Experimental and numerical investigation of PWR Tube Support Plate (TSP) clogging formation mechanisms

International audienceCorrosion product deposits in the secondary side of PWR Steam Generators (SG) may result in Tube Support Plate (TSP) clogging majorly composed of magnetite (Fe3O4), which can lead to heavy consequences for nuclear reactor operation and safety issues such as primary-to-secondary leaks. It appears that TSP clogging is mainly driven by magnetite particle deposition and iron precipitation, which can be strengthened by flashing and electrokinetics mechanisms under the specific TSP geometric configuration. TSP clogging formation involves thus complex thermohydraulic, physical and chemical processes while the contribution of each phenomenon and the influence of operating conditions such as secondary fluid velocity, pH and temperature on TSP clogging are still unheralded. COLENTEC two-phase flow loop tests in 2015 provided the first representative experimental results of TSP clogging build-up and showed deposit growth rate in accordance with French power plant feedbacks. Numerical calculations showed the electrokinetics may play a predominant role in TSP clogging formation whereas no significant contribution of magnetite particle deposition occurs provided that the size of magnetite particles is close to 1 µm and the total iron concentration is less than 1 ppm