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view: The nuclear nemesis —Saleem H Ali

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 damage can be dispersed more quickly

Ten years have passed since Pakistan conducted its first fateful nuclear test. As if to ominously commemorate this bittersweet anniversary, we had the first recorded accident at a nuclear facility this week at Khushab in which two people were killed.

At the time of the nuclear tests in 1998, I wrote a brief article about the environmental impact of a nuclear explosion which the Pakistani media was reluctant to cover, given the revelry of the hour. It is perhaps time to revisit that theme now that we are a more “mature” nuclear power.

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 Pakistan’s nuclear tests were released, the Pakistani public was struck with awe with the powerful glow which illumined the mountain under which the explosions took place. The glowing Chaghai mountain has been immortalised now in a rather awkward sculpture in Islamabad.

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. 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 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 rapidly 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. 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.

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. In the case of the Chernobyl disaster (which was not even a deliberate explosion), a study conducted by the US Centre 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.

Even the usually reticent US Defence Nuclear Agency has stated that “accidents have occurred...which released radioactive contamination because of fire or high explosive detonations”. 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 South Asians also follow in their footsteps when it comes to something as supremely consequential as nuclear weapons?

Dr Saleem H Ali is associate dean for graduate education at the University of Vermont’s Rubenstein School of Environment and on the adjunct faculty of Brown University’s Watson Institute for International Studies. Email: saleem@alum.mit.edu

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