ML20236W734
| ML20236W734 | |
| Person / Time | |
|---|---|
| Site: | Kewaunee  |
| Issue date: | 11/30/1987 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML111650568 | List: |
| References | |
| SG-87-11-010, SG-87-11-10, WCAP-11644, NUDOCS 8712080197 | |
| Download: ML20236W734 (166) | |
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I KENAUN'EE' i STEAN GENERATOR SLEEVING' REPORT (Mechanical Sleeves) 1 I k' NOVEMBER,.1987. ' I' p I e". ( PREPARED FOR WISCONSIN PUBLIC SERVICE I A 1 WESTINGHOUSE ELECTRIC CORPORATION STEAM GENERATOR TECHNOLOGY DIVISION I
-, P.O. BOX 855 1 PITTSBURGH, PA 15230 I o.
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I TABLE OF CONTENTS Section Title Page e
1.0 INTRODUCTION
1-1 2.0 SLEEVING OBJECTIVES AND BOUNDARIES 2-1 \ 2.1 Objectives 2-1 2.2 Sleeving Boundary 2-1 2.3 Report Applicability 2-3 3.0 DESIGN 3-1 3.1 Sleeve Design Documentation 3-1 3.2 Sleeve Design Description 3-1 1 3.3 Design Verification: Test Programs 3-6 3.3.1 Design Verification Test Program Summary 3-6 3.3.2 Corrosion and Metallurgical Evaluation 3-7 ; 3.3.3 Upper and Lower Joints 3-17 3.3,4 Test Program for the Lower Joint 3-35 3.3.4.1 Description of Lower Joint Test Specimens 3-35 3.3.4.2 Description of Verification Tests for , the Lower Joint 3-35 3.3.4.3 Leak Test Acceptance Criteria 3-37 3.3.4.4 Results of Verification Tests for Lower Joint 3-39 l o 1 4680M:49/110387-2
TABLE OF CONTENTS (Continued) Section Title Pace e 3.3.5 Test Program for the Upper Hybrid Expansion Joint (HEJ) 3-44 3.3.5.1 Description of the Upper HEJ Test Specimens 3-44 3.3.5.2 Description of Verification Tests for the Upper HEJ 3 46 3.3.5.3 Results of Verification Tests for the Upper HEJ 3-46 3.3.6 Test Program for the Flued / Fixed Mockup 3-60 3.3.6.1 Description of the Fixed / Fixed Mockup. 3-60 3.3.6.2 Description of Verification Tests for the fixed / Fixed Hockup 3-62 3.3.6.3 Results of Verification Tests for the Fixed / Fixed Mockup 3-62 3.3.7 Effects of Sleeving on Tube-to-Tubesheet Weld 3-64 3.4 Analytical Verification 3-65 3.4.1 Introduction 3-65 , 3.4.2 Con.ponent Description 3-65 3.4.3 Material Properties 3-67 3.4.4 Code Criteria 3-67 3.4.5 Loading Conditions Evaluated 3-67 3.4.6 Methods of Analysis 3-72 3.4.6.1 Model Development 3-73 ; 3.4.6.2 Thermal Analysis 3-75 I 3.4.6.3 Stress Analysis 3-76 11 4680M:49/110387-3
l: V' TABLE OF CONTENTS (Continued) L .. , Section: Iltle Pace 3.4.7 Results of Analyses '3-78 3.4.7.1 Primary Stress" Intensity 3-78 3.4.7.2 Range of Primary Plus Secondary Stress Intensities ~ 3-80
-3.4.7.3 Range of Total Stress Intensities 3-86 3.4.8 References 3-88 4 3.5 Special Considerations 3-89 3.5.1 Flow Slot Hourglassing 3-89 3.5.1.1 Effect on' Burst Strength .3-89 3.5,1.2 Effect on Stress Corrosion Cracking (SCC) Margin 3-89 3.5.1.3 Effect on Maximum Range of Stress Intensity and Fatigue Usage Factor 3-89 l
'~ 3.5.2 Tube Vibration Analysis 3-90 3.5.3 Sludge Height Thermal Effects 3-90 3.5.4 Allowable Sleeve Degradation 3-90* 3,5.4.1 Minimum Required Sleeve Thickness 3-90 3.5.4.2 Determination of Plugging Limits 3-94 3.5.4.3 Application of Plugging Limits 3-95 3.5.5 Effect of Tubesheet Interaction 3-98 3.5.6 Structural Analysis of the Lower Joint 3-98 3 3.5.6.1 Primary Stress Intensity 3-98 3.5.6.2 Range of Primary Plus Secondary Stress Intensities 3-98 iii 4680M:49/111187-4 L -
TABLE OF CONTENTS (Continued) Section Title Pace
- 3.5.6.3 Range of Total Stress Intensities 3-101 3.5.7 Effect of an Axial Tube Lock-up on Fatigue usage Factor 3-103 3.5.8 Minimum Sleeve Hall Thickness 3-103 3.5.9 Evaluation of Operation with Flow Effects Subsequent to Sleeving 3-106 3.5.9.1 One Sleeve Per Tube 3-109 3.5.9.2 Two Sleeves Per Tube 3-111 3.5.9.3 Flow Effects Summary 3-113 4.0 PROCESS DESCRIPTION 4-1 -
4.1 Tube Preparation 4-1 - 4.1.1 Tube End Rolling (Contingency) 4-1 4.1.2 Tube Cleaning 4-3 4.1.2.1 Net Cleaning 4-3 , 4.1.2.2 Dry Cleaning 4-4 4.2 Sleeve Insertion and Expansion 4-4 4.3 Lower Joint Seal 4- 5 i 1: 4680M:49/110387-5
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TABLE OF. CONTENTS (Continued)' > Seetion' Ti tl e'.' Pace:
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4.4 Upper' Hybrid' Expansion. Joint (HEJ)- '4 6 4.5 : Process Inspection Sampiin'g~ Plan- / 4-6 g 4.6 Establishment of Sleeve' Joint Main Fabrica-tion Parameters- 4 4.6.1 Lower Joint > 4-7 4.6.2 Upper HEJ 4-7 t-5.0 SLEEVE / TOOLING POSITIONING TECHNIQUE- ',5-1 6.0' NDE INSPECTABILITY 6-1
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6.1 Eddy Current Inspections 6-1
. i l 6.2 Summary 6-6 7.0 'ALARA CONSIDERATIONS'FOR SLEEVING OPERATIONS 7-1 7.1 Nozzle Cover and Camera Installation / Removal- 7-2 7.2 Platform Setup / Supervision 7-2 1
7.3 Radwaste Generation 7-3 7.4 Health Physics Practices and Procedures 7-5 11 1 L,. l U v. v-4680M:49/110387-6
TABLE OF CONTENTS (Continued) Section Title Page 7.5 Airborne Releases 7-6 7.6 Personnel Exposure Estimate 7-7 8.0 INSERVICE INSPECTION PLAN FOR SLEEVED TUBES .8-1 l l
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vi 4680M:49/110387-7 _ _ _ _ _ _ _ _ _ _ _ _ _ - _ m._-_.----------- " - -" - - " ^ ' " " ~ ^ - - ~ - - " ^ - - - - --
4 LIST OF TABLES , Table Title. Pace
.c 3.1-1 ASME Code and Regulatory Requirements. 3-2 3.3.2-1 Summary'of Corrosion Comparison Data for 3-9 Thermally Treated Alloys 600 and 690 3.3.2-2 Effect of Oxidizing Species on 'he t SCC Suscepti- 3-14 bility of Thermally Treated Alloy 600 and 690 C-rings in Deaerated Caustic 3.3.3-1 -Design Verification Test Program - Corrosion 3-18 3.3,3-2 Residual Stresses at [ ]a.c.e 3-22 3.3.3-3 Results of Negnesium Chloride Tests at [ 3-25 ja.c.e 3,3.3-4 Results of Magnesium Chloride Tests at [ 3-26
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3.3.4.3-1 Maximum Allowable Leak Rates For Kewaunee 3-38 Generators 3.3.4.4-1 Test Results for the As rolled Lower Joints 3-41 3.3.5.3-1 Test Results for HEJ's Formed Out of Sludge (Fatigue 3-48 and Extend Operation Tests Incl.) 3.3.5.3-2 Test Results for HEJ's Formed Out of Sludge 3-50 (Static Axial Load Leak Test, SLB and Reverse Pressure Test Incl.) j i d I I vii 4680M:49/111187-8
LIST OF TABLES (Continued) Table Iltle Pace 3.3.5.3-3 Test Results for HEJ's Formed In Sludge 3-52 , (Fatigue and Reverse Pressure Tests Includ.) 3.3.5.3-4 Test Results for HEJ's Formed in Sludge (Axial 3-54 Load Leak Test and Post-SLB Test Included). 3.3.5.3-5 Upper HEJ Test Results 3-55 3.3.6.3-1 Test Results for Full Length Sleeves Formed and 3-63 Leak Tested in Fixed / Fixed Hockup (In sludge and Out of Sludge). 3.4.4-1 Criteria for Primary Stress Intensity Evaluation 3-60 (Sleeve)
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3.4.4-2 Criteria for Primary Stress Intensity Evaluation 3-69 (Tube) , 3.4.4-3 Criteria for Primary Plus Secondary and Total 3-70 Stress Intensity Evaluation (Sleeve) 3.4.4-4 Criteria for Primary Plus Secondary and Total 3-71 Stress Intensity Evaluation (Tube) 3.4.7.1-1 Umbrella Pressure Loads for Design, 3-79 Faulted, and Test Conditions 3.4.7.1-2 Results of Primary Stress Intensity Evaluation 3-81 (Upper Hybrid Expansion Joint) Primary Membrane Stress Intensity, Pm i
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viii 4680M:49/111187-9
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I LIST OF TABLES'(Continued) Table' Tltie. Page N /b 3.4.7.'l-3 Results of Pr.imary Stress Intensity, Evaluation . 3-82
'(Upper Hybrid Expansion Joint) ,
} Primary Membrane Plus Bending Stress Intensity, Pg+P' b 3.4.7.2-1 Pressure and Temperature Loadings for Maximum 3-83 l Range of Stress Intensity and< Fatigue Evaluations 3.4.7.2-2 ,Results of Maximum Range of Stress Intensity 3 a5 Evaluation (Upper Hybrid Expansion Joint) n
'3.4.7.3-1 Results of Fatigue Evaluation (Upper Hybrid . 3-87 Expanston Joint) 3.5.4-1 Regulatory Guide 1.121 Criteria ' 3 .
3.5 6.1-1 Results of Primary Stress Intensity Evaluation 3-99 (dower Joint) Primary Membrane Stress Intensity, P 3.5.6.1-2 Results of Primary Stress Intensity Evaluation 3-100 (Lower Joint) Primary Membrane Plus Bending Stress. Intensity, P( + Pb 3.5.6.2-1 Results of Maximum Range of' Stress Intensity 3-102 Evaluation (Lower Joint) 3.5.7-1 Results of Maximum Range of Stress Intensity- 3-104
<. Evaluation. Axial Tube Lockup 3.5.7-2 Results of Fatigue Evaluation. Axial Tube Lockup 3-105 ix 4680M:49/110387-10 G j
- LIST OF TABLES (Continued)
Table Title Page 3.5.9-1 Sleeving Parameters Example Under Normal 3-110 Conditions (One Sleeve Per Tube) 3.5.9-2. Sleeving Parameters Example Under Normal 3-112 Conditions (Two Sleeves Per Tube) 4.0-1 Sleeve Process Sequence Summary 4-2 7.3-1 Estimate of Radioactive Concentration in 7-4 Water per Tuba Honed (Typical) t , . 1 I i x 4680M:49/110387-11
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,' Fiqure ' Tit 1e Page a 2.2-1 Sleeving Boundary ( .3a ,c.e Sleeves 2-2 m
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, 3;2-1 . Installed Sleeve with Hybrid Expansion- 3-3
'Uppe'r Joint Configuration:
3.2-2' Sleevr Lower , Joint Configuration 3-5 3.3.2 SCC' Growth Rate for C-rings (150 percent'YS and- 3-11 TLT) in 10 percent NaOH 3.3.2-2 Light Photo micrographs illustrating IGA'After. ~ $12 5000 Hours Exposure of Alloy 600 and 690 C-Rings to 10% Na0X'at 332*C (650*F) 3.3.2-3 SCC Depth.for C-Rings (150 percent YS) in. 3-15' 1 8' percent Na 50 2 4 3,3.2-4 Reverse U-bend Tests at 360*C (680*F') 3-16 3.3.3-1 Location'and Relative Magnitude of Residual 3-19 Stresses Induced by Expansion 3.3.3-2 Schematic of HEJ Section of Sleeve 3-21 3.3.3-3 Residual Stresses Determined By Corrosion Tests 3-23 in MgCl2 (Stainless Steel) or Polythionic Acid (Alloy 600) 3,3.3-4 Results of C-Ring Tests of Type 304 Heat 3-24 No. 605947 in Bolling MgCl 2 xi
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4680M:49/110387-12
LIST OF FIGURES (Continued) _; Figure Title Pace 3.3.3-5 Axial Residual Stresses in Tube / Sleeve Assembly 3-29 at a Depth of 0.001 2.0.0004 in. at Five locations Along Length of Transition 3.3.3-6 Circumferential Residual Stresses in Tube / Sleeve 3-30 Assembly at Depth of 0.001 1 0004 in, at Five Locations Along Length of Transition 3.3.4.1-1 Lower Joint As-rolled Test Specimen 3-36 3.3.5.1-1 Hybrid Expansion Joint (HEJ) Test Specimen 3-45 I 3.3.5.1-2 HEJ Specimens for the Reverse Pressure Tests 3-47 3.3.6.1-1 Fixed / Fixed Mockup - HEJ 3-61 3.4.2-1 Hybrid Expansion Upper Joint / Roll Expanded Lower Joint Sleeve Configuration 3-66 - 3.5.4-1 Application of Plugging Limits 3-96
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6.1-1 Absolute Eddy Current Signals at 6-3 400 kHz (Front and Rear Colls) 6.1-2 [ l a,c.e Calibration Curve 6-5 6.1-3 Eddy Current Signals from the ASTM Standard, 6-7 Machined on the Sleeve 0.D. of the Sleeve / Tube Assembly Without Expansion ( Cross Hound Coil Probe ) - xil 4680M:49/110387-13
s 4a. 1. g , yd ' * .1 : LIST OF FIGURES (Continued)' S g z. /Fiqure Title ~ Page. !E. 6.1-4 Eddy Current Signals from the ASTM Standard... '6-8 Machined on the Tube 0.0. of the. Sleeve / Tube l Assembly Without Expansion (' Cross Wound Coll i Probe-) t
.c 6.1-5 Eddy Current Signal's from the Expansion Transition 6-9 Region of the Sleeve / Tube Assembly (Cross Wound Coll Probe )
.y 6 .1 '-6 Eddy Current Calibration Curve for ASME Tube. 6-10 a
~ Standard at [ J .c.e and a Mix Using the Cross Wound Coii Probe 6 1-7 Eddy Current Signal from a 20 Percent Deep Hole, ~6-11:
Half the Volume of ASTM Standard. Machined'on the Sleeve 0.0 in the Expansion Transition Region.of the Sleeve / Tube Assembly (Cross Wound Coil Probe) t 6.1-8 Eddy Current Signal from a 40 Percent ASTM 6-12 l: ' Standard, Machined on the Tube 0.0. In the Expansion Transition Region of the Sleeve / Tube Assembly (Cross Wound Coil Probe) 4 i 6.1-9 Eddy Current Response of the ASTM Tube Standard 6-13 j at the End of the Sleeve Using the Cross Wound ) ? Coil Probe and Multifrequency Combination l 1 xiii 4680M:49/110387-14 g
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l.0 ' INTRODUCTION The document herein contains the necessary technical information to support
, licensing of the sleeving repair process as applied to the Kewaunee (WPS)
-Model 51 steam generators. As a result of extensive development programs in steam generator repair, Westinghouse has developed the capability to restore degraded steam generator. tubes by means of a sleeve.
To date, approximately 22,000 steam generator tubes at six operating nuclear power plants world-wide have been successfully sleeved, tested, and returned to service by Westinghouse. Both mechanical-joint and brazed-joint sleeves ~of Alloy 600, 690, and_ bimetallic 625 and 690 have been installed by a variety of-techniques - hands-on (manual). installation, Coordinate Transport (CT) system installation, and Remotely Operated Service Arm (ROSA) robotic installation.
, Westinghouse sleeving programs have been successfully implemented after , _ approval by licensing authorities in the U.S. (NRC - Nuclear Regulatory Commission), Sweden (SKI - Swedish Nuclear Power Inspectorate), and Japan (MITI - Japanese Ministry-of International Trade and Industry).
The sleeving technology was originally developed to sleeve degraded tubes
~(including leakers) in Westinghouse Model 27 series steam generators. A process and a remote sleeve delivery system (CT) were subsequently developed and adapted to Westinghouse Model 44 series steam generators in large scale programs at two operating plants. This technology has also been modified to facilitate installation of sleeves in a' plant with non-Westinghouse steam generators. -
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1 l 4680M:49/110387-15 1-1 1 e
2.0 SLEEVING OBJECTIVES AND BOUNDARIES 2.1 OBJECTIVES Kewaunee (WPS) is a Westinghouse-designed 2 loop pressurized water reactor rated at 1650 MWt. The unit utilizes two vertical U-tube steam generators. The steam generators are Westinghouse Model 51 Series containing heat transfer tubes with dimensions of 0.875 inch nominal OD by 0.050 inch nominal wall thickness. The sleeving concept and design are based on observations to date that the tube degradation due to operating environmental conditions has occurred near the tubesheet areas of the tube bundle. The sleeve has been designed to span the degraded region in order to maintain these tubes in service. The sleeving program has two primary objectives: 3fl
- 1. To sleeve tubes in the region of known or potential _ tube degradation. ;
- 2. To minimize the radiation exposure to all working personnel (ALARA) 2.2 SLEEVING BOUNDARY Tubes to be sleeved will be selected by radial location, tooling access (due to channel head geometric constraints), and eddy current indication elevations and size. An axial elevation tolerance of one inch will be remployed to allow for any potential eddy current testing position indication inaccuracies and degradation growth. Tube location on the tubesheet face, sleeve length, tooling dimensions, and tooling access permitted by channelhead bowl geometry define the sleeving boundaries. Figure 2.2-1 shows estimated radial sleeving boundaries for ( Ja c,e sleeves as determined by a geometric radius computed from the channelhead surface-to-tubesheet primary face clearance distance minus the tooling clearance distance. (The actual "as is" bowl geometry will be slightly different in certain areas.) These are the sleeving boundaries for a generic Westinghouse series 51 steam generator and represents the maximum sleeving potential with a [ ]a,c.e sleeves.
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- Y y Tubes within'fhe sleeving boundary that are degraded'beyond the plugging limit
]"*C sleeve er , but not within the axial restrictions of the [ -
not~within the radial sleeving boundary will'be plugged. The actual sleevable
. region may be modified based on tool length or other variables.
-The' actual tube plugging / sleeving map'for each steam generator will be provided as p:rt of the software d' deliverables at the conclusion of the sleeving effort.. .
The specific tubes to be sleeved in each steam generator will be determined; based on the following parameters: , a 1 1, No indications beyond an elevation spanned by the sleeve pressure boundary which are greater than the plugging limit. 1
- 2. Concurrence on the eddy current analysis of the' extent and location of the
' degradation.
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-2.3 REPORT APPLICABILITY
[ 3a .c.e 1 1 I 1 4680M:49/103187-18 { 2-3 1
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3.0 DESIGN
- 1 3.1 SLEEVE DESIGN DOCUMENTATION The Keaunee steam generators were built to the 1965 edition of Section III of the ASME Boiler and Pressure Vessel Code, however, the sleeves have been designed and analyzed to the 1983 edition of Section III of the Code through i the winter 1983 addenda as well as applicable Regulatory Guides. The associated materials and processes also meet the requirements of the Code.
The specific documentation applicable to this program are listed in Table ( 3.1-1. 1 : p 3.2 SLEEVE DESIGN DESCRIPTION n. The reference design of the sleeve, as installed, is illustrated in Figure' 3.2-1. [ , 3a ,c.e At the upper end, the sleeve configuration (see Figure 3.2-1) consists of a section which is [ Ja ,c.e This joint configuration is known as a hybrid expansion joint (HEJ). [ ga .c.e i In the process of sleeve length optimization and allowing for axial tolerance in locating defects by eddy current inspection, the guideline was the lower
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most elevation of the upper joint's hard roll region is to be positioned a i minimum of 1 inch above the degraded area of the tube. 4680M: 49/103187-!9 3-1
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W 3 y TABLE-3.1-l' ASME CODE AND REGULATORY REQUIREMENTS Item Applicable Criteria Reautrement Sleeve'DesignL .Section III N8-3200, Analysis
,. NS-3300,. Wall. Thick-~ j t
ness. Operating Requirements Analysis Conditions-J
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Reg. GulJe 1.83 1 S/G Tubing Inspec-tibility l keg. Guide 1.12) . Pluggirig Margin a Sleeve Material Section 11 Material Composition - e ~i Section III NB-2000, Identifica- .,.
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tion, Tests and j Examinations. i Code Case N-20 Mechanical Proper-ties . i 1 Sleeve Joint 10CFR100 Plant Total Primary-Secondary Leak Rate' 1 I Technical Specifications Plant Leak Rate l l 1 4680M:49/1031.87-20 3-2 I- ; 17
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1 Figure 3.2-1 - Installed Sleeve with Hybrid Expansion Upper Joint Configuration l M 3-3
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k At the lower end, the sleeve configuration (Figure 3.2-2) consists' of arsection whichisi . Ja,c,e The lower end of the sleeve has a preformed section to facilitate the seal formation and to reduce residual stresses in the sleeve. 1 The sleeve, after installation, extends above the top of the tubesheet and i spans the degraded region of the original tube. Its length is controlled by- j the insertion clearance between the channel head inside surface and the-primary side of the tubesheet, and the tube -degradation location above the'.tubesheet. The remaining design parameters such as wall thickness and material are selected to enhance design margins and corrosion resistance and/or to meet ASME .. Boiler and Pressure Vessel Code requirements. The upper joint is located so as I to provide a length of free sleeve above it. This length is added so that if . in the unlikely event the existing tube were to become severed just above the upper edge of the mechanical joint, the tube would be restrained by the sleeve J knd lateral and axial motion, .and subsequent leakage would be limited. Restrictied lateral motion would also protect adjacent tubes from impact by the severed tube. The upper end of the sleeve is tapered in the' thickness to reduce the effect of double wall in eddy current signal iriterpretation. To minimize stress concentrations and enhance inspectability in the area of the upper expanded region, [
),a,c,e,f i
The sleeve material, thermally treated Alloy 690, is selected to provide - additional resistance to stress corrosion cracking. (See Section 3.3.2 for l further details on the selection of thermally treated Alloy 690). ' 4680M:49/111187-22 3-4
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3.3 DESIGN VERIFICATION: TEST PROGRAMS 3.3.1 DESIGN VERIFICATION TEST PROGRAM
SUMMARY
The following sections describe the material and design verift:ation test ' programs. The purpose of these programs is to verify the ability of the l sleeve concept to produce a sleeve capable of spanning a degraded. region in a steam generator tube and maintain the steam generator tubing primary-to-secondary pressure boundary under normal and accident conditions. This i program includes assessment of the structural integrity and corrosion
]
resistance of sleeved tubes. 1 A data base exists from previous test programs which o rifies the adequacy of the sleeve design and process. The results of much of tuls testing is I directly apclicable to the present sleeving program. The sleeve material is a' Ailoy 690 (UNS 066900) manufactured to the requirements of ASME 58-163 with, supplemental requirements of Code Case N-20. The material has been thermally j treated (TT) to enhance its resistance to corrosion in steam generator primary , water and secondary-side water environments. This TT material has been used -
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in previous sleeving programs. l Most previous testing of the sleeve design has been for sleeves to be installed into Model 44 steam generators. However, the standardized sleeve may be installed in either Model 44 or 51 steam generators. The installation j of the sleeves by the combination of [ 3a ,c.e j3 the same as that verified and used in previous sleeving programs. In i addition, the operating cc,nditions are cimilar for sleeves in the Model 44 and 51 steam generators. Thus, the results of the earlier testing programs are considered to be applicable to Model 44 and 51 steam generator sleeving programs. The objectives of the mechanical testing programs included: l Verify the leak resistance of the upper and lower sleeve to tube joints. l 4680M:49/10318T-24 3-6 i
l
- Verify the structural strength of the sleeved tube under normal and
! accident conditions. Verify the fatigue strength of the sleeved tube under transient loads considering the~ remaining design life objective of the reactor plant. 1
- Confirm capability for installation of sleeves in tubes with conditions '
such as deep secondary side hard sludge and tubesheet denting.
- Establish the process parameters required to achieve satisfactory installation and performance. These parameters are discussed in '
Section 4.6. The acceptance criteria used to evaluate the sleeve performance is leak rate based on the plant technical specifications. Over 100 test specimens were i Used in the various test programs to verify the design and to establish , process parameters. Testing encompassed static and cyclic pressures, temperatures, and loads. The testing also included evaluation of joints fabricated using Alloy 600 sleeves as well as Alloy 690 sleeves in Alloy 600 tubes. While the bulk of the original qualification data is centered on Alicy 600 sleeves', a series of verification tests were run using Alloy 690 sleeves to demonstrate the effectiveness of the joint formation process and design with either material. Additionally an engineering evaluation of those properties which would affect joint performance was made and di-sclosed no areas which would result in a change of joint performance. The sections that follow describe those portions of the corrosion (sections 3.3.2-3.3.3) and mechanical (sections 3.3.4-3.3.6) verification programs that are relevant to this sleeving program. 3.3.2 CORROSION AND METALLURGICAL EVALUATION The objectives of the corrosion evaluations'are (1) to verify that thermally treated Alloy 690 is a suitable material for use in steam generator e9vironments and (2) to verify that sleeving does not have a detrimental effect on the serviceability of the existing tube or the sleeve components. The material of construction for the steam generator tubes of the Westinghouse 4E50M:49/110387-25 3-7
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design, including the steam generators at the Kewaunee site, is Alloy 600 in the mill annea',ed condition. Alloy 600 is a high nickel austenitic alloy that is nominally 72 percent nickel, 14-17 percent chromium, and 6-10 percent iron. The sleeving material proposed for sleeving the Kewaunee steam generators is Alloy 690 in the thermal treated (TT) condition. Alloy 690 is also a high .tickel austenitic material but contains a higher chromium content a.nd a correspondingly lower nickel content and has a nominal composition of 50 percent nickel, 30 percent chromium,. and 9 percent iron. Alloy 690 TT is recommended in lieu of Alloy 600 MA or Alloy 600 TT. , Laboratory testing has shown the Alloy 690 TT to have a resistance to corrosion in steam generator environments that is equal or better than Alloy 600 in either heat treated condition. The higher chromium content of Alloy 690 is believed to be responsible for this enhanced corrosion resistance. In addition, the alloy is thermally treated to further enhance its stress corrosion cracking resistance properties. .- j i Alloy 690 TT is the current tubing material of construction recommended by j Westinghouse for steam generator applications. - l The stress corrosion cracking performance of thermally treated Alloys 600 and - 69C in both off-chemistry secondary side and primary side environments has been extensively investigated. Results have continually demonstrated the additional stress corrosion cracking resistance of thermally-treated Alloys 600 and 690 as compared to mill annealed Alloy 600 material. Direct comparison of thermally treated Alloys 600 and 690 has further indicated an additional margin of SCC resistance for thermally treated Alloy 690. (Table 3.3.2-1). The caustic SCC performance of mill annealed and thermally treated Alloys 600 and 690 were evaluated in a 10 percent NaOH solution as a function of temperature from 288'C to 343*C. Since the test data were obtained over various exposure intervals ranging from 2000 to 8000 hours, the test data were - normalized in terms of average crack growth rate determined from destructive examination of the C-ring test specimens. No attempt was made to distinguish ' between initiation and propagation rates. 4680H:49/103187-26 3-8 w_.. -
I Table 3.3.2-1
SUMMARY
OF CORROSION COMPARISON DATA FOR THERMALLY TREATED ALLOYS 600 AND 690
]
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- 1. Thermally treated Alloy 600 tubing exhibits enhanced SCC and IGA l resistance in both secondary-side and primary-side environments when compared to the mill annealed condition, i l
- 2. Thermally treated Alloy 690 tubing exhibits additional SCC resistance compared to thermal treated Alloy 600 in caustic, acid sulfate, and ,j primary water environments.
- 3. The alloy composition of Alloy 690 along with a thermal treatment prov' ides I additional resistance to caustic induced IGA. ,
- 4. The addit' ion of 10 percent CuO to a'10 percent deaerated NaOH environment reduces the SCC resistance of both thermal treated Alloys 600 and 690.
Lower concentrations of either CuO or NaOH had no effect, nor did additions of Fe34 0 and SiO2 '
- 5. Alloy 690 is less susceptible to sensitization than Alloy 600.
A m' 4680M:49/103187-27 3-9
=
- _ _ _ _ _ _ - _ _ _ _ _ - l
i The crack growth rates presented in Figure 3.3.2-1 indicate that thermally treated Alloys 600 and 690 have enhanced caustic SCC resistance compared to that of Alloy 600 in the mill annealed condition. The performance of thermally treated Alloys 600 and 690 are approximately equal at temperatures of 316*C and below. At 332*C and 343*C, the additional SCC resistance of ~ thermally treated Inconel Alloy 690 is observed. In all instances the SCC morphology was intergranular in nature. The enhanced performance of thermatly treated Alloy 690 at higher temperatures is a result of a lesser temperature dependency. j i I C-ring specimens were tested in 10 percent NaOH solution at 332*C to index the relative intergranular attack (IGA) resistance of Alloys 600 and 690. , Comparison of the IGA morphology for these C-rings stressed to 150 precent of
]
the 0.2 percent yield strength is presented in Figure 3.3.2-2. Mill annealed , Alloy 600 is characterized by branching intergranular SCC extending from a' 200M front of uniform IGA. Thermally treated Alloy 600 exhibited less SCC , i and IGA limited to less than a few grains deep. Thermally treated Alloy 690 j exhibited no SCC and only occasional areas of intergranular oxide penetrations j that were.less than a grain deep. ; 1 The enhancement in IGA resistance can be attributed to two factors; heat - treatment ano alloy ' composition. A characteristic of mill annealed Alloy 600 C-rings exposed to a deaerated sodium hydroxide environment is the formation of intergranular SCC with uniform grain boundary corrosion (ICA). The relationship between SCC and IGA is not well established but it does appear that IGA occurs at low or 1, intermediate stress levels and at electrochemical potentials where the general corrosion resistance of the grain boundary area is a controlling factor. Thermal treatment of Alloy 600 provides additional grain boundary corrosion resistance 3.long with additional SCC resistance. In the case of Alloy 690, the composition provides an additional margin of resistance to IGA and the thermal treatment enhances the SCC resistance. The addition of oxidizing species to deaerated sodium hydroxide enviror.ments
- results in either a deleterious effect or no effect on the SCC resistance of thermally treated Alloys 600 and 690 and depends on the specific oxidizing '
4680M:49/103187-28 3-10 ww____._ __
0 H O i 5 a 3 N 0 0 1 5l n 8 i 0 ) I 4 T L 3 T d n a 0 ) S 3l Y
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8 - 1 0C 3* % 0 F 3( 5 1 (
- e r
( s e u g n r t i t u l 0 a 2 r R C a r0 3 e p r o f e0l - m e p8 t m e R a e l 0T 1 h t T 3 o w A TT MTT G r C 5 C h 7l 000 _- S t 5 009 0 w 666 l 0 - 3 o r 1 1 1 1 2 G Oel e 3 k) 0 3 c r0 . l 9 e r aH 5l 2 u g Cr/ 5 - - -
- _ - - __ i F
m
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if,'
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.. I Figure 3.3.2 2. Lignt Photormetograons illustratmg IGA after 5000 Hours Esposure of inconel Allov 600 and 690 C Rings to 10% NaOH at 3320C (6300F).
3-12 a a. s ( '. Il
specie and concentration (Table 3.3.2-2). The addition of 10 percent copper oxide to 10 percent Sodium hydroxide decreases the SCC resistance of. thermally treated Alloys 600 and 690, and also modifies the SCC morphology with the presence of transgranular cracks in the case of Alloy 690. The exact mechanism responsible for this change is not well understood, but may be related to an increase in the specimen potential that corresponds to a transpassive potential, which may result in an alternate cracking regime. The specific oxidizing specie and the ratio of oxidizing. Specie to sodium hydroxide concentration appear to effect the cracking mode. The apparent deleterious effect on SCC resistance is eliminated by lowering the copper oxioe or sodium hydroxide concentration. Mill annealed and thermally-treated Alloys 600 and 690 were also evaluated in 8 percent sodium sulfate environments. The room temperature pH value at the beginning of the test was adjusted using either sulfuric acid and ammonia.' As the pH is lowered, the SCC resistarice for mill annealed and thermally-treated Alloy 600 is decreased. In comparison, thermally treated Alloy 690 did not crack even at a pH of 2. the lowest tested (Figure 3.3.2-3). The primary water SCC t'est data are presented in Figure 3.3.2-4. For the beginning-of-fuel-cycle water chemistries, 10 of 10 specimens of mill annealed Alloy 600 exhibited SCC, while 1 of 10 specimens.of thermally-treated Alloy 600 had cracked in exposure times of about 12,000 hours. In the end-of-fuel-cycle water chemistries. 9 of 10 specimens of mill annealed Alloy 600
~
exhibited SCC, while 3 of 10 specimens of thermally-treated Alloy 600 had cracked. After 13,000 hours of testing, no SCC has been observed in the mill annealed or thermally-treated Alloy 690 specimens in either tmst environment. Continuing investigation of the SCC resistance of Alloys 600 and 690 in primary water environments has shown mill annealed Alloy 600 to be susceptible l to cracking at high levels of strain and/or stress. Thermal treatment of l Alloy 600 in the carbide precipitation region enhances its SCC resistance. The performance of Alloy 690, both mill annealed and thermally treated, demonstrates primary water SCC resistance and is oelieved to be due to alloy l composition. l 4680M:49/103187-31 . 3-13 l . i
I
- qfi'
. Table 3.3.2-2 EFFECT OF OXIDIZING SPECIES ON'THE. SCC SUSCEPTIBILITY 0F. THERMALLY TREATED ALLOY 600 AND 690 C-RINGS IN DEAERATED CAUSTIC i .
' ~
. Temperature Exposure Alloy Alloy'- J t Environment- '(*C) ~ Time-(Hr[) '600 TT 690 TT >
1
-.m l(l 10 Percent NaOH + 316' 4000 . Increased Increased .
10 Percent Cu0 Su s cept i b i l l_ ty* Su s,c e p t i b i l i ty *
'10 Percent NaOH'+ '332 2000. No effect ' No effect t' 1 Percent'Cu0 l' Percent NaOH +- 332' '4000 No effect No effect
~
1 Percent Cv0
- 1. '
F 10 Percent NaOH + 316 4000- No'effect No effect 10 Percent Fe34 0 10 Percent NaOH +' 316 4000 No effect No effect' 10 Percent.510 2
*Intergranular and transgranular SCC, i.-
l l l l
- j. 2- .4680M:49/103187-32 3-14 i I
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/ 0 3 NC DrC 4 .
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- u 08 2O l 0864 20 1 u 1 m m
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3.3.3 UPPER AND LOWER JOINTS All the cata presented in Section 3.3.2 relative to the corrosion and stress
, corrosion cracking resistance of thermally created Alloys 600 and 690 are
, applicable to the s~leeve. A similar corrosion verification test program has been conducted to demonstrate that the residual stresses induced in the parent tubing by the expansion process does not degrade the integrity of the tubing. Table 3.3.3-1 identifies the various tests which have been performed and the findings. A discussion of the significant tests follows. The expansion processes for both the lower and upper joints involve a combination of ( Ja ,c.e The stresses in the sleeve, based on tube to tubesheet data, should be as shown schematically at B and C on Figure 3.3.3-1, which are also judged acceptable, particularly in view of the corrosion rasistance of the thermally treated sleeve material. Stress levels in the Outer tube are also influenced by the expansion technique. For an outer tube expansion produced solely by [ Ja ,c.e The absolute magnitude of these stresses will depend on the specific diametral expansion.
~
~
Res' dual stresses on the OD and ID of surrogate Type 304 S.S. tubing which was expanded to varying amounts of (
)a,c.e 4680M:49/103187-35 3-17 '.
Table 3.3.3-1 DESIGN VERIFICATION TEST PROGRAM - CORROSION . ISSUE FINDINGS , _8 C e
- 1. CORROSION AND STRESS CORROSION
- 2. CORROSION AND STRESS CORROSION CRACKING OF LOWER SLEEVE JOINT
- 3. CORROSION AND STRESS CORROSION CRACKING OF UPPER JOINTS
- 4. CORROSION AND STRESS CORROSION CRACKING IN ANNULUS l
4680M:49/110387-36 1 3-18 !
l l e
*6d
.t O
(
~
Figure 3.3.3 Location and Relative Magnitude of Residual Stresses Induced by Expansion 3-19 L____________...__________________ "
l The specimen design is shown in Figure 3.3.3 2 and the test parameters are i { listed in Table 3.3.3-2. (
.)
a l l I
.(
, 1 3a ,c.e 1
1 C j 1 I \ l j a 3 .c.e No cracking 'was detected on the 00 surface of any specimen. These results indicate that the OD stresses are below the threshold required to cause cracking in the stainless steel'(less than 10 to 15 ksi). !
)
.j To summarize the results of this test- ;
i o [ l l
*\
l
)A,c,e I
4680M:49/110387-38 1 3-20 i
!1l!I!IilllI1lil> -
\l11
. 2 s
a*n~* 1 e a v i e l e S f o n i o t . , c e S - J . E i l f o i c t a m . e h c S 2 ' 3 3 . 3 e r u g i F C' I
~
a 3w (.F N ll\ll!!I i-!
m, , i Table 3.3.3-2 1
)
.1 RESIOUAL STUSSES AT [
'ja ,c.e )
a,c.e l I l i 1 1 l l I a i 1 l l l 4680M:49/103187-40 3-22 l 1
/
1 a.c.e l' l w-l 1 I i 1 i l { I; l 1 Figure 3.3.3 Residual Stresses Determined by Corrosion Tests in figCl2 (Stainless Steel) or Polythionic Acid (Inconel-60C ; . 3-23 !
N 1 4 I _ A.J .e I i l
.i :
1 j I J 1 1 I I Figure 3.3.3 Results of C-Ring Tests of Type 304 - Heat No. 605947 in Boiling MgCl 2 3-24 I 1 _
l i Table 3.3.3-3 RESULTS OF MAGNESIUM CHLORIDE TESTS AT [ j a,c.e 1,C , e i 4 o O 4680M:49/103187 43 3-25
Table 3.3.3-4 RESULTS OF MAGNESIUM CHLORIDE TESTS AT C l a,c.e a.c.e
- l 4680M:49/103187-44 3-26 l
n:
. I:
1 i f- ' o, .[ 3a .c.e.
... Confirmation that the 00; stresses on the_ parent ~ tubing are very: low tensile-or >
compressive:was obtained by X-ray diffraction analysis of an Alloy 600 tube expanded 30 1If. s'and by:the parting / layer removal' technique, as shown below: ' p/ - X-RAY ' RESIDUAL STEESS' MEASUREMENTS OF HEJ JOINT: CD OF TUBE. a.C,e 1 i (a) in.un-expanded tube above upper most transition (b) in un-expanded tube below lower most transition CONCLUSION: Residual stresses on OD of tube are compressive and results are consistent with MgCl test findings. 2 1 r 4680M:49/103187-45 3-27
sc. . . l; i
- p
.. }
1 The residual. stresses in a HEJ with an Alloy 600.HA tube / Alloy 690 TT' sleeve. were measured using the parting / layer removal technique. The conditions.of- [' the joint were.as follows: '~ a a
- o Nominal Tube 00 - 0.875 inch a,c.e
-o Nominal Sleeve'0D - 0.740 inch
'l The results of these tests are summarized in Figures 3.3.3-5 and 3.3.3.6.
These results show an excellent correlation with the MgCl 2 tests and the i results of the x-ray measurements. .The OD surface of the tube was-in compression in the axial direction at all locations along-the expansion transitions. The ID surface was in tensio'n in the- axial direction in the ] expansion transitions with the highest measured stress located at the
-hydraulic transition. In the circumferential direction, both surfaces of the ,
tube were generally in compression although low tensile ~stressec, about 5 ksi ' or lower, measured on'the tube ID in the fully hydraulic expanded region and- . on the OD in the unexpanded tube near the hydraulic expansion transition. The' OD surface of the sleev'e was also in compression in the axial and ,l circumferential directions except for one measurement that was in tension (about 5 ksi) in the axial direction in the [ l a,c,e . The ID. surface of the sleeve had areas where the stresses were as high as about.25 ksi in either the axial or circumferential
. direction. Residual stresses of this magnitude should not effect the special '
thermally treated sleeve material. l 4680ti:49/103187-46 3-28 l \ .-
. l lll!l l)lllllljl 11
.I 1llI 4 l1l1 e.
- c. - -
a
~
1, n i o , ft oi . s - h n t a pr eT D f e : t o a _ h yt l g b n me eL _ s sg An o el . vA e es . l n S o
/i .
et ba uc To L - n - . ie v si
. eF s
st ea . r t . Sn i l a4 u0 d0 . i0 s e R+ - l1 n~ a0 - i0 x A0 -
- L 5
3 3 3 e c r u , g t i 4 F 3-
,u s
~ s m
I w*r* u fllllll ! Ill rl
1 _ YM 3
am . .. , , u - - ,
.f.
dn:$ji g
; w ,
- y Polythj,onic' Acid l Tests ,
,~ .
f To confirin that the MgC1. 7 results, util.izing stainless . steel surrogate ce tubing, are applicible to Alloy 600 tubing, a' corresponding stress; indexing
... l -
test was performed with sensitized Alloy 600 tubing exposed to polythionic acid on the 10. The.results, indicated below support the MgCl2 findings. Material - Sensitized Alloy 600 tubing
.. ( r 4-
[. t j ac.e Summary - -The results of the various stress indexing tests indicate that the residual stress imposed on.the parent tubing by the HEJ process are of a sufficiently low magnitude as to not constitute a C6nc rn. [ 3acC,e , Primary Wa_ter Tests i I f
' Two tests to cenfirm the primary water stress corrosion cracking resistance of HEJ's have been conducted. A se::: mary of the results of these tests is as
. follows
'4680M:49/101187 49' 3-31 l
+ f( 3, .i s
+ ,
fQ ,
. +
c , ,
,. u b t _ , - ,jp j' , . pS0*f- Primary Water Tes ts i o .. <, -
, n !
.Materiali- a.. 'Allpy 600 mill . annealed. tubing with known' susceptibility to" *
. primary water. stress corrosion cracking. j gc
.b. Allo'y'600 special' thermal.ly,treateo' sleeves.
'l'f i
. .j Expanston. Matrix:
a,c,e a
. Number,of
- Specimens. t
.i
- 1 1
4 1 a 4
-1 3
,t
,i \
4 *Not within the' normal expansion ranges f$r HEJ' fieu installation. Total. Expansion, AD, inch - [ J A 'C
-l l dR Test Eriviror'me'nti 1 '!
.4
=
Temperature: 680*F '
. Pressure: Primary side - 2850.psig Secondary Side - 1450 psig ,
Chemi3try: Primary Side - Hydrogenated Pure water . Secondary Side Pure water i
~
Results: 2000 hour exposure with no primary to secondary leakage. Destructive examination detected i:o tube wall degradation. I 750*F Steam Tests: Material - a. Alloy 600 mill annealed tubing with knewn susceptibility to - primary and pure water.
- b. Alloy 600 special thermally treated sleeves. '
4680M:49/110387-50 3 m
%lQ %- ,
y
.o- ,
- w. ,
'rI F:i ,ry( , ,
q t
' Expansion' Matrix:
a .c,e . p:' . ; l --,s
; ,. x:14 umber of ?
- - Soecimens
'2 y w 2 c2 N *Not withi.n. normal expansion ranges for HEf field installation. ,
4 JNOTE Total .. E x pan s ion ', '[
,a,c.e e
Yast Environment: 1emperatura: ~750*F Pressure: Secondary and Primary at the same_ pressure 7: Chenti stry: Hydrogenated pure water. v
. ,4 Results: 17C0 hour exposure with no degrad& tion of tube or sleeve defect by 4- NDE including ID ECT and 00 UT or by tiestrui;tive examination.
In addition, both temperature and stress influence'the time required to initiate primary water stress corrosior.. cracking (PWSCC). Calculations have been made using an equation suggested by the Srookhaven National LaboratoryI } For the prediction of PHSCC. [ )
)% cA
- 1) R. B6ndy and D. van Rooyen, A Model for Predicting the Initiation and Propagation of Stress Corrosion Cracking of Alloy 600 in High Temperature Water.
'4680M:49/110387-51 3-33 m
~-
~; 4 O aos m ,
' * ;: t , , ,
2 h n. q ,
.J'.
~
$a. 'o: For(MA'. Alloy 60d-linPrimary. Water:
4 cv . -
- a,cie m ,
J 1-. ; ; i. , f..
- 3. . .
.4 Y
a f ' ( el
-i , .o for Typical Primary Temperature conditions:
a,c,e-(
-Pressure Total.
Residual (Hoop) (Hoop)' , Temp. Stress Stress Stress
~ Location- "K ksi ksi ks!
-a , c . e Pard-roll transition HEJ joint Postulation of PHSCC at the HEJ vs Hard Roll Transition:
a,c,e o The time to initiate PHSCC.at the HEJ is calculated to be a factor of ( . j a c.e 4680M:49/103187-52 a 3-34 y, l :
. n.
A, ;
, 'I Q
~
, , 3.3.4 TEST PROGRAM FOR;THE LOWER JOINT m
3.3.4;1' DESCRIPTION OF LOWER JOINT. TEST SPECIMENS The-tube /tubesheet mockup was manufactured so that.it was representative of-
~
4 4
.r the' partially rolled tube to.tubesheet joint (Figure 3.3.4.1-1) of.the'model 44/51 steam ~ generators. The'Kewaunee steam generator tubes are partial. depth .l rolled:inside the tubesheet. Th'e formation of lower mechanical rolled joint' ' !
'of tube / sleeve is simulated by the mockup. The tube was examined with a 8 'C'*
fiberscope, [ 3 cleaned by swabbing, and % re-examined-with the fiberscope. Then the preformed sleeve.(made of Thermally.
, Treated Alloy 600 or 690) was inserted into the tube and the lower joint formed. [
' i' 3a ,c.e .
3.3.
4.2 DESCRIPTION
OF VERIFICATION TESTS FOR THE LOWER JOINT The as-fabricated specimens for the Model 44/51 (as' discussed in Section. 3.3.1 Model 51 parameters and conditions are similar to those of.Model 44
~
parameters and conditions) were tested in the sequence described below.- Note that the tests.of the Alloy 690 sleeve are similar to those performed on the Alloy 600' sleeve except that the steam Line Break (SLB) and Extended. Operation ,- Period (EOP) tests were not considered necessary based on previous l data.
- 1. . Initial leak test: The leak rate was determined at room temperature' ,
3110 psi and at 600*F, 1600 psi'. These tests established the leak rhte of the lower joint af ter it has been installed in the stealt generator and
.. prfor to long-term operation.
- 2. The specimens were fatigue loaded for 5000 cycles.
l
- 3. The specimens were temperature cycled for 25 cycles. 4 l
4680M:49/103187-53 - 3-35 N .
}
ti ,. 9 1
~
.. b c,e ,i j
l I) i i i l.: i l l Figure 3.3.4,1 Lower Joint As-Rolled Test Specimen 3-36
V
- 4. The specimens'were leak tested at 3110 psi room temperature and at 1600 (
psi 600*F. This established the leak rate after a simulation of 5 years
~ '
of normal operation (plant heatup/cooldown cycles) produced by steps 2 and 3. l l Several specimens were removed from this test sequence at this point and were subjected to the E0P Test. See Step 7, below. t
- 5. The specimesis were leak tested while being subjected to SLB conditions.
I
- 6. The specimens were leak tested as th Step I to determine the post-accident leak rate.
- 7. The E0P test was performed after Step 4 for three as-rolled specimens.
3.3.4.3 LEAK TEST ACCEPTANCE CRITERIA - Site specific or bounding analyses have been performed to determine the allowable leakage during normal operation and the limiting postulated accident condition. The leak rate criteria that have been established are based on Technical Specifications and Regulatory requirements. Table 3.3.4.3-1 shows tile leak rate criteria for the Kewaunee steam generators. These criteria can ; be compared to the actual leak test results to provide verification that the mechanical sleeve exhibits no leakage under what would be considered normal ) operating conditions and only slight leakage under the umbrella test conditiens used. It should be noted that any leakage experienced is well within the allowable limits. Leak rate measurement is based on counting the number of drops leaking during a 10-20 minute period. Conversion to = volumetric measurement is based on assuming 19.8 drops per milliliter. , 4680M:49/103187-55 3-37 ' __m_ _ - _ - _ _ . _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _
9 i I TABLE 3.3.4.3-1. ... g MAXIHUM ALLOWABLE-LEAK RATES FOR KEHAUNEE STEAM GENERATORS -
\
a Allowable Leak Allowable Leak-
, Condition Rate 4 Rate per. Sleeve *-
d ,e - W Normal .35 gpm Operation- (500 gpd) I
'[.
b Limiting Leak Rate Leak Rate'per Sleeve ; Postulated b,d,e Accident ' Condi, tion . , .
, (Steamline Break)
Based on [2000]d e sleeves.per steam generator.
+. Standard. Technical Specification Limit for i steam. generator.
++E [ ;
l i
') b , d , e The analysis assumes primary and secondary coolant initial inventories of IPCilgm and 0.lFC1/gm of Dose Equivalent I-131, respectively. In addition, as a result of the reactor trip, an todine spike is initiated I which increases the iodine appearance rate in the primary coolant to a
.value equal-to 500 times'the equilibrium appearance rate. .
l I r 1. 4680M:49/103187-56 3-38
k j? 3.3.4}4 RESULTS OF. VERIFICATION TESTS FOR' LOWER JOINT u It should be noted that in many cases reference is made to " Simulated"'
~
conditions. In fact these: test conditions simulate only one key aspect of operation. For example, in the case of the fatigue testing, 5000 cycles were used. This number does not represent the number of cycles expected in'one year, it actually represents the number of' expected yearly cycles multiplied. by a suitable factor to establish an accelerated test condition. On that basis the test results provide data which is conservative in nature and exceed the actual operating conditions. The other parameters associated with.the thermal-cycle test, for example the temperature ramp, hold time and temperature gradient, are accelerated to. achieve appropriate test results within an abbreviated time frame. Consequently the test results obtained and
~ discussed throughout the rest of this report are those of accelerated ,
conditions designed to test the sleeve at its endurance limit. Sleevin'g
- qualification tests demonstrate that'under extreme accelerated test conditions leakage is minimal so:that in the actual operating case the sleeves will l, perform within acceptable leakage margin. Additionally by using that same test series for all sleeve designs it is possible to measure' consistency in
~
- i. process modification and or small changes in the overall design to facilitate l
as assessment of their effect on total sleeve performance. , Reference is occasionally made to the " leakage-reducing" qualities of the mechanical joint design. This is in reference to the phenomena (observed in the test data) which shows'that as the mechanical joints operate, if they exhibited leakage at the outset of the test, the rate of leakage decreases gradually with operation, to zero in most cases. This characteristic has been observed consistently in all mechanical joint testing. Another consistent characteristic observed in the testing of mechanica.1 joints ; i l-is that the leakage, when observed, is generally higher at room temperature conditions and, as in the case of the leakage-reducing phenomena, decreases as. j the temperature is elevated. This characteristic has lead to the almost I 4680M:49/103187-57 3-39
.~
4
- 9 a-b:
y E g,
!k, exclusive:use of the room temperature hydrostatic. test inLthe process,.
4 tchling',. personnel, procedure. and: demonstration phases associated-with a plant 1 specific sleeving operation. The test results for1the Model 44/51 lower' joint specimens a're' presented-in Table 3.3,4.4-1. The specimens did not leak before or during fatigue-
-loading. After simulating five years of normal operation.due to [.
'3"'C All of~the three as-rolled specimens were leak-tight during the Extended Operating Period (EOP) test.
l
, For the Alloy'690. sleeve tests the following were noted: '
Specimens MS-2 (Alloy 690 Sleeve): Initial leak rates at all pressures - L and at normal. ope ~ rating pressure following thermal' cycling were [ 1 .
^*
\ l s ja,b,c.e ] i 1 'E i 1 l 1 I i t L* 4680M:49/110387-58 3-40
a n. I $
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b, f. .' s en . ; \;. l U. E 9
'M >
l i.g ag. h.. t
) 1 Sm .
M b O. S.
.5
.2 M
P
, W .
i
- f. ,
. p .
. = . on
>k e
$ .e5 g.
.. w . w a .m8
.se E
m EK e E M w b ' g 41
+
M W W 6 h so E s to t u S C e M v e
@ P D art ee
- W h b W e S
.ar N 4 O G **
e N P em w SmW =* N as- e h ) 3-41 D-
*e
la e r - f jj p
,,tts ,
- ., n- l
\ =
N. ' O 4 in g .p' e
- P
- '
1 l l 1
' den, M-
- b. '
1 N l O l
- q q
; a- . l e 8 1
1 0 *" u l
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- 3. 1 m i 3
a m M. te i e 9 en 8 8
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h 6
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. toe ma 1
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a k j e 8 3-43
r p , j t- ,
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~
Specimen MS-3( ' Alloy 690 Sleeve): (-
~
a b,c.e 3
-Specimen MS-7 (Alloy 690 Sleeve): (
i j a,b,c.e i 3.3.5' TEST PROGRAM FOR THE UPPER HYBRID EXPANSION JOINT (HEJ)' Thediscussioncontainedin'Section3.3.4.4isrelevanttotestingingeneIal and applies in the following tests. conducted on upper joints as well 1 3.3.
5.1 DESCRIPTION
OF THE UPPER HEJ TEST SPECIMENS' Two types of'HEJ test speci7 ens were fabricated for the Model 44 testing (
, 3*' 'C . The first type was a short specimen as shown in Figure 3.3.5.1-1. Some of these specimens were fitted with pots containing a hard sludge simulant to test the structural effects of sludge on the
~
joint. The only type of sludge simulated in this program was-hard sludge. Soft sludge effects were bounded by the hard sludge effects and by the out-of-iiludge conditions. [ , Ja ,b.c Leakage was collected and measured as it issued from the annulus between the tube and sleeve. This type of'
, specimen was used in the majority of the tests. '
~
The second type of test specimen was a modification of the first type. It was utilized in the reverse pressure tests, i.e., for LOCA and sec.ondary side 4680h:49/110387.-62 3-44
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.w Figure 3.3.5.1 Hybrid Expansion Joint Test Specimen (The Leak Path, if Any Leakage Exists, is
'- Shown by the Dotted Lines) a 1
3-45
1 hydrostatic pressure-tests. As shown in Figure 3.3.5.1-2, the specimen was modified by [ , e Ja ,b c The possible reverse cressure test leak path is shown in Figure 3.3.5.1-2. Only specimens like Figure 3.3.5.1-1 (excluding the sludge conditions) were used in the Alloy 690 HEJ specimen fabrication as the effects of sludge had been established in the earlier Model 44 tests. i 3.3.
5.2 DESCRIPTION
OF VERIFICATION TESTS FOR THE UPPER HEJ The verification test program for the HEJ was similar to that for the lower joint. The HEJ was subjected:to fatigue loading cycles and temperature cycles to i
' ~
simulate five years of normal operation and the leak rate was determined before'and after this simulated normal operation. For a number of the , specimens,'the leak rate was also determined as a fanction of static axial loads which were bounded by the fatigue load. It is important to note that the fatigue load used in testing was that which was caused by loading / unloading. Hence, it was judged necessary to determine that the leak rate at static and fatigue conditions were comparable. The upper HEJ specimens were also subjected to t'he loadings / deflections corresponding to a steam line break l- (SLB) accident and the leak rate was determined during and after this j simulated accident. The upper HEJ was also leak tested while being subjected to two reverse pressure conditions, a LOCA and a condition which simulated a secondary hydrostatic test. An extended operation period test was also j performed. 3.3.5.3 RESULTS OF VERIFICATION TESTS FOR THE UPPER HEJ The test results are presented in Tables 3.3.5.3-1 through 3.3.5.3-5. l i ) i 4680M:49/103187-64 3-46 1 ( .- i
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i Figure 3.3.5.1 HEJ Specimens for the Reverse Pressure Tests (The Leak Path, if Any Exists, is Shown by the Dotted Lines) 3-47
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TABLE 3.3.S.3-3 (Page 2 of 2) TEST RESULTS FOR HEJ'S FORMED IN SLUDGE (FATIGUE AND REVERSE PRESSURE TESTS INCL.) (CONT)
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.As.canibe.seen'from. Table 3.3.5.3-1, the HEJ's formed out-of-sludge, i.e., in alr', nad an' average initial leak rate of approximately [ ]b ca ..
ap the' normal' cprating. cond; tion- of 600*F and 1600 psi,. Af ter simulating five;yeacs of normal? operation due to 5000 fatigue cycles and 29 to 32
,' : temperature cycles, the' leak rate was' [ )b.c.e at ths normal operating condition. Furthermore, for the EOP test,'.1.e., after simulating thirty-five years of normal operation due to 209 temperature cycles. and a total of 35000 fatigue cicles, the leak rate was [ 1.b,c.e Table 3.3 5.3-2 contains. data for upper HEJ's formed out-of-sludge. It includes.the same basic-test data as Table 3.3.5.3-1,21.e. , initial leak rcte~
data. However -it includes static axial. load leak tests, SLB and reverse. pressure tests in place of the fatigue and E0P-tests included in Table 3.3.5.3 1. Five 'of the six specimens were leaktight at normal operating sconditions -curing the initial leak test. The leak rate during static axial sleeve loads Jbounded by the fatigue load and caused by normal operating conditions was measured for four out-of-sludge ~HEJs. [- ['C These 3ame four specimens were then ' subjected to the SLB temperature, pressure and axial load conditions. [ l _{ 3 , , )b,c.e The results for the post-SLB leak test, at the same temperature and pressure conditions, I were similar to the during-SLB results, [
)b,c.e The results for the out-of-sludge HEJ reverse pressure test are shown in Table l 3.3.5.3-2. For both the simulated LOCA and secondary side hydrostatic I pressure test the leak rate was zero for the two specimens tested. l The process used for forming HEJ's in sludge, in Tables 3.3.5.3-3 and i
3.3.5.3-4, was the reference process, per Table 4.0-1 except that the 4 l 4660M:49/110387-76 3-58
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1- j a,c.e The initial leak rate of the first group of upper HEJs formed .in sludge' w'as: f C
]b c.e at the normal operating condition as is shown -in Table 3c3.5.3-3. Only one specimen had a C j b,c.e After-exposure cif the speciaiens to five years of simulated normal operation due to-fatigue and. temperature cycling, the averagt. leak rate remained very low, C
l bc.e at the 600*F and 1600 psi condition. . The resblts:of the reverse pressure test for the in-sludge upper HEJs are also. shown in Tab?c 3.3.5.3-3. [
'Ja ,b,c It was alscr zero for the simulated secondary side hydrostatic .' pressure test.
Table 3.3,5.3-4 also contains data for HEJs formed in-sludge. It includes the same basic initial leak tests as Table 3.3.5.3-3. However. It includes axial load leak test and post-SLB leak tests in place of the fatigue and reverse pressure tests included in Table 3.3.5.1-2. .All of the four specimens were leaktight during the initial leak test, per Table 3.3.5.3-4. Two specimens did not leak at any static axial load and two others did not leek until a compressive load of 2950 lbs was reached. kowever, the two leak rates at 2950 lbs were low, ( l b,c.e for specimens Number PTSP-23 and PTSP-33, respectively. The average leak rate for the four specimens during the SLB test was ( 3a .C,e In general, the leak rates for static loads were approximately the same as for dynamic (fatigue) loads of the same magnitude. However, a specific set of specimens wes not subjected to both types of loads. l 4680M:49/103187-77 3-59
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), nh J r i .?
s. The test data generated for the ' Alloy 690 and Alloy 625/690 samples is presented in Table 3.3.5.3-5. The.following observations were noted: .i Specimen S-5 (Alloy 690): [ Ja ,b,c were four.d at initial . leak . testing at' room temperature (R.T.1. At 600*F, the leak rates reduced t significantly and remained below [ Ja ,b,c during a subsequent. thermal cycling test. This specimen was formed with a tube diametral; bulge that was smaller than will be used in the fiela. 1 1 3
. Specimens'S-8 (Alloy 690); B-4, B-6, and B-7 (Alloy 625/690 - 0.740 in. I Sleeve Dia.), and BA-ll (Alloy 625/690- 0.630' in. Sleeve Dia.): These n' ~ ' '
i
.five specimens all exhibited moderate to small or very small leaks, mostly -{
during the initial leak testing at R. T. In all cases, by the end of the testing, including thermal cycling and. fatigue in some cases, the leak, rates had reduced to zero (or near zero), illustrating the ieakage ] reducing characteristic of rolled joints. i Specimen SA-1 (Alloy 625/690, 0.630 Sleeve Dia.): This specimen exhibited 1 zero leak rate at initial testing, both R.T. and 600 F. Small leak rates were found at R.T. after fatigue testing; however, they reduced to very small values, less than 0.5 drops / min. after testing. This specimen
,j was formed with a tube diamatral bulge at the low end of the field accept 1nce range. j I
3.3.6 TEST PROGRAM FOR THE FIXED / FIXED HOCKUP 3.3.
6.1 DESCRIPTION
OF THE FIXED / FIXED MOCKUP The fixed / fixed full scale mockup is shown in Figure 3.3.6,1-1. This mockup simulated the section of the steam generator from the primary face of the l
< -i l; 4680M:49/103187-78 3-60 i
~'
l_
A c.e h Figure 3.3.6.1 Fixed-Fixed Mockup - HEJ (For the HEJ In-Situ Leak Tests. The Leak Path, if Any Exists, is Shown by the Dotted Lines) 3-61
s s
'l
'N-I I J ,
tubesheet to the first support plate. ,The bottom plate of the mockup (
^
represented the bottom of the tubesheet, the middle plate'. simulated the top of , j 1 the tubesheet.and the upper p, late simulated the first support plate. The- {
. tubes were rol1 expanded int'o the bottom plate to simulate the tube /tubesheet
.-l
- joint and into the upper plate to simulate a dented tube' condition at-the tube-
{ support plate. The term " fixed / fixed" was derived from the fact that the I
~
tubes were fixed at these two locations. There were thirty-two' tubes in two clusters-of sixteen. A sludge simulant composed of alumina was. formed around one cluster of. sixteen. Alloy 600 sleeves, thirty inches long, were installed in the' tubes by [ '
].a.c,e Each tube' was perforated between the upper. and lower joints to simulate tube degradation and thereby provide a primary-to-secondary leak path. End plugs were. welded 3
to the tubes to permit pressurization with water. No fixed / fixed mockup tests
]
were performed on the Alloy 690 samples based on the results of the earlie_r j , tests performed. 3.3'6.2 DESCRIPTION OF VERIFICATION TESTS FOR THE FIXED / FIXED MOCKUP 1 J l The fixed / fixed mockup was used first to verify the full length sleeve installation parameters and tooling. It was then used to measure the leak rate of the lower joint and upper HEJ. This leak rate was determined with the. 1 sleeve-installed in a tube fixed at the tubesheet and dented at the first support plate, i.e., for the fixed / fixed condition. 3.3.6.3 RESULTS OF VERIFICATION TESTS FOR THE FIXED / FIXED MOCKUP Table,3.3.6.3-1 contains leak test results recorded for full length sleeves formed and tested in-situ. In the fixed / fixed mockup, in-sludge and out-of-sludge. All of the room temperature initial leak tests produced ( 1 j .b,C a 1 4680M:49/110387-80 3-62 L
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,These initial leak' rate.results.were similar to the initial leak rate results in.which t'he short specimens were structurally unconstrained.during forming of ,
the upper HEL Therefore, it was concluded that the results of the other several-tests performed only on short specimens would be similar if.th'e test , had been performed in-situ, in the ftxed/ftxed mockup. During.the pre-test evaluation, it was determined th'at the fixed / fixed mockup' duplicated tho.most-stringent structural-loading conditions for sleeves. Therefore, it was l_ ' concluded that all'of the testing with short specimens was valid. 'Secause the model 44 loads envelope the mddel 51: loads, thisLtesting.'is considered applicable to model 51 units and consequently validates the results for.both ! units. l 3.3.7 EFFECTS OF SLEEVING ON TUBE-TO-TUBESHEET WELO The effect of hard rolling'the sleeve'over the tube-to-tubesheet weld was examined th the sleeving of 0.750 inch 00 tubes. Although the sleeve installation roll torque used in a 0.750 inch;00 tube is less than a .875 inch O tube, the radial forces transmitted to the weld are comparable. Evaluation
~
of the 0 750 inch tubes showed no. tearing or.other degrading effects on the
' weld after hard rolling. Therefore. no significant effect on the ,
I tube-to-tubesheet veld is expected for the largsr G.875 inch 00 tube configuration. l I 1 1 i 4680M:49/iO3187-82 3-64
a m
' a.'
~r ,
os a 'n' 3.4 = ANALYTICAL VERIFICATION
- 1. 3,
4.1 INTRODUCTION
This section contal'slthe n structural evaluation ofcthe sleeve and tube assembly with HEJ, sleeve' material Alloy 690 and sleeve length'( 'J ,c.e I a in relation to the requirements of the ASME LBoller and Pressure. Vessel Code,
.Section'III, Subsection NB, 1983 Edition (Reference 1)
The analyses include primary stress int'ensity' evaluations, maximum range of stress intensity evaluations,-and fatigue evaluations for various mechanical and thermal conditions which umbrella 'the loading conditions specified by the Westinghouse Equipment. Specification G-677031, Revision 4 (Reference'2). 3.4.2 COMPONENT DESCRIPTION The general configuration of the sleeve-tube assembly with HEJ is presented in Figure 3.4.2-1. The critical portions of the sleeve-tube assembly are two joints. the upper and lower Hybrid Expansion Joints (HEJ). and straight sections of the sleeve , and tube between the two joints. The finite element model developed contains both upper and lower joints. A detailed stress evaluation for the upper joint is addressed in this section. Structural analysis of the lower joint is i presented in Section 3.5. The tolerances used in developing the models were such that the maximum sleeve and tube outside diameters were evaluated in combination with-the minimum sleeve wall thickness. This allowed maximum I stress levels to be developed in the roll transition regions. 1
- 1) Sleeve Material Alloy 600 is considered in Section 3.5.
I l
)
4680M:49/103187-83 3-65 I
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i I Figure 3.4.2 Hybrid Expansion Upper Joint / Roll Expanded . Lower Joint Sleeve Configuration - 3-66 l-
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.3.4.3 MATERIAL PROPERTICS
~
I
; The sleeve. material is Alloy.690 described in ASME Code Case N-20
.(Reference 3). The tube material is 58-163 (Alloy 600).
l-F An air' gap.was included between the tube and sleeve below the HEJ-as well as. between thel tube and the tubesheet. Although this space may be. filled with secondary. fluid, assuming the physical properties of air for these elements.ls conservative for the thermal analysis. Primary. fluid physical properties were. used forLthe gap medium above the HEJ. All material properties used in the analyses were as specified in the ASME Boiler and Pressure. Vessel Code, Section III, Appendix 1 (Reference 4) and Code Cases-(Reference 3L . 3.4.4 CODE CRITERIA The ASME Code Stress Criteric which must be satisfied are given in Tables 3.4.4-1 through 3.4.4-4. 3.4.5 LOADING CONDITIONS EVALUATED
'The loading conditions are specified below:
- 1. Design conditions
" a. Primary side design conditions P - 2485 psig T - 650*F
- b. Secondary side design conditions P = 1085 psig ,
T - 600*F
- c. Maximum primary to secondary pressure differential - 1600 psig, T - 650*F
- 1) Sleeve material Alloy 600 is considered in Section 3.5.
4680M:49/103187-85 3-67 WG -
Table 3.4.4-1 CRITERIA FOR PRIMARY STRESS ' INTENSITY EVALUATION (SLEEVE) a,c,e
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1 1 I J l l 4680M:49/103187-86 3-68
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.s Table 3.4.4-2 CRITERIA FOR PRIMARY STRESS INTENSITY EVALUATION (TUBE) a,c.e I
I i I I i l l 4680M: 49/103187-87 l l 3-69 j
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TABLE 3'.4.'4-3: W
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, , CRITERIA'FOR PRIMARY PLUS SECONDARY' AND--TOTAL'5 TRESS INTENSITY EVALUATION ,
1 > (SLEEVE) a,c.e s
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v l l 1 l 46COM:49/103187-88 3-70 I
TABLE 3.4.4-4 ~ CRITERIA FOR PRIMARY PLUS SECONDARY AND TOTAL STRESS INTENSITY EVALUATION (TUBE) a,;,e
~ _,
e 4680M:49/103187-89 , 3-71
1 p., j/ ' :i- Let
+
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- d. "Hartmum secondary to primary pressure differential ~- 670 psig,
,T = 650'F
- 2. Full lloadJsteadyestateconditions'are:
Primary side pressure - 2235:psig
~
l 2 Hot' leg temperature - 616.8'F Cold leg temperature =l552.3*F Secondary side pressure - 705 psig Feedwater temperature - 427.3*F Steam temperature - 506.3*F Zero load reactor coolant temperature 547.0*F i Other operating conditions are specified in Tables 3.4.7.1-1 and ' 3.4.7.2-1. . l 3.4.6 METHODS OF ANALYSIS Structural analysis of the sleeve-tube assembly includes finite element model development, thermal.. pressure stress and thermal stress ~ calculations, primary - membrane'and primary membrane plus bending stress intensity evaluation, primary plus secondary stress intensity range evaluation, and fatigue ' evaluation for various mechanical and thermal conditions which umbrella the loading conditions specified by the appropriate Design and Equipment Specifications. Two computer programs, WECAN and HECEVAL, are used in structural analyses of the sleeved tubes. TheNECANprogram(ReferenceJ5)performsthermalandstressanalysesofthe structure. Pressure stress is calculated separately for a 1000 psi primary and a 1000 psi secondary pressure. The results of these " unit pressure" runs are then scaled to the actual primary side and secondary side pressures corresponding to the load conditions considered in order to determine the total pressure stress distribution. 1 l' . Thermal analysis provides the temperature distribution needed for thermal stress calculations. Thermal stress calculations are performed for fixed l l 4680M:49/103187-90 ~ 3-72 1
times under: thermal transients. These times for the total pressure and 3 thermal analysis are chosen for:the anticipated. maximum and minimum. total
^
stresses'in. critical regions of the structure.
?- Total-stress' distribution is determined by combining the pressure and thermal stress results, t
Total' stress calculations as well as stress evaluations are carried out by the . WECEVAL computer program (Reference 6). WECEVAL is a multi-purpose code which performs ASME Code, Section III,' Subsection NB stress evaluations. At any given point or'section of the model, the program WECEVAL is used to determine the total stress distribution per the Subsection NB requirements. That is, the total stress at a given cross-section through the thickness, so-called analysis section, ASN, is categorized into membrane, linear bending, and non-linear components which are compared to Subsection NB allowables. In { addition, complete transient histories at given locations on the model are l used to calculate the total cumulative fatigue usage factor per Code Paragraph " NB-3?l6.2. 3.4 6.1 MODEL DEVELOPMENT.
-l A finite element model was developed for evaluating the sleeve design. Some significant considerations in developing the model are:
- 1. The model has been divided in two parts: upper model and lower g model. Structural integrity of the whole model was provided by all l direction. coupling of the nodes along the upper model and lower model interface.
- 2. Mechanical roll fixities between the sleeve and tube at the hard roll regions were achieved by coupling the interface nodes in the radial direction. For conservatism, locations of contact in the
\rl- 1 ', i 1
'4680M:49/103187-91 1
3-73 i
.: l
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' sleeve-tube ' interfaces along the upper hard roll' region' contain elements which share nodes. This approximates a rigid fix by the
- t. rolling process involved. Additional axial coupling' was ~ effected also
- for the 'iower. sleeve-tube and tube-tubesheet interface nodes.
- 3. 'The. interface nodes along the upper and lower hydraulic expansion-
. regions of the HEJ were coupled in the radial direction for temperature and thermal stress runs.- In the cases when pressure may' penetrate into the interface, the interface nodes along there areas were disconnected for pressure stress runs.
- 4. By. varying the boundary conditions at a specified region of the model, conditions of either intact. tube or discontinuous tube were simulated. ;
The element types chosen for the finite element analysis were the following WECAN (Reference 5) elements:
,_ - a,c.e -
x 1 d All the element types are quadratic, having a node placed in the center of each surface in addition to nodes at each corner. 4680M:49/111187-92 3-74
;1 , .c=
J W 3 4.6.2- THERMAL-ANALYSIS The purpose of the thermal analysis is to provide the temperature distribution-needed for thermal stress evaluation.
- Thermal transient analyses were performed for the.following events:
Small step load increase Small step load decrease Large step load decrease Hot standby operations Loss of load Loss of power Loss of secondary flow Reactor trip from full power The plant heatup/cooldown, plant loading / unloading and steady fluctuation events were considered under thermal steady state conditions. The finite element-types chosen for the thermal analysis were [
),a.c.e In order to perform the WECAN thermal analysis, boundary conditions consisting of fluid temperatures and heat transfer coefficients (or film coefficients) for the corresponding element surfaces are necessary. The conditions considered in the thermal analysis are based on the following assumptions:
- The temperature induced stresses are most pronounced for sleeves in the hot leg (where the temperature difference between the primary and secondary fluids is a maximum) and therefore, only the hot leg i-sleeves were considered. This condition bounds the thermal stresses on the cold leg.
4680M:49/103187-93 3-75
l . p, ,K L .I , 4 The sleeves may be installed in nearly any tube-in-the generator. [ l Thus', to be conservative, it is assumed that the sleeve to be evaluated is sufficiently close to the periphery of the bundle that-- ..
- it experiences the water temperature exiting the downcomer.
I s Special- hydraulic and thermal analysis was performed to define the primary and. , secondary side fluid temperatures. and film coefficients as a function' of time. i Both boilin'g and convective heat transfer correlations were taken into l consideration. ! 3.4.6.3 ' STRESS ANALYSIS - ( - A WECAN (Reference 5) finite element model was used to determine the stress-1 levels in the tube / sleeve configuration. { Elements simulating the medium between the tube and the sleeve were considered as dumy elements. The element types employed were [ Jac.e Based on the results demonstrating the applicability of a linear elastic , analysis, thermally: induced and pressure induced stresses were calculated separately and then combined to determine the total' stress distribution using' .- i the WICEVAL computer program (Reference 6). ~ Pressure Stress Analysis-i
'For superposition. purposes, the WECAN model was used to determine stress.
distributions induced separately by a 1000 psi primary pressure and a 1000 psi
~ secondary pressure. The results of these " unit pressure" runs were then scaled .
to the actual primary side and secondary side pressures corresponding . l et i l L4680M:49/111187-94 3-76
M 1*. to the ' loading _ condition considered in order to determine the total _ pressure stress distribution. ' The two modeling considerations.In determining the unit pressure load stress
' distributions were' tube intact and tube discontinuous. Therefore, the following unit pressure loading conditions were evaluated to determine the maximum anticipated stress levels induced by primary and secondary pressures:
Primary pressure - tube intact Primary pressure - tube discontinuous Secondary pressure - tube intact Secondary pressure - tube discontinuous The end cap forces due'to the axial pressure stress induced in the tube away , from discontinuities were taken into consideration. Thermal Stress Analysis The WECAN model was used to determine the thermal stress levels in the tube / sleeve configuration that were induced by the temperature distribution calculated by the thermal analysis. Thermal stresses were determined for each. steady state solution as well as for the thermal transient solutions at those times during the thermal transient which were anticipated to be limiting from a stress standpoint. Combined Pressure Plus Thermal Stress Evaluation As mentioned previously.. total stress distributions were determined by combining the unit pressure and thermal stress results as follows: P ori ' total
- 1000 I ' unit primary pressure 4680M:49/103187-95 3-77 l
sec .
- 1000 unit secondary pressure 1
thermal . This procedure was performed with the program HECEVAL (Reference 6). Stress and Fatique Evaluation i Stress and fatigue evaluation were completed using the program WECEVAL-(Reference 6). The program HECEVAL performed primary stress intensity l evaluation, primary plus secondary stress intensity ringe evaluation, and fatigue evaluation of the sleeved tube assembly. Complete transient histories at given locations on the model were used to ! calculate the total cumulative fatigue usa,'e factor per Code Paragraph NB-3216.2. For the fatigue evaluation, the effect of local discontinuities f was considered. l 3.4.7 RESULTS OF ANALYSES Analyses were performed for both intact and discontinuous tubes. Design and operating transient parameters (pressure, temperature, etc.) were selected from the applicable Westinghouse Design Specifications for the Model 44 and 51 Series steam generators in such a manner as to be conservative in structural effect and frequency of occurrence. Fatigue and stress analyses of the sleeved tube assembly have been completed in accordance with the requirements of the ASME Boiler and Pressure Vessel Code, Section III. I 3.4.7.1 PRIMARY STRESS INTENSITY I I i The umbrella loads for the primary stress intensity evaluation are given in , l Table 3.4.7.1-1.
'l 4680M:49/103187-96 3-78 j i
i
TABLE 3.4.7.1-1 c. I-UMBRELLA PRrSSURE LOADS FOR I 1 DESIGN, FAULTED, AND TEST CONDITTONS a,C,e 1 l l l 1 l l 1 I 4680M:49/103187-98 I 3-79 (
.f' l
k-f. f[ 4 The resultsCof primary's' tress intensity evaluation for the analysis sections
- are summarized in Tables;3.4.7 1-2 and 3.4.-7.1-3. All primary ~ stress- ,
, intensities-for the sleeved tube assembly are well within allowable.ASME Code
- limits. .
TTheLiargest value of the ratio'" Calculated Stress Intensity / Allowable Stress.
~
Intensity".of [ . 3a ,b',c
~
!: 3.4.7.2 RANGE OF PRIMARY PLUS~ SECONDARY STRESS INTENSITIES { l Table 3.4.7.2-l?contains the pressure and-temperature loads for maximum range' .) of stress' intensity evaluations as well as~for fatigue evaluation. The { maximum range of stress intensity values for the sleeved tube assemblies are { summarized'in' Table 3.4.7.2-2. l
. i The requirementslof the ASME Code, Paragraph NS-3222.2, were met for all test cases'.
i 1 J I i 0 I 1 I l j l i i 4 I 4680M:49/103187-97 3-80 I L-
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t O E U F E R Y n U P R - o c S G A 55 50 05 0 5 5 0 5 5 G I M 37 80 68 6 5 3 F ( N T I 28 56 04 8 1 U 8 8 3 4 4 I A R 21 21 22 1 1 2 2 1
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/
9 g I e f f f ro a e y a T I n o o o oP yu L r d l e 4 D i b s s t dt a n r: H N r s s s s cl al ac eu b e m c o be 0 O u o o o eu i mt 8 C T L t L RF tl u r e Uo 6 $ SF T P S
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==.
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E f 3.4.7.3_ RANGE OF TOTAL STRESS INTENSITIES 4 iBased on th3' sleeve dekign criteria the fatigue analysis considered a design
~
life objectt'te of 40 years for the sleeved tube asseia511es. Tsbie 3.4.7.2-1, describes the umbreIla transient conditions used in the' fatigue analysis.
.Because of possible opening of the interface between the sleeve and the tube
- '~
along the hydraulic expa9sion regions, the maximum-fatigue strersgth reduct:lon
- g factor of'5.0 (NB-3222.4(3)) was applied in the radial direction at the " root" interface nodg.s c7 tre hard roll region. The results of the fatigue analysis for.the sleeved tube assemblies. are suminarized in Table 3.4.7.3-1.
All of the cumulative usage factors.are below the allowable value of 1.0 specified in the ASME Code. q 1 l
- I
. I
~I
.]
i l 4680M:49/103187-104 I 3-86 \ a
- c.
i -.
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.i j
'3.4.8_. REFERENCES.
1
'6 ff.
1 1. ASME-Boiler'and Pressure Vessel Code, Gection III, Subsection NBj, 1983-
..'l "
Edition, July 1 1983.- y
~
j
- 2. . Equipment. Specification G-677031, Westinghouse. Revision 4, March'20,. l
'1975, 3; ASME'Boller_an'd Pressure' Vessel Code, Code Cases. Case:N-20, 1983' Edition, July 1, 1983.
- 4. ASME Boiler and Pressure Vessel Code, Section III, Appendix l', 1983~
Edition, Julyzl, 1983. , j
- l 5 .~ WECAN, WAPPP and FIGURES II, F. JJ Bogden Editor, Second Edi. tion, May :
1981,~ Westinghouse Advanced System-Tech, ology, Pittsburgh, PA' 15235.
- 6. J. M. Hall, A. L. Thurman; "HECEVAL',:A Computer Code to Perform ASME 8PVC Evaluations'Using Finite Element Model Generated Stress States,"
Westinghouse, April, 1985.
- 1 1
1 1 I i : 1' l l l 4680M:49/103187-106 3-88 4 1 J
, 3 , 4 1
31 0 '3.5 SPECIAL' CONSIDERATIONS 3.5.1 FLOW SLOT HOURGLASSING y Along the. tube-lane, the tube support plate has several long rectangular flow slots that have the potential to deform'into an'" hourglass" shape with
'significant denting. The effect of flow-slot hourglassing is to move.the neighboring' tubes laterally'inward to.the tube' lane from their initial' positions. 'The maximum bending would occur.on the innermost row of tubes in the center of the flow slots.
3.5.1.1- EFFECT ON BURST STRENGTH
'The effect of bending. stresses on'the burst strength'of tubing has been studied. Both the axial: and circumferential crack configurations were investigated. .(
3a ,e,f 3.5.1.2 EFFECT ON STRESS CORROSION CRACKING (SCC) MARGIN Based on the results of a caustic corrosion test program on mill-annealed. tubing, the bending stress magnitude due to flow-slot hourglassing is judged
'to have only.a small effect, if any,- on the SCC resistance margins. Two'long term modular model boiler tests have been' conducted to address the effect of bending stressec on SCC. No' SCC or Inter Granular Attack (IGA) was detected by destructive examination. It is to be noted that thermally treated Alloy 600 and 690 have additlenal SCC resistance compared to the resistance of mill annealed Alloy 600. tubing.
3.5.1.3 EFFECT ON MAXIMUM RANGE OF STRESS INTENSITY AND FATIGUE USAGE FACTOR In addition to the above two considerations, one should also consider the effect of the hourglassing induced bending stresses on maximum range of stress intensity and fatigue usage factor of the sleeve. Taking into account the j" bourglassing induced bending stress along with the transient pressure and L l' 4680M:49/103187-107 3-89 l I E _ _
.i
- v. f .,
-~ thermal stress, the largest value of maximum stress intensity would be 59.70 KSI:(allowable 79.80 KSI), fatigue usage factor is negligible. .
3.5.2 , TUBE VIBRATION' ANALYSIS . Analytical assessments have been performed to predict nodal natural frequencies and related dynamic bending stresses attributed to flow-induced Vibration for sleeved tubes. The purpose of,the assessment was to evaluate the effect on the natural frequencies, amplitude of vibration, and bending stress due to installation of various lengths of sleeves. I
-Since the level of stress is significantly below the endurance limit for the tube materialJand higher natural frequencies result from the use of a sleeve / tube versus an unsleeved-tube, the sleeving modification does not ;
contribute'to cyclic fatigue. i 3.5.3 SLUDGE HEIGHT THERMAL EFFECTS h In general. with at least 2.0 inches of sludge, the tubeshee't is isotheraal at
~
the bulk temperature of the primary fluid. The net effect of the sludge is to , reduce tube /tubesheet thermal effects. 3.5.4 ALLOWABLE SLEEVE DEGRADATION
'3.5.4.1 MINIMUM REQUIRED SLEEVE THICKNESS q The minimum' required sleeve wall thickness, t , to sustain normal and r
accident condition loads is calculated in accordance with the guidelines of Regulatory Guide 1.121, as outlined in Table 3.5.4-1. In this evaluation, the surrounding tube is assumed to be completely degraded; that is, no design credit is taken for the residual strength of the tube. The sleeve material may be either thermally treated Alloy 600 or thermally i , treated Alloy 690. It has been shown that the mechanical properties of Alloy , 600 are very similar to those of Alloy 690. In particular, the yield strength l and ultimate strength are very similar. l l l 4680M;49/103187-108 3-90 l
l Table.3.5.4-1 REGilLATORY GUIDE 1.121 CRITERIA
- 1. Noimal_and Upset Condition Loadinas Normal Operations Criterion: Su 1 90 58 tri Loading: P - 2250 psia p
P - 720 psia AP = 1530 ,'st s Hence, miminum required sleeve wall thickness t, is OP . R' t ~~"I } 1"Ch r"5[-0,5f.P p +P)3 which is [ ] a,c.e percent of the nominal wall thickness. Upset Conditions
.J Criturion: S j- 39.59 ksi ,
P p e 2600 ps'a { P3 = 1035 psia AP - 1565 psi
. {
AP . R
"'C
Hence, t r *S y - 0.5 (Pp+P) =[ ] inch s which is [ Ja.c.e percent of the nontinal wall thickness. l
- 2. hccident Condition Loadincs
- a. LOCA + SSFj i l
l The major contribution of LOCA and SSE loads is the bending stresses j at the top tube support plate due to a combination of the support-I motion, inertial loadings, and the pressure differential across the ' tube U-bend resulting from the rarefaction wave during LOCA. Since the sleeve is located below the first support, the LOCA + SSE bending stresses in the sleeve are quite small. The governing event for the sleeve therefore is a postulated secondary side olowdown. 4680M:49/103187-109 3-91
pip <
~. ,
ifG > w.- 4i [. . K& 1
. Table-3.5.4-1 (cont.)
.b. FLB + SSE' S q
m. The maximum primary-to-secondary pressure differential.. occurs'during>' k' ,
~ a postulated feedline break (FLB) acci den tl. Aga , because of the sleeve location. .tk SSE bending stresses are smail:. Thus,.the~ <
governing stresses for the minimum wall thickness requirement are .
.the' pressure membrane stresses.
1, Criterion: P, i smaller of 0.75 u r 2.45,i.e. 63.4 ksi Loadings: Pp-2650psig ' Ps"0 AP - 2650 AP . R - Hence, t '" "I r 0.7 S uy 5U +;P) p 3 or, [ ) .
C. percent of. nominal wall.
[ The required sleeve' wall thickness is-[
-[
13C. l[ lC percent minus growth and uncertainty, f tould be the' plugging criteria with confirmation of. leak-before-break. A h -- [ . JC percent criteria would permit [ jac,e per cent for growth j l .and uncertainty. d
- 3. , Leak-Before-Break Verification ~
~
' The leak-before-break evaluation for the sleeve is based on leak rate and burst pressure test data obtained on 7/8 inch 00 x 0.050 inch wall and 11/16 inch OD x 0.040 inch wall cracked tubing with various amounts of uniform thinning simulated by machining on the tube 00. The margins to burst during a postulated SLB (Steamline Break Accident) condition are a "
[ function of the mean radius to thickness ratio, based on a maximum permissible leak rate.of-0.35 gpm due to a normal operating pressure . differential of 1530 psi. i L. 4680M:49/103187-110 3-92
i'
, t a; d- 4 2,
J- -Table ;3.5.4-1 (cont.i Lusing a'mean radius to thickness factor of-9.5 for1. the nominal'sle?ve;
' the current Technical Specifications, allowable a leak' rate of. 35 gpe, a SLB pressure differentia 1' of 2560' psi,' and:the nominal leakf and nominal
. burst curves,'a 29.8 percent margin exists between the burst crack length
'and the leak crack-length. For a sleeve thinned 51 percent-through wall over a 1.0 inch axial flength, a 24.8. percent margin to burst is
-demonstrated. 'Thus:the leak-before break behavior'is'corfirmed'for unthinned and~ thinned conditions.>
t,
'w e
m- , i 4680M:49/103187-111 3-95 n
t . Since 9egulatorjLGuide'l.121 15'to be' addressed, it is permissible to derive the allowable stress lim!!s based on expected' lower bound materia'l prcperties,
~
as opposed *o the. Code minimum values. Expected Strength properties.were
.obtained from statistical analyses of tensile test data of. actual production ,
tubing. These data were used for the lower tolerance limits of material. Lower tolerance ~~ limit, LTL, means'there is 95 percent of confidence that 95 percent of the sleeve / tubes will have strength greater than LTL. 3.5.4.2 DETERMINATION OF PLUGGING LIMITS The minimum acceptable wall thickness and other practices.in Regulatory Guide 1.121 are used to determine a plugging limit.for the sleeve. This Regulatory Guide was written to provide guidarice for the determination of a plugging limit for steam generator-tt.bes undergoing localized tube wall thinning and can be conservatively applied to sleeves. Tubes with sleeves which are 4 determined to have indication of degradation of the sleeve in excess of the plugging limit would have to be repaired or removed from service. As provided in paragraph C.2.b. of the Regulttory Guide, an additional thickness degradation allowance shculd-be factured into the minimum acceptat'le
~
tube wall thickness to establish the operational tube thickness acceptance for continued service. Paragraph C 3.f. of the Regulatory Guide provides that the basis used in setting tne operational degradation allowance include.the method and data used in predicting the continuing degradation and consideration of eddy current measurement errors and other significant eddy current testing parameters. l As outlined in Section 6.0 of this report, the capability of eddy current inspection of the sleeve and tube in the sleeve area has been demonstrated. The [ ]c e eddy current measurement uncertainty value of [ 3"' of the tube wall thickness is appropriate for use in the
-determination of the operational tube thickness acceptable for continued i serv)ce and thus determination of the plugging limit. ~l 4680M:49/103187-ll2 3-94 L_______---____ __
Paragraph C.3.f of the Reg. Guide specified that the basis used in setting the operational degradation analysis include the method and data used in predicting. the continuing degradation. To. develop a value for continuing degradation sleeve experience must be reviewed. No degradation has been detected to date. on Westinghouse designed sleeves and no sleeved tube has been removed from service due to degradation of any portion of the sleeve. This result would be expected due in part to the changes in the sleeve material relative to the tube and the lower heat flux due to the double wall in the sleeved region. It is the position of Westinghouse Electric that since no degradation has been detected in the sleeves, presently any allowance for continuing degradation [ ]c.e would be an arbitrary value not supported by the data and would represent a conversatism in addition to the safety factors implicit in the determination of minimum acceptable tube wall thickness using Reg. Guide ,
'.121.
I In summary, the operational sleeve thickness acceptable for continued service includes the minimum acceptable wall thickness ([ Ja,b,c of wall thickness, see Table 3.5.4-1), the combined allowance for eddy current uncertainty and
~
operational degradation ([ Ja.c of wall thickness as recommended by Westinghouse). These terms total to 59% resulting in a plugging limit as determined by Regulatory Guide 1.121 guidelines of 41% of the wall thickness. The plugging limit for the tube, where applicable as defined below is as specified in the Technical Specifications for the non-sleeved portions of the tube, currently 50% of the tube wa'i thickness. 3.5.4.3 APPLICATION OF PLUGGING LIMITS Sleeves or tubes which have eddy current indications of degradation in excess of the plugging limits must be repaired or plugged. Those portions of the tube and the sleeve (shown in Figure 3.5.4-1) for which indications of wall
~
degradation must be evaluated are summarized as follows: l 1 .
- 1. 4680M:49/111187-113 3-95
. - - - . ._- _ _ _ __ D
; ' ! Q,C,e 1
1 i i f I t i I i ( i i, l 4 l i t i 4 i
) I i
1 l' l
.I i !
t i i l'
]
1
'l i
i f l ! I i Figure 3.5.4-1 Application of Plugging Limits !
- l. 3-96 r __ ..
i
f 1 l'
- 1) Indications of, degradation in'the entire length of the sleeve must be
,; . . evaluated against the sleeve plugging limit. l t!
., 2) Indication of tube degradation of any type including a complete guillotine break in the tube between the bottom of the upper joint and the top of the lower roll expansion does not require th'at the tube be removed from' service.
'3)- The' tube plugging limit continues to apply to the portion of.the tube in the upper joint and in the lower roll expansion. As noted above the sleeve plugging _limir applies to these areas also.
- 4) The' tube' plugging limit continues to apply to that portion of the tube l4 above'the top of the upper-joint. ,
l .. 1 L l . y
'}l -'I 4680M:49/103187-115 3-97
o 3.5.5 'EFFECT OF TUBESHEET INTERACTION Since the pressurefis normally higher on the primary side of the tubesheet than on the secondary side, the tubesheet becomes concave upward. Under these { conditions, the tubes protruding from the top of'the tubesheet will fotate from the vertical. Thi; rotation develops' stresses in the sleeved tube v. assembly. Analysis performed showed that these stresses do not affect significantly the fatigue usage factors. I 3'.5.6 . STRUCTURAL ANALYSIS OF THE LOWER JOINT 3.5.6.1 Prima ~ry. Stress Intenstty The res'J1ts of primary stress Intensity evaluation for the analysis sections located at the lower.-joint are summarized in Tables 3.5.6.1-1 and 3.5.6.1-2. All primary stress intensities for'the sleeved tube assembly at the lower joint meet the ASME code limits. - 3.5.6.2 Range of Primary Plus Secondary Stress Intensities ~
' Primary plu's secondary stress at the Lower Joint are developed by the pressure acting on'the sleeve, tube and tubesheet ligament surfaces (primary stress),
and by thermal stress and deformations imposed by the tubesheet motion. (secondary stress). The tubesheet motion results from the primary and
;. secondary side pressure and interactions among the tubesheet, support ring, channel head, and the stub barrel. The worst case, tube intact, was analyzed. The maximum range of-stress intensity values for the sleeved tube assembly are summarized in Table 3.5.6.2-1.
3 i The requirements of the ASME Code, paragraph NB-3222.2 were satisfied. i 4683M:49/110387-1 3-98
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I 3.5.6,3 Range of Total Stress Intensities '1 The fatigue analysis considered a design life objective of 40 years for the sleeved tube assemblies. The maximum fatigue strength reduction facter of 5.0 was applied in the radial direction at the " root" interface nodes of the hard roll region. All of the cumulative usage factors are negligible, hence, they are below the allowable value of'I.0 specified in the ASME Code. O 4683M:49/110387-4 3-101
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qi f, 1 3.5.7 EFFECT OF AN AXIAL TUBE LOCK-UP ON FATIGUE USAGE FACTOR
.In this analysis, only one tube is corsidered to be locked-up at the first i tube support plate under.100 percent power conditions.
The following effects on'the stress components of the locked-up tube were analyzed: effect.of primary and secondary pressure stresses
- effect of thermal stresses in the assembly effect of tubesheet rotations
- effect of axial thermal displacements in tube, tube / sleeve, an'd wrapper /shell regions The effects of. pressure drops across the tubesheet and the tube support plates as well as the tubesheet-tube support plate assembly interactions were tak'en into account for central locked-up tubes while they were neglected for the outermost tubes. The results of maximum range of stress intensity and fatigue evaluations are given in Tables 3.5.7-1 and 3.5.7-2 For the central locked-up tubes, only the sleeve for the worst case, i.e.,
tube discontinuous, was considered. It is seen that the requirements of the ASME Code are satisfied for both outermost and central axi.al locked-up sleeved tubes. 3.5.8 Minimum Sleeve Wall Thickness Nominal and minimum sleeve wall thickness was analyzed. Taking into account plus [ 3"'C inches for corrosion /errosion, the recommended sleeve wall thickness is:
~ ~ ~~
Nominal Sleeve Wall Thickness Minimum Local Sleeve Wall Thickness 4683M:49/103187-6 3-103
e. e. c, a. I .
.I
_ S . S D OEE ITL TAB ALA RUN CO N LL O AL I CA T A U L A V E Y T I S N E I T N P S I E - U LM F - 1 S - BU OI
- S K AM S 7 E C WI EK
. RO L OX G LA N 5 T S E LM A 3 A R F B .
E' 0 TU s , L B f e A G L b T N A u A I T R AX t , M s o H I m r I X I e A t M D S u E O ' F T M F O AU OI LM S S UI EK T CX G _ L LA N _ U AM A S C R . E R S S U U O O U U N N I I T T T C A C N O A C C N T S S O N I I I I e D e D e T v - v v A E e e E e e E e C B e b B e b B e O U l u U l u U l L T S T T S T T S y2
w g
=. E _
G A S U R EO LT 0 0 0 0 0 BC N AA 1 1 1 1 1 O NF I O - T L A L U - A L P ~ 2 A V U -
- E K 7 C s E O e -
5 U L b s G u e 3 I E T b T S u E L A UT F t s T B o l A F L E m a
. T O A G r r I A e t S X S t n T A U e L Ol C U ER e e e e e S VO l l l l l E I T b b b b b R TC i i i i i AA g g g g g LF i i i i i U l l l l l M g g g g g U e e e e e C N N N N N S S U U O O U U
. N N I I T T T N N C O O A C C
, N T S S O N I I I I e D e D e
- T v v v A E e e E e e E e C B e b B e b B e O U l u U l u U l L T S T T S T T S
~ YZm
a. [ e 3.5 3 EVAlllATION OF OPERATION WITH FLOW EFFECTS SUBSEQUENT To SLEEVIN3 The most recent. Emergency Core Cooling System (ECCS) performance analysis, - i, completed for Kewaunee was .done to support operation'at. up to.10 percent ' equivalent steam generator tube plugging (SGTP). This analysis was not! ~~
-performed by Westinghouse. However, this analysis.and the corresponding non-LOCA evaluation'are considered applicable for thel steam generator sleeving; d program with a combination of plugging and sleeving flow restriction . equal te or less.than the restriction due to 10 per cent tube plugging. In addition, in support of the steam generator' sleeving program,' Westinghouse has performed an -
evaluation of selected LOCA and non-LOCA transients to demonstrate that use of-
' sleeves resulting 'in' a plugging equivalency of up to 10 per cent' will'notlhave -
an adverse affect on the' thermal-hydraulic' performance of the plant. For the ! accidents-as evaluated, the effect of a combination'of plugging and ' sleeving up l < to the equivalent.of 10 *per cent tube plugging would not be expected .to resdt . in any design or regulatory limit being exceeded. Thisresultwould'bethe: I
- same for fuel from any supplier for which a LOCA analysis with a basis of'10; percent tube plugging has acceptable results.
i j
.. i Since the fuel in the Kewsunee plant is from a-supplier other than d Westinghouse, the evaluation of the transients below vas based on the -
assumption of thermal hydraulic similarity to Westinghouse 14 x'14 Standard ; fuel. Wisconsin Public Service and the fuel supplier have performed an I evaluation of large break LOCA and other LOCA type transients with;a basis of' 10 percent tube plugging. The items listed below were evaluated fer a sleeving < and pl.ugging combination equivalent to 10 per cent tube plugging and the results indicated no adverse effects. Small Break LOCA Containment Integrity Short and Long Term Mass and Energy Releases Containment Integrity Main Steamline Break Reactor Blowdown Vessel and Loop Forces , Steam Generator Tube Rupture - Hot Leg Switchover Prevention of Potential Boron Precipitation + . 4683M:49/111187-9 3-106
~
l _ __o
3 .. lh cp , 4 L . . -l 1
- The effect of sleeving on the non-LOCA transient analyses and design trant.,ient evaluations has.been reviewed. ' Analyses of the level of sleaving and plugging E- E . discussed in this report have shown that the Reactor Coolant System (RCS) flow
. rate will' not be-less than the Thermal Design Flow rate. The. Thermal Design
~
'~
, Flow rate is the value. uset in~ the non-LOCA safety analyses and is designed to be less than the minimum RCS flow rate that eccurs.under normal. or degraded conditions. Since the reduced RCS flow rate is not less than the assumed flow.
rate'(Thermal- Design Flow), the non-LOCA safety analyses are bounded by the anticipated maximum amount of steam generator tube slesving ([ ]d.e sleeves per steam generator). Therefore, the steam generator sleeve installation up to the equivalent of 10 per cent plugging would not invalidate any iicn-LOCA safety analyses. Also, the design transients are established
' based on the Thermal' Design Flow and any combination of plugs and sleeves which does not rasult in an RCS flow rate less than Thermal Design Flow would not h0te an adverse effect on the evaluation of the design transtants. Any smaller number of sleeves would have less of an effect.
For the Series 51 steam generators in Kenunee,10 percent of the total tubes
.. < .(33SS tubes per S/0) equals 338 tubes of any one steam generator. The ECCS analysis abdel typically is set up such that a uniform steam generator. tube
. plugging condition -is modeled. The NRC staff has required that the LOCA analysis for a ' plant with steam generator tube plugging model the maximum tube plugging level present in any of the plant steam generators.
Inserting a sleeve into a steam generator tube results in a reduction of primary coolant floc The anticipated total number of sleeves to be installed-into the Kewaunee steast generators 'is [ ]d e. For the purposes of this section, it is assumed that [ ]d.e tubes in each steam generator will be sleeved. The evaluation of flow effects for sleeving at Kewaunee assumes the use of [ Ja.c.e inch long' sleeves which are expected to be long enough to span the degraded areas in the tubesheet region and to place the upper joint above the sludge pile in either the hot or cold leg side of the steam generators. The flow effects of this sleeve length bound a range of sleeve
. lengths ([ la.c.e inches) which could be used in the sleeving of the !
Kewaunee steam gencrators. l 4683M:49/111187-10 3-107 l l~ L ! E
L < k # l-The flow reduction through a tube due to the installation of a sleeve can be 7 considered' equivalent- to a portion of the flow loss due to a plugged tube. The hydraulic equivalency. ratio of the number of: sleeved tubes required to result .- in the same flow loss 'as that due to a' plugged tube. can be used to determine the allowable nnaber.of plugs and sleeves in combination. The hydraulic - equivalency ratio determined at nominal conditions is independent of the fuel in the reactor. The hydraulic equivalency ratio for LOCA fluid conditions was established using flow rates based on the most recent Westinghouse analysis
~ with Westinghouse supplied fuel. The hydraulic loss coefficients used to
-determine the flow' reduction for nominal conditions are as follows:: for an unsleeved tube ~-[ Jsb c e, for a sleeve.in the hotleg and of the tube b
[ l .c.e, for a sleeve in the cold leg and of the tube-[
- ]b,c.e,and for two; ands sleeved [ l ,c.e. The hydraulic loss coefficients used to b
determine the flow aduction for LOCA conditions are as follows: .for an unsleeved tube [ ]b,c.e,-for a sleeve-in the hotleg end of the tube- -
'[ l b.c.e for a sleeve in the cold leg end of the tube [z .']b,c.e. and for two ends rieeved [ l b.c.e. All of these coefficients are based on the nominal. tube inside diameter. The hydraulic equivalency ratios for both one and two sleeves installed into a tube have been developed as outlined in the ~
following sections. l 1 1 b l
-)
4683M:49/111187-11 3-108 i
- n. .
i1
- 3.5.9.1 ONE SLEEVE PER TUBE ~
For a' single [ ja,c.e inch.siseve installed .in the hot leg of a~ tube the
. primary coolant flow reduction per. tube is.approximately equal to ( -]b,c.e percent of normal flow under nominal conditions. This reduction in primary coolant flow equates to a hydraulic equivalency ratio of [
-]b,c.e. sleeved' tubes to one plugged tube under normal conditions. . For a sleeve installed on.
the cold leg side the flow reduction per tube is approximately [ ]b,c.e.per cant which equates to a hydraulic equivalency ratio of ( l b.c.e, Using the [ .]b,c.e to 1 ratio for sleeves installed on the cold leg side-
- and the 10 percent tube plugging limit for Kewaunee, Table 3.5.9-1 provides en example of the number of additional plugs which could be installed based on . '
(' ]d,e sleeves installed per steam generator and nominal conditions. Nota ( ]d,e sleeved tubes are equivalent to approximately [. }b d.e plugged tubes or [. I b, die percent plugging.-
' For typical predicted LOCA fluid conditions the flow reduction for a sleeve on the hot leg side is approximately [ ]b c.e per cent or a hydraulic
]b,c.e. For a sleeve on the cold leg side the
~
equivalency ratio of ( values are [ ]b,c.e respectively. For the condition presented acove for Kewaunee the most limiting equivalent plugged condition in the two steam generators occurs in steam generator B where 214 tubes are currently plugged. It is seen in Table 3.5.9-1 that with d [ i d,e tubes sleeved there'would be a margin of ( l ,e tubes (124 minus [ ]d e) available for additional plugging before exceeding the equivalent of 10 percent SGTp for nominal fluid conditions. Note, because of the larger hydraulic equivalency ratio for LOCA conditions, using the nominal condition hydraulic equivalency ratio to determine plugging margin to 10 per cent plugging is conservative. L, i 4683M:49/111187-12 3-109
s .. 4 l
.j
~
TABLE 3.5.9-1
.j
.5LEEVING PARAMETERS EXAMPLE UNDEP. NORMAL CONDITIONS
- .(ONE SLEEVE PER TUBE) c,. . . A _ B Steam Generator Total equivalent plugged '338 tubes allowed-338 ]
~
Maximum possible sleeves Y' Maximum possible sleeved tubes-Equivalent plugged tubes Existing plugs 128~ 214
~ " '
Total. equivalent plugged tubes l Percent equivalent SGTP
. (Based on 3388 tubes /SG)
No. of additional plugs allowed - - l $ l 1 I l 1
.\
i 4683M:49/103187-13 I 3-110 l
3.5.9.2 TWO SLEEVES PER TUBE When a single tube has one [ la.c.e inch sleeve on the hot-leg side and a
-second [ ]a c.e inch. sleeve on the cold leg side the primary coolant flow loss per tube is approximately equal to [ ]b,c.e percent of normal flow.
This reduction in primary coolant flow equates to a hydraulic equivalency ratio of [ ]b,c.e sleeved tubes to one plugged tube during nominal fluid conditions. Using this [ ]b,c.e to I ratio and the assumed 10 percent tube plugging limit for Kewaunee. Table 3.5.9-2 provides an example of the number of additional plugs which could be installed based on '[. ]d,e sleeves installed for [ ]d,e tubes per steam generator dur'ing nominal conditions with two sleeves per tube. Note that [ jd.e double sleeved tubes are - equivalen: to approximately [ ]b,c.e plugged tubes, or [ ]b,c.e percent plugging under normal conditions. For typical predicted LOCA fluid conditions the flow reduction for a s1eeve on the both ends of the tube is approximately [ ]b,c.e per cent or a hydraulic
. equivalency ratio of [ ]b,c.e, I
For the condition presented above for Kewaunee, the most limiting equivalent plugged tube condition in the two steam generators occurs in steam generator B where 214 tubes are currently plugged. It is seen in Table 3.5.9-2 with ( l d,e tubes double sleeved, there would be a margin of [ ]d,e tubes (124 minus [ ]d e) available for additional plugging before exceeding the basis of the LOCA and non-LOCA analyses with 10 percent SGTP. Note, because of the larger hydraulic equivalency ratio for LOCA conditions using the nominal - a condition hydraulic equivalency ratio to determine plugging margin to 10 per cent plugging is conservative.
. The method and values of hydraulic equivalency and flow loss per sleeved tube q outlined above and in the previous section can also be used for a combination l . of one and two sleeves per tube. Due to the many possible combinations, such a combination is not provided in this report.
4683M:49/111187-14 3-111 l i l
, c:.
r 1-i q TABLE 3. 5.9-2 .
~l -
- SLEEVING PARAHETERS'-EXAMPLE UNDER' NORMAL CONDITIONS'
. (ONE SLEEVE PER TUBE)? I I I
p . .
- n. L
- A' ^- -
B
. Steam Genera'ter-Total equivalent plugged' '.338 338-tubes allowed-
- - b,d,e, Maximum.possible sleeves.
. 1l l_ .Max16tum' possible sleeved
-tubes E.quivalent plugged . tubes al Existing plugs' 128 214 1
p Total-equivalent plugged tubes- . Percent equivalent SGTP (Based on 3388' tubes /SG) i No. of additional plugs. allowed -, j! l 4683M:49/103187-15 3-112 [. '
m *, s, . 1 ms , ,
.) ; , '
Q;- /
-? '
3.'5.9.3 FLOW UFECTS SUMMAPtY- '
,c
* ' The effects of sleeving on'LOCA and non-LOCA transient analyses have been reviewed. No adverse result'is indicated for sleeve and p!ua combination up'to an eiluivalent of 10 per. cent SGTP.' ine cisting ECC5 performance analysis 1and
? the corresponding non-LOCA evaluation are considered-applictble for the steam
( generator sleeving program with a combination of plugging and sleeving ficw restriction equal to or less than 10 percent tube pluggings : Steam generst;r-sleeve installation up to the equivalent.of 10_ percent plugging would ntt [ invalidate any non-LOCA safety analyses or the evaluation of design transients. The' results of evaluations show that any combination of sleeving and plugging. may be' utilized at Kewaunee as long as the effective SGTP of 10 percent is not:
' ~
exceeded. Given the maximum number of tubes which may be sleeved, Tables 3.5.9-11and3.5.9-2provides-thenumberofadditionalplugspersteamgenerator' that could be installed;at the present plugging levels of Kewaunee without exceeding the 10 percent SGTP.
.. As a result of tube plugging and sleeving, primary side fluid velocities in the steam generator tubes will increase. The effect of this velocity increase on 3- th'e sleeve end tube has been evaluated assuming a conservative limiting condition in which 10 percent of the tubes are plugged. As a reference, normal flow velocity through a tube is approxitaately [ ]C i't/sec, for the unplugged condition. iiith 10 percent of the tubes plugged, the fluid velocity through an non-plugged and non-sleeved tube is [ ]b,c ft/sec, and for.a tube with a sleeve, the 19eal fluid velocity in the sleeve region is estimated at [' ]h,c.e ft/sec. Because these fluid velocities are less than the inception velocities for fluid impacting, cdvitation, and erosion-corrosion, the potential for tube degradation due to these mechanisms is lo.w.
Accordingly, using the assumptions stated in Section 3.5.9, no ECCS results more adverse than those tii the existing Kewaunee safety analysis are indicated for equivalent tuhe plugging projected to occur at Kewaunee Nuclear Power Plant with up to i ]d,e sleeves installed per steam generator using [ ]a.c.u sj,,yes, 4683M:49/111187-16 3-113 ____- _ ._-______m
~~
js- i' s < s q h
' ,?
4.0.. PROCESS DESCRIPTION The: sleeve installation consists of a series of steps' starting.wlth tube.end, preparation (if required) and' progressing.through sleeve-infertion,. hydraulic
~
expansion;at'both'theLlower joint.and upper Hybrid: Expansion Joint-(HEJ) regicos, hard roll. joining at both joint locations,: and joiht inspection. The-sleeving sequence.ar.d process are outlined in Table 4.0-1; All'these steps are described in the following sections. 4.1 . TUBE' PREPARATION t: There are two steps involved in~ preparing the. steam generator tubes.for the sleeving operation. These. consist of light-rolling (as required) at the tube end and. tube' cleaning. - 4.1.1 TUBE END ROLLING (CONTINGENCY) If gaging or inspection of tube inside diameter measurements indicate a need for. tube end rolling to provide a uniform tube opening for sleeva insertion, a light mechanical rolling operation will 'be performed. This is sufficient'to ' prepare the mouth of the tube for sleeve insertion without adversely affecting the original tube hard roll or the tube-to-tubesheet wcld. Tube end rolling will be performed only'as a contingency.
~
Testing of similar lower joint configurations in Model 27 steam generator-o sleeving programs at a much higher torque show'd e no effect or the tube-to-tubesheet weld. Because the radial forces transmitted to the tube-to-tubesheet weld would be lower for a larger Model 51 sleeve than fcr the above test configuration no effect on the weld as a result of the light roll is expected. i 4683M:49/110387-17 4_1
.______________=____._______ .i
TABLE 4.0-1 SLEEVE PROCESS SEQUENCE
SUMMARY
4,C.e h l 1 l l l 1 l 1 4683M:49/103187-18 4-2 _'_______,__.__________._]
. i
l j , i 4.1.2 TtBE CLEANING The sleeving process includes cleaning tne inside diameter area of tubes to be sleeved to prepare the tube surface for the hybrid expansion joint and the
~
lower joint by removing loose oxide and foreign material. Cleaning also . I reduc'es the radiation shine from the tube inside diameter thus contributing I to reducing ;aan-rem exposure. l Tube cleaning may be accomplished by either wet or dry methods. Both l processes have been shown to provide tube inside diameter surfaces compatible I with mechanical joint installation. The selection of the cleaning process . used is dependent primarily on the installation technique utilizeri, the scale - of the sleeving ooeration (small scale vs. large reale sleeving), and the ; customers site specific rad-waste requirements. Evaluation nas demonstrated that neither of these processes remove any significant fraction of the tube wall' case material. I 4.1.2.1 Hti CLEANING t Tube cleaning will be performed using a f I j a.c.e l A waste handling system is used to collect the [
),a c.e And the oxide removed from the tube 10. [
i l i l 1 1
~
l a.c.e There may also be an inlet to the l l. suctio'n pump which subsequently pumps the debris and water directly to the l 4 l Pl ant' waste disposal system. ) 1 J 4683M:49/110387-19 4-3 l 4
-m _
4.1.2.2 DRf CLEANING \ The dry cleaning process is similar to the wat cleaning process with the notable exception that the water jet and the attendant systems needed to handle the effluent are omitted. The dry cleanleg process is typically more applicable to hands-on (manual) or small scale sleeving operations. In order to remove loose oxide debris produced by the dry cleaning operatico, the tuba interior is swabbed utilizing a fluid (typically delonized water or Isopropyl alcohol) soaked felt pad to an elevation slightly less than the cleanea length, but above the top of the installed sleeve.
~
4.2 SLEEVE INSERTION AND EXPANSION The following paragraphs describe the insertion of the sleevai and ratndrels and the hydraulic expansion of the sleeves at both the low 6r joint and upper HEJ tocations. The sleeves are fabricated under controlled conditions, serialized, machined. - cleaud, and inspected. Tney are typically placed in plastic bags, and ' packaged in protective styrofoam trays inside wood boxes. Upon receipt at the ~] site, the boxed sleeves are stored in a controlled area outside containment l and as required moved to a low radiation, controlled region inside containment. Here the sealed sleeve box is opened and the sleeve removed, inspected and placed in a protective sleeve carrying case for transport to the steam generator platform. Note that the sleeve packaging specification is extremely stringent and, if unopened, the sleeve package is suitable for long term storage. [ 71 ,c.e 1 4683M:49/110387-20 _ _ _ ]
I [ O I l l
]C This process is repeated until all sleeves are installed and hyt,aulically expanded.
4.3. LOWER J0lNT SEAL At the primary face of the tubesheet, the sleeve is joined to the tube by a [ l
.l 3,a,c.e i
The appropriate extent of hard roll expansion of the sleeve is attained by I [ Ja .c.e The hard roller torque is calibrated on a standard torque calibrator prior to initial hard rolling operations and subsequently recalibrates at the beginning of each shift for automatic tooling. This control and calibration process is a technique used throughout industry in the installation of tubes in heat exchangers, l l 4683M:49/110387-21 4-5 1
4.4 UPPER HYBRIO EXPANSION JOINT (HEJ) R The HEJ first utilizes a C - Ja ,c.e An upper hard roller is inserted into the sleeve until it is ' positioned at the prescribed axial location. The hard roller is then operated for a fixed time. At the end of this time the roller will have expanded to its set diameter and the total tube diametral expansion will have been accomplished. The maximum torque of the hydraulic or air operated drive motor is set at a value which is sufficient to achieve the desired tube expansion. 4.5 PROCESS INSPECTION SAMPLING PLAN In order to verify the final sleeve installation, an eddy current inspection will be performed on all sleeved tubes to verify that all sleeves received the required hydraulic and roll expansions. The basic process check op 100 percent of the sleeved tubes will be: .
- 1. Verify presence of lower hydraulic expansion zone. .
- 2. Measure lower hydraulic expansion and roll average diameter and verify location within the lower hydraulic expansion. -
- 3. Verify presence of Upper hydraulic expansion 2one.
- 4. Measure upper hydraulic expansion and roll average diameter and verify location within the upper hydraulic expansion.
- 5. Check for the presence of any anomalies.
In order to monitor the sleeving process, an in-process application of the eddy current profilometry may be performed to obtain sleeve ID data. As acceptable diameters are verified and the sleeving process is proceeding as anticipated, this inspection may be eliminated. These average diameters will be evaluated versus the expected tolerances established through the design i requirements, laboratory testing results, and previous experience. This evaluation will determine whether or not the equipment / tooling is performing -i satisfactorily. If process data is determined to be outside of expected ranges, a non-conformance report is issued and further analysis performed. ' 4683M:49/103187-22 4-6 _ _ . _ _ _ _ _ . - . _ _ _ _ . _ _ _ _ . _ . _ _ _ _ _ - - - - - - - _ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - " - - - - " - - - ' - - - - - - - - - - - - " ' - - - - - - - ' - - - ' - - - - - - - - - - - - - ^ ~~- ~ ~ ~ ~ ~ '
4 o If required, mechanical measurement may be used in lieu of eddy current to.
. perform! sleeve' installation acceptance and in-process monitoring evaluations.
Undersized diameters will be corrected by?an~ additional' expansion step to
- .. . produce.the desired de~ gree of expansion. 0versized diameters will be.
dispo'sitioned byfa: specific evaluation process.on.an individual tube basis, to- !- determine their acceptability with respect to:specified sleeving parameters. l If it"Is necessary to renove a sleeved tube from service as judged by an evaluation of a specific sleeve / tube configuration,4 tooling and processes will--
.be available to plug the sleeve or the lower portion of the sleeve will be removed and the: tube'will be plugged.
As mentioned previously,'the basic process dimensional verification will be completed'and evaluated for 100' percent of all installed sleeves. 4.6' ESTABLISHMENT'0F SLEEVE JOINT MAIN FABRICATION PARAMETERS 4.6.1 LOWER JOINT The main parameter for fabrication of acceptable lower joints is sleeve [
].a.c.e gj,,y, g 3a ,c.e is determined by '(
).a.c.e Accordingly, rolling torque was varied to ,
a achieve the desired sleeve [ 'J c.e in the original Model 44 program (also applicable to the model 51). [
] "'C was achieved was used throughout the program
~
verification testing. 4.6.2 UPPER HEJ The main parameter for fabrication of HEJ's (in-sludge and out-of-sludge) which met the leak rate acceptance criteria was ( l
- 3a ,c e 1 1
4683M:49/103187-23 , L1___ _ __ __ _ _
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]"'C
, ,tRefer to
. ' Section. 3.3.5.3:.for an additional discussion of. the' roll expansion torque forL
.the in-sludge.. case.)
Irr the'first sleeving project performed by Westinghouse. hydraulic expansion 1
.' axial 1 length was also evaluated. [.
J."'C >-Therefore in later' programs.'the HEJ hydraulic expansion. axial' length 0
- , . N e
ya~.b',c.e 1 i i ( 4 l
- s. ~4683M:49/103187-24 4-8
4 i. i i 5.0 SLEEVE / TOOLING POSITIONING TECHNIQUE With all positioning techniques, the process actually used to install the sleeves (hydraulic expansion, mechanical rolling, etc.) will not be changed due to the use of any sleeve / tooling positioning technique. It is the l processes which the sleeves are subjected to that are critical to a successful ! installation; the technique used to position the sleeves and tooling is.not critical so long as it does not affect the sleeve installation processes. Some techniques used.to position the sleeve installation tooling'are: fully robotic (ROSA and SM-10HS) and hands-on (manual.', or the combination of two er more tooling installation modes utilized is dependent upon many variables and what is mutually decided between the utility and Westinghouse. l l 9 4683M:49/103187-25 5-1
g d , i f[# t ;' (i 6.0 NDE INSPECTABILITY
~
The Non-Destructive Examination OlDE) development effort has concentrated on l , two aspects.of~the sleeve system. F.irst, a method of confirming that the , l'f joints meet' critical process'dtmensions'is' required. Secondly, it must be - s'hown that the tube / sleeve assembly is capable'of being evaluated through subsequent routine in-service inspection. In both of these efforts, the inspection process has relied upon eddy current technology. Previous sleeve insta:lations have had baseline and subsequent in-service inspections of the sleeved tubes. Presently, no change has been observed in l any of thetin-service eddy current inspections compared to the baseline-
. inspections.
6.1 EDDY CURRENT INSPECTIONS The eddy current inspection equipment, techniques, and results presented herein. apply to the proposed Westinghouse sleeving process. Eddy current l- Inspections are routinely carried out on the steam generators in accordance with the plant's Technical Specifications. The purpose of these inspections is to detect at an early state tube degradation that may have occurred during plant operation so that corrective action can be taken to minimize further degradation and reduce the potential for significant primary-to-secondary leakage. The standard inspection procedure involves the use of a bobbin eddy current j probe, with two circumferentially wound coils which are displaced axially along the probe body. The coils are connected in the so-called differential mode; that is, the system responds only when there is a difference in the properties of the material surrounding the two coils. The coils are excited by using an eddy current instrument that displays changes ingthe material surrounding the coils by measuring the electrical impedance of the coils. Presently, this involves simultaneous excitation of the coils with several different test frequencies. ; l 4683M:49/103187-26 6-1
1 l I The outputs of the various frequencies are combined and recorded. The i combined data yleid an output in which signals resulting from conditions that do not affect the integrity of the tube are reduced. By reducing unwanted ~ signals, improved inspectability of the tubing results (i.e., a higher nignal-to-noise ratio). Regions in the steam generator such as the tube ~ supports, the tubesheet, and sleeve transition zones are examples of areas where multifrequency processing has proven valuable in providing improved inspectability. After sleeve installation, all sleeved tubes are subjected to an eddy current , inspection which includes a verification of correct sleeve installation for ! process control and a degradation inspection for baseline purposes to which all subsequent inspections will be compared, j t While there are a number of probe configurations that lend themselves to enhancing the inspection of the tLbe/ sleeve assembly in the regions of configuration transitions, the crosswound coil probe has been selected as offering a significant advancement over the conventional bobbin coil probe, yet retaining the simplicity of the inspection procedure. . Verification of proper sleeve installation is of critical importance in the a sleeving process. The process control eddy current verification is conducted ! utilizing one frequency in the absolute mode with a crosswound coil probe. The purpose is to provide "in-process" verification of the existence of proper hydraulic expansion and hard roll configurations and also to allow determination of the sleeve process dimensions both axially and radially. ; I Figure 6.1 1 illustrates the coil response and measurement technique for typical sleeve / tube joint. The inspection for degradation of the tube / sleeve assembly has typically been performed using crosswound coil probes operated with multifrequency excitation. For the straight length regions of the tube / sleeve assembly, the inspection of the sleeve and tube is consistant with normal tubing - inspections. In tube / sleeve assembly joint regions, data evaluation becomes more complex. The results discussed below suggest the limits on the volume of - ! degradation that can be detected in the vicinity of geometry changes. l 1 4683M:49/103187-27 6-2
.: \
A ' -- a. ,e o Figure 6.1 Absolute Eddy Current Signals at 400.khz (Front and Rear Coils) 6-3
1 b The detection ~and quantification of' degradation'at the. transition regions of: the sleeve / tube: assembly depends'upon the signal-to-noise ratio between the
^
degradation. response.and the transition response. As a general rule, lower
. frequencies tend to suppress the' transition s'ignal. relative.to-the degradation .
signal at th0' expense.of..the ability to quantify. Similarly, the inspection of the tube through the sleeve requires the:.use of' low frequencies to achieve- ' detection with an. associated loss in quantification. Thus, the search for an-optimum eddy current inspection represents a tradeioff between detection and quantification. With.th6 crosswound coil. type inspection, this optimization d' leads to'a primary inspection frequency for the sleeve'on the order of [ lC and for the tube and. transition regions on.the order of [ a',C,& 3 l a.c.e phase angle versus degradation F1'gure 6.1-2 shows a typical [- depth curve for the sleeve from which 00 sleeve penetrations can be assessed. In the regions of the parent tube above the sleeve, conventional bobbin coil j or crosswound coil inspections will continue to be.used. However, since the diameter of the sleeve is smaller than that of the tube, the fill factor of a - probe inserted through the sleeve may result in a decreased detection Capability for' tubing degradation. Thus, it may be necessary to inspect the *! unsleeved portion'of the tube above the' sleeve by inserting a standard size probe through the U-bend from .the unsleeved leg of the tube, j for the tube' sleeve combination, the use of the crosswound probe, coupled with, j a multifrequency mixing technique for further reduction of the remaining noise-signals significantly reduces the interference from all discontinuities (e.g. 1 transition) which have 360-degree symmetry, providing improved visibility for l discrete discontinuities. As is shown in the accompanying figures, in the i laboratory this technique can detect OD tube wall penetrations with acceptable
-signal-to-noise ratios'at the transitions when the volume of metal removed is
- equivalent to the ASME calibration standard.
~
l i l I l l 4683M:49/103187-29 6-4
t
.L" . e l
1 l j
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1 l
~
i Figure 6.la2 - [ ]a.c.e Calibration Curve
- )
65 l. (- l
s m , , J'E Y y The response from the tube / sleeve assembly. transitions with the crosswound. coil _is shown,in. Figures 6.1-3,;6.1-4, and 6.1-5 for'the sleeve' standards, tubestandards'andLtransitions,respectively. Detectability in transitions is.
- enhanced'by the combination of the:various frequencies. For the cross-wound.
probe, two' frequency cornbinations are shown; [
- 4
']a,b,c e- Figure 6.1-6 shows the phase / depth curve l for-the tube.using this combination. As examples'of the detection capability.
at the: transitions, Figures 6.'l-7 and 6.1-8 show the responses of a 20 percent. 00 penetration in the sleeve and 40 percent 00 penetration in the tube, respe::tively. For inspection of the region at th'.e top end of the sleeve, the trar,sition ^ response. signal-to-noise ratio is about a factor of four less. sensitive than that of the expansions. Some additional.inspectability has been gained by tapering the-wall thickness at.the top'end of the sleeve. This reduces the i end'-of-sleeve signal by'a factor of approximately two. The crosswound coll, however, again significantly reduces the response of the sleeve end. Figure . 6.1-9 shows;the response of various ASME tube calibration-standards placed at the end of the sleeve using the. cross-wound coil and'the [ 3a ,c.e , frequency combination, t'ote that under these conditions, degradation at the top end of the sleeve / tube assembly can be detected.
, 6.2:
SUMMARY
Conventional. eddy current techniques have been modified to incorporate the more recent technology in the inspection of the sleen/ tube assembly. The resultant inspection of the sleeve / tube assembly involves the use of a cross-wound cotl' for the straight regions of the sleeve / tube assembly and for the transition regions. The advent of MIZ-18 digital E/C instrumentation and its attendant increased dynamic' range and the availability of 8 channels for four raw frequencies has expanded the use of the crosswound coil for sleeve - inspection. While there is a significant enhancement in the inspection of-portions of the assembly using the cress-wound coil over conventional bobbin - coils, sfforts continue to advance the state-of-the-art in eddy current 4683M:49/iO3187-31 6-6 L
._. _. . _ _ _ _ = __
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+
I i... l
. Figure 6.1-3 - E.C. Signals from the ASTM Standaed, flachined on the Sleeve 0.D. of the Sleeve-Tube Assembly Without Expansion (Cross Wound Coil Probe) 1 6-7
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l i w - I J Figure 6.1 E.C. Signals from the ASTri Standard, Machiried on the Tube . 0.0. of the Sleeve-Tube Assembly Without Expansion (Cross Wound Coil Probe)
'" 6-8 I. .
- s .
a,c,e , I f f i 1 !' Figure 6.1 E.C. Signals f rm the Expansion Transition Region of !. the Tube-Sleeve Assembly (Cross Wound Coil Probe) i 6-9 l
- - - - - - -_____w
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- i figure 6.1 EddyCurrgng'galibrationCurveforASMETubeStandardat
[ ] and a Mix U:;ing the Cross Wound Coil Probe - 6-10 b ___ _ . _ _ _ _ _
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- ,'[. ,
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[ 1 L l l t 1' 1 j' i l l'i ~ !;:; i 1_ _ i l l4 E.C. Signal from a 20% Deep Hole, Half the Voltsne of ASTM L; '
. Figure 6.1-7 -
Standard, Machined on the Sleeve 0.D. in the Expansion Transition Region of the Sleeve-Tube Assembly (Cross Wound Coil Probe) 1-1 6-11
-- __ . _ _ - _ _ _ - - - - _ - - - _ - _ _ _O
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4 Figure 6.1 E.C. Signal from a 40% ASTM Standard, Machined on the Tube 0.D. in the Expansion Transition Region of Sleeve-Tube Assembly (Cross Wound Coil Probe) i 9 l l \
, 6-12 l-
________x__-_____________-___
gi gy . . i;, .. & , L+ f .\ .m v : ', .a f.i.i;j.h
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Eddy Current Response of the ASME Tube standard at the End of the Sleeve Using the Cross Wound Coil Probe and Multifrequency Combination 6-13
L.. 3
- ') *i qq
- q w 1
[ . inspection techniquet. As' advanced state-of-the-art' techniques,are developed-and vertfled,;they.will be utilized. For the present,:the. cross-wound coil l; probe represents an. inspection' technique.that provides additional' sensitivity
- and support for. eddy current techniques as'a viable means of. assessing the
. tube / sleeve: assembly; 0
'. m 4
y g G 9 4683M:49/103187-39 6-14
...]
1 7.0 ALARA CONSIDERATIONS FOR SLEEVING OPERATIONS
- The repair of steam generators in operating nuclear plants requires the utilization of appropriate dose reduction techniques to keep radiation
- exposures A3 Low As Reasonably Achievable (ALARA). Westinghouse maintains an extensive ALARA program to ininimize radiation exposure to personnel. This program includes
- design and idiprovement of remote and semi-remote tooling.
[ including state-of-the-art robotics; decontamination of steam generators; the use of shielding to minimize radiation exposure; extensive personnel training utilizing mock-ups; dry runs; and strict qualification procedures. In addition, computer programs (REMS) exist which can' accurately track radiation exposure accumulation. The ALARA aspect of the tool design program is to develop specialized remote tooling to reduce the exposure that sleeving personnel receive from high radiation fields. A design objective of a remote delivery sleeving system is
. to eliminate channel head entries and to complete the sleeving project with total exposures kept to a minimum, i. e., ALARA. A manipulator arm can be . Installed on a fixture attached to the steam generator manway after video cameras and temporary nozzle covers have been installed. A control station operator (C50) then manually operate controls to guide the manipulator arm through the manway and attach a baseplate to the tubesheet. The installation of the arm requires only one platform operator to provide visual observation and assistance with cable handling from the platform. The control station for the remote delivery system is located outside containment in a specially designed control station trailer. As previously indicated, under some conditions positioning of sleeve / tooling with the base Robotic system may not be practical. In these circumstances alternate techniques may be utilized.
such as hands-on (manual position, alternate robotic or semi-remotely operated equipment or a combination of the two. The control of personnel exposures can also be effected by careful planning, training, and preparation of maintenance procedures for the job. Tnis form of administrative control can help to provide that the minimum number of a personnel will be used to perform the various tasks. Additional methods of minimizing exposure include the use of remote TV and radio surveillance of all platform and 4683M:49/103187-40 7_1
-u _ - _ _ _ _ _ _ _ _ _ _ _ _ -
channel head operations and the monitoring of perisonnel exposure to identify high exposure areas. Local shielding will be used whenever possible to reduce the general area background radiation levels at'the work stations inside - containment. 7.1 N0ZZLE COVER AND CAMERA INSTALLATION / REMOVAL The installation of temporary nozzle covers in the reactor coolant pipe nozzles in preparation of .the' steam generators for sleevirg operations may require channel head entries. The covers are installed to prevent the accidental dropping of any foreign objects (i.e., tools, nuts, bolts, debris, etc.) into the reactor coolant loops during sleeving operations. In the event that an accident didl occur, an inspection of the loop would be required and any foreign objects or debris found would be retrieved. The impact on schedtle and radiation exposures associated with these recovery operations would far exceed the-time and exposures expended to install er remove loop nozzle covers. Consequently, it is considered an ALARA-efficient procedure to utilize temporary nozzle covers during sleeving operations. The use of video monitoring systems to observe rcbotic operationt in the channel head may require manual installation. The installation of overview . cameras to monitor sleeving operations may require a full or partial channel head entry. The installation and removal of th!s equipment in the steam generators are the only anticipated potentials requirements for channel head entrie: during the sleeving project. 7.2 PLATFORA SETUP / SUPERVISION I The majority of the radiation exposures recorded for the sleeving program is f expected to result primarily from personnel working on or near the steam generator platforms and in the channel head for hands-on operations. The .j l 4683M:49/103187-41 l 1 7-2 l i j .m
.O t- . . .
l~ l t setup and checkout of equipment for the various sleeving processes, installation / removal of tooling, and the operaticn of the tooling are the ! -" major sources of radiation ru,osure. In addition to channel head' video monitoring systems, visc I ' mitoring and supervision by one or more workers-on' the platform will be rs t. ed for a major part of the sleeving schedule. Experience has shown that ry s response to equipment adjustment requirements is efficiently accomplished by having a platform worker standing by in-a relatively low radiation area during operations. Worker standby stations have ranged from the low radiation fields behind the biological shield to lead blanket shielding installed on the platform. _Even though radiation levels on the platform are much-lower than channel head levels, a substantially larger amount of time will be spent on the platforms giving rise to personnel-exposures. An evaluation of radiation surveys around the steam' generators should indicate appropriate standby stations. 7.3 RADWASTE GENERATION The surface preparation of tubes for the installation of sleeves requires that
- . . the oxide film be removed by a honir.g process. A flexthone attached to a flexiole rotating cable will be used to remove the oxide film on the inside' ,
surface of the steam generator tubes. The volume of solid radwaste is expected'to consist of spent hones, flexible honing cables,. hone filter assemblies (optional), [ ]"'C.and the normal anti-C consumables associated with steam generator maintenance. The anti-C consumables are the utility's responsibility and will not be addressed in this report. For the [ l a,c.e approximately thirty tubes can ba honed before the hone is changed for process control and [
].a.c.e A typical estimate of the radioactive concentration from a boned tube transported by the C Ja .c.e is given in Table 7.3-1. These concentrations are based on a e general area radiation level of 4R/HR. The tube hones as well as the tubes
[ Ja .c.e Consequently, radiation levels of the spent hones are normally 1-2 r/hr based on field measurements in previous sleeving projects. 4683M:49/103187-42 . 7-3
.f1 k ', g ,ry:
'f , # i
".l[ E ,. . ;. . , ,
t u TABLE 7.3-t "
.j ESTIMATE OF. RADI0 ACTIVE CONCENTRATION IN HATER PER TUBE. HONED'(TYPICAL) =
.e ..' I'l ( , i a,c,e k 1: ASSUMPTIONS 1 o
. 1) Tube honed 45 inches (in length) )
-'2) ' Water flow; rate of 0.6 gallons'per tube honed.
-l
\
- 3) Essentially all radioactivity removed from tubes honed. L 1
I i 1 4683M:49/103187-43 - 7-4 l
a W f f The flexible honing cable used to rotate the' hone ins!de the tubes.ls also flushed durirg the honing process. However, the construction of the stainless steel cable will cause radioactivity to build up over the course of the project. :T<adiation levels. on segments of.the cable cocid reach 5-10 R/Hr contact' dose rates.for major sleeving jobs < It.is expected that an average of one cable per steam generator will be used.during the sleeving project. The cables are consumables and are drummed as solid radwaste. 7.4 HEALTH PHYSICS PRACTICES AND PROCEDURES a The Health Physics (HP) requirements for sleeving will.be those estabished by the licensee. Westinghouse will provide radiological engineering assistance, as needed, to assist in coordination of the radiological aspects of the Westinghouse activities. Open communications between involved parties will be maintained so that the best possible health physics practices can be established for the sleeving program. The HP procedures of the utility will 'l
- be the guidelines followed during the' sleeving operation. However, in
' specific instances where beneficial changes to the techniques are mutually
. . recognized but not covered in these HP procedures, appropriate changes will;be made according to established change procedures.
The field service procedures which are prepared by. Westinghouse for the complete setup of equipment and subsequent sleeving operations include the specific radiologically related responsibilities, prerequisites and precautions. These will further minimize exposure and control contamination. 3 i Hockup training at the Westinghouse Waltz Mill Training Center includes the following radiological practices: l o Technical skill training while dressed in full Anti-C clothing including bubble hoods. ) o Identification of high radiation zones on the work platform and emphasis of minimizing stay times. ( l 4683M:49/103187-44 i 7-5 ! 1 j
L. lf '
,f
,y ll. 1E
* , y I
o . Handling ofLcontaminated tcols and chang'eout of contaminated nandrels.
, 'E .
Y- ' 4 o ' Location and usefof waste'disposalLcontainers. . [ - Westinghouseimplementsanextensivetraining.andqualificationprogramto
. prepare. supervisory,: maintenance'and operations personnelLfor' field implementation of the sleeving process. Satisfactory completion of this:
training program verifles-that the personnel. addressed are qualified to
~
perform all: assigned operations from e. technical as well as radiological M' aspect in' keeping with'the ALARA principais. The qua_1tffcation program censists of two phases: Phase I - classroom Phase II - mockup Phase.I + Consists of. classroom training and addresses subject material-that-is related to the overall-sleeving program. The Phase I instructors, generate and administer'an examination for Phase'I training of' sufficient difflculty to demonstrate that'a trainee has sufficient knowledge of the material
- presented. This examination is written'. All trainees will be tested. A ,
minimum grade of 80 percent is required. The test results shall be< documented are retained for audit.
-1
' Phase II - Consists of hands-on.and mockup sleeving training during which the trainee must demostrate a capability to perform a-function or operation in a j limited amount of time. If team training is required, each trainee must be able to' perform all tasks required of the team.
7.5 AIRBORNE RELEASES 4 The implementation of the proposed sleeving processes in operating nuclear plants has indicated that the potential for airborne releases is minimal. The , 1 major operations include [ ]"'C and sleeve installation. F l l 4683M:49/103187-45 j 7-6 I _ J
g , i Experience has shown that these sleeving procerses do not contribute.to airborne releases. , 7.6 PERSONNEL EXPOSURE ESTIMATE' o The total personnel exposures for steam generator sleeving operations will depend on several plant dependant and process related factors. These may. Incil:de, but not be limited to; the scope of work (quantity of sleeves, etc), 9 plant rad!ation levels, ingress / egress to the work stations, equipment performance and overall cognizance of ALARA principles. Consequently, the projection of personnel exposures for each specific plant must be performed at the completion of mockup training when process times for each operation have been recorded. The availability of. plant radiation levels and worker-process times in the various radiation fields will provide the necessary data to' project' personnel exposure for the sleeving project. The calculation of the total MAN-REM exposure for completing a sleeving project may typically be expressed as"follows: P = ((N .0)+S) .N g 3 3 g
.s. >
P - Project total exposure (MAN-REM) N3 = Number of sleeves Installed / steam generator D - Exposure / sleeve' installed 3 i Sg - Equipment setup / removal exposure per steam generator l 4 Ng = Number of steam generators to be sleeved This ecuation and appropriate variations are used in estirrating the total
, personnel exposures for the sleeving project-. -~. ,
I
'4683M:49/103187-46
t 7-7
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. , ' 'l
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( hy- ManNemexposureresultsobtainedduring'arecentWestinghousesteamgenerator- . sleeving operation showed-approx mately 50 to.100 millirem / tube,:using the Remota Operating Service Arm (ROSAh ' er
' Man rem exposure results obtataed from recent Westinghouse: steam. generator , j ma'nual sleeving' operations show approximately.300 man-rem for sieeving of 650 f
tubes. This estimate is based on chemical decontamination of the steam j y , generator channel heads inclu'ing d approximately.4. feet inside the steam' .- generator. tubes with a- resulting field of approximately 4 R/HR,
-l
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i li 4683M:49/103187-47 7-8 i
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I) ; 8.0 INSERVICE' INSPECTION PLAN FOR SLEEVED TUBES
, In addrlssing current NRC requirements, the need exists to perform periodic
. inspections of the supplemented pressure boundary. This new pressure boundary.
/ consists of the sleeve with a joint at the primary face'of the tubesheet and a joint at the opposite end of.the sleeve.-
l . p The inservice inspection program will consist of the following. Each sleeved L tube will be eddy current inspected on completion of installation to obtain a-baseline signature to which all subsequent inspections will be compared. Periodic inspections to monitor sleeve wall conditions will-be performed in accordance with the inspection secticr. of the plant Technical Specifications. This inspection will be performed with multi-frequency eddy current equipment. 1 a. e t i-i i
'4683M:49/111187-48 g_1
_ _ _ _ _ _ _ _ _ _ i
.,:-y-\'
N252.6A 1 i t,- i Attachment 7 l l ' to Lett'er'from'D.'C. Hintz (WPSC) to Document Control Desk (NRC) ~j Dated November 30, 1987 i 1 1 I
.1 Description, Safety Evaluation, and Significant. Hazards Determination l
'l Of Proposed Administrative Change -]
4 i 1, k 1 i, l I l
.i 4
I l 1
- :--------___ _j
e O *
' Document Control Desk N252418 : =
November 30, 1987 > Page 1 'If DESCRIPTION, SAFETY EVALUATION, AND SIGNIFICANT HAZARDS DETERM7 NATION 0F PROPOSED ADMINISTRATIVE CHANGE c Description of the Proposed Administrative Change: Page TS 4.2-6 .-" The first paragraph, TS 4.2.b.3.c.1, has been changed to reference TS 3.4.a.4, v l l rather than 3.4.a.5. Safety Evaluation of the Proposed Change: Page TS 4.2-6
- e
() TS Amendetnt No. 63 consolidated specifications in TS 3.4.a resulting in a 1' renumbering of paragraphs within the section, but inadvertently failed to update , y the reference in section TS 4.2.b.3.c.1. This change corrects the subject reference. Since this proposed change would not alter any existfng surveillance requirements, but is merely an editorial correction, it is administrative in nature and has no effect on the public's health and safety. , s Significant Hazards Determination for the Proposed Change: Page TS 4.2-6 Tne proposed change does not alter existing surveillance requirements. Its pur-pose is to correct a subject reference as a result of paragraph renumbering in r. TS Amendment No. 63. Therefore, this change would not: ,, b
- 1. Involve a significant increase in the probability of occurrence or in the ;
consequences of an accident previously evaluated. Since the proposed change - would not change present surveillance requirements, it could not increase the probability or consequences of an accident.
- 7
- 2. Create the possibility of a new or different type of accident from any n previously analyzed. Steam generator surveillance will continue in accor-J c .
a ~#. % Document Control Desk
. November 30, 1987 Page 2 gi dance'with the intent of the existing specification. Therefore, the ch4nge could not result in a new or d.ifferent type of accident.
- 3. Involve a significant decreasu in the margin of safety. Since the intent of the existing specification viill remain ir, tact, there would be no decrease in the margin of safety if the change is approved.
Therefore, there are no significant hazards associated with thii:, change. n l l I
)
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