Corrosion of 9CrODS Exposed to Supercritical Water

The Supercritical Water Reactor (SCWR) is one of the Generation IV power plant designs envisioned for its high thermal efficiency and simplified core. One of the major materials issues for the development of this reactor is the corrosion resistance of the cladding and structural materials exposed to supercritical water at a temperature between 500ºC and 600ºC. 9CrODS is a promising material for such an application; it is an oxide dispersion strengthened steel containing yttrium rich oxide nano-particles.

The oxide layer formed on the 9CrODS alloy was characterized using microbeam X-Ray diffraction and fluorescence. This technique enables a detailed analysis of the microstructure of the oxide layer because it has a resolution up to 0.2 μm. The samples were corroded at the Supercritical Water Corrosion Loop at the University of Wisconsin. 9CrODS samples studied were exposed to supercritical water at two temperatures (500ºC and 600ºC) for 3 exposure times for each temperature (2, 4 and 6 weeks). Consequently, we were able to study the influence of temperature and exposure time on the evolution of the microstructure of the oxide layers formed on 9CrODS. From this analysis, a modelization of the evolution of the oxide microstructure is reviewed in this study.