Progress on the development of H-concentration probes in eutectic lead-lithium: Synthesis and characterization of electrochemical sensor materials

Dynamic tritium concentration measurement in lithium-lead eutectic (17% Li-83% Pb) is of major interest for a reliable tritium testing program in ITER TBM and for an experimental proof of tritium self-sufficiency in liquid metal breeding systems. Potentiometric hydrogen sensors for molten lithium-lead eutectic have been designed at the Electrochemical Methods Lab at Institut Quimic de Sarria (IQS) at Barcelona and are under development and qualification. The probes are based on the use of solid state electrolytes and works as Proton Exchange Membranes (PEM). In this work, the following compounds have been synthesized in order to be tested as PEM H-probes: BaCeO ₃, BaCe _0.9Y _0.1O _3-δ, SrCe _0.9Y _0.1O _3-δ and Sr(Ce _0.9-Zr _0.1) _0.95Yb _0.05O _3-δ. Potentiometric measurements of the synthesized ceramic elements have been performed at different hydrogen concentrations at 500 °C. In this campaign, a fixed and known hydrogen pressure has been used in the reference electrode. The sensors constructed using the proton conductor elements BaCeO ₃, SrCe _0.9Y _0.1O _3-δ and Sr(Ce _0.9-Zr _0.1) _0.95Yb _0.05O _3-δ exhibited quite stable output potential and its value was quite close to the theoretical value calculated with the Nernst equation (deviation less than 100 mV). Unstable measurement was obtained using BaCe _0.9Y _0.1O _3-δ as a solid state electrolyte in the sensor.