ML042050076

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Presentation of 07/20/04 Meeting with Arizona Public Service, Palo Verde Regarding ASME Relief Requests and Order Relaxation
ML042050076
Person / Time
Site: Palo Verde  Arizona Public Service icon.png
Issue date: 07/20/2004
From: Winsor M
Arizona Public Service Co
To:
Office of Nuclear Reactor Regulation
pham b m, nrr dlpm lpdiv-2, 301-415-8450
Shared Package
ML042260388 List:
References
EA-03-009
Download: ML042050076 (75)
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Text

APS/NRC Meeting July 20 2004 y,.

Discussion of A600 Repair/inspection issues and associated relief requests Mike Winsor Director, Nuclear Engineering Arizona Public Service Co

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Purpose Discuss CE plant alliance efforts to develop a methodology for replacement of pressurizer heater sleeves and provide information to the NRC on needed relief requests.

Provide additional information on Palo Verde RR

  1. 25 "Palo Verde CEDM inspection" Provide additional information on Palo Verde RR
  1. 24 "Removal of RV head vent orifice"

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Agenda Background and Alliance Efforts - Mike Winsor Overview of A600 Replacement Program Pressurizer heater sleeve repairlreplacement history Cooperative efforts between APS, Entergy, and SCE to develop a mid-wall heater sleeve replacement option Pressurizer Modification using the Mid Wall technique Rex Meeden Palo Verde CEDM Nozzle Inspection RR #25 Mike Melton Palo Verde Reactor Head Vent Orifice Relocation Mark Radspinner

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Palo Verde A600 Replacement Program Aggressive and Systematic Replacement Program based on relative susceptibility (temperature and yield strength)

  • Initiated Replacement Program in Fall 1991 with Unit 2 Hot Leg Instrument Nozzles (75 ksi Yield Strength)

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AGOG Nozzle Replacements A600 Nozzle ReplacerncnLs Nozzle Location U of Completion Date Nozzles/Unit Pressurizer Instri-ument Nozzles 7

Unit I SprinEg 1992 7

Unit 3 Full 1992

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_Unkit 2 Sprwiag 1993 H-lot Lc-Instrument/Sampliniig Unit 2 Fall 1991 No__

___s tI Un 2 Fall 2000 9

Unt~l 3 ) Fall 2001) 9 9 Unit I Spliln 2001 I-lot Legr Spare R1D Nozzles }

8 Unit 2 Fall 2000 8

Unit I *Spriz 12)001

____________________________8 U11L SFall 2001 I-lot Leg Inservicc WTD 10 Unit. I Fall 2002 Nozzles

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[it 3 Sprina 20030 10 Unit 2 Scheduled lor Completion Spring 2005 Pressurizer Heater Sleeves

-36 Unit 2 Fall 2003 36 Unlit 3 SCI1CCILIIeCI lbr Completion Fall 2004

_ _ _ __ 36 nllt I SCh1duleCd f1br Completion Fall 2005 Red indicates I-lf-tnozzle Rcpairs. Black indicates Full Nozzle (no remnant) Repairs

A600 Nozzle Replacements

  • Replacement of Unit I Pressurizer Heater Sleeves scheduled for Fall 2005 will complete nozzle L

replacement plan for all A600 nozzles/penetrations at Hot Leg Temperature or above

  • Strategically plan for upper head replacement and dissimilar butt weld examinations and mitigation techniques

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Palo Verde Pzr Heater Sleeve Repair/Replacement Program Pressurizer heater sleeve status Unit 2 completed replacement in Fall 2003 using pad repair

  • 36 day installation duration
  • 32 REM installation dose Original schedule for Palo Verde heater sleeve replacement Unit 1 scheduled for Fall 2005 Unit 3 scheduled for Fall 2007 It..

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Alliance Efforts to Address PZR Heater Sleeves Arizona Public Service Co., Entergy Nuclear Inc.,

and Southern California Edison Co., agreement to support development of a mid-wall heater sleeve replacement technique

  • Develop a common replacement technique to leverage licensing, developmental, training, and tooling costs
  • Welding Services Inc and Structural Integrity to provide technical and field services
  • Began in spring of 2004 following Palo Verde U3 February SNO outage l,

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Pressurizer Heater Sleeve Replacement Schedule

  • Palo Verde will be the lead plant with its 3R1 1 Fall 2004 outage and U1R12 Fall 2005 outage
  • Waterford 3 Spring 2005

Palo Verde Unit 1 and 3 Pressurizer Heater Sleeve Repair And Remnant Sleeve Flaw Evaluation NRC Presentation Rex Meeden July 20, 2004

Pressurizer Heater Sleeve Repair Agenda

  • Pro-Active Strategy
  • Pad Repair
  • Midwall Repair

- Concept

- Relief Requests #28

- Design and Analysis

- Tooling

&#29 (Rex Meeden)

(Rex Meeden)

(Dick Mattson)

(Pedro Amador)

(Pedro Amador)

(Michael Lashley)

(Pete Riccardella) its jr.

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- Welding Development

- NDE Program

- Triple Point Flaw Evaluation

  • Conclusions

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Pressurizer Heater Sleeve Original Strategy

  • February 2004: Implement pad repair during replacement steam generator outages Unit 2 - pad repair complete fall 2003 Unit I -fall 2005

- Unit3-fall 2007

  • MNSA contingency

- 2 Mechanical Nozzle Seal Assemblies (MNSAs) installed, U3RIO (Spring 2003)

- Relief Request #17 granted 2 cycles of operation

  • Plan supported by failure rate analysis

- Yield strength of material Industry experience

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Pressurizer Heater Sleeve Revised Strategy

  • March 2004 - Unit 3 forced outage

- BMV identified 1 leaking heater sleeve nstalled MNSA - third MNSA in unit 3

- Radiological exposure of 3 REM Management decision to accelerate unit 3 repair from fall 2007 to fall 2004

- Planned repair of 36 heater sleeves

- Remove 3 MNSAs

- No need to exercise 2nd cycle of operation granted in-RR #17

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Pressurizer Heater Sleeve Repair Pad Repair iE ORIGINAL

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ATTACHMENT 4.31' WELDS v

ALLOY 600 SLEEVE w;5Ad-,

Pressurizer Heater Sleeve Repair Pad Repair

Pressurizer Heater Sleeve Repair Pad Repair

  • Unique concentric ring configuration favors rectangular pad e Installation dose - 32 REM
  • Installation duration - approximately 36 days
  • Other utilities likely to incur more dose due to different sleeve configuration

Pressurizer Heater Sleeve Repair Midwall Repair

Pressurizer Heater Sleeve Repair Midwall Repair ORIGINAL ATTACHMENT ORIGINAL ALLOY 600 SLEEVE ALLOY 600 OVERLAY REPAIR ALLOY 690 SLEEVE 2.375' LOW ALLOY STEEL HEAD

Midwall Sleeve Repair

  • Relatively small weld volume, effective throat increased
  • Extensive welding development program conducted
  • Qualified NDE procedure to support repair
  • Projected installation dose - 23.5 vs. 32 REM

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0 Projected installation duration -20 vs. 36 days

  • 8.5 REM savings/PV Unit (2 Units to do)
  • Potential savings for 5 CE alliance Units REM approximately 50

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Pressurizer Heater Sleeve Repair Relief Request #28

  • Ambient temperature temper bead versus preheat/post weld soak temper bead welding.
  • Ultrasonic examination in place of radiography required by section Xl ('92 Edition '92 Addenda)
  • Liquid penetrant examination of midwall weld area prior to welding and final weld surface/heat affected zone after welding
  • Relief Request #28 is similar to Relief Request #23 (previously approved for Unit 2 pad repair)
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Pressurizer Heater Sleeve Repair Relief Request #29

  • Leave postulated flaws in remnant sleeve and J-Weld w/o full characterization or successive examinations a Section Xl flaw evaluation complete; worst case flaw modeled Linear elastic fracture mechanics (LEFM) and elastic plastic fracture mechanics (EPFM) utilized EPFM precedence established by Entergy for reactor head
  • Corrosion analysis

- WCAP-15973-P Rev.1 demonstrates that the limiting CE plant lifetime following half sleeve repair isl 94 years 1 4 1 ff M,

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ASME Code Evaluations

  • ASME Code, Section Xl evaluations-

@ Elastic-Plastic Fracture Mechanics evaluations

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Pressurizer Heater Sleeve Mid-wall ReDair ConceDt

Section III Evaluations

  • Load Definition

- Original design basis (pressure/thermal transients)

  • Stress Analysis

- Three-dimensional finite element analysis

- 900 model with appropriate boundary conditions

  • Section III Evaluations

- Stress criteria

- Fatigue evaluation (60 years of extrapolated 40 year cycles) i

- Attachment mid-wall weld is the controlling location

Finite Element Model

Section Xl Evaluations Postulated axial flaw in sleeve, overlay, and J-groove weld

  • Stresses extracted from Section III analyses
  • Linear elastic fracture mechanics (LEFM) techniques utilized
  • Residual stress analyses for similar plant
  • Fatigue crack growth analyses
  • Limited life based upon LEFM analyses
  • Acceptability to end-of-life (including 20 year license renewal period) demonstrated utilizing elastic-plastic fracture mechanics (EPFM) techniques
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Fracture Mechanics Finite Element Model

Basis for EPFM Approach

  • Controlling transients occur at operating temperature

- Well above upper shelf on Charpy impact energy curve

- Pressurizer material possesses considerable ductility in this regime EPFM is the more appropriate technology for ductile materials (such as the Palo Verde pressurizer at upper shelf)

  • Ample precedent exists in ASME Code, Section Xl for the use of EPFM and appropriate treatment of safety factors

- Appendix C for Flaws in Austenitic Piping

- Appendix H for Flaws in Ferritic Piping

- Appendix K for Assessment of RPVs with Low Upper Shelf Toughness

  • These code appendices all specify reduced safety factors (SFs) for secondary (strain controlled) loading conditions, and permit EPFM instability analysis ak\\\\IL

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ASME Code Evaluation Conclusions

  • Proposed mid-wall repair concept is acceptable because:

Design meets ASME Code,Section III criteria Remaining postulated defect in Alloy 600 material is acceptable for life of plant plus life extension CR~r w 1

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Sequential Repair Procedure

-WSI Nozzle Severing Tool

-Depth of cut selected to fin.

maxinize weld area work envelope I

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ID Sever Tool with Articulating Arm

Sequential Repair Procedure SMANDREL CLAMP I nstallati o POSITIONING COLLAR -O O

a Positioning Collar L.o cates A\\xia Illy

- Self Ce nte ri ng Feat ure L ocate s'

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Radially Tool Extends through the first Heater Tray INSTALLATION TOOL

Sequential Repair Procedure

Sequential Repair Procedure

  • SSAT with Replacement is, Sleeve and Ai gnment Shaft Pilhated in
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Internal Alignment Tool

Sequential Repair Procedure Sleeve External Alignment Tool

-Shims instaclled Clamping Device Installed

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Tool is Mvandirel or 0OD Mounted

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Zero Force Clamp Installation

Sequential Repair Procedure

  • Mid-Wall Weld Head Front-End

-Video

-Wire Feed Inert Gas Delivery

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Sequential Repair Procedure

Sequential Repair Procedure

- Water Cooled Copper Front End Piece after Machining

- Core component of torch assembly

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Sequential Repair Procedure

  • As Welded.

Configuration layers and 118" weld deposit M\\1i n imaI b uild -u p beyond sleeve t

wall thickness

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Sequential Repair Procedure

  • Post Weld Clean-Up G rind/abrade surface of weld to:
  • Remove any build-up beyond bore ID I 11 Prepare weld surface for final NDE I.....

Sequential Repair Procedure

Sequential Repair Procedure

PZR "Bazooka" Mockup

PZR "Bazooka" Mockup W.

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Welding Development Program Extensive welding development program conducted to address potential triple point!

welding solidification anomaly

- Over 13 weld samples produced to date

-Triple point cross sections examined at high magnification

- Welding parameters refined & improved

  • Demonstrated ability to repeatedly produce defect-free welds with no solidification anomalies at the weld root

Early Sample with Cracking at Weld Root (50x)

Recent Weld Sample (50x)

(Typical of 6 production welds produced)

A-690 Tube A-2

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Weld Process Conclusions

  • OE and initial shop trials produced cracks at weld root
  • Further process variable changes were able to reliably resolve the "triple point" issue
  • Process has been refined to produce reliable and repeatable high quality welds

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Mid-Wall Repair NDE

  • PVNGS is committed to the '92 Edition/'92 Addenda of ASME Code, Section Xl
  • IWA-4170(b) requires repairs and replacements to be performed in accordance with the Construction Code, or all or part of later editions and addenda thereof, and code cases
  • Weld to be examined per Section 111 NB-5000, guidance to be taken from N-638-0

- PT of pressurizer bore before welding

- Final PT of weld surface and adjacent base metal

- Volumetric examination with straight beam and angle beam transducers

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Midwall Repair NDE Surface Examination

- PT examination prior to welding to ensure surface is free of defects Final PT examination of weld surface and adjacent base metal

  • Volumetric Examination

- Straight beam examination to a depth of 0.25" Surface of weld and adjacent heater sleeve to ensure no lack of bond or lack of fusion and to detect any reflectors that could interfere with the angle beam examination

- Angle beam examination to a depth of 0.25"

  • Scanning looking in both direction for axial reflectors
  • Scanning looking in both direction for circumferential reflectors

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Mid-Wall Repair NDE Demonstration of Midwall Repair NDE Volumetric Examination

  • Straight beam examination

- Welded mockup with flat bottom holes

  • Angle beam examination

- Welded mockup with OD/ID circumferential and axial EDM notches and end drilled holes

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NDE of OD Axial EDM Notched Sleeve

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NDE of OD Circumferential EDM Notched Sleeve I_:7MMIMM

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NDE of ID Circumferential EDM Notched Sleeve

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Pressurizer Mid-Wall Repair UT Inspection Coverage 0.25" 0.25" 0.25"

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Pressurizer Heater Sleeve Repair Midwall Repair NDE Timeline Completed Items Review applicable codes and standards to define inspection requirements Design and fabricate calibration standard and preliminary test samples Design/build/test development scanner Design, procure, and machine prototype probes/heads/wedges Perform preliminary examination on test samples Scheduled Items Design and fabricate final demonstration blocks - 7/30 Perform technique demonstration - 8/5 and 8/6 Finalize NDE procedure - 8/17 Compile demonstration package and procedure qualification - 8/20 NDE personnel training - 8/23

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Mid-Wall Repair NDE NDE meets applicable ASME Code requirements (Section Xl, 111, and V) j X Technique will be Demonstrated on a Mid-wall Welded Mockup

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Triple Point Flaw Evaluation

  • Although triple point flaws not expected, ASME Section Xl applied to establish NDE detection and acceptance criteria, considering:

Flaw Acceptance Standards (IWB-3500)

Fracture Mechanics Flaw Evaluation Criteria (IWB-3600)

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ASME Section Xl Allowable Flaw Standards Allowable flaw sizes in accordance with Section Xi Pre-service Inspection Standards IWB-3514.3, Austenitic Piping IWB-3514.4, Dissimilar Metal Welds

  • Established for Paths 1 and 2 (see Figure)
  • Applicable to austenitic piping, including wrought stainless and Ni-Cr-Fe piping material and associated weldments
  • If no indications are detected that exceed these limits:

welds are considered clean in accordance with ASME Section Xl, IWB-3112, and no successive examinations, in accordance with ASME Section Xl, IWB-2420 are required

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Triple Point Flaw Evaluation Paths

ASME Section Xl Fracture Mechanics Flaw Evaluation Employ Fracture Mechanics principles to determine crack growth rates and end of life allowable flaw sizes Strictly applicable only to Inservice (not Pre-service) Inspections t

When employed, introduce requirement for successive examinations per IWB-2420

  • Applied to mid-wall triple point evaluation to demonstrate conservatism of Section Xl Standards

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Evaluation Results for Postulated Path I Flaw 0.120 0.100 0.080 C) a)

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- Sec. Xi Standards Crack Growth; a-init=0.05

-Crack Growth; a-init=0.095 M -

Sec. Xl Allowable (End of Eval.Period)

F'1 Detectability range (0.010" to 0.01 5") for

. circumferential triple point cracks 0.000 0

10 20 30 Operating Time (yrs.)

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Evaluation Results for Postulated Path 2 Flaw 0.400 U

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Sec.XI Standards

-Crack Growth; a-init=0.09

-Crack Growth; a-init=0.26 I

Sec. Xl Allowable (End of Eval.Period) 1-I t...

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I Detectability range (0.040" to 0.050") for laminar-type triple point cracks I

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10 20 30 40 50 Operating Time (yrs.)

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Summary of Triple Point Flaw Evaluation Results Postulated Allowable Flaw Sizes Allowable Flaw Sizes Flaw per Section XI per Fracture Mechanics Evaluation Location Standards Initial Flaw Size*

End-of-Evaluation Period Path 1 0.0166" 0.095" 0.112" Path 2 0.0522 0.26" 0.36" IX1 i"

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  • Approximate flaw size that would Allowable in sixty years.

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Pressurizer Heater Sleeve Repair Conclusions

  • Midwall repair requires less machining and significantly less welding than pad repair
  • Palo Verde would save 8.5 REM per unit by*

implementing the midwall repair in lieu of the pad repair

  • Other utilities would likely incur more dose than Palo Verde by implementing pad repair due to sleeve configuration JAr F-, SSeY,xc a-H L

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Pressurizer Heater Sleeve Repair Conclusions Cont'd Requesting relief to utilize GTAW ambient temperature temper bead process for midwall repair (RR28)

Requesting relief to leave the postulated flaw in place wlo full characterization and successive exams (RR29)

Requesting relief to utilize EPFM for flaw evaluation

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Pressurizer Heater Sleeve Repair Conclusions Cont'd X Successive volumetric examinations in addition to Section Xl/NRCB 2004-01 exams are not required

- Qualified welds

- ASME flaw margin demonstrated

  • Successive volumetric examinations would eliminate CE alliance dose reduction' benefit
  • NRC concurrence needed to support Unit 3 fall 2004 outage IV1 P;,4

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. 1s Relaxation Request Non 25 on Inspection Coverage for Palo Verde Unit I NRC Presentation Mike Melton July 20, 2004

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Background===

  • Arizona Public Service Company (APS) requested relaxation from the requirements of first revised order EA-03-009, section IV.C.(5)(b).
  • The NRC requested analysis be performed to substantiate inspection coverage below the weld for Unit 1 CEDM Nozzles 84, 87 and 93 were acceptable.
  • APS has completed an additional finite element analysis (FEA) of CEDM Nozzles 84, 87 and 93 using the as-built J-weld configuration for these nozzles.
  • APS recently submitted revised analysis

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Actual Inspection Coverage Proposed 00Dsane O

Distance Inspection DDitne Covered by Penetration Nozzle Angle Coverage in Covered by PT Below No.

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Relaxation UT Below Weld Request Weld 84 35.7 0.40" 0.28" 1.0 "

87 51.5 0.35" 0.20" 0.8" i

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AsBuilt J-Weld Configuration (penetration No. 84, 87 and 93)

L = As-Built J-Weld Heights Nozzle 84 = 2.24"

.19' UIN R INSPECTION AREA Nozzle 87 = 2.62" Nozzle 93 = 1.76" SEE OETAIL 'G6 UNINSPECTED AREA CHAMfER FACE -

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ZERO POINT PLUG MELO TYPICAL PENETRATION NO'S I ETAIL "G" D

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Revised Stress Analysis

  • Hoop stress distribution for as-built J-weld configuration I
  • Methodology same as discussed in relaxation request (letter 102-05075-CDM/SAB/RJR, dated March 19, 2004.)
  • Accounted for instrumentation measurement uncertainty
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Crack Growth Calculation

  • For the three penetrations with incomplete coverage, a through-wall axial flaw was postulated
  • The upper end of the flaw was located at the location where inspection coverage stopped L
  • The lower end of the flaw was located where the stresses dropped to zero
  • Maximum stresses anywhere along the crack were used to calculate the stress Intensity factor
  • Crack growth model of MRP-55 used 4

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Conclusions

  • No crack growth below the weld for any undetected flaws in penetration No. 84,87 and 93
  • Undetected flaws will not reach weld bottom before next inspection
  • Provides an acceptable level of quality and safety for a full operation cycle ldlx = ;

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Follow-up Requested

  • APS has submitted the analysis and revised table for Unit 1 to support a full cycle of operation

- Currently under 7.7 month limited operation

  • The relaxation for Unit 3 CEDM inspection coverage was previously submitted and needs NRC approval for the 2004 fall outage

- Outage start October, 2004 I I ~-y:t7 I

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Reactor Vessel Head Vent Line Orifice Relocation I

j NRC Presentation Mark Radspinner July 20, 2004

Relief Request 24

  • APS requested relief from Order requirement IV.C.(1 )(b) for the head vent line nozzle with integral orifice

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- UT of each nozzle ID and an assessment to determine if leakage has occurred into the interference fit zone OR

- ET or PT of wetted surface

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Vent Line and Orifice

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Vent Line Orifice

+ NUREG 0737 Item II.B.1 Requirement

- Remotely operated RCS vent system

- Stipulated must not lead to an unacceptable increase in the probability of a LOCA

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  • Meet 1 OCFR50.46 acceptance General Design Criteria criteria and

- Palo Verde construction status allowed optimal orifice location

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Vent Line and Orifice 0 X 1./

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Relief Request 24

  • Proposed alternative of surface exam of vent nozzle J-groove weld and orifice attachment weld
  • Combined with IV.C.(1 )(a)-required bare I metal visual exam, felt to provide acceptable level of quality and safety
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NRC SER

  • Relief granted for one cycle, Unit 1 only, in recognition of magnitude of radiation 1

exposure (hardship) that would be incurred considering lack of developed tooling and methods to remove orifice

Unit 3 Preparation Status Developing remote tooling for orifice removal

. Developing orifice relocation package

- ASME Code Class Break reconciliation

  • Will require PT of one existing butt weld to meet Class 1 requirements

- Design and licensing basis reconciliation

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Orifice Relocation CZ

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1IOCFR5O.59

+ Meets NUREG 0737 Requirements

+ Meets GDC Requirements

+ No/minimal increase in frequency of occurrence or consequences of accident or malfunction

Expectation

  • Full compliance with Order requirements
  • Developed methods and tooling to minimize radiation exposure (basis for granting of Relief Request)

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