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For the development of the remote elemental analysis method in a radiation environment based on the laser-induced breakdown spectroscopy (LIBS), the radiation effects on the laser oscillation properties of the single crystal (SC) Nd:YAG microchip laser (MCL) were investigated and compared with those of ceramic Nd:YAG MCL. The laser oscillation properties were measured under gamma ray irradiation as a function of dose rate. The effects on the SC MCL properties were very small compared to those on the ceramics, indicating minimal radiation effects on the LIBS signal when using SC MCL. Pulse energy and oscillating build-up time (BUT) were measured for cumulative dose exceeding 1400 kGy. The pulse energy remained stable under irradiation. The BUT also remained stable, demonstrating negligible optical loss accumulation that could affect laser properties even at the demonstrated cumulative dose. The results indicate that the effects of dose rate and cumulative dose on SC MCL laser properties are minimal. The SC MCL was then integrated into the LIBS system, and the gadolinium signal was successfully measured at a dose rate of 5 kGy/hr. These findings highlight the radiation tolerance of SC MCL for remote LIBS applications in harsh radiation environments. [ABSTRACT FROM AUTHOR]

In this experimental study, two-dimensional elemental mapping of simulated fuel debris was conducted by laser-induced breakdown spectroscopy (LIBS). Since the real fuel debris was unavailable as a sample, simulated fuel debris was prepared from predicted materials including compounds and metals. An Nd:YAG laser at the second harmonic was used to generate plasma on the sample surface, and the optical emission from plasma was detected using an echelle spectrometer in the visible wavelength range from 435 to 650 nm. Due to the size and complexity of the collected dataset, the conventional data analysis method was ineffective; consequently, there arose a need to design a new data analysis method for study purposes. Therefore, in the present study, a method that is based on label-free chemometric methods, such as Principal Component Analysis and Multivariate Curve Resolution-Alternative Least Square methods, were implemented to obtain the spatial and spectral information regarding each constituent within the simulated sample. The study results demonstrated that the integration of LIBS and chemometric methods is a highly effective tool to obtain qualitative information regarding samples (e.g. fuel debris) with little or no prior knowledge. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]