The fuel consists of uranium rods 5 millimeters in diameter and 33 cm (13 inches) long .
The EBR-II core can accommodate as many as 65 experimental sub-assemblies for irradiation and operational reliability tests, fueled with a variety of metallic and ceramic fuels-the oxides, carbides, or nitrides of uranium and plutonium, and metallic fuel alloys such as uranium-plutonium-zirconium fuel.