ML16130A563

Supplement to Response to Request for Additional Information Regarding License Request to Adopt Dominion Core Design and Safety Analysis Methods and to Address the Issues Identified in Westinghouse Documents ..

ML16130A563
Person / Time
Site:	Millstone
Issue date:	05/02/2016
From:	Mark D. Sartain Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CAC MF6251, SN 16-084A
Download: ML16130A563 (5)

Text

~~

Dominion Nuclear Connecticut, Inc.

5000 Dominion Boulevard, Glen Allen, VA 23060

• ~"-;*'BDom1n1on

.//

,/'-.

1 Web Address: www.dom.com

'(

May 2, 2016 U.S. Nuclear Regulatory Commission Serial No. 16-084A Attention: Document Control Desk NRA/VVDC RO Washington, DC 20555 Docket No. 50-423 License No. NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 SUPPLEMENT TO RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO ADOPT DOMINION CORE DESIGN AND SAFETY ANALYSIS METHODS AND TO ADDRESS THE ISSUES IDENTIFIED IN WESTINGHOUSE DOCUMENTS NSAL-09-5, REV. 1, NSAL-15-1, AND 06-IC-03 (CAC NO. MF6251)

By letter dated May 8, 2015, Dominion Nuclear Connecticut, Inc. (DNC) submitted a license amendment request (LAR) for Millstone Power Station Unit 3 (MPS3). The proposed amendment would revise the Technical Specifications (TS) to enable use of the Dominion nuclear safety analysis and reload core design methods for MPS3 and address the issues identified in three Westinghouse communication documents. In a letter dated January 8, 2016, the Nuclear Regulatory Commission (NRC) transmitted a request for additional information (RAI) to DNC related to the LAR. DNC responded to the RAI questions in letters dated January 28 and February 25, 2016. In an email dated February 24, 2016, the NRC transmitted an RAI to DNC related to the content of the TS changes proposed in the LAR. DNC responded to the RAI questions in a letter dated March 23, 2016. In a conference call with the NRC on *April 14, 2016, the NRC requested supplemental information to the RAI response for Questions 1 and 2. The attachment to this letter provides the supplemental information.

If you have any questions regarding this submittal, please contact Wanda Craft at (804) 273-4687.

Sincerely,

~~ Vicki L, Hdll NOTARY*rnJBLIC

• i.

Mark D. Sartain Commonwealth of Virginia Reg. Ii 140542 Vice President - Nuclear Engineering My Comniission*Expires May 31, 2018.

COMMONWEALTH OF VIRGINIA COUNTY OF HENRICO The foregoing document was acknowledged before me, in and for the' County and Commonwealth aforesaid, today by Mark D. Sartain, who is Vice President - Nuclear Engineering of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is duly autt)orized 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 d ~tf day of .!11Ay , 2016.

My Commission Expires: 5 18

• I j {J VLC~Notary Public i}, I 21 UR_Q

Serial No. 16-084A Docket No. 50-423 Page 2 of 2 Commitments made in this letter: None

Attachment:

Supplement to Response to Request for Additional Information Regarding License Amendment Request to Adopt Dominion Core Design and Safety Analysis Methods and to Address the Issues Identified in Westinghouse Documents NSAL-09-5, Rev. 1, NSAL-15-1, and 06-IC-03 (CAC No. MF6251) cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 R. V. Guzman Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08-C2 11555 Rockville Pike Rockville, MD 20852-2738 NRG Senior Resident Inspector Millstone Power Station Director, Radiation Division Department of Energy and Environmental Protection 79 Elm Street Hartford, CT 06106-5127

Serial No. 16-084A Docket No. 50-423 ATTACHMENT SUPPLEMENT TO RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO ADOPT DOMINION CORE DESIGN AND SAFETY ANALYSIS METHODS AND TO ADDRESS THE ISSUES IDENTIFIED IN WESTINGHOUSE DOCUMENTS NSAL-09-5, REV. 1, NSAL-15-1, AND 06-IC-03 (CAC NO. MF6251)

DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3

Serial No. 16-084A Docket No. 50-423 Attachment, Page 1 of 2 By letter dated May 8, 2015, Dominion Nuclear Connecticut, Inc. (DNC) submitted a license amendment request (LAR) for Millstone Power Station Unit 3 (MPS3). The proposed amendment would revise the Technical Specifications (TS) to enable use of the Dominion nuclear safety analysis and reload core design methods for MPS3 and address the issues identified in three Westinghouse communication documents. In an email dated February 24, 2016, the NRC transmitted an RAI to DNC related to the content of the TS changes proposed in the LAR. DNC responded to the RAI questions in a letter dated March 23, 2016. In a conference call with the NRC on April 14, 2016, the NRC requested supplemental information to the RAI response for Questions 1 and

2. This attachment provides the supplemental information.

RAl#1 New proposed Action b in insert A to LCO 3.2.2.1, Action b, proposes a 4-hour Completion Time (CT) to reduce thermal power until the heat flux hot channel factor F0 (Z) is within its limits. What is the technical basis for a completion time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> instead of the 15-minute completion time in LCO 3.2.2.1, Action a(1)? No technical basis was provided in the CTS or the LAR to support this CT. Please provide the technical justification.

DNC Supplemental Response The technical justification for a 4-hour completion time for Action b to LCO 3.2.2.1 Action b(1 ), instead of the 15-minute completion time in LCO 3.2.2.1 Action a(1 ), can be explained through a comparison of the different scenarios under which the LCOs are entered:

Action a(1) of LCO 3.2.2.1 is entered when surveillance requirement 4.2.2.1.2.b is not met. This surveillance requirement is to address an active violation of Fa(Z) limits.

When measured Fa(Z) is above its limit, a 15-minute action time is appropriate to return Fa(Z) within the limit as quickly as possible.

In contrast, Action b(1) is entered when surveillance requirement 4.2.2.1.2.c is not met.

This surveillance requirement is to address the condition when the non-equilibrium (or transient) Fa(Z) limit has not been met. In this case, measured Fa(Z) is not currently above its limit but could exceed its limit if a normal operation transient occurs. A 4-hour completion time is appropriate because if a normal operation transient were to occur based upon fission product (Xe) time scales, 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> is sufficient time to restrict axial flux difference -(AFD) limits and thermal power so that core peaking factors are not exceeded.

Serial No. 16-084A Docket No. 50-423 Attachment, Page 2 of 2 In addition, reducing power and controlling/reducing AFD to be within new limits (and any resultant actions such as insertion of control rods) within a 15-minute time frame could lead to the initiation of a normal operation transient and make it more likely that core peaking factors could be violated. A 4-hour completion time allows for deliberate operator actions to minimize the initiation of a normal operation transient.

RAl#2 New proposed Action c in inserl A to LCO 3.2.2.1, Action b, proposes a 72-hour CT to reduce the power range neutron flux - high trip setpoints by 1% for each 1% that the thermal power level is reduced. What is the technical basis for a 72-hour CT to adjust the power range neutron flux - high trip setpoints instead of the 4-hour CT allowed elsewhere in CTS (e.g., existing LCO 3.2.1.1 Action a.2 or .LCO 3.2.2.1, Action a(1))?

Please provide the technical justification.

DNC Supplemental Response The power range neutron flux - high trip setpoints are reduced to protect against the consequences of a severe accident when surveillance requirement 4.2.2.1.2.c has not been met. A 72-hour CT is appropriate for this action because of the very low probability of a severe accident occurring (as opposed to a normal operation transient) and because Action b(1)a (AFD limit reduction) and Action b(1)b (THERMAL POWER reduction) are performed under a 4-hour CT, which reduces possible initial conditions that form the starting point for a severe accident. Minimizing or reducing possible initial conditions that form the starting point for a severe accident increases the likelihood that achievable power shapes that could occur during a severe accident have already been considered in the safety analysis calculation.