ONS-2016-042, Notification of External Flood Modifications Completion

Notification of External Flood Modifications Completion

ML16131A671
Person / Time
Site:	Oconee
Issue date:	04/29/2016
From:	Batson S Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ONS-2016-042, TAC MF1012, TAC MF1013, TAC MF1014
Download: ML16131A671 (4)

Text

Scott L. Batson

(~DUKE Vice President

~ ENERGY Oconee Nuclear Station Duke Energy ON01 VP I 7800 Rochester Hwy ONS-2016-042 Seneca, SC 29672 o: 864.873.3274

t. 864.873. 4208 April 29, 2016 Scott. Batson@duke-energy.com A TIN: Document Control Desk 10 CFR 50.54(f)

U.S. Nuclear Regulatory Commission Washington, DC 20555 Duke Energy Carolinas, LLC (Duke Energy)

Oconee Nuclear Station, Units 1, 2 and 3 Docket Numbers 50-269, 50-270, 50-287 Renewed License Numbers DPR-38, DPR-47, and DPR-55

Subject:

Notification of External Flood Modifications Completion

References:

1. NRC Letter; Confirmatory Action Letter - Oconee Nuclear Station, Units 1, 2, and 3 Commitments to address external Flooding Concerns, dated June 22, 2010, (ADAMS Accession No. ML101730329).

2. NRC Letter; Oconee Nuclear Station, Units 1, 2, and 3 - Modifications to Address External Flooding Hazards, dated September 20,2012, (ADAMS Accession No. ML12219A163).

3. Duke Energy Letter, Establish the Fukushima Flood Response as the Basis to Govern*

Flood Mitigation Modifications kom Postulated Upstream Dam Failure, dated August 8, 2014 (Accession No. ML14225A540).

4. Duke Energy Letter, Revised Flood Hazard Reevaluation Report per NRC's Request for Additional Information, dated March 6, 2015 (Accession No. ML15072A106).

5. NRC Letter, Oconee Nuclear Station, Units 1, 2, AND 3 - Interim Staff Response To Reevaluated Flood Hazards Submitted In Response To 10 CFR 50.54(f) Information Request- Flood-Causing Mechanism Reevaluation (TAC NOS. MF1012, MF1013, AND MF1014), dated September 24, 2015, (Accession No. ML152398261).

6. Duke Energy Letter, Supplemental Information Regarding NRG 2008 and 2012 Requests for Information Pursuant to 10 CFR 50.54(f) Pertaining to External Flooding at Oconee Nuclear Station (ONS) Revision 1, dated January 8, 2016(Accession No. ML16015A430).

7. NRC Letter, Oconee Nuclear Station, Units ( 2, AND 3 - Staff Assessment Of Response To Request For Information Pursuant To 10 CFR 50.54(F) Flood-Causing Mechanisms Reevaluation (GAG Nos. MF1012, MF1013, AND MF1014) and Path Forward on Confirmatory Action Letter, dated April 14, 2016 (Accession No. Pkg. ML15356A161; Letter ML15352A207 [Public] ; Enclosures 1 & 2; ML15356A158 [Non-Public]).

Ladies and Gentlemen, On June 22, 2010 a Confirmatory Action Letter (CAL) (Reference 1) to address Oconee Nuclear Station flooding concerns was issued to Duke Energy. A NRC letter dated September 20, 2012 (Reference 2) stated that the agency intended to maintain the CAL active until it could be superseded by regulatory action related to Fukushima responses. j} D / D N{(~

ONS-2016-042 April 29, 2016 Page2 On August 8, 2014 Duke Energy submitted a letter to the NRC (Reference 3) to document that Oconee flood modifications would be based on the Flooding Hazard Reevaluation Report (FHRR) flood analysis.

Duke Energy submitted its final FHRR on March 6, 2015 (Reference 4) and on September 24, 2015, the NRC provided an Interim Staff Assessment of the re-evaluated flood hazards (Reference 5). The Assessment established flooding levels for a deterministic, beyond design basis, Jocassee Dam failure flood at Oconee Nuclear Station, to be defined by the FHRR failure analysis results.

On January 8, 2016, Duke Energy submitted a supplemental information letter to the NRC which described the Jocassee Dam failure flooding response for Oconee Nuclear Station (Reference 6). This letter included a list of five (5) modifications being constructed at the site to support mitigation of Jocassee Dam failure floods. The modifications are: Relocation of the1 OOkV (FANT) Back-up Power Line, East Slope Scour Protection, Intake Dike Scour Protection, Discharge Diversion Wall, and Turbine Building Drain Isolation. A description of these modifications is included in the enclosure to this letter.

On April 14, 2016 the NRC issued a Final Staff Assessment of the FHRR (Reference 7) and concluded that the 2015 FHRR flood analysis is acceptable for the purpose of meeting the terms of the June 22, 2010 CAL.

This letter is informing the NRC that, in support of CAL closure, all five modifications associated with Jocassee Dam failure flooding mitigation are field construction complete as of April 26, 2016.

This letter contains no new regulatory commitments.

Should you have any questions or require additional information, please contact David Haile of the ONS Regulatory Affairs Group, at (864) 873-4742.

• Sincerely, Scott L. Batson Vice President Oconee Nuclear Station

ONS-2016-042 April 29, 2016 Page 3 cc:

Ms. Catherine Haney, Region II Administrator U.S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 Mr. William Dean, Director, Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike M/S 0-13H16 Rockville, MD 20852-2738 Ms. Anne Boland, Director, Division of Operating Reactor Licensing U.S. Nuclear Regulatory Commission One White Flint North*

11555 Rockville Pike M/S 0-8E1A Rockville, MD 20852-2738 Mr. Jack Davis, Director, Japan Lessons Learned Project Division U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike M/S 0-13H 16 Rockville, MD 20852-2738 Mr. James R. Hall, Project Manager (ONS)

(by electronic mail only)

U.S. Nuclear Regulatory Commission 11555 Rockville Pike, M/S 0-8G9A Rockville, MD Mr. Jeffery Whited, Project Manager (by electronic mail only)

U.S. Nuclear Regulatory Commission 11555 Rockville Pike M/S 0-881 A .

Rockville, MD 20852 Mr. Eddy Crowe NRC Senior Resident Inspector Oconee Nuclear Station

ONS-2016-042 April 29, 2016 Enclosure EXTERNAL FLOODING MODIFICATIONS Flooding Modification Description Levels 100kV (FANT) Relocate the back-up power transmission line towers above the Back-up Power floodplain to supply emergency power through CT-5 to the site.

1 1 Line Tower This modification includes the acquisition of new right-of-way and Relocation relocation of 22 transmission towers.

Protect the Condenser Circulating Water (CCW) embedded piping (cooling water supply) by armoring the eastern slopes supporting East Slope the site grade. This modification includes approximately 2 Scour 150,000 ft 2 of scour protection (rip rap, concrete block, shotcrete, 1, 2, & 3 Protection energy dissipaters, gabion mattresses) on the east slopes of the ONS power block, to prevent flood waters from eroding the embankment.

Protect the intake dike and th~ e_mbedded Condenser Circulating Water piping (cooling water supply) by armoring the Intake Dike in high water velocity locations and providing grass cover support as Intake Dike approved by FERC. The modification includes scour protection 3 Scour 1, 2, & 3 (shotcrete) where the Intake Dike meets the east bank, and an Protection auxiliary drain system at the bottom of the intake dike slope to improve drainage for the existing good grass cover that is credited for preventing flood waters from eroding the embankment.

Protect the _Condenser Circulating Water imbedded piping (cooling water supply) and reduce initial flooding levels by directing water Discharge away from the site grade. The modification includes a 206' long 4 1, 2, & 3 Diversion Wall flood diversion wall, with a top elevation of 828' msl, located near the Condenser Circulating Water discharge structure and designed to deflect flood waters away from the ONS Power Block.

Turbine The modification includes one manually operated weir gate located 5 Building Drain at the entrance of a 72" Turbine Building drain line to prevent flood 1 Isolation waters from back-flowing into the building basement.

The modifications being constructed at the site to support dam failure flood mitigation are applicable to a range of postulated flood levels, including the Jocassee breach event in the FHRR (Reference 4 ). The range of flooding levels are characterized by the following three categories:

1. Flooding levels with peak levels below site grade at 796' msl.

2. Flooding levels above site grade but below 803.5' msl (the top of the SSF flood walls).

3. Flooding levels above the SSF flood walls (addressed by mitigating strategies).

Additional modifications, associated with the mitigation strategies for NRG Order EA-12-049, will be provided as required by that Order.