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Plain lithium hydride, which can be bought on the open market, is probably not the kind that the bomb-builders use. Natural lithium contains two isotopes, L17 and L16, which behave differently in a fusion reaction. Most guessers believe that L16 is the preferred isotope. The hydrogen in the compound is probably deuterium (H²). So the compound may be described as "lithium-six deuteride."
What happens when a charge of lithium-six deuteride is ignited is almost anyone's guess. A great many reactions are possible, and many must surely take place (see diagram). The main reaction is the combination of L16 with H², forming two atoms of helium (He4) and giving off a flood of energy. Since helium is the final product, the well-designed bomb should produce as much of it as possible, but side reactions are likely. Neutrons from the reacting plutonium are apt to hit lithium atoms, turning them into helium and tritium (H³). Tritium may hit deuterium, yielding helium and a free neutron. The bomb-com-pounders may include other ingredients (e.g., lithium seven and ordinary hydrogen), and these will react in characteristic ways.
One big question: How much original tritium must the dry bomb contain? It may be possible to use none of it except in the boosted detonator, but some guessers believe that a small amount of tritium in the main charge is needed to promote the reaction. It will tend to re-create itself, acting like a chemical catalyst. Other guessers think that free neutrons from the detonator will create enough tritium (by combining with lithium six) to keep the reaction going at full speed.
It may even be possible to get along with no tritium in the detonator. A highly efficient fusion bomb may raise the temperature high enough to ignite the lithium hydride. Or perhaps it may, by "implosion." cause the fusion of a core made of deuterium alone.
If a fusion bomb can be made really "dry," with no tritium at all. a new era of nuclear energy has arrived. Every fission bomb in the world's stockpiles can then be upgraded into an H-bomb, with hundreds or thousands of times its original power. They will have to be reworked slightly and surrounded by a reasonable amount of lithium-six deuteride.
This task should be no strain on any bomb-possessing nation. Lithium is abundant, and its L16 isotope (7.9% of the total) is not hard to separate. Deuterium is found in nature as about 1/5,000 of the hydrogen in water. As nuclear prices go, it is cheap and easy to obtain. Measured by its explosive effect, lithium-six deuteride is cheap indeed. One pound, if all of it reacts, has the explosive effect of 23,000 tons of TNT. Any desired amount can be used in a single bomb. Twenty-two tons of it, efficiently fired, would be equivalent in explosive force to one billion tons of TNT.
Bombs of this size may never be assembled. Even if considerably smaller, they would be hard to deliver, and they would "overbomb" a small area, digging a deep crater instead of spreading their killing effect over the living film that covers the surface of an inhabited region. There is a way, however, of getting around this disadvantage.