Evaluation of Wall Thinning Affects caused by the Superposition of FAC and Liquid Droplet Impingement with the COMSY Code

Topics :

Flow Accelerated Corrosion
FAC prediction tools

ABSTRACT :

The surveillance of wall thinning effects in piping and vessels is one of the key issues for the safe operation of nuclear power plants, as wall thinning may cause spontaneously occurring component failures. Wall tinning is typically caused by the following flow-induced degradation mechanisms: Flow-accelerated corrosion (FAC), liquid droplet impingement erosion (LDI) and cavitation erosion (CE). For the safe identification of system areas which are sensitive to wall thinning, a comprehensive plant-wide strategy needs to be applied, considering the effects and superposition of different degradation modes.

The COMSY code, developed by AREVA NP, incorporates (among others) degradation models for FAC, LDI and CE. This functionality makes it possible to identify system areas susceptible to wall thinning based on system parameters in combination with material data. This includes also the superposition of flow-induced degradation effects which may occur locally. Within the scope of this paper an example will be given for the identification and detailed evaluation of a sub-system affected by the superposition of FAC and LDI in a PWR.