Electrochemical Impedance Spectroscopy (EIS) used as a diagnostic tool of oxygen sensors for molten lead - Bismuth eutectic alloy (44.5% Pb - 55.5% Bi)

One of the coolants proposed for accelerator drive systems (ADS) and Generation IV nuclear reactors is molten lead. A key parameter in the use of molten lead as a coolant is the oxygen activity in the liquid alloy. Potentiometric oxygen sensors for molten metals have been developed in the Electrochemistry Laboratory at Institut Quimic de Sarria since 1998. In this paper we used Electrochemical Impedance Spectroscopy as a diagnostic tool to evaluate the sensor status in service operations. The following parameters have been evaluated: sensor impedance at different temperatures and the effect of using a reductive and a low oxygen content as covering gases, effect of metal oxides accumulation at the ceramic element of the sensor and measurement of the impedance of a short-circuited sensor.