Kinetic Study of Magnetite Precipitation Using a High-Temperature Flow-Through Loop: Experimental Apparatus and Testing Procedure

An accurate understanding of material degradation mechanisms and the behavior of the key corrosion products of the materials of construction in nuclear systems is essential in minimizing radiation fields to ensure nuclear worker safety. There are no high-temperature data available on the precipitation constant (k_p) of magnetite. Knowledge of this kinetic constant and its temperature dependence would allow for more accurate predictive modeling of the fouling of primary-side sections such as the steam generators. This work summarizes a modification of an experimental loop test section to study the kinetics of magnetite precipitation at temperatures relevant to Canada deuterium uranium (CANDU) reactor primary heat transport systems (PHTSs). A high-temperature, high-pressure flow-through loop was used to simulate the PHTS environment. A cooler test section representative of the temperature range in a typical CANDU-6 steam generator was used to induce supersaturation and precipitation down the length of the cooler. Work is ongoing to accurately quantify both the dissolved aqueous iron in the bulk coolant and the quantity of the precipitated magnetite on the pipe wall, with initial findings reported here.