbedepositedbasedonthe shortdurationoftheeventandtheimpermeablematerialsurroundingthepowerblockarea, preventingdebrisandsedimentbeingentrainedinfloodwaters.Thisareaisconcreteormacadam.
Thishardmaterialwillalsopreventscour,soitisnotconsideredanissue.Sincethedesignbasisdoes notdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
References:
CCSS020.13014Rev1,USARChapter2 5.
Noadditionaldetrimentaleffectswereidentified.SinceneitherthedesignbasisnortheMSFHI identifiedanyothersignificantdetrimentaleffects,thesevaluesaremarkedN/A.
References:
USARChapter2,FHRR 6.
NospecificadditionaleffectshavebeenidentifiedduringaLIPevent.Itisreasonabletoassume therewillbewindsassociatedwiththestorm.However,theraindurationoftheLIPeventisonly60 mins.ThepowerblockinternalareasarenotfloodedasaresultoftheLIP.Sinceneitherthedesign basisnortheMSFHIidentifiedthisasanissue,thesevaluesaremarkedN/A.
References:
Therewillbenoadversegroundwatersurchargeeffects.Theshortdurationofinundationand impermeablematerialssurroundingthepowerblockareawouldpreventanychangeinthe groundwater.Criticalstructuresareratedforanadditional250psfsurchargeloading.Thisitemis consideredbounded(B)bytheexistingdesignbasis.
References:
CCSS020.13014Rev1,DesignCriteriaManualSectionII.G.2 8.
Nospecificwarningtimeisidentified.AsoutlinedintheRAIresponsediscussingtheinterimactions, siteprocedureswillprovideguidanceintheeventofsevereweather.Theseactionscommencebased onweatherreportsoronexternalagencycontactingthecontrolroomwithnotificationofimpending severeweather.Theshiftmanagerthendirectsactionsbasedontheenvironmentalthreat.Basedon therunupofthefloodlevelsassociatedwithaLIP,thereisadequatetimeforthesitetorespondby shuttingdoors,hatchesandotheractionsneededtoprecludefloodingofvitalareas.Sincethedesign basisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
References:
CCSS020.13014Rev1,FHRRSection5,RAIResponsetoInterimActions,RAEP02830 Flooding,RAEP02810TornadoorHighWinds,RAEP02870StationIsolation,USARChapter2
Page8of16 9.
AsdiscussedinItem8thereisnospecifiedwarningtime.However,ascanbeseeninthevarious hydrographsinAttachment17ofCalcCCSS020.13014Rev.1,floodingabovegradefromLIPtakes approximately51minutestoaffectthecriticaldoors.Thisallowstheonsitepersonnelsufficienttime toensuredoors,hatchesetc.tobeclosedtopreventwateringress.AsstatedintheFHRRand subsequentRAIassociatedwithInterimactions,ithasbeendeterminedthattheseactionsare sufficienttoprotectsafetyrelatedequipment.Onedoordoesfloodpriorto51minutes,Door334.
Thisdooropensintotheturbinebuildingandwaterrisesabovethefloorelevationatapproximately 21minutes.AsdiscussedinSection5oftheFHRR,thereisacurbthatprotectssafetyrelated equipmentbelow585ftifwaterweretoenterthisdoor.Ascanbeseenbythehydrograph,the actualdepthofthewateris6.1in,whichisbelowthefloodheightprotectionprovidedbythecurb (8inperDrawingA0005).Therearemanydrainagepathstothelowerelevationsandthevolumeis sufficienttoprecludefloodingofsafetyrelatedequipment.Thisdoorisclosedaspartofsite responsetoincreasingwaterlevels.SincethedesignbasisdoesnotdiscussthisissueandtheMSFHI does,itisconsiderednotbounded(NB).
CalculationCCSS020.13014Rev.2,whichusedrefinedmethodology,reducedthewaterlevelstoa 585ftelevation,whichisthedoorsillheight,forallcriticaldoorsexceptforDoor334discussedabove anddeterminedtonotbeanimpact.Threeadditionaldoorstothewatertreatmentbuildingare subjecttominorfloodingandhavenoimpactonsafetyrelatedequipment.
References:
CCSS020.13014Rev1Attachment17,USARChapter2,FIP,FHRRSection5,RAI ResponsetoInterimActions,USARChapter2.
10.
Thetotalsiteinundationperiodinthepowerblockareais0.5hourswithonlyshortdurationsoftime abovethesillsforcriticaldoors.SincethedesignbasisdoesnotdiscussthisissueandtheMSFHI does,itisconsiderednotbounded(NB).
CalculationCCSS020.13014Rev.2,whichusedrefinedmethodology,reducedthewaterlevelstoa 585ft.elevation,whichisthedoorsillheight,forallcriticaldoorsexceptforDoor334discussed aboveanddeterminedtonotbeanimpact.Threeadditionaldoorstothewatertreatmentbuilding aresubjecttominorfloodingandhavenoimpactonsafetyrelatedequipment.
Ref.CCSS020.13014Rev.1Attachment17,USARChapter2,FIP,FHRRSection5,RAIResponseto InterimActions,USARChapter2 11.
ThesiteremainsaccessibleduringtheLIP.AsshowninFigure4.7.3ofcalculationCCSS020.13014 Rev.1,accessroadswillhavevaryingdepthsofwater.Thereareseveraldifferentaccesspointsto thesite.Thelowlyingareaswillhavepondingbutwillnotpreventsiteaccess.TheLIPisofshort duration,hasrelativelyshallowdepthsandhaslowwatervelocity.Sincethedesignbasisdoesnot discussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
References:
CCSS020.13014Rev.1Attachment17,USARChapter2,FIP,FHRRSection5,RAI ResponsetoInterimActions,USARChapter2 12.
PlantmodesarenotdiscussedintheUSARrelatedtofloodingevents.TheUSARdidnotidentifyany floodingimpactstothepowerblockorsafetyrelatedequipment.TheFLEXstrategydoesidentify differentresponsesbasedonplantmodeandtheavailabilityofsteamgeneratorsforheattransfer.
SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded (NB).
References:
USARChapter2,FIP,RAIResponsetoInterimActions
Page9of16 13.
NoadditionalfactorswereidentifiedassociatedwiththeLIP.Theeventisshortdurationandhaslow watervelocity,sowaterborneprojectilesarenotexpected.Sinceneitherthedesignbasisnorthe MSFHIidentifiedthisanissue,thesevaluesaremarkedN/A.
References:
USARChapter2,FHRR
Page10of16 Table1b-FloodCausingMechanismA(PMSS)orBoundingSetofParameters
FloodScenarioParameterPMSS Plant DesignBasis Flood FLEX Design BasisFlood Hazard MSFHI MSFHI Bounded (B)or Not Bounded (NB)
FloodLevelandAssociatedEffects 1.MaxStillwaterElevation 583.7ft 583.7ft 585.81ft NB 2.MaxWaveRunupElevation 590.3ft 583.7ft 589.88ft B
3.MaxHydrodynamic/Debris Loading(psf)
Not discussedin USAR Not discussed inUSAR SeeNote3 NB 4.EffectsofSediment Deposition/Erosion Not discussedin USAR Not discussed inUSAR SeeNote4 NB 5.Otherassociatedeffects (identifyeacheffect)
N/A N/A N/A N/A 6.ConcurrentSiteConditions 590.3ft 585ft 585.9ft NB 7.EffectsonGroundwater 250psf 250psf SeeNote7 B
FloodEventDuration 8.WarningTime(hours)
Varies Varies SeeNote8 NB 9.PeriodofSitePreparation (hours)
Not discussedin USAR Not discussed inUSAR SeeNote9 NB 10.PeriodofInundation(hours)
Not discussedin USAR Not discussed inUSAR 2.5 inthepower blockarea NB 11.PeriodofRecession(hours)
Not discussedin USAR Not discussed inUSAR SeeNote11 NB Other 12.PlantModeofOperations Not discussedin USAR Not discussed inUSAR Mode16 NB 13.OtherFactors N/A N/A N/A N/A
Page11of16 Additionalnotes,N/Ajustifications(whyaparticularparameterisjudgednottoaffectthe site),andexplanationsregardingthebounded/nonboundeddetermination 1.
AllelevationvalueswillbeintheSiteDatum,IGLD55,unlessnotedotherwise.SincetheMSFHIvalueis abovethedesignbasis,itisconsiderednotbounded(NB).
References:
CCSS020.13017Rev.0,CCSS020.13022Rev.0,FHRRSections2.1.4,2.1.8&3.7.4,USAR Section2.4.2.2.1 2.
WaverunupisdiscussedinNote6asitrelatestostormsurgeinpowerblockarea.SincetheMSFHI valueisbelowthedesignbasis,itisconsideredbounded(B).
Reference:
FHRRSections2.1.4&2.1.8 3.
Nospecificdebrisloadingwasprovidedinthestormsurgecalculationsrelatedtotheeffectsonpower blockstructures.However,thestormsurgewaterdepthisonlyslightlygreaterthantheLIPwaterdepth, andthewatervelocitiesaresignificantlyless.AsshownintheLIPtable,thesafetyrelatedstructures havesignificantmarginsrelatedtotheeffectsfromflooding.Therefore,nodetrimentaleffectsare expectedfromthePMSS(SeeNote7).NospecificdebrisloadingwasaccountedforinthePMSSmodel.
Thesiteisflatterrainandsurroundedbymarshland.Nosignificantdebrisisexpectedtobetransported tothepowerblockareabasedonthelowvelocitiesofthePMSSeventandthemultitudeofobstacles, i.e.fencelines,aroundthepowerblockareapreventingdebristransport.CalculationCCSS020.13017 Rev.0assumptionsstatethattheVBScouldbeaffectedduringthestormsurgeeventinthatsomeofthe blockscouldbedislodged.Theeffectofanydislodgedbarriersisassumedtobeminimalsincebarrier overtoppingisthefloodingmechanism.TheVBSisasecurityfeature,notadesignfloodbarrier.
SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
References:
CCSS020.13022Rev.0,FHRRSection3.7.4,CCSS020.13017Rev.0 4.
DavisBesseislocatedonflatterrain.TheUSARdoesnotdiscussfloodinginthepowerblockareaand thereforevelocityandscourwerenotaddressed.ThePMSSisashortdurationandlowvelocityevent (seeNote7).Thepowerblockandsurroundingareaaremostlymacadamandconcrete.Basedonthese hardmaterials,shortdurationandlowwatervelocities,scourisnotanissue.Thesesameparameters minimizesoildepositioninthepowerblockarea.Sincethedesignbasisdoesnotdiscussthisissueand theMSFHIdoes,itisconsiderednotbounded(NB).
References:
CCSS020.13017Rev.0 5.
Noadditionaldetrimentaleffectswereidentified.
SinceneitherthedesignbasisnortheMSFHIidentifiedthisasanissue,thesevaluesaremarkedN/A.
Reference:
CCSS020.13022Rev.0,FHRRSection3.7.4,CCSS020.13017Rev.0.
6.Discussconditionsthatcouldexistconcurrentwiththisfloodcausingmechanismorcombinedeffect flood(e.g.highwinds,iceformation,etc.)
ThespecificadditionaleffectidentifiedduringaPMSSeventisthePMWE,whichisrequiredtogenerate thePMSS.ThepowerblockareaisfloodedasaresultofthePMSS.Waverunupvaluesassociatedwith thePMSSincreasethefloodheightaroundthepowerblockby0.1ftduetowind.Thisincreasesthe standingwaterelevationfrom585.81ftto585.9ft.ThePMSSisashortdurationevent,andthe standingwaterinthepowerblockarearecedesinapproximately2.5hours.Thenewhazardremains boundedwithregardtothestormsurgeimpactontheearthenberms.Thedesignvaluefortheseberms
Page12of16 is590.3ftandtheMSFHIvalueis589.88ft.TheUSARdoesnotspecificallyaddressfloodingfromthe PMSSwithregardtostandingwaterandwaverunupeffectsinthepowerblockarea.Sincethedesign basisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
CalculationCCSS020.13017Rev.1usedarefinedanalysistoevaluatethePMSSevent,whichresulted innofloodinginthepowerblockarea.
References:
CCSS020.13022Rev.0,FHRRSection3.7.4,CCSS020.13017Rev.0 7.
Therewillbenogroundwatersurchargeeffects.Theshortdurationofinundation,approximately2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />,andimpermeablematerialssurroundingthepowerblockareawouldpreventanychangeinthe groundwater.Thepowerblockstructuresaredesignedforgroundwaterlevelsupto584ft.The auxiliarybuilding,containmentstructureandturbinebuildingdesignincludesa250psfsurchargeload.
Theintakestructurehas500psfsurchargeloadinitsdesign.ThesestructuresareeitherCategory1or Category2andareevaluatedformoresignificantloadsthanthosepresentedbythePMSS.Perthe DesignCriteriaManual,allwallsforCategory1seismicstructuresandCategory2nonseismicstructures aredesignedwithhydrostaticandhydrodynamicloadsuptothe584ftlevel.Theseloadsincludesoil andwaterloads.SeismicCategory1structuresareevaluatedwithloadsappliedinconjunctionwiththe seismicloads.TheseloadsaresignificantlygreaterthantheloadsfromthePMSSevent;thereforeno adverseconsequencesresultfromthePMSS.ThehydrostaticloadingfromthePMSSisasfollows:
Ifthehydrostaticloadweredirectlyappliedtothewallasagroundwatersurchargeload,thestructure designshavesufficientmarginstoprecludeanyadverseeffects.Also,thegroundwaterstudyperformed in2007indicatesthatgroundwatertendstoflowawayfromthepowerblockarearatherthan accumulatingagainstthepowerblocksubgradewalls.Thiswouldreduceanysurcharge.Sincethe designbasisdoesdiscussthisissue,itisconsideredbounded(B).
CalculationCCSS020.13017Rev.1usedarefinedanalysistoevaluatethePMSSevent,whichresulted innofloodinginthepowerblockarea.
References:
CCSS020.013017Rev.0,Groundwaterstudy,DesignCriteriaManualSectionII.G.2.6 MaximumLoadsonBuildings Observation Site NearestBuildings Max Velocity (fps)
MaxFlow Depth(ft)
Max Hydrostatic Load(psf)
Max Hydrodynamic Load(psf)
C4 AuxBuildingNorth 0.4 2.45 152.88 0.31 C13 ContainmentStructure 0.3 2.03 126.67 0.17 C14 AuxBuildingWest 0.6 1.18 73.632 0.69 C20 Intake Structure/Turbine 1.1 2.08 129.79 2.34 C22 TurbineBuilding 1.1 2.40 149.76 2.34
Page13of16 8.
Nospecificwarningtimeisidentified.AsoutlinedintheRAIresponsediscussinginterimactions,site procedureswillprovideguidanceintheeventofsevereweather.Theseactionscommencebasedon weatherreportsoranexternalagencycontactingthecontrolroomwithnotificationofimpendingsevere weather.Theshiftmanagerthendirectsactionsbasedontheenvironmentalthreat.Reviewofthedata presentedincalculationCCSS020.03017Rev.0indicatestheactualstormsurgetakeshoursto develop.Theshortesttimeshownfortheonsetofsitefloodingissixhours.ThePMSSdevelopment requireshighwindstooccur.Basedonthelengthoftimerequiredandthehighwindconditionneeded aswellastheantecedentlakelevelrequiredthesitewouldhaveenteredtheTornadoandHighWinds andtheStationFloodingprocedures.Thesitewouldhaveamplewarningtimetopreparebyshutting doors,hatches,andotheractionstoprecludefloodingofvitalareas.Additionally,theEmergency ResponseOrganization(ERO)wouldbestaffediftheseconditionsweretooccur,providingadditional staffasneeded.SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsidered notbounded(NB).
References:
CCSS020.013017Rev.0,FHRR,USARChapter2,RAIResponse,RAEP0283Flooding,RA EP02870StationIsolation,RAEP02810TornadoorHighWinds 9.
AsdiscussedinItem8thereisnospecifiedwarningtime.However,ascanbeseeninthevarious hydrographsandENERCONReportFNOCDB101PR001,thebuildupforthePMSStakesseveralhours.
Theshortesttimeidentifiedfortheonsetoffloodinginlowlyingsiteareasisthreehours.Areascloser tothepowerblockdonotbegintoflooduntilsixhoursafterthebeginningofthestorm.Thisallowsthe onsitepersonnelsufficienttimetoensuredoors,hatchesetc.tobeclosedtopreventwateringress.As statedintheFHRRandsubsequentRAIassociatedwithinterimactions,proceduralactionsaresufficient toprotectsafetyrelatedequipment.
SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
CalculationCCSS020.13017Rev.1usedarefinedanalysistoevaluatethePMSSevent,whichresulted innofloodinginthepowerblockarea.
References:
CCSS020.013017Rev.0,FHRR,USARChapter2,ENERCONReportFNOCDB101PR001,RAI Response,RAEP0283Flooding,RAEP02870StationIsolation,RAEP02810TornadoorHighWinds.
10.
AreasaroundthepowerblockbegintofloodatT+6hourswithwaterrisingabovesitegradeof584ft.
Watercontinuestoriseforapproximatelytwohoursandthenbeginstorecede.Waterwillrecede below584ftbyT+12hoursforatotaldurationabove584ftofsixhours.Criticaldoorsandopeningsare locatedatthe585ftelevation.Theperiodofinundationabove585ftisapproximately2.5hoursinthe powerblockarea.
StagingAreaBisflooded,precludingthereceiptofNSRCequipmenttosupportPhase3activities.The designatedstagingarea,StagingAreaB,andtheassociatedhaulpathareinundatedforapproximately 44hours.FloodingbeginsatT+3hours,peaksbyT+8hoursandslowlyrecedes.Thestormsurgewill alsoimpactthesiteaccessviatheroadways.AsdiscussedinNote11,someofthesiteaccessroadsare floodedfor14hours.AlternatesstagingareashavebeenevaluatedinENERCONReportFNOCDB101PR 001.ThesealternateareasaredryorhaveminimalfloodingandwillbeavailableduringaPMSSevent.
AsdiscussedinNote8thesitewouldprepareforthepotentialinundationandroadwayfloodingthrough executionoftheEPproceduresuptoandincludingthestationisolationprocedure.Asthesitesaccess becomesthreatenedtheEROwillmobilizeandadditionalsitepersonnelwillbedesignatedtosupport thestation.
SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
CalculationCCSS020.13017Rev.1usedarefinedanalysistoevaluatethePMSSevent,whichresulted innofloodinginthepowerblockarea.
Page14of16
References:
CCSS020.013017Rev.0,FHRR,USARChapter2,ENERCONReportFNOCDB101PR001,RAI Response,RAEP0283Flooding,RAEP02870StationIsolation,RAEP02810TornadoorHighWinds 11.
ThePMSSinthepowerblockisabovethe585ftelevationfor2.5hours.Thefloodedareasaroundthe site,includingtheaccessroads,remainfloodedforasignificantlylongerperiod.Asdiscussedabove, StagingareaBisfloodedinexcessof44hoursasitisalowspotonthesite.Thenorthaccessroad beginstofloodatT+3hours,peaksatT+5hours,andisfloodedfor14hours.Severalotherroadwaysare alsofloodedforasignificantperiod.ThePMSScalculationsdidnotevaluateroadwaysexternaltothe site.AsdiscussedinNote10,thesitehasastationisolationprocedurethataddressesactionsinthe eventafloodwouldpreventsiteaccess.ENERCONReportFNOCDB101PRestimatesthefloodwaters recedingfromthelowspotsonsitewithin44hoursoftheonsetofflooding,butbasedontopography andnaturaldrainageofStagingAreaB,itsavailabilityisindeterminate.Alternatestagingareasare availableasdiscussedinNote10.ExistingEROprocessesrecognizetheneedtobeabletosupportthe sitesneedsintheeventofastationisolationevent,includingdeliveryofadditionalpersonneland supplies.Asdiscussedinthestationfloodingprocedure,higherelevationroadwaysaredesignatedas themostlikelytoclearfirstintheeventofflooding,basedontheirelevations.
SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
References:
ENERCONReportFNOCDB101PR001,CCSS020.13017Rev.0,RAIResponse,RAEP0283 Flooding,RAEP02870StationIsolation,RAEP02810TornadoorHighWinds 12.
PlantmodesarenotdiscussedintheUSARrelatedtofloodingevents.TheFLEXstrategydoesidentify differentresponsesbasedonplantmodeandtheavailabilityofsteamgeneratorsforheattransfer.
SincethedesignbasisdoesnotdiscussthisissueandtheMSFHIdoes,itisconsiderednotbounded(NB).
References:
FIP,USARChapter2 13.
NoadditionalfactorswereidentifiedassociatedwiththePMSS.Thefloodinginthepowerblockarea hasashortdurationandlowwatervelocity,sowaterborneprojectilesarenotexpected.Sinceneither thedesignbasisnortheMSFHIidentifiedthisasanissue,thesevaluesaremarkedN/A.
References:
Page15of16 2.3. NEI1206,Rev.2,SectionG.4-EvaluationofMitigatingStrategiesfortheMSFHI 2.3.1NEI1206,Rev.2,SectionG.4.1-AssessmentofCurrentFLEXStrategies TheoverallplantresponsestrategiestoanELAPandlossofultimateheatsinkevent canbeimplementedasdescribedintheFinalImplementationPlanusingthe current FLEXprocedures,equipmentandpersonnel,providedthefollowingmodificationsare implemented:
- a. TriggerpointsestablishedtoallowforpredeploymentofN+1equipment.
- b. UtilizationofalternateNSRCstagingareas,ifrequired.
2.3.1.1 Conclusion-ModifyFLEXStrategy.
2.3.2NEI1206,Rev.2,SectionG.4.2-AssessmentforModifyingFLEXStrategies:
TheexistingFLEXmitigationstrategiescanbeimplementedwithrelativelyminor modifications.
TheMSFHILIPeventproducesrainfallamountsthat challengethecurrentFLEX mitigationstrategies.LIPwaterlevelsfloodtheN+1equipmentdeploymentpath,and itremainsfloodedforanextendedperiodoftime.TheLIPalsofloodsthedesignated sitestagingareaforNSRCequipmentreceiptaffectingPhase3activities.
AlternatestagingareashavebeenidentifiedandverifiedtobeavailableduringaLIP eventtosupportreceiptofNSRCequipment.Atriggerpointwillbedevelopedtoallow forpredeploymentofN+1equipmentpriortofloodingofthedeploymentpath.
Thecurrentmitigationstrategytimelinecontainssufficientmarginforlocalfloodwaters torecedepriortotherequiredFLEXNactionsorequipmentdeploymentasdescribedin theFIPforFLEXPhase1andPhase2actions.Theuseofalternatestagingareasisalso anoptionthatiscurrentlyaddressedintheSAFERPlaybook,whichwouldallowfor completionofFLEXPhase3actions.
TheMSFHIPMSScausesfloodingoftheNSRCstagingareaatthesiteprecludingitsuse.
ThePMSSalsofloodstheN+1equipmentdeploymentpath.Thefloodingofthispath doesnotoccuruntilthreehoursintotheeventallowingsufficienttimeforthepre deploymentofN+1equipment.
AlternatestagingareashavebeenidentifiedandverifiedtobeavailableduringaPMSS eventtosupportreceiptofNSRCequipment.Atriggerpointwillbedevelopedtoallow forpredeploymentofN+1equipmentpriortofloodingofthedeploymentpath.
Page16of16 Thecurrentmitigationstrategytimelinecontainssufficientmarginsanddiversityto allowsuccessfulimplementationoftheFLEXstrategyusingFLEXNequipmentforPhase 1andPhase2actions,aswellastheversatilitytousethealternatestagingareasto supportPhase3activities.
NorevalidationisrequiredasthesechangesdonotaffecttheFLEXstrategy implementationtimelines.
2.4. References
- 1. FHRRRev1-ML14070A108LetterFENOCtoNRC-Dated3/11/2014,L1404, FirstEnergyNuclearOperatingCompany(FENOC)ResponsetoNRCRequestfor InformationPursuantto10CFR50.54(f),RegardingtheFloodingAspectsof Recommendation2.1oftheNearTermTaskForce(NTTF)ReviewofInsightsfromthe FukushimaDaiichiAccident
- 2. FHRRRev2-ML15750A023-LetterFENOCtoNRC-Dated2/25/2015,L15043, RevisiontoFloodHazardReevaluationReportinResponsetoNearTermTask ForceRecommendation2.1(TACNo.MF3721)
- 3. RAIresponse-ML14198A400-LetterFENOCtoNRCDated7/17/2014,L14 235,SupplementtoFloodHazardReevaluationsReportinResponsetoNearTerm TaskForceRecommendation2.1
- 4. StaffAssessment-ML15239B212LetterNRCtoFENOC-Dated9/3/2015, DavisBesseNuclearPowerStation,Unit1InterimStaffResponseToReevaluated FloodHazardsSubmittedInResponseTo10CFR50.54(f)InformationRequest FloodCausingMechanismReevaluation(TACNO.MF3721)
- 5. NORMLP7221,DavisBesseFloodingMitigatingStrategyAssessmentSupport Document