A steady state FAC model and its application on practical geometries by means of CFD

Authors : Y.G. Zheng, C.B. Liu                 

Company : Institute of Metal Research, CAS
                   

Country : China

Topics

Flow Accelerated Corrosion
FAC prediction tools

ABSTRACT :

Flow-accelerated corrosion (FAC) has caused a large number of ruptures and leaks mainly in the secondary loop of the plants worldwide, such as the fatal accidents at Surry power plant in the U.S. and at the Mihama nuclear station in Japan. In recent years, FAC phenomena have also been discovered in some Chinese nuclear power plants which have operated for more than 15 years. So it is urgent for Chinese power plant operators, engineers and scientists to establish a complete strategy to combat FAC.

This paper presents a steady state FAC model based on the M.I.T. model concerning the hydrodynamic enhancement in the mass transfer process and the growth of the magnetite film on carbon steel. CFD software is invoked to calculate the precise flow pattern and mass transfer coefficient at the surface. The three-dimensional distribution of FAC locations in fully developed flow in some practical geometries, e.g. bends and tees, will also be discussed. Using this method, the geometry factor on certain component along a pipeline can be precisely calculated. What's more, the exact positions with high FAC thinning rate can be determined; as a result, the outage time spent on UT measurement will be reduced remarkably. Finally, the model is used to explain a FAC failure happened in a Chinese nuclear power plant.