Corrosion Behavior of Different Metallic Materials in Supercritical Carbon Dioxide at 550°C and 250 bars

In the framework of a new generation of nuclear reactors, typically sodium fast reactors, supercritical carbon dioxide (CO(2)) with a Brayton cycle (at 550 degrees C and 250 bars) is identified as a promising energy conversion system to replace the traditional steam generators. Nevertheless, the long-term integrity of the heat exchanger structure in this environment has to be proven over at least 20 years. To this purpose, the corrosion behavior of different metallic materials under static CO(2) at 550 degrees C and 250 bars is studied. The materials under study are one 9 wt% Cr ferrito-martensitic steel (T91) and several austenitic steels. The results about the nature of the corrosion product, morphology, and kinetics of formation were analyzed by glow discharge optical emission spectroscopy, scanning electron microscopy, wavelength-dispersive spectroscopy, and x-ray diffraction. A corrosion mechanism of the different steels is proposed and the most promising materials for heat exchanger applications are discussed.