ML20066H506
| ML20066H506 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 11/30/1990 |
| From: | Cranford E, Tilda Liu, Valasek L WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19310E538 | List: |
| References | |
| IEB-88-011, IEB-88-11, WCAP-12728, NUDOCS 9101290168 | |
| Download: ML20066H506 (225) | |
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_ . _ _ _ . _ . _ . _ - . , _ . . . _ _ _ . . . _ _ . . . _ _ . _ . . _ . _ _ _ _ _ _ . . . _ _ _ . _ . _ . - . _ . . _ _ .~ .. _.._._ 4 1 - WESTINGHOLfSE CLASS 3 l i WCAP 12728 e 1 t t l EVALUATION OF-THERMAL STRATIFICATION FOR THE BEAVER VALLEY UNIT 1 1 " PRESSURIZER SURGE LINE-NOVEMBER 1990 T. H. Liu F. J. Witt L. M. Valasek S. Tandon E. L. Cranford J. F. Petsche i Verified by g Verified by M C Jc4 4 K. C. Chang Gd. C. Schmertz /. G . Approved by 4 / < 8 + Approved by '# rr ( . . .d. . 4 ', R. B.'Fatel, Manager 5. 5. Palusimy, Man (ger-System Structural Analysis Diagnostics and Monitoring ' Technology
'l ,
l l l WESTINGHOUSE ELECTRIC CORPORATION Nuclear and Advanced Technology. Division P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728 l c 1990 Westinghouse Electric. Corp. l
.a e-l 4633,eiC2HO 10 . _ . - . . . - - - . ~. . . , - , . - . . _ . . . - . - - .- .- -._______-_-______.l
l ! l I i. 1 i TABLE OF CONTENTS 1 Section Title Page , l EXECUTIVE
SUMMARY
xvii
1.0 INTRODUCTION
AND UPDATE OF DESIGN TRANS!ENTS 1 1.1 Introduction 1-1 1.1.1 System Description 1-1 ' . 1.1 2 Thermal Stratification.I t 2 Surge Line 1 > 1.1.3 Surge Line Stratification Program 1-3 , 1.2 Update of Design Transients 1-4 1.2.1 System Design Information 1-4 1.2.2 Stratification Effects Criteria 1-5 1.2.3 P' ant Monitoring 1-5 1.2.4 Heat Transfer and Stress Analysis 1-6 1.2.5 Stratification Profiles 1-7 1.2.6 Development of Conservative Normal and 1-7 L%;et Transients 1.2.7 Temperature Limitations During Heatup 1-8 and Cooldown 1.2.8 Historical Data 1-8 1.2.9 Development of Heatup and Cooldown Design. 1-9
* ~
Transients With Stratification 1.2.9.1 ( Ja,c.e Transients 1-10 1.2.9.2 Fluctuation Transients 1-14 1.2.9.3 Transient Basis Exceedances 1 1.2.10 Striping Transients 1 1.3 Conclusions 1-15' 2.0 STRESS ANALYSES 2-1 2.1 Piping System Structural Analysis 2-1 2.1.1 Introduction' 2-1 2.1.2 Discussion 2-2 4631s/102960 10 jjj
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4 TABLE OF CONTENTS (cont.) Section Title Page , 1 l l 2.1.3 Results from Beaver Valley Unit 1 Analysis 2-5 2.1.4 Conclusions .2-5 2.2 Lo:al Stress Due to Non-Linear Thermal Gradient 2-6 2.2.1 Explanation of Local Stress 2-6 2.2.2 Superposition of Local and Structural Stresses 2-6 2.2.3 Finite Element Model of Pipe for Local Stress 2-7 2.2.4 Pipe Local Stress Results- i# 2.2.5 Unit Structural Lead Analyses For Pipe 2-8 l 2.2.6 RCL Hot leg Nozzle Analysis 2-8 l 2.2.7 Conservatisms 2-9 ) 2.3 Thermal Striping 29 2.3.1 Background 2-9 . 2.3.2 Thermal Striping Stresses 2-9 ! 2.3.3 Factors Which Affect Striping Stress 2-10' . 2.3.4 Conservatisms 2-12 3.0 ASME SECTION III FATIGUE USAGE FACTOR EVALUATION 3-1 3.1 Code and Criteria 3-1 t 3.2 Analysis for Thermal Stratification 3-1 3.2.1 Stress Input 3-1 3.2.2 Classification and Combination of Stresses- 3-2 3.2.3 Cumulative Fatigue Usage Factor Evaluation 3-2 3.2.4 Simplified Elastic-Plastic Analysis 3-3 3.2.5 Fatigue Usage Results 3-4 3.3 Conservatisms in Fatigue Usage Calculation' 3-4 3.4 References 3-5 l .. 4snuto2660 to jy.
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l l
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TABLE OF CONTENTS (cont.) 4 , . Section 7itle .Page l ? 4.0 FATIGUE CRACK GROWTH EVALUATION 4-1 4.1 Introduction 4-1 4.2 Initial Flaw Size 4-2 4.3 Critical Locations for FCG 4-2 4.4 .Results of FCG Analysis 4-3 4.5 References 4-3 5.0 ASSESSMENT OF LEAK-BEFORE-BREAK 5-1 5.1 Background 5-1 5.2 Methodology 5-1 5.3 Material and Fracture Toughness Properties 5-1 5.4 Loading Conditions 5-2 5.5 Results 5-3 5.6 Conclusions 5-4 5.7 References 5-4
6.0 CONCLUSION
S 6-1, APPENDIX A - LIST OF COMPUTER PROGRAMS A-1 APPENDIX B - FATIGUE CYCLE APPROACH VS, DESIGN TRANSIENTS- B-1 1 e 4633t/10290010
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I LIST OF TABLES . Table Title Page 1-1 :MPORTANT DIMENSIONLESS GROUPS FOR SIMILITUDE IN 1-16 HYDRODYNAMIC TESTING 1-2 STRATIFICATION POTENTIAL BASED ON RICHARDSON NUMBER 1-17 1-3 NOTES FOR TRANSIENT DEVELOPMENT FLOW CHART 1-18 1-4 SURGELINE TRANSIENTS WITH STRATIFICATION HEATUP (H) 1-21 AND C00LDOWN (C) - 200 CYCLES TOTAL 1-5 $ URGE LINE TRANSIENTS WITH STRATIFICATION NORMAL AND 1-23 UPSET TRANSIENT LIST 1-6 STRATIFICATION PROFILES 1-25 1-7 HEATUP - C00LDOWN TRANSIENTS 1-26 1-8 DESIGN TRANSIENTS WITH STRATIFICATION 1-27 1-9 PLANT OPERATIONAL CONSTRAINTS 1-28 1-10 OPERATIONS SURVEY 1-29 1-11 HEATUP DATA
SUMMARY
(PZR - HOT LEG) TEMP. DIFFERENCE AND 1-30 TIME DURATION FOR EACH PHASE 1-12 C00LDOWN DATA
SUMMARY
(PZR - HOT LEG) TEMP. DIFFERENCE AND 1-31 TIME DURATION FOR EACH PHASE 1-13 TRANSIENT TYPES 1-32 1-14
SUMMARY
OF FATIGUE CYCLES FROM [ Ja,c.e 1,33 1-15
SUMMARY
OF PLANT MONITORING TRANSIENTS WITH STRENGTH OF 1-34 STRATIFICATION (RSS) 1-16
SUMMARY
OF MONITORED TRANSIENT CYCLES (ONE HEATUP) 1-36 1-17
SUMMARY
OF % TIMES AT MAXIMUM TEMPERATURE POTENTIAL RMTPg 1-37 1-18 SURGE LINE TRANSIENTS - STRIPING LOADS FOR HEATUP (H) 1-38 AND C00LDOWN (C) 0 I
- j l
i 4633,/102990 10 yjj e
LIST OF TABLES (cont.) Table Title Page
- 2-1 COMPARISON OF WECAN AND ANSYS RESULTS FOR LINEAR 2-13
- STRATIFICATION - Case 2 2-2 COMPARISON OF WECAN ( Ja.c.e AND 2-14 ANSYS ( JC RESULTS FOR CASE 3 2-3 TEMPERATURE PROFILES IN PRESSURIZER SURGE LINE 2-15 2-4 2-16 BEAVERVALLEYSURGELIN['MAflMUMLOCALAXIALSTRESSES AT ( )
2-5
SUMMARY
OF LOCAL STRATIFICATION STRESSES IN THE SURGE 2-17 LINE RCL N0ZZLE 2-6
SUMMARY
OF PRESSURE AND BENDING INDUCED STRESSES IN THE 2-18 SURGE LINE RCL N0ZZLE FOR UNIT LOAD CASES 2-7 STRIPING FREQUENCY AT 2 MAXIMUM LOCATIONS FROM 15 TEST RUNS 2-19 3-1 CODE / CRITERIA 3-6 , 4-1 FATIGUE CRACK GROWTH RESULTS FOR 10% WALL INITIAL FLAW SIZE 4-4 5-1 STEPS IN A LEAK-BEFORE-BREAK ANALYSIS 5-6 5-2 LBB CONSERVATISMS 57 5-3 ROOM TEMPERATURE MECHANICAL PROPERTIES OF THE PRESSURIZER 5-8 SURGE LINE MATERIALS AND WELDS OF THE BEAVER VALLEY UNIT
. 1 PLANT 5-4 TENSILE PRCPERTIES FOR THE SURGE LINE MATERIAL AT 135'F 5-9 AND 653*F 5-5 FRACTURE TOUGHNESS PROPERTIES FOR 316 STAINLESS STEELS 5-10 AND WELDS 5-6 TYPES OF LOADINGS 5-11 5-7 NORMAL AND FAULTED LOADING CASES FOR LBB EVALUATIONS 5-12 5-8 ASSOCIATED LOAD CASES FOR ANALYSES 5-13 5-9
SUMMARY
OF LOADS AND STRESSES AT THE CRITICAL LOCATIONS 5-14 , 5-10 LOAD CASES, LOCATION AND TEMPERATURES CONSIDERED FOR 5-15 LEAK-SEFORE-BREAK EVALUATIONS , 4Q33e /10299010 yjjj
LIST OF TABLES (cont.)
- Table Title Page 5-11 LEAKAGE FLAWS FOR THE LEAK-BEFORE-BREAK ANALYSES 5-16 5-12 RESULTS OF STABILITY EVALVATION 5-17 m
I d I e6J3t'10299010 3
1 i LIST OF FIGURES
. Figure Title- Page 1 Determination of the Effects of Thermal Stratification . xxii 1-1 Simplified Diagram of the NSSS 1-39 i
i 1-2 Reactor Coolant System Flow Diagram (Typical Loop) 1-40 1-3 RCS Pressurizer 1-41 1-4 Estimate of Flow Stratification Pattern in Elbow Under 1-42 Pressurizer 1-5 Transient Development flow Chart 1-43 1-6 Beaver Valley Pressurizer Surge Line Monitoring Locations 1-44 1-7 Plant A Pressurizer Surge Line Monitoring-Locations 1-45 1-8 Plant B Pressurizer Surge Line Monitoring Locations 1 ' 1-9 Plant C Pressurizer Surge Line Monitoring Locations 1-47. 1-10 Temperature Profile (6.5-inch 10 Pipe) 1-48 1-11 Dimensionless Temperature Profile (14.3-inch 10 Pipe) 1-49 1-12 Surge Line Stratification 1-50 1-13 Surge Line Hot-Cold Interface Locations 1-51 1-14 Hot-Cold Interface Location From' Temperature Measurements' 1-52 1-15 Inadvertant RCS Depressurization (AT = 260'F in Surge Line) 1-53 1-16 Steam Bubble Mode Heatup 1-54 1-17 Steam Bubble Mode Cooldown- 1-55 1-18 Heatup ( Ja,c.e =1-56 1-19 Cooldown ( Ja,c.e 1-57 1-20 Heatup ( Ja,c,e 1-58 1-21 Cooldown [ Ja,c e 1-59' 1-22 rieatup [ )"'C 1 . 463h/10290010 i 7j
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l i I LISTOFFIGURES(cont.) I figure Title Page. . 1-23 Cooldown( la,c,e 1-61 1-24 Heatup ( Ja,c.e 1-62 i 1-25 Cooldown ( Ja,c,e 1 63 1-26 Heatup ( Ja,c.e 1 64
- l. 1-27 Cooldown ( -Ja,c.e 1-65 l
1-28 ( Ja,c.e Location 1 - Heatup (4 days)' 1-66 1-29 ( Ja.c.e Location 2 - Heatup (11 Days) 1-67 1-30 ( Ja,c.e Location 1 - Heatup (7 Days) 1-68 , 1-31 ( Ja,c.s location 1 Fatigue Cycles - Heatup -(11 Days) 1-69 1-32 Plant C Location #1 (3 Days) 1-70 1-33 Comparison of Design to Monitored Transients 1.71 - 1-34 Comparison of Design to Monitored Transients 1-72' 2-1 Determination of the Effects of Thermal Stratification 2-20 2-2 Stress Analysis 2 21 2-3 Typical Pressurizer Surge Line Layout 2-22 2-4 Cases 1 to 4: Radial Temperature Profiles 2-23 2-5 Case 5: Radial and Axial Temperature Profile 2-24 i 2-6 Finite Element Model of-the Pressurizer Surge Line Piping 2-25 General View 2-7 Finite Element Model of the Prescurizer Surge Line Piping 2-26 Hot Leg Nozzle Detail 2-8 Thermal Expansion of the Pressurizer Surge'Line Under 2-27 Uniform Temperature i 2-9 Case 2 (linear, Temperature Profile.at Hot Leg Nozzle 2-28
.q 2-10 Case 2 (linear) Temperature Profile-at Pressurizer Elbow 2-29 l I- i
.m.nu oo x$3-
_ _ _ _ ....-_.;.... - - - . . . . _ = _ _ _ _ _ _ _ . - - _ ..
i l LIST OF FIGURES (cont.) Figure Title Page l 2-11 Thermal Expansion o' Pressurizer Surge Line Under Linear 2-30 Temperature Graf;,nt 2-12 Bowing of Beams Subject to Top-to-Bottom Temperature Gradient 2-31 2-13 Case 3 (Mid-Plane Step): Temperature Profile at Hot leg Nozzle 2-32 2-14 Case 3 (Mid-Plane Step): Temperature Profile at Pressurizer 2-33 Nozzle 2-15 Case 4 (Top Half Step): Temperature Profile at Hot Leg Nozz.e 2-34 2-16 Case 4 (Top Half Step): Temperature Profile at Pressurizer 2-35 Elbow 2-17 Case 5: Axial and Radial Temperature Profile 2-36 2-18 Case 5: Axial and Radial Temperature Profile at Hot Leg Nozzle 2-37 2-19 Case 5: Axial and Radial Temperature Profile at Pipe Bend 2-38 2-20 Case 5: Axial and Radial Temperature Profile at Pressurizer 2-39 Elbow 2-21 [ 3a,c.e Profile 2-40 2-22 Beaver Valley Unit 1 Pressurizer Surge Line 2-41 2-23 Conclusions - Global Stress Analysis 2-42 4 2-24 Local Stress in Piping Due to Thermal Stratification 2-43 2-25 Independence of Local and Structural Thermal Stratification 2-44 Stresses Permits Combination by Superposition 2-26 Test Case for Superposition of Local and Structural Stresses 2-45 2-27 Local Stress - Finite Element Models/ Loading 2-46 2-28 Piping Local Stress Model and Thermal Boundary Conditions 2-47 2-29 Surge Line Temperature Distribution at [ la.c.e Axial 2-48 i Locations " 2-30 Surge Line Local Axial Stress Distribution at [ Ja,c,e 2-49 Axial Locations i 4m.nmeo io x3$$
LIST OF FIGURES (cont.) Figure Title Page . 2-31 Surge (ige,LocalAxialStressonInsideSurfaceat 2-50
- [ ] Axial Locations -
2-32 Surge (ige'LocalAxialStressonOutsideSurfaceat 2-51 ( ) Axial Locations 2-33 Surge Line Temperature Distribution at Location ( Ja,c.e- 2-52 2-34 SurgeLineLgegl,AxialStressDistributionat 2 Location ( ) 2-35 SurgeLineTgmgegatureDistributionat 2-54 Location ( ) 2-36 SurgeLineLgegl,AxialStressDistributionat '2-55 i Location ( ) 2-37 SurgeLineTgmgegatureDistributionat 2-56 Location ( ) 2-38 SurgeLineLgegl,AxialStressDistributionat 2-57 . Location [ ] 2-39 Surge _LineTgmgegatureDistribution-at 2-58 - Location ( ) 2-40 SurgeLineLgegl,AxialStressDistributionat 2-59 Location L ) 2-41 Surge Line Temperature Distribution at Location ( Ja,c.e 2-60 2-42 SurgeLineLgegl,AxialStressDistributionat 2-61 Location ( ) 2-43 Surge Line RCL Nozzle 3-D WECAN Model #1 2-62 2-44 Surge Line RCL Nozzle 3-D WECAN Model #2 2-63 l 2-45 Hot leg Nozzle Stress Analysis 2-64 2-46 Surge Line Nozzle Temperature Profile Due to Thermal- 2-65 Stratification 4 2-47 Surge Line Nozzle Stress . Intensity Due to Thermal .2-66 Stratification - 2-48 Surge Line Nozzle Stress in Direction Axial to Surge Line Due 2-67
- to Thermal Stratification l
ce33:nesseo 10 gjy
. u __ _ _ . _ . . . , _ _ . . _ . . _ , _ _. . , . _ , _ _ _ . _ _ , , _ _ _
d LIST OF FIGURES (cont.) Figure Title Page 2-49 Surge Line Nozzle Stress Intensity Due to Pressure 2-68 2-50 Surge Line Nozzle Stress Intensity Due to Pressure. 2 2-51 Surge Line Nozzle Stress Intensity Due to Bending 2-70 2-52 Surge Line Nozzle Stress in Direction Axial to Surge Line 2-71 Due to Bending Showing Magnified Displacement 1 2-53 Surge Line Nozzle Stress Intensity.Due to Bending Showing ~ Magnified Displacement 2-72 /! 2-54 Surge Line Nozzle Stress Intensity Due to Bending 2-73 z 2-55 Results 2-74 2-56 Local Stress Conservatism 2-75 2-57 Background - Thermal Striping Analysis 2-76 2-58 Thermal Striping Fluctuation 2-77 2-59 Stratification and Striping Test Models 2-78 2-60 Thermal Striping Temperature Distribution 2-79 2-61 Striping Finite Element Model 2-80
- 2-62 Thermal Striping Stresses 2,-81 2-63 Factors Affecting Thermal Striping Stress 2-82 2-64 AttenuationofThermalStripingPotentialbygoggular Conduction (Interface Wave Height of (
2-83 -
) )
2-65 Conservatisms in Thermal Striping Analysis 2-84 4-1 Determinination of the Effects of Thermal Stratification 4-5 on Fatigue Crack Growth 4-2 Fatigue Crack Growth Methodology 4-6 4-3 Aspects of the Fatigue Crack Growth Evaluation 4 - 4-4 Fatigue Crack Growth Rate Curve for.Austenitic Stainless Steel 4-8 , 1 4-5 Fatigue Crack Growth. Equation for Austenitic Stainless Steel 4-9 4-6 Fatigue Crack Growth Critical Locations '4-10 4633s/1C2HO10 gy
. , + - - - , ;----....__ --u-.,_-. - ,L..-.
LIST OF FIGURES (cont.) Figure Title Page , 4-7 Fatigue Crack Growth Controlling Positions at Each Location 4-11 4-8 Fatigue Crack Growth Conservatisms 4-12 5-1 Minimum True Stress-True Strain Curve for 316 Stainless 5-18 Steel at 653*F 5-2 Minimum True Stress-True Strain Curve for 316 Stainless 5 Steel at 135'F 5-3 Sketch of Analysis Model for Beaver Valley Unit 1 Pressurizer 5-20 Surge Line Showing Node Points, Critical Locations, Weld Locations and Type of Welds B-1 ( la,c.e, Location 1, Observed Transients B-2 B-2 Typical Heatup Design Transient Distribution Applied To B-3 One Heatup Cycle 0~3 I B-4 ja,c,e I 1 l 4633:1102990 10 yyj t
l 1 l EXECUTIVE
SUMMARY
The pressurizer of a Westinghouse type pressurized water reactor maintains and
- con.rols pressure in the reactor coolant system (RCS) via the pressurizer surge line which connects to a hot leg of the primary loop. The pressure is maintained such that boiling is suppressed and departure from nucleate boiling is prevented.
The flow path for a typical reactor coolant loop is from the reactor vessel to the inlet plenum of the steam generator. High temperature reactor coolant ficws through the U-tubes in the steam generator, transferring heat to the secondary water, out of the tubes i'to the outlet plenum to the suction of the reactor coolant pump. The reactor coolant pump increases the pressure head of the reactor coolant which flows back to the reactor vessel. r The pressurizer vessel contains steam and water at saturated conditions with
~
the steam-water interface level between 25 and 60% depending on the plant operating conditions. From the time the steam bubble is initially drawn during the heatup operation to hot standby conditions, the level is maintained at approximately 25%. During power ascension, the level is increased to approximately 60%. Investigations of primary coolant water flow into and out of the pressurizer have shown that significant temperature differences may exist in the surge line from end-to-end and from top-to-bottom during heatup or cooldown. Unanticipated large surge line pipe displacements have been experienced and temperature differences exceeding 250'F in a pipe cross section have been noted. Thermal stratification (layering of different temperature water) has been measured over significant time periods. The unexpected magnitudes of the pipe displacements and temperature differences exceed those defined in the design transients, suggesting that thermal design transients should be updated to incorporate the effects of the stratification. Such an update is performed
- 1 for Beaver Valley Unit 1 in this report and the structural response is evaluated. A similar evaluation has been performed for Beaver Valley Unit 2 '
as documented in WCAP-12093 and WCAP-12093 Supplements 1, 2 and 3. l I 463W10290010 gj j
t i l Of particular significance to surge line stratification are the normal l charging and letdown function provided by the Chemical and Volume Control , System and the suction and return lines associated with the Residual Heat l Removal System (RHRS). The former directly controls the RCS mass inventory . l and therefore affects flow in the sui line. The RHRS is used to remove heat from the RCS and thereby influences :solant temperature and consequently i coolant volume through thermal expe,nsion and contraction. I Other systems which affect surge line flow conditions are main spray flow supplied to the pressurizer from one or two cold legs and the pressurizer electric heaters. Spray operatien does not significantly alter the total RCS mass inventory but does reduce system pressure by condensing some of the steam in the pressurizer. The pressurizer heaters, when energized, generate steam and, as a result, increase RCS pressure. Thermal stratification in the pressurizer surge line is the direct result of the difference in densities between the pressurizer water and the generally cooler het leg water. The lighter pressurizer water tends to float on the l " l cooler heavier het leg water. The potential for stratification is increased ! as the difference in temperature between the pressurizer and the hot leg l increases and as the insurge or outsurge flow rates decrease. l At power, when the differer.ce in temperature between pressuriter and hot leg is relatively small (less than 50'F) the extent and effects of stratification have been observed to be small. However, during certain modes of plant heatup i and cooldown, this difference in temperature can be relatively large end-to-end, in which case the effects of stratification must be accounted for. A diagram of the approach taken to evaluate significant stratification is given in figure 1. l l A rather extensive data base has been obtained by pressurizer surge line transient monitoring including results from the Beaver Valley Unit 1 plant.
~
The dr.ta consist of pressures, displacements, operational status and l temperature monitored along the surge line. The most relevant data are those . associated with heatup and cooldown. l 4633s/:0399C 10 yyjjj 1
i An extensive study was made of the available data base. From this study a set ,, of conservative design transients was developed which incorporated the 1 characteristics of thermal stratification in the pressurizer surge line. This 4 . set formed the basis for the stress and fatigue analyses and the leak-before-break evaluation summarized below, i I The stress analyses were performed in three steps. Finite element structural ) or system stress analyses were made to determine p'ipe displacements, support I reaction leads and force and moment loads. These loads were used as input to the fatigue, fatigue crack growth and leak-before-break evaluations. Both l I axial and radial variations in the pipe metal temoeratures were included as appreoriate. Specifically, eleven cases of thermal stratification were analyzed reflecting temperature differences in the surge line up to 335'F. Stratification at operating temperatures as well as heatup and cooldown temperatures was analyzed consistent with the observed thermal stratification cata. The loads were found te be acceptable for all design conditions including the updated transients to account for thermal stratification. Local stresses were calculated for the top-to-bottom non-linear thermal gradients in the surge line at the mest critical locations which represent a bounding of hot-to-cold interface levels as implied from the-test cbservations. Three-dimensional finite element models of both pipe and nozzles were used. The total stress is required for the fatigue analyses. Such stresses were ! found by suoerposition of the structural stresses and the local stresses. Thermal striping due to the oscillction of the hot and' cold stratified boundary was also evaluated. The concern is with the stresses due to the differences between the pipe inside surface wall temperatures and the average 1 through wall temperature. Finite element analyses were also made for this I case. The ASME Section 111 fatigue usage factor due to thermal striping alone- j (* was found to be well below the ASME Section III code criterion of 1. 9 i 46Mt/tC2990 to xjg
I l l 1 Fatigue usage factors were evaluated based on Section III of the ASHE Code for l the total stresses using the updated design cycles which includes the effect . c' stratification. Due to the non-axisymmetric nature of the stratification loading, stresses due to all loadings were obtained from finite element , analysis and then combined on a stress component basis. Peak stresses were calculated for each transient. The combined usage factor was less than the ASME Section III code criterion of 1. Five events exceeding a system AT of 320'F were included in the analysis. The above usage factors do not include the effects of striping. Because the nature of striping damage is at a much higher frequency, varies in location due to fluid level changes and is maximized at a different location than the ASME usage factor, it was assumed to be more appropriate to determine a total usage factor by conservatively adding the above calculated usage factors and tne striping usage factors. This gave a maximum total usage factor which is still less than the ASME Code allowable of 1.0. To determine the sensitivity of the pressurizer surge line to the presence of small cracks when subjected to the updated transients, fatigue crack growth
- analyses were performed. Various initial surface flaws were assumed to exist. The flaws were assumed to be semi elliptical with a six-to-one aspect ratio. The largest initial flaw assumed to exist was one with a depth equal to 10% of the wall thickness, the maximum flaw size that could be found acceptable by Section XI of the ASME code. There is currently no fatigue crack growth rate curve in the ASME Code for austenitic stainless steels in a water environment. However, the fatigue crack growth curve for austenitic stainless steel used in the analyses is the one currently in the 1989 Edition of Section XI of the ASME Code for an air environment.
1 The locations, representative of all cross-sections of the surge line where thermal stratification could occur, were evaluated for fatigue ersck grouth. The transients exceeding a system AT of 320'F were included in the analysis. The maximum growth of a flaw assumed initially to have a depth of - 10% of the wall was seen to remain well below one-half the wall for fell
~
service life. cuwamvo xx
.3 A leak-before-break analysis was performed for the surge line of Beaver Valley . Unit 1. Particular attention was given to thermal stratification which changes the operating loads somewhat anC imposes large bending stresses during the lower temperature heatup and cooldown :enditions.
Seven separate leak-before-break evaluations were performed to envelop the stress states due to thermal stratification. The temperature for the evaluatlons ranged from 135'F to 653*F with top-to-bottom temperature differences up to 320'F considered. A forced cooldown situation through a shutdown stratification due to unidentified leakage at operating temperature was evaluated. Long term maximum stratification situations were also evaluated. Leak-before-break was demonstrated at operating temperature with and without stratification. Leak-before-break was also demonstrated for the forced cooldown situation and for long term maximum stratification. Essed on the current understanding of the thermal stratification phenonmenon, it is concluded that thermal stratification has very limited imcact on the integrity of the pressurizer surge line of the Beaver Valley Unit i nuclear power plant. The forty year design life is not impacted. . l l 4 i l l l l l l 6633s/102990 10 yyj l
i e! MONITORING AND TRANSIENT , DEFINITION 1
..=
~
u _1L y STRIPING SYSTEM LOCAL ' STRESS STRESS- STRESS ANALYSES ANALYSES- ANALYSES - V V V ; ASME CODE FATlGUE LEAK-BEFORE-BREAK CRACK FATlGUE ANALYSES GROWTH i ANALYSES ANALYSES Figure 1. Determination of the Effects of Thermal Stratification 4633sA02HQ 10 ggjj v
SECTION 1.0 4 INTRODUCTION AND UPDATE 0F DESIGN TRANSIENTS 1.1 Introduction 1 l 1.1.1 System Description l The primary function of the reactor coolant system (RCS)-is t'o transport heat from the reactor core to the steam generators for the production'of steam (figure 1-1). The system pressure is ' maintained and controlled by the q pressurizer, such that boiling is suppressed and departure-from nucleate- j boiling (DNB) is prevented. The RCS integrity is insured by the overpressure I protection of the pressurizer' safety and-relief valves. ' The Beaver Valley Unit 1 RCS consists of three similar heat transfer loops connected to the reactor vessel. Each-loop contains a~ reactor coolant pump'- l (RCP) and a steam generator. The system also includes a pressurizer, connecting piping, pressurizer safety and relief valves, and'a relief tank. l { The flow path for a typical reactor coolant loop is from the reactor vessel to -l I the inlet plenum of the steam generator (figure 1-2). High temperature ~ ( reactor coolant flows through the U-tubes in the. steam generator,' transferring heat to the secondary water, out of the tubes into the outlet plenum to the- ] I suction of the reactor coolant pump. The reactor coolant pump increases-the - pressure head of the reactor coolant which flows -back to the reactor vessel. The pres:.v tzer vessel (figure 1-3)- contains steam and water' at saturated conditions *with the steam-water interface between 25 and 60% depending ~on the-plant operating conditions. From the time -the steam bubble is initially drawn during the hedp operation to hot standby conditions, the -level is maintained at approximately 25%.'During power ascension, the level is. increased to approximately 60%. 6 4700s/*'14P 'O {.)
.i-..- .._i.._. -
l 1 As illustrated in figure 1-2, the bottnm of the pressurizer vessel is connected to the hot leg of one of the coolant loops by the surge 1.ine', a 14 ., inch schedule 160 stainless steel pipe, a portion of which is almost s horizontal, that is, slightly pitched down toward the hot leg. -. The simplified diagram-shown in figure 1-2 indicates the auxiliary systems that interface with the RCS. Of particular significance to surge line stratification are the normal charging and letdown function provided by the Chemical and Volume Control System -(CVCS), and the suction and return lines' associated with the Residual Heat Removal System (RHRS). The former directly-controls the RCS mass inventory'and therefore affects flow in the surge line. The RHRS is used to remove heat from the RCS and thereby influences coolant temperature and consequently coolant volume through thermal expansion and , contraction. Other systems which affe t surge line flow conditions are main spray flow supplied to the pressurizer from one or two cold legs and the pressurizer - electric heaters. Spray operation does not significantly alter-the total RCS mass inventory, but does reduce system _ pressure by condensing some of the *j steam in the pressurizer. The. pressurizer heaters when energized generate steam and as a-result increase RCS pressure.
~
1.1.2 armal Stratification In the Surge Line h Thermal stratification in the pressurizer surge line is the direct result of-the difference in densities between the pressurizer water and-the generally cooler _ hot leg water. The lighter pressurizer water tends to float on the cooler heavier _ hot leg water. _The potential for stratification is increased as the difference in temperature between the pressurizer and the hot __ leg increases and as the insurge or outsurge flow rates decrease. At power, when the difference in temperature between pressurizer and hot leg is relatively small (less than 50*F) the extent and effects of: stratification - have been observed to be small. However, during certain modes of plant heatup noo.nouso m 12
e I L l and cooldown, this difference in temperature can be large, in which case the
. effects of stratification must be accounted for.
l A common approach for assessing the potential for stratification is to . l evaluate the Richardson Number-(tables 1-1 and!1-2).which is the ratio of the l thermal density head diametrically across the-pipe to'the.. fluid flow dynamic 3 head, or Ri = geDaT 2 U u where Ri = Richardson number - t g = gravitation coni cnt U = hot fluid velocity AT = hot-to-cold fluid temperature difference D = pipe inside diameter
]
B = water temperature coefficient of thermal expansion For a range of surge line flow rates from approximately.700 gpm down to a bypass flow of approximately 1 to 5 gpm and ai = 320*F, the Richardson j 1 number is greater than the-value of 1 which is required to initiate - stratification. Thus under this range of conditions, the flow has-the-
]
potential to be stratified due to the-relatively large' hot-to-cold fluid temperature difference combined with the low; hot fluid velocity. To eliminate l stratification (i.e., Ri smaller tha'n 1) a flow-velocity of over 2.4 fps 1 l (approxi;tely700gpm)isneeded(figure 1-4). I 1.1.3 Surge Line Stratification Program 1 The surge line stratification program for Beaver Valley . Unit 1 consist of two. major parts: .
, (a) Plant monitoring and update of design transients coo.nomo io 1 3.
l
l l i \ l I e . l (b) ASME III stress, fatigue cumulative usage factor (CUF), fatigue crack growth (FCG) and leak-before-break (LBB) analyses . 1.2 Vodate of Desion Transients - Because the Beaver Valley Unit 1 and Unit 2 plants are similar in geometry, , and because both units have similar-operational guidelines, the transients t generated in the Beaver Valley Unit 2 analysis (WCAP-12093) will be used as a I baseline for creating Beaver Valley Unit 1 transients. 'First, _the development of these baseline _ transients is demonstrated. Next, Beaver Valley Unit 1-historical records are used to modify the transient' set.to account for pressurizer / hot leg temperature differences of greater than 320*F-(as illustrated later, this temperature difference was a limit defined =in the generation of the Unit 2 transients, see Supplement 3 of WCAP-12093). Finally, monitoring information from one actual heatup is used to ensure that-the baseline transients envelope Beaver Valley 1-transient activity. l l 1.2.1 System Design Information (table 1-3) The thermal design transients used for the Beaver Valley-Unit 1 Reactor Coolant System, including the pressurizer surge 1.ine, are defined in-Westinghouse Systems Standard Design Criteria (SSDC) documents SSDC 1.3. , The design transients for the surge line consist of two major categories: (a) Heatup and Cooldown transients - table 1-4 (b) Normal and Upset operation transient - table 1-5. By definition, the emergency and faulted transients are not considered in the ASME III Section NB fatigue life assessment of components. In the evaluation of surge line stratification, the current definition of normal and upset design events and the number of occurrences of the design events remains unchanged (" Label", " Type", and '" Cycles" columns of table 1-5). , The total number of current heatup-cooldown cycles (200) remains unchanged. (table 1-4). The definition of heatup-cooldown events and the number of . vowwoo no 14
occurrences (" Label",'" Type" and " Cycle" columns'of table 1-4) is updated to - reflect monitoring data, as described later. In al1 cases, the-definition of surge line flow temperature is modified to replace the original uniform temoerature by a' maximum stratif.ication temperature differential (" MAX AT " and " Nominal" columns on tables I strat 1-4 and 1-5). 1.2.2 Stratification Effects Criteria (table 1-3) To determine the normal and upset pipe. top-to-bottom temperature difference, "ai strat " (tables 1-4 and 1-5), the following conservatism is introduced. For a given event, the ai strat in tb pi,' will be the' difference between the "iaximum pressurizer temperature -i P minimum hot leg temperature, even-when they do not occur simultaneously. ( I-l ja,c,e l 1.2.3 PlantMonitoring(table 3-3) Surge line stratification data-from-[- - Ja c,e Westinghouse plants,
~
including Beaver Valley Unit 2 (figures 1-6 to 1-9) has been utilized in this analysis in developing the baseline transients. The data was obtained by continuous monitoring of the piping 00 temperature, displacements and plant parameters.- 4700s/102490 10 1-5 .
The data is sufficient to characterize stratification temperatures in the pipe-during critical operating transients and heatup-cooldown operation.--Also, the" . data is sufficient to verify that the pipe movements are consistent with analytical predictions, within an accuracy normally expected from hot- - I functional tests', as discussed in section 2.'1. The monitoring of plant parameters is sufficient to correlate measured i temperature fluctuations to changes in operation. In particular, it is apparent that temperature fluctua'tions are due to-flow insurge (into the-pressurizer) and outsurge (out of the pressurizer) which in: turn.are due to= differential pressure in the system.- While a simple-and definite mechanistic relationship between plant operation and insurge and outsurge has not been achieved, the data indicate.that a steady state stratified condition can be~ altered by any of the following events: (a) Expansion of the pressurizer bubble (b) RCP trip in the surge line loop (c) Safety injection (d) Large charging - letdown mismatch (e) Large spray rates In light of these observations, the update of design' transients is based on- ' plant monitoring results, operational-experience and plant operational procedures. Conservatisms have been incorporated-throughout the process'in the definition of transients (cycles, aT) and in the analysis, as described I in.the report. 1.2.4 Heat Transfer and Stress Analysis (table 1-3)- The correlation of measured pipe 00 temperature to ID temperature distribution t is achieved by heat transfer analysis as'well as previous experience with flow at large Richardson numbers (Rin1) (figures 1-10 and 1-11). 4 l l coo.nomo io 1-6
. -.- . .. -. - . ~ . . . . - . .. --- - _ _ _ _ _ - _ _
i These analyses and test data available to_date show that a stratified flow condition,[ > Ja,c e is a proper and conservative depiction of the flow '
. condition inside the pipe at large AT.and low flow rates (Ri>1).
An additional conclusion from the heat transfer and stress analyses'is that. [ ja c.e 1.2.5 Stratification Profiles Table 1-6 summarizes the major stratification profile character,istics. The monitored data shows a consistent axial temperature profile along the-horizontal portions of the ( .)a,c,e surge lines monitored (figures 1-12, 1-13 & 1-14). For purposes of analysis, this temperature profile was divided in [ la,c.e regions or " locations" along the pipe axis (figure'l-14). 1.2.6 Developn,ent of Conservative Normal and Upset Transients (table _1-3) Several conservatisms are introduced in the definition of the normal and upset 1 i thermal transients (tables 1-4, 1-5, 1-7 and 1-8). (
)a,c.e 4700s/IC299010 g7
l l l l
-l
( l
.1
.1 i
,ja.C,e t
[ q The normal and upset transients are listed in tables 1-4 and 1-5. 1.2.7 Temperature Limitations During Heatup and Cooldown (tables 1-3 arid'1-9) The maximum expected temperature difference.between the pressurizer and the 4 hot leg expected for . Beaver Valley is 320'F, therefore, this limit is used-in-creating the baseline transients. However, based on a review of historical ! records, this temperature difference was. exceeded during five of the heatups i-and cooldowns. These exceedances have been incorporated into the trar.:;ent-set as described later. I With the RCL cold, the pressurizer pressure (and therefore temperature)'is- - limited by the cold overpressure mitigation system (CONS). f L l f Practically, plants operate to minimize cowntime and heatup-cooldown time,- when power is not being generated.- The times at large AT are therefore L reasonably limited, as discussed later. 1.2.8 Historical Data (table 1-3)- , Since not all heatup and cooldown parameters affecting stratification are formally limited by Technical Specification or' Administrative controls, it is necessary to consider plant operational procedures and heatup-cooldewn
~
practices to update the original heatup and cooldown design transient' curves of SSDC 1.3 (figures'l-16 and 1-17). ' aco,nouso no 1.g l
To this end, a review of procedures, operational data, operators experience, l , and historical records was conducted for [ ]a,c.e Westinghouse PWR plants, including Beaver Valley Unit 1 (table 1-10). i The heatup and cooldown operations information acquired from this review is summarized in tables 1-11 and 1-12, [ 3a,c.e l The information is divided into heatup and cooldown tables and diagrams. The i diagram presents the pressurizer water and hot leg temperature profiles versus time. The varieus phases of the process are identified by letters along the diagrams' abscissa and in tables 1-11 and 1-12, 1.2.9 Development of Heatup and Cooldown Design Transients With Stratification As described above, the database of information used to update the heatup and cooldown transients, included the following: a) Typical heatup and cooldown curves, as developed from review of procedures, operational data and operators experience, b) Transients as monitored at [ ]a,c,e plants c) Historical records of critical lheatup and cooldown temperatures The heatup and cooldown transients are presented in the following sections as [ ]a,c,e and in similar fashion to the normsl and upset transients. Table 1-13 gives the general characteristics of the two types of transients observed. e 4700s/102 % 0 10 1.g
l 1.2.9.1 ( ]a,c.e Transients , A) Monitoring Transient Summary I . For a given monitored location, plots of temperature difference versus time were generated (figures 1-28, 1-29, 1-30, and 1-31). Two parameters were plotted, the pipe top to bottom temperature difference (labeled " surge line") ! and the pressurizer to hot leg temperature difference (labeled " system"). Only heatup data was available, discussion of cooldown transients-follows in section G. It is clear from the curves (figures 1-28,1-29,1-30, and 1-31) that for the observed neatups, (
]a,c,e while the Beaver Valley Plants, Units 1 and 2 (figures 1-28 and 1-29, respectively) had moderate thermal transient activity.
i For conservatism, the envelope from measured transients in all plants is - applied to define the transients, even though there was only a moderate level l i of these transients observed at both Beaver Valley plants. - l l B) Fatigue Cycles The fatigue cycles were obtained using the technique illustrated on figure 1-31, ( l l Ja,c e , C) Strength of Stratification l Plant monitoring data indicate that for the various transients observed the AT in the pipe (top to bottom) is not as large as the AT in the system o cc,no w io 1 10
- - . . . . ~ . - . - . - . . . _ - . . . . . . . . . . . - - . . . . - - . . . . . - -
.l 1
J (pressurizer to hot leg). The ratio of'ai in the pipe to AT in' the system 4 will be referred.-to as " strength of stratification".
- (-
la,c,e It should also.be notedlthat the maximum strength of stratification observed.was 0.95.- D) Number of Stratification Cycles (table 1-16) Plant monitoring data-indicated the significant events which could occur during a given heatup. [ 4 f W 4 ja,C,9 I i i l b aroosnousc 1o l 3.$$ i _ _ - _ _ _ _ _ _ _ _ _ _ _ - _ _ _ . , . . . . - . ~ . - . . . - _ . , , -
d i i I 1 h E) Maximum Temoerature Potential 1 The key factor in thermal stratification of the surge line is' the temperature; q ! -difference between the pressurizer and hot legn(section'l.2). This -t temperature difference is clearly maximized.dur.ing :the heatup-and cooldown,- ! when the plant is in mode 5 cold shutdown (hot . leg less -than' 200*F)1and the
- 1. .
! pressurizer bubble has been drawn with the reactor ~ coolant pump running- q l (pressurizer temperature larger than 425'F). ( l i i 1 ga,c.e - F) Final Cycles and Stratification Ranges i i I ( -i 4 f l i l i i ! l l )a,c,e }. 9 T me.iioasa so 1-12 d
i ( Ja,c.e For Heatup: i = 1 to 24, j = 1 to 6, k = 1 to 4 , The 24 transients produced are conservatively summed, based on ATi range, into 9 transients (H1 to H9). For cooldown i = 1 to 30, j = 1 to 6, k = 1 to 5 The 30 transients produced are conservatively summed, based on ATi range, into 7 transients (C1 to C7). G) Cooldown Transients The procedure used in heatup is applied to develop transients for plant cooldown. ( l
)a,c.e 1
l l 4 roc.ncan,>io 1 13
4 h i l
-1.2.9.2 [ .]a,c.e Transients
[ i -[ { l 1 ja,c,e . 1 1.2.9.3 Transient Basis Exceedances As indicated previously, trased on a review of the Beaver Valley 1 operating records, there were five events which had a system delta .T greater than the transient basis assumed upper limit of 320*F. Since none of these' system-delta temperatures were greater than'[.
.1 l i l
l L ,
)a,c.e '
Therefore, the addition'of these cycles conservatively e.ccounts for the events.- in which the system delta' temperature exceeded 320*F. 1.2.10--Striping Transients
^
Because of the nature of thermal striping stresses,-the maximum stratification. value rather than.the fatigue range'is~to be used.. This results.in' larger - values of stratification temperature. (
)a,c.e voo<nouso ,o 3 34
1.3 Conclusions Design transients were updated to inco porate stratification. The transients l
. were developed to conservatively represent-the cyclic effects of stratifi-cation at the Beaver Valley Plants. Additionally, the Beaver Valley 1 ,
monitoring data for one heatup was examined relative to the transients used in the fatigue analysis. Based on this comparison, it w6s determined -that the transients used in the analysis envelope Beaver Valley 1_ cyclic activity._ To further illustrate the margin included in the development of these_heatup transients, a simplified fatigue factor calculation is provided in figures 1-33 and 1-34 This comparison indicates that the design transients have a-factor of conservatism of approximately ( ja,c.e O e l
.tce. noise in 1-15
1 TABLE 1-1 ! i I iMPORTANT.DIMENSIONLESS GROUPS FOR SIMILITUDE IN HYORODYNAMIC TESTING 1 i Peremeter Symeel Definteen Sognessanos 1 Weiecaen kwton i O AP 2eV L 8
. Preneure torce,certs force factor 2 Caveseen nunter 0 17 - 8,),V 8 Seesure enerencenone
%rce 3 Aeynosce numoet me eVO a morna forcevocas mece 4 Suoune runner Si ric V vortes enocong Nemaancy+
oertie force 8 I $ Woou numoer We oOV er inome forceeurteci>*eneon force 6 froues numoer Pr V'90 arterne forcegrerey teste 7 meneroeon nuneer R. sepoiev8 suoyerwy iorcemene force tWested Prouco nuneer) 8
& Ewer nuneer Eu AP'sV Pfeesure forceheres Nete 9 Press tweet Pr *C.R Mononun o#usweyrm onuewer t0 Pocast numeer Po eVDC2 Convectwo near eeruser-(Re e Pr) conoucaw most wateser L88 11 Grasnoi numeer Qt 0 pg4Tla s Mercy forcerveseus forte
- 12. Reyteepn nunter Re LstgAATIuA 8
(Gr u Pr) NOMENCLATVE C = easede nest p a accesoresen of grerrer e = corner # = pnsecure cr = ewtece Wr4sen P e = Stet fluel preseW9 e = mermes coneasevey 7, = ause vapor pressure d = voeumore essensem osedtesent L.D = cnereciensac omeneene AT = teues temoerunsre cneMge Y = ltse vesessy
< .orton sneceng tunesstey a = necosey 1444s 121644 10
{.{6
l l l TABLE-l-2 STRAT!FICATION POTENTIAL BASED ON RICHARDSON NUMBER
- Stratification potential exists if RJ. > 1 a,c.e l
e e 4 4 34841 2fM410 ,7
1 l 1 TABLE 1-3 , NOTES FOR TRANSIENT DEVELOPMENT FLOW CHART . l (See Figure 1-5) (1) System Design Information: This includes the Following Documents. System Standard Design Criteria 1.3F,1.3X,1.3 Rev. 2 etc. (Cycles, Press, Tpress, TRCS, Surge Rate) SSDC Were Reviewed to Obtain Events and Cycles. Design Events and Cycles Were Not Altered. (2) Criteria was Established to Determine Effects of a Design Event on the Surge Line. The Following Conservative Criteria was Established. ( i l i ja,c.e (3) Plant Monitored Data Reviewed from the Following: o Beaver Valley o Plants [ la,c e 4rco,nomo ic 1.ig
TABLE 1-3 (Cont'd.) . NOTES FOR TRANSIENT DEVELOPMENT FLOW CHART Pipe Temperatures Obtained From RTD's and System Parameters Obtained from Plant Computer. [ 4 l
}d,C,0 i
arcos 102490 to 1.lg I 1 l l
l
-l I
TABLE 1-3 (Cont'd.) NOTES FOR TRANSIENT DEVELOPMENT FLOW CHART , (
)a,c.e (10) Design transients developed for stratification and striping affects in l surge line 4
.nconom in 1-20
TABLE 1-4 SURGELINE TRANSIENTS WITH STRATIFICATION . HEATUP (H) AND COOLDOWN (C) - 200 CYCLES TOTAL a,c.e TEMPERATURES (*F) i s o l l 1 l l I 4700s/102490 to ,
1 i i l TABLE 1-4 (Cont'c) SURGELINE TRANSIENTS WITH STRAT!FICATION i HEATUP (H) AND COOLDOWN (C) - 200 CYCLES TCTAL , a,c.e ! TEMPERATURES ('F') I l l l I l i i I
*Incut for maxim 1:Ing moment range only I/O = Insurge - Outsurge F = Fluctuation ,
i e O 4 4 ucunwoo 1-22
l l WESTINGHOUSE PROPRIETARY CLASS 2 I 1 1 TABLE 1-5 l l SURGE LINE TRANSIENTS WITH STRATIFICATION NORMAL AND UPSET TRANS!!NT LIST TEMPERATURES t 'F ) MAX NCMINAL LABEL TYPE CYCLES 6T ' Strat _ a,C,0 e WI e 4 me.namo io 1-23
l TABLE 1-5 (Cont'c.)' SURGE LINE TRANSIENTS WITH STRATIFICATION NORMAL AND UPSET TRANSIENT LIST TEMPERATURES (*F) MAX NOMINAL ~ , LABEL TYPE CYCLES AT PRZ T RCS T 3 d.C,e e i be 4 e 9 ocacion a in 1-24
i 1 I l TABLE 1-6 i STRATIFICATION PROFILES I
. l l
[ ja,c.e
- .roo.,io24m io 1-25
TABLE 1-7 HEATUP - C00' ?0WN TRANSIENTS . o Transients Were Developed Based On: , Typical Heatup Cooldown Curves Envelope (Plus Margin) of Events (Transients) Monitored Historical Data on Temperature Plateaus ( ja,c.e , 1 i l l l
=
me,nouie io , 1-26
1 l TABLE 1-8 DESIGN TRANSIENTS WITH STRATIFICATION
\
o- Heatup and Cooldown Combined With Other Events o Design Transient Criteria l l C I l l
. ja,c,e o Input for Local and Structural Analysis Defined - Plus Nozzle o Striping Transients Defined to Consider Maximum Stratification Cycles !
Ngardless of Range i l; I l i l m .
, . c, ,, ,, --
L- ' TABLE 1-9
. PLANT OPERATIONAL CONSTRAINTS;
' i o Tech Spec-or-Administrative Limit of:-[ I)a,c.e Between = :. surizer-and Spray Temperatures. i o Reactor Coolant System Pressure of ( Ja,c,e requ' ired for-RCP operation ( -]a,c,e o Cold Overpressure Mitigation Requires - Minimize Pressure at' Low RCS Temperatures (Appendix G Curves)'-' Steam Bubble Beneficial for Minimizing LTOP.
5 o Overall Gaal to Maximize Time at Power-l' o Recent Administrative Limits on Minimum RCS Temperature Prior to;
. Pressurizer Heatup '
A I 1 4 6 mviamo io 1.pg
, Jb
TABLE 1-10 OPERATIONS SURVEY o Summary of Plants Surveyed NO. OF YEARS OF OPERATION PLANT LOOPS l (MAXIMUM) [ { ' l ja.c.e 1 i o Deviewed Typical Heatup Cooldown Process I o Reviewed Administrative / Tech Spec Limitations o Reviewed Historical Events and Time Durations o Developed Heatup - Cooldown Profiles L I . l l uoo."ca.eo io 1 29 ( 5 m
4 9 O A S
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\
k w 1-30
a _- ._ - - _. __ _ T AttLE 1-12 C00t00WN DAT A SUlmtARY (PZR - HO T L E G ) T E W' . Dif f ERENCE AND f itfE DURAfl0N FOR E ACH PHASE i a.c.e t i [ l
)
c-- e w o* 5 i 4700s/102490: 10
s, a -
+ -,a,w,o n --w,,, - ------ - ~ - - ~ ~ - - - - - - - -
TABLE 1-13 TRANSIENT TYPES i 1 ( e ! 3a,c.e l l 4 co w ic 4n io 1-32
TABLE 1*14
$UMMARY OF FAi!GUE CYCLES FROY [ la c.e Cycle Delta Range ('F ) Cycle Delta Range ('F)
- - a,c.e NCTE: The celta range represents the relative severity ( AT) of eacn transient following the fatigue cycle acoroach.
noo nomo io 1 33
TABLE 1-15
SUMMARY
OF PLANT MONITORING TRANSIENTS WITH STRENGTH OF STRATIFICATION (RSS) . ( Ja,c e ( )a,c.e Beaver Valley Unit 1 Beaver Valley Unit 2 Coserved 00 served Observed 00 served Cycles RSS (1) Cycles RSS (1) Cycles RSS(1) Cycles RSS (1) _ a,c.e OBSERVED TRANSIENTS GROUPED BY STRENGTH OF STRATIFICATION (RSS) INTERVALS No. Observed % of RSS Cycles Total a,c.e l eund e mean coo.nca.o io 1 34
1 TABLE 1-15 (cont.) '
SUMMARY
OF PLANT MONITORING TRANSIENTS WITH STRENGTH OF STRATIFICATION (RSS) l RSS J % of Transients l __ _ a c.e i RELATIVE NUMBER OF CYCLES OF l STRENGTH OF STRATIFICATION (RNSSj) ) AFTER GROUPING 4 RSSj RNSSj Strength of
% Transients (2) j Stratification (1) a,c.e Nomenclature:
(1) Strength of Stratification (RSS) (2) Relative Number of Cycles of Strength of Stratification (RNSS) 4700s/102490 10 1-35
TABLE 1-16
SUMMARY
OF HONITORED TRANSIENT CYCLES (ONE HEATUP) . Plant No. of Cycles __. a,c.e. Avg. Monitored Cycles: 5.75 = x; Selected No. of Design Cycles: 36.5 (edded 30% to observed maximum number of cycles, plant A) DESIGN DISTRIBUTION APPLIED TO MAX NUMBER OF TRANSIENTS EXCEPTED MULTIPLIED BY 200 HEATUP OR C00LDOWN CYCLES l Nc. of iransients RSS __ a,c.e I am noo.neuse to 1-36
l i l TABLE 1-17 )
SUMMARY
OF % TIMES AT ! MAXIMUM TEMPERATURE POTENTIAL
- RMTP g HEATUP a,c.e W
- J Note: Recorced Range of Systems AT and RTMP from Plant A (9 heatups, 7 cooldowns)g Plant B-(8 heatups, 7 cooldowns) e v oov1cusoso 1 37
TABLE 1-18 i SURGE LINE TRANSIENTS - STRIPING LOADS , FOR HEATUP (H)' and COOLDOWN (C) _ a,c.e , i r k I a t T k i 5 4 m oco.ncu.o io 1-38 ;
I 5TDM GBBA2tR e>
< ' D
_w4v v J ;
' b y v no _k Y v v cuar aw Y '
D k J l . ~ i me 4 Figure 1-1. Simplified Diagram of the NSSS ,
- ooo.,o.a.o i.
1 39 a
Anassiery Spray (CVCS)
< r I I aseo-em a si. p, W 4 6
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<>== Diaryng t,,,e s r **e= fnHRS)
(CVCS) { -_ Leseown Low ecycs i figure 1-2. Reactor an! ant System Flow Diagram (Typical loop)
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l l I l 1 Aux Spray ==*- 1 i'
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- Spray l From Loop CL 9,,
- -
- Spray From Loop CL Surge Line Connecting i
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i l l l Figure 1-3. RCS Pressurizer l moronne io l 1 41 , I
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Figure 1-4. Estimate of Flow Stratification Pattern in Elbow Under Pressurizer am:ene ,e l
l l 1 l l 1 l 1 s l 1 syltIM 0(11GN l MONitoa80 th80RMAfl0N DATA 01 (3)
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t a ' I l Figure 1-7. Plant A Pressurizer Surge Line Monitoring Locations ? -c a n n w i. ,_ i i i s
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- rigure 1-9. Plant C Pressurizer Surge Line Monitoring Locations i l
on. man ic 1 47 , 1 l 1
i ] , i Temperature (*F) e,c.c i y 8 t i Angle 6 (Degrees) Figure 1-10. Temperature Profile (6.5-inch ID Pipe) 4700s/092890 le
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a,c,e 1
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. rm.,.n i.
1
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. e Temperature (*F) a,c.e ?
IR 5 Time (Hours) Figure 1-17. Steam Bobble Mode Cooldown
a,Cac 700 600 t h400
$: 6 300 1-Wn 100 O
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til 200 100 O TIE I I .I l8 s g gg .g l l l l' b !. l ll 1 - 3 5 l I I I I II I A B C DE F G 1J K i 11 I figure 1-26. lleatup [ l a.c.e l - mmmo io l l __e.- 6
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I j 4700s/092890 10 , i -f
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SECTION 2.0
~
STRESS ANALYSES Flow diagram figure 2-1 describes the procedure to :fetermine the effects of thermal stratification on the pressurizer surge '.1ne ba sed on transients developed in section 1.0. ( 3a,c.e Section 2.1 Addresses the structural or global effect of stratification Section 2.2 Addresses the local stress effects due to the nonlinear portion of the temperature profile Section 2.3 Addresses the total stress effects due to the oscillation of
. the hot-to-cold boundary layer (striping) plus the thermal stratification stress 2.1 Picino System Structural Analysis i
2.1.1 Introduction i The thermal stratification computer analysis of the piping system to determine i the nipe displacement, support reaction loads as well.as moment and force loads in the piping is referred tc as the piping system structural analysis. These loads are used as input to the leak-before-break, fatigue, and fatigue crack growth evaluations. The thermal stratification condition consists of
- both axial and adial variations in the pipe mc
- al temperature, as described in section 1.0. The model consists of straight pipe and elbow elements for
. the ANSYS computer code. (
l* l la,c,e These studies verified the suitability of the ANSYS computer code for the thermal stratification antlysis. ( ja,c e
...*'*'o 2-1
-l l
( 7 ja,c.e 2.1.2 Discussion The piping layout for a typical surgeline is shown in figure 2-3. The rigid suoport, Ril, originally installed to reduce deadweight and seismic loads provides resistance to the displacements caused by thermal. stratification. ( e i i r 4 I ja,c e
. .,'am io 2-2
.. . . . , , - - - . - _ . . . - . . . . . . - . . . . . - - . . . . - . . . . - . . . - . . . . . . .. -. . . . . . . . . . . . . . - . . . . . - - . - . ~ . - . . . - .
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l s l l l i [
}
3a,c.e s c6345/101C9010 g.4
- - - - . ~ . -- . - . . - . . ..- . - . - - . -
4 2.1.3. Results from Beaver Valley Unit IT Analysis
+
The pressurizer surge.line of Beaver Valley-Unit 1 was structurally analyzed
. . based on-both a no pipe whip restraint-contact configuration-and the existing- j gaped configuration. During this period, the. pipe whip restraint l gaps were; j
~
shimmed to a set ofl design values. On the last' heat-up, the: monitoring data ~ g obtained showed no whip _ restraint:was. in' contact becausef of LtheLimposed - I operating procedure. On.the cooldown cyi.le, however, a conservative l assumption was made -in the fatigue analysis to reflect. a potentials of contact-for the configuration even thoughLthe~same imposed operatingtprocedure remain effective. After this cycle, the pipe whip; restraint gaps will be enlarged to ~ ] allow for all thermal: movement.- 4 During one past plant specific heat-up under the_non-conthet configuration,-- 1 i l- the-measured displacement of 1.90 inches'in the verticar direction:at whip restraint St.R-4 (Node 184) compares well with. the calculated displacement of; 1.97 inches at a pipe- AT of 160*F.' LIn the analysis, the calculated . piping- - stress due to thermal stratification was' reviewed tolensure:thatjthe system
. will-not collapse in a " hinge-oment" mechanism; ' The primary plusTsecondary. 4 stress limit for this piping stress:is given by ASME III,lSection:NB 3600,: 4 Equation 12 as 3.0 S,. The. calculated _ stress intensity _ range wa'sidetermined from the methodology in ASME III, Section NB-3685. The maximum Equation 12 stress intensity range, which occurs at the hot leg nozzle,:is 49.9 +,si. This
~
is less than the Code allowable value of 53.0:ksi.. Thisworresp;nda to a' bounding thermal stratification case with the system ATL='320'F._ The maximum Equation 13 stress intensity range is 36.4 ksi as.. compared to the Code allowable of 50.1 ksi. For the case where the system AT = 320*F was exceeded from'Section'l.2.9, ; L the higher system 60= 335'F was considered in' the structural analysis. The- -l maximum equation (12) stress. intensity range is 52.0 ksi for the non-contract-
~
l configuration, which-is also smaller than the allowable 53.0 ksi.- 2.1.4 Conclusions-Analytical studies with the ANSYS and WECAN computer codes have confirmed the I validity of using an equivalent linear radial -temperature profile to represent 46Ns/10299010 2-5 e a . - . .- . -- - . . .,. -. ..
L l i i the thermal stratification for displacement and loads. Good. agreement was -; obtained between the ANSYS results and the measured displacements _with thermal stratification. Eleven cases of thermal stratification were: analyzed using.- the JNSYS-code for the Beaver Valley Unit I surgeline. Results-for all other , cases of stratification were obtained by interpolation, The resulting loads , on the pressurizer and hot ?eg nozzles are acceptable. The surge line pipe- , stress satisfies the ASME til NB-3600 Code Equation 12 limits. Pipe movements will be reviewed for-clearance considerations.. The above conclusions are summarized in figure 2-23. 2.2 ' Local Stress Due to Non-Linear Thermal Gradient 2.2.1 Explanation of Local Stress Figure 2-24 depicts the local-axial-stress components in a-beam with a sharply _ nonlinear metal temperature gradient. Local axial stresses-develop due to the.. restraint of axial expansion or contraction. This restraint _is provided-by - the material in-the adjacent beam cross section.- For a lineer top-to-bottom-temperature gradient, the local a 'al stress would not exist. (P .' e
}a,c,e 2.2.2 . Superposition of Local and Structural Stresses For the purpose of this ciscussion, the stress resulting from the global structural analysis (section 2.1) will be referred tozas " structural stress."
[
]a,c.e Local and structural stresses may be superimposed to obtain
~
the total stress. This is true because linear elastic analyses are performed , and the two stresses are ind3 pendent of one another as summarized in figure
.2-25. -
e,mim io 2-6
Figure 12-26 presents the results of a test case that was performed to l
. demonstrate the validity of superposition.. As shown in the figure, the. super- 1 1
position of locci and structural stress is valid. [ q l - j .- )a,c.e 2.2.3 Finite Element Model of Pipe for Local. Stress ' t A-short description of the pipe finite element model-is shown in figure 2-27. The model with thermal boundary-conditions is'shown in figure 2-28. Due to symmetry of the geometry and thermal loading, only half of the cr'oss section; was required for modeling and analysis.. -[~ l
,a,c.e 2.2.4 Pipe local Stress Results Figure 2-29 shows -the teciperature distributions through the pipe wall (
i i j )a,c,e 4434,1102900 10 ___ - . - _ _ _ . _ _ _ _ _ _ _ _ . _ . _ _ .mw.- y c e.d hi- *s_ ' &
,. s .i l- -t [ 1
.)a,c e 2.2.5 Unit Structural Load. Analyses For Pipe-In order to accurately superimpose local and: structural. stresses', several additional stress analyses were performed using the 2-0 pipe model. -( j i
t i a l [
*ja,c.e
\
2.2.6 RCL Hot Leg Nozzle' Analysis-- Two RCL surge line nozzle models were developed to evaluate;th'e effects cf thermal stratification. These two models-are shown in-figures 2-43 and 2-34 ( -t ja,c.e Figures 2-46 thru 2-54 present color contour-plots of temperature and' stress , distribations in the surge line RCL' nozzle. .A summary of local stresses in the RCL nozzle due to thermal stratification is given:in-table-2-5. . A summary r of pressure and bending stressas for' unit loading is sbawn inLtable 2-6. . . . 4 Results of the local stress analysis are summarizer in figure'2-55.- l 4634s/102990 10 2-8 'l r _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . ._ ; _. . . , . - . _ _ _ ._..__m_, _ ,
2.2.7 Conservatisms Conservatisms in the local stress analysis are listed on figure 2-56. [ ja,c.e 2.3 Thermal Striping 2.3.1 Background (figure 2-57) At the time when the feedwater line cracking problems in PWR's were first discovered, it was postulated that thermal oscillations (striping) may significantly contribute to the fatigue cracking problems. These oscillations were thought to be due to either mixing of hot and cold fluid, or turbulence in the hot-to-cold stratification layer from strong buoyancy forces during low flow rata conditions. (See figure 2-58 which shows the thermal striping fluctuation in a pipe). Thermal striping was verified to occur during subsequent flow model tests. Results of the flow model tests were used to l* establish boundary conditions for the :;tratification analysis and to provide striping oscillation data for evaluating high cycle fatigue. Thermal striping was also examined during water model flow tests performed for l the Liquid Netal Fast Breeder Reactor primary pipe loop. The stratified flow ( was observed to have a dynamic interface region which oscillated in a wave pattern. (See figure 2-59 for test pipe sizes, thermocouple locations, and table 2-7 for typical frequency of striping oscillations.') These dynamic oscillations were shown to produce significant fatigue damage (primary crack initiation). The same interface oscillations were observed in experimental studies of thermal striping which were performed in Japan by Mitsubishi Heavy Industries. 2.3.2 Thermal Striping Stresses Thermal striping stresses are a result of differences between the pipe inside surface wall and the average through wall temperatures which occur with time, due to the oscill: tion of the hot and cold stratified boundary. (See figure 2-60 which shows the w ical temperature distribution through the pipe wall). 4634 2l01090 to 2.g
(
~
- )a,c.e The peak stress range and stress intensity is calculated from a 2-D finite element analysis. (See figure 2-61 for a description of tne model.) [
- ] a , c , r' -The methods used to determine alternating stress intensity are defined in the ASME code. Several' locations were evaluated in order to determine the location where stress intensity was e maximum.
Stresses were intensified by K3 to account for the worst stress concentration for all piping element in the surge'line. The worst piping element was the butt weld. ( 3a,c.e 2.3.3 Fe. tors Which Affect Striping Stress The factors which affect striping are listud in figure 2-63: (-
's ja,c.e an.iioiao to 2-10 me v- -e ee w
..;... . . ~ . . . ~ . . . . . . - . . - ~ . _ . ~ . . . _ . . . . .- . . . . . . . . . . _ . . - . . . .
b t [ i i t 1 I I l l l l l Ja,C,0 l 4634s/102M010 2-11
[ ya.c.e 2.3.4 Conservatisms The conservatisms in the striping analysis are listed in figuro 2-65. The major conservatism involves the combination of meximum striping usage factor with fatigue usage factor from all other stratification considerations. The [ ja c.e , 3
& AS/10299G 10 ,
TABLE 2-1 COMPARISON OF WECAN AND ANSYS RESULTS FOR LINEAR STRATIFICATION - Case 2 (Displacements in Inches) ANSYS/WECAN (JOBANSF)WECAN (AGJAQLM) ANSYS (PERCENTAGE) a,c.e M M 4m.iio'" ' 2-13
TABLE 2-2 COMPARISON OF WECAN ( Ja,c.e A' , ANSYS [ la,c.e RESULTS FOR (- E3 Case 3L/ Case 3 Lecation Direction WECAN Case 3 ANSYS Case 3L (Percentage)
~
a,c.e i Case 3L ANSYS: DCISKXY, 11/12/88 o.orm ; 2-14
TABLE 2-3
. TEMPERATURE PROFILES IN PRESSURIZER SURGE LINE
- - 8,C,0 1
4 M h c l l l l l i l I l l 4e34,noioso io 2-15 t
l TABLE 2-4 BEAVER VALLEY SURGE LINE - MAXIMUM LOCAL AXIAL STRESSES AT ( Ja,c.e Local Axial Stress (psi) Location Surface Maximum Tensile Maximum Compressive a,c.e M N D ( 3a,c.e L 9 e i
.u .iioien io 2-16
TABLE 2-5 t
SUMMARY
OF LOCAL STRATIFICATION STRESSES IN THE SURGE LINE RCL N0Z2LE ! Linearized Stress Peak Stress Intensity Range (psi) Intensity Rance (osi) Diametral Location Location Inside- Outside Inside Outside a,c.e l l 5 4
. m .n oion ia 2-17
l l l TABLE 2-6
SUMMARY
OF PRESSURE AND BENDING INDUCED STRESSES . IN THE SURGE LINE RCL NDZZLE FOR UNIT LOAD CASES All Stress in psi Linearized Stress Peak Stress Intensity Range Intensity Range Diametral Unit Loading Location Location Condition Inside Outside Inside Outside
~
] a,c,e 4
'I 3
~
0634s/101090 10 2-18
TABLE 2-7
- STRIPING FREQUENCY AT 2 NAXIMUM LOCATIONS FROM 15 TEST RUNS Smuume l -
SrCoO l l 6 E esuse W 9 I 344ls/12f S84 to 2-19
OETERMINATION OF THE EFFECTS OF THERMAL STRATIFICATION a,c,e 4 l l l
~
Determination of the Effects of Thermal Stratification Figure 2-1. 149ts/121544 to 2-20
a,c.e Figure 2-2. Stress Analysis 3491s/ t 2154410 gg
l l . l Z o X PRESSURIZER Y
&' i Y
i
?
-j$f SP2 6 FT l
i 3 FT Spl ; M 27 FT , ll SNUSSER , I SNUSSER q4 Ril j i 21 FT RCL i i HOT LEG s 10 FT I i Figure 2-3. Typical Pressurizer Surge Line Layout u.i.n o u.io 2-22
. r-
- acre r 1
i s l I i I l I I f 4 l
.i Figure 2-4. Cases 1 to 4: Radial Temperature Profiles m, nmea ,o 2 23
i a,c,e '
- l i
l l - l I t i i t Figure 2-5. Case 5: Radial and Axial Temperature Profile 1491s /121$4810
e a,c.e l l I 1 Figure 2-5 Finite Element Model of the Pressurizer _ Surge Line Piping General View mi.n ma io 2-25
i a,c.e 1 l l l I Figure 2-7. Finite Element Model of the Pressurizer Surge Line Piping Hot Leg Nozzle Detail wsnvsuno 2-26
- a ,c .e i
i l l Figure 2-8. Thermal Expansion of the Pressur't.er Surge Line Under Uniform Temperature 3491$/121544 to g,y
i a,c.e i l i .i 1 I e I l 5 i Figure 2-9. Case 2 (linear) Temperature Profile at Hot leg Nozzle i R f i mi ntisu io 2-28 i a
__ - . ~ - - -- . . - -.
- 6 , c ,0 I
l l l l~ l Figure 2-10. Case 2 (linear) Temperature Profile at Pressurizer Elbow mi.name io 2-29
a,c,e l l i l l Figure 2-11. Thermal Expansion of Pressurizer Surge Line Under Linear Temperature Gradient m i n n s io 2-30
a,c.e Figure 2-12. Bowing of Beams Subject to Top-to-Bottom Temperature Gradient mi.einis44 to 2-31
a,c.e T M Figure 2-13. Case 3 (Mid-Plane Step): Temperature Profile at Hot Leg Nozzle 3491s/B2tS83 to
a,c.e 7' t
.t Figure 2-14. Case 3 (Mid-Plane Step): Temperature Profile at Pressurizer Nozzle 3491s/l21588 to
e. c, . a _ l e z z o N g e l t i o t t a l e i f o r P e r _ u _ . t a r e - p - m _ . e T
)
p e t S f l a H p o T ( 4 e s a C 5 1 2 e r u g i F o t 8 8 5 1 2 1
/
ts 9 4 3
?%
a.c.e ? M Figure 2-16. Case 4 (Top Half Step): Temperature Profile at Pressurizer Elbow 3491s/121588 to
- a,c.e
~0 N,
u cn Figure 2-17. Case 5: Axial and Radial Temperature Profile-3491s/121588 to
a,c.e m. Figure 2-18. Case 5: Axial and Radial Temperature Profile at Hot leg Nozzle uewuis ..
G a.c.e ru 8 us co Figure 2-19. Case 5: Axial and Radial Temperature Profile at Pipe Bend m ,.n meese
a c.e Y w d Figure 2-20. Case 5: Axial and Radial Temperature Profile at Pressurizer Elbow miuim ..
1 1 i a,c.e !
\
l. l l l l l l l. Figure 2-21. ( Ja,c.e Profile
> i.nsisu io 2-40
e 2, gg ) . % I A d 1 C \e,
- Q' e n
s (4C i i e L e
> b_
',e 3, S g
r u (, ' r e v e .%
'o
.Ni z
r u s e~ "' g s e r o
@ )* e P 1
C t e Ds
- i n
e S% ck i t y
- e C
l
'" l a
V r _ e _c v i O _ a S f@C e
,w9 B
D S D h L C . E W D L E L E W P O
@ M c 2
2 2 e r u g I F H S C e i F Ae o n _ t 0 9 90 19 .
/s 4
3 . 6 4 y3 _
o Temperature Profiles Established Through Parametric 1 Study o Good Agreements on Measured and Calculated . Displacements at Node 182
- o Eleven (11) Cases Analyzed to Calculate All Required Loading Conditions o Pressurizer and Hot Leg Nozzle Loads Acceptable o Piping Stress Within Code Limits l
o Pipe Movements to be Reviewed Against Clearance Figure 2-23. Conclusions - Global Stress Analysis 4634s/10 h09010 2-42
d c .e n.> b w Figure 2-21. Local Stress in Piping Due to Thermal Stratification 34Gis/82tS8818
~ ~ , * ,
l
a,c.e a 4 J e 4 1 i Y Figure 2-25. Independence of local and Structural Thermal Stratification Stresses Permits Combination by Superposition uo.nusu to 2-44
e,c.e l I l l Figure 2-26. Test Case for Superposition of Local anc Structural Stresses . no,.n mse ,o 2-45
~
a,c.e l l a l ' l Figure 2-27. Local Stress - Finite Element Models/ Loading 34plen2tS44to 2-46
a,c.e i Figure 2-28. Piping Local Stress Model and Thermal Boundary Conditions u i.misa io 2-47
a o c,e l i . l l l l l-l l l Figure 2-29. Surge Line Temperature Distribution at [ Ja,c.e Axial Locations mi.n sius io 2-48
ace r a l i i l l Figure 2-30, Surge Line Local Axial Stress Distribution at [ la,c.e . Axial locations mwmin io 2-49
a,c,e l I 4 l Figure 2-31. Surge Line Local Axial Stress on Inside Surface at [ ]a,c.e Axial locations i uv.nvue so g.59 l
1 a,c,e l l l l l l l I figure 2-32. Surge Line Local Axial Stress on Outside Surface at - [ Ja,c.e Axial Locations m,.nnsse ,o g.53
- -,,,- - - - - - - - - - w -.
s a c.e
~
e a, N Figure 2-33. Surge Line Temperature Distribution at Locatien [ l a,c.e t - - - _ _ _ -
d _.C,e N. u. <a Figure 2-34. Surge Line Local Axial Stress Distribution at Location [ ]a,c.e 3491s/021580 to
4 I a,c.e to e E i Figure 2-35. Surge Line Temperature Distribution at Location [ ] * *C
l 4
-- _d c.e
~
8 w w i Figure 2-36. Surge Line Local Axial Stress Distribution at location [ Ja c.e mi.m s .. b
a,c.e Y \ 8' Figure 2-37. Surge Line Temperature Distribution at Location [ la c.e 3491s/123S48 to
;: i , :
e, C. d-e. c, a] [ n i o t a c o L t a n i o t u b
. i r
t s i D s s e r t S l i a x A l a c o L e n i L eg r u S _ 8 3 2 e r 4 u g
. i F
e i e s i - u, i. m 3 , r.uN 4 1
I d,C,e E
**C'"
Figure 2-39. Surge Line Temperature Distribution at Location [ ] m.. mis i.
a,c.e P w to Figure 2-40. Surge Line local Axial Stress Distribution at location [ ]a,c.e
a,C,e i t i l N. s O i I i 1 1 figure 2-41. Surge Line Temperature Distribution at Location [ ]a,c.e
}eets/92tS88 to
l i 1 a,c.e i i N. I W n 4 4
- ]
Figure 2-42. Surge Line Local Axial Stress Distribution at location [ ]*' 349 t s/ tits 8818
a.c.e
'?
O figure 2-43. Surge Line RCL Nozzle 3-D WECAN McAe1 #1 3491s/126%8 le
c i a,c.e i 4
-i i .
m ' e
! m w
j ( s j 1 ) a Figure 2-44. Surge Line RCL Nozzle 3-D WECAN Model'f2 3496s/824588 le t O
- 9 9 e 3 ...-t-, -
g - - c.
Figure 2-45. Hot Leg Nozzle Stress Analysis o Two 3-Dimensional Models Developed o Loading included Pressure Bending Moments Stratification o Stratification Profile Based on Observation During RCP Trip p ursn vus ,o 2 64
l . a,c.e I t 7 8 Figure 2-46. Surge Line Nozzle Temperature Profile Due to Thermal Stratification 3491s/121588 ID
a,c.e '? E Figure 2-47. Surge Line Nozzle Stress Intensity Due to Thermal Stratification 349ts/12tS38 to e
. , I e,
c, a e u D e n i L e g r u S t o l i a
. x A
n i o t c e i r D n i n s o s i e l r a t c S i f e i l t z a z r o t N S e l n a i m L r e e h g T r u o S t 8 4
,. a 2 i
_ - em i r u ' 2 g i " F 2
?O
e. c. a _. e r u s s e r P t o e u D y t i s n e t
. n I
s s e
. r t
S l e z z o N e n i L e g r u S 9 4 2 e r u g i F 0 . 1 8 8 5 1 2 1/ 5 19 4 1 7$
e.
- c. .
a_ e r u s s e r P o t e u D y t i s n e t i n s s e r t S l e z z o N e i n L e g r u S 0 5 2 e r u g i F
~ 0 1
8 t 2 I
/
is
- - S 4
3 o ee r a
-_ _____ _ _ _ - . _ . - - - . =
l a,c.e -i
-i 1
I , i 1, - T m. a M
?
T ;
.i d
Figure 2-51. Surge Line Nozzle Stress Intensity'Due to Bending .' P 3491s/321588 IS If g m - - ,s > g wiu: .--s'g.cn, - .- -
.cv >-
a ,c,e .
'i 4
j N 5 2 il Fisce 2-52. ~ SurgeLineNozzle-StressinDirectionAxialtoSurgeLineDuetoBandingShowing Magnified Displacement
.. . ri
- - _.--.--m. ... .. , _ , . , _ . - ~: , , . . _ _ . . ..~.E.._ y ,
\. __ _ . , . . _ _ _ _ I ace c c l i 4 1 1 i t N 8 M N i i
~
Figure 2-53. Surge Line Nozzle Stress Intensity Due.to Bending Showing Showing Magnified Displacement ~ 3491s/128588 10
-x.:-. . ._ . ._ _ ., _ _ -. , . _ , , .._ ,..i
I, t; iiI :'., !! ;! s f ;: ' I t ! !! ! , i!!, , : l,.!l! llll!i e. c, a J_ g s n d n e B t o m u e D y t i s n t e n I s s e r
. t S
l e z z o N
'e n
i L e g . r u S 4 5 2 e r u g i F 0 3 8
- - 8 5
3 2 8
/
is 9 4 3 o ~u re
, . 2:,
Figure 2-55. Results a,c,e o Stress Profiles Developed for Pipe Cross-Section o Maximum Stresses Occur on inside Surface Near Interface o Results Consistent with Theory o Stresses to be Combined with Structural Bending b e 1491s'121144 10 2*74
Figure 2-56. Local Stress Conservatism 1 o The Hot / Cold Fluid Interface is Assumed To Have Zero Width. A More Gradual Change From Hot To Cold Would Significantly Decrease Local Stresses.
- o Stresses Are Based On Linear Elastic Analysis Even Though Stress Levels Exceed Material Yleid Point.
i l ' i 4 1 4 9 9 usw,1,sse so 2 75 1
l l l Feedwater une in PWR's Flow Tests For LMF8R t
, Experimental Tests in Japan
- Mitsubishi Heavy industries, Ltd.
Thermal Striping Affects ASME Fatigue Analysis
- Temperature Fluctuations at Boundary
- Thermal Discontinuity Stresses Usage Factor for Fatigue Ufo I
i
-i l
l Figure 2-57. Background - Thermal Striping Analysis l usivi21ssa to 2-76
1 1 l
)
. a,c.e l
Figure 2-58. Thermal Striping Fluctuation . ues.n mse ,o 2-77
. . . o . .
_ a c.e to I N cx> Figure 2-59. Stratification and Striping Test Models 349ts/l21558 to
ad E m . m, .a l
' a,Cie l
l .
+s e
N Figure 2-60. Thermal Striping Temperature Distribution - J' _ , . . . . 2-ze
G Y. m D x a C e d C a ope . C em E CD c em er b a M 984 t N O L 3 CD e-e e n C k 2-80
a,c.e Figure 2-62. Thermal Striping Stresses . m i n m .4ia 2-81
l l I _ _ a,c.e Figure 2-63 Factors Affecting Thermal Striping Stress mi.n ma io 2-82
. . . . . . . . . . . . . .6 r
a,c.e Figure 2-64. Attenuation of Thermal Striping Potential by Molecular - Conduction (Interface Wave Height of [ Ja c.e) m i n u m io 2-83
-- a,c.e 0
Figure 2-65. Conservatisms in Thermal Striping Analysis m i.n n su ic 2-84 l l
SECTION 3,0 , ASME SECTION 111 FATIGUE USAGE FACTOR EVALUATION-3.1 Code and Criteria Fatigue usage factors for the Beaver Valley Unit 1 surge.line were evaluated based on the requirements of the ASME B & PV Code, Section III (1), Subsection-NB-3600, for piping components. The more detailed techniques of_NB-3200 were- i! employed, as allowed by NB-3611.2. The fatigue evaluation required for-level-A and B service limits in NB-3653 is summarized in table 3-1. ASME 111 fatiguo usage factors were calculated for [ Ja,c.e points in.- the surge line piping using. program _WECEVAL(2). The transient i_nput data used-in the fatigue analysis were provided in Section 1.0 with~~ system AT in exceedance of 320'F reconciled. 3.2 Analysis for Thermal Stratification With thermal transients redefined to account for thermal stratification as-described in section 1.0, the stresses in the piping components were established (section-2) and fatigue usage factors were calculated. Due to the non-axisymmetric nature of the stratification loading, stresses:due to all loadings were obtained from finite element analysis and then combined on a stress component basis. 3.2.1 Stress input Stresses in the pipe wall due to internal pressure, moments and thermal stratification loading were obtained from the WECAN 2-D analysis'of a 14 inch, schedule 160 pipe. [. ' ja,c.e 3-1
[
'i
'f
.)a,c.e i
3.2.2 Classification and Combination ofLStresses I As described in 3.3.1 the total stress in the pipe wall.was determined for each transient load case. Two types of stress were calculated - Sn (Eq 10), to determine elastic plastic penalty factors, K,, and Sp -(Eq 11) peak stress. For most components in the surge line (girth butt welds, elbows, bends) no gross structural discontinuities are present. As a result,Ethe-code-defined "0" stress (NB-3200), or C 3ElaaT, abiblin Eq-(10); of NB-3600 is zero. Therefore, for these components, the Eq. (10) stresses are due-to pressure and moment. [ For-the RCL hot leg nozzle, the results.of the 3-D finite element.WECAN
- analysis of the nozzle were used to determine "Q" stress for
- transients with .
! stratification in the nozzle. Note also that the Eq. (10) stresses . included appropriate stress intensification using the secondary stress indices from 1 ! NB-3681. Peak stresses, including the total surface stress from all loadings - pressure, moment, stratification - were then calculated for each transient. !. I i ja,c.e 3 3.2 3 Cumulative Fatigue Usage Factor Evaluation 4 Program WECEVAL uses the n S and p S stresses' calculated for each transient to determine usage factors at selected locations in the pipe cross section. ., Using a standard ASME method, the cumulative damage calculation is performed $ according to NB-3222.4(e)(5). The inside and outside pipe wall usage factors a q. 4ms/102990 to 3-2
a were evaluated at (' Ja,c,e through the pipe wall of the , 2-0 WECAN model (figure 2-28). This includes: ;
- 1) Calculating the Sn and Sp ranges, K , and Salt for every possible combint. tion of the [ la, ,e. transient load sets, 1
- 2) For each value of Salt, use the design fatigue curve to-determine .j the maximum number of cycles which would be allowable if this type of cycle were the only one acting. These values, N1 , N 2 ...N n '
were deterndned from Code figures I-9.2.'1 and I-9.2.2, curve C, for : austenitic stainless steels.
- 3) Using the actual cycles of each transient _loadset supplied to
, WECEVAL, ni,n2*"n, calculate the usage factors Uy ,
U 2
*U n from U$ = ng /N4 . This is-done for:all possible.
11 combinations. If N $is greater than 10 cycles, the value of V4 is taken as zero. ( ja,c.e
- 4) The cumulative usage factor, Ucum, is calculated as Ucum =V3+U2
+ ... + U n. The code allowable value is 1.0.
3.2.4 Simplified Elastic-Plastic Analysis When code Eq. (10),nS , exceeded the 3Sm limit, a simplified elastic plastic
. analysis was performed per N8-3653.6. This required separate checks of expansion stress, Eq. (12), and Primary Plus Secondary EACluding Ihermal Bending Stress, Eq.
(13), Thermal Stress Ratchet, and calculation of the elastic plastic penalty factor, i L
. n.,i- to 33 l L
Ke, which affects the alternating stress by Salt " K e bp /2. The K, values for all combinations were automatically calculated by WECEVAL. Thermal stress ' ratchet was also checked. Eq. (13) is not affected by thermal stratification in the pipe where no gross structural discontinuities exist, but is required to be verified
- at the nozzle. Eq. (12) was evaluated in the Global ANSYS analysis by checking the worst possible range of stress due to the expansion bending moments (section 2).
3.2.5 Fatigue Usage Results The maximum usage factors were [ ]a,c,e at the elbow (nodes 192 to 194, figure 1-16) and [ Ja,c.e at the RCL nozzle safe end (node 171, figure 1-16). The above usage factors do not include the effects of striping. Because the nature of striping damage is at a much higher frequency, varies in location due to fluid level changes and is maximized at a different location than the ASME usage factor, it was assumed to be more e - opriate to determine a total usage factor by conservatively adding the above calculated and striping usage factors. This results in a total U cum f( ) ' ' , less than the Code allowable-of 1.0. 3.3 Conservatisms in Fatigue Usage Calculation The above calculated ASME usage factors contain the inherent conservatisms known to be in the ASME Code methods. These include the conservatism in the elastic plastic penalty factor, K,, the method of combining loadsets based on descending S alt' and the factor of 2 on stress and 20 on cycles in the design fatigue curve. Also, due to input limitations in program WECEVAL, the maximum value of peak stress intensification for all loading types was used. This was conservative at girth butt welds, since K1 = 1.2, K2 = 1.8, K3 = 1.7 in NB-3681 and K=1.8 was used in I WECEVAL for all stresses. 4 un,naiosm 3-4
3.4 References 3-1. ASME Boiler and Pressure Vessel Code, Section III,1986 Edition. 3-2. WCAP-9376, WECEVAL, ,omputer Code to Perform ASME BPVC Evaluations Using Finite Element Mo' , Generated Stress States, April, 1985. [ Proprietary) 3-3. [ ]a,c.e 3-4. [ ja,c.e 9 4 4en,n ot oso io 3-5 l l
TABLE'3-1 ! 1 CODE / CRITERIA /
-i
'1 -
o ASME B&PV Code,'Sec. III, 1986 Edition
- -NB3600 NB3200 -;
o Level A/B Service Limits Primary Plus . Secondary Stress Intensity .5 3Sm (Eq. 10) Simplified Elastic-Plastic Analysis Expansion Stress, S, 5 3Sm (Eq. 12) - Global Analysis-Primary Plus Secondary Excluding Thermal Bending < 3Sm (Eq. 13) 4 ' Elastic-Plastic Penal.ty Factor 1.0 5 K, 3 3.333 Peak Stress (Eq.11)/ Cumulative Usage Factor (tJcum) S
- K 3 /2 (Eq.14) alt ep Design Fatigue Curve Ucum 5 1.0 L
l-l l 2 e>,,,,,,,. 36
L SECTI'ON T4.0' FATIGUE CRACK GROWTH EVALVATION'. 4.1 Introduction f To determine the sensitivity of the pressurizer' surge line.to-the presence of small cracks when subjected' to the transients discussed in section 1.0, :j i fatigue crack growth analyses were performed. The transients exceeding a
~
- l. system AT of 320*F were included. This section summarizes the analyses and-results.
L Figure 4-1 presents a general flow diagram of the overall process. The methodolccy consists of seven. basic steps as shova in. figure 4-2. Steps 1 thru 4 are discussed in sections 1 and 2_of this report. Steps 5 thru 7 are specific to fatigue crack growth and.are discussed in this section and summarized in figure 4-3. There is presently no fatigue crack growth rate-curve in the ASME Code for 1 austenitic stainlets steels in a water environment.. However, a great deal'of work has been done recently which supports-the development of such a curve. An extensive study was performed by the Materials Property Council Working a L Group on Reference Fatigue Crack Growth concerning the crack growth behavior I of these steels in air environments, published in reference 4-1. A. reference curve for stainless steels.in air environments, based on this work, is in the 1989 Edition of Section XI of the ASME Code. This curve is shown-in figure 4-4. A compilation of data-for austenitic stainless steels'in a PWR water environment was made by Bamford (reference 4-2),'and it was found that the l effect of the environment on the crack growth rate was very small. For this
, reason it was estimated that the environmental factor should bel set at 1.0 in- L the crack growth rate equation from. reference 4-1. Based on these works
. (references 4-1 and 4-2) the. fatigue crack growth law'used in the analyses 'is as shown in figure 4-5.
umnocuo io 41
4.2 Initial Flaw Size Various initial surface flaws were assumed to exist. The flaws were assumed to be semi-elliptical with a six-to-one aspect ratio. -The largest initial - flaw assumed to exist was one with a depth equal to 10% of the wall thickness, the maximum flaw size that could be found acceptable by Sectican XI of the ASME i c od:, . . 4.3 Critical Locations for FCG b All five locations (as referred to in section 1.2.5), representing all cross J sections of the surge line where thermal stratification could occur, were evaluated for fatigue crack growth. Figure 4-6 identifies the five locations. The location [ ]a,c e stratification profile exists at the surge line RCL nozzle when the RCP pump is not running and, therefore, turbulent mixing caused by flow in the main RCL piping is not occurring. This effect was observed in the surge line monitoring programs (section 1.2.3.) This temperature profile develops a lower inside wall local axial tensile stress than developed at other locations (see table 2-4 in section 2.0). Based upon the above discussion, location ( ]a,c e is not a critical location for fatigue crack growth. For completeness, however, fatigue crack growth calculations were performed at location [ ]a,c.e , Figure 4-7 identifies the positions at each location where fatigue crack growth was checked. These positions [ ]a,c.e are controlling positions because the global structural bending stress is maximum at positions [ ]a,c.e while the local axial stress on the inside surface is maximum at positions [ Ja,c.e 4.4 Results of FCG Analysis O esults of the fatigue crack growth analysis are presented in table 4-1 for a 10% wall initial flaw. The maximum depth for full service life was less than ' 25% of the wall. The transients exceeding a system at of 320'F had almost no impact on the results.
. m ,/ / i // ,
Z // !/ e/ i ,
'/ / // /
i / / / //// I [l / / s o-s Y ) /l, **to ll 'l, / l l / / .' / i i a f //
/ / f / //
/ / t il l s
//
)
, /,//
/
,l - --
/ // /
l ,g, / 20 x too iot ,g a a.. t;n Figure 4-4 Fatigue Crack Growth Rate Curve for Austenitic Stainless Steel
<nwee,seo ,o 4.g
ga 3 C F S E AK .30
. on where
= , rack Growth Rate in inches / cycle fa C = 2.42 x 10 -20 F = frequency factor (F = 1.0 for temperature below 800'F)
S = R ratio correction (S = 1.0 for R = 0; S = 1 + 1.8R for 0 < R < .8; and S = -43.35 + 57.97R for R > 0.8) E = Environmental Factor (E = 1.0 for PWR) AK = Range of stress intensity factor, in psi / in R = The ratio of the minimum Ki (Kimin) to the maxin.bm Ky (KImax)* l l Figure 4-5. Fatigue Crack Growth Equation for Austenitic Stainless Steel asus/esiseo to 4.g
1 I 1 l l l l _ a,c.s i Fatigue Crack Growth Critical Locations ~ Figure 4-6.
.us.wsee io 4-10
1 1 l
- a,c.e :
I l l l Figure 4-7, fatigue Crack Growth Controlling Positions at Each Location ; f l 4635s/091890 10 - 4-11 _ _ _ _ _ _ _ _ _ _._. __ _ _ - _ . - - - -__ _.-.~.
1 l { o Plant operational transient data have shown that the conventional design transients contain significant conservatisms I
- a,c e o FCG analysis assumes crack growth on every cycle Figure 4-8. Fatigue Crack Growth Conservatisms 4ns.nocwo ic 4-12 I' 's, i ,.......w,,. . . . _ _ _ _ _
i SECTION 5.0
< ASSESSMENT OF LEAK-BEFORE-BREAK
- 5.1 Backgret.nd The recent concern for thermal stratification in pressurizer surge lines has prompted the analyses presented in previous sections. 'Specifically, thermal stratification has been shown to impact normal operating loads and to have the potential for imposing large thermal bending loads during-the heatup and cooldown transients. Also under the current surge line configuration, the normal operating leads are identical to those of Beaver Valley Unit 2 as reported in Reference 1. The discussion of section 1.0 concludes that prior thermal stratification transients used in the evaluation of Beaver Valley Unit 2 (see Reference 1) are also applicable to Beaver Valley Unit 1 with the exception of plant specific transients which exceeded a system AT of 320*F.
These transients are accounted for in the analyses of' sections 3.0 and 4.0. In this section, leak-before-break for the pressurizer surge line is assessed taking into account thermal stratification. The leak-before-break methodology is reviewed and the analyses are summarized. Conclusions are drawn, 5.2 Methodology i The steps of the leak-before-break methodology are reviewed in table 5-1. Items 2, 3 and 8 are addressed in sections 2, 1 and 4 of this report, respectively. This section addresses items 1, and 4 through 7. -The l conservatisms used in this section are listed in table 5-2. 5.3 Material and Fracture Toughness Properties Applicable material properties were obtained from the Certified Materials Test Report and are given in table 5-3. The material-is SA376 TP316, a wrought product form, or its worked equivalent. The ASME code minimum' properties are I / 4625s 4 00190 10 5-1 _ . - . - - - . . . - . , , - , , - , , . , . . , . , , . ~ ~ . . . - . . . . . . .~ ,- . .-- . _ - -. - - , _ - ,-
i also given in table 5-3. It is seen that the measured properties well exceed those of the code. As seen later, properties at 653'F and 135'F are required
- for the leak rate and stability analyses. Industry data at room temperature and 650*F were used as a basis for determining tensile properties at the required -
temperatures. The required average and minimum properties are given in table 5-4 along with the modulus of elasticity. The stress strain curves required for the stability analyses are given in figures 5-1 and 5-2. The curve at 653'F was obtained by application of the Nuclear Systems Materials Handbook (reference
- 2). The curve for 135'F was obtained from experimental data. Fracture toughness properties are given in table 5-5 taken from references 3 through 6.
Conservative estimates of toughness were chosen by using the material footnoted by d. 5.4 Leading Conditions i Because thermal stratification can cause large stresses at heatup and cooldown temperatures in the range of 455'F, a review of stresses was used to identify the worst situations for LBB applications. The loadings states so identified are given in table 5-6. Two locations, nodes 171 and 196, as shown 'in figure ' 5-3, are the most critical for LBB evaluation. Node 196 at the pressurizer nozzle is the critical location for normal operation at 653'F while node 171 at the het leg junction is the critical location during heatup and cooldown with the pressurizer nominally at 455'F. There are field welds at both locations being SMAW following a GTAW root pass. l i Seven loading cases were identified for LBB evaluations as given in table 5-7. Cases A and B are normal operating conditions with a ( e
- )a,c.e 463)s/102390 10 5-2
. - - - .- - _-. . . - --- .-. - . . = = _ . - -.
l [ e 4 ja.c.e Thus, there are seven LBB analyses to be performed as outlined in table 5-8. The loads appropriate for these cases are given in table 5-9. 'The stresses are also given. The minimum wall thickness is.1.246 in. The seven cases for analyses as associated with location anc temperatures are given in table 5-10. 5.5 Results Beaver Valley Unit 1 employs a shutdown specification of 3.0 gpm unidentified leakage in response to Regulatory Guide.l.45. The leakage size flaw then is the one giving 10 gpm. Leakage flaws were calculated for the seven cases using the methodology of section 5.0 of reference 7. The results are given'in table 5-11. , J-integral stability evaluations were made Tor each of the cases for faulted loads and a flaw size twice the leakage flaw. Since the absolute sum method. was used in combining the load components for determining the faulted loads,.a margin on load is not required. The J-integral analyses were made using the EPRI Handbook procedure (reference 8). The stability _results are given in table 5-12. Significantly, the calculated J values are all less-than'the J f 3000 in-lb/in 2, max Critical flaw sizes were obtained using the limit load procedure as outlined in SRP 3.6.3 (reference 9), accounting for the SMAW weld by using the appropriate Z-formula. The instability flaw-sizes so determined are also given in table 5-12. Stability margins on laakage flaws in excess of 2 are again demonstrated. l
.us.n enee io 5-3
5.6 Conclusions Considering the results of the prior sections and this section, the LBB criteria outlined in tabla 5-1 have been met and thus LBB has been demonstrated for the Beaver Valley Unit 1 pressurizer surge line considering thermal stratification; specifically, o LBB exists at operating temperature without stratification. o LBB exists at operating temperature with stratification, o LBB exists for forced cooldown due to leakage. o LBB exists for extended stratification. 5.7 References i 1. Brice-Nash, R. L. et. al., Evaluation of Thermal Stratification for the Beaver Valley Unit 2 Pressurizer Surgeline, WCAP-12093, December 1988 and Supplements: . Supplement 1 - Additional information in support of the Evaluation of Thermal Stratification for the Beaver Valley Unit 2 , Pressurizer Surge Line, February 1989. Supplement 2 - Additional information in support of the Evaluation of Thermal Stratification for the Beaver Valley Unit 2 . Pressurizer Surge Line, August 1989, i Supplement 3 - Evaluation of Pressurizer Surge Line Transients Exceeding 320*F for Beaver Valley Unit 2, July 1990. 4
- 2. Nuclear Systems Materials Handbook, Part 1 - Structural Materials, Group 1 - High Alloy Steels, Section 4, ERDA Report TID 26666, November 1975 Revision.
- 3. Palusamy, S. S. and Hartmann, A. J., Mechanistic Fracture Evaluation of Reactor Coolant Pipe Containing a Postulated Circumferential Through-Wall Crack, WCAP 9558, Rev. 2, May 1981 (Westinghouse Proprietary Class 2). .
.uwme.n o 5-4
1 i Landes, J. D. and McCabe, D. E., Elastic-Plastic Methodology to Establish 4 I i R-Curves and Instability Criteria - Topical Report on Toughness i Characterization of Austenitic Stainless Steel Pipe Weldments, R&D l Document No. 86-20'/-PSALE-R1, Westinghouse R&D Center, February 13 1986. ;
- 5. Palusamy, S. S., Tensila and Toughness Properties of Primary Piping Weld Metal for Use in Mechar.istic Fracture Evaluation, WCAP-9787, May,1981-(Westinghouse Proprietary Class 2).
- 6. Bamford, et. al., The Effects of Thermal Aging on the Structural =
Integrity of Cast Stainless Steel Piping for Westinghouse Nuclear Steam Supply Systems, WCAP-10456, November,1983 (Westinghouse Proprietary ~ Class 2).
- 7. Roarty, D. H. et. al., Technical Justification for Eliminating Primary Loop Pipe Rupture as the structural design basis for Beaver. Valley Unit 1, WCAP-11317, March 1987 (Westinghouse Proprietary Class 2).
- 8. Kumar, V., German, M. D. and Shih, C. P., "An Engineering Approach for Elastic-Plastic Fracture Analysis," EPRI_ Report NP-1931, Project 1237-1,.
Electric Power Research Institute, July 1981. j
- 9. USNRC Standard Review Plan 3.6.3, Leak-Before-Break Evaluation ;
Procedures, NUREG-0800. l l l e i on,ma.m 5-5
- - _..- - - - .~.. - . - - - - , _ _ . _ . . . - - .-
l l l TABLE 5-1 STEPS IN A LEAK-BEFORE-BREAK ANALYSIS . (1) Establish material proporties including fracture toughness values . (2) Perform stress analysis of the structure (3) Review operating history of the structure (4) Select locations for postulating flaws (5) Determine a flaw size giving a detectable leak rate - (6) Establish stability of the selected flaw (7) Establish adequate margins in terms of leak rate detection, flaw size and lead. (8) Show that a flaw indication acceptable by inspection remains small throughout service life. 6 l I I 463Ss/091490 10 5-6
l TABLE 5-2
. LBB CONSERVATISMS
, o Factor of 10 on Leak Rate o Factor of 2 on Leakage Flaw o Algebraic Sum of Loads for Leakage o Absolute Sum of Loads for Stability o Average Material Properties for Leakage o Minimum Material Properties for Stability o Lower Bound Fracture Toughnet.s Properties e Conservative EPFM J Analyses o Conservative Limit Lead Analyses 0
.uwm .o io 5-7
TABLE 5-3 ROOM TEMPERATURE MECHANICAL PROPERTIES OF THE PRESSURIZER SURGE LINE MATERIALS AND WELDS OF THE BEAVER VALLEY UNIT 1 PLANT , 0.2% Offset Ultimate : Heat No./ Product Yield Stress Strength . Serial No. Form (psi) (psi) a,c,e l 1 I i ASME Code Minimum Requirements Pipe, Pioe Bend, SA376 TP316 30,000 75,000 Elbow Weld ER308 N.A.a 80,000 N.A. - not applicable i c n.,o i..o io 5-8
TABLE 5-4 , TENSILE PROPERTIES FOR THE SURGE LINE MATERIAL AT 135'F and 653*F 4 Yield Stress (psi) UltimateStrength(psi) Nodulus of Temperature Elasticity (*F) Average Minimum Average Minimum (psi x 106) a c.e e a 4 e + 463Ssc9189010 5-9
TABLE 5-5 FRACTURE TOUGHNESS PROPERTIES FOR 316 STAINLESS STEELS AND WELDS , O Test le Material Temperature (*F) (in-lb/in2) T mat Reference _a.c.e SA376 TP316 3 SA376 TP316 4 Weld 5 d Weld 6 i . 1 J 1 t 1 1
.ns.,coi .o se 5 10 l
l I TABLE 5-6
, TYPES OF LOADINGS , Pressure (P) )
OssdWeight(OW) Normal Operating Thermal Expansion (TH) Safe S' ;tdown Earthquake and Seismic Anchor Motion (SSE)a
- - a,c.e aSSE is used to refer to the absolute sum of these loadings.
! .1 l 4u w oo m e 5-11 ( 1 -
TABLE 5-7 NORMAL AND FAULTED LOADING CASES FOR LBB EVALUATIONS . CASE A: This is the normal operating case at 653'F consisting of the . algebraic sum of the leading components due to P, DW and TH.
- a,c.e I
CASE D: This is the faulted operating case at 653*F consisting of 'i the absolute sum (every component load is taken as positive) of P, DW, TH and SSE. < a,c.e 4ns. w seeie 5-12
TABLE 5-8
- ASSOCIATED LOAD CASES FOR ANALYSES A/D This is here-to-fore standard leak-before-break evaluation.
- a,c.e
~ -
l a6356/09189010 5-13
-- - . . .- .-. - -. . . . . - . - . - - . . - . - . - _ . _ ~ - - - - - . _.
k TABLE 5
SUMMARY
OF LOADS AND STRESSES AT THE CRITICAL LOCATIONS . 00 = 14 in., Minimum Wall Thickness =-1.246 in. Force Stress Moment Stress Total Nede Case F(1bs) op (psi) M(in-lbs) og(psi) . Stress (psi): a,c.e 196 A 233208 4674 1996626- 13638. 18312
- - .a,c.e ,
- . i 196 0 242850 4867 2478764 16931 '21798, t
1 1 I ' i 4 t I
~
463Ss/101000.10 5
- l
..ue TABLE 5-10 0 LOAD CASES, LOCATION AND TEMPERATURES CONSIDERED FOR LEAK-BEFORE-BREAK EVALUATIONS Temperature (*F)
Case Node Leak Rate Stability A/D 196 653 653
- - a,c.e l
l l l l l l W ese l l l l l' l l l l l l i d 635v0018901 5-15
_ _ _ - . e i TABLE 5-11 l LEAKAGE FLAWS FOR THE LEAK-BEFORE-BREAK ANALYSES . l l Case Node location Leakage Flaw (in.)
- A/D 196 3.36 a,c,e l
l l 4 9 1 aus.nooteo to 5-16
1 TABLE 5-12
, RESULTS OF STABILITY EVALVATION . J-INTEGRAL ANALYSES Criteria-Crack U T J .J,pp lc mat max Length 2 2 2 Case Node (in-lb/in)- (in-lb/in ) (in)'- (in-lb/in ) T,pp a,c.e g 6.72 7 a,c e L _ _ -,
a LIMIT LOAD ANALYSES (SMAW) Faulted Load Case Node Critical Flaw Size (in.) 0 13.3 a N. A. - Not Applicable, J,pp < J;c
. ns.no n.oio 5-17
.. ... . .__D
4.c e l a Figure 5-1. Minimum True Stress-True Strain Curve for 316 Stainless Steel at 653*F
.in.mia.o io 5-18
.i.... .. . . . .. -
g E '
l e Q i
~
- a,c.e
- l i
)
i 9 Figure 5-2. Minimum True Stress-True Strain Curve for 316 Stainless Steel at 135*F p 4 us.,m '" ' 5-19 l l -----__ _ _ _ _ _ _ _ _ . _ _ . _ _ _ _ _
~
1
- a,c.e Figure 5-3. Sketch of Analysis Model for Beaver Valley Unit 1 Pressurizer i
Surge Line Showing Node Points, Critical Locations, Weld ~ Locations and Type of Welds 4635s/091390 10 5-20
l
6.0 CONCLUSION
S o Extensive generic and plant specific data evaluations have been performed and- ,
+ design transients have been updated-for ~ thermal stratification. Finite element stress analyses have been performed and ASME Code stress' limits are i
met. The total fatigue usage factor including the effect of thermal striping is less than the ASME Code requirement of 1. Fatigue ' crack growth is-limited with a hypothesized flaw 10% through the wall estimated to grow to.about 25% through the wall for full service life. In these fatigue analyses, transients- l to date which exceeded a system AT of 320*F are included. Leak-before-break was established for operating conditions and for~ bounding high-load thermal stratification cor.ditions.
~
Based on the current. understanding of the thermal stratification phenomenon, ; it is concluded that thermal stratification has~very limited impact on integrity of the pressurizer surge line of the Beaver' Valley Unit linuclear power plant. The forty year design life is not impacted. The surge line has been demonstrated to exhibit leak-before-break. i 4 I I mweemo io 6-1
I i i APPENDIX A' LIST OF COMPUTER-PROGRAMS This appendix lists and summarizes the computer codes used in the analysis of stratification in-the Beaver Val _ ley Unit-1 pressurized surge line. The codes. are:
- 1. WECAN
- 2. WECEVAL-
- 3. STRFAT2
- 4. ANSYS
- 5. FCG
, A.1 WECAN A.1.1 Description WECAN is a aestinghouse-developed, y neral purpose ~ finite element program. .It contains universally accepted two-dimensional and three-dimensional-isoparametric elements-that can be used in many different types of finite element analyses. Quadrilateral and triangular structural elements are used for plane strain, plane stress, and .sxisymmetric analyses. Brick'and wedge structural elements are used for three-dimensional analyses. Companion heat conduction elements are used for steady state heat conduction analyses and-transient heat conduction analyses. A.1.2 Feature _Used The temperatures obtained from a static heat conduction analysis, or'at a specific time in a transient heat conduction analysis, can be automatically input to a static structural analysis where the heat conduction elements are replaced-by corresponding structural elements.- Pressure and external loads can also be include in the WECAN structural-analysis. Such coupled
- . thermal-stress analyses are a standard _ application used extensively on an industry wide basis.-
1 m w ie n e io A-1
, - ~ - - - - _ - _ _ _ _ - - -:
A.1.3 Program Verification Both the WECAN program and input for the WECAN verification problems, currently numbering over four hundred, are maintained under configuration control. Verification problems include coupled thermal-stress analyses for the quadrilateral, triangular, brick, and wedge isoparametric elements. These problems are an integral part of the WECAN quality assurance procedures. When a change is made to WECAN, as part of the reverification process, the configured inputs for the coupled thermal-stress verification problems are used to reverify WECAN for coupled thermal-stress analyses. A.2 WECEVAL A.2.1 Description WECEVAL is a multi purpose program which processes stress input to calculate ASME Section III, Subsection NB equations and usage factors. Specifically, , the program performs primary stress evaluations, primary plus secondary stress intensity range analysis, and fatigue analysis for finite element models generated and run using the WECAN computer program. Input to WECEVAL consists of card image data and data extracted from the output TAPE 12's generated by WECAN's stress elements. The program reads the input data, performs the necessary calculations, and produces summary sheets of the results. The required stresses are read from the WECAN TAPE 12's and placed onto intermediate or restart files. The user may then catalog these files for use in later evaluations. The stress state for a particular loading condition is obtained by. a ratio-superposition technique. This optimal stress state is formed by manipulating the signs of the applied loads to generate the largest possible stress magnitude. A.2.2 Featt- lJsed. WECEVAL has many options and features which enhance its versatility. Among those used for this evaluation were:
- m w u n as ic A-2
l I d
- 1. The ability to perform simplified elastic plastic analysis pe'r NB-3228.5, l, including the automatic calculation'of .Ke ' factors and removal of thermal bending stresses from the maximum range of-stress intensity evaluations, w
- 2. Built-in ASME 'atigue curves-plus provisions for accepting user-defined:
fatigue curves.
- 3. Equivalent moment linearization technique, along with the ability to 1 corre'et for the radius effects in cylindrical and spherical. geometries, l I
l
- 4. The ability to limit the interactions among load conditions during the ,
fatigue analysis, 1
- 5. Generating input for the fatigue n ack growth program FCG. j A.2.3 Procram Verification WECEVAL is verified to Westinghouse procedures by independent calculations _ of- ,
ASME III NB Code equations and comparison to WECEVAL results.- A.3 STRFAT2 A.3.1 Descriotion i STRFAT2 is a program which computes the alternating peak stress on the inside surface of a flat plate and the usage factor due to striping on. the surface. The program is applicable to be used for striping on .the inside . surface of a l pipe if the. program assumptius are. considered to apply for the particular q pipe being evaluated. I For striping the fluid temperature is a sinusoidal variation with numerous ! cycles. e The frequency, convection film coefficient,.and pipe material properties are input. l mwmass io A-3 l l-
The program computes maximum alternating stress based on the maximum difference between inside surface skin temperature-and.the-average through , l wall temperature, n. A.3.2 Feature Used The program is used to calculate striping usage factor based on a ratio of actual cycles of stress for a specified length of time divided by allowable cycles of stress at maximum the alternating stress level. Design fatigue curves for several materials are contained into the program. However, the user has the option to input any other fatigue design curve, tat designating that the fatigue curve is to be user defined. A.3.3 Program Verification STRFAT2 is verified to Westinghouse procedures by independent review of the stress equations and calculations. 4 A.4 ANSYS _ A.4.1 Description ANSYS is a public domain, general purpose finite element code. A 4.2 Feature Used The ANSYS elements used for the analysis of stratification effects in- the surge and RHR lines are STIF 20 (straight pipe), STIF 60 (elbow and bends) and STIF14 (spring-damper for supports). A.4.3 Program Verification As described in se: tion 2.1, the application of ANSYS for stratification has , been independently verified by comparison to WEST 0YN (Westinghouse piping] l
?
w,nnuvo g4
f analysis code) and WECAN (finite element code, section101). The1 results-from'-
, ANSYS are_also verified against' closed form solutions for? simple beam configurations.
?
A.5 FCG t j j A.S.1 Description TheFCGcomputerprogrammodelsfatiguecrack1growthusing/ linear:elas' tic fracture mechanics methods. -In order l to provide a realistic model of. crack-growth the design transients.which are input are automatically scheduled evenly over the life of the-system or component. 1 A.5.2 Features Used The program options enable -calculation of crack tip. stress intensity factors (Kj ) for surface flaws and embedded flaws in a :large number = of. geometries, under any loading condition. Crack growth results are. determined :for each year of operation, and summarized in- tabular form at;the end ofL the output,~ at 10 year intervals. A.S.3 Program Verification
-1 The program has been verified by performing alternate calculations.and placed-under Westinghouse configuration control. The calculations using this program were presented and approved by the NRC staff in connection with several applications.
t mwuma io A-5
L l APPENDIX B
--, FATIGUE CYCLE APPROACH VS. DESIGN TRANSIENTS The fatigue cycle approach is acceptable based on the following:
i The mean stress is more than accounted for by the relative severity of the heatup/cooldown design transients. Figure B-1 (plant A). shows the actual worst case transient distribution observed with a maximum operating system i AT of 275'F. Figure B-2 shows the heatup/cooldown design transients distribution applied to an operating system 6T of 275'F. Note that the l relative magnitude and number of cycles considered in the design transients is considerably more severe than those observed. Furthermore, since stress is proportional to AT and the average AT in the design transients is considerably higher than the average AT of the observed transients, it can be concluded that the mean stress effect not considered in the fatigue cycle-apprcach is more than acccunted for by the. relative severity of the design , transients. Figure B-3 shows the heatup design transient distribution superimposed on the worst case distribution observed. I o L e l mw'ma 'a B-1 l i
i i i i i i
- 300 80 a,c,e 60 40 20 200 i
ro i I - 50 4 000 s-d o 50 0
~
TIE (HOURS) Figure B-1. [ ]a,c.e Location 1 - Observed Transients 3492s/122788 to i
. ~ .- 2 , i
E m e. c, .
, a ._
l e .-- c y C m p t o t e a e H w e n O r s. o t t w d i e l p p A n i o .- g t u b i
- r t
s i D t . n i e s n a 2 r e. T n g i s e D - p u t a e H l a i c p y T 1 2 B e r u g i - F e - o
- t 8
8 7 2 2 1
/
s 2 9 4 3
?w -
1 h.
S 6 6 e I 4 aum I k l l w e i J
.E
,G Y1MC h a
B-4 _ _ _ _ _ _ _ _ _}}