ML14035A067

Steam Generator Tube Inspection Report

ML14035A067
Person / Time
Site:	North Anna
Issue date:	01/14/2014
From:	Gerald Bichof Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML14035A067 (8)

Text

4 VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 January 14, 2014 U.S. Nuclear Regulatory Commission Serial No.14-015 Attention: Document Control Desk NAPS/JHL Washington, D.C. 20555 Docket No. 50-338 License No. NPF-4 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 1 STEAM GENERATOR TUBE INSPECTION REPORT Pursuant to Technical Specification 5.6.7 for North Anna Power Station Unit 1, 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 1 fall 2013 outage.

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

Page Kemp at (540) 894-2295.

Very truly yours,

'#zJd 2Iz%'

1 Gerald T. Bischof Site Vice President Attachment Commitments made in this letter: None

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4.

Serial No.14-015 Docket No. 50-338 180-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 NRC Senior Resident Inspector North Anna Power Station 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

44 ,

Serial No.14-015 Docket No. 50-338 180-Day SG Report ATTACHMENT NORTH ANNA UNIT 1 180-DAY NRC REPORT REGARDING STEAM GENERATOR TUBE INSPECTION PER TECHNICAL SPECIFICATION 5.6.7 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

4.

Serial No.14-015 Docket No. 50-338 180-Day SG Report Page 1 of 5 FALL 2013 - NORTH ANNA UNIT 1 STEAM GENERATOR INSPECTIONS The following satisfies the North Anna Power Station Technical Specification (TS) reporting requirement section 5.6.7. During the North Anna Unit 1, fall 2013 refueling outage, steam generator (SG) inspections in accordance with TS 5.5.8.d were completed for all three steam generators ("A", "B"and "C").

This was the first inspection under the modified Technical Specifications resulting from TSTF-510, Revision 2, "Revision to Steam Generator Program Inspection Frequencies and Tube Sample Selection." This was also the second inspection of the second inspection period for each steam generator.

Initial entry into Mode 4 occurred on October 8, 2013 (1602 hours0.0185 days <br />0.445 hours <br />0.00265 weeks <br />6.09561e-4 months <br />); therefore, this report is required to be submitted by April 6, 2014. The Unit 1 SGs had operated for 222.4 Effective Full Power Months (EFPM) at the time of this inspection.

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 all three of the North Anna Unit 1 steam generators:

• Video examination of both the Hot Leg (H/L) and Cold Leg (CIL) channel heads (as-found / as-left), specifically including all plugs, the divider plate weld region, and the regions of each bowl as required by NSAL-12-1.

• 100% full-length inspection utilizing bobbin coil probe for all tubes except for Row 1 U-bends.

• 28% (993 Tubes) hot leg top of tubesheet (+/- 3") utilizing rotating coil probe divided as follows: 570 tubes (- 50% of 5 tube periphery) plus 214 tubes (50% of sludge pile region) plus 209 tubes across bundle interior outside of the sludge pile region.

• 16% (570 tubes) cold leg top of tubesheet (+/- 3") utilizing rotating probe (- 50% of 5 tube periphery)

• 100% Row 1 (98 tubes in each SG) U-bend region utilizing rotating coil probe

• Special interest inspections of dents/dings > 5 volts and all "New" dents with rotating coil probe. Results identified in Table 1 below.

• Special interest inspections included a sampling of the largest H/L over-expansions (OXP), a sampling of the largest C/L OXP, plus a sampling of the H/L historical manufacturing burnish mark (MBH) indications using the rotating coil probe. Results identified in Table 1 below.

• Special interest inspections of all: bulge (BLG), possible loose part (PLP), and TSP wear indications with rotating coil probe. Results identified in Table 1 below.

• Inspection of all bobbin coil I-codes (i.e., possible indications) with rotating coil probe.

Results identified in Table 1 below.

Serial No.14-015 Docket No. 50-338 180-Day SG Report Page 2 of 5 Table 1 - +Point Probe Examination Summary KEY: tubes I indications / indications tested SG"A" SG"B" SG'C" with +Point Wear 5/6/6 4/6/6 1/4/4 PLP 4/4/4 0/0/0 0/0/0 New Dent a 2 Volts 0/0/0 0/0/0 2/2/2 Dents > 2 Volts and <5 Volts* 252/304/6 69/77/0 125/145/3 Dents 5 Volts 17/18/18 6/7/7 9/10/10 BLG 2/3/3 4/4/4 2/2/2 Hot Leg MBH 53/62/23 53/60/21 51/56/20 Hot Leg OXP 279/344/26 83/94/21 598/1015/54 Cold Leg OXP 260/319/8 250/387/7 634/1015/15

• includes two new dents.

The following secondary side inspections were performed in each of the North Anna Unit 1 steam generators:

• Steam drum visual inspections covering all accessible subcomponents such as the primary and secondary moisture separators, drain piping, feedring piping, and other interior surfaces/ components.

" Video inspection of the upper tube bundle U-bend area and anti-vibration bar (AVB) supports

• Video inspection of the uppermost tube support plate (TSP), i.e., 7 th TSP in the periphery area and in-bundle at selected tube columns. The 4 th, 5 th, and 6 th TSPs were also video inspected in the center bundle area as accessed from the 7 th TSP handhole.

• Video inspection of the inside interface of the feedring to J-nozzle joints.

• UT thickness measurements were taken in selected regions of the feedring in all three SGs during the NIR23 outage for the purpose of monitoring flow assisted corrosion (FAC) related degradation.

b. Degradationmechanisms found Prior to this outage, TSP wear was the only degradation mechanism classified as "existing" in the North Anna Unit 1 SG tubing. Several other mechanisms were classified as "potential" (i.e., AVB and foreign object wear, pitting within the top of tubesheet sludge region, and hot leg top of tubesheet intergranular attack (IGA)/ outer diameter stress corrosion cracking (ODSCC) within the sludge pile region). It is primarily these damage mechanisms that were targeted by this inspection. Wear at the TSPs was the only indication of tube degradation identified during this (1 R23) examination.

During the ultrasonic testing (UT) grid point measurements of the SG "A" feedring, localized erosion was identified outside of the normal grid point measurement locations on the left side reducer extension between J-Nozzles #1 and #2. The thickness of this localized region measured 0.350 inch in 2011 and 0.306 inch in 2013, resulting in a thickness reduction of 0.044 inch over one-cycle of operation. In response to this localized wall loss, additional UT examinations were performed in SG "A" between J-nozzles #1 through #4 and also in the

Serial No.14-015 Docket No. 50-338 180-Day SG Report Page 3 of 5 surrounding areas adjacent to each of the 35 feedring J-nozzles. These additional UT examinations revealed other regions of localized wall thinning, specifically a region between J-nozzles #3 and #4 and a second region between J-nozzles #2 and #3. Within these regions, two localized minimum thickness values were observed and measured 0.263 inch and 0.267 inch respectively. Additionally, three other localized readings (all below 0.285 inch) were also observed. These readings (unlike the first two) aligned in the circumferential direction, for a total circumferential involvement of less than 60 degrees. This condition has been evaluated in detail in Engineering Technical Evaluation ETE-NA-2013-0052 "Evaluation of FAC wear on the Unit 1 "A" Steam Generator Feed Ring", where it is shown that the SG "A" feedring is acceptable to return to service and operate for a single cycle, without violating structural integrity, at which time the feedring will either be reanalyzed or remediated through repair activities.

c. Nondestructive examination techniques utilized for each degradationmechanism Inspections focused on the following degradation mechanisms listed in Table 2 utilizing the referenced eddy current techniques.

Table 2 - Inspection Method for Applicable Degradation Modes Classification Degradation Location Probe Type Mechanism Bobbin -- Detection DeTMetion Potential Tube Wear Anti-Vibration Bars Bobbin Bobbin and +Pointm - Sizing Flow Distribution Bobbin - Detection Potential Tube Wear Baffle Bobbin and +PointTM- Sizing Bobbin - Detection Existing Tube Wear Tube Support Plate Bobbin and +PointTM - Sizing Straight Leg & AVB Bobbin - Detection Potential Tube Wear Tangents Bobbin or +PointTM- Sizing (Row 8, 14, 25)

Tube Wear Bobbin - Detection Potential (foreign objects) Freespan and I-S +PointTM - Sizing Hot Leg Top-of- Bobbin and +PointTM - Detection Potential ODSCC Tubesheet Sludge +PointTM - Sizing Pile Area Hot Leg Top-of-Proactive Tubesheet Sludge TM Inspections PWSCC Pile Area and +Point - Detection and Sizing Within Tubesheet Anomaly locations Relevant/Informational ODSCC Row 1 U-bends +PointTM - Detection and Sizing Inspection PWSCC Relevant/Informational Freespan and Tube Bobbin - Detection Inspection ODSCC Supports +PointTM- Sizing Relevant/Informational Bobbin and +PointTM- Detection Inspection OD Pitting Top-of-Tubesheet +PointTM - Sizing

Serial No.14-015 Docket No. 50-338 180-Day SG Report Page 4 of 5

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications Table 3 summarizes the 16 indications (TSP wear) identified during this inspection that are relevant to tube integrity. These are the only indications of tube degradation identified during this examination. All of the indications were caused by shallow volumetric tube degradation at TSP land contact points and are characteristic of tube support plate vibration and wear. Of the 16 reported indications, 3 are repeat indications (SG "A" R2-C25, R2-C91, and R15-C9). The 13 remaining indications were reported for the first time during the 2013 inspection. However, based upon historical look-ups only 2 of the 13 indications are really new. These two new indications are both located in SG "B" tube R13-C96. The remaining 11 indications are traceable back to a previous outage. Of the three repeat indications, none of them exhibited detectable growth since the 2007 inspection, including the largest wear flaw identified (16%TW). None of the affected tubes were plugged. Table 3 also provides additional information relevant to the condition monitoring and operational assessment.

Table 3 - Tube Degradation Summary Axial Circ. Max Upper Bound Length Length Depth Depth After 3 Row Col Location ETSS (in) (in) (%TW) Cycles SG A 1 54 06H -0.57 96910.1 0.56 0.45 9 37.7 A 2 25 06C -0.54 96910.1 0.67 0.43 16 44.8 A 2 66 06C -0.49 96910.1 0.62 0.48 10 38.7 06C -0.57 96910.1 0.48 0.45 5 33.7 A 2 91 04C -0.47 96910.1 0.73 0.37 9 37.7 A 15 9 03H +0.39 96910.1 0.36 0.39 8 36.7 B 1 98 05C +0.24 96910.1 0.80 0.34 11 39.7 05C -0.47 96910.1 0.52 0.42 6 34.7 B 12 96 05C -0.58 96910.1 0.58 0.37 9 37.7 B 13 96 05C -0.61 96910.1 0.41 0.37 4 32.6 05C +0.29 96910.1 0.28 0.32 4 32.6 B 14 96 05C -0.54 96910.1 0.55 0.45 11 39.7 C 3 79 04C +0.32 96910.1 0.82 0.36 8 36.7 05C -0.49 96910.1 0.87 0.36 7 35.7 05C -0.26 96910.1 1.10 0.36 4 32.6 05C +0.28 96910.1 1.07 0.39 11 39.7

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

Serial No.14-015 Docket No. 50-338 180-Day SG Report Page 5 of 5

f. The number and percentage of tubes plugged to date, and the effective plugging percentage in each steam generator A total of two (2) tubes are plugged in the North Anna Unit 1 steam generators. Both plugged tubes are in SG "C" and represent an effective plugging percentage in SG "C" of 0.06%. The effective plugging percentage in SGs "A" and "B" is 0%. The overall effective plugging percentage for all three SGs is 0.02 %.

g. The results of condition monitoring,including the results of tube pulls and in-situ testing The Condition Monitoring Evaluation was completed and SGs "A", "B", and "C" did not exceed any performance criteria during the cycles since the spring 2009 inspections in SGs "B" and "C" and the fall 2011 inspections in SG "A". No findings from the fall 2013 inspection invalidated the previous operational assessment for any steam generator. Condition monitoring requirements were met. Therefore, tube pulls and in-situ pressure testing were not necessary.