ENEA experience in oxygen measurements

Impurity detection in liquid metals is one of the most important tasks in the development of Accelerator Driven Subcritical (ADS) system technologies. Dissolved oxygen and metal oxides are the most dangerous impurities that could affect the Pb(44.5%)–Bi(55.5%) eutectic alloy cooling/target system, especially in consideration of the potential for system plugging. Accurate measurement of oxygen concentration in heavy metal coolants or targets for nuclear applications, whether liquid lead–bismuth eutectic or pure lead, is a critical issue in defining the need for active oxygen control to first of all prevent contamination of the liquid system by lead and bismuth oxides, and, in addition, to ensure efficient corrosion protection of iron-based alloy structures in contact with the coolant/target if the self-healing oxide layer method of corrosion protection is chosen. Due to this twofold aspect of the management of dissolved oxygen, the monitoring of oxygen concentration becomes of primary importance. This paper will focus on the development of an on-line oxygen monitoring system and more particularly on the description of the test to define the reliability of the electrochemical sensors. In addition, it will address the question of how such systems can be improved.