Structure[edit]
PuO2 crystallizes in the fluorite motif, with the Pu4+ centers organized in a face-centered cubic array and oxide ions occupying tetrahedral holes.[3] PuO2 owes its utility as a nuclear fuel to the fact that vacancies in the octahedral holes allows room for fission products. In nuclear fission, one atom of plutonium splits into two. The vacancy of the octahedral holes provides room for the new product and allows the PuO2 monolith to retain its structural integrity.
Properties[edit]
Plutonium dioxide is a stable ceramic material with an extremely low solubility in water and with a high melting point (2,744 °C). The melting point was revised upwards in 2011 by several hundred degrees, based on evidence from rapid laser melting studies which avoid contamination by any container material.[4]
Due to the radioactive alpha decay of plutonium, PuO2 is warm to the touch. As with all plutonium compounds, it is subject to control under the Nuclear Non-Proliferation Treaty.
Synthesis[edit]
Plutonium spontaneously oxidizes to PuO2 in an atmosphere of oxygen. Plutonium dioxide is mainly produced by calcination of plutonium(IV) oxalate, Pu(C2O4)2·6H2O, at 300 °C. Plutonium oxalate is obtained during the reprocessing of nuclear fuel as plutonium is dissolved in a solution of nitric and hydrofluoric acid.[5] Plutonium dioxide can also be recovered from molten-salt breeder reactors by adding sodium carbonate to the fuel salt after any remaining uranium is removed from the salt as its hexafluoride.