Fast Zirconium Oxidation Using Supercritical Water

A novel route for fast zirconium oxidation is reported, using supercritical water, for the case of Zircaloy-4 tubes that are used to clad nuclear fuel pellets in pressurized water reactors. An adherent and dense monoclinic zirconia layer 28 µm thick is obtained after 5 h of supercritical water oxidation at 500 °C. The zirconia crystallites are about 13 ± 2 nm in size. This technique reduces the time needed to oxidize Zircaloy-4 from several weeks to a few hours when standard conditions are being used.