ML20112K055
| ML20112K055 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/31/1985 |
| From: | ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY |
| To: | |
| Shared Package | |
| ML13309B527 | List: |
| References | |
| CEN-299(S), NUDOCS 8504090319 | |
| Download: ML20112K055 (123) | |
Text
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!t3 EVALUATION OF STEAM GENERATOR a I TUBE AND DIAGONAL SPACER STRIP %
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A Zii Prepared by: ---- j C-E Power Systems j Combustion Engineering, Inc. i F Windsor, CT ]
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m T 7 e 7 h LEGAL NOTICE h n . == e THIS REPORT WAS PREPARED AS AN ACCOUNT OF WORK SPONSORED E a BY ColWUSTION ENGINEERING, INC. NEITHER COM8USTION ENGINEERING NOR ANY PERSON ACTING ON ITS BEHALF: f j -
- g. A. MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS OR 5
IWWED INCLUDING THE WARRANTIES OF FITNESS FOR A PARTICULAR y S PURPOSE OR MERCHANTA58UTY, WITH RESPECT TO THE ACCURACY, -- COMPLETENESS, OR USEFULNESS OF THE INFORMATION CONTAINED IN THIS 5 = REPORT, OR THAT THE USE OF ANY INFORMATION, APPARATUS, METHOD, 9 OR PROCESS DISCLOSED IN THIS REPORT MAY NOT INFRINGE PRIVATELY L
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OWNED RIGHTS;OR aa E. ASSUMES ANY UASluTIES WITH RESPECT TO THE USE OF,OR FOR = m DAMAGES RESULTING FROM THE USE OF, ANY INFORMATION, APPARATUS, METHOD OR PROCESS DISCLOSED IN THIS REPORT. S ? 9 4] E -el W
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SAN ONOFRE NUCLEAR GENERATING STATION - UNIT 2 SOUTHERN CALIFORNIA EDISON C0. EVALUATION OF STEAM GENERATOR TUBE AND DIAGONAL SPACER STRIP INTERACTION AND WEAR MARCH, 1985 PREPARED BY C-E POWER SYSTEMS COMBUSTION ENGINEERING, INC. WINDSOR, CT
EXECUTIVE
SUMMARY
A recent inservice inspection of San Onofre Unit 2 steam generators revealed flaw indications on tubes at the inner periphery of the tube bundle in both steam generators. The indications were located at the intersection of the tubes with the longest diagonal spacer strips (batwings) located in the tube bundle bend region. Based on evaluation of the nondestructive eddy current examination data, analysis, and testing, it is concluded that the indications are tube wear resulting from flow induced vibration of the steam generator tubes and the batwings. A conservative tube plugging and staking program was implemented to meet Southern California Edison's objectives of assuring safe operation and preventing tube leaks through Cycle 2. The pattern of plugging and staking is based on a program consisting of flow distribution and structural analysis, flow visualization testing, and wear evaluations. The resulting plugging and staking pattern assures that operation through Cycle 2 will not wear an unplugged tube in excess of the values used as a basis for tube plugging criteria in the San Onofre Unit 2 Technical Specifications. Further, additional conservatism has been demonstrated through tube burst and leakage testing perforned on degraded tubes. N i
EVALUATION OF STEAM GENERATOR TUBE AND DIAGONAL SPACER STRIP INTERACTION AND WEAR TABLE OF CONTENTS EXECUTIVE
SUMMARY
1.0 INTRODUCTION
1.1 Purpose
1.2 Background
1.3 Approach 2.0 STEAM GENERATOR DESIGN DESCRIPTION 2.1 Introduction 2.2 Steam Generator Internal Structures 2.3 Principle Flow Paths 2.4 Affected Internal Structures 3.0 NONDESTRUCTIVE EXAMINATION EVALUATION 3.1 Introduction 3.2 Eddy Current Examination Technique 3.2.1 Multifrequency Eddy Current Examination with Bobbin Coil Probe 3.2.2 Specialized Eddy Current Techniques 3.3 Eddy Current Examination Technique Verification 3.3.1 Validation of Examination Techniques 3.3.2 Eddy Current Examination Accuracy 3.4 Characterization of Indications 3.4.1 Number and Location of Indications 3.4.2 Eddy Current Indication Geometry 3.4.3 Analysis of Indications and Geometry . 3.5 Summary of Results 4.0 EVALUATION OF DEGRADATION MECHANISM 4.1 Introduction 4.2 Flow Distribution Analysis 4.2.1 Thermal-Hydraulic Modeling 4.2.2 Kinetic Energy of Fluid in Central Cavity ii
4.3 Tube / Batwing Flow Visualization Testing 4.3.1 Test Model and Flow Loop 4.3.2 Test Matrix 4.3.3 Test Results and Conclusions 4.4 Tube Wear Mechanism 4.4.1 Wear Calculation Methodology 4.4.2 Tube Wear liodel 4.4.3 Determination of Wear Volumes 4.5 Flow Load Analysis of Tube / Batwing Assembly 4.5.1 Frequency Analysis 4.5.2 Tube Response to Secondary Flow 4.5.3 Tube / Batwing Contact Forces 4.6 Tube Wear Evaluation and Projection 4.6.1 SONGS-2 Steam Generator Tube Wear 4.6.2 Predicted Tube Wear 4.6.3 Wear Projection Based on Operating History 4.6.3.1 Effect of Sliding Distance on Wear of a Tube 4.6.3.2 Effect of Force on Wear of a Tube 4.6.4 Batwing Wear Evaluation and Resultant Stress 4.6.4.1 Wear Progression at Batwings 4.6.4.2 Stresses at Batwings 4.7 Summary of Results 4.7.1 Flow Visualization Testing 4.7.2 Wear Mechanisms 4.7.3 Wear Calculations 4.7.4 Wear Projections 4.7.5 Batwing Stresses 5.0 PLUGGING AND STAKING PROGRAM 5.1 Introduction 5.2 Tube Plugging 5.3 Tube Staking 5.4 Structural Adequacy of Plugged and Staked Tubes 6.0 SUPPARY AND CONCLUSIONS APPENDIX - DEGRADED TUBE BURST AND LEAKAGE TESTING A.1 Introduction A.2 Test Specimens and Testing Equipment A.3 Test Results iii
LIST OF TABLES TABLE NUMBER TITLE 3.4-1 SONGS-2 Steam Generator 88 Batwing / Tube Degradation Summary 3.4-2 SONGS-2 Steam Generator 89 Batwing / Tube Degradation Sumary 3.4-3 SONGS-2 Steam Generator Tube Indications Greater Than 20% Evaluation Summary 4.2-1 Thermal Hydraulic Analysis Results Sumary 4.3-1 Tube / Batwing Flow Visualization Test Matrix 4.3-2 Tube / Batwing Movements vs. Water Flow Rate 4.4-1 Wear Test Data for Tubes 4.5-1 Contact Forces, Unit Load Case 4.5-2 Contact Forces with Prior Wear 4.6-1 Comparison of Wear for Tube Wear Models A, B, and C Appendix A-1 Leakage and Burst Testing of Worn Tubes A-2 Test Matrix, Degraded Tube Burst and Leakage Testing I iv
LIST OF FIGURES FIGURE NUMBER TITLE 2.1-1 SONGS-2 Steam Generator Arrangement 2.2-1 Eggcrate Tube Support Details 2.2-2 SONGS-2 Steam Generator Bend Region Tube Supports 2.2-3 SONGS-2 Steam Generator Vertical Support Grid Assembly 2.3-1 Steam Generator Principal Flowpaths 2.4-1 Batwing Arrangement in Central Stay Cylinder Region 2.4-2 Horizontal Span Tube Bundle Geometry 2.4-3 Steam Generator Central Cavity Region (Scrapped Unit) 2.4-4 SONGS-2 Steam Generator Upper Batwing Assembly 2.4-5 SONGS-2 Steam Generator Lower Batwing Assembly 3.3-1 Wear Mark Standard 3.3-2 Eddy Current Depth Estimate vs. Actual Single and Multifrequency on Simulated Wear 3.4-1 SONGS-2 Steam Generator 88 ECT Hot Side Batwing Indications, End of Cycle 1 3.4-2 SONGS-2 Steam Generator 88 ECT Cold Side Batwing Indications, End of Cycle 1 3.4-3 SONGS-2 Steam Generator 89 ECT Hot Side Batwing Indications, End of Cycle 1 3.4-4 SONGS-2 Steam Generator 89 ECT Cold Side Batwing Indications, End of Cycle 1 3.4-5 San Onofre 2, Steam Generator 88 Flaw Depth vs. Tube Wear Angle 3.4-6 San Onofre 2, Steam Generator 89 Flaw Depth vs. Tube Wear Angle 4.3-1 Flow Visualization Model 4.3-2 Front View of Visualization Flow Test Model with Window Removed v
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4.3-3 Top "Eggerate" Tube Support, Immediately Below Batwing F ,7. J.?f . y . p c . s :: 4.3-4 Vertical Grid Tube Support Viewed from Below [.Y%..; .w.j ...,
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4.4-2 San Onofre 2, Steam Generator Tube / Batwing Strip Wear ~# f. , gr ;
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- Geometry
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F i y;. y ,- i 4.4-3 San Onofre 2, Steam Generator 88 Correlation of Wear Models ;.O:~f.1, with ECT Indication Characterization 'f i .c T GhW: .: '
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4.4-4 San Onofre 2, Steam Generator 89 Correlation of Wear Models i.3 .. ::N with ECT Indication Characterization s.' A ( : tg.
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4.4-5 Wear Volume vs. Depth of Indentation for Wear Model A \v ] -:C.: 4 ( 4.5-1 Finite Element Model (,f .'U-N , y.
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9 4.6-1 San Onofre II Cycle 1 Thermal Power vs. Time *W, i 'l - - 2 ,$*f*;% f 1,; 5
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; Degradation and Tube Plugging and Staking Pattern Implemented y
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LIST OF FIGURES (Cont'd.) FIGURE NUMBER TITLE 5.3-1 Typical Stake Installation 5.4-1 Total Wear Volume vs. Wear Depth Appendix A-1 Schematic of CE/EPRI Tube Burst and Leak Rate Test Facility A-2 Typical SONGS-2 Leak Rate Tests for Inconel 600 Tubes vii l l
1.0 INTRODUCTI0ff 1.1 PURPOSE This report provides the evaluation of steam generator tube flaw indications identified at the San Onofre Nuclear Generating Station, Unit-2 (SONGS-2) and provides the basis for operating that Unit through Cycle 2.
1.2 BACKGROUND
A tube inspection program was conducted on both SONGS-2 steam generators during the first refueling outage. The inspection included a multifrequency eddy current test of all unplugged steam generator tubes. In the diagonal spa,cer strip (batwing) region of the U-bends, the eddy current test results identified 33 degraded and 12 defective tubes and 26 degraded and 22 defective tubes in steam generators E-088 and E-089, respectively. These degraded and defective tubes in each steam generator were found to exhibit wear characteristics. This report describes the characterization, evaluation and corrective action taken as a result of these findings. Further, the report substantiates the conclusion.that operation of SONGS-2 through Cycle 2 will not result in undue risk to the public health and safety. 1.3 APPROACH - In order to determine the extent of tubing wear at SONGS-2 and identify corrective actions to be taken, the following approach was pursued: o Eddy current data was evaluated and its accuracy verified.
o Thermal-hydraulic / vibration analysis and testing were done to determine the steam generator tube wear mechanism and develop a tube wear prediction model. o The tube wear predicted through Cycle 2 operation was then used to develop the tube plugging / staking program implemented. For SONGS-2, the plugging and staking was based on the objective of wear not resulting in through wall degradation of unplugged tubes exceeding 64% prior to the end of Cycle 2. 9 W .
2.0 STEAM GENERATOR DESIGN DESCRIPTION
2.1 INTRODUCTION
The geometry of the SONGS-2 steam generator in the region affected by wear is complex. This section provides a general description of the steam generator internal structures discussed in other sections of this report. The descriptions provided herein reflect the original steam generator design. A typical steam generator is shown in Figure 2.1-1. The two SONGS-2 steam generators are designed to transfer 3410 MWt from the reactor coolant system to the secondary system, producing 6 2 approximately 15.13 x 10 lb/hr of 900 lb/in saturated steam when provided with 445 F feedwater. 3
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The lower portion of this shell (below the tube sheet) encloses 7 1.O m c , ,.. x,+ - primary system coolant. That portion of the shell above the tube Jfe y lC t.T sheet encloses both primary and secondary system fluid. ,. l-Y _d.y.,. i .A/'.. * ' , '. E Each steam generator has 9350, 3/4 inch 0.D. , Inconel U-tubes per WTl '~ . ~ [% ' i steam generator with a nominal wall thickness of 0.048 inch. These
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secondary sides of the steam generator above the tube sheet. g:J_ ..~ .f l. . Q ,. . t , . . . ' - .* The flat tube sheet is supported at the center by a forged stay k ,. , , , ((
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tube sheet, j3 .. g . s .; n :.. ,- Tubes are supported against lateral vibrations by carbon steel s:n .i, . .f ...-:. 5
" egg crates" (Figure 2.2-1) at intervals of 38 inches or less along ? >.. / .*.u.
their entire vertical length. In the bend region and along their 'd.'s *. .> As .
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e. horizontal length, the tubes are spaced and supported by diagonal . j;-: -
" batwing" spacer strips and by vertical support grids as shown in g% . .;.1.
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REFERENCES (Section 2.2) 2.2-1 Final Safety Analysis Report, San Onofre Nuclearing Steam Generating Station Units 2 and 3, Docket No. 50-361 (Unit 2) and 50-362 (Unit 3). 1 6
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2.3 PRINCIPAL FLOW PATHS The steam generator principal flow paths are illustrated in Figure 2.3-1. Reactor coolant enters the bottom of the steam generator through the single hot leg inlet nozzle, flows through the U-tubes, and exits through the two cold leg outlet nozzles. A vertical divider plate and stay cylinder separate the inlet and outlet plenums in the lower head. Feedwater enters the steam generator through the feedwater nozzle where it is distributed via a feedwater distribution ring. From the distribution ring the feedwater mixes with recirculation flow and moves down the downcomer to the tube sheet elevation. The downcomer in the steam generator is an annular passage formed by the inner surface of the steam generator shell and the cylindrical shroud that encloses the vertical U-tubes. Upon exiting from the bottom of the downcomer, secondary flow is directed inward toward the center of the tube sheet and upward among the vertical U-tubes and the central stay region. It is this upward flow that imposes loads on the tubes and batwings which are discussed in other sections of this report. Heat transferred from the primary side converts approximately 30% of the secondary flow into steam at 100% power. 10
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2.4 AFFECTED INTERNAL STRUCTURES The affected steam generator internal components which are the subject of this report are the steam generator tubes in the bend region and the diagonal " batwing" spacer strips. This "dorred" section of U-tubes, at the top of the opening above the central stay
- cylinder, is depicted in Figure 2.1-1. The intersection of the tubes
! and batwings at the inner periphery of the central stay cavity, as depicted in Figure 2.4-1, is the specific area affected. As mentioned previously, the steam generator tubes are 3/4 inch 0.D. Inconel having a wall thickness of 0.048 inch. The tubes are installed in the tube sheet on a 1 inch triangular pitch and form an inverted U-shape around the central stay cylinder from the hot inlet side to the cold outlet side (see Figure 2.1-1). In the horizontal section of tubes in the dome region the vertical pitch is increased from 1.0 inch to 1.75 inches (see Figure 2.4-2). The betwings are carbon steel strips of 0.090 x 2.0 inches cross section of varying length. The purpose of the batwings is to prevent the tubes from impacting one another and to maintain tube spacing in the bend region. Based on the 1.0 inch tube pitch, the nominal gap between a steam generator tube and the adjacent batwing is 0.013 inch. Batwings in the central opening have an unsupported length that varies from approximately 14 inches to 36 inches as depicted in Figure 2.4-1. Photographs of steam generator internals (Figure 2.4-3) show the configuration of the tubes and batwings in the
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central stay cylinder region. At its upper end each batwing is notched for connection to a wrapper bar which runs around the outside of the tube bundle (see Figure 2.4-4). The batwing to wrapper bar connection is made by a fillet weld and is free floating (i.e., not secured to any other steam generator internal structure). The lower end of the diagonal leg of the batwing consists of a horizontal strip and is secured to the upper most eggcrate as shown in Figure 2.4-5. The connection between the horizontal and diagonal legs of the 12 l
batwing is made by three full penetration welds; ground smooth to l eliminate any surface discontinuities. The diagonal leg of the j batwing crosses the steam generator tubes at an angle of 60' 15' which results in the potential for an approximately four inch line of contact between the tube and the batwing. i 5 f 1 i f 13
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SECTION "A A" l FIGURE 2.4-1 BAT WING ARRANGEMENT IN CENTRAL STAY CYLINDER REGION
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1 1 0.116" ( l e i JL I 44042' . d , 1.75" 0.75" 90026' 44o42" FIGURE 2.4-2 HORIZONTAL SPAN TUBE BUNDLE G50 METRY i i 15
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BATWING l N STEAM GENERATOR TUBE 1 - l l l FIGURE 2.4-4 SONGS-2 STEAM GENERATOR UPPER " BATWING" ASSEMBLY 17
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3.0 N0NDESTRUCTIVE EXAMINATION EVALUATION
3.1 INTRODUCTION
i This section describes the nondestructive eddy current examination of the SONGS-2 steam generators that was conducted during its first refueling outage which commenced in October 1984. The information provided specifically addresses the tube / batwing indications and includes discussions of the eddy current examination technique employed, the verification of the technique, and the data obtained. 3.2 EDDY CURRENT EXAMINATION TECHNIOUE The eddy current examinations of the SONGS-2 steam generators were performed in two phases. The first phase was a detection process in i which standard bobbin coil probes end multifrequency testing was used to detect the presence of flaws. The second phase involved the evaluation of the indications detected and consisted of the use of specialized probes as well as specialized reduction and analysis of the bobbin coil data. These examinations and the subsequent data analysis yielded the circumferential extent, length, and depth of the flaws detected as well as their location with respect to the adjacent batwing (i.e., bottom or top contact). 3.2.1 Multifrequency Eddy Current Examination with Bobbin Coil Probe The majority of the eddy current testing was performed using a .580 SFRM (spring flex residual magnet) probe. The test frequencies used were 400 kHz and 200 kHz differential and 300 kHz and 100 kHz absolute. The probes utilize two coils wound circumferential1y around the probe with a physical separation between coils. The use of two separate coils allows either a single coil to be excited (absolute test) or both coils to be excited and electronically compared (differential test). Evaluation of the data, using standard 19
i multifrequency analysis techniques, allowed determination of the flaw < depths and the elevation of the indications relative to the tube sheet or the nearest structural member (e.g., batwing). l 3.2.2 Specialized ~ Eddy Current Techniques Several other types of probes were employed to further evaluate the ! flaw indications. An 8 x 1 probe was used to determine the circumferential extent of indications and to determine the number of indications at a specific elevation (i.e., whether one or both sides of the steam generator tube were affected). The 8 x 1 probe employs eight " pancake" coils mounted separately around the circumference of the probe and is spring mounted in such a manner as to contact the inner surface of the tube. Since each coil can be separately evaluated the extent of the indication can be approximated. Profilometry testing was also performed in the affected area. This test also employs eight pancake coils and is configured in a manner similar to the 8 x 1 probe except that the coils are mounted in the probe body rather than being spring loaded. The inside diameter geometry of the tube was mapped based on this data. The results of the profilometry testing revealed no discernable denting or deformation of the tube associated with the indications. In addition to standard data analysis, the bobbin coil data was analyzed to determine the length of the indications. The extent of the indications was compared to a known reference eddy current signal (four inch batwing) to determine the actual length of the flaws as
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discussed in Section 3.4.2. 3.3 EDDY CURRENT EXAMINATION TECHNIQUE VERIFICATION i 3.3.1 Validation of Examination Techniques Indications in the effected area were initially diagnosed as volumetric material loss based on the eddy current signal amplitudes and extent of the signals in the axial direction of the tube. The i 20 l
I geometry of the indications was further characterized as tapered volumetric material loss as determined by the indication location l with respect to the batwing strip and by use of specialized eddy current testing methods as discussed above. The axial length of the indications was determined by comparison of the signal extent of the indication to the extent of the batwing signal. The circumferential extent of the indications was determined from the 8 x 1 data and the indication shape was detennined using the duration of the signal on each coil detecting the indication. The depth was detennined from the bobbin coil data. In order to verify that the geometry was as predicted by the eddy current data, wear samples which contained simulated wear marks having several wear angles; depths varying from 10% to 75% (in approximately 10% increments); and a batwing angle of 60 were manufactured (see Figure 3.3-1). These samples were tested using the same techniques used for field examinations. The subsequent evaluation of the signals from the wear samples corroborated the geometry observed from the actual steam generator data. Prior to plugging in Unit 2 steam generators each tube containing an eddy current indication was retested to verify indication depth and location. This provided a validation that the original depth was properly analyzed and is a recheck of the tube location, (i.e., line and row number). The depth of each indication was determined by analysis of the primary frequency (400kHz differential) data. This data was then reanalyzed by an independent analyst. Where questions or. ~ data interpretation arose, a third analyst, an ASNT Level III eddy current inspector reviewed the results to determine the proper depth. All batwing indications were then analyzed on the mix frequency and other channels for final depth determination. In all cases the most conservative (largest) of the depth results was assigned to the l indication. l 21 l
l This process of redundant analysis, multiple testing of the indications l with various techniques, the tube verification program, and evaluation l of the wear standards assures the validity of the data. i 3.3.2 Eddy Current Examination Accuracy Laboratory tests of samples containing simulated wear, with characteristics similar in depth and length to the observed indications, were performed using the same techniques as used in the field examinations. Figure 3.3-2 graphically represents the results of the laboratory tests. The tests were performed both with and without carbon steel strips positioned intimately against the wear surface. This represents the extremes of the influence of the carbon steel strip signal upon the wear signal. The test results were evaluated by several analysts to determine the uncertainty of the eddy current depth predictions. The laboratory test results show that indications below the reportable level (<20% through wall) are generally below the threshold of detection. Accuracy over the range of 20 to.60% (through wall degradation) varies from 14% to 10% of through wall degradation. As the depth of the indications increase the accuracy improves. As described in Section 3.3.1 the SONGS-2 steam generator eddy current data were evaluated by several independent analysts. For all valid data, the more conservative of the results were used. l Accordingly, it is expected that the results of the examination of the SONGS-2 steam generators is more accurate than the worst case uncertainty represented by Figure 3.3-2. l 22 I 1
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l 3.4 CHARACTERIZATION OF INDICATIONS 3.4.1 Number and Location of Indications l Evaluation of the eddy current data in the affected region indicates that the largest number of flaw indications are located at the intersection of the tubes and the diagonal " batwing" strips. Indications are confined to relatively small regions of the tube bundles and are present in both hot and cold U-bend segments of both steam generators. The rows most affected are the interior peripheral rows, that is, the rows nearest the central stay cylinder opening. The wear indications were confined to tubes bounded by tube lines 71 and 106. At some locations, wear indications extended into the bundle beyond the first row tube. The location of the worn tubes and the extent of wear are shown on Figures 3.4-1 through 3.4-4 for both the hot and cold U-bend segments of steam generators 88 and 89, respectively. Tables 3.4-1 and 3.4-2 summarize the indications by tube row and line number, percent degradation, and hot or cold side of the U-bend for steam generators 88 and 89, respectively, for indications greater than or equal to 20% through wall. 3.4.2 Eddy Current Indication Geometry An evaluation of the indication geometry was performed. Simulated wear marks of various geometries, consistent with potential wear of a tube at the interface with a batwing were formed in the laboratory and the eddy current data from these samples was compared to the SONGS-2 eddy current data in an attempt to characterize the indications. The ~ comparison indicated that the SONGS-2 indications were likely the result of wear on the tubes as a result of interaction with the batwings. As discussed, the configuration of indications was deduced i to be slanted on a shallow angle as shown in Figure 3.3-1. The depths and length of wear indications were derived from a representative 25
sample of indications from both steam generators (25 samples per generator). Plots of wear depth vs tube wear angle for the sampled indications are shown on Figures 3.4-5 and 3.4-6. i 3.4.3 Analysis of Indications and Geometry Further evaluation of the wear indications was performed to determine whether they were present at both top and bottom of the interface between batwings and tubes and to' calculate the volume of metal removed at each tube. Table 3.4-3 presents a summary of the evaluation results. The results show that the vast majority of indications are at the bottom of the interface and the number of wear indications and the volume of wear per tube is similar for both steam generators. l l 26
l TABLE 3.4-1 SONGS-2 STEAM GENERATOR 88 BATWING / TUBE DEGRADATION
SUMMARY
R0W LINE PERCENT DEGRADATION LOCATION
- l' TUBES WITH > 44% THRUWALL It.'DICATIONS 29 73 49 DC 33 77 52 DH 35 77 48 DH 34 78 50 DC 39 91 48 DH 37 95 52 DC 32 100 71 DH 31 101 45 DH 27 105 63 DH 32 76 46 DC 37 93 48 DC 38 82 55 DH TUBES WITH 20% - 43% THRUWALL INDICATIONS 24 70 37 DH 27 71 24 DC 29 73 38 DH 31 75 39 DH 24 DC 34 76 40 DH 20 DC 34 . 78 43 DH 35 79 40 DH 36 80 31 DH 22 DC 36 78 22 DC 37 81 26 DC 38 82 23 DC .
37 83 42 DH 41 33 35 DH 39 85 27 DH 20 DC 39 87 31 DC 27 DH 45 87 23 DH 20 DH c.DC - Diagonal Spacer Strip, Cold Side of U-bend DH - Diagonal Spacer Strip, Hot Side of U-bend 27
R0W LINE PERCENT DEGRADATION LOCATION
- TUBES WITH 20% - 43% THRUWALL INDICATIONS (Cont'd.)
38 88 23 DC 20 DH 39 89 22 DC 38 90 28 DH 39 91 20 DC 40 86 31 DH i 38 94 43 DC 37 95 31 DC 20 DH 27 DH 39 95 28 DC 20 DH 41 95 37 DC 43 95 26 DC 49 95 28 DH 20 DC 37 93 25 DH 39 93 25 DH 41 93 40 DH 40 92 24 DH 38 92 37 DH 40 96 28 DC 20 DH 36 96 . 40 DH 35 97 39 DC 38 DH 33 99 38 DH 26 DC 28 104 35 DC 20 DH 33 101 36 DH 31 103 35 DH 28-
TABLE 3.4-2 SONGS-2 STEAM GENERATOR 89 BATWING / TUBE DEGRADATION
SUMMARY
R0W LINE PERCENT DEGRADATION LOCATION
- TUBES WITH y_ 44% THRUWALL DEGRADATION 34 78 48 DH 39 79 51 DC 37 81 48 DC 38 82 61 DH 39 83 57 DC
, 37 83 54 DC l 38 84 69 DH 58 DC 38 86 48 DH 39 87 48 DH 39 89 64 DH 38 90 45 DC 60 DH 39 91 95 DC 41 91 44 DH 38 92 47 DH 37 93 47 DC 37 95 56 DH 35 97 48 DH 34 98 48 DC 33 99. 46 DH 31 101 59 DH 49 DC 32 102 48 DH 29 103 51 DH TUBES WITH 20% - 43% THRUWALL DEGRADATIONS 28 72 23 DC 29 73 22 DC 20 DH 32 76 40 DC 20 DH 34 76 21 DC 34 78 28 DH 20 DC 36 78 38 DC
*DC - Diagonal Spacer Strip, Cold Side of U-bend DH - Diagonal Spacer Strip, Hot Side of U-bend 29
l R0W LINE PERCENT DEGRADATION LOCATION WPES WITH 20% - 43% THRUWALL DEGRADATIONS (Cont'd.) l 35 79 21 DH l 31 DC l 36 80 43 DC l 23 DH 38 80 24 DC 40 80 38 DC l 37 81 42 DH 39 81 33 DC 38 82 . 20 DC 37 83 33 DH 39 83 22 DH 39 85 39 DC 39 87 28 DC 38 88 40 DH 40 88 22 DH i 42 88 41 DH 44 88 38 DH 46 88 23 DH 41 89 26 DH 1 40 90 20 DH 29 91 22 DH 43 91 25 DH 49 91 24 DH 23 DC 38 92 22 DC 37 93 20 DC 45 93 38 DH 46 94 33 DH 38 94 33 DH 37 DC 37 95 32 DH 36 96 37 DC
, 46 96 35 DH 33 99 32 DC 29 103 20 DC 27 105 31 DH i
i l l l
L TABLE 3.4-3 l f SONGS-2 STEAM GENERATOR TUBE INDICATIONS GREATER.THAN 20% EVALUATION
SUMMARY
STEAM GENERATOR 88 STEAM GENERATOR 89 Hot leg Cold Leg Hot Leg Cold Leg Numb!r of Indications 39 27 39 31 Volume Removed 49.32 26.68 57.82 45.60 3 3
, (x10 )in Total Volume 76.00 103.42 3 3 ,- Removed (x10 )in .
. Total Volume 1.15 1.48 Removad/ Indication
3 3 (x10 )in Total Volume 179.42 Removed (Both SGs) 3 x10 , in 3 Average Volume 1.32 Removed / Indication (Both SGs)x103 ,in 3 l
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4.0 EVALUATION OF DEGRADATION MECHANISM
4.1 INTRODUCTION
This section describes the analysis and testing activities undertaken l to: (1) quantify the effects of physical phenomena causing observed tube degradation, and (2) project the extent of wear through SONGS-2 Cycle 2. The steam generator secondary side flow distribution in the central stay cylinder region was calculated to determine the velocities, densities, and steam qualities which act on the batwings and tubes. The results were used in support of flow visualization testing conducted to determine the structural behavior of the tubes and batwings. The results of the flow visualization testing, in combination with calculated flow parameters, were employed in dynamic and quasi-static finite element analyses to determine tube to batwing interaction forces and stresses on the tubes and batwings. Geometric relationships for batwing rotation into the tubes were formulated and compared with eddy current data for worn tubes. A best estimate model was constructed and tube wear to the end of Cycle 2 was estimated from the relationship of calculated tube to batwing interaction forces during Cycle 1 and projected for Cycle 2. 4 Subsections 4.2 through 4.6 describe the approach employed in the evaluation of the tube degradation mechanism. In additiu., the j . Appendix to this report describes a test program conducted to detennine the significance of wear on tube integrity. 39
4.2 FLOW DISTRIBUTION ANALYSIS The purpose of this section is to describe the flow distribution analysis done in support of flow visualization testing and determination of structural behavior of the tubes and batwings. 1 4.2.1 Therm l-Hydraulic Modeling The analytical model of the SONGS-2 steam generator was developed using the ATH0S (Analysis of the Thermal Hydraulics Of Steam Generators) computer program. ATH0S is a three dimensional, two-phase, steady state and transient code for thermal-hydraulic analysis of recirculating V'-tube steam generators. The ATHOS model includes specifications for geometric detail, transport correlations, and operating conditions. The transport correlations used by the ATH0S code include the primary and secondary side heat transfer coefficients and the fluid friction factors in the axial and cross flow directions. A large number of nodes (432) were used in the U-bend region in order to calculate the thermal-hydraulic conditions in adequate detail to l study their influence on tube wear. The analysis was performed for 100%, 50% and 20% power operating conditions. The steam generator design data, the transport correlations, and the operating conditions at the three power levels mentioned were used.to determine the thermal-hydraulic characteristics of the SONGS-2 steam generator. The results of this modeling were used to define the flow characteristics in the stean generator central cavity region. 4.2.2 Kinetic Energy of Fluid in the Central Cavity The kinetic energy of the fluid in the central stay cylinder cavity region is the source of _the excitation producing batwing and tube vibration. Table 4.2-1 lists the average values of flow parameters for 40 I
homogeneous flow derived from the analysis. The secondary fluid velocities were higher on the hot side where densities are lower, however, values were averaged over the cavity region to minimize the effects of flow discontinuities imposed by the computational grid. The kinetic energy values were used as a basis of the flow visualization tests described in Section 4.3. The kinetic energy and dynamic pressure of the secondary fluid were also calculated at 100% power using the algebraic flow option in the ATH0S code. The resulting average thermal-hydraulic conditions and kinetic energy are also suninarized in Table 4.2-1. The results of homogeneous flow and algebraic slip represent an upper and lower bound of the fluid kinetic energy leaving the central cavity. The lower and upper bounds defined by the thermal hydraulic models were used to define testing ranges discussed in Section 4.3. Analyses discussed in Section 4.5 used the conservative upper bound information. l
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i TABLE 4.2-1 THERMAL HYDRAULIC ANALYSIS RESULTS
SUMMARY
Homogeneous Flow l Power Density Axial Velocity Mass Flow Kinetic Energy Dynamic Pressure 3 Level Lbm/Ft Ft/Sec Lbm/Sec Ft-//Hr- Lbf/Ft 2 100% 12.8 15.3 358 470 x 10 44 46.51 50% 20.7 5.9 223 43 x 10 4 11.12 20% -28.1 1.4 73 0.3 x 10 0.87 Alg braic Slip (100% Power) Dynamic Density Axial Velocity Mass Flow Kinetic Energy Pressure Vapor 3 3 Lbm/Ft Ft/Sec Lbm/Sec Ft-Lbf/Hr Lbf/Ft Fraction Liquid Vapor liquid Vapor 2.0 4 47.1 8.0 10.9 229 57.7 x 10 12.72 '0.606 1 l l l l 42 i e
l 4.3 TUBE / BATWING FLOW VISUALIZATION TESTING A flow visualization test model was constructed in order to visually observe the behavior of the various structural elements in the presence of prototypical, high velocity, turbulent flow within the tube bundle central cavity. Flow parameters for the test series were, in part, developed from the thermal hydraulic analysis discussed in Section 4.2. The focus of this testing is on: (a) The fluid-elastic behavior of the long unsupported batwing strips in the steam generator above the central tube bundle cavity, (b) The tube / batwing interaction, and (c) The vibratory characteristics of the tubes. Information obtained from the above listed observations, make it possible to properly model the tube and batwing strip flow 16ading in the subsequent structural analyses. This was considered essential due to the variability of the turbulent, two-phase flow in the steam generator central cavity which is beyond the state-of-the-art to model by analytical methods alone. A description of the test model and loop, test matrix, and swnmary of the test results and conclusions 3re provided in the following subsections. 4.3.1 Test Model and Flow Loop l l l l l The flow visualization model, shown in Figure 4.3-1, contained all the design features presett in the SONGS-2 steam generators. The actual batwing strip / tube bundle interface, representative of the longest unsupported batwing strip, is illustrated in Figure 4.3-2. Actual eggerate tube supports were used to support'the vertical tube 43
I l l l leg as shown in Figure 4.3-3. The vertical tube support grid is depicted in Figure 4.3-4. The actual double slotted batwing center l support with perforated restraining plate, as shown in Figure 4.3-5, I was built into the test model' All of the model internals, including I the Inconel 600 tubing, were made from actual steam generator parts. For this reason, all clearances, tolerances, gaps and critical spacings in the model were the same as in an actual steam gercrator. The model contained a total of 36 tubes and eight batwing strips, which are identified in Figure 4.3-6. The tubes were bent 90" about a 10 inch radius and represented more than half of each U-bend tube. Batwing strips I, II and III had nominal clearances and chamfered leading edges, which were typical of SONGS-2 steam generators. Strips IV and V had flat leading edges. Strips VI, VII and VIII had chamfered leading edges and were thinned by 0.015 inches on either side near the edges to simulate an increased clearance due to wear. The flow loop which was used is shown in Figure 4.3-7. It has been used for numerous flow induced vibration test programs for CE applications as well as for outside contracts. The flow capacity of the test loop was increased to model the SONGS-2 steam generator flow values. Ports for boroscope equipment were used to obtain data. Location of the boroscopes is shown on Figure 4.3-1. 4.3.2 Test Matrix The test matrix presented in Table 4.3-1 was performed, utilizing water flow with the velocity adjusted such that the equivalent fluid pressure is represented. The 3000 GPM water flow test case, representative of the thermal hydraulic analysis algebraic slip flow prediction, is a lower bound of the actual steam generator dynamic l head. Similarly, the 6000 GPM water flow test case is representative of the thermal hydraulic analysis homogeneous flow prediction which represents an upper bound of the actual steam generator dynamic head. 1 44 i i
Although testing was conducted at flows of 1000 GPM and 2000 GPM, no data was taken at these test ccnditions due to the small vibration amplitudes (i.e., no contact) observed at the tube / batwing interface. l 4.3.3 Test Results and Conclusions l Table 4.3-2 presents a sumary of the flow visualization test data. l The following observations are of particular importance: a) Batwing motion at the elbow is quasi-static and exhibits a maximum amplitude of 0.735 inch for all flows above 3000 gpm (equivalent to approximately 50% power level). This translates to a pressure loading of 0.1 psi acting on the batwing strip (see Section4.5.3). b) The observed " fluttering" behavior of batwing supports the postulated wear mechanism (see Section 4.4). The results and conclusions of the flow visualization tests are summarized as follows: 45
Batwing Drift The batwings were calculated to have a first mode natural frequency of 7.0 Hz. The movement at 7.0 Hz, however, consists of a small amplitude " fluttering" movement and is not representative of rapid large amplitude movement. The large amplitude movements recorded in Table 4.3-2 were randomly drifting movements having a frequency much less than 1 Hz. The batwing strips tended to pair off and move together. ht random intervals th'e pairs would switch off (i.e., i Strip II would be paired with Strip I for a short time, then Strip II would switch off and pair up with Strip III). Occasionally three strips would move together for a short time, however, this was a relatively infrequent occurrence. In summary, violent, large amplitude motion of the batwings does not occur. Instead, a Bernoulli effect appeared to be producing the relatively-slow large amplitude swings. Low Amplitude Resonance At the intersection of the batwing strips and the first row of tubes, amplitudes ranging from 10 to 50 mils for the strips and 0 to 30 mils for the tubes (out-of-plane) occurred for flow rates of 4000 GPM and higher (seeTable4.3-2). The differential movement between the tubes and batwing strips appeared to occur at the 7.0 Hz batwing natural frequency resulting in a mild flutter. Substantial steady loads, caused by the batwing drift and pairing off, can be characterized as quasi-steady state loads in the region experiencing - tube wear. Based on this behavior, an analysis methodology was l 46
formulated, which is representative of the observed behavior. A moderate increase (approximately 15%) in normal load may be appropriate to consider, however, to account for the mild
" fluttering".
l In-Plane Tube Movement j- While no measurable in-plane tube movement was found, it is, however, virtually certain to be occurring in the SONGS-2 steam generators as a result of the high fluid pressure at the horizontal run of the tubes in the U-bend region. The methodology used to calculate these movements is presented in Section 4.5.2. Increased Clearances Batwing strips VI, VII and VIII, which had, by design, an increased clearance between the tubes, experienced only marginally larger move-ments at the tube bundle interface. Although the marginal difference was too small to quantify based on visual observations, the effect of increased gaps resulting from wear is thus expected to be limited. l l t l 1 47
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i Batwing Edge Design The leading edge chamfer, applied to some of the batwing strips used in the test, appeared to have no effect on the behavior of the ! strips. 1 ! These results were used to develop a more realistic dynamic model of the tube / batwing interaction and to validate assumptions regarding the degradation mechanism and wear projections. 4 i 48
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TUBE / BATWING FLOW VISUALIZATION TEST MATRIX Tuba Bundle Entrance Batwing Approach Flow Flow at Top of Cavity Test y y Fluidgres. y y Fluidpres. Flow Rate model S.G. pV model S.G. V Water @ R.T.+ (GPM) (Water) (Ft/Sec) (2-Phase) (Ft/Sec) 29 2 (Lb/Ft ) (Water) (Ft/Sec) (2-Phase). (Ft/Sec) h 2 (Lb/Ft ) Comments 1 1000 1.19 - 1.37 3.05 - 9.01 Test (No Data) 2 2000 2.38 - 5.48 6.09 - 35.9 Test-(No Data) 3 3000 3.57 - 12.3 9.14 - 80.9 Test 4 3046 3.62 6.43 12.7 9.27 16.5 83.2 San Onofre 2 S.G. 100% Power W/ Slip 5 4000 4.75 - 21.9 12.2 -
~44 Test 6 5000 5.94 -
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+ Water at room temperature, density = 62.4 lbm/ft 3, 1
.a
l TABLE 4.3-2 TUBE / BATWING MOVEMENTS VS. WATER FLOW RATE WATER FLOW VELOCITY @ ROOM TEMP. 3000 4000 5000 6000 (GPM) (GPM) (GPM) (GPM) AVERAGE
- PEAK TO PEAK OUT-0F-PLANE MOVEMENTS (MILS)
- 1. TUBE - @ INTERSECTION WITH BATWING C-5 15 15 15
- 2. BATWING - @ ELB0W, f << 1.0 Hz 265 370 425 435 n
- @ TOP INTERSECTION W/ TUBEn f = 7 Hz 5 <20 >20 25
- @ BOTTOM INTERSECTION W/ TUBE fn =7 Hz 20 30 30 30 MAXIMUM +* PEAK TO PEAK OUT-OF-PLANE MOVEMENTS (MILS)
- 1. TUBE - @ INTERSECTION WITH BATWING 0-5 20 20 20 I
- 2. BATWING - @ ELB0W, f << 1.0 Hz 435 735 735 735
- n
- @ TOP INTERSECTION W/ TUBEn f = 7 Hz 10 40 40 40
- @ E0TTOM INTERSECTION W/ TUBE n f = 7 Hz 30 30 50 40 l
l
- Avsrage of maximum peak to peak movements observed for all eight (8) batwings.
++ Maximum movement observed for any batwing.
50
ENLARGED CLEAR f BACK . l l QUARE EDGED STRIPS 2i cCG 4 :_ _
= ==
[UILT DIMENSIONS SECTION "A-A" BORESCOPE LOCATION TYP.4 PLACES _ /
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, 1 ( p : = VWd
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1 FIGURE 4.31 FLOW VISUAllgTION MODEL l
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- ; __ . ! i t FIGURE 4.3-2 FRONT VIEW 0F VISUALIZATION FIGURE 4.3-3 TOP "EGGCRATE" TUBE FLOW TEST MODEL WITH WINDOW REMOVED SUPPORT. IMMEDIATELY BELOW " BATWING"
_ _ _ _ _ - _ _ _ _ _ - - __________l
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L . . : ;.s. .; ,< ~ . . : , . 9 uo . p .g, q g..; ( :7.;g.p3,, 3 W . .. ~z T ,;, M,3. . .g ;,. - M yl15k'k:.~\'W . Q.: d ;8 0l $ $% $ hY?:J$Nk: Y'&CW FIGURE 4.3-5 LOWER PORTION OF " BATWING" TUBE SUPPORT STRIPS, VENTILATED CLAMPINr, PLATE AND SLOTTED BAR 53 1
1 I 1 i 4 f D-1 ] C-1 B-1 l A9 ' A7 A5 A3 A1 I d i /1 I C _i w 8 a a 5 Vill Vil VI V IV 111 11 I E BATWIN3 STRIP l.D. 4 Af FIGURE 4.3-6 FLOW VISUALIZATION TEST TUBE / BATWING IDENTIFICATION SCHEME t-54
i j -
) EXPANSION
' L JOINT i RETURN LINE R FL O W --=- j CONTROL VALVE WITH R5 VA8LE p TUBE n MANUAL BY-PASS BUNDLE SECTION - / 4 hd g
' AIR SUPPLY O
PRESSURE FILTER 4,000 GALLON AIR HEADER REGULATOR AIR-WATER TANK SEPARATOR
= ' '
g L .J 3 RTD I I TEMPERATURE SENSOR I I (- > 1
- VENTURI FLOW 2 X 4000 GPN l GLOBE METERS EXPANSION CENTRIFUGAL i
MITERED ELBOW v [ VALVES JOINT PUMPS i WITH VANES / ^ e FLOW
-_ v D 12" SCH. 10 3 PIPING Q). .. .
SAND LINED FIGURE 4.3-7 CONCRETE PEDESTAL l FLOW VISUALIZATION TEST LOOP 1
4.4 TUBE WEAR MECHANISM The purpose.of this section is to provide an understanding of the wear mechanism and describe the wear model which has been used to project SONGS-E tube wear through Cycle 2. Results from the flow visualization tests (Section 4.3) have shown that the batwing motions were quasi-static in nature. Tube motions were observed to be of a. vibratory nature. For this reason it is postulated that the tube / batwing wear m chanism could be approximated as the result of static contact forces between the batwing and the 2 tubes and the vibratory motions of the tubes in their own plane. The wear mechanism produced by these motions is a type of wear which can be represented by Archard's equation for wear. 4.4.1 Wear Calculation Methodology In this section, the wear volume calculations using Archard's equation are discussed. Additionally, wear data obtained fram various tests are converted to an Archard type wear coefficient in order to compare SONGS-2 results to those from different sources. Archard's Equation is: V = 10-12 gp n 3 where: V= Wear Volume (in ) K= Wear Coefficient (Material Dependent, in2 /lb) 1 F = n Normal Force Between Surfaces (1b)
- E= Total Slipping Distance (in) l Each term in the equation was calculated as follows
a) Normal Force (F n) was calculated from the observed batwing motion (Section 4.3) and the out-of-plane frequency of the tube. 56
m . _ , - . . _ _ . . _ _ -. ._ l~ b) Sliding Distance (E) was calculated from the dynamic pressure (Section 4.2). The in-plane fundamental frequency of the tube, and the duration of application of the dynamic pressure ! (operating history for Cycle 1). c) Wear Volume (V) was obtained from the results of eddy current testing by calibrating a tube wear model to the results (see Section 4.3). d) Wear Coefficient (K) was computed from V, Fu , and E. The tube wear model that was e>tablished can be considered representative
- if the calculated wear coefficient compares reasonably with j coefficients derived from tests as discussed below.
l
- Table 4.4-1 presents the results of variety of different tests for 1 which wear was converted to an Archard type wear coefficient to
- provide a comparison of results from different sources. As can be
- seen, a wide range of wear coefficients were obtained,-reflecting a dependence on test apparatus, test method, and specific wear phenomena. The information, nevertheless, provides a reasonable i basis for comparison to the calculated wear coefficient of the tube wear model_as a means of checking its validity. Furthermore, certain tests have more than one data point allowing an assessment of trends in wear progression. In particular, the results of Test Case T2 of j Table 4.4.-1 were used to develop a sample wear progression curve
{ (Figure 4.4-1). . Note that the wear rate decreases as a function of ) time. This is due to the " wearing in" process, which gradually j increases the contact area, thus reducing contact surface pressure, t A review of the data presented illustrates that there are significant differences between the " initial average wear coefficient" and the f "long term wear coefficient". These differences are primarily due to the " wearing-in" process. This same decrease in wear coefficient is expected to apply to the tube / batwing interaction. 57 ,
I I l 4.4.2 Tube Wear Model Both the eddy current data (Section 3.4) and the flow load analysis, presented in Section 4.5, suggest a wear configuration similar to that illustrated in Figure 4.4-2. It is, therefore, iraortant to know the range of angular penetration in order to calculate wear l volumes. To this end, several wear models were considered and the predicted relationship between depth and angle compared to data from l eddy current testing (Figures 4.4-3 and 4.4-4). I
- The first model assumed nominal clearances (0.013 inch) and rigid l body batwing rotation. It assumed that wear was shared equally I between the tube and batwing, and was evenly distributed between top and bottom contact points. While batwing wear is probable, the data I
obtained from eddy current tests does not support this model. This has been designated as Model "B". The second wear model assumed a prying action of the rotating batwing between tube columns. Such a prying action could double the initial j nominal clearance. This model assumed no batwing wear. The' data
- obtained from eddy current tests does not support this model. This has been designated as Model "C".
1 l The best estimate wear model is a hybrid of models "B" and "C" and has been designated Model "A". This irodel incorporates both batwing l wear and prying action. In Figures 4.4-3 and 4.4-4, typical SONGS-2 steam generator eddy
. current data ~ is plotted and corrpared with the tube wear models discussed above. Agreement is good for the "A" model, with the "B" model_ serving as a lower bound for the data.
"C" acts as an upper boun'd for a majority of the ecidy current l Model
{ data plotted. The larger wear angles in Figures 4.4-3 and 4.4-4 i 58
could be the result of wider than nominal spacing between tube rows, in addition to the prying action of the rotating batwings between tube . columns. As a further check of the best estimate wear model used in subsequent wear projections, the eddy current data points were used to generate the curve "ECT" in Figures 4.4-3 and 4.4-4. The best linear fit produced lines which ran nearly parallel to lines "A", "B" and "C". The "ECT" line was close to line "A" and bounded by lines "B" and "C". Therefore, it is concluded that wear model "A", is the degradation mechanism most appropriate for use in analyses presented in Sections 4.6 and 5.4. 4.4.3 Determination of Wear Volumes The relationship between wear volume and maximum wear depth is dependent on the tube and batwing geometries and the three wear models described in Section 4.4.2. The wear volume on the tube can be approximated to be a wedge shaped volume as shown in Figure 4.4-2 for any of the wear scenarios under consideration. Since a unique relationship exists between the depth of wear and the wear angle, it is possible to calculate the wear volume as a function of maximum wear depth. The wear volume function is plotted for the A wear model in Figure 4.4-5. 59
m - - ~ _ - , _- -_mm, MATERIAL: INCONEL 600 TUBES / CARBON STEEL SUPPORTS INITIAL LONG TERM WEARg0EFF.WEARg0EFF. SUPPORT TYPE OF CLEARANCE NORMAL FORCE K K TEST CASE f WETRY CONTACT (IN.) (LBS.) (IN.2/LB) '(IN.2/LB) ENVIRONMENT T1. KWU Early Drilled Tangen. Diam. 1.124 0.46 0.013 482 Pure Pressurized Water Fretting Tests Bore Sliding 0.020 with Oxygen Content < 10 ppb. July 28, 1980 Hole Eggcrate Tangen. 0.026 1.124 - 20.34 - Not 482* Pure Pressurized Water Sliding Between 2.248 10.17 Avail. with Oxygen Content < 10 ppb.
+ Some Parallel Impact Strips T2. XWU Auto- Eggcrate Tangen. 0.026 1.124 80.0 1.67 482 Pure Pressurized Water clave Fretting (Left) Sliding Between with Oxygen Content < 10 ppb.
Tests with + Some Parallel 8 Eggcrate Tube Impact Strips Supports Jan. 12, 1981 Eggcrate " " 1.124 40.0 0.52 482 F Pure Pressurized Water (Right) with Oxygen Content < 10 ppb. T3. AECL Fret- Drilled Sliding Diam. 0.09 364.5 Not 500 F Pressurized Water ting Tests on Bore + 0.015- Avail. (pH = 8.5 - 9.5) S/G Materials Hole Impact 0.030 0.09 182.3 " 1979-1980 T4. AECL Fret- Drilled Sliding Diam. 0.9 Not 63.4 545-554 Pressurized Water ting Tests for Bore + 0.015 Avail. (pH = 8.9 - 9.4) CE 1978-1982 Hole Impact Drilled Sliding Diam. 1.0 Not 322.9 545-552 F pressurized Water Bore + 0.016 Avail. (pH = 8.8) Hole Impact - Notes: (1) Average K Values for First 10 7 or 108 Cycles Including Initial " Wear-in" Period (2) Long Term K Values Which Exclude Initial " Wear-in" Period
o MATERIAL: INCONEL 600 TUBES / CARBON STEEL SUPPORTS INITIAL LONG TERM SUPPORT TYPE OF CLEARANCE NORMAL FORCE WEAR K {0EFF. WEAR K' $0EFF. TEST CASE GE0 METRY CONTACT (IN.) (LBS.) (IN.2/LB) (IN.2/LB) ENVIRONMENT S1. KWU Auto- Eggcrate Tangen. 0.026 1.124 636.5 Not 482* Pure Pressurized Water clave Fretting (Left) Sliding Between Available with Oxygen Content < 10 ppb. Tests with + Parallel Eggcrate Tube Some Strips Supports Impact Jan. 12, 1981 Eggcrate 1.124 482.0 Not (Right) Available S2. AECL Drilled Sliding Diam. 1.0 Not 47.1 545-552*F Pressurized Water Fretting Bore + 0.016 Available (pH = 8.8) . Tests for CE Hole Impact 1978-1982 8 Notes: (1) Average K Values for First 107 or 10 Cycles Including Initial " Wear-in" Period. (2) 8.ong Term K Values Which Exclude Initial "Waar-in" Period.
60 ' l ' I I l g i
~
INITIAL WEAR-IN PERIOD ;- 50 - i g G j 0gWEARBA " b ' 40 - E 1 g 30 - i
= '
/
20 p po* 1 j,.
+>4 10 -
[' _
' ' ' I ' ! ' I '
l O'0.0 0.2 0.4 0.6 0.8 1.0 CYCLES x 108 FIGURE 4.4-1 i TYPICAL WEAR PROGRESSION LONG TERM TREND i
l l
\
O
\
. h I /
I / I I i ' l ' i l
- I I t 4.0 IN, i ,l ,
i i 2.0 IN. l\ l l* l ! l
< l i
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i ( l t l i
/
/
I WEAR
, REGION l I
MAXIMUM CONTACT Foac5 l t t l/ l l FIGURE 4.4 2 4 SAN ONOFRE 2 STEAM GENERATOR TUSE/ BATWING gjV STRIP WEAR GEOMETRY t f3
100 _ 0 A ECT* C 80
' NOTE - BEST LINEAR FIT OF J ECT DATA it:
E" - O 2
- e - O i
m e C l V 4C - h 1 5 m - O O o 20 --- O- - - LOWER BOUND OF DATA USED t 0 ' ' '
- O 1.0 2.0 3.0 TUBE WEAR ANGLE, DEGREES FIGURE 4.4-3 SAN ONOFRE 2. S.G. No. 88 CORRELATION OF WEAR MODELS WITH ECT INDICATION CHARACTERIZATION 4
i
100 - B A ECT* C
~
80 - 1 i d n v
- NOTE - BEST LINEAR FIT OF ECT DATA 4
i 50 _ Q
' E
& o O R
I t O O
- g. _ O
- 3 -
i 5 m - O LOWER BOUND OF DATA USED 20 -- - --- -- ' O a . . O 1.0 2.0 3.0 o TUBE WEAR ANGLE, DEGREES FIGURE 4.4-4 SAN ONOFRE 2, S.G. No. 89 CORRELATION OF WEAR MODELS WITH ECT INDICATION CHARACTERIZATION
i i i . . . - i g [w
. d - -
4 1 il l 10 . b WEAR LUME (TUBE - T x 8 - 2 J
$ 6 #
[ S 9 > x 6 I 4 i i i
/ '
/
- /
0 0.2 0.4 0.6 0.8 1.0 ; d/t FIGURE 4.4 5 WEAR VOLUME vs DEPTH OF INDENTATION FOR WEAR MODEL A 66
4.5 FLOW LOAD ANALYSIS OF TUBE / BATWING ASSEMBLY The calculation of tube motions and tube / batwing forces are presented in this section. 4.5.1 Frequency Analysis Tubes A modal analysis of the affected tube rows (23 to 45) was performed using the ANSYS computer program. The finite element model is shown in Figure 4.5-1. Due to symmetry, only one-half of each tube row was modeled. Appropriate boundary conditions were applied at the lower eggerate, upper eggcrate, and the vertical support. The tube frequency calculations were performed considering the apparent mass and contained mass of the fluid on the outsioe and the inside of the tubes. Figure 4.5-2 presents the resulting tube frequencies versus tube row. The same finite element model was utilized to determine the out-of-plane stiffness of the tubes for forces applied at the points where the tubes intersect the top and bottom edges of the batwing. Figure 4.5-3 presents the stiffness of each tube for loads applied at either the top or bottom intersection with the adjacent batwing. An ANSYS superelement having these tube stiffnesses was generated and used in the tube / batwing contact force analysis to support wear projections. Batwing A modal analysis of the batwing spacer strip was also performed using the ANSYS computer program. The three-dimensional finite element model employed is described in Section 4.5.3. The tubes contacting the batwing were modeled as spring elements providing elastic supports. Four cases were analyzed which represent the batwings 67
entering the tube bundle at tube rows 27, 31, 35 and 38. For the i first mode of vibration the batwing frecuencies obtained were 14.9 I Hz, 11.0 Hz, 8.5 Hz, and 7.1 Hz, respectively. (The effect of I apparent mass is included in these results.) These modes exhibit both bending and torsional motion in the long portion of the batwing. Figure 4.5-4 is an isometric view of a typical first mode shape which shows relative displacements and provides a general picture of first mode behavior. 4.5.2 Tube Response to Secondary Flow The sliding motion of the tube in concert with the forces between batwings and tube contribute to the observed wear. The method of calculating the tube displacement is discussed in this section. The in-plane tube displacement at the interface with the batwing is the mult of dynamic pressure on the horizontal section of the tube U-beno. The finite element model and boundary conditions employed in this analysis are identical to those described in Section 4.5.1. The tube loads were statically applied in the vertical direction to the horizontal span of the tubes to calculate tube horizontal de-flections at the point where the tubes cross the batwing. The tube horizontal deflections at the point where the tubes cross the l batwings as a function of tube row is presented in Figure 4.5-5. These horizontal deflections are used in Section 4.6.1 to calculate the sliding distance in the wear analysis. 4.5.3 Tube / Batwing Contact Forces The contact forces between each batwing and the adjacent tubes were calculated by a three-dimensional finite element model shown in Figure 4.5-6, which represents one-half of the symmetrical strip. The nodes numbered in the figure are located so that the tubes on rows 23-45 would contact nodes 23-45 on the bottom edge of the strip 68 m,---- c- w- , --- - --i ,y -r----* e
and nodes 123-145 on the top edge of the strip. The model was provided with a pinned support on the plane of symmetry; additionally, a condition of nonsymmetrical deformation was also imposed. Further support was provided by compression - only spar elements, oriented perpendicular to the plane of the batwing, connecting it with the adjacent tubes. Each spar element was provided relatively rigid properties. The appropriate tube stiffnesses were obtained by connecting these spars to a i substructural stiffness matrix generated from the tube model j described in Section 4.5.1. This basic model is adaptable to l represent any batwing strip in the central cavity region of the tube l bundle. l An equivalent uniform lateral pressure corresponding to the force required to deflect the batwing elbow 0.735 inch (see Table 4.3-2) was calculated to be 0.1 psi. Each batwing strip was statically loaded by this pressure deflecting the batwing into the lower-numbered adjacent tube line. This load was applied over the portion of the batwing in the central cavity region; the portion of the batwing inside the tube bundle was not loaded. The resulting distribution of contact force between each batwing and the adjacent tubes (assuming uniform clearance between batwings and tubes) is shown in Table 4.5.-l. In the table, each batwing is identified by the lower numbered adjacent tube line. Tubes are l designated as Al-A4 on the lower-numbered line and 81-84 on the higher-numbered line. As the tabulation shows, the maximum contact force always occurs on the first tube (Al). The force on the second tube (A2) varies from approximately 27% of this maximum value for the batwing with the longest span to zero (i.e., no contact) for the four strips with the shortest spans. No contact occurs with the third and fourth tubes A3 and A4, respectively. In all cases, contact with tubes Al and A2 is at the bottom edge of the batwing. The contact forces with tubes 81-B4 are seen to be less than 20% of 69 l
the force on A1. They peak on tube 82 and attenuate rapidly going deeper into the bundle. In all cases these forces result from contact with the top edge of the batwing. Non-uniform clearance, resulting from prior wear or manufacturing misalignments, would alter the contact force distribution. The finite element model was used to investigate the effect of non-uniform clearance by arbitrarily imposing wear-induced clearances on the Al and A2 tubes. Results for four of the batwings are shown in Table 4.5-2. In the table, Case No. 1 on each strip is the case of uniform clearance while Case Nos. 2-7 represent increasing amounts of prior wear. It is seen that prior wear reduces the contact forces on the Al tube and can cause the A3 tube to sustain significant contact forces. i 70 1
l TABLE 4.5-1 CONTACT FORCES (LB) i UNIT LOAD CASE (0.1 psi) (g) Tube Position (3) Location Al A2 A3 A4 81 82 B3 84 4 69,107 3.25 0 0 0 .17 .29 .18 .08 70 3.44 0 0 0 -
.48 .25 .06 106 3.49 0 0 0 .22 .32 .21 .09-71,105 4.16 .10 0 0 .38 .46 .29 .13 72,104 (3) 4.33 .22 0 0 .44 .51 .33 .15 73,103 4.50 .33 0 0 .49 .56 .37 .17 74,102(3) 4.67 .45 0 0 .55 .61 .41 .20 75,101 4.84 .57 0 0 .60 .66 .45 .23 76,100 (3) 5.01 .70 0 0 .65 .71 .50 .27 77,99 5.17 .83 0 0 .70 .76 .54 .30 78,98 (3) 5.34 .97 0 0 .75 .82 .59 .34 79, 97 5.51 1.10 0 0 .80 .87 .63 .38 80,96 (3) 5.69 1.24 0 0 .84 .93 .69 .43 h,'h 5.86 1.38 0 0 .88 .98 .74 .47 92,94 6.03 1.52 0 0 .92 1.03 .79 .52 88 (3) 6.20 1.66 0 0 - 96
. 1.08 .84 .56 Notes: (1) Batwing location is determined by the adjacent tube line with the lower number.
(2) Tube position is defined as follows: Inboard Outboard , Load Tubes Al-A4 are on the lower-numbered line. (3) Forces obtained by interpolation or extrapolation from adjacent strips. 71
l TABLE 4.5-2 CONTACT FORCES (LB) WITH PRIOR WEAR UNIT LOAD CASE (0.1 PSI) BATWING CASE
- LOCATION NO. Al A2 A3 A4 1 4.17 .10 0 0 2 2.11 2.26 0 0 3 3.10 .58 .54 0 71,105 4 2.05 1.55 .75 0 5 2.90 .00 1.38 0 6 1.97 .75 1.68 0 7 2.37 .00 1.95 .06 1 4.84 .57 0 0 2 3.31 2.14 0 0 3 4.01 .92 .41 0 i 75,101 4 3.20 1.60 .61 0 5 3.88 .32 1.11 .01 6 3.08 1.00 1.31 .01 7 3.61 0 1.61 .16 1 5.51 1.09 0 0 2 4.33 2.25 .05 0 3 4.83 1.31 .41 0 79,97 4 4.20 1.81 .59 0 5 4.70 .87 .95 .01 6 4.07 1.36 1.12 .08 7 4.56 .38 1.40 .19 1 6.01 1.52 0 0 l 82, 94 2 5.00 2.39 .19 0 84, 92 3 5.46 1.51 .53 0 4 86, 90 4 4.94 1.91 .69 0 88 5 5.28 1.27 .93 .02 6 4.75 1.66 1.08 .05 7 5.14 .87 1.30 .18 I
- Case No. (1) Uniform Clearance, no Prior Wear.
- (2) Tube Al-50% Wall Degradation, Tube A2-0%.
3)TubeAl-50%,TubeA2-25%.
- 4) Tube Al-75%, Tube A2-25%.
- 5) Tube Al-75%, Tube A2-50%.
(6) Tube Al-100%, Tube A2-50%. (7) Tube Al-100%, Tube A2-75%. i i 72 l
- == : =- - .
i _= /_=./ .' Upper Edge of i = !. = / / Batwing I E !.=._ / Lower Edge of j_=fg/ [ Batwing f i f/ .
?? ;
l VerticalSupportJ /
./
l d..l d- Upper Eggerate llElllEIlll 1R0.R!H.l EllElli ERIERO ( MEEl l EEENH TUSE ROWS 23 TO 45 MODEL Lower Eggerate FIGURE 4.51 FINITE ELEMENT MODEL 73
i i . . g i i . . i i . . i i i i i i i i g g g ! = . l E p 5s - a w g - l >: .
!g ,w .
8 m - E
- 50 _
I e R a a i i A R 9 0 0 l l l l l l 9 a j l 20 25 30 35 40 45 TUBE ROWS FIGURE 4.5 2 TUBE ROW FREQUENCIES 74
. _ _ _. . . _ . _ _ =
1 1
)
l 500
', \ -- AT BOTTOM OF BATWING
~
. \
U AT TOP OF BATWING { \
\ :
s : \* : a 3a - T _ N \ $ E
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S s 200 Ny _ Di - N . N . 100 % -
=
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l 0 i i i8 I iiiiI e i i i l i i i e i i i i i 20 25 30 35 40 46 l 1 TUBE ROWS FIGURE 4.5-3 OUT OF PLANE TUBE STlFFNESS 75
l i l
/ II
/ .
f s, 1 ,
%g I %
i .s I >
, NOTE: DISPLACEMENTS ARE PER.
PENDICULAR TO THE UNDE-f FORMED (DOTTED LINE) GEOMETRY I Il I l i N l FIGURE 4.5-4 SAN ONOFRE BATWING-MODE SHAPE 76 l
45 , , , , y y i _ 40 _ l . 35 l g . a- - us m - 3 . 30 _ y . 25
~
i - 20 = i e a I a = n a I a = a = I ' i a = l i e i i 0.000 0.001 0.002 0.003 0.004 0.005 TUBE HORIZONTAL DEFLECTIONS AT BATWING, INCHES lI
~ FIGURE 4.5-5 TUBE HORIZONTAL DEFLECTION vs TUBE ROW
5 24.5" I I PLANE OF i [ SYMMETRY (4 I 4 g 44 1 1 4 1 4 i el I 4 134 1 I ROW #23 131 38 13.5" l X l 34 1 33 127 32 1 31 I M 12 29 1 21 29 4 i
*- 6.75" -
1 I I \\\\\ l n t s. s\\ 60.250 FIGURE 4.54 TUBE / BATWING CONTACT FORCES FINITE ELEMENT MODEL 7E
l 4.6 TUBE WEAR EVALUATION AND PROJECTION This section evaluates tube wear as indicated by the eddy current examinations in SONGS-2 steam generators as it relates to the wear projections for Cycle 2 operation. 4.6.1 SONGS-2 Steam Generator Tube Wear The analysis was performed using Archard's equation for wear: l V = 10-12 gp n where:V = Wear Volume (in3 ) obtained from the eddy current data and tube wear model A in Section 4.4.3; K = Specific Wear Coefficient (in2 /lb);
- Fn = Normal Force between Surfaces (1bs.) determined by i
applying a distributed load upon a batwing strip and calculating the forces between the strip and tubes (See Section 4.5.3); E = LT, where 1 L = Sliding Distance (in/ day) developed by calculating the inplane natural frequencies (Section 4.5.1) and multiplying by tube displacements due to fluid pressure
- (Section 4.5.2);
T = Number of equivalent full flow days. An equivalent full flow day (EFFD) is defined by the flow energy equal to one day of operation at 100% power. r f 79
Section 4.2.2 presented a comparison of fluid kinetic energies at 20%, 50% and 100% power. From this comparison, approximately eleven 50% days are required to impart the energy of one 100Y day. Comparing the product of dynamic pressure (Section 4.2.1) and normal force (batwing deflection from Table 4.3-2), approximately seven 50% days are required to equate the wear of one 100% day. By inspections, operation at less than 50% power adds negligible amounts to the number of full flow days. The operating history of Cycle 1, a sample of which is shown on Figure 4.6-1, shows that San Onofre 2 operated 302 days at 100% power and 51 days at 50% power. This equates to approximately 309 equivalent full flow days. Archard's equation was applied to each tube that was indicated to be worn as a result of the eddy current examinations. A specific wear coefficient for each worn tube was then calculated. The wear coefficient for each generator was then obtained by computing the mean wear coefficient of the corresponding worn tube inventory. Results of these calculations indicate that, based on 309 equivalent full flow days, the average wear coefficients are 36.5 in2/lb and 2 35.4 in /lb for steam generators 88 and 89, respectively. These wear coefficients compare favorably with the coefficients from ( wear tests presented in Section 4.4.1 confirming the validity of the tube wear model selected. 4.6.2 Predicted Tube Wear i The analysis of the batwing / tube configuration, presented in the previous sections, defines the batwing to tube interaction forces and the relative displacements between the strips and tubes. The calculated forces and displacements are related to the predicted wear through Archard's wear equation. l l 80
f The analysis predicts attenuation of the strip-to-tube contact force with penetration into the tube bundle. Typically, with uniform tube-to-batwing clearances, the contact force reduces to zero at the third tube into the bundle, i.e., the strip does not contact the third tube. Wear is predicted on the first two rows of tubes, except at the shorter batwings where only the first row tube would be expected to wear. ! With uniform clearances the behavior described above is only typical for early stages of wear and for perfect tube batwing alignment. Any prior wear or misalignment due to manufacturing tolerances would result in non-uniform clearances which alter the contact force distributions. When increased clearances of up to one tube wall thickness on the first two tube rows are considered, significant contact forces are shown to occur on the third tube row while contact l forces on the first row decrease slightly. Second row contact forces may increase or decrease depending on the relative clearance between j the batwing and the first two tubes, i The consequences of non-uniform clearances on the wear pattern are clear. A first or second row tube out of position by as little as 0.024 inch could result in higher wear on second row tubes than on first row tubes or in third row tube wear in addition to first and second row wear. Anomalies of this type were observed in the eddy current indications from SONGS-2. Similarly,moderatewear(50-100%
- wall degradation) on a first row tube can be expected to lead eventually to wear on an in-line third row tube, even though no wear occurs initially on the third row. This accounts for the numerous
- third row indications which occur on SONGS-2.
4.6.3 Wear Projection Based on Operating History
, The preceding sections discussed the relationship of wear volume to the force batwings exert on a tube and the sliding distance of the tube as defined by Archard's equation. Archard's equation concludes 81 l
I \ that volume of wear is proportional to the force exerted by a batwing on a tube and the sliding distance of the tube. This section
- describes how this relationship was used to predict wear as a 4
function of observed wear. I 4.6.3.1 Effect of Sliding Distance on Wear of a Tube: Sliding has been shown to be proportional to fluid dynamic pressure, ! the in-plane frequency of the tube, and the number of cycles of tube vibration. Fluid dynamic pressure and tube frequency relate to wear rate and the number of cycles of vibration relate to the time the fluid dynamic pressure has been applied. Since tube frequency is a constant, and the dynamic pressure acting , on a tube is also a constant for any given power level, the effect of i sliding on wear can be directly related to the time the dynamic l pressure has been applied, equivalent full flow days (EFFD). That 1 is, V 2
<. V 1 ,
l Where V2= predicted wear volume during Cycle 2 V 7= observed wear volume during Cycle 1 EFFD2= Predicted equivalent full flow days during Cycle 2 EFF01= Equivalent full flow days during Cycle 1 4.6.3.2 Effect of Force on Wear of a Tube: The tube to batwing contact forces are presented in Section 4.5, Table 4.5-2 shows that:
- 1) Force on first row tubes (A1) is at a maximum before wear is initiated, and decreases with increasing tube wear.
82
l 1
- 2) Force on second row tubes (A2) decreases after the wall thickness has been worn beyond 25%.
The forces presented in Table 4.5-2 are baced on the effects of quasi-static deflection. In Section 4.3 it was concluded that an increase in the load of approximately 15% to account for the effect of the 7Hz mild fluttering may be appropriate. It can be concluded that the force on tubes worn beyond 25% of the wall thickness has peaked during Cycle 1 and that the effect of the force on these tubes after Cycle 1 will not increase. Thus, for tubes worn beyond 25% of the wall thickness, the effect of force on wear is constant. Combining the effects of sliding and force of tubes with wear beyond 25% of the wall thickness, l Y 2
"Y 1
h21 L. Cycle 1 operation resulted in 309 equivalent full flow days (EFFDg ) and Cycle 2 operation is projected to result in 265 equivalent full flow days (EFFD ). Therefore, from the above relationship, the 2 projected volume of wear at a tube at the end of Cycle 2 is 1.86 times the volume of wear at the tube at the end of Cycle 1 for wear model A. The projected depth of wear at the end of Cycle 2 was computed from . the volume to depth relationship (Figure 4.4-5 and plotted as a function of the depth of wear at the end of Cycle 1 on (Figure 4.6-2). For example, a tube worn 45% at the end of Cycle 1 is projected to wear to 64% at the end of Cycle 2. l l 83
The projected flaw depth established by Figure 4.6-2 may not be accurate for tubes worn less than 25% at the end of Cycle 1 because the batwing to tube force is likely to increase until 25% wear has occurred. However, during Cycle 2, wear in these tubes can not be l expected to grow to a depth larger than the projection for tubes worn 25% at the end of Cycle 1. As a check of the dependence of the wear predictions on the wear model selected (Model A), calculations of projected wear using volume to depth relationships for the three wear models (A,B, and C) were ( performed for 20%, 30%, 40%, and 50% wal'1 degradations at the end of Cycle 1. The results are shown in Table 4.6-1. As can be seen, the projected wear varies by only a few percent between models and can effectively be assumed independent of the wear model. 4.6.4 Batwing Wear Evaluation and Resultant Stress
- The. progression of wear of batwings and the stresses on th;. worn batwing are discussed in this subsection.
4.6.4.1 Wear Progression at Batwings Since Inconel tubing materials and carbon steel batwing material wear at approximately the same rate, it is expected that the volume of material removed from a batwing equals the volume removed from the tube it contacts; The geometry associated with batwing wear would lead to a groove beginning at the point of contact and extending diagonally across the batwing. Figure 4.6-3 shows the extent of the wear when tube wear has extended to 100% of the wall thickness. A4
4.6.4.2 Stresses at Batwings The finite element model described in Section 4.5.1 was used in the stress analysis of the batwings. The batwing was subjected to a uniform lateral pressure of 0.1 psi corresponding to the force required to deflect the batwing elbow 0.735 inches (see Table 4.3-2). Bending stresses were calculated at critical sections along the batwing as shown on Figure 4.6-4. These sections are: Node 4 Weld between horizontal and diagonal portions of the batwing, Node 6 Location of maximum out-of-plane deflection of the batwing, and Node 14 Location of contact between batwing and tube. Stresses of 5.3 Ksi, 6.9 Ksi, and 9.6 Ksi were obtained at nodes 4, 6, and 14, respectively. The stress of 5.3 Ksi at node 5 was obtained based on the weld geometry shown on Figure 4.6-4. The joint consists of three full penetration welds which are ground smooth. The stress at node 14 is based on an unworn batwing. The effect of material removed by wear on the moment of inertia of the section was calculated and a stress intensification factor based on the ratio of moments of inertia of an unworn and worn batwing was calculated. The geometry used to define batwing wear is based on the wear progression discussed in Section 4.6.4.1. 85
The calculated stress, including stress intensification, at node 14 is 12.0 Ksi. This is below the endurance limit of 12.5 Ksi as defined by Figure I.9.1 of Reference 4.6.1. The value for the endurance limit defined in Figure I.9.1 includes an allowance for stress range about a mean stress. The behavior of the batwing is such that the stress ranges about zero. 86
REFERENCES (Section 4.6) 4.6.1 Appendix I-9, ASME Code Section III, 1983. . 9 87
TABLE 4.6-1 COMPARISON OF WEAR FOR TUBE WEAR MODELS A, B, AND C Wear at End of Cycle 1 Projected Wear at End of Cycle 2 Wear Model A B C 20% 27 29 26 30% 44 45 39 40% 57 58 55 50% 71 73 70 88
199 -- --
.- 3418 7
7_ gg -- -- - - - - - - . __ _ J .. . _ _ - . ._ _ _.. ... . __ ._ . ._ 3960 M _ - -- - - _. __ -. .. . _ __ .
. __ . _ _ .. 2728 78 2387 Q
h - - - - - - - - - - - -- - -. . - - _. .- - - . -. - - 8 G.
.a g - _ _ ._ . .- ._ - . . . _ . . ._ __ . . _ . .. _. _. ._ ._ _. .
_ _ .. _ _ 2946 3 1785 b m 58 - - - -- - - - -- -- - - - -- .-- --- -- -- .-- . . . .. .- - g-u 5 4g _ .. . . _ . .. .._ _ _ . _ . . _ .. _. _ .. . '. _ .. .- . ..
.- 1364 g a; a .,
g W g 3g . _ . . _. _ _ . ._ _ _ _ . . __ _ .._ ._ __ _ -. 1923
- n. O> .
g n. 23 _ . _ . . _ _ _ - __ .._ _ __ . . ._ . - 682 u
- - - - - - -- - -- -- -- - -- - - - - - 341 isb19 B . . . . : . . : : : . : : : : . : . . . 8 4 31 ma e naa 5 12 is a e 11 ne a e 5 ma a 13 aa 3 is IEL 1 JM.1 FU.1 IIML 1 APIL 1 IIAL I As,1 1983 1994 1984 !!B4 llB4 IIB 4 13 FIGURE 4.6-1 SAN ONOFRE 11 CYCLE 1 THERMAL POWER vs TIME
1e g 9 m .? 4-
- lt M
- _m -
o E!! y e :M 3,;l -
- m
. M_ '@ m
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- .: z -g
;- = =
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.. h.
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-6
A
< 4.00" r (CONTACT AREA) t 0.090" } 0.028" 1.57" FIGURE 4.6-3 BATWING WEAR CORRESPONDING TO 100% TUBE WEAR 91 2
N '
\ ,.
N "
\ -
\
\
\ .
y , v.. . m y,.. WELD JOINT FIGURE 4.6 4 BATWING NODE POINTS 92
4.7
SUMMARY
OF RESULTS Q f.ik. 1[I-
. ~.
4.7.1 Flow Visualization Testing _y _ '{$l_. e f; [ f 46 f i; y 5 :. w.1
. *py $ 4, y '
There were two important observations as a result of the flow
] -@. l t l . y. . . .
visualization testing: pib % [ 'y
,. i i: i f 4 c.
. w- ~.
- 1) Batwing motion at the elb,w consists of a combination of ?
.@.9 $, ,
, .y .-
quasistatic large amplitude motion limited by the pairing off of .i j.'/g. p3_,- - F 'g adjacent batwings and a small amplitude fluttering of the }lf y-g'l. . batwings at a frequency of 7.0 Hz. This combined motion results 'n ..
. / 4.'.
in a head between the betw'ng and tube consisting of a static 4 g]-3. kj portion resulting from the deformed shape of the batwing plus a y p}j dynamic portion resulting from the small amplitude vibration. f'JDy/ f.v w.J% yn The small amplitude vibration is estimated to increase the static W:1 y ; . A. . :. load by approximately 15%. g {&[S k S.\,1
- 2) Increased clearances between the batwing and the tube caused only K,; u %........ . - :
a marginal increase in the small amplitude vibration indicating @% g M.N . g - -.I - that dynamic loads from vibration are not significantly affected
',.'$.sll1.:;4...;.3 by the increased gap which will occur as a result of wear. I c;W. .. 3 .. J T. . +
g{pi...
'g .
n 4.7.2 Wear Mechanisms [* q, p.;,f. m.g.f. [L
'] * '
{,1 's The motions observed in the flow visualization test model led to '. postulated wear mechanism consisting of static contact forces and X . .J",s f Y [ s .y.. V
- T .~ . .
$ .4 g ,
f ; r. ,s , sliding due to tube motion. This is a type of wear which can be represented empirically by Archard's equation. AJEf(
- j. l E( .
, ; ng , .-
4.7.3 Wear Calculations ^2.f $.,2 _ ) fn. 'i, ;.l . I D D;;. The parameters of Archard's equation (volume of wear, force between _s_ y # batwings and tubes, and the sliding distance of tubes) were
....x.g..... -
.. N,c h *'IwA n:O:
calculated and the resultant wear coefficient compared to wear A M.t. M i> ge s f' s. t s . . ., t.y .14 m. Yh' 'Y.h1 5( K.g;, N -% 3 e. Ms
e - MSig E coefficients derived from wear tests. The favorable comparison f obtained supported the validity of the wear model selected to calculate wear volumes. _ 4.7.4 Wear Projections = The effect of sliding distance and normal force on a tube were examined to determine how changes in these parameters relate to i changes in wear rate for SONGS-2 Cycles 1 and 2. The results show that, for tubes which exhibit 25% or greater wear at the end of Cycle 1, wear at the end of Cycle 2 can be projected from the wear at the _ end of Cycle 1. For tubes worn less than 25% at the end of Cycle 1, - the prediction may be less precise, but the wear of these tubes is , bounded by the wear of tubes which exhibit 25% wear at the end of - [ Cycle 1. Wear rates were calculated for all tubes in the affected region. 4.7.5 Batwing Stresses Stresses on the batwings were calculated. The calculation performed y included the effect of batwing wear comensurate with tube wear. The results show that the stresses calculated are below the endurance limit of the material, demonstrating continued batwing integrity. ' E F 5 + 5 F r I e g t' 94
+ .. .
, f-, % ,v. ~.v,. ,
. < . .; g. ,- - 4ar Y ' ,_
- Q e j,: ,
[k,k j h cG;;g ;. '
\,. e .4.,
5.0 PLUGGING AND STAKING PROGRAM {p] / {\ .;;~1 ? 9 ':, i __ :" ;
5.1 INTRODUCTION
N9~. 1 f.; f:,f:; 49, . : 't?
..f This section discusses the steam generator tube plugging and staking T. - /
.. g ., .:.. M.y .: .
program implem' anted at SONGS-2. This program was based on the 3;]:ye ..b .! O-
.7 results of the testing, analysis and resulting wear projections 4.+. C.y <
% v .:. s L-described in Section 4.0 and was formulated to assure that wear would n,yd, ,q; a - .;; M not exceed the value that is the basis for the SONGS-2 Technical -
l.:. .O .;. f.';# j Specification tube plugging criteria. AG.
'..,e x.
. -.,r:.
.[,hy
- m. -
. ; ,. .. , r The plugging program is further described in Section 5.2. ! f .'s 7 M ' ; ^
,y.c.
- v. : .
'.f.:. 'g ..f!2 .
Tube " staking" to prevent tubes frore severing and damaging other ?g.g.: gl-tubes was also implemented. The staking progran is described in p)$. 7~..-~.
. :. .s.-
Section 5.3. 5 .Y.; ;. p y
'S , j$ e ; f _
.; ..v : .,...
5.2 TUBE PLUGGING ?..,J. + - 7 0.,
,p 3. < 7
' ..y ? .., ,# . 1.
9.. . v : '; _" y
. ~ ,
The extent of plugging at SONGS-2 was developed to conform to SCE's F-1,'..r.:"'T,...: 1.e. .w objective of operating through at least Cycle 2 without exceeding 64% fQ}:{-y ,: through wall degradation. Based on the evaluation of projected wear A42rC . <fe . using the wear rate information presented in Section 4.0, a 3 .: . . pQ '.'g. ] conservative set of criteria for removing tubes from service was fQ?. .!C,. . " ^'.. . specified. E,' . iG g.' .s
.-...q. ,,..;..,..9- 3 These criteria include plugging (or staking) tubes which exhibit or $w-i % c .' f i~.i -
are projected to exhibit wear as follows: S-[v-' '. *3,i-! I-lf.:f.. .fll o Wear 120% through the end of Cycle 1. if. .y .e,%,- o .v.y
=
a 3 Tubes surrounding those tubes with wear 1 44% through Cycle 1. o Generally, tubes surrounding those tubes with wear 1 20% through d{gl.. t eY.A. n . Cycle 1 (if the worn tube is in the first 3 rows). [. , g(V.' : .$ .
~i k ? j k Rfl.A . '& d ' '. . .
,, 'i ,S 4,, - db . .-
k Based on the predicted wear in Section 4.0, these criteria would " provide for no more than 29% wall degradation, for unplugged tubes, - through the end of SONGS-2 Cycle 2. The plugging pattern used in the -- SONGS-2 is shown in Figures 5.2-1 and 5.2-2 for steam generators 88 m and 89, respectively. - I mE Tr I M E'-M
=
0 h W 2-96
=
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. . . ,- , . . -+ 2 . . +. nm-a ' - < n- - 'm .- - - ~ L ~ ' ' ~ "? ' " ..:;
gp' ... 3 .
'l l k.: \ ..
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[ 5.3 TUBE STAKING n h.?'IN.Q. A-h'- l,';. ? i The objectives of staking tubes were to: 1) prevent the severing of f. p .~ ~;. O n^ tubes and 2) provide an additional wear surface to retard wearing of by'N, . . tubes in succeeding rows. f'*? ; .1 ,; i M_3f F [." The criteria used to stake tubes was the potential for a tub.e being . , . .3. , - .4. worn through prior to the end of Cycle 2. Tubes which exhibit the ,' $y;2:.s. . ,k ( .,,, greatest degradation (peripheral row) and for which the largest wear is (,$. .,.1, q.' 4J, } ' predicted over the next cycle were staked. Since maximum degradation (..y, l.. ,$ and maximum projected wear is generally confined to the tubes ;jdf.
,. ~ . ;l imediately adjacent to the central cavity,11 tubes in Generator 88 lJyy J
3 and 18 tubes in Generator 89 are stakable in accordance with the p' . g 4 criterion discussed. . . , , g +. SC Fw: ';Y .;'
'..] ,y
,m i.-:ni.. .w The final number of locations used in implementing the staking program :.
, is more conservative than that which would be consistent with the ?, J. . f. ; J : . prediction of wear obtained in Section 4. All peripheral tubes
- contained within tube lines 71 through 106 were staked (Figures 5.2-1
[.] h.
?! M. i fj }
P' D and-2). ?. ;7. ' .e .3
> . 4
%.6,. -
. 3 ,; ;:
( Figure 5.3-1 shows the design and use of the stakes used in the 'c V
- P cM .. -
; 7..
peripheral tubes of SONGS-2 steam generators. The design allows a T; d single stake to restrain both of the tube / batwing intersections on the
<. '. ef f U-bend of an individual tube. The stake assembly is composed of a ]$/."+
.1 <
rigid rod and length of flexible cable. The rigid portion simplifies 2
- 3. c ; ,
J([.f N,f,7 insertion of and retention of the cable portion which spans the two 4 90 bends and the horizontal portion of the tube. The assembly is dimensioned so that the cable extends from approximately 6" below the f:. ;J . . (m.y .- - w . v f.. batwing on the insertion side to below the top eggerate tube support R :j i.li. 1 : at its free end. Thus, the cable is positioned within the tube and 1-4.s.4b d_. %; "
,1 i
- extends beyond the batwing intersections. M,y2 .c5 d"6...;."
.? .9(M The stake assembly is fabricated from type 304 stainless steel material ['.:l.ja:(.
] and has nominal diameter of 1/2" throughout. [M..hlg. A
-Q: ,:.~. c i * ' '
s]% ,4
. )Q.y 99 g%fic'e r
+ -
!!).I.;Y U
- v. . n_ a:, .: -
..i ' y
.. g ;. w i,?y ;, e
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..n s.a .~ :: c2 %,; J h ., %. .., y
. ' . $, t * ' g N' . ['
N
,' fw s. , .. ,8. t R , L .; ,
. .y : .u; : -
. .' . 3'.
y[.s-..t.kW L' 2
- EQ?w,.Q spr
., p .
y.. The rigid portion is assembled from 4 or 5 straight lengths that are M.% .; a,).. .,g
.~ 7 .r..
H assembled with alternating male / female threaded joints. The cable ends !.a ;O, ,.. . ,,;; s .
+ .v
,. are as follows: . .: . , L,M...c,i '
v . g
,: ; w3?:.. - , . .. ..:. . u.! .
f. a) The leading end is tapered to facilitate insertion around the two ?. F 90 bends in the U-tube. 6,9..O. p y_7._-W 9 . * : ,, v , - 3 4 . < , , . y : .' . .. .,_
.+-.-
The trailing end is provided with a special adapter which receives I b) ^
.'. ' p. ' , ~. 5 . , . %;,...s %..'?. .- .. ?
y the cable and provides for a threaded connection to the straight rod 4 Q. /rp; g C. , . , , . / portion. The adapter has sufficient length to prevent it passing ' % e ' A, % >. % h .x;7 e a Lp through a 90' bend.
. O.* .3. ; .
g Wk
- v. y - , ....,q .
'; s , . . t. , y
'4 For insertion of the assembly the cable and top rod section is inserted . . 'v , V ', .*-
- y u. .;;..
- - upward into the tubes from the primary head of the steam generator. 6,. .X ,. '. ;
i' @,. ..y f.c ,4 ,{ . . The remaining 3-4 rods are successively threaded together as the cable ~
$ is forced around the 90 bends and into its final position. The lower j
a..
;.: .i.. , .:u c. - :eg.f.., ?
rod end is inserted / recessed above the bottom face of the tube sheet to . .4 f. - c - U~,d ..s. .:
- c* W i a location slightly above the end of the welded tube plug used to seal g r.
e this end of the tube. The opposite tube end is sealed with a C-E Jy;[ p: g:i' 3 .i ' rolled mechanical tube plug. i.)'d:(.3.' 5 $
, , + .
... n.- >:- ;
f p.;c 45% 3
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m FLEXIBLE STAK E f 5 0.5" DIA (STAIN- .
- L SS STEEL CABLE ' _
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MECHANICAL PLUG WELDED TUBE $ (INCONEL) PLUG (INCONEL) FIGURE 5.3-1 TYPICAL STAKE INSTALLATION 101
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, A.; ; % .
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+
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Thr rinary G u.tfon af t!e staki is t3 f rovide additional material D-l,*M; y ..... ,.-
,3, <
( within the tube to resist wear progression. The stake, for example, h provides approximately 200% additional cross-sectional area to the M(ylY;V~?
- ' e .....
tube and results in a significant increase in the volume of material g4w ,.; ..v 7 n rA - s
,.'.- being worn. Figure 5.4-1 illustrates the potential advantage of the j/.p,,. h 1 y,.- :
Y
' stake in the wear volume prediction. The wear volume to penetrate to ' ? @Q: .._.f,n.J' ,
L the centerline of the stake is approximately .11 in 3, as shown in the i M 5: d v j figure, which is an order of magnitude greater than the wear volume g.Qf Q 32 .3 g% U to penetrate the tube wall, i.e., 0.008 in 3. The wear capacity of Qg .i j
,. .. . t .
j the staked peripheral tubes is significantly enhanced by the addition j of the stakes. h[fe -7 ij.". _.-
;g 2 , jgfry
.~
The time to wear 50% through the stake can be projected on the basis of j.A. . ,-. 4 ,~ ,.u L-o . .
,s.-
observed wear during the first cycle of operation of SONGS-2. For the
- f. 7 ,
, . . . v. ' .:
~
18 month operation period (June 1983 to December 1984) a maximum wear W
/
N '9. '. .n
.-...g 1
e indication of 95% thru wall was measured. From Figure 4.4-5 the Y h *. ~l' 5 associated wear volume is approximately 0.0068 in3 . The wear volume M. p 5. . . - 7' 3 of .11 in for wear to the centerline of the stake is a factor of ?' .*- r Vf J* 5,> .c
' . , .: a.'. .
16.2 times the measured indication. Assuming 3 constant wear rate, a J.ih ::.. . ,
^
j s - the time predicted to wear the stake 50% through its thickness is .T..j i :C ( ..( u 16.2 x 18 months = 291.6 months. On this basis it is concluded that Ij.. m o.g cyi . j/ it would take the stake more than 24 years to wear 50% through its l.E . e t ' thickness. h [ ,((D..H bi .' M y.3 ^ . .a .y
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SUMMARY
AND CONCLUSIONS .
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w . * - This section summarizes the results of the characterization, D. Y.c..;;.. ..fR evaluation and corrective actions taken as a result of wear 4 j.. [. . T .. indications found in the SONGS-2 steam generators. W " f*' w :#.. ,: .v.s., n..- y_ , , ' - *#':" .
- 1. Analysis and testing has been performed which:
fdf(.;g)L; Q:f.:w. . .
- g. .
r ,,47 . s..?-_ a) verified the accuracy of the SONGS-2 eddy current test pid 9".. results, k,$. ; J Q0: WG, .W b) defined and confirmed a credible tube wear mechanism, and Whb., Q~.:.y k _ a w , r. .: 2 7. . c) resulted in prediction of tube wear for SONGS-2 Cycle-2 g:@j.y .4r 's operation. ();. . , :-
.Q: N:lf. A;.
- 2. The SONGS-2 eddy current testing identified a pattern of tube ,f 3g ../ , e degradation at the inner periphery of the central stay cylinder gj . L. ?
cavity. t.: .
- ; . z- -.
g3f t.: 1.; n
,m; < -
- 3. The pattern of tube degradation was qualitatively identified and %!M, _ Jg'aa ..
quantitatively defined. NS ..[ T.a . . .p q. l
.; . ....e
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- 4. The pattern of future tube degradation was predicted based upon 'ii;$. ' ' ,,'. ,f 1 v ,
known factors and measurable parameters.
. h,1. :;M!. .'-f "
- 5. The effects of the tube wear mechanism were limited by plugging i:Niepk 3;i .;
w .. or staking all tubes projected to wear more than 29 percent f@w. f.; . . T . through-wall by the end of Cycle 2. 2 $. sN;; . %y.;e i-l ' The maximum 29 percent projected wear in unplugged tubes is fisC.
. . , . - . . .), e, 4y.t
. .2 conservatively less than the 64 percent end-of-cycle basis for
?)P. w.
SONGS-2 tube plugging. It is therefore concluded that operation : :. M.w a (:.y;il.@e .E f., .. . of SONGS-2 through Cycle-2 will not result in undue risk to wik. he .y. pMy@3/
'. ; y .c
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public health and safety. Furthennore, tube burst and leakage F'n s ,%@ M. s n P. ,.. testing, discussed in the Appendix, has demonstrated additional
,. [. g.,.. W ...,m. .
7- conservatism beyond that represented by the 64 percent 7. :G,3. ,aN, . O through-wall criteria utilized at SONGS-2. !$g:.%?s. 4.
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5 E + APPENDIX DEGRADED TUBE BURST AND LEAKAGE _ TESTING
\
A.1 INTRODUCTION l \' The objective of this test program was to determine the significance of a observed wear indications on tube integrity. This was accomplished by [ conducting a series of simul 9ted wear tests on internally pressurized [ sections of steam generator tubing in the laboratory and observing the failure mechanism (leak or rupture). Also determined was the effect on a degraded tube of a simulated steam line break pressure transient. b Leakage rates for 100% through wall defects were also obtained at _ operating temperatures and pressures. Data was generated for three 5 assumed tube wear configurations similar to models "A", "B" and "C", as ? defined in Section 4.4.2 of this report. The three operating E conditions were tested: (1) 100% power steady state. (2) pressure spike due to main steam line break (MSLB) and (3) post MSLB steady state. [ E Margin against bursting at normal operating pressure differentials for postulated 50% and 75% wall degradations are also presented. E
- A.2 TEST SPECIMENS AND TESTING EQUIPMENT Tube specimens were fabricated by milling preselected angles into Inconel 600, 0.048 in, wall tubing. In all cases, the last few mils of material were removed with a fine file. In the case of leakage test specimens, the final filing was performed with the primary side of the tube pressurized with water, to a value equivalent to the primary to secondary differential pressure. Performance of the final filing with
[ the sample pressurized insured prototypical behavior of the samples. Y b s F gg A-1 m E
. r u. u <. m . . . . . . . ; r .s. . - t - .n . , :, c m - - ~ .m s v -- .. - - r. . .;~ ~ .- .g ,_w. ,3 g.;.3 .
5 ** ~ :. m 7 N,N [ '- [,
%p'*i , p.u: :
y 16 8. v v. e,.ffilQ.ry ,ny .q; N o + n:s a.. _;$ d A 1.8 megawatt high pressure test loop and associated test model were a h.$, : .d, ,.h. . M utilized to simulate the primary and secondary conditions of a nuclear ,,i QJ et.C d.
- f steam generator. The tube specimens were installed in a Graylok
.p:,u. . .e(.f., .c Q--
v flange, located in the side of the vessel. 4%Yg 3.- 4 % & i. v 3
$. gik.'i;'s;; %
- p The test loop piping arrangement utilized to accurately control and measure the fluid leaking through the tube specimen is provided in Q..n...,i.:[h d.c.. w
? Figure A-1. The primary fluid was directed from the test loop through {QM).[$'p .
t dt . - .? one of five honed flow orifice plates to the test specimen. Prior to j3 9 f % . .'C;f . performing the leak rate test, fluid was bypassed around the specimen $ g [r..(Q[ f [ T and returned to the loop. This ensured that the fluid up to the ?..S ] A .- 1 3.. . L specimen was at the desired pressure and temperature. As the leak test .y:q:ft.% dj commenced, fluid flow through the tube specimen was maintained for two h:D;k
)y minutes before the test specimen was isolated and leak rate f.yli 9
-% 3 :mkbh.
+. measurements begun. U Tr Q:jf.,. -
.t .?. ,
_ 4:, . ;. . Qk.,- .1 J, ** i :8 A
; e. .p.
'9. . - 7 All test parameters, as well as fluid flow through the selected orifice '
- %-n.4 %. O~ J .
~t plate and tube specimen, were monitored. Leak rate measurements for ~ l v, W. I. ?,
1 ranges of 0.1 to 20 gallons / minute were possible. A computer program k.M}}h n ,. .a , . . . u-
- - was used for plotting primary pressure and temperature, secondary /
- , - g ;;.~ ., .y pressure, and leak rate (GPM) versus time. . ? ) P ,, .'-
- .: c. : 'x e . . .. e s.
N ,. ? / . I.;, ' J The sequence for leak test sample preparation and conducting the
. .. . T . Co. ..
.a
,. testing was as follows: .v c ': :!
..- f y :).y > e r
u < . p.w;w .: . 4.3
.W t (1) Tube samples were prepared by milling and/or filing the sample .
'c
~~
to appropriate geometry, while pressurized to 1350 psi, (normal I.3 4 operating pressure differential at full power aP = 2250 - 900 = N{h).f. e m.. 6.%; '. f i
- t. . 1350 psid), at room temperature. h (.Dc'
.!{ ] [ " [0. ". (2) The sample was then inserted into the EPRI leak test model and bi o. . ,. h[ ,e :n w the leakage rate was measured at 2250 psi and 600 F primary Qf..f,ff . temperature and 900 psi secondary (aP = 1350 psid). f, .{, % 5.'
- 1. ;.
- g. M s c
,g;h $f;. '.5h f; s.., e. .. Mj. "4. 4 y," . %,*., - e.
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.. i*
f , =- ,g.
~
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.;. .-;% , . N t .yq' ?.'
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. . '; . ? = - N-
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ERId (3) Secondary pressure was then decreased to 500 psi such that aP = 2250 - 500 = 1750 psid, and the leakage rate was again measured. (4) Primary pressure was then reduced to 1300 psi 0 380"F primary temperature and secondary pressure was reduced to zero (AP = 1300
- 0 = 1300 psid).
A.3 TEST RESULTS Results of the leakage and burst testing of simulated defective tubes are presented in Table A-1. For the range of wear angles tested (see Table A-2), the initial leakage ranged from less than 0.08 GPM to 0.63 GPM. In no case did the tube leakage increase to as much as 1.0 GPM per tube, even during the simulated main steam line break (MSLB) spike. The largest long term post steam line break steady state leakage was 0.77 GPM. Therefore, all of the through wall defects behaved in a controlled manner, and a " leak-before-break" type of behavior has been demonstrated. Results of the burst testing of 50% and 75% wall degradations was equally gratifying. The lowest 50% degradation tube burst pressure was 8450 psi. This provides a margir of 6.2 against bursting at the normal operating pressure differential across the tube wall. The lowest 75% degradation tube burst pressure was 5000 psi. This provides a margin of 3.7 against bursting at the normal operating pressure differential across the tube wall which exceeds Regulatory Guide 1.121 guidance of 3.0 for non-pluggable tube imperfections. Typical tube leakage test data is illustrated in Figure A-2. This data was taken at prototypical temperature and pressures over an extended time period. A-3
TABLE A-1 LEAKAGE AND BURST TESTING OF WORN TUBES LEAKAGE RATE (GPM) SAMPLE % 1 2 3 BURST DEFECT THRU- NORMAL OPERATION MSLB - SPIKE POST MSLB S.S. PRESSURE I.D. WALL AP = 1350 PSID P = 1750 PSID AP = 1300 PSID (PSIG) A-1 103 0.23 - - - A-2 100 0.63 - - - A-3 100 0.15 - - - A-5 50 - - - 9825 A-6 75 - - - 7200 A-7 1C0 0.11 0.11 0.08 - A-8 100 0.37 0.42 0.38 - A-9 100 0.12 0.12 0.13 - B-1 100 0.13 0.44 0.38 - B-2 100 0.49 0.62 0.55 - B-3 100 0.61 0.94 0.77 - B-4 50 - - - 8725 B-5 50 - - - 8450 B-6 75 - - - 6700 C-7 100 0.17 0.56 0.45 - C-8 100 <0.08 0.48 0.37 - C-9 100 0.14 0.74 0.71 - C-10 50 - - - 8800 C-11 75 - - - 5000 \ A-4
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$ I.D. W1LL ANGLE DIFE:T P =225_1 33I P =i25 W P =1300 PSI sy.'U:#r.:N. . > a, LENGTH P = 901 )SI P = 50 PSI P=0 M. - N.?;.: ? /. .
LW T = 601* F T = 60:*F T = 380 F -K 2 : (.f.M.. %. 7 (%) (DEG.) (IN.) T = 53! F T = 46 *F T = 212 F e d (GPri) (GPi- ) (GPM) i,.M; 351 1 M:n
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b A-3 100 1.75* 1.57
? A-7 100 1.75* 1.57 4. :. :? j -t.4 4 A-8 100 1.75 1.57 I " # '.i 2 ' ' 2 f A-9 100 1.75* 1.57 Test Data to be Recorded F X '5 .t i~,1 v
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i B-1 100 1.56* 1.76 7?i
.O - ;H B-2 100 1.56" 1.76 f.4.. if 3 B-3 100 1.56* 1.76 K .C -t .%. n'. .: .:_ y. ...r' ..2 . s.
C-7 100 2.15 1.27
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B-4 50 0.88* 1.57 41.f .. [::-4'3 . i B-5 50 0.88 1.57 Test Data to be Recorded '.le-
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i APPENDIX B Evaluation of Tube Wear in San Onofre Units 2 and 3 ) Steam Generators (0'Donnell and Associates Report) m -}}