Characterization and re-activation of oxygen sensors for use in liquid lead–bismuth

Control of oxygen concentration in liquid lead–bismuth is one of the most important tasks to develop accelerator driven systems. In order to improve the reliability of oxygen sensors, re-activation treatments were investigated as well as characterization of oxygen sensors for use in liquid lead–bismuth. The oxygen sensor with a solid electrolyte of yttria-stabilized zirconia and a Pt/gas reference electrode showed almost the same electromotive force values in gas and liquid lead–bismuth, respectively, as the theoretical ones at temperatures above 400 °C or 450 °C. After long-term use of 6500 h, the outputs of the sensor became incorrect in liquid lead–bismuth. The state of the sensor that indicated incorrect outputs could not be recovered by cleaning with a nitric acid. However, it was found that the oxygen sensor became a correct sensor indicating theoretical values in liquid lead–bismuth after re-activation by the Pt-treatment of the outer surface of the sensor.