MOX fuel

Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material, usually consisting of plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an alternative to the low-enriched uranium (LEU) fuel used in the light water reactors that predominate nuclear power generation. For example, a mixture of 7% plutonium and 93% natural uranium reacts similarly, although not identically, to LEU fuel. MOX usually consists of two phases, UO₂ and PuO₂, and/or a single phase solid solution (U,Pu)O₂. The content of PuO₂ may vary from 1.5 wt.% to 25–30 wt.% depending on the type of nuclear reactor. Although MOX fuel can be used in thermal reactors to provide energy, efficient fission of plutonium in MOX can only be achieved in fast reactors.

One attraction of MOX fuel is that it is a way of utilizing surplus weapons-grade plutonium, an alternative to storage of surplus plutonium, which would need to be secured against the risk of theft for use in nuclear weapons. On the other hand, some studies warned that normalising the global commercial use of MOX fuel and the associated expansion of nuclear reprocessing will increase, rather than reduce, the risk of nuclear proliferation, by encouraging increased separation of plutonium from spent fuel in the civil nuclear fuel cycle.

Mixed oxide

In chemistry, a mixed oxide is a somewhat informal name for an oxide that contains cations of more than one chemical element or cations of a single element in several states of oxidation.

The term is usually applied to solid ionic compounds that contain the oxide anion O²⁻ and two or more element cations. Typical examples are ilmenite (FeTiO₃), a mixed oxide of iron (Fe²⁺) and titanium (Ti⁴⁺) cations, the mineral perovskite and oxides sharing the perovskite structure and garnet. The cations may be the same element in different ionization states: a notable example is magnetite Fe₃O₄, which contains the cations Fe²⁺ ("ferrous" iron) and Fe³⁺ ("ferric" iron) in 1:2 ratio. Other notable examples include the ferrites,strontium titanate SrTiO₃ (which, despite its name, contains Ti⁴⁺ cations and not the TiO₃²⁻ anion), yttrium aluminum garnet Y₃Al₅O₁₂, and many more. Sometimes the term is applied loosely to solid solutions of metal oxides rather than chemical compounds

Mixed oxides are intermediate between a metal oxide and a metal salt. Sometimes mixed oxides are the salts of weak metallic acids. Most other times they are just two different oxides that bond together strongly.