ML14058A035

Meeting Slides on Oconee Flood Protection and the 10 CFR 50.54(f) Response

ML14058A035
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Site:	Oconee
Issue date:	02/04/2014
From:	Office of Information Services
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References
FOIA/PA-2012-0325
Download: ML14058A035 (29)

Text

Officia se Only - Setiins ive U.SNR Oconee Flood Protection and the 10 CFR 50.54(9 Response Background Material 1

SUS.NRC Protecing rnd thefbr mmt People Outline

, Site Background

1. Issue Background s 10 CFR 50.109 Backfit s Principal 10 CFR 50.54(f) Questions Regarding Oconee Flood Protection Issue s Summary of Licensee Response

, Detailed Summary of Licensee Response to 10 CFR 50.54(f) Letter

• 50.54(f Letter Review Team

, Team Members

• Principles of Risk-informed Decision Making Process Used

, Summary of Random Dam Failure Frequency of Licensee

Response

10/3/2012

MidCai use ni -y*-ensle US, R aIIna! aao n- tt' n Site Background Oconee Nuclear Station

- Three nuclear units located inSeneca, SC

- Operational in1973-74 Plant located down river of Lake Keowee and Lake Jocassee Only nuclear plant inthe United States that relies on hydro-electric generators located inone dam as emergency power source

- Plant relies on the Standby Shutdown Facility (SSF) to maintain reactor shutdown incase of fires, floods, or sabotage events.

10/3/2012 3

SU.S.NRC "TLITUL ca~IREG in.P ople twkd R UV andLde I MIUS Enrm'tomfe IU1U IyNIIL The Jocassee Dam 10/3/2012 4

USA IUColm1, RJ Aerial View of the Oconee Site and Lake Keowee

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10/3/2012 5

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(,7A--,UyNR 0U.SNRCr 0 nsi Inform ve

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Issue ackground s NRC inspection identified flood protection issue with Oconee Standby Shutdown Facility (SSF).

- Potential lack of adequate flood protection and defense-in-depth upon loss of SSF

- Five-foot walls constructed over SSF entrances to protect against Jocassee Dam failure based on unavailable inundation studv

- Duke Hydro/FERC Inundation Study completed inearly 1990s.

Estimated flood heightsUpto 16.8 ftabove SSF grade level

- Dam random failure frequency was significantly underestimated.

- White finding on specific deficiency

@Staff response

- Performed backfit analysis

- Issued 10 CFR 50.54(f) letter for Duke to address external flooding concerns

- Evaluation of current fleet for flood vulnerabilities underway

- Security interface with NSIR and DHS 10/3/2012 6

?U.S.NRCteaina "Ihucinf and&fmEnroman hPopks The SSF Flood Barriers

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illulal U S eSL SU.SNRC Pe*t

• cl h~Pope aRdM,~em meat4" 10 CFR 50,109 Backfit Evaluation s Backfit evaluation: external flooding iswithin Oconee's licensing basis. Licensee did not address Jocassee dam failure as asource of external flooding.

1. Staff determined increased flood protection isa backfit.

• "Adequate Protection" based backfit isbest approach,

- No defense-in-depth: 3-unit core damage event with ultimate failure of each containment.

- Regulatory expectations for external flood protection includes dam hazards.

1. Cost-benefit estimate of $3million inmodifications.

Modifications on the order of $13 million justified.

10/3/2012 8

al Use On -S*nsiti'e

-U.S.NRC Inform PoctinfPgopI anddu~

Emr~orneist Principal 10 CFR 50.54(f Questions Regarding Oconee Flood Protection Issue

1. Explain the bounding external flood hazard at Oconee and the basis for excluding consideration of other external flood hazards, such as those described inthe Inundation Study, as the bounding case.

2. Provide your assessment of the Inundation Study and why itdoes or does not represent the expected flood height following aJocassee Dam failure.

3. Describe indetail the nuclear safety implications of floods that render unavailable the SSF and associated support equipment with aconcurrent loss of all Alternating Current power.

10/3/2012 9

• IJCIterna,,

.S.N . Lcensee Response Tidbits to be added inpackage s Duke offered to increase entrance wall heights by 2.5 feet.

@Question of whether to perform 1Dvs. 2D study from Duke telecon e Duke telecon on discussion of frequency s Maintenance of Jocasse Lake levels as interim fix.

s NRC staff still has questions on the total inventory from Bad Creek and Jocassee during conditions of PMP.

s FERC report and the condition of Jocassee Dam embankment leakage

@Discussion of Duke's reliability approach over a statistical approach on failure frequency 10/3/2012 10

I USU VJII ~~lILIVe Oll

()US1NRC I nal foat'bn Detailed Summary of Licensee Response to 10 CFR 50.54(f Letter 10/3/2012 11

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Off iciý,Use Or~-Sensitijv USSARC Prowling mep dThe Ex+,07rom eview Team

, Scope

- Review submittal as ifNRC isreconstituting a design basis flood for Oconee

- All modes/events causing external flooding will be assessed

- All modes/events causing Jocassee dam failure will be assessed

. Diverse team of SES and senior technical staff with expertise in:

- Engineering

- Risk Assessment

- Seismology

- Hydrology

- Project Management 10/3/2012 12

Ij .S.NRCber ifici ee OnIl ensitiv

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USRCInte Proe pandthe°o-Team M embers nform ti SES- Management Melanie Galloway (DD/DRA)

David Skeen (DD/DE)

Sam Thomas (DD/DORL - acting)

DRA - Risk Assessment and Dam Failure Frequency Mike Franovich (BC/APOB)

Jeff Circle (APOB)

James Vail (APOB)

DE Structural Kamal Manoly (BC/EMCB)

Raman Pichumani (EMCB)

NRO - Seismic Goutam Bagchi (SL:NRO/DSER)

NRO. Hydrology Kenneth See (NRO/DSER/RHEB)

DORL - Project Management Melanie Wong (BC/LP)

Leonard Olshan (LP)

Jon Thompson (LP)

Contributing SES Members Mike Case (D/DPR)

Timothy McGinty (DD/DORL)

Sher Bahadur (DD/DE - acting) 10/3/2012 13

US.NC Ij lNeWInfor ion Nro~tiqPeopk axd OwEm.-numml Principles of Riskoinformed Decision Making Process Used

• Risk insights are integrated with considerations of defense indepth and safety margins,

, Traditional engineering analysis provides insight into available margins and defense indepth

• Topics considered insupport of options

- Likelihood of dam failure

- Flood analysis (nominal and PMP lake levels)

- Seismic analysis

- Basis for continued operation

- Security 10/3/2012 14

'U.S.NRC TIENDST ES'SElA:REýlAATORY COMUSSJON Proteet n Peopl and the Exvim~wm~e Integra'ted Decision Ma kinc Jr

'00 10/3/2012 15 I4nptrnqd Information

COffalIUseO0 y Sensve

-~II..NRC Perspective of Oconee re i event Protection

ial Use - Sen 'tive

• -$jJS.NRC VNI UJ.

SIAMNLU PrvfrcnPeopk mmd IARR)I WA OMINON tAEmvirornmtn 0

rnal In in Summary of Random Dam Failure Frequency of Licensee Response 10/3/2012 17

~US.NRC Prow in;People anidA Buttress Dams Dams over 50 Feet Tall Over 50 Feet High Arch Dams 1.E-03 NRC Developed Random Failure Frequency for Over 50 Feet Jocassee High Concrete Dams Over 50 Feet High 0

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I 6 Earth Dams Over 50 Feet High Gravity Dams 0 1.E04 Over 50 Feet High Masonry Dams 0 Over 50 Feet 0 High Multi-Arch Dams Over 50 Feet High Licensee-Developed Random Failure Frequency for Jocassee (Taken From IPEEE Submittal)

Rockfill Dams Over 50 feet 1.E-05 I I I I high 1 2 3 4 5 6 7 8 T Total Type 10/3/2012 cAUse0 -Sensi'e 10/32012Off, 1 18

Pro*cwig Pelapkd dwExtiroomeat Probability Density of Jocassee.Dam Failure Frequency

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10/3/2012 19

ILSNRC. ClKIIter Prowecinq Peopic a hEmaemmee is uý`Infor* n*.*

Summary of Hydrology Aspects of Licensee Response 10/3/2012 idUse 0 ly - nsi ye 20 Inte IIjformatio'h

?jS.LNRC \QIoa t oi~n~

PmlroI~gw Peopte ndtAm Enziromnni, Flood Analysis for Oconee Nuclear Station The licensee proposed to use the Hydrologic Engineering Center River Analysis System (HEC-RAS) to model and estimate the flood depth at the ONS.

. HEC-RAS isa one-dimensional hydraulic model used to model networks of canals and reaches of rivers.

- Typically, one-dimensional models are not appropriate near complex topography and submerged structures

- Limitations of using a one dimensional model:

@Flow path isparallel to stream path s Quantities such as velocity are uniform across the river.

1. Quantities such as velocity are uniform with depth.

10/3/2012 21

• wJ.S.NRCD CILD U--T dmPrown URAY LGAKREM 000M eple wdlAErmarment Flood Analysis for Oconee Nuclear Station.

Site Topography at Oconee Nuclear Station.

10/3/2012 22

U.SNRC nlI

'goSendRC Flood Analysis for Oconee Nuclear Station.

Two dimensional (Depth Averaged) hydraulic models allow for modeling unusual flow patterns over complex topography. Two-dimensional models are applicable under the following circumstances Flow varies in2dimensions Cross-stream Circulations

, Split flow around objects or topography

° Complex floodplains Two-dimensional models are capable of investigating areas near submerged structures and over complex topography.

Since the topography inthe immediate vicinity of the ONS iscomplex and inclose proximity of the Keowee dam a two-dimensional model isneeded to adequately represent the complex flow at the site.

10/3/2012 0 iaIU nly-Se iti e 23 S Internal In on

Io1"ding Poppk andIfk Enrironume Flood Analysis for Oconee Nuclear Station 1983 Study (Case 1)(Documented by KA Anthony inMemo) s Failure time of 2hours e Median breach width of 575 ft

@Maximum flood height of 4.7 ft (Sunny Day Failure) e PMF not considered

• t* reswondatby building a 5ft flood wall 1992 Study (Study Requested by FERC)

- Failure time of 4hours

- Median breach width of 575 ft

- Maximum flood height of 12.5 ft (Sunny Day Failure)

- Maximum flood height of 16.8 ft (PMF with dam failure)

- Predicted flood overtops SSF after 5hours

- Licensee took no action

. No explanation was given for adjusting failure time from the 1983 value (2hours) to the 1992 value (4hours),

- The licensee claims that their chosen value of 4hours for the failure time isconservative based on the time of failure for Hell Hole dam (18 Hours).

10/3/2012 Offi IUse 0 Sensiti 24 mntnform on'10

0 Sal i y-SeFn ayse jJS.NRC People Prlciqn andthse Ernsrnnrent Internal I rmation Sensitivity of Flood Analysis Any reduction inthe failure time for Jocasseee dam will directly reduce the amount of response time. For example, a reduction inthe failure time from 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to 2hours would mean the SSF would overtop in3hours not 5hours, causing core damage to occur 2hours earlier.

° Also any reduction inthe time of failure for Jocassee dam would increase the maximum flow rate and flood height 10/3/2012 /. Official Us,

uu.ricia yum un-,)e~n ve)

CUS.NRC IIe4ýtlvn Summary of Seismic Aspects of Licensee

Response

10/3/2012 26

Official Ue ly - Sens ive JU.S.NRC PopIa

!4atectin; andta frirornneu ernal rmati n Inadequacies of Jocassee Dam Seismic Fragility Based on Duke 2007 Submission s Updated seismic hazard curves are not current s Liquefaction analysis of sandy material was not done by Duke

1. Assumed failure modes do not include catastrophic failure surface s Increased vertical settlement over time implies probability of soft material at base of dam which may have a liquefaction potential 10/3/2012 27

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Drnal In ion ProwlinD amd iopso a*ki nrgFoac Decision-making Factors 10/3/2012 28

r2j.SNRC 1 UN' TFNW ULI 7~ MtAUU COMSI'UN en, Overall Staff Conclusions The NRC staff met to assess the Licensee's response.

Two options emerged:

--an engineering solution of installation of watertight doors to the SSF

--an analytical approach of further analysis by the licensee Further regulatory action will be required.

Interim operation appears feasible with an additional licensee commitment.

The presentation will provide background to options and pros and cons to each.

10/3/2012 29