Oxygen has a fundamental role for the safe operation of GEN IV reactors cooled by Heavy Liquid Metals, HLM. The use of oxygen sensors and dosing the gas in the environment are key issues for the chemistry control of HLMs, in particular when corrosion of structural materials is of concern. In fact, the oxygen concentration must be high enough to grow a protective oxide scale on the surface of the construction materials (steels) in order to prevent their dissolution in the liquid metal. On the other hand, a certain threshold must not be exceeded to prevent precipitation of oxides within the flow paths of the plant. For measuring and controlling the concentration of dissolved oxygen in liquid lead alloys, electrochemical sensors were developed and have been studied for several years.
This study focuses on the work carried out in the CVR, in the convection loop COLONRI I, containing liquid Lead-Bismuth Eutectic, LBE. This vertical loop has several locations where sensors can be placed for monitoring of the local oxygen content. A research study was initiated on the aim of assessing the response and reliability of the sensors in various locations, when different gases were dosed in the liquid metal. For over 1000 hours the sensors were monitored as variables, such as oxygen content and temperature, were changed. Their response as a function of their position was qualitatively evaluated and discussed.