Text

Updated Steam Generator Tube Inspection Report
	ML23305A041
Person / Time
Site:	Braidwood
Issue date:	11/01/2023
From:	; Constellation Energy Generation
To:	; Office of Nuclear Reactor Regulation
Shared Package
ML23305A039	List: BW230048, Outage 23 and Unit 2 Refueling Outage 23 Steam Generator Tube Inspection Reports to Reflect TSTF-577 Reporting Requirements; ML23305A041; ML23305A042;
References
	BW230048
	Download: ML23305A041 (1)
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Enclosure 1 Braidwood Station, Unit 1 Updated Steam Generator Tube Inspection Report E 1 - 1 of 25 Braidwood Station, Unit 1 Updated Steam Generator Tube Inspection Report Introduction In Reference 1, Constellation Energy Generation (CEG) submitted a request for an amendment to Renewed Facility Operating License No. NPF-72 for the Braidwood Station (Braidwood), Unit 1 to adopt Technical Specifications Task Force (TSTF)-577, "Revised Frequencies for Steam Generator Tube Inspections" and Reference 2, Supplement to Application to Revise Technical Specifications to Adopt TSTF-577, "Revised Frequencies for Steam Generator Tube Inspections". Reference 1 and 2 were approved by the Nuclear Regulatory Commission (NRC) in Reference 3. As noted in Reference 2, "CEG will submit SG Tube Inspection Reports meeting the revised TS 5.6.9 requirements within 60 days after implementation of the license amendment at Braidwood." Based on NRC approval (Reference 3) TSTF-577 was implemented at Braidwood Station on September 13, 2023.

Braidwood Unit 1 Technical Specification (TS) 5.6.9, "Steam Generator Tube Inspection Report," states "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 5.5.9, 'Steam Generator (SG) Program'." This enclosure provides the revised 180-day report with the revised Braidwood Unit 1 TS 5.6.9 reporting requirements in accordance with References 3. Each Braidwood Unit 1 TS 5.6.9 reporting requirement is listed below along with the associated information based on the inspection performed during the Braidwood Unit 1 Cycle 23 October 2022 refueling outage (A 1 R23), which was the last inspection of the Braidwood Unit 1 replacement steam generators (Reference 4). This report follows the template provided in Appendix G to the Electric Power Research Institute (EPRI) Steam Generator Management Program: Steam Generator Integrity Assessment Guidelines, Revision 5 (Reference 5), which provides additional information beyond the Braidwood Unit 1 TS 5.6.9 reporting requirements.

1. Design and operating parameters The original SGs at Braidwood Unit 1 were replaced in 1998 with four Babcock & Wilcox replacement Steam Generators (SGs), which have thermally treated Alloy 690 tubing. The SGs had operated for four fuel cycles since the previous inspection at A 1 R 19. Table 1 provides the Braidwood Unit 1 SG design and operating parameter information.

E1 - 2 of 25 Table 1: Braidwood Unit 1 - Steam Generator Design and Operating Parameters SG Model / Tube Material /

Number of SGs per Unit

' Number of tubes per SG I Nominal Tube Diameter/ Tube Thickness Support Plate Style / Material Last Inspection Date Effective full power months (EFPM) Since Last Inspection i Total Cumulative SG EFPY Mode 4 Initial Entry Observed Primary-to-Secondary Leak Rate Nominal Thot at Full Power Operation

Loose Parts Strainer I

Degradation Mechanism Sub-Population i SG program guideline deviations I since last Inspection i SG Schematic 1

i ___________ -------- -

Babcock & Wilcox (Canada) Replacements / Alloy I

690TT I 4 6,633 / 0.6875 in. / 0.040 in Lattice Tube Support Grids and Fan Bars/

stainless steel i October 2022 i

i 68.801 EFPM [5.734 effective full power years i

I I (EFPY)] (from A1R19 to A1R23)

I I 22.71 EFPY (as of A1R23)

I I

i I 10/18/2022 from A 1 R23 No observed leakage I

617°F Each main feedwater pump has small diameter holes in an inlet strainer to prevent the introduction of I

i foreign material into the piping leading to the SGs.

I Tubes located on the periphery of the tube bundle are !

in the highest cross-flow region and were considered in i the A 1 R23 Degradation Assessment to be more susceptible to foreign object wear.

None See Figure 1 I

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TEH Tube Support Arrangement for Braidwood Unit 1 B&W Replacement SGs Notes:

TEC - Tube End Cold Leg TEH - Tube End Hot Leg TSC - Top-of-Tubesheet Cold Leg TSH - Top-of-Tubesheet Hot Leg 01 C - 09C - Lattice Grid Tube Supports on Cold Leg side 01 H - 09H - Lattice Grid Tube Supports on Hot Leg side F01 - F1 0 - U-Bend Fan Bar Tube Supports E1 - 4 of 25

2. The scope of the inspections performed on each SG (TS 5.6.9.a) and if applicable, a discussion of the reason for scope expansion The following inspections were performed during A 1 R23 to ensure that 100% of the tubes were inspected during the period as required by TS 5.5.9.d.2 Primary Side Eddy Current Scope:

100% full-length bobbin coil eddy current examination of all in-service tubes in all four SGs.

All Hot leg Dent & Dings >2.0 volts, Plus-Point probe in all four SGs.

57% peripheral array (X-Probe) examination on the Hot Leg for potential foreign objects and associated wear (peripheral locations are where crossflow velocities are the highest) 43% of peripheral array (X-Probe) examination Cold Leg for potential foreign objects and associated wear.

There was no scope expansion required or performed during the A 1 R23 eddy current inspections.

In addition to the eddy current inspections, visual inspections were also performed on both the primary and secondary sides. Primary side visual inspections included the channel head bowl cladding and the divider plate. Secondary side visual inspections were performed at the top of the tubesheet for the detection of foreign objects, assessment of hard deposit buildup in the tube bundle interior kidney region, and for determining the effectiveness of the tubesheet cleaning performed in the four SGs.

3. The nondestructive examination techniques utilized for tubes with increased degradation susceptibility (TS 5.6.9.b)

Tubes located on the periphery of the tube bundle are in the highest cross-flow region and were considered in the Degradation Assessment (DA) to be more susceptible to foreign object wear, especially near the tubesheet where most foreign objects are located. As a compensatory measure, tubes in this region were tested with an array (X-probe) which has increased sensitivity for detection of foreign objects and foreign object wear close to the tubesheet This scope encompassed 57% of the hot leg tubes and 43% of the cold leg tubes from the top-of-tubesheet to the 1st tube support (01 C/01 H).

4. For each degradation mechanism found: The nondestructive examination technique utilized (TS 5.6.9.c.1)

Steam Generator eddy current examination techniques used (see Table 2 below) were qualified in accordance with Appendix H or Appendix I of the EPRI PWR SG Examination Guidelines Revision 8. Each examination technique was evaluated to be applicable to the tubing and the degradation mechanisms found in the Braidwood Station Unit 1 SGs during A 1 R23.

E1 - 5 of 25 Table 2: Non-Destructive Examination (NOE) Techniques for Each Existing Degradation Mechanism Found During A 1 R23 Location Fan Bar (U-bend)

Lattice Grid (Horz. Support)

Foreign Object at top of tubesheet or lattice grid (D) = Detection (S) = Sizing Degradation Orientation Mechanism Wear Vol Wear Vol Wear Vol Probe EPRIETSS Bobbin 1-96041.1 (D) 96004.3 (D&S)

Bobbin 96004.3 (D&S)

Array 1790X.1 (D)

+Point 21998.1 (S)

+Point 27902.1 (S)

EPRI ETSS Rev 6

13 13 0

4 2

5. For each degradation mechanism found: The location, orientation (if linear),

measured size (if available), and voltage response for each indication. For tube wear at support structures less than 20 percent through-wall, only the total number of indications needs to be reported (TS 5.6.9.c.2)

Volumetric wear at support structures was the primary degradation mechanism detected during the A 1 R23 inspection. The wear indications detected were located at either fan bar U-bend or horizontal lattice grid tube support structures. Table 3 provides the number of indications reported during the A 1 R23 inspection Table 3: Number of Indications Detected for Each Degradation Mechanism in A1R23 Degradation 1ASG 1BSG 1C SG 1DSG Total Mechanism Indications Indications Indications Indications Fan Bar (U-bend 8

18 39 21 86 support) wear Lattice grid 3

4 3

1 11 Support Wear Foreign Object 5

1 10 0

16 Wear A detailed listing of all the Fan Bar wear indications reported during the A 1 R23 inspection including the measured voltages and depths from the bobbin coil is provided in Attachment A (same data as submitted under Reference 4).

E1 - 6 of 25 Table 4 provides a listing of all the lattice grid wear indications reported during the A 1 R23 inspection including the measured depths from the bobbin coil.

Table 4: A1R23 Lattice Grid Wear Indications A1R23 Voltage SG Row Col Location Depth (3/4TW)

(Bobbin) 1A 39 70 01H-1.16 11 0.64 1A 75 108 07H -1.22 5

0.21 1A 118 71 01C +0.99 6

0.31 1B 47 24 08H -1.43 6

0.27 1B 87 24 01C -0.82 9

0.43 1B 90 107 07H +0.48 9

0.49 1B 119 70 02C +0.76 11 0.72 1C 9

92 05C -1.62 8

0.42 1C 47 56 05H -1.68 6

0.28 1C 73 90 05H +1.41 4

0.20 1D 41 70 08H -1.61 6

0.22 Table 5 provides a listing of all the foreign object wear indications reported during the A 1 R23 inspection including the measured voltages and depths from the plus-point probe.

Indications of tube wear at support structures are provided regardless of percent through-wall depth and the voltages provided correspond to the bobbin coil.

Table 5: A 1 R23 Foreign Object Wear Indications

+ Point

+Point Axial Circ SG Row Col Location (Voltage)

Depth Extent Extent (3/4TW)

(in)

(deg) 1A 96 107 TSH+0.12 0.15 12 0.31 49 1A 98 107 TSH +0.12 0.15 12 0.26 54 1A 97 108 TSH +0.22 0.16 12 0.26 55 1A 17 138 TSH+0.17 0.24 16 0.20 60 1A 20 139 TSH +0.04 0.10 9

0.17 66 1B 98 47 TSH +0.00 0.27 17 0.17 43 1C 18 3

TSC +1.08 0.11 13 0.22 45 1C 20 3

TSC+0.17 0.15 14 0.17 54 1C 18 5

TSC +2.22 0.51 42 0.25 66 1C 93 54 TSH +0.12 0.35 19 0.36 45 1C 6

59 TSC +0.26 0.26 23 0.28 62 1C 3

64 TSC +0.22 0.41 34 0.28 72 1C 2

65 TSC +0.12 0.37 31 0.28 74 1C 1

72 TSH +0.28 0.06 6

0.11 35 1C 5

72 TSH +0.28 0.61 25 0.22 66 1C 2

73 TSH +0.25 0.08 8

0.14 43 E1 - 7 of 25

6. For each degradation mechanism found: A description of the condition monitoring assessment and results, including the margin to the tube integrity performance criteria and comparison with the margin predicted to exist at the inspection by the previous forward-looking tube integrity assessment (TS 5.6.9.c.3). Discuss any degradation that was not bounded by the prior operational assessment in terms of projected maximum flaw dimensions, minimum burst strength, and/or accident induced leak rate. Provide details of any in situ pressure test.

A condition monitoring (CM) assessment was performed as required by the Braidwood Unit 1 SG program. The tube degradation detected during the A 1 R23 inspection was due to fan wear, lattice grid wear and foreign object wear at the tubesheet. The deepest indication for each mechanism met condition monitoring analytically as shown in Figures 2, 3 and 4a and 4b below. The margin to the structural and condition monitoring limit curve for each detected wear indication can be determined from Figures 2, 3 and 4a and 4b. The CM limit curves include uncertainties for material properties, NOE depth sizing, and the burst pressure relationship. Because the deepest flaws have a depth less than the conservatively determined CM limit for all degradation mechanisms, the structural integrity performance criterion was met for the operating interval prior to A 1 R23. A summary of the CM results from A 1 R23 as compared to the predictions from the most recent prior inspection (A 1 R 19) is provided in Table 6.

E1 - 8 of 25 Figure 2: Condition Monitoring Results for Fan Bar Wear Bobbin. ETSS H-9-6004 3 i

E1 - 9 of 25 Figure 3: Condition Monitoring Results for Lattice Grid Wear Bobbm. ETSS H,96004 3 Ax,ai Extent fine hos)

E1 - 10 of 25 Figure 4a: Condition Monitoring Results for Foreign Object Wear (ETSS 27902.1)

Army, ET5S H-27902.l s

E1-11of25 Figure 4b: Condition Monitoring Results for Foreign Object Wear (ETSS 21.998.1)

Array, ETSS H-21998.l E1 - 12 of 25 Table 6: Comparison of Prior QA Projections to As-Found Results Parameter A 1 R23 Projection A1R23 As-Found Inspection Interval 5.83 EFPY (from A 1R19) 5.734 EFPY Fan Bar Wear Maximum Depth 34.8 3/4TW 16%TW Lattice Grid Wear Maximum Depth 28.0 3/4TW 11 3/4TW Foreign Object Wear Maximum Depth

< 57.6 3/4TW 42 3/4TW Tube-to-tube Wear 31.7%TW None The most severe indication in A 1 R23 had an estimated depth of 42% TW from the plus-point probe exam. Since foreign object wear is a random event and there had only been 2 of 7 new foreign object wear indications that required to be plugged, one tube for being over the 40% Tech Spec limit and the other tube having the part remaining. There was no prediction for new foreign object wear made during the prior inspection in A 1 R 19.

Because volumetric wear indications will leak and burst at essentially the same pressure, accident-induced leakage integrity is also demonstrated. Operational leakage integrity was demonstrated by the absence of any detectable primary-to-secondary leakage during the operating interval prior to A 1 R23. Because tube integrity was demonstrated analytically, in-situ pressure testing was not required nor performed during A 1 R23. There were no tube pulls planned or performed during A 1 R23.

7. For each degradation mechanism found: The number of tubes plugged during the inspection outage (TS 5.6.9.c.4). Also, provide the tube location and reason for plugging.

Tables 7a & b provides the number of tubes plugged for each degradation mechanism detected, location, and reason for plugging during A 1 R23 As a result of the A 1 R23 SG inspections, performed in accordance with TS 5.5.9.d, the modes of tube degradation found were Fan Bar wear, Lattice Grid wear, and secondary side foreign object (FO) wear.

One tube (1 C SG R18-C5) was plugged for FO Wear for exceeding the tech spec criteria of 40% TW. The other tube (1 C SG R93-C54) was plugged for both FO Wear (19% TW) and an Eddy Current possible loose part (PLP) indication which could not be visually inspected.

In addition, 12 tubes were plugged as a preventative measure when the FO could not be removed or properly characterized from visual inspections. Inspection results justified a 5-cycle inspection interval with no adverse consequences for all four SGs.

E1 - 13 of 25 Table 7a: Number of Tubes Plugged, location and Reason for Each Degradation Mechanism in A1 R23 (TS 5.6.9.c.4)

SG Row Col Location Reason for Plu~rninq 1C 18 5

TSC +2.22 Exceeded TS criteria of > 40%

1C 93 54 TSH +0.12 Tube had FO wear and ECT PLP present 1C 1C 1C 1C 1C 1C 1C 1C 1C 1C 1C 1C 94 53 TSH Preventatively plugged 1 91 54 TSH Preventatively plugged 1 93 54 TSH Preventatively plugged 1 95 54 TSH Preventatively plugged 1 92 55 TSH Preventatively plugged 1 94 55 TSH Preventatively plugged 1 109 60 TSH Preventatively plugged 2 111 60 TSH Preventatively plugged 2 113 60 TSH Preventatively plugged 2 108 61 TSH Preventatively plugged 2 110 61 TSH Preventatively plugged 2 112 61 TSH Preventatively plugged 2 Notes:

1: All bounding tubes related to tube 93-54 were No Degradation Detected (NOD) and no PLPs with ECT. Visual inspections could not be performed on this location.

2: No wear, but FO was visually seen, but unable to confirm description Table 7b: Number of Tubes Plugged for Each Degradation Mechanism in A1R23 (TS 5.6.9.c.4)

Deqradation Mechanism 1ASG 18 SG 1CSG 1D SG Total Fan Bar Wear 0

0 0

Lattice Grid Wear 0

0 0

Foreiqn Object Wear 0

0 2

0 0

Preventative 0

0 12 0

0 Total Pluqqed during A 1 R23 0

0 14 0

14

8. The repair methods utilized, and the number of tubes repaired by each repair method (section 5.6.7.c.5).

Not Applicable

9. An analysis summary of the tube integrity conditions predicted to exist at the next scheduled inspection (the forward-looking tube integrity assessment) relative to the applicable performance criteria, including the analysis methodology, inputs, and results (TS 5.6.9.d). The effective full power months of operation permitted for the current operational assessment.

E1 - 14 of 25 Based on application of conservative U-bend support structure (fan bars) and lattice grid wear growth rates and foreign object susceptibility, the condition of the Braidwood Unit 1 SG tubes has been analyzed with respect to continued operability of the SGs without exceeding the SG tube integrity performance criteria at the next scheduled SG inspection in the Spring of 2030 (A 1 R28).

Fan Bar Wear Operational Assessment (OA)

For the Fan Bar OA, the Mixed Arithmetic/Simplified Statistical method from Section 8 of Reference 5 was used. Using this method, a worst-case end-of-cycle (EOC) depth was projected by applying NOE uncertainties and a growth allowance to the deepest flaw returned to service. This projected EOC depth is then compared to an allowable EOC depth which is calculated using a Monte Carlo analysis which incorporates uncertainties in the burst pressure relationship and material properties.

The deepest fan bar indication returned to service was 16% TW. The NOE sizing parameters for ETSS 96004.3 are a slope of 0.97, an intercept of 2.50, and a standard error of 3.10.

Using the slope and intercept, a best estimate real depth of 18.0% TW (0.97 x 16 + 2.5) is obtained for an indication with a measured depth of 16% TW.

The standard error of 3.10 from ETSS 96004.3 is the technique uncertainty. Adjusting this value upward to an upper 95th percentile gives an N DE uncertainty of 5.1 % TW (3.10 x 1.645). Adding this uncertainty to the best estimate value of 18.0% TW from the previous paragraph yields a bounding real depth of 23.1 % TW (18.0 + 5.1) returned to service.

This hypothesized real depth of 23.1 % TW must then be grown at an upper 95th growth rate for the next inspection interval. For this operational assessment, wear at support structures is being evaluated for five fuel cycles of 1.5 EFPY each The highest upper 95th percentile growth rate for any steam generator over the last two inspection was 0.93% TW per EFPY.

Since the growth rates are so low for fan bar wear at Braidwood Unit 1, a conservative growth rate of 1.5% TW per EFPY was used in the operational assessment. This value conservatively bounds the maximum growth rate from the last two operating intervals. Applying a growth of 7.3% TW (1.0 x 7.3) gives a bounding real depth at the end of the upcoming inspection interval of 34.1 % TW (23.1 + 7.3). For a flaw with an assumed bounding length of 1. 7 inches, the allowable structural depth at the end of the upcoming inspection cycle is 57.1 % TW. Since the projected depth of 30.4% TW is less than 57.1 % TW, there is reasonable assurance that structural integrity will be maintained for Fan Bar wear for the next five cycles of operation.

Lattice Grid Wear OA For lattice grid wear, the OA was performed in a manner similar to what was done for fan bar wear. Unlike fan bar wear, however, there is too little data from which to calculate a reliable upper 95th percentile growth rate. There were eleven (11) lattice grid wear indications reported during the A 1 R23 outage. The deepest indication measured 11 % TW with a bobbin probe One (1) of these indications were newly reported, not present in past history. The largest growth was 11 % TW over an operating interval of 5.733 EFPY giving a maximum growth rate of 0.52%TW per EFPY. Similar to fan bar wear, since the growth rates for lattice grid wear are so low, growth rate of 1.0% TW per EFPY will be used for this operational assessment.

E1 - 15 of 25 The lattice grid flaws are typically short and occur at one edge of a lattice grid. However, since length measurements were not made for these indications, a bounding flaw length of 3.5 inches from the longest lattice grid intersection of 3.15 inches was assumed. This length was obtained from the "high bar" lattice grids which was from the maximum lattice grid length of 1.01" sized during A 1 R23. This is very conservative based on the flaw lengths observed in previous outages Using the same Mixed Arithmetic/Simplified Statistical method Section 8 of Reference 5 and the same bobbin ETSS (96004.3), a best estimate real depth of 13.2% TW (0.97 x 11 + 2.5) is obtained for a measured depth of 11 % TW. Applying upper 95th percentile NOE uncertainties yields a bounding real depth of 18.3% TW (13.2 + 1.645 x 3.1) returned to service. Further applying a growth rate of 1.0% TW per EFPY (as discussed above) over 7.3 EFPY gives a projected real EOC depth of 25.6% TW (18.3 + 1.0 x 7.3). For a flaw with an assumed bounding length of 3.5 inches, the allowable structural depth at the end of the upcoming inspection cycle is 56.0% TW. Since the projected depth of 25.6% TW is less than 56.0% TW, there is reasonable assurance that structural integrity will be maintained for lattice grid wear for the next five cycles of operation.

Tube Wear from Existing, Remaining, and New Foreign Objects OA Largest depth indication detected during A 1 R23, was a 42% TW. All of the foreign objects that were classified as potentially causing tubes wear, Priority 1, were removed from the steam generators or tubes preventively plugged around the object(s). The remaining objects were classified as Priority 3, not potentially causing tube wear based on their composition, size and/or low-flow location. This included objects such as sludge rocks and tube scale which are considered benign based on no known history of causing tube wear. A summary of the OA results predicted at the next inspection (or longer) is provided in Table 8.

Table 8: Comparison of OA Projections at Next SG Inspection to Structural Limits Degradation Mechanism Maximum depth(%) Predicted Structural limit (wear) at Next Inspection depth(%)

Fan Bar U-bend support 30.4 57.1 Lattice Grid support 25.6 56.0 Existing FO Wear 34.0 59.0-66.3% (technique and length dependent)

Remaining FOs

< 20%TWWear 60-75% (technique and length dependent)

New FOs Limiting flaw won't challenge 60-75% (technique and structural or leakage integrity length dependent) after 5 operating cycles

10. The number and percentage of tubes plugged to date, and the effective plugging percentage in each SG (TS 5.6.9.e).

Table 9 shows the number of tubes plugged before and after the A 1 R23 outage and the percentage of tubes currently plugged (total and effective). No sleeves have been installed in Braidwood Unit 1.

E1 - 16 of 25 Table 9: Tube Plugging to Date (Number and Percentage per SG) (TS 5.6.9.e) 1ASG 18 SG 1C SG 1D SG Total Total Pluqqed prior to A 1 R23 32 40 16 1

89 Total Plugged during A 1 R23 0

0 14 0

14 Total Stabilized during A 1 R23 0

0 1

Total Pluqqed throuqh A 1 R23 32 40 30 1

103 Total Percent Plugged through 0.48%

0.60%

0.45%

0.02%

0.39%

A1R23

11. The results of any SG secondary-side inspection (TS 5.6.9.f). The number, type, and location (if available) of loose parts that could damage tubes removed or left in service in each SG.

Secondary Side Scope:

Sludge lancing in all four SGs including "post sludge lance" Foreign Object Search and Retrieval (FOSAR)

Feedring Inspection (1A SG)

Steam Drum Internal Inspections (1A & 1 B SG)

Upper Bundle Inspection ( 1 A SG)

Secondary Side Visual Inspections of Tubesheet and FOSAR Secondary side tubesheet visual inspections were performed following sludge lancing activities in all four SGs. High flow regions of the annulus, no tube lane and periphery (6-8 tubes deep) were visually inspected for foreign material. Additionally, eight columns for the full depth of the tube bundle interior ("kidney" region) were evaluated for sludge lancing effectiveness and sludge accumulation.

Secondary side foreign object search and retrieval (FOSAR) inspections at the tubesheet were performed in all four SGs. This included visual examination of tube bundle periphery tubes from the hot leg and cold leg annulus and center no tube lane. Twenty-one (21) foreign object locations all of which were assumed metallic, were identified by visual inspections and/or eddy current examinations and are summarized in Table 10 Foreign object wear is the primary degradation mechanism of concern at Braidwood-1 based on previous history. In A 1 R23, one tube was plugged for FO Wear of 42% TW, one tube was plugged for FO wear of 19% TW with an ECT PLP still present, and 12 other locations were plugged as a preventative measure when the FO could not be removed or properly characterized from visual inspections.

Visual inspections included both the annulus and no-tube lane at the top of the tubesheet in all four steam generators. These visual inspections included looking into the tube bundle at all peripheral and no-tube lane locations. The eddy current examinations included tubesheet array probe inspections of all tubes in the high-flow regions at the periphery and no-tube lane on both the hot (~3800 tubes) and cold sides (~2900 tubes) in all four steam generators. With these extensive inspections and subsequent object removal, there is reasonable confidence that no object capable of causing significant tube degradation remains in the tube bundle adjacent to in-service tubes.

E1 - 17 of 25 A total of 14 metallic or potential metallic foreign objects within the tube bundle in SGs A, B, and C were not removed during A 1 R23 and are included in the total list of all foreign objects remaining in the SGs in Table 10.

A top of tubesheet in-bundle visual inspection in a sample of tube columns was also performed in each SG for the purpose of assessing and trending the level of hardened deposit buildup in the kidney region.

Based upon the extensive secondary side inspections, object removals, and engineering assessments performed during the 1AR23 outage, there is reasonable assurance that during the next five operating cycles foreign object wear will not exceed the structural and leakage integrity performance criteria.

Table 10: Foreign Object Summary SG Affected Location Ref ID A1R23 Disposition Status Material Tubes NIA Object was removed.

1A Below TSC A001 Nearest adjacent tubes were NOD with Retrieved Gasket Manway ECT Hand hole No further actions required in A 1 R23.

Object identified with visual inspections 1A R104-C73 TSC A003 and was removed. All affected and Retrieved Gasket R105-C72 bounding tubes are NOD with ECT No further actions required in A 1 R23.

Object identified with visual inspections 1A R 104-C79 TSC A004 was removed. All affected and bounding Retrieved Gasket R105-C78 tubes are NOD with Bobbin.