RS-12-162, Company, Llc’S 180-Day Response to NRC Request for Information Pursuant to 10CFR50.54(f) Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident

Company, Llc’S 180-Day Response to NRC Request for Information Pursuant to 10CFR50.54(f) Flooding Aspects of Recommendation 2.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident

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

10 CFR 50.54(f)

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 Regulatory Commission 180-Day Response to 50.54(f) Letter NTTF Recommendation 2.3: Flooding November 27, 2012 Page 2 For flooding Recommendation 2.3 (walkdowns), Enclosure 4 of Reference 1 states that within 180 days of the NRC's endorsement of the walkdown process (Reference 2), each addressee will submit a final response, including a list of any areas that are unable to be inspected due to inaccessibility and a schedule for when the walkdown will be completed. This letter provides the Byron Station, Units 1 and 2 180-day response to Reference 1 for Flooding Recommendation 2.3.

Conditions identified during the walkdowns were documented and entered into the corrective action program. Performance of the walkdowns provided confirmation, with two exceptions, that flood protection features are in place, are in good condition and will perform as credited in the current licensing basis. The two deficiencies will be restored to their original design for resolution of the issues. to this letter provides the requested information for Byron Station Units 1 and 2.

This letter contains no new regulatory commitments.

Should you have any questions concerning the content of this letter, please contact Ron Gaston at (630) 657-3359.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 27th day of November 2012.

Respectfully, Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosures:

1.

Flooding Walkdown Report In Response To The 50.54(f) Information Request Regarding Near-Term Task Force Recommendation 2.3: Flooding for the Byron Station, Units 1 and 2 cc:

Director, Office of Nuclear Reactor Regulation Regional Administrator - NRC Region III NRC Senior Resident Inspector - Byron Units 1 and 2 NRC Project Manager, NRR - Byron Units 1 and 2 Illinois Emergency Management Agency - Division of Nuclear Safety U.S. Nuclear Regulatory Commission 180-Day Response to 50.54(f) Letter NTTF Recommendation 2.3: Flooding November 27,2012 Page 2 For flooding Recommendation 2.3 (walkdowns), Enclosure 4 of Reference 1 states that within 180 days of the NRC's endorsement of the walkdown process (Reference 2), each addressee will submit a final response, including a list of any areas that are unable to be inspected due to inaccessibility and a schedule for when the walkdown will be completed. This letter provides the Byron Station, Units 1 and 2 180-day response to Reference 1 for Flooding Recommendation 2.3.

Conditions identified during the walkdowns were documented and entered into the corrective action program. Performance of the walkdowns provided confirmation, with two exceptions, that flood protection features are in place, are in good condition and will perform as credited in the current licensing basis. The two deficiencies will be restored to their original design for resolution of the issues. to this letter provides the requested information for Byron Station Units 1 and 2.

This letter contains no new regulatory commitments.

Should you have any questions concerning the content of this letter, please contact Ron Gaston at (630) 657-3359.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 27th day of November 2012.

Respectfully,

.~~

Glen T. Kaegi Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosures:

1. Flooding Walkdown Report In Response To The 50.54(f) Information Request Regarding Near-Term Task Force Recommendation 2.3: Flooding for the Byron Station, Units 1 and 2 cc:

Director, Office of Nuclear Reactor Regulation Regional Administrator - NRC Region III NRC Senior Resident Inspector - Byron Units 1 and 2 NRC Project Manager, NRR - Byron Units 1 and 2 Illinois Emergency Management Agency - Division of Nuclear Safety

U.S. Nuclear Regulatory Commission 180-Day Response to 50.54(f) Letter NTTF Recommendation 2.3: Flooding November 27, 2012 Page 3 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)

Joseph V. Bellini/Corp. SME 11/7/12 FLOODING WALKDOWN REPORT IN RESPONSE TO THE 50.54(t) INFORMATION REQUEST REGARDING NEAR-TERM TASK FORCE RECOMMENDATION 2.3: FLOODING Preparer:

Reviewer:

Approver:

Lead Responsible Engineer Branch Manager:

Senior Manager:

Corporate Acceptance:

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 m 7 1

A.

.!li.ILilili

.. E.

... *.l.

. ~ e 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

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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.

Thescopeofthefloodingwalkdownwasdevelopedfollowingadetailedreviewofallrelevantlicensing

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.

Themethodologyandacceptancecriteriafortheevaluationoffloodprotectionfeatureswasdeveloped

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.

Withtwoexceptions,inspectionsofwalls,floorsandpenetrationsconfirmedthatcreditedfloodbarriers

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,andanyotherthatcouldnotbeimmediatelyjudgedasacceptable,wereenteredintothe

CorrectiveActionProgram(CAP)fordispositionresultinginthesetwodeficiencies.

Whetherconduitsfrommanholesorcablevaultscouldprovideapathforgroundwaterorrainwaterto

safetyrelatedbuildingswasconsideredrelevanttothewalkdownscope.Conduitsfrommanholes/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

recommendationsthatwereintendedtoclarifyandstrengthentheregulatoryframeworkforprotection

againstnaturalphenomena.

OnMarch12,2012,theNRCissuedaninformationrequestpursuanttoTitle10oftheCodeofFederal

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

InEnclosure4ofReference3,theNRCrequestedthatlicenseesperformfloodprotectionwalkdownsto

identify and address plantspecific degraded, nonconforming, or unanalyzed conditions and cliffedge

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effects(throughthecorrectiveactionprogram)andverifytheadequacyofmonitoringandmaintenance

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

oftheRockRiver,ataboutrivermile115fromtheconfluencewiththeMississippiRiver.Theplantsite

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).

TheByronRiverScreenHouseistheonlystructurewhichcouldbeaffectedbyfloodsontheRockRiver.

This structure is designed for the combined event flood and waves produced by a 40 mph wind. The

makeupwatersystemfortheultimateheatsinkconsistsofacombinationoftheRiverScreenHouseSX

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).

Thelocalintenseprecipitation(LIP)eventcausesonlyminorlocalflooding.Gradinganddrainageatthe

ByronSitearedesignedtoensurethatnofloodingofsafetyrelatedfacilitieswilloccurforeventsassevere

astheLIP.Italsohasnoappreciableeffectonthemaximumperchedgroundwaterelevationof824feet

(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

feetto883feet.NoneoftheaboveroadswouldbeaffectedbythePMFfromtheRockRiver.Other

principalroadsintheareaareIllinoisStateHighway72,about3milesnortheastandIllinoisHighway64,

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

walkdownprocedure(Reference2),endorsedbytheNRConMay31,2012,willbeusedasthe

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.

Presentinformationrelatedtotheimplementationofthewalkdownprocess(e.g.,detailsof

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.

Documentanycliffedgeeffectsidentifiedandtheassociatedbasis.Indicatethosethatwere

enteredintothecorrectiveactionprogram.Alsoincludeadetaileddescriptionoftheactions

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)

InacollaborativeeffortwithNRCstaff,NEIdevelopedandissuedreport1207[Rev0A],Guidelinesfor

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

(Reference1)statingthattheendorsedfloodingwalkdownprocedure(Reference2)willbeusedasthe

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

floodingevents.ThisincludedreviewoftheByronUpdatedFinalSafetyAnalysisReport(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

andtheRefuelingWaterStorageTank(RWST)tunnelexteriorhatcheswereinspectedto

ensurerunofffromLIPiskeptoutofthesafetyrelatedbuildings.

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x Anoutdoorwalkdownwasconductedtoverifythatplantmodificationsimplementedsince

originalconstruction,suchassecuritybarrierinstallationandchangestotopography,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

Section7ofNEI1207.AFloodingWalkdownReport(thisreport)waspreparedtoaddressthe

items outlined in the Requested Information section of the Recommendation 2.3:  Flooding

enclosurefromthe10CFR50.54(f)letter.



c. ReasonableSimulations

PerNEI1207(Reference2),reasonablesimulationincludesthefollowing:

x Verifythatanycreditedtimedependentactivitiescanbecompletedinthetimerequired.Time dependentactivitiesincludedetection(somesignalthattheeventwilloccur,hasoccurred,oris

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,isprovidedbelow.ThecontentsofeachitemweredevelopedinaccordancewithReference2,

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,allsafetyrelatedequipmentisprotectedfromariverfloodbyvirtueofitslocationabovethe

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

pumpswouldbeflooded.AsbackuptotheSXmakeuppumps,nonsafetyrelatedwellsareprovided.

The wells and well pumps are above the PMF level, are powered from essential (Class 1E) power

sources,andthusarecapableofsupplyingmakeuptotheUHSintheeventofalossoftheSXmakeup

pumpscoincidentwithalossofoffsitepowerasaresultofthePMF.Thisdesignhasbeendeemed

acceptable(Reference13,SER3DesignCriteriaforSSC).Theriverscreenhouseistheonlystructure

thatcouldbeaffectedbyfloodingontheRockRiverandisdesignedforthecombinedeventflood,

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

maximumwaveeffectsofacoincident40mphoverlandwindweresuperimposedonthecombined

eventwaterlevelattheriverscreenhouse.Thewaverunupswerecalculatedtobe2.77ftand4.71ft

forthesignificantandmaximumwaves,respectively.Therefore,thedesignbasisCEFis703.39ftwith

maximumwaves(Reference13,Section2.4.3.9),andistheelevationusedduringthewalkdowns.

Upstreamdam/landslideblockagefailuresanddownstreamlandslideblockagecancauseorincrease

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

considerednegligibleinthecurrentlicensingbasis.Sincethereisnogorgedownstream,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(westernhalfofthemainpowerblockstructure).The

analysisassumesthatlocalsurfacedrainagesystemsdonotfunctionduringtheLIPevent.Theareas

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).

ByronUFSARSection2.4addressesadditionalfloodingmechanismsthatareeithernotcriticalornot

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

maximumwaverunupelevationof703.39ft.(Reference13,Sections2.4.3.9).TheenginefortheSX

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 relatedequipmentislocatedintheTurbineorRadwastebuildings.Allofthebuildingswithexterior

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

wheresafetyrelatedfacilitiesarelocated(Auxiliary,ContainmentandFuelHandlingbuildings).Local

surfacedrainagesystemsareassumednottofunctionduringtheLIPevent.Theareassurroundingthe

plantaregradedtodirectsurfacerunoffawayfromtheplant(UFSARSection2.4.2.3,Reference13).To

preventwaterfromenteringareascontaining essentialequipment/systems,incorporated reinforced

concretecurbsorsteelbarriersareprovidedaboveelevation870.82ft(Reference19and20).

In general, all flood protection features designed to protect safetyrelated equipment are passive

incorporatedfeatures,andassuchdoesnotinvolveinvokinganyprocedures.Theonlyactivefeatures

arethesumppumpsintheSXrooms.Thesearecreditedinthecurrentlicensingbasisasprotecting

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)

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AsindicatedinSection3d,inspectionguidancewasdeveloped,supplementingNEI1207,toprovide

morespecificcriteriaforjudgingacceptance.Allobservationsthatcannotbeimmediatelyjudgedas

acceptablewereenteredintothesitesCorrectiveActionProgram(CAP)whereanevaluationofthe

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

includedtheexternalhatchesthatprovideaccesstotherefuelingwaterstoragetankpipingtunnels,

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,suchassecuritybarrierinstallationandchangestotopography,donotadverselyaffect

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

areconduits thatturnup andterminateabovegradelevelsuch thatnopathforwaterisprovided.

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)roomwasidentifiedasdegraded(ReferenceIR01414231).Theseobservations,andanyother

thatcouldnotbeimmediatelyjudgedasacceptable,wereenteredintotheCorrectiveActionProgram

(CAP)fordispositionresultinginthesetwodeficiencies.

Areviewoftheexternalhatchesprovidingaccesstotherefuelingwaterstoragetankpipingtunnels,

confirmedthehatchesarelocatedatanelevationabovethemaximumLIP.

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ItwasidentifiedthatthecurrentcalculationdoesnotaddresstheadditionoftheNewServiceBuilding

ortheinstallationoftheContainmentAccessFacilitiesandhasbeenenteredintoCAPfordisposition

(ReferenceIR01396000).

ThefloodprotectionfeaturesincorporatedintheByrondesignprovideeffectivebarriersforkeeping

external flooding from reaching safetyrelated systems and equipment. Water entering these areas

wouldbeaccommodatedbythefloordrainsystem.However,thewalkdownsanddocumentreviews

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

Presentinformationrelatedtotheimplementationofthewalkdownprocess(e.g.,detailsofselectionof

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

(Reference2).TheByronwalkdownteamincludedthreeSargent&Lundyemployeesaswellasthe

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

availablephysicalmargin(APM),werefinalizedafterthefeaturewalkdownwascompleted,andthe

identificationofobservationsenteredintoCAP.Walkdownswereconductedfollowingtheguidanceof

NEI1207andnoexceptionsweretakentotheguidance.



f.

RequestedInformationItem2(f)-FindingsandCorrectiveActionsTaken/Planned

Resultsofthewalkdownincludingkeyfindingsandidentifieddegraded,nonconforming,orunanalyzed

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

Withtwoexceptions,theinspectionsofwalls,floorsandpenetrationsconfirmedthatcreditedflood

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)roomwasidentifiedasdegraded(ReferenceIR01414231.Theseobservations,andanyother

thatcouldnotbeimmediatelyjudgedasacceptable,wereenteredintotheCorrectiveActionProgram

(CAP)fordispositionresultinginthesetwodeficiencies.

Atotalof14IRsweregeneratedintheprocessofperformingthewalkdowns.These,alongwiththe

resolutionstatus,aredescribedbelowandlistedinTable2withresolutions,intheConclusionssection

ofthisreport.

x IRs01395377and01395379identifyminorcorrosiononwatertighthatchesthatprovideaccess

totheAuxiliarybuildingviatheRefuelingWaterStorageTank(RWST)tunnels.

x IR01395487identifiedabandoneddrainlineslocatedontheseRWSThatchesthatshouldbe

sealed.Note,thesedrainsareabovethemaximumPMPwaterlevelsofloodingoftheAuxiliary

buildingisnotaconcern.

x IR01395406identifiedafloorsleeveintheriverscreenhouseSXmakeuppumproomasnot

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

factthatvisualinspectionofthewallsandfloorsadjacentto thesetanksandthroughouttheplant

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

beevaluatedusingtheAPMsandotherinformation,suchasthespecificSSCsthataresubjectedto

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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Revision1



Table2providesthelistoftheIRsgeneratedandenteredintothestationcorrectiveactionprogram

(CAP)asaresultofthewalkdown.ThestatusofeachIRatthetimeofthisreportisindicated.Noneof

theseIRsresultedinanoperabilityconcern.



Table1:FeaturesIncludedintheWalkdownScope

Type

1. ofVisual

Inspections

1. ofSimple

Simulations

1. ofComplex

Simulations

1. ofDrillsor

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

corrosiononUnit1RWSTtunnel

hatch

Closetoworkrequest.

Actionedtoworkorder01563689

01395379

Identificationofminorsurface

corrosiononUnit2RWSTtunnel

hatch

Closetoworkrequest.

Actionedtoworkorder01563690

01395406

Oneoffourfloorpenetrationsin

slabdoesnotcalloutfloodseal.

None.PreviousIR1139072

acceptedgapinan

adjacentpenetrationdue

toelevationofelectrical

componentsinroom.

Closednofurtheractionsrequired

01395487

IdentificationofRWSTtunnelhatch

abandoneddrains.Drainislocated

abovePMPheight,butprovidesa

ventpathintoAux.Bldg.

Installsealindrains.



AT139548704istrackingresolution.

01395996

Evidenceofpastwaterintrusionon

1A/2ASXPProom.

ClosedtoCAPtrending.

Closednofurtheractionsrequired

01395999

Evidenceofpastwaterintrusionon

1B/2BSXPProom.

ClosedtoCAPtrending.

Closednofurtheractionsrequired

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NTTFRecommendation2.3(Walkdowns):Flooding

ExelonCorporation

11/02/12

Revision1



IRNumber

Description

ProposedResolution

Status

01396000

LIPfloodingcalcdoesnotaddress

theadditionofNewServiceBldgor

ContainmentAccessFacilities.

Reconstitutionofcalc

duringthe2.1Flood

HazardAssessment.

AT139600002istrackingresolution

01396507

Evidenceofpastwaterintrusionon

Unit1AuxiliaryBldg.El.346walls.

ClosedtoCAPtrending.

Closednofurtheractionsrequired

01396509

Evidenceofpastwaterintrusionon

Unit2AuxiliaryBldg.El.346walls.

ClosedtoCAPtrending.

Closednofurtheractionsrequired

01396742

Spareconduitrequiresfloodseal

installed

Replaceseal.

Actionedtoworkorder01563694

01396746

Spareconduitrequiresfloodseal

installed

Replaceseal.

Actionedtoworkorder01563695

01404340

ConcreteslabperformingaPMP

curbinstalled12lowerthandesign

drawing.

Correctdeficientcondition.

Installconcretetoheight

requiredondrawings.

Actionedtoworkorder01574214

01407641

Loosebolton2A/2DMSIVroom

PMPcurb

Tightenloosebolt.

Actionedtoworkrequest410721

01414231

Identificationofdegradedcaulking

on1A/1DMSIVroomPMPcurb

Removeandreinstallper

S993.

Actionedtoworkrequest415856



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NTTFRecommendation2.3(Walkdowns):Flooding

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11/02/12

Revision1



Page21



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