Evaluation Methods for Corrosion Damage of Components in Cooling Systems of Nuclear Power Plants by Coupling Analysis of Corrosion and Flow Dynamics (III) : Evaluation of Wall Thinning Rate with the Coupled Model of Static Electrochemical Analysis and Dynamic Double Oxide Layer Analysis

Flow accelerated corrosion (FAC) is divided into two processes: a corrosion (chemical) process and a flow dynamics (physical) process. The former is the essential process to cause FAC and the latter is the accelerating process to enhance FAC occurrence. The chemical process in the surface boundary layer is analyzed to evaluate FAC rate. Contributions of flow dynamics on wall thinning rate due to FAC are expressed as a function of mass transfer coefficient but not that of flow velocity. FAC evaluation procedures were divided into 5 steps as follows. (1) Flow pattern and temperature in each elemental volume along the flow path were obtained with 1D computational flow dynamics (CFD) codes, (2) corrosive conditions, e.g., oxygen concentration and electrochemical corrosion potential (ECP) along the flow path were calculated with a hydrazine oxygen reaction code, (3) precise flow patterns and mass transfer coefficients at the structure surface were calculated with 3D CFD codes, (4) danger zones were evaluated b...