CFD analysis of turbulent flow in a PWR feedwater suction line for the prediction of local area susceptible to FAC-caused wall thinning

Many of failures caused by wall thinning in carbon steel piping systems/components have been experienced worldwide and occurred in most of types of nuclear power plants. It has been well known that such wall thinning is caused by the flow-accelerated corrosion (FAC). Especially, intensive research to understand the parameters affecting FAC was initiated from Surry unit 2 wall thinning failure in 1986 and many regulatory technologies have been developed to guarantee the integrity of piping systems/components since the accident occurrence. In this work the flow field inside piping system with the same geometrical and flow conditions as those of the failed pipe at the Surry unit 2 was analyzed and the shear stress distributions was calculated to predict the local region of pipe wall highly susceptible to FAC-caused wall thinning by using computational fluid dynamics (CFD). For a real accident, break initiated in the connection region of straight pipe and elbow near the inlet part of bend which was the thinnest area, which accords with weak region expected by CFD analysis. (author)