ML20198K478

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Summary of 971204 Meeting W/Licensee & Representatives from W Re Proposed 3 Volt Alternate Repair Criteria for Plants Unit 2 Sg.List of Attendees & Handout Encl
ML20198K478
Person / Time
Site: South Texas STP Nuclear Operating Company icon.png
Issue date: 01/06/1998
From: Alexion T
NRC (Affiliation Not Assigned)
To:
NRC (Affiliation Not Assigned)
References
NUDOCS 9801150007
Download: ML20198K478 (73)
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<- NUCLEAR REGULATORY COMMISSION I

WASHINGTON, D.C. asseH001 ,

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LICENSEE: STP Nuclear Operating Company FACILITY: . SOUTH TEXAS PROJECT, UNIT 2

SUBJECT:

SUMMARY

OF DECEMBER 4,1997, MEETING ON PROPOSED 3-VOLT

, ALTERNATE REPAIR CRITERIA FOR THE UNIT 2 STEAM GENERATORS l

- On Decomt sr 4,19g7, the NRC staff met with the licensee and representatives from

! Westinghouse on the above subject. Meeting attendees are listed in Attachment 1. The handout provided by the l6censee (with the exception of proprietaiy portions) is in Attachment 2.

The purpose of the licensee's presentation was to inform the staff of their planned approach for an earty March 1998,1: cense amendment application for 3 volt altemate repair criteria (ARC) and to obtain staff fewlback. The licensee indicated that thsy desired NRC approval in time for their i October 1998, Unit 2 refueling outage.

The licensee's presentation included a discussion on the planned ARC, analysis of indications-restrained from-burst (IRB) leak tests, analysis for steam line break (SLB) hydraulic loads on tube suppor1 plates (TSPs), status of TSP displacement analysis, intomals inspe:: tion plan, and tube ,

expansion process. The licensee indicated that the portions of the presentation on analysis for l j SLB hydraulic loads on TSPs, status of TSP displacement analysis, and tube expansion process contain proprietary information and thus those portions of the handout are not attached to this summary. By letter from Westinghouse to NRC 1.aled December 2,1997, Westinghouse indicated they will comply with the requirements of 10 CFR 2.790 to provide proprietary and non-proprietary versions of the meeting handouts together with an aWidavit as soon as the proprietary

and non-propnetary versions have been prepared.

^

The licensee also highlighted differences between their proposed appiication and the application l for Byron and Braidwood, which was approved by the staff. Differences include: (1) increasing the allowable TSP displacement from 0.10 to 0.15 inches, (2) decreasing the bounding leak rate for IRBs from 6.0 gallons-per-minute (opm) to 5.5 gpm, (3) reducing the design factor applied to RELAP5 loads used !n the structural analysis of the TSPs for an SLB at hot standby conditions from 1.5 to 1.1, (4) changing the expansion process of tubes at the intersections with the TSPs to a constant volume process, (5) cutting the tube at the top of the tubesheet following

+

expansions at the TSPs to eliminate residual axial stresses from expansions and inserting a sleeve stabiluter, and (6) increasing the number of operating cycles before inspecting expanded  !

tubes from 1 to 2 cycles of operation. l

The staff thinked the licensee for heir presentation and for the opportunity to provide early comments on the licensee's plans. The staff indicated that although a similes application was J . approved for Byron and Braidwood, the stafs evaluation of 3-volt ARC at South Texas will need i to stand alone and the differences discussed above will require careful review, in addition, the  ;

l 9801150007 990106 PDR ADOCK 05000499 ""

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2 staff indicated that N also is very interested in the areas of voMage-growth and Hs long-term concems from the Braidwood/ Byron evaluation. Finaly, due to the number and ' ,, niexity of the issues involved, the staff indicated that the licensee keep to its schedule of submnd:tj the application no later than earty March 1998.

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  • 1 Thomas W. Alexion, Project Manager Project Directorate IV-1 Division of Reactor Projects I!!/IV Office of Nuclear Reactor Regulation Docket No. 50-499

Attachment:

1. List of Meeting Attendees
2. Meeting Handout cc w/atts: See next page

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staff indicated that it also is very interested in the areas of voltage-growth and its long term >

t'~ concems from the Braidwood/ Byron evaluation. Finally, due to the number and complexity of the ,

issues involved, the staff indicaied that the licensee keep to its schedule of submitting the  ;

application no later than early March 1998.

ORIGINAL SIGNED BY:

Thomas W. Alexion, Project Manager Project Directorate IV 1 Division of Reactor Projects lil/IV Office of Nuclear Reactor Regulation Docket No. 50-499

Attachment:

1. List of Meeting Attendees
2. Meeting Handout cc w/atts: See next page 4

DISTRIBUTION:

HARD COPY E-MAIL Docket File S. Collins /F. Miraglia (SJC1/FJM)

PUBLIC R. Zimmerman (RPZ)

PD4-1 r/f E. Adensam (EGA1)

OGC C. Hawes (CMH2)

ACRS T. Martin (SLM3) e T. Alexion (TWA)

J. Donoghue (JED)

E. Sullivan (EJS)

M. Lynch (MDL)

S.- Coffin (SMC1)

J. Tsao (JCT)

Document Name: ST12497.MTS OFC PM].PJM:t LA/PD4-1 (A)BC/EMCB BC/SRXB 3

. MAME TAleIb CHawdb ESullivan fk TCollind .

Yff97 U/ 0/97 -

DATE- (2/b7 12/5/9 7 -

COPY / YES\NO YES/NO YES/bO) YES/NO

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eg OFFICIAL RECORD COPY ofj

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o . STP Nuclear Operating Company south Texas, Units 1 & 2 ,

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Mr. David P. Loveless Jack R. Newman, Esq.

-t Senior Resident inapoctor - Morgan,' Lewis & Bocklus U.S. Nuclear Regulatory Commission 1800 M Street, N.W.

P. O. Box 910 - Washington, DC 20036-5869 Bay City, TX 77414 Mr. Lawrence E. Martin Mr. J. C. Lanior/M. B. Lee Vice President, Nuc. Assurance & Lloonsing City of Austin STP Nuclear Operating Co,T+sriy Electric Utility Department P. O. Box 289 721 Barton Springs Road Wadsworth,TX 77483

  • Austin,TX 78704

- Rufus S. Scott Mr. M. T. Harth Associate General Counsel

- Mr. W. C. Gunst - STP Nuclear Operating Company City Public Service Board P. O. Box 61867 P. O. Box 1771 Houston,TX 77208 4

San Antonio, TX 78296 Joseph R. Egan, Esq. .

Mr. G. E. Vaughn/C. A. Johnson Egan & Associates, P.C.

' Central Power and Light Company 2300 N Street, N.W.

P, O. Box 289 Washington, DC 20037 MailCode: N5012 ,

Wadsworth, TX 74483 Office of the Govemor ATTN: Andy Barrett, Director INPO Environmental Policy Records Center P. O. Box 12428 700 Galleria Parkway Austin, TX 78711 Atlanta, GA 30339 3064 Arthur C. Tate, Director Regional Administrator, Region IV Division of Compliance & inspection U.S. Nuclear Regulatory Commission Bureau of Radiation Control Texas Department of Health 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 1100 West 49th Street Austin,TX 78756

' Dr. Bertram Wolfe 15453 Via Vaquero Texas Public utility Commission Monte Sereno, CA 95030 ATTN. nAr. Glenn W. Dishong 7800 Shoal Creek Blvd.

Judge, Matagorda County Suite 400N z Matagorda County Courthouse Austin, TX 78757-1024 4

1700 Seventh Street Bay City, TX 77414 Mr. William T. Cottle President and Chief Executive Officer

~_ CTP Nuclear Operating Company-South Texas Project Electric Generating Station ~

P. O. Box 289 +

Wadsworth, TX 77483 aw w-w m e-% r ,,-w e-e - .-+ wwwrm+-4w,-s'a w w ,ww--.- ,--v v v -v-, -

MEETING BETNEEN STP NUCLEAR OPERATING COMPANY AND NRJ PROPOSED 3 VOLT ALTERNATE REPAIR CRITERIA FOR THE UNIT 2 STEAM GENERATORS December 4,1997 timmt Ornanization T. Alexion NRC J.Donoghue NRC E. Sullivan NRC M. Lynch NRC S. Coffin NRC J. Tsao NRC A. Keim NRC E. Debec NRC C. McIntyre STP R. Baker STP W. Hanison STP J. Conly STP C. Keating Westinghouse R. Smith Westinghouse C. Hu Westinghouse H. Lagally Westinghouse T, Pittorie Westinghouse ATTACHMENT 1

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  • South Texas Project Electric Generating Station Unit 2 Steam Generator 3-Volt Alternate Repair Criteria SOUTH TEXAS PROJECT ELECTRIC GENERATING STATION UNIT 2 STEAM GENERATOR 3-VOLT ALTERNATE REPAIR CRITERIA NRC BRIEFING DECEMBER 4,1997 1

ATTACHMENT 2

South Texas Project Electric Generating Station Unit 2 steam Generator 3 Volt Alternate Repair Criteria Agenda introduction Ron Baker Overview Of Planned ARC . Tom Pitterle Analysis OfIRBLeak Tests Herm Lagally Analysis For SLB Hydraulic Loads On TSPs' Chris Hu Status Of TSP Displacement Analysis Rich Smith Internals Inspection Plan Tom Pitterle

-Tube Expansion Process Bob Keating

> Discussion 2

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~ South Texas Project Electric Gener: ting Station': j

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  • l South Texas Project Electric Gen: rating Station
  • Unit 2 Steam Generator 3 Volt Altemate Repair Criteria Meeting Objectives Present South Texas approach to implementing 3-volt alternate repair criteria Identify NRC concerns regarding 3-volt alternate repair criteria or differences from prior applications P

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i south Tcxas Project El:ctric Generating Station  :

L - Unit 2 steam Generator 3. Volt Alternate Repair Criteria Goal for Management of Unit 2 Steam Generators Operate safely and officiently without mid-cycle inspections and without repairs to expanded tubes Employ voltage-based repair criteria as necessary

  • Maintain RCS flow margin
  • Maintain tubes in service for cold-leg LOCA core cooling
  • Increase tube burst margin of safety

. Eliminate potential burst cycle length limitations

. Reduce cost 5

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south Texas Project Electric Generating Station

~ Unit 2 Steam Generator 3-Volt Alternate Repair Criteria ,

South Texas Approach to 3-Volt Repair Criteria Provide additional margin to burst

- Positively lock hot leg support plates over tube degradation '

instead of dynamic analysis only Develop secondary-side inspection and physical modification of tube expansions Implement during normal S/G inspection window Address Byron TTS circumferential cracking at expanded tubes

- Lower hydraulic expansion residual stresses at STP - Cut tube at TTS following expansions to relieve stress

- Install sleeve to bridge tube cut

- Use conservative hydraulic sleeve repair at TTS 1

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South Texas Project Electric Generating Station

- Unit 2 Steam Generator 3. Volt Alternate Repair Criteria b

l Unit 2 Steam Generator Design Characteristics .

Mill-annealed Alloy 600 tubing -- 3/4" OD x 0.043" wall Preheater with flow distribution baffle ~9" above TTS Drilled stainless steel TSPs Hot leg hydraulic tube sheet expansions shot-peened l

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South Texas Project Electric G:nerating Station

Unit 2 Steam Generator 3. Volt Alternate Repair Criteria Unit 2 Steam Generator Degradation History No tubesheet expansion cracking No cracking at cold leg preheater hydraulic expansions No DSI extending outside TSP crevices No PWSCC or circumferential cracking at TSP crevices t

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r -- I south Texas Project Electric Generating Station Unit 2 Steam Generator 3-Volt Alternate Repair Criteria Unit 2 Total Distorted Support Plate Indications Inspection No. of DSI Max Mean Year Extent DSI Location Voltage Voltage 1993 100 % 22 1st,2nd,3rd support plates 0.98 1 Cold leg preheater baffle support i

1995 20% 19 1st,2nd,3rd support plates 1.60 1997 1,0100) Predominantly 1st,2nd,3rd 1.86 0.48 support plates ,

(1)- 581 tubes plugged in 2REOS where MRPC confirmed axial c acking Although number of DSIs increased from 1995 to 1997. fhe voltage growth was small 2REO5 plugging resulted from high MRPC confirmation rate oflow-voltage 9

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south Texas Project Electric Generating station  !

Unit 2 Steam Generator 3-Volt Alternate Repair Criteria History ot'Model"E" Steam Generators with Voltage-Based Repair Criteria Laborelec and Tractabel applied voltage-based repair criteria at Doel-4 in 1991 Laborelec utilized bobbin coil relationships for leak and burst in 1992 Tractabel completed TSP deflection analysis for Doel-4 and Tihange-3 in 1993

- Cracks were not sufficiently uncovered during MSLB

. loading to lead to a tube burst issue 10-volt repair criteria established 10-volt criteria used for model "E" since 1993 without exceeding RG 1.121 burst margins Doel-4 replacement in 1996 Tihange-3 replacement in 1998 11

  • - South Texas Project Electric Generating station Unit 2 Steam Generator 3 Volt Altemate Repair Criteria Economics of 3-Volt Repair Criteria Estimate $1.8M to implement ARC Estimate $1.2M 2REO6 plugging cost without any ARC Estimate $1.8M for 2REO6 sleeving of MRPC-conf ~irmed DSIs Estimate $20M exposure for mid-cycle inspections 12

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. - South Texas Project Electric Generating Station

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Unit 2 Steam Generator 3-Volt Alternate Repair Criteria Discussion Topics -

Elements of ARC with Limited TSP Displacements Similarities to Braidwood-l 3 Volt ARC Same methodology Differences from Braidwood-l 3 Volt ARC

  • -Acceptable TSP displacement
  • Leak rate for indications restrained from burst (IRB) .
  • Expandedjoint at TTS Tube expansion process Analysis Methods for Burst Probability Analysis Methods for SLB Leakage Program Plan t

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.. South Texas Project Electric Generating Station Unit 2 Steam Generator 3-Volt Altemate Repair Criteria Elements of ARC with Limited TSP Displacement Hydraulic tube expansion at 3 elected TSP intersections / tubes to " lock" tube to TSP Eliminates axial rupture as a concem for hot leg indications Expansion applied to hot leg intersections 3 volt ARC with limited TSP displacement applied to hot leg indications and GL 95-051-volt ARC applied to cold leg indications Selection of tubes for expansion SLB hydraulic loads from RELAP5 analyses TSP displacements and selection ofintersections for expansion from dynamic structural analyses Tube expansion process Hydraulic expansion of tube diameter above and below TSP Constant volume expansion process for South Texas application Top of tubesheetjoint for expanded tubes Eliminate TTS residual axial stresses that result from expansions at TSPs que. w w.um m a-pe 3 inn l

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.. South Texas Project Electric Generating Station Unit 2 Steam Generator 3. Volt Alternate Repair Criteria Elements of ARC with Limited TSP Displacement SG StructuralIntegrity Assessments NDE assessment for TSP cracking at time of ARC implementation Visual inspection of accessible TSP supports in one SG at time of ARC implementation Tube Integrity Assessments Condition monitoring and operational assessments SLB burst probability and leakage analysis methods specific to limited TSP displacement conditions Tube inspection requirements same as GL 95-05 for 1- volt ARC 1

Q tapesparcWcWell.97everview. ppt 4 12/1 97 e

.. South Texas Project Electric Generating Station Unit 2 Steam Generator 3 Volt Altemate Repair Criteria Similarities with Braidwood 3 Volt ARC volt ARC for hot leg indications with expansion at TSPs 1-volt ARC per GL95-05 for cold leg indications - no expansions Analysis methods for SLB loads and TSP displacements

  • Hydraulic loads (RELAPS) and dynamic displacement analyses same as for Braidwood Differences in SG geometry, TSP supports and operating conditions of Model E versus Model D4 of Braidwood Con.c ervative factor of 1.5 applied to RELAP5 loads for SLB at normal operating conditions to bound uncertainties in analysis Hydraulic expansion above and below TSP to " lock" tube to TSP Sleeved hydraulic expansion same as Braidwood

. Some differences in expansion process Methods' for SLB tube burst probability analyses and leakage 4

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=.. - ' South Texas Project Electric Generating Station

- Unit 2 Steam Generator 3 Volt Alternate Repair Criteria -

Differences from Braidwood 3-Volt ARC Allowable TSP displacement increased from 0.1" to 0.15"

  • Based on final analyses ofleak tests for IRBs

-Braidwood displacement limit selected prior to test results to permit other program efforts such as displacement analyses to proceed in parallel -

-Supports reduction in number of tubes / intersections requiring expansion

+ Supports reduction in tube expansion stiffness requirement which leads to e diameter reduction and some reduction in potential for corrosion Axial burst probability remains negligible, independent of the number of indications

-Burst probability for a throughwall indication extending 0.15" outside of TSP is < 10 l5 per indication

-Negligible burst probability even if apply bounding assumption that all displacements expose throughwall cracks at all intersections Bounding SLB leak rate for an IRB is reduced from 6.0 to 5.5 gpm Based on final analyses ofIRB leak tests Minor influence on calculated leak rates Design factor of 1.1 applied to RELAP5 loads for SLB at hot standby conditions

. Low probability of SLB event at hot standby conditions due to miminal operating time spent at hot standby conditions -

Low combind frequency of SLB event and hot standby conditions supports

. smaller design factor than applied at normal operating conditions

' Redundant expansions not included in tube expansion matrix Q1spexpercWcWell 97everview-Prt ' 6 12/3.97 e

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.- Soath Texas Project Electric Generating Station Unit 2 Steam Generator 3 Volt Alternate Repair Criteria -

Improvements to Braidwood 3-Volt ARC Expansion process changed to a constant volume expansion

  • Considerable improvement in expansion diameter control

-Redue s field repeat expansions to assure minimum diameter expansion is obtained Increased pull force capability (stiffness) obtained for the same expansion diameter as prior timed expansion process

-Supports reduction in minimum and maximum expansion diameters

  • Smaller expansion diameter reduces potential for corrosion cracking Expansion joint added at TTS in expanded tubes Tube cut at TTS following expa .sions at TSPs to eliminate residual axial stresses from expansions Sleevedjoint with hydraulic expansion (similar to TSP expansions) above TTS and mechanical hardroll in tubesheet Type ofjoint currently used as a stabilizer for TTS circumferential indications Hydraulic expaasion at plugged tube temperatures (about 550 F) compared to TTS expansion at T3 ,,(about 616 F for Braidwood hardroll expansion cracking)

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.. - South Texas Project Electric snerating Station j Unit'2 Steam Generator 3. Volt Alternate Repair Criteria l

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- South Texas Project Electric Generating Station Unit 2 steam Generator 3. Volt Altemate Repair Criteria  ;

Major Conservatisms in ARC f

TSPs assumed to displace and stay displaced at maximum values attained during SG depressurization in ~ first second of the transient l

  • Tube primary to secondary pressure drop is s normal operating value when maximum displwement occurs
  • Pressure <irops, and TSP displacements decrease to small values prior to tube pressure drop building to 2560 psi at typical by 5 to 15 minutes into event
  • Plate stiffness would return TSPs to ~ nonnat operating positions (relative to '

the tube) prior to large increase in tube pressure drop since the TSP displacement is clastic For satisfying 0.15" TSP displacement limit, RELAPS SLB hydraulic loads are increased by design factors of 1.5 at full power conditions and 1.1 at hot standby conditions Prior sensitivity analyses for Braidwood ARC have shown that RELAPS loads bound other analysis codes Bounding leak rate of 5.5 gpm is a very conservative application ofIRB leak test results

  • IRB test throughwall crack lengths much greater than anything expected with a 3-volt repair limit
  • Throughwall crack lengths of 0.52"- 0.64" and biadder pressurization to free span burst pressures > 2560 psi are basis for 5.5 gpm Largest pulled tube indications between 11 and 23 volts, which provide an upper EOC voltage for a 3 volt repair limit, have throughwall lengths < 0.5"
  • Bounding leak rate applied to every IRB in Monte Carlo analyses independent of crack size or local (<0.15") TSP displacement

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.- south Texas Project Electric Generating station Unit 2 steam Generator 3. Volt Alternate Repair Criteria Major Conservatisms in ARC (cont'd)

Tube expansion design limit of 0.15" TSP displacement is a very .

conservative application of fRB leak test results

+ IRB test results based on crack extensions outside TSP up to 0.22"

+ Leak rates not strongly influenced by crack extension outside TSP

-Leak rates dominantly dependent upon TW crack lengta which dictates crack opening area which is also restricted by crack face contact wini the TSP Tube expansion design limit of 0.15" TSP displacement provides Jr.rge burst margin comp:', red to ~ 0.3" necessary to limit axial burst probability to negligible levels Applicable even under bounding assumption that TSP displacements expose a threughwall crack at every TSP intersection on hot leg 3-volt repair limit conservatively applied

  • Structural considerations support repair limits on order of 10 volts or more

+ Technical requirements would establish repair limit as needed to satisfy allowable leakage limits Actual SG conditions of packed TSP crevices would prevent TSP displacement in a SLB event and would reduce leakage to negligible levels IRB leak rates and TSP displacements based on maximum tube-to-TSP hole clearance with no crevice restrictions Qtspnparenrdnrcll 97ownkw.r14 10 int 7

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    • South Texas Project Electric Generating Station Unit 2 Steam Generator 3. Volt Alternate Repair Criteria i Analysis Methods for SLB Burst Probability l i

Hot leg indications

. Calculate burst probability for axial tensile nipture

-Conservatively assumes all indications have cellular corrosion patches

  • Burst correlation (tensile rupture pressure vs. voltage) given in EPRI database reports NP-7480-L, Addenda

- Addendum 2 to be issued in March 1998 per NRC/ industry database update protocol

  • Ar ' lysis methodology same as for OL 95-05 analysis e Axial tensile r , ;ure probability need not be calculated since negligible due to '

limited SLB TSP displacement Cold leg indications All requirements of GL 95-05 are applicable to 1 volt ARC for ccid leg ,

indications Hot leg and cold leg burst probabilities can be summed to obtain total burst probability Q1apesevewswell.97eweview ppt ll Im1 e

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.. South Texas Project Electric Generating Station Unit 2 Steam Generator 3. Volt Alternate Repair Criteria Analysis Methods for SLB Leak Rate Hot leg leak rate

  • Analysis method same as applied for Braidwood 3-volt ARC 1

+ General Monte Carlo r.nalysis methodology

-Burst pressure sample obtained from GL 95-05 hxial burst pressure vs.

voltage correlation for each voltage sample

-If burst pressure < 2560 psi for SLB, IRB leak rate assigned to voltage sample

-If burst pressure > 2560 psi, leak rate obtained from GL 95-05 freespan leak rate correlation Coldlegleak r :

+ Free span GL 95 05 leak rate analysis methods applied for 1-volt ARC Combining hot and cold leg leak rates

  • Add hot and cold leg leak rates with each calculated at 95% confidence
  • Cold leg leak rate expected to be negligible compared to hot leg value

-Small number oflow-voltage indications

  • Separate values demonstrate importance of relative leakage between hot and cold legs If cold leg leak rate exceeds 10% of allowable lesk rate limit, hot and cold leg leakage would be added on a SG sample basis prior to determining 95%

confidence value

  • 10% value used as indicator of significant cold leg leakage Q tapespwcWcWcll.970weview ppt 12 in91

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.. South Texas Project Electric Generating Station Unit 2 Steam Generator 3 Volt Altemate Repair Criteria Program Plan for Implementing ARC EPRI to issue IRB leak rate report in early 1998 Completion of technical report for 3-volt ARC

  • Complete SLB TSP displacement analyses

-Identify tubes and TSP elevations requiring expansion to limit maximum TSP displacement to 3.15"

-Define stiffness (pull force) requirements for TSP expansions and TTS Joint

  • Finalize TSP expansion and TTS joint designs

-Expansion diameters required to meet stiffness requirements

  • Complete report Field implementation at South Texas Unit 2 in Fall 1998
  • Implementation of 3 volt ARC for hot leg and 1 volt ARC for cold leg
  • Expand required tube / TSP intersections and at TTS

-Includes bobbin profilometry to confirm minimum expansion diameter

-Baseline + Point coil inspection at expansions

  • Eddy current analysis for TSP cracking or misdrilled, overlapping holes
  • Visualinspection of accessible TSP support welds in one SG
  • Removal of two tubes, four intersections for destructive examination confinnation of crack morphology Q tspeaparcWcWell.97oserview ppt 13 11397 L

.- South Texas Project Electdc Generating Station  ;

Unit 2 Steam Generator 3 Volt Alternate Repair Criteria Long-Term SG StructuralIntegrity Inspections  !

SG (non-tube) structural integrity inspections to follow industry '

guidelines being prepared for submittal to the NRC Inspections of TSP expansions and TTS joint

  • Deplug and inspect 20% of expansions after two cycle intervals
  • First inspection after two cycles of operation

-Interval supported by no indications found at TSP expansions in Braidwood ,

inspection, by no indications found in preheater TSP hydraulic expansions and by corrosion evaluation perfonned for Braidwood hydraulic expansions

  • TTS sleeve has eliininated TS expansion cracking as an expanded tube concern d

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" Unit 2 Steam Generator 3. Volt Alternate Repair Criteria 1

Typical Test Sequence Leak test with crack axially centered on the TSP in increments to -

~2300 psid Measure crack properties (length, tube diameter, throughwail length  !

and width, and TW width profile)  :

Offset leak tests from ~2300 psid to facility limit  !

Measure crack properties Pressurize with bladder to ~70% of predicted freespan burst pressure Measure crack properties Offset leak test from about ~2300 psid to facility limit Leak test with crack axially centered on TSP Pressurize with bladder to predicted freespan burst pressure Measure crack properties Offset leak test from ~2300 psid to facility limit Leak test with crack axially centered on TSP 1 Measure crack properties 12/2/97 2 l

O Test Matrix for Indications Restricted from Burst (IRBs)- As Tested Th. J. J Crack length Frte Crack to 13P oft # IRadder Test Tube Specimen Span Prtss.

N Dia. Type, leak h Press. Inadder Prrss. Age

& Test i Ofbet

.25.45 .45.60 .60 .75 (rj 0.0" 0.10" l 0.15" 0.0" 0.10" 0.15" k h) 1-1 7/8 CorrSatg. 0.62" If II II II II,C 0.15 8161G l-2 , 7/8 Corr 5arg. 0.62" 1I II II II It, C C.15 8161E 1-6 3/4 Corrosion 0.74~ II II II II II.C 0.!0 2008E l-7 3/4 CorrEatg. 0.60" II II II II 0.10 2051A 2-1 7/8 Corr 5arg. 0.515" II II II II II,C 0.15 8161A 2-45 7/8 Conesion II II II, C C C,11 0.15 4C218 0.29" 2-7 3/4 CorrSarg. C C II II II, C 0.10 2051E 0.577" 2-8 3/4 Laser Cut 0.55" 11 II II,C None IRB-LC-2 2-10m 3/4 Corrosion 0.425" Ii 11 II, C II II,C 0.10 20510 4-1 7/8 Conusion 0.24" C C 0.15 4B214 1

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l Notes: 1. H is hot test d cr ding -- , _, C is a room tesgerature nest

-2. Test sequences mM pressurizing wish a bl=Abr typiceNy to the free span burst pessure. Test 41 iM incseinental 'uscsenses j p in binabr pessure beyond that equivalent to a fiee span basst. Tests 2-42-10,11-1,11-2,12-1 and 12-7 i=rh=le bindder pressuriantions below and at the free span burst pessure. Bla ' der pess. is perfanned to open the crack beyond that obtained widiic the pessure capability of the facility.

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3. Ienk tests in sniall leak test facility prior to E46e pessurization and large facihty aAer pessurization. All odier tests in large leak test facility.  ;
4. Specinien has two twoughault cracks 90* apart.

i S. Two essentiaNy co-planer cracks (0.012" circunferemial offset) separated by a lipment at 0365* from the end of the longer j segment.  !

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south Texas Project Electric Generating Station Unit 2 steam Generator 3. Volt Altemate Repair Criteria Crack Length Measurements In-process measurements

  • Dye penetrant print on silastic mold

- Accurate totallength of throughwall ponion

- Does not provide total crack length or non throughwalllength

- Visual, using toolmaker's miscroscope

- May not reveal ends of tight cracks

- Actual cracks tested are longer than apparent cracks

- Conservative method in head-to head comparison with dye penetrant

- Visual, with microscope and back lighting for throughwall cracks

- Resolution requires 1 mil crack opening; may miss TW ends

- May miss throughwall length not nonnal to line of sight

- Conservative: actual crack tested may be longer than apparent crack Post-test measurement

  • Destructive testing - fractography; selected specimens

- Pre-test throughwall length differentiated from test induced crack tearing

- Shon duration, high temperature exposure of samples creates visible oxide layer on crack surface In process measurements demonstrated to be conservative compared to fractography

- Actual cracks (fractography) longer than apparent cracks (in-process measurements) ,

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scath Texas Project Electric Generating Station Unit 2 steam Generator 3. Volt Alternate Repair Critena l l

Crack Structural Behavior l t

Short Cracks (<0.4")

High burst pressures  !

- Small crack opening at SLB Ap

  • Interaction with TSP not expected Long Cracks (0.4" - 0.75")

- Burst pressures in excess of SLB 6p

- Interaction with TSP expected for crack >0.55" throughwall .

- Limiting crack length is 0.75" (span of TSP) .

Crack elongation not significant for pressures up to the predicted freespan burst pressure Expected freespan crack tearing - 250 mils

  • Observed IRB crack tearing < 50 mils

- Exceptions: Tests 12 and 2-1 which tore 90 mils and 64 mils respectively due to opening of previously unobserved (non-throughwall) crack segment

- Test 12-7 tore 183 mils when subjected to pressurization at 6200 psid vs. the predicted burst pressure of 3950 psid Limiting throughwall crack length for SLB Ap is 0.75" for 3/4" dia. ,

tube Freespan burst; no TSP constraint

  • Based on Lower Tolerance Limit (LTL) material properties
  • Risk of SLB burst longest acceptable crack is negligible 12U197 6

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South Texas Project Electric Generating station Ur.it 2 steam Generator 3. Volt Alternate Repair Criteria r

Adjustment of Measured Leak Rates for SLB Conditions {

Method of normalizing test data to standard conditions of 615 F primary temperature,15 psia secondary pressure from EPRI NP-7480-L, Volume 1, Appendix B

- Accounts for choking due to steam flash at crack exit l

- Accounts for fluid density differences, since leak rate is measured at room temperature Accounts for crack structural effects related to material property temperature effects Only increasing pressure data were utilized within a tolerance of 40 psid Hysteresis effect of tube skews results

- Higher pressurization re-sets the crack opening; subsequent lower pressure leak test is invalid data point 40 psid tolerance based on engineeringju ment Maximum test Ap and " steady state" op examined for correlations

- Max imum Ap provides physically more correct leak rate due to crack opening response to maximum pressure 8

12/2/97

South Texas Prdect Electric Gen: rating Station Unit 2 Steam Generator 3 Volt Altemate Repair Criteri Leak Rate Results - Flow Pressurization Tests Test Initial Crack Length SLB Leak Rate  :

Specimen (in.) (gpm)

Total TW Offset No Offset 2-4 0.600 0.290 0.37 0.37 2-10 0.551 0.425 1.70 1.70 2-1 0.640 0.515 1.65 0.93 2-7 0.660 0.577 4.10 NR l-1 0.626 0.620 3.70 2.30 12 0.645 0.620 3.20 NR l-7 0.600 0.600 4.10 3.2 16 0.760 10.7401 . f51501 ' 3.40 ni u, .w _ 2 , . . _ .. -

41 0.670 0.240 No test No test Il-1 0.710 0.600/ 5.00 4.00 0.110 11-2 0.729 0,630 5.30 NR 12-1 0.607/ 0.518/ 3.20 3.20 0.465 0.360 12-7 0.590 0.375/ 3.90 3.90 0.256 The following tests are excluded: 11-7 crack length is >> than the limiting length of 0.750 in.; 2-8 is a laser-cut flaw.

Il-7 0,813 0.809 6.20 6.20 2-8 0.554 0.550 6.1 2.30 12/2/97- 9

South Texas Project Electric Generating Station e

Unit 2 Steam Generator 3. Volt Alternate Repair Criteria Leak Rate Results - Bladder Pressurization Tests  !

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Test SLB (2560 psid) Leak Rate (gpm) i Specimen OfTset No Offset 2-4 1.9 1.3  :

2-10 1.6 1.6 4 2-1 3.1 3.2 .

2-7 3.7 4.2 l-1 2.4 3.5 ,

1-2 2.8 2.7 l-7 3.3 3.2 l-6 5.0 4.8 41 4.2 2.5 11-1 5.0 5.0 11-2 5.3 4.9 g, ye ,.:. . . .. . - '. .m,y .ye' s ' ,.,.y,s 77 ,~

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12-7 3.3 3.2 The following tests are excluded: 11-7 crack length is >> than the limiting length of 0.750 in.; 2-8 is a laser-cut flaw.

11-7 5.2 5.7 .

2-8 No test No test 12/2 S 7 10 _

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  • i South Texas Project Electric Generating Station l Unit 2 Steam Generator 3. Volt Altemate Repair Criteria )

l L

i Summary of Tests 11-7 and 2-8 Test 11-7 (3/4" dia.) l

  • Crack length: 0.813" total, 0.809 throughwall

- Much greater than limiting crack of 0.75"

  • Crack centered on TSP for non-offset test ,

- Therefore double ended offset of 0.059" total for non-offset test

- Test included as a very conservative bounding test

- Observed trends are consistent with other test of shoner cracks

  • Conclusions

- Leak rates from this test are excluded from justification of offset due to extreme crack length

- Results demonstrate that cracks at TSPs in excess oflimiting crack length do not pose significant risk of burst or excessive leak rate Test 2-8

  • Laser cut specimen included to evaluate method of simulating cracks
  • Structurally non-representative of cracks I

- Rounded crack tips allow plastic hinge opening of crack

- Smooth, wide throughwall opening does not represent crack Conclusions

- Laser cut specimens do not adequately simulate cracks

- Leak rate data excluded fnom database

- Specimens are useful to demonstrate structural trends 12/2/97 11

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South Texas Project Electric Generating Station l Unit 2 Steam Generator 3. Volt Altemate Repair Criteria Sum mary of Leak Test 12-1 (7/8" dia.)

Specimen had two cracks 90 apart Principal crack: 0.607" total,0.515" throughwall

  • Secondary crack: 0.465" total, 0.360" throughwall j

- Both cracks <0.001" wide; back light measurement not  ;

possible Flow pressurization to 2680 psid

  • Principal crack opened to ~0.005" l
  • Secondary crack did not open .

- Offset SLB Ap leak rate < 3.2 gpm Bladder pressurization to 3310 psi, ~70% of predicted freespan burst ,

- No additional opening of principal crack Slight increase in length of principal crack

  • Secondary crack did not open
  • Offset SLB Ap leak rate = 4.2 gpm ,

Bladder pressurization to predicted freespan burst (4850 psi)

Principal crack opened to 0.022" Principal crack TW length increased to 0.630"

  • Secondary crack opened to 0.005" ,
  • Secondary crack TW length increased to 0.391"

- Combined crack leak rate = 5.7 gpm Conclusions Up to near the predicted principal crack burst pressure, secondary crack does not contribute to leak rate Confirms field and model boiler conclusions that leak rate dominated by principal crack

-12/2/97 12 i

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south Texas Project Electric Generating Station l Unit 2 Steam Generator 3 Volt Altemate Repair Criteria i

Leak Rate Assessment for Tubes with Two Cracks Leak rate is an exponential function of the throughwall length of each crack segment, not the total apparent throughwall crack i length  ;

Leakage is dominated by the longer crack

- Supporting data from pulled tubes (Plants AA and AB) with indication voltages of10-11 volts Supporting data from model boiler test specimens

- Data show that secondary cracks are much shorter than the  :

principal crack (see exception below)

Exception: Plant S pulled tube with 22.9 volt indication ,

- Two cracks; 0.50 inch and 0.41 ir :h long

- Calculated leak rate for longer crack was > 3 times the i

calculated leak rate of the shorter crack Conclusion

- The longer crack on a tube with more than one crack dominates the leak rate

- - Confinned by pulled tubes, including the Plant S tube

- Confinned by IRB leak tests, specimen 12-1 t

12/2/97 13.

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South Texas Project Electric Generating Station  ;

Unit 2 Steam Generator 3. Volt Alternate Repair Criteria j i

Probability Assessment for Two Cracks ,

at a TSP Intersection j Location of throughwall crack is not near the edge of the TSP

- Pulled tubes,16 available from Plants AA and AB  ;

- Indication voltages 1-16 volts

- 1 of 16 located at -0.1 inch from edge of TSP

- 12 of 16 located >0.2 incli from edge of TSP

- Remainder near center of TSP Top TSP is the highest loaded TSP Maximum displacement is in a localized area of the highest-loaded TSP incidence of ODSCC is dominantly at the lower TSPs Probability of the two cracks occurring at the maximum displacement location is extremely low .

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South Texas Project Electric Generating Station .

e i Unit 2 steam Generator 3 Volt Allemate Repair Criteria i t

Summary of Leak Rate Uncertainty Assessment Sources of uncertainty Fluctuation ofleak rate over duration of test

- Estimated uncertainty: *3.1%

  • Maximum vs. average op for reported leak rates

~ Estimated uncertainty: 10%

- Applies for botmding leak rate test; upper limit leak rate reponed  ;

  • Leak rate adjustment procedure for SLB conditions

- Estimated uncertainty: negligible Adjustment magnitude of 610% l

- Uncertainty a small percentage of adjustment magnitude  :

  • Test loop calibrations .

- Estimated uncertainty: +0.1%

- Based on u as ofindependently calibrated orifices  ;

Summary of uncertainty on bounding leak rate

  • Based on upper and lower limits of uncertainties, combined uncertainty varies from -7% to -13%
  • Negative values indicate that test-based bounding leak rate is conservatively high, i.e., value is overstated 1

11/2/97- 15 4

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.* . 1 South Texit Project Electric Generating Station Unit 2 Steam Generator 3. Volt Alternate Repair Criteria Applicability of Test Data to 3/4" and 7/8" Diameter Tubes Correlation of SLB leak rates

- Total crack length

- Direct measurement in test sequence

- Test measurements are conservative compared to post-test destructive examination

  • Crack throughwall flow area

- Crack throughwall width measured during test sequence

- Both total area and limiting area considered .

- Greater uncertainty than crack length only 3 crackopeningmeasurement l

3 crack tip area uncertainty 3 TSPinteraction calculation SLB leak rate correlates well with both crack. length and flow area Obsen'ation

- No apparent difference between data for 3/4" dia. tubu and data for 7/8" dia tubes  ;

Conclusion

- SLB leak rates are independent of the tube diameters tested

- Leak rate data apply equally for 3/4" and 7/8" dia, tubes 12/2/97 16 l

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South Texas Project Electric Generating Station Unit 2 Steam Generator 3. Volt Alternate Repair Criteria Eflect of Tube Diameter - Offset Tests 1

Offset Lmk Rate vs. Througswell Crack Length for Flow and sadder Pressurization l e

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South Texas Project Electric Generating St.ition Unit 2 Steam Generator 3. Volt Alternate Repiir Criteria Effect of Tube Diameter - Zero Offset Tests Zero Offset Leak Rate vs. Throughwall Crack Length for Flow and Bladder Pressurization 10 0 o

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south Texas Project Electric Generating station Unit 2 steam Generator 3 Volt Altemate Repair Criteria Comparison of Leak Rates for Offset Tests and Non-Offsct Tests SLB leak rates correlated to crack throughwall lengths Offset tests

  • Non-offset tests Observations
  • Both flow -pressurized and bladder-pressuiized tests correlate well with crack throughwall length Bladder pressurized tests include slightly greater scatter due to crack opening and TSP interaction Correlations for offset tests and non-offset tests are essentially the same'

- correlations are tlie same at limiting crack length Conclusions Leak rates are principally dependent on total crack length Crack offset in the measured range does not significantly affect leak rates Same conclusions reached when correlations are based on crack flow area 12/2/97 19

Correlation With Throughwall Crack Length- .

Offset Tests Offset Leak Rate vs. Throughwall Crack Length for Flow and Bladder Pressurization -

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12/2/97 20 t

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12/2/97 12

1 South Texas Project Electric Generating Station Unit 2 Steam Generator 3. Volt Alternate Repair Criteria Offset Leak Rate as a Function of Crack Offset No correlation found between offset test SLB leak rates and offset test throughwall crack length for either flow-pressurized or bladder-pressurized tests Conclusion Leak rates do not depend on the crack offset within the offset range tested Confirms prior conclusion on leak rate vs. total crack length I

12/2/97 23

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South Tcxas Project Electric Generating St: tion Unit 2 Steam Generator 3-Volt Alternate Repair Criteria l

Leak Rate Correlation with Offset Throughwall Length Offset Leak Rate vs.Throughwall Length Outside TSP for Flow and Bladder Pressurizatlan

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south Texas Project Electric Generating station Unit 2 Steam Generator 3-Volt Alternate Repair Criteria ,

Range of Offsets Supported by Tests Initial tests setup based on total crack length outside TSP Therefore, throughwall crack length outside TSP shorter Typical of field detection which is based on total crack length Later tests set up based on throughwall length outside TSP Therefore, total crack length outside TSP greater than setup criteria ( 0.10" for 3/4" tubes; 0.15" for 7/8" tubes)

Maximum crack offset tested 0.208" (0.173"TW) for flow pressurization (Test Il-2) 0.185" (0.154 "TW) for flow and bladder pressurization (Test 11-1)

Crack extension during test provides leak rate margin by extending the throughwall length outside of the tube A part of the total crack extension is throughwall extension Total crack extensions

- 0.019"(Test 11-2)

- 0.047"(Test Il-1)

Conclusions A minimum of 0.15" crack offsetjustified by tests Sources of margin

- Total crack is longer than throughwall crack; therefore limiting

- 0.75" crack potential throughwall offset is less than 0.15"

- Offset lengths >>0.15" tested, without implications

- Test measurements of crack lengths are conservative

. ~.,.

i t.

Summary of Total Length' and TW Length Outside TSP and Crack Extension Due to Pressurization

. Total Total Crack length 'IW Length Crack Elongation - Max. AP Applied -

Test Crack Outside TSP Outside TSP inch psid -

Length at Start N - N m N m N -

ofTests (in.)

3/4" Diamete- Specimens (9.19" mominal othet) 6 0.735 0.09! 0.094 0.070 ~ 0.070 0.0016 0.021 2732 3220 1-7 0.600 0.103 0.100 0.09I- 0.100 0.021 0.025 2836' 2970  !

2-7 0.660 0.101 0.100 0.088 0.087 0.011 0.0I4 2900 3700 ,

2-8 ' O.553 0.107 [2]. 0.104 {2] 0.012 12] 3115 (2)

, 2-10 0.551 0.100 0.106 0.005 0.081 0.003 0.024 NA 4960 Il-7 0.820 0.111 0.109 C.102 0.100 0.009 0.009 2683 4850 12-7 0.590 0.104 0.116 0.100 0.100 0.045 0.183'" 2659 62fW8 1

t 1

4 L

~ , , . _ _ , _ _ . ~ . . .

~ _ ..

., 3..

Sununary of Total Length and TW Leni $h Outside TSP and Crack Extension Due to Pressuaization Total Total Crack Length TW $ngth ' Crack Elongation : Mai AP Applied -

Outside TSP = Outside TSP inch --paid.

Test. 1 Crack Length at Start > ==**r * ==**r N- ==**r N- ==

rmeeriseess rmseriemese r mseriemese reasurissese r meentasses ressmanismese 5 r meerisseen r meentesame (in.) -

7/8" Diesmeter Specimieses (0.15" meedeel eNeet)

' l-1 0.620 0.152 0.150 ' O.147 0.147 - 0.013 0.013 2751 4250 I.2 0.640 0.210 0.150 0.145 0.085 0.090 0.099 -2387 4000 2-1 0522 0.150 0.150 0.134 0.132- 0.064- 0.097 3006- 14500

~ 2-4 0.600 0.150 : 0.150 0.0 0.076 0.011 0.017 2716 5550 4-1 0.650 [3] 0.129.0.167 [3] 0.099,0.112 [3] 0.015 NA 6000M' O.670 0.006-Il-1 0.710 - 0.185 ' [0.185S ~ 0.150 0.154 0.045 0.047 2561 3670 '

11-2 0.729 ' ' O.208 ~ ' O.180 0.173 0.150 0.019 0.020- 2548 4075-12-1 0607 0.158 0.165 0.105 0.151 0.039 0.051 2604' -4850 0.465 0.018 '

Note 1. - Bladder pressurization of 6200 psi exceeded free span burst estianate of 3950 psi and contributed to the larter "uncrease in crack lengen.

Note 2. Bladder pressurization condition not tested.

Note 3. Flow pressurization condition not sessed. Initial test was bladder pressurization at > SLB DP.

Note 4. Specisnen ultimately prer . W with bladder to 11350 psid. Tube burst outside the TSP.

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South Texas Project Electric Gen rating Station

- Unit 2 Steam Generator 3. Volt Altemate Repair Criteria t-Limiting Displacement for Long Cracks Leak rate is not dependent on offset length if total crack area is not increased Crack area is not increased if crack flank contact length does not project outside ofTSP Long cracks interact with TSP Crack flanks contact TSP

- Maximum contact length in tests estimated at 0.3 inch Limiting crack is 0.75" for ARC

- Therefore crack tips are 0.225"

- 0.225"(crack tip) + 0.3 (contact length) + 0.225" = 0.75" Conclusion Maximum crack offset can be 0.225" without increasing the crack area 12/2/97 28

Seth Texas Project Electric Generating station

  1. - Unit 2 Steam Generator 3. Volt Alternate Repair Criteria .

~

Conclusion - Bounding Leak Rate ,

The bounding SLB leak rate based on the IRB tests is 5.5 gpm

- Measured leak rates are adjusted to standard

. conditions utilizing the method of EPRI NP-7480-L, VI, App.B Standard SLB conditions 2560 psid pressure differential-615 F primary temperature

- 15 psia secondary pressure ,

Leak rate depends dominantly on the total crack length Leak rate dependence on offset length is not supported by the IRB tests for crack lengths including the limiting crack length Two cracks .vithin the TSP region do not significantly affect the leak rate

- Leak rate is doininated by the principal crack Tests on specimens with two crack showed that the secondary crack does not contribute to the leak rate until the tube is pressurized to the freespan burst pressure

- The added leak rate at this condition is minor

- Occurrence of critical duplicate cracks is extremely unlikely_

12/2/97 29 i

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South Texas Project Electric Generating Station U+

Concession - Allowable Crack Offset A minimum crack-to-TSP offset of 0.15" is supported by the IRB -

tests Throughwall offsets greater than 0.15 tested; throughwall length increased during test Margins above this value are demonstrated by the test

- Crack morphology: Throughwall length is less than total crack length

- Field crack length measurement: Total crack length is measured Acceptable crack-to-TSP offset of 0.217" is demonstrated by the IRB tests The maximum in-process measured offset was 0.208" Post-test fractography fixed the true offset at 0.217"

- Test in-process crack length measurement conservative; post-test destructive examination shows that actual cracks are longer Long cracks (> ~0.55") interact with the TSP to reduce available flow area and increase acceptable offset 9

- Calculated acceptable offset for limiting crack is 0.225"

- Cracks less than limiting crack have reduced leak rates 12/2/97 30

i

, - . South Texas Project Electric Generating Station .;

Unit 2 Steam Generator 3-Volt Alternate Repair Criteria i.

SG Internals Inspection Plan e

t I

. Q1erenfanNucwell.97somspection. ppt . - 120/97 s

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t South T xas Project Electric Generating Station

_ Unit 2 Steam Generator 3. Volt Alternate Repair Criteria SG Internals Inspection Plan Discussion Topics Objectives

Background

Secondary Side Access Recommended Inspection Plan i

Q1spexperewcWc t l.9750mspection. ppt 12/y97

South Texas Project Electric Generating Station Unit 2 Steam Generator 3-Volt Alternate Repair Criteria SG Internals Inspection Plan Objectives Demonstrate integrity ofload path within SG internals to limit TSP displacement TSPs TSP support bars and wedges

  • Stayrods Wrapper supports SG internals load path Stayrods and vertical support blocks are most imponant in limiting TSP displacement TSPs transmit the load to the surrounding support structures Degradation of base materials and welds due to SCC, corrosion, erosion, or fatigue is not considered likely 3

Qtspegarcwswell.97sCM; JaPPt 12/367

South Texas Project Electric Generating Station Unit 2 Steam Generator 3-Volt Altemate Repair Criteria oas rui,i w.w

\ =i LVerticalBar 3 o.

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  • V###/#/##/###/#A N TSP Wrapper /

Partition Plate i

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TSP Support Configurations Vertical Ba r Su pport S

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, South Texas Project Electiic Generating Station Unit 2 Steam Generator 3-Volt Alternate Repair Criteria 0.38" Fillet Weld 0.38" Fillet Wedge 0%%%%4 VNNVf/////NT//8W/dfNfdif//A

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\/ Wedges

\ Wrapper Note: Some locouans Have only Two Wedges

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(Not to Scale)

TSP Support Configurations Wedge Support 5

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} . South Texas Project Electric Generating Station Unit 2 Stearn Genentor 3-Volt Altemate Repair Criteria-

Background

Industry experience (domestic and foreign)

EDF type ofintemals degradation not reported in domestic plants No load path degradation reported in Westinghouse SGs without denting Westinghouse Owners Group SG Internals Degradation Program NEI recommendation for intemals inspection cunently being drafted Review of manufacturing records for Model E SG planned Benefit of type 405 SS vs. carbon steel TSPs TSP ligament erosion-corrosion and cracking are low wsceptibility events for stainless steel plates i . mited accessibility For Model E SGs Large percentage of openings located in preheater and below first TSP where most ODSCC indications have occurred Extensive in-bundle hut leg visual inspection is not practical due o geometry and tooling limitations Extent of secondary side visual inspection based on existing accessibility, risk of " sticking" visual probes, and radiation exposure Inspection method Eddy current and selective visual inspections Q:19esparc\nrcWell 97$0mspection prt In97

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) South Texas Project Electric Generating Station

. Unit 2 Steam Generator 3 Volt Alternate Repair Criteria Secondary Side Access Total of 20 secondary side openings exist in_each SG with 7 located in preheater and 11 located above or below flow distribution baffle (FDB)

Ognings for hot leg access

. Four - 2" inspection openings (0-1,0-2,0-3,0-4 ports)- located below FDB (Plate A)

. Four- 2" inspection / sludge lance openings (A-1, A-2, A-3, A-4 ports)-located above FDB Two - 6" (4.5" wrapper) handholes (A-5 and B-1 ports) - located on tubelane and above FDB One - 8.75" (1.875" wrapper) handhole (D-2 port) - located 90 degrees from tubelane and below first TSP (Plate C)

  • ^ Two - 16" secondary side manways (13 A and 13 B port).

Openings for preheater access One - 2" inspection / sludge lance opening (D-1 port) - located 40 degrees from feedwater nozzle and above preheater plate D.

Two - 2" inspection / sludge lance opening (E-1 and E-2 ports)-located 40 and 90

. degrees from feedwater nozzle and below preheater plate G.

One - 2" opening (G-1 port) - located 40 degrees from feedwater nozzle and below preheater plate H

+ One _- 6" (4.5") wrapper opening (G-2)- located 90 degrees from feedwater nozzle at preheater plate H.

One - 2" opening (H-1 port) - located 90 degrees frem feedwater nozzle and preheater plate K.

- l One - 8.75" (1.875" wrapper) handhole (D-3 port) - located 90 degrees from tubelane and below preh' eater plate D Q tapeaper*WrchesIl-9750merection. ppt iTyp7

0.

3 South Texas Project Electric Generating Station Unit 2 Steam Generator 3. Volt Altemate Repair Criteria Planned Internals Inspection at 2RE06 -

All steam generators Low frequency bobbin inspection of all TSP ligaments

- Plus Point confirmation,ifindication found by bobbin Visual inspection oflower FDB venical support bar welds in all four SGs Visual verification of wrapper alignment One steam generator Using the A-5 opening - below the first TSP (plate'C)

Inspect

- Hot leg vertical support bar welds below plate C and above FDB

- Wedge svelds below plate C and above FDB

- Stayrod spacers

- Patch plate plug welds

- Wrapper support block welds between wrapper and shell Bases forInspection Plan Low likelihood of TSP degradation with 405 SS plates No historical degradation of TSP support welds including Braidwood visual inspection Inspection of supports for first TSP which has largest number ofindications

- No basis to assume that susceptibility to potential weld degradation is dependent on location within the SG _

Utilization of existing SG access penetrations cup.x,.uwcwen.,7soi ,.ci; ,,i 8

i23s2-

,d-.

d South Texas Project Electric Generating Station Unit 2 Steam Generator 3 Volt Alternate Repair Criteria 165' + . Wedge

. . Back Up Bar -

148' 140'

, 127' Plate C 115' n 106*

r e Partition Plate 7

w. " " . . /

I i 84' s e i

74*

Plate B 65' s

40' 32' 15' Note: Plates B and C are not at Same Elevation:

They Are Shown Offset for Clarity

, Plates B / C Support Locations QtspexpercWehrcll 9750mspection. ppt I

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-, South Texas Project Electric Generating Station  ;

Unit 2 Steam Generator 3-Volt Alternate Repair Criteria 165*

a Back Up Bar .

+ - Wedge D Wedge Shim 140 Stayrod Locatios s (Unit 2 Only)  ;

\ 127'

- 115' 4

" 106*

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lJ e a

' 74*

E 65*

  • 53' 40'.

32' 15' Plate A Support Locations h

30 QWgersweWcil.97som.p.cgonpp e --r -m ,--m - -

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