ML16202A066

Steam Generator Tube Inspection Report

ML16202A066
Person / Time
Site:	North Anna
Issue date:	07/12/2016
From:	Gerald Bichof Virginia Electric & Power Co (VEPCO)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
16-248
Download: ML16202A066 (8)

Text

VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 July 12, 2016 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 2 STEAM GENERATOR TUBE INSPECTION REPORT Serial No.16-248 NAPS/JHL Docket No.

50-339 License No.

NPF-7 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 Spring 2016 outage.

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

Donald R. Taylor at (540) 894-2100.

Very truly yours, Site Vice President Attachment Commitments made in this letter: None

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 Serial No.16-248 Docket No. 50-339 180-Day SG Report

ATTACHMENT NORTH ANNA UNIT 2 180-DAY NRC REPORT REGARDING STEAM GENERATOR TUBE INSPECTION PER TECHNICAL SPECIFICATION 5.6.7 VIRGINIA ELECTRIC AND POWER COMPANY (D9MINION)

Serial No.16-248 Docket No. 50-339 180-Day SG Report

Serial No.16-248 Docket No. 50-339 180-Day SG Report

. SPRING 2016 - NORTH ANNA UNIT 2 STEAM GENERATOR INSPECTIONS During the North Anna Unit 2 Spring 2016 outage, steam generator (SG) inspections were completed in accordance with Technical Specification (TS) 5.5.8.d for steam generators "A" and "C". Transmittal of this report satisfies the reporting requirement specified in TS 5.6.7.

The Unit 2 steam generators have accrued 18.4 Effective Full Power Years (EFPY) of operation as of the end of Cycle 24 (March, 2016).

Initial entry into Mode 4 occurred on April 8, 2016 (0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br />); therefore, this report is required to be submitted by October 5, 2016.

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 petformed in accordance with the Specification 5. 5. 8, "Steam Generator (SG) Program." The report shall include: 1

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

Video examination of both channel heads (as-found I as-left).

100% full~length inspection utilizing bobbin coil probe for all tubes except for Row 1 U-bends 28% 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 17% of cold leg top of tubesheef (+/-3") utilizing rotating coil probe with tube sample constituting 56% of all tubes within five tubes of the bundle periphery 100% Row 1 (98 tubes) U-bend region utilizing rotating coil probe Special interest inspections of dents/dings with rotating coil probe (Sample:

100% of dents/ding _::: 5 Volts; all new dents)

Special interest rotating-coil probe exams of largest voltage tubesheet overexpansions (OXP) (SG "A" 39 hot leg and 7 cold leg tests, SG "G" 80 hot leg and 19 cold leg tests)

Inspection of all bobbin coil I-codes (i.e., possible indications) with rotating coil probe. Results identified in Table 1 below.

Serial No.16-248 Docket No. 50-339 180-Day SG Report Table 1 - Bobbin Probe Indication I Special Interest Exam Summary KEY: tubes I indications I indications tested with SG"A" SG"C"

+Point I-Codes and S-Codes 2/2/1 9/9/9 New Dent**

71818 01010 Dents ~ 5 Volts**

2/2/2 1 / 1 / 1 Hot Leg Straight Dent 10/10/8 61616 U-bend Dent 29 / 31 / 8 11/13/1 Cold Leg Straight Dent 8/8/1 9 / 12 / 0 Hot Leg Straight Manufacturing Burnish 14 / 14 / 14

/ 11/11/11 Mark (MBH)

U-bend MBH 21210 41410 Cold Leg Straight MBH 10/11/0 12/14/0 Historical Hot Leg OXP 353 / 451 / 39 503/790180 Historical Cold Leg OXP 149/17017 603 / 998 / 19 No Tube Expansion 01010 1/ 1 / 1

• • Included in the dent totals The following secondary side inspections were performed in steam generators "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 a.nd anti-vibration bar (AVB) supports.

Visual inspections of J-nozzle to feedring internal interface for flow assisted corrosion in the carbon steel portions of the tee and inlet sections.

Visual inspections of upper tube support plates via ih 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. Degradation mechanisms found No indications of degradation were detected in SG "A", although 8 new dents were

• reported in 7 tubes with 5 new dents occurring at AVB #1. The new dents were scattered throughout the bundle rather than clustered near each other. *The new dents ranged from 2.0 to 2.4 volts, were examined with a rotating probe, and

showed no signs of degradation.

Serial No.16-248 Docket No. 50-339 180-Day SG Report The eddy current inspection identified four indications of degradation in three different tubes in SG "C".

Tube R2-C13 contains a tube-to-tube support plate wear indication at the second support plate on the cold leg side. The indication coincides with broach land location. This tube remains in service.

Tube R2-C93 contains a tube-to-tube support plate wear indication at the third suppo*rt plate on the cold leg side. The indication coincides with broach land location. This tube remains in service.

Tube R47-C49 contains two foreign object wear indications at the third support plate on the cold leg side.. The. indications coincide with the broach opening location rather thanthe broach land. This tube was plugged and stabilized.

c. Nondestructive examination techniques utilized for each degradation mechanism The 2016 tube inspections focused on the degradation mechanisms listed in Table'2 utilizing the referenced eddy current techniques.

\\

Table 2 - Inspection Method for Applicable Degradation Modes

• * -: *~ ' :. *.*... "..,..

.::,~.. Degradation** *.... -

. * ** : clissificati6n'*:i* ' Mechanism r.,,,,* !

Potential Potential Existing Potential Potential Potential

• potential Location.*._~ *,,_ L * * :. **.Probe Type*. * *.

Tube Wear Tube-Wear Tube Wear Tube Wear Tube Wear (foreign objects)

Anti-Vibration B~rs Flow Distribution Baffle (FOB)

Tube Support Plate (TSP)

Freespan & AVB tangents (Row 8, 14, 26)

Freespan, Top-of-Tubesheet (TTS),

FOB, and TSP IGA/ODSCC Hot Leg TTS sludge pile critical area OD Pitting TTS sludge pile critical area Bobbin - Detection Bobbin and +Point' -

Sizing Bobbin - Detection Bobbin and +Point' -

Sizing Bobbin - Detection Bobbin and +Point' -

Sizing Bobbin - Detection Bobbin or +Point'-

Sizing Bobbin and +Point' -

Detection

-+:Point' - Sizing Bobbin and +Point 11v 1

Detection

+Point' - Sizina Bobbin - Detection

+Point' - Sizing

Relevant/Informational PWSCC Inspection Relevant/Informational IGA/ODSCC Inspection PWSCC Relevant/Informational IGA/ODSCC Inspection.

Relevant/Informational IGA/ODSCC Inspection Hot leg TTS sludge pile critical area and within-tubesheet anomalv locations Row 1 U-bends

Freespan, FOB, TSP TTS outside the critical area Serial No.16-248 Docket No. 50-339 180-Dav SG Report

+Point' - Detection and Sizing

+Point 11v 1

- Detection and Sizing Bobbin - Detection

+Point' - Sizing

+Point' - Detection and Sizing

d. Location, orientation (if linear), and measured sizes (if available) of service induced indications Tube R2-C 13 contains a tube-to-support wear indication at the second support plate on the cold leg side. The indication coincides with broach land location and has been maximum depth sized at 12% through wall using Examination Technique Specification Sheet (ETSS) 96910.1.

The indication extends 0.45 inches in the axial direction and has an arc length of 49° in the circumferential direction. This tube remains in service.

T_ube R2~C93 contains a tube-to-support wear indication at the third support plate on the cold leg side. The indication coincides with broach land location and has been maximum depth sized at 6% through wall using ETSS 96910.1.

The indication extends 0.40 inches in the axial direction and has an arc length of 42° in the circumferen.tial direction. This tube remains in service.

Tube R47-C49 contains two foreign object wear indications at the third support plate on the cold leg side. The indications coincide with the broach opening location rather than the broach land. One indication has been maximum depth sized at 33% through wall using ETSS 27901.1. The indication extends 0.29 inches in the axial direction and has an arc length of 56° in the circumferential direction: The other indication has been maximum depth sized at 20% through*

wall using

• ETSS 27901.1.

The indication extends 0.13 inches in the axial direction and has an arc length of 35° in the circumferential direction. The foreign object that caused the wear is no longer in contact with the tube.

e. Number of tubes plugged du,ring the inspection outage for each degradation mechanism Two tubes were plugged during this inspection. Both tubes were removed from service by plugging with stabilizers installed on the cold leg side.

Tube R47-C49 contains two foreign object wear indications at the third support plate on the cold leg side. One indication has been maximum depth sized at

Serial No.16-248 Docket No.*50-339 180-Day SG Report 33% and the other indication has been maximum depth sized at 20% through wall.

Tube R46-C49 identified a foreign object in contact with the tube at the third support plate o_h the cold leg side. The foreign object appears to be wedged within a broach opening adjacent to the tube but has not caused wear on that tube. This location is inaccessible and the foreign object cannot be retrieved.

f.

The number and percentage of tubes plugged to date, and the effective plugging percentage in each steam generator Table 3 summarizes the current tube plugging status for North Anna Unit 2 steam generators.

Table 3:.... Current Tube Plugging Status

~

I

., Number" 0f *:

..,J ~-., *,..

.,:,_: ~-1*Li9g~a_.J- *.:'.,.... ~:..,...

$t~ar:n Gener~tbr.: "*. * -Tubes. ** *.**.. Percent Pluaaed,.

A 1

• 0.03%

B 0

0.00%

c 7

0.19%

Total 8

0.07%

g. The results of condition monitoring, including the results of tube pulls and in-situ testing The Condition Moriitoring and Operational Assessment (CMOA) concluded that the structural integrity, accident leakage, and operational leakage performance criteria have all been met for SG "A" and "C".

None of the inspection results from this outage would invalidate the CMOA prepared for SG "B".

Th_erefore, condition*

monitoring has been met for the just completed operating interval and thus tube pulls and in-situ pressure testing were not necessary.