ML16356A468

Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(F) Information Request - Flood-Causing Mechanism Reevaluation

ML16356A468
Person / Time
Site:	Seabrook
Issue date:	12/21/2016
From:	Lauren Gibson Japan Lessons-Learned Division
To:	Mccartney E Nextera Energy
Gibson L, NRR/JLD, 415-1056
References
CAC MF6782
Download: ML16356A468 (3)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 21, 2016 Mr. Eric McCartney Site Vice President Seabrook Station NextEra Energy 626 Lafayette Road Seabrook, NH 03874

SUBJECT:

SEABROOK STATION, UNIT 1 - INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST- FLOOD-CAUSING MECHANISM REEVALUATION (CAC NO. MF6782)

Dear Mr. McCartney:

The purpose of this letter is to provide a summary of the U.S. Nuclear Regulatory Commission (NRC) staff's assessment of the reevaluated flood-causing mechanisms described in the November 7, 2016, flood hazard reevaluation report (FHRR) submitted by NextEra Energy Seabrook, LLC (the licensee) for Seabrook Station, Unit 1 (Seabrook) (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16314D429).

By letter dated March 12, 2012, the NRC issued a request for information pursuant to Title 10 of the Code of Federal Regulations, Section 50.54(f) (hereafter referred to as the 50.54(f) letter)

(ADAMS Accession No. ML12053A340). The request was issued as part of implementing lessons learned from the accident at the Fukushima Dai-ichi nuclear power plant. Enclosure 2 to the 50.54(f) letter requested that licensees reevaluate flood-causing mechanisms using present-day methodologies and guidance. Concurrent with the reevaluation of flooding hazards, licensees were required to develop and implement mitigating strategies in accordance with NRC Order EA-12-049, "Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML12054A735). On March 30, 2015, the Commission provided the staff requirements memorandum (SRM) (ADAMS Accession No. ML15089A236) to COMSECY-14-0037, "Integration of Mitigating Strategies for Beyond-Design-Basis External Events and the Reevaluation of Flooding Hazards," dated November 21 , 2014 (ADAMS Accession No. ML14309A256), affirming that licensees need to address the reevaluated flooding hazards within their mitigating strategies for beyond-design-basis external events.

Revision 2 of Nuclear Energy Institute (NEI) guidance document NEI 12-06, dated December 2015, includes a methodology for performing a mitigating strategies assessment (MSA) with respect to the reevaluated flood hazards. On February 29, 2016, the NRC staff published Japan Lessons-Learned Division (JLD) Interim Staff Guidance (ISG)

JLD-ISG-2012-01, Revision 1, "Compliance with Order EA-12-049, 'Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events"' (ADAMS Accession No. ML15357A142), in the Federal Register (81 FR 10283). This ISG endorses Revision 2 of NEI 12-06 (ADAMS Accession No. ML16005A625). Based on the

E. McCartney guidance provided in Revision 2 of NEI 12-06, flood event duration parameters and applicable flood associated effects should be considered as part of the Seabrook MSA. The NRC staff will evaluate the flood event duration parameters (including warning time and period of inundation) and flood-related associated effects developed by the licensee during the NRC staff's review of the MSA.

In addition to the MSA, in order to complete its response to the information requested by to the 50.54(f) letter, the licensee is expected to submit an integrated assessment or a focused evaluation, as appropriate, to address the reevaluated flood hazards that exceed the current design basis, as described in the NRC letter, "Coordination of Request for Information Regarding Flooding Hazard Reevaluation and Mitigating Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML15174A257). This letter describes the changes in the NRC's approach to the flood hazard reevaluations that were approved by the Commission in its SRM to COMSECY-15-0019, "Closure Plan for the Reevaluation of Flooding Hazards for Operating Nuclear Power Plants" (ADAMS Accession No. ML15209A682).

The NRC staff has reviewed the information submitted by the licensee in its FHRR and has summarized the results of the review in the tables provided as an enclosure to this letter.

Table 1 provides the current design-basis flood hazard mechanisms. Table 2 provides the reevaluated flood hazard mechanisms; however, the reevaluated flood hazard mechanisms bounded by the current design basis (Table 1) are not included. The NRC staff has concluded that the licensee's reevaluated flood hazards information, as summarized in the enclosure, is suitable for the assessment of mitigating strategies developed in response to Order EA-12-049 (i.e., defines the mitigating strategies flood hazard information described in Nuclear Energy Institute (NEI) guidance document NEI 12-06, "Diverse and Flexible Coping Strategies (FLEX)

Implementation Guide") for Seabrook. Further, the NRC staff has concluded that the licensee's reevaluated flood hazard information is a suitable input for other flooding assessments associated with the 50.54(f) letter. The NRC staff plans to issue a staff assessment documenting the basis for these conclusions at a later time.

If you have any questions, please contact me at (301) 415-1056 or e-mail at Lauren.Gibson@nrc.gov.

Sincerely, Lauren Gibson, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket No. 50-443

Enclosure:

Summary of Results of Flooding Hazard Re-Evaluation Report cc w/encl: Distribution via Listserv

E. McCartney SEABROOK STATION, UNIT 1 - INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST - FLOOD-CAUSING MECHANISM REEVALUATION DATED December 21, 2016 DISTRIBUTION:

PUBLIC JLD R/F RidsNRRJLD Resource LGibson , NRR LQuinn-Willingham , NRO RidsNroDsea Resource RidsNrrDorllpl1-2 Resource RidsNrrDorl Resource RidsNrrPMMillstone Resource RidsRgn1 MailCenter Resource RidsN rrLASLent RidsOgcMailCenter Resource RidsOpaMail Resource RidsAcrsAcnw_MailCtr Resource CCook, NRO ARivera-Varona , NRO KErwin, NRO ACampbell , NRO MWillingham , NRO LHibler, NRO BHarvey, NRO MShams, NRR RRivera-Lugo, NRO GBowman , NRR ADAMS Accession Nos.: PKG: ML16356A479; LTR: ML16356A468; ENCL: ML16347A175 *via email NRR/JLD/ NRO/DSEA/EHM1/BC OFFICE NRR/JLD/JHMB/PM* NRR/JLD/JHMB/BC(A) NRR/JLD/JHMB/PM LA NAME LGibson Slent MBensi

• GBowman LGibson DATE 12121/16 12/21/16 12/21/16 12/21/16 12/21/16 OFFICIAL AGENCY RECORD