A comparison of Stefan and Phase Field modeling techniques for the simulation of melting nuclear fuel

Simulations of heat transfer in UO2 at very high temperatures incorporating the effects of phase transitions are being conducted to help support the design and analysis of experimental work being conducted as part of nuclear safety research. This work includes the interpretation of the behaviour of nuclear fuel under conditions where centerline melting may occur. Models based on the Stefan formulation and Phase Field approach are derived from fundamental principles and implemented using recently published material properties. Both simulations compare well with laser flash experiments in recently published literature. The Phase Field model is recommended for further development due to its versatility in handling heat sources and robustness in simulating the evolution of the solid-liquid interface. These points are demonstrated with an example simulation of centerline melting resultant from fission heating for fuel performance analysis.