Spectral characterization of actinide signatures for nuclear remote sensing applications

It is of interest to the defense community to develop new ways to assess a nuclear event at a distance. Distinguishing between a nuclear and non-nuclear fireball and determining the nuclear material and amount present in the fireball are necessary to inform response accordingly. Spectroscopy provides potential avenues for remote detection of nuclear material, and methods can be developed to monitor nuclear proliferation. In this work, signatures of interest are determined for spectroscopic probing of the nuclear fireball. These signatures and their variation with temperature and other environmental factors yield insight into fundamental processes occurring within the nuclear fireball and can be used to generate predictive models that simulate spectra that may be produced from potential devices. This dissertation focuses on spectral signatures that may be generated from the actinide material and strongly emitting fission products in a nuclear fireball free from the interference of high explosives and engineering materials that may be present in the fireball produced from a conventional weapon. Experiments were performed to determine emission and absorption signatures that result when uranium is subjected to excitation under different conditions (shock tube heating, laser ablation, dust cloud combustion). Using a figure of merit approach to predict which fission product signatures would emit most strongly, selected products assembled in mixtures of varying proportion were subjected to varying degrees of excitation by unconventional and conventional explosives to observe the resulting signatures. Laser ablation of uranium from prior work aided in the identification of signatures for further study. In controlled conditions reminiscent of the high-temperature, early time nuclear fireball, shock tube heating of uranium powder was performed to determine the appearance and variation of atomic signatures at high temperatures. Dust cloud combustion experiments provided some insight into lower temperature conditions in which uranium does not combust in the vapor phase due to strong oxide containment, thereby producing no emission or absorption signatures. This highlighted the effect of method of excitation on the appearance of U signatures since signatures did appear in laser ablation testing in similar temperature regimes, but were condensing from a high-temperature plasma state instead of being heated from room temperature particulate. This further underscored the need for alternative signatures to glean information about the actinide from excitation of fission products. Various formulations, different ratios of Cs and Sr containing carbonates, and two fission product mixtures emulating the fast, independent distributions of U235 and Pu239, were excited in flash powders to observe differences in the resulting signatures. Further testing was performed on combinations of Cs and Sr in the presence of varying metals and high explosives to determine if they could be detected and differentiated between at a standoff distance. These formulations could be distinguished between using spectral methods, which proved promising for future remote sensing applications. From these experiments, uranium particle combustion behavior was characterized, high-temperature uranium emission signatures were obtained, and fission product signatures with the greatest potential for future work were determined.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Weerakkody, Emily Nelum

Contributors dc:contributor

• Glumac, Nick G
• Krier, Herman
• Stephani, Kelly
• Brewster, M Q
• Phillips, Mark

• Uranium plasma
• Absorption spectroscopy
• Uranium combustion
• Shock tube heating

Statement dc:rights

• © Emily Nelum Weerakkody 2021

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/113007

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/113007