Zirconium is the chemical element with atomic number 40, symbol Zr.

It was discovered by Martin Heinrich Klaproth in Berlin, who extracted it from zircon in 1789 in the form of oxide. But it was not until 1824 that Jöns Jacob Berzelius isolated it as metal in Stockholm, Sweden. In 1999, a thin piece of zircon crystal 4.4 billion years old was found in Australia: apart from certain meteorite fragments, it is the oldest known terrestrial object10.

It is a transition metal belonging, with titanium and hafnium, to column IVb of the periodic table.

It is three times more abundant than copper in the earth's crust, of which it composes 0.0165% up to a depth of 16 km11 (mainly in the form of zircon ZrSiO4 and zirconia also called zirconia or baddeleyite (en) or dioxide of zirconium ZrO2).

"Zirconium" is derived from "zircon", the name of the ore from which it was first extracted. The latter comes from the German Zirkon, a name created by the geologist and mineralogist Abraham Gottlob Werner in 1783, which Martin Heinrich Klaproth decided to take over in 1789. The formation of the German word remains obscure and could come from the Arabic of Zarkûn, which would stem from the Persian zargûn meaning "color of gold".

Main article: Isotopes of zirconium.
Zirconium has 33 known isotopes, with a mass number varying from 78 to 110, and 5 nuclear isomers. Among these isotopes, four are stable, 90Zr, 91Zr, 92Zr and 94Zr, and are present in nature in a ratio 51/11/17/17 with a natural radioisotope, primordial nuclide, 96Zr which disintegrates by double ¦Â decay with a observed half-life of 2.0 ¡Á 1019 years 12.

The standard atomic mass assigned to zirconium is 91.223 ¡À 0.002 u.

Production and reserves
Its main ore, ZrSiO4 zircon sometimes occurs in the form of a precious stone, the hyacinth. It is generally associated with titanium and hafnium. The mass content of hafnium is approximately constant and equal to 2%. Zircon is a constituent of granites, it is concentrated in the sands resulting from the decomposition of granite.

World production of zircon is around 1.25 million tonnes per year. China has significant production which enables it to supply its domestic market13.

Because of its excellent properties at high temperatures, and coupled with its low absorption of neutrons, it is used in the construction of nuclear reactors operating at less than 400 ¡ã C, including in particular water reactors.

Zirconium in metallic form is used to make the sheath of ¡°pencils¡± of fissile fuel pellets introduced into pressurized water reactors of a nuclear power plant. It is then a purified zirconium alloy (notably purified from hafnium which is a neutron poison present in natural ore at concentrations between 1 and 3%). This use represents 90% of the production of zirconium metal. However, zirconium metal represents only a small percentage of the use of the zirconium element, of the order of 1% 15.
For its physicochemical properties (resistance to corrosion, resistance to irradiation, great penetration of slow neutrons, preservation of properties at high temperature), this metal is used in the nuclear or chemical industry, in the form of alloys such than Zircaloy (with tin, iron and chromium) or glass of zircon used for the confinement in a sarcophagus of radioactive waste (eg plutonium). According to current research [ref. necessary], this type of sarcophagus could contain radioactivity for at least 2,000 years, which is still far from the minimum of 100,000 years required for the most dangerous radioactive waste16.


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