ML15238B691

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

ML15238B691
Person / Time
Site:	Quad Cities
Issue date:	09/04/2015
From:	Tekia Govan Japan Lessons-Learned Division
To:	Bryan Hanson Exelon Generation Co, Exelon Nuclear
Govan T, NRR/JLD, 415-6197
Shared Package
ML15238B672	List: ML15238B691 ML15239B215
References
TAC MF1108, TAC MF1109
Download: ML15238B691 (7)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 September 4, 2015 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

QUAD CITIES NUCLEAR POWER STATION, 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 (TAC NOS. MF1108 AND MF1109)

Dear Mr. Hanson:

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 11, 2014 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13081A037), flood hazard reevaluation report (FHRR) submitted by Exelon Generation Company, LLC (Exelon, the licensee) for Quad Cities Nuclear Power Station, Units 1 and 2 (Quad Cities), 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 1O 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 this information 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.

B. Hanson 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 guidance documents currently being finalized by the industry and NRC staff) for Quad Cities. 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.

In addition, NEI 12-06 "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide" is currently being revised. This revision will include a methodology to perform a Mitigating Strategies Assessment (MSA) with respect to the reevaluated flood hazards. Once this methodology is endorsed by the NRC, flood event duration parameters and applicable flood associated effects should be considered as part of the Quad Cities 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).

B. Hanson If you have any questions, please contact me at (301) 415-6197 or e-mail at Tekia.Govan@nrc.gov.

Sincerely, dtc~

Tekia V. Govan, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-254 and 50-265

Enclosure:

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

ENCLOSURE:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

Quad Cities, Units 1 & 2 Table 1. Current Design Basis Flood Hazards for Use in the MSA I Mechanism Stillwater Waves/ Design Basis Reference I Elevation Run up Hazard Elevation I I

Local Intense Precipitation I

Not included Not included Not included FHRR Enclosure 1 Section 2.c in DB in DB in DB Streams and Rivers 603.0 ft Not 603.0 ft FHRR Enclosure 2 Table 1 MSL 1912 applicable MSL 1912 Failure of Dams and Onsite Water Control/Storage Structures I i

Not included

• Not included Not included FHRR Enclosure 2 Table 1 in DB  ! in DB in DB I

Storm Surge

! I I No Impact No Impact No Impact FHRR Enclosure 2 Table 1 I

on the Site on the Site I on the Site Identified Identified I Identified I

I Seiche I No Impact No Impact No Impact FHRR Enclosure 2 Table 1 on the Site on the Site on the Site Identified Identified Identified Tsunami No Impact No Impact No Impact FHRR Enclosure 2 Table 1 I

on the Site on the Site on the Site Identified Identified Identified i

Ice-Induced Flooding i I

Not included Not included Not included FHRR Enclosure 2 Table 1 in DB in DB in DB I

i *-***--~ ---

Channel Migrations/Diversions No Impact No Impact No Impact FHRR Enclosure 2 Table 1 on the Site on the Site on the Site Identified Identified Identified Note: Reported values are rounded to the nearest one-tenth of a foot.

Quad Cities, Units 1 & 2 Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA Max-doors by Safety Related 598.4 ft Minimal 598.4 ft Table 4-2 in Enclosure 2 of the Structures, Systems and MSL 1912 MSL 1912 January 13, 2015 Response to Components Request for Additional Information (ML15021A179)

Failure of Dams and Onsite Water Control/Storage Structures Combined Event: Riverine, Dam 600.9 ft 4.1 ft 605.0 ft FHRR Enclosure 2, Table 1 Failure and Waves MSL1912 MSL 1912 July 3, 2014 Response to Request for Additional Information (See RAI Item

1. 2) ML14238A384 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 ML152388672 LTR: ML152388691 ENCL: ML152398215

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