As-cast microstructures in U-Pu-Zr alloy fuel pins with 5-8Â wt.% minor actinides and 0-1.5Â wt% rare-earth elements

►Microstructures consist of high-Zr inclusions surrounded by a high-actinide matrix. ►Alloys with rare-earth (RE) elements contain inclusions that are high in REs. ►Concentrations of U and Zr vary inversely in the matrix. ►Am occurs in the matrix and with high-RE inclusions.