Lithium is a member of the alkali metals family and is an important component in lithium-ion batteries. It also plays a major role in the control of the pH level of the coolant in the primary water circuits of pressurized water reactors. In addition to its uses in nuclear power plants, it is a valuable ingredient for biochemistry research.
There are two naturally occurring isotopes of the element: 7Li and 6Li. The former is the more abundant of the two, accounting for approximately 92.5 percent of the natural lithium supply. Although it is no longer produced in the United States, the isotope is still available for research purposes. This makes it the most important of the two in terms of relevance to the world at large.
A good example of this is the self-diffusion experiment in which a graphite electrode is dipped into an electrolyte containing the isotopes. It is then cycled in a new cell containing six-Li. While this may not sound like much, the lithium and its related isotopes play a major role in controlling the chemistry of PWR cooling systems.
Lithium is also a good source of tritium, the key element in nuclear fusion. It is also used in thermonuclear weapons as well as as part of a radioactive isotope that is used in medical research. However, as it is a relatively rare element in nature, its production is a challenging task. Thus, the US Department of Energy has been funding research into methods for producing the metal.