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. 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.
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, that could be targetted on any city in the world.
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.
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.
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.
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.)
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 the final factor.
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 of course is not
available in storage nor could it be collected from volunteers in a few days.
The injured who reached hospitals would have to be assayed for radioactivity,
for the safety of the staff, which would cause a serious bottle-neck and delay
in most hospitals. The result of this huge overload of cases is that most of
the injured would die, even though prompt treatment might have saved them.
Relatively few would even get reached by rescue teams before they were moribund
or dead; the majority would probably die in hours or days without any analgesic,
and without food, water, or any assistance.
If the bomb exploded at ground level instead of high above
the city, the main difference would be an enormous crater four hundred metres
across and seventy metres deep. All the dirt, rock, or masonry excavated would
be made into radioactive dust and small debris. The larger particles would
quickly descend in the immediate vicinity, and the finer particles and dust
would descend in minutes or hours, mainly downwind from the site of the
explosion. The radiation dose to people exposed to this fallout would depend
upon many factors, and would be enough to be lethal to anyone in the open or in
a frame house for several hundred kilometres downwind. A simple basement
"fallout shelter" would afford good protection. It would be necessary
to spend a week or more in a fall-out shelter, and it would be impossible to
judge when it would be safe to leave without a radiation survey meter or advice
from public health authorities. The area of blast damage would be smaller by
perhaps a half, compared with an air-burst, though an earthquake effect would
add to structural damage to buildings. The number of immediate deaths might be
about half of those from an air-burst, but unless survivors could find
protection from fall-out there would be many deaths from radiation sickness
days or weeks after the bomb.
If a bomb in the 10- to 20-kiloton range were to be exploded
near ground level or in a ship in the harbour, the areas of blast, heat, and
burn damage would be much smaller, perhaps reaching out to only one-tenth of
the distances estimated for the one-megaton air-burst. The numbers of
immediately killed and severely injured people would be counted in thousands,
not hundreds of thousands. Exploded on land, the bomb would vaporize all people
and buildings in the immediate vicinity, and make a crater that might be as
much as one hundred metres in diameter. If in the harbour, there would be a
crater in the harbour floor and a tidal wave, but the outstanding feature would
be a radioactive downpour because much of the water in the harbour would be
made radioactive and thrown high into the air as fine and coarse spray. The
explosion at ground level of this type of bomb would probably not cause a
firestorm, so rescue operations for the injured might have some degree of
success. In either case, radioactive fallout would be serious, and might make
the city, and an area of countryside stretching tens of kilometres downwind,
uninhabitable for weeks or years. There would be a number of deaths from
radiation sickness, for which there is really no effective medical treatment.
The total amount of radioactivity might be comparable with the Chernobyl disaster,
more or less depending on many circumstances.
This is a small "hydrogen bomb" in the 1 to 10 kiloton range without
the outer casing of uranium, which, in an ordinary hydrogen bomb stops the
neutrons that are formed, and converts them into additional explosive power.
The neutron bomb thus emits a spray of neutrons that is lethal for a distance
of a few hundred metres. These neutrons, unlike the X-rays from the explosion,
penetrate a considerable thickness of concrete or steel protection, like
defence posts or the sides of a tank. They are designed for
"battlefield" use, not for use against cities. It is commonly said
that neutron bombs spare buildings, but we believe this is a misconception. The
blast effect would be reduced by about half, and would still be enormous.
It is worth considering what circumstances might result in
one or just a few nuclear bombs exploding, as opposed to a major nuclear war.
We hope, but we cannot be sure, that a nuclear attack by one of the "great
powers" against a smaller country (which has been threatened several times
since 1945) would never be carried out for any reason whatever. There have been
serious risks of war involving smaller military powers with nuclear weapons,
such as India, Pakistan, and Israel. Clear or veiled threats of nuclear attack
have been made by these countries, and might be again. Such use would most
probably be directed at cities, and the bombs delivered by aircraft or
relatively short-range rocket. It might be air-burst or ground-burst, with
bombs in the ten- to one-hundred kiloton range. A megaton bomb from one of the
big nuclear arsenals might destroy a city, after accidental or unauthorized
launch of an intercontinental missile or a submarine-launched missile. A
terrorist type of attack is perhaps the most likely risk, and might be done by
criminals for blackmail or ransom, or might be directed by an unidentified
hostile government against a country too powerful for a declaration of war to
be considered. It is possible that a 'hydrogen bomb' might be acquired from one
of the superpower arsenals, and delivered by ship to the harbour of a port.
More likely is a bomb in the ten-kiloton range exploded at ground level in a
city, or in a ship. An accident to a nuclear weapon, such as dropping it down a
silo or from an aircraft, would not cause a full-scale nuclear explosion, but
could scatter kilograms of plutonium by detonation of the high-explosive
charge. To cause a nuclear explosion, the charge has to be detonated absolutely
simultaneously all round the nuclear core, which is done by special electric
circuits. Accidental detonation by a shock would not do this, but one wonders
whether an electrical fault or a lightning stroke could ever do it.
The above description was set in the context of a North American city. As proliferation of nuclear weapons continues, there is a greater risk that a tropical city may be attacked. In such circumstances, the deaths and injuries from firestorms and flash burns would be higher than in the North American context, because many of the dwellings would be of light construction, and a higher proportion of the population would be likely to be in the open at the time of the explosion. The distances quoted from ground zero are derived from a number of secondary sources, which do not all agree. Basically the numbers are derived from United States government measurements made during the years before 1963, when test nuclear explosions were permitted in the atmosphere. It does not really matter if some of these distances are not accurate. Similarly, even if the estimates of deaths and injuries are considerably over-stated, the consequences of exploding a nuclear bomb and giving rise to a disaster even approaching this magnitude - anywhere on earth - remain completely unacceptable. The only way to abolish this risk is to get rid of all the nuclear bombs in the world.