Award Date

8-1-2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

David Hatchett

Second Committee Member

Kenneth Czerwinski

Third Committee Member

Frederic Poineau

Fourth Committee Member

William Culbreth

Number of Pages

137

Abstract

This research explores a novel method of increasing the solubility of uranium oxides and other actinide oxides in room temperature ionic liquids (IL) using direct dissolution. The goal is to further expand our knowledge of actinide dissolution and possible nuclear fuel cycle material applications using ionic liquids. The novelty of the methods is focused on the use of oxidizing gas generated using air passed through an ozone generator. While examples of dissolution exist in IL using acidic functionalized ionic liquids, the solubility of all possible oxide species was not demonstrated. Also, the addition of aqueous acid to IL containing actinide oxides has been successfully demonstrated. However, the presence of large concentrations of water and secondary acid species complicates both the speciation and recovery of the actinides electrochemically using IL systems. Thus the direct dissolution of U3O8, UO2, and UO3 with air generated oxidizing gas was evaluated separately in n-trimethyl-n- butylammonium bis(trifluoromethanesulfonyl)imide [Me3NnBu][TFSI] without acid functionalization or addition of secondary species such as HTFSI. These soluble species for each compound were analyzed spectroscopically and characterized electrochemically with the goal of recovering the actinide materials at the electrode surface. Methods including cyclic voltammetry, bulk deposition, and pulse deposition electrochemical techniques were utilized to obtain uranium deposits at the electrode surface. These deposits were then analyzed by scanning electron microscopy and x-ray diffraction. These same processes and instrumental analyses were then applied to a mixture of uranium oxides. The goal of this dissertation work is to provide a robust pathway for the recovery of oxide material similar to spent fuel, and to provide comparison to modern techniques of nuclear material separation and recovery. This method will show that uranium oxides, regardless of molecular form, can be dissolved and recovered using the same methods to create a consistent procedure that can contribute to technological advances or waste-reducing alternative processes in the nuclear fuel cycle. This dissertation hypothesizes a pathway to directly dissolve uranium oxides with minimal outside contaminants in a manner that allows for spectroscopic and electrochemical analysis, ultimately resulting in the recovery of uranium oxide.

Keywords

electrochemistry; ionic liquid; radiochemistry; room temperature ionic liquid; uranium; uranium oxide

Disciplines

Analytical Chemistry | Chemistry | Inorganic Chemistry

File Format

pdf

File Size

2900 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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