ML13126A206

Supplement to Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order EA-12-049)

ML13126A206
Person / Time
Site:	Millstone
Issue date:	04/30/2013
From:	Grecheck E Dominion Nuclear Connecticut, Dominion
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
12-161C, EA-12-049
Download: ML13126A206 (5)

Text

Dominion Nuclear Connecticut, Inc. D 5000 Dominion Boulevard, Glen Allen, VA 23060 Domin iote Web Address: www.dom.com 10 CFR 2.202 April 30, 2013 EA-12-049 Attention: Document Control Desk Serial No.: 12-161C U.S. Nuclear Regulatory Commission NL&OS/MAE: RO Washington, D.C. 20555-0001 Docket Nos.: 50-336/423 License Nos.: DPR-65 DOMINION NUCLEAR CONNECTICUT, INC. NPF-49 MILLSTONE POWER STATION UNITS 2 AND 3 SUPPLEMENT TO OVERALL INTEGRATED PLAN IN RESPONSE TO MARCH 12, 2012 COMMISSION ORDER MODIFYING LICENSES WITH REGARD TO REQUIREMENTS FOR MITIGATION STRATEGIES FOR BEYOND-DESIGN-BASIS EXTERNAL EVENTS (ORDER NUMBER EA-12-049)

On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued Order EA-12-049, "Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" (the Order) to Dominion Nuclear Connecticut, Inc. (DNC). DNC responded to the Order by letters dated March 26, 2012, October 25, 2012, and February 28, 2013 (Serial Nos.12-161, 12-161A and 12-161B, respectively).

The purpose of this letter is to supplement the Overall Integrated Plan that was provided in DNC's February 28, 2013 letter. The additional information is provided for Millstone Units 2 and 3 in the attachment to this letter.

If you have any questions, please contact Ms. Margaret Earle at (804) 273-2768.

Sincerely, Eugene S. Grecheck VICKI L.HULL Vice President Nuclear Engineering and Development Commonwealth of Virginia Dominion Nuclear Connecticut, Inc. F y omision140342 Expires May 31, 2014 COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by Eugene S. Grecheck who is Vice President Nuclear Engineering and Development of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of the Company, and that the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this 5 0'day

' of prLi 2013.

My Commission Expires:

Notary Public (SEAL)

Serial No. 12-161C Docket Nos. 50-336/423 Order EA-12-049 Page 2 of 2 Attachment Commitments made by this letter: No New Regulatory Commitments cc: Director of Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 13H16M 11555 Rockville Pike Rockville, MD 20852-2738 U. S. Nuclear Regulatory Commission, Region I Regional Administrator 2100 Renaissance Blvd.

Suite 100 King of Prussia, PA 19406-2713 Mr. J. S. Kim NRC Project Manager Millstone Units 2 and 3 U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 C 2A 11555 Rockville Pike Rockville, MD 20852-2738 Ms. J. A. Kratchman U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 09 D2 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No. 12-161C Docket Nos. 50-336/423 Order EA-12-049 Attachment Supplement To Millstone Units 2 and 3 Overall Integrated Plan Requirements for Mitigation Strategies For Beyond-Design-Basis External Events Millstone Power Station Units 2 and 3 Dominion Nuclear Connecticut, Inc. (DNC)

Serial No. 12-161C Docket Nos. 50-336/423 Order EA-12-049 Attachment, Page 1 of 2 Supplement To Millstone Units 2 and 3 Overall Integrated Plan Requirements for Mitigation Strategies For Beyond-Design-Basis External Events By letter dated February 28, 2013, Serial No. 12-161B, DNC provided an Overall Integrated Plan (OIP) to address Beyond-Design-Basis (BDB) events at Millstone Units 2 and 3 as required by Order Number EA-12-049, dated March 12, 2012. It was stated that the OIP was based on conceptual design information and that final design information and revisions would be provided via updates. Various open items were inserted into the OIP to identify information that would be provided or confirmed at a later date. This attachment provides the basis for closure of Open Item No. 2 for Unit 2 and Open Item No. 3 for Unit 3.

Millstone Unit 2:

Open Item No. 2 - Preliminaryanalyses have been performed to determine the time to SG overfill without operator action to reduce AFW flow, time to SG dryout without AFW flow, and time to depletion of the CST. Final durations will be provided when the analyses are completed.

The analysis for secondary side inventories and heat removal has been finalized. Slight changes were observed from the preliminary values reported in the OIP. These changes are as follows:

1) The time to steam generator (SG) overfill decreased from 2.6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> to 1.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

As stated in the OIP, operators would be assigned within the first 15 minutes of the event to control flow in order to maintain proper SG level. The throttling would be performed locally using the auxiliary feedwater (AFW) regulating valves or their bypass valves at the turbine driven auxiliary feedwater (TDAFW) pump.

Operators could access the area in less than 5 minutes to begin to control AFW flow in order to maintain SG levels. Therefore, the basis for acceptability stated in the OIP remains valid for the reduced SG overfill time of 1.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

2) The time for SG dryout increased from 50 minutes to 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. This provides additional time, if needed, to perform a manual start of the TDAFW pump as part of the Phase 1 core cooling strategy.

3) The time to depletion of the water supply from the condensate storage tank increased from 7.2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> to 8.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. This provides additional time to setup and engage Phase 2 BDB equipment as part of the long-term core cooling strategy.

The finalized analysis also confirmed the statement that the site pond was capable of providing core cooling supply for greater than 20 days to each unit.

This response closes Open Item No. 2 for Millstone Unit 2.

Serial No. 12-161C Docket Nos. 50-336/423 Order EA-12-049 Attachment, Page 2 of 2 Millstone Unit 3:

Open Item No. 3 - Preliminaryanalyses have been performed to determine the time to steam generator overfill without operator action to reduce AFW flow, time to steam generator dryout without AFW flow, and time to depletion of the useable volume of the DWST. The final durations will be provided when the analyses are completed.

The analysis for secondary side inventories and heat removal has been finalized. Slight changes were observed from the preliminary values reported in the OIP. These changes are as follows:

1) The time to steam generator (SG) overfill decreased from 2.0 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> to 1.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.

As stated in the OIP, operators would be assigned within the first 15 minutes of the event to control flow in order to maintain proper SG level. AFW flow rate can be controlled by locally throttling the AFW header isolation valves. Operators could access the area in less than 5 minutes to begin to control AFW flow in order to maintain SG levels. Therefore, the basis for acceptability stated in the OIP remains valid for the reduced SG overfill time of 1.3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />.

2) The time for SG dryout increased from 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to 1.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. This provides additional time, if needed, to perform a manual start of the turbine driven auxiliary feedwater (TDAFW) pump as part of the Phase 1 core cooling strategy.

3) The time to depletion of the water supply from the demineralized water storage tank (DWST) increased from 20.9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> to 22.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. This provides additional time to setup and engage Phase 2 BDB equipment as part of the long-term core cooling strategy.

The finalized analysis also confirmed the statement that the site pond was capable of providing core cooling supply for greater than 20 days to each unit.

This response closes Open Item No. 3 for Millstone Unit 3.