ML14058A028

NRR Lt Meeting on Oconee Flood Protection and the 10 CFR 50.54(f) Response

ML14058A028
Person / Time
Site:	Oconee
Issue date:	10/21/2008
From:	Office of Nuclear Reactor Regulation
To:
Shared Package
ML14055A421	List: ML090570117 ML090680737 ML091620669 ML092020480 ML092940769 ML100280954 ML101750619 ML101890803 ML102990064 ML103410042 ML12268A404 ML14055A410 ML14055A411 ML14055A474 ML14058A015 ML14058A016 ML14058A017 ML14058A018 ML14058A019 ML14058A020 ML14058A021 ML14058A022 ML14058A023 ML14058A024 ML14058A025 ML14058A026 ML14058A027 ML14058A028 ML14058A029 ML14058A030 ML14058A031 ML14058A032 ML14058A033 ML14058A034 ML14058A035 ML14058A036 ML14058A037 ML14058A038 ML14058A039 ML14058A040 ML14058A042 ML14058A043 ML14058A044 ML14058A045 ML14058A046 ML14058A047 ML14058A048 ML14058A049 ML14058A050 ML14058A051 ... further results
References
FOIA/PA-2012-0325
Download: ML14058A028 (11)

Text

' / O~~ffcil, ý$e nly - Sensiti/ve j**-S.NRC0--ntrnt Oconee Flood Protection and the 10 CFR 50.54() Response NRR LT Meeting October 21, 2008 October 21, 2008 1

U Pm.NRC

,I LAl COM \CU*11Interna Objectives Purpose

-Summarize the licensee's responses

-Discuss the staff's evaluation and options

-Discuss possible paths forward

-To receive LT feedback on the merits of possible paths forward October 21, 2008 2

t PmS.linR

-* L*I't IIInItera S

Background

II rmt" Duke Hydro/FERO Inundation Study completed inearly 1990s. Estimated flood heights up to 16.8 ft above SSF grade level

- First identified by inspectors in1994.

• Floods inexcess of 5ft lead to three-unit core damage event.

, Staff identified an under-estimate inlicensee's random dam failure frequency for Jocassee.

, Staff discovery that the Jocassee dam failure issue had not been adequately resolved.

, Issued 10 CFR 50.54(f) letter for Duke to address flooding concerns.

October 21, 2008 3

.NARC Principal 10 CFR 50.54(f Questions Regarding Oconee Flood 1.Explain the bounding external flood hazard at Oconee and the basis for excluding consideration of other external flood hazards, such as those described inthe Inundation Study, as the bounding case.

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

3.Describe indetail the nuclear safety implications of floods that render unavailable the SSF and associated support equipment with aconcurrent loss of all Alternating Current power.

October 21, 2008 4

\Unhcia us e Iy-ens ive

-US,NRC I

.,jnrnal I n Prokix;Propkaidt du Emnment 50.54(f Letter Review Team Scope

- Review submittal as ifNRC isreconstituting adesign basis flood for Oconee

- All modes/events causing external flooding will be assessed

- All modes/events causing Jocassee dam failure will be assessed s Topics considered indevelopment of.options:

- Likelihood of dam failure

- Flood analysis

- Seismology

- Basis for continued operation

- Security October 21, 2008 5

se Only - SeniTlive

• U.S.NRC4OfOf, \ fotio_

NiedinghPopk .diEivrome, Overall Summary of Licensee's Response

, Inundation levels based on current drought conditions

-Supports continued operation

, 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" October 21, 2008 6

IKUS.NRC frTLULAICOWW.u cvI UTUR u yeUHoov Overall Summary of Staff's Review of Licensee's

Response

Interim continued operation appears feasible with additional licensee commitment of water management Licensee failed to fully address site flood height (e.g,,

adequate protection)

- No analysis for random Jocassee Dam failure at full pond level

- An inadequate seismic analysis

- Did not perform a Probable Maximum Precipitation (PMP) analysis

, Future planned analysis for dam failure isnot acceptable

- Issues on time-to-failure, breach size, and choice of flood model

, Current and future reliance on probability arguments is not acceptable October 21, 2008 7

U.S.NRC '~K~nIIrt.j9 2 Options for Path Forward adt6 Euwoanma Izulicq Peapk

, Options represent choice between engineered and analytical approaches

• An engineered solution

- Installation of watertight doors to the SSF

- Has not been committed to by licensee

• An analytical approach

- Analysis was proposed by the licensee October 21, 2008 8

of Option 1

\ý I'dMUDITUDS UM [Li.IL*l ARIM CNMMlI.%*

h'°*a ped&Summary -

Engineered Solution (Installation of watertight doors)

Pros Cons

1. Independent of all Licensee might delay sources of flood and acceptance of this inundation level solution

1. Fully addresses adequate protection

• Fewer NRC staff resources required for inspections and review Timely and defensible to internal and external stakeholders October 21, 2008 9

• )UOSNRC Summary o Option 2 Further Analytical Solution Pros Cons s Improved estimate of flood , Aresolution timeframe may be prohibitive inundation level to define amount of protection to be

• Licensee has inappropriately eliminated failure modes applied High degree of uncertainty in s Licensee-proposed solution dam breach analysis Analysis plan for Feb. 2010 is not adequate

• Calculated inundation level may result ina further engineered solution

° Probability approach isnot acceptable

, Requires very extensive staff review resources October 21, 2008 ONfli e Iy-S sV, 10 Internal In rm ionn

. USNRC PmingPekpI Ui~ rownmt andW Outline of Presentation to Licensee on October 30, 2008 Management Meeting

, State basis for interim continued operation

. State NRC position on dam failure frequency (probability) argument

- NRC will not expend staff resources on an approach which will not contribute to asolution

- Licensee's proposed probability approach of eliminating failure modes with inappropriate bases isnot acceptable to NRC staff

• State NRC position on preferred option

, State regulatory vehicle to pursue

- An order

- AConfirmatory Action Letter October 21, 2008 11