The Environmental Impact of a Nuclear Explosion

Saleem H. Ali*




Now that we have had almost three months to absorb the euphoria
surrounding our nuclear tests, let us for a moment step back and reflect upon the
ecological implications of a nuclear explosion. Beyond the macho satisfaction
of showing our ostensible strength to the world, there are some critical
choices which we will need to make in the near future. My aim here is not to
argue for or against nuclear weapons but rather to present the facts about
their impact so we can keep our vision in perspective. What would happen to
our lives, and those of other organisms, if there was an above-ground nuclear
explosion, either incidental or accidental? Though the probability of such an
apocalyptic event is relatively small, the impact has the potential of being
so cataclysmic that it warrants serious discussion.

When the photographs and video footage of Pakistanís nuclear tests were
released, the Pakistani public was struck by awe with the powerful glow which
illumined the mountain under which the explosions took place. Though this was
partly a photographic trick, which highlighted the infrared (or heat) energy
that the explosion generated, it was still an austere and ominous preview of
what a nuclear explosion can do. From casual conversations with citizens
around the country soon after the tests, I gained an impression that most
Pakistanis think of nuclear weapons as just another more powerful kind of
weapon. The magnitude of even a modest nuclear explosion has not yet surfaced
to cognition in most minds. So let us try and recount what actually happens
when a nuclear bomb explodes, such as the 13-kiloton bomb which exploded over
Hiroshima in 1945. Although this was a very primitive nuclear device, it
managed to kill over 45,000 people within 24 hours of the blast and several
generations continue to languish as casualties.

Unlike conventional explosives which rely on the energy generated
by chemical combustion, nuclear weapons rely on the extreme energy which is generated when an atomic reaction takes place in which one element is converted into another element (for example when hydrogen is converted to helium). The
difference in the energy which is generated is immense. For example a sphere
of plutonium about the size of a cricket ball is capable of producing an
explosion equivalent to 20,000 tons of TNT.

There are basically three types of nuclear bombs which have been
developed.
The first kind are atomic bombs which use fission reactions, or the splitting
of atomic nuclei to generate energy. This is the kind of bomb which was
dropped by the Americans on the Japanese cities of Hiroshima and Nagasaki in
1945. The second variety are thermonuclear devices which use an atomic trigger
and a uranium jacket to start a fusion reaction in which lighter elements such
as hydrogen are forced to undergo a fusion reaction to combine and form a
heavier element. The energy liberated from 0.5 kg (1.1 lb) of hydrogen-isotope
fuel is equivalent to that of about 29 kilotons of TNT, or almost three times
as much as from the uranium in an atomic bomb. The environmental impact of
both these bombs would, however, be similar though the magnitude would be
greater in the case of a thermonuclear device. The third kind of nuclear
weapon is the neutron bomb which is a modified thermonuclear device that does
not have a uranium jacket and thus reduces the chance of widespread
radioactive fallout. The neutrons generated from the thermonuclear device can,
however, generate radioactivity within a small impact radius, killing life but
without causing widespread fallout destruction to buildings and infrastructure
(the neutron bomb is thus a tactical weapon).

The greatest devastation can be caused by a nuclear device when it is
actually detonated slightly above ground rather than on the ground itself
because the expanse of the damage can be dispersed more quickly. The
detonation of a nuclear device about five hundred meters above land would
first generate an enormous fireball, whose radiant energy would travel at the
speed of light in all directions. The intense heat generated at several
thousand degrees Celsius would incinerate all organic material within seconds.
Even stable substances such as sand would be thermally changed to glass. The
extreme temperatures would cause otherwise harmless combustion processes to
release deadly pyrotoxins that would travel as gaseous clouds beyond ground
zero. For example, a woolen suit when burned at extreme temperatures can
release enough hydrogen cyanide to kill seven people.

The shockwave generated by the blast would travel at the speed of sound
shaking the foundations of buildings and bringing them down within a matter of
minutes. The damage radius increases with the power of the bomb, approximately
in proportion to its cube root. If exploded at the optimum height, therefore,
a 10-megaton weapon, which is 1000 times as powerful as a 10-kiloton weapon,
will increase the distance tenfold, that is, out to 17.7 km (11 mi) for severe
damage and 24 km (15 mi) for moderate damage. Meanwhile, looming over the
scene would be the proverbial mushroom cloud. Propelled by the intense
pressure differentials, the cloud would suck up debris and hurl it several
miles into the earthís atmosphere. This cloud , depending on the intensity of
the blast would blanket the area with a pall that could last for several days,
blocking out sunlight and causing severe microclimatic changes. After the
extreme heat of the blast has dissipated, the debris cloud would block
sunlight, thereby decreasing the proximate temperature below freezing. The
effect would be similar to the global temperature decreases which occurred in
1991 when Mount Pinatubo erupted in the Philippines. Even below ground nuclear tests can cause severe seismic variations that can lead to earthquakes and
tremors within a thousand mile radius. Indeed, the earthquake in Afghanistan,
soon after our nuclear tests (in which over 5,000 people were killed) may
have been more than a coincidence.

The most insidious environmental damage of a nuclear explosion would,
however, result from the release of radioactive materials that would generate
intensely penetrating energy capable of causing cellular damage for years to
come. Carcinogenic (cancer-causing) and teratogenic (initiating birth defects)
effects of radiation have been documented from the Hiroshima and Nagasaki
blasts as well as the Chernobyl nuclear reactor meltdown. In the case of
Chernobyl (which was not even a deliberate explosion), a study conducted by
the Center for Disease Control and Yale University estimated that out of the
115,000 people evacuated as a consequence of the 1986 incident, 24,000 would
have a doubled risk of acquiring acute leukemia.

This discussion may seem irrelevant to many people who believe that
since we are simply developing the weapons as a deterrent, there is no point in
thinking about their actual use. What we must remember is that there is always
the chance of an accident. Indeed, there are documented cases of accidents
involving nuclear weapons tests in many parts of the world. Several islands in
the South Pacific are uninhabitable for this very reason. Even the usually
reticent US Defense Nuclear Agency has stated that ìaccidents have
occurred...which released radioactive contamination because of fire or high
explosive detonations.î
It is very true that the West has no moral authority to dictate terms of
disarmament to us when their own record is so dismal. However, like other
instances of colonial emulation, must we also follow in their footsteps when
it comes to something as supremely consequential as nuclear weapons?


*(Doctoral Candidate and Voorhees Scholar, Massachusetts Institute of Technology)