ML031330767

Cycle 11 (U2C11) 12-Month Steam Generator (SG) Inspection Report and Metallurgical Examination Report on Tube Removed from Steam Generator

ML031330767
Person / Time
Site:	Sequoyah
Issue date:	05/05/2003
From:	Salas P Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML031330767 (147)

Text

Tennessee Valley Authority, Post Office Box 2000, Soddy-Daisy, Tennessee 37384-2000 May 5, 2003 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washirgton, D.C. 20555 Gentlemen:

In the Matter of ) Docket No. 50-328 Tennessee Valley Authority SEQUOYAH NUCLEAR PLANT - UNIT 2 CYCLE 11 (U2C11) 12-MAONTH STEAM GENERATOR (SG) INSPECTION REPORT AND METALLURGICAL EXAI41NATION REPORT ON TUBE REMOVED FROM SG

Reference:

Sequoyah Nuclear Plant (SQN) - lnit 2 - Unit 2 Cycle 11 (U2C11) 90-Day Steam Generator Report for.

Voltage Based Alternate Repair Criteria In accordance with the requirements of Sequoyah Unit 2 Tchnical Specification 4.4.5.5.b, TVA is submitting the 12-month SG Inspection Report that includes the results of inservice inspections performed during the U2CII refueling outage.

In addition, TVA is providing the final report for the metallurgical examination of SG tube R12C45 that was pulled from SG No. 4 during the SQN I2C11 refueling outage. The final report is a follow-up to the preliminary report that was provided by TVA' s reference letter. provides the 12-month SG Inspection Report. provides the Metallurgical Examination Report.

There are no commitments contained in this letter. This letter is being sent in accordance with NRC RIS 2001-05.

Pnted on ecycled paper

U.S. Nuclear Regulatory Commission Page 2 May 5, 2003 Please direct questions concerning this issue to me at (423) 843-7170 or J. D. Smith at (423) 843-6672.

Li nsing and Industry Affairs Manager JDS:DVG Enclosures cc (Enclosures):

Mr. Michael L. Marshall Jr., Senior Project Manager U.S. Nuclear Regulatory Commission Mail Stop O-8G9A One White Flint North 11555 Rockville Pike Rockville, Maryland 20852-2739 R. J. Adney, LP 6A-C J. L. Beasley, OPS 4A-SQN M. J. Burzynski, BR 4X-C D. L. Koehl, POB 2B-SQN J. E. Maddox, LP 6A-C NSRB Support, LP 5M-C R. T. Purcell, OPS 4A-SQN J. A. Scalice, LP 6A-C K. W. Singer, LP 6A-C E. J. Vigluicci, ET 1A-K WBN Site Licensing Files, ADM 1L-WBN EDMS, WTC A-K (Re: S64 020729 800 and W03 021218 800)

I:License/Steam Generators/U2C11 12-Month SG Report and Final Metallurgical Report

ENCLOSURE 1 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT (SQN) UNIT 2 UNIT 2 CYCLE 11 REFUELING OUTAGE 12-MONTH STEAM GENERATOR INSPECTION REPORT

Sequoyah Nuclear Plant Unit 2 Cycle 11 Refueling Outage April 2002 12 Month Report Prepared By: S~~~~g_ l/ ttA L\-C LZ Verified By: Verified# By: @49r+A/S/

TABLE OF CONTENTS TABLE OF CONTENTS 2 INTRODUCTION 3 SG TUBE INSERVICE INSPECTION SCOPE 4 SG TUBE INSPECTION RESULTS 5 SECONDARY SIDE INSPECTION SCOPE AND RESULTS 9 CONCLUSIONS 10 REFERENCES II DEFINITIONS 12 I/sglsqnlu2c11/documents/reports/12 month report 2

INTRODUCTION During the scheduled Sequoyah Nuclear Plant (SQN) Unit 2 End of Cycle 11 (EOC-1 1) refueling outage, extensive inservice inspections were conducted in all four steam generators (SGs). The SQN Unit 2 Cycle 11 Degradation Assessment projected the extent of the various active and potential degradation mechanisms based on industry experience of plants with Westinghouse Model 51 SGs. The inspection was focused on the detection and evaluation of the active and potential degradation mechanisms.

The results of the inspections were classified as follows:

SG1 SG2 SG3 SG4 Bobbin Coil C-2 C-2 C-2 C-3 U-Bend +Pt C-3 C-1 C-1 C-1 TTS +Pt C-2 C-2 C-2 C-2 Dented TSP +Pt C-2 C-3 C-1 C-1 Freespan Dents +Pt C-1 C-1 C-3 C-1 The Alternate Repair Criteria (ARC) for axial outside diameter stress corrosion cracking (ODSCC) at tube support plates (TSPs) continued during this inspection. The report required within 90 days by Generic Letter 95-05, Attachment 1, Section 6.b. was transmitted to NRC by a separate transmittal.

During SQN Unit 2 Cycle 11 Refuel Outage tube support plate intersections were removed from a SQN steam generator to confirm axial ODSCC as required by Generic Letter 95-05 and industry correspondence with the NRC. Attached is the metallurgical examinations performed for tube intersections removed from the Steam Generator.

This report fulfills the reporting requirements of SQN Technical Specification section 4.4.5.5.b for reporting results of SG inservice inspection within 12 months.

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SG TUBE INSERVICE INSPECTION SCOPE The SQN Unit 2 SG tube inservice inspection (ISI) initial sample and expansion samples for all SGs and all damage mechanisms was as follows:

100% full-length bobbin examination in all 4 SGs 100% hot leg top of tubesheet (TTS) WEXTEX expansion transition region examination in all 4 SGs with +Point probe.

100% Row 1, 2, and 3 and 20% of Row 4 U-Bend examinations in all 4 SGs with magnetic biased ZETEC +Point Low Row U-Bend Rotating probe.

100% >2 volt hot leg dented TSP intersections in all 4 SGs with +Point probe.

100% of <2 volt dented TSP intersections were examined during the bobbin coil examination utilizing the qualified technique for detection of PWSCC. This required extensive analyst training and testing.

20% sample of hot leg freespan dents from TTS to the second hot leg TSP All test techniques used for detection were EPRI Appendix H qualified examination techniques and validated for use at SQN. NDE uncertainties were quantified for analysts and techniques utilized for sizing.

Refer to Attachment 1 for the quantity of the above examinations.

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SG TUBE INSPECTION RESULTS As a result of plugging 91 tubes EOC-1 1, Unit 2 SGs are 2.9% plugged. SQN Unit 2 is analyzed for up to 15% tube plugging. SQN Unit 2 utilized the Westinghouse rolled plugs during Cycle 11 RFO. Refer to Attachment 2 for a summary of tubes plugged and Attachment 3 for the identification of tubes plugged by damage mechanism.

The plugging status of each SG is described in Table I below:

Table I SG SGSG3 SG2 .. 2SG.Ttal .

Previously Plugged 47 123 82 51 303 Plugged EOC-11 20 19 18 34 91 Total Tubes Plugged 67 142 100 85 394 Percent Plugged 2.0% 4.2% 3.0% 2.5% 2.9%

Main steam line break accident differential pressure is 2560 psi (Pressurizer safety valve setpoint plus 3 percent), and 1.43 times this value provides the accident structural pressure lower limit of 3661 psi. The Steam Generator tubing operating pressure differential during fuel cycle 11 was 1387 psi (2235 psi RCS pressure minus 848 psi Main Steam pressure). Three times the normal differential pressure provides the normal operating structural pressure lower limit of 4162 psi.

Calculation for tube lower limit burst pressures were performed using TubeWorks Version 1.10 by E-Mech Technology, Inc.

Degradation Mechanisms Detected PWSCC U-Bend The U2C11 Degradation Assessment predicted ten tubes to be plugged due to axial or circumferential PWSCC in the Row 1, 2, or 3 U-bend region. Row 1 and 2 U-Bends were heat treated In-Situ during the Cycle 6 RFO, however, they had operated several cycles prior to heat treating. It is believed that cracking initiated in the first few cycles in Row 1 and 2 and may have continued to grow to detectable levels.

One PWSCC U-bend axial indication was identified in SG 1 RI C78 at H07+3.95. The NDE indicated values were 67.92% average depth, 0.24 inches in length, 99% max. depth, and 1.32 max. volts.

Condition Monitoring was performed on this indication with a lower limit burst pressure determined to be 4453 psi. This indication did not exceed the voltage screening criteria for performing In-Situ pressure testing.

Two PWSCC U-bend circumferential indications were identified in SG1. The most limiting of these indications was in SGI RI C21 located at H07+4.22 which had a circumferential extent of 45 degrees (i.e.

0.38 inches), 98% Max. Depth, and 1.67 Max. volts. The other indication was in SG1 R1 C28 which had a circumferential extent of 45 degrees (i.e. 0.38 inches), 64% Max. Depth, and 2.58 Max. Volts. These two tubes were In-Situ pressure tested to confirm structural and leakage integrity. Both tubes withstood 3 times normal operating pressure differential with zero leakage detected.

All PWSCC U-bend axial and circumferential indications satisfied Condition Monitoring performance criteria and all were plugged.

PWSCC TTS Axial The U2C11 Degradation Assessment predicted twenty tubes to be plugged due to axial PWSCC at TTS.

All PWSCC TTS axial indications were plugged on detection and sized using the +Point probe.

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A total of 20 PWSCC axial indications were identified. All of these axial indications were below the top-of-tubesheet and therefore could not burst due to the additional structural strength provided by the tubesheet. Also, axial indications will not allow a tube to be pulled out of the tubesheet. The most limiting PWSCC axial indication was in SG4 R2 C37 at HTS-1.55 (located 1.55 inches below the top of the tubesheet) which had NDE indicated values for average depth of 74.65%, maximum depth of 99%, length of 0.17 inches and 0.22 max. volts. Condition Monitoring assumed this indication was free-span and calculated a lower limit burst pressure of 4562 psi. None of the PWSCC TTS Axial indication exceeded the voltage screening criteria for In-Situ pressure testing.

All PWSCC TTS axial indications satisfied Condition Monitoring performance criteria and all were plugged.

PWSCC TTS Circumferential The U2C11 Degradation Assessment predicted ten tubes to be plugged due to circumferential PWSCC at TTS. All PWSCC TTS circumferential indications were plugged on detection and sized using +Point probe.

A total of 6 circumferential indications were identified. All of the PWSCC TTS circumferential indications were below the top-of-tubesheet, however all were analyzed as if they were freespan. Condition Monitoring was performed on all these indications with the most limiting indication in SG4 R12 C60 located at HTS-0.36. This indication had NDE indicated variables which measured 82% max. depth, 97 degrees circumferential extent, and 0.98 max. volts. Condition Monitoring assumed this indication was free span and calculated a lower limit burst pressure of 6955 psi All PWSCC TTS circumferential indications were below the screening criteria for performing In-Situ pressure testing for leakage. All PWSCC TTS indications met condition monitoring performance criteria.

All PWSCC TTS circumferential indications were plugged.

ODSCC TTS Axial The U2C11 Degradation Assessment predicted eighteen tubes to be plugged for axial ODSCC at TTS. All ODSCC-TTS axial indications were plugged on detection and sized using the +Point probe.

A total of eight ODSCC axial indications were identified. Condition Monitoring was performed on each.

The most limiting ODSCC axial TTS indication was SG3 R6 C80 located at HTS -0.02. This indication had an NDE indicated length of 0.25 inches, average depth of 27.83%, maximum depth of 76% and a max.

volts of 0.18 (indications with low voltage such as this one are very likely to have the phase angle pulled by other signals such as deposit or sludge and therefore it is very unlikely that this flaw is as severe as the depth indicates). Condition Monitoring assumed this indication was free span and conservatively calculated a lower limit burst pressure of 5680 psi All ODSCC TTS axial indications were below the In-Situ voltage screening criteria for performing In-Situ pressure testing for leakage. All ODSCC TTS axial indications met condition monitoring performance criteria. All ODSCC TTS axial indications were plugged.

ODSCC TTS Circumferential The U2C1 1 Degradation Assessment predicted ten tubes to be plugged for circumferential ODSCC at TTS. All ODSCC TTS circumferential indications were plugged on detection and sized using the +point probe.

A total of three TTS ODSCC circumferential indications were identified. Condition Monitoring was performed on each. The limiting ODSCC TTS circumferential indication is SG2 Ri 0 C39 located at HTS

+0.00. This indication had NDE indicated variables which measured a circumferential extent of 650 ,a maximum depth of 72% and max. volts of 0.17. Condition monitoring calculated a lower limit burst pressure of 7394 psi.

All ODSCC TS circumferential indications were below the screening criteria for performing In-Situ pressure testing for leakage. All ODSCC TTS circumferential indications met condition monitoring performance criteria. All ODSCC TTS circumferential indications were plugged.

ODSCC Axial Free Span at Dent I/sg/sqn/u2cl /documents/reports/I2 month report 6

One tube (SG3 R12 C2) was discovered with a ODSCC axial indication in the free span just above the top of tubesheet (HTS+0.98). This indication was associated with a dent. Condition Monitoring was performed on this indication. The indication had NDE indicated values of 0.15 inches long, an average depth of 35.40%, a maximum depth of 75%, and a max. voltage of 0.30. The calculated lower limit burst pressure for this indication was 8218 psi.

This indication was below the screening criteria for performing In-Situ pressure testing for leakage, however, TVA choose to perform In-Situ pressure testing on this tube with the results being zero leakage detected at 3AP. This ODSCC Axial Free Span at dent indication met condition monitoring performance criteria. This tube was plugged.

PWSCC TSP Axial The U2C1 I Degradation Assessment predicted ten tubes to be plugged for PWSCC TSP Axial indications.

All PWSCC TSP Axial indications were plugged on detection and sized by +Point probe.

Two PWSCC TSP axial indications were detected. The limiting indication was SG1 R8 C67 with NDE indicated values of 37.06% average depth, 0.34 inches in length, 62% max. depth, and 0.87 max. volts.

The calculated lower limit burst pressure for this indication was 6803 psi.

All PWSCC TSP axial indications were below the screening criteria for performing In-Situ pressure testing for leakage. The PWSCC TSP axial indications met condition monitoring performance criteria. All PWSCC TSP axial indications were plugged.

ODSCC TSP Axial The ARC for axial ODSCC at TSPs continued to be implemented this inspection and a detailed condition monitoring and operational assessment report has been transmitted separately.

AVB WEAR Based on past indications and growth rate data from past outages, two tubes were predicted to be plugged for AVB wear. A total of 85 indications in 50 tubes were detected. One tube (SG1 R33 C51) exceeded the 40% repair limit and was plugged. The 40% repair limit is conservative for SQN Unit 2 SGs for structural and leakage performance criteria (i.e. the 40% Max. Depth plugging limit precludes leakage).

Condition Monitoring assumed the axial length of the AVB Wear indications to be the width of the AVB (0.375") Therefore, the most limiting indication of 42% maximum depth had a calculated lower limit burst pressure of 6049 psi.

AVB Wear indications met condition monitoring performance criteria.

Cold Leg Thinninq The U2C1 I Degradation Assessment predicted two tubes to be plugged for cold leg thinning. A total of 126 indications were detected in 118 tubes with four indications exceeding the repair limit of 40% through wall and therefore plugged. The 40% repair limit is conservative for SQN Unit 2 SGs for structural and leakage performance criteria. Condition Monitoring assumed the axial length of Cold Leg Thinning to be the tube support plate thickness (0.75"). Therefore, the most limiting indication with an NDE indicated value of 53% maximum depth had a calculated lower limit burst pressure of 4431 psi.

Cold Leg Thinning indications met condition monitoring performance criteria.

Volumetric Indications Four volumetric indications were identified during the U2C11 inspection. +Point probe examinations and bobbin coil examinations were performed on each. Three indications were OD and one was ID.

For the OD indications, the best available sizing technique used a combination of two examinations. The sizing qualification for ODSCC HTS +Point was utilized to obtain axial length. Cold Leg Thinning maximum depth sizing (determined by bobbin coil - ETSS 96001.1 Rev 6 Jan 2001) was utilized.

Condition Monitoring was performed on all indications. The most limiting indication was SG2 R22 C25 at H02+44.84. This indication had an NDE indicated axial length of 0.27 inches and a maximum depth of 27%. The calculated lower limit burst pressure was 7411 psi. Two of these Volumetric indications were at the top-of -tubesheet and characterized as most probably wear from a loose part. The third volumetric I/sglsqn/u2clt/documentslreportsll2 month report 7

indication was in the free span between the second and third hot leg tube support plate. This indication was detected by the bobbin coil examination and confirmed as a volumetric by +Point examinations. This indication was non-crack-like.

The ID indication was approximately one half inch below the top-of-tubesheet. WCAP-15128 sizing was utilized for this indication. The NDE indicated values were 0.26 inches in axial length, 85% max. depth, 47.07% average depth, and 0.71 max. volts. The calculated lower limit burst pressure was 5978 psi. This indication was found in history and the max. volts were relatively unchanged, therefore it was characterized as a manufacturing flaw.

The volumetric indications met condition monitoring performance criteria. All four volumetric indications were plugged.

Preventive Pluqqina During the SQN Unit 2 Cycle 11 refuel outage, TVA took a very conservative approach to disposition two tubes. Two tubes (SG3 Rl C17 and SG4 R3 C8) were examined in the U-bend region multiple times by the Low-Row-+Point probe and acceptable data could not obtained. VA made the decision to plug these tubes because a flaw could have been present where the data was not acceptable. TVA also plugged 4 tubes in each channel head in order for the Flexi-Rail to be installed during future outages. FlexiRail will be mounted to these plugs in future outages and this enables the manipulators moves to be performed remotely via computer instead of by personnel. This will expedite manipulator movements and therefore reduce personnel dose. In summary, TVA conservatively plugged tubes preventively during the Unit 2 Cycle 11 outage to ensure compliance with all industry standards and to ensure the safe and reliable operation of the unit until the next refuel outage.

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SECONDARY SIDE INSPECTION SCOPE AND RESULTS Cracked Support Plate Indications Cracked tube support plate indications (CSIs) are indications of cracks in the tube support plates and not necessarily indicative of tube degradation. These are detected during 100% automated analysis of bobbin data.

SQN Unit 2 SGs do not have extensive support plate cracking. Cracked TSPs were evaluated for potential star drop-out conditions and none were identified. Therefore, design basis function of the support plate has not been lost. There is also no evidence of wrapper drop or wrapper degradation.

Upper Internals Inspection Upper internals inspections were performed in SGs 1and 4 during this inspection. The inspection is performed for evidence of erosion I corrosion , cracked welds, deposit buildup, or any other service-induced degradation. No degradation was detected.

Slud-ie Lancinq Sludge lancing was performed during the Unit 2 Cycle 11 RFO. The following amounts of sludge was removed: SG1 - 46 pounds; SG2 - 23 pounds; SG3 - 35 pounds; SG4 - 26 pounds.

Foreign Object Search and Retrieval (FOSAR)

Foreign object search and retrieval was completed on all four SGs prior to closure and all identified foreign objects were retrieved.

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CONCLUSIONS The NDE testing completed on the SQN Unit 2 SGs and plugging of defective tubes met the Technical Specification and ASME Section Xi code requirements for inservice inspection and structural and leakage integrity has been demonstrated; therefore, each SG has been demonstrated operable.

Utilization of one Altemate Repair Criteria continued in accordance with the Unit 2 Technical Specification Surveillance Requirement 3/4.4.5.4.a.10.

Based on the criteria of 10 CFR 50.59, TVA concludes that the integrity of the SQN Unit 2 SGs was maintained during Cycle 11 operation and will be maintained through fuel Cycle 12 and does not represent an unreviewed safety question.

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REFERENCES

1. WCAP-15579, "Burst Pressure Data for Steam Generator Tubes with Combined Axial and Circumferential Cracks", Westinghouse Proprietary Class 2, Westinghouse Electric Company LLC, September, 2000.

2. WCAP-15128, Rev. 3, "Depth-Based SG Tube Repair Criteria for Axial PWSCC at Dented TSP Intersections", Westinghouse Proprietary Class 2, Westinghouse Electric Company LLC, June, 2000.

3. Keating, R. F., and Begley, J. A., "Steam Generator Tubing Flaw Handbook", EPRI Report TR-1001191-L, EPRI, Palo Alto, CA, January2001.

4. 'PWR Steam Generator Examination Guidelines", Performance Demonstration Database, Appendix A, Technique Specification Sheets, ETSS 96702, EPRI, Palo Alto, CA, January, 1999.

5. EPRI TR-107197, "Depth Based Structural Analysis Methods for SG Circumferential Indications, EPRI, Palo Alto, CA, November, 1997.

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DEFINITIONS

+Point - An RPC eddy current probe in which two coils are placed against the same contact surface with their axis 90 degrees apart. When the probe face is viewed, the coils create the appearance of a

'+'. This configuration minimizes the eddy current response to tubing geometry changes or support structures and is presently considered the probe with the best overall crack detection capabilities.

ARC - Alternate Repair Criteria C01 - First cold leg tube support plate intersection C02 - Second cold leg tube support plate intersection C03 - Third cold leg tube support plate intersection C04 - Fourth cold leg tube support plate intersection C05 - Fifth cold leg tube support plate intersection C06 - Sixth cold leg tube support plate intersection C07 - Seventh cold leg tube support plate intersection EOC - End of Cycle EPRI - Electric Power Research Institute H01 - First hot leg tube support plate intersection H02 - Second hot leg tube support plate intersection H03 - Third hot leg tube support plate intersection H04 - Fourth hot leg tube support plate intersection H05 - Fifth hot leg tube support plate intersection H06 - Sixth hot leg tube support plate intersection H07 - Seventh hot leg tube support plate intersection ODSCC - Outside Diameter Stress Corrosion Cracking PDA - Percent Degraded Area PWSCC - Primary Water Stress Corrosion Cracking RFO - Refuel Outage RPC - Literally 'Rotating Pancake Coil' eddy current probe. This term is also used to describe eddy current probes in which the coil face contacts the tube wall while rotating and being pulled through the tube axially such that the examination path is helical.

SQN - Sequoyah Nuclear Power Plant TSP - Tube Support Plate TTS - Top of Tubesheet WEXTEX - Westinghouse Explosive Tube Expansion I/sg/sqn/u2cII/documents/reports/2 month report 12

ATTACHMENT I SQN UNIT 2 CYCLE 11 RFO NUMBER AND EXTENT OF TUBES EXAMINED

SUMMARY

OF SEQUOYAH UNIT 2 CYCLE 11 SG EDDY CURRENT INSPECTIONITUBE PLUGGING RESULTS EDDY CURRENT EXAM TYPE SG1 SG2 SG3 SG 4 Total Full Length Bobbin Coil 3341 3265 3306 3337 13249 U-Bend Plus Point 281 257 275 287 1100 Top of Tubesheet Plus Point 3341 3265 3306 3337 13249 Freespan Plus Point 26 30 30 4 90 H01 Plus Point 13 22 33 3 71 H02 Plus Point 2 4 2 0 8 H03 Plus Point 6 14 1 0 21 H04 Plus Point 4 4 2 2 12 H05 Plus Point 23 7 2 5 37 H06 Plus Point 37 11 14 3 65 H07 Plus Point 83 30 87 38 238 Diagnostic/PID Plus Point 36 40 33 132 241 Total Exams Completed 7193 6949 7091 7148 28381 Total Tubes Examined 3341 3265 3306 3337 13249 I/sg/sqn/u2c1 Ildocuments/reports/2 month report I

ATTACHMENT 2 SQN UNIT 2 CYCLE 11 RFO

SUMMARY

OF SG TUBE PLUGGING

SUMMARY

OF SEQUOYAH UNIT 2 CYCLE 11 SG EDDY CURRENT INSPECTIONTUBE PLUGGING RESULTS PLUGGING STATUS SG1 SG2 SG3 SG 4 Total Previously Plugged Tubes 47 123 82 51 303 Damage Mechanism AVB WEAR 1 0 0 0 1 COLD LEG WASTAGE 1 3 2 5 11 ODSCC HTS AXIAL 1 0 2 4 7 ODSCC HTS CIRC 0 1 0 2 3 ODSCC TSP AXIAL 0 0 1 2 3 ODSCC AXIAL FREESPAN DNT 0 0 1 0 1 PREVENTATIVE 0 0 1 I 2 PWSCC HTS AXIAL 3 4 3 6 16 PWSCC HTS CIRC 0 1 0 5 6 PWSCC TSP AXIAL 1 1 0 0 2 PWSCC U-BEND AXIAL 1 0 0 0 1 PWSCC U-BEND CIRC 2 0 0 0 2 VOLUMETRIC INDICATION 2 1 0 1 4 FOR FLEXI RAIL SYSTEM 8 8 8 8 32 Plugged Cycle 11 20 19 18 34 91 TOTAL TUBES PLUGGED 67 142 100 85 394 Effective Plugging Percentages SG 1 2.0%

SG 2 4.2%

SG 3 3.0%

SG 4 2.5%

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ATTACHMENT 3 SQN UNIT 2 CYCLE 11 RFO T. . USTEAM

. .G GENERATOR D. I MECH TUBES PLUGGED BY DAMAGE MECHANISM SG ROW COL INDICATION LOCATION . CHARACTERIZATION 33 51 42 AV2-.11 AVB WEAR Total: I I 43 60 47 C0I+.00 C/L WASTAGE Total: I I 19 80 SVI HTS+.58 LOOSE PART WEAR Total: I I 1 23 SAI HTS+.05 ODSCC HTS AXIAL Total: I 1 2 36 TBP +0.00 OTHER-Flexi Rail 2 44 TBP +0.00 OTHER-Flexi Rail 1

I 2 52 TBP +0.00 OTHER-Flexi Rail 1

2 60 TBP +0.00 OTHER-Flexi Rail I

6 36 TBP +0.00 OTHER-Flexi Rail

. I 6 44 TBP +0.00 OTHER-Flexi Rail 6 52 TBP +0.00 OTHER-Flexi Rail T 6 60 TBP +0.00 OTHER-Flexi Rail Total: 8 2 9 SAI HTS-.50 PWSCC HTS AXIAL I 2 34 SAI HTS-.89 PWSCC HTS AXIAL 19 39 SAI HTS-2.51 PWSCC HTS AXIAL 3

Total: 8 67 SAI H06-.10 PWSCC TSP AXIAL I I Total: 1 78 SAI H07+4.11 PWSCC UBEND AXIAL I

1 21 SCI H07+4.27 PWSCC UBEND CIRC Total:

1 28 SCI H07+10.61 PWSCC UBEND CIRC Total:

GadTotal:S-I 2 44 55 SVI HTS+.50 VOLUMETRIC Total:

20 I/sg/sqn/u2c11/documents/reports/I2 month report 2

ATTACHMENT 3 SQN UNIT 2 CYCLE 11 RFO

- STEAM GENERATOR 2 PLUGGED TUBES BY DAMAGE MECHANISM SG ROW COL INDICATION LOCATION CHARACTERIZATION 2 33 75 SVI C02-.10 C/L WASTAGE 2 36 77 SVI C01-.23 C/L WASTAGE 2 44 34 SVI C01-.03 C/L WASTAGE Total: 3 2 10 39 SCI HTS+.00 ODSCC HTS CIRC Total: I 2 2 36 TBP +0.00 OTHER-Flexi Rail 2 2 44 TBP +0.00 OTHER-Flexi Rail 2 2 52 TBP +0.00 OTHER-Flexi Rail 2 2 60 TBP +0.00 OTHER-Flexi Rail 2 6 36 TBP +0.00 OTHER-Flexi Rail 2 6 44 TBP +0.00 OTHER-Flexi Rail 2 6 52 TBP +0.00 OTHER-Flexi Rail

2. 6 60 TBP +0.00 OTHER-Flexi Rail Total: 8 2 6 56 SAI HTS-.60 PWSCC HTS AXIAL 2 7 24 SAI HTS-.19 PWSCC HTS AXIAL 2 18 17 SAI HTS-3.17 PWSCC HTS AXIAL 2 22 60 SOl HTS-.80 PWSCC HTS AXIAL Total: 4 2 37 64 SCI HTS-6.34 PWSCC HTS CIRC Total: I 2 39 48 SAI HOI+.36 PWSCC TSP AXIAL Total: I 2 22 25 SVI H02+44.84 VOLUMETRIC Total: 1 Grand Total SG-2: 19 I/sg/sqn/u2clI/documents/reports/12 month report 3

ATTACHMENT 3 SQN UNIT 2 CYCLE 11 RFO STEAM GENERATOR 3 TUBES PLUGGED BY DAMAGE MECHANISM SG ROW COL INDICATION LOCATION CHARACTERIZATION 3 41 32 46 C02-.24 C/L WASTAGE 3 45 37 48 C02-.26 CIL WASTAGE Total: 2 3 12 2 SAI HTS+.98 ODSCC F-SPAN AXIAL Total: I 3 4 78 SAI HTS-.07 ODSCC HTS AXIAL 3 6 80 SAI HTS-.03 ODSCC HTS AXIAL Total: 2 3 34 32 DSI HOI+.02 ODSCC TSP AXIAL Total: I 3 2 36 TBP +0.00 OTHER-Flexi Rail 3 2 44 TBP +0.00 OTHER-Flexi Rail 3 2 52 TBP +0.00 OTHER-Flexi Rail 3 2 60 TBP +0.00 OTHER-Flexi Rail 3 6 36 TBP +0.00 OTHER-Flexi Rail 3 6 44 TBP +0.00 OTHER-Flexi Rail 3 6 52 TBP +0.00 OTHER-Flexi Rail 3 6 60 TBP +0.00 OTHER-Flexi Rail Total: 8 3 1 17 TBP +0.00 PREVENTIVE-Geometry Total: I 3 1 54 SAI HTS-.48 PWSCC HTS AXIAL 3 5 16 SAI HTS-5.26 PWSCC HTS AXIAL 3 19 65 SOl HTS-2.92 PWSCC HTS AXIAL Total: 3 Grand Total SG-3: 18 I/sg/sqn/u2cI1/documents/reports/12 month report 4

ATTACHMENT 3 SQN UNIT 2 CYCLE 11 RFO STEAM GENERATOR 4 TUBES PLUGGED BY DAMAGE MECHANISM SG ROW COL INDICATION LOCATION CHARACTERIZATION 4 35 19 SVI C02-.08 C/L WASTAGE 4 39 73 SvI C02-.12 C/L WASTAGE 4 43 32 SVI C01-.12 C/L WASTAGE 4 44 35 SVI C01-.13 C/L WASTAGE 4 46 41 SVI C02-.10 C/L WASTAGE Total: 5 4 9 17 SAI HTS-.01 ODSCC HTS AXIAL 4 15 34 SAI HTS-.04 ODSCC HTS AXIAL 4 19 26 SAI HTS-.03 ODSCC HTS AXIAL 4 29 45 SAI HTS-.18 ODSCC HTS AXIAL Total: 4 4 7 24 SCI HTS-.14 ODSCC HTS CIRC 4 9 59 SCI HTS-.14 ODSCC HTS CIRC Total: 2 4 12 16 SAT H02+.32 ODSCC TSP AXIAL 4 12 45 DSI H01+.09 ODSCC TSP AXIAL Total: 2 4 2 36 TBP +0.00 OTHER-Flexi Rail 4 2 44 TBP +0.00 OTHER-Flexi Rail 4 2 52 TBP +0.00 OTHER-Flexi Rail 4 2 60 TBP +0.00 OTHER-Flexi Rail 4 6 36 TBP +0.00 OTHER-Flexi Rail 4 6 44 TBP +0.00 OTHER-Flexi Rail 4 6 52 TBP +0.00 OTHER-Flexi Rail 4 6 60 TBP +0.00 OTHER-Flexi Rail Total: 8 4 3 8 TBP H07+7.85 PREVENTIVE-RBD Total: I 4 2 37 SAI HTS-1.55 PWSCC HTS AXIAL 4 2 40 SAI HTS- 1.02 PWSCC HTS AXIAL 4 11 26 SAT HTS-5.58 PWSCC HTS AXIAL 4 13 60 SAI HTS-4.40 PWSCC HTS AXIAL 4 15 8 SAI HTS-2.75 PWSCC HTS AXIAL 4 15 70 SOl HTS-4.22 PWSCC HTS AXIAL Total: 6 4 12 60 . SCI HTS-.34 PWSCC HTS CIRC 4 15 60 SCI HTS-3.61 PWSCC HTS CIRC 4 18 60 SCI HTS-3.37 PWSCC HTS CIRC 4 20 45 SCI HTS-3.63 PWSCC HTS CIRC 4 24 9 SCI HTS-2.67 PWSCC HTS CIRC Total: 5 4 25 44 SVI HTS-.62 VOLUMETRIC Total: 3 Grand Total SG-4: 34 I/sg/sqn/u2ct /documentslreports/I2 month report 5

ENCLOSURE 2 TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT (SQN) UNIT 2 FINAL METALLURGICAL REPORT FOR STEAM GENERATOR TUBE R12C45

i Westinghouse Non-Proprietary Class 3 SG-SGDA-03-12 April 2003 Revision 00 TUBE EXAMINATIONS FOR THE SUPPORT OF SEQUOYAH UNIT 2 STEAM GENERATORS VOLTAGE-BASED REPAIR CRITERIA

Westin-house Non-Proprietary Class 3 TUBE EXAMINATIONS FOR THE SUPPORT OF SEQUOYAH UNIT 2 STEAM GENERATORS VOLTAGE-BASED REPAIR CRITERIA FINAL REPORT SG-SGDA 12 APRIL 2003 Prepared for the Tennessee Valley Authority Prepared by: A _

Thomas Magee, Westin ouse Reviewed byy( (

Roert E. Gold, Consulting Metallurgist Approved by: / KZ i Robert Sterdis, Manager, Steam Generator Design and Analysis C© 2003 Westinghouse Electric Companv LLC 2000 Dav Hill Road 'P.O. Box 500 Windsor. Connecticut 06095-0500

____________ All Rights Rcserved

COPYRIGHT NOTICE This report has been prepared by Westinghouse Electric Company LLC, for the Tennessee Valley Authority. Information in this report is the property of and contains copyright information owned by Westinghouse Electric Company LLC and/or its subcontractors and suppliers. It is transmitted to you in confidence and trust, and you agree to treat this document and the information contained therein in strict accordance with the terms and conditions of the agreement under which it was provided to you.

As a representative of the Tennessee Valley Authority, you are permitted to make the number of copies of the information contained in this report which are necessary for your internal use in connection with your implementation of the report results for your plant(s) in your normal conduct of business. Should implementation of this report involve a third party, you are permitted to make the number of copies of the information contained in this report which are necessary for the third party's use in supporting your implementation at your plant(s) in your normal conduct of business if you have received the prior, written consent of Westinghouse Electric Company LLC to transmit this information to a third party or parties. All copies made by you must include the copyright notice in all instances.

© 2003 Westinghouse Electric Company LLC 2000 Day Hill Road P.O. Box 500 Windsor, Connecticut 06095-0500 All Rights Reserved

TABLE OF CONTENTS Section No. Description Page No.

1.0 Introduction ..................... 8 2.0 Removed Tube Characteristics ..................... 10 3.0 Sectioning Plans ..................... 15 4.0 Leak Rate and Burst Testing ..................... 21 4.1 Introduction ..................... 21 4.2 Test Methods ..................... 22 4.3 Leak Test Results ..................... 23 4.4 Burst Test Results ..................... 24 4.5 Post-Burst Observations ..................... 26 5.0 Fractography ..................... 73 5.1 Procedure ..................... 73 5.2 Results ..................... 74 6.0 Metallography of Defects ..................... 104 6.1 Procedure ..................... 104 6.2 Results ..................... 104 7.0 Tensile Tests ..................... 117 8.0 Discussion / Conclusions ..................... 121 9.0 References ..................... 123 SG-SGDA 12 Page 2

LIST OF TABLES No.Title Page 2-1 Pulled Tube R12C45 Section Lengths and Characteristics ................................... 13 2-2 Summary Of NDE Results ................................................. 14 4-1 Leak Rate Summary for TSP1 ................................................. 29 4-2 Burst Test Results .................................................. 30 5-1 Summary of Depths and Extent of Cracking for the Burst Openings ................... 77 5-2 Tube R12C45 TSP1 (Secondary and Main Crack) Burst Macrocrack Depth Profile ........ 78 5-3 Tube R12C45 TSP1 (Main Crack) Burst Macrocrack Depth Profile ........... ........ 79 5-4 Tube R12C45 TSP2 Burst Macrocrack Depth Profile .......................................... 80 5-5 Tube R12C45 TSP3 Burst Macrocrack Depth Profile .......................................... 81 7-1 Tensile Properties ................................................. 118 SG-SGDA-03-12 Page 3

LIST OF FIGURES No.Title Page 3-1 Sectioning Diagram for Piece 2 .................................................... 16 3-2 Sectioning Diagram for Piece 3 ..................................................... 17 3-3 Sectioning Diagram for Piece 4 ..................................................... 18 3-4 Sectioning Diagram for Piece 5A.................................................... 19 3-5 Sectioning Diagram for Piece 5 .................................................... 20 4-1 Leak Rate as a Function of Pressure Differential for TSP1 (Section 3B) ............. 31 4-2 Pressure and Temperature Plots for TSP1 .................................................... 32 4-3 Secondary Side Autoclave Temperatures and Pressures ...................................... 33 4-4 Post-Burst Visual Observations of TTS Region ................................................... 34 4-5a Photograph of TTS Burst Area, 00 Face ..................................................... 35 4-Sb Photograph of TTS Burst Area, 900 Face .................................................... 36 4-5c Photograph of TTS Burst Area, 1800 Face ..................................................... 37 4-5d Photograph of TTS Burst Area, 2600 Face .................................................... 38 4-Se Photograph of TTS Burst Area, 2700 Face .................................................... 39 4-6 Post-Burst Visual Observations of TSP1 Region .................................................. 40 4-7a Photograph of TSP1 Burst Area, 00 Face ..................................................... 41 4-7b Photograph of TSP1 Burst Area, 900 Face ..................................................... 42 4-7c Photograph of TSP1 Burst Area, 1800 Face .................................................... 43 4-7d Photograph of TSP1 Burst Area, 2300 Face .................................................... 44 4-7e Photograph of TSP1 Burst Area, 2700 Face .................................................... 45 4-8 Post-Burst Visual Observations of TSP2 Region .................................................. 46 4-9a Photograph of TSP2 Burst Area, 00 Face .................................................... 47 4-9b Photograph of TSP2 Burst Area, 15 Face .................................................... 48 4-9c Photograph of TSP2 Burst Area, 900 Face ..................................................... 49 4-9d Photograph of TSP2 Burst Area, 1800 Face .................................................... 50 Page 4 SG-SGDA-03-12 Page 4

LIST OF FIGURES (Continued)

No.Title Page 4-9e Photograph of TSP2 Burst Area, 2700 Face ............................................. 51 4-10 Post-Burst Visual Observations of TSP3 Region ............................................. 52 4-1la Photograph of TSP3 Burst Area, 00 Face ............................................. 53 4-1 lb Photograph of TSP3 Burst Area, 900 Face ............................................ 54 4-l lc Photograph of TSP3 Burst Area, 1300 Face ............................................. 55 4-lid Photograph of TSP3 Burst Area, 1800 Face ............................................. 56 4-1 le Photograph of TSP3 Burst Area, 2700 Face ............................................ 57 4-12a Photograph of Section 2B Freespan Burst Area, 00 Face ..................................... 58 4-12b Photograph of Section 2B Freespan Burst Area, 90° Face ................................... 59 4-12c Photograph of Section 2B Freespan Burst Area, 1800 Face ................................. 60 4-12d Photograph of Section 2B Freespan Burst Area, 2000 Face ................................. 61 4-12e Photograph of Section 2B Freespan Burst Area, 2700 Face ................................. 62 4-13a Photograph of Section 4-lA Freespan Burst Area, 00 Face .................................. 63 4-13b Photograph of Section 4-lA Freespan Burst Area, 150 Face ................................ 64 4-13c Photograph of Section 4-1A Freespan Burst Area, 900 Face ................................ 65 4-13d Photograph of Section 4-lA Freespan Burst Area, 180° Face .............................. 66 4-13e Photograph of Section 4-lA Freespan Burst Area, 270° Face .............................. 67 4-14a Photograph of Section 5A1 Freespan Burst Area, 00 Face ................................... 68 4-14b Photograph of Section 5Al Freespan Burst Area, 900 Face ................................. 69 4-14c Photograph of Section 5A1 Freespan Burst Area, 1150 Face ............................... 70 4-14d Photograph of Section 5Al Freespan Burst Area, 1800 Face ............................... 71 4-14e Photograph of Section 5A1 Freespan Burst Area, 2700 Face ............................... 72 5-1 TSPl Left Burst Opening Macrocrack Depth Profile ........................................... 82 5-2 TSPI Right Burst Opening Macrocrack Depth Profile ......................................... 83 5-3 TSP2 Burst Opening Macrocrack Depth Profile ............................................ 84 Page 5 SG-SGDA-03-12 Page 5

LIST OF FIGURES (Continued)

No.Title Page 5-4 TSP3 Burst Opening Macrocrack Depth Profile ................................................... 85 5-5 TSP1 Burst Opening Fractograph Showing Part Throughwall Corrosion ............ 86 5-6 TSP1 Burst Opening Fractograph of Crack Mouth ............................................... 87 5-7 Close-Up of TSP1 Crack Mouth ..................................................... 88 5-8 TSP1 Burst Opening Fractograph of Crack Tip .................................................... 89 5-9 Close-Up of TSP1 Crack Tip ..................................................... 90 5-10 TSP1 Burst Opening Fractograph of Part Throughwall Corrosion after Cleaning ..................................................... 91 5-11 TSP1 Burst Opening Fractograph of Crack Mouth after Cleaning ....................... 92 5-12 Close-Up of TSP1 Crack Mouth after Cleaning ................................................... 93 5-13 TSP2 Burst Opening Fractograph Showing Part Throughwall Corrosion ............ 94 5-14 TSP2 Burst Opening Fractograph of Crack Mouth ............................................... 95 5-15 Close-Up of TSP2 Crack Mouth ..................................................... 96 5-16 TSP2 Burst Opening Fractograph of Crack Tip .................................................... 97 5-17 Close-Up of TSP2 Crack Tip ..................................................... 98 5-18 TSP3 Burst Opening Fractograph Showing Part Throughwall Corrosion ............ 99 5-19 TSP3 Burst Opening Fractograph of Crack Mouth ............................................. 100 5-20 Close-Up of TSP3 Crack Mouth ..................................................... 101 5-21 TSP3 Burst Opening Fractograph of Crack Tip ................................................... 102 5-22 Close-Up of TSP3 Crack Tip ..................................................... 103 Page 6 SG-SGDA-03-12 SG-SGDA-03-12 Page 6

LIST OF FIGURES (Continued)

No.Title Page 6-1 Low Magnification View of TSP1 Transverse Section (Unetched) ........ ........... 107 6-2 Deepest Crack on the TSP1 Transverse Section, Position 1 in Figure 6-1 (Nital Etch) ................................................. 108 6-3 Low Magnification View of TSP2 Transverse Section (Unetched) ....... ............ 109 6-4 Deepest Crack on the TSP2 Transverse Section, Position 2 in Figure 6-3 (Nital Etch) .110 6-5 Deep IGA on the TSP2 Transverse Section, Position 9 in Figure 6-3 (Nital Etch) ................................................. 111 6-6 Low Magnification View of TSP3 Transverse Section (Unetched) ....... ............ 112 6-7 Deepest Crack at TSP3, Position 1 in Figure 6-6 (Nital Etch) ............................ 113 6-8 Scratch Crack, Position 6 in Figure 6-6 (Nital Etch) .......................................... 114 6-9 Scratch Crack, Position 7 in Figure 6-6 (Nital Etch) .......................................... 115 6-10 Close-Up of Position 6 Scratch Crack (Nital Etch) ............................................ 116 7-1 Stress-Strain Curve for Specimen 3C1 ................ ................................ 119 7-2 Stress-Strain Curve for Specimen 5A2 ................................................ 120 Page 7 SG-SGDA-03-12 Page 7

Section

1.0 INTRODUCTION

Sequoyah Unit 2 (Sequoyah-2) is owned and operated by the Tennessee Valley Authority (TVA). Sequoyah-2 is a four loop Westinghouse designed pressurized water reactor sited on the banks of the Chickamauga Reservoir. The plant, which has a nominal rating of 1117 net MWe, commenced commercial operation in 1982 and has since accumulated over 13 EFPY of operation. The steam generators are of the Model 51 type manufactured by the Westinghouse Electric Corporation. Each steam generator contains 3388 heat transfer tubes. The mill annealed NiCrFe Alloy 600 steam generator tubes are nominally 0.875 inch in outer diameter and have a nominal wall thickness of 50 mils. The tubes are mounted in a low alloy steel tubesheet that is approximately 21.7 inches thick (including cladding). The tube-to-tubesheet crevices were closed using the WEXTEX process, in which tubes were explosively expanded. The tubes pass through seven carbon steel tube support plates (TSPs) that are 0.75 inch thick each, through drilled holes that have a nominal diameter of 0.891 inch.

To reduce the number of tubes that needed to be plugged due to the presence of detectable axial outside diameter stress corrosion cracking (ODSCC), Sequoyah-2 initiated an alternative repair criteria (ARC) program.

During the cycle 11 refueling outage (spring 2002), TVA selected one steam generator tube from Sequoyah Unit 2 for removal and laboratory non-destructive and destructive examinations to maintain the ARC. The tube selection and laboratory examination were in compliance with ARC requirements that were established in GL95-05 (Reference 1). The tube that was removed, R12C45, was from steam generator 4, and included three support plate intersections.

The tube was cut below the fourth support, pulled from the generator and delivered to Westinghouse's Remote Metallographic Facility of the Science and Technology Department (STD) for non-destructive and destructive examinations. The emphasis of the laboratory SG-SGDA-03-12 Page 8

activities was to perform tube integrity testing and to characterize the depth and type of defects that caused the ECT indications. All examinations and testing presented in this report were treated as safety-related and are in accordance with the Westinghouse Quality Assurance program (Reference 2), which satisfies the requirements of OCFR50 Appendix B. This examination was initiated by the Reference 3 work authorization and was monitored under the Westinghouse SAP network number 110118.

SG-SGDA-03-12 Page 9

Section 2.0 REMOVED TUBE CHARACTERISTICS Westinghouse removed sections from the hot leg side of R12C45 from Sequoyah-2 steam generator 4 during the cycle 11 refueling outage. The tube sections were removed by cutting just below the fourth tube support plate. A maximum force of 3578 lbs was required to pull the tube out of the generator (Reference 4). This translates to a tensile stress of 27,600 psi. This was well below the yield strength of the material.

The tube was cut into eight sections as it was pulled through the tubesheet (the terms "section" and "piece" are used interchangeably throughout this report). Most cuts were made at an angle that was slightly less than 900 to the axis of the tube. The tube was "nicked" as a means of establishing orientation at the top of each tube section on the side of the tube opposite the divider plate. The tube was cut in convenient lengths to preserve the areas of interest. Each section was identified with the tube section number. Care was taken to avoid contaminating the outer surface of the tube by lead shielding.

Table 2-1 lists the sections, their lengths and their location. Sections 4 and 5 dropped out of the tubesheet during the pulling operation and into the steam generator channel head. They were still attached to the remaining tube in the tubesheet and because of radiation exposure concerns, were cut to longer lengths and later cut into smaller sections with a tube cutter at an angle of 90° to the axis of the tube. These sections were identified and marked as to the top and bottom of each section.

The table also compares the lengths measured in the field, as noted in Reference 4, with the lengths measured in the laboratory. The laboratory measured lengths are used in this report.

Based on the labeling that was placed on each tube and the match between lengths in Reference 4 and those measured in the lab, it was verified that the correct pieces were received and were labeled correctly.

Page 10 SG-SGDA 12 SG-SGDA-03-12 Page 10

After initial inspection the end of the tube sections were deburred to facilitate the laboratory examinations. As the tube sections were cut into smaller pieces, the identification and traceability of specimens was maintained in accordance with the Reference 5 procedure. The designation of each cut specimen includes the number of the original piece. For instance, specimen 2B was cut from piece 2. Pieces cut from section 4 and 5 were given labels that began with a "41" and "51", respectively. Pieces cut from section 4A and 5A were given labels that began with a "4A" and "5A", respectively. An orientation system was arbitrarily chosen to aid in the description of the tube specimens. The O orientation of each specimen was related to a tube pull grind mark at the bottom of the tube piece (the tube sections were marked on the side facing the periphery), and 900 is clockwise of 0° when looking in the upward (primary flow) direction.

Unless otherwise stated, this orientation system is used throughout this report.

The field eddy current (ECT) data were re-evaluated as part of the tube examination. Also, as part of the laboratory examination, the TSP crevice regions of the tubes were eddy current inspected in a manner consistent with the field inspection. Table 2-2 presents a summary of field and laboratory eddy current data obtained on the pulled tubes for the TSP crevice regions of interest. The data is presented in a manner to allow for one-to-one comparison of the field and laboratory results. Bobbin coil calls were made using 400/100 kHz MIX data from the differential mode. +Point probe calls were made from the +Point coil using 300 kHz differential mode data.

Table 2-2 shows that the re-evaluation of the bobbin data showed results that were similar to the original field evaluation. The re-evaluation of the TSP1 +Point data confirmed the presence of one large amplitude indication, but two additional low-amplitude indications were identified.

The re-evaluation of the TSP2 and TSP3 +Point data also identified additional low-amplitude indications.

In general, the laboratory examinations, without the support and its associated deposits, the signal to noise ratio for the indications improved. The laboratory ECT data for TSP1 showed indication responses that were significantly larger in amplitude than the field data. The large Page 11 SG-SGDA-03-12 Page 1

change in the amplitude response is consistent with the opening of ligaments within the degraded regions by the tube removal process. The similarity of the shape of the Lissajous responses (pre-and post-tube removal) suggests that there was no extension of the degraded region. The +Point responses had characteristics of circumferential involvement suggesting the opening of cellular corrosion by the axial stresses of the tube removal. The laboratory ECT data showed a bobbin coil indication that was identified at the location of TSP2. The indication, however, was distorted by the tube removal process such that meaningful measurement of the degradation response could not be performed. As with the indications in TSPI, the indications in TSP2 had +Point response characteristics indicative of circumferential involvement suggesting the opening of cellular corrosion by the axial stresses of the tube removal. The laboratory ECT data for TSP3 showed that the indication, as was determined in the MIX channel, was slightly different than that observed in the field.

Page 12 SG-SGDA-03-12 Page 12

TABLE 2-1 PULLED TUBE R12C45 SECTION LENGTHS AND CHARACTERISTICS

-Lngth, Leng h,-As As Reported in Measured inLab Sectio Reference 4

-n : - :(inches) ^(inches) Remarks. --

1 30.750 30 3/4 Included TTS Region 2 30.750 30 3/4 3 34.000 33 3/4 Included TSPI Region 4A 9.000 9 4 30.000 29 5/8 Included TSP2 Region 5A 25.000 25 5 32.063 32 Included TSP3 Region 6 26.625 26 3/4 Page 13 SG-SGDA-03-12 Page 13

TABLE 2-2

SUMMARY

OF NDE RESULTS Field Eddy Current.  :-Re-Evaluated Field ECT Laboratory Eddy Current Bobbin Coil - +Point Bobbin Coil +Point Bobbin Coil' +Point

• Volts / Designation Volts / Designation / Length (in.)' - Volts / % . Volts / % / I(in.) Volts/ % Volts / % / I (in.)

TSPI 3.35 / DSI 1.89 / SAI /0.58 3.26 /91 A 0.24 /54 / 0.33 6.92 / 88 A 0.38 /48 / 0.29 0.24 / SAI / 0.29 B 0.15 / <20 / 0.30 B 0.16 / 25 / 0.35 0.24 / SAI / 0.32 C 0.08 / P / 0.24 C 0.09 / 25 / 0.19*

D 0.22 /28 /0.21 D 0.32 /23 /0.35 E 2.02 / 87/0.7 E 4.33 /95 /0.72 TSP2 0.95 / DSI 0.26 / SAI / 0.52 0.60 / 66 A 0.24 /44 / 0.71 Dist. A 0.24 / 35 /0.73

._____________ B 0.13/PI/0.58 B 0.21/36/0.73 TSP3 0.44 / DSI 0.16 / SAI / 0.49 0.46 / DSI A 0.20/51 / 0.28 0.59 / 53 A 0.22 / 25 /0.38 B 0.09/<20/0.18 C 0.19/22/0.71 C 0.22/<20/0.75

• - Measurement from the Pancake coil NDD - No Detectable Degradation SAI - Single Axial Indication DSI - Distorted Support Indication PI - Possible Indication N/A - Not Appropriate Dist. - Data distorted by tube removal artifact such that a meaningful measurement was not possible SG-SGDA-03-12 Page 14

Section 3.0 SECTIONING PLANS Figures 3-1 through 3-5 show how relevant pieces from tube R12C45 were sectioned. The O orientation and the top/bottom direction were maintained on each subsection by a small white paint mark.

Page 15 SG-SGDA-03-12 Page 15

30%3/4 12 u

ei 7%

Figure 3-1. Sectioning Diagram for Piece 2.

Page 16 SG-SGDA-03-12 Page 16

333/4 TSP# 1 TSP#1 Region 10 I'^1;l ) Pc.3B2B2 Leak Test Burst Test v jX \ ~~to ExanineI ost-Burst . " \ ~~Axial Cracks Visual+Photc ' M2534 10 5 3/8 Figure 3-2. Sectioning Diagram for Piece 3.

CO5 P age 17 SG-SGDA-03-12 SG-SGDA-03-12 P;?age 17

-+0.3

-4 8 /

ct 2~~~~~~~~~-.

29 /s I 360° TSP#2 TSP#2

~TSP#2 Region ei LSEX r~~~~~~~~~~~~~~~~~~~C.411$ZA P.4 S2 Pc.41B2B of Burst Opening Transverse Section Leak Screen to Examine Burst Test _Axial Cracks

lost-Burst M2530 Visual+Photao 10 Freespan 17 346 urst Test Pst-Burst Visual+Photo \

Figure 3-3. Sectioning Diagram for Piece 4.

CQ2 Page 18 SG-SGDA-03-12 Page 18

IVisual+Photo ;i 10 25 Fmspan 11 /8 Fi4 mIq g.ur eSect i o ni n g Di a gr a m f o F3i-4 c 5 As 3i Page 19 SG-SGDA-03-12 Page 19

!,k, 55 't, V; 'I I" ;(1 180° 2700 360° Pc.5lB2Al 32 LAJ . / and SE Axial Cracks of Bur BNarBurst Opening TSP#3 r531 10

_TWO#Region Leak Screen Burst Test Post-Burst Visual+Phota 12FuD 7

Figure 3-5. Sectioning Diagram for Piece 5.

Page 20 SG-SGDA-03-12 SG-SGDA-03-12 Page 20

Section 4.0 LEAK RATE AND BURST TESTING 4.1 Introduction The primary purpose of the leak and burst testing was to provide information to support Generic Letter 95-05 (Reference 1) requirements. Also of importance was determining if degraded tube sections exceeded the US Nuclear Regulatory Commission Regulatory Guide 1.121 (Reference

6) requirements on burst strength. The most limiting requirement is that the tube must sustain three times normal operating pressure differential (3NOP) without burst. 3NOP is approximately 4142 psi for Sequoyah-2 (Reference 7) at temperature, or 4544 psi for room temperature testing (9.7% correction factor - Reference 8). The less limiting requirement of 1.4 times steam line break (SLB) pressure is also of interest. For Sequoyah-2, 1.4 x SLB is 3584 psi at temperature (Reference 7), or 3932 psi for room temperature testing. Lubricated foil was used during the Sequoyah-2 burst test; Reference 9 demonstrated that an additional correction factor was not needed for lubricated foil.

The details of how the leak and burst test results support GL 95-05 are not provided in this report.

The TTS region was not leak tested, since it did not have a field NDE indication. The TSP2 and TSP3 regions were only screened for leakage, in accordance with the Reference 10 request and the Reference 7 and Reference 11 responses. The screening test consisted of pressurizing the inside of the test specimens using 400 psig helium followed by pressurization to MSLB pressure at room temperature. Since neither TSP2 or TSP3 leaked during any part of the screening tests, they were not subjected to at temperature leak tests. TSP1 was subjected to the helium leak test and leakage was discovered. TSP1 (section 3B) was consequently subjected to leak tests at an elevated temperature. Leak testing was performed at normal operating pressure (NOP), at steam line break (SLB), and at intermediate pressures. Burst testing was performed on all three TSP regions, the TTS section and three freespan sections without NDE indications (sections 2B, 4-IA and SA1). Burst testing was performed at room temperature.

Page 21 SG-SGDA-03-12 Page 21

4.2 Test Methods The leak test was performed without fixtures that simulate the constraints of TSP intersections.

The ends of the tube were sealed with Swagelok fittings with connectors that allowed simulated primary water to flow in and out of the sample. Primary side conditions of the tube sample were obtained by connecting the tube sample to a primary side autoclave (AC1) using insulated pressure tubing. The secondary side was simulated by placing the tube sample into a second autoclave (AC2). The pressure of AC2 was adjusted to obtain the required pressure differential between the primary and secondary side. Any water vapor in excess of the AC2 pressure was condensed. The condensed water was measured to obtain the primary side leak rate.

Leak test conditions for the tubes ranged from Normal Operating Conditions (NOC) to Steam Line Break (SLB) conditions. For the NOC tests, the primary side pressure and temperature were nominally 2235 psi and 61 1F, respectively. The NOC secondary side temperature and pressure, provided by AC2, were nominally 610°F and 854 psi, respectively, producing a target pressure differential of 1381 psi. At SLB conditions, the AC2 pressure was dropped to produce a nominal differential pressure of 2560 psi. Actual test temperatures for section 3B were significantly different from nominal conditions due to the presence of a relatively large leak.

Room temperature burst tests were performed using a system separate from the leak test system.

The rate of pressurization was 200 psi/second or less. The internal pressure of the specimen was recorded digitally through a data acquisition system.

TSP2 (section 4-1B), TSP3 (section 5-lB), TTS (section B) and three freespan sections (sections 2B, 4-lA and SAl) showed no evidence that they would leak during burst testing.

These specimens were tested without restraints, bladders or foils. These specimens were pressurized to failure without intermediate hold points.

The other burst test specimen, section 3B (TSPI), had shown significant leakage during leak testing. To complete a valid burst test, it was necessary to cover the source of the leakage with a bladder and lubricated foil. This specimen was semi-restrained by a simulated support system (that included a tubesheet and support plate simulation) designed to mock the conditions in the SG-SGDA-03-12 Page 22

Sequoyah-2 steam generators under accident conditions. The centerline of the TSP1 region on section 3B was positioned 2 inches above the centerline of the support plate simulation. The specimen was pressurized through a fitting that connected the top of the specimen with the pressurization equipment.

Following the completion of burst testing, the burst areas were visually characterized and photographed. Photographs were taken and sketches were made of the full 3600 circumference of tube to characterize other shallow OD patches not part of burst crack. The diameter of the tubing near each burst opening was also recorded.

4.3 Leak Test Results Table 4-1 presents a summary of the leak test results from TSP1. Figure 4-1 presents a plot of the leak rates as a function of average pressure differential. Figure 4-1 shows that the leak rate through the crack was an exponential function of the pressure differential. This behavior is due to a change in the orifice size.

Figure 4-2 presents plots of the pressures and temperatures that were measured during the tests and in between tests. Of particular interest is the temperature and pressure on the secondary side.

Figure 4-3 presents a plot of the secondary side temperatures and pressures alongside the saturated vapor line. Figure 4-3 shows that the first nine tests were conducted to the right of the saturation line. Tests 10 and 11 were conducted on the saturated vapor curve and thus condensation occurred within the secondary side autoclave; there is a possibility that some of the leakage was not measured from these two tests only. However, the secondary side autoclave was designed with its exit at the bottom of the autoclave, thus causing any condensation to exit the autoclave so that it can be measured. Also, test 10 was repeated by test 11, suggesting that a steady state condition had been reached. The test 10 and 11 leak measurements are therefore considered accurate.

A leak rate of less than 0.0012 gpm at NOC pressure and 0.1666 gpm at SLB pressure was established for this tube.

Page 23 SG-SGDA-03-12 SG-SGD A-03-12 Page 23

4.4 Burst Test Results The burst test results are shown in Table 4-2.

Section B (TTS)

The section with the TTS region burst at 11,453 psig. This burst pressure is only 300 psi less than that of the undegraded freespan section 2B. This burst was well above 3NOP. An artifact of the tube pulling operation may have influenced this burst pressure. In this particular case, the burst did not occur at the crack with the deepest corrosion (located roughly at the 680 orientation).

The burst opening was centered at the TTS and was an axial fishmouth opening. The burst opening was located at the 2600 orientation. Corrosion was evident on the burst opening.

Numerous short secondary cracks were noted around the circumference of the tube at the TTS elevation. These were oriented mostly in the axial direction but there was some circumferential element that opened during the burst test. Corrosion was not noted outside of the TTS region.

Section 3B (TSP1)

The section containing TSP1 burst at 5391 psig. This was the lowest burst pressure observed from the pulled Sequoyah-2 tubing. This sample was burst tested under semi-restrained conditions and utilized foil and a bladder to allow for a valid burst. The burst occurred in the center of the foil.

The 5391 psig burst pressure was above the temperature corrected 1.4 x SLB pressure (3932 psig) and the temperature corrected 3NOP pressure (4544 psig). This pressure exceeds all GL 95-05 (Reference 1) requirements. Since this support plate intersection had the largest eddy current indication, it can be inferred that the corrosion in the Sequoyah-2 generators does not present an integrity concern.

The burst opening was centered on the centerline of the TSP1 region. The burst opening occurred at the 2300 orientation and was an axial fishmouth opening with a significant secondary Page 24 SG-SGDA-03-12 Page 24

opening attached to the main opening. This closely coincides with observed reddish deposits noted in Figure 3-3. It also occurred within 900 of the thinnest part of the tube wall. Corrosion was evident on the burst face and numerous secondary cracks were observed. However, cracking was not observed outside of the TSPl region.

Section 4-lB (TSP2)

The section with the TSP2 region burst at 6579 psig. This burst pressure is less than the undegraded freespan sections. However, this burst was well above 3NOP. The burst opening was centered on the centerline of the TSP2 region and was an axial fishmouth opening. The burst opening was located at the 15° orientation.

Corrosion was evident on the burst face and numerous secondary cracks were observed.

However, cracking was not observed outside of the TSP2 region.

Section 5-lB (TSP3)

The section with the TSP3 region burst at 8237 psig. This burst pressure is less than the undegraded freespan sections. However, this burst was well above 3NOP. The burst opening was centered on the centerline of the TSP3 region and was an axial fishmouth opening. The burst opening was located at the 1300 orientation.

Corrosion was evident on the burst face and numerous secondary cracks were observed.

However, cracking was not observed outside of the TSP3 region.

Sections 2B, 4-IA and SAl (Freespan)

Three freespan burst tests were conducted. All were within 82 psi of each other; the lowest burst pressure was 11,743 psig. Corrosion was not observed on any of the burst test specimens from freespan sections. All freespan bursts were axial fishmouth openings.

Page 25 SG-SGDA-03-12 Page 25

4.5 Post-Burst Observations Table 4-2 presents a summary of the post-burst dimensions.

Section B (TTS)

Figure 4-4 presents a drawing that summarizes some of the post-burst visual observations of the TTS vicinity. Figures 4-5a through 4-Se present photographs of the burst area. The figures show an axial burst opening. The burst was centered on the TTS. The burst opening was mainly composed of non-corroded metal; only the center 0.11 inch had evidence of corrosion.

There was a band of axial cracks and some cellular corrosion that extended around the circumference of the tube, centered on the TTS, that was 0.2-0.3 inch wide. This corrosion appeared to be very shallow between 3150 and 450 (including 00). There was no corrosion noted outside of this narrow band at the TTS.

Section 3B (TSP1)

Figure 4-6 presents a drawing that summarizes some of the post-burst visual observations of the TSP1 region. Figures 4-7a through 4-7e present photographs of the TSP1 region. The figures show a burst opening that was mostly axial; the opening was composed of a main crack and a significant secondary crack, separated by a "sliver" of metal that remained partially attached to the left side of the burst opening. It was evident that a portion of the burst opening crack had been throughwall. The burst occurred close to where reddish deposits had been noted (Figure 3-3); it is unlikely that an external heat source had converted magnetite to hematite as was the case at the top of the tubesheet. The burst opening occurred entirely within the bounds of the TSP region. There was cracking above and below the burst opening (which was captured in the SEM depth profile measurements); however this cracking was also bound by the TSP region. No corrosion was observed outside the TSP region.

There was some significant secondary cracking on both sides of the burst opening. These secondary cracks that were opened by the burst test were both axial and circumferential and had SG-SGDA-03-12 Page 26

the appearance of cellular corrosion mixed with some IGA. The axial component of the secondary corrosion was documented by metallography.

Section 4-1B (TSP2)

Figure 4-8 presents a drawing that summarizes some of the post-burst visual observations of the TSP2 region. Figures 4-9a through 4-9e present photographs of the TSP2 region. The figures show a burst opening that was mostly axial, but was slightly out of parallel with the axis of the tube. The top of the burst opening occurred entirely within the bounds of the TSP region; however there was some ductile tearing that extended just below the bottom of the TSP region.

This ductile tearing was a result of the burst test but was not a result of corrosion; there was no corrosion observed outside the TSP region.

Secondary cracks were found on both sides of the burst opening. These secondary cracks were almost entirely axial; however some minor cellular corrosion was observed. No thick deposits remained within the TSP2 region after the burst test.

Section 5-lB (TSP3)

Figure 4-10 presents a drawing that summarizes some of the post-burst visual observations of the TSP3 region. Figures 4-1 la through 4-lie present photographs of the TSP3 region. The figures show a burst opening that was axial and was centered on the TSP region. The burst opening itself extended above and below the TSP region; however corrosion on the burst opening was bound by the TSP region. All of the secondary corrosion was also found within the bounds of the TSP region.

There was secondary corrosion found on most of the circumference of the TSP3 region, although about a fourth of the circumference was obscured by the presence of thick gray deposits that remained on the tube even after the swelling of the tube from the burst test. These secondary cracks were mostly axial; there was a lot of shallow cellular corrosion however.

Page 27 SG-SGDA SG-SGDA-03-1212 Page 27

Two axial cracks were found entirely within two installation scratches. These scratch cracks were observed to be "medium deep". These scratch cracks were also bound by the bottom of the TSP region, but did not extend the full length of the scratch that was within the TSP3 region.

Sections 2B, 4-IA and 5A1 (Freespan)

Figures 4-12a through 4-12e present photographs of the burst area for section 2B. Figures 4-13a through 4-13e present photographs of the burst area for section 4-lA. Figures 4-14a through 4-14e present photographs of the burst area for section 5A1. These freespan bursts all had similar results. In each of the three tests the figures show that the tube swelling has occurred evenly around the circumference of the tube, that each had an axial burst opening, and in no case was corrosion of any kind observed on a freespan burst test sample.

Page 28 SG-SGDA-03-12 Page 28

TABLE 4-1 LEAK RATE

SUMMARY

FOR TSP1 Prssure (psi) - Temperature F) LaRte, Test Delta P Primary Secondary Pnmary Secondary (gal/rnin)

Min 1434 2298 864 598 605 1 Max 1457 2323 867 600 611 0.0012 Avg 1443 2309 865 599 608 Min 1483 2348 862 596 606 2 Max 1511 2374 865 601 610 0.0020 Avg 1504 2368 864 598 609 Min 1428 2293 864 593 607 3 Max 1489 2354 866 595 611 0.0020 Avg 1460 2325 865 595 609 Min 1681 2153 466 571 533 4 Max 1765 2231 472 581 554 0.0132 Avg 1706 2175 469 573 540 Min 1695 2167 472 576 519 5 Max 1707 2179 472 578 527 0.0125 Avg 1704 2176 472 577 523 Min 2108 2139 31 576 406 6 Max 2158 2193 35 581 470 0.0405 Avg 2124 2156 32 579 429 Min 2125 2155 29 582 353 7 Max 2126 2156 30 584 372 0.0403 Ag_ 2125 2155 30 583 363 Min 2129 2157 28 586 325 8 Max 2131 2159 29 590 334 0.0396 Avg 2130 2159 29 588 329 Min 2350 2413 62 592 328 9 Max 2359 2422 63 598 346 0.0691 Avg 2356 2418 62 596 338 Min 2597 2705 107 603 346 10 Max 2603 2710 110 605 347 0.1639 Avg 2600 2708 108 604 346 Min 2584 2694 106 603 346 11 Max 2591 2698 111 605 347 0.1666 A

Ag_ 2588 2696 109 604 346 Page 29 SG-SGDA 122 SG-SGDA-03-1 Page 29

TABLE 4-2 BURST TEST RESULTS Section lB 3B 4-lB 5-lB 2B 4-IA 5A1 Location TTS TSP1 TSP2 TSP3 Freespan Freespan Freespan Burst Pressure (psig) 11,453 5391 6579 8237 11,743 11,809 11,825 Burst Angular Position 2600 2300 150 1300 2000 150 1150 Burst Length (inch) 1.575 0.600 0.638 0.875 1.938 2.007 2.007 Burst Width (inch) 0.425 0.123 0.138 0.238 0.391 0.459 0.391 Pre-Burst Wall Thickness, 00 (inch) 0.0560 0.0548 0.051 0.051 0.0563 0.050 0.0543 Pre-Burst Wall Thickness, 900 (inch) 0.0546 0.0580 0.051 0.051 0.0541 0.051 0.0480 Pre-Burst Wall Thickness, 180° (inch) 0.0484 0.0526 - - 0.0484 - 0.0504 Pre-Burst Wall Thickness, 2700 (inch) 0.0511 0.0503 - - 0.0504 - 0.0563 Post-Burst Max. Diameter (inch) 1.135 0.975 0.950 1.000 1.184 1.190 1.190 Post-Burst, 900 from Max. Diameter 1.010 0.950 0.875 0.875 0.875 1.020 1.007 (inch)

• Note - this burst pressure was influenced by the TIG weld. See the discussion in the Metallography section.

Page 30 SG-SGDA-03-12 Page 30

0.18 -_

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Figure 4-1. Leak Rate as a Function of Pressure Differential for TSP1 (Section 3B).

Page 31 SG-SGDA-03-12 Page 31

1 2 3 4 678 9 1011 3000

= 1500 1000 500 0

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650 600 550 L

2 500 I450 400 350 300 250 0 1000 2000 3000 4000 5000 6000 7000 8000 Tm (scmis)

Figure 4-2. Pressure and Temperature Plots for TSP1.

SG-SGDA-03-12 Page 32

1200 1000 - Saturation (urv

• Tests

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250 300 1 l 350 1 1 400 1 1 450 500 550 600 650 Secondary Side Temperature (F)

Figure 4-3. Secondary Side Autoclave Temperatures and Pressures.

SG-SGDA-03-12 Page 33 SG-SGDAX03-12 Page 33

+0.75"

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CD (O SG-SGDA-03-12 Page 34

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C oIT SG-SGDA-03-12 Page 40

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SG-SGDA03-12 Page 46

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SG-SGDA-03-12 Page 52

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Section 5.0 FRACTOGRAPHY 5.1 Procedure Following the completion of burst testing, the right face of the burst openings from all three TSP regions were sectioned, to characterize the corrosion by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometry (EDS), and to obtain depth profiles of the corrosion by SEM. A depth profile was also obtained from a secondary crack from TSP 1.

A longitudinal section was removed from each tube and processed to remove any particulates from the fracture surfaces to minimize charging during the SEM examination. Operation of the SEM/EDS followed the manufacturer's instruction. ASTM has not published procedures for fractography examinations. However, surfaces examined by SEM in accordance with accepted scientific principles and EPRI guidelines can be compared with fractographs presented in various fractography textbooks, such as "Metals Handbook, Volume 12, Fractography", 9 th Edition, American Society of Metals, 1985.

Fractographs were taken of the entire fracture surface of each burst opening that had corrosion at approximately 77X. These fractographs were then aligned end to end to complete a photomontage of each crack surface. The depth of degradation was measured at 1/2 inch increments on each montage using the same steel ruler. These measurements were then divided by the magnification to obtain the defect depth, divided by 0.050 inch (the nominal tube wall thickness) to obtain the fraction throughwall, and then multiplied by 100 to obtain the percent throughwall.

Page 73 SG-SGDA-03-12 Page 73

5.2 Results Burst Opening Depth Profiles Table 5-1 provides a summary of the depth profiles. Tables 5-2 through 5-5 provide the measurements from the depth profile and include the location and size of ligaments of uncorroded metal. Figures 5-1 through 5-4 show plots of the depth profile data, including the location and size of the ligaments.

The TSP1 crack was 100%TW. The secondary crack extended from about 0.275 to 0.55 inches above the bottom of the TSP. This secondary crack was also 100%TW. The longest microcrack (the distance between ligaments) was 0.24 inch.

The TSP2 and TSP3 crack profiles were similar. These depth profiles were relatively uniform and both of these crack extended the full width of the support plate region; however (as was noted during the visual examination) the cracks did not extend outside of the TSP region in any case. The longest microcrack from either of these two support plate regions was 0.21 inch. For TSP3 a 69%TW secondary crack was identified 40 mils to the left of the burst opening by metallography.

TSPl Burst Opening Fractography Figure 5-5 presents a fractograph of a part-throughwall portion of the main crack from the TSP1 region. The delineation between the corrosion near the OD surface and the ductile tearing near the ID surface is easily seen. Figure 5-5 shows that this corrosion was OD initiated. Figures 5-6 and 5-7 show closer views of the TSP1 crack surface near the crack mouth. There is a considerable amount of foreign debris on the crack surface. This is typical when a bladder/foil with lubricant is required to perform a burst test. Besides the debris, the grain facets are semi-well defined. The somewhat rounded appearance of the grain facets suggests a thick surface oxide or deposit. The rock candy appearance of the crack surface is indicative of intergranular corrosion.

Page 74 SG-SGDA-03-12 Page 74

Figures 5-8 and 5-9 show closer views of the main crack near the crack tip. There is considerably less debris near the tip and the grain facets are better defined than at the mouth. Figure 5-8 also shows some debris on the ductile tearing portion of the burst opening, thus suggesting that the debris was introduced to the crack surface after the burst.

An examination was conducted after an attempt was made to clean the surface of the left burst face with deionized water and acetone. The surface was then lightly carbon coated using a sputtering technique to reduce charging of non-conductive debris. Figure 5-10 shows a part-throughwall area after cleaning. Figures 5-11 and 5-12 show close-ups of the mouth of the crack. Most of the debris was removed, and in comparison to Figure 5-7, the grain facets are better defined. This suggests that much of the deposit/oxide at the mouth is easily removed and thus much of it may have been deposited on the crack surface, such as might happen with the use of a bladder/foil with lubricant during a burst test, rather than grown on the crack surface during operation of the generator.

TSP2 Burst Opening Fractography Figure 5-13 presents a fractograph of a part-throughwall portion of burst opening crack from the TSP2 region. The delineation between the corrosion near the OD surface and the ductile tearing near the ID surface is easily seen. Figure 5-13 shows that this corrosion was OD initiated. Figures 5-14 and 5-15 show closer views of the TSP2 crack surface near the crack mouth. The rock candy appearance of the crack surface is indicative of intergranular corrosion. The grain facets are semi-well defined. The somewhat rounded appearance of the grain facets suggests a thick surface oxide or deposit.

Figures 5-16 and 5-17 show closer views of the main crack near the crack tip. The crack tip is similar in appearance to the crack mouth.

SG-SGDA-03-12 Page 75

TSP3 Burst Opening Fractography Figure 5-18 presents a fractograph of a part-throughwall portion of burst opening crack from the TSP3 region. The delineation between the corrosion near the OD surface and the ductile tearing near the ID surface is easily seen. Figure 5-18 shows that this corrosion was OD initiated. Figures 5-19 and 5-20 show closer views of the TSP3 crack surface near the crack mouth. The rock candy appearance of the crack surface is indicative of intergranular corrosion. In contrast to the surface of the TSP2 region crack, the grain facets from TSP3 are well defined, suggesting a thinner oxide.

Figures 5-21 and 5-22 show closer views of the main crack near the crack tip. The crack tip is similar in appearance to the crack mouth.

Page 76 SG-SGDA-03-12 Page 76

TABLE 5-1

SUMMARY

OF DEPTHS AND EXTENT OF CRACKING FOR THE BURST OPENINGS Mathematical Crack Maximum Average Total.

Depth 'Depth Length Numrber of Support (%TW) (%TW) (in) Microcracks Note TSP1 (Left Side) 100.0 75.4 0.625 6 (a)

TSP1 (Right Side) 100.0 74.0 0.619 6 (b)

TSP2 71.4 52.2 0.750 11 TSP3 62.6 51.2 0.743 11 (c)

Note (a) - Includes all of the secondary crack plus part of the main crack Note (b) - Includes only the main crack Note (c) - Deeper cracks were identified by metallography than the maximum depth by SEM Page 77 SG-SGDA 12 SG-SGDA-03-12 Page 77

TABLE 5-2 TUBE R12C45 TSP1 (SECONDARY AND MAIN CRACK) BURST MACROCRACK

- DEPTH PROFILE From Ductile From Ductile From 'Ductile

TSP Corrosion Ligament *TSP - Corrosion Ligament TSP Corrosion Ligament Bottom Depth Width Bottom Depth -Width Bottom Depth Width' (inch) (%TW) (inch) (inch) (%TW) (inch) (inch) (%TW) (inch) 0.018 0 0.262 76 0.505 100 0.025 0 0.268 78 0.512 100 0.032 0 0.275 74 0.518 100 0.038 0 0.282 66 0.525 100 L3 / 0.025 0.045 0 0.288 22 L2 / 0.036 0.532 100 0.051 0 0.295 39 0.538 100 0.058 0 0.301 53 0.545 100 0.064 0 0.308 63 0.551 100 0.0675 0 0.314 70 0.558 100 0.071 25 0.321 74 0.564 100 0.078 22 LI / 0.005 0.328 76 0.571 97 0.084 17 L5 / 0.018 0.334 82 0.578 95 0.091 32 0.341 84 0.584 92 0.097 45 0.347 88 0.591 92 0.104 46 0.354 91 0.597 92 0.111 50 0.361 95 0.604 90 L4/ 0.016 0.117 53 0.367 100 0.611 88 0.124 57 0.374 100 0.617 84 0.130 58 0.380 100 0.624 82 0.137 58 0.387 100 0.630 78 0.143 58 0.393 100 0.637 70 0.150 58 0.400 100 0.643 72 0.157 57 0.407 100 0.650 71 0.163 58 0.413 100 0.657 62 0.170 62 0.420 100 0.663 58 0.176 63 0.426 100 0.670 55 0.183 63 0.433 100 0.676 51 0.189 62 0.439 100 0.683 38 0.196 61 0.446 100 0.689 24 0.203 67 0.453 100 0.6925 0 0.209 67 0.459 100 0.696 0 0.216 69 0.466 100 0.703 0 0.222 68 0.472 100 0.709 0 0.229 67 0.479 100 0.716 0 0.236 69 0.486 100 0.722 0 0.242 67 0.492 100 0.729 0 0.249 70 0.499 100 I 0.736 0 0.255 72 0.742 0 0.749 0 Page 78 SG-SGDA-03-12 Page 78

TABLE 5-3 TUBE R12C45 TSP1 (MAIN CRACK) BURST MACROCRACK DEPTH PROFILE From - Ductile From Ductile 'From Ductile TSP Corrosion Ligament TSP Corrosion Ligament TSP - Corrosion Ligament Bottom Depth Width Bottom Depth Width Bottom Depth Width (inch) (%TW) (inch) (inch) (%TW) (inch) *(inch) (%/oTW) (inch) 0.000 0 0.252 75 0.503 100 0.006 0 0.258 75 0.510 100 0.013 0 0.265 77 0.516 100 0.019 0 0.271 79 0.523 100 0.026 0 0.277 80 0.529 100 0.032 0 0.284 80 0.535 100 0.039 0 0.290 88 0.542 100 0.045 0 0.297 100 0.548 100 0.052 0 0.303 100 0.555 100 0.058 0 0.310 100 0.561 100 0.065 0 0.316 100 0.568 100 0.067 0 0.323 100 0.574 94 0.071 25 0.329 100 L2 /0.023 0.581 92 0.077 15 0.335 100 0.587 93 0.084 0 L4 /0.020 0.342 100 0.594 90 0.090 41 0.348 100 0.600 86 0.097 0 0.355 100 0.606 86 Ll /0.018 0.103 43 0.361 100 0.613 85 0.110 45 0.368 100 0.619 80 0.116 48 L3 /0.007 0.374 100 0.626 77 0.123 61 0.381 100 0.632 72 0.129 63 0.387 98 0.639 62 0.135 62 0.394 90 L5 /0.004 0.645 63 0.142 59 0.400 88 0.652 63 0.148 62 0.406 82 0.658 58 0.155 57 0.413 75 0.665 52 0.161 64 0.419 65 0.671 48 0.168 64 0.426 62 0.677 37 0.174 64 0.432 59 0.684 21 0.181 63 0.439 59 0.686 0 0.187 65 0.445 59 0.690 0 0.194 64 0.452 59 0.697 0 0.200 65 0.458 58 0.703 0 0.206 67 0.465 72 0.710 0 0.213 66 0.471 73 0.716 0 0.219 67 0.477 75 0.723 0 0.226 69 0.484 83 0.729 0 0.232 70 0.490 93 0.735 0 0.239 70 0.497 100 0.742 0 0.245 73 0.748 0 0.755 0 Page 79 SG-SGDA-03-12 Page 79

TABLE 5-4 TUBE R12C45 TSP2 BURST MACROCRACK DEPTH PROFILE From Ductile From Ductile From Ductile TSP Corrosion Ligament TSPl0 Corrosion Ligament TSP- Corrosion Ligament Bottom Depth Width Bottom. Depth, Width Bottom Depth Width

(inch) (%TW) (inch) (inch) (%TW) (inch) (inch) -( oTW) .(inch)

-0.003 0 0.256 64 0.515 65 0 0 0.262 65 0.521 65 0.003 21 0.268 64 0.527 65 0.009 29 0.275 62 0.534 63 0.015 31 0.281 60 0.540 61 0.022 33 0.287 61 0.546 61 0.028 31 0.293 61 0.552 57 0.034 29 L6 0.011 0.299 60 0.558 59 0.040 32 0.305 60 0.564 56 0.046 38 0.312 57 0.571 55 0.052 41 0.318 56 0.577 48 0.059 45 0.324 52 0.583 44 L3 /0.017 0.065 47 0.330 52 0.589 54 0.071 49 0.336 55 0.595 54 0.077 49 0.342 56 0.601 58 0.083 48 0.349 53 L9 /0.027 0.608 60 0.089 50 0.355 39 0.614 58 0.096 51 0.361 55 0.620 58 0.102 50 0.367 49 0.626 51 0.108 52 0.373 57 0.632 54 0.114 55 0.379 61 0.638 52 0.120 53 L5 /0.024 0.386 61 0.645 50 0.126 52 0.392 67 0.651 48 L2 /0.014 0.133 50 0.398 66 0.657 49 0.139 47 0.404 66 0.663 43 0.145 47 0.410 63 0.669 41 0.151 45 0.416 59 0.675 39 L10/ 0.020 0.157 55 0.423 57 0.682 46 0.163 56 L7 /0.017 0.429 59 0.688 45 0.170 56 0.435 60 0.694 43 0.176 54 0.441 62 0.700 42 0.182 50 0.447 68 0.706 38 0.188 52 0.453 71 0.713 35 0.194 53 0.460 70 L4 /0.017 0.719 32 LI /0.013 0.200 51 0.466 65 0.725 37 0.207 52 0.472 65 0.73 1 37 0.213 57 0.478 66 0.737 35 0.219 59 0.484 68 0.743 30 0.225 61 0.490 67 0.7495 21 0.231 56 0.497 65 0.7500 0 0.238 61 L8 /0.017 0.503 63 0.756 0 0.244 60 0.509 62 0.762 0 0.250 61 Page 80 SG-SGDA-03-12 Page 80

TABLE 5-5 TUBE R12C45 TSP3 BURST MACROCRACK DEPTH PROFILE From Ductile From - Ductile -From 'Ductile TSP Corrosion Ligament TSP Corrosion Ligament TSP Corrosion Ligament Bottom Depth Width Bottom Depth Width - Bottom Depth Width (inch) (%TW) (inch) (inch) (%TW) (inch) (inch) (%TW) -:(inch) 0.000 0 0.261 58 0.515 62 0.007 0 0.267 61 0.521 60 0.013 11 0.274 59 0.528 62 0.020 21 0.280 57 0.534 62 0.026 21 0.287 57 0.541 56 0.033 25 0.293 56 0.547 57 0.039 29 L6 1 0.007 0.300 56 0.554 56 0.046 42 0.306 56 0.560 53 0.052 42 0.313 58 0.567 53 0.059 42 0.319 57 0.573 53 0.065 48 0.326 60 0.580 55 0.072 50 0.332 60 0.586 54 L8 / 0.007 0.078 48 0.339 57 0.593 53 L9 / 0.008 0.085 49 0.345 56 L3 0.012 0.599 58 0.091 49 0.352 53 0.606 54 0.098 50 0.358 57 0.612 58 0.104 45 L5 0.013 0.365 57 0.619 58 0.111 42 0.371 54 0.625 59 0.117 42 0.378 52 0.632 58 0.124 42 0.384 55 0.638 58 0.130 31 L7/0.019 0.391 54 L2 /0.010 0.645 58 0.137 34 L4 0.007 0.397 47 0.651 58 0.143 45 0.404 49 0.658 56 0.150 50 0.410 51 0.664 53 0.156 54 0.417 57 0.671 54 0.163 56 0.423 58 0.677 53 0.169 58 0.430 56 0.684 54 0.176 62 0.436 55 0.690 54 0.182 63 0.443 55 0.697 53 0.189 58 0.449 54 0.703 50 L1O/ 0.024 0.195 53 0.456 53 0.710 47 L1 / 0.007 0.202 59 0.462 54 0.716 45 0.208 57 0.469 55 0.723 44 0.215 55 0.475 57 0.729 40 0.221 55 0.482 57 0.736 32 0.228 55 0.488 59 0.743 25 0.234 60 0.495 60 0.749 9 0.241 58 0.502 61 0.750 0 0.248 58 0.508 61 0.756 0 0.254 58 0.762 0 Page 81 SG-SGDA-03-12 Page 81

100 - I 90 - - Depth ProEie U Ligarrnts 70-60-

' 50 /

~40-30-20 _ _ .

10 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Axial Distance Above Support Plate Bottom (in)

Figure 5-1. TSPI Left Burst Opening Macrocrack Depth Profile.

Page 82 SG-SGDA-03-12 Page 82

100

- {-Depth Profib I 90 -@ Mgan\tI \

80 70 60

. 50 40 30 II 20 10 11 0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Axial Distance Above Suport Plate Bottom (in)

Figure 5-2. TSPI Right Burst Opening Macrocrack Depth Profile.

Page 83 SG-SGDA-03-12 Page 83

100 90 - - Depth Profie

• Ligaments 80 70

~60-

50 40-30 0'

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Axial Distance Above Support Plate Bottom (in)

Figure 5-3. TSP2 Burst Opening Macrocrack Depth Profile.

SG-SGDA-03-12 Page 84

100

- Depth Profile ______ - 1-90 La 80 70 - ~~-

R 60

'- 50

40 30  :~~ I 20 10 T C XIT I T 0

I1 E 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Axial Distance Above Support Plate Botton (in)

Figure 5-4. TSP3 Burst Opening Macrocrack Depth Profile.

Page 85 SG-SGDA-03-12 Page 85

-t I

Iw

.9I

'f I.

q ,,JL 2^'2~ -  :: --

Figure 5-5. TSP1 Burst Opening Fractograph Showing Part Throughwall Corrosion.

Page 86 SG-SGDA-03-12 Page 86

Figure 5-6. TSP1 Burst Opening Fractograph of Crack Mouth.

SG-SGDA-03-12 Page 87

Figure 5-7. Close-Up of TSPI Crack Mouth.

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Figure 5-8. TSP1 Burst Opening Fractograph of Crack Tip.

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Figure 5-9. Close-Up of TSP1 Crack Tip.

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Figure 5-10. TSP1 Burst Opening Fractograph of Part Throughwall Corrosion after Cleaning.

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Figure 5-11. TSP1 Burst Opening Fractograph of Crack Mouth after Cleaning.

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9I 4 :s N, " -7; 1-6, W Figure 5-12. Close-Up of TSP1 Crack Mouth after Cleaning.

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Figure 5-13. TSP2 Burst Opening Fractograph Showing Part Throughwall Corrosion.

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Figure 5-14. TSP2 Burst Opening Fractograph of Crack Mouth.

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Figure 5-15. Close-Up of TSP2 Crack Mouth.

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Figure 5-16. TSP2 Burst Opening Fractograph of Crack Tip.

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Figure 5-17. Close-Up of TSP2 Crack Tip.

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Figure 5-18. TSP3 Burst Opening Fractograph Showing Part Throughwall Corrosion.

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Figure 5-19. TSP3 Burst Opening Fractograph of Crack Mouth.

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Figure 5-20. Close-Up of TSP3 Crack Mouth.

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Figure 5-21. TSP3 Burst Opening Fractograph of Crack Tip.

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Figure 5-22. Close-Up of TSP3 Crack Tip.

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Section 6.0 METALLOGRAPHY OF DEFECTS 6.1 Procedure Light optical metallography (LOM) was conducted using transverse samples removed from all three TSP regions. The sample locations are more clearly defined in the sectioning diagrams section (refer to Section 3.0).

The transverse sections were selected to document the mode of cracking (IGA or IGSCC) and to provide depth of degradation information. In addition, the sample from the TTS region was selected to show how multiple OD initiated defects were positioned around the circumference.

Also, the sample selected from TSP3 was to characterize the cracks found within installation scratches that were observed after the burst test.

The transverse samples were mounted in the direction shown by the large arrows in the Section 3.0 sectioning diagrams. Each sample was ground with SiC papers, followed by diamond wheels using polishing oil, followed by diamond aerosol sprays, leaving the edge to be examined with a mirror finish. Transverse samples were also examined and photographed in the as-polished condition.

Selected defect areas were then examined and photographed after an electrolytic nital etch. The electrolytic nital etch was chosen to highlight the relationship between the cracks and the grain boundaries.

6.2 Results TSPI Region Axial Cracks The sample from the TSP1 region (mount number M2534) was cut from an area with deep secondary cracks adjacent to the burst opening. No attempt was made to find the deepest secondary crack; this sample was obtained to characterize the cracks in the TSP1 region.

SG-SGDA-03-12 Page 104

Figure 6-1 presents the unetched view of the entire sample. The OD initiated cracks were found only next to the burst opening. Three positions were examined; all three positions were similar.

Figure 6-2 shows the deepest of the cracks that were found on this sample (taken from position 1 after etching). The deepest crack on this sample was 39%TW. Figure 6-2 shows that the cracks were discrete and had no or few branches. The cracks were intergranular with no IGA between cracks. The transverse section will only show the axial component of cracks; however the visual exam showed that circumferentially oriented cracks were made visible by the burst test. It can therefore be concluded that the cracking at the TSP1 region was cellular corrosion and axial IGSCC. IGA was not observed at the TSP1 region.

TSP2 Region Axial Cracks The sample from the TSP2 region (mount number M2530) was cut from an area with secondary cracks adjacent to the burst opening. No attempt was made to find the deepest secondary crack; this sample was obtained to characterize the cracks in the TSP2 region.

Figure 6-3 presents the unetched view of the entire sample. The OD initiated cracks were found only next to the burst opening; however there was shallow IGA at all of the other positions examined. Thirteen positions were examined; positions 1 and 2 had IGA at the OD surface with deeper IGSCC; positions 3-13 was mostly shallow IGA. Figure 6-4 shows the deepest of the cracks that were found on this sample (taken from position 2 after etching). The deepest crack on this sample was 43%TW. Figure 6-4 shows that the IGSCC cracks had no or few branches at the deeper locations; however the region around the cracks were surrounded by shallow (10%TW) IGA.

Figure 6-5 presents one region of deeper IGA (position 9, 20%TW); however most of the IGA on this sample was only 3-4 grains deep. The post-burst visual observations characterized this region as having almost nothing but axial cracks but with minor cellular corrosion. It is likely that the cellular corrosion that was observed visually was actually the shallow IGA. The cracking at the TSP2 region can be characterized as relatively shallow IGA with deeper IGSCC penetrations.

Page 105 SG-SGDA-03-12 Page 105

TSP3 Region Axial Cracks and Scratch Crack The sample from the TSP3 region (mount number M2531) was cut from an area with secondary cracks adjacent to the burst opening. No attempt was made to find the deepest secondary crack; this sample was obtained to characterize the cracks in the TSP3 region. It was also cut in a manner to capture the scratch cracks that were located at the 300 orientation.

Figure 6-6 presents the unetched view of the entire sample. The OD initiated cracks were found at each of the seven positions examined. Figure 6-7 shows the deepest of the cracks that were found on this sample (taken from position 1, after etching). The deepest crack on this sample was 69%TW. This is deeper than the maximum depth measured from the SEM depth profile of the burst opening. Figure 6-7 shows that the IGSCC cracks had no or few branches at the deeper locations; however the region around the cracks were surrounded by shallow (1O%TW) IGA. The post-burst visual observations characterized this region as having some patches of cellular corrosion. It is likely that the cellular corrosion that was observed visually was actually the shallow IGA. The cracking at the TSP3 region can be characterized as relatively shallow IGA with deeper IGSCC penetrations.

Figures 6-8 and 6-9 show the scratch cracks located at positions 6 and 7, respectively. The scratch crack at position 6 is 42%TW, the one at position 7 is 24%TW. Figure 6-10 presents a close-up of the position 6 scratch crack at the OD surface. At the OD surface grains, there is possible evidence of elongated grains; however these are less than a typical (non-elongated, Sequoyah-2 tube R12C45) grain deep. Elongated grains would result from an installation scratch and the cold working of the surface may serve as an initiation site for IGSCC.

SG-SGDA-03-12 Page 106

ll  : . -...

i Figure 6-1. Low Magnification View of TSP1 Transverse Section (Unetched).

Page 107 SG-SGDA-03-12 Page 107

^S-o ".-

Figure 6-2. Deepest Crack on the TSP1 Transverse Section, Position 1 in Figure 6-1 (Nital Etch).

Page 108 SG-SGDA-03-12 Page 108

Figure 6-3. Low Magnification View of TSP2 Transverse Section (Unetched).

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-- 4c 3',.,. .

,g- - .*

4 -

A ur

• Ž p-s A-C 2A2-v frLyZ-

- 'X

'- 4 * -2s--

-, A)"

- I,' - *-'-

Fr -'-A-,-. -

r'- '

L -r - *t%*,,-. r&N.v N Zaf' t

• A r--

- .t-b, b

N-N

-- .4

% 't r-

- a"--'-.

' '%.J Figure 6-4. Deepest Crack on the TSP2 Transverse Section, Position 2 in Figure 6-3 (Nital Etch).

Page 110 SG-SGDA-03-12 Page 110

I o.0 in ri -

-**m***4 i *, **-~ -f _ sJ %

t _,

_- ~ ~ ~

... ~ \.. 5< rr >~^ 7 *; '-

6.

• r ~._.,,,

• 4 - *.t

-)-L - 5 *4 *

• vr*~w szQr0a~

Figure 6-5. Deep IGA on the TSP2 Transverse Section, Position 9 in Figure 6-3 (Nital Etch).

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4q, Figure 6-6. Low Magnification View of TSP3 Transverse Section (Unetched).

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..-.~~~~~~~~~~~~u......

-~~~~~

• 1 A A~~~~~~~~~~~r Figure 6-7. Deepest Crack at TSP3, Position 1 in Figure 6-6 (Nital Etch).

Page 113 SG-SGDA 12 SG-SGDA-03-12 Page 113

I

==

I 4U)25 il

______________- - -t

-N I:

3/4 .-. 1/24.

S r jf'* - -

Figure 6-8. Scratch Crack, Position 6 in Figure 6-6 (Nital Etch).

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Figure 6-9. Scratch Crack, Position 7 in Figure 6-6 (Nital Etch).

Page 115 SG-SGDA-03-12 Page 115

Figure 6-10. Close-Up of Position 6 Scratch Crack (Nital Etch).

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Section 7.0 TENSILE TESTS The mechanical properties (i.e., yield strength, ultimate strength, percent elongation) of R12C45 were determined through two room temperature tensile tests of full cross section tubular specimens. The full cross section tubular specimens were fitted with snug fitting stainless steel plugs (mandrels) machined in accordance with ASTM Standard Method E8. A crosshead speed of 0.1 inch/minute was used.

Both tensile test specimens were from freespan regions. The specific pieces tested were 3C1 and 5A2.

Table 7-1 provides the results of the room temperature tensile tests. Figures 7-1 and 7-2 present the stress-strain curves obtained from the tensile tests. The results in Table 7-1 show that the results for the two tensile tests are nearly the same. As was mentioned previously, the pull forces needed to remove the tube from the generator were quite low and well below the yield strength of the material, thus the tube pulling operation did not influence the tensile test results. These results show a relatively high strength material, but a 58 ksi yield strength is typical for this vintage tubing.

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TABLE 7-1 TENSILE PROPERTIES ISy,,

Tensile Su, Yield Ultimate Gage Strength; Tensile Length Area: 0.2% Offset Strenth Sy+Su Sample ~in; in ksi ksisi 3C1 6.2 0.134451 58.6 110.8 169.4 5A2 5.575 0.13526 58.4 109.5 167.9 Average 58.5 110.2 168.7 SG-SGDA-03-12 Page 118

120000 -

100000 -

1* - -/- 1.-0

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

--. 1- . - . - - ------- ' ks i 80000 -

cn 60000

---

-- 0.2%YS =58.6 ksi .

40000 -

20000 -

I-0-

I 0.00 0.05 0.10 0.15 0.20

. . I ....

0.25 0.30 0.35

. l . 4 0.40

. L .. ..

0.45 I

0.50 0.55 Total Strain (inm)

Figure 7-1. Stress-Strain Curve for Specimen 3C1.

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120000 100000 - . il ..... X,!Xy UTS= 109.5 ksi 80000X 4.

60000*--

-_ .---. I =

0.2%YS 58.4ksi I~I

~ ~ ~~~~~~~~~~~.

_ K~~~-d -.....-....-....-.

0X . ... 1 :n t <~~~~~~~~~~~~~~

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 Total Strain (in/n)

Figure 7-2. Stress-Strain Curve for Specimen 5A2.

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Section 8.0 DISCUSSION / CONCLUSIONS The non-destructive and destructive examinations of Sequoyah-2 steam generator tube R12C45 confirmed the presence of OD initiated degradation within the support plate crevices and at the top of the tubesheet.

The corrosion was limited to the support plate crevices and the crevice formed at the TTS by the tubesheet and sludge on the tubesheet. All three support plate regions had axial intergranular ODSCC. The TSP1 region also had cellular corrosion without any evidence of IGA. The TSP2 and TSP3 regions had relatively shallow IGA in addition to the ODSCC.

The maximum depth of corrosion in TSP1 was 100%TW. The maximum depth of corrosion in TSP2 was 71%TW. The maximum depth of corrosion in TSP3 was 69%TW.

The Sequoyah-2 tube was found to have typical tensile and ultimate strengths. This tube had the typical high strength of most early Westinghouse supplied steam generators (usually 58 ksi or greater yield strength is considered high strength).

Tube Integrity The TTS region, the freespan tubing and the TSP regions all had burst pressures well in excess of the most limiting Reference 6 requirements of three times the normal operating pressure differential.

Leakage was measured from the TSP1 region only. A leak rate of 0.17 gpm was established for SLB conditions. After leak testing had been completed, TSP1 was tested with bobbin, plus-point and pancake coils. The bobbin voltage increased significantly as a result of leak testing. This is after the bobbin voltage increased from the forces needed to pull the tube out of the generator.

The leak rate that was measured in the laboratory is not representative of the leak rate that would have occurred at SLB conditions in the generator; the leak rate is considerably higher as a result of ligaments that were weakened or broken during the tube pull. The TSP1 crack was not truly Page 121 SG-SGDA-03-12 Page 121

axial, but was slanted slightly out of axial towards the circumferential direction. It is likely that the tube pull forces would have damaged some of the ligaments that were present in this crack.

The testing performed on tube R12C45, and the results of the tests, satisfy the Alternative Repair Criteria of Reference 1.

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Section

9.0 REFERENCES

1. "Voltage-Based Repair Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking," United States Regulatory Commission Generic Letter 95-05, August 3, 1995.

2. Westinghouse Electric Quality Management System, Revision 5, October 1, 2002.

3. TVA Contract Work Authorization No. N2002-007, Revision 01, June 14, 2002.

4. "Sequoyah Tube Pull," E-Mail from G.T. Estes to T.P. Magee et al., May 3, 2002.

5. "Steam Generator Tube Sample Identification," Westinghouse Science and Technology Department Procedure MR 0201, Rev 0, June 18, 2002.

6. U.S. Nuclear Regulatory Commission Regulatory Guide 1.121, "Basis for Plugging Degraded PWR Steam Generator Tubes", August 1976.

7. "RE: Requests concerning CWA N2002-007 - U2 SG Tube Exam," E-Mail correspondence from E.D. Camp to M.H. Cothron et al., May 21, 2002.

8. "Steam Generator In Situ Pressure Test Guidelines," Revision 1, EPRI Document TR-107620-RI, June 1999.

9. "Steam Generator Tube Integrity, Volume 1: Burst Test Validation of Rupture Criteria (Framatome Data)," EPRI EP-NP-6865-L, Volume 1, June 1991.

10. TVA-02-90, Correspondence from E.A. Dzenis to D.L. Lundy, May 20, 2002.

11. "RE: Requests concerning CWA N2002-007 - U2 SG Tube Exam," E-Mail correspondence from T.A. Pitterle to D.R. Gregg et al., May 23, 2002.

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