In a relatively crude sense, 6 Li can be thought of as consisting of an alpha particle ( 4He) and a deuteron ( 2H) bound together. When bombarded by neutrons, 6 Li disintegrates into a triton ( 3 H) and an alpha:6 Li + Neutron = 3 H + 3 He + Energy.This is the key to its importance in nuclear weapons physics. The nuclear fusion reaction which ignites most readily is2 H + 3 H = 4 He + n + 17.6 MeV,or, phrased in other terms, deuterium plus tritium produces 4He plus a neutron plus 17.6 MeV of free energy:D + T = 4 He + n + 17.6 MeV.Lithium-7 also contributes to the production of tritium in a thermonuclear secondary, albeit at a lower rate than 6Li. The fusion reactions derived from tritium produced from 7 Li contributed many unexpected neutrons (and hence far more energy release than planned) to the final stage of the infamous 1953 Castle/BRAVO atmospheric test, nearly doubling its expected yield.
Types of Fusion Reactions:Boosted Fission<br /><ul><li>Boosted Fission is the earliest application of fusion weapons. </li></ul>The center of the fissile core includes small amounts of deuterium and tritium gas.<br />These gases react with the core producing a faster fission reaction of the nuclear material producing more energy than the standard fission reaction.<br />
Boosted Fission Continued<br />Tested on May 24, 1951, the Greenhouse Item was the first test of boosted fission technology<br />The reaction utilized cryogenic liquid deuterium-tritium instead of gas.<br />The use of boosted fission technology increased the energy yield of the weapon by over 200% compared to the regular fission reaction.<br />
Types of Fusion Reactions: Staged Radiation Implosion<br />Otherwise known as “Teller-Ulam” weapons, this type of fusion reaction involves the usage of lighter elements such as hydrogen and lithium.<br />The use of the lighter elements removes the yield limits of fission technology and reduces the cost of producing the weapon.<br />
Staged Radiation Implosion Continued<br />This weapon is a two-stage process including the fission trigger which starts the reaction in a compartment separate from the fusion material.<br />This type of reaction releases a larger amount of energy due to the fusion reaction and the fissioning of the trigger mechanism at a fast pace due to the neutrons generated in the fusion process.<br />
Staged Radiation Implosion Continued<br />The first test of a staged fusion weapon was codenamed Ivy Mike and was conducted on October 31, 1952.<br />Fission-Fusion-Fission weapons can either be considered “clean” or “dirty” weapons:<br />Clean: produce more than 50% of the yield from fusion. Enriched Uranium is used.<br />Dirty: They generate a large amount of fission fallout during the reaction due to relatively cheap materials used for the jacketing of the weapon.<br />
Types of Fusion Reactions:The Alarm Clock/Sloika (Layer Cake) Design<br />The idea of a an ‘alarm clock’ style weapon predates that of a staged fusion device.<br />This system uses a spherical assembly of concentric shells using primarily Uranium-235 or Plutonium-239.<br />The amount of fusion that can be achieved is only 15-20% of the yield and cannot increase beyond this amount making this reaction inefficient in comparison.<br />
The Alarm Clock Design Continued<br />Due to its comparative inefficiency in terms of destructive power, the United States did not consider it a viable option for the arsenal and therefore did not pursue the development of the design.<br />The first test, RDS-6s, was conducted on August 12, 1953 by the Soviet Union<br />
The Alarm Clock/Sloika (Layer Cake) Design<br />
Chemical Equation<br />6Li + Neutron = 3H + 3He + Energy<br />The equation above is a general representation of a fusion reaction<br />The components:<br />6Li can be thought of as the combination of the alpha particle (4He) and deuteron (2H)<br />When the 6Li is struck with Neutrons, it deteriorates into a triton (3H) and an alpha particle along with excess energy producing a nuclear explosion.<br />
Sources<br />Pike, John. "Hydrogen Bomb / Fusion Weapons." Blog. 8 Mar. 2005. Web. 30 May 2010. <http://www.globalsecurity.org/wmd/intro/h-bomb.htm>.<br />Sublette, Carey. "Section 1.0 Types of Nuclear Weapons." The Nuclear Weapon Archive - A Guide to Nuclear Weapons. 1 May 1998. Web. 30 May 2010. <http://nuclearweaponarchive.org/Nwfaq/Nfaq1.html#nfaq1.5>.<br />
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