A candidate matrix material for inert matrix fuel (IMF), yttria-stabilised zirconia (YSZ) has been doped with Nd3+ as a surrogate for Pu3+. To simulate and assess the effects of fission gas accommodation and alpha decay on the microstructure, samples of (Y0.1425,Nd0.05,Zr0.8075)O1.904 have been irradiated with 2 MeV 36Kr+ ions, at fluences of 1×1014 and 5×1015 cm−2, and 200 keV 4He+ ions at fluences of 1×1014, 5×1015 and 1×1017 cm-2. Analysis by transmission electron microscopy (TEM) of thin sections prepared by focussed ion beam (FIB) milling revealed damage was only observed at the highest 36Kr+ and 4He+ fluences. Monte Carlo simulations using the TRIM code showed that it is only at these fluences that the level of atomic displacements was sufficient to result in observable defect cluster formation within the material.