Uranium dioxide

Uranium dioxide (ceramic glazes and glass.

Production

Uranium dioxide is produced by hydrogen.

UO₃ + H₂ → UO₂ + H₂O at 700°C (970K)

This reaction takes part in the enrichment of uranium for nuclear fuel.

Chemistry

Structure

The solid is isostructural with (has the same structure as) neptunium have the same structures

Oxidation with oxygen

Uranium dioxide is oxidized in contact with oxygen to the triuranium octaoxide.

3UO₂ + O₂ → U₃O₈ at 700°C (970K)

Aqueous electrochemistry

The spent nuclear fuel page for further details.

Oxidation of uranium metal

It has been reported that water causes the rate of the oxidation of both uranium metal to increase when compared with the situation which exists when water is absent.[1]

Uses

Nuclear Fuel

fuel rods in nuclear reactors.

Note that the zirconium cladding material. This low thermal conductivity can result in localised overheating in the centres of fuel pellets. The graph below shows the different temperature gradients in different fuel compounds. For these fuels the thermal power density is the same and the diameter of all the pellets are the same.

Colour for ceramics glaze

All uranium oxides were used to colour glass and ceramics. Uranium oxide-based ceramics become green or black when fired in a reducing atmosphere and yellow to orange when fired with oxygen. Orange-coloured porcelain.

Prior to 1960, uranium oxides were used as coloured glazes. It is possible to determine with a Geiger counter if a glaze or glass contains uranium oxides.

Other use

neutron radiation absorber and moderator, and steel as the matrix, whose high thermal conductivity allows easy removal of decay heat.

Depleted uranium dioxide can be also used as a TiO₂, and Co₃O₄ catalysts. Much research is being done in this area, DU being favoured for the uranium component due to its low radioactivity. ^[2] Use of uranium dioxide as a material for rechargeable batteries is investigated. The batteries could have high power density and potential of 4.7V per cell.

Another investigated application is in photoelectrochemical cells, for solar-assisted hydrogen production. UO₂ is used as a photoanode.

Semiconductor properties

Uranium dioxide is a single crystal silicon.

Its breakdown voltages and with lower susceptibility to the CMOS tunneling breakdown.

The Seebeck coefficient of uranium dioxide at room temperature is about 750 µV/K, a value significantly higher than the 270 µV/K of thallium tin telluride (Tl₂SnTe₅) and thallium germanium telluride (Tl₂GeTe₅) and of tellurium alloys, other materials promising for thermopower applications and Peltier elements.

The helium, in the crystal lattice may also cause gradual long-term changes in its properties.

The stoichiometry of the material dramatically influences its electrical properties. For example, the electrical conductivity of UO_1.994 is orders of magnitude lower at higher temperatures than the conductivity of UO_2.001.

Uranium dioxide, like U₃O₈, is a ceramic material capable of withstanding high temperatures (about 2300 °C, in comparison with at most 200 °C for silicon or GaAs), making it suitable for high-temperature applications like thermophotovoltaic devices.

Uranium dioxide is also resistant to rad-hard devices for special military and aerospace applications.

A Schottky diode of U₃O₈ and a p-n-p transistor of UO₂ were successfully manufactured in a laboratory.

References

1. ^ Barrett SA, Jacobson AJ, Tofield BC, Fender BEF (1982). "The preparation and structure of barium uranium oxide BaUO_3+x". Acta Crystallographica B 38: 2775-2781. DOI
2. ^ Hutchings GJ (1996). "A Uranium-Oxide-Based Catalysts for the Destruction of Volatile Chloro-Organic compounds". Nature 384: 341-343.