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The tubes containing the fuel pellets are sealed: these tubes are called fuel rods. The finished fuel rods are grouped into fuel assemblies that are used to build up the core of a power reactor. Cladding is the outer layer of the fuel rods, standing between the coolant and the nuclear fuel.
Uranium dioxide or uranium(IV) oxide (UO 2), also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used as MOX fuel.
At 1,800 °C (3,270 °F), the cladding oxides melt and begin to flow. At 2,700–2,800 °C (4,890–5,070 °F) the uranium oxide fuel rods melt and the reactor core structure and geometry collapses. This can occur at lower temperatures if a eutectic uranium oxide-zirconium composition is formed.
Inside each fuel rod, pellets of uranium, or more commonly uranium oxide, are stacked end to end. Also inside the core are control rods, filled with pellets of substances like boron or hafnium or cadmium that readily capture neutrons. When the control rods are lowered into the core, they absorb neutrons, which thus cannot take part in the chain ...
As 2011, of the total nuclear fuel used, MOX provides about 2%. [6] Licensing and safety issues of using MOX fuel include: [16] Plutonium oxide is substantially more toxic than uranium oxide, making fuel manufacture more difficult and expensive. As plutonium isotopes absorb more neutrons than uranium fuels, reactor control systems may need ...
Nuclear fuel rods become progressively more radioactive (and less thermally useful) due to neutron activation as they are fissioned, or "burnt", in the reactor. A fresh rod of low enriched uranium pellets (which can be safely handled with gloved hands) will become a highly lethal gamma emitter after 1–2 years of core irradiation, unsafe to ...
Yellowcake is used in the preparation of uranium fuel for nuclear reactors, for which it is smelted into purified UO 2 for use in fuel rods for pressurized heavy-water reactors and other systems that use natural unenriched uranium. Purified uranium can also be enriched into the isotope U-235.
It mainly consists of nuclear fuel and control elements. The pencil-thin nuclear fuel rods, each about 12 feet (3.7 m) long, are grouped by the hundreds in bundles called fuel assemblies. Inside each fuel rod, pellets of uranium, or more commonly uranium oxide, are stacked end to end.