| Author(s) |
Allison R. Probert, Ethan Hisle, Mary Sevart, Mitchell Mika, Alexander Swearingen, Cynthia Adkins, Karen Wright, Jason Schulthess, Luca Capriotti, Assel Aitkaliyeva |
| Abstract Scope |
Current models for predicting the thermal properties of U-Pu-Zr fuels rely on measurements from unirradiated alloys, using empirical correction factors to account for predicted porosity and sodium infiltration of fission gas bubbles. However, these correlations are based on data from fuels with burnups limited to less than 2 at. %. Understanding the evolution of thermal properties throughout the fuel due to complex irradiation-induced behaviors is crucial, especially at higher burnups where behaviors such as constituent redistribution and lanthanide migration are more pronounced, potentially leading to compromised heat transfer and localized hot spots. To address this data gap, we measured local composition, porosity, and thermal diffusivity of a 10.9 at. % burnup U-19Pu-10Zr sample to determine thermal conductivity with respect to radial position. EPMA, SEM, and thermoreflectance analysis revealed four distinct zones with varying compositions and porosity, significant redistribution of U, Pu, and Zr, and degraded thermal conductivities across each zone, with large variations compared to early-life samples. The redistributive behavior, porosity, and thermal conductivity were evaluated against current predictive capabilities in BISON and MFUEL, showing inconsistent agreement. These findings highlight the importance of expanded data to develop and validate models that account for irradiation-induced changes in fuel properties, which are crucial for enhancing fuel performance, optimizing reactor operation, and ensuring safety at higher burnups. |