ML14058A035
| ML14058A035 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/04/2014 |
| From: | Office of Information Services |
| To: | |
| Shared Package | |
| ML14055A421 | List:
|
| References | |
| FOIA/PA-2012-0325 | |
| Download: ML14058A035 (29) | |
Text
U.SNROfficia se Only -Setiins iveOconee Flood Protection and the10 CFR 50.54(9 ResponseBackground Material1 SUS.NRCProtecing People rnd the fbr mmtOutline, Site Background
- Issue Background s 10 CFR 50.109 Backfits Principal 10 CFR 50.54(f)
Questions Regarding Oconee FloodProtection Issues 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 LicenseeResponse10/3/2012 MidCai use ni eUS, R n- a I Ina! ao a tt' nSite Background Oconee Nuclear Station-Three nuclear units located in Seneca, SC-Operational in 1973-74Plant located down river of Lake Keowee and LakeJocasseeOnly nuclear plant in the United States that relies onhydro-electric generators located in one dam asemergency power source-Plant relies on the Standby Shutdown Facility (SSF)to maintain reactor shutdown in case of fires, floods,or sabotage events.10/3/2012 3
SU.S.NRC IU1U IyNIILca~I "T ITUL L R REG I UV MIUStwkd in.P ople and Lde Enrm'tomfe The Jocassee Dam10/3/2012 4
USA RJ IUColm1,Aerial View of the Oconee Site and Lake Keowee-I... _,. ,,,,10/3/2012 5'I 0U.SNRC 0 nsi ve(,7A--,UyNR r Inform .--Issue ackground s NRC inspection identified flood protection issue withOconee 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 againstJocassee Dam failure based on unavailable inundation studv-Duke Hydro/FERC Inundation Study completed in early 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 externalflooding concerns-Evaluation of current fleet for flood vulnerabilities underway-Security interface with NSIR and DHS10/3/2012 6
?U.S.NRCteaina "Ihucinf hPopks and &fmEnroman The SSF Flood Barriers10/3/2012 Ofca -s~ -.: F-:..ae ..Ul ..U .ram , ; .' ., ....~ ,10/3/2012 Off~ icia -S~t~7 illulal U S eSLSU.SNRCPe*t *cl h~Pope aRd M,~em meat4"10 CFR 50,109 Backfit Evaluation s Backfit evaluation:
external flooding is within Oconee'slicensing basis. Licensee did not address Jocassee damfailure as a source of external flooding.
- Staff determined increased flood protection is a backfit.* "Adequate Protection" based backfit is best approach,
-No defense-in-depth:
3-unit core damage event with ultimatefailure of each containment.
-Regulatory expectations for external flood protection includesdam hazards.# Cost-benefit estimate of $3 million in modifications.
Modifications on the order of $13 million justified.
10/3/2012 8
al Use On
-U.S.NRC InformPoctinf PgopI and du~ Emr~orneist Principal 10 CFR 50.54(f Questions Regarding Oconee Flood Protection Issue1. Explain the bounding external flood hazard at Oconeeand the basis for excluding consideration of otherexternal flood hazards, such as those described in theInundation Study, as the bounding case.2. Provide your assessment of the Inundation Study andwhy it does or does not represent the expected floodheight following a Jocassee Dam failure.3. Describe in detail the nuclear safety implications offloods that render unavailable the SSF and associated support equipment with a concurrent loss of allAlternating Current power.10/3/2012 9
- IJ .S.N CIterna,,
.Lcensee ResponseTidbits to be added in packages Duke offered to increase entrance wall heights by 2.5feet.@ Question of whether to perform 1 D vs. 2D study fromDuke telecone 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 fromBad Creek and Jocassee during conditions of PMP.s FERC report and the condition of Jocassee Damembankment leakage@ Discussion of Duke's reliability approach over astatistical approach on failure frequency 10/3/2012 10 I USU VJII Oll ~~lILIVe()US1NRC I nal foat'bnDetailed Summary of Licensee Responseto 10 CFR 50.54(f Letter10/3/2012 11
/'fOff iciý,Use Or~- Sensitijv USSARCProwling mep d The Ex+,07rom eview Team, Scope-Review submittal as if NRC is reconstituting a design basisflood for Oconee-All modes/events causing external flooding will be assessed-All modes/events causing Jocassee dam failure will beassessed.Diverse team of SES andexpertise in:-Engineering
-Risk Assessment
-Seismology
-Hydrology
-Project Management senior technical staff with10/3/2012 12 ifici ee OnIl -- ensitivUS RCInte nform tiIj .S.NRCber Pro e p and the°o-T e a m M e m b e r sSES- 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 -SeismicGoutam 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 MembersMike Case (D/DPR)Timothy McGinty (DD/DORL)
Sher Bahadur (DD/DE -acting)10/3/2012 13 US.NC Ij lNeWInfor ionNro~tiq Peopk axd Ow Em.-numml Principles of Riskoinformed Decision MakingProcess Used* Risk insights are integrated with considerations of defense in depth and safety margins,, Traditional engineering analysis provides insightinto available margins and defense in depth* Topics considered in support of options-Likelihood of dam failure-Flood analysis (nominal and PMP lake levels)-Seismic analysis-Basis for continued operation
-Security10/3/2012 14
'U.S.NRCTIEND ST ES 'SElA:REýlAATORY COMUSSJON Proteet n Peopl and the Exvim~wm~e ted Decision MaIntegra'kincJr'0010/3/2012 I4nptrnqd Information 15 COff alIUseO0 y Sensve-~II..NRC Perspective of Oconee re i event Protection
- -$jJS.NRC VNI UJ. SIAM NLU IARR)I WA OMINONPrvfrc nPeopk mmd tAEmvirornmtn 0 ial Use -Sen 'tivernal In i nSummary of Random Dam FailureFrequency of Licensee Response10/3/2012 17
- ~US.NRCProw in; People anid AButtress DamsOver 50 FeetHighArch DamsOver 50 FeetHighConcreteDams Over 50Feet HighEarth DamsOver 50 FeetHighGravity DamsOver 50 FeetHighMasonry DamsOver 50 FeetHighMulti-Arch Dams Over 50Feet HighRockfill DamsOver 50 feethighTotalDams over 50 Feet Tall1.E-03NRC Developed Random Failure Frequency forJocasseeI6I0'I0001.E04Licensee-Developed Random Failure Frequency for Jocassee
( Taken FromIPEEE Submittal) 1.E-05I I I I1 2 3 4 5 6 7 8 TType10/3/2012 10/32012Off, cAUse 0 -Sensi'e 118 Pro*cwig Pelapkd dw Extiroomeat Probability Density of Jocassee.Dam Failure Frequency
~: ~a... ~.~ ,10/3/2012 19 ILSNRC. Cl KIIter Prowecinq Peopic a is hEmaemmee Summary of Hydrology Aspects ofLicensee Response10/3/2012 idUse 0 ly -n si y eInte I I jformatio'h 20
?jS.LNRC
\QIoa oi~n~tPmlroI~gw Peopte nd tAm Enziromnni, Flood Analysis for Oconee Nuclear StationThe licensee proposed to use the Hydrologic Engineering CenterRiver Analysis System (HEC-RAS) to model and estimate the flooddepth at the ONS..HEC-RAS is a one-dimensional hydraulic model used tomodel 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 is parallel to stream paths Quantities such as velocity are uniform across the river.# Quantities such as velocity are uniform with depth.10/3/2012 21
- wJ.S.NRCU--T CILD D LGAKREM URAY 000MdmPrown eple w dlAErmarment Flood Analysis for Oconee Nuclear Station.Site Topography at Oconee Nuclear Station.10/3/2012 22 U.SNRC nlI'goS endRC Flood Analysis for Oconee Nuclear Station.Two dimensional (Depth Averaged) hydraulic models allow for modelingunusual flow patterns over complex topography.
Two-dimensional modelsare applicable under the following circumstances Flow varies in 2 dimensions Cross-stream Circulations
, Split flow around objects or topography
° Complex floodplains Two-dimensional models are capable of investigating areas nearsubmerged structures and over complex topography.
Since the topography in the immediate vicinity of the ONS is complex andin close proximity of the Keowee dam a two-dimensional model is neededto adequately represent the complex flow at the site.10/3/2012 0 iaIU nly-Se iti e 23S Internal In on Io1"ding Poppk and Ifk Enrironume Flood Analysis for Oconee Nuclear Station1983 Study (Case 1) (Documented by KA Anthony in Memo)s Failure time of 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />se Median breach width of 575 ft@ Maximum flood height of 4.7 ft (Sunny Day Failure)e PMF not considered
- reswondatby building a 5 ft flood wall1992 Study (Study Requested by FERC)-Failure time of 4 hour4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />s-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 5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />s-Licensee took no action.No explanation was given for adjusting failure time from the 1983value (2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) to the 1992 value (4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />),-The licensee claims that their chosen value of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> for the failuretime is conservative based on the time of failure for Hell Hole dam (18Hours).10/3/2012 Offi I Use 0 Sensiti 24mnt nform on'10 jJS.NRCPrlciqn People and thse Ernsrnnrent 0 Sal i y -SeFn ayseInternal I rmationSensitivity of Flood AnalysisAny reduction in the failuretime for Jocasseee dam willdirectly reduce the amount ofresponse time. For example,a reduction in the failure timefrom 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> to 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> wouldmean the SSF would overtopin 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> not 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />,causing core damage tooccur 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> earlier.° Also any reduction in the timeof failure for Jocassee damwould increase the maximumflow rate and flood height10/3/2012
/. Official Us, uu.ricia y um un-,)e~n ve)CUS.NRC I Ie4ýtlvnSummary of Seismic Aspects of LicenseeResponse10/3/2012 26 Official U e ly -Sens iveJU.S.NRC ernal rmati n!4atectin; PopIa and ta frirornneu Inadequacies of Jocassee Dam SeismicFragility Based on Duke 2007 Submission s Updated seismic hazard curves are notcurrents Liquefaction analysis of sandy material wasnot done by Duke# Assumed failure modes do not includecatastrophic failure surfaces Increased vertical settlement over timeimplies probability of soft material at base ofdam which may have a liquefaction potential 10/3/2012 27 11Viciai usA enm.Drnal I n ionProwlinD iopso amd nrgFoacDecision-making Factors10/3/2012 28 r2j.SNRC en,UN' TFNW 1 7~ ULI MtAUU COMSI'UNOverall 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 thelicenseeFurther regulatory action will be required.
Interim operation appears feasible with an additional licensee commitment.
The presentation will provide background to options andpros and cons to each.10/3/2012 29