ML20128N197
| ML20128N197 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 03/31/1985 |
| From: | WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML20128A500 | List: |
| References | |
| SG-85-03-056, SG-85-3-56, TAC-57847, TAC-57848, WCAP-10820, NUDOCS 8506030195 | |
| Download: ML20128N197 (154) | |
Text
1 WESTINGHOUSE PROPRIETARY CLASS 3 WCAP 10820 SG-85-03-056 NORTHERN STATES POWER COMPANY
- PRAIRIE ISLAND NUCLEAR GENERATING PLANT ~
LICENSE AMENDMENT REQUEST DATED MAY 17, 1985 LHIBIT D PRAIRI(ISLANDUNITS1AND2 3
STEAM GENERATOR SLEEVING REPORT (BrazedSleeves)
A l
March 1985 I
PREPARED FOR NORTHERN STATES POWER COMPANY WESTINGHOUSE ELECTRIC CORPORATION.
STEAM GENERATOR TECHNOLOGY O! VISION '
P.O. 80X 855 PITTSBURGH, PA 15230 B506030195 850517 PDR ADOCK 05000282 P
1 PROPRIETARY INFORMATION NOTICE TRANSMITTED HEREWITH ARE PROPRIETARY AND/OR NON-PROPRIETARY VERSIONS OF DOCUMENTS FURNISHG TO THE NRC IN CONNECTION WITH REQUESTS FOR GENERIC AND/OR i
PLANT SPECIFIC REVIEW AND APPROVAL.
3 IN ORDER 10. CONFORM TO THE REUIREMENTS OF 10CFR2.790 CF THE COMMISSION'S REDULATIONS CCNCERNING THE PROTECTION OF PROPRIETART INFORMATION SO SUBMITTED TO THE NRC, THE INFORMATION WHICH IS PROPRIETART IN THE PROPRIETARY VERSIONS IS CONTAINED WITHIN BRACKET 5 AND WHERE THE PROPRIETARY INFORMATION HAS BEEN DELETED IN THE NCN-PROPRIETART YERSIONS WLY THE BRACKETS RENAIN, THE INFORMATION THAT WAS CONTAINED WITHIN THE BRAQCETS IN THE PROPRIETARY VERSIONS HAVING BEEN DELETE. THE JUSTIFICATION FOR CI. AIMING THE INFORMATION S0 DESIDNATED AS PROPRIETARY IS INDICATED IN BOTH VERSIONS BY MEANS OF LOWER CASE LETTERS (a) THROUGH (g) CONTAINED WITHIN PARENTHESES LOCATED AS A SUPERSCRIPT DHEDIATILY FOLLOWING THE BRACKETS DCI.0 SING EACH ITEM OF INFORMATION BEING IDENTIFIED AS PROPRIETART OR IN THE MARGIN OPPCSITE SUCH INFORMATION. THESE LWEE CASE LbTTERS REFER TO THE TYPES CF INFORMATICN WESTINGHOUSE C l
HQ.DS IN CCNFDENCE IDENTIFIED IN SECTIONS (4)(ii)(a) through (4)(ii)(g) 0F THE AFFIDAVIT ACCOMPANTING THIS TRANSMITTAL PURSUANT 1010CFR2.790(b)(1).
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.5efan me, the undertigned authcHty, ;:ersonally acceared Actert A. Wiesamann, who, being by se duty sworn ac::rding to 1aw, deposes and says that he is authcM:ed to exec:::a nis Affidavit en behalf of Westinghouse ElectMc, Car'h:cration ("'ustingneuse) and c:a:
the avements of fact set forth.in this Affidavit are true and carne:
to the best of his knowiecge, infemation, and belief:
l k.C&:.b/dhtL Rccer: A. Wtesamann, Manager Regula:sry and Lssislative Afdairs 9
?. worn ta and subscMbed befere me this I
ay d
of N?A-980.
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1 c-(1)
I am '*anagar of.iequia::ry and Lstistadve Afdairs in ce.'fuclea.r.
, Tec:utcicqy Oivision of Wesdngneusa Ilec:Hc C:r;crtden, and as sucn, I have teen s;ecidically deleta:ad ce funcden ef. rev'iewing.
ca ;;rc;Mecary infor=aden scugh
= be wicheid from ',.unlic ds-closure in annectten wie nuclear power plant licansing er nie-anMng precandings, and as aucertzad 22 airply for its witanoiding 4
en behalf of ce Westnghcuse Watar Reac=r Divisicas.
3 (1)
I am maMag tis Afdidavit in anfcmanca wita 6.e ; revisions of 10CFR Section Z.750 cf me C mnission's regulations and in c:njunc-efen wt2 es Westingacusa applica:1cn fdr wicheiding ac==canying t.H s Affidavit.
1 (2)
I have personai Icicwledge of es crt: aria and precadures utilized by Westinghouse fluclear Energy Systams.in designadng infomaticn as a trade seerst, privileTed or as enfidential c:nnercial or financial infor:ation.
(4) pursuant := ce previsicas of garsgrach (b)(4) of tec.ica 2J90 cf the C nnitsion's reguladens, ce fellowing is fur.ished for en-sidaraden by ce Camission in datar.nining whether cae informaden scudit to be withheld fica public disclosure saculd be wicheid.
(,1 )
The infoma:1.cn scught :n be wicheid frca public dis-closure is cuned and has been he'id in c=nfidenca by Westingneuse.
(ii)
The infomaden is of a type cus :maH1y held in c=nfi-danca by Wesdnghcuse and not cust:maMiy disclosed ts the puhtic.
Westngncuse has a ratienal basis fer deramining ce types of infer =aden cus :marily' held in anfidenca by it and, in that annecden, udit:ss a systam := detsmine when and whecer :: ncic car ain cyces of infoma:icn in
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The acclicaden of eat rfstan and de suc-sunca of :::at systam.c=nstitutar Wa.sdngneuss ;cif cy anc.:revides ce ratienal basis required.
Uncer eat systam,. fe.
- .ica is held is c=nfidenca if it falls irt one or enre of saveral types, es releasa of eich sigitt resuit in ce toss of' an exizdng or pesandal c=mcatttve advantag'a, as fatic*s:
4 (a)
The information reves.ls ce disdnsnistrfne aspec s of a precass (or c=msenant, structure, t=ci, maced, i
et=.).whert. prevention of its usa by any of Wesdngncuse's
, c=mpetitsrs wie. cut licanse frem Wesdnghcusa c=nst-tutas a capetitive. ecncuric advanuge over ocer c=mmanies.
4 1
I,t consists cf su' porting data. including tast data, (h) s e
retadve ts a. pmcass -(or c=mmenent, stncture, t=ci, maced, et=.), en applicadon of *1ch data secres a, c=mpatitive eencaic adva'atage, e.g., by optimi:a:1cn or impreved.markatability.'
(c)
Its use by a. c=mcedtsr would reduca his exsanditure f
of resourcas or imersve his c==cetitive posiden in'"
the design, manufacture, shipment, insullatien, assur '
anca of quality, or licatsing a simitar prcduct.
(d)
It nyeals c=st or prica infonaden,, productica casac-ites, budget levels, or c=mercial stratagies of Wesdnghcuse, its cat:mers er suoptiers.
(e)
It revents assecu of past, prssent, or futurs Westngacuse cr cus::: er *undec :favelecanc stans and :r yr-s W
- ccancial c
- m.orcial value :: Westinqncusa.
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(f)
It =nuins ;atanucle' fdams, for wnich ;a:an: pec-taction my be casirtale.
(g)
It it not ce prcper y of.W.es.dnghcuse, but ast be tres. tad. as prc=rieurf by Westnghcuse ac=rding :=
agreements with ce cwner.-
Thors art scund ;citcy esascar behind the Westngneuse systam wnf,ch include the falicwing:
(a)
The use of s'uch inforuden by Wesdnghcuse gives Westinghouse a c=mmeddve advanage over in c:mpetit:rs.
It is, thersfers, wicheid fran disc!caure ta protect the Wesdnghousa capatitive ;csition.
(b)
It 11 i..Tw,-tid.T ahicn is marketable in any ways.
The extant to wirich such ind:mation is a'vailaata ts c=mpetttsrs diminishes the Westingneuse ability :s sail prcducu and sardcac invetving :he usa cf =e i..iur don.
(c) lisa by our c=mpetit:r would.;ut Westingneuse at a c=meetitive disadvantage by
- . ucing his ex:enditure cf rescurtas at our expense.
(d)
Each c=mcenent of pr:grietar/ infumeNcn pertinent to a'pardcular c:mcatitive advanuge is ;ctantially as valuable as ce c::al c=mcatitive advanuge.
If c=meedt:rs ac:;uirs c:meenenu cf pr crieur/ infor.a-den, any cne c=m:enant my be One key :s :ne entirt pu le, therehy deceiving Westngneuse of a c=ce:1:1ve advanuge.
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1 (a)
Unres:Mc:ad, discicsure wculd jeccarci:s ce ;csition of prcminenca cf Westnghcuse in :::e worid Tuarkat,
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and cereby give a market advanuge t: ce pedtien in esse cun:Mes.,.,
(f)
The Westinghouse capacity t: invest ccrpcrata assats.
. in research and development dacends upon the suc: ass
, in entaining and mainu'fning a. ccmcatitive advanuge.
(iii)
The,infor. cation is being transmittad ts ce Ccamissien in c=nfidenca and, under ce provisicas of 10CTR Secten 2.750, it. is to be recaived in c=nfidenca by: ce Ccamissicn.
(iv)
The infor.natica scustn: to be pretactad is not availatie in public scurtas t: the best of our kncwledge and belf ef.
+
s (v)
Tha wr.wrietary infdr. nation scught ta he withfield in this submittai is that wirfctr is apprccriataly marked IE.57-40(20)
- scuthern California Edison Repain Reser." (Propr'ieury).
This report has beert prepared for aqd is being submit:ad ts ca Staff at ca request of Scuther$ California Ediscn.
- The resc'rt details the design of ce sleeves cat are tz be installed in ce San Cncfre Unit 1 s.aam generatcrt.
The rescrt. also includes the design analysis, the east veMfica,-
+
tion program and dascMptions of ca expanded mec::anical plug, ce rulled plug and ce channel head dec=numinaten peccass.
This is.% etien is part of cat whien will' enable Wesdngneusa to:
j (a)
Accly for ;atan; prc:acton.
a
.l.h1f'.i% ja$?!Str.L,5i$Z & $;?:?2rR & W,-k &p fQ" d:'.*'.
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Opti::ri:a staam geners=r :: air tachnicues ~.: ex.and' l
ce sertica life cf staam genersurs.
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(c)
Assist its cust:mers ti catain NRC apprcval.
d)
Justt?/ es design basis f:r the stasm generat:r repairs and insull.aden maceds.
3 Furcer.. mis informaden has substantial c:::::ercial value i
as fo11cws-(4)
Westin@cusa plans ta sell ce resair technicues and.
equipment described. in part by ce infor=ation.
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(b)
Westinghouse can sail repair servicas tasad usen ce experienca gained and. da installaden equipment and methods developed.
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c Pu211e dfseicsure of this infor::atien' is likely t: ciuse t
substantiat harm en de c==petitive positica of Wesdaghcuse
' becausa (1) it would result in ce icss of valuatie pa: ant J'I rights, and (2) it would enhanca the ability of c=meedt:rs to design, maliufacture, veriff and sell staam generst:r t
repair techniques for c=mmerdal power reac=rs wiecut
c35Eensurata expenses.
/
The development of ce methods and ecui;: ment desc-ihed in-part by es informaden is ce result of acclying tne resultz '
i of many years of experienca in an intansive 'ksdnghcuse ef"cre and ce ex:enditure of,a c:nsicersnie sum cf =cney.
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In order for c:meetit:rs of Westinghcuse.: d==ticata.$.is infer =aticn. similar engineering pregrams 4uld have a be perhr=ed and a significant =anecwer afbr., having.::e rumistte talent and ex;:erienca, wuld have t: he ex;: ended for steam generat:t repair tachnicues..
Fur.her 2:e deponetit sayeth not.
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1 BRAZE 0 SLEEVE REPORT TABLE OF CONTENTS I
Section Title Page
1.0 INTRODUCTION
1-1 2.0 SLEEVING OBJECTIVES ANO SLEEVING,BOUNOARIES 2-1 3
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2.1 Objectives 2-1 L
2.2 Sleeving Boundaries 2-1
~
l 3.0 OESIGN 3-1 3.1 Sleeve Design Documentation 3-1 3.2 Sleeve Design Description 3-1 3.3 Design Verification: Test Programs 3-6 3.3.1 Design Verification Test Program Stanary 3-6 3.3.2 Corrosion and Metallurgical Evaluation Program 3-7 3.3.2.1 Corrosion and. Metallurgical Evaluation 3-22 of Brazed Joint Region 3.3.2.2 Corrosion and Metallurgical Evaluation 3-28 of the Lower Joint 3.3.3 Test Program for the Lower Joint 3-30 3.3.3.1 Description of L3wer Joint Test Specimens 3-30 3.3.3.2 Description of Veriffcation Tests for 3-30 the Lower Joint-3.3.3.3 Leak Test Acceptance Criteria 3-31 3.3.3.4 Results of Verification Tests for Lower Joint 3-32
~
3.3.4 Test Program for the Brazed Joint 3-33 3.3.4.1 Description of Brazed Joint Specimens 3-33 3.3.4.2 Description of Verification Tests for the Braze Joint 3-33 3.3.4.3 Results of Verification Tests of Braze Joints 3-33 1819c/0235c/031185:5 2 i
1
=
l TABLE OF CONTENTS (Continued) 2
[
Section Title Page 3.3.5 Effects of $1'eeving on Tube-to-Tubesheet Weld 3-34 M
f 3.3.6 Susuary of Test Results 3-34 7
3.4 Analytical Verification 3-43 3
i 3.4.1 Introduction 3-43
'1 3.4.2 Component Description 3-43
{
3.4.3. Material Properties 3-44 E
I; 3.4.4 Code Criteria 3-44
~
3.4.5 Loading conditions Evaluated 3-44
[
3.4.6 Methods of Analysis 3-45 3.4.6.1 Model Development 3-45 I
I 3.4.6.2 Thermal Analysis 3-46 f
3.4.6.3 Stress Analysis 3-47 4
r 3.4.7 Results of Analyses 3-49 h-g 3.4.7.1 Primary Stress Intensity 3-50 h
p 3.4.7.2 Range of Primary and Secondary y
k Stress Intensities 3-50
[
3.4.7.3 Range of Total Stress Intensities 3-51 3
3.4.8 References 3-52 2
i 3.5 Special Considerations 3-64 3.5.1 Flow Slot Hourglassing 3-64
[
3.5.1.1 Effects on Burst Strength 3-64
^
h 3.5.1.2 Effects on Stress Corrosion Cracking Margin 3-64
{
3.5.1.3 Effect on Fatigue usag4 3-64
[
3.5.2 Tube Vibration Analysis 3-65
{
3.5.3 Sludge Height Thermal Effects 3-65 2
f 3.5.4 Allowable Sleeve Degradation 3-65 3.5.5 Effect of Tubesheet/ Support Plate Interaction 3 70 E
3.5.6 Comprehensive Cyclic Testing 3-70 L
3.5.7 Evaluation of Operation with Flow Effects
-f 7
Oue to Sleevin9 3-71
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3.5.8 Alternate Sleeve Materials E
3 74 y
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1819c/0235c/031185:5 3 gj I
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1 TABLE OF CONTENTS (Continued)
Section Title Page 4.0 PROCESS OESCRIPTION 4-1 4.1 Tube Preparation 4-1 4.1.1 -Tube End Rolling (Contingency.)
4.1 3
4.1.2 Tube Honing 4.3 4.1.2.1 Wet Honing 4.3 e
4.1.2.2 Ory Honing 4-1
-4.1.3 Fiberoptic Inspection (Contingency) 4-4
~
4.2 Sleeve Insertion and Expansion 4-4 4.3 Lower Joint Seal 4-6 4.4 Braze Joint Process 4-7 4.4.1 Brazing Material 4-7 4.4.2 Flux Application 4-7 4.4.3 Brazing Operation
' 4-7 4.5 Sleeve Inspection 4-8.
4.5.1 Process Inspection Sanpling Plan 4-8 4.5.2 Ultrasonic inspection 4-9 4.6 Establishment of Sleeve Joint Main Fabrication Parameters 4-10 4.6.1 Lower Joint 4-10 4.6.2 Upper Joint 4-10 5.0 SLEEVE / TOOLING POSITIONING TECHNIQUE 5-1 5.1 Renotely Operated Service Arm (ROSA) 5-1 5.2 Alternate Positioning Techniques 5-3 1819c/0235c/031185:5 4 ggg Au-
1 TA8LE OF CONTENTS (Continued)
Section
~
T,itle pg 6.0 NOE INSPECTABILITY 6-1 6.1 ultrasonic 8 raze Inspection 6-1 6.1.1 Principle of Operation 6-1 6.1.2 Ultrasonic System 6-2 i
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6.2 Eddy Current Inspections 6-5 6.3 Summary 6-10 7.0 ALARA CONSIDERATIONS FOR SLEEVING OPERATIONS 7-1 7.1 ROSA Sleeving Operations 7-2 7.2. Manipulator Erd Effectors 7-2 7.2.1 Sleeve / Tooting End Effectors 7-2 7.2.2 In-Process Operations 7-3 7.3 Control Station in Containment 7-3 7.4' Potentials for Worker Exposure 7-3 7.4.1 Nozzle Cover and Camera Installation / Removal 7-4 7.4.2 Platfom Setup / Supervision 7 7.5 Radwaste Generation 7-5 7.6 Airborne Releases 7-7 7.7 Personnel Exposure Estimate 7-7 8.0 INSERVICE INSPECTION PLAN FOR SLEEVED TUBES 8-1 1819c/0235c/031185:5 5 jy
1 LIST OF TABLES Table Title Page 3.1-1 ASME Code and Regulatory Requirements 3-3 3.3.2-1
- Summary of Corrosion Comparison Data for 3-12 Thermally Treated Inconel Alloys 600 and 690 3
e 3.3.2-2 Effect of Oxidizing Species on the SCC Suscepti-3-13 bility of Thermally Treated I-600 and I-690 C-rings in Deaerated Caustic.
3.3.2-3 Test Program Objectives 3-14 3.3.2-4 Metallurgical / Corrosion Objectives and Test Performed 3-15 3.3.2-5 Summary of Previously Conducted Sleeve Corrosion and 3-16 Metallurgical Evaluation Program for Brazed Sleeves 3.3.2.1-1 Acceptance Criteria for Microstructure Characterization of Brazed Joint Area 3-25 3.3.2.1-2 Summary of Grain Size Measurements 3-26
- 3. 3. 2.1'-3 Results of Controlled Potential Testing of Brazed 3-27 Inconel Alloy 690 Sleeves 3.3.3.3-1 Allowable Leak Rates For Model 51 Steam Generators 3-35
-3.3.3.4-1 Test Results for the Model 44 As-rolled Lower 3-36 Joints 3.3.4.2-1 Test Matrix for Braze Joint 3-39
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3.3.4.3-1 Test Results for Braze Joint 3-40 1819c/0235c/031185:5 6 y
E 1
LIST OF TA8LES (Continued)
Table Title Page 3.4.4-1 Criteria for Primary Stress Intensity Evaluation 3-54 (Sleeve) 3.4.4-2 Criteria for Primary Stress Intensity Evaluation 3-55 (Tube) 3.4.5-1 Operating Conditions 3-56 e
3.4.7.1-1 Umbrella Pressure Loads for Design, Upset, Faulted, and Test conditions 3-57 3.4.7.1-2 Results of Primary Stress Intensity Evaluations 3-58 Primary Membrane Stress Intensity, P, 3.4.7.1-3 Results of Primary Stress Intensity Evaluations 3-59 Primary Membrane Plus Bending Stress Intensity.
P, + P '
b 4
3.4.7.2-1 Pressure and Temperature Loadings for Maximum 3-60 Range of Stress Intensity and Fatigue Evaluations 3.4.7.2 2 Results of Maximum Range of Stress Intensity 3-62 Evaluation 3.4.7.3-1 Results of Fatigue Evaluation 3-63 i
3.5.4-1 Regulatory' Guide-1.121 Criteria 3 67
}-
4.0-1 Sleeve Process Sequence Summary 4-2 7.5-1 Estimate of Radioactive Concentration in 7-6 Water per Tube 1819c Vi
1 LIST OF FIGURES Figure Title Page 2.2-1 Sleeving Boundary [
]a,c.e Sleeves 2-3 3.2-1 Reference Sleeve Design 3-4 3.2-2 Sleeve Lower Joint Configpration 3-5 3
3.3.2-1 SCC Growth Rate for C-rings (*150 percent YS and 3-18 TLT) in 10 percent NaOH 3.3.2-2
' Micro Structure 3-19 3.3.2-3 SCC Depth for C-Rings (150 percent YS) in 3-20 8 percent Na 50 2
4 3.3.2-4 Reverse U-bend Tests at 360*C (680*F) 3-21 3.3.2.2-1 Location ano elative Magnitude of Residual 3-29 Stresses Induced by Expansion 3.3.3.1-1 Lower Joint As-rolled Test Specimen 3-41 3.3.4.1'-1 Sleeving Mockup 3-42 3.3.5.1-2 HEJ Specimens for the Reverse Pressure Tests 3-31 3.3.6.1-1 Fixed-Fixed Mockup -
3-44 3.4.2-1 Sketch of Brazed Sleeve Design 3-53 4.5.2-1 A Typical UT Inspection Trace 'of a Braze Joint 4-12
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vii 1819c/0235c/031185:S 8
1 LIST OF FIGURES Figure Title g"
6.1.1-1 Ultrasonic Testing of the Brazed Joint 6-12 6.1.1-2 Response of Focused Ultrasonic Transducer 6-13 6.1.2-1 Ultrasonic Scan.of Braze Rpgion Sample M5 6-14 3
6.1.2-2 Ultrasonic Scan of-Braze Region Sample MI 6-15 6.1.2-3 Double Wall Radiograph of Calibration Specimen M5 6-16
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6.1.2-4 Double Wall Radiograph of Calibration Specimen MB 6-17 6.1.2-5 Ultrasonic System Resolution Reference 6-18 6.1.2-6 Ultrasonic Inspection Process 6-19 6.2,1 Eddy Current Signals from the ASTM 6-20 Standard, Machined on the Tube 0.0. of r
the Sleeve / Tube Assembly Without Expansion (conventional Differential Coil Probe) 6.2.2 -
- Eddy Current Signals from the 6-21 Expansion Transition Region of the Sleeve / Tube Assembly (Conventional Differential Coil Probe).
6.2.3 Eddy Current Calibration Curve for ASME 6-22 Sleeve Standard.at [
]a,c.e with the Conventional 01fferential Coil Probe
.1819c/0235c/031185:5 9 Vili i
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1 LIST OF FIGURES Figure Title Page 6.2.4 Eddy Current Signals from the ASTM 6-23 Standard, Machined on the Sleeve 0.0.
of the Sleeve / Tube Assembly Without Expansion g
i 6.2.5 Eddy Current Signals from the ASTM 6-24 Standard, Machined on the Tube 0.0.
of, the Sleeve / Tube Assembly Without Expansion ( Cross Wound Coil Probe )
~
6.2,6 Eddy Current Signals from the Expansion 6-25 Transition Region of the Sleeve / Tube Assemoly ( Cross Wound Coil Probe )
6.2.7 Eddy Current Calibration Curve for ASME 6-26 Tube Standard at [
]3'C and a Mix Using the Cross Wound Coil Probe 4
6.2.8 Eddy Current Signal from a 20 Percent Deep 6-27 Hole, Half the Volume of ASTM Standard, Machined on the Sleeve 0.0. in the Expansion Transition Region of the Sleeve / Tube Assembly (Cross Wound Coil Probe) 6.2.9 Eddy Current Signal from a 40 Percent ASTM 6-28 Standard, Machined on the Tube 0.0. in Expcision Transition Region of the Sleeve / Tube Assembly (Cross Wound Coil
-Probe) ix 1819c/0235c/031185:5 10
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1 LIST OF FIGURES Figure Title Page 6.2.10 Eddy Current Response of Square and 6-29 Tapered Sleeve Ends Compared to the Expansion Transitions for the -
Conventional Bobbin Coil Probe 6.2.11 Eddy Current Response of the ASTM Tube 6-30 Standard at the End of the Sleeve using I.
the, Cross Wound Coil Probe and l
Multtfrequency Conbination
~
6.2.12 Eddy Current Signatures of the Braze Region 6-31
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6.2.13 Eddy Current Signatures of the Braze Region 6-32 6.2.14 Braze Region Geometry used to Generate Eddy 6-33 Current Braze Signatures 6.2.15 100 KHz Eddy Current Signatures for various 6-34 l
Braze Widths and Braze Thickness 6.2.16 Effect on E.C. Braze Response of 1/4" EDM lootch 6-36 Thru the Tubewall l
q 1819c/0235c/031185:5 11 X
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1 J
1.0 INTRODUCTION
As part of its ongoing steam generator repair prograns, Westinghouse has developed the capability to restore degraded steam generator tubes by means of a sleeve. This technology may be applied to the steam generators of Prairie Island Units 1 and 2 with the objective of. restoring the pressure boundary of such tubes and prolonging the availability of the steam generator heat exchange system.
To date..nearly 15,000 steam generator tubes at six operating nuclear power plants world-wide have been successfully sleeved, tested, and returned to service by Westinghouse. Both mechanical-joint and brazed-joint sleeves of Inconel 600, Inconel 690, and bimetallic Inconel 625/Inconel 690 have been installed by a variety of techniques - Coordinate Transport (CT) system installation,= hands-on (manual) installation, and Remotely Operated Service Arm (ROSA) robotic installation. Westinghouse sleeving prograns have been -
successfully implemented.after approval by licensing authorities in the U.S.
(NRC - Nuclear Regulatory Commission), Sweden (SKI - Swedish Nuclear Power Inspectorate), and Japan (MITI - Japanese Ministry of International Trade and Industry).
^
a The sleeving technology was originally developed to sleev,e 6,929 degraded tubes (including leakers) in a plant with Westinghouse Model 27 series steam generators. Process improvements and a remote sleeving system were subsequ4ntly developed and adapted to a Westinghouse Model 44 series steam generator.with utliization in full scale sleeving operations at two operating plants (2,971 and 3,000 sleeves). This technology has also been modified to facilitate installation of 2,036 sleeves in a non-Westinghouse steam generator.. Most recently, the latest Westin@ house sleeving technology was successfully applied durin'g a demonstration at a European site in a model 51
^
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t 1819c/0235c/030885:5 12 1-1 e
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I 2.0 SLEEVING OBJECTIVES AND SLEEVING BOUNDARIES
)
2.1 OBJECTIVES
.Both Frairie Island Units are Westinghouse-designed 2 loop pressurized water reacta rl rated at 1650 MWt each. The two units utilize a total of four vertical U-tube steam generators. The steam generators are Westinghouse Model 51 Series containing heat transfer tubes with dimensions of O'.875 inch naninal 00 by 0.050 inch nominal wall thicknes's.
a The sleeving co,ncept and design are based on observations to date that the tube degradation due to environmental attack has occurred near the tubesheet areas of the tube bundle. ' The sleeve has been designed to span the degraded region in order to maintain these tubes in service.
The sleeving program has two primary objectives:
1.
To sleeve tubes in the region of known or potential tube degradation.
- 2..To minimize the radiation exposure to all working personnel (ALARA) a 12 SLEEV;NG B00kOARIES Tubes to be sleeved will be selected by radial location, tooling access (due to channel head geometric constraints), and eddy current indication elevations and size. An axial elevation tolerance of one inch will be employed to allow for any potential eddy current testing position indication inaccuracies and
' degradation growth. Tube location on the tubesheet face, tooling dimensions, and tooling access permitted by channelhead bowl geometry define the sleeving boundaries. Figure 2.2-1 shows an estimated radial sleeving boundary for a
[
]*'C'8 sleeve as determined by a geometric radius computed from the channelhead surface-to-tubesheet primary face clearance distance minus the tooling clearance distance. (The actual "as is" bowl geometry will be
~
slightly different in certain areas.) This is the sleeving boundary for a generic Westinghouse series 51 steam generator and represents the maximum sleeving potential with a [
]a,c.e sleeve. This information along 1819c/0235c/030885:5 13 2-1
-m
1 with addy current inspection data provides the inputs to evaluate each tube as a candidate for the sleeving process. Tubes within the sleeving boundary that are degraded beyond the plugging limit but not within the axial restrictions of the [
]C sleeve or not within the radial sleeving boundary will be plugged. The actual sleevable region may be decreased based on tool length.
The actual tube plugging / sleeving map for each steam generator will be provided as part of the software deliverables 9t the conclusion of the i
sleeving effort.
p The specific tupes to be sleeved in each steam generator will be determined based on the following parameters:
1.
8eo opposite channelhead side tube indicatio1s and no indications at an elevation not spanned by the sleeve pressure boundary which are greater than the plugging limit.
2.
Concurrence on the eddy current analysis of the extent and location of the degradation.
w l
l l
1819c/0235c/030885:5 14 2-2
a-a,c.e 2
[
] S L E E V I N G T U B E S H E E T C L E A'R A N C E R A D I A N O U T L I N E i
SERIES 51 i
a.c.e j
[
] SLEEVE REGION 1946 i
OUTSIDE REGION 1442 I
TOTAL TUBES 3388 un m uuu 45
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t Figure 2.2-1 O
e
1 3.0 DESIGN 3.1; SLEEVE DESIGN DOCUMENTATION The Prairie Island steam generators were built to the 1965 edition of Section III of the ASME Boiler and Pressure Vessel Code, however, the sleeves have been designed and analyzed to the 1983 edition of Section III of the Code through the sunner 1983 addenda as well as applicable Regulatory Guides. The i
associated materials and processes also meet the requirements of the Code.
The specific documentation applicable to. this program are listed in Table 3.1-1.
3.2 SLEEVE DESIGN DESCRIPTION The reference design of the sleeve, as installed, is illustrated in Figure 3.2-1.
[
F ja,c e -
At the upper end, the sleeve configuration (see Figure 3.2-1) consists of a section which is [
i 1819c/0235c/030885:5 15 3-1 l
L
1 4
s
]8'C
The lower end of the sleeve has a preformed section to facilitate the seal formation and to reduce residual stresses in the sleeve.
The sleeve, after installation, extends above the top of the tubesheet and r
. spans the degraded region of the original tube. Its length is controlled by the insertion clearance between the channel head inside surface and the
~
primary side of the tubesheet, and the tube degradation location above the
~ tubesheet. The remaining design parameters such as wall thickness and material are selected to enhance design margins and corrosion resistance and/or to meet ASME Boiler and Pressure Vessel Code requirements. The upper j:
joint is located to provide a length of free sleeve above it. This length is
[
added so that if the existing tube were to become severed just above the upper edge of the brazed joint, the tube would be restrained by the sleeve and "
therefore axial notion, and subsequent leakage, would be limited. Lateral motion would also be restricted, protecting adjacent tubes from 1mpact by the severed tube.
l To minimize stress concentrations and enhance inspectability in the area of the upper expanded region, [
3,a,c.e.f l
l The sleeve naterial, thermally treated Inconel 690 or 600, is selected to provide additional resistance to stress corr'osion cracking. (See Section 3.3.2
~
for further details on the selection of thermally treated Inconel 600 and 690).
I I
1819c/0235c/030885:5 16 3-2 l
A
1 TABLE 3.1-1 ASME CODE Ah0 REGULATORY REQUIREMENTS Item Applicable Criteria Requirement Sleeve' Design Section III h8-3200, Analysis N8-3300, Wall Thick-ness Operating Requirements Analysis Conditions Reg. Guide 1.83 S/G Tubing Inspec-tibility Reg. Guide 1.121 Plugging Margin Sleeve Material Section II Material Composition Section III k8-2000, Identifica-tion, Tests and ExaminationsSection IX Braze Material Code Case N-20 Mechanical Proper-ties Sleeve Joint 10CFR100 Plant Total Primary-Secondary Leak Rate Technical Specifications Plant Leak Rate Section IX Brazing Requirements Code Case N-421 Application of Radiant Brazing 1819c/0235c/030885:5 17 3-3
1 8
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1 Figure 3.2-2 Sleeve Lower Joint Configuration
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3-5 t
1 3.3 DESIGN VERIFICATION: TEST PROGRAMS 3.3.1 OESIGN VERIFICATION TEST PROGRAM
SUMMARY
The following sections describe the material and design verification test programs. The purpose of these programs is to verify the ability of the sleeve concept to produce a sleeve capable of spanning a degraded region in a steam generator tube and maintain the s, team generator tubing primary-to-
- secondary pressure boundary under normal and accident conditions. This program includes assessment of the structural integrity and corrosion resistance of slpeved tubes.
A substantial data base exists from previous test programs which verifies sleeve design and process adequacy. Much of this testing is applicable to this sleeving program. The sleeve materials to be used, thermally treated nickel-chromium-tron alloys (Inconel 600 or 690), are identical to those used in prior sleeving programs. The standardized mechanical sleeve design is the same as that used in prior sleeving programs. The fabrication of sleeve / tube jointsby[
]C has been verified in previous programs. Rigorous mechanical testing programs were conducted to verify the sleeve design for various steam generator models, including the Model 44, which has the same tube dimensions as the Model 51.
In addition to being dimensionally similar, analysis has demonstrated that the operating conditions of a Model 44 steam generator envelope those of a Model
- 51. Thehfore, much of the Mortel 44 testing is directly applicable to the c
Model 51 steam generators.
The objectives of the mechanical testing programs included:
i l
Verify that the leak resistance of the upper and lower sleeve to tube j
joints meet the leak rate acceptance criteria.
Verify the structural strength of the sleeved tube under normal and accident conditicns.
1819c/023Sc/030885:5 18 3-6
1 O
Verify the fatigue strength of the sleeved tube under transient loads r'epresenting the remaining life of the plant.
Confinn capability to perform sleeving under conditions such as deep secondary side hard sludge and tube support ' plate denting
- ' Establish the process parameters required to achieve satisfactory installation and performance. These parameters are discussed in Section 4.6.
The acceptance criteria used to evaluate the sleeve performance are leak rates based on the plant technical specifications. Numerous test specimens were used in the various test prograns to verify the design and the process parameters. Testing encompassed static and cyclic pressures, temperatures, and loads. The testing also. included evaluation of joints fabricated using Inconel 600 sleeves as well as Inconel 690 sleeves in Inconel 600 tubes.
While the bulk of the original qualification data is centered on Inconel 600 sleeves, a series of limited scope verification tests were run using Inconel 690 sleeves to demonstrate the effectiveness of the joint formation process and design with either material.
a
.The sections that follow describe those portions of the corrosion (sections 3.3.2) and mechanical (sections 3.3.3-3.3.5) verification programs that are relevant to this sleeving program.
3.3.2 CORROSION AND METALLURGICAL EVALUATION PROGRAM The basic objective of the corrosion and metallurgical evaluation programs conducted was to verify that the sleeving c6ncepts and procedures employed did not introduce any new mec'hanism that could result in premature tube or sleeve degradation.
Inconel Alloy 600 and Inconel Alloy 690 (I-600 and I-690) are austenitic
~
nickel-base alloys. I-600 has been extensively used, originally in the mill annealed condition, as steam generator tubing in pressurized water reactors.
4 1819c/0235c/030885:5 19 3-7
1 In recent years, attempts to enhance the IGA-SCC (Intergranular, Attack-Stress
~
Corrosion Cracking) resistance of I-600 have focused on the application of a themal treatment in the carbide' precipitation temperature range (593* to 760*C). Microstructural modifications have concentrated on the grain boundary region since the SCC morphology in I-600 is predominantly intergranular. The maximum enhancement in caustic and primary water SCC performance was correlated with the presence of a semicontinuous grain-boundary carbide
_ precipitate.
g Inconel Alloy 690, which contains a higher. chromium content (30 percent) than Inconel Alloy 600 has also indicated the ability to exhibit improved IGSCC resistance when thermally treated in the carbide precipitation region.
The stress corrosion cracking perfomance of thermally treated (TT) Inconel Alloys 600 and 690 in both off-chemistry secondary side and primary side environments has been extensively investigated. Results have continually demonstrated the additional stress corrosion cracking resistance of thermally-treated Inconel Alloys 600 and 690 compared to mill annealed Inconel Alloy 600 material. Direct comparison of thermally treated Inconel Alloys 600' and,690 has further indicated an increased margin'of SCC resistance for thermally treated Inconel Alloy 690. (Table 3.3.2-1).
The caustic SCC performance of mill annealed and thermally treated Inconel Alloys 600 and 690 were evaluatad in a 10 percent NaOH solutica as a function of temperature from 288'c to 343*C. Since the test data cere obtained over various exposure intervals ranging from 2000 to 8000 hours0.0926 days <br />2.222 hours <br />0.0132 weeks <br />0.00304 months <br />, the test data were normalized in tems of average crack growth rate determined from destructive examination of the C-ring test specimens. No attempt was made to distinguish between initiation and propagat'on rates.
The crack growth rates presented in Figure 3.3.2-1 indicate that thermally treated I-600 and I-690 have enhanced caustic SCC resistance compared to that of. I-500 in the. mill annealed condition. The performance of thermally treated I-600 and'I-690 are approximately equal at temperatures of 316*C and below.
' At 332*C and 343*C, the additional SCC resistance of thermally treated Inconel 1819c/0235c/030885:5 20 3,3
't l'
s e
-Alloy 690 is observed. In all instances the SCC morphology, was 'intergranular in nature. The superior perfor':iance of thermally treated I-690 at higher temperatures is a result of a lesser temperature dependency.
Testing in 10 percent NaOH solution at 332*C was performed to index the relative intergranular attack-(IGA) resistance of I-600 and I-690.- Comparison of_ the IGA :norphology for I-600 and I-690 rings stressed to 150 precent of the 0.2 percent yield. strength is present,ed in Figure 3.3.2-2.
Mill annealed I-600 is characterized by branching intergranular SCC extending from a 200u front.of uniform IGA. Thermally treated I-600 exhibited less SCC and an IGA front limited sto less than a' few gra' ins deep. Thermally treated I-690 exhibited no SCC and only occasional areas of intergranular oxide
~
. enetrations, limited to less than a grain deep.
p The enhancement in IGA resistance can be attributed to two factors;' heat treatment and alloy composition. A characteristic of mill annealed I-600 C-rings exposed to deaer.ated sodiun hydroxide environment is the presence of intergranular. SCC along with uniform grain boundary corrosion referred to as intergranular attack (IGA). The relationship'between SCC and IGA is not well established but it does appear that IGA occurs at low or intermediate stress levels and at electrochemical potentials where the general corrosion *
. resistance of the grain boundary area is a controlling factor. Thermal treatment of I-600 provides additional grain boundary corrosion. resistance
- along with additional SCC resistance. In the case of I-690, the composition providds-an' additional margin of resistance to IGA and the thermal treatment enhances the SCC resistance.
--The addition of oxidizing species to deaerated sodium hydroxide environments results in either a deleterious effect or nd effect on the SCC resistance of thermally treated I-600 and I-690 depending on the specific oxidizing specie' and concentration (Table 3.3.2-2).
The addition of 10 percent copper oxide to
-10 percent sodium hydroxide decreases the SCC resistance of thermally treated I-600 and I-590, and also modifies the SCC morphology with the presence of
~
)
- transgranular crack's. The exact mechanism responsible for these changes is
- not well understood, but it is believed to be related to an increase in the specimen potential, corresponding to a transpassive potential, which results s
1819c/0235c/030885:5 21 9
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1 in an alternate cracking regime. The specific oxidizing specie arid'the ratio of oxidizing specie to sodium hydroxide concentration appear, to play an important role. By lowering the copper oxide or sodium hydroxide concentration, the apparent deleterious effect on SCC resistance is eliminated.
Mill annealed and thermally-treated I-600 and I-690 were also evaluated in a number of 8 percent sodium sulfate environments. The room temperature pH value, at the beginning of the test, was adjusted using sulfuric acid and 3
ammonia. Test results are presented in Figure 3.3.2-3.
As the pH is lowered, decreased SCC resistance for mill annealed'and themally-treated I-600 is observed, but thermally treated I-690 material did not crack even at a pH of 2, the - Towest tested.
4 The primary water SCC test data are presented in Figure 3.3.2-4.
For the beginning of fuel cycle water chemistries,10 of 10 specimens of mill annealed I-600 exhibited SCC, while 1 of 10 specimens of thermally-treated I-600 had cracked. In the end of the fuel cycle water chemistries, 7 of 10 specimens of mill annealed I-600 exhibited SCC, while 3 of 10 specimens of themally-treated I-600 had cracked. After 13,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of testing, no SCC has been observed in the mill annealed or thermally-treated I-690 specimens in either test environment.
Continuing investigation of the SCC resistance of I-600 and I-690 in primary water environments has showi mill annealed I-600 to be susceptible to cracking at high fevels of strain and/or stress. Themal treatment of I-600 in the carbide precipitation region greatly improves its SCC resistance. The performance of I-690, both mill annealed and thermally treated, demonstrates highly desirable p'rimary water SCC resistance, presumably due to alloy composition.
The evaluation of the brazed sleeve design relative to material and corrosion issues has been performed as part of previous sleeving programs. The sleeve material used for some of the previous sleeving programs was thermally treated Inconel Alloy 600, while an alternate sleeving material that has been used was thermally treated Inconel Alloy 690. Sufficient comparison of corrosion perfomance data for Inconel Alloy 600 and 690 has been inade which allows the i
1819c/0235c/030885:5 22 3-10 e
- - - =
.. - - ~
e - - -,,. - -,,,,,
---,--.--y r-
-y
1 previous testing results generated for brazed Inconel Alloy 600.to 'tne
-applicable for brazed Inconel Alloy 690. The basic objectives of the corrosion and metallurgical evaluation programs were to verify that the sleeving concepts and procedures do not introduce any new mechanism that will result in premature tube or sleeve degradation. These programs consisted of appropriately designed material and corrosion tests addressing the microstructural conditions in both the sleeve and tube following the braze cycle (refer to Tables 3.3.2-3 and 3.3.2-4).
Table 3.3.2-5 summarizes the
~1 results obtained from previous sleevd verification programs.
t e
1819c/023Sc/030885:5 23 3-11
,~
-.---,1-
---r--
e-
1 Table 3.3.2-1 SupetARY OF CORROSION COMPARISON DATA FOR THERMALLY TREATED INCONEL ALLOYS 600 ANO 690 1.
Thenna11y treated Inconel 600 tubing exhibits enhanced SCC and IGA -
resistance in-both secondar~-side and primary-side environments when compared to the mill annealed condition.
2.
Thenna11y tneated Inconel 690 tubing exhibits additional SCC resistance compared to thermal treated Inconel 600 in caustic, acid sulfate, and primary water environments.
3.
The alloy composition of Inconel 690 along with a thermal treatment provides additional resistance to caustic induced IGA.
4.
The addition of 10 percent Cu0 to a 10 percent deaerated NaOH environment reduces the SCC resistance of both thermal treated I-600 and I-690. Lower concentrations of either Cu0 or NaOH had no effect, nor did additions of Fe3 4 and SiO '
0 2
5.
Inconel Alloy 690 is less suscepttL.* to sensitization than Inconel Alloy 600..
6.
Inconel Alloy 600 and 690 have comparable pitting resistance.
e l
I h
IS19c/0235c/030885:5 24 3-12 t
t I
1 Table 3.3.2-2 EFFECT OF OXIDIZING SPECIES ON THE SCC SUSCEPTIBILITY OF THERMALLY. TREATED I-600 AND I-690 C-RINGS IN DEAERATED CAUSTIC Temperature Exposure Environment
(*C)
Time (Hrs)
I-600 TT I-690 TT 10 Percent NaOH +
316 4000 Increased Increased 10 Percent Cu0 Susceptibility
- Susceptibility
- 10 Percent NaQH +
332 2000 No effect No effect 1 Percent Cu0
~
1 Percent Na0H +
332 4000 No effect No effect 1 Percent Cu0 10 Percent NaOH +
.316 4000 No effect No effect 10 Percent Fe3 4 0
10 Percent NaOH +
316 4000 No effect No effect
'10 Percent SiO 2
- Intergranular and transgranular. SCC.
181?c/0235c/030885:5 25 3-13
1 3:
TABLE 3.3.2-3 TEST PROGRAM OBJECTIVES MAIN ASPECTS OF THE METALLURGICAL /
CORROSION PROGRAM FOR BRAZED JOINTS 4
o CHARACTERIZE MICR0 STRUCTURAL AND MECHANICAL
^
PROPERTY CHANGES OCCURRING IN THE TUBE AND SLEEVE MATERIAL o
VERIFY. CORROSION RESISTANCE OF BRAZED AREA USING ACCELERATED LA80RATORY TEST TECHNIQUES AND ENVIRONMENTS 8
o VERIFY OVERALL CORROSION RESISTANCE OF TU8E/
SLEEVE SRAZED AREA UNDER HEAT TRANSFER CONDITIONS IN SIMULATED PRIMARY AND SECONDARY-SIDE ENVIRONMENTS e
I i
1819c/0235c/030885:5 26 3-14
p 1
1 TA8LE'3.3.2-4
-METALLURGICAL / CORROSION OBJECTIVES Ah0 TESTS PERFORMED Issue Test / Environment 1.' 'Effect of high taperature brazing cycle ~on:
l a.. Tensile properties of
-. Tensile tube and sleeve b.
Microstructure Metallographic examination, hard-
[
ness transverse, optical and scan-
. L-ning microscopy c.
Possible sensitization of.
o Huey tube and sleeve l
p
- d.. Possible diffusion of 00 SEM/DAX, microprobe analysis and i
contaminants bending e.
Corrosion resistance of Isothermal tube and sleeve o 10 percent NaOH l
o Sulfate o Chloride
- (
o Primary Water o Pure Water o AVT 2.
Residual stress ' level o -X-ray residual stress measure-ment i
o SCC 3.
Effect of residual brazed flux o Pressurized capsule
- primary water
- AVT 4
Compatability of Au-Ni braze
' Isothermal Corrosion Tests alloy 5.
Performance of tube /sleev' Model boiler
~
brazed assemblies in simulated
- primary and secondary-side
~
s environments 6.
Corrosfon impact of annulus Model boiler between sleeve and tube.
- 1819c/0235c/030885:S 27 3-15 I
- g.......,... -........,
1 i
TABLE 3.3.2-5 (Continued) l.
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i k-F:
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1819c/0235c/030885:5 29 3-17 b ' ' - "-
SCC GROWTH RATE FOR C-RINGS
~
3 (150% YS AND TLT) IN 10% NaOH Average Crack Growth.
Rate ( j.tm/Hr.)
Temperature ( F) 550 575 600 630 eso 1
I I
i 1
O 1600 MA e
i 600 TT m
1690 TT 10-1 y
s;
.2 10
=
~
10-I I
I I
I I
I 200 300 310 320 330 340 350 Temperature ( C)
~.
Figure 3.3.2-1
e
)
..+
a.c.e l:
- ),
t m.
Figure 3.3.2-2. Light Photomicrograohs Illustrating IGA after 5000 Hours Exposure of Inconel Alloy 600 and 690 C. Rings to 10% NaOH at 3320C (630 F).
0 3 19
SCC DEPTH FOR C-RINGS (150% YS)
IN 8% NA SO 2
4 Maximum Crack. Depth,' gm Inches 1000
^
.040 80.000 ppm Na2SO4 332*C (630*F) 800 IN 600 MA 5000 Hours
~
g 600 C-rings,150% YS
.024 400
.016 IN 600 TT 200
.008 IN 690 TT UT81 i
i i
a 2
3 4
5 6
7 10 Room Temperature, pH Figure 3.3.2-3
- s AEVERSE U, BEND ESTS AT 360 C (680 F)
~
BEGINNING:OF FUEL CYCLE PRIMARY WATER Cumulative Number Cracked 10 j uAsm 100
/
8 6
~
gg 2
TTsoo O
TT 8 MA 690 -
O I
I I
I I
I END OF FUEL CYCLE PRIMARY WATER
~
Cumulative Number Cracked 10 100
^"
8
[
[
6 4
50 f
TTeoo 2-s O
/
n em. uA em_
g i
I l
i I
I I
j 0
2000 4000 6000
.8000 10,000 12,000 14,000 1
Exposure Time.(Hours)
.., o...,s,.. m,
Figure 3.3.2-4 e
1 1
l
~
3.3.2.1 CORROSION AND METALLURGICAL EVALUATION OF THE 8 RAZE 0 JOINT REGION 1.
Microstructural Characterization The objective of this phase was to determine the magnitude of any microstructural changes, to determine the level of sensitization within the brazed / heat affected zone areas, and to determine to what extent the mechanical properties of the tube / sleeve material were altered. Acceptance g
criteria for each of these issues are presented in Table 3.3.2.1-1.
Microstructural changes were evaluated by grain size measurements. Changes in
[
the brazed and heat affected -zones were campared to the unbrazed regions. Two
~
orazed joints were axially sectioned at 60* intervals and metallographically examined. Grain size measurements were taken of both the tube and sleeve in the joint areas. Representative grain size measurements are presented in
-' Table 3.3.2.1-2.
(
]b,c.e All measured grain size numbers met the
-acceptance criteria.
The level of sensitization within the brazed and heat affected zone was
- evaluated using the Reactivation Polarization tests. For these tests, a metallographically polished cross-section was passivated by maintaining the specimens potential in the passive range and then rapidly decreasing the electrode potential to the open circuit value. For no chromium depletion, the passive film remains intact; if chromium depletion is present, the passive film will. break down at tne chromium-impoverished region, causing rapid breakdown of the adjacent film. Optical microscopy examination of the polished cross-section provides a direct inteipretation of sensitization. The acceptance criterion for sensitization using the reactivation polarization
- test is based on the metallographic appearance of the polished cross-section
-after exposure. [
5 1819c/023Sc/030885:5 30 3-22 9
--s--
. - - ~.
.--.n.
3a,c,e Reactivitation polarization tests performed on brazed joints produced using Westinghouse's current heat source techniques-indicate [
3,c,e b
~
Tensile tests performed on brazed joints indicate a [
.]b,c.e Based on ASME Section IX requirements for braze process qualification, the tensile strength of a brazed joint which fails outside' of the braze must not be more than 5 percent below the specified tensile strength of the base metal in the annealed condition. Tensile tests performed on brazed ' joints at 600*F (316*C), as part of the ASME Code'
-Qualification for the Westinghouse braze process, indicated acceptable tensile strength. All Code requirements have been met.
2..
STRESS CORROSION CRACKING RESISTANCE The brazing process for the upper joint introduces microstructural changes in
. botn the mill annealed Inconel Alloy 600 tube and the newly installed sleeve.
Under isothermal conditions the corrosion an'd,5CC resistance of specific regions within the brazed' area were evaluated and compared with the extensive data base which exists for both mill annealed and thermally heated Inconel Alloys 600 and 690. Specific areas evaluated were: 1) Areas exhibiting the largest degree of grain growth, 2) areas of the original mill annealed outer
~
tube which were affected by the braze cycle and remained as the primary pressure boundary, 3) areas within the heat affected zone of the sleeve corresponding to the end of the braze alloy flow.
1819c/023Sc/030885:5 31 3-23 m.
l 1
C-rings taken from brazed joints in the specific areas noted ab,ove were exposed to [
]**C under controlled potential conditions.
Evaluation of stress corrosion cracking (SCC) behavior using conventional innersion tests usually involves prolonged test periods and often provides poor reproducibility from test to test. Electrochemical 1y controlled corrosion tests, which are designed to, allow thp metal potential to be controlled at known values, have the distinct advantages that SCC can often be initiated in days, that crack propogation rates can be increased by orders of
~
magnitude, and that reproducibility of test data is generally very good.
Controlled potential tests of a few days duration have been used to evaluate
~
the relative SCC resistance of both ad11-annealed and thermally treated Inconel Alloys 600 and 690.
The sleeve material, thermally treated Inconel Alloy 690, has been shown to
~
exhibit additional stress. corrosion cracking resistance to that of mill anealed and thermally treated Inconel Alloy 600 material when highly strained reverse U-bends were exposed to 680*F pure and primary water environments.
The stress corrosion cracking of thermally treated Inconel 690 in 4
off-chemistry secondary-side environments has been extensively investigated.
Results have continually demonstrated the additional stress corrosion cracking resistance of thermally-treated Inconel Alloy 690 compared to mill annealed and thermally treated Inconel Alloy 600 material.
Table 3.3.2.1-3 sunnarizes the results obtained for the controlled potential tests performed on C-rings cut from Inconel Alloy 600/Inconel Alloy 690 brazed joints. Results indicated no reduction in the SCC resistance of either the tube nor sleeve due to the' brazed cycle.
1819c/0235c/030885:5 32 3-24
e:
, J.f
.y
..t Table 3.3.2.1-1.
. ACCEPTANCE CRITERIA'FOR MICROSTR'UCTURE
-~ CHARACTERIZATION'0F BRAZED JOINT' AREA if,e 1
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1819c/0235c/030885:5 33 3-25'
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Table 3.3.2.1-2
SUMMARY
OF GRAIN SIZE MEASUREMENTS ASTM Specimen Axial
. Radial Grain Size Number Number Location location (*)
Tube Sleeve b,c.e
-)
e A
f s
I.
l I
I t
t t
1 1819c/0235c/030885:5 34 3-26
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l
)
. TABLE 3.3.2.1-3 RESULTS OF CONTROLLED POTENTIAL TESTING OF BRAZE 0 INCONEL ALLOY 690 SLEEVES TEST PARAMETERS a,b c e
)
t TEST RESULTS Maximum Crack C-ring Specimen Location Depth (mils) b,c.e
.1819c/0235c/030885:5 35 3-27
1
.3.3.2.2 CORROSION AND METALLURGICAL EVALUATION OF THE LOWER JOINT ~
~ All the data presented in Section 3.3.2 relative to the corrosion and stress corrosion cracking resistance of thermally treated Inconel Alloys 600 and 690 -
are applicable to the sleeve.
-The expansion processes for the lower-joint involves a combination of
- 3'
[
e Ja,c.e The stresses in the sleeve, based on tube to tubesheet data, should be as shown at 3 and C on Figure 3.3.2.2-1,'which are also judged acceptable, particular.ly in view of the corrosion resistance of the thermally treated' sleeve material. Stress levels in the outer. tube are also influenced by the expans ton techniqu'e. For an outer tube expansion produced [
l 3a,c.e Confirmation diat the residual stresses at the tube 00 surf ace caused by the expansion 'were innocuous with regard to corrosion degradation was shown by accelerated controlled potential tests.
~
l 1319c/0235c/030885:5 36 3-28
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- 0 Location and Relative Magmtude of Residual Stresses V
Induced by Expanse 3-29
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3.3.3 TEST PROGRAM FOR THE LOWER JOINT 3.3.3.1 OESCRIPTION OF LOWER JOINT TEST SPECIMENS The tube /tubesheet mockup was manufactured so that it was representative of the tube /tubesheet joint. (Figure 3.3.3.1-1) of the model 44 and 51 steam generators. The tube was then examined with a fiberscope, [
.]ac.e cleaned by swabbing, and re-examined with the 3
fiberscope. Then the preformed sleeve (Thermally Treated Inconal 600 or Thermally Treated Inconel 690) was inserted into the tube and the lower joint
- l formed.
e
[
3a.c.e t
t 3.3.
3.2 DESCRIPTION
OF VERIFICATION TESTS FOR THE LOWER JOINT
' The as fabricated specimens for' the Model 44 were tested in the sequence described below. Note that the tests of the Inconel 690 sleeve are similar to to those performed on the Inconel 600 sleeve except that the Steam Line Break (St.8) and E0P (' Extended Operation Period ) tests were not considered necessary based on previous results. As discussed in Section 3.3.1, Model 51 parameters and conditions are bounded by Model 44 parameters
- and conditions.
l.
Initial leak test: The leak rate was determined at room temperature, 3110 psi and at 6&F,1600 psi. These tests established the leak rate of the lower joint after it has been installed in the steam generator and prior to long-term o/eration.
2.
The specimens weae f atigue loaded for [
]a,c.e 3._ The specimens wert temperature cycled for [
3ac.e 1819c/0235c/030885:5 37 3-30
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- 4.. The specimens were leak tested at 3110 psi room tempera.ture ~and at 1600 psi 600*F.~
This Established the leak rate after 5 years of simulated nonnal operation (plant heatup/cooldown cycles' produced by steps 2 and 3.
Several specimens were removed from this test sequence at this point and were subjected to the E0P Test.. See Step 7, below.
5.
The. specimens were leak tested wh,ile being subjected to SLB conditions.
4 6.
The specimens were leak tested as in Step 1 to determine the post-accident igak rate.
7.
The E0P test was performed after Step 4 for three as-rolled specimens.
3.3.3.3 LEAK TEST ACCEPTANCE CRITERIA Site specific or bounding analyses have been performed to determine the allowable leakage during normal operation and the limiting postulated accident condition. The leak rate criteria that have been established are based on Technical Specifications and Regulatory requirements. Table 3.3.4.3-1 shows the leak rate criteria for the Model 51 steam generators. These criteria can 4He compared to the actual leak test results to ~ provide verification that the sleeve exhibits no leakage or slight leakage that is well within the allowable limits. Leak rate measurement is based on counting the number of drops leaking' during a 10-20 minute period. Conversion to volumetric measurement is based on assuming.19.8 drops per milliliter.
1 1819c/0235c/030885:5 38 l
3-31
+-mm-
,_.c
m-1 3.3.3.4 RESULTS OF VERIFICATION TESTS FOR LOWER JOINT The test results for the Model 44 lower joint specimens are presented in Table
'3.3.3.4-1.
These results apply to the model 51, since Model 44 conditions bound Model 51 condition:, The specimens did not leak before or during fatigue loading. After five years of simulated normal operation due to
[
e
-Ja,c.e All of the three as-rolled specimens were leak-tight during the Extended Operating Period (.EOP) test.
For the Inconel 690 sleeve tests the following were noted:
Specimens MS-2 (Inconel 690 Sleeve): Initial leak rates at all pressures and at normal operating pressure following thermal cycling were [
d ja,b,c.e Specimen MS-3 (Inconel 690 Sleeve): [
l;
}a,b,c.e I'
l Specimen MS-7 (Inconel 690 Sleeve': [
i I
ya,b,c.e 1319c/0235c/030885:5 39 3-32, 4
'3.3.4 TEST PROGRAM FOR THE BRAZED JOINT 1The major part of the test program for the braze joint consisted of showing
' that a continuous braze band was produced by the brazing process.and satisfac-tory results were obtained when the joint was tested for braze joint qualification in accordance with ASME Boiler Code,Section IX.
3.3.
4.1 DESCRIPTION
OF BRAZE 0 JOINT SPECIMENS a
The braze joints were fabricated. in the mockup shown in Figure 3.3.4.1-1.
The tubes were [
]b,c.e The sleeve was inserted into the tube and sleeving operation was performed as discussed in Section 4.0.
After ultrasonic _ testing,(UT) of the braze zone, a section of the sleeve / tube was cut for mechanical strength testing.
3.3,4.2 OESCRIPTION OF VERIFICATION TEST FOR THE BRAZE JOINT d
The ' test matrix is represented 'in Table 3.3.4.2-1.
3.3.4.3 RESULTS OF VERIFICATION TESTS OF, BRAZE JOINTS All specimens showed presence of continuous braze bands. Accordingly, 'all of the ten specimens were leaktight. Previous tests have shown that leaktight braze joints with continuous braze band remained leaktight as fatigue cycling, temperature cycling and SLB loads are imposed on them. Based on such previous experiences, these' tests were not repeated on these joints.
(_
]a.c.e These tests also bound the model 51 steam generator conditions.
1819c/0235c/030885:5 40 3-33 i
g
[
3a.c.e 3.3.5 EFFECTS OF SLEEVING ON TuSE-TO-TU8ESHEET WELD e
The effect of [
g.
_]a,b,c.e e
3.3.6
SUMMARY
OF TEST RESULTS Inconel 600_ sleeves installed in the past in accordance with the design process exhibited average leak rates of [
]C'8 whereas Inconel 690 sleeves installed by the same process had [
3 'Cd 8
under normal operating conditions after comparable testing. The leak rate exhibited by Inconel 600 sleeves was [
Ja,c.e of the allowable per sleeve leakage The leak rate for the con;inuous braze band joint is
[
3.a.C,e In general, the average leak rate for lower -joints was unaffected by thermal and fatigue cycling. Strengths of both lower and braze joints had values exceeding any loading that is expected to occur during the steam generator operation.
1819c/0235c/030885:5 41 3-34 o
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TA8LE 3.3.3.3-1.-
'ALLOWA8LE LEAK RATES FOR !
^
TYPICAL-MODEL-51 STEAM GEftERATORS (hormal Operation).
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TA8LE 3.3.4.2-1
+-
TEST MATRIX FOR BRAZE JOINT
?
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~ iTABLE 3.4.41. JrtrarA>on nrear statss mtwstTv tvewarten p a c,e u iv e.'. 4 4, e i. 7 s i e f 5' g S' l ,y l * ..4 s' l i < Y hf d 9 1 7. + ~ b r r. l.- i< I. + [ r A - y , d I: . e.. 4 .s* L b I .9 m n,27 \\ p. 4. ) p I. l'I t. ~ f -. l. .3 U ' 1 -(. 6 (' ' f,1 2-/~ ~ [-~.: /; .+ L. - < - i... m _... _._._. + ~ g- ,1 .t h t E,i * - TABLE :3.4.4 a. CRTTERfA roR paixapy $7,g3 ys.q,, g y. (TUEE F a,c,e . x cs 1 k 4 s.' G f P' f d.- t i.'- s . j e ?' a i + '%,~ e A s I , h k ). ' Wh ' f 3.. g r,. - i ? l 'p L $,3 e,. 1. 4 k 3 's.; 3
- Air
,, t t -3 i in ; h+ 's j l~ t 3 - s 'F,.' e N b O+. b -a j ~ '; U. ,,s'"g r 9 -k u 9 I ,( . 9 S .) T 9 Y Y' p. Q
- G,-
.i =c 6-s -t - t e 6 A g .. L' ( g I 4 .g .m, 4 - s _ ,a 9- ..f ~ ' g' 1, p g N'-(.. i '_4;l ~ <y N 6 t y. 3-55 1 .c.- an < .m --JJ 5 T 7 e 4-p,,p ' I . I s TABLE 3.4.5-1 ' OPERATING CON 0!TIONS NO. OF OCCURRENCES , CONDITION TO SE ANTICIPATED NORMAL OPERATING CONDITIONS Plant.Heatup-200 Plant Cooldown 200 Plant Loading 5: Minute 18,300 Plant Unloading 55 Minute 18,300 Small Step Lead increase 2,000 Small Step Load Decrease 2,000 Large Step Lead Decrease 200 Hot Standby Operations 18.300 Turbine Roll Test ' 10 ' Steady State Fluctuations = 4 UPSET CONDITIONS Loss of Lead 80 Loss of Power 40 3; Loss of Flow ' 80 Reactor Trip from' Full Power 400 FAULTED CONDITIONS Reactor Coolant Pipe Break i Steam Line Break 1 Feed Line Break I -TEST CONDITIONS Primary Side Hydrostatic _ Test 5 Secondary Side _ Hydrostatic Test 5 3-56 wr w-m n me p ) TABLE 3.4.7.1-1 4 UMBRELLA PRESSURE LOADS FOR DESIGN, UPSET, FAULTED, AND TEST CONDTIONS o a,c.e CONDITIONS .). Design Design ~ Primary ~ Design Secondary Upset loss of Load Loss of Power Loss of Flow Reactor Trip from Full Power F"aul ted Reactor Coolant P,1pe Break Steam Line Break Test . Primary Side Hydrostatic Test Secondary Side Hydrostatic Test 1 i I i 3-57 i. ~ TABLE 3.4.7.1-2 RESULTS OF PRIMAR't STRESS INTENSITY' EVALUATIONS PRIMARY MEMBRANE STRESS INTENSITY p, CALCULATED HAXIMUM ALLOWABLE OF' STRESS STRESS RATIO INTENSITY. INTENSITY, CALCULATED S.I. LOCATION CONDITIONS KSI KSI ALLOWABLE S.I. TUBE INTACT a,c,e U e e 9 e 4 9 m e a 0 - 'y .4 ~ TABLE 3.4.7.1-3 REfutTS OF PRIMARY STRESS INTENSITY EVALUATIONS PRIMARY MEMBRANE'PLUS BENDING STRESS INTENSITY, P,+ Pb CALCULATED MAXIMUM ALLOWABLE 0F STRESS STRESS RATIO INTENSITY, INTENSITY, CALCULATED S.I. LOCATION CONDITIONS KSI KSI ., ALLOWABLE S.I. TUBE INTACT a,c,e 9 9 9 + d e m 4 9 g ) eW ,u* N e 9 G e K M E I >_= 4 M 2 f
- st
= 5 s _S My b N q k N C T a O w 'E w .a G 4 W 4 3 x >= w w E w 8 e M 8 m W E t-W M 4 M C M w e e U Ch. .e 4 e O 9 3-60 6 s s ' 'e TABLE 3.4.7.2 Cont) ( PRESSURE AND TE WERATURE LOADINGS FOR MAXIMim RANGE'- 0F STRESS INTENSITY AND FATIGUE EVALUATIONS' a,C,e i l i e 49 'l e I ? 1 i i 4 ] 7 e g 88 U. 4 e G S 5 ~ b5 W=w >= m. .Ew '4 5 E. N Y a : to
- N w
E h 44 T .m mI I e. M .E B m e j m M a e e e. 4 [ 9 3-62 _m._. u.. h TABLE 3.4.7.3-1 RESULTS OF FATIGUE EVALUATION CUMULATIVE USAGE ALLOWABLE USAGE FACTOR -LOCATION-FACTOR TUBE INTACT a,c.e 1.0 1.0 D 1.0 e e 1.0 e 4 } I ~ 4h o. h e 9 3 3.5 SPECIAL CONSIDERATIONS I ' 3.5.1 FLOW SLOT HOURGLASSING Along the tube-lane, the tube support plate has several long rectangular flow slots ' t'. t: have the potential to defona into an " hourglass" shape with significant denting. The effect of flow-slot heurgleit.ing is to mye the neighboring tubes laterally inward to the tube lane from their initial positions. - The maximum bending would occur on the innermost row of tubes in the center of the flow slots. The following discussion considers the effects ^ of flow slot hourglassing on'the sleeved tube. 3.5.1.1 EFFECT ON BURST STRENGTH The effect of bending stresses on the burst strength of tubing has been studied.- Both the axial and circunferential crack configurations were investigated,. [ 3a,e f. 3.5.1.2 EFFECT ON STRESS CORROSION CRACKING (SCC)' MARGIN Based on the results.cf the caustic corrosion test program on : nill-annealed tubing, the bending stress magnitude due to flow-slot hourglassing is judged to have only a small effect, if any, on the, SCC resistance margins. Two long term moddlar model boiler tests have been conducted to address the effect of bending stresses on SCC. No SCC or IGA was detected by destructive examination. It -is to be noted that thermally treated Inconel 600 and Inconel ) 690 have additional SCC resistance compared to mill annealed Inconel 600 t ' tubing. 3.5.1.3 EFFECT ON FATIGUE USAGE - In addition _to the above two considerations, one should also consider the effect of the hourglassing-induced bending stresses on the fatigue usage factor of the sleeve. This is included in the fatigue analysis by recognizing that the stress induced by this motion is a mean stress. Mean stress effects 1319c/0235c/030885:5 55 3-64 7- y are included in the S-N fatigue curve used in the analysis, hence hourglassing induced bending stresses are included in the fatigue ^ analysis. 3.5.2 TUBE VIBRATION AhALYSIS Analytical = assessments have been performed to predict modal natural frequencies and related dynamic pending stresses attributed to flow-induced vibration for sleeved tubes. The pu,rpose of,the assessment was to evaluate the effect on the natural frequencies, amplitude of vibration, and bending [ stress due to installation c* <arious lengths of sleeves. I Since the level of stress is significantly below the endurance' limit for the ~ { tube material and higher natural frequencies result from the use of a j sleeve / tube versus an unsleeved-tube, the sleeving modification does n,ot contribute to cyclic fatigue. 3.5.3 SLUOGE HEIGHT THERMAL EFFECTS In general, with at least 2.0 inches of sludge, the tubesheet is isothermal at the bulk temperature of-the primary fluid. The net effect of the sludge is to reduce tube /tubesneet thermal effects. 3.5.4 ALLOWABLE SLEEVE OEGRADATION Minimum required sleeve wall thickness, 't, to sustain normal and accident r condition loads are calculated in accordance with the guidelines of' Regulatory c Guide 1.121, as outlined in Table 3.5.4-1. In this evaluation, the surrounding tube is. assumed td be completely degraded; that is, no design credit is taken for the residual strength of,the tube. The sleeve material may be either thermally treated Inconel 600 or thermally treated Inconel 690. It has been shown that the properties of Inconel 600 are very similar to those of Inconel 690. In particular, the yield strength and ultimate' strength are very similar. 1819c/0235c/030885:5 56 3-65 9 . The properties of'I-600 were used in these analyses because the, data ' base for I-600 is larger. than the-data base for I-690, thus allowing the use of a smaller tolerance factor. f 3 J 8 o I L I ( e i l 1819c/0235c/030885:S_57 3 66 i 1 I -4 w~_ g ,y-- nw-, w i Table 3.5.4-1 REGULATORY GUIDE 1.121. CRITERIA 1.- Normal Operation Determine t, mininum required sleeve wall thickness. r a. Yield 1 Criterion: S 1 39.59 ksi' y . Loading: .P, = 2213 psia Ps = 636 psia. _AP = 1577 psi AP. R +P)=[ ] inch a,c,e Hence, tr*5 - 0.5 P Y-p s whichis[35]a,c.e percent of the nominal wall thickness (of 0.039 inches]a,ce 3 L - b. Ultimate Criterion: 'Su1 90.58 ksi Loading: P, = 2213 psia P = 636 psia AP = 1577 psi 3 6P. R Hence, tr*5
- b-
] inch a,c.e [-0.5(P +P)' p s / -which is [- ] a,c.e. percent of the nominal wall thickness [ 3a,c.e, t .2.. Accident Condition Loadings .a. LOCA + SSE The major contribution of LOCA and SSE loads is the bending stresses at the top tube support-plate due to a combination of the support motion, inertial loadings, and the pressure differential across the tabe U-bend resulting from the rarefraction wave during LOCA. Since the sleeve is located below the first support, the LOCA + SSE
- ~-
1819c/023k/030885:5 58 3-67 m: I e v 4 w - ye -4 ,---g-a w,,. w w Table 3.5.4-1 (cont.) bending stresses in the sleeve are quite small. The governing event for. the sleeve therefore is a postulated secondary side blowdown. b. FLB + SSE The maximum primary-to-secondary presquee differential occurs during i a postulated feedline break (FLB) accident. Again, because of the sleeve location, the SSE bending. stresses are small. Thus, the governing stresses for the minimum wall thickness requirement are the pressure membrane stresses. Criterion: P,< smaller of 0.75 or 2.45,i.e. 63.41 ksi u Lloadings: P, = 2650 psia P3=0 aP = 2650 psi aP R Hence,-tp = M - 0.5 P, + Fy * [ ] 4 3: Leak-Before-Break verification The leak before break evaluation for the sletve is based on leak rate and burst pressure test data obtained on [ -]a.c cracked tubing with various amounts of unifonn, thinning simulated by machining on the tube 00. The margins to burst during a-postulated SLB ( Steamline Break Accident ) condition are a function of the mean radius to thickness
- ratio, based on a maximum pemissible leak rate 'of 0.35 gpm due to a nonnal operating pressure differential of 1500 pH.
l - 1819c/0235c/030885:5 59 3-58 n.- , ~ - - -a a< -) -Table 3.5.4-1 (cont.) A 25 percent margin exists between the burst crack length and th'e leak crack length. This margin was identified using a nean radius to ~ thickness.factorof[ Ja,c for the nominal sleeve, the' current Technical ~ Specifications allowable' leak rate of 0.35 gpm, a SLB pressure differential of 2560 psi, and the nominal leak and nominal burst curves. For a sleeve thinned 54 perdent through wall over a 1.0 inch axiaf 1 length, a 17 percent margin to burst is hemonstrated. Thus the leak-before break behavior is confirmed for unthinned and thinned conditions. 1 d 9 .. I T 1819c/0235c/030885:5 60 3-69 p 3 3.5.5 EFFECT OF TU8ESHEET/ SUPPORT PLATE INTERACTION Since the pressure is normally higher on the primary side of the tubesheat than on the secondary side, the tubesheet normally becomes concave upward. Under this condition, the tubes protruding from the top of the tubesheet will rotate from the vertical. This rotation depends on the boundary condition assumed for the edge of the tubesheet. Previous calculations 'of the tubesheet deflection, using a finite element model of the tubesheet which includes the i effects of the adjacent channel head an'd the stub barrel, resulted in a plot that is in agreement with the theoretical deflection formula for circular ~ plates with fixed edges, provided that the shear deflection is included. Calculations showed 'that [ ]C This stress was added to the cyclic etress in the fatigue evaluation. Note that this stress can be eatioed to account for different ap's that occur in different events. However, the seismic stress, as shown abcVe, is not ~ critical to the fatigue usage which was found to be low.
- 3. 5.,6 COMPREHENSIVE CYCLIC TESTING 8
The Comprehensive Cyclic Test was designed to simulate the loadings produced by the hestup/cooldown and load / unload transients on the upper tuce-to-sleeve joint. _ This test was initially intended to be used in conjunction with the Axial' Shear Fatigue Test (a 5,000 cycle fatigue test) to evaluate the sealing integrity of the tube-to-sleeve joint after the application of c/clic loadings. They also would provide experimental confirmation of the capability of. the joints to withstand fatigue loadings. Based on analytical comparisons, the fatigue test produced fatigue that was substantially greater then that which would have been produced in the Comprehensive Cyclic Test. Also, the fatigue test produced more fatigue than was calculated to ~ occur due to the inservice transient conditions. Therefore, it was determined that the Comprehensive Cyclic Test 'was not needed in addition to the fatigue test in determining the fatigue integrity of the tube-to-sleeve joint. 1819c/0235c/030885:5 51 3 70 ~ / s. 3.5.7 EVALUATION OF OPERATION WITH FLOW EFFECTS OUE TO SLEEV,ING ~ An ECCS perfomance analysis considering 5 oercent uniform steam generator tube plugging, SGTP, has been completed for the forthcoming Westinghouse fuel reload of the Prairie Island Units. This safety analysis assumed up to 5 i percent tube plugging in the steam generators of either plant and took credit for the current 2.28 value of total core peaking factor. This study and the corresponding 'non-LOCA study are considered applicable for the steam generator sleeving program as regards Westinghouse-supplied fuel. The accidents evaluated include LOCA and non-LOCA transients as well as consideratico of the effects on the nuclear design and thermal-hydraulic performance with the existing plant reactvr internals. For the accidents considered in that study, the core and system parameters either remained within their proper limits (i.e., peak clad tempergture, ONBR, RCS pressure, etc.) or the impact of the additional tube plugoing was shown to be negligibly small. Inserting a sleeve into,a steam generator tube results in a reduction of primary coolant flow. The selected sleeving program at Prairie Island involves the 36 inch long sleeve. For a 36 inch sleeve located on the hot-leg si.de, the primary coolant flow loss per tube is'approximataly equal to 3.0 - percent of normal flow. - This reduction in primary coolant flow equates to a . hydraulic equivalency ratio of 33 sleeves to one plugged tube. f-Using this ratio in conjunction with the, existing tube plugging level, the follcwing tables are established for the maximum possible number of sleeves (1,946 sleeves per steam generator). Note that 1,946 sleeves are equivalent - to 60 plugs, or 1.8 percent plugging. ^ e [ ^' g 1819c/023Sc/030885:5 62 3-71 _____l._____----.__---- I Prairie Island Unit 1 ~ S/G 1 S/G 2 Maximun number of tubes to be sleeved 1,946 (57 percent) 1,946 (57 percent) Equivalent Plugged Tubes 60 (1.8 percent) 60 (1.8 percent) Existing Plugged Tubes 43 (1.3 percent) 18 (0.5 percent) ~ total Equivalent Plugged Tubes 103 (3.1 percent) 78 (2.3 percent) Prairie Island Unit 2 SIG 1 S/G 2 Maximun number of tubes to be sleeved 1,946 (57 percent) 1,946 (57 percent) Equivalent Plugged Tubes, 60 (1.8 percent) 60 (1.8 percent) Existing Plugged Tubes 46 (1.4 percent) 95 (2.8 percent) (as.ofOctober,1984) Tptal Equivalent Plugged Tubes 106 (3.' percent) 155 (4.6 percent) For the steam generators in either of the Prairie Island Units, 5 percer.t of the total tubes (3388 tubes per S/G) equals 169 tubes plugged in any one steam generator. The ECCS analysis model is such that a uniform steam generator ttbe plugging condition is modeled. The NRC staff has required that the LOCA ar.31ysis of a plant with steam generator tube
- plugging model the maximun tube plugging level present in any of the plant steam generators.
For the conditions presented above for Prairie Islano 1, the limiting equivalent. plugged tube condition in the two stest, generators is 103 tubes, which provides ma-gin of 66 tubes (169 minus 103) available for additional plugging (or any equivalent combination of sleeves and plugs) before exceeding the basis of the LOCA analysis with 5 percent SGTP. With a smaller number of 1819c/0235c/030885:5 63 3 72 - -i mummm e sleeves, the margin of tubes available for additional plugging would be larger. With c.ily 500 sleeves per steam generator,110 tubes (169 minus 59) ~ ~ would be available for additional plugging. For Prairie Island Unit 2, the limiting equivalent plugged tube condition th the two stema generators is 155 tubes, which provides margin of 14 tubes (109 ) minus 155) available for additional plugging (or any equivalent combination of sleeve; and plugs) before exceeding the basis. of the LOCA analysis with 5 percent SGTP. With only 500 sleeves per steam generator, 49 tubes (169 minus ? 111) would be available for additional p' lugging. Accordingly, no ECCS results more adverse than those in the existing Westinghouse fuel safety analysis are l anticipated for equivalent tube plugging projected to occur at the Prairie l -Island Units with up to 1,946 sleeves per steam generator, given that the existing vessel internals remain in place. l l )' The effect of sleeving on the non-LOCA transient analyses has been reviewed. { Analyses of the level'of. sleeving and plugging discussed in this report have shown that the Reactor Coolant System flow rate will not be less than the Thermal Design Flow rate. The Thermal Design Flow rate is that which is assumed in the non-LOCA. safety analyses and is designed to be less than the minimum RCS flow rate that could occur under normal or degraded conditions- .Since the reduced RCS flow rate is not less than the assumed flow rate (Thermal Design Flow), the non-LOCA safety analyses are not adversely impacted - by this anticipated maximum amount of steam generator tube sleeving (1,946 sleeves per steam generator). Any smaller number of sleeves would have less of an.effect.. The reduced RCS flow rate is within the bounds of the Safety Analysis Report for non-LOCA transient analyses and causes no safety concerns. In addition, as a result'of tube plugging arid, sleeving, prin'ary side fluid l velocities in the steam ge'narator tubes will increase. The effect of this velocity' increase on the sleeve and tube has been evaluated assuming a conservctive limiting conditio7 in which 10 percent of the tubes are plugged. As a reference, normal flow velocity through a tube is approximately 21.6 ft/sec, for the unplugged condition. With 10 percent of the tubes plugged, } the fluid velocity through an unplugged tube is 23.5 ft/sec., and for a tube { with; a sleeve, the local fluid velocity in the sleeve region is estimated at 31.5 ft/sec. This velocity increase causes no safety concerns. L I 1819c/0235c/030885:5 64 3-73 ~ ~ ~ ~ ~ ~ ~ ~ ~ ' ~ ~ ~ ~ ' j 3.5.8 ALTERNATE SLEEVE MATERIALS As was mentioned above in Section 3.4.3, Inconel as a sleeve material is covered by the ASME Code Case N-20. The design stress intensity value S, for both materials 1690 and I600 covered by the Case N-20 is identical (S, - 26.6 ksi). Therefore, for these materials, Primary Stress Intensity and Maximm Range of Stress ' Intensity allowables are similar. Only pressure stresses were considered when calculating Primary Stress Intensity. The i maximm Primary Membrane Stress Intensity was f[mnd at the analysis section on the straight portion of the tube. Hence, the ratto " Calculated Maximum ~ Pritury Membrane Stress Intensity / Allowable Stress Intensity" which was critical for the minimum sleeve thickness of [ 3a,c.e does not depend upon the sleeve material (Inconel 690 or Inconel 600). Thermal stress, and hence maximum range of stress intensity and fatigue usage factor, could depend upon the mechanical properties of the sleeve material. The a dulus of elasticity of Inconel 600 is higher than that of Inconel 690 by about -7 percent. However, the coefficient of thermal expansion of Inconel 690 is higher than that of Incone'l 600. Past analytical experience indicates that the e-mismatch between I690 and IS00 as the sleeve material increase thermal stre,sses. Therefore, the results of the Maximum Range of Stress Intensity and Fatigue Evaluations for the sleeve and tube assembly with 1690 as the s,leeve material are conservative relative to those which would be calculated with 1600 as a sleeve material. 1819c/0235c/030885:5 65 3-74 3. 4.0 PROCESS DESCRIPTION ~ The sleeve installation consists of a series of steps starting with tube end preparation (if required) and progressing through sleeve insertion, hydraulic expansion at both the upper and lower joints hard roll joining of the lower i -joint, brazing of the upper joint and joint inspection. The sleeving sequence "is outlined in Table '4.0-1. All.these steps are described in the following sections.. 4.1 TUBE PREPARATION There are two steps involved in preparing the steam generator tubes for the sleeving operation. These consist of light rolling (as required) at the tube end and tube honing. -
- 4.1.1 TUBE END ROLLING (CONTINGENCY).
If gaging or. tube inside diameter measurements indicate a need for tube end rolling to provide a uniform tube opening for sleeve insertion, a light mechanical rolling operation will be performed. This is sufficient to prepare the mouth of the tube for sleeve insertion without adversely affecting the -
- original tube hard roll or the tube-to-tubesheet weld. Tube end rolling will be-performed only as a contingency.
' Testini of similar lower. joint configurations in model 27 steam generator sleeving programs at a much higher torque showed no effect on the tube-to-tubesheet weld. Because the radial forces transmitted to the tube-to-tubesheet weld would b'e much lower for a larger model 51 sleeve than for the tuove test configuration no effect dn,the weld as a result of the light roll is expected. ~ IS19c/0235c/030885:5 66 4-1 b_. , +. ...,..... - -.. = ~. -...-.- 3.7,, 1 t.;:. .t - w... e f TABLE 4.0-1~ .v ' SLEEVE-PROCESS SEQUEleCE SLN WtY-7 c. ]-' 4 !I, ' s ~ a,c.e - ...c. 4 7 s 4 - a." l'. _ s.. - - j / ,hm.'., -3 W m 95? ,f}* xy. x ..I 2 1-; 7.* ', r n.,E . [ j t f ,,. ?l' ,v.., ' s -1 _ {.:- e-
- r... ' _
d &.q, . a -; .g .,4.. .-,n-- - y
- v.
1 l, ~ g -..l A I s. ,s. 4 l .:q:. 1 l ) J b-a. n .g : s. _.",. ; -.- i r b 4' ) ..~ p 11819c/0235c/030885:5-67 4-2 i
- jvJ.-
t ,g, J ] 4 9 9 f 1 ? g, e-WN ,>,7-
- f- '
-.g'g.-<,*-t -t,.,, -e L 1 4.1.2 TUBE HONING The sleeving process includes honing the 10 area of tubes to be sleeved to prepare the' tube surface for the upper brazed joint and 'the lower joint by removing loose oxide and foreign material. Honing also reduces the radioactive shine from the tube bundle, thus contributing to reducing man-rem exposure. -1 a Tube honing may be accomplished by either wet or dry methods. Both processes have been shown to provide tube inside diameter surfaces compatible with j brazed and mechanical joint installation. The.. selection of the honing process used is dependent primarily on' the installation technique utilized, the scale of the sleeving operation (small scale vs. large scale sleeving), and the customers site specific.tecnnical requirements. Evaluation has demonstrated that neither of these processes remove any significant fraction of the tube . wall base material. 4.1.2.1 WET HONING Tube honing will be-performed using a [ 4 3a,c.e A limit switch is included in the system design that will prevent the insertion drive from reversing' direction until the desired length of the tube has been honed. A waste handling system may be used to collect the [ ],8'C the s. hone debris, and the oxide removed from the tube 10. [ Ja,c,e There may also he an inlet to the 1819c/0235c/030885:5 68 4-3 3 suction punp which subsequently punps the debris and water directly to the' plant waste disposal system. 4.1.2.2 ORY HONING The dry hone process is similar to the wet hone process with the notable exception that the water jet and the atten>! ant systens needed to handle the effluent are omitted. The dry hone process is Aypically more applicable to . hands-.on (manual) or small scale sleeving operations. In order to remove. loose oxide debris produced by the dry honing operation, the tube interior is twabbed utilizing a fluid (typically deionized water or ~ isopropyl alcohol-) soaked felt pad to an elevation slightly less than the honed length, but above the top of the installed sleeve. 4.1.3 -. FIBEROPTIC -INSPECTION (CONTINGENCY) As a contingency option to spot check that tube ID surfaces have been honed, a fiberscope inspection may be performed on some of the tubes to be sleeved. Tubes to be fiberscope inspected would be selected randomly throughout thet actual honing process.. This fiberscope inspection would be accomplished prior ^ to sleeve insertion.. 4.2 St.EEVE INSERTION ANO EXPANSION . The process of sleeving the tubes is carried out using remotely operated equipment. The following paragraphs describe the insertion of the sleeves and mandrels and the hydraulic-expansion of the sleeves at both the upper and lower joint locations. The Westinghouse supplied sleeves are provided complete with braze ring pre-installed and flux pre-applied over ge braze area. . The sleeves are fabricated under controlled conditions, serialized, ma:hined, cleaned, and inspected.. They are typically placed in plastic bags, and packaged in protective styrofoam trays inside mod boxes. Upon receipt at the 1819c/0235c/030885:5 69 i site, the boxed sleeves are moved to a low radiation, controlled ~ region near the steam generator. Here the sealed sleeve box is dpened and the sleeve removed, inspected and installed on the expansion mandrel. Note that the - sleeve packaging specific, Mon is extremely stringent and, if left unopened, the sleeve package is suitable for long term storage. I The mandrei is connected to the h.igh pressure fluid source, e.g., Haskel Expansion Unit (HEU), via high pressu,re flexible stainless tubing. The delivery system is manipulated to locate the guide tube attached to it near the manway. The mandrel / sleeve assembly 'is then inserted into the guide tube. After the delivery system positions the sleeve upper end below the tube to'be restored, [ 't ]a,c.e The delivery system is manipulated to locate the guide. tube near the manway for, mandrel withdrawal / inspection and loading
- of the next sleeve / mandrel assembly. This process is repeated until all sleeves are installed and hydraulically expanded.
o In the event that a sleeve becomes jammed after only partial insertion, contingency methods and tooling are used to temove the jammed sleeve. The - tube will then be dispositioned by way of a non-conformance report after considering the appropriate input. 1819c/0235c/030885:5 70 4-5 WESTINGHOUSE PROPRIETARY CLASS 2 4.3 LOWER JOINT SEAL At the primary face of the tubesheet, the sleeve is joined to the tube by a ( ,3a,c.e The contact forces between the sleeve and, tube due to the initial hydraulic ~ - expansion are sufficient to keen the sleeve from rotatino during the [ 3,a,c.e The appropriate extent of [
- 3a,c.e
.C Ja.c.e This process is repeated until all installed sleeve lower. ends are [ ] 1819c/0235c/030885:5 71 4-6 r 3 = = ~4.4 BRAZE JOINT PROCESS After the sleeves have been [ ]a,c,e at the lower sleeve ends, the upper joints are brazed as discussed below, e 4.4.1 BRAZING MATERIAL 3_ The' brazing material is a noble metal, alloy of [ ].ac.e A gold-based filler metal was chosen to produce a strong joint with high resistance to corrosion,* good ductility, and compatibility with Inconel 600 or 690 sleeves and the Inconel 600 base material of the tube. The liquidus and solidus temperature of the braze are [ ]a,c.e The filler metal is fabricated into a [ l ja,c.e 4.4.2 FLUX APPLICATION. A flux is applied to the sleeve in the sleeve assembly process. The flux is used as a. wetting agent to facilitate braze flow and as a protective agent for
i ja,c.e .4.4.3 BRAZING OPERATION The brazing operation consists' of the following steps. 1.- Insertion The braze heater is inserted into the installed sleeve in the same manner as described for Mandrel / Sleeve Loading with the remote delivery system. (Reference Section 4.2.) [ 1819c/0235c/030885:5 72 4-7 c 1. g 3-r t ja,c.e ~ 4.5 SLEEVE INSPECTION 4.5.1 PROCESS SAMPLING PLAN ' In order'to verify: the. final sleeve instal 5ation, an eddy current inspection will be performed on all sleeved tubes to verify that all sleeves received the required hydraulic and roll expansions. The basic process check on 100 percent of the sleeved tubes will be: l' Verify ' lower hydraulic ' expansion average diameter ~ 2. Verify lower roll and location w'ithin the lower hydraulic expansion and average. diameter -3. Verify upper hydrauli expansion average diameter ~ 1819c/023Sc'/030885:S 73 4~8 me W ~ l 'q v-Tubes not satisfying the basic process-check criteria will be,dispositioned on an individual tube basis. lIn order to nonitor the sleeving process after each operation from each lot, eddy current data on a percentage of the sleeves will be performed to obtain. sleeve ~ ID data.~- As confidence is gained that the sleeving process is proceeding as anticipated, the lot sizes will-be increased and percentages reduced. These average diameters will be eval,uated versus the expected tolerances established through the design requirements, laboratory testing results,' and' previous experience. This evaluation will determine whether or - not the equipment / tooling is perfonning satisfactorily. If process data is - determined to be outside of expected ranges, further analysis will be ~ performed. If required, Diatest may be used in lieu of eddy current to perform sleeve ~ installation acceptance and in-process monitoring evaluations. Undersized . diameters will be corrected by.an additional expansion step to produce the desired degree of expension. Oversized diameters will be dispositioned by a specific evaluation process on an individual tube basis. If it is necessary to remove a sleeved tube from service as judged by.an evaluation of a spe,cific sleeve / tube, configuration, tooling and processes will .be available to plug the sleeve or the lower portion of the sleeve will be removed and the tube will be plugged. y .e~~ As mentioned previously, the basic process dimensional verification will be completed and evaluated for 100 percent of all installed sleeves. 4.5.2 ULTRAS 0dIC. INSPECTION The final stage of the brazing operation is the inspection of the braze joint for continuity. This ~is performed with an ultrasonic technique described in Section 7.0 of this report. This insp'ction is performed.to confirm the. leaktightness and structural integrity. of the brazed joint between the sleeve and the steam generator. tube. 1819c/0235c/030885:5'74 4,9 ~ h s 1 t: I e The UT and effector is inserted into the sleeve in the same mannsr'as described for Mandrel / Sleeve Insertion with the delivery system. (Reference Section 4.2.) The linear translation and rotational motion of the ultrasonic. probe.is controlled with equipment located in a remote low radiation area. A typical UT trace from a braze joint is shown in Figure 4.5.2-1. T '4.6 ESTA81.ISMENT OF SLEEVE JOINT MAI,N FA8RICATION PARAMETERS '4.6.1 LOWER JOINT e The main parameter for fabrication of acceptable lower joints is sleeve [ ].a,c.e 3),,,,g ya.c.e is a function of the [ 3.a.c.e Accordingly, rolling torque was varied to . achieve the desired sleeve [ ]C in the orioinal Model 44-program (also applicanle to the andel 51). [ ,]C was achieved was used throughout the program verification testing. 4.6:2 UPPER JOINT The upper brazed joint parameters were defined by the need to arrive at a leak [ tight, mechanically acceptable joint. These parameters are divided into-2 areas as follows. Theutilizationofa[- .]C heat source has eliminated bulky equipment and time consuming complicated control system handling, resulting in . higher production efficiency and'better braze process control. [ 3a,c.e The specific brazing parameters (heatup, holdtime, etc.) are recorded in the l Brazing process Specification. 1 4 1819c/0235c/030885:5 75 4-10 e -e -v ) i [ a,c.e 6 a 1 A r 1819c/0235c/030885:5 76 '4-11 t j 122s4 2 3 a.c.e f d Figure 4.5.21. A Typical UT Inspection Trace of a Braze Joint 4 12 0 g y u 5.0, SLEEVE / TOOLING POSITIONING TECHNIQUE. 5.1 REMOTELY OPERATED SERVICE ARM.(ROSA) -ROSA is a general purpose six axes all-electric computer-controlled robot used for nuclear service work. Its function is.to serve as a remotely controlled. tool positioner and thereby reduce worker radiation exposure. The major ROSA system components include the mechanical arm with a servo controller and the supervisory computer control console contained within a trailer located .outside containment. The operator issues. commands to the supervisory computer through the control console and keyboard. The supervisory computer interprets these commands.and calculates the desired angulae positions for each axis of the mechanical ann. These desired angular' positions are then sent to the servo controller. 'The servo controller drives each axis to its desired position, and sends status information-back to the supervisory computer. This cycle -is continuously ' xecuted at a high rate of speed, providing smooth and e -controlled motions. One application of ROSA is its use as a "No Entry" tool positioner for primary side -steam generator operations. The term "No Entry" signifies that ROSA installation / removal, tool. changing, and tool. operations are performed without -.any personnel passi,ng through the plane of the manway's outer surface. 1 ROSA is loaded into the channel head by use of a ramp loading fixture mounted to the manway flange. The tool end of ROSA is clamped to this fixture. Through a combination of ROSA movements and linear movements of the loading fixture, ROSA is loaded into the channel head such that its base end and four i hydraulic camlocks end up approximately 2 inches below the tubesheet. From there,'a joystick controller in the coptrol trailer is used to drive the These camlock' are then pressurized to 750 camlocks up and into the tubes. s psi, generating the necessary frictional holdi,ng force to secure ROSA to the 'tubesheet. The tool end of ROSA is then unclamped from the loading fixture. With the base end of ROSA secured to the tubesheet, ROSA is programmed to reach out through the manway such that tools can be manually installed or 5-1 1819c/0235c/030885:S 77 1 removed. ROSA is then programmed to pull the tool in through..the manway ~nd a up to =the tubesheet. The ROSA computer is initialized with the mounting location of the base (row . and column) and with the tool being used. The operator can then enter row and column commands through a. keyboard and ROSA will automatically position the . tool underneath the desired tube.,LThe tubesheet is divided into regions which .are used by the computer to generate a tool pa,th from the present location of the tool to its destination tube. Although-the computer maintains the tool's-row and column position its actual row and column position is still verified every6 hour. Tools which are positioned by ROSA include:
- 1) -Eddy Current Tool
- 2) Mechanical Plugging Tool-
- 3) Lower Hardrolling Tool
- 4) Sleeving Adapter Tool -
used for honing, swabbing, fiberscoping, sleeve insertion, expansion, brazing and ultrasonic testing e s -All these tools are, controlled from inside containment,. independently from ROSA. ROSA is programmed to move the sTeeving adapter tool to a. location over the anway so th4t there is an assembly wi,ndow above the unway to change out the various tools which it can position. The tools typically have low light level cameras or fiberscopes mounted on them. These cameras or fibersc' opes are used to help verify exact positioning of the^ tool under the desired tube, toiveriff that sleeves, hardrollers, braze heaters, UT probes, etc., 'are fully thserted (contacting the tube end) before initiating their operations and to assist in determining the tooling performan:e. ~ The three axis joystick controller can be used to make minor position and orientation adjustments of the tool so that it is correctly } aligned with the tube. ~ 1819c/0235c/030885:5 78 t v r_ I s 5.2, ALTERNATE POSITIONING TECHNIQUES Under some conditions, positioning of sleeves / tooling with the base R0iA robotic system may not be practical. In these circumstances, an, alter late positioning technique may be utilized. These alternate techniques m;y include alternate robotic or semi-remotely-operated equipment, hands-on (manual) positioning and installation, or the combination of two or. more tooling subsystems into one larger tooling system. 4 Note that with all positioning techniques, the processes actually used to install ~ the sleeves [ ]C will not be changed due to the use of an alternate ~ sleeve / tooling positioning technique. It is the processes to which the sleeves are subjected that are critical to their successful installation; the technique used to position the sleeves and tooling is not critical so long as it does not affect the sleeve installation processes. e r i i i n i 1819c/0235c/030885:5 79 5-3 1 ' r 6.0 NOE INSPECTABILITY ' The NOE development effort has concentrated en two aspects of the brazed sleeve. ~ First, consideration was given to a method of verifying,that the upper and lower joints meet the design requirements. Second, tne tube / sleeve assembly must be capable of being evaluated through subsequent routine in-service inspection. In both of these efforts it has been necessary to rely as much as possible on existing technology for the inspection process. The technologies that are being addressed are ultrasonic and eddy current for the routine inspection. 6.1 ULTRASONIC BRAZE INSPECTION ~ 6.1.' IINCIPLE OF OPERATION The ultrasonic inspection of the brazed joint is based on the idea that an r acceptable brazed joint will transmit essentially all the ultrasonic energy incident upon it. On the other hand, an inadequate brazed joint will reflect - some of the energy incident upon it. 4 -]'C An ultrasonic wave is launched by the appils;ation of a pulse to a piezoelectric transducer. The wave propagates in the couplant medium (water) un,til it strikes the sleeve. Ultrasonic energy is both . transmitted and reflected at the boundary. The reflected wave returns to the transducer where it is converted back to an electrical signal which.is amplified and displayed on an oscilloscope. The transmitted wave propagates r in the sleeve until it reaches the outside surface of the sleeve. If brazing material is present,. the wave propagat9s through the joint into the tube. When the wave reaches the outside of the tube,'it is reflected back toward the transducer through the brazed joint to the sleeve-couplant interface. When [ the ultrasonic wave reaches the sleeve-couplant interf ace, some energy is transmitted through the interface to the transducer. The transmitted energy results in a signal on the oscilloscope screen. The reflected energy continues to propagate in the sleeve assembly losing energy each time it reacnes the sleeve-couplant interf ace. The resulting oscilloscope display 1819c/0235c/030885:5 80-6-1 v --c -e .-.w-e -4 n -n --m, ,m. ~n ,w ,,,---,.<,-nmw, gw-,-e,vn,, 3 from a sound brazed joint is a large signal, from the sleeve-couplant interface, followed by a decaying series of smaller " echoes" spaced by the time of travel in the sleeve-tube assembly. If there are some void regions _in the braze, a complex combination of these two signal patterns will result. Thus, by observing the' patterns in the reflected. pulse and comparing them to ~ patterns observed with joints of a known quality, a quality can be assigned to the brazed joint. 'i To provide additional resolution, an investigation into the use of [ l .]a,c.e was conducted. The response of the [' ' ~ Ja.c.e in the braze region is shown in Figure 6.1.1-2. The resultant wave fom for a good braze is characterized by the [ 4 1 ']C These patterns differ from those generated with the [ I ]a,c,e The next result is that the [ .)b.c.e The, conclusion is that an ultrasonic transducer which is [ la,c.e provides the optintam inspection of the braze. - 6.1.2 ' ULTRASONIC SYSTEM To test.the feasibility' and to develop an ' inspection procedure, a test bed was ' constructed. [ o i - 1819c/0235c/030885:5 81 6-2 9-7 h-w -s-= y ,m-. .e. ___,,,-.,e- -r--- ey ) s 3 r i m 1819c/0235c/030885:5 82 6-3 r 1 b ) 4 e = r 1319c/023Sc/030885:5 83 6-4 z s ]a.ce To accomplish these operations, a remote mechanical handling system was developed. i 6.2 E00Y CURRENT INSPECTIONS ~ The e(dy current inspection equipment, techniques,'and results presented herein apply to the proposed Westinghouse sleeving process for use in steam generators which have 0.875" 00 by 0.050" nominal wall. Due to the similarities between the Series 51 and Series 44 steam generator designs and the fact that approximate'ly 6000 sleeves made from thermally treated Inconel 600 with mechanical joints are currently installed in Series 44 steam generators,.it is expected that similar addy current inspection results will be obtained with equipmen't and techniques developed for the Model 51 steam generators. Eddy current inspections are routinely carried out on the steam genera, tors in accordance with the plant's Technical Specifications. The purpose of these inspections is to detect at an early state tube degradation that may have occurred during plant operation so that corrective action c,an be taken to minimize'further degradation and reduce th'e potential for significant primary-to-secondary leakage. r The standard inspection procedure involves the use of a bobbin eddy current probe, with two circunferentially wound coils, which are displaced axially along the probe body. The coils are connected 'in the so-called differential mode; that is, the system responds only when there is a difference in the properties of the material surrounding the two coils. The coils are excited by using an eddy current instrunent that displays changes in the material surrounding the coils by measuring the electrical impedance of the coils. In the past, eddy current instruments normally excited the coils at a single '1819c/023Sc/030885:5 84 6-5 .m. ..--.-n -,,,v,-g r- -ww- -,,,,-c.,w., n-g en- ,- --, pang- 1 i i frequency. However, Westinghouse and the i,ndustry are now using ~ multi-frequency instrumentation for the inspection of steam generator tubing. This involves simultaneous excitation of the coils with several different test frequencies. . The. outputs of the various frequencies are, combined and recorded. The combined data yield an output in which signals resulting from conditions that do not affect the integrity of the tube are reduced. By reducing unwanted signals, improved inspectability of th'e' tubing results (i.e., a higher signal-to-noise ratio). Regions in the steam genera'.or such as the tube ~ supports, the tubesheet, and sleeve transition zones tre exmples of areas where mitifrequency processing has proven valuab1e in oroviding-improved inspectability. A number of eddy current probes and signal processing systems are available for the eddy current inspection of the tube / sleeve assembly. In addition to the conventional bobbin coil probe, there are a rotating pancake coil and a cross-wound coil probe. Any of these probes may be used with either single frequency or altifrequency instrumentation. After sleeve installation, all sleeved tubes are subjected to a series,of eddy, c.arrent inspections (.Some of these inspections are part of'a process control procedure to verify correct sleeve installation. However, each tube / sleeve assembly also receives an eddy current inspection for basel.ine purposes to which all subsequent inspections will be c'ompared. / Verifi$ation of proper sleeve installation is of critical importance in the sleeving process. An "in-process" eddy current inspection is conducted utilizing one frequency in the absolutg ede arith a conventional bobbin coil probe. This inspection is performed during sle'eving installation to provide "in-process" verification of the existence of proper hydraulic expansion and hard roll configurations and also to allow determination of the sleeve process dimensions,both axially and rsdially, using the strip chart recording. The inspection for degradation of the tube / sleeve assembly has typically been performed using conventional bobbin coil probes operated with mitifrequency 1819c/0235c/030885:5 85 6-6 3 excitation. For the straight length regio 0s of the tube / sleeve assembly,' the inspection of the sleeve and tube is consistant with normal tubing inspections. In tube / sleeve assembly joint regions, data evaluation becomes more complex. The results discussed bel suggest the limits on,the volume of degradation that can be detected in the vicinity of geometry changes. For the _ parent tube, these limits are on the order.of two to three times the response of the ASME calibration standard using the conventional bobbin coil probe. The detection and quantification of degradation at the transition regions of the sleeve / tube assembly depends upon the. signal-to-noise ratio between the degradation response and the transition response. As a general rule, lower frequencies tend to suppress the transition signal relative to the degradation signal at the expense of the ability-to quantify. Similarly, the inspection .of the tube through the sleeve requires the use of low frequencies to achieve detection with an associated loss in quantificaton. Thus, the search for an optimun eddy current inspection represents a trade-off between detection and quanti fication. With the conventional bobbin type inspection, this optimization leads to a primary inspection frequency for the sleeve on _the order of [- ':a,c.e and for the tube and transition regions on the order of 1 ],,c.e Figure 6.2.1 shows the response of the ASME tube calibration standard using a conventional bobbin coil. Figur? 6.2.2 shows the response of a typical. expansion transition at the same frequencies as Figure 6.2.1 but at a factor of two lower sensitivity for the non-mixed channels. In Figures 6.2.1 and,6.2.2, the results of combining the 50 kiiz and 150 kHz responses to eliminate the transition signals are depicted, hote that in the transition regions a signal with twice the amplitude of the standard would be detectable. _ However, with present instrumentation the actual noise level from i the electronics limits the usefulness of this approach. i For those regions of the sleeve where the assembly has no transitions, a conventional bobbin coil inspection provides detection and quantification capability. Figure 6.2.3 shot. a typical [ 3a,c.e phase angle versus degradation depth curve for the sleeve from which 00 sleeve penetrations can be assessed. o IS19c/023Sc/030885:5 86 6-7 i ./ In.the regions of the parent tube above the sleeve, conventional ~ bobbin coil _-inspections will continue to be used. Mcwever, since*the diameter of the sleeve is _ smaller than t54t of the tube, the fill factor of a probe inserted through.the sleeve may result in a decreased detection capability for tubing degradation. Thus, it may be necessary to inspect the unsleeved portion of the tube above the sleeve by inserting-a standard size probe through the ' U-bend from the unsleeved leg of the tube. 3 While there are a number of probe configurations that lend themselves to . improving the inspection of the tube / sleeve assembly in the regions of configuration transitions, the cross-wound coil probe has been selected as offering a'significant improvement over the conve'ntional bobbin coil probe, yet retaining the simplicity of the inspection procedure. The overall inspection procedure involves the use of the cross-wound probe which significantly reduces the responses of the transitions, coupled with a multifrecuency mixing. technique for further reduction of the remaining noise signals. This system reduces the _ interference from all discontinuities which have 360-degree synenetry, providing improved visibility for discrete discontinuities. As is shown in the accompanying figures, in the laboratory this technique can detect 00 tube wall per.etrations with acceptable signal-to-noise ratios at the transitions when the volume of metal removed is equivalent to the ALME calibration standard. The sigrlificant reduction of response from the tube / sleeve assembly transitions due to the use of the cross-wound coil is shown by a comparison of Figures 6.2.4, 6.2.5, and 6.2.6 for the sleeve standards, tube standards and transitions, respectively. Again, this is further improved by the combination of the various-frequencies. - ( 4 i i Ja,c.e Figure 6.2 7 shows the phase / depth curve for the tube using i this combination. As' examples of the detection capability at the transitions. Figures 6.2.8 and 6.2.9 show the responses of a 20 percent 00 penetration in the sleeve and 40 percent 00 penetration in the tube, respectively. 1819c/023Sc/030885:5 87 6-8 l O In. ) s The, preceding discussion has centered around the inspection of, the e'xpansion transition regions of. the assembly. For inspection of the region at the top end of the sleeve, the transition response using the conventional bobbin -inspection is -still larger than that of the expansion regions as,shown in Figure 6.2.10. Thus, the signal-to-noise ratios for this part of the tube / sleeve assembly is about a factor of four less sensitive than that of the expansions. Some improvement has been gained by tapering the wall thickness at the top end of the sleeve. This reduces the end-of-sleeve signal by a 1-factor.of approximately.two. The crosswound coil, however, again significantly reduces the response of the. sleeve end. Figure 6.2.11 shows the response of various ASME tube calibration standards placed at the end of the sleeve using the cross-wound coil and the [ ]a,c.e frequency combination. Note that under these conditions, degradation at the top end of the sleeve / tube assembly can be detected. In the braze region conventional eddy current inspection techniques were evaluated.to determine the impact of the braze on the eddy current response of the joint. To begin, the eddy current response of the braze region prior to I brazing and the braze region without the braze ring were obtained in Figure
- 6. 2,.12.
[ .]'C As,a result of this, it is a simple matter to distinguish between a braze that has been heated to a point where the braze has flowed and one that has not, allowing for process verification. r Comparison of Figure 6.2.13 with the eddy current signature of a typical braze ' joint with S/8" sleeves, Figure 6.2.12, reveals that the gross features of the waveforms are similar. To-begin, the braze signature indicates that the braze groove has emptied. In addition, there is a subtle change in the waveform originatiing fran the second transition zone. This change is most noticeable inthe[' ]b.c,e To confirm this, another series of simulations were 1819c/0235c/030885:5 88 6-9 t i 3 stupied. These simulations involved inserting rings of braze paterial of' various widths and thicknesses into' the braze region,* Figure 6.2.14. The resultant [ .]b,c.e eddy current signaturen are found in Figure 6.2.15. Examination of the response of the [ . ]b,c.e braze simulation reveals that the response displays the character 'of the braze sample of Figure 6.2.16, confirming the speculation that the braze is indeed visible _to addy current inspections. 3-A further comparison of the response of the various braze widths shows that there.is a [ )D,C,e Since the response of the braze is a unique function of the braze flow, each joint has its own eddy current signature. As a result, an eddy current base line of each joint will be obtained against which all subsequent inspections i can be compared., Significant changes in the eddy current signatures may in(icate degradation within the braze region. 6.3
SUMMARY
Both ultrasonic and eddy current techniques have been evaluated for the inspection of the sleeve assembly. Ultrasonic techniques provide a viable means of assessing braze flow and extent. Eddy current techniques wi.ll provide a viable means of assessing the sleeve assembly for in-service inspection.
i Conventional eddy current techniques have been modified to incorporate the most recent technology in the inspection of the sleeve / tube assemoly. The resultant inspection of the sleeve / tube assembly involves the use of both a conventional bobbin coil for the straight regions of the sleeve / tube assembly and a cross-wound coil for the transition regions. It should be emphasized that the transition regions of the assembly, where the cross-wound coil and multifrequency processing are necessary for degradation detection, comprise 1819c/0235c/030885:5 89 6-10 L-
4
)
only a small percentage of the overall sleeve / tube assembly,.Thus-the conventional inspection would constitute the bulk of 'the eddy current inspection. While there is a significant improvement in the inspection of portions of the assembly using the cross-wound coll, efforts continue to advance the, state-of-the-art in eddy current inspection techniques. As improved techniques are developed and verified, they will be utilized. For the present, the cross-wound coil, probe represents an inspection technique that provides additional sensitivity and suppqrt for eddy current techniques 3
as a viable means of assessing the tube / sleeve assembly.
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- 7.0 - ALARA CONSIDERATIONS FOR SLEEVING OPERATIONS 3
The repair of' steam generators in operating nuclear plants requires the utilization of appropriate dose reduction techniques to keep radiation exposures As low As Reasonably Achievable ( ALARA). Westinghouse maintains an extensive ALARA program to minimize radiation exposure to personnel. This program includes: design and improvement of remote and semi-remote tooling, including state-of-the-art robotics; decontamination of steam generators; the 1
use of shielding to minimize radiation exposure; extensive personnel training utilizing mock-ops; time trials; and str.ict qualification procedures. In addi, tion, computer programs (REMS) exist which can accurately track radiation exposure accumulation.
The ALARA aspect of the tool design program is to develop specialized remote 7
tooling to reduce the exposure that sleeving personnel receive from high radiation fields. A design objective of the remote delivery sleeving system is to_ eliminate channel head entries and to complete the sleeving project with
- total' exposures kept to'a minimum, 'i. e., ALARA. The manipulator arm is 7
installed on a fixture attached to the steam generator manway after video t
cameras and temporary nozzle covers have been installed. The control station operator (CS0) then manually operate controls to guide the manipulator-arm
, through the manway and attach the baseplate to the tubesheet. The installation of the arm requires.only one platform operator to provide. visual observation and assistance with cable handling from the platform. 'The control station for the' remote delivery systen.is located outside containment in a specially designed control station trailer, e
The control of_ personnel exposures can also be effected by careful planning, training, and preparation of maintenagce precedures for the job.. This form of achninistrative control can ensure that the minimum number of personnel will be
- used to perform the various tasks. Additional methods of minimizing exposure include the use of remote TV and radio surveillance of all platform and channel head operations and the monitoring of personnel exposure to identify
'high exposure areas for timely improvement. Local shielding will be used whenever possible to reduce the general area background radiation levels at 1819c/0235c/030885:5 91 7-1
. u u.
)
the work stations inside containment. A combination of these technigiJes is expected to be used in this steam generator sleeving project.
7.1 ROSA SLEEVING OPERATIONS The Remotely Operated Service Arm (ROSA) is,a remotely-operated robotic, general purpose tool positioning system designed for perfonning various maintenance tasks in the steam generator channel head and other radiologically i
hostile environments. The systen is op'erated renotely fran the control station located outside containment up to 200 feet from the channel head. The
~
arm is designed to accept'a family of end effectors that are used to implement the various processes used in. steam generator tube
- maintenance.
7.2. MANIPULATOR ENO EFFECTORS The ROSA system is designed to assist in performing' a wide variety of tasks in the channel he'ad. This is accomplished by firstly attaching the appropriate end effector to the arm. The end effectors are designed for specific or multi-purpose use during sleeving operation. Some current applications of-remote manipulators are steam generator eddy current inspection, plug weld repair, tube end repair, mechanical plug installation, and tube sleeving operations. An end effector is equipped with a standardized quick disconnect V-band coupling for manual attachment to:the mani,pulator fran the steam generator platform. The arm is extended through the manway,and the quick disconnect coupling is oriented at right an'gles to the axis of the manway.
This allows the changing of-end effectors outside direct shine of the manway
/
radiatien beam, minimizing radiation exposure.
7.2.1 SLEEVE / TOOLING ENO EFFECTOR 5 i
The sequence of process steps and associated tooling required to complete a.
-stema generator tube sleeving project results in many end effector changes.
T'1e sleeving operations of tube end rolling-(contingency), tube honing, fiberscoping (contingency), sleeve /mancrel insertion and expansion, lower hard roll, brazing, ultrasonic testing, process verification eddy current inspection, and baseline eddy current inspection will require a significant 1319c/023Sc/030885:5 92 7-2
I s
a 4
nuinber of tool changes during the project The platform operator will'be
~
required to change end effectors of increasing compl'exity from fiberscope and' lower hard roller tooling to the more complex brazing and sleeve / mandrel
~
insertion and expansion tooling systems. The number and frequency of changes will depend on the scope of the sleeving project.
7.2.2 IN-PROCESS OPERATIONS 3
The necessity of having a platform operator available near the platform extends into the in-process sleeving operations. The useful life of a hone is expected to be limited to approximately 5-50 tubes (depending on the honing process utilized) before the hone will need to be replaced. The fiberscope
~
inspection seque'nce may require various lengths of fiberscopes to reach all of the tubes during the inppection. The sleeve / mandrel insertion and expansions operations are expected to require the major part of the in-process time spent on the platform. The removal of spent expansion mandrels and the installation of the new sleeve / mandrel unit may have to be done manually from the platform. The hard rolling, brazing, ultrasonic testing, and eddy current operations will require auch less time on the platform.
7.3 CONTROL STATION IN CONTAINMENT The process control stations for the various sleeving processes will be-located in containment in a low radiation area near the steam generator platforms. These erk stations are required to operate and control the individual sleeving processes and are independent of the ROSA systems controls i
located outside containment. The variation in service requirements such as air, water, electricity, radwaste generation, and proximity of controls-to-processes makes the in-containment control stations a necessity.
7.4 POTENTI ALS FOR WORKER EXPOSURE The continued development of the ROSA sleeving process is expected to significantly reduce the radiation exposure to workers in comparison to previous sleeving projects. The elimination of channel head entries for the installation and removal of sleeves and sleeve tooling fixtures will keep 1819c/0235c/030885:5 93 7-3
3 J
personnel out of the high radiation fields of the steam generator-cha'nnel heads. The majority of the sleeving operations will be done from the control stations with one or two workers stationed on or near the platform. However, in the preparation of the steam generators for sleeving operations, entries into the channel heads may be required.
7.4.1 N0ZZLE COVER ANO CAMERA INSTALLATION / REMOVAL Theinstallationoftemporarynozzleco'versinbereactorcoolantpipe nozzles in preparation of the steam generators for sleeving operations will require channel head entries. The covers are installed to prevent the accidental dropping of any foreign objects (i.e., ' tools, nuts, bolts, debris, etc.) into the reactor coolant loops during sleeving operations. In the event that an accident did occur, inspections of the loops would be required and any foreip objects or debris found would have to be retrieved. The impact on schedule and radiation exposures associated with these recovery operations would far exceed the time,and exposures (less than 1 minute) expended to install or remove loop nozzle covers. Consequently, it is considered an ALARA-efficient procedure to utilize temporary nozzle covers during sleeving oper,ations.
The use of video acnitoring systems to observe ROSA operations in the channel head will also require manual installation. The installation of overview cameras to monitor, sleeving operations will require a full or partial channel head entry to be installed.
/
The insballation and removal of this equipment in the steam generators are the only sche'duled requirements for thannel head entry during the sleeving project.
7.4.2 PLATFORM SETUP / SUPERVISION The majority of the radiation exposures recorded for the sleeving program is expected to result primarily from personnel working on or near the steam generator platforms. The secup and checkout of equipment for the various sleeving processes, the installation / removal of ROSA, the changing of end effectors,- and the operation of the sleeve / mandrel insertion and expansion
'1819c/0235c/030885:5 94 7-4
i s
syptem are the major sources of radiation, exposure. In addition to channel head video monitoring systems, visual:monitaring and supervision by one or more workers on the platform will be required for a major part of the sleeving schedule. Experience has shown that rapid response to equipment adjustment requirements is efficiently accomplished by having a ' platform worker standing by.in a relatively low radiation area during operations. Worker standby stations have ranged fran the low radiation fields behind the biological
~
shield to -lead blanket ' shielding installed on the platform. Even though radiation levels on the platfonn are'much lower than channel head levels, a.
substantially larger amount of time will, be spent on the platforms giving rise
~
to personnel exposures. An evaluation of radiation surveys around the steam generators should indicate appropriate standby stations.
7.5 RA0 WASTE GENERATION e
The surface preparation of tubes for the installation of sleeves requires that the oxide film be removed by a honing process. A flexihone attached to a flexible rotating cable will be used to remove the oxide film on the inside
. surface of' the steam generator tubes. The volume of solid radwaste is expected to consist of spent hones, flexible honing cables, hone filter assemblies (optional), radioactive water from tube h'oning, and the normal
. anti-C consumables, associated with steam generator maintenance. The anti-C consumables are usually the customer's responsibility and will not be addressed in this report.
Forthe[
]aJ,e approximately thirty tubes can be honed before the hone.is changed for process centrol and [
i.
a
- ].,c.e A typical estimate of the radioactive concentration fron a honed tube and t,ransported by the [
ja,b,c.e The flexible honing cable used to rotate the hone inside the tubes is also
[
3ac.e during the honing process. The construction of the stainless 1819c/0235c/030885:5 95 7-5
.)
TA8LE 7.5-1'
~
ESTIMATE OF RADIOACTIVE CONCENTRATION IN WATER PER TUBE HONE 0 (ThPICAL Percent Inventory-Activity
' Isotope
. Concentration.
(uci)
-(uci/cc of H O) 2 b,c.e t
)
ASSUMPTIONS
~
- 1) Tube honed 48 inches (in length)
- 2) Water flow rate of [
]Cper'tubehoned t
' 3) Essentially all = radioactivity removed from tubes honed.
1819c/0235c/030835:5.96 7-6
3 1
(
steel cable,however, will cause radioactivi.ty to build up ov.er.the course of
'the project. Radiation levels on segments of the cabfe could [
]b,c.e It is expected that an average of one cable per steam generator will be used during the sleeving
. project. The cables are consumables and are drummed as solid radwaste.
-7.6 AIRBORNE RELEASES 3
i
- The implementation of the proposed sleeving processes in operating nuclear plants has indicated that the potential for airborne releases is minimal. The major' operations include [
3a,c.e and sleeve installation.
Experience has shown that these sleeving processe's do not contribute to
~
airborne releases.
4 1
7.7 PERSONNEL EXPOSURE ESTIMATE The total personnel exposures for steam generator sleeving operations will depend on several plant dependant and process related factors. These may include, but not be limited to; the scope of work (quantity of sleeves, etc),
plant radiation levels, ingress / egress to the work stations, equipment performance and overall cognizance of ALARA principles. Co,nsequently, the projection of persoonel exposures for each specific plant must be performed at the completion of mockup training when process times for each operation have been recorded. The availability of plant fadiation levels and worker process times in the various radiation fields will provide the necessary data to project personnel exposure -for the sleeving project.
1 The calculation of the total MAh-REM exposure for completing a sleeving project may typically be expressed as fiollows:
P=N 0 +Sg.Ng 3
~
P = Project total exposure (MAN-RE;4)
~
N = Number of sleeves installed T
1319c/023Sc/030885:5 97 7,7 L
g i
Os = Exposure /sieeve installed Sg = Equipment: setup / removal exposure per ste'am generator
~
Ng = %mber of steam generators to.be sleeved This equation and appropriate variations are used in estimating the total personnel. exposures for the sleeving project.
n
~
d
~'
1819c/0235c/030885:5 98 7-8
3 s
8.0 INSERVICE INSPECTION PLAN FCR SLEEVED TUBES To address NRC requirements, the operating plant nust perfom periodic inspections of the supplemented pressure boundary. This new pres,sure boundary consists of the sleeve with a joint at the primary face of the tubesheet and a.
joint at the opposite end of the sleeve.
The inservice inspu tion program will consist of the following. Each sleeved tube will be eddy current inspected on completion of installation to obtain a baseline signature to which all subsequent inspections will be compared.
Periodic inspections to monitor sleeve wall conditions will be performed in accordance with the inspection section of the plant Technical Specifications.
This inspection will be performed with multi-frequency eddy curre'it equipment. The plugging criterion for the sleeves is established in Section 3.0 of this report.
As part of the inspection.of the sleeved tubes, there will be a series of pressure / leakage tests. These tests are in' tended to test the integrity of the mechanical and brazed joint against leakage at both primary and secondary pressure loadings. The tests will be conducted a't the conclusion of the sleeving operation and will be performed by the owner in accordance with Applicable requireme.nts of the ASME Code and plant procedures. Periodic pressure testing of the sleeved tubes will also be performed in accordance with the plant Technical Specifications.
f t
o 1819c/023Sc/030885:5 99 8-1
.