ML20203H670

Rev 0 to non-proprietary Version of BAW-10232, OTSG Repair Roll Qualification Rept (Including Hydraulic Expansion Evaluation)

ML20203H670
Person / Time
Site:	Arkansas Nuclear
Issue date:	01/31/1998
From:	FRAMATOME
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Shared Package
ML20203H667	List: 1CAN029805, Forwards non-proprietary Version of Rev 0 to BAW-10232, OTSG Repair Roll Qualification Rept (Including Hydraulic Expansion Evaluation) ML20203H670
References
BAW-10232, BAW-10232-R, BAW-10232-R00, NUDOCS 9803030285
Download: ML20203H670 (46)

Text

_ _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _

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BAW-10232 REV 00 JANUARY 1998 g

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OTSG REPAIR ROLL QUAI.lFICATION REPORT I

(INCLUDING HYDRAULIC EXPANSION EVALUATION) l

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FTl NON-PROPRIETARY FRAMATOME TECHNOLOGIES P.O. BOX 10935 LYNCHBURG, VA 24506-0935 COPY NO.

28 288!!! !!888812 P

PDR BAW-10232 REV 00 FRAMATOME TECtINOLOGIES

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This document is the non-proprietary version of the H

proprietary document BAW-10232P-00.

In order for this document to meet the non-proprietary

criteria, certain blocks of information were withheld.

The bass.s for determining what information to withhold was based on the two criteria listed below.

Depending upon the applicable

criceria, the criteria code, (c) or (d),

represents the withheld infor-ation.

4 (c) - The use of the information by a competitor would decrease his expenditures, in time er resources, in designing, producing or marketi.g a similar product.

(d) - The information consists of test data or other similar data concerning a process, method or component, the application of which resuits in a competitive advantage to FTI.

I I

BAW-10232 REV 00 FRAMATOME TECilNOLOGIES

TABLE OF CONTENTS PAGE

1.0 INTRODUCTION

...............................1-1

1.1 Background

...............................1-:

.......1-1 1.2 Purpose 2.0 EXECUTIVE

SUMMARY

...............................2-1 3.0 REPAIR ROLL DESCRIPTION....................

3-1 I

.... 3-1 3.1 Design 3.2 Installation

...............................3-1 3.3 Procesa Verification.........................

3-2 4-1 4.0 DESIGN RFQUIREMENTS 4-1 4.1 General 4.2 Design and Operational Loading Conditions....

4-1 5.0 DESIGN VERIFICATION

...............................5-1 5.1 Calculation of Tube Loads

...................5-1 I

5.2 Design Verification Testing............

.....5-2 5.2.1 Mockup Preparation and ECT Testing...

5-4 3

5.2.2 Leak Tcsting................,........

5-6 3

5.2.3 Thermal and Fatigue Cycling..........

5-8 5.2.4 Ultimate Load Test...................

5-9 5.3 Effect of Tube Hole Dilation on Joint...... 5-11 Strength 5.4 NDE Examination Effects on Final............

5-16 Repair Roll Length 5.5 Repair Roll Effect on Axial Tube Load.......

5-17 5.6 Tube Crevice Evaluation.................... 5-17 5.6.1 Tube Denting Test Summary...........

5-18 5.6.2 Tube Installation...................

5-19 I

5.6.3 Trapped Water Volumes...............

5-20 5.6.4 Testing Observations................

5-20 5.7 Effects of Tube Hydraulic Expansion........ 5-21 5.7.1 Hydraulic Expansion Residual Crevice.5-21 I

and Ligament Stress 5.7.2 Change in Tube Axial Preload........

5-22 5.7.3 Summary.............

............... 5-23 6.0 EVALUATION OF REPAIR ROLL LIFE.....................

6-1 6.1 Tube Integrity in Repair Roll................

6-1 I

6.2 Tubesheet Corrosion Beyond Repair Roll.......

6-2

7.0 CONCLUSION

S

.........................7-1 I

8.0 REFERENCES

...............................8-1 I

FRAMATOME TECHNOLOC4ES i

BAW-10232 FEV 00 I

I

'InBLE OF CONTENTS-CONTINUED I

PAGE APPENDIX A: ETSS for Bobbin and MRPC Examination...............A-1 of OTSG Tube Repair rolls hPPENDIX B: Repair roll Exclusion Zones........................B-1 LIST OF TADLES PAGE TABLE TITLE 4.1 B&W OTSG (177FA) Performance Characteristics 4-2 4.2 B&W (177FA) Steam Generator Tube Repair.

4-3 40 Year Design Loadings 5-2 5.1.1 Axial itbe Load Summary.

5-4 5.2.1. Tube Installation Data I

5.2.2 Tulm Installation Torque and Roll Lengths 5-6 5.2.3 Leak Test Results 5-7 5-9 5.2.4 Fatigue Test Axial Load Cycles I

5.2.5 Ultimate Load Test Results 5-10 5.3.1 Tube Hole Dilation Allcwables.

5-12 5.6.1 Tube Installation Data 5-19 5.6.2 Tube and Crevice Volume Data 5-20 5-23 5.7.1 Tube Change in Length.

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I LIST OF FIGURES FIGURE TITLE PAGE 3.1 Tube Repair Roll Sketch............................... 3-3 5.1 OTSG General Arrangement.............................. 5-3 5.2 OTSG Tube Repair Roll Limitations.................... 5-14 I

(All plants except Oconee 1,2,3) 5.3 OTSG Tube Repair Roll Limitations.................... 5-15 (Oconee Units 1,2,3) 5.4 Hydraulic Expansion Test Mockup Assembly............. 5-24 I

5.5 Repair Roll Expansion Test Mockup Assembly........... 5-25 I-FRAMATOME TECHNOLOGIES H

BAW-10232 REV 00

fl I

LIST OF ABBREVIATIONS 3

DELTA Roll expander toolhead ECT Eddy Current Testing EFPY Effective Full Power Year ETSS Examination Technique Specification Sheet F*

P Star HX Hydraulic Expansion ID Inside Diameter IGA Inter-granular Attack MAI Multiple Axial Indications

(

MIC Micrometer NDE Nondestructive Examination OD Outside Diameter OTSG Once-Through Steam Generator PWSCC Primary Water Stresa Corrosion Cracking RFO Refueling Outage RPC Rotating Pancake Coil RSG Recirculating Steam Generator RT Roll Transition SAI Single Axial Indications SCC Stress Corrosion Cracking TSID Tubesheet Bore ID 2D Two Dimensional 3D Three Dimensional FR AMATOME TECHNOLOGIES iii BAW-10232 REV 00

I 1.O INTRODUCTION

1.1 Background

Eddy current inspection of OTSG tubes has resulted in the l

detection of indications within the tubesheet region.

These indications have been identified as single or multiple axial indications (SAI or MAI),

single circumferential indications I

(SCI), or volumetric (VOL) indications which require repair or plugging per typical plant technical specifications.

The indications are generally characterized as ID stress corrosion cracks (IDSCC) in the existing tube roll transitions.

The volumetric indications have been characterized as intergranular attack (IGA).

Such indications represent well documented degradation mechanisms in steam generator tubing.

IDSCC occurs in susceptible alloy 600 material under the combined action of primary water, elevated temperature, and suste.ined tensile stresses which exist in the roll transition region of the tubes.

Some of the tubes in the ANO-1 OTSG's have OD defects characterized as IGA in the upper tubesheet.

These defects are distributed between the tube roll transition and the secondary face of the tubesheet.

indications detected in OTSG's is The number of tubes expected to increase in time.

If degradation continues then a repair method may either be desirable or necessary to maximize I

the number of tubes left

.n service for continued operation. One such repair method is to perform a tube roll expansion (repair roll) within the tubesheet beyond the existing degraded location.

g 1.2 Puruose The purpose of this document is to provide a

technical justification to implement a tubesheet region repair roll in degraded tubes in OTSG's.

A repair roll which is installed beyond the degraded region of tubing provides a frictional joint of undegraded tubing within the tubesheet bore, creating a new primary pressure boundary within the tube.

The structural aspects of the repair must be demonstrated in accordance with

I NRC Regulatory Guide 1.121, by establishing an engagement distance sufficient to withstand the axial tube loadings imposed FRAh!ATOME TECHNOLOGIES l-l BAW-10232 REV 00 i

4 I

by normal operating condition and worst case f aulted condition differential pressures and thermal displacements.

The repair roll leakage must meet requirements for maintaining plant l'eakage within technical specification limits.

If a repair roll is located near the secondary face, then a crevice region will exist betweer. the original roll and the repair roll.

The customer requirements from Entergy for the I

Arkansas Nuclear One Unit 1 OTSG tubes include performing an evaluation of installing a hydraulic expansion of the tube within the tubenheet to close the crevice, This hydraulic I

expansion eliminates any concerns associated with potential tube denting due to the Obrigheim effects of a trapped water volume.

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FRAMATOME TECilNOLOGIES 1-2 B AW-10232 REV 00 I

2.0 EXECUTIVE

SUMMARY

Eddy current inspection of OTSG tubes has revealed tubes with indications at the roll transition within the tubesheet region.

These indications have been characterized as either

axial, circumferential, or volumetric defects which may exceed the current plugging limit for the tubes.

The axial indications have been predominantly attributed to stress corrosion cracking of the tube roll transitions.

The volumetric indications have been characterized as IGA.

A process has been developed to repair these tubes allowing them to remain in service.

This repair process consists of creating a new mechanical tube-to-tubesheet-structural joint by rolling a new joint below the region of tube defects.

This type of repair has been previously qualified and implemented by FTI for Westinghouse Model 27 recirculating steam generators (RSG's) at Connecticut Yankee, Westinghouse Model 44 RSG's at Point Beach 2 and Indian Point 2,

Westinghouse Model 51 RSG's at DC Cook Unit 1, and Babcock & Wilcox OTSG's at Oconee Unit 1 (8.6).

The qualification of the mechanical joint is based on establishing a mechanical roll length which will carry all of the structural loads imposed on the tubes with required margins.

A series of tests and analyses were performed to establish this I

length.

Tests that were performed included

leak, tensile,

fatigue, ultimate

load, and eddy current measurement uncertainty.

The analyses evaluated plant operating and faulted I..

loads in addition to tubesheet bow effects.

Testing and analysis evaluated the tube springbr

,d radial contact stresses due to temperature, pressure.

aesheet bow.

The repair roll is defined as a (d) long, defect free roll expansion beyond the original roll expansion.

An optional hydraulic expansion may be performed to close the crevice between the tube and tubesheet bore prior to performing the roll expansion.

These repair methods are shown in Figure 3.1.

The repair roll consists of one roll positioned approximately I

(d) inches (or greater) beyond the original roll.

The repair roll length is (d) as defined by the physical length of the roller pins used in the expander tool.

No extra roll length is I

provided in this method for ECT measurement uncertainty.

No extra roll is needed to cover crack migration from the original I

FRAMATOME TECHNOLOGIES 21 B AW-10232 REV 00 m

I

roll, since the repair roll does not overlap the original roll.

When the repair roll is located deep in the tubesheet a trapped volume will exist in the crevice between the tube and tubesheet bore.

To decrease water ingress, this volume can be reduced by performing a hydraulic expansion of the tube to close the crevice prior to the repair roll installation.

Reducing the trapped volume minimizes the possibility of tube denting during l

heatup.

The worst case operational leak rates for repairing all 15,531 tubes in each OTSG (31,062 tubes total) will be less than (d)

GPD, assuming all tubes have 100%

through wall defects.

A conservative estimate of MSLB leak rates is (d)

GPD at (d) psi I

differential.

The tubes which require repair are known to be susceptible to I

stress corrosion cracking.

Therefore, the new roll transitions may also exhibit defects.

The defects are readily detected by eddy current inspection during normal refueling outage inspections.

Based on the FTI qualification performed, as well as the history for similar industry repair rolls, there are no new safety issues associated with a repair roll.

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- smrosm ec - ooms m

e mm _

3.0 REPAIR ROLL DESCRIPTION 3.1 Desirin The roll joint consists of installing a roll expansion away from the original roll in the region of unexpanded tubing beyond the degraded section within the tubesheet.

The roll expander used for reroll qualification has a total roller length of (d)

I inches with an ef fective length of (d) between the tapered ends.

If the defects in the tubesheet require that the repair roll be placed deep in the tubesheet, then an optional hydraulic I

expansion of the tube may be performed before the repair roll expansion.

Figure 3.1 provides a sketch of the repair roll and optional hydraulic expansion.

The repair roll may be located within or beyond the hydraulic expansion region.

A lubricant is used to lubricate the rollers and enhance the quality of the rolls.

The objective of the repair roll is to place a (d) effective roll away from any existing tube defects to satisfy leakage and load capacity requirements.

3.2 Installation I

The repair roll is typically performed remotely using a

manipulator and a DELTA plugging type tool head.

A control system is used to position and install the new roll expansion.

The nominal required torque is (d)

(

(d) minimum) using the standard qualified tooling.

Spacers between the tool and I

tubauheet or tube end are used to establish the proper ro] l depth for candidate tube locations. If the repair roll will be located deep in the tubesheet, then an optional hydraulic I

expansion may be performed to close the crevjp ibove the roll expansion.

The following is a summary of the tube repair roll installation prc<:es s :

I The DELTA tool is first. calibrated to deliver a roll torque of (d) and to properly measure diameter.

The target tubes are roll expanded to the torque setpoint.

A time history of the torque and diametral expansion is recorded onto disk.

I FRAMATOME TECHNOLOGIES 31 BAW 10232 hEV00

I

'N Based upon field experience, after (d) rolls are performed, the tool is removed and a calibration check is performed.

The next group of tubes are then rolled.

After tube repair rolls are completed, post ECT examination is 4l performed.

This ECT examination confirms the proper tubes were expanded, verifies proper diametral expansion, and verifies the nr.s (d) roll expansion is free of degradation.

If any anomalies are noted at any time during the process, a Non-Conformance Report (NCR) is written for disposition by

I Engineering.

3.3 Process Verification Standard pre-repair roll eddy current techniques are used to identify candidate tube locations for repair and determine where the lowermost defect is located.

After repair roll instdlation, bobbin profilometry or equivalent techniques are used to generate a plot which identifies the new roll expansion length and relationship to the existing defect, and MRPC or equivalent techniques are used to verify that there are no defects in the required roll length region.

Bobbin profilometry may also be used to verify the effectiveness of the hydraulic expansion process.

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FRAMATOME TECIINOLOGIES 3-2 BAW-10232 REV 00

Figure 3.1: Typical-Tube Repair Roll Sketch

( c)

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.W I

'I FRAMATONE TECHNOLOGIES 33 BAW-10232 REV 00

4.O DESIGN REQUIREMENTS 4.1 General The US NRC Draft Regulatory Guide 1.121 [8.1) prescribes safety factors of 3 on normal operating differential pressure and ASME Code design margins for faulted conditions, respectively.

These factors have been used as the basis for establishing a suitable repair roll length for recirculating steam generator (RSG) tubes.

[

I

( c)

)

I The repair roll shall be of sufficient length such that the expansion alone (without any support from the original tube expansion and tube seal weld) provides the necessary structural strength to satisfy the normal and faulted tube loadings.

In

addition, the roll shall provide a mechanical seal between the existing tube and tubesheet.

The new joint shall provide leak limiting capability, assuming a full 360* circumferential sever immediately outboard of the new roll region.

Leakage must be I

maintained well below the technical specification limits, g

The repair roll becomes the new ASME Code pressure boundary. The r

new roll carries the structural loadings and performs the function of isolating the primary water from the secondary water.

The degraded tube between the minimum required repair I

roll length and the tube end can be excluded from future periodic inspection requirements because it is no longer part of the pressure boundary once the repair roll is installed.

4.2 Desian and Ocerational Loadino Conditions I

The design, operational, and accident temperatures and pressures for the Babcock & Wilcox 177 FA OTSG's are provided in Table I

4.1.

The resulting OTSG tube loads are summarized in Table 4.2.

I FRAMATOME TECHNOLOGIES 4-1 B AW-10232 REV 00 I

TABLE 4.1: B&W OTSG (177FA) PERFORMANCE CHARACTERISTICI PRIMARY SECONDARY QESIGN CONDITIONS SIDE SIDE Desi n Pressure, psia I

(c)

]

0 Design Temperature, 'F

[

(c)

]

Number of Tubes (DB 1)

[

(c)

]

LEVEL A (NORM AL OPERATING) CONDITIONS (100% Full Power)

Pressurc, psia

[

(c)

]

Temperature, Inlet, 'F(DB 1)

[

(c)

]

Temperature, Outlet, *F (DB 1)

[

(c)

]

Flow Rato, Ibm /hr per generator (OCO-1,2,3)

(

(c)

]

Flow Rate, Ibm /hr per generator (TMI 1)

I (c)

]

Flow Rate, Ibm /hr per generator (DB-1)

[

(c)

]

Flow Rate, Ibm /hr per generator (CR 3)

[

(c)

]

Flow Rate, Ibm /hr por generator (ANU 1)

[

(c)

]

I Heat Transferred, BTU /hr per generator (OCO 1,2,3)

[

(c)

]

Heat Transferred, BTU /hr per generator (TMI-1)

[

(c)

]

Heat Transferred, BTU /hr per generator (DB-1)

[

(c)

]

Heat Transferred, BTU /hr por generator (CR-3)

[

(c)

]

Heat Transferred, BTU /hr per generator (ANO-1)

[

(c)

]

Typical Full Load Pressure Drop (Max psi)

[

(c)

]

LEVEL D (FAULTED) CONDITIONS Main Steam Line Break or Main Feedwater Line Break Maximum Pressure, psia

[

(c)

]

(See additionalloads in Table 4.2)

Loss of Coolant Accident I

Maximum Pressure, psia

[

(c)

]

(See additionalloads in Table 4.2)

I FRAMATOME TECHNOLOGIES 4-2 BAW-10222 REV 00

TABLE 4.2:B&W (177FA) STEAM GENERATOR TUBE REPAIR 40 YEAR DESIGN LOADINGS OTSG TUBE OPERATING LOADS LOAD SET TRANSIENT TRANSIENT TUBE NUMBER DESCRIPTION CYCLES LOAD (LBS) or (IN LBS) s (c)

(c) 1 HEATUP (Transients 1 A 1B,1C,9 COOLDOWN 11,15,17 A,17 B)

(c)

(c) 2 0% TO 15% PWR (Transients 2A,28,14) 15% TO 0% PWR (c)

(c) 3 REMAINING (Transients 3,4,5,6,7,8)

TRANSIENTS (c)

(c)

I Operating Basis Earthquake OBE (NORMAL)

SSE Safe Shutdown Earthquake (FAULTED)

~

(c)

Main Steam Line Break 1

MSLB (Due to pressure and thermal differentials)

(Due to Dynamic Tube Loading)

(FAULTED)

I.

F = Force (LBS), M = Moment (IN-LBS)

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FRAMATOME TECHNOLOGIES 4-3 BAW-10232 REV 00

I 5.0 DESIGN VERIFICATION The design verification as described in this section develops the OTSG specific required

.ength for the repair roll.

This development begins by evaluating the design and operating conditions for OTSG plants.

A summary of the analysis methodology and results is provided.

Additionally, a summary of the repair roll testing is provided which supports the analysis in I

determining the final roll length.

The process NDE requirements follow which describe the necessary post-repair roll verification actions and provide a review of previous testing methods and associated uncertainties.

The following is a summary of the design verification methodology:

I Determine tube loadings during normal and faulted conditions.

Perform design verification testing.

Prepare rolled tube samples.

Perform leak tests.

Perform thermal and axial load cycling.

Perform final leak tests.

Perform ultimate load tests.

Determine exclusion zones for application of

( d )

repair roll length based on tube hole dilation effects.

• Evaluate the effect of the reroll process on the tube axial load.

I Evaluate potential for tube denting due to trapped water in the tube to tubesheet crevice.

Establish tube hydraulic expansion to minimi::e tube denting.

I 5.1 Calculation of Tube Loads All of the critical physical dimensions and materials of construction of the original design are summari::ed in Figure 5.1.

The performance characteristics of OTSG's are identified in Table I

4.1.

The following key factors affect the repair roll length as they

[

(c)

):

Normal operating primary to secondary differential pressure o

Faulted condition primary to secondary differential pressure o

o Primary inlet and outlet temperatures o Secondary outlet hteam) temperature o 100% Power temperatures of shell/ wrapper, tube, and tubesheet 5-1 BAW-10232 RSV 00 FRAMATOME TECHNOLOGIES

1 I

The pressure and thermal differentials are uced in the analysis to I

calculate the loads imposed on the tubes during normal and faulted conditions.

The primary inlet, outlet, and steam temperatures factor into tho analysis by determining the effect on the joint strength as a result of the expansion differences between the tube and tubesheet.

The controlling required joint strength loads (from Table 4.2) for Level A and Level D conditions are summarized below in Table 5.1.1.

I Table 5.1.1: Axial Tube Load Summary Axial Average Primary Tensile Tube Temp Pressure Load (lbs)

(*F)

(psi)

Leval A: Cooldown

[

(c)

]

Transient Level D: MSLB Accident ANO-1,CR-3,DB-1,TMI-1

(

(c)

]

ONS-1,0NS-2,0NS-3

[

(c)

]

I S.2 Design Verification Testing Mechanical tests were performed during the qualification to evaluate various roll lengths at room temperature conditions.

The test data was then corrected by analysis to obtain the final required

length, as described in Section 5.3, for operating conditions.

Tests performed consisted of leak testing, axial load

cycling, thermal

cycling, and ultimate load tests.

Normal operation and faulted conditions were simulated during testing.

A total of (

(d)

] were tested.

Note that previous similar tube repair roll tests had been performed which produced acceptable results.

Thus, this allowed focus on the anticipated I

required torque which minimized the sample size.

Note also that test loads were increased per the ASME Code to accommodate the sample size.

FRAMATOME TECHNOLOGIES 52 B AW-10232 REV (X)

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l Figure 5.1 OTSG General Arrang' ment i

(C) i lI lI i

i

)

i 1

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l 4I i

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' I-53 BAW 10232 REV 00 FRAMNIT.)ME TECHNOLO6.Gs I

. ~ -.,,... -..

'.he tube to tubesheet crevice was clean when the test roll expansions were performed. Tube degradation is currently observed

,I in the upper tubesheet roll transition.

Based upon numerous OTSG tube pulls, there is no evidence of significant crevice deposit s in this region; therefore testing was performed without simula*1.ng l

deposits.

Lower tubesheet crevices are known to contain deposits, and thus the potential effects of these deposits will need to be addressed prior to application of the tube repair rolls in the l

lower tubesheet.

5.2.1 Mockup Preparation and ECT Testing The tuben used in the mockup were [

(d)

]

nickel-chromium-iron alloy 600, heat 93452.

This tubing possessed I

a yield strength (

(d)

}

psi.

The mockup dimensions of tubesheet bore, surface roughness, and measured tube ID are recorded in Table 5.2.1.

The tubesheet I,

bore range tested was

(

(d)

] This hole size is near the high end of the (

(d)

] in operating OTSG's.

Figure 5.5 shows the i.epair roll Expansion Test Mockup Assembly.

Table 5.2.1: Tube Installation Data BLOCK TS BORE (c)

EXPANDED

-HOLE DIAMETER TUBE ID (INCH)

(INCH)

ID MIC DELTA I

(d)

I ID MIC: Measured ID us:.ng micrometers, DELTA: Tube ID as indicated by the DELTA inscallation tool.

54 B AW 10232 REV 00 FRAMATOME TECHNOLOGIES

I The tube samples wer2 roll expanded using a modified FTI Model number [

(c)

) roll expander mounted on the DELTA tool.

The field expansions are perf ormed with an [

(c)

]

espander mounted on the DELTA tool.

The expandern used for qualification testing and field application have the same critical dimensions.

These expanciero produce [

(c)

) with [

(c)

] end.

Both the qualificaion tool and the field tool are torque controlled.

The primary difference between the I

qualification axpander and the field expander is the length of the expander cago.

The qualification expander was modified in length to allow proper axial positioning in the test block.

The tube rolling maximum delivered torques and roll lengths are provided in Table 5.2.2.

Roll lengtho are shown for both pnysical I

measuremento and eddy current test inspection measured values.

The actual length was determined by measuring from the tube end to the end of the roll expansion.

The configuration resulta in a roll length [

(c)

) because the rollers overlapped the endo of the two tube sections, which in conservative.

The acquisition and analycio was performed in accordance with l

Examination Techn$que Specification Sheets in Appendix A.

[

(c)

)ECT testing was acquired witn [

(c)

]

probe.

The [ (c) ) ECT testing was acquired with (

(c)

I

] probe.

Refer to Appendix A for details on these probes.

Each cample was acquired (d) for both techniques, except for cample (c), which has only [

(c)

).

Tube expansion 10 a torque controlled process.

To conservatively account for the torque required to expand the tube into contact I

with the tubecheet bore, a high yield Ptrength tube was used.

Since less torque is required to expand lower yield strength

tubing, tests performed using the high yield tubing are more conservative than testa perf o.ined with the low yield tubing.

"'ho average error for the eddy current roll length is (d) inch at (d) kHz for a RPC probe with a standard deviation of (d)

The average error was (d) inch at (d) NH: with a bobbin probe with a standard deviation of (d)

I 14.AMA'IOME TECllNOLOGIES 55 BAW.10232 REV 00 I

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I Table 5.2.2: Tube Installation Torque and Roll Lengths BLOCK ROLL CALC'D ECT ROLL ECT ERROR

-IlOLE TORQUE ROLL LEl1GTil (IliCH)

(I!1Cil)

(Ill-LBS )

LE11GTit RPC Bobbin RPC Bobbin (111C11)

(d) kilz (d) kilz (d) kilz (d) kilz (d)

(d)

(d)

(d)

(d)

(d)

(d)

I I

AVG.

(d)

(d)

The roll length of (d) was measured following the ultimate load test by pulling the tube from the tubesheet.

5.2.2 Leak Testing Room temporar*re hydrostatic pressure tests were performed at (d) psi on the mockup samples.

This value exceeds both 3 x normal operating pressure and 1.43 x MSLB pressure.

The purpose of this test is to look for gross leakage or structural failure of the joints.

No mechanical change or gross leakage in the samples were noted.

Only one

[

(d)

).

FRAMATOME TECilNOLOGIES 5-6 BAW-10232 REV 00

I The hydrostatic test was repeated after thermal and load cycles of the samples.

Again, no mechanical change was noted in the joints.

l There was no visible leakage in any sample during the second hydrostatic test.

l loom temperature leak tests wcre performed on the samples at (d) psi.

This was done both before and after thermal / load cycling was i

applied to the.imples.

IJote that room temperature leak tests are conservative since higher temperatures increase the joint tightness due to thermal expansion dif ferences between IG00 tube and carbon steel tubesheet.

The results of the leak tests are I

presented in Table 5.2.3.

1 The leak testing at (d) resulted in an average leak rate of I

(

(d)

] before load testing. The final leak testing at [

(d)

] after thermal cycles and axial load cycles (cyclic testo discussed in 5.2.3). The average of initial and final leak rates (

(d)

)

Table 5.2.3: Leak Test Results BLOCK I!JITIAL LEAK FI!JAL LEAK

-lIOLE RATE AT (di RJ.TE AT (d)

(I!J'/liR)

(Ill'/IIR)

(d)

(d)

(d)

AVERAGE (d)

(d)

I I

FRAMATOME TECINOLOGIES 5-7 BAW.10232 REV 00

I If all 15,531 tubes in each upper head of the two OTSG's are repaired by tube repair roll, the worst case normal operational leakage is (d)

GPD. This value is conservative due to:

It assumes all tubes have 100% through wall defects.

Operating differential pressure of (d) compared to the test pressure of (d).

I The tubes tested were severed 360 degrees.

• The average tested roll length was (d) compared to a nominal repair roll length of (d).

• The tube has & higher coefficient of thermal expansion than the tubesheet, therefore the rolled joint would be tighter at I

operating temperatures than at room temperature.

A ccnservative estimation of leakage at MSLB differential I

pressure (

(d)) is based on increasing the leak rate by the square of the pressure ratio, or (d)

This results in l

a (d) leak rate.

This method is not considered exact, but conservative, since the higher primary pressure during the MSLB event will tighten the roll expanded joint.

Normally the leak rate would be expected to increase according to the square root of the pressure ratio. Therefore, the worst case MSLB leak rate at (d) is estimated to be (d) for 15,531 tube endo per OTSG (31,062 total tube ends).

This value is conservative for the reasons mentioned above.

5.2.3 Thermal and Fatigue Cycling The two mockup blocks were cycled cycled

[

I (d)

]

These thermal cycles were performed to allow for any relaxation in the tube to tubesheet joint due to differential thermal i

expansion of the Inconel and carbon steel.

Axial load cycling was performed to simulate the applied loads imposed on the OTSG tubes due

(

(d)

)

These loadings are based on normal operating transients expected to occur over a 40 year design life of the OTSG's from Table 4.2.

I FRAMATOME TECHNOLOGIE; 58 BAW 10232 REV 00 j

l I

The loadings from Table 4.2 are adjusted by increasing the number of cycles for the first and second load sets and by increasing the applied force for the third load set.

These adjustments are based on a

quantity of (d) samples to conservatively envelope the testing of (d) samples.

Table 5.2.4 summarizes the load sets for loading range and cycles developed f rom Table

4. 2 data.

lio tube motions were observed during this test, thus all samples successfully passed.

Table 5.2.4 Fatigue Test Axial Load Cycles LOAD AXIAL TEST NUMBER OF SET LOADIllG RANGE CYCLES (LBS) 1 (d)

(d) 2 (d)

(d) 3 (d)

(d)

I 5.2.4 Ultimate Load Test An ultimate load test was performed to axially load the tube jcints until failure.

This test was performed with ID 97 ipper fingers inside the tube pulled by a hydraulic jack using a I

manual pump.

In each case the applied applied (

(d)

)

The loads are summarized in Table 5.2.5.

Tube movement was monitored by a dial indicator mounted on the mockup block and reacting off the mandral of the ID gripper [

(d)

) Tne final pullout loads were used to establish the required roll length in Section 5.3.

I I

I m s, m s, m cim moc.mS

~

e m.io m -

I Table 5.2.5: Ultimate Load Test Recults I

BLOCK ROLf4 ROLL MAXIMUM MAXIMUM LOAD

-IlOLE TORQUE LE!1GTil PULL LOAD CUMULATIVE (Ill-LBS )

(IliCil)

(LDS)

TUBE MOVEMENT (IliCH)

(d)

(d)

(d)

(d)

I

[

(d)

I I

(d)

)

Applying 3 one-sided 95 percent tolerance limit factor of (d)

(ref erence 8.4) to the standard deviation of (d) lbs results in a minimum joint load capacity of (d) lbs.

This value exceeds the I

I

,m mresi m C,isoteems 3.ie om.,em mev.

I I

minimum required strength of (d) lbs for an Oconee MSLB condition.

Thus, all samples were acceptable.

A (d) roll length I

will be conservatively assumed to correspond to this load of (d) i lbs.

This load will be used to determine the maximum tube hole dilation allowed due to tubesheet bow.

5.3 Effect of Tube Hole Dilation on Joint Strength The load testing summarized in Section 5.2 was performed in tubesheet mockups with as-fabricated bore diameters.

In an operating OTSG, the tubesheet bore diameter can change during l

certain operating conditions due to the combined effects of primary to secondary gessure differential and thermal loads.

These loads cause the tubenheet to bow in one direction or the other, depending on the particular condition being evaluated.

The bowing of the tubesheet will in turn cause the diameter of the tubesheet bore to increase or decrease, depending on its location.

I The change in diameter is a maximum at the face of the tubesheet, and decreases to zero at the neutral axis.

An increase in diameter will decrease the contact stress between the roll joint I

and the tubesheet, which reduces the pullout strength.

This effect on the strength of the repair roll joint was evaluated analytically, and an exclusion zone was defined to ensure that the repair roll joint is installed only in locations where the effects of tubesheet bow do not reduce the joint strength below what is required to sustain all required loads.

The largest amount of tubesheet bow is predicted to occur during a MSLB

event, where the maximum primary to secondary pressure differential occurs in conjunction with the largest predicted tube I

tensile loads.

Both tubesheets will bow inward (towards the secondary side) as a result of these loads.

The tubesheet bore hole diameter on the primary side will increase near the periphery I

(where the tubesheet is in tension from the bow effect) and decrease near the center (where the tubesheet is in compression).

On the secondary side the effect is reversed, i.e.,

the bore hole I

diameter will decrease on the periphery and increase in the center.

I The initial preload of the repair roll joint was estimated from measurements of tube diametral springback.

Testing was performed by i n s '.. l l i n g a repair roll j oint. into a split tubesheet block, measur;us the diameter at the joint location, and then removing the tubesheet block.

The diameter of the tube in the joint region FRAMATOME TECIINOLOGIES 5 11 BAW 10232 REV 00

I expands after removal of the block.

The dif ference between the as-installed diameter and the " relaxed" diameter is the spring back, and is a representation of contact stress.

(d) test samples were evaluated, resulting in an avers.ge spring back of (d)

The room temperature radial (contact; stress was calculated from I

these results to be (d) psi.

The minimum axial load capacity for a (d) rolled joint at room temperature conditions was determined in Section 5.2.4 to be (d) lbs.

The required strength of the joint for worst case nomal operating and accident conditions are given in Table 5.3.1.

Two bounding conditions were considered as discussed above, including a normal operating cooldown transient and a MSLB.

Two dif ferent load cases for the MSLB transient we:re evaluated, the first being a bounding case for the non-Oconee plants, and the second being applicable for Oconee-1, 2,

and 3.

A finite element analysis was performed to determine the amount of tubesheet bow for each case, as well as the resulting hole dilation as a function of tube j

position and location within the tubesheet thickness.

For each of the three cases evaluated, an allowable tubesheet bore hole dilation was calculated such that the joint strength remained I

adequate to sustain the axial loads defined in Table 5.3.1.

These calculations were based on the minimum joint strength of (d) lbs determined in Section 5.2.4, and the installed contact stress I

determined in the spring back testing discussed above.

Table 5.3.1:

Tube llole Dilation Allowables F.

Fuu Fau.e Max Tube Load (lbs)

(d)

(d)

(d)

Roll Length Maximum Allowable Tube Hole Dilation (inch)

(d)

(d) l (d) l (d)

The calculated tube hole dilations due to thermal and pressure differentials were compared to the allowable dilations.

The I

maximum tube hole dilations occur in the periphery of the tubesheet for rolls near the tube end for both upper and lower tubesheet.

Maximum tube hole dilations occur near the center of the tubesheet at the secondary faces of the tubesheets.

The application of a (d) long roll expansion is limited to those I

portions of the tubesheet where the calculated dilation is less than the allowables.

I

" ^ * ~ ' " ' ' ' " " " "

' " ^ " ^ ' " " ' " ' ' ' " '

I

A roll length of (d) is used for the determination of exclusion zones presented in Figares 5.2 and 5.3.

Figure 5.2 graphically summarizes the tube repair roll exclusion zones for all OTSG I

plants except Oconee 1,

2, and 3.

Figure 5.3 graphically summarizes the tube repair rol) exclusion zones for OTSG's at I

Oconee 1,

2, and 3.

Zones 3,

5, 8,

and 11 are based on maintaining any roll transition (d) from the seccndary face.

Thio (d) conservatively allows the tube to remain engaged in the tube hole in the unlikely event of a tube severance at the new roll transition.

The exclusion zones are described in detail in Appendix B and the tubes in each zone are tabulated in Tables B.1 through B.6.

j

't I

I I

I I

I FRAMATOME TECliNOLOGIES 5 13 gAw.10232 REV CO

1 l

l l

l F_LGURE 5.2: OTSG TUBE RXEAIR ROLL LIMITATIONS (All plants except Oconee 1,2,3)

I t

i e

a k

(d)

I I

II 1

I 4

5 14 BAW-10232 REV 00 FRAMATOME TECliNOLOGIES q

l a...e-,...

.n,-

l l

EIGURE____5.3: OTSG TUBE REPAIR ROLL LIMITATIONS (Oconee Units 1,2,3)

I I

h t

i I

(d) i I

i i

t 1

i e

i i

1 5

1 1

o k

4 FRAMATOME TECilNOLOGJ.S 5 15 BA V 10232 REV 00 e

_,-.,_-__,_..m,

._,_.y...

_____._,.--..._,,-.,.~_s,

..w.

m-

I 5.4 lion-Destructive Examination Effects on Final Repair Roll Location I

A minimum actual roll length of (d) is used to determine the areas that a repair roll can be performed.

However, this length does not include ECT measurement uncertainty.

The location of the (d) if performed adjacent to a defect, shall include an allowance for the uncertainty associated with the ECT measurement I

technique used to evaluate the defect.

The finel repair roll acceptance criteria that is developed for I

OTSG's must be evaluated using standard steam generator eddy current techniques.

Post-repair roll bobbin profiles are required I

to verify expannion, show the new roll transition (s), and provide measurements of the undegraded roll beyond the defect.

Measurement tolerances associated with remote eddy current measurements must be factored into the final value.

Bobbin and RPC eddy c rent methods were both used to veriff the accuracy and uncertair../ in determining repair roll lengths in 5/-

tubing.

This test.ing was performed to determine the error as. ociated with the liDE method that will be used in the steam generator to define the actual locations of the defect and the roll transition.

ECT analysis of rotating pancake coil (RPC) and bobbin coil data was perf ormed to determints the distance f rom the bottom end of the roll transition to a simulated sever.

Each eddy current pull was i

analyzed (d)

A total of[

(d)

The ECT errors were predominantly conservative, hat is ECT underestimated the roll length.

As a conservative practice, since I

(

(d)

]

The factor for a 95% one-sided tolerance limit based (d) samples (bobbin) is (d),

from reference 8.4.

Thus, the additional discance from the defect to the repair roll due to ECT uncertainty will be based on the error c f (d) for bobbin and the factor of I

(d) times the standard deviation of (d)

The distance from the defect to the rull transition is (d) times the standard aeviation of ECT error, plus the average error:

D=

[

(d)

]

FRAMATOME TECHNOLOGIES 5 16 BAW.10232 REV 00

I 5.5 Repair Roll Effect on Axial Tube Load Sir ce the OTSG tubes are fixed on each end, the reroll process will induce an axial load into the tubes.

This load was determined by measuring how much the tube elongates due to the I

reroll process.

The average teut result elongation from the reroll proceau is (d;

inch.

This elongation produces a compressive axial load of approximately (d) and a compressive stress of (d) poi in the tube.

This axial load would act to reduce the maximum cooldown and MSLB accident tube loads.

The increase in compressive load during plant heatup, and during other events which cause the tubes to be in compression, is considered to be insignificant.

I 5.6 Tube Crevice Evaluation Testing was performed to define the optimum hydraulic expansion to limit tubesheet ligament stress, while assuring a tube /tubesheet crcvice less than that which could result in tube denting. The l

crevice volume that exists between the tube and tubesheet bore increases as the depth of the roll increases.

The diametral clearance varies from (d) to (d) for ti range of tube OD's I

and tubesheet bore ID's in the Oconee-3, Di is Besse, and ANO-1 OTSG's.

Tha diametral clearance varies from (d) to (d) for the range of tube OD's and tubesheet bore ID's in the Oconee-1, I

Oconee-2, TMI-1, and CR-3 OTSG's.

The crevice voluttie is a maximum of (d) cubic inches per inch of length for the (d) clearance.

Therefore, starting a roll (d) from the primary face would produce a maximum trapped crevice of (d) and a maximum volume of (d) cubic inches.

If a crevice fills with water at a low temperature, then the pressure in the crevice will increase as the temperature rises cue to the expansion of the water.

The specific volume of saturated water increases 32 percent as the temperature increases f rom 70*F to 532*F (zero power condition).

To avoid denting of the tube the expanding water needs time to leak past the roll or the volume of the crevice needs to be minimized.

The OTSG tube is able to experience an elastic diametral contraction of approximately I

(d) due to external pressure and return to its original diameter.

Therefore an initial diametral clearance of (d) would be able to accommodate t.he expansion of trapped water during I

heatup without denting, assuming no leakage past the repair roll.

I FRAMAWME TECHNOLOGIES 5-17 BAW-10232 REV 00

I The minimum observed leak rate from section 5.2.2 was (d) cubic inch per hour at (d) pai.

The water in the maximum postulated f

crevice volume would expand (d) times (d) cubic inches, or (d) cubic inches during a normal heatup.

The time required for this additional volume of water to leak out is approximately (d) baned on the minimum leak rate.

The nominal heat up rate is 40'F per hour, from 90*F to 5 3 0*F.

Therefore, (d) hours might be available for leakage to occur, allowing (d) cubic inch of water to leak out and a possible tube dent of (d) cubic inch.

5.6.1 Tube Denting Test Summary l

Testing was performed to confirm if tube denting would occur during rapid heatup of a trapped water volume.

This testing I

included fabrication of (d) and tubesheet mockups as shown in Figure 5.4.

The tubes were first roll expanded near the primary face of the tubesheet.

Next the mockups were cubmerged in water I

to allow the crevice to fill with water.

The tubes in samples [

(d)

]

The water was retained in the I

crevice during this hydraulic expansion by keeping the primary fact end oriented downwards.

The only water that was removed was due to the expansion process.

The hydraulic expansion was perf ormed with the insitu pressure test toolheads secured at each end of the tube.

These tools [

(d)

]

Af ter hydrau.lic expansion, these (d) were roll expanded near the secondary race of the tubesheet to seal the crevice.

The crevice for samples (d) were also filled with water, but no hydraulic expansion was performed prior to the roll expansion I

to seal the crevice.

The tube ID was measured at (d) inch increments from (d) inches to (d) inches and (d) inches to (d) inches from the primary end of each tube sample.

The tubes were plugged on the primary end and the volume of each tube was measured by filling with water.

An amount of water equal to half the tube volume was placed in each tube and the tubes were sealed at the secondary end.

This water was inside the tubes to allow for internal pressure to build up during the thermal cycle, similar to the primary pressure inside the OTSG.

The effects of the internal pressure are (1) to decrease the leakage past the roll expansion and (2) to increase the pressure required to dent the tube wall.

Tube stickout measurements were taken at both ends of each tube sample.

I FRAMATOME TECilNOLOGIEs 5 18 BAW.10232 REV 00

The (d) samples without hydraulic expansions,[

(d)

)

The (d) samples with hydraulic expansions, [

(d)

}

I After the thermal cycle was finished, tube stickout measurements were repeated.

There was no change in tube stickout dile to the I

thermal cycle process.

The Swagelok plug was removed from the secondary end of each sample.

The volume of water was measured, then the tune volume was measured.

The Swagelok plug at the I

primary tube end was removed and tube ID measurements were repeated.

Visual examination of the

samples, showed that (d) tubes, samples (d) had dented during the thermal cycle.

5.6.2 Tube Installation The tube installation data is summarized in Table 5.6.1.

The (d) heats of alloy 600 tubing used were (d) ksi and (d) kei yield strength.

The mockup block material was ASTM 1018 carbon steel round bar with a nominal OD of (d) inches, a bored hole ID ranging from (

(d)

] and a length of (d) inches.

I Table 5.6.1: Tube Installation Data

~

Tube Tube Tube Tube Mockup Primary Sample Primary Secondary Secondary Heat /

Yield OD 10 Bore Roll Number Roll Roll Roll Lot (ksi)

(inch)

(inch)

Diameter Torque Diameter Torque Diameter (inch)

(in Ib)

(inch)

(in :b)

(inch)

(d)

I I

I 31, ex.)ez,2aevee ram.,x1eme reci1xetecies

I I

5.6.3 Trapped Water Volumes The volume of water trapped in the crevice and in the tube is I

nummarized for each sample in Table 5.6.2 before and after hydraulic expansion (HX). These calculations consider a crevice length of (d) due to the (d) roll expansion at each end of the I

(d) long mockup blocks.

Example:

Volume = (PI/4 ) * (TSID'- TOBEOD')

(LENGTH)

(d) cubic inch Sample H1: Volume = (PI/4)*(

(d)

)*( (d))

=

Table 5.6.2: Tube and Crevice Volume Data Sample Calculated Calculated Calculated Crevice Tube Volume Tube Volume Number Crevice Crevice Volume Volume Af ter Before Thermel Af ter Thermal I

Volume Def a --

After HX Thermal Cycle Cycle Cycle HX (cu. inchi (cu. inch)

(cu. inch)

Measured ;ral)

Measured (mit I

(d)

I (d)

I i

(d) cubic inch (PI/4)

• ((d))

(2)

• Dent Volume

=

=

The crevice volume increases approximately (d) based on the size of the dents for samples (d).

5.6.4 Testing Observations 1,

[

I (d)

I l

's 5 20 BAw.10232 REV 00 FRAMATOME TECHNOLOGIES I

l I

[

(d)

)

2.

[

i (d)

)

I 3.

[

(d)

)

5.7 Effects of Tube Hydraulic Expansion 5.7.1 liydraulic Expansion Residual Crevice and Ligament Stress Testing was performed with the prototype tube hydraulic expanoer using a computer controlled pressure and volume tracking system.

I The hydraulic expansion of the tube into contact with the tubosheet was observed to occur at (d) poi and (d) pai for tubes with a yield of (d) and (d) respectively.

The additional pressure above contact with the tubesheet bore resultn in a tubesheet ligament stress approximately (d) the applied pressure.

For example, if contact occurs at (d) and the pressure is increased to (d) then the maximum hoop streus at I

the tubesheet bore surface is

[

(d)

) kai.

The change in tubesheet ligament outside dimension is (d) inca per (d) of applied pressure, based on thick shell theory

[8.5)as shown in Equation 5.7.1.

Ecuation 5.7.11 I

Delta OD = (2) * (0) (OR) (IR* 2) (2 -ng).

( F.)

(OR^2 - IR'2)

(d) pai Applied Pressure, psi Where:

0

=

(d) inch Outside Radius OR

=

=

(d) inch Inside Radiuc IR

=

=

I Poisson's ratio 0.30 nu

=

=

30.2 E6 psi Modulus of Elasticity E

=

=

I mimmme recimomes 3.u os

)o m Re m

I I

The change in tubesheet bore ID is calculated in Equation 5.7.2.

Again, for an applied (d) psi the ID will increase (d) inch.

Ecuation 5.7.2f Delta ID = (2) * (0) (IR)_

(OR"2) (1 + nu) + (IR* 2 ) (1-2 *nu)_

(E)

(OR"2 - IR"2)

The hydraulic expansion of a (d) inch OD tube to (d) inch tubosheet bore results in a (d) change in circumference and I

approximately a (d) kai increase in yield strength.

Assuming a final (d) yield strengt' the tube OD can relax a distance equivalent to the reduction tube OD based on removing a (d)

I psi pressure.

This is app.sximately (d) inch based on Equation 5.7.1, a tube ID of (d) inch, a tube OD of (d)

inch, and a modulus value (B) of 31 E6 psi.

As the pressure is released, the tubesheet will relax (d) inch as the pressure decreases from (d) psi to (d) pai, based on a change in tubesheet ligament stress from 20 ksi to zero.

The I

tube will follow the tubenheet for this same change in bore ID and tube OD.

Since the tube was plastically deformed above (d) to (d) pai, as the pressure drops from (d) poi to O psi the I

tube OD will continue to relax an additional (d) inch.

Therefore, a negligible preload will exist between the tube and tubesheet following a hydraulic expansion, and a diametral crevice of approximately (d) inch would be formed.

Increasing the maximum applied pressure to (d) psi would resulu in a tubesheet ligament stress of approximately (d), which is (d)

I percent of the minimum yield strength of the tubesheet material.

T1.e diameter increase of the tubo OD and tubasheet bore ID would be (d) from above.

The relaxation of the tube and tubesheet would be almost equal, so that (d) would remain.

5.7.2 Change in Tube Axial Preload The hydraulic expansion of the tube in the tubesheet region will result in a (d) of the tube.

This change in tube length ic calculated based on testing done with a hydraulic expansion (d)

I inches in length and a range of tube OD expansions of (d) to (d)

Table 5. 7.1 summarizes the change in tube length.

The length (d) is approximately (d) for each (d) change in tube OD.

Therefore, a nominal (d)

OD tube expanded into a I

nominal (d) tubesheet bore would experience a length (d) of (d)

. This (d) will (d) the tube tensile load by (d) lbs.

The tube roll expansion would recover (d), resulting in a I

net (

(d)

) in tensile loading.

The additional tube loading due to hydraulic expansion does not change the repair roll limitations illustrated in Figure 5.2.

The tubesheet holes at a radius greM r than (d) do not experience dilation near the secondary face.

Therefore, the joint strength is aufficient to carry the tube loading.

The normal operating and 5 22 BAW.10232 REV 00 FRAMA*IOME TECHNOLOGIES

I MSLB accident tube loads decrease to (d) percent of the periphery loads for the center loads.

Again, resulting in sufficient joint strength.

Tablo 5.7.1: Tube Change In Length Tube Heat /

OD OD Length Length Change Change Sample Yield Before After Before After in OD in I

Stresb Length I

I (d)

(d)

(d)

(d)

('d )

(d)

(d)

(d) i g

5.7.3 Summary Expanding an OTSG tube into contact with the tubesheet bore will result in approximately a (d) diametral crevice.

Application of an additional (d) poi beyond the pressure that the tube contacts the bore will result in approximately a (d) diametral crevice and

.ipproximately (d) of yield stress in the ligament.

And application of an additional (d) pai beyond contact will result in a (d) crevice, but will also stress the ligam*nt to (d) percent of yield.

A tube diametral crevice of (d) is the maximum allowed to prevent any tube denting during heatup with trapped water.

I Therefore, application of a hydraulic eroansion process shall assure contact of the tube with the bore and a maximum additional pressure of (d) pai, and a traximum total applied pressure of (d) psi.

This method will prevent tube denting and minimize ligament stresses.

The tu"e repair roll limitations shown on Figure 5.2 and tabulated in Appendix B are still applicable.

I FRAMATNtB TECHNOLOGIES 5 23 BAW 10232 REV 00

-m

~Am

,.-%.hAwmA4--_e.e&_m,m---.dd-We Ww--e.-aa.-edes.,w__mm e

s4w

.wde,A4-3 de 4.hm a, _

.g-mA.-hw m-sa-.

am-em..-

LesmA=A-Newk----

-=-=-p.---

l l FIGURE 5.4: liydraulic Expansion Test Mockup Assembly lI

I lI (d)

!I

!I iI

I I

]

4 I I

1 I

msmemimems 3.x

..,om,mv.

O e--.--.w.,

..-- --~ ~

w-,-.

,-e,,-n w,

_m-..-r4---

m._m.msa um.ama

-.-m..

aa a._s.w n-a._ea.-4.----.4----_,--a-..-sw-wA,,w.4-e>##w m-m.".+rwm-&-

Me.-..=-AAJ4--

--ehe=4mam64 MA a

l

!I FIGURE 5.5: Repair roll Expansion Test Mockup Assembly

>I 4

ilI i

I (d)

!I

. I E

s I

I 4

I t

' I g

FRAMATOME TECHNOLOGIES 5 25 BAW 10232 REV00

I I

6.0 EVALUATION OF REPAIR ROLL LIFE G.1 Tube Integrity in Repair Roll The significant tube degradation mechanisma in OTSG t.ubenheets have been characterized as ID PWSCC and OD IGA.

These degradation mecnanisma in the elevated stress regions assoc.ated with a roll tranoition can potentially limit the life of the repair roll.

Non-destructive eddy current examinations, laboratory examinations of pulled tube samples, and accelerated corrosion tents have all ahown that PWSCC will occur in the roll I

transitions of alloy 600 tubing. Laboratory testa indicate that tensile atresoes accelerate the rate of SCC and moderately affect the rate of IGA.

The operating temperature can also af fect the I

corrosion rate in the roll transitions.

For

example, intergranular corrosion tendo to occur mainly in the elevated temperature region of the hot leg verous the cold 109 The presence of the high stress r.rea in the new roll transition, along with high hot leg temperature (

(d) at DB-1) indi=ateo l

that the new roll transit. ion will be ounceptible to IDSCC an in the exiating roll transition.

The main difforence between the original roll transition and the transition created by the repair roll in the full vessel otrena relief performed during manufacture.

Since the repair roll I

stresses may be higher than th'.sae in the steam generator after manufacture, the time to cracking for the new transition is expected to be less than the time for the original tranoition.

Whether the rerall transitions last ao long ao the original tube I

roll tranaitions or not la uncertain.

The rerolls are expected to last a

minimum of a

few cycles before SCC occura.

Additionally, for those tuben which are hydraulically expanded prior to the re-roll,

'he hydraulic expansion transition is expected to have lower at mtibility to SCC than the original roll transition, due to the..stive residual attens levela.

I Because the tubes experienced a thermal treatment dur'ng the full vessel stress relief, they still have good realotance to SCC.

I Any cracks th t develop are expected to grow slowly.

Also, standard ECT inspection during normal refueling outage activities I

FRAMATOME TECHNOLOGIES 61 nAW.10232 REV 00

I has proven successful in detecting these defects in the early stages of progression to facilitate future repair or plugging.

6.2 Tubenheet Corrosion Beyond Repair Roll The tubesheet material is expected to be unaffected by corrosion after installing a reroll, even if defects currently exist outside the new pressure boundary.

The lack of concern for j

tubesheet corrosion is based on the restrie-ted flow area for primary water to interact with the tubesheet and the lack of oxygen in the primary system during normal operating conditions.

The existing roll transition defects represent the only flow g

path that could initiate tubesheet corrosion.

The repair roll i

3 is located a

sufficient distance from the original roll transition or any existing defects, such that defects will be unaffected by the repair roll.

The flow path through these I

detects is not sufficient to initiate corrosion or transport any l

corrosion products in an oxygen free environment.

The fluid flow between the tube and tunesheet is restricted by the repair i

roll.

Tnerefore, crevice corrosion is not expected to affect

}

the life of the repair roll.

I I

I I

I I

I I

I

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7.0 CONCLUSION

S This evaluation has shown that application of a tubesheet region repair roll at OTSG plants is acceptable.

The following conclusions are provided.

1.

A roll length of (d) is structurally adequate to satisfy all of the loading requirements for the HRC Regulatory Guide 1.121 and the leakage limits applicable to the OTSG plants technical specifications.

2.

The qualification is valid for locating the roll expansion in the upper tubesheet of OTSG's with the exception of the I

exclusion zones identified in Appendix B.

Application of tube repair rolls in the lower tubesheet is contingent upon verification of roll joint strength with crevice deposito.

3.

If 15,531 tube ends per generator were

repaired, the

, I conservative worst case leakage would be approximately (d)

GPD under normal operating conditions.

A conservative estimate of MSLB leak rates is (d)

GPD at (d) psi differential.

4.

The recommended design parameters for a field implemented repair roll joint are as follows:

(d) separated from existing defects and roll transitions, providing (d) of new eff ctive roll I

(d) in-lbs nominal installation torque ((d) minimum)

Installation depth no closer than (d) from the secondary tubesheet face.

5.

The repair roll is applicable to repairing ID or OD, axial, I

volumetric, or circumferential defects.

Testing was performed under the conservative assumption that the tube is severed.

6.

Applying a hydraulic expansion prior to making a repair roll I

near the secondary face of the uppor tubesheet minimizes the potential for Obrigheim denting of the tube above the roll.

Although it does not affect the structural integrity of the

tube, potential denting could reduce tube inspection flexibility through tube ID reduction.

I FRAMATOME TEClINOLOGIES 71 BAW.10232 REV 00

I I

8.0 REFERENCES

8.1 NRC Regulatory Guide 1.121 (Draft), " Bases for Plugging Degraded PWR Steam Generator Tubes".

8.2 ASME Boiler and Proscure Vessel Code,Section III, Subsection !G and Division I Appendices, 1989 Edition.

8.3 EPRI TR-103024, Steam Generator Reference Book, December 1994.

8.4

Natrella, Mary

Gibbons,

" Experimental Statistics",

National I

Bureau of Standards, Handbook 91, page T-15.

8.5 Roark & Young, Formulas for Stress and Strain, Fifth Edition.

8.6 BAW-2303P, Revision 03, "OTSG Repair Roll Qualification Report",

October 1997.

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I 81 BAW 10232 REV 00 FRAMATOME TECilNOLOGIES I

lI APPENDIX As ETSS for Bobbin and MRPC Examination of OTSG Tube Repair Rolls I

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-I g

w, I

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I TRAMATOME TECIINOLOGIES A1 BAW 10232 REV 00

I APPENDIX B: Reroll Exclusion Zrsnes 9

I Exclusion Zone Summarv for Non-Oconee Plants (See Figure 5,2)

(d)

Exclusion Zone _Eugtmarf for Oconee Plants (See Figure 5.3) 1

(

.m..

1 (d)

\\

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Tables B.1 through

,,6 summarize the tubes in the exclus1]n zones where a (d) rero21 application is limited by tube hole di3at'on effects on joint strength.

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- I I

I (d)

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1

[-

e., -

em.,em x

- o,e m.0 - s

_