Text

Rev 5 to CEN-620-NP, Series 44 & 51 Design SG Tube Repair Using Tube Rerolling Technique
	ML20248M056
Person / Time
Site:	Prairie Island
Issue date:	05/31/1998
From:	; ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:	;
Shared Package
ML20036E425	List: ML20248M054; ML20248M056;
References
	CEN-620-NP, CEN-620-NP-R05, CEN-620-NP-R5, NUDOCS 9806120302
	Download: ML20248M056 (86)
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+: : lllllllllllllllllllllllllllllll H : H : ll+: :: l l :+Ft CEN-620-NP Revision 05-NP ABB COMBUSTION ENGINEERING May 1998 Series 44 & 51 Design Steam Generator Tube Repair Using A Tube Rerolling Techniaue FINAL REPORT ABB Combustion Engineering Nuclear Power Windsor, Connecticut lll: ::: : :::::::::::::::::::::::::::::::::::::::::::P A B RD 9806120302 980608 Mpp yDR ADOCK 05000282 PDR

l LEGAL NOTICE THIS REPORT WAS PREPARED AS AN ACCOUNT OF WORK SPONSORED BY ABB COMBUSTION ENGINEERING. NEITHER ABB COMBUSTION ENGINEERING NOR ANY PERSON ACTING ON ITS BEIIALF:

A. MAKES ANY WARRANTY OR REPRESENTATION, EXPRESS OR IMPLIED INCLUDING THE WARRANTIES OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY, WITH RESPECT TO THE ACCURACY, COMPLETENESS, OR USEFULNESS OF THE INFORMATION CONTAINED IN THIS REPORT, OR THAT THE USE OF ANY INFORMATION, APPARATUS, METHOD, OR PROCESS DISCLOSED IN THIS REPORT MAY NOT INFRINGE PRIVATELY OWNED RIGHTS; OR B. ASSUMES ANY LIABILITIES WITH RESPECT TO THE USE OR FOR DAMAGES RESULTING FROM THE USE OF, ANY INFORMATION, APPARATUS, METHOD OR PROCESS DISCLOSED IN THIS REPORT.

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CEN-620-P, Rev. 05-P ii

l ABSTRACT A- technique : posented for repairing degraded steam generator' tubes in . Westinghouse preswrized watcA reactors with Series.44 and 51 design steam generators. The technique

- alleviates the need for plugging or sleeving those steam generator tubes with defects in the tubesheet region.

Instead :of traditional repair techniques (plugging and sleeving), the degraded tubes will be rerolled above the original-tubesheet hard roll to form a new leaktight joint above the initial tubesheet roll transition zone. This technique will re-establish the pressure boundary between the

, primary and secondary side systems and provide the necessary stnictural capability for operational

- and upset conditions.

' This report details analyses and testing performed to verify the adequacy of the roll transition 4 zone reroll process for returning nuclear steam generator tubes back to service. It demonstrates

~t hat rerolling tubes, with defects in the tubesheet region, is an acceptable repair technique.

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I s CEN-620-P, Rev.,05-P iii -

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1 TABLE OF CONTENTS )

Section' Title Page ABSTRACT iii

1.0 INTRODUCTION

1-1 1.1 Purpose 1-1 1.2 Background 1-1 2.0 QUALIFICATION CRITERIA 2-1 2.1 Technical Specification 2-1 2.2 Acceptance Criteria 2-1 3.0

SUMMARY

3-1

4.0 REFERENCES

4-1 5.0 DESIGN DESCRIPTION OF REROLL JOINT AND 5-1 INSTALLATION EQUIPMENT 5.1 Reroll Joint Design 5-1 5.2 Repair Of A Defective Rerolled Tube 5-2 5.3 Reroll Joint Installation Equipment 5-2 5.4 ALARA Considerations 5-5 6.0 TEST PROGRAM 6-1 6.1 Test Matrix 6-1 6.2 . Tests Reauired On Coupons 6-2 l

CEN-620-P, Rev. 05-P. iv x _ = -_

TABLE OF CONTENTS (Continued)

Page Section Title TEST RESULTS 7-1 7.0 Coupon Preparation 7-1 7.1 Toraue Development 7-3 7.2 Test Procedure 7-4 7.3 Phase 1 - F* Coupon Results 7-7 7.4 Phase 1 - EF* Coupon Results 7-9 7.5 Phase 2 - Additional F* And EF* Coupon Results 7-10 7.6 7.7 Tube Growth Tests 7-12 7.8 Roller Life 7-13 7.9 Discussion 7-13 8.0 STRUCTURAL CONSIDERATIONS 8-1 8.1 Reroll Joint Configuration 8-1 8.2 Plun And Sleeve Program Applicability 8-24 8.3 References 8-26 9.0 EDDY CURRENT EXAMINATION 9-1 9.1 Installation Verification 9-1 9.2 Rotatina Probe Examination 9-1 10.0 EFFECT OF REROLLING ON OPERATION 10-1 CEN-620-P, Rev. 05-P v

LIST OF TABLES Table No; Title Page

.3-1 Phase 1 - F* Reroll Test Matrix 3-3.

3-2 Phase 1 - EF* Reroll Test Matrix 3-4 3-3 Phase 2 - Additional F* And EF* Reroll Test Matrix 3-5.

7-1 F* Torque Development 7-3 7-2 EF* Torque Development 7-4 7-3 F* Mechanical Test Results 7-16 7-4 F* Hydrostatic Leak Test Results 7-17 7-5 - EF* Mechanical Test Results 7-18 7-6 EF* Hydrostatic Leak Test Results 7-19 7-7 Additional F* And EF* Reroll Mechanical Test Results 7-20 7-8 Additional F* And EF* Hydrostatic Leak Test Results 7-22 8-1 Axial Member Physical Properties - Westinghouse Series 8-6 "44" Steam Generators for the First Rerolled Joint Location Case with Tube Lock-up 8-2 Axial Member Physical Properties - Westinghouse Series 8-7 "51" Steam Generators for the First Rerolled Joint Location Case with Tube Lock-up 8-3 Axial Loads in Locked Tube - Westinghouse Series "44" 8-8 j Steam Generators for the First Rerolled Joint Location Case {

8-4 . Axial Loads in Locked Tube - Westinghouse Series "51" 8-9 Steam Generators for the First Rerolled Joint Location Case

8 Axial Member Physical Properties - Westinghouse Series 8-13 "44" Steam Generators for the Second Rerolled Joint Location Case with Tube Lock-up CEN-620-P, Rev 05-P vi ,

_=______:__.

4 LIST OF TABLES (Continued)

Table No; Title P_ age

'8-6 Axial Member Physical Properties- Westinghouse Series 8-14 "51" Steam Generators for the Second Rerolled Joint Location Case with Tube Lock-up -

8-7 Axial Loads in Locked Tube - Westinghouse Series "44" 8-15 Steam Generators for the Second Rerolled Joint Location Case 8-8 Axial Loads in Locked Tube - Westinghouse Series "51" 8-16 Steam Generators for the Second Rerolled Joint Location Case 8-9 Axial Member Physical Properties - Westinghouse Series 8-19 "44" and "51" Steam Generators for the First Rerolled Joint Location Case without Tube Lock-up 8-10 Axial Loads in Non-Locked Tube - Westinghouse Series - 8-20 for "44" and "51" Steam Generators for the First Rerolled Joint Location Case 8-11 Axial Member Physical Properties - Westinghouse Series 8-22 "44"and "51" Steam Generators for the Second Rerolled Jo'mt Location Case without Tube Lock-up 8-12 Axial Loads in Non-Locked Tube - Westinghouse Series 8-23 "44"and "$1" Steam Generators for the Second Rerolled Joint Location Case

'8-13. Tubesheet Ligament Stresses for Westinghouse Series 8-25 "44"and "51" Steam Generators at Design Conditions

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. . CEN-620-P, Rev. 05-P . vii t

LIST OF FIGURES Figure No. Title Page 5-1 Reroll Joint Configuration 5-6 5-2 Remote Control Manipulator 5-7 5-3 Rotation Station And Controls 5-8 5-4 Brushing Tool 5-8 5-5 Hydraulic Expansion Equipment 5-9 5-6 Tube Roll Expander 5-9 7-1 Typical Expansion Trace 7-24 i

7 Typical Torque Trace - Wet Sludge Sample 7-25 {

l 7-3 Typical Torque Trace - Dry Sludge Sample 7-26 J 8-1 Rerolled Tube Model And Environment 8-3 8-2 Tube Schematic - Series "44" Steam Generators for the 8-4 First Rerolled Joint Location Case 8-3 Tube Schematic - Series "51" Steam Generators for the 8-5 First Rerolled Joint Location Case i 8-4 Tube Schematic - Series "44" Steam Generators for the 8-11 Second Rerolled Joint Location Case 8-5 Tube Schematic - Series "51" Steam Generators for the 8-12 Second Rerolled Joint Location Case I

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-, CEN-620-P, Rev. 05-P viii m

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1.0 INTRODUCTION

l< 1.1 Purpose :

, The purpose of this report is to provide information sufficient to back licensed F* 'and EF' analyses in support of a 10CFR50.59 safety evaluation allowing installation of reroll joints in .

Westinghouse-designed. Series 44 and 51 steam generators with. degraded tubes in the

tubesheet region. This report demonstrates that reactor operaR 1 with a tube' reroll joint in-the steam. generator tubes will not increase the probability or consequence of a postulated accident condition previously evaluated.' Also it will not create the possibility of a new or.

different kind of accident and will not reduce the existing margin of safety..

. ABB Combustion Engineering Nuclear Operations (ABB CENO) provides two types ofleak limiting rerolljoints for Westinghouse Series 44 and 51 steam generator tube repair. The first joint type can be located anywhere in the [

].

The. steam generator tube with the reroll joints meets the structural requirements of tubes which are not degraded.

Design criteria for the reroll joints were prepared to ensure that all design and licensing requirements are considered. Analyses and testing have been performed on the tube reroll joints to demonstrate that the design criteria are met.

The effect of rerolljoints on steam generator heat removal capability and system flow rate are discussed in Section 10 of this report.

After the reroll joints are installed, an examination is performed using eddy current (ET) techniques. The ET examination serves as a method to verify that the rerolljoint was [

-] in the steam generator tube and to assure that F* and EF* criteria of

- undegraded hard roll tube length above previous indications are met by the reroll process.

Plugs' or sleeves will be installed if the reroll procedure is not successful or if there is unacceptable degradation of steam generator tubes due to the process.

1.2IBackaround i The operation of Pressurized Water Reactor (PWR) stearn generators has, in some instances, resulted in localized corrosive attack at the roll transition zone region and in the'tubesheet crevice region ~of the steam' generator. tubingL This corrosive attack results'in a localized reduction in steam generator tube . wall thickness. Steam generator tubing has been designed 2 CEN-620-P, Rev. 05-P. ~Page1-1 I

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- with considerable margin between the actual wall thickness and the wall thickness required to meet structural requirements. Thus it has not been necessary to take corrective action unless structural limits are being approached, L Historically, the corrective action taken where steam generator tube wall degradation has been

< severe has been to install plugs at the inlet and outlet of the steam generator tube when the reduction in wall thickness reached a calculated value referred to as a plugging criteria. An additional repair option has been to bridge the defect utilizing a sleeve. Eddy current (ET) examination has been used to measure steam generator tube degradation and the tube plugging criteria accounts for ET measurement uncertainty.

Installation of steam generator tube plugs removes the heat transfer surface of the plugged tube from service and leads to a reduction in the primary coolant flow rate available for core cooling. Installation of steam generator sleeves does not significantly affect the heat transfer removal capability of the tube being sleeved and a large number of sleeves can be installed without significantly affecting primary flow rate. However, there is a minor reduction in flow rate associated with large numbers of sleeves and potential accessibility concerns as well.

'The use of a tube reroll process will alleviate these concerns as well as leave the tube'in a condition to perform repairs at a later time.

LCEN-620-P, Rev. 05-P Page 1-2

2.0 QUALIFICATION CRITERIA 2.1 Technical Specification Westinghouse Series 44 and 51 Steam Generators 2.1.1 Design and Operating Ratings Primary Operating / Design Temperature: 590T / 6507 Primary Operating / Design Pressure: 2235 psig / 2485 psig Secondary Operating / Design Temperature: 4947 / 550T Secondary Operating / Design Pressure: 635 psig /1085 psig 2.1.2 Steam Generator Tube Data Tube Hole Drilling (min./ max.): .888/.893 inches Tube Nominal O. D.: .875 inches Tube Nominal Wall: .050 inches Tube Wall Reduction Due to Rolling: 4-6%

2.2 Acceptance Criteria The following acceptance criteria were used to assess the performance of rerolled joint coupon specimens during testing.

2.2.1 The established torque values shall yield a [ ] percent tube wall reduction.

These values were chosen as a means of bounding the original equipment manufacturing specifications. This range of values reflects ABB's experience in plug and sleeve rolling in steam generator tubes. Also, the larger range accommodates the uncertainties associated with remote field applications.

2.2.2 The rerolled tube joint shall exhibit no movement relative to the tubesheet during simulation of cyclic loading conditions.

2.2.3 The rerolled tube joint shall exhibit no movement relative to the tubesheet at push and/or pull test forces which represent the maximum load experienced by the tube under operating or accident conditions with the tube unrestrained at the support plates.

These loads are [ ], for reroll joints both above and below the neutral axis of the tubesheet. The loads associated with a tube in the restrained condition are less than these values.

CEN-620-P, Rev. 05-P . Page 2-1

2.2.4 The rerolled tubejo:nt shall exhibit leak rates that can be used to determine the number of reroll joints that can be installed per plant technical specifications when subjected to secondary side pressure levels equal to three times the operating or upset condition pressure differential. Section 7.0 defines the basis for the test pressure selection.

2.2.5 The roller expander shall produce consistent rolls of bright metal surface finish. There shall be no measurable signs of wear which could effect the rolled joint over the proposed { j life of the roller expander, assuming a planned lubrication interval of fifty rolling operations.

2.2.6 Non-destructive examination techniques shall be utilized to verify that the hydraulic expansion (where applicable) and reroll joint were [ ]and that F* and Elevated F* (EF*) criteria of undegraded hard roll tube length above previous indications are met by the reroll process.

Based on the experience developed with the reroll process in field applications, bobbin coil profilometry evaluation shall be utilized as an additional acceptance criterion in order to ensure that sufficient additional hard roll expansion has occurred.

2.2.7 . A post maintenance visualinspection for leakage with pressurization of the secondary side will be performed as part of the reroll process. The post maintenance leak check with the secondary side pressurized provides additional assurance that the F* and EF*

reroll repair process has not introduced a significant primary to secondary side leakage path. The visual inspection for leakage on the primary side will be conducted with the secondary side filled with water to above the top of the tube bundle and pressurized to at least 100 psig. Visual inspections will begin after a four (4) hour hold at the selected pressure. Acceptable leakage is defined as no visible drops of water after one (1) minute of observation of the tubes with new F* and EF* rerolls. This value can be utilized to determine the acceptability of the repair as it relates to the plant design basis limits. The pressurization of the secondary side is controlled by existing plant procedures.

2.2.8 The tube reroll joint shall not adversely affect system flow rate or heat transfer capability of the steam generator tube.

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I l- CEN-620-P, Rev. 05-P . Page 2-2 I

1

3.0

SUMMARY

A total of [ ] coupons consisting of [ >

j for F* and EF*

qualification were subjected to a rigorous qualification program. The program was performed in two phases; the first phase is shown in Tables 3-1 and 3-2, and the second phase is shown in Table 3-3. The program was designed to test variables and off-nominal conditions that could

be experienced during field operations. These variables included the expected range _of tube hole diameters, rolling torques'and variable conditions in the tube to tubesheet annulus. Such conditions include the presence of sludge in both wet form and dry, compacted form. The [

] effective length roll expander (for reroll joints below the tubesheet neutral axis) 'and the

[ ] effective length roll expander (for reroll joints above the tubesheet neutral axis) were used to prepare all test coupons. The complete test matrices are included as Tables 3-1 through 3-

,. 3.

Torque values associated with a [ ] percent tube wall reduction were established using production equipment. The minimum torque value [ ] used in the test

! program yielded a [ ] percent tube wall reduction, and the maximum torque value [

] used in the test program yielded a [ ] percent tube. wall reduction.

m The nominal value was established at [ ]. The tooling and control systems

-used in the test programs represent the present technology for reroll production equipment.

As technological advances are made, the updated equipment may be utilized upon completion oflaboratory verification.

The Phase I samples in Tables 3-1 and 3-2 were mechanically cycled at a load range of[

], then hydrostatically tested. The Phase 2 reroll samples were thermally. cycled at a temperature range of [ ] and were mechanically cycled at a load range of [ ], then hydrostatically tested. The addition of the thermal cycling for Phase 2 was intended to add a level of !

conservatism to the program. These samples were used to determine the effect on the rolled joint of conditions in the steam generators, such as; the range of tube hole diameters, range of rolling torques and variable conditions in the tube to tubesheet annulus. The results of these ,

tests revealed no joint slippage and minimal leak rates. These leak rates can be used to determine the number of tubes that can be rerolled per the plant technical specifications. .

The samples were hydroststically tested at three pressure levels from the primary and !

secondary side. These pressures were [ ] psi for Phase 1 and [

] psi for Phase 2. The samples were held for a period of time ranging from five

. minutes to twenty-four hours for the normal operating differential pressure and for thirty minutes for the accident conditions'and monitored for leakage. The clean F* and EF* test ;

cases were leaktight at all primary side pressures, while the contaminated samples from Zion and Prairie Island showed minimal leakage at the these test pressures. The dry sludge samples exhibited minimal leakage during the' secondary side test. The details of these test results are discussed in Section 7. _ Samples were push or pull tested, depending on which phase of the program was being performed. The push test samples were loaded to a predetermined load of

.[- . ] while the' pull test samples were loaded to failure.

CEN-620-P, Rev. 05-Pi Page 3-1 ~

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Samples which had been rerolled were sectioned and revealed a bright, smooth surface after completion of the rolling operation. There were no indications of degradation of the tube due to the reroll process.

CEN-620-P, Rev. 05-P ~ Page 3-2 i.

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l l Table 3-1 i

Phase 1 - F* Reroll Tmt Matrix se@p '198 TESTS 9E' .3 g , e' **

, "~ p^ !$k' > -

<4 - 3 . jigps-CASE VARIABLES NO.OF TUBE HOLE CYCLE PUSH / HYDRO COUPONS PULL

x ;;e -

3 4 ;3; , , ,, , g,, ag in _

1 2

3 3a 4

5 6

7 8

9

- Note 1: Test roller expanders at intervals of 50,100 and 200. l

Pull tests performed on two samples for these cases.

CEN-620 P, Rev. 05-P Page 3 -_ _ _ _ _ _ _ - _

Table 3-2 Phase 1 - EF* Reroll Test Matrix

. TESTS ,

CASE VARIABLES NO. OF TUBE IIOLE CYCLE PUSil liVDRO COUPONS i:a: , ,

1 2

3 4

5 6

CEN-620-P, Rev. 05-P Page 3-4

~ - -

- ~ - - - - - - - - - - - -- - - - - ~

r-

[-

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!6 Tabic 3-3 Phase 2 - Additional F* And EF* Reroll Test Matrix l

09 ' >, ;;;p - 71STS ,'W## fi$

CASE- VARIABLES ROLL SMPLS Cr Cu PULL He Hs t

e , < , , e.g ,*: 4l nagg iM W BBR ' MFeh ' A*? Mi*3 ' 24 ' --

Ia.

Ib-2a 2b.

3a 3b 4

5 6

7 8

.9 10 1

l CT- THERMAL CYCLE He - PRIMARY HYDROSTATIC q Cu - MECHANICAL CYCLE Hs - SECONDARY HYDROSTATIC j

' ALL COUPON HOLE SIZES TO BE .893" AND ALL ROLLING TORQUES TO BE SET AT MINIMUM VALUES j 3

TESTS TO BE PERFORMED @ ~528'F 5EN-620-P, Rev. 05-P Page 3-5

- = = _ _ . .-

4.0 REFERENCES

4.1 Nuclear Power Business Nuclear Quality Assurance Manual, QAM-100, Fourth Edition, Revision 4.

4.2 Quality Assurance Procedures Manual, QPM-101, Revision 0.

4.3 Quality Plan No. 2004396-QP-94-014, Rev. 00, " Project Quality Plan for the Development and Qualification of a Tube Re-Roll Process for Westinghouse Steam Generator Tubes."

4.4 STD-400-153, Rev.00, " Test Plan for the Development and Qualification of a Steam Generator Tube Re-Roll Process for Westinghouse Series "44" and "51" Steam Generators."

4.5 00000-OSW-007, Rev. 00," Test Procedure for the Development and Qualification of a Steam Generator Tube Re-Roll Process for Westinghouse Series "44" and "51" Steam Generators."

4.6 Project Plan No. PP-2006735, Rev. 01, " Project Plan for Additional Reroll Qualification Testing" 4.7 00000-OSW-019, Rev. 00, " Test Procedure for the Additional Development and Qualification Of A Steam Generator Tube Reroll Repair Process" 4.8 Telecopy to Dave Stepnick of ABB-CE from Richard Pearson of Northern States Power, dated December 21,1994. Design input on F-Star /L-Star Plugging Criteria.

4.9 TR-ESE-887, Rev. 00, " Test Report for the Qualification of the Roll Transition Zone Sleeve Rolled Joint for Westinghouse "D" Series Steam Generators."

4.10 CENC 1599, " Qualification Testing of Combustion Engineering Mechanical Tube Plug with Aodendum A."

4.11 Test Report No. WO-94-205, " Test Report for the Additional Development and Verification of the Transition Zone Sleeve Rolled Joint for 3/4" Steam Generator Tubes."

4.12 Drawing No. C-SGN-217-458, Rev. 04, " Reroll Joint Configuration."

4.13 Qualification Report, GBRA 014 020, " Steam Generator Tube Repair by Tube Reexpansion."

(ABB Reaktor) 4.14 "Doel 2 - Tube Reexpansion, ABB Conclusions about July Demonstration," 08/13/90. (ABB Reaktor) 4.15 " Repair of SG Tubes by Rerolled Expansion - Corrosion Test." (Laborelec Labs) 4.16 Memo No. PENG-95-015, " Testing of Steam Generator Tubesheet Reroll Samples," A. B.

Goulet to E. P. Kurdziel, dated January 23,1995.

CEN-620-P, Rev. 05-P Page 4-1

4.17 Memo No. WO96186, " Test Results for Re-Roll Qualification Program," D. G. Stepnick to E.

P. Kurdziel, dated October 11,1996.

4.18 00000-OSW-010, Rev 00," Test Procedure For The Life Testing Of Roll Expanders."

4.19 TR-400-002, Rev. 00, " Test Report For The Life Testing Of Roll Expanders With Decreased Lubrication Frequency."

4.20 Report No. A-ABBCE-9419-ll19, Revision 00, " Evaluation of Tube Re-Rolling for Westinghouse Series 44 & 51 Steam Generators."

4.21 Specification No. 00000-OSW-009, Rev. 00, " Design Specification for Re-Rolled Joints in Steam Generator Tubes."

4.22 Telecopy to Dave Stepnick of ABB-CE from Richard Pearson of Northern States Power, dated September 1,1996. Design Input on EF-Star /L-Star Plugging Criteria.

4.23 Memo No. 96177.DS, " Continuation Of Reroll Qualification Test Program," D. Stepnick to E. Pohl, dated October 1,1996.

4.24 Memo from D. Proctor to D. G. Stepnick, " Top Of Tubesheet Reroll Collapse Test," dated September 19,1996.

4.25 Memo No. PENG-96-496, " Testing of Steam Generator Tubesheet Reroll Samples," A. B. l Goulet to Dane Proctor, dated December 4,1996.

4.26 Report No. 97-TR-FSW-009, " Test Report On The Pull Testing Of Reroll Joints In Steam Generator Tubes," dated February 15,1997. ;

4.27 Report No. MISC-PENG-TR-106, " Load Cycle and Axial Load Testing of Reroll Samples,"

dated October 10,1997.

4.28 Report No. 97-TR-FSW-021," Test Report On Additional Reroll Qualification Testing," dated October 10,1997.

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CEN-620-P, Rev. 05-P Page 4-2 l l

.: 5.0L DESIGN DESCRIPTION OF REROLL JOINT AND INSTALLATION EQUIPMENT

'5.1 - Reroll Joint Desian Reference 4.21 contains requirements for .the reroll joint and its' installation. The joint -

becomes the [

]. . The reroll joint design is based upon the '

technology previously developed at ABB. Included in this category is the experience of ABB ,

.Reaktor in the areas of [

. j, and the experience of ABB Combustion Engineering in the areas of [

]. ABB has installed over

[ ] using rolling technology and over [ ] using similar technology.

The reroll joint geometry is shown in the drawing presented in Figure 5-1. Multiple reroll joints may be used in a tube. The critical parameters concerning the joint geometry were developed by the original equipment manufacturer using F* and EF* analyses. Based on these analyses, it was determined that up to [

]. In addition, it was determined

. that up to [ ] upon completion of the reroll would meet EF* criteria. Per the analyses, [

1 Based upon information provided by utility personnel who owned and operated Series 44 and 51 steam generators, ABB-CE determined that the original hard roll length in steam generator tubes ranged from a minimum of one and one halfinches to a maximum of two and three quarter inches. Based upon this information, ABB-CE decided to [

] from the steam generator tube end. This joint is put in place using a [

]. This geometry places the bottom edge of the reroll joint a [ ] from the maximum height of the original roll transition.

In order to reduce the potential for leakage to develop during the cycle, the original roll transition region of those tubes which will have a reroll joint installed can be hard rolled prior

.to the reroll joint being installed. Hard rolling the original roll transition zone region is a

preventive measure which will partially seal the existing cracks and prevent them from being opened by the hydraulic expansion step of the reroll process.

As part of the reroll joint,'a hydraulic ~ expansion may be performed prior to the hard roll l p.*ocess step. This hydraulic expansion utilizes current steam generator sleeving technology.

l ; The hydraulic expansion consists of a [ . : .

1 L fiom the tube end and extending past the hard roll region. This process step serves a number l

CEN-620-P, Rev. 05-P !

[ Page 5-1 b

e.

I of purposes; first, to remove any unexpanded region between the original and new hard rolls; second, to provide a gradual transition from expanded to unexpanded tube above the reroll joint; and third, to minimize the amount of crevice products between the tube and tubesheet upon process completion.

Through the use of process control, the tube wall reduction from the hard roll will be limited from l l percent minimum to [ ] percent maximum. This range of wall reduction ensures an acceptable reroli joint under the variety of conditions tested unde- this program.

This range of roll expansions is consistent with the results of previous studit, performed by ABB on sleeve and plug rolling, as well as industry experience demonstrating this range to provide optimum structural integrity for hard rolled joints.

5.2 Espair Of A Defective Rerolled Tube If a tube is found to have an unacceptable rerolled joint, the tube can be rerolled multiple times above the first reroll. The reroll may be performed as long as there is adequate tube length available. When multiple rerolljoints are unacceptable or not possible, the tube can be sleeved in order to keep it in service or it can be taken out of service with standard mechanical tube plugs at both ends of the tube. In either case, approved methods to perform the processes are in place.

5.3 Reroll Joint Installation Eauipmen._t The equipment used for the remote installation of rerolled joints in a steam generator is made l

i up of the following basic systems:

1

1. Remote Controlled Manipulator

2. Rotation Station

3. Tube Brushing / Cleaning Equipment

4. Tube Expansion Equipment

5. Tube Rolling Equipment

6. Tube Eddy Current Equipment These systems, when used together, allow installation of the reroll joints without entering the steam generator, in this way, personnel exposure to radiation is held to a minimum.

The tooling and methods described in the following sections represent the present technology for rerolled joint installation. As technological advances are made in the installation process, the updated techniques may be utilized upon completion oflaboratory verification by ABB-CE.

l CEN-620-P, Rev. 05-P Page 5-2

p L .

l 5.3.1 Remote Controlled Manipulator

The remote controlled manipulator (Figure 5-2) serves as a transport vehicle for repair and inspection inside a steam generator hot leg or cold leg plenum.

l. The manipulator consists of two major components; the' manipulator leg and the

- manipulator arm. The. manipulator leg is installed between the tubesheet and the-

- bottom of the primary head and provides axial (vertical) movement of the arm. The manipulator arm is divided into the head arm, probe arm and swivel arm. Each arm is moved independently with encoder position controlled electric motors. The swivel arm allows motion for tool alignment in various types of tube pitches. Computer control of

' the manipulator allows the operator to move tools from outside the manway and accurately position them under the proper tube against the tubesheet.

5.3.2 Rotation Station The rotation station (Figure 5-3) mounts on the end of the manipulator arm through the use of a locking dovetail arrangement. The rotation station delivers the various tools required for the reroll operation to the proper location. Cameras mounted on the rotation station are used to verify location as well as aid in the entry of tools into the I tube. Proper elevations for the various tools are obtained through the use of hardstops. The rotation station also provides controlled rotation to some of the tools used in the reroll operation. The station is controlled through the use of a torque

- monitoring system, which trips the station off when the preset torque value is reached.

5.3.3 Tube Brushing / Cleaning Equipment The initial step in the reroll process involves cleaning the tube inside surface with a stainless steel wire brush (Figure 5-4),' or equivalent. The purpose of this step is to remove the majority of the tube surface contamination that forms during power plant operation. The removal of this material allows for efficient operation of the rolling tool,' as the working of the tube is transferred to the control station as torque, with no foreign material introduced into the rolling pins that could lead to tool inefficiencies.

Additionally, the removal of the oxide layer will aid in roller life. An air motor rotates

. the brush tool as it is inserted into the end of the tube. At the appropriate elevation, the tool is reciprocated over the reroll area a total of one time. An interference fit between the tube and the brush assures a clean surface upon completion of this process step.

, 5.3.4 Tube Expansion Equipment For F* reroll joints, the hydraulic expansion equipment (Figure 5-5) is used to

. minimize the amount of crevice products between the tube and tubesheet prior to hard rolling the steam generator tube. - The' expansion tool consists of a mandrel and a

bladder that contains ' demineralized water which is used as the pressurization fluid.

When the hydraulic expansion tool is pressurized, the bladder acts directly against the .

CEN-620-P, Rev, 05-P - Page 5-3

inside surface of the tube causing expansion of the tube. A tool hardstop is provided for proper tool vertical positioning.

The hydraulic expansion unit contains a pressure transducer which is set to the proper pressure setting prior to use. The pressure transducer signal is fed back to the display screen's strip chart recorder in' order to record the pressure reached during the

. expansion cycle.

An expansion pressure is utilized to move the tube into contact with the tubesheet and move debris trapped between the tube and tubesheet away from the area. This hydraulic expansion does not add to the structural integrity of thejoint and no credit is taken during analysis of thejoint.

The hydraulic expansion may be used with any of the reroll joints (Figure 5-1).

However, due to equipment teachability and tube access concerns, it is typically.used only on the lower two reroll elevations.

5.3.5 Tube Rolling Equipment The tube rolling equipment (Figure 5-6) is used to expand the tube into intimate contact with the tubesheet, forming a structurally adequate leak limiting joint. The rolling tool is positioned under the proper tube using the manipuhtor, which is then used to insert the tool into the tube. The rolling tool utilizes a hardstop to position it vertically in the proper location.

The rolling equipment consists of the air motor, tube expander, torque readout and torque calibration unit. The torque readout and settings of the rolling tool are verified on the torque calibration unit prior to rolling of the tube. The tube is expanded to a torque which has been demonstrated by testing to provide a leaktight joint. The torque .

trace appears on the display screen's strip chart recorder and is used for evaluation of the rolling process on the individual tubes. The torque trace is used as the official record of the processe A second roll is performed to verify the torque level reached on the first reroll. The evaluation of the torque trace is the basis for acceptance or rejection of the rerolljoint since the joint integrity is based on percent wall thinning. A rolled joint which fails to meet the acceptance criteria may be rerolled. This is done by repeating the process at an elevation above the first reroll.

5.3.6 Tube Eddy Current Equipment After the reroll joints are installed, an examination is performed using eddy current (ET) techniques. The ET examination serves as a method to verify that the rerolljoint was [- ] in the steam generator tube and to assure proper tube expansion. . Also, the examination assures that the F* and EF* criteria of undegraded hard roll tube length above previous indications are met by the reroll l

L process.

L H - .

CEN-620-P, Rev. 05-P Page 5-4

[

i

~ _

~ 5.4 ALARA Considerations The steam generator repair operation is designed to minimize personnel exposure during re-roll operations. The manipulator is installed from the manway without entering the steam generator. It is operated remotely from a control station outside the containment building. The positioning accuracy of the manipulator is such that it can be remotely positioned without having'to install templates in the steam generator.

The rotation station is designed so that the dovetail fitting quickly attaches to the manipulator.

The rotation station is designed to quickly engage the individual rerolling tools. The tools are simple in design and all operations are performed remotely using tools held by the manipulator.

Each tool can be changed at the manway in 10-15 seconds. A tool operation is performed on .

, several tubes rather than performing each tool operation on the same tube before proceeding to the next tube. This reduces the number of tool changes which are required. If tool repair is necessary, the tool is removed and reroll operations continue using a spare tool. Tool repair

!- is completed off the platform in a low radiation area.

Air, water and electrical supply lines for tooling are designed and maintained so that they do not become entangled during operation. This minimizes personnel exp are on the steam generator platform. All equipment is operated from outside the containment building.

In summary, the steam generator operation is designed to minimize personnel exposure to ionizing radiation and is in full compliance with ALARA standards.

f

- CEN-620-P, Rev.' 05-P Page 5-5

Figure 5-1 Reroll Joint Configuration CEN-620-P, Rev. 05-P Page 5-6

l 1

1 Figure 5-2 Remote Control Manipulator CEN-620-P, Rev. 05-P Page 5-7

Figure 5-3 Rotation Station And Controls f

i Figure 5-4 Brushing Tool I CEN-620-P, Rev 05-P Page 5-8

O O.

Figure 5-5 Hydraulic Expansion Equipment Figure 5-6 Tube Roll Expander

' CEN-620-P, Rev. 05-P Page 5-9 1

h' .

' 6.0 TEST PROGRAM b

6.1 Test Matris ;

Three test matrices were developed to test the reroll joint over a range of test conditions.

LThese matrices' are shown in Tables 3-1 through 3-3. The matrices represent a range of-

conditions to which the rerolled joint was tested. A total of[ ] coupons were tested -

l- -for each test case for the program. A-description of each of the test conditions and type of tests is given below.

/

6.1.1 Tube Dimensions Various heats ofInconel 600 tubing were.used in this program. The material was

~

purchased from Sandvik Steel Co. and from Valinox Nucleaire. The tubing was

, purchased to nominal dimension of .875"_ O.D. x .050" wall, however, the tube wall dimensions were not uniform, varying from a minimum of .047" to a maximum of

.051" This was accounted for in the measurement step of sample preparation.

6.1.2 Tube Hole Size Changes in diameter affect the amount of wall thinning the tube will experience and require that the roller expander perform consistently over a range. A range of tube hole sizes was tested in the reroll program. This range of hole sizes represents actual 1tubesheet drill hole sizes per the original equipment manufacturer's specification. The

' hole sizes tested were the [

].

6.1.3 Surface Finish The tube holes for this program were bored to produce a surface finish of[ ] RMS.

The tubes were purchased to a [ ] RMS outside diameter surface finish and were received with a [ ] RMS finish.- These variables were constant throughout the test program.

6.1.4 Torque Setting

' A minimum and maximum _ torque setting was developed as part of this program. As described earlier, these settings are defined as the torque required to produce approximately [ ' ] percent tube wall thinning. Test cases in the F' program performed the reroll using a [ ]

-percent wall thinning. Test Cases in the EF* program also performed the reroll using

.[ ~ ] percent wall thinning.

~

. CEN-620-P, Rev. 05-P. Page.6-1

_ _ - _ - _ _ _- - _. _= - _ _ _

J 6.1.5 - Sludge Conditions The probability exists that sludge will be present in the~ annulus between the tube and

" - tubesheet during rerolling operations. Sludge in both the wet and dry condition was introduced into the annulus prior to performing the reroll. A [

] for the wet sludge test cases. This same [ -

J was performed. This extra preparation step assured a [

J. The sludge formulation was based upon sludge analysis performed by [ J.

In addition to the tests performed with simulated sludge formulations, tests were performed on tubes which had been removed from the Prairie Island and Zion steam generators. These tube samples represented a more accurate plant operating condition j due to the presence of a service induced oxide and sludge formulation.

6.1.6 Roller Expander Roller expander geometry is a constant with the essential variables being the cage diameter, slot dimensions, helix angle, roll dimensions and taper of the internal mandrel. This roller expander geometry is based upon experience gained in plug and sleeve installation programs. The [ ] effective length roll expander was used to prepare all test coupons for the F* program, while the [ ] effective length roll expander was used to prepare all test coupons for the EF* program.

6.1.7 Effective Roll Length In addition to the two roll lengths investigated per the previous section, samples were prepared with an effective length of 1.00". This length is just short of the F* length of

- 1.03" and 1.07" applicable to Prairie Island and Zion respectively. This set of tests was performed in order to verify the adequacy of the minimum F* distance which was calculated in the F* analysis.

6,2 Tests Reauired On Coupons For the first phase of the program, the test procedure requires a hydrostatic leak test after rerolling the tube into the block. Upon completion of the hydrostatic leak test, the coupons were subjected to cyclic loading tests, after which the coupons were hydrostatically leak tested a second time. The hydrostatic leak tests were performed from the secondary side in order to increase the conservatism of the test.' A primary side hydrostatic leak test was also performed in order to conform to the requirements of Reg. Guide 1.121. Finally, the coupons were subjected to a push test to determine the load at which joint movement occurs.

CEN-620-P, Rev, 05-P Page 6-2

4 l For the second phase of the program, some of the test variables were changed. The coupons

' were prepared with minimum torque values and maximum hole sizes. This was done to ensure a conservative test. The samples were then thermally cycled [ .

l

j. . Upon completion of the thermal cycling, the coupons were subjected to cyclic loading tests, after which the coupons were hydrostatically leak tested. The hydrostatic leak tests were l performed from the primary and secondary sides. The primary side hydrostatic leak test was also performed in order to conform to the requirements of Reg. Guide !.121. Finally, the coupons were subjected to a pull tests to determine the load at which joint movernent occurs.

i I

1 CEN-620-P, Rev. 05-P. ~ Page 6-3

___._._____..._____.._.___________________________w

p -

..g' s

_ 7.0 TEST RESULTS s7.1 Coupon Preparation 1

Mock 'tubesheets were machined with different size tube holes as defined in the test matrix.

E : Additionally, a split block'with a nominal hole size was machined. This block was used to -

develop the torque range required to meet the acceptance criteria.

7.1.1 ~ Tube Installation L Steam generator tubes were cut to six inch lengths and rolled into the tubesheet blocks at the lower end of the blocks. This was done to' anchor the tube in the block and to

~

- simulate the original hard roll. If the particular coupons required sludge conditions, the

.' sludge was brushed onto both the tube outside surface and the tube hole inside surface prior to locking the tube in place. Measurements required for tube wall reduction

. calculations were taken prior to installing the tube into the block.

17.1.2 Tube Bmshing The tube inside surfaces were brushed using a stainless steel wire bmsh. The coupons were placed in a test stand and the rotation station was used to perform the brushing operation. The brush tool was reciprocated over the length of the tube one time to complete the cleaning operation.

7.1.3 Tube Expansion Where. applicable, the tubes were expanded into the blocks using the hydraulic expansion equipment described. earlier. The bladder length- used for coupon preparation was [ ].

The use of a 1 ] for Phase 1 testing does not detrimentally affect the test results in any way. 'An [ ] was used to expand the tube into the block. There was no effect on tube expansion due to various pressure settings.'- A typical expansion trace, as recorded on the strip chart, is shown

' in Figure 7-1,

.7.1.4. Tube _ Rerolling The rerolling operation was performed by fixturing the coupon into a rolling stand.

=The[ _ -] roll expander was used for all F* rerolling tests and the [ ] roll expander was used for all EF* tests. The test matrix defined the torqr..levels that were required for coupon preparation. A typical torque trace, as recorded u the strip chart (torque is along the Y-axis, while time is' along the X-axis), is shown in Figure 7-2 for a coupon prepared with wet sludge. The wet sludge is easily pushed from behind the tube and there is a smooth, steady increase in torque.-

P i iCEN-620-P Rev 05-P!:

Page 7-1 4 i ;

m_____

A typical torque trace, as recorded on the strip chart, is shown in Figure 7-3 for a coupon prepared with dry, hard sludge. The dry, hard sludge is fragmented and moved about during the rolling operation. The torque setpoint is reached over a longer period oftime.

7.1.5 Coupon Numbering The following numbering system was used to identify the coupons.

Phase 1 - F* Program B1,B2,B3 Case 1 [ ]

Al, A2, A3, 3, 8 Case 2 [ ] l A4,A5,A6 Case 3 [ ]

1,2 Case 3a [ ]

C l, C2, C3, 5, 6 Case 4 [ ]

C4,C5,C6 Case 5 [ ]

Dl,D2,D3 Case 7 [ ]

El,E2,E3 Case 8 [ ]

F1,F2,F3 Case 9 [ ]

Phase 1 - EF* Program 110-3 Case 1 [ ]

90-4 Case 2 [ ]

140-3 Case 3 [ ]

90-5 Case 4 [ ]

110-4 Case 5 [ ]

130-1,130-2 Case 6 [ ]

Phase 2 - Additional F* And EF* Reroll Program 11-1 through 11-5 Case la [ ]

12-1 through 12-5 Case Ib [ ]

21-1 through 21-5 Case 2a [ }

22-1 through ' 2-5 Case 2b [ ]

31-1 through 31-5 Case 3a [ ]

32-1 through 32-5 Case 3b [ ]

4-1 through 4-3 Case 4 [ ]

5-1 through 5-3 Case 5 [ ]

6-1 through 6-3 Case 6 [ ]

7-1 through 7-6 Case 7 [ .]

8-1 through 8-6' Case 8 [ ]

9-1 through 9-3 ' Case 9 [ ]

10-1 through 10-3 Case 10 [ ]

CEN-620-P, Rev, 05-P Page 7-2 c

-- - = _ _ . _ - _ - _ _ - - _ _ - _ _ _ . - _ _ _ - _ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _

,7.2 Toraue Development -

- The first step in the program was to develop torque levels associated with tube wall thinning of

.' [ ..

] percent.1 This was done by using the split block arrangement. Tubes were placed in the split block,' rolled, then measured to determine wall thinning. Tables 7-1 and 7 give the values for the various torques using the i j effective length roll for the F*

program and the [ ] effective length roll for the EF* program.

Based upon this information, maximum and minimum torque values were first chosen for the -

[ ] effective length rolls. These values were [ ] for the minimum torque

' setpoint, [ ] for the nominal torque setpoint and [ ] for the maximum torque setpoint.: These were the torque settings that were utilized during the testing process.

' Additionally, a test coupon was rolled to the system limited (based on supply air) torque value of[ j; This sample, with a wall thinning of [ ], successfully passed cyclic, push and hydrostatic testing.

! Table 7 F* Toraue Development Toraue (in-lbs)- Wall Thinning (%) - Toraue (in-lbs) Wall Thinning (%)

1 I

I I

j 1 CEN-620-P, Rev, 05-P Page 7 o;

Table 7 EFa Toraue Devlopment f

Toraue (in-lbs) Wall Thinning (%) Toraue (in-lbs) Wall Thinning (%)

7.3 Test Procedure References 4.5 and 4.7 are the detailed procedures describing all step-by-step activity for the test program. This section summarizes the procedure used to conduct the various tests on the coupons. Tables 7-3 through 7-5, at the end of this section, summarize all of the test results.

7.3.1 Thermal Cycling Tests I- The additional reroll samples prepared for phase two of this program were thermally cycled between [ ]. This was done to simulate the l heatup and cooldown cycles that a power plant experiences.

7.3.2 Mechanical Cycling Tests Normal operating and postulated accident conditions result in cyclical axial and flexure loading conditions on the steam generator tube and tubesheet. The maximum tubesheet loadings result from a flexure pattern where tubesheet ligament stress across the majority of the tubesheet is tensile above the neutral axis and compressive below the neutral axis. For rerolijoints below the neutral axis, the compressive stress would tend to close the tubesheet hole during operating conditions, thus increasing the tube to tubesheet joint contact pressure. For reroll joints above the neutral axis, the tensile stress could open the tubesheet hole during operating conditions, thus potentially reducing the_ tube to _ tubesheet joint contact pressure. An extensive test and qualification program on the Roll Transition Zone Sleeve rolled joint (Reference 4.9),

has shown that the tubesheet flexure has no effect on the joint structural integrity or leak tightness. Therefore, only axial loads were applied to test coupons during the

. rerolljoint cyclic test program.

' CEN-620-P, Rev. 05-P - Page 7-4

j. The rerolled joints were subjected to a cyclic axial load test to demonstrate structural capability of thejoint. The loads used for the Phase I cyclic tests were based upon the operating loads experienced by a tube in a locked condition, as this was assumed to be the worst case loading condition on the tubes. These loads are [

]. For Phase 2, the worst case loading was determined to be on ajoint in the unlocked condition under accident conditions. These loads are [

J. Section 8 provides an analysis of this condition. The loading was applied to these rerolled joints using an MTS Testing l Machine. [ ].

Phase 1 - F* And EF* Tests Most coupons prepared for F* Cases 1 through 5 were [

1. Sample nos. I through 6 were pull tested only. The ;

rerolled joints for F* test Case 9 were conservatively loaded between [ ]

for a total of [ ] cycles. Coupons prepared for EF* Cases 1 through 3 were I 1. I

j. These samples were used to determine the effect on the rolled joint due to conditions expected in the steam generators, such as; the I ,

]. i l

Phase 2 - Additional F* And EF* Reroll Tests All coupons tested for the additional reroll testing program were [

1. I 1

7.3.3 Push And Pull Tests ,

Phase 1 - F* And EF* Tests As described in the previous section, steam generator tubes are subjected to loading conditions while in operation. The maximum loads to which the tube is subjected are

[

]. The rerolled coupons were push tested to a load of [ ] for the F* coupons and [ ] for the EF* coupons using an MTS Testing Machine. Coupons from F* Cases 1 through 5 and EF* Cases I through 3 exhibited [ ] at this load and the test was terminated. Coupons from F*

Cases 7 and 9 were pushed to failure. The failure occurred due to tube buckling at a load of [ ]; the rerolled joint did not [ ]. Two samples from test cases 2,3a and 4 were pull tested to failure. The minimum load was [ ]

CEN-620-P, Rev. 05-P Page 7-5

Phase 2 - Additional F* And EF* Reroll Tests For the additional reroll test program, the samples were pulled to failure. It was decided that pulling the samples represented a more conservative approach than the push test. The reroll joints failed at a minimum load of [ ] The maximum failure load was [ ]

7.3.4 Hydrostatic Leak Tests Phase 1 - F* And EF* Tests Hydrostatic leak tests were performed on the coupons before and after cyclic testing.

The tests were performed from the secondary side in order to increase the conservatism of the test. The test was performed at [

].

The first pressure level represents the operating pressure differential.

The ASME Code hydrostatic test pressure of:

- 1.25 x Primary Design Pressure = 1.25 x 2485 psi = 3106 psi is the basis for the second test pressure. For added conservatism, ABB-CE increased :

the pressure another [ ] for the third test pressure.

All samples except the samples [ ] exhibited leaktightness. Samples Cl,C2 and C3 had an [

].

In order to comply with the guidelines of Regulatory Guide 1.121, which call for a test pressure of three times-the operating differential, F* Test Case 7 coupons were pressurized to [ ] from the primary side. [

1

' Phase 2 - Additional F* And EF* Reroll Tests The same approach as above was taken with the additional reroll tests which were

. performed. Some samples were tested from the primary side and others from the .

secondary side, per the test matrix. The pressures at which the samples were tested

.was raised slightly and the hold times were increased, leading to a more conservative test condition. The first pressure was [ ], followed by

[ _ _

- ], then [ - ]. All of the clean samples tested from the primary side exhibited leak tightness, while the samples tested from the secondary side exhibited varying degrees ofleakage, ranging from a low of

[ ].

CEN-620-P, Rev. 05-P ? Page 7-6.

= - - = _ - -

1 l

7.3.5 Collapse Tests The possibility exists that sludge will be present in the annulus between the tube and tubesheet during rerolling operations. The moisture in wet sludge, trapped between

. two rerolled joints, has the potential of flashing to steam under operating temperatures.

The pressure build up during this event will be released either through the rolled joints or by a collapse of the tube. Test coupons containing [

]. I 7.4 . Phase 1 - F* Coupon Results Test Case 1 - [ ]

Coupons B1,B2 and B3 of this test case successfully passed all phases of testing.

I 1

. Test Case 2 - [ ]

Coupons A1, A2, A3,3 and 8 of this test case successfully passed all phases of testing.

[

]

Test Case 3 - [ ]

Coupons A4, A5 and A6 of this test case successfully passed all phases of testing.

I 1

Test Case 3a - [ ]

Coupons 1 and 2 of this test case successfully passed the pull tests.

I 1 i

. Test Case 4 - [ ]

l-

[ Coupons Cl, C2, C3, 5 and 6 of this test case successibily passed all phase of testing. l ,

l 1

CEN-620-P, Rev. 05-P Page 7-7

I !

']

Test Case 5.. [ ]

Coupons C4, C5 and C6 of this test case successfully passed all phases of testing.

I 1

Test Case 6 - [ ]

See Section 7.7 for the results of the [ ] test.

Test Case 7 - [ ]

. Coupons Dl, D2 and D3 of this test case successfully passed the push tests and the primary side hydrostatic leak test.

I 1

Test Case 8 - [ ]

I 1

I' l.

I l

l 1

CEN-620-P, Rev. 05-P Page 7 L

l Test Case 9 - [ ]

Coupons F1, F2 and F3 of this test case successfully passed all phases of testing.

I 1

' 7.5 Phase 1 - EF* Coupon Results -

Test Case 1 - l ]

Coupon 110-3 of this test case successfully passed all phases of testing.

I 1

Test Case 2 - [ ]

Coupon 90-4 of this test case . successfully passed all phases of testing.

1 Test Case 3 - [ ]

Coupon 140-3 of this test case successfully passed all pnases of testing.

I 1

Test Case 4 - [ ]

~ Cou'pon 90-5 of this test case successfully passed all phases of testing.

[

1 Test Case 5_- [ ]

' Coupon 110-4_of this test case successfully passed all phases of testing.

I 1

LCEN-620-P, Rev, 05-P L Page 7 w

Test Case' 6 - l l 1

l ].

l l 'I l ].

7.6 Phase 2 - Additional F* And EF* Coupon Results Test Case la - [ ]

Coupons Il-1 through Il-5 successfully passed all phases of testing.

1 i

1 1

Test Case Ib - [ j Coupons 12-1 through 12-5 successfully passed all phases of testing.

I

].

Test Case 2a [ ]

Coupons 21-1 through 21-5 successfully passed all phases of testing. ;

l 1 ;

I i Test Case 2b - l ] I Coupons 22-1 through 22-5 successfully passed all phases of testing.

I 1 )

CEN-620-P, Rev. 05-P' Page 7-10 i

i

r; I

l. :

Test Case 3a - [ ]

Coupons 31-1 through 31-5 successfully passed all phases of testing.

I 1

Test Case 3b -'[ ]

Coupons 32-1 through 32-5 successfully passed all phases of testing.

I 1

Test Case 4 - [ ]

Coupons 4-1 through 4-3 successfully passed all phases of testing.

I-l 1

Test Case 5 - I- 1 Coupons 5-1 through 5-3 successfully passed all phases of testing.

I 1

Test Case 6 - [ ] I l

Coupons 6-1 through 6-3 successfully passed all phases of testing.

1-1 ,

Test Case 7 - [ ]

l

. Coupons 7-1 through 7-6 successfully passed all phases of testing.

CEN-620-P, Rev. 05-P ' Page 7-11 c______

I' 1

Test Case 8 - [ ] l Coupons 8-1 through 8-6 successfully passed all phases of testing.

I

]

I Test Case 9 - [ ]

Coupons 9-1 through 9-3 successfully passed all phases of testing.

I

] The pull tests yielded a minimum load at failure of[ ]

Test Case 10 - [ ]

Coupons 10-1 through 10-3 successfully passed all phases of testing. .

I i

I 7.7 Tube Growth Tests

An additional area of concern was the area of steam generator tube growth or contraction l during the rerolling operation. Three coupons were prepared and measured prior to the' ,

rerolling operation. The samples were then hydraulically expanded over a length of three and '

one halfinches, a length which represents the amount of unrolled tube that will be expanded in t

~ he steam generators. The coupons were then subject to a torque that resulted in [ ] ;

percent wall thinning. The results are shown below~.

i i

i L CEN-620-P, Rev. 05-P. - Page 7-12

f Tube 'Nh. Initial Length Expansion Length Reroll Length Change

.1. - 6.060" [ ] [ ] [ ]

2- 6.068" [ ]- [ ] [' -]

3 6.069" '[ ] [ ] [ ]

' The change in length due to the [ ] and the length change due to the [ ], for an overall length change of, on average,

[ J. This represents a [ ] over a 48" long tube span.

7.8 Roller Life ABBlCE has a large volume of experience with rolling operations. References 4.16 and 4.17 '

document life testing performed on roller expanders during sleeve roll qualification testing.

This data is applicable to the current program, since similar roller designs are employed and

. similar materials are involved. In both of the referenced programs, there was no [

].

7.9 Discussion Torque values associated with tube wall thinning of i ] were enablished using production rolling equipment. These values were established by rolling tube samples in a split block and recording the torque trace. The tubes were then removed from the block, sectioned and measured to determine wall thinning. Based upon the acceptance criteria established, which bracketed original equipment manufacturing criteria and reflected ABB-CE rolling experience, torque values for the [ ] and [ ] effective length rollers in the range of[ ] were established.

Phase 1 F* And EF* Tests Using the torque values established, the tests called 'out in the test matrices were performed.

All samples were prepared using a production control system and tooling. All [ ]

coupons, representing various steam generator conditions, were tested and met the acceptance criteria. The low torque coupon (Al-A3) preparation resulted in torques above the minimum value of [ ]. This occurred due to an overshoot of the intended value by the system. However, it still resulted in a low wall thinning value of approximately [ . . ] percent.

Cyclic load ranges of[ ] and [ . . ] were used to test both the F* !

. and EF* coupons for a total of[ ]. The load values were based on the worst case !

loading that the tube.would experience'(depending upon location in the tubesheet) and cycling

. the tube through the total amount of load cycles.the tube experiences during operation,

..regardless ofloading conditions. This approach assures a high degree of conservatism. Under i 1

.CEN-620-P, Rev. 05-P - , Page 7-13 ;

=x- - - :

1 w

these loading conditions, [

u j.:

A push test load of[ ] was applied to all Phase I reroll joint coupons. This value represents a load greater than the maximum tube loading conditions described earlier. The tests were stopped before joint failure was observed. [

J As an additional test, six coupons were pushed to failure. Failure occurred by tube buckling at [ J.

Hydrostatic leak tests were performed on all coupons before and after cyclic loading. . The test pressures represented a secondary side hydrostatic test and a primary side hydrostatic test. All tests were performed from the secondary side of the coupons, which represents a high degree of conservatism. The ASME Code hydrostatic test pressure of [

J. An additional [ . ] was then applied to increase the factor of safety further. [ ] coupons were tested from the primary side at a pressure of

[ J. This represents a pressure greater than the three times operating differential pressure set forth in Regulatory Guide 1.121.

All coupons held pressure for a [ ] minimum at each pressure level with no

.. observable leakage except for the coupons with [ 1 There was no leakage at the pressure differential of 2000 psi, while the coupons exhibited an 1.

j at 4120 psi. [

1 I

1

. Base 2 F* And EF* Reroll Tests l The test samples we p'epared ucording to the test matrix shown in Table 3-3. All coupons -

were prepared with a' low torque trip point and large hole diameter (.893") in order to increase the conservatism of the test. All of these samples were [

' J.

CEN-620 P, Rev. 05-P Page 7 4

All of the samples.were also mechanically cycled from [ 1 Under these loading conditions, [ ].

Hydrostatic leak tests were performed on all coupons after cyclic loading. The test pressures represented a secondary side hydrostatic test and a primary side hydrostatic test. Tests were performed from the primary and secondary side of the coupons. The test pressures were [

J.This latter value represents a pressure greater than the three times operating differential pressure set forth in Regulatory Guide 1.121.

All 'of the clean coupons coupons tested from the primary side held pressure with no observable leakage, while the tubes from Zion and Prairie Island exhibited [

] The coupons tested from the secondary side showed low levels ofleakage. These coupons exhibited an [

1 CEN-620-P, Rey, 05-P ' : Page 7-15

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CEN-620-P, Rev. 05-P Page 7-24 j

4 l

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Figure 7-2 Typical Torque Trace - Wet Sludge Sample CEN-620-P, Rev, 05-P Page 7-25

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l Figure 7-3 Typical Torque Trace - Dry Sludge Sample CEN-620-P, Rev. 05-P Page 7-26

F-

-g-8.0 STRUCTURAL CONSIDERATIONS

n t .

An analysis was performed to generate conservatively high loads to be used in the test program

~ discussed in Section 7.0. The " worst" case loading condition was found to be for a tube n_ot locked at the first support plate during the faulted accident condition of Main Steam Line Break.~ This condition produces higher loads on the tube than an analysis that considers only

pressure differential since the loading due to the thermal expansion between the rerolled and original weld joints must also be evaluated. Both conditions of the tube locked and p_o_t locked

- in the first support plate are evaluated.

The operating and design conditions for all of the Westinghouse Series 44 'and 51 plants (Reference 8.3.1) are considered. Only the " worst" case operating / design conditions for each of the Series 44 and 51 steam generators are used in the analysis. This analysis addresses two (2) rerolled joint location cases. In the first case the rerolled joint is 18.345 inches and 17.375 inches from the secondary face of the tubesheet for the Series 44 and 51 units, respectively. In

, the second case the rerolled joint is 2 inches from the secondary face of the tubesheet for both series steam' generators which is the maximum elevation allowed per Reference 83.2. A structural evaluation for the rerolled tube geometry is modeled in Figure 8-1.

8.1 Reroll Joint Configuration 8.1.1: ' Axial Loading for the First Rerolled Joint Case with Tube Lock-up The rerolled tube schematics for both the Westinghouse Series 44 and 51 steam generators are shown in Figures 8-2 and 8-3, respectively, for the first location case.

The rerolled joint is 18.345 inches and 17.375 inches from the secondary face of the tubesheet for the Series 44 and 51 units, respectively. The stmetural model is a system of. axial members with properties and boundaries as shown in Tables 8-1 and 8-2 for Series 44 and 51 steam generators, respectively. The material properties (i.e., modulus of elasticity and mean coefficient of thermal expansion) are taken from Reference 8.3.6.

The axial load on the rerolled tube is due to the thermal expansion between Points A and B. No axialloading due to pressure exists between Points A and B because Points A and B are externally balanced.

From Figure 8-1, the tube at Point A is locked in the first tube support above the tubesheet and is therefore, forced to move with the surrounding secondary shell. The axial load, F, is a function of the spring constants for the lower and upper tubes between

- Points A and B, the location of the rerolled tube joint in the tubesheet, and the forced

displacement between the tube and shell/tubesheet arrangement between Points A and B5 The thermal growth of the lower tube, upper tube, shell, and tubesheet is represented by 6, and the equivalent spring stiffness of the lower and upper tube by K .

Therefore, from Table 2, page 5-70, of Reference 8.3.4; the total spring stiffness for the flower and upper tubein seriesis:

CEN-620-P, Rev. 05-P l Page 8-1

O I 1 From equation 15.142, page 15-27, of Reference 8.3.5; the spring stiffnesses for the lower and upper tubes, individually, (where A, E, and L are their cross-sectional areas, modulus of elasticity, and tube lengths, respectively) are:

1 1 1 1 From the model in Figure 8-1, the forced tube displacement,Sta, due to temperature is:

1 1 Also, from equation 15.142, page 15-27, of Reference 8.3.5; the axial load, F, is:

1 1 The calculations from the above equations result in a [

] for the Series 44 and 51 steam generators, respectively, due to tube lock-up in the first support plate. The results are tabulated in Tables 8-3 and 8-4.

CEN-620-P, Rev. 05-P Page 8-2

i Figure 8-1 Rerolled Tube Model and Environment CEN-620-P, Rev. 05-P Page 8-3

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Tube Schematic - Series 44" Steam Generators for the '

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. 8.1.2 ' Axial Loading for the Second Rerolled Joint Location Case The rerolled tube schematics for both the Westinghouse Series 44 and 51 steam generators are shown in Figures 8-4 and 8-5, respectively, for the second rerolled l

1 - location case. The rerolled joint is 2 inches from the seconday face of the tubesheet for both series steam generators. The structural model is a system of axial members with properties and boundaries as shown in Tables 8-5 and 8-6 for Series 44 and 51 steam generators, respectively. The material properties (i.e. modulus of elasticity and mean coefficient of thermal expansion) come from Reference 8.3.6. The axial load on the rerolled tube is due only to the thermal expansion between Points A and B.

The calculations use the same equations that are detailed in Section 8.1.1 and result in a[

1

l. The results are tabulated in Tables 8-7 and 8-8.

l CEN-620-P, Rev. 05-P Page 8-10

. . _ . -_- _ _ _ _ _ - . _ _ _ _ _ - _ - _ - _ - _ _ _ = - _ _ _ _ _ - _ _ _ _ - . - _ _ _ _ _ _ _ _ _ __ .. .

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- Tube ~ Schematic - Series "44" Steam Generators for the Second Rerolled Joint Location Case i;

CEN-620-P, Rev. 05-P. .Page 8-11

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Figure 8-5 Tube Schematic - Series "51" Steam Generators for the Second Rerolled Joint Location Case i

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8.1.3 Axial Loading for the First Rerolled Joint Case with No Tube Lock-up

{

The rerolled _ tube schematics for both the Westinghouse Series 44 and 51 steam generators are shown in Figures 8-2 and 8-3, respectively, for the first location case.

The rerolled joint is 18.345 inches and 17.375 inches from the secondary face of the j tubesheet for the Series 44 and 51 units, respectively. The structural model is a system of axial members with properties and boundaries as shown in Table 8-9 for Series 44 and 51 steam generators. The material properties (i.e. modulus of elasticity and mean coefficient of thermal expansion) come from Reference 8.3.6. The maximum axial load on the rerolled tube is obtained when it is not locked into the first support plate during the faulted accident condition of Main Steam Line Break.

From Figure 8-1, at Point A, the tube is not locked in the first tube support above the tubesheet and is therefore, free to move independently of the surrounding secondary shell. The axial load, F, is the sum of the axial load, Fa, due to the tube's thermal expansion between points B and C and the axial load, Fp, due to the pressure differential. The axial load, F , is a function of the spring constant for the lower tube between points B and C, the location of the rerolled tube joint in the tubesheet, and the forced displacement between the tube and tubesheet arrangement at this location.

The thermal growth of the tube and tubesheet is represented by 5, and the spring stiffness of the tube by K.

From equation 15.142, page 15-27, of Reference 8.3.5; the spring stiffness for the q tube (where A, Ew, and Lnc are the cross-sectional areas, modulus of elasticity, and tube length, respectively)is:

1 1 From the model in Figure 8-1, the forced tube displacement,Srma, between Points B and C due to temperature is:

l I Also, from equation 15.142, page 15-27, of Reference 8.3.5; the axial load, Fa, due to

' thermal expansion is:

I 1 The axial load, F,, due to pressure differential is:

I 1 where:

P2 and Pi are the Secondary and Primary Pressures, respectively.

CEN-620-P, Rev. 05-P '

Page 8-17

4 R. and R4 are the outer and inner tube radii, respectively.

Therefore, the total axial load, F, is:

1 1 l The calculations from the above equations result in a l I

j. For the [

] for both the Series 44 and 51 l steam generators. The results are tabulated in Table 8-10.

I 1

l J

CEN-620-P, Rev. 05-P Page 8-18 l

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8.1.4 Axial Loading for the Second Rerolled Joint Case with _N_o Tube Lock-up The rerolled tube schematics for both the Westinghouse Series 44 and 51 steam generators are shown in Figures 8-4 and 8-5, respectively, for the second rerolled location case. The rerolled joint is 2 inches from the secondary face of the tubesheet for both series steam generators. The structural model is a system of axial members with properties and boundaries as shown in Table 8-11 for Series 44 and 51 steam generators. The material properties (i.e. modulus of elasticity and mean coefficient of thermal expansion) come from Reference 8.3.6. The maximum axial load on the rerolled tube is obtained when it is nE locked into the first support plate.

The calculations use the same equations that are detailed in Section 8.1.3 and result in a l ] for the Series 44 and 51 steam generators, respectively, at [ J. For the [

] for the Series 44 and 51 steam generators, respectively. The results are tabulated in Table 8-12.

CEN-620-P, Rev, 05-P l' age 8-21

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' 8.1.5 ' Tubesheet Ligament Stresses -

In calculating the tubesheet ligament stresses for'the Westinghouse Series 44 and 51 steam generators; the tubesheet ligament stresses in Reference 8.3.3 for a Series 44 are used as a basis for determining these stresses acting on the rerolled tube joint. These tubesheet ligament stresses are also applicable to the Series 51 steam generators based on the follow' mg observations.

1 Tubesheet bending stresses are inversely proportional to the thickness squared. The Series 51 thinner tubesheet increases these stresses by a factor of[ ).

2. The large ligament efficiency of the Series 51 steam generators results in a decrease in stress by a factor of[ l.

3. The product of the above two factors is unity, so the two types of generators are evaluated the same.

Based upon the tubesheet ligament stresses for the desian condition (i.e. tubesheet differential pressure of 1750 psi) in Reference 8.3.3 and the location of the rerolled tube joint from the tubesheet surface (primary or secondary face); the linear interpolation for the maximum tubesheet ligament stress at the re-rolled tube joint location, Sw, is:

1 I The tubesheet ligament stress results at the design condition for various rerolled locations are tabulated in Table 8-13.

I 1 8.2 Elug and Sleeve Program Applicability As previously discussed, ABB/CE has extensive experience in the area of rolling. The mechanical plug rolling program and the advanced sleeve rolling program both utilize torque levels similar to those developed for the tube reroll program. Numerous analyses and test programs _have been performed to support the plug and sleeve installation processes.

Discussions of these programs can be found in References 4.7 and 4.8 that were mentioned in Reference 8.3.7.

CEN-620-P, Rev. 05-P . Page 8-24

r-Table 8-13 Tubesheet Ligament Stresses for Westinghouse Series "44" and "51" Steam Generators at Design Condition

TUBESHEETJ fTUBE REROLLED LOCATIONi l-LIGAMENT!

w +

STRESSESb

~

Jyp' _

l 1

l l

CEN-620-P, Rev. 05-P Page 8-25 ,

i

+

8.3 References 8.3.1 Westinghouse Steam Generator Standard Information Package, January 04,1982 (REF 002).

8.3.2 Northern States Power Co. (Richard P. Pearson) Fax to ABB-CE (David Stepnick), dated 9/9/96 8.3.3 " Primary / Secondary Boundary Components Steady State Stress Evaluation", prepared by P.

Wedler, Westinghouse Electric Corp., April 1965 (REF-96-001).

8.3.4 Mark's " Standard Handbook for Mechanical Engineering", 8th Edition,1979.

8.3.5 Mechanical Engineering Reference Manual", by Michael R. Lindeberg, P.E., 9th Edition, 1994.

8.3.6 - ASME Boiler and Pressure Vessel Code,Section III for Nuclear Power Plant Components, 1986 Edition, no addenda.

8.3.7 ABB-CE Report No. CEN-620-P, Revision 01-P, " Series 44 & 51 Design Steam Generator Tube Repair Using a Tube Re-Rolling Technique", April 1995.

8.3.5 Westinghouse Report No. WCAP-14225, Revision 1, Table 2-3.

lCEN-620-P, Rev. 05-P - Page 8-26

l

,l 9.0 EDDY. CURRENT EXAMINATION '

9.1 -Installation Verification )

i Upon completion of the reroll process, an eddy current technique, using a bobbin coil or rotating.

coil probe, is employed to verify that the hydraulic expansion, where applicable, and reroll joint

. have been [ ] in the tube.-

9.2 Bobbin Coil Profilometry

Bobbin coil profilometry compares the diameter of the tubing against a known calibration standard and provides differences among the diameters of the original hard roll, the new hard roll, and the unrolled tubing. Field experience has demonstrated that a reroll expansion which results in less than .

[- ] diametrical difference between the original hard roll and the reroll provides additional L assurance of an acceptable reroll.

l 9.3 Rotatina Probe Examination Upon completion' of the installation, an MRPC probe, or equivalent, is pulled through the rerolled tube to detect tube indications. Since the parent tube, with known ECT indications, has been .

worked with both a hydraulic expansion and a hard roll, an inspection is necessary to determine if the original indications have changed. The rotating probe results will be compared with previous test results in order to determine whether or not the original indications have propagated. This test will.be. used to verify that the F* and EF* criteria of undegraded hard roll tube length above previous indications are met.

- CEN-620-P, Rev. 05-P Page 9-1 w________-

i 10.0 EFFECT OF REROLLING ON OPERATION The effect of any tube repair process on the system operation involves flow rate and heat transfer.

For'the-case of flow rate, the reroll process will have no detrimental effect. -There are no restrictions to primary coolant flow introduced by this process, with the exception of a tube collapse condition.

As described in Section 7.4, collapse test; were conducted on samples with sludge deposits placed

.in the annulus between the tube and tubesheet. Tube collapse was not seen in any of these samples.

lliowever, a test sample was prepared with (no sludge, but) a full column of water in the annulus between the tube and tubesheet. The water was trapped between the original tube rolled joint and the last reroli joint (located approximately 2 inches from the secondary face of the tubesheet). The sample was placed in an oven for approximately eight hours at 650*F. Tube collapse, in the form of a localized I.D. bulge, was seen at the midpoint between the two rolled joints. This is a self relieving condition (as more volume is added to the annulus as the bulge is forming) and the collapse process was stopped before tube I.D. to I.D. contact was made. A 1/2" O.D. go-no-go gage was successfully passed through the bulged area. This is an' extremely conservative case, since it is unlikely that there would be a complete absence of sludge, allowing the annulus to be filled with pure water.-

The overall resistance to heat truisfer between primary and secondary side of the steam generator consists of primary side film resistance, the resistance to heat transfer through the tube wall, and the secondary side film resistance. Since there is no flow rate change with the exception of a tube collapse condition, there is no change in primary side film resistance. Since the rerolling operation takes place in the tubesheet region, there is no effect on heat transfer through the tube wall nor on secondary side film resistance.

In summary, the rerolling operation does not affect the primary system flow rate or the heat transfer capability of the steam generators.

! 4 l

CEN-620-P, Rev. 05-Pf Page 10-1

= -_ - __. _ . _ - _ _

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1.0 INTRODUCTION

SUMMARY

4.0 REFERENCES

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SUMMARY

4.0 REFERENCES

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