Electrical resistivity behaviour of alumina flow channel inserts in PbLi

Abstract In order to minimize the pressure drop induced on a liquid metal flowing in a strong magnetic field, the insertion of ceramic insulators in the PbLi pipes of a fusion breeding-blanket is being seriously considered. These components are known as Flow Channel Inserts. Fully dense alumina ceramic specimens in the shape of furnace crucibles were supplied to the Research Centre Řež, Czech Republic, for electrical measurements at close to operational conditions. The aim of the experiments was to monitor the alumina insulator’s behaviour with time and temperature in an intimate contact with hot PbLi alloy. Therefore, several set of PbLi cooling-heating cycles between 200 and 430 °C were programmed while the alumina resistance was recorded. After the test, the chemical compatibility between the alumina and the alloy was examined by means of the microstructural study of the cut pieces. Under polarization condition and close to the PbLi operational temperature, the FCI required insulating properties can be concluded. Since the calculated conductivity values are comparable with that obtained in vacuum condition, the absence of influence in the alumina behaviour of both the previously applied thermal treatment and the contact with the hot static alloy is therefore deduced. As concluded from SEM and EDX analyses, the initial alumina microstructure was found unaltered after the high temperature tests performed in contact with PbLi, concluding the suitable chemical compatibility between the ceramic and the hot metal alloy.