Analysis of geological materials containing uranium using laser-induced breakdown spectroscopy

Abstract

Laser induced breakdown spectroscopy (LIBS) is a rapid atomic emission spectroscopy technique that can be configured for a variety of applications including space, forensics, and industry. LIBS can also be configured for stand-off distances or in-situ, under vacuum, high pressure, atmospheric or different gas environments, and with different resolving-power spectrometers. The detection of uranium in a complex geological matrix under different measurement schemes is explored in this paper. Although many investigations have been completed in an attempt to detect and quantify uranium in different matrices at in-situ and standoff distances, this work detects and quantifies uranium in a complex matrix under Martian and ambient air conditions. Investigation of uranium detection using a low resolving-power LIBS system at stand-off distances (1.6m) is also reported. The results are compared to an in-situ LIBS system with medium resolving power and under ambient air conditions. Uranium has many thousands of emission lines in the 200-800nm spectral region. In the presence of other matrix elements and at lower concentrations, the limit of detection of uranium is significantly reduced. The two measurement methods (low and high resolving-power spectrometers) are compared for limit of detection (LOD). Of the twentyone potential diagnostic uranium emission lines, seven (409, 424, 434, 435, 436, 591, and 682 nm) have been used to determine the LOD for pitchblende in a dunite matrix using the ChemCam test bed LIBS system. The LOD values determined for uranium transitions in air are 409.013 nm (24700 ppm), 424.167 nm (23780 ppm), 434.169 nm (24390 ppm), 435.574 nm (35880 ppm), 436.205 nm (19340 ppm), 591.539 nm (47310 ppm), and 682.692 nm (18580 ppm). The corresponding LOD values determined for uranium transitions in 7 torr CO 2 are 424.167 nm (25760 ppm), 434.169 nm (40800 ppm), 436.205 nm (32050 ppm), 591.539 nm (15,340 ppm), and 682.692 nm (29080 ppm). The LOD values determine for uranium emission lines using the medium resolving power (10000 λ/ λ) LIBS system for the dunite matrix in air are 409.013 nm (6120 ppm), 424.167 nm (5356 ppm), 434.169 nm (5693 ppm), 435.574 nm (6329 ppm), 436.205 nm (2142 ppm), and 682.692 nm (10741 ppm). The corresponding LOD values determined for uranium transitions in a SiO 2 matrix are 409.013 nm (272 ppm), 424.167 nm (268 ppm), 434.169 nm (402 ppm), 435.574 nm (1067 ppm), 436.205 nm (482 ppm), and 682.692 nm (720 ppm).The impact of spectral resolution, atmospheric conditions, matrix elements, and measurement distances on LOD are discussed. The measurements will assist one in selecting the proper system components based upon the application and the required analytical performance.

Significance of ambient conditions in uranium absorption and emission features of laser ablation plasmas

“…LA-OES (or LIBS) meets most of these criteria (rapid analysis, fieldable, no sample preparation), albeit with some challenges with regard to characterization and identification of nuclear materials (e.g., U). The electronic complexity of high-Z elements, or elements with high partition functions, such as U, generates congested spectra in which specific emission features are challenging to discern without high-resolution spectroscopic equipment [2,3,5,15,19,20]. Furthermore, samples may only contain trace amounts of U in a multiconstituent matrix, allowing emission features of more abundant target constituents to obfuscate those of U [13,18].…”

“…Notably, LA-OES proves practical in detecting isotopic shifts of elements including U [21][22][23][24][25][26][27]. Reported U detection limits employing LA-OES are on the order of parts per million (ppm) [20,28,29]. However, previous investigations also suggest that the U signal varies significantly with ambient conditions using different LA spectrometric techniques [30].…”

Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

“…Prior literature results report LODs for U over a wide range from 3–50,000 ppm 6, 24–26, 28 in LIBS studies. The 2DFS showed enhanced emission intensity relative to LIBS by factors of 5–35×, resulting from LIF pumped by the ECDL.…”

Quantitative Analysis of Cerium-Gallium Alloys Using a Hand-Held Laser Induced Breakdown Spectroscopy Device

“…Nuclear forensics is one such application where LIBS has found significant application [1]. Several studies have demonstrated the ability of LIBS to detect nuclear material in matrices relevant to the nuclear community, such as geological deposits [2,3], uranium ores [4,5], and surrogate nuclear debris [6]. Other studies validated the use of LIBS in nuclear safeguard applications, including analysis of IAEAswipe samples [7], nuclear reprocessing plant activities [8], and standoff detection of radiological threat materials [9].…”