ML20126M300
| ML20126M300 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 10/31/1992 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19303F172 | List: |
| References | |
| WCAP-13484, WCAP-13484-R01, WCAP-13484-R1, NUDOCS 9301080264 | |
| Download: ML20126M300 (142) | |
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WESTINGilOUSE CLASS 3 WCAP-13484 SG-92-08-028 Rev 1 BEAVER VALLEY UNITS 1 AND 2.
WESTINGilOUSE SERIES 51 STEAM GENERATOR SLEEVING REPORT Laser Welded Sleeves October 1992 C1992 Westinghouse Electric Corporation All Rights Reserved WESTINGilOUSE ELECTRIC CORPORATION NUCLEAR SERVICE DIVISION P.O. BOX 355 PITTSBURGil, PA 15230 wt w o we. m :n:
TABLE OF CONTENTS Section Title Page
1.0 INTRODUCTION
11 1.1 Report Applicability 1.[
1.2 Sleeving Boundary 12 2.0 SLEEVE DESCRIPTION AND DESIGN 2-1 2.1 Sleeve Design Description 21 2.2 Sleeve Design Docurnentation 22 3O ANALYTICAL VERIFICATION 3-1 3.1 Strectural Analysis 3-1 3.2 Thermal Hydraulic Analysis 3-1 4.0 MECH ANIC AL TESTS 4-1 4.1 Mechanical Test Conditions 4-1 4.2 Acceptance Criteria 4-1 4.3 Lower Sleeve Joint 44 4.4 Free Span Joint Mechanical Testing 4-7 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 - As-Welded 5-3 Condition 5.3 Corrosion Resistance of Free Span Laser Welded Joints - with Post Weld 5-10 Heat Treatrnent 5.4 Corrosion Resistance Evaluation of Lower Tubesheet 5-10 Laser Welded Joints 5.5 Effects of HEJ Sleeving on Tube-to-Tubesheet Weld 5-12 5.6 Outside Diameter (OD) Surface Condition 5-14 5.7 References 5-15 6.0 INSTALLATION PROCESS DESCRIFTION 6-1 6.1 Tube Preparation 6-1 6.2 Sleeve Insertion and Expansion 6-2 6.3 Lower Joint liard Roll (Tubesheet Sleeves) 6-4 WF04WocNP lbX)82692 i
TAllLE OF CONTENTS (contin'ued)
Section Title Page
~ 6.4 General Description of Laser Weld Operation 6 6.5 Inspection Plan' 6 6.6 References 6-6 7.0 NDE INSPECTABILITY 7-1 7.1
_ inspection Plan Logic
~-7-1 7.2 General Process Overview of Ultrasonic Inspection
._7-2
.' 7.3 Eddy Current inspection 7-6 7.4 Alternate Post-Installation Acceptance Methods 7-26 7.5 Insenice Inspection Plan for Sleeved Tubes
--7-27 7.6 References 7-28 s
- WRM50-tocNhibA)32692 ii P-rir T'Frfr
LIST OF TABLES Table Title Page 21 ASNIE Code and Regulatory Requirements 24 3-1 Summary of Niaterial Properties Tube Material 3-15 Solution Annealed inconel 600 3-2 Summary of hiaterial Properties Sleeve Material 3-16 Thermally Treated Alloy 690 3-3 Summary of Material Properties 3-17 Tubesheet Material SA-508 Class 2 3-4 Summary of Material Properties 3-18 Air 3-5 Summary of Material Properties 3-18 W ater 3-6 Criteria for Primary Stress Intensity Evaluation 3-19 Sleeve - Inconel 690 3-7 Criteria for Primary Stress Intensity Evaluation 3-19 Tube - Inconel 600 3-8 Criteria for Primary Plus Secondary Stress Intensity Evaluation 3-20 Sleeve - Inconel 600 3-9 Criteria for Primary Plus Secondary Stress Intensity Evaluation 3-20 Tube - Inconel 600 3-10 Summary of Normal Operating Transient Events 3-21 3-11 Umbrella Pressure Loads for Design, Faulted, and Test Conditions 3-22 3-12 Summary of Maximum Primary Stress Intensity 3-23 Full Length Tubesheet Laser Welded Sleeve Sleevefl'ube Weld Width of [
}"
WPO4 Woc:ltV082492 iii w._....
LIST OF TAllLES (Cont)
Tuble Title Page
- Maximum Range of Stress Intensity and Fatigue 3 24 -
3 13 Full Length Tubesheet Laser Welded Sleeve
- SleeveUube Weld Width of (
}"
Upper LWJ: Hydraulically Expanded Lower LWJ: Hydraulically Expanded 3-14 Maximum Range of_ Stress Intensity and Fatigue -
3-25 Full Length Tubesheet Laser Welded Sleeve l
SleeveRube Weld Width of [
1" Upper LWJ: Hydraulically Expanded Lower LWJ: Hydraulically Expanded 3 15 Maximum Range of Stress Intensity and Fatigue
-3 26 Support Plate Laser
1" 3 16 Maximum Range of Stress Intensity and Fatigue 3 27 Full Length Tubesheet Laser Welded Sleeve Sleevenube Weld Width of (
]"
Upper LWJ: Hydraulically Expanded Lower LWJ: Hydraulically Expanded 3 17 Maximum Range of Stress Intensity and Fatigue 3 28' Full Length Tubesheet Laser Welded Sleeve Sleeve 6ube Weld Width of [
]"
Upper LWJ: -Hydraulically Efpanded -
Lower LWJ: Hydraulically Expanded-3 18 Generic Tube Sleeving Calculations - Flcr Reduction and Hydraulic
- 3 53_.
Equivalency for Series 51 SGs 41 Mechanical Test Program Summary
=4-2 4-2 Maximum Allowable Leak Rates for Series 44 and 51 Steam Generators -
4 4-3 Test Results for As-Rolled Lower Joints 4-6 wPo4so wc: twos 249 iv i
l LIST OF TAllLES (Cont)
Table Title Page 4-4 Test Results for Lower joints with Excen"onal CmiGons 4-8 for Tube and Sleeve 4-5 Additional Tests Results for Lower Joints with Exceptional 4-9 Conditions foi Tube and Sleeve 4-6 Lower Joint Test Results (with Seal Weld) 4-10 4-7 Free Span Joint Maximum Stress Relief Temperature 4-13 48 Free Span Joint Leak Rate and Loading Data 4-14 5-1 Summary of Accelerated 750 F Steam Corrosion Test Results 5-8 for YAG Laser Sleeve Welds 5-2 Corrosion Resistance Evaluation of Lower Tubesheet 5-13 Laser Welded Sleeve Joints 6-1 Sleeve Process Sequence Summary 6-3
+
e
$1 WFN50-tocNP,1bS82692 V
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LIST OF FIGURES Figure -
Title Page 1-1 Example 12-inch Support Plate Sleeve Coverage in a-Series 51 Steam Generator' i-3 21 Tubesheet Laser Welded Sleeve Installed Configuration 25-2-2 Support Plate Laser (Velded Sleeve Installed Configuration
'2-6
~
3-1 Schematic of Tubesheet Sleeve Configuration 3 29 3-2 Channel Head / Tubesheet / Shell Model 3-30 3-3 Thermal / Hydraulic Boundary Conditions 3 31 Tubesheet Sleeve Analysis'
--3-4 Channel Head / Tubesheet / Shell Model 3-32; Primary Pressure Boundary Conditions 3-5 Channel Head / Tubesheet / Shell Model 3-33 Distoned Geometry Primary Pressure Loading 3-6 Boundary Condition for Unit Primary Pressure 3-34 Intact Tube: P u >. P sc -
e 3
3-7 Boundary Condition for Unit Primary Pressure 3-35' Intact Tube: Peu < Psec
'38 Boundary Condition for Unit Primary Pressure 3-36 '
Severed Tube: Peu > P sc 3
39 Boundary Condition for Unit Primary Pressure 3-37' Severed Tube: Peu < P sc 3
3-10 Boundary Condition for Unit Secondary Pressure 3 38
-Intact Tube:' Ppm > P sc 3
3-11 Boundary Condition for Unit Secondary Pressure 39 =
~
Intact Tube: Peu < P sc 3
. WPo450 tocNP:lt@82692 vi
LIST OF FIGURES (Cont).
. Figure --
Title Page 3 12 Boundary Condition for Unit Secondary Pressure 3-40 Severed Tube: Peu > P c 3t 3-13 Boundary Condition for Unit Secondary Pressure 3 Severed Tube: Peu < Psec 3 14 ANS Location - Lower LWJ 342 3 15 ANS Location - Upper LWJ -
3-43 3 16 Comparison Between Predicted and Measured Leak Rates 44?
3-17 Leak Rate Versus Crack Length 3-45 Series 51 Sleeves 3 18 Burst Pressure Versus Crack Length 3-46 Comparison of Test Results 3-19 Burst Pressure Versus Crack Length 347 Series 51 Sleeve 3 20 Hydraulic Equivalency Number for Series 51 Steam Generators 3-54 4-1 Tubesheet Sleeve Lower Joint Test Specimen
- 45 4-2 Free-Span Laser Welded Joint Test Specimen 4-11'-
5-1
- Accelerated Corrosion Test Specimen for Welded Joint Configuration 52-52 Accelerated Corrosion Test Specimen for Roll Transition Configuration 5-4 53 IGSCC in Alloy 600 Tube of YAG Laser Welded Sleeve -
-5 5 Joint After 109 Hours in 750*F Accelerated Steam Corrosion Test wroaso-toctwos:m vii
LIST OF FIGURES _(continued) -
- Figure
. Title Page 5 Cumulative Percent Cracking For CO: Laser Welded 5-6~
Sleeves in 750'F Accelerated Steam Corrosion Test 5-5 Cumulative Percent Cracking For CO Laser Welded
.57 2
Sleeves in 750*F Accelerated Steam Corrosion Tests 5-6 Cumulative Percent Cracking For YAG Laser Welded 9 Sleeves in 750'F Accelerated Steam Corrosion Test 5-7 hiinor IGSCC in Alloy 600 Tube of Stress Relieved 5-11' YAG Laser Welded Joint After 1000 Hours in 750*F Accelerated Steam Corrosion Test 1 Ultrasonic inspection of Welded Sleeve Joint 3 7-2 Typical Digitized UT Waveform 7 73 C-Scan From UT Examination of an Acceptable Laser Weld 7-7 7-4 UT Setup Standard 7-8' L
7-5 C-Scan from UT Examination of an Equipment Setup 79 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).
l l
l WPO450 tocIb/082492 viii
!~
LIST OF FIGURES (continued)
-- Figure Title'
- Page 7-9 Eddy Current Signals from the ASTN1 Standard,
- 7-15 hiachined on the Tube O.D. of the SleeveRube 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) 7-11 Eddy Carrent Calibration Curve for ASTM Tube 7 17 Standard at [
_ l'" and a Mix Using the Cross Wound Coil Probe 7 12 Eddy Current Signal from a 20% Deep Hole, 7-18 Half the Volume of ASTM Standard, Machined on the Sleeve O.D. in the Expansion Transition Region of the SleeveHube Assembly (Cross Wound Coil Probe).
7 13 Eddy Current Signal from a 40% ASTM
. 7 19 Standard, Machined on the Tube O.D. in the Expansion Transition Region of the SleeveRube Assembly (Cross Wound Coil Probe)
[
7-14 Eddy Curent Response of the ASTM Tube Standard
'7 20 at the 'dnd of the Sleeve Using the Cross Wound Coil Probe and Multifrequency Combination -
7 15 Crosswound [
l'" Eddy Current Baseline of 7 22 Laser Weld 7 16 :
Crosswound Mix Eddy Current Response Baseline of 7 23 Laser Weld 7-17 Crosswound [
1"* Eddy Current Response After.
7-24 40% Flat Bottomed Hole was Placed in OD of
. Tube at Center of Weld wrouwisaann IK l
1,IST OF FIGURES (continued)
Figure Title Page 7-18 Crosswound Mix Eddy Current Response Mter 40?c -
7-25 Flat Bottomed Hole was placed in OD of Tube at Center of Weld WPtM 53 toc NP.lb.U81692 X
j j
I 2
fl'.0 INTRODUCTION -
o Under Plant Technical Specification requirements steam generator tubes are periodically inspected for -
]
degradadon using non-destructive examinadon techniques. If established inspection criteria are exceeded, j
the tube must be removed from service by plugging or the tube must otherwise be brought back into-compliance with the Technical Specification Criteria. - Tube sleev:ng is one technique used to return the tube to an operable condidon. Tube sleeving is a process in which a smaller diameter tube or sleeve is positioned to span the area of degradadon. It is subsequently secured to the tube, forming a new pressure boundary and structural element in the area between the attachment points.
p Tius document was prepared to summarize the technical information developed to support licensing _of the --
laser welded sleeve installation process.
His report addresses two distinct types of sleeves - a tubesheet sleeve and a support plate sleeve. Each of these sleeve types has_ several insta!!ation options which can be applied. The tubesheet sleeve is-appropriate for all plants which have degradation at the top of the tubesheet, since ths-lower joint.is formed at the bottom of the tubesheet. - The support plate sleeve may be installed to bridge degradation located at tube support plate locations or in the free span section of the tube.
E Installation and inspection options will be selected in advance of performing the field campaign.- This determination will be made based on degradation history, current degradation rates, utility steam generacor -
maintenance strategy, schedule, and cost. Thus, the application can be optimited to utility needs by applying the proper combination of ' modular' sleeve-tube joint options.
n 1,1 Report Applicability This report is applicable to Westinghouse Series 51 steam generators installed at Duquesne Light Company's Beaver Valley Units I and 2. These steam generators are U tube heat exchangers with mill-annealed Alloy 600 heat transfer tubes which have a 0.875 inch nominal outside diameter (OD) and 0.050 inch nominal wall thickness.
Data is presented to support the applicadon of two sleeve designs: tubesheet and tube support plate.
Moreover, with each design, several utility selectable application options are provided. The sleeve size and opdons are:
Tube support plate sleeve:
12 inch long
. welding with post weld heat treatment
. : welding without post weld heat treatment WPO4501 ltVC42792 11
Tubesheet sleeve
. ~ 27. inches to 36 inches long [
l'
. straight or bowed (enhanced for peripheral coverage)
. - upper weld joint with post weld heat treatment
-. upper v :ld joint without post weld heat treatment
. -lower joint with seal weld
. lower joint without seal weld The slecves described herein have been designed, analyzed, or tested to meet the service requirements of.
the Series 51 steam generators through the use of conservative and enveloping thermal boundary conditions and structural loadings. The structural analysis and mechanical performance of the sleeves are based on installation in the hot leg of the steam generator, [
Y
~
1.2 Steeving floundary Tubes to be sleeved will be selected by radial location, tooling access (due to channelhead geometric constraints), sleeve length, and eddy current analysis of the extent and location of the degradation.-
The boundary.is determined by the amount of clearance below a given tube, as well as tooling and robot delivery system constraints. At the time of application the exact sleeving boundary will be developed.
For reference purposes, a typical Series 51 Rosa 111 sleeving coverage map for 12 inch long support plate sleeves is shown in Figure 1 1.
wiwsc>tawosw2 12
.e 0
t Figure 1 1 Example 12 inch Support Plate Sleeve Coverage in a Series 51 Steam Generator WP14%I Itv08 t@ 2 13
2.0 SLEEVE DESCRIPTION AND DESIGN 2.1 Sleese Design Description Tube sleeves effectively restore a degraded tube to a condition consistent with the tube's design requirements. The design of the sleeve and sleeving process is predicated on the design rules of Section III Subsection NB, of the ASME Code. Also, the sleeve design addresses dimensional constraints imposed by the tube inside diameter and installation tooling. These constraints include variations in tut e wall thickness, tube ovality, tube inside diameter, tube to tube sheet joint variations and runout / concentricity variations created during tubesheet drilling or alignment of tubesheet and support plate holes.
2.1.1 Tubesheet Sleeve The reference design of the tubesheet sleeve, as installed, is illustrated on Figure 2-1. At the upper end, the sleeve configuration consists of a section which is hydraulically expanded. The hydraulic expansion of the upper joint brings the sleeve into contact with the parent tube to achieve the proper titup geomeoy for welding. Following the hydraulic expansion, an autogenous weld, i.e., a weld which is performed without the addition of filler metal, is made between the sleeve and the tube using the laser welding process. This joint configuration is known as a laser welded joint (LWJ).
The tubesheet sleeve extends from the tubesheet primary face to above the tube degradation. 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 are to be positioned a [
L t.C The upper joint is located so as to provide [
p.
At the lower end, the sleeve configuration consists of a section which is [
wanso.2 wos292 2-1
- u,
2.1.2 Tube Support Plate Sleese The support plate sleeve is shown in Figure 2-2. Each end of the sleeve has a hydraulie expansion region within which the weld is placed. The weld configuration is the same for both upper and lower joints and is the suae as the upper weld in the tubesheet sleeves. [
3ue I
1"'
q The sleeve material. thermally treated Alloy 690, was selected to provide additional resistance to stress corrosion cracking.
2.2 Sleeve Design Documentation -
The sleeves are designed and analyzed according to the 1986 edition of Section ill of the American 1
Society of Mechanical Engineers (AShE) Boiler and Pressure Vessel Code, as well as applicable United States Muclear Regulatory Commission (USNRC) Regulatory Guides, The associated caterials and processes also meet the rules of the-AShE Boiler and Pressure Vessel Code. Specific documents applicable to this program are listed in Table 21.
q l
2.2.1 Weld Qualification Program The laser welding process used to install [
1". nominal OD sleeves into 0.875 inch nominal OD tubes was qualified per the guidelines of the AShE Code which specify the generation of a procedure
- qualification record and welding procedure specification.
wms : twos:o2 2
Specific welding processes were/will be generated for:
Sleeve weld joints made outside of the tubesheet
- Sleeve weld joints made outside of the tube <heet with thermal treatment Repair or rewelding of sleeve joints
- Sleeve weld joints made within ;,e tubesheet These processes address the weld joints necessary for installation of any of the two types of sleeves discussed earlier.
To provide similitude between the specimens and the actual installed welds, representative field processes are used to assemble the specimens. The laser welded joints are representative in length and diametral expansion of the hydraulic expansion zone. The sleeve and tube materials are consistent with the materials and dimensional conditions representative of the field application. Essential welding variables, defined from ASME Code Case N 395, are used to develop the weld process. [
.ja.
2.2.2 Weld Qualification Acceptance Criteria L
l For the qualification of the process the Felds shall be free of ctacks and lack of fusion and meet design requirements for weld throat and minimum leakage path. The welds shall' meet the liquid penetrant requirements of NB 3530.
L P
!=
l" wpm 50 2ilwos2602 2-3 l
1 m
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Table 21 ASME CODE AND REGULATORY REQUIREMENTS Item Applicable Criteria Reauirement a.c.e -
Sleeve design Sleeve Material Sleeve Joint 4 -
WiO4W2:lWorl2492 2-4
- i
-.a
a,c e f
i
~
m Figure 21 Tubesheet Laser Welded Sleeve Installed Configuration
.. WPO4542,ltvos (N2
-25
=......
1 9
a.c,e I
i t
t i
r T
y k
i i
r Figure 2 2
- Support Plate Laser Welded Sleeve Installed Configuration-WPLM50-2.ltd*1092 2-6' I
j
3.0 ANAL 3TICAl. YFillFICATION This section of the report provides the analytical justineation for the laser uelded sleeves. Section 3,1 deak with the structural justincation, and Section 3.2 provides the thermal /hydraulie just10 cation, 3.1 Structural Analpis Section 3 I summarites the structural analysis of the tubesheet and tube support plate laser welded sleeves.
The loading conditions considered in the analysis umbrella the condidons specified in the Beaver Valley Uruts I and 2 steam generator design speci0 cations. References (1)- (4). 'lhe analysis includes Onite element model development, a heat tramfer and thermal stress evaluation a primary stress intensity evaluation, a primary plus secondary stress range evaluadon, and a fadgue evaluadon for mechanical and thermal condidons. Calculadons are also perfonned to establish minimum wall requirements for the sleeve, and a corresponding plugging limit for tubes whete sleeves have been installed. Finally, the analysis addresses a number of special consideradons as they affect the adequacy of the sleeve designs, 3.1.1 Component Description 3.1.1.1 Tubesheet Sleese lhe design of the tubesheet sleeve, as installed, is illustrated in Figure 21. The sleeve extends from the tubesheet primary face to above the tube degradadon zone, in order to allow for eddy cunent uneenainty in denning the degradation zone, the sleeve length is such that it extends a minimum of [
l' "
above the tube degradadon zone.
At the lower tubehleeve interface, the sleeve configuration consists of a section (
ju At the upper end of the sleeve, the sleeve consists of a secdon that l
}" A schemade of the tube / sleeve interfaces and the various l
}" is provided in Figure 31.
3.1.1.2 Tube Support Plate Sleese-The installed configuration of the tube support plate sleeve is shown in Figure 2 2, The sleeve is 12 inches long, and is !
ju WPO4504.1WD&2791 3I
3.1.2 Summary of Material Properties lhe material of construedon for the tubing in Westinghouse designed Series $1 steam generators is a nickel base alloy. Alloy 6fX)in the rnlli armealed (MA) condit',n. The sleeve material is also a nickel base alloy. thermally treated Alloy 690. Summaries of the applicable rnechanical. therrnal, and strengdi propenies for the tube and sleeve materials are provided in Tables 31. and 3 2.respecdvely. The sleese esaluadon also includes the response of the tubesheet which is constructed of SA 508. Class 2 Carbon sicel. A sumrnary of the applicable properties for the tubesheet rnaterial is provided in Table 3-3.
Thermal properties for uit and water, used in performing the heat transfer analysis, are provided in Tables 3-I and 3 5.
3.1.3 Applicable Crileria The applicable criteria for evaluating the sleeves is set forth in the ASME Code. Section !!!. Subseedon ND 1986 Edidon Reference (5). Although the lower joint in the tubesheet sleeve is classified as a seal weld, it is also evaluated to the ASME Code criteria, in establishing minimum wall requirements for plugging limits. Regulatory Guide 1.121. Reference (6), is used. A summary of the applicable stress and fadgue limits for the sleeve and tube are sununarized in Tables 3 6 through 3 9.
3.1.4 1.ouding Conditions Considered The analysis considers a full duty cycle of events that includes, design, normal. upset, faulted. and test condidons. [
]" A summary of the applicable transient'
'f conditions is provided in Table 310. Umbrella pressure loads for Design. Faulted and Test conditions are summarized in Table 311, 3.1.5 Analysis Methodology The analysis of the laser welded sleeve designs udlizes both conventional and finite element analysis 4
techniques Several finite element models are used for the analysis. For the tubesheet sleeve analysis.
I
]" Typically the tubesheet sleeve modelincorporates a " unit cell" of the tubesheet, based on an effecdve radial area surrounding the tube in the tubesheet, For Series 51 steam generators the type and extent [
]" is evaluated. The tolerances used in developing i
1 WPO450-);WOS2792 32
-. _. -.. ~.
(
i the sleese models are such that l lu The low er laser welded joint fLWh fo' We tubedeet sleeve is (
t
- u The analysis also considers bodi {
-l ju in addition to the sleeve models, a separate model of the tubesheet, channel head, and lower shell was developed and used to calculate tubesheet rotations under combined pressure and temperature loadings.
Resulting loads imposed on the sleeve as a result of the tubesheet rotations are applied to the sleeve model in the form of radial pressures on the model outer boundary, A plot of the tubesheet, channel head, and shell model is shown in Figure 3 2.
3.1.6 Ilent Transfer Analysis The first step in calculating the stresses induced in the sleeves as a result 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, eight transients were selected for evaluation. They include the following events:
, a.C W
4 0
. WIN $0-hlWO82792 33 z -
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The plant heatup/cooldown, plant leading / unloading and steady state fluctuation events are evaluated as pseudo steady state conditions.
In perforndng the heat transfer analysis. [
1" A sketch of the rnode! boundary conditions for the heat transfer analysis are shown in Figure 3 3.
In order to deternune the appropriate boundary conditians for the heat tramfer analysis, [
ja 3.1.7 Tubesheet/ Channel llead/Shell Evaluation As discussed above, loads are imposed on the sleeve as a result of tubesheet' rotations under primary to secondary pressure drops. For this evaluation, tubesheet rotations are established for two' reference loading conditions, a primary and secondary applied pressure, and subsequently scaled to actual-transient conditions. The boundary conditions and su6 sequent deformed geometry for the primary pressure load case are shown in Figures 3 4 and 3 5, respectively, Once the stress solutions for the reference load cases are obtained. [
ju -
1 3.1.8 Stress Analysis-In performing the stress evaluation for the sleeve models, [
L L
}" The gap opening is simulated by decoupling nodes above and below the weld location for distances ranging from [
]" Sketches -
of the model boundary conditions for the primary side reference pressure cases are shown in Figures 3 6 wN450 3:Ib22792 3-4 u
. =...
2
through 3 9. Sketches of the model boundary conditjons for the secondary side reference pressure cases
-are shown in Figures 310 through 313.
- The analpis considers [
ju e-ne effects of[
ju Finally. [
ju The total stress distribution in the sleeve to tube assembly is determined by combining the calculated -
stresses as follows:
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,,a s
l l
l l
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3.1,9 ASSIE Code Evaluation t
The AShtE Code evaluadon is perfarmed using a Westinghouse proprietary computer code. The evaluation is performed for specifle " analysis sections" ( ASNs) through the Gnite element model. The ASNs evaluated to determine the acceptability of the sleeve design are shown in Figure 314 for the lower LWJ and in Figure 3-15 for the upper LWJ.
The umbrella loads for the primary stress intensity evaluation have been given previously in Table 311.
The largest magnitudes of the ratio " Calculated Stress Intensity / Allowable Stress Intensity" are [
]"
for primary membrane stress intensity, and [
]" for primary membrane plus bending stress intensity, respectively. For the algebraic sum ol principal stresses, the limiting rado of" Calculated Stress Intensity /
Allowable Stress intensity" is [
]" The analysis results show that the primary stress intensities for the laser welded sleeved tube assembly are within the allowable ASME Code limits. A summary of the 1
limiting stress conditions is provided in Table 312.
Primary plus secondary stresses in the assembly are [
]" Based on the sleeve design criteria, the fatigue analysis considers a design objective of 40 years for the sleeved tube assemblies. Because of possible opening of the interface between the sleeve and the tube along the '
hydraulic expansion regions, the maximum fatigue strength reduction factor of(
]" The results of maximum range of stress intensity and fatigue evaluations are summarized in Tables 3-13 through 3-15.
3.1.10 Minimum Required Sleeve Thickness The he,a transfer area of steam generators in a pWR nuclear steam supply system (NSSS) comprises over 50 percent of the total primary system pressure boundary. The steam generator tubing, therefore, represents a primary barrier against the release of radioactivity to the environment. For this reason.
-conservative design criteria have been established for the maintenance of tube structural integrity under the postulated design-basis accident condition loadings in accordance with Section III of the ASME Boiler and Pressure Vessel Code.
Over a period of time under the influence of the operating loads and environment in the steam generator,.
some tubes may become degraded in local areas. To determine the condition of the tubing,in-service inspeedon using eddy-current (EC) techniques is performed in accordance with the guidelines of US NRC -
Regulatory Guide 1.83, Reference (7).- Partially-degraded tubes with net wall thicknesses greater than the :
' minimum acceptable tube wall thickness are satisfactory for continued service, provided that leak before.
break is established, and that the minimum required tube wall thickness is adjusted to take into account possible uncertainties in the EC inspection, and an operational allowance for continued tube degradation until the ncxt scheduled inspection.
L wPO450<W82792 36
_ ~ _ - =
Re US NRC Regulatory Guide 1.121,' Reference (6) describes an acceptable method for establishing the limiting safe conditions of tube degradation in the steam generators beyond which tubes found defective by the established in-service inspection should be removed from service. De amount of degradadon recorded by EC tesdng is customarily expressed as a percentage of the design nominal tube wall thickness, and the acceptable degradation is referred to as the tube plugging margin.
Briefly, the regulatory guideline consists of verifying that (1)in the c e of tube thinning or wall loss, or for pardal through-wall cracks, the remaining tube wall can still meet applicable stress limits during normai and accident loading conditions, and (2)in the case of tube cracking, the leak-before-break criteria is sausfied. Confirmadon of leak-before-break assures that the maximum permissible crack length to protect against burst under accident loadings is greater than the crack length that would result in leakage at the Technical Specification limit during normal operation.
The allowable tube plugging margin, in accordance with Regulatory Guide 1.121, is obtained by incorporating into the minimum required thickness, a growth allowance for continued operation until the -
next scheduled inspection and also an allowance for eddy current measurement uncertainty.
Since Regulatory Guide 1.121 constitutes an operating criterion,it is permissible to derive the allowable stress limits based on expected lower bound material properties, as opposed to the Code minimum values.
Expected strength properties are obtained from statistical analyses of tensile test data of actual production tubing. Lower bound statistical tolerance limits, LTL, for yield and ultimate strength values are computed -
in c.ccordance with the accepted industry practice such that there is a l
]" than LTL values. He applicable values for the sleeve analysis are a yield strength of [
]" and an ultimate strength of [
]", as taken from Reference (8).
in es.ablishing the safe limiting condition of a sleeve in terms of its remaining wall thickness, the effects
--of loadings during both the normal operation and the postulated accident conditions must be evaluated.
He applicable stress esiteria 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.
Considerations of the secondary and peak stresses from operating transients are relevant from the viewpoint of fatigue and related implications of the occurrence of through-wail cracking, if any.- The implications and consequences of cracking, however, are accounted for in the-leak before-break requirement.- In the unlikely event of unacceptably reduced design margin due to the increased secondary and peak stresses in the localized degraded tube regions, the tube integrity would be safeguarded against any adverse consequences through leak before-break.
He minimum required sleeve wall thickness, to, to sustain normal and accident condition loads is calculated [-
WN450 3:ltvu82792 37
--r l,
c-L n.
.,sn-
-w=
]" For. compuung t,,, the pressure stress equation NB-3324.1 of the o
Code is used. That is, APr xR-3 P, - o. 5 (Pg P,)
+
3.1.10.1 Normal / Upset Operation Loads The limidng stresses during normal and upset operating conditions are the primary membrane stresses due to the primary-to secondary pressure differential AP, across the tube wall. During normal operation at-100?r full power, the primary side pressure, P,, is !
ju De limits on primary stress, P, for a primary-to-secondary pressure differential AP,, are as follows:
Normal: P, < S/3 = 30.33 ksi Upset: P. < Sy = 37.00 ksi Using the pressure stress equation, the resulting values for t,, are [
o ju 3.1.10.2 Accident Condition Loadings LOCA + SSE The dominant loading for LOCA and SSE loads occurs at the top tube support plate in the form of.l
~
bending stresses in the tubes. At TSP intersections below the top TSP, LOCA loads drop off dramatically..
- Since the sleeve is located at the [
}"
i FLB + SSE:
He 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.
the FLB + SLB transient, the applicable pressure loads are [
}" The applicable criteria for faulted loads is:
P, < lesser of 0.7 S or 2.4 S.
i S,=[.
1" wnuso-m m:m 3-8 i
b-
. P. < 0.7 S, = {.
1" Using the pressure stress equation the resulting value for t,is [
]"
o In summary, considering all of the applied loadings, the minimum required sle:ve wall thickness is calculated to be [
]" remaining wall for nominal operating cond tions.
3.1.10.3 Iturst Strength Requirements in addition to the limits on allowable stresses discussed previously, the following requirements on the burst strength of degraded tubes (sleeves) are also to be satisfied:
(l} Margin to burst under normal AP, (2) Verification of leak'-before-break 3.1.10.3.1 Margin to Burst Under Normal Operating AP, For tube burst margin. the factor of safety (FS) may be determined on the basis of stress as the ratio of the ultimate strength (S ) and the tube stress (S) due to the normal operating AP,.. The FS based on stress '
meets the US NRC requirement. The margin calculated is analogous to the establishment of allowable stress intensity as one-third of the ultimate strength of,the material.
With t, = [
}" S is calculated:
o a,c 4
4 l
WP0450-3Ilb/082792 3-9 i-er.
M
.%m n
w.
,-m9 g.
.e.e s'y---
.%u
.mu y
,m e
- m. e a
es e
.u Where the tube is undegraded, t
=[
]"
o Thus, it is concluded that the margin to burst, FS y,3, under normal operating AP, for thinned, partial through wall cracked, and undergraded tubes, is satisfied.
3.1.10.3.2 Leak 11efore Ilreak Verification The rationale behind this requirement is to limit the maximum allowable (primary-to-secondary) leak rate during normal operation such that the associated crack length (through which the leakage occurs) is less than the critical crack length corresponding to the maximum postulated accident condition pressure loading. Thus, on the basi; of leakage monitoring during normal oper; tion, unstable crack growth is not expected to occur in the unlikely event of the limiting accident.
The largest permissible crack length is determined using results from a computer program (CRACKFLO) '
that has been developed for predicting leak rates through axially oriented cracks in a steam generator tube.
(sleeve). The CRACKFLO leakage model has been developed for single axial cracks and compared with leak rate test results from pulled tube and laboratory specimens. Fatigue crack and SCC leakage data have.
been used to compare predicted and measured leak rates as shown in Figure 316, Generally good agreement is obtained between calculation and measurement with the spread of the data being somewhat greater for SCC cracks than for fatigue cracks. Figure 317 shows normal operation leak rates for the -
sleeves as a function of crack length. Leak rates are shown both for the mean data and for the [
]"
For the Beaver Valley steam generators, an administrative leak rate of 250 gpd (0.174 gpm) per steam generator has been established. For a nominal wall sleeve, the largest permissible crack length associated with a specification limit of 0,174 gpm leak rate during normal operation using the [-
}" curve is found to be [
]" Beyond this crack length, the leakage would exceed the administrative limit requiring plant shutdown for corrective action.
Burst pressure versus axial crack length data from multiple sources are shown in Figure 318 as taken from [
wKu$0.Libo82N2 1
3 10
gu The Belgian burst curve for the sleeves is shown in Figure 3-19. It is observed that a throughwall crack
!cngth of [
1" is required under FLB conditions. Comparing die criucal crack length for burst under FLB conditions to the critical crack lengdi for leakage. [
]" it is concluded that the leak-before break behavior is confirmed for the Beaver Valley sleeves.
3.1.11 Determination of Pluggir.g Limits The minimum acceptable wall thickness and otner recommended practices in Regulatory Guide 1.121 are used to determine a plugging limit for the sleeve. This Regulatory Guide was written to provide guidance for the detemunation of a plugging limit for steam generator tubes undergoing localized tube wall thinning 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 service.
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 tube thickness acceptable for continued service. Paragraph C.3.f. of the Regulatory Guide specines that the basis used in setting the operational degradation allowance include the method and data used in predicting the continuing degradation and consideration of eddy current measurement errors and other signincant eddy current testing parameters. The conventional eddy current measurement uncertainty value of 10 per cent of the tube wall thickness is appropriate for use in the determination of the operational tube thickness acceptable for continued service and thus determination of the pluSE ng limit.
i Paragraph C.3.f of the Regulatory Guide specified that the basis used in setting the operational degradation analysis include the method and data used in predicting the continuing degradation. To develop a value for continuing degradation, sleeve experience must be reviewed. Westinghouse designed sleeves have had up to 8 years of operation, No degradation has been detected to date on Westinghouse designed wim50 L1tvo82792 3-11
i i
i mechanleal joint sleeves and no sleeved tube has been removed from service due to degradauon of any ponion of the sleeve. This result can be attributed to the changes in the sleeve material reladve to the tube and the lower heat flux due to the double wall in die 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 109 of die sleeve wall as an allowance for continued degradadon is used in thi analysis.
In summary, the operational tube ducknen acceptable for continued service includes the mirdmum acceptable tube wall duckneu (
}" the combined allowance for eddy cunent uneenalnty and operational degradation [
l" These terms total to (
1" resulting in a plugging'-
lindt as deterndned by Regulatory Guide 1.121 recommendations ofI
]" of the sleeve wall thicknew.
The plugging lindt for the tube, applicable as defined below,is as specified in the Techtdeal Specifications for the norsleesed portions of the tube. currently 409 of the tube wall thickness.
3.1.12 Application of Plugging 1.imits Sleeves or tubes which have eddy curreni indications of degradation in excess of the plugging limits must i
be repaired or plugged. Those portions of the tube and the sleeve for which indicadons of wall degradation must be evaluated are summarized as follows:
a.e F
h
~
5 msammm 3 12
i 3.1.13 Structural Analysis of Weld Widths of[
]"
The analysis results thus far are for sleeses with interfacial weld widths of [
}" for the upper l
and lower LWJ's. Sleeves with interfacial weld widths of [
}" inch have aho been an.d>ted and are reponed in this subsecdon. The Gnite element model used to evaluate the 1 j"
weld uidths was tes ked to accommodate the new weld widths. De case of hydraulically espanded upper 3
LWJ and hydraulically espanded and roll espanded into the tube lower LW) is conddered, he change I
in the weld widths does not alfeet the results of the limiting erou sections for the l l" weld.
Therefore, only results for the madmum range of stress intenslty and fatigue evaluations are tabulated.
He preuure, asial force and selected thermal strew runs are re-computed with the revised Onite element modek. he thermal strew runs re computed are those giving the largest contributions to madmum range of streu intensity. The results of maxirnum range of streu intensity and fatigue evaluations are presented in Tables 316 and.bl7, it is demon 4 rated that the laser welded sleeves with interfacial sleese/ tube weld widths of I
}" satisfy the requirements of the ASME Code. Seedon 111. Note l
that these results are aho applicable to the tube suppirt plate sleeses.
3.1.14 Special Considerations 3.1.14.1 Flow Slot liourglassing i
Along the tube lane, the tube support plate has several long rectangular 00w slots diat have the potential to deform into an "hourglaw" shape with signincant denung The effect of Dow slot hourglassing is to I
move the tubes adjacent to the flow slot laterally towards the tube lane from their initial pmitions introducing added bending strenes in the tubes. The madmum bending stress occurs in the innermost t
tow of tubes in the center of the now slots. De added bending stress has a negligible effect of the sleeses since the bending stress is a mean stress ar.s the analysis accounts for madmum mean stress ettects through use of the ASME Code fatigue curves.
3.1.14.2 Tul>e Vibration Analysis An analysis has been performed to predict modal natural frequencies and related dynamic bending stresses ciributed to Dow induced vibration of sleeved tubes,- The purpose of the analysis is to calculate the natural frequencies, amplitude of vibration, and bending stress of a sleeved tube. [
t
(
t WPO4soltMM892 3 13 l-
3.1.14.3 Sludge lleight Thermal l'.ffects In yeneral, u tth at least l l" of sludge, the tubesheet is kothermal at the bulk ternperature of the i
primary fluid. The net ef fect of the sludge k to reduce tube /tubesheet thermal stress effects, r
3.1.14.4 Effect of Tubeshect/ Support Plate Interaction i
t As a result of tubesheet bow under preuure loath, the tubes protruding from the top of the tubesheet totate from vertical. Tho, rotation results in added bernling suewes in die sleesed tube auembly, Analysh f
f esults show these streues do not signilleantly allect the fatigue us, age results.
I 3.1.15 Ann!pis Conclusions t
Dased on the results of this analysis, the design of the laser welded tubesheet sleeve and the tube supp>rt.
plate (Iceve are concluded to meet the requirements of the ASME Code. The applicable plugging limh for the sleese is l I" of the initial wall ilucknew. The plugging lirult for the tube h currently 409 of the tube wall thicknew, as specilled in the Technical Specilicadons for the non sleeved ponions of the tube.
3.1.16 References i
1.
Design Specilleation 412AN, "Duquesne Light Company Deaver Valley Power Station Unit No.
- 1. Steam Generator lleat Transfer Tube Sleeving, ASME Boller & Pressure Vessel Code, Section 111, Code Case 1. Safety Claw 1", Resision O. 7/20/92.
2.
Design Specification Addendum 677032,"Duquesne Light Company Beaver Valley Power Station Unit No,1. Reactor Coolant System "$1" Series Steam Generators", Revision 5, 1/28/76, 3.
Design Specification Addendum 952406 "Duquesne Light Company 11eaver Valley Power Station Unit No. 2, Reactor Coolant System "$1" Series Steam Generators", Revision 4.12/11/78.
t 4
Design Specification G 677164, Reactor Coolant System "$ 1" Series Steam Generators", Revision 1, 12/18/69 5.
"ASME Boiler and Pressure Vessel Code. Section 111. " Rules, For Construction of Nuclear Power Plant Components", The American Society of Mechanical Engineers, New York, N.Y;.1986.-
i 6.
USNRC Regulatory Guide I;121. "Dases for Plugging Degraded PWR Steam Generator Tubes (For Comment)", August,1976,
-i
-1; womo+ imam
.3 14 i
I 4
,._..._._..- _ a -.- _ _ _
.,_.._._l
TAllLE 31 SUSIStARY Ol' SIATERIAL PROPERTIES tulle SIATERIAL SilLL ANNEAL,ED ALLOY 600 TEMPERATURE FF) 70 2*
3"O 4W 5"O ful 700 PROPERTY Young's Malulus 31.00 30.20 29.90 29.50 29.0.1 2x.70 28.20 -
ps: x 1.0E06 Coef0cient of Thennal 6.90 7.20 7.40 7.57 7.70 7.R2 7.94 Expanuon in/ int F x 1.0E 06 Denuty 7.94 7.92
_ 7.90 7.89 7.X7 7.R$ -
7.R3 lb sec hn* x 1.0E.N Thermal Conducunty 2.01 2.11 2.22 2.34 2.45
. 2.57 -
2.68
(
litu/sec in F x 1.0E.N Specine Heat 41.2 42.6 43.9 44.9 43.6 47.0 47,9 fltu.in/lb sec F STRENGTH PROPERTIES (KSI)
Sm 23.30 23.30 23.30 23.30 23.30
-23.30 23.30.
Sy 35.00 32.70 31.00 29.80 28.80 27.90 27.00 Su 8010
= 80.00 80.00 80.00
'80.00 8010 80.00 N
~
3 15 U
--.m e.
.h u..% c.
c.ms-
_,,-.,.r,=,u-,
.,-e -d b v.w w y,-,..--m.i.rw.
.-_-,-g,,.--
ec'<mf.
w e
.y.
.. - + -.
TAllt.E 3 2 SU51.\\1 Ally OF 51 A I Eltl AL PitOPEltTIES St.EEVE SI ATEltlAL TilEIIS1 ALLY TitEATED ALLOY 690 i
TEMPER ATURE i' F) 70 2""
300 4"U 50" 6""
75 0 PROPERTY youngN Modulus 3030 29.70 29.20 2N.xu 28.30 27.NO 27.30 psi t 1.0E06 Coef ficient of Thennal 7.76 7.x5 7.93 x.02 X.09 8.16 x.25 E x p.in sion m/inr F t 1.0E 06 Density 7h2 7 59 7.56 7.56 7.54 7.51 7.51 4
lb-sec hn' s 1.0E-4 4 Thennal Conductivity 1.62 1.76 1.9 2.N 2.18 2.31 2.45 lita'sec-in. F x 1.0E-N Specine llcat 41.7 43.2 44.8 45.9 47.1 47.9 49.0 Blu in/lb secVF STRENGTH PROPERTIES (KSl>
Sm 26.fd) 26.t/l 26.f4) 26.td) 26.60 26h0 26 60 Sy 40.0()
36.x0 34 60 33.00 31.80 31.10 30.60 Su 8010 80.00 80.00 80.00 80.00 M0.00 S0.00 t
I w Iwa 11wr439:
3 16
TAllt.E 3-3
SUMMARY
OF MATERIAL PROPERTIES TUllESilEET MATERIAL.
SA 508 Cl. ASS 2 TEMPERATURE r F) 7" 2*
IN PROPERTY Young's Modulus 29.20 2x.50 2X180 27.40 27.00 26.40 25.30 psi s 1 O D vi Coef ficient of Thenn:d 6.50 h.67 6.87 7.07 7.25 7.42 7.59 E xpansion ut ttti e F s 1.0E Oh Density 7.32 7.3 7.29 7.27 7.26 7.24 7.22 lb.sec /in' t 1,0E-N Thennal Conduct:uty 5.49 5.5h 5.53 5.46 5.35 5.19 5.02 Btu'sec in F s 1.0E-N Specific Heat 41.9 44.5 46.8 48.8 50.8 52.8 55.1 Btu.in'lb-sec "F STRENGTH PROPERTIES t KSI)
Sm 26.70 26.70 26.70 26.70 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 80f0 801x)
NO.00 801XI 80.00 p
3-17
u an.
an
-a a
.a.
.a 2
- ~. -
. a u,
.i l
TAllLE 3-4 SU5151ARY OF SIATERIAL PROPERTIES AIR TEMPERARTRE PF) j 70 200 300 400 500 No 700 PROPERTY 1
Density 10.63 X.99 7.79 6.89 6.17 5.54 5.11 lb-sec /in' x 1.0E UX 1
Thermal Conductivity 3.56 4.03 4.47 4.91 5.35 5.78 6.20 Bru/sec-in/F x 1.0E-07 Specine Heat 9.27 9.31 9.38 9.46 9.55 9.66 9.78 Blu.in/lb-wc #F x 1.0E+01 i
TABLE 3 5 SUSIStARY OF 51ATERIAL PROPERTIES WATER l
TEMPERATURE ('F) 70 200 300 400 500 600 700 PROPERTY Density 9.28 9.01 8.58
'81M 7.34 6.35.
4.65 2
lb-sec /in' x 1.0E45 Thermal Conducuvity 8.46
' 9.07 9.14 8.89 8.24 6.9 -
4.42 Btu /sec in.*F x 1.0E-06 Specine Heat 3.8?
3.88' 3.96 4.12
' 4.37 5.26 8.51 Btu-in/lb-sec 'F x 1.0E+02 l
WPO450 h!b/082892 3-18 l
~
,m.
,aw.,,n.,--
c e--
Ln~.
w
--m-
TABI.E 3 6 CRITERIA FOR PRI>lARY STRESS INTENSITY EVALUATION SLEEVE - ALLOY 690 CONDITION CRITERIA LINilT (KSI)
DESIGN P, s S.
P, s 26.60 P + P, s 1.5 S, P + P, s 39.90 i
i FAULTED P, s.7 S, P, s 56.00 P,+ P, s 1.05 S, P + P, s 84.00 i
EST P, s 0.9 S, P, s 36.00 P + P, s 1.35 S, P + P, s 54.00 i
i ALL P +P: + P, s 4.0 S, P +P,+P35 106.4 i
i CONDITIONS Note: P, (i=1.2.3) = Principal stresses TAllLE 3-7 CRITERIA FOR PRIS1ARY STRESS INTENSITY EVALUATION TUBE ALLOY 600 CONDITION CRITERIA LIh11T (KSI)
DESIGN P, s S, P, s 23.30 P + P, s 1.5 S.
P + P, s 34.95 i
i FAULTED P, s.7 S.
P, s 56.0 P + P, s 83.88 P + P, s 1.05 S, i
i l
L.
l HST P, s 0.9 S, P, s 31.50 P + P, s 1.35 S, P + P,5 7.25.'
4 i
i P +P: +P s 93.20 -
l}
ALL-P +P: + P s 4.0 S, i
3 i
3 L
CONDITIONS l-Note: P,(i=1,2,3) = Principal stresses l
W F W O.1:lb M 2892 3 19
A TAllLE 3-8 CRITERIA FOR PRl51ARY PLUS SECONDARY STRESS INTENSITY EVALUATION SLEEVE. ALLOY 690 CONDITION CRITERIA LlhilT (KSI)
NORNI AL. UPSET, P, + P, + Q s 3 S,*
P, + F, + Q s 79.8 and'EST-NORh1 AL, UPSET, Cumulative Fatigue Usage 1.0 and 'EST
- Range of Primary + Secondary Stress Intensity TAllLE 3 9 CRITERIA FOR PRIS1ARY PLUS SECONDARY STRESS INTENSITY EVALUATION tulle - ALLOY 600 CONDITION
. CRITERI A
- LlhilT (KSI)
NORh1AL, UPSET, P,.+ P, + Q s 3 S,*
P, + P + Q $ 69.9 and TEST NORNIAL, UPSET, Cumulative Fatigue Usage 1.0 and TEST
- Range of Primary + Secondary Stress Intensity.
l
)
1 a
WPM 504,1W08.492 -
~
3-20 j
i j
h
TAllLE 310 SU5151ARY OF NORS1AL OPERATING TRANSIENT EVENTS CLASSIFICATION CONDITION CYCLES j
Normal a.c.e Upset Faulted Test WM) 50 3:ltM1692 3 21
TAllLE 311 UMBRELLA PRESSURE LOADS FOR DESIGN, FAULTED, AND TEST CONDITIONS PRESSURE LOAD, PSIG PRIMARY SECONDARY CONDITIONS Design b,e Design Primary Design Secondary Faulted Reactor Coolant Pipe Break Feedline Break Steam line Break -
Loss of Secondary Pressure Test Primary Side Hydrostatic Test Secondary Side flydrostatic Test Tube Leak Test Primary Side Leak Test Secondary Side Leak Test WIW50 3:lWO82692 3-22 y
.-ry w
ye
-.ep--
.e-g a
c
-+4
,,----g--
e.
g
TAILLE 312 SU5151ARY OF 51AXI51U51 PRl51ARY STRESS INTENSITY FULL LENGTil TUBESilEET LASER WELDED SLEEVE Sleeve /fube Weld Width of (
)"
Calculated Allowable Calcu med Component S.I. (KSI)
S.I. (KSI)
Allowable a.e a,e Straight Sections Sleeve 26.20 Upper LWJ:
Sleeve 36.00 Tube 47.25 Weld 31.50 Lower LWJ:
Sleeve 26.60 Tube 23.30 Weld 23.30 uw l===
w PO454 kituta:492 3-23
"-----_:---.:___.___.__a_ _ _ _ _ _ _,
TABLE 313 -
MAXIMUM RANGE OF STRESS INTENSITY AND FATIGUE FULL LENGTH TUDESilEET LASER WELDED SLEEVE Sleeve / Tube Weld Width of[
-]"
Upper LWJ: Hydraulically Expanded.
Lower LWJ: Hydraulically Expanded Calculated Allowable Calculated Component S.I. (KSI)
S.I. (KSI)
Allowable a.c a,c Straight Sections Sleeve 79.80 Upper LWJ:
Sleeve 79.80 Tube 69.90 Weld 69.90 Lower LWJ:
79.80 Tube 69.90 Weld 69,90 Cumulative Fatigue Usage Factor-
[
}" s 1.0 -~
l -.
l WPO450 3;lb/082692 3-24
i I
TAllLE 314 -
51AXIN1U51 RAN'G'E OF STRESS INTENSITY AND FATIGUE FULL LENGTH TUllESHEET LASER WELDED SLEEVE-Sleeserrube Weld Width of [
}"
Upper LWJ: Hydraulically Expanded Lower LWJ: Hydraulically Expanded and Hard Rolled into Tube Calculated Allowable Calculated Component S.I. (KSI)
S.I. (KSI)
Allowable Straight ac ae Sections Sleeve 79.80 Upper LWJ:
Sleeve 79.80 Tube 69,90
. W eld 69.90 Lower LWJ:
Sleeve 79.80 -
Tube 69.90 Weld 69.90
~
I' Cumulative Fatigue Usage Factor
[
]" 5, 1.0 l..
I l
l l
WW 50.1;lW2892
-3 25
'.L
- TAllLE 315 MAXIMU$1 RANGE OF STRESS INTENSITY AND FATIGUE
~
-SUPPORT PLATE LASER WELDED SLEEVE Sleeve / rube Weld Width of[
]"
Calculated Allowable Cakulated Component S.I. (KSI)
S.I. (KSI)
Allowable a,c a,e Straight 79.80 Sections Sleeve Upper and Sleeve 79.80 Lower LWJ:
Tube 69.90 69,90 Weld Cumulative Fatigue Usage Factor
[
1" g,1.0 WPO4504:1tvw2692 3-26 i
'l
I TAllLE 316 SIAXI51UM RANGE OF STRESS INTENSITY AND FATIGUE FULL LENGTil TUllESilEET LASER WELDED SLEEVE Sleeve / Tube Weld Width of[-
]"
i Upper LWJ: liydraulically Expanded 11 draulically Expanded Lower LWJ:
3 Calculated Allowable Calculated Component S.I. (KSI)
S.I. (KSI)
Allowable '
Straight
~
a,e a,e Sections Sleeve
~
79.80 Upper LWJ:
Sleeve -
79.80 Tube 69.90 Weld
- 69.90 Lower LWJ:
-Sleeve 79.80 Tube 69.90 Weld 69.90 Cumulative Fatigue Usage Factor i
1" s 1.0 e
3-27
TAllLE 317.
MAXIMUM RANGE OF STRESS INTENSITY AND FATIGUE FULL LENGTil TUllESilEET LASER WELDED SLEEVE Sleeve / Tube Weld Width of[
-1" Upper LWJ: Ilydraulically Evanded Lower LWJ: liydraulically Expanded Calculated Allowable Q1culated Component S.I. (KSI)
S.I. (KSI)
Allowable Straight a.c a.c Sections Sleeve 79.80 -
Upper ~ LWJ:
Sleeve 79.80 Tube 69.90-Weld 69.90 Lower LWJ:
Sleeve 79.80 Tube 69.90 Weld 69.90' Cumulative Fatigue Usage Factor I
]" 5,1.0
' Thermal bending stresses removed per NB-3228.5 (a)
WPG450-3:1b/082692 3-28
n.c f
Figure 3 a Schematic of Tubesheet Sleeve Configuration WPGt50-3.Ib(081492 3 29 1
r i
i.e t
~
Figure 3-2 Channelheadtrubesheet/Shell Model wimso-).twost492 3-30
e,c -
- Figure 3-3
-Thermal / Hydraulic Boundary Conditions-Tubesheet Sleeve Analysis wrc,4so.ubtsim 3 31
nst
-1
-t i
-l
-I
.l l
Figure 3-4
- Channelhead/Tubesheet/Shell Model Primary Pressure Boundary Conditions
- l; l
-)
wPO45nibios1492 -
3
a,c.e.
- l
~
T l --
s Figure 3 5 -
-Channelhead/Tubesheet/Shell Model l';
Distorted Geometry Primary Pressure Loading l
. WPO450-3:lbtA1492 3~33
a.c.e i
l Figure 3 6 Boundary Condition for Unit Primary Pressure intact Tube: Pm > Psec l
i-WPA' 50 3:19081492 3 34-l l
a,c..
1 i
w I
l' Figure 3 7 Boundary Condition for Unit Primary Pressure intact Tube: P m < Psse i
WEM)4):ltyO$ l492 3 35
, - a.c.e.
1-I Figure 3 8 Boundary Condition for Unit Primary Pressure Severed Tube: Pm > P :e 3
wm4m:tbesi492 3 36-
j c.e I
1 l
l Figure 3-9 Boundary Condition for Unit Primary Pressure l
Severed Tube: P r u < P,sc l
WF08S3;ib/081492 3 37 I -
l
a,c.e Figure 3-10 Boundary Condition for Unit Secondary Pressure Intact Tube: Pm > Psse wrm50-3:iwa u92 3 38
a.c,.
I-Figure 3-11 Boundary Condition for Unit Secondary Pressure Intact Tube: Pm < Psic wax 5piwost402 3,39
1 i
n.c.e t
I i
e
/
Figure 3-12 Boundary Condition for Unit Secondary Pressurt Severed Tube: Pm > P se wm50..uwosi49:
3-40
i 1
,P n.c,e f
l t
Figure 3-13 Boundary Condition for Unit Secondary Pressure Severed Tube: Pm < Psic WPO450 3;itvo61492 -
3-41
- a.c.e j
Figure 3-14 ASN Locadca - Lower LWJ WPO450 3:Itv082192 3-42
a.c.c _
Figure 3-15 ASN Locados - Upper LWJ WPO4543.Itvo82192 3-43
u-
~
Figure 3-16 Comparison Between Predicted and Measured Leak Rates WP04$0 3 lhM2192 3-44
a.c
~
Figure 3-17 Leak Rate Versus Crack Length Series 51 Sleeves WPO450 3:ltr082192 345
a,c,3.
(
I l
l l
1 l
l l
Figure 3-18 Burst Pressure Versus Crack Length.
Comparison of Test Results WI08501.lbrJ82192 I
3M
I
. a.c.e -
Figure 3-19 Burst Pressure Versus Crack Length Series 51 Sleeve WPO4!>3.ltA)82192 347
s J7; ' USNRC Regulatory Guide 1.83c Rev: IJ"in-Service inspection of Pressurized Water Reactor Steam
- Generator Tubes. July 1975.
R WCAP-12522. "laconel Alloy 600 Tubing - Material Burst and Strength Propenies/* Jf Ai Begley,'J.
Lc Houtman.1/o0.
3.2 Thermal /llydraulie Analysis 3.2.1 Safety Analyses and Design Transients The emergency core cooling system (ECCS) performance analysis being performed for Series 44 and 51-steam generator plants supports operation at up to 20 per cent equivalent steam generator tube plugging (SGTP)in each steam generator. (Refer to Ref.1.) For the evaluation of acceptable number of sleeves?
a uniform plugging level of 20% is considered. This analysis and the corresp ' ding non-LOCA evaldation -
are considered applicable for the steam generator sleeving program with a combination of plugging and :
sleeving flow restriction equal to or less than the restriction due to the acceptable plugging level ;In j addition, in support of the steam generator sleeving program, Westinghouse has donc an evaluation of.
selected LOCA and non-LOCA transients to verify that use of sleeves resulting in a plugging equivalency
-of up to 20 percent in the most plugged steam generator.will not have an adverse affect on the thermal hydraulic performance of the plant. -For the accidents as evaluated, the effect of a combination -
of plugging and sleeving up to the limits of the existing analysis would not result.in any design or-regulatory limit being. exceeded.
The items listed below were evaluated for a sleeving and plugging combination equivalent to the existing L tube plugging limits and the results indicated no adverse effects:
Large Break LOCA Small Break LOCA LOCA Hydraulie Forcing Functions Post LOCA boron requirements Time to switch over the ECCS to hot leg reeirculation The steam generator tube rupture (SGTR) accident is analyzed to ensure that the offsite iloses remain -
~
below 10CFR100 limits. Re primary parameters affecting the conclusion are the extent of fuel failure assumed for the accident, the amount of primary to secondary break flow through the ruptured tube, and' the mass released to the atmosphere from the ruptured' steam generator. He amount of fuel failure -
assumed for the FSAR -SGTR analysis is 19 which is assumed to be independent of the transient conditions. The primary to secondary break flow and the mass released to the atmosphere are primarily.
dependent upon the RCS and secondary thermal hydraulic parameters.
wnwn Hwos:s92 3 48 I
An evaluation was performed which demonstrated that the effect of up to 20% steam generator tube plugging on the SGTR analysis would be acceptable. The SGTR evaluation was based on a uniform plugging level of 20%. De evaluation bounds the effect of non-uniform plugging with the most plugged steam generator at or less than 20% plugging. hus with the combined sleeving and plugging, up to the limit based on the LOCA evaluation, the operating RCS temperature and steam pressure will not be reduced below the values for the evaluated tube plugging level. On this basis, the evaluation performed for the presiously esaluated tube plugging level limit is applicable for the combined tube plugging and sleesing, and it is concluded that the sleesing will not change the previous conclusion that the SGTR analysis will remain acceptable.
The clieet of sleesing on the non LOCA transient analyses has been reviewed. Since the effect of the reduced RCS Gow rate at the tube plugging limit has been evaluated for the non LOCA safety analyses, these analyses bound the equivalent effect of steam generator tube sleesing. Therefore, the steam generator sleeve installation up to the equivalent of plugging limit would not invalidate any non-LOCA safety analyset Evaluations of the level of sleeving and plugging discussed in this report have shown that the Reactor Coolant System now rate will not be less than that for the analyzed plugging level. De effect of the reduction in RCS Gow rate for the analyzed plugging level on the design transients has been evaluated and has no impact. Any combination of plugs and sleeves which does not result in an RCS flow rate less than that for the analyzed plugging level would not have an adverse effect on the previous evaluation of the design transients.
3.2.2 Equisalent Plugging Lesel The insertion of a sleeve into a steam generator tube results in an increase in flow resistance and a reduction in primary coolant now in the sleeved tube. Furthermore, the insertion of multiple sleeves (tubesheet and/or tube support plate sleeves) wili 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 portion 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.
De calculation of the flow reduction and equivalency number for a sleeved tube is dependent upon several parameters: 1) the tube geometry,2) the sleeve geometry, and 3) the steam generator primary flow rate and temperature. These parameters are used to compute the relative difference in flow resistance of sleeved and unsleeved tubes operating in hydraulic parallel. This difference in resistance is then used to compute the relative difference in now between sleeved (W,) and unsleeved (W
,) tubes. He hydraulie y
equivalency number is then simply:
w w o. m nu m 3-49
- = = - --
--___-__-.___--_.__-__-______.-____...___________-a----_-
..c.e d
The hydraulic equivalency number can be computed for both normal operating conditions and off normal
?
conditions such as a LOCA. For LOCA conditions, the equivalency number is established using flow rates i.
consistent with the renood 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 hydraulie equivalency number for normal operation is more limidng than for postulated LOCA conditions.
As a result of the tiow reduction in a sleeved tube and the insulating effect of the double wall at the sleeve b
i location, the heat transfer capability of 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 Guid dow. In
- other words, the heat transfer equivalency number is larger than the hydraulic equivalency number. Thus, the hydraulie equivalency number is limiting.
The specine 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 Guid. --For this situation, the reduction in heat transfer i
- capability of sleeved tubes would have a benencial reduction on the heat transferred from secondary to
[
primary Guids.
The goal of the hydrau;ie equivalency number calculations described below is to generate conservative results which envelop the results for all plants which have Series 51 steam generators. As such it was -
- necessary to consider the e ect o a wide variation in primary Cow conditions for normal operation. Flow ff f
rates for these parametric calculations ranged from [ _
)^"
It-was determined that the most limiting results (largest Gow reduction and smallest hydraulic equivalency number for a sleeved tube) occur with (
)*" -
In addition to the effect of variations in the primary coolant conditions, the effect of differences in nominal :
f tube geometries was evaluated. For the 51 Series steam generators there are some differences in the tube geometry in the tubesheet region, specineally, in the length of the expanded or rolled region. For some -
plants, this zone is short (24 inches)._while for others with a full-depth roll it extends throughout the full thickness of the tubesheet (2122 inches). Parametrie calculations were completed to determine the specific tube con 0guration which produces the most conservative result; this geometry was then used in developing the final reported results.
p Many combinations of tubesheet (both hot and cold legs) and tube support plate sleeves have been
' considered in calculating the flow reduction and hydraulic equivalency. However, to ensure that the 4
_ wPtM50-FINM2N2 L50
results are enveloping, only the longest sleeves were used in the calculadons. Dese included a 36-inen long tubesheet sleeve and a 12 inch long tube suppon plate sleeve. The 36 inch long tubesheet sleeve is expected to be long enough to span the degraded areas in the tubesheet and places the upper joint above the sludge pile in either the hot or cold legs. The flow effects of this sleeve length bound a range of l
possible tubesheet sleeve lengths which could be specified for any future sleeving program (27 to M inches).
The parametric calculations considered four configurations with regard to the location of sleeves:
- 1) No tubesheet sleeves with various combinations of support plate sleeves in both hot and cold legs.
j
- 2) No tube suprert plate sleeves only hot and/or cold leg i
tubesheet sleeves,
Now wat the third configuration includes only cold leg tube support plate sleeves and no hot leg sleeves.
The reason for this selection is that, because of the effect of the variation in primar,y fluid temperature in the two legs of the tube bundle, suppon plate and tubesheet sleeves located in the cold leg produce slightly more conservative results (greater flow reduction) compared to an idendeal number and placement of hot leg sleeves. Similarly, slightly more conservative results are obtained when support plate sleeves are located at the higher plate locations. For these reasons, the results presented herein are generally limited to only those panleular sleeve locations which yield the more conservative results.
Table 318 presents a summary of the hydraulic equivalency numbera for the limiting combinations of '
tubesheet and support plate sleeves in 51 Series steam generators. From Table 318, the hydraulle equivalency number for a configuration with no tubesheet sleeve and four support plate sleeves is [
]" and occurs when the sleeves are positioned at the top four suppon plates in the cold leg (#3, #4,
- 5, and #6). This means that about f
]" sleeved tubes of the type specified would have the same net flow reduction as a single plugged tube. - Similarly, if sleeves were also installed in both hot and cold leg -
tubesheets, the equivalency nutnber would decrease to !
]" for a configuration with four support plate sleeves (Set #21 for suppon plate locations #5 and #6 in both legs).
The information presented in Table 3-18 has also been used'to construct Figure 3 20. This figure.
- graphically illustrates the enveloping hydraulie equivalency numbers for 51 Series steam generators based on normal operating condidons.
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The total equivalent number of plugged tubes is the sum of the number of plugs associated with sleeving (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 infonnation is near the tube plugging lindt 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.
- 2) ae'aal tube and sleeve geometries, and 3) actual locadons 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:
a.c where:
a.c 3.2.3 Fluid Velocity As a result of tube plugging and sleeving, primary side fluid velocities in the steam generator tubes will-increase. The effect of tids velocity increase on the sleeve and tube has been evaluated assuming a limiting condition in which 207c of the tubes in a 51 Series steam generator are plugged.
Using the conservatively high primary flow rate defined previously [
1"*, for a 0"a plugging condition. the velocity through an unplugged tube is approxJmately [
]"'. With 201 of the tubes plugged. the fluid velocity through an unplugged and unsleeved tube is about [
)"*, and for a tube with a single tube support plate sleeve, the local velocity in the sleeve region is. computed to be
{
}"'
However, these velocides are unduly conservative as a result of the assumed enveloping.
. primary flow rate and temperatures.
m wPo4504two82692 3-52
Table 318 Generic Tube Sleeting Calculations Flow Reduction and Ilydraulle Equivalency for Series 51 SGs b.c
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l If these calculations are repeated using more typical primary fluid conditions [
j
]"', the esumated velocities are significantly lower I
]"', lhese more typical velocities are smaller dian the incepdon velocides for l
fluid impacting, cavitation, or erosion corrmion for inconel tubing. As a result, the potendal for tube deeradation due to these mechanisms is low.
3.2.4 Flow Effects Surnmary The effects of sleeving on LOCA and non LOCA transient analyses have been reviewed. No adverse l
result is indicated for sleeve and plug combinations up to an equivalent of the analyted steam generator level of up to 20 per cent in each steam generator. The ECCS performance analysis and the conesponding non LOCA evaluations are considered applicable for the steam generator sleeving program with a combinadon of plugging and sleeving flow restriedon equal to or less than the analyred tube plugging level. Steam generator sleeve installadon up to the equivalent of the analyzed plugging level would not -
invalidate any non-LOCA safety analyses or the evaluadon of design transients.
'the results of evaluadons show that any combinadon of sleeving and plugging may be utilized as long as the effective analyzed plugging level using the hydraulic equivalency number for normal operadon, is not exceeded.
Accordingly, using the assumptions stated in this Section, sleeve.installadon up to the lindt of the equivalent plugging level using laser welded sleeves in the tubesheet and at the tube support plates will not have an adverse effect on the nonnal operadon, design transients, and postulated accident condidons.
3.2.5 Heferences
- 1. WCAp 12966 Duquesne Light Co. Deaver Valley Power Station Units I and 2,20 percent Steam Generator Tube Plugging Analysis Program Engincring & Licensing Report," 11/91. (Wesdnghouse Proprietary Class 2) 1 f
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4.0 MECilANICAl, TESTS Mechanical tests are used to provide additional infortnation related to sleeve joint performance. Unit test cells are used for rnechanical testing. A unit test cell or specimen is one which is a single sleeve joint and sufficient tube and sleeve length to bound transidon effects. For tubesheet specimens, a collar is used to simulate the effect of the tubesheet. De wall thickness of the collar has been selected to simulate the radial sulinew of the steam generator's tubesheet.
Mechanical testing was irudally applied to flybrid Expansion joint sleeving since it was not possible to analytically describe the interaedon between the sleeve and tube. Widle welded joints can be modelled, these tests hase been applied to verify the analytical models used.
4.1 Mechanical Test Conditions Mechanical testing is primarily concerned widi leak resistance and joint strength. During tesdng specimens are subjected to cyclie thermal and mechardcal loads, simuladng plant transients. The4 magnitude of these forces and temperatures are vetermined from plant normal operating and postulated accident conditions. I pu Other specimens are subjected to tensile and compressive loads to the point of mechanical failure. Rese tests demonstrate that the required joint strength exceeds the loading the sleeve joint would receive during normal plant operations or accident condidons.
These conditions are summarized in Table 41, though specific test condidons (displayed in data tables) may vary duS to evoludon of the tesdng process.- Test parameters have also been modified slighdy oser time as more refined analysis of plant loading condidons are applied.
4.2 Acceptance Criteria Leakage characteristics of the sleeve should be such that minimal (significantly less than the Technical Specificadon allowable) leakage through the sleeve joint is observed during normal operadon. During accident conditions analyses which model steam release to the environment, expected leakage must be less than the leak rates assumed in the analyses described in Section 15 of the Beaver Valley Power Stadon FSAR. Table 4-2 shows the bounding Beaver Valley steam generator leak rate criteria. [
[
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Table 41 i
Mechanical Test Program Summary I
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Table 4 2-Maximum Allowable Leak Rates for lleaver Valley Steam Generators Allowable Leak Rare Most Allowable Condition All SGs Limitine SG Leak Rate per Sleeve
- e,de Normal Orwration
~
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Postulated
~
Accident Condition
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- WF0450-4:ltNX)192 4-3
Widle 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 the case where a seal weld is not applied, the
- leakage characteristics must be evaluated.
i
- For tensile and compressive testing, loads exceeding I' 1"' indicate acceptable joint performance.
- 4.3 1,ower Sleeve Jnint The lower tubesheet sleeve joint is offered with and without a :,eal weld. Otherwise the joint construction is identical with a hydraulie expansion and hard roll zone; the same fabrication parameters are used with both joints.
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 tensile and compressive loading.
4.3.1 Ilesults o' Testing: No Seal Weld The test results for the Series 51 lower joint specimens are presented in Table 4 3. The specimens did -
not leak before or during fatigue loading. After simulating five years of normal operation due to { _.
]"' All of the three as rolled specimens were leak-tight during the Extended Operating Period (EOP) test.
For the tests the following joint performance was noted:
Specimens MS-2: Irdtial leak rates at all pressures and at normal operating pressure following thermal cycling were [
jac..
Specimen MS 3: [
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.4 1.c.e Figure 41 Tubesheet Sleeve Lower Joint Test Specimen WN450-4NP;lh090192 45 l
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pu 4.3.2 Description of Additional Test Programs - HEJ Lower Joint With Exceptional Conditions and No Seal Weld Additional test programs were performed to verify acceptable performance of the sleeve lower mechanical joint to accommodate exceptional conditions w hich may exist in the steam generator tubes and anticipated 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 4-4.
Each process operation and sequence of operations employed in fabricating each test sample was consistent
- with those specified for sleeves to be installed by field procedures. In addition, the exceptional tube -
conditions and changes to the sleeving process parameters described in Table 4-5 were include >J in the--
assembly of tube and collar sub assemblies.
4.3.3 Resuits of 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. They were then subjected to the fatigue, thermal cycling, compressive, and tensile _.
test as defined in Table 4-1. The results of this testing are summarized in Table 4 6. "Ihe results of this test demonstrate acceptable tensile / compressive load capacity with no joint leakage.
4.4 Free Span Joint Mechanical Testing Free span joints are representative of the tubesheet sleeve upper joint and both joints of the tube' support plate sleeves. This joint configuration, where there is no tubesheet backing the tube, is simulated using a test specimen as shown in Figure 4 2.
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" 1.
Specimen Number 511 N12 513 M4 h15 M6 M7 M8 M9 (Leak rate in drops per minute)
SPECIMEN COMPRESSIVE TENSILE NUMBER LO AD (lbs.)
LOAD (Ibs.)
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4 Figure 4 2 Free Span Laser Weld Joint Test Specimen WMM W4.Itut41 92 4 11
Eleven free span weld specimens were fabricated using representadve field parameters. All specimens were then stress relic J to account for the mechardeal property effects resuldng frorn thertmd treatment.
4.4.1 Thennal Treatment of Specimens All test specimens were given a streu relief heat treatment in the range of [
("'. The temperature source was a radiant heater installed inside the sleeve widch was centered on the weld. The maximum temperature anained by the tube was measured by thermocouple attached to the tubes outer surface and summarited in Table 4 7 4.4.2 Free.
.. Joint Test Results The welds were subjected to leak tesung (
1"'
No leakage was exhibited (Table 4 8). Some specimens were subjected to tensile and comprenive loading to failure; acceptable results were obtained.
Two welds were metallurgically examined following fadgue testing (L 552 and L 555). Based on tids examination
[
pn Several compressive specimens were examined fol! ewing testing (L 540, L 543) and exhibited notcidng or a high degree of straining in the sleeve and tube at the weld interface, llowever this notching effect was not present in untested or fadgue tested specimens Since compressive loading of the sleeve is not expe:tenced in operadon, tids effect will not have any impact on the sleeve weld integrity.
l, 4.4.3 Impact of Tube Fixity on Free Span Weld Perfonnance Under certain conditions tubes may become locked to the support plate structure of the steam generator, normally during operadon at full temperature (approximately 60(PF). Upon cool down, differential thermal expansion rates between the sleeve and steam generator structure can impact tensile loads on 2 -sibe. l pu i
pu W19 W 4;lt M 2492 4 12
Table 4 7 Free Span joint Maximum Stress Reller Temperature Specimen Number Matimum Temperature ('F1 a.e,e
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Table 4 8 Free Span Joint Leak Rate and Loading Data Leak Rate after 3M00 Fatigue initial Leak Rate Cycles @ 600'F Specimen Room Temperature Room Temperature Compressise Tensile Load Number 1600 psi 1600 psi Load (Ibs)
(Ibs) s,c.e L 536 L 540 L 543 L 544 L 546 L 548 L 550 L 551 L !$2 L 55 Leak rate is in drops per minute.
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4.4.4 Results of rised Tulie Free Span Welding:
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5.0 STRESS CORROSION TESTING OF 1,ASER WEl,DED SLEEVE JOINTS
' The resistance of tiie laser welded sleeve joint to in service corrosion is related to the resistance of the Alloy 600 tubing to intergranular stress conosion cracking (IGSCC). De sleeve material, Alloy 690 *IT, j
has been demorntrated to be highly resistant to IGSCC under steam generator conditions (Reference 1).
Stresses in die tubing, either service imposed or residual, are a major factor determining the response of the material in terms of IGSCC. Two sources of residual stresses in the laser welded sleeving proces are al minor stresses related to the hydraulle expansion during sleeve placement and b) residual suesses that occur as the molten weld pool solidifies.
Els section sununarlies results of a tesdng program to evaluate the Primary Water Stress Corrosion Cracking (PWSCC) resistance of laser welded upper sleeve joints used to install sleeves in degraded steam -
t generator tubing. He testing was conducted under condidons widch accelerate conosion in steam generator materials that inay be susceptible to stress corrosion cracking in long tenn steam generator service. Some of the laser welding processes included in these corrosion tests are representatJve of the weld parameters used but were produced using a CO laser, ne CO laser process has been used 2
2 previously in field sleeving applications.
5.1 Corrosion Test Description An accelerated conosion test developed by Westinghouse is used as a means to evaluate the resistance of steam generator materials to degradadon in steam generator primary water environments. De test produces the same type of degradadon duough intergranular stress corrosion cracking that has been.
j observed in some mill annealed Alloy 600 steam generator tubing. De test has also been found to provide
~
the same relative ranking of material resistance to IGSCC that has been observed in service.
l De accelerated test is conducted in an autoclave operating at 750*F (400*C) with steam at 3000 psig. %e steam contains [
l'" The ID of the specimen is exposed to the 3000 psi doped steam while the OD sees undoped steam at 1500 psi.
Ec configuration of the laser welded specimen used in this corrosion program is a free-span upper joiot as illustrated in Figure 5 1 He sleeve joints were fabricated using equipment and practices representative of in field sleeving operadons. He [
}'" test environment is introduced to the inside of the sleeve and has access to the ID of the sleeve and, on one side of the weld joint, to the OD of the sleeve,-
the ID of the tube and the weld. The other side of the weld joint and the outside of the tube are exposed to the 1500 psi steam environment, ne 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 the weld under stress conditions representative of those in the generator, wiU450 5.lM22192 51
a,b.c Figure 51 Accelerated Corrosion Test Specimen for Welded joint Configuration wnw50 5:Iwas1:92 52
The corrosion performance of the sleeve weld joints is compared with that of tube roll transitions exposed to the same test environment, he roll transiuon control samples illustrated in Figure 5-2 are representative of the transitions found at the top of the tubesacet in full depth, hard rolled steam generator tubes. De inclusion of the potentially PWSCC susceptible conDguration (the roll transition) in the test provides verincation of the aggressiseness of the corrosion test environment. Any variability in the aggressiveness from one autoclave run to another is accounted for by having roll transition controls in each run.
The time to-crack of the test sample is measured in the accelerated test. For both weld samples and roll transitions, cracking time is denned by the appearance of through wall cracks which is reflected in the loss of the 1500 psi differentiai pressure (3000 psi ID,1500 psi OD) across the weld and tube.
5.2 Corrosion Resistance of Free Span Laser Welded Joints As Welded Condition Most of the welded joint corrosion samples and all the roll transition sections were fabricated from mill annealed Alloy 600 tubing from Heat NX-1019. His is a high carbon heat (0.06Wc C) which previous testing has shown to be sensitive to PWSCC and has been used in a variety of corrosion test programs over the past several years. A set of CO: laser welded samples was also fabricated from a lower carbon (0.029c' C) mill annealed Alloy 600 tubing Heat NX-9621, which has exhibited susceptibility to PWSCC.
He lower carbon heat was included to determine if the carbon difference produced adverse metallurgical changes during welding. [
yu l
pu De response of laser welded joints to the accelerated corrosion conditions is shown in Figures 5 4 and 5-5 for CO: laser welds and in Table 5-1 and Figure 5-6 for Nd:YAG laser welds. Rese Ogures are log normal distribution plots of the cumulative percentage of samples exhibiting cracking as a function of time. De as welded joints generally exhibited times for through wall IGSCC in [
1" than that of the roll transitions. One tubing heat. Heat NX-2721, exhibited [
]" in the as-welded joint as in the roll transition.
[
pu WN450-5 lht82192 5-3
a,b.c
. Figure 5 2 Accelerated Corrosion Test Specimen for Roll Transition Configuration -
- WI9450 5:Ib/081292 54
l a,b,e Figure 5 3 IGSCC in Alloy 600 Tube of YAG Laser Welded Sleeve Joint After 109 Hours in 750*F Steam -
Accelerated Corrosion Test WPO450-5:ltw'081292 -
5-5
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a,b e Fig'.re 5-4 Cumulative Percent Cracking for CO Laser Welded Sleeves in 750*F Accelerated Steam Corrosion Test WPO450-5:1MM1292
. 5-6
4.b,e Figure 5 5 Cumulative Percent Cracking for CO, Laser Welded Sleeves in 750*F Accelerated Steam Corrosion Test WP0450 5;1bo82192 57
Table 51 '
Summary of Accelerated 750 F Steam Corrosion Test Results for TAG Laser Sleese Welds' ax.e.
~
CLW Conduction Limited Weld E CMP - Continuous Molten Pool ume to SCC is the time of pressure drop in test, i.e., time for through wall crack to from.'
Test terminated at 1000 bours-no through wall SCC.
WPN50-$:lb/082192 58
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a,b e i
o Figure 5-6 Cumulative Percent G s Mng for YAG Laser Welded Sleeves in 750*F Accelerated Steam Corrosion Test wro4545 was:192 59
I
.\\M t 5.3 Corrosion Resistance of Free Span Laser Welded Joints With Post Weld lieat Treatment Since stress corrosion cracking is related to a large extent to residual stresses, a reduction in the residual stress level will enhance the corrosion resistance of the weldedjoint. During the CO: laser weld program, extensive development of a post weld heat treatment was performed. A local stress relief treatment [ -
]'" was developed. The development program deterndned that [
l'" would reduce the level of residual stresses.
without significant ndcrostructural changes.
The effectiveness of a stress reliefis evident in Figure 5-4 where a [
j" in the time to cracking in heat treated welds over "as fabricated" welds can be seen. The beneficial effect of stress relief is also evident in the Nd:Y AG laser welds (Figure 5 6) in both the conduction limited weld (CL) and continuous molten pool (CMP) weld regimes. The test of the stress relieved CL joints [
]". This represents more than [
]" in time to cracking over that of the as welded joint. The corrosion tests of the stress relieved continuous mo'lten pool welds were also terminated after [
}"
hours with no indication of cracking.
The effect of the stress relief can also be seen in the cross section of the heat treated CL shown in Figure 5 7. [
]" In addition there was no evidence of the minor corrosion at the weld surface noted previously in the as welded, corrosion test
- sample, 5.4 Corrosion Resistance Evaluation of Lower Tubesheet Sleeve Laser Welded Joints i
Accelerated steam testing was performed on specimens representative of the lower tubesheet sleeve joint.
These specimens were the same as those used for mechanical testing as illustrated in Figure 4-1, except a seal weld was added at the elevation of the tube clad (Figure 2-1). For control purposes, tube roll transition specimens were used as reference standards.
These specimens were subjected to the steam test de cribed in Section 5.1 for a time period of s
[
]" The results, tabulated in Table 5-2, demonstrate [
]"
WPo450 5:lb/082192 5-10
a,b,e Figure 5 7 Minor IGSCC in AUoy 600 Tube of Stress Relieved YAG Laser Welded Sleeve Joint after 1000 Hours in 750*F Steam Accelerated Corrosion Test WRM50 5:Ibd82192 5-11
t
. 5.5-EITects of IIEJ Sleesink on Tube to Tubesheet Weld
- 5.5.1 l,ower llEJ Joint
-'The effect ol' hard rolling the sleeve over the tube to tubesheet weld was examined in the sleeving of!
O.750 inch OD iubes. Although the sleeve installation roll torque used in a 0.750 inch OD tube is less than a'.875 inch OD tube, the radial forces transmitted to the weld are cotuparable. Evaluation of the 0.750 inch tubes showed no tearing or other degrading effects on the weld after hard rolling. Therefore, no signiticant effect on the tube to tubesheet weld is expected for the larger 0.875 inch OD tube contipuration.
~ 1 i
5.5.2 1,ower Seal Weld l
As may be the case for flush or recessed welds, l ju
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Table 5 2 Corrosion Resistance Evaluation of Lower Tubesheet Laser Welded Sleese Joints Mod:up: Alloy 600 MA (Heat 7368.0.875 in. OD) tube, mechanically expanded into steel collar Sleeve:
Alloy 690TT a,e.e Autoclave W
Spec No.
Type Specimen Number Hrs.
Result.s A slow leak was present at the start of the last run in Autoclave 11. At a cumulative exposure time of about 205 hrs, the leak rate during the last run in Autoclave i1 increased, but was not detected until a pressure plot was made at the end of the run. Specimen CH.SR-01 was found to exhibit minor leakage at the end of the run. It is assumed that the initiation time of the leak in CTLSR-01 corresponds to the time at which the leak rate increased in Autoclave 11.
w a nso.5 w os:192 5 13
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5,6 Outside Diameter (OD) Surface Condition Since 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, De 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 of longitudinal 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. De pulled tube was analyzed for the presence of contaminants.
on the OD surface and beneath the OD surface The microprobe analysis detected Fe, P. Sii Cu, Ca and '
Na on the tube OD,' but there was no indication of diffusion into the tube.
In addition to the above tests, archive tubes from two plants were welded and a microanalytical examination was made for contaminant ingress before and after welding. Before welding, [
1" -
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 i -
jo.
To summarize, several observations have been made 'for a variety of Alloy 600 samples heated to temperatures from [
]"in the presence of typical secondary side chemical species.
No significant diffusion, corrosion, or embrittlement of the tubing has been found.
wmm5 mosm 2 5-14
4 6
- 5.7-! References -
1.
" Alloy 690 for Steam Generator Tubing Applications," EPRI. Report NP-6997 SD, Final; Report for -
Program S408 6. _ October 1990.-
1
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6.0 INSTALLATION PROCESS DESCRIPTION Re following description of the sleeving process pertains to current processes used. Westinghouse continues to enhance it's tooling and processes through development programs. As enhanced techniques are developed and verined they will be utilized. Use of enhanced techniques which do not materially affect the technical justification 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.
The sleeves are fabricated under controlled conditions, serialized, cleaned, and inspected. They are 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 and as required moved to a ',ow 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.
De 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 joim, hard rolling the lower tubesheet joint locations, welding the upper joint, visual inspection and eddy current inspection. The 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. Rese
]
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. His is sufficient to prepare the mouth of the tube for sleeve insertion without adversely affecting the original tube hard roll or the tube-to-tubesheet weld. Tube end rolling will be performed only as a contingency.
Testing of similar lower joint configurations in Series 27 steam generator sleeving programs at a much higher torque showed no adverse effect on the tube to tubesheet weli Because the radial forces WPO450-6 lNOR2192 61
transmitted to the tube-to-tubesheet weld would be lower for a larger Model 44 and Si tube than for the above test configuration, no effect on the weld as a result of the light roll is expected.
6.1.2 Tube Cleaning (Optional) _
L The sleeving process includes cleaning the inside diameter area of tubes'to be sleeved to prepare the tube
~
surface for the upper and lower joint formation by removing frangible oxides and foreign material.
Evaluation has demonstrated that this process does not remove any significant fraction of the tube wall base material.
The interior surface of eacb candidate tube will be cleaned by a (
f" The hone brush is mounted on a flexible drive shaft that is driven by an pneumatic-motor and carries reactor grade deionized flushing water to the hone bmshJ The hone brush is driven to a predetermined height in the tube that is greater than the sleeve length in order to adequately clean the l:
joint area. [.
l'" he Tube Cleaning End Effector mounts to a tool delivery robot and consists of a 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 l
generator platform. De conduit acts as a closed loop system which serves to guide the drive shaft / hone bmsh 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 process. However, test programs are 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.
l 6.2 Sleese Insertion and Expansion
~
l 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 l
consists of two pneumatic camlocks, dual pneumatic gripper assemblies, a pneumatic translation cylinder, f
a motorized drive assembly, and a sleeve delivery conduit.
The tool delivery robot draws the S ALEE through the manway into the channel head. It then positions the S ALEE 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 until it is able to be gripped by the translating upper gripper.
WPO450 6:lb/082192 6-2 l'
- Table 6-1.'
Sleeve Process Sequence Summary TUBE PREPARATION-1)
Light Mechanical Roll Tube Ends
- (if necessary)'
2)-
Clean Tube Inside Surface -
(Opdonal).
SLEEVE INSERTION 3)-
.- Insert. Sleeve / Expansion. Mandrel Assembly :
. Hydradlically Expand Sleeve Top and 4)
Bottom Joints =
-TUBESHEET LOWER JOINT 5)
Roll Expand Tubesheet Lower Sleeve
- FORMATION End'
- WELD OPERATION
. 6)
Weld Upper Tubesheet Sleeve Joints-p ju.
7)
Weld. Upper and Lower Support Plate Sleeve Joints INSPECTION 8)
Visually ' Inspect - Lower ~_Tubesheet Sleeve Weld (if performed) 9)
Ultrasonically Inspect Sleeve Welds -
t (Free span welds only on a' sample plan)
- STRESS RELIEF 10).
Post Weld Stress Relief Sleeve Welds-
[
ju INSPECTION 11)
' Baseline Eddy Curreht Sleeves.
wPO4546:lbt)80392 -
.6-3
De 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.
Irwertion 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 support plate sleeves, the support plate 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 support plate. 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. The 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 Sleeve / Tube Expansion Controller (S/TEC), 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.
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 subsequer.t 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 inscrtion sequence. The SALEE is then repositioned to receive another sleeve / mandrel assembly.
i 6.3 Lower Joint Hard Roll (Tubesheet Sleeves)
At the primary face of the tubesheet, the sleeve is joined to the tube by a mechanical hard roll (following the hydraulie expansion) performed with a roll expander [
1"' The control of the mechanical expansion is maintained through (
gue 6,4 General Description of Laser Weld Operation Welding of the upper tubesheet sleeve joint and the upper and lower tube support plate sleeves will be accomplished by a specially developed laser beam transmission system and rotating weld head. This wmo. ewe 80N:
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l system employs a Nd:YAG. laser energy source located in a trailer outside of containment The energy of.
- the laser is delivered to the steam generator platform junction box through a liber optic cable: The liberL -
= opdc contains an intrinsic safety wire which protects personnel in the case of damahe to the liber. The weld head is connected to the platform junction box by a prealigned fiber optic _ coupler. Each weld bead contains the necessary opdes, liber termination and tracking device to correcdy focus the laser beam on the interior of the sleeve.
The weld head / liber optic assembly is precisely positioned within the hydraulic expansion region using the SALEE (described earlier) and an eddy current coit 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 welding process the head is rotated around the inside of the tube to produce the weld. A motor, gear train, 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 ASNfE code, are computer controlled at the weld operators stadon. The essential variables per code case N-395 are monitored and documented for field weld acceptance.
6.4.1 Rewelding-Under some condidons, the initial attempt at making a laser weld may be interrupted before comptedon.
Also, the UT examinadon of a completed initial weld may result in the weld being rejected In these cases, an addidonal weld, having the same nominal characteristics as the initial weld.- will be made close to and either inboard or outboard of the inidal weld. If a perforation of the sleeve is suspected in the -
initial weld area, the repair weld will be located inboard of the initial weld. Otherwise, the repair weld will be located outboard of the initial weld, 6.5 Inspection Plan In order to verify the final sleeve installation, inspections will be performed on sleeved tubes to' verify-installadon and to establish a baseline for future eddy current examination of the sleeved tubest Specific NDE processes are discussed in Section 7.0.
If it is necessary to remove a' sleeved tube from service as judged by an evaluation of a specific sleeve / tube configuration, tooling and processes are available to plug the tube.
1
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' 6.6 References
-L
'ASME Boiler and Pressure Vessel Code, Secdon XI,' Article IWB-4300,1989 Edition.-1989 Addenda.
1
- 3. - Boone.'P J..." ROSA !!!,' A Third Generation Steam Generator Service Robot Targeted ' t Reducing -
a
,[
Steam Generator Maintenance Exposure," CSNI/UNIPEDE _ Specialists Meeting - on Operating -
Experience with Steam Generator, paper 6.7,-Brussels 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.
4 s'
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_. 7,0 - NDE_ INSPECTABILITY '
= The welding parameters are computer controlled at the weld operator's station. The. essential' variables, Jper ASNE 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 efficacy 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, 7.! Inspection Plan Logic The basic tubesheet sleeve inspection plan shall consist of:
A.
Eddy Current Examination (Section 5.2) [
ld 1.
Demonstrate presence of upper and lower hydraulic expansions 2.
Demonstrate-lower roll joint presence 3.
Determine location of upper weld i'
4.
Record baseline of entire sleeved tube for future inspections d
B.
Ultrasonic inspection (Section 5.1) [
I or alternate methods (Section 7.4).
1.
- Demonstrate quality of upper weld 2.
Determine width of the upper weld C.
Visual Inspection [
]d 1.
Exhibit presence and full circumference continuity oflower weld, if seal weld option selected D: Weld Process Control [
l d
l 1.
Demonstrate weld process parameters comply with qualified weld process specification The basic tube support plate sleeve inspection of the sleeved tubes shall consist of:
I A.
Eddy Current Examination (Section 5.2) [
]*
1.
Demonstrate presence of upper and lower hydraulic expansions 2.-
Determine location of upper weld and lower welds '
3.
Record baseline of entire sleeved tube for future inspections WPO450-7:ltiO80392 7-1
B.
Ultrasonic inspection (Section 5.1) [.
l' or alternate methods (Section 5.3)-
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 ne ultrasonic inspection process is based on further refinements of_ past well-known and field-proven f
techniques used on brazed and CO: laser welded sleeves installed by Westinghouse.-
The inspection process developed for application to the laser weids incorporates the basic idea of 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 weld joint 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.
Appropriate transducer, instrumentation and delivery systems have been designed and techniques established to demonstrate detectability and resolution of relevant defects at the interface. [
i
.f ja.c4 7.2.1 Principle of Operation and Data Processing of Ultrasonic Examination 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 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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JOINT Figure 71 Ultrasonic inspection of Welded Sleeve Joint wrusso.7:itvo80392 g
1
- De transtnined wave propagates in the sleeve until it reaches the outside surface of the sleeve. If weld
[
materialis present, the wave continues to propagate through the weld joint into the tube. Wis wave then
. reaches the outer wall (back wall) of the tube and is reflected to the transducer. The resulung UT instrument display from a sound weld joint is a large signal from the sleeve-couplant interface,' followed-by a back wall " echo" spaced by the time of travel in the sleeve weld. tube assembly (Tud. If no weld material is present. another pattern is observed widi the large signal from the sleeve ID followed by a reflection from the sleeve OD (Tu). De spacing of these echoes depends upon the time of travel in the-sleeve alone. If there are 3ome void regions in the weld, a complex combination of these two signal' patterns will result. Dus, by observing the patterns in the reflected pulse, a quality can be asigned to l
the weld joint.
The condition of the surface at the entry point of the sound energy, as well as subsequent grain structure of the weld fusion zone, determines the level of energy that reaches the back wall of a " fused. sleeve / tube section. To provide the required resolution and ability to maximite energy input to the interface.
appropriately focused transducers have been chosen. (
ju.
An automated system is used for digitizing and storing the UT wave forms [
j.u 7.2.2 Ultrasonic inspection Equipment and Tooling The probe system is delivered by the Westinghouse ROSA zero entry system. De various subsystems include the water couplant. UT, motor drives, electrical systems and data display / storage.
The probe motion is accomplished via rotary and axial drive modules which allow a range of speeds and.
1 axial advance per 360' scan of the transducer head. De axial advance allows for overlap providing a -
high degree of overlapping coverage without sacrificing resolution or sensitivity.
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.
wiw$0-7;ltm0%2
.74
i a,e -
e Figure 7 2 Typical Digitized UT Waveform WP)450 7:thMO%2 75 4
De permanent record of the inspection is a color pilot C scan derived from the digitized and sto;ed A-Sean waieforms. Figure 7 3 is an example of an acceptable laser weld C scan. De UT instrument is used with the gate modules synchronized to die front wall (sleeve I.D.) signal. (
ya-
' 7.2.3 1.aser Weld Test Sample Results.
The calibration standards consist of; (a) Equipment setup standard -solid Alloy 690 thick walled tube (wall thickness 0.10(r').
(b) A sensitivity / resolution check " workmanship" standard, a typical laser welded sleeve / tube assembly, The UT techniques were developed to assure that the Cat bottom holes and notches of the setup standard -
(described in Figure 7-4) were detectable and measurable. A hard copy color plot, Figure 7 5 shows the C-scan of the setup standard. (
yn The "workmanstdp" standard was prepared using the typical weld process. The sample was inspected before further processing was done. A set of two notches was introduced in the outside diameter across -
the weld. These notches extended across the width of the weld. The notches simulate a " breach" or leak path across the weld. (
ja.
A " notched workmanship standard C-scan plot is shown in Figure 7-6.- The equipment is set up using.
the thick-walled tube standard to allow the operator ease in identifying and setting the UT instrument gates and gain. The setup standard presents uniform signals and is repeatable for every A-scan.
7.2,4. Ultrasonic Inspection Summary The UT laser weld inspection system can confirm that there is a metallurgical bond between the sleeve and the tube. The system is used to determine any existence of leak path across the weld and a minimum -
acceptable weld width for 360 degrees around the circumference.
-7,3 ' Eddy Current Inspection Upon conclusion of the sleeve installation process, a final eddy current inspection is performed on every j installed sleeve to provide interpretable baseline data on the sleeve and tube; This information is gathered
'.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 oood weld material, etc.
i I
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Figure 7 3 '
C-Scan from UT Examination of an Acceptable Laser Weld WPO450 ?;1tvo80392 77
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Figure 7-4 ITT Setup Standard WPO450-7.1b/080392 78.
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Figure 7-5 C Scan from UT Examination of Equipment Setup Standard WFW50 7:ltv080392 7-9
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i I
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i Figure 7 6 C-Scan from UT Examination of Workmanship Sample of a Laser Welded Steeve with Two EDM Notches WPO450 7 Ib/080192 7-10
- 7.3.11 Eddy Current Inspection Principle of Operation U
~
- The eddy current inspecuon eqmpment, 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's Technical Specificationsc The purpose of these inspections is' to detect'at
. an early stage tube degradation that may hase occurred during plant operation so that appropriate action can be taken to ndnindze further degradation and reduce the potential for significant priinary-to-secondary
_ j
- 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 conneited in the so-called differential mode; that is, the system responds only when there is ~a difference in the properties of the material surrounding the two coils. The coils are excited by using an eddy current 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 test frequencies.
De outputs of the various frequencies are combined and recorded. The' 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 suppor' plate, tubesheet laser weld area and sleeve.
transition zones are examples of areas where multifrequency processing has proven valuable in providing improved inspectatn.ity.
i 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.
There are a number of probe configurations that lend themselves to enhancing the, inspection of the sleeve / tube assembly m the regions oflaser weld as well as configuration transitions. The crosswound l
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.-
The inspection for degradation of the sleeve / tube assembly has typically been performed using crosswound i;
- 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 assemblyjoint regions; data evaluation becomes more complex. The results discussed below l
ll suggest the limits on the volume of degradation that can be detected in the vicinity of the laser weld and l
geometry changes.
i I
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U 7.3.2. Transition Region Eddy Current inspection The detection and quandfication of deeradation at the transition recions of the sleese/ tube assembly
~
' depend upon the signal-to-noise ratio between the degradation response and the transition response.- As-a general rule, lower frequencies tend to suppress the transition signal relative to the degradation signal
- at the expense of the ability _to quantify the.degradadon. Similarly, the inspection _of the tube through the -
sleeve requires the use of low frequencies to achieve detection with an associated loss in quantification.
Thus, the search for an opumum 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 indicadons -
can be assessed.
For the tube / sleeve combination, the use of the crosswound probe, coupled with a muldfrequency mixing technique for further reduction of the remaining noise signals significantly reduces the interference from all discontinuides (e.g., a diameter transition) which have 360-degree symmetry, providing improved visibility for discrete discontinuides. 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 when the volume of metal removed is equivalent to the ASNE calibration standard.
The response from the sleeve / tube assembly transitions with the crosswound coil is shown in Figures 7-8, j.
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.
frequency combinations are shown; the [
l'" combination provides the overall detection capability while the [
]'" combination provides improved sensitivity for the sleeve and some quantificadon capability for the tube. Figure 711 shows the phase / depth curve for the tube using this combination. As examples of the detection capability at the transitions, Figures 7-12 and 713 show the-responses of a 20 percent OD penetration'in the sleeve and 40-percent OD penetradon in.the tube, respectively.
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 four less sensitive than that of the expansions. Some addidonal inspectability has_been -
gained by tapering the wall thickness at the top end of the sleeve. This reduces the end-of-sleeve signal by a factor of approximately two. The crosswound coil, however, again significantly reduces the respocse of the sleeve end. Figure 714 shows the response of various ASNE tube calibration standards placed at the end of the sleeve using the cross-wound coil and the [
l'" frequency combination) Note that under these conditions, degradation at the top end of the sleeve / tube assembly can be detected.
5:
WPO450 7.1M)80392 7-12
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L Figure 7 7
[
]* Calibration Curve WPO450 7;ltwix0M 7 13
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Figure 74 Eddy Current Signals from the ASTM Standard, Machined on the Sleeve O.D. of the Sleeve /fube Assembly Without Expansion (Cross Wound Coll Probe)
WP1130 7:Ibt80192 7-14
l Q.c.A Figure 7 9 Eddy Current Signals from the ASTM Standard Machined on the Tube O.D. of the Sleete/ Tube Assembly Without Espansion (Crms Wound Coll Probe)
WIst$0 7;1N080392 7-15
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1 Figure 710
~
Eddy Current Signals from the Expansion Transition Region of the SleeveRube Anembly (Cross Wound Coll Probe).
W104501.1t=%0%2 7 16
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9 Figure 711 Eddy Current Calibration Curve for ASTM Tube Standard at [
1"'
and a Mix Using the Cross Wound Coll Probe WiO4547:lt>V80392 7-17
4 Figure 712 Eddy Current Signal from a 20% Deep IIole, limit the Volume of ASTM Standard, Machined on the Sleese O.D. In the Expansion Transition Region of the Slee seffube Assembly (Cross Wound Coll Probe)
W194$0-7:IWO80392 7.I8
.___m- _ _ ___-._____.___ _____ _. _
i t
a
?
Figure 713 Eddy Current Signal from a 4G% ASTM Standard, Machined on the Tube O.D. In the Expansion Tramition Region of the Sleeve / Tube Assembly (Cross Wound Coll Itobe)
WPO4$M:ltvo80392 7 19 C
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F6gure 714 Eddy Current Response of the ASTM Tube Standard at the End of the Sleese Using the Cross Wound Coll Probe and Multifrequency Combination 4
g 7 20
The cases considered atme cover the following laser welded and mecharucal sleeve / tube pressure boundanes inspecuon areu:
- 7) The enure length of the tubesheet sleeve extending from the upper weld down to the end of the sleeve.
3)
The entire length of the tube from We bot leg tube entry to the top support of the cold leg, with the excepuon of the followtng areas:
3a) The length of tubing terween the upper and lower welds of each TSP sleeve.
3b) The length of tubtng between the upper weld of a tubesbeet sleeve, down to the tube length bebtnd the hardroll area of the tubesheet sleeve.
Note that mdtcadon of tube degradauon of any type including a complete break in the tute between the upper weld lotnt and the lower weld joint does not require that the tube be removed from service.
Alsc in a free span joint with more than one weld the weld closest to the cod of the sleeve represents the joint to te inspected and the hmst of sleeve inspecuon.
7.3.3 Laser Weld Region Eddy Current inspection Not a part of the preceding inspecdon zone definitions, eddy current inspecdon of the laser welded joint itself was reviewed in an addidonal study, he test sample used for this study was a prototypical laser weld in an expanded sleeve zone of a sleeve / tube a::sembly. De weld was inspected before and after the intfoduction of a 407c thru wall 3/16 inch diameter flat bottom hole placed on the outside surface of the tube at the centerline of the weld, his weld presents an axisymmetric condidon 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.
~
Figure 715 shows the [
l'" response from the weld zone and Figure 716 shows the successful
[
j"" mix response using cross wound coils.
Dei l'" combinadon has proven to be optimum for detection in the weld zone, particularly at the tube I.DJsleeve O.D. interface. Figures 717 and Figure 718 show the response of the 40% FBH using (
}'" and mix, respectively.
7.3A Eddy Current inspection Summary Convendonal eddy current techniques have been modified to incorporate the most recent technology in the inspecdon of the sleeve / tube assembly. De resultant inspection of the sleeve / tube assembly involves wPO4$o-7 IW10M2 7-21
~9 a.c,e Figure 715 Crosswound (50 kilzl"' Eddy Current Baseline of Laser Weld
- WPO450-7:lbt40M2 7 22
____:--1__
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s Figure 716 Crosswound Mix Eddy Current Response Baseline of Laser Weld WPO450-7:lb/080392 7-23
l i
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Figure 717 Crosswoorv3 [50 kHzl"' Eddy Current Response After 40%
Flat Bottomed Hole was Placed in O.D. of Tube at Center of Weld
%TO450-7;lWO60392 7 24 L
s ac Figure 718 Crosswound Mix Eddy Current Response After 40%
Flat Bottorned Hole was Placed in O.D. of Tube at Center of Weld WBM$0-hIb'080392 7-25
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 theavailability 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 and verified, they will be utilized after 10CFR50.59 review. For the present, the cross-wound coil probe represents an inspection technique that provides 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 [
ju.
I p,
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 rigor of the alternate methods.
7.4.1 Ilounding Inspections
[
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P' WPO450 7.!bilOOo92 7-26
7.4.2 Workmanship Samples One technique to support the acceptance of indeterndnate welds is to compare the UT signals obtained -
from workmanship samples having surface roughness or local undercuts with the " indeterminate" UT signals obtained in the field. This would show that the indeterminate finding was due to surface roughness or local undercut and substantiate the case for accepting the weld.
7.4.3 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. (
l' I
l' In summary, Westinghouse proposes to apply ulternate 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 Inservice Inspection Plan for Sleeved Tubes The need exists to perform periodic inspections of the supplemented pressure boundary. -The insenice 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.
i l
b.
Periodic inspections will be performed to monitor sleeve and tube wall' conditions in accordance with l
the inspection section of the individual plant Technical Specifications.
The 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. The possibility for tube degradation in free span lengths is extremely smail, as plant data have shown that this area is less -
susceptible than other locations. Any tube indication in this region will require further inspection by-l alternate techniques (i.e., surface riding probes) prior to acceptance of that indication. Otherwise the tube shall be removcd from service by pluggint,. Any change in the eddy current signature of the sleeve and.
l wF0450-7.1b/100692 7-27
sleeve / tube joint region will require further inspection by alternate techniques prior to acceptance.
Otherwise the tube containing the sleeve in question shall be removed from senice by plugging.
7.6 References -
1.
Stubbe, J., Birthe, J. Verbeek, K., " Qualification and Field Experience of Sleeving Repair Techniques:
CSNI/UNIPEDE Specialist Meeting on Operating Experience with Steam Generators, paper 8.7, Brussels, Belgium. September 1991.
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