FAC and Current Status of Two-phase FAC Test Facilities

Flow-accelerated corrosion (FAC) causes wall thinning in carbon steel piping, vessels, and components when these parts are exposed to flowing water (single-phase) or wet steam (two-phase). FAC has plagued Nuclear Power Plants (NPPs) and fossil power plants for many years. Undetected, FAC will cause an abrupt rupture of components without a warning of leaks. Due to FAC, fatalities and a considerable economic loss occurred at Surry Unit 2 in 1986 in the USA and at Mihama Unit 3 in 2004 in Japan. As a result, FAC became a major issue for NPPs. FAC occurs under both single and two-phase flow regimes. This paper describes FAC and the current status regarding global two-phase test facilities. An overview of the characteristics of FAC, including the type known as two-phase FAC, was presented here. Several small-scale test loops have been developed to investigate the parameters which influence FAC. A number of large-scale FAC test facilities capable of simulating NPP conditions have been developed, such as the BENSON test rig, the CRIEPI test loop, the TEPCO system, and the CIROCO loop. The results obtained from these facilities have been used to develop computer codes to predict two-phase FAC