Masters Theses

Date of Award

8-2019

Degree Type

Thesis

Degree Name

Master of Science

Major

Chemistry

Major Professor

Craig Barnes

Committee Members

David Jenkins, Konstantinos Vogiatzis, Stephen Chmely

Abstract

The overarching goal of this research has been to develop and understand a low-temperature protocol for the digestion of zirconium nuclear fuel cladding. The basic goal will be to reduce the used cladding to low-level radiological waste that can be disposed of more easily and at a reduced cost. A "blue sky" goal will be to eventually recycle the cladding to be reused in industrial processes. A hypothesis of this project is that by using various sulfur chloride compounds, the digestion of Zircaloy® can be converted to zirconium(IV) tetrachloride (ZrCl₄) at low temperatures and the purification/decontamination can be accomplished through a crystallization using thionyl chloride or other sulfur chloride reagents. Three sulfur chloride reagents were investigated, thionyl chloride (SOCl₂), sulfur dichloride (SCl₂) and sulfur monochloride (S₂Cl₂). At 150 °C for each of these reactions the speed at which they digest the metal is very different. For SOCl₂ (2.937 g Zr, 1.3 times of excess SOCl₂), 30 - 40 hours; SCl₂ (3.033 g Zr), 28 hours; and S₂Cl₂ (2.950 g Zr, 2.5 times excess of S₂Cl₂), 3 hours. Recrystallization of ZrCl₄ was accomplished using SOCl₂ and preliminary study of ZrCl₄ in SOCl₂ was conducted. A cloud point technique was used to determine the solubility. This was accomplished by dissolving ZrCl₄ in SOCl₂ then removing SOCl₂ at a specific temperature until crystallization occurred. The solubility was high at high temperature and was very temperature dependent over the range of 0 °C to 50 °C, the solubility increased by a factor of almost 4. Understanding the solubility will aid in the development of a purification strategy due to high-temperature dependence.

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