Uranoxidpellets

Uranoxidpellets, or uranium oxide pellets, are the basic solid fuel elements used in many commercial nuclear reactors. They are small, cylindrical ceramic blocks composed mainly of uranium dioxide (UO2). In some reactor types, uranium-plutonium mixed oxide (MOX) pellets are used as an alternative to UO2.

Manufacture begins with converting and enriching uranium to reactor-grade material, followed by forming a fine UO2 powder. The powder is pressed into pellets and then sintered at high temperature to achieve a dense, stable UO2 crystal. Pellets are machined to strict tolerances and given surface finishes to minimize stress during handling and operation. The oxygen-to-uranium ratio and impurity levels are carefully controlled.

Use in reactors: Pellets are loaded into corrosion-resistant cladding tubes, typically made of zirconium alloys, to form fuel rods. Multiple rods are assembled into a fuel assembly that is inserted into the reactor core. As the reactor operates, fission produces heat; fission products accumulate as gas and solid phases inside the pellets, causing swelling and stress that are accommodated by design.

Variants and fuel cycles: In addition to standard UO2 fuel, MOX fuel combines uranium and plutonium oxides. Spent pellets remain highly radioactive and are subject to strict regulatory handling, cooling, and disposal or reprocessing requirements as part of the nuclear fuel cycle.