Nuclear weapon

A nuclear weapon is a weapon which derives its destructive force from the nuclear reactions of nuclear fission and/or fusion. As a result, even a nuclear weapon with a small yield is significantly more powerful than the largest conventional explosives, and a single weapon is capable of destroying an entire city.

Effects of a nuclear explosion

The energy released from a nuclear weapon comes in four primary categories:

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• Blast—40-60% of total energy
• Thermal radiation—30-50% of total energy
• Ionizing radiation—5% of total energy
• Residual radiation (fallout)—5-10% of total energy

The amount of energy released in each form depends on the design of the weapon, and the environment in which it is detonated. The residual radiation of fallout is a delayed release of energy, while the other three forms of energy release occur immediately.

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The damage from each of the three initial forms of energy release differs with the size (or "yield", see below) of the weapon. Thermal radiation drops off the slowest with distance, so the larger the weapon the more significant the impact of this effect. Ionizing radiation is strongly absorbed by air, so it is only dangerous by itself for smaller weapons. Blast damage falls off more quickly than thermal radiation but more slowly than ionizing radiation.

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The energy released by a nuclear weapon is generally measured by the explosive power of an equivalent amount of trinitrotoluene, known as the weapon's yield. The yield of nuclear weapons may be rated as equivalent to several kilotons or megatons of TNT. The first fission weapons had yields measurable in the tens of kilotons, while the largest practical hydrogen bombs had yields around 10 megatons. In practice, nuclear weapon yields will vary significantly, from fractional kiloton weapons designed for tactical use on the battlefield (eg. the man-portable Davy Crockett warheads developed by the United States), to the record 50-megaton Tsar Bomba created by the Soviet Union.

Related Topics:
Trinitrotoluene - Yield - Kiloton - Megaton - Davy Crockett - United States - Tsar Bomba - Soviet Union

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Although a nuclear weapon is capable of causing the same destruction as conventional explosives through the effects of blast and thermal radiation, it does so by releasing much larger amounts of energy in a much shorter period of time. Most of the damage caused by a nuclear weapon is not directly related to the nuclear process of energy release, and would be present for any explosion of the same magnitude.

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In human terms, nuclear weapons are enormously destructive. A weapon with a ten-megaton yield would be capable of destroying an entire modern city, while a weapon with a hundred-megaton yield (although the deployment of such a weapon would be considered impractical) would set wooden structures and forests alight up to 60-100 miles (100-160 km) from ground zero{{fn|1}}. A nuclear weapon detonated in the upper atmosphere will also generate an electromagnetic pulse which can disrupt or disable electronic communications and instruments over a wide area, causing more difficulties for those who survive the effects of a detonation.

Related Topics:
City - Ground zero - Atmosphere - Electromagnetic pulse

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