Text

Interim Staff Response to Reevaluated Flood Hazards Submitted in Response to 10 CFR 50.54(f) Information Request - Flood Causing Mechanism Reevaluation
	ML15355A416
Person / Time
Site:	Cooper
Issue date:	12/22/2015
From:	Tekia Govan; Japan Lessons-Learned Division
To:	Limpias O; Nebraska Public Power District (NPPD)
	Govan, Tekia NRR/JLD 415-6197
References
	TAC MF4712
	Download: ML15355A416 (5)
	v • d • e

OFFICIAL USE ONLY SECURITY RELATED INFORMATION UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. Oscar A. Limpias Vice President-Nuclear and CNO Nebraska Public Power District Cooper Nuclear Station 72676 648A Avenue P.O. Box 98 Brownville, NE 68321 December 22, 2015

SUBJECT:

COOPER NUCLEAR STATION - INTERIM STAFF RESPONSE TO REEVALUATED FLOOD HAZARDS SUBMITTED IN RESPONSE TO 10 CFR 50.54(f) INFORMATION REQUEST-FLOOD-CAUSING MECHANISM REEVALUATION (TAC NO. MF4712)

Dear Mr. Limpias:

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 February 3, 2015 (Agencywide Documents Access and Management System (ADAMS)

Accession No. ML15041A523), flood hazard reevaluation report (FHRR) submitted by Nebraska Public Power District (the licensee) for Cooper Nuclear Station (Cooper), 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 reevaluate 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.

Enclosure two transmitted herewith contains Security-Related Information. When separated from the Enclosure, this document is decontrolled.

OFFICIAL USE ONLY SECURITY RELATED INFORMATION

0. Limpias The NRC staff has reviewed the information submitted by the licensee and has summarized the results of the review in the tables provided as Enclosure 1 to this letter. Table 1 provides the current design-basis flood hazard mechanisms. Table 2 provides reevaluated flood hazard mechanisms; however, reevaluated hazard mechanisms bounded by the current design-basis (Table 1) are not included. Because Table 2 includes security-related information, Enclosure 1 contains the redacted version of Table 2. Enclosure 2 is withheld from public disclosure and restores the security-related information to Table 2.

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 Cooper. 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, Nuclear Energy Institute (NEI) guidance document 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 Cooper 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).

OFFICIAL USE ONLY SECURITY RELATED INFORMATION

0. Limpias If you have any questions, please contact me at (301) 415-6197 or e-mail at tekia.govan@nrc.gov.

Docket No. 50-298

Enclosures:

1. Summary of Results of Flooding Hazard Re-Evaluation Report (Redacted Version)

2. Summary of Results of Flooding Hazard Re-Evaluation Report (Non-Public Version) cc w/encl: Distribution via Listserv Sincerely,

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Tekia Govan, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation OFFICIAL USE ONLY SECURITY RELATED INFORMATION

ENCLOSURE 1:

SUMMARY

TABLES OF REEVALUATED FLOOD HAZARD LEVELS

Cooper Nuclear Station Table 1. Current Design Basis Flood Hazards for Use in the MSA1 Mechanism Local Intense Precipitation Streams and Rivers Other SSCs Intake Structure Stillwater Elevation Not included in DB 903.4 ft NVD88 903.4 ft NVD88 Waves/

Runup Not included in DB Not applicable Not

! applicable Design Basis T Hazard Elevation Not included I,'

in DB 903.4 ft 1

NVD88 903.4 ft NAVD88 Failure of Dams and Onsite Water Control/Storage

, Structures I

Offiste Dam Failure Not included ; Not included

'1 in DB in DB Not included in DB Storm Surge Seiche Tsunami Ice-Induced Flooding I

I No Impact 1

on the Site Identified No Impact on the Site Identified No Impact on the Site Identified i Not included in DB 1

Channel Migrations/Diversions I I

Not included in DB No Impact on the Site Identified No Impact

! on the Site Identified No Impact on the Site Identified Not included in DB Not included in DB I

I I

No Impact on the Site Identified No Impact on the Site Identified No Impact on the Site Identified I, Not included in DB I

I I

Not included in DB Note 1: Reported values are rounded to the nearest one-tenth of a foot.

Reference FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 FHRR Addendum A, Table 3.14-1 I I I

I I

Cooper Nuclear Station Table 2. Reevaluated Flood Hazards for Flood-Causing Mechanisms for Use in the MSA 1*2*3 Mechanism Stillwater I

Waves/

Reevaluated Reference Elevation Run up Hazard Elevation I Local Intense Precipitation I

I 903.9 ft I

Minimal 903.9 ft FHRR Addendum A, I

NAVD88 I

NAVD88 Table 3.14-1 Streams and Rivers I

I 903.6 ft I

904.1 ft FHRR Addendum A, Other SSCs 0.5 ft Table 3.14-1 &

NAVD88 I

NAVD88 FHRR Table 2.2-12 I

FHRR Addendum A, Intake Structure 903.0 ft 5.4 ft 908.4 ft Table 3.14-1 &

NAVD88 I

NAVD88 FHRR Section 2.2.4.2 Failure of Dams and Onsite I

Water Control/Storage I

Structures3

[Redacted]

4

[Redacted] I [Redacted]

[Redacted]

I

[Redacted]

Note 5 ----------------------------------------

I [Redacted]