Plasma emission intensity expansion of Zr metal and Zr oxide via microwave enhancement laser-induced breakdown spectroscopy†

In this study, we aimed to understand the effects of microwaves on plasma emission intensity between Zr metal and Zr oxide using microwave-enhanced laser-induced breakdown spectroscopy (MWE-LIBS), designed for analyzing nuclear fuel debris mixtures of metals and oxides. Previous studies have shown Zr excitation and ionization enhancement by microwaves, but the effects between metals and oxides were unclear. Hence, we examined the MWE-LIBS on various Zr sample types, including metals and oxides, as they are both used in nuclear fuel rods. Preliminary results by 3D microscope imaging suggest that MWE-LIBS may potentially reduce crater formation, although further investigation is needed to confirm this effect. The results from high-resolution spectrometer analysis also showed consistent enhancements in Zr atomic, ionic, and molecular emissions, regardless of sample type. The intensity emission was increased over 100 times, resulting in low continuum emissions for all sample types. Microwave irradiation did not significantly affect continuum background emissions but caused a significant increase in Zr emission lines, leading to a higher signal-to-noise ratio (SNR) across all sample types. Microwaves affect Zr metals and oxides similarly, lowering the excitation temperature and increasing ionization, despite their different melting temperatures. This study highlights the effectiveness of MWE-LIBS in analyzing Zr metals and oxides in nuclear fuel debris.