ML081490152

Spring 2008 Refueling Outage Steam Generator Tube Inspections

ML081490152
Person / Time
Site:	Surry
Issue date:	06/10/2008
From:	Siva Lingam NRC/NRR/ADRO/DORL/LPLII-1
To:	Christian D Virginia Electric & Power Co (VEPCO)
Lingam, Siva NRR/DORL 415-1564
References
TAC MD8615
Download: ML081490152 (6)

Text

June 10, 2008 Mr. David A. Christian President and Chief Nuclear Officer Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711

SUBJECT:

SURRY POWER STATION, UNIT NO. 2, SPRING 2008 REFUELING OUTAGE STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD8615)

Dear Mr. Christian:

On May 5, 2008, the U.S. Nuclear Regulatory Commission staff participated in a conference call with Surry Power Station, Unit No. 2 representatives regarding their spring 2008 refueling steam generator tube inspections. Enclosed is a summary of that conference call.

If you have any questions regarding this summary, please contact me at 301-415-1564.

Sincerely,

/RA/

Siva P. Lingam, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-281

Enclosure:

Summary of Conference Call cc w/encl: See next page

ML081490152 *transmitted by memo dated OFFICE NRR/LPL2-1/PM NRR/LPL2-1/LA NRR/DCI/CSGB/BC NRR/LPL2-1/BC NAME SLingam MO=Brien AHiser MWong DATE 06/09/08 06/09/08 5/12/08* 06/10/08

SUMMARY

OF CONFERENCE CALL STEAM GENERATOR TUBE INSPECTIONS SURRY POWER STATION, UNIT NO. 2 DOCKET NO. 50-281 On May 5, 2008, the U. S. Nuclear Regulatory Commission (NRC) staff participated in a conference call with Surry Power Station, Unit No. 2 (Surry 2) representatives (the licensee) regarding their spring 2008 refueling outage steam generator (SG) tube inspections. A summary of the information discussed follows.

Surry 2 has three Westinghouse model 51F SGs. Each SG has 3,342 thermally treated Alloy 600 tubes with an outside diameter of 0.875 inches and a nominal wall thickness of 0.050 inches. The tubes are hydraulically expanded for the full depth of the tubesheet at each end. The tubes are supported by stainless steel support plates with quatrefoil-shaped holes. The U-bend region of the tubes installed in Rows 1 through 8 was thermally treated after bending in order to reduce stress.

At the time of the May 5, 2008, conference call, tube inspections were still in progress. A summary of the information provided during this call is below:

• There was no primary-to-secondary leakage in the cycle preceding the 2008 inspections.

• No secondary side pressure tests were performed.

• In SGs B and C, the following was the planned scope of inspection:

o 100% of the tubes were inspected full length with the bobbin coil except for the U-bend region of the row 1 tubes. Any tubes identified with a U-bend offset (similar to what was observed at Seabrook) were inspected with a +PointTM coil in the tubesheet region since these tubes may have an elevated susceptibility to cracking.

The data from all tubes were reviewed for this offset.

o 50% of the tubes were inspected with a +PointTM coil from 3-inches above the hot-leg top of tubesheet to the hot-leg tube-end focusing on the critical area (secondary side sludge pile).

o The U-bend region of 100% of the row 1 tubes were inspected with a +PointTM coil (from the seventh hot-leg tube support to the 7th cold-leg tube support).

o 100% of the dents and dings that were greater than 5 volts (as determined from the bobbin inspection) were inspected with a +PointTM coil.

o 20% of the dents and dings that were greater than 2 volts but less than 5 volts (as determined from the bobbin inspection) were inspected with a +PointTM coil.

o 100% of the over-rolls in the hot-leg were inspected with a +PointTM coil.

o 50% of the over-expansions in the tubesheet region on the hot-leg and the 10 largest over-expansions in the tubesheet region on the cold-leg were inspected with a +PointTM coil.

o 100% of the tubes that were not expanded or were only partially expanded into the tubesheet were inspected with a +PointTM coil throughout the tubesheet region.

o All bobbin I-codes were inspected with a +PointTM coil.

Enclosure

• Axially and circumferentially oriented primary water stress corrosion cracking was observed in SGs B and C near the hot-leg tube end so the scope of the inspections was expanded to include a +PointTM coil inspection of all tubes in SGs B and C from the hot-leg tube end to 4-inches above the hot-leg tube end. In addition, the inspections were expanded to include inspecting 20% of the tubes in SG A with a +PointTM coil from the hot-leg tube end to 4-inches above the hot-leg tube end. No other expansions were implemented at the time of the conference call (other than for tubes adjacent to possible loose parts).

• A magnetically biased +PointTM coil was used to inspect the initial indications detected near the hot-leg tube end in SGs B and C. These inspections were performed at a slower speed (i.e., 0.4-inches per second) and confirmed the presence of the original indications.

• Wear at the anti-vibration bars was detected. The indications exhibited minor (i.e.,

non-significant) growth since the prior inspections.

• One tube was identified with wear from a loose part. The indication was present during the last inspection (approximately 32-percent through-wall). The part was no longer at the location of the wear scar. The indication had not been sized at the time of the conference call. A new method for sizing these types of indications will be used this spring 2008 refueling outage.

• Overall, the inspections were approximately 94% complete in SG B and 50% complete in SG C at the time of the call. The tube end inspections were complete in SGs B and C and were commencing in SG A at the time of the call.

• No unusual or unexpected results (except for the indications near the tube end) were detected during the outage.

• All tubes exceeding the tube repair criteria will be plugged. In addition, tube end indications will be left in service if they satisfy the criteria of the interim alternate repair criteria for tubesheet indications (approved later by the NRC on May 16, 2008).

• Historical data reviews were performed during the outage. No issues were identified as a result of these reviews.

• The only crack-like indications detected during the outage occurred with 1-inch of the hot-leg tube end. In SG B, 39 tube end indications were detected in 37 tubes. Of these 39 indications, 9 were axially oriented and 30 were circumferentially oriented. All of the indications were within 0.17 inches of the tube end. Only one of these indications exceeded the criteria of the interim alternate repair criteria. This indication measured 117 degrees in circumferential extent. In SG C, 21 tube end indications were detected in 20 tubes. Of these 21 indications, 6 were axially oriented and 15 were circumferentially oriented. All of the indications were within 0.18 inches of the tube end. Two of these indications exceeded the criteria of the interim alternate repair criteria. These indications measured 109 degrees and 117 degrees in circumferential extent.

• No tubes were identified for in-situ pressure testing (based on industry guidelines). No tubes were scheduled to be removed for destructive examination.

• Based on the results to-date, all tubes satisfied the structural and leakage integrity performance criteria during the previous operating cycle (i.e., prior to end-of-cycle 21), and all tubes that will remain in service will satisfy the structural and leakage integrity performance criteria until the next planned inspection (end-of-cycle 22).

• If a crack-like indication is detected near the tube end in SG A, the plan is to expand the inspection to include 100% of the tube ends in SG A.

• In SGs A, B, and C, a high-volume bundle flush, foreign object search and retrieval, and sludge lancing were planned. In addition, a top down visual (video) inspection on the secondary side of the steam generator to the top (seventh) tube support plate was planned

for SGs B and C, and an ultrasonic inspection of one feedring component was scheduled in SG C.

• Eddy current data quality is verified during the inspections.

The NRC staff did not identify any issues that warranted immediate follow-up action during the conference call.

Surry Power Station, Units 1 & 2 cc:

Mr. David A. Christian Office of the Attorney General President and Chief Nuclear Officer Commonwealth of Virginia Virginia Electrical and Power Company 900 East Main Street Innsbrook Technical Center Richmond, Virginia 23219 5000 Dominion Boulevard Glen Allen, VA 23060-6711 Mr. Chris L. Funderburk, Director Nuclear Licensing & Operations Support Ms. Lillian M. Cuoco, Esq. Dominion Resources Services, Inc.

Senior Counsel Innsbrook Technical Center Dominion Resources Services, Inc. 5000 Dominion Blvd.

120 Tredegar Street, RS-2 Glen Allen, Virginia 23060-6711 Richmond, VA 23219 Mr. Matt Adams, Director Mr. Donald E. Jernigan Nuclear Safety & Licensing Site Vice President Surry Power Station Surry Power Station Virginia Electric and Power Company Virginia Electric and Power Company 5570 Hog Island Road 5570 Hog Island Road Surry, Virginia 23883-0315 Surry, Virginia 23883-0315 Senior Resident Inspector Surry Power Station U. S. Nuclear Regulatory Commission 5850 Hog Island Road Surry, Virginia 23883 Chairman Board of Supervisors of Surry County Surry County Courthouse Surry, Virginia 23683 Dr. W. T. Lough Virginia State Corporation Commission Division of Energy Regulation Post Office Box 1197 Richmond, Virginia 23218 Dr. Robert B. Stroube, MD, MPH State Health Commissioner Office of the Commissioner Virginia Department of Health Post Office Box 2448 Richmond, Virginia 23218