ML14058A083

Email from D. Aird, RES to F. Ferrante, NRR GI-204 Dam Failure Comm. Plan Answer

ML14058A083
Person / Time
Site:	Oconee
Issue date:	01/13/2012
From:	David Aird NRC/RES/DRA
To:	Ferrante F NRC/NRR/DRA
Shared Package
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References
FOIA/PA-2012-0325
Download: ML14058A083 (3)

Text

q Ferrante, Fernando From: Aird, David '[-- j Sent: Friday, January 13, 2012 1:25 PM To: Ferrante, Fernando Cc: Perkins, Richard

Subject:

RE: GI-204 Dam Failure Comm. Plan Answer Fernando, Thanks for taking a look at my various responses. I agree that we are converging on the same answer and now understand why not to take ownership of the IPEEE responses especially considering the questionable numbers assigned to dam failures.

-.. r)*vid______________________

naviri Outside of Scope In the Oconee Nuclear Station su mi

/icensee estimated the im-pact from flooding due to failure of a large upstream dam but also concluded that it this is a low probability event and, therefore, did not pose a severe accident vulnerability.-

Outside of Scope

On Oconee, one of the confusions on what the dam frequency represents is that the licensee parsed failure modes by separating seismic and treating the probability of failure due to overtopping individually (using limited hydrologic data). This approach came from an earlier PRA study effort titled NSAC-60, specific to Oconee. The failure modes which the licensee included were primarily embankment piping and foundation failures with a very narrow focus on dams that met the same characteristics of Jocassee Dam, resulting in a lower value than would generally be obtained by using dam failures from all failure modes and years of operations of the general large dam population (which is how they derived the value listed in the IPEEE, which again was based on NSAC-60 approach).

Outside of Scope

Richard, "

Thanks, David Aird Reliability and Risk Engineer RES/DRA/PRB (301) 251 - 7926 Mailstop: CSB-4CO7M Location: 04-C25

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