TMI-13-048, Response to Request for Additional Information - Submittal of End of Interval Relief Request RR-12-01

Response to Request for Additional Information - Submittal of End of Interval Relief Request RR-12-01

ML13078A329
Person / Time
Site:	Three Mile Island
Issue date:	03/18/2013
From:	Jesse M Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RR-12-01, TMI-13-048
Download: ML13078A329 (3)

Text

10 CFR 50.55a TMI~13-048 March 18,2013 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-50 NRC Docket No. 50~289

Subject:

Response to Request for Additional Information - Submittal of End of Interval Relief Request RR-12-01

References:

1) Letter from M. D. Jesse (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "Submittal of End of Interval Relief Request RR-12~01 ," dated October 5, 2012

2) Letter from P. Bamford (U.S. Nuclear Regulatory Commission) to M. J. Pacilio (Exelon Generation Company, LLC), "Three Mile Island Nuclear Station, Unit 1 - Request for Additional Information Regarding End~of-Interval Relief Request RR-12-01, Pressurizer Nozzle-to-Head Weld Exams (TAC No. ME9788)," dated February 25,2013 In the Reference 1 letter, Exelon Generation Company, LLC (Exelon) submitted for your review Relief Request RR-12-01 associated with the third Inservice Inspection (lSI) interval for Three Mile Island Nuclear Station (TMI), Unit 1. RR-12-01 concerns requirements for examination of pressurizer relief nozzle welds that were examined in the fall 2011 refueling outage. In the Reference 2 letter, the U.S. Nuclear Regulatory Commission Staff requested additional information. Attached is our response to that request.

There are no regulatory commitments in this letter.

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

Michael D. Jess Director - Licen ,ing egulatory Affairs Exelon Generatf ompany, LLC

Attachment:

Response to Request for Additional Information - Relief Request RR-12-01 cc: Regional Administrator, Region I, USNRC USNRC Senior Resident Inspector, TMI USNRC Project Manager, [TMI] USNRC

Attachment Response to Request for Additional Information - Relief Request RR-12-01

Response to Request for Additional Information Relief Request RR-12-01 Page 1 Question:

1.) The submittal does not include any statement regarding past inspection results, including preservice.

The NRC staff is concerned that there could be a weld repair done during fabrication. If the repair used a Nickel-based alloy filler metal, the joint could be susceptible to primary water stress corrosion cracking. Therefore, describe the results of all past inspections, including preservice, as well as any repairs that have been done to the subject pressurizer relief nozzle-to-vessel welds.

Response

The three nozzles associated with this relief request are fabricated from A-508, Class 1 material and are welded to the pressurizer upper head SA-212, Grade B material using Specification 70A 1 flux core weld material. There are no Nickel-based alloy materials associated with the three nozzle welds included in this relief request. Review of the original fabrication records for the nozzle welds indicates repairs were completed during original fabrication on Weld RCT0002PR0003N. These repairs were completed prior to post weld stress relief and did not use Nickel-based alloy materials.

The three nozzles received ultrasonic examinations during the first, second, and third inservice inspection intervals along with a preservice ultrasonic examination. No unacceptable conditions were identified during any of the ultrasonic examinations. No repairs have been performed on these nozzles since original fabrication. The preservice examination noted several small amplitude laminar type indications in the head base material. All indications were less than 100% Distance Amplitude Curve (DAC) and were not recorded during subsequent inservice examinations so interference with angle beam examinations has not occurred. Inservice examinations were performed using different calibration standards and techniques to comply with newer ASME Section XI requirements and are attributed to the reason the laminar reflectors were not recorded during subsequent inspections. During the 1988 examination of weld RCT0002PR0004N a small amplitude <<100% DAC) mid-wall indication was identified by angle beam probe to be in the weld adjacent to the original nozzle weld preparation surface. The indication was sized using amplitude drop methods and evaluated as acceptable to ASME Section XI, IWB-3512 requirements. The indication was not noted during any other examinations due its small size.