ML16246A202

Response to Request for Additional Information Regarding Relief Request for Dissimilar Metal Butt Weld Examinations

ML16246A202
Person / Time
Site:	Calvert Cliffs
Issue date:	09/01/2016
From:	David Gudger Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
CAC MF7291
Download: ML16246A202 (4)

Text

Exelon Generation 200 Exelon Way Kennett Square. PA 19348 www.exeloncorp.com 10 CFR 50.55a September 1, 2016 U.S. Nuclear Regulatory Commission ATIN: Document Control Desk Washington, DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Unit 2 Renewed Facility Operating License No. DPR-69 NRC Docket No. 50-318

Subject:

Relief Request for Dissimilar Metal Butt Weld Examinations

References:

1) Letter from D. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Relief Request for Dissimilar Metal Butt Weld Examinations," dated March 5, 2015

2) Letter from D. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Relief Request for Dissimilar Metal Butt Weld Examinations," dated November 24, 2015

3) Letter from D. Gudger (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Relief Request for Dissimilar Metal Butt Weld Examinations," dated January 28, 2016

4) Email from R. Guzman (U.S. Nuclear Regulatory Commission) to 11 T. Loomis (Exelon Generation Company, LLC), Calvert Cliffs Request for Additional Information - Relief Request No. RR-ISl-04-11 (CAC No.

MF7291 )," dated August 9, 2016 In the Reference 3 letter, Exelon Generation Company, LLC (Exelon), proposed an alternative to the requirements of 10 CFR 50.55a(g)(6)(ii)(F) regarding examination coverage of dissimilar metal butt welds on the basis that complying with the specified requirement would result in hardship or unusual difficulty for Calvert Cliffs Nuclear Power Plant, Unit 2. A similar relief request was submitted for Unit 1 in the Reference 1 letter. In the Reference 2 letter, responses to requests for additional information were supplied for the Unit 1 relief request.

In Reference 4, the U.S. Nuclear Regulatory Commission requested additional information.

Attached is our response.

Relief Request for Dissimilar Metal Butt Weld Examinations September 1, 2016 Page2 There are no regulatory commitments in this letter.

If you have any questions concerning this letter, please contact Tom Loomis at (610) 765-5510.

Respectfully, David T. Gudger Manager - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Attachment:

Response to Request for Additional Information - Relief Request RR-ISl-04-11 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, CCNPP USNRC Project Manager [CCNPP]

S. T. Gray, State of Maryland

Attachment Response to Request for Additional Information - Relief Request RR-ISl-04-11

Relief Request for Dissimilar Metal Butt Weld Examinations Relief Request RR-ISl-04-11 Response to Request for Additional Information Page 1 Question:

Recent operational experience with the ISi of dissimilar metal butt welds in nuclear power plants include several instances of human errors in the application of qualified nondestructive examination procedures. Licensee Event Report No. 2016-002 dated April 14, 2016 (ADAMS Accession No. ML16106A304) describes an event at Calvert Cliffs Nuclear Power Plant, Unit 1 (CCNPP1) on February 20, 2016, which identified an 81.8 percent through-wall flaw. This flaw had been previously examined in 2010, with techniques which appear to be similar to those used on CCNPP2 in 2011 as described in the January 28, 2016 submittal, without identifying the true extent of the through-wall flaw. Please describe lessons learned from the February 2016 CCNPP1 event which will be applied to the 2017 CCNPP2 examinations to insure the quality and effectiveness of the ultrasonic examinations.

Response

The Nondestructive Evaluation (NOE) Improvement Focus Group (NIFG) was formed to address NOE reliability and extent of condition actions in response to North Anna dissimilar metal weld operating experience. The operating experience occurred early in 2012 and involved the missed detection of flaws during ultrasonic examinations performed according to the ASME Boiler and Pressure Vessel Code,Section XI, Appendix VIII, Supplement 10. Exelon 11 has implemented the needed 11 requirements of NFIG according to the Nuclear Energy Institute (NEI) Guideline for the Management of Materials Issues (NEI 03-08).

During the 2016 examination, an improved scanner was used that increased the data quality. The ASME Section XI, Appendix VIII qualified technique also included a larger aperture search unit, additional examination angles, lower frequency, beam skewing, and enhanced focusing. This improved data enhanced the image of the previously reported axial flaw. After reviewing the data, it was determined that this optimized technique provided sufficient data to detect the connection of the previously reported shallow axial flaw and the embedded indication that was also present in previous examination data.

Exelon will use the current qualified examination techniques and the NEI 03-08 "needed" elements for effective and reliable examination of the dissimilar metal welds in 2017.