Nuclear Terrorism

The New Terrorism and Weapons of Mass Destruction

Terrorist actions by the 'new' terrorists - religious fundamentalists, particularly Islamic Fundamentalist groups and American Christian white supremacists - are likely to become increasingly frequent and violent, whereas secular terrorists tend to exercise constraint and to avoid killing many when killing a few suits their purposes. Religious fundamentalists are unlikely to feel any moral constraint about killing very large numbers of people.

In fact, mass killing by weapons of mass destruction may fit well into the Armageddon and apocalyptic visions of some religious groups, some of which believe that they are under divine instruction to maximize killing and destruction. The likelihood that terrorist violence by fundamentalist groups will escalate to indiscriminate mass killing is the greatest future terrorist risk and remains the primary byproduct of increasing religious terror and decreasing radical political terror.

The best way the new terrorists can achieve their objective is to use a weapon of mass destruction. There is therefore clearly a danger, some would say an inevitability, that new terrorists will acquire or develop and use weapons of mass destruction whether they are chemical, biological or nuclear. Recent experience - the use of nerve agents by the AUM group in Tokyo and the use of anthrax in the US for example - shows that biological and chemical weapons are unpredictable and difficult to use effectively (i.e., causing a large number of casualties). Effective dispersal of both biological and chemical weapons is very difficult. This suggests that chemical and biological weapons will not well serve the purposes of the new terrorists. To fulfil their aims, future new terrorists are more likely to undertake nuclear attacks than biological or chemical ones. Nuclear attacks are not only more likely to succeed but their Armageddon nature is likely to appeal to fundamentalists.

Nuclear Terrorism

There are a number of nuclear terrorist activities that a terrorist group may become involved in:

  • stealing or otherwise acquiring fissile material and fabricating and detonating a primitive nuclear explosive;
  • making and detonating a radiological weapon, to spread radioactive material;
  • attacking a nuclear-power reactor to spread radioactivity far and wide;
  • attacking the high-level radioactive waste tanks at reprocessing plants to spread the radioactivity in them;
  • attacking a plutonium store to spread the plutonium in it;
  • stealing or otherwise acquiring a nuclear weapon from the arsenal of a nuclear-weapon power and detonating it; and
  • attacking, sabotaging or hijacking a transporter of nuclear weapons or nuclear materials.

All of these types of nuclear terrorism have the potential to cause large numbers of deaths. Of the activities listed above, nuclear terrorists would probably prefer to set off a nuclear explosive, perhaps using a stolen nuclear weapon or more likely using a nuclear explosive fabricated by them from acquired fissile material. Terrorists would be satisfied with a nuclear explosive device that is far less sophisticated than the types of nuclear weapons demanded by the military, which have predictable explosive yields and very high reliability.

Terrorist could make a nuclear explosive from highlyenriched uranium (HEU) or plutonium. The most simple nuclear explosive uses the 'gun technique' in which a mass of enriched uranium less than the critical mass is fired down a gun barrel, for example, into another less-than-critical mass of uranium. The sum of the two masses is greater than critical. The gun technique cannot be used to assemble a supercritical mass of plutonium in a nuclear explosive device since this requires a technique called implosion. The implosion technique can, however, be used to assemble a super-critical mass of HEU. In a nuclear explosive using the implosion design, a sphere of plutonium or HEU is surrounded by conventional high explosives. When exploded, the high explosive uniformly compresses the sphere of fissile material. The compression reduces the volume of the sphere of fissile material in the core and increases its density. The critical mass is inversely proportional to the square of the density. The original less-than-critical mass of fissile material will, after compression, become super-critical, and a fission chain reaction and nuclear explosion will take place.

Two or three people with appropriate skills could design and fabricate a crude nuclear explosive. The size of the nuclear explosion from such a crude nuclear device is impossible to predict. But even if it were only equivalent to the explosion of a few tens of tonnes of TNT it would completely devastate the centre of a large city. Such a device would, however, have a strong chance of exploding with an explosive power of at least a hundred tonnes of TNT. It is a sobering fact that the fabrication of a primitive nuclear explosive using plutonium or HEU would require no greater skill than that required for the production and use of the nerve agent produced by the AUM group and set off in the Tokyo underground.

Instead of exploding a nuclear weapon, a terrorist group may decide to attack a nuclear facility. Nuclear facilities are particularly difficult to defend against an attack with, for example, a hijacked large commercial airliner. And nuclear reactors and tanks holding highlevel liquid wastes could be sabotaged by one or more insiders turning off the systems cooling the reactor core or the high-level waste tanks, causing in each case a catastrophic release of radioactive material.

Effects of the Explosion of a Primitive Nuclear Explosive

The largest conventional bombs used in warfare so far had explosive powers equivalent to about ten tonnes of TNT. The largest terrorist explosion so far has been equivalent to about two tonnes of TNT. A nuclear explosion equivalent to that of 100 tonnes of TNT in an urban area would be a catastrophic event, with which the emergency services would be unable to cope effectively.

Exploded on or near the ground, such a nuclear explosive would produce a crater, in dry soil or dry soft rock, about thirty metres across. For small nuclear explosions, with explosive powers less than a few kilotons, the lethal action of radiation covers a larger area than that affected by blast and heat. The area of lethal damage from the blast produced by a 100-tonne nuclear explosion would be roughly 0.4 square kilometres; the lethal area for heat would be about 0.1 square kilometres; and that for prompt radiation would be roughly 1.2 square kilometres.

Persons in the open within 600 metres of such an explosion would very probably be killed by the direct effects of radiation, blast or heat. Many other deaths would occur, particularly from indirect blast effects from the collapsing buildings and from being thrown into objects or from falling debris. Heat and blast will cause fires from broken gas pipes, petrol in cars and so on. The area and extent of damage from fires may well exceed those from the direct effects of heat.

A nuclear explosion at or near ground level will produce a relatively large amount of early radioactive fall-out. Heat from fires will cause the radioactive particles to rise into the air; they will then be blown downwind, eventually falling to the ground under gravity at rates and distances depending on the velocity of the wind and the weather conditions. The area significantly contaminated with radioactive fall-out will be uninhabitable until decontaminated. The area concerned may be many square kilometres and it is likely to take a long time to decontaminate it to a level sufficiently free of radioactivity to be acceptable to the public.

An explosion of this size, involving many hundreds of deaths and injuries, would paralyze the emergency services. They would find it difficult even to deal effectively with the dead. Many, if not most, of the seriously injured would die from lack of medical care. In the UK, for example, there are only a few hundred burn beds in the whole National Health Service. There would also be considerable delays in releasing injured people trapped in buildings. And, even for those not trapped, it would take a significant time to get ambulances through to them and then to transport them to a hospital. Therefore, a high proportion of the seriously injured would not get medical attention in time to save them. Experience shows that when large explosions occur in an urban area, panic sets in which also affects the trained emergency personnel. This panic would be considerably exacerbated by the radioactive fall-out accompanying a nuclear explosion.

Measures to Counter Terrorism with Weapons of Mass Destruction

If a terrorist group wants to fabricate a biological, chemical or nuclear weapon of mass destruction it must acquire, legally or illegally, one or more of a number of key materials. To make nerve agents, the terrorist group would need supplies of phosphoryl chloride and dimethylamine for example; for biological weapons it would need access to anthrax, smallpox, plague or botulinum bacteria; for nuclear weapons it would have to acquire plutonium or highly enriched uranium; and for radiological weapons it would need significant amounts of a radioactive isotope, such as caesium-137.

Clearly, action to prevent the acquisition by terrorists of weapons of mass destruction should focus on the physical protection of the key materials. This protection must take into account the relatively small amounts of the materials needed to make a weapon of mass destruction.

Effective measures would concentrate on:

  • control of materials, equipment and technologies that could be used by terrorists to produce weapons of mass destruction including legal penalties on those who violate control measures;
  • intelligence measures specifically designed to identify and monitor terrorists' programmes to develop and produce weapons of mass destruction;
  • methods of strengthening the chemical and biological weapons conventions; and
  • the national control of commercial suppliers of materials that could be used to produce biological and chemical weapons of mass destruction.

Of particular importance is the protection of fissile materials that could be used to fabricate nuclear explosives, including civil plutonium separated from spent nuclear-power reactor fuel elements.

The Importance of Good Intelligence

The importance of effective intelligence in countering terrorism cannot be over estimated. Monitoring the communications of terrorist groups - the activity known as signal intelligence (SIGINT) - has been crucial to this end. Modern terrorists can, however, take steps to protect their communication systems, including, for example, the use of encryption, frustrating the efforts of SIGINT.

The penetration of new terrorist groups by undercover intelligence agents or double agents (human intelligence or HUMINT) is therefore of critical importance. In fact, counter-terrorism is likely to succeed only if HUMINT can be made effective. This is why it is not going to be easy to defeat the new terrorists.

Experience shows that setting up effective intelligence activities against terrorist groups is extremely challenging. Rivalries between intelligence agencies within countries and lack of co-operation in intelligence matters between countries seriously reduce the effectiveness of intelligence. Effective and single leadership of national agencies and international co-operation between national agencies are the keys to good counter-terrorism intelligence.

The intelligence and security agencies, in their fight against the new terrorism, face an awesome task that will require the acquisition of any new technological developments relevant to counter-terrorist activities, a close study of new terrorist threats, and, perhaps most importantly, an imaginative approach to the issues.

Frank Barnaby is a nuclear physicist and consultant for the Oxford Research Group

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