Sensitivity study of thermal hydraulics to corrosion of heat exchange tubes in steam generator

A leakage accident occurs in the circulating water system in PWRs, impurity ions enter the SG with the secondary circuit feed water and cause electrochemical corrosion of the heat transfer tubes (HTTs). Based on the hide out and return mathematical model in the SG, a coupled mathematical model of mass transfer-electromigration-hydrodynamics of impurity ions in the secondary boiling channel of SG is deduced. The accuracy of the mathematical model is verified by ex-periments, and the effects of heat flux density (Peq), flow velocity (Peu), impurity ion concentration (Pec) and relative solubility of impurity ions (Kp) on impurity ions migration and electrochemical corrosion are analyzed and discussed. The results show that Peq mainly controls the diffusion of impurity ions and thus affects the migration rate of impurity ions. The mass transfer of impurity ions driven by Peq can enhance the reduction of H+, thereby accelerating the corrosion rate of HTTs. Peu mainly affects the synergistic effect of convective mass transfer and electromigration during the migration of impurity ions, and charge transfer mainly controls the electrochemical corrosion of HTTs surface with the increase of Peu. The Pec on the surface of HTTs changes linearly with time, and the corrosion rate increases with the increase of Pec. The corrosion rate of HTTs is proportional to Kp, and Kp is a main factor that causes different corrosion rates in different location of HTTs. In this paper, a coupled model for the sensitivity of thermal-hydraulic parameters (Peq, Peu, Pec and Kp) in SG to electrochemical corrosion of HTTs is proposed for the first time. The research results can provide important support for the development of corresponding response strategies, schemes for the life prediction of HTTs and the safety maintenance of nuclear power plants.