Oxygen sensors for Heavy Liquid Metal coolants: Calibration and assessment of the minimum reading temperature

• Published in: Journal of nuclear materials 2017-04, Vol.486, p.197-205
• Main Authors: Bassini, S., Antonelli, A., Di Piazza, I., Tarantino, M.
• Format: Article
• Language: English
• Subjects: Air temperature; Bismuth; Conductivity; Coolants; Copper; Copper oxides; Electric potential; Electrodes; Electrolytes; Heavy liquid metals; Heavy metals; Internal reference electrode; Ion currents; Liquid metals; Metal oxides; Molten salt electrolytes; Oxygen; Oxygen probes; Partially stabilized zirconia; Platinum; Potentiometric oxygen sensor; Residual stress; Sensors; Solid electrolytes; Studies; Temperature; Temperature effects; Yttria stabilized zirconia; Yttrium oxide; Zirconia; Zirconium dioxide
• ISSN: 0022-3115; 1873-4820
• DOI: 10.1016/j.jnucmat.2017.01.031

Oxygen sensors for Heavy Liquid Metals (HLMs) such as lead and LBE (lead-bismuth eutectic) will be essential devices in future Lead Fast Reactor (LFR) and Accelerator Driven System (ADS). Potentiometric sensors based on solid electrolytes were developed in recent years to this purpose. Internal reference electrodes such as Pt-air and Bi/Bi2O3 liquid metal/metal-oxide are among the most used but they both have a weak point: Pt-air sensor has a high minimum reading temperature around 400 °C whereas Bi/Bi2O3 suffers from internal stresses induced by Bi volume variations with temperature, which may lead to the sensor failure in the long-term. The present work describes the performance of standard Pt-air and Bi/Bi2O3 sensors and compares them with recent Cu/Cu2O sensor. Sensors with Yttria Partially Stabilized Zirconia (YPSZ) electrolyte were calibrated in oxygen-saturated HLM between 160 and 550 °C and the electric potential compared to the theoretical one to define the accuracy and the minimum reading temperature. Standard Pt-air sensor were also tested using Yttria Totally Stabilized Zirconia (YTSZ) to assess the effect of a different electrolyte on the minimum reading temperature. The performance of Pt-air and Cu/Cu2O sensors with YPSZ electrolyte were then tested together in low-oxygen HLM between 200 and 450 °C. The results showed that Pt-air, Bi/Bi2O3 and Cu/Cu2O sensors with YPSZ measured oxygen in HLMs down to 400 °C, 290 °C and 200 °C respectively. When the YTSZ electrolyte was used in place of the YPSZ, the Pt-air sensor measured correctly down to at least 350 °C thanks to the superior ionic conductivity of the YTSZ. When Cu/Cu2O and Pt-air sensors were tested together in the same low-oxygen HLM between 200 and 450 °C, Cu/Cu2O sensor worked predictably in the whole temperature range whereas Pt-air sensor exhibited a correct output only above 400 °C. •Oxygen sensors for HLMs with different reference electrodes and stabilized zirconia electrolytes.•Calibration of oxygen sensors in oxygen-saturated HLMs in a wide temperature range.•Assessment of the accuracy and the minimum reading temperature of the oxygen sensors in HLMs.