Ashwin P. Rao

Date of Award

3-2020

Document Type

Thesis

Degree Name

Master of Science in Nuclear Engineering

Department

Department of Engineering Physics

First Advisor

Michael B. Shattan, PhD

Abstract

This work investigated the capability of a portable LIBS device to detect and quantify dopants in plutonium surrogate alloys, specifically gallium, which is a common stabilizer used in plutonium alloys. The SciAps Z500-ER was utilized to collect spectral data from cerium-gallium alloys of varying gallium concentrations. Calibration models were built to process spectra from the Ce-Ga alloys and calculate gallium concentration from spectral emission intensities. Univariate and multivariate analysis techniques were used to determine limits of detection of different emission line ratios. Spatial mapping measurements were conducted to determine the device's ability to detect variations in gallium concentration on the surface of sample. Chemometric techniques were implemented to build predictive calibration models from the entire spectral data set. Partial least-squares regression was determined to produce the superior calibration model for predicting Ga content in a Ce-Ga alloy. The results demonstrated the SciAps Z500-ER can be coupled with advanced multivariate analytical routines to efficiently and rapidly provide quantitative analysis of impurities in plutonium surrogate metal. By using a handheld LIBS device in lieu of traditional mass spectrometry methods, the chemical analysis time can be reduced to mere seconds. This has direct applications for several national security applications including directly enabling Pu pit production teams to meet the 80 pit-per-year production goal outlined in the 2018 Nuclear Posture Review.

AFIT Designator

AFIT-ENP-MS-20-M-115

DTIC Accession Number

AD1102512

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