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6/5/03 31 Penetration #1 Weld Profile
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Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Page 1: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

6/5/03 31

Penetration #1 Weld Profile

Page 2: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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10.0

10.5

11.0

11.5

12.0

12.5

13.0

13.5

14.0

14.5

15.0

0 60 120 180 240 300 360

1 2 3 4 1a 2a 3a 9 10 11 12 13 14 15 16 17 Noz. End 1

STP / BMINozzle No. 1

Penetration #1 Leak Path

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Penetration #46 Axial Scan

Page 4: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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9.0

9.5

10.0

10.5

11.0

11.5

12.0

12.5

13.0

13.5

14.0

14.5

15.0

0 60 120 180 240 300 360

1 2 3 4 1a 2a 3a 9 10 11 12 13 14 15 16 17 Noz. End 1

STP / BMINozzle No. 46

Penetration #46 Leak Path

Page 5: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Penetration #34 Fabrication Discontinuity

Page 6: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Enhanced Visual

Page 7: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Penetration Overview

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Penetration #1 Visual

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Confirmatory Examinations

• Bobbin coil eddy current on penetration ID– Penetration #1 displayed a tube ID surface-breaking flaw– Penetration #46 displayed a tube ID sub-surface flaw– Two other reference penetrations displayed no flaws

• Array coil eddy current on J-Groove weld– Penetration 1, 46, 33 & 5 others scanned – No flaws identified

Page 10: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Eddy Current Probe Operation

• 18 coil array• X coil windings• 2 rows of 9 coils• 1.6” coverage

1 83 517

15 19

Probe Motion

12

34

5 7

6 89

1011

1213

14

15

16

17

18

J-Probe

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Eddy Current Probe

Page 12: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Eddy Current J-Groove Probe

Page 13: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Calibration Setup

Page 14: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

6/5/03 44

Penetration 33 J-Groove exam

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Additional Confirmatory Inspections and Tests

• Wastage UT (phased array)• Other

– Rod test– Bubble test– Profilometry– Visual of tube ID– Visual of vessel bore– Metallurgical sample – Boat sample

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Developing Technology to Identify Wastage

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CAUSE ANALYSISand STATUS

Steve ThomasManager, Plant Design

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What Was Found

• Residue on two nozzles

• Total of five flaws in the two nozzles

• One flaw in each nozzle provides a leak path– Only one flaw fully penetrated nozzle

• Three embedded flaws

• Discontinuities

• Grinding marks

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Other Observations

• No flaws in the 55* other nozzles

• No evidence of circumferential cracks

• No evidence of ID initiated cracks

* Penetration #31 will be examined during repair

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CoreDamage

Small-BreakLOCA

Large-BreakLOCA

Consequential Damage(Damage to Other BMI

Nozzles, etc.)

PreventControl Rod

Drop

NozzleEjection0.6" Hole

CladdingBlowout

Release ofNozzle Tube

Fragment

Circ Crack >~95%of Nozzle Cross

Section Near Rootof Weld

Wastage CavityUncovering

Large CladdingArea

Thru-Wall CircCrack 100%

Around NozzleAbove Weld

Intersecting Groupof Axial and CircThru-Wall Cracks

Above Weld

Significant HeadWastage in

Annulus, at Clad,or on Head

Surface

ASME CodeStressMargins

Exceeded

NozzleLeak

Initiation ofOD Circ CrackBelow Weld

Circ Crack Growthand Possibly

Coalescence ofMultiple Circs

Incipient HeadWastageDeep inAnnulus

Turning of Circ-Axial Weld

Flaw into Alloy600 Nozzle

Tube

Initiation ofDetectable ID

Circ FlawBelow Weld

Initiation ofDetectable ID

Axial Flaw

Initiation ofDetectable OD

Axial FlawAbove Weld

Initiation ofDetectable ID

Circ FlawAbove Weld

Initiation ofDetectable OD

Circ FlawAbove Weld

Very LargeLoss of Weld

BondBetween

Nozzle & Weld

Initiation ofDetectable

Circ-Axial Weldor Butter Flaw

Initiation ofDetectable Axial-

Radial Weld orButter Flaw

Growth/Coalescenceof Circ-AxialWeld Flaw

Growth/Coalescenceof Axial-Radial

Weld Flaw

Growth/Coalescence of ID

Axial Flaw (in Depthand PossiblyDownward)

Growth/Coalescence ofOD Axial Flaw

Downward

Growth/Coalescence of

Above WeldCirc Flaw

Head LowAlloy Steel

Rupture

Leakage fromRefueling Cavity

Above Head

Modified MRP Failure Modes and Effects Analysis for Reactor Vessel Heads

Large EarlyRelease Color Key:

L o wProbabilityNot Actionable

Actionable

Crack GrowthDriven by Stress

Corrosion Cracking

Crack GrowthDriven by

EnvironmentalFatigue

High CycleFatique

Fatigue fromNormal

OperatingTransients

High-CycleFatigue

Vibration onLower Nozzle

Flow InducedVibration

Number ofOutages and

Trips

WeldingResidualStresses

PressureStresses

FabricationResidualStresses

Nozzle RollStraighteningDuring Mat’lProcessing

Surface ColdWorking from

Machining

Sever UpperNozzle Tube

Section

Damage toBottomReactor

Vessel Area

Damage toFuel Pins

Damage toSteam

GeneratorTubes or

Tubesheet

Other LooseParts Damage

Pre-ExistingBoron Depositson Bottom Head

Surface

Growth/Coalescence

of Lack ofFusion Areas

Lack of WeldFusion Areas

fromFabrication

Alloy 600Sensitization

During MaterialProcessing

FabricationFlaws in the

VesselCladding

Grinding ofWeld During

HeadFabrication

Grinding ofNozzle Tube IDor OD During

Installation

Weld Hot Crackingand Other Weld

FabricationDefects/

Contaminants

SurfaceContaminants onNozzle Tube ID &OD During Install

NozzleStraightening

AfterInstallation

Surface Defectsin Nozzle Tube

from Processing/Fabrication

VolumetricDefects in

Nozzle Tubefrom Mat’l

Processing

Off WaterChemistry

Conditions inPast

Increase in Susceptibility to SCC Initiation for Alloy 600 Nozzle Tube

13

Increase in Susceptibility to SCCInitiation for 182 Weld and Buttering

A

Coalescence ofMultiple Flaws

B

B

ContainmentBuildingLeakage

A

C

C

ResinIntrusions

PreviousChemistry

Excursions/Contamination

Startup WaterChemistry (Hot

Functionals)

D

Aging Degradation

Accident Events

Boric Acid CorrosionRCS Leakage

Plant Operation

Loose Parts Release

Head FabricationPartial Nozzle

EjectionLimited by Collar

Damage toThimble Tube

E

EFlow Blockage

Accousticale f fec ts

Concentricity

Differentialcooling of

assym. weld

S4O6Tetrathionate

LocalMachining

DD

E

E

June 2, 2003

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PWSCC May Not Be the Cause

SBLOCA(Circumferential Cracking)

Vessel Wastage(Significant Leakage)

Loose Parts(Circumferential Cracking)

Nozzle Leak

PWSCC

WeldFabrication Flaw

(hot cracking)

ChemicalAnomaly

Nozzle AlloySensitization

Cold workingStraightening

FatigueFlow VibrationThermal Cycle

FabricationFlaw, Stress

Risers(Grinding, Weld Repair)

PotentialConsequences

CurrentCondition

CrackPropagation

InitiatingCondition)(

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Tube Coldworking Not a Likely Contributor

1976 Combustion Engineering Nuclear Fabrication Practice 101-3-0 states:

5.8.1 REMINDER: Use the bull’s eye level and alternate welds as necessary to insure alignment

5.8.4 Cold straighten, as necessary, all tubes which are out of alignment

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Page 24: Penetration #1 Weld Profile · Initiation of OD Circ Crack Below Weld Circ Crack Growth and Possibly Coalescence of Multiple Circs Incipient Head Wastage Deep in Annulus Turning of

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Analysis Shows Minimal Displacement During Welding