ML051810694
| ML051810694 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/08/2005 |
| From: | Pickett D NRC/NRR/DLPM/LPD2 |
| To: | Singer K Tennessee Valley Authority |
| Pickett D, NRR/DLPM, 415-1364 | |
| References | |
| TAC MC6428 | |
| Download: ML051810694 (7) | |
Text
July 8, 2005 Mr. Karl W. Singer Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801
SUBJECT:
SEQUOYAH NUCLEAR PLANT, UNIT 2
SUMMARY
OF CONFERENCE CALL WITH TENNESSEE VALLEY AUTHORITY REGARDING THE SPRING 2005 STEAM GENERATOR TUBE INSPECTION RESULTS (TAC NO. MC6428)
Dear Mr. Singer:
On May 10, 2005, the U.S. Nuclear Regulatory Commission (NRC) staff participated in conference calls with Tennessee Valley Authority representatives regarding the ongoing steam generator tube inspection activities at the Sequoyah Nuclear Plant, Unit 2. Enclosed is a brief summary of the conference call prepared by the NRC staff.
If you have any questions about this material, please contact me at (301) 415-1364.
Sincerely,
/RA/
Douglas V. Pickett, Senior Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-328
Enclosure:
As stated cc w/enclosure: See next page
July 8, 2005 Mr. Karl W. Singer Chief Nuclear Officer and Executive Vice President Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801
SUBJECT:
SEQUOYAH NUCLEAR PLANT, UNIT 2
SUMMARY
OF CONFERENCE CALL WITH TENNESSEE VALLEY AUTHORITY REGARDING THE SPRING 2005 STEAM GENERATOR TUBE INSPECTION RESULTS (TAC NO. MC6428)
Dear Mr. Singer:
On May 10, 2005, the U.S. Nuclear Regulatory Commission (NRC) staff participated in conference calls with Tennessee Valley Authority representatives regarding the ongoing steam generator tube inspection activities at the Sequoyah Nuclear Plant, Unit 2. Enclosed is a brief summary of the conference call prepared by the NRC staff.
If you have any questions about this material, please contact me at (301) 415-1364.
Sincerely,
/RA/
Douglas V. Pickett, Senior Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-328
Enclosure:
As stated cc w/enclosure: See next page DISTRIBUTION:
PUBLIC PDII-2 r/f MVaaler RidsNrrPMDPickett RidsNrrLABClayton RidsNrrDlpmLpdii2 RidsOgcRp YDiaz-Castillo KKarwoski PKlein CLauron MLesser LLund GMakar LMiller NMorgan EMurphy MMurphy JTerrell MYoder JJolicoeur RidsAcrsAcnwMailCenter RidsRgn2MailCenter (SCahill)
ADAMS Accession No.: ML051810694 NRC-001 OFFICE LPD2-2 PM:LPD2-2 LA:LPD2-2 SC:EMCB SC:LPD2-2 NAME MVaaler DPickett BClayton LLund by memo dated BMozafari for MMarshall DATE 07/ 07/ 05 07/ 07/ 05 07/ 07/ 05 06 / 07 /05 07/ 08/ 05
OFFICIAL RECORD COPY
Enclosure
SUMMARY
OF CONFERENCE CALL TENNESSEE VALLEY AUTHORITY STEAM GENERATOR TUBE INSPECTION RESULTS FOR THE SPRING 2005 REFUELING OUTAGE SEQUOYAH NUCLEAR PLANT, UNIT 2 On May 10, 2005, the staff of the Materials and Chemical Engineering Branch, Division of Engineering, Office of Nuclear Reactor Regulation, participated in a conference call with Tennessee Valley Authority representatives regarding the ongoing steam generator (SG) tube inspection activities at Sequoyah Nuclear Plant Unit 2.
Sequoyah Unit 2 has four Westinghouse Model 51 SGs. Each SG contains about 3400 mill-annealed Alloy 600 tubes with an outside diameter (OD) of 0.875 inches and a wall thickness of 0.050 inches. Each U-tube is roll-expanded for approximately 2.75 inches from the bottom of the tubesheet, and is secured into the remaining portion of the tubesheet by the Westinghouse Explosive Tube Expansion process. The tubesheet is approximately 21-inches thick and each tube is expanded for essentially the full thickness of the tubesheet. Each SG contains seven carbon steel tube support plates with drilled holes, through which the tubes pass.
Prior to the phone call, the licensee was provided with discussion points to help facilitate the phone conference. In response, the following information was provided verbally by the licensee during the call.
Primary-to-secondary leakage; secondary-side pressure tests No primary-to-secondary leakage was observed during the recently-completed operating cycle.
Therefore, no secondary-side pressure tests will be performed during this outage.
Exceptions to industry guidelines The licensee had two exceptions to the Electric Power Research Institute (EPRI) Pressurized Water Reactor (PWR) Steam Generator Examination Guidelines, Revision 6:
The first exception involves the flaw detection sensitivity of the Mitsubishi Heavy Industries Intelligent Array Probe (MHI probe). The MHI probe did not meet the Revision 6 sensitivity criteria for the detection of flaws that are situated between the probe coils as the probe passes through the U-bend section of the tube. The Revision 6 methodology was established primarily for a particular vendor of the array probe and made no effort to accommodate variations.
Whereas the Revision 6 methodology was used for establishing 80 percent sensitivity, the method used by the licensee for the MHI probe obtained 70 percent sensitivity or better. The deviation was successfully utilized during the Peer Review process at EPRI-Charlotte to qualify the MHI probe to be used for the detection of primary water stress-corrosion cracking (PWSCC) in low-row U-bends.
For the second exception, an appropriate flaw data set was not available to qualify the MHI probe for the detection of OD stress-corrosion cracking (ODSCC) flaws in the tube U-bends in accordance with the EPRI PWR Steam Generator Examination Guidelines, Appendix H. The licensees comparative tests between the MHI and +Point' probes showed comparable sensitivity to U-bend cracks. The licensee also added that the MHI probe was used as a screening tool for the +Point' probe in the U-bends.
Description of the inspections At the time of the call, the licensee stated that approximately 60 percent of the examinations were complete.
The licensees inspection plan for all four SGs (unless otherwise noted) was as follows:
Full-length bobbin examination on 100 percent of the tubes Hot-leg top-of-tubesheet (TTS) examination using a rotating probe over a depth of +2/-8 inches on 100 percent of the tubes Cold-leg TTS examination using a rotating probe over a depth of +2/-8 inches on 20 percent of the tubes Inspection of 100 percent of the over-expansions within the tubesheet and at the TTS using a rotating probe U-bends using a rotating probe on 100 percent of the tubes in Rows 1 - 4 U-bends using the MHI probe on 100 percent of the tubes in Rows 5 - 8 in SGs 1 and 3 U-bends using the MHI probe on 100 percent of the tubes in Rows 5 - 10 in SGs 2 and 4 100 percent of the freespan dings greater than or equal to 2 volts using a rotating probe from the TTS to the tube support plate H07 Rotating coil examination of 100 percent of the hot-leg tube support plate dents greater than or equal to 2 volts Rotating coil examination of 20 percent of the cold-leg tube support plate dents greater than or equal to 2 volts Rotating coil examination of 100 percent of all manufacturing burnish marks associated with a dent/ding Rotating coil examination of 100 percent of all dents associated with anitvibration bars (AVB)
Rotating coil examination of 100 percent of all dings in the tube U-bends Rotating coil examination of 100 percent of all indications that experienced a greater than 1 volt increase (from bobbin) since the last outage Summary of the identified indications to-date Based on the previous operational assessment, the licensee stated that they had expected to plug at least 150 tubes by the end of the outage, but they were on track to plug a fewer number of tubes. One tube was plugged for AVB wear, which measured greater than 40 percent in depth. Two tubes were plugged for cold-leg thinning, which also measured greater than 40 percent in depth. No indications in the U-bends were identified. The licensee detected approximately 1700 axially-oriented OD indications at the tube support plates, seven of which exceeded 2 volts. The largest of these indications, in terms of voltage, for each steam generator are as follows:
Steam Generator Largest indication, volts 1
1.95 1
1.97 3
2.36 4
1.67 The licensee stated that their tube plugging criteria for ODSCC at tube support plates follows the alternate repair criteria in Generic Letter 95-05.
At the time of the call, the tubes scheduled to be plugged due to SCC at the TTS were as follows:
Degradation Type Largest indication, volts No. tubes plugged axial ODSCC 0.46 11 circum. ODSCC 0.26 3
axial PWSCC 1.09 5
circum. PWSCC 0.38 2
At the time of the call, the licensee had not yet sized the TTS indications. Tubes with indications of cracking at the TTS were plugged upon detection.
In situ pressure testing plans The licensee stated that none of the indications detected thus far exceed the in situ pressure testing criteria.
Schedule for remaining SG-related activities The licensee expected that all eddy current examinations would be completed by May 11, 2005, and that the remainder of the SG tube inservice inspection would be completed by May 13, 2005. The licensee will continue to look for and characterize all indications that show a greater than 1 volt increase since the last outage.
Sludge lancing, loose parts At the time of the call, secondary-side sludge lancing activities were beginning. After sludge lancing, the licensee will perform a foreign object search and retrieval, as the licensee acknowledged the existence of foreign objects.
May 13, 2005 phone call from the licensee On May 13, 2005, the licensee notified the NRC Project Manager that there were no new findings of significance, and that a total of 43 tubes were plugged.
Mr. Karl W. Singer Tennessee Valley Authority SEQUOYAH NUCLEAR PLANT cc:
Mr. Ashok S. Bhatnagar, Senior Vice President Nuclear Operations Tennessee Valley Authority 6A Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 Mr. Larry S. Bryant, 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