Model for Estimating of Flow-Accelerated Corrosion Rates through Pipe Bend in Nuclear Power Plants

摘要

Flow-Accelerated Corrosion (FAC) problems are encountered frequently in different components of both the primary and secondary cooling circuits of a pressurized water reactor, as well as in boiling water reactor nuclear power plants (NPPs). Several existing tools are available to predict FAC rates for simplified configurations, such as flow through straight pipes, based on empirical correlations. Their predictive capability is, however, limited for relatively complex configurations, such as pipe joints, T-sections, and sudden expansions. These configurations are widely encountered in NPPs and are more susceptible to FAC. To reasonably estimate FAC rates in such geometries, a detailed local and spatial resolution of flow and chemistry are required. This can be achieved by performing a detailed computation of the flow that accounts for chemical reaction and geometric complexity. The detailed flow field can subsequently be used to compute material loss rate due to corrosion. This paper presents a model for estimating the flow-accelerated corrosion where computation fluid dynamic is used to estimate mass-transfer boundary layer through a bend. This is coupled with the electrochemical kinetic model of electrochemical reactions governing corrosion of the pipe materials. The kinetic model is solved to estimate corrosion rate as a function of bend geometry and carrier fluid chemistry.