About Chemical Reactions in a Hydrogen Bomb

A hydrogen bomb, or H-bomb, is a type of nuclear weapon that uses staging of both fission and fusion reactions to create a thermonuclear explosion. Precise details of the chemical reactions inside a hydrogen bomb are classified, but, through leaks from former bomb designers and some speculation, the general process is fairly well understood.

Function

Nuclear fusion is a process in which two atoms combine into a single larger atom, releasing large amounts of energy. Because it occurs only at excessively high temperatures and pressures such as those found in the core of the sun, where hydrogen fuses into helium, controlling fusion on earth is exceedingly difficult. The basis for the H-bomb is the Teller-Ulam configuration, which uses the huge energy released by nuclear fission to create the conditions necessary to ignite fusion in a secondary stage of the bomb. Fission is a process roughly the opposite of fusion: It releases energy through the physical smashing of an atomic nucleus into smaller parts. In addition to these two stages, an H-bomb might have a third stage consisting of depleted uranium or other fissile material.

History

The original idea to use fission to create an environment for fusion is credited to physicist Enrico Fermi, a participant in the Manhattan Project, though it was not developed due to practical considerations as the scientists focused on creating a working fission bomb during WWII. The Soviets tested hydrogen bomb models as early as 1949, though with less than optimal results in generating a fusion reaction. Developments in the United States, however, led to tests in 1951 that suggested that the basic concept was possible. On November 1, 1952, the full-scale test of Ivy-Mike yielded an explosion of 10.4 megatons, more than 450 times greater than the bomb dropped on Nagasaki.

Features

The primary section of a hydrogen bomb is a fission trigger, not unlike the atomic bombs dropped on Japan. In a hydrogen bomb, however, this reaction occurs within a radiation case that temporarily contains the energy of the fission reaction and transfers the energy to the second stage. Though the exact mechanism remains unknown, it is believed that a small amount of gas between the two stages and a uranium sheath around the fusion fuel contribute to the compression. When the fuel in the fusion portion of the bomb goes critical---that is, reaches temperatures and pressure high enough for fusion---vast amounts of energy are released.

Types

There are three main types of mechanism theorized to harness the energy of the fission stage to create fusion. The first is simply that the fission reaction releases X-ray protons whose mass is great enough to produce sufficient pressure by radiation. The second, called foam plasma pressure, suggests that a foam encasement around the fusion fuel is heated by the fission reaction to the point that it changes into a plasma, which transfers heat and pressure to the fusion core. Finally, the tamper-pusher ablation theory proposes that the fusion fuel, in a lead or uranium casing, is simply crushed by the detonation of the primary stage in a manner sufficient to spark fusion.

Significance

The largest bomb ever exploded was a hydrogen bomb, Russia's Czar Bomba, detonated in 1961. The last U.S. test of a hydrogen bomb was in 1991. The testing ban since that time remained in effect through the second term of George W. Bush, despite the announcement in 2007 that the U.S. would develop new compact hydrogen bombs for submarine-launched warheads. Despite attempts to stem nuclear proliferation, hydrogen bombs and the chemistry inside them remain guarded secrets and potent weapons in a world at war.

Resources

• Teller-Ulam design
• Hydrogen bomb
• Fusion weapons