Characterisation of ion beam irradiated zirconolite for pu disposition

A number of mineral systems retain significant actinide fractions over geological timescales, rendering them metamict as a result of ot-decay events. These systems can be viewed as natural actinide wasteforms and are a useful guide when designing synthetic materials for the disposition of actinide species arising from civilian and military nuclear activities. The effect of radiation damage on synthetic materials can be simulated by a number of different techniques including incorporation of short lived actinide species into the structures and irradiating samples with heavy charged particles. In this study a polycrystalline zirconolite sample was irradiated with 2 MeV Kr⁺ ions at a fluence of 5 × 10¹⁵ ions cm^-2. The irradiated surface area of the sample was analysed using grazing incidence X-ray diffraction (GIXRD) and grazing incidence X-ray absorption spectroscopy (GIXAS). Pristine samples were also analysed for comparative purposes. GIXRD gave information on the amorphous character of the irradiated surface and GIXAS was used to investigate the effect of irradiation on valence and coordination of key elements in the zirconolite structure.