• Yellowcake (also called urania) is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores.
• It is a step in the processing of uranium after it has been mined but before fuel fabrication or enrichment. Yellowcake concentrates are prepared by various extraction and refining methods, depending on the types of ores.
• Typically, yellowcakes are obtained through the milling and chemical processing of uranium ore forming a coarse powder that has a pungent odor, is insoluble in water, and contains about 80% uranium oxide, which melts at approximately 2880 °C.
• Yellowcake is used in the preparation of uranium fuel for nuclear reactors, for which it is smelted into purified UO₂ for use in fuel rods for pressurized heavy-water reactors and other systems that use natural unenriched uranium, like heavy-water reactors.

Source: Wiki