Long term degradation of electrical insulation of Al 2O 3 under high flux fission reactor irradiation

Abstract

Long term increase of electrical conductivity under irradiation was observed in some Al 2O 3 (polycrystal and single crystal alumina) specimens in in situ electrical measurements in the High Flux Isotope Reactor in the framework of the Japan/USA collaboration called JUPITER project. Especially, chromium doped single crystal alumina showed substantial increase of electrical conductivity at moderate doses of ∼0.1 dpa, which had similarity to the phenomenon called radiation induced electrical degradation (RIED). Irradiation to doses above 0.1 dpa did not cause a further degradation of electrical conductivity, but instead resulted in an improvement in insulating ability. Behavior of the observed increase of electrical conductivity is described in conjunction with the reported phenomena in RIED and some mechanisms responsible for the observed increase are speculated from the results obtained.