ML18047A370

Cycle 1 Steam Generator Tube Inspection Report

ML18047A370
Person / Time
Site:	Watts Bar
Issue date:	02/16/2018
From:	Simmons P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML18047A370 (15)

Text

Tennessee Valley Authority, Post Office Box 2000, Spring City, Tennessee 37381 Febru ary 16, 2018 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C, 20555-0001 Watts Bar Nuclear Plant, Unlt 2 Facility Operating License No. NPF-96 NRC Docket No. 50-391

Subject:

Watts Bar Nuclear Plant (WBN) Unit 2 - Gycle 1 Steam Generator Tube lnspection Report ln accordance with the requirements of WBN Technical Specification (TS) 5.9.9, "Steam Generator Tube lnspection Report," the Enclosure provides the 180 Day Steam Generator lnspection Report for Unit 2 Cycle 1. 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 Kim Hulvey, Site Licensing Manager, at 423-365-7720.

Respectfully, Paul Simmons Site Vice President Watts Bar Nuclear Plant

Enclosure:

Watts Bar U2R1 180 Day Steam Generator Tube lnspection Report cc: See Page 2

U.S. Nuclear Regulatory Commission Page 2 February 16, 2018 Enclosures cc (Enclosures):

NRC Regional Administrator - Region II NRC Project Manager - Watts Bar Nuclear Plant, Unit 1 NRC Senior Resident Inspector - Watts Bar Nuclear Plant, Unit 1

Enclosure Watts Bar U2R1 180 Day Steam Generator Tube Inspection Report

SG-SGMP-17-35 Revision 0 WESTI NG HOUSE NON-PROPRI ETA RY C LASS 3 January 2018 Watts Bar U2Rl 180 Day Steam Generator Tube Inspection Report

WESTINGHOUSE NON-PROPRJETARY CLASS 3 Author's Name:

Jesse S. Baron SG Management Programs Verifier's Name:

William R. LaMantia SG Management Programs Manager's Name:

David P. Lytle, Manager SG Management Programs Reviewer's Name:

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

Tammy C. Sears SG-SGMP-17-35 Revision 0 Watts Bar U2R1 180 Day Steam Generator Tube Inspection Report Prepared for:

Tennessee Valley Authority Signature I Date

• ElectronicallrApproved Signature I Date

• ElectronicallrApproved Signature I Date

• E/ectronicallrApproved Signature I Date

~+1£61 TVA Watts Bar SG Program Owner Reviewer's Name:

Daniel P. Folsom TV A NOE Level III Signature I Date For Pages All For Pages All For Pages All For Pages All For Pages All

• Electronically Approved Records are Authenticated in the Electronic Document Management System SG-SGMP-17-35 Revision 0

©2018 Westinghouse Electric Company LLC All Rights Reserved January 2018 Page 2 of 12

Revision Date Oa December 2017 0

January 2018 SG-SGMP-17-35 Revision 0 Record of Revisions Description Preliminary draft for Tennessee Valley Authority review and comment.

Incorporated comments from Tennessee Valley Authority, final approved and issued.

January 2018 Page 3 of 12

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 (NDE) Techniques Utilized for Each Degradation Mechanism........................ 7

d. Location, Orientation (if Linear), and Measured Sizes (if Available) of Service Induced Indications........... 9

e. Number of Tubes Plugged During the Inspection Outage for Each Degradation Mechanism...................... I 0

f. The Number and Percentage of Tubes Plugged to Date and the Effective Plugging Percentage in each SG 11

g. The Results of Condition Monitoring, Including the Results of Tube Pulls and In-Situ Testing.................. 11 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 U2Rl Steam Generator Eddy Cu1Tent inspection Scope................................................... 7 Table 2-2: Number oflndications Detected for Each Degradation Mechanism.................................................. 7 Table 2-3 : NDE Techniques for Each Existing or Potential Degradation Mechanism........................................ 8 Table 2-4: Watts Bar U2R 1 Volumetric Indications - All SGs............................................................................ 9 Table 2-5: Watts Bar U2Rl Anti-Vibration Bar Wear Indications - All SGs.................................................... JO Table 2-6: Watts Bar U2R I Tube Support Plate Wear Indications - All SGs.................................................... 10 Table 2-7: Number of Tubes Plugged for Each Degradation Mechanism......................................................... 11 SG-SGMP-17-35 Revision 0 January 201 8 Page 4of12

1.0 Introduction The first in-service. inspections (ISI) of the Watts Bar Unit 2 (WBN2) steam generators (SGs) were performed during the fall 2017 refueling outage designated as U2R I.

The U2R I inspection was performed after 0.74 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 U2RI 180-Day Steam Generator Tube Inspection Report" as required by the WBN2 Technical Specifications.

The steam generators at WBN2 are a Westinghouse Model D3 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.

"tnfi.,Vihrmian Burr Figure 1-1: Tube Support Arrangement for Watts Bar Unit 2 Model D3 Steam Generators Notes:

H/C/AV = Hot Leg Support/Cold Leg Support/Anti-Vibration Bar (A YB) Location 1-ITS/CTS = Hot Leg Top ofTubesheet/Cold Leg Top ofTubesheet 1-ITE/CTE = Hot Leg Tube End/Cold Leg Tube End SG-SGMP-17-35 January 2018 Revision 0 Page 5 of J 2

2.0 180 Day Steam Generator Tube Inspection Report Jn accordance with WBN2 Technical Specification Section 5.7.2. J 2, "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 U2Rl SG inspections.

There arc 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 U2R I.

a.

The Scope of Inspections Performed on each SC The inspection program addressed the known degradation observed in the Watts Bar Unit 2 SGs during the pre-service inspection, potential in-service SG tube degradation mechanisms and included proactive examinations to address areas where no degradation is anticipated but monitoring is performed regardless.

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:

• J 00% bobbin inspection of all open tubes in all four SGs full length and tube Rows J 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 l 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 oftubesheet region from HTS+2/-2 inches.

• 50% Combination bobbin and A1rny probe inspection from C06 to CTS-2 inches. This inspection included all CL peripheral tubes two (2) tubes deep.

• I 00% +POJNT or Array probe inspection of DNTs and DNGs.?:. 5 Volts in the HL straight lengths, U-bcnds and the top tube support plate (TSP) on the CL side

• 20% +POINT or Array probe inspection of all DNTs and DNGs.?:. 2 Volts

• I 00% +POINT probe inspection of any ONT or DNG signal located within J.0 inch or less of a manufacturing burnish mark (MBM).

• +POINT or AJTay probe inspection of tubes surrounding known locations of foreign objects from the pre-service inspection.

• +POI NT or Array probe inspection of all tubes within a two (2) 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 HO I and all tubes within one (1) tube of this location at the same elevation. An anomaly in the support plate was identified at this location during the pre-service inspection.

• +POINT probe inspection of bobbin tube-to-tube proximity (PRO or PRX) signals > 1.25 Volt.

• I 00% 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 H L and CL inclusive of the entire divider plate to channel head weld and all visible clad surfaces.

The Watts Bar U2R I inspection included all tubes with prior indications of degradation. The table below summarizes the number and type of eddy current examinations perfonned during U2R I excluding the special interest inspection scope.

SG-SGMP-17-35 Revision 0 January Page 6 of 12

Table 2-1: Watts Bar U2R 1 Steam Generator Eddy Current Inspection Scope Eddy Current Exam Type SG I SG 2 SG3 SG 4 Full Length Bobbin 4,200 4,197 4,214 4,204 CL R l-R4 Low Row Bobbin 451 452 454 454 1-1 L RI -R4 Low Row Bobbin 451 450 454 454 U-Bend +Point R l-R4 451 450 454 454 I-IL +Point Tubesheet 4,651 4,647 4,668 4,658 CL Straight Leg X-Probe C06 to CTS-2 inch 2,662 2,649 2,711 2,705 Jn addition to the NOE 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 tubeshcct 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.

FinaJJy, visual inspection was also performed of the SG upper internal components in SG 1 and SG4 during Watts Bar U2R 1.

b. Degradation Mechanisms Found Volumetric tube wear was the only degradation mechanism detected during the U2RJ inspection.

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 U2RJ.

These indications arc not considered an active or ongoing in-service degradation mechanism but are listed for completeness. Table 2-2 below shows the number of indications reported for each degradation mechanism during the U2R 1 inspections. It is notable that no indications of stress corrosion cracking were detected during U2R I.

Table 2-2: Number of Indications Detected for Each Degradation Mechanism Degradation Mechanism SGI SG2 SG3 SG4 Total Volumetric Indications (Pre-Service) 12 3

8 15 38 Wear at Tube Support Plates 0

0 5

0 5

Wear at Anti-Vibration Bars 3

5 I

8 17

c.

Nondestructive Examination (NDE) Techniques Utilized for Each Degradation Mechanism Table 2-3 provides the NOE techniques that were used for the detection of each degradation mechanism considered as existing or potential for the U2R I inspection. NOE 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 U2R 1 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 of ETSSs.

SG-SGMP-17-35 Revision 0 January 20 I 8 Page 7 of 12

Table 2-3: NDE Techniques for Each Existing or Potential Degradation Mechanism Degradation Mechanism ETSS Detection Technique Existinir Volumetric Indications due to B: '.27091.1 Tube Fabrication and Installation B: 2709 1.2 (Pre-Service)

B: 96041.1 Wear at

-1 Pt: I 0908.4 AVBs A: 17908. I A: 17908.2 B: 96042. 1 Wear at A: 11956. 1 A: 11956.2 Tube Support Plates A: 11 956.3 A: 11956.4 Potential B: 27091.1

\\Vear due to

+Pt: 2 1998. I Foreign Objects A: 1790X.1 A: I 790X.3 Tube-to-Tube B: 13091.2 Contact Wear B: 96005.3 OD Pitting of the Tube Material

+Pt: 21998.1 A: 24998.1

-I Pt: 20511. I Ax Axial and Circumferential

+Pt: I I I 524 Cir PWSCC at the TTS 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 Axial ODSCC B: 1284 11 at Tube

-I Pt: 128424 Suooort Plates A: 20402.1 Axial and Circumferential

+Pt: 9651 1.2 PWSCC in the or Low Row U-bcnds

+Pt: 99997.1 B: 1284 11 or ODSCC at 8:24013.I B: 10013.1 Tube Dents and Dings

+Pt: 2240 I. I A: 20400.1 A: 20403.I

-1 Pl: 128424 Ax SCC at Tube Bulges and

+Pt: 128425 Ax Overexpansions

-I Pt: 21410.1 Cir A: 20400.1 Ax/Cir Axial ODSCC in the Freespan B: 1284 13 A: 20403. I ODSCC at Dents and Dings

+Pt: 2240 1.1 Coincident with an MBM diififi~stk

/.'

,,,,/.rn*

Tu Gh: 20406.1 Anomalous Gh: 20507. 1 Indications Gh: 20508. 1 Gh: 20509. 1 t-l't: 1 l'OINT !'robe A: Array Probe Acronym Definitions for Table 2-3 Gh: Ghent !'robe A \\/13: A nti ~ Vibration Bar Ax: Axial n: Bobbin Probe Cir: Circumkrcntial ETSS: Eddy current Technique Speci fication Sheet SG-SGMP-17-35 Revision 0 tv!BM: Manufacturing Burnish Mark OD: Outer Diameter ODSC'C: Outer Diameter Stress Corrosion Cra..:king PV*/SCC: Primary Water Stress Corrosion Crm:king SCC: Stress Cono~ i on Cracking TTS: Top of the Tubcshcct January 2018 Page 8 of 12

d. Location, Orientation (if Linear), and Measured Sizes (if Available) of Service Induced Indications Table 2-4 through Table 2-6 provide a listing of all pre-service and service-induced indications reported during the U2R l inspection including the estimated depths from the associated NDE technique and an indication of whether the tube has been plugged.

Table 2-4: Watts Bar U2R I Pre-Service Volumetric Indications - All SGs SG I

I I

I I

I I

I I

I I

I 1

I I

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-SGMP-17-35 Revision 0 Row 3

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

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

3 8

9 20 2 1 2 1 2 1 23 27 28 29 30 30 38 Col Location 99 C l4 38 C l2 55 C l 3 18 AV !

98 C l4 83 C14 73 C l3 80 C l4 65 CO i 77 C l4 87 C14 48 HOS 72 AV4 72 C l4 73 C l4 103 HO!

110 HOl 16 H03 28 C IO 31 COl 37 C l 3 41 COi 43 COi 46 HOI 42 HO!

42 HO!

58 H06 42 HO !

87 HO!

106 C ll 84 H04 44 HO?

46 HO?

3 1 H06 31 H06 3 1 H06 77 C09 46 H04 95 H04 100 C l3 14 C IO 35 C lO 84 H04 Inch I Indication 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 1.52 VOL 0.2 VOL 25.26 VOL 29.55 VOL

-2.74 VOL 0.5 8 VOL 0.62 VOL 0.44 SVI 33.1 9 VOL 13.37 VOL 12.32 VOL 2.74 VOL 3.88 VOL 1.46 VOL 4.89 VOL 1.75 VOL 1.1 2 VOL 40.09 VOL 1.97 VOL 2.96 VOL 12.0 1 VOL 2 1.84 VOL 30.94 VOL 22.43 VOL 9.99 VOL 2.03 VOL 17.06 VOL 7.3 1 VOL 22.89 VOL 25.6 VOL

36. 1 VOL 9.02 VOL 8.8 VOL 3.39 VOL

'YoTW 17 23 II 14 18 46 5

24 8

6 41 18 39 17 30 14 46 11 48 57 14 20 15 32 2 1 II 2 1 38 2 1 10 20 10 10 18 14 7

13 20 16 30 20 23 15 Plugged?

No No No No No Yes - Pre-Service No No No No Yes - Pre-Service No Yes - Pre-Service No No No Yes-U2RI No Yes - Pre-Service Yes - Pre-Service No No No No No No No No No No No No No No No No No No No No No No No January 20 18 Page 9 of 12

Table 2-5: Watts Bar U2R l Anti-Vibration Bar Wear Indications - All SGs SG Row Col Location Inch!

Indication 01.,TW Plugged?

l 40 79 AV2 0.16 PCT 10 No I

36 91 AV3 0.18 PCT 14 No I

24 108 AV4 0.18 PCT 15 No 2

24 8

AV2 0

PCT 15 No 2

35 85 AV3 0

PCT 14 No 2

22 8

AV3 0.19 PCT 11 No 2

30 23 AV4 0.12 PCT 11 No 2

)"

6 AV4 0.16 PCT 13 No 3

30 105 AV3

-0.09 PCT 10 No 4

42 65 AV3 0.16 PCT 11 No 4

44 40 AV3 0

PCT 8

No 4

42 40 AV3 0.21 PCT 14 No 4

42 36 AV3

-0.11 PCT 15 No 4

44 28 AV3 0.12 PCT 10 No 4

41 24 AV3 0.17 PCT 8

No 4

38 2 1 AV3 0.12 PCT 14 No 4

33 14 AV3 0.04 PCT 9

No Table 2-6: Watts Bar U2R 1 Tube Support Plate Wear Indications - All SGs SG Row Col Location Inch!

Indication

%TW Plugged?

3 48 66 C06

-0.26 PCT 5

No 3

49 61 C06

-0.21 PCT 7

No 3

49 60 C06

-0.14 PCT 10 No 3

48 60 C06

-0.28 PCT 11 No 3

47 60 C06

-0.24 PCT 14 No

e.

Number of Tubes Plugged During the Inspection Outage for Each Degradation Mechanism There were eight (8) tubes plugged during the Watts Bar U2R I SG in-service inspection. Only one (l) tube was required to be plugged in accordance with the plant Technical Specification requirements due to having a measured depth of 40% through-wall (TW) or greater. This was a 46% TW volumetric indication in SG2 at tube location Row 5 Column 110 as listed in Table 2-4.

The remainders of tubes were plugged for preventative measures including two (2) restricted tubes, one (I) for an indication of penneability variation and four ( 4) due to a foreign object which was unable to be retrieved. Table 2-7 below provides the numbers and percentages of tubes plugged following U2R 1 and the subsequent sections elaborate on the plugging basis.

Regarding the restricted tube locations in SG2 which were plugged, a complete test of the full tube length was not able to be obtained on the first data collection attempt. However, a full test was later completed using alternate means which included data collection from the opposite leg and/or use of downsized eddy cutTent probes. These tubes were plugged in order to eliminate the possibility of being unable to collect data along the full tube length and evaluate condition monitoring at future inspections.

One tube in SG3 had a permeability vanat1on indication in the tube material fully contained within the U-bend region. The use of alternative eddy current probes, such as a Ghent probe, to clear the permeability indication was not an option since the solid body Ghent probe is not capable of traversing the U-bend region. Condition monitoring was subsequently demonstrated through the use of a combination of simulated eddy cu1Tent flaw signal injection and engineering SG-SGMP-17-35 Revision 0 January 2018 Page I 0of12

assessment of potential degradation mechanisms. This tube was plugged for its potential to mask degradation at future inspections.

Four tubes were plugged due to a foreign object located at the hot leg top of tubesheet which was unable to be retrieved. The object was identified as a piece of weld slag which was rigidly contained in between a group of four tubes. Multiple retrieval attempts from all accessible angles and orientations were made to remove the object from the SG and none were successful. Three of the tubes surrounding the foreign object had possible loose part indications (PLPs) from the eddy current test program, although none of the four surrounding tubes had indications of wear. All four tubes were stabilized with a cable stabilizer traversing the tubesheet region and plugged.

Table 2-7: Number of Tubes Plugged for each Degradation Mechanism SCI SG2 SG3 SG4 Total Plugged Tubes prior to U2R 1 23 27 6

16 72 Plugging Reason Tubes Plu1mcd during U2R1 Volumetric Indication from Pre-Service 0

I 0

0 I

Restricted Tube 0

2 0

0 2

Permeability Variation 0

0 I

0 I

Foreign Object Unable to be Retrieved 0

4 0

0 4

Total Plugged Following U2RI 23 34 7

16 80 Percentage Plugged Following U2R I 0.49%

0.73%

0.1 5%

0.34%

0.43%

f.

The Number and Percentage of Tubes Plugged to Date and the Effective Plugging Percentage in each SG Table 2-7 in the previous section provides the number and percentage of tubes plugged to date.

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 perfonned as required by the Watts Bar Unit 2 steam generator program. Volumetric tube wear was the only in-service degradation mechanism detected during the Watts Bar U2R 1 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 U2R 1.

The deepest indication of A VB wear had an estimated depth of 15% TW which is significantly less than a conservatively determined C M limit of66%TW. The deepest indication of TSP wear had an estimated depth of 14%TW which is significantly less than a conservatively determined CM limit of 64%TW. The largest volumetric indication from the pre-service measured 46%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 burst pressure relationship. Since the deepest fiaws have an estimated depth less than the associated CM limits, the structural integrity performance criterion was met for the operating interval preceding U2R1.

The limiting pressure differential associated with accident induced leakage integrity is much lower than the three times normal operating pressure differential associated with the CM limits SG-SGMP-17-35 Revision 0 January 2018 Page 11 of 12

for structural integrity.

Therefore, CM for accident-induced leakage integrity was also demonstrated since volumetric wear indications will leak and burst at essentially the same pressure.

Operational leakage integrity was demonstrated by the absence of any detectable primary-to-secondary leakage during the operating interval prior to U2R l. Since tube integrity was demonstrated analytically, in-situ pressure testing was not required nor performed during the U2Rl outage. No tube pulls were planned or perfo1med during U2Rl.

Primary and Secondary Side Visual Jnspection Results Visual inspections were perfonned on both the primary and secondary sides during U2R 1 in accordance with Westinghouse nuclear safety advisory letter NSAL-12-1.

Primary side inspections included visual inspections of all previously installed tube plugs as well as the channel head bowl cladding and the divider plate. The installed tube plug inspections showed no conditions indicative of degradation.

However, the inspections of the channel head bowl cladding and the divider plate 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 man way opening. A site condition report (CR) was initiated to document the condition and an associated engineering evaluation was perfo1med. The conclusion of the engineering evaluation was that acceptable margin exists for maintenance of structural integrity of the SG channel head base metal for at least six cycles of operation.

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. The secondary side FOSAR inspections perfo1med 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 25 foreign objects were removed from the top of the tubesheet region.

Any foreign objects not able to be retrieved were characterized and an analysis performed to demonstrate acceptability of continued operation without exceeding the tube integrity performance criteria. A limited top of tubesheet in-bundle visual inspection was also performed for the purpose of assessing and trending the level of hardened deposit buildup in the kidney region. Finally, there were no structurally significant anomalies observed during inspection of the upper internals of SG 1 and SG4. Only a limited amount of foreign material was observed and retrieved during the upper internals inspections.

Therefore, no potential for the upper internal components to have an effect on SG tube integrity.

SG-SGMP-17-35 Revision 0 January 2018 Page 12of12