Simultaneous analysis of gadolinium and surface imaging using a fiber-coupled acoustic wave-assisted microchip LIBS system

Abstract

This paper reports a pioneering attempt at simultaneously analyzing gadolinium (Gd) distribution and surface imaging of surrogate debris samples with homogeneous and heterogeneous composition using a fiber-coupled acoustic wave-assisted microchip laser-induced breakdown spectroscopy (AW-mLIBS) system. This system must be applied to the remote analysis of fuel debris at the Fukushima Daiichi Nuclear Power Station (FDNPS). In the AW-mLIBS system, a microchip LIBS was used to measure the Gd distribution maps in the mixed oxide samples. Whereas, during elemental mapping by microchip LIBS, the laser-plasma acoustic waves were simultaneously recorded by microphone and applied for surface imaging of the samples. Additionally, the laser-plasma acoustic waves can be used to adjust the best-focusing position of the microchip LIBS because the acoustic wave amplitude is the strongest at the near best-focusing position. According to the measurement results, the emission spectra of the surrogate debris showed that the optical emission lines at 501.5 nm and 510.3 nm were suitable for Gd detection in the fuel debris sample. For Gd quantification, calibration curves were established from the intensity ratio of Gd/Ce emission lines, yielding the detection limits for Gd in the range of 0.04–0.09 wt% with a relative standard deviation of 3.9%. The surface imaging for the surrogate debris samples was successfully performed by collecting the laser-plasma acoustic waveforms during LIBS elemental mapping.