Long-term Stability of Oxygen Sensitive Membrane using Ruthenium Complex for Corrosion Monitoring of Radioactive-waste Repository

In order to monitor corrosion risk of radioactive-waste repository, a fiber-optic oxygen sensor for long-term use was proposed and its durability at high temperature was evaluated. The sensing mecha-nism is based on quenching of luminescence by oxygen. Many kinds of Ruthenium complexes which have different counter-anion and ligand were utilized as oxygen-sensitive dye. Several Ru-complexes were dispersed into silicone resin. Excitation is achieved with a blue LED (470 nm) and the emitted light at around 610 nm is collected by optical fiber. The sensing membranes showed high sensitivity and quick response to gaseous and dis-solved oxygen. Comparison of sensitivity and durability of the Ru-complexes were performed. Degradation behaviors of the sensors in air at 150 ºC were investigated. Also short-term degradation test in hot water (80 ºC) was conducted. Screening of the sensors is un-derway to find the most stable sensor in such environment by this test.