ML13056A102

Meeting Slides on Oconee Flood Issue Jocassee Dam Failure Frequency

ML13056A102
Person / Time
Site:	Oconee
Issue date:	02/06/2013
From:	NRC/NRR/DRA
To:
References
FOIA/PA-2012-0325
Download: ML13056A102 (6)

Text

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• 1 Oconee Flood Issue Jocassee Dam Failure Frequency Division of Risk Assessment U NRTED GUIVA MRYC'M Cl:GL.AR CTATES fSSIoC (~taIU-se4Thlyý-S-eGM~RAte4Ye-ate9 gProettqIeople

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Derivation of the Random Jocassee Frequency Two Catastrophic Failures Derived from NPDP -

National Performance of Dams Program

- Frenchman (Montana)

" Failure in 1952

" 63-ft height (some literature shows it as 44-ft)

" Low hazard class

- Skagway (Colorado)

" Failure in 1965

" 79-ft height

" Significant hazard class USNýRY I'm-Io k Ne l .d U.

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Failure Modes That Constitute The Jocassee Dam Catastrophic Failure Frequency

" Random ("sunny day") failure

- Overtopping due to random failure

- Piping or seepage

- Foundation and structural defects

- Other

" PMP (Probable Maximum Precipitation) - PMF (Probable Maximum Flood)

- Results in overtopping

" Seismic

- Results in a catastrophic foundation/structural failure

- Overtopping potential due to wave.

- Evaluation done for Duke in 2007 calculates Jocassee HCLPF at 0.22g for slide initiation.

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(OfficiaLU~se Only - Sec f't*Relat d for tion --

Parsing The Frequency Of Random

("Sunny Day") Failure Modes

• Pros

- Get higher resolution of failure modes contributing to the catastrophic failure frequency.

- Concentrate on specific engineering/operational improvements to reduce overall frequency.

• Cons

- Cannot statistically justify if the overall catastrophic failure data is sparse.

- Method is not well developed relying on the assumption that each failure mode is statistically independent without consideration of common cause.

- Uncertainty needs to be addressed for each failure mode which might yield distributions that are too wide to be confidently used.

SN C off~i9 JrUlp - ecurit Rela dnforf tion

Com(parison o andom am Failures by Type Buttress Dams Over 50 Feet Dams over 50 Feet Tall High Arch Dams 1.E Over 50 Feet High Concrete Dams Over 50 Feet High 0

.4-,

f Ib Earth Dams I lI Over 50 Feet High 0

• Mean Gravity Dams Over 50 Feet High Masonry Dams I

1.)

1.E I -Median Over 50 Feet 0 High 0 Multi-Arch Dams Over 50 Feet High Rockfill Dams Jocassee Over 50 feet high 1.E-05 .4 Total 1 2 3 4 5 6 7 8 T Type 4

~U.S.NRC -~

6

Evaluation

• Uncertainty bands are narrowest for rockfill (similar to Jocassee) and earthen dam types.

• Mean and median (5 0th percentile) frequencies are in the 10-4 to 1O-per year range.

5

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