Keywords

Diffusion, microsructure, intermetallics, uranium, iron, microscopy

Abstract

U-Zr metallic fuels cladded in Fe-alloys are being considered for application in an advanced Sodium-Cooled Fast Reactor (SFR) that can recycle the U-Zr fuels and minimize the long-lived actinide waste. To understand the complex fuel-cladding chemical interaction of the U-Zr metallic fuel with Fe-alloys, a systematic multicomponent diffusion study was carried out using solid-to-solid diffusion couples. The U-10 wt.% Zr vs. pure Fe diffusion couples were assembled and annealed at temperatures, 630, 650 and 680°C for 96 hours. Development of microstructure, phase constituents, and compositions developed during the thermal anneals were examined by scanning electron microscopy, transmission electron microscopy and X-ray energy dispersive spectroscopy. A complex microstructure consisting of several layers that include phases such as U6Fe, UFe2, ZrFe2, α-U, β-U, Zr-precipitates, χ, ε, and λ was observed. Multiphase layers were grouped based on phase constituents and microstructure, and the layer thicknesses were measured to calculate the growth constant and activation energy. The local average compositions through the interaction layer were systematically determined, and employed to construct semi-quantitative diffusion paths on isothermal U-Zr-Fe ternary phase diagrams at respective temperatures. The diffusion paths were examined to qualitatively estimate the diffusional behavior of individual components and their interactions. Furthermore, selected area diffraction analyses were carried out to determine, for the first time, the exact crystal structure and composition of the χ, ε and λ-phases. The χ, ε and λ-phases were identified as Pnma(62) Fe(Zr,U), I4/mcm(140) Fe(Zr,U)2, and I4/mcm(140) U3(Zr,Fe), respectively.

Notes

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Graduation Date

2013

Semester

Summer

Advisor

Sohn, Yongho

Degree

Master of Science in Materials Science and Engineering (M.S.M.S.E.)

College

College of Engineering and Computer Science

Department

Materials Science Engineering

Degree Program

Materials Science and Engineering

Format

application/pdf

Identifier

CFE0004908

URL

http://purl.fcla.edu/fcla/etd/CFE0004908

Language

English

Release Date

August 2013

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Subjects

Dissertations, Academic -- Engineering and Computer Science, Engineering and Computer Science -- Dissertations, Academic

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