Isotopic analysis of uranium by LIBS

CARLOS A. RINALDI; FELIX POZZI, MARCELO N.; BOGGIO, NORBERTO G; JUAN VOROBIOF

Mexico

Conferencia; Colloquium Spectroscopicum Internationale XLI & I Latin American Meeting on LIBS; 2019

Autonomous University of Mexico, Mexico

There are several advantages for using laser ablation (LA) for nuclear material detection, which include minimal sample preparation, near instantaneous detection, and isotope detection.The well known laser ablation methods used forelemental and isotope analysis are: LA-inductively coupled plasma-mass spectrometry (LA-ICP-MS), LA-laser absorption spectroscopy (LA-LAS), and LA-optical emission spectroscopy (LA-OES), commonly called LIBS. One of themain advantages of OES is noninvasive and near instantaneous detection and identification of elements in the sample.The detection of special nuclear materials (SNMs), such as uranium and thorium, is of particular interest tomany agencies around the world, i.e., International Atomic Energy Agency (IAEA) . Many of the applications require a safe, simple, easy-to-use, portable method that is able to accurately identify and detect low concentrations of theelements of interest. Chemometrics coupled with LIBS is a suitablecombination for the determination of isotope ratios in air at atmosphericpressure using poorly resolved lines. The extraction of the information from the LIBS spectra, Figure 1, was achieved by using multivariate techniques1 such as principal component analysis (PCA) and projection to latent structures2,3 (PLS).The use of the PLS1 technique that aids in the construction of the multivariate calibration model can accurately determine the 235U/238U isotope ratios.The accuracy obtained for the determination of the 235U/238U isotope shift is considered suitable for a surface measurement which interrogates a few hundreds of nanograms of mass per pulse. It is important to note that single shot analysis is possible at the cost of the precision of the results. Typically, the precision will be in the range from 4 to 10% depending on the enrichment level, which is compatible for use an alarm instrument in complementary access inspection.