The effect of high pressure steam on the oxidation of low-Sn Zircaloy-4 at temperatures between 700 and 900 °C

To see the effect of high pressure steam on the oxidation of low-Sn Zircaloy-4, we measured the weight gain of low-Sn Zircaloy-4 claddings at temperatures between 700 and 900 °C under steam pressure up to 10 MPa. High pressure steam enhanced the oxidation, and the measured weight gain by oxidation was exponentially proportional to the applied steam pressure. The cubic rate law was still applicable to the oxidation under high pressure steam. High pressure steam made poor-quality monoclinic oxide containing many cracks. Rapid transformation of tetragonal oxide to monoclinic oxide due to high pressure steam seems to be the reason for the formation of poor-quality monoclinic oxide.