ML14318A381
| ML14318A381 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 12/22/2014 |
| From: | Thadani M Plant Licensing Branch 1 |
| To: | Heacock D Dominion Nuclear Connecticut |
| Thadani M | |
| References | |
| TAC MF4472 | |
| Download: ML14318A381 (4) | |
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NUCLEAR REGULATORY COMMISSION
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..,.o Mr. David A. Heacock President and Chief Nuclear Officer Dominion Nuclear Connecticut, Inc.
lnnsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711 WASHINGTON, D.C. 20555-0001 December 22, 2014
SUBJECT:
MILLSTONE POWER STATION, UNIT NO.2-STAFF EVALUATION OF THE 2014 REFUELING OUTAGE STEAM GENERATOR TUBE INSPECTION (TAC NO. MF4472)
Dear Mr. Heacock:
By letter to the U.S. Nuclear Regulatory Commission (NRC), dated June 26, 2014 (Agencywide Documents Access and Management System Accession No. ML14188B190), Dominion Nuclear Connecticut, Inc. (the licensee) submitted information summarizing the results of its 2014 steam generator (SG) tube inspections at Millstone Power Station, Unit 2 (MPS2). These inspections were performed during the 22nd refueling outage at MPS2.
The NRC staff has completed its evaluation of the licensee's report and concludes that the licensee provided the information required by MPS2 Technical Specifications. The NRC staff also concludes that there are no technical issues that warrant follow-up action at this time, since the SG tube inspections at MPS2 appear to be consistent with the objective of detecting potential tube degradation. The inspection results appear to be consistent with industry operating experience at similarly designed and operated units. The NRC staff's evaluation is enclosed.
Please contact me at (301) 415-1476, or by email at Mohan.Thadani@nrc.gov, if you have any questions on this issue.
Docket No.: 50-336
Enclosure:
Staff Evaluation cc w/encl: Distribution via Listserv Sincerely,
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Mohan C. Thadani, Senior Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 STAFF EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE STEAM GENERATOR TUBE INSPECTIONS PERFORMED DURING THE 2014 REFUELING OUTAGE 22 MILLSTONE POWER STATION, UNIT N0.2 DOMINION NUCLEAR CONNECTICUT, INC.
DOCKET NO. 50-336 By letter dated June 26, 2014 (Agencywide Documents Access Management System Accession No. ML14188B190), Dominion Nuclear Connecticut, Inc., the licensee, submitted information summarizing the results of its 2014 steam generator (SG) tube inspections performed during refueling outage 22 at Millstone Power Station, Unit No. 2 (MPS2).
MPS2 has two SGs, each one containing 8,523 thermally treated Alloy 690 tubes. Each tube has a nominal outside diameter of 0.75 inches and a nominal wall thickness of 0.0445 inches.
The tubes were hydraulically expanded at both ends for the full depth of the tubesheet. The tubes are supported by type 410 stainless steel lattice grids.
The licensee provided the scope, extent, methods, and results of its SG tube inspections in the document referenced above. In addition, the licensee described corrective actions (i.e., tube plugging) taken in response to the inspection findings. The tubes in SG 2 were inspected during this outage.
After reviewing the information provided by the licensee, the staff has the following comments and observations:
The licensee identified an obstruction in a tube located at row 49, column 108 caused by a plastic object that had melted and adhered to the inside of the tube. The material was subsequently removed and the tube was honed and swabbed to further clean the region.
The tube was examined with a +Point' probe, and the licensee determined that no tube degradation had occurred. In addition, a subsequent bobbin probe inspection revealed that no detectable residual material remained inside the tube. To ensure that no other tubes had similar material in the tube within the tubesheet region, a review of eddy current data was performed. As a result of this review, the licensee concluded that no other objects of this type were present in any other steam generator tube.
Based on a review of the information provided, the NRC staff concludes that the licensee provided the information required by the MPS2 Technical Specifications. In addition, the NRC staff concludes that there are no technical issues that warrant follow-up action at this time, since the inspections appear to be consistent with the objective of detecting potential tube degradation. The inspection results appear to be consistent with industry operating experience at similarly designed and operated units.
ML14318A381 Sincerely, IRA/
Mohan C. Thadani, Senior Project Manager Plant Licensing Branch 1-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation RidsN rrPM Millstone RidsAcrsAcnw_MaiiCTR AJohnson, NRR
- SE INPUT: ML14304A319 OFFICE NRR/LPL 1-1/PM NRR/LPL 1-1/LA NRR/ESGB/BC NRR/LPL 1-1/BC NRR/LPL 1-1/PM NAME MThadani KGoldstein GKulesa*
BBeasley MThadani DATE 12/10/2014 12/02/2014 11/09/2014 12/19/2014 12/22/2014