Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Klassen, Robert J.

2nd Supervisor

St. Lawrence, Sterling

Affiliation

Canadian Nuclear Laboratories

Co-Supervisor

Abstract

The purpose of this thesis is to examine the properties of Zr-2.5%Nb pressure tube material in the transverse direction. Through testing at room temperature, material properties such as the strain hardening, strain rate sensitivity and apparent activation volume were investigated. The effects of Zr+ ion-implantation occurring at 300°C, simulating irradiation-induced damage, and the strain rate of loading on these properties were also investigated.

Two methods of testing were performed: in-situ micro-pillar compressions and nanoindentation testing. Ion-implantation was observed to increase material strength and hardness. However, certain implanted micro-pillars displayed early localized failure that reduced strength. This finding warrants further investigation, particularly as irradiation occurs at high temperatures in reactor conditions. Displacement rate change tests yielded an increase in stress with increased displacement rate, while tests performed at constant indenter displacement rates provided mixed results on the effect of strain rate.

Summary for Lay Audience

Nuclear energy provides an attractive solution to the challenge of meeting electricity production demands while reducing carbon emissions, and avoiding sacrifices typically associated with other green methods of power production. The research presented in this thesis examines the mechanical properties of the zirconium alloy, Zr-2.5%Nb, which is used in the pressure tubes of CANDU nuclear reactors. Specifically, the effects of irradiation at 300°C on the material properties, measured by performing tests at a very small size scale, are investigated.

Testing was performed at room temperature using nanoindentation compression and in-situ micro-pillar compressions performed within an electron microscope. The complex modes of deformation occurring within the pressure tube material were characterized by assessing the materials’ response to rate of loading, depth of indentation, and prior ion irradiation (analogous to neutron irradiation) performed at 300°C. The results of this study indicate that the Zr-2.5%Nb micro-pillar samples show a tendency to undergo strain localization when irradiated with zirconium ions at 300°C. This unique finding appears to be a characteristic of the effect of the high irradiation temperature, which indicates that more research is needed to understand the effect of ion irradiation at high temperatures.

The limited application of the results presented to in-service pressure tubes must be acknowledged. Elements of the testing performed, such as ion-implantation, do not perfectly replicate actual in-service conditions. The findings presented are specific to Zr-2.5%Nb tested at room temperature, and with Zr+ ion-implantation performed at 300°C.

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