Thermal conductivity measurement methods for dispersion MTR fuel characterization

Mai, Tommy
(2026)

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Authors
Supervisors
Pardoen, Thomas  
 ;
Sven Van den Berghe
Abstract
The thermal characterization of high-density uranium-silicide dispersion fuels is essential for the qualification of high-assay low-enriched uranium (HALEU) fuel systems intended for the LEU conversion of high-performance material test reactors (MTRs) such as BR2. As irradiation progresses, microstructural evolution and fuel-matrix interactions can significantly affect thermal transport, making reliable thermal conductivity measurement methods essential for both fuel development and post-irradiation examination. This thesis addresses this need through two complementary approaches targeting macroscopic bulk behavior and microscopic thermal transport phenomena. The main contribution of this thesis is the development and consolidation of two complementary experimental approaches for thermal conductivity characterization of dispersion fuels across different length scales. At the macroscopic scale, the existing pulse-heating MALDONADO-method is developed into a more complete analytical and experimental framework adapted to thin fuel plates, while establishing the basis for its extension toward higher-temperature and hot-cell measurements. At the microscopic scale, the entirely new developed design and simplified manufacturing process for thermal suspended bridge microdevices (MEMS-TSB), progresses from an initial low-yield fabrication process to a reproducible, 100% yield, off-the-shelf device platform, providing a practical route toward localized characterization of individual fuel and matrix constituents. Together, these developments provide complementary tools for connecting the microstructural evolution with the macroscopic thermal performance of high-density uranium-silicide dispersion fuels. The limitations identified for both approaches and the resulting recommendations provide a pathway toward quantitative thermal conductivity measurements over an extended temperature range and, ultimately, under irradiation-relevant conditions.
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Mai, T. (2026). Thermal conductivity measurement methods for dispersion MTR fuel characterization. https://hdl.handle.net/2078.5/280038