ML16084A788

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

ML16084A788
Person / Time
Site:	Duane Arnold
Issue date:	03/31/2016
From:	Minarik A Japan Lessons-Learned Division
To:	Vehec T NextEra Energy Duane Arnold
Minarik A, NRR/JLD, 415-6185
Shared Package
ML16084A767	List: ML16084A788 ML16084A903
References
CAC MF3683
Download: ML16084A788 (5)

Text

UNITED ST ATES NUCLEAR REGULATORY COMMISSION WASHINGTON, O.C. 20555-0001 March 31, 2016 Mr. Thomas A. Vehec Site Vice President Next Era Energy Duane Arnold Energy Center 3277 DAEC Road Palo, IA 52324-9785

SUBJECT:

DUANE ARNOLD ENERGY CENTER- INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST - FLOOD-CAUSING MECHANISM REEVALUATION (CAC NO. MF3683

Dear Mr. Vehec:

The purpose of this letter is to provide a summary of the U.S. Nuclear Regulatory Commission (NRC) staff's assessment of the re-evaluated flood-causing mechanisms described in the March 10, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML14072A017), flood hazard reevaluation report (FHRR) submitted by NextEra Energy Duane Arnold , LLC (the licensee) for Duane Arnold Energy Center (Duane Arnold) , as well as supplemental information resulting from requests for additional information and audits.

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 licensees to re-evaluate flood-causing mechanisms using present-day methodologies and guidance. Concurrently 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 Staff Requirements Memoranda (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.

The NRC staff has reviewed the information submitted by the licensee 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.

T. Vehec 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 Duane Arnold . Further, the NRC staff has concluded that the licensee's reevaluated flood hazard information is a suitable input for other assessments associated with Near-Term Task Force Recommendation 2.1 "Flooding".

The NRC staff plans to issue a staff assessment documenting the basis for these conclusions at a later time .

Revision 2 of NEI 12-06 includes a methodology to perform a Mitigating Strategies Assessment (MSA) with respect to the reevaluated flood hazards. On February 29, 2016, the NRC staff published Japan Lessons-Learned Division Interim Staff Guidance (ISG) JLD-ISG-2012-01 ,

Revision 1, "Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requ irements for Mitigation Strategies for Beyond-Design-Basis External Events," (ADAMS Accession No. ML15357A142) in the Federal Register(81FR10283). This ISG endorses Revision 2 of NEI 12-06 (ADAMS Accession No. ML16005A625), dated December 2015.

Based on the guidance provided in Revision 2 of the NEI 12-06 guidance document, flood event duration parameters and applicable flood associated effects should be considered as part of the Duane Arnold 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.

As stated above, Table 2 of the enclosure to this letter describes the reevaluated flood hazards that exceed the current design-basis. In order to complete its response to the information requested by Enclosure 2 to the 50.54(f) letter, the licensee is expected to submit an integrated assessment or a focused evaluation , as appropriate, to address these reevaluated flood hazards, 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).

T. Vehec If you have any questions, please contact me at (301) 415-6185 or e-mail at anthony. minarik@nrc.gov.

Anthony Minarik, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket No. 50-331

Enclosure:

Summary of Results of Flooding Hazard Re-Evaluation Report

ENCLOSURE:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

Duane A rnold Energy Cent'er Table 1. Current Design Basis Flood Hazards for Use in the MSA I - -

Mechanism Stillwater Waves/ Design Basis Reference Elevation Run up Hazard Elevation Local Intense Precipitation Not included I Not included Not included FHRR Section 3.1 in DB in DB in DB I

Streams and Rivers I I!

764.1 ft MSL 2.9 ft 767 .0 ft MSL FSAR Section 2.4.3 &

! FHRR Section 3.9 i

i i

--***~

Failure of Dams and Onsite  !

Water Control/Storage i Structures I

No Impact on the Site rNo Impact on the Site No Impact on the Site FHRR Section 3.3 Identified Identified Identified I

Storm Surge I Not included Not included Not included FHRR Section 3.4 in DB in DB in DB Seiche I I

Not included Not included  ! Not included FHRR Section 3.5 in DB in DB l in DB I

Tsunami Not included I Not included Not included FHRR Section 3.6 in DB in DB in DB I 1 Ice-Induced Flooding I

No Impact No Impact No Impact FHRR Section 3.7 on the Site I on the Site on the Site Identified Identified Identified Channel Migrations/Diversions I

No Impact No Impact No Impact FHRR Section 3.8 on the Site on the Site on the Site Identified Identified Identified I

Note 1: Reported values are rounded to the nearest one-tenth of a foot.

Duane Arnold Energy Center Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Mechanism Stillwater Waves/ Reevaluated Reference Elevation Run up Hazard Elevation Local Intense Precipitation

! Turbine Building - Door Location 758 .0 ft MSL Minimal 758 .0 ft MSL Email from Nextera Energy i #124 (ML16089A396)

Turbine Building - Door Location 758 .2 ft MSL Minimal 758.2 ft MSL Email from Nextera Energy

1. 136 (ML16089A396)

Turbine Building - Door Location 758 .2 ft MSL Minimal 758 .2 ft MSL Email from Nextera Energy

1. 137 (ML16089A396)

Turbine Building - Door Location 758.0 ft MSL Minimal 758.0 ft MSL Email from Nextera Energy

1. 154 (ML16089A396)

Streams and Rivers

' Cool Season Flood 765.2 ft MSL 2.6 ft 767.8 ft MSL Email from Nextera Energy (ML16089A396)

Note 1: The licensee is expected to develop flood event duration parameters and applicable flood associated effects to conduct the MSA. The staff will evaluate the flood event duration parameters (including warning time and period of inundation) and flood associated effects during its review of the MSA.

Note 2: Reevaluated hazard mechanisms bounded by the current design basis (see Table 1) are not included in this table Note 3: Reported values are rounded to the nearest one-tenth of a foot.

PKG ML16084A767; LTR: ML16084A788; ENCL: ML 16XXXXXXX *via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSEA/RHM2/TR* NRO/DSEA/RHM2/TM*

NAME AMinarik Slent Mlee RRivera-Lugo DATE 3 /21/16 3 /24/16 3 /25/16 3 /30/16 OFFICE NRO/DSEA/RHM2/BC* NRR/JLD/JHMB/BC NRR/JLD/JHMB/PM NAME ARivera MShams AMinarik (TGovan for)

DATE 3 /25/16 3 /30/16 3 /31/16