Eutectic crystallization in the UO2–Al2O3–HfO2 ceramic phase diagram

In the frame of the Generation IV Sodium Fast Reactor (SFR) safety studies, a core catcher with a sacrificial material could be placed at the bottom of the nuclear reactor. Its role is to dilute the (U, Pu)O2 molten fuel in case of a hypothetical core meltdown accident. A Al2O3–HfO2 ceramic is a candidate for the sacrificial material. To understand how the molten fuel would mix with this sacrificial material, the UO2–Al2O3–HfO2 system was investigated at CEA Cadarache PLINIUS corium platform. The eutectic position of the UO2–Al2O3–HfO2 was determined: the eutectic temperature is 1728±22 °C (2001±22 K) and the eutectic composition is 30 wt% UO2–35 wt% Al2O3–35 wt% HfO2. Then, the pseudo-binary UO2–(50 wt% Al2O3–50 wt% HfO2) phase diagram has been proposed.