Abstract
An experimental circulating water loop was built to follow the formation, the transport, and the deposition of iron oxides in the feedwater system of the secondary circuit of PWR plants. The test section was made from carbon steel while all other parts of the loop were made from stainless steel. Tests were performed for 18 days to 101 days in one-phase flow conditions at 150 L/h with a linear velocity between 0.92 m/s and 1.1 m/s at 220°C in an ammonia (NH3) and hydrazine (N2H4) medium. A magnetite (Fe3O4) film appeared on the surface of carbon steel tubes within a few days. Iron oxides were also present on stainless steel segments as goethite (FeOOH) at room temperature and as magnetite at 220°C. The oxide film on carbon steel was heterogeneous and its thickness varied from several μm to 40 μm, while the oxide film on stainless steel did not exceed 2 μm.
