Laser-Induced Breakdown Spectroscopy (LIBS) Measurement of Uranium in Molten Salt

Abstract

In this current study, the molten salt aerosol-laser-induced breakdown spectroscopy (LIBS) system was used to measure the uranium (U) content in a ternary UCl-LiCl-KCl salt to investigate and assess a near real-time analytical approach for material safeguards and accountability. Experiments were conducted using five different U concentrations to determine the analytical figures of merit for the system with respect to U. In the analysis, three U lines were used to develop univariate calibration curves at the 367.01 nm, 385.96 nm, and 387.10 nm lines. The 367.01 nm line had the lowest limit of detection (LOD) of 0.065 wt% U. The 385.96 nm line had the best root mean square error of cross-validation (RMSECV) of 0.20 wt% U. In addition to the univariate calibration approach, a multivariate partial least squares (PLS) model was developed to further analyze the data. Using partial least squares (PLS) modeling, an RMSECV of 0.085 wt% U was determined. The RMSECV from the multivariate approach was significantly better than the univariate case and the PLS model is recommended for future LIBS analysis. Overall, the aerosol-LIBS system performed well in monitoring the U concentration and it is expected that the system could be used to quantitatively determine the U compositions within the normal operational concentrations of U in pyroprocessing molten salts.

Review of Candidate Techniques for Material Accountancy Measurements in Electrochemical Separations Facilities

“…Such a finding is supported by experimental studies in glove-box studies using both uranium and actinide surrogate materials. Williams et al developed and tested linear calibration curves for uranium spectral lines for an aerosol-LIBS measurement (at 367.01, 385.96, and 387.10 nm), reporting that that they achieved accurate calibration curves via linear regression analysis 64 ; similar results were likewise reported for Ce and Gd (55.2-and 564.2-nm lines, respectively) used as U/Pu surrogates. 65 As such, these response curves (along with their estimated limit of detection) could in principle be used to simulate the instrument response within a flow sheet model.…”

“…Laser-induced breakdown spectroscopy was first proposed for electrochemical sampling measurements because it can be performed at significant distance from its intended target, potentially simplifying its implementation and potentially allowing for deployment above the electrorefiner vessel. [62][63][64][65] LIBS has been considered for both in situ 63 and ex situ 65 deployment. The deployment scenario would drive latency of measurement (low for in situ measurements and medium to high for ex situ).…”

Survey and Assessment of Computational Capabilities for Advanced (Non-LWR) Reactor Mechanistic Source Term Analysis.

“…Williams developed a system which aerosolizes molten salts for analytical applications, utilizing laser-induced breakdown spectroscopy (LIBS) to measure elemental concentration in the aerosols [274][275][276]. A specific nebulizer design is used to generate aerosols of LiCl-KCl salt systems containing Ce and U.…”

Quantitative prediction of rare earth concentrations in salt matrices using laser-induced breakdown spectroscopy for application to molten salt reactors and pyroprocessing

“…Moreover, the benefits of in situ, standoff, on-line, multi-elemental analysis with LIBS outweigh the higher performance of more traditional techniques in industrial applications. LIBS has been used to analyse various types of solid 15,[19][20][21][22][23][24] , liquid 17,[25][26][27][28][29][30] and aerosol 31,32 samples containing rare earth and actinide elements. Research on using LIBS for analysing salt matrices for pyroprocessing or molten salt reactors has been led by the Phongikaroon group 15,26,31,32 (based in Virginia, USA).…”