ML15026A089
| ML15026A089 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 02/05/2015 |
| From: | Hall J Plant Licensing Branch II |
| To: | Batson S Duke Energy Corp |
| Whited J | |
| References | |
| TAC MF3613 | |
| Download: ML15026A089 (4) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 February 5, 2015 Scott Batson Vice President, Oconee Nuclear Station Duke Energy Corporation 7800 Rochester Highway Seneca, SC 29672-0752
SUBJECT:
OCONEE NUCLEAR STATION, UNIT 2- REVIEW OF THE STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT FOR 2013 REFUELING OUTAGE (TAC NO. MF3613)
Dear Mr. Batson:
By letter dated March 3, 2014, Duke Energy Carolinas, LLC (the licensee) submitted information summarizing the results of the 2013 steam generator tube inspections at Oconee Nuclear Station (ONS) Unit 2. Additional information provided by the licensee during a conference call on September 8, 2014, is summarized in the enclosure to this letter. These if"1spections were performed during refueling outage 26. This information was submitted in accordance with ONS, Unit No. 2, Technical Specification (TS) 5.6.8, "Steam Generator Tube Inspection Report."
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of your submittal, as documented in the enclosed evaluation. The NRC staff concludes that the licensee has provided the information required by the TSs and that no additional follow-up is required at this time. This completes the NRC staff efforts for TAC No. MF3613.
If you have any questions regarding this matter, I may be reached at 301-415-4032 or via e-mail at Randy.Hall@nrc.gov.
Sincerely,
~li/Je Gimes R. Hall, Senior Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-270
Enclosure:
As stated cc w/encl: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 OFFICE OF NUCLEAR REACTOR REGULATION REVIEW OF THE STEAM GENERATOR TUBE INSPECTION REPORT FOR 2013 OCONEE NUCLEAR STATION UNIT 2 DOCKET NO. 50-270
1.0 INTRODUCTION
By letter dated March 3, 2014, 1 Duke Energy Carolinas, LLC (the licensee) submitted information summarizing the results of the 2013 steam generator tube inspections at Oconee Nuclear Station, Unit 2 (ONS-2) .. Additional information provided by the licensee during a conference call on September 8, 2014, is summarized below.
2.0 BACKGROUND
ONS-2 is a two-loop pressurized-water reactor with once-through steam generators (OTSGs) manufactured by Babcock & Wilcox, Canada. The ONS-2 OTSGs are replacement OTSGs that were installed during the spring 2004 refueling outage. The replacement OTSGs consist of 15,631 thermally treated Alloy 690 tubes that have been hydraulically expanded into the tubesheet to a depth of 13 inches. Tube support is provided by 15 Type 410 stainless steel tube support plates (TSP) of trifoil broach design; however, there are some round drilled openings at the 14th TSP.
3.0 EVALUATION The first inservice inspection of the replacement OTSGs at ONS-2, fall 2005, revealed unexpected, widespread wear degradation of the tubing at TSP locations (TSP wear). ONS-1 and ONS-3 have also experienced this widespread TSP wear degradation.
The licensee provided the scope, extent, methods, and results of their steam generator 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.
On September 8, 2014, the licensee clarified the following during a conference call:
- The following tubes were plugged during the latest refueling outage. In OTSG A, the tubes in Row 86 Column 121 (R86C121) and R98C127. In OTSG B, the tubes in R59C1, R95C1, R60C6, R89C7, R97C7, R77C10, R143C53, R11C54, R141C58, and R56C119.
1 Agencywide Documents Access and Management System Accession No. ML14066A100.
- No degradation of the installed plugs was noted during the plug visual inspection.
- No degradation was noted during the secondary side inspection at the tube support plates.
- There are 37 indications of tube-to-tube wear in 31 tubes in OTSG A, and 25 indications of tube-to-tube wear iri 20 tubes in OTSG B. The 0.95 probability with 50 percent confidence interval (95/50) groWth rate is 1.4 percent per effective full power year (EFPY). These tube-to-tube wear indications have been present since the first inspection after installation.
- There are 13470 indications of TSP wear in 7406 tubes in OTSG A, and 9714 indications of TSP wear in 5455 tubes in OTSG B. There is an increasing trend in the number of indications, but the majority of indications are in the 5 to 9 percent through wall range.
Approximately 600 of the indications are greater than 20 percent through wall. The 95/50 growth rate in OTSG A is 2. 7 percent per EFPY, and the 95/50 growth rate is 3.2 percent per EFPY in OTSG B. The severity of the TSP and tube-to-tube wear indications found in the OTSGs has been bounded by the operational assessment projections performed by the licensee.
Based on a review of the information provided, the Nuclear Regulatory Commission (NRC) staff concludes that the licensee provided the information required by their 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. Most of the inspection results appear to be consistent with industry I operating experience at similarly designed and operated units, with the exception of the large number of TSP wear indications. While the number of TSP wear indications is higher than other similarly designed and operated plants, the growth rates are not high and the.wear is being effectively managed through the licensee's Steam Generator Program.
Principal Contributor: Andrew Johnson Date: February 5, 2015
February 5, 2015 Scott Batson Vice President, Oconee Nuclear Station Duke Energy Corporation 7800 Rochester Highway Seneca, SC 29672-0752
SUBJECT:
OCONEE NUCLEAR STATION, UNIT 2- REVIEW OF THE STEAM GENERATOR TUBE INSERVICE INSPECTION REPORT FOR 2013 REFUELING OUTAGE (TAC NO. MF3613)
Dear Mr. Batson:
By letter dated March 3, 2014, Duke Energy Carolinas, LLC (the licensee) submitted information summarizing the results of the 2013 steam generator tube inspections at Oconee Nuclear Station (ONS) Unit 2. Additional information provided by the licensee during a conference call on September 8, 2014, is summarized in the enclosure to this letter. These inspections were performed during refueling outage 26. This information was submitted in accordance with ONS, Unit No. 2, Technical Specification (TS) 5.6.8, "Steam Generator Tube Inspection Report."
The U.S. Nuclear Regulatory Commission (NRC) staff has completed its review of your submittal, as documented in the enclosed evaluation. The NRC staff concludes that the licensee has provided the information required by the TSs and that no additional follow-up is required at this time. This completes the NRC staff efforts for TAC No. MF3613.
If you have any questions regarding this matter, I may be reached at 301-415-4032 or via e-mail at Randy.Hall@nrc.gov.
Sincerely,
/RAJ James R. Hall, Senior Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-270
Enclosure:
As stated cc w/encl: Distribution via Listserv DISTRIBUTION:
PUBLIC RidsNrrPMOconee Resource RidsNrrLASFigueroa Resource LPL 1-2 R/F RidsRgn1 MaiiCenter Resource RidsNrrDeEsgb Resource RidsNrrDorllpl2-1 Resource RidsAcrsAcnw_MaiiCTR Resource AJohnson, NRR/ESGB KKarwoski, NRR/ESGB JWhited, NRR/DORL Accession No.: ML15026A089 *via memo OFFICE LPL2-1/PM LPL2-1/LA ESGB/BC* LPL2-1/BC(A) LPL2-1/PM NAME JWhited SFigueroa GKulesa RPascarelli JH~II DATE 01/29/15 01/29/15 12/17114 02/04/15 02/05/15 OFFICIAL RECORD COPY