Testing and performance of electrolytic oxygen meters for use in liquid sodium

The performance of yttria-doped thoria ceramic electrochemical oxygen meters in liquid sodium is described. Tests were carried out using laboratory loops. Temperature coefficients of the oxygen meters have been measured between 3800C and 4800C, and the response to changes in oxygen level using cold-trap temperatures from 1250C to 2500C was determined. The ceramic has been shown to give good performance over lifetimes exceeding 400 days in some cases. The temperature coefficients and response to oxygen level changes are in good agreement with thermodynamic predictions. The effect of running the meters in high-oxygen sodium has been studied and a general mode of failure has been shown to be grain-boundary attack by oxygen/sodium solutions. The effect of #betta#-radiation on the meters has been studied. The meters with a metal/metal oxide reference electrode were unaffected by dose rates up to 52860 mGy h-1. Meters with an air reference electrode do show an effect as a voltage reduction at levels down to 2420 mGy h-1. This effect was temperature-dependent and was insignificant at 5000C. (orig.)