Calibration of YSZ Oxygen Sensor for Use in a Lead-alloy Coolant System

Abstract

Liquid lead-bismuth eutectic (LBE) may see extensive use as a coolant fluid, and perhaps also as a spallation target, in the next generation nuclear energy system. However, it is very corrosive to the common steels used in nuclear installations. This corrosion problem can be prevented by the formation of a protective oxide layer on the exposed surface of steel. For this purpose, accurately measuring and controlling the oxygen concentration in liquid LBE is very important. Electrochemical oxygen sensors with In/In 2 O 3 and Bi/Bi 2 O 3 reference systems can be used as in situ devices for measuring the oxygen concentration in liquid LBE. YSZ (Yttria Stabilized Zirconia) oxygen sensor with molten bismuth saturated with oxygen as a reference, has been selected to measure the oxygen concentration in LBE coolant system. The oxygen concentration difference across the solid electrolyte and the resultant oxygen ion conduction inside the electrolyte establish an electromagnetic force (EMF) that is used to measure the ppb level of dissolved oxygen concentration in liquid LBE. In this paper, the sensitivity of an YSZ oxygen sensor has been evaluated. Sensor calibration curves in liquid LBE at 450 o C have been obtained.