Thermal measurements and computational simulations of three-phase (CeO2–MgAl2O4–CeMgAl11O19) and four-phase (3Y-TZP–Al2O3–MgAl2O4–LaPO4) composites as surrogate inert matrix nuclear fuel

Abstract

This study investigates the temperature dependent thermal conductivity of multiphase ceramic composites for simulated inert matrix nuclear fuel. Fine grained composites were made of CeO2–MgAl2O4–CeMgAl11O19 or 3Y-TZP–Al2O3–MgAl2O4–LaPO4. CeO2 and 3Y-TZP are used as UO2 surrogates due to their similar structures and low thermal conductivities. Laser flash analysis from room temperature to 1273K (1000°C) was used to determine the temperature dependent thermal conductivity. A computational approach using Object Oriented Finite Element Analysis Version 2 (OOF2) was employed to simulate the composite thermal conductivity based on the microstructure. Observed discrepancies between experimental and simulated thermal conductivities at low temperature may be due to Kapitza resistance; however, there is less than 3% deviation between models and experiments above 673K (400°C) for both compositions. When the surrogate phase was replaced with UO2 in the computational model for the four-phase composite, a 12–16% increase in thermal conductivity resulted compared to single phase UO2, in the range of 673–1273K (400–1000°C). This computational approach may be potentially viable for the high-throughput evaluation of composite systems and the strategic selection of inert phases without extensive sample fabrication during the initial development stages of composite nuclear fuel design.