Abstract
The results from a series of oxygen sensor calibrations in a lead-bismuth eutectic (LBE) system are presented. The yttria-stabilized zirconia (YSZ) | Bi/Bi_2O_3 sensors developed at LANL (LA-OS) are shown to behave quite uniformly according to the Nernst law. The sensors are being calibrated in a small stainless steel (316L) LBE container with controlled gas injection (helium or its mixture with oxygen or hydrogen). The apparatus is placed on a rocker to stir LBE. To study the dynamic range and responses, some sensors have been subject to swings between oxygen saturation and depletion limited by magnetite dissociation, and thermal cycling. The measured emf agrees with the theoretically predicted limits very well. For sensor calibrations the oxygen in LBE is first adjusted to a desired level estimated from the Nernst law at the highest calibration temperature. The apparatus is then closed. After certain waiting time, the LBE temperature is gradually reduced in controlled ramps, and the OS output is recorded. It is found that the V-T curves first follow the constant oxygen concentration lines according to the Nernst law, then turn to the oxygen saturation line. The uncertainty of the sensor output is preliminarily estimated to be within 20% of the theoretical value.
