Low-temperature fast-neutron and gamma irradiation of alumina

Abstract

Structural stability of the plasma sprayed alumina has been studied after its exposure to 4 K fast-neutron and gamma irradiation. The fast-neutron fluence ( E>0.1 MeV) was 1.8×10 22 n m −2. As shown by X-ray diffraction and high-resolution transmission electron microscopy (HRTEM), the microstructure of alumina consisted of crystalline regions and regions which underwent considerable disordering (i.e. amorphization) during plasma spray deposition. This microstructure has been basically preserved during irradiation. Consequently, the irradiation-induced amorphization has not intervened at this neutron fluence. The light-brown appearance of the irradiated alumina indicated the formation of isolated point defects (colour centres). The accompanying near-isotropic swelling resulted in a small increase in lattice spacing, as measured by X-ray diffraction. The HRTEM provided no evidence for void formation in alumina during 4 K irradiation.