ML20038B617
| ML20038B617 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 11/30/1981 |
| From: | Manan Patel WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML19268A489 | List: |
| References | |
| SG-81-06-067, SG-81-6-67, WCAP-9989, NUDOCS 8112080437 | |
| Download: ML20038B617 (97) | |
Text
{{#Wiki_filter:__ _- - _ _ _ _ _ . _ I, ' ~ . yy a .) > > > 3. Li - th ~ > > >- 3 > 3 , I
- k. . '
Y , 1 1
^
W10k&"X_ 2' _ j_ g _-/'is ' ,% .f, s ' , ~ . . , < ' , ) , ~ ,. -J . s ' .., - . : .]
e s STEAM GENERATOR TUBE Pl.UGGING MARGIN ANALYSIS FOR THE VIRGIL C. SUtHER NUCLEAR POWER PLANT UNIT N0. 1 M. R. PATEL, Ph.D. NOVEMBER 1981 APPROVED: (J/ L. Houtman, Manager Tpplied Structural-Mechanics Work Perfomed Under Charge No. UCG-6407, YNGP-120 This document contains infomation proprietary to Westinghouse ~1ectric Corporation; it is submitted in conf
- fence and is to be used sol ly for This-the purpose for which it is furnished and returned unon request.
document and such infomation is not to be reproduced, transmitted, disclosed or used otherwise in whole or. in part without authorization of Westinghouse Ilectric Corporation, Nuclear Energy Systems. WESTINGHOUSE ELECTRIC CORPORATION Nuclear Energy Systems P.0, Box 355 Pittsburgh, Pennsylvania 15230 SG-81-06-067
ABSTRACT _ This report describes the analyses and testing used for determining the plugging margin for the Virgil C. Sumer Nuclear Power Plant Based on the results, a (CGE) steam generator (Model D3) tubing., minimum tube wall thickness requirement jofthe nominal (0.043 inch) wall is established in accordance with the
, o , b , c.
guidelines of USNRC Regulatory Guide 1.121. Assuming ~ ~ for continued corrosion and eddy-current measurement uncertainties, a piogging margin of 55% of the nominai wall is recomended. The loss in the primary flow area resulting from the localized tube- ., c ,o to-tube support plate defonnation due to the maximum postulated
~
~ ~
}
a, 6, o loadingwascalculated[ L. 1 i l tii-
d NOMENCLATURE e = tube ovality, (OD,-0Dmin)/0Dnom f = natural frequency Hz g = gravitational constant ID = inside diameter, inch k = shape factor L = crack length (axial.); inch , 0D = outside diameter, inch , P = burstpressure,pskorksi F = normalitcd burst pressure, PRg(Sy+S u )t P = collapse pressure, psi or ksi Fe = n rmalized collapse pressure, PcR ,/Sy t P = primary bending stress (intensity), psi or ksi 3 P = primary side or tube inside pressure, psi 9 P, = primary membrane stress (intensity), psi or ksi P = secondary side or tube outside pressure, psi g Q = leak rate, gpm or secondary stress (intensity), psi R = mean radius of tube U-bend, inch R = inside radius of tube, Tn/2 inch R,
= mean radius of tube, (ID+00)/2 inch R = outside radius of tube, OD/2 inch g
g = Room Ter@erature (N75*F) S,
= code allowable ~ stress intensity for design, psi or ksi S = material ultimate strength, psi or ksi u
-V-
)
NOMENCLATURE (CONTlNUED ) S y
= material yield strength, psi or_ksi T = temperature, *F. Subscripts h, c, and s refer to hot leg, cold leg and steam, respectively.
t = tube wall thickness, inch t min
= minimum required thickness
=
aP 9 , primary-to-secondary pressure differential, psi aP, = secondary-to-primary pressure differential, psi A = nomalized crack length, L/ t Abbreviations: AVB = Antivibration bars ECT = Eddy-Current test FDB = Flow distribution baffle FIV = Flow. induced vibrations J FLB = (main) feedline break (accident) FS = Factor of Safety LOCA = Loss-of-coolant Accident LTL = (Statistical) Lower Tolerance Limit l NSSS = Nuclear steam supply system PCT = Peak claa temperature PWR = Pressurized Water Reactor SI = Stress Intensity SLB = (main) steam line break (accident) SSE = Safe shutdown earthquake T/H = Themal-Hydraulic TSP = Tube support plate l
- vi-
,, _ - = ,
TABLE OF CONTENTS Title Page Section 1' 1 INTRODUCTION Regulatory ' Requirement for Tube Plugging 1' l.1 Program Scope and Summary 2 ! 1.2 7 2 INTEGRITY REQUIREMENTS AND CRITERIA 2.1 Functional and Safety Requirements ~ ~7
. Tube Bundle Integrity Requirements 9 2.2 ~
2.3 Locally Degraded Tube Inte'grity Requirements 10 11 2.4 Tube Stress Classification 2.5 Criteria and Stress Limits 13 3 LOADS AND ASSOCIATED ANALYSES
'19 3.1. Normal Operating Loads 19 3.2 Accident Condition Loads 20 20 3.2.1 SSE Loads 3.2.2 LOCA Loads 23 30 3.2.3 FLB/SLB Loads i
57 4 RESULTS OF ANALYSES AND EVALUATION 4.1 Functional Integrity Evaluation 58 4.1.1 Level D Servi.;e Condition Stresses SE 4.1.2 Primary Flow Area teduction 59 4.2 Minimum Wall Requirements for Degraded Tubes 61 4.2.1 Normal Plant Conditions 62 4.2.2 FLB/SLB+SSE '62 4.2.3 LOCA+SSE 63 .- e
- vii-
TABLE OF CONTENTS -(CONTINUED) i Section Ti tle Page
~5 BURST STRENGTH REQUIREMENTS 71 5.1 Leak-Befdre-Break Verification 72 5.2 Margin to Burst Under Normal AP 74 5.2.1 Tube with a Thru-Wall Penetration 75-5.2.2 Thinned Tube 76 6 PLUGGING MARGIN RECOMMENDATION '
83 7 REFERENCES 85 Appendix A DERIVATION OF LOWER BOUND. TOLERANCE LIMITS FOR 87 STRENGTH PROPERTIES OF 0.75"00'X 0.043" WALL MILL-ANNEALED I-600 TUBING
\
\
s
- vii i-
LIST OF ILLUSTRATIONS Page Fi gure Tit?e 4 1-1 Typical Sectional View of a 03 Steam Generator 5 1-2 Schematic of a Model D3 SG Tube Bundle Internals CGE Response Spectra for OBE Analysis [5] (X-direction 42 3-1 is along hot leg, Z by RH i<ule) 43 3-2 Synthesired SSE Acceleration Time History for the X-direction 44
~
3-3 Specified Floor Response Spectrun and the Accel.eration Time History Response Spectrum for X-Direction Mathematical Model for the Seistric Analyses 45 3-4 46 3-5 Schematic of Tube Sundle Internals-to-Shell Connections in the Seismic Analysis Model ' 47 3-6 Typical Pfimary Fluid Press,ure Time- Histories Following a LOCA - Modet 11-thru 15 h -
]~ (See Figure o. . b : c.
3-7 for Node Locations) LOCA Rarefaction Wave Analysis Model 48 3-7
- Horizontal Displacements of Node 12 Due to LOCA . 49-3-8 A, b,c RarefactionWaveLoading-{_
( - a 50 3-9 In-plane Bending Moments.at__ Node 15 Due to LOCA
-~ ~
0, h r+ Rarefaction Wave Loading -; ( 51 3-10 In-plane Rotation of Node 12 Due_to LOCA Rarefaction ' 0, E, c._ WaveLoading-[ [ , 52 0'#, 3-11
-Horizontal Displacement o(f Node 12 Due to LOCA Ra - 4 ction Wave Loading= _
Tube End Reactions at the Top TSP Due to LOCA Rare- S3 3-12 a, b,0 factionWaveicading-[ ] 54 3-13 Resultant of LOCA Rarefaction Wave Induced Tube End ReactionsattheTopTSP-{ ] 3 , ,,, , ; 55 Resultant of LOCA Rarefaction Wave Induced Tube Enda 3-14 2,",' ReactionsattheTopTSP-{ ( )
-ix-
LIST OF ILLUSTRATIONS (CONTINUED) Figure Title Pace 3-15 Tube Stresses From LOCA Shaking [9] (These stresses 56 are approximately at Nodes 13 and 15 in Figure 3-7) 4-1 Schematic of a Tube-Tube Support Plate Crush' Test 66 4-2 Tube Distortion Data Obtained from the Tube-TSP 67 Crush Test 4-3' Results of Pressure Collapse Tests on Distorted Tube- 68 TSP. Collar Assemblies 4-4 Correlation Between Tube Ovality an'd Collapse Pressure 69 5-T ,- Results from a Typical Leak Rate Test (Test 78
#SGTLR-40, L=0.524 i'nch) 5-2 Correlation Between Crack Length vs Leak Rate During '
~ 79 ,
, Normal Operation (0.75" 00 x 0.043" t Tubing,'jg a r o,C 5-3
~ J Relationship Between Normalized Burst Pressure and 80 Axial Crack Length of SG Tubing 5-4 Minimum. Expected Burst Strength of 0.75"0D x 0.043" 81 Wall I-600 MA Tubing 5-5 Variation in. Margin to Burst as a Function ~ ' " '
82 of Mean Radius-to-Thickness Ratio.'of the Tube 2 6 y ep# 9
- wm .
6 @ 7
-M
LIST OF TABLES Page Table Title 16 2-1 Tube Stress Classification CGE Tube Strength Properties for R.G.1.121 Analyses 17 2-2 (0.75" 00 x 0.043" Wall Mill-Annealed I-600) Primary Loop Piping Stiffness Matrix (1bs/in, 32 3-1 in-lb/ rad) Steam Generator Lower Column Support Stiffness 33 3-2 Matrix (1bs/in, in-lb/ rad)
. Steam Generator Upper Lateral Support Stiffnesses 34 3-3 Steam Generator Lower Lateral Support Stiffnesses 35 3-4 3-5 In-Plane Tube Support Plate.- Local Shell Stiffnesses 36 3-6 Maximum Axial Tube Stresses Due to SSE Loading 37
~ Maximum In-Plane Tube Support Plate SSE Loads 38 3-7 feak Tube Responses Due to the LOCA Rarefaction Wave 39
' 3-8 Loading 3-9 Maximum Axial Stresses In the Tube U-bend Due to the 40
. LOCA Rarefaction Wave Loading 3-10 Maximum Tube Support Plate Loads Due to LOCA Rare- 41 faction Wave Loading of Individual Tubes 4-1 Sumary of Maximum Stress Intensity Calculations for 65 a, b, c the CGE ]
5-1 Summary of Burst Pressure and Leak Rate Test Matrices 77 for CGE Tubing A-1 Lower Tolerance Limits for Model D Mill-Annealed Tubing 89 Strength Properties A-2 CGE Tube Strength Prc.perties for A.G.1.121 Analyses X (0.75" OD x 0.043" Wall Mill-Annealed I-600)
-xi -
__ _ _ =
SECTION 1 INTRODCTION 1.1 Regulatory Requirement for Tube plugging The heat transfer area of steam generators in a PWR nuclear steam supply system 'NSSS) can comprise well over 50% of the total primary system pressure boundary. The steam generator tubing therefore represents an integral part of a major barrier against the release of activity to the environment. Accordingly, conservative design criteria have been established to assure structural integrity of the tubing under the postulated design-basis accident condition loadings [1]*. However, over a period of time under the influence of the operating loads and environment in the steam generator, some tubes may become defective due to localized wall degradation or cracking. In order to safeguard against the failure of degraded tubes, inservice inspection using eddy-current (EC) techniques is performed in accordance with the guidelines of USNRC Regulatory Guide 1.83 [2]. Partially deoradcG tuoes witt a wall thickness greater than the minimum acceptable tube wall thickness are acceptable for continued service, provided the minimum required tube wall thickness, is adjusted to account for the EC orobe erro and an operational allowance for continued degradation until the next scis.duled inspection. The USNRC Regulatory Guide 1.121 [3] describes an acceptable method for establishing thn limiting safe conditions of tube degradation beyond which defective tubes as established by the EC inspection must be repaired or removed from service. The amount of degradation as recorded by the EC testing is customarily expressed as a percentage of the design nominal tube wall thickness, and the acceptable degradation is referred to as the (tube) plugging margin.
- Numbers in brackets designate references at the end.
1.2 Program Scope and Sumary This report describes the results of analyses and testing performed on the Virgil C. Sumer Nuclear Pcwer Plant (CGE) steam generator tubing . for establishing the tube plugging margin. The GE unit has a 3-loop NSSS which includes Model D3 steam generators. A section3l view of a Model C3 steam generator'is shown in Figure 1-1. Figure 1-2 shows a schematic drawing of the tube: bundle which consists of 4674 U-tubes made of mill-annealed Inconel-600 (5B-163) alloy. Lataral support for the tube is provided by the seven (7) tube support plates (TSP) in the straight region. In the U-bend region, the out-of-plane moticn of tube bends is limited by coupling the U-bends with two (2) sets of aki-vibratiom bars. The nominal tube dimensions are: 0.75" OD x 0.043"t. The minimum tube wall requirements were calculated in accordance with the criteria of USNRC Regulatory Guide 1.121, entitled " Bases for Plugging Degraded PWR Steam Generator Tubes". The basic requirements consist of:
- 1) Verifying that, in the case of tuce thinning, the remaining tube wall can meet applicable stress limits during normal and postulated 1 accident condition loadings, and
- 2) In the case of tube cracking, with or without any thinning, the .
maximum allowable leakage during nonnal operation is limited to assure leak-before-break. Additional requirements consist of verifying the margin to burst under normal operation and margin against c,ollapse during a LOCA. ; Thus, the program requirements consisted of: l l
- 1) Analyses to establish applicable loads and integrity evaluations for tubes subjected to these loads, and
.o- }
- 2) Leak rate and burst pressure tests to establish the maximum alluwable leakage during operation consistent with the leak-before-break requirement.
In connection with the tube bundle integrity evaluation, i' should be noted that coth the safety and functional requirements must be 3 l
'e satisfied. The safety requirement which, in f3ct, is the basis of the Regulatory Guide 1.121 criteria, governs the limiting safe condition of (localized) tube degradation beyond which defective tubes, as established by in-service inspection, should be repaired or removed from service. The functional requirstment, on the other hand, applies to the ovenil degradation of the tube bundle in tems of its heat removing capability and the impact on the peak clad temperature due to the primary coolant flow restriction through the tube bundle following a LOCA (to be evaluated in conjunction with SSE). AlthougL.
both the safety and functional requirements were sat!sfied, the subject metter of this report deals mainly with the safety requirements associated with the plugging margin criteria in Regulatory Guide 1.121. Specific criteria and the corresponding allowable limits and/or margins associated with the safety and functional requirements are discussed in the next section. In the two sections after that, details of tube loadings during the various plant conditions are discussed and related analyses, results and evaluations are given. Section 5 contains the discussion of ourst strength requirements and leak-before-Lnta< verification. Jinally, the recernmended wbe plugging margin is provided in Section 6. 3
s i e _ eIe e , y] _ ,, f a; UP?Il 3EAD
/ i\ .r
"" l CTLINDER i
? N ZSS MOISTUne 'i -
4 / ! l-
\ I' -
3 SEPARATOR, MI b- M l N J- i* ~% 7-7- r ti
- l"jY ;
g
; I r
- l. It i
-(I 'i I g l "ki, q k'.,/h ,, 1 DRAIN PIPES' Urrn. Suzu. ,
- l "- - ex ,
- 4. i- i t
N xIn-cECx ruTz DOW N M l
. b INTERMEDIATE DRAEf ?I?E ASSIM3Y.T ,
I
- g j 7
{ DECK PLATI
= 1 .i.
l
=
SWELL 7ANE ASSESLT g.. g T3ANSITION CONE $ , t, .. ; .
\-Wir 3 1
. l -
l TU3ES I \ TN i
~
- 11 ANII-VI3RACCN 3ARS I .,
t ' i-.C.'.: - . , 1 i gg et d, , . .' '. . ll-% i , STAT 3CDS ,
- i 1 SPACERS
} .
.l , I, , , . .
a . i 3' i . . , 4 TU3E SUP?CET 7LATES -
- 9. .
3
-': rEEDwArza WRAPPER d*
-I h yozzLE .
STU3 BAR E.
,f g
t 4 1 mus e= T. I l l- TU3ESHEIT p oIvTDEa run I .
, CsAuNn. sEAD .- .
i l Figure 1-1. Typical Sectional View of a 03 Steam Generator w ,
1 I r A l 1214 Q wR APPEN S*)PPORT A N D4 3 I A4 WALLI ULOCKS l 7$Og' D 7 SpAtgs lut NG RPE5
= = 6.00 3 Tuat SUPPOM 2.2 S a _,
STAYROO5 6 etitt$ sN#4tRMC5i _ a f,6 sfuet
\'
,'- r; 1,
~%
a m-_ _, s '- - 1; _ .- Eb - _ _.[ -
~__
. \,, .
6
,75 - - 4 3,2$ _~
.- - - 2 3.2% tSt PtC $
T Y P. y_- _ _____ _ . - r
-- -tLog il 2 4.50 3 ,
~
~
_ 26* DI A. L____ l ,
}s
- -. 7
_p ( - - - y u - _3 " _m p g un c e l " 2 wri-viaa nioh eaa5
. * (50u,Rt C8055 SECicN)
- -la2S 27 22S 7 , - -2t2h '*' 0 0 __ _ - - . _ _ = _ w. -m
_; ___ m 4 3'h C} 240 - - .
- 53.45 a.
OuitRuo11 f ' 100E
- ..2 - __
-- r n x .,m- s-== -m-
.% m 4 /- ,m
,; .v 2 :) 2 2
a
- ._ m I
m._ i___ m we
=
mica = me
=swan= .eaea s w .an.n w .swa. wm.as emm. 6=.4.su.w.m .
.o m -m .
i i i I I l a* aseiwe enam me tasa4 m w mm .
\lE I 5 Tg me
.,L,_I_ y I
%38 NOTE 8 PHFHE AIER RfCtOH si T VRC At. ,"4.ame.
m w e .,m*'.g awei d,g"*gj,"@ sw se 7 --s FOR HODEL*O' SIE Au CEtilRATOR. E"JJ,Y d l * * * * * " " vfRsf KArtON SHOuto BE M40( AS pga Spgcuit otTAtt, fuSL PL Alf 4 8AfftfPL AT ES
@WH AAPPER 55t H SLY 6 AHRIL F . ', a e 1 - 2 . Schematic of a Model D3 SG Tube Bundle Internals
SECTION 2 INTEGRITY REQUIREMENTS AND CRITERIA The steam generator tubing represents an integral part of a barrier against the release of radioactivity into the atmosphere. In the eunt of a primary loss-of-coolant accident (LOCA), the tubing also provides the necessary heat sink, intially for the core cooldown and later on, for __ " matntaining the plant in the safe shutdown condition. Thus, it is important to establish the structural integrity of the steam generatoF tubing.. This is accomplithed based on analyses 3 testing and
~
in-service inspection. The tube bundle can therefore sustain the loads during nonnal operation and the various postulated accident conditions without a loss of function or safety. 2.1 Functional and Safety Requirements ,_ Tube wall- degradation is caused by a number of different factors such as environment-induced corrosion (includes intergranular attack and stress-corrosion cracking), erosion due to the fluid friction, and fretting wear fram the mechanical and flow-induced vibrations., y _ c However, a potential for additional wai: degradation may exist locally in some tubes, at tnt, top of the tubesheet* and in the region of tube-TSP (tube support plates) intersections. This is due to the combination of the fretting wear and corrosion-induceJ defects and the higher potential of chemical and heat flux concentrations in these regions.
- Tubes in these units are full-depth expanded within the tubesheet.
7
Based on steam generator operational history, the whole tube bundle is subjected to only a small, but probably a more or less unifonn, tube wall loss over the design. total operating period of the unit. On the other hand, a. few tubes within the bundle may degrade locally to the extent that either the removal of these tubes from service or local repair to restore integrity is sufficient for continued safe operation of the unit. Because of these two rather distinct modes of tube degradation, it is possible to separate the functional and safety requirements into.those affecting the integrity of (1) the overall tube bundle, and (2) a locally thinned or ~ degraded tube. In the subsequent discussions, tubes associated with the above two modes of degradation are referrred to as the " median" and the
" thinned or locally degraded" tube. The median tubing correspond's to the minimum expected strength properties of the overall tube bundle. That is, a median tube represents a tube with the #' b' end-of-design life minimum wall (
~ -
r - j ._ .
2.2 Tube '.1dle Integrity Requirements TMe requirements are based on the assum; tion that removal of a small
.sumber of tubes free service does not impair the structural and functional capability of the overall tube bundle *, Specifically, the following two criteria are to be satisfied assuming the median tube properties, that is, end-of-design period thinning concurrent with the
~
- drawing minimum tube wall.
- 1) For Level D Service Conditions, the primary stresses do not exceed the stress limits specified in Appendix F of Section.
III of the ASME B&PV Code (hereinafter referred to as the Code).
- 2) The loss of tube bundle flow area due to, the corbination of the cross-sectional distortion and/or collapse of a
~ e,c limited number of tubes due to the postul'ated ,
[ loads does not increase the primary flow resistance of the system 4,C J L i
- In the event of extensive tube plug 3i ng, plant derating and/or reanalyses associated with functional requirement verificatio t _ ac *
,may be necessary. [" ___
M h t
. g ..
2.3 Locally Degraded Tube Integrity Requirements As previously indicated, potential for tube wall degradation other than due to nominal erosion-corrosion could exist at certain typical locations in the tube bundle. Even though such localized degradation is known to be confined over a small portion of the tubing (and hence of no adverse consequence to the functional capability of 'the bundle), it is objectf onable froni, the viewpoint of a potential tube rupture if the associated depth of penetration is relatively large. Therefore , . to assure that there are no safety consequences as a result of random tube failures, a conservative bound on acceptable degradation for continued operation must be established along with the in-service inspection and leakage monitoring requirements for-the detection of - defected tubes. Guidelines in Regulatory Guide 1.83 [2] for EC inspection and Regulatory Guide 1.121 [3] .forddbiipl.ughing margin ~ calculations provide the bases for detemin'ing the' limiting safe condition of a locally degraded tube. - - - The remainder of the report describes the analyses and testing perfomed . to establish the tube plugging margin in accordance with the intent of
~
Regulatory Guide 1.121 [3]. For tube degrad'ati"6Mn excess of the established plugging margin, it is required that the tube be repaired or removed (by plugging or otherwise) from service in order to assure continued safe operatior. The intent of Regulatory Guide 1.121, as applicable to this analysis, is sumarized below: In the case of tube thinning due to the mechanical and chemical wastage, and genera"ized intergranular attack, the remaining tube wall must be shown to be capable of meeting the applicable strength requirements with adequate allowance for the EC measurement errors and continued erosion-corrosion until the next scheduled outage. The strength requirements are specified in J
terms of allowable primary stress limits and margins to failure by burst during normal operation and by collapse following a LOCA. ,
- For tube cracking due to fatigue and/or stress corrosion, a specification on, maximum allowable leak rate during normal operation must be established such that the associated crack will not lead to a tube rupture during a postulated worst case accident condition pressure loading. If the leak rate exceeds the specification, the plant must be shutdown and corrective actions taken to- restore integrity of the unit.
2.4 Tube Stress Classification The most limiting loads for establishing the tube integrity are imposed ~'
'-~ '
dur;ing the Level 0 service conditions;7- -
- u. b e . .
, t k
There are two general considerations which must be accounted for in ' determining the classification of stresses; namely, the location in i the structure and the nature of the loading.
' a b,c s
(
;;The
~
tube stress classification for various locations in the tube bundle under the different types of loadings is summarized in Table 2-1. The notation P, mfen to general primary medrane stmss, Pb refers to primary bending stress, aad Q refers to~ secondary stress.
-1 1 '-
, At the top TSP, a distinction is made between bending stresses in. median tubes and locally-thinned tubes. In the U-bend region the anti-vibration bars (AVB's) couple the- tubes for motion out of the plane of the U-bend so that out-of-plane bending is ~ resisted a,t by the entire bundle. [
~~ a,e A distinction is made.between self-exicted flow induced vibration (FIV) stresses and flow induced vibration from other causes. A self-excited vibration mechanism could be established if flow 4 velocities exceed critical values for fluidelastic vibration. 1 When the vibration amplitude increases, however, the amount of damping in the vibrating tube also increases. The vibration l
} amplitude of cyclic bending stresses are limited by the amount of __ , 4 i dampinginthesystem.((
~
1
\
! l l
-. ~* i l
)
2.5 Criteria and Stress Limits
- a,C e
- ISummary of these calculations is given in Table 2-2. Detailed calculations are included in Appendix A.
e
- 4,C m
M e e e Normal Plant Conditions: The primary-to-secondary pressure differential cP$ should not produce a primary membrane stress in excess of the yield stress of the tube material at operating temperature, that is,
,- A , b, f-
$m1 3 y ~
Postulated Accident Conditions: Loadings associated with a primary (LOCA) or a secondary side (SLB/FLB) blowdown, concurrent with the SSE should be accomodated with the margin determined by the stress limits specified for Level D Service Conditions in Appendix F of the Code. That is, during LOCA+SSE, FLB+SSE, and SLB+SSE: For Locally-Thinned Tubing
- at , b u t-P m i smaller of; (2.4 ' S,, 0. 7 Su ) " l ,, ;
a, b, C P, + Pb1 , FortheMedianTubingI j L 3 a, b, c p _ 4. h c i P m
+P b*
- ~
The shape factor k is a function of the cross-section of the a, b, r component being evaluated:y I
r As far as the consideration of the secondary and peak stresses in the evaluation of the locally thinned tube is concerned, it is noted that the effects of these stresses will be manifested into racheting, fatigue and/or corrosion-fatigue types of_ mechanisms associated _ g# with tube cracking if that should occur, s. f. um.
*6 9
- 0
- O 1
TABLE 2-1 TUBE STRESS CLASSIFICATION
, a, 6, c, h
t I W O ww-e M . e o O OO
p-4 TABLE 2-2
- CGE TUBE STRENGTH PROPERTIES FOR RG 1.121 ANALYSES (0.75" OD. x 0.043" WALL MILL-ANNEALED I-600)
- - a,b,c Temperature, *F Yield Strength, Sy ksi ,
Code Value Lower Tolerance Limit (LTL) Ultim te Strength, Su ksi '
- Dode Vafue
' Lower Tolerance Limit ,,
Allowable Stress Intensity, S ,ksi Code Value Lower Tolerance Limit i
- , et i b.c NOTES: 1.
2.
- 3. _
m
SECTION 3 LOADS AND ASSOCIATED ANALYSES In establishing the safe limiting condition of a degraded tube in terns of its remaining wall thickness, effects of loadings during both the normal - o., C . operation and the postulated accident conditions must be evaluated. r, _s 3.1 Normal Operating Loads The limiting stresses during normal and upset operating conditions are the primary membrane stresses due to the primary-to-secondary pressure differential AP across the tube vall. During normal operati n at 9 100% full power, the pressure and therr. conditions are as follows [5]. Primary Side:
- aib,C.
)
4 1 Secondary Side: i
~
~
e, b, c
~
~
... .- o 0,',c. ,
I 3.2 Accident Condition Loads } For the faulted plant condition evaluation, the postulated. Level D , 1 Service Condition events are: Safe Shutdown Earthquake (SSE), Loss-of-Coolant Accident (LOCA), main Steam Line Break (SLB) and main Feed Line Break (FLB) accidents. The tube integrity evaluation is cerfonned for tha SSE loads in conjunction with the bIowdown loads, that is, LOCA+SSE, FLB+SSE, and SLB+SSE loads. Mathematical models, , analyses and resulting tube bundle loadings are discussed separately for each of these events. I j 3.2.1 SSE i.aads , l 1 4 Seismic (SSE) loads are developed as a result of the motion of- i the ground during an earthquake. Plant specific response spectra for CGE were used to obtain the loads and stresses in _ g , . the tube bundle internals. l m
-20~-
Inout Excitations The seismic excitation for the linear analysis was in the form of response spectra at the steam generator supports. The three orthogonal components of the earthquake were applied simultaneousiv to perfom the analysis. Figure 3-1 shows the three components for the OBE case. The SSE analyses for this study used 150% of the OBE ace.elerations. The X-direction is along the hot leg, positive toward the reactor vessel; Y is vertical, positive upward and Z is by right hand rule, in the
, general direction of the crossover leg.
~# , C b
The synthesized SSE acceleration time history for the X-direction is shown in Figure 3-2. Fipure 3-3 shows the corresponding acceleration time history spectrum superimposed on the specified floor response spectrum in the X-direction. Modeling Details The analyres were performed using the WECAN Computer Code. The mathematical model consisted of three-dimensioncl lun. ped mass, beam, and pipe eierents as well as general matrix inp.F (STIF27) to represent the CGE specific steam generator uppar lateral and lower suppor,t stiffnesses and the reactor coolaat 9 ## ' loop piping . tiffriess. 1 L - I
- , 4.c , ,. For the rest of the structure, mass and ' structural , g damping coefficients were input to realize [
damping at the lowest and highest significant frequencies of the structure. Figure 3-4 shows the mathematical model with selected node numbers. The primary loop piping and the lower column support stiffnesses were input as 6x6 STIF27 matrices as given in Tables 3-1 and 3-2, respectively. The upper and lower lateral support restraints were represented by compression-only (single-acting) gap-spring elements in the nonlinear analysis. The upper and lower lateral support configurations and the - associated stiffnesses are given in Tables 3-3 and 3-4,
, g respectively. 4
' - ~ ~
- ~
The modeling of the tube bundle internals-to-shell connections is shown schematically in Figure 3-5. The TSP-local shell stiffness combinations were obtained from detailed finite element analyses and are summarized in Table 3-5. The local shell stiffness at the top TSP location is higher than at lower TSP locations because of its proximity to the upper lateral e - o,hc supports. L
= a a I
L j l l l l l 1 r
Analysis Output The analysis output pertinent to the subject evaluation consists of the tube bundle stresses and the maximum in-plane TSP loads.
.i s
a As expected, the nonlinear analysis yields higher stresses and loads because of the anclification effect due to the gap M between the tube bundle intemals and the shell. ["
-o a
3.2.2 LOCA Loads LOCA loads are developed as a result of transient flow and pressure
" ~'
fluctuations following a postulated main coolant pipe break. <. h ax .
4
" -- a,G
~
- LOCA Rarefaction Wave Analyses The principal tube loading during a LOCA is caused by the rare-4~ -
faction wave in the primary fluid. ,* #'t
, e .
~
=
f $ t c
~
l I 4 i . e s 'I 4 The pressure-time histories to be input in the structural analyses were obtained from transient thennal-hydraulics (T/H) analyses ,a,b c using the MULTIFLEX Code, _( d b
- t. .
i
~
i , 1 For the rarefaction wcVe induced loadings, the predomii. ant Mtion oftheU-bendsisintheplaneo.theU-bend.{ , a,e t t
) The WECAN Prooram was used for these dynamic analyses. Figure 3-7 shows the node and element numbering for a typical single tube model.
ne
. -- .- - . _ - , ~ _ . .- ,-. -
The tube model consisted of three-dimensional straight pipe and elbow elements. [ i r L - a,e l m= e. . ,, m . . , -.,o e *' * *
, ,, , . ,w.m, e- --* - w -+e*-' N**m=-- * " * * * - --- - e-- --- ,+, g .= ,,
^ ~
...._ - --. _ . - - _=.: - --
- :--.-.. .m..
-- - - . .--._ . - -_ _ _ _. _..._ __ __ _ _ _ .__ _ _.. , __-. , T'._.__'.'___
~
._ . _ _ __ _ _ _ _ __T~_.~._.__.--- ____ --.- _ - - --_-.. .-_ _ ___.-_. _____ j
__ - _.._ . . . . - . _ _ . - .- . . ~ -. _. ..... muim.+. sam asa.m.eum--e- w_ -+ * *
--e...e_, m-O -6 ha- W"" -* -6
'~
- . _. _ . . -. _ ....-.. -- - - - - - ~:--..
-We e.-- ,w ..
. m-mm me w -ee -me ee . # 6 * *- * * * '" ' - "" " '
.**--e
- Mw m . e% ea%m.eies m+m _geh. me -__m"** **
- h** **- **"' " '
**'* hen * .g-m-wi--m-w m_w * * - * " '**
,,-e- N . . emme=_ gh4 * *
---- --. J
- 26-i
0,c.
'~~~~~~~~~~~: . . - _ . _ - . . . .. .
= = - - -. . . ._. - . . - - - - - - -
. '.T__.~.. .. . . - . . _ _ _ _ . . . . _. . ... ._... ._._ _.. -
.~~ . . . .
~ ' ~ ~ ~ ^ ^ --
- In addition to the pressure bending loads, the rarefaction wave analysis includes the pressure membrane stra.sses due to the primary-tc-secondary AP9 and the' effect of fluid friction and centrifugal forces.
- t Rarefaction Wave Induced Tube Loads The peak tube responses subject to the LOCA rarefaction wave induced loading are sumarized in Table 3-8 for the various cases analyzed.
Time-history plots of some of the more important response variables are shown in Figures 3-9 thru 3-12. Comparison of these results lead to the following two major inferences. a e (
- N .---N.Neg. w.
6* e.m. , - . e. . w-
" -i-44. e-Am b ee dii.a
--=.Omi w m m.
" .g ...a w.gm... g. ,
9""*"NW
- ,gg _
.N m h *'
-p .
.M ==- .-. .--
O @
~
. 27.
The maximum axial stresses in the U-bends are sumarized in Table 3-9. As pointed out earlier, the significant stresses result from the pressure differential across the U-bend as i.he rarefaction wave passes through it. . . _ .. Rarefaction Wave . Induced TSP Loads The tube motion due to the LOCA rarefaction wave induced loading is restrained at the TSP locations, thus resulting ir .ction - 1
~~~~ ~ ~ __ c ,q forces in the pl ates. {-
~~~~~~
~ ~ ~~ " ~, ~__ -~ ~~j__
.. ~. ._.
._.----.~.__.- - . , . . - .
_ :XXL_. " ~ ~ l _^^ ~ -T_ . _
~~ ~ ~~
r.- ~ ;- ~ ~ ~ ~ ~~ ~ '~^ ~ ~ ~ ~ i
~
.,e,-ru.- i.r.**N-*-
_. . -- . _._. ~ - - - _"-- _ . .__. .. s_
.] A susenary of the peak reactions for the cases analyzed is included in Table 3-10.
-n o
__ _ . _ . _ - __. .. . . - - -_. - b
-.m + r p m- . w s .. .
..Om h e.w. u._MN
~
-.-,__._.____l~ --- .
mw s .a...
* * . . .*r- g a w. 4w, . ,m am ah . . -
- e. .
.- - - 1 i
w a, c.
~~~
~ -- -
^- --~
.-_. . _ :~~~ ~ ~- . _ . - .- - - . .. __.
--z- __. :: =:T- TT- . _ _ - . -
~~~~~~~' ~~ '~
- -- - - - ~ 7 _ _ ___ . . . _ _ . _ . .
__ _ ._ _ _ . _ _ _ _ _ a For a given tube group, the resultant TSP force was calculated by multiplying the single tube force (from both tube ends) with the number of tub'es in that group. The total TSP load at a given time was then obtained by combining the resultant forces C
~
~~~
~~
'~~~- d "'C-
~
n The maximum loads were calculated
* ~~ ~~-
(=^__ ~
~~ ~ ^~~
r r ~~_T : :' __ ----- -.-
' ~ ~~ ~ ~
_.l.~~'~_Z_~___.____ ~ ~ ~ ~ ' ~Z ._~ ' ' ' ~~~. '__T_Z_- ~_'.~
. _ _z : - ~ -- _ -- -- :: :_z-~2_
- ^ ~~~~~ ~~ .
--_: ::= :. :_~~.=:~^~ ~-~ - - ._ :-- - :__.
~~
LOCA Shaking Loads Concurrent with the rarefaction wave loading during a LOCA, the tube bundle is subjected to additional bending loads di2 to the shaking of the steam generator c-" sed by the break hydraulic; i_~ '
~~~~'~ ~~~ ~
and reactor coolant loop motion. ( N
- ~ =
-m= e
-=p , ..._. - - .
-ee_e..% _ __, ,. , _
,__ _ . .. -_e -
. e. -
na
The tube U-bend stresses due to LOCA shaking were detemined in a previous analysis [5]. Figure 3-15 shows the stress history at approximately the location of the maximum rarefaction wave induced stresses. It is to be noted that the stresses in.
-Figure 3-15 represent the resultant of both the in-plane and out-of-plane stress components, and that the peak magnitude does not occur at the same time as the rarefaction wave induced peak stresses (given in Table 3-8).
3.2.3 FLB/SLB Loads During the postulated FLB/SLB accidents., the predominant primary tube stresses result from the APg loading. The paak-differentia pressure for these events were first determined. These secondary side blowdown transients are based on an instantaneous, full double-ended rupture of the main feedline/ steamline, _ o. b.8
- 2 1 5
I
\
-y \
J In addition to the primary pressure stresses, axial bending ' stresses in the tubes are developed as a result of flow induced
, o,@
vibrations and tube-baffle interaction. {
O h. C.
- - --- - - ~ . _ _ _ _ __ - - - -- -- - ., M u
=
- w _
" ., e em-e - * ** '-
, .w.
m- __ ,, mo - eW'*** me-,,m.
-.-w_ ,em e.
, ,, _w**
wmmew*-
+ _
w***-
- so we.mmem* *===H* "" " '" **
,,-.m.-en--e. **
ammmme- *M* ao--e m .wa m -e -mm** s * *N-
- - w-mm, o
,,ymeemeW'"**" m-
-e-*-"M _ _
,mmem- ' * "- ""*
,, win- pw **
_,,_ . ew.we--** *
-W
, _,,, a...m-- *we"* *"
,w w ** **-
suamw~6- * " - ' " -'"" _w_
.__.--- -=~ ~ ~ ~^ ^
m= - e-+< 6-sa mmm.e- W p,,_--
~ ~ ~'
' - ' " " - ,,__ . _ . . - = -
~~~- - ~ ~~~ ~' ~ ~ '
- - - . --.----- , , .e ------pn-*
,_, - _m-- e-= ** - * '-" ~
ep,Me N"'"*'
~* '
, , , , ,.. wee---*"* _
, , _ mm-"- """
,,mA
.4we--a--"~ " " - - "~~'
u,,.-s- .aW" .ww- *- "
.em-m a..,w-- - - - -'*""
p e =.mer*"* *~ * ~ -
,,,,_-_,w
~ .
.e-,a- - = = -=*- * * * - '
,.w-=
I e 0
2 TABLE 3-1 PRIMARY LOOP PIPING STIFFNESS MATRIX (1bs/in,in-lb/ rad) _. ob UX
~ ~
UY
- ~ - - - -. -4 -.-_wm. .- .,. _
--Who e. m.- = _e .-e. e, --.m o m- e .m - - . p - ., , ,, , , g ..,, , ,
* ** ' * * - --- - eee-M es. %m-e.ma w,m. ,e,,, w,,, ,, ., .,
M m O
= m 9m em-es- - u. m l
1 l l r TABLE 3-2. l j t [ STEAM GENERATOR LOWER COLIMI SUPPCRT-STIFFNESS MTRIX , (1bs/in,in-lb/ rad) k e .
,m-a,b c
UX . UY . . . . - . . ._ l 5 UZ RX - RY __ _ f' RZ b I l 1
~
I
. v--
1 i TABLE 3-3 STEAM GENERATOR UPPER LATERAL SUPPORT STIFFMESSES l l l Series Combination of Local Shell Support Stiffness (lb/in) Stiffness and Sup
, (lb/in) port Stiffness
,qg
)
-~*
l e e
** gr m e l
. l 9
[ ( Steam Generator Shell
. = . -
K 4 [ --> y 3 --*Z m . - s J Springs act in Compression Only. K 3 s- w l Spring K3 includes the tension stiffness of the snubbers.
O TABLE 3-4 STEAM GENERATOR LOWER LATERAL SUPPORT STIFFNESSES i X K 3 X)
%VvY Z M W^
- Springs Act in compression Only, b
' I
. - --.- - - - - e ... . __
. = . - .
"" " p- eum m ..m , ,,
e n w
- m e e em- e-we. - .
m w
- 35-
TABLE 3-5 IN-PLANE TUBE SUPPORT PLATE - LOCAL SHELL STIFFNESSES TSP Location KTSP,lbs/in. Kshell,lbs/in, K lbs/in.
, a , bi d.
4**hm N e ' " aw%.. m.m *e w- enungu
-"h6mm M e m e e he '
m W - eg, g hs N 'S 9%
- --_. . ,, , d*
\ O
""
- M*w wmo -w- , , ,
* * * " h*-#eeme Nw %,
weh =em mN=hmW -
-h*e
- %e-- - - .-
.-. .. % .=m--
e 9 'W W e
- 36-
)
) 4lt . j l .
c . _ b 0 s .. t c e r s i i D s y l a _ n e A n h ag t m l n i u Pi w r d t f n e c oe r e B a p t ; S u s _ O t e n s _ e n n . o o p e ng p s m e an o G - t i l i
;P d c f
, i ll I
D A nen _ I D s s O e r L t s i!E S e S b 0 u t t T. l E s e r s l r o d i D i s f n y i D e S s b 6 l e -
- E a c l l
3 S n n S A e e E E e r b L R y n e u B T r a f t A S ' o l g e T t hn r e E s i h B i fd e t J t l l on n T - e a f e tB l o b 9 h p A 1 O - e . I T f n i X o al s A r - p a t p H e h ng u n ll l n o e i M i an h I X l n l i Pd d t e
- n n r M o a ot a l, N ne
\' .
j
- B e s n t e a c s l e s p p e
- s r I
n er t S
) )
1 2 ( ( n i o : t S a E c T o O L N e b T u _
^
d8 l
TABLE 3-7 MAXIMUM IN-PLANE TUBE SUPPORT PLATE SSE LOADS TSP Number Nonlinear Analysis ' Response Spectrum _ Analysis- ai bi G
*& e66-me. - m h.- m p.,
, . , 1
. I l
l NOTES: (1) In-plane loads are loads in the plane of the plate (horizontal plane). (2) Loads are in kips. l
- 38-
1Ifl c, h e O
~
G N I D A O 4 L E V A . W N . O 7 I - T 3 C A e F r E
~
. ug R
A i R F 8 A n
- C i 3 O L s E. n l E1 o
B i i A T t T a O c T o l E U e D d o S n E S o N t O P r S e E f R e r E B s U e T s e K h A t E n P e r a p n i . s r e b m u N i &' 1
TABLE 3-9 MAXIMUM AXIAL STilESSES IN THE TUBE U-BEND 00E TO THE LOCA RAREF4CTION WAVE LOADING
~ m D ob o t.
L _ ~.
? _
" .y
- Rarefaction wave AP loading. Maximum total stress also occurs at these nodes.
The maximum stress
+ Primary-to-secondary is more or less uniform AP,around the bend and is_ mainly duej to cap the APcap force whichforce rapidly plus fluid friction an drops due to the primary side depressurization.
e
4 TABLE 3-10
~
MAXIMUM TUBE SUPPORT PLATE LOADS 00E TO LOCA RAREFACTION WAVE LOADING OF INDIVIDUAL TUBES s ( r
-' C4 , bi C,
== .-- ... .. , ,_
~-
n m.<,.m--e_ m* - M M**** g,,em eme.* 6'hh..
^^ ~ ~~ - ---
\ . _ . - - . . ._ _ _ ,
* *es*,e-e . ..e.. . ,,_,,,h l
. ..~. -. -
, . e ,,_ _ ._,- . _. - == -, _ _ _ .. - .
.m m-* *'M
..es.* -em-
-. -m eww. e.-eh-
- *66
-. N m N= .- as. . %,
- ~ ~ - -
~~~~-
. . -.. .- L------
t \ WI M l i t
. 41;
- . ~ , _ ..,-- , - - . - -- -
i
- 9. , b, e-
- - A.6,c ;
, , g;
._ - i
_ .i I w i e . l I L i Figure 3-1. CGE Response Spectra for OBE Analysis [5] (X direction is along hot leg, Z by RH Rule)
- t. l
l ,,,,,e nn T. . . l 1 rTTlIl ...... l l hIil i i jt t ,, i II
.zooo c ,y o,n -
{.qi..... ., . .. s s i s i. i s
~
iia i si Isi Figure 3-2. S hesi ed SSE Acceleration Time History for the 3 Olhti p 4 i i I 1 i l
' l i
2 L __ Figure 3-3. Specified Floor Response Spectrum and the Acceleration Time History Response Spectrum for X-Direction b ! . i
a , b, c, W i 1 i
.- ~
Figure 3-4, Mathematical Model for the Seismic Analyses
s J I I i
- - a . b , e.
i _
, t
.i , r t f 1 ) 8 1 i f i ( l . . . . . i . _ . . 1 1 F J i , i i 1 { ., , ' %. ,
"~~~~--_._ -
M, / ,, l ._ / - 3
. ../ .
{
..,~- ,8 % .%,'<
i
~
.. q ~ ~ ~ _ c .-
r . g
. ~ . _ .
-. - - . - l
- * . , . ., . .;7 .
~. m _
- . ~ _ _ . .. x
_N ' m .i l _ . . __.-.__ , l t l
,_ ' s . _} j -
i
--I --
i . 4
' i
} l 4 3, .
. %w._
i
~
m ~'--
' . . .' 1 1 , , '~ ~ , , - - - . . . 3 - _ _ . _ , _ . . _
) x !
- s. % . - - - -
~_
.~ .
l ._
~
.. h _ . . .
i ._ . l Figure 3-5. Schematic of Tube Bundle Internals-to-Shell ! Connections in the Seismic Analysis Model e l
,w,.---,,nn,mn,- -, --,,,..._,,,,..,an-mm,,,,---_- , . . ~ .....,-w.--., --,wa.-,n,n-.,-.-,-- v-c.--nn.-v.. ..,
t e O
- b a t.
. _ __ 1 - .
g 1 --
; I
_.-l - _ _ _ _ , _ . _ _ _ _ , ,i 8
,i
. _ _ _ _ _ _ _ _ __ _ _ . . . _ _ . t
. - . - . . - - . _ , _ _ _ _ . _ . . . - - - . . _ . l
_ --- -- --- .s
~t
_ _ _ ___ _ _.__m__ _.. _ _ _ _ . _ . _ _ . _ .
= !
) . .
ll u
...- ,c
>m 1
t
-' e - _ . ._ : -: ' =._-
l. 1 i 1 t l I l Figure 3-6. Typical FollowingPrimary a LOCA -Fluid NodesPressure 11 thru 15,Time (Histories J c.h.s e , ie_ es .. s., a. . . ....a._s
1 l
, a,bic 1
i I 0 i . i 1 i Figure 3-7. LOCA Rarefaction Wave Analysis Model l 4 m,b,c l' 1 t Figure 3-8. Horizontal Displacements of Node 12 Due to '
* > b > '-
- p. LOCA Rarefaction Wave LoadingE
' 3 J
. .w.
,b y E
i I 2 e Figure 3-9. In-plane Bending Moments at Node 15 Due to LOCA Rarefaction Wave Loading - , 1 J ,_ '
-%3 b ., c g
i i Figure 3-10. in-plane Rotation of Node 12 Due to LOCA 7 ~ , 'a , '
- RarefactionWaveLoadinJf I
I
. . j i
I 1 l l l _.w 1 l l l l l l i l I i
! l l
l l L -. Figure 3-11. Horizontal Displicement of Node 12 Due
,_ to LOCA Rarefaction Wave Loading - ,
g L-- - a,b > c Figure 3-12. 'labe End Reactions at the Top TSP Due to J.0CA Rarefaction Wave loading -j m , e , c-- {
--u.,.
t i i i i i i l l 1 I i
~
Figure 3-13. Resultant of LOCA Rarefaction Wave Induced Tube End Reactions at the Top TSP - F ' ,b.,c_ L l
~
q
,b ,'
i !
+
i _f L Figure 3-14 Resultant of LOCA Rarefaction Wave Induced Tube End Reactions at the Top TSP -
<- , b s c-
{ ] l
- aibi t
J j . i 4
?
I i i 2 i I i 1 l .
. W Figure 3-15. Tube Stresses From LOCA Shaking [9] (These stresses I are approximately at Nodes 13 and 15 in Figure 3-7) i l
1 i i -56
.. . - - - =. . _ . . _ _ .- .. , _ _
t t SECTION 4 RESULTS OF ANALYSES AND EVALUATION Loads and stresses generated from the analyses described in the previous section were used to verify the following requirements: (1) Safety requirements on a locally degraded tube, viz.,
' - a , b, c (2) ' Functional requirements a'ssociated with the overall tube bundle integrity (assuming median tubes)" during and following the Level D Service Condition loadings, that is:
a,c
# O, b, e g
M me 1 Although the tubing was evaluated for acceptance for both the functional and safety requirements, as indicated earlier, only details of evaluations to the Regulatory Guide 1.121 criteria (that is, degraded tube safety requirements) are discussed in this report. However, for
^
coupleteness, the following suusnary of evaluatibns to verify compliance l to the functional. requirements is included. The remainder of the section deals with the minimum required tube wall thickness calculations. The discussion of allowable leak rate limit and verification of leak-before , break is contained in the next'section. 4.1 Functional Integrity Evaluation
~o, I
~
~
, The evaluation consisted of verifying that the tube primary stresses and the reduction in the primary flow area of the tube bundle under the limiting faulted !
loads were within the specified acceptance limits. 4.1.1 Level D Service Condition Stresses' A i
}Thisloadingcondition is most limiting for the case of locally degraded (thinned) tubing and is considered later in the determination of the I minimum required thickness (of a degraded tube).
og
~
[
~
l
, Results of the LOCA and'SSE analyses i discussed in the previous section were used to compute the maxi- 1 mum P,+ Pb stress intensity in the tube U-bends. Results of this computation are summarized in Table 4-1.
l 1 1 G 'b,c i i i s 4.1.2 Primary Flow Area Reduction The in-plane TSP loads due to LOCA and SSE are transmitted to the shell through the support wedges resulting in local distortion and/or collapse of distorted tubes'(due to external AP g following ~ qb,C a LOCA). n 1 i The TSP reactions due to the LOCA and SSE loads were obtained
- using elastic analyses described in the previous section. d0 i 4
e e
, o. 6, Figure 4-3 shows the test correlation between the tD's and corresponding collapse pressures P c in a n ndimensionalized form. The tests were run at room temperature with tubes inserted into drilled collars simulating the TSP. The. tube-collar assemblies wem deformed in a vise to obtain various tube AD's to be tested.
e -o, '# O r W
m a h ,0. 1 i i
%u.
Tire resultant increase in the tube bundle oricary flow resistance rezasents a very small percentage . increase -in the overall system resistance and, therefore, will not impair the intended function of the steam generator ~
~
') '
[ _ 4.2 Minimum Wall Requirements for Degraded Tubes 3 G i b .0- [ , t
~
L
4.2.1 Nomal Plant Conditions
, - a, b, c f
s 4.2.2 Fi.B/SLB+SSE
, . Ai b,e e
l I
~%b5 s -
- 4.2.3 LOCA+SSE
, a, b, c t
Ik I i . Tne collapse pressure is significantly affecced by the ovality. An analytical correlation between the collapse pressure and the tube ovality was developed using a large defomation, lowr bound limit analysis. The validity and conservatism of the analytical cormlation was verified against the results of room tenperature collapse pmssure tests, conducted in-house and elsewhere [63, on mill-annealed 0.75" OD x 0.043" t oval tuks. Ficure 4-4 shows the comparison of analytical predicted (norinalized) collapse pressures with those obtained from the tests.
2 i w s . Burst strength requirements associated with leak-before-break and margin to . burst- under normal operating AP$ are discussed in the next section. 64
TABLE 4-1
SUMMARY
OF MAXIMUM STRESS INTENSITY CALCULATIONS _ a,$ 4 A l s i I i e e 9 e 4 f a 6
, A.b d . .I 1
1
,l 1
s ., Figure 4-1. Schematic of a Tube-Tube Support i Plate Crush Test l .ca.
)jf!J!> l' J? .
. . l' .
. . i
. i l-
._t l .
_s _e
, . _T
_h s u r
; i .
C i i . P i S
, . T
- i. - . ' '
,! i e
b u
; i T
* ' . . .i .
- . j .t e .
6 i -Iii h
. t
.. i .
.,i l m
o t i .t l .g l tl. l,g F F
, - i Te i
l
, i.
,tii ij ll.
a t I b
; . ll i l, o i
-l
' a i
t
. ' i-
. i
, i a
D gi: i n j i o
- ' - 6 t
. r
.' j, .
- - . o t
s
~i D
' i
~
. . 3 . . -
e h U T 2 4 e r u g i F
.2w -1lI!- '
I , g
Qhe ii I t i i Figure 4-3. Results of Pressure Collapse Tests on Distorted Tube - TSP Collar Assemblies
i I f ? m 6 3 m 4/1 Q L i C1. I i@ m C1. to P W O O T C C h
.a g=
W G C e i 4 3
'W c
GJ G 3 a QJ CD C Q w M C W 6 6 O O Y I T U 8 6 3
~'
. e J
SECTION 5 BURST STRENGTH REQUIREMENTS In addition to the limits on allowable stresses and margin to collapse due
- to external pressure discussed previously, the following requires 'ts on the burst (pressure) strength capability of the degraded tubing mus also be shown to be satisfied. gy >
o w m
- w w w 4
* % M -e.
e e-p N _ _ . . e .__ . . 4 5.1 Leak-Before-Break Verification The rr.tior: ale behind this requirement is to limit the maximum allowable (primary-to-secondary) leak rate during normal operation such that the associated crack length (through which the leakage occurs) is less than - the critical crack length corresponding to the maximum postulated accident condition pressure loading. Thus, on the basis of leakage monitoring during nomal operation, it is assured that an unstdble crack growth leading to tube rupture would not occur in the unlikely event of the limiting accident. For the CGE units, the maximum technical specification allowable leak rate is 0.33 gpm per steam generator. Results of the leak rate tests were used to detemine the maximum allowable crack length during normal
, operation corresponding to this Tech. Spec. limit. C ._
^ '
~ ~~
s
] Front this -
correlation, the largest pemissible crack length .(associated with Tech. Spec. limit of 0.33 gpm leak rate) during nomal operation is W.44 inch. Beyond this length, the leakage would exceed the Tech. Spec. limit, requiring a plant shutdown for a corrective action.- _ S, data "1se much larger than in Table 5-1 is required for a meaningful statirtical evaluation. Such a data base was created by compiling the results of a large number of burst pressure. tests performed on various Westinghouse steam generator tubing, within Westinghouse and elsewhere [7]. Because of the variations in tube sizes and mechanical properties, the data was non-dimensionalized and is shown in Figure 5-3. Results for the CGE tests in Table 5-1 were included in .F1oute 5-3 to verify that the lower bound (shown by the solid line) established by broad data base is applicable to the CGE tubing evaluation.
-n
SA s e, r n i s r Applicability to Thinned Tubing The applicability of leak-before-break is also required to be verified for the case of a tube with cracking superi@osed on thinning. In connection with the burst pressure and leak rate behavior of a tubing, the following should be noted. o.h
" 3e
?
S by d 73-
L s 5.2 Margin to Burst Under Nonnal AP According to the R.G.1.121 guidelines, a factor of safety (FS) of 3 is required against failure by bursting under the normal operating. pressure
- differential.
= .
( k e e_-. 74-
5.2.1 Tube with Thru-Walt Degradation
) a, b,c Y
l i l
. i e
[ s h m e e
. I i
w m she
l l l For a thinned tube with a superimposed crack, the value of FS would be even higher as indicated by the results in Figure 5-5. 5.2.2 Thinned Tube For the case of a predominantly thinning mode of tube degradation (that is no thru-wall cracking and hence no leakage pricr to e failure), the minimum tube wall thickness must be established o , 6. O e
-w .
O
.e 4
1 4
TABLE 5-1
SUMMARY
OF BURST PRESSURE AND LEAK RATE TEST MATRICES FOR CGE TUBING I Burst Pressure Tests Specimen ID No. Axial Crack Length, L inch
-
- o, b, e, 3900-JAB-81 #1 -
#2
#6
#7
#8
#9
~
#10
#11 ,
. s Leak Rate Testsz ,3 Specimen ID No. Axial Crack Length, L inch
, o . b.e SGTLR-39 #3 SGTLR-29 SGTLR-40 #4A SGTLR-41 #5 s j
, ,m
-77
A.b 1 i s u Figure 5-1. Results from a Typical Leak Rate Test (Test
#SGTLR-40,1{. ' ] a,b,c t
, 0 , 0 , *-
' 1 i
s J Ffgure 5-2. Correlation Between Crack Lenath vs. Leak Rate During Normal Goeration p.75'r OD x 0.043" Tubing,7' ,,4,c L __. 7 er C S g I<n I" N 10 e.* C
' 43 I
i.w i IV
- ats
'k N
'e M
- =
fM 4 i C l"4 0 6 3 m IA W L CL M en b 3-
.C 6@
N E u O 2" C G3 3 a C: C. S wt C Q M 4
- c N
6 3 LCl". W
)
i .
9 f . c C w M 3 k C O u3 e s== W W 10 2 ! ~ m
, mer C.
r C I. c C i
*m W.
C C
.C M
C c 4J b M M b II ED G3 a U G3 CL. x LAJ E i I C
!. Y e
LO
$,bG3
'\ 73
.6 i
s
. o1
, 4,b i
l
- i l
t f 2 i i i l i i : I I i s Figure 5-5. Variation in Margin to Burst as a Function of Mean Radius-to-Thickness Ratio of The Tube .
SECTION 6 Pt.UGGING MARGIN REC 0Pt4ENDATION
, Based on analyses in the previous sections, a minimum wall } a,b.:
( USNRC ]is necessary to satisfy the stress limit and strength requirements of Regulatory Guide 1.121. [ l # ' b, o i-The allowable degradation must incorporate additional allowances for any corrosion under continued operation until the next scheduled inspection and the measurement uncertainties using the Eddy Current'(EC) probes. .An estimate of the corrosion allowance can be made based on the corrosion rate history of similarly designed and operated units and the projected inspection interval. , - 4. b,e L J
~
~~
~~
Thus, the recoEnded tube plugging margin for GE C isT55% of nominal wall. e 9
l SECTION 7 REFERENCES
- 1. "ASME Boiler and Pressure Vessel Code, Section III, " Rules, For Construction of Nuclear Power Plant Components", The American Society of Mechanical Engineers , New York, N.Y. ,1977.
- 2. USNRC Regulatory Guide 1.83, "In-Service Inspection of Pressurized Water Reactor Steam Generator Tubes", July 1975.
USNRC Regulatory Guide 1.121 " Bases for Plugging Degraded PWR Steam Generator 3. Tubes (For Comnent)", August 1976. 4 Timoshenko, S., " Strength of Materials - Part II", Third Ed. , Yon Nostrand Reinhold Co. , New York, N.Y. ,1958, p. 353.
- 5. DeRosa, P.P., et. al., " Evaluation of Steam Generator Tube. Tubesheet and Divider Plate Under Combined LOCA plus SSE Conditions", WCAP-7832 Westinghouse Nuclear Energy Systems, Pittsburgh, PA., April 1978.
- 6. Small, N.C., " Plastic Collapse of Oval Straight Tubes Under External Pressure",
ASME Paper #77-PVP-57, June 1977.
- 7. Vacins, M. et. al., " Steam Generator Tube Integrity Program - Phase I Report,"
NUREG/CR-Of18, September 1979. l
APPENDIX A DERIVATION OF LOWER BOUND TOLERANCE LIMITS FOR STRENGTH PROPERTIES OF 0.75" OD x 0.043 WALL MILL-ANNEALED I-600 TUBING Expected strength properties to be used for the CGE tubing evaluation were obtained' from statistical analyses of tensile test data of actual production tubing.( j O e 4 i t i i
% .)
.A7.
r N l
\
4 Table A-1 sunnarizes the calculations of statistical analyses of test data of the mill-annealed Inconel-600 tubing for CGE. The LTL's for the allowable design stress intensity were obta.'ned from the LTL's on yield and ultimate strengths in accordance with the rules in Appendix III of Section III of the ASME Code. Details of these calculations are given in Table A-2. 3 e
-M=
TABLE A-1 LOWER TOLERANCE LIMITS FOR MODEL D MILL-ANNEALED TUBING STRENGTH PROPERTIES a b. c. ' 1 x l s t i P I
, .n
TABLE A-2 z. CGE TUBE STRENGTH PROFERTIES FOR RG 1.121 ANALYSES (0.75"0D x 0.043" WALL MILL . ANNEALED I-600)
% 4 i
I i i i I i e l I i l W i _____}}