Feasibility Study of the Internal Zr/ZrO2 Reference Electrodes in Supercritical Water Environments

A specifically designed reference electrode was developed for analyzing the electrochemical behaviors of alloy materials in supercritical water (SCW) environments and identifying the associated electrochemical parameters. The internal Zr/ZrO₂ reference electrodes constructed for high-temperature conditions were manufactured and adopted to measure the electrochemical corrosion potential (ECP) of the sample in SCW environments. Before the electrochemical analysis, the oxidation behaviour of zirconium would be investigated in SCW environment. The mass gain of zirconium is assumed due to formation of ZrO₂ and there was only 78% of the original thickness of zirconium existed after the 1300 h immersion test in SCW environments with 8.3 ppm dissolved oxygen. In deaerated SCW environments, the thickness of zirconium is about 88% of the original one. The outcome indicated that the laboratory-made Zr/ZrO₂ reference electrode was able to continuously operate for several months and delivered consistent and steady ECP data of the sample in SCW environments.