Prediction of FAC Rate under Two-Phase Flow in an Experimental System Using Pipe Wall Thinning Prediction Software FALSET

Abstract

Flow-accelerated corrosion (FAC) is a pipe wall thinning phenomenon caused by a combination of thermal-hydraulic, water chemistry, and material factors. The current management of the pipe wall thinning of Japanese nuclear power plants is based on the thinning rate and residual lifetime evaluated using the measured pipe wall thickness. While current management has the advantage of directly identifying the residual wall thickness of pipes and the timing of replacement and repair, there are issues with management for piping sections and systems where the actual residual lifetime cannot be accurately identified because it has not been measured or because it is difficult to measure. To rationalize the current management, we have been developing FALSET, a pipe wall thinning prediction software, to improve its prediction accuracy and to study its specific applications in wall thinning management. However, the actual plant includes watersteam two-phase flow systems in its thinning management targets. In this study, we updated the two-phase flow FAC prediction model by applying the concept of the water single-phase flow FAC prediction model, and confirmed the prediction performance by comparing the predicted and measured wall thinning rates for an experimental system with a low chromium content.