ML13056A103

Briefing on Draft Information Notice - Potential Nonconservative Screening Value for Dam Failure Frequency in Probabilistic Risk Assessments.

ML13056A103
Person / Time
Site:	Oconee
Issue date:	02/06/2013
From:	Office of Information Services
To:
References
FOIA/PA-2012-0325
Download: ML13056A103 (1)

Text

I1 Briefing on Draft Information Notice - "Potential Nonconservative Screening Value for Dam Failure Frequency in Probabilistic Risk Assessments" Presenter:

• Fernando Ferrante

Purpose:

• To inform NRR Senior Management about a draft Information Notice (IN) being prepared by NRR/DRA to alert addressees of a potentially nonconservative screening value for dam failure frequency.

Expected Outcome:

• An understanding of the background, basis, and intent of the draft IN Process:

Background:

• Issue originated with a performance deficiency related to maintenance activities impacting flood barrier protection

• Previously developed dam failure estimates used by licensees were reassessed in light of this finding

" NRR/DRA pursued independent estimation of dam failure estimates

• Generic implications of re-assessment spurred a submittal to the Generic Issue Program (GIP)

Discussion:

" Re-evaluation of previous dam failure estimates indicates the potential for nonconservative screening values having been used in the past

• Using a nonconservative screening dam failure frequency may result in underestimating the risks to the plant associated with external flooding or loss of heat sink from the failure of upstream and downstream dams or levees Current concurrence status:

• Draft IN has been concurred by RES, NRO

• NMSS also on concurrence path

• Draft Information Notice is expected to be issued shortly after final concurrences obtained Conclusions and Recommendations:

Staff expects concurrence on draft IN to be completed in the short-term, and finalized IN would be issued soon. A submittal to the GIP has been accepted after initial screening and a decision on its status is also anticipated in the short-term. Recent events have increased general interest on external flooding risk to nuclear power plant sites. The conclusions contained in the IN are not impacted by these events as the discussion is focused on dam failure frequency estimation, hence the staff recommends completing the issuance process as soon as possible. Follow-up actions are expected to be addressed through the GIP, if issue is accepted as an official Generic Safety Issue.