ML12102A014

Response to Request for Additional Information Regarding Relief Request Serial #11-MN-002

ML12102A014
Person / Time
Site:	Mcguire
Issue date:	03/29/2012
From:	Repko R Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML12102A014 (4)

Text

REGIS T. REPKO Vice President L ,-,-:"Energy, McGuire Nuclear Station Duke Energy MG01 VP / 12700 Hagers Ferry Rd.Huntersville, NC 28078 980-875-4111 980-875-4809 fax regis. repko@duke-energy.

com I./March 29, 2012 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 No. 50-370 Relief Request Serial #11-MN-002 Response to Request for Additional Information By letter dated October 3, 2011, Duke Energy submitted Relief Request (RR) 11 -MN-002 to request authorization to extend the inservice inspection (ISI) interval for the McGuire 2 reactor vessel Category B-A and B-D welds from 10 years to 20 years so that the third 10-year ISI interval examinations can be deferred until calendar year 2024.On March 6, 2012, the Nuclear Regulatory Commission (NRC) staff electronically requested additional information regarding this RR. The attachment to this letter contains Duke Energy's response to the NRC questions.

Duke Energy requests NRC approval of this relief request by September 1, 2012.If you have any questions or require additional information, please contact P.T. Vu at (980) 875-4302.Sincerely, Regis T. Repko Attachment www. duke-energy comr U. S. Nuclear Regulatory commission March 29, 2012 Page 2 xc: V. M. McCree, Region II Administrator U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE, Suite 1200 Atlanta, GA 30303-1257 J. H. Thompson, Project Manager U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop O-8G9A Rockville, MD 20852-2738 J. Zeiler NRC Senior Resident Inspector McGuire Nuclear Station ATTACHMENT Relief Request 11-MN-002 Response to NRC Request for Additional Information Relief Request 11 -MN-002, Response to NRC Request for Additional Information Attachment, Page 2 of 2 Question 1: Table 2 states that three indications were identified in the RV beltline region during the most recent/SI.a. Please identify the RV beltline forging and/or weld materials where the three beltline indications were discovered.

b. Please state whether additional recordable indications were discovered in any of the subject Examination Category B-A or B-D (beltline and non-beltline) components, other than those reported in Table 2, even if the indications were found to be acceptable based on the ASME Code, Section Xl, IWB-3500 acceptance standards.

Response: la. All three of the noted beltline indications are located in the Intermediate Shell Forging (Item 2 in Table 3 of Relief Request 11-MN-002).

1 b. During the most recent examination, a total of 76 recorded indications were identified during the performance of Examination Category B-A and B-D examinations, including the three indications stated in Table 2. All of the recorded indications were determined to be acceptable per IWB-3500, Table IWB-3510-1 of the ASME Code Section XI, 1989 Edition, with no further evaluation required.Question 2: Please state whether any of the SA-508, Class 2 RV forgings at McGuire 2 are susceptible to intergranular separations (underclad cracking), based on the criteria specified in Regulatory Guide (RG) 1.43, "Control of Stainless Steel Weld Cladding of Low-Alloy Steel Components," Revision 1, March 2011.Response: It was assumed in the calculation of the McGuire Unit 2 RV through-wall cracking frequencies (TWCF), that the SA-508, Class 2 RV forgings are susceptible to intergranular separations (underclad cracking).

This assumption was considered to be conservative and an evaluation was not performed to determine whether the SA-508, Class 2 RV forgings at McGuire Unit 2 meet the criteria specified in Regulatory Guide 1.43, Revision 1.Question 3: ASME Code Case (CC) N-648-1, "Alternative Requirements for Inner Radius Examination of Class 1 Reactor Vessel Nozzles, Section X1, Division 1," is listed as "Conditionally Acceptable" in Table 2 of RG 1.147, "Inservice Inspection Code Case Acceptability, ASME Section XI, Division 1,," Revision 16, October 2010. Please state whether the previous examinations of the Examination Category B-D, Nozzle Inside Radius Sections, which utilized the visual examination methods of CC N-648-1, in lieu of volumetric examination methods, met the condition specified in Table 2 of RG 1.147.Response: The visual examination methods of CC N-648-1 (in lieu of volumetric examination methods) used to inspect the Category B-D, Nozzle Inside Radius Sections, met the condition specified in Table 2 of RG 1.147.