The actinide oxides are currently the predominant fuel type of nuclear reactors. The majority of existing light water reactor (LWR) plants nowadays utilizes uranium dioxide as fuel. During irradiation, plutonium (²³⁹Pu) is created through neutron capture by ²³⁸U and chemically stabilized in the UO₂ crystal lattice. Although part of this plutonium is subsequently fissioned in the reactor, it is still present in significant amounts in the fuel at the end-of-life. In order to utilize this resource, a number of countries have chosen to adopt a plutonium recycling policy. This consists of separating the residual plutonium from the spent fuel and employing it as new fuel in a mixture with uranium dioxide (mixed oxide fuel or MOX). In this way, the quantities of (enriched) uranium needed for fuel production and the volume of nuclear waste for final disposal are drastically reduced. In the conception of the new generation of nuclear plants (“Gen IV”) plutonium recycling in high Pu content MOX in fast neutron reactors is envisaged for efficient, clean, and cost-effective nuclear power generation. Nevertheless, the use of this type of fuel requires accurate thermophysical data to ensure safe reactor operation. In particular, the high plutonium content and the in-pile redistribution of uranium and plutonium, driven by large radial temperature gradients in fast reactor oxide fuel during irradiation, require knowledge of the entire UO₂-PuO₂ phase diagram.

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Materials Today (2010) 13(11), 52-55
doi: 10.1016/S1369-7021(10)70204-2