MOX fuel, or mixed oxide fuel, is made of a mixture of plutonium and uranium oxides. The uranium is generally depleted uranium, as the plutonium substitutes for U235.
       MOX fuel is a conventional nuclear fuel used in standard commercial nuclear reactors in major European nuclear-using countries. It is the second most common fuel, just after uranium fuel.
       The only difference with the basic nuclear fuel, made only of uranium and known as UO2 fuel, is that MOX fuel contains a small proportion of plutonium mixed with a higher proportion of uranium (MOX stands for Mixed uranium and plutonium OXides).
       Plutonium is naturally produced from uranium irradiation in the reactor core. After three to four years, the spent UO2 fuel contains about 1% of plutonium. Plutonium is recovered during the reprocessing operation and separated from the other elements contained in the spent fuel (uranium and ultimate waste).
       Plutonium is a common chemical element, with fissionable characteristic that makes it a prime choice for heat and energy production. The fissionable feature of plutonium makes it possible to use it as a reliable source of energy given that the proper technological structures are put in place: one pellet of MOX has the same energy output as one tonne of coal.
       The first MOX fuel elements were manufactured in the late 1950s. Countries such as France, Germany, and Switzerland have been using MOX fuel in commercial nuclear power plants for many years. 35 commercial nuclear power reactors are currently loaded with MOX fuel in Europe: 20 in France, 10 in Germany, 3 in Switzerland, and 2 in Belgium. Up to 70 reactors world-wide are scheduled to be using this fuel by 2010 including Japan, Russia and the United States. The operational and safety record of MOX use and manufacturing is excellent and comparable to UO2 fuel.
       Around 1,800 MOX fuel assemblies have been manufactured, mainly in Europe.