Electrochemical oxygen sensors for on-line monitoring in lead–bismuth alloys: status of development

This paper presents the state of development of oxygen sensors based on the electromotive force (emf) measurement at null current, using yttria stabilized zirconia as solid electrolyte for application in liquid lead–bismuth eutectic (LBE), which is envisaged as a nuclear coolant or as a spallation target in accelerator driven system (ADS) for nuclear waste transmutation. The assembly procedure, the calibration method, as well as the summary of the various validation tests undergone in both static and loop facilities are presented so as to define a real state of achievement and the basics needs for further studies. The sensors are efficient, accurate, rapid and reliable for research loops. However, the poor mechanical resistance as well as the effect of traces of impurities, promoting an increasing time-drift under certain conditions, are to be further studied to improve the sensor reliability for a nuclear use. The oxygen and chromium solubilities were reassessed in the process of the sensor testing, those relations are also given and discussed.