Zirconium alloys for supercritical water reactor applications: Challenges and possibilities

The corrosion behavior of model Zr-based alloys at 500 °C is assessed by long term (up to 400 days) corrosion testing in an effort to evaluate their potential for use in the supercritical water reactor and to assess the influence of alloying elements on corrosion behavior. The corrosion weight gains from such systematic testing are seen to be a factor of five higher than those measured at 360 °C but the protectiveness ranking of the alloys is similar. Detailed characterization of the oxide layers to rationalize the differences in corrosion behavior was performed using synchrotron radiation and systematic differences are observed in protective and non-protective oxides, especially near the oxide–metal interface. The overall corrosion rate of the best Zr-based alloys compared favorably with those of other alloys being considered for use in the supercritical water reactor.