Simulation of radiation damage in zirconolite by swift heavy ion irradiation

Synroc mineral specifically zirconolite has been proven a potential candidate for the immobilization of high level radio-active wastes released from nuclear weapons and nuclear reactors due to its superior properties viz. high radiation and aqueous resistance and high waste loading. It is being studied since decades to isolate the environment from hazardous effects of α-decay events by simulating with low energy heavy (1-1.5 MeV Kr⁺ and Xe⁺) and light (30-200 keV He⁺) ions. In present study, single phase zirconolite samples prepared by solid state reaction method, were irradiated using 120 MeV Au⁺ ions. In-situ XRD along with micro-Raman spectroscopy techniques were employed to investigate the induced effects of swift heavy ions. Disappearance of characteristic diffraction peaks and appearance of broad diffuse scattering bands, confirmed the amorphization of zirconolite. Also, trend of amorphization with fluence was linear at lower fluences followed by a saturation at the higher fluences, inferring the formation of ion tracks. The ion fluence dependent Raman investigation was also in accordance with the XRD observations. In summary, swift heavy ion produced columnar defects, vacancies and induced micro-strains which led to the bonds distortion and eventually amorphization of the zirconolite. (author)