Krypton irradiation damage in Nd-doped zirconolite and perovskite as potential ceramics for inert matrix fuel and plutonium disposition

Understanding the effect of radiation damage and noble gas accommodation in potential ceramic hosts for plutonium disposition is necessary to evaluate the long-term behaviour during geological disposal. Polycrystalline samples of Nd-doped zirconolite and Nd-doped perovskite were irradiated ex-situ with 2 MeV Kr + at a dose of 5x10 15 ions.cm -2 to simulate plutonium nuclei recoil during alpha decay. The feasibility of thin section preparation of both pristine and irradiated samples by Focussed Ion Beam sectioning was demonstrated. After irradiation, the Nd-doped zirconolite revealed a well defined amorphous region separated from the pristine material by a thin (40-60 nm) damaged interface. The Nd-doped perovskite contained a defined irradiated region composed of an amorphous region surrounded by damaged regions. In both samples, as revealed by electron diffraction, the damaged regions and interface have a structure in which the fluorite sublattice is present while the pristine lattice is absent. In addition in Nddoped perovskite, the amorphisation dose depended on crystallographic orientation and possibly sample configuration (thin section and bulk). In Nd-doped perovskite, Electron Energy Loss Spectroscopy study revealed a change in Ti coordination associated with the crystal to amorphous transition.