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Plutonium dioxide

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Plutonium dioxide

Plutonium(IV) oxide

Identifiers
CAS number 12059-95-9 YesY
ChemSpider 10617028 N
Jmol-3D images Image 1
Properties
Molecular formula O2Pu
Molar mass 276.06 g mol−1
Appearance Dark yellow crystals
Density 11.5 g cm-3
Melting point

2400 °C, 2673 K, 4352 °F

Boiling point

2800 °C, 3073 K, 5072 °F

Structure
Crystal structure Fluorite (cubic), cF12
Space group Fm3m, No. 225
Coordination
geometry
Tetrahedral (O2–); cubic (PuIV)
Hazards
Main hazards Radioactive
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.[1]

Structure

PuO2 crystallizes in the fluorite motif, with the Pu4+ centers organized in a face-centered cubic array and oxide ions occupying tetrahedral holes.[2] 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.

Synthesis

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.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.

Applications

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.

Physicist Peter Zimmerman, following up a suggestion by Ted Taylor, demonstrated that a low-yield (1-kiloton) nuclear weapon could be made relatively easily from plutonium oxide.[3]

Toxicology

Plutonium oxide is highly toxic to humans, especially via inhalation.[4] As with all plutonium compounds, it is subject to control under the Nuclear Non-Proliferation Treaty. Due to the radioactive alpha decay of plutonium, all of its compounds, PuO2 included, as well as plutonium metal, are warm to the touch.

See also

References

External links

  • Space Radioisotope Power Systems Safety

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