Spinel ceramics with Al2O3/MgO ratios of 1.00, 1.01, 1.10 or 1.48 were irradiated with fast neutrons (E > 0.1MeV) to a fluence of 3.8 x 1023/m2 at 1700C or 5.7 x 1023/m2 at 190C. There was no obvious difference in property changes between these 2 irradiation conditions. The extent of the macroscopic length change due to these treatments increased almost linearly with increasing Al2O3 content. The specimens were isochronally annealed at up to 1000C and, during annealing, the macroscopic length of the specimens began to decrease at about 200C and shortened monotonically up to 550C. The length then increased slightly up to 650C, and decreased again up to 800C, making a small peak. These final value corresponded to the length of the specimen before irradiation. The shrinkage between 200 and 550C and between 650 and 800C was attributed to the recombination of Frenkel pairs of anions. The expansion between 550 and 650C was attributed to an order-disorder transition in the cation distribution.

Neutron-Induced Damage in Near-Stoichiometric Spinel Ceramics Irradiated Below 200C and its Recovery due to Annealing. T.Yano, A.Insani, H.Sawada, T.Iseki: Journal of Nuclear Materials, 1998, 258-263, 1836-41