MNS-14-061, Relief Request 13-MN-003 Limited Weld Examinations Response to Request for Additional Information

Relief Request 13-MN-003 Limited Weld Examinations Response to Request for Additional Information

ML14224A011
Person / Time
Site:	Mcguire
Issue date:	07/29/2014
From:	Capps S Duke Energy Carolinas, Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
MNS-14-061, TAC MF3477
Download: ML14224A011 (5)

Text

Steven D. Capps Vice President

%ENERGY. McGuire Nuclear Station Duke Energy MG01VP 1 12700 Hagers Ferry Road Huntersville, NC 28078 o: 980.875.4805 f: 980.875.4809 Steven.Ca pps@d uke-energy.com Serial No: MNS-14-061 July 29, 2014 10 CFR 50.55a U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Duke Energy Carolinas, LLC (Duke Energy)

McGuire Nuclear Station Unit 2 Docket Number 50-370 Relief Request 13-MN-003 Limited Weld Examinations Response to Request for Additional Information (TAC NO. MF3477)

By letter dated February 6, 2014, Duke Energy submitted Relief Request (RR) 13-MN-003 for certain welds with limited examinations.

By letter dated June 18, 2014, the NRC issued a Request for Additional Information (RAI) regarding this RR. Attached is Duke Energy's response to this RAI.

If you have any questions or require additional information, please contact P. T. Vu of Regulatory Affairs at (980) 875-4302.

Sincerely, Steven D. Capps Attachment O(J-7 UbL www.duke-energy.com

U. S. Nuclear Regulatory Commission July 29, 2014 Page 2 xc:

Victor McCree, Region II Administrator U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, GA 30303-1257 G. Edward Miller, Project Manager U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2738 John Zeiler NRC Senior Resident Inspector McGuire Nuclear Station

Enclosure Duke Energy Corporation McGuire Nuclear Station, Unit 2 Relief Request # 13-MN-003, 2EOC21 Limited Weld Examinations Response to Request for Additional Information

Duke Energy's responses to the NRC's RAI regarding Relief Request 13-MN-003, documented in PIP M 05921 - Limited Weld Exams:

RAI Question #1 What is the normal operating temperature and pressure for the subject welds (2ELDHX- HD-FLG &

2RCHPSS-OUT-1)?

Duke Energy Response:

a. 2ELDHX-HD-FLG ( Excess Letdown Heat Exchanger Head to Flange weld)- The weld, located in the proximity of the Excess Letdown Heat Exchanger, normally is isolated. Normal conditions are typically 100 - 120 F and 35 - 45 psig. The excess letdown flow path is an alternate letdown path from the Reactor Coolant (NC) System that is available in the event that the normal letdown path is inoperable.

The excess letdown flow path provides additional letdown capability during the final stages of unit heatup. The path removes some of the excess reactor coolant due to expansion of the system as a result of the NC System temperature increase. During 2EOC22 startup, the maximum temperature seen just downstream of the Excess Letdown Heat Exchanger was approximately 165 F and the maximum pressure seen was approximately 90 psig. Should an accident occur and the excess letdown heat exchanger be required, it is likely the weld would see near NC System temperatures and pressures.

b. 2RCHPSS-OUT-1(Reciprocating Charging Pump Nozzle to Flange weld) - This weld, located on the suction stabilizer of the Chemical and Volume Control (NV) reciprocating charging pump, is normally exposed to the Volume Control Tank (VCT) Pressure and temperature. Normal pressure is approximately 35-40 psig and normal temperature is approximately 85-95 F. This pump is not typically used outside of periodic operation for functional testing purposes.

RAI Question #2 What environmental conditions are the subject welds, (2ELDHX-HD-FLG & 2RCHPSS- OUT-I), exposed to (e.g., system transients, vibration, flow)?

Duke Energy Response:

a. 2ELDHX-HD-FLG - Normally the weld is isolated and simply exposed to Containment Temperature. If required, the excess letdown path way is exposed to reactor coolant temperature.

b. 2RCHPSS-OUT This weld is normally exposed to the VCT outlet temperature (85-95 F) and pressure (35-40 psig). With the Reciprocating Charging Pump typically off, the location would not be exposed to any vibration or flows. This weld, for the RI-ISI Program, postulated degradation mechanisms were thermal fatigue, IGSCC and Vibration. The WOG RI-ISI Program included all piping welds in the thermal fatigue category.

RAI Question #3 Describe the materials of constructionfor the stainless steel head, weld metal, and carbon steel flange in weld 2ELDHX-HD-FLG?

Duke Energy Response:

a. The head is SS-304 SA-240, the flange is F.S. SA -105-11 with a 3/16" T.K. SS 304 overlay (on the ID).

2ELDHX-HD-FLG used AISI Type 310 filler metal and the SS-304 (head to flange overlay) portion of the weld used AISI Type 308 filler metal.

Duke Energy Corporation McGuire Nuclear Station, Unit 2 Relief Request No. 13-MN-003, Response to Request for Additional Information

RAI Question #4 Describe the weld metal used in 2RCHPSS-OUT-I?

Duke Energy Response:

a. Weld 2RCHPSS-OUT-1 was made using ER308L welding rod.

RAI Question #5 Has Duke performed a review of applicable operating experience for the subject welds?

If so, did this review identify any industry operating experience of similar system welds developing service induced cracking or failure?

Duke Energy Response:

a. No, Duke had not performed a specific OE review for the subject welds during development of the original relief request 13-MN-003. However, Duke had performed an OE search to support the McGuire-2 Risk Informed ISI (RI-ISI) program during the 3 rd interval. This OE review "Review of Piping Failure History for Applicability of any New Degradation Mechanisms to the Risk Informed Inservice Inspection Program" covered damage mechanisms for all RI-ISI locations. The review resulted in no changes made to the RI-ISI program at McGuire-2.

Duke Energy Corporation McGuire Nuclear Station, Unit 2 Relief Request No. 13-MN-003, Response to Request for Additional Information