Low Temperature Performance of LBE Oxygen Sensors with Different Reference Electrodes

Abstract

Lead-bismuth eutectic alloy (LBE) is one of the most important candidate coolant materials for lead-cooled fast reactor (LFR). However, the corrosion of LBE on structural materials will lead to the failure of materials and threaten the safe operation of reactors. At present, controlling the concentration of dissolved oxygen in LBE within 10–6–10−8wt.% is an effective method to inhibit the corrosion of structural materials by LBE. Therefore, the online monitoring of LBE oxygen concentration is an essential method to achieve effective control of oxygen concentration in practical applications. Currently, the LBE oxygen sensor with proven performance usually uses Bi/Bi2O3 or Pt/air as the reference electrode. Their minimum operating temperatures are 350 and 400 ℃, which can hardly meet the test requirements at the cold leg with operating temperatures lower than 300 ℃. To find out the reference electrode which is suitable for low temperature application, potentiometric oxygen sensors with different reference electrodes including Cu/Cu2O, In/In2O3, LSM/air, and LSCF/air were tested in oxygen saturated LBE at the temperature range from 200 to 450 ℃. The applicability of the reference electrode in the low temperature range was evaluated comprehensively through the stability and accuracy of the signal output at different temperatures. The results show that the Cu/Cu2O reference electrode has high accuracy and stability from 247.89 to 451.27 ℃. However, the signal fluctuates greatly and the EMF deviates greatly at a lower temperature of 197.69 ℃. The In/In2O3 reference electrode has good stability over the test temperature range, but significantly deviates from theoretical E over the test temperature range. The LSCF/air reference electrodes have good accuracy and stability over the test temperature range, which possess good lower temperature application properties. The LSM/air reference electrodes have good accuracy from 499.68 to 351.24 ℃, deviated greatly less than 300.88 ℃. This study can provide references for the selection of LBE oxygen sensors for low temperature applications.