Microstructural evaluation of U-rich U-Zr alloys under near-equilibrium condition

► Formation of delta phase in U-rich U-Zr alloys has been confirmed. ► Delta phase (UZr2) forms only under prolonged aging treatment in as-cast alloys. ► Volume change accompanying the δ-phase formation may affect in-pile fuel behavior. ► A model of particle coalescence has been proposed here.