ML16248A006

Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request - Flood-Causing Mechanism Reevaluation (CAC Nos. MF7710 and MF7711)

ML16248A006
Person / Time
Site:	Prairie Island
Issue date:	09/16/2016
From:	Lauren Gibson Japan Lessons-Learned Division
To:	Northard S Northern States Power Company, Minnesota
Shared Package
ML16248A005	List: ML16248A006
References
CAC MF7710, CAC MF7711
Download: ML16248A006 (6)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 September 16, 2016 Mr. Scott D. Northard Acting Vice President Northern States Power Company - Minnesota Prairie Island Nuclear Generating Plant 1717 Wakonade Drive East Welch, MN 55089-9642

SUBJECT:

PRAIRIE ISLAND NUCLEAR GENERATING PLANT, UNITS 1 AND 2 - INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST - FLOOD-

. CAUSING MECHANISM REEVALUATION (GAG NOS. MF7710 AND MF7711)

Dear Mr. Northard:

The purpose of this letter is to provide a summary of the U.S. Nuclear Regulatory Commission (NRG) staff's assessment of the reevaluated flood-causing mechanisms described in the May 9, 2016 (Agencywide Document Access and Management System (ADAMS) Accession No. ML16133A041 ), flood hazard reevaluation report (FHRR) submitted by Northern States Power Company, a Minnesota corporation (the licensee), doing business as Xcel Energy, for Prairie Island Nuclear Generating Plant, Units 1 and 2 (Prairie Island), as well as supplemental information resulting from the NRC's audit of the FHRR.

By letter dated March 12, 2012, the NRG 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 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 NRG 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 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 2 1, 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 NRG staff has reviewed the information submitted by the licensee and has summarized the results of the NRC's review in the tables provided as an enclosure to this letter.

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

Sincerely, Lauren K. Gibson, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-282 and 50-306

Enclosure:

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

ENCLOSURE:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

Prairie Island Nuclear Generating Plant, Units 1 & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA Mechanism Stillwater Waves/ Design Basis Reference Elevation I Run up Hazard Elevation Local Intense Precipitation I

I Not included Not included Not included FHRR Sections 1.5, 2.1.3 & Table 4 I I in DB in DB in DB I

I I

Streams and Rivers I i

Mississippi River Probable 703.6 ft 3.1 ft 706.7 ft FHRR Section 1.5.1 & Table 4 Maximum Precipitation NGVD29 NGVD29 I

Failure of Dams and Onsite Water Control/Storage Structures I 676.5 ft Not 676.5 ft FHRR Section 1.5.2 & Table 4 NGVD29 applicable NGVD29 I

I I Storm Surge i

I Not included Not included Not included FHRR Section 1.5 & Table 4 in DB in DB in DB I

Seiche Not included Not included Not included FHRR Section 1.5 & Table 4 in DB in DB in DB I

I Tsunami I I Not included Not included Not included FHRR Section 1.5 & Table 4 in DB in DB in DB I

I

' Ice-Induced Flooding i I Not included Not included Not included FHRR Section 1.5 & Table 4 in DB in DB in DB I I

, Channel Migrations/Diversions Not included Not included _I Not included FHRR Section 1.5 & Table 4 in DB in DB in DB

_ _ _ _ _ _ _ _j _ _ _ _ _ _ _

~-

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

Prairie Island Nuclea r Generating Plant, Units 1 & 2 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 Minimal 695.4 ft FHRR Section 2.1.2 & Tables 4 and 5 I 695.4 ft NGVD29 NGVD29 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 ML16248A005; LTR: ML16248A006; ENCL: ML16245A763 *via email OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRO/DSEA/RHM2ffR* NRO/DSEA/RHM2/BC

• NAME LKGibson Slent PChaput ARiveraVarona DATE 09/13/2016 09/ 9 /2016 09/1 /2016 09/ 1 /2016 OFFICE NRR/JLD/JHMB/BC (A) NRR/JLD/JHMB/PM NAME GBowman LKGibson DATE 09/15/2016 09/ 16/2016