Plutonium(IV) oxide is the
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
PuO
2. This high melting point solid is a principal compound of
plutoniumPlutonium is a rare transuranic radioactive element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and...
. It can vary in color from yellow to olive green, depending on the particle size, temperature and method of production.
PuO
2 crystallizes in the
fluoriteFluorite is a halide mineral composed of calcium fluoride, CaF
2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Cubic crystals up to 20 cm across have been found at Dalnegorsk, Russia...
motif, with the Pu
4+ centers organized in a face-centered cubic array and oxide ions occupying tetrahedral holes.
Plutonium(IV) oxide is the
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the
formulaA chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
PuO
2. This high melting point solid is a principal compound of
plutoniumPlutonium is a rare transuranic radioactive element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and...
. It can vary in color from yellow to olive green, depending on the particle size, temperature and method of production.
Structure
PuO
2 crystallizes in the
fluoriteFluorite is a halide mineral composed of calcium fluoride, CaF
2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon. Cubic crystals up to 20 cm across have been found at Dalnegorsk, Russia...
motif, with the Pu
4+ centers organized in a face-centered cubic array and oxide ions occupying tetrahedral holes. PuO
2 owes 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 PuO
2 monolith to retain its structural integrity.
Synthesis
Plutonium metal spontaneously oxidizes to PuO
2 in an atmosphere of oxygen. Plutonium dioxide is mainly produced by
calcinationCalcination is a thermal treatment process applied to ores and other solid materials in order to bring about a thermal decomposition, phase transition, or removal of a volatile fraction. The calcination process normally takes place at temperatures below the melting point of the product materials...
of plutonium(IV) oxalate, Pu(C
2O
4)
2·6H
2O, at 300 °C. Plutonium oxalate is obtained during the
reprocessingNuclear reprocessing separates components of spent nuclear fuel.Reprocessing serves multiple purposes, whose relative importance has changed over time:*Producing plutonium for nuclear weapons...
of nuclear fuel.
Applications
PuO
2 is used in mixed oxide (MOX) fuels for
nuclear reactorA nuclear reactor is a device in which nuclear chain reactions are initiated, controlled, and sustained at a steady rate.The most significant use of nuclear reactors is as an energy source for the generation of electrical power and for the power in some ships...
s. Plutonium-238 dioxide is used as fuel for several deep-space spacecraft such as the
'New Horizons' Pluto probeNew Horizons is a NASA robotic spacecraft mission currently en route to the dwarf planet Pluto. It is expected to be the first spacecraft to fly by and study Pluto and its moons, Charon, Nix, and Hydra. NASA may also approve flybys of one or more other Kuiper Belt Objects.New Horizons was launched...
. The isotope decays by emitting α-particles which then generate heat (see
radioisotope thermoelectric generatorA radioisotope thermoelectric generator is an electrical generator which obtains its power from radioactive decay. In such a device, the heat released by the decay of a suitable radioactive material is converted into electricity by the Seebeck effect using an array of thermocouples.RTGs can be...
). There have been some safety concerns, as an accidental orbital earth re-entry may lead to the break-up and/or burn-up of the 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 TaylorTheodore Brewster Taylor , was a prominent Mexican-born American theoretical physicist and nuclear weapons designer.- Biography :...
, demonstrated that a low-yield (1-kiloton) nuclear bomb could be made relatively easily from plutonium oxide.
Safety
As with all
plutoniumPlutonium is a rare transuranic radioactive element. It is an actinide metal of silvery-white appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen and...
compounds, it is subject to control under the
Nuclear Non-Proliferation TreatyThe Treaty on the Non-Proliferation of Nuclear Weapons, also Nuclear Non-Proliferation Treaty is a treaty to limit the spread of nuclear weapons, opened for signature on July 1, 1968...
. Due to the radioactive
alpha decayAlpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle, and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
of plutonium, all of its compounds, PuO
2 included, as well as plutonium metal, are warm to the touch. Plutonium is highly toxic to humans, especially via inhalation.
External links