Effect of swirl flow on wall thinning phenomenon by flow accelerated corrosion

Flow Accelerated Corrosion (FAC) is a pipe wall thinning phenomena to be monitored and managed in the power plants with high priority. In the accident investigation of Mihama-3 pipe failure, it was reported that noticeable swirl flow may arise in the failure pipeline and affect the wall thinning trend. At present, the management of the pipe wall thinning has been conducted with conservative evaluation of the thinning rate and the residual lifetime of the piping based on the wall thickness measurements. However, the effect of the swirl flow on the wall thinning is not considered. In this study, the correlation between the swirl flow and the trend of the wall thinning was evaluated using our physics model. It was found that the wall thinning near the orifice becomes marked when the tangential velocity of the inflow is fast. (author)