Characterisation of ThO₂-CeO₂ sintered pellets fabricated by POP and CAP processes using impedance spectroscopy technique

Pellets of ThO₂-CeO₂ have been fabricated as a surrogate material for ThO₂-PuO₂ fuel being considered for use in Indian Advanced Heavy Water Reactor (AHWR). The green pellets were prepared by two different routes, namely, powder pellet route (POP) and coated agglomerate pelletisation route (CAP) and sintered in both oxidizing and reducing atmosphere. Preliminary investigations using impedance spectroscopy has been carried out on these samples. The electrical conductivity of sintered pellets was found to be significantly affected by the chemical inhomogeneity and porosity present in pellets. Higher conductivity has been observed for the pellets sintered in reducing atmosphere compared to those sintered in air. The results indicate that impedance spectroscopy can be used as a tool for evaluation of pellets in terms of chemical in terms of chemical homogeneity and non-stoichiometry. (author)