Other Uranium Nuclear Fuels

Uranium metal. Metallic uranium as a nuclear fuel is unimportant compared with uranium(IV) oxide. It is manufactured by reducing uranium(IV) fluoride with metallic magnesium or calcium, whereby the mixture as a result of the temperature increase (Mg), or with the help of ignition pellets, burns up producing liquid uranium metal  

Uranium metal unimportant as a fuel compared with uranium(IV) oxide. 

The starting material for the manufacture of enriched uranium metal, uranium(IV) fluoride, is produced by reducing enriched uranium(VI) fluoride with hydrogen or chlorohydrocarbons. 

Uranium-plutonium mixed oxides Uranium-plutonium mixed oxides (MOX) are becoming increasingly important, since plutonium is produced during the reprocessing of spent fuel elements. In these mixed oxide fuel elements a mixture of uranium(IV) and plutonium(IV) oxides with a plutonium content of 3 to 4% is utilized instead of ca. 4% 235u-enriched uranium(IV) oxide. Such fuel elements have similar nuclear physical properties to the standard elements with and can therefore be used in their place. 

In their manufacture uranium(IV) oxide is mixed with the appropriate quantity of plutonium(IV) oxide, the mixture pressed into pellets and then sintered (termed coprocessing in the USA). Uranium(IV) oxide is produced by one of the above-described processes and plutonium(IV) oxide from the aqueous nitrate solution produced during reprocessing by precipitating it as plutonium oxalate and calcining the oxalate. 

---

Uranium-235 can be concentrated by gaseous diffusion and other physical processes, if desired, and used directly as a nuclear fuel, instead of natural uranium, or used as an explosive. 

Several components are required in the practical appHcation of nuclear reactors (1 5). The first and most vital component of a nuclear reactor is the fuel, which is usually uranium slightly enriched in uranium-235 [15117-96-1] to approximately 3%, in contrast to natural uranium which has 0.72% Less commonly, reactors are fueled with plutonium produced by neutron absorption in uranium-238 [24678-82-8]. Even more rare are reactors fueled with uranium-233 [13968-55-3] produced by neutron absorption in thorium-232 (see Nuclear reactors, nuclear fuel reserves). The chemical form of the reactor fuel typically is uranium dioxide, UO2, but uranium metal and other compounds have been used, including sulfates, siUcides, nitrates, carbides, and molten salts. 

One of the many problems of nuclear power is the availability of fuel uranium-235 reserves are only about 0.7% those of the nonfissile uranium-238, and the separation of the isotopes is costly (Section 17.12). One solution is to synthesize fissile nuclides from other elements. In a breeder reactor, a reactor that is used to create nuclear fuel, the neutrons are not moderated. Their high speeds result in... 

High-level wastes consist of spent nuclear fuel and reprocessed wastes. Isotopes of uranium make up by far the majority of high-level wastes, accounting for about 94 percent of the mass of all such wastes. An additional 1 percent consists of plutonium isotopes, and the remaining 5 percent, of isotopes of other elements. 

Nuclear Fuel Reprocessing. Spent fuel front a nuclear reactor contains - tsy easy cwpu Mc-py, ant many other radioaclive isnlopes (fission products). Reprocessing involves the treatment of the spent fuel to separate plutonium and unconsumed uranium from other isotopes so that these can be recycled or safely stored. 

---