Thermodynamic Modelling of the Destruction of the Surface Cr2O3 on Alloy 230 in the Impure Helium Atmosphere of a Gas Cooled Reactor

Fabien Rouillard; Céline Cabet; Stéphane Gossé; Krzysztof Wolski; Michèle Pijolat

doi:10.4028/www.scientific.net/MSF.595-598.429

Paper Titles

Development of Strain in Oxides Grown in Steam Tubes
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Altering Corrosion Response via Grain Boundary Engineering
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Modelling of Corrosion Induced Stresses during Zircaloy-4 Oxidation in Air
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Thermodynamic Modelling of the Destruction of the Surface Cr₂O₃ on Alloy 230 in the Impure Helium Atmosphere of a Gas Cooled Reactor
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Comparison of the High Temperature Surface Reactivity in Impure Helium of Two Materials for Gas Cooled Reactors
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Kinetic Study of the Low Temperature Internal Oxidation of Nickel Based Model Alloys Exposed to PWR Primary Water
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Chemical Evolution in the Substrate due to Oxidation: A Numerical Model with Explicit Treatment of Vacancy Fluxes
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Corrosion of T91 Steel in LBE: Contribution to the Study of the Pb–Bi–O–Fe–Hg System - Thermodynamic Description of PbO–Fe₂O₃
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Thermodynamic Modelling of the Destruction of the Surface Cr₂O₃ on Alloy 230 in the Impure Helium Atmosphere of a Gas Cooled Reactor

Abstract:

Above a given temperature called TA, the chromium rich oxide which has been developed on the surface of Haynes 230® and model NiCrWC alloys at a lower temperature becomes unstable in impure helium: carbon monoxide is released. Actually, oxide is reduced by carbon from the alloy. A thermodynamic model is developed to rationalize the variation of TA as a function of the partial pressure of CO in the gas phase. It was found that, at the early stages of the scale reduction, the relevant reaction occurs at the oxide/metal interface between chromia and carbon from the alloy. The interfacial activity of carbon in the alloy can be calculated based on measurements of the interfacial weight percentage of chromium and using ThermoCalc® software. Excellent agreement is observed between experimental values of TA and theoretical predictions.