bwr instrument penetration j-groove weld examinations · 7 © 2016 electric power research...

© 2016 Electric Power Research Institute, Inc. All rights reserved.

Bret Flesner

Sr. Technical Leader, NDE Innovation

International Light Water Reactor Materials

Reliability Conference and Exhibition

August 2016

BWR Instrument Penetration

J-Groove Weld ExaminationsNDE Development & On-site

Examination Results

2© 2016 Electric Power Research Institute, Inc. All rights reserved.

Contents

2012 N11B instrument nozzle event

N11B fabrication history

BWRVIP Inspection Focus Group actions

– NDE mock-up design and fabrication

– Manual phased array technique development

On-site examination results


BWR Instrument Penetration Configurations

BWR Instrument Penetrations

– Penetrate the side of the RPV

– Partial penetration weld configurations

Alloy 600 with anti-ejection notch

Alloy 600 without anti-ejection notch

– 2012 leak

Stainless steel penetration tubes and weld

materials

Carbon steel penetration tubes with Alloy

82/182 weld material

– Also have some nozzle-to-shell weld style

instrument penetration configurations

Previous leaks associated with this configuration


Summary of N11B Event and

Fabrication Records Review


2012 leakage event

Minor leakage identified in 2012

– Post refueling outage system pressure

test (a.k.a. “the Hydro”)

Outage extended to perform ASME

Code repair

Fabrication records were reviewed

– Alloy 600 penetration tube

– Alloy 182 J-groove weld material

– Construction-era repair

First-of-a-kind leak in a US BWR

– Previous US BWR/4 instrument

penetration leak was located in a safe-

end, near a butt-weld

Repaired configuration:


Fabrication History & Construction-era Repair

RPV fabrication started by Babcock & Wilcox

(circa 1969)

N11B instrument penetration tube damaged

– Occurred sometime after RPV heat-

treatment

Chicago Bridge & Iron removed penetration

tube and most of the J-groove weld material

– 0.19-inch / 5mm (minimum) layer of

original J-groove weld material left in place

New Alloy 600 penetration tube installed with

new Alloy 182 J-groove weld (circa 1970)

– No subsequent heat treat of N11B J-

groove weld

– N11B is the only construction-era repair of

this type in the utilities fleet of 12 BWR’s


2012 ASME Code Repair

“Half-nozzle” repair performed in 2012

– Temper bead welding

– SCC resistant materials

Pressure boundary relocated to outside

surface of the RPV

Original J-groove weld left in place

Weld pad configuration provided the

necessary scan access for future

interrogation of the J-groove weld

– Ultrasonic examination techniques were not

available at time of discovery

– Weld pad was small enough to allow for

interrogation of J-groove weld material by

scanning from outside surface of RPVInspected region

Un-inspected region


BWRVIP NDE Development Activities


BWRVIP NDE Mock-up Fabrication (BWRVIP-IP-1)

BWRVIP surveyed BWRVIP member fleet

– Obtained nozzle configurations

Mock-up fabricated from a section of canceled

BWR/6 RPV material

– Fabrication complete early 2014

– Contains two BWR instrument penetrations

– Manufactured cracks located in J-groove weld

Two flaws propagate into low-alloy RPV material

Supplemented flaw population using existing H9

weld mock-ups

– Flaws contained with penetration tube material

– Contains one region of simulated erosion

Located on bore-hole surface


NDE Technique Development

Manual phased array technique from OD of RPV (inside drywell) developed late 2014

Large probe and wedge combination originally designed for H9 weld examinations

2.25MHz longitudinal wave 32-element array

7.04” focusing curvature to produce 0.25” focal spot in Alloy 82/182 H9 welds

Probe and wedge also qualified for RPV examinations in accordance with ASME Section XI, Appendix VIII, Supplements 4 & 6

– PDI-UT-12; “Procedure for Manual Phased Array Ultrasonic Examination of Reactor Vessel Welds”

– Detected all six flaws located in the J-groove welds

It was very difficult to verify flaw extent into the low-alloy RPV material



Inside surface geometry and “triple point” imaged in examination data

J-groove weld interface notimaged in longitudinal wave data– No visible landmark

of fusion line



All J-groove weld flaws detected

Similar responses between flaws contained within weld volume and those that propagated into low-alloy RPV material– Manual plotting of flaws

or flaw “tips” was not a reliable method of determining extent into low alloy RPV material


NDE Technique Development (Supplemental Technique)

Supplemental technique developed in 2015

Objectives:

– Develop a manual phased array technique to

supplement the primary flaw detection technique

– Increase sensitivity

– Image RPV to J-groove weld interface

– Reduce ability to detect flaws contained

within J-groove weld material

J-groove weld flaws readily detected

with primary technique

– Detect areas of potential erosion of the

bore hole surface

2.25MHz array coupled to shear wave

wedge



Austenitic J-groove weld material clearly imaged in UT data– Provides reliable “landmark” for positioning of flaws and flaw “tips”

– Flaws contained within J-groove weld material were not readily detected

– No need to rely on manual indication plotsLow-alloy RPV

material

J-groove weld

material



Circumferential scan


NDE Technique DevelopmentDifficult to identify flaw

response located

within “weld noise”

Easy to identify flaw

response not located

within “weld noise”

Primary

detection

technique


NDE Technique Development (video)


On-Site Examination


On-Site Examination

Inspection vendor contracted to perform an ultrasonic

examination

– Primary objective: verify no flaws are present in the low-alloy RPV

material surrounding the J-groove weld

– Secondary objective: Determine if flaw is located within J-groove

weld material (for BWR fleet knowledge)

Not identifying a flaw would be an indicator that the flaw is

contained within penetration tube material

Inspection vendor completed procedure demonstration at

EPRI during January & February 2016


On-Site Examination

One circumferential flaw reported along penetration tube to J-groove weld interface

– Extended from inside surface to “triple point” location

– Flaw location and size would create a leakage path to outside surface of RPV

– Flaw contained entirely within Alloy 182 weld material and/or Alloy 600 penetration tube material

Embedded weld-related fabrication flaws identified within J-groove weld material

– Not connected to inside surface

No indications were identified during the shear wave examination of the low-alloy RPV material

View from inside RPV,

looking out towards drywell


On-Site Examination

BWR N11B flaw Typical PWR CRDM flaw


On-Site Examination

BWRVIP mock-up flaw that propagates ~30% through J-groove weld

Suspected circumferential flaw in N11B that propagates 100% through J-groove weld

Reported flaw exhibits nearly identical ultrasonic characteristics as simulated SCC flaws in mock-up

Comparison between mock-up flaw and reported indication


Conclusions

The demonstrated examination procedure worked well– Geometric and metallurgical responses were nearly identical between

BWRVIP mock-up scan and on-site examination = Good on-site implementation

Planar flaw reported along Alloy 600 penetration tube – to – Alloy 182 J-groove weld interface– Relief request being prepared using the UT results as a basis coupled

with the Linear Elastic Fracture Mechanics (LEFM) analysis that projects 9 years between subsequent exams

Alloy 600 penetration tube material not examined, but identified J-groove weld flaw would create leakage path– Not possible to examine penetration tube material from OD of RPV

surface


Conclusions

MRP proposed further development of phased array

technique for PWR applications

– BMI penetration J-groove welds was selected for initial

development

– Probe will need to be smaller

– Recommend scanning canceled PWR bottom heads with PWR

optimized probe design before fabrication of NDE mock-ups


References

Mock-up fabrication and development of

initial flaw detection technique

– BWRVIP-282: BWR Vessel and Internals

Project, Nondestructive Evaluation

Development

2014. http://www.epri.com/abstracts/Pages/Pro

ductAbstract.aspx?ProductId=0000000030020

03088

Development of supplemental shear wave

technique

– BWRVIP-290: BWR Vessel and Internals

Project, Nondestructive Evaluation

Development 2015. EPRI, Palo Alto, CA: 2015.

3002005570. http://www.epri.com/abstracts/Pa

ges/ProductAbstract.aspx?ProductId=0000000

03002005570

NDE Mock-up information, including flaw

information

– BWRVIP-03 Revision 18, Section 14.14.1,

BWRVIP-IP-1

https://membercenter.epri.com/abstracts/Pages

/ProductAbstract.aspx?ProductId=0000000030

02005571

Inspection vendor demonstration

– BWRVIP letter 2016-034 (interim

documentation)

– Will be documented in BWRVIP-03 Revision 19

Summary of on-site examination

– Will be documented in 2016 NDE Development

Update

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000003002003088

http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000003002005570

https://membercenter.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000003002005571


BWR Instrument Penetration J-Groove Weld Examinations

Questions?

Bret Flesner ([email protected])

Jeff Landrum ([email protected]) BWRVIP Inspection Task Manager

mailto:[email protected]

mailto:[email protected]


Together…Shaping the Future of Electricity


Supporting Information: Bore Hole Examination

Ultrasonic examination of bore hole

surface

– Same probe and wedge combination as

supplemental shear wave examination

– Used a separate set of focal laws that

were focused along the bore hole surface



When no erosion is present:

– Probe directed straight towards bore

hole surface

Bore hole response forms straight

vertical line

– When probe is skewed side to side, the

bore hole response quickly diminishes



When erosion is present:

– Probe located adjacent to erosion,

while skewed towards eroded region

A bore hole response pattern appears

when skewed towards eroded area

Mid-point location is region of erosion



Probe directed straight towards bore

hole surface (erosion present)

– Probe positioned directly in line with

eroded region, and directed straight

towards bore hole surface

– A slight inwards shift of the bore hole

responses becomes visible

– The amount of inwards shift represents

amount of material that has eroded

Measured 0.161” (4.1mm) material loss

versus ~0.2” (5.1mm) actual

bwr instrument penetration j-groove weld examinations · 7 © 2016 electric power research...

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