51313-02668-Modeling Nuclear Containment Steel Liner Corrosion

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Product Number: 51313-02668-SG

ISBN: 02668 2013 CP

Author: Alberto Sagues

Publication Date: 2013

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Some instances of local corrosion of steel containment liners have taken place on the liner surface that is in contact with the external concrete shell. The corrosion has been associated with foreign material left at the steel-concrete interface creating a region where passivity breakdown is promoted on the steel surface. Local corrosion is expected to have been aggravated by the formation of a macrocell with a large cathodic surface area provided by the rest of the liner surface and additional embedded reinforcement. A corrosion multiscale finite element model is used to aid in evaluating the relative importance of the parameters that determine the rate of local corrosion and to improve long term performance forecasting. The model assumes Butler-Volmer kinetics for the corrosion reactions and includes transport terms for the species responsible for the cathodic reaction. System geometry accounts for spatial distribution of the liner and embedded reinforcement. Variables examined include polarization and transport parameters time and temperature and anode and cathode macrocell sizes. Model outputs are the distribution of potential and concentration in the system volume with derived distribution of corrosion rate on the liner surface and associated durability estimate for various plausible corroding region sizes and configurations. The results are contrasted with actual recorded corrosion instances to refine choice of model parameters. Application of the findings for rational projection of future performance and for improved assessment of existing structures is discussed as well as issues to be resolved in more advanced modeling approaches.