Transport processes in steam generator crevices. II. A simplified method for estimating impurity accumulation rates

An approximate, yet accurate method for calculating average volume concentrations of impurities and corrosion products in Pressurized Water Reactor (PWR) Steam Generator (SG) tube/tube support plate crevices has been developed. The method is based on the assumption that the real concentration profiles can be approximated by ideal step functions. The method yields analytical expressions for such important parameters as the rate of accumulation of impurities, corrosion current density, liquid velocity, saturation, transition time, and wetted length. It is shown that, under normal operating conditions of a PWR SG, we can estimate the corrosion rate even when only meager information is available for the physical parameters of the system. The method also permits prediction of the accumulation of impurities in crevices for long times, if the corresponding experimental measurements are available only for short times. Long-term predictions from the model describe the experimental data with great accuracy. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.