WBL-24-022, Cycle 5 Steam Generator Tube Inspection Report
| ML24137A267 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 05/16/2024 |
| From: | Anthony Williams Tennessee Valley Authority |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| WBL-24-022 | |
| Download: ML24137A267 (1) | |
Text
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TENNESSEE VALLEY AUTHORITY Post Office Box 2000, Spring City, Tennessee 37381 WBL-24-022 May 16, 2024 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 5 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 the Unit 2 Cycle 5 (U2R5) outage. 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 new regulatory commitments contained in this letter. Please direct any questions concerning this matter to Jonathan Johnson, WBN Licensing Manager, at jtjohnsonO@tva.gov.
Anthony L. Williams IV Site Vice President Watts Bar Nuclear Plant
U.S. Nuclear Regulatory Commission WBL-24-022 Page 2 May 16, 2024
Enclosure:
Tennessee Valley Authority - Watts Bar Nuclear Plant - Unit 2 - Watts Bar U2R5 - 180 Day Steam Generator Tube Inspection Report cc: (w/o Enclosure):
NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant NRC Project Manager - Watts Bar Nuclear Plant
WBN-24-022 E1 of 1 ENCLOSURE Tennessee Valley Authority Watts Bar Nuclear Plant Unit 2 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 2 of 20 Introduction In accordance with WBN Unit 2 Technical Specification Section 5.7.2.12 ³Steam Generator Program' and Technical Specification Section 5.9.9 ³Steam Generator Tube Inspection Report,' this report documents the scope and results of the Watts Bar Nuclear (WBN) Unit 2 Refueling Outage 5 (U2R5) replacement steam generator (RSG) inspections. In addition, there are fourteen specific reporting requirements associated with the 180 Day Report in the EPRI Steam Generator Management Program:
Steam Generator Integrity Assessment Guideline, Revision 5, Attachment G. Each numbered reporting requirement listed below is followed with the associated information based on the inspections performed during WBN U2R5.
The WBN U2R5 inspection during the fall of 2023 was the first inspection since steam generator (SG) replacement in June of 2022. The U2R5 inspection included primary and secondary side inspections.
The primary side inspections included 100% eddy current testing on all SG tubing as well as visual inspections. The secondary side inspections included sludge lancing, foreign object search and retrieval (FOSAR), and visual inspections.
- 1.
Design and Operating Parameters.
Watts Bar Nuclear Plant (WBN) Unit 2 Replacement Steam Generators (RSGs) were installed during the Unit 2 Cycle 4 refueling outage (U2R4) (June 2022). The WBN Unit 2 RSGs are of a similar design to the original steam generators (OSG) which had a vertical shell and continuous bend U-tubes with an integral preheater. WBN Unit 2 is a Westinghouse four-loop plant with Westinghouse Model 68 Axial Extent Preheater (AXP) RSGs. Figure 1-1 and Figure 1-2 below provide the schematic design and the tube support structure locations for the WBN Unit 2 RSGs. Table 1-1 summarizes the RSG information.
Table 1-1 Steam Generator Design and Operating Parameters SG Model / Tube Material / # SGs per Unit Westinghouse Model 68AXP / Alloy 690TT/ 4
- of tubes per SG / Nominal Tube Diameter / tube thickness 5128 / 0.75 in. / 0.043 in.
Support Plate Style / Material Advance Tube Support Grid / 409 stainless Steel Last Inspection Date Preservice 2020 EFPM Since Last Inspection 15.906 EFPM (1.3255 EFPY)
Total Cumulative SG EFPM 15.906 EFPM (1.3255 EFPY)
Mode 4 Initial Entry 11/25/2023 Observed Primary-to-Secondary Leak Rate Below Detection Nominal Thot at Full Power Operation 617ºF Loose Parts Strainer The Model 68AXP has a feedwater flow distribution box with small diameter holes (0.29')
acting as strainers to prevent the introduction of significant foreign objects into the SGs Degradation Mechanism Sub-Population The U2R5 CMOA considered the perimeter tubes wear rate as different from the interior tube wear rates.
SG program guideline deviations since last Inspection None Steam Generator Schematic See Figure 1-1 and Figure 1-2 below.
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 3 of 20 Figure 1-1: Schematic Design for Watts Bar Unit 2 Model 68AXP Replacement Steam Generators
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 4 of 20 Figure 1-2: Tube Support Structure for Watts Bar Unit 2 Model 68AXP Replacement Steam Generators
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 5 of 20
- 2.
The Scope of Inspections Performed on each SG The U2R5 inspection program addressed the known eddy current signals observed in the Watts Bar Unit 2 RSGs during the pre-service inspection and potential RSG tube degradation mechanisms relevant to the design and material of the Watts Bar Unit 2 RSG tubing. The inspections were performed with qualified non-destructive examination (NDE) techniques for each potential mechanism. The defined primary side base scope that was implemented in all four SGs included:
100% bobbin coil inspection of all open tubes in all four SGs full length. This was accomplished with either a standard bobbin probe or a combination bobbin and array coil probe.
Array or RPC for all tubes identified within the high fluid velocity or transition fluid velocity zones, plus a minimum of three periphery tubes deep (Reference 1):
o HL up to the first support o
CL up to the sixth support 100% array probe or +POINT probe of DNGs 2 volts in all SGs.
100% array probe or +POINT of BLGs, GEOs, MBMs, OXPs, and ADIs in all SGs.
+POINT or array probe Special Interest inspection of new wear indications detected with the bobbin coil.
+POINT or array probe Special Interest inspections of tube locations with non-resolved bobbin probe signals from the base scope inspection to characterize the underlying condition.
+POINT or array probe Special Interest inspections of tube locations with non-resolved PLP signals from the base scope inspection program. Tubes surrounding all PLP signals were inspected to ensure tubes with possible wear have been fully discovered.
100% visual inspection of all installed tube plugs from the primary side on both the HL and CL (WBN Unit 2 had zero plugs installed prior to U2R5).
The Watts Bar U2R5 inspection included all tubes with prior indications (no %TW were in baseline inspection). The tables below summarize the number and type of eddy current examinations performed during U2R5.
Table 2-1: Watts Bar U2R5 Steam Generator Eddy Current Inspection Base Scope Eddy Current Exam Type SG 1 SG 2 SG 3 SG 4 Total Full Length Bobbin Exams 4874 4874 4874 4874 19,496 HL VS3-HTE Bobbin Exams 254 254 254 254 1,016 CL VS3-CTE Bobbin Exams 254 254 254 254 1,016 HL Periphery Array Exams (H01-HTE) 1102 1102 1102 1102 4,408 CL Periphery Array Exams (C06-CTE) 595 595 595 595 2,380 Notes:
(1)
All bobbin exams were performed with a 0.610 inch probe diameter (2)
All bobbin exams were performed at 50 IPS (inches per second)
Table 2-2: Watts Bar U2R5 Steam Generator Eddy Current Inspection Special Interest Scope Eddy Current Exam Type SG 1 SG 2 SG 3 SG 4 Total
.610 HL RPC Special Interest 0
6 0
2 8
.560 CL RPC Special Interest 0
29 3
0 32
.610 HL Array Special Interest 10 44 10 5
69
.610 CL Array Special Interest 16 79 16 16 127
.580 HL RPC U-Bend Special Interest 0
1 0
0 1
.580 CL RPC UBend Special Interest 0
3 0
0 3
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 6 of 20 In addition to the eddy current inspections, visual inspections were performed on both the primary and secondary sides. Primary side inspections included the entire divider plate to channel head weld and all clad surfaces in both the HL and CL of all four SGs. No tubes were plugged and therefore no visual inspection of plugs was performed. The secondary side visuals were performed at the top of tube sheet (TTS) and in the preheater distribution box. The secondary side visuals were conducted to detect foreign objects, assess hard deposit buildup in the tube bundle interior, and to evaluate the effectiveness of the cleanings performed on the four SGs.
No primary or secondary side scope expansion was required for U2R5 inspections. All primary and secondary side visual inspections were completed satisfactory with no degradation or anomalies reported.
3.
Nondestructive Examinations Techniques Utilized for Tubes with Increased Degradation Susceptibility There were no tubes designated as having increased degradation susceptibility during the U2R5 inspection. Following the arrival of the replacement steam generators on site (January of 2019) and before installation, a pre-service baseline inspection was performed. Service induced degradation mechanisms were not expected nor discovered during the pre-service inspection (PSI).
- 4.
Nondestructive Examinations Techniques Utilized for Each Degradation Mechanism Found Table 4-1 below provides the NDE techniques that were used for the detection of each degradation mechanism considered to be existing or potential for the U2R5 inspection.
Table 4-1: NDE Techniques for Each Potential Degradation Mechanism for U2R5 Degradation Mechanism Classification Detection Technique EPRI ETSS U-Bend Support Structure Wear Potential Bobbin Bobbin Array 96004.1, Revision 14 96044.3, Revision 0 17908.5, Revision 1 Horizontal Tube Support Grid Wear Potential Bobbin Array 96004.1, Revision 14 17908.5, Revision 1 Foreign Object Wear Potential Bobbin Bobbin Array Array
+PT 96004.1, Revision 14 27091.X, Revision 2 17906.1, Revision 0 17906.3, Revision 0 27902.1, Revision 2 Tube-to-Tube Wear Potential Bobbin Array
+PT 13091.1, Revision 0 13902.1, Revision 0 13901.1, Revision 1
- 5.
Location, Orientation (if linear), Measured Size (if available), and Voltage Response for Each Indication.
There were no existing degradation mechanisms identified prior to WBN U2R5. After the completion of the in-service inspection (ISI) during U2R5, the following two degradation mechanisms were identified:
- 1. Wear at U-bend Support Structures
- 2. Wear at Horizontal ATSGs Table 5-1 below shows the total number of wear indications detected for the two degradation mechanisms identified in U2R5. A total of 386 indications in 262 tubes were detected during U2R5. No wear due to foreign objects was detected.
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 7 of 20 Table 5-1: Number of Indications Detected for Each Degradation Mechanism +/- All SGs Degradation Mechanism SG1 SG2 SG3 SG4 Total U-bend Support Structure Wear 0
3 0
3 6
Horizontal ATSG Wear 55 258 44 23 380 There are a total of 380 indications of ATSG wear in all SGs and six indications of U-bend support wear in all SGs. Table 5-2 provides all support structure wear greater than or equal to 20 percent through-wall (6 total indications). All 6 indications greater than or equal to 20 percent through-wall are due to wear at horizontal ATSGs. Table 5-3 provides all U-bend support structure wear detected in U2R5.
Table 5-2: Watts Bar U2R5 Horizontal ATSG Wear ( 20% TW) +/- All SGs SG Row Col Loc Inch Volts Indic
%TW Characterization Resolution 2
15 86 H07
-0.71 1.02 PCT 20 Horizontal ATSG Wear Plugged 2
76 107 C03 0.63 1.09 PCT 20 Horizontal ATSG Wear Plugged 2
92 93 C04 0.77 2.28 PCT 28 Horizontal ATSG Wear Plugged 2
105 68 C05 0.71 1.38 PCT 22 Horizontal ATSG Wear Plugged C06 0.85 1.62 PCT 24 Horizontal ATSG Wear 3
95 38 C03 0.81 1.04 PCT 20 Horizontal ATSG Wear Plugged Notes:
(1) All indications reported by bobbin probe were confirmed with array probe.
(2) All tubes listed were preventively plugged and stabilized. All tubes with 15% TW or more were preventatively plugged.
Table 5-3: Watts Bar U2R5 U-bend Support Structure Wear +/- All SGs SG Row Col Loc Inch Volts Indic(1)
%TW Length (in.)(2)
Characterization Resolution 2
98 67 VS2 1.01 0.38 PCT 13 0.32 U-bend Support Structure Wear Plugged (3)
VS4 0.76 0.48 PCT 14 0.45 U-bend Support Structure Wear VS5 1.03 0.33 PCT 12 0.42 U-bend Support Structure Wear 4
98 63 VS4 0.81 0.29 PCT 11 0.26 U-bend Support Structure Wear Return to Service 4
101 64 VS4 0.77 0.24 PCT 11 0.30 U-bend Support Structure Wear Return to Service 4
102 67 VS2 1.08 0.29 PCT 11 0.21 U-bend Support Structure Wear Return to Service Notes:
(1)
All indications reported by bobbin probe were confirmed with array probe.
(2)
Flaw length measured with the array probe.
(3)
Tube at Row 98 / Column 67 was preventatively plugged. All tubes with three or more wear indications were preventatively plugged. is a listing of all wall loss indications detected during U2R5.
- 6.
A Description of the Condition Monitoring Assessment and Inspection Results for Each Degradation Mechanism Found Condition Monitoring Assessment Summary The WBN U2R5 inspection was the first in-service inspection performed following the replacement of the WBN Unit 2 SGs during U2R4. For this reason, there were no existing degradation mechanisms prior to the U2R5 inspection. All degradation was bounded by the previous operational assessment as shown in Table 6-1. A condition monitoring (CM) assessment was performed as required by the steam generator program. The only tube degradation detected during the U2R5 inspection was Wear at tube support structures. This can be sub-divided into U-bend Support Structure Wear and Horizontal Grid Wear (Wear at ATSGs). Following the U2R5 inspection, U-bend Support Structure Wear and Horizontal Grid Wear are existing degradation mechanisms.
During U2R5, a total of 6 wear indications at U-bend Support Structures in 4 tubes were identified. The largest indication was measured to be 14% TW in SG2 at R98 / C67 at support VS4. A bobbin probe was
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 8 of 20 used to measure the indication and it was sized using ETSS 96004.1. The depth of indications ranged from 11%TW to 14%TW. Steam generators 2 and 4 were the only generators with U-bend Support Structure wear. Both generators had 3 indications apiece. Table 5-3 includes a summary of all U-Bend Support wear including location, size, measured voltage, depth, and resolution. All indications for U-Bend Support Structure wear were within the CM limit of 50.2%TW (Axial Thinning Model). This limit incorporates material uncertainties, burst pressure uncertainties, and NDE measurement uncertainties at 95% probability and 0.50 confidence level (95/50). The CM support structure bounding length is 2.5 inches. The largest indication was 14% TW, and the largest flaw length was 0.45 inches. Since all wear indications were less than 50.2%TW and less than 2.5 inches in length, structural performance criteria has been satisfied. No In-Situ pressure testing was required.
During U2R5, there were a total of 380 wear indications at Horizontal Support Structures in 262 tubes.
The largest indication detected was 28%TW in SG 2 at R92 / C93 at support C04. The largest indication was detected using a bobbin probe and sized using ETSS 96004.1. The largest indication of 28%TW had a length of 0.34 inches which was sized with an array probe. The largest flaw length was measured to be 0.36 inches. As recorded in Table 5-2, the majority of indications are located in SG2. During the inspection, 55 indications were identified in SG1, 258 in SG2, 44 in SG3, and 23 in SG4. The CM limits for ATSG wear were determined to be 50.7%TW (Axial Thinning Model) with 2 inches as the limiting axial flaw length (full width of ATSG). Material uncertainties, burst pressure uncertainties, and NDE measurement uncertainties at 95% probability and 0.50 confidence level (95/50) were accounted for when determining the CM limits. The maximum measured depth of 28%TW and the largest measured flaw length of 0.36 inches are below the bounding CM limits. Thus, structural integrity requirements have been met for the Horizontal Support Structure degradation detected in the U2R5 inspection. No In-Situ pressure testing was required.
Satisfaction of structural integrity implies satisfaction of leakage integrity at accident conditions since steam line break accident condition pressure differential for pop-through is smaller than 3 PNO for pressure-only loading of volumetric flaws. Therefore, CM has been satisfied for degradation associated with ATSG support structure wear and U-bend support structure wear indications at the Watts Bar U2R5 inspection.
Projected and As-Found Inspection Results In the forward looking operational assessment developed by TVA during U2R4 for the justification of fuel-cycle-five-operation, the arithmetic strategy was utilized to determine the maximum through wall allowed to maintain 3 P safety margin for four potential degradation mechanisms. The four potential degradation mechanisms included loose parts wear, ATSG wear, U-bend wear, and tube to tube wear. By implementing the arithmetic strategy, the flaw length, through wall percentage, and 95th percentile burst pressure limits were calculated. The bounding percent through wall limits listed in Table 6-1 are compared to the actual results from U2R5 inspections. All results were bounded by predictions. The minimum full power steady state main steam pressure during fuel cycle 5 was 993 psig and was above the minimum projected.
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 9 of 20 Table 6-1: Comparison of OA Projections to Inspection Results Parameter WBN U2R4 Projected Limiting Value (1)
WBN U2R5 Observed Inspection Interval (EFPY) 1.3448 1.3255 U-Bend Support Wear (%TW) 46 14 ATSG Wear (%TW) 46.4 28 Loose Parts Wear (%TW) 40 N/A Tube to Tube Wear (%TW) 50.6 N/A Notes:
(1)
All projected percent through wall indications have a 95th percentile probability to burst at a pressure greater than 3 P.
- 7.
The number of Tubes Plugged During the Inspection Outage for Each Degradation Mechanism Found There were a total of 57 tubes plugged during U2R5. A total of 56 tubes were preventatively plugged due to Horizontal Support Structure (ATSG) wear. Only 1 tube was preventatively plugged for U-bend Support Structure Wear. This tube is located in SG2 at Row 98 / Column 67. Table 7-1 provides the total number of tubes plugged for each degradation mechanism.
Table 7-1: Total Number of Tubes Plugged for Each Degradation Mechanism SG 1 SG 2 SG 3 SG 4 Total Tubes Plugged prior to U2R5 0
0 0
0 0
Plugged for U-bend Support Structure Wear 0
1 0
0 1
Plugged for Horizontal ATSG Wear 5
45 6
0 56 Total Plugged Tubes to Date 5
46 6
0 57 Percentage Plugged to Date 0.0975%
0.897%
0.117%
0.0%
0.278%
- 8.
The Repair Methods Utilized, and the Number of Tubes Repaired by Each Repair Method No repair methods were utilized during WBN U2R5.
- 9.
Analysis Summary of the Tube Integrity Conditions Predicted to Exist at the Next Scheduled Inspection Relative to the Applicable Performance Criteria Including Analysis Methodology, Inputs, and Results A simplified deterministic and a full bundle, fully probabilistic, OA method were used to predict tube integrity conditions at the next scheduled inspection. Both methods were utilized in order to provide added confidence that the SG structural and leakage performance criteria will be maintained until the next inspection. The deterministic model evaluated all SGs while the fully probabilistic model only
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 10 of 20 determined probability of burst (POB) and probability of leakage (POL) for the limiting steam generator, SG2. In both models, a two cycle (2.7002 EFPY) interval was justified before the next inspection with conservatism in place. The flaw population in all SGs meet the structural integrity performance criteria of 3750 psid at 95% probability and 50% confidence levels for at least 2.7002 EFPY of operation. For pressure-only loading of volumetric flaws, satisfaction of the structural integrity implies satisfaction of leakage integrity at accident conditions since steam line break accident condition pressure differential for pop-through is smaller than 3 PNO. Table 9-1 and Table 9-2 list the associated inputs for the OA methods.
Table 9-1: Watts Bar U2R5 U-bend Support Structure Wear Growth Comparison All SGs Number of Indications 6
Number of Tubes 4
Maximum Depth (%TW) 14 Maximum Length (in.)
0.45 Average Growth (%TW/EFPY) 11.17 Maximum Growth (%TW/EFPY) 12.67 95th Percentile Growth (%TW/EFPY) 13.25 Number of Tubes Plugged 1
Table 9-2: Watts Bar U2R5 Horizontal ATSG Wear Growth Comparison Steam Generator SG 1 SG 2 SG3 SG 4 All SGs Number of Indications 55 258 44 23 380 Number of Tubes 41 169 32 20 262 Maximum Depth (%TW) 17 28 20 13 28 Maximum Length (in.)
0.29 0.36 0.26 0.33 0.36 Average Growth (%TW/EFPY) 10.41 11.13 11.05 9.87 10.94 Maximum Growth (%TW/EFPY) 14.91 23.12 17.15 11.92 23.12 95th Percentile Growth (%TW/EFPY) 13.36 14.91 14.91 11.57 14.91 Number of Tubes Plugged 5
45 6
0 56 Deterministic Method Simplified methods of projecting the worst case degraded tube are designed to provide conservative approximations of fully probabilistic calculations that consider the entire projected flaw population and the variety of possible outcomes for a given inspection interval. In the simplified techniques, the worst case flaw is projected using conservative assumptions coupled with uncertainties that are combined using the mixed Arithmetic/Monte Carlo calculation strategies. This method involves a single tube analysis that will provide a conservative estimate for the projected end of cycle (EOC) lower 95th percentile burst pressure.
For the deterministic method, the limiting degradation mechanism is U-bend support structure wear.
After 2.7002 EFPY, it is predicted that the worst-case U-bend wear would be no greater than 56.47%TW.
The EOC material structure limit is 56.5%TW (Axial Thinning Model) for U-bend wear, therefore
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 11 of 20 performance criteria would be met. Table 9-3 provides maximum depths predicted at the next scheduled inspection for the worst case degraded tube.
Table 9-3: Watts Bar U2R5 Deterministic Operational Assessment Summary Degradation Mechanism (Wear)
Maximum Depth Predicted at Next Inspection (%TW)
EOC Structure Limit (%TW) (1)
OA Margin to EOC Structural Limit
(%TW)
OA Interval (EFPY)
U-bend Support (Return to Service) 56.47 56.5 0.03 2.7002 (2 cycles)
U-bend Support (Undetected) 55.78 56.5 0.72 2.7002 (2 cycles)
ATSG (3) 63.93 67.45 (2) 3.52 2.7002 Cycles)
Notes:
(1) The EOC Structural Limit is used to assess the OA projected flaw size. Therefore, the projected flaw size was adjusted to account for NDE measurement uncertainty at 95/50.
(2) EOC Structure Limit determined with length of 0.37 inches.
(3) Results shown for returned to service flaw population. Projected results for undetected ATSG wear flaws are not shown because the POD(0.95) value of 12% TW is bounded by the largest returned to service flaw.
As shown in Table 9-3, the projected maximum depths are all less than the EOC structural limit depths.
For u-bend wear projections, the maximum growth rate is 12.67%TW/EFPY and the upper 95th percentile growth used is 13.25%TW/EFPY. For ATSG wear projections, a more detailed growth rate evaluation is performed by segmenting the SG2 outer perimeter tubes from the interior region since the growth rates are slightly higher in the perimeter tubes. The upper 95th percentile growth rate of the SG2 perimeter region is 14.91%TW/EFPY which is used in the deterministic OA projections.
Fully Probabilistic Method Fully probabilistic methods provide a wider range of inputs that include distributions of detected and undetected flaw sizes and distributions of degradation growth rates, combined with uncertainties for material property, burst relation, and NDE measurement. The OA of ATSG and U-bend Support wear degradation mechanisms is performed using fully probabilistic methods through application of a Westinghouse developed software package referred to as Full Bundle Model (FBM). The assumed quantity and depth distribution of undetected ATSG wear is determined by postulating a total (detected and undetected) flaw depth distribution which is simulated with the POD function to produce both detected flaw and undetected flaw size distributions. The total flaw depth distribution is iterated until the simulated detected flaw distribution aligns with the observed detected flaw distribution at U2R5.
A full bundle, fully probabilistic methodology was used to predict the conditions at the next inspection only for SG2 which is the limiting SG. For the fully probabilistic method, the limiting degradation mechanism is ATSG wear. After 2.7002 EFPY, the projected POB for combined ATSG wear is 4.606%,
which is below the 5% limit as shown in Table 9-4.
Table 9-4: Watts Bar U2R5 SG2 Two-Cycle Fully Probabilistic OA Results POB
(%)
POL
(%)
Burst Pressure (psi)
Leak Rate (gpm)
U-bend Support Wear 0.169 0.000 4309 0
Horizontal ATSG Wear Combined 4.606 0.010 0
Horizontal ATSG Wear, Perimeter 4.376 0.010 3777 0
Horizontal ATSG Wear, Interior 0.241 0.000 4162 0
Limit Max 5
Max 5
Min 3750 1
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 12 of 20 As shown in Table 9-4, the projected POB and POL were all within the 5% limit for two cycles of operation. All calculated burst pressures were greater than the minimum 3 P of 3750 psid. Thus, the OA supports the next inspection to be performed at the end of 2 operating cycles during U2R7.
- 10.
The Number and Percentage of Tubes Plugged to Date and the Effective Plugging Percentage in Each SG Table 10-1 below provides the number of tubes plugged and plugging percentage as of the end of U2R5.
No sleeves have been installed and therefore there is no correction for effective plugging percentage.
Table 10-1: Number and Percentage of Tubes Plugged at Completion of U2R5 SG 1 SG 2 SG 3 SG 4 Total Tubes Plugged prior to U2R5 0
0 0
0 0
Plugged for U-bend Support Structure Wear 0
1 0
0 1
Plugged for Horizontal Support Structure Wear 5
45 6
0 56 Total Plugged Tubes to Date 5
46 6
0 57 Percentage Plugged to Date 0.0975%
0.897%
0.117%
0.0%
0.278%
Allowable Percent Tubes Plugged 12%
12%
12%
12%
12%
- 11.
The Results of Any SG Secondary Side Inspections Scope of Secondary Side Inspection Activities In all four SGs, visual inspections were conducted on the top of the tubesheet following sludge lancing activities including:
- 1. Sludge lancing effectiveness and FOSAR in 100% of the annulus to a minimum of 3-5 tubes deep.
- 2. Sludge lancing effectiveness and FOSAR in 100% of the tube lane to a minimum of 3-5 tubes deep.
- 3. All Possible Loose Parts (PLPs) identified by eddy current program.
FOSAR and Eddy Current Resolution Extensive eddy current inspections took place on the primary side capable of detecting foreign objects and (PLPs). Detection mechanisms were present with the inspection exam scope. This included a 100%
full length bobbin probe inspection program and a minimum 3 tube deep array probe peripheral inspection on the HL and CL to detect foreign objects and foreign object wear. The array probe inspection program went to the 6th support on the cold leg side. During the inspections, no foreign object wear was detected. Three PLP signals from eddy current inspections were reported and investigated.
PLP signals are investigated and dispositioned as they may detect a foreign object. All PLP signals were located at the TTS and visually inspected from the secondary side. Table 11-1 summarizes the PLP signals, the resolution, and justification for returning to service. No foreign objects were observed at any of the three locations upon visual inspection.
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 13 of 20 Table 11-1: Watts Bar U2R5 PLP Signals SGID Row Col Volts Ind Locn Inch1 Disposition Justification 2
81 94 2.13 PLP HTS 0.5 Return to Service No object observed with visual inspection. NDF on +Pt 3
18 125 1.09 PLP CTS 0.32 Return to Service No object observed with visual inspection. NDF on +Pt 4
69 18 0.66 PLP CTS 0.29 Return to Service No object observed with visual inspection Following sludge lancing, FOSAR was performed in each steam generator to remove remaining foreign objects (sludge rocks and tube scale are not considered foreign objects). The secondary side FOSAR inspections performed in all four SGs included visual examinations of the tube lane, annulus, and periphery tubes (to at least 3-5 tubes into the tube bundle). A total of seven foreign objects were identified through visual inspections at the TTS as summarized in table 11-2. All foreign objects were either removed or evaluated by size and location as acceptable to remain for the following two cycles of operation. A total of four foreign objects were retrieved while three foreign objects were not retrieved and were dispositioned to remain. All three objects not retrieved were within the size dimensions acceptable for two cycles of operation (Reference 1). Table 11-2 lists all foreign object dimensions and material type.
Table 11-2: Watts Bar U2R5 Identified Foreign Objects Preheater Box Visual Inspections All four preheater boxes were visually inspected during U2R5. No active degradation was found following the completion of the inspection. A total of 24 foreign objects were observed in all SGs following the completed inspections. Of the 24 objects, 22 were successfully removed while two were left in the preheater box. The materials observed included weld slag, scale, sludge rock, gasket material, wire bristle material, fibrous material, tape material, rubber, and graphite. The two remaining foreign objects were determined to be of small diameter and will not cause tube degradation in the next two cycles of operation. These two foreign objects were recorded as fibrous material and scale. The fibrous material (SG/FO ID 1002) had the following dimensions in inches: 0.9 x 0.01 x 0.01. The scale material (SG/FO ID 3005) had the following dimensions in inches: 0.3 x 0.01 x 0.25.
No degradation was identified during secondary side inspections, including the preheater distribution box.
SG/FO ID Retrieved?
FO Description Leg Row/Col New/Legacy Dimensions (inch.)
1001 No Wire Bristle CL 3/24 New 0.375 x 0.01 2004 Yes Weld Slag CL 58/102 New 0.375 x 0.06 x 0.06 3001 Yes Gasket Material CL 10/54 New 1 x 0.075 x 0.125 3002 No Gasket Material HL 21/76 New 0.5 x 0.075 x 0.125 4001 No Fiber Material HL 6/39 New 0.2 x 0.8 x 0.02 4002 Yes Gasket Material CL 11/56 New 0.5 x 0.1 x 0.2 4003 Yes Gasket Material CL 23/81 New 1 x 0.4 x 0.2
April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 14 of 20
- 12.
The Scope, Method, and Results of Secondary Side Cleaning Performed in Each SG Top of Tubesheet Sludge Lancing During the WBN U2R5 inspection, sludge lancing was performed at the secondary side top of tubesheet in all four steam generators. There are two main purposes of the cleaning process. The first is to remove soft sludge and hardened deposits (such as sludge, scale, and foreign objects) that preferentially form at the top of the tubesheet (TTS), and the second is to force and filter out any loose parts or foreign objects that have migrated to the SG secondary side top of tubesheet during operation. Given a total EFPY of 1.3255, minimal sludge was expected to be removed during the sludge lancing process. The largest amount of sludge removed came from SG1 and SG2 at 4.75 lbs each. The mass of deposit material and debris removed by the cleaning process is summarized in Table 12-1 below. Due to a single cycle of RSG operation, there is no tube integrity effects of deposits and very little concentration of deposits in the center of the bundle. With a single data point of sludge removed, there is no trending over time. The deposit trending between SGs is considered reasonable for a first sludge lance. No water level perturbations were observed during the past fuel cycle. The main steam pressure was very steady after approximately the first two weeks of operation.
Table 12-1: Watts Bar U2R5 Sludge Lance Deposit Removal Summary SG1 (lbs.)
SG2 (lbs.)
SG3 (lbs.)
SG4 (lbs.)
Total (lbs.)
4.75 4.75 2.75 3.75 16
- 13.
The Results of Primary Side Component Visual Inspections Performed in Each SG SG Channel Head Bowl Visual Inspections Visual inspections were performed in the channel head bowl on both the hot and cold leg channels during WBN U2R5. Visual inspections of the SG divider plate, inclusive of the entire divider plate-to-channel head weld and all visible clad surfaces, were performed in accordance with Westinghouse NSAL-12-1.
This inspection was performed using the SG manway channel head bowl cameras. Satisfactory inspection results were observed in all SGs with no indications of cladding surface degradation. No breaches in the cladding or cracking in the divider-to-channel head weld were identified. These inspections are driven by industry operating experience and EPRI guideline recommendations.
Tube Plug Inspections WBN Unit 2 had zero plugs installed prior to U2R5. Therefore, no inspections were performed on the tube plugs for signs of leakage or degradation.
- 14.
Any Plant-Specific Reporting Requirements, if Applicable.
There are no plant-specific requirements to report.
References
- 1. Westinghouse Document, SG-CECO-21-002, Foreign Object Limits Analysis for the Sequoyah Unit 1 and Unit 2 Replacement Steam Generators, Revision 2 dated February, 2024
, Watts Bar U2R5 Percent Wall Loss Indications April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 15 of 20 SG Row Col Volts
%TW Locn Inch1 Characterization Resolution 1
1 2
0.29 11 C04
-1.02 ATSG Wear Returned to Service 1
1 66 0.26 11 H04
-0.95 ATSG Wear Returned to Service 1
1 78 0.35 12 H05
-0.88 ATSG Wear Returned to Service 1
1 80 0.22 10 H07
-1.06 ATSG Wear Returned to Service 1
1 82 0.29 11 H07
-0.93 ATSG Wear Returned to Service 1
1 88 0.23 10 C11
-1.01 ATSG Wear Returned to Service 1
1 98 0.3 12 C09
-0.98 ATSG Wear Returned to Service 1
2 1
0.34 12 C03
-1.05 ATSG Wear Returned to Service 1
3 96 0.28 11 H06
-0.89 ATSG Wear Returned to Service 1
4 27 0.17 9
C06
-0.9 ATSG Wear Returned to Service 1
4 127 0.23 10 C06
-0.93 ATSG Wear Returned to Service 1
5 2
0.19 9
C04
-1.07 ATSG Wear Returned to Service 1
6 1
0.38 13 C03
-0.95 ATSG Wear Plugged 1
6 1
0.75 17 C03 0.76 ATSG Wear Plugged 1
6 1
0.62 16 C05 0.64 ATSG Wear Plugged 1
6 1
0.33 12 C06 0.69 ATSG Wear Plugged 1
6 1
0.21 10 C08 0.65 ATSG Wear Plugged 1
7 124 0.18 9
C03 0.69 ATSG Wear Returned to Service 1
8 1
0.39 13 C03 0.67 ATSG Wear Returned to Service 1
8 1
0.26 11 C06
-0.9 ATSG Wear Returned to Service 1
8 29 0.18 9
C11 0.59 ATSG Wear Returned to Service 1
8 127 0.26 11 C03
-0.85 ATSG Wear Plugged 1
8 127 0.55 15 C03 0.73 ATSG Wear Plugged 1
10 1
0.45 14 C05 0.71 ATSG Wear Returned to Service 1
11 126 0.2 10 C03
-0.92 ATSG Wear Returned to Service 1
14 89 0.28 11 H07
-1.12 ATSG Wear Returned to Service 1
22 125 0.28 11 C09
-0.86 ATSG Wear Returned to Service 1
31 4
0.25 11 C06
-0.93 ATSG Wear Returned to Service 1
44 7
0.19 9
C03 0.71 ATSG Wear Returned to Service 1
46 119 0.13 8
C03
-0.83 ATSG Wear Plugged 1
46 119 0.22 10 C06
-0.81 ATSG Wear Plugged 1
46 119 0.38 13 C07
-0.83 ATSG Wear Plugged 1
47 120 0.14 8
C03
-0.78 ATSG Wear Returned to Service 1
50 9
0.2 10 C06
-0.93 ATSG Wear Returned to Service 1
56 11 0.14 8
C05 0.76 ATSG Wear Returned to Service 1
56 13 0.22 10 C03
-1.09 ATSG Wear Returned to Service 1
58 13 0.29 11 C06 0.69 ATSG Wear Returned to Service 1
64 113 0.17 9
C03
-0.93 ATSG Wear Returned to Service 1
67 16 0.21 10 C05
-0.85 ATSG Wear Returned to Service 1
68 111 0.09 8
C05 0.85 ATSG Wear Returned to Service 1
82 103 0.31 12 C05
-0.83 ATSG Wear Returned to Service 1
83 102 0.29 11 C03
-0.83 ATSG Wear Plugged 1
83 102 0.25 11 C05
-0.86 ATSG Wear Plugged 1
83 102 0.38 13 C06
-0.83 ATSG Wear Plugged 1
83 102 0.29 11 C07
-0.81 ATSG Wear Plugged 1
88 97 0.21 10 C05
-0.88 ATSG Wear Returned to Service 1
90 33 0.37 13 C03
-0.91 ATSG Wear Returned to Service 1
97 40 0.28 11 C04 0.62 ATSG Wear Plugged 1
97 40 0.34 12 C05
-1.02 ATSG Wear Plugged 1
97 40 0.43 13 C06
-0.96 ATSG Wear Plugged 1
99 82 0.22 10 C06
-0.83 ATSG Wear Returned to Service 1
99 84 0.39 13 C05 0.81 ATSG Wear Returned to Service 1
100 83 0.19 9
C04 0.88 ATSG Wear Returned to Service 1
100 83 0.21 10 C06
-0.88 ATSG Wear Returned to Service 1
103 68 0.2 10 C05
-0.82 ATSG Wear Returned to Service 2
1 30 0.13 8
C11 0.38 ATSG Wear Returned to Service 2
1 44 0.53 15 H05
-0.83 ATSG Wear Plugged 2
1 46 0.39 13 H04
-0.95 ATSG Wear Returned to Service 2
1 46 0.28 11 H05
-0.97 ATSG Wear Returned to Service 2
1 50 0.37 13 H05
-0.97 ATSG Wear Returned to Service 2
1 56 0.19 9
C11 0.41 ATSG Wear Returned to Service 2
1 80 0.24 10 H08 0.66 ATSG Wear Returned to Service 2
1 90 0.49 14 H03 0.86 ATSG Wear Returned to Service 2
1 100 0.26 11 C10
-0.9 ATSG Wear Returned to Service 2
2 29 0.22 10 C09
-0.97 ATSG Wear Returned to Service 2
2 37 0.33 12 C08
-0.88 ATSG Wear Returned to Service 2
2 83 0.22 10 H09 0.65 ATSG Wear Returned to Service 2
2 107 0.29 11 C10
-0.92 ATSG Wear Returned to Service 2
3 46 0.24 11 H05
-0.9 ATSG Wear Returned to Service
, Watts Bar U2R5 Percent Wall Loss Indications April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 16 of 20 SG Row Col Volts
%TW Locn Inch1 Characterization Resolution 2
3 90 0.33 12 H05
-0.97 ATSG Wear Returned to Service 2
3 100 0.26 11 H08
-0.98 ATSG Wear Returned to Service 2
4 43 0.27 11 H05
-0.83 ATSG Wear Returned to Service 2
4 95 0.2 10 C09 0.43 ATSG Wear Returned to Service 2
4 127 0.2 10 C03
-0.97 ATSG Wear Returned to Service 2
5 90 0.32 12 H05
-0.85 ATSG Wear Returned to Service 2
5 94 0.49 14 H07 0.75 ATSG Wear Plugged 2
5 94 0.54 15 H08
-0.7 ATSG Wear Plugged 2
5 108 0.69 17 H07 0.73 ATSG Wear Plugged 2
5 126 0.33 12 C03
-0.9 ATSG Wear Returned to Service 2
7 86 0.31 12 H05
-0.95 ATSG Wear Returned to Service 2
7 86 0.41 13 H09 0.72 ATSG Wear Returned to Service 2
7 124 0.18 9
C03
-0.8 ATSG Wear Returned to Service 2
8 93 0.56 15 H09 0.76 ATSG Wear Plugged 2
9 38 0.6 16 H10
-0.98 ATSG Wear Plugged 2
9 66 0.35 12 H10 0.81 ATSG Wear Returned to Service 2
14 125 0.29 11 C06
-0.67 ATSG Wear Returned to Service 2
15 86 1.02 20 H07
-0.71 ATSG Wear Plugged 2
16 67 0.67 16 H09 0.67 ATSG Wear Plugged 2
16 69 0.27 11 H10 0.59 ATSG Wear Returned to Service 2
16 95 0.39 13 C10
-0.94 ATSG Wear Returned to Service 2
16 125 0.5 15 C03 0.54 ATSG Wear Plugged 2
19 126 0.32 12 C05
-0.95 ATSG Wear Returned to Service 2
19 126 0.37 13 C06
-0.9 ATSG Wear Returned to Service 2
23 124 0.2 10 C03 0.59 ATSG Wear Returned to Service 2
24 125 0.24 11 C03 0.54 ATSG Wear Returned to Service 2
26 125 0.64 16 C06
-0.72 ATSG Wear Plugged 2
27 124 0.2 10 C03 0.56 ATSG Wear Returned to Service 2
31 124 0.23 10 C06
-0.72 ATSG Wear Returned to Service 2
32 123 0.25 11 C06
-0.57 ATSG Wear Returned to Service 2
41 120 0.29 11 C03 0.57 ATSG Wear Returned to Service 2
48 119 0.24 11 C05 0.59 ATSG Wear Returned to Service 2
50 119 0.24 11 C04
-0.79 ATSG Wear Plugged 2
50 119 0.23 10 C05 0.75 ATSG Wear Plugged 2
50 119 0.21 10 C06 0.67 ATSG Wear Plugged 2
56 117 0.18 9
C05 0.76 ATSG Wear Returned to Service 2
57 116 0.51 15 C07 0.48 ATSG Wear Plugged 2
58 115 0.24 11 C05
-0.82 ATSG Wear Returned to Service 2
58 115 0.39 13 C05 0.75 ATSG Wear Returned to Service 2
59 114 0.22 10 C06 0.54 ATSG Wear Returned to Service 2
61 114 0.34 12 C05 0.64 ATSG Wear Returned to Service 2
63 114 0.24 11 C04
-0.82 ATSG Wear Returned to Service 2
63 114 0.25 11 C06 0.65 ATSG Wear Returned to Service 2
64 111 0.21 10 C05 0.78 ATSG Wear Returned to Service 2
64 113 0.22 10 C05
-0.85 ATSG Wear Returned to Service 2
65 112 0.21 10 C04
-0.85 ATSG Wear Plugged 2
65 112 0.35 12 C06 0.75 ATSG Wear Plugged 2
65 112 0.35 12 C10
-0.95 ATSG Wear Plugged 2
66 111 0.52 15 C05 0.64 ATSG Wear Plugged 2
66 111 0.19 9
C06 0.72 ATSG Wear Plugged 2
67 110 0.2 10 C05 0.57 ATSG Wear Returned to Service 2
67 112 0.22 10 C05
-0.85 ATSG Wear Returned to Service 2
67 112 0.21 10 C05 0.73 ATSG Wear Returned to Service 2
68 107 0.22 10 C03
-0.84 ATSG Wear Returned to Service 2
68 109 0.58 15 C03 0.59 ATSG Wear Plugged 2
72 109 0.18 9
C04
-0.79 ATSG Wear Returned to Service 2
74 105 0.46 14 C03
-0.82 ATSG Wear Returned to Service 2
76 107 1.09 20 C03 0.63 ATSG Wear Plugged 2
77 104 0.36 12 C03 0.63 ATSG Wear Returned to Service 2
78 103 0.22 10 C06
-0.55 ATSG Wear Returned to Service 2
78 105 0.24 11 C03 0.54 ATSG Wear Returned to Service 2
83 100 0.27 11 C03 0.82 ATSG Wear Returned to Service 2
84 99 0.29 11 C03 0.76 ATSG Wear Returned to Service 2
85 96 0.27 11 C03
-0.76 ATSG Wear Returned to Service 2
86 33 0.21 10 C04
-0.77 ATSG Wear Returned to Service 2
86 95 0.23 10 C03
-0.76 ATSG Wear Returned to Service 2
86 95 0.28 11 C05 0.7 ATSG Wear Returned to Service 2
86 97 0.27 11 C03
-0.8 ATSG Wear Plugged 2
86 97 0.4 13 C03 0.79 ATSG Wear Plugged
, Watts Bar U2R5 Percent Wall Loss Indications April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 17 of 20 SG Row Col Volts
%TW Locn Inch1 Characterization Resolution 2
86 97 0.22 10 C05 0.72 ATSG Wear Plugged 2
87 32 0.26 11 C04
-0.81 ATSG Wear Returned to Service 2
87 96 0.31 12 C03 0.56 ATSG Wear Returned to Service 2
87 96 0.2 10 C06 0.53 ATSG Wear Returned to Service 2
87 98 0.28 11 C03 0.56 ATSG Wear Returned to Service 2
87 98 0.24 11 C08 0.59 ATSG Wear Returned to Service 2
88 31 0.18 9
C04
-0.8 ATSG Wear Plugged 2
88 31 0.33 12 C05
-0.85 ATSG Wear Plugged 2
88 31 0.42 13 C07
-0.84 ATSG Wear Plugged 2
88 31 0.2 10 C08
-0.89 ATSG Wear Plugged 2
88 33 0.24 10 C04
-0.9 ATSG Wear Returned to Service 2
88 33 0.28 11 C06
-0.9 ATSG Wear Returned to Service 2
88 95 0.23 10 C04
-0.79 ATSG Wear Returned to Service 2
88 97 0.76 17 C03 0.59 ATSG Wear Plugged 2
89 34 0.32 12 C03
-0.93 ATSG Wear Plugged 2
89 34 0.33 12 C06
-0.92 ATSG Wear Plugged 2
89 34 0.76 17 C07
-0.87 ATSG Wear Plugged 2
89 94 0.3 12 C06 0.48 ATSG Wear Returned to Service 2
89 96 0.22 10 C03
-0.74 ATSG Wear Plugged 2
89 96 0.32 12 C03 0.79 ATSG Wear Plugged 2
89 96 0.76 17 C05 0.75 ATSG Wear Plugged 2
89 96 0.62 16 C06
-0.72 ATSG Wear Plugged 2
90 33 0.3 11 C07
-0.8 ATSG Wear Returned to Service 2
90 35 0.3 11 C04
-0.88 ATSG Wear Returned to Service 2
90 35 0.47 14 C06
-0.85 ATSG Wear Returned to Service 2
90 85 0.23 10 C04
-0.81 ATSG Wear Returned to Service 2
90 87 0.24 10 C04
-0.85 ATSG Wear Returned to Service 2
90 93 0.23 10 C06 0.79 ATSG Wear Returned to Service 2
90 95 0.76 17 C03
-0.85 ATSG Wear Plugged 2
90 95 0.35 12 C03 0.85 ATSG Wear Plugged 2
90 95 0.26 11 C05
-0.85 ATSG Wear Plugged 2
90 95 0.46 14 C05 0.7 ATSG Wear Plugged 2
90 95 0.61 16 C06
-0.78 ATSG Wear Plugged 2
90 95 0.39 13 C07 0.79 ATSG Wear Plugged 2
91 36 0.24 10 C05
-0.82 ATSG Wear Returned to Service 2
91 36 0.25 11 C07
-0.87 ATSG Wear Returned to Service 2
91 86 0.21 10 C03
-0.83 ATSG Wear Returned to Service 2
91 86 0.31 12 C06
-0.9 ATSG Wear Returned to Service 2
91 92 0.27 11 C03
-0.85 ATSG Wear Returned to Service 2
91 92 0.33 12 C04 0.74 ATSG Wear Returned to Service 2
91 94 0.26 11 C03 0.61 ATSG Wear Plugged 2
91 94 0.41 13 C06 0.53 ATSG Wear Plugged 2
91 94 0.34 12 C07 0.57 ATSG Wear Plugged 2
92 37 0.22 10 C06
-0.91 ATSG Wear Returned to Service 2
92 91 0.52 15 C03 0.59 ATSG Wear Plugged 2
92 93 2.28 28 C04 0.77 ATSG Wear Plugged 2
92 93 0.5 15 C06 0.62 ATSG Wear Plugged 2
93 36 0.42 13 C07
-0.82 ATSG Wear Returned to Service 2
93 36 0.29 11 C08
-0.87 ATSG Wear Returned to Service 2
93 38 0.56 15 C06
-0.85 ATSG Wear Plugged 2
93 38 0.2 10 C07
-0.89 ATSG Wear Plugged 2
93 84 0.24 10 C03
-0.81 ATSG Wear Returned to Service 2
93 88 0.59 15 C03 0.59 ATSG Wear Plugged 2
93 92 0.52 15 C04 0.8 ATSG Wear Plugged 2
93 92 0.52 15 C06
-0.72 ATSG Wear Plugged 2
94 37 0.32 12 C07
-0.9 ATSG Wear Returned to Service 2
94 37 0.23 10 C08
-0.88 ATSG Wear Returned to Service 2
94 39 0.23 10 C05
-0.81 ATSG Wear Plugged 2
94 39 0.33 12 C06
-0.86 ATSG Wear Plugged 2
94 39 0.35 12 C08
-0.86 ATSG Wear Plugged 2
94 77 0.18 9
C03
-0.79 ATSG Wear Returned to Service 2
94 83 0.24 10 C03
-0.83 ATSG Wear Returned to Service 2
94 85 0.25 11 C03
-0.79 ATSG Wear Returned to Service 2
94 87 0.28 11 C02
-0.84 ATSG Wear Plugged 2
94 87 0.36 12 C03
-0.79 ATSG Wear Plugged 2
94 87 0.22 10 C05 0.72 ATSG Wear Plugged 2
94 87 0.16 9
C06 0.52 ATSG Wear Plugged 2
94 89 0.83 18 C03 0.79 ATSG Wear Plugged 2
94 89 0.2 10 C04
-0.78 ATSG Wear Plugged
, Watts Bar U2R5 Percent Wall Loss Indications April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 18 of 20 SG Row Col Volts
%TW Locn Inch1 Characterization Resolution 2
94 89 0.2 10 C06 0.67 ATSG Wear Plugged 2
94 91 0.26 11 C03 0.82 ATSG Wear Plugged 2
94 91 0.46 14 C04 0.77 ATSG Wear Plugged 2
94 91 0.55 15 C06
-0.75 ATSG Wear Plugged 2
95 42 0.19 9
C07
-0.85 ATSG Wear Returned to Service 2
95 82 0.27 11 C03
-0.86 ATSG Wear Returned to Service 2
95 84 0.21 10 C05
-0.84 ATSG Wear Returned to Service 2
95 86 0.53 15 C03 0.61 ATSG Wear Plugged 2
95 88 0.25 11 C03
-0.82 ATSG Wear Returned to Service 2
95 90 0.31 12 C03
-0.85 ATSG Wear Plugged 2
95 90 0.69 17 C03 0.8 ATSG Wear Plugged 2
95 90 0.32 12 C04
-0.82 ATSG Wear Plugged 2
95 90 0.24 10 C06
-0.7 ATSG Wear Plugged 2
96 41 0.36 13 C05 0.76 ATSG Wear Plugged 2
96 41 0.74 17 C06
-0.93 ATSG Wear Plugged 2
96 41 0.85 18 C07
-0.87 ATSG Wear Plugged 2
96 41 0.21 10 C08
-0.9 ATSG Wear Plugged 2
96 43 0.3 12 C03
-0.8 ATSG Wear Returned to Service 2
96 43 0.22 10 C06
-0.88 ATSG Wear Returned to Service 2
96 69 0.17 9
C03
-0.86 ATSG Wear Returned to Service 2
96 83 0.48 14 C03
-0.82 ATSG Wear Returned to Service 2
96 85 0.21 10 C04 0.8 ATSG Wear Plugged 2
96 85 0.58 15 C06
-0.62 ATSG Wear Plugged 2
96 87 0.37 13 C03
-0.85 ATSG Wear Plugged 2
96 87 0.57 15 C03 0.79 ATSG Wear Plugged 2
96 89 0.25 11 C04 0.59 ATSG Wear Returned to Service 2
97 40 0.23 10 C05 0.75 ATSG Wear Plugged 2
97 40 0.35 12 C07
-0.83 ATSG Wear Plugged 2
97 40 0.44 14 C08
-0.83 ATSG Wear Plugged 2
97 80 0.21 10 C03
-0.79 ATSG Wear Returned to Service 2
97 82 0.27 11 C03
-0.82 ATSG Wear Returned to Service 2
97 84 0.53 15 C03
-0.81 ATSG Wear Plugged 2
97 84 0.33 12 C07
-0.9 ATSG Wear Plugged 2
97 86 0.18 9
C04 0.82 ATSG Wear Returned to Service 2
97 86 0.23 10 C08
-0.86 ATSG Wear Returned to Service 2
97 88 0.97 19 C03 0.8 ATSG Wear Plugged 2
97 88 0.35 12 C04 0.8 ATSG Wear Plugged 2
97 88 0.36 12 C06
-0.75 ATSG Wear Plugged 2
98 43 0.18 9
C04 0.76 ATSG Wear Returned to Service 2
98 67 0.38 13 VS2 1.01 U-bend Support Structure Wear Plugged 2
98 67 0.48 14 VS4 0.76 U-bend Support Structure Wear Plugged 2
98 67 0.33 12 VS5 1.03 U-bend Support Structure Wear Plugged 2
98 73 0.26 11 C03
-0.9 ATSG Wear Returned to Service 2
98 79 0.35 12 C03
-0.85 ATSG Wear Returned to Service 2
98 81 0.39 13 C03
-0.82 ATSG Wear Returned to Service 2
98 83 0.22 10 C03 0.85 ATSG Wear Returned to Service 2
98 83 0.22 10 C04 0.8 ATSG Wear Returned to Service 2
98 85 0.24 10 C08
-0.88 ATSG Wear Returned to Service 2
98 85 0.25 11 C10
-0.85 ATSG Wear Returned to Service 2
99 74 0.26 11 C03
-0.93 ATSG Wear Returned to Service 2
99 78 0.25 11 C03
-0.84 ATSG Wear Returned to Service 2
99 82 0.33 12 C03
-0.79 ATSG Wear Returned to Service 2
99 84 0.18 9
C03
-0.82 ATSG Wear Plugged 2
99 84 0.58 15 C04 0.8 ATSG Wear Plugged 2
99 84 0.25 11 C05 0.8 ATSG Wear Plugged 2
100 47 0.21 10 C05 0.73 ATSG Wear Returned to Service 2
100 67 0.16 9
C03
-0.92 ATSG Wear Returned to Service 2
100 75 0.34 12 C03
-0.92 ATSG Wear Returned to Service 2
100 81 0.69 17 C03 0.62 ATSG Wear Plugged 2
101 68 0.28 11 C03
-0.86 ATSG Wear Returned to Service 2
101 76 0.45 14 C03
-0.92 ATSG Wear Returned to Service 2
101 80 0.18 9
C04 0.77 ATSG Wear Returned to Service 2
101 80 0.2 10 C05
-0.74 ATSG Wear Returned to Service 2
102 49 0.3 11 C06
-0.83 ATSG Wear Returned to Service 2
102 59 0.3 12 C06
-0.85 ATSG Wear Returned to Service 2
102 67 0.31 12 C03
-0.88 ATSG Wear Returned to Service 2
102 69 0.29 11 C05 0.8 ATSG Wear Returned to Service 2
102 71 0.25 11 C03
-0.84 ATSG Wear Returned to Service 2
102 73 0.13 8
C06 0.79 ATSG Wear Returned to Service
, Watts Bar U2R5 Percent Wall Loss Indications April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 19 of 20 SG Row Col Volts
%TW Locn Inch1 Characterization Resolution 2
102 75 0.3 11 C04 0.81 ATSG Wear Returned to Service 2
102 77 0.71 17 C03
-0.87 ATSG Wear Plugged 2
102 79 0.45 14 C03 0.8 ATSG Wear Plugged 2
102 79 0.63 16 C04 0.82 ATSG Wear Plugged 2
102 79 0.23 10 C05
-0.77 ATSG Wear Plugged 2
103 56 0.17 9
C06
-0.85 ATSG Wear Returned to Service 2
103 60 0.47 14 C06
-0.88 ATSG Wear Returned to Service 2
103 64 0.2 10 C04
-0.86 ATSG Wear Returned to Service 2
103 66 0.25 11 C05 0.69 ATSG Wear Returned to Service 2
103 72 0.29 11 C06
-0.8 ATSG Wear Returned to Service 2
103 72 0.31 12 C07
-0.91 ATSG Wear Returned to Service 2
103 74 0.25 11 C03
-0.83 ATSG Wear Returned to Service 2
103 76 0.23 10 C04 0.78 ATSG Wear Returned to Service 2
104 55 0.23 10 C06
-0.83 ATSG Wear Returned to Service 2
104 55 0.2 10 C07
-0.89 ATSG Wear Returned to Service 2
104 59 0.22 10 C04
-0.88 ATSG Wear Returned to Service 2
104 59 0.43 13 C05
-0.93 ATSG Wear Returned to Service 2
104 63 0.2 10 C04
-0.88 ATSG Wear Returned to Service 2
104 65 0.18 9
C05 0.74 ATSG Wear Returned to Service 2
104 67 0.24 10 C03
-0.86 ATSG Wear Returned to Service 2
104 67 0.27 11 C04
-0.88 ATSG Wear Returned to Service 2
104 69 0.18 9
C04
-0.91 ATSG Wear Returned to Service 2
104 71 0.23 10 C05 0.69 ATSG Wear Returned to Service 2
104 73 0.25 11 C04 0.81 ATSG Wear Returned to Service 2
105 60 0.2 10 C03
-0.82 ATSG Wear Returned to Service 2
105 60 0.34 12 C06
-0.88 ATSG Wear Returned to Service 2
105 62 0.22 10 C05 0.69 ATSG Wear Returned to Service 2
105 62 0.19 9
C06 0.76 ATSG Wear Returned to Service 2
105 66 0.49 14 C03
-0.86 ATSG Wear Plugged 2
105 66 0.28 11 C04
-0.86 ATSG Wear Plugged 2
105 66 0.41 13 C05
-0.88 ATSG Wear Plugged 2
105 66 0.45 14 C06
-0.9 ATSG Wear Plugged 2
105 66 0.24 10 C07
-0.89 ATSG Wear Plugged 2
105 68 0.47 14 C03
-0.89 ATSG Wear Plugged 2
105 68 0.32 12 C04
-0.93 ATSG Wear Plugged 2
105 68 0.2 10 C05
-0.9 ATSG Wear Plugged 2
105 68 1.38 22 C05 0.71 ATSG Wear Plugged 2
105 68 0.24 10 C06
-0.9 ATSG Wear Plugged 2
105 68 1.62 24 C06 0.85 ATSG Wear Plugged 2
105 68 0.22 10 C07
-0.89 ATSG Wear Plugged 3
2 51 0.2 10 H06
-0.99 ATSG Wear Returned to Service 3
2 55 0.26 11 H06
-0.99 ATSG Wear Returned to Service 3
4 1
0.33 12 C05 0.47 ATSG Wear Returned to Service 3
4 127 0.35 12 C03
-0.79 ATSG Wear Returned to Service 3
6 71 0.41 13 H06
-0.84 ATSG Wear Returned to Service 3
83 102 0.25 11 C03 0.71 ATSG Wear Returned to Service 3
85 100 0.21 10 C03 0.71 ATSG Wear Plugged 3
85 100 0.24 11 C06
-0.99 ATSG Wear Plugged 3
85 100 0.25 11 C07
-0.9 ATSG Wear Plugged 3
86 99 0.26 11 C06
-0.92 ATSG Wear Returned to Service 3
88 95 0.21 10 C04
-0.88 ATSG Wear Plugged 3
88 95 0.5 14 C05
-0.95 ATSG Wear Plugged 3
88 95 0.46 14 C06
-0.9 ATSG Wear Plugged 3
88 97 0.78 17 C07
-0.97 ATSG Wear Plugged 3
89 94 0.37 13 C03
-0.77 ATSG Wear Returned to Service 3
89 94 0.35 12 C04
-0.8 ATSG Wear Returned to Service 3
89 96 0.31 12 C07
-1 ATSG Wear Returned to Service 3
90 95 0.24 11 C03
-0.88 ATSG Wear Plugged 3
90 95 0.29 11 C05 0.69 ATSG Wear Plugged 3
90 95 0.21 10 C06
-0.9 ATSG Wear Plugged 3
90 95 0.37 13 C07
-0.95 ATSG Wear Plugged 3
91 94 0.25 11 C05 0.71 ATSG Wear Returned to Service 3
92 37 0.19 9
C05 0.74 ATSG Wear Returned to Service 3
92 87 0.26 11 C03 0.8 ATSG Wear Returned to Service 3
92 93 0.33 12 C04
-0.92 ATSG Wear Returned to Service 3
93 36 0.25 11 C06
-0.81 ATSG Wear Returned to Service 3
93 92 0.27 11 C07
-0.97 ATSG Wear Returned to Service 3
94 37 0.22 10 C03 0.84 ATSG Wear Plugged 3
94 37 0.38 13 C05 0.77 ATSG Wear Plugged
, Watts Bar U2R5 Percent Wall Loss Indications April 2024 Watts Bar U2R5 180 Day Steam Generator Tube Inspection Report R0 Page 20 of 20 SG Row Col Volts
%TW Locn Inch1 Characterization Resolution 3
94 37 0.71 17 C06
-0.89 ATSG Wear Plugged 3
94 91 0.27 11 C06
-0.95 ATSG Wear Returned to Service 3
95 38 1.04 20 C03 0.81 ATSG Wear Plugged 3
95 90 0.42 13 C03 0.69 ATSG Wear Returned to Service 3
97 88 0.28 11 C05 0.69 ATSG Wear Returned to Service 3
101 78 0.39 13 C03
-0.95 ATSG Wear Returned to Service 3
102 73 0.26 11 C05 0.73 ATSG Wear Returned to Service 3
102 79 0.44 14 C03
-0.95 ATSG Wear Returned to Service 3
102 79 0.2 10 C05
-0.93 ATSG Wear Returned to Service 3
103 72 0.28 11 C03
-0.92 ATSG Wear Returned to Service 3
104 57 0.2 10 C04
-0.96 ATSG Wear Returned to Service 3
104 65 0.3 11 C07
-0.97 ATSG Wear Returned to Service 3
104 67 0.41 13 C03 0.76 ATSG Wear Returned to Service 3
104 67 0.18 9
C04
-0.81 ATSG Wear Returned to Service 3
105 64 0.22 10 C05 0.88 ATSG Wear Returned to Service 4
6 127 0.3 11 C03
-0.93 ATSG Wear Returned to Service 4
6 127 0.2 10 C03 0.81 ATSG Wear Returned to Service 4
7 66 0.42 13 H09
-0.89 ATSG Wear Returned to Service 4
8 127 0.26 11 C03 0.74 ATSG Wear Returned to Service 4
11 76 0.36 12 C11
-0.99 ATSG Wear Returned to Service 4
11 126 0.21 10 C03 0.74 ATSG Wear Returned to Service 4
12 77 0.22 10 C11
-0.99 ATSG Wear Returned to Service 4
15 78 0.29 11 C11
-0.99 ATSG Wear Returned to Service 4
16 75 0.32 12 C11
-0.98 ATSG Wear Returned to Service 4
36 123 0.17 9
C06
-0.89 ATSG Wear Returned to Service 4
39 98 0.19 9
C10
-0.95 ATSG Wear Returned to Service 4
46 119 0.19 9
C03 0.84 ATSG Wear Returned to Service 4
69 110 0.16 9
C04 0.85 ATSG Wear Returned to Service 4
90 95 0.19 9
C06
-0.51 ATSG Wear Returned to Service 4
93 36 0.24 11 C06
-0.87 ATSG Wear Returned to Service 4
94 91 0.27 11 C03
-0.89 ATSG Wear Returned to Service 4
95 76 0.16 9
C03
-0.95 ATSG Wear Returned to Service 4
98 63 0.29 11 VS4 0.81 U-bend Support Structure Wear Returned to Service 4
101 64 0.24 11 VS4 0.77 U-bend Support Structure Wear Returned to Service 4
102 49 0.18 9
C05
-0.84 ATSG Wear Returned to Service 4
102 67 0.29 11 VS2 1.08 U-bend Support Structure Wear Returned to Service 4
104 67 0.19 9
C03
-0.9 ATSG Wear Returned to Service 4
104 67 0.19 9
C06
-0.9 ATSG Wear Returned to Service 4
105 60 0.26 11 C05
-0.84 ATSG Wear Returned to Service 4
105 60 0.21 10 C06
-0.79 ATSG Wear Returned to Service 4
105 64 0.32 12 C06
-0.86 ATSG Wear Returned to Service