R & D on oxygen sensor for liquid Pb-Bi

Abstract

The formation of the oxide layer is one of the key factors for the corrosion resistance of structural materials against the Pb-Bi melt. The formation of the protective oxide layer is dependent on the oxygen content in the Pb-Bi melt. The R&Ds are carried out to establish the on-line measuring and controlling system of the oxygen content in the Pb-Bi melt. A tube-type oxygen sensor has been developed using the solid electrolyte of yttria stabilized zirconia, YSZ(8-mole% Y_2O_3). The basic characteristics have been investigated under the gas/gas and the gas/Pb-Bi melt environments; i.e. the reference gas is the He gas with 10% oxygen and the oxygen content of the measured gas is varied from 0.05% to 0.1%, and the air used as reference gas/Pb-Bi with saturated oxygen solution. The temperature ranges from 350 to 600℃. The potentiometer for high impedance, KEITHLEY617,is employed. The dependency of the measured voltage on temperature was validated under the stable condition with sufficient holding time. The measured voltage under the stable condition was describable by the theoretical formulation in the gas/gas throughout the temperature range and in the air/Pb-Bi at the temperature higher than 450℃. The material and structure of electrode will be optimized to improve the dynamic response and the integrity of the sensor.