ML14035A067

North Anna Power Station, Unit 1, Steam Generator Tube Inspection Report

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

Text

4VIRGINIA ELECTRIC AND POWER COMPANYRICHMOND, VIRGINIA 23261January 14, 2014U.S. Nuclear Regulatory Commission Attention:

Document Control DeskWashington, D.C. 20555Serial No.NAPS/JHLDocket No.License No.14-01550-338NPF-4VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)

NORTH ANNA POWER STATION UNIT 1STEAM GENERATOR TUBE INSPECTION REPORTPursuant 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. Theattachment to this letter provides the steam generator tube inspection report for theNorth 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,1'#zJd 2Iz%'Gerald T. BischofSite Vice President Attachment Commitments made in this letter: None,(bJ 4.Serial No. 14-015Docket No. 50-338180-Day SG ReportPage 2 of 2cc: U.S. Nuclear Regulatory Commission Region IIMarquis One Tower245 Peachtree Center Avenue, NESuite 1200Atlanta, Georgia 30303-1257 NRC Senior Resident Inspector North Anna Power StationDr. V. Sreenivas NRC Project ManagerU. S. Nuclear Regulatory Commission One White Flint NorthMail Stop 08 G9A11555 Rockville PikeRockville, Maryland 20852 44 ,Serial No. 14-015Docket No. 50-338180-Day SG ReportATTACHMENT NORTH ANNA UNIT 1180-DAY NRC REPORT REGARDING STEAM GENERATOR TUBE INSPECTION PER TECHNICAL SPECIFICATION 5.6.7VIRGINIA ELECTRIC AND POWER COMPANY(DOMINION) 4.Serial No. 14-015Docket No. 50-338180-Day SG ReportPage 1 of 5FALL 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, steamgenerator (SG) inspections in accordance with TS 5.5.8.d were completed for all three steamgenerators

("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 SampleSelection."

This was also the second inspection of the second inspection period for each steamgenerator.

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 isrequired to be submitted by April 6, 2014. The Unit 1 SGs had operated for 222.4 Effective FullPower Months (EFPM) at the time of this inspection.

Italicized wording represents TS verbiage.

The required information is provided under eachreporting 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 SGThe following primary side inspections were performed in all three of the North Anna Unit 1steam 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 theregions of each bowl as required by NSAL-12-1.

• 100% full-length inspection utilizing bobbin coil probe for all tubes except for Row 1U-bends.* 28% (993 Tubes) hot leg top of tubesheet

(+/- 3") utilizing rotating coil probe divided asfollows:

570 tubes (- 50% of 5 tube periphery) plus 214 tubes (50% of sludge pileregion) 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 5tube 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 rotatingcoil 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. Resultsidentified in Table 1 below.* Special interest inspections of all: bulge (BLG), possible loose part (PLP), and TSPwear 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. 14-015Docket No. 50-338180-Day SG ReportPage 2 of 5Table 1 -+Point Probe Examination SummaryKEY: tubes I indications

/ indications tested SG"A" SG"B" SG'C"with +PointWear 5/6/6 4/6/6 1/4/4PLP 4/4/4 0/0/0 0/0/0New Dent a 2 Volts 0/0/0 0/0/0 2/2/2Dents > 2 Volts and <5 Volts* 252/304/6 69/77/0 125/145/3 Dents 5 Volts 17/18/18 6/7/7 9/10/10BLG 2/3/3 4/4/4 2/2/2Hot Leg MBH 53/62/23 53/60/21 51/56/20Hot 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 1steam generators:

• Steam drum visual inspections covering all accessible subcomponents such as theprimary and secondary moisture separators, drain piping, feedring piping, and otherinterior 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., 7th TSP in theperiphery area and in-bundle at selected tube columns.

The 4th, 5th, and 6th TSPs werealso video inspected in the center bundle area as accessed from the 7th 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 threeSGs during the NIR23 outage for the purpose of monitoring flow assisted corrosion (FAC) related degradation.

b. Degradation mechanisms foundPrior to this outage, TSP wear was the only degradation mechanism classified as "existing" inthe 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 hotleg top of tubesheet intergranular attack (IGA)/ outer diameter stress corrosion cracking(ODSCC) within the sludge pile region).

It is primarily these damage mechanisms that weretargeted 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 sidereducer extension between J-Nozzles

1. 1 and #2. The thickness of this localized regionmeasured 0.350 inch in 2011 and 0.306 inch in 2013, resulting in a thickness reduction of0.044 inch over one-cycle of operation.

In response to this localized wall loss, additional UTexaminations were performed in SG "A" between J-nozzles

1. 1 through #4 and also in the Serial No. 14-015Docket No. 50-338180-Day SG ReportPage 3 of 5surrounding areas adjacent to each of the 35 feedring J-nozzles.

These additional UTexaminations revealed other regions of localized wall thinning, specifically a region between J-nozzles #3 and #4 and a second region between J-nozzles

1. 2 and #3. Within these regions,two localized minimum thickness values were observed and measured 0.263 inch and 0.267inch respectively.

Additionally, three other localized readings (all below 0.285 inch) were alsoobserved.

These readings (unlike the first two) aligned in the circumferential direction, for atotal 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 onthe Unit 1 "A" Steam Generator Feed Ring", where it is shown that the SG "A" feedring isacceptable 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 repairactivities.

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

Table 2 -Inspection Method for Applicable Degradation ModesClassification Degradation Location Probe TypeMechanism Bobbin -Detection Potential Tube Wear Anti-Vibration Bars Bobbin -DeTMetion Bobbin and +Pointm -SizingFlow Distribution Bobbin -Detection Potential Tube Wear Baffle Bobbin and +PointTM-SizingBobbin -Detection Existing Tube Wear Tube Support Plate Bobbin and +PointTM

-SizingStraight 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

-SizingHot Leg Top-of- Bobbin and +PointTM

-Detection Potential ODSCC Tubesheet Sludge +PointTM

-SizingPile AreaHot Leg Top-of-Proactive Tubesheet Sludge TMInspections PWSCC Pile Area and +Point -Detection and SizingWithin Tubesheet Anomaly locations Relevant/Informational ODSCC Row 1 U-bends +PointTM

-Detection and SizingInspection PWSCCRelevant/Informational Freespan and Tube Bobbin -Detection Inspection ODSCC Supports

+PointTM-SizingRelevant/Informational Bobbin and +PointTM-Detection Inspection OD Pitting Top-of-Tubesheet

+PointTM

-Sizing Serial No. 14-015Docket No. 50-338180-Day SG ReportPage 4 of 5d. 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 arerelevant to tube integrity.

These are the only indications of tube degradation identified duringthis examination.

All of the indications were caused by shallow volumetric tube degradation atTSP land contact points and are characteristic of tube support plate vibration and wear. Of the16 reported indications, 3 are repeat indications (SG "A" R2-C25, R2-C91, and R15-C9).

The13 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 newindications are both located in SG "B" tube R13-C96.

The remaining 11 indications aretraceable 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 SummaryAxial Circ. Max Upper BoundLength Length Depth Depth After 3SG Row Col Location ETSS (in) (in) (%TW) CyclesA 1 54 06H -0.57 96910.1 0.56 0.45 9 37.7A 2 25 06C -0.54 96910.1 0.67 0.43 16 44.8A 2 66 06C -0.49 96910.1 0.62 0.48 10 38.706C -0.57 96910.1 0.48 0.45 5 33.7A 2 91 04C -0.47 96910.1 0.73 0.37 9 37.7A 15 9 03H +0.39 96910.1 0.36 0.39 8 36.7B 1 98 05C +0.24 96910.1 0.80 0.34 11 39.705C -0.47 96910.1 0.52 0.42 6 34.7B 12 96 05C -0.58 96910.1 0.58 0.37 9 37.7B 13 96 05C -0.61 96910.1 0.41 0.37 4 32.605C +0.29 96910.1 0.28 0.32 4 32.6B 14 96 05C -0.54 96910.1 0.55 0.45 11 39.7C 3 79 04C +0.32 96910.1 0.82 0.36 8 36.705C -0.49 96910.1 0.87 0.36 7 35.705C -0.26 96910.1 1.10 0.36 4 32.605C +0.28 96910.1 1.07 0.39 11 39.7e. Number ofmechanism tubes plugged during the inspection outage for each active degradation No tubes were plugged during the subject inspection.

Serial No. 14-015Docket No. 50-338180-Day SG ReportPage 5 of 5f. 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 pluggedtubes are in SG "C" and represent an effective plugging percentage in SG "C" of 0.06%. Theeffective plugging percentage in SGs "A" and "B" is 0%. The overall effective pluggingpercentage for all three SGs is 0.02 %.g. The results of condition monitoring, including the results of tube pulls and in-situ testingThe Condition Monitoring Evaluation was completed and SGs "A", "B", and "C" did not exceedany 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 notnecessary.