ML17171A229

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Supplemental Information for Generic Letter 2004-02
ML17171A229
Person / Time
Site: Millstone Dominion icon.png
Issue date: 06/13/2017
From: Sartain M D
Dominion, Dominion Nuclear Connecticut
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
17-244, GL-04-002
Download: ML17171A229 (6)
v • d • e


Text

.,,._ / .. Dominion Nuclear Connecticut, Inc. 5000 Dominion Boulevard, Glen Allen, VA 23060 Dominion Web Address: www.dom.com June 13, 2017 U.S. Nuclear Regulatory Commission Attention:

Document Control Desk Washington, DC 20555 DOMINION NUCLEAR CONNECTICUT, INC. MILLSTONE POWER STATION UNIT 3 Serial No. NRA/WDC Docket No. License No.17-244 RO 50-423 NPF-49 SUPPLEMENTAL INFORMATION FOR GENERIC LETTER 2004-02 In a teleconference with the Nuclear Regulatory Commission (NRC) on May 17, 2017, Dominion Nuclear Connecticut, Inc. (DNC) provided clarifying information related to our response to Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation during Design Basis Accidents at Pressurized Water Reactors," for Millstone Power Station Unit 3 (MPS3). Specifically, the NRC asked for a brief summary of the differences in strainer head loss tests M3-2 and M3-6 conducted in 2006, and predicted strainer submergence levels following a loss of coolant accident.

The attachment to this letter provides DNC's response to the NRC's questions and supplements the information provided in previous GL 2004-02 correspondence.

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

Sincerely, Mark D. Sartain Vice President

-Nuclear Engineering and Fleet Support Dominion Energy Nuclear Connecticut, Inc. COMMONWEAL TH 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 and Fleet Support of Dominion Energy Nuclear Connecticut, Inc. 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 / 3-ila day of , 2017. My Commission Expires:

Commitments made in this letter: None.

Notary Public Commonwealth of Virginia Reg. # 7629412 Expires August 31, 20.l.i

./

Attachment:

1. Supplemental Information Related to GL 2004-02 cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd Suite 100 King of Prussia, PA 19406-2713 Richard 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 ( Serial No.17-244 Docket 'No. 50-423 Page 2 of 2 I I ATTACHMENT Serial No.17-244 Docket No. 50-423 SUPPLEMENTAL INFORMATION RELATED TO GL 2004-02 DOMINION NUCLEAR CONNECTICUT, INC. MILLSTONE POWER STATION UNIT 3 Serial No.17-244 Docket No. 50-423 Attachment, Page 1 of 3 In a teleconference with the Nuclear Regulatory Commission (NRC) on May 17, 2017, Dominion Nuclear Connecticut, Inc. (DNC) provided clarifying information related to our response to Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized Water Reactors," for Millstone Power Station Unit 3 (MPS3). Specifically, the NRC asked for a brief summary of the differences in strainer head loss tests M3-2 and M3-6 conducted in 2006 and predicted strainer submergence levels following a loss of coolant accident (LOCA). This attachment provides DNC's response to the NRC's questions and supplements the information provided in previous GL 2004-02 correspondence.

Supplemental Information

-Differences in Strainer Head Loss Tests M3-2 and M3-6 Strainer head loss Tests M3-2 and M3-6 were essentially identical except for the dates the tests were performed and strainer fin pitch. Test M3-2 was performed in early in September 2006 and M3-6 was performed in late September 2006. Both tests used Ottawa River water and were affected by biological activity, but the tests performed in late September and in October (Tests M3-6 to M3-10) exhibited elevated head losses due to excessive biological growth and/or formation of air bubbles within the debris bed and test module. Because of the excessive biological activity associated with Tests M3-6 to M3-10, the results of these tests were not used for determining the appropriate strainer area. This information was addressed in the MPS3 RAI 6, Issue 3a response in a letter to NRC dated December 20, 2010 (ML 103620562) and the Millstone 3 Reduced-Scale Test Report MIL3-34325-TR-001.

Strainer head loss Tests M3-6 and M3-8 had the same strainer area but different fin pitch. The results of these tests were used in confirming that fin pitch has little effect on thin-bed head loss. Tests M3-7, M3-9, and M3-10 had the same fin pitch but different strainer areas. Test M3-8 had a different fin pitch and strainer area than Tests M3-7, M3-9 and M3-10. However, since fin pitch has little effect on thin-bed head loss, the results of Tests M3-7 to M3-10 were used in confirming that head' loss decreases with increasing strainer area. Supplemental Information

-Predicted strainer submergence levels following a LOCA During review of previous MPS3 GL 2004-02 correspondence, DNC determined that information related

  • to the strainer submergence levels was unclear and the submergence levels were not consistently measured from the containment floor. The sketch below is provided to clarify the predicted strainer submergence levels following a small break LOCA (SBLOCA) and a large break LOCA (LBLOCA).

The difference in water levels for the SBLOCA and the LBLOCA is due to addition of reactor coolant system and accumulator water during the LBLOCA. For both

  • , I " Serial No.17-244 Docket No. 50-423 Attachment, Page 2 of 3 scenarios, water level is depicted when the Recirculation Spray System (RSS) pumps start, and when the Refueling Water Storage Tank (RWST) is empty. The water levels are measured from the containment floor. The water levels shown in the sketch are updated from those provided in the previous DNC letters dated February 29, 2008, March 13, 2009, and September 16, 2010, due to a revised Analysis of Record (AOR) performed in 2014. The revised AOR was a result of implementation of a design change that 1) replaced the RWST level switches with level switches*

having less uncertainty, 2) increased the RWST maximum temperature, and 3) increased service water intake temperature.

LBLOCA SBLOCA LBLDCA SB LO CA --------------------------------------*-------------------.,...---

WATER LEVEL AT ass PUMP STOP <RWST EMPTY>

z ..... ..... ..... TOP OF STRAINER -* ?-u.. WATER LEVEL AT * * * *

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  • IL (') z ..... -* .... I I-LL z -IO I I-LL Serial No.17-244 Docket No. 50-423 Attachment, Page 3 of 3 z ..... z '¢ I I-I IL I-fJ"' LL a:'>
  • l> SECTION B-B REF: 25212-59700 SH.2
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