Lithium fusion reactions with

Tritium is produced in heavy-water-moderated reactors and sometimes must be separated isotopicaHy from hydrogen and deuterium for disposal. Ultimately, the tritium could be used as fuel in thermonuclear reactors (see Fusionenergy). Nuclear fusion reactions that involve tritium occur at the lowest known temperatures for such reactions. One possible reaction using deuterium produces neutrons that can be used to react with a lithium blanket to breed more tritium. 

The D-T reactor is technologically more complex than the D-D reactor because of the need to facilitate the second reaction (which takes place outside the plasma) and because very energetic neutrons must be slowed down to allow the reaction with lithium to lake place. However, the conditions needed to achieve net power output are less demanding than for the D-D fuel reactor. The D-T reaction will probably be exploited first, but its ultimate, very long term use may be limited by the availability of lithium. See also Lithium (For Thermonuclear Fusion Reactors). 

Natural lithium consists of 7.42% Ti and 92.58% Ti. Much of the tritium (fH) used in experiments with fusion reactions is made by the capture of neutrons by Ti atoms. 

The fusion reaction system appears to have the qualities we are seeking in a power source for the future. There is no shortage of the input materials, deuterium and lithium, and the power system will use them in only small quantities. As a result, an energy system based on their use will have a long life, potentially thousands of years. No by-product, such as carbon dioxide, will be placed in the environment by the fusion reactors. The radioactive waste problem from fusion reactors will be ten thousand to a million times less severe than that associated with a breeder reactor system. These factors lead to the recognition of the fusion reaction as the best possible candidate for the base load energy source to replace fossil fuels. 

The lithium is in the form of an alloy with magnesium or aluminium which retains much of the tritium until it is released by treatment with acid. Alternatively the tritium can be produced by neutron irradiation of enriched LiF at 450° in a vacuum and then recovered from the gaseous products by diffusion through a palladium barrier. As a result of the massive production of tritium for thermonuclear devices and research into energy production by fusion reactions, tritium is available cheaply on the megacurie scale for peaceful purposes. The most convenient way of storing the gas is to react it with finely divided uranium... 

This reaction is favored because it occurs at an appreciable rate at a lower temperature (20,000,000 K) than other possible fusion reactions. Tritium is a radioactive isotope of hydrogen, with a half-Ufe of 12 years, which does not occur significantly in nature. For use in this fusion reaction tritium must be made by reaction of the lithium isotope of mass 6 with a neutron ... 

At the present stage of controlled nuclear fusion experiments, exclusively light elements (isotopes of hydrogen, helium, boron, and lithium) are considered as possible fuel candidates for a future fusion power station this chapter, therefore, deals only with fusion reactions between light elements. Moreover, this chapter is devoted only to the basics of physics, the technological aspects of the field being covered by Chap. 60 of Vol. 5. 

The plasma must also have a high density for a sufficient time to permit the fusion reaction to occur. Laser heating of frozen deuterium-tritium pellets confined in a magnetic field is a method that has been tested. The neutrons formed react with lithium in an outer mantle, a reaction in which new tritium is formed. This reactor type is called Tokamak and is used in research projects in the USA and England. Similar reactors are used in France, Russia and Japan. 

In the hydrogen bomb the DT-reaction is also essential. In practice lithium deu-teride, LiD, and some tritium are used. Very high temperature and pressure are necessary for the fusion reaction to start. It is obtained by letting a conventional atomic bomb (a fission bomb), combined with the thermonuclear fuel, explode. At this fission reaction tritium is also generated. 

Lithium is, and is expected to be, important in advanced nuclear appHcations. Among the fusion reactions that have been proposed for power generation, the one between deuterium and tritium has the best prospect for success because it requires the lowest plasma temperature. Tritium is prepared from Hthium. As coolants in a possible fusion reactor, fused lithium metal or molten fluorides of Hthium and berylHum have been proposed. For breeder reactors a molten salt fuel is used, compKJsed of beryUi-um fluoride, thorium fluoride and uranium fluoride together with the fluoride of the isotope Li. 

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