ML20056D895
| ML20056D895 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 05/31/1993 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19310D609 | List: |
| References | |
| WCAP-13699, WCAP-13699-R01, WCAP-13699-R1, NUDOCS 9308180237 | |
| Download: ML20056D895 (193) | |
Text
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WESTINGHOUSE CLASS 3 .;
WCAP-13699 SG-93-054)23 Rev.1 -
l LASER WELDED SLEEVES ,
'FOR
. 3/4 INCH DIAMETER TUBE FEEDRING-TYPE AND WESTINGHOUSE PREHEATER STEAM GENERATORS Generic Sleeving Report i
1 May 1993 c *
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01993 Westinghouse Electric Corporation ,
All Rights Reserved WESTINGHOUSE ELECTRIC COPSORATION NUCLEAR SERVICES DIVISION .
P.O. BOX 355 PITTSBURGH, PA 15230
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,.93Oli190237 930813 W:
PDR ;ADOCK 05000454- f
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- WPF1147A-T:1b/052893 r
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ABSTRACT
'Ihis report provides the technical basis for licensing the use of the Westinghouse Laser Welded Sleeve (LWS) technique to return a 3/4 inch diameter tube with indications of degradation to an operable condition. This report summarizes the generic design, stmetural, thermal-hydraulic, materials and inspection analyses and corrosion and mechanical tests, as well as installation processes of two distinct types of sleeves. It addresses a tubesheet sleeve and a tube support sleeve for Combustion Engineering feedring-type steam generators and for Westinghouse Models D3, D4, D5, El and E2 preheater-type steam
. generators, all of which utilize 3/4 inch outside diameter tubes.
The Westinghouse LWS technique has been licensed previously for use within 7/8 inch diameter steam
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generator tubing, has been installed and is in operation. That technology base and the technology base for the hybrid expansion joint (HEJ) technique for sleeving are utilized herein with the described evaluations to form the technical basis for the LWS technique for 3/4 inch diameter tubing.
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l TABLE OF CONTENTS Section Title Page
1.0 INTRODUCTION
1-1 1.1 Report Applicability 1-2 1.2 Sleeving Boundary 1-3 1.
2.0 SLEEVE DESCRIPTION AND DESIGN 2-1
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2.1 Sleeve Design Description 2-1 l
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. 2.1.1 Tubesheet Sleeve 2-1 2.1.2 Tbbe Support Sleeve 2-2 2.1.3 Sleeving of Previously Plugged Tubes 2-3 2.2 Sleeve Design Documentation 2-3 2.2.1 Weld Qualification Program 2-3 l
2.2.2 Weld Qualification Acceptance Criteria 2-4 3.0 ANALYTICAL VERIFICATION 3-1 3.1 Structural Analysis 3-1 3.1.1 Component Description 3-1.
3.1.2 Summary of Material Properties 3-2 3.1.3 Applicable Criteria 3-3 3.1.4 Loading Conditions Considered 3-3 3.1.5 Analysis Methodology 3-3 3.1.6 Heat Transfer Analysis 3-8 3.1.7 Tubesheet/Channelhead/Shell Evaluation 3-9 3.1.8 Stress Analysis 3-9 3.1.9 ASME Code Evaluation 3 10 3.1.10 Minimum Required Sleeve Wall Thickness 3-11 3.1.11 Determination of Plugging Limits 3-12 3.1.12 Application of Plugging Limits 3-13 3.1.13 Analysis Conclusions 3-13 3.2 'Ihermal Hydraulic Analysis 3-49
. 3.2.1 Safety Analysis and Design Transients 3-49 3.2.2 Equivalent Plugging Level 3-49 3.2.3 Fluid Velocity 3 3.3 Sleeved Tube Relative Flow Induced Vibration Assessments 3-58 3.3.1 Flow Induced Vibration Evaluation Methodologies 3-58 3.3.2 Effects of Damping on Relative Evaluations 3-60 3.3.3 Flow Induced Vibration Results and Conclusions 3-60 3.4 References 3-74
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TABLE OF CONTENTS (cont) l
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Section Title Page l i
l 4.0 MECHANICAL TESTS 4-1 i 4.1 Tubesheet HEJ Tests - 3/4 Inch Tube Sleeve 4-2 ;
4.1.1 Case No.1 - Westinghouse Steam Generator (WSG) 4-2 j 4.1.2 Case No. 2 - CE Feedring Steam Generator 4-13 l 4.2 Tubesheet HEJ, Free Span and Tubesheet LWS Tests - 7/8 Inch Tbbe Sleeves 4-20 ~ -
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4.3 Acceptance Criteria - 7/8 Inch Tubesheet HEJ Sleeves 4-23 f
4.4 Results of Testing - 7/8 Inch Sleeves 4-23 .
j 4.4.1 HEJ Lower Joint 4-23 I
4.4.2 Free Span Joint Mechanical Testing 4-28 4.5 References 4-34 5.0 STRESS CORROSION TESTING OF LASER WELDED SLEEVE JOINTS 5-1 5.1 Corrosion Test Description 5-1 5.2 Corrosion Resistance of Free-Span Laser Welded Joints- 5-2 As-Welded Condition 5.3 Conosion Resistance of Free-Span Laser Welded Joints-with Post Weld 5-3 Stress Relief 5.4 Corrosion Resistance Evaluation of Lower Tubesheet Sleeve- 5-4 Laser Welded Joints 5.5 Effects of Sleeving on Tube-to-Tubesheet Weld 5-4 5.5.1 Lower HEJ Joint 5-4 51 2 Lower Seal Weld .
5-4 5.6 Outside Diameter Surface Condition 5-5 5.7 References 5-17 6.0 INSTALLATION PROCESS DESCRIPIlON 6-1.
6.1 Tube Preparation 6-1 6.1.1 Tube End Rolling (Contingency) 6-1 -
6.1.2 Tube Cleaning 6-2 6.2 Sleeve Insertion and Expansion 6-2 ,
6.3 HEJ Lower Joint (Tbbesheet Sleeves) 6-4 6.4 General Description of Laser Weld Operation 6-5 6.5 Rewelding 6-5 6.6 Post-Weld Heat Treatment [ ]" 6-6 6.6.1 Post-Weld Heat Treatment Tooling . 6-6 6.6.2 Post-Weld Heat Treatment Process 6-6 6.7 Inspection Plan 6-14 6.8 References 6-14 WPF1147A-T:1blD60193 iii
l TABLE OF CONTENTS (cont)
Section Title Page 7.0 NDE INSPECTABILITY 7-1 7.1 Inspection Plan Logic 7-1 7.2 General Process Overview of Ultrasonic Inspection 7-2 7.2.1 Principle of Operation and Data Processing of Ultrasonic Examination 7-2
.. 7.2.2 Ultrasonic Inspection Equipment and Tooling 7-4
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7.2.3 Laser Weld Test Sample Results 7-6 7.2.4 Ultrasonic Inspection Summary 7-6 7.3 Eddy Current Inspection 7-11 7.3.1 Eddy Current Inspection Principle of Operation 7-11 7.3.2 Transition Region Eddy Current Inspection 7-12 7.3.3 Laser Weld Region Eddy Current Inspection 7-2.0 i
l 7.3.4 Eddy Current Inspection Summary 7-24 7.4 Alternate Post Installation Acceptance Methods 7-24 7.4.1 Bounding Inspections 7-24 7.4.2 Workmanship Samples 7-27 7.4.3 Other Advanced Examination Techniques 7-27 7.5 Inservice Inspection Plan for Sleeved Tubes 7-27 7.6 References 7-28 WPF1147A-T:HA)S2693 jy
LIST OF TABLES
- Table Title Page 2-1 ASME Code Rules and Regulatory Requirements 2-5 3-1 Summary of Material Properties Alloy 600 Tube Material 3-14 3-2 Summary of Material Propenies-Sleeve Material- 3-15 ,.
'Ihermally Treated Alloy 690 3-3 Summary of Material Properties- 3-16 -
Tubesheet Material SA-508 Class 2 3-4 Summary of Material Propenies Air 3-17.
3-5 Summary of Material Properties Water 3-17 3-6 Criteria for Primary Stress Intensity Evaluation 3-18 (Sleeve)-Alloy 690 l 3-7 Criteria for Primary Stress Intensity Evaluation 3-18 (Tube)-Alloy 600 3-8 Criteria for Primary Plus Secondary Stress 3-19 Intensity Evaluation Sleeve-Alloy 690 3-9 Criteria for Primary Plus Secondary Stress 3-19 Intensity Evaluation Tube-Alloy 600 3-10 Summary of Transient Events 3-20 3-11 Umbrella Pressure Loads for Design, 3-22 Faulted, and Test Conditions 3-12 Stress Modification Factors 7/8 Inch to 3/4 Inch Tube Sleeves 3-23 3-13 Tubesheet Comparisons for Westinghouse Steam Generators 3-24 3-14 Comparison of Tubesheet Stresses for FSG and Series 51 3-25 Steam Generators RTF1147A-T.1bOS2693 v
LIST OF TAllLES (cont)
Table Title Page I
3-15 Transient Stresses at Sleevernibe Weld-Series 51 SG 3-26 3-16 Ratio of Model D, E and FSG to Series 51 SG Transient Stresses 3-27 L
- 3-17 Summary of Maximum Primary Stress Intensity-Full Length 3-28 ,;
Tubesheet Laser Welded Sleeve-Sleeve /Ibbe Weld i
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, Width [ ]" [ ]
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3-18 Maximum Range of Stress Intensity and Fatigue- 3-29 ]
Full Length Tubesheet Laser Welded Sleeve-Sleeve /Ibbe ,
Weld Width [ ][ J j 3-19 Summary of Minimum Wall Thickness Calculations-Laser Welded Sleeve 3-30 3-20 Summary of Recommended Plugging Margins-Laser Welded Sleeves 3-31 3-21 Ilydraulic Equivalency Sensitivity Study 3 53 3-22 3/4 lach Tube-Laser Welded Sleeve Evaluations-Tube and 3-63 Sleeve Cross Sectional Properties 3-23 3/4 Inch Tube-Laser Welded Sleeve Evaluations-Sleeve 3-64 Position Definitions and Lengths 3-24 Laser Welded Sleeve Relative Evaluations lbbe 65 Density Distribution Estimates
. 3-25 Laser Welded Sleeve Superelement Geometry and Nodes 3-66 for Models D3, D4 and D5 SGs 3-26 Model E2 LWS Superclement Geometry and Nodes 3-67 3-27 FSG (Specific Case) LWS Superelement Geometry and Nodes - 3-68 WPFil47A-T:lh052893 vi
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LIST OF TABLES (cont) .'
Table Title Page j i
3-28 Relative Flow Induced Vibration Evaluation Results- 3 {
for Laser Welded Sleeve Configuration with Various Tube Suppon Plate Boundary Conditions f i
4-1 Case No.1 - Westinghouse Steam Generator Mechanical Test 4-3 ,
Program Summary-Tubesheet HEJ Tests -3/4 Inch Tube Sleeves l
t 4-2 Typical Bounding Maximum Allowable Leak Rates for 4-6 -
Feedring-Type and Preheater Steam Generators ;
I 4-3 Verification Phase Test Results-Lower Joint 4-8 ,
(HEJ)-Alloy 690 Sleeve for 3/4 Inch Tube 4-4 Case No. 2-FSG Mechanical Test Progmm Summary- 4-14 i Tubesheet HEJ Tests-3/4 Inch Tube Sleeves (FSG) ;
4-5 Verification Phase Test Results-I.ower Joint 4-15 . [
(HEJ)-Alloy 690/625 Bimetallic Sleeve for 3/4 Inch Tbbe (FSG) ;
4-6 Mechanical Test Program Summary-Tubesheet HEJ Tests- 4-22 7/8 Inch Tube Sleeves 4-7 Verification Test Results for HEJ Lower Joints- 4-24 7/8 Inch Sleeves ,
4-8 Verification Test Results for HEJ Lower Joints with Exceptional 4 f Conditions for Tube and Sieeve - 7/8 Inch Sleeves ,
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4-9 Additional Verification Tests Results for HEJ Lower Joints with 4-27 Exceptional Conditions for Tube and Sleeve - 7/8 Inch S1ceves - ;
4-10 HEJ Lower Joint Test Results (with Seal Weld) - 7/8 Inch Sleeves 4-31 ;
4-11 Free Span Joint Maximum Stress Relief Temperature - 7/8 Inch Sleeves 4-32 I
4-12 Free Span Joint Leak Rate and Loading Data - 7/8 Inch Sleeves 4-33 !
WIT 1147A-T:Ib/052893 vii
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LIST OF TABLES (cont)
Table Title Page 5-1 Sununary of Accelerated 750*F Steam Corrosion Test Results 5-12 for YAG Laser Sleeve Welds 5-2 Corrosion Resistance Evaluation of Lower Tubesheet 5-15
. Laser Welded Sleeve Joints 6-1 Sleeve Process Sequence Summary 6-3 47F1147A T lt,052693 viii
LIST OF FIGURES Figure Title Page 2-1 Tubesheet Full-Length Laser Welded Sleeve 2-6 Installed Configuration 2-2 Tubesheet Elevated Laser Welded Sleeve 2-7 Installed Configuration .
2-3 Tube Support Laser Welded Sleeve Installed Configuration 2-8 3-1 Schematic of Tubesheet Sleeve Configuration 3-32 3-2 Upper LWJ Comparison Model-Full Model 3-33 3-3 Upper LWJ Comparison Model-Weld Zone 3-34 3-4 ASN Location-Upper LWJ 3-35 3-5 Finite Element Model of FSG Channel 3-36 Head /Tubesheet/Shell 3-6 FSG Channel Head /Tubesheet/Shell Model Primary 3-37 Pressure boundary Conditions and Deformed Geometry 3-7 FSG Channel Headmibesheet/Shell Model Tubesheet 3-38 Expansion Boundary Conditions and Deformed Geometry ]
l 3-8 Finite Element Model of Sleeve / Tube Weld for Thermal 3 9-Transient Stresses 3-9 Thermal Hydraulic Tubesheet Sleeve Analysis Boundary 3-40 -
Condition
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3-10 Boundary Condition for Unit Primary Pressure 3-41
[ ]"# Peu > Psse 3-11 Boundary Condition for Unit Primary Pressure 3-42
[ ]"# Ppm < Psw l
%7F1147A-T:1bC52893 ix
LIST OF FIGURES (cont)
Figure Title Page 3-12 Boundary Condition for Unit Primary Pressure 3-43
[ ]"" Pym > Psse 3-13 Boundary Condition for Unit Primary Pressure 3-44
- [ ]"" Ppm < Psee 3-14 Boundary Condition for Unit Secondary Pressure 3-45
[ ]"# Ppm > P33c 3-15 Boundary Condition for Unit Secondary Pressure 3-46 i ]"" Ppm < Psse 3-16 Boundary Condition for Unit Secondary Pressurc [ 3-47
]"" Ppm > P3sc I
3-17 Boundary Condition for Unit Secondary Pressure [ 3-48
]"" Pro < Psse 3-18 Hydraulic Equivalency Number 3/4 In. OD Tube, Model D S/G 3-55 3-19 Hydraulic Equivalency Number 3/4 In. OD Tube, Model E S/G 3-56 3-20 Hydraulic Equiva'ency Number 3/4 In. OD Tube, FSG - 3-57 i
3-21 LWS Effects on Stability Ratio [ 3-70 ju
. 3-22 LWS Effects on Stability Ratio [ 3-71 ju,
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3-23 LWS Effects on Turb. Response [ 3-72 3ua 3-24 LWS FJfects on Turb. Response [ 3-73 g-ju, 4-1 Tubesheet Sleeve Lower Joint Test Specimen 4-4 WPn H7A-TJtM:893 x
LIST OF FIGURES (cont)
Figure Title Page 4-2 Free-Span Laser Welded Joint Test Specimen 4-30 5-1 Accelerated Conosion Test Specimen for Welded Joint 5-6 Configuration l
5-7 5-2 Accelerated Corrosion Test Specimen for Lower Tubesheet Sleeve Welded Joint Configuration
- 5-3 Accelerated Corrosion Test Specimen for Roll Transition 5-8 Configuration 5-4 IGSCC in Alloy 600 Tube of YAG Laser Welded Sleeve 5-9 Joint After 109 Hours in 750 F Steam Accelerated Corrosion Test l 5-5 Cumulative Per Cent Cracking For CO2 Laser Welded 5-10 Sleeves in 750*F Accelerated Steam Corrosion Test 5-6 Cumulative Per Cent Cracking For CO2 Laser Welded 5-11 Sleeves in 750*F Accelerated Steam Corrosion Tests 5-7 Cumulative Per Cent Cracking For YAG Laser Welded 5-13 Sleeves in 750 F Accelerated Steam Corrosion Test 5-8 Minor IGSCC in Alloy 600 Tube of Stress Relieved 5-14 YAG Laser Welded Sleeve Joint After 1000 Hours in 750*F Steam Accelerated Corrosion Test 5-9 Illustration of Path of IGSCC in the Alloy 600 5 Tube of Lower Tubesheet Sleeve Welded Joint Crack
- Initiated at Point A and Progressed to Point B .
6-1 Laser Welded Sleeve With Reweld 6-9 WPF1147A-T:ltt052893 xi
LIST OF FIGURES (cont)
Figure Title Page 6-2 Vertical Test Stand Mock-up 6-10 6-3 Initial Stress Relief Test Samples Detailed 6-11 6-4 Field Prototypic Stress Relief Test Samples Detailed 6-12 6-5 Typical Stress Relief Power Profile 6-13 l
l 7-1 Ultrasonic Inspection of Welded Sleeve Joint 7-3 7-2 Typical Digitized UT Waveform 7-5 7-3 C-Scan From UT Examination of an Acceptable Laser Weld 7-7 7-4 UT Setup Standard 7-8 7-5 C-Scan from UT Examination of an Equipment Setup 7-9 Standard 7-6 C-Scan from UT Examination of Workmanship Sample 7-10 of a Laser Welded Sleeve with two EDM Notches 7-7 [ ]"" Calibration Curve 7-13 7-8 Eddy Current Signals from the ASTM Standard, 7-14 Machined on the Sleeve O.D. of the Sleeve / rube Assembly Without Expansion (Cross Wound Coil Probe) 7-9 Eddy Current Signals from the ASTM Standard, 7-15 Machined on the Tube O.D. of the Sleeve / rube Assembly Without Expansion (Cross Wound Coil Probe) 7-10 Eddy Current Signals from the Expansion Transition 7-16 Region of the Tube / Sleeve Assembly (Cross Wound Coil Probe)
W7Fil47A-TJba)52603 xii
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Figure Title Page 7-11 Eddy Current Calibration Curve for ASTM Tbbe 7-17 Standard at [ ]"# and a Mix Using the Cross Wound Coil Probe
) 7-12 Eddy Current Signai from a 20 Per Cent Deep Hole, 7-18 ,
Half the Volume of ASTM Standard, Machined on - I the Sleeve O.D. in the Expansion Transition ^ '
Region of the Sleeve /fube Assembly (Cross Wound ,
Coil Probe) r 7-13 Eddy Current Signal from a 40 Per Cent ASTM 7-19 Standard, Machined on the Tube O.D. in the Expansion Transition Region of the Sleeve / rube Assembly (Cross Wound Coil Probe) 7-14 Eddy Current Response of the ASTM Tube Standard 7-21 at the End of the Sleeve Using the Cross Wound Coil Probe and Multifrequency Combination I
7-15 Crosswound [ ]"" Eddy Current Baseline of 7-22 Laser Weld 7-16 Crosswound Mix Eddy Current Response Baseline of 7-23 Laser Weld 7-17 Crosswound [ ]"# Eddy Current Response After 7-25 l 40 Per Cent Flat Bottomed Hole was Placed in OD of . j Tbbe at Center of Weld ,
7-16' Crosswound Mix Eddy Current Response After 40 Per Cent 7-26 .
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Flat Bottomed Hole was placed in OD of Tbbe at . -
l Center of Weld i
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1.0 INTRODUCTION
Under Plant Technical Specification requirements steam generator (SG) tubes are periodically inspected for degradation using non-destructive examination techniques. If established inspection criteria are exceeded, the tube must be removed from service by plugging or the tube must be brought back into !
compliance with the Technical Specification Criteria. Tube sleeving is one technique used to return the (
tube to an operable condition. hbe sleeving is a process in which a smaller diameter tube or sleeve is positioned to span the area of degradation. It is subsequently secured to the tube, forming a new pressure !
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- boundary and structural element in the area between the attachment points.
This report presents the technical bases developed to support licensing of the laser welded sleeve ,
installation process for use in 3/4" diameter tubing. Two distinct types of sleeves are addressed, a tubesheet sleeve and a tube support sleeve. Each of these sleeve types has several installation options which can be applied. Dere are two types of tubesheet sleeves. De first one extends the full length of the tube within the tubesheet, is joined to the tube in the vicinity of the tubesheet bottom and is referred to as the full length tubesheet sleeve (FLTS). The other type extends over approximately one-third of the ;
tube length within the tubesheet, is joined to the tube approximately 14 inches above the tubesheet bottom and is referred to as the elevated tubesheet sleeve (ETS). De latter type of sleeve allows much greater radial coverage of the bundle,i.e., installation closer to the bundle periphery, than the FLTS. he FLTS is appropriate for all plants which have degradation at the top of the tubesheet, and/or within the tubesheet above the lower joint since the lower joint is formed at the bottom of the tubesheet. Depending on the j length of the FLTS and elevation of the lowest baffle / support in the bundle, this sleeve may also address :
degradation above the tubesheet top. He ETS is appropriate for all plants with SG tubes which'have degradation at the top of the tubesheet, and/or within a distance of several inches below the top of the ;
tubesheet. Depending on the length of the ETS and elevation of the lowest baffle / support in the bundle, this sleeve may also address degradation above the tubesheet top. De tube support sleeve (TSS) may be installed to bridge degradation located at tube support locations or in the free span section of the tube.
The types of tube supports include flow distributica banic. drilled plates and grids (a.k.a., "eggerates").
i Ris technical basis forlaser welded sleeves is applicable to Combustion Engineering feedring-type steam generators, (FSGs) and Westinghouse Model D3, D4, DS, El and E2 steam generators of the
. preheater-type design (PSGs), all of which utilize 3/4 inch OD tubing. *
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1.1 Report Applicability Each FSG tube bundle contains both U-tubes and modified U-tubes. The modified U-tubes are designed j such that the bends at the bundle top have horizontal extent. All of the FSG heat transfer tubes are Alloy 600 and have a nominal OD of 3/4 inch and a nominal wall thickness of 0.048 inch. The PSGs .
are U-tube heat exchangers with Alloy 600 heat tansfer tubes which have a 3/4 inch nominal outside :
diameter (OD) and OD43 inch nominal wall thickness. De Model D3/4, El and initial E2 steam i
- Denotes change. .
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I generators have mill annealed tubes; the Model D5 and later E2 steam generators have thermally treated j tubes.
I Data are presented to support the application of two sleeve designs; tubesheet and tube support. Moreover, with each design, several utility selectable application options are provided. The sleeve length and options are:
Tube support sleeve
- 12 inch long (15 inches long for the grid supports of the FSGs) ,,
- welding with post weld heat treatment (without post weld heat treatment is an option for shorter term ..;
operation).
Tubesheet sleeve
- 27 inches to 36 inches long [ ]6 (Variations apply for some models)
- upper weld joint with post weld heat treatment (without post weld heat treatment is an option for .;
shorter term operation). ,.
The sleeves described herein have been designed and analyzed to meet the service requirements of the FSGs and the PSGs through the use of conservative and enveloping thermal boundary conditions and stmetural loadings. Previous testing of sleeve lower mechanicaljoints of sleeves for 3/4 inch OD and 7/8 ,
inch OD tubes has been utilized. It has been determined that the results of these tests are applicable to ,
the lower mechanical joints of sleeves for the 3/4 inch OD tubes in this report, provided that confirmatory ,
leak tightness tests at room temperature are performed. (The mechanical lowerjoint is discussed because t
the laser weld for this location is optional; the mechanical joint is required.)
Similarly, previous testing of upper and lower laser welds of sleeves for 7/8 inch OD tubes has been performed. The results of that program are also applicable to the corresponding joints of the sleeves for ,
3/4 inch OD tubes in this report. The test data for the laser welded sleeves for 7/8 inch OD tubes are l provided here as bases in addition to the analytical bases for the upper and lower laser welds of this .
sleeve. ,
1 The structural analysis and mechanical performance of the sleeves are based on installation in the hot leg .
of the steam generator.- [
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t 1.2 Sleeting Boundary ,
Tubes to be sleeved will be selected by radial location, tooling access (due to channelhead geometric constraints), sleeve length, and eddy cunent analysis of the extent and location of the degradation. I The boundary is determined by the amount of clearance below a given tube, as well as tooling and robot j
. delivery system constraints. At the time of application, the exact sleeving boundary will be developed. ;
Owing to the constant development of tooling, designs and processes, essentially 100 per cent coverage of the tubesheet map, for tubesheet and tube support sleeves,is expected. ,
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2.0 SLEEVE DESCRIPTION AND DESIGN
' 2.1 Sleeve Design Description Tube sleeves can effectively restoic a degraded tube to a condition consistent with the design requirements, i.e., the strength and pressure retaining capabilities of the tube. 'Ih: design of the sleeve [
and sleeve weld is predicated on the design rules of Section Ill, Subsection NB, of the American Society of Mechanical Engineers Boiler & Pressure Vessel Code (ASME Code). Also, the sleeve design addresses ,
.. dimensional constraints imposed by the tube inside diameter and installation tooling. These constraints include variations in tube wall thickness, tube ovality, tube inside diameter, tube to tubesheet joint variations and runout / concentricity variations.
2.1.1 Tubesheet Sleeve j 2.1.1.1 Full-Length Tubesheet Sleeve ,
The reference design of the full-length tubesheet sleeve. as installed, is illustrated in Figure 2-1. At the upper end, the sleeve configuration consists of a section which is hydraulically expanded. The hydraulic expansion of the upperjoint brings the sleeve into contact with the parent tube to achieve the proper fitup geometry for welding. Following the hydraulic expansion, an autogenous weld is made between the sleeve '
and the tube using the laser welding process. This joint conflguration is known as a laser welded joint (LWJ) and in this case, it occurs in the free span, i.e., above the tubesheet.
The FLTS extends from the tubesheet primary face to the free span, i.e., above the tubesheet top. The tube degradation may be anywhere between the upper and lower joints. In the process of sleeve length optimization and allowing for axial tolerance in locating degradation by eddy current inspection, the guideline is that the welds and rewelds are to be positioned a [
jut, The upper joint is designed to provide [ ,
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At the lower end, the sleeve configuration consists of a section which is [
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3us 2.1.1.2 Elevated Tubesheet Sleeve t
The ETS is illustrated in Figure 2-2. It is applicable to the steam generators in wisch the tubes were installed in the tubesheet by the roll expansion process. These include the' [ . --
]"". The ETS is similar to the FLTS in that it is designed to address tube degradation in the tube frec ;
span and in the vicinity of the tubesheet top. However, unlike the FLTS,it is limited to these applications [
and is not designed to address degradation in the remainder of the tube within the tubesheet. l 1
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2.1.2 Tube Support Sleeve :
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- The sleeve material, thermally treated Alloy 690, was selected to provide additional resistance to stress ]
corTosion cracking. ;
4 2.1.3 Sleeving of Previously Plugged Tubes .
Previously plugged tubes must meet the same requirements as sleeving candidates as never-plugged, active I
tubes. An example of this requirement is that the minimum distance, as measured along the tube axis between degradation and the location of the sleeve welds, is the same in both cases. Another example .
is that the tube deplugging process performed by Westinghouse at part of the sleeving process is designed to leave the tube in a condition to be retumed to service unsleeved, excluding the degradation which j caused the tube to be plugged in the first place. 'Ihe deplugging process is designed to leave the tube-to- :j tubesheet weld and tube portion adjacent to the weld in a condition to perform the pressure boundary ;i function without any added integrity from the sleeve-to-tube lower joint.
2.2 Sleeve Design Documentation-l The sleeves are designed and analyzed according to the 1989 edition of Section III of the Amencan. ;
Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, as well as applicable United States Nuclear Regulatory Commission (USNRC) Regulatory Guides. (As of the date of this report, the . j 1989 edition is the latest edition approved by the NRC.) The associated materials and processes also meet {
the rules of the ASME Boiler and Pressure Vessel Code. Specific documents applicable to this program l are listed in Table 2-1. The sleeving codes, i.e., IWB-4300, first approved in the Section XI Div.1,1989 '
Addenda, dated March 1990 are used in this evaluation as guidelines. i i
2.2.1 Weld Qualification Program !
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b The laser w ' elding processes to be used to install [ ]"" nominal OD sleeves in the 3/4 inch !
nominal OD tubes of the FSGs and the [ ]"# nominal OD sleeves in the 3/4 inch OD tubes of , 'l' the PSGs are being qualified per the guidelines of the ASME Code. These requirements specify thef generation of a procedure qualification record and welding procedure specification. j All of these processes have been qualified, used in the field and have produced structures which are now ]
j operating, for [ ]"' sleeves for 7/8 inch OD tubes. The laser welding processes used to install
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[ ]"' nominal OD sleeves in 7/8 inch nominal OD tubes, (a.k.a., the "7/8 inch sleeves") were qualified per the guidelines of the AShE Code. The processes for the larger-diameter sleeve / tube joints ,
require requalification for the smaller-diameter sic:ve/ tube joints. His is due to a change in two of the ,
essential variables,in excess oflimits as defined in AShE Code Section XI IWB-4313.1. 'Iherefore, the f
welding processes are being qualified specifically for the 3/4 inch tube steam generators (a.k.a., the "3/4 inch sleeves"). i r
Specific welding processes will be genented for:
- Sleeve weld joints made outside of the tubesheet 9
- Sleeve weld joints made outside of the tubesheet with thermal treatment ,
- Repair or rewelding of sleeve joints 3
- Sleeve weld joints made within the tubesheet Representative field processes are used to assemble the specimens to provide similitude between the specimens and the actual installed welds. The laser welded joints are representative in length and ;
diametral expansion of the hydraulic-and-roll-expansion zones. The sleeve and tube materials are consistent with the materials and dimensional conditions representative of the field application. Essential ;
welding variables, defined in AShE Code Section IX, Code Case N-395 and Section XI, IWB-4300 are f used to develop the weld process. [
]"# ;
The documentation specified by AShE Section XI (sleeving codes '89 Addenda) may be provided at any reasonable time before the actual sleeving job. This weld qualification documentation is typically r submitted to the customer no later than the date of submission of the field procedures. E 2.2.2 Weld Qualification Acceptance Criteria For the qualification of the process, the acceptance criteria specify that the welds shall be free of cracks ,
and lack of fusion and meet design requirements for weld throat and minimum leakage path. The welds i shall meet the liquid penetrant test requirements of NB-3530. ;
t h
'f i
WPF1147A 2:lt@52693 2-4 i
Table 2-1 ASME CODE RULES AND REGULATORY REQUIREMENIS Item . Applicable Criteria Reouirement Sleeve design Section III NB-3000 Design
. Operating Requirements Analysis Conditions Reg. Guide 1.83 SG Tubing Inspectability Reg. Guide 1.121 Plugging Limit Sleeve Material Section II Material Composition Section III NB-2000, Identification, Tests and Examinations Code Case N-20-3 Mechanical Properties Sleeve Joint 10CFR100 Predicted Str.am Line Break Leak Rate Technical Specifications Operating Primary-to-Secondary Leak Rate Section IX Weld Qualification Code Case N-395/Section IX/ Laser Welding Essential -
Section XI Variables, procedure qualification record, sleeving procedure .
specification, certified [
~ design report, etc.
WPF1147A-2:1b/D52693 2-5
a,c.e l
'~
[ .
l- l 1
i I
i 1
Figure 2-1 Tubesheet Full-Length Laser Welded Sleeve Installed Configuration WPFil47A-2:&052693 2-6'
i t
L a,c.e l
t i
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i i
e 2
F I
e
(
-0 ,
i 1
.}
i 9
l
.. j
.: t Figure 2-2 -
t 5
Tubesheet Elevated Laser Welded Sleeve !
Installed Configuration 5
WPF1147A.2:1bCS2693 7,7 +
.i ,
1
a,c.e i
L t
f
~ .
Figure 2-3 Tube Support Laser Welded Sleeve Installed Configuration WPF1147A 2:Ib/052693 2-8 I
I i
l 3.0 ANALYTICAL VERIFICATION 1
This section of the report provides the analytical justification for the laser welded sleeves. Section 3.1 deals with die structural justification, Section 3.2 provides the thermal / hydraulic justification, and Section 33 addresses flow induced vibration concerns for laser welded sleeving.
3.1 Structural Analysis
. Section 3.1 summarizes the structural analysis of laser welded sleeves for feedring and preheater steam generators with 3/4 inch tubes in Combustion Engineering (CE) and Westinghouse plants, respectively.
The analysis has been performed by modifying the results of the previously completed laser welded sleeving evaluation for Westinghouse steam generators with 7/8 inch tubes (Reference 1), accounting for any necessary changes in geometry and loads. It should be noted that the loading conditions considered in the analysis represent an umbrella set of conditions based on the applicable design specifications, and are defined in Reference 2. The analysis includes development of the finite element models, a heat transfer and thermal stress evaluation, a primary stress intensity evaluation, a primary plus secondary stress ;
range evaluation, and a fatigue evaluation for mechanical and thermal conditions. Calculations are also performed to establish minimum wall requirements for the sleeve. Finally, the analysis addresses a ;
number of.special considerations as they affect the adequacy of the sleeve designs.
3.1.1 Component Description F
3.1.1.1 Tubesheet Sleeve The design of the full length tubesheet sleeve, as installed, is illustrated in Figure 2-1. [
3a.c.e At the lower tube / sleeve interface, the sleeve configuration consists of a section [ _}
ja.c l At the upper end of the sleeve, the sleeve consists of a section that [
]"' A schematic of the tube / sleeve interfaces and the various [ ]*
- is provided in Figure 3-1. l P
i L
i I
WPF1147A-3:ltWs2893 3-1 I
i 3.1.1.2 Elevated Tubesheet Sleeve The installed elevated tubesheet sleeve is illustrated in Figure 2-2. [
ja.c.e At the lower tube / sleeve interface of roll expanded tube joints only, the sleeve configuration consists of .
a section [ .
~
]* *
t
]*'* A schematic of the tube / sleeve -
interfaces and the various [ ]*'* is provided in Figure 3-1. l 3.1.1.3 Tube Support Sleeve De installed configuration of the tube support sleeve is shown in Figure 2-3. The sleeve is nominally -
12 inches (15 inches for the grid support) long, and is [
ja.c 11.2 Summary of Material Properties he material of construction for the tubing in Westinghouse and CE steam generators with 3/4 inch tubes is a nickel base alloy, Alloy 600 in either a mill annealed (MA) or thermally treated (TI) condition. De sleeve material is also a nickel base alloy, thermally treated Alloy 690. Summaries of the applicable mechanical, thermal, and strength properties for the tube and sleeve materials are provided in Tables 3-1 .
and 3-2, respectively. De sleeve evaluation also includes the response of the tubesheet,' which is ,
constructed of SA-508, Class 2 Carbon steel for both Westinghouse and CE units. A summary of the applicable properties for the tubesheet material is provided in Table 3-3. Thermal properties for air and ~
water, used in performing the heat transfer analysis, are provided in Tables. 3-4 and 3-5, respectively. He fatigue curve used in the analysis of the laser welds corresponds to the code curve for austenitic and ;
nickel-chromium-iron (Inconel).
WPFII47A-3:!bo52893 3-2
3.1.3 Applicable Criteria The applicable criteria for evaluating the sleeves is defined in the ASME Code,Section III, Subsection NB,1989 Edition, Reference 3. The lower joint in the tubesheet sleeve may contain a seal weld. The seal weld is included and evaluated to the ASME Code criteria as a structural weld and (this is the conservative configuration). In establishing minimum wall requirements for plugging hmits, Regulatory Guide 1.121, Reference 4,is used. A summary of the applicable stress and fatigue limits for the sleeve and tube is given in Tables 3-6 through 3-9.
3.1.4 Loading Conditions Considered The loadings considered in the analysis represent an umbrella set of conditions and are defined in Reference 1. The analysis considers a full duty cycle of events that includes design, normal, upset, ,
i faulted, emergency and test conditions. A summary of the applicable transient conditions is provided in Table 3-10. This duty cycle considers all relevant transients for both FSGs and PSGs with 3/4 inch tubes. ,
l The applicable temperatures and pressures are based on the design specifications for the steam generators.
l Umbrella pressure loads for Design, Faulted, Emergency and Test conditions are summarized in j Table 3-11. .!
3.1.5 Analysis Methodology i
A detailed evaluation of[
9 Ja,c.e WPFil47A-3:lWO52893 3-3
i
[ ,
ja.c.e ne analysis has also investigated the potential effects of the various [
jae.e ,
I Since the size of the tubes and sleeves [
3ae.e ,
The analysis of the laser welded sleeve designs utilizes both conventional and finite element analysis techniques. Several finite element models are used for the analysis (Reference 1). For the tubesheet sleeve analysis, [
]'# Typically, the tubesheet sleeve model incorporates a [ - ]*# in ,
the tubesheet. The analysis considers both [
as All PSGs and FSGs are full-depth expanded in the tubesheet. However in spite of the actual y configuration, the limiting geometry, judged to be a partial (tubeshset)' depth expansion at the bottom of the tubesheet,]*# is considered in this analysis. De tolerances used in developing'the sleeve models are such that [
]*# The results - .
for the upperjoint for the tubesheet sleeve are concluded to conservatively apply to the tube suppon plate sleeve. This is based on the temperature and pressure loads for the tubesheet sleeve for all transient conditions being greater than or equal to those for the tube suppon sleeve. ,.
- The nominal width (interfacial axial extent) of the laser weld joining the tube and sleeve for all joints is.
]*# However, qualification tests for the weld process are expected to show that the welds may -? .
[.
be as small as [ .]*# Thus,in performing this analysis, a weld width of [ .]*# was considered. 'Iherefore, the stress and fatigue results reponed later in the repon are for the' limiting weld geometry, or the [ ]*# width. ,
i 5
i t
wPF1147A 3:lt&52893 l
'3-4
-1
)
l 3.1.5.1 Sleeve / rube Size Considerations As indicated earlier, results from the previously completed evaluation of sleeving for 7/8 inch tubes (Reference 1) are to be used to form a basis to demonstrate acceptability of sleeving for 3/4 inch steam generatortubes. [
?
-i
. J.;
ja.c.e Since the designs of the [
t 7
f E
i ja.c.e These factors were developed by [
r O
t e r M -'
, S4S -
t
~
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. WPF1147A 3ilb/D52893 3-5 !
-I
l l
1 These modified stresses were then used in the subsequent ASME code evaluation to demonstrate acceptability of the sleeve design for both Westinghouse and CE model steam generators with 3/4 inch .
tubes.
3.1.5.2 Tubesheet Rotation EITects Loads are imposed on the sleeve as a result of tubesheet rotations under pressure and temperature ,
conditions. Reference 1 established the tubesheet rotations for five reference loading conditions for l Westinghouse Series 44 and 51 steam generators. The five reference loading conditions consisted of [ , j
]^
- The[
]*
- loadings. The [ ;
, L
]* *. 'Ihis section establishes the applicability of the tubesheet rotation loadings determined in Reference 2 to the laser welded sleeves for the PSGs as well as for the FSGs.
Differences among the geometries of the Westinghouse steam generators are given in the top part of Table 3-13. Plate bending equations may be used to compare the stresses in the perforated part of the tubesheet for the different geometries. As is shown in the bottom part of Table 3-13, the bending stresses l produced by pressure are [
f ja.c.e -
The geometry of the FSGs is markedly different from the Westinghouse steam generators, since the diameter of FSG tubesheets are larger with a central stay between the channelhead and tubesheet.
Accordingly, a finite element analysis was performed for the FSG to determine the tubesheet rotations produced by the five reference pressure and temperature conditions. Figure 3-5 shows the finite element ,
model of the channel head, stay, tubesheet, and lower shell. The boundary conditions and deformed geometry for the [ ,
i I
l l
] S". Thus the results ]
obtained for the Series 51 steam generator sleeves in Reference 1 are conservative when applied to the FSGs.
I WWtl47A-3:1WOS2893 '
3-6 n - - - - - -- -
l l
As was descdbed in Reference 1, [
3*'*
3.1.5.3 Thermal Transient Comparisons Since the size of the tubes and sleeves are not identical for the Series 51 SG (7/8 inch) and the PSGs and
. FSGs (3/4 inch), a potential exists that the [
ja.c.e The [ ]*# ransients t used in the Reference 1 evaluation were applied to the Series 51 SG, and stresses were calculated for the times selected in the Reference 1 analysis. Axial stresses and stress intensities were tabulated at the weld and the inside and outside surfaces adjacent to the weld. 'Ihese stresses are given in Table 3-15 for each of the transients. The WECEVAL LC# in the last column of Table 3-15 refers to the load condition mtmber of the thermal transient stresses used in the Reference 1 fatigue -
analysis.
Thermal boundary conditions [
]*#. These transients were applied to the appropriate finite element model (PSG or FSG sleeve / tube geometry), and stresses calculated at selected times comparable to those selected in the Reference 1 evaluation.
As for the Series 51 model, [
]'##
WPF1147A-3:lWOS2893 3-7
8 L
3.1.6 IIcat Transfer Analysis A detailed heat transfer analysis [ ;
-i i
ja.c.e j The first step in calculating the stresses induced in the sleeves as a tesult of the thermal transients is to ;
perform a heat transfer analysis to establish the temperature distribution for the sleeve, tube, and tubesheet. .
Based on a review of the transient descriptions, [ ]*
- enveloping transients were selected for evaluation 3 in the previous 7/8 inch tube sleeve anc. lysis (Reference 1). They include the following events: [
~ ~
LC ,
i The [
i i
I I
ja.c i
i In performing the heat transfer analysis for the enveloping transients, [
l
. -)
1
~ l
]*'* A sketch of the model boundary conditions for the heat transfer ;
analysis are shown in Figure 3-9.
1 In order to determine the appropriate boundary conditions for the heat transfer analysis, [ j ja.c I I ja.c ;
l l
l WPF1147A-3:1b/052893 3-8 I
3
I 3.1.7 Tubesheet/Channelhead/Shell Evaluation A detailed tuteheet/channelhead/shell evaluation for 7/8 inch tube sleeves was performed in Reference 1. l
- This previously completed analysis has determined that [ ,
I
. ]^ C ;
+
3.1.8 Stress Analysis -l t
in performing the stress evaluation for the sleeve models. [
i
]^
- Sketches of the model !
t boundary conditions for the primary side pressure cases are shown in Figures 3-10 through 3-13. Sketches of the model boundary conditions for the secondary side pressure cases are shown in Figures 3-14 through j 3-17. It should be noted for both sets of loads that the end cap load on the tube is not included, but is considered in a separate load case. ;
The analysis considers [ l [
i t
ja.c i
The effects of[
f i
]^#
Finally, [
ja.c : ~l
?
The total stress distribution in the sleeve-to-tube assembly is determined by combining die !
calculated stresses as follows:
,[
WPT!147A-3:1ho$2893 3-9 l I
-i
ows = PPR (c) unit primary pressure /1000
+ Psg (c) unit secondary pressure /1000
+ (c) thermal transient stress
+ Pgg (c) unit axial loart /1000 Note that the 7/8 inch tube sleeve evaluation has determined that [
ja.c 3.1.9 ASME Code Evaluation he ASME Code evaluation was performed using a Westinghouse proprietary computer code. De f
evaluation was performed for specific analysis sections (ASN's) through the finite element mcdel. De ASN's evaluated to determine the acceptability of the sleeve design are shown in Figure 3-4 for the upper LWJ.[
]'# f De umbrella loads for the primary stress intensity evaluation have been given previously in Table 311.
Delargest magnitudes of the [
ja.c i
The results for maximum range of stress intensity and fatigue are summarized in Table 3-18 for the tube being [
')
j a.c .
.Re analysis results show the AShE Code limits to be satisfied.- <
. i In evaluating seismic stresses, [
. Ja.c.e .
WPF1147A-3:lt>052893 3-10 O
&=__=__-_____-_--____-_-____-__ _ _.
r
[
ja.c 3.1.10 Minimum Required Sleeve Wall Thickness In establishing the safe limiting condition of a sleeve in terms ofits remaining wall thickness, the effects ofloadings during both the normal operation and the postulated accident conditions must be evaluated.
The applicable stress criteria are in terms of allowables for the primary membrane and
- membrane-plus-bending stress intensities. Hence, only the primary loads (loads necessary for equilibrium) need be considered.
~
For computing t, ,, the pressure stress equation NB-3324.1 of the Code is used. 'Ihat is, AP3 x R 3
=
t,*.
P, - 0.5 (P; + Po)
Separate calculations are performed for the Model D, Model E, and Feedring steam generators.
Normal / Upset Operation Loads The limiting stresses during normal and upset operating conditions are the primary membrane stresses due to the primary-to-secondary pressure differential AP 3 across the tube wall. The limits on primary stress, P , for a primary-to-secondary pressure differential AP,i are as follows:
Normal: P, < S/3 Upset: P,<Sy Accident Condition Loadines LOCA + SSE The dominant loading for LOCA and SSE loads occurs [
ja.c FLB/SLB + SSE:
The maximum primary-to-secondary pressure differential occurs during a postulated feedline break (FLB) accident. Again, [ ]*# the SSE bending stresses are small. Thus, the governing stresses for the minimum wall thickness requirement are the pressure membrane stresses. For WPflI47A.3:1h052893 3-11 L
t i
the FLB + SSE transient, the applicable pressure loads are [ [
]** The applicable criteria for faulted loads is:
i P, < lesser of 0.7 Su or 2.4 S, A summary of the resulting minimum required wall thicknesses are given in Table 3-19. Also provided l in Table 3-19 is a summary of the limiting minimum wall requirement for each model steam generator {
considering all of the loading conditions.
3.1.11 Determination of Plugging Limits l
i ne minimum acceptable wall thickness and other recommended practices in Regulatory Guide 1.121 are ,
used to determine a plugging limit for the sleeve. The Regulatory Guide was written to provide guidance j for the determination of a plugging limit for steam generator tubes undergoing localized tube wall loss and can be conservatively applied to sleeves. Tubes with sleeves which are determined to have indications . ,
of degradation of the sleeve in excess of the plugging limit, would have to be repaired or removed from senice. ;
t As recommended in paragraph C.2.b. of the Regulatory Guide, an additional thickness degradation ;
allowance must be added to the minimum acceptable tube wall thickness to establish the operational sleeve ;
thickness acceptable for continued service. Paragraph C.3.f. of the Regulatory Guide specifies that the i basis used in setting the opemtional degradation allowance include the method and data used in predicting l the continuing degradation and consideration of NDE measurement errors and other significant eddy current testing parameters. An NDE measurement uncertainty value of[ ]*
- of the sleeve wall ,
thickness is applied for use in the determination of the operational sleeve thickness acceptable for continued service and thus determination of the plugging limit. ,
i Paragraph C.3.f of the Regulatory Guide specifies that the bases used in setting the operational degradation analysis include the method and data used in predicting the continuing degmdation. To develop a value :
for continuing degradation, sleeve experience must be reviewed. To date, no degradation has been !
detected on Westinghouse designed mechanical joint sleeves and no sleeved tube has been removed from . l service due to degradation of any portion of the sleeve. This result can be attributed to the changes in .
l the sleeve material relative to the tube and the lower heat flux due to the double wall in the sleeved ,
region. Sleeves installed with the laser weld joint are expected to experience the same performance. As ,
a conservative measure, the conventional practice of applying a value of [ ]*
- of the sleeve wall, applied as an allowance for continued degradation, is used in this evaluation.
1 In summary, the operational sleeve thickness acceptable for continued service includes the minimum - i acceptable sleeve wall thickness, and' the combined allowance for NDE uncertainty and operational ]
degradation [ ]***. A summary of the resulting plugging limits as determined by Regulatory q Guide 1.121 recommendations are given in Table 3-20. 1 I
i WPF1147A&lhoS2893 l 3-12 l
In Paragraph IWB-3521.1 of Section XI of the AShE Code, it is stated that a 40 per cent tube plugging limit may be utilized for tubing with r/t <8.7. He sleeve r/t is 8.7 and therefore would qualify for the AShE Code 40 per cent tube plugging limit. The results of Table 3-20 confirm this result.
3.1.12 Application of Plugging Limits Sleeves which have eddy cu! Tent indications of degradation in excess of the plugging limits must be repaired or plugged. Rose ponions of the sleeve for which indications of wall degradation must be
- evaluated are summarized as follows:
. 1) [
+
ja.c
- 2) [
a ja.c
- 3) [ ]*# !
- 4) [
ya.c
- 5) [ !
ja.c j 1
l 3.1.13 Analysis Conclusions [
Based on the results of this analysis, the design of the laser welded tubesheet sleeve and the tube support plate sleeve are concluded to meet the requirements of the AShE Code. "Ihe applicable plugging limit [
for the sleeves is 40 per cent of the nominal wall thickness.
. I i
f t
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i I.
r s
wm1CA-MWOS2893 .h 3-13 r
1 Table 3-1 Summary of Material Properties Alloy 600 Tube Material TEMPERATURE ('F) 70 200 300 400 500 600 700 .
PROPERTY Young's Modulus 31.00 30.20 29.90 29.50 29.00 28.70 28.20
~.
psi x 1.0E06 Coefficient of Thennal 6.90 7.20 7.40 7.57 7.70 7.82 7.94 Expansion in/inf'F x 1.0E-06 Density 7.94 7.92 7.90 7.89 7.87 7.85 7.83 2 d lb-sec /in x 1.0E44 Thermal Conductivity 2.01 2.11 2.22 234 2.45 2.57 2.68 Btu /sec-in *F x 1.0E44 Specific Heat 41.2 42.6 43.9 44.9 45.6 47.0 47.9 l Btu-in/lb-sec2 , p ]
STRENGTH PROPERTIES (tsi)
Sm 2330 2330 2330 2330 2330 2330 2330 Sy 35.00 32.70 31.00 29.80 28.80 27.90 27.00 Su 80.00 80.00 80.00 80.00 80.00 80.00 80.00
%TF1147A-3.lbC52893 3-14
Table 3-2 Summary of Material Properties Sleeve Material l Thermally Treated Alloy 690 TEMPERATURE ('F) 70 200 300 400 500 600 700
. PROPERTY Young's Modulus 3030 29.70 29.20 28.80 2830 27.80 2730 psi x 1.0E06 i Coefficient of Thermal 7.76 7.85 7.93 8.02 8.09 8.16 8.25 Expansion in/inf'F x 1.0E-06 ,
Density 7.62 7.59 7.56 7.56 7.54 7.51 7.51 l lb-sec /ind x 1.0E-04 2 ,
Thermal Conductivity 1.62 1.76 1.9 2.G4 2.18 231 2.45 Bru/sec-in 'F x 1.0E-04 Specific IIcat 41.7 _ 43.2 44.8 45.9 47.1 47.9 49.0 Blu-in/lb-sec2 .,p STRENGTH PROPERTIES ,
(ksi)
Sm 26.60 26.60 2().60 26.60 26.60 26.60- 26.60 Sy 40.00 36.80 34.60 33.00 31.80 31.10 30.60 ,
Su 30.00 80.00 80.00 80.00 80.00 80.00 80.00
'i
, 'f 1
i l
1 WPF1147A-3:1h052893 3-15 l
Table 3-3 Summary of Material Properties Tubesheet Material SA-508 Class 2 TEMPERA 7URE (*F) .
70 200 300 400 500 600 700 PROPERTY ,
Young's Modulus 29.20 28.50 28.00 27.40 27.00 26.40 2530 psi x 1.0E06 CoefDcient of Thennal 6.50 6.67 6.87 7.07 7.25 7.42 7.59 Expansion inftnf'F x 1.0E-06 k Density 7.32 73 7.29 7.27 7.26 7.24 7.22 2
lb-sec find x 1.0E44 Thermal Conductivity 5.49 5.56 5.53 5.46 5.35 5.19 5.02 ,
Btu /sec-in 'F x 1.0E44 Specific Heat 41.9 44.5 46.8 48.1 50.8 52.8 55.1 Btu-in/lb-sec2 ,.p STRENGTH PROPERTIES (ksi)
Sm 26.70 26.70 26.70 2.6.70 26.70 26.70 26.70 Sy 50.00 47.50 46.10 45.10 44.50 43.80 43.10 Su 80.00 80.00 80.00 80.00 80.00 80.00 80.00 i
i WPF1147A.3:lt@52893 .
3-16 l
,1
I i
Table 3-4 l
Summary of hiaterial Properties .;
Air l
TEMPERATURE ( F) {
70 200 300 400 500 600 700 i PROPERTY Density 10.63 8.99 7.79 6.89 6.17 5.59 5.11 !
~ 2 Ib-sec /ind x 1.0E48 i
. Thermal Conductivity 3.56 4.03 4.47 4.91 535 5.78 6.20 l
i Bru/sec-in *F x 1.0E-07 t Specific Heat 9.27 931 938 9.46 9.55 9.66 9.78 j 2 i Btu-in/lb-sec *F x 1.0E+01 f
Table 3-5 Summary of Material Properties ;
Water ;
TEMPERATURE ('F) !
70 200 300- 400 500 600 700 ;
PROPERTY i
Density 9.28' 9.01 8.58 8.04 734 635 4.65 i Ib-sec2 / dn x 1.0E45 i Thermal Conductivity 8.46 9.07 9.14 8.89 8.24 69 4.42 i Btu /sec-in *F x 1.0E-06 Specific Heat 3.82 3.88 3.96 4.12 437 5.26 8.51 2
Btu-in/lb-sec *F x 1.0E+0' l
f
. (
i r
t
.l I
r l
r RTF1147A-3;1t.052693 3-17 ;
i TaNe 3-6 Criteria for Primary Stress Intensity Evaluation l Sleeve - Alloy 690' j CONDmON CRITERIA . LIMIT (KSI) l DESIGN P, 5 S, P,5 26.60 P + Pb$ 1.5 S, i
P3 + Pbs 39.90' ,
FAULTED P ,s .7 S, P,5 56.00 _.,. 'l P3 + Pb s 1.05 S, P3 + Pb5 84.00 .
l TEST P, 50.9 Sy P,5 36.00 ..
P3 + Pb51.35 Sy P3 + Pb5 54.00 EhERGENCY P, 5 Sy P, s 40.00 ;
P3 + P bs 1.5 Sy P3 + Pb5 60.00 [
-i ALL P +P2 + P3 s 4.0 S, 3
P +P2 +P35106.4 3 :
CONDmONS l F
Note: Pi (i=1,2,3) = Principal stresses f TaNe 3-7 :l Criteria for Primary Stress Intensity Evaluation -l Tube- Alloy 600 a i
CONDmON CRITERIA LIMIT (KSI) . :{
DESIGN P, 5 S. P, s 23.30 P + Pb 51.5 S, 3
P3 + P b5 34.95 j FAULTED P, s 7 S, P,5 56.0 . j Pj + Pb 51.05 S, . P3 + Pb s 83.88 [
TEST P, s 0.9 Sy P, s 31.50 ..
l P3 + Pb51.35 Sy P3 + P b547.25 : l EhERGENCY P, 5 Sy P, s 35.00 ;- 'f-P3 + P bs 1.5 S y- P3 + P 3s.52.5 7 ALL . P3 +P2 + P3 5 4.0 S, P3 +P2+P 3s 93.20 CONDmONS Note: P3 (i=1,2,3) = Principal stresses ,
WPF1147A.3:Ibe52893 [
3-18' i
I
-l Table 3-8 j
1 Criteria for Primary Plus Secondary Stress '
Intensity Evaluation .
Sleeve Alloy 690 CONDITION CRITERIA LIMIT (KSI),
NORMAL, UPSET, P+P+Q53S*
3 b m P3 + P b+ Q 5 79 8 j
'*' t and TEST L
=
NORMAL, UPSET, Cumulative Fatigue Usage 1.0 i
~
and TEST .;
t i
- - Range of Primary + Secondary Stress Intensity l
- i Table 3-9 f 1 Criteria for Primary Plus Secondary Stress - ;
intensity Evaluation . -
Tube - Alloy 600 {.
CONDITION CRITERIA LIMIT (KSI) ,l i
' NORMAL, UPSET, P + Pb + Q 5 3 S,* P3 + P b+ Q s 69.9 ;
3 ..,
and TEST Cumulative Fatigue Usage 1.0 !
NORMAL, UPSET, and TEST !
=!
- i l
- - Range of Primary + Secondary Stress Intensity i
'i l
i WPF1147A-3:1bl052893 3-19
. .e -
t Table 3-10 !
Summary of Transient Events ,
i a
CLASSIFICATION CONDITION CYCLES i h
s 4
Normal a,c.e ;
F l
1 I
i t
Upset ,
[
h
. r s
I i
i
(
4 i
WPF1147A 3:1N052893 3-20 i I
Table 3-10 (continued) ,
Summary of Transient Events t
CLASSIFICATION CONDITION CYCI FS l
-t
__ a,c.e !
Faulted
?
l F
Emergency 1
1 r
P Test ,
i
?
. t l
WITil47A-3:ltW526:03 3-21 i l
Table 3-11 .;
Umbrella Pressure Loads for !
Design, Faulted, and Test Conditions -l PRESSURE LOAD, PSIG l
?
CONDITIONS PRIMARY SECONDARY l t
t Desien b,c -
Design Pnmary Design Secondary Pnmary to Secondary Boundaryll) l Secondary to Primary BoundaryW l f
Faulted t Reactor Coolant Pipe BreakW l Feedline Break Steam line Break RC Pump Locked Roto 83) :
Control Rod EjectionW Test Pnmary Side Hydrostatic Test I
Secondary Side Hydrostatic Test Tube Izak Test A Tube Leak Test B Tube 12.ak Test C j Tube Izak Test D !
Pnmary Side Izak Test Secondary Side Leak Test j Emergency Small LOCA0)
Small SLBW Complete Loss of Flow M !
CE Loss of FW Flow - Cold FW Hot Dry SG j CE Complete Loss of Secondary Side Pressure . j t
jbe j
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- 4) - [ ]b.c '
- 5) I ]Ac *
- 6) [ ]b.c
- 7) [ ]be l i
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WPF1147A-3:1be52893 3-22 ;
Table 3-12 Stress Modification Factors 7/8 Inch to 3/4 Inch Tube Sleeves
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Table 3-13 Tubesheet Comparisons for Westinghouse Steam Generaton 3,C,e 4
. WPF1147A-3:1bD52893 3-24
E Table 3-14 Comparisons of Tubesheet Stresses for FSGs and Series 51 Steam Generators a,C,e 9
9 4
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Table 3-15 Transient Stresses at Sleeve / rube Weld - Series 51 SG a,c.e l
WPF1147A-3;1h052893 1 3-26
Table 3-16 Ratio of Models D, E, and FSGs to Series 51 SG Transient Stresses 3,C,e a
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Table 3-17 Summary of Maximum Primary Stress Intensity Full Length Tubesheet Laser Welded Sleeve i
Sleeve / Tube Weld Width of[ Ja.c
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Table 3-18 Maximum Range of Stress Intensity and Fatigue Full Length Tubesheet Laser Welded Sleeve Sleeve / Tube Weld Width of[ ]* *
[ ' ]*#
Calculated Allowable Calculated l' Component S.I. (KSI) S.I. (KSI) Allowable
- - a,c - - a,c Sleeve 79.80 Tube 69.90 Weld 69,90 Cumulative Fatigue Usage FactorC)
[ ]^s1.0 (1) With thermal bending stress removed per NB-3228.5(a).
(2) including Ke factors for simplified Elastic-plastic analysis.
WPF1147A-3:1be52893 3-29
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I Table 3-19 Summary of Minimum Wall Thickness Calculations Laser Welded Sleeve a,c,e '
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l Table 3-20 Summary of Recommended Plugging Margins l Laser Welded Sleeves l a,c.e l
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3-38
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Thermal / Hydraulic Boundary Conditions ;
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Iloundary Condition for Unit Primary Pressure
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h 3.2 ThermalIlydraulic Analysis ,
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3.2.1 Safety Analyses and Design Transients I
From the standpoint of system effects, safety analyses and system transients, steam generator tube sleeving has the same effect as tube plugging. Sleeves, like plugs, increase both the flow resistance and the thermal resistance of the steam generator.
,- Each NSSS is analyzed to demonstrate acceptable operation to a level of plugging denoted as the plugging limit. When the steam generators include both plugs and sleeves, the total effect must be shown to be ,
. within the plugging limit. To do this, an equivalency relationship between plugged and sleeved tubes . !
needs to be established. 'Ihe following section derives a hydraulic equivalency number. 'Dtis number !
represents the number of sleeved tubes which are hydraulically equivalent to a single plugged tube. It is .
I a function of various parameters including 1) the number and location of sleeves in a tube,2) the steam generator model, and 3) the operating conditions. Conservative bounding values are determined so that a single number applies to a given steam generator model and tube sleeve configuration. j Once the hydraulic equivalency number is established, the equivalent plugging level of a steam genemtor and NSSS can be determined. This equivalent plugging level must remain within the plugging level l established for the plant 3.2.2 Equivalent Plugg:ng Level l The insenion of a sleeve into a steam generator tube results in an increase in flow resistance and a .
reduction in primary coolant flow in that tube. Furthermore, the insertion of multiple sleeves (tubesheet f and/or tube support sleeves) will lead to a larger flow reduction in the sleeved tube compared to a nominal unsleeved tube. The flow reduction through a tube due to the installation of one or more sleeves can be considered equivalent to a ponion of the flow loss due to a plugged tube. A parameter termed the ;
' hydraulic equivalency number" has been developed which indicates the number of sleeved tubes required ;
to result in the same flow loss as that due to a single plugged tube.
. The calculation of the flow reduction and equivalency number for a sleeved tube is dependent upon: 1) the !
~
tube geometry,2) the sleeve geometry, and 3) the steam generator primary flow rate and temperature. l These parameters are used to compute the relative difference in flow resistance of sleeved and unsleeved ,
tubes. operating in parallel. This difference in resistance is then used to compute the relative difference
-in flow between sleeved (Wdv) and unsleeved (Wundv) tubes. The hydraulic equivalency number is then simply:
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l WPF1147A-3:1bl052893 j 3-49 ;
i 1
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The hydraulic equivalency number can be computed for both normal operating condidons and off-normal conditions such as a LOCA. For LOCA conditions, the equivalency number is established using flow rates consistent with the reflood phase of a post-LOCA accident when peak clad temperatures exist. The equivalency number for normal operation is independent of the fuel in the reactor. In all cases, the hydraulic equivalency number for normal operation is more limiting than for postulated LOCA conditions.
As a result of the flow reduction in a sleeved tube and the insulating effect of the double wall at the sleeve location, the heat transfer capability o'a sleeved tube is less than that of an unsleeved tube. An evaluation of the loss of heat transfer at normal operating conditions indicated that the percentage loss of heat transfer .
capability due to sleeving is less than the percentage loss associated with the reduction in fluid flow. In other words, the heat transfer equivalency number is larger than the hydraulic equivalency number. Thus, ,
the hydraulic equivalency number is limiting. _
The specific LOCA conditions used to evaluate the effect of sleeving on the ECCS analysis occur during a portion of the postulated accident when the analysis predicts that the fluid in the secondary side of the steam generator is warmer than the primary side fluid. For this situation, the reduction in heat transfer capability of sleeved tubes would have a beneficial reduction on the heat transferred from secondary to primary fluids.
Hvdraulic Eouivalency Calculation The goal of the calculations described below is to develop conservative values of hydraulic equivalency to bound all possible sleeve configurations that might be considered for steam generators with 3/4 inch' 2
tubes. The steam generators included FSG configurations with heat transfer areas of 88,500 ft and 103,600 ft2Hydraulic equivalency numbers are generated for a tube with each of the following tubesheet sleeve configurations and up to 12 tube support sleeves.
- 1) No tubesheet sleeve
- 2) One tubesheet sleeve (hot or cold leg)
- 3) Two tubesheet sleeves (hot and cold leg) ,
Based on previous evaluations (Reference 1), the most conservative sleeve configurations and operating . ~
conditions were selected for determining hydraulic equivalency. A sensitivity study was then performed with the least conservative limit of the same configurations and operating conditions to verify that the l parameters selected were consenative.
Previous evaluations have shown that for any given sleeve, location of the sleeve in the cold leg at the highest tube suppon elevation gave the lowest (most conservative) value of equivalency number.
Therefore, for each sleeve configuration examined, the maximum possible number of sleeves were located WPFil47A 3;RWS2893 3-50 1
)
i
in the cold leg at the higher tube support elevations. Additional dynamic structural evaluations would be required to verify sleeves in the cold legs of PSGs because of the additional effects of the preheater crossflow). Also, the longest tubesheet sleeve (36 inches) was used for all calculations. This sleeve gives j
- a lower equivalency value than shoner sleeves. Only one tube support sleeve length (12 inches)is under !
consideration for the Westinghouse Models. The longest TSS (15 inches for the " grid" (eggerate)) was ,
used for the FSGs.
Operating conditions affect equivalency to a smal!:r degree, with high v6ues of primary flow or That and !
,- low values of Tcold 81 Ving the most conservative values of equivalency. 'Ihe following values of these f parameters were selected for each of the . steam generator models. These operating conditions are at the 2
. conservative end of the typical range for the particular model. For the FSG models, the 88,500 ft generator was chosen because it gave the lowest hydraulic equivalency numbers.
Operating Conditions Used for Hydraulic Equivalency Calculations Parameter Conservative Parameter Value .l FSG Model D Model E Primary Flow - GPM 170000 100000 100000 ;
Primary Thot - F 615 620 626 Primary Tcoid - 'F 540 543 555 ;
Calculated values of hydraulic equivalency are presented for these three steam generator models as a [
function of sleeve configuration in Figures 3-18 through 3-20. 'Ihe table at the bottom of each figure displays the values of hydraulic equivalency plotted along with the configuration of tube suppon plate sleeves for each case. Notice that the tube support plate sleeves fill up the cold leg, top tube support plate l locations first and then spill over to the hot leg. This procedure conservatively minimizes the hydraulic {
equivalency for each tube suppon plate sleeve configuration. ;
Hydraulic Eauivalency Sensitivity Study i
. In order to confirm previous evaluations with respect to the most conservative values for sleeve l configuration and operating conditions, a sensitivity study was performed with the Model D. Sleeve ~!;
configuraGons with one tubesheet sleeve and up to 12 tube support sleeves, presented in Figure 3-18, were (
used as the reference configurations. The following four cases made up the sensitivity study. ]
I
- Reference case, tube support plates in the cold leg, conservative operating conditions (high primary l flow and That, low Teola)
Sleeves shifted to the hot leg WPF1147A.3:1b,052893 3-51
- Least conservative operating conditions (low primary flow and Toop high Teoid)
- LOCA operating conditions The operating conditions for the various cases are as follows:
Parameter Model D Operatine Condition Least Reference Conservative LOCA* ,
Primary Flow 100000 gpm 89000 gpm 20000 lbm/hr Primary Thot - F 620 612 522 .
Primary Tcoid - *F 534 558 522 Primary Pressure-psia 2250 2250 37
- LOCA conditions are superheated vapor during the reflood phase Table 3-21 presents the hydraulic equivalency values for the sensitivity study cases. For each variant from the reference case, the ratio to the reference case hydraulic equivalence value is also tabulated. The table .
shows that in every case, the reference equivalency ratio is equal to or smaller than the variants. The equivalency numbers of Figures 3-18 through 3-20, therefore, can be used as bounding values for each model, all sleeve configurations and at all operating conditions.
The total equivalent number of plugged tubes is the sum of the number of plugs associated with sleeving .l (number of sleeves divided by the hydraulic equivalency number) and the actual number of plugged tubes.
In the event that the total plugging equivalency derived from this information is near the tube plugging -
limit for a particular plant application, then less conservative, plant-specific equivalency calculations may be completed to justify increased sleeving. Rather than using the preceding conservative, enveloping -
conditions, these calculations could make use of: 1) actual plant primary side operating conditions, l'
- 2) actual tube and sleeve geometries, and 3) actual locations of the tubesheet and support plate sleeves.
The method and values of hydraulic equivalency and flow loss per sleeved tube outlined above can be ;
used to represent the equivalent number of sleeves by the following formula-I P, = P, + { (Ns,g;) + P, where:
P, = Equivalent number of plugged tubes P, = Number of tubes actually plugged S=i Number of active tubes with a sleeve combination "i" ,
N i ,ya,i = Hydraulic equivalency number for a sleeve configuration "i" P=c Equivalent number of plugged tubes due to other sleeve designs -
WPFil47A-3:1b/052893' 3 i
Table 3-21 Hydraulic Equivalency Sensitivity Study Least Conservative LOCA Operating TSP Ref. Hot Leg Sleeves Operating Cond. Conditions Sleeves Case Value Ratio Value Ratio Value Ratio a,c,e
. 0 1
3 5
7 9
12 WIT 1147A-3;1bl052893 3-53
i 3.2.3 Fluid Velocity l l
As a result of tube plugging and sleeving, primary side fluid velocities in the steam generator tubes will - ;
increase. The effect of this velocity increase on the sleeve and tube has been evaluated assuming a !
limiting cordition in which 20 per cent of the tubes in a steam generator are plugged.' l i
Using the conservatively high primary flow rates defined previously for the various models with j 20 per cent of the tubes plugged, the fluid velocities through an unplugged and unsleeved tube are in the ,
range [ ]^ *#. For a tube with a single tube suppon plate sleeve, the local velocity in the sleeve -
region is computed to be [ ]* *#. These velocities are smaller than the inception velocities for '
fluid impacting, cavitation, or erosion-corrosion for Inconel tubing. As a result, the potential for tube ,
degradation due to these mechanisms is low. l f
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Figure 3 20 j Hydraulic Equivalency Number 3/4 In, OD Tube, FSG i
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I 3.3 Sleeved Tube Relative Flow Inducc.! Vibration Assessments f
ne purpose of this Section is to provide the bases, methodology overview, salient parameters and results which together show acceptability of tube modifications itnplicit with installation of laser welded sleeves in terms of tube flow induced vibration (FIV) and wear potential. The two viable vibration mechanisms ;
for tubes in steam generator tube bundles are due to cross flow turbulence and fluidelastic excitations.
It is noted that the mechanisms of axial flow turbulence and vortex shedding are not considered viable as f
major causative mechanisms based on field experiences and, hence, are not addressed further. l Results from these assessments are intended to show that the litniting cases of a tube modification caused by laser welded sleeves do not cause significant potential field issues with respect to FIV responses. .
These results, along with the experience that FIV problems have not occurred in field SG straight-legs, I i
either of FSG or PSG design, are intended to provide adequate assurance that laser welded sleeves are acceptable in each of the designs considered. j i
3.3.1 Flow Induced Vibration Evaluation Methodologies j Westinghouse capabilities and methodologies for the evaluations of flow induced vibrations are under j continuous development (see References 7 through 15). To perform the subject evaluations a relative analysis method was developed and used. This relative method is described below.
i The first case considered for each laser welded sleeve configuration was that a laser welded sleeve has ;
been installed in a tube and, at the same time, the tube is conservatively assumed to be severed through l 360 degrees of arc at some location within bounds of the length of the sleeve. The second, and reference l case, is that of the unmodified (nominal) tube. Ratios of the vibration responses for these cases provide [
the desired relative results, which are then put into perspecuve relative to actual field and test operating experiences to provide the required demonstration of acceptability. These evaluations address three ,
specific laser welded sleeve (off nominal) configurations. 'They are characterized as: [
] ,*'" [ '
. ]^# and [ ,
]*# These configurations are defined in Table 3-23 and in Figures 2-1, ,
i 2-2, and 2-3, respectively.
In these relative evaluations, it is necessary to establish all vibration response related parameters which
- vary between the two cases being compared. A sleeved and separated tube produces physical changes m ;
the stmetural tube system, relative to the nominal case, such that the length of that system may be !
increased and / c7 its cross-sectional properties decreased. Each of these effects results in both reduced !
natural frequencies and changed mode shapes. Because damping is known to be a strong function of l frequency, it too must be considered explicitly, i i
WPFil47A-3:lbOS2893 l 3-58 c 5
, , , - - - ~ - . . , __ _ _ _ _ _ _ _ _ . _ . _ _ . _ . _ _ _ _ _ _ _ _ _ _ . . _ _ _ _ _ _ _ _ . _ _ _ _ _ _ _
Linear system vibration responses for both the turbulence and fluidelastic mechanisms are obtained with the Westinghouse proprietary computer code FASTVIB. Initial separate evaluations are typically performed, as in this case.
Another Westinghouse computer program, WECAN, provides for the generation of a finite element model of the tube and tube support system in the form of a linear superelement. The finite element model provides the vehicle to define the mass and stiffness matrices for the tube system as well as the geometry of the tube and tube support plate. This information is used to determine the modes (eigenvalues) and mode shapes (eigenvectors) for the linearly supported tube being considered. Table 3-22 provides the tube and sleeve cross sectional properties used in the creation of the 20 developed superelements. Schematics
. of the superelements showing the tube, tube support, and saint structures geometry and node designations are provided in Tables 3-25 through 3-27. Table 3-25 gives this information for the Models D, Table 3-26 is for the Model El/2, and Table 3-27 addresses the FSGs. l Inputs to the FASTVIB code are, typically, the mass and stiffness matrices, the secondary fluid flow velocity and density distributions, a set of pre-determined permissible boundary conditions for each tube (or tube span) in the bundle to be evaluated, the fluidelastic constant, beta, and damping appropriate to the flow, boundary conditions, and the lower limit value to the reduced velocity parameter. Because the ,
present evaluations are relative, however, several of these inputs are not required. Notable among these are the velocity distributions and the beta values. ,
The secondary side fluid density distributions used for the present evaluations were developed from three-dimensional flow studies for each of the SG models being considered. For the Models D and E, ATIIOS computer code results were used. The FSG distributions were based on the THIRST code as reported in Reference 16. Density as a function of elevation was extracted from these code results in a region of the cold leg near the periphery of the bundle. These density distributions were intentionally chosen to provide conservative evaluation results as they have nearly the highest values in the bundle at the selected full ;
power operating conditions. They are given in Table 3-24 for each of the relevant SGs clong with the associated equivalent tube density profiles. It is these latter profiles which are input to the WECAN superclement models to form the tube mass matrices.
t
. These evaluations are intentionally and conservatively limited to hot leg geometries for each SG model. l'
~
(Additional dynamic structural evaluations would be required to verify in the cold legs of PSGs because of the additional effects of the preheater crossflow.) Specific boundary conditions considered for each ,
tube location are typically obtained on the basis of results from the application of Monte Carlo methods. ,
However, in this present evaluation, the boundary conditions considered are conservatively chosen as up ,
to two missing tube supports at the four lowest (true) tube supports a.k.a., TSPs on the hot leg side. :,
included in these conditions are: 1) all supports active,2) any one support inactive,3) any two supports -
inactive, including the conservative case of two consecutive supports inactive. In all cases the fifth and i higher supports are assumed to provide pinned tube support.
I 5
i WPF1147A-3.us052893 6 3-59 l
Output from a FASTVIB evaluation is usually comprised of the fluidelastic stability ratio and the root-mean-square turbulence vibration amplitude. Because these are relative evaluations, the output (results) here becomes ratios of appropriate stability ratios and root-mean-square turbulence vibration amplitudes. These results can be presented in many different forms. Generally,it is instmetive to produce maps showing the worst case boundary condition result at each tube location considered in the tube bundle. Since these relative evaluations are being performed on a conservative " worst expected case tube ;
condition" basis, there is only one evaluation result for each of two mechanisms and ten boundary r conditions for the three sleeve configurations in each of five SG models. Thus, the presentation format chosen for these evaluations is a table. This table is presented and discussed below. . j 3.3.2 Effects of Damping on Relative Evaluations ,
Tube damping plays the very important role of establishing tube vibration and stress magnitudes for both the fluidelastic and turbulence mechanisms once all other system and forcing function parameters are established. For these relative evaluations, damping is important because of the change in frequencies brought about by the introduction of the sleeve, and the conservative assumption of a severed tube, with their associated, but independent, changes in effective tube system geometry. ,
t In order to establish the magnitude of the effects of damping on the FIV evaluation results and the difference in these damping effects given different damping relations associated with different SG straight-leg conditions, a parametric evaluation was completed. This evaluation was accomplished before the final relative evaluations and was intentionally made independent of the mode shape integral effects. Results ;
from these parametric evaluations are provided in Figures 3-21 through 3-24. These four figures illustrate I the basis for our developed damping position for these laser welded sleeve FIV evaluations. They f demonstrate that; 1) it is beneficial to consider damping for these relative evaluations of FIV responses [
at all frequencies and frequency changes due to the introduction of a laser welded sleeve and an assumed severed tube, and,2) the results are insensitive to the choice of absolute damping relation of which SG model is used. Given this latter result, damping originally developed for a specific SG straight-leg ,
evaluations was chosen for use in all the present laser welded sleeve and nominal tube configuration ;
evaluations. Based on physical considerations associated with the various tube / sleeve configurations, .
it is expected that this chosen damping relation is relevant and conservative for laser welded sleeve configurations and relevant for the nominal configurations. , j i
3.3.3 Flow Induced Vibration Results and Conclusions ,
The subject laser welded sleeve FIV evaluation results are provided on Table 3-28. As can be seen from f this Table, each of the five SG configurations forms a sub-table. On each of these sub-tables both !
fluidelastic and turbulence results are presented for all the boundary conditions considered and for each f of the three sleeve configurations considered. The boundary conditions are varied between pinned and open at the four lowest true tube support plates. Again, each individual result is the ratio of the FASTVIB predicted response for the vibration mechanism and sleeve configuration indicated at the top of the l 3
WPFil47A-3:&/052893 3-60
columns to the FASTVIB predicted response for the nominal sleeve configuration subjected to the same mechanism and conditions. ;
Fluidelattie Stability ;
The Model D3 results, given in columns 6,7 and 8 of Table 3-28, show that there are only three !
configurations with a ratio exceeding 1.10, which implies a 10 per cent increase for the sleeved .j configuration over nominal. The first of these is for the ELEV sleeve, a.k.a., ETS, configuration and ;
- shows about 21 per cent increase for the case of open boundary conditions at the lowest two (consecutive) !
~
plates. The last two are for the FLTS configuration and show about 29 per cent increase for the lowest I
. TSP open condition, and about 53 per cent for open boundary conditions at the lowest two (consecutive) l plates. ;
The Model D4 results show that there are only five configurations with a ratio exceeding 1.10. The first two of these are for the ELEV sleeve configuration and show about 12 per cent increase for the lowest i TSP open condition, and about 19 per cent for open boundary conditions at the lowest two plates. The last three are for the FLTS configuration and show about 45 per cent increase for the lowest TSP open j condition, about 48 per cent for open boundary conditions at the lowest two (consecutive) plates, and l about 28 per cent for open boundary conditions at the first Oowest) and third plates. ;
The Model D5 results are very nearly identical to those for the Model D4.
The Model E results are also very nearly identical to those for the Model D4 with only minor variations ,
in the percentages for each of the (same) configurations (see the table).
~l The FSG results also show that the same five configurations have a ratio exceeding 1.10. In this case the results for the ELEV sleeve configuration show about 14 per cent increase for the lowest TSP open j condition, and about 21 per cent for open boundary conditions at the lowest two plates. The last three )
are again for the FLTS configuration and show about 38 per cent increase for the lowest TSP open
~
condition, about 53 per cent for open boundary conditions at the lowest two (consecutive) plates, and I about 16 per cent for open boundary conditions at the first and third plates. ll Because there are no known unacceptable cases of straight-leg fluidelastic vibration and wear conditions in SGs where design conditions are prevalent at any of the field units where the subject SG models are ]
cmployed, the fluidelastic stability ratio increases implied by the results discussed above and presented 1 in Table 3-28, are expected to be acceptable.
WPrlt47A 3:H&52R93 3-61
-. - ~ .- - . .- - , -. . .. .
Turbulence Restionse The turbulence response results, given in columns 9,10 and 11 of Table 3-28, show that there are more cases where the turbulence ratios exceed 1.10 than there are fluidelastic cases for the same SG model.
However, it is well known on the bases of both tests and field results that the absolute turbulence response for the nominal condition case for the hot leg in any of the SG models considered is quite small, on the order of tenths of mils. Thus, it is fully expected that there would be no real vibration and wear issues introduced into any of these SG models if the turbulence amplitudes were increased t,; the largest ratio in the table, which is about 3.5. It is also expected that, at these higher amplitudes, the turbulence .
response would remain below the endurance limit and, therefore, would not change the tube / sleeve system fatigue evaluation outcome relative to the nominal case. .
%TF1147A-3:1b052893 3 62
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l-l' WPFI147A-3:lt@52893 -
3-64
Table 3-24 Laser Welded Sleeve Relative Evaluations Tube Density Distribution Estimates 3,C.C .
.. WIT 1147A-3:lb/032893 3-65
_ _ _ _ ____.__ _ _______ ._ . _ . _ _ . _ _ _ . . _ . _ _ _ . _ _ . . _ - , . _ _ ~ - _ . , _ . _ . - _ . _ , . _ - _ _ _ - . . _ _ ,.~ - _ .. _ .--_._, _ _ . . - . . . __ _ _.
Table 3-25 Laser Welded Sleeve Superelement Geometry and Nodes for Models D3, D4 and DS SGs a,c.e l
l WPFil47A-3:1WD52893
_ 3-66.
Table 3-26 Model E2 LWS Superelement Geometry and Nodes i
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Relative Flow Induced Vibration Evaluation !
Results for Laser Welded Sleeve Configuration ;
with Various Tube Support Plate Boundary Conditions
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i 3.4 References !
F
- 1. WCAP-13088, Rev.1, " Westinghouse Series 44 and 51 Steam Generator Generic Sleeving Report ,
Laser Welded Sleeves," January 1993. (Westinghouse Proprietary Class 2)
- 2. " Design Specification 412A24. " Laser Welded Sleeves for 3/4 Inch Diameter Tubes of Plants with ;
Combustion Engineering Feedring Steam Generators and Westinghouse Model D3/4/5 and El/2 Steam Generators," April 1993. (Westinghouse Proprietary)
- 3. "ASME Boiler and Pressure Vessel Code,Section III, " Rules, For Construction of Nuclear Power Plant Components," The American Society of Mechanical Engineers New York, NY,1989, ;
- 4. USNRC Regulatory Guide 1.121, " Bases for Plugging Degraded PWR Steam Generator Tubes (For Comment)," August 1976. l
- 5. USNRC Regulatory Guide 1.83, Rev.1, "In-Service Inspection of Pressurized Water Reactor i Steam Generator Tubes, July 1973. [
- 6. WCAP-12522, "Inconel Alloy 600 Tubing - Material Burst and Strength Properties," J. A. Begley, .[
J. L. Houtman, January 1990. ;
- 7. " Overview on the Development and Implementation of the Methodologies to Compute Vibration and Wear of Steam Generator hbes," Frick, T.M., Sobek, T.E., Reavis, J.R., Proceedings of the ASME Symposium on Flow Induced Vibrations, Vol. 3, Vibrations in Heat Exchangers,1984, New Orleans, LA, USA. ;
k
- 8. " Summary of Preheat Steam Generator Experienccs and the Basis for a Turbulent Force Modeling !
Procedure," Frick, T.M., Transactions of the 8th International Conference on Structural Mechanics !
in Reactor Technology,1985, Vol. D, paper D3/2, pps 283-287.
- 9. "Counterflow Preheat Steam Generator Vibration Program," Proceedings of the 2nd International l
Topical Meeting on Nuclear Power Plant Thermal Hydraulics and Operations, Pitterle, T.A., Frick, ,
T.M., Singleton, N.R., Tokyo, JP, Session 10/5, April 1986. !
i
- 10. " Extraction of Turbulence Generated Input Forces Acting on a Steam Generator Tube," Kendig, .
R.P., Frick, T.M., Noise-Con 87,1987, pps 77-82.
- 11. " Tube Vibration Measurements on a Feedring Steam Generator," Curlee, N.J. Jr., Frick, T.M.,
Mabon, l.D.,1985 ASME WAM, Conference on Thermal Hydraulics and Effects on Nuclear Steam Generators and Heat Exchangers, H1D Vol. 51, pps 43-55. ;
i WPF1147A.3;1tW52893 3-74
- 12. " Flow Induced Vibrations and Wear of Steam Generator Tubes," Connors, H.J., Nuclear ,
Technology, Vol. 55, November 1981, pps 311-331 {
-13. " Methodologies for the Computation of Steam Generator hbe Wear with Applications for Turbulence in the U-Bend Region," R. Waisman and T.M. Frick, Joint ASCFJASME Mechanics, l Fluids Engineering, and Biomechanics Conference, San Diego, CA, July 9-12,1989. .
- 14. "U-Bend Shaker Test Investigation of hbe/AVB Wear Potential " H.J. Conners and F.A. Kramer,
- International Conference on Flow-Induced Vibrations, Proceedings of the Institution of Mechanical !
Engineers, May 1991.
~
- 15. " Simulation of Flow-Induced Vibration Characteristics of a Steam Generator U-Tube," E.R. France and HJ. Cornors, International Conference on Flow-Induced Vibrations, Proceedings of the l
Institution of Mechanical Engineers, May 1991,
- 16. "Thennal Hydraulic Analysis of a Combustion Engineering Series 67 Steam Generator," EPRI Report NP-1678 January 1981.
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I WPF2147A-3.ndD52893 3-75 t
_b
t 4.0 MECHANICAL TESTS ;
Mechanical tests are used to provide [ j t
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,- Mechanical testing was previously applied to both Hybrid Expansion Joint (HEJ) (lower joint) and laser t
welded (free span and lower joint) sleeving to confirm analyses that evaluated the interaction between the
. sleeve and tube. Mechanical testing is primarily concerned with leak resistance and joint strength, !
including fatigue resistance. A consistent characteristic observed in the testing of HEJ lower joints for sleeves is that leakage, when observed,is generally higher at room temperature (RT) and normal operation, ,
steamline break (SLB) and greater-than-SLB pressure differential conditions than at elevated temperatures ;
and other applied-load conditions. This result obviates all of the combined or separate elevated temperature leak tightness and applied-load types of tests and permits qualification of these 3/4 inch HEJ [
lower joints on the basis of the RT leak tightness test and the previous testing. During testing, some of j the specimens were subjected to cyclic thermal and mecha'ilcal loads, simulating plant transients. [
l
]* C ' Other specimens were subjected to tensile and compressive loads to the point of mechanical failure. These tests demonstrate that the required joint strength exceeded the loading the sleeve joint would receive during normal plant operations or accident conditions.
Section 4.1 summarizes previous mechanical tests and results for HEJ 3/4 inch tube sleeves which are applicable to the installation of the lower HEJ of this tubesheet sleeve in 3/4 inch tubing, based on confirmatory room temperature leak tightness pressure tests. ('Ihe mechanical lower joint is discussed because the laser weld for this location is optional; the mechanical joint is required.) Section 4.2 summarizes previous mechanical tests and results for the lower joint of the 7/8 inch HEJ sleeve. The 7/8 inch sleeve results show the adequacy of obtaining the required strength of the roll expanded portion
. of the HEJ. based on optimal roll thinning of the sleeve. This same method is used to achieve the required strength of the roll expanded portion of the HEJ for the 3/4 inch sleeves. Section 4.2 also summarizes previous mechanical tests and results for 7/8 inch laser welded joints. These data were
~
provided to show that tests corroborated the analyses for those joints. Therefore, verification by analysis is sufficient for the 3/4 inch laser welded sleeve joints. :
WPFI147A4nxoS2793 4-1
i 4.1 Tubesheet IIEJ Tests - 3/4 Inch Tube Sleeves l 4.1.1 Case No.1 - Westinghouse Steam Generator (WSG) j i
The mechanical tests of the tubesheet lower joint (HEJ), povided for another Westinghouse 3/4 inch OD f (nominal) tube steam generator are applicable to the 3/4 f ach OD (nominal) tubes of the FSGs and PSGs.
The test conditions are listed in Table 4-1 and the generi. , allowable, primary-to-secondary leak rates are {
listed in Table 4-2. The test results are provided in Tabh 4-3. As discussed earlier, the HEJs are formed in tube-to-tubesheet joint unit cells. End caps are installed on the collar and sleeve top, per Figure 4-1, ,
to permit the samples to be pressurized. The end caps are threaded to permit tensile and compressive l loading.
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wPFil47A-4:lb/052793 4-2
Table 4-1 Case No.1 - Westinghouse Steam Generator Mechanical Test Program Summary Tubesheet HEJ Tests - 3/4 Inch Tube Sleeves a,c.e I
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y 4.1.1.1 Acceptance Criteria - 3/4 Inch Tube HEJ Sleeve (WSG)
For push-out and pull-out tests, all joints shall exhibit loads for initial slip, where obsenable, or loads for start of non-linear load-deflection, above the O to 2200 lb. push / release effective axial loads that were applied during the fatigue tests. He leak rate criteria are based on typical Technical Specifications and Regulatory requirements. Table 4-2 shows the leak rate criteria for the FSGs and PSGs.
4.1.1.2 Results of Verification Tests - 3/4 Inch Tube HEJ Sleeves (WSG)
The test results for the HEJ (lower joint) specimens are presented in Table 4-3. For normal operating
- conditions, i.e.,1485 to 1600 psi at RT and 600*F, [
ja.c.e in the case of the fatigue testing, this number of cycles (30,000) represents the number of expected yearly cycles multiplied by a suitable factor to achieve an accelerated test condition. On that basis the test results provide data which are conservative in nature and exceed the actual operating conditions. The other parameters associated with the thermal cycle test, for example, such as temperature ramp, hold time and temperature gradient are accelerated to achieve meaningful test results within an acceptable time frame.
Consequently, the test results obtained and discussed are those of accelerated conditions designed to test the sleeve at the endurance limit he results do not imply that after a specific length of operating time the sleeves will begin to leak. Rather they demonstrate that under extreme accelerated test conditions leakage is small or zero, providing assurance that in the actual operating case the sleeves will perform at a zero leakage base. Additionally, by using that same test series for all sleeve designs it is possible to measure consistency in process modification and/or small changes in the overall design to facilitate an assessment of the effect on total sleeve performance.
I ja.c.e General Note: In the test portions of this report, the units of primary-to-secondary side differential i pressures are listed simply as " psi," rather than "psid." The secondary side pressures were zero psig.
WPFil47A-4:thoS2793 4-5
~
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Table 4-2 -
Typical Bounding Maximum Allowable Leak Rates for Feedring - Type and Preheater Steam Generators Allowable Leak Rate Most Limiting Allowable Condition Plant Sleeved SG, com (crx1) Leak Rate per Sleeve ** ;
Model Model D E FSG -
_ __ d.e
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- Based on installation of 2000 tubesheet sleeves with non-welded lower joints - for plant.
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The conclusions reached as a result of the test progam are:
A consistent characteristic observed in the testing of mechanical joints is that the leakage, when observed, is generally higher at room temperature (RT) conditions. This characteristic has lead to the increased use of the room temperature hydrostatic test in process, tooling, personnel, procedure and demonstration phases.
For the lower joint, initialleak rates, both at room temperature and at 600 F, [
. ]*## As stated earlier in this report, if the FSGs or PSGs of individual plants require minor modifications to the qualified HEJ processes, due to environmental or other conditions, these needs will be addressed in the specific preparations for the repair project. Any additional qualifications will be documented separately. Note: Leak rate measurement is based on' counting the number of drops leaking during a 10-20 minute period. Conversion to volumetric measure is based on assuming 19.8 drops per milliliter.
Thermal cycling between 120'F and 600'F, for the lower joint, had no detectable adverse influence on joint leak rate. 'Ihe leak rate after testing remained at [ ]*##
Fatigue tests of the HEJ had no discernable adverse effect on joint leak resistance or structural integrity.
ja.c.e
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For push-out and pull-out tests, all joints tested exhibited loads for initial slip, where observable, or loads for stan of non-linear load-deflection, above the effective axial loads that were applied during the fatigue tests.
'Ihe leak rates observed during a simulated stean: line break test were well below the acceptance criteria.
The leak rates observed during a simulated LOCA remained at [
),"# which is far below the acceptance limit.
WPF1147A-4 lb/Os2793 4-7
a,c,e Table 4-3 (Page 1 of 5)
Verification Phase Test Results - Lower Joint (IIIU)
Alloy 690 Sleeve for 3/4 Inch Tube -j
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Verification Phase Test Results - Lower Joint (IIEJ)
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Verification Phase Test Results - Lower Joint (IIEJ)
Alloy 690 Sleeve for 3/4 Inch Tube
- WPFil47A-4:1b/052793 4-11
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Table 4-3 (Page 5 of 5)
Verification Phase Test Results - Lower Joint (HEJ)
Alloy 690 Sleeve for 3/4 Inch Tube .
Notes to Table 4 3
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I WPF1147A4:1b/052793 4-12
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I 4.1.2 Case No. 2 - Feedring Steam Generator l De verification based on mechanical tests of the tubesheet lower joint (IIEJ) previously performed for an FSG [also applies to the installation of these sleeves in these FSGs. He previous case involved a 0.631 inch OD (nominal) sleeve, of a bimetallic configuration, consisting of Alloy 690 as the base metal, of 0.034 inch nominal wall thickness, metallurgically joined to a thin outerlayer of, approximately 0.0075 inch thickness, Alloy 625. Herefore, the composite wall thickness was nominally 0.0435 inch.]"" The test conditions are listed in Table 4-4.
. i-4.1.2.1 Acceptance Criteria - 3/4 Inch IEJ Sleeve (FSG)
. l De acceptance criteria for these strength tests were the same as for those listed for Case No.1. The leak l' rate criteria for these tests are also listed in Table 4-2.
4.1.1.2 Results of Verification Tests - 3/4 Inch Tube IIEJ Sleeves (FSG)
From the test results obtained (Table 4-5), the following conclusions were reached:
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Table 4-4 Case No. 2 - FSG Mechanical Test Program Summary i Tubesheet HEJ Tests - 3/4 Inch Tube Sleeves
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Table 4 5 (Page 4 of 5)
Verification Pha<e Test Results - I,cwer Joint (IIIU)
Alloy 690/625 Bimetallic Sleeve for 3/4 inch Tube (FSG) .
bes WPFil47A-4:lWOS2793 4,gg
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Table 4-5 (Page 5 of 5)
Verification Phase Test Results - Lower Joint (IIEJ)
Alloy 690/625 Ilimetallie Sleeve for 3/4 Inch Tube (FSG)
(Notes to Table 4-5) b,c,e 1.
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. 3.
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6.
7.
8.
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I WPF1147A-4:1NOS2793 4-19
4.2 Tubesheet IIEJ, Free Span and Tubesheet LWS Tests - 7/8 Inch Tube Sleeves i
he same type of testing as shown for the 3/4 inch sleeve HEJs was performed for 7/8 inch nominal OD tube sleeves (Reference 1) and are applicable. The 7/8 inch sleeves were installed previously and are in successful operation. He 7/8 inch tube Westinghouse steam generators are very similar in design and manufacture to the 'ESGs and PSGs. 7herefore, all of the 7/8 inch free span and tubesheet LWS testing, as well as the tubesheet HEJ testing, applies to the respective areas of the 3/4 inch sleeves of the FSGs and PSGs. All of the applicable results of the 7/8 inch sleeve testing are included here.
It has beer, pointed out earlier in this report that sleeve-to-tube welds are verified by analysis and that no laboratog testing is required. However, considerable weld testing was also performed for the previous, .
7/8 inch sleeve program. He applicable results of that program are provided here as additional bases for the 3/4 inch sleeve weld. [ ,;
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t WPF1147A-4:Ib/052893 4-20 4
h
Because of the [
]* As pointed out earlier in this report, if the sleeving of FSGs or PSGs requires minor modifications to the qualified HEJ processes due to emironmental or other unique conditions and this entails testing, these needs and potential tests at RT conditions will be addressed and documented separately.
The test conditions summarized in Table 4-6 (specific test conditions displayed in data tables) may vary
- due to evolution of the testing process. Test parameters have also been modified slightly over time as
- l more refined analysis of plant loading conditions are applied.
The generic, allowable, primary-to-secondary leak rates are listed in Table 4-2 and the results are provided in Tables 4-7 through 4-12. The test samples were fabricated per Figure 41.
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l WPFil47A-4.nA52793 1
4-21
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Mechanical Test Program Summary Tubesheet IIEJ Tests - 7/8 Inch Tube Sleeves i
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4.3 Acceptance Criteria - 7/8 Inch Tubesheet HEJ Sleeves
'The leak rate criteria that have been established are based on typical Technical Specifications and q Regulatory requirements. Table 4-2 shows the generic leak rate cdteria for the Series 44 and 51 steam generators.
While the laser weld joint is hermetic and exhibits no leakage, in practice the lower joint of a tubesheet sleeve may be installed with or without a seal weld. In die case where a seal weld is not applied, the leakage chamcteristics must be evaluated. The values of the fabrication parameters of the HEJ are independent of the plan to weld or not to weld the sleeve.
~
[
]*" indicate acceptable joint performance.
4.4 Results of Testing - 7/8 Inch Sleeves 4.4.1 IIEJ Lower Joint As discussed earlier, the joints are formed in unit cell collars. End caps are then installed on the collar and sleeve (Figure 4-1) to permit the samples to be pressurized. The end caps are threaded to permit I tensile and compressive loading.
l 4.4.1.1 No Seal Weld The test results for the Series 44 and 51 lower joint specimens are presented in Table 4-7. The specimens I
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For the tests the following joint performance was noted:
Specimen MS-2: Initialleak rates at all pressures and at normal operating pressure following thermal cycling were [
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'1 Specimen MS-7: l l ja.b.c.e l
4.4.1.2 Description of Additional Test Programs -IIEJ Lower Joint With Exceptionni Conditions and No Sen! Weld Additional test programs were performed to verify acceptable performance of the sleeve lower mechanical joint to accommodate exceptional conditions which may exist in the steam generator tubes and conditions which may be encountered during installation of sleeves.
These exceptional conditions in steam generator tube characteristics and sleeving operation process parameters included:
. shorter lengths of roller expanded lower tube joints shorter lengths of roller expanded lower sleeve joints
. The specific exceptional tube conditions and changes to the sleeving process parameters tested in the first program, are shown in Table 4-8.
Each process operation and sequence of operations employed in fabricating each test sample was consistent -
with those specified for sleeves to be installed by Deld procedures. In addition, the exceptional tube conditions and changes to the sleeving process parameters described in Table 4-9 were included in the assembly of tube and collar subassemblies.
WPF1147A-4:1b.052793 4-25
r- . - -,. ,
Table 4-8 Verification Test Results for liFJ Lower Joints with Exceptional Conditions for Tube and Sleeve - 7/8 Inch Sleeves a,c.c NOTES:
l l. The W sleeve end et RT 3 botnied pmumly de,ng de exes angererve cargmem test. Steeve lengths he an sukqwnt sleews were shocened 1 The weld between em steen and te sees end cap of RT 2 fasted preeewly. .
'WPF1147A-4:1tV052793 *g *
~ 4-26 '
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4.4.1.3 Lower Joint Testing with Seal Weld Nine specimens were fabricated in collars with laser seal welds added to the sleeve end at the elevation of the tubesheet clad. Rey were then subjected to the fatigue, thermal cycling, compressive, and tensile ,
test as defined in Table 4-6. De results of this testing are summarized in Table 4-10. [
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4.4.2 Free Span Joint Mechanical Testing ,
Free spanjoints are representative of the tubesheet sleeve upperjoint and bothjoints of the tube support sleeves. His joint configuration, where there is no tubesheet backing the tube, is simulated using a test .
specimen as shown in Figure 4-2.
l Eleven free span weld specimens were fabricated using representative field parameters. All specimens were then stress relieved to account for the mechanical property effects resulting from thermal treatment.
'i All free span test specimens were given a stress relief heat treatment in'the. range of [
]^** The temperature source was a radiant heater installed inside the sleeve which was centered on the weld. The maximum temperature anained by the tube was measured by thermocouple l attached to the tube outer surface and summarized in Table 4-11. De temperature was ramped up [ !
]^ C'* Following stress relief the -
thermocouple attachments were filed off. ;
4.4.2.1 Free Span Joint Test Results ne welds were subjected to leak testing [
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l, 4.4.2.2 Impact of Tube Fixity on Free Span Weld Performance ;
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Under certain conditions tubes may become locked to the support plate structure of the steam generator, l normally during operation at full temperature (approximately 600*F). Upon cool down, differential 4
i WPF1147A-tibl052793 l 4-28 j
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4.4.23 Results of Fixed Tube Free Span Welding i~
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HEJ Lower Joint Test Results (with Seal Weld) - 7/8 Inch Sleeves j I
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Table 4-11 Free Span Joint Maximum Stress Relief Temperature - 7/8 Inch Sleeves Specimen Number Maximum Temperatur ('F)
_ _ a.c e L-536 L-540 L-543 L-544 .
L-546 L-548 .
L-550 L-551 )
i L-552 L-555 !
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Table 412 ,
Free Span Joint Leak Rate and Loading Data - 7/8 Inch Sleeves P AC'C - _ .
6 Specimen Number
. L-536 1 540 6
l 543 1 544 ,
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. I 55 Leak rate is in drops per minute. !
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4.5 References
- 1. - WCAP-13088, Rev.1, " Westinghouse Series 44 and 51 Steam Generator Sleeving Report (Laser-Welded Sleeves),".1/93 (Westinghouse Proprietary Class 2) -
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t-5.0 STRESS CORROSION TESTING OF LASER WELDED SLEEVE JOINTS l He material used for sleeving, Alloy 690 TT (thermally treated), has been uemonstrated to be highly resistant to intergranular stress corrosion cracking (IGSCC) under steam generator conditions :
(Reference 1). He resistance of the laser welded sleeve joint to in-senice corrosion is directly related ;
to the resistance of the Alloy 600 tubing to intergranular corrosion cracking. Stresses in the tubing, either I i
senice operating stresses or residual stresses, are a major factor in determining the response of the material in terms of IGSCC. Two potential sources of residual stresses in the laser welded sleeving
,- process include a) minor stresses related to hydraulic expansion during sleeve placement and b) residual f stresses that may be introduced as a result of welding.
His section summarizes the results of a testing program to evaluate the resistance of laser sleeve weldments in steam generator tubing to primary water stress corrosion (PWSCC). The testing was ,
conducted under conditions which accelerate corrosion in steam generator materials that may be susceptibic to stress corrosion cracking during long term steam generator senice. The laser welding processes used to fabricate the samples for these tests are representative of the neodymium pulsed YAG (Nd:YAG) laser currently used for sleeve welding and the CO: laser previously used in a field sleeve welding application. ;
5.1 Corrosion Test Description An accelerated corrosion test developed by Westinghouse is used as a means tu evaluate the resistance of steam generator materials to degradation in steam generator primary water environments. De test produces the intergranular stress corrosion cracking type degradation that has been observed in some mill annealed Alloy 600 steam generator tubing, but in a reduced time period. De test has also been found to provide the same relative ranking of heats of tubing material in terms of resistance to IGSCC that has been observed in senice. ;
The accelerated test is conducted in an autoclave operating at 750*F (400 C) with steam at 3000 psig. ,
The steam contains [ ]*" with each ion at !
30 ppm as a sodium salt. The ID of the specimen is exposed to the 3000 psi doped steam while the OD
. sees undoped steam at 1500 psi.
The configuration of the laser welded specimens used in the corrosion testing of a free-span upperjoint {
as illustrated in Figure 5-1. The sleeve joints were fabricated using equipment and practices representative of field sleeving operations. The doped steam test environment is introduced to the inside of the sleeve i and has access to the ID of the sleeve, one side of the weld joint, and to the OD of the sleeve and the ID of the tube on the same side of the weld joint. The other side of the weld joint and the OD of the tube ,
are exposed to the 1500 psi, undoped steam environment. The 1500 psi differential across the tube wall ;
simulates the active loading that is present in operating steam generators. In this way it is possible to test i the weld under ness conditions representative of those in the generator.
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The configuration of the lower tubesheet sleeve weld joint is illustrated in Figure 5-2. As in the case of the free span weld corrosion test, the doped steam em'ironment is introduced to the ID of the sleeve and has access to the one side of the weld. He OD of the tube is exposed to the undoped steam, t
The corrosion performance of the sleeve weld joint is compared with that of tube roll transitions exposed to the same test environment. The roll transition control samples illustrated in Figure 5-3 are representative of the transitions found at the top of the tubesheet in full depth, hani rolled steam generator tubes. The inclusion of the potentially PWSCC susceptible configuration (the roll transition) in the test provides verification of the aggressiveness of the corrosion test environment. Any variability in the .
aggressiveness of the emironment from one autoclave run to ancther is accounted for by having roll !
transition controls in each run. .
The time for a corrosion crack to progress through the tube wall of the test sample is measured in the accelerated corrosion test. For both roll transitions and sleeve welds, a through wall crack will result in a decrease in the 1500 psi differential (3000 psi ID,1500 psi OD). The time at which the differential pressure changes is recorded as the time to sample failure.
1 5.2 Corrosion Resistance of Free-Span Laser Welded Joints - As Welded Condition Corrosion tests have been performed on laser welded sleeve joints fabricated by the CO2 laser Process and by the pulsed Nd:YAG laser process. They are both included in this discussion because there are similarities in the :orrosion resistance of the joints fabricated by these laser welding methods.
Most of the weldedjoint corrosion samples and roll transition sections were fabricated from mill annealed Alloy 600 tubing from Heats NX-1019 and NX-7368. These are high carbon heats (0.04 per cent C) which previous testing has shown to be sensitive to PWSCC, and which have been used in a variety of corrosion test programs over the past several years. A set of CO2 laser welded samples was also fabricated from a lower carbon (0.02 per cent C) mill annealed Alloy 600 tubing, Heat NX-9621, which has exhibited susceptibility to PWSCC. The lower carbon heat was included to detennine if the carbon difference produced adverse metallurgical changes during welding. [
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De response of laser welded joints to the accelerated corrosion conditions is shown in Figures 5-5 and 5-6 for CO 2welds and in Table 5-1 and Figure 5-7 for Nd:YAG laser welds. Rese figures are log-normal distribution plots of the cumulative percentage of samples exhibiting cracking as a function of time. The ,
as-welded joints generally exhibited times for through wall IGSCC in [
]" than that of the roll transitions. One tubing heat, NX-2721, exhibited about
[ ]" for cracking for the roll transition and the as-welded joints. [
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i 5.3 Corrosion Resistance of Free-Span Laser Welded Joints - With Post Weld Stress Relief Because stress corrosion cracking is dependent to a large extent on residual stresses, a reduction in the .
residual stress level in the laser sleeve weldments will enhance the corrosion resistance of the weldedjoint.
During the CO 2laser weld program, extensive development of a post weld stress relief heat treatment was conducted. A local stress relief treatment [ ]"' was developed. The stress relief parameters developed, [ ]"', reduce the residual stresses significantly without significant microstructural changes.
he effectiveness of a stress relief treatment is evident in Figure 5-5 where a minimum [
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]"' in the time to cracking in heat treated welds over as-fabricated welds can be seen. The beneficial effect of stress reliefis also evident la the Nd:YAG laser welds (see Figure 5-7) made with both CLW and CMP parameters. The test of stress relieved CLW and CMP parameter weld joints [
]" This indicates more than a ten fold increase in time to cracking compared to that of an as-welded joint. The effect of the stress relief can also be seen in the cross section of the heat treated CLW weldment shown in Figure 5-8. Only minor IGSCC-[ ,
]" corrosion test. His suggests a decrease in the cracking rate of stress relievedjoints to [
]" as-welded joints. In addition, there was no evidence of the minor corrosion at the weld surface that was noted previously for an as-welded corrosion test sample.
WP1147A-5:1h"J52793 5-3
5.4 Corrosion Resistance Evaluation of Lower Tubesheet Sleeve Laser Welded Joints Post weld stress relief heat treatment is [
]" Accelerated corrosion testing was performed on specimens representative of the as-fabricated lower tubesheet sleeve joint for 0.875 inch diameter tubing, with the sample configuration shown in Figure 5-2. For control purposes, tube roll transition specimens were included in the corrosion tests as reference standards.
The specimens were subjected to the steam test conditions described in Section 5.1 for a [ '
]" The corrosion test results, tabulated in Table 5-2, show that the roll transition samples [ ]" with previous tests of roll transition samples. One of the welded .
sleeve samples, sample C1LSR-01, [
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5.5 Effects of Sleeving on Tube-to-Tubesheet Weld )
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l 5.5.1 Lower HEJ Joint The effect of hard rolling the sleeve over the tube-to-tubesheet weld was examined in the sleeving of i 0.750 inch OD tubes. Evaluation of the 0.750 inch tubes showed no tearing or other degrading effects on the weld after hard rolling.
5.5.2 Lower Seal Weld .
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Ju WPil47A 5:1b/052793 5-4
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5.6 Outside Diameter Surface Condition Because the sleeving operation is conducted from the primary side, no operations are conducted on the '
tubing OD surface. In operational steam generators, the outside surfaces of the tubes can collect boiler water deposits and scales. These are typically oxides or minerals in the thermodynamically stable form ,
of the constituent elements, magnetite being the most prominent deposit. At the temperatures of the tubing OD during the sleeve weldings and thermal treatment, these compounds are typically stable and do not thermally decompose. All such compounds have molecular structures that are too large for diffusion into
.- the lattice of the Alloy 600 tubing. Reactions between these stable oxides and minerals and the alloying elements of the Alloy 600 tubing are thermodynamically unfavorable. Consequently the presence of boiler sludge / scale species on the OD surfaces of tubes that receive the temperatures associated with LWS is not expected to produce deleterious tube-sludge / scale interactions.
Three tests performed as a part of the development of a sleeve brazing technique, also support the preceding discussions. The first test involved a laboratory evaluation in which a braze cycle was applied to tubing in contact with simulated plant sludge. The braze cycle involved [
]". Bend tests oflongitudinal sections removed from the brazed area showed no embrittlement as a result of the thermal cycle or exposure to the sludge stimulant. A second test involved microprobe analyses of polished metallographic cross sections. Results indicated the presence of Fe, Ni, Cr, Cu and Zn on the tube OD surface, but no evidence was found of diffusion into the tubing. A third test involved removal of a tube from an operating plant which was brazed in the region of sludge. The pulled tube was analyzed for the presence of contaminants on the OD surface and beneath the OD surface. The microprobe analysis detected Fe, P, Si, Cu, Ca and Na on the tube OD, but there was no indication of diffusion into the tube. l In addition to the above tests, archive tubes from two plants were welded and a microanalytical s examination was made for contaminant ingress before and after welding. Before welding, [ ,
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. A final test involved metallographic observations of three areas on a U-bend of Alloy 600 tubing which was coated with sludge and heat treated in air [ f
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To summarize, several observations have been made for a variety of Alloy 600 samples heated to j temperatures from [ ]"in the presence of typical secondary side chemical species.
No significant diffusion, corrosion, or embrittlement of the tubing has been found.
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1 Accelerated Corrosion Test Specimen for Welded Joint Configuration j 1
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Figure 5-4 i-IGSCC in Alloy 600 Tube of YAG Laser Welded -
Sleeve Joint After 109 Hours in 750T Steam Accelerated Corrosion Test
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Figure 5-5 Cumulative l'er Cent Cracking for CO, Laser Welded Sleeves ;
in 750T . Accelerated Steam Corrosion Test WP1147A-5:1boS2793 5-10
a,c.e Figure 5-6 Cumulative Per Cent Cracking for CO, Laser Welded Sleeves in 750*F Accelerated Steam Corrosion Test WP1147A-5:1NO52793 5-11
Table 5-1 Summary of Accelerated 750*F Steam Corrosion Test Results for YAG Laser Sleeve Welds
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- Welded Sleese Joint after 1000 Hours in 750*F Steam Accelerated Corrusion Test t
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Corrosion Resistance Evaluation of ;
Lower Tubesheet Laser Welded Sleeve Joints ,
i Mockup: Alloy 600 MA (Heat 7368,0.875 in. OD) tube, mechanically expanded into steel collar {
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Illustration of Path of IGSCC in the Alloy 600 Tube of Lower Tubesheet !
Sleeve Welded Joint. Crack Initiated at Point A and Progressed to Point B WP1147A 5;1MJ52793 5-16
' 5.7 References
- 1. " Alloy 690 for Steam Generator Tubing Applications," EPRI Report NP-699'-SD, Final Report for 3 Program S408-6, October 1990.
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6.0 INSTALLATION PROCESS DESCRIPTION The following description of the sleeving process pertains to current processes used. Westinghouse continues to enhance the tooling and processes through development programs. As enhanced techniques are developed and verified they will be utilized. Use of enhanced techniques which do not materially affect the technical justificadon presented in this report are considered to be acceptable for application.
Section XI, Article IWB-4330 (Reference 1), of the ASME Code is used as a guideline to determine which variables require requalification. ,
I The installation processes described in this section were developed and used for the installation of 7/8 inch sleeves. In the cases where sleeve / tube configuration diameters would require it, the corresponding y
processes will be requalified for the 3/4 inch sleeves. ]
The sleeves are fabricated under controlled conditions, serialized, cleaned, and inspected. They are l typically placed in polyethylene sleeves, and packaged in protective styrofoam trays inside wood boxes.
Upon receipt at the site, the boxed sleeves are stored in a controlled area outside containment aad as required moved to a low radiation, controlled region inside containment. Here the sealed sleeve box is opened and the sleeve removed, inspected and placed in a protective sleeve carrying case for transport to the steam generator platform. The sleeve packaging specification is extremely stringent and, if unopened, the sleeve package is suitable for long term storage.
Sleeve installation consists of a series of steps starting with tube end preparation (if necessary) and progressing through tube cleaning, sleeve insertion, hydraulic expansion at both the lower and upper joint, hard rolling the lower tubesheet joint locations, welding the upper joint [
]*. visual inspection and eddy current inspection. 'Ihe sleeving sequence and process are outlined in Table 6-1. These steps are described in the following sections. More information on the currently used equipment can be obtained from References 2,3, and 4.
6.1 Tube Preparation There are two steps involved in preparing the steam generator tubes for the sleeving operation. These
. consist of rolling at the tube mouth and tube cleaning. Tube end rolling is performed only if necessary to insert a sleeve.
6.1.1 Tube End Rolling (Contingency)
If gaging or inspection of tube inside diameter measurements indicate a need for tube end rolling to provide a uniform tube opening for sleeve insertion, a light mechanical rolling operation will be performed. This is sufficient to prepare the mouth of the tube for sleeve insertion without adversely affecting the original expanded tube or the tube-to-tubesheet weld. Tube end rolling will be performed only as a contingency.
WP1147A-6:1b!052603 6-1 l
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Testing of the rolling of all three of the types of tube welds,i.e., tube OD weld (for the protruding tube ;
joint), recessed and flush, has been performed and has been confirmed to be acceptable based on mechanical considerations. Westinghouse has performed tube end rolling of all of these types of tube welds in the field.
6.1.2 Tube Cleaning The sleeving process includes cleaning the inside diameter area of tubes to be sleeved to prepare the tube l surface for the upper and lower joint formation by removing boric acid, frangible oxides and foreign .
, {
material. Evaluation has demonstrated that this process does not remove any significant fraction of the tube wall base material. Cleaning also reduces the radiation shine from the tube inside diameter, thus .
contributing to reducing man-rem exposure. ,
The interior surface of each candidate tube will be cleaned by a [
]"" The hone bnish is mounted on a flexible drive shaft that is driven by an pneumatic ,
motor and carries reactor grade deionized flushing water to the hone brush. The hone bnish is driven to ;
a predetermined height in the tube that is greater than the sleeve length in order to adequately clean the !
joint area. [ ;
]"" The Tube Cleaning End Effector mounts to a tool delivery robot and consists of a j guide tube sight glass and a flexible seal designed to surround the tube end and contain the spent flushing water. A flexible conduit is attached to the guide tube and connects to the tube cleaning unit on the steam generator platform. The conduit acts as a closed loop system which serves to guide the drive shaft / hone l brush assembly through the guide tube to the candidate tube and also to carry the spent flushing water to an air driven diaphragm pump which routes the water to the radioactive waste drain.
i Currently tube cleaning is required as part of the sleeve installation piocess. However, test programs are l planned to evaluate the necessity of this process step. Should subsequent testing indicate acceptable weld [
results without it, as judged by weld performance meeting the mechanical, leakage inspection criteria defined in this document, honing may be dropped from the installation sequence. To implement welding without honing, the weld would be requalified and a "no-hone" weld process specification prepared. ;
6.2 Sleeve Insertion and Expansion
+
When all the candidate tubes have been cleaned, the tube cleaning end effector will be removed from the -
^
tool delivery robot and the Select and Locate End Effector (SALEE) will be installed. The SALEE consists of two pneumatic camlocks, dual pneumatic gripper assemblies, a pneumatic translation cylinder, a motorized drive assembly, and a sleeve delivery conduit t
WP1147A-6:1br052603 6-2
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Table 61 Sleeve Process Sequence Summary TUBE PREPARATION 1) Light Mechanical Roll Tbbe Ends (if necessary)
- 2) Clean Tube Inside Surface ,
i SLEEVE INSERTION 3) Insert Sleeve / Expansion Mandrel Assembly +
- 4) Hydraulically Expand Sleeve Top and Bonom Joints TUBESHEET LOWER JOINT 5) Roll Expand Tubesheet Lower Sleeve FORMATION End ;
WELD OPERATION 6) Weld Upper and Lower Support Sleeve Joints
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INSPECDON 8) Visually Inspect Lower Tubesheet
STRESS RELIEF 10) Post Weld Stress Relief Sleeve Welds
[ _]" ,
. INSPECTION 11) Baseline Eddy Current Sleeves i
f WP1147A4:1b/052693 6-3 i
The tool delivery robot draws the SALEE througt the manway into the channel head. It then positions the SALEE to receive a sleeve, tilting the tool such that the bottom of the tool points toward the manway and the sleeve delivery conduit provides linear access. At this point, the platform worker pushes a sleeve / mandrel assembly through the conduit untilit is able to be gripped by the translating upper gripper.
The tool delivery robot then moves the SALEE to the candidate tube. Camlocks are then inserted into nearby tubes and pressurized to secure the SALEE to the tubesheet.
Insertion of the sleeve / mandrel assembly into the candidate tube is accomplished by a combination of. ,
SALEE's translating gripper assembly and the motorized drive assembly which pushes the sleeve to the desired axial elevation. For tube support sleeves, the support is found by using an eddy current coil which .
is an integral part of the expansion mandrel. The sleeve is positioned by using the grippers and translating cylinder to pull the sleeve into position to bridge the tube support. For tubesheet sleeves, the sleeve is positioned by use of a positive stop on the delivery system.
At this point, the sleeve is hydraulically expanded. 'Ihe bladder style hydraulic expansion mandrel is connected to the high pressure fluid source, the Lightweight Expansion Unit (LEU), via high pressure flexible stainless tubing. The Lightweight Expansion Unit is controlled by the Sleeverrube Expansion Controller (SfrEC), a microprocessor controlled expansion box which is an expansion control system previously proven in various sleeving programs. The SfrEC activates, monitors, and terminates the tube expansion process when proper expansion has been achieved.
i The one step process hydraulically expands both the lower and upper expansion zones simultaneously.
The computer controlled expansion system automatically applies the proper controlled pressure depending upon the respective yield strengths and diametrical clearance between the tube and sleeve. The contact forces between the sleeve and tube due to the initial hydraulic expansion are sufficient to keep the sleeve from moving during subsequent operations. At the end of the cycle, the' control computer provides an indication to the operator that the expansion cycle has been properly completed.
When the expansion is complete, the mandrel is removed from the expanded sleeve by reversing the above insenion s quence. The SALEE is then repositioned to receive another sleeve / mandrel assembly.
6.3 IIFJ Lower Joint (Tubesheet Sleeves)
In the tubesheet, the sleese is joined to the tube by a hard roll (following the hydraulic expansion) performed with a roll expander [
]*" Control of the mechanical expansionis maintained through [
3au i-WP1147A-6:1WO52693 6-4
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6.4 General Description of Laser Weld Operation $
Welding of the upper tubesheet sleeve joint and the upper and lower tube support sleeve joints will be :
accomplished by a specially developed laser beam transmission system and rotating weld head. This system employs a Nd:YAG laser energy sou ce located in a trailer ortside of containment. The energy of the laser is delivered to the steam generator plationn junction box through a fiber optic cable. The fiber -
optic contains an intrinsic safety wire which protects personnel in the case of damage to the fiber. The f weld head is connected to the platform junction box by a prealigned fiber optic coupler. Each weld head ;
contains the necessary optics, fiber termination and tracking device to correctly focus the laser beam e-the interior of the sleeve.
The weld head /flber optic assembly is precisely positioned within the hydraulic expansion region using the SALEE (described earlier) and an eddy current coil located on the weld head. At the initiation of )
welding operations, the shielding gas and laser beam are delivered to the welding head. During the l welding process the head is rotated around the inside of the tube to produce the weld. A motor, gear train, j and encoder provide the controlled rotary motion to deliver a 360 degree weld around the sleeve circumference.
The welding parameters, qualified to the rules of the ASME code, are computer controlled at the weld operators station. The essential variables per Code Case N-395 are monitored and documented for field !
weld acceptance.
6.5 Reuelding -
Under some conditions, the initial attempt at making a laser weld may be interrupted before completion.
- Also, the ultrasonic test (UT) examination of a completed initial weld may be indeterminate resulting in the weld being rejected. In these cases, an additional weld, having the same nominal chsracteristics as the initial weld, will be made close to and either inboard or outboard of the initial weld. If the sleeve / tube has not been perforated by the interrupted weld, an additional weld, having the same nominal l characteristics as the original weld, will be made in the expansion zone near the original weld either [
inboard or outboard of this initial wall. If a perforation of the sleeve is suspected in the initial weld area, l
. the repair weld will be located inboard of the initial weld. Otherwise, the repair weld will be located outboard of the initial weld. If the sleeve / tube were perforated during intermption of the initial weld, the I
. tube would be removed from senice.
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6.6 Post-Weld Heat Treatment [ ]"
6.6.1 Post-Weld Heat Treatment Tooling he tooling required to perform the stress relief process consists of four basic items: j
- a. A fiber optic probe
- b. A heater (production) probe l
- c. A pop-up end effector .
- d. A production and effector De fiber optic probe is used in conjunction with the pop-up end effector. He end effector places a probe ,
within the proper zone to perform the stress relief operation. [ ;
-] This is done by using the ROSA robotic arm and the SALEE to sequentially place production probes at the proper welded sleeve / tube interfaces, including reweld locations, followed by application of the stress relief process.
6.6.2 Post Weld Heat Treat Process ,.
De laser welded joints (LWJ) exhibit [ ,
f' Westinghouse has extensive experience in stress relief processes from prior work on U-Bend and support plate heat treat programs. He objective of the laser weld post-weld heat treatment is to relieve residual stresses in the sleeve / tube that may be introduced by application of the welding process, he length of - j sleeve / tube heat treatment spans the weld and the adjacent heat affected zone.
~
To satisfactorily relieve the residual stresses, it was necessary to develop the optimal heat up, soak, and-ramp down power cycles. Several physical factors affect the control of tube temperature within the ,
required temperature band:
- 1. De tube is predominantly cooled by radiation, with minor effects of conduction and convection.
- 2. De physical configuration (power density) of the heat source affects heat distribution within the tube. ;
wPit47A4:lt/052693 '
6-6 i
- 3. The heat source and the heated portion of the tube cannot be excessively long. Under certain boundary conditions of tube fixity, excessive compressive stresses can occur within the tube during heat treatment. This could result in bowing or barreling of the tube.
- 4. The process has to account for weld axial positional tolerances as well as heater axial positional tolerances.
To address these factors, the heat source was sized such that it heated the weld and heat affected zone with
/ sufficient margin to allow for axial position variations.
Given the heat source, laboratory tests were performed which addressed the following issues:
l
- a. Nominal heat source power.
I
- b. Initial heat source power profile to expedite the time required to achieve acceptable tube temperatures.- I l
- c. Acceptable soak powers and temperatures. i l
- d. Effect of varying tube emissivities.
- e. Effect of a misplaced heater.
- f. Circumferential tube temperature profile,
- g. Axial tube temperature profile,
- h. Sleeve to tube temperature gradient.
The stress relief process was verified through extensive mockup testing. The test mockup shown in -
Figure 6-2 was used for stress relief process testing. The initial sleeve / tube samples are shown in Figure 6-3. [
3u The sleeve / tube samples used for final process development were pmtotypic of the field sleeveAube joint configuration, shown in Figure 6-4. The weld centerline was positioned [
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WP1147A-6:1bruS2603 6-13
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6.7 Inspection Plan ;
In order to verify the final sleeve installation, inspections will be performed on sleeved tubes to verify ,
installation and to establish a baseline for future eddy current examination of the sleeved tubes. Specific NDE processes are discussed in Section 7.0.
if it is necessary to remove a sleeved tube from senice as judged by an evaluation of a specific sleeve / tube configuration, tooling and processes are available to plug the tube.
6.8 References
- 1. ASME Boiler and Pressure Vessel Code,Section XI, Article IWB-4300,1989 Edition,1989 Addenda.
- 2. Boone, P. J., " ROSA III, A Third Generation Steam Generator Senice Robot Targeted at Reducing Steam Generator Maintenance Exposure," CSNI/UNIPEDE Specialists Meeting on Operating j Experience with Steam Generator, paper 6.7, Bmssels, Belgium, September 1991.
- 3. Wagner, T. R., VanHulle, L, " Development of a Steam Generator Sleeving System Using Fiber Optic Transmission of Laser Light," CSNI/UNIPEDE Specialists Meeting on Operating Experience with ;
Steam Generators, paper 8.6, Brussels, Belgium, September 1991.
- 4. Wagner, T. R., " Laser Welded Sleeving in Steam Generators," AWS/EPRI Seminar. Paper IID, Orlando, Florida, December 1991.
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7.0 NDE INSPECTABILITY 7he welding parameters are computer controlled at the weld operator's station. 'Ihe essential variables, per ASME Code Case N-395, are monitored and documented to produce repeatability of the weld process.
In addition, two non-destructive examination (NDE) capabilities have been developed to evaluate the success of the sleeving process. One method is used to confirm that the laser welds meet critical process dimensions and acceptable weld quality. The second method is then applied to establish the necessary baseline data to facilitate subsequent routine in-service inspection capability.
The installation processes described in this section were developed and used for the installation of 7/8 inch sleeves. In the cases where sleeve / tube configuration diameters require it, the corresponding processes will be requalified for the 3/4 inch sleeves.
l l 7.1 Inspection Plan Logic The basic tubesheet sleeve inspection plan shall consist of:
A. Eddy Current Examination (Section 7.3) [ ]d
- 1. Demonstrate presence of upper and lower hydraulic expansions
- 2. Demonstrate lower roll joint presence 3
- 3. Determine location of upper _ weld j
- 4. Recerd baseline of entire sleeved tube for future inspections !
D. Ultrasonic Inspection (Section 7.2) [ ]d or alternate methods (Section 7.4).
- 1. Demonstrate quality of upper weld
- 2. Determine width of the upper weld d
C. Visual Inspection [ J l
- 1. Exhibit presence and full circumference continuity oflower weld, if seal weld option selected D. Weld Process Control { ]d
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t WPil47A-7:1b/052793 7-1
The basic tube support sleeve inspection of the sleeved tubes shall consist of: ,
A. Eddy Cunent Examiriation (Section 7.3) [ ]*
- 1. Demonstrate presence of upper and lower hydraulic expansions
- 3. Record baseline of entire sleeved tube for future inspections B. Ultrasonic Inspection (Section 7.2) [ ]* or alternate methods (Section 7.4) ,
- 1. Determine quality of the upper and lower welds -
- 2. Determine if minimum width requirement of the upper and lower welds is met.
C. Weld Process Control [ ]d
- 1. Demonstrate weld process parameters comply with qualified weld process specification 7.2 General Process Overview of Ultrasonic Examination The ultrasonic inspection process is based on further refinements of past well-known and field-proven a techniques used on brazed and CO2 laser welded sleeves installed by Westinghouse. ;
The inspection process developed for application to the laser welds uses the transmission of ultrasound to the interface region (i.e., the sleeve OD/ tube ID boundary) and analyzing the amount of reflected energy from that region. An acceptable weldjoint should present no acoustic reflections above a calibrated limit ~
at the weld interface, but produce reflection from the tube OD that is above a calibrated limit.
Appmpriate transducer, instrumentation and delivery systems have been designed and techniques ,
established to demonstrate detectability and resolution of relevant defects at the interface. [
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- 7.2.1 Principle of Operation and Data Processing of Ultrasonic Examination ,
e The ultrasonic inspection of a laser weld is schematically outlined in Figure 7-1. An ultrasonic wave is launched by the application of a pulse to a piezoelectric transducer. The wave propagates in the couplant WP1147A-7:1WQ52793 7-2
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Figure 7-1 Ultrasonic Inspection of Welded Sleeve Joint 471147A-7:1tA!52793 7-3
t medium (water) until it strikes the sleeve. Ultrasonic energy is both transmitted and reflected at the ,
boundary. The reflected wave returns to the transducer where it is converted back to an electrical signal, which is amplified and displayed on a UT instrument oscilloscope. .
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An automated system is used for digitizing and storing the UT wave forms [ f 3us 7.2.2 Ultrasonic Inspection Equipment and Tooling
. The probe system is delivered by the Westinghouse ROSA zero entry system. The various subsystems include the water couplant, UT, motor drives, electrical systems and data display / storage. .
. i The probe motion is accomplished via rotary and axial drive modules which allow a range of speeds and axial advance per 360' scan of the transducer head. The axial advance allows for overlap providing a high degree of overlapping coverage without sacrificing resolution or sensitivity.
-1 The controls and displays are designed for trailer mounting outside containment. The system'also provides for easy periodic calibration of the UT subsystem on the steam' generator platform.
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'Ihe permanent record of the inspection is a color plot C-scan derived from the digitized and stored A-Scan waveforms. Figure 7-3 is an example of an acceptable laser weld C-scan. 7he UT instrument is used ;
with the gate modules synchronized to the front wall (sleeve I.D.) signal. [ ;
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7.2.3 Laser Weld Test Sample Results ;
l Ultrasonic test process criteria are developed by UT examination and subsequent destructive analysis of
.' sleeve weld samples. Process criteria are qualified by generating a variety of weld samples, some of which are modified to assure marginal and rejectable structural conditions. The samples are ultrasonically i examined, and the UT acceptance criteria are applied. No structurally unacceptable. welds may be. ;
accepted for the process / criteria to be qualified. .
Once qualified, the process requires a setup standard for calibration prior to weld examination.-
r The standard consists of a machined Alloy 690 thick-walled tube with the following reference reflectors (Figure 7-4):
- Tube ID machined to expaneded sleeve ID dimension.
- Tube OD machined to expanded sleeve OD dimension.
- Tube OD machined to parent tube OD.
l
- Simulated weld with minimum weld width allowable per structural criteria.
OD Flat bottomed hole with bottom at sleeve / tube interface dimension.
A plot of the setup standard scan is shown in Figure 7-5. (This figure depicts the UT setup standard for the 7/8 inch sleeve; a corresponding standard will be made for the 3/4 inch sleeve.) The plot shows the sleeve backwall reflection (gate 1) C-scan, the tube backwall reflection (gate 2) C-scan, and axial and
. circumferential section B-scans. A combined scan showing alogical combination of the gate 1 and gate 2 conditions as they relate to pre-determined thresholds is also available. A signal above the threshold in {
. gate 2 while gate 1 is below threshold indicates a region of weld.
7.2.4 Ultrasonic Inspection Summary 1 The UT laser weld inspection system can confirm that there is a metallurgical bond between the sleeve and the tube. 'Ihe system is used to determine any existence ofleak path across the weld and a mirdmum acceptable weld width for 360 degrees around the circumference.
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7.3 Eddy Current Inspection l 3
Upon conclusion of the sleeve installation process, a fina! eddy current inspection is performed on every !
installed sleeve to provide interpretable baseline data on the sleeve and tube. This information is gathered f by an eddy current process which utilizes a double cross wound coil. The double crosswound coil is designed to minimize the effects of geometry and weld zone changes that are 360'in nature,i.e.: upper and lower hydraulic expansion transition areas, roll expansion transition areas, top of sleeve, the band of good weld material, etc.
7.3.1 Eddy Current Inspection Principle of Operation ;
.- l De eddy current inspection equipment, techniques, and results presented herein apply to the proposed Westinghouse sleeving process. Eddy current inspections are routinely carried out on the steam generators in accordance with the Plant Technical Specifications. The purpose of these inspections is to detect at an ;
early state tube degradation that may have occurred during plant operation so that corrective action can be taken to minimize further degradation and reduce the potential for significant primary-to-secondary leakage.
The standard inspection procedure involves the use of a bobbin eddy current probe, with two !
circumferentially wound coils which are displaced axially along the probe body. The coils are connected in the so-called differential mode; that is, the system responds only when there is a difference in the i properties of the material surrounding the two coils. De coils are excited by using an eddy current -l instrument that displays changes in the material surrounding the coils by measuring .the electrical impedance of the coils. Presently, this involves simultaneous excitations of the coils with several different j test frequencies. l The outputs of the various frequencies are combined and recorded. He combined data yield an output [
in which signals resulting from conditions that do not affect the integrity of the tube are reduced. By reducing unwanted signals, improved inspectability of the tubing results (i.e., a higher signal-to-noise ratio). Regions in the steam generator such as the tube support plate, tubesheet laser weld area and sleeve transition zones are examples of areas where multifrequency processing has proven valuable in providing improved inspectability.
- After sleeve installation all sleeved tubes are subjected to an eddy current inspection which includes a ;
verification of correct sleeve installation for process control, degradation inspection and establishing a ;
baseline for all subsequent inspection comparison.
t There are a number of probe configurations that lend themselves to enhancing the inspection of the I
sleeve / tube assembly in the regions oflaser weld as well as configuration transitions. ne crosswound coil probe has been selected since it provides an advancement in the state-of-the-art over the conventional bobbin coil probe, yet retains the simplicity of the inspection procedure.
- wP1147A-7:lbr052793 j 7-11
_ _ ~,
I 7he inspection for degradation of the sleeve / tube assembly has typically been performed using crosswound !
coil probes operated with multifrequency excitation. For the weld free straight length regions of the sleeve / tube assembly, the inspection of the sleeve and tube is consistent with normal tubing inspections. .
In sleeve / tube assembly joint regions, data evaluation becomes more complex. The results discussed below l suggest the limits on the volume of degradation that can be detected in the vicinity of the laser weld and geometry changes. t i
7.3.2 Transition Region Eddy Current Inspection .
. 1 The detection and quantification of degradation at the transition regions of the sleeve / tube assembly ;
- I depend upon the signal-to-noise ratio between the degradation respons And te transition response. As '
a general mle, lower frequencies tend to suppress the transition signal mae to +he degradation signal at the expense of the ability to quantify the degradation. Similarly, the inspection of the tube through the ,
sleeve requires the use of low frequencies to achieve detection with an associated loss in quantification.. l Thus, the search for an optimum eddy current inspection represents a trade-off between detection and ;
quantification. With the crosswound coil type inspection, this optimization leads to a primary inspection frequency for the sleeve on the order of [ ]"" and for the tube and transition regions on the order of [ ]"". !
Figure 7-7 shows a typical [ ]"" calibration curve for the sleeve from which OD sleeve indications !
t can be assessed.
For the tube / sleeve combination, the use of the crosswound probe, coupled with a multifrequency mixing ;
technique for further reduction of the remaining noise signals significantly reduces the interference from . ;
all discontinuities (e.g., a diameter transition) which have 360-degree symmetry, providing improved ;
visibility for discrete discontinuities. As is shown in the accompanying figures, in the laboratory this !
technique can detect OD tube wall penetrations with acceptable signal-to-noise ratios at the transitions l when the volume of metal removed is equivalent to the ASME calibration standard. j i
The response from the sleeve / tube assembly transitions with the crosswound coil is shown in Figures 7-8, 7-9 and 7-10 for the sleeve standards, tube standards and transitions, respectively. Detectability in ;
transitions is enhanced by the combination of the various frequencies. For the crosswound probe, two ,
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frequency combinations are shown; the [ ]"# combination provides the overall detection.
capability while the [ ]"' combination provides improved sensitivity for the sleeve and some ,
quantification capability for the tube. Figure 7-11 shows the phase / depth curve for the tube using this ,
combination. As examples of the detection capability at the transitions, Figures 7-12 and 7-13 show the ,
responses of a 20 per cent OD penetration in the sleeve and 40 per cent OD penetration in the tuba respectively. t i
For the inspection of the region at the top end of the sleeve, the transition response signal-to-noise ratio {
is about a factor of fourless sensitive than thu of the expansions. Some additional inspectability has been WP1147A-7:1NOS2793 r 7-12 ;
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- Eddy Current Signals from the ASTM Standard, Machined on the Sleeve O.D. of the Sleeve / rube Assembly Without Expansion (Cross Wound Coil Probe)'
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i Figure 7 9 Eddy Current Signals from the ASTM Standard Machined on the Tube O.D. of the SleeveHube Assembly Without Expansion (Cross Wound Coil Probe)
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Figure 710 Eddy Current Signals from the Expansion Transition Region .I of the Sleeve / rube Assembly (Cross Wound CoilIYobe) ,
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Eddy Current Calibration Curve for ASTM Tube Standard at [ l'"
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l-Figure 712 Eddy Current Signal from a 20 Per Cent Deep Hole, Half the Volume of ASTM Standard, Machined on the Sleeve O.D. In the Expansion Transition Region of the j Sleeve / Tube Assembly (Cross Wound Coil IYobe) j
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Eddy Current Signal from a 40 Per Cent ASTM Standard, Maddoed on the Tube O.D. in the :
Expansion Transition Region of the Sleeve /fabe AnemWy (Cras Wound CeB Probe) .[
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i gained by tapering the wall thickness at the top end of the sleeve. His reduces the end-of-sleeve signal by a factor of approximately two. He crosswound coil, however, again significantly reduces the response l of the sleeve end. Figure 7-14 shows the response of various AShE tube calibration standards placed at the end of the sleeve using the cross-wound coil and the [ ]"# frequency combination. Note that under these conditions, degradation at the top end of the sleeve / tube assembly can be detected. .
De cases considered above cover the inspection of laser-welded and IEJ pressure boundaries in these areas:
(i) De entire length of the tube support sleeve between the upper and lower welds.
(ii) The entire length of the tubesheet sleeve extending from the upper weld down to the end of the sleeve. -
(iii) 7he entire length of the tube from the hot leg tube entry to the top support of the cold leg, with the exception of the following areas: ,
iila) The length of tubing between the upper and lower welds of each TSS.
iiib) The lerigth of tubing between the upper weld of a tubesheet sleeve, down to the tube length behind the hardroll area of the tubesheet sleeve. ,t l
Note that indication of tube degradation of any type including a complete break between the upper j weld joint and the lower weld joint does not require that the tube be removed from service. [
Also, in a free span joint with more than one weld, the weld closest to the end of the sleeve !
represents the joint to be inspected and the limit of sleeve inspection. f 7.3.3 Laser Weld Region Eddy Current Inspection t
ne only zone not addressed in Section 7.3.2 is the zone where the laser weld exists. f The hsis for the ECT of this structure was developed by test, using a prototype laser weld. The test !
sample used for this study was a prototypical laser weld in an expanded sleeve zone of a sleeve / tube -!
assembly. The weld was inspected before and after the introduction of a 40 per cent thru-wall 3/16 inch l diameter flat bottom hole placed on the outside surface of the tube at the centerline of the weld. This +
weld presents an axisymmetric condition similar to the transition geometry which is demonstrated by the ;
low phase angle signal similar to transition signals. The weld also displays a material disturbance by its ,
distinct lobes which can be successfully mixed out. l 1
Figure 7-15 shows the [ ]"# response from the weld zone and Figure 7-16 shows the successful , .[
]"# mix response using cross-wound coils. f
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Figure 714 Eddy Current Response of the ASD1 Tube Standard at the End of the Sleeve Using the Cams Wound Coil Probe and Af ultifrequency Combination WP1147A-7;1t@52793
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Crosswound [ ]"' Eddy Current Baseline of Laser Weld ,
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Figure 7-16 f
l Crosswound Mir Eddy Current Response Baseline of Laser Weld I
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7he [ ]"' combination has proven to be optimum for detection in the weld zone, particularly at the tube I.DJsleeve O.D. interface. Figures 7-17 and Figure 7-18 show the response of the 40 per cent FBH using [ ]"' and mix, respectively.
7.3.4 Eddy Current Inspection Summary Conventional eddy current techniques have been modified to incorporate the most recent technology in the inspection of the sleeve / tube assembly. The resultant inspection of the sleeve / tube assembly involves the use of a cross-wound coil for the straight regions of the sleeve / tube assembly and for the transition regions. The advent of digital E/C instrumentation and its attendant increased dynamic range and the '
availability of eight channels for four frequencies has expanded the use of the crosswound coil for sleeve -
inspection. While there is a significant advancement in the inspection of portions of the assembly using the cross-wound coil over conventional bobbin coils, efforts continue to advance the state-of-the-art in -
eddy current inspection techniques. As enhanced techniques are developed, they will be utilized after they are verified. For the present, the cross-wound coil probe represents an inspection technique that pro \ ides additional sensitivity and support for eddy current techniques as a viable means of assessing the sleeve / tube assembly.
7.4 Alternate Post Installation Acceptance Methods Ultrasonic or volumetric inspection is the prime method for post-installation weld quality evaluation, with eddy current examination being used as the prime in-service examination technique. However, there are cases, due [
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In support of accepting UT indeterminate welds, several alternate strategies will be applied, as agreed to by the implementing utility and Westinghouse. While this summary is not meant to preclude other methods,it is included to provide an indication of the riger of the alternate methods.
7.4.1 Bounding Inspections ,
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- j. Crosswound [ ]"' Eddy Current Response After 40 Per Cent
- i. Flat Ilottomed Hole was Placed in 0.D. of Tube at l ' Center of Weld
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Figure 7-18 Crosswoutui Mir Eddy Current Response After 40 Per Cent }
Flat Bottomed Hole was Placed in O.D. of Tube at Center of Weld t
WP1147A-7:thc52793 7-26 t
.I yss 7.4.2 Workmanship Samples 1
yss 7.43 Other Advanced Examination Techniques As other advanced techniques become available and are proven suitable, Westinghouse may elect, with utility concurrence, to alter its post-installation inspection program. [
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P In summary, Westinghouse proposes to apply alternate inspection techniques with utility concurrence as they become available. It is intending that this licensing report not preclude the use of these inspections as long as they can be demonstrated to provide the same degree or greater ofinspection rigor as the initial use methods identified in this report.
7.5 Insenice Inspection Plan for Sleeved Tubes The need exists to perform periodic inspections of the supplemented pressure boundary. The inservice inspection program will consist of the following:
a.' The sleeve will be eddy current inspected upon completion of installation to obtain a baseline ,
signature to which all subsequent inspections will be compared.
- b. Periodic inspections will be performed to monitor sleeve and tube wall conditions in accordance with .
_,- the inspection section of the individual plant Technical Specifications.
WP1147A-7:Ib952793 7-27
a 1he inspection of sleeves will necessitate the use of an eddy current probe that can pass through the sleeve ID. For the tube span between sleeves, this will result in a reduced fill factor. 'Ihe possibility for tube l degradation in free span lengths is extremely small. Plant data have shown that this area is less j j
susceptible to degradation than other locations. Any tube indication in this region will require further inspection by alternate techniques (i.e., surface riding probes) prior to acceptance of that indication. {
Otherwise the tube shall be tcmoved from senice by plugging. Any change in the eddy current signature of the sleeve and sleeve / tube joint region will require further inspection by alternate techniques prior to ;
i acceptance. Otherwise the tube containing the sleeve in question shall be removed from senice by :
plugging. -
l 7.6 References . j
- 1. Stubbe, J., Birthe, J Verbeek, K., " Qualification and Field Experience of Sleeving Repair Techniques: j CSNI/UNIPEDE Specialist Meeting on Operating Experience with Steam Generators, paper 8.7, ;
i Brussels, Belgium, September 1991.
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