ML13056A099

Meeting Slides on Oconee Ssf Flood Barrier Breach Sdsp - Lessons Learned

ML13056A099
Person / Time
Site:	Oconee
Issue date:	02/06/2013
From:	NRC/NRR/DRA
To:
References
FOIA/PA-2012-0325
Download: ML13056A099 (13)

Text

Oconee SSF Flood Barrier Breach SDP-Lessons Learned Mike Franovich, DRA.

Jeff Circle, DRA/APOB.

James Vail, DRA/APOB.

Paul Bonnett, DIRS/IRIB.

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RUNIED STATESNUCLEAR REGULATORYCOMMISSION ProtectingPeopleand the Environment

Objectives

• Purpose

- To inform the ET and LT of the lessons learned from the disposition of the Oconee Standby Shutdown Facility (SSF) wall SDP finding.

• Measure for Success

- ET and LT members understand safety and security issues of this finding.

- ET and LT members understanding of the continuous improvement of the SDP appeal process.

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Discussion Topics

• Background of finding.

" Technical lessons learned.

• Process lessons learned.

• Actions taken.

" Considered future actions.

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The Flood Scenario Rupture of Jocassee Dam Fý i koý OcneSt ProtectingPeople and the Environment

The Flood Barrier Finding

, ' .... Licensee opened an access cover

- ,. uncovering a previously cut hole in the wall on August 13, 2003.

- Should have done a 10CFR50.65 (a)(4) assessment immediately.

- Should have done a 10CFR50.59

'T .. evaluation after 90 days.

Licensee opportunities to identify issue N _ - June 2, 2005 NRC inspectors notified the licensee of condition.

Licensee issued PIP (condition K report in their corrective action system). Corrective action not 1 F - -

taken.

August 3, 2005 NRC inspectors Five-foot flood wall questioned lack of corrective action protecting the doorway. and licensee issued a further PIP.

n outside wall with access pl~ate

• Opening sealed on August 3, 2005.

on inside of SSF building.

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Background

• August 17, 2006 - SERP meeting assessed as preliminary WHITE based on a blended qualitative and quantitative risk-informed approach (pre-IMC 0609 App M).

• August 31, 2006 - Choice letter sent to licensee.

• October 5, 2006 - Licensee provided written response to choice letter and waived regulatory conference.

• Nov. 22, 2006 - Final significance determination issued. WHITE based on qualitative erosion of defense-in-depth, but includes quantitative CDF based on apportioning flood frequency to flood height.

• December 20, 2006 - Licensee appeals the final significance determination.

Requests NRC to accept incomplete, un-docketed new information.

• March 1, 2007 - Appeal panel upholds WHITE finding.

• May 3, 2007 - Licensee requests reassessment of final significance determination.

• June, 2007 - Assembled a team to review new information. Flooding expert review of data on random dam failure.

• June 28, 2007 - Follow up telecom with Licensee on dam failure questions and comments.

• July 17, 2007 - Licensee response to analysis questions by email.

• October, 2007 - Final Determination Letter pending.

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Jocassee Dam Random Failure Frequency Licensee developed random dam failure frequency for IPEEE submittal based on rockfill dam failures per population of earthen, rockfill, and composite dams.

- Severely underestimated frequency by an order of magnitude at 1.4E-5 per year.

• As part of the second appeal, DRA/APOB investigated the derivation of this frequency.

Found that 2 failures in 14,425 dam-years was more appropriate for Jocassee which yielded a frequency of 1.8 x 10. Oper year 90% credible interval of [6.5 xl 0-5 /yr, 3.4 xl 0 -4 /yr]

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Technical Lessons Learned Investigation of Dam Failure Frequencies http://crunch.tec.army.miI/nid/webpages/nid.cfm

.http://npdp.stanford.edulindex.htmI Failures Dam-years Mean All Arch Dams 2 9101 2.1 E-04 All Buttress Dams 2 9819 1.9E-04 All Concrete Dams 10 110227 9.3E-05 All Earth Dams 366 2240403 1.6E-04 All Gravity Dams 28 122798 2.3E-04 All Masonry Dams 5 21692 2.2E-04 All Multi-Arch Dams 0 240 1.5E-04 All Rockfill Dams 7 55872 1.3E-04 All Stone Dams 2 11365 1.7E-04 All Timber Crib Dams 3 6536 3.6E-04 Total 425 2605987 1.6E-04 Failures Dam-years Mean Buttress Dams Over 50 Feet 0 1876 2.OE-04 Arch Dams Over 50 Feet 2 5667 2.8E-04 Concrete Dams Over 50 Feet 0 19215 8.2E-05 Earth Dams Over 50 Feet 56 144810 3.8E-04 Gravity Dams Over 50 Feet 7 19542 3.2E-04 Masonry Dams Over 50 Feet 0 1987 2.OE-04 Multi-Arch Dams Over 50 Feet 0 77 2.4E-04 Rockfill Dams Over 50 feet 4 19900 2.1 E-04 Total 69 213184 2.4E-04

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Licensee Evaluations

• Only two IPEEEs addressed dam failure floods quantitatively - Ft Calhoun and Diablo Canyon. Everyone else only addressed probable maximum precipitation and screened out dam failure as low probability.

• Unfortunately, there were few dam failure data sources around back then, so many plants used the estimate published in NUREG/CR-5042. The data source for the estimate in NUREG/CR-5042 was the Oconee PRA - NSAC/60. The estimate of 2.5E-05/dam-year in NSAC/60 was done in error by an order of magnitude and it propagated throughout the industry.

References:

- NUREG/CR-5042, "Evaluation of External Hazards to Nuclear Power Plants in the United States.

- NSAC/60, "Oconee PRA" wUw w NTED STATES NGUCLEAR RGATORY COMMISSION iuiic1e~

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Process Lessons Learned

" Process did not account for situations where licensee did not communicate to the regional office and waived participation in a regulatory conference.

• Process did not accept new information prior to final determination.

• Without a regulatory conference, communication was impacte to program office and regional management of potential greater-than-green SDP findings.

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Actions Taken

• IMC0609 in draft revision to account for:

- Licensees may present new information provided that they informed the agency either during a regulatory conference or in writing before the final significance determination is made.

- New information has to be submitted within the 30-day appeal period.

- Using best available information to determine final significance in a timely manner.

- NRR concurrence with regional management on accepting an appeal.

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Actions Taken (cont'd)

• Training conducted to regional Senior Reactor Analysts (SRAs) in recent counterparts meeting.

• Met with NSIR to inform DHS on potential dam and other outside infrastructure vulnerability.

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Considered Future Actions

" NRR Program Office Director and/or Deputy Director should be informed of all greater-than-green findings.

• Exploration of licensing and potential backfit requirement for protection against most likely flood.

• Generic communication to licensees on flooding.

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