The thorium is a chemical element of symbol Th and of Atomic number 90.

Thorium is a Métal of the family of the Actinides.

He was discovered in 1829 by Jöns Jacob Berzelius and was named according to Thor, god Scandinavian of the thunder.

Properties

Thorium keeps its glare silver plated during several months thanks to the oxide which protects it; the thorium oxide is one of best refractory materials with a melting point of 3300 °C.

All the Isotope S of thorium are radioactive; natural thorium is made up only of the only isotope thorium-232 at very radioactive long period (14 billion years).

Thorium-232 is a fertile isotope; by absorbing a Neutron, it is transmuted into radioactive thorium-233, which disintegrate in Protactinium -233, radioactive isotope which disintegrates in its turn in Uranium -233 fissile .

Layers

The thorium ores are the Thorite, the Thorianite and especially the Monazite. There are large layers in Brittany, in Australia, India and Turkey.

Use

• electrode, Cathode: thorium has a very strong emission of electrons and, for this reason one uses it in the electrodes of tubes with discharge in coating of the filaments of Tungstène, like for cathodes of many electronic devices.
• nuclear energy: the abundance of thorium-232 is 3 times larger than that of uranium-238 (the other fertile natural isotope); thorium thus constitutes an important reserve of nuclear energy, because of its abundance (it could thus provide more energy than joined together uranium, coal and oil); its use requires the development of a new die of nuclear reactors breeder S.

• optical glasses: the thorium compounds increase the Index of refraction glass and decrease the aberrations.

• mantle incandescent: one uses the very bad thermal Conductivité of thorium oxide (in mixture with oxide of Cérium) to increase the temperature of the sleeves of lighting and thus their luminosity.
• produced refractory (crucible): by addition of thorium oxide, one obtains a type of Porcelaine very hard and resistant to the high temperatures.

Control nuclear matters

See also: Control of the nuclear matters

Thorium is a nuclear matter whose detention is regulated (R1333-1 Article of the code of defense).

Simple: Thorium

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