WHY IS MAGNESIA SPINEL A RADIATION-RESISTANT MATERIAL

Side-by-side irradiation of stoichiometric MgAl2O4 and alpha-Al2O3 in JOYO shows that the radiation-induced microstructural evolution to exposure of less than or equal to 6 dpa proceeds by very different paths in these two materials. The large difference in dislocation loop evolution appears to account for the ease of void swelling in alpha-Al2O3 and the strong resistance to void formation in MgAl2O4. Irradiation of MgAl2O4 to much higher exposure (22-230 dpa) in FFTF confirms the details of the dislocation evolution, which involves a progressive change in Burgers vector and habit plane as interstitial loops increase in size. Constraints unique to the MgAl2O4 crystal structure do not allow the formation of dislocation network structures that favor swelling.