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CA0000274

AECL-12026

AECL Experience in Fuel Channel Inspection

Experience d'EACL en inspection des canauxde combustible

G. Van Drunen, R. Gunn, W.R. Mayo, D.A. Scott

June 1999 juin

AECL

AECL EXPERIENCE IN FUEL CHANNEL INSPECTION

by

G. Van Drunen, R. Gunn, W.R. Mayo and D.A. Scott

Components & Systems DivisionNondestructive Testing Development Branch

Chalk River LaboratoriesChalk River, ON KOJ 1 JO

1999 June

Paper presented by H. Wong at 5th COG/IAEA Technical Committee Meeting on Operational Safety Experience ofPressurized Heavy Water Reactors. Mangalia, Romania, 1998 September 6-10.

AECL-12026

A> AECL EACLEXPÉRIENCE D'EACL EN INSPECTION DES CANAUX DE COMBUSTIBLE

par

G. Van Drunen*, R. Gunn**, W.R. Mayo* et D.A. Scott **

RÉSUMÉ

L'inspection des canaux de combustible (CC) du réacteur CANDU est effectuée pour s'assurer de l'exploitation sûreet économique du réacteur. Les CC du réacteur CANDU ont des propriétés qui présentent des défis uniques enmatière d'essais non destructifs (END). La paroi mince de 4 mm du tube de force exige que l'on détecte etcaractérise de manière fiable des défauts ayant jusqu'à environ 0,1 mm de profondeur. Cette épaisseur est inférieured'un ou deux ordres de grandeur à la valeur généralement jugée très préoccupante pour les tuyaux en acier et lesappareils sous pression. Une seconde caractéristique spéciale est que les capteurs utilisés pour l'inspection doiventfonctionner dans le coeur du réacteur - souvent à moins de 20 cm du combustible hautement radioactif.

Les travaux effectués sur l'inspection des CC du réacteur CANDU remontent à plus de trois décennies. Au cours decette période, le personnel d'EACL a fourni le matériel et effectué ou supervisé des inspections en cours de servicedans environ 250 CC, qui s'ajoutent à plus de 8 000 examens de CC avant l'entrée en service. Ces inspections onteu lieu dans chaque réacteur CANDU existant à l'exception de ceux d'Inde et de Roumanie. Au début, lesinspections étaient axées sur la mesure des variations de dimensions (dimensionnement) provoquées par l'expositionà une combinaison de neutrons, de contraintes et de température élevée. L'expansion des activités d'inspectionvisant à inclure l'inspection volumétrique (pour la recherche des défauts) a débuté au milieu des années 70 avec ladécouverte de la fissuration par hydruration différée dans les joints dudgeonnés de Pickering 3 et 4. La découverted'autres types de mécanismes de formation de défauts dans les années 80 a entraîné la généralisation des inspectionsavant l'entrée en service et en cours de service. Ces exigences croissantes, pour satisfaire les besoins autantréglementaires qu'économiques, ont mené à la mise au point d'un large éventail de technologies d'inspection quicomprend maintenant les essais de concentration de l'hydrogène, d'intégrité structurale des composants du coeur, dedétection des défauts et de mesure des variations dimensionnelles.

Dans la présente communication, les auteurs examinent les exigences actuelles en matière d'inspection des CC pourle réacteur CANDU. Ils décrivent également le matériel et les techniques mis au point pour satisfaire à cesexigences. En conclusion, ils examinent les travaux en cours à EACL qui visent à offrir des services d'inspectiondes CC les plus perfectionnés.

Composant et des systèmesMise au point des essais non destructifs

Laboratoires de Chalk RiverChalk River (Ontario) K0J 1J0

Juin 1999

* Énergie atomique du Canada limitée, Laboratoires de Chalk River, Chalk River (Ontario) KOJ 1J0, Canada** Énergie atomique du Canada limitée, 2251, rue Speakman, Mississauga (Ontario) L5K 1B2, Canada

AECL-12026

AECL

AECL EXPERIENCE IN FUEL CHANNEL INSPECTION

by

G. Van Drunen*, R. Gunn**, W.R. Mayo* and D.A. Scott **

ABSTRACT

Inspection of CANDU fuel channels (FC) is performed to ensure safe and economic reactoroperation. CANDU reactor FCs have features that make them a unique non-destructive testing(NDT) challenge. The thin, 4 mm pressure-tube wall means flaws down to about 0.1 mm deepmust be reliably detected and characterized. This is one to two orders of magnitude smaller thanis usually considered of significant concern for steel piping and pressure vessels. A secondunique feature is that inspection sensors must operate in the reactor core—often within 20 cm ofhighly radioactive fuel.

Work on inspection of CANDU reactor FCs at AECL dates back over three decades. In thattime, AECL staff have provided equipment and conducted or supervised in-service inspections inabout 250 FCs, in addition to over 8000 pre-service FCs. These inspections took place at everyexisting CANDU reactor except those in India and Romania. Early FC inspections focussed onmeasurement of changes in dimensions (gauging) resulting from exposure to a combination ofneutrons, stress and elevated temperature. Expansion of inspection activities to includevolumetric inspection (for flaws) started in the mid-1970s with the discovery of delayed hydridecracking in Pickering 3 and 4 rolled joints. Recognition of other types of flaw mechanisms in the1980s led to further expansion in both pre-service and in-service inspections. These growingrequirements, to meet regulatory as well as economic needs, led to the development of a widespectrum of inspection technology that now includes tests for hydrogen concentration, structuralintegrity of core components, flaws, and dimensional change.

This paper reviews current CANDU reactor FC inspection requirements. The equipment andtechniques developed to satisfy these requirements are also described. The paper concludes witha discussion of work in progress in AECL aimed at providing state-of-the-art FC inspectionservices.

Components & Systems DivisionNondestructive Testing Development Branch

Chalk River LaboratoriesChalk River, ON K0J 1J0

1999 June

* Atomic Energy of Canada Limited, Chalk River Laboratories, Chalk River, Ontario, K0J 1 JO, Canada** Atomic Energy of Canada Limited, 2251 Speakman Drive, Mississauga, Ontario, L5K 1B2, Canada

AECL-12026

1. INTRODUCTION

CANDU reactors contain 380 (CANDU 6) or 480 (CANDU 9) fuel channels (FCs) like thatshown in Figure 1. The in-core, pressure-retaining component is the 104 mm diameter x 4.1 mmwall thickness, zirconium alloy (Zr-2.5 wt% Nb) pressure tube (PT). It supports the fuel andcarries the D2O heat-transport fluid. The simple tubular geometry invites highly automatedinspection, and that approach has largely been adopted for all inspections.

Like all nuclear heat-transport pressure boundaries, CANDU reactor FCs require rigorousinspection, before installation and periodically during service. The primary short-termmotivation for inspection is usually safety; one needs to demonstrate that new tubes are fit for theintended service and that in-service tubes have not suffered unacceptable generic degradation.However, FC inspection is also an intrinsic component of plant life management.

In CANDU reactor FCs, periodic inspection extends much further than detection of flaws byvolumetric inspection. Figure 2 is a schematic of the various features that FC inspections mustaddress. Section 3.1 will show that many of these features have more to do with plant-lifemanagement issues than safety concerns.

This paper summarizes the evolution of CANDU reactor FC inspection requirements and thenon-destructive testing (NDT) technology developed or adapted in AECL to address thoserequirements. Most attention is given to in-service tubes. However, manufacturing/installationinspections are briefly discussed, because they provide relevant background to support AECL'scurrent approach to in-service inspection.

2. MANUFACTURING/INSTALLATION INSPECTIONS

2.1 Inspection Requirements

FC manufacturing inspections are specified in the component specifications and procedures foreach reactor. As the highest-stressed pressure-retaining component, the PT has received thegreatest amount of attention. Early CANDU reactors like Nuclear Power Development (NPD)and Douglas Point relied on the best possible quality that tube manufacturers, with state-of-the-art inspection equipment, could offer. That consisted of ultrasonic testing (UT) using nominally45° shear wave beams for volumetric inspection and normal beam UT for wall thicknessverification. The earliest volumetric reference flaw depth was 0.125 mm. In the mid-1970s, thatwas reduced to the present depth of 0.075 mm; at about that time a second ultrasonic inspectionwas , added. In the early 1980s, a requirement for eddy current testing (ET) was added, asexplained in the next section.

Installation inspections are concerned with garter spring (GS) spacer location and rolled jointquality: The latter includes visual inspection of the rolled surface and the rolling tool,dimensional checks on the extent of rolling, and a leak test of each joint.

2.2 Manufacturing/Installation Inspection Experience

All CANDU reactor PTs have been manufactured, and inspected, to AECL specifications.Ultrasonic inspections are conducted to cover 100% of the tube wall by spiral scanning with 45°shear wave beams aimed in four directions at 90° to each other [1]. Eddy current inspection isachieved in a similar fashion by scanning surface probes over the inner (ID) and external (OD)tube surfaces.

Complementary ultrasonic and eddy current inspections during PT manufacture were added inthe early 1980s because some types of flaws had a small probability of escaping detection [2].Unfavourable orientation and transparency to ultrasound resulted in some flaws being difficult todetect reliably with UT alone. CANDU reactor PTs are by no means unique in that respect. Aconsiderable body of literature has appeared over the past 10 to 15 years dealing with reliabilityof NDT technologies in many engineering and non-engineering situations [3]. Figure 3 [4]illustrates the benefit of ET plus UT for a particular class of manufacturing flaws in PTs. Forflaws -0.1 mm deep, the combined probability of detection/rejection is about double that for ETor UT alone. This clearly demonstrates the benefit of using independent techniques that rely ontotally different physical principles for flaw detection. Note that the probabilities of Figure 3 areextremely pessimistic in that they represent a 95% confidence lower bound. It is estimated thatin actual practice the chances of missing a flaw deeper than 0.15 mm is less than one in 10 000for pressure tubes manufactured after 1980. (For comparison, the possibility of a failure inairport security checks and medical "NDT" diagnostics has been reported as typically 10 to15%.) The complementary ET and UT currently employed on new CANDU reactor PTsprovides the most rigorous inspection regime used for any tubular product in the world.

Installation inspections are carried out by tube installers. GS spacer location is verified usingmanual or automated eddy current equipment. AECL developed the transmit-receive eddycurrent method for this test in 1983, and has supplied the equipment for the last five CANDU 6stations as well as the systems used during retubing of the four Pickering A reactors. We arecurrently assembling the GS location tooling that will be used during channel installation in theQinshan reactors. Rolled joint inspections are performed using borescopes and mechanicalmeasurement tools. Leak tightness of rolled joints is assured with a helium leak test of eachjoint.

3. IN-SERVICE INSPECTION

3.1 In-service Inspection Requirements

In-service inspection requirements originate from two very distinct sources: safety andeconomics.

Minimum, safety-driven, FC inspections are dictated in Canada by a standard, CAN/CSA-N285.4 [5]. The current (1994) version requires periodic examination of a small sample ofchannels for the following:

1) Volumetric inspection (for flaws).2) Pressure tube to calandria tube (PT/CT) gap measurements.3) PT internal diameter and wall thickness.4) Position of FC on its bearings.5) PT material surveillance.

Inspections to satisfy these requirements are only intended to verify that there has been nogeneric deterioration in the FC condition. Reactor safety is the main driving force. Inspectionscope and limited sample size do not permit more definitive conclusions to be drawn from theinspection results.

In this paper, Requirements 2) and 3) above are combined under the heading Dimensional/Integrity Inspection. Requirement 4) is usually satisfied by fuelling machine travel or reactorface measurements. With the exception of Requirement 4), the requirements can presently onlybe satisfied by entry into defuelled channels.

CSA standards are re-issued/revised every five years. The next version, in 1999 or 2000, isexpected to contain some changes in FC inspection requirements.

In addition to the minimum CSA requirements listed above, a number of other requirements havesurfaced over the years. These are primarily driven by plant-life management or fitness-for-service concerns. Non-destructive measurement of various FC parameters is almost alwaysmuch less expensive than seeking the answers through channel removals and destructiveexaminations. Also, a non-destructive approach usually permits investigation of a larger numberof channels, and hence statistically valid results can be obtained. To obtain the same degree ofconfidence by destructive means would be prohibitively expensive in terms of monetary cost andradiation exposure. Inspection requirements driven by fitness-for-service are included in Figure2. They primarily include:

• detailed characterization of flaws,• clearance between horizontal reactivity mechanisms (RMS) and CTs,• GS spacer location,• oxide thickness measurement, and• surface roughness measurement.

3.2 Dimensional/Integrity Inspections

Dimensional measurements on experimental CANDU reactor PTs date back to the early 1960s[6,7]. A primary focus of these early inspections was the effect of neutron flux on the stability ofdimensional features like diameter [8]. Up to about 1985, dimensional measurements at allCANDU reactors were performed with equipment that evolved from that developed by AECL inthe early 1960s. AECL staff were also directly involved in many of these inspections at powerreactors.

Monitoring FC integrity includes the following:

• GS spacer location is achieved using a transmit-receive eddy current technique for spacerswith welded girdle wires. Spacers that fit tightly on the PT with unwelded girdle wires donot always respond to the eddy current approach after reactor start-up; ultrasonic methodsoffer some promise, but no method approaching 100% reliability has been demonstrated asyet.

• PT/CT gap is measured with eddy current methods. Accuracy can be improved significantlyby using ultrasonic PT wall-thickness compensation.

• Channel deflection or sag can be calculated from curvature or slope (inclination)measurements.

All of these test methods have been delivered into defuelled channels by a variety of deliverydevices. With the exception of SLARette (see Section 3.5), AECL experience has been withentry into drained channels that were isolated with freeze plugs or blank-off flanges on thefeeders. That led to the term "dry" inspections. Since about 1980, a STEM* -drive deliverymachine, as described in Reference [9], has been used. Table 1 summarizes these types ofinspections conducted by AECL at power reactors.

3.3 Volumetric Inspection

Early (pre-1974) inspections for service-induced flaws in CANDU reactor PTs were onlyconcerned with those on internal surfaces [6,7]. Fuel/tube interaction effects such as frettingwear, scratching and crevice corrosion were the only postulated flaw-generation mechanisms.Flaw detection expanded into true volumetric inspection using ultrasonic and eddy currenttechniques in the mid-1970s. That was triggered by the recognition of delayed hydride crackingat high-stress rolled joints, and the possibility of hydride blister formation in the 1980s [10].

Direct AECL involvement in in-service volumetric inspection of PTs diminished in the mid-1980s with the commissioning of Ontario Hydro's CIGAR** system [11]. CIGAR has providedroutine inspection services to the majority of CANDU reactors since 1986. Meanwhile, an activeR&D program in FC NDT was maintained in AECL to develop inspection technology that isutilized on systems like CIGAR and SLAR (see Section 3.5). In addition, we conducted full-scale inspections at a number of power reactors, as summarized in Table 2. Inspections werealso done, and continue today, on NRU loop tubes.

Both CANDU and NRU inspections were performed with the same "dry" channel equipmentoriginally developed and used for pre-service inspections [9]. It utilizes both UT and ETmethods for flaw detection and characterization. Ultrasonic inspections utilize similartransducers and beam configurations to those in manufacturing and CIGAR inspections [11]; i.e.,four focussed 45° shear wave beams at 90° apart.

Storable Tubular Extendible MemberChannel Inspection and Gauging Apparatus for Reactors

3.4 Material Surveillance

Of the three material surveillance requirements of CSA/CAN-N285.4, only one can currently beachieved non-destructively, deuterium/hydrogen (D/H) concentration determination. The onlyproven method for this test is micro-sampling, which involves the removal of a smooth, thin,surface layer sufficient for precision deuterium and hydrogen analysis (accuracy is ±1 ppm forconcentrations <30 ppm). The tooling and analysis methods were developed by AECL [12,13].Micro-sampling tools have evolved over the past decades. Early designs required channelisolation and draining; the most recent design operates in a flooded channel and is delivered bystation fuelling machines. In all sampling campaigns to date, AECL has participated in some orall aspects of: tool manufacture or refurbishment, taking samples from reactors, and sampleanalysis. Table 3 [14] summarizes the extensive use of D/H sampling technology in CANDUstations.

Considerable effort has been invested in comparing sampling results with D/H concentrationsmeasured on bulk specimens. Excellent agreement between the two methods is illustrated inFigure 4 [15].

3.5 SLAR Experience

Spacer location and repositioning (SLAR) is a FC remediation process for earlier reactors withloose fitting GS spacers. Two versions exist: (a) a fully remote, fuelling-machine-based SLARsystem designed to visit all channels in a reactor during one extended outage, and (b) SLARette[16], a less automated but much more portable system designed to efficiently visit about 50channels during a normal maintenance outage.

Though not specifically an inspection tool, both SLAR and SLARette rely heavily on identicalinspection technology for their operation. They include inspections for 100% of final GSlocations and a volumetric UT scan over a 60-degree zone at the bottom of each PT along its fulllength. The GS location information permits prediction of PT/CT years-to-contact. The eddycurrent technique for locating spacers developed by AECL is one of the three key enablingtechnologies that make spacer repositioning feasible. A combination of eddy current andultrasonics is used to automatically locate spacers, measure the PT/CT gap and perform flawdetection. AECL developed the SLARette delivery machines and most of the SLAR inspectionsub-system, including automated data analysis. Figure 5 shows the latest model SLARettedelivery machine; Figure 6 is a schematic representation [17]. A number of complete SLARettesystems have been supplied to CANDU utilities. There has also been considerable AECLinvolvement in on-reactor SLARette activities, as summarized in Table 4.

4. AECL CHANNEL INSPECTION SYSTEM

Historically, FCs, including inspection activities, have been one of the more significantcontributors to the incapacity factor of CANDU reactors. Design improvements and operatingguidelines have addressed all known FC problem areas. However, activities like periodic and in-

service inspection are unlikely to decrease. There is regulatory pressure for increased inspectionof FCs. The desire of reactor operators of older units to obtain the longest possible life fromtheir PTs is also likely to require increased inspection, in order to assemble convincing evidenceto justify continued operation at full-rated power. Such inspections would likely involve largersamples of channels to obtain improved statistics. To avoid significant impact on capacityfactors, inspections would have to be much faster than are possible with existing systems. Morerapid and comprehensive inspections would permit reducing much of the conservatism inherentin the current practice of relying on calculated predictions for factors like reactor operating point(ROP) settings. To prepare for this anticipated ongoing need for inspection services by ouroperating reactors, AECL has decided to upgrade its FC inspection capability. Effort willconcentrate on providing efficient inspection services to CANDU 6 reactors.

Careful review of requirements, present as well as future, was used to define the capabilities ofan AECL "wet" FC inspection system; i.e., not requiring feeder isolation or freeze plugs. Majorcriteria in defining our directions were:

use of proven technology to the greatest extent possible,achieve a significant decrease in inspection time per channel as well as total inspectiontime,modern digital data acquisition, processing and archiving,optimized system for use at CANDU 6 sites around the world,highest possible inspection reliability,a system capable of easy upgrading to satisfy future needs.

The system will be assembled around an Advanced SLARette Delivery Machine. Adapting it todeliver a full-scope inspection capability will involve only relatively minor changes, such as:

replace the SLARette tool with an inspection head,modify the design of the calibration tube (Item 3, Figure 6), and

- develop a new design for the umbilical cable connecting the inspection head toinstrumentation.

Table 5 lists some technical features of the system. The work is underway with a Mark 1version, capable of satisfying all code requirements, scheduled to be operational in the fall of1999.

5. SUMMARY

• The relatively simple tubular geometry of CANDU fuel channels makes it possible toperform rigorous and efficient inspections.

• Manufacturing inspection of FC components is as stringent as present NDT technologyallows.

• In-service inspection of FCs includes tests for chemical composition, dimensions,functionality of components, as well as volumetric examination for flaws.

7

Building on over three decades of experience and thousands of channel entries for a variety ofinspection purposes, AECL has embarked on assembling a state-of-the-art FC inspectionsystem capable of satisfying both present and anticipated inspection requirements.

6. REFERENCES

1. B.A. Cheadle, C.E. Coleman and H. Licht, "CANDU-PHW Pressure Tubes: TheirManufacture, Inspection and Properties", Nuclear Tech., vol. 57, pp. 413-425 (1982).

2. W.R. Mayo, "Reliability of Nondestructive Testing", Canadian Society for NondestructiveTesting Journal, vol. 12/4, pp. 14-20 (1991).

3. M.G. Silk, A.M. Stoneham and J.A.G. Temple, "The Reliability of Non-destructiveInspection", Adam Hilger, Bristol (1987).

4. D. Horn, personal communication.

5. Canadian Standards Association, CAN/CSA-N285.4-94, "Periodic Inspection of CANDUNuclear Power Plant Components, A National Standard of Canada" (1994).

6. H.P. Koehler and P.A. Ross-Ross, "Pressure Tube Inspections In-Pile", AECL report,AECL-1845 (1963).

7. J. Widger, J. Escott, M. McManus and D. Nelson, "In-Reactor Pressure Tube GaugingEquipment", AECL report, AECL-3426 (1969).

8. P.A. Ross-Ross, V. Fidleris and D.E. Fraser, "Anisotopic Creep Behaviour of ZirconiumAlloys in a Fast Neutron Flux", Canadian Metallurgical Quarterly, vol. 11, pp. 101-111(1972).

9. G. Van Drunen and F.L. Sharp, "Eddy Current Inspection of Installed CANDU PressureTubes", Procs. Sixth Int. Conf. On NDE in the Nuclear Industry, Paper 8310-012,pp. 691-700 (1984).

10. E.G. Price, "Highlights of the Metallurgical Behaviour of CANDU Pressure Tubes", AECLreport, AECL-8338 (1984).

11. M.P. Dolbey, "CIGAR, An Automated Inspection System for CANDU Reactor FuelChannels", Procs. 8th Int. Conf. On NDE in the Nuclear Industry, ASM, pp. 105-111(1986).

12. R: Joynes and C.A. Kittmer, "The evolution of Pressure Tube Sampling Tools for LifeAssessment", Procs. of Canadian Nuclear Society Annual Conference (1989).

13. P. Janzen; R. Joynes, L.W. Green and V. Urbanic, "Monitoring Pressure Tube Health byMicro-Sampling", Presented at 4th COG/IAEA Technical Committee Meeting on Exchangeof Operational Safety Experience of PHWRs, Kyong-Ju, Korea (1996).

14. M.J. King, personal communication.

15. C.A. Kittmer, personal communication.

16. D.J. Burnett, "SLARette Operations at CANDU 6 Stations", Procs. Third Int. Conf. OnCANDU Maintenance, Canadian Nuclear Society, pp. 165-168 (1995).

17. R.R. Bodner, "Advanced SLARette Delivery Machine, ibid., pp. 175-179 (1995).

Table 1Dimensional/Integrity Inspections at Power Reactors

Date

1993

1992

1989

1989

1989

1986

1981

1979

1968/88

Site

KANUPP

Pickering 4

Embalse

Pickering 3

Pt. Lepreau

Pt. Lepreau

Wolsong 1

Embalse

Pt. Lepreau

Gentilly 2

NPD

No. ofChannels

8

5

11

20

1

2

14

14

14

14

11

NDE Techniques

Gap, Dimensional

Dimensional

Spacer, Gap, Dimensional

Dimensional

CT: Dimensional, Video

Spacers, Dimensional, Video

Dimensional

Dimensional

Dimensional

Dimensional

Dimensional

10

Table 2Volumetric Inspections at Power Reactors

Date

1993

1990

1989

1986

1986/90

1986

1985

1983

1982/89

1981

Site

KANUPP

Pt. Lepreau

Embalse

Pickering 1

Pickering A

Pickering 4

Bruce 4

Bruce 1

Pickering B

Bruce B

Darlington

Pt. Lepreau

Embalse

Wolsong 1

Wolsong 1

Embalse

Pt. Lepreau

Gentilly 2

No. of Channels

8

1

11

2

1560

2

1

1

1520

1920

1920

380

380

380

14

14

14

14

NDE Techniques

ET,UT

ET, UT

ET, UT

ET

ET (retube)

ET

ET

UT

ET (few UT) (pre-service)

ET (pre-service)

ET (pre-service)

ET (few UT) (pre-service)

ET (few UT) (pre-service)

ET (few UT) (pre-service)

ET

ET

ET

ET

11

Table 3Sampling In-Reactor Pressure Tubes for D/H Concentration

Date

1987 June

1987 December

1988 April

1988 October

1988 December

1989 April

1989 April

1990 September

1990 September

1990 September

1992 April

1992 July

1992 September

1993 June

1993 September

1993 November

1993 December

1994 May

1994 August

1995 May

1995 May

1995 November

1996 Spring

1997 November

1997 December

1997 December

1998 January

1998 March

1998 March

Reactor Site

NPD

Pickering 4

Pickering 3

Bruce 3

Pickering 4

Bruce 2

Point Lepreau

Pickering 4

Gentilly 2

Bruce 1

Point Lepreau

Bruce 2

Wolsong 1

Bruce 3

Gentilly 2

KANUPP

Bruce 4

Bruce 3

Bruce 2

Pickering 5

Bruce 6

Bruce 3

Gentilly 2

Kursk 5

Bruce 6

Point Lepreau

Bruce 6

Wolsong 1

Gentilly 2

TOTAL

Number of Samples

42

60

40

80

80

80

30

172

9

80

40

2

30

8

24

32

20

40

50

20

4

3

40

8

24

56

3

16

40

1133

Tubes Sampled

8

20

10

20

20

20

10

43

3

20

10

1

10

2

6

6

5

10

10

5

1

1

10

1

6

14

1

4

10

287

12

Table 4AECL Involvement in CANDU 6 SLAR/SLARette Campaigns

Station

G2 SLARette

Point Lepreau

Embalse

Wolsong 1

Status

100% Complete

100% Complete

33% Complete

54% Complete

13

Table 5Technical Features of AECL Channel Inspection System

Delivery Machine

FlawDetection/Characterization

Dimensional/IntegrityInspections

Material Surveillance

Reinspection

- based on proven ASDM design- axial overlap at push-rod junctions

assures full-length coverage- can access all CANDU 6 channels

- full-length scan of a channel in <3 h- complementary UT and ET- full coverage of entire PT

- will rely largely on long-proveninspection technology

- multiple axial and circumferentialsampling tools will permit testing at fourdifferent locations with a single channelentry

- this sampling option will minimizedemands on fuelling machines

- video and replication capability toprovide best possible data for fitness-for-service analysis.

- significant expansion room for new orspecialized inspections.

fVtl MNMtMIUUM IVM

0 CMAMt* tUM11 <M*MMM KM rvti iHttrit (NO iHino un,ti iu«iit twitortvoi IMUf

Figure 1: Fuel Channel Assembly

15

FUEL CHANNELNDE

LENGTH

FLAWS- detection- length- depth- root tip radius

SURFACE ROUGHNESSOXIDE THICKNESS

DIAMETER

CT/RMCLEARANCE

GARTERSPRINGLOCATION

WALL THICKNESS

HID CONCENTRATION HYDRIDE BLISTERS

Figure 2: Fuel Channel NDE

16

1.00

0.75

.QCti 0.50

_QO

0.25

Joint ET/UT Rejection Probabilities

T SPOT 333 UT rejection probabilityB BAL ET rejection probability• ETuUT rejection probability

'/I Lower-bound rejection probability at 95% confidence'.* level, calculated by the optimized probability method.

0.1 0.2 0.3 0.4

Through-wall Extent of Flaw (mm)0.5

Figure 3: Lower-bound ET, UT, and combined rejection probabilities, calculated for 95%confidence level.

17

Pressure Tube Deuterium ConcentrationsThrough-Wall Pellets vs. Surface Samples

400

350

300

[ppm

(0+•>

Pel

h

250

200

150

100

50

•

I i

50 100 150 200 250 300

Samples (ppm)

350 400 450

Figure 4: Comparison of deuterium concentrations obtained from bulk (pellet) specimens andmicro-samples.

18

Figure 5: Photo of Advanced SLARette Delivery Machine (ADM).

19

AECL-12026

ISSN 0067-0367

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