Evaluation of the response time of H-concentration probes for tritium sensors in lead-lithium eutectic alloy

Dynamic tritium concentration measurement in lead-lithium eutectic 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 using different solid-state electrolytes for molten lead-lithium eutectic have been reported and tested by the Electrochemical Methods Lab at Institut Quimic de Sarria (IQS). In the present work the following ceramic elements have been synthesized and characterized by X-ray diffraction (XRD) in order to be tested as a Proton Exchange Membranes (PEM) H-probes: BaCeO₃, BaCe_0.6Zr_0.3Y _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 shifting from a fixed hydrogen partial pressure at the working electrode to high purity argon. In this experimental campaign a fixed and known hydrogen pressure has been used in the reference electrode. The goal of these experiments is to evaluate the sensor response time when the hydrogen concentration in the environment is rapidly changed. All experiments have been done at 500 °C and 600 °C. The sensor constructed using the proton conductor element BaCe_0.6Zr_0.3Y_0.1O _3-δ exhibited stable output potential and its value was close to the theoretical value calculated with the Nernst equation. In contrast, the sensors constructed using the proton conductor elements BaCeO₃ and Sr(Ce_0.9-Zr_0.1)_0.95Yb_0.05O _3-δ showed higher deviations between experimental and theoretical data, and long response times.