ML17320A121

Clarification to the Reply to a Notice of Violation, EA-16-090

ML17320A121
Person / Time
Site:	Millstone
Issue date:	11/03/2017
From:	Stoddard D Dominion Energy Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
16-2048, EA-16-090
Download: ML17320A121 (2)

Text

Dominion Nuclear Connecticut, Inc.

5000 Dominion Boulevard, Glen Allen, VA 23060 Web Address: www.dom.com November 3, 2017 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION Serial No.

MPS Lic/TFO Docket Nos.:

License Nos.:

CLARIFICATION TO THE REPLY TO A NOTICE OF VIOLATION, EA-16-090 16-2048 RO 50-336 50-423 DPR-65 NPF-49 By letter dated, May 4, 2016 (ML16125A122), the Nuclear Regulatory Commission (NRG) issued Notice of Violation (NOV) EA-16-090 to Dominion Nuclear Connecticut, Inc. (DNC) regarding corrective actions taken to address failures of the Millstone Power Station Unit 3 (MPS3) turbine driven auxiliary feedwater control system.

The NRG specified that "Dominion's corrective actions for multiple failures of the Unit 3 turbine driven auxiliary feedwater (TDAFW) control system have not fully considered all potential failure modes, leading to continued unreliable operation due to linkage and control system problems. This resulted in an overspeed trip of the Unit 3 TDAFW system in February 2016."

DNC has addressed the direct cause of the TDAFW overspeed trip, and the TDAFW pump has satisfactorily completed all required technical specification surveillances. Additionally, the TDAFW pump successfully started on a valid engineered safety features demand on June 12, 2016.

In the June 3, 2016, response to NOV EA-16-090 (ML16162A1710), DNC committed to a reliability enhancement to "implement a design change to improve the control valve bonnet oversized stuffing box to address the condition that contributed to the February 22, 2016 TDAFW pump overspeed trip."

In a September 29, 2016 follow-up to the NOV response (ML16278A602), DNC reported on the results of a comprehensive evaluation of additional methods to improve design and operating margins within the TDAFW pump linkage and control system. In the response, DNC noted that "DNC plans to implement a design change to replace the control valve bonnet oversized stuffing box to address the condition that contributed to the February 22, 2016 TDAFW pump overspeed trip." This implied that the design would result in a smaller stuffing box.

However, the design process identified the issue can be corrected by changing the design of the stuffing box, the style of the packing, or both. Based on the vendor recommendation and industry operating experience, DNC will install a different style stuffing box and packing that will minimize the steam and water leakage through the packing to reduce the chance of a corrosive environment in the spherical bushing.

I*

Serial No. 16-2048 Docket Nos. 50-336/423 Page 2 of 2 The TDAFW pump remains fully operable and in compliance with its Technical Specification requirements. The direct cause of the overspeed condition has been corrected and the TDAFW pump has successfully passed the last six quarterly operational readiness tests.

Installation of the new stuffing box and packing is the last reliability enhancement that will establish full compliance with the provisions of 10 CFR 50 Appendix B, Criterion XVI. As stated in the June 3, 2016 reply to the NOV, the date for full compliance remains November 30, 2017.

If you have any questions or require additional information, please contact Mr. Jeffry Langan at (860) 444-5544.

Sincerely, Daniel G. Stoddard Senior Vice-President and Chief Nuclear Officer Dominion Energy Nuclear Connecticut, Inc.

Commitments made in this letter: No additional commitments cc:

U.S. Nuclear Regulatory Commission Regional Administrator Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman NRC Senior Project Manager U.S. Nuclear Regulatory Commission, Mail Stop 08-C2 One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station