RNP-RA/10-0130, Steam Generator Tube Inspection Report
| ML110190222 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 01/13/2011 |
| From: | Castell C Progress Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RNP-RA/10-0130 | |
| Download: ML110190222 (15) | |
Text
Progress Energy TS 5.6.8 Serial: RNP-RA/10-0130 JAN 132011' United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261/LICENSE NO. DPR-23 STEAM GENERATOR TUBE INSPECTION REPORT Ladies and Gentlemen:
In accordance with the H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2, Technical Specifications (TS) Section 5.6.8, "Steam Generator Tube Inspection Report," Carolina Power and Light Company, also known as Progress Energy Carolinas, Inc., submits the attached report.
The attachment to this letter provides the steam generator tube inspection report information for Refueling Outage 26 (RO-26) required by TS Section 5.6.8.
If you have any questions concerning this matter, please contact me.
Sincerely, Curt Castell Supervisor - Licensing/Regulatory Programs CAC/psf Attachment c: NRC Resident Inspector, HBRSEP L. A. Reyes, NRC, Region II B. L. Mozafari, NRC, NRR AC)C) I Progress Energy Carolinas, Inc.
Robinson Nuclear Plant ope 3581 West Entrance Road Hartsville, SC 29550
Attachment to Serial: RNP-RA/10-0130 Page 1 of 14 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 REFUELING OUTAGE 26 STEAM GENERATOR TUBE INSPECTION REPORT This report summarizes the Steam Generator (SG) Tube Inspection Program and the results of the examination that was performed at the H. B. Robinson Steam Electric Plant (HBRSEP),
Unit No. 2, during Refueling Outage 26 (RO-26), as required by the HBRSEP, Unit No. 2, Technical Specifications (TS) Section 5.6.8, "Steam Generator Tube Inspection Report."
Scope of Inspections The Steam Generator Tube Inspection Program, during RO-26, included the use of the following three styles of probes:
- 1) A Multi-frequency Bobbin Coil Probe.
- 2) A Motorized Rotating Pancake Coil (MRPC) with Plus Point Coil (+Pt), Pancake Coil, and Shielded Pancake Coil on the attached probe head.
- 3) A Flexible Head Plus Point (+Pt) Probe.
Bobbin Coil (1) examinations were performed on 100% of the inservice tubes in the three steam generators. Full-length Examinations were performed except for Rows 1 and 2, which were inspected from the tube end to top tube support on both Hot Leg (HL) and Cold Leg (CL). Tubes inspected with the bobbin probe were monitored for tube slippage.
The low row U-Bends (rows 1 and 2) are not inspected using the Bobbin Coil Probe due to the small radius in the bend. These tube segments are inspected with the Flexible Head Plus Point Probes (3).
The Top of Tubesheet examinations were performed using a MRPC head with all 3 probe coil types (2). Also, all special interest examinations in the tubesheet, and straight section of the tubing used this probe type.
Flexible Head Plus Point (+Pt) exams, also referred to as Plus Point exams in this document, were performed in the three steam generators. Plus Point (3) exams were performed on 100% of the U-bends on rows 1 and 2 of Steam Generator "A" and on approximately 50% of the U-bends on rows 1 and 2 of Steam Generators "B" and "C."
Plus Point exams were performed on approximately 50% of the tubes on the hot leg at the top of the tubesheet from 4 inches above the tube sheet to 2 inches below the tubesheet. Periphery tubes (i.e., exterior two rows) were inspected on hot leg and cold leg sides including the tube lane in the steam generators from 4 inches above the tubesheet to 2 inches below the tubesheet. Hot leg tubes, in the RO-26 Plus Point inspection plan, that contain bulges, over expansions or dents
Attachment to Serial: RNP-RA/10-0 130 Page 2 of 14 in the tubesheet regions were inspected from 4 inches above the tubesheet to 17 inches below the top of the tubesheet.
Additional Plus Point (+Pt) inspections included a sample of previously identified indications as well as hot leg and cold leg bobbin "I-code" indications that could represent potential degradation of the tube wall (including U-bends), and the unexpanded tube (SG "A" R1C47 cold leg tube sheet [CTS]), and partially expanded tube (SG "B" R25C10 CTS). Inspections by Plus Point (+Pt) coils were performed on surrounding tubes to bound the tubes exhibiting possible loose parts (PLP) signals identified during this inspection effort.
During RO-26, HBRSEP implemented a one-time-only technical specification change referred to as an alternate repair criterion. The following commitments were provided in the license amendment application:
- Monitor for tube slippage as part of the Steam Generator Tube Inspection Program.
All inservice tubes were inspected for tube end slippage. No slippage was identified.
" Perform a one-time verification of the expansion locations to determine if any significant deviations exist from the top of the tubesheet to the bottom of the expansion transition (BET). If any significant deviations are found, the condition will be entered into the plant corrective action program.
HBRSEP AR 00390931 discusses the expected variation in BET position based upon design and manufacturing uncertainties. AR 00390931 documents the maximum expected BET depth of 0.96 inches.
Two tubes are incompletely expanded within the tubesheet region and are therefore not candidates for application of the alternate repair criteria technical specification.
SG "A" R1C47 SG "B" R25C10 Two additional tubes have BET positions below 0.96 inches and are considered to meet the criteria of significant deviations in BET position.
SG "A" R20C35 SG "B" R11C70 Other than these four tubes, there are 578 tubes with BET locations greater than 0.3 inch from the top of the tubesheet (TTS).
SG "A" 120 SG "B" 151 SG "C" 307
Attachment to Serial: RNP-RA/10-0130 Page 3 of 14 Inspect areas of inservice steam generator tubes within the tubesheet that are not fully expanded. The 17.28 inch tubesheet inspection limitation will not be applied to the areas of these tubes that are not fully expanded.
At the time of the HBRSEP inspection, the NRC had not reviewed and approved any technical evaluations justifying BET depths over 0.3 inches to serve as a basis for the submitted technical specification change. The NRC indicated that they will approve the temporary technical specification change for H* if HBRSEP inspects the tube portions within the tubesheet for tubes with BET further than 0.5 inches below the TTS. HBRSEP inspected the tube ends (16 total) not fully expanded within the tubesheet to at least 0.5 inches from the top of the tubesheet.
No degradation or slippage was identified in any of these tube ends.
Attachment to Serial: RNP-RA/10-0 130 Page 4 of 14 The following table summarizes the HBRSEP RO-26 Eddy Current Testing inspection campaign.
Abbreviations are defined at the end of this report.
Condition__ Tube Information Condition SG "A" SG "B" SG "C" Design Number of Tubes 3214 3214 3214 Installed Plugs (pre-inspection) 7 14 11 Bobbin Examinations Probe SG "A" SG "B" SG "C" Full Length 2842 2834 2839 (HTE-CTE)
Cold Leg Straight 365 366 364 (06H-CTE)
Hot Leg Straight 182 183 181 (06H-HTE)
Hot Leg Candy Cane 183 183 183 (06C-HTE)
Bobbin Total Tubes 3207 3200 3203 RPC Examinations Probe SG "A" SG "B" SG "C" Low Row U-Bends 182 92 91 Top of Tubesheet 2154 2288 2370
(+4" / -2")
Tubesheet Region 311 271 179
(+4" / -17.28")
Special Interest, PLP, LPI, LPS, Dents, 182 362 268 Historical, Benign RPC Total Inspections 2833 3022 2910
Attachment to Serial: RNP-RA/10-0 130 Page 5 of 14 Active Degradation Mechanisms The term Active Degradation Mechanism is no longer used in the Electric Power Research Institute (EPRI) steam generator guidelines. Current industry guidelines refer to existing degradation and potential degradation.
EPRI 1013706, "Pressurized Water Reactor Steam Generator Examination Guidelines," Revision 7, October 2007, defines Active Damage Mechanism as:
Historical term that is now synonymous with the term "existing" degradation that is found in the "EPRI Steam Generator Integrity Assessment Guidelines."
EPRI 1019038, "Steam Generator Integrity Assessment Guidelines," Revision 3, November 2009, defines Active Degradation as:
Term used in the Steam Generator Technical Specifications synonymous with the term existing degradation used in this guideline.
EPRI 1019038, "Steam Generator Integrity Assessment Guidelines," Revision 3, defines Existing Degradation as:
Indications of degradation previously and/or currently observed in a Steam Generator.
Existing degradation mechanisms are those mechanical or corrosive processes that have been previously observed at HBRSEP. Three types of tube degradation have been previously identified at HBRSEP and are therefore considered existing.
- Wear due to loose parts or possibly due to outage maintenance activities
- Wear at anti-vibration bar (AVBs) to tube intersections
- Wear at tube support to tube intersections Nondestructive Examination Techniques There has been no indication of corrosion related degradation in any of the HBRSEP, Unit No. 2, steam generators. Volumetric indications of various types of wear have been previously identified such as:
- Anti-Vibration Bar Wear
- Tube Support Wear
" Wrapper Modification Wear
" Potential Maintenance Equipment Wear
" Geometric Conditions at Tubesheet Interface
" Loose Parts Wear
Attachment to Serial: RNP-RA/10-0130 Page 6 of 14 Potential degradation mechanisms are those mechanical and corrosive processes that have not been discovered in prior inspections in the steam generators but are judged to have a potential to occur in the current inspection period based on industry experience and/or laboratory data. The RO-26 inspection plan included the following types of indications:
0 Volumetric Indications at Expansion Transition 9 Primary-Side Stress Corrosion Cracking (PWSCC) and Outside Diameter Intergranular Attack/Stress Corrosion Cracking (ODSCC) at Tubesheet Expansion Transitions
- ODSCC in Sludge Piles and Free Span Locations
- ODSCC at Tube Supports
- PWSCC at Bulges and Over-expansions in the Tubesheet
- PWSCC in the Tubesheet Tube Ends
Attachment to Serial: RNP-RA/10-0130 Page 7 of 14 The Nondestructive Examination (NDE) techniques utilized were taken from the EPRI quality assured database (EPRIQ) and are listed below with their corresponding Examination Technique Specification Sheets (ETSS).
Degradation Mechanism Location Probe Technique ETSS Size Variable Bobbin 96001.1 Mechanical, Loose Wear Parts +Pt 21998.1 Depth Wear AVB Bobbin 96004.2 Depth Bobbin 96004.2 Wear Supports +Pt 21998.1 Depth ODSCC Circ. @ TTS +Pt 21410.1 PDA or crack angle ODSCC Axial @ TTS +Pt 128424 Depth 128425 PWSCC Circ. @ TTS & below +Pt 20510.1 PDA or crack angle PWSCC Axial @ TTS & below +Pt 20511.1 Depth Bobbin 128413 alternate 96008.1 Depth ODSCC Axial @ Sludge Pile, Free Span, Supports +28424
+Pt 1244Depth 128425 ODSCC or Axial Row I and 2 U- +Pt 96511.2 (alternate below)
PWSCC BendDepth ODSCC or Circ Row 1 and 2 U- 96511.2 PWSCC Bend 96511.1 Depth ODSCC or Sample of Dings and +Pt 96703.1 Depth PWSCC Dents Bobbin 96005.2 Pitting TTS +Pt 21998.1 Depth Note: All ETSS are from EPRI Appendix H unless prefixed with an "I". Both Appendix H and Appendix I ETSS are listed for axial ODSCC inspections in the event that difficulties arise during the first time implementation of the Appendix I techniques.
Attachment to Serial: RNP-RA/10-0 130 Page 8 of 14 Service Induced Indications The measured wear depths for the indications are listed in the following tables. Existing wear indications have not changed significantly from previous inspections. Indications that had significant depth or were associated with a loose part were plugged.
Note: Inchl is the distance above reference location.
SG "A" Indications with % Depth Through Wall.
2010 .2007 2004 2002 Row Column Volts % Depth Location Inch 1 % Depth % Depth % Depth 1 1 0.2 15 CTS 13.63 13 19 10 7 1 0.34 19 CTS 0.58 18 18 14 7 1 0.24 17 CTS 0.59 14 18 14 1 2 0.14 13 CTS 13.67 13 15 11 11 2 0.19 16 CTS 0.57 17 20 11 1 3 0.29 19 CTS 15.66 17 19 13 13 3 0.34 19 CTS 0.54 16 22 12 1 4 0.27 17 CTS 15.61 18 20 20 16 4 0.26 17 CTS 0.51 19 19 10 16 4 0.15 15 CTS 0.85 13 17 1 5 0.27 19 CTS 15.76 16 16 7 1 6 0.31 18 CTS 15.59 17 17 11 23 7 0.14 16 CTS 0.5 17 19 11 26 9 0.24 15 CTS 0.55 16 21 13 23 14 0.7 26 HTS 0.08 23 24 26 33 15 0.19 17 CTS 0.63 16 21 9 37 20 0.24 15 HTS 0.61 15 17 15 40 25 0.23 18 CTS 0.47 18 21 14 40 25 0.3 19 CTS 0.68 14 18 42 30 0.14 12 HTS 0.68 13 16 11 42 30 0.15 13 HTS 0.9 14 16 42 30 0.26 18 CTS 0.47 16 19 13 43 33 0.22 17 CTS 0.56 14 18 10 43 33 0.21 17 CTS 0.58 13 17 44 36 0.2 13 CTS 0.64 18 18 14 44 36 0.24 15 CTS 1.75 15 19 hist 43 37 0.19 17 CTS 0.55 15 19 10 43 37 0.26 18 CTS 1.75 16 20 10 33 41 0.54 23 HTS 0.1 22 25 26 34 41 0.58 24 HTS 0.07 23 24 25 45 41 0.2 13 CTS 0.66 17 20 19 27 44 0.44 21 05C -0.82 21 45 47 0.22 14 CTS 2.7 15 18 13 45 47 0.25 15 CTS 6.61 18 20 11
Attachment to Serial: RNP-RA/10-0 130 Page 9 of 14
____-_: ,SG "A" Indikations with %0/Depth Through Wall 2010 2007 2004 2002 Row Column Volts % Depth Location Inchl1 % Depth % Depth O/% Depth 45 52 0.36 18 CTS 0.55 18 21 17 45 52 0.31 17 CTS 0.61 19 22 45 52 0.2 13 CTS 3.67 15 18 8 41 53 0.78 29 HTS 0.08 27 27 29 24 54 0.49 22 03H -0.7 24 25 20 44 57 0.23 14 CTS 0.5 16 21 21 44 57 0.27 15 CTS 0.57 20 19 44 57 0.1 10 CTS 1 13 16 44 57 0.21 14 CTS 1.94 16 19 44 57 0.23 15 HTS 0.77 13 17 12 44 57 0.26 16 HTS 1.27 15 18 14 43 60 0.34 18 CTS 0.59 19 22 17 42 63 0.25 15 CTS 0.63 15 20 11 42 63 0.32 17 CTS 0.72 18 18 42 63 0.16 13 HTS 0.62 12 15 13 40 68 0.32 18 HTS 0.64 17 19 16 40 68 0.24 15 HTS 0.77 17 18 15 36 74 0.22 15 HTS 0.66 13 16 12 31 80 0.26 17 CTS 0.59 16 19 11 26 84 0.26 17 CTS 0.61 15 19 13 23 86 0.3 17 CTS 0.66 17 19 13 23 86 0.21 18 CTS 3.05 13 18 19 87 0.29 17 CTS 7.69 16 19 12 1 89 0.26 16 HTS 15.59 14 16 13 11 91 0.2 15 CTS 0.56 18 18 11 91 0.24 16 CTS 0.67 17 19 12 7 92 0.18 15 CTS 0.63 15 17 9 SG "A" New RO-26 Indications 40 68 0.31 17 CTS 0.63 Leave in service 40 68 0.31 17 CTS 0.89 Leave in service 1 92 0.23 15 HTS 10.85 Leave in service SG "B" Indications with % Depth Through Wall 2010 2007 2004 2002
.'Row Column Volts % Depth Location Inch 1 % Depth % Depth % Depth 1 1 0.22 15 CTS 9.13 13 15 15 1 1 0.15 18 CTS 12.43 17 17 1 1 0.53 22 CTS 12.63 21 20 16 1 1 0.08 16 CTS 13.12 14 22 25 1 1 0.2 18 CTS 15.51 17 17 16 2 1 0.24 13 CTS 5.56 15 15
Attachment to Serial: RNP-RA/10-0130 Page 10 of 14 SG "B" Indications with % Depth -Through Wall
.2010 . 2007. 2004 2002 Row Column Volts % Depth Location Inch 1 % Depth % Depth % Depth 2 1 0.2 12 CTS 10.22 17 17 17 2 1 0.3 18 CTS 11.63 17 17 16 6 1 0.24 17 CTS 0.52 15 15 15 7 1 0.15 15 CTS 0.66 13 13 14 7 1 0.21 12 CTS 1.18 13 17 15 7 1 0.24 13 CTS 12.8 16 16 19 11 2 0.31 15 CTS 0.56 17 19 17 16 4 0.25 19 CTS 0.5 17 16 15 23 7 0.27 18 HTS 0.68 14 14 16 26 9 0.85 19 HTS 0.62 19 20 17 25 11 0.68 26 04C -0.64 24 23 7 16 0.26 19 CTS 16.11 18 17 17 37 20 0.22 13 CTS 0.61 17 17 37 20 0.22 13 CTS 0.63 15 16 20 37 20 0.77 18 HTS 0.6 15 17 40 25 0.51 20 CTS 0.64 22 16 21 40 25 0.16 11 CTS 0.65 20 22 40 26 0.16 11 CTS 0.43 16 18 4 32 0.44 NQS CTS 3.12 20 20 4 32 0.37 NQS CTS 6.1 18 18 2 41 0.47 22 CTS 1.19 18 18 2 42 0.54 24 CTS 1.46 27 26 24 34 44 0.7 28 HTS 0.07 26 26 3 45 0.36 19 CTS 1.42 19 19
.4 47 0.29 17 CTS 1.42 16 14 4 47 0.3 17 CTS 1.44 16 15 4 48 0.33 19 CTS 1.59 17 17 4 48 0.77 30 CTS 3.34 28 27 5 48 0.79 28 CTS 1.53 28 27 27 4 49 0.33 18 CTS 1.5 20 17 5 49 0.72 28 CTS 1.69 27 26 28 4 50 0.33 19 CTS 1.88 16 15 11 53 0.65 26 CTS 1.27 26 25 43 60 0.33 18 CTS 0.59 18 18 27 65 0.46 23 03H 0.07 19 18 1 67 0.14 INR 06C -0.54 25 18 10 1 67 0.1 1NR 06C 0.61 24 17 7 40 67 0.14 13 CTS 0.54 13 13 40 68 0.31 18 CTS 0.63 18 18 34 76 0.37 18 CTS 1.92 21 21 33 78 0.37 19 CTS 0.61 16 17 18 33 78 0.37 19 CTS 0.68 18 17 18
Attachment to Serial: RNP-RA/10-0 130 Page 11 of 14
_ _SG "B" Indications with 0 Depth Through Wall 2010 2007 2004 2002 Row Column Volts, % Depth Location Inch 1 %'Depth % Depth % Depth 26 84 0.39 19 CTS 0.67 17 20 20 23 86 0.36 18 CTS 0.62 19 18 16 89 0.39 18 CTS 0.6 21 21 1 92 0.08 13 HTS 2.02 12 13 13 1 92 0.24 17 HTS 2.88 16 15 17 1 92 0.15 15 HTS 13.91 15 13 14 2 92 0.25 17 CTS 11.2 14 17 15 SG "B" New RO-26 Indications 1 1 0.18 18 CTS 14.57 Leave in service 7 5 0.43 21 HTS 0.2 Leave in service 1 21 0.72 29 04C -0.59 Leave in service 35 30 1.29 40 FBC 0.47 Plug/Stabilize 36 30 1.33 40 FBC 0.45 Plug/Stabilize 38 30 0.66 27 FBC 0.42 Plug/Stabilize 39 30 0.65 27 FBC 0.43 Plug/Stabilize 40 30 2.78 60 FBC 0.52 Plug/Stabilize 43 33 0.26 14 CTS 0.67 Leave in service 3 43 0.42 21 CTS 1.38 Leave in service 4 43 0.62 26 03C -0.62 Leave in service 10 46 0.37 19 HTS 3.16 Leave in service 34 61 0.45 22 05C -0.86 Leave in service 28 63 3.04 64 02H -0.58 Plug 1 92 0.26 17 CTS 10.41 Leave in service SG "C" Indications with % Depth Through Wall 2010 2007. 2004 2002
,Row Column Volts % Depth Location Inchi % Depth % Depth % Depth 7 1 0.21 18 CTS 0.58 15 15 15 44 38 0.31 16 HTS 0.55 17 17 16 34 50 0.61 23 HTS 0.04 23 24 14 34 51 0.45 19 HTS 0.03 20 21 7 35 51 0.37 17 HTS 0.06 18 19 44 57 0.3 16 HTS 0.51 17 16 16 44 57 0.28 15 HTS 1.19 16 15 15 44 57 0.3 20 CTS 0.7 18 19 33 75 0.61 23 03H -0.77 21 35 75 0.24 19 CTS 1.49 17 17 33 78 0.2 13 HTS 0.72 14 18 18
.3 91 0.69 25 HTS 0.34 25 24 23 SG "C" New RO-26 Indications 18 7 0.75 28 05C -0.63 Leave in service
Attachment to Serial: RNP-RA/10-0130 Page 12 of 14 8 15 1.2 37 04C -0.58 Plug/Stabilize 25 15 0.53 23 03C -0.65 Leave in service 6 27 0.99 31 02H -0.57 Leave in service 39 41 0.87 31 03H -0.55 Leave in service 15 45 0.24 16 02H -0.8 Leave in service 32 46 2.34 51 03H -0.56 Plug 28 61 0.61 24 O0A -1.08 Leave in service 30 69 0.42 20 02H -0.71 Leave in service 23 70 1.01 33 05C -0.86 Plug/Stab 27 71 1.44 41 04C -0.57 Plug 8 76 0.63 26 04H -0.82 Leave in service 8 85 0.31 18 03H -0.73 Leave in service Wear at Anti Vibration Bars Tube Information 2010 2007 2004 2002 2001 (RO-26) (RO-24) (RO-22) (RO-2 1) (RO-20)
SG Row Column Location % DEPTH % DEPTH % DEPTH % DEPTH % DEPTH Z-22899 Z-8652 Z-8652 Z-8652 Z-8652 Z-8652 C 37 45 03A 29 9 10 7 6 6 C 37 45 04A 26 7 10 6 4 3 C 35 61 02A 23 6 7 6 5 5 C 35 61 03A 25 7 5 5 3 5 C 35 61 04A 5 1 5 2 C 38 62 02A 18 4 6 4 3 4 C 38 62 03A 39 15 15 14 11 13 C 45 42 02A 18 C 40 52 04A 9 C 35 61 O0A 12 C 38 62 04A 13 C 35 73 04A 16 C 32 78 03A 12 B 40 30 02A 9 B 35 36 03A 13 B 37 72 O0A 12 B 37 72 03A 11 Note: Wear at AVBs was measured in RO-26 with two standards, Z-22899 and Z-8652.
Standard Z-22899 indicates greater wear depth; however, when comparing the data to that of Eddy Current Testing results obtained using Z-8652 during the last four inspections, no increase in wear rate was noted.
Wear at Supports Wear indications were interrogated and conservatively sized by the Plus Point probe. These indications, as well as those from previous inspections, are included in the table above as percent depth through wall. The observation that pre-existing depths did not increase implies that the
Attachment to Serial: RNP-RA/10-0 130 Page 13 of 14 cause of wear is no longer present for these indications. It is likely that the wear has not been support wear, but was caused by a transient loose part that is no longer present at that location.
Number of Tubes Plugged During RO-26 A total of twelve tubes were plugged during the RO-26 Steam Generator inspection/repair effort.
These twelve tubes showed signs of mechanical wear believed to have been caused by either foreign material (loose parts wear) or maintenance activities. In Steam Generator "B," seven tubes were plugged, six of those tubes being stabilized. In Steam Generator "C" five tubes were plugged, two of those tubes being stabilized.
Tubes Plugged to Date In 1984, the HBRSEP, Unit No. 2, steam generators were replaced with Westinghouse Model 44F steam generators with alloy 600 thermally treated tubes. The current analysis supports up to 6% tube plugging. Prior to RO-26 there were 32 plugged tubes. With the 12 tubes plugged in RO-26, there are a total of 44 plugged tubes out of a population of 9642 for the three steam generators. This brings the total plugging to 0.5% as compared to the analysis limit of 6%.
Condition Monitoring As has already been stated, the only degradation identified was due to mechanical wear.
- All mechanical wear indications remaining in service, listed previously as percent through wall, have depths that are significantly less than the condition monitoring limit.
- Most of these indications were reported in previous inspections. Comparisons of current percent through wall depths to previous inspection results indicate no significant growth of previously reported indications.
- All tubes with indications that remain in contact with a loose part have been plugged and stabilized. Indications caused by a loose part that is no longer present are not expected to grow during the two operation cycles.
- The tubes remaining in service that have been identified with indications will be inspected every two refueling cycles.
Therefore, the structural and leakage limits are expected to be satisfied until the next scheduled steam generator inspection.
Tube Pulls There were no tube pulls in RO-26.
Insitu Testing There was no insitu pressure testing in RO-26.
Attachment to Serial: RNP-RA/10-0130 Page 14 of 14 Evaluation of Primary to Secondary Leakage Rate A steam generator primary-to-secondary leak in Steam Generator "A" was documented in the February 2008 timeframe, during Cycle 25 operation (AR 265599). The leakage varied during cycle 25, averaging less than 0.020 gpd, and never exceeding 0.040 gpd over about a five month period. It was possible to measure this small leakage in Cycle 25 because a fuel assembly was leaking and providing a high primary side source term. The leaking fuel assembly was removed from service during RO-25. Cycle 26 and Cycle 27 have been free of leaking fuel; therefore, the primary-to-secondary leakage cannot be detected. The RO-26 steam generator inspection plan included ECT inspections of all in-service Steam Generator "A" tubes to increase the potential identification of the source of this leakage.
No steam generator inspections, tube repairs or plugging took place during RO-25. The leakage in Steam Generator "A" is believed to exist below the minimum detectable level. All open tubes were inspected in Steam Generator "A" during RO-26. No site for potential leakage was detected and no tubes were plugged in Steam Generator "A."
Utilizing the bounding value of 0.040 gpd and assuming this leakage was from the region below H*, the portion of the tubes 17.28 inches below the top of the tubesheet, the operational leakage is increased by a factor of 1.82 when calculating an accident leakage. This increase in measured (operational) leakage results in a calculated (accident) leakage of 0.073 gpd.
Tube slippage Tube slip monitoring was performed on all tube ends for which bobbin data was collected. For RO-26 this was all open tubes in all three steam generators. No indications of tube slippage were identified.
Abbreviations:
CTS - Cold leg top-of-tubesheet 02C - Cold leg second support plate HTS - Hot leg top-of-tubesheet 02H - Hot leg second support plate FBC - Flow distribution baffle on cold leg side 03C - Cold leg third support plate CTE - Cold leg tube end 03H - Hot leg third support plate HTE - Hot leg tube end 04C - Cold leg fourth support plate INR - Indication not recordable 04H - Hot leg fourth support plate NQS - Non-quantifiable signal 05C - Cold leg fifth support plate 02A - Anti-vibration bar 2 05H - Hot leg fifth support plate 03A - Anti-vibration bar 3 06C - Cold leg sixth support plate 04A - Anti-vibration bar 4 06H - Hot leg sixth support plate PDA- Percent degraded area