The detonation of a single nuclear bomb or "warhead" would cause a local disaster on a scale that few people in the world have seen and survived. However, it should not be confused with the effects of a nuclear war, in which many nuclear bombs would be exploded. That would cause the end of civilization in the countries concerned, and perhaps over the whole world, as well as radioactive contamination of whole continents, and terrible damage to the environment and ecology.

The effect of a single bomb would depend on its power, and where it exploded -- high in the air or at ground level -- and whether in a densely populated and built-up area like a city or in open country like an attack on a missile silo.

The nuclear bombs available to the great military powers of the world (China, France, Israel, Russia, United Kingdom, United States) range in power from several megatons down to a few kilotons (and some even smaller).

A "megaton" is the explosive power of one million tons of TNT. A "kiloton" is the power of one thousand tons of TNT. Bombs likely to be available to terrorist organizations or governments other than the great military powers would be in the 10- to 100-kiloton range. Bombs made by amateurs might not explode with the full power they were designed for.

[FOOTNOTE: TNT stands for tri-nitro-toluene, a high explosive commonly used in shells and bombs throughout the Second World War. Weight for weight, its explosive power is roughly equal to that of dynamite.]

The two bombs that have been exploded over cities, Hiroshima and Nagasaki in Japan in August 1945, were in the ten- to twenty-kiloton range.



A ONE-MEGATON BOMB DETONATED IN THE AIR

First, we will look at the result of a single bomb of one megaton detonated at an altitude of 2,500 metres above a city, to cause maximum blast effects. This is believed to have been a main part of the targeting strategy of the Soviet Union and the United States during the "Cold War". The Russian and U.S. governments have stated that missiles would not remain targetted on cities. However, thousands of missiles and warheads are still deployed. They could be targetted on any city in the world in a matter of minutes, and re-targetted to their original targets in seconds.



Flash and fireball

The first effect of a nuclear explosion in the air is an intense flash of light, as quick as a lightning flash but a thousand times as bright. It is accompanied by a powerful pulse of heat radiation, sufficient to set fire to light combustible material out to a distance of fourteen km., and to paint or wood at half that distance. There is also an intense pulse of X-rays, sufficient to be lethal at a distance of three km.; in fact that would be a rather small factor, since people that close would all or nearly all be killed by the blast that follows.

Immediately after the flash, a "fireball" forms in the air and rises for several seconds, blindingly bright and radiating much heat. On a clear day or night, people up to eighty km. away who happened to be facing that way, or who turned their eyes to look where the flash came from, would be temporarily or permanently blinded.

Within ten km. of "ground zero" (which is the point directly under the explosion) all parts of the body exposed to the flash would be burned deeply into the flesh. Superficial burns would be caused at greater distances, out to fifteen km. at least. Clothing that caught fire would cause many more burns.

The weather conditions prevailing, and the time of day the bomb exploded, would both influence the degrees of damage. For example, the radii for skin burns and blindness would depend on the weather. Mist or fog reduces the range of the heat and light rays; on the other hand, darkness dilates the pupils of the eyes increasing the probability of severe eye damage from the flash.



Blast

Starting at the same instant, but travelling more slowly (like the sound of thunder following a lightning flash) is an enormously powerful blast wave. It would destroy even reinforced concrete buildings for a radius of two km., and ordinary brick or timber frame houses out to eight km. Major damage to houses would extend out to fourteen km., and windows would be broken at twenty or thirty km. People at a distance, if they realized what had happened when they saw the flash, would have a few seconds to lie down, or even to dive into a ditch or hollow, before the blast hit.

Within three km., almost everyone would be killed, either directly by the blast or by collapsing or flying masonry. At eight km., it is estimated that about fifty per cent of people would be killed by the effects of the blast.

Immediately following the blast wave would be hurricane force winds, first outwards from the explosion, and many seconds later inwards to replace the air that went out. Within four km., the wind would be of tornado force, six hundred km./hr., sufficient to drive straws into wooden utility poles or glass splinters into people, but of course over a much wider area than a tornado. People in the open would be picked up and hurled into any object strong enough to be still standing.



Firestorm

Many fires would have been started by the first flash. Burst fuel tanks, gas mains, and collapsed buildings would provide more fuel, and it is likely that confluent fires would cause a "firestorm". This is when coalescent fires cause sufficient updraft to form their own wind, blowing inwards from all sides and thereby increasing the intensity of the fire. The temperature even in basements and bomb shelters rises above lethal levels, and all available oxygen is used by the fire.

The wind blowing inwards is of gale force, so that even strong uninjured people would have difficulty walking or trying to run outwards away from the fire.



Delayed Radiation ("fallout")

A nuclear explosion, as well as giving off a great pulse of radiation at the time, leaves everything in the vicinity radioactive. In the case of an "air-burst" as just described, most of the radioactive products would be gaseous, or completely vaporized, and would rise with the fireball and come down slowly, if at all. There might be a rainstorm containing radioactivity, as there was at Hiroshima; and the rubble within a kilometre or two of the ground zero would be radioactive. This might hamper later rescue efforts, and affect the very few survivors from that central area, but would not be a major factor.

In any nuclear bomb explosion, a large fraction (a minimum of one-third) of the original fissile material (plutonium or U-235) does not get destroyed. This would result in widespread contamination, increasing the late risk of cancer for those who survived ten to twenty years. (These amounts of plutonium and uranium would have no immediate toxic effects.)



Rescue Problems

If the bomb exploded squarely over the centre of a city, no rescue services within the area of major structural damage would be able to function. All down-town hospitals would be destroyed, and there would be no electricity, water, or telephone communication in the area served by city utilities.

Rescue services from outside would be hampered by impassable roads and the central area of severe damage would be inaccessible. The number of injured in the peripheral area would be so great that emergency services of surrounding cities would be completely overloaded, as would be any surviving suburban hospitals and all the hospitals of neighbouring cities. Even to be seen by a doctor and given analgesics, the injured from one city would need to be distributed among all the hospitals of North America.

The destroyed city would be radioactive. Decisions to attempt rescue work would depend first on a survey of the area by a specialist team with appropriate protection, and then on a policy decision as to how much radiation the rescue teams should be permitted. Willingness of the team members and their unions to accept the risk would be a final factor.



Medical Problems

The estimates for a city of one million or two million struck by a single one-megaton bomb are that around one third of the inhabitants would be killed instantly or fatally injured, one third seriously injured, and the rest uninjured or only slightly injured. That number of injured, if they could be distributed throughout the hospitals of North America, would occupy something like a third of the total number of beds; and of course no hospital can deal adequately with such an influx of urgent cases within a few days.

There might be fifty times as many cases of severe burns as there are burn beds in the whole of North America. A whole year's supply of blood for transfusion would be needed immediately, and

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