ML032270584
| ML032270584 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 08/15/2003 |
| From: | Chernoff M NRC/NRR/DLPM/LPD2 |
| To: | Scalice J Tennessee Valley Authority |
| Chernoff, M H, NRR/DLPM, 301-415-4041 | |
| References | |
| TAC MB6629 | |
| Download: ML032270584 (7) | |
Text
August 15, 2003 Mr. J. A. Scalice Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
WATTS BAR UNIT 1 -
SUMMARY
OF NRCS REVIEW OF STEAM GENERATOR TUBE INSERVICE INSPECTION REPORTS FROM THE SPRING 2002 OUTAGE (TAC NO. MB6629)
Dear Mr. Scalice:
By letters dated March 12, March 14, and June 14, 2002, Tennessee Valley Authority (TVA) submitted a summary of the degraded steam generator tubes that remained in service based on the F* alternate repair criteria, a summary of the degraded steam generator tubes that were plugged, and an analysis of the degraded tubes that remained in service based on the voltage-based alternate repair criteria during the Watts Bar Unit 1 Cycle 4 refueling outage in the spring of 2002. By letter dated November 1, 2002, TVA submitted the report that describes the complete results of the spring 2002 steam generator tube inservice inspection. TVA submitted these reports pursuant to Watts Bar Unit 1 Technical Specification 5.9.9.
The results of the staffs review of these submittals are enclosed. As discussed in the enclosure, the staff concludes that TVA has provided the information required by the Watts Bar Unit 1 Technical Specifications and that no additional followup is required. The enclosed evaluation completes our review of the submittals under TAC No. MB6629.
If you have any questions regarding this matter, please contact me at (301) 415-4041.
Sincerely,
/RA/
Margaret H. Chernoff, Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-390
Enclosure:
NRC Evaluation
cc w/
Enclosure:
See next page
ML032270584 OFFICE PDII-2/PM PDII-2/LA EMCB PDII-2/SC NAME MChernoff BClayton SE Input AHowe DATE 8/14/03 8/14/03 3/30/03 8/15/ 03
Mr. J. A. Scalice Tennessee Valley Authority WATTS BAR NUCLEAR PLANT cc:
Mr. Karl W. Singer, Senior Vice President Nuclear Operations Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. James E. Maddox, Vice President Engineering & Technical Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. William R. Lagergren Site Vice President Watts Bar Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Spring City, TN 37381 General Counsel Tennessee Valley Authority ET 11A 400 West Summit Hill Drive Knoxville, TN 37902 Mr. Robert J. Adney, General Manager Nuclear Assurance Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Mark J. Burzynski, Manager Nuclear Licensing Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801 Mr. Paul L. Pace, Manager Licensing and Industry Affairs Watts Bar Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Spring City, TN 37381 Mr. Larry S. Bryant, Manager Watts Bar Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Spring City, TN 37381 Senior Resident Inspector Watts Bar Nuclear Plant U.S. Nuclear Regulatory Commission 1260 Nuclear Plant Road Spring City, TN 37381 Rhea County Executive 375 Church Street Suite 215 Dayton, TN 37321 County Executive Meigs County Courthouse Decatur, TN 37322 Mr. Lawrence E. Nanney, Director Division of Radiological Health Dept. of Environment & Conservation Third Floor, L and C Annex 401 Church Street Nashville, TN 37243-1532 Ms. Ann P. Harris 341 Swing Loop Road Rockwood, Tennessee 37854 David Lochbaum Nuclear Safety Engineer Union of Concern Scientists 1707 H Street, NW, Suite 600 Washington, D.C. 20006-3919
U.S. NUCLEAR REGULATORY COMMISSION EVALUATION OF SPRING 2002 (END OF CYCLE 4)
STEAM GENERATOR INSPECTION REPORTS WATTS BAR UNIT 1 DOCKET NO. 50-390 By letter dated March 12, 2002, Tennessee Valley Authority (TVA) submitted a summary of the degraded steam generator (SG) tubes that remained in service based on the F* alternate repair criteria during the Watts Bar Unit 1 Cycle 4 refueling outage in the spring of 2002. By letter dated March 14, 2002, TVA submitted a summary of the degraded SG tubes that were plugged.
By letter dated June 14, 2002, TVA submitted an analysis of the degraded SG tubes that remained in service based on the voltage-based alternate repair criteria. By letter dated November 1, 2002, TVA submitted the report that describes the complete results of the spring 2002 SG tube inservice inspection. TVA submitted these reports pursuant to Watts Bar Technical Specification (TS) 5.9.9.
Watts Bar Unit 1 has four Westinghouse Model D3 SGs. The tubes of these SGs are fabricated with mill-annealed Alloy 600. The tubes in the tubesheets are installed with a full-length hard-roll joint. The tube support plates use drilled-hole configurations and are made of carbon steel.
In the June 14, 2002, letter, TVA reported that it had detected 152 degraded tubes having axial outside diameter stress corrosion cracking (ODSCC) indications at the tube support plate intersections. TVA performed the condition monitoring and operational assessments of these indications as a part of the voltage-based alternate repair criteria in the plant TSs. For the condition monitoring assessment, TVA calculated the maximum burst probability and steam line break leak rate of the four SGs at the end of Cycle 4 to be 8.3 x 10-5 and 0.0075 gallons per minute (gpm), respectively. This result is much lower than the acceptance criteria of 1.0 x 10-2 and 1 gpm, respectively.
For the operational assessment, TVA used a bounding growth rate distribution taken from other similar plants because the small number of axial ODSCC indications detected during the Cycle 4 refueling outage did not provide a meaningful crack growth rate distribution. Using the conservative growth rates, TVA predicted that at the end of Cycle 5 the highest burst probability and leak rate would be 7.79 x 10-3 and 0.419 gpm, respectively. TVA implemented the voltage-based alternate repair criteria for the first time during the Cycle 4 refueling outage.
TVA submitted the condition monitoring and operational assessment of the circumferential indications detected at the top of the tubesheet in the June 14, 2002, letter. For the condition monitoring assessment, TVA performed in situ pressure tests on the 15 worst tubes. All 15 tubes withstood three times normal operating pressure without leaking. For the operational assessment, TVA projected that the structural integrity of the circumferential indications would be acceptable at the end of Cycle 5 based on the percentage of degraded area (PDA) of the indications as compared to the structural limit PDA. This methodology is based on the Electric Power Research Institute Steam Generator Integrity Assessment Guidelines. TVA plugged all tubes with circumferential indications.
Enclosure To monitor the circumferential indications at the expansion transition zones, TVA inspected 100 percent of the hot leg tube region at the top of the tubesheet using the +Point probe in all four steam generators during the Cycle 4 refueling outage. TVA also inspected 20 percent of the cold leg tubes in the top of the tubesheet region in SG 4 using the +Point probe.
Based on its review of the above inspection reports, the staff concludes that TVA has provided the SG tube inspection information required by Watts Bar TS 5.9.9 and that no additional follow-up is required.