Quantification of irradiation induced structural disorder in nuclear waste-form ceramics with μ-luminescence spectroscopy of lanthanides

Abstract

The investigation of radiation damaged or metamict minerals and their synthetic analogues has increased appreciably over the past two decades, stimulated by the potential use of mineral-like ceramics as waste forms for the immobilisation of reprocessed spent nuclear fuel and other radioactive waste. In this research field, however, a fast and inexpensive technique operating in the micrometre range may open up new opportunities in the characterisation of radiation damage. We present first results of a heavy-ion (Au) irradiation-study of the important nuclear waste-form matrices zircon (ZrSiO4), xenotime-(Y) (YPO4) and zirconolite (CaZrTi2O7). Bulk, poly-crystalline ceramics were irradiated with accelerated heavy ions (Au) with energies up to 35 MeV. Comparably high heavy-ion energies are chosen to ensure irradiation penetration-depths of 4 - 5 µm accessible to the spatial resolution of optical confocal spectrometers. Summary: We use surface-sensitive, grazing-incident X-ray diffraction of irradiated bulk ceramic pellets for the estimation of the amorphous fraction produced and demonstrate how photoluminescence spectroscopy may be used as a tool for the characterisation and quantification of irradiation-induced structural damage in nuclear waste-form materials on a µm-scale. Ln3+ ions are common substitutes on regular lattice sites in respective ceramic hosts. Their luminescence emissions may be used as structural probe and are very sensitive to their local crystal field.