nde inspections of the nru calandria vessel - part 1: nru

UNRESTRICTED/ILLIMITÉ

NDE Inspections of the NRU

Calandria Vessel

Part 1: NRU and ET Inspections

3rd International CANDU In-Service

Inspection and NDT in Canada

2010 June 14-17

Presenters: R. Lakhan & R.H. Lumsden

Overview

• First Presentation

–Overview of NRU

–Low-Resolution ET for Corrosion Assessment

–Hi-Resolution ET Scanning of Inside Vessel Surface

–ET Marking of Repair Locations

–ET Repair Inspection Technique

• Second Presentation

–Mk. I and II Inspection Tools

–UT Inspection Techniques

–Summary

UNRESTRICTED/ILLIMITÉ 2

Inspection Progression

• Heavy water leak discovered in May 2009

• Visual inspection in the annulus confirmed the leak

• Leak located 10 meters below the reactor deck

• Above bottom flange, which is welded to the vessel wall

• Access through 120 mm diameter reactor positions

• Reactor shutdown, de-fuelled, and partially drained in mid. June

• Seven inspection campaigns required to determine the vessel

condition and provide information for a repair strategy

• Combination of ET and UT


May

Combined

ET-UT

High

Resolution

ET

PA-UT

Wall

Thickness

UT

Vertical

Strips

UT

Below

Weld

ET

Marking

ET/UT

Repair

June July Aug. Sept. Oct. Nov. Dec.

Leak

Detected

What is NRU?


STANDBY MOTOR D.C.

HEAVY WATER PUMP

PUMP MOTOR A.C.

FUELING

MACHINE

NEUTRON BEAM HOLES

BOTTOM RING

THERMAL SHIELDS

FUEL RODS

SHELDING BLOCKS

CONCRETE SHELDING

DECK PLATE

THERMAL SHIELDS

ALUMINUM TANK

NEUTRON BEAM HOLES

WARM HEAVY WATER

HEAT EXCHANGER

PROCESS WATER

COOLED HEAVY WATER


Plan View of the NRU Reactor Vessel

Adjuster Rod

Isotope Production Sites

Fuel Rods

Blocked Sites

Control Rods

Dummy Rods

Flux Detectors

Vacant Sites

Experimental Irradiation Sites

Experimental Test Loops

Vessel Overview


Re-entrant

Cans

Through

Tubes3.5 m

Top-of-Reactor (TOR)

Reactor

Vessel

Leak

Site

10 m

Annulus

Material: Aluminum 5052, 8 mm Thick

Leak of the NRU Calandria Vessel


Heat Baffle

Lower Weld

Annulus

Leak Site

Inner Wall

Water

ReflectorVessel(D20)

Tapered Flange


ET Probe Design Approach

• All ET probes developed and manufactured in-house

• Transmit-Receive type probes used in all designs

• FEM Modelling used to design probes, optimize parameters,

and simulate signals of possible flaw types

• Two coil configurations used: G3 and G4

G4 mode

Scan

Direction

G3 mode

Scan

Direction

+ +T R

++

R

T

Combined ET-UT

• Vessel partially drained of heavy water

• Measurement of wall thickness and detection and sizing of corrosion

• Combined 3 T/R ET array and conventional UT head

• UT – Far Surface/ET – Near Surface

• ET Large Diameter Coils with Large Spacing

• ET Maximize Penetration (6-7 mm)

• ET monitored Lift-off for data quality (1 mm or less)

• UT probes from AFCIS

• UT 10 MHz, 9.5 mm Diameter

• Minimum thickness UT can reliably measure - 3 mm


May

Combined

ET-UT

High

Resolution

ET

PA-UT

Wall

Thickness

UT

Vertical

Strips

UT

Below

Weld

ET

Marking

ET/UT

Repair


Leak

Detected

UT

ET

Combined ET-UT

• Two methods chosen due to Aluminum Oxide/

Hydroxide layer on vessel wall

• Data acquisition and preliminary data analysis on TOR

• Very complementary ET confirming UT and vice versa

• Camera on separate tool inside the vessel for

guidance

• Limited visibility due to water in vessel and turbidity

• Required very close liaison with procurement,

manufacturing, designers, transportation, inspectors,

quality assurance, and operations.


May

Combined

ET-UT

High

Resolution

ET

PA-UT

Wall

Thickness

UT

Vertical

Strips

UT

Below

Weld

ET

Marking

ET/UT

Repair


Leak

Detected

Corrosion No Corrosion

ET Probe and Corrosion Signal


• Frequencies: 500 Hz, 2000 Hz, 4000 Hz, 10000 Hz

• Sizing curves developed for sizing wall thickness

Ch. 1 Ch. 2 Ch. 3

Ch. 1

Ch.2

Ch. 3

44 mm

UNRESTRICTED/ILLIMITÉ12

High Resolution ET Probe

• Re-inspects areas with external corrosion

• Inspection of near surface

• Accurately locate the leak site

• Frequencies: 2500, 5000, 7500, 15000 Hz

• Measuring wall thickness 4 mm or less

R01 R02 R03

R04 R05 R06 R07

T01 T02 T03

T05 T06 T07 T08

T04

Scan

Direction

56 mm

May

Combined

ET-UT

High

Resolution

ET

PA-UT

Wall

Thickness

UT

Vertical

Strips

UT

Below

Weld

ET

Marking

ET/UT

Repair


Leak

Detected


Hi-Resolution ET Signal of Leak Site

Leak Site

Comparison of Results:

Wall Thickness Map


May

Combined

ET-UT

High

Resolution

ET

PA-UT

Wall

Thickness

UT

Vertical

Strips

UT

Below

Weld

ET

Marking

ET/UT

Repair


Leak

Detected

High Resolution ETConventional UT

Leak Site


ET Marking Phase

• Inspect corroded areas and accurately mark flaw locations

• Complete 360 ET scanning of near surface

• Scanning direction: horizontal

• Frequencies: 2500, 5000, 7500, 15000 Hz

• Sizing curves for wall thickness 4 mm or less

• Using a mixture of amplitude and phase curves for sizing

• High frequency phase curves best for localized flaws

• 32-Coil Transmit-Receive Array Probe

May

Combined

ET-UT

High

Resolution

ET

PA-UT

Wall

Thickness

UT

Vertical

Strips

UT

Below

Weld

ET

Marking

ET/UT

Repair


Leak

Detected


32-Coil High Resolution Array Probe

G3 and G4 modes operate separately by changing adapters

Scan

Direction

1-R7

2-T8

3-R6

4-T7

5-R4

6-T6

7-R3

8-T5

9-R7

10-T8

11-R6

12-T7

13-R5

14-T6

15-R4

16-T5

1-T4

2-R8

3-T3

4-R5

5-T2

6-R2

7-T1

8-R1

9-T4

10-R3

11-T3

12-R2

13-T2

14-R1

15-T1

1R-R8

CFN02

CFN04

CFN06

CFN08

CFN10

CFN12

CFN14

CFN16

CFN18

CFN20

CFN22

CFN24

CFN26

CFN28

CFN30CFP29

CFP27

CFP25

CFP23

CFP21

CFP19

CFP17

CFP15

CFP13

CFP11

CFP09

CFP07

CFP05

CFP03

CFP01

1-T16

2-T15

3-T14

4-T13

5-T12

6-T11

7-T10

8-T9

9-T8

10-T7

11-T6

12-T5

13-T4

14-T3

15-T2

16-T1

1-R16

2-R15

3-R14

4-R13

5-R12

6-R11

7-R10

8-R9

9-R8

10-R7

11-R6

12-R5

13-R4

14-R3

15-R2

16-R1

G3 mode G4 mode

120 m

m

“The Brick”

Inspection Planning


Position Verification


LASERBaffle

Bolt Resolver: Horizontal Position

Encoder: Vertical Position

• Inspect region in a single pass

• Position probe and hold at the deepest flaw location

• Deploy tool to mark location

• Mark “wings” for visual clarity

• Marks used to position the welding electrode

Elevation Above

Taper Transition

Taper Transition

Mark Directly

Above Tmin▬ ● ▬

Marking of Repair Locations


Distance to Tmin

Marking In Vessel


Tool Arm

Nuclear

Grade Marker

Mark

Pneumatic Cylinder

Post Repair ET Probes

• ET for detection of surface-breaking flaws in repair

• Used as an alternative to liquid penetrant testing

• Based on X-Probe coil layout and operation

• Simultaneous operation of G3 and G4 modes

• Provides detectability to linear flaws in the transverse and

longitudinal directions, and volumetric flaws

• Smaller coils spacing to achieve higher resolution

• Higher frequencies to inspect surface only


May

Combined

ET-UT

High

Resolution

ET

PA-UT

Wall

Thickness

UT

Vertical

Strips

UT

Below

Weld

ET

Marking

ET/UT

Repair


Leak

Detected

UNRESTRICTED/ILLIMITÉ22

ET Post Repair Probes

• Frequencies: 7.5, 15, 25, 50 kHz

• External multiplexer located on the reactor deck

• Two probe variants: horizontal and vertical orientation

depending on weld bead direction

Scan

Direction

Scan

Direction

48 mm

Example Signals – EDM Notch Plate

• Signals obtained on Flat Plate

• EDM notches

–1.5, 2, 3 and 5 mm deep

–1.5, 3, and 10 mm long


ET Performance Demonstration Samples

• Weld overlay test sample

• EDM notches 0.5 to 3 mm deep, 3 to10 mm long

• All notches 0.125 mm wide

• Flaws on crown, in valleys and in heat affected zones

• ET technique for detecting flaws in crown and valleys



Example Signal – Qualification Sample

Signals obtained with Post Repair ET Probe

Fatigue Crack Samples


• Three fatigue crack specimens manufactured

• Only detectable with florescent PT, ET and UT

• Each sample contained 14 cracks

• Two specimens destructively analysed

• 6 to 16 mm long

• 2 to 5 mm deep

Example Data – Mock-up Sample


G4 Mode

G3 Modewww.nrucanada.ca

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nde inspections of the nru calandria vessel - part 1: nru

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