ML14133A603

Request for Additional Information (Supplemental) Regarding Fukushima Lessons Learned - Flooding Hazard Reevaluation Report

ML14133A603
Person / Time
Site:	North Anna
Issue date:	05/14/2014
From:	V Sreenivas Plant Licensing Branch II
To:	Heacock D Virginia Electric & Power Co (VEPCO)
Sreenivas V, NRR/DORL/LPLII-1
References
TAC MF1106, TAC MF1107
Download: ML14133A603 (5)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 May 14, 2014 Mr. David A. Heacock President and Chief Nuclear Officer Virginia Electric and Power Company 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

NORTH ANNA POWER STATION, UNITS 1 AND 2: REQUEST FOR ADDITIONAL INFORMATION (SUPPLEMENTAL) REGARDING FUKUSHIMA LESSONS LEARNED- FLOODING HAZARD REEVALUATION REPORT (TAC NOS. MF11 06 AND MF11 07)

Dear Mr. Heacock:

By letter dated November 26, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13325B122), the U.S. Nuclear Regulatory Commission (NRC) staff issued a request for additional information (RAI) to Virginia Electric and Power Company (Dominion) regarding the North Anna Power Station, Units 1 and 2, flood hazard reevaluation report submitted in response to NRC's March 12, 2012, 50.54(f) letter (ADAMS Accession No. ML12053A340). The licensee responded to these RAis by a letter dated December 13, 2013 (ADAMS Accession No. ML13357A100).

RAI 3.4-1 requested, in part, that the licensee provide evaluations of failure mechanisms applicable to the service water reservoir impoundment using present-day guidance, methods, and data, including an evaluation of the potential for seismically-induced failure of the service water reservoir impoundment dike under site-specific seismic hazards defined using present-day guidance and methods. The licensee responded by stating that site-specific seismic hazard reevaluation will be completed in March 2014.

By letter dated March 31, 2014, the licensee submitted seismic hazard and screening report (ADAMS Accession No. ML14092A416), which concludes that North Anna screens in for a seismic probabilistic risk assessment as the results of the screening evaluation indicates that the ground motion response spectrum (GMRS) exceeds the safe shutdown earthquake (SSE).

The NRC staff has determined that additional information is needed for RAI 3.4-1 to complete its review.

A response to the enclosed RAI is needed within 30 days of this issuance before the NRC staff can complete the review. Should you have any questions, please me at 301-415-2597.

Sincerely,

. Sreenivas, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-338 and 50-339

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv

INTERIM STAFF EVALUATION AND REQUEST FOR ADDITIONAL INFORMATION (RAI) (SUPPLEMENTAL)

FUKUSHIMA LESSONS LEARNED FLOODING HAZARD REEVALUATION REPORT VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-338 AND 50-339 Supplemental RAI No. 3.4-1 By letter dated November 26, 2013 (Agencywide documents Access and Management System (ADAMS) Accession No. ML133258122), the U.S. Nuclear Regulatory Commission (NRC) staff issued a request for additional information (RAI) to Virginia Electric and Power Company (Dominion) regarding the North Anna Power Station, Units 1 and 2, flood hazard reevaluation report submitted in response to NRC's March 12,2012, 50.54(f) letter (ADAMS Accession No. ML12053A340). RAI 3.4-1 requested, in part, that the licensee provide evaluations of failure mechanisms applicable to the service water reservoir impoundment using present-day guidance, methods, and data, including an evaluation of the potential for seismically-induced failure of the service water reservoir impoundment dike under site-specific seismic hazards defined using present-day guidance and methods.

The licensee responded (ADAMS Accession No. ML13357A100) to RAI 3.4-1 by stating that site-specific seismic hazard reevaluation will be completed in March 2014 and that the "adequacy of the seismic qualification for the service water reservoir impoundment dike may have to be revisited depending on the results of the seismic reevaluation and resulting station

[probabilistic risk assessment] reevaluations." The licensee further indicates that "even if the impoundment dike were to fail as a result of the seismic event, the design of the emergency dike and diversion trench prevent water from the service water reservoir from reaching the plant." The RAI response does not provide information about the seismic capacity or performance of the emergency dike to support a conclusion that it would be available in the event that the service water reservoir impoundment dike were to fail under a seismic event.

The licensee's seismic hazard and screening report (ADAMS Accession No. ML14092A416) submitted by the licensee on March 31, 2014, concluded that North Anna screens in for a seismic probabilistic risk assessment as the results of the screening evaluation indicates that the ground motion response spectrum (GMRS) exceeds the safe shutdown earthquake (SSE).

Request for Supplemental Information:

The licensee is requested to provide justification for the seismic capability of the service water impoundment under the updated seismic hazard. In that case, the licensee is requested to:

Evaluate the seismic performance of the service water reservoir impoundment dike considering the updated seismic hazard information for the site and considering all relevant seismic failure modes. Relevant seismic failure modes include, but are not limited to, slope stability, Enclosure

settlement, cracking and resulting potential for internal erosion, as well as liquefaction and lateral spreading.

The licensee is requested to provide a technical basis for the ability of the emergency dike to withstand the updated seismic hazard such that it is able to convey sufficient outflow from a postulated seismically-induced failure of the service water impoundment dike system.

Specifically, the licensee is requested to provide the following supplemental information related to the dike failure flood hazard analyses:

• Postulate plausible service water reservoir impoundment dike failure scenarios, and estimate breach parameters conservatively, including width, time, and breach outflows from the reservoir.

• Provide information related to the seismic stability and/or failure analyses of the emergency dike system to evaluate the seismic performance of the emergency dike under the updated seismic hazard considering all relevant seismic failure modes (e.g.,

slope stability, settlement, cracking and resulting potential for internal erosion, as well as liquefaction and lateral spreading).

If the seismic failure of the emergency dike system is deemed credible, the licensee is further requested to:

• Postulate failure scenarios of the emergency dike caused by a seismic event and/or piping event caused by upstream breach flow and to evaluate the corresponding flooding impacts on the plant site. If the consequences (i.e., floods) from the plausible seismic failure scenarios are judged not to affect the site, provide a detailed justification for this conclusion, including the effectiveness of the emergency dike and intercepting channel system.

• Provide electronic versions of the input files used for any hydrologic flood routing related to the dike failure flood analyses.

• Confirm whether or not the dike failure flooding scenario will be included in the Integrated Assessment, and provide relevant associated effects and flood event duration parameters (as applicable), including the warning time the site will have to be prepare for the dike failure, the period of time the site is inundated, and the period of time necessary for water to recede off the site.

As an alternative to a postulated failure of the service water impoundment and subsequent analysis of the emergency dike and (if applicable) site flooding, the licensee may provide justification for the seismic capability of the service water impoundment under the updated seismic hazard. In that case, the licensee is requested to:

• Evaluate the seismic performance of the service water reservoir impoundment dike considering the updated seismic hazard information for the site and considering all relevant seismic failure modes. Relevant seismic failure modes include, but are not limited to, slope stability, settlement, cracking and resulting potential for internal erosion, as well as liquefaction and lateral spreading.

ML14133A603 *via email OFFICE NRR/DORLILPL2-1/PM NRR/DORLILPL2-1/LA NRO/DSENRHMB/BC*

NAME VSreenivas SFigueroa CCook for Ken Erwin DATE 5/13/14 5/14/14 5/12/14 OFFICE NRR/DORLILPL2-1/BC NRR/DORLILPL2-1/PM NAME RPascarelli VSreenivas DATE 5/14/14 5/14/14