WBL-19-041, Cycle 2 Steam Generator Tube Inspection Report

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Cycle 2 Steam Generator Tube Inspection Report
ML19239A131
Person / Time
Site: Watts Bar Tennessee Valley Authority icon.png
Issue date: 08/27/2019
From: Anthony Williams
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
WBL-19-041
Download: ML19239A131 (18)
v • d • e


Text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 WBL-19-041 August 27, 2019 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391 10 CFR 50.4

Subject:

Watts Bar Nuclear Plant (WBN) Unit 2 - Cycle 2 Steam Generator Tube Inspection Report In accordance with the requirements of WBN Technical Specification (TS) 5.9.9, "Steam Generator Tube Inspection Report," the Enclosure provides the 180 Day Steam Generator Inspection Report for Unit 2 Cycle 2. This report is required to be submitted within 180 days after the initial entry into MODE 4 following the completion of an inspection performed in accordance with TS 5.7.2.12, "Steam Generator (SG) Program." The report provides the complete results of the tube inspections.

There are no regulatory commitments in this submittal. Please direct any questions concerning this matter to Tony Brown, Site Licensing Manager, at 423-365-7720.

nt ony L. Williams IV Site Vice President Watts Bar Nuclear Plant

Enclosure:

Watts Bar U2R2 180 Day Steam Generator Tube Inspection Report cc: See Page 2

U.S. Nuclear Regulatory Commission WBL-19-041 Page2 August 27, 2019 Enclosures cc (Enclosures):

NRC Regional Administrator, Region II NRR Project Manager NRC Senior Resident Inspector

Enclosure Watts Bar U2R2 180 Day Steam Generator Tube Inspection Report

S(;..Cl>l\\lP-19-11 Revision 1 T25 190819 200 WBsTINGHOUSBNON-PllOPRIETARY Cl.ASS 3 Aagast2019

  • ** * -* APP'ROV.ED

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....... *l-end.........

Letter No. W-8321 0et*:

August 19. 2019.

.,.....WIUIY,..**n -

W8EP. (N)

BY: Beth A. Jenkins r Watts Bar U2R2 180 Day Steam Generator Tube Inspection Report PROJECT Watts Bar DISCIPLINE N

CON1RACT 11054 UNIT 2 ---

DESC. SG Tube 180 Day ln$.pection R.cm<>rt -U2R2 DWG/DOCNO.

SG-CDMP-19-11 SHEET OF REV.

  • 01 DATE 08/19/19 ECN/DCN F-11-,E___....._N_/_A __

EDMS, WT CA-K

-This record was final approved on 8114/20192:10:44 PM. (This s1atamentwaa added by the PRIME aysblm upon HBvalldatlon)

WESTINGHOUSE NON-PROPRIETARY CLASS 3 Author's Name:

SG-CDMP-19-11 Revision 1 Watts Bar U2R2 180 Day Steam Generator Tube Inspection Report Prepared for:

Tennessee Valley Authorify Signature / Date Bradley T. Carpenter

  • Elt;t;troaiqd/Y.Approved Component Design & Management Programs Verifier's Name:

Signature / Date Lucas Hickey

  • El<<trolliullv Approved Component Design & Management Programs Manager's Name:

Signature I Date Michael B. Bradley, Manager

  • Eleetroaically Approved Component Design & Management Programs Reviewer's Name:

Signature/ Date Jeremy W. Mayo TV A SG Program Manager Reviewer's Name:

Si~ I Date TammyC. Sells

- L ~

°t'h>M TV A Watts Bar SG Program Owner Reviewer's Name:

Signature / Date For Pages All For Pages All For Pages All For Pages All For Pages All For Pages Daniel P. Folsom TV A NDE Level III l)~\\~-

~

)/.:2( /7 All I

  • EledroaiCIIIJT Ap~ R<<:0rd111n AatiHJllticllllld ill dltl Eleclrollic Doc,,__t ~t 9p,-,

C2019 Westlagboase Electrlc Company LLC SG-CDMP-19-11 Revision 1 All Rights Reserved August2019 Pagel of1S

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

Revision Date Oa 6/3/2019 0

7/1/2019 1

See EDMS SG-CDMP-19-11 Revision 1 Record of Revisions Description Draft provided for Tennessee Valley Authority review and comment.

Incorporated review comments from the Tennessee Valley Authority. Final approved original issuance of document Revised section g of the report to correctly identify the largest pre-service volumetric indication on a tube remaining in service consistent with the listing of these indications in Table 2-4 of section d. Changes are identified with a bar in the left-hand marJ?;in.

August2019 Page 3 oflS

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

Table of Contents 1.0 Introduction...................................................................................................................................................... 5 2.0 180 Day Steam Generator Tube Inspection Report......................................................................................... 6

a. The Scope of Inspections Performed on each SG............................................................................................ 6
b. Degradation Mechanisms Found...................................................................................................................... 7
c. Nondestructive Examination (NOE) Techniques Utilized for Each Degradation Mechanism........................ 8
d. Location, Orientation (if Linear), and Measured Sizes (if Available) of Service Induced Indications......... 10
e. Number of Tubes Plugged During the Inspection Outage for Each Degradation Mechanism...................... 13
f. The Number and Percentage of Tubes Plugged to Date and the Effective Plugging Percentage in each SG 13
g. The Results of Condition Monitoring, Including the Results of Tube Pulls and In-Situ Testing.................. 14 List of Tables and Figures Figure 1-1: Tube Support Arrangement for Watts Bar Unit 2 Model D3 Steam Generators................................. 5 Table 2-1: Watts Bar U2R2 Steam Generator Eddy Current Inspection Scope...................................................... 7 Table 2-2: Number oflndications Detected for Each Degradation Mechanism during U2R2............................... 7 Table 2-3: NOE Techniques for Each Existing or Potential Degradation Mechanism........................................... 8 Table 2-4: Watts Bar U2R2 Pre-Service Volumetric Indications-All SGs......................................................... 10 Table 2-5: Watts Bar U2R2 Anti-Vibration Bar Wear Indications-All SGs....................................................... 11 Table 2-6: Watts Bar U2R2 Tube Support Plate Wear Indications-All SGs....................................................... 12 Table 2-7: Watts Bar U2R2 Circumferential ODSCC at HTS Indications -All SGs........................................... 12 Table 2-8: Watts Bar U2R2 Axial ODSCC at TSP Indications -All SGs............................................................ 12 Table 2-9: Number of Tubes Plugged for each Degradation Mechanism............................................................. 13 SG-CDMP-19-11 Revision 1 August2019 Page 4 oflS
      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

1.0 Introduction The second in-service inspections (ISi) of the Watts Bar Unit 2 (WBN2) steam generators (SGs) were performed during the spring 2019 refueling outage designated as U2R2. The U2R2 inspection was performed after 1.995 effective full power years (EFPY) of plant operation. The inspections included eddy current testing of the SG tubing as well as primary side visual inspections, secondary side visual inspections and secondary side cleanings. This report documents the "Watts Bar U2R2 180-0ay Steam Generator Tube Inspection Report" as required by the WBN2 Technical Specifications. The steam generators at WBN2 are a Westinghouse Model 03 preheater-type design where the majority of the feedwater enters near the top of the tubesheet on the cold leg side and the tubing is made from mill annealed Alloy 600 (Alloy 600MA) material. Figure 1-1 below provides the arrangement and location designation of the tube support structures for the WBN2 SGs.

Ul Ul.

Figure 1-1: Tube Support Arrangement for Watts Bar Unit 2 Model 03 Steam Generators Notes: H/C/AV = Hot Leg Support/Cold Leg Support/Anti-Vibration Bar (A VB) Location HTS/CTS = Hot Leg Top of Tubesheet/Cold Leg Top of Tubesheet SG-CDMP-19-11 Revision I HTE/CTE = Hot Leg Tube End/Cold Leg Tube End August2019 Page 5 ofl5

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

2.0 180 Day Steam Generator Tube Inspection Report In accordance with WBN2 Technical Specification Section 5.7.2.12, "Steam Generator Program", and Technical Specification Section 5.9.9, "Steam Generator Tube Inspection Report", this report documents the scope and results of the Watts Bar U2R2 SG inspections.

There are seven specific reporting requirements associated with the Technical Specification. Each lettered reporting requirement listed below is followed with the associated information based on the inspections performed during U2R2.

a. The Scope of Inspections Performed on each SG The inspection program addressed the known degradation observed in the Watts Bar Unit 2 SGs during the pre-service inspection or the first in-service inspection as well as potential SG tube degradation mechanisms relevant to the design and material of the Watts Bar Unit 2 SG tubing.

The inspections were performed with qualified non-destructive examination (NDE) techniques for each existing and potential mechanism. The defined scope that was implemented in all four SGs included:

  • 100% bobbin inspection of all open tubes in all four SGs full length and tube Rows 1 through 4 to the top tube support plate from both the hot leg (HL) and cold leg (CL) sides.
  • 100% +POINT probe inspection of tube Rows 1 through 4 from the top tube support plate on the HL side to the top tube support plate on the CL side.
  • +POINT probe 'Special Interest' inspections of tube locations with non-resolved bobbin and/or Array probe signals.
  • 100% +POINT probe inspection of the hot leg top of tubesheet region from HTS+2/-2 inches.
  • 50% Combination bobbin and Array probe inspection from C06 to CTS-2 inches in a checkerboard pattern. This inspection included all CL peripheral tubes two tubes deep.
  • 100% +POINT or Array probe inspection of DNTs and DNGs 2'.: 5 Volts in the HL straight lengths, U-bends and the top tube support plate (TSP) on the CL side
  • 20% +POINT or Array probe inspection of all DNTs and DNGs 2'.: 2 Volts
  • 100% +POINT probe inspection of any DNT or DNG signal located within 1.0 inch or less of a manufacturing burnish mark (MBM).
  • +POINT or Array probe inspection of tubes surrounding known locations of foreign objects from the first in-service inspection.
  • +POINT or Array probe inspection of all tubes within a two tube pitch of the region surrounding any foreign object wear or possible loose part (PLP) locations.
  • +POINT probe inspection of SG3 tube Row 47 Column 48 at HOl and all tubes within one tube of this location at the same elevation.
  • +POINT probe inspection of bobbin tube-to-tube proximity (PRO or PRX) signals > 1.25 Volt.
  • 100% visual inspection of all installed tube plugs from the primary side on both the HL and CL side.
  • Visual inspection in all SGs of channel head primary side HL and CL inclusive of the entire divider plate to channel head weld and all visible clad surfaces.

The Watts Bar U2R2 inspection included all tubes with prior indications of degradation. The table below summarizes the number and type of eddy current examinations performed during U2R2 excluding the special interest inspection scope.

SG-CDMP-19-11 Revision 1 August 2019 Page 6 of 15

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

Table 2-1: Watts Bar U2R2 Steam Generator Eddy Current Inspection Scope Eddy Current Exam Type SGl SG2 SG3 SG4 Full Length Bobbin 4200 4190 4213 4204 CL Rl-R4 Low Row Bobbin 451 450 454 454 HL Rl-R4 Low Row Bobbin 451 450 454 454 U-Bend +PointR1-R4 451 450 454 454 HL +Point Tubesheet 4651 4640 4666 4658 CL Straight Leg X-Probe C06 to CTS-2 inch 2641 2640 2665 2654 In addition to the NDE and primary side inspections discussed, visual inspection was performed in all SGs in order to determine the deposit and foreign object removal effectiveness of the tubesheet cleaning process applied. This was followed by a foreign object search and retrieval (FOSAR) inspection performed at the top of the tubesheet in all four SGs. Finally, visual inspection was also performed of the SG upper internal components in SG2 and SG3 during Watts Bar U2R2.

b. Degradation Mechanisms Found The following degradation mechanisms were detected during the U2R2 inspection:

Volumetric Indications (Pre-Service)

Mechanical Wear at Anti-Vibration Bars (A VBs)

Mechanical Wear at Tube Support Plates (TSPs)

Circumferential Outer Diameter Stress Corrosion Cracking (ODSCC) at the Hot Leg Top of Tubesheet (HTS)

Axial ODSCC at TSPs All of the in-service volumetric wear indications detected were located at tube intersections with either TSPs or A VBs. Volumetric indications generated during tube manufacture and bundle assembly and initially detected during the pre-service inspections were also detected during U2R2.

These indications are not considered an active or ongoing in-service degradation mechanism but are listed for completeness. Circumferential ODSCC at the HTS and Axial ODSCC at TSPs are new degradation mechanisms for Watts Bar Unit 2 first observed during U2R2.

Table 2-2 below shows the number of indications reported for each degradation mechanism during the U2R2 inspections.

Table 2-2: Number oflndications Detected for Each Degradation Mechanism during U2R2 Degradation Mechanism Volumetric Indications (Pre-Service)

Wear at Tube Support Plates Wear at Anti-Vibration Bars Circumferential ODSCC at HTS Axial ODSCC at Tube Support Plates SG-CDMP-19-11 Revision l SGl SG2 13 2

0 0

5 8

0 0

1 0

SG3 SG4 8

15 18 1

1 21 2

3 5

2 Total 38 19 35 5

8 August2019 Page 7 of 15

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)
c. Nondestructive Examination (NDE) Techniques Utilized for Each Degradation Mechanism Table 2-3 provides the NDE techniques that were used for the detection of each degradation mechanism considered as existing or potential for the U2R2 inspection. NDE techniques are also listed which were available for diagnostic testing, resolution and confirmation of anomalous indications. All the examination technique specification sheets (ETSSs) used during U2R2 are from the electric power research institute (EPRI) database. In some cases a variable 'X' is used in the listing of techniques in Table 2-3 which is in reference to a series ofETSSs.

Table 2-3: NDE Techniques for Each Existing or Potential Degradation Mechanism SG-CDMP-19-11 Revision 1 Dee:radation Mechanism ETSS Detection Technioue

:.~., ;, l',f ~JtE~1tiii2~;./':.i,1;: :.;);1;\\;,1 i ~?:},;'( *: i;,'*.,~*.;>!!'{;/.'\\,,,O*';t*;*.:-z):j>j)i.f" Volumetric Indications due to B: 27091.1 Tube Fabrication and Installation B: 27091.2 B: 96041.1

+Pt: 10908.4 Wear at A: 17908.1 AVBs A: 17908.2 A: 17908.4 A: 17908.5 B: 96042.1 Wear at A: 11956.1 Tube Support Plates A: 11956.2 A: 11956.3 A: 11956.4

,f', /Potential, :,

4

.-~-,/. :*-:~:,,,-,

,. ~ -.;* 1, B: 27091.1 Wear due to

+Pt: 21998.1 Foreign Objects A: 1790X.1 A: 1790X.3 Tube-to-Tube B: 13091.2 Contact Wear B: 96005.3 OD Pitting of the Tube Material

+Pt: 21998.1 A: 24998.1

+Pt: 20511.1 Ax Axial and Circumferential

+Pt: 111524 Cir PWSCC at the TIS A: 20501.1 Ax A: 20500.1 Cir

+Pt: 128424 Ax Axial and Circumferential

+Pt: 128425 Ax ODSCC at the TTS

+Pt: 21410.1 Cir A: 20400.1 Ax/Cir AxialODSCC B: 128411 at Tube

+Pt: 128424 Sunnort Plates A: 20402.1 Axial and Circumferential

+Pt: 96511.2 PWSCCin the or Low Row U-bends

+Pt: 99997.1 ODSCC B: 128411 or B: 24013.1 B: 10013.1 ODSCC at

+Pt: 22401.1 Tube Dents and Dings and Axial

+Pt: 21410.1 PWSCC at Dents A: 20400.1 A: 20403.1 PWSCC B: 96012.1 A: 20500.1 August2019 Page 8 ofl5

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

Del!l'adation Mechanism ETSS Detection Technique

+Pt: 128424 Ax SCC at Tube Bulges and

+Pt: 128425 Ax Overexpansions

+Pt: 21410.1 Cir A: 20400.1 Ax/Cir B: 128412 Axial ODSCC in the Freespan B: 128413 A: 20403.1 ODSCC at Dents and Dings

+Pt: 22401.1 Coincident with an MBM

+Pt: 21410.1 mr-~~i:~tj~~I *...L * ~:{~:~'~,&~~~iL1\\: i:.r&~it;t~~ v~*~ ~.,.' -: ~~-:~-~r~~l

+Pt: +POINT Probe A: Array Probe A VB: Anti-Vibration Bar Ax: Axial B: Bobbin Probe Cir: Circumferential Anomalous Indications Gh: 20406.1 Gh: 20407.1 Gh: 20507.1 Gh: 20508.1 Gh: 20509.1 Acronym Definitions for Table 2-3 Oh: Ghent Probe MBM: Manufacturing Burnish Mad<

OD: Outer Diameter ODSCC: Outer Diameter Stress Corrosion Cracking PWSCC: Primmy Water Stress Cmrosion Cracking ETSS: Eddy cwrent Technique Specification Sheet sec: Stress Cmrosion Cracking TI'S: Top of the Tubesheet SG-CDMP-19-11 Revision 1 August2019 Page9 of15

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d. Location, Orientation (if Linear), and Measured Sizes (if Available) of Service Induced Indications Table 2-4 through Table 2-9 provide a listing of all pre-service and service-induced indications reported during the U2R2 inspection including the estimated depths from the associated NOE technique and an indication of whether the tube has been plugged.

Table 2-4: Watts Bar U2R2 Pre-Service Volumetric Indications -All SGs SG 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

1 1

2 2

2 2

2 3

3 3

3 3

3 3

3 4

4 4

4 4

4 4

4 4

4 4

4 4

4 4

SG-CDMP-19-11 Revision 1 Row 6

3 10 10 14 14 28 30 31 32 32 34 34 35 38 39 41 5

5 21 25 27 19 21 22 32 38 38 38 40 1

3 8

9 20 21 21 21 23 27 28 29 30 30 38 Col Location 74 ms 99 C14 38 C12 55 C13 18 AVI 98 C14 83 C14 73 C13 80 C14 65 COi 96 C14 77 C14 87 C14 48 HOS 72 AV4 72 C14 73 C14 103 HOI 110 HOl 16 H03 28 ClO 31 cot 37 C13 41 COi 43 COi 46 HOI 42 HOI 42 HOI 58 H06 42 HOl 87 HOI 106 Cll 84 H04 44 H07 46 H07 31 H06 31 H06 31 H06 77 C09 46 H04 95 H04 100 C13 14 ClO 35 CIO 84 H04 lncbl Indication

-G.19 VOL 0.08 VOL

-2.5 VOL 32.84 VOL 3.8 VOL 1.69 VOL 0.49 VOL 28.64 VOL 1.84 VOL 2.4 VOL 0.52 VOL 1.52 VOL 0.2 VOL 25.26 VOL 29.55 VOL

-2.74 VOL 0.58 VOL 0.62 VOL 0.44 SVI 33.19 VOL 13.37 VOL 12.32 VOL 2.74 VOL 3.88 VOL 1.46 VOL 4.89 VOL 1.75 VOL 1.12 VOL 40.09 VOL 1.97 VOL 2.96 VOL 12.01 VOL 21.84 VOL 30.94 VOL 22.43 VOL 9.99 VOL 2.03 VOL 17.06 VOL 7.31 VOL 22.89 VOL 25.6 VOL 36.1 VOL 9.02 VOL 8.8 VOL 3.39 VOL

%TW 30 17 23 11 14 18 46 5

24 8

27 6

41 18 39 17 30 14 46 11 48 57 14 20 15 32 21 11 21 38 21 10 20 10 10 18 14 7

13 20 16 30 20 23 15 Plugged?

Ya-U2R2 No No No No No Ya-Pre-Service No No No No No Ya -Pre-Service No Ya -Pre-Service No No No Ya-U2Rl No Ya-Pre-Service Ya -Pre-Service No No No No No No No Ya -Pre-Service No No No No No No No No No No No No No No No August2019 Page 10 ofl5

-* This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

Table 2-5: Watts Bar U2R2 Anti-Vibration Bar Wear Indications -All SGs SG 1

1 1

1 1

2 2

2 2

2 2

2 2

3 4

4 4

4 4

4 4

4 4

4 4

4 4

4 4

4 4

4 4

4 4

SG-CDMP-19-11 Revision 1 Row 24 36 40 42 43 22 23 24 25 30 32 35 35 30 28 29 29 33 34 38 41 41 41 41 41 41 42 42 42 42 42 42 44 44 49 Col Location 108 AV4 91 AV3 79 AV2 90 AV3 54 AV3 8

AV3 6

AV4 8

AV2 9

AV2 23 AV4 15 AV2 85 AV3 93 AV2 105 AV3 79 AV3 79 AV3 90 AVl 14 AV3 13 AV2 21 AV3 24 AV2 24 AV3 74 AV3 88 AV3 90 AV4 94 AV3 29 AV2 29 AV3 36 AV3 40 AV2 40 AV3 65 AV3 28 AV3 40 AV3 60 AV4 Inchl Ind 0.11 PCT 0.19 PCT 0.16 PCT

-0.10 PCT 0.14 PCT 0.19 PCT 0.20 PCT 0.16 PCT 0.23 PCT 0.16 PCT 0.16 PCT

-0.10 PCT

-0.10 PCT

-0.10 PCT 0.14 PCT 0.14 PCT 0.64 PCT O.Q7 PCT 0.21 PCT 0.16 PCT 0.02 PCT 0.00 PCT 0.14 PCT

-0.10 PCT 0.03 PCT 0.16 PCT 0.19 PCT 0.14 PCT

-0.20 PCT 0.21 PCT 0.25 PCT 0.17 PCT 0.19 PCT

-0.20 PCT

-0.30 PCT

  • foTW 15 17 10 15 12 14 16 17 16 11 12 18 13 12 10 10 10 9

11 16 10 12 11 12 10 13 18 11 20 10 16 15 12 10 10 Plugged?

No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No No August2019 Page 11 of 15

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Table 2-6: Watts Bar U2R2 Tube Support Plate Wear Indications -All SGs SG Row Col Location Inchl Ind

%TW Plugged?

3 46 56 cos

-0.26 PCT 5

No 3

46 56 C06

-0.21 PCT 7

No 3

46 61 cos 0.00 PCT 12 No 3

47 56 C06

-0.21 PCT 6

No 3

47 57 C06

-0.19 PCT 6

No 3

47 59 CO2 0.00 PCT 7

No 3

47 59 cos 0.12 PCT 12 No 3

47 60 C06

-0.19 PCT 21 No 3

47 64 C06 0.00 PCT 10 No 3

48 60 C06

-0.19 PCT 21 No 3

48 61 CO2 0.00 PCT 6

No 3

48 61 cos

-0.26 PCT 11 No 3

48 64 cos 0.00 PCT 18 No 3

48 64 C06 0.00 PCT 9

No 3

48 65 cos

-0.02 PCT 22 No 3

48 66 C06

-0.19 PCT 16 No 3

49 60 C06

-0.24 PCT 19 No 3

49 61 C06

-0.21 PCT 13 No 4

49 74 C06

-0.26 PCT 5

No Table 2-7: Watts Bar U2R2 Circumferential ODSCC at HTS Indications - All SGs Circ Plug and SG Row Col Location Inchl Ind

%TW Ext.

PDA<1>

(deg)

Stabilize 3

17 53 HTS

-0.05 SCI 99 155 25.5 Yes 3

49 37 HTS

-0.08 SCI 83 182 19.2 Yes 4

10 72 HTS

-0.07 SCI 70 86 10.4 Yes 4

21 70 HTS

-0.11 SCI 62 104 8.4 Yes 4

21 71 HTS

-0.06 MCI 59 187 12.9 Yes (1)

PDA calculated using depth profiling over the entire flaw circumferential extent.

Table 2-8: Watts Bar U2R2 Axial ODSCC at TSP Indications -All SGs SG Row Col Location Inchl Ind 0/oTW Axial Plugged?

Ext. (in.)

1 7

8 H04 0.00 SAi 37 0.14 Yes 3

9 11 H03

-0.01 SAi 62 0.23 Yes 3

14 20 H02 0.02 SAi 74 0.5 Yes 3

17 6

H02

-0.03 MAI 54 0.36 Yes 54 0.28 3

40 57 H03 O.o2 SAi 50 0.28 Yes 3

41 80 H03 o.oi SAi 50 0.28 Yes 4

10 3

H02 0.06 SAi 50 0.28 Yes 4

11 53 H04 0.12 SAi 71 0.29 Yes SG-CDMP-19-11 Revision 1 August2019 Page 12 of 15

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)
e.

Number of Tubes Plugged During the Inspection Outage for Each Degradation Mechanism There were fourteen tubes plugged during the Watts Bar U2R2 SG in-service inspection. One tube was plugged due to a volumetric indication traceable to pre-service that was located within the F*

distance. Eight tubes were plugged due to axial ODSCC at TSP intersections. Five tubes were plugged and stabilized due to circumferential ODSCC at HTS.

Both cracking degradation mechanisms are new degradation mechanisms for Watts Bar Unit 2. Table 2-9 below provides the numbers and percentages of tubes plugged following U2R2.

T bl 2 9 N b

f T b Pl a e - :

um ero u es Ulllle d fi oreac hD

d. M h.

egra ation ec amsm SGl SG2 SG3 SG4 Total Plugged Tubes prior to U2R2 23 34 7

16 80 Plufflll2 Reason Tubes Plu22ed durinz U2R2 Volumetric Indication from Pre-Service 1

0 0

0 1

Axial ODSCC at TSP 1

0 5

2 8

Circumferential ODSCC at HTS 0

0 2

3 5

Total Plugged Following U2R2 25 34 14 21 94 Percentage Plugged Following U2R2 0.53%

0.73%

0.30%

0.45%

0.50%

One of the tubes plugged in SG 1 was a volumetric indication newly reported during U2R2 but observable in eddy current data history back to the pre-service inspection. While the measured depth was less than the Technical Specification plugging limit of 40% through-wall, this particular indication was located within the F* tubesheet expansion depth where no degradation is permitted.

Therefore, the tube was plugged during U2R2.

The remaining tubes were plugged due to indications of cracking degradation which are plugged on detection according to the requirements of the WBN2 Technical Specification.

f.

The Number and Percentage of Tubes Plugged to Date and the Effective Plugging Percentage in each SG Table 2-9 in the previous section provides the number and percentage of tubes plugged to date.

SG-CDMP-19-11 Revision 1 August2019 Page 13 of 15

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)
g. The Results of Condition Monitoring, Including the Results of Tube Pulls and In-Situ Testing Condition Monitoring, Tube Pulls and In-Situ Testing A condition monitoring (CM) assessment was performed as required by the Watts Bar Unit 2 steam generator program. Volumetric tube wear, Axial ODSCC and Circumferential ODSCC were the in-service degradation mechanisms detected during the Watts Bar U2R2 inspection. All of the in-service volumetric wear indications detected were located at tube intersections with either A VBs or TSPs. Volumetric indications generated during tube manufacture and assembly and initially detected during the pre-service inspections were also detected during U2R2. Axial ODSCC indications were observed at TSP intersections.

Circumferential ODSCC indications were observed at the HL side of the top of the tubesheet.

The deepest indication of A VB wear had an estimated depth of20%TW which is significantly less than a conservatively determined CM limit of 66% TW. The deepest indication of TSP wear had an estimated depth of 22% TW which is significantly less than a conservatively determined CM limit of 64%TW. The largest volumetric indication from the pre-service inspection, on a tube remaining in-service, measured 32% TW which is less than a conservatively determined CM limit of 58%TW. These CM limits include uncertainties for material properties, NDE depth sizing, and the corresponding burst pressure relationship.

Since the deepest volumetric flaws have an estimated depth less than the associated CM limits, the structural integrity performance criterion was met for the operating interval preceding U2R2.

The largest indication of axial cracking had an equivalent average depth of65.4% TW and average length of 0.313 inch. A flaw of this character has a burst pressure of 4300 psig and a ligament tearing pressure of 4143 psig including all material and NDE uncertainties at 95/50 probability and confidence levels. This calculated burst pressure exceeds the CM limit of 3APNoP of3840 psi and calculated ligament tearing pressure exceeds the limiting accident differential pressure of2560 psi.

Therefore, the CM limits for structural and leakage integrity are satisfied for indications of axial ODSCC.

The largest indication of circumferential cracking had a calculated Percent Degraded Area (PDA) of25.5. A conservative CM limit for this form of degradation is a PDA of 55. Therefore, the SG structural performance criterion has been satisfied for this flaw. The average depth of the flaw was calculated to be 59.2% TW which results in a ligament tearing pressure of 5441 psi when considering all material and NDE uncertainties at 95/50 probability and confidence levels. This is well in excess of the limiting accident differential pressure of 2560 psi, and therefore the SG leakage integrity performance criterion is also satisfied.

Operational leakage integrity was demonstrated by the absence of any detectable primary-to-secondary leakage during the operating interval prior to U2R2.

Since tube integrity was demonstrated analytically, in-situ pressure testing was not required nor performed during the U2R2 outage. No tube pulls were planned or performed during U2R2.

Primary and Secondary Side Visual Inspection Results Visual inspections were performed on both the primary and secondary sides during U2R2 in all four SGs. Primary side inspections performed in accordance with Westinghouse Nuclear Safety Advisory Letter NSAL-12-1 included the hot leg and cold leg divider plate, inclusive of the divider plate-to-channel head weld, and all visible clad surfaces of the SG channel head. The NSAL-12-1 examinations performed during U2Rl showed visually apparent evidence of minor indications of degradation of the cladding in SG 1 located on the hot leg side just above the primary manway opening. This indication was re-inspected during U2R2. The conclusion of the engineering evaluation performed after U2Rl was that acceptable margin exists for maintenance of structural SG-CDMP-19-11 Revision 1 August2019 Page 14 of 15

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)

integrity of the SG channel head base metal for at least six cycles of operation. This conclusion was considered to remain applicable following the U2R2 inspection. No new indications were reported from the visual examinations of the channel head cladding.

All previously installed tube plugs were visually inspected from the primary side in all four SGs.

The inspection results were satisfactory and showed no indication of tube plug leakage or failure.

Prior to the secondary side foreign object search and retrieval (FOSAR) inspections, sludge, scale, foreign objects, and other deposit accumulations at the top of the tubesheet were removed as part of the top of tubesheet sludge lancing process. A total of 76.5 pounds of deposit was removed as a result of sludge lancing from all four SGs in total. The secondary side FOSAR inspections performed in all four SGs included visual examination of tube bundle periphery tubes from the hot leg and cold leg annulus and center no-tube lane. A total of sixteen foreign objects were identified, nine of which were removed from the top of the tubesheet region. None of the objects known to be remaining in the SGs at the tubesheet elevation following the FOSAR are metallic. Any foreign objects remaining in the SGs were characterized and an analysis performed to demonstrate acceptability of continued operation without exceeding the tube integrity performance criteria.

Secondary side inspections of the steam drum upper internals were performed in SG2 and SG3 during U2R2 to assess for structural integrity, degradation, excessive deposits, flow-assisted corrosion, blockage and overall sound condition. There were no anomalies observed during the steam drum upper internals inspections and therefore no potential effects on SG tube integrity.

SG-CDMP-19-11 Revision 1 August2019 Page 15 of15

      • This record was final approved on 8/14/2019 2:10:44 PM. (This statement was added by the PRIME system upon its validation)
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