ML113180296
| ML113180296 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/10/2011 |
| From: | Price J Virginia Electric & Power Co (VEPCO), Dominion |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 11-625 | |
| Download: ML113180296 (5) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RIcHMOND, VIRGINIA 23261 November 10, 2011 u.s. Nuclear Regulatory Commission Serial No.11-625 Attention: Document Control Desk NLOS/ETSR1 One White Flint North Docket No. 50-338 11555 Rockville Pike License No. NPF-4 Rockville, MD 20852-2738 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
NORTH ANNA POWER STATION UNIT 1 - N1-14-CMP-001 USE OF WELD OVERLAYS AS AN ALTERNATIVE REPAIR TECHNIQUE FOR STEAM GENERATOR HOT LEG NOZZLES RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION In a March 30, 2011 letter (Serial No.11-120), as supplemented on June 29, 2011 (Serial No.11-366), Dominion requested NRC approval for proposed alternatives to certain (ASME Code) Section XI-2004 Edition requirements associated with Steam Generator hot leg nozzle repairs. The proposed alternative will permit the application of a full structural weld overlay on the Steam Generator hot leg nozzles for North Anna Unit 1. The weld overlays are required to mitigate the potential for primary water stress corrosion cracking (PWSCC) susceptibility. In an October 25, 2011 E-mail, the NRC staff requested additional information to complete the review of the proposed alternative examination requirements for the weld overlays. The attachment to this letter provides the requested information.
Dominion continues to request review and approval of this request to support implementation of the alternative repair technique during the North Anna Unit 1 spring 2012 refueling outage, currently scheduled to begin in March 2012.
If you have any questions regarding this submittal, please contact Mr. Thomas Shaub at (804) 273-2763.
Very truly yours, J. a rice Vi e Pr sident - Nuclear Engineering Attachment Commitments made in this letter: None
Serial No.11-625 Docket No. 50-338 Response to Request for Additional Information Alternative Weld Overlay Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region" Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, Georgia 30303-1257 Mr. J. E. Reasor, Jr.
Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.
Suite 300 Glen Allen, Virginia 23060 NRC Senior Resident Inspector North Anna Power Station Dr. V. Sreenivas NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 F6, Rockville, Maryland 20852 Ms. K. R. Cotton NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 G-9A Rockville, Maryland 20852 Mr. M. M. Grace Authorized Nuclear Inservice Inspector North Anna Power Station
Serial No.11-625 Docket No. 50-338 Attachment RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION RELIEF REQUEST N1-14-CMP-001 Virginia Electric and Power Company (Dominion)
North Anna Power Station Unit 1
Serial No.11-625 Docket No. 50-338 Response to Request for Additional Information Alternative Weld Overlay Attachment Page 1 of2
Background
In a March 30, 2011 letter (Serial No.11-120), as supplemented on June 29,2011 (Serial No.11-366), Dominion requested NRC approval for proposed alternatives to certain (ASME Code)Section XI - 2004 Edition requirements associated with Steam Generator hot leg nozzle repairs. The proposed alternative will permit the application of a full structural weld overlay on the Steam Generator hot leg nozzles for North Anna Unit 1.
In the June 29, 2011 letter, Dominion responded to the staff's request for additional information (RAI). The NRC staff has reviewed the RAI response and requested the following additional information to complete the review.
NRC Question
- 1. The NRC final rule (76 FR 36232) published in Federal Registry on June 21,2011, amended Title 10 of the Code of Federal Regulations (10 CFR) 50.55a to incorporate by reference (with conditions on its use) ASME Code Case N-770-1.
Paragraph (g)(6)(ii)(F) of 10 CFR 50.55a describes examination requirements for class 1 piping and nozzle DM butt welds. 10 CFR 50.55a(g)(6)(ii)(F)(1) states that licensees of existing and operating pressurized water reactors (PWRs) as of July 21,2011, shall implement the requirements of ASME Code Case N-770-1, subject to the conditions specified in paragraphs (g)(6)(ii)(F)(2) through (g)(6)(ii)(F)(10) of this section, by the first refueling outage after August 22, 2011.
- a. As a result of issuance of the NRC final rule 76 FR 36232, the staff requests the licensee to clarify whether the proposed examinations in the subject relief request satisfy the requirements of 10 CFR 50. 55a(g)(6)(ii)(F). If not, please provide justifications.
- b. Identify all pertinent requirements in ASME Code Case N-770-1 that apply to RR N1-14-CMP-001 and will be complied with.
Dominion Response
- a. The examinations for the proposed Steam Generator hot leg nozzle overlays will satisfy the requirements of 10 CFR 50.55a(g)(6)(ii)(F).
- b. Each examination requirement and associated acceptance standard of ASME Code Case N-770-1 will be complied with for the Steam Generator hot leg nozzle weld overlays.
Serial No.11-625 Docket No. 50-338 Response to Request for Additional Information Alternative Weld Overlay Attachment Page 2 of2 NRC Question
- 2. The licensee's response to the staff's RAI (i.e., NRC Question 5) dated June 29,2011, stated that 'The requirements of ASME Code Case N-504-4 Section (e) will not be satisfied and do not apply to the weld overlay. In accordance with Attachment 1, Section A 1.2.2, Subsection (d)(3) of our March 30, 2011 submittal, the stainless steel filler material is applied as a buffer layer only and is not considered weld reinforcement nor will it be counted towards the design thickness requirements specified for the weld overlay."
Paragraph Q-2000(d) of Appendix Q to the ASME Code,Section XI, states, in part, that "first layers of at least 5 FN are acceptable, provided the carbon content of the deposited weld metal is determined by chemical analysis to be less than 0.02%."
The staff finds that even if the buffer layer is not considered as weld reinforcement nor will it be counted towards the design thickness requirements specified for the weld overlay, the requirements of Paragraph Q-2000(d) of Appendix Q to the ASME Code,Section XI, should apply to minimize the potential for cracking. If a stainless steel buffer layer is used that has a delta ferrite content of 5 FN as part of weld overlay installation, discuss whether the carbon content of the buffer layer will be determined by chemical analysis to be less than 0.02%. If not, please provide justifications.
Dominion Response The austenitic stainless steel filler metal used to reduce the potential for hot cracking in the Alloy 52M weld overlay will also have sufficient delta ferrite to minimize the potential for hot cracking in the austenitic stainless weld deposit. Specifically for the North Anna Unit 1 SG overlay, the certified material test report (CMTR) for the wire to be used documents a bare wire chemistry of 0.02% Carbon and a Weld Research Council (WRC)-1992 Diagram delta ferrite of 9FN. When tested as required by ASME III NB-2433.1 using the magnetic delta ferrite determination method, this wire produced a gas tungsten arc weld deposit containing 9FN.