Raman K. Mishra

Analysis of barium borosilicate glass matrix for uranium determination by using ns-IR-LIBS in air and Ar atmosphere

Abstract In this paper, an attempt to explore the use of laser induced breakdown spectroscopy (LIBS) technique for determination of uranium in the vitrified simulated high level barium borosilicate waste glass matrix was made with a commercial portable LIBS system. The emission spectrum of the waste glass being very complex, detailed study was done for proper choice of the emission lines. Investigations were carried out to optimize the experimental parameters like laser energy and acquisition delay time for the analysis. Calibration curves were obtained for two emission lines of U in these glasses. Effect of Ar atmosphere was also studied and the signal intensity was found to be ∼5 times higher than in air atmosphere The emission lines used for normalization with vast difference in the upper energy level compared to the line of interest were found to give poor precision in air. In the Ar atmosphere, this effect was found to be much less significant and such emission lines can be used as an internal standard to achieve precise calibration curves. LIBS approach will be useful for real time determination of U in such samples, eliminating quantitative dissolution step required in many other analytical techniques like solution based ICP-MS/OES.

Thermally Grown Oxide Layer on Aluminized Superalloy 690 Substrate and its Stability in Nitrate-Based Environment

Aluminides were formed on Ni-Cr-Fe based superalloy 690 substrates using pack aluminization process at 1273 K in controlled atmosphere. Thermal oxidation of aluminized specimens was carried out at 1273 K for a total period of 4 hours in air. The thermally grown oxide layer was examined using X-ray diffraction (XRD) studies on top surface and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) analysis along the cross-section of the sample. The oxide layer developed on aluminized superalloy 690 substrate consisted of Al2O3 layer with a thickness of about 2 μm. The oxidized specimens were exposed in nitrate-based environment (simulated high-level nuclear liquid waste) at 373 K for a total period of 216 hours. A good adherence of aluminide coatings was noticed even after prolonged exposure in nitrate-based solution with a little amount of material dissolution from the edges of the specimens. XRD studies on exposed specimen indicated existence of Al2O3 layer on the top surface, which is believed to have resulted in good adherence of aluminide coatings.

Comparison of univariate and multivariate data analysis models for uranium quantification in Trombay historical nuclear waste glass

Abstract Laser induced breakdown spectroscopy recently has been investigated for analysis of nuclear waste glass for uranium quantification. The initial obtained accuracy and precision was ~15%. In this paper, we have compared the analytical merit of the univariative and multivariative PLSR regression models for the determination of U in barium borosilicate simulated waste glass containing significant amount of U. The analytical merit of a Czerny-Turner spectrograph with high spectral resolution and Echelle spectrograph with broadband spectrum recording capacity were compared using spectra simultaneously record from the same plasma. For univariative calibration the superiority of Czerny-Turner spectrograph over the Echelle has been demonstrated here. Multivariative chemometric PLSR model was found to drastically improve the results. It was also observed that selection of spectral window for analysis significantly affects the analytical merit of multivariative analysis. Echelle though shows relatively inferior analytical merit, but by applying Analytical spectral dependant PLSR in Echelle spectra, a much higher degree of improvement was observed. Using ASD-PLSR and Czerny-Turner spectrograph generated spectra an accuracy and precision of 2–2.5% was achieved in this study.