ML12039A161

Steam Generator Tube Inspection Report

ML12039A161
Person / Time
Site:	North Anna
Issue date:	01/25/2012
From:	Gerald Bichof Virginia Electric & Power Co (VEPCO), Dominion
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
11-673
Download: ML12039A161 (8)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 January 25, 2012 U.S. Nuclear Regulatory Commission Serial No.11-673 Attention: Document Control Desk NAPS/JHL Washington, D.C. 20555 Docket No. 50-339 License No. NPF-7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 2 STEAM GENERATOR TUBE INSPECTION REPORT Pursuant to Technical Specification 5.6.7 for North Anna Power Station Unit 2, Dominion is required to submit a 180-day steam generator tube inspection report. The attachment to this letter provides the steam generator tube inspection report for the North Anna Unit 2 fall 2011 refueling outage.

Should you have any questions or require additional information, please contact Mr.

Jay Leberstien at (540) 894-2574.

Very truly yours, Gerald T. Bischo Site Vice President Attachment Commitments made in this letter: None

Serial No.11-673 Docket No. 50-339 180-Day SG Report Page 2 of 2 cc: U.S. Nuclear Regulatory Commission Region II Marquis One Tower 245 Peachtree Center Avenue, NE Suite 1200 Atlanta, Georgia 30303-1257 Mr. J. E. Reasor, Jr.

Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.

Suite 300 Glen Allen, Virginia 23060 NRC Senior Resident Inspector North Anna Power Station Ms. K. R. Cotton NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G9A 11555 Rockville Pike Rockville, Maryland 20852 Dr. V. Sreenivas NRC Project Manager U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G9A 11555 Rockville Pike Rockville, Maryland 20852

Serial No.11-673 Docket No. 50-339 180-Day SG Report ATTACHMENT NORTH ANNA UNIT 2 180-DAY NRC REPORT REGARDING STEAM GENERATOR TUBE INSPECTIONS PER TECHNICAL SPECIFICATION 5.6.7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

ý 4 Serial No.11-673 Docket No. 50-339 180-Day SG Report Page 1 of 5 FALL 2011 - NORTH ANNA UNIT 2 STEAM GENERATOR INSPECTIONS During the North Anna Unit 2 fall 2011 outage, steam generator (SG) inspections were completed in accordance with TS 5.5.8.d for SG "A" and "C". Transmittal of this report satisfies the North Anna Power Station Technical Specification (TS) reporting requirement specified in Section 5.6.7.

The Unit 2 steam generators have accrued 14.4 Effective Full Power Years (EFPY) of operation as of the end of Cycle 21 (August, 2011).

Initial entry into Mode 4 occurred on November 14, 2011 (2323 hours0.0269 days <br />0.645 hours <br />0.00384 weeks <br />8.839015e-4 months <br />); therefore, this report is required to be submitted by May 12, 2012.

Italicized wording represents TS verbiage. The required information is provided under each reporting requirement as follows:

A report shall be submitted within 180 days after the initial entry into Mode 4 following completion of an inspection performed in accordance with the Specification 5.5.8, "Steam Generator(SG) Program." The report shall include:

a. The scope of inspections performed on each SG The following primary side inspections were performed in SG "A" and "C":

• Video examination of both channel heads (as-found / as-left) including previously installed tube plugs

• 100% full-length inspection utilizing bobbin coil probe for all tubes except for Row 1 U-bends 0 26% of hot leg top of tubesheet (+/- 3") utilizing rotating coil probe with tube selection including 50% of the secondary side critical area in the sludge zone, 50% of all tubes within five tubes of the bundle periphery, and other randomly sampled locations

• 16% of cold leg top of tubesheet (+/- 3") utilizing rotating coil probe with tube sample constituting 50% of all tubes within five tubes of the bundle periphery

• 100% Row 1 U-bend region utilizing rotating coil probe/steam generator

• Special interest inspections of dents/dings with rotating coil probe (Sample:

100% of dents/ding > 5 Volts; 3% of dents/ding > 2 Volts and < 5 Volts)

• Inspection of all bobbin identified I-codes (i.e. possible damage indications) with rotating coil probe (Sample: 2 tests in each SG)

• Special interest rotating coil probe exams of largest voltage tubesheet overexpansions (OXP) (SG "A" sample: 28 hot leg and 6 cold leg tests; SG "C" sample: 72 hot leg and 22 cold leg tests)

• Rotating coil probe examinations of all hot leg historical manufacturing brandish mark (MBH) indications

Serial No.11-673 Docket No. 50-339 180-Day SG Report Page 2 of 5 The following secondary side inspections were performed in SG "A"and "C":

• Steam drum visual inspections to evaluate the cleanliness and structural condition of all accessible subcomponents including moisture separators, drain systems, and interior surfaces.

• Drop down examinations through the primary separators to assess the cleanliness and structural condition of the upper tube bundle and anti-vibration bar (AVB) supports.

• Visual inspections of J-nozzle to feedring internal interface for flow assisted corrosion.

• Visual inspections of upper tube support plates via 7 th tube support plate (TSP) handholes to assess structural condition and cleanliness, including that of TSP wedges and associated welds.

• Ultrasonic thickness measurement of selected feedring locations.

b. Active degradationmechanisms found No tube degradation was identified during this examination and no new tube denting was identified during this examination.

c. Nondestructive examination techniques utilized for each degradationmechanism The 2011 tube inspections focused on the degradation mechanisms listed in Table 1 utilizing the referenced eddy current techniques.

Serial No.11-673 Docket No. 50-339 180-Day SG Report Page 3 of 5 Table 1 - Inspection Method for Applicable Degradation Modes Degradation Classification Mechanism Location Probe Type Bobbin - Detection Potential Tube Wear Anti-Vibration Bars Bobbin and +PointTM - Sizing Flow Distribution Baffle Bobbin - Detection Potential Tube Wear (FDB) Bobbin and +Pointtu- Sizing Tube Support Plate Bobbin - Detection Existing Tube Wear (TSP) Bobbin and +PointTM - Sizing Freespan & AVB Bobbin - Detection Potential Tube Wear tangents (Row 8, 14, 26) Bobbin or +PointTM- Sizing Tube Wear Freespan, Top-of- Bobbin and +PointTu-Potential Tubesheet (TTS), FDB, Detection (foreign objects) and TSP +PointTM - Sizing Intergranular attack (IGA)/outside Hot Leg TTS sludge pile Bobbin and +Point -

Potential diameter stress Detection corrosion critical +PointTM - Sizing cracking (ODSCC)

TTS sludge pile Bobbin - Detection Potential OD Pitting critical area +PointTM - Sizing Primary water Hot leg TTS sludge pile Relevant/Informational stress corrosion critical area and +PointTM - Detection and Inspection cracking within-tubesheet Sizing (PWSCC) anomaly locations Relevant/Informational IGA/ODSCC +PointTM - Detection and Inspection PWSCC Sizing Relevant/Informational Freespan, Bobbin - Detection Inspection IGA/ODSCC FDB, TSP +Point TM - Sizing Relevant/Informational TTS outside the +Point TM - Detection and Inspection critical area Sizing

Serial No.11-673 Docket No. 50-339 180-Day SG Report Page 4 of 5

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications No service induced tube indications were identified during the fall 2011 examination.

UT thickness measurements were taken in selected regions of the SG "A" and SG "C" feedring during this outage for the purpose of monitoring flow assisted corrosion (FAC) related degradation. All measurements exceeded the minimum design requirement of 0.350 inch by a significant margin.

e. Number of tubes plugged during the inspection outage for each active degradation mechanism No tubes were plugged during this inspection.

f. Total number and percentage of tubes plugged to date Table 2 summarizes the current tube plugging status for North Anna Unit 2 steam generators.

Table 2 - Current Tube Plugging Status Number of Steam Generator Plugged Tubes Percent Plugged A 1 0.03%

B 0 0.00%

C 5 0.14%

Total 6 0.06%

g. The results of condition monitoring, including the results of tube pulls and in-situ testing The Condition Monitoring Assessment concluded that SG "A" and "C" did not exceed any performance criteria during the period preceding the fall 2011 inspection. No findings from the fall 2011 inspection invalidated previous operational assessments for any of the three steam generators and the condition monitoring requirements were met. Therefore, tube pulls and in-situ pressure testing were not necessary.

Serial No.11-673 Docket No. 50-339 180-Day SG Report Page 5 of 5

h. The effective plugging percentage for all plugging in each SG There are no sleeves installed in the North Anna Unit 2 steam generators; therefore, the effective plugging percentage remains the same as stated in (f) above.