Mapping of rare earth elements in nuclear waste glass–ceramic using micro laser-induced breakdown spectroscopy

• A dedicated micro-LIBS system was set up to perform fast elemental mapping.
• Mapping was conducted on a Mo-rich nuclear waste glass–ceramic for the first time.
• Mo, Ca, Sr, Eu, Nd, La, Pr, Al, Fe and Zr were detected in one spectral range.
• Crater size was about 5 μm on crystallites of the sample.
• Fractionation behavior of elements was investigated by principal components analysis.

A micro-LIBS system was set up based on a quadruple Nd:YAG laser at 266 nm coupled with a microscope. Elemental mapping was performed on a Mo-rich glass–ceramic sample containing CaMoO4 crystallites hundreds of microns in length and about 25 μm in section diameter. The topography of single-shot laser-induced craters was characterized using an atomic force microscope (AFM), which revealed a crater size less than 7 μm. Mappings of Mo, Ca, Sr, Al, Fe, Zr and rare earth elements such as Eu, Nd, Pr and La were undertaken. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was conducted to validate the micro-LIBS analysis. Principal components analysis calculation was used to investigate the correlation of elements in the two phases of glass–ceramic. Correlation between Ca, Sr, rare earth elements and Mo indicates their preferential incorporation into the calcium molybdate crystalline phase. Anti-correlation between Fe, Zr, Al and Mo revealed their affinity to the glass phase.