ML042890259
| ML042890259 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 11/08/2004 |
| From: | Robert Pascarelli NRC/NRR/DLPM/LPD2 |
| To: | Singer K Tennessee Valley Authority |
| Pascarelli,R J,NRC/NRR/DIPM,415-1245 | |
| References | |
| TAC MC1048 | |
| Download: ML042890259 (6) | |
Text
November 8, 2004 Mr. Karl W. Singer Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
WATTS BAR NUCLEAR PLANT, UNIT 1 - STEAM GENERATOR TUBE INSERVICE INSPECTION REPORTS FOR THE END-OF-CYCLE 5 REFUELING OUTAGE IN 2003 (TAC NO. MC1048)
Dear Mr. Singer:
By letter dated October 13, 2003 (ADAMS Accession No. ML032901021), Tennessee Valley Authority (TVA) submitted a list of the steam generator (SG) tubes that were plugged or sleeved during the Watts Bar Nuclear Plant (WBN), Unit 1, End-of-Cycle 5 refueling outage. By letter dated October 13, 2003 (ADAMS Accession No. ML032901026), TVA submitted a list of SG tubes that remained in service using the alternate repair criteria F*. By letter dated January 15, 2004 (ADAMS Accession No. ML040220171), TVA submitted a 90-day report that contained an analysis of the degraded tubes that remained in service using the voltage-based alternate repair criteria. By letter dated July 19, 2004 (ADAMS Accession No. ML042040158),
TVA submitted its response to the U.S. Nuclear Regulatory Commission (NRC) staffs request for additional information.
The NRC staffs review of these submittals is attached. The NRC staff concludes that TVA has provided the information required by the WBN, Unit 1, Technical Specifications and that no additional follow-up is required at this time. The attached evaluation completes the reviews of the submittals under TAC No. MC1048.
If you have any questions regarding this matter, please contact me at (301) 415-1245.
Sincerely,
/RA/
Robert J. Pascarelli, 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
ML032901021), Tennessee Valley Authority (TVA) submitted a list of the steam generator (SG) tubes that were plugged or sleeved during the Watts Bar Nuclear Plant (WBN), Unit 1, End-of-Cycle 5 refueling outage. By letter dated October 13, 2003 (ADAMS Accession No. ML032901026), TVA submitted a list of SG tubes that remained in service using the alternate repair criteria F*. By letter dated January 15, 2004 (ADAMS Accession No. ML040220171), TVA submitted a 90-day report that contained an analysis of the degraded tubes that remained in service using the voltage-based alternate repair criteria. By letter dated July 19, 2004 (ADAMS Accession No. ML042040158),
TVA submitted its response to the U.S. Nuclear Regulatory Commission (NRC) staffs request for additional information.
The NRC staffs review of these submittals is attached. The NRC staff concludes that TVA has provided the information required by the WBN, Unit 1, Technical Specifications and that no additional follow-up is required at this time. The attached evaluation completes the reviews of the submittals under TAC No. MC1048.
If you have any questions regarding this matter, please contact me at (301) 415-1245.
Sincerely,
/RA/
Robert J. Pascarelli, 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 Distribution: PUBLIC PDII-2 R/F EHackett MMarshall RPascarelli SCahill, RII OGC ACRS LLund MMurphy BClayton (Hard Copy)
ADAMS Accession No.: ML042890259 NRR-106 OFFICE PDII-2/PM PDII-2/LA EMCB PDII-2/SC NAME RPascarelli BClayton LLund MMarshall DATE 11/8/04 11/8/04 7/31/04 11/8/04
Mr. Karl W. Singer SEQUOYAH NUCLEAR PLANT Tennessee Valley Authority cc:
Mr. Ashok S. Bhatnagar, Senior Vice President Nuclear Operations Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Michael J. Lorek, General Manager Nuclear Engineering Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Randy Douet Site Vice President Sequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, TN 37384-2000 General Counsel Tennessee Valley Authority ET 11A 400 West Summit Hill Drive Knoxville, TN 37902 Mr. John C. Fornicola, Manager Nuclear Assurance and Licensing Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Fredrick C. Mashburn Senior Program 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 ATTN: James D. Smith Sequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, TN 37384-2000 Mr. David A. Kulisek, Plant Manager Sequoyah Nuclear Plant Tennessee Valley Authority P.O. Box 2000 Soddy Daisy, TN 37384-2000 Senior Resident Inspector Sequoyah Nuclear Plant U.S. Nuclear Regulatory Commission 2600 Igou Ferry Road Soddy Daisy, TN 37379 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 County Mayor Hamilton County Courthouse Chattanooga, TN 37402-2801 Ms. Ann P. Harris 341 Swing Loop Road Rockwood, Tennessee 37854
Enclosure U.S. NUCLEAR REGULATORY COMMISSION EVALUATION OF FALL 2003 (END OF CYCLE 5)
STEAM GENERATOR INSPECTION REPORTS WATTS BAR NUCLEAR PLANT, UNIT 1 DOCKET NO. 50-390 By letter dated October 13, 2003 (ADAMS Accession No. ML032901021), Tennessee Valley Authority (TVA) submitted a list of the steam generator (SG) tubes that were plugged or sleeved during the Watts Bar Nuclear Plant (WBN), Unit 1, End-of-Cycle 5 (EOC-5) refueling outage in 2003. By letter dated October 13, 2003 (ML032901026), TVA submitted a list of SG tubes that remained in service using the F* alternate repair criteria (ARC). By letter dated January 15, 2004 (ML040220171), TVA submitted a 90-day report that contained an analysis of the degraded tubes that remained in service using the voltage-based ARC. By letter dated July 19, 2004 (ML042040158), TVA submitted their response to the U. S. Nuclear Regulatory Commission (NRC) staffs request for additional information. A summary of the NRCs evaluation of the WB EOC-5 refueling outage is provided below.
WB Unit 1 has four Westinghouse Model D3 SGs, which have 3/4-inch diameter, 0.043-inch thick (nominal) mill annealed Alloy 600 tubing. These SGs have carbon steel drilled-hole support plates and a flow distribution baffle. The tubes were hard roll expanded for the full length of the tubesheet.
In the October 13, 2003 letters, TVA reported that, in addition to the 300 tubes that were plugged and the 148 tubes that were sleeved, 22 additional tubes were allowed to remain in service using the F* ARC. In the January 15, 2004 letter, TVA identified a total of 654 bobbin signals that were identified as outside diameter stress corrosion cracking (ODSCC) at tube support plates. TVA reported that the condition monitoring evaluation for EOC-5 for maximum probability of tube burst (POB) was 7.81x10-4 and the steam line break leakage was 0.060 gpm.
These values were much lower than the reporting threshold of 1.0x10-2 and the acceptance limit of 1.0 gpm, respectively. In addition, both values were less than projected, based on the previous inspection data. The End-of-Cycle 6 (EOC-6) operational assessment projection for the POB was 2.34x10-3, and the EOC-6 operational assessment projection for the amount of leakage was 0.175 gpm.
However, the projected number of indications for EOC-5 as a function of voltage distribution was underpredicted. The NRC staff noted that probability of detection (POD) value of 0.6 may have inadequately accounted for the missed or newly-initiated flaws, and such underprediction could result in exceeding the acceptance limits in the future. The NRC staff asked TVA to discuss what corrective actions have been taken or are planned for the future to address the underprediction of indications. TVA responded that Generic Letter 95-05, Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking, required licensees to apply a constant POD value of 0.6, which tends to result in underprediction of lower voltage indications and overprediction of higher voltage indications. TVA stated that a voltage-dependent POD methodology will be utilized during the WBN EOC-6 inspection, once the methodology is approved by the NRC.
In responding to the NRC staffs concern regarding whether axial ODSCC indications were prone to significant bobbin voltage growth, TVA indicated that they performed +Point' examinations of the larger bobbin voltage indications left in service during Cycle 5. TVA stated that voltage readings obtained during the +Point' examinations confirmed the voltage readings obtained during the bobbin exams. TVA noted that none of the +Point' voltages from the EOC-5 inspection were greater than the voltages as determined from the bobbin coil.
The NRC staff reviewed the licensees pulled tube examination report dated May 20, 2004 (ML041480443), which confirmed the presence of OD-initiated axial degradation within several tube support plates, and confirmed the presence of OD-initiated circumferential cracking in one tube at the top-of-tubesheet. The report also indicated that the burst and leakage tests were consistent with the existing ODSCC voltage-based ARC database.
The NRC staff finds that the licensee has provided the information required by their Technical Specifications and commitments regarding the F* and voltage-based ARC. The results from the examination discussed in the reports referenced above appear to be consistent with industry operating experience at similarly designed and operated plants. As a result, the NRC staff concludes that there are no technical issues that warrant NRC staff follow-up at this time.