Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

David W. Shoesmith

Abstract

This thesis reports a series of investigations examining the corrosion process of used nuclear fuel under permanent disposal conditions. The motivation of the project is that the safety assessment of deep geological disposal of spent nuclear fuel requires a fundamental understanding of the processes controlling fuel corrosion which could lead to the release of radionuclides to the geosphere from a failed container.

One primary objective of this project was to develop a computational model in order to simulate fuel corrosion under the disposal conditions. A series of simulations based on COMSOL were designed and developed to determine the influence of redox conditions, with the emphasis on α-radiolysis and steel vessel corrosion products, on the corrosion rate of spent fuel.

A second objective of this project was to develop a more detailed understanding of the H2O2 decomposition process and its influence on UO2 (nuclear fuel) corrosion. The radiolytically produced H2O2 is the primary driving force for nuclear fuel corrosion under disposal conditions. The influence of several variables (potential, pH, carbonate/bicarbonate, and fission products) on the reactivity of H2O2 has been evaluated. Their influence on the surface composition and electrical conductivity of UO2 was found to significantly affect the surface redox reaction rates and alter the overall fuel corrosion rate. The analytical techniques include electrochemical measurements (CV, CSV, ECORR, LPR, EIS) and surface/solution analyses (SEM, XPS, ICP-AES).