Uncontrolled Nuclear Fusion: The H-Bomb

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Hydrogen or thermonuclear bombs are probably the most deadly of all nuclear weapons. The large energy release per unit mass of fuel makes H-bombs very efficient. This allows for the building of bombs with much greater yields than fission bombs. The Soviet scientist Andrei Sakharov first proposed the idea in 1948, but it was the Americans who detonated the first H-bomb, code named Ivy Mike, on November 1, 1952. The bomb used liquid deuterium as fuel and had a yield of 10.4 MT, about 700 times more powerful than the A-bomb dropped on Hiroshima. A second 15-MT bomb, code named Bravo, was tested on the island of Bikini near the Marshall Islands in 1954. Since then, several hydrogen bomb tests have been conducted. The Soviet Union conducted tests in 1953 and 1961; the British detonated an H-bomb in 1957. France conducted a test in 1960, as did China in 1964. Fortunately, hydrogen bombs have never been used in a military conflict.

Figure 1 Radiation units.
Figure 1 A modern warhead carrying a hydrogen bomb.

An H-bomb is essentially a three-stage weapon (Figure 1). In the first stage or trigger, a small amount of plutonium is detonated (explosion), as in a conventional A-bomb. In the second stage, the immense energy in the form of x-ray-radiation compresses and heats up a solid mixture of lithium deuteride (a source of tritium) and deuterium (a) located in the center of the bomb to millions of degrees (implosion), triggering the thermonuclear reaction. The fusion reaction produces an ample supply of neutrons so powerful they can initiate fission (explosion) of otherwise unfissionable casing of depleted uranium. This is the third stage and the one that produces most of the radioactive fallout.

Question: Why doesn’t the sun blow up like a hydrogen bomb?

Answer: The main difference between the sun and the hydrogen bomb is that the sun contains very few heavy hydrogen isotopes. The proton-proton reaction that results from normal hydrogen atoms proceeds about a billion times more slowly than a strong deuterium-tritium reaction at the same temperature and pressure.


Neutron Bombs

Neutron bombs are small (less than one kiloton) thermonuclear bombs designed to produce a high-intensity burst of radiation over a relatively small area. Instead of absorbing the neutrons inside the weapon, the neutrons are allowed to escape into the environment. Because neutrons are absorbed by the air, neutron bombs have limited yields, and so are effective over relatively small areas. Since heat and blast effects are minimal, they work primarily on biological systems and are dubbed as anti-personnel bomb. Because of this many consider these weapons as highly immoral that could be used prematurely in regional conflicts which can lead into full-scale nuclear war.


(1) Toossi Reza, "Energy and the Environment:Sources, technologies, and impacts", Verve Publishers, 2005

Additional Comments

(a) The first device used liquid helium at cryogenic temperatures.

Further Reading

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