ML14058A029

(Redacted) NRR Lt Meeting on Oconee Flood Protection and the Jocassee Dam Hazard

ML14058A029
Person / Time
Site:	Oconee
Issue date:	10/21/2008
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML14055A421, ML24365A140	List: ML14058A029
References
FOIA/PA-2012-0325
Download: ML14058A029 (17)

Text

icial s Only -

en tPe-lterna, Info ation

,-*ý)U.S.NRC Internal n%

Oconee Flood Protection and the Jocassee Dam Hazard NRR LT Meeting October 21, 2008 1015/2012 Oft ciI Use only -S di~ve Iri t fltjion official 48'O

- Sens.i"e

-USNRC

ýIO n QC Objectives Purpose

- To discuss the specific questions raised

• summarize the licensee's responses

• discuss the staffs evaluation

• discuss possible paths forward

- To receive LT feedback on

• staffs evaluations

" merit of possible paths forward 10/5/2012 Offi.,al Only. -.

1y J

e 2

lntem I a*jimatVon 1

rD

-.72-1+

officJ I

G~- SensitiyMe f~naI U.S RC Us Agenda (not to be included)

• Review of issue and site background

• Prior staff work in backfit evaluation

• 10 CFR 50.54(f) Letter

• Evaluation of Licensee's Response

" Team members

" Overview of options based on review'of 50.54(f) response

" Risk-informed decision making process

- Assessing the licensee's response to the 10 CFR 50.54(f) letter Topics considered in support of decision

• Likelihood of dam failure

• Flood analysis (nominal and PMP lake levels)

• Seismic analysis

• Security

• Basis for continued operation

• Conclusions and Recommendations

Pros and cons of options

" Summary 10/5/2012 Oial Up0.5Sen ltive 3

- n"fa,,rorr IýU.S.NRC IRIV6 ln-'rrM U

IrnPadI InforraM*

Summary 10/5/2012 0

Use n-Sens e

4 2

Sensit nal

-,qvUS.NRC OMf'*se Only - Sen yve ItlInf r~m~

1015/2012

'~cfI~sV(1l-Sens dve

"ý Inlyas;ý 5

,q'VU.S.NRC SitUse Backsgrv Site Background Oconee Nuclear Station

- Three nuclear units located in Seneca, SC

- Operational in 1973-74

- Plant located down river of Lake Keowee and Lake Jocassee

- Only nuclear plant in the United States that relies on hydro-electric generators located in one dam as emergency power source

- Plant relies on the Standby Shutdown Facility to maintain reactor shutdown in case of fires, floods, or sabotage events.

10/5/2012 10)5/2012 O

U all nýy-s"e 3

Offici I ly

°- 'nsitive inaI 17 folrm aat io n

ýU_.S.NRC The Jocassee Dam 10/5/2012 on"lrnae Ny Sens!

7

~Iy.Sensi~e 7

~VTTNOMw~e Only-)4nsitiep NJ II C Int~gnaij6mation ApriaI Vipw of tho 0c~nne Site.

4

Official Use Only ensi ýve Inter I

Infor io Issue Background

• 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 study DUKe Hydro/FERU inundation Study cbMpletea in early 1990s.

Estimated flood heiahts uo to IR 8.ft above SSF grade level

-:-Dam ranaom 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 10/5/2012 9enti9 The SSF Flood Barriers 1015/2012 105/01 Ffti~i~r~i 10 5

Lificial Us On ý-Sen~sitive ýIern~a IGation Off*al U0 l Only-Sen e

10 CFR 50.109 Backfit Evaluation

" Backfit evaluation: external flooding is within Oconee's licensing basis. Licensee did not address Jocassee dam failure 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 ultimate failure of each containment.

Regulatory expectations for external flood protection includes dam hazards.

" Cost-benefit estimate of $3 million in modifications.

Modifications on the order of $13 million justified.

10/6/2012 I

-lSens'I

, tUSNRC Internal t ation 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 in the Inundation Study, as the bounding case.

2.

Provide your assessment of the Inundation Study and why it does or does not represent the expected flood height following a Jocassee Dam failure.

3.

Describe in detail the nuclear safety implications of floods that render unavailable the SSF and associated support equipment with a concurrent loss of all Altemating Current power.

10/5/2012 09 al U se ns e

12 6

C-neWmation

~.JTTeAT

'QfficIaIUs~6?~-Sens~#.(e A.*U.S.NRC

\\ma.-nkooa*o Licensee Response to 10 CFR 50.54(f) Letter Question I

• Dams are constructed with adequate freeboard to accommodate the effects of probable maximum precipitation (PMP).

• Design of Jocassee was to the same seismic input as Oconee site.

• FERC study was not to assess credible flood heights for Oconee site.

" Random "sunny day" failure of Jocassee not credible due to design, construction, and inspections conducted.

" Embankment failures should be excluded.

10/5f2012

\\,fcial U Only -

aSe 13 l~zz1 ¶i.nfm rniýn A

-'-,U.SNRC Io all-Licensee Response to 10 CFR 50.54(f) Letter Question 2

• The FERC Inundation study is the only study on record.

• Licensee feels that it is not applicable to Oconee since it was developed to determine evacuation plans.

• Piping failure of Jocassee Dam was not considered credible and of low frequency based on response to question 1.

• Questions on timing of Keowee Dam failure after overtopping.

10/5/2012

-enst

/

14

\\X.JfiirnaInforr~,p 7

o*ifor rhatjio U&SNRC snaIn Sen~e Licensee Response to 10 CFR 50.54(f) Letter Question 3

• Licensee states that SSF will survive flood based on assumption that Jocassee Dam failure will produce flood heights of less than 5-ft.

• For floods greater than 5-ft, the SSF will be unavailable leading to early core damage.

• Licensee assumes reactor shutdown in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> with floodwater reaching site in 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.

• Core damage will occur in 8 to 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> with containment failure in 59 to 68 hours7.87037e-4 days <br />0.0189 hours <br />1.124339e-4 weeks <br />2.5874e-5 months <br />.

10/5/2012 0

"i¶*a Only-S- %We 15 Intemaknfor 5&6n

-tS NRC

ý=z

..5 0.54(f) Letter Review Team

" Scope Review submittal as if NRC is reconstituting 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 10/5/2012 Otffcial U Onl-Sesifive 16 Intema Ia ormati*p 8

Official Use ly -

q-ýtU.SNRC 10/5/2012 Team Members SES - Management Melanie Galloway (DD/DRA)

David Skeen (DD/DE)

Sam Thomas (DD/DORL - acting)

DRA - Risk Assessment and Dam Failure Frequency Mike Franovich (BCIAPOB)

Jeff Circle (APOB)

James Vail (APOB)

DE - Structural Kamal Manoly (BC/EMCB)

Raman Pichumani (EMCB)

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

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

DORL - Project Management Melanie Wong (BCILP)

Leonard Dishan (LP)

Jon Thompson (LP)

Contrlbuting SES Members Mike Case (DIDPR)

Timothy McGinty (DD/DORL)

Sher Bahadur (DD1DE - acting)

O)kiLUs 4n Sensla e 1

I n't,* IInonfo ton*

n 17 SUSNRC

-cI lusxOnV\\ Sens#'ve

\\Jtea nfoknatln 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.

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

10/5/2012

\\o1i~rcial Us m Se$)tive a

nt 9n 18 9

Se itiv

.tnaI Information Ue0 -%en~site Jv5.SNRCt wri LIC-504 Risk-informed Decision Making Process [create new title w/o ref to 504]

Assessing the licensee's response to the 10 CFR 50.54(f) letter and supporting information Topics considered in support of options

- Likelihood of dam failure

- Flood analysis (nominal and PMP lake levels)

- Seismic analysis

- Security

- Basis for continued operation Note: THIS IS A PLACEHOLDER 10/6/2o12 1*, 1.Us,*On. Se ie 19 In W

ýalInfor 00

-5tUSiNRC YOf Integrated Decision Making 1015/2012 0

e 20 T Intem 1nformte 10

?nfcia~' Uon l,ýý

• }U.S.N RC o

n

-II,l e

OfIr'ýnternal ir~*= ssil:

S '.

Perspective of Oconee Credible Event Protection Ali-.J Adiklate Prdbtciefn Pocii AssuredAssured 1O?~2O12Official Uslfy Sen ve 21

'Lnjwlpall IlfntcNal9R-'

.~L~)USNRC Only ensitive U.S.NRC fo on Summary of Licensee's Response to 50.54(f) Questions

• Inundation levels based on current drought conditions.

• Commitment to increase current flood walls to 7.5 feet by February 2009.

• Further analysis by February 2010.

• Heavy reliance on test and inspection of dam.

• Seismic failure is not credible

• Other dam failure modes (i.e., overtopping) not credible.

• • • • • • • • • • • • • • • • • • UNDER DEVELOPMENT

• 101512012 Official U n -. Sen *ve 22 11

9ff1qc se Only-SeQ!

eernal (ll ation I Buttess DOM¶ Ow, 60 Feet High I

Arch Denrim Owi 50 FMg 3

CC'Onne Feed Hight 4

Ert~h Darrvi High a Gravity Demm Om, S0 Feel High I Mazeemy Darns u

High 7 Mui-Arch Dami GVSi, SO Feet High I

RockiiiRMmS Owe SO rest high T Total 101512012 Dm OIIZ U

ý Sen nve t1~emal nfd J, Dams over 50 Feet Tall I E-3 1RC Ove,,ioped Random.k,,Falm Fr.q-enCy I.,

11E-04 fFI me-an L1cenl-Dft.ecopeO Rendom Fail-. Frsqnemy for Jocn.-e ( Te.M. Fra,,

1PEER So.111tett 1

2 3

4 5

0 7

8 T

Typa 0 d~al Use n -Sens'rve 23 101512012 Use 9(n\\ - Sen.Ave InNpp(infofqiý 24 12

/Infor"'atin O

a, z e~..Sen nive

-3tU.S.INRIC Iesallt~

Flood Analysis for Oconee Nuclear Station Choice of Hydraulic Model [consolidate 21-27 into 2 slides-points to make-time to failure not conservative, breach size not conservative, adequacy of 1-D model indeterminate due to complex site topography; keep slide 22]

In their 50.54(f) response letter, 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 is a one-dimensional hydraulic model used to model networks of canals and reaches of rivers. One-dimensional models are limited to situations where the following are true.

" Flow path is parallel to stream path

" Quantities such as velocity are uniform across the river.

" Quantities such as velocity are uniform with depth.

Typically, one-dimensional models are not appropriate if the area of interest is located near complex topography and submerged structures because the fluid structure interactions tend to violate the assumptions given above.

10/5/2012 Offiru sSeruteve 25

,nt VUJ,nfor=*

fc iL~

r O ly e

r~US1NRC OfficiLUA Only -\\Sen,-Owe Internal Infori1mtion Flood Analysis for Oconee Nuclear Station.

Site Topography at Oconee Nuclear Station.

'.J~l ema S74"'.e~

10/5/2012 26 13

Officia e Oni

- Se itiveItrnal n1 atio 0Cal Use On ý-Sensiti e kUS.NRC Oýýnai 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 in 2 dimensions 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 in the immediate vicinity of the ONS is complex and in close proximity of the Keowee dam a two-dimensional model is needed to adequately represent the complex flow at the site.

101512oa2 oca ly*-*spal"* e 27

\\,emdftf~aon

...U.S.NRC Internal Infok* n Flood Analysis for Oconee Nuclear Station.

Choice of Dam Breach Parameters Definitions Breach width, B - The maximum size of opening that develops in the dam over a specified period of time. Typically the opening is assumed to be trapezoidal in shape. The opening can be characterized by its side slope and the bottom or median width (See Figure).

lime of failure - the time for the breach opening to fully develop. The development is typically assumed develop linearly in time.

101512012 28 14

Flood Analysis for Oconee Nuclear Station.

1983 Study (Case 1) (Documented by KAAnthony in Memo)

Failure time of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> Median breach width of 575 ft Maximum flood height of 4.7 ft (Sunny Day Failure)

PMF not considered Licensee responded by building a 5 ft flood wall f992 Study (Study Requested by FERC)

Failure time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> 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 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> Licensee took no action 10/512012 u

29

-ýU.SNRC Flood Analysis for Oconee Nuclear Station.

No explanation was given for adjusting failure time from the 1983 value (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 failure time is conservative based on the time of failure for Hell Hole dam (18 Hours).

10/5/2012 nsitiv 30 15

o ciase Onl ensitive I al Informatio rstU.S.NRC O

i al Information Flood Analysis for Oconee Nuclear Station.

Any reduction in the failure time for Jocasseee dam will directly reduce the amount of response time. For example, a reduction in the failure time from 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 /> would mean the SSF would overtop in 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 to occur 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 time of failure for Jocassee dam would increase the maximum flow rate and flood height (See Figure).

Vidataon In Peak Flowrate From Dam Break 1

2 3

4 5

=

ysU~n 5,1 sJbtve 3

X

.4teka.

=irasin' 1015/2012 31 c1~T1-)r QsOny-Se~peltT~

~J 2

~~

~~

Iner ation Inadequacies of Jocassee Dam Seismic Fragility Based on Duke 2007 Submission Scaled input motion with Factor of Safety. Updated seismic hazard is not current

• Liquefaction analysis of sandy material was not done by Duke

• Assumed failure modes do not include catastrophic failure surface Increased vertical settlement over time implies probability of soft material at base of dam (i.e.,

liquefaction potential)

• [this slide needs to be clearer]

10/5/2012

\\Offciad~l nty-Senji'v3 32 16

F.,*

i (nYorma 'on A

, U T

TIOffici UseOlySenve

,:-'Jocassee Dam Seismic Fragility FERC 2004 Part 12 Report [delete this slide]

• FERC 99 to 04 report shows a 5-year steadily higher vertical settlement

• There may be soft material near the base of dam 10/5/2012 O

Yve 33 17