Single crystals of the spinel were heavily irradiated with 0.1MeV fission neutrons to fluences that ranged from about 1026 to about 2 x 1027/m2 at 658 or 1023K. It was found that, at 658K, no voids could be observed at fluences of up to 2.29 x 1027/m2. However, ¼[110] interstitial loops formed. These loops changed their habit plane from (111) to (110) with increasing neutron fluence. At 1023K, the ¼[110]-type interstitial loops grew to form stacking fault networks that comprised stacking faults on each of the 6 equivalent {110} planes. Minute voids also formed preferentially on, or near to, stacking faults after a fluence of 1.37 x 1027/m2. A limited number of very small cavities, which led to a volumetric swelling of only 0.07%, were also observed after a fluence of 2.17 x 1027/m2.

K.Fukumoto, C.Kinoshita, F.A.Garner: Journal of Nuclear Science and Technology, 1995, 32[8], 773-8