Electrical properties of ceramics during reactor irradiation

Twelve different types of polycrystal and single crystal Al₂O₃ (alumina and sapphire) specimens of varying grades of purity were irradiated for three reactor cycles in a removable beryllium position in a High Flux Isotopes Reactor (HFIR) at Oak Ridge National Laboratory at a temperature of 720-760 K up to a maximum dose of 3 dpa while a dc electric field of 200 V/mm was applied. The recently completed Temperature Regulated In Situ Test (TRIST) facility in the HFIR was used to perform in situ measurements of electrical conductivity. In addition, three Al₂O₃ specimens were simultaneously irradiated without a continuously applied dc electric field. In situ electrical conductivity measurements were performed on the specimens before, during and following each irradiation cycle. Behavior of electrical conduction in Al₂O₃ was studied, with special emphasis on detection of any long-term increase of the electrical conductivity.