Test-Reactor Study of the Effect of Zirconia Coating of Inconel … · 2019. 6. 26. · Coating Inconel X-750 Spacer cells Method 1 –thin coatings Method 2 –thick coatings Cleaning

Westinghouse Non-Proprietary Class 3 Westinghouse Electric Sweden AB. All Rights Reserved.

1 WSE 12.1_Bl23 rev 2, 2017-04-24

WAAP-11382

Test-Reactor Study of the Effect of Zirconia Coating

of Inconel Spacer Cells on Shadow Corrosion

Clara Anghel

Magnus Limbäck

Gunnar Westin

Terje Tverberg

Björn Andersson

Michael Leideborg

Jonathan Wright

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WAAP-11382

Overview

• Shadow corrosion: Background

• Remedies

• Materials and Coating Methods

• In-reactor testing

• Results and Discussions

• Summary

• References

3

Westinghouse Electric Sweden AB. All Rights Reserved.Westinghouse Non-Proprietary Class 3

WAAP-11382

Shadow corrosion: Background

▪ It is well known since many years

▪ It is an enhanced local corrosion that occurs mostly in BWRs on zirconium-based

alloys which are in contact or in close proximity to another more noble metal or alloy.

It is a generic phenomena that is normally

harmless

Cha

tela

inA

et a

l., A

NS

20

00

Shadow of a control rod handle on a

Zircaloy-2 fuel channel2 Cycles, 25 MWd/kgU

No Crud high visibility

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WAAP-11382

Corrosion of Zr-based alloys in BWRs

Shadow corrosion

ESSC

Zr-based alloys: BWR corrosion mechanisms

Source: R. Adamson & P. Rudling, 2013

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WAAP-11382

Shadow corrosion of Zr-based alloys in BWRs

• There is a trend for saturation

of the oxide thickness with

fluence or burnup.

• Generally, shadow corrosion

do not cause fuel performance

problems.

• The upper curve is a special

case of shadow corrosion

called Enhanced Spacer

Shadow Corrosion, ESSC, that

caused fuel failures in the past.

Normal

Shadow

corrosion

Shadow corrosion data from various BWR fuel vendors

claddings. Source: R. Adamson & P. Rudling, 2013

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WAAP-11382

Galvanic corrosion mechanism

Aim: To reduce the shadow corrosion development on Zry-2

by coating of Inconel X-750 spacer cells with ZrO2

An

od

e

(-)

Cathode

(+)

e-

Source: M. Ullberg et al, SKI report 2004:28

E1 (Inconel) E2 (Zircaloy)

Typical remedies for the galvanic corrosion process

• Disconnect the electrical joint between the dissimilar metals (using and

insulator) - difficult to maintain the insulator properties in reactor

• Coatings: coat either the anode or the cathode to generate a decrease in the

corrosion potential between the two metals

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WAAP-11382

Coating Inconel X-750 Spacer cells

Method 1 – thin coatings Method 2 – thick coatings

Cleaning Inconel X-750 spacer

cells in acetone and deionized

water; drying at 150C

Tap coating with 0.2M Zr(OPrn)4

alkoxide solution, coating rate

∼0.6 cm/min

Hydrolysis in air for 10min, heat

treatment in air at 100 °C, 1h

and at 500°C for 1h.

Dense homogeneous thin

films of ZrO2: 100 nm; 200 nm

Repeat 3 or 5 times (0.4M Zr(OPrn)4)

Produce the base coating using

Coating method 1

Tap coating with ZrO2 -nanoparticle

containing containing PEG and

DEG, coating rate ∼1.8 cm/min

Dried in air for 10min, heat

treatment in air at 100 °C, 15 min.

Repeat up to 6 times

Heat treatment at 500°C for 1h.

Thick films of ZrO2: 300 nm; 600 nm;

1.2 µm; 2.4 µm; 4.5 µm; 9 µm

PEG – Polyethyleneglycol

DEG - Diethyleneglycol

Treatment with a dilute alkoxide

solution from Method 1.

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WAAP-11382

SpecimensTotal thickness of the coating

[µm]

W3A02M 0.1

W5A04M 0.2

W3A10 0.3

W3A20 0.6

W3A40 1.2

W3A80 2.4

W3A150 4.5

W3A300 9.0

Coated Inconel X-750 Spacer cell specimens

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WAAP-11382

Inconel X-750 Spacer cell specimens

Un-coated spacer

cell specimen

Spacer cell specimen

W3A02M

Spacer cell specimen

W3A20

Coating thickness 100 nm Coating thickness 600 nm

TRITON11 is a trademark or registered trademark of Westinghouse Electric Company LLC, its affiliates and/or its subsidiaries

in the United States of America and may be registered in other countries throughout the world. All rights reserved.

Unauthorized use is strictly prohibited. Other names may be trademarks of their respective owners.

Spacer cells that are used in the SVEA-96 Optima3 10x10 fuel design and in

the TRITON11 11x11 fuel design, includes sleeve-type cells with four long

linear supports (contact lines)

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WAAP-11382

Irradiation in Halden

Standard fully re-crystallized LK3 Zircaloy-2 instrumentation

tube equipped with spacer cells

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WAAP-11382

Irradiation in Halden

Fast neutron fluence (>1 MeV) for the 21 spacer

cell specimens

Temp.

[°C]

Pressure

[MPa]

Water Flow

[kg/s]

Duration

[FPD]

Fast Neutron

Flux

[n/cm2/s]

278 - 288 7.1 - 7.3 0.6 – 0.7 1490.09 –

0.16·1014

PeriodConductivity

[µS/cm]

O2

[ppb]

H2

[ppb]

1st cycle Loop 4)

(July – Oct 2005) 0.1 250 - 300 50 - 100

2nd cycle (Loop 10)

(Jan – March 2006) 0.3 - 0.5 250 - 300 50 - 100

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WAAP-11382

In-reactor testingSpacer cell specimens

Specimen No. Specimen IDAxial pos.

[m]

Coating thickness Fluence Flux

[µm] [1021 n/cm2] [1014 n/cm2/s]

21 Standard5 1.450 0 0.121 1.101

20 W3A02M 1.395 0.1 0.130 1.169

19 W5A04M 1.370 0.2 0.134 1.200

18 W3A20 1.345 0.6 0.138 1.231

17 W3A150 1.320 4.5 0.142 1.261

16 Standard4 1.295 0 0.146 1.290

15 W3A40 1.270 1.2 0.150 1.318

14 W3A10 1.245 0.3 0.154 1.345

13 W3A80 1.220 2.4 0.157 1.369

12 W5A04M 1.195 0.2 0.160 1.391

11 Standard3 1.150 0 0.165 1.423

10 W3A300 1.125 9.0 0.167 1.437

9 W3A02M 1.100 0.1 0.168 1.447

8 W3A150 1.075 4.5 0.169 1.454

7 W3A20 1.050 0.6 0.170 1.460

6 Standard2 1.000 0 0.171 1.465

5 W3A300 0.950 9.0 0.171 1.461

4 W3A40 0.925 1.2 0.170 1.455

3 W3A10 0.900 0.3 0.169 1.446

2 W3A80 0.875 2.4 0.168 1.434

1 Standard1 0.850 0 0.166 1.420

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WAAP-11382

Post Irradiation Examination of the Zircaloy-2 tube

• Visual inspection

• Oxide thickness measurements:

– Axially at 9 different orientations: 0, 20, 40, 90, 130, 230, 270,

320 and 360

– Circumferentially in the shadow area of the spacer cell specimens

measured from 0 to 360 orientation, with steps of about 0.35 and

axially every 1 mm

The oxide measurement system: Fischer developed probe and a Fisherscope Eddy 560C-S desktop

instrument. The instrument uses the eddy current lift-off principle where changes to the probe impedance (and

corresponding instrument signal) are proportional to oxide thickness. The instrument was calibrated before and

after the measurements using standard foils of known thickness on an un-irradiated reference cladding tube of

the same design as the test tube. The accuracy of the oxide thickness measurement equipment is ±2 µm.

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WAAP-11382

Results of the oxide thickness measurements

• Shadow corrosion occurred on the

cladding tube under all spacer cell

specimens

• The thickness of the oxide formed

in the shadow area was strongly

affected by the thickness of the

ZrO2 coating on the Inconel X-750

spacer cells.

• Small effects were observed for

coating thicknesses below 2.5 μm

• Coating thicknesses of 4.5 and

9 μm reduced the shadow

corrosion with 26 to 42%.

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WAAP-11382

Contour plots of the oxide thickness in the spacer

shadow area

Significant improvement provided by

the 4.5 µm ZrO2 spacer cell coating

Area under the un-coated

spacer cell Standard2

Area under the spacer cell specimen W3A150

with a coating of 4.5 µm

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WAAP-11382

Oxide thickness axial variation measured on the Zircaloy-2

instrumentation tube at an orientation of 40

Direct contact spacer cell – Zry-2 tube4

.5 µ

m

4.5

µm

9 µ

m

9 µ

m

Sta

nd

ard Sta

nd

ard

Sta

nd

ard

Sta

nd

ard

Sta

nd

ard

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WAAP-11382

Oxide thickness axial variation measured on the Zircaloy-2

instrumentation tube at an orientation of 270

No effect of flux level above threshold level

non-contact mode

9 µ

m

9 µ

m

4.5

µm

4.5

µm

Sta

nd

ard

Sta

nd

ard

Sta

nd

ard

Sta

nd

ard

Sta

nd

ard

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WAAP-11382

Summary

• Good in-reactor performance of the coatings produced on the Inconel X-750 spacer cells

• Shadow corrosion occured under all the spacer cell specimens

• The thickness of the oxide formed on the Zircaloy-2 tubing in the shadow area was strongly affected by the thickness of the ZrO2 coating on the Inconel X-750 spacer cells:

– Small effects were observed for coating thicknesses below 2.5 μm

– Coating thicknesses of 4.5 and 9 μm reduced the shadow corrosion with 26 to 42%.

• No effect of flux level above threshold level on the shadow corrosion performance

• The results confirm the electrochemical nature of the shadow corrosion and galvanic corrosion mechanism as a driver for the oxide growth in the shadow area of the spacer cells.

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WAAP-11382

References

Andersson B., Limbäck M., Wikmark G., Hauso E., Johnsen T., Ballinger R.G. and Nystrand A.C., ”Test

Reactor Studies of the Shadow Corrosion Phenomenon”, Zirconium in the Nuclear Industry: Thirteenth

International Symposium, Annecy, France, June 10-14, 2001, Moan G.D. and Rudling P. (Eds.), STP1423,

ISBN: 0-8031-2895-9; ISSN: 1050-7558

Adamson R.B. & Rudling P., ”Properties of zirconium alloys and their applications in light water reactors

(LWRs)”, in “Materials Ageing and Degradation in Light Water Reactors: Mechanisms and Management”,

©Woodhead Publishing Limited, 2013, DOI : 10.1533/9780857097453.2.151.

Châtelain A., Anderson B., Ballinger R.G.,Wikmark G., ”Enhanced Corrosion of Zirconium-Base Alloys in

Proximity to Other Metals: The Shadow Effect”, International Topical Meeting on Light Water Reactor Fuel

Performance, Park City, UT, USA, 2000.

Châtelain A. R., ”Enhanced corrosion of zirconium-based alloys in proximity to other metals: the "shadow

effect”, MS thesis, Massachusetts Institute of Technology. Dept. of Nuclear Engineering, 2000.

Zwicky H-U., Lohner H., Andersson B., Wiktor C-G., Harbottle J.: “Enhanced Spacer Shadow Corrosion

on SVEA Fuel Assemblies in the Leibstadt Nuclear Power Plant”. ANS Topical Meeting on LWR Fuel

Performance, Park City, Utah, April 10-13, 2000.

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WAAP-11382

References

Lysell G., Nystrand A.-C. & Ullberg M.,” Shadow corrosion mechanism of Zircaloy”, Proceedings of the 14th

International Symposium on Zirconium in the Nuclear Industry, Stockholm, Sweden, June 13-17, 2004, pg.

445.

Treeman N. M.,”Electrochemical study of corrosion phenomena in zirconium alloys”, MS thesis,

Massachusetts Institute of Technology. Dept. of Nuclear Engineering, 2005.

Kim Y.-J. et al., “Photoelectrochemical Investigation of Radiation Enhanced Shadow Corrosion

Phenomenon”, 16th Int. Symposium on Zirconium in the Nuclear Industry, Chendu, China, May 9-13, 2010.

Ramasubramanian N., Shadow corrosion, Journal of nuclear materials 328, p. 249-252 (2004)

Ullberg M. et.al, SKI Report 2004:28, Shadow Corrosion Mechanism of Zircaloy (2004)

Lemaignan C., Impact of β- radiolysis and transient products on irradiation-enhanced corrosion of

Zirconium alloys, Journal of Nuclear Materials 187, p. 122-130 (1992)

Kucuk A. & Cheng B., Laboratory Investigation on Shadow Corrosion Phenomenon, EPRI 1021032 (2010)

Edsinger K., Enhanced Spacer Shadow Corrosion (ESSC) of BWR Fuel at Kernkraftwerk Leibstadt, (KKL),

EPRI, Palo Alto, CA, and Kernkraftwerk Leibstadt AG, Leibstadt Switzerland, Technical Report 1009736

(2004)

Documents

Test-Reactor Study of the Effect of Zirconia Coating of Inconel … · 2019. 6. 26. · Coating Inconel X-750 Spacer cells Method 1 –thin coatings Method 2 –thick coatings Cleaning