BWR Instrument Penetration J-Groove Weld … the RPV vessel plates were manufactured by B&W, and fabrication of the RPV was initiated by B&W \ 縀㤀㘀㤀尩. The bottom head\ഠand

$Page 1: BWR Instrument Penetration J-Groove Weld … the RPV vessel plates were manufactured by B&W, and fabrication of the RPV was initiated by B&W \ 縀㤀㘀㤀尩. The bottom head\ഠand$
© 2016 Electric Power Research Institute, Inc. All rights reserved.

Bret FlesnerSr. Technical Leader, NDE Innovation

International Light Water Reactor Materials Reliability Conference and Exhibition

August 2016

BWR Instrument Penetration J-Groove Weld Examinations

NDE Development & On-site Examination Results

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

Contents

2012 N11B instrument nozzle eventN11B fabrication historyBWRVIP Inspection Focus Group actions

– NDE mock-up design and fabrication– Manual phased array technique developmentOn-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:

Presenter

Presentation Notes

A 2008 BWR instrument leak was identified during the hydro at a US BWR/4 plant, but that RPV was fabricated with set-in style instrument penetration nozzles. The leak was in the safe-end material as a result of an aggressive boring operation. The penetration tube was fabricated by butt-welding a SS forging to the instrument penetration tube. The forging was then bored in place, leaving higher residual stresses on the inside surface. The flaw was repaired using a weld overlay. INPO ICES#235051:


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

Presenter

Presentation Notes

All the RPV vessel plates were manufactured by B&W, and fabrication of the RPV was initiated by B&W (~1969). The bottom head and lower shell sections were sent to Rotterdam for completion while the upper sections were sent to CB&I for completion. Rotterdam installed the CRD stub tubes, shroud support plate, shroud support legs, etc., and then shipped the completed lower assembly to CB&I. CB&I joined the completed upper and lower assemblies. The CB&I / Rotterdam work was completed in 1970. What appears to be weld butter is actually the remnant portion of the original J-groove weld. This also made this weld joint much narrower than the others, providing less access for welding.


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 RPV

Inspected region

Un-inspected region

Presenter

Presentation Notes

The penetration tube material cannot be examined by scanning from the RPV surface because the air gap between the penetration tube and RPV bore hole prevent the ultrasonic energy from propagating into the tube material. Therefore the sound beams can only propagate into the tube material in the region where the J-groove weld is fused to the tube wall.


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

Presenter

Presentation Notes

The BWRVIP-IP-1 mockup also contains six flaws that initiate in the Alloy 82/182 J-groove weld and/or butter material. Of the six flaws, three are oriented axially (that is, radially), and three are oriented circumferentially. The depths of the flaws are approximately 1/3-t, 2/3-t, and 100% (that is, 3/3-t) in through-weld depth, with two flaws (one axial and one circumferential) for each of those depths. These six flaws are all manufactured fatigue cracks of known lengths and depth, and are similar to those implanted in the non-IGSCC austenitic and dissimilar metal piping weld ASME Section XI, Appendix VIII qualification specimens. Two of the flaws (one circumferential and one axial) propagate out the sides of the J-groove weld and into the low-alloy RPV material. Flaws that extend out the top of the J-groove weld material, and into the low-alloy RPV material, are represented in the BWRVIP H9 and BWRVIP H12 shroud support mockups, so this scenario was not included in the limited J-groove weld volume of the BWRVIP-IP-1 mockup. The penetration tubes contain a combined total of twelve EDM notches that were compressed shut using the hot isostatic pressing (HIP) method, creating alternative flaws as described in ASME Section XI, Appendix VIII, Supplement 10, Paragraph 2.3. Implanting actual cracks in the penetration tube material would require excavation of the base material that would be filled in with austenitic weld material, resulting in spurious reflectors surrounding each flaw that are not characteristic of service-induced flaws. The PWR vessel head specimen requirements listed in 10 CFR 50.55a were used a basis for the design inputs for the BWRVIP mockup, when applicable.


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

Presenter

Presentation Notes

Equipment used: Zetec OmniScan 32/128PR Same instrument qualified for RPV, weld overlay, DMW’s, etc. GE Inspection Technologies 32-element linear array Same probe and wedge combination qualified for examination of RPV welds


NDE Technique Development

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


NDE Technique Development

All J-groove weld flaws detectedSimilar 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

Presenter

Presentation Notes

This probe and wedge combination was originally optimized for H3 core shroud examinations, but the design was well suited for this supplemental examination. Since the probe contained 48-elements, the 64-channel Z-Scan PA UT instrument had to be utilized in lieu of the 32-channel OmniScan instrument. Technical Justification of Technique Lowest refracted angle 35° shear minimum Using shear wave angles lower than 35° would generate longitudinal waves within the component. Highest refracted angle* 50° shear This is the highest angle where it was still possible to obtain an electronic focal point within the near-field of the ultrasonic beam. Sector scan increment* 0.3° maximum This value was selected as it results in an approximate 1mm (0.04”) resolution in the area of interest surrounding the J-groove weld material. Electronic focal point* 209mm (8.2”) of “Half-path” This is the value required for the 40° examination angle to intersect the clad to base metal interface. This value results in the focal position of the 50° examination angle being located near the J-groove weld root. Optimized probe position* 155mm (6.2in) for penetration #1 and 158mm (6.2in) for penetration #2. Raster scanning is then performed over the surface necessary for the full sweep of 35° to 50° examination angles to interrogate the area of interest surrounding the J-groove weld material. These positions result in the 40° shear wave examination angle impinging on the clad-to-base metal interface near the J-groove weld toe while the 50° beam angle impinges near the J-groove weld root. Minimum time base* Start at 95mm (3.7in) “true depth” and extend for a range of 85mm (3.3in). This range encompasses the region beginning approximately 20mm (0.8in) above the J-groove weld root and extends to approximately 20mm (0.8in) beyond the clad to base material interface. Note: Variables marked with an asterisk (*) should be verified and optimized for instrument penetration configurations that are not contained within the BWRVIP mock-up inventory, provided beam intensity simulation results are similar to those that were obtained when modeling the BWRVIP mock-up geometry. For example, examination of instrument penetrations that penetrate RPV’s that are thinner than the BWRVIP mock-up will likely use a reduced focal point and reduced scan surface position while the sector scan would be comprised of examination angles beyond 50°.


NDE Technique Development (Supplemental Technique)

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 plots

Low-alloy RPV material

J-groove weld material


NDE Technique Development (Supplemental Technique) Circumferential scan

Low-alloy RPV material

J-groove weld material


NDE Technique DevelopmentDifficult to identify flaw

response located within “weld noise”

Easy to identify flaw response not located within “weld noise”

Primary detection technique

Presenter

Presentation Notes

When a flaw was detected with the primary longitudinal wave technique, a supplemental examination was performed in the region using this shear wave technique. The primary purpose is to identify if the flaw has propagated into the low-alloy RPV material. If a flaw is detected with the longitudinal wave technique, but is not detected with the shear wave technique, it is concluded that the flaw is wholly contained within the J-groove weld material. If the flaw is barely detected with the shear wave technique, and is located within the region of “weld noise” it is concluded that it is contained entirely within the J-groove weld material. If the flaw is easily detected with both probes, and the flaw “tip” propagates outside of the “weld noise”, it is concluded that the flaw has propagated into the low-alloy RPV material. This determination by observing the flaw “tip” location with respect to the “weld noise”, so there is no need to rely on imprecise manual UT plots.


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

Presenter

Presentation Notes

The inspection vendor developed their own examination procedure that utilized the basic inspection strategy developed by BWRVIP. The inspection vendor modified the technique so that it was compatible with their 16-channel GE-IT Phasor XS portable phased array instruments. The inspection vendor then demonstrated their procedure at EPRI using the same BWRVIP Instrument Penetration and Shroud Support H9 weld mock-ups that were utilized by BWRVIP/EPRI. At first, the utility and vendor tried to develop an automated UT examination procedure. After several attempts, it became clear that it was not practical to adapt the vendors automated piping scanner to this unique configuration. There was no time to design, fabricate, and test a custom purpose built scanner, so this manual UT inspection strategy was utilized.


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

Presenter

Presentation Notes

The planar flaw was identified at the approximate 3-o'clock location. Several embedded weld fabrication indications were also identified, most prominently at the 9-o’clock location. Only the indication identified at the 3-o’clock location exhibited the stacked pattern of responses that is typical of SCC-type flaws. The on-site examination was performed by the inspection vendor, but EPRI and the utility Level III personnel also scanned the penetration tube.


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

Presenter

Presentation Notes

Recommended further enhancements to supplemental technique: Search unit frequency 3.5MHz The desired outcome of this supplemental ultrasonic examination technique is to only detect portions of flaws that extend into the low-alloy RPV material, making it easier to determine if flaws detected with other techniques have actually propagated into the low-alloy RPV material. The 2.25MHz shear wave frequency utilized for the practical examination of the BWRVIP mock-up detected several flaws contained within the J-groove weld. Increasing the search unit frequency to 3.5 MHz increases sensitivity while reducing penetrating ability. As such, the 3.5MHz frequency should more adequately image the J-groove weld fusion line and should reduce the likelihood that flaws contained within the J-groove weld material are detected. Increasing the frequency to 3.5MHz also allows for the physical size of the probe to be reduced, improving the ability to maintain contact, because the increased frequency extends the near-field depth. Primary active aperture 37.4mm The 37.4mm primary aperture was required to achieve effective focusing capabilities with the 50° focal law utilizing the electronic focusing requirements (i.e. The 37.4mm aperture of the 3.5MHz frequency creates a near field length of 135mm in depth with the 50° focal law. The depth to the top of the inspection regions is approximately 134mm) Secondary active aperture 18mm Several secondary aperture values were evaluated using beam intensity simulations. The 18mm secondary aperture produces the most tightly focused beam in the inspection regions. Number of elements 32 The number of elements was reduced from 48 to 32 so that the search unit would be compatible with most manual phased array UT instruments; which typically are limited to 32 active element configurations. If an automated phased examination technique is to be utilized, increasing the number of elements as appropriate per the system capabilities should yield better results. Primary active pitch (center-to-center spacing of elements) 1.17mm This value was determined by dividing the optimized primary aperture by 32 so that the probe design would be compatible with most manual phased array UT instruments. If an automated phased examination technique is to be utilized, reducing the primary active pitch to ~0.62mm and increasing the number of elements to ~60, in order to maintain the optimized 37.4mm aperture, should result in optimized performance by reducing the severity of grating lobes at higher steering angles.


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/ProductAbstract.aspx?ProductId=000000003002003088

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/Pages/ProductAbstract.aspx?ProductId=000000003002005570

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=000000003002005571

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

Documents

BWR Instrument Penetration J-Groove Weld … the RPV vessel plates were manufactured by B&W, and fabrication of the RPV was initiated by B&W \ 縀 㤀㘀㤀尩. The bottom head\ഠand

BWR Instrument Penetration J-Groove Weld … the RPV vessel plates were manufactured by B&W, and fabrication of the RPV was initiated by B&W \ 縀㤀㘀㤀尩. The bottom head\ഠand