| I. MATERIALS > THE SIX NUCLEAR MATERIALS > Lithium-6 |
Description: a lithium isotope, a natural light metal
Production: enrichment of natural lithium in lithium-6 by chemical
exchange
Use: Production of tritium
Radioactivity: not radioactive
Comment: fertile material
Lithium, the lightest of the metals, exists in nature but not in a
free state. It is found in igneous rocks and in the water of numerous
mineral sources. Making up 0.006% of the earth's crust, it is more
plentiful than tin or lead and ten times more plentiful than uranium.
Natural lithium is a mixture of two isotopes, lithium-6 (7.5%) and
lithium-7 (92.5%). It is usually enriched in lithium-6 by chemical
exchange.
The Minister of Industry closely oversees lithium enriched into
lithium-6, because the irradiation of lithium-6 creates a thermo-
nuclear material. Armaments manufacturers use lithium to produce
tritium in two ways. They create tritium at the industrial level in
nuclear reactors by bombarding lithium targets with neutrons. They can
also create tritium inside a nuclear warhead by bombarding withneutrons a compound containing lithium. The Americans use lithium
hydride for boosted fission warheads and lithium deuteride principally
for the fusion stage in thermonuclear warheads (see Deuterium). The French military may use lithium deutero-tritiide. The use of a lithium compound to
replace tritium in a warhead avoids the necessity of replacing tritium
periodically because of its short period.
From the civilian nuclear perspective, lithium-6 is used as a source
of tritium for experimentation on fusion.
Lithium is not reactive. It is chemically toxic, and the reaction between lithium hydride and water is particularly dangerous; but these
problems concern the workers mainly. The greatest threat to the general population and to the environment is indirect. The production of lithium traditionally requires a large quantity of mercury, and the manufacturing plants have generated considerable pollution by this heavy metal. For this reason, the CEA, cooperating with Cogéma, has studied two new procedures for isotopic separation: "Chromotography by ion exchange on resin and ion exchange in melted salts" [CEARa 95].
The CEA developed its procedure for isotopic separation using mercury at the CEN [Nuclear Studies Center] at Grenoble and also studied
lithium at the CEN at Saclay and probably at Pierrelatte. France produced lithium-6, with mercury, in the Cogéma factory at Miramas, which began industrial operations in 1962. As of 2001 that factory was apparently no longer in operation (see Miramas in the section on Sites).
--actualisé 25/8/01
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