ML20006C668
| ML20006C668 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 11/30/1989 |
| From: | Coslow B, Maurer B, Mutyala B WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML16341F529 | List: |
| References | |
| WCAP-12416, NUDOCS 9002080361 | |
| Download: ML20006C668 (156) | |
Text
{{#Wiki_filter:.-y .mo.s.ssa.--..e.v.++.,~. -* - . .. . . - g g -8 g' W. l6 ') .1 .f '-
, a ar ut .q .
'f N g_ # y.
-; p #
er 4 - 1- _ .__ .. . - e , s , w
+' '
~
~
4 S' e ... W' '
., .W . ,
# s 5 .
. A- .+ ,
5 , 'g. 3 d n '
+
/ , 4 x -
\, a k
- 4
.s. , ,
i _4 t' r t
,1 at * -
9
,
- 9 . g* ..
{ .* 'h
' Y *'
e. g 4 Q
.+.
m,
'. t 4
- .)
g. 4 8
,p . 'S j.e Y. ,
_4
'e g- h . 4 '(.
g, I h +. 4 m 4 -
,~
s _*8 .
. 4
(
'. -h' { b-' f a , :
m ,g..
- 1
.. g e.'..
e . 1e, .
< . . ~
r -
- s 'f' 4
4
?
- s g_ . . ,
3 D: 1 . . tg . g - g a $
- e' 9 y s
*' 9
,}
} , 4- , ;g
% y , < * - -
a
- s -
1, g , .
+-
7
O '
_h -
> +
g 4 -
,, 9 p' ,
S
.e
.. N
' ' 8
4 V i l
*' .' . .. .'c , . .. m f, e
- 6 c , . . . .- g
.ar , . .
5-
. . ~ - 3
.g .b t~ r ,
E
, y s 4"e.
4 f O + '
+
N 4 , s >. . e - # 4 _.,'h
; u-, .
w..
]
[ " ' b WESTINGHOUSE CLASS 3-I WCAP-12416 L .
,a f
EVALVATION Of THERMAL STRATIFICAT10N FOR THE DIABLO CANYON UNITS 1 AND 2 PRESSURIZER SURGE LINE i November, 1989 f c B. J. Coslow B. R. Mutyala
, B. F. Maurer L. M. Valasek 1
Verified by: / /[ 4 // M - K. C.' Chang' Verified by: >- [* -
- 5. A. Swady' (
Approved by: *C b SalIl R. BY Fatel, Manager Approved by: _- M h / W f 5. 5. falusa'my, Manager Systems Structural Analysis Structural Materials and Development Engineering Work Performed Under Shop Orders LFUJ-134 Jg
- b-WESTINGHOUSE ELECTRIC CORPORATION Nuclear and Advanced Technology Division
- P.O. Box 2728 Pittsburgh, Pennsylvania 15230-2728 3970s/182489 10 - !
L ;
-j ;r -
x , ACKNOWLEDGEMENT
! .- {
The authors wish to acknowledge the efforts of G. A. Antaki, E. L. Cranford, ;
', K. R. Hsu, E. R. Johnson, R. Krishnan, T. H. Liu, J. F. Petsche, D. H. Roarty, ,
P. L; Strauch and T. M. Washko for their assistance in performing analysis on 1 which the results of this report are based.
~
I r . l t f 1 O f
,=
9 h'
.e.
1 TI ww em. i. is
i TABLE OF CONTENTS
^
Title Page ,. Section ..
SUMMARY
xii .l 1-1
1.0 INTRODUCTION
AND UPDATE OF DESIGN TRANSIENTS 1 1-1 1.1 Introduction 1.1.1 System Description 1-1 1.1.2 Thermal Stratification In The Surge Line 1-2 1.1.3 Surge Line Stratification Program 1-3 Update of Design Transients 1-4 1.2 1.2.1 System Design Information 1-4 l 1.2.2 Stratification Effects Criteria 1-5 l 1.2.3 Plant Monitoring 1-5 1.2.4 Heat transfer and Stress Analyses 1-10 1.2.5 Stratification Profiles 1-11 , 1.2.6 Development of Conservative Normal and 1-11 ~ I Upset Transients 1.2.7 Temperature Limitations During Heatup 1-13 , and Cooldown 1.2.8 Historical Data 1-13 j 1.2.9 Development of Heatup and Cooldown Design 1-14 Transients With Stratification 1.2.9.1 ( Ja,c.eTransients 1-15 1.2.9.2 ( la.c.e Transients 1-19 r 1.2.10 Striping Transients 1-19 P 1.3 Summary 1-20 - 2.0 STRESS ANALYSES 2-1 - 2.1 Piping Systern Structural Analysis 2-1 . 2.1.1 Introduction . 2-1 2.1.2 Discussion on Diablo Canyon Surge Line Analysis 2-2 wo nnm so ;;;
c TABLE Of CONTENTS (cont.) o Section Title Page a s
,2.1.3 Results for Diablo Canyon Units 1 and 2 Surge Line 2-3 2.1.3.1 Displacements 2-3 2.1.3.2 Reactions 2-4 2.1.4 Conclusions 2-4
< 2.2 Local Stress Due to Non-L'inear Thermal Gradient 2-5 2.2.1 Explanation of Local Stress 2-5 2.2.2 Superpositien of Local and Structural Stresses 2-5 b 2.2.3 finite Element Model of Pipe for Local Stress 26 2.2.4 Pipe Local Stress Results 2-6 2.2.5 Unit Structural Load Analyses for Pipe 2-7 2.2.6 RCL Hot leg Nozzle Analysis 2-7
- 2.2.7 Additional Clarification on Superposition 2-8 e of Stresses
.- 2.2.8 Conservatisms 2-9
^ - 2.3 Thermal Striping 2-9 2.3.1 Background 2-9 2.3.2 Additional Background Information 2-10 2.3.3 Thermal Striping Stresses 2-12
- 2.3.4 Summary of Striping Stress Considerations 2-13 2.3.5 Thermal Striping, Total Fluctuations and Usage 2-14 Factor 2.3.6 Conservatisms 2-15 5
3.0 ASME SECTION 111 FATIGUE USAGE FACTOR EVALVATION 3-1 3.1 Code and Criteria 3-1 0 3.2 Previous Design Methods 3-1 3.3 Analysis for Thermal Stratification 3-2 3.3.1 Stress input 3-2 an.no.u io jy l l
I h- ; TABLE OF CONTENTS (cont.) t
~
- )
Section_ Title Page . i 3.3.2 Classification and Combination of Stresses 3-4 3.3.3 Cumulative Fatigue Usage Factor Evaluation 3-4 3.3.4 Simplified Elastic-Plastic Analysis 3-6 3.3.5 Fatigue Usage Results 3-6 3.4 Conservatisms in Fatigue Usage Calculation 3-7 4-1
1.0 CONCLUSION
S A-1 APPENDIX A - LIST OF COMPUTER PROGRAMS E-1 APPENDIX B - LIST OF REFERENCES . 0 e 6 b 3070s/102a8910 y
, . _ - m_ -
[ l l LIST OF TABLES l Table Title Page 1-1 IMPORTANT DIMENSIONLESS GROUPS FOR SIMILITUDE IN 1-22
'; HYDRODYNAMIC TESTING ;
12 STRATIFICATION POTENTIAL BASED ON RICHARDSON NUMBER 1-23 i 1-3 SURGELINE TRANSIENTS WITH STRATIFICATION HEATUP (H) 1-24 AND COOLDOWN (C) - 200 CYCLES TOTAL ; 14 SURGE LINE TRANSIENTS WITH STRATIFICATION NORMAL AND 1-25 UPSET TRANSIENT LIST l 1-5 STRATIFICATION PROFILES 1-27 1-6 HEATUP - COOLDOWN TRANSIENTS 1-28 1-7 DESIGN TRANSIENTS WITH STRATIFICATION 1-29 18 OPERATIONS SURVEY 1-30
. 1-9 HEATUP DATA
SUMMARY
(PZR - HOT LEG) TERP. DIFFERENCE AND 1-31 TIME DURATION FOR EACH PHASE i
. 1-10 COOLDOWN DATA
SUMMARY
(PZR - HOT LEG) TEMP. DIFFERENCE'AND 1-32 .
. TIME DURATION FOR EACH PHASE 1-11 TRANSIENT TYPES 1-33 1-12
SUMMARY
OF FAT!GUE CYCLES FROM DIABLO CANYON UNIT 1 1-34 MONITORING DATA , 1-13
SUMMARY
OF PLANT MONITORING HEATUP/COOLDOWN TRANSIENTS 1-35 WITH STRENGTH OF STRATIFICATION (RSS) 1-14
SUMMARY
OFMON!!0REDTRANSIENTCYCLES(ONEHEATUP) 1-37 1-15
SUMMARY
OF % TIMES AT MAXIMUM TEMPERATURE POTENTIAL RHTP g 1-38 1-16 SURGE LINE TRANSIENTS - STRIPING FOR HEATUP (H) AND 1-39 C00LDOWN (C) er I m e.no m eio yg
I l LIST OF TABLES (cont.) Table Title Page , l TEMPERATURE DISTRIBUTIONS IN DIABLO CANYON 2-16
- 2-1 PRESSURIZER SURGE LINE ,
2-17 ; 2-2 DIABLOCANYONSURGELINEMAXIMUM,ggtAXIAL *' STRESSES AT [ ] t 2-18
SUMMARY
OF LOCAL STRATIFICATION STRESSES IN THE DIABLO CANYON 2-3 SURGE LINE AT THE RCL N0ZILE 2-19 , 2-4
SUMMARY
OF PRESSURE AND BENDING INDUCED STRESSES IN THE DIABLO CAllYON SURGE LINE RCL N0ZZLE FOR UNIT LOAD CASES STRIPING FREQUENCY AT 2 MAXIMUM LOCATIONS FROM 15 TEST RUNS2-20 2-5 2-21 2-6 Ft.0W RATES AND RICHARDSON NUMBER FOR WATER MODEL FLOW TESTS ; 2-22 , 2-7 RESULTS FROM TWO HIGHEST THERMOCOUPLE LOCATIONS 2-8 ASME E0 VAT 10N 12 STRESS
SUMMARY
2-23 l 2-24 2-9 THERMAL STRATIFICATION DISPLACEMENTS AT SUPPORTS AND RUPTURE
- RESTRAINTS
~
2-10 REACTIONS AT N0ZZLES 2-25 , L a 2 r l l me.nm i. vii
m LIST OF FIGURES l
, Figure Title Page ;
y 1-1 Simplified Diagram of the RCS 1-40 l 1-2 -Reactor Coolant System Flow Diagram (Typical Loop) 1-41 ! 1-3 RCS Pressurizer 1-42 ; 1-4 Estimate of Flow Stratification Pattern in Elbow Under 1-43 Pressurizer i 1-5 Diablo Canyon Pressurizer Surge Line Stratification 1-44 ASME 111 and Qualification Program
- 1-6 Transient Development Flow Chart 1-45 !
1-7 Ja.c.e Pressurizer Surge Line Monitoring Locations ( 1-46 1-8 Diablo Canyon Unit 1 Pressurizer Surge Line 1-47 ; Monitoring Locations 1-9 [ )"'C Pressurizer Surge Line Monitoring Locations 1-48 [ i 1-10 ( la.c.e Pressurizer Surge Line Monitoring Locations 1-49
. 1-11. Reactor Coolant Pump Cut-off Transient location Approximately 1-50 10' From RCL Nozzle Safe-End ;
12 Reactor Conlant Pump Cut-off Transient RCL Nozzle Safe-End 1-51 HL 1-13
- Transient Typical of RC Pump Cut-off 1-52 1-14 Temperature Profile (6.5-inch 10 Pipe) 53 1-15 Dimensionless Temperature Profile (14.3-inch 10 pipe) 1-54 I l
1-16 Surge Line Stratification 1-55 i 1-17 Surge Line Hot-Cold Interface Locations 1-56
]
1-18 Typical [ Ja.c.eTemperatureProfiles 1-57 I 1-19 Inadvertent RCS Depressurization (AT = 260'F in Surge Line) 1-58
, 1-20 Steam Bubble Mode Heatup 1-59 I
i I l mwieme io yjjj
1 i LISTOFFIGURES(cont.) l Figure Title Page. , j 1-21 Steam Bubble Mode Cooldown 1-60 ,l 1-22 Heatup( )"' 1-61 l 1-23 Cooldown( l 1-62
'f Heatup Diablo Canyon 1-63 +
1-24 .: i Cooldown Diablo Canyon 1-64 . 1-25 :
'Heatup( 1-65 1-26 Jac.e
' Ja c.e 1-66 1-27 Cooldown(
Heatup ( 1-67 1-28 Ja.c.e 1-68 1-29 Cooldown( Ja.c.a Location 1 - Heatup (7 Days) 1-69 1-30 ( )"'C Location 1 - Heatup (4 Days) 1-70 1-31 ( )"'C ., Diablo Canyon Unit 1 Location 1 Fatigue 1 - 1-32 Cycles - Heatup (11 Days) ,, 1-33 Thermal Cycle Distribution Assumed For One Heatup Cycle 1-72 i i 1-34 ( )a,c.e Indication of Striping Thermal Cycles' Assumed For One Heatup 1-74 . 1-35 Determination of the Effects of Thermal Stratification 2-26 ,. 1 Stress Analysis 2-27 2-2 Diablo Canyon Pressurizer Surge Line Layout 2-28 >
=
2-3 Diablo Canyon Surge Line Model and Temperature Profile 2-29 2-4 ~ s 1 an. nome io ix
~
s L l LIST OF FIGURES (cont.)
. Figure Title Page ,
- , 2-5 Local Stress in Piping Due to Thormal Stratification 2-30 2-6 Independence of Local and Structural Thermal Stratification 2-31 ;
. Stresses Permitting Combination by Superposition :
2-7 Test Case for Superposition of Loes) and Structural Stresses 2-32 - 2-8 Local Stress - Finite Element Models/ Loading 2-33 2-9 Piping Local Stress Model and Thermal Boundary Conditions 2-34 2-10 Surge Line Temperature Distribution at [ la.c.e Axial 2-35 Locations 2-11 Surge Line Local Axial Stress Distribution at ( Ja c.e 2-36 Axial Locations 2-12 Surge (ge,LocalAxialStressonInsideSurfaceat 2-37
, ( ) Axial locations .. 2-13 Surge yge, Local Axial Strass on Outside Surface at 2-38
( ) Axial Locations
. 2-14 Surge Line Temperature Distribution at Location ( ))a,c.e 2-39 2-15 Surge Line Loga}'gxial Stress Distribution at 2-40 Location ( })
2-16 Surge Line Traperature Distribution at Location ( ))a c.e 2-41 2-17 SurgeLineLoga}'gxialStressDistributionat 2-42 Location ( }) 2-18 Surge Line Temperature Distribution at Location ( ))a,c.e 2-43 2-19 SurgeLineLoga}'gxialStressDistributionat 2-44 Location ( }) S 2-20 Surge Line RCL Nozzle 3-0 WECAN Model #1 2-45
, 2-21 Surge Line RCL Nozzle 3-D WECAN Model #2 2-46 . 2-22 Surge Line Nozzle Stress Intensity Due to Thermal 2-47 Stratification 2-23 Surge Line Nozzle Stress Intensity Due to Eending Showing 2-48 :
Magnified Displacement wo.newsn ,
s p LIST OF FIGURES (cont.) Title Page-Figure-2- 4 9 -- 2-24 Thermal Striping Fluctuation. , Stratification and Striping Test Models 2-50 2 45 ' 2-51 - 2-26' Water Model of LMFBR Primary Hot Leg " 2-52 2-27. - Atter.uationofThermalStripingPotentialbyNgiggiar
.?
Con %ction (Interface Wave Height of (. ] 2-53 2 - Thermal Striping Temperature Distribution 2-54 _. 2-29 -Striping Finite Element Model 3-8 3-1 Fatigue calculation Locations o e 4 w
]
' 3970sn02449 'O xi
t
SUMMARY
+ -
-- This report presents the methods, data, analysis and qualification results for
~~
the Diablo Canyon Units 1 and 2 pressurizer surge lines including thermal e stratification.
-The report is divided into four sections. Appendix A is a list of computer codes used in this work. Appendix B is a list of references used in this work. The sections are presented in order, reflecting the logical progression of evaluations and analyses:
o Section 1.0 " Introduction and Update of Design Transients" presents the methods and data used to update the design thermal transients to incorporate- the effects of flow stratification in the
.- surge line.
.- o Section 2.0 " Stress Analysis" describes the global and local stress effects of stratification, including striping.
o Section 3.0 "ASME III Fatigue Usage Factor Evaluation" provides the evaluation results of the ASME III fatigue life of the surge line-subject to all design transients plus the effects of stratification. o Section 4.0 " Conclusions" summarizes the results of the evaluations cf the effects of stratification in the surge line. o Appendix A " Computer Codes" is a list and description of computer
.. codes used in this work.
.o Appendix B " References" is a list of applicable references used in this work..
. un.nempo
j
,The work presented.in this report leads to the.following conclusions: l
_l (a)- Based on" plant monitoring'results from Westinghouse PWR's (including- g Diablo Canyon Unit 1)- and flow stratification test data, the thermal' . 1 designLtransients for the surge line have been updated to 3 incorporate the effects of. stratification. . -- j
~(b) The' global structural and local stresses and loads in the surge line ,
-piping and support system meet ASME III Code allowables. The l
. maximum cumulative fatigue usage factor is [ Ja.c.e for all l
- design transients including 250 heatup and cooldown cycles of design l life, compared to the Code allowable of 1.0.
f L - Also, the maximum stresses due to thermal expansion (with stratification), l pressure and; weight meet ANSI 831.1 Code Equation 14 allowables for the existing as-built piping layout and support configuration. , l' In summary, based on the current understanding of the thermal stratification , D -phenomenon, it is concluded that thermal stratification does not affect the ., integrity'of the pressurizer surge line of the Diablo Canyon Units 1 and 2
-nuclear power plants. The design life (including 250 heatup and cooldown occurrences) and-ASME III Code compliance are not affected.
O D w
. wo.name so ,;;;
a , -
i t SECTION
1.0 INTRODUCTION
AND UPDATE OF DESIGN TRANSIENTS
... 1.1' Introduction .. 1.1.1 System Description
! The primary function of the reactor coolant system (RCS) is to transport' heat from the reactor core to the steam generators for the production of steam.
.The Diablo Canyon Units 1 and 2 RCS consists of four similar heat transfer
- loops connected to the reactor vessel (figure 1-1). Each loop contains a reactor coolant pump (RCP) and a steam generator. The system also treludes a pressurizer, connecting piping, pressurizer safety and relief i alves, and a relief tank.
,_ The flow path for a typical reactor coolant loop is from the reactor vessel to
' 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 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 pressurizer vessel (figure 1-3) contains steam and water at saturated conditions with the steam-water interface level between 25 and 60% of the volume 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%.
7 As illustrated in figure 1-2, the bottom of the pressurizer vessel is connected to the hot leg of one of the coolant loops by the surge line, a 14 inch stainless-steel pipe, amnon . io 31
. . _ . w
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 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 operation 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. . 1.1.2 Thermal Stratification In the Surge Line . 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 and cooldown, this difference in system temperature could be as large as , 320'F, in which case the effects of stratification must be accounted for. A common approach for assessing the potential for stratification is to evaluate the Richardson Number (tables 1-1 and 1-2) which is the ratio of the thermal density head diametrically across the pipe to the fluid flow dynamic head, or
"'""" 1-2
~
' ^
8 -
,.9 L
e w b ,; Ri=.QBDAT- 1
-v 2 :
E.s : where-
; Ri: = Richardson. number ;
- g. =. . gravitation constant V~ = hot fluid velocity (see' figure 1-4) '
AT '== ~ hot-to-cold _. fluid temperature, difference-
~
0 = ' pipe inside diameter 8 = coefficient of thermal expansion of water x e 'For a range of surge line flow rates from approximately 700 gpm down to a. bypass flow of approximately 1 to 5 gpm and AT = 320*F, the Richardson number ^is greater than the'value of-1 which is required to initiate s stratif'. cation. .Thus under this range of conditions, the: flow has the potential to be stratified-due to the relatively large hot-to-cold fluid 1 Ltemperature difference combined with the low hot fluid velocity. To~ eliminate- [ : stratification'(i.e., Ri smaller than 1) a flow velocity of over 2.4 fps (approximately 700 gpm) is needed. -i 1.1'3 Surge Line-Stratification Program The surge line stratification program for Diablo Canyon Units 1 and 2 consists of three major parts: (a) Update of-design transients l
* (b) ASME 111 stress and fatigue cumulative usage factor (CUF) analyses
;s 1
= (c) Monitoring of the Unit 1 surge line i i
j Figure 1-5 shows the steps required to complete this program, l u 1 1 n - -. me.nomi in 1-3 N,u. -
ff-1.2 Update of Design Transients The method used te update the design transients for stratification is illustrated in figure 1-6 and is discussed in this section. . 1.2.1 System Design Information The thermal design transients for the Diablo Canyon Units 1 and 2 Reactor Coolant System, including the pressurizer surge line, 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 (b) Normal and Upset operation transients. By definition, the emergency , and f aulted transients are not considered in the ASME 111 Section NB , fatigue life assessment of components. in the evaluation of surge line stratification, the FSAR chapter 3.9N definition of normal and upset design events and the number of occurrences of the design events remains unchanged. The total number of current heatup-cooldown cycles (250 for Diablo Canyon) remains unchanged. However, sub-events and the associated number of occurrences (" Label", " Type' end " Cycle" columns of tables 1-3 and 1-4) are defined to reflect monitoring data, as described later.
~
In all cases, the surge line flui6 temperature distribution is modified from the original uniform temperature to a stratified distribution with the maximum - temperature differentials and the associated nominal temperatures (" MAX AT " and " Nominal" columns on tables 1-3 and 1-4). strat SSDC 13 was not updated to incorporate surge line data. The monitoring data from four plants was used to create a transient set with stratification for heatup and cooldown transients.
- and cooldown transients with 3070s/102449 10
i : i' . R 9% 1 y:' ' h ! stratification replaced'.the S500.1.3 heatup'and cooldown transients. .The. l
' balance of the normal and upset trr.nsients defined in SSDC~1.3 was used in the-
'l ,
- surge line' evaluation' except' that the transients were assumed to cause thermal- ,
;, stratification ( !
M y 3a,c.e- ; 3,s ; i"
-It should be-noted that some of the transients defined in-SSDC 1.3 assume no insurge or outsurge and are therefore not considered to cause thermal , stratification.- ]
11'.2.2 ' Stratification Effects Criteria- ' r To determine the normal and upset pipe top-to-bottom temperature difference,. '!
"ATstrat ,(tablo 1-3 and 1-4), the following conservatism is introduced. !
For-'a given event,'the AT strat in the pipe will be based on the di'forence l
.between'the maximum pressurizer temperature and the minimum hot leg-
, temperature, even though they may not occur simultaneously.
.[
i 1 s !
.3 4
ja,c.e J 1.2.3 Plant Monitoring
~ Surge'line stratification-data have been obtained from more than a dozen
~
Westinghouse' plants. Figures 1-7 through 1-10 show the instrumentation configuration for four of these plants. The data was obtained by continuous
.- me.nomua 1-5 w a.
1 monitoring of the piping 00 temperature,- displacements and plant parameters. , The pipe temperatures were obtained from RTD's located on the outside of surge .,
.line. ' Plant parameters were obt'ained from the plant computer. Figure 1-8 .
represents the Diablo Canyon Unit 1 monitoring configuration. , The data, in all cases, sho'ws the presence of stratification. in' the surge . lines. The stratification observed is assumed to behave under the influence of gravity and consequently will have an axial profile lofined by the slope of # the pipe. The data interpretation herein is an attempt to classify and characterize observed thermal conditions. There are two basic causes of thermal stratification. Thermal stratification' can be initiated either by.( J"' or the [ , L . Ja,c.e This is the . h ! condition which'this report addresses. 1 [ l t. L -
~
w t ja,c.e wwin . 36 l. r .
- >+ g -f _; ' t {? 1
'O.:
J -e ' f
)a.c.e
'The establishment of a highly stratified condition is best described by ;
- considering ~the following typical transient-example. This transiknt is based. !
; on an observed reference plant transient which was caused by the cut-off of !
the P.CP in the same-loop as' the surge line. l
.,; Typical Transient
Description:
. (RCPCutofffigure1-11) 2 q
i
. . i
,M..
i o
}&,C,0
' wrancam io 1,7 s1 _,
5 e < f I . - :
, e: -
-., ,s_.
t.'f
.)
. rr . .;
. s
_ [ .. . L
'N f
i > 4 .#'
- 7. ! ;, i >
l. f L > r, l' , l' J l,> ll . \ l-l
.)a,c.e ,
One' interpretation of the cause and effects of the transient _just described is..
~
as follows:
- (- .
4 O l w i 3a,c.e 4.., iou i. 1g
'h- -' : '.
ys .
+ ,
K@i:^,,v: ; - ,
'c eggg) . ,' >
^
.i
- g i
- - [-
.)'
J . :. , 1 Li J <
.- o.
l 1 U$ . s (_ - n 1
-)
1 1
., j l
.l J
. l 1
,i; 9 - s 5 ja.c.e Lr i l The'dats ..re sufficient'to characterize stratification temperatures in the l pipe .du-ing' critical operating- transients and heatup cooldown operation. '
. Also .the data are sufficient to verify that the pipe movements are consistent with analytical predictions, within an accuracy normally expected from hot j 19.~L functional and/or power ascension tests, as discussed in section 2.1. I
, 1 The monitoring of plant parameters is sufficient to correlate measured temperature fluctuations to changes in operation. In particular, it is apparent that temperature fluctuations are due to flow insurge (into the l pressurizer) and outsurge (out of the pressurizer) which in turn are due to l l
w e.ne m .io g_g n.
I l 7 Ldifferential pressure in the system. While a simple _ quantitative' mechanistic relationship between plant operation and .insurge and outsurge has not been ,
'found, the data' indicate that a steady state stratified condition can be ialtered by any of the following events: ,~
.l a) Expansion of ths pressurizer bubble [>
b) RCP trip in the surg,line loop ' c) Safetyinjection l l d) Large charging . letdown mismatch e) Large spray rates 4 In light of these observations, the update of design transients is based on 1
~
l _ piant monitoring.results, operational experience and plant operational i procedures. Conservatisms have been incorporated throughout the process in (, " -the definition of transients (cycles, AT) and in the analysis, as described l t in.the report.- , 1.E.4 ; Heat Transfer and Stress Analyses
.1
'The correlation of measured pire 00 temperature to 10 temper:ture distribution .
L >is achieved by heat transfer analysis as well as previous experience with flow at large Richardson numbers (Rini) (figures 1-14 and 1-15). L These analyses and tist data available to date show that a- stratified flow
-condition,[
la,c,e is a proper and conservative depiction of the flow q I p condition inside t.he pipe at large aT and low flow rates (Ri>1). L i An additional conclusion from the heat transfer and stress analyses is that - [ ,- ya.c,e
=
m e,no m ein 1-10 i l l
(( . l 1
~
1
'1.2.5 Stratification Profiles I
e- Table 1-5 cummarizes the major. stratification profile characteristics. The I pg monitored data shows a consistent axial temperature profile along =the ! LM horizontal portions of the surge lines monitored. The axial temperatura profile is a function of the geometric ~ characteristics-1
~of each line. Each line monitored showed a definite relationship between I axial length of stratification and slope of the line. Figure 1-16 depicts n-typical axial stratification profile. Note that the actual length of ,
y stratification is dependent on the volume of 'the insurge. Low volume insurges
~ tend to stratify a shorter d'istance along the line. Similarly large volumeL l y
insurges stratify longer distances provided the slope of the line is low . .; enough. As the slope increases, sma'ilor sections of the line will be affected , by stratification. . The slope also affects the type of stratification
)
interface. As the slope is increased the flow characteristics'of the interface are affected. There are two basic interface types; one which is J
', narrow and highly.* fined is characteristic of laminar flow. The other is i l
-characteristically' wide and a product of tur.bulent flow. The flow becomes-
. turbulent at the interface when forewd to a higher level than gravity would normally dictate. Fler velocity is also an integral part of this ralationship.
Figure 1-17 shows a crcss section of the pipe with the various hot and cold- I fluid interface levels c.reated by a laminar flow or static steady state conditions. ( l l l l ( )a,c.e 1.2.6 Development of Conservative Norral and Upset Transients , l' Transients in the surge line were characterized as either due to insurges or outsu'rges (1/0) from the pressurizer or fluctuations. Insurges and outsurges u i me, nome io - 1_11
Kl o s
- are the more severe transients and result in;the greatest change in tempera- ,
li ture in the- top or bottom of the' pipe. An insurge' may cool the ~ bottom of the - pipe significantly, toLverylclose to the temperature of the RCS hot leg..
- Conversely, an outs' urge can sweep the line'and heat the pipe to close to the .,_
temperature of. the pressurizar. .The thermal transients are shown in figure
'l-18.
v All normal and upset transientr. that were postulated to cause insurge or o o'ite.rge were ( )**C. Tha maximum systen delta T was calculated regardless of simultaneity between the RCS tenperature and the PZR temperature. In addition certain high cycle. normal W condition t'ransients such as steady state fluctuat'ons weir [' ja,c.e
,1
. Fluctuations, as'coposed to'the insurge-outsurge translants, are caused by relatively insignificant surges and result in variations in the hot-cold ,
interface level. These variations *in the interface level do not change the ~ overall global displacement of the pipe and hence are modeled as changes in
-the dept.h of the interface zone.
Ine redefinition of the thermal fluid conditions experienced by-the surge line
'< during normal and upset transients was necessary in order to neglect ths 1 indirectly observqd fluid temperature distributions. These redefined thermal fluid conditions were developed based on the existing design. transient system parameters assumed to exist at the time of the postulated transient and the; knowledge gsined from the monitoring programs. The redefined thermal fluid conditions conservatively account for the thermal stratification phenomena.
Several conservatisms were introduced in the redefined normal and upset thermal transients (tables 1-3, 1-4, 1-6 and 1-7). , (a) Full stratification cycles are assumed for all transients, except for . steady state fluctuations, unit loading and unloading, and reduced
~
temperature return to power, where level fluctuations are sufficiently conservative based on flow rate and observations. l wo.:, cues so 1 3g L _ - : 21_ --
.w .
- n. ,
lf :t' w ,
'(b) The temperature of stratification was based on the minimum hot l'eg l
1 temperature at any time during the~ transient (for bottom of pipe) and i g the maximum pressurizer temperature (for top of-pipe). Figure 1-19 j , y . shows a case'where this resulted in a very conservative 260'F i l? stratification transient although the maximum temperature difference 1 2s 'at'any point in time was about 50*F. i
' ' i (c) The current number of design cycles of each event is unchanged.
'The normal ~and upset transients modified to account for the stratification.
4 phenomena are listed-in tables 1-3 and 1-4.
. 1.2.7 Temperature Limitations During Heatup and Cooldown Pacific Gas andE' lectric has put in place procedures to limit the system AT
,. .on future h.5atups.
, The-maximum permitted temperature difference between the pressurizer and the i
, hot leg for Diablo Canyon Units 1 and 2 is now 300*F during heatup. Therefore the maximum system AT is assumed- to remain below this value for all future 4
(
.heatups. ,
With.the:RCL cold, the pressurizer pressure (and therefore temperature) is limited by the cold overpressure mitigation system (COMS).
- Practically, plants operate to minimize downtime and heatup-cooldown time, e' ' ,
-when power is not being generated. The times at large aT are therefore 1 reasonably limited, as discussed later.
1.2.8 Historical Data 2 Since not'all heatup and cooldown parameters affecting stratification are
- formally livnited by Technical Specification or Administrative controls, it is
- necessary to reconsider plant operational procedures and heatup-cooldown practices to update the original heatup and cooldown design transient curves of SSDC 1.3 (figures 1-20 and 1-21).
i mn.mme io . 1 13
wesTIN!M0ust PRIPRitTARY class 2 1 To this and, a review of procedures, operational data, operator experience,
)"'C Westinghouse PWR plants and historical records was conducted for.( -
including Diabic Canyon (table 1-8). The heatup at d 'ooldown operations information. acquired from this review is
' summarized in tables 1-9'and'1-10. Heatup and cooldown diarams for four of these plants are given in figures 1-22 thru 1-29. The diagram presents t'he pressurizar water and hot leg temperature profiles versus time. The various phases of the process are identified by letters along the diagrams' abscissa
-and in tables 1-9 and 1-10.
as 1.2.9 Development of Heatup and Cooldown Design Transients With Stratification The following sections describe the covelopment of transieras with stratification for a-typical plant design life of 200 heatup-cooldown cyr.les
-and:40 years operation. The Diablo Canyon surge line is designed for 250 ,
heatup-cooldown cycles. For the case of Diablo Canyon, this additional effect , is considered by increasing the number of cycles for each transient by 25% as , noted in transient tables 1-3 and 1-16. . The following sections also indicate that the typical system AT (pressurizer temperature minus hot leg temperature) is limited to 320*F. Diablo-Canyon
-procedures now limit the system AT to 300*F during heatup (reference 1).
For this reason, transients H1 and H2 of table-1-3 are limited to a system AT of 300'F for evaluation of the surge lines at Diablo Canyon Units 1 and 2. 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
- precedures, operational data and operators experience.
r b) Transients as monitored at teveral plants, including Diablo Canyon Unit 1 c) Historical recordt, of critical heatup and cooldown temperatures me,nomeae 1 14 _
jg . a w The heatup~and cooldown transients are presented in the following sections as
'[' .)a,c.e and in O similar fashion,to the normal:and upset transients. Table 1-11 gives the w general characteristics of the two types'of transients observed.
x The heatup cooldown transion't labels have the following logic:
- 1. Transients H1 through H12 correspond to insurge or outsurge transients postulatedduringheatups(H).
,;2.; Transients HF1A through HF3 correspond to fluctuation transients postulated during heatups (HF).
- 3. Transients C1 through C9 correspond to insurge or outsurge transients
, postulated during cooldown (C).
- 4. Transient CF1 represents the fluctuation transients postulated for
, cooldownsL(CF).
1;2.9.1- [ Ja c.e Transients A)'MonitoringTransientSummary i
-For.a given monitored location, plots of temperature difference versus time
- were generated (figures 1-30 and 1-31 are examples of relatively high transient activity). Two parameters were plotted, the pipe top to bottom ;
temperature difference-(labeled " surge line") and the pressurizer to hot leg l
' temperature difference (labeled " system"). l y It is clear from figures 1-30 and 1-31 that for the observed heatups, (
),a,c.e
'Q-For conservatism, the envelope from measured transients is applied to define the transients, wwmmo .
1-15
- 3?[
7o , B)l~FatigueCycles-4 Tho' fatigue. cycles were' obtained using the technique illustrated for Diablo Canyon on ' figure 1-32, (- 5
]C Figure 1-34 illustrates-the difference between the design transients and the transients ,
observed at plant A. C) Strenath of Stratification iPlant 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
-(pressurizer to hot leg). The ratio of'AT in the pipe to AT in the system
- will be referred to as " strength of stratification".
E' ja,C,9 mwieme io 1-16 l
{@h[ a
]a
o;n ' f;
;\
4
- E 'D): Number of Stratification Cycles (table'.1-14) i
~
hv * ' Plant monitoring data indicated the significant events which could occur. c , ;- Lduring a given heatup. l [- j Y
'j
-1
,j-1
.t h
. .v i
ja.c.e i E )' Maximum Temperature Potential i
.The key: factor in thermal stratification of the surge-line is the temperature difference between the pressurizer and hot leg (section 1.2). This-tempera-ture difference is _ clearly maximized during the heatup and cooldown, when the ;
-plant is in mode 5 cold shutdown (hot leg less than 200'F) and the pressurizer bubble has:been drawn with the reactor coolant pump running (pressurizer
,o temperature larger than 425'F). [
r ya,c.e
< w o.na m io 1 37 ,
- e
.l
j 4
' .I
?! ;g ,a V
t 1!
' F) Final-Cycles'and Stratification Ranoes. i i ,
. } a . C ',0 .
'( , -?
t a
.g I
r k i e 41 I. e b 9 a e
-1 1
e e 4 I
]8 Ce9
. i wo nouse so. l_lg
)
<<.4
- p. 4
,s'ss_-_.._____.____n__.___.__._______________ . _ _ __,_ _ __ _ _ _ _ _ _ _ _ _ _ - - - - - - - - - - _ - - - - . _ - _ _ _ _ _ _ _ _ _ _ _ _ _ __
1 y' lrp)]', y= i ) 'x }
. Eiample:, ,
i c- [ 1
-)a,c.e t
]
. G): Cooldown Transients
.s
< The procedure used. in heatup is applied to develop transients for plant l
[
-'s cooldown. ~[
. 1
)
ja.c.e j
, 112.9.2 [ ]a,c.e Transients I q
'[.
L , if , p 1 ja,c.e ; r 1.2.10 Striping Transients j f, . Mean stress effects are included in determining the' usage factor contributed b.9 thermal striping. Fatigue cycles like those shown in figure 1-32 were not ! used in the development of the striping design tran.sients. [' Ja,c.e It should be
- mn. noun io .
1 19 m ,
Ac
.1 1
l noted.that each striping transient' cycle-is assumed to initiate a discrete hot.
~
to cold fluid interface that will be attenuated with time (see section_2.3 for -' discussion). Figure.1-35 shows the relative magnitude'and frequency of the
- striping transients for one heatup or cooldown' with respect to the system AT- *
-(PRIT - RCST). The highest pipe AT (pipe TTop pipe Tbot) observed
'during heatup never exceeded ( ).a.c.e However, the design striping ..
transients consider [ 1)ac.e transients at pipe AT's greater _than [ .)a c.e.
- Striping-transients use the labels tiST and CST denoting striping transients :
(ST).. [' Jac.e Refer to section-2.3 for additional infctmation on thermal-. striping. 1.3 Summary ..
~ Wodification of-the pressurizer surge line transients to account for thermal stratification was accomplished by replacing the existing heatup and cooldown
- transients with a new set of transients that us.re based on actual monitoring
. data from several_ plants. The new heatup and cooldown transients.are provided-in table.1-3. Analysis-of the monitoring data resulted inithe conclusion that I
)"'C 'In order to' assure conservative design it is necessary to not only replace the existing heatup and cooldown .
transients but to modify the existing normal and upset transients to account for the effects of stratification. Modification of the existing normal and upset transients (table 1-4) is accomplished by first interpreting these previously defined transients in wwiome in 1-20
~-- ^ ' - ' ' ' ' ^ ^
e -. . JD& . j b - 1 p!. ) s . . J
-terms of the type of stratification phenomena they are expected to produce ;
(:- I
- +
(a. l i
>l' av l N:
.i Ja.c.e This. .c 45 is considered to be a. conservative representation of what the transients would actuallycimpose on the pipe.. ,
f
- . . r in. summary, the existing heatup and cooldown transients were replaced by.a set -
of transients that were developed entirely from the monitoring data of several-
, < plants (including that from Diablo Canyon-Unit 1). . The existing normal and
. upset transients were modified-to consider the effects of thermal c_ .
stratification.- (l I t' ja C,9 i s ,; i 2 e'
.i..
t
, , m o.nc m .io i 1-21 E ;
U.l 2.,
1 TABLE 1-1
~1MPORTANT DIMENSIONLESS GROUPS-FOR SIMILITUDE -
IN HYDRODYNAMIC TESTING peessesse 9posal Osenseen Wa= weensen wenn f CAP /8pv8,L meeewo tweervune 'ees teser 3 Ceressen awa ter e 88. -8,/*/ meamwe one,opeefmome tome - 3 moynoce numcor me- ev0. ' weene sosce/vecews seres a saevne awiser se @ vones aneceng W coste tesse - 3 wooer numeer we a0Va , ,,,,e, g,,,,,,,,,,,ngen tems g piogge numeer Fr v'/90 WWFee 88'espgerer lesse y asessmen nuneer m. aago/,v' suoyene, teos,coes teste stesseenpeuse maimert a gesy numeer tu Ap/,9 mesase sammenes tece . 9 Pques neses, pr ,c) idemeeum h rp.c-eeussey - io peau nunner pe evock Convecese noe w . ine . >> esanassenoseinser
~
L8 ,'esAT/.8 Sweyster j __- r Reco
~
ig g,eense numoer et 13 Reveign nunser % L's%98&Flese - iGr a m) secestesCLATupB. C = esente Moe 9
- enese ssen of gremer p . eensey 9 e omeswo
, . aateos enca 8
- ea sttowe presame e . smenne sonesesey 7 a sus vesar seessue 3 e acesseee esponeen essesent LD e enesessvens amensens AT . aws immeeresse enenge V = Itse vesser 7 =tonsasnecongsemener a a vacoast e
6 wo.neme so 1 22
s 1
-TABLE 1-2 STRATIFICATION POTENTIAL BASED ON RICHARDSON NUMBER T 4 i
- Stratification potential exists if Ri > 1. -
..c..
l
.h
?
e
- o t
~
.i f
M i G
; O e'
3s7o,no24as to . 1-23
+,
j r TABLE i-3.' , i SURGELINE TRANSIENTS WITH STRATIFICATION ' h~ HEATUP'(H) AND C00LDOWN (C) - 200 PLANT CYCLES TOTAL * , 1 S.C.4
, s l
h I l
.l i
1 e.
.:t s
0 t. i 2970s/102449 10
.A'_
TABLE 1-4
- $ URGE LINE TRANSIENTS WITH STRAT!P! CATION i ,
NORasAL=AND UPSET TRANSIENT LIST-t+s' a.C.9 I s
.w..
4 I t i
- 4> .
1 4
.j 4.
\
l l I s i i t
'[ v
,j i
3070s/102449 10 g,
6
- v. .
Q - 5 T n f G TABLE 1-4,(Cont'd.) 7
' SURGE LINE TRANS!ENTS'WITH STRATIFICATION NORMAL AND UPSET: TRANSIENT. LIST. i iM S.C.0- .
-9
+ .
b
.7
.-s
- i 4
f r e
!e L
e
$i e
t C i L e I e W< 1 i 1 r wwiome in 1-26
. ..c -d, y- vpm, ,. ,.wr,m ,
wm ..
.)
4 1
.]
O TABLE-l1-5. 1
-. 1 STRATIFICATION PROFILES: J y; [- '
Y t'." hf w.
- s. ..:
r 1:: ja,c,e s' :;. i,. a, . g r w e ,1 fg . 1 g, 'hk f-wo. nam. io 1-27 .
l
' TABLE 1-6~
HEATUP .COOLDOWN TRANSIENTS' o Transients Were Developed Based On:-
- Typical Heatup Cooldown Curves f, '
- Envelope (Plus Margin).of Events (Transients) Monitored
- Historical Data on Temperature Plateaus. c 1
.[ ,
! l i:
l I l l l
)a.c.e ,
l-. 4 l I w o,no m e ,o . 1 2a l
- w. ..
j Q: i
;e- , ;
I
+
-\h ,{
i TABLE'1-7 I, DESIGN TRANSIENTS WITH STRATIFICATION j E, lf o Heatup- and Cooldown Combined With; Other Events -
- =
'o: ' Design Transient Criteria.
. 1
.[1 ]
1 l' e o ,.- .]a,c.e , l. t pt
. o Input.for' Local and Structural Analysis Defined - Plus Nozzle t
p lo Striping Transients Defined to Consider Maximum Stratification Cycles
- Regardless of Range u
l l i 1. ! . ' lt t i : ;. L. i
- 3970s/102449 10 .
}.29 I' . . - . .-
. - . . .. ~.
'I ,
.j. .
- 7n' . TABLE 1-8 Y OPERATIONS SURVEY ,
o I P
-: o Summary of Plants Surveyed -
i 1 YEARS OF OPERATION NO. OF PLANT- LOOPS (MAXIMUM) ! a,c,e 1 j l 1 l I l l I
,l o Reviewed Typical Heatup Cooldown Process
.o. Reviewed Administrative / Tech Spec Limitetions .;
o Reviewed Historical Events and Time Durations o' Developed Heatup - Cooldown Profiles e m o.n m io 1-30 o
. - n.,
r : . - .
... _.ry; s.
+
TABt.E 1-9 HEATUP DATA SUNIARY (PZR - HOT LEG)' TEMP. DIFFERENCE AND TIIE DORATION FOR EACH PHASE i'
-a.c.e 4
i 4 W 8 w w i 4 3970s/102489:to
_ . ,,.. . . . .. .. - . ...y .,
. e TABLE 1-10 COOLDOWN DATA SU WARY' (PZR - HOT LEG) TEaIP. DIFFERENCE AND TIIIE DURATION FOR EACH PHASE
'1 a.C.e w
O w to 3970s/102489:10
. . b '
.b
- q. g ,
~- , - . , .- n ..- - . . , , , ,,.wn.. , _ s ,. ,+a . n
, w m;p p e qu gg m een e n, n,, ~. m gn~ma -0 h ik - '
L t
, -TABLE 1-11:
A' - TRANSIENT-TYPES .
-)
l [ j
> .. .1 1
_4 1 i I ti q l 4 i f
.. {
)<-
t r T' 'Ny- ; f_ J p , 1, k l $.' i na b. m s
-a,c,e - -j r j y
, N '. i 3 4 b s 1
<k E
,- t 3 e i t S-t t t,u -.l 0-p e # I $
-1
. t t-n ig b ' 1 1 f-', 7 I j; u
- I
}: n s i
- 7. .
.I
.l h 'n Y v-1 t i g
r .a ;i L i
> v i>
l 11 L ; it ! t. i: I: o- . ; p m e.ne:usio 1-33 i e (- g J [ 1 4: .[ e e i b'N'ha*N-dSJERSLudo s AwCL- s m.-_&-----u- o- - - - -
TABLE 1-12
SUMMARY
OF FATIGUE' CYCLES FROM DIABLO CANYON UNIT 1 1 MONITORING DATA Cycle DeltaRange'(*F) Cycle Delta Range ('F)- . a,c.e I i 9e 4 NOTE: The delta range represents the relative severity (AT) of each transient following the fatigue cycle' approach. D me.ncu.. io 1 34
E, ' C' TABLE 1-13
SUMMARY
OF-PLANT WONITORING HEATUP/COOLDOWN TRANS!ENTS 1 WITH STRENGTH OF STRATIFICATION (RSS)1
+ 1
,-- [ la.c.e Diablo Canyon Unit 1 [ la,c.e-4' Dbserved Dbserved Observed
, Cycles RSS(1) Cycles RSS(1) Cycles RSS-(1) a,c.e-P i
Ia. - l . . OBSERVED TRANSIENTS GROUPED BY STRENGTH OF STRATIFICATION (RSS) INTERVALS No. Observed % of RSS - Cycles Total ! i a,c.e
. 4
<4 Note: -The No. of groups is reduced by combining the intervals .70 < x ,
< .8 and .60 < x < .70 % of total = 3.2% for the interval-
.60 < x < .80~
me,nomi io 1-35
I j. x ' TABLE 1-13 (cont.)
SUMMARY
Of PLANT MONITORING HEATUP/COOLDOWN TRANSIENTS' WITH STRENGTH OF STRATIFICATION (RSS) L RSS J % of Transients a,c.e5 . l l- RELATIVE NUMBER OF CYCLES OF l STRENGTH OF STRATIFICATION (RNSSj) AFTER GROUPING 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) . 4 e 0 h me.nem. io 1-36
--TABLE-1-14
SUMMARY
OF MONITORED TRANSIENT CYCLES (ONE HEATUP) e Plant No. of Cycles a.9,e f Avg. Monitored' Cycles: 15.75 = x; Selected;No. of Design Cycles: 36.5. (added 30% to observed maximum number of !
. cycles, planta) 0 DESIGN DISTRIBUTION APPLIED TO MAX NUMBER OF TRANSIENTS EXCEPTED MULTIPLIED BY 200 i HEATUP OR C00LDOWN CYCLES No. of Transients RSS a,c.e j
g. 4 m e.nc m .io i_37
iQ
~
s tj i', ., u?n , i 1 -
+
( - TA8LE 1-15:
SUMMARY
.OF % TIMES AT > j MAXIMUN TEMPERATURE POTENTIAL , 4
' [
...l
~
&,C,9 I
i
'l e
S
% I e
e t [. . l-a e
.. L e
o. S wo.ncm .io 1-38
.1
t g7 -i b ,
];
[ TABLE 1-16 SURGE LINE TRANSIENTS - STRIPING .; FOR HEATUP (H) and COOLDOWN (C) i l
-a,c.e J
~
]
1 1 1
. .e l{t'
.1 For Diablo Canyon Units 1 and 2, surge line designed for 250 heatup-cooldown cycles. Actual number of transient cycles used in fatigue analysis.is 1.25 x number shown.
S 4 3670s/102449 10 - g.g
4 i D M D %==:::s V
,?
%=:::.:d U*2 ,
I w - , I I D @ -
@ t g J w w yf v'
% N, %
I .
%v w
I w w
-l i 9""' 2~1- Simplified Diagram of the RCS l
/
1-40
- tu s
;.. . ;; e .
- v. . - .
p ___
.: " -.;}
~
s
'f'-
m , I Assesey spey IcWc80 l l meeseur casesse , Semese Pneup w < >
-j O -
anum -i 7 1 r seesspense O 6 scwoes censLee - - esseLee 41,pecae ", (*,siest _ _ u messenessesse N ~ mesessestemppuense necesses . ,' essesmessest ! spesem Westas
- _ i _
t
' ~
i . Leessemame scwcap t ! Figure 1-2. Reactor Coolant System Flow Diagram (Typical loop)l sem.neme ,o )
, ,. . . .....;_ . . . .-. . . _ . ~ _ .....-_-_;
a m j f l; Aux. Spray * - i e it.6 7 g A
. -
- Spray From *
~
Loop CL ., l
-
- Spray .
From Loop CL - [ f Surge Line Connecting
- to Loop HL i
L . l': Figure 1-3. RCS Pressurizer 1970s/102449 10 g.g ,
.a, .
. , - 4'. ..
. .. . a .: ., , s.j N
4 1 k Hot Flow Iresse Ptessurizer Tg ,,, =[ ]*****
& A a,e*e W w '
i i i . - v.iocsiy-[ ] _ I I I i/ - 9 9,9 4 I e I I I I I 8 - a,o,e -; 6 I I I v.socisy -[ ]
\ % \% \
s .
\
._ / ___., f3 N% -
t
. ___ . _w h
-sioenen mm*,c T e Tg= _
i i
'. t t
i Figure 1-4. Estimate of Flow Stratification Pattern in Elbow Under Pressurizer j me.,iem i. - .
.,n... _
".' : ;, . . ., -- ! !fL i; ,i ! ' hi!:
'. ' A-j~ :,^ .
Y . 4
~ .
x , m . a , r g o ., r - s P . n y e c s n sMn n agnn a en + i o
.r nee ee4e Auee3i e e t
a eses 3v g i c . s f e----- s i s l a u Q d n a .
~
I s I - s I e s e - s e st ne E n ed M o v e r S s E 5a t A n Et n
%i o
m e A r A o S p Aeg i t o - D r a e c f i - s s e s g y n f i rs I t i a a , e n " r sA e t . 0 9 S s e n n e e , a s o s e m n - sre e en e i ms s e s Mep no t p L es se s iu i n e t oen ey e s o g e n e r : de ess c de, 8 4 en pse E. ml ie t ss eA s n s e I Mn ea cc Asia sa uss e e, y s W 'I C P n e e r g e e S i r u r e z s r t s u : u en s te ei s - sd ue I de e - f s m r t e n P ed r n . e n i s n n Se r i n o o o y it C n - s a a r e e C - e p s - e e 9 l o n n b e a . e i n D y s 5 . 1 e r 80 u 9 8 g 4 7 i 0 F H s 0 - 7 9 3 1.
I e , e ; 4
. systsu ossen neuvosas
-* mapeemattees Data g
til (M 3, i staanacanon . ensarvaanwen < spectscatsma stnens ama6ves , em te
* ~ ~
ace r a
~
t. l :. t t .; l eillT04 scat sata E m saamments tim e Buent.Gemen , e cymes.esmen . asenne=s e tiennem7,,..seus .
- Gemen + esoneneres tiennem assonnw.
Figure 1-6. Transient Development Flow Chart i I l \ 1 ! an. nome in 1-45 l~. l .f.. J l; -l
e j.
~~
a sCeci l l -. l
~
E ' l t e I i I l
'h 9
A o, i l - 4 1 r t 9 Figure'l-7. [ . ]*'C Pressurizer-Surge Line Monitoring Locations - w ooin w ie U 1
=
l
,~ .,' -4 , ,
- E 4 e e e
.I k .
- m. . _ _ . _ __.m._ _ _ __ . .. . _ ,_. . _ . _ _ _ . . . . . _.__.m__
__ _ L '.
,-o .,
e ,6,- ---- ,-- 2----- - - - - - - - , - - . - . - - - - m'- V Y_f
, ? h' ,,
a r P e i a ~ f
.: t O. .
4 e v . y. 4
, .Q h p
Y h . M 4
. h. ,
-[-
s . t e-I i
- d. 's',
l .. 1 m a L W N
" i b
.., 3 en en i W
i 6 i A-M
- .md se=
C l"D C O A '. c-4 U C b e O N e M y' W L 3 On - open
. LA.
i 4 l 4 2~ 4 E a 1 i 4-1-47 l 1: j
--A# _ e.- - - a 4 A 4 .-om. .as.. ,- a.- cr.. 4-u_.. -
[
.g'r ,,
j- i
.u E f.re i, 9
(5 4
'h' <
Q !- , 4.' , U. ~ Q- -_ - ,
. i
_ l-I' i 5 f
'h.
s 4
~ ~
1 are
& 6
,ur .
u N . we b 3
.m M
6 gh . t h t i U
- i. a M~
m w 9
-O s
- M W
L 3 - Ch . z 3t g t I a 8, R 1-48
E 7
?,
_-s I *
- c. g , i o
n ,~ + o 1
'j._ _l
.i 1
u , x ; 1 i
... .j
.* 1 4- , , , ,7 I
i I P D 4
-i b
t Figure 1-10. [ Ja c.e Pressurizer Surge Line Monitoring Locations r
.-m e.no m eio 3 4g "'i. _. _
N e a k
. =
e,e.e L i A T i E -! b i
.: 4 Figure 1-11. Reactor Coolant Pump Cut-off Transient.
"''** . Location Approximately 10'-From RCL Nozzle Safe-End .
-m- - g _- _ _ _ s . - . , v.s--.y ,m__._ p-_,,.____- .- _,.y2 _ _ _ _ __ . _ _ . _ _ . ,_ _ _ . _ _ __ , _ m _,,,_ .___. _m_ .c
._m____ _ _ , . . , , . _, _ . , ,,, _ __.._2 ,,,m, , _ , _ _x. , _ , _ ,_._,y, _ . mm,
".c
._4 es.e
'l ) I
)
I i .I W 4 . w w 1 1 t e L Figure 1-II. Reactor Coolant Pump Cut off Transient RCL g Nozzle Safe-End ! n=n.m. .
- l. -
2 a c.e l . i fid
- c. ( -
l t l l l 1 l s 4 Figure 1-13. Transient Typical of RC Pump Cut-off 1-52
. llfl!l llfl
\)i!!li!1I\l i I. i
. e, c,
. a ,
i t
)
e p _ i P D I
) h s c e i n
e r 5
. g 6
( e e D
- l i
f ( o r P B . e l e t r u g a n r e p A T m e 4
) 1 F
1 ( e r u e r i g
. t u F a
r
. e p
m e T u. i u. r w 7:H _
;i l'
W'
~
Angle, idegrees)
. . , c,.
W 1 US 6 I Dimensionless Temperatwe,0 4 i Figure 1-15. Dimensionless Temperature Profile (14.3-inch ID Pipe) wea ez.ee.e l
. , e o , ,
, . .,-f. <. ~w-- . ., ,,~~,w. . ,, . . . . . , , , . , , . . . . . . . . . , , , , , ,,,...# .,% .. y-4,,. -ww,< ..%. .- ......%,...
t e L. . 4 W._./ 5 3
. =
h
. .t M
s L e h
- o. :: j k !l J
. 0 t
t R 1-55 1 m_ __ __
. _ . . . . ~ _ . . . . . _ _ _ . . _ __. . __
k l r i h 3-
, ?
i l 6
- a,c,e 1
I l i 6 I i I
+
i i I Figure 1-17. Surge Line Hot-Cold Interface Locations wo.nu ie 1 56
.r
' f v
W i- a,c.e 1 m Figure 1-18. Typical ( Ja.c.e Temperature Profiles uro.ncuse so 19 I
4 !
~
- 1 l
l
.ma a,c,e j i
.. j i l, 1
. 1 1
r i i i L v
.I i.
r
.- i l
i P i F
.-(
~
Figure 1-19. Inadvertent RCS Depressurization (AT = 260*f in Surge Line) me.nem..ie 1-58
i 4 es e e
' 9 1:
a 5 0 9
- E j
- s i-. !
x h W c E _ t'
'~
j
$,_ \ t i
t j h. R 1-59
I ( Temperahre (F) , a,c,e-B co m o k i ! rnne (Hours) Figure 1-21. Steam Bubble Mode Cooldown m um i. *.
' e 4 8 e
^9 %
0 4
._ . . . , , , _-.- ,._-, .~...- .. ---._ - , ~ . . . . . _ . . - - , _ _ . , - _ _ . _ ___44-.. , . , _ . . . . . _ - . - - - - . _ -
<5 ,4
* ..e . e l
y n e Coc 600 k. een E 400 + 3 .
- e-w 4
s g di ses 300 ! 4
- a.
t I tal
'l 200 ;
100 ' O T IE , e e 8 e* .ss . t l l ! e ll l l i A B,C F F' G IJ J' M D.E se ) ! Figure 1-22. Heatup [ .]a,c.e nrw,em se
. , .,. . . . . . . . . . __, _ __ ~ _ . . . . - _ . -
l - l 700 a ,c ..e l-600 t 500 Y < E f"i w : F 200 t soo - o I TIE ' III I 11 i 111 1 11 ABCF F*H D F" E G l
)
I Figure 1-23. Cooldown [ lC ; we.nes .e I a -
, . * % e [
e - y, , . . , , . , i4a. - .-w-,. ._-c--
. -1e. . ,e- - + - - - - - - - - - - - .
~
b 4 700 - a,c,e i soo l soo , w 400 er ' 3 e-t 7 5 a 300 a 0 r e.s 4 F zoo : ioo i o ie =Mi y ; 1I IIII le e i0 NNI Il e AB E. F. F 'G I 1*J K (; II- t D Figure 1-24. Heatup Diablo Canyon , 1 w nes l
.. .. . _ . - . - . . _ _ . - . . _ . . . ~ . . ~ _ _ _ . . . _ _ . _ - . . ....,._...__._____.____.-____.._________.-._.J
l i I l v. v~ i
, i
- l 1
i ___s j l I
- ==bL g f e
. I v ,
O 1 cm .
- .t
___w v 8 ___y ; m N. , e4 { e b 3 ei op w 6 I ___"o ___E4
~8 8, $ $ 8_
s $ $ ' J. 3WA1YW3alW31 : [ . 2 5 o h 1-64
I I 4 i i l i l e- ! 1
- u. !
= 1 I
l l
--a
- E,9, e=
u
- -6 4-i
....w i 4
....c - ;
....y a E ,
e N, L
& i
- -c ;;
9 IIIIAR! J. 3Wftavw3dW31 e i E R ! 1-65
N I
)
4
,es
- v. . -
e
- ).
I l
.j 3
1 i i U. .
-- = -
. t
?
- r 8 >
v
, 't e
~ ,
--- we ?
i
--- w h
.o, w
c
.. gg ,
l t. I @ - l 8 $ , $ -l. i
- 4. 3WhAYW3dW31 e
,. I, c f n 1-66
N I i a,c,e , 700 , i 600 4 k. tas er 400
- 3 ,
. p O 4 6
a. 300 -
.I F
d 200 100 O
, , , l i- . , ,, ,
1 I I I! l I 11 1 - A B C DE p- G IJ N !' Il Figure 1-28. Heatup [ ]# nwi.m. ..
.~; '
_ . _ . . . . . . . . . . . _ . , _ - , - _ _ . , ..____..s. . _ . . . . - . . . . . - . _ _ _ . _ - _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
l
,-- a,c,e 700 600 i
- k. .
I w v w 4 i 6 5 soo l w l' b 200 100 0 r a l 1 l l l . l l l l l A B C E F H i D G
; i
( i Figure 1-29. Cooldown [- ],a,c e 3 w .. .. a e
*
- O
- O %
.- _ . . . , . , . , . . , . , , . . . . . - . . - ,_.4_ _ . , , - - , - _ , .m, - . - - , . . . . . . . . . . . . . - . _ . . - , , . . . . . , _._._,m.,. . . ,
I' e 1 i' o.
- o. ;
m
, I
\
... j i
i l i l I' 7x sE s w e D n
.I
. i
~ l g >
', 3 1 1
a 8
- e t
_I i
.I i
Ri ; cw ! e i k LA. 4 4 ' k88kkk 8 8 8 1 3Wnivw3dH31 vi930 ) a 1-69
i s i tP
- 1 a,c,e l l
325 i 300 ' . .1 275 F 250 225 200 . j { 175 . i 150 . , g i25 ;
< 100 75 50 i
25 0
. 1 Figure 1-31. ( Ja c.e Location 1 - Heatup (4 Days) mwica.. ie 1-70
. . .-- ,- -o
, a,c.c e e 4 4 I i k. l W t-i T
~
dr hs
- e. . I esa t-4 4 t-d i
1 4 Figure 1-32. Diablo Canyon Unit 1 Location 1 fatigue Cycles - Heatup (11 Days) ww,.w i.
. . _ . . . . . . . _ . _ . . . . ~ . _ . . , , - . _ _ _ . . . . _ . , . , , . . . - . . , , _ . , _ . . _ , . . _ . . . _ . . . . _ _ _ _ _ , _ . - _ . _ . . . , . _ . _ . .
- e _ z; l
l l t e d.e W N N 1 i l t 1 i 4 i i Figure 1-33. Thermal Cycle Distribution Assumed for One Heatup Cycle m e.ne m ,e i
*
- e e e e O f
, . - - - -, - , . ...,-..-++-,-.---..~-e..n.
.: - , . , , - - _ - --_ _- _ _ . - - . _ _ _ _ . . _ . _ =. - . _ . _ _ _ _ . = . ,_ _ _ . _ - _ , _ _ _ . _ _ _ - _ _ . - _ _ _ _ _ . _ _ . _ _ _ _ . _ _ _ _ _
- -- , , . . . -.......2 --._y., ..%,. . ....u.m..+,,mu.... .-,.m..~..._..s. ~ . - ._m.-_u.....-.m..'. .#.m.~.m. . - .
5
. .. I i'
- v .
}
.' 1 !
.)
's e ^j
! 1 1
i i P 1 ! l i I 7 s i L. i f - i g
. I U.
. Wm I
e l
?
?
! '.
- 4 e
4 T
, n 4
l e=e I J -> 4 g a> 4 l b , i gesang - a . 3 s - j .
~
mma um - 1 x 1 1 1-73 i i 1 I
- l
m ,s.,,., - 6 ..._--es- .-_,__,.s-- , 4 94 2 _ s- e.__ a 4 .4_ I L
)
I h e D 4 . e k ! S ' E 8 M , 4 l v , m t r i F -
.b -
b w - d w C e
- C O
M 9 er= eel e-C
=
4 O M e . M t. Of
- O .
.r.
N b t i. E s E R 1-74
Y. ) I' ? SECTION 2.0 f STRESS ANALYSES l L* : l Flow diagram figure 2-1 describes the procedure to determine the effects of ' L thermal stratification on the pressurizer surge line based on transients i developed in section 1.0. [ ; l L'
, la.c.e i
Section 2.1 Addresses the structural or global effect of stratification f Section 2.2 Addresses the local stress effects due to the nonlinear ; portion of the temperature profile j
, Section 2.3 Addresses the total stress effects due to the oscillation l of the hot-to-cold boundary layer (striping) plus the ji
. thermal stratification stress '
2.1 Piping System Structural Analysis j i 2.1.1 Introduction 1 The thermal stratification computer analysis of the piping system to determine .
. the pipe displacement,-support reaction loads as well as moment and force leads in the piping is referred to as the piping system structural analysis. ;
These leads are used as input to the ASME stress and fatigue evaluations. The thermal stratification condition consists of both axial and diametric variations in the pipe metal temperature, as described in section 1.0. The model consists of straight pipe and elbow elements for the ANSYS computer
- code. [
)*' These studies verified the suitability of the ANSYS computer code for the thermal stratification analysis. [ Ja.c.e
- an.ncues to 2-1
, - ,n. -- -,. , - - , - - - - - . , -,
~
l 4
;. ? -[- j J
l j ja.c.e 1 4 2.1.2 Discussion On Diablo Canyon Surge Line Analysis t l The piping layout for Diablo Canyon Surge line is shown in figure 2-3. The
- piping layouts and restraints for the Unit 1land 2 surge lines are similar.
The Unit 1 line is 14 inch schedule 140, and the Unit 2 line is 14 inch , schedule 160. The rigid support, Ril, originally installed to reduce l
- deadweight and seismic loads provided resistance to the displacements caused ,
by therma'l stratification. Toaccommodatepredicted(references 1&2) Units i 1 and 2 surge line pipe movements induced by thermal stratification and , ; thereby mitigate stress and loading effects, this rigid support was replaced , ; with a snubber. ( l 4 Ja.c.e The 11 cases provide sufficient data to evaluate all the
, transients defined in tables 1-3 and 1-4. .
The pressurizer and RCL temperatures defined in table 2-1 reflect the , , approximate system delta T and not [- Ja,c.e System delta T was only used to define the boundary conditions (thermal anchor movements at both ends of surge line). ( 3a,c.e senvienes to g.g
l , i
.)
, i 2.1.3 Results for Diablo Canyon Units 1 and 2 Surge Line i The calculated piping stress due to thermal stratification for Diablo Canyon l
.- Units 1 and 2 surge lines is reviewed to ensure that the system will not collapse in a ' hinge-moment" mechanism. The secondary stress limit for this . piping stress is given by ASME III. Section NB 3600, Equation 12 as 3.0 Sm.
I ! The maximum stress intensity range, which occurs at [ ? 1 I la.c.e A summary of maximum ASME code Equation 12 l l stresses are presented in table 2-8. It should be noted that ASME III code stress indices were used at all locations except ( Ja.c.e evaluation used the results of finite element analyses for i secondary stresses in lieu of code stress indices to reduce conservatism tu calculate Ke factor and equation 12. C2was defined ( i la,c.e However, [ ASME I!! code K stress indices for buttwelds were conservatively applied to i
. add conservatism.
2.1.3.1 Displacements The maximum piping movements at supports and rupture restraints due to maximum thermal stratification for Diablo Canyon Units 1 and 2 surge lines are : reviewed to ensure that piping will not interfere with rupture restraints, and adequate snubbers and spring hangers travel exist (reference 4). A summary of maximum thermal displacements at supports and rupture restraints are presented s in table 2-9. A comparison of analysis vs. measured vertical piping movements is also *
. performed. Node 5140 of figure 2-4 corresponds to the approximate lanyard location 3 where the comparison is made. A vertical displacement of -1.8 inches was observed for pipe AT of 215'F. A vertical displacement of -2.3 inches was calculated for same AT of 215'F and at same location (node 5140).
It should be noted that the maximum displacement of -1.6 inches (anywhere in the pipe) was calculated at node 5170 for pipe AT of 270*F (see table 2-9).
""''"" 2-3 .
i i I j 2.1.3.2 Reactions l 4 The maximum reaction-loads at both ends (nozzles) of Diablo Canyon Units 1 and 2 surge lines are presented in table 2-10 for information. It should be noted -'
, i that' these actual loads and loads from all individual transient cases are used l to calculate ASME stresses and fatigue cumulative usage factors at both the .-l hot leg and the pressurizer nozzle. Stresses are provided in table 2-8 and usage factors provided in section 3.0. )
2.1.4 Conclusions ; Analytical studies with the ANSYS and WECAN computer codes have confirmed the validity of using an equivalent linear diametric temperature profile to represent the thermal stratification for displacement and loads (reference l 3). Comparison between the analysis results and the plant measured 3 displacements was performed. Eleven cases of thermal stratification were , analyzed using the ANSYS code for the Diablo Canyon Units,1 and 2 surge " [ lines. Results for all other cases of stratification were obtained by . { interpolation. The actual loads on the pressurizer and hot leg nozzles were , used in evaluation. The surge line pipe stress satisfied the ASME !!! NB-3600 l Code Equation 12 limits. i Also, the maximum stresses due to thermal expansion (with stratification), pressure and weight meet ANSI B31.1 Code Equation 14 limits for the existing as-built piping layout and support configuration. G l E ' unciome ic 2-4 ' E
i > t 2.2. Local Stress Due to Non-Linear Thermal Gradient "Qt
. 2.2.1 Explanation of Local Stress .
Figure 2-5 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 i the material in the adjacent beam cross section. For a linear topeto-bottom temperature gradient, the local axial stress would not exist. (
( 3a,c.e 2.2.2 Superposition of Local and Structural Stresses For the purpose of this discussion, the stress resulting from the global structural analysis (section 2.1) will be referred to as " structural stress." { Ja,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 independent of each other as summarized in figure 2-6. Figure 2-7 presents the results of a test case that was performed to demonstrate the validity of superposition. As shown in the figure, the super-position of local and structural stress is valid. [ ja,c.e nn. nome in
, 2-5 L_
- u. , , 4
-4 2.2.3 Finite Element Model of P'pe i for Local Stress
> )
A short description of the pipe finite element model ,is shown'in-figure.2-8. :-
'The model with thermal boundary conditions .is shown in figure 2-9. Due to '
symmetry of the geometry and thermal loading,. only half-of the cross section . e was required forimodeling and analysis.. [ , l
.i -p t
L l
-l ja c.e ,
2.2.4 Pipe Local Stress Results l-. Figure 2-10 shows the temperature distributions through the 14 in. schedule - [ .... 160 pipe wall ( r j. t ll ~ 1 Ja:C,e nn,namo so g.g
yf ll b [:
, t,-
2 10 ja,c.e 2.2.5 Unit Structural Load Analyses for Pipe In order to accurately superimpose local and global structural stresses,
,. - several additional stress analyses were performed using the 2-D pipe model. 1
(- !
~
l ja,c.e
-2.2.6; RCL Hot Leg Nozzle Analysis i m
Two RCL surge line nozzle models were developed to evaluate the effects of l thermal stratification. These two models are shown in figures 2-20 and 2-21. I ja.c.e Figures 2-22 and 2-23 present sample color contour plots of stress intensity distributions in the surge line RCL nozzle due to stratification and moment loading, respectively. A summary of local stresses in the RCL nozzle due to
"" * " c 2'" ' '
2-7
=-
o- , i
. thermal-stratification is given:in table.2-3. 'A' summary of: stresses for_ unit
~
i pressure and' bending applied ~is'shown in table 2-4.
. 2.2.7' Further Clarification on-Superposition of. Stresses , ,
4-In~ order to further clarify the process used to obtain total' stress at any . . , point lin the pipe wall,- the following step-by-step procedure is listed. :
-l i
' t k
4 l 0 ja.c.e This method of superposition makes it possible to accurately evaluate a large number of stress conditions (fatigue transients) with a minimal amount of an.nouse in 2-8
finite element analysis. The process of scaling and summation is handled by the program WECEVAL during the fatigue analysis. 2.2.8 ~Conservatisms
- Conservatisms in the local stress analysis are listed below:
- 1. The' hot / cold fluid interface is assumed to have zero width. A more gradual change from hot to cold would significantly decrease local stresses.
- 2. Stresses are based on linear elastic analysis even though stress levels exceed the material yield point.
2.3 Thermal Striping l i 2.3.1 ' Background ' At the time when the feedwater line cracking problems in PWR's were first discovered, it was postulated that thermal oscillations (striping) may 1 significantly contribute to the fatigue cracking problems. These oscillations I 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 rate conditions. (See figure 2-24 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 establish boundary conditions for the stratification analysis and to provide striping oscillation data for evaluating high cycle fatigue. I Thermal striping was also examined during water model flow tests performed for the liquid Metal 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 2-25 for test pipe sizes, thermocouple locations, and table 2-5 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 w ,,no m eso g.9 i
i
)
studies of. thermal' striping which were performed in Japan by Pitsubishi Heavy
~ Industries. '
'2.3.2 Add'itional Background Information -
. j Thermal striping was examined during 1/5 scale water model flow tests .
performed for the Liquid Metal Fast Breeder Reactor primary pipe loop. These
' tests were performed by Westinghouse at the Waltz Mills test facility. In order to measure striping, thermocouples were positioned at 5 locations in the hot' leg piping system (three in the small diameter pipe and two in the large diameterpips.) The inside diameters of the large and small pipes were 6-1/2 .,
- l. and 4 inches, respectively. Figure 2-26 shows the test setup and locations of the thermocouples. (Figure 2-25 shows. test pipe sizes with circumferential positionofthermocouples.) Thermorcuple locations were selected [ :l Ja.c.e The l
'thermocouplesextended( Ja,c.e into the fluid. The flow rates and- ,
corresponding Richardson numbers for each pipe size are shown in table 2-6. , A total of ( Ja,c.e tests were performed and evaluated. Three , parameters were measured during the water tests which help define thermal striping: frequency of fluctuations, duration, and amplitude of delta fluid temperature. The ( Ja c.e were recorded in the discussion of test results and are presented in table 2-7. L The frequencies of the temperature fluctuations from these test results were reported to be in the range of ( Ja,c.e As shown in table 2-7, the (- , , ja,c,e [ ja,c,e
""""" 2-10
s - The flow model test results are used'to osain. frequency and duration +
' parameters which are used in the striping evaluation. The frequency-and duration parameters are considered to be functions of- the flow rate and
.; Lbuoyaicy forces between the hot and cold water interface, and not pipe diameter'and wall-thickness '(
[4
-i jac;e' l
1
-When all-other factors are equal, it has been shown that the thermal striping j stressis'( Ja c.e j A typical value of usage factor was calculated with the [
.. Ja.c.e ,, f,)),,,,
2 ( 1 ' ja.c.e-I This distribution corresponded to (: Ja c.e considered to occur at a stress level calculated with frequencies of ( a
),a,c.e respectively. Calculations revealed that-there was (' !
~
Ja,c.e in the usage factor when a [ frequency of .30 hz was used vs. the worst frequency distribution shown
)"'C -Therefore,( )"'
- was assumed in all usage factor calculations.
For'the Diablo Canyon Pressurizer surge line, the frequency of ( .)a,c.e c was used in the.[ 3a,c.e 3971,1102449 10 pgg e
7 ( . 1 As:shown in table 2-7,1the amplitude of AT varies from ( f 1)a,c.e of the full AT between the hot and' cold fluid. temperatures. For the Diablo Canyon Surge line,.the amplitude was assumed to be at [ ja,c.e as shown by the curve:in figure 2-27. This is-conservative since a higher AT. results in higher stress. The maximum duration of thermal striping from table 2-7 shows that thermal striping occurred for ( )"'C For the Diablo Canyon pressurizer surge line, thermal striping was considered to occur. ( .
)a.c.e -
.J 2.3.3' Thermal Striping Stress 6s q l
Thermal striping stresses are a result cf differences between the pipe inside , surface wall and the average through wall temperatures which occur with time, due to the oscillation of the hot and cold stratified boundary. (See figure' 'q 2 *d8 which shows the typical temperature distribution through the pipe wall). l (1
)a,c.e The peak stress range and stress intensity is calculated.from a 2-D finite 4
element analysis. (See figure 2-29 for a description of the model.) ( ,
]a,c.e 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 a maximum. Stresses-were intensified by K3 to account for the worst stress concentra-tion for all piping element in the surge line. The warst piping elements were the butt weld and the tapered transition, m i.ne m ein 2-12
lI w . 6 ja,c,e
-2.3.4 - Summary of Striping Stress Considerations
( t e m
.g
o
.g'.
O ' e'
$.' e
.?
.e t
ja.c.e un.ncu.. i. 2-13
w,, . n.
-s
. a F
, ,
- i'.
h l. -
, < -[ ,
'4
% l
,~ , . .
l
, - ,:. 1 l- j n w' f.
e.
-1 4 ;
a hI
;' ?, ' f li '. ,
.. j '
{
-i q.
l l 1
-1
.)a c.e . .4
- 1. .;\
2.3.5 Thermal Striping -Total Fluctuations'and Usage Factor ,
~
l Thermal striping transients are shown at a AT level and number of cycles.
.s , . -[s P
4 1 9 4' $. I e O ja C,0 mi.n omo io 2-14
pa , f r ( u " l& i; ' ,
. [' .
_ 7. . . "I4L.: s d ja c.e 2;3.6 Conservatisms ! The conservatisms in the striping analysis are: striping occurs at one location; surface film coefficients assume high values with constant flow; and conservative design transients are used. The major conservatism involves the
, combination of maximum. striping usage factor with fatigue usage factor from all other stratification considerations. The ( ,,
ja,c.e q j
.i I
v.. 3
-I ?
1 i
- wi.name i.
2-15 4
~'l *j'--
1
@ l
.( -.a'- gj
. TABLE 2-1 iTEMPERATURE DISTRIBUTIONS IN DIABLO CANYON PRESSURIIER SURGE LINE
'O 8,C.S' !
.a A^l l
'iw
. f; 1
1 t 1 t' i= i e S G-4
't a
1 l o e I l l I 1 t l
-- miinomo io 2-16 l
l-
[ _ r o i[ t i d
. TABLE 2-2 se DIABLO CANYON SURGE ~LINE MAXIMUM LOCAL' AXIAL' STRESSES.AT [- 'Ja,c.e I.
a Local. Axial Stress -(psi) L: Locat' ion Surface Maximum Tensile Maximum Compressive i 4 c.e-b6 l b ; 1
- p. .
L Notes: Local thermal stresses shown are for a AT = 260'F. V > The results for all individual transient cases of thermal L stratification as defined in section 1.0 are~ obtained by interpolation-
- u
? from this case. , L O' ,
- 3+.
3971s/1024t910 2-17
m ,
- S , ,
,e ., e p- ,
TABLE 2-3:
SUMMARY
0F LOCAL STRATIFICATION STRESSES IN TiiE DIABLO CANYON SURGE LINE AT THE' RCL N0ZZLE q: All Stress'in psi Peak Stress - '.- + Linearized Stress Intensity Rance' . Intensity Range' ;, Diametral
' Location Location- Inside- Outside Inside Outside ,
a,C,e h-d
, e l
l'
=
l' l. l*. w s noz m so g.$g l: l' l!
i l l l TABLE 2-4 I
SUMMARY
OF PRESSURE AND BENDING INDUCED' STRESSES , io
- i - IN'THE DIABLO CANYON SURGE LINE RCL N0ZZLE FOR UNIT LOAD CASES I All Stress in psi Linearized Stress Peak Stress Intensity Range Intensity Range Diametral ~ Unit Loading Location Location Condition Inside Ou,tside Inside Outside a,c.e.
',4'.'
9 - a
'O?
f P i.: l-l l. a n.,iem. 'a 2-19
' c[w - - -
r
, s +
.] i
, -; (p ' . , -
e
? 't l.
TABLE 2-5 j
' STRIPING FREQUENCY AT 2' MAXIMUM LOCATIONS FROM 15 TEST RUNS- :! -
.i l
t
} , . g i j
N ' 3,C,e l 1 1
-I u .
o
~
l t; bi. .i 1, [ '! l
. 'l o.
'1 1
e y ,t . 1 4 I . 4 a 3071s/102444 10 pg
-1 s i
k P
> TABLE 2-6 FLOW RATES AND RICHARDSON NUMBER-FOR WATER MODEL FLOW. TESTS'- ;
Cold Water i
. Flow Rate
.x Pipe Section (GPM) Ri
. e 4,C,9 9
h 9 t . s;
, , e e
-l l -:.! . s l.
l; f' i l [. I-
)
l I' I s '1 I- :e
' ' .*S i
l
,, 1 o
i
~.,
1
- nrisito24ao 10 g.g}
L
- m ,, - .- , .-
- l. -m t
.s w.,
-TABLE 2 i RESULTS FROM TWO HIGHEST ~THERMDCOUPLE LOCATIONS >
4
- TOTAL DURATION-
' FREQUENCY ~(HZ)- - # CYCLES /.~ AMPLITUDE (% OF POTENTIAL)
% .- % - % . LGTH IN~ %- %. % '. .
MIN. (DURATION) MAX. (DURATION) AVG. (DURATION) TIME (SEC) MIN. (CYCLES) MAX.'(CYCLES) AVGi (CYCLES)- l ~ a eC.# :M7
. h.
i M e N N
- ~.
-{
\ 'p l
lj a 4 r _; '
.f!
397Is/102489:10 ~.
.n
.f
- e. , * * .
e ; *
.'. *U r _.. -_. _ _ _ _ . .. . _
s 4. . . ;,1, , .
; y;, y , , .<. 1
~.. .
4
+ ) t ? '?n lfSh i. .. i i '-
~:
- P TABLE 2-8.
1, ASME EQUATION 12 STRESS
SUMMARY
Maximum Stress Allowable Stress
; Component = (ksi) 3.0 Sm (ksi) 8,C,e
.~ . '
.. 5
'.'l
i p. eueSw 4
._5 4
9 b4
.' \ { ':
T i G m f 1 s t
, mi.mme io 2-23 s 3 -;
t
7,- , 3 si. ~ ,
- a. ,
' n : I l- TABLE 2-9 q THERMAL. STRATIFICATION DISPLACEMENTS AT SUPPORTS AND RUPTURE RESTRAINTS : 1
. Support or. Node:
-Point Z *1 Restraint.- X Y- *
(VERTICAL) ; t . a,c.e [
.9
- 1-25SL for Unit 2
** 70-27SL for Unit 2 .
# 1-24 for Unit 2
- 6. ' ## 70-595L for Unit 2 .
v
+ 1-23V for Unit'2
.l-.
1971s/102449 10 , c - - - - - . _ - . - - - - _ - - _ - - - - _ - _ - _ - - - _ _ _ - _ _ - . - - . - - _ - _ _ _ _ - _ - _ _ _ _ _ - _ _ _ _ _ _ _ . _ - _ _ _ _ _ _ _ _ - - _ . - - _ . _
k
,I $i I
( < ic 1 TABLE 2-10 ;
. REACTIONS AT N0ZZLES 1 J
+ '
Nozzle- Fx Fy Fz . Nx. .My Mz.
....;.. (kips) (kips) (kips) (in-K). (in-K) (in-K) )
l i L' a,c.e D 1 y
. h.
6 .. Note: Maximum Nozzle Loads For Existing Support Configuration.
=
L . . -
- 1. '*: .
~.
t' ! t I l
-eg 4
un nouse:o 2.g5 t-r
)
u. 1 Y , l DETERMIN AMON OF TMt IFFICTS OF THERMAL STRAtlpiCATION a,c.e ... -i t ..
}
s 4 Y
$ z I'-
E t t
't t
4 ' g i . I .. .
. I.
7 p i ,.i Figure 2-1. Determination of the Effects of Thermal Stratification t
. m iinoaseto 2-26 l'.
s I i , II. . 1 1 I
.(
I. t t E , j
- s. \
f 9 e,c.e
-t n-i.
i v i-t 4 - l i,;3-i P Figure 2-2. Stress Analysis 3971s/102449 10 l 2-27 l i
b
, .5 t
('. l' ,
=
u Y- - o y PRESSURIZER .
-m e .
l "o Z X i ( $
. g Sp2 6 FT 3 FT '
Spl ll Myf 27 FT ~ t ib SNUBBER - SNUSSER~ I RII RIGID
'g'*' CHANGED TO. -J 21 FT -SNUBBER RCL HOT LEG-1O FT 8 t 1
1. i L. Figure 2-3, Diablo Canyon Pressurizer Surge Line Layout ws.name no g.gg
=
s b
..s a
J 4
, Y
- T l H - g -1 Z
- X ,
T H N 5360 5310 5340
~
3-10RR. l; 5250 3-3RR
- .- 5230 5210 3-4R 5270 ,
3-11RR 51-23V L.' - 5260
.10-86SL s
l
. 5170- 5180 a D '
'3-5RR 51-24V 5130 ,
10-13SL i' 5140 5100 l 3-6RR 25SL 5000 5110 3-7RR
-5040 5070 '
3-9RR L -T 3-8RR T r- H HL l-
\ A r
[ ,-
' 'T T = Hot Leg Temp -
HL T = Cold Temp C
- T = Hot Temp = Pressurizer Temp H
e i Figure 2-4. Diablo Canyon Surge Line Model and Temperature Profile j l l . , senviouse in 2-29 I
4: I l l e
~-
Q e' S G 9
'1
.- G E
ahd M U ee M.e
'4 6.
en N O w ... 4 4 b. b
.C e-N W
b W, M S-a N N . b L t I a. I __ i 2-30
6 a ,c ;
..>w i
-l
~ .
.P - -
'l 1
i l i i
.w> ,
i
- . p i
Figure 2-6.. Independence of Lecal and Structural Thermal Stratification Stresses Permitting Combination by Superposition mi.ime in 2-31
1, D , p l 9 M. 4 Cit .. ;
-q J -
D
\
i s e r
.-b>r 1
i q 1 i 3 r , 1 I: i 1-f 1 1 . l-i k l L. Figure 2-7. Test Case for Superposition of Local and Structural Stresses I I e I.
* .i i
3ef ts/10246910 2-32 l-ic ,
- p. !
)
i o
+
* - - - a,c,* '
,e.
?
i I i I ~
. i t
t r ! i i i i t 1 [ -t l E 1 1 l >
.1 l
Figure 2-8. Local Stress - Finite Element Models/ Leading 1 l l =>i.non io 2-33 - L-
.i 1
)!
$ 1
- a.c.a . l
- . I 6
1 e .i I i
)
3 r i
.s I
I i I
. i i
e Figure 2-9. Piping Local Stress Model and Thermal Boundary Conditions
- nn.nu.n io 2-34
s
.c ,
a,c,o r _ . 1 I 1 1 e, i e h i t t,
~
I l-t . l
- t b
r . 1 '. k 1 l .
. . p 1
1: ,_ Figure 2-10. Surge Line Temperature Distribution at [ j a.c.e g,g,) , Locations
- wn.nn. se 2-35
-m,-
a,c,o l i-i a 1 r i t t t e i l. Figure 2-11. Surge Line Local Axial Stress Distribution at ( 1"'C Axial locations } en.n u." " - 2-36 i
a,c,0. t l, ' 4. [ I ! , t [ i
=
r
-i i
N. Figure 2-12. Surge Line Local Axial Stress on Inside Surface at ( Jac.eAxiallocations !- an.nm.. ie ) 2-37 l: { 1 1, .
a,c,o- ) i-
-. i W .,
1 i
- i t
h i I e ! . P i. t i l h i r 1 4 i
.i 4
1: 4 Figure 2-13. Surge Line Local Axial Stress on Outside Surface at ( Ja,c.e Axial Locations l-an.nuae is 2-38
l
)
J P ls ,c ,e )
. i
+
t i O
* ?
9 ,! i m
- h. -
f' w g . ehaI 9 A a se 9 8-8 b -I
= w i
.N-O k
6 3 a 9 ; L '!
@ 'i C
u , 3 W T A l N D L
- 3 On e-LA. .
e: 1 I F 1 9 Ia . t 2 I l 1 2-39 t l' l~ l '. 1 I
i i [
~-
'_I' ;
t ,C i t l g 0 9 W. U. m enef E M 4 8 a a 4 8 b a
.M O
.. g M
W
. b a
N N K 4 W s S 3 W N w l
. N W
b 3
.m 8 I b t
I a 5 R 2-40 L
Ie i h l l 8,Cet e
.[-
4 ! l e t. 5 U. N s r s-
& h 4
8 a 5 E I' 4 j 8 !
* & y I ( )
.th ca C
. e.
W L 3 i a - 4 j i k 9 W c e ves b 3 W m 4 $ 4 N W
' L 3
e-N h r i t t I; ;
- 1 2
R 2-41 L i
'- . . . .~ .
l-l' 1 - _ t L 1 I l l i t i I i m, b N
=
o Figure 2-17. Surge Line Local Axial Stress Distribution at location [ ]C w..,. 1 .. 4 4
, - . + - - , , .-,i.,, ,
- - _m.,-,,-, .., s-ew . ,.-~.m.._, . , , - , - , . . ...,w.. . -m .-.,,.m. mm ..,__., a.,___.-u__.m. .'W
F. ',
, [I _
I 1 r
; ,a .c .e ;
i e ; h
- e. '
- u. ,
.I m
8
.ud '
9 8, ema 9 8 e e6e0 [ I k' (a
. e M i eH h +
- 4. .
i
.D.e 9
L l C or. l ,. a . b u i D M l 1 l l ,- l
- i 1- N 1 @
\ k l '* 3 1 .me v l \
. ......... J l c ,
- e :
3 1 l , I R j 2-43 i i
~ -
~ .- ,
d to. b h _ e n e 1 Figure 2-19. Surge Line Local Axial Stress Distribution at Location [' l*' . m i ., ..m. .. 9 y =..y-re,-.. a , r - , ec 4 -- ,., , - .< ,r -.,-,,e , --
..imw_.w% , e,w.,e,, - ,- r , _c-.w,w.-r em<--4v-=~ , i-m r s e- +C+=-s=
- e*+sav w-
- e-
4 4 3 - = ,..u - _ = a + a #s.,- , 5 : ! 4 3.A w ,r. C .l i t ' f
.( '
r G , U *
'i e 5 I
i a : (
=
4 I 4 e r r f L, , t m i t M s , w a i O , W e- g N
. a b 7 5
O~ N. ? N W 6 l- % l l 4 . , l e
'a R
?
2-45 1 i I t, 1 L: ' '
1.* i l 1
's 4
- u-S: .,
e O~ _ . . >' I e j 1 l I i 4 j i l 1 1 A N, m .l, j suo t s w cm- . M ' I
~
. N N e' 'i
.g . ;
a . . V I. E l: .r med l. I o O t sung N
- i. N O t
L 3 *
.O b r
i 9 y l 4 a e I t t 2 l
- l. .
f 2-46 - I 1 ..
e ;,
-: m J
g ;. , , -s s ~': _.;;- p ro. Jh N n
~
Figure 2-22. Surge Line Nozzle Stress Intensity Due to Thermal Stratification enusu ,,
- v. e + w ~ v.' -. - -w- *- *<ew-* 4^m**M+-- e'"9we4- amv % wv--
- d
- w r+v+e '*'w---+- +-e-e*~er a.-m--*r u -. 2a--m--*-m.2 w2eu--a eu---.--==----sA=u-ma-'ww-
n ., - -- .a ., r - - - .---- . . - . - - . . . 4 I 4 Cet s. l l l
$- e i i
r F 1 e
.r
'^
j O l
. 2 ;
.t, -i M .
ene N :
.E.
N 'i "N - N t
. 3
. 1 :
N N I l- -l I
*l k3 ci -
2-4B 9
+
i I i
)
i
= . !
i h n.c i i J 9 i r s , ! n r 4 "d f .c , .. ( , i i i Figure 2-24. Thermal Striping Fluctuation ; an.nes . in 2-49
- u. i l$'
p- . 1 F i .
) ) -g N*
s
- f. .
).
I i 1 -1 I
.- )
# i
# l
! l l
l 1
- i i
l l
- i e==
etd W l W -
>=
l I i e .' I b i d V5
+ . , s -
M i 9 I U ew ese 6 3 w a d , e . i I + I 0 e i 2 4 E 2-50 ,
tb l 4 n 3,,o
' mum aus.N -
)
v iA ; 1 ee F"}as se j l [tenanos e - I
% me =4 e y sw-fscenenass.er C j
( - () ' SWEP -[ ] I g, w ,,,, q =;
- . .,, m - ,
ewe v M ; 3 - w 1 sw = __ 4
.f teennst 9 y l'
l-k- i
- W. - ** -,
- /.
L _
"Y
-l, Y i
unaewe ! i 1 1 I i l' '
.. g Figure 2-26. Water Model of LMFBR Primary Hot Leg u n n c u se so y.9 l-, - -
t
, i l
1 i _ t.c.e -] 1 s i j
)
i
. i 1
t i I o 1 l i
.s 1 men. .
L ( , 1 . 4
-Figure 2-27. Attenuation of Thermal Striping Potential by Molecular Conduction (Interface Wave Height of ( Ja c.e l.
M?lt/1p4M 10
- i. 2-52 l.
5
m i i 1 l 1 i 1 i
^
l
'l
;I
- i
'"""" - 1 a.c.e 1
1 i i
?'- ,,
e.' . ; l s I l i l '.
- l l
l 1 y ,9. 1 9. 1 s; . A Figure 2-28. Thermal Striping Temperature Distribution i e 4 n n.n m ..i. 2-53 , _I._mm.m_ -
a-Aas we--* = s i
'l i I
j e e c .
- ' e Ue i Y* 0 l
e
- 4 i
- 1 1
1 1 I j 1 1 1 I I
.i fed
- l W
I . k e )
.- e a
.e i
o-9
. efee b -f e .r 9
. 'I h $
N j s . N T '
+ .m \
6 s t s s ' t O 4 t
, [G F
2 I a. 2 E 6 1 2-54 4.-
I SECTION 3.0 j ASME SECTION !!! FATIGUE USAGE FACTOR EVALUATION I
]
3.1 Code and Criteria l Fatigue usage factors for the Diablo Canyon Units 1 and 2 surge line were ; evaluated based on the requirements of the ASME B & PV Code, Section !!! (reference 5), Subsection NB-3600, for piping components. The more detailed . techniques of NB-3200 were employed, as allowed by NB-3611.2. ASME 111 1 fatigue usage factors were calculated for the surge line piping using program WECEVAL(reference 6). ] in the plant-specific analysis, [ la.c.e The cases selected in the fatigue 9, analysis are the in-line component in each profile region with the highest 0 . and K stress indices defined by the ASME Code. At 50 bends, K indices for butt seldt were conservatively app' led to add conservatism. r- 3.2 Previous Design Methods
- Previous metnod of e typical surge line piping fatiguo evaluat',or, used the NB-3653 technicues. bet with thermal transients defined by W SSDC 1.3 F and 1.3.X (references 7 and 8), assuming the fluid surges to sweep tre surge line piping with an axisymmetric temperature loading on the pipe inside wall.
These evaluations produced typical usage factors of approximately [ Ja c.e at girth butt welds, [ )"'C at elbows and bends, and [ Ja,c.e at the RCL hot leg nozzle crotch region. Effects of stratification were not included in previous typical design analyses. t it must be noted that the above typical usage factors are conservative since, in the design process, calculations are carried to the point where results nn, nome io 31
- i
i meet code requirements, and are not further refined to reduce the usage j factor. It also must be noted that the Diablo Canyon previous design analyses is based on B31.1 Code, not ASME Code. 3.3 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 2.0) 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 ela:aent analysis and then combined on a stress component basis, i
n 3.3.1 Stress input Stresses in the pipe wall due to internal pressure, moments and thermal ' stratification loadings were obtained from the WECAN 2-D analyses of 14 inch, schedule 160 and schedule 140 pipes. For a given. load condition, the total ,e , stress in ibe pipe is determired b/ superpetition of strasses due to pressure,. ' moment and local strctification offsets. The stresses in the finito element toodel due to sael, of these types of Icading were first determine 4' for nominal valses of load and stered on computer tapes. [ , i i
)a,c.e e n n.n m a ie 3-2
c4 U Scale factors were then developed for each load condition based on actual pressure, moment and stratification loading for each condition and stress I indices for the component being evaluated. ( , j i ,-*.. j
\
l J 1 J l L
.la,c.e C3 and C2 t
, determined from ASME Code Subsection NB-3681 for the component being evaluated.
O, The total stress at each node point in the finite element model is then i
- determined by t,uperposition of the individual contributions as follens; i i
f 1 (
)ac>e The finite element model stresses on tape are the six stress components at each node point in the model.
~ After determining the total stress components for each load condition defined
' 8-in tables 1-3 and 1-4, program WECEVAL proceeds with the fatigue evaluation i
according to NB-3222.4. In the evaluation, stress concentration effects are nn nome in 33 1 b
i conservatively considered by applying the maximum peak stress index from NB-3681 (K , K ' K ) for.the component being evaluated to the total 3 2 3 . stress. , 3.3.2_ Classification and Combination of Stresses l As described in 3.3.1 the total stress in the pipe wall was determined for f i each transient load case. Two types of stress were calculated - Sn (Eq 10), to datermine elastic-plastic penalty factors, K,, and Sp (Eq 11) peak 4 i stress. For most components in the surge line (girth butt welds, elbows, bends) no gross structural discontinuities are present. As a result, the code-defined "Q" stress (N1-3200), or C 3 EleaT, - ebib lin Eq (10) of NB-3600 is zero. Therefore, for these components, the Eq. (10) stresses ; are due to pressure and moment. . i. For the RCL hot leg nozzle, the results of the 3-D finite element WECAN ,
~
analysis 51 the nut 4e wert used to datermine "0" stress for transients with stratificativ.in the nozzle. . Note also that the Eq. (10) stresses included , #i appropriate '. tress intensification using the secondcry strows indices from , NB-3601. 4 Peak stresses, including the total surface stress frem all loadings - pressure, moment, stratification were then calculated fer cach transient. i i
)ac.e 3.3.3 Cumulative Fatigue Usage Factor Evaluation
- Program WECEVAL uses the n S and p S stresses calculated for each transient j 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 NS-3222.4(e)(5). The inside and outside pipe wall usage factors were evaluated at [ ')a,c.e through the pipe wall of the 2-0 WECAN model, nn.nu.. io 34
The mesh of the finite element model is such that ( Ja.c.e are defined by the element boundaries and node points in the circumferential direction (see figure 3-1-). Thus,( Ja.c.e , virtually comprise the entire model. The values of stress at each section for each loading are contained on computer tapes used in the evaluation. l Usage factors were calculated at selected node points in the finite element model on the pipe wall surface, corresponding to the analysis sections. These ' node points were selected based on review of the local stress profiles and previous analysis results where maximum usage factors were calculated. ( Ja.c.e The maximum usage factor was then reported for the - global location. The usage factor calculations include:
- 1) ' Calculating the S n and S p ranges, K , and Salt f r every O. possible combination of the ( Ja, ,e transient lesd sets.
- 2) for each value of Salt, use the design fatigue curvc to determine f' the maximum number of cycles which would be allowable if this type of cycle were the only one acting. Those values, Ny , N 2 *N n '
were detcrmined from Code figures I-9.2.1 and I-9.2.2, curvo C, for auctenitic stainless steels.
- 3) Using the actual cycles of each transient loadset supplied to WECEVAL, ny,n2'"n, calculate the usage factors V3 ,
U ...U 2 n from Ug = ng/Ng . This is done for all possible 11 combinations. If N gis greater than 10 cycles, the value of
, Ug is taken as zero.
(
)a c.e m wpusoe 3-5
[ ja.c.e
- 4) The cumulative usaga factor, Ucum, is calculated as Ugy,= U3 '
The code allowable value is 1.0.
+U2+****U. n
^
l 3.3.4 . Simplified Elastic-Plastic Analysis When code Eq. (10),nS , exceeded the 35m limit, a simplified elastic-plastic analysis was perforned per NB-3653.6. This requires separate checks of expansion stress, Eq. (12), and Primary Plus Secondary Excluding Thermal Bending Stress, Eq. (13), and Thermal Stress Ratchet, and calculation of the elastic-plastic penalty factor, Ke, which affects the alternating stress by Salt = K, Sp/2. The K, values for all combinations were automatically calculated by WECEVAL. Thermal stress ratchet is also checked oy WECEVAL. Eq. (13) is not affected by thermal stratification in the pipe where no gross , structural discantinuities exist, but reuuired tc be verif4ed at the nozzle. r Eq. (12) was evaluated in the G1 be.1 ANSYS analysh by checking ths worst ,$ possible range of stren due to the expansion bending moments (section 2.0), e . I, It should bt noted that ASAE equation 10 is calculated oy WECEVAL for ever/ 1 combination at each cross section evaluated at each g'lobal location to determine the elastic plastic penalty facters, Ke. The valves of Ke are stored on tape te be used h tha suesequent usace f6ctor csiculation. The various locations for which Eq.10 was exceeded can be obtained by detailed review of the computer runs. In the whole of the analysis, [ is assumed to be exceeded at all points and Eq.12 and 13 are addressed as Ja.c.e Due to the nature of the thermal stratification loading, - [ Ja.c.e is the more critical for qualification. 3.3.5 Fatigue Usage Results e The maximum Usage factor was [ Ja c.e, which is less than the code allowable of 1.0. un, nome io 36 __ - _ _ __ _ _ ___- _ _ - _ _ a
J j<#
'+ ASME Code Section III stress indices were used for all components except (
V, Ja c.e [ )a,c.e evaluation used the i results of finite element analyses for secondary stresses in lieu of Code stress indices. - The above usage' factors included the effects of striping. Because the nature
'*~
of str.iping 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 determined to be more appropriate to calculate a total + usage factor by conservately adding the ASME and striping usage factors. , 3.4 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 Salt, and the factor of 2 on stress and 20 on cycles in the S,- design fatigue curve.
Also, due to input limitations _in program AL, the maximum value of peak stress intensification for all loading typ -ss used. This was conservative at girth butt welds, since Kg = 1,2, K2 E 3 = 1.7 in NB-3681 and K=1.8 was used in WECEVAL for all str-1 1
un nema 37 j
I
+
i e,c.e R i l e
.j i,
i 1 1 _1 1 j 1 l 1 1 1 l 1 l
.p '
1 .' > l-l' i l l.. L f' i
- l. 4 g
lr - I 'a l '. , f-Figure 3-1. Fatigue Calculation Locations nninou io 3-8 p.
i SECTION 4.0 i
, CONCLUSIONS [
l.. -Based'on the monitoring and analysis results presented in the report the . L following conclusions are reached: ; The global structural and local stresses in the surge line piping and existing support system meet ASME III Code allowables. The maximum cumulative fatigue usage factor is [ la.c.e for all applicable ' transients including the 250 heatup and cooldown cycles (design life),
-compared to the Code allowable of 1.0.
.Also, the maximum stresses due to thermal expansion (with stratification), I pressure and weight meet ANSI B31.1 Code Equation 14 allowables for the existing as-built piping layout and support configuration.
In summary, based on current piping and support configuration and the l ' understanding of the thermal stratification phenomenon, it is concluded that
, thermal stratification does not affect the integrity of the pressurizer surge line of the Diablo Canyon Units 1 and 2 nuclear power plants. The design life (including 250 heatup and cooldown events) and ASME~ III Code compliance are not affected for the existing as-built piping layout and support configuration.
l l. l b mn.iwanno 41
L g <i 5 APPENDIX A
. LIST 0F COMPUTER PROGRAMS
.y This appendix lists and summarizes the computer' codes used in the analyses of stratification in the Diablo Canyon Units 1 and 2 pressurizer surge lines.
, The codes-are:
- 1. WECAN
- 2. WECEVAL-
- 3. STRFAT2
- 4. ANSYS A.1 WECAN i A.1.1' Description
.: s WECAN is 'a Westinghouse-developed, general 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 axisymmetric analyses. Srick and wedge
. structural elements are used for three-dimensional analyses. Companion heat 1 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 a
thermal-stress analyses are a standard application..used extensively on an industry wide' basis. l l an. nome io A-1 ) l m _. _ I
-i ii -
LA.1'.'3 Program Verification i Both the WECAN program and input for 'the WECAN verification problems, currently numbering over four hundred, are maintained under configuration ,. l control.- Verification problems include ' coupled thermal-stress analyses for the quadrilateral, triangular, brick, and wedge isoparametric elements. These l problems are an integral part'of the WECAN quality assurance procedures. When l
' l 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, u
L 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, dP 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 f 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. 1 A.2.2 Feature Used r WECEVAL has many options and features which enhance its versatility. Among those used for this evaluation were: an.nomo io A-2
r
-1. The ability to perform simplified elastic plastic analysis per 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.
A.
- 2. Built-in ASME fatigue curves plus provisions for accepting user-defined
_,. fatigue curves.
- 3. Equivalent moment linearization technique, along with the ability to correct for the radius effects in cylindrical and spherical geometries, j
- 4. The ability to limit the interactions among load conditions during the fatigue anaiysis, A.2.3 -Program 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 Description ,
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 pipe if the program assumptions are considered to apply for the particular pipe being evaluated. For striping the fluid temperature is a sinusoidal variation with numerous 4 cycles. , 1 The frequency, convection film coefficient, and pipe material properties are input. l l isn, nome to A-3 l l l
i i The program computes maximum alternating stress based on the maximum-difference'between inside surface skin temperature and the average through ' wall temperature. A.3.2 Feature Used The pro; ram 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, by 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. s 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 line are STlf 20 (straight pipe), STIF 60 (elbow and bends) and STIF14 , (spring-damper for supports). L A.4.3 Program Verification As described in section 2.1, the application of ANSYS for stratification has been independently verified by comparison to WESTDYN (Westinghouse piping]
'""" A-4
.:)
.,k
analysis code) and WECAN (finite element. code, section 8.1).- The results from ANSYS are'also verified ageinst closed form solutions for simple beam configurations. i I
~l 9
4 i i r 4 =- .to. un.name no g_g
g, . p APPENDIX B LIST OF REFERENCES 4 r, 1. -PG&E letter No. DCL-89-021, January 30,1989, " Response to NRC Bulletin 88-11, Pressurizer Surge Line Thermal Stratification," Docket Nos. 1, ' 50-275, OL-DPR-80 and 50-323, OL-DPR-82.
- 2. WPGE-SSAD-7689, "Diablo Canyon Unit 1 Analysis of Pressurizer Surge Line Stratification," July 1988, Westinghouse Proprietary Class 2. -
- 3. WCAP-12067, Revision 1, January 1989, " Evaluation of Thermal Stratification for the South Texas Units 1 and 2 Pressurizer Surge Line,"
Westinghouse Proprietary Class 2. !
-i
. l 4.- PG&E letter, August 18, 1989, from P: Hirschberg to M. Miller, !
" Pressurizer Surge Line Stratification."
- 5. ASME Boiler and Pressure Vessel Code, Section 111, 1986 Edition. ;
1 I4
- 6. WCAP-9376, WECEVAL, A Computer Code to Perform ASME BPVC Evaluations i
Using Finite Element Model Generated Stress States, April, 1985. ! (Proprietary)
- 7. W Systems Standard 1.3.F, Rev. O. (Proprietary) i
- 8. W Systems Standard 1.3.X, Rev. 0 (Proprietary)
.. l l
- )
r 3973s/1024a010 g.} _.}}