ML042570286

Summary of Telephone Conference with TVA Re Sequoyah Unit 1 Preservice Steam Generator Tube Inspections

ML042570286
Person / Time
Site:	Sequoyah
Issue date:	09/10/2004
From:	Robert Pascarelli NRC/NRR/DLPM/LPD2
To:
Pascarelli,R J,NRC/NRR/DIPM,415-1245
References
TAC MC3377
Download: ML042570286 (4)

Text

September 10, 2004 LICENSEE: Tennessee Valley Authority FACILITY: Sequoyah Nuclear Plant, Unit 1

SUMMARY

OF JUNE 17, 2003, TELEPHONE CONFERENCE WITH THE TENNESSEE VALLEY AUTHORITY REGARDING THE PRESERVICE STEAM GENERATOR TUBE INSPECTIONS AT SEQUOYAH UNIT 1 (TAC NO. MC3377)

On June 17, 2003, a telephone conference was held between the staff of the U.S. Nuclear Regulatory Commission (NRC) and representatives of Tennessee Valley Authority (TVA). The purpose of the meeting was to discuss the design of the replacement steam generators for Sequoyah Nuclear Plant, Unit 1, and the scope and results of the preservice inspection.

The manufacturer of the Sequoyah replacement steam generators was the same manufacturer of the steam generators at Ulchin 4, a Korean plant. Ulchin 4 experienced a steam generator tube rupture in 2002, which was associated with a bulge in a tube (i.e., a manufacturing related defect). The bulge was located slightly above the top of the hot-leg tubesheet. The rupture occurred after only a few cycles of operation.

With respect to the design of the replacement steam generators, the licensee indicated the following:

Manufacturer: Doosan Designer: ABB (now Westinghouse)

Tube Manufacturer: Sandvik Tube material: thermally treated Alloy 690 Tube outside diameter: 0.75-inch Tube wall thickness: 0.043-inch Number of tubes per steam generator: 4983 Tube support design: Lattice Tube support material: 409 stainless steel Tube Pitch: Triangular, 1.0625-inch Expansion Method: Hydraulic The licensee also indicated that the Korean manufacturer performed a qualification and verification program to validate the adequacy of the hydraulic expansion. This qualification program was reviewed/observed by Westinghouse personnel. The ratio of the diameter of the tube to the tubesheet hole in the replacement steam generators is greater than that used in the original Sequoyah steam generators (i.e., the clearance between an unexpanded tube and the tubesheet is smaller in the replacement steam generators).

2 The Ulchin 4 steam generators, in contrast to the Sequoyah replacement steam generators, have several different features. For example, the Ulchin 4 tube material is mill annealed Alloy 600 and the tubes were fabricated by Babcock & Wilcox (B&W) Specialty Products. At the time the Ulchin 4 steam generators were fabricated, Ulchin 4 was the only commercial unit with tubes fabricated by B&W Specialty Products. The tubes in the Sequoyah replacement steam generators were fabricated by Sandvik. The Ulchin 4 steam generator tubes were explosively expanded into the tubesheet (rather than hydraulically expanded as was done for the Sequoyah replacement steam generators). The Ulchin 4 steam generators were based on the CE System 80 steam generator design.

With respect to the preservice inspection, the TVA representatives indicated the following:

Profilometry was performed on 100-percent of the tubes from the tube end through the first tube support. The profilometry was done in the shop (i.e., Korea), in both the hot- and cold-leg of the steam generator using a specialized bobbin probe with Zetec profiling software. During this examination, no bulges were identified; however, several tubes were identified as requiring re-expansion (i.e., the tube was not fully expanded as a result of original application of the hydraulic expansion).

100-percent of the tubes were examined full length with a bobbin coil probe. This examination was done in the U.S. A few geometry indications were identified in the tubesheet region that were attributed to the tubesheet drilling process.

The U-bend region of 100-percent of the tubes in Rows 1 through Row 3 were examined with a +Point coil The top of tubesheet region (+3-inches to inches) of 100-percent of the hot-leg tubes were examined with a +Point coil.

Approximately 100 special interest locations were examined with a

+Point coil.

A rotating ghent probe (a transmit/receive probe) was used to examine a few permeability type indications.

The licensee indicated that the rotating probe used during the examination not only had a

+Point coil but also a pancake coil. The pancake coil data was also evaluated.

As a result of the preservice inspection, one tube was identified with manufacturing damage (i.e., a mar on the tube) in the U-bend area and was plugged. The manufacturing damage was attributed to a modification made in the U-bend area during the fabrication process. Another tube was plugged as a result of a geometry/lift-off signal in the U-bend region. Several other tubes were plugged as a result of flow-induced vibration concerns. In total, 20 tubes were plugged in the four steam generators (4 in SG A, 6 in SG B, 5 in SG C and 5 in SG D).

3 Based on the results of the preservice inspections, the design of the steam generator, and an understanding of the cause of the tube rupture at Ulchin 4, TVA concluded that they do not have the same conditions in their steam generator as was present in Ulchin 4. The staff did not identify any issues with the licensees conclusions.

Please direct any inquiries to Ken Karwoski at 301-415-2752, or [KJK1@nrc.gov].

/RA/

Robert J. Pascarelli, Project Manager, Section 2 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-327 cc: See next page

ML042570286 NRC-001 OFFICE PDII-2/PM PDII-2/LA PDII-2/SC (A)

NAME RPascarelli BClayton MMarshall DATE 8/23/04 8/23/04 9/10/04 Tennessee Valley Authority SEQUOYAH NUCLEAR PLANT cc:

Mr. Karl W. Singer Mr. Pedro Salas, Manager Chief Nuclear Officer and Licensing and Industry Affairs Executive Vice President Sequoyah Nuclear Plant Tennessee Valley Authority Tennessee Valley Authority 6A Lookout Place P.O. Box 2000 1101 Market Street Soddy Daisy, TN 37384-2000 Chattanooga, Tennessee 37402-2801 Mr. David A. Kulisek, Plant Manager Mr. Ashok S. Bhatnagar, Senior Vice President Sequoyah Nuclear Plant Nuclear Operations Tennessee Valley Authority Tennessee Valley Authority P.O. Box 2000 6A Lookout Place Soddy Daisy, TN 37384-2000 1101 Market Street Chattanooga, TN 37402-2801 Senior Resident Inspector Sequoyah Nuclear Plant Mr. James E. Maddox, Vice President U.S. Nuclear Regulatory Commission Engineering & Technical Services 2600 Igou Ferry Road Tennessee Valley Authority Soddy Daisy, TN 37379 6A Lookout Place 1101 Market Street Mr. Lawrence E. Nanney, Director Chattanooga, TN 37402-2801 Division of Radiological Health Dept. of Environment & Conservation Mr. Randy Douet Third Floor, L and C Annex Site Vice President 401 Church Street Sequoyah Nuclear Plant Nashville, TN 37243-1532 Tennessee Valley Authority P.O. Box 2000 County Mayor Soddy Daisy, TN 37384-2000 Hamilton County Courthouse Chattanooga, TN 37402-2801 General Counsel Tennessee Valley Authority Ms. Ann P. Harris ET 11A 341 Swing Loop Road 400 West Summit Hill Drive Rockwood, Tennessee 37854 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. Mark J. Burzynski, Manager Nuclear Licensing Tennessee Valley Authority 4X Blue Ridge 1101 Market Street Chattanooga, TN 37402-2801