ML17290B232

Nuclear Regulatory Commission Report for the Audit of NextEra Energy Seabrook Flood Hazard Re-evaluation Report Submittal Relating to the Near-Term Task Force Recommendation 2.1-Flooding for Seabrook Station, Unit 1

ML17290B232
Person / Time
Site:	Seabrook
Issue date:	10/31/2017
From:	Frankie Vega Beyond-Design-Basis Management Branch
To:	Nazar M NextEra Energy Seabrook
Vega F
References
CAC MF6782, EPID L-2015-JLD-0019
Download: ML17290B232 (24)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 October 31, 2017 Mr. Mano Nazar President and Chief Nuclear Officer Nuclear Division NextEra Energy Seabrook, LLC Mail Stop: EX/JB 700 Universe Blvd.

Juno Beach, FL 33408

SUBJECT:

NUCLEAR REGULATORY COMMISSION REPORT FOR THE AUDIT OF NEXTERA ENERGY SEABROOK, LLCS FLOOD HAZARD REEVALUATION REPORT SUBMITTAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR SEABROOK STATION, UNIT 1 (CAC NO. MF6782; EPID L-2015-JLD-0019)

Dear Mr. Nazar:

The purpose of this letter is to provide you with the final audit report which summarizes and documents the U.S. Nuclear Regulatory Commissions (NRCs) regulatory audit of the Flood Hazard Reevaluation Report (FHRR) submitted by NextEra Energy Seabrook, LLC (NextEra, the licensee), related to Seabrook Station, Unit 1 (Seabrook). The FHRR was submitted as part of implementing lessons learned from the 2011 accident at the Fukushima Dai-ichi nuclear plant. Specifically, the FHRR documents the results of the flood hazard reevaluation being completed as part of NRC Near-Term Task Force Recommendation 2.1.

By letter dated October 21, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML15292A259), the NRC informed you of the staffs plan to conduct a regulatory audit of NextEras FHRR submittal for Seabrook. The audit was intended to support the NRC staffs review of the licensees FHRR and the subsequent issuance of a staff assessment documenting the staffs review. The audit was conducted over several interactions with the licensee via teleconferences and/or webinars on December 16, 2015, February 11, 2016, April 27, 2016, June 20, 2016, June 23, 2016, and August 10, 2016. The audit was performed consistent with NRC Office of Nuclear Reactor Regulation Office Instruction LIC-111, Regulatory Audits, dated December 29, 2008 (ADAMS Accession No. ML082900195). The details of the audit were discussed with Shaun Kline of your staff.

M. Nazar If you have any questions, please contact me at (301) 415-1617 or by e-mail at Frankie.Vega@nrc.gov.

Sincerely,

/RA/

Frankie Vega, Project Manager Beyond-Design-Basis Management Branch Division of Licensing Projects Office of Nuclear Reactor Regulation Docket No. 50-443

Enclosure:

Audit Report cc w/encl: Distribution via Listserv

M. Nazar NUCLEAR REGULATORY COMMISSION REPORT FOR THE AUDIT NEXTERA ENERGY SEABROOK FLOOD HAZARD REEVALUATION REPORT SUBMITTAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR SEABROOK STATION, UNIT 1 DATED OCTOBER 31, 2017 DISTRIBUTION:

PUBLIC DLP R/F RidsNRRDLP Resource RidsNrrPMSeabrook Resource MShams, NRR RRivera-Lugo, NRO CCook, NRO LQuinn-Willingham, NRO RidsNroDsea Resource RidsNrrLASLent RidsNrrDorlLPL1 Resource RidsRgn1MailCenter Resource ACampbell, NRO BHarvey, NRO SDevlin-Gill, NRO FVega, NRR MWillingham, NRO LHibler, NRO ADAMS Accession No.: ML17290B232

• via email OFFIC NRR/DLP/PBMB/PM NRR/DLP/PBMB/LA NRO/DSEA/RHM1/TR* NRO/DSEA/RHM1/TL E

NAME FVega SLent LQuinn-Willingham LHibler DATE 10/19/2017 10/18/2017 10/23/2017 10/24/2017 OFFIC NRO/DSEA/RHM2/BC NRR/DLP/PBMB/BC NRR/DLP/PBMB/PM E

NAME SDevlin-Gill MShams FVega DATE 10/27/2017 10/29/2017 10/31/2017

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 AUDIT REPORT BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR THE AUDIT OF NEXTERA ENERGY SEABROOK FLOOD HAZARD REEVALUATION REPORT SUBMITTAL RELATING TO THE NEAR-TERM TASK FORCE RECOMMENDATION 2.1-FLOODING FOR SEABROOK STATION, UNIT 1 DOCKET NO. 50-443 BACKGROUND AND AUDIT BASIS By letter dated March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued a request for information to all power reactor licensees and holders of construction permits in active or deferred status, pursuant to Title 10 of the Code of Federal Regulations (10 CFR),

Section 50.54(f), Conditions of Licenses (hereafter referred to as the 50.54(f) letter). The request was issued in connection with implementing lessons learned from the 2011 accident at the Fukushima Dai-ichi nuclear power plant, as documented in the NRCs Near-Term Task Force report. Recommendation 2.1 in that document recommended that the NRC staff issue orders to all licensees to reevaluate seismic and flooding hazards for their sites using current NRC requirements and guidance. Subsequent staff requirements memoranda associated with SECY-11-0124 and SECY-11-0137 instructed the NRC staff address this recommendation through the issuance of requests for information to licensees pursuant to 10 CFR 50.54(f).

By letter dated November 7, 2016 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16314D429), NextEra Energy Seabrook, LLC (NextEra, the licensee), submitted its Flood Hazard Reevaluation Report (FHRR) for Seabrook Station, Unit 1 (Seabrook). The NRC is in the process of reviewing the aforementioned submittal and has completed a regulatory audit to inform the licensee of its review of the submittal, identify any similarities/differences with past work completed, and ultimately aid in its review of licensees FHRR. This audit summary is being completed in accordance with the guidance set forth in NRC Office of Nuclear Reactor Regulation Office Instruction LIC-111, Regulatory Audits, dated December 29, 2008 (ADAMS Accession No. ML082900195).

AUDIT LOCATION AND DATES The audit was completed by document review via the electronic reading room (ERR) and teleconferences/webinars held on December 16, 2015, February 11, 2016, April 27, 2016, June 20, 2016, June 23, 2016, and August 10, 2016.

Enclosure

AUDIT TEAM Title Team Member Organization Team Leader, NRR/JLD Lauren Gibson NRC Branch Chief, NRO/DSEA Aida Rivera NRC Branch Chief, NRO/DSEA Christopher Cook NRC Technical Manager Richard Rivera-Lugo NRC Lead Hydrologist Michelle Bensi NRC Contractor Lyle Hibler NRC Contractor Chris Bender Taylor Engineering, Inc.

Contractor William Miller Taylor Engineering, Inc.

Contractor Pat Fitzpatrick Taylor Engineering, Inc.

Contractor Greg Zimmerman Oak Ridge National Laboratory Contractor Scott DeNeale Oak Ridge National Laboratory Contractor Kevin Stewart Oak Ridge National Laboratory DOCUMENTS AUDITED of this report contains a list that details all the documents reviewed by the NRC staff, in part or in whole, as part of this audit. The documents were located in an ERR during the NRC staff review.

AUDIT ACTIVITIES In general, the audit activities consisted of the following actions:

• Review background information on site topography and geographical characteristics of the watershed.

• Review site physical features and plant layout.

• Understand the selection of important assumptions and parameters that would be the basis for evaluating the individual flood-causing mechanisms described in the 50.54(f) letter.

• Review model input/output computer files, such as FLO-2D, Delft3D, and HEC-Hydrologic Modeling System (HMS), to gain an understanding of how modeling assumptions were programmed and executed. of this report provides more detail and summarizes specific technical topics (and resolution) of important items that were discussed and clarified during the audit. The items discussed in Attachment 2 may be referenced/mentioned in the staff assessment in more detail. of this report provides details regarding the licensees storm surge analysis discussed during the audit.

CLOSEOUT TELECONFERENCE MEETING During the April 27, 2016, webinar, the NRC staff identified information that needed to be provided on the docket. The licensee submitted the requested information on May 10, 2016 (ADAMS Accession No. ML16137A504). During the August 10, 2016, teleconference, the NRC staff identified certain information that needed to be provided on the docket in order to resolve some of the items discussed during the audit. The licensee committed to submit an addendum to the FHRR on the docket.

On December 21, 2016 (ADAMS Accession No. ML16356A479), the NRC staff issued the Interim Staff Response letter for the reevaluated flood-causing mechanisms described in the FHRR and the audit was henceforth considered closed.

Attachments:

1. Seabrook Station, Unit 1 Audit Document List

2. Seabrook Station, Unit 1 Information Needs and Response Summary

3. Seabrook Station, Unit 1 Storm Surge Summary

ATTACHMENT 1 Seabrook Station, Unit 1 Audit Document List

1. ENERCON, 2015 Calc. No. FPL-081-CALC-001, Delft3d Bathymetry and Topography Calculation, Revision. 0, Includes Attachments B and C, July 21, 2015, 62 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1271, FLP-081-CALC-001_DELFT3D Bathymetry and Topography Calculation Rev 0. Located in the Certrec Electronic Reading Room.

2. ENERCON, 2015, Calc. No. FPL-081-CALC-002, Precipitation Events Calculation, Revision 0, Includes Attachments A and B, August 26, 2015, 62 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1275 FPL-081-CALC-002 Precipitation Events Calculation Rev0. Located in the Certrec Electronic Reading Room.

3. ENERCON, 2015, Calc. No. FPL-081-CALC-003, Noreaster Climatology Calculation, Revision 0, Includes Attachments A and B, March 3, 2015, 46 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1276, FPL-081-CALC-003_Noreaster Climatology Calculation Rev 0. Located in the Certrec Electronic Reading Room.

4. ENERCON, 2015, Calc. No. FPL-081-CALC-004, 10% Exceedance High and Low Tides Calculation, Revision 0, Includes Attachments A and B, August 26, 2015, 28 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1278, FPL-081-CALC-004-10% Exceedance High and Low Rev 0.

Located in the Certrec Electronic Reading Room.

5. ENERCON, 2015, Calc. No. FPL-081-CALC-005, Sea Level Rise Calculation, Revision 0, Includes Attachments A and B, July 31, 2015, 17 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1281, FPL-081-CALC-005_Sea Level Rise Calculation Rev0. Located in the Certrec Electronic Reading Room.

6. ENERCON, 2015, Calc. No. FPL-081-CALC-006, Dam Screening and Evaluation Calculation, Revision 0, Includes Attachments A, B and C, March 3, 2015, 23 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1285, FPL-081-CALC-006_Dam Screening and Evaluation Calculation Rev 0.

Located in the Certrec Electronic Reading Room.

7. ENERCON, 2015, Calc. No. FPL-081-CALC-007, Ice Effects Calculation, Includes Attachment A, Revision 0, August 27, 2015, 16 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1286, FPL-081-CALC-007 Ice Effects Calculation Rev0. Located in the Certrec Electronic Reading Room.

8. ENERCON, 2015, Calc. No. FPL-081-CALC-008, Tsunami Source Calculation, Revision 0, Includes Attachments A and B, August 26, 2015, 23 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1290, FPL081-CALC-008_Tsunami Source Calculation Rev0. Located in the Certrec Electronic Reading Room.

9. ENERCON, 2015, Calc. No. FPL-081-CALC-009, Hurricane Wind and Pressure Field Calculation, Revision 0, Includes Attachment B and C, August 26, 2015, 39 pages,NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1291, FPL081-CALC-009 Hurricane Wind and Pressure Field Calculation. Located in the Certrec Electronic Reading Room.

10. ENERCON, 2015, Calc. No. FPL-081-CALC-010, DELFT3D Surge Model Geometry Calculation, Revision 0, Includes Attachments B and C, August 27, 2015, 59 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1294, FPL-081-CALC-010 DELFT3D Surge Model Geometry Calculation Rev

0. Located in the Certrec Electronic Reading Room.

11. ENERCON, 2015, Calc. No. FPL-081-CALC-011, Delft3D Surge Model Calibration Calculation, Revision 0, Includes Attachments B and C, August 27, 2015, 76 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID, 1298, FPL-081-CALC-011 Delft3D Surge Model Calibration Calculation Rev 0.

Located in the Certrec Electronic Reading Room. Located in the Certrec Electronic Reading Room.

12. ENERCON, 2015, Calc. No. FPL-081-CALC-012, HEC-HMS Hydrology Model Development Calculation, Revision 0, Includes Attachment A, B, and C, August 26, 2015, 67 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1302, FPL-081-CALC-012_HEC-HMS Model Development and Calibration Calculation Rev0. Located in the Certrec Electronic Reading Room.

13. ENERCON, 2015, Calc. No. FPL-081-CALC-013, HEC-HMS Warm/Cool Season Probable Maximum Flood PMF Hydrologic Calculation, Revision 0, Includes Attachments A, B, C, D, E, and F, August 26, 2015, 67 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1306, FPL-081-CALC-013 HEC-HMS Warm-Cool Season Probable Maximum Flood (PMF)

Hydrologic Calculation Rev. 0. Located in the Certrec Electronic Reading Room.

14. ENERCON, 2015, Calc. No. FPL-081-CALC-014, Probable Maximum Tsunami (PMT)

Calculation, Revision 0, Includes Attachments A, B, C and D, August 27, 2015, 66 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1314, FPL-081-CALC-014 Probable Maximum Tsunami (PMT)

Calculation_Rev0. Located in the Certrec Electronic Reading Room.

15. ENERCON, 2015, Calc. No. FPL-081-CALC-015, FLO-2D Bathymetry and Topography Calculation, Revision 0, Includes Attachments A, B and C, July 23, 2015, 25 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1314, FPL-081-CALC-015_FLO-2D Bathymetry and Topography Calculation Rev 0. Located in the Certrec Electronic Reading Room.

16. ENERCON, 2015, Calc. No. FPL-081-CALC-016, Probable Maximum Storm Surge (PMSS), Wave Runup, Combined Effects, and Low Water Calculation, Revision 0, Includes Attachments A, B, C, and D, September 11, 2015, 106 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1321, FPL-081-CALC-0016_Probable Maximum Storm Surge (PMSS) Wave Runup Combined Effects and Low Water Calculation Rev 0. Located in the Certrec Electronic Reading Room.

17. ENERCON, 2015, Calc. No. FPL-081-CALC-017, Seiche Calculation, Revision 0, Includes Attachments A. B, and C, August 26, 2015, 31 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1323, FPL-081-CALC-017_Seiche Calculation Rev 0. Located in the Certrec Electronic Reading Room.

18. ENERCON, 2015, Calc. No. FPL-081-CALC-019, FLO-2D Evaluation of Local Intense Precipitation (LIP) Calculation, Revision 0, Includes Attachments A, C, D and E, August 17, 2015, 62 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1325, FPL-081-CALC-019_FLO2D Evaluation of Local Intense Precipitation (LIP) Calculation Revision 0. Located in the Certrec Electronic Reading Room.

19. ENERCON, 2015, Calc. No. FPL-081-CALC-021, Hydrostatic and Hydrodynamic Loading Calculation, Revision 0, Includes Attachment A, September 2, 2015, 30 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1333, FPL-081-CALC-021_Hydrostatic and Hydrodynamic Loading Calculation Rev 0. Located in the Certrec Electronic Reading Room.

20. ENERCON, 2015, Calc. No. FPL-081-CALC-024, Hurricane Climatology Calculation, Revision 0, Includes Attachments A, B, C, and D, August 20, 2015, 43 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1329, FPL-081-CALC-024 Hurricane Climatology Calculation Rev 0. Located in the Certrec Electronic Reading Room.

21. ENERCON, 2015, Calc. No. FPL-081-CALC-025, Site-Specific Local Intense Precipitation (LIP) Calculation, Revision 0, Includes Attachments A, B, and C, August 27, 2015, 34 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1310, FPL-081-CALC-025-Seabrook-LIP-Rev 0. Located in the Certrec Electronic Reading Room.

22. ENERCON, 2016, Calc. No. FPL-081-CALC-016, Probable Maximum Storm Surge (PMSS), Wave Runup, Combined Effects, and Low Water Calculation, Revision 1, Includes Attachments A, B, C, and D, March 2, 2016, 104 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1590, FPL-081-CALC-016 PMSS Wave Runup Combined Effects and Low Water Calc Rev1 (recd 3-2-16). Located in the Certrec Electronic Reading Room.

23. ENERCON, 2016, Calc. No. FPL-081-CALC-016, Probable Maximum Storm Surge (PMSS), Wave Runup, Combined Effects, and Low Water Calculation, Revision 2, Includes Attachments A, B, C, and D, October 5, 2016, 110 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 2022, FPL-081-CALC-016 PMSS Wave Runup Combined Effects and Low Water Calculation Rev 2. Located in the Certrec Electronic Reading Room.

24. ENERCON, 2016, Calc. No. FPL-081-CALC-024, Hurricane Climatology Calculation, Revision 1, Includes Attachments A, B, C, and D, March 2, 2016, 43 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1544, FPL-081-CALC-024 Hurricane Climatology Calculation Rev 1 signed. Located in the Certrec Electronic Reading Room.

25. ENERCON, 2016, Calc. No. FPL-081-CALC-021, Hydrostatic and Hydrodynamic Loading Calculation, Revision 1, Includes Attachment A, October 17, 2016, 31 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, , Flood Hazard Reevaluation Audit, Item ID 2028, FPL-081-CALC-021_Hydrostatic and Hydrodynamic Loading Calculation Rev 1. Located in the Certrec Electronic Reading Room.

26. NextEra (NextEra Energy Seabrook, LLC.), 2015, Flooding Hazards Reevaluation Report, Seabrook Station, Revision 0, Enclosure to Letter from Dean Curtland to the U.S. Nuclear Regulatory Commission, Document Control Desk,

Subject:

Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding - Submittal of Flooding Hazards Reevaluation Report",

SBK-L-15181, September 25, 2015, ADAMS Accession No. ML15274A245 (non-publicly available).

27. NextEra (NextEra Energy Seabrook, LLC.), 2015, Input and output files, Contained on a hard drive, transmitted to NRC as part of the audit.

28. NextEra (NextEra Energy Seabrook, LLC.), 2016, Flooding Hazards Reevaluation Report, Seabrook Station, Revision 1, Enclosure to Letter from Eric McCartney to the U.S. Nuclear Regulatory Commission, Document Control Desk,

Subject:

Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding - Submittal of Flooding Hazards Reevaluation Report",

SBK-L-16175, November 7, 2016, ADAMS Accession No. ML16314D429 (non-publicly available).

29. NextEra (NextEra Energy Seabrook, LLC.), 2016, Addendum A to the Flooding Hazards Reevaluation Report, FPL-081-PR-002, Revision 0, March 2, 2016, 13 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1540, Addendum A to FPL-081-PR-002 Rev 0 Flooding Hazard Reevaluation Report w. Located in the Certrec Electronic Reading Room.

30. NextEra (NextEra Energy Seabrook, LLC.), 2016, NRC Question 3 Response 3-30-16, March 30, 2016, 2 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1581, IN03_LIPRoofDrainage_Final_signed. Located in the Certrec Electronic Reading Room.

31. NextEra (NextEra Energy Seabrook, LLC.), 2016, Information Need #4: Reevaluated Flood Level, March 29, 2016, 6 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1581, IN04_ReevaluatedFloodLevel_Final_signed. Located in the Certrec Electronic Reading Room.

32. NextEra (NextEra Energy Seabrook, LLC.), 2016, Seabrook Flood Hazard Reevaluation Report Audit: Bathymetric Anomalies White Paper, Revision 0, Document Number NEESBX087, January 11, 2016, 3 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1486, SeabrookFHRRAudit_BathymetricAnomaliesWhitePaper_Rev0. Located in the Certrec Electronic Reading Room.

33. NextEra (NextEra Energy Seabrook, LLC.), 2016, Seabrook Flood Hazard Reevaluation Report Audit: Bathymetric Anomalies White Paper, Revision 2, Document Number NEESBX087, Signed January 28, 2016, 8 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1526, SeabrookFHHR Audit_BathymetricAnomaliesWhitePaper_Rev2_signed. Located in the Certrec Electronic Reading Room.

34. NextEra (NextEra Energy Seabrook, LLC.), 2016, Seabrook Flood Hazard Reevaluation Report Audit: Bathymetric Anomalies White Paper, Revision 6, Document Number NEESBX087, March 2, 2016, 11 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1548, SeabrookFHRRAudit_BathymetricAnomaliesWhitePaper_Rev6_signed. Located in the Certrec Electronic Reading Room.

35. NextEra (NextEra Energy Seabrook, LLC.), 2016, Response to Request for Additional Information Regarding the Seabrook Flooding Hazard Reevaluation Report Enclosure to Letter from Michael Ossing to U.S. Nuclear Regulatory Commission, Document Control Desk,

Subject:

Response to Request for Information Regarding the Seabrook Flooding Hazards Reevaluation Report, SBK-L-16044, included a DVD, March 28, 2016, ADAMS Accession No. ML16098A468 (publicly available).

36. NextEra (NextEra Energy Seabrook, LLC.), 2016, Letter from Michael Ossing to U.S.

Nuclear Regulatory Commission,

Subject:

Seabrook Station Re-evaluated Bounding Flood Elevation for Riverine Flooding, SBK-L-16073, May 10, 2016, ADAMS Accession No. ML16137A504 (publicly available).

ATTACHMENT 2 Seabrook Station, Unit 1 Information Needs and Response Summary Information Information Need Description Response Summary Need No.

1 Figures The licensee provided higher quality electronic versions of the requested figures (NextEra, 2016a).

Background:

Figures contained in the Flood Hazard Reevaluation Report (FHRR) (NextEra, The NRC staff reviewed the provided figures and determined 2015) lack visual clarity. they were sufficient to resolve the information need request.

Request: Provide (on the docket) standalone, high quality versions of the following figures for use in the NRCs staff assessment:

a) FHRR Figure 4-8, Seabrook Mannings - n b) FHRR Figure 4-12, Maximum Flow Depths: East c) FHRR Figure 4-13, Maximum WSEL, East d) FHRR Figure 4-14, Maximum Flow Depths: West e) FHRR Figure 4-15, Maximum WSEL, West f) FHRR Figure 4-21, Example of Difference Time-Distributed Hyetographs g) Figure 5-1 in Section 5.1 of Calculation No. FPL-081-CALC-012 (ENERCON, 2015a) 2 All Flood-Causing Mechanisms - Comparison In a letter to NRC dated March 28, 2016 (NextEra, 2016a), the of Reevaluated Flood Hazard with Current licensee stated that the CLB flooding information used for Design Basis comparison in FHRR Section 5 is consistent with the CDB for

Background:

Recommendation 2.1 of the 50.54(f) flooding at Seabrook. The comparisons in FHRR Section 5 are (NRC, 2012a) letter provides instructions for the not affected by the change in terminology and remain valid for FHRR. Under Section 1, Hazard Reevaluation a comparison of the reevaluated values in the FHRR to the Report, Items c and d, licensees are requested to CDB.

perform:

The NRC reviewed the information provided by the licensee c) Comparison of current and reevaluated and determined it was sufficient to resolve the information need flood causing mechanisms at the site. request.

Provide an assessment of the current design basis flood elevation to the reevaluated flood elevation for each flood-causing mechanism. Include how the findings from Enclosure 4 of this letter (i.e.,

Recommendation 2.3 flooding walkdowns) support this determination. If the current design basis flood bounds the reevaluated hazard for all flood causing mechanisms, include how this finding was determined.

d) Interim evaluation and actions taken or planned to address any higher flooding hazards relative to the design basis, prior to completion of the integrated assessment described below, if necessary.

Section 3.0 of the Seabrook FHRR (NextEra, 2015) provides a description of the current licensing basis (CLB) for each flood hazard. The FHRR then provides comparisons of the reevaluated flood hazards with the CLB for each flood hazard mechanism.

Request: Clarify and, where necessary, correct the description and/or comparison of the reevaluated flood hazard to the current design basis (CDB).

3 Local Intense Precipitation-Roof Drainage The licensees response (NextEra, 2016b) expanded on information provided in the FHRR and calculation packages,

Background:

Section 4.1.4 of the FHRR (NextEra, i.e. FPL-081-CALC-019, FLO-2D Evaluation of Local Intense 2015) describes how roof drainage from rainfall Precipitation Calculation (ENERCON, 2015b).

onto buildings and rooftops was handled in the FLO-2D modeling, and it states, The analysis The response confirmed that all roof drains are assumed to be assumes roof drains are nonfunctional; runoff from blocked (with one exception as described in the next building rooftops is routed directly to the ground paragraph) (NextEra, 2016b). The licensee also described adjacent to the building. how roof drainage routing is dependent upon roof configuration: (1) drainage from flat roofs without parapets is divided equally along the edges of the roof and is assumed to However, it is not clear how and where roof be distributed evenly along each edge, (2) drainage from drainage was distributed to the surrounding grid sloped roofs without parapets flows off the lowest edges and is elements in the FLO-2D modeling. Furthermore, assumed to be divided equally among the edges and Section 4.1.4 of the FHRR states (NextEra, 2015), distributed evenly across each edge, and (3) water is assumed A levee component was added to the model to to be trapped and accumulated on roofs with parapets until it represent the parapet structures. overflows the parapet, then the overflow is assumed to be distributed evenly along the edges of the parapets (NextEra, The staff agrees that the assumption of 2016b).

nonfunctional roof drains allows water to flow to the ground and provides a conservative flooding The licensee described an exception to the blocked-drain estimate. However, the assumption that roof assumption for the roof of the Service Water Cooling Tower, drains are blocked, such the water is stored on whose roof drains are directed into the cooling water pool, parapet roofs, is not conservative with regards to which would in turn overflow out the ventilation ports on the flooding. That is, water storage on building roofs north and south sides of the building (NextEra, 2016b). All due to parapets could represent a substantial water collected on this roof is therefore assumed to be equally decrease in the overall water volume on the site. divided between the north and south ventilation discharge ports This modeling approach is not conservative for LIP and evenly distributed along the length of each port (NextEra, flooding since the runoff could flow to the ground. 2016b).

Request: Provide discussion or clarification The licensee stated that, in addition to the assumption that the pertaining to the following: roof drains are blocked, the site storm drain system was also assumed to be blocked at grade level gratings during the LIP a) Clarify how roof drainage was routed in the event (NextEra, 2016b). If the storm drains were not blocked, model and demonstrate that the model then the site drainage system would carry more flow away from implementation accounts for roof drainage the site than what is introduced by the roof drains; hence, the in a manner consistent with actual roof

drainage. If roof drainage is routed to a resulting flooding water surface levels would be no greater than concentrated discharge point, provide a the scenario analyzed in the FHRR (NextEra, 2016b).

description of how the model simulated localized flooding impacts due to The NRC reviewed the information provided by the licensee concentrated discharge, and, if necessary, and determined it was sufficient to resolve the information need provide sensitivity analysis results that request.

demonstrate the significance of localized flooding impacts from roof drainage.

b) Provide justification for the use of levees for simulating parapet walls, which effectively store rainfall occurring over buildings and could result in reduced LIP flood levels. Provide an analysis that shows the effect of allowing water falling on roofs to drain to the site grounds where the LIP depths exceed the wall height.

4 Probable Maximum Flood - Reevaluated Flood The licensees response (NextEra, 2016c) expanded on Level information provided in the FHRR and calculation packages, FPL-081-CALC-012, HEC-HMS Hydrology Model

Background:

Section 5.2 of the FHRR states that Development Calculation, FPL-081-CALC-013, and HEC-the reevaluation of riverine flooding determined a HMS Warm/Cool Season Probable Maximum Flood PMF bounding flow volume from the All-Season Hydrologic Calculation (ENERCON, 2015a; ENERCON, 2015c).

Probable Maximum Flood (PMF) to be 26,158 cfs

[cubic feet per second], which is significantly less In its response and discussed during the April 27, 2016 than the CLB value of 136,500 cfs (NextEra, 2015). webinar, the licensee identified, tabulated and summarized a According to Section 4.2.2.1 of the FHRR, variety of differences in the way the PMF flow was calculated in calibration of the U.S. Army Corps of Engineers the CLB analysis and in the FHRR (NextEra, 2016c). While Hydrologic Engineering Center - Hydrologic the overall watershed drainage area was approximately the Modeling System (HEC-HMS) model used for same for the two analyses, the CLB divided the watershed into reevaluation was not possible due to a lack of gage 2 subbasins and the FHRR used 13 subbasins. The amount of information. impervious surface within the watershed was increased by about 60% in the FHRR analysis. The probable maximum Request: Discuss the primary differences in how precipitation (PMP) rainfall increased from 23.8 inches (in) over the PMF flow volume was estimated for the CDB 24-hour (hr) (in the CLB analysis) to 30.3 in over 72-hr (in the and for the FHRR, and explain how the FHRR FHRR analysis). The FHRR analysis incorporated 5 dams,

value was determined to be reasonable, given a whereas no dams were included in the CLB analysis (NextEra, lack of model calibration. Discuss the basis for 2016c).

value of the time of concentration used in the reevaluation of the hazard and with respect to the The time of concentration (Tc) value in the CLB analysis was value reported in the FSAR [Final Safety Analysis derived from a modified Kirpich method that incorporated the Resport]. Discuss the basis for the Muskingum difference in elevation along the length of the basin, whereas coefficient and the rationale for using flow velocity the FHRR analysis used a Soil Conservation Service Unit rather than flood wave celerity in the coefficient Hydrograph Method applicable to coastal regions (such as the computation. Delmarva peninsula) (NextEra, 2016c). The CLB analysis did not use reach routing for its two subbasins, but the FHRR analysis used the Muskingum method in HEC-HMS model (NextEra, 2016c).

The NRC staff considered the licensees response, including the responses to Information Need # 4a and #6, and determined this information need is resolved.

4a Streams and Rivers - Follow-up to Information The licensees responses to Items #4 and #4a aided the staffs Need #4 understanding of the models assumptions (including Tc and definition of routing parameters) and the application of the

Background:

The staff reviewed the response to model. The licensee also provided a discussion, during the Information Need #4, audit, to support not having originally reported a reevaluated IN04_ReevaluatedFloodLevel_Final_signed.pdf flooding elevation for flooding in river and streams in the FHRR (NextEra, 2016c), provided in the Electronic by utilizing the storm surge model flooding results.

Reading Room and determined that further information is needed to assess the PMF flow rate Regarding item (1) of 4a Information Need, the licensee and elevation for the site. presented contributing factors during the webinar that account for the large difference in the peak PMF rate between the CLB

1) The staff notes that the reevaluated peak and the FHRR. The contributing factors were adjusted from PMF runoff rate (26,000 cfs) is significantly CLB to FHRR, including watershed area, impervious area, lower than the CLB value (136,000 cfs), rainfall duration and depth, numbers of sub-basins, rainfall due to using much longer time of loss, rainfall-runoff transformation method, and reach routing concentration (e.g., adjusted Tc = 19 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br /> method.

for the reevaluation of sub-basin number 3, while Tc = 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for the CLB of the whole The licensee also discussed, during the webinar, the two watershed). Given the size of the basin, different time-of-concentration formulas used in the CLB and the time of concentration used in the FHRR analyses. The licensee indicated that the formula for

analysis in the FHRR may be unreasonably the CLB analysis was originally used in California. The formula long. for the FHRR analysis was originally created for use in Florida.

The NRC staff recognized that both formulas were typical

2) The staff notes that the licensees flow-regression equations but they were created from different data velocity approach can make the Muskingum sets. The licensee did not fully describe the selected formula K value larger than expected, when used to calculate the longer hour (e.g. 19 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br /> for sub-basin compared to staffs results of flood-wave-

1. 3) for the Tc.

celerity approach. If the K value is not calibrated (due to the lack of recorded For item (2) of 4a, during the webinar, the licensee explained flows), other physically-based reach routing that the Muskingum K values were appropriately calculated (such as the Kinematic Wave routing, etc.) with a flow-velocity approach. The licensee stated the flow-must be used. velocity approach could be reasonably used to replace the flood-wave-celerity approach.

Request: Provide justification for the Tc parameters used in HEC-HMS to estimate peak During the webinar, the licensee explained how the PMF flow. Provide a comparison of time of discharge would not be a dominant factor on the flood concentration values computed using other elevation at the Seabrook site. The licensee explained that methods, and discuss the applicability of each when the PMF, approximately 26,000 cfs, was added to the method. For the reach routing, include a tidal wave model to calculate the flood elevation, the discussion of the adequacy of the selected increments of flood elevation would be minimal, approximately parameter values (e.g. flood-wave-celerity 2 inches.

approach to calculate the Muskingum K value).

In a letter dated May 10, 2016 (NextEra, 2016d), the licensee described that the peak PMF water surface elevation was insensitive to higher PMF flow contributions and references Figure 7.2 (not included here or in the letter) within Calculation FPL-081-CALC-016, Revision 1, Probable Maximum Storm Surge (PMSS), Wave Runup, Combined Effects, and Low Water Calculation, (ENERCON, 2016). The licensee basis for concluding insensitivity to the PMF flow contribution is based on the PMF flow be small relative to the tidal flows into Hampton Harbor and the topography/bathymetry of the harbor, contributing channels and the site at high tide conditions.

The NRC reviewed the information provided by the licensee and determined it was sufficient to resolve the information need request.

5 Hazard Input to the Integrated Assessment - In its response (NextEra, 2016a), the licensee stated that the Flood Event Duration Parameters riverine and dam break flooding mechanisms do not result in site flooding, so event duration and warning time parameters

Background:

The Closure Plan for the are not needed for these flooding mechanisms. However, the Reevaluation of Flooding Hazard for Operating licensee stated that the LIP event does result in site flooding, Nuclear Power Plants (COMSECY-15-0019) and duration and warning time parameters will be addressed in (NRC, 2015) requests the licensee to perform an the licensees Mitigating Strategies Assessment (NextEra, additional assessment(s) of the plants response to 2016a).

the reevaluated hazard if the reevaluated flood hazard is not bounded by the current design basis. The NRC reviewed the information provided by the licensee Flood scenario parameters from the flood hazard and determined it was sufficient to resolve the information need reevaluation serve as the input to the focused request.

evaluation and additional assessment. To support efficient and effective evaluations, staff will review flood scenario parameters as part of the flood hazard reevaluation and document results of the review as part of the staff assessment of the flood hazard reevaluation. While the FHRR does provide a partial set of flood duration parameters for LIP in FHRR Table 4-3 and for PMF in FHRR Table 4-21, some parameters (e.g., warning time and the period of site preparation) were not evaluated (NextEra, 2015)

Request: If available, provide the applicable flood event duration parameters (see definition and Figure 6 of the Guidance for Performing an Integrated Assessment, Japan Lessons-Learned Division (JLD) Interim Staff Guidance (ISG) JLD-ISG-2012-05; NRC, 2012b) associated with mechanisms that trigger an additional assessment using the results of the flood hazard reevaluation.

This includes (as applicable) the warning time the site will have to prepare for the event (e.g., the time between notification of an impending flood event and arrival of floodwaters on site) and the period of time the site is inundated for the mechanisms that are not bounded by the current design basis. If available, provide the basis or source of information for the flood event duration, which may include a description of relevant forecasting methods (e.g., products from local, regional, or national weather forecasting centers) and/or timing information derived from the hazard analysis.

6 Streams and Rivers - Probable Maximum Flood During the webinar, the licensee presented flood elevations varied with time for the combined tidal wave, PMF, and dam

Background:

As stated in FHRR Section 4.2.6, the breach (Figure 4-32). The licensee stated that the re-reevaluated PMF peak flow was found to be evaluated bounding flood elevation for riverine flooding is 26,158 cfs and is associated with the All-Season 4.55 ft. North American Vertical Datum of 1988 (stillwater PMP (NextEra, 2015). However, the FHRR does elevation), as determined in Calculation FPL-081-CALC-016, not state a reevaluated peak water surface Revision 1 (ENERCON, 2016), which the licensee posted to its elevation associated with the All-Season PMP ERR. The licensees review of Figure 7.2 in Calculation FPL-event. 081-CALC-016 concluded that the peak PMF water surface elevation was insensitive to higher PMF flow contributions due Request: Provide the reevaluated streams and to two factors: (1) the small contribution of PMF flow relative to rivers PMF scenario flood hazard stillwater the tidal flow through the Hampton Harbor inlet, and (2) the elevation at the Seabrook site, and wave runup hypsometry of the Harbor and contributing channels, especially effects, if applicable, and the CDB flood elevation at high tide levels.

appropriate for comparison.

The NRC reviewed the information provided by the licensee and determined it was sufficient to close the information need request. Because no PMF elevation for the stream and river hazard for the Seabrook site was provided in the FHRR, the NRC staff asked the licensee to provide a supplement or a letter with the numerical value of PMF elevation for CLB and

FHRR. The licensee submitted the requested information on May 10, 2016 (NextEra, 2016d).

7 Dam Breach Flow Estimation During the audit, the licensee did not present the confidence intervals or the input parameter sensitivity for the licensees

Background:

The total PMF inflow to Hampton selected dam-breach flow equation. Instead, the licensee Harbor, including dam breach flow occurring during presented seven inflow points of the PMF event to the the PMF event, was computed to be 58,913 cfs downstream of Seabrook site (NextEra, 2015; ENERCON, (FHRR Section 4.4.8) (NextEra, 2015). For the 2015d). The flow rate of peak PMF at each inflow point at the sunny day dam failure case, the dam breach flow downstream Seabrook site were presented (ENERCON, was computed as 18,363 cfs (FHRR Table 4-22). 2015c). All the inflows were within Hampton Harbor. As In FHRR Section 4.3 and on FHRR Table 4-22, the shown on the flood elevation diagram in the FHRR (Figure 4-dam breach flows were described as the 32), the licensee indicated that the dam breach outflow plus computational results of regression equations. In PMF would have minimal impact on the maximum flood FHRR Section 5.3, the licensee states that, The elevation at the Seabrook site, approximately a 2 inch scenario was modeled within the HEC-HMS increment (NextEra, 2015).

hydrologic model, which resulted in a flow volume of 18,363 [cfs] at Hampton Harbor. Based on the information provided by the licensee during the audit, the NRC staff noted that the dam breach flow would not The staff was not able to find a dam breach flow be a dominant flow to contribute flood elevation at the simulation within the HEC-HMS model using the Seabrook site, and also noted that the tidal wave, plus PMF peak flows for each potentially critical dam that and dam-breach flow would not inundate the Seabrook site.

resulted in, or used, a combined peak flow of Therefore, the confidence intervals and the input parameter 18,363 cfs at Hampton Harbor. In the FHRR, sensitivity for the licensees selected dam-breach flow equation Table 4-22 indicated that the 18,363 cfs of dam is not needed.

breach flow is for Seabrook site, not at Hampton Harbor (NextEra, 2015). The NRC reviewed the information provided by the licensee and determined it was sufficient to resolve the information need Request: Clarify how the dam breach flows were request.

incorporated into the HEC-HMS model, and indicate whether the model input specific to this scenario was previously provided. Include in the discussion which previously submitted model input and output files are consistent with the FHRR description. Clarify that the peak flood elevations associated with the reevaluated dam break flood hazards are described for the Seabrook site.

Clarify whether the flood hazard specified for Hampton Harbor is intended to be representative of Seabrook site hazard.

Consistent with guidance document JLD-ISG-2013-01, Guidance for Assessment of Flooding Hazards Due to Dam Failure, (NRC, 2013) the licensee is requested to present the confidence intervals for the procedure selected, and evaluate the effect of model selection and input parameter sensitivity on the results of the analysis. Justify the approach used to represent dam breach peak flows in a conservative manner.

Sources:

1. ENERCON, 2015a, Calc. No. FPL-081-CALC-012, HEC-HMS Hydrology Model Development Calculation, Revision 0, Includes Attachment A, B, and C, August 26, 2015, 67 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1302, FPL-081-CALC-012_HEC-HMS Model Development and Calibration Calculation Rev0. Located in the Certrec Electronic Reading Room.

2. ENERCON, 2015b, Calc. No. FPL-081-CALC-019, FLO-2D Evaluation of Local Intense Precipitation (LIP) Calculation, Revision 0, Includes Attachments A, C, D and E, August 17, 2015, 62 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1325, FPL-081-CALC-019_FLO2D Evaluation of Local Intense Precipitation (LIP) Calculation Revision 0. Located in the Certrec Electronic Reading Room.

3. ENERCON, 2015c, Calc. No. FPL-081-CALC-013, HEC-HMS Warm/Cool Season Probable Maximum Flood PMF Hydrologic Calculation, Revision 0, Includes Attachments A, B, C, D, E, and F, August 26, 2015, 67 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Item ID 1306, FPL-081-CALC-013 HEC-HMS Warm-Cool Season Probable Maximum Flood (PMF)

Hydrologic Calculation Rev. 0. Located in the Certrec Electronic Reading Room.

4. ENERCON, 2015d, Calc. No. FPL-081-CALC-006, Dam Screening and Evaluation Calculation, Revision 0, Includes Attachments A, B and C, 23 pages, March 3, 2015, NextEra Online Reference Portal, FPL-081-CALC-006_Dam Screening and Evaluation Calculation Rev 0.

Located in the Certrec Electronic Reading Room.

5. ENERCON, 2016, Calc. No. FPL-081-CALC-016, Probable Maximum Storm Surge (PMSS), Wave Runup, Combined Effects, and Low Water Calculation, Revision 1, Includes Attachments A, B, C, and D, March 2, 2016, 104 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1590, FPL-081-CALC-016 PMSS Wave Runup Combined Effects and Low Water Calc Rev1 (recd 3-2-16). Located in the Certrec Electronic Reading Room.

6. NextEra, 2015, Flooding Hazards Reevaluation Report, Seabrook Station, Revision 0, Enclosure to Letter from Dean Curtland to the U.S.

Nuclear Regulatory Commission, Document Control Desk,

Subject:

Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding - Submittal of Flooding Hazards Reevaluation Report", SBK-L-15181, September 25, 2015, ADAMS Accession No. ML15274A245 (non-publicly available).

7. NextEra, 2016a, Response to Request for Additional Information Regarding the Seabrook Flooding Hazard Reevaluation Report Enclosure to Letter from Michael Ossing to U.S. Nuclear Regulatory Commission, Document Control Desk,

Subject:

Response to Request for Information Regarding the Seabrook Flooding Hazards Reevaluation Report, SBK-L-16044, included a DVD, March 28, 2016, ADAMS Accession No. ML16098A468 (publicly available).

8. NextEra 2016b, NRC Question 3 Response 3-30-16, March 30, 2016, 2 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1581, IN03_LIPRoofDrainage_Final_signed. Located in the Certrec Electronic Reading Room.

9. NextEra, 2016c, Information Need #4: Reevaluated Flood Level, March 29, 2016, 6 pages, NextEra Online Reference Portal, Fukushima Project, Seabrook, Flood Hazard Reevaluation Audit, Item ID 1581, IN04_ReevaluatedFloodLevel_Final_signed. Located in the Certrec Electronic Reading Room.

10. NextEra, 2016d, Letter from Michael Ossing to U.S. Nuclear Regulatory Commission,

Subject:

Seabrook Station Re-evaluated Bounding Flood Elevation for Riverine Flooding, SBK-L-16073, May 10, 2016, ADAMS Accession No. ML16137A504 (publicly available).

11. NRC (U.S. Nuclear Regulatory Commission), 2012a, Letter from Eric J. Leeds, Director, Office of Nuclear Reactor Regulation and Michael R. Johnson, Director, Office of New Reactors, to All Power Reactor Licensees and Holders of Construction Permits in Active or Deferred Status,

Subject:

Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dai-Ichi Accident, March 12, 2012, ADAMS Accession No. ML12056A046.

12. NRC (U.S. Nuclear Regulatory Commission), 2012b, Guidance for Performing the Integrated Assessment for External Flooding, Japan Lessons-Learned Project Directorate, Interim Staff Guidance JLD-ISG-2012-05, Revision 0, November 30, 2012, ADAMS Accession No. ML12311A214.

13. NRC (U.S. Nuclear Regulatory Commission), 2013, Guidance For Assessment of Flooding Hazards Due to Dam Failure, Japan Lessons-Learned Project Directorate, Interim Staff Guidance JLD-ISG-2013-01, Revision 0, July 29, 2013, ADAMS Accession No. ML13151A153.

14. NRC (U.S. Nuclear Regulatory Commission), 2015, Closure Plan for the Reevaluation of Flooding Hazard for Operating Nuclear Power Plants, Commission Paper COMSECY-15-0019, June 30, 2015, ADAMS Accession No. ML15153A104.

ATTACHMENT 3 Seabrook Station, Unit 1 Storm Surge Summary During the audit, the NRC staff identified concerns related to the licensees storm surge analysis contained in the FHRR Revision 0 (NextEra, 2015). Over the course of the audit the licensee provided additional information in the electronic reading room which the NRC staff reviewed. No formal information needs were submitted to resolve the NRC staff concerns. In order to address the NRC staffs concerns, the licensee submitted FHRR Revision 1 (NextEra, 2016c), posted revised calculation packages (ENERCON, 2016a; ENERCON, 2016b; ENERCON, 2016c), and additional documentation, Seabrook Flood Hazard Reevaluation Report Audit: Bathymetric Anomalies White Paper Revisions 0 and 2 (NextEra, 2016a; NextEra, 2016b) for NRC staff review. During the NRC staffs review of the licensees storm surge analysis, the staff evaluated the details of the probabilistically based aspects of the storm selection which were not included in the FHRR. The NRC staff review of the FHRR Revision 1 will be discussed in the staff assessment.

References:

ENERCON, 2016a, Calc. No. FPL-081-CALC-016, Probable Maximum Storm Surge (PMSS), Wave Runup, Combined Effects, and Low Water Calculation, Revision 1, Includes Attachments A, B, C, and D, 104 pages, March 2, 2016, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, FPL-081-CALC-016 PMSS Wave Runup Combined Effects and Low Water Calc Rev1 (recd 3 16). Located in the Certrec Electronic Reading Room.

ENERCON, 2016b, Calc. No. FPL-081-CALC-016, Probable Maximum Storm Surge (PMSS), Wave Runup, Combined Effects, and Low Water Calculation, Revision 2, Includes Attachments A, B, C, and D, 110 pages, October 5, 2016, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, FPL-081-CALC-016 PMSS Wave Runup Combined Effects and Low Water Calculation Rev 2. Located in the Certrec Electronic Reading Room.

ENERCON, 2016c, Calc. No. FPL-081-CALC-024, Hurricane Climatology Calculation, Revision 1, Includes Attachments A, B, C, and D, 43 pages, March 2, 2016, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, FPL-081-CALC-024 Hurricane Climatology Calculation Rev 1 signed. Located in the Certrec Electronic Reading Room.

NextEra, 2015, Flooding Hazards Reevaluation Report, Seabrook Station, Revision 0, Enclosure to Letter from Dean Curtland to the U.S. Nuclear Regulatory Commission, Document Control Desk,

Subject:

Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding -

Submittal of Flooding Hazards Reevaluation Report", SBK-L-15181, September 25, 2015, ADAMS Accession No. ML15274A245 (non-publicly available).

NextEra, 2016a, Seabrook Flood Hazard Reevaluation Report Audit: Bathymetric Anomalies White Paper, Revision 0, Document Number NEESBX087, 3 pages, January 11, 2016, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, SeabrookFHRRAudit_Bathymetric Anomalies WhitePaper_Rev0. Located in the Certrec Electronic Reading Room.

NextEra, 2016b, Seabrook Flood Hazard Reevaluation Report Audit: Bathymetric Anomalies White Paper, Revision 2, Document Number NEESBX087, 8 pages, Signed January 28, 2016, NextEra Online Reference Portal, Fukushima Project, Seabrook, NTTF 2.1 Flooding, Seabrook FHHR Audit_BathymetricAnomaliesWhitePaper_Rev2_signed. Located in the Certrec Electronic Reading Room.

NextEra, 2016c, Flooding Hazards Reevaluation Report, Seabrook Station, Revision 1, Enclosure to Letter from Eric McCartney to the U.S. Nuclear Regulatory Commission, Document Control Desk,

Subject:

Response to NRC 10 CFR 50.54(f) Request for Information Regarding Near-Term Task Force Recommendation 2.1, Flooding -

Submittal of Flooding Hazards Reevaluation Report", SBK-L-16175, November 7, 2016, ADAMS Accession No. ML16314D429 (Non-publicly available).