Date of Graduation

5-2017

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Degree Level

Graduate

Department

Mechanical Engineering

Advisor/Mentor

Millett, Paul C.

Committee Member

Nair, Arun K.

Second Committee Member

Huitink, David

Keywords

Applied sciences; Mesoscale; Microstructure evolution; Modeling and simulation; Nuclear fuel; Phase field; Pore migration

Abstract

A phase-field simulation model is being presented that captures the thermal-gradient-driven migration of pores in oxide fuel associated with fuel restructuring. The model utilizes a Cahn-Hilliard equation supplemented with an advection term to describe the vapor transport of fuel material through the pore interior due to gradients in vapor pressure. In addition, the model also captures changes in a migrating pores’ morphology. Simulations demonstrate that the model successfully predicts pore migration towards the hottest portion of the fuel, the centerline. The simulations also demonstrate changes in pore shape that are in agreement with previous experimental observations. Initially isotropic pores are shown to evolve during migration into either a lenticular or a prolate morphology depending on the vapor transport conditions. In addition to the isotropic pores; elliptical initial morphologies are also shown to migrate and experience shape change. This model is the first to simulate the vapor transport mechanism and concurrent changes to a pore’s shape during migration. It is a necessary step in performing accurate simulations of the unique and complicated process known as oxide fuel restructuring.

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