ML13308B332

Meeting Presentation for November 4, 2013 Public Meeting Regarding Bmi Leakage

ML13308B332
Person / Time
Site:	Palo Verde
Issue date:	11/04/2013
From:	Arizona Public Service Co
To:	Jennivine Rankin Plant Licensing Branch IV
Rankin J
References
TAC MF2871, TAC MF2872, TAC MF2873
Download: ML13308B332 (54)

Text

Palo Verde Unit 3 Palo Verde Unit 3 Bottom Bottom-Mounted Instrument (BMI)

Mounted Instrument (BMI)

Bottom Bottom-Mounted Instrument (BMI)

Mounted Instrument (BMI)

Nozzle #3 Leak Nozzle #3 Leak November 4, 2013 November 4, 2013

Palo Verde Participants/Attendees Dwight Mims Senior Vice President Regulatory & Oversight Dwight Mims Senior Vice President, Regulatory & Oversight Jack Cadogan*

Vice President, Nuclear Engineering Ron Barnes*

Director, Nuclear Regulatory Affairs Ken House*

Director, Design Engineering Ken House Director, Design Engineering Mike McLaughlin Director, Technical Support Mark Fallon Director (acting), Palo Verde Communications Tom Weber*

Department Leader, Nuclear Regulatory Affairs Mike DiLorenzo Department Leader, Program Engineering Brian Cable Manager, Unit 3 Operations Doug Hansen*

Senior Consulting Engineer, Program Engineering / Principal Level III Ed Fernandez*

Senior Metallurgist, Engineering Programs / PWROG MSC Chairman Gene Montgomery Senior Engineer, Design Engineering (Mechanical NSSS)

Scott Bauer Regulatory Affairs Manager, STARS k

ld d

Dave Waskey Manager, Welding and Component Repair Design, Areva Doug Killian Technical Consultant, Areva Michael Lashley Associate, Structural Integrity Associates, Inc.

NOTE:

• identifies presenters 2

Agenda

• Discovery and Initial Response Ron Barnes

• NDE Action Plan and Results Doug Hansen

• Causal Evaluation Ed Fernandez Causal Evaluation Ed Fernandez

• Repair Plan Ken House

• Relief Request Tom Weber

• Closing Comments Jack Cadogan g

g 3

Desired Meeting Outcomes

• Awareness/understanding of:

Condition and current status

- Condition and current status

- Non-destructive examination (NDE) methodology and results gy

- Causal evaluation methodology, results to date

- Repair plan/technique

- Relief Request

• APS/Palo Verde understands NRC

/

l d

h questions/concerns related to this issue 4

Discovery and Initial Discovery and Initial

Response

Response Ron Barnes Di N

l R

l Aff i Director, Nuclear Regulatory Affairs

Unit 3 Reactor BMI N l

1. 3 Control Element Drive Mechanism BMI Nozzle #3 2010 2010 2013 2013 In-core Instrumentation Nozzles Nozzles 6

BMI Nozzles

• Fixed in-core instrumentation 61 t

ti

• 61 penetrations

• 3.0 outside diameter 0

i id di J-groove weld

• 0.75 inside diameter

• J-groove weld

• Alloy 600 nozzle material Reactor Vessel 7

Initial Response

• Event Notification (ENS) to NRC

• Response Teams established - tiered Response Teams established tiered approach

- Non-destructive Examination (NDE) Team to characterize flaw characterize flaw

- Engineering/Repair Team

- Project Management Team

- Causal Evaluation Team

• Communication Plan implemented Included NRC and industry stakeholders

- Included NRC and industry stakeholders

• Leveraged industry expertise/experience in all aspects of response 8

Decision Tree BMI Leak Identified BMI Leak Identified BMI Leak Identified BMI Leak Identified Inform NRC/ Industry I f ti l

Tree Characterize flaw UT/ECT in tube Informational helium test Weld indication of bubble (confirmed) 1 Axial flaw in tube OR OR A

AND AND Determine Perform Circumferential flaw in tube Consult industry 1

1 Repair and remnant analysis 10% expansion No flaw detected in tube boat sample location J-weld ECT Perform enhanced visual (VE)

Remove boat sample Confirmed Not Confirmed OR OR 4

4 2

0% e pa s o Flaw analysis of expansion AND AND J-weld ECT Enhanced Visual Go to axial Expand 100%

Flaw analysis of expansion A

2 OR OR Accept as is Repair as needed Repair OR OR Accept as is Repair as needed NOTES 1.

For characterized flaws, J-weld and a Boat Sample will be considered.

2.

If the EPRI demonstrations identify significant limitations, then expansion beyond 10 CFR 50.55a will be re-evaluated.

3.

Flaw evaluation and expansion are applicable to pressure boundary areas only.

4 A

d fi d b i

ti d

1 2

3 4

Accept as is Repair as needed 4.

As defined by inspection procedure.

4 9

Non Non--Destructive Destructive Examination (NDE)

Examination (NDE)

Examination (NDE)

Examination (NDE)

Action Plan and Results Action Plan and Results Doug Hansen S

i C

l i E

i P

E i

i Senior Consulting Engineer, Program Engineering Principal Level III

Bare Metal Visual Examination (VE)

• Examinations performed per Code Case N722-1 All 61 l

i d

• All 61 nozzles examined

• Nozzle #3 was the only one with leakage noted 11

Wastage Examination Nozzle #3 Results Nozzle #3 Results

• Phased Array Ultrasonic Testing C

d t d f th t id

- Conducted from the outside

- Adjacent to nozzle #3

- Focus on degradation (wastage) in the vessel Focus on degradation (wastage) in the vessel shell at the nozzle bore

• Examination demonstration:

- South Texas Project (STP) mock-up and technique

- All mock-up flaws were detected p

• Examination results:

- No indication of wastage was detected 12

Helium Bubble Test 13

Video Here Video Here 14

J-Groove Weld Eddy C

t T ti Current Testing

• On the decision tree

• On the decision tree

• Technology not available to place coil at the to place coil at the helium area 15

Ultrasonic & Eddy Current Testing

• Similar to reactor vessel closure head examinations examinations

• Conducted from the nozzle inside diameter

• Single probe with multiple techniques g

p p

q

• Techniques demonstrated at EPRI:

- TOFD (time of flight diffraction)

• Both axial and circumferential

- Additional techniques used:

• Inside diameter eddy current Inside diameter eddy current

• 45 degree shear-wave UT; looking down

• Zero degree UT; looking perpendicular to the surface 16

Ultrasonic Testing Demonstration (EPRI NDE Center)

(EPRI NDE Center)

• Mock-up design and f b i ti l

2013 fabrication early 2013 Flaw locations: inside and outside diameter and outside diameter Flaw orientations: axial, off angle, and circumferential

• Results: all flaws d t t d detected 17

Nozzle #3 TOFD Graphic 360 360 Degree slice Degree slice 360 360 Degree slice Degree slice Deepest 0.378 Deepest 0.378 Deepest 0.378 Deepest 0.378 Zoomed in to show

~0.4 of nozzle of 1.125 total thickness Zoomed in to show

~0.4 of nozzle of 1.125 total thickness Axial Indications Axial Indications Nozzle OD Nozzle OD Nozzle OD Nozzle OD Weld Weld Area Area Weld Weld Area Area 18

BMI Nozzle #3 Bubbles visually observed at 42 degrees 1

2 3

4 Deepest: 0.378 eepest 0 3 8 Longest: 1.88 Overall width: 72º (1.87) 19

Conclusions/Summary

• BMI nozzle #3 Only visual leaking nozzle

- Only visual leaking nozzle

- Helium validated leak location

- No inside diameter indications detected No inside diameter indications detected

- Multiple axial ultrasonic indications

• APS Principal Level III

• Two WesDyne Level IIIs

• WesDyne Chief Engineer

• EPRI independent reviewer EPRI independent reviewer

• All other nozzles (60)

- No unacceptable indications p

20

Causal Evaluation Causal Evaluation Causal Evaluation Causal Evaluation Ed Fernandez S

i M

ll i

E i

i P

Senior Metallurgist, Engineering Programs PWROG MSC Chairman

Causal Evaluation Team Composition Team Composition

• Station core team Station core team

- Consisting of station personnel and industry peers including Structural Integrity, Westinghouse and AREVA

• Industry groups PWROG M t i l S b itt (MSC)

- PWROG Materials Subcommittee (MSC)

- EPRI Material Reliability Program (MRP)

INPO

- INPO 22

Causal Evaluation Process Process

• Failure modes and effects analysis (FMEA)

Failure modes and effects analysis (FMEA)

- Palo Verde Corrective Action Program (CAP)

Cause Analysis Manual

- Reviewed and informed by EPRI MRP-206 Inspection and Evaluation Guidelines for Reactor Vessel Bottom-Mounted Nozzles along Reactor Vessel Bottom Mounted Nozzles along with Operating Experience lessons learned

- Developed a summary of potential causal factors based on input from EPRI, Westinghouse, AREVA, STP and Structural Integrity Associates Integrity Associates 23

Causal Evaluation FMEA Nozzle Leak Axial-Radial Weld or Butter Flaw Circ-Axial Weld or Butter Flaw RPV Surface Breaking Lack of Fusion ID/OD Axial Flow in Tube ID/OD Circ Flaw in Tube Off Water Chemistry C

diti i P t

Natural Circulation Inside the Nozzle T b Primary Water Environment Environmental Fatigue Primary Water Environment Volumetric Defects in Nozzle Tube from Matl Surface Defects in Nozzle Tube from Processing Alloy 600 Heat Treatment Tube Material Repairs Weld Repairs Startup Water Chemistry T-hot Functional Operating Conditions Conditions in Past Tube Weld hot Cracking and Other Weld Fabrication f

/

Surface Contaminants Lack of Weld Fusion Areas from b

Tube from Mat l Processing Processing Fabrication Treatment Grinding of Nozzle Tube or ld Nozzle Roll Straightening During Matl Nozzle Straightening After Cold Working p

R i I t i

Operational Impacts Previous Chemistry Excursions/

Contamination Mechanical Vibration Material Stress Environment Defects/

Contaminants Contaminants Fabrication Weld During Mat l Processing After Installation Resin Intrusions p

p of Rx Work 24

Probable Cause

• Probable cause

- Crack initiation was likely due to a weld defect exposed to primary water environment resulting in primary to primary water environment, resulting in primary water stress corrosion cracking (PWSCC)

• Probable causal factors Probable causal factors

- Material

• Alloy 600

• Near surface weld defect

- Stress

• Weld residual stress

• Weld repairs and grinding

- Environment

- Environment

• Primary water

• Temperature

• Operating environment 25

Causal Evaluation Additional Analyses Additional Analyses

• Collection of boat sample Collection of boat sample

• Sample content

- RCS leak entrance point RCS leak entrance point

- Weld defect

- Axial crack

- Area of high reflectivity

- Unaffected Alloy 600 and 182 t

i l material 26

BMI Nozzle #3 Bubbles visually observed at 42 degrees 1

2 3

4 Deepest: 0.378 eepest 0 3 8 Longest: 1.88 Overall width: 72º (1.87) 27

Boat Sample Dimensions 28

Causal Evaluation Boat Sample Boat Sample

• Metallurgical analysis and test plan Metallurgical analysis and test plan

- Visual inspections

- Liquid penetrant (PT)

- X-ray radiography

- High-resolution replication

- Scanning Electron Microscopy (SEM)

- Energy Dispersive Spectroscopy (EDS)

M t ll h

- Metallography 29

Conclusions/Summary

• The UT results are characteristic of PWSCC PWSCC

• The initiation likely occurred at a weld defect which was exposed to the primary defect which was exposed to the primary water environment resulting in PWSCC

• Boat sample removal and metallurgical Boat sample removal and metallurgical analysis and testing are planned 30

Repair Plan Repair Plan Repair Plan Repair Plan Ken House Director Design Engineering Director, Design Engineering

Repair Options Considered

• Half-nozzle repair selected Code compliant repair

- Code compliant repair

- Proven technology extensive industry experience p

- ALARA

- Permanent repair

• Other options considered:

E t l

h i

l l

- External mechanical plug

- Inner diameter temper bead (IDTB) repair 32

Half-Nozzle Repair Alloy 600 Alloy 600 182 Filler Temper Bead Pad 52M Filler Alloy 690 p

Temper Bead Pad 33

Extensive Mock-Up Preparation 34

Bore Machining Mock-Up 35

Temper Bead Pad Mock-Up 36

Weld Pad 37

Repair Timeline

• Commenced work: 10/27/2013 T

B d P d C l t 11/02/2013

• Temper-Bead Pad Complete: 11/02/2013

• Half-Nozzle Complete: 11/07/2013 38

Repair Analyses Corrosion Assessment ASME ASME Analyses 39

ASME Section III Class 1 Analysis

• Stress and fatigue analysis consistent with original reactor vessel design specification original reactor vessel design specification requirements

- Stress loads (normal/upset/emergency/faulted Stress loads (normal/upset/emergency/faulted conditions)

- Fatigue loads (thermal transient) 40

Corrosion Assessment

• Small gap between original Alloy 600 nozzle and new Alloy 690 nozzle will exist following and new Alloy 690 nozzle will exist following repair

• Low-alloy steel corrosion rate due to interaction with primary coolant in operating reactors has proven to be extremely small

• WCAP 15973 documents method for evaluating

• WCAP-15973 documents method for evaluating corrosion of low alloy steel following half-nozzle repairs

• Palo Verde plant-specific analyses are in progress, which follow the WCAP methodology 41

Remnant Analysis Remnant Analysis 42

Remnant Analysis for Relief Request

• Finite Element Analysis previously done for a representative Palo Verde BMI nozzle representative Palo Verde BMI nozzle configuration

- Pressure, thermal and residual stresses

• AREVA performed a fracture mechanics analysis on a postulated maximum remnant fl i

l di ti fl t

i f

flaw including conservative flaw extension for crack growth during one operating cycle

• Analysis demonstrates the weld flaw

• Analysis demonstrates the weld flaw maintains structural integrity and is acceptable 43

Summary/Conclusions

• Palo Verde implementing half-nozzle repair on Unit 3 nozzle #3 on Unit 3, nozzle #3 Code compliant repair Permanent repair backed by extensive Permanent repair backed by extensive industry experience Repair bounds probable cause(s)

• The remnant analyses support the relief request 44

Relief Request Relief Request Relief Request Relief Request Tom Weber Department Leader Nuclear Regulatory Affairs Department Leader, Nuclear Regulatory Affairs

Palo Verde Applicable ASME Codes

• Design Code for reactor vessel ASME III 1971 Edition Winter 1973 Addenda

- ASME III 1971 Edition, Winter 1973 Addenda

• Construction Code ASME III 1974 Edition Winter 1975 Addenda

- ASME III 1974 Edition, Winter 1975 Addenda

• Repairs/Replacements

- ASME XI 2001 Edition 2003 Addenda

- ASME XI 2001 Edition, 2003 Addenda

• Palo Verde 3rd ISI Interval

- Unit 1 thru 7-17-2018 Unit 1 thru 7 17 2018

- Unit 2 thru 3-17-2017

- Unit 3 thru 1-10-2018 46

Relief from ASME Code

• Two separate relief requests Restart analysis

- Restart analysis Duration of one operating cycle

- Long-term evaluation o g te e a uat o Detailed analysis including fatigue crack growth Operation beyond next operating cycle 47

Relief from ASME Code

• Removal of defects IWA 4421 Defects shall be removed or

- IWA 4421, Defects shall be removed or mitigated in accordance

- IWA 4422.1a, A defect is considered removed when it as been reduced to an acceptable size IWA 4422 1b Alt t l th d f t

l

- IWA 4422.1b, Alternately, the defect removal area and any remaining portion of the defect may be evaluated and the component accepted in accordance with the appropriate flaw evaluation provisions of Section XI 48

Relief from ASME Code

• Characterization of flaws in J-groove weld IWA 3100(a) Evaluation shall be made of flaws

- IWA 3100(a), Evaluation shall be made of flaws detected during an inservice examination as required by IWB-3000 for Class 1 pressure retaining components retaining components

- IWA 3300(b), Flaws shall be characterized in accordance with IWA-3310 through IWA-3390...

- IWA 3420, Each detected flaw or group of flaws shall be characterized by the rules of IWA-3300 to establish the dimensions of the flaws. These ab d

o o

a dimensions shall be used in conjunction with the acceptance standards of IWB-3500.

49

Relief from ASME Code

• Successive examinations IWB 2420(b) If a component is accepted for

- IWB 2420(b), If a component is accepted for continued service in accordance with IWB-3132.3 or IWB-3142.4, the areas containing flaws or relevant conditions shall be reexamined during the next three inspection periods listed in the schedule of the inspection periods listed in the schedule of the inspection program of IWB-2400 50

Proposed Alternative per 10 CFR 50 55a(a)(3)(i) 10 CFR 50.55a(a)(3)(i)

• Implement design repair on outside surface of Unit 3 reactor vessel

• Relocate pressure-retaining weld

• Analyze a postulated maximum flaw in remnant J-groove weld

• Duration of relief to be one operating cycle 51

Basis for Relief Request

• ASME Code compliant half-nozzle repair N

t h

l il bl f

• No technology available for characterization of flaws in J-groove weld

• Analysis of postulated maximum flaw

• Analysis of postulated maximum flaw demonstrates remnant flaw remains acceptable for one operating cycle acceptable for one operating cycle 52

Relief Request Summary

• Proposed alternative provides an acceptable level of quality and safety for acceptable level of quality and safety for the next operating cycle

• Separate ASME Relief Request to address Separate ASME Relief Request to address successive ASME Code examinations and operation beyond the next operating cycle p

y p

g y

53

Closing Comments Closing Comments Closing Comments Closing Comments Jack Cadogan Vice President Nuclear Engineering Vice President, Nuclear Engineering