Plutonium(IV) oxide
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| Names | |
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IUPAC name
Plutonium(IV) oxide
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Systematic IUPAC name
Plutonium(4+) oxide
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| Other names
Plutonium dioxide
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| Identifiers | |
12059-95-9 
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| 3D model (Jmol) | Interactive image |
| ChemSpider |
10617028 
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| ECHA InfoCard | 100.031.840 |
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| Properties | |
| O2Pu | |
| Molar mass | 276.00 g·mol−1 |
| Appearance | Dark yellow crystals |
| Density | 11.5 g cm−3 |
| Melting point | 2,390 °C (4,330 °F; 2,660 K) |
| Boiling point | 2,800 °C (5,070 °F; 3,070 K) |
| Structure | |
| Fluorite (cubic), cF12 | |
| Fm3m, No. 225 | |
| Tetrahedral (O2−); cubic (PuIV) | |
| Hazards | |
| Main hazards | Radioactive |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is ?) |
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| Infobox references | |
Plutonium(IV) oxide is the chemical compound with the formula PuO2. This high melting-point solid is a principal compound of plutonium. It can vary in color from yellow to olive green, depending on the particle size, temperature and method of production.
PuO2 crystallizes in the fluorite motif, with the Pu4+ centers organized in a face-centered cubic array and oxide ions occupying tetrahedral holes. PuO2 owes its utility as a nuclear fuel to the fact that vacancies in the octahedral holes allows room for fissile 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.
Plutonium dioxide is a stable ceramic material with an extremely low solubility in water and with a high melting point (2,390 °C).
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.
Plutonium metal 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 HNO3/HF. 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.
PuO2, along with UO2, is used in MOX fuels for nuclear reactors. Plutonium-238 dioxide is used as fuel for several deep-space spacecraft such as the 'New Horizons' Pluto probe as well as in the Curiosity rover on Mars. The isotope decays by emitting α-particles which then generate heat (see radioisotope thermoelectric generator). There have been concerns that an accidental orbital earth re-entry might lead to the break-up and/or burn-up of a spacecraft, resulting in the dispersal of the plutonium, either over a large tract of the planetary surface or within the upper atmosphere.
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