RS-12-162, Company, LLCs 180-Day Response to NRC Request for Information Pursuant to 10CFR50.54(f) Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident
| ML12332A380 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 11/27/2012 |
| From: | Kaegi G Exelon Generation Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RS-12-162 | |
| Download: ML12332A380 (25) | |
Text
RS-12-162 November 27, 2012 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
Exelon Generation Company, LLCs 180-day Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding the Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident
References:
- 1. NRC Letter, Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident, dated March 12, 2012
- 2. NRC Letter, Endorsement of Nuclear Energy Institute (NEI) 12-07, Guidelines For Performing Verification Walkdowns of Plant Flood Protection Features, dated May 31, 2012
- 3. Exelon Generation Company, LLCs 90-day Response to NRC Request for Information Pursuant to 10 CFR 50.54(f) Regarding Recommendations 2.1 and 2.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident (Flooding), dated June 11, 2012 On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued Reference 1 to all power reactor licensees. Enclosure 4 of Reference 1 contains specific Requested Actions, Requested Information, and Required Responses associated with Recommendation 2.3 for Flooding. On June 11, 2012, Exelon Generation Company, LLC (EGC) submitted the 90-day response requested in Enclosure 4 of Reference 1, confirming that EGC would use the NRC-endorsed flooding walkdown procedure (Reference 3).
U.S. Nuclear Nuclear Regulatory Regulatory Commission Commission 180-Day Response Response to 50.54(f) Letter Letter NTTF Recommendation 2.3: Flooding 2.3: Flooding November 27,2012 November 27, 2012 Page 2 flooding Recommendation For flooding Recommendation 2.3 2.3 (walkdowns),
(walkdowns), Enclosure Enclosure 44 ofof Reference 1 states statesthat thatwithin within 180 days of of the the NRC's NRC's endorsement of the walkdown walkdownprocess process (Reference 2), 2), each addressee addressee willsubmit will submitaafinal finalresponse, response, including includingaalist listofofany anyareas areasthat thatare are unable unable toto be be inspected due due toto inaccessibility and inaccessibility and a schedule schedule forfor when the the walkdown walkdown will be completed.
will be completed. ThisThis letter letter provides provides the the Byron Station, Byron Station, Units Units11andand 22 180-day 180-day response response to Reference Reference 11 forfor Flooding Flooding Recommendation 2.3.
Conditions identified Conditions identifiedduring duringthethewalkdowns walkdownswere weredocumented documented and and entered entered into into the corrective corrective action program. Performance Performanceof ofthe thewalkdowns walkdownsprovidedprovided confirmation, confirmation, with two exceptions, that with two flood protection flood protection features features are in in place, are are in in good good condition condition and and will perform as will perform as credited in the current licensing basis.
basis. The Thetwotwo deficiencies deficiencieswill will be be restored restored tototheir theiroriginal original design designfor for resolution of resolution of the the issues.
issues. 1 to to this this letter letter provides provides the the requested requestedinformation informationfor forByron Byron Station Station Units Units11and and2.2.
This letter contains no new regulatory regulatory commitments.
you have any questions Should you questions concerning concerning the the content content ofof this this letter, letter, please please contact contactRon RonGaston Gaston at (630) 657-3359.
II declare declare under penalty of perjuryperjury that thatthe the foregoing foregoingisistrue trueand and correct.
correct. Executed on on the the 27th 27th day of November 2012.
Respectfully,
.~~
Glen T. Kaegi Director - Licensing Licensing & & Regulatory RegulatoryAffairs Affairs Exelon Generation Generation Company, LLC
Enclosures:
- 1. Flooding Flooding Walkdown Walkdown ReportReport InIn Response Response To To TheThe 50.54(f) 50.54(f) Information Information Request RequestRegarding Regarding Near-Term Task Force Recommendation Recommendation 2.3: 2.3: Flooding Flooding for the Byron Station, Units 1 and 2 cc: Director, Office of Nuclear Nuclear Reactor Reactor Regulation Regulation Regional Administrator Administrator -- NRCNRC Region Region III III NRC Senior Resident Inspector - Byron Byron UnitsUnits 11and and 22 NRC Project Manager, NRR - Byron Byron Units Units 11andand 22 Illinois Emergency Management Illinois Emergency Management AgencyAgency -- Division Division of Nuclear Safety Safety
U.S. Nuclear Regulatory Commission 180-Day Response to 50.54(f) Letter NTTF Recommendation 2.3: Flooding November 27, 2012 Page 3 Enclosure 1 Flooding Walkdown Report In Response To The 50.54(f) Information Request Regarding Near-Term Task Force Recommendation 2.3: Flooding for the Byron Station, Units 1 and 2 (22 pages)
FLOODING WALKDOWN REPORT IN RESPONSE TO THE 50.54(t) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.3: FLOODING for the BYRON NUCLEAR POWER STATION 4450 N. GERMAN CHURCH ROAD BYRON IL, 61010 Facility Operating License No. NPF-37 / NPF-66 NRC Docket No. 50-454/50-455 m7 1
~A. .!li.ILilili
. .... .. E.. . e.. .*.l.
Exelon Generation Company, LLC 4300 Winfield Road Warrenville IL, 60555 Prepared by:
Sargent & Lundy LLC 55 E. Monroe Chicago IL, 60603 100% Report, Rev. 1, 11/02/12 (Supersedes Rev. 0 in its entirety)
Signature Preparer:
Reviewer:
Approver:
Lead Responsible Engineer Branch Manager:
Senior Manager:
Corporate 11/7/12 Acceptance: Joseph V. Bellini/Corp. SME
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Contents
1. EXECUTIVE
SUMMARY
............................................................................................................................... 2
2. PURPOSE .................................................................................................................................................... 3
a. Background ............................................................................................................................................ 3
b. SiteDescription ...................................................................................................................................... 4
c. RequestedActions ................................................................................................................................. 5
d. RequestedInformation .......................................................................................................................... 6
3. METHODOLOGY ......................................................................................................................................... 7
a. OverviewofNEI1207(WalkdownGuidance) ...................................................................................... 7
b. ApplicationofNEI1207 ........................................................................................................................ 8
c. ReasonableSimulations ......................................................................................................................... 9
d. WalkdownInspectionGuidance .......................................................................................................... 10
4. RESULTS ................................................................................................................................................... 11
a. RequestedInformationItem2(a)-DesignBasisFloodHazards......................................................... 11
b. RequestedInformationItem2(b)-CLBProtectionandMitigationFeatures..................................... 12
c. RequestedInformationItem2(c)-FloodWarningSystems............................................................... 13
d. RequestedInformationItem2(d)-FloodProtectionSystem/BarrierEffectiveness .......................... 13
e. RequestedInformationItem2(e)-ImplementationofWalkdownProcess....................................... 15
f. RequestedInformationItem2(f)-FindingsandCorrectiveActionsTaken/Planned ......................... 15
g. RequestedInformationItem2(g)-Cliff-EdgeEffectsandAvailablePhysicalMargin....................... 17
h. RequestedInformationItem2(h)-Planned/NewlyInstalledFloodProtectionEnhancements........ 18
5. CONCLUSIONS.......................................................................................................................................... 18
6. REFERENCES ............................................................................................................................................. 20
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- 1. EXECUTIVE
SUMMARY
In response to the Nuclear Regulatory Commission (NRC) Request for Information regarding NearTerm
Task Force (NTTF) Recommendation 2.3, a flooding walkdown was conducted at Byron Nuclear Power
Station to verify that plant features credited in the current licensing bases (CLB) for protection and
mitigation from external flood events are available, functional, and properly maintained. The flooding
walkdownwasconductedbetweenJuly31andAugust2,2012.AnadditionalwalkdownatByronfortwo
featuresidentifiedduringtheBraidwoodwalkdownswasperformedonAugust23,2012.
The scope of the flooding walkdown was developed following a detailed review of all relevant licensing
documents. Since Byron is situated above the probable maximum flood (PMF) level, the station relies
entirely on passive features incorporated in the design to keep water out of the plant, specifically site
runoff from a local intense precipitation (LIP) event and groundwater. The flooding walkdown scope
consistedoffourmainparts.
x Thewalls,floorsandpenetrationsthroughthewallsandfloorsintheRiverScreenHouseEssential
ServiceWater(SX)MakeupPumpDieselDrivecubicleswereinspected.
x TheMainSteamIsolationValve(MSIV)Rooms,RadwasteTruckBay,FuelHandlingBuildingandthe
RefuelingWaterStorageTank(RWST)tunnelexteriorhatcheswereinspectedtoensurerunofffrom
LIPiskeptoutofthesafetyrelatedbuildings.
x Anoutdoorwalkdownwasconductedtoverifythatplantmodificationsimplementedsinceoriginal
construction, such as security barrier installation and changes to topography, do not adversely
affectplantfloodingprotection.
x The belowgrade structures (i.e., basement walls and basement slabs and penetrations through
thesewallsandfloors)inthemainpowerblockwereinspected.TheseareasarecreditedintheCLB
tokeepgroundwaterandrunofffromLIPoutofthesafetyrelatedbuildings.
The methodology and acceptance criteria for the evaluation of flood protection features was developed
based on Nuclear Energy Institute (NEI) report 1207 [Rev 0A](Reference 2), Guidelines for Performing
VerificationWalkdownsofPlantProtectionFeatures.
Visualinspectionsofwalls,floorsandpenetrationsthroughthewallsandfloorswereconductedtoverify
there are no observable structural deficiencies that may impact the structures ability to perform its
intendedfloodprotectionfunction.
With two exceptions, inspections of walls, floors and penetrations confirmed that credited flood barriers
areinplaceandarecapableofperformingtheirintendedfunction.AsmallslabthatservesasanLIPcurb
betweentheRadwasteTruckBayandtheAuxiliaryBuildingwasobservedasnotperdesign.Theslabis
actuallyinstalled12belowthedesignedelevation(0.82belowtheLIPfloodlevel).CaulkingaroundtheLIP
curb located in the 1A/1D Main Steam Isolation Valve (MSIV) room was identified as degraded. These
observations, and any other that could not be immediately judged as acceptable, were entered into the
CorrectiveActionProgram(CAP)fordispositionresultinginthesetwodeficiencies.
Whetherconduitsfrom manholesorcablevaults couldprovide apathfor groundwater orrainwaterto
safety related buildings was considered relevant to the walkdown scope. Conduits from manholes/cable
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vaultsgenerallyarenotroutedtosafetyrelatedbuildingsatByron.Inafewcases,thereareconduitsthat
turnupandterminateabovegradelevelsuchthatnopathforwaterisprovided.Groundwater/rainwater
leakagethroughconduitsintosafetyrelatedbuildingsatByronwasnotidentified.ConduitsatByrondonot
provideapathforgroundwaterorrainwatertoentersafetyrelatedbuildings(Reference21).
Asmallportionofthetotalfloorandwallareaswithinthewalkdownscopeweredeemedinaccessibleand
were not inspected. Reasonable assurance that these portions of the walls and floors are acceptable is
basedonthefactthatvisualinspectionofthewallsandfloorsinthesebuildingsandthroughouttheplant
revealednodeficienciesordegradationthatwouldpreventperformanceoffloodprotectionfunctions.
Therearenodeferredcomponents/areasrequiringfuturereview.
Performanceofthewalkdownsprovidedconfirmation,withtwoexceptions,thatfloodprotectionfeatures
are in place, are in good condition and will perform as credited in the current licensing basis. The two
deficiencies will be restored to their original design for resolution of the issues. Observations not
immediatelyjudgedasacceptablewereaddressedanddispositionedundertheCorrectiveActionProgram
resultinginthesetwodeficiencies.
Atotalof14IssueReports(IRs)wereenteredintheCAPasaresultofthiseffort.TheseIRsaredescribedin
Table2intheConclusionsectionofthisreport.
TheoutcomeoftheCAPdispositionincludedtwodeficiencyfindings.Therearenoobservationsawaiting
finaldispositioninCAP.
- 2. PURPOSE
- a. Background
InresponsetothenuclearfueldamageattheFukushimaDaiichipowerplantduetotheMarch11,2011
earthquakeandsubsequenttsunami,theUnitedStatesNuclearRegulatoryCommission(NRC)established
theNearTermTaskForce(NTTF)toconductasystematicreviewofNRCprocessesandregulations,andto
make recommendations to the Commission for its policy direction. The NTTF reported a set of
recommendations that were intended to clarify and strengthen the regulatory framework for protection
againstnaturalphenomena.
On March 12, 2012, the NRC issued an information request pursuant to Title 10 of the Code of Federal
Regulations,Section50.54(f)(10CFR50.54(f)or50.54(f))(Reference3)whichincludedsix(6)enclosures:
x [NTTF]Recommendation2.1:Seismic
x [NTTF]Recommendation2.1:Flooding
x [NTTF]Recommendation2.3:Seismic
x [NTTF]Recommendation2.3:Flooding
x [NTTF]Recommendation9.3:EP
x LicenseesandHoldersofConstructionPermits
In Enclosure 4 of Reference 3, the NRC requested that licensees perform flood protection walkdowns to
identify and address plantspecific degraded, nonconforming, or unanalyzed conditions and cliffedge
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effects (through the corrective action program) and verify the adequacy of monitoring and maintenance
procedures.(Seenotebelowregardingcliffedgeeffects.)
Structures,systems,andcomponents(SSCs)importanttosafetyaredesignedeitherinaccordancewith,or
meettheintentof,AppendixAto10CFRPart50,GeneralDesignCriteria(GDC)2.GDC2statesthatSSCs
important to safety at nuclear power plants must be designed to withstand the effects of natural
phenomena, including floods, without loss of capability to perform their intended safety functions. For
flooding walkdowns, identifying/addressing plantspecific degraded, nonconforming, or unanalyzed
conditions (through the corrective action program) and verifying the adequacy of monitoring and
maintenanceproceduresisassociatedwithfloodprotectionandmitigationfeaturescreditedinthecurrent
design/licensing basis. New flood hazard information will be considered in response to Enclosure 2 of
Reference3.
OnbehalfofExelonGenerationCompany,LLC(Exelon),thisreportprovidestheinformationrequestedin
theMarch12,50.54(f)letter;specifically,theinformationlistedundertheRequestedInformationsection
ofEnclosure4,paragraph2(athroughh).TheRequestedInformationsectionofEnclosure4,paragraph
1 (a through j), regarding flooding walkdown procedures, was addressed via Exelons June 11, 2012,
acceptance(Reference1)oftheindustrywalkdownguidance(Reference2).
NoteRegardingCliffEdgeEffects
Cliffedge effects were defined by the NTTF Report (Reference 5), which noted that the safety
consequencesofafloodingeventmayincreasesharplywithasmallincreaseinthefloodinglevel.While
theNRCusedthesametermastheNTTFReportintheMarch1250.54(f)informationrequest(Reference
3), the information the NRC expects utilities to obtain during the Recommendation 2.3: Flooding
Walkdowns is different. To clarify, the NRC is now differentiating between cliffedge effects (which are
dealt with under Enclosure 2 of Reference 3) and a new term, Available Physical Margin (APM). APM
informationwillbecollectedduringthewalkdowns,butwillnotbereportedintheresponsetoEnclosure4
of Reference 3. The collected APM information will be available for use in developing the response to
Enclosure2ofReference3.
- b. SiteDescription
ByronStationislocated3milessouthwestofByroninOgleCounty,innorthcentralIllinois,and2mileseast
of the Rock River, at about river mile 115 from the confluence with the Mississippi River. The plant site
occupiesabout1300acresandincludesaportionofWoodlandCreek,whichisanintermittentstreamanda
3mile long tributary to the Rock River. The elevations of the Rock River at the site corresponding to
themeanannualflowandtheprobablemaximumflood(PMF)are672.0feetand708.3feet,respectively.
(AllelevationshereinrefertoUSGS1929datum).Theplantgradeandfloorelevationis869.0feetand870
feetUSGS29,respectively.ThePMFlevelisbelowtheleveloftheplantgradefloor;therefore,itwillhave
no damaging effect on any safetyrelated structure, except the river screen house at the Byron Station
whichisdiscussedbelow(Reference13,Section2.4.1.1).
The Byron River Screen House is the only structure which could be affected by floods on the Rock River.
This structure is designed for the combined event flood and waves produced by a 40 mph wind. The
makeup water system for the ultimate heat sink consists of a combination of the River Screen House SX
makeuppumpsanddeepwells.Thedeepwells,locatedattheplantsite,areabovethePMFwaterlevels
andusedformakeupwhenevertheriverscreenhouseisunavailable.TheRiverScreenHouseisdesigned
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forthecombinedeventflood.ThecombinedeventfloodstagefortheRockRiverattheriverscreenhouse
is698.68feet.Themaximumwaverunupplussetupis4.71feet.Topreventdamageduetoflood,the
floorelevationisestablishedat702feetanda4foothighfirewallenclosestheareawheresafetyrelated
equipmentislocated(Reference13,Section3.4.1.1).
The local intense precipitation (LIP) event causes only minor local flooding. Grading and drainage at the
ByronSitearedesignedtoensurethatnofloodingofsafetyrelatedfacilitieswilloccurforeventsassevere
as the LIP. It also has no appreciable effect on the maximum perched groundwater elevation of 824 feet
(Reference13,Sections2.4.2.3and3.4.1.1,andReference14,DCST03BY/BR).
The structures that house safetyrelated equipment are the Containment, Auxiliary and Fuel Handling
buildings. These structures all have reinforced concrete walls below grade level. The only exterior,
personnel, or equipment access to these buildings is at grade level or above. All pipes penetrating the
exteriorwallsareprovidedwithwaterpenetrationsleeves.Waterstopsareprovidedinallhorizontaland
verticalconstructionjointsinallexteriorwalls,asrequired(Reference13,Section3.4.1.3).
Accesstotheplantsitewouldbemaintainedduringanyfloodconditions.ThesiteisboundedbyCounty
Highway2(GermanChurchRoad),DeerpathRoad,andRazorvilleRoad.Theroadelevationsvaryfrom769
feet to 883 feet. None of the above roads would be affected by the PMF from the Rock River. Other
principal roads in the area are IllinoisState Highway 72, about3 miles northeast and Illinois Highway 64,
about4milessouth.TheplantsiteisalsoaccessiblefromtheChicagoandNorthWesternRailroadwhichis
about3milesnortheastofthesite.Groundtopographyalongtherailroadtracksishighandthetracksare
wellabovethePMFleveloftheRockRiver(Reference13,Section2.4.1.1).
- c. RequestedActions
PerEnclosure4ofReference3,theNRCrequeststhateachlicenseeconfirmuseoftheindustrydeveloped,
NRCendorsed,floodwalkdownprocedures orprovideadescriptionofplantspecificwalkdownprocedures.
In a letter dated June 11, 2012 (Reference 1), Exelon confirmed that the flooding walkdown procedure
(Reference2),endorsedbytheNRConMay31,2012,willbeusedasthebasisforthefloodingwalkdowns.
OtherNRCsrequestedactionsinclude:
(1) PerformfloodprotectionwalkdownsusinganNRCendorsedwalkdownmethodology;
(2) Identifyandaddressplantspecificdegraded,nonconforming,orunanalyzedconditions,aswellas,
cliffedge effects through the corrective action program, and consider these findings in the
Recommendation2.1hazardevaluations,asappropriate;
(3) Identifyanyotheractionstakenorplannedtofurtherenhancethesitefloodprotection;
(4) Verifytheadequacyofprograms,monitoringandmaintenanceforprotectionfeatures;and
(5) ReporttotheNRCtheresultsofthewalkdownsandcorrectiveactionstakenorplanned.
Per Enclosure 4 of Reference 3 also states, If any condition identified during the walkdown activities
represents a degraded, nonconforming, or unanalyzed condition (i.e. noncompliance with the current
licensingbasis)foranSSC,describeactionsthatweretakenorareplannedtoaddresstheconditionusing
theguidanceinReference6,includingenteringtheconditioninthecorrectiveactionprogram.Reporting
requirementspursuantto10CFR50.72shouldalsobeconsidered.
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- d. RequestedInformation
PerEnclosure4ofReference3,
- 1. TheNRCrequeststhateachlicenseeconfirmthatitwillusetheindustrydeveloped,NRCendorsed,
floodingwalkdownproceduresorprovideadescriptionofplantspecificwalkdownprocedures.As
indicatedpreviously,ExelonsletterdatedJune11,2012(Reference1),confirmedthattheflooding
walkdown procedure (Reference 2), endorsed by the NRC on May 31, 2012, will be used as the
basisforthefloodingwalkdowns.
- 2. The NRC requests that each licensee conduct the walkdown and submit a final report which
includesthefollowing:
- a. Describe the design basis flood hazard level(s) for all floodcausing mechanisms, including
groundwateringress.
- b. Describe protection and mitigation features that are considered in the licensing basis
evaluationtoprotectagainstexternalingressofwaterintoSSCsimportanttosafety.
- c. Describeanywarningsystemstodetectthepresenceofwaterinroomsimportanttosafety.
- d. Discuss the effectiveness of flood protection systems and exterior, incorporated, and
temporary flood barriers. Discuss how these systems and barriers were evaluated using the
acceptancecriteriadevelopedaspartofRequestedInformationitem1.h.
- e. Present information related to the implementation of the walkdown process (e.g., details of
selectionofthewalkdownteamandprocedures,)usingthedocumentationtemplatediscussed
inRequestedInformationitem1.j,includingactionstakeninresponsetothepeerreview.
- f. Results of the walkdown including key findings and identified degraded, nonconforming, or
unanalyzed conditions. Include a detailed description of the actions taken or planned to
addresstheseconditionsusingtheguidanceinRegulatoryIssuesSummary200520,Revision1,
Revision to NRC Inspection Manual Part 9900 Technical Guidance, "Operability Conditions
AdversetoQualityorSafety,"includingenteringtheconditioninthecorrectiveactionprogram.
- g. Document any cliffedge effects identified and the associated basis. Indicate those that were
entered into the corrective action program. Also include a detailed description of the actions
takenorplannedtoaddresstheseeffects.SeenoteinSection1aregardingtheNRCschangein
positiononcliffedgeeffects.
- h. Describe any other planned or newly installed flood protection systems or flood mitigation
measures including flood barriers that further enhance the flood protection. Identify results
andanysubsequentactionstakeninresponsetothepeerreview.
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- 3. METHODOLOGY
- a. OverviewofNEI1207(WalkdownGuidance)
In a collaborative effort with NRC staff, NEI developed and issued report 1207 [Rev 0A], Guidelines for
PerformingVerificationWalkdownsofPlantProtectionFeatures,datedMay2012(Reference2).TheNRC
endorsed NEI 1207 on May 31, 2012 with amendments. NEI 1207 was updated to incorporate the
amendments and reissued on June 18, 2012. On June 11, 2012, Exelon issued a letter to the NRC
(Reference 1) stating that the endorsed flooding walkdown procedure (Reference 2) will be used as the
basisforthefloodingwalkdowns.NEI1207providesguidanceonthefollowingitems:
x Definitions
o IncorporatedBarrier/Feature
o TemporaryBarrier/Feature
o ExteriorBarrier/Feature
o CurrentLicensingBasis(CLB)
o DesignBases
o Inaccessible
o RestrictedAccess
o Deficiency
o FloodProtectionFeatures
o ReasonableSimulation
o VisualInspection
o CliffEdgeEffects
o AvailablePhysicalMargin
o VarietyOfSiteConditions
o FloodDuration
x Scope
o BasisforEstablishingWalkdownScope
o IdentifyFloodProtectionFeatures(WalkdownList)
x Methodology
o DevelopWalkdownScope
o PrepareWalkdownPackages
o WalkdownTeamSelectionandTraining
o PerformPreJobBriefs
o InspectionofFloodProtectionAndMitigationFeatures
General
IncorporatedorExteriorPassiveFloodProtectionFeatures
IncorporatedorExteriorActiveFloodProtectionFeatures
TemporaryPassiveFloodProtectionFeatures
TemporaryActiveFloodProtectionFeatures
ProcedureWalkthroughandReasonableSimulation
o ReviewofTheMaintenanceandMonitoringofFloodProtectionFeatures
o ReviewofOperatingProcedures
o DocumentationofAvailablePhysicalMargins
o DocumentingPossibleDeficiencies
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o RestrictedAccess,orInaccessible
x AcceptanceCriteria
x EvaluationandReportingResultsofTheWalkdown
x RelatedInformationSources
x Examples
x WalkdownRecordForm
x SampleTrainingContent
x WalkdownReport
- b. ApplicationofNEI1207
AtByron,theapproachtothefloodingwalkdownsincludedthreephases:
Phase1-Preparation,Training,DataGathering,andScoping
Exelon developed a fleetwide program and training course for walkdown team members to
providecompleteandconsistentimplementationofNEI1207guidelines.Inaddition,allwalkdown
teammemberscompletedtheapplicableNANTeLtrainingandtesting.Datagatheringbeganwith
identificationofstationspecificlicensingcommitmentsandstationdesignbasisrelativetoexternal
flooding events. This included review of the Byron Updated Final Safety Analysis Report (UFSAR)
(Reference13),identificationofdrawingsshowingfloodprotectionfeaturesandreviewofstation
proceduresandcalculationsrelativeexternalfloodingevents.Awalkdownscopewasdevelopedto
capturefeaturescreditedasperformingafloodprotectionfunctioninthecurrentlicensingbasis.A
walkdownlistwaspreparedidentifyingthespecificfeaturestobeinspected.Foreachfeatureon
thewalkdownlist,awalkdownpackagewaspreparedforusebythewalkdownteaminperforming
anddocumentingthewalkdown.
ThescopedevelopedforthewalkdownsatByronincludedthefollowing:
x The floors and walls enclosing the service water (SX) makeup pump rooms in the river
screenhouse.Scopeincludedinspectionofallpenetrations.
x The floors and exterior watertight walls (up to max groundwater water level) of the
Auxiliary building. The Containment building was not included in the inspection scope
becausetheexteriorwallsandthefloorarecreditedwithleaktightnessbasedonperiodic
ILRTtesting,andthelowestelevationofthebuildingisabovethemaximumgroundwater
elevation.
x Whetherconduitsfrommanholesorcablevaultscouldprovideapathforgroundwateror
rain water to enter safety related buildings was considered relevant to the walkdown
scope. Conduits from manholes/cable vaults generally are not routed to safety related
buildings at Byron. In a few cases there are conduits that turn up and terminate above
gradelevelsuchthatnopathforwaterisprovided.ConduitsatByrondonotprovideapath
forgroundwaterorrainwatertoentersafetyrelatedbuildings.
x TheMainSteamIsolationValve(MSIV)Rooms,RadwasteTruckBay,FuelHandlingBuilding
and the Refueling Water Storage Tank (RWST) tunnel exterior hatches were inspected to
ensurerunofffromLIPiskeptoutofthesafetyrelatedbuildings.
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x Anoutdoorwalkdownwasconductedtoverifythatplantmodificationsimplementedsince
original construction, such as security barrier installation and changes to topography, do
notadverselyaffectplantfloodingprotection.
Phase2-InspectionsandReasonableSimulations
Visual inspection of each feature was performed on the walkdown and the results were
documentedontheapplicableWalkdownRecordForms.Theconditionofeachfeatureasobserved
on the walkdowns was compared to the acceptance criteria defined in the Supplemental
Walkdown/Inspection Guidance (Reference 17). No reasonable simulations were conducted at
Byronsinceallfeaturesareincorporatedpassive.
Phase3-FinalReporting
The Walkdown Record Forms were completed and assembled into a package that included a
summaryandacoverpagetodocumentamanagementreviewoftheentirepackage.Completion
of the Walkdown Record Forms was performed in accordance with the guidance provided in
Section 7 of NEI 1207. A Flooding Walkdown Report (this report) was prepared to address the
items outlined in the Requested Information section of the Recommendation 2.3: Flooding
enclosurefromthe10CFR50.54(f)letter.
- c. ReasonableSimulations
PerNEI1207(Reference2),reasonablesimulationincludesthefollowing:
x Verify that any credited time dependent activities can be completed in the time required. Time dependent activities include detection (some signal that the event will occur, has occurred, or is
occurring), recognition (by someone who will notify the plant), communication (to the control
room),andaction(byplantstaff).
x Verifythatspecifiedequipment/toolsareproperlystagedandingoodworkingcondition.
x Verifythatconnection/installationpointsareaccessible.
x Verifythattheexecutionoftheactivitywillnotbeimpededbytheeventitisintendedtomitigate
or prevent. For example, movement of equipment across unpaved areas on the site could be
impededbysoftsoilconditionscreatedbyexcessivewater.
x Reviewtherelianceonthestationstafftoexecuterequiredfloodprotectionfeatures.Ifduringthe
review several activities are identified to rely on station staff, then perform and document an
evaluationoftheaggregateeffectonthestationstafftodemonstrateallactionscanbecompleted
asrequired.
x Verify that all resources needed to complete the actions will be available. (Note that staffing
assumptionsmustbeconsistentwithsiteaccessassumptionsinemergencyplanningprocedures.)
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x Showthattheexecutionoftheactivitywillnotbeimpededbyotheradverseconditionsthatcould
reasonably be expected to simultaneously occur (for example, winds, lightning, and extreme air
temperatures).
x Personnel/departments that have responsibility for supporting or implementing the procedure
shouldparticipateinthesimulationeffort.
x The simulation should demonstrate that the personnel assigned to the procedure do not have
otherdutiesthatcouldkeepthemfromcompletingtheirfloodprotectionactivitiesduringanactual
event.Actionsthatwouldbeperformedinparallelduringaneventshouldbesimulatedinparallel;
notcheckedindividuallyandtheresultscombined.
x Reasonablesimulationneednotrequiretheactualperformanceofthenecessaryactivitiesifthey
have been previously performed and documented or it is periodically demonstrated and
documentedthattheactivitiescanbecompletedinthecreditedtime.
Thepurposeofreasonablesimulationsistoverifyrequiredfloodprotectionproceduresoractivitiescanbe
executed as specified/written. Byron flood protection features do not include any temporary or active
featuresthatrequireimplementationofaprocedureforperformanceofmanual/operatoractionsinorder
forthefeaturetoperformitsintendedfloodprotectionfunction.Therefore,noprocedurewalkthrough,or
ReasonableSimulation,wasconductedatByronStation.
- d. WalkdownInspectionGuidance
AWalkdownInspectionGuidancewasdevelopedbyExelontosupplementNEI1207(Reference2),based
largelyonAppendixAofNEI1207(Examples).Theguidancewasintendedtosupplement,notsupersede,
NEI1207andprovideinspectionguidanceforspecificfeatures,listedbelow.
x IncorporatedorExteriorPassiveFeatures:
o SiteElevationsandTopography
o EarthenFeatures(i.e.,FloodProtectionBerm,Dike,Levee)
o ConcreteandSteelStructures
o Wall,Ceiling,andFloorSeals(e.g.PenetrationSeals,CorkSeals)
o PassiveFloodBarriersorWaterDiversionStructures
o DrainsandCatchBasins
o PlugsandManholeCovers
o DrainagePathways(Swales,SubsurfaceDrainageSystem,etc.)
o PipingandCableVaultsandTunnels,ElectricalCableConduit
o FloorHatches
o FlapGate/BackwaterValve/DuckbillValve
o FloodWall
x IncorporatedorExteriorActiveFeatures:
o CreditedWaterTightDoors
o CreditedNonWatertightDoors
o Pumps
o WaterLevelIndication
o GateValves
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x TemporaryPassiveFeatures:
o PortableFloodBarriersandInflatableRubberSeals
o FloodGate
x TemporaryActiveFeature
o Pumps
- 4. RESULTS
TheinformationrequestedinReference3,Enclosure4,underparagraph2oftheRequestedInformation
section, is provided below. The contents of each item were developed in accordance with Reference 2,
AppendixD.
- a. RequestedInformationItem2(a)-DesignBasisFloodHazards
Describe the design basis flood hazard level(s) for all floodcausing mechanisms, including groundwater
ingress.
TheByronStationdesignbasisforexternalfloodingisdescribedinByronUFSARSections2.4and3.4
(Reference13)andDCST03BY/BR(Reference14).Byronisdesignedtobeprotectedfromtheeffects
ofriverflooding(basedontheprobablemaximumflood(PMF))andlocalintenseprecipitation(LIP).In
additionByronisdesignedtobeprotectedagainstgroundwateringress.
WiththeexceptionofthesafetyrelatedEssentialServiceWater(SX)makeuppumpsintheriverscreen
house, all safetyrelated equipment is protected from a river flood by virtue of its location above the
PMF elevation and by being housed within floodprotected structures. The PMF level has been
determinedtobeatelevation708.3ft.TheSXmakeuppumps,whichprovideUltimateHeatSink(UHS)
makeupduringlongtermreactorcooldown,aremountedatanelevationof702ftandenclosedbya4 fthighconcretefirewall.ThePMFlevelwould,therefore,be2.3ftoverthefirewallandtheSXmakeup
pumps would be flooded. As backup to the SX makeup pumps, nonsafetyrelated wells are provided.
The wells and well pumps are above the PMF level, are powered from essential (Class 1E) power
sources,andthusarecapableofsupplyingmakeuptotheUHSintheeventofalossoftheSXmakeup
pumps coincident with a loss of offsite power as a result of the PMF. This design has been deemed
acceptable (Reference 13, SER 3 Design Criteria for SSC). The river screen house is the only structure
that could be affected by flooding on the Rock River and is designed for the combined event flood,
describedfurtherbelow.Thedesignbasesfortheriverscreenhouse,underbothhighandlowwater
conditions, are discussed in Reference 13, Subsections 2.4.3 and 2.4.11, respectively. All other
structuresare161feetormoreabovethePMFleveloftheRockRiver.
The design basis combined event flood (CEF) stillwater elevation is 698.68 ft. The significant and
maximum wave effects of a coincident 40mph overland wind were superimposed on the combined
eventwaterlevelattheriverscreenhouse.Thewaverunupswerecalculatedtobe2.77ftand4.71ft
forthesignificantandmaximumwaves,respectively.Therefore,thedesignbasisCEFis703.39ftwith
maximumwaves(Reference13,Section2.4.3.9),andistheelevationusedduringthewalkdowns.
Upstream dam/landslide blockage failures and downstream landslide blockage can cause or increase
floodsbycreating:(1)afloodwavesurchargethroughthereleaseofasignificantwatervolumeovera
short period of time and (2) backwater through the blockage of flow and/or conveyance reduction,
respectively. Anupstreamfailurefloodwavedissipatesrapidlyinadownstreamdirection.Sincethe
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siteareaisremotefromupstreamgorgetypetopographyandthenearestdamis22milesupstream,an
increase in elevation of the Rock River near the site from an upstream failure floodwave was
considered negligible in the current licensing basis. Since there is no gorge downstream, backwater
fromadownstreamlandslideblockagewasalsoconsiderednegligible.Allthesafetyrelatedstructures
areprotectedagainstthisevent.(Reference13,Section2.4.2.2)
Byronmainpowerblockbuildingsaresituatedatgradeelevation869feet,wellabovethePMFlevel.
Theportionsofthebuildingsubstructureslocatedbelowthemaximumgroundwaterlevelaredesigned
topreventgroundwateringress.Thedesignbasisgroundwaterelevationis824feet.Allsubstructures
below grade elevation 869 ft at the Byron site are designed to withstand full hydrostatic head of
groundwater.(Reference14,DCST03BY/BR)
ThedesignbasisLIPresultsinamaximumwatersurfaceelevationof870.82ftintheimmediatestation
areawheresafetyrelatedfacilitiesarelocated (westernhalfofthemain powerblockstructure). The
analysis assumes that local surface drainage systems do not function during the LIP event. The areas
surrounding the plant are graded to direct surface runoff away from the plant. The station floor
elevationisatelevation870ft,0.82footbelowthemaximumLIPfloodelevation.Byitsverynature,the
LIPeventandassociatedrunoffoccursoverashortperiodoftime(Reference13,Section2.4.2.3).
Byron UFSAR Section 2.4 addresses additional flooding mechanisms that are either not critical or not
boundingforByron.ProbablemaximumsurgeandseichefloodingisnotboundingforByronbecause
thereisnolargebodyofwaternearthesitewheresignificantstormsurgesandseicheformationscan
occur. The station will not be subjected to the effects of tsunami flooding because the site is not
adjacenttoacoastalarea.
- b. RequestedInformationItem2(b)-CLBProtectionandMitigationFeatures
Describeprotectionandmitigationfeaturesthatareconsideredinthelicensingbasisevaluationtoprotect
againstexternalingressofwaterintoSSCsimportanttosafety.
The only safety related equipment at Byron Station that could be impacted by flooding is the SX
makeuppumps.Thesepumpsareinstalledintheriverscreenhouseatelevation702ftandarehoused
withina4foothighfirewall.Thewallsoftheseroomsaredesignedtobefloodprotectedtoelevation
706 ft. The CEF stillwater level is 698.68 ft. Superimposing the wind wave effect will result in a
maximum wave runup elevation of 703.39 ft. (Reference 13, Sections 2.4.3.9). The engine for the SX
makeuppumpsismountedonitssubbaseatelevation703.71feet.Theengineshaftcenterlineisat
elevation 705.33 feet and the lower battery post elevation is approximately 703.67 feet. It is
anticipatedthatthiselevationwouldbelimitingunderfloodconditions.ThisisabovetheCEFpluswave
runupelevationandisanticipatedtobetheelevationatwhichtheenginewouldstop.Intheunlikely
eventthattheenginesarerenderedinoperablebyafloodlevelinexcessof703.67feet,theplantsite
deepwellswillbepoweredfromtheirrespectiveUnit1EngineeredSafetyFeatures(ESF)buses.These
deepwellswillthenprovidemakeupfortheSXcoolingtowers(Reference13,Section2.4.10).
SafetyrelatedequipmentislocatedbelowgradeintheAuxiliaryandContainmentbuildings.Nosafety related equipment is located in the Turbine or Radwaste buildings. All of the buildings with exterior
wallsbelowgrade,includingtheTurbineandRadwastebuildings,aredesignedtobewatertightupto
plantfloorelevation870feet,whichisabovethegradeelevation869feet.Potentialsourcesofexternal
flooding of the main power block buildings are LIP and groundwater ingress. The design basis
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groundwater elevation is 824 ft. All substructures below elevation 869 feet at the Byron site are
designedtowithstandfullhydrostaticheadofgroundwater(Reference14,Section12.1.4).LIPhasbeen
determinedtoresultinamaximumwatersurfaceelevationof870.82ftintheimmediatestationarea
where safetyrelated facilities are located (Auxiliary, Containment and Fuel Handling buildings). Local
surfacedrainagesystemsareassumednottofunctionduringtheLIPevent.Theareassurroundingthe
plantaregradedtodirectsurfacerunoffawayfromtheplant(UFSARSection2.4.2.3,Reference13).To
prevent water from entering areas containing essential equipment/systems, incorporated reinforced
concretecurbsorsteelbarriersareprovidedaboveelevation870.82ft(Reference19and20).
In general, all flood protection features designed to protect safetyrelated equipment are passive
incorporatedfeatures,andassuchdoesnotinvolveinvokinganyprocedures.Theonlyactivefeatures
are the sump pumps in the SX rooms. These are credited in the current licensing basis as protecting
against internal flooding (not part of the NTTF Recommendation 2.3 flooding walkdowns) but are
providing an additional function of removing water leaks from external sources in the SX rooms.
Therefore,thepumpswerenotincludedinthefloodingwalkdownscope.
Thelicensingbasisdoesnotexplicitlyaddressflooddurationoradverseweatherconditionsconcurrent
with flooding, presumably because the protection features are all incorporated passive. In addition,
Byronfloodprotectionfeaturesaredesignedtofunctionduringanyplantmodeofoperation.
- c. RequestedInformationItem2(c)-FloodWarningSystems
Describeanywarningsystemstodetectthepresenceofwaterinroomsimportanttosafety.
PerUFSARSection9.2.1.2.4(Reference13),leakdetectionisprovidedbymeansofsystemflowand
pressuredropinstrumentationandleakdetectionsumpsintheAuxiliarybuildingbasementwherethe
essentialservicewaterpumpsareinstalled.The1Aand2Aessentialservicewaterpumpsarelocated
inonecompartmentandthe1Band2Bpumpsarelocatedinaseparateadjacentcompartment.Each
compartmentcontainsanessentialservicewatersump.Eachsumphastwosumppumps.Although
designedtodetectinternalflooding,theleakdetectionsumpswillalsodetectsignificantgroundwater
ingress into these rooms (Reference 16). These alarms are not credited in the CLB for detecting
externalgroundwaterleakage,andwerenotrequiredtobeinspected.
- d. RequestedInformationItem2(d)-FloodProtectionSystem/BarrierEffectiveness
Discuss the effectiveness of flood protection systems and exterior, incorporated, and temporary flood
barriers.Discusshowthesesystemsandbarrierswereevaluatedusingtheacceptancecriteriadevelopedas
partofRequestedInformationItem1.h[inEnclosure4oftheMarch12,2012,50.54(f)letter]
Section6ofNEI1207definesacceptanceas:
Flood protection features are considered acceptable if no conditions adverse to quality were
identified during walkdowns, verification activities, or program reviews as determined by the
licenseesCorrectiveActionProgram.Conditionsadversetoqualityarethosethatpreventtheflood
protection feature from performing its credited function during a design basis external flooding
eventandaredeficiencies.DeficienciesmustbereportedtotheNRCintheresponsetothe50.54(f)
letter.
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As indicated in Section 3d, inspection guidance was developed, supplementing NEI 1207, to provide
more specific criteria for judging acceptance. All observations that cannot be immediately judged as
acceptable were entered into the sites Corrective Action Program (CAP) where an evaluation of the
observationcanbemade.
Walkdownswereconductedtoverifytheexteriorwalls,floorsandseals,creditedwithkeepingwater
out of safetyrelated areas containing safety related equipment, are capable of performing their
intended function based on visual observations. Flood protection features inspected at Byron also
included the external hatches that provide access to the refueling water storage tank piping tunnels,
and the interface between the Radwaste building and the Auxiliary building radwaste tunnel. The
purpose of the walkdowns is to verify conformance with the Byron current licensing basis. The
adequacyofthecurrentlicensingbasiswillbeaddressedinresponsetoNTTFRecommendation2.1.An
outdoor walkdown was conducted to verify that plant modifications implemented since original
construction, such as security barrier installation and changes to topography, do not adversely affect
plantfloodingprotection.
Acceptancecriteriaforvisualinspectionsperformedduringthewalkdownsweredevelopedtoidentify
conditionsadversetoqualityandincludedthefollowingconsiderations:
x Floodprotectionconfigurationisinaccordancewithdesigndrawingsandthestationscurrent
licensingbasis.
x Visualinspectiondidnotidentifymaterialdegradationperestablishedacceptancecriteria
(discussedpreviously).
x Whenapplicable,PMsorperiodicinspectionsareinplace,withintheirrequiredperiodicity,and
ofadequatescope.
x Notopographychanges,includingsecuritybarrierinstallations,comparedtoconditions
assumedinthecurrentdesignbasissitedrainageevaluation.
Whetherconduitsfrommanholesorcablevaultscouldprovideapathforgroundwaterorrainwaterto
enter safety related buildings was considered relevant to the walkdown scope. Conduits from
manholes/cablevaultsgenerallyarenotroutedtosafetyrelatedbuildingsatByron.Inafewcasesthere
are conduits that turn up and terminate above grade level such that no path for water is provided.
ConduitsatByrondonotprovideapathforgroundwaterorrainwatertoentersafetyrelatedbuildings
(Reference21).
With two exceptions, inspections of walls, floors and penetrations confirmed that credited flood
barriersareinplaceandarecapableofperformingtheirintendedfunction.Asmallslabthatservesas
an LIP curb between the Radwaste Truck Bay and the Auxiliary Building was observed as not per
design(ReferenceIR01404340).Theslabisactuallyinstalled12belowthedesignedelevation(0.82
belowtheLIPfloodlevel).CaulkingaroundtheLIPcurblocatedinthe1A/1DMainSteamIsolationValve
(MSIV) room was identified as degraded (Reference IR 01414231). These observations, and any other
thatcouldnotbeimmediatelyjudgedasacceptable,wereenteredintotheCorrectiveActionProgram
(CAP)fordispositionresultinginthesetwodeficiencies.
A review of the external hatches providing access to the refueling water storage tank piping tunnels,
confirmedthehatchesarelocatedatanelevationabovethemaximumLIP.
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ItwasidentifiedthatthecurrentcalculationdoesnotaddresstheadditionoftheNewServiceBuilding
ortheinstallationofthe ContainmentAccessFacilitiesandhas beenenteredintoCAPfordisposition
(ReferenceIR01396000).
The flood protection features incorporated in the Byron design provide effective barriers for keeping
external flooding from reaching safetyrelated systems and equipment. Water entering these areas
would be accommodated by the floor drain system. However, the walkdowns and document reviews
resultedinobservationsthatcouldnotimmediatelybejudgedasacceptable.Thesewereenteredinto
thecorrectiveactionprogramfordisposition.TheSXmakeuppumproomsintheriverscreenhouseare
designedtoprovidefloodprotectionfromCEFlevelfloodingoftheriver.Theexteriorwallsofthemain
powerblockbuildingsaredesignedtopreventingressofgroundwater.
Inadditiontothesewalkdowns,thestationstructuralmonitoringprogram(Reference15)providesfor
ongoing verification of flood barrier effectiveness by identifying/trending areas affected by
groundwateringress.
- e. RequestedInformationItem2(e)-ImplementationofWalkdownProcess
Present information related to the implementation of the walkdown process (e.g., details of selection of
the walkdown team and procedures) using the documentation template discussed in Requested
Information Item 1.j [in Enclosure 4 of the March 12, 2012, 50.54(f) letter], including actions taken in
responsetothepeerreview.
Station walkdowns were implemented in accordance with the guidelines provided in NEI 1207
(Reference 2). The Byron walkdown team included three Sargent & Lundy employees as well as the
ByronLeadResponsibleEngineerforfloodingissues.Allteammembersarefamiliarwiththestation
licensingbasisrelativetoexternalflooding,werebadgedatByronandcompletedbothNANTeLbased
training and Exelon specific training on implementation of the NEI 1207 guidelines. The Sargent &
LundyteamconsistedoftwomechanicalengineersfamiliarwithByronStationandonecivilengineer.
Therewerenocasesrequiringateammemberwithaspecificknowledge.Atleasttwoteammembers
performed all visual inspections. Walkdown results were documented using the NEI 1207
recommended form. Walkdown packages, one for each feature, were prepared in advance and
included the NEI 1207 walkdown form with Parts A and B already completed as well as reference
drawings and documentation. The remaining parts of the walkdown forms, including documenting
available physical margin (APM), were finalized after the feature walkdown was completed, and the
identificationofobservationsenteredintoCAP.Walkdownswereconductedfollowingtheguidanceof
NEI1207andnoexceptionsweretakentotheguidance.
- f. RequestedInformationItem2(f)-FindingsandCorrectiveActionsTaken/Planned
Results of the walkdown including key findings and identified degraded, nonconforming, or unanalyzed
conditions.Includeadetaileddescriptionoftheactionstakenorplannedtoaddresstheseconditionsusing
theguidanceinRegulatoryIssuesSummary200520,Rev1,RevisiontoNRCInspectionManualPart9900
TechnicalGuidance,OperabilityConditionsAdversetoQualityorSafety,includingenteringthecondition
inthecorrectiveactionprogram.
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Thewalkdownscopewasdevelopedtoconfirmthatfloodprotectionfeaturescreditedinthecurrent
licensingbasisareacceptableandcapableofperformingtheircreditedfloodprotectionfunctions.For
Byron Power Station, the scope primarily consisted of visual inspections of floors and exterior
watertightwallsbothintheRiverScreenHouseSXMakeupPumproomsandinthemainpowerblock.
Thescopeincludedvisualinspectionofallapplicablepenetrationsandassociatedseals.Inaddition,an
outdoor walkdown was conducted to confirm credited surface drainage provisions have not been
impacted by changes to topography, such as installation of new security barriers. Inspections of
creditedwalkdownfeatureswereperformedbythewalkdownteamfollowingtheguidanceprovidedin
NEI 1207 and were documented in walkdown packages using the NEI 1207 walkdown forms.
WalkdownrecordformsarenotsubmittedtotheNRC,butasdiscussedinSection7ofReference2,are
retained onsite for NRC inspection. Observations of degraded, nonconforming or unanalyzed
conditionsweredocumentedandenteredintothestationcorrectiveactionprogram(CAP).
ObservationsNotImmediatelyJudgedasAcceptable
With two exceptions, the inspections of walls, floors and penetrations confirmed that credited flood
barriersareinplaceandarecapableofperformingtheirintendedfunction.Asmallslabthatservesas
an LIP curb between the Radwaste Truck Bay and the Auxiliary Building was observed as not per
design(ReferenceIR01404340).Theslabisactuallyinstalled12belowthedesignedelevation(0.82
belowtheLIPfloodlevel).CaulkingaroundtheLIPcurblocatedinthe1A/1DMainSteamIsolationValve
(MSIV) room was identified as degraded (Reference IR 01414231. These observations, and any other
thatcouldnotbeimmediatelyjudgedasacceptable,wereenteredintotheCorrectiveActionProgram
(CAP)fordispositionresultinginthesetwodeficiencies.
A total of 14 IRs were generated in the process of performing the walkdowns. These, along with the
resolutionstatus,aredescribedbelowandlistedinTable2withresolutions,intheConclusionssection
ofthisreport.
x IRs01395377and01395379identifyminorcorrosiononwatertighthatchesthatprovideaccess
totheAuxiliarybuildingviatheRefuelingWaterStorageTank(RWST)tunnels.
x IR 01395487 identified abandoned drain lines located on these RWST hatches that should be
sealed.Note,thesedrainsareabovethemaximumPMPwaterlevelsofloodingoftheAuxiliary
buildingisnotaconcern.
x IR 01395406 identified a floor sleeve in the river screen house SX makeup pump room as not
requiringafloodseal.Furtherinvestigationrevealedthisnottobeanissueandtheissuewas
closed.
x IR01396000identifiedthePMPfloodingcalculationdidnotappeartoaddresstheadditionof
theNewServiceBuildingandtheContainmentAccessFacilities.
x IRs01395996,01395999,01396507and01396509documenttheevidenceofpastgroundwater
intrusion.
x IRs01396742and01396746identifytheneedtoreplaceinstalledventsealsinspareconduits
withanapprovedfloodseal.
x IRs01407641and01414231identifyalooseboltanddegradingcaulkingonPMPcurbslocated
withintheMainSteamIsolationValve(MSIV)rooms.
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x IR01404340identifiedtheslabfunctioningasaPMPcurbbetweentheradwastebuildingtruck
bayandtheAuxiliarybuildingisnotinstalledperthedesigndrawings.
ObservationsDesignatedthroughCAPasDeficient
x IR01404340identifiedtheslabfunctioningasanLIPcurbbetweentheradwastebuildingtruck
bayandtheAuxiliarybuildingisnotinstalledperthedesigndrawings.
x IR01414231identifieddegradedcaulkingontheLIPcurblocatedwithinthe1A/1DMainSteam
IsolationValve(MSIV)room.
ObservationsAwaitingFinalDispositioninCAP
None.
RestrictedAccessAreas
None.
InaccessibleAreas
AportionoftheexteriorwalllocateddirectlybehindtheRecycleHoldupTanks(0AB01TA/TB)andthe
RegenerationWasteDrainTank(0WX25T)wasdeemedinaccessibleduetothecloseproximityofthe
tankstothewall.Reasonableassurancethattheseportionsofthewallsareacceptableisbasedonthe
fact that visual inspection of the walls and floors adjacent to these tanks and throughout the plant
revealednodeficienciesordegradationthatwouldpreventperformanceoffloodprotectionfunctions.
Thereisnoconduitorpipingpenetrationslocatedwithintheseareas,andwaterstopsareprovidedin
allhorizontalandverticalconstructionjointsinallexteriorwalls(Reference13,Section3.4.1.3).
- g. RequestedInformationItem2(g)-Cliff-EdgeEffectsandAvailablePhysicalMargin
Documentanycliffedgeeffectsidentifiedandtheassociatedbasis.Indicatethosethatwereenteredinto
the corrective action program. Also include a detailed description of the actions taken or planned to
addresstheseeffects.
Cliffedge effects were defined in the NTTF Report (Reference 5) as the safety consequences of a
floodingeventmayincreasesharplywithasmallincreaseinthefloodinglevel.AsindicatedinSections
3.12 of NEI 1207 (Reference 2), the NRC is no longer expecting the Recommendation 2.3: Flooding
Walkdownstoincludeanevaluationofcliffedgeeffects.TheNRCisnowdifferentiatingbetweencliff edgeeffects,whichareaddressedinEnclosure2ofReference3,andAvailablePhysicalMargin(APM).
AsindicatedinSections3.13ofNEI1207(Reference2),APMdescribesthefloodmarginavailablefor
applicablefloodprotectionfeaturesatasite(notallfloodprotectionfeatureshaveAPMs).TheAPMfor
eachapplicablefloodprotectionfeatureisthedifferencebetweenlicensingbasisfloodheightandthe
floodheightatwhichwatercouldaffectanSSCimportanttosafety.
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APMinformationwascollectedduringthewalkdownsinaccordancewithguidanceprovidedinNEI12 07 and the final resolution to FAQ006 (Reference 22). APM was collected to primarily support the
responsetoEnclosure2ofReference3and,assuch,isnotincludedinthisreport.APMdeterminations
did not involve calculating cliffedge effects (i.e. the safety consequences). During the Integrated
Assessment(seeEnclosure2ofReference3),thecliffedgeeffectsandtheassociatedsafetyriskswill
be evaluated using the APMs and other information, such as the specific SSCs that are subjected to
floodingandthepotentialavailabilityofothersystemstomitigatetherisk.
Since the walkdowns were completed prior to the final resolution of FAQ006 (Reference 22), APM
informationwascollectedanddocumentedontheWalkdownRecordFormusingtheoldapproach;
thatis,asimplemeasurementofthedifferencebetweenthelicensingbasisfloodheightandtheflood
heightatwhichwatercouldaffectanSSCimportanttosafety.
- h. RequestedInformationItem2(h)-Planned/NewlyInstalledFloodProtection
Enhancements
Describe any other planned or newly installed flood protection systems or flood mitigation measures
including flood barriers that further enhance the flood protection. Identify results and any subsequent
actionstakeninresponsetothepeerreview.
x ModificationoftheLIPcurbbetweentheradwastebuildingtruckbayandtheAuxiliarybuilding
toreflectexistingdesigndrawingsisrequired(ReferenceIR01404340).
x Replacementofcaulkingonthe1A/1DMSIVroomLIPcurbisrequired(ReferenceIR01414231).
x Noadditionalenhancementsareplanned.
x ThePEERreviewdidnotresultinanychangestothewalkdownprocessormethodology.
- 5. CONCLUSIONS
With two exceptions, inspections of walls, floors and penetrations confirmed that credited flood
barriersareinplaceandarecapableofperformingtheirintendedfunction.AllIRsenteredintotheCAP
havebeenaddressedwith2IRsbeingdeficiencies.
Asmallportionofthetotalfloorandwallareaswithinthewalkdownscopeweredeemedinaccessible
and were not inspected. Reasonable assurance that these portions of the walls and floors are
acceptable is based on the fact that visual inspection of the walls, floors and penetrations in these
buildings and throughout the plant revealed no deficiencies or degradation that would prevent
performanceoffloodprotectionfunctions.
IR01404340identifiedtheslabfunctioningasanLIPcurbbetweentheradwastebuildingtruckbayand
theAuxiliarybuildingisnotinstalledperthedesigndrawings.IR01414231identifieddegradedcaulking
ontheLIPcurblocatedwithinthe1A/1DMainSteamIsolationValve(MSIV)room.Thesedeficiencies
willberestoredtooriginaldesign.
Therearenoadditionalenhancementsplanned.
Table1providesasummaryofthenumberandtypeoffeaturesincludedinthewalkdownscope.
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Table 2 provides the list of the IRs generated and entered into the station corrective action program
(CAP)asaresultofthewalkdown.ThestatusofeachIRatthetimeofthisreportisindicated.Noneof
theseIRsresultedinanoperabilityconcern.
Table1:FeaturesIncludedintheWalkdownScope
- ofVisual #ofSimple #ofComplex #ofDrillsor
Type
Inspections Simulations Simulations Exercises
Incorporated/ExteriorPassive 39 0 0 0
Incorporated/ExteriorActive 0 0 0 0
TemporaryPassive 0 0 0 0
TemporaryActive 0 0 0 0
Totals 39 0 0 0
Table2:IRsGeneratedinCAP
IRNumber Description ProposedResolution Status
01395377 Identificationofminorsurface Closetoworkrequest. Actionedtoworkorder01563689
corrosiononUnit1RWSTtunnel
hatch
01395379 Identificationofminorsurface Closetoworkrequest. Actionedtoworkorder01563690
corrosiononUnit2RWSTtunnel
hatch
01395406 Oneoffourfloorpenetrationsin None.PreviousIR1139072 Closednofurtheractionsrequired
slabdoesnotcalloutfloodseal. acceptedgapinan
adjacentpenetrationdue
toelevationofelectrical
componentsinroom.
01395487 IdentificationofRWSTtunnelhatch Installsealindrains. AT139548704istrackingresolution.
abandoneddrains.Drainislocated
abovePMPheight,butprovidesa
ventpathintoAux.Bldg.
01395996 Evidenceofpastwaterintrusionon ClosedtoCAPtrending. Closednofurtheractionsrequired
1A/2ASXPProom.
01395999 Evidenceofpastwaterintrusionon ClosedtoCAPtrending. Closednofurtheractionsrequired
1B/2BSXPProom.
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IRNumber Description ProposedResolution Status
01396000 LIPfloodingcalcdoesnotaddress Reconstitutionofcalc AT139600002istrackingresolution
theadditionofNewServiceBldgor duringthe2.1Flood
ContainmentAccessFacilities. HazardAssessment.
01396507 Evidenceofpastwaterintrusionon ClosedtoCAPtrending. Closednofurtheractionsrequired
Unit1AuxiliaryBldg.El.346walls.
01396509 Evidenceofpastwaterintrusionon ClosedtoCAPtrending. Closednofurtheractionsrequired
Unit2AuxiliaryBldg.El.346walls.
01396742 Spareconduitrequiresfloodseal Replaceseal. Actionedtoworkorder01563694
installed
01396746 Spareconduitrequiresfloodseal Replaceseal. Actionedtoworkorder01563695
installed
01404340 ConcreteslabperformingaPMP Correctdeficientcondition. Actionedtoworkorder01574214
curbinstalled12lowerthandesign Installconcretetoheight
drawing. requiredondrawings.
01407641 Loosebolton2A/2DMSIVroom Tightenloosebolt. Actionedtoworkrequest410721
PMPcurb
01414231 Identificationofdegradedcaulking Removeandreinstallper Actionedtoworkrequest415856
on1A/1DMSIVroomPMPcurb S993.
- 6. REFERENCES
- 1. Exelon Letter to U.S. Nuclear Regulatory Commission. Exelon Generation Company, LLCs 90Day
Response to March 12, 2012 Request for Information Pursuant to Title 10 of the Code of Federal
Regulations50.54(f)RegardingRecommendations2.1and2.3,oftheNearTermTaskForceReview
ofInsightsfromtheFukushimaDaiichiAccident(Flooding).June11,2012.
- 2. Nuclear Energy Institute (NEI), Report 1207 [Rev 0A]. Guidelines for Performing Verification
WalkdownsofPlantProtectionFeatures.May2012[NRCendorsedMay31,2012;updatedandre issuedJune18,2012].
- 3. U.S.NuclearRegulatoryCommission.LettertoLicensees.RequestforInformationPursuanttoTitle
10oftheCodeofFederalRegulations50.54(f)RegardingRecommendations2.1,2.3,and9.3ofthe
NearTermTaskForceReviewofInsightsfromtheFukushimaDaiichiAccident.March12,2012.
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ManualActionsinResponsetoFire.NUREG1852.October2007.
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Century,TheNearTermTaskForceReviewofInsightsfromtheFukushimaDaiichiAccident.July12,
2011.
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ResolutionofDegradedorNonconformingConditionsAdversetoQualityorSafety.NRCInspection
Manual. Part 9900: Technical Guidance. Regulatory Issues Summary 200520, Revisions 1.
September26,2005.
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NTTFRecommendation2.3(Walkdowns):Flooding
ExelonCorporation
11/02/12
Revision1
- 7. InstituteofNuclearPowerOperations.FukushimaDaiichiNuclearStationFuelDamageCausedby
EarthquakeandTsunami.INPOEventReport111.March15,2011.
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Damage Event. Inspection Manual. Temporary Instruction 2515/183. ML113220407. November
2011.
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Engineering Features at Nuclear Power Plants. Inspection Manual. Inspection Procedure 62002.
Section03.01(h),Dams,EmbankmentsandCanals.
- 10. U.S.NuclearRegulatoryCommission.EvaluateReadinesstoCopewithExternalFlooding.Inspection
Procedures.Attachment71111.01.AdverseWeatherProtection.Section02.04.
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1.102.
- 13. ByronUFSAR,Rev.13
- 14. Byron/BraidwoodStructuralProjectDesignCriteria,DCST03BY/BR,Rev.23
- 15. ExelonProcedureERAA450,Rev.1,StructuresMonitoring
- 16. DrawingM48,Sheet19,Rev.AE
- 17. SupplementalWalkdown/InspectionGuidance,Rev.1,August17,2012
- 18. CalculationWRBYPF10,Rev.4D,EffectofLocalProbableMaximumPrecipitation(PMP)atPlant
Site
- 19. DrawingsS899,Rev.Z,S900,Rev.AB,S973,Rev.XandS974,Rev.Z
- 20. DrawingA47,Rev.AK
- 21. Drawings6E03680,Rev.AFand6E03681,rev.AL
- 22. FAQ006,Rev.4,9/13/12
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