Scenarios Caitlin Dever, Kevin Daub, and Heidi Nordin May 19-23, - - PowerPoint PPT Presentation

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Analysis of the Corrosion Behaviour of Vapour-Deposited CrN Coated Zirconium under Normal Operation and Accident Scenarios

Caitlin Dever, Kevin Daub, and Heidi Nordin

May 19-23, 2019

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Introduction

• Zircaloy-based fuel claddings prone to excessive hydrogen

evolution during LOCA

• Use of nitride-based coatings may be used for:
• Increased hardness, protection against wear, corrosion

resistance, and to reduce hydrogen ingress

• Commercially available CrN coatings were applied by PVD on

Zircaloy-2 and Zr-2.5Nb substrates

• Investigations focused on corrosion resistance, accident

tolerance, and the effects of irradiation Zr(s) + 2H2O(g) → ZrO2(s) + 2H2(g)

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Physical Vapour Deposition

• Vacuum deposition process using plasma sputtering

bombardment

• Relatively thin films may be deposited (2-4 μm)
• Deposited coatings may be harder and more corrosion

resistant than coatings deposited through cathodic arc deposition or electroplating

Ar+

Sputtering Target Sputtered Target Atom Substrate Thin Film Sputtering Gas 1 µm

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Experimental

• Zircaloy-2
• Uncoated
• CrN-coated
• CrN-coated and scratched
• Scratches made with milling

tool, approximately 40 µm deep

• Zr-2.5Nb
• Uncoated
• CrN-coated

Coatings and materials studied

Uncoated CrN-coated CrN-coated and scratched

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As-Prepared CrN-coated Zircaloy-2

Chromium Nitrogen Zirconium

1 μm 1 μm 1 μm 1 μm

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Experimental

• Solution included D2O adjusted to pHa25°C 10.5 using LiOH
• System purged with Ar for 4 hours prior to test start
• Specimens tested at 300 °C, exposed in autoclave in 30 day

increments up to a total exposure of 120 days Aqueous Corrosion Testing

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CrN-coated Zircaloy-2 Aqueous Corrosion Testing

120 days scratched 120 days non-scratched

A B

2 μm μ μ μ μ μ μ 10 μm

B A A B

10 μm μ μ μ

A

C

Oxide

μ μ 2 μm μ

B

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CrN-coated Zircaloy-2 Aqueous Corrosion Testing – 120 days

Chromium Nitrogen Oxygen Zirconium

200 nm 200 nm 200 nm 200 nm 200 nm

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CrN-coated Zircaloy-2 Aqueous Corrosion Testing

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CrN-coated Zircaloy-2 Aqueous Corrosion Testing

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Experimental

• Specimens exposed in an Ar-purged quartz tube with a water

flow rate of 1.5 mL/min Steam Oxidation Testing 24 h at 400 °C 24 h at 1000 °C 24 h at 400 °C cool 6 h at 1000 °C

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CrN-coated Zircaloy-2 Steam Oxidation Testing

200 µm

Zircaloy-2 ZrO2 2 mm Zircaloy-2

100 µm

CrN ZrO2 Zircaloy-2 1.4 mm CrN

2 µm

CrN CrN ZrO2

200 µm

Zircaloy-4 ZrO2 1.8 mm Zircaloy-4

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Experimental

• Exposed in reactor to pHa25°C 10.7 adjusted using LiOD

In-reactor Testing 1.37×1013 n/cm2/s 280 °C 0 n/cm2/s 280 °C 325 °C 325 °C

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Zircaloy-2 Exposed In-Flux

280 °C 325 °C Uncoated CrN-coated

2 µm 2 µm 2 µm 2 µm

Zr-oxide Zr-oxide Cr-oxides Cr-oxides

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Zr-2.5Nb Exposed In-Flux

2 µm 2 µm 2 µm 2 µm

280 °C 325 °C Uncoated CrN-coated Zr-oxide Zr-oxide Cr-oxides Cr-oxides

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Weight Gains of CrN-coated Zircaloy-2 and Zr-2.5Nb Tested In-reactor

5 10 15 20 25 30 35 40 280°C - no flux 280°C - in flux 325°C - no flux 325°C - in flux Average Mass Gain (mg/dm2) Zr-2.5Nb Zr-2.5Nb coated

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5 10 15 20 25 30 280°C- no flux 280°C - in flux 325°C - no flux 325°C - in flux Average Mass Gain (mg/dm2) Zircaloy-2 Zircaloy-2 coated Zircaloy-2 coated+scratched

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Deuterium Ingress of CrN-coated Zircaloy-2 and Zr-2.5Nb Tested In-reactor

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Conclusions

• PVD CrN-based coatings have been found to survive on

Zircaloy-2 under aqueous corrosion conditions and reduce

• verall deuterium ingress
• PVD CrN-based coatings may lower steam oxidation
• When scratched, coating adherence is not compromised and

further oxidation is limited

• When exposed out-of-flux and in-flux at 280 °C and 325 °C,

PVD CrN-based coatings resist severe surface oxidation

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Acknowledgements

• Reka Szőke (IFE-Halden) for in-reactor exposure testing
• Linruo Zhao (NRC) for coating deposition through PVD
• Connor Davis (CNL) for autoclave testing
• Sridhar Ramamur (Western University) for steam exposure

testing

• Clinton Mayhew (CNL) for SEM analysis
• Brad Payne (CNL) for SIMS analysis
• Alan Britton and Ryan Macleod (CNL) for HVEMS analysis
• Travis Casagrande (McMaster University) for FIB lift-outs
• Andreas Korinek (McMaster University) for TEM/EELS analysis

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Thank you. Merci.

Questions?

Presenting author’s email contact: heidi.nordin@cnl.ca

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Experimental

• Uniaxial tensile tests conducted at RT and 300 °C
• Specimens tested to set strains:
• 0.5%
• 1%
• 1.5%
• 2%
• Al block used to heat specimens to 300 °C
• Uniaxial Tensile Testing

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Uniaxial Tensile Tests

• CrN-coated Zircaloy-4 tested at 300 °C to 2% strain

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Uniaxial Tensile Tests

Test Temperature (°C) Strain (%) Presence of small cracks 25 0.5 No 25 1 No 25 1.5 No 300 1 No 300 1.5 No 300 2 Yes 300 2.5 Yes