ML11312A243
| ML11312A243 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/04/2011 |
| From: | Price J Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 11-577C | |
| Download: ML11312A243 (4) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 November 4, 2011 10 CFR 100, Appendix A U.S. Nuclear Regulatory Commission Serial No.:
11-577C Attention: Document Control Desk NL&OS/GDM R1 Washington, DC 20555 Docket Nos.:
50-338/339 License Nos.:
NPF-4/7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
NORTH ANNA POWER STATION UNITS I AND 2 REVISED RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (RAI)
LONG-TERM ACTIONS TO ADDRESS SEISMIC ANALYSIS CONSIDERING THE AUGUST 23, 2011 EARTHQUAKE By letter dated October 13, 2011, the NRC requested additional information regarding the long-term actions that Dominion was planning to implement for North Anna Power Station to address the seismic loading associated with the August 23, 2011 earthquake.
In one specific RAI question, the NRC requested Dominion to "discuss the post-restart (i.e., long-term) actions in place (i.e., those included within the corrective action program) to evaluate seismically qualified piping and pipe supports, including those structures, systems, and components (SSCs) discussed on pages 4 and 5 of the September 17, 2011, submittal, to demonstrate compliance with the licensing and design basis and/or applicable design basis code criteria/requirements, when these evaluations consider seismic loadings, (OBE and DBE) derived from the August 23, 2011, seismic event, combined with all other applicable load cases." By letter dated October 28, 2011 (Serial No.11-577B), in the response to question 3 on pages 4 through 7, Dominion provided the requested information that described Dominion's long-term plan for performing seismic analysis of new and replacement equipment considering the August 23, 2011 earthquake seismic loading, i.e., its Seismic Margin Management Plan.
Subsequent to this submittal, NRC and Dominion management discussed the proposed long-term action during conference calls on November 3 and 4, 2011.
As a result of these interactions, Dominion has determined that the response provided in the October 28, 2011 letter requires revision.
Therefore, the description of the Seismic Margin Management Plan that Dominion will be implementing as a long-term action following the restart of North Anna Units 1 and 2 is described below and supersedes in its entirety the specific RAI response provided in the October 28, 2011 letter to the NRC question stated above.
Serial No. 11-577C Docket Nos. 50-338/339 Page 2 of 4 The lack of evidence of damage at the North Anna Power Station is a strong indicator of the seismic margin existing at the station. That margin is the result of conservative original design and maintenance of those conservatisms. Dominion will maintain the same conservative methods when analyzing or modifying the station in the future.
Dominion will ensure going forward that any design modification to the plant will, at a minimum, maintain sufficient seismic design margin to account for the August 23, 2011 earthquake.
To ensure adequate seismic margins are maintained for plant SSCs, Dominion will revise the design change process for North Anna Power Station to require explicit evaluation of plant modifications for the effects of the August 23, 2011 earthquake using In-Structure Response Spectra (ISRS) for the event for the Containment, Auxiliary Building, and other buildings containing safety related SSCs developed based on actual time-histories recorded during the event.
In support of future plant design changes, the evaluation of plant SSCs will require design verification and code compliance with the stresses, loads, accelerations, and displacements generated from the analysis with the design basis ISRS and the analysis with the ISRS for the August 23, 2011 earthquake, whichever are higher.
This approach will be used for the evaluation of plant SSCs including piping components, supports, and equipment nozzles that are affected by the design change.
These evaluations for the August 23, 2011 earthquake, which are in addition to the requirements of the plant's existing design basis, will employ all applicable codes, standards, damping, and other criteria used for the design basis earthquake condition.
Evaluations made for the August 23, 2011 earthquake will be documented within design calculations, prepared in accordance with Dominion's Quality Assurance Program, to support plant design changes.
As discussed in our letter dated October 28, 2011 (Serial No. 11-577B), Dominion plans to revise the North Anna Power Station Updated Final Safety Analysis Report (UFSAR) to document: 1) the recorded August 23, 2011 seismic event, 2) a summary of the evaluation and results of the seismic analysis of the recorded event completed per Regulatory Guide (RG) 1.167/EPRI NP-6695, 3) design controls of the Seismic Margin Management Plan, and 4) incorporation of RG 1.166, "Pre-Earthquake Planning and Immediate Nuclear Power Plant Operator Post-Earthquake Actions," and 1.167, "Restart of a Nuclear Power Plant Shut Down by a Seismic Event," into the North Anna licensing basis. Prior to discontinuing the use of the Seismic Margin Management Plan for plant modifications, Dominion will notify the NRC.
It is Dominion's intent to remain engaged with the NRC and industry to determine subsequent actions to address the recommendations emanating from the Fukushima Daiichi Task Force and GI-199 resolution. The results of these two initiatives will be considered as part of Dominion's implementation of the Seismic Margin Management Plan.
Serial No. 11-577C Docket Nos. 50-338/339 Page 3 of 4 If you have any questions or require additional information, please contact Mr. Gary D.
Miller at (804) 273-2771.
Sincerely, J. Wan Price Vte sident - Nuclear Engineering Commitments contained in this letter:
- 1. Implement Seismic Margin Management Plan as discussed above.
- 2. Dominion will notify the NRC prior to discontinuing the use of the Seismic Margin Management Plan.
COMMONWEALTH OF VIRGINIA
)
COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by J. Alan Price who is Vice President - Nuclear Engineering, of Virginia Electric and Power Company. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.
Acknowledged before me this LAA-L)day of __,__OV_-_"__
2011.
My Commission Expires:
4I' Izo )
Gniler Lynn Rutherford NOTARY PUBLIC Notary Public Commonwealth of Virginia Reg. # 310847 My Commission Expires 4/30/2015
Serial No. 11-577C Docket Nos. 50-338/339 Page 4 of 4 cc:
Regional Administrator U.S. Nuclear Regulatory Commission - Region II Marquis One Tower 245 Peachtree Center Ave. NE Suite 1200 Atlanta, Georgia 30303-1257 NRC Senior Resident Inspector North Anna Power Station M. Khanna NRC Branch Chief-Mechanical and Civil Engineering U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9E3 11555 Rockville Pike Rockville, MD 20852-2738 R. E. Martin NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 P. G. Boyle NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G-9A 11555 Rockville Pike Rockville, MD 20852-2738 J. E. Reasor, Jr.
Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.
Suite 300 Glen Allen, Virginia 23060