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 exp osure of less than or equal to 6 dpa proceeds by very different paths in these two materials. The large difference in dislocation loop evolu tion appears to account for the ease of void swelling in alpha-Al2O3 a nd the strong resistance to void formation in MgAl2O4. Irradiation of MgAl2O4 to much higher exposure (22-230 dpa) in FFTF confirms the deta ils of the dislocation evolution, which involves a progressive change in Burgers vector and habit plane as interstitial loops increase in si ze. Constraints unique to the MgAl2O4 crystal structure do not allow t he formation of dislocation network structures that favor swelling.