Laser-Induced Breakdown Spectroscopy (LIBS) Determination of Cerium and Uranium in Molten Salt Aerosol

摘要

In an electrochemical process, uranium is electrochemically dissolved from used nuclear fuel (UNF) at an anode and deposited at a cathode for reuse. This reprocessing technology offers many advantages including its small foot print, high radiation tolerance, and proliferation resistance. However, as part of the process chemistry, fission products, rare earth elements, and transuranic (including Pu) accumulate in the molten salt electrolyte over time. This buildup of materials poses material accountancy and safeguards concerns. The current process for measuring this buildup of materials involves drawing, transporting, and preparing a sample for analysis using inductively coupled plasma mass spectrometry (ICP-MS). Recently, laser-induced breakdown spectroscopy (LIBS) methods have been explored as an alternative to the ICP-MS method. LIBS measurements can be done within us and with little to no sample preparation. However, implementing LIBS into pyroprocessing poses many challenges based on past molten salt LIBS studies (for example, analysis conducted at the top surface of the molten salt experienced issues with material splashing, surface perturbations, and surface films which influenced the repeatability of the measurement). Recently, Virginia Commonwealth University has used LIBS to detect cerium in a molten salt aerosol. Results have shown that this technique may overcome many of the aforementioned challenges. The main motivation of this work is to further study cerium and uranium in a molten salt aerosol. Here, a preliminary Ce study has been conducted and the figures of merit for Ce in the molten salt aerosol-LIBS system were found to be 131 ppm for the univariate approach and 326 ppm for the multivariate approach.