Thermal conductivity measurement of the interaction layer between UMo and Al produced by high-energy heavy ion irradiation

Here, we report the first direct thermal conductivity measurement results for Al–UMo interaction layer (IL), which is typically observed in UMo/Al dispersion fuel plates under irradiation. The investigated IL was formed by irradiating Al coated UMo substrate using 80 MeV iodine ions at 180^∘C up to 3.03×10¹⁷ ions/cm² fluence. Microstructural characterization indicated that the induced IL is amorphous with an approximately (U_0.8,Mo_0.2)Al_5.3 stoichiometry, which is similar to that formed under in-pile irradiation. Focused ion beam (FIB) was used to prepare nine specimens of various lengths from the IL that could be suspended across a microfabricated device for thermal conductivity measurement. The measured thermal conductivity values of the IL were significantly lower than the values for both the original UMo fuel and the Al. The successful measurement of the Al–UMo IL provides valuable information for the development and qualification of UMo/Al dispersion fuels for research and test reactor conversion applications, and further demonstrates the promising capabilities of utilizing the suspended bridge method in nuclear fuel research.