Author

Jason C. Wood

Date of Award

3-2020

Document Type

Thesis

Degree Name

Master of Science in Nuclear Engineering

Department

Department of Engineering Physics

First Advisor

Michael Shattan, PhD

Abstract

The role of enriched 6Li in nuclear applications makes the ability to detect and monitor lithium enrichment activity imperative. Detecting levels of enrichment of this isotope currently requires sensitive, complex equipment operated by highly-trained technicians, which is prohibitive to rapid detection of enrichment activity. While commercial companies market portable laser induced breakdown spectroscopy (LIBS) with the ability to detect elements on the order or parts per million concentrations, they have not yet been demonstrated to possess the ability to quantitatively determine isotopic concentrations of lithium. This research performs single-pulse LIBS experiments under laboratory conditions to determine concentrations of 7Li and 6Li in solid samples of lithium hydroxide monohydrate in low-pressure argon environments. Spectra containing the atomic emission of lithium near 670.8 nm are collected in LIBS experiments. Chemometric analysis techniques (principal components regression, partial least squares regression, and neural networks analysis) are applied to these collected spectra to develop calibration curves for this equipment. This analysis suggests that bulk lithium isotopic assay can be determined via LIBS in situ to within a 95% confidence interval in as little as ten minutes for enrichment levels from 3 to 75%. Evidence of plasma self-absorption in isotopic emission spectra is also measured for the first time. Separately, observation of molecular emissions from LiH and LiO was attempted.

AFIT Designator

AFIT-ENP-MS-20-M-124

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